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JANUARY 2021 ISSN 1030-2662 01 The VERY BEST DIY Projects! 9 771030 266001 $995* NZ $1290 INC GST INC GST What’s new: Altium 365 & Altium Designer 21 AM/FM/SW Bass Block Digital Digital Radio Radio Subwoofer MiniHEART Heartbeat Simulator Mini Digital AC Panel Meters New AVR Micros from Microchip how good are they? awesome projects by On sale 27 December 2020 to 23 January 2021 Our very own specialists have developed this fun and challenging Arduino® compatible project to keep you entertained this month with special prices exclusive to Club Members. BUILD YOUR OWN: Motherload Datalogger The data-logger project to end all data-logger projects! CLUB OFFER BUNDLE DEAL 5495 Imagine you find that power has been cut from your freezer. Knowing when, and being alerted, could save a lot of spoilage - this is the data-logger to do it with! More than just a temperature sensor, it could also be set up for humidity, smoke detection, PIR movement, or light detection, and with many other Arduino-compatible sensor too. $ SAVE 20% With Google Cloud platform capabilities; you can log and chart your data into an easily accessible Google spreadsheet and even send emails to yourself. A totally open-source datalogger for you to experiment with. KIT VALUED AT $71.30 SKILL LEVEL: Intermediate WHAT YOU NEED: 1 x UNO with Wi-Fi Board 1 x Arduino Compatible Data Logging Shield 1 x 150mm Socket to Socket Jumper Leads 40pk 1 x Economy Breadboard Jumper Kit 1 x 28 Pin Header Terminal Strip PLUS your choice of Sensor Modules XC4411 XC4536 WC6026 WH3032 HM3211 $39.95 $19.95 $5.95 $4.50 95¢ • CLOUD CAPABLE • EMAIL ALERTS • LARGE NUMBER OF INPUTS SEE STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/motherload-datalogger See other projects at www.jaycar.com.au/arduino 20% Off Arduino® Compatible Sensor Modules! SOIL MOISTURE SENSOR MODULE Automate your garden and use this module to detect when your plants need watering. • Analogue output • Current less than 20mA • 3.3 – 5VDC Input XC4604 WAS $4.95 A must for any security application. • Wide operating range and delay times changeable via two potentiometers • Delaying time: 0.3-18s • 5 – 20VDC Input XC4444 WAS $5.95 NOW NOW 3 $ PIR MOTION DETECTOR MODULE 4 95 $ SAVE 20% 75 SAVE 20% DUAL ULTRASONIC SENSOR MODULE. TEMPERATURE AND HUMIDITY SENSOR MODULE NOW NOW Measure distances up to 4.5m. Use it to add obstacle avoidance to your next robotics project. Uses just two digital pins • Sensor Angle: <15 degrees • Detection Distance: 2cm – 450cm • 5VDC Input XC4442 WAS $7.95 6 $ 35 SAVE 20% Got a great project or kit idea? If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com Shop the catalogue online! Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * Measure both temperature and humidity. Features resistive-type humidity sensor. • 0 ºC - 50 ºC +/- 2 ºC temp range • 20 – 80% +/- 5% humidity • 1Hz sample rate • 3 – 5VDC Input XC4520 WAS $9.95 795 $ SAVE 20% Looking for other projects to do? See our full range of Silicon Chip projects at jaycar.com.au/c/silicon-chip-kits or our kit back catalogue at jaycar.com.au/kitbackcatalogue www.jaycar.com.au 1800 022 888 Contents Vol.34, No.1 January 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 10 Automotive Electronics, Part 2 In the second part of this series we take a look at the electronic control modules (ECM) found in modern vehicles – by Dr David Maddison 32 Review: Altium 365 and Altium Designer 21 Altium 365 is a cloud-based companion to Altium Designer. It lets others view your design without them needing an Altium subscription, along with many additional features like version control for paying customers – by Tim Blythman 48 How to use the MPLAB X Development Environment MPLAB X is a multi-platform, free download from Microchip which is used to code, program and debug PIC and AVR micros – by Tim Blythman 82 AVR128DA48 & Curiosity Nano Evaluation Board Microchip’s AVR128DA48-based evaluation kit provides an easy way for you to test out a powerful new AVR micro – by Tim Blythman This AM/FM/SW Digital Receiver is based around a single BK1198 radio IC, controlled by an Arduino Nano. As a result, it uses a modest number of parts and assembly is relatively straightforward – Page 20 102 El Cheapo Modules: Mini Digital AC Panel Meters In last month’s article we described a variety of DC panel meters; this month we’re looking at the AC equivalents – by Jim Rowe Constructional Projects 20 AM/FM/SW Single-Chip Digital Radio This radio uses a BK1198 radio IC and an Arduino Nano, so it only requires a small number of extra components to build. It covers the AM band from 5131629KHz, FM from 87-108MHz and SW from 6.4-22MHz – by Charles Kosina 40 MiniHeart: A Miniature Heartbeat Simulator The MiniHeart produces a low-level soothing heartbeat sound. The beat rate and volume is adjustable; an off timer can also be set. It’s powered by two AAA cells – by John Clarke Altium 365 allows for easy management of layouts between multiple users through shared component libraries, version control, a shared editor/viewer and much more – Page 32 The MiniHeart is a battery-powered heartbeat simulator. It has an adjustable rate of 42-114bpm at a frequency of 45-51Hz – Page 40 68 The Bass Block Subwoofer This 4W subwoofer is easy to build and pumps out plenty of bass. It measures approximately 40cm tall, 27cm wide and 24cm deep – by Nicholas Dunand 78 Busy Loo Indicator This project uses a reed switch and a magnet to detect when the toilet door is closed and flashes a bright light to signal someone’s busy – by John Chappell Your Favourite Columns 61 Serviceman’s Log One good turn deserves another – by Dave Thompson 75 Circuit Notebook The Bass Block is a compact 4W subwoofer with a frequency response of 40100Hz at ±3dB and 25-150Hz at ±5dB – Page 68 (1) A reliable solar lighting system (2) Converting a cheap welder to a high-current battery charger (3) Radiating test antenna for AM radios 94 Vintage Radio 1963 Philips Musicmaker MM1 mantel radio – by Assoc. Prof. Graham Parslow Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback siliconchip.com.au 93 Product Showcase 100 Silicon Chip Online Shop 107 Ask Silicon Chip 111 Market Centre Australia’s magazine 112 Noteselectronics and Errata 112 Advertising Index The new AVR chips from Microchip are faster and have more functions than the older types while generally costing less – Page 82 January 2021  1 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. Nicolas Hannekum, Dip. Elec. Tech. 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 Recommended & maximum price only. 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 Editorial Viewpoint More articles than space – a good problem to have! In the October 2020 issue, I wrote about wanting to publish a range of articles, including some of historical interest and others about the latest technology. This has created a bit of difficulty; while we have a good mixture of different articles, I am struggling to fit all this content into the magazine. You might be wondering why I don’t just print magazines with more pages. That is not as easy as it sounds. For a start, our printing and mailing costs would go up, and given the general economic malaise caused by COVID-19, I am reluctant to increase our expenditures. Note that we have not increased the magazine cover price for more than seven years now – an unprecedented period in the magazine’s history. Another problem is that if I print magazines with more than 112 pages on our current paper stock, they might not fit into the binders that we sell. We also sometimes have problems with the centre sections tearing out in larger magazines. Printing on thinner paper would solve these problems, but result in worse print quality; something I am not keen on. Another option is for me to reduce the number of constructional project articles in some issues. Since taking over the magazine in August 2018, I have stuck faithfully to my predecessor’s guideline of having four such articles in every issue. I think he was right that this strikes a good balance, but perhaps I should make the occasional exception and run three project articles in some months. That would allow us to include more feature articles. I think that makes sense, but I wonder what our readers would think of that. The other option is to raise the cover price (which I am still trying to put off as long as possible) and then use the extra revenue to print larger magazines with more content. That’s assuming we don’t lose too many readers when the price goes up. But I still couldn’t publish large issues too often, or we would run into the over-full binders problem I mentioned above. That makes me think that perhaps dropping to three projects per issue from time to time is the best solution. It also occurred to me that we could run some smaller, simpler projects (which I want to do anyway; again, trying to strike a balance) which will free up more space for feature articles. That’s what we’ve done in this issue, running a clever little four-page project which allows us to have five features plus all our usual columns. It’s a good solution, but we can’t always come up with shorter projects that are worth publishing and building (and what seems like a small project initially can often balloon into a major one!). One of the biggest problems with these simple projects is that often when someone has an idea, we have published something very similar before, and I don’t want to keep reploughing the same ground. If you have strong feelings one way or another about what I have written here, you are welcome to provide some feedback (eg, by sending an e-mail to silicon<at>siliconchip.com.au). That will help guide my decision-making when it comes to figuring out which articles to run in future issues, based on what our readers want. Printing and Distribution: 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”. Odd GPO socket might be a phone socket I would like to comment on the query in Ask Silicon Chip, December 2020 on old electrical sockets, specifically, one with four flat pins (p107). I am wondering if it was actually a telephone socket, as he mentions it was in a small room (which could be a telephone room, for quietness and privacy). There was an old plug and socket standard used for moving the telephone to another room before the more recent Telecom plugs and sockets, and the modern RJ11 modular sockets. It had two horizontal blades in the centre, with another horizontal blade below and a vertical blade on top. I saw several of these in older homes in Adelaide in the 1950s when I started as a Trainee Technician. Brian Dunn, Old Noarlunga, SA. John Hunter, the author of the Sep- tember 2020 article on the history of GPOs, replies: That plug was used where telephones were wired as a portable service. Usually, the phone was connected permanently via a terminal block. It was used on the Bakelite 300 and 400 series telephones, until the 1960s, when the ‘modern’ AWA-developed six-pin plug came into being for the new 800-series telephones. Tiny Xmas Tree shines on 12 months later The Tiny Xmas Trees I built from the project in last year’s SILICON CHIP magazine (November 2019; siliconchip.com.au/Article/12086) are still shedding light and bringing joy to the world. The colours progressively dropped out as the battery voltage fell, but the red LEDs are still going. Most Xmas novelties don’t last till January, so my mobile of four trees is doing very well. A new set of batter- ies and we’re ready for Christmas and hopefully a better New Year! Dave Dobeson, Berowra Heights, NSW. Fluke DMM repair strikes home I have just read, with great interest, about the repair of a Fluke model 77 DMM in the Serviceman’s Log, December 2020. I own a model 75 instrument, also purchased in the early 1980s, and I had to replace the fusible resistor about 25 years ago after making a mistake using the meter. At that time, Philips was the local agent for Fluke in NZ, and I was able to buy a replacement from their trade store (Philips disappeared shortly after). I was not even aware that the DMM also incorporated two spark gaps until I read the article; a hasty check confirmed that mine are still intact – whew! These DMMs are a model of good design and construction and definitely precede the ‘throw-away’ era. Trevor Woods, Auckland, NZ From crystal sets to GPS Nicholas Vinen’s editorial in the October 2020 issue struck a chord with me, and prompted a reflection on my involvement in the electronics hobby over the last 65 years or so. When the October 2020 issue of Silicon Chip arrived in the mail, I was deeply immersed in the resuscitation of an HP5100 frequency synthesiser. This 1964-vintage piece of test equipment is the archetypical boat anchor – one of the largest and heaviest units produced by Hewlett Packard – and is breathtakingly involved in its design and construction. Editor's note: see Serviceman’s Log starting on p61 for Rob’s repair story. The Editor pointed out that he wanted to preserve a fresh and dynamic 4 Silicon Chip Australia’s electronics magazine siliconchip.com.au outlook to modern-day electronics in the magazine, and cited some exciting new articles nearing publication. He also wrote about the importance of FPGAs and ASICs as foundations of most modern technology, yet acknowledged the many articles of a historic nature that had been submitted by passionate readers hoping to have their favourite subject broadcast to the world. Maintaining a balance for his readership was a complex and conflicting objective. Looking back over the decades, to those days before tablets, mobile phones, computers and television, the primary interest for hobbyists was AM radio reception. Radio and Hobbies catered for true beginners and experts alike. Back then, we shopped at McGraths, Waltham Trading and Radio Parts for our components, and much later at Hamfests and government disposals sales. In 1956, black and white TV arrived in Australia in time for the Melbourne Olympic Games, and sure enough, RTV&H (as it became known) published TV