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JANUARY 2020 ISSN 1030-2662 01 The VERY BEST DIY Projects! 9 771030 266001 $ 95* NZ $12 90 9 INC GST INC GST A BRAND NEW VALVE PREAMP based on a BRAND NEW VALVE like you’ve never seen before: the 6P1 Control multiple trains on one layout Add DCC to your model train layout with Arduino Hifi speakers have optional subwoofers/stands Easy-to-build bookshelf speakers Updating your phone from iPhone to Android? Migrating without tears – or losing your data! Emergency Power: What to do before the lights go out! awesome projects by On sale 26 December 2019 to 23 January, 2020 Our very own specialists are developing fun and challenging Arduino® - compatible projects for you to build every month, with special prices exclusive to Club Members. PROJECT OF THE MONTH: Real Time Morse Decoder Listen to secret coded messages on the shortwave radio with this real time Morse code to text translator! This project uses a 567 Tone Decoder IC to filter out unwanted audio and feeds a clear signal to the Arduino for real time decoding on the OLED screen. This project comes in two parts, with the filter on a separate PCB and the Arduino shield containing a buzzer and a push button for Morse sending practice. Of course, you could always attach your own Morse key! • REAL TIME DECODER • DECODE AT SPEEDS UP TO 20 WORDS PER MINUTE (WPM) • BUILT-IN PRACTICE BUZZER CLUB OFFER BUNDLE DEAL 5995 $ SAVE 40% SKILL LEVEL: Intermediate KIT VALUED AT: $102.35 SEE PARTS LIST & STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/morse-code-decoder See other projects at www.jaycar.com.au/arduino WHERE TO FIND MORSE CODE? Any shortwave radio receiver with Single Sideband (SSB) function can receive JUST 2795 $ Morse code to use with this project. PCB ETCHING KIT Ideal for anyone needing to etch a circuit board. Complete with assortment of double-sided copper boards, etchant, working bath & tweezers. HG9990 LISTEN TO CB, HAM RADIO & MORSE CODE COMPACT WORLD BAND RADIO WITH PLL & SSB • FM/MW/SW/LW/AIR bands • Phase-Locked Loop (PLL) for stable reception • Single Side Band (SSB) to listen to morse code etc. • 1000 pre-set stations • Expandable antenna • Requires 4 x AA batteries • 150(W) x 95(H) x 30(D)mm AR1780 ONLY 795 $ ONLY 129 $ POST CHRISTMAS SALE FLYER OUT NOW! OVER 200 PRODUCTS ON SPECIAL! HURRY! Act now to avoid disappointment! Shop the catalogue online! Free delivery on online orders over $70 Conditions apply SMD IC BK1198 RADIO RECEIVER All-in-one radio receiver chip that will do AM, FM and shortwave from 2.7-22MHz. Comes in 16-pin SOIC package. ZK8829 ONLY 1995 $ Assembly required. CRYSTAL RADIO KIT Enjoy AM broadcasting without using battery or any other power source. KV3540 Your club. Your perks! Keep up to date with the latest offers and what’s on! visit www.jaycar.com.au/makerhub www.jaycar.com.au 1800 022 888 Contents Vol.33, No.1 January 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 10 What to do before the lights go out . . . Unfortunately, power outages are a fact of life these days – and Murphy says they will occur at the worst possible time. Here we look at some of the ways you can prepare for the inevitable blackouts and how to survive them – by Nicholas Vinen 32 Migrating from iPhone to Android without tears! Many people have switched their allegiance from Apple to one of the (often much cheaper) Android phones out there. But how do you transfer your contacts, data, messages and anything else without risking losing the lot? – by Dr David Maddison 85 El Cheapo modules: “Intelligent” 8x8 RGB LED Matrix Serial (single wire) control allows each LED to display over 16 million different colours or primary colours at 256 brightness levels. And they can be cascaded for large, really eye catching displays – by Jim Rowe Constructional Projects 20 A low-voltage valve audio preamp It doesn’t look like a “normal” valve – in fact, it has a soft blue glow – but this “Nutube” twin triode from Korg can operate from really low anode voltages. So low, in fact, that we have made a preamp that runs on a 9V battery – by John Clarke 40 Tunable HF Preamp for Software Defined Radio (SDR) SDR is a great way to get into radio listening – but most have woeful performance at HF. Build this little tunable preamp and your SDR will really sing! – by Charles Kosina Want your house to be the only one in the street with lights on during a blackout? Read our tips! – Page 10 Updating from an iPhone to an Android phone should be easy but there are many traps for young players! – Page 32 Wow! A preamplifier that opeates from 7-22V DC using a brand new, tiny twin triode valve! – Page 20 44 Add DCC to your model train layout with Arduino! Running one loco is so passé! Now you can add a Digital Command Control (DCC) system and run as many trains on the same track as you wish – and control signals, crossings, train lights . . . whatever you like! – by Tim Blythman 70 Easy-to-build Bookshelf Speaker System For not much money you can build this great little speaker system – and it even has optional subwoofers which can double as speaker stands – by Phil Prosser 92 Low cost, high precision thermometer calibrator Accurately measuring temperature is notoriously difficult. Here’s a cheap way to ensure your analog and digital thermometers are correct – by Allan Linton-Smith If you use SDR, you’ll know it’s deaf on HF! Build this Tunable HF Preamp and you won’t believe how much better it can be ‑– Page 40 Your Favourite Columns 62 Serviceman’s Log When things go wrong . . . really wrong – by Dave Thompson 96 Circuit Notebook (1) 3.2MHz reference derived from 10MHz (2) Micromite Mk2 development board with Microbridge (3) 12V, 20W instrument practice amplifier 100 Vintage Radio Panasonic “Radarmatic” R-1000 – by Ian Batty Everything Else 2 Editorial Viewpoint   106 Ask SILICON CHIP 4 Mailbag – Your Feedback 111 Market Centre     61 Product Showcase 112 Advertising Index   90 SILICON CHIP ONLINE SHOP 112 Notes and Errata Add an Arduino DCC system to your model train layout and you can have many locos operating at the same time! – Page 44 Build these bookshelf speakers for your TV, hifi or computer system – they’re economical and easy to construct – Page 70 www.facebook.com/siliconchipmagazine SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc Bao Smith, B.Sc Tim Blythman, B.E., B.Sc Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Art Director & Production Manager Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson, B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (12 issues): $105.00 per year, post paid, in Australia. For overseas rates, see our website or email silicon<at>siliconchip.com.au Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 * Recommended & maximum price only. Printing and Distribution: Editorial Viewpoint You need blackout and disaster plans Our feature article in this issue (page 10) is on the topic of domestic backup power systems. I actually wrote this a couple of months ago, but we didn’t have room to fit it until now. That’s a pity, because it could have helped tens of thousands of Sydneysiders who were without power for up to a week after the brief but destructive storm on the 26th of November. Our office is in the Northern Beaches area, where 1900 homes lost power, with some still blacked out a week later. Luckily we were spared. The office lights flickered a few times as the storm shot through, and I sensed that we could lose power at any time. We did not – but many others were not so lucky. This goes to show that even if you live in the heart of a major city, you are not immune from extended blackouts. Where a natural event causes widespread damage, repair crews (which may be insufficiently staffed due to cutbacks) end up spread too thin. That means that it can take a long time for them to get around to restoring power to your area. But in this case, without getting into the politics, surely there are many legitimate questions, deserving answers, regarding the length of time restoration has taken following what amounted to a fairly localised weather event in the nation’s largest city. And if the pundits are to be believed, we can expect significant load shedding this summer (particularly January and February) in the Eastern states as generating capacity continues to decline. You should have a plan to deal with power outages, in case it happens to you. And it could happen at any time. The backup power article attempts to cover a variety of ways that you can keep the lights on, and your fridge running – enough that you can live moreor-less normally with the power out; for some time, at least. Those who have a bit more time and money to spend on preparation could potentially come up with a plan to keep going for weeks, if necessary. And as recent events showed, it’s hardly far-fetched to expect that if the power does go out, it could be out for a long time, regardless of where you live. It’s also a good idea to keep plenty of water or other long-lived drinkable fluids on hand, along with food that won’t easily spoil. A severe disaster could prevent you from getting food and drink for some time due to supply problems. This will also help if you can’t keep your fridge cold during an extended blackout; at least you will still have food after the uneaten contents have spoiled. If you live in a bushfire-prone area, it would be an especially good idea to have large rainwater storage tanks along with pumps that will let you spray that water even without mains power. A petrol-powered water pump (and plenty of hose!) is ideal. But an electric pump with battery backup is better than nothing; at least you would be able to wet the area around your house. I hope it also goes without saying that if you are in a bushfire-prone area, you also need to have an escape plan. If the experts can’t stop a fire, you probably can’t either. Having said that, there are plenty of cases where homeowners – whether by good luck or good management – were able to save their properties (and in some cases, their neighbours’). The bottom line is that it’s better to be prepared. I hope that my article gives you some ideas as to what you might need to ‘ride out’ a blackout (or worse), and more importantly, spurs those who have not really thought about it deeply, to do something, before it’s too late! Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia’s electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”. The future of radio in Australia Mid last year, ACMA asked for comments on the future delivery of radio services in Australia (see: siliconchip. com.au/link/aaxz). The following is a summary of my submission. In the opening paragraphs of the Consultation paper, ACMA only mentions the number of listeners to commercial radio and ignores the significant numbers of listeners to the ABC and community radio. For the last 10 years in capital cities, 105 high-power AM and FM transmitters have been radiating the same programs as 19 DAB+ digital transmitters, which are also transmitting additional programs. The operating costs and electricity consumption will continue until AM and FM are switched off. This happened in Norway, and within a year, listener numbers had recovered. In regional areas, there are four national and one local ABC programs, compared to 11 broadcasts via DAB+ in the capital cities. SBS is limited to self-funded village coverage with a single program, compared to seven in the capital cities. This is unfair to 40% of Australians. It also ignores the 470,000 people in remote Australia who receive their radio via fixed satellite dishes via Viewer Access Satellite Television (VAST) signals, which contain a variety of ABC, SBS, Aboriginal and religious broadcasts. They also made no mention of those people who have no radio after they leave their homestead or village, since the ABC switched off high-frequency (shortwave) broadcasts on 31st January 2017. This is pretty incredible, considering that the ABC is the “Emergency Broadcaster”! Similarly, Radio Australia was also switched off; China Radio International now uses those high-frequency broadcast ranges, and can be heard 4 Silicon Chip everywhere in the Pacific, not just in the 13 cities carrying Radio Australia on FM. For the future, DAB+ is ideal for high population density areas such as capital cities. But it is not suitable for broadcasting over larger areas, due to the very high frequencies used and the limit of eight transmission channels. In regional areas, DRM+ can operate in the abandoned TV channels 0-2, which are unsuitable for digital TV. There are 168 DRM+ channels available in that band, and the signals travel longer distances. This will enable regional listeners to have the same variety of ABC/SBS programs. In remote areas, high-powered highfrequency DRM can cover the whole of Australia from a central transmitter site. A single DRM transmitter could transmit ABC News Radio and Grandstand, which are already live nationally. The Emergency Warning System can wake a DAB+ or DRM radio, increase the volume and switch to an audible warning message if the receiver is in the area of the emergency. Maps and detailed text messages can also be received and displayed. Digital broadcasting is the cheapest method of program distribution for broadcasters and listeners; the mobile phone network is patchy or non-existent in regional and remote areas. Please read my full submission on the ACMA website (IFC 13/2019-Submission 4; siliconchip.com.au/link/ aaxz). One final note: in my submission, I suggested that DRM+ could be transmitted on multiple adjacent 100kHzwide channels from a single modulator. RFMondiale has now released a six-channel modulator which can carry 18 audio programs. This would allow regional listeners (40% of the population) to have the same range Australia’s electronics magazine of ABC and SBS programs as those in capital cities. Alan Hughes, Hamersley, WA. Editor’s note: you say that FM and AM could be switched off, but it is frustrating that DAB+ broadcasts still cut out in the Sydney Harbour Tunnel, Eastern Distributor and I assume other tunnels like the Cross-city Tunnel and Lane Cove Tunnel. Presumably, this is due to the set-up and/or design frequency range of the amplifiers powering the leaky waveguides which provide radio and phone reception in the tunnels. Turning an iPad into an illuminated magnifier Thank you for such a great magazine. I am continually amazed by the project and ingenuity involved. I am particularly looking forward to the next DCC Controller. I wanted to share with you the use of a common electronic device that many of your readers may appreciate. This simple idea came about because I was building your DAB+/FM/AM Tuner (January-March 2019; siliconchip. com.au/Series/330). I needed a way to see the SMD components better while building it. After looking at traditional LED illuminated magnifier lenses, searching the web on an iPad for similar devices, my daughter said: why not use the built-in magnifier function on the iPad? I found a scrap piece of plastic approximately the size of the iPad and made a cut-out in the corner for the camera, and arranged it so that the iPad would sit securely on it. I attached this to an unused suction base to securely hold it on my workbench. I then added some Jaycar stick-on white LEDs to the underside. This works very well. As the camera is at the bottom left of the iPad, siliconchip.com.au Helping to put you in Control UR32 Industrial Cellular Router Integrating embedded cellular modem and dual SIM function, the UR32 provides 3G/4G cellular network with 150 Mbps download and 50 Mbps uplink. It also has 2 ethernet ports and WiFi(optional. SKU: ULC-032 Price: $349.95 ea + GST Current Proving Switch 0.2-20A Check ac motors current with this “CT” style AC current proving switches, the sensing range (set point) being adjustable 0.2-20 Amps. SKU: NTR-280 Price: $79.95 ea + GST Temperature and Humidity Sensor Wall mount temperature and humidity sensor, linear 4 to 20 mA output. SKU: RHT-003 Price: $219.95 ea + GST Dual 5 Digit Process Indicator Fully programmable via front buttons this dual 5 Digit Process Indicator (48X96 mm) features two 4-20mA Inputs and 24 VDC Powered. SKU: DBI-035 Price: $179.95 ea + GST Vantage Pro2 BACnet Weather Station Kit Full weather station kit based around a Vantage Pro2 with a BACnet MS/TP gateway. Kit options include wireless versions and additional UV and solar radiation sensors. SKU: ECS-2001 Price: $1224.00 ea + GST 4 Button Pendant 4 Button Control Station Pendant marked UP-DOWN and RIGHT-LEFT with Emergency Stop button. SKU: HNE-1042 Price: $79.95 ea + GST Current Transducer Split core hall effect current transducer provides a 0-5VDC output for a 0-50ADC current in the primary conductor. SKU: WES-070 Price: $109.00 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. 6 Silicon Chip the open area allows me to work on the PCB, including soldering, while using the iPad magnification to see what I am doing. The same thing could be done with a mobile phone, but the larger screen size of the iPad is a significant advantage. It is excellent, with an excellent depth of field. It is effortless to inspect solder joints using this rig. Thanks again for a great magazine. Peter Kable, Balmain, NSW. Toyota Hybrid battery info Firstly, let me congratulate your magazine as being one of the first media outlets to adequately explain how impressive the Toyota Hybrid system is (December 2019; siliconchip.com.au/Article/12172). After much research and after taking the vehicle for a test drive, my wife and I made the decision (in February 2019) to purchase the Toyota Corolla Hybrid and we haven’t looked back. Despite being used to driving a manual for many years, we have been very impressed with the performance of this car and the seamless transition from petrol to electric drive (and vice versa), as well as the excellent fuel economy and range. As you wrote in the editorial, “Toyota deserves praise”. For a few years now, we have been saying that our next vehicle would be an electric one (an “EV”), but we don’t feel that (particularly country) Australia has adequate infrastructure in place to make this a feasible option. With some prompting from our daughter (an engineer), and because our Subaru Outback was getting old, we made the decision to buy a hybrid. And after some shopping around, we found the price a pleasant surprise. We were also much pleased with the knowledge of the salespeople who were able to answer all of our questions. I would like to point out that in your article and editorial, you didn’t mention that the hybrid battery is comprised of nickel-metal hydride cells, not lithium-ion as was the case with the earlier Prius models and many other brands, as well as most Evs. This point (and the resulting lack of fire hazard) seems to have been lost on many people, and in particular the NSW RMS. They issued us two small triangular EV stickers which must be put on our number plates, to warn emergency services personnel of the vehicle being a fire risk in an auto accident. This despite the fact that NiMH cells have a good safety record. However, I was impressed that when I asked the Toyota salespeople about the hybrid battery. They immediately told me that it was a NiMH type. Ian Gabriel, Wauchope, NSW. How are very weak GPS signals decoded? The article on how satellite navigation (GNSS) works in the November 2019 issue of Silicon Chip (siliconchip. com.au/Article/12083) has lots of good information on the different types of GNSS systems. I liked the section where it describes that four or more satellites are required to adjust the GPS receiver time clock. The receiver clock is adjusted until all the satellites indicate the same latitude and longitude point on Earth. This Australia’s electronics magazine siliconchip.com.au also allows the GPS receiver to be used as a low-cost, accurate time or frequency reference, taking advantage of the very accurate atomic clocks that each satellite has onboard. But there is one thing that was not covered. In the section on GNSS receiver start-up, the author mentions that it takes 12.5 minutes to download the almanac data for all satellites. But he does not describe why it takes so long. It also does not go into much detail about how low the received satellite signal strength is. So how does the GPS receiver recover the satellite signals that are buried in electrical noise, when a large, high-gain antenna is not used? I read a book called “GPS: A guide to the next utility” by Jeff Hurn which explains this, on pages 50-54. The book is from 1989, so it’s a bit out of date in places, but it has a down-to-earth, lovely way of describing how GPS works. A simplified explanation is that the message data is continually being repeated and the receiver monitors several of these transmissions in a row, ‘averaging’ them until the message has been clearly received. Each data bit received during a single transmission indicates that it was ‘mostly’ a high or low data level. So it takes several sequences to figure out the digital bit levels for sure. Some tricks are used to achieve this, such as knowing the PRN codes of satellites which are in range after downloading the almanac data for all satellites. Maybe someone else could write in with a more complete explanation of how this is achieved. Roderick Wall, Mount Eliza, Vic. Overcoming test lead resistance errors I have some comments regarding test lead resistance, mentioned by Colin O’Donnell in a letter in the August issue Mailbag section (page 12). I have an old ute which doesn’t get used enough to keep the battery charged. I thus set up a 10W solar panel which runs through a simple controller to keep the battery fully charged. I used to have a problem when checking conditions in that I would first check the battery voltage, then the charge current. Sometimes before leaving the vehicle, I would do a last-minute voltage check. In haste, I would change the meter range but forget to swap the leads. That little ‘click’ told me I needed to remove the cover and replace another fuse. My solution was to modify the controller by putting a 0.1W 5W resistor in series with the output. Current (mA) could therefore be measured as mV across the resistor x 10. This way, I could leave the meter set to volts and not have to swap range or leads over when measuring voltage or current. This effectively creates an ammeter but with the shunt in the device rather than the meter. The resistor is wired at the rear of two through-panel sockets (like banana sockets except they are small ones that fit meter probes). This is a possible idea for Colin, who bemoaned the resistance of meter leads. By having the shunt at source, the resistance of the leads has no bearing on the current measurement. He could use his ESR meter to calibrate a shunt for the purpose. Sometimes, I need to measure the current draw of devices powered by small batteries made from AA or AAA cells. I made a simple rig to make this easy. I cut two ‘fingers’ of siliconchip.com.au good reasons to use Switchmode – the repair specialists to industry and defence one Specialised service Benefit from our purpose-built facilities, efficient and effect service. Since 1984 we have specialised solely in the repair and calibration of all types of power supplies and battery chargers up to 50kVA two Turn around time We provide three levels of service: standard (10 days), standard plus (4 days), emergency (24 hours) three four Access to Technicians and Engineers Talk directly to our highy skilled Technicians and Engineers for immediate technical and personal assistance. Quality Assurance Accredited to ISO 9001 with SAI Global and ISO 17025 with NATA. Documented, externally audited management systems deliver a repeatable, reliable service five Convenience and certainty We provide fixed price quoes after assessment of goods and cost-effective maintenance, tailored to meet your individual needs Take advantage of our resources. REPAIR SPECIALISTS TO INDUSTRY AND DEFENCE ACCREDITED FOR Switchmode Power Supplies Pty Ltd TECHNICAL COMPETENCE Unit 1/37 Leighton Place, Hornsby NSW 2077 Australia Tel 61 2 9476 0300 Email: service<at>switchmode.com.au Website: www.switchmode.com.au thin sheet copper, slightly narrower than a cell. I soldered a fine multi-strand wire near the end of each of these. I then cut a ‘finger’ of that springy plastic that comes with components and kits, slightly larger than the copper. This was roughened and a copper strip glued to each side using five-minute epoxy (clamped lightly to keep it flat). Now I can pull the battery back against the spring in the device and insert the ‘finger’, across which I connect another 0.1W resistor, so I can measure the voltage across it. I also have two wired copper fingers for measuring voltage while the device is operating, although it’s often possible to get meter leads to reach into the battery compartment anyway. Joe Edgecombe Coondle, WA. Vibrator “buffer” / “timing” capacitor value is critical In regards to Ian Batty’s comments on vibrator operation, in the Mailbag section of the November 2019 issue, he states that the capacitor across the vibrator transformer secondary, which is sometimes called the “timing capacitor”, should instead be referred to as the “buffer capacitor”. However, note that the term “timing capacitor” was used by what was the world’s largest vibrator manufacturer: P. R. Mallory and Co. This company not only developed the first commercially-available vibrator power supply, but was the primary supplier to the US car radio market throughout the valve era. Mallory did extensive research and development work over the roughly 25 years of the technology, continually improving vibrator design and operating life. Australia’s electronics magazine January 2020  7 I refer to a 1947 publication by Mal- understood, capacitors were selected building and repairing vibrator power lory, “Fundamental Principles of Vi- based on what gave minimum spark- supplies agrees with Mallory’s design brator Power Supply Design” down- ing. The problem was that while there methods. Some designs I tried before loadable from: siliconchip.com.au/ may have been no sparking or high I knew the proper procedure resulted link/aay2 transient voltages, contact material in sticking vibrator contacts because At 135 pages long, it is clear that a transfer took place, which resulted in the capacitor value was too high; even vibrator power supply is not the sim- the contacts eventually sticking. though there was no sparking. Upon ple device which it is often assumed The breakthrough came with the re- understanding how the buffer circuit to be, trapping so many unwary peo- alisation that for maximum vibrator really worked, this ceased to be a probple who attempt to work with them. life, there must be zero voltage across lem altogether. On the subject of the timing or buff- the contacts when they close and open. John Hunter, er capacitors, the chapter, “Timing Only when the contacts are closed can Hazelbrook, NSW. Capacitor Considerations”, goes into current flow without detriment. some detail as to why the term ‘timSo the value of this capacitor must A possible solution to DAB+ noise ing’ is used. be chosen so that, when combined I built your DAB+/FM/AM Radio It is true that some means must be with the properties of the primary (January-March 2019; siliconchip. provided to prevent the sudden flux winding, the voltage at the switched com.au/Series/330), and I would like collapse, when the contacts open and side of the winding is the same as the to say thanks for a great project. I’d destructive voltages may be produced; battery voltage. This ensures the cor- also like to thank Tim Blythman, who RAYMING and a capacitor is the most common TECHNOLOGY rect ‘timing’ of the change-over, so that helped me to find some solder joints I way of doing this. it occurs and whenPCB there Assembly is no voltageServices dif- missed on a connector. PCB Manufacturing Some early designs instead used ference across the contacts. As a follow-up to the question from Fuyong Bao'an Shenzhen China a voltage-dependent resistor (made A much more detailed description D. P. about noise coming from the 0086-0755-27348087 under the “Globar” brand in the US) of this can be found from page 107 on- headphones (Ask Silicon Chip, OcSales<at>raypcb.com across the secondary. A very few sim- wards in the PDF mentioned above. tober 2019, and his follow-up in the ply used ordinary resistors. Some deIf the timing capacitor is chosen like November issue), I too suffered headwww.raypcb.com signs even relied only on circuit load- this, efficiency and vibrator life will be phone noise. ing to keep the peak voltage to a safe maximised. However, it is difficult to Mine was always present but just level. choose the perfect value, as the vibra- tolerable. On occasion, after 15-30 One example I have of this is a 12V tor contact spacing changes over time, minutes of use, the signal would disfluorescent lamp, where the fluores- therefore reducing the duty cycle. Ad- appear entirely, and the noise level cent tube itself, connected directly ditionally, the supply voltage also var- would rise. Fiddling with the antenna across the transformer secondary, ies as the battery is charged and dis- would sometimes fix this. prevents the voltage rising above the charged, and this too has some bearing On investigation. I discovered the tube’s arc voltage. Current limiting for on the correct capacitor value. aerial connection was shorted at times. correct tube operation is inherent to As such, the capacitor value used is So I removed the SMA connector and the transformer, having a high leak- usually slightly higher in value than discovered that a little too much solage inductance. the ideal. Mallory’s recommendation der had flowed through the mountHowever, limiting peak voltages and is for a 65% slope of the primary wave- ing holes, causing it to almost short preventing contact sparking is only form during the vibrator dead time. at the innermost point. Presumably, part of the criteria for correct vibrator This is chosen to be a reasonable com- this must have been forming a highoperation. Indeed, if this is all that is promise, protecting against high tran- resistance path, with expansion from required, the capacitance is not par- sient voltages over the normal range of heat making it worse and eventually ticularly critical, and a wide range of operating conditions, but not using a forming a dead short. values will do the job. value so high as to cause problematic After fitting a new SMA connecAt the beginning of the technolo- contact material transfer. tor, fractionally further off the board gy, before the science was adequately My own extensive experience with than the first one, all this noise disap- RAYMING TECHNOLOGY Fuyong Bao'an ,Shenzhen, China Tel: 0086-0755-27348087 email: sales<at>raypcb.com web: www.raypcb.com PCB Manufacturing and PCB Assembly Services 8 Silicon Chip Australia’s electronics magazine siliconchip.com.au peared. Signal strength also improved three-fold. Perhaps this snippet of information may be helpful to your correspondent. Thanks again for a fantastic magazine. Phil Jenner, Adelaide, SA. Restoring carbon contacts the easy way I am prompted to write in by the letter from John Benfer in the Mailbag section of your December 2019 issue. When the button functions fail on an old remote, I dismantle it and renew the carbon on the contact pads using a 9B pencil (available at the local newsagent). This method is simple and cheap, and works fine. I hope this may help my fellow “fix it, don’t throw it” technical peers. Ben McGee, East Hills, NSW. Battery Management board replacement Lithium-ion rechargeable batteries are great, but rather expensive. When the internal Battery Management System (BMS) fails outside of the short warranty, as they do, the financial loss is considerable. Battery Management System replacements are not to be found in our local electronic stores. Recently, a mate asked me to look at his expensive but deceased 12V 22Ah golf cart battery. I measured 0V across the terminals. After some surgery, we open it up to find the set of 4 x 11 18650G 7.2Wh cells fully charged and delivering 16V, and plenty of watts when accessed directly. We tried a controlled discharge from 16V to 12V in the hope that it would reset the chip, to no avail. We also disconnected both main leads and the three to the intermediate cell packs, now at 3.2V, 6.4V and 9.6V. Alas, the board seems defunct. As usual, the cause is not evident. In any case, those minute SMD components make a repair daunting, even if we could determine the cause of the fault. Many different types of BMS exist, some for single or multiple cells, some checking for even voltage charge on each cell bank (as in this case). Some sense charging temperature (this one doesn’t) and some have short-circuit protection (not sure in this case). So, it seems like a good idea for Silicon Chip to first investigate the feasibility of designing a drop-in replacesiliconchip.com.au ment board with several options. It would be great if it could support both high and low current batteries, especially for 12V batteries with various lithium chemistries. There is an increasing need; can you help? How about an article describing typical BMS operations and options, and how to fix an over-discharged battery? David Kitson, Perth, WA. Response: we will consider this, but various BMS boards are readily available at ridiculously low prices. With a bit of searching, chances are you will find a replacement BMS for your mate’s battery at a fraction of what it would cost you to buy the parts to build one. Here’s an example that we found after just a few seconds of searching, which may work for you at just $3: siliconchip.com.au/link/aay1 New home wanted for electronic components I have been into electronics most of my life. Reading your letters pages, it seems many people are still interested in learning, which is very laudable. I have taught electronics part-time for close to 50 years and still enjoy dabbling. I have accumulated a considerable supply of bits and pieces, and donated quite a lot to a local high school last year. I have gone through my stuff and found more assorted electronics parts, but it seems the school is not interested. Rather than throwing these parts out, I would be happy to give them to anyone interested. While some of it may be considered rubbish by others, it may be of use to someone younger just starting out. If anyone is interested, they can come and look and throw out anything they don’t want. I have about two cardboard cartons worth, including some components, motors, mechanical bits and pieces etc. When I was younger, I used to go to TV repair shops and ask them for old chassis they were throwing out, and then stripped out the components. I realise these days you can buy everything quite cheaply, but it still goes against the grain for me to throw stuff out. Alex Danilov, alex.aldan<at>gmail.com Naremburn, NSW. SC Australia’s electronics magazine January 2020  9 Want your house to be the only one in the street with lights on? Emergency backup power during blackouts Have you thought about how an extended blackout would disrupt your life? They may not be common where you live, but that will change, especially if a natural disaster occurs. A widespread, extended blackout could go beyond inconvenient, to life-threatening. But you can build a system to run some lights and critical appliances when mains power is not available, for days if necessary. A few months ago, we came home to find the power was out. While this is not a common occurrence, it does happen from time to time. I have experienced several blackouts over the last decade or so; mostly short (under one hour) but occasionally longer (three or four hours). Some of my family members who live in the Blue Mountains (west of Sydney) have experienced multi-day blackouts, which are annoying, to say the least! For us, the power came back on not long after we got home, and we were able to resume our regular routine. That included bathing my daughter and putting her to bed; something that would have been very difficult to do in the dark and with no hot water (our gas water heater has an electric igniter). 10 Silicon Chip This loss of power got me thinking about what I would do if there were a longer blackout, especially in the evening, when we rely heavily on electricity. An extended blackout would cause us a great deal of difficulty. So I started looking into possible solutions. A disturbing development This blackout caused me some grief beyond just that time without power. When we had a roller shutter installed which can block the rear exit to our home, I insisted that it must have battery backup so that a fire at the front of the house (where power comes in) could not result in both main exit routes being blocked. We paid quite a lot of money to have this battery backup system installed. by Nicholas Vinen Australia’s electronics magazine But only two-and-a-half years later, during this short blackout, it totally failed. Arriving home to the dark house, I tried to put the shutter up, but it didn’t respond. That weekend, I dismantled the cabinet in which it was housed, only to find the gel cell batteries in the UPS (interruptible power supply) had gotten so hot that they melted and were leaking acid! (See Photo1) I ran some quick sums and discovered that these two 7.2Ah SLA cells were expected to deliver upwards of 100A each when the UPS was operating. No wonder they failed so spectacularly! Anyway, I’m told that these SLAs, even in normal service, only last a couple of years. That’s hardly ideal for a safety-critical application, especially siliconchip.com.au Photo2: the APC SMX1500RMI2U is one of the commercial Uninterruptable Power Supplies I considered before discarding the idea and building my own. It costs around $2000. Many UPS data sheet give no indication of the expected runtime or battery capacity, only the maximum power. To APC’s credit, they do give you the battery capacity for this unit at 311Wh (approximately 25Ah <at> 12V) and provide a runtime chart, which shows a runtime of just under five hours at 50W. That’s better than your average computer UPS but not so great when you consider the price. Photo1: while not really obvious from this angle, the two SLA batteries in this UPS were badly distorted and buckled and it was very difficult to remove them. You can see some of the acid that was leaking out on the clear plastic sheet underneath them. all that high-end computer UPSes had pretty poor battery capacity given their high prices (see Photo2). I wanted something that would ideally last at least 24 hours, and I was becoming increasingly concerned that the SLA/gel cell batteries used in almost all UPSes are not good long-term prospects. There had to be a better way, so I started investigating other possibilities. This article is not intended to describe all the ways that you could provide emergency backup power. There are just too many options. But I will list some things I learned while researching my particular problem. I will also describe the backup system that I eventually put together. Backup power options Perhaps the ultimate way to insulate yourself from mains grid power fail- given their inaccessibility in my case. I had to find a proper solution to this. I looked online for higher-quality UPSes, especially those with a longer standby time at light load. The UPS that we had been supplied would last for less than an hour even with no load. That simply wouldn’t do as we can’t guarantee that we would be home if the power goes out again. I found some commercial UPSes online with a longer standby time; in some cases, eight to twelve hours, or more. They cost thousands of dollars, though, and I found oversiliconchip.com.au ures is to have an off-grid system, such as a solar-charged battery bank system. However, that brings up a whole new set of problems. As you will be generating your own 230V AC power, you need to make sure that you have sufficient redundancy that one component failure will not mean a total loss of power. After all, off-grid systems can fail, and if yours does then you will be without power until you fix it. If you don’t have spare parts on hand, that could take days or weeks, depending on how hard it is to get replacement parts. So you need to know what you are doing if this is your plan to improve the reliability of your home electrical supply. You will also need a big battery bank and big solar array, to ensure that it can meet your power needs, regardless of weather and usage patterns. That’s a Photo3: our 800W+ UPS project from the May-July 2018 issues would have worked in my situation, except that it was a bit large to fit in the space I had available. My eventual solution involved a much larger and different type of battery, partly because of my desire for a longer runtime, but also because I am told that AGM leadacid batteries last a lot longer on standby than the lithium-based (LiFePO 4 ) rechargeable batteries we used in this UPS. The LiFePO 4 batteries are very good in ‘deep cycle’ applications, but that is not so important when you only only have the occasional blackout. Australia’s electronics magazine January 2020  11 Photo4: the Jaycar MG4508 inverter generator is good value at $899 (retail, including GST). It runs off petrol (3.7l tank) and has a continuous power rating of 1.6kW, which is enough to run all but the biggest appliances. Depending on the load, a tank of petrol could last for many hours, and even a modest jerry can would have enough capacity to refill it several times over. However, you will need to make sure you have fresh petrol on hand to use a generator like this. It goes off eventually, so you can’t just fill a can and forget about it. You also need a well-ventilated area to operate a generator due to fumes. significant challenge, and such a system is likely to require a significant upfront investment. You could consider installing a small off-grid type system to run a limited portion of your domestic appliances, and retain the grid connection, so that you have two sources of power. Such a system could be a lot smaller and cheaper, and the chance of it failing on the same day as a loss of grid power is very low. But building such a system ‘just in case’ could still be quite expensive and time-consuming. Anyway, I don’t have any suitable places to mount solar panels, so I had to think of another solution. I considered a small battery system (charged from the mains and/or other sources), or a petrol/diesel generator. A generator is the cheapest solution. For example, Jaycar Cat MG4508 is a 2kVA petrol inverter generator which retails for $899 (Photo4). Providing you have enough fuel, this could keep you going for several days or even weeks without mains power (eg, during a natural disaster), keeping your fridge/freezer cold and running other critical appliances. The three main disadvantages of such a system are that most are not automatic (you normally have to fire up the generator and plug your appliances into it, ruling it out in my case), that petrol and diesel fuels cannot be left in the tank long-term and that a generator cannot be used in an enclosed space. So if you live in a unit, it may not be a practical solution for you. Fuel can go bad if left sitting for a long time (more than 3-12 months, depending on how it’s stored and the ambient temperature). So unless you are continually turning over a small supply of petrol, you will have to go out of your way to keep fresh fuel on hand in case you need it. I have an electric mower, so I don’t keep petrol at home. It may be possible to drain some from your car’s tank in an emergency, but anti-siphoning de- vices (to stop petrol theft) make that difficult. You could purchase a generator and wait until there’s a blackout to get some petrol; but if the blackout is widespread, the fuel station pumps may be non-functional which could leave you totally out of options. A small battery system cannot deliver anywhere near the total energy that a generator can, but does have a few advantages. Battery systems can automatically take over during mains power failures, and they can be augmented with a generator for longer outages. And batteries can sit around charged for years, ready to go, so they are low-maintenance. You will pay more for a decent battery backup system than a generator, even though it won’t run your loads for anywhere near as long. And batteries do need to be replaced eventually. So there’s no ideal solution. Other possible solutions Having decided that I needed a battery system, my thoughts turned to how to extend its run-time in case of a long blackout, as might be caused by a natural disaster. The difficulty in keeping fresh fuel on hand (and getting fuel out of a car tank) put me off the idea of using a generator. So, what about using my car as a generator? I am constantly turning over the fuel in its tank, and it already has an engine and alternator; it just lacks the high-voltage output of a generator. Just about any 12V inverter will run from a car electrical system. This could provide 230V AC to run appliances and/or recharge a battery backup system during an extended blackout. But a typical car or SUV alternator is only designed to provide maybe 100A Photo5: this Jaycar 2000W pure sinewave inverter is under $500 including GST (catalog code MI5740). It could be useful as part of a battery power back-up system, or to connect in to an automotive electrical system to provide mains power from the vehicle’s fuel supply. But note the caveats presented in the article, especially that a car alternator generally cannot provide more than about 100A, so you risk flattening the car battery drawing upwards of 1000W from the inverter for long periods, even with the engine running! 12 Silicon Chip Australia’s electronics magazine siliconchip.com.au Photo6: Jaycar has a range of 12V solar panels (this is Cat ZM9058, 120W) which could be kept in your shed and pressed into service in an emergency, to charge a battery back that powers your appliances though an inverter. If you choose to go this route, make sure you have all the cables you need on hand. It would also be a good idea to have an MPPT Solar Charger. Jaycar sells inverters with built-in solar chargers (eg, Cat MI5722 & MI5724). If you are desperate, you can connect panels directly across a battery, if you monitor the voltage carefully and disconnect them if it rises too high. continuously; possibly a bit more or less, depending on the model. That’s barely enough to run a 1000W inverter at full load. Such an inverter could drain the car battery even with the engine running. There’s also the question of whether the car’s alternator will deliver full current with the engine idling. Many require 2000RPM or more for maximum output. That is something that would need to be verified for your vehicle. Despite these provisos, a 1000W pure sinewave inverter can be purchased for just a few hundred dollars (Photo5), so it may be a worthwhile investment as a last-resort method of recharging a backup battery during a prolonged blackout. You would need to periodically monitor the vehicle battery voltage if using such a rig. If you found that the battery was being discharged even with the engine running, you’d need to disconnect the inverter and allow the vehicle battery to recharge before connecting it again. Having to do this periodically could be quite annoying, but it would be better than having no means of keeping your appliances running at all. Temporary solar panels As I mentioned above, I don’t have any good locations for permanently mounting solar panels, but I did consider installing a mains-charged backup battery power system while also keeping some panels on hand for emergency use (Photo6). These could be laid out in our yard and wired up to an MPPT solar charger attached to siliconchip.com.au the battery when needed. That would allow me to power our appliances using solar power during the day (weather permitting) and possibly even recharge the battery during the day, to keep it going overnight, if we experience an extended multi-day blackout. The only disadvantages are the purchase cost of the panels and the solar charger, and the need to store both. But if you experience an extended blackout, I think you will be thankful to have them. So it’s an option worth considering. Determining power requirements So I set about researching a battery-based system with mains power to keep the battery on standby, and recharge it after a blackout. The first thing I did was measure the size of the space I had available, where the old UPS was fitted. I considered using the UPS design that we published, which was based on two 12V LiFePO4 batteries (May-July 2018; siliconchip.com.au/Series/323). But I measured our prototype and found that it was too large to fit in the available space. I could have probably built a smaller version of this design, but I wanted to take a different approach, for reasons I am about to explain. The next thing I did was to measure the maximum power draw of the motor powering our roller shutter, and found it to be just under 400W. So a relatively small inverter and battery would do the job, as long as the standby power Australia’s electronics magazine consumption was low enough. (Our 2018 design could deliver twice this power, so it would have worked, if it had fitted.) After some more thought, I decided that while a 400W inverter would do the job, it wouldn’t cost much more to get a bigger inverter and battery. That would let us run other appliances during a blackout. I considered whether it was feasible to build a system which could keep the fridge and freezer cold for about 24 hours, and maybe run a few other appliances intermittently, such as lights, a television etc. It would have to fit in the cabinet space available, though, and I didn’t want to spend a huge amount of money on it. I also wanted a system that would need minimal maintenance over a long period; ideally, 10+ years. One reason for this is that, as I mentioned above, the electronics would be sealed inside a cabinet which would make regular maintenance difficult. I also could easily forget to check the battery as it would be “out of sight, out of mind”. Choosing a battery I quickly ruled out using flooded or gel-cell (SLA) lead-acid batteries, as they have an insufficient lifespan. Many UPS vendors recommend replacing even good-quality SLAs after 2-3 years (mine didn’t even last three years!). After some research, I also rejected LiFePO4 lithium-based rechargeable batteries. This is because, while they are well-suited to deep-cycle applications, they do not last so well on January 2020  13 Photo7: this Fullriver 200Ah AGM battery is good value, if a bit unwieldy. I was told to expect a 6-7 year lifespan. I was hoping for a system that could be left alone for around ten years, hence, my decision to buy a slightly more expensive battery. standby. There is some talk online that if kept constantly on charge, LiFePO4 cells degrade significantly within a few years. Also, they have much lower continuous discharge current ratings compared to similarly-sized (and priced) lead-acid batteries. That meant that an LiFePO4 battery suitable for my application would be well over $1000. Consider that a 100Ah LiFePO4 battery, typically around the $1000 mark, is only rated to deliver 50A. That’s barely enough to run a 500VA/400W inverter, just barely adequate to power my shutter and nothing else. I didn’t want to use a lithium-ion battery due to their reputation for catching fire if there’s a fault, especially considering it would be inside a timber cabinet. That left me with only one real choice: one or more lead-acid AGM (absorbed glass mat) batteries. A good AGM battery has a very high charge and discharge current for its size and can have a long life on standby; typically more than five years and, in the case of top-quality batteries, up to ten Some back-of-the-envelope calculations showed that a 100Ah 12V battery or 50Ah 24V battery would be able to power my fridge/freezer for around 24 hours in typical weather, based on the figures on its Energy Star sticker. Such a battery would also last days on standby, assuming an inverter idle current of no more than about 1A. I made a shortlist of suitable batteries. Two of the best options were the Chinese-made FullRiver HGL200-12 200Ah standby AGM battery (Photo7) and the American-made Lifeline GPL30HT 150Ah deep-cycle AGM battery (Photo8). 14 Silicon Chip Photo8: this is the battery I wound up with, a Lifeline 150Ah deep-cycle AGM unit. It’s rated for around 500 full discharge cycles and can be charged or discharged at up to 150A, or discharged a bit faster, at the risk of a shorter lifespan. That’s enough to support a 1500-2000W inverter with just the one battery. It should be able to deliver an average of 100W, enough to run a typical fridge/freezer for more than 24 hours. Both batteries came to me highly recommended as being of good quality. The FullRiver battery is cheaper, despite having a 33% higher capacity. I was told to expect a 6-7 year working life while the Lifeline battery might reach the 10-year mark that I was hoping for. That, plus its smaller size and lower weight (43.5kg compared to 57.6kg) clinched it for me, despite the higher cost. Interestingly, the 150Ah Lifeline battery supports charging at up to 150A (and presumably, discharging at a similar level; enough to run a 1500VA inverter) while the higher-capacity FullRiver battery is only rated for charging at 40A. The maximum specified discharge rate for the FullRiver battery is 120A for 1 hour. So it would be suitable for running an inverter up to about 1200W, although you can see that you lose a fair bit of its usable capacity at such a high discharge rate – 120Ah is 40% less than when discharging at the 20-hour rate where capacity is 200AH. permanently connected to the battery. This would be a cheap approach, as a basic but decent charger can be had for around $100 and a similar quality 1kW inverter is just a few hundred dollars. But the main problem with this is that any time the attached appliance(s) are used (eg, the shutter put up or down), this would draw tens of amps from the battery, likely reducing its lifespan. Worse, this would almost certainly cause the charger to switch from float charging to bulk/absorption, and if that happened regularly, the battery would not last long. The other problem is that I didn’t know how long the charger and inverter would last when powered 24/7. Low-cost devices might fail in less than 10 years, making the purchase of Charger and inverter choices I then had to figure out what charger and inverter to use. I briefly considered buying a battery charger and a separate inverter, and leaving both Photo9: my Victron Multi Plus Compact 1500VA 12V inverter/ charger (what a mouthful!). It comes with the battery cables and NTC thermistor prewired. It’s also supplied with pluggable terminal blocks for the mains input and output, but these need to be wired up (in my case, to the ends of a bisected extension cable) before it can be used. Australia’s electronics magazine siliconchip.com.au an ultra-reliable battery a bit pointless. What I really needed was a UPSlike scheme where the appliances would run off mains when available, only switching to inverter power during blackouts. That way, the battery would have no load most of the time and could just be kept in float/maintenance mode. And ideally, the hardware to achieve this should be designed for long-term use, to meet my longevity goal. I subsequently noticed a local shop (Battery Business – a few doors down from our office) [www.battery-business.com.au] advertising Victron Energy Compact Inverter/Charger units on their website. While a little expensive, these would do precisely what I wanted. They contain a large toroidal transformer which charges the battery fast when mains power is available. That same transformer is then used in reverse for the inverter function. So they have a battery charging capability that’s well-matched to their inverter power. And as I later discovered, a deeply discharged battery recovers best if it’s recharged with the maximum available current. Another useful aspect of this Victron “Multi Plus Compact” series of inverter/chargers is their relatively small size. Their 800VA, 1200VA, 1600VA and 2000VA versions are all just 375mm tall, 214mm wide and 110mm deep. That’s only slightly wider than the Lifeline battery I chose (at 170mm), and would just fit into my cabinet. Photo10: the MK3-USB interface, needed to connect a computer to the Victron inverter for configuration or monitoring. Photo11: the cables after being terminated and clamped in the supplied plugs. They plug straight into the bottom of the unit, effectively making it into an appliance. The inverter chassis is Earthed via the plug’s Earth pin. The 500VA Multi Plus Inverter is somewhat smaller, and there are also larger models (up to 5000VA or even higher), but the “Compact” series seemed right in the sweet spot for me. So that left me with the choice of the four models mentioned above. While all four would run my shutter, I found the higher-power models attractive for a few reasons: 1) The 1200VA and 1600VA models are not that much more expensive than the 800VA (depending on where you buy them). 2) While 800VA is enough to run a fridge, it might not be enough to start the compressor reliably. Stalling it could lead to motor burn-out. The peak power of these inverters is twice the VA rating, but I wasn’t sure if that would be enough on the lower-power models. 3) The watts rating of each model is slightly lower than the VA rating (as you would expect), but it falls even further at elevated ambient temperatures. At 65°C (which the inside of my cabinet could reach), the 800VA inverter can only deliver 400W, which is barely enough for my needs. The 1200VA unit can deliver 600W under the same conditions, with the 1600VA (800W) and 2000VA (1000W) units doing even better. So I decided to purchase the 1600VA inverter/charger (Photo9), plus the separate USB interface module needed to configure and monitor it (Photo10; more on that later). While these units have reasonable default settings, and there are DIP switches for changing common options, I wanted to be able to set it up to match my battery requirements as closely as possible. I could have saved a little bit by buying both the battery and inverter/ charger online. But given that the staff at the shop down the road had already given me helpful advice, and I was likely to get better after-sales (and warranty) service from them, I decided to pay that little bit extra. This came out to $1126 for the battery, $1440 for the inverter/charger and $90 for the USB interface, for a total of $2656 including GST. So this is not a cheap system, but I am hoping that I can rely on it longterm. Ventilation          Photo12: two internal RJ45 sockets are provided for the VE.Bus interface. You can use either one. I cut a patch cord in half and ran it out through the supplied rubber grommet, then terminated it to an RJ45 wallplate so I can configure the inverter without having to open up the cabinet it’s inside. siliconchip.com.au Australia’s electronics magazine AGM batteries have vents, but I am told that they will not outgas during normal charging or discharging; only if they are abused or about to fail. Still, I had some concerns about the buildup of hydrogen/oxygen gas in my cabinet. It isn’t a totally enclosed January 2020  15 space, but neither is it especially well ventilated. As recommended in the Victron manual, I managed to avoid installing the inverter above the battery; instead, it is behind it, so any gas evolved will not flow directly into the inverter. I also mounted a small, low-noise, longlife fan in the cabinet, blowing air out through the only gap. This would help remove any gas which did build up in that space. This is something you have to keep in mind with lead-acid batteries. They can generate hydrogen gas, and if it builds up in an enclosed space, it’s an explosion hazard. So don’t forget to consider that when designing a backup battery system. The fan I fitted will also help reduce the temperature in the cabinet if the inverter/charger is working hard. Setting it up It took a couple of weeks for the inverter/charger to arrive, and as soon as it did, I went about setting it up. Before purchasing it, I was aware that the user manual stated that “This product should be installed by a qualified electrician”. In Australia, if such a device is installed with fixed mains wiring, you do need a licensed electrician to install it (the rules in New Zealand are different). However, other than the lack of internal battery, this device is essentially just a UPS (interruptible power supply). So if it is fitted with a standard mains plug and socket via a method which complies with the wiring rules, then it can be treated as an appliance. In this case, it is legal (and safe) to install without any special licenses, in NSW at least (other states may have more strict rules). The inverter/charger’s mains input and outputs are supplied with pluggable terminal blocks that have integral cable clamps, but no cables attached. So all you need to do is cut an extension cord in half, unplug these terminals, open them up, wire the Active, Neutral and Earth wires where indicated, then attach and tighten down the cable clamps to ensure the cables are properly retained (Photo11). There are two essential things that you must make sure of when you do this: one (and this is critical), the plug end of the extension cord must go to the terminal designated as the mains input, and the socket end must go to the terminal designated as the mains output. These are clearly labelled. The other is that you need to make sure that the cable you’re using has a sufficiently high current rating and that it is thick enough to be firmly clamped by the mounded plastic of the pluggable terminal block covers. I found the 10A cables I used a little thin to compress securely in the cable clamps, so I added a couple of layers of black heatshrink tubing around it to bulk it up a bit. It was then clamped nicely in place. Once you’ve wired up the plug and Screen1: the initial VEConfigure screen with charger and inverter status at left and some basic options at right, including the all-important maximum input current, which I’ve set to 10A to suit my cable. 16 Silicon Chip socket, plug them in and verify that you have low-resistance continuity from the Earth pin of the plug to the socket, and also from the plug to the inverter’s chassis. It’s also a good idea to check that there is a very high resistance from the Active and Neutral pins on the plug to the Earths. By default, the inverter/charger can draw up to 16A, however, there is a DIP switch to reduce this to 4A and with the USB interface, you can set the maximum current draw to just about any value, including 10A or 15A, to suit normal extension leads with either standard 10A or 15A plugs and GPOs. This is one of the main reasons I decided to purchase the USB interface; so I could set the maximum current draw to 10A, to suit the GPO and cable I am using. Given that the 1600VA inverter can charge the battery at up to 70A, drawing around 4.5A from the mains, that leaves me with about 5.5A or 1250W available at the output. That’s more than enough for me, and that’s about how much power my inverter can deliver at 40°C anyway. So for me, standard 10A input and output cables are suitable. USB interface Victron Energy uses a protocol they call “VE.Bus” to interface between various devices including inverters, control panels, computers etc. This operates over a Cat5-type cable up to 10m long. As I mentioned, I purchased their Screen2: the grid configuration screen. I’m not feeding power back into grid but this inverter apparently supports that. You would need an agreement with your power company before enabling this, and the unit would also definitely have to be installed by an electrician if connected to the grid. Australia’s electronics magazine siliconchip.com.au MK3-USB interface so that I could connect to the VE.Bus port on my inverter/ charger from a laptop computer. The required software is a free download (see links below). I had no trouble getting this up and running, and the software is quite easy to use. In addition to changing the inverter settings, you can monitor its operation, including battery voltage, charging mode etc. This is quite handy for me, given that my inverter is inside a cabinet. I can plug in the MK3-USB interface via a panel-mount RJ45 socket and check what the inverter is doing. This should also let me reset it if there is a fault (eg, an overload), although I believe that the inverter will auto-reset after a fault by default. The screen grabs below show the various options and displays available via the free VEConfigure software. Battery connections The Victron inverter/charger comes pre-fitted with 1.5m-long, thick battery cables pre-terminated with eyelet lugs suitable for the M8 screw terminals on my Lifeline battery. The battery came with matching hardware, so connecting up the inverter was easy. The inverter/charger has an internal fuse; however, they recommend fitting one at the battery as well. Jaycar has a range of bolt-down and battery terminal fuses which are suitable for this purpose. The inverter/charger also comes pre- wired with an NTC thermistor for sensing battery temperature, for temperature compensation during charging. This is encapsulated in an eyelet lug, which is placed over the ground lug on the battery to make physical contact, for temperature sensing. I then set about wiring up the RJ45 panel-mount socket I mentioned earlier. You have to open the inverter’s front panel up to make the connection, which is something I did before powering it up for the first time (Photo12). I cut a Cat5 patch cable in half, opened up the inverter (which involves the removal of just four screws) and plugged it into one of the two internal sockets; either will do. I then cut a small hole in the multi-size rubber grommet supplied with the inverter and fed the cable out through the bottom. I was then able to re-install the cover panel. I used a ‘toolless’ RJ45 wallplate socket from Jaycar. This has punchdown style connections at the rear, but it comes with a plastic cover plate which also serves as the punchdown tool. Wiring this up is a little confusing; while they show which colour wire goes where, there are unfortunately two colour coding schemes for Cat5/ Cat6 cable. So I had to check the order of the colours in the existing plug, then make sure that I had the wires connected to the socket terminals labelled 1-8 in the same order. Once you’ve fed the bare wires Screen3: the inverter settings. I left these all at the default values, except that I raised the low-battery cut-out from 10.5V to 11.0V to protect my battery from over-discharge, as that is the manufacturer’s specification. siliconchip.com.au through the appropriate terminals, you firmly push the plastic block down over them, which cuts through the insulation and makes the connections. The rear clamshell of the socket then locks together, stopping it from coming apart. This left me with an RJ45 wallplate socket ‘captive’ to the inverter/charger, which I connected to the Victron USB interface via another short patch cable, and plugged it into my laptop. Once I had downloaded and launched their free software and powered the inverter up, I was able to access the control panel and confirm that it was charging the battery. I could then configure various parameters related to battery charging, inverter operation etc. I didn’t change any settings I didn’t fully understand. I adjusted the maximum mains current to 10A and chose an appropriate charging profile for my battery. One of the excellent features of this device is the fact that once the battery has been on ‘float’ charge for 24 hours (typically around 13.8V), it will drop into ‘storage’ mode, holding the battery terminals at around 13.2V (2.2V/ cell). This extends battery life. It will then periodically bring the battery back up to 14.4V (2.4V/cell) for around one hour a week, which helps to prevent electrolyte stratification and also ensures that the cells remain evenly charged. All of this should mean that the battery lasts as long as possible. Screen4: the charger configuration. I chose the Victron AGM profile as it most closely matched my battery. It specifies a charge voltage of 14.4V and float of 13.8V, compared to my ideal settings of 14.3V±0.1V and 13.2V, but it does incorporate a 13.2V storage mode after 24 hours. Australia’s electronics magazine January 2020  17 One slight disappointment is that I discovered that if you set your own battery charge voltages, the unit disables temperature compensation entirely. Temperature compensation can only be used by selecting one of the pre-set charging profiles. My battery specifies a bulk charge voltage of 14.3V±0.1V at 25°C, so the built-in profiles that charge to 14.4V are only just within spec. But I think using one of those is probably better than setting the charge voltage to 14.3V and losing temperature compensation. That could lead to severe overcharging at high ambient temperatures, above 35°C, where the charge voltage should ideally drop down to around 14.0V. Extra features I also bought a Jaycar PS2011 panelmount 15A ‘cigarette lighter’ socket, SZ2042 inline blade fuse holder, 15A fuse, 25A automotive power cable and 8mm ID eyelet connectors. I mounted the cigarette lighter socket on my cabinet and wired it back to the battery terminals via the fuse. I also purchased a Jaycar MP3692 dual USB car charger with voltage display. Plugging this into the cigarette lighter socket is a really easy way to monitor the battery voltage, and it also means I can charge USB devices without the inefficiency of the inverter. In future, I can potentially even charge the battery from solar panels wired in via this cigarette lighter plug (although only at 15A/200W, but that’s better than nothing). Conclusion So far, my backup power system has been running well. The shutter worked identically before and after I switched off the mains power to the inverter/charger. I had no clue that it was running off the battery, except for the change in the status LEDs. I haven’t tested the ‘fridge yet, but with a 3000W inverter surge rating, I’m confident that it will start up and run just fine. References & links Lifeline GPL-30HT 150Ah battery source: siliconchip.com.au/link/aava Lifeline GPL-30HT 150Ah battery data sheet: siliconchip.com.au/link/aavc Fullriver HGL200-12 200Ah battery source: siliconchip.com.au/link/aavd Fullriver HGL200-12 200Ah battery data sheet: siliconchip.com.au/link/aave Victron Energy Multi Plus Compact Inverter Charger (12V/1600VA/70A) source: siliconchip.com.au/link/aavf Victron Energy Multi Plus Compact Inverter Charger (12V/1600VA/70A) user manual: siliconchip.com.au/link/aavg Victron Energy MK3-USB interface: siliconchip.com.au/link/aavh VEConfigure software download: siliconchip.com.au/link/aavb Screen5: the inverter incorporates a “multiswitch” relay which can be triggered upon various conditions such as loss of mains power, battery voltage low etc. I haven’t wired mine up to anything but it appears to be a very flexible feature. 18 Silicon Chip SC DO YOU OWN AN ELECTRIC CAR? If so, you could well be driving an emer-gency home power supply right now! As some readers may recall, five years ago I purchased a Nissan LEAF. And for most of those five years, every time there was a blackout I thought about that BIG, powerful battery sitting down in my garage, wondering how I could press it into service as a source of power. I’ve always dismissed the idea because the thought of getting across ~360V DC made me shudder! But, as it turns out, I’ve been looking at a glass half empty instead of a glass half full! I came across a website not long ago which pointed out that, in common with many electric vehicles, the Nissan LEAF also has a 12V lead-acid “house” battery which powers all the “normal” 12V vehicle functions excepting, of course, the traction motor. This battery is kept fully charged (when the car is running) by the high voltage DC battery via a DC-DC converter – so it should always be ready to use. The website demonstrated how to fool the car into believing it was turned on and running so that the 12V battery would be kept charged until the high voltage battery was discharged, so its protective circuitry would kick in. All I needed to do was to buy a 12VDC to 230V AC inverter – as in this article – and connect it to the 12V battery. Doh! Why didn’t I think of that before! So now, 1kW inverter at the ready, I’m anxiously(!) awaiting the next blackout to put the theory into practice. You’ll find the website I’m referring to via siliconchip.com.au/link/aavi Ross Tester Screen6: this control panel can be launched from the VEConfigure software. It mimics the physical control panel which you can purchase for use with the inverter/charger, allowing you to switch the inverter on and off, change its current limit and monitor its state in real-time. Australia’s electronics magazine siliconchip.com.au Wiring Harness Solutions B- B- B+ B+ Ampec Technologies Pty Ltd Tel: 02 8741 5000 Email: sales<at>ampec.com.au A “retro” design that’s as modern as tomorrow . . . “Nutube” miniature valve stereo preamplifier by John Clarke Valves are old hat, right? Not any more, they’re not! Korg and Noritake Itron of Japan recently released their Nutube 6P1 twin triode. Its party trick is a very wide range of operating voltages, from just a few volts up to 200V, and meagre power consumption. That makes it ideal for a battery-powered stereo preamplifier. You’ll enjoy the sound as well as the retro green glow! A re you one of those people who simply “loves” the be a very popular student project, right up to and including nostalgic sound of valves, both in power amplifiers their “major work”). Even if you have built valve gear with high voltage supand preamps? But valves are relatively expensive, plies before, we think you will find the unusual construction and the high-voltage power supplies typically required make of the Nutube 6P1 dual triode quite fascinating. building a valve preamp a bit of a pain. We’ve taken some care with this design, so that it fits into However, at least the part is no longer true with Korg’s Nutube 6P1 twin-triode. It works perfectly fine with a plate a very cool (and professional) looking extruded aluminium voltage of just 6-12V, and the heater power and voltage re- case, with the inputs and outputs at the rear and a power switch and volume knob at the front. And of course, we’ve left quirements are also modest. a window in the clear So building a front panel so that you preamp around it is can see that “warm” a cinch, and it’s a blue tube glow. suitable project for • Power supply: 7-18 VDC; draws 29mA <at> 9V DC One of the fascibeginners and shool • Gain: up to 15dB at maximum volume setting nating aspects of the students, as there are • Distortion: around 0.07% at 200mV RMS output from 20Hz to 5kHz (see Figs.1 & 2) Nutube is that it’s no dangerous volt• Frequency response: 20Hz-20kHz, +0,-0.6dB; -3dB at about 7Hz & 80kHz (see Fig.3) designed and built ages involved. similarly to a vacu(In fact, for this • Channel separation: typically >45dB (see Fig.4) reason alone we an- • Signal to noise ratio: 83dB with respect to 270mV in, 2V out, 20Hz-22kHz bandwidth um fluorescent display (VFD). So the ticipate that this will • Maximum output level: 2V RMS with 9V supply, 2.8V RMS with 12V supply Specifications 20 Silicon Chip Australia’s electronics magazine siliconchip.com.au Features Yes, it really is a thermionic valve (or tube as the Americans like to say). But this Nutube 6P1, shown here from the underside, is quite unlike any valve you’ve come across before. For a start, those blue windows (see opposite) really do glow blue! heater glow looks like two green squares, similar to large VFD pixels. Its performance is pretty good, too. Distortion levels below 0.1% are possible across a wide range of frequencies with a little care during calibration. See the spec panel, Figs.2 & 3 and Fig.12 to get an idea of how well it performs. This Nutube preamp can run from a DC supply between 7V and 18V, with only a modest current draw. It can also be powered using a 9V battery that is housed within the enclosure. If you want to be able to switch between signal sources, you can mate this Nutube Preamplifier up with the SILICON CHIP Six-way Stereo Audio Input Selector with Remote Control that we described in the September 2019 issue (www. siliconchip.com.au/Article/11917). Nutube 6P1 dual triode Korg developed the Nutube 6P1 in collaboration with Noritake Itron of Japan. While it is a directly-heated triode with a filament, grid and plate connections, its construction more resembles a vacuum fluorescent display (VFD) than a traditional valve (or tube). Two Nutube triodes are encapsulated in a rectangular glass envelope. Each triode is effectively a single-pixel VFD. The internal construction has the heater filament as a fine-gauge wire • Stereo valve preamplifi er • Based on the recently released Korg “Nutube” dua l triode • Visible plate glow • 30,000-hour Nutube life • Safe low-voltage supply (7-18V DC) • Low power consumptio n • Battery or plugpack pow ered • Onboard volume contro l • Internal balance and dis tortion adjustments • Switch-on and switch-of f noise eliminated • Power supply reverse polarity protection • No transformers needed • Inputs and outputs are in-phase running across the front, with the metal mesh grid located below that. Behind the grid is the plate (also called the anode), which is phosphor-coated and glows when the filament is heated. The filament wire is held taut, and because of this, it can vibrate similarly to a stringed musical instrument. (The Nutube is, after all, sold by a musical instrument manufacturer). This vibration is not necessarily a wanted feature, as it can be the source of microphonics – where external sound can couple to the filament and this alters (or modulates) the audio signal being amplified in the triode. The result is that this vibration is heard in the sound output. The microphonics can be minimised using careful construction methods. This includes protecting the Nutube from surrounding air vibrations, by using flexible wiring and including a vibration-damped mounting. In operation, the Nutube draws very little current, with It’s tiny – just 115 x 50 x 125mm – and built into this snazzy extruded case from Jaycar, it really looks the part. Performance is no slouch, either! siliconchip.com.au Australia’s electronics magazine January 2020  21 design includes two trimpots to set the grid bias of each triode. There are three ways to make these adjustments. One is to adjust the trimpots so the Nutube plate glows brightest for each channel, which will generally give good performance. Another method is to use a signal source and multimeter to adjust the grid bias for maximum output signal level, or better still, by observing the distortion products and setting each trimpot for the desired result. Freely-available computer software can be used to measure the distortion and view the waveform. This allows for easily setting up the desired distortion characteristic. We describe what software you need and how to use it in a panel later in this article. Fig.1: load lines for the Nutube triode showing the relationship between anode (plate) voltage (horizontal axis), anode/cathode current (vertical axis) and gridcathode voltage (labels on curves). The area below the black dotted line is the continuous safe operation envelope. each filament requiring just 17mA. Total heater power for the two triodes is around 25mW. The grid and plate current total around 38µA. The Nutube is best operated with a plate voltage between 5V and 30V, and the load-line curves (Fig.1) reveal that within this voltage range, the grid voltage needs to be above the cathode filament. This is different from the traditional triode, where plate voltages are much higher, and the grid voltage is usually negative with respect to the cathode. The Nutube operating point would typically be set so that the distortion from each triode is at a minimum and so that maximum dissipation is not exceeded. To achieve this, our 10 Nutube Preamplifier THD vs Frequency Fig.2 shows the total harmonic distortion plus noise (THD+N) figure as a percentage, plotted against frequency and output level. As you can see from Fig.3, the performance is best with an output level in the 100-400mV RMS range. This is a typical level that you might feed into a 100W (or thereabouts) stereo amplifier to get a reasonable listening volume. Such an amplifier would generally have a full power sensitivity between 1-2V RMS. Below 100mV RMS output, noise starts to dominate the THD+N figure. In other words, preamp performance at lower volume levels is limited by its 83dB ultimate signal-tonoise ratio (SNR). Above 400mV RMS, triode non-linearities dominate. The rise in distortion with frequency is mild, with THD+N only increasing by about 50% between 1kHz and 10kHz. The 23/10/19 12:56:49 10 22kHz bandwidth 80kHz bandwidth 2 1 0.5 0.2 0.1 0.05 0.02 23/10/19 12:58:58 2 22kHz bandwidth 1 0.5 0.2 0.1 0.05 0.02 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.2: a plot of total harmonic distortion, including noise, Fig.2 against signal frequency. These measurements were made at about unity gain, with around 200mV RMS in/out, and with two different filter bandwidths. The blue curve (20Hz-22kHz) includes the distortion products and noise which are audible to the human ear, while the red curve (20Hz-80kHz) includes higher harmonics for more realistic readings at higher frequencies (8kHz+). 22 Nutube Preamplifier THD vs Level, 1kHz 5 Total Harmonic Distortion (%) Total Harmonic Distortion (%) 5 0.01 Preamplifier performance Silicon Chip 0.01 0.01 0.02 0.05 0.1 0.2 0.5 Output Level (Volts) 1 2 3 Fig.3: distortion plotted against output level. This graph demonstrates that the output Fig.3 level is the largest determining factor in the preamp’s distortion performance. At low levels, noise begins to intrude, while at high levels, the waveform shape gets ‘squashed’ and so distortion increases significantly. The middle section, where distortion is lowest, is the range in which the preamp will generally be used. Australia’s electronics magazine siliconchip.com.au measurement shown in red on Fig.2 is with an ultrasonic (80kHz) bandwidth in order to measure the harmonics of higher test frequencies. The blue trace gives a most realistic measurement up to about 10kHz, then falls off due to the 22kHz filter limit cutting out the harmonics. You may wish to compare Figs.2 & 3 to Fig.12, which shows a spectral analysis of the distortion at 1kHz and around 200mV output. As you can see from Fig.12, this method of reading the distortion gives much the same result as the Audio Precision system used to produce Figs.2 & 3. Fig.4 demonstrates that the preamp has a very flat response, with no peaks or wobbles. The output is down well under 1dB by 20Hz at the bass end, and an even smaller fraction of a decibel by 20kHz at the upper end. This plot has an extended frequency range of 10Hz-100kHz so you can get an idea of the actual -3dB points. Fig.5 shows the channel separation. This is produced by feeding a signal into the right channel, monitoring the left channel output level and sweeping the test signal across the audible frequency range. The channels are then swapped, and the test is repeated. As you can see, there is more coupling from the right channel to the left, and the separation figures are not amazing, at around 45-68dB. However, this is more than good enough for a stereo system, and sounds panned entirely to the left or the right will still appear to be coming from just one speaker. Fig.6 is a scope grab showing the output of the preamp (at the top, yellow) at around 200mV and 1kHz, with the ~0.07% residual distortion signal below, in blue. You can see that this is primarily third harmonic, with some second harmonic. Fig.7 shows the much higher-level distortion present in the output if the triode is adjusted further away from its ideal operating point. This is around 0.3% THD+N, the majority of which is second harmonic distortion. Fig.8 shows the noise residual when the output level is +3 Circuit description The full circuit is shown in Fig.9. One of the triodes in the Nutube provides amplification for the left channel (V1a), while the other triode is used for the right channel (V1b). These are connected as common-cathode amplifiers, where the cathode filament is referenced to ground. The signals are applied to the grids, and the resulting amplified signals appear at the corresponding anode (or plate). The anode loads are 330kΩ resistors from the positive supply, with 150Ω/100µF low-pass filters to prevent supply noise from reaching the anodes. The Nutube triodes have relatively low input impedances at the grids and high output impedances at the anodes, so op amp buffers are used at both ends. IC1a and IC2a ensure that the grids are driven from low impedances. IC1b and IC2b minimise the anode loading, as they have very high input impedances of 600MΩ, which is effectively in parallel with 1MΩ resistors. These op amps have very low noise (3.3nV/√Hz) and distortion (0.00006% <at> 1kHz & 3V RMS) figures when operated at unity gain. Therefore, these op amps do not affect the sound of the signals. The properties of the Nutube triodes dominate any effect that the op amps have on the signals. We’ll now describe the signal path in more detail, but only for the left channel, as both channels are almost identical. The input signal is fed in via RCA socket CON1a and passes through a 100Ω stopper resistor and ferrite bead (FB1). These, in conjunction with the 100pF capacitor, significantly attenuate RF signals entering the circuit, which could result in unwanted radio frequency detection and reception. The signal is AC-coupled to 50kΩ volume control VR1a via a 470nF DC blocking capacitor. This capacitor removes any DC voltage that may be present at the input to prevent pot crackle, and also produces a low-frequency Nutube Preamplifier Frequency Response 23/10/19 13:01:58 +2 -0 Relative Amplitude (dBr) -1 -2 -3 -30 -50 -60 -70 -80 -5 -90 50 100 200 5k 10k 20k 500 1k 2k Frequency (Hz) 50k Fig.4: the preamp’s frequency response is commendably flat. This plot extends down Fig.4 to 10Hz and up to 100kHz so that you can see the roll-off at either end. The slight difference between the response of the two channels above 10kHz is likely due to slightly different biasing; we had purposefully biased the two channels slightly differently to see the difference in distortion. siliconchip.com.au left-to-right coupling right-to-left coupling -40 -4 10 20 23/10/19 13:10:17 -20 0 -6 Nutube Preamplifier Channel Separation -10 left channel right channel +1 Relative Amplitude (dBr) much lower. This is a fairly typical wideband white noise signal. -100 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.5: this shows the preamp’s channel separation. It’s quite decent up to about 2kHz, Fig.5 with more than 60dB separation between channels. The main concern with signal coupling from one channel to another is that it introduces distortion; however, as this is not an ultra-lowdistortion device, it isn’t that big of a concern. We included this plot mostly for completeness. Australia’s electronics magazine January 2020  23 6V Vaa 100nF SUPPLY/2 6.8k 10 F LEFT IN CON1a FB1 100 100pF VR2 10k 470nF 100nF VR1a 50k LOG ADJUST G1 BIAS 25V 1M 25V 1 IC1a 2 33k 10 F 8 3 TPG1 4 Fig.6: the output of the unit with the triode biasing adjusted for lowest distortion. The yellow trace is the output signal, while the blue trace is the distortion residual (ie, the yellow trace with its fundamental removed). It contains significant second and third harmonics. IC1: OPA1662 VOLUME 6V Vaa SUPPLY/2 100nF 5.1k RIGHT IN CON1c ADJUST G2 BIAS 1M VR3 10k 470nF 100 FB2 100pF VR1b 3 50k LOG 100nF 2 TPG2 33k 8 1 IC2a 10 F 4 25V IC2: OPA1662 POWER S1 DC INPUT 7 – 18V CON2 Fig.7: this plot is the same in Fig.6, but the triode biasing has been adjusted away from its optimal condition. Total harmonic distortion has risen to around 0.3%, with the second harmonic now the dominant distortion signal. Fig.8: the output of the preamp with no input signal. Some devices produce more high-frequency or more low-frequency noise. In this case, it appears quite close to white noise. 24 Silicon Chip + CON3 D4 1N5819 A Vaa K REG1 TPS70960 9V BATTERY (BAT1) 1 10 F 25V 3 IN EN OUT GND NC 5 4 2 Fig.9: the input signals from CON1a and CON1c pass through RF filters and volume control pot VR1 before being AC-coupled to ultra-low-distortion buffer op amps IC1a & IC2a. These feed the signals to the grids of V1a & V1b, while VR2 and VR3 allow you to adjust the DC grid bias levels. The inverted output signals at the anodes of V1a & V1b are ACcoupled to the inputs of buffer op amps IC1b and IC2b. The signals are then re-inverted by op amps IC3a & IC3b before being fed to the outputs via the contacts of RLY1. VR4 allows the gain of the two channels to be matched. IC4 controls RLY1’s coil so that it switches on around five seconds after power is applied, and switches off immediately upon power removal, eliminating clicks and thumps. roll-off below about 7Hz. The signal is then AC-coupled from VR1a’s wiper to the non-inverting input (pin 3) of op amp buffer IC1a via a 100nF capacitor. Pin 3 of IC1a is biased near to half the supply voltage via a 1MΩ resistor that is tied to a half supply rail (Supply/2). The input bias current at pin 3 of IC1a will cause the DC voltage level to shift from this half supply level due to the Australia’s electronics magazine siliconchip.com.au 6V Vaa SUPPLY/2 150 100 F 8 1M 330k 100nF A1 G1 V1a F2 2.2k 5 IC1b 6 2 7 3 8 4 1 RLY1a NC 150 8 4 LEFT OUTPUT CON1b NO 4 F1 3 1 2 10 F 25V 1 IC3a 5 1 VR4 10k C IC4 TPS70960 4 IC1 – IC3 25V E K K 25V B A A 10 F Vaa OR 6V BC547 1N4148 1N5819, 1N4004 Vaa 100k 10 F 25V SUPPLY/2 V1: NUTUBE 6P1 6V Vaa SUPPLY/2 150 IC3: OPA1662 Vaa OR 6V 100 F 25V 1M 330k 5.1k 100nF A2 G2 V1b F2 2.2k 5 F3 IC2b 6 6 7 5 IC3b 10 F 25V 7 RLY1b NC 150 RIGHT OUTPUT CON1d NO 270 100k 6V 10 F SUPPLY/2 25V Vaa JP1 Vaa Vaa OR 6V 6V SUPPLY/2 TP6V 2.2 F RLY1 5V 6V 10k K D3 1N4004 A 100 F 10k 25V TPGND CERAMIC 33 6V 100k A 180k K D1 1N4148 47 F 100k 100k 2 3 1M 10 F 6V IC4: LM358 D2 1N4148 8 IC4a 1 A 6 K 5 IC4b 4 100k 47 F 270 10k 100k 100k C 7 10k B Q1 BC337 E 5.1k 100k 100k SC 2020 NUTUBE STEREO VALVE PREAMPLIFIER current flowing through the 1MΩ resistor. This causes the signal voltage to rise about 0.5V above the half supply rail, reducing the maximum symmetrical voltage swing. But since the nominal supply voltage is 9V (down to 7.2V if the 9V battery is getting flat), the signal swing is still sufficient to prevent signal clipping of line-level audio signal levels. IC1a’s output drives V1a’s grid (G1) via a 10µF coupling siliconchip.com.au capacitor. This grid is DC-biased via a 33kΩ with a voltage that’s set using trimpot VR2. This is adjusted to set the operating point and hence, the distortion produced by V1a. V1a’s plate anode load is a 330kΩ resistor which connects to either the Vaa or 6V supply via a 150Ω decoupling resistor. Which supply is used depends on the position of jumper JP1. When a 9V battery is used for power, using the Australia’s electronics magazine January 2020  25 fixed 6V selection prevents anode (plate) voltage variations as the battery discharges. When used with an external regulated supply, the Vaa setting would be selected. The high-impedance amplified anode signal is again AC-coupled op amp buffer IC1b via a 100nF capacitor. IC1b is also biased to half supply via another 1MΩ resistor to Supply/2. This 1MΩ resistor loads the anode, reducing the Nutube anode signal to 75% of the unloaded signal. This is unavoidable in a circuit with such high impedances. Note that the signal at the triode’s anode is inverted compared to that applied to the grid. In some cases, it is important to maintain the phase of audio signals between the inputs and outputs. So the output signal from the triode is reinverted by op amp IC3a, connected as an inverting amplifier. VR4 is included so that the gain of IC3a can be adjusted. The gain of IC3b in the right channel is fixed at -2.3 times (-5.1kΩ ÷ 2.2kΩ), so the gain for IC3a is typically set at a similar level. The gain may need to be slightly different between the two channels to get equal gains for both outputs, due to variations in gain between the two triodes at similar bias levels. Finally, the signal from IC3a is AC-coupled with a 10µF capacitor to remove the DC voltage and DC-biased to 0V with a 100kΩ resistor. The output is fed through a 150Ω isolation resistor to prevent oscillation of IC3a should long leads with a high total capacitance be connected. To prevent noises when power is switched on and off, the output signal passes to the output RCA sockets via a pair of relay contacts that are open when power is off. At power-on, the relay is only switched on to allow signal through to the output terminals after everything has settled down. At power off, the relay is switched off immediately. This isolates the signal while the power supply voltages decay. Filament current Just like a traditional valve, the Nutubes have heater filaments. These are connected between F1 and F2 for V1a, and between F2 and F3 for V1b. So the F2 connection is shared between the two. There are two ways to drive the filaments. One is to supply current to F1 and F3 via separate resistors and have the common F2 terminal tied to ground. In this case, the resistors are chosen for 17mA flowing in each filament, giving a total filament current of 34mA. But in our circuit, we connect the filaments in series, so the same 17mA flows through each filament for a 17mA total current but with twice the voltage across the filaments. This is a more efficient way to drive the filaments, and saves power when using batteries. In our circuit, F1 is tied to ground, F2 is left open and current supplied via a 270Ω resistor from 6V to F3 ((6V - 0.7 - 0.7) ÷ 270Ω = 17mA). Note that F2 and F3 are bypassed to ground with 10µF capacitors. This reduces noise in the circuit. There is one extra consideration when the filaments are in series. As the Nutubes are directly heated, V1b’s cathode will be 0.7V higher than V1a, due to the voltage drop across V2’s filament before the current reaches V1. This changes the bias voltage requirement at the grid (G2) for V1b compared to G1 for V1a. The extra voltage required for G2 is provided by having a wider voltage range for VR3 due to a lower-value resistor connecting it to the 6V supply compared to VR2. Note that the grid bias voltage derived from VR2 and VR3 26 Silicon Chip is relative to the output of 6V regulator REG1. This is a fixed voltage, so the grid bias voltage does not vary with the supply voltage. Power supply When no DC plug is inserted into DC socket CON2, the internal 9V battery supplies power to the circuit, via CON2’s normally-closed switch connecting the negative of the battery to ground. When a power plug is inserted, then power is from the DC input and the battery negative is disconnected. Power switch S1 connects power to the rest of the circuit whether from the battery or an external source, while diode D4 provides reverse polarity protection. REG1 is a low-dropout, low quiescent current 6V regulator. It is included to maintain a constant grid voltage for the Nutube when power is from a battery, as battery voltage naturally varies over time. The 6V rail also powers relay RLY1. The input of REG1 is bypassed with a 10µF capacitor, while a 2.2µF ceramic capacitor filters the output. This output capacitor has the required low ESR (effective series resistance) to ensure stability at the regulator output. The half supply rail is derived by two 10kΩ resistors connected in series across the anode supply for V1. It is bypassed with a 100µF capacitor to reduce noise and lower the rail impedance. Power switching and output isolation As mentioned earlier, the relay contacts at the left and right outputs connect the signals some time after power-up and disconnect the signals quickly when power is switched off. IC4, Q1, RLY1 and associated components provide this signal switching. IC4a and IC4b are two halves of an LM358 single supply, low-power dual op amp. They are used as comparators with hysteresis. Hysteresis is provided by 100kΩ resistors from their outputs to their non-inverting inputs, while the nominal comparator threshold at these inputs is set around 2V when the output is low and 4V when the output is high. So in each case, the output goes high when the voltage at the inverting input drops below 2V, and then goes low again when the voltage at the inverting input rises above about 3.5V (you might expect 4V, but the LM358’s output can’t swing to the positive rail). In other words, there is about 1.5V of hysteresis. RLY1 is initially off, and when power is applied via switch S1, several things happen. Firstly, power is supplied via D1 to the preamplifier circuitry, including REG1, V1 and IC1-IC4. The supply and signal coupling capacitors begin to charge up to their operating conditions. At the same time, the inverting pin 2 input to IC4a is pulled high, to near the incoming supply voltage, via the 100kΩ and 180kΩ resistors connecting to switch S1. Diode D1 prevents more than 6.5V from being applied to this pin. The 180kΩ and 1MΩ resistors form a voltage divider so that their junction tends to sit at around 5.5V when there is more than 6.5V at the anode of D4. This is above the pin 3 voltage, and so the output of IC4a goes low, near 0V. Pin 3 is therefore around 2V. Diode D2 is reverse-biased and pin 6, the inverting input of IC4b, is initially held high near to 6V, due to the 47µF capacitor being initially discharged. The 10kΩ resistor in series with the capacitor reduces the pin 6 voltage down to about 5.7V initially. This is above the 4V at the non-inverting pin 5 input, so Australia’s electronics magazine siliconchip.com.au the output of IC4b will be low. Pin 5 will be at 2V. The low output of IC4b means NPN transistor Q1 is off, and the relay is off. The relay contacts will be open, so no audio passes through to the output. As the 47µF capacitor charges via the 10kΩ and 100kΩ resistors, after about five seconds, the voltage at pin 6 will drop below the voltage at the pin 5 input (2V). The output of IC4b then goes high, driving transistor Q1 and switching on RLY1. The audio signals are then connected to the left and right channel output sockets. Note the 47µF capacitor with a parallel 270Ω resistor and series 33Ω resistor between the collector of Q1 and the coil of RLY1. The 33Ω resistor is included so that the 5V-rated relay coil is initially driven with 5V rather than the full 6V of the supply. Then, as the 47µF capacitor charges, the voltage to the relay coil is reduced until it is instead supplied current via the 270Ω resistor. This reduces relay coil voltage and current, saving power but still holding the relay’s contacts closed. The value of the 270Ω resistor means that the current drawn by the relay coil drops from 30mA initially down to about 12.8mA, extending battery life. When power is switched off via S1, the pin 2 voltage at IC4a’s input immediately drops to 0V. That voltage is below the pin 3 voltage, so IC4a’s output goes high. Diode D2 conducts and pulls pin 6 of IC4b above the pin 5 threshold, so IC4b’s output immediately goes low. Q1 switches off and the relay contacts open. This all happens well before the supply capacitors in the circuit have time to drop significantly in voltage. So the output signals are cut before anything in the circuit can misbehave. The 10kΩ resistor between the diode D2 and the 47µF capacitor is so that the pin 6 input to IC4b can be immediately taken high, without having to wait for the 47µF capacitor to discharge. 1 double-sided PCB coded 01112191, 98 x 114mm 1 set of front and rear panel labels (see text) 1 extruded aluminium enclosure with clear end panels, 115 x 51 x 119mm [Jaycar HB6294] 1 Korg Nutube 6P1 double Triode thermionic valve (V1) [RS Components 144-9016] 1 1A DPDT 5V relay (RLY1) [Altronics S4147] 1 SPDT sub-miniature toggle switch (S1) [Altronics S1421] 1 double stereo horizontal PCB-mount RCA socket assembly (CON1) [Altronics P0211] 1 PCB-mount DC power socket (CON2) [Jaycar PS0520, Altronics P0621A] 1 2-pin 2.54mm pitch vertical polarised header (CON3) [Jaycar HM3412, Altronics P5492] 1 inline plug to suit CON3 [Jaycar HM3402, Altronics P5472 + P5470A x 2] 1 3-way pin header, 2.54mm pitch with shorting block (JP1) 2 5mm-long ferrite RF suppression beads, 4mm outer diameter (FB1,FB2) [Altronics L5250A, Jaycar LF1250] 1 9V battery 1 9V battery clip with flying leads 1 13-16mm diameter knob to suit VR1 1 8-pin DIL IC socket (optional) 1 100mm cable tie 4 15mm-long M3 tapped spacers 2 M3 x 25mm Nylon or polycarbonate panhead machine screws 4 M3 x 6mm panhead machine screws 2 M3 hex nuts 1 No.4 x 8mm self-tapping screw 1 90mm length of medium-duty hookup wire 1 solder lug 4 PC stakes Construction Semiconductors The Nutube stereo preamplifier is built using a doublesided PCB coded 01112191 which measures 98 x 114mm. It is housed in an extruded aluminium enclosure with clear end panels, measuring 115 x 51 x 119mm. Fig.10 has the PCB assembly details. Start by fitting the surface mount parts. Mostly, these are used because the same parts are not available in throughhole packages. They are not difficult to solder using a finetipped soldering iron. Good close-up vision is necessary, so you may need to use a magnifying lens or glasses to see well enough. These parts are IC1, IC2 and IC3, REG1 and its associated 2.2µF ceramic capacitor. Make sure that each component is orientated correctly before soldering it, ie, rotated as shown in Fig.10. The ceramic capacitor is not polarised. For each device, solder one pad first and check alignment and readjust the component positioning by reheating the solder joint if necessary before soldering the remaining pins. If any of the pins become shorted with solder, solder wick can be used to remove the solder bridge. But note that pins 1 & 2 and pins 6 & 7 of both IC1 and IC2 connect together on the PCB, so a solder bridge between these pins is acceptable. Continue construction by installing the resistors (use your DMM to check the values), followed by the two ferrite beads. Each bead is installed by using an offcut length of wire (from siliconchip.com.au Parts list – Nutube Valve Preamp 3 OPA1662AID dual op amps, SOIC-8 (IC1-IC3) [RS Components 825-8424] 1 LM358 dual op amp, DIP-8 (IC4) 1 TPS70960DBVT 6V regulator, SOT-23-5 (REG1) [RS Components 900-9876] 1 BC337 NPN transistor (Q1) 2 1N4148 small signal diodes (D1,D2) 1 1N4004 1A diode (D3) 1 1N5819 1A schottky diode (D4) Capacitors 3 100µF 25V PC electrolytic 2 47µF 16V PC electrolytic 10 10µF 25V PC electrolytic 1 2.2µF X7R SMD ceramic, 2012/0805 package [RS Components 6911170] 2 470nF MKT polyester 6 100nF MKT polyester 2 100pF ceramic Resistors (all 0.25W, 1% metal film) 5 1MΩ 2 330kΩ 1 180kΩ 10 100kΩ 2 33kΩ 4 10kΩ 1 6.8kΩ 3 5.1kΩ 2 2.2kΩ 2 270Ω 4 150Ω 2 100Ω 1 33Ω 1 dual-gang logarithmic 50kΩ 9mm PCB-mount potentiometer (VR1) [Jaycar RP8760] 2 10kΩ horizontal 5mm trimpots (VR2,VR3) 1 10kΩ top-adjust multiturn trim pot 3296W style (VR4) Australia’s electronics magazine January 2020  27 SECURE TO CASE the resistors) feeding the wire through it and then bending the leads down through 90° on either side to fit the PCB. Push each bead all the way + – D4 CON2 down so that it sits flush against the PCB beDC in TPS70960 CON3 CON1 fore soldering its leads. L R 7-18V 2.2 F – FB2 FB1 NO Install diodes D1-D4 next. Take care to ori+ TP6V REG1 10 F* entate each correctly, as shown in the overJP1 NC Vaa lay diagram, and make sure each is in its corS C 100pF 100pF rect position (ie, don’t get the different types Q1 BC337 mixed up) before soldering. COIL 47 F 6V Following this, fit the IC socket for IC4. N 470nF 470nF 100k 5.1k D3 Make sure that the socket is seated flush 150 150 10k against the PCB and that it is orientated corVR2 10k VR3 10k rectly. It’s best to solder two diagonally opposite pins of the socket first and then check that it sits flush with the board before soldering the 10 F* 10 F* D2 remaining pins. TPG2 GND TPG1 19121110 5.1k You could skip the socket and solder IC4 straight to the board. This would improve longIC4 IC3 LM358 term reliability but would make it much more 10 F difficult to swap or replace IC4 should that be VR4 10k 100  F * 100  F * necessary. The MKT and the two 100pF ceramic capaciN S tors can now go in, followed by the electrolytic D1 capacitors. The polarised electros must be orientated with the correct polarity, ie, with the longer IC2 IC1 lead into the pad marked with the + sign. GND 10 F* F1 Now install the two single-turn trim pots, VR2 100nF 10 F* A1 F2 A2 G2 G1 F3 100nF and VR3. These might be marked as 103 rather VR1 50k Log S S than 10kΩ. Next, mount multi-turn trimpot VR4. FOAM S1 Orientate it with the adjusting screw positioned NUTUBE 6P1 TWIN TRIODE POWER Volume to the left, as shown. It also may be marked as 103 instead of 10kΩ. S = M3 x 15mm LONG STANDOFF CABLE N = M3 x 25mm LONG NYLON OR SC TIE The next step is to fit Q1 by splaying its leads 2020 POLYCARBONATE SCREW WITH NUT slightly to suit the hole arrangement on the PCB. Also install PC stakes for GND, TPG1, TPG2 and Fig.10: all the Nutube preamp components mount on one doubleTP6V. The three-way header for JP1 and the twosided PCB as shown here. They are mostly standard parts, but way header for the battery lead can be mountIC1-IC3 and REG1 are only available in SMD packages. The ed now, followed by RLY1, CON1, CON2 and Nutube (V1) is in a SIL-type package with right-angle leads that switch S1. are surface-mounted to pads on the top of the board. The whole Potentiometer VR1 is mounted and soldered assembly slides into an extruded aluminium case. in place and is secured against the PCB using a Wiring cable tie around the pot body. This stops force on the shaft from breaking the solder joints or lifting tracks Crimp and/or solder the battery wires to the header socket off the board. terminals after cutting these wires 60mm long. Then insert Feed the tie through the holes in the PCB on each side of these terminals into the header socket shell, making sure the pot, and tie it underneath. you get the red and black wires in the correct positions, as Nutube V1 is mounted so that the front glass is vertical and marked on the PCB. with its leads soldered to the top pads on the PCB, similar An Earth wire is also required to prevent hum injection to a surface-mount component. Pins F1 and F3 at each end to the circuit if the case is touched. This connects the metal of the Nutube utilise two adjacent leads on the Nutube decase to the GND terminal on the board. Solder it to the solvice. In addition to the leads, it is supported by two 15mmder lug at one end and the GND terminal on the board at the long tapped spacers, one on either side of the device, which other. Heatshrink tubing can be used over the lug terminal hold a piece of foam against the Nutube envelope. and PC stake for GND. Secure these spacers to the PCB using short machine When the case is assembled, the solder lug is captured in screws fed in from the underside of the PCB. the top corner end-cap screw, adjacent to the RCA terminals. We will later sandwich the foam between the spacers and Powering up and testing the Nutube, stopping it from flexing its leads too much. Also fit one 15mm standoff at each end of the battery outline on If you are planning to use a battery to supply power, conthe PCB (see photos). nect a jumper shunt in the 6V position for JP1. That way, The sides of the battery are held in by two M3 x 25mm any voltage changes from the battery will not affect the anNylon or polycarbonate screws passed up from the underode plate voltage. If using a DC plugpack, use the Vaa posiside of the PCB and secured with M3 nuts. tion for JP1. 