construction projects. For teenagers like me, being able to tackle something as challenging as a television receiver was super cool, and I learned a lot about electronics through the successful completion of a 21-inch set. It served the family for quite a few years into the sixties. Then came the Playmaster hifi amplifiers – just mono in their first implementation, and we all just had to build one. And to ensure a well-rounded hobbyist education, we ventured into carpentry by building vented enclosures housing high-performance loudspeakers, usually imported from England. With the introduction of stereo, our parents despaired as to where another monster speaker enclosure could be crammed into the family living room of the day! The idea of a career in electronic engineering was starting to form, and in 1965, I completed a course in electrical engineering at the University of Melbourne. Unlike in today’s job market, there were many jobs available for electrical engineers. At the start of the course, I fully expected to find employment on the production side of the then-burgeoning consumer electronics industry. While electron tubes were still being manufactured in Sydney and Adsiliconchip.com.au elaide, Fairchild had just invented the silicon epitaxial planar transistor, and its natural offspring, the integrated circuit. Manufacturing had commenced in Melbourne, and we were confident of being able to find challenging but satisfying jobs within the electronics industry. But the rise of the US and Japanese electronics majors led to a major shift away from Australia for investments in this industry, and any childhood ambitions of pursuing a career in electronics faded fast in the mid-sixties. As it turned out, I spent most of my working life working for ICI and later Orica, and my electronics interests were served simply through ongoing hobby work at home. The spectacular advances in technology will continue, and it won’t be so long before today’s neophytes become tomorrow’s seniors. Looking back for them, it will be just as astonishing as it is for earlier generations like mine. No matter what, the fundamental laws of economics, physics, electromagnetic theory and circuit theory won’t change. Nor will the need to troubleshoot poorly performing equipment using common sense, logic and the application of those laws. The future of our amazing hobby is assured, and Silicon Chip magazine and its contributors will play an ongoing role in communicating new and important stuff to us all. Rob Fincher, McCrae, Vic. Logic-level Mosfet needed for 3.3V operation I was relaxing today, reading the December issue of Silicon Chip. I found the article on the 3GHz radar module (siliconchip.com.au/Article/14674) interesting; I think it is very cute. I noticed, top left of page 52, there was a suggested circuit using an IRF540. Since the output level of the module is likely 3V, but the gate threshold of that Mosfet is about 3V and can be as high as 4V, it might not switch on fully and could overheat with a high drain current or a big drain load. There are logic-level Mosfets available, where the gate threshold is around 1.5V or in the range 1-3V, and like the IRF540, can switch some pretty hefty loads. A common handy little Mosfet I find Australia’s electronics magazine January 2021  5 for switching small relays and small devices etc with a logic-level input is the BS270. Its threshold voltage is about 2V. These are pretty convenient to add to logic circuits etc to switch something like small lamps, LEDs, PCB relays etc. The convenient part is that no resistors are required, which are needed with a BJT. Hugo Holden, Minyama, Qld. Response: you have a point; we should have specified a logic-level Mosfet for that job. We even sell a suitable device in our Online Shop, the CSD18534KCS (siliconchip.com.au/Shop/7/4177), which is rated to handle 73A & 60V. While it is designed for a 5V gate drive, it will generally switch loads above 10A with a 3.3V gate drive. We agree that the BS270 is a handy device, as are the similar 2N7000 (through-hole TO-92) and 2N7002 (SMD SOT-23). Hydrogen storage of electricity The letter on hydrogen storage on p4 of your September issue reminded me of a recent visit to Matiu/Somes Island. The guide pointed out a hydrogen storage system there; see www. futureenergy.nz/about/case_study_ matiu_somes.htm I enjoy reading Silicon Chip magazine and learn from it. Malcolm Wheeler, Wellington, NZ. Comment: we also briefly mentioned hydrogen storage of electricity on our article on Grid-Scale Energy Storage (April 2020, p23; siliconchip.com.au/ Article/13801). Confusion over RTL SDR bias tee In his May 2020 article on RTLSDR Modules (siliconchip.com.au/ Article/14429), Jim Rowe mentions on page 66 that the bias tee is enabled by default. That did instil a bit of paranoia about potentially damaging it at some stage, as I plan to order that unit. It seemed odd to me that it would default to enabled. I found a note on www.rtl-sdr.com (in the user guide section) which states “Note that the legacy DVB-T TV drivers will activate the bias tee by default”. So perhaps this has been fixed with the latest drivers. Regardless, this is more than a little confusing, especially for those who intend to use it with Windows and SDRSharp. 6 Silicon Chip I was slightly disappointed that the price of the unit went up just before I ordered it (by $5). But I must compliment them on their speed; I placed the order on Thursday and received it on Monday, even though I’m in regional NSW. Phil Porritt, Inverell, NSW. Jim Rowe responds: frankly, I found the information regarding enabling of the bias tee quite conflicting and confusing too. That’s why I wrote what I did; I didn’t intend to “instil a bit of paranoia” in readers. I still think that removing SMD inductor L13 is a good idea – unless you want to power an up-front preamp or preselector, of course. Software security is still abysmal The “Editorial Viewpoint” in your February 2020 issue seems to have an error close to the end; it says “Most recent CPUs and operating system an ‘NX’ bit’” which makes no grammatical sense. I believe you are referring to making the stack and the data segments non-executable by setting the ‘NX’ bit on those parts. After nearly 50 years of programming experience, I am disappointed to see the same mistakes occurring over and over again; do people learn nothing? I think the major problem is that anyone can call themselves a computer programmer, without any formal training or qualifications whatsoever. Dave Horsfall. North Gosford, NSW. Response: you are right. In the original editorial text, that sentence read “Most recent CPUs and operating system have something called an ‘NX bit’ which helps to reduce the chance such a flaw can be exploited, but can’t totally prevent buffer overflow attacks.” Untrained programmers are part of the problem, but time pressure from management and poor organisation are probably factors too. Fixed wireless preferred over NBN Your tale in the June 2020 editorial, “National Broadband Not-work?”, is depressingly familiar to me. I also experienced many months of appalling corporate inefficiency at the hands of Telstra and NBN. The amount of frustrating telephone time spent in pursuit of even simple requests, plus frequent phone and broadband outages on copper, led Australia’s electronics magazine me to terminate all wired service with Telstra and NBN. My small office on Sydney’s lower North Shore now uses a 4G wireless internet connection that runs between 50Mb and 120Mb per second (averaging 75Mb), depending on the time of day. The monthly cost is around $60/100GB plus $30/month for two VOIP lines. In terms of peaceful internet access, I have never been happier. If I should ever move, I can take the 4G modem and my phone services with me – no call centre interaction required. VOIP providers such as Maxotel are these days really well organised, with locallybased tech-savvy operators. I fervently hope that I never have to return to cable of any description. Peter Felton, Willoughby, NSW. Solar panel orientation: are we doing it wrong? According to an article from the ABC (siliconchip.com.au/link/ab5t), instead of using the usual ‘rule of thumb’ of orientating solar photovoltaic panels to the North, angled based on your latitude, it would be much better to have a 50/50 mix of PV panels facing either East or West. That could mean that one homeowner has all their panels facing East and another West, or people could have a mix of the two. If you think about it, this makes sense, since it will provide more power during the morning and afternoon demand peaks, better matching supply with demand. It will also help to reduce those very high mains voltages that we can sometimes see in the middle of sunny days, as well as preventing grid-tied inverters from going offline due to high mains voltages. Read the article for yourself and see if you think they are right. Edison Zhang, Chippendale, NSW. Testing solar panels Congratulations to Dennis Stanley for his Automatic Solar Panel Checker design you published in Circuit Notebook, October 2020 (siliconchip.com. au/Article/14601). The only downside that I can see is that it won’t work on 12V panels. Apart from that, it is streets ahead of the tester I made up years ago. My tester just had a voltmeter, ammeter and a rocker switch to place a load of either 9W or 18W across the panel. siliconchip.com.au Regarding the comments about faulty panels in the article, I have seen several defective panels. Some have been cheap grid connect-panels – typically rated at 60V opencircuit and 4A short-circuit. These faulty panels have an open-circuit voltage of about 55V, and short-circuit current in strong sunlight of about 1A. On the positive side, I still have a few BP panels (BPX47C) that were manufactured before 1980, rated at 33W. A test last week in intense sun with a 9W load gave me 16.0V at 1.66A. So these 40+-year-old panels are still working OK. I had the privilege of being shown through the BP solar panel factory in Sydney in the early 2000s. At the time, The solar panel shown above has a clear fault where it is discoloured due to overheating. they were making BP panels and Solarex panels on two different manufacturing lines. I have some BP 36W panels and Solarex 37W panels, manufactured in 1987, which are still working well. I have seen a lot more faulty Solarex 37W panels than the BP types. The quality of BP panels fell sharply when they started making 68W panels. A very large percentage developed high-resistance solder joints between cells. The adjacent photo show where these faults have caused severe heating, which makes them easy to identify, but most faulty panels had no obvious external signs. These panels had been installed in strings of four. Faulty panels could not be identified by just checking the opencircuit voltage and short-circuit current, as when a panel was short-circuited, the fault disappeared, only to return some days later. That is why I made up a resistive tester, which draws enough current to identify faulty panels without making the fault go away. I have found that BP 80W (12V) panels have very few problems, and BP 160W (24V) panels are also of good quality. I have seen panels with delamination problems, often identifiable by tarnishing of the copper connecting strips. The result is low insulation resistance, causing gridconnect inverters to shut down or not start up. These faulty panels can be used in off-grid (12/24V) setups with no problems. I reused some with that fault more than two years ago (because they were free), and they are still working well. I have also reused two panels from a house that caught fire. The heat on the panels was so great, the junction boxes were melted into blobs and had to be cut off with a Dremel to access the tinned copper strips coming out of the panel. I repainted the backs of the panels, and they are still working well after more than two years. Honey Trina imported a batch of panels with faulty laminations – again, mostly identified by looking at the tarnishing. But Trina panels before and after that batch are high quality. Second-hand ET panels are of excellent quality, and can be occasionally found on Gumtree for $20-40 each. I believe most solar panels are very robust, but a good tester is essential to ensure you don’t buy rubbish secondhand panels. Sid Lonsdale, Cairns, Qld. Chiming clock projects wanted I like chiming clocks. That is, ones with real bells rather than artificial electronic noisemakers. I have a couple of old wind-up wall clocks that sound good, with real striking parts. But I don’t always remember to keep them wound up. Also, they aren’t accurate timekeepers, needing frequent adjustment. It would be great to have a hybrid system, based on a quartz resonator for convenience and accuracy, but one that can trigger a solenoid for the traditional hour, half & quarter strikes on a bell, bar, tube or some other actual metal resonator. Even a “faceless” clock would serve, as it’s the accurate chiming at proper intervals that matters. I can always have an ordinary clock as well, just to look at the time. I guess there would be a need for some sort of display though, and some interfacing for setting it up. 8 Silicon Chip Australia’s electronics magazine siliconchip.com.au There are some fairly expensive long-case clocks available, quartz-regulated and with real chimes, but these are over-styled and not desired. While I love reading Silicon Chip and get out my soldering tools on occasion, I have insufficient design skills for such a project. I wonder if someone there would be inclined to consider this idea, and maybe even develop an article or project kit. There must be people who, like me, much prefer the sound of real chimes, and would appreciate not having to keep winding and adjusting a purely mechanical clock. J. P., Penrose, NSW. Comment: We have a project design coming up in the February issue which uses solenoids to strike wind chimes. Perhaps that could be adapted to do what you are asking. We will consider what needs to be