28 Silicon Chip 270 10k 10k 9V BATTERY BAT1 100k 100k Australia’s electronics magazine 100nF 180k 1M 1M 4148 10 F* 100k 100k 100k 33k 100nF 10 F* 270 100k 100k 330k 10k 100k 150 4148 100 F 47 F 5.1k 150 2.2k 10 F* 100nF 2.2k 100nF 330k 6.8k 100k 33k 10 F* 1M 1M IC1,2,3 : OPA1662 * 25V minimum 01112191 REV.B 4004 1M C 2019 100 RLY1 33 NUTUBE PREAMPLIFIER 100 5819 siliconchip.com.au This photo also shows the completed PCB – use it in conjunction with the component overlay opposite. The flying lead visible in this photo and those below earths the aluminium case to the PCB to minimise hum. Initially set VR2 and VR3 to midway. Apply power to the circuit from a 7-18V DC supply. Check that TP6V is between 5.88 and 6.12V. Also check the relay switches on after about five seconds; you should hear it click in. Adjust VR2 so that the left-hand plate of the Nutube lights up at its brightest. Similarly, adjust VR3 so that the right-hand plate of the Nutube glows brightest. If using a supply that’s over 12V, make sure the grid voltage is less than 2.5V; otherwise, the device’s maximum dissipation rating will be exceeded. The grid voltage for each Triode can be measured at TPG1 and TPG2, relative to the GND PC stake. VR4 adjusts the output of the left channel so that it can match the right channel in level. This can be done by connecting up the preamplifier to your sound system and rotating VR4 so both channels have the same output level, just by listening. For more accurate adjustments, you need a signal generator. You can use a standard hardware-based signal generator, or computer software. You will also need suitable leads to connect the generator to the RCA inputs. For connection to a computer, you typically need a stereo lead with RCA plugs one end and a stereo 3.5mm jack plug at the other. Leads for a hardware signal generator will require an RCA plug one end and a connector for the generator, such as a BNC plug, at the other end. Apply a 1kHz signal of about 1V RMS to the right channel preamplifier input (red input socket). Monitor the right channel output with a multimeter set to measure AC volts. Set the volume control for about 500mV signal at the output. Adjust VR3 for maximum signal, but when doing this, adjust the volume control so the level does not exceed about 500mV. That’s required to ensure the signal is not clipped. When the maximum level is found, take note of the level reading. Now apply the same signal to the left channel (white RCA input) and measure the left channel output. Do not change the volume setting, but you may need to adjust VR4 for a suitable level, not much more than 500mV. Adjust VR2 for maximum signal as before. Now adjust VR4 so that the measured level is the same as that already measured in the right channel. If you wish to set the grid bias more accurately, spectrum analyser software can be used. The spectrum analyser will show the distortion products of the preamplifier, including the fundamental and harmonics. The fundamental is the reproduction of the actual applied signal. With a perfect preamplifier, without distortion, you would only see the fundamental at the output. However, with a real preamplifier, there will be noise and distortion. This will show up in the analyser as other spikes rising above the noise floor. Typically, the distortion will have second, third, fourth, fifth harmonics etc. For a 1kHz signal, the fundamental (first More views of the completed PCB from the front (at left) and the rear (above). Neither photo has the 9V battery in place but its support standoffs and screws are ready for it. siliconchip.com.au Australia’s electronics magazine January 2020  29 Free audio signal generator and analyser software If you want an audio signal generator that runs on a computer, you can use the free Audacity software (siliconchip.com.au/link/aaxk). This is available for Windows, macOS, GNU/Linux and other operating systems. Download and install the version that suits the operating system on your computer. Once installed and running, select Generate -> Tone and then set the waveform to sine, frequency to 1kHz and volume to maximum (ie, set the level value to one). You can also set the duration over which the tone is generated. Press the play button for the audio to start. Another good, easy-to-use option is WaveGene (siliconchip.com. au/link/aaxl). For spectrum analysis, you could use WaveGene in combination with WaveSpectra (siliconchip.com.au/link/aaxl). See the setup instructions at: siliconchip.com.au/link/aaxm We used Visual Analyser, available from siliconchip.com.au/link/ aaxn, mainly because this allows the actual measured waveform to be seen as a ‘scope’ view, along with the output spectrum. Once you have installed the signal generator and spectrum analyser software, it’s a good idea to use it to analyse the performance of your computer sound interface. That can be done with a cable with 3.5mm stereo jack plugs at each end, with one end plugged into the sound input and one into the sound output. To do this with Visual Analyser, on the main screen, then select “floating windows mode” and then the Scope, Spectrum and Wave need to be opened from the top row of selections. Select a 1kHz sinewave for the Wave generator, select interlock (that causes both A and B channels to change together) for the output levels and bring up the output level on the waveform generator. Then press the on/off button below the output level slider. The on/off selection at the top left of the main screen also needs to be selected so that the analyser measures the signal. Both will show “off” when the signal is generated and measured. You can choose to view the A channel (left) or B channel (right), or both, in the main settings channel selection. We chose to use a 16,384 sample FFT window and a sampling rate of 44.1kHz in the main menu. Output gain (adjustment along the top row at right) was set just below maximum, yielding the lowest distortion figure of 0.0626%. In our case, noise is mostly more than 80dB below the fundamental (see Fig.11). That indicates that this is not a particularly good sound card, but good enough to evaluate the distortion from the Nutube Preamplifier. Now the Nutube Preamplifier can be connected between the computer sound input and output. Adjust signal levels using the volume control and/or the signal generator level so that the waveform is not clipped (ie, so the top of the sine wave is not plateauing) and instead showing a clean sinewave. In the main menu, you can select the left channel (A) and adjust trimpot VR2 for the lowest distortion reading, with minimal harmonics – see Fig.12. This shows the waveform as a clean sinewave, with the analyser showing the main 1kHz fundamental at 0dB level and the second harmonic (2kHz) at around -70dB. The third, fourth and sixth harmonics are at a similar level. Once you’ve finished tweaking VR2, select the right Channel (B) and adjust VR3 for the lowest distortion reading. VR4 can then be adjusted while viewing in the A channel of the analyser, so that fundamental level is the same as that in the B channel. Fig.13 shows the waveform and spectrum when the grid bias (with VR2) is adjusted incorrectly. The top half of the sine waveform is very rounded, and the second harmonic is only 10dB below the fundamental. The distortion reading is around 30%. 30 Silicon Chip Fig.11: a screen grab of the free Visual Analyser PC software performing a ‘loopback’ test, with the sound card output fed directly into its input. This lets you analyse the distortion inherent in the system. In this case, the reading is 0.0626% THD+N at 1kHz. You therefore won’t get a reading lower than that when measuring the performance of external devices like the Nutube preamp. Fig.12: now we have connected the Nutube preamp ‘in the loop’ between the sound card output and input, using two stereo jack plug to red/white RCA plug cables. The output levels have been set to 41% full-scale, which corresponds to around 250mV RMS, The distortion reading has only risen slightly, to 0.07%, because the Nutube preamp and sound card distortion figures are similar. Fig.13: here is the same test as Fig.14, but the triode grid bias voltage adjustment is completely wrong. You can see the heavily distorted sinewave in the “Oscilloscope” window, with many harmonics in the spectrum analysis. The THD reading is 30%. This is about as bad as it gets; more realistically, a slightly misadjusted grid bias voltage can lead to distortion levels in the 0.1-1% range. Australia’s electronics magazine siliconchip.com.au Where can you buy a 6P1 Dual Triode? As mentioned in the parts list, the 6P1 is available from RS Components (https://au.rs-online.com). So far they are the only local source we’ve found (and who has stock). We have to warn you, though, it’s not a cheap device: RS Components list it as $78.98 each (inc GST, plus postage)! (RS stock no is 144-9016). We would expect prices will eventually come down as they become more popular and more suppliers carry them. harmonic) would show as a peak at 1kHz, with the second harmonic at 2kHz, the third harmonic at 3kHz, the fourth at 4kHz etc. These harmonic distortion products hopefully will be at a lower level than the fundamental, and not all harmonics will necessarily be present. Once you can see this, you can adjust the grid bias for minimum distortion. For that matter, you could also adjust it for maximum distortion, if that’s what you’re after! The completed PCB simply slides into the extruded case sothat (See panel opposite). the pot shaft and switch emerge from the front panel. No PCB screws are necessary as it is held tight by the front and rear case ends. Final assembly The Nutube Preamplifier PCB is housed inside an aluminium enclosure with clear end panels, measuring 115 x 51 x 119mm. If you are not using a battery for power, unplug the battery clip from CON3 to prevent the contacts from shorting onto a part of the circuit. The end panels include 3mm-thick foam plastic that can be used as padding for the Nutube device. The end pieces just require this foam to be placed within the outer surround, where the end panels connect to the aluminium body. The central pieces that cover the window and the buttonshaped pieces for the corner securing holes are not required for the case. Cut out a piece of foam 38 x 17mm and place this behind the Nutube. This is held between the two 15mm standoffs at the rear of the Nutube. Note that the enclosure has a specific top and bottom orientation for both the aluminium extrusion and end panels. The front and rear panels have a slightly different profile at the top and bottom edges. While the top edge is straight, the lower edge has a slightly lower moulding below the two left and right corner holes. That matches the same profile on the aluminium extrusion. Holes need to be drilled for the volume potentiometer and power switch at the front and the DC socket and RCA sockets at the rear. The required front panel hole locations are shown on the label artwork of Fig.14. These can also be downloaded as PDF files from the SILICON CHIP website. A small portion along the top edge of the RCA terminal housing plastic needs to be shaved or filed off, as it is slightly too high to fit in the case otherwise. Less than 1mm needs to be removed. You can place the labels on the inside of the panels, cutting around the outside perimeter of each label. Or you can cut out the smaller-sized inner perimeter so the labels can be affixed to the outside of the end pieces. For more detail on making labels, see www.siliconchip. com.au/Help/FrontPanels If the panel label is to be inside the end panel, a paper label could be used. For the front panel, the central window in the artwork will need to be cut out with a hobby knife, to expose the Nutube. The RCA sockets should be secured to the rear panel with the self-tapping screw, and with the rear edge of the PCB touching the inside of the rear panel. You can then slide the PCB into the case on the second slot up from the bottom. Don’t forget to attach the GND solder lug to the top corner screw at the rear adjacent to the RCA sockets. The wire end of the solder lug will need to be orientated diagonally inward, so it does not foul the end cap border. Additionally, the anodising layer on the aluminium is a good insulator. It will need to be scraped off at the point where the solder lug makes contact with the screw entry point to ensure good contact with the metal. Finally, the rubber feet provided with the enclosure can now be fixed to the base using their self-adhesive. SC Nutube Preamplifier L + Power + Volume + SILICON CHIP + + + 7 to18VDC (Centre +) www.siliconchip.com.au R + + + OUT IN Vo Fig.14: the 1:1 front and rear panel artwork can also be used as a template. V1 requires a 43 x 15mm cutout; the volume control a 10mm hole and the power switch a 5mm hole. On the rear panel, the RCA sockets require 10mm holes where shown with a 3mm hole in the middle; the DC socket is 5mm. These can also be downloaded from siliconchip.com.au siliconchip.com.au Australia’s electronics magazine January 2020  31 Migrating from iPhone to Android... without losing anything! Some people prefer Apple iPhones, while others prefer Android phones. But what if you decide, for whatever reason, to switch from the iPhone you’ve used for a few years to an Android model? You could ‘start fresh’, discarding your history including text messages, app data etc. But that can be very inconvenient. You can bring most of this data across from one system to the other, but it isn’t easy, and there are lots of different ways to do it. Read on to find out just how . . . T here will likely never be a resolution to the eternal debates of which phone system is better: Apple iPhone (iOS) vs Google Android-based phones (made by numerous manufacturers). The point of this article is not to convince you one way or the other. But after many years of using an iPhone, I decided to switch to Android, and found that it wasn’t that easy to make a seamless transition. Before I describe what I had to do to make the switch, I’ll briefly describe the reasons why people choose one system over the other. Proponents of Apple point to extremely tight integration between the hardware and operating system as a benefit, whereas Android offers more hardware competition between devices. This is mostly because Google allows other manufacturers to use their Android operating system. Apple has very tight control over its Apps, whereas Google exercises less control. Apple has traditionally had an excellent reputation against unauthorised inby Dr David trusion by hackers, although there have 32 Silicon Chip been some infamous intrusions, especially with iCloud data. While Android systems also emphasise security, quite a few Apps have been pulled from the Google Play Store when malware was found lurking within. Apple offers excellent hardware quality, but higherend Android devices are competitive. However, Android phone quality varies wildly, with some cheaper devices being markedly poor. Regarding hardware, Apple also makes PCs, watches, tablets and other phones and so can offer consistent and integrated performance between the devices. But in the Android world, it is really only Samsung that offers a full range of such devices. Apple users seem to prefer relative simplicity, tight integration and strong support from the manufacturer. In contrast, Android users seem to prefer lower cost (or better value) devices, easier expandability and more hardware flexibility. But some Android vendors also offer excellent support (eg, Samsung, Maddison based on my experience). Australia’s electronics magazine siliconchip.com.au Samsung DeX with phone plugged into docking station allowing keyboard, monitor, ethernet, USB ports and mouse functions to provide desktop-like functionality. This illustrates the flexibility of the Android OS. Image credit: Maurizio Pesce, Creative Commons Attribution 2.0 Generic license. Despite apparent differences, both iOS and Android have similar origins. Both are based on Unix-like operating systems. iOS started with the open-source Darwin (BSD) system, while Android is based on a modified Linux kernel running a ‘virtual machine’. I hope that the following description of my transition will help others who wish to do the same. But note that my experiences may or may not be directly applicable to your particular situation. Before I get to the actual migration process, I will describe what motivated me to make the switch, and go into more detail on some of the key advantages and disadvantages of the two platforms. My motivation to change I initially used the iPhone because that was supplied by an organisation I used to work for, as it was the corporate standard. After leaving that organisation, I needed to up- Warning! The information in this feature is presented as a guide only – any procedures you undertake are entirely at your own risk. The success of the procedures described in this article cannot be guaranteed, as devices and software – even two apparently identical phones – can be subtly different, not to mention almost continually changing. SILICON CHIP cannot be held responsible for any data loss incurred following any procedure described here. Please do plenty of research beforehand and make sure to back up all data before attempting any transfers. siliconchip.com.au grade my phone, so I decided to purchase a newer iPhone (a 64GB iPhone 6S), as that was the simplest upgrade path. It was easy to transfer all of the data such as contacts, memos, pictures etc from the old phone to the new one. That new iPhone was fine for a while, until the stored data had filled most of its available memory. I then found it necessary to start deleting Apps and transferring data such as photos off the phone, to make room. This is where a major difference between the iPhone and Android operating system became apparent. My preferred option was to keep this data on the phone rather than maintaining one set of files on the phone and one set off the phone. But iPhones do not offer the option to add more storage with a micro SD card. Nor, it must be said, do all Android phones. Most do, but there are exceptions! My phone’s memory was mostly full of photos I had taken, along with map data. I didn’t want to migrate this data to Apple’s iCloud storage system, so I stopped using the phone You can find instructions on the Internet about how to find the location and file name(s) of your iTunes backup on your PC to make an extra copy if necessary. Note also that there is software available that can extract data such as photos, messages and contacts from your iTunes backup but the backup MUST NOT BE ENCRYPTED. Everything we’ve read suggests that is close to impossible to extract data from an encrypted iTunes backup (presumably that’s the whole point of encryption!). Australia’s electronics magazine January 2020  33 Another competitor to iOS and Android? Apart from Android and iOS operating systems, another phone OS on the horizon is the open-source Harmony OS from Chinese company Huawei. This was speculated to replace Android OS in its phones due to US Government sanctions. But it now appears it will be used not in phones, but in “Internet of Things” (IoT) devices. And regardless of its intended use, recent (November 2019) media reports suggest it is “years away” from availability. Other operating systems for mobile devices include Windows 10 Mobile, BlackBerry 10, Tizen, Sailfish OS, Ubuntu Touch, Plasma Mobile, PureOS, PostmarketOS and KaiOS. as a camera and started using a dedicated camera instead. To liberate space to keep using this phone, I deleted numerous Apps such as OSM street maps (which I used to view maps ‘offline’), various unused pre-loaded Apps from Apple such as GarageBand and KeyNote (1.7GB and 630MB respectively) etc. I then became alarmed because as I deleted Apps to liberate memory, the spare memory would continue to ‘disappear’. This was despite the fact that I had disabled automatic updates for the operating system and nearly all my Apps. The continual battle to free up storage on my phone, plus the positive experiences of friends and associates with Android devices, lead me to consider making the switch. The most crucial difference for me was the ability to add extra internal memory with an internal micro SD card, something that Apple phones do not allow. I also like the more open and accessible file system on Android devices. Note that not all Android phones have micro SD card slots, which is a pity, as many of them are otherwise excellent devices. But for me, the lack of expandability is a deal-killer. You generally pay a lot more for a phone with more internal storage, than a similar amount of storage on a micro SD card would cost. And often, after you purchase a phone, higher capacity cards become available, allowing you to expand the storage to a level that was not available at the time of purchase. I purchased a Galaxy S10 with 512GB of internal storage (a 1TB version is now available in Australia). The highest internal capacity currently available in the iPhone is 512GB. More on SD cards These internal micro SD cards can be used to generally increase the storage of the device. But they are most useful for holding the photos and videos you take, which tend to take up the majority of the flash storage space. Moving an App from phone memory to SD card memory where supported by App, phone and Android version. Another application where SD card storage of data is handy is the Open Street Maps (OSMAnd) App. An OSM map for Australia is several hundred megabytes, while for the United States (and other similarly populous countries), it is several gigabytes. I use such maps for travelling, as I might not have a data connection. The ability to store such memory-consuming data on a removable and replaceable card instead of in the phone’s memory (or to shift it offline) is obviously a big advantage. While many Android Apps can be stored and run off a memory card on earlier OS versions, fewer support this in later versions. This is generally not such a good idea, since the SD card is usually slower than the internal storage, and you lose access to the App if you swap cards. To see if an App can be transferred to SD storage on your Android phone, go to go the Settings menu, then select the App and then the Storage tab for that App. If your version of the App, the phone and the OS supports moving an App to the SD card there will be an option to “Change storage to the SD card” (or change it back) – see above On my new phone, apart from OSMAnd, Apps that can be transferred to the SD card include AliExpress, AvenzaMaps, Google Earth, Epson iPrint, GPSLogger, Photos, Shazam, Sky Map, Google Translate, Waze, and Wikipedia. SD card capacity The highest capacity SD card available will soon be 1TB. RS-232, Android and iOS As an example of the difference between interfacing hardware with the two types of phones, consider RS-232 serial connections. Contrary to popular belief, many devices still use RS-232, such as many astronomical telescopes, amateur radios, point-of-sale devices, microcontrollers, scientific instruments, data loggers, RFID readers, irrigation controllers, fire alarm panels, glucose meters and many other specialised devices. It is relatively easy to interface an RS-232 device to an Android phone, but with iOS, a special Lightning-to-serial cable is neces34 Silicon Chip sary. Such a cable is made by Redpark (http://redpark.com/), with the intention you write your own software for it with a supplied SDK (software development kit). Apple won’t approve any App for the App Store for use with this cable or any other RS-232 devices! In general, any device to be connected to an iPhone has to be made under license of the MFi program (siliconchip.com.au/ link/aawu). The other option for connecting more hardware to an iPhone is to ‘jailbreak’ it. Australia’s electronics magazine siliconchip.com.au Plugging a hard disk into your Android phone You can connect an external hard disk to your Android phone with an OTG adaptor. The disk should ideally be formatted with exFAT so it can be recognised on Windows, Mac and Linux and there are no realistic file or volume size limitations. Some external hard disks already come with that format. Android also natively supports the FAT32 file system (4GB file size limit), but there are Apps to support NTFS (the default Windows file system) as well. If using an external hard disk for an extended time, you may need to use an externally-powered OTG cable to keep the phone charged. Otherwise, it will drain the phone battery quickly if the disk is powered via USB. Incidentally, SD cards are typically formatted with FAT32 up to 32GB, and exFAT for 64GB and beyond. I’ve seen sites allowing pre-orders for such cards at around US$450. Android theoretically supports cards up to 2TB, but not all devices have this capability. According to Samsung, their recent phones (such as the Galaxy S10) support SD cards up to 512GB. With SD cards, storage is essentially unlimited because as soon as one SD card is full, you can swap in another. You can keep the old card(s) so that you can still view older photos and videos etc. However, swapping cards is a bit impractical (if not downright unfriendly is some phones!) so you are generally better off using the largest card you can. If larger cards become available, you can transfer the data from one to the other using a PC. But the small physical size of SD cards does mean they can be easily kept in a wallet etc. So you can cart a few around, to show others the media stored within. In my case, I installed a 64GB card in my new phone, which cost about $20. This isn’t a huge expansion to the already large memory on my phone, but as mentioned above, I can easily expand this later if I run out of space. For convenience, it is best (at least initially) to buy a micro SD card with an adaptor to suit a full-size SD card slot. That may make it easier to connect to a laptop or desktop computer. Some brands of micro SD cards include the SD adaptor as a bonus. Like Apple, some Android providers also offer free or paid-for cloud storage. For example, Samsung in Australia offers 5GB of free storage for new accounts with no current option for extra paid storage beyond 5GB. (Accounts created on or before 31 May 2019 had 15GB). With Android or iOS and a Google account, you get free unlimited storage of photos up to 16MB in size and videos up to 1080p (1920 x 1080 pixels). Apple has consistently refused to add internal SD card support to their phones. It seems that they would rather have people upgrade their phone to another Apple model with more memory or purchase extra iCloud storage, beyond the 5GB included free with every phone. Extra iCloud storage is offered in sizes of 50GB, 200GB An Apple Lightning to SD Card Camera Reader adapter. siliconchip.com.au and 2TB for A$1.49, A$4.49 and A$14.99 per month at the time of writing. That works out to around $17.88 per year for 50GB of iCloud storage. By comparison, 50GB of SD card storage has a one-time cost of around $14. SD card ‘virtual memory’ For Android users, there is a way to use an SD card on a phone as though it was regular phone memory (rather than in the form of extra storage space). However, this is not generally recommended, and not all manufacturers support it. It is called “Adoptable Storage” and the SD card becomes part of the phone OS and cannot be removed without resetting the phone. In other words, if your phone had 128GB of internal memory and you added a 128GB SD card configured appropriately, you would effectively have a 256GB phone. As mentioned above, one of the biggest problems with this is that the SD card storage is generally a lot slower than the internal storage, so this could slow the phone down significantly. But it might be worthwhile doing if you have an old phone with a small amount of memory, and you want to give it a new lease of life. USB OTG (Android) and Lightning (iOS) connectivity Many Android devices also support USB “On The Go” or OTG. This is a standard that enables a device to use its charging/communications port to also connect a USB device such as a flash drive, hard drive, keyboard, mouse, printer, camera etc. Some memory storage devices and SD card adaptors are available for the iPhone. These connect via the iPhone ‘Lightning’ connector. But in general, external hardware connectivity is much more limited on the iPhone, even though Apple provides specifications for prospective manufacturers of such devices (see siliconchip.com.au/link/aavz). Some iPhone adaptors are described as “OTG” devices which “convert” a standard Apple Lightning connector to USB, but these do not provide true OTG capability. There are also official Apple products such as Lightning-to-USB A Samsung OTG adapter. It connects to the phone with a USB-C male and has a USB female connector on the other end. It acts as a USB host, enabling a wide range of accessories to be connected. Australia’s electronics magazine January 2020  35 This shows the SDR Touch App with a cheap dongle used as a software defined radio (SDR), connected to an Android phone with an OTG adapter and an external antenna. Screen grab from a YouTube video “SDR Touch with RTL SDR (RTL2832), HTC One X, Android 4.1 Jellybean” https://youtu.be/ QArle2hHO54 There are many Apps available for SDRs (which are directly connected to the phone rather than remotely controlled on a network) on Android but not iOS. camera adaptors for downloading photos from an external DSLR camera to the iOS device, or for reading from and writing to an SD card. Ultimately, though, the USB port used on Android phones from many different manufacturers means that a greater number of accessories are available. Transferring from Apple to Android Many people who have considered migrating from Apple to Android have nixed the idea, due to the difficulty of transferring data from the old to the new device. For many people, this is the main factor inhibiting them from making the change; this was certainly the case for me. Having said that, when some people purchase a new phone, they have no desire to preserve old data and therefore, these concerns do not apply. Or in some cases, you might only wish to transfer basic data such as contacts, which is not difficult. Most Android phones come with proprietary software (or free downloads thereof) to enable common categories of data to be transferred with ease. This typically includes contacts, messages (SMS and MMS but not iMessages), photos and videos. This transfer software may also copy typed memos, voice memos, voice mails, documents, favourite web sites and calendar entries. Videos on an iPhone are in the form of MOV files. This is a different format than the MP4 standard, which is used by Android devices. So to use them on an Android phone, you have to convert them to a compatible format. Or you can do as I did and install the free VLC media player, which can play MOV files as well as many other formats. In my case, the Samsung “Smart Switch” software copied the MOV files to my new phone, but I had to install VLC One item I couldn’t transfer across I have a thermal imaging camera, the FLIR Systems FLIR One. At the time of purchase, one could choose either a Lightning connector to suit the iPhone or a USB connector for an Android phone. I purchased the Lightning version, but it’s now quite useless to me, as there is no adaptor available for it to connect to a USB socket. 36 Silicon Chip to play them. I also had to spend a little time looking before I found where they had been stored on the new phone. Apple’s “Live Photos” are not supported by Android. These are photos recorded in the form of short video segments. CopyTrans (www.copytrans.net) is PC software which is billed as an alternative to iTunes. This lets you backup and manage your iPhone data on a PC, but does not handle transfers to Android. But it does claim to enable you to change the Live Photo format to one that can be used on an Android device; see siliconchip.com.au/link/aaw0 Two of the greatest difficulties in transferring data from iPhone to Android are with WhatsApp chat messages and Apple iMessages. This will be discussed in some detail later. Apple users will not be used to having an accessible file system. It is helpful to use a supplied or downloaded file manager to have a look around your phone to see where various files are stored in the Android file system. Files can also be seen if you connect the phone to a PC and you will see its internal directory structure and file names. Transfer software Some programs can transfer data directly from an iCloud or iTunes backup to a new Android phone. This can be especially helpful if you no longer have the original iPhone, eg, if it was lost, sold or destroyed. Manufacturer-supplied transfer software supplied with new phones are as follows: • Google Pixel devices have built-in support for transferring data; see siliconchip.com.au/link/aaw1 Data that can be transferred includes SMS messages and iMessages, phone and iCloud Contacts, phone and iCloud Calendars, photos and videos (except HEIF photos), Apps (if available for Android). Most music will transfer but not if it has iTunes Digital Rights Management (DRM) protection (usually bought before April 2009). Music downloaded from Google Play won’t either but see siliconchip.com.au/link/aaw2 for more details. • HTC uses a software product called Sync Manager installed on a PC to transfer data from an iTunes backup to a new HTC Android phone (siliconchip.com.au/link/ aaw3). Data that can be moved includes iPhone contacts, calendar, SMS, photos, videos, wallpaper and bookmarks. • Huawei Android phones can have data imported from an iOS phone with Phone Clone (siliconchip.com.au/ Australia’s electronics magazine siliconchip.com.au link/aaw4). Also see https://consumer.huawei.com/au/ emui/clone/ • LG phones can import data from iPhones with the LG Mobile Switch (Sender) App (siliconchip.com.au/link/ aaw5). Note that software has to be installed on both the old and the new phone. For more detail, see siliconchip. com.au/link/aaw6 • Motorola US documents refer to a Migrate App on the Google Play Store, although it appears not to be present at the time of going to press. According to this link, it has been retired siliconchip.com.au/link/aaw7 See also siliconchip.com.au/link/aaw8 and siliconchip.com.au/ link/aaw9 • Nokia has no official information on their website about transferring iPhone data to one of their Android phones, but relevant information is provided by Vodafone Australia, at: siliconchip.com.au/link/aawa • Oppo phones suggest using Clone Phone software to transfer information from the old iPhone to their Android phones, see siliconchip.com.au/link/aawb • Samsung phones can use Samsung Smart Switch Mobile on the new Android phone for phone-to phone-transfers (siliconchip.com.au/link/aawc). Also see www.samsung. com/au/apps/smartswitch/ for transfers via a PC or Mac.    Data that can be transferred from iOS includes contacts, calendar entries (device content only), messages, photos, music (DRM-free content only, not supported for iCloud), videos (DRM-free content only), call logs, memos, alarms, WiFi settings, wallpapers and documents.    In my case, I found that a direct transfer between phones (iPhone to Android) gave the best results. Make sure the batteries of both devices are fully charged before proceeding. Samsung state that Smart Switch requires 500MB of free space on the old phone. However in my case, I did not have that amount of free space, and it still worked. • Sony Xperia phones can use Xperia Transfer Mobile (siliconchip.com.au/link/aawd). The following data can be transferred: contacts, calendar events, call log, text messages (SMS), multimedia messages (MMS), photos, music, videos, documents, Apps (not supported from iOS) and App data (will be transferred if the App allows it). Transfers can be made from an iPhone via USB, WiFi or iCloud. Third-party phone data transfer software • Phone Transfer for Windows (siliconchip.com.au/link/ aawe) can transfer contacts, call logs, text messages, music, photos, movies and calendar data. • iSkysoft Phone Transfer for Mac (siliconchip.com.au/ link/aawf) also runs on Windows and can transfer contacts, messages, calendar entries, photos, music and video. • Phone Transfer (siliconchip.com.au/link/aawg) is available for Windows or Mac. • RecoveryAndroid (www.recovery-android.com) for Windows or Mac can transfer contacts, photos, videos, music, messages and calendar data. There is a special version for Motorola phones at: siliconchip.com.au/link/aawh siliconchip.com.au Expanding iPhone memory While no extra memory such as an internal SD card can officially be added to an iPhone, some people have replaced the memory chip in an iPhone with a higher capacity version. This procedure requires extremely high levels of skill, experience, equipment and risk. It is not recommended for the faint-hearted. One video documenting the procedure of increasing the memory of an iPhone 6S from 16GB to 128GB titled “Upgrade iPhone 6S 16GB Storage to 128GB” can be viewed at https://youtu.be/ v5WDDZqhn2s You can also get this procedure done in the markets of Shenzen, China, or buy equipment to do it yourself. See Fig.8 and the video titled “How I Upgraded My iPhone Memory 800% - in Shenzhen, China”; see https://youtu.be/rHP-OPXK2ig (it documents the desoldering and resoldering process of the memory chip, and practice attempts, and uses a different memory reflashing process than the previous video). If you attempt such a procedure, you must have secure backups as you will need to copy the data back to the new (blank) chip. • dr.fone Switch (siliconchip.com.au/link/aawi) allows a variety of transfers to be made between different phones. It can transfer a total of 15 file types: photos, videos, contacts, contact blacklist, messages, call history, bookmarks, calendar, voice memo, music, alarm records, voicemail, ringtones, wallpaper and notes. Transfers can be made either directly between devices or from an iCloud backup to Android. There is also a desktop version of the software, which requires both the old and new phones to be plugged into the computer. • MobiKin (siliconchip.com.au/link/aawj) allows the transfer of contacts, SMS, music, videos, photos and books from an iPhone to a new Android phone. • Android Switch (www.android.com/switch/) is the method provided by Google to transfer data from an iPhone; however, it appears to only transfer calendar, contacts, and photos. There are many other Apps to transfer either partial data from phone to phone, as well as techniques that don’t require any extra software. My experience I initially decided to use “Syncios” for my phone swap, because of its claimed ability to transfer iMessages as well as other user data. While it initially seemed to transfer data, including iMessages, I noticed that it had caused my phone to start resending old messages to various phone contacts. This included messages that were many years old! As soon as I discovered this, I deleted the transferred messages and started again, only to have the same thing happen again. Needless to say, this was highly embarrassing. I contacted Syncios support, but my queries went unanswered. Syncios has a money-back guarantee, but after about two weeks of no response from them, I had to seek Australia’s electronics magazine January 2020  37 “Rooting” your Android device “Rooting” an Android device is the equivalent of “jailbreaking” in the iOS world. This means making unauthorised firmware modifications to the device to enable you to install software or perform other operations not normally permitted by the factoryissued device. Both processes are to be strongly discouraged unless you are highly technical and know what you are doing. If done incorrectly, this may result in: • loss of warranty of the device • the possibility of “bricking” the device, ie, rendering it unusable and unrepairable • exposing the phone to security threats. a refund of the US$29.95 (around AUD $45) I paid from PayPal. Fortunately, this claim was successful. I then decided to use Samsung Smart Switch – with success, although it doesn’t transfer iMessages. Transferring iMessages iMessages are difficult to transfer from iOS to Android. iMessages are a proprietary Apaircradfple form of text and media messages, for use between iPhones. These messages appear in the same App as regular text and media messages. An iMessage can be distinguished from a regular text (SMS) or media (MMS) message because it is in a blue rather than green bubble on the iPhone texting App. iPhones transfer text or media messages in the form of iMessages using an internet connection rather than the phone system. While regular text and media messages can be transferred from iOS to Android by many methods, iMessages use a proprietary storage method and are not so easy to transfer. As I mentioned above, Syncios claimed to perform that task but caused me serious problems, so I had to abandon it. Most iOS-to-Android transfer software will copy all your standard SMS and MMS messages, but you might not get iMessages. If you have essential iMessages, you could keep them on your old iPhone, or they can be extracted from iPhone backups using one of several iPhone backup viewing and extraction tools. Losing iMessages when transferring from an iPhone can be a big deal for some ‘power users’. See the article titled “Apple trapped me on iOS — perhaps forever” at siliconchip.com.au/link/aawm for the experience of one user. Also see “iPhone’s blue bubble won’t let me stray to the Galaxy S8” at siliconchip.com.au/link/aawn We haven’t tested either method, but you can copy iMessages off the phone to a computer (but not another Android phone) using iMazing (siliconchip.com.au/link/aawk) or iSMS2droid (https://isms2droid.com). If you are planning to move to Android in the future, I suggest that you turn off iMessages now, so that your phone number will be deregistered from the iMessages server. You will receive regular messages instead (which can easily be copied later), and your correspondents will get used to you not having iMessage. This last point may be important since without iMessage enabled, others will no longer be able to send you messages in places where there is no mobile service, but there is internet access, such as on some aircraft. If you don’t turn off iMessages and you move to Android, people with iPhones will think that they are sending you messages. But you will never get them, since they will be sitting in Apple’s iMessage servers! So you need to remember to switch this off before getting rid of your old phone. To turn off iMessages on your iPhone, go into Settings and then tap Messages and then toggle iMessage to off. Turn of Facetime at the same time. You can also deregister iMessages if you no longer have your phone but have the same number; see siliconchip.com.au/link/aawl Build your own phone? If you are not satisfied with any commercial phone offerings, you could try building your own, or source one from a non-mainstream manufacturer. There is a Kickstarter project called “MAKERphone” which is intended for educational purposes. See above and their website at siliconchip.com.au/link/aawv See also the video titled “Build Your Own Phone with MAKERphone” at https://youtu.be/S702qykR9zs The Fairphone (www.fairphone.com/en/) is a modular phone 38 Silicon Chip that is specifically designed to be easy to repair, “sustainable” and based on materials that are ethically sourced. The latest model is the Fairphone 3, which runs Android 9. It is currently available on pre-order for approximately €450.00 (around AUD $730) plus shipping from Europe. Someone was keen enough to build their own iPhone from spare parts. See the video titled “How I Made My Own iPhone in China ” at https://youtu.be/leFuF-zoVzA Australia’s electronics magazine siliconchip.com.au Some WazzapMigrator screens There is an Android App called PieMessage (siliconchip. com.au/link/aawo) that enables iMessages to be used on an Android device; however, it appears to be no longer under active development. It also requires you to have an OSX device such as an Apple Mac and it requires an expert level of knowledge to set up. See a 2016 review of PieMessage at siliconchip.com.au/link/aawp Migrating WhatsApp messages One of the trickiest Apps to migrate data from the iPhone to Android is the popular messaging software WhatsApp. The developer of this App has made no special provision for data migration, and it is not merely a matter of copying across data. It is complicated since WhatsApp can only be registered on one phone at a time for a given user. It used to be possible to transfer WhatsApp data from iOS to Android, but those older methods no longer work. The only way I found to migrate this App data without losing past messages and multimedia files was with the aid of a paid App (A$9.49) called WazzapMigrator; see www.wazzapmigrator.com WazzapMigrator works as follows. You make an unencrypted iTunes backup (the process will not work if it is encrypted). You extract a file from the backup on your PC or Mac called ChatStorage.sqlite, plus a folder called Media. Any iTunes data extractor can be used for this job, but a free one is supplied on the WazzapMigrator website, and it also has links to others. You then connect your Android phone to your PC or Mac and copy these two files to the Download folder on the phone. You first uninstall WhatsApp from your phone if it is installed. Then you install WazzapMigrator from the Google Play Store onto the phone. When you run that App, it should find the iPhone backup files in the Download directory of the phone and you then siliconchip.com.au just follow the instructions. When finished, go to the Google Play Store on the phone and install WhatsApp Messenger, activate it with your phone number and press the Restore button of the WhatsApp Messenger App. All the chats and media from your iPhone should be there. As with any software installation, things can go wrong. So you should browse the WazzapMigrator website and chat forums on that site before proceeding, as well as watching the installation videos. One problem I encountered is that I was locked out of WhatsApp App for about ten minutes. This was because the WazzapMigrator tool internally uses an old version of WhatsApp, and they don’t like an old version being installed, even temporarily. This doesn’t always happen, but I did get my valuable messages and media across. Judging from the forum activity on the WazzapMigrator website, support for this App seems extremely good. I, for one, was very happy with the result. Note that these instructions are current at the time of going to press but follow instructions from the WazzapMigrator website in case there have been changes. Other possible methods of transferring WhatsApp messages that we haven’t tested are using: • dr.fone - Restore Social App (siliconchip.com.au/link/aawq) • Backuptrans iPhone WhatsApp to Android Transfer (siliconchip.com.au/link/aawr) • iCareFone - WhatsApp Transfer, Backup & Restore (siliconchip.com.au/link/aaws) There are other reported methods which appear to be more complicated. You can read the official WhatsApp FAQ on the subject (siliconchip.com.au/link/aawt) which states “Note: You can’t migrate your messages across different types of phone”. SC Australia’s electronics magazine January 2020  39 Dramatically improve performance of SDR – especially at HF Tunable HF Preamplifier by Charles Kosina with Gain Control There are many cheap Software Defined Radio (SDR) modules available which perform brilliantly at VHF/UHF but they generally have poor HF (3-30MHz) performance. They also suffer from wide-open front ends, which makes them susceptible to cross-modulation from strong signal sources. This simple tunable preamplifier greatly improves SDR HF performance. It has (optional) gain control and can run off a 5V supply or phantom power. M The Mosfet’s gain is controlled by ost SDRs (and many other nector CON1, then to the PCB via pin radio receivers) can benefit header CON2 and onto DPDT switch varying the DC voltage on the second from a preamp to boost the S1, which passes it to one of two trans- gate, using potentiometer VR1 which formers. This provides two different has padder resistors at either end, to signal from the antenna. This one is nice and simple, low in tuning ranges, allowing the tuning to limit its wiper voltage to the useful range. cost, easy to build and works well over be more selective. T1 covers a range of about 5-11MHz, Fixed gain can be provided by most of the HF range. It can be built with variable or fixed while T2 covers 11-24MHz. Both are omitting VR1 and changing the resisgain. Variable gain is ideal as it allows tuned by dual variable capacitor VC1, tor values, as described in the circuit you to avoid overload on strong sig- with its two gangs wired in parallel to diagram. Q1’s drain load is the primary of nals, while still taking advantage of give a 6-200pF range. The tuned signal is then fed to gate transformer T3, with a 1.25mH inthe improved selectivity of a tuned 1 of dual-gate Mosfet Q1. The signal is ductance. The other end connects to front end. It’s a fairly compact unit when com- DC-biased from the nominally +5V rail the +5V rail which is bypassed by a pleted, and runs from a 5V power sup- via a 150kΩ resistor and 10nF low-pass 10nF capacitor. The 75µH secondary is ply, which in some cases can come filter capacitor, to reject supply noise. connected similarly, and the signal is AC-coupled to outfrom the receiver itput SMA connector self via the Preamp’s Features & specifications CON3 via another output lead, using Tuning range:....... 5-24MHz in two ranges (wider tuning range possible) 10nF capacitor. ‘phantom power’. Alternatively, if The circuit of the Bandwidth:........... typically 50-250kHz (varies with tuned frequency) the device is to be HF Preamp is shown Gain:.................... typically 34-36dB phantom powered in Fig.1. via CON3, jumper The input signal Power supply:...... 