changed to achieve that. Edison Voicewriters for a good home I have both a recorder and a player of the 1950s Edison brand Voicewriter model, shown in the photos below. I am a combined geek and bowerbird from way back, but I don’t have the resources to repair/display them, so I would like them to go to a good home. The only date I can find on either of them is 25th August 1952. There is also some cabling (some of which is rubberinsulated and so has deteriorated), and a mains transformer (presumably for use with 240V AC). Thank you for your magazine. I have returned to electronics (my first career) in my later life, and you have provided me with a much-needed update on technologies such as Arduino and the like. John Evans, Macgregor, ACT. SC john.evans111111<at>gmail.com Articles on arc welding wanted As a long-time reader/subscriber, I would like to suggest that an article about electric welding would be of interest to your readers, including me. There has been a steady evolution of electric arc technology, particularly in the MIG and TIG processes. Inverter technology has reduced the size and weight of welding machines, which used to derive their power from a mains frequency transformer, and the price of the machines and ease-of-use now put them into the hands of DIY hobbyists. Microcontrollers are now at the heart of most welders, controlling not just the basics like voltage and amperage used, but also pulse frequency and even wave shape. I think this would make an informative and interesting article for Silicon Chip, and I would also like to suggest that a DIY project could be developed and published, perhaps building a controller to upgrade a simple, low-cost analog welding machine. One DIY project I undertook was to make a batterypowered DC MIG welder. As I don’t have mains power, and the vehicles I need to repair are out in a paddock, it was a worthwhile project. I had a MIG welder that consisted mainly of a large transformer with two outputs, for low and high power. It didn’t even have a rectifier, so it welded with AC, which is not optimal for mild steel. I replaced the transformer with a 5S 12P pack of Li-ion 18650 cells that I made up, and to power the wire-feed motor, I added a small PWM motor speed controller module. I found that there was room to add a 100A motor speed controller to regulate the power output, but the thin electrode wire I was using (0.6mm) and the ability to control the wire feed speed obviated the need to control the power output. My need was to repair body rust damage on my car to pass the rego inspection, requiring me to cut out the rust and fabricate patches which I successfully welded in place. Grinding down the weld bead, applying a cosmetic filler and then painting produced a very good result, and so the car passed the rego inspection, without having to resort to using “bog”! Very pleased, I was. Chris Battle, Coffs Harbour, NSW. siliconchip.com.au Australia’s electronics magazine January 2021  9 Automotive Electronics Part II – ECM Types by Dr David Maddison Last month, we provided an overview of how automotive electronic control modules (ECMs) work, described how they communicate and listed some of the many types used. We also described the operation of the engine control unit (ECU) in detail. Now we’ll concentrate on the other ECM types found in modern vehicles. T here are very many electronic control modules we could describe; probably enough to fill the magazine! So we have selected the following few as representative and diverse systems. others must be replaced. For details on how data can be extracted from an ACM, see the video and instructions at siliconchip.com.au/link/ab4k Also see the video titled “KIA Airbag control module (ACM) Airbags use MEMS devices to determine if a severe impact has occurred and activate pyrotechnic devices to generate gas to fill the airbags (Fig.28). The ACM usually contains capacitors to store power during a crash in case vehicle power is lost. ACMs store data about the crash that caused them to activate such as speed, throttle setting, brake application, seat belt usage and other data at the time of impact. The ACM uses data such as seat occupancy, occupant weight and crash severity to determine whether to inflate airbags, which airbags to inflate, when to inflate them and how rapidly to inflate them. We published an in-depth article on airbag systems in our November 2016 issue (siliconchip.com.au/Article/10424). In the event that a car is repaired after airbag activation, the ACM has to be either replaced or reset via hardware and/or software means. Some models can be reused a limited number of times; 10 Silicon Chip Fig.28: the Toyota Prius airbag control module is fairly typical. It integrates sensors to detect an impact with a processor to determine which airbags to fire, and components to send pulses to the airbag(s) to trigger them. The large capacitors allow it to continue operating for some time, even if the vehicle wiring or battery is damaged by the impact. Australia’s electronics magazine siliconchip.com.au Fig.30: a body control module with integral fuses from a 2017 Alfa Romeo Giulia. Note the numerous connectors which go to buses, sensors and actuators. Source: pacificmotors.com Fig.29: an ABS pump and control module from a Mazda 2. The electronic control module is the black case at the bottom, with the hydraulic valve body between it and at the pump at the top. Source: abssteuergeraet.com Soul 2016 14 15 SRS Airbag Module Reset via OBD CAN Lines” at https://youtu.be/iz14cIOZhpU Our article on OBD2 in the September 2020 issue (siliconchip.com.au/Article/14576) also described how to reset airbag computers using OBD2 in certain vehicles. Anti-lock braking system (ABS) Modern ABS systems use a speed sensor on each wheel, a hydraulic valve for each brake line, a pump (see Fig.29) and an electronic controller. If a particular wheel decelerates faster than others during braking, suggesting that locking up is imminent, hydraulic pressure is released from that brake and then rapidly reapplied to ‘pulse’ the brakes and allow the vehicle to be steered during hard braking. The pressure lost due to pulsing the brake line is made up by the hydraulic pump. An ABS can release and reapply brake pressure as much as 15 times per second. Brake assist (BAS) This system was first developed by Daimler Benz TRW/ LucasVarity. It increases brake pressure in an emergency. An emergency is sensed by such factors as the speed at which a foot is removed from the accelerator and applied to the brake. Once an emergency is assessed, full braking force is applied to the maximum permitted by the ABS system. The rationale for this system is that most drivers do not apply the brakes forcefully enough in an emergency. It has been shown to be highly effective in reducing rear-end collisions. Body control module (BCM) The BCM controls and monitors less critical devices on a vehicle’s body such as power windows, mirrors, heatsiliconchip.com.au ing and cooling, lighting, anti-theft immobiliser etc (see Figs.30 & 31). See the videos titled “BCM Trouble: Ranger & BT50” at https://youtu.be/IBEzMVtXuX4 and “Took apart a 20132017 Ford fusion BCM body control module” at https:// youtu.be/cO3FSrXfQpA Catalytic converter / oxygen sensor While not actually ECMs, cats are an essential component of the emissions control system for gasoline engines and integrate with the ECU and electronic oxygen sensors, described last month. Catalytic converters (cats) convert nitrous oxides, hydrocarbons and carbon monoxide to nitrogen, water and carbon dioxide (see Figs.32 & 33). For them to work well, the engine has to be within a narrow band of air-fuel ratios; otherwise, there is too much or too little oxygen and the converter won’t function properly. Modern vehicles have oxygen sensors before and after the converter to monitor the oxygen content in the exhaust stream. The oxygen data is sent to the ECU to ensure optimal conditions inside the converter by adjusting engine characteristics. A converter has two sections. The first reduces NOx to Security concerns The extensive computerisation and networking of cars opens up new opportunities for malicious individuals. It is possible to clone electronic key fobs, as described in our article “History of Cyber Espionage and Cyber Weapons, Part 1” in the September 2019 issue, on page 19 (siliconchip. com.au/article/11911). It’s also possible to spy on vehicle occupants, as described on page 21 of that issue. Those with malicious intent can also (possibly) take control of a car. Hopefully, security flaws are being patched as they are discovered, preferably before that! See the videos titled “How to Hack a Car: Phreaked Out (Episode 2)” at https://youtu.be/3jstaBeXgAs and “Hackers Remotely Kill a Jeep on a Highway” at https://youtu. be/MK0SrxBC1xs Australia’s electronics magazine January 2021  11 Fig.31: the architecture of a Texas Instruments body control module system. MCU is the microcontroller unit, LDO is low-dropout regulator, ESD is electrostatic discharge protection, MSDI is multiple switch detection interface, MUX is multiplexer, HS and LS refers to high side and low side switches and BTSI is brake transmission shift interlock. nitrogen, the second oxidises CO to CO2 and hydrocarbons to water and CO2. The ECU constantly cycles between slightly rich (oxygen poor) and slightly lean (oxygen rich) because the first stage needs to be oxygen-deficient and the second stage needs to be oxygen-rich to work. See the video titled “See Through Catalytic Converter” at https://youtu.be/ekQcy6GN1pM There are also catalytic converters for diesel engines. They oxidise CO and hydrocarbons but for NOx control, other systems are used, such as urea injection (“diesel exhaust fluid”, DEF, marketed as AdBlue or other names) into the exhaust and an additional special catalyst. Cylinder deactivation In some engines, especially six and eight cylinder types (but also those with four and even three cylinders!), some of the cylinders can be shut down under light driving conditions to save fuel (see Figs.34(a) & (b)). In GM vehicles, this technology is known as Active Fuel Management. It involves special valve lifters, a special manifold assembly and appropriate control by the ECU. Greater fuel economy (up to 12% improvement in GM vehicles) can be obtained without downsizing the engine. The extra power of a larger engine is available when needed. As of 2019, the GM system has now evolved to Dynamic 12 Silicon Chip Fuel Management (DFM), where as many cylinders as need be can be deactivated. Other manufacturers have similar systems. For more details, see our article in the January 2009 issue on cylinder deactivation in Honda V6 engines (siliconchip. com.au/Article/1268). Electronic stability control (ESC) ESC (also known as ESP, or electronic stability program) is an extension of the ABS or VSC system. Additional sensors are added such as a steering wheel angle sensor and a MEMS gyroscope (see Fig.35). If there is a mismatch between the vehicle’s intended direction (as determined by the steering wheel angle) and the actual direction of travel (as determined by the gyroscope), one or more wheels are braked to realign the vehicle into the intended direction. This is now a mandatory system in all new vehicles in the USA, Canada and EU. Two different ways that traction and stability control can be implemented, as used on older and newer vehicles, are shown in Figs.36 & 37. Fuel composition module This module is used in vehicles that can run on E85 ethanol as well as normal fuel (E10 or E0). They measure the exact amount of ethanol in the fuel and pass the information Australia’s electronics magazine siliconchip.com.au Fig.32: a catalytic converter with exhaust going left to right. HC stands for hydrocarbons, NOX is nitrogen oxides and CO is carbon monoxide. They are transformed to water (H2O), CO2 and nitrogen (N2). There are two different catalyst sections, plus oxygen sensors at the inlet and outlet which feed data to the ECU. to the ECU to manage timing, quantity of fuel injected and maximum boost level (see Fig.38). When switching between E0 and E85, the fuel could be anywhere from 0% up to about 85% ethanol. Higher ethanol concentrations require wider injector pulses as ethanol has about half the energy per litre of petrol. However, ethanol also acts as an octane booster and charge cooler, allowing for more timing advance and higher boost levels, provided there is enough fuel delivery capacity. Knock sensor The knock sensor (Figs.39 & 40) detects engine ‘knocking’ that happens when the air-fuel mixture ignites before the spark. This can be due to inappropriate fuel, excessive cylinder pressure, insufficient air-fuel ratio, excessive turbo or supercharger pressure, high operating temperature, carbon deposits or other reasons. Knock can cause severe engine damage due to the high pressures generated. A knock sensor generally uses a piezoelectric or inductive sensor attached to the engine block or head that acts like a microphone. It is tuned to be sensitive to the frequency of engine knock of the specific engine. Knock information is sent to the ECU and engine adjustments such as timing, fuel mixture or boost pressure are made to reduce or eliminate knock. Fig.33: a screengrab from the “See Through Catalytic Converter” video (https://youtu.be/ekQcy6GN1pM). Much heat is generated during the catalysis process. Catalysts also contain valuable platinum, palladium and rhodium, making them expensive and a target for thieves in some places. These sensors are sensitive enough that they can normally detect incipient knock before it is a problem and make slight adjustments to avoid it. This allows vehicles to take advantage of high-octane fuel (providing better power and economy when it is used) while still allowing lower octane fuel to be used without risk of damage. Launch control Launch control is built into a number of high-performance vehicles. Like traction control, its purpose is to limit wheel spin, but unlike traction control, it maintains the engine at the maximum RPM possible for the best acceleration from a stationary position (see Fig.41). Some wheel slip may be permitted, consistent with maximum acceleration. The GM Camaro ZL1 adjusts engine torque 100 times per second to maximise acceleration without excessive slipping. Such systems require an electronic accelerator pedal (throttle-by-wire) or a transmission brake. Traction control modules can be added to certain vehicles as aftermarket accessories, or launch control can be part of other engine control functionality. See the video from Australian company Haltech titled “How Launch Control Works” at https://youtu. be/5g2YFquhGtE Fig.34(a) & (b); in Honda’s cylinder deactivation system, the ECU uses a solenoid to control oil pressure to a set of pistons. When pressure is applied (left), the primary and secondary arms are locked together, so the intake and exhaust valves operate normally. When pressure is removed (right), the arms unlock, and the valves no longer open. The ECU switches off the fuel injectors and spark plugs for those cylinders at the same time. siliconchip.com.au Australia’s electronics magazine January 2021  13 The 42V electrical system In the 1990s, there was a proposal to change the standard voltage of a car electrical system from 12V to 42V. A fully charged regular car battery is 12.6-12.9V and a typical float charging voltage is 13.8V, which is about what the average voltage of the car electrical system runs at and what accessories are rated for. That rounds to 14V, so 42V is then triple the standard car electrical system voltage. The voltage chosen had to be under 50V due to shock hazards. A higher standard voltage was chosen because it allows for a lighter wiring harness; three times the voltage means one third the current for the same power, and the thickness of wiring is dependent on current, not voltage. A further advantage of a higher voltage is that motors such as window winders, electric power steering pumps etc can be smaller and lighter. Disadvantages are that the higher DC voltage requires more expensive switches due to more arcing, there was already a lot of support for the 12V system, and the need for the 42V system was reduced with the development of more efficient motors and multiplexed data buses requiring less wiring. Also, most hybrids have dual-voltage electrical systems anyway. The Audi SQ8 (mentioned last month) has a separate 48V volt system for its electric supercharger, and there are other vehicles with similar setups for start/stop systems etc. While there are cars out there with 42V electrical systems (mainly luxury vehicles), in the end, the benefits just weren’t worth the cost of switching and so most manufacturers haven’t bothered. 12/14V remains the dominant standard, at least for now. Fig.35: Electronic Stability Control (ESC, sometimes called ESP or VSC [vehicle stability control]) uses the ABS hydraulic actuator to brake individual wheels, to pull the vehicle back into line when traction is lost. This photo shows four wheel speed sensors, a steering angle sensor, yaw-rate sensor, the controller and the hydraulic unit. Mass airflow sensor (MAF) A MAF measures the amount of air by mass (and temperature as an auxiliary function) flowing into a fuel-injected engine (see Fig.42). This data is used by the ECU to deliver the correct air-fuel ratio in both open-loop and closed-loop modes (in conjunction with the oxygen sensor in the latter mode). It is important to measure the mass of air rather than its volume, because the volume varies according to air temperature and pressure, but a given mass of air will always have the same amount of oxygen. Most MAF devices use either a hot wire or moving vane technology for mass measurement. Airflow is controlled by the throttle body which contains a butterfly valve. These days it is usually motorised (‘drive-by-wire’) and also has a throttle position sensor to communicate throttle position to the ECU. The ECU monitors the accelerator pedal position and sets the throttle position. In the absence of a MAF, a manifold absolute pressure (MAP) sensor can be employed. In this case, mass airflow is calculated by knowing the air temperature and engine RPM and using a lookup table for fueling. For a turbo or supercharged engine (forced induction), both a MAF and MAP are normally used. Fig.36: traction and stability control systems can take various forms. This older design uses a second electronically-controlled throttle butterfly to reduce engine torque when wheel spin is detected (more modern systems would send signals to the existing motorised throttle). The main input signals are from the wheel speed sensors, which are shared with the anti-skid system. 14 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.37: more modern vehicles use a single electronic control unit for anti-lock braking ABS), traction control (TCS) and stability control (ESC). In addition to the wheel speed inputs, it has a yaw rate sensor and a steering angle sensor, which it can compare to determine if the vehicle is travelling in the intended path or not. As throttle closure takes time, traction control systems will also adjust spark timing (possibly even disabling it) to quickly reduce engine output when the wheels spin during acceleration. Parking assist or self-parking This feature was first demonstrated in 1992 on Ford’s Futura concept car. Then in 2003, Toyota offered it in their Japanese Prius model. Self-parking cars can fit into smaller spaces than many drivers can achieve manually. A self-parking system requires a motorised steering wheel (normally via the electric steering assistance system) plus several sensors such as ultrasonic distance sensors, radar and cameras to provide inputs to the car computer systems about surrounding obstacles, so the car can be manoeuvred into position (see Fig.43). Both parallel and perpendicular parking can be performed, depending on the system. See the video titled “Park Assist Pilot allows 2020 Volvo XC90 T6 to Park itself” at https://youtu.be/ujF1veCdHZs Rain sense module (RSM) The RSM detects water on the windshield and activates the wipers at an appropriate speed or interval (see Figs. 44&45). It may also perform other functions, as in the Hella brand unit shown. It operates on the principle of total internal reflection of a light beam. This occurs with no water on the upper (outside) reflecting surface, but if water is present, some light is lost and the loss of signal is interpreted as rain. Late model Teslas also use their video cameras to detect rain. These systems generally have a sensitivity setting controlled by the driver. Regulated voltage control (RVC) RVC regulates the battery charging voltage based on estimated or measured battery temperature and state-of-charge (SoC). Benefits include improved fuel economy due to the alternator only providing power when necessary, and longer lamp and switch life due to more accurate voltage control. The RVC system maintains the battery at 80% SoC or 13.0V to avoid unnecessary charging. On GM vehicles, the alternator is controlled by the “L” terminal. The PCM (powertrain control module) sends a 5V variable duty cycle signal to it to control the output voltage from 11V to 15.5V. Editor’s note: this is a somewhat controversial system as it means that the battery will go flat quicker when parked and besides the inconvenience, this can also lead to premature battery failure. We have had several letters in Mailbag in the past from readers complaining about vehicle battery undercharging. Traction control system (TCS) The purpose of a TCS is to stop the driven wheels losing traction during acceleration, especially on slippery surfaces such as wet or oily roads (see Fig.46). In most modern vehicles, it is now part of the ESC system, but it might also be Fig.38: a GM ethanol fuel sensor module. It determines the percentage of ethanol in the fuel flowing through it. This is used to apply corrections to the engine map to optimise operation at a wide range of percentages. siliconchip.com.au Fig.39: a cutaway diagram of an engine knock sensor. The mass on top of the piezoelectric crystal helps tune the device to be sensitive to the frequency of the knock vibrations. It is essentially a microphone that’s very sensitive to particular frequencies. Australia’s electronics magazine January 2021  15 Fig.40: the knock sensor can be mounted directly to the engine head or attached to it via a bracket, as shown here. Some vehicles (usually those with larger engines) can have multiple knock sensors. They are sensitive enough to detect ‘incipient’ knock before it’s noticeable to the driver, or can cause any damage. Fig.41: a Lingenfelter ‘aftermarket’ combined RPM limiter, timing retard controller and launch controller intended for racing applications for GM Gen V V8 engines. integrated with the ABS system and the ECU. It monitors wheel speed and if there is a mismatch between the speed of the driven wheels, or between the driven and undriven wheels, engine power power is reduced or a wheel may be braked (via the ABS electrohydraulic system) to stop the slipping wheel spinning excessively. In our article on fluidics (August 2019; siliconchip.com. au/Article/11762), we described how traditional automatic transmissions were controlled via a complicated series of channels, valves and solenoids through which transmission fluid flowed (the valve body). This created a fluidic computer to change gears as needed. This technology has now been replaced with a TCU that operates the transmission via electronic solenoids (see Fig.47). It uses many inputs such as engine RPM, throttle position, recent driving history, speed, whether the vehicle is going uphill or downhill, whether the wheels have traction or not, torque converter slippage, transmission temperature, traction control system state, cruise control state etc. These TCU inputs are analysed and outputs are gener- ated to control the automatic transmission via solenoids to change gears, control hydraulic pressures, to lock the torque converter and to instruct the ECU to momentarily reduce or even “blip” the throttle during gear changes. The TCU also monitors natural wear in the transmission such as of the clutches, and it makes alterations to transmission operation to compensate for wear. Outputs are also sent to other control modules such as the cruise control and error codes for faults can also be generated to be shown on dash warning lights and the OBD system. Like ECUs, aftermarket TCUs are available. These might be used when a modern engine and transmission have been retrofitted into a classic car, or for drag racing. An aftermarket TCU uses the more basic inputs of engine and road speed, throttle position or manifold vacuum and selected gear. See the video titled “1966 GTO: TCI Transmission Controller V8TV” at https://youtu.be/X3EmzS7VSMk TCUs can also be remapped. Typical changes made are the point of torque converter lockup, gear change points and shift speed. Some vehicles are said not to be shipped with optimal TCU settings from the factory and benefit greatly from changes. One such vehicle is apparently the 2017 Land Fig.42: looking into a Holden Commodore MAF sensor. The wires are electrically heated and the mass of air flowing past them cools them. The current required to keep the wires at a constant temperature is therefore proportional to the mass of air moving past them. Source: Wikimedia user Jeff3205. Fig.43: a Ford Active Park Assist module for self-parking. It coordinates inputs from range sensors and controls the steering. The driver controls the accelerator (speed) and transmission (forward/reverse) via prompts from the onboard screen. Transmission control unit (TCU) 16 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.44: the operation of a typical vehicular rain sensor. Total internal reflection is achieved with no rain, but there is some signal loss with water on the glass. Source: Wikimedia user Puppenbenutzer, CC BY 3.0. Cruiser 200; see siliconchip.com.au/link/ab4l Here is a video of how an original factory TCU is reflashed. Make sure the battery doesn’t go flat during the reflashing process! It’s titled “Programming a GM TCM with an Autel” and is at https://youtu.be/DtmiQD_pzC4 Autel is a brand of proprietary scan tool that uses J2534 communications (which was described briefly last month). Apart from the modules described above, there are numerous others, often particular to certain manufacturers or models. Other types of modules include: • adjustable pedal module • airbag control module • electronic vehicle information centre • heated seat module • instrument cluster • memory seat module • passenger and driver door module Fig.45: a schematic of an electronically controlled automatic transmission. Source: after Clemson University Vehicular Electronics Laboratory. • • • • sentry key immobiliser module sunroof module throttle control module wireless charging module for phones Drive-by-wire As in modern aircraft, in many modern vehicles mechanical linkages between the controlling device (such as a gear shifter) have been replaced with electro-mechanical servos. Examples include steering, brakes, throttle, gear shifting and when some are combined together, automatic parking. Currently, full steering-by-wire systems are illegal in most places; there is a requirement for a mechanical linkage to the Fig.46: a Hella combined rain and light sensor, which activates the wipers and headlights. They are generally attached to the windscreen above the rear vision mirror. Artificial lighting is distinguished from natural lighting due to different spectra. This particular sensor is of modular construction, and car manufacturers can choose additional functionality such as humidity measurement, a solar sensor to adjust the air conditioning, adjustment of head-up display brightness and adaption to windscreen conditions such as dirt. It is connected to the rest of the vehicle systems by both LIN and CAN buses. Source: Hella. siliconchip.com.au Australia’s electronics magazine January 2021  17 Fig.47: some components of the