5V DC <at> 30mA JP1 is inserted, alis fed into chassislowing the DC supmount BNC con- Connectors:.......... BNC input, SMA output (can be varied) 40 Silicon Chip Australia’s electronics magazine siliconchip.com.au 2 #0.5T IF T1 WOUND ON TOROIDAL CORE 1T IF T1 WOUND ON 2.2 H CHOKE 2.7k ##0.5T IF T2 WOUND ON TOROIDAL CORE 2T IF T2 WOUND ON 2.2 H CHOKE A LED1 ^13T SECONDARY IF T1 WOUND ON TOROID 22T SECONDARY IF T2 WOUND ON TOROID T1 R2 22k 2 10nF Q1 1.25mH BF1105 G1 VC1a 3-142pF 75 H D G2 10 H (22T^) 10nF CON3 10nF COILCRAFT PWB-16-AL 16:1 JP1 (FIT ONLY WHEN SUPPLYING PHANTOM POWER VIA CON3) VC1b 3-60pF T2 0.5-2T## OPTIONAL 5V SUPPLY (REMOVE JP1) T3 10nF S 150k 1 10nF S1b + – 1 OPTIONAL GAIN CONTROL 2.2 H (13T^) 0.5-1T# CON2 VR1* 100k  K S1a CON1 R1 22k CON4 * IF GAIN CONTROL IS NOT NEEDED, SHORT ALL PINS OF VR1 & CHANGE VALUES OF R1 TO 100k, R2 TO 150k BF1105 LED G2(3) SC 20 1 9 TUNABLE HF PREAMPLIFIER K A G1(4) D(2) S(1) Fig.1: the circuit is quite simple, especially given its performance. It has a gain of around 35dB and a tuning range up to about 24MHz as shown (but can be extended to about 30MHz). VC1 a and b is a miniature dual variable capacitor, typically sold as a tuning capacitor for small radio receivers. ply voltage to flow through T3’s secondary and into the +5V rail. This is then modulated with the output signal which is coupled in from T3’s primary. Two versions You can build the device in two different versions. Version 1 has T1 & T2 wound on toroidal ferrite cores. These are not that easy to get, and winding the turns it tedious, but they have the advantage of a very high unloaded Q, up to 350. Version 2 is easier to build as T1 & T2 are based on readily-obtainable axial RF inductors, which are each about the size of a 1W resistor. The primary winding is just one or two turns of wire around the inductor body. These inductors exhibit a surprisingly high Q, up to 120 in the range of interest. Obtaining the parts The output transformer is a broadband Coilcraft device. I got mine as a free sample, but they are also readily available from element14. The tuning capacitor comes from Jaycar and many other sources, including eBay. The SMA output connector is readily available on eBay, with one local seller listing ten for $6.59. The other components are reasonably standard parts. Those which are not available from Jaycar or Altronsiliconchip.com.au ics can be purchased from Digi-key, Mouser, element14 etc. Changing the frequency range If you changed the 2.2µH inductor to 1µH, that would give you a tuning range of about 12-30MHz, giving you almost full coverage of the HF band. If building Version 1, with the toroidal ferrite cores, this could be achieved by reducing the number of secondary windings on T1 by about one third. If building version 2, using RF chokes, simply substitute a 1µH choke. Construction The Tunable HF preamp is built on a double-sided PCB coded CSE190502, measuring 79.5 x 29mm. Refer to the overlay diagram, Fig.2, along with the photos to see how it all goes together. Fig.2(a) shows Version 1, with T1 & T2 wound on ferrite toroidal cores, while Fig.2(b) shows Version 2, using the RF chokes with turns of wire around the outside of each to make them into transformers. We used 0.25mm insulated wire but enamelled copper (ENCU) wire would also be satisfactory. Many of the components are SMDs, with 2012 (metric) / 0805 (imperial) capacitors and 3216 (metric) / 1206 (imperial) resistors. I find that an SMD board now takes me less time to assemble than one with Australia’s electronics magazine through-hole components, and none of the parts on this board are difficult to solder. Start by fitting the SMD passives. Tack one end down, then solder the other end and wait for the joint to solidify before refreshing the first joint. Then mount dual-gate Mosfet Q1 with its larger tab orientated as shown above, followed by transformer T3, with its pin 1 dot at upper left. Follow with edge-mount connector CON3, which is placed over the edge of the board before soldering its pins top and bottom. Make sure the middle contact pin is on the correct side to match with its pad. Then fit the pin headers where shown. If you are building Version 1, now is the time to wind and mount the toroidal transformers. T1 has a half-turn for its primary (best fitted after the secondary has already been soldered to the board) and 13 equally-spaced turns for its secondary. Try to wind the secondary so that it spans just over half the core, meaning the start and end correspond with the PCB pads (see photos). T2 also has a half-turn primary but a 22-turn secondary, which is wound to cover the entire circumference of the core (not shown for clarity in Fig.2(a); see the photo) and then brought back across the core to terminate to the other secondary pad on the PCB. Once you’ve wound the secondaries January 2020  41 The same-size photo below shows version 2, with the enlarged inset at left showing how the one and two-turn primary windings are added. The PCB pads for the “earthy” end of the primaries are directly under the 2.2µH and 10µH chokes. Fig.2a (top) is the component overlay for version 1, using two toroids for T1 and T2 with primaries and secondaries wound through them. Fig.2b (bottom) shows version 2, an identical overlay but using axial RF chokes instead, with primaries of one or two turns of thin wire around them. and soldered them to the PCB pads, you can solder one end of each primary, pull it tight across the core and then trim it and solder the other end. If you’re building Version 2, you just need to wind one turn of 0.25mm wire (ENCU or insulated) around the body of the 2.2µH inductor and fit it for T1 as shown, with the added windings as the primary, and wind two turns around the 10µH inductor and use it as T2; again, the added windings are the primary. If you’re using a trimpot for VR1, fit it now. If you want the gain to be externally adjustable, solder leads onto the three terminals of your chosen potentiometer and attach a three-pin plug to the other end. Alternatively (and more simply), cut female-female jumper leads in half and solder the exposed ends to the pot terminals. The sockets at the other end can be plugged into the PCB header later. Now fit the variable capacitor. Remove the knob first, then attach the body to the PCB using the two supplied screws through from the underside. Solder the three pins, then re-attach the knob to the shaft, which passes through a hole in the PCB. Leave LED1 off for now. Preparing the case Now place the PCB assembly in the case, sitting on its spacers, and slide it so that CON3 touches the side of the case. Measure the distance from the centre of CON3 to the top of the box. Then measure that same distance on 42 Silicon Chip the outside, from the top of the box near CON3, and mark where the hole will need to be drilled. Remove the PCB and drill a small hole there, then enlarge it to 7mm. Check that the connector fits through the hole with the spacers sitting on the bottom of the box. If so, deburr it. Otherwise, you may have to enlarge it slightly. Once it fits, drill a small hole at the opposite end of the box and enlarge it to around 10mm, then check that the BNC socket fits. Once it does, deburr that hole too and again, clean out the swarf. Now remove the spacers from the PCB, push CON3 through the hole you drilled and mark out the four mounting hole positions. Also mark the location where LED1 will protrude through the base, once it has been installed, and mark a suitable location for the DPDT switch. Note that a 5mm LED will have to clear the PCB once fitted. Drill the marked holes to 3mm, then enlarge the LED hole to 5mm, and the switch hole until the switch fits. Deburr all the holes and clean off the swarf. If you’re building the Preamp with an external gain control, now is also a good time to figure out where the pot will be mounted and drill and deburr a suitable hole. If you are going to be supplying external power, drill a hole for the DC socket now. It would make sense to move the BNC socket slightly towards one side of the case to make more room for the DC socket. Australia’s electronics magazine Final assembly The last component to be fitted to the board is the LED. It’s mounted on the opposite side to most of the other components, and its longer lead must face towards the pad marked “A” on the PCB. Push its leads through their holes so that the lens is fully down onto the PCB, then slot the board in place holding the leads, and use them to push the LED lens through its mounting hole while CON3 is hard against the edge of the case. Prop the board up so that the LED lens is not being pushed back into the hole, attach a couple of the board mounting screws to ensure it’s in position, then solder and trim LED1’s leads. After that, insert the remainder of the PCB mounting screws. Mount the BNC socket in the hole you made earlier and solder a short length of hookup wire to its middle pin. Connect this wire to the lower terminal of CON2, to the left of the header for S1, as shown in Figs.2(a) & (b). You don’t need to connect the RCA socket shield, as it’s grounded to the metal box and this connects to board ground via CON3’s shell. All that’s left now is to wire up and fit switch S1. Crimp a length of 6-way ribbon cable into the IDC connector shell, so that the red wire will be towards the top when plugged into the header on the board such that the cable exits to the left (ie, towards the nearest board edge). siliconchip.com.au Now separate and strip the wires at the other end. Starting with the red wire, solder them to the following switch terminals: NC1, NC2, COM1, COM2, NO1, NO2. In this case, the numbers 1 and 2 refer to the two switch poles. It doesn’t matter which is 1 and which is 2, as long as you are consistent. It also doesn’t matter which side of the switch you consider to be NC and which is NO. Once the wires have been soldered and the switch mounted in the base, plug the IDC socket into the header as shown in the photos. If using a DC socket to feed in external power, solder wires to its two tabs; if your socket has three tabs, plug in a plugpack and use a DMM to figure out which is positive and which is negative. Mount the socket in the hole you made earlier, then terminate the leads to CON4, either by soldering them directly to its pins (see PCB for polarity) or by attaching a two-way header socket to the wires. As with the pot, you can cut a femalefemale jumper lead in half and then solder its bare ends to the DC socket. The other ends will plug straight into CON4. Alternatively, if using phantom power from the radio receiver via CON3, place a jumper shunt on JP1 now. If you’re fitting an external gain control pot, mount this now, and plug its terminals into the pin header soldered in place of VR1. The lead soldered to the anti-clockwise end of the pot (as viewed from the front) plugs into the left-most terminal of the VR1 header, with the PCB viewed right-side-up. Using it Now it’s just a matter of screwing Parts list – Tunable HF Preamp 1 double-sided PCB, code CSE190502, 79.5 x 29mm 1 diecast aluminium case, 115 x 65 x 30mm [Jaycar HB5036, Altronics H0421] 1 BF1105 dual-gate SMD Mosfet (Q1) 1 5mm or 3mm LED (LED1) 2 small toroidal ferrite cores, 12.5mm OD, 7.5mm ID, 5mm thick (T1/T2) [eg, TDK B64290A0044X830] OR 2 axial RF chokes, 2.2µH & 10µH [Jaycar LF1514 + LF1522, Altronics L7014 + L7022] 1 Coilcraft PWB-16-AL transformer (T3) [element14] 1 chassis-mount BNC socket (CON1) 1 edge-mount SMA socket (CON3) 3 2-pin headers (CON2,CON4,JP1) 1 chassis-mount DC socket (optional) 1 shorting block/jumper shunt (for JP1) 1 DPDT toggle or slide switch (S1) 1 3-pin header (for VR1) 1 3x2-pin header (for S1) 4 6.3mm Nylon M3 tapped spacers 8 M3 x 6mm machine screws 1 1m length of 0.25mm diameter enamelled copper or insulated wire 1 1m length of light-duty hookup wire 1 50mm length of 6-way ribbon cable (for S1) 1 6-pin IDC socket (for S1) Capacitors 5 10nF 50V SMD ceramic capacitors, 2012/0805 size, X7R dielectric 1 dual variable capacitor (VC1) [Jaycar RV5728] Resistors (all SMD 3216/1206 size, 1%) 1 150kΩ 2 22kΩ* 1 2.7kΩ 1 100kΩ linear chassis-mount potentiometer (VR1) OR 1 100kΩ multi-turn vertical trimpot (VR1) * or 1 100kΩ + 1 150kΩ for fixed gain (omit VR1 & 3-pin header) the lid onto the box, connecting your antenna to CON1, your radio to CON3, hooking up a 5V power supply (if using external power), and switching S1 to the appropriate band. You may wish to label the case to indicate which position is for the lower tuning range and which is for the upper. With power applied, check that LED1 lights. Switch to your SDR’s spectrum analyser view and set the range to 3-30MHz. Check that adjusting VC1 changes which frequencies are being amplified, and that VR1 (if fitted) allows you to control the gain. Check also that S1 switches bands and that the two ranges are roughly as expected. As VC1 is not calibrated, you will need to use a spectrum display to see what frequency you are tuning in, although you can ‘blind tune’ by simply adjusting VC1 and S1 for maximum signal at your desired frequency. Then adjust VR1 (if fitted) for the best reception without overloading the receiver. Shown a little larger than life size, this is the completed PCB (in this case version 1 with toroids) mounted in the diecast case. S1 is shown here mounted off the board but the Altronics S2075 slide switch could probably be SC mounted directly. siliconchip.com.au Australia’s electronics magazine January 2020  43 A Complete Arduino DCC Controller Digital Command Control (DCC) is a great way to control multiple trains on a model railway layout. Unfortunately, commercial DCC systems can be quite expensive. Here we present an Arduino-compatible Controller shield that can form the basis of a DCC system. It can also be used as a DCC booster or even as a high-current DC motor driver. by Tim Blythman Y ou can put together this DCC controller, which incorporates a base station and optionally also a programmer, for a fraction of the price of a commercial unit. Combine it with a PC, and you have a potent and flexible model railway control system. It’s based on the Arduino platform, and it’s easy to build. You can also add boosters to the system easily, just by building a few more shield boards. DCC is still the ‘stateof-the-art’ in terms of offthe-shelf model railway systems, so if you have a model railway layout but don’t have a DCC system (or have a DCC system that’s inadequate for your needs), now is the time to upgrade! We published an Arduino-based DCC Programmer for Decoders in our October 2018 issue (siliconchip.com. 44 Silicon Chip au/Article/11261). Since then, we have had numerous requests for a DCC Base Station or Booster. Therefore, we have created this DCC Power shield, which is the final piece of the puzzle. Adding this (and an appropriate power supply) to the Programmer, in conjuction with DCC-capable locos, results in a complete DCC system. As this is an Arduino-based project, the following description assumes that you are familiar with the Arduino IDE (Integrated Development Environment). To download the free IDE software, go to siliconchip.com. au/link/aatq A complete DCC control system can be made by adding a Uno board and the DCC Programmer Shield (which we described in the October 2018 issue) to the DCC Power Shield, as shown here. Fit the DCC Programmer Shield with stackable headers, so it can be sandwiched between the other two boards, and take care that nothing shorts out between the adjacent boards. You may need to trim some of the pins on the underside of the DCC Power Shield. Australia’s electronics magazine siliconchip.com.au Two locos, one track – but both are under individual control of the DCC system. As you can just see, the loco in front even has its headlight on – also switched on or off at will via DCC. Want more than two trains? DCC has up to 10,000 addresses available! We are using version 1.8.5 of the IDE for this project, and suggest that if you have an older version installed, that you upgrade it now. What is DCC? We went into a bit of detail on DCC in the DCC Programmer article, so we’ll only cover the basics here. If you want to learn more, read the aforementioned article from October 2018, and possibly the article describing DCC in detail from February 2012 (siliconchip.com.au/Article/769). DCC is designed to allow multiple model trains to be controlled on a single track, with the same set of tracks carrying power for the trains and also digital control commands. Older command controls systems exist; we detailed the construction of one such system (in five parts!) in 1998. This was named the Protopower 16, and it was based on another system called CTC16. This worked similarly to the system used to control multiple servo motors on model aircraft. But that system was limited to 16 locomotives, while Digital Command Control has around 10,000 addresses available; probably well beyond the scope of most model railroads (and many full-scale railroads too!). The most basic method of model train control is for a single throttle to apply a variable DC voltage to the track, which drives the train’s motor directly. Instead, a DCC base station delivers a high-frequency square wave to the track. The base station encodes binary control data into this signal by varying the width of each pulse (see Fig.1). A digital decoder on each vehicle siliconchip.com.au receives commands and also rectifies the AC track voltage to produce DC. The decoder then uses this to drive the motor and can also control lights, sound effects (like a horn or engine) or even a smoke generator. There are also accessory decoders which can be used to control things such as points and signals using the same DCC signals. The DCC standard is produced by the National Model Railroad Association (based in the USA; see siliconchip. com.au/link/aaww). These standards are available for download, which means that anyone can use them. As a result, many different manufacturers are making DCC-compatible equipment. Our Base Station will work with many commercially-available decoders. There is a vast array of manufacturers of DCC equipment, so we can only test a small subset. All of those we have tested have worked well, as should be expected from a proper application of the standard. Terminology A Base Station in DCC terminology is, essentially, the brains of the sys- • • • • • • • • tem. Typically it receives commands from attached throttles controlled by people, or perhaps a computer. These commands then dictate what DCC data needs to be sent to the trains to control them. The Base Station generates a continuous stream of DCC data packets to control and update all trains, signals and points as needed. A Booster is a simple device which takes a low-level DCC signal and produces a DCC signal of sufficient power to drive a set of tracks. Many smaller DCC systems consist of a single unit which combines a Base Station with a Booster, while larger systems might have separate units, including multiple Boosters. Our DCC Power Shield works as a Booster. An attached and properly programmed Arduino board can be used as the Base Station smarts, thus creating a basic DCC system in a single unit. Extra DCC Power Shields can be deployed as separate Boosters, with an Arduino attached to monitor each and check for faults. When programmed with the DCC++ software, the Arduino board and DCC Power Shield can be combined with Features & specifications Based on the Arduino Uno Provides a DCC output of 12-22V peak at up to 10A, or more with some changes Can operate as a base station or booster Compatible with DCC++ and JMRI (DecoderPro/PanelPro) software Opto-isolated input for use as DCC slave Works with our DCC Programmer shield from the October 2018 issue Can also be used as a brushed motor driver All Arduino pin assignments configurable via jumpers Australia’s electronics magazine January 2020  45 “0" BIT “1" BIT +12V to +22V TIME 0V –12V to –22V 58 s 58 s 100 s 100 s SC 2020 Fig.1: the DCC waveform is a square wave with a frequency around 5-8kHz. Binary data to control trains, signals, points etc is encoded in the pulse widths. The BTN8962TA ICs we’re using are ideally suited to delivering such a signal at up to 10A or more. See the panel “How DCC works” on pages 44 & 45 of the October 2018 issue for more information. 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 A A A A A A A A 0D D D D D D D D0 C C C C C C C C 1 ADDRESS PREAMBLE START BIT our earlier DCC Programming Shield to create a compact, economical and fully-featured DCC system. Power source A DC power source is needed to run the DCC Power Shield. The DCC standards suggest that Boosters should produce 12V-22V peak, so your chosen power source needs a regulated DC output in this range. For modest current requirements (up to around 5A), a laptop power supply is a good choice. Many of these have a nominal 19V DC output at several amps. Any fully DCC-compatible trains and decoders should handle this fine, but it’s worth checking any that you aren’t sure about. Decoders are supposed to work down to around 7V. Given that the track, wiring and locomotives are bound to drop some voltage, a 12V ‘power brick’ type supply works well enough for driving trains. However, we found that this sometimes wasn’t enough to allow decoder programming to occur. If you need more current than a lap- DATA START BIT START BIT CHECKSUM END PACKET BIT top power supply can provide, you will need to find a dedicated power supply in the 12-22V range. Many suitable high-power ‘open frame’ switchmode supplies are available from various suppliers. One thing to note is that while some Arduino boards (including genuine boards) can tolerate up to 20V on their VIN inputs, some clones use lower-rated voltage regulators which can only handle 15V. We have provided an option for a zener diode to help manage this variation; read on for more information on how the circuit works. DCC Power Shield circuit The circuit of the DCC Power Shield is shown in Fig.2. Its key function is to turn a steady DC voltage into a DCCmodulated square wave. For this, we need a full H-bridge driver. To keep it simple, we have used a pair of BTN8962 half-bridge driver ICs (IC1 and IC2). The BTN8962 comes in a TO-263-7 package, which is a surface-mounting part, although quite a large one. It is not difficult to solder. There are two of these, one driving each side of the track. They are supplied with out-ofphase input signals to produce the required alternating output drive. Their supply pins (pins 1 & 7) are connected directly across the incoming DC supply from CON1, labelled VIN. A 100µF electrolytic capacitor bypasses this supply. While this may seem like a low value to use, the current drawn by IC1 and IC2 is quite steady as when one output goes high, at the same time, the other goes low. The outputs of IC1 and IC2 connect to screw terminal CON2, and then onto the tracks. The state of the IN pins (pin 2) determines whether the output pins (4 & 8) are driven high or low. The SR input pin controls the output slew rate. We’ve tied this to ground to give the fastest possible slew rate. The “INH” pins (pin 3) need to be brought high to enable the outputs. These are connected together and have a 100kΩ pull-down resistor so that the outputs default to off. The enable signal connects back to an Arduino pin via a 10kΩ resistor and jumper JP1, allowing the Arduino to enable or disable the outputs as required. JP1 lets any Arduino digital pin connect to the enable signal, to suit the software used. The IS pins (pin 6) on IC1 and IC2 are outputs that source a current proportional to the current being drawn from the output of each IC (plus a small offset current, which is compensated for in software). These currents are combined in a ‘diode-OR’ circuit formed by diodes D1 & D2 and then fed to a 1kΩ resistor to convert the combined current into a voltage. This then passes to an RC low-pass filter (20kΩ/100nF) for smoothing. The 2ms time constant means that peaks in the current due to the rapidly changing The three PCBs which make up the DCC system: on the left is a “standard” Arduino UNO board (or one of its many clones); centre is the optional DCC Programmer (from our October 2018 issue) while at right is the DCC Power Booster Shield. All three boards are made to conveniently plug together. 46 Silicon Chip Australia’s electronics magazine siliconchip.com.au VIN VIN POWER IN 2 100 F 35V 1 +5V CON1 2.2k DCC IN + 1 D3 1N4148 1 7 2 K 2 A CON3 C  6 3 B 10k 2 3 1k 1k ENABLE OPTO DIR 1k 1 DCC OUT VIN IC2 7 2 BTN8962TA CON2 VS 6 5 2 3 JP3 ENABLE INH 1 10k DIR 4,8 GND A K OUT CONTROL LOGIC IN Q1 BC549 D2 1N4148 JP1 IS 10k ENABLE BTN8962TA SR E 5 4 6 5 330 8 7 VS A K 100nF OPTO1 6N137 IC1 D1 1N4148 IS SR CONTROL LOGIC IN OUT 4,8 INH GND 100k 1 1k VIN 2 4 6 K   A K K 1k 6N137 JP2 ISENSE A 100nF ZD1 (OPTIONAL) K +5V SC DCC CONTROLLER/BOOSTER DCC signal are ignored, but faults can still be detected quickly. The resulting smoothed voltage is fed to one of the Arduino analog input pins via jumper JP2, to allow the Arduino to monitor the track current. JP2 allows any of the Arduino analog inputs to be used to monitor track current, again allowing us to choose whichever pin suits the Arduino software. The IS pins will also source current if IC1 or IC2 detect an internal fault condition; as far as the software is concerned, this is equivalent to a very high current being drawn from the output and is treated the same way. Bridge driving signals The input signal to pin 2 of IC2 comes from another one of the Arsiliconchip.com.au A K BTN8962TA 8 20k 1 C ZD1 1N4148 A 8 2020 E LED1 A BC549 B K A LED2 ENABLE A5/SCL A4/SDA 1 3 A3 A2 A0 A1 VIN GND GND +5V +3.3V +5V RESET DC VOLTS INPUT 5 ICSP ARDUINO UNO, DUINOTECH CLASSIC, FREETRONICS ELEVEN OR COMPATIBLE LEDS +5V +5V D1/TXD D0/RXD D3/PWM D2/PWM D4/PWM D5/PWM D7 D6/PWM D8 D10/SS D9/PWM D12/MISO D11/MOSI GND D13/SCK AREF SCL USB TYPE B MICRO SDA DIR 4 1 4 7 Fig.2: as with many Arduino shields, the circuit’s smarts are on the Arduino itself. The shield consists primarily of two integrated half-bridge drivers (IC1 & IC2), a transistor inverter (Q1), a high-speed optocoupler for feeding in external DCC signals (OPTO1), two LEDs for status monitoring and some headers to allow the Arduino pin mappings to be changed if necessary. duino digital outputs via a 10kΩ series resistor. Once again, any Arduino digital pin can be used, and this too is selected by a jumper shunt on JP1. A simple inverter circuit produces the out-of-phase signal to drive the IN pin of IC1. The signal that goes to pin 2 of IC2 is also fed to the base of NPN transistor Q1 via a 1kΩ resistor. Q1’s collector is pulled up by a 10kΩ resistor to the ENABLE line. So as long as ENABLE is high, meaning the outputs of IC1 and IC2 are active, input pin 2 of IC1 is inverted compared to input pin 2 of IC2. Opto-isolated input To allow a separate base station to be used, an optoisolated input is provided at CON3. This can accept a logic-level DCC signal, or even a ‘track Australia’s electronics magazine voltage’ (12-22V) signal from another DCC system. The signal at CON3 passes through a 2.2kΩ series resistor and into the LED of OPTO1. 1N4148 diode D3 is connected in reverse across this LED, to protect it from high reverse voltages. If a logic-level DCC signal is applied to CON3, then the polarity markings need to be observed, as current will only flow through OPTO1 when the voltage at pin 2 is high. A bipolar DCC signal can be connected either way around. OPTO1 is a 6N137 high-speed optoisolator which has a nominal forward current of 10mA. Thus the 2.2kΩ resistor is suitable for voltages up to around 22V, ie, the maximum expected from a DCC system. The output of OPTO1 is supplied January 2020  47 <OPTO 1 0 2 4 #3 #5 7 #6 8 20kW 4148 10kW 10kW 100nF Q1 5V GND VIN 1k W 330W ANALOG A0 A1 A2 A3 A4 A5 09207181 Rev F with 5V from the Arduino board, bypassed by a 100nF capacitor. A 330Ω pull-up resistor sets the logic high level. The output from OPTO1’s pin 6 is fed via a 1kΩ protection resistor to jumper JP3. This allows the DCC signal to be fed directly to the input of bridge drivers IC1 & IC2. In this case, a jumper on JP1 can be used to feed the same signal to one of the Arduino’s digital pins, which would then be configured as an input. Due to the open-collector output of OPTO1, this signal is inverted compared to that applied to CON3. But this can be solved simply by reversing the connections from CON2 to the tracks. This reversibility of the DCC signal is a necessary feature, as a locomotive may be placed on the track either way and must be able to work with an inverted signal. The only time this matters is when different boosters feed two adjoining tracks. In that case, you will need to make sure that the signals are in-phase. Other features Status LEDs LED1 & LED2 are connected to the ENABLE signal with 1kΩ current-limiting resistors to GND and 5V respectively. So if ENABLE is high, green LED1 lights up, and if it’s low, red LED2 lights up instead. If ENABLE is highimpedance, such as when the Arduino is in reset, neither LED lights. A single bi-colour LED could be fitted either for LED1 or LED2 to achieve the same effect. If fitted, ZD1 feeds DC from CON1 to the VIN input of the Arduino board. Its value is chosen to limit the Arduino input voltage to a safe level at the maximum expected voltage from CON1. Silicon Chip + – CON3 DCC IN 1k W OPTO1 6N137 4148 10kW A 2.2kW D3 K 1kW 4148 DCC POWER SHIELD LED2 1 ZD1 1 D1 48 TX RX JP2 D2 LED1 10001n98F210770128910 1kW 1kW 100kW ENABLE IC1 BTN8962 CON2 DIGITAL JP1 IC2 BTN8962 DCC OUT #9 13 12 #11 #10 DIR 100mF RESET 3V3 +DC IN– GND 1 CON1 AREF SCL SDA Fig.3: the seven-pin halfbridge driver ICs are mounted on the left, near the power input (CON1) and track (CON2) terminals. The jumper positions shown here are those required to use both the open-source DCC++ software and our example sketches. The jumpers are mostly handy if you want to use this shield as a DC motor driver, so that you can connect the required SC Ó2020 functions to PWM pins. For example, for 22V into CON1, ZD1 can be an 8.2V type, so 13.8V is fed to the Arduino VIN pin. A 1W, 8.2V zener diode can pass up to 120mA, which should be enough to power the Arduino and any connected shields. We’ve left enough space to fit a 5W zener diode if you need more current than that, although if you’re going to be applying less than 22V to CON1, you could also use a lower voltage zener, which could then pass more current before reaching its 1W limit. For situations where the voltage on CON1 is suitable for direct connection to VIN (typically under 15V for clones or 20V for genuine Arduino boards), then a wire link can be fitted in place of ZD1. However, it would still be a good idea to fit a low voltage zener (eg, 3.3V) as this will reduce the dissipation in the Arduino’s regulator. Just make sure that the voltage fed to the Arduino’s VIN pin will not drop below 7V. If you aren’t sure whether your Arduino can handle more than 15V, check the onboard regulator. It’s usually in an SOT-223 three-pin SMD package with a hefty tab. Genuine Arduino Uno boards usually have an NCP1117 regulator, rated to handle up to 20V. Clones often have an AMS1117 instead, which is only rated to 15V. If ZD1 is left off, the supplies are separate (although their grounds will be connected). This allows the Arduino to be powered via its USB connector, eg, from a controlling computer. DCC Programming Many DCC Base Stations have a separate output for programming decoders. In other words, programming is not done via the main high-current output Australia’s electronics magazine driver, which is usually kept connected to the layout. For this reason, you may wish to have the DCC Power Shield and October 2018 DCC Programmer shield plugged into the same Arduino. The DCC++ software is designed to handle this. However, this does complicate the power supply arrangements a bit. Firstly, the DCC Programmer shield has a maximum supply voltage of 15V, so regardless of the type of Arduino board you are using, you will need to ensure that the VIN pin is no higher than 15V. Also, in this case, it would be best to build the DCC Programmer shield without the MT3608 boost module, and fit the jumper shunt on CON8 between pins 1 and 2, so that the VIN supply is used for programming power. The DCC Programmer shield can draw up to 200mA from VIN, so the dissipation of ZD1 will increase substantially. You will need to choose its value carefully, or use a 5W zener. Another option, if the system will always be connected to a computer, is to build the DCC Programmer Shield with the MT3608 boost module and fit it below the DCC Power Shield, then leave out ZD1 from the Power Shield. The DCC Programmer Shield will then be powered from the computer’s 5V USB supply, while the DCC Power Shield is still powered via CON1. Construction The DCC Power Shield is built on a double-sided PCB in a typical Arduino shield shape, coded 09207181 and measuring 68.5 x 55mm. Use the overlay diagram, Fig.3, as a guide during construction. Start by fitting IC1 and IC2. As you siliconchip.com.au can see, although these are surfacemounting components, they are quite large. Because of this, and the fact that they sit on large copper pours, it will require quite a bit of heat to make good solder joints. Flux paste and solder braid (wick) will come in handy, as will tweezers. Apply some flux paste to the pads first, to make soldering easier. Working on one at a time, start by tacking one of the end pins in place to locate the device. Once you are happy that each is centrally located within the footprint, load some solder on the tip of your iron and apply it to each of the smaller pads. Ensure that the resulting solder fillets are solid. Use the solder braid to remove any solder bridges. The two end pins, numbers 1 and 7, are ground and power respectively. It’s a good idea to add a bit of extra solder to these pins to help with current and heat handling. Finally, solder the large tab of each device. Hold the iron tip at the point where the tab meets the pad on the PCB. Heat the pad until it melts solder applied to it. Feed in solder until a rounded, but not bulging fillet is formed and allow it to cool. Next, fit the 12 resistors. The PCB silkscreen is marked with the values, and you should check these match with a multimeter as they are fitted, to ensure they are the correct value. Solder close to the PCB, then trim the leads close to the underside. Then install the three small 1N4148 diodes (D1-D3) where shown in Fig.3, ensuring that they are correctly orientated If fitting ZD1, do that now. Make sure that its cathode band faces towards the top of the PCB. Then mount the rectangular MKT capacitors, which are not polarised. Now install NPN transistor Q1, with its body orientated as shown. You may need to crank the leads out to fit the PCB pads. Solder it in place, ensuring it is pushed down firmly against the PCB. If you plan to fit another shield above this one, then its top should not be more than 10mm above the PCB. The electrolytic capacitor should be mounted on its side to allow another board to be stacked above this one. Its longer, positive lead must go in the pad towards the top of the board as shown. Fit OPTO1 next. Check that its notch or pin 1 dot faces in the direcsiliconchip.com.au Parts list – Arduino DCC Controller 1 Arduino Uno or equivalent 1 12-22V DC high-current supply (see text) 1 double-sided PCB coded 09207181, 68.5mm x 55mm 1 set of Arduino headers, standard male or stackable (1 x 6-way, 2 x 8-way, 1 x 10-way) 2 2-way 5/5.08mm pitch PCB-mount screw terminals (CON1,CON2) [Jaycar HM3172, Altronics P2032B] 2 15-way pin headers (JP1,JP3) 1 14-way pin header (JP1) 2 6-way pin headers (JP2) 4 jumper shunts/shorting blocks Semiconductors 2 BTN8962TA half-bridge drivers, TO263-7 (IC1,IC2) [Digi-key, Mouser] 1 6N137 high-speed optoisolator, DIP-8 (OPTO1) 1 BC549 100mA NPN transistor (Q1) 1 green 3mm LED (LED1) 1 red 3mm LED (LED2) 1 1W or 5W zener diode to suit your situation (ZD1; see text) 3 1N4148 signal diodes (D1-D3) Capacitors 1 100µF 35V electrolytic 2 100nF MKT Resistors (all 1/4W 1% metal film) 1 100kΩ 1 20kΩ 3 10kΩ tion shown. Carefully bend the pins to allow it to fit into the PCB pads and solder it in place. Headers The various headers should be fitted next. Note that if you already know which Arduino pins will be used for the DIR, ENABLE and ISENSE signals and they will not change, you could omit JP1-JP3 and fit wire links in their places. To connect to the Arduino, you can use either regular headers or stackable headers. We recommend using the Arduino board as a jig to ensure that the pins are square and flush to the PCB. Stackable headers can be more tricky to mount as they need to be soldered from below. If possible, use those with 11mm-long pins (some that have 8mm pins, which don’t leave much room to solder). Thread the headers through the shield and into the Arduino board. Flip the whole assembly over so that the shield is resting flat against the pins, then solder the end pins of each group in place to secure the headers. You can then remove the shield from the Arduino board and solder the remaining pins in place, before retouching the end pins. It’s easiest to use single-row pin headAustralia’s electronics magazine 1 2.2kΩ 5 1kΩ 1 330Ω ers for JP1-JP3, snapped to length and soldered side-by-side for JP1 and JP2. If you are snapping 40-way headers to do this, you will need at least two. Rather than fitting JP3 as a separate two-way header, you can make the top two rows of JP1 longer by one pin (ie, 15 pins rather than 14). The last step in the construction is to fit the two screw terminals to CON1 and CON2, with their wire entry holes facing the outside edge of the board. Ensure that they are flat against the PCB; this is particularly important if you need to stack a shield above this one. You may need to trim the underside of CON2, as this could foul the DC jack of an attached Uno board. Similarly, the underside of CON1 comes close to the metal shell of the USB connector of an attached Uno. It’s a good idea to add a layer of electrical tape on top of the USB connector on the Arduino board, to make sure they can’t short if the boards flex. Jumper settings We suggest that you connect DIR to D10, ENABLE to D3 and ISENSE to A0, as shown in Figs.2 & 3. This suits our software. There are triangular silkscreen markings on the PCB to indicate the default jumper locations for JP1. January 2020  49 To use the board as a DCC Booster with our supplied software, add a fourth jumper across JP3 at upper-right. Software There are a few different ways this shield can be used, and each has its own software requirement. We’ll describe a few of these possibilities. The following assumes that you have fitted the jumpers to the default locations described above. DCC++ We mentioned the DCC++ software in our October 2018 article. It is designed to work with either an Uno or Mega board; we paired it with the Uno previously, and the discussion in this article assumes the same. The Uno is adequate to work with the JMRI (Java Model Railroad Interface) software and will naturally cost less than a Mega. The DCC++ project also includes a Processing-based GUI application for your PC that can interface with the Base Station, although this has been customised to work with a layout belonging to the DCC++ software designer. Alternatively, you can use JMRI. We also covered this software in the previous article. JMRI can be downloaded from www.jmri.org/download/ index.shtml There are versions for macOS, Windows and Linux. It can even be run on Raspberry Pi single-board computers. Follow the installation instructions, including installing Java if necessary. As we mentioned, our hardware is compatible with DCC++ in base station mode. There is more information, including the required Arduino sketch, available for download from: https://github. com/DccPlusPlus/BaseStation This software is designed to work with several commonly-available Arduino motor driver shields. But these shields need some modifications to work, whereas our hardware only requires the correct jumpers to be set. The default setting in DCC++ for the MOTOR_SHIELD_TYPE of ‘0’ will work with our hardware. Open the Arduino IDE, select the Uno board and its serial port via the menus and open the DCC++ Base Station sketch that you’ve downloaded. Then upload the sketch to the Uno. If Screen1: while JMRI’s DecoderPro program has many features, it also has a set of basic tools for controlling trains. This throttle window allows speed, direction and light functions to be controlled. You can even switch track power directly; the green icon at upper right mimics the status LEDs on the shield. 50 Silicon Chip you open the serial monitor at 115,200 baud, you will see a banner message; this indicates that the Base Station software is working as expected. You can also interact with the Base Station through serial commands. The protocol is detailed in the PDF file that is included in the DCC++ Base Station project ZIP file. Once you have tested this, close the Serial monitor and open the DecoderPro program. Go to Edit -> Preferences, and under Connections, choose DCC++ as System Manufacturer, DCC++ Serial Port as System connection. Ensure that the serial port setting matches that of the Uno. Save the settings and close DecoderPro, so that it can reload the new settings. Re-open DecoderPro and under Edit -> Preferences, choose Defaults, and ensure that the name of the new connection name is used for all connections (instead of “Internal”). Unless you have other hardware you want to use, you should select DCC++ for all options. Save, close and re-open DecoderPro again. Click the red power button in DecoderPro and ensure that it turns green. The LED on the DCC Power Shield should switch from red to green. The simplest way to drive trains is to select Actions -> New Throttle, set the locomotive address and manipulate the controls (see Screen1). Screen2: while very basic, our standalone sketch named “DCC_Single_Loco_Control.ino” allows power, speed, direction and lights to be controlled by commands in the serial monitor. The software can be modified to control multiple locos. Advanced Arduino users could use it as the basis of an automated layout control system. Australia’s electronics magazine siliconchip.com.au JMRI can do a lot of different things, so we suggest you read its manual to find out about its capabilities. The JMRI project also includes PanelPro, which can be used to design track and signal diagrams for controlling a model layout. Adding the DCC Programmer If you have already built the DCC Programmer, then the Arduino board is already programmed to work with the DCC Power Shield, and the DCC Power Shield can be added to the stack, ideally at the top. As noted earlier, the choice of zener diode and power supply will be more complicated if you want to construct an all-in-one setup. Since this is likely to be a smaller system, we suggest that a modest power supply will be suitable. Using the DCC++ software with JMRI is the same as noted above. Using it as a booster When a signal is fed in via the optoisolated input (CON3), the DCC Power Shield is effectively working as a booster. The signal can be from another Base Station or system, with the DCC Power Shield turning that signal into a more powerful DCC signal that can be used to drive trains. While it might not seem that an Arduino is needed in this case, it’s a good idea to have one as we can program it to monitor the DCC signal and intervene if there is a problem. So we’ve written a sketch to allow an Arduino to take on this supervisory role. There are two main conditions to check for. Firstly, we want the booster to be able to protect the shield if too much current is being drawn from it. This could be due to an overload or even a short circuit, such as a metal object being dropped across the tracks. Thus, our sketch continually monitors the voltage present on its A0 pin via its internal analog-to-digital converter (ADC). If it gets above a certain threshold, the power to the track is cut by pulling the ENABLE pin low. A timer starts and the sketch attempts to re-apply power after it expires. If the short circuit is still presiliconchip.com.au Using the DCC Booster Shield as a motor driver The DCC Booster Shield can be used as a high-current motor driver shield. In this case, the signal on the DIR pin determines the motor direction, and a pulse-width modulated signal is applied to ENABLE to control the speed. The BTN8962 has active freewheeling, so no external diodes are needed. If used like this, LED1 and LED2 will both appear to be on at the same time, with green LED1 becoming brighter and red sent, then the over-current condition re-occurs, power is cut again and the timer re-starts. The other condition we need to consider is if the incoming DCC signal is lost. This could be for any reason, such as if the connection to CON3 is broken or the upstream DCC Base Station has a fault. In any case, when there is no signal at CON3, the input to IC1 is held high and IC2’s input is low. There is then an unchanging DC voltage across the tracks. This may not sound like a problem, but some DCC locomotives can be programmed to undergo ‘DC conversion’. When a locomotive decoder detects that there is a steady DC voltage present, the locomotive behaves as if it was on a conventional ‘single-throttle’ layout and will typically set off in one direction at full speed (hopefully not towards the end of the track…). This feature was initially added to allow DCC locomotives to be used on conventional layouts, perhaps as an aid to LED2 dimmer as the duty cycle increases. As noted earlier, the 100µF electrolytic capacitor is adequate for a DCC application. A larger value may be needed for motor driving. We suggest leaving ZD1 off, as larger motors will create hefty spikes at the end of each drive pulse. Keeping the two supply rails separate will prevent this from damaging the Arduino board. owners transitioning to DCC from DC systems. Fortunately, the DC conversion feature can be turned off in the decoder by setting a configuration variable. You can use a DCC Programmer such as from our October 2018 article to do this. In any case, the sketch detects that the DCC signal is no longer changing and pulls the ENABLE line low, disabling the track output and preventing such runaways. To enable the use of the optoisolated input, add a jumper across JP3. Leave the jumper on ‘DIR’ for pin D10 in place; D10 is set as an input in the software and is used to monitor the incoming DCC signal. The Booster sketch is called “DCC_ Shield_passthrough_supervisor.ino”. This uses a library to perform the precision timing needed to generate the DCC waveform, called “TimerOne”. This can be installed via the Library Manager by searching for “timerone” or from the ZIP file we have included with our software package. Open the sketch, select the Uno and the serial port and upload it. Disconnect the USB cable and connect your power source to CON1. The red LED should light. Connect a valid DCC signal to CON3 and the green LED should light. You should then have a valid DCC signal at CON2. The DCC Power Shield can be combined with an Arduino Uno and DC power supply to create a basic DCC system. Using our standalone sketch or JMRI’s DecoderPro program, this combination can be used to control DCC-equipped trains, points and signals on a model railway layout. Australia’s electronics magazine January 2020  51 Where do you get those HARD-TO-GET PARTS? Many of the components used in SILICON CHIP projects are cutting-edge technology and not worth your normal parts suppliers either sourcing or stocking in relatively low quantities. Where we can, the SILICON CHIP On-Line Shop stocks those hard-to-get parts, along with PCBs, programmed micros, panels and all the other bits and pieces to enable you to complete your SILICON CHIP project. SILICON CHIP On-Line SHOP www.siliconchip.com.au/shop A standalone sketch We’ve also created a simple standalone sketch that produces a DCC signal, suitable for controlling a single locomotive. The decoder identification number has been set to 3 (which is the default for new, unprogrammed decoders), although it can be changed in the code. We suggest you use this option if you want to try out DCC for the first time. We can’t offer advice on fitting decoders; there are so many options for both decoder choices and how they are connected. The companies that make the decoders do offer advice (and many have custom decoders to suit specific locomotives). After all, they want to make it easy for you to buy their products. Our standalone sketch also requires the “Timer One” library mentioned above, so make sure that is installed Set the jumpers on the shield to the default positions and connect the Uno to the computer. Open the “DCC_Single_Loco_Control.ino” sketch and select the Uno board and its serial port. Press the Upload button to compile 52 Silicon Chip and upload the sketch, then open the Serial Monitor at 115,200 baud (see Screen2). You can now enter commands as numbers which correspond to the desired locomotive speed, in 128 steps. Thus, numbers from -127 to 127 are accepted. You should ensure that 28/128 step speed mode is set on your locomotive decoder. Type “P” (upper case) to turn track power on and “p” (lower case) to turn it off. The power will automatically turn off if current over half an amp is detected. You can also use “A” and “a” to turn on and off the loco’s headlights. The program is elementary, but it has several unused functions to send all manner of DCC packets to the track. If you are comfortable with Arduino, you should have no trouble adapting it to do something more advanced. Current limitations Using the specified components and the DCC++ software, the shield can easily deliver up to 10A. This is mostly limited by the screw terminal connectors. The DCC++ software also has a hard-coded current limit which kicks in at around 10A. Of course, the software limit is easy to change, but any hardware changes should be done with care. The output driver ICs are capable of handling around 30A, with the PCB tracks topping out around 20A. In any case, everything runs cool well below the 10A limit, so maintaining this limit is good for component longevity. DCC has a wide range of operating voltages, so to increase output power, it may be easier to increase the supply voltage. Most locomotives use PWM speed control on their motors, so a higher supply voltage simply means a lower PWM duty cycle (and thus current consumption) for the same speed. We haven’t done any tests above 10A, but if you are set on increasing the current capacity of the DCC Power Shield, then you should ditch the screw terminal connectors and solder thick copper wires directly to the board (ideally, to the power pins of IC1 & IC2). If the wires can handle 20A, then your modified DCC Power Shield should have no trouble doing that. To go higher than this will probably mean that IC1 and IC2 need some heatAustralia’s electronics magazine sinking, as well as even thicker wires. We suggest that you instead consider using more, smaller boosters. For example, you could modify the Booster sketch to monitor and drive multiple DCC Power Shields stacked above it. A larger system If you are planning a system with multiple Boosters, either because you need the power or it otherwise makes sense to do so, then there are a few minor caveats. When running multiple boosters, avoid daisy-chaining the DCC signal from one Booster to the next. Instead, fan out the DCC signal from one Base Station to all the Boosters. Many commercial base stations have a low-powered DCC signal output (Digitrax names this Railsync), which is ideally suited for this purpose. The first problem with a daisy-chain configuration is that if one Booster goes down, then so do all those that are downstream, as the DCC signal will be shut off. Secondly, each Booster also has a small but measurable delay in propagating the signal. In our case, this is around 4µs, due to the switching time of the BTN8962s. This delay is not usually a problem, but it may become one at the boundary where the tracks from two Boosters meet (where there would typically be an insulator, to prevent one Booster feeding another Booster’s section of track). Where the tracks meet, a train may be briefly fed by both the Boosters. If there is a delay between the signals from the two Boosters, then it may appear to be a short circuit if the two Boosters are delivering opposite polarity voltages at that instant. This is less likely to occur if the Boosters are well synchronised, which should be the case if all are being fed the same signal. You should also ensure that the Boosters are fed with similar supply voltages, so that one Booster does not try to power another Booster’s track when the train bridges their join. You must also ensure that the Boosters are wired with the correct polarity where the tracks meet. 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KJ9033-KJ9042 ORRP $29.95 Buy online & collect in store EA NEW LOW PRICE HALF PRICE SAVE UP TO $30 HEATSHRINK PACK NOW 99 1495 $ 95 SAVE $5 99.3% Tin / 0.7% copper Contains 160 lengths of different lead free. 1 & 0.71mm (dia.) sizes in a handy storage case. available. Rosin cored. WH5524 WAS $19.95 200g rolls. WAS $24.95ea. 0.71mm NS3088 1mm NS3094 Comes with programmable electronic building blocks including sound, light and touch. Building blocks are connected in a snap with magnetic Pogo Pins. Users can simply assemble the blocks to make creative gadgets without needing to write any code. Ages 7+. KJ9190 NOW FROM $ LEAD-FREE SOLDER $ Each kit includes a detailed sketchbook with examples and templates to work through. 