ABS, ECS and TCS in a typical vehicle. Some components are shared and communicate with each other over the vehicle’s data bus. In this diagram, ESC is instead labelled VSC while TSC is labelled TRAC. steering rack. However, in some countries there are already cars on the road with no such mechanical linkage, including the Infiniti Q50 from 2014 onwards. Electric servo operation of steering is possible and is used in most current vehicles. Drive-by-wire systems allow for more design flexibility, less weight and better computer control over vehicle systems and potentially, more reliability. Computer control might be seen as a bad thing as there are possible security (malicious hacking issues) enabling unauthorised persons to take control over the car, and the possibility of an electronic failure rendering the vehicle uncontrollable. However, that can happen with mechanical linkages too. The technology has proven safe and effective on aircraft and is accepted. Drive-by-wire leads the way to autonomous vehicle operation. Note that conventional mechanical systems such as powerassisted steering or brakes will still work even if the power assistance servo fails. This might not be the case in drive-by-wire or brake-bywire systems, unless safety measures are taken such as multiple levels of redundancy and a software “voting” system in the event of a communications failure between the brake SC system and the pedal (see Fig.48). Interesting videos “Reading The Extracted Memory From A Car ECU With A Raspberry Pi”: ............. https://youtu.be/zdgA86pbkw0 “Open source car engine management”: ................................................. https://youtu.be/C1D5B7BNGqA A DIY repair of an ECU: “Ford OBD-1 ECM Repair” ................................................. https://youtu.be/B0Dj40Dkszo “Airbag Crash Data Reset” ................................................. https://youtu.be/KzoKndbYgLo “Automotive Electronic Modules Types” ................................................. https://youtu.be/BG4N2dBgJrQ Fig.48: a brake-by-wire system. HMI stands for human-machine interface, BLDC is brushless electric DC motor. Note the use of 42V. Source: after Wikimedia user Rhoseinnezhad. 18 Silicon Chip Australia’s electronics magazine siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build Ampec Technologies Pty Ltd Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au *** System Assembly All the hard parts are already done for you! E-Z-2-Build Digital AM/FM/SW Receiver Our DAB+/FM/AM Radio from 2019 is very capable and has been extremely popular. But it is somewhat complicated and costly to build. Not this one, though! It uses the BK1198 digital radio chip which is cheap and readily available, and requires only a handful of discrete components to work. The resulting radio covers the AM and FM broadcast bands plus shortwave from 2.7 to 22MHz. by Charles Kosina 20 Silicon Chip Australia’s electronics magazine siliconchip.com.au T he design of radio receivers has changed dramatically in recent years. For many years, the standard AM receiver was a superheterodyne circuit with a mixer stage that combined the incoming signal with a local oscillator. The resulting intermediate frequency signal was then further amplified and fed into an envelope detector that extracted the audio component. Finally, audio amplification was provided to drive a loudspeaker. When transistors replaced valves, initially, the design philosophy remained much the same. Such receivers (and those which preceded them, such as super-regenerative and tuned radio frequency [TRF] receivers) required multiple tuned circuits, many of them adjustable. But with the advancement of technology, analog circuits have largely been replaced by digital techniques. The BK1198 is a good example of this. Its functions are described in the following PDF document from Jaycar: siliconchip.com.au/link/ab5n Jaycar sells the mono version of the BK1198 separately (Cat ZK8829), as part of a prebuilt AM/FM portable radio (AR1458) or in their “Cardboard Radio” kit (Cat KJ9021). We reckoned that we could do more with the chip, and build a more capable radio, hence this design. If you don’t mind using an external speaker, it fits into a low-cost Jiffy box. Alternatively, you can use a larger box and include an internal speaker. Either way, it delivers 0.9W to the 8Ω speaker. The current band, tuning range and frequency are displayed clearly on a backlit character LCD screen. It also has a tone control, volume control, on/off switch and headphone socket. So basically, it has everything you need for listening to AM, FM and SW broadcasts and not much else, and it’s easy to drive. It runs off a 9-12V AC plugpack or 12V DC external battery. The PCB has been designed with a mixture of SMD and through-hole components; we can’t avoid having SMDs since the BK1198 is not available in any through-hole packages (a common situation these days). That being the case, we decided to use some larger passive SMDs to keep the overall device compact, without making it too hard to put together. Performance Performance is reasonable for such a simple design. On the FM band, I found an internal wire length to be quite adequate to pick up many stations in the Melbourne area with good quality. I do have line-of-sight to the Mt Dandenong towers, however. The AM band suffers from interference from various sources, and switchmode power supplies in the vicinity will create background noise. Moving away from such sources gives reasonable quality. I got the best results by taking it into my car and running it off the car battery. On the short wave bands, a 1µV sig- Fig.1: block diagram of the BK1198 radio receiver chip, on which this project is based. All you have to do is tell it which band(s) you want to listen to, display its details and amplify the audio output. siliconchip.com.au Australia’s electronics magazine Coverage: AM: 513-1629kHz FM: 87-108MHz SW1: 6.4-10.25MHz SW2: 2.7-10.25MHz SW3: 9.8-15MHz SW4: 14.0-22MHz (1kHz steps) (100kHz steps) (5kHz steps) (5kHz steps) (5kHz steps) (5kHz steps) nal is detectable, and a 10µV gives a reasonable signal-to-noise ratio. Circuit description While the simplest radio designs using the BK1198 require only a few discrete components plus an audio amplifier, my design is rather more ambitious, but thanks to the use of an Arduino Nano, still manageable. The circuit I came up with is shown in Fig.1. There are two ways of controlling the BK1198 radio chip (IC4), selected by the MODE pin (pin 5). If this pin is tied low, it’s controlled by serial data on the SCLK and SDIO pins. While this would appear to be the sensible approach, documentation on how to do this is rather sparse, and the translation from Chinese leaves a lot to be desired. My design leaves this as a future option, but for now, an analog tuning approach is used. This means that we have the jumper on LK1 pulling MODE up to 3.3V. A voltage on the BAND pin (pin 15) selects the band that the BK1198 operates on. There are a total of 18 preprogrammed frequency ranges available, and the simplest way is to have a voltage divider connected to TUNE1 (pin 1), which is the tuning supply voltage and very close to 1.2 V. But I have used a different approach. The required voltages are: • AM 2 (513–1629kHz, 9kHz steps); 300mV • FM 1 (87–108 MHz, 100kHz steps): 33mV • SW10 (2.7–10.25MHz, 5kHz steps): 1033mV • SW11 (9.8-22MHz, 5kHz steps): 1100mV The appropriate voltage is generated by IC2, an MCP4822 12-bit digital-toanalog converter (DAC). The user controls the band using 6-position rotary switch S2. Why six position? I decided to split up each of the shortwave bands into two (more on why I did this later). January 2021  21 SC Ó BK1198 BASED DIGITAL AM/FM/SW RADIO RECEIVER Fig.2: despite receiving FM and AM in three different bands, the radio circuit is relatively simple thanks to the all-in-one BK1198 digital radio receiver chip (IC4). JFETs Q3 and Q4 provide extra RF gain for shortwave and FM signals respectively, while inductors L1-L4 provide preselection for different shortwave frequency ranges. Tuning and band switching is controlled by the Arduino Nano using DACs IC3 (12-bit, for band selection) and IC6 (16-bit, for tuning). IC1 is the audio amplifier. 22 Silicon Chip Australia’s electronics magazine siliconchip.com.au 16 x 2 LCD MODULE IC1, IC3, IC6 D2-D5 K A siliconchip.com.au Australia’s electronics magazine 8 I C4 4 1 16 8 1 January 2021  23 The frequency tuning voltage is generated by another DAC, the DAC8551 (IC6), which has 16-bit resolution. It needs to be more accurate than the band selection voltage, hence the higher resolution. The reference voltage for this DAC is the 1.2V on pin 1 of IC4 (TUNE1). This ratiometric approach ensures that an accurate voltage will be generated regardless of the BK1198 chip variations. If we take the FM band as an example, there are 210 channels spaced at 100kHz intervals. The change in channel voltage is thus 1200mV ÷ 210 = 5.7mV. One bit of the 16-bit DAC represents about 18.3µV (1.2V ÷ 216), so the digital value steps by about 311 to switch from one channel to the next. This is more than an adequate safety margin in resolution It gets a bit tighter on the shortwave bands. There are 2440 channels spaced at 5kHz on the 9.8–22MHz band. This is only 490µV between channels, or a step-change of 27 in the digital data. Again, we have a sufficient safety margin. But a 12-bit DAC would have less than two steps between channels, which would be quite inadequate. There are two RF inputs on the BK1198 chip. It receives the FM signal at pin 2. Reference designs include a preamplifier using an NPN transistor, but I opted to use a grounded-gate JFET as this gives good gain and a high stability margin. The second RF input is on pin 4, and is for the AM and SW bands. This presented something of a design challenge. For the AM band, a ferrite rod of about 400µH is required. An internal varicap tunes the ferrite rod to the correct frequency. But there are not many pre-wired ferrite rods available – the only one Jaycar sells is their Cat LF1020. I found the performance of this one not very satisfactory. A better option is to use their LF1012 ferrite rod, which is 180mm long and 9mm diameter. With 65 turns of 24AWG (0.5mm diameter) enamelled copper wire, this gives considerably improved performance. The Q of such a coil is not particularly high, and it is preferable to use Litz wire, but it is challenging to strip and tin each strand. Litz wire is used on the LF1020, and it’s possible to very carefully remove this winding and slip 24 Silicon Chip it on the longer rod, giving an almostideal solution. Shortwave tuning I felt that a low-noise preamplifier was desirable for the SW bands, so I chose the J310 JFET for this as well. Because I wanted some degree of tuning on this preamplifier, I used different inductors for the various bands, which brings me back to why I divided up the shortwave bands into two. My original intention was to use a readily available varicap diode, type BB201, which has a range of about 20–110pF with a tuning voltage of 10–0.5V. This tuning voltage was to be generated by the second DAC in IC3, and amplified by a rail to rail op-amp running off 12V. The varicap range is such that it would cover the appropriate band with the chosen inductor. By using an appropriate formula, the tuning voltage could be calculated by the micro. However, this just did not seem to work at all; the best result obtained was with the varicap set to minimum capacitance regardless of the band or frequency. Based on the BK1198 documentation, I gathered that its internal varicap only operated on the AM band. But I suspect that it also works on the SW bands, although the documentation does not describe this. The op amp and varicap of the original prototype were therefore unnecessary, so I removed them in the final design. You will see that there is a 2.2kΩ resistor from the drain of Q3 to +8V. Originally, this was a 1000µH RF choke, which was fine for the shortwave bands, but it completely killed the AM band because the 100pF capacitor in series resonated within the Quirks with the BK1198’s shortwave tuning My original prototype had a problem with its SW10 shortwave range; I found it to actually cover 3.1–10.1MHz rather than the expected 2.7-10.25MHz range. As the ranges are set at the factory by internal programming, this could have been an anomalous chip. Replacing the chip gave me the correct range. Fortunately, if this happens to you, it is easy to correct by altering just a few numbers in the program code. Australia’s electronics magazine AM band and formed a very effective series-resonant trap. By replacing it with a resistor, the HF performance is not significantly affected, and it has a minimal effect on the AM band. Small signal diodes D4 & D5 provide some measure of protection against voltage spikes being picked up on the SW antenna, for example, during a thunderstorm. Obviously, they cannot protect against a direct or even nearby strike, but will prevent damage to Q3 from general lightning activity. The 100pF coupling capacitor, in combination with the inductor L1-L4 selected by rotary switch S2a peaks the shortwave preamp response around the selected frequency band. Band selection details Getting back to band selection, S2b selects from equally-spaced voltages between 0 and 5V, generated by a chain of 2.2kΩ resistors between 5V and 0V. The selected tap is fed to the internal analog-to-digital converter (ADC) of the AVR ATmega328 chip on the Arduino Nano module. This ADC has a 10-bit resolution, so that the values read are approximately 0, 204, 409, 613, 818 and 1023. By truncating the last two digits we get 0, 2, 4, 6, 8, and 10. Then dividing by two and adding one gives the selected band number, from one to six. The Arduino code then uses a lookup table to find the value needed to generate the appropriate band select voltage for the BK1198 chip. This is a more versatile arrangement than using a resistor network to generate the voltage directly, as it can easily be programmed to select any of the different bands available. Switch positions 3 and 4 both select the 2.7-10.25MHz band, and switch positions 5 and 6 both select the 9.822MHz band. However, different inductor values are chosen as part of the SW filter by S2a for each shortwave position. The Arduino Nano module is available at very low cost and has the advantage of providing regulated 5V and 3.3V outputs, which are needed by other devices in the circuit. Most of its I/O pins are used. The LCD module is the popular 16x2 type that is widely available. The SCL and SDA lines of the Nano are routed to the BK1198 chip in case someone can work out how the siliconchip.com.au BK1198 serial interface works. The Nano is a 5V device, while the BK1198 runs from 3.3V. So schottky diodes D2 and D3 are used (along with pull-up resistors to 3.3V) to prevent damage to the BK1198 IC. Tuning is controlled via incremental rotary encoder RE1. The falling edges of its output pulses generate an interrupt on the INT0 pin (Arduino digital input D2), at which point the state of analog/digital input A3 is read. If it is high, the frequency is increased by the appropriate step, and if low, it is decreased. This scheme works with either momentary or level type encoders. The pushbutton switch integrated with the rotary encoder is connected to INT1 (digital input D3). This is used to toggle between the step sizes on different bands. On the AM band, the spacing in Australia is 9kHz, but the toggle allows for 1kHz step size as well. On the FM band, only a 100kHz step size is used, as it does not take too long to sweep across the band. All four shortwave bands have step sizes that can be set to 5kHz, 50kHz and 500kHz. Audio amplification The audio output section is fairly straightforward. The OUT pin of the BK1198 chip (pin 13) is capacitively coupled to volume control potentiometer VR2. The tone control potentiometer (VR3) at minimum resistance gives a -3dB point of about 700Hz. This works by forming a variable low-pass filter in combination with the 2.2kΩ resistor and 100nF capacitor. The audio amplifier is an SSM2211 chip which will deliver about 0.9W into 8Ω. The phono jack is configured to cut off the signal to the loudspeaker when phones are inserted. To prevent hearing damage, a 560Ω resistor reduces the output level to the headphones. Power supply The original idea was to run the radio from a 12V DC plugpack. There are plenty of switchmode ones available, but they generate so much hash as to make the AM band all but useless. You could use one which has an iron-cored transformer, but they are almost impossible to buy new now. Fortunately, Jaycar still sells a 9V AC plugpack, the MP3027. We use this and rectify its output using bridge recsiliconchip.com.au Case holes required for the receiver. No diagram is shown for these as none of them are super-critical. tifier BR1. The resulting pulsating DC is filtered by a 2200µF capacitor and applied to the input of 7805 regulator REG1. Don’t be fooled though – this regulator is not producing a 5V output. A resistive divider between its output, GND pins and the actual circuit ground (0V) lifts its output to 8V while retaining decent regulation. The Nano module has a 5V regulator, which powers the ATmega328 micro and also the audio amplifier. We don’t want this regulator to drop too much voltage or else it could overheat. Tests showed that with sustained maximum audio output, this regulator does not overheat as long as its input voltage is no higher than about 8V. So REG1 is essentially a pre-regulator for the Arduino’s own 5V regulator. Note that you could use a 7808 for REG1, leave out the 330Ω resistor and replace the 180Ω resistor with a wire link or 0Ω resistor. However, 7808s are not as common to find as 7805s are. By the way, the 100nF capacitor across the input to bridge rectifier BR1 may seem redundant, but it helps to filter out any unwanted RF picked up by the supply leads. Debugging interface A simplified RS232 serial interface is provided by transistors Q1 and Q2, which operate as level shifters. This was included purely for debugging purposes in development, operating at 38,400 baud with the usual 8,N,1 enAustralia’s electronics magazine coding. These components (and their 15kΩ drain pull-up resistors) may be omitted if you don’t plan to fiddle with the software. Software The firmware is written in BASCOM, a versatile BASIC-like language that compiles into native AVR code. On power-up, the receiver retrieves the last frequency and step size for the set band from EEPROM. The LCD module shows the selected band on the top line and the set frequency on the bottom line. When another frequency is selected by the tuning knob, the new set frequency and current step size is written into the EEPROM after about half a second. Sourcing the components We know that sourcing components can be a challenge, so the ones used in this design were carefully chosen so that they are available from local suppliers such as Jaycar, Altronics and element14. In some cases, you might have to buy multiples of the one item. Some of these items might be available more cheaply on eBay, AliExpress or Banggood, if you don’t mind the longer lead time. For the full details, see the parts list below. Construction Refer now to the PCB overlay diagram, Fig.3. The BK1198 radio is built on a PCB coded CSE200902A which January 2021  25 measures 127 x 88mm. If you have some experience soldering surfacemount components, the assembly should not present any problems for you. If you don’t, you might want to practice with something simpler first. Start by fitting IC6, the 16-bit DAC. It’s in an eight-pin fine-pitch (0.65mm) package and does require special care. First, locate its pin 1 dot in the top corner and line it up with the pin 1 indicator on the PCB. Spread some flux paste over the pads, place the chip and carefully tack down one corner pin. Use a magnifier to verify that the other seven pins are correctly located over their pads. If not, re-melt the solder on that tacked pin and gently nudge it into position. Repeat until it is precisely located, then solder all the pins and again use a magnifier to check for bridges between pins. If you find any, add extra flux paste and clean up the bridge(s) using solder wick. The remaining ICs have twice the pin pitch (1.27mm), so they should be fairly easy in comparison. Use a similar technique to fit those, making sure in each case to check the pin 1 orientation before soldering. Follow with the four small transistors and the four diodes. Don’t get the different types of transistors or diodes mixed up. The orientation of each transistor will be obvious, but you will have to check (probably under magnification) for the cathode stripe on 26 Silicon Chip the diodes to determine their correct orientations. The SMD resistors and capacitors are all either 2.0 x 1.2mm or 3.2 x 1.6mm, so again should be fairly easy and they are not polarised. The SMD resistors will be printed with a tiny code on top that identifies their value (eg, 183 [18 x 103] or 1802 [180 x 102] indicates 1.8kΩ) while the capacitors will be unmarked. Make sure each component goes in the correct location as per Fig.3. Through-hole parts Next, fit the low-profile through-hole parts: the 1W resistor, axial inductors and the bridge rectifier (watch the orientation – the positive terminal should be marked). The watch crystal, X1, is laid over on its side and held down with a loop of wire soldered to the board (use a component lead offcut). Be careful bending and soldering its leads because they will be very thin, and you don’t want them shorting against each other or the crystal case. Continue by fitting taller parts like trimpot VR1 (with its adjustment screw towards BR1), polarised headers CON1-CON3, CON7 & CON9 and SMA sockets CON5 & CON6. Also fit the 3-pin header for LK1, and place the shorting block between pins 1 & 2 and the socket strips for the Arduino Nano. Note that you don’t need CON3 unless you plan to use the serial debugAustralia’s electronics magazine ging feature, and most of the other headers could be left off if you prefer to solder flying leads straight to the board. That will make the final construction steps a bit more tricky, though. Also, if you live in a strong signal area, you could use FM antenna connector CON6 off the board and just solder a length of wire to its central pad. Now mount the Arduino Nano module, which can be soldered straight to the board (it’s usually supplied with pin header strips) or optionally, plugged in via female sockets soldered to the board. Either way, make sure that its pinout matches the PCB silkscreen. With that in place, fit the sole electrolytic capacitor, ensuring its longer lead goes to the pad marked with a + symbol. The last part to fit on this side of the board is inductor L8, which is wound using six turns of 0.5mm diameter enamelled copper wire on a 5mm diameter former (such as the shaft of a 5mm drill bit). Space out the windings so that the coil is 7mm long, then cut it to length, strip the enamel off the ends of the wires (using emery paper or a sharp knife), tin the wires and solder the coil to the board where shown. Underside components We have seen LCDs with pins 1 (GND) and 2 (+5V) swapped, so check your screen. If pin 2 is GND, you will need to cut the header pins off and add siliconchip.com.au Fig.3 (left): the PCB uses a mix of SMD and through-hole components. Start by fitting the only fine-pitch SMD, IC6, then the remaining SMDs (don’t forget the two caps under the Nano!), followed by the topside through-hole parts and finally, those which mount on the underside (mainly the display and controls). There are a few optional components, such as the debugging header CON3. This diagram also shows most of the external wiring. At right, the photo shows the assembled PCB mounted in the case. Note that this is an early prototype board so there could be some minor differences between this and the PCB overlay opposite. wires to cross these connections over. The LCD screen mounts on the underside of the board. Solder its header strip in place, then check that it has a pin header attached; if not, solder it now. Plug it into the socket and attach it to the board using the tapped spacers and machine screws. With the LCD in place, the remaining underside components can be fitted: rotary encoder RE1, rotary switch S1, volume control potentiometer VR2 and tone control potentiometer VR3. Preparing the ferrite rod antenna As explained earlier, you probably won’t find a 400µH ferrite rod that comes pre-fitted with a coil. The easiest and best solution is to also buy a smaller ferrite rod antenna, such as the Jaycar LF1020, carefully remove the windings from that rod and then gently slip them over the longer rod. If you can’t (or don’t want to) do that, instead wind 65 turns of 0.5mm enamelled copper wire onto the rod, and strip and tin the ends, ready for attachment to the PCB via flying leads. Programming You can program the Arduino Nano module separately, or plugged into the main board, but it’s easier before you plug it in. As the code is written in BASCOM, you can’t use the Arduino IDE to program the chip. We suggest a free prosiliconchip.com.au gram called AVRDUDE or (preferably) its Windows graphical version, AVRDUDESS. Download and install it from: https://blog.zakkemble.net/avrdudessa-gui-for-avrdude/ Launch it and find the dropdown under the label “Presets” in the upper right-hand corner of the window, click the drop-down and select the “Arduino Nano (ATmega328P)” option. In the upper left-hand corner, modify the COM port number to match your Nano. Once you have plugged it in, you can find its port number in Windows’ “Bluetooth and other devices” Settings page. Under the “Flash” heading, click the “...” button and find the radio HEX file (available as a download from the SILICON CHIP website). Then ensure “Write” is selected just below this and Radio Source Code As usual, we will be making the source code available for this project, along with the HEX file. The firmware was written in BASCOMAVR, a version of the BASIC language that compiles to native Atmel AVR code. So it is quite easy to modify. BASCOM is commercial software; there is a free demo version available which can produce binaries up to 4KB in size, but the radio software is larger than that. A full license for the software costs around $150 (it’s available from a few different online shops) Australia’s electronics magazine press “Go”. Messages will appear at the bottom of the window, hopefully indicating that the programming was successful. The most likely cause of any problem an incorrect port selection. Finally, unplug the USB cable from the Arduino Nano module and plug it into your radio board. The board assembly is now complete. Testing It’s a good idea to do a little bit of testing before you put the board in the case, as it is easier to debug and fix in its current state. You will need some sort of antenna connected to verify that the radio is working – at this stage, the FM antenna is probably the easiest to organise. A length of wire might be good enough for initial testing. You will also probably want to temporarily connect an 8Ω speaker between pins 1 and 3 of CON7. Position the board so that you can see the LCD and access the controls, and connect a 9V AC or 12V DC power supply to CON1. Verify that the LCD backlight switches on and you get a sensible display on the LCD screen. If you can’t see the characters, try adjusting trimpot VR1. If the backlight doesn’t come on, then that points to a power supply problem – check the output of REG1 and verify that it is a steady 8V or so. If you still don’t get any display, then there may be a problem with the programming of the Arduino Nano January 2021  27 module, or perhaps the Nano or LCD are not making good contact with their sockets. Assuming the display looks OK, rotate S2 to get the unit into FM mode and then try turning RE1 to find a station. 