1495 95 SAVE $5 NEURON INVENTOR KIT MEGA BOARD WITH WI-FI NOW 19 EA 95 $ SAVE $12 99 $ NOW 24 $ NOW 4795 NEW LOW PRICE See our long distance remote relay project at: www.jaycar.com.au/lora-remote LIGHT DUTY HOOK-UP WIRE PACK $ 54 NOW Radio transmitting devices must be used in accordance with Australian Communications & Media Authority guidelines www.acma.gov.au SAVE $8 $ HALF PRICE! PROGRAMMABLE ROBOT CODEY ROCKY ROBOT KIT YOUR CODING COMPANION! Kids can learn coding and AI while they play. Comes in two parts: Codey (detachable mainboard) equipped with more than 10 electronics modules that can be controlled via code. Rocky (car) that lets you take Codey anywhere you want. Support AI and IoT. Cloud storage. Ages 6+. KR9230 WOOD CONSTRUCTION KITS Watch a film, build a marble run or play with your steam train with these quality DIY kits. They actually work too! Ages 14+. Projector - Intermediate 172pcs. 5hr build time. KJ9044 WAS $49.95 NOW $44.95 SAVE $5 Waterwheel - Intermediate 233pcs. 6hr build time. KJ9046 WAS $49.95 NOW $44.95 SAVE $5 Steam Train - Advanced 349pcs. 8hr build time. KJ9045 WAS $69.95 NOW $54.95 SAVE $15 ON SALE 26.12.2019 - 23.01.2020 KJ9046 NOW FROM 4495 $ SAVE UP TO $15 YOUR DESTINATION FOR: Workbench Essentials $ SAVE UP TO 100 ON THESE 3D PRINTERS • 2.8" TOUCHSCREEN PANEL • WI-FI, USB & ETHERNET CONNECT • AUTOMATIC FILAMENT FEEDING • 3.5" TOUCHSCREEN PANEL • WI-FI AND USB CONNECT NOW • 4.3" COLOUR TOUCH SCREEN • DUAL COLOUR PRINTING • SILICON PRINTING PLATFORM NOW 549 NOW 799 $ 1199 $ SAVE $50 FINDER Fully assembled and ready to use. Features slidein build plate, assisted levelling, filament-run-out detection and more. Single non-toxic PLA filament option keeps your creations simple and fun. • Prints up to 140(L) x 140(W) x 140(H)mm TL4220 WAS $599 $ SAVE $100 SAVE $100 ADVENTURER 3 DUAL FILAMENT Control print jobs via the cloud using FlashCloud and/or Polar Cloud. Small but compact structure with no angular design. Ready to use and no levelling printing. Removable, heatable and bendable plate. Built-in camera function. • Prints up to 150(L) x150(W) x150(H)mm TL4256 WAS $899 Allows you to combine colours and materials creating high-quality prints. Oversized bed screws for leveling the print bed. Dual cooling fans. SD memory card slot. • Prints up to 300(L) × 300(W) × 400(H)mm TL4410 WAS $1299 SAVE UP TO $50 SAVE UP TO $50 NOW NOW 299 169 $ $ SAVE $50 SAVE $30 0-15VDC, 0-40A REGULATED LAB POWER SUPPLY 20MHZ USB OSCILLOSCOPE Highly efficient & reliable. Variable output voltage and current limiting. Overload and over temperature protected. LCD backlit display. MP3091 WAS $349 Ultra portable. USB interface plug & play. Automatic setup. Waveforms can be exported as Excel/Word files. Includes 2 probes. QC1929 WAS $199 SAVE UP TO 40% NOW NOW 24 $ $ SAVE 15% 30 DRAWER PARTS CABINET NOW 11 95 5495 95 $ SAVE 40% Ideal for workshop use. 6 rows of 5 drawers, each one measuring 50(W) x 30(H) x 115(D)mm. Free standing or wall mountable. HB6323 WAS $29.95 SAVE 20% 0-15V ANALOGUE BENCH VOLTMETER SOLDER FUME EXTRACTOR Quick and easy to read display of volts. Choose either 3V and 15V scales via separate banana plugs. Zero offset adjustment. QP5040 WAS $19.95 Removes dangerous solder fumes from the work area. Ball bearing high volume fan. ESD safe. TS1580 WAS $69.95 Spare filter pk5 TS1581 $9.95 (sold separately) 40% OFF NOW NOW 795 $ 895 $ SAVE 40% LONG NOSE PLIERS Perfect for adjusting and bending components, picking up dropped nut, etc. Stainless steel. Soft plastic handles. 145mm long. TH1893 WAS $13.95 More ways to pay: NOW 2395 $ SAVE 40% SAVE 40% RATCHET CRIMPING TOOL PLUG REMOVAL TOOL Allows you to insert or unscrew F-Type or BNC connector that has been in-place for a while. Comfortable grip. Carbon steel. 255mm long. TD2000 WAS $14.95 FOR F-TYPE CONNECTORS Strong, heavy duty tool for crimping F-Type CATV connectors onto RG6 or RG59 coax cable. Ideal for cable TV or RF distributions system installers. TH1831 WAS $39.95 NOW 6995 $ SAVE $30 SOLAR POWER METER Optimises solar panel installations by finding optimum locations for the panels. Expressed as Watts per square metre (W/m²), or British thermal units per square foot (BTU/ft²). Includes carry case. QM1582 ORRP $99.95 NON-CONTACT THERMOMETER Professional infrared thermometer allows you to measure high temperatures with safety. 4.5 Digit display. 30:1 distance to spot ratio. Temp range: -50 to 1000°C. QM7226 WAS $249 BACKLIT LCD SAVE $50 CAT III INSULATION TESTER/MULTIMETER Suitable for high voltage insulation testing up to 4 gigaohms at up to 1000V. It also has AC/DC voltage and low resistance multimeter functions. Moulded storage case and holster included. See website for details. QM1493 WAS $249 NOW NOW 199 $ 4000 DISPLAY COUNT 219 $ SAVE $30 55 YOUR DESTINATION FOR: Sight, Sound & Power SAVE UP TO $50 20% OFF THESE ANTENNAS NOW 119 $ NOW 4795 $ SAVE $12 RECEIVER NOW 99 $ SAVE $20 SAVE $50 MINI UHF LOG PERIODIC ANTENNA 2.4GHZ WIRELESS 1080P HDMI AV SENDER Ideal reception solution for areas with medium levels of signal. Can be installed vertically or horizontally with 7.5dB gain. 20 elements. LT3151 WAS $59.95 2 X 15WRMS STEREO AMPLIFIER WITH BLUETOOTH® TECHNOLOGY SENDER Stream music via Bluetooth from your smartphone or tablet for a true wire free experience. RCA & Bluetooth® audio inputs. 12VDC. AA0522 WAS $119 Provides crystal clear digital transmission of 1080p Full HD HDMI signals up to 15m. AR1905 ORRP $169 NOW 5495 $ NOW SAVE $15 95 SAVE $20 SLIMLINE INDOOR UHF/VHF ANTENNA COMPOSITE AV TO USB VIDEO RECORDER Compact with built-in amplifier, ideal for homes or apartments. Receives signals up to 25km from transmitter. LED signal strength meter. Stand or wall mountable. LT3158 WAS $69.95 Easily record composite video signals to a USB flash drive. Great for converting old video cassette or camcorder sources to digital video files. AC1790 WAS $99.95 NOW 79 $ WIRELESS UHF MICROPHONE HEADSET SYSTEM 95 SAVE $20 Compact, lightweight and rechargeable. 10W Amplifier. USB Playback. 12-18hrs talktime. Ideal for trade shows, parties and events. AM4053 WAS $99.95 HALF PRICE DISPLAYPORT TO DISPLAYPORT LEADS Connect a video source to a display device such as a computer monitor. Plug plug. 1.8m or 3.0m available. WQ7450-WQ7454 SAVE $100 NOW 2995 $ NOW SAVE $10 DUAL INPUT 20A DC/DC 19 $ WITH USB 4-CHANNEL FAST BATTERY CHARGER 95 MULTI-STAGE BATTERY CHARGER SAVE $10 Compatible with most types of rechargeable batteries. Charges Li-ion, Ni-MH and Ni-Cd batteries. • 1A USB outlet MB3701 WAS $39.95 Fully automatic operation for keeping batteries charged constantly. Includes reverse polarity protection to keep your battery safe. MB3519 WAS $29.95 This 12.8V 7.5Ah battery features up to 10 times the battery life cycle, faster recharging and reduced number of charges than its lead-acid equivalent. This means it will need replacing less often saving you time and money in the long run. SB2201 See in-store or online for details. UP TO 35% OFF 5495 $ 39 $ 12V MINI DC UNINTERRUPTIBLE POWER SUPPLY Keep your equipment running longer during a power outage. 2.5A output. DC power. Built-in rechargeable Li-ion battery. Integrated smart charger. 3 interchangeable DC connectors supplied. MP5240 WAS $69.95 click & collect JUST 79 $ SAVE $100 Portable battery storage box with multiple connection points and built-in functions. Suits batteries up to 330(W) x217(H)x185(D)mm. Twin output sockets and USB charge sockets. HB8502 WAS $99.95 Fully-enclosed with fold up metal carry handles. Approved 3-wire power cord & US style 2 pin 110 - 115V socket. 240VAC- 115VAC isolated. • 120W - 1000W models available MF1080 - MF1086 NOW 79 $ 95 SAVE $20 NOW FROM 104 $ SAVE 10% NOW NOW SAVE 20% • LONG LIFE • RECHARGE FASTER NOW 199 $ ISOLATED STEPDOWN TRANSFORMERS BATTERY BOX WITH VOLTMETER & USB NBN REPLACEMENT BATTERY - LITHIUM DEEP CYCLE NOW Keeps your 12V auxiliary battery topped up from either main engine power when driving (either 12V or 24V systems), or solar when available. Fully automatic. Compatible with all types of Leadacid batteries (Gel, AGM etc) plus Lithium LiFePO4. MB3683 WAS $299 6/12V LEAD ACID BATTERY CHARGER 800MA NEW LOW PRICE 56 995 $ 79 $ NOW FROM 95 4995 $ EA ALL-IN-1 BATTERY TESTER SAVE $20 SAVE UP TO 35% DESKTOP POWER SUPPLIES Ideal for use with various types of consumer electronic devices, telecommunication devices, office facilitites, industrial equipment etc. LED indicator. 12V, 19V & 24V available. MP3242 - MP3248 NOW 30M POWER CABLE 15A twin core for auto and marine applications. WH3077 WAS $69.95 Buy online & collect in store 1395 $ 40% OFF ON SALE 26.12.2019 - 23.01.2020 Test all types of batteries including standard AA/ AAA/C/D/9V batteries, button cells and lithium batteries such as those used in digital cameras. QP2253 WAS $23.95 Note: Batteries not included YOUR DESTINATION FOR: IT & Security SAVE UP TO $100 NOW $ SAVE $7 Extend your Ethernet network connection over already installed power connections up to 300m away. Speeds up to 500Mbps allow HD streaming, fast file transfer & more. YN8355 WAS $119 10% OFF SMART LOCKS DUAL BAND GENERATE CODES ON A SMARTPHONE NOW 199 $ Unlock by simply swiping your finger or by using an app on your Smartphone. Up to 1000 unlock records. Over 2800 continuous unlocks. Charge via USB. IPX7 weatherproof rated. LA5140 WAS $79.95 6995 $ SAVE $10 LUGGAGE PADLOCK WITH FINGERPRINT SCANNER Unlock this modern padlock using your fingerprint. Built-in rechargeable battery and conveniently charged from USB (cable included). IP66 waterproof. LA5129 WAS $79.95 In the Trade? POE NETWORK SWITCHES Featuring the latest 802.11AC wireless standards for solid streaming, fast gaming, and interrupt-free networking. Up to 1200Mbps. Dual Band Wi-Fi. One-Touch WPS connection. YN8392 WAS $99.95 Reduces the need for mains power at devices such as IP cameras, routers etc to operate. Ultra-fast data transfer. 5-Port 10/100Mbps YN8074 WAS $119 NOW $79 SAVE $40 10-Port 10/100/1000Mbps YN8049 WAS $229 NOW $179 SAVE $50 NOW Ultra-easy pairing setup. 2-way audio communication - so it can be used for access control functions. IR LEDs for night time use. Includes USB mains power adaptor and USB charging cable. QC3849 WAS $69.95 1080P WI-FI IP CAMERA WITH SECURITY ALARM NOW NOW 5495 $ SAVE $15 SAVE $30 Can work stand-alone to record audio and video or expanded with sensors (sold separately) to turn it into a security system. QC3870 WAS $129 ALSO AVAILABLE: PIR Sensor QC3876 WAS $29.95 NOW $19.95 SAVE $10 Panic Button QC3872 WAS $19.95 NOW $11.95 SAVE $8 Reed Sensor QC3874 WAS $19.95 NOW $11.95 SAVE $8 WI-FI RFID ACCESS KEYPAD 59 $ 99 $ 720P WI-FI IP CAMERA WITH INFRARED LEDS 95 SAVE $10 RECHARGEABLE SOLAR SENSOR LIGHT Act as a deterrent against thieves with its security camera appearance. Built-in rechargeable battery. PIR movement sensor. SL3239 WAS $69.95 STORES UP TO 10 FINGERPRINTS NOW SAVE UP TO $50 20% OFF WI-FI IP CAMERAS SAVE $10 BLUETOOTH® CONTROLLED PADLOCK WITH FINGERPRINT SCANNER 95 AC1200 WI-FI ROUTER Trace cables even when they are in a bundle or hidden. Also checks telephone line polarity and status i.e ring/busy/idle. XC5083 WAS $99.95 SMART LOCK DEADBOLT KIT WITH BLUETOOTH® TECHNOLOGY 79 $ SAVE $20 NETWORK CABLE TRACER SAVE $30 NOW FROM 79 95 SAVE $30 $ 6995 NOW 69 $ NOW $ Ideal for IT, or phone systems installations, PA, sound reinforcement etc. 6U to 12U in Swing or Fixed frame. See in-store or online for full range. 6U Flat Packed HB5170 WAS $179 NOW $139 SAVE $40 6U Assembled HB5171 WAS $199 NOW $149 SAVE $50 12U Flat Packed HB5174 WAS $239 NOW $169 SAVE $70 6U Swing Frame HB5180 WAS $269 NOW $199 SAVE $70 12U Swing Frame HB5182 WAS $349 NOW $249 SAVE $100 POWERLINE ETHERNET EXTENDER Reads most memory cards in use today, USB cable included. See website for details. XC4926 WAS $19.95 NOW 19" RACK MOUNT ENCLOSURES SAVE $20 ALL-IN-1 USB 2.0 CARD READER STORES UP TO 15 FINGERPRINTS UP SAVE TO $100 99 95 Replace traditional door locks and enable users to gain access by using an App via Bluetooth® on their smartphone or tablet, or a unique passcode entered on the keypad. Long battery life. Fits doors 32-48mm thick. LA5095 WAS $229 139 $ NOW 12 $ NOW FROM Control doors remotely with your Smartphone via free app. Used as a standalone access card reader or controlled by an external access controller. Includes a timer function allowing people to access for a temporary period of a time. 12VDC. LA5358 WAS $249 • IP65 RATED • FREE APP NOW 199 $ SAVE $50 NOW 2995 $ NOW 49 $ 95 SAVE $10 THEFT PREVENTION KIT DUMMY CAMERA Includes 2 x dome cameras, 2 x bullet cameras and a CCTV security window sticker to warn thieves off. LA5336 WAS $59.95 SAVE $5 PRESSURE ACTIVATED MAT ALARM WITH SIREN & STROBE Easy to install, slide the pressure sensitive pad under your door mat to be notified of guests arrival or to surprise and deter wouldbe intruders. Loud 120dB+ siren. Requires 1 x 9V battery. LA5218 WAS $34.95 NOW 2495 $ SAVE $10 WIRELESS DRIVEWAY & ENTRY PIR ALERT KIT Triggers an alarm when movement is detected in a driveway or entryway. Detects movement up to 6m range. Transmitter & receiver requires 3 x AA batteries each. IP44 rated. LA5178 WAS $34.95 57 YOUR DESTINATION FOR: Outdoor/In-Car Accessories SAVE UP TO $80 JUST 699 $ NOW FROM 169 $ NEW LOW PRICE 2KW SINE WAVE INVERTER GENERATOR SAVE UP TO $80 Includes a 4-stroke petrol engine, a low voltage electrical generator, and a pure sine wave inverter to give you clean mains power. Parallel stacking option. Rugged and reliable with integrated carry handle. MG4508 MPPT SOLAR CHARGE CONTROLLERS High efficiency and reliable. Detects voltage inputs automatically and can be left on permanently. LCD backlit display. 12/24V 30A MP3735 WAS $249 NOW $169 SAVE $80 12/24/36/48V 50A MP3731 WAS $349 NOW $299 SAVE $50 15,600MAH POWER BANK WITH USB TYPE-C NOW Huge capacity with 3 x USB ports to stop your gadgets going flat. Charge via the 2.4A USB type-A sockets or use the USB type-C socket for fast 3A charging. MB3806 WAS $59.95 5995 $ SAVE $40 NOW 4995 $ SAVE $10 2 FOR 34 $ SOLAR LED LIGHT KIT Compact, lightweight perfect for camping. Includes 3.5W monocrystalline solar panel, 6V 4AH SLA battery, 2 x built-in and 3 x individually switched LED lights on leads, mains, in-car & solar chargers included. MB3699 WAS $99.95 • 240VAC • STURDY FRAME NOW FROM 1995 90 $ SAVE $5 5W LED WORK LIGHT Amazing light output. Low heat, fold-out stand. High/low light modes. Includes 6 x AA batteries. SL2869 $19.95ea. SAVE UP TO $20 10 & 30W SLIMLINE LED WORK LIGHTS Provides plenty of ultra-white bright light and uses far less power than traditional counterparts. IP65 weatherproof rated. SL2866/SL2867 SAVE UP TO $80 ON THESE UHF RADIOS 0.5W UHF RECHARGEABLE 3W UHF TRADIES PACK NOW 3W UHF RECHARGEABLE IP67 RATED 249 $ 80 Channel. Up to 10km range. Floating, submersible up to 1m. CTCSS. Backlit LCD. Charger included. DC1074 WAS $129 SAVE $80 OVER 20% OFF NOW 4995 6995 $ CAR AMPLIFIER WIRING KITS 4 DOOR POWER LOCK KIT NOW FROM NOW A complete 8G wiring kit for installing an amplifier into your vehicle. See website or in-store for kit inclusions. AA0442 WAS $64.95 39 $ SAVE 30% 4-CHANNEL WIRELESS REMOTE CONTROL RELAY Control up to 4 different devices with a single controller and key fob remote. Relay contacts are rated 5A at 14VDC. Transmission distance: 30m typical (300m+ max line of sight). LR8824 WAS $99.95 click & collect SAVE 25% SAVE 20% Diagnose your cars problem. Plugs into OBD-II port and transmits speed, RPM, fuel consumption, etc via Bluetooth to your Smartphone. PP2145 WAS $69.95 NOW 99 SAVE $30 2995 4995 SAVE 25% NOW $ $ $ ENGINE CODE READER IP67 RATED NOW NOW $ 58 IN-STORE ONLY PR SAVE $40 80 Channel. Up to 5km range. CTCSS and more. Rechargeable batteries and dual charging cradle included. Sold as a pair. DC1027 ORRP $109 80 Channel. Rechargeable batteries. Includes: 2 x 3W waterproof floating UHF radios with CTCSS, up to 10km range (line-of-sight), 2 x speaker/ mics, VOX headset & 12V car chargers. DC1076 WAS $329 NOW 69 $ 1495 95 $ SAVE 20% IN-CAR LAPTOP POWER SUPPLIES Keep your laptop charged on the road. Models to suit most computers on the market. Check website for compatibility. 90W MP3338 WAS $49.95 NOW $39.95 SAVE $10 150W MP3472 WAS $74.95 NOW $59.95 SAVE $15 Buy online & collect in store Low cost central locking kit, so when you unlock the drivers door the other three doors automatically unlock. LR8812 WAS $39.95 SAVE 35% AUTOMOTIVE FUSE PACK 120 standard size automotive fuses housed in a 6 compartment storage box. 20 x 5A, 10A, 15A, 20A, 25A & 30A fuses included. SF2142 WAS $23.95 ON SALE 26.12.2019 - 23.01.2020 CLEARANCE ORDER ONLINE, COLLECT IN STORE Listed below are a number of discontinued (but still good) items that we can no longer afford to hold stock. Please ring your local store or search our website to check stock. At these prices we won't be able to transfer from store to store. STOCK IS LIMITED. ACT NOW TO AVOID DISAPPOINTMENT. Sorry NO RAINCHECKS. SECURITY AUDIO & VISUAL Cat. No WAS NOW SAVE Cat. No WAS NOW SAVE 2 Way DisplayPort Splitter AC1755 $49.95 $34.95 $15 1080p AHD Pan-Tilt-Zoom Bullet Camera QC8676 $299 $199 $100 4 Input HDMI 2.0 Switcher with Remote Control AC1745 $59.95 $44.95 $15 1080p Wi-Fi Dash Camera with GPS QV3865 $189 $159 $30 60W Speaker Attenuator Wall Plate AC1751 $34.95 $21.95 $13 1080p Wi-Fi IP Camera with Recording and IR QC3843 $99 $84 $15 100W Speaker Attenuator Wallplate AC1665 $49.95 $34.95 $15 1296p Event Camera with GPS for Bikes QV3870 $99 $69 Analogue Audio to Digital MP3 Converter GE4103 $39.95 $29.95 $10 12V Infrared Flush Mount Reversing Camera QC3534 $99.95 $79.95 Bidirectional IR Extender over Cat5e - 100m AR1809 $59.95 $49.95 $10 700TVL Bullet Camera with IR QC8653 $79.95 $59.95 $20 Digital Indoor/Outdoor TV Antenna LT3137 $10 720p AHD Dome Camera with IR QC8639 $99.95 $69.95 $30 $79.95 $69.95 $30 $20 Dual Laser & LED Light Show with DMX Control SL3410 $80 AHD to HDMI Converter AC1778 $99.95 $79.95 $20 HDMI to AV Composite Converter AC1720 $99.95 $79.95 $20 Car Boot / Hatch Release LR8834 $10 LED Projector with HDMI & USB AP4003 $50 Ceiling Mount Alarm with Remote Control LA5215 $34.95 $29.95 $5 Slimline LCD Wall Bracket 42"- 80" CW2865 $44.95 $34.95 $10 Wireless PIR Solar Light Sensor to suit LA-5592 Controller LA5599 $99.95 $49.95 $50 Wireless Infrared Headphones Twin Pack AA2037 $99.95 $69.95 $30 Wireless Gateway Home Automation Controller LA5570 World Band AM/FM/SW/LW/AIR PLL Radio with SSB AR1945 $50 Wireless Home Automation Main Controller Economy LA5592 $249 $179 $199 $169 $129 $149 IT/COMMS Cat. No $39.95 $29.95 $189 $99 $99.95 $49.95 $90 $50 POWER WAS NOW SAVE Cat. No WAS NOW SAVE 5/5.8GHz 9dBi Wireless Networking Antenna AR3288 $39.95 $29.95 $10 10,000mAh Quick Charge™ Dual USB Power Bank MB3725 $59.95 $39.95 $20 5m SMA Coaxial Cable WC7804 $44.95 $34.95 $10 2 Outlet Power Garden Stake MS4097 $19.95 $12.95 $7 5W UHF CB Radio Tradies Pack DC1069 $449 $349 $100 20m Heavy Duty Mains Extension Lead PS4200 $34.95 $29.95 $5 5W VHF MARINE RADIO TRANSCEIVER DC1096 $134 $119 $15 3 x Oslon Osram LED Torch ST3487 $9.95 $4.95 $5 AC600 Outdoor Wi-Fi Extender with POE YN8349 $119 $79 $40 4 Port USB Mains Power Adaptor MP3446 $29.95 $24.95 $5 Advanced 2W 80 Channel UHF Transceiver with CTCSS DC1049 $69.95 $59.95 $10 4,000mAh Elegant Powerbank with LED Torch MB3716 $19.95 $14.95 $5 PoE Power Splitter YN8414 $14.95 65W Desktop Power Supply MP3249 $59.95 $39.95 $20 $10 $9.95 $5 Telephone Isolation On Hold Kit YT6070 $29.95 $19.95 $10 8-Channel Wireless Light Controller for Vehicles MS6210 $69.95 $59.95 UHF 5dBi Fibreglass Antenna with 5m Cable DC3078 $99.95 $79.95 $20 Air Vent Phone Cradle with Wireless Qi Charging HS9058 $29.95 $24.95 $5 USB 3.0 Type-C Hub and Card Reader XC4308 $79.95 $49.95 $30 Dual USB Wall Charger with LED Night Light MP3429 $19.95 $14.95 $5 USB 3.0 Type C Multi Card Reader XC4751 $39.95 $24.95 $15 Lantern LED COB 280 Lumen with Red LED Flasher ST3426 $14.95 $9.95 $5 USB 3.0 Type-C to DisplayPort Converter XC4971 $39.95 $24.95 $15 Mains and USB Power Hub with Smartphone Cradle MS4103 $19.95 $9.95 $10 VGA to Composite and S-Video Converter XC4871 $39.95 $34.95 $5 Portable RCD with 4 x 15A Sockets to 15A Mains Plug MS4047 $99.95 $89.95 $10 HARDCORE Cat. No OUTDOORS WAS NOW SAVE Cat. No WAS NOW SAVE 3000A True RMS AC High Current Clamp Meter QM1568 $69.95 $49.95 $20 1:16 RC Drift Car GT4248 $39.95 $34.95 $5 4 Wheel Drive Motor Chassis Robotics Kit KR3162 $20 1:58 RC Boat Twin Pack with Inflatable Pool GT3771 $79.95 $69.95 $10 $10 $49.95 $29.95 Arduino Compatible ESP-13 Wifi Shield XC4614 $39.95 $34.95 $5 6 in 1 Survival Torch with Storage compartment ST3133 $19.95 Arduino Compatible GPS Receiver Module XC3712 $49.95 $39.95 $10 600 Lumen Rechargeable LED Spotlight ST3316 $79.95 $64.95 $15 Digital Tachometer QM1448 $79.95 $59.95 $20 Alcohol Breath Tester QM7304 $54.95 $34.95 $20 Economy Non-Contact Thermometer QM7215 $59.95 $49.95 $10 Bluetooth® Heart Rate Monitor with App XC0392 $19.95 $9.95 $10 Inspection Camera with Record Detachable Wireless Screen QC8712 $80 Chariot RC Battle Car GT4250 $79.95 $69.95 $10 $40 $299 $219 $9.95 LED Dot Matrix Display for Arduino - Red XC4621 $34.95 $24.95 $10 Fuel Cell Breathalyser with LED Display QM7308 Non-Contact Thermometer with Dual Laser Targeting QM7221 $30 Motion Drone with Gravity Sensor GT4134 $39.95 $34.95 $5 Non Contact Body Thermometer with Smartphone App QM7201 $49.95 $39.95 $10 Portable 7.5L 12V Cooler / Warmer GH1366 $89.95 $49.95 $40 Remote Control Power Boat GT3773 $79.95 $69.95 $10 PC Programmable Line Tracer Kit KJ8906 $139 $109 $44.95 $39.95 $5 Pro Sound Level Meter with Calibrator QM1592 $379 $279 $100 Raspberry Pi Media Player Kit XC9012 $169 $139 $30 More ways to pay: $169 $129 59 UP TO 50% OFF NOW 19 $ 12V 1.5W SOLAR TRICKLE CHARGER 95 SAVE $10 Perfect for keeping your boat, car, tractor, motorcycle or any 12V battery topped up. Trickle charge to compensate for natural battery discharge. Dash/Windshield mount (suction cups supplied). MB3504 WAS $29.95 Note: PCB not included. 44 $ 95 1995 $ PLUG & PLAY SAVE $10 2.5" USB 3.0 SATA HDD ENCLOSURE Protect and transport your valuable data. Accommodates 2.5” HDD (up to 3TB capacity). Ultra fast data transfer speeds up to 80Mbps. Easy installation. XC4686 WAS $29.95 This little unit detects hidden wired and wireless DESKTOP PCB HOLDER SAVE $15 cameras through Suitable for working with different the units lens finder. 5 PORT USB shaped components, CHARGING STATION connectors, etc. Hold NOW Comes with a set of earphones. QC3506 Charge up to 5 USB devices at the PCBs of up to 200 x WAS $99.95 same time. Includes 6 dividers and 140mm. Adjustable power supply. WC7766 angle. TH1980 SAVE $5 SAVE WAS $59.95 WAS $19.95 1495 300W HOT AIR REWORK STATION Provides more uniform heat transfer making SMD chip removal safe and effective. 100-500°C temperature range • Pushbutton / digital display • 160(L) x 113(W) x 123(D)mm TS1645 WAS $149 NOW ESD SAFE SOLDER/DESOLDER REWORK STATION 2745 $ HALF PRICE 99 $ 720P WIRELESS RECEIVER AND CAMERA KIT NOW 5995 $ $40 Add a wireless camera to any existing 720p, 1080p or 3MP AHD compatible DVR. Up to 100m wireless range. IR night vision. QC8663 ORRP $199 QUICK HEAT UP Complete solder/desolder station for professional and hobbyist use. 60W Soldering pencil and 300W rework blower. Dual digital display. Adjustable temperature. Quick heat-up. TS1648 WAS $249 NOW 119 199 $ $ SAVE $30 IP66 RATED SAVE $100 BOASTS A POWERFUL 2.4A PER PORT $ NOW NOW CAMERA DETECTOR SAVE UP TO $50 Converts your digital signal into analogue (RCA) stereo audio. Accepts either TOSLINK (optical) or digital coaxial. AC1715 WAS $54.95 ALSO AVAILABLE Analogue to Digital Audio Converter AC1716 WAS $59.95 NOW $29.95 SAVE $30 NOW BATTERY POWERED NOW DIGITAL TO ANALOGUE AUDIO CONVERTER SAVE $50 2 FOR 4990 $ SAVE 35% 1M WATERPROOF LED FLEXIBLE STRIP LIGHTS Fully encapsulated & versatile. Can be daisy chained for longer length. Submersible up to 1m. 60LEDs. 12VDC ZD0579 RRP $39.95 EA TERMS AND CONDITIONS: REWARDS / NERD PERKS CARD HOLDERS FREE GIFT, % SAVING DEALS, DOUBLE POINTS & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / membership at time of purchase. Refer to website for Rewards / membership T&Cs. IN-STORE ONLY refers to company owned stores and not available to Resellers. Page 6: Multibuys: 2 x 5W LED Work Light $34.90 applies to 2 x SL2869. Page 7: Clearance. In-store only promotion, not available to Resellers. No rainchecks. Page 8: Multibuys: 2 x 1m LED Flexible Strip Lights for $49.90 applies to 2 x ZD0579. For your nearest store & opening hours: 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide Aspley 1322 Gympie Rd Aspley,QLD 4034 PH: (07) 3863 0099 HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer were confirmed at the time of print but delays sometimes occur. Please ring your local store to check stock details. Occasionally there are discontinued items advertised on a special / lower price in this promotional flyer that has limited to nil stock in certain stores, including Jaycar Authorised Resellers. These stores may not have stock of these items and can not order or transfer stock. Savings off Original RRP. Prices and special offers are valid from catalogue sale 26.12.2019 - 23.01.2020. PRODUCT SHOWCASE 20% Off WiFi Boards at Jaycar As part of their post-Christmas sale, Jaycar stores are offering a 20% saving on a range of their popular XC3802 WiFi Boards until 23 January. Included in the sale are: The ESP8266 WiFi Mini Mainboard <at> $19.95 (was $24.95) The ESP32 Mainboard with WiFi and Bluetooth <at> $31.95 (was $39.95) The Arduino-compatible UNO XC3800 Board with WiFi <at> $31.95 (was $39.95) and XC4411 The Arduino + WiFi Megaboard with ESP8266 chip <at> $47.95 (was $59.95). And if you’re into long range data XC4421 communications which doesn’t need a mobile phone network, they also have a big saving on the LoRa Wireless Communication shield Contact: for $49.95 (was $69.95). Jaycar Electronics (all stores) See the long distance (H/O) 320 Victoria Rd Rydalmere, NSW 2116 remote relay project at Tel: 1800 022 888 www.jaycar.com.au/ Web: www.jaycar.com.au lora-remote RayMing Technology: much more than a PCB maker! RayMing Technology is an Electronics Manufacturing Service (EMS) provider, specifically, offering PCB manufacturing and PCB assembly. EMS is a specialised form of Contract Manufacturing (CM). EMS companies allow equipment manufacturers to improve their efficiency, allowing them to focus more on Research and Development (R&D). RayMing Technology has more than 10 years of experience providing EMS services. EMS services are not only used to make consumer products, but also medical products, industrial products as well as products for defence, aerospace and telecommunications. Electronic manufac- Contact: turing is rapidly and RayMing Technology constantly evolving. You 12#, 2nd Fu’an Industrial City, Dayang Developneed a flexible partner ment Zone, Fuyong St, Bao’an, Shenzhen, China to keep pace with rapid Tel: (0011) [86] 0755 2734 8087 changes in technology. Web: www.raypcb.com Johanson Dielectrics Advanced Motor EMI Filters Strict electromagnetic compatibility (EMC) requirements and noisier electronic environments are threatening to increase the cost of filtering required for brushed DC motors. These filters must reject all forms of noise and also handle high DC currents, without being costly. Johanson Dielectrics advanced monolithic EMI filters meet these requirements. Traditional common-mode filtering approaches include lowpass filters comprised of capacitors and/or inductors that attenuate signals above the cutoff frequency. The traditional options are two-capacitor differential filters, three-capacitor filters (one X-cap and two Y-caps), feed-through filters, common-mode chokes, LC filters, or combinations of these. These days, the lower-cost options like two-capacitor or threecapacitor filters can no longer meet all EMC requirements. Other solutions like common-mode chokes offer good rejection over a wide frequency range, but are expensive when they must carry several amps. Monolithic EMI filters provide significantly more RFI suppression than a common-mode choke in a much smaller package, and they are not affected by the direct current requirement, because they connect between the lines and ground. These filters from Johanson Dielectrics combine two balanced shunt capacitors in a single package, with mutual inductance cancellation and a shielding effect. The key to their performance is the very low inductance and matched impedances. Monolithic EMI filters can be effective from 50kHz to 6GHz, filtering both common-mode and differential-mode noise. Sometimes EMI filters can interfere with PWM-based motor control, so the right filter must be chosen for the job. Johanson Dielectrics provides an on-line tool that simplifies filter choice. They are also working on integrated solutions Contact: that mount direct- Johanson Dielectrics ly on the housing, 4001 Calle Tecate, Camarillo, CA 93012, USA without the need Tel: (0011) [1] 805 389 1166 Web: www.johansondielectrics.com for a PCB. Unleash your creativity and simplify your development while saving money… The customisable Curiosity Nano Development Platform includes costeffective Curiosity Nano boards and the versatile Curiosity Nano Base for Click boards to provide you with an excellent starting point for creating innovative designs. Curiosity Nano boards feature a variety of PIC and siliconchip.com.au AVR MCUs, allowing you to easily evaluate different architectures for your design. They also offer full programming and debugging capabilities to support you throughout your development process. Each Curiosity Nano board is compatible with the Curiosity Nano Base for Click boards. This base Australia’s electronics magazine includes a socket that fits all Curiosity Nano boards plus three mikroBUS sockets that will enable you to effortlessly expand your design with sensors, connectivity modules and more. For more details visit the hotlink: Contact: Microchip (Aust/NZ) Tel: (02) 9868 6733 Website: http://siliconchip.com.au/link/aay5 January 2020  61 SERVICEMAN'S LOG When things go wrong – really wrong Dave Thompson Sometimes a job comes along which seems like it’ll be straightforward, but really isn’t. This can happen even if that job is well within your field of expertise. Here’s one story where everything and anything seemed to go wrong. If you’ve read my previous columns, you will know that I started out servicing planes for Air New Zealand and then later, moved on to computer repair, which mainly involves swapping modules and fiddling with software. While I have repaired plenty of other electronics, especially audio gear (as I’m a bit of a muso), I’m still essentially an amateur serviceman in fields outside of those two. While I have repaired (and sometimes failed to repair) everything from an abacus to a Zimmer frame, my main focus for the past 25 years has been computers, with the odd curly job fired my way. As something of a keen amateur, I am not shackled too tightly to the conventions (and regulations) that real servicemen are legally and technically required to abide by. That’s not to say I’m a cowboy; far from it. With all the work I do, I always strive to adhere to the relevant standards and codes of practice. After all, they have typically been put in place to ensure safety and integrity. Before doing anything unfamiliar, I do my best to research the task ahead. For example, I wouldn’t just decide one day to re-wire my house. I could probably do it successfully, but I wouldn’t take the risk. All the re-wiring work I’ve done has been under the supervision of a 62 Silicon Chip qualified electrician who has then inspected and signed off on it. It would be madness just to pile in and do this type of work without some oversight by a professional, yet plenty of DIYers do. In many cases, no harm ensues, but if it all goes wrong, the house burns down, and maybe someone along with it; an outcome I find unthinkable. But sometimes a job comes along where despite being well qualified for it, it all goes wrong anyway. I think we have all had Australia’s electronics magazine those jobs where, in retrospect, they seemed doomed from the start; no matter how hard you try to dig yourself out of the hole you’re in, the hole just keeps getting deeper! While these jobs are thankfully few and far between (for me at least!), I’ve had a few over the years, and the following tale is one of those cases. This happened many years ago and did more to educate me on obtuse points of consumer law, and just how far some companies will go, than anything before or since. I’ll set the scene, and you can decide siliconchip.com.au Items Covered This Month • • • • The trials and tribulations of fine print Sony 8FC-100W digital clock radio repair Daikin aircon repair USB flash drive repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz whether or not the chips should have fallen the way they did. It all started so innocently It began when I received an urgent call from a client who ran a high-profile car sales yard in town. I’d been looking after their office computers for a year, after taking over that task from the retired tech who’d set up their offices. Due to their importance as a client, I always tried to do any servicing or maintenance as promptly as possible. They had half a dozen sales staff, a receptionist and the owners on-site, all of whom had their own desktop-style workstation. These were all networked together in a semi-typical ‘star’ configuration, where each computer runs its own version of Windows and grabs important business files via mapped drives from a designated central server machine. This server should ideally be a purpose-designed unit with redundant power supplies, RAID-configured, hotswappable hard drives and a dedicated server operating system such as Linux or Windows Small Business Server. But in the real world, such machines can be pretty expensive to buy and maintain, so many small businesses just use a standard PC in a server role instead. This car yard was no different; their server was one of the owner’s machines, set up with the necessary drive and file shares. This made some sense, as it was the most powerful computer in the office. As such, all the scanning, printing, photo-processing and faxing jobs were done on or through this machine over the network. This type of configuration usually works well and as long as nothing particularly challenging happens, and siliconchip.com.au backups are being kept, disaster recovery isn’t too much of a problem, even if the server goes down. The backedup data can simply be copied to and shared on any of the other machines, networked machines’ mapped drives adjusted and life goes on. On that fateful morning, I got a call that the owner’s machine wouldn’t start and they were dead in the water. Could I come and take a look? Fortunately, they were only a few blocks from my then-workshop, and they were visibly relieved when I turned up within around ten minutes. As it was still early, there weren’t many tyre-kickers around, and thankfully there wasn’t much for the staff to do but sit around drinking coffee and talking cars (or rubbish!), so I had some breathing space. As described over the phone, the machine wouldn’t fire up at all, and it looked for all intents and purposes to be completely dead. In situations like this, I usually take the machine back to my workshop where I can properly troubleshoot it, and that’s what I did. On the bench, it appeared Christchurch’s notoriously rubbish postquake power supply had claimed another victim. The power supply was dead and so was the motherboard, as I discovered when I tried a Australia’s electronics magazine known-good power supply in place of the old one. I’d been advising these guys since they became my client to get a UPS (uninterruptible power supply) but as everything had been fine – until now – they (like many others) assumed their office was the exception rather than the rule. At least the hard drive appeared to be OK, so no data had been lost. I called and told them the bad news; they’d need a new computer. I also talked them into a UPS. In the meantime, they could think about insurance claims, but I suggested that I’d better build a new box straight away to get them going. They were fine with this, so I proceeded to strip the old box down; we could at least reuse the case. As I pulled it apart, I noticed a PCI expansion card that had a parallel port-style plug on the riser. It certainly looked like a typical parallel port, and this is what their large office printer/ scanner/copier/fax had been connected to. As many modern motherboards don’t sport a parallel port, I assumed at the time that it was a simple expansion card to allow them to connect this large printer/copier. Replacing the motherboard, CPU and RAM was unremarkable and only took a few hours. I also replaced the hard drive; if the machine had gotten January 2020  63 a power spike bad enough to fry the motherboard, it could have done some subtle damage to the drive too. Copying their data back and regenerating the shares was easy; the problems started when I took the machine back and reconnected their printer. With the vast majority of printers, installing them is a breeze. As long as you know the make and model number, drivers and utilities that support the printer are usually downloadable from the manufacturer’s web site. But I couldn’t find any mention of this printer at all on their site, and Windows didn’t pick it up as it does with many other printers. When I pressed the business owner for details on the printer, he informed me that it was a leased machine and not to worry too much about it as they’d get a technician from the lease company to come out to re-install it. Frankly, this was a relief, as I was out of ideas as to how to get this thing working. I tidied up the rest of what I could and they were back up and running that afternoon, bar the printer. As the manufacturer is one of the biggest names in printers, scanners, cameras and other consumer electronics, I had no doubt their guy would have the car yard up and selling old clunkers to the unsuspecting public before too long. The plot starts to curdle And that’s where things stood until the following morning, when I got another call from the car yard. Apparently, there was a problem with me messing with the printer, and the technician was getting all prickly about it and berating the owner, threatening all manner of ramifications. Technically, the car yard leased the printer; it was owned by the manufacturer, and the lease agreement states that nobody can touch the printer but the company’s representatives. That’s all fine, but apparently (and unbeknownst to me), they considered the expansion card to be part of the printer! This put the car yard owner in breach of his lease terms, and the manufacturer’s reps were now throwing shade on both of us because of it. I advised the owner that if he’d told me that the machine was leased, I wouldn’t have touched the thing with a barge pole, yet he didn’t, so I did. 64 Silicon Chip As I hadn’t yet been paid for the job, this caused me some stress, as did the vague threats made via the car yard owner from the printer people about my legal liability. That day certainly turned out very differently than I thought it would! And things just kept getting better; that afternoon, with the lease technician spending hours on-site trying to get the printer going with no luck, the car yard owner again called to tell me that the technician had taken the expansion card out of the machine and had supposedly found it physically damaged. Apparently, this explained why the printer wasn’t working. As I had been the one to swap it out, they reckoned that I must have caused the damage, and therefore was liable for both the card and any time this other guy spent trying to get it going. I’ve installed more expansion cards than most blokes have had meat pies, so I thought it very unlikely that I’d done any damage to it, especially without realising it. When I asked what sort of damage they found, I was told that there was an obvious mark on it, where it looked like a screwdriver had slipped and had gouged a track on the board. According to the tech, this was why the card wasn’t working and the printer not operational. I certainly don’t remember doing anything of the sort. When I asked how much the card was to replace I almost fell over; they quoted $4,500, and reckoned I was fortunate as this would be for a second-hand card; new ones were double that price! It turns out the printer was a deprecated model, and new cards were Australia’s electronics magazine no longer available. Also, as this one was the only card left and had to be imported from Australia, I would be liable for freight charges, a temporary printer rental for the time it would take to get the card as well as the technician’s fees to install it. All this certainly got me riled up; for a start, how could a PCI parallel port expansion card possibly cost that much, no matter how special it is? It would be cheaper if it was made out of pure platinum! And I’m pretty sure I didn’t stab this one with a screwdriver; if it was damaged, how do I know it wasn’t the other guy taking it out who did it? I called the lease company and asked to be put in touch with someone who could clear this up. I ended up talking to the New Zealand manager and he was as toxic as they come, threatening me with legal action. Dealing with them was thoroughly unpleasant, and my feeling is they went out of their way to make things difficult. I felt like I needed a shower after hanging up the phone. I wasn’t about to roll over, so I asked to see the damaged card myself and to at least have the right of repair. A cut track isn’t insurmountable, and if I couldn’t fix it, perhaps I could find someone else to do it. I was confident the card could be totally rebuilt for way less than four-and-a-half large! They reluctantly agreed and told me I could pick it up from the car yard the following day. I arrived to find the staff passing it around the office, trying to spot the supposed damage. I couldn’t see anything on it either, no matter how closely I looked (and I looked very closely!). siliconchip.com.au When I mentioned potential damage due to static, the yard owner commented that a courier had delivered it just as it was. There was no packaging, static or otherwise, with just a courier sticker protecting it. At this point, I realised that repair was not going to be feasible, and was reasonably sure the lease company had deliberately sent it like this. When I raised this point with them later, they confirmed it by stating that after talking with their legal team (!) the card was considered unserviceable as soon as I’d removed it and as such, they wouldn’t accept a repaired card anyway. They threatened to recover the money from me or the car yard, as we had jointly violated the terms of their lease. Nice people, and I’ll certainly never buy one of their products, no matter how good they are supposed to be. The owner goes to bat for me When all seemed lost, I found an ally in the car yard owner. He was more than happy with my service record and was appalled at how he and I were being treated and bullied by these people. After wading through the original documentation for the printer lease, he discovered that under the terms of the contract, the printer should have been regularly upgraded. Their printer had been due for that upgrade almost 18 months before all this happened. The leasing company had neglected to do this, essentially dumping this older model on the car yard. When the owner confronted them with this information, they immediately started back-pedalling and apologising and offered to install the very latest machine with free upgrades and anything else they could chuck in to sweeten the deal. The yard owner also stipulated that they also drop any claims against me and this they did, claiming that they had been talking about it and had already decided to upgrade the printer due to the cost and hassles of getting that second-hand PCI card for such an old machine. While that part still didn’t ring true, I was past caring and was hugely relieved. That sort of money is a major deal to a micro-business like mine, and I didn’t appreciate all the drama associated with it either. 66 Silicon Chip While all this was all going down, I’d spent much of my time panicking, studying points of law and even discussing it with a lawyer friend of mine, who fortunately hates corporate bullying and was happy to offer his advice for nothing. If push came to shove, I might well have been liable for those costs, especially if the lease company and car yard had both turned their guns on me; even though I’d only done as instructed, and had no way of knowing that I was doing anything wrong. Thankfully it all worked out, but you can be sure that these days, I check the lease status of similar hardware before I got anywhere near it. Sony 8FC-100 flip-card clock radio repair J. W., of Hillarys, WA is a regular contributor to Serviceman’s Log. This time, he repaired a clock radio which is as much electro-mechanical as it is electronic… A friend rang and asked if I could have a look at his broken clock radio. I told him that I would see what I could do. When he dropped it off, I was a bit nonplussed as it was much older than I thought. It’s the type of mechanical clock which has the numbers on cards which flip over under the control of a synchronous motor and set of gears, using the mains frequency as a time reference. I looked up the model number on the ‘net and found a service manual printed in 1972, so the clock is about 45 years old. I took it out to the workshop and powered it up. The radio worked, but the clock did nothing. So I took off the back cover and found that the radio module was behind the clock section, so I would have to remove the radio Australia’s electronics magazine to get to the clock mechanics. The radio PCB had several wires soldered to different tracks. I took a photo in case one or more broke off during the repair process. With the radio removed, I took out a few more screws and removed the clock module entirely. I could see a small motor with the rotor visible through a section of the case that was cut out. The rotor had some green and white tape stuck on it, so when the motor was spinning, it would be visible through the front cover as an indication that it was running. I tried to turn the rotor by hand; it moved, but a small piece of dried-up tape fell out. Maybe this was causing the low-power motor to stall. I plugged the clock back in, and the motor started to spin, with the clock now functioning. Even though some of the tape had fallen off, the rest still seemed to be stuck on well, so I decided to leave it alone, and not tempt fate by trying to dismantle the mechanism any further. The time and alarm are set using concentric shafts that protrude through the case. These connect to a system of gears. A microswitch riding on an adjustable cam activates the alarm, so that it triggers at the correct time. It’s quite a complicated mechanical device when compared to the all-electronic models that followed in later years. I put everything back together in reverse order, although it was difficult to determine the exact placement as the radio PCB obscured the clock module when trying to get them both back in the case. After some frustration, I had it all back together and powered it up as a final check. To my disappointment, the radio no longer worked. So off with the rear panel again. I siliconchip.com.au eventually found a black wire which had broken off the PCB; it was lucky that I had taken that photo earlier so I knew where to solder it back on again. Now it all worked well, and after leaving it running for a few days, I returned it to my friend. In fact, it belonged to his wife, and she was happy to have her ‘antique’ clock running again. Daikin Air Conditioner repair M. B., of Parramatta, NSW made two discoveries when his aircon failed. Firstly, sometimes you have to fix something yourself when even the experts give up, and secondly, parts may test OK, but they can still be faulty. Here is the story of how he tracked down and fixed the fault... A couple of weeks ago, thankfully as the weather was starting to get a bit cooler, my wife pointed out that our air conditioner was pumping out room temperature air. I repair cancer treatment machines for a crust and am reasonably confident about my abilities to fix most things around the home, but I’ve never tackled an air conditioner. So I rang the company who had installed it. The serviceman duly turned up, checked the refrigerant levels and found they were OK. After removing the top cover of the outdoor unit, he found that several error LEDs were lit. He said that given the age of the unit, it was unlikely that replacement PCBs were still available, and if they were, would probably be very expensive and possibly close to the cost of a new unit. I wasn’t surprised to hear this, so I asked the serviceman to get back to me about a quote for a replacement and got on with my day. After a few days, I hadn’t heard back from them, so I decided to check eBay for replacement boards. All three PCBs (Controller, Active Module and Power Filter) were still available and at a reasonable price, nowhere near the $3000 that a replacement unit would cost. I found to my surprise that I could get the boards directly from Daikin at roughly the same price as those listed on eBay. They would even take the boards back that I didn’t use and didn’t charge a restocking fee, which was a pleasant surprise. So I decided to try my hand at becoming an air conditioner mechanic. I bought all three from Daikin’s Warsiliconchip.com.au wick Farm (Sydney) warehouse for a total of $640. I wasn’t sure which PCB I needed; I would simply return the others once I’d figured that out. I was pleasantly surprised to find a free installation manual via a Google search. YouTube also had a couple of repair videos that, while not covering my exact symptoms, were at least for my specific model and gave me a bit more familiarity with it. So, emboldened, I lifted the lid and started to investigate. The YouTube video mainly talked about the boards failing due to corrosion. Even though these boards are covered by a protective lacquer, 10 years exposed to the elements would no doubt test it. My controller PCB didn’t look too bad compared to the ones in the videos, but was still covered in insect debris and dirt, and the lacquer was starting to perish in parts. The other two PCBs didn’t look too bad, so I dusted them down and removed the controller PCB to give it a thorough clean. I reinstalled it, crossed my fingers and powered it back on. It still didn’t work. I eventually figured out what all three boards do. The Controller PCB hosts the microcontroller, IGBTs and bridge rectifier. The “Active Module” is a Mosfet-based Power Factor Correction (PFC) device with an external inductor. The Filter PCB filters the incoming mains and the PFC-corrected DC output of the Active Module. There are five LEDs on the Power Filter board, one green and four red. The green LED is a ‘heartbeat’ to indicate that the microcontroller is active while the other four show error codes. Since the heartbeat LED was flashing, I suspected that the controller PCB was OK. The first two error LEDs were flashing, and according to the manual, this meant that one of the three thermistors on the aircon was faulty. The manual gave a method to test the three thermistors, which attach to the controller board via a single plug. It even gave a graph of the resistance vs temperature for these thermistors. So, armed with three glasses of water of various temperatures and a temperature probe connected to my multimeter, I checked all three thermistors on the loom. Removing the loom wasn’t too difficult. After plotting each, it seemed that they were all Australia’s electronics magazine January 2020  67 within cooee of what I’d expect, judging by the graph. I was still sure that most of the controller PCB was working, but now had some doubt about the thermistor interface. The part of the PCB dealing with the thermistors could be faulty. But not having new thermistors to hand, no proper circuit diagram, and since they tested OK, I decided to bite the bullet and swap in a new controller board. This was relatively easy. The only tricky part was needing to apply some thermal paste to the bridge rectifier and IGBT module heatsinks. So, with bated breath, I switched the circuit breaker back on. Nothing! Well not exactly nothing; the indoor unit ran for a couple of minutes before the whole thing shut down again. I checked the error LEDs again, and they were flashing in an identical pattern to before. After thoroughly reading the manual again, I discovered that in the indoor unit remote control could give more detail as to the cause of the fault. It indicated that the faulty thermistor was on the outdoor unit heat exchanger. This checks the temperature of the outdoor radiator. I was still puzzled by this, as all the thermistors had tested OK. I hadn’t purchased the thermistors on my first trip to Warwick Farm, as I couldn’t think of any reason why they would go bad. So I headed down to Warwick Farm again, to return the Active Module and the Power Filter PCB, and to pick up a thermistor set. To get to the condenser thermistor, most of the panels had to be taken off. I took plenty of photos to make sure I could put everything back together in the right place. But when I went to turn the unit back on again, it wouldn’t start at all! I thought I must have messed up when I re-connected the mains wiring. Thankfully, the manual has a diagram of the mains connection, and I discovered that I’d swapped the incoming and outgoing wires because the 1.5mm cable to the indoor unit and the incoming 2.5mm gauge wiring looked much the same in my photos. Anyway, having fixed that, I crossed my fingers and powered it up. The A/C fired up straight away, with no error LEDs lid, and cool air came out of the indoor unit! Success! I’m still puzzled as to how the thermistors had become faulty and why 68 Silicon Chip they passed my tests but were still bad enough to cause a controller fault. This is something I have not come across before in my field. I would like to know how the microcontroller determines that a thermistor is faulty. It must expect a very specific change in resistance during the start-up procedure. I ended up spending a total of $550, which is a lot less than a new aircon unit would have cost. I might be able to get some of that back by selling my still-working original controller board on eBay. USB flash drive repair D. M., of Toorak, Vic had some pictures on a faulty USB drive that he didn’t want to lose. It’s often (but not always) possible to recover files from flash drives. Luckily, he was able to do it... I had an old USB flash drive that stopped working about ten years ago. It contained some pictures I wanted to keep, but which I never backed up. This flash drive is a folding type; I did some research and discovered that these often fail due to broken internal wiring, which means it should be fixable. So I kept the drive, hoping that one day I could recover the data. To start the recovery process, I first had to carefully remove the plastic housing without damaging the enclosed circuit board. I used a ‘spudger’ tool which is like a plastic screwdriver with a wide wedge, to separate closely joined surfaces that are pressure-fitted or adhered together. Having exposed the circuit board, I established with a multimeter that the drive had failed due to a break in the flexible circuit board that formed the fold-out connector. So I had to join a new set of wires directly to the circuit board to bypass the damage. To do this, I had to work out which PCB pads were the connections GND, Vcc, D+ and D-. Getting GND and Vcc mixed up would likely be fatal to the device, but if you get D+ and D− swapped, it will typically still be detected as a USB device, but it will not work. The usual colouring scheme for USB 1.1 or 2 is GND (black or blue), Vcc or +5V (red or orange), D+ (green) and D(white or gold). Note that the device was a four-wire USB 1.1/2 device, not USB 3 which uses more wires. There is usually no indication on the circuit board as to which pin is which, so refAustralia’s electronics magazine The circuit board of the recovered USB drive. The connector with the defective flexible circuit board has been held down with tape to expose the solder pads, so that wires can be soldered to them for data recovery. erence needs to be made to the original connector. To make the connection, I cut an old USB cable in half and kept the end with the Type-A plug. I then stripped the four exposed wires and soldered them to the pads on the memory stick circuit board, after having determined, based on the original cable, which end was GND. I first tried an old drive for practice soldering the very small wires. I then moved onto the recovery target. Once the wires were soldered correctly, I connected the drive to a computer. It detected a USB device, but I could not access it, so I swapped the D+ and D- wires. I then plugged it back in, and it worked immediately, so I copied its contents to the computer. I was delighted to have gotten my photos back. The pinout of a USB Type-A connector. The white area (top) is the cavity while the dark area (bottom) is solid material. Pin 1 is Vcc or +5V, 2 is D-, 3 is D+ and 4 is GND. Doublecheck and triple-check that you get the corrections right, referring to the old connector, as it may be hard to figure out the connections from the SC circuit board alone. siliconchip.com.au AUSTRALIA’S OWN M CARLO M ITO EWN AUS TIR IA ’S N E E R C S H C U O T MICROMITE NK BA EEC CRA HSP UCK TOC F PROG REE Since its introduction in February 2016, RAMMI Buy eit N tell us wher V1 or V2 Ba G h for and w ich project yo ckPack, u want it e’ll prog FREE O FRraEmEit for yo PRO F CHARGE u, Buy eit GRAMM I! Geoff Graham’s mighty Micromite BackPack has proved to be one of the Smost ince versatile, its introduction in Februaryand 2016, most economical tell us her V1# or V2 BaNG hich p ckPack for and w Geoff Graham’s mighty Micromite easiest-to-use visual display and touchscreen control systems available – not only here in Australia but around the world! we’ll p roject you wan , FREE O rogram it for yot it BackPack proved to be of the mostBackPack: versatile,the most economical and easiest-to-use visual display andPLUS, published There are has three versions of one the Micromite original V1, published February 2016; the Micromite in November u, F C # Supers eded but HARGE! still avail to orderbe able touchscreen control systems not only here in 2017. Australia around the world! There nowV2 four versions 2016, and now there’s the V2 available BackPack –published in May The but main difference between the are V1 and versions is the V2 can plugged #); the Micromite PLUS, published in November 2016, of the Micromite BackPack: V1, published February 2016 (now superseded straight into a computer USBthe fororiginal easy programming or re-programming “in situ”, while the V1 requires a separate programmer – YES, if you the V2the BackPack published in May 2017 over and now there’s the V3 July If you your wish,own themasterpiece! Micromite (which is wish Micromite can be programmed and over again, for BackPack published published projects, orinfor you2019. to develop programmed inisBASIC) can be in programmed andsoover againeasy – fortopublished for you to develop your own masterpiece! The Micromite programmed a version ofover BASIC it’s quite learn andprojects, write yourorown! BACKPACK MicromiteBackPack BackPack V3– May – Jul1719 V2! – May Micromite Plus BackPack V2! Micromite BackPack V1 – Feb–16Nov 16 Micromite Micromite BackPack Plus BackPack – Nov17 16 Micromite The V3 BackPack is the most We have taken the best The Micromite LCD BackPack features of the Micromite combines a full colour touchLCD and the 64 a lowsensitive LCDExplore panel with and put them together ontorunning cost 32-bit microcontroller single board. Use itIt to supercharge your aa BASIC interpreter. packs an incredible BackPack oran justamazingly as a convenient and amount of project power at cheap price cost-effective controller module. and will leave you thinking up project after KIT INCLUDES: project where you could put it to good use. PCB, 2.8-inch touchscreen and lid Programmed PIC32MX470F512H-120/PT KIT INCLUDES: 3.3V LDO regulator plus Mosfets for PWM control backlight PCB MCP120-270 supply supervisor 2.8-inch touchscreen with 320x240 pixels 20MHz low-profile crystal Microcontroller (programmed with your choice) and IC socket greenlow-dropout SMD LED regulator 3.3V micro USB & (ceramic microSD types sockets All capacitors supplied) Right-angle switch 10kΩ resistortactile and 100Ω trimpot SMD capacitors and resistors Pin headers (male and female) pin headers andand shorting block Tapped spacers machine screws mounting hardware UB3 lid (laser-cut 3mm acrylic) MicromiteBackPack BackPackV1PLUS Kit SC3321) (Cat SC4024) – $70.00 Micromite Kit (Cat – $65.00 The V2 version of the We have taken the best Micromite LCD BackPack features of the Micromite incorporates the MicroLCD Backpack and athe bridge, which adds USB Explore 64 them interface andand theput ability to together onto a single to it's program/reprogram theboard. PIC32Use chipit while supercharge your BackPack project or just as a onboard. And the BackPack V2 also adds convenient and cost-effective software control over the LCD controller backlight. module. KIT INCLUDES: KIT PCB,INCLUDES: 2.8-inch touchscreen and lid PCB (green) PIC32MX470F512H-120/PT (programmed with your choice) 2.8-inch with 320x240 3.3V LDOtouchscreen regulator plus Mosfets forpixels PWM control backlight Programmed microcontrollers MCP120-270 supply supervisorand IC sockets Mosfets for PWM-controlled backlight dimming 20MHz low-profile crystal 3.3V greenlow-dropout SMD LED regulator All capacitors (ceramic sockets types supplied) micro USB & microSD 2SMD 1kΩtactile & 2 10kΩ resistors switch Pin headers (male and female) SMD capacitors and resistors UB3 lid (laser-cut 3mm acrylic) pin headers and shorting block Tapped spacers, machine screws and Nylon washers mounting hardware Micromite V2 KitKit (Cat(Cat SC4237) – –$70.00 Micromite BackPack BackPack PLUS SC4024) $70.00 The latest version of the convenient and powerful yet! Micromite LCD BackPack It has all the features of the V1 incorporates the Microand V2 BackPacks and supports bridge, which USB both 2.8in andadds 3.5ina touchscreen displays plus interface and the ability to five new optional features: extra memory, a realprogram/reprogram the PIC32 chip while it's time clock, infrared receiver, temperature, onboard. And the BackPack V2 also adds humidity and pressure sensors and more! software control over the LCD backlight. KIT INCLUDES: PCBINCLUDES: (green) KIT 3.5-inch colour touchscreen with 480x320 pixels PCB (green) Programmed microcontrollers and IC sockets 2.8-inch touchscreen with 320x240 pixels 3.3V low-dropout regulator and IC sockets Programmed microcontrollers All capacitors (through-hole backlight ceramic dimming Mosfets for PWM-controlled types supplied) 3.3V low-dropout regulator 2 1kΩ & 2 10kΩ resistors All capacitors (ceramic types supplied) Pin headers (male and female) 2Mosfets 1kΩ & 2for10kΩ resistors PWM-controlled backlight dimming Pin headers (malemachine and female) Tapped spacers, screws and Nylon washers UB3 acrylic)black 3mm acrylic) UB3lid lid(laser-cut (laser-cut3mm matte/gloss Tapped spacers, machine screws and Nylon washers MicromiteBackPack BackPackPLUS V3 KitV2(CatKitSC5082) – $75.00 Micromite (Cat SC4327) – $70.00 For more information search for all BackPack articles siliconchip.com.au Individual PCBs and microcontrollers areMicromite also available separately foratall Micromite BackPacks Specialised components for MICROMITE BACKPACK projects published in SILICON CHIP Parking Assistant Black/clear/blue UB5 lid & ultrasonic sensor: siliconchip.com.au/Shop/7/3338 Boat Computer VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 $7.50 $25.00 Super Clock VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 DS3231 real-time clock (RTC) with mounting hardware: siliconchip.com.au/Shop/7/3491 DS3231+ rechargeable LIR2032 cell: siliconchip.com.au/Shop/7/3519 Energy Meter DS3231 real-time clock (RTC) with mounting hardware: siliconchip.com.au/Shop/7/3491 DS3231 + rechargeable LIR2032 cell siliconchip.com.au/Shop/7/3519 ACS718 20A isolated current monitor IC: siliconchip.com.au/Shop/7/4022 Main PCB [04116061 RevI]: siliconchip.com.au/Shop/8/4043 Matte black UB1 lid: siliconchip.com.au/Shop/19/3538 $25.00 $5.00 $7.50 $5.00 $7.50 $10.00 $15.00 $10.00 Voltage/Current Reference Short form kit: All parts including PCB, but not including the BackPack module, case, power supply, PCB pins and wire siliconchip.com.au/Shop/20/3987 Matte black or blue UB1 lid: SC4084/SC4193 Main PCB [04110161] as separate item: siliconchip.com.au/Shop/8/3988 $99.00 $10.00 $12.50 DDS Signal Generator AD9833 DDS module: siliconchip.com.au/Shop/7/4205 $25.00 Deluxe eFuse IPP80P03P4L04 P-channel Mosfet (2 rqd): siliconchip.com.au/Shop/7/4318 LT1490ACN8 op amp (2 rqd): siliconchip.com.au/Shop/7/4319 BUK7909-75AIE N-channel SenseFET (2 rqd): siliconchip.com.au/Shop/7/4317 Main PCB [18106171] siliconchip.com.au/Shop/8/4370 Matte black UB1 lid: siliconchip.com.au/Shop/19/4316 $4.00 $7.50 $7.50 $12.50 $7.50 Radio IF Alignment AD9833 DDS: siliconchip.com.au/Shop/7/4205 $25.00 Altimeter/Weather Station DHT22/AM2302 temp. & humidity sensor: siliconchip.com.au/Shop/7/4150 $7.50 1A/500mA Li-ion/LiPo charger board: siliconchip.com.au/Shop/7/4308 $15.00 GY-68 pressure/altitude/temperature sensor: siliconchip.com.au/Shop/7/4343 $5.00 5V 0.8W 160mA solar panel: siliconchip.com.au/Shop/7/4339 $4.00 Tariff Super Clock VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 DS3231 real-time clock (RTC) with mounting hardware: siliconchip.com.au/Shop/7/3491 $25.00 $5.00 GPS-synched Frequency Reference Short form kit: All SMD parts and PCB. Not including BackPack module, case, power supply, GPS module, connectors and a few through-hole parts: siliconchip.com.au/Shop/20/4762 $80.00 VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 $25.00 Main PCB [04107181] as a separate item: siliconchip.com.au/Shop/8/4728 $7.50 FOR MORE DETAILS ON ANY OF THESE BACKPACK PROJECTS OR COMPONENTS, LOG ONTO SILICONCHIP.COM.AU/SHOP AND SEARCH FOR THE ITEM OF INTEREST siliconchip.com.au Australia’s electronics magazine January 2020  69 Easy-to-build Active Hifi Bookshelf Speakers with Optional Subwoofers Part 1 – by Phil Prosser These high fidelity monitor speakers are designed for use with TVs, computers or recording equipment. They’re inexpensive and easy to build, yet have excellent audio quality, with low distortion and a fairly flat frequency response. So if you’re looking for high-quality DIY bookshelf speakers without spending the earth, these are for you. Optional matching subwoofers extend the bass significantly, and provide much higher output levels. M odern TVs are becoming thinner and sleeker all the time. As much as this trend shows the great leaps in display technology, there are a few laws of physics that limit the quality and capacity of the internal speakers, which must fit in a similarly tiny space. Let’s face it; the speakers on pretty much all modern TVs sound pretty bad and some provide very poor voice intelligibility. The ideal solution is an external set of speakers and an 70 Silicon Chip Shown here with their optional subwoofers (which also act as handy stands) these two-way, ported bookshelf speakers are economic and easy to build. Australia’s electronics magazine siliconchip.com.au Trade-offs amplifier connected to the TV. For the greatest convenience, the amplifier can be contained within the speakers themselves. The speakers can generally be plugged into the television line-out (or headphone) output, so the television volume control can still be used. Any speakers which will work well with a TV are also very suitable for providing high-quality output from a PC, for watching movies and music, playing games or for sound and movie editing. These high-quality speakers have a built-in power amplifier, so the fit the bill perfectly. I’ve designed them to be compact so that they don’t take up too much space. But in some cases, particularly for TV and movie use, you may want more bass than a small enclosure can provide. So the optional matching bass enclosures extend the frequency response and also incorporate their own amplifier, giving a higher maximum volume too. Design goals My goals in designing these speakers were to achieve: 1. a modest size for the bookshelf speakers, at around 200mm wide, 300mm deep and 400mm high. 2. a flat and well-behaved impedance curve. 3. a decent maximum volume of at least 100dB SPL at 1 meter without undue distortion. 4. a -3dB frequency response of 40Hz to 20kHz for the bookshelf speakers alone. 5. a flat output, nominally ±3dB across the 40Hz to 20kHz range. 6. a matching subwoofer, extending the bass response and taking over from the monitors up to about 90Hz. 7. timber construction, allowing readily-available materials to be used. 8. simplicity of construction, to make it easy for DIYers. 9. low cost; under $300 for the basic stereo bookshelf system, and no more than $150 on top of that to add two subwoofers. 10. integrated power amplifiers for neatness. For the optional subwoofers, my additional goals were: 1. response down to about 35Hz, requiring a volume of around 35l and an 8-inch (20cm) driver. 2. the ability to use the subwoofers as speaker stands for the bookshelf speakers. 3. (or) an option to build a subwoofer in a rectangular shape so it could be hidden under a desk. 4. an active crossover that splits the signal between the bookshelf and subwoofer units. 5. integrated power amplifiers for the subwoofers. 6. maximum dimensions of around 200mm wide, 300mm deep and 800mm tall. The dimensions ended up 210 x 296 x 280mm for the speakers and 210 x 296 x 800mm for the subwoofers. siliconchip.com.au When designing this project, we have had to make a trade-off between cost and performance. There are some very costly options for drivers that promise exceptional performance. While serious audiophiles may be happy to spend many hundreds of dollars on a single driver, we believe that such expense is not necessary for excellent performance. The results we achieved confirm that theory. By using readily-available, reasonably-priced drivers, and a basic crossover, measurements and listening tests show that these shine in a small two-way monitor system. Performance of the bookshelf speakers alone is very good, but they do lack a little at the bass end, so you can expect a more ‘full’ sound if you also build the optional subwoofers. Both the bookshelf and subwoofer speakers are ‘active’, ie, there is an amplifier built into one of each pair. This allows them to be plugged straight into your TV or PC without needing to build a separate amp. Some of the trade-offs that I needed to make while working on this design include: • Size: I wanted to keep the speakers relatively small, which limited the driver size and enclosure volume, meaning they don’t produce really deep bass. • Enclosure material: I selected 15mm plywood or MDF, which is cheap and easy to get, even though I would have preferred to use thicker material. • Finish: I decided on a stained or varnished timber finish to keep the cost down and make construction simple. Paint or carpet could be applied if desired. • Drivers: the drivers I chose, while low in cost and producing excellent sound quality, had some characteristics which made crossover design a bit tricky. This makes the crossovers a bit more expensive, but the driver cost is low enough to offset that. Electronics For simplicity, one bookshelf speaker contains a stereo amplifier to power both speakers, with a passive crossover in each unit. This makes the pair fully self-contained, except for the power supply (see Fig.1). We’re using a ‘brick’ type AC-to-DC switchmode mains power supply, so no mains wiring is required. They are quite cheap and efficient for the amount of power they provide. Similarly, if you’re building the optional subwoofers, one subwoofer contains a stereo power amplifier to drive itself and the other (passive) subwoofer, plus an active crossover which distributes the appropriate signals to both subwoofers, and to the pair of bookshelf speakers. This arrangement is shown in Fig.2. A separate power ‘brick’ is used to power the subwoofer amplifier, meaning two are required for the whole system. The amplifier modules we’re using are Class-D amplifiers, based on the TDA7498 IC. These produce plenty of power without breaking the bank. We considered using an LM3886-based or discrete amplifier for these speakers, but could not warrant the associated increase in cost and complexity. The type of amplifier we’re using is often described as a “plate amplifier”. We have chosen to use a brick power supply for the speakers as it makes construction much simpler, and eliminates the need for any mains wiring in the project. So if you are Australia’s electronics magazine January 2020  71 STEREO AUDIO INPUT POWER POWER POWER AMPLIFIER INPUT INPUT OUTPUTS POWER AMPLIFIER OUTPUTS PASSIVE CROSSOVER PASSIVE CROSSOVER PASSIVE CROSSOVER PASSIVE CROSSOVER STEREO AUDIO INPUT SC POWER 20 1 9 Fig.1: the configuration of the basic bookshelf speaker system. The left and right audio signals, and 24V DC power, is fed into one of the speakers (it could be left or right, depending on how you wire it up internally). One of its internal power amplifier channels feeds the tweeter and woofer via a passive crossover, while the other channel drives a pair of wires connecting to the other speaker. This also has an internal passive crossover, conditioning these signals before they pass to its tweeter and woofer. confident with woodwork and happy to wire up the amplifiers, this may be a good project to try out. It is important to note that the line-level output from the subwoofer is high-pass filtered, so when the subwoofers are used, the monitors are not required to produce low-frequency signals. In this configuration, the cone excursion on the monitors is much lower than in the full range configuration. As a result, the mid-range is much clearer, and the system is capable of a much higher sound output level. Monitor speaker design considerations The bass driver selected is an Altronics C3038 130mm (5-inch) Aluminium cone driver. After much testing and analysis, we decided upon this as it performed well by itself in a modest enclosure. This driver can also be used in a two-way system crossing over at about 3kHz, which is above the normal vocal frequency range, leading to less audible distortion. It is also excellent value for money. We decided on this after surveying several smaller 100mm (4-inch) drivers. All of these fell short in the bass department. We also considered larger drivers, in the 150-180mm (6-7 inch) range. Many of these can deliver good bass, but all push the enclosure size well above the 16 litres we settled on. This is itself a compromise, as our original design goal was sub10 litres. The Altronics C3038 driver has 20-40W stated power handling, a frequency response of 46Hz to 10kHz, voice coil diameter of 25mm, overall diameter of 130mm and 87dB <at> 1W/1m sensitivity. These specifications are mostly typical of a driver this size. Its party trick is its very extended frequency response, right up to 10kHz. That allows us to easily integrate this with a tweeter in a two-way system. Having said that, it’s best to avoid feeding signals right up to 10kHz into this driver, as we found it had some rather unruly behaviour up there, which we had to address with 72 Silicon Chip POWER ACTIVE CROSSOVER HIGH OUT LOW OUT POWER AMPLIFIER SC 20 1 9 Fig.2: the bookshelf speaker internals are identical if you build the full version with the subwoofers. However, the incoming signal now goes into the first subwoofer, where it’s split into high and low components. The two high outputs go to the stereo input on the first bookshelf speaker, and then onto the other bookshelf speaker as before. The low-frequency signals go to a second power amplifier within the first subwoofer, and its outputs directly feed the two larger woofers in each bass cabinet. the crossover electronics. If you drive this unit at 30W, you can achieve over 100dB SPL at one metre. That is seriously loud in a home setting. It’s about as loud as a jackhammer at close range. While small in stature, these drivers can provide some solid output. Modelling this driver in the proposed enclosure showed that we could achieve an “extended bass shelf” alignment (Fig.3), where we are squeezing out a little bass extension at the expense of flatness at lower frequencies. It is a good compromise for smaller speakers. Note that when the optional subwoofers are added to the system, they take over frequencies below 90Hz, so a flatter overall response is achieved. We chose to make the enclosure reasonably narrow, with an external width of 21cm. This allows the speaker to sit on a desktop or bookshelf without taking up much room. The height and depth of the speaker were then chosen to deliver the required 16 litres internal volume. The remaining dimensions are 297mm deep and 390mm high. The depth of 297mm allows a standard 1200 by 600mm piece of plywood to be cut in half to make the side and top panels, minimising waste and cost. A second aspect of the box is the layout of the bass driver and tweeter. You will note that we have butted the tweeter right up to the bass driver. The reason for this is to minimise the separation of the centres of the tweeter and bass driver. As a listener moves their head around, keeping these close Australia’s electronics magazine siliconchip.com.au 0 Effect of tweeter resonance on crossover behaviour Attenuation (dB) -5 -10 Ideal Uncorrected Corrected -15 -20 -25 -30 200 Fig.3: we plugged the Altronics C3038 woofer parameters into WinISD and experimented with the dimensions of a small vented enclosure, achieving the response shown here. This provides a slightly extended bass response at the expense of slightly less flatness in the bass frequency response. Given that the deviation is less than 1dB, you’re unlikely to notice it. And the bass response is extended by around 10Hz, which is very worthwhile. minimises differences in the distance from each driver to the listener’s ear. The result is that the sound of the speakers remains constant around the listening area. In other words, these speakers deliver a good off-axis response. The crossover The C3038 bass driver performs quite well at lower frequencies. We decided to cross the driver over to the tweeter at about 3.2kHz, allowing it to cover the critical 300-3000Hz range of the human voice. Unfortunately, this driver has some severe breakup modes in the 9-11kHz frequency range, as a result of the very stiff cone utilised. This creates a group of peaks and dips in the upper-frequency range. At first, we tried a crossover that did not specifically treat these peaks, and quickly realised our mistake! The second version of the crossover included special filters to “notch out” these peaks. This worked but made the 2k 20k Frequency (Hz) Fig.4: the tweeter’s impedance varies with frequency, affecting the operation of the crossover. The blue line shows a simple crossover with a 4Ω Ω resistive load. The red curve shows the same crossover with the Vifa tweeter as the load. The green curve shows the corrected response of our tweaked crossover, with a compensation network to reduce the tweeter resonance effect. crossover very large and expensive. We then decided to try a second-order crossover, and combined the filter into the crossover. The roll-off, and indeed the impedance of the bass section, has been designed to attenuate the 9-11kHz peaks more than usual. One consequence of this tweaking is that the impedance of the speaker dips to about 4Ω in the 2.5-5kHz range. This will not fuss most amplifiers. The final bass driver output is very clean and has none of the harshness of the unfiltered driver output. The tweeter We really wanted to choose a good tweeter, as when a tweeter is too peaky or harsh, the result is a speaker that causes fatigue after prolonged listening. The tweeter chosen also needs to support a crossover frequency as low as reasonable, to allow us to avoid sending signals in the 9-11kHz region to the bass driver. Fig.5: the final circuit of the crossover, with the extra filtering for the woofer to effectively cut out signals in the 9-11kHz breakup region. This also incorporates an RLC network (3.9Ω Ω/22µF/900µH) to smooth out the tweeter response due to the resonance shown in Fig.4, plus a 5.6Ω Ω/12Ω Ω resistive divider to match the levels and impedances of the two drivers to suit a single signal source. siliconchip.com.au Australia’s electronics magazine January 2020  73 You don’t have to build the subwoofers – if you don’t want to use the subs as stands, the two main speakers are ideal for use with a computer, MP3 player, etc (albeit at the expense of some bass). Because they’re self-powered, they will plug straight into virtually any sound source, from “line out” to headphone sockets . . . So we selected a Vifa tweeter, Altronics Cat C3019. This is a very good tweeter at a fair price, but does present the designer with the challenge of a significant impedance peak at around 1.75kHz. This impedance peak is a result of tweeter resonance. The tweeter employs ferrofluid in the air gap in the magnet assembly. This aids in cooling the voice coil, and usually damps the driver resonance. So, in most ferrofluid tweeters, the driver impedance is quite flat through resonance. The C3019 tweeter is kind of ‘in-between’. The impedance of the tweeter is nominally 4Ω, but at 1.75kHz it peaks at about 10Ω. We need to deal with this peak. Fig.4 shows the behaviour of an ideal first-order crossover in blue, the actual response in red and the corrected response in green. The correction is implemented with an LCR trap, comprising (in our case) an inductor of around 1mH, a 22µF capacitor and a 3.9Ω resistor. This does add cost to the project, but it is essential to achieving a good sound. A peak like the one shown without the correction circuit is responsible for many tweeters sounding harsh and ‘tiring’. The resultant second-order passive crossover circuit is shown in Fig.5. This is a reasonably complex crossover for a two-way speaker, but it’s necessary to achieve the desired sound quality. All three resistors can be 5W wirewound types. The capacitors are not too hard to get, either; the 6.8µF capacitors can be either metallised polypropylene or non-polarised electrolytic types. I decided to go with the former, but electros are fine. Given its high value, the 22µF capacitor needs to be electrolytic. That just leaves us with the question of where to get, or how to make, 390µH and 900µH air-cored inductors with low DC resistances, so that they are as close to ideal inductors as possible. Luckily, it turns out that you can simply purchase full reels of enamelled copper wire (ECW) on spools, and the spooled 74 Silicon Chip wire will already have roughly the right inductance values! We tested reels from Altronics (and these are specified in the parts list). We’re not sure about reels from other vendors. You would have to measure their inductances yourself. It’s really lucky that a 100g reel of 1mm diameter ECW works out to pretty much exactly 390µH. We actually wanted 1mH for L3, but a 100g reel of 0.8mm diameter ECW measures 900µH, and that’s close enough. All that difference does is shift our crossover point from 3.0kHz to 3.2kHz. Using the whole reels like this relieves constructors of the job of tediously winding custom inductors. The three inductors are mounted on the crossover PCB perpendicularly to one another, ie, one faces north/south, one east/west and one up/down. This means they are ‘orthogonal’, so their magnetic fields will not interact. Otherwise, we would get an unwanted air-cored transformer between two or more of the inductors, and the crossover would not work as intended. Inbuilt amplifier The pre-built amplifier modules we’re using don’t cost a lot but still deliver great performance. As avid hobbyists, entertaining the thought of buying a pre-built amplifier module was a hard concept to deal with… but we are thankful we did. This amplifier will deliver about 30W RMS into two 8Ω speakers, which is more than enough for anything short of a monster party. When paired with the matching subwoofers, the monitors never see frequencies below about 90Hz, so 30W is actually a very serious amount of power indeed. The amplifier accepts stereo line-level inputs. As mentioned earlier, the amplifier uses an external power supply, which is connected by a 2.5mm barrel plug. This keeps things very simple and avoids mains wiring inside the speaker. Australia’s electronics magazine siliconchip.com.au Bookshelf Speakers Parts List – to build one pair Enclosures 2 130mm (5in) 40W aluminium cone woofers [Altronics C3038] 2 25mm (1in) 100W Vifa BC25SC55 tweeters [Altronics C3019] 1 plate amplifier assembly (see below) 2 passive crossover assemblies (see below) 2 600 x 1200mm sheets of 15mm marine ply 4 2m lengths of 15 x 15mm or 20 x 20mm ‘quad’ timber 80 8G x 25-28mm self-tapping countersunk wood screws 20 8G x 15mm self-tapping countersunk wood screws 16 8G x 10-12mm self-tapping countersunk wood screws 2 105mm lengths of 40mm diameter PVC pipe 1 80 x 40mm sheet of 1.5mm thick aluminium 1 roll of thin foam tape (eg, door seal tape) 1 pack of large staples (or a small box of 40mm nails) 1 bag of Lincraft single-size thick wadding or similar lightweight acoustic poly wadding 4 sheets of 120 grit sandpaper 1 sheet of 240-400 grit sandpaper 1 small tin of timber varnish 1 small tin of matte or satin black paint 1 430-475ml tube of acrylic gap filler 1 dual red/black binding post [Altronics P9257A] 1 1m length of heavy-duty figure-8 wire 1 250ml bottle of PVA wood glue Additional parts for a pair of subwoofers 2 200mm (8in) 70W polypropylene woofers [Altronics C3088] 1 subwoofer plate amplifier assembly (see below) 3 600 x 1200mm sheets of 15mm marine ply 6 2m lengths of 15 x 15mm or 20 x 20mm ‘quad’ timber 2 130mm lengths of 75mm diameter PVC pipe 100 8G x 25-28mm self-tapping countersunk wood screws 16 8G x 15mm self-tapping countersunk wood screws 8 8G x 10-12mm self-tapping countersunk wood screws 1 80 x 40mm sheet of 1.5mm thick aluminium 6 sheets of 120 grit sandpaper 1 sheet of 240-400 grit sandpaper 1 dual red/black binding post [Altronics P9257A] 1 1m length of heavy-duty figure-8 wire Plate amplifier assembly 1 135 x 160mm sheet of 1.5mm thick aluminium 1 TDA7498-based 100W + 100W amplifier, blue PCB (available from eBay) 1 24V 5-6A “brick” type mains power supply with 2.5mm ID DC barrel plug 1 2.5mm inner diameter chassis-mount DC barrel socket [Altronics P0623] 1 red panel-mount RCA socket [Jaycar PS0259] 1 black panel-mount RCA socket [Jaycar PS0496] 1 dual red/black binding post [Altronics P9257A] 1 dual 10kΩ logarithmic potentiometer [Altronics R2334, Jaycar RP3756] 1 3-way 3.96mm crimp housing and pins [Altronics P5643 + 3 x P5640A, Jaycar HM3433] 1 knob to suit potentiometer siliconchip.com.au 8 M3 x 6mm machine screws 8 3mm ID shakeproof washers 4 10mm to 25mm long M3-tapped Nylon spacers 1 1m length of single-core shielded wire 1 1m length of dual-core shielded wire 1 1m length of heavy-duty figure-8 wire 1 length of 5mm diameter heatshrink tubing 1 small tube of thermal paste 1 can of flat black spray paint, suitable for aluminium Passive crossover 1 double-sided PCB, code 01101201, 137 x 100mm 3 2-way 5/5.08mm pitch PCB-mount terminal blocks (CON1CON3) 1 900µH air-cored inductor (L1; full roll 0.8mm diameter ECW#) [Altronics W0407] 2 390µH air-cored inductors (L2,L3; full roll 1mm diameter ECW#) [Altronics W0408] 1 22µF 100V axial crossover capacitor [Jaycar RY6912] 2 6.8µF 100V axial crossover capacitor [Jaycar RY6956 or RY6906] 1 12Ω 5W 5% wirewound resistor 1 5.6Ω 5W 5% wirewound resistor # ECW = Enamelled 1 3.9Ω 5W 5% wirewound resistor Copper Wire 4 large plastic cable (zip) ties Subwoofer plate amplifier assembly All the parts specified for the bookshelf plate amplifier assembly above, except the aluminium sheet, plus: 1 250 x 165mm sheet of 1.5mm thick aluminium 1 red panel-mount RCA socket [Jaycar PS0259] 1 black panel-mount RCA socket [Jaycar PS0496] 1 double-sided PCB, code 01101202, 132 x 45mm 6 2-way 5/5.08mm pitch PCB-mount terminal blocks (CON4CON9) 6 8-pin DIL sockets (for IC1-IC6; optional) 2 ferrite beads (FB1,FB2) 8 M3 x 6mm machine screws 8 3mm ID shakeproof washers 4 10mm to 25mm long M3-tapped Nylon spacers 6 NE5532 dual low-noise op amps (IC1-IC6) 1 LM317 1.5A adjustable regulator (REG1) 2 1N4004 400V 1A diodes (D1,D2) 1 1N4148 small signal diode (D3) Capacitors 1 470µF 50V 105°C electrolytic 2 220µF 25V electrolytic 8 47µF 35V 105°C electrolytic 1 10µF 35V electrolytic 8 150nF 63V MKT 6 100nF X7R multi-layer ceramic 3 100pF NP0/C0G ceramic Resistors (all 1/4W 1% metal film) 3 100kΩ 2 33kΩ 4 22kΩ 4 7.5kΩ 2 5.6kΩ 4 4.7kΩ 1 270Ω 2 100Ω 1 10Ω Australia’s electronics magazine 8 12kΩ 1 3.3kΩ 2 10kΩ 1 1.8kΩ January 2020  75 We have specified a TDA7498-based amplifier module available from eBay. These are theoretically capable of driving 80W into an 8Ω speaker, but we are running it from a lower voltage than the maximum. We selected this TDA7498-based module after purchasing and testing many other amps. Fig.6: the expected SPL output levels of the 130mm woofers (green) compared to the 200mm woofers (grey), both at 30W. Not only do the larger diameter woofers put out a higher SPL across the board, but they also have -3dB roll-off point around 10Hz lower, at about 35Hz compared to 45Hz. Fig.7: the simulated speaker cone excursion values (in mm) for the 130mm woofers (green) and 200mm woofers (grey). The 200mm woofers have reasonable (<4.5mm) cone excursions down to their -3dB point of 35Hz, while the 130mm woofers run into excursion limitations and thus distortion at a much higher frequency at this power level; around 100Hz. Fig.8: SPL output vs frequency for the 130mm woofers (green) and 200mm woofers (grey) at the highest practical power level for each; 7.6W and 30W respectively. By limiting the 130mm bass power to 7.6W, cone excursion is kept within reason, but the maximum SPL is around 10dB lower compared to the larger woofers. 76 Silicon Chip Two main groups of amplifiers were credible candidates for this project, based on the TPA3116 and TDA7498 ICs. Both are Class-D amplifier chips, and both operate from a single supply rail. They are highly efficient, have a tiny heatsink by linear standards and are very affordable. We considered using linear amplifiers, for example, discrete amplifiers or amps based on the LM3886 IC. These would deliver slightly better performance, but they all require dual-rail power supplies, and that leads us down the path of putting transformers, rectifiers and mains wiring inside the speaker. They would also cost more, and generate more heat inside the enclosure. Looking at the Class-D options of the TPA3116 and TDA7498, we bought a range of devices to test. We found a few problems with most of the Class-D amplifiers on the market at the current time. Some are marketed as “2.1 channel” amplifiers, with a subwoofer output and stereo main speaker outputs. Unfortunately, none of these incorporate filtering on the main outputs, meaning that full-range signal, including the range sent to the subwoofer, is sent to the main speakers. This is a failing that makes these devices virtually useless. The heatsinking of many of the designs is very poor. In many cases, the heatsink is held down with a single screw. This is such a fragile design we cannot bring ourselves to use it inside a loudspeaker. It seems random as to which amplifiers have good contact between the amplifier IC and the heatsink. But that is something we can fix. Also, the voltage rating of capacitors on many of these products is very close to the operating voltage. That might not sound worrying, but it is. The reliability of electrolytic capacitors is strongly dependent upon how far from their maximum ratings they are operated (this includes temperature, voltage and ripple current). We pulled the 25V rated capacitors from one amplifier, which ran them at 24V, and tested them on a power supply. Every single one failed catastrophically at 26-28V. This is far too close for us to recommend their use. The TDA7498-based amplifiers can operate at up to 32V DC, and the amplifier we selected has solid mechanical construction. Given we are specifying a 24V plugpack to power the amplifier, we have a good voltage margin on the electrolytic capacitors. As a bonus, the amplifier we recommend does not include volume controls, and has simple input and outputs on screw connectors/plugs. This makes it very affordable. You should be able to find the recommended amplifier for about USD $9 (~AUD $14) each, which is far less than we could build a discrete or LM3886-based amplifier for. We also picked up a 24V 6A plugpack from eBay for less than AUD $35. By integrating the amplifier, input connectors, speaker output sockets and volume control to an aluminium panel, we can build a standalone amplifier, ready to install inside the rear of a monitor speaker. Subwoofer design The optional subwoofers provide several benefits. Their larger 200mm (8-inch) drivers can handle significantly more continuous power than the drivers in the bookshelf speakers, as they have 40mm (1.5-inch) voice coils. Additionally, the length of the voice coil and suspension allows greater Australia’s electronics magazine siliconchip.com.au X Fig.9: a ‘far-field’ measurement of the loudspeaker system response, for one monitor and one subwoofer. The response is fairly flat from around 60Hz to nearly 20kHz, varying by just a few dB. The peak at 50Hz was reckoned to be due to sound reflections off a nearby wall. Fig.10: these ‘near-field’ measurements paint a more accurate picture of the system’s low-end response. The 50Hz peak is no longer so noticeable, and the bass can be seen to extend down to a little below 40Hz. cone excursion. This results in the driver having a linear travel of well over ±4.5mm. This, combined with the fact that the cones have a greater area than the bass drivers in the bookshelf speakers, means that the subwoofers are much better-suited to handling low frequencies at high power levels. To illustrate the difference, Fig.6 shows the output of WinISD simulating the sound pressure levels (SPL) across a range of frequencies, from the subwoofer driven at 30W (grey curve) and from the bookshelf speaker at 30W (green curve). This shows that the subwoofer increases the bass output by about 3-5dB and extends the bass response by about 10Hz, down to around 35Hz. But this is not the whole story. Fig.7 shows the modelled cone excursion for both speakers. At 30W, the Altronics C3088 driver in the subwoofer remains well below its 4.5mm linear excursion to about 35Hz. When driven hard, this driver gracefully limits the excursion without damage. But at 30W, the much smaller driver in the monitor speaker would be trying to move ±7mm at about 38Hz, which is far beyond its capability. The speaker simply cannot do this, and the cone hits the end of its mechanical excursion, causing distortion. Also, while the speaker is at its excursion extremes, the voice coil is not entirely in the magnetic field of the ‘air gap’. So not only is there distortion in the bass, but all . . . but if you do build the subwoofers, they make fine stands for the main speakers. And because bass is non-directional, you can aim the boxes where little fingers won’t do any harm to the speaker drivers. siliconchip.com.au Australia’s electronics magazine January 2020  77 other output from the driver is distorted too. Obviously, by turning the volume down, the monitor speaker works very well, but we do need to recognise that the laws of physics impose limitations on what we can ask of the speaker. Adding the subwoofers then allows us to avoid sending frequencies below 90Hz to the bookshelf speakers, thus avoiding the distortion described above. These signals are instead reproduced by the subwoofers. This has the additional benefit of significantly increasing the power available for the monitor speakers to generate mid-range and treble frequencies, as all the bass signal has been diverted to a separate amplifier. Ideally, the monitor speakers should not reproduce any more than about 7-10W worth of sub-100Hz signals, as this limits the cone excursion to a more manageable 3-4mm. The achievable bass SPL in this case is obviously less. Fig.8 shows the maximum practical low-frequency output 78 Silicon Chip achievable by the C3088 and C3038 drivers. The active crossover we use to split the signal between the subwoofers and monitor speakers allows the monitors to be driven at full power across their range, bringing the achievable SPL up to match the subwoofer. Regarding the subwoofer enclosures, we have kept their width and depth the same as the monitor speaker. This allows the subwoofers to be “hidden” as speaker stands. This gives us a convenient 35-litre enclosure in which to mount the Altronics C3088 driver. You may have noticed a problem with this: the 200mm woofer drivers are unlikely to fit in the usual way into a 210mm-wide cabinet. But because this is a subwoofer, and operates only up to 90Hz, its sound propagation is quite omnidirectional. We exploit this fact, and mount the driver on the side of the enclosure, rather than on the front. Australia’s electronics magazine siliconchip.com.au Fig.11: the full circuit of the active crossover which is used to split the incoming stereo signal, so that the highfrequency components can be fed to the pair of monitor speakers. The lowfrequency components are mixed to a mono signal, buffered by IC1a and then fed to the subwoofer amplifier, which can drive one or two subs. The circuit runs off the same nominally 24V DC supply used to power the subwoofer amplifier, regulated to 18V and with a 9V halfsupply rail generated for signal biasing. (Inset above): the 2 x 80W class-D stereo amplifier which we purchased on ebay for less than $20 including postage. You couldn’t build one for anything like this price and it does the job nicely! Similarly, we have placed the port on the rear of the box, as its exact location is not critical. These can all be moved if your application demands. Overall performance Measuring speaker frequency responses is difficult if you don’t have an anechoic chamber. However, we gave it a go, using a Behringer ECM8000 measurement microphone, a low-noise microphone preamplifier and the Speaker Workshop PC software. Near-field measurements can be made with accuracy up to a modest frequency (say, around 1kHz). Far-field measurements are heavily affected by reflections and room resonances, but are more representative of how a speaker system actually sounds in use. The measurements presented here are a mix of both. First, let’s look at the far-field measurements shown in siliconchip.com.au Fig.9. These were made outdoors, with the speaker about 3m from the nearest structure. You can see a peak at 50Hz, which is due to reflection from the structure. The near-field measurements below give a better insight into the low-frequency response of the speakers. Moving the mic to a location closer to the boxes, approximately 50cm from the speaker and located equidistant between the subwoofer and monitor speaker, gives the bass response shown in Fig.10. The measured -3dB point is 34Hz. There remains a small artefact in the 50Hz region. Other than this, the response is as expected, very flat indeed. The keen-eyed will note that the second plot is a couple of dB higher than the first. This is just because the microphone is closer to the speaker. The response is as smooth and deep as the graphs suggest. Should you build these speakers, we think you will Australia’s electronics magazine January 2020  79 be delighted with the sound, and your wallet won’t be too much lighter! Active Crossover design As mentioned earlier, an active crossover is used to split the incoming stereo audio signal into three different paths: left and right signals to feed to the monitor speakers, which contain little information below 90Hz, plus a third mono signal for the subwoofers which has the signals below 90Hz from both channels (bass sounds in recordings are often in mono anyway, as having them in stereo doesn’t add much). The subwoofer amplifier is identical to the monitor amplifier, except for the addition of this active crossover, which is custom-designed. We cannot stress how important this is to achieve good performance in an active system, and in protecting the monitor speaker from unwanted bass signals. The active crossover board implements a fourth-order Linkwitz-Riley filter, which has a roll-off of 24dB per octave. The crossover point is at 90Hz. A fourth-order crossover giving a very steep filter slope has been chosen to ensure that, even when the subwoofer is very close to the listener, you cannot localise the sub. This makes it seem like the bass signals are coming from the same place as the other signals, ie, the monitor speakers. The second benefit is that with a fourth-order crossover, minimal bass is sent to the monitors, and this prevents the excessive cone excursions mentioned earlier, which can dramatically increase distortion (and not just in the bass, either). At 90Hz, the high-pass filtered signal level is just onequarter of the unfiltered level. At 45Hz, just 1% or so of the signal power is sent to the monitors. The reproduction quality of the monitors is therefore significantly enhanced, because the cone is effectively stationary, and not moving with the bass. So the voice coil is always in the air-gap. The crossover is implemented as a “state-variable filter”, which is essentially four integrators in series. Its circuit is shown in Fig.11. The input signals are fed through a ferrite bead and 100pF capacitor to ground, to filter out any RF signals which may be picked up, then are AC-coupled to the active filter integrators. The phase shift of each integrator is set by the RC values; in our case, 12kΩ and 150nF. The left-channel crossover is implemented with op amps IC1b, IC2a, IC2b, IC3a & IC3b along the top, while the right channel comprises IC4b, IC5a, IC5b, IC6a and IC6b. They are otherwise identical. One unusual aspect of this filter is that it uses nested feedback. The second and fourth stages have feedback resistors to the non-inverting input of the first stage, while the third and fifth stages have feedback resistors to the inverting input of the first stage. The high-pass output is taken from the output of the first stage in each case. The low-pass outputs are from the fifth stages. These are mixed 1:1 using a pair of 4.7kΩ resistors, then fed to buffer IC1a, which then sends the signal for driving the subwoofer amplifiers. Usually, the op amps in a circuit like this would run from positive and negative rails (a “split supply”), with the signals being ground-referenced. But in this case, we want to operate the amplifier from a DC switch-mode supply, ideally 24-32V. The 24-32V input is low-pass filtered by a 10Ω series resistor and 470µF capacitor, then fed to REG1, an LM317 adjustable regulator, to give a nice clean 18V DC output to run all the op amps. Two 4.7kΩ resistors across this 18V rail generate a 9V half-supply rail which is buffered by op amp IC4a and an RC low-pass filter. This is used to DCbias all the signals, so they stay within the op amps’ 0V and 18V supply rails. The signals are then AC-coupled again at the outputs, and re-biased to 0V to remove this DC offset. Conclusion If you’re interested in building these loudspeakers (whether as standalone bookshelf speakers or with the subwoofers), now is a good time to start gathering the parts required, as shown in the parts list. Next month, we’ll describe how to build both sets of cabinets, along with the required electronics. SC The tools you’ll need . . . The passive crossover (shown here close to life size) will be described (along with box details) in Part II next month. 80 Silicon Chip Circular saw Sawhorse Jigsaw Drill with drill bits and screwdriver bits Countersinking bits Large adjustable hole saw (a jigsaw could be used instead) Caulking gun Router Sanding block Set of large clamps Staple gun (not essential but makes construction easier) Heavy gloves (protect hands from splinters when sanding) Australia’s electronics magazine siliconchip.com.au New Year New Gear Build It Yourself Electronics Centres® 499 $ SAVE $100 K 8400 Everything to get building in 2020. 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Rating NOW $109 $ SAVE 25% *Phone for illustration purposes. 99 RRP X 3300 SAVE 25% ANBI is an isolator which prevents your battery from draining when not in use by isolating the negative terminal. Also a great anti-theft device! Ideal for cars, boats, caravans, even mowers! Installs in a few minutes. Anderson Style Cables Part UV Colour $ N 2090 Ultimate charging station! $ 49.50 Neon Flex Rope LED Lighting Use it in long lengths for stunning coloured lighting effects or cut and shape into your own custom “neon” signs. Ultra flexible outer sheath. Cuts every 50mm. 12V input, bare end connection works great with P 0610A 2.1mm DC jack. IP65 weatherproof. 5m reels. A 0289A See last page for store locations or visit altronics.com.au Accessories: X 3273 Straight joiner $3.50 • X 3274 90° joiner $3.50 • X 3277 Motion switch $16.50 • X 3275 Touch dimmer $6.95 Illuminated Magnifier for fine micro tasks Say to goodbyein! e ey stra Why pay $300 for a MaggyLamp®? The inspect-a-gadget illuminated desk magnifier is an absolute bargain at $60, we believe ours is every bit as useful. An incredible visual aid for detailed inspection and work on fine items with full clarity through either the 3 dioptre lens or 12 dioptre insert. Tackle complex miniature tasks with confidence! 