28 Silicon Chip Adjust VR2 to get a sensible volume from the speaker. If you can pick up stations then it’s all looking good. If not, you might need a better antenna, or you could have a problem in or around transistor Q4, IC4, crystal X1 or audio amplifier IC1. Australia’s electronics magazine If you want to test the other bands, then you will need to connect up a shortwave antenna to CON5 and/or the ferrite rod to CON2. Assuming it all checks out, proceed to finish the build. If you run into problems, it’s always a good idea siliconchip.com.au Parts list – AM/FM/SW Digital Receiver 1 double-sided PCB coded CSE200902A, 127 x 88mm 1 5V Arduino Nano module 1 16x2 blue backlit alphanumeric LCD module 1 220 x 160 x 80mm IP65 sealed ABS enclosure or similar with black 3mm acrylic laser-cut lid/panel, 193 x 109mm(?) (fits internal speaker), OR 1 UB2 Jiffy box, 197 x 113 x 63mm (no internal speaker) 1 10kW single-turn mini vertical (SIL) trimpot (VR1) [eg, element14 9317236] 2 9mm vertical 10kW potentiometer (VR2, VR3) [eg, element14 1191725] 1 2.2µH axial RF inductor (L1) [eg, element14 1167666] 1 4.7µH axial RF inductor (L2) [eg, element14 1180375] 1 10µH axial RF inductor (L3) [eg, element14 1180270] 1 33µH axial RF inductor (L4) [eg, element14 1857853] 1 100µH axial RF inductors (L9) [eg, element14 2858897] 1 1m length of 0.5mm diameter enamelled copper wire (L8 and possibly L10) 1 400µH ferrite rod (L10) 1 coil taken from ferrite rod antenna (L10) 1 32768Hz watch crystal (X1) [Jaycar RQ5297] 1 rotary encoder with inbuilt pushbutton (RE1) [eg, element14 2663519] 1 SPST chassis-mount toggle switch (S1) 1 2-pole, 6-position rotary switch (S2) [Jaycar SR1212] 3-4 knobs (to suit VR2, VR3 [if fitted], RE1 & S2) 3 2-pin polarised headers (CON1,CON2,CON9) [Jaycar HM3412] 3 2-pin polarised plugs (for CON1,CON2,CON9) [Jaycar HM3402] 2 3-pin polarised headers (CON3,CON7) [Jaycar HM3413] 2 3-pin polarised plugs (for CON3,CON7) [Jaycar HM3403] 2 right-angle or vertical PCB-mount SMA sockets (CON5,CON6) [eg, element14 2612349] 1 6.35mm switched stereo chassis-mount jack socket (CON8) [Jaycar PS0184 or similar] 2 15-pin female header sockets (for the Nano; can be cut down from longer strips) 1 16-pin female header socket (for the LCD) 1 3-pin header with jumper/shorting block (LK1) 1 2.1mm inner diameter bulkhead barrel socket [Jaycar PS0522 or similar] 1 8W 1W full-range speaker driver (eg, 76mm if mounting in a larger box) or an external 8W speaker) 4 knobs (size as required) 4 8mm-long M3 tapped spacer (for mounting LCD) 4 15mm-long M3 tapped spacers (for mounting PCB to box) 12 M3 x 5mm panhead machine screws 4 M3 x 10mm countersunk head screws various lengths of shielded and hookup wire to carefully inspect all of your solder joints, while also verifying that the right parts are in the right locations, and any polarised components have not been soldered in the wrong way around. Final construction If you’re building the radio into the smaller and cheaper UB2 Jiffy box, siliconchip.com.au Semiconductors 1 SSM2211SZ or NCS2211DR2G 1.5W audio power amplifier, SOIC-8 (IC1) [element14 2464727] 1 MCP4822-E/SN dual 12-bit DAC, SOIC-8 (IC3) [element14 1439414] 1 BK1198VB digital radio receiver, SOIC-16 (IC4) [Jaycar ZK8829] 1 DAC8551IDGKT 16-bit DAC, VSSOP-8 (IC6) [element14 1693841] 1 7805 5V 1A linear regulator (REG1) 2 2N7002 N-channel Mosfets, SOT-23 (Q1,Q2) [element14 1764537] 2 MMBFJ310LT1G N-channel VHF/UHF JFETs, SOT-23 (Q3,Q4) [element14 1431340] 1 DB104 bridge rectifier, DIP-4 (BR1) 2 BAT54T1G schottky diodes, SOD-123 (D2,D3) 2 1N4148WS signal diodes, SOD-323F (D4,D5) Capacitors (through-hole) 1 2200µF 16V electrolytic Capacitors (SMD M3216/1206-size) 4 10µF 25V X7R ceramic 3 1µF 25V X7R ceramic Capacitors (SMD M2012/0805-size) 1 10µF 25V X7R ceramic 9 100nF 50V X7R ceramic 2 10nF 50V X7R ceramic 1 1nF 50V X7R ceramic 1 100pF 50V C0G/NP0 ceramic 1 33pF 50V C0G/NP0 ceramic 3 18pF 50V C0G/NP0 ceramic Resistors (all SMD M3216/1206-size 1% thick film unless otherwise specified) 1 10MW M2012/0805-size 1 270kW M2012/0805-size 1 220kW 1 56kW 1 18kW 5 15kW 1 10kW 2 4.7kW 7 2.2kW 1 560W 1 330W 1 180W 2 100W 1 100W 1W 5% axial you can either use our laser-cut lid, or drill and cut holes in the lid that came with your box. Fig.4 shows the details of the cutouts in our custom lid. You could cut a piece of ~3mm thick plastic to this size and make the cut-outs, but it’s probably easier to just print this (it’s available as a PDF download from our website) and use it as a template on Australia’s electronics magazine (code 106) (code 274) (code 224) (code 563) (code 183) (code 153) (code 103) (code 472) (code 222) (code 561) (code 331) (code 181) (code 101) (code brown black brown gold) the existing Jiffy box lid. The laser cutter can’t make countersunk holes for the PCB mounting screws, so whether you’re using a premade lid or cutting your own, you will need to use a countersinking tool to profile those four holes on the outside face of the panel. It’s also a good idea to attach a panel label. The artwork we’ve prepared January 2021  29 The see-through case shows how the electronics mounts to the lid/front panel – and because you can see the “works”, also adds to the intrigue of this radio! is available as a PDF download from siliconchip.com.au Print it onto adhesive paper (see siliconchip.com.au/Help/FrontPanels for details) or print it onto regular paper and laminate it. You can then cut the panel to size and cut out the holes with a sharp hobby knife. But before you glue it to the lid, attach the PCB to the rear so that you can hide the mounting screws. The radio board attaches to the back of the lid using the 15mm spacers, with countersunk screws through the lid and regular machine screws holding the PCB to the spacers. Once the panel has been glued in place, you can attach the nuts to hold the potentiometer(s), rotary encoder and rotary switch to the panel, then attach the knobs (after cutting down any shafts which are too long). The power on/off switch (S1) and headphone socket (CON8) mount in the hole provided on the front panel. You will also need to drill a hole somewhere in the side of the box for the barrel power socket. While you’re at it, decide where in the case you are going to mount the ferrite rod, and if fitting an internal speaker, that too (you will need to drill sound and mounting holes). Once you drop the lid into the box, the FM and SW sockets will be accessible via holes in the left-hand side. Alternative, smaller . . . and slightly cheaper . . . version As mentioned earlier in the text and shown in the parts list, we have made a second version of the AM/FM/SW receiver which is not only more compact, it is also a little cheaper to build. It uses the same BK1198 receiver module; in fact, the electron­ ics is virtually identical. The main difference is that it doesn’t have an internal speaker, relying instead on headphones or earpieces. (The photo above shows a 3.5mm adapator plugged into a standard 6.35mm socket, so it will take the vast majority of headphone types.) The other difference is that it uses a standard UB2 jiffy box instead of the more expensive (and larger) ABS case. The photos show how the assembled BK1198 receiver board is an easy fit in the smaller case. Construction is basically the same as the larger version. Like the 30 Silicon Chip Australia’s electronics magazine siliconchip.com.au Temporarily insert the lid into the box and mark out the locations, then drill these holes large enough to get cables onto those connectors. One of the last steps is to make up the wires and plugs for the ferrite rod, power supply and switch and speaker/ headphone socket. For the ferrite rod, this is simple; you just need to attach a two-way plug to the end of a short piece of shielded cable or twin-lead. The polarity doesn’t matter, but it must be long enough to reach CON2 before the lid is attached to the case. Solder this to the primary winding on the ferrite rod. If you’re using a pre-made coil, it might have two pairs of wires, so use the pair with the highest (but noninfinite) resistance reading between them. The power wiring is slightly more complicated (see Fig.3); one pin of CON1 (it doesn’t matter which) goes straight to the outer barrel contact of the socket, while the other pin goes to the central pin contact via switch S1. If your switch has more than two contacts, pick two which are connected when the switch toggle is down but open when up. One possible pitfall is that barrel sockets often have three solder tabs, one of which is disconnected when a plug is inserted. So make sure the outer barrel contact you solder to is not that one. It’s easiest to check by inserting a plug, then soldering to the tab which has continuity to the outer barrel. Finally, wire up the headphone socket and speaker as per Figs. 1 &3. Start by identifying the switched and unswitched tip and ring contacts on the socket and joining them together, turning it into a mono socket. Connect the sleeve tab back to the middle pin of the plug for CON7. The contacts which connect to the ring and sleeve when a plug is inserted then go to pin 1 of CON7. Then wire the unused pair of head- larger version, the PCB assembly “hangs” from the case lid, with suitable cutouts for the display, controls and ’phones socket. phone socket contacts to one end of the speaker, and the other end of the speaker back to pin 3 of CON7. Note that if you’re building it into the UB2 Jiffy box and using an external speaker, you will have to run a pair of wires out of an extra hole in the case to your external speaker. Alternatively, fit a two pin (or more) connector somewhere on the box, with a matching plug for the external speaker. One good option for this external speaker is to use an unpowered computer speaker, which usually has a 3.5mm jack plug fitted, then use a 3.5mm jack socket to connect it back to the radio board. Once all this wiring is complete, you can plug all the wires into the appropriate headers on the board, then give it all a final test before buttoning it up (ie, attaching the lid to the box). You should be able to do this using the selftapping screws supplied with the box. You can now enjoy listening to your radio! Front panel artwork, as shown in the photo opposite, can also be downloaded from siliconchip.com.au – this can also SC be used as a drilling template. Lid drilling detail for the Jiffy Box version. This, along with front panel artwork to suit is available from siliconchip.com.au siliconchip.com.au Australia’s electronics magazine January 2021  31 “Hands On” Review by Tim Blythman and Altium Designer, which we use to design PCBs and draft circuits, can trace its history back over 30 years to the Australian-designed Protel PCB software. With design complexity increasing, collaboration is becoming even more critical, and this is what Altium 365 aims to achieve. We also have a brief overview of some new features in AD21. A s part of our review of Altium Designer 20 in December 2019 (siliconchip.com.au/Article/12176), we attended the “Altium Roadshow”, which is only one of many events held for Altium subscribers. They also regularly hold ‘webinars’ and other online information and education sessions. As we noted in that review, many people are still using versions of Altium Designer as old as version 14. But us- ers who want to make full use of Altium 365 will need to run Altium Designer 20 or later. Altium 365 You might have seen a glimpse of Altium 365 in our April 2020 Product Showcase (siliconchip.com.au/ Article/13816). That short piece hinted that Altium 365 is pitched at those Where it all began: hands up if you remember the now-30-year-old Autotrax (and its companion Traxedit), seen here running on the first personal computer that SILICON CHIP owned – a 128kb, twin floppy IBM PC! 32 Silicon Chip Australia’s electronics magazine siliconchip.com.au with no CAD tools or experience, but this is far from the full story. Altium 365 (of which Altium 365 Viewer is only a small part) is a cloud-based companion to Altium Designer and provides tools and features which, we think, will be useful to many people. In our review of Altium Designer 20, we noted that being such a small team, we are not sure how we would make use of the cloud features of Altium 365. Most of our PCBs are planned, designed, built and tested by one or two people. With working from home now more common, we decided to look more closely at Altium 365’s features for those occasions when feedback or collaboration are needed. It turns out that it has other features that are very useful to us too. In fact, many people who have never used Altium Designer could make good use of Altium 365. There are four different ways of working with Altium 365. The Viewer is similar to the one built into Altium Designer. You can click on items to see properties and even render and navigate a 3D view of the PCB or assembly. The Viewer can be embedded in an external webpage (for example, on your own website), with configurable features such as a variety of export formats. Naturally, you can’t edit files using the Viewer. The Viewer also lacks the collaborative features of Altium 365. Altium 365 Basic At its simplest level, Altium Viewer allows designs (circuits, PCB etc) to be viewed in a web browser by anyone – see Screen1. You don’t need an Altium subscription or even an Altium Live registration. The Viewer is found at www.altium.com/viewer/ You can go there right now, click on “View Example Project” and get a pretty good idea of what it can do. Altium Viewer allows several CAD and CAM formats to be uploaded and viewed; not just Altium Designer files. For example, Altium Viewer supports loading and viewing EAGLE designs, and support for KiCad files is planned. To use Altium 365 Basic, you need to register on the Altium Live website. The process here is similar to most online services; your account is linked to an email address. If you are currently using Altium Designer, then you most likely have an Altium Live registration already and use it for your Altium license. If you have an Altium subscription, then you can also make use of the Standard version of Altium 365, which includes integration with