60 $ SAVE $9.95 X 4205 5 Dioptre X 4204 3/12 Dioptre Sale pricing ends January 31st 2020. Now with dual 4K HDMI outputs! Project Parts ‘a’ Plenty Pi 4 Fan Case R-Pi Cameras 1080p HD video & 8 megapixel still shot. Z 6306A IR filter removed for low light/night time use. Z 6305A 8MP Z 6306A 8MP NOIR The Latest Raspberry Pi® 4 The latest Pi 4 is now capable of running two monitors at once - in 4K resolution too! It’s also equipped with USB 3.0, upgraded CPU and a choice of 2GB or 4GB RAM. Micro sized desktop computing has arrived! 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Sale Ends January 31st 2020 Build It Yourself Electronics Centres Western Australia » Perth: 174 Roe St » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au Victoria 08 9428 2188 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave NEW! 13.95 $ Z 6444 Find a local reseller at: altronics.com.au/resellers Please Note: Resellers have to pay the cost of freight & insurance. Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. Queensland 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St A high speed metal geared servo with 2kg/cm torque. Weighs 14.5 grams. 180 degree rotation (±90°). » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd 08 8164 3466 02 8748 5388 © Altronics 2019. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. B 0092 DIY Tinkerers Kit For Arduino $ .95 Using Cheap Asian Electronic Modules by Jim Rowe Intelligent 8x8 RGB LED matrix This month we’re looking at a module with an 8x8 matrix of 64 ‘intelligent’ RGB LEDs. Each LED can display over 16 million different colours, or primary colours at 256 brightness levels. The LEDs are controlled serially via a single wire, and multiple modules can be cascaded to build a much larger display. That makes for all sorts of useful applications! W e looked at some 8x8 LED display modules in an earlier article in this series, back in the June 2017 issue (siliconchip.com.au/Article/10680). We thought it was worth writing this one up too, as it is significantly more flexible and just generally more useful. It uses RGB (red/green/blue) LEDs rather than monochrome (single colour) LEDs. Each LED can display up to 256 brightness levels for each of the three colours, to give a total of 16,777,216 (256 × 256 × 256) different colours. siliconchip.com.au In this module, each RGB LED has its own built-in serial data register, latch register and decoder/driver, so no separate controller is needed. All 64 LEDs of the module are connected in sequential (daisy-chain) fashion, so that serial data can be fed into the first LED of the module and passed through to the other LEDs in turn. If you want to use multiple modules, the data output from the 64th LED on the first module can be fed to the first LED of the next module to Australia’s electronics magazine program its LEDs as well. And so on. This module is based on an impressive device: the WS2812B intelligent control LED made by WorldSemi, based in Dongguan, Guangdong province, China (between Guangzhou and Shenzhen, and near Hong Kong). I should note that some of the modules currently available use a ‘clone’ of the WS2812B device, the SK6812, made by another Chinese firm: Shenzhen Sikewei Electronics. Although the timing specs for the SK6812 differ a little from those of the WS2812B, January 2020  85 Fig.1: the SMD package size and pinout of the WS2812B (and equivalent) chips. Internally, it’s made from multiple semiconductor dies, tied together with bond wires and encapsulated with a plastic lens on top. Note that the package orientation marking is located on pin 3, rather than pin 1. ► Fig.2: as well as the red, green ► and blue LED dies, the WS2812B incorporates a controller/driver IC, which includes a serial latch plus three linear LED drivers with 8-bit DACs. they are quite compatible with most of the available software. You can find these WS2812B/ SK6812-based 8x8 RGB LED modules on the internet from various vendors, many of them available via sites like eBay or AliExpress (www.aliexpress. com/item/32671025605.html). The prices vary quite a bit. You can find them for between $8 and $26 each. So it pays to search around! Now let us look at the WS2812B IC to see how it works. This description applies to the SK6812 as well. The WS2812B LED chip Inside its small (5 x 5 x 1.6mm) fourlead SMD package, shown in Fig.1, this device houses a trio of LEDs as well as a serial controller IC. It looks deceptively simple, but you can see from the block diagram (Fig.2), there’s quite a lot inside. It includes a 24-bit shift register, a 24-bit latch, three eight-bit DACs (digital-to-analog converters) coupled to a driver for each LED and even a buffer amplifier to boost and reshape the serial data output, ready for feeding to the next WS2812B. Fig.3 shows how a string of 64 WS2812B devices are connected to make up the module. This is simplified by showing just three of the 64 devices. The data stream from the MCU is fed into pin 4 (DIN) of the first device, while the output from pin 2 (DOUT) is connected to pin 4 of the next device, and so on. One of the slightly interesting features of this chip is that unlike other daisy-chained shift registers, it doesn’t feed the top-most ‘overflow’ bit of the shift register to the output, for feeding into the next device. Rather, the output is held in a static state until all 24 bits have been shifted into the register (presumably, tracked via a counter register), at which point it no longer shifts in any new bits. The input is then connected to the output buffer via an internal switch. This means that the first 24 bits of data shifted into the daisy chain determine the state of the first device. With the more typical (and simpler) shift-through design, the first bits of data end up in the last device – ie, you have to shift in the data in reverse order. So, presumably the reason for this unusual scheme is to avoid the need to reverse the order of data being sent to an array of these devices. The only other components are the 100nF bypass capacitors on the +5V supply line, with one next to each device. The 1000µF reservoir capacitor is external to the module. The physical layout of the 64-LED array, which measures 65 x 65mm, is shown in Fig.4. The input connections for the module are at lower left, while the output connections are at upper right. Each WS2812B device can draw up to 18mA from the +5V supply during operation, so a single 64-LED module can draw as much as 1.152A. That’s why it’s recommended that even using a single module, the +5V supply for the module should not come from your MCU (Arduino or Micromite, etc), but from a separate DC supply. It’s even more important to do this when you’re using several modules in cascade. This is also why that 1000µF capacitor is needed on the +5V supply line. Fig.3: cascading multiple WS2812B devices is simple. The DOUT (data out) pin of one device is simply connected to the DIN (data in) pin of the next device. The 5V and GND pins are all connected in parallel, with a 100nF bypass capacitor close to each device. 86 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.4: this shows the layout of the 8x8 RGB LED matrix. As you would expect, the LEDs are laid out in a grid. The data input is at lower left and data output at upper right (along with the supply pins), so that multiple modules can be daisy-chained. It’s a pity that the output isn’t at lower right, as that would make chaining modules considerably easier. Driving the module The LEDs in these modules are programmed serially via a single wire, as mentioned earlier. But they use a special pulse width modulation (PWM) coding system for the data, shown in Fig.5. The timing for a zero bit, a one bit and the RESET/LATCH pulse for a basic WS2812B device are shown at the top of Fig.5; this is used in most of the currently-available 8x8 modules. The corresponding timings for the latest WS2812B-V4 version of the device are shown adjacent. There are subtle differences in data bit timing between the two versions. The main difference is that the WS2812B needs a RESET/LATCH pulse lasting more than 50µs, while the WS2812B-V4 needs a longer pulse of more than 280µs. Timing for the SK6812 device is similar to that for the WS2812B, with a zero bit composed of a 300ns high followed by a 900ns low, a one bit composed of a 600ns high followed by a 600ns low, and the RESET/LATCH pulse needing to be 80µs or more. The centre section of Fig.5 shows the 24-bit data packet used to program a single WS2812B LED. There are eight bits for each of the three colours, with each colour’s data byte sent MSB (most-significant-bit) first. So the total time needed to refresh one LED is either 30µs or 26.4µs, depending on the version of the WS2812B chip. Fig.5 also shows the colour data being sent in GRB (green-red-blue) order, but some of the WS2812B or equivalent siliconchip.com.au This 8x8 RGB LED module uses WS2812B ICs. The data and power connections are made via two 3-pin male headers on the underside of the PCB. Fig.5: the WS2812B uses a custom 1-wire serial protocol, with the duration of the positive pulse distinguishing between a zero and one bit. Unfortunately, different versions of the chip require different timings, although it is possible to choose timings which will suit all versions. Note the much longer latch pulse required for the V4 chips. Also, while many chips expect colour data in the green, red, blue order shown here, some use the more standard red, green, blue order. Australia’s electronics magazine January 2020  87 devices used in these modules require the data to be sent in RGB order. As a result, much of the software written for these modules allow the colour byte order to be changed to suit the specific devices being used. The 64-LED data stream used to program all of the WS2812B LEDs in a single 8x8 module is shown at the bottom of Fig.5. As you can see, the 24 bits of data for each of the 64 LEDs are sent in turn, followed by a RESET/ LATCH pulse. This pulse instructs all of the WS2812Bs to transfer the data in their shift register into the latch register, changing the colour and brightness of its LEDs to the new values. So one complete refresh cycle for an 8x8 module takes very close to 1970µs (1.970ms) or 1969.6µs (1.969ms), depending on which version of the WS2812B is being used. As a result, the display can be refreshed up to 500 times each second (or a fraction of this with multiple modules, eg, 100 times per second for five modules daisychained). Driving it from an Arduino Thanks to the single-wire data programming system used by the WS2812B device, it’s physically quite easy to drive this module from an Arduino. As shown in Fig.6, all that’s needed is a wire connecting the module’s GND pin to one of the Arduino GND pins, together with a wire with a 390W se- While the underside of this module uses headers for external connections, some modules provide SMD pads rather than holes. It can be worthwhile to shop around, but there is a risk that you may come across clones which are not fully compatible. ries resistor connecting the module’s DIN pin to one of the Arduino’s digital I/O pins. Wires from the module’s +5V and GND pins are then used to supply it with 5V power, with a 1000µF capacitor used as a reservoir to ensure that the 5V power remains constant. Writing the required Arduino ‘sketch’ (program) is a little complicated due to the unusual PWM coding system used. Luckily, several Arduino software libraries have been written to drive a string of WS2812B/ SK6812 devices. You’ll find suitable programs in various places on the Web, most of them fairly simple and straightforward. Many of them make use of a library of routines for the Arduino written by the Adafruit people and called “Adafruit_NeoPixel”. To get you started, I’ve written a sketch called “RGBLED_Matrix_ sketch.ino”, which is available for download from the Silicon Chip website. It uses the Adafruit_NeoPixel library, which can be downloaded from https://github.com/adafruit/Adafruit_ NeoPixel (or via the Arduino IDE’s Library Manager). This sketch allows you to produce one of nine different patterns on the module, simply by sending a digit (from 1 to 9) to the Arduino from your PC’s serial port (eg, via the IDE’s Serial Monitor). For example, sending a “1” produces a changing rainbow pat- Fig.6: it’s effortless to hook up an Arduino module to one of these LED arrays. You just need to connect the grounds together, plus connect a 390W resistor from any of the Arduino I/O pins to the DIN pin of the module. As mentioned in the text, due to the LED current demands, a separate >1A 5V DC supply is needed to power the module(s). 88 Silicon Chip Australia’s electronics magazine siliconchip.com.au tern, sending a “3” produces a display of all LEDs glowing mid-green, sending a “6” produces a pattern of white dots ‘chasing’ each other, etc. While this may not sound terribly exciting, it should give you a good idea of what’s involved in driving these modules from an Arduino. Driving it from a Micromite Driving one of the modules from a Micromite again isn’t easy, mainly because of the PWM bit encoding scheme. After trying to make unorthodox use of MMBasic’s built-in SPI communications protocol (with no luck), I realised that I would need an embedded C function similar to Geoff Graham’s SerialTX module. CFUNCTIONs allow native ‘machine language’ code to be added to an MMBasic program. This would let me send the serial data streams to the LED module with the right encoding and at the right speed. I was rather daunted at the prospect of writing this CFUNCTION. But Geoff Graham advised me that a suitable function had already been created by Peter Mather, one of the Micro- mite ‘gurus’ on The BackShed Forum (siliconchip.com.au/link/aavx). I eagerly downloaded Mr Mather’s CFUNCTION, and tried using it with a small MMBasic program to drive a module with 64 WS2812B LEDs. The results were a bit disappointing, with a variety of unexpected errors. This prompted me to try using my DSO to check the pulse timing of the bitstream being sent to the WS2812B LEDs, to compare it to the required timing shown in Fig.5. I subsequently found a few differences, which seemed likely to explain the problems I was having. After an exchange of emails with Mr Mather, I learned that his CFUNCTION had been written about four years ago to suit the original WS2812 LEDs. He suggested a couple of changes to it to make the pulse timing more compatible with the WS2812B, SK6812 and WS2812B-V4 devices, and also guided me regarding how to make the changes easily without having to recompile his code. I made the suggested changes and tried it all again. Now the timing of the pulse stream was much closer to that needed by the WS2812B/SK6812 devices, and, lo and behold, the modules gave the correct displays from my test program. I then proceeded to write an expanded version of my original MMBasic test program to provide readers with a suitable demo program to run on a Micromite. This program is called “RGB LED matrix test program.bas”, and again you can download it from: siliconchip.com.au/Shop/6 This program displays a ‘rainbow’ of coloured stripes on the 64-LED SW2812B/SK6812 module, then clears the display for another five seconds before repeating the cycle. While simple, again I hope it will give you a good idea as to how a Micromite can be used to drive these modules. To achieve different kinds of display (including dynamic displays), all you need to do is use the MMBasic part of the program to change the ‘pixel’ data stored in the colours() array. You can find some useful links on this module below: Documentation: siliconchip.com. au/link/aavv Datasheets: siliconchip.com.au/ link/aavy and siliconchip.com.au/ SC link/aavw Fig.7: driving a “neopixel” LED array from a Micromite is nearly identical to an Arduino: the two grounds connected together, and a 390W resistor (or just a direct connection) from one of the Micromite’s I/O pins to the LED array DIN pin. The software is a bit more complicated, but if you start with our sample code, it should work straight away. siliconchip.com.au Australia’s electronics magazine January 2020  89 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 139, COLLAROY, NSW 2097 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip. YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS ATtiny2313 ATtiny816 ATtiny861 PIC12F202-E/OT PIC12F617-I/P PIC12F675-E/P PIC12F675-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1459-I/P PIC16F1507-I/P PIC16F88-E/P PIC16F88-I/P PIC16LF88-I/P PIC16LF88-I/SO For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS Remote-Controlled Timer (Aug10) ATmega328P PIC16F1459-I/SO ATtiny816 Development/Breakout Board (Jan19) PIC16F84A-20I/P Thermometer/Thermostat (Mar10), Rudder Position Indicator (Jul11) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sept19) PIC16F877A-I/P Temperature Switch Mk2 (June18), Recurring Event Reminder (Jul18) PIC18F2550-I/SP Door Alarm (Aug18), Steam Whistle (Sept18) White Noise (Sept/Nov18) Remote Control Dimmer (Feb19), Steering Wheel Control IR Adaptor (Jun19) PIC32MM0256GPM028-I/SS Car Radio Dimmer Adaptor / Voltage Interceptor (Aug19) PIC32MX170F256D-501P/T Courtesy LED Light Delay for Cars (Oct14), Fan Speed Controller (Jan18) PIC32MX170F256B-50I/SP IR-to-UHF Converter (Jul13), UHF-to-IR Converter (Jul13) PC Birdies *2 chips – $15 pair* (Aug13), Driveway Monitor Receiver (July15) Hotel Safe Alarm (Jun16), 50A Battery Charger Controller (Nov16) Kelvin the Cricket (Oct17), Triac-based Mains Motor Speed Controller (Mar18) Heater Controller (Apr18), Useless Box IC3 (Dec18) Tiny LED Xmas Tree (Nov19) PIC32MX270F256B-50I/SP Microbridge & BackPack V2 / V3 (May17 / Aug19), USB Flexitimer (June18) PIC32MX795F512H-80I/PT Digital Interface Module (Nov18), GPS Speedo/Clock/Volume Control (Jun19) Five-Way LCD Panel Meter / USB Display (Nov19) Wideband Oxygen Sensor (Jun-Jul12) dsPIC33FJ64MC802-E/SP Auto Headlight Controller (Oct13), 10A 230V Motor Speed Controller (Feb14) dsPIC33FJ128GP306-I/PT Automotive Sensor Modifier (Dec16) dsPIC33FJ128GP802-I/SP Nicad/NiMH Burp Charger (Mar14), Remote Mains Timer (Nov14) $15 MICROS RF Signal Generator (Jun/Jul19) Four-Channel DC Fan & Pump Controller (Dec18) Programmable Ignition Timing Module (Jun99), Fuel Mixture Display (Sept00) Oscar Noughts And Crosses (Oct07), UV Lightbox Timer (Nov07) 6-Digit GPS Clock (May-Jun09), 16-bit Digital Pot (Jul10), Semtest (Feb-May12) Battery Capacity Meter (Jun09), Intelligent 12V Fan Controller (Jul10) Super Digital Sound Effects (Aug18) 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) Micromite Mk2 (Jan15) + 47F, Low Frequency Distortion Analyser (Apr15) Micromite LCD BackPack [either version] (Feb16), GPS Boat Computer (Apr16) Micromite Super Clock (Jul16), Touchscreen Voltage/Current Ref (Oct-Dec16) Micromite LCD BackPack V2 / V3 (May17 / Aug19), Deluxe eFuse (Aug17) Micromite DDS for IF Alignment (Sept17), Tariff Clock (Jul18) GPS-Synched Frequency Reference (Nov18) ASCII Video Terminal (Jul14), USB Mouse & Keyboard Adaptor (Feb19) Maximite (Mar11), miniMaximite (Nov11), Colour Maximite (Sept/Oct12) Touchscreen Audio Recorder (Jun/Jul 14) $20 MICROS 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb-May 13) Digital Audio Signal Generator (Mar-May10), Digital Lighting Cont. (Oct-Dec10) SportSync (May11), Digital Audio Delay (Dec11) Driveway Monitor Transmitter (July15), Fingerprint Scanner (Nov15) Quizzical (Oct11), Ultra-LD Preamp (Nov11), LED Musicolor (Nov12) MPPT Lighting Charge Controller (Feb16), 50/60Hz Turntable Driver (May16) PIC32MX470F512H-I/PT Stereo Audio Delay/DSP (Nov13), Stereo Echo/Reverb (Feb 14) Cyclic Pump Timer (Sep16), 60V 40A DC Motor Speed Controller (Jan17) Digital Effects Unit (Oct14) Pool Lap Counter (Mar17), Rapidbrake (Jul17), Deluxe Frequency Switch (May18) Useless Box IC1 (Dec18), Remote-controlled Preamp with Tone Control (Mar19) PIC32MX470F512H-120/PT Micromite PLUS Explore 64 (Aug 16), Micromite Plus LCD BackPack (Nov16) PIC32MX470F512L-120/PT Micromite PLUS Explore 100 (Sep-Oct16) UHF Repeater (May19), Six Input Audio Selector (TWO VERSIONS, Sept19) Universal Battery Charge Controller (Dec19) $30 MICROS Garbage Reminder (Jan13), Bellbird (Dec13), GPS Analog Clock Driver (Feb17) PIC32MX695F512L-80I/PF Colour MaxiMite (Sept12) LED Ladybird (Apr13) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19) SPECIALISED COMPONENTS, HARD-TO-GET BITS, ETC VARIOUS MODULES & PARTS - WS2812 8x8 RGB LED matrix module (El Cheapo Modules 26, JAN20) $15.00 - Si8751AB 2.5kV isolated Mosfet driver IC (Universal Battery Charge Controller, DEC19) $5.00 - I/O expander modules (NOV19): PCA9685 – $6.00 ~ PCF8574 – $3.00 ~ MCP23017 – $3.00 - SMD 1206 LEDs (Tiny LED Xmas Tree, NOV19): 10 yellow – $0.70 ~ 10 amber – $0.70 ~ 10 blue – $0.70 ~ 10 cyan – $1.00 ~ 1 pink – $0.20 - ISD1820-based voice recorder / playback module (Junk Mail Repeller, AUG19) $4.00 - 23LCV1024-I/P SRAM (DIP) and MCP73831T charger ICs (UHF Repeater, MAY19) $11.50 - MCP1700 3.3V LDO regulator (suitable for USB Mouse & Keyboard Adapator, FEB19) $1.50 - LM4865MX amplifier IC & LF50CV regulator (Tinnitus/Insomnia Killer, NOV18) $10.00 - 2.8-inch touchscreen LCD module with SD card socket (Tide Clock, JUL18) $22.50 - ESP-01 WiFi Module (El Cheapo Modules, Part 15, APR18) $5.00 - MC1496P double-balanced mixer IC (DIP-14) (AM Radio Transmitter, MAR18) $2.50 - WiFi Antennas with U.FL/IPX connectors (Water Tank Level Meter with WiFi, FEB18): 5dBi – $12.50 ~ 2dBi (omnidirectional) – $10.00 - NRF24L01+PA+NA transceiver with SNA connector and antenna (El Cheapo 12, JAN18) $5.00 - WeMos D1 Arduino-compatible boards with WiFi (SEPT17, FEB18): ThingSpeak data logger – $10.00 ~ WiFi Tank Level Meter (ext. antenna socket) – $15.00 - ERA-2SM+ MMIC & ADCH-80A+ choke (6GHz+ Frequency Counter, OCT-DEC17) $15.00 - Geeetech Arduino MP3 shield (Arduino Music Player/Recorder, VS1053, JUL17) $20.00 - 1nF 1% MKP (5mm lead spacing) or ceramic capacitor (Wide-Range LC Meter, JUN18) $2.50 - MAX7219 LED controller boards (El Cheapo Modules, Part 7, JUN17): 8x8 red SMD/DIP matrix display – $5.00 ~ red 8-digit 7-segment display – $7.50 - AD9833 DDS module (with gain control) (for Micromite DDS, APR17) $25.00 - AD9833 DDS module (no gain control) (El Cheapo Modules, Part 6, APR17) $15.00 - CP2102 USB-UART bridge $5.00 - microSD card adaptor (El Cheapo Modules, Part 3, JAN17) $2.50 - DS3231 real-time clock module with mounting spacers and screws (El Cheapo, OCT16) $5.00 DCC BASE STATION HARD-TO-GET PARTS (CAT SC5260) (JAN) SUPER-9 FM RADIO (NOV 19) Two BTN8962TA motor driver ICs & one 6N137 opto-isolator CA3089E IC, DIP-16 (SC5164) MC1310P IC, DIP-14 (SC4683) 110mm telescopic antenna (SC5163) Neosid M99-073-96 K3 assembly pack (two required) (SC5205) TINY LED XMAS TREE COMPLETE KIT (SC5180) $30.00 $3.00 $5.00 $7.50 $6.00 ec. (NOV 19) Includes PCB, micro, CR2032 holder (no cell) and all other parts. Also includes 12 red, green and white LEDs plus four extra 100W resistors. PCB available in green, red or white. $14.00 siliconchip.com.au/Shop/ MICROMITE LCD BACKPACK V3 (CAT SC5082) (AUG 19) KIT – includes PCB, programmed micros, 3.5in touchscreen LCD, laser-cut UB3 lid, mounting hardware, SMD Mosfets for PWM backlight control and all other mandatory on-board parts Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) - DHT22 temp/humidity sensor (Cat SC4150) - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temperature/pressure sensor - BME280 temperature/pressure/humidity sensor (Cat SC4608) - DS3231 real-time clock SOIC-16 IC (Cat SC5103) - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) - 10µF 16V X7R through-hole capacitor (Cat SC5106) GPS SPEEDO/CLOCK/VOLUME CONTROL 1.3-inch 128x64 SSD1306-based blue OLED display module (Cat SC5026) MCP4251-502E/P dual-digital potentiometer (Cat SC5052) (JUN 19) $75.00 $30.00 $7.50 $5.00 $10.00 $3.00 $5.00 $1.50 $2.00 $15.00 $3.00 TOUCH & IR REMOTE CONTROL DIMMER (FEB 19) N-channel Mosfets Q1 & Q2 (SIHB15N60E) and two 4.7MW 3.5kV resistors (Cat SC4861) $20.00 IRD1 (TSOP4136) and fresnel lens (IML0688) (Cat SC4862) $10.00 MOTION SENSING SWITCH (SMD VERSION) (FEB 19) Short form kit (includes PCB and all parts, except for the extension cable) (Cat SC4851) $10.00 SW-18010P vibration sensor (S1) (Cat SC4852) $1.00 DAB+/FM/AM RADIO (JAN 19) Main PCB with IC1 pre-soldered Main PCB with IC1 and surrounding components (white box at top right) pre-soldered Explore 100 kit (Cat SC3834; no LCD included) Set of extra SMD parts (contains most SMD parts except for the digital audio output) Extendable VHF whip antenna with SMA connector: 700mm ($15.00) and 465mm ($10.00) PCB-mounting SMA ($2.50), PAL ($5.00) and dual-horizontal RCA ($2.50) socket GPS-SYNCHED FREQUENCY REFERENCE SMD PARTS (CAT SC4762) Includes PCB and all SMD parts required (NOV 18) $60.00 $80.00 $69.90 $30.00 $80.00 SUPER DIGITAL SOUND EFFECTS KIT (CAT SC4658) (AUG 18) PCB and all onboard parts (including optional ones) but no SD card, cell or battery holder $40.00 USB PORT PROTECTOR COMPLETE KIT (CAT SC4574) All parts including the PCB and a length of clear heatshrink tubing (MAY 18) $15.00 MICROMITE EXPLORE-28 (CAT SC5121) (SEPT 19) SC200 AMPLIFIER MODULE (CAT SC4140) (JAN 17) hard-to-get parts: Q8-Q16, D2-D4, 150pF/250V capacitor and five SMD resistors $35.00 Complete kit – includes PCB plus programmed micros and all other onboard parts $30.00 micro bundle – PIC32MX170F256B-50I/SO + PIC16F1455-I/SL Australia’s$20.00 electronics magazine siliconchip.com.au 90Programmed Silicon Chip *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # P&P prices are within Australia. O’seas? Place an order on our website for an accurate quote. 01/20 PRINTED CIRCUIT BOARDS & CASE PIECES Price For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT DATE PCB CODE 100DB STEREO AUDIO LEVEL/VU METER HOTEL SAFE ALARM UNIVERSAL TEMPERATURE ALARM BROWNOUT PROTECTOR MK2 8-DIGIT FREQUENCY METER APPLIANCE ENERGY METER MICROMITE PLUS EXPLORE 64 CYCLIC PUMP/MAINS TIMER PCB SET MICROMITE PLUS EXPLORE 100 AUTOMOTIVE FAULT DETECTOR MOSQUITO LURE MICROPOWER LED FLASHER MINI MICROPOWER LED FLASHER 50A BATTERY CHARGER CONTROLLER PASSIVE LINE TO PHONO INPUT CONVERTER MICROMITE PLUS LCD BACKPACK AUTOMOTIVE SENSOR MODIFIER TOUCHSCREEN VOLTAGE/CURRENT REFERENCE VI REFERENCE CASE PIECES (BLACK / BLUE) SC200 AMPLIFIER MODULE 60V 40A DC MOTOR SPEED CON. MAIN PCB ↳ MOSFET PCB GPS SYNCHRONISED ANALOG CLOCK ULTRA LOW VOLTAGE LED FLASHER POOL LAP COUNTER STATIONMASTER TRAIN CONTROLLER PCB SET EFUSE SPRING REVERB 6GHz+ 1000:1 PRESCALER MICROBRIDGE MICROMITE LCD BACKPACK V2 10-OCTAVE STEREO GRAPHIC EQUALISER ↳ FRONT PANEL ↳ CASE PIECES RAPIDBRAKE DELUXE EFUSE ↳ UB1 LID VALVE RADIO MAINS SUPPLY (INC. PANELS) 3-WAY ADJUSTABLE ACTIVE CROSSOVER ↳ FRONT/REAR PANELS ↳ CASE PIECES (BLACK) 6GHz+ TOUCHSCREEN FREQUENCY COUNTER ↳ CASE PIECES (CLEAR) KELVIN THE CRICKET SUPER-7 SUPERHET AM RADIO PCB ↳ CASE PIECES & DIAL THEREMIN PROPORTIONAL FAN SPEED CONTROLLER WATER TANK LEVEL METER (INC. HEADERS) 10-LED BARAGRAPH ↳ SIGNAL PROCESSING FULL-WAVE MOTOR SPEED CONTROLLER VINTAGE TV A/V MODULATOR AM RADIO TRANSMITTER HEATER CONTROLLER DELUXE FREQUENCY SWITCH USB PORT PROTECTOR 2 x 12V BATTERY BALANCER USB FLEXITIMER WIDE-RANGE LC METER (INC. HEADERS) ↳ WITHOUT HEADERS ↳ CASE PIECES (CLEAR) TEMPERATURE SWITCH MK2 LiFePO4 UPS CONTROL SHIELD RASPBERRY PI TOUCHSCREEN ADAPTOR RECURRING EVENT REMINDER BRAINWAVE MONITOR (EEG) SUPER DIGITAL SOUND EFFECTS DOOR ALARM STEAM WHISTLE / DIESEL HORN DCC PROGRAMMER (INC. HEADERS) ↳ WITHOUT HEADERS OPTO-ISOLATED RELAY (INC. EXT. BOARDS) JUN16 JUN16 JUL16 JUL16 AUG16 AUG16 AUG16 SEP16 SEP16 SEP16 OCT16 OCT16 OCT16 NOV16 NOV16 NOV16 DEC16 DEC16 DEC16 JAN17 JAN17 JAN17 FEB17 FEB17 MAR17 MAR17 APR17 APR17 MAY17 MAY17 MAY17 JUN17 JUN17 JUN17 JUL17 AUG17 AUG17 AUG17 SEP17 SEP17 SEP17 OCT17 OCT17 OCT17 DEC17 DEC17 JAN18 JAN18 FEB18 FEB18 FEB18 MAR18 MAR18 MAR18 APR18 MAY18 MAY18 MAY18 JUN18 JUN18 JUN18 JUN18 JUN18 JUN18 JUL18 JUL18 AUG18 AUG18 AUG18 SEP18 OCT18 OCT18 OCT18 01104161 $15.00 GPS-SYNCHED FREQUENCY REFERENCE 03106161 $5.00 LED CHRISTMAS TREE 03105161 $5.00 DIGITAL INTERFACE MODULE 10107161 $10.00 TINNITUS/INSOMNIA KILLER (JAYCAR VERSION) 04105161 $10.00 ↳ ALTRONICS VERSION 04116061 $15.00 HIGH-SENSITIVITY MAGNETOMETER 07108161 $5.00 USELESS BOX 10108161/2 $10.00 FOUR-CHANNEL DC FAN & PUMP CONTROLLER 07109161 $20.00 ATtiny816 DEVELOPMENT/BREAKOUT PCB 05109161 $10.00 ISOLATED SERIAL LINK 25110161 $5.00 DAB+/FM/AM RADIO 16109161 $5.00 ↳ CASE PIECES (CLEAR) 16109162 $2.50 REMOTE CONTROL DIMMER MAIN PCB 11111161 $10.00 ↳ MOUNTING PLATE 01111161 $5.00 ↳ EXTENSION PCB 07110161 $7.50 MOTION SENSING SWITCH (SMD) PCB 05111161 $10.00 USB MOUSE AND KEYBOARD ADAPTOR PCB 04110161 $12.50 LOW-NOISE STEREO PREAMP MAIN PCB SC4084/193 $10.00 ↳ INPUT SELECTOR PCB 01108161 $10.00 ↳ PUSHBUTTON PCB 11112161 $10.00 DIODE CURVE PLOTTER 11112162 $12.50 ↳ UB3 LID (MATTE BLACK) 04202171 $10.00 FLIP-DOT (SET OF ALL FOUR PCBs) 16110161 $2.50 ↳ COIL PCB 19102171 $15.00 ↳ PIXEL PCB (16 PIXELS) 09103171/2 $15.00 ↳ FRAME PCB (8 FRAMES) 04102171 $7.50 ↳ DRIVER PCB 01104171 $12.50 iCESTICK VGA ADAPTOR 04112162 $7.50 UHF DATA REPEATER 24104171 $2.50 AMPLIFIER BRIDGE ADAPTOR 07104171 $7.50 3.5-INCH LCD ADAPTOR FOR ARDUINO 01105171 $12.50 DSP CROSSOVER (ALL PCBs – TWO DACs) 01105172 $15.00 ↳ ADC PCB SC4281 $15.00 ↳ DAC PCB 05105171 $10.00 ↳ CPU PCB 18106171 $15.00 ↳ PSU PCB SC4316 $5.00 ↳ CONTROL PCB 18108171-4 $25.00 ↳ LCD ADAPTOR 01108171 $20.00 STEERING WHEEL CONTROL IR ADAPTOR 01108172/3 $20.00 GPS SPEEDO/CLOCK/VOLUME CONTROL SC4403 $10.00 ↳ CASE PIECES (MATTE BLACK) 04110171 $10.00 RF SIGNAL GENERATOR SC4444 $15.00 RASPBERRY PI SPEECH SYNTHESIS/AUDIO 08109171 $10.00 BATTERY ISOLATOR CONTROL PCB 06111171 $25.00 ↳ MOSFET PCB (2oz) SC4464 $25.00 MICROMITE LCD BACKPACK V3 23112171 $12.50 CAR RADIO DIMMER ADAPTOR 05111171 $2.50 PSEUDO-RANDOM NUMBER GENERATOR 21110171 $7.50 4DoF SIMULATION SEAT CONTROLLER PCB 04101181 $7.50 ↳ HIGH-CURRENT H-BRIDGE MOTOR DRIVER 04101182 $5.00 MICROMITE EXPLORE-28 (4-LAYERS) 10102181 $10.00 SIX INPUT AUDIO SELECTOR MAIN PCB 02104181 $7.50 ↳ PUSHBUTTON PCB 06101181 $7.50 ULTRABRITE LED DRIVER 10104181 $10.00 HIGH RESOLUTION AUDIO MILLIVOLTMETER 05104181 $7.50 PRECISION AUDIO SIGNAL AMPLIFIER 07105181 $2.50 SUPER-9 FM RADIO PCB SET 14106181 $2.50 ↳ CASE PIECES & DIAL 19106181 $7.50 TINY LED XMAS TREE (GREEN/RED/WHITE) SC4618 $7.50 HIGH POWER LINEAR BENCH SUPPLY 04106181 $7.50 ↳ HEATSINK SPACER (BLACK) SC4609 $7.50 DIGITAL PANEL METER / USB DISPLAY 05105181 $7.50 ↳ ACRYLIC BEZEL (BLACK) 11106181 $5.00 UNIVERSAL BATTERY CHARGE CONTROLLER 24108181 $5.00 NEW PCBs 19107181 $5.00 BIG-DIGIT 12/24-HOUR CLOCK PROCESSOR 25107181 $10.00 ↳ DISPLAY PCB 01107181 $2.50 STUDIO 350 POWER AMPLIFIER 03107181 $5.00 BOOKSHELF SPEAKER PASSIVE CROSSOVER 09106181 $5.00 ↳ SUBWOOFER ACTIVE CROSSOVER SC4716 $7.50 ARDUINO DCC BASE STATION 09107181 $5.00 NUTUBE VALVE PREAMPLIFIER 10107181/2 TUNEABLE HF PREAMPLIFIER Australia’s$7.50 electronics magazine PRINTED CIRCUIT BOARD TO SUIT PROJECT DATE PCB CODE Price NOV18 NOV18 NOV18 NOV18 NOV18 DEC18 DEC18 DEC18 JAN19 JAN19 JAN19 JAN19 FEB19 FEB19 FEB19 FEB19 FEB19 MAR19 MAR19 MAR19 MAR19 MAR19 APR19 APR19 APR19 APR19 APR19 APR19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 JUN19 JUN19 JUN19 JUN19 JUL19 JUL19 JUL19 AUG19 AUG19 AUG19 SEP19 SEP19 SEP19 SEP19 SEP19 SEP19 OCT19 OCT19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 DEC19 04107181 16107181 16107182 01110181 01110182 04101011 08111181 05108181 24110181 24107181 06112181 SC4849 10111191 10111192 10111193 05102191 24311181 01111119 01111112 01111113 04112181 SC4927 SC4950 19111181 19111182 19111183 19111184 02103191 15004191 01105191 24111181 SC5023 01106191 01106192 01106193 01106194 01106195 01106196 05105191 01104191 SC4987 04106191 01106191 05106191 05106192 07106191 05107191 16106191 11109191 11109192 07108191 01110191 01110192 16109191 04108191 04107191 06109181-5 SC5166 16111191 18111181 SC5168 18111182 SC5167 14107191 $7.50 $5.00 $2.50 $5.00 $5.00 $12.50 $7.50 $5.00 $5.00 $5.00 $15.00 $.00 $10.00 $10.00 $10.00 $2.50 $5.00 $25.00 $15.00 $5.00 $7.50 $5.00 $17.50 $5.00 $5.00 $5.00 $5.00 $2.50 $10.00 $5.00 $5.00 $40.00 $7.50 $7.50 $5.00 $7.50 $5.00 $2.50 $5.00 $7.50 $10.00 $15.00 $5.00 $7.50 $10.00 $7.50 $5.00 $5.00 $7.50 $2.50 $5.00 $7.50 $5.00 $2.50 $10.00 $5.00 $25.00 $25.00 $2.50 $10.00 $5.00 $2.50 $2.50 $10.00 MAR01 MAR01 JAN04 JAN20 JAN20 JAN20 JAN20 JAN20 04103011 04103012 01102041 01101201 01101202 09207181 01112191 06110191 $15.00 $15.00 $10.00 $10.00 $7.50 $5.00 $10.00 $2.50 We also sell an A2 Reactance Wallchart, RTV&H DVD, Vintage Radio DVD plus various books at siliconchip.com.au/Shop/3 Low-cost, high-precision By Allan Linton-Smith Many digital thermometers have readouts with a 0.1°C resolution but rarely are they accurate to within ±0.1°C. Despite their claims, some can be several degrees out, giving a false sense of accuracy. This simple, low-cost thermometer checker will tell you just how accurate your thermometer is. In some cases, you may even be able to adjust the thermometer to be more accurate. T here are many reasons why you might need an accurate thermometer. Checking to see if someone (especially a child) has a fever is an everyday use case. This requires pretty good accuracy, as the difference between a normal-but-elevated temperature (as can happen when someone has been exercising, crying etc) and a fever is just fractions of a degree. Or maybe you’re a keen chef, and you want to use processes like tempering chocolate, where you need to heat the chocolate to a temperature within a fairly small window, eg, 31-33°C. A 1°C error could mean that you think you’re in the window, but you aren’t, and the batch could be ruined. Whatever the reason for using it, if you have a thermometer that will read out to within 0.1°C, you want to know if it’s at least “in the ballpark” before you trust its display fully. This simple device allows you to do that. In some industries such as food manufacture, storage and distribution, temperatures are critical. This is especially true when food poisoning is a potential problem. So in these cases, it is essential to check that your thermometers are accurate. A device like this is therefore invaluable. This design is based on the LM35CAZ IC, a temperature sensor that has been available for some time now. But it has really come down in price lately. If managed correctly, it can be expected to give readings within ±0.2°C at 25°C. 92 Silicon Chip It works over a -40°C to +110°C range, but its accuracy is not as good when reading temperatures further away from room temperature. It’s worth building this yourself because other devices with precise temperature readings, eg, ±0.1°C, are not commonly available and are very expensive. For example, the Fluke 9142 and 9143 are excellent calibrating instruments with a display accuracy of ±0.2°C over their full range, but we recently spotted a used one for sale for over $5,000! Some say that glass thermometers are very accurate. Usually, their accuracy is accepted as ±0.5 divisions, which typically translates to ±1°F or ±0.5°C, but they are becoming quite rare. And they are still susceptible to reading errors, some of which are described in the side panel. When designing this device, we found that there are a few temperature sensor ICs that are even more accurate, such as the LMT70, but we decided against using this (for now) for a few reasons. One is that it only comes in a tiny SMD package (0.94 x 0.94mm) which is hard to work with. Another is that its output voltage is non-linear and requires a lookup table or polynomial curve-fitting to convert to a temperature reading. You can buy them pre-soldered to a module, but these test boards cost more than $50, which is not worth it for slightly better accuracy. Australia’s electronics magazine siliconchip.com.au The three DMMs are reading the outputs of the LM35s but we have also inserted the probes of five cheap digital thermometers and two lab-grade glass thermometers into the device. The cheap thermometers have a 0.5°C spread, quite a bit larger than the 0.2°C difference between the LM35s. To give you an idea of how hard it is to measure temperature precisely with a digital sensor, here is a passage from the LMT70 data sheet: “Although the LMT70 package has a protective backside coating that reduces the amount of light exposure on the die, unless it is fully shielded, ambient light will still reach the active region of the device from the side of the package. Depending on the amount of light exposure in a given application, an increase in temperature error should be expected.” “In circuit board tests under ambient light conditions, a typical increase in error may not be observed and is dependent on the angle that the light approaches the package. The LMT70 is most sensitive to IR radiation. Best practice should include end-product packaging that provides shielding from possible light sources during operation.” reading on the multimeter display means that the temperature is 15.5±0.2°C. Note that the LM35CA is only guaranteed to be within ±0.5°C at 25°C, but in reality, a typical sample of the device is within ±0.2°C from around -25°C to 50°C. The reason for using three different devices is threefold. First, it increases your confidence that you have an accurate reading when they are all giving similar results. Second, it also lets you get an idea of which sensors read a little higher or lower than the others. And third, it also lets you check that the case is at an even temperature before making your readings. In the photo above, with all three giving readings within 0.2°C of each other, note how the cheap digital thermometers with their probes inserted into the same metal case, and presumably reading the same temperature, are Circuit details The LM35CAZ is a precision integrated-circuit temperature sensor with an output voltage linearly proportional to the temperature in degrees Celsius. It requires no external calibration or trimming. It is low in cost, can operate on a wide variety of single supply voltages and has low self-heating. There’s little to the circuit besides three of these devices, and a battery to power them, as shown in Fig.1. IC1-IC3 can run from a wide supply range of 4-20V, so they are very well suited to be powered from a 9V battery. The output of each device can be measured by a multimeter connected across one of CON1-CON3, set to its 1V range or thereabouts (ideally, with 1mV resolution). IC1IC3 have a nominal 0V output at 0°C, rising by 10mV/°C. So, for example, in the photo above showing a 155mV siliconchip.com.au V+ Fig.1: the circuit couldn’t be much simpler; it’s just the three LM35s with a shared 100nF bypass capacitor, power switch S1 and a 9V battery for power. Australia’s electronics magazine IC1 LM35CAZ OUT GND LM35 CAZ METER+ METER– CON1 GND V+ OUT V+ IC2 OUT LM35CAZ GND METER+ 100nF METER– CON2 ON/OFF S1 V+ IC3 OUT LM35CAZ GND SC METER+ METER– BAT1 9V CON3 2020 January 2020  93 Accurate temperature measurement is not easy . . . Making precise temperature readings (say to within ±0.1°C) is difficult. Devices to do this are not commonly available and are very expensive! For example, if your backyard weather thermometer is showing 40°C, it could actually be 38°C or 42°C. It could even be much higher or lower than this if your thermometer is poorly sited (eg, near an air conditioner or road) or in a poorly designed enclosure or bad position, which allows its reading to be affected by direct sunlight. Assuming you have a linear sensor, you can calibrate it using a stirred ice bath (to determine its reading at 0°C) and vigorously boiling pure water (100°C), both at sea level. But unless you do this correctly, your readings could still be out considerably. For example, at around 300m elevation, the boiling point of water is about 98.9°C. Normal day-to-day atmospheric pressure variations can have a small effect on the boiling point, too. Any salt in the water or ice can have a dramatic effect on both the boiling and freezing points. According to the CRC Handbook of Chemistry and Physics, 2.92% sodium chloride in solution reduces the melting point of ice by 0.19°C and increases the boiling point by 0.05°C. A practical thermometer calibration method is given at www.nfsmi.org/documentlibraryfiles/PDF/20130806025735.pdf Even if your calibration method is flawless, you also need to know that the sensor response is perfectly linear to have confidence in readings between the two extremes. Even IC-based temperature sensors like the LM35 suffer from some level of non-lin- all reading high (by about 0.5-1°C) and also have a considerably greater spread than the LM35CA devices. You must use the LM35CA version for accuracy, as the LM35/LM35A/LM35C/LM35D cannot achieve the same accuracy. (Note: the “Z” suffix indicates a TO-92 package). Note though that the LM35CA is limited to measuring in the range of -40°C to +110°C, while the less accurate LM35 and LM35A versions can measure from -55°C to +150°C. The three multimeters we’ve used here are low-cost devices that you can get for a few dollars from Jaycar, and we’ve found that they are very accurate. They have a voltage accuracy rating of ±0.5%, which equates to an additional error of just ±0.1°C in the temperature readings. To demonstrate the accuracy of the LM35CAs, we also Parts list – Thermometer Calibrator 1 diecast aluminium box, approx. 115 x 90 x 55m [eg, Jaycar Cat HB5042] 3 LM35CAZ temperature sensors [eg Mouser LM35CAZ/NOPB, Digi-key LM35CAZ/NOPB-ND, RS Cat 5335878] 3 voltmeters [eg, Jaycar Cat QM1500] 3 red banana plug-banana plug leads 3 black banana plug-banana plug leads 3 black chassis-mounting banana sockets 3 red chassis-mounting banana sockets 1 chassis-mounting 9V battery holder 1 9V battery clip with flying leads 1 9V battery (alkaline recommended)] 1 100nF ceramic, MKT or greencap capacitor 1 SPST toggle switch 1 small piece of protoboard 1 3mm ID solder lug 1 M3 x 10mm machine screw and nut 1 adhesive TO-3P or TO-247 insulating washer 1 small tube adhesive heatsink compound [eg Jaycar NM2014] various lengths of ribbon cable or hookup wire 94 Silicon Chip earity, even though they are designed to be as linear as possible. It isn’t just electronic sensors that suffer from accuracy problems, either. As one meteorologist pointed out, even the meniscus (bulge in the top of a column of liquid in a tube) in a mercury or alcohol thermometer can lead to significant inaccuracies in the readings. He also mentions: “… mercury freezes at -38.8°C. It becomes increasingly less malleable as it approaches that temperature and makes low temperatures with mercury thermometers of no value. The 18th century observers of the Hudson’s Bay Company using thermometers provided by the Royal Society were unaware of the problem ...” Because of problems like this, interpreting historical air and sea temperature data is quite tricky! have two laboratory-grade analog thermometers measuring the same temperature. As shown in the separate photo, they are both reading just under 16°C, just slightly higher than the figures shown on the DMMs. Do not buy cheap LM35 sensors online if you are expecting accuracy, or even for them to function. We also purchased several LM35Ds cheaply on the internet to compare, but NONE of them worked at all! So it is essential to obtain them from a reputable supplier (eg, the ones mentioned in the parts list). Construction We recommend that you build this into a diecast aluminium box. This will not only provide some shielding, it allow you to check glass thermometers and to help maintain a uniform and stable temperature, without any thermal gradients. The sensors have very little self-heating, but it is still present; the large thermal mass of the case helps to mitigate this. The LM35s also detect temperature variations through their pigtails. If these are exposed to small amounts of heat variations, such as human breath or wind, it can disturb the measurements and give false readings. By placing the ICs inside a metal box, we can eliminate these errors. Solder the three LM35s to a small piece of protoboard, veroboard or similar. Join their V+ and GND leads together, V+ 1N4148 A V+ K IC1 OUT LM35 GND METER+ METER– A D1 1N4 148 18k SC K Fig.2: by adding three components to each LM35, you can measure temperatures below 0°C. Australia’s electronics magazine 2020 A D2 1N4 148 LM35 K GND V+ OUT siliconchip.com.au Thermocouple LM35CAZ +200 to +1750°C -40 to +150°C ±0.5 to ±5°C ±0.2°C at 25°C Variable 0.2°C/year Non-linear Linear Self-powered 4-20V DC 0.1-10s 2-15s Susceptible Susceptible High Moderate Table 1 shows the typical parameters of various temperature sensors, while the graphs at right show the errors in the different iterations of the LM35. 2.5 LM35D 2.0 TEMPERATURE ERROR (°C) Thermistor RTD Range -100 to +325°C -200 to +650°C Accuracy ±0.05 to ±1.5°C ±0.1 to ±1°C Stability <at> 100°C 0.2°C/year 0.05°C/year Linearity Exponential Fairly linear Power Small current Small current Response 0.1-10s 1-50s Interference Rarely Rarely Cost Low to moderate High LM35C 1.5 1.0 LM35CA 0.5 TYPICAL 0.0 ±0.5 LM35CA ±1.0 LM35C ±1.5 ±2.0 ±2.5 ±75 ±25 25 75 125 175 TEMPERATURE (°C) and solder the 100nF capacitor across these rails. Also connect pairs of wires to the GND and OUT terminals of each device, plus one pair of wires between the V+ and GND rails. Ideally, the pairs of wires should be figure-8 cable (eg, stripped from ribbon cable). If you are using individual wires, it’s best to twist them together so that any interference is mostly cancelled out between the two conductors. Now glue the three TO-92 plastic packages to the inside of the diecast box using thermally conductive adhesive. We used Jaycar NM2014 adhesive thermal paste. Drill holes in the case for the power on/off switch and 9V battery holder, plus holes for the three pairs of banana sockets in the lid. Also drill a 3mm hole for the chassis grounding screw, near the battery holder, and one or two extra holes in the lid for analog thermometer calibration, if desired. Deburr all the holes and mount these parts. Then solder the pairs of wires from the LM35 GND and OUT terminals to the banana sockets, with the OUT terminals going to the red sockets. The remaining pair of wires then goes to the switch (V+) and case (GND). Solder the other switch terminal to the red lead from the 9V battery, so that V+ is connected to the battery when the switch is in the on position (usually down). Using it Avoid using this device in a windy environment or one with rapidly changing temperatures, such as near a window that’s exposed to full sun where clouds may pass by. Ideally, it should be used indoors with still air in an environment with a stable temperature. Switch it on and allow everything to stabilise for around SC 20 minutes before using it for best results. While it might seem like overkill, placing the project in a diecast case has several benefits – it’s shielded, of course, and the thick aluminium provides some thermal inertia. Placing the LM35CAZs inside the box also means they will be less affected by external variants. Of course, a smaller diecast case could be used, providing the various components will fit. siliconchip.com.au C009 Join the remainingFigure GND wire to the vs black wire of the 9V 9. Accuracy Temperature (Ensured) battery to the solder lug and attach it to the inside of the case using an M3 machine screw and nut (not shown below). Stick the insulating washer on the inside of the case directly below the analog thermometer insertion holes in the lid. This will provide the thermometers with a bit of a ‘cushion’ so that they do not break when inserted. Now connect the battery clip to the battery, slot it into its holder and switch on the power. Use a red and black pair of banana plug leads to connect one of the DMMs to one of the pairs of binding posts, and check that you get a reading that’s fairly close to ambient temperature. For example, if it’s around 25°C where you are, you should get a reading around 250mV. Verify that all the outputs are similar values. Australia’s electronics magazine January 2020  95 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. 3.2MHz reference derived from 10MHz Modern digital communication techniques require extreme frequency accuracy; a few hertz out will prevent the message from being decoded. A friend recently asked me how he could derive an accurate 3.2MHz from a 10MHz GPS-disciplined oscillator. I came up with this circuit using a modified AD9850 DDS module and an Arduino Nano. Both are readily available from various online sources. The 10MHz reference signal is fed into CON1, an SMA socket, with jumper JP1 providing nominal 50W termination. This signal is amplified by one stage of a 74HC04 hex inverter (IC1a), operating as an RF amplifier. This boosts 96 Silicon Chip the reference signal swing up to CMOS voltage levels (ie, about 5V peak-topeak). The 1MW resistor between the inverter stage's output and input puts it into linear mode, so it acts as an excellent amplifier up to about 20MHz. The 15pF capacitor prevents parasitic oscillation from being superimposed on the 10MHz waveform. The signal is further buffered and 'squared up' by IC1b. The AD9850 module comes with an onboard 125MHz oscillator. This is a 4-pin module and is easily removed. The 10MHz signal from the output of IC1b is then fed to the appropriate oscillator pad using a length of hookup Australia’s electronics magazine wire (the pad is directly above C8). The software for the Arduino Nano is straightforward. On power-up, a RESET pulse is sent to the AD9850, then five bytes are sent to set its output frequency, followed by a pulse on FU_ UD. For a 3.2MHz output with 10MHz reference clock, the tuning word required is hex 51EB851F. This can be calculated as FOUT × 232 ÷ CLKIN, or it can be worked out using the Analog Devices online calculator, available at: siliconchip.com. au/link/aau0 The hex bytes sent to the AD9850 are 00, 51, EB, 85, 1F; each one is loaded with a pulse on WCLK. These are written from inputs D0-D7 on the AD9850 to digital outputs D4D11 on the Arduino Nano. Once the siliconchip.com.au bytes are loaded, the processor stops. The software is written in BASCOM, rather than the Arduino IDE, but it still works on a Nano since it uses an AVR micro. The output signal from the AD9850 is fed into the base of a JFET configured as a common source amplifier. It has a tuned circuit between the positive supply and its drain, which gives a reasonable sinewave at the output. The main spurs of the spectrum are at multiples of the 10MHz, and are more than 30dB down from the fundamental at 20MHz, 30MHz and 40MHz (see scope grabs). I have no way of measuring phase jitter, but the frequency counter readout is steady at 3.2MHz. The tuned output transformer is made from a 22µH RF choke, which has an unloaded Q of more than 100. The secondary is five turns of thin insulated wire over the “cold” end of the choke. Power comes from a source determined by jumper JP2. We can select an external 7.5-9V supply from CON3, or phantom power can be obtained from the output connector, CON2. The 5V regulator on the Arduino has limited capacity, and supplies the AD9850, so don’t go above 9V or it may overheat. Mosfets Q2 and Q3 provide a simplified RS232 debugging interface. It may safely be left out. Jumpers JP3 and JP4 between D2/D3 and GND allow for future expansion. I have designed a PCB for this circuit and the pattern can be downloaded from the Silicon Chip website (siliconchip.com.au). It's designed to fit in a 111 x 60 x 30mm diecast box (Jaycar HB5062) which provides good shielding. Apart from the RS232 interface, all components are through-hole types; however, the discrete component footprints are designed so that SMDs can also be used. The software (Converter.bas/.hex) can also be downloaded from the Silicon Chip website. Charles Kosina, Croydon, Vic. ($80) Circuit Ideas Wanted siliconchip.com.au Above: the output waveform from the frequency reference at 3.2MHz. Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia’s electronics magazine January 2020  97 Micromite Mk2 dev board with Microbridge This Micromite development system is an update of my Micromite Mk2 breadboard adaptor, which was previously published in Circuit Notebook (October 2016; siliconchip.com.au/ Article/10306). It’s built on a 77mm x 64mm double-sided PCB and uses a quick-release ZIF socket for the Micromite chip (IC1). It has a "Microbridge" onboard (IC2), which provides a USB serial port via CON1 and also allows the Micromite PIC32 chip to be reflashed (eg, if a newer version of MMBasic is released). The board also includes sockets for an alphanumeric LCD (CON4), colour touchscreen with SD card (CON5), headers for making connections to all Micromite pins (CON8-CON10) plus header CON11, which is suitable for connecting a 2KB EEPROM 98 Silicon Chip (11AA160T-I/TT) or DS18B20 digital temperature sensor. Also, four-pin header CON7 breaks out the SPI interface. Jumper JP1 selects whether the board is powered from USB connector CON1, and CON2 provides a convenient point to draw power from the 3.3V and 5V rails, or feed in power to the 5V rail. The rest of the circuit is quite similar to the Micromite BackPack V2 (May 2017; siliconchip.com. au/Article/10652). Some connections such as the RS and EN lines for the alphanumeric LCD and the RESET and DC lines for the touchscreen can go to any Micromite pin. Therefore, these lines are not directly connected to any pins on IC1, but rather to headers CON3 and CON6. These can then be connected to the Australia’s electronics magazine pins of your choice using jumper wires. The PIC16F1455 for the Microbridge can be purchased pre-programmed from the Silicon Chip Online Shop (siliconchip.com.au/Shop/9/4263) or it can be programmed as explained in the Microbridge article (May 2017; siliconchip.com.au/Article/10648). The EAGLE ECAD files, PCB pattern, Gerber files, component layout and parts list for this design can be downloaded in a ZIP file from the Silicon Chip website. Gianni Pallotti, North Rocks, NSW ($75). siliconchip.com.au 20W instrument practice amplifier This basic instrument practice amplifier has inputs for four instruments and a basic mixer which feeds into an integrated 20W power amplifier. The whole thing runs from a 12V battery or mains supply. As instruments typically have their own volume controls (and volume can be adjusted based on how they are played), there are no volume or gain controls. Instead, the instrument signals fed into CON1-CON4 and are AC-coupled straight into a virtual-earth mixer with a fixed gain of around two times. The 330kW input impedance suits most pickups. The mixed signals are amplified and inverted by op amp IC1, a JFETinput type to keep the input impedance high. Its non-inverting input is held at half the supply voltage due to a voltage divider filtered by a 47µF capacitor to remove supply noise. Diode D2 ensures that this rail drops quickly at switch-off. The signal from IC1 is AC-coupled to input pin 1 of IC2, a dual power amplifier configured in bridge mode. This can drive a 4W speaker, and must do so to get the rated 20W with a 12V supply. The upper stage is configured with a gain of +201 times while the siliconchip.com.au lower stage has a gain of -200 times, therefore driving the speaker in bridge mode with a total gain (in this stage) of 401 times. The feedback is a little complex but consider that the signal at the inverting input of the upper op amp must match the incoming signal in closedloop mode. This AC signal also appears at the junction of the two 10W resistors. If you consider the lower amplifier to be a standard inverting configuration, its gain is therefore -200 times (-1 × 2kW ÷ 10W; ignore the lower 10W resistor as it has no effect here). Next, consider that the junction of the 2kW resistor and 10W resistor is the 'virtual earth' point of the inverting amplifier and therefore, there is no AC signal there. That means you can consider the two 10W resistors to be in parallel in terms of the behaviour of the upper amplifier stage, and so its feedback resistor network is 1kW at the top and 5W at the bottom, for a total gain of 201 times (1kW ÷ 5W + 1). Taking account the gain of two in the preamplifier stage (IC1), total system gain is around 800 times, enough to get the full 20W into 4W (which requires around 9V RMS) with an input Australia’s electronics magazine signal of around 10mV RMS. If using a higher impedance speaker, the supply voltage can be increased up to about 24V to maintain a reasonable power level. A laptop supply might be a good choice in that case. The capacitors connected between BS1/BS2 (pins 11 & 7) and output pins 10 and 8 are necessary to achieve maximum power with low distortion, especially at lower frequencies. However, if you don't need the full 20W, you can leave them off and instead connect BS1/BS2 directly to +Vs (pin 9). LEDs1 & 2 light up to show when there is output, and their brightness is proportional to the signal level. Each output also has a Zobel network (100nF/1W) which is required for stability. Fuse F1 and diode D1 provide reversed supply polarity protection as F1 will blow in this case, or if there is some other circuit fault. IC1 needs to be mounted on a heatsink rated at no more than 4°C/W to avoid thermal shutdown at high power levels. A slightly smaller heatsink could be used if the 20W power rating is not required, or will only be achieved in short bursts. Petre Petrov, Sofia, Bulgaria. ($70) January 2020  99 Vintage Radio By Ian Batty Your radio is tuned and ready Panasonic’s Radar Matic R-1000 Transistors and clockwork combine to provide convenience and elegance in this 1965 Japanese radio. In the early days of electricity, houses were only wired up for electric lighting, so when other electricity-powered accessories became available, initially you had to run them off the light sockets. I was fascinated to learn that multinational giant Panasonic was founded by an impoverished Japanese businessman whose first product was a light socket double-adaptor. The early days of Panasonic Konosuke Matsushita, born in 1894, came from an affluent turned impov- 100 Silicon Chip erished family and had an apprenticeship cut short due to the business collapsing. He found another apprenticeship at a bicycle shop before landing a job with the Osaka Electric Light Company. He was eventually promoted to a position as an electrical inspector. When his invention, a new and improved light socket, left his boss unimpressed, 22-year-old Matsushita decided to set up his own business. But he struggled to balance manufacturing and marketing, with his sockets not being popular enough. The company nearly went bankrupt until an unexpected order of 1000 insulator plates for fans came in. As the company was rapidly expanding, Matsushita saw the potential for an efficient bicycle lamp, but wholesalers were skeptical about the stated 40 hour lifespan. Matsushita decided to send the lamp directly to bicycle store owners. This led to a marked increase in orders. Matsushita focussed on mass production of electrical consumer goods, lowering the sales price and thus in- siliconchip.com.au creasing the percentage of people who could afford it. This finally put Matsushita and the National brand on the map. Now the company is called Panasonic; it is one of Japan’s largest consumer electronics company today. were used from the earliest phonographs until the 40s. Being mechanical, there’s no battery-draining electric motor, so the R-1000 is as economical on batteries as comparable manuallytuned sets. The Panasonic R-1000 Circuit description The 50s and 60s saw intense competition in postwar Japan. Sony’s Masaru Ibuka, co-founder with Akio Morita, was famous for grumbling when his company’s technological leadership resulted in it being dubbed a “guinea pig”. It’s easy to think of Matsushita’s National brand as following in Sony’s wake. The set described here, though, is not merely a follower. It has one particularly innovative feature: autotuning. This is quite different from the “auto-tune” software used by hip-hop artists like Kanye West and T-Pain, or pop singer Cher! I was offered this set by a fellow HRSA member to review; he’d collected several of these fine examples of 60s ingenuity, and it was a pleasure to examine their workings. The receiver section uses a configuration that had become more-or-less standard by the year this set was released, 1965. Using ten germanium PNP transistors and three diodes, it’s a seven-transistor superhet with a threetransistor control circuit. Converter TR1, a 2SA102, is a drift type, superior to the alloyed-junction OC44. This circuit uses collector-base feedback. Many such circuits will stop working if you try to inject a signal into the converter base. Unusually, this converter does use a padder, 170pF capacitor C5. I’ll elaborate on this later. The 455kHz IF signal from the converter is fed to the first IF amplifier, based around transistor TR2, via first IF transformer T1. It’s the conventional arrangement, with tuned, tapped primary and untuned, untapped secondary. TR2, a 2SA101, operates in a standard gain-controlled circuit. Base bias current through 68kW resistor R4 is under 100µA, allowing the rectified DC from the demodulator to take effective control of the first IF stage gain as received signal strength rises. TR2’s base is bypassed to ground via 10µF capacitor C8. It’s an electrolytic, pretty much a no-no at radio frequencies (even 455kHz) as any deterioration in C8 is likely to cause IF instability. If you get an R-1000 with an IF circuit which oscillates or shows other bad behaviour, be sure to replace C8. The first IF stage has collector-base neutralisation, confirming that the 2SA101 operates similarly to an OC45. Second IF transformer T2 also has a tapped, tuned primary with an untuned, untapped secondary. T2’s primary is shunted by 220kW resistor R6. It’s there to broaden out T2’s response and increase the IF bandwidth. TR2’s collector load comprises T2 at intermediate frequencies and 2.2kW resistor R8 at DC, bypassed for IF by 30nF capacitor C11. With no signal, the junction of T2 and R8 sits about 1.3V above ground, so OA70 diode D1 is normally not in conduction. Panasonic innovation There’s no easy comparison for this set. The Toshiba 15M-915, from around 1968, has 15(!) transistors but a very similar overall design. Sony appears to have waited until they offered AM/FM portables before including automatic tuning. These examples aside, some automatic/preset tuned valve radios were offered as early as the late 1930s. So it looks like Panasonic were the first to market with auto-tuning transistor radios. They followed up in the early 70s with their RF-6070 AM/FM set, also using a spring motor mechanism. Spring-powered auto-tuner The radio comes in a “leather” finish black case with bright inset metalwork, including the speaker grille, tuning dial and metal frame. The flip-out handle at the back is a winder for the clockwork motor. Since this auto-tuning radio predated the availability of variable-capacitance diodes (varicaps) with capacitance ratios approaching 10:1, an all-electronic system was not possible for the broadcast band at the time. So the folks at Panasonic used a proven method: a spring motor. These siliconchip.com.au Australia’s electronics magazine The left (above) and right (below) sides of the Radar Matic R-1000 shown at close to actual size. The case is plastic with a leather-like finish, while the grille and sides are metal. January 2020  101 When the auto-tuning switch (S2) is pressed, it energises relay K1 which shorts out the audio stage. This then moves a lever connected to the relay, which applies pressure to a spring. This action unlocks an impeller to move a series of gears to rotate the spring motor. The impeller comprises four blades, plus two that control the spring motor’s rotational speed via air resistance. The spring motor adjusts the tuning capacitor (C1/C6) until a signal is detected. This signal is then converted to an IF signal by the 2SA102 (TR1) before being filtered and amplified by TR2 and TR3. This signal is detected in the trigger stage (TR8 & D3) before being amplified by TR9 and then causing relay K1 to open. This then returns the lever to its original position, locking the impeller and thus stopping the adjustment of the tuning capacitor. As signal strength rises and the AGC circuit comes into action, TR2’s bias is reduced, and its collector current falls. This causes the voltage across R8 to fall, and very strong signals will reduce R8’s voltage drop to the point that D1 begins to conduct. This conduction will shunt some of the IF signal at converter TR1’s collector to ground, thus extending the range of the AGC circuit. TR3 feeds third IF transformer T3, with a tuned, tapped primary and untuned, untapped secondary. T3’s secondary feeds demodulator diode D2, also an OA70, and capacitive voltage divider C20/C21. At only 3pF, C20 has little effect on the demodulator, and we’ll look at that signal pickoff soon. Demodulator D2’s output feeds M1, an integrated resistor-capacitor filter. M1’s audio output goes to 10kW volume control pot R15. There’s also a connection, via 8.2kW resistor R14, back to TR2’s base (the first IF amplifier). 10µF capacitor C8 filters the audio signal, delivering the smoothed AGC signal to TR2. The audio output section uses TR4 (2SB173) and TR5 (2SB171) in a di102 Silicon Chip rect-coupled circuit. The DC operating conditions are established by the voltage divider formed by resistors R16 & R17, holding TR4’s base at a constant voltage, and stability is maintained by local negative feedback due to emitter resistor R18. Unusually, this stage also has collector bias applied to the base of TR4 via 10kW resistor R17. These two DC feedback paths allow the designers to assume a constant base bias for TR5, which gains DC stability from emitter feedback via 1kW resistor R20. Direct coupling eliminates some capacitors, giving a reduced component count and potentially improving low-frequency response. TR5’s collector feeds the primary of phase-splitting transformer T4, and its tapped secondary provides the antiphase signals to drive the Class-B output stage comprising transistors TR6 & TR7, both 2SB176s. The output stage gets around 150mV of forward bias, stabilised for temperature, from MT-250 thermistor “Th”. Local collector-base feedback is applied by 6.8nF capacitors C18/C19. Output transformer T5 matches the collectors of TR6/TR7 to the 8W Australia’s electronics magazine speaker, which is connected via the headphone socket. There’s also overall audio feedback from the speaker/ earphone to TR5’s base via 150kW resistor R25. Auto-tune circuit The auto-tuning circuit begins with capacitive divider C20/C21. The signal developed across C21 is applied to the primary of transformer T6. T6’s secondary is connected to an internal ceramic filter. Similar to a quartz crystal, this is a piezoelectric device with a very narrow frequency response; in other words, it has a very high Q. Ceramic filters are cheaper than quartz crystals, and substitute well if very high precision is not needed. This filter’s -3dB bandwidth is exceptionally narrow, so it will only pass a signal when the frequency is very close to 455kHz. The filter’s output feeds a conventional IF amplifier stage, based around transistor TR8, which in turn feeds conventional IF transformer T7. T7’s output goes to OA90 diode D3, and its rectified DC output drives the direct-coupled combination of TR9/TR10. siliconchip.com.au Since TR9 only gets bias when D3 is rectifying a 455kHz signal, TR9 is usually cut off and TR10 gets forward base bias via 18kW resistor R32. R32’s biasing would normally put TR10 into full conduction and would pull auto-tuning relay K1 into closure. But even with TR9 inactive, TR10 is usually off. In normal operation, relay contacts K/1-2 are open, so TR10’s emitter circuit is open; no collector current flows and relay K1 does not close. The autotune circuit is dormant until the user presses the AUTO TUNING bar and closes S2. This supplies battery current to K1 and cuts off DC supply to the audio preamp and RF/IF stages as S2/3-4 is open. K1 closes immediately, so before the user can release S2, emitter current is supplied to TR10 (and power to amplifier TR8) so that TR10 holds K1 in. Search contact K1/3-4 will also be open, allowing “Local/DX” switch S3 to take control of second IF amplifier TR3’s gain, while search contact K1/56 shorts TR5’s base to ground, muting the audio, and K1’s armature releases a brake on the spring motor, allowing it to drive the tuning capacitor. siliconchip.com.au As the spring motor rotates, the signal frequency from the converter sweeps across the IF amplifier’s bandpass. As the signal’s frequency reaches the sharp bandpass peak of the ceramic filter, it will pass a signal through amplifier TR8 to D3. D3’s rectified DC output will bias TR9 strongly on. When TR9 switches on, it shorts out the forward bias on TR10, so TR10 cuts off and K1 releases, resulting in the spring motor’s brake being applied. Search contact K1/5-6 opens, unmuting the audio, K1/1-2 opens, turning off TR8 and TR10 and K1/3-4 closes, returning TR3 to maximum gain. During auto-tuning, the K1/3-4 contacts open and remove the short across Local/DX switch S3. This connects R12 (1.2kW, DX) or adds R11 (4.7kW, LOCAL) in series with R13, progressively reducing TR3’s emitter current, and thus its gain. This is used to determine how strong the received signal at a particular frequency needs to be for the autotuning sweep to stop, to reject weak stations if necessary. If auto-tuning cannot detect a station, pressing in the manual tuning thumbwheel allows conventional tuning. Australia’s electronics magazine Tuning capacitor C1/C6 uses semicircular “straight line capacitance” plates that allow full 360° rotation, hence the use of padder C5. It’s a similar construction to that used in the DKE38 Kleinempfanger described in the July 2017 issue (siliconchip. com.au/Article/10728). However, the R-1000 uses air spacing while the DKE38 (from the 1930s) used a plastic dielectric. Motor speed regulation I remember, as a small child, taking an old alarm clock to bits. Imagine my surprise when, having dismantled the escapement (the part that goes “tick, tock”), the hands spun like a fan! A balance wheel regulator would be over-engineering for the Radar Matic’s spring motor, but it does need some kind of speed control. The solution is to use a step-up gear train connected to the motor at the “input” end, and a four-bladed paddle wheel at the “output”. As the paddle spins, air friction balances the driving force to give a reasonably constant drive train speed. It dissipates energy, so it’s a bit like an electronic shunt regulator. January 2020  103 The auto-tuning switch (S2) is at the top-left of the chassis just under the ferrite rod. The main PCB is at the right, while the smaller copper-plated sheet at left holds the tuning gang, spring motor and auto-tuning relay K1. The PCB wiring diagram is reproduced from the service manual which can be found at Kevin Chant’s website (www.kevinchant.com/uploads/7/1/0/8/7108231/r-1000.pdf). Power switch S1 and Auto-tuning control switch S2 are shown in the off position, while Local/DX switch S3 is in the DX position. 104 Silicon Chip Australia’s electronics magazine siliconchip.com.au The underside of the chassis sits at the front of the case as seen by the location of the tuning dial. The sensitivity switch (Local/DX S3) is also visible at the far-right, centre end of the chassis. An orange strip of tape hangs off the chassis and is used to hold the batteries in place. Cleaning up this set The review set was in good cosmetic condition, so a light clean had it looking just fine. The auto-tune feature was a bit fussy, working best with the set upside-down. Clockwork mechanisms don’t tolerate dust, grime or gummy lubricants well, so I cleaned the mechanism with an evaporating contact cleaner. Be aware that popular “rust easers”, based on fish oil, are not ideal for lubricating fine mechanisms. After that, it worked a lot more consistently. How good is it? Like the Sony TR-712, it’s madly sensitive: 55µV/m at 600kHz and 27µV/m at 1400kHz for 50mW output. Unsurprisingly, these readings are for signal+noise to noise (S+N/N) figures of 6dB and 7dB respectively. For the more standard 20dB S+N/N it’s 150µV/m at 600kHz and 110µV/m at 1400kHz. In testament to this set, it can just pick up 774 ABC Melbourne inside my screened room – no easy feat. The converter’s 455kHz sensitivity of 1.35µV for 50mW output backs up the air interface figures. As this converter uses base injection, it wasn’t possible to test at the base with 600kHz and 1400kHz signals. I had to use my standard method of coupling to the tuned primary via a 10pF capacitor. This has the advantage of minimal detuning of the cirsiliconchip.com.au cuit and giving a repeatable indication for testing. IF bandwidth is ±1.8kHz at -3dB and ±34kHz at -60dB. AGC allows some 6dB rise for a signal increase of more than 40dB. Audio response from antenna to speaker is 130-2200Hz. From volume control to speaker, it’s 125~4000Hz. At 50mW, total harmonic distortion (THD) is around 3% with clipping at 200mW for a THD of 10%. At 10mW output, it is 2.5%. The auto-tuning feature managed to stop at every local station and was able to reliably detect my reference “weak station”, ABC 594 at Horsham as well as 7BU in Burnie, Tasmania. On test, it would reliably stop on a 600kHz signal of 150µV/m on DX, and about 1.3mV/m on Local. Other versions A later version of this radio was released, the R-1100, then an AM/FM version, the RF-6070. I would love to get my hands on an RF-6070. Later Panasonic offerings in the Radar Matic range with mechanical drives appear to use reversing electric motors. Japanese part coding The Japanese Industrial Standard (JIS) semiconductor coding is somewhat more helpful than the chaotic RETMA system. The JIS distinguishes polarities, technologies and applications, but chemistry (germaniAustralia’s electronics magazine um/silicon) and power rating are not coded for. Transistors starting with 2SA are high-frequency PNP BJTs, 2SB are audio-frequency PNP BJTs, 2SC are highfrequency NPN BJTs, 2SD are audiofrequency NPN BJTs, 2SJ are P-channel FETs (both JFETs and Mosfets) and 2SK are N-channel FETs (both JFETs and Mosfets). Disassembly and reassembly To dismantle, first carefully remove the winding key by pulling it off – you may need to gently lever it on both sides. Remove the two Philips screws on the back cover. Undo the snaps at the bottom edge and the back will then come off easily. The chassis is held down by redanodised screws. For reassembly, be sure to align the Local/DX switch’s lever tab with the slide attached to the case, reattach the back and its screws, then push the winding key onto its splined shaft. Be aware that auto-tune switch S2 connects power to the RF/IF and audio preamp stages and contact corrosion will prevent this. If you have an R-1000 that’s “dead”, but drawing some 3~5mA, this is probably just the output stage’s quiescent current. A quick DC voltage check will show whether S2 is working correctly. You can find more photos of this set at Radiomuseum: siliconchip.com.au/ link/aapr SC January 2020  105 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Arduino GSM Remote Monitor won’t compile Model railway crossing using stepper motors We are building your GSM Remote Monitoring Station project from the March 2014 issue (siliconchip.com. au/Article/6743). We are having some difficulties compiling the sketch. We are getting the following error: Have you ever published a project that uses stepper motors to raise and lower the boom gates of a model ‘Z’ scale railway crossing? I want to design and make 3D-printed model railway boom gates and ‘X’ crossing signs with flashing red lights. 3D printers are now becoming more affordable so that we can make things to scale, for all the parts of the railway city scene. (M. S., Lalor Park, NSW) • It doesn’t seem that we have published such a design. However, we have published some relevant articles: 1) Model railway level crossing control, March 1996 (siliconchip.com.au/ Article/6051): which is intended to drive model railway boom gates actuated by DC motors. 2) Manual Control Circuit for a Stepper Motor, June 1997 (siliconchip.com. au/Article/4870): which mentions the possibility of doing what you describe, but doesn’t show the control part of the circuit that would be required. Arduino: 1.8.9 (Windows Store 1.8.21.0) (Windows 10), Board: “Arduino/Genuino Uno” GPRS_Monitor:103:4: error: expected constructor, destructor, or type conversion before ‘(‘token ISR(WDT_vect) { ^ I hope you can help us. (T. K., via e-mail) • This appears to be caused by changes to the Arduino IDE software since that project was released. We downloaded the Arduino IDE v1.0.5r2, and it compiles on that version (this project is actually older than V1.0.5r2). We found this at the following website: https://www.arduino.cc/en/Main/ OldSoftwareReleases#1.0.x However, it should compile correctly if you add “#include <Arduino. h>”, without the quotation marks, to the top of the .ino file. We haven’t bothered to update the code to work with newer versions of the Arduino IDE, since that project is now obsolete. It is about to be superseded by the 4G Remote Monitoring Station, which will be published in the February 2019 issue. Using DCC for slot racing Hi, I want to build a cheap DCC unit for slot racing (Faller AMS). How do I go about doing this? (P. B., via e-mail) • We have designed a DCC booster/ base station which is described in this issue (starting on page 44). It is capable of 10A output and is Arduino-based. This may be what you are looking for, but we have not tested this project with any slot car systems. 106 Silicon Chip 45V 8A Linear Bench Supply diode confusion I am building your High Power Linear Bench Supply (October-December 2019; siliconchip.com.au/ Series/339). I received the two PCBs that I ordered today. I noted and read the errata, pointing out that D6 is an SB380 Schottky diode. While populating the board (Rev H), I discovered that the circuit and the board are not in agreement. D5 on the board overlay has its cathode going to the output terminal (CON1) of the supply and the anode going to the negative rail of the filter caps. It is labelled as an SB380, as is D6. Diode D6 has its anode also on the output terminal of the supply, with the cathode going to the positive rail of the filter capacitor. Can you advise what is correct here, please? (G. McN., Torquay, Qld) • It seems that the labels for diodes Australia’s electronics magazine D5 and D6 have been swapped on the PCB and in the PCB overlay diagram (Fig.6 on p70, November 2019). Diode D5 is actually the one closest to the large filter capacitor, and it should be a 1N5404 type, although you can use an SB380 instead. Diode D6 is closer to the board edge and must be an SB380. The SB380 is between ground and the positive output, to shunt any reverse current from the current sink or clamp negative voltages applied to the output. Its lower forward voltage is beneficial here. The 1N5404 protects the output devices in cases where the output is higher than the positive rail and has been chosen for lower leakage. If both D5 and D6 are fitted as SB380 as marked, then everything will still work as expected, it’s just that the SB380s are a bit more expensive. Alternative transformer for Linear Bench Supply I’m building your High Power Linear Bench Supply from the October-December 2019 issues (siliconchip.com. au/Series/339). You specified a Vigortronix 500VA 40-0-40 toroidal transformer from element14, but I would prefer to order one from RS. I found one made by Scandinavian Transformer with similar specs and a similar price: https://au.rs-online.com/web/p/ toroidal-transformers/1176073/ It’s about 9mm taller than the specified transformer, at 68mm tall compared to 61mm tall. Its diameter is slightly smaller, 135mm compared to 138mm. Will this fit in the case? (T. S., Balcatta, WA) • There’s around 20mm from the top of the transformer to the lid on our prototype. The transformer mounting nut sits about 3mm above the top of the transformer, so a transformer that is 9mm higher should clear the lid by about 8mm. So we can’t see any reason why it wouldn’t fit, although you might like to fit an insulating layer above the transformer and mounting bolt. This will prevent the transformer from besiliconchip.com.au ing shorted out accidentally if the lid is pressed down enough to flex and touch the mounting bolt or cup, creating a shorted turn. Sourcing parts for the Linear Bench Supply I’m among the minority who don’t have a computer or access to online ordering. I’m interested in building your Linear Power Supply, but some of the parts are from online sellers such as Digi-Key, element14 etc. I’m not sure if they will take orders over the phone or via post. I’m also not sure where to get the SB380 80V 3A diode. I have purchased from RS before, but I had to purchase 10 parts when I only wanted one. Because of the above, I’m reluctant to build any projects that don’t exclusively use parts from Jaycar and/or Altronics. Sometimes you supply hardto-get parts, which is good. One part I’m not sure about is the resistor listed as 0.015W 2W-3W in the parts list and circuit diagram, but shown as 15mW 3W on page 70 of the November 2019 issue (Fig.6, the PCB overlay). 15mW is quite different from 0.015W as I think 15mW is a very high value; 0.015W is almost a piece of wire. (P. G., Culburra Beach, NSW) • We have just heard that Altronics are thinking of putting together a short-form kit (minus transformer and case). If they go ahead with that, it should alleviate most of your concerns. But you raise some points which are worth discussing. Choosing parts for us is always a compromise for many reasons. It’s very difficult to come up with ideas for new projects that only use parts from Jaycar and Altronics. If we can design such a project, often we have to compromise some of our performance goals to stick to that limited range of parts. Even if you don’t have a computer, many libraries offer free use for their members. This may be an option for you. With regards to the resistor, the terminology mW refers to a unit of 1/1000th of an ohm, also written milliohm. The unit MW (using a capital M) is a megohm, or one million ohms. So they are very different scales. With regards to the SB380, we got ours from Digi-key, and they will supply to hobbyists. In fact, while they strongly prefer taking orders via the siliconchip.com.au internet (and that will be easier for most customers), they do still accept phone orders via their Australian tollfree phone number: 1800 285 719. It’s true that in some cases, you might need to order in larger quantities than you need to make it worthwhile. The postage rates for small orders can appear to be expensive, but note that both Digi-Key and Mouser offer free express delivery for most orders over $60. And it only takes a few expensive parts to reach that threshold. The Bench Supply can be built without the SB380, although there would be nothing to prevent the output going negative due to the action of the minimum load current sink, and externally applied voltages could more easily damage it. We don’t recommend leaving it out. LoRa Chat Terminal screen not working I built the Arduino LoRa Chat Terminal with QWERTY keyboad described in Circuit Notebook (August 2019; siliconchip.com.au/Article/11779). The screen powers up and shows a line across it. It responds to key presses, eg, the space bar turns the screen on and the ESC key turns the screen off, the “#” key seems to send data, but that is it. No letters show on the screen or anything other than the line. I’m wondering if anyone else has had problems and if and how they fixed it. The Arduino system has been a real learning curve for me. (P. K., via e-mail) • After corresponding with the designer of that circuit, we have concluded that he has shown the wrong connections from IC2 to the LCD12864 display module. The correct connections are as follows: 1) pins 1-8 (GPB0-GPB7) on IC2 go to pins 7-14 (D0-D7) on the display; 2) pins 23-25 (GPA2-GPA4) on IC2 go to pins 15-17 (CS1, CS2 & RST) on the display; 3) pins 26-28 (GPA5-GPA7) on IC2 go to pins 4-6 (RS, R/W & EN) on the display. DAB+ Radio thumps when changing bands I built your DAB+ Radio from the January-March 2019 issues (siliconchip. com.au/Series/330). I got the radio working but have a problem and would Australia’s electronics magazine appreciate a few tips to track down the fault. When I change between AM to FM or DAB+ modes and back again, there is a slight pause as the software loads for the new reception mode. Just as the new reception starts, I get a loud thump from my speakers. It’s so bad that it’s activating the speaker protector on the amplifier. For some reason, my radio is generating up to -3.1V DC on the RCA audio outputs momentarily as I change reception modes, ie, AM to FM to DAB+ etc. This explains the thumping from the speakers. I used a Multimeter with min/max to record the peaks at -3.1V and +0.5V DC on the RCA audio outputs. At first, I thought my 5V DC supply plugpack mightn’t be supplying sufficient current, but I swapped to a dedicated 5V DC bench supply (approximately 540mA current draw). There are no dips or current increases while changing radio reception modes. I also tried direct feeding the 5V DC to the Aux +5V connector of the radio board. I suspect there is something not right with the operation of REG4 to maintain the -5V DC supply (I don’t think the 5V DC supply is faulty as everything else is working fine). Might I have a problem with REG4 and the -5V DC supply due to a longer or shorter than expected REG4SD pulse from the Explore 100 and software? Can I temporarily intercept the REG4SD signal to ensure the REG4 is maintaining the -5V DC supply continuously and see what happens? Any suggestions you have to fix this problem would be appreciated. (P. McG., Loftus, NSW) • That is a strange problem. Thumps are generated by the radio chip when it changes bands, but the muting function of analog multiplexer IC6 (where the S0 & S1 inputs are low) is intended to stop those. We still noted some noise from our prototypes on changing bands, which we put down to sudden changes in the radio chip’s power consumption coupling through the audio outputs. But it is nowhere near as severe as what you are describing. One thing to check is that there is close to 0V DC on pins 5 and 14 of IC6 when the radio output is silent, or the volume is very low. If there is significant DC on these pins, that will lead to loud thumps when IC6 switches beJanuary 2020  107 tween these inputs and pins 1 and 12, which are connected to ground. For that matter, check that you read near 0V on pins 1 & 12 of IC6 too. If that checks out, it would be worthwhile looking for any significant AC pulses on the various supply rails during band switching, especially the -5V rail which you have mentioned as a potential concern. If you do find a large pulse on one of those rails during band switching, that could explain this fault. If so, you would need to track down its source, such as a bad solder joint. Also check the soldering around IC5 and its associated components, especially those shown between IC6 and IC5 on the circuit diagram, as a bad joint on any of those components could cause your symptoms. Unfortunately, it’s possible to have SMD solder joints which look good on a casual inspection but have not adhered to either the PCB or the component, resulting in a high-resistance connection. The REG4SD pin (pin 21 on CON3) is pulled low during initialisation and left there, so it should be continuously low during normal operation, including changing modes. You can check this with a DMM, but we doubt this is the source of your problem. One other issue is that many people seem to be having poor connections at CON3 (the header between the radio board and the Explore 100). If there was an intermittent connection here, it could cause what you are seeing. Check that is is making good contact. Although perhaps unrelated, we had a few reports that the headphone amplifier transistors (Q1-Q4) were getting hot. They found that increasing the value of the 2.2kW resistors in series with D1 & D2 fixed this. You should check this, as if the current through these transistors is too high, it might be excessively loading the audio rails and causing them to sag momentarily. How to program a WeMos D1 R2 mini I built the WiFi Water Tank Level Meter (February 2018; siliconchip. com.au/Article/10963), and have been working on a beekeeping project for a long time. This project enabled me to log data via a two-wire connection to a beehive, then monitor this information using ThingSpeak. 108 Silicon Chip However, for various reasons, I needed to reinstall the Arduino IDE. I then needed to reload the Arduino ESP8266 code, as described on page 27 of the February 2018 issue. This seemed to work; however, there is no WeMos D1 R2 mini in the Board Manager list that I can select, only a WeMos D1 R2. Can I get the WeMos D1 R2 mini entry back? I look forward to buying your magazine each month; this has been a regular occurrence for many years. (M. O. G., Loftus, NSW) • We installed the latest Arduino IDE and ESP8266 boards profile (2.5.2) to check this, and it seems that you are right. There is no longer a board entry called “WeMos D1R2 mini”. However, there is one called “LOLIN (WEMOS) D1 R2 & mini”, which we think is the right option. Advice on programming ESP8266 boards I purchased a Jaycar WiFi Relay Controller kit which combines their Cat XC4418 with XC4411 (“Uno with WiFi”). I realise that this is not your project design, but you may be able to help me. I put it together and successfully uploaded the Uno and ESP8266 files but cannot upload the data. I keep getting the error message “SPIFFS UPLOAD FAILED”. Note that the Boards Manager in my Arduino IDE shows options of FLASH SIZE and FS instead of FLASH SIZE and SPIFFS as described in the Jaycar instructions. I am sure many of your readers will have a go at this project and may run into the same problems as me. Thanks in advance for any light you can shed on this problem. (G. C., Alstonville, NSW) • We don’t have that board handy, but we tried the upload procedure with another ESP8266-based board, using the same settings as you, and were able to make it work. We suggest that you turn on the verbose output option; go to File → Preferences and then tick the two boxes next to “Show verbose output during:”. This should give you a more detailed error message. If you are still having problems, we suggest that you report the details of your problem via its Github repository: https://github.com/Jaycar-Electronics/ WiFi-Relay-Controller/issues We can see that someone else ran Australia’s electronics magazine into a problem some time ago and posted it via that site, and a response/ fix was given two days later. Many of Jaycar’s recent projects are also on Github. Here is an abbreviated version of the output from the ESP Data Upload Tool that we got: esptool.py v2.7 Serial port COM32 Connecting.... Chip is ESP8266EX Features: WiFi Crystal is 26MHz MAC: 5c:cf:7f:11:c3:40 Uploading stub... Running stub... Stub running... Changing baud rate to 460800 Changed. Configuring flash size... Auto-detected Flash size: 4MB Compressed 3121152 bytes to 45012... Writing at 0x00100000... (33%) Writing at 0x00104000... (66%) Writing at 0x00108000... (100%) Wrote 3121152 bytes (45012 compressed) at 0x00100000 in 1.5 seconds (effective 17000.3 kbit/s)... Hash of data verified. Leaving... Hard resetting via RTS pin... Using SPI on Micromite LCD BackPack I am a long-time reader of electronic magazines since the 60s and a subscriber to Silicon Chip since the early 2000s, but have only just been getting into the Micromite after working with Arduino. I read that the 2.8in and 3.5in LCDs stop other SPI devices from working. Is this because there is only one SS/CS line? I would have thought that something like a 74HC138 1-of8 decoder activated by the CS line would have solved this problem, or am I missing something? (G. McK., Corinella, Vic) • We have had success in the past in communicating with other SPI devices along with the LCD touchscreen. That this is possible is confirmed in the Micromite manual. You can’t just open the SPI peripheral at the start of the program and leave it open. You will get error messages which read “SPI already open”. If the code is carefully written to make sure that the SPI peripheral is closed when calling LCD or touch functions, other SPI devices can coexist, as long as they have their own CS pin. siliconchip.com.au Subscribe to SILICON CHIP and you’ll not only save money . . . but we GUARANTEE you’ll get your copy! When you subscribe to SILICON CHIP (printed edition) in Australia, we GUARANTEE that you will never miss an issue. Subscription copies are despatched in bulk at the beginning of the on-sale week (due on sale the last THURSDAY of the previous month). It is unusual for copies to go astray in the post but when we’re mailing many thousands of copies, it is inevitable that Murphy may strike once or twice (and occasionally three and four times!). So we make this promise to you: if you haven’t received your SILICON CHIP (anywhere in Australia) by the middle of the month of issue (ie, issue datelined “June” by, say, 15th June), send us an email and we’ll post you a replacement copy in our next mailing (we mail out twice each week on Tuesday and Friday). Send your email to: silicon<at>siliconchip.com.au 4 4 4 4 4 Remember, it’s cheaper to subscribe anyway . . . do the maths and see the saving! Remember, we pick up the postage charge – so you $ave even more! Remember, you don’t have to remember! It’s there every month in your letter box! Remember, your newsagent might have sold out – and you’ll miss out! Remember, there’s also an on-line version you can subscribe to if you’re travelling. Convinced? We hope so. And we make it particularly easy to take out a subscription - for a trial 6-month, a standard 12-month or even a giant 24-month sub with extra savings. To subscribe, go to our website (siliconchip.com.au/subs) and enter your details. Or, you can call our office on (02) 9939 3295 or mail us your details. We accept payment by PayPal, Visa, Mastercard, EFT/Direct Deposit or Cheque/ Money Order (sorry, we don’t accept Amex or Diner’s). We’re waiting to welcome you into the SILICON CHIP subscriber family! siliconchip.com.au Australia’s electronics magazine January 2020  109 We ran some tests with a 23LC1024 RAM IC and were able to get it working in a program which also used the LCD and touch functions. We suspect it may be a bit slower because of the need to open and close the SPI peripheral frequently. It is not possible to make use of the touch interrupt, as the SPI bus could be in use when the interrupt is triggered, but you can still use other touch functions. So yes, it is possible, but you have to be very careful about opening and closing SPI devices to make it work reliably. SC200 Amplifier troubleshooting I have had a major set back with one SC200 amplifier module that I built (January-March 2017; siliconchip. com.au/Series/308). I am using PCBs and hard-to-get components from the Silicon Chip Online Shop. The first unit I built passed all tests after construction and works fine. The second passed tests and was undergoing a music listening test, at low volume, when it suddenly set fire to the 220W resistor between the emitters of Q11 and Q12. After removing the output transistors from the PCB, I found the following: • Q10: OK • Q11: OK • Q12: base-collector shorted & base-emitter open • Q13: shorted all junctions • Q14: OK • Q15: shorted all junctions • Q16: shorted all junctions • 220W between emitters of Q10 and Q11: burnt out • 220W to the base of Q11: damaged • 0.1W upper pair (Q13, Q14): OK • 0.1W lower pair (Q15, Q16): blown! All the other parts seem OK. There were no shorts to the heatsink! I have been into electronics since I was around 12, now 66. I can’t put this down to anything, but maybe bad luck. But any thoughts from your end would be welcome. (M. O’C., Taupo, NZ) • It does seem like you have had a major catastrophe. Most likely, it was due to a faulty component. This could have been a transistor, and maybe Q12 or Q13 was the culprit. The remaining components would have been destroyed as a consequence 110 Silicon Chip of the initial fault, and it is hard to say which set the destruction off. The surviving transistors may be partially damaged. It would be worth replacing all the transistors and checking all the resistors before powering it up again. Note that all the components responsible for pulling the output down (Q12, Q15, Q16 and associated resistors) have all been destroyed. That suggests that something pulled the output up hard, and these components operated to get it back near 0V, and burned out in the process. Q13 and Q11’s base resistor were the only other components damaged. That makes us suspicious that it was Q13 that failed short-circuit initially, but there’s no real proof of that. It is just a guess. Unfortunately, when building amplifiers, sometimes things like this can happen! Automatically switching between battery banks I have a 24V “standalone” solar system. I recently upgraded the batteries but kept the old ones which were still serviceable. I set them up as a separate back-up system with its own panels and inverter. When the voltage of one battery bank gets low, I can switch over to the other system. How can I make this automatic? (R. H., Newmeralla, Vic) • Our Threshold Voltage Switch design might be suitable (July 2014; siliconchip.com.au/Article/7924). This can be used to switch a relay based on the voltage of a 24V battery bank. The voltage level at which the relay activates is adjustable. Altronics sells a kit for this project (Cat K4005), as does Jaycar (Cat KC5528). Building a cheaper 350W amplifier Many years ago, I bought 5 PCBs to build your Studio 350 Power Amplifier (January & February 2004; siliconchip.com.au/Series/97). I have started building the modules now, and I am facing problems with some of the parts. Can I use cheaper MJL3281A & MJL1302A transistors instead of the specified MJL21193G & MJL21194G output transistors without any other modifications? Also, since 150W into 8W is enough for my needs, can I remove one pair Australia’s electronics magazine of the power transistors? I was also thinking of using a smaller transformer, eg, a 300VA unit with 2 x 43V or 2 x 45V secondaries. I don’t know if other changes are needed. • We think you’re better off using the specified parts rather than substituting others. There’s no way of knowing for sure whether they will work; we have not tested those lower-cost transistors in this amplifier. The substitutes you have suggested have a higher DC gain and higher gainbandwidth product. In theory, these are good things, but they will potentially affect the stability of the amplifier. Without testing them, we can’t say for sure whether these differences will cause any problems. In the worst case, it could lead to oscillation and possibly destruction of the transistors. That would negate any savings you make by buying cheaper transistors. Having said that, the specs on those transistors are impressive for their price, so you might consider building up one unit with them and seeing how it goes. If they do blow, you can use the originally specified parts for all five modules. To answer your second question, yes, you can remove one pair of output transistors and their emitter resistors if you are not driving 4W loads. No other changes should be necessary. The 4W load scenario is considerably harder on the output devices than 8W loads, hence all four pairs of devices are needed to deliver the full rated 350W. Finding old Electronics Australia articles How do I buy copies of Electronics Australia magazines? (G. M., Maitland NSW) • Complete Electronics Australia magazines are no longer available for sale. We have a set of archival copies and can photocopy or scan specific articles on demand. A list of some articles we’ve already scanned is available at: https:// siliconchip.com.au/Shop/15 You can pay to download one or more of these. The two entries at the top allow you to order a photocopy or scan of any article not already listed. If taking that option, please be sure to separately enter the year and month of publication and the name of each article that you want. SC siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP KIT ASSEMBLY & REPAIR PCB PRODUCTION FOR SALE VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au DAVE THOMPSON (the Serviceman from S ILICON C HIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com MISCELLANEOUS LOOKING FOR: Set of Dick Smith Electronics catalogues from 1975-1982. Must be in pristine condition. Will pay $200 for the set (inc. postage), only one set needed. Contact Melanie (on behalf of inquirer on 02 8832 3100) ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects like audio, video, programming etc. Many of them are in poor condition. Some of the books may not be for sale, but the vast majority are available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip.com.au/link/aawx Silicon Chip silicon<at>siliconchip.com.au Issues Getting Dog-Eared? Keep your copies safe with these handy binders Are your Silicon Chip copies getting damaged or dog-eared just lying around in a cupboard or on a shelf? REAL VALUE AT $19.50 * PLUS P & P Order online from www.siliconchip.com.au/Shop/4 See website for overseas prices or call (02) 9939 3295. ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia’s electronics magazine January 2020  111 Coming up in Silicon Chip Underground Mapping, Pipe Inspection and Leak Finding Dr David Maddison explains the numerous techniques and devices which can be used to find wires, pipes and other structures underground. In some cases, it is possible to build a complete map of everything near the surface. This is critical when digging in urban or suburban areas, to avoid damaging existing services or, in the worst case, starting a fire or a flood! 4G Remote Monitoring Station It’s often necessary to know what’s going on in a remote location, such as whether your boat battery is low, or if it is taking on water. Now that 2G is gone, and there’s talk of 3G being phased out, this is best done via 4G. Our new Arduino-based remote monitoring station can send updates over 4G mobile data or via SMS, and can even be used to switch things on and off at a distance. Micromite Air Quality Monitor An easy-to-build device which measures the concentration of Volatile Organic Compounds (VOCs) in the air and displays it on a colour LCD, both as a numeric reading (in parts-per-billion) and as a graph, showing how it changes over time. Use it to monitor your home, office, or anywhere else that you might experience poor air quality. Low-cost Hifi Bookshelf Speaker System, Pt.2 These medium-sized bookshelf speakers are made from a sheet of plywood and a couple of drivers from Altronics. While they are quite cheap to build, they certainly don’t sound cheap! And if you build the optional subwoofers, using a similar construction method, you get decent bass too, plus bonus speaker stands. Low-distortion Direct Digital Synthesiser This two-channel digital signal generator can produce very low distortion sinewaves across the audio frequency band (20Hz-20kHz), plus several other waveform shapes. The output levels are independently adjustable over a wide range, and the channels can also be phase-locked with a 0-360° phase offset. Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The February 2020 issue is due on sale in newsagents by Thursday, January 30th. Expect postal delivery of subscription copies in Australia between January 28th and February 14th. Advertising Index Altronics...............................81-84 Ampec Technologies................. 19 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEACH PCB Assembly............... 5 LEDsales................................. 111 Microchip Technology................ 65 Ocean Controls........................... 6 RayMing PCB & Assembly.......... 8 Rohde & Schwarz.................. OBC SC Micromite BackPack............ 69 Silicon Chip Binders............... 111 Silicon Chip Shop...............90-91 Silicon Chip Subscriptions..... 109 Switchmode Power Supplies....... 7 The Loudspeaker Kit.com......... 67 Vintage Radio Repairs............ 111 Wagner Electronics..................... 9 Notes & Errata Discrete pump timer, Circuit Notebook, November 2019: the diodes are all shown correctly orientated, however the anode (“A”) and cathode (“K”) markings have all been swapped. Also note that the 12V version of the Cyclic Pump Timer was in the July 2017 issue, not July 2016. 45V 8A Linear Bench Supply, October-December 2019: in the PCB overlay diagram (Fig.6) on page 70 of the November issue, the types and labels for diodes D5 and D6 are swapped. D5 is on the left and should be a 1N5404 type, while D6 is closer to the edge of the board and should be an SB380. The PCBs supplied for this project have the same error on their silkscreen printing. The circuit will still function correctly if both diodes are SB380s. LoRa Chat Terminal, Circuit Notebook, August 2019: the connections from IC2 to the LCD12864 display module are incorrect. The correct connections are: 1) pins 1-8 on IC2 go to pins 7-14 on the LCD; 2) pins 23-25 on IC2 go to pins 15-17 on the LCD; 3) pins 26-28 on IC2 go to pins 4-6 on the LCD. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes FREE OPTIONS Bundle! New Product! RIGOL DS-1000E Series RIGOL DS-1000Z Series RIGOL MSO-5000 Series 450MHz & 100MHz, 2 Ch 41GS/s Real Time Sampling 4USB Device, USB Host & PictBridge 450MHz, 70MHz & 100MHz, 4 Ch 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 399 FROM $ ex GST 599 FROM $ ex GST 1,448 ex GST Multimeters Function/Arbitrary Function Generators New Product! 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