Altium Designer. To access these services, you need to go to http://365. altium.com/ and log in to your Altium Live account. Apart from the Viewer, Altium 365 is based around the concept of “Workspaces”, which are typically tied to an Altium Licence and thus a specific organisation. The easiest way of getting access to a particular Workspace (and also easily set up an Altium Live login) is to be invited by someone who has access to that Workspace. An invitation sends an email which will also prompt for information to complete the registration process, if that has not already happened. After that, you’ll be taken to the Workspace. Altium 365 Basic is intended for those users who don’t Screen1: even if you don’t have an Altium Live account, you can use Altium 365’s Viewer. It can handle several CAD formats and provides a similar view and interface to Altium Designer. Screen2: the Projects view in the web portal shows a preview of each project and a brief summary, including information about recent changes. Clicking on any project allows it to be viewed, with a similar interface to Altium Designer. Altium 365 Viewer siliconchip.com.au Australia’s electronics magazine January 2021  33 With external parties, it is often desirable to carefully control the way that designs are shared, especially in fields where ‘intellectual property’ is tightly guarded. Rather than having to import a file, the cloud nature of Altium 365 allows projects to be stored and managed online (see Screen2). Typically, a project will be uploaded by someone using Altium Designer. Once a project is opened, the window appears very similar to the Viewer, but with more options, including a function to open it in Altium Designer. Many different views are available in Altium 365 Basic, besides those which are available in Altium Designer. For example, Project History provides a graphical, chronological view of changes that have occurred in a project (as shown in Screen3). Altium 365 Standard have an Altium subscription and don’t use Altium Designer, but work closely with those who do. For example, inside our small organisation, the staff members who lay out our articles do not need to use Altium Designer, but could benefit from being able to view and comment on designs, or even render specific views of a PCB for publication. One of the apparent benefits is being able to share information with those outside your organisation, such as PCB manufacturers and assemblers. Effectively, Altium 365 Standard is available for all Altium Designer 20 users who have a current subscription. It is well integrated into AD20. Apart from logging in to use your license, you just need to activate the Workspace within Altium Designer. Indeed, this is probably the best way to make use of it. To start using Altium 365, click on the cloud icon at upper right and click on the Workspace, which will connect Altium Designer to the Workspace (Screen4). While Altium 365 Basic allows Altium Designer files to be viewed online, Altium 365 Standard also provides the option to make files available online. Unlike other cloud solutions where the files are simply stored elsewhere, a formal version control system (based on the widely used open-source VCS Git) keeps synchronised copies (and backups) both locally and remotely. This means that, for example, others who have access to your Workspace can not only see the current version of the design but can also go back and look at how it evolved, who made what changes, and even ‘undo’ mistaken edits. To use these features, from the Projects Panel, right-click the project name and click the “Make Project Available Online…” option. A dialog box appears, allowing some properties to be set (Screen5). Set the option to Enable Formal Version Control unless you have your own version control system in place. After this, the project moves to the Altium 365 workspace. Some extra status icons appear in the Projects Panel relating to the version control. Some more menu options Screen3: the History feature in the web portal shows a summary of changes to a project, and is a visual guide to the version control, such as edits and releases and who made them. The three-dot buttons in the corner of each panel allow a snapshot to be downloaded or cloned. Screen4: the small cloud icon in the top right corner of Altium Designer can be used to connect to your company’s Workspace and thus Altium 365. Our Workspace is named Concord Pro, reflecting that Altium 365 is a progression of the older Concord platform. The Basic version of Altium 365 provides these menu options for managing your workspace. It’s all very intuitive to navigate and work with. 34 Silicon Chip Australia’s electronics magazine siliconchip.com.au Screen5: connecting Altium Designer to Workspace on Altium 365 adds the option of making projects available online and can provide version control, which is recommended unless you use your own internal version control. relating to version control appear too (see Screen6). Updating the ‘cloud’ version of your project is as simple as saving it, then using the Version Control menu to commit the file or project. If you don’t save, you are prompted to do so, ensuring this happens when needed. At this stage, the files are available in the cloud, but are not necessarily visible to other users in the Workspace. By default, they are not visible to anyone except administrators and the person who uploaded them. This aspect is carefully controlled so that you can limit who can view and edit your files. These features are even handy for people working solo, as they now have access to cloud-backed versions of their designs. It’s useful as a backup if nothing else. Sharing projects with other people can be done with varying degrees of granularity. There are options to provide view-only or full (edit) access, as well as being able to set up groups of people to streamline this process (see Screen7). Once designs have been shared like this, users with Basic access can view the designs. One useful collaborative feature is the ability to place comments on the designs. Comments can be applied to schematics (circuit diagrams) or PCB files, and can be viewed and edited through both Altium Designer and the Altium 365 Basic portal. This streamlines communication between those who have access to Altium Designer and those who do not. Once the issue has been resolved, the comment can be marked as such and it disappears, so as not to clutter the display. Once a PCB design is complete, the design goes through a ‘release’ process, which produces an output job (for example, creating Gerber files). After this, the Manufacture section is populated with the output files, which can also be viewed through the web portal. Sharing As well as integrating with those people who are working siliconchip.com.au Screen6: joining a workspace and enabling version control adds numerous options to the Projects panel. Simply committing the project will prompt for any other actions that need to be done before the project is synchronised and up to date. Screen7: when connected to a workspace, new icons appear that reflect the state of the project, including whether it is correctly synchronised with the online version control. Pushing changes into shared projects is as simple as rightclicking and choosing the correct option; you will be prompted to save if necessary. Australia’s electronics magazine January 2021  35 Screen8: the component search window provides many fields, including some optimised for specific component types. Parts can be compared, including live information like supplier stock levels and prices. on files using Altium 365 Basic, it’s also possible to share designs with people who don’t. In this case, the recipient is sent a link, and the file is made available through the Altium 365 Viewer interface. Either a generic link can be generated (making the file available to anyone who has the link), or the link can be sent directly to a specific person, which also makes it possible for that person to comment. The links expire after 48 hours. Components Managing component and part libraries is also integrated into Altium 365. This makes it easy to monitor component designs, check that they are consistent and current, and manage their life cycle. Once logged in to the Altium 365 workspace in Altium Designer, you have access to the Workspace’s shared component library (see Screen8). This is accessible through the web portal (Altium 365 Basic) too. The Library Migrator menu item under File menu can be used to import a local library into Altium 365. This shared component library is one of the most useful features for us, so once one member of the team has created a component symbol and footprint, anyone can use it from then on. Mechanical integration Altium 365 Standard also offers tools relating to managing workflows. The MCAD Plugins option offers interfaces to Solidworks, Autodesk Inventor and PTC Creo. More similar options might become available in the future. This allows people working on aspects of the mechanical design or even marketing to be involved without requiring a full Altium license. 36 Silicon Chip Our review of Altium Designer 20 covered some of the handy mechanical design features that are now available. Beyond being able to view and import mechanical designs in, say, Solidworks, it’s possible to make edits to the mechanical design and push those changes back to Altium Designer. Changes need to be effected within Altium Designer and saved back into the cloud; these changes can then be checked from within Solidworks. Unfortunately, we don’t use any of these tools, so we weren’t able to test these features out. Altium 365 Pro The kind folks at Altium also allowed us to try an evaluation version of Altium 365 Pro. This works similarly to Altium 365 Standard, integrating Altium Designer 20 with the cloud portal, but offers more features. If you have used Altium Concord Pro or Vault, then you might be familiar with some of the features of Altium 365 Pro. Component management A significant feature of Altium 365 Pro is component management, which goes beyond what is available in the Standard version. These features are available through the Properties panel and the Components panel. Much of what Altium 365 can do with components is drawn from the Octopart database (https://octopart.com/) which is operated by Altium. Octopart aggregates supplier and manufacturer data, which is accessed seamlessly through Altium 365. Altium 365 Pro can also draw on other supply chain information Australia’s electronics magazine siliconchip.com.au Screen9: the Components panel now shows (at the bottom) information about which projects appears (Where Used). This can help streamline component changes and replacements by flagging which projects might need to be changed as a consequence of a component change. Screen10: Altium 365’s component management makes it easier to deal with obsolete parts by flagging the component state and allowing parts to be updated as needed. providers, such as IHS Markit. There’s even the option of customising the progression of the component lifecycle through its various transitions. This can be viewed through the web portal, but can only be set through Altium Designer 20, once it has connected with an Altium 365 Pro workspace. With all libraries and projects connected through the cloud platform, other features become possible. For example, the Component Panel now features a “Where Used” section (Screen9). When a part is selected, this section displays the projects which use a given component. This provides an easy way to deal with part obsolescence or manufacturing problems with a particular component. When a part needs to be replaced or altered, Where Used can quickly identify the affected projects and allow them to be adjusted as necessary (Screen10). This might involve creating a new version of the part, perhaps with a different footprint to correct a manufacturing issue. Or a new part can be substituted once an old part is unavailable. Changes to projects can be tagged with the reason for the change under version control, providing traceability. Component templates Another feature that Altium 365 Pro includes is Component Templates, which are templates for common components such as resistors. The principle is that a circuit can be laid out using template components, which have only the minimum necessary information attached (for example, resistance). This prevents the schematic design from being bogged down with needing information that is not necessary at that stage. The other parameters can be configured later. siliconchip.com.au For example, a resistor can be set to require composition, current rating, diameter or lead pitch (amongst others) or none of these at all. Default values can be set too. Templates are set up with sample data in the Altium 365 Pro workspace, so these can be used immediately. Like some of the other Pro features, this appears to be aimed at larger teams, where one team member might be responsible for drawing the circuit, and another can work independently on choosing the correct parts to use. Parts Requests Another feature which is handy for larger teams, especially those that may have dedicated staff for maintaining component libraries, is Parts Request. As the name suggests, a user can request a part to be created and added to the Library. There are fields for manufacturer part number, request state, component type, date required and room to add attachments (for example, data sheets) and notes. The act of assigning the task triggers an email to the necessary person to initiate the process. This is done through the web portal, so can be initiated by anyone with an Altium Live login. Teams Altium 365 Pro also offers the option to customise and tailor people’s roles (and their capabilities) via team management. Larger organisations might need to create finegrained permissions, especially if there are similar roles within different projects, requiring differing policies. A simplified version of the Teams option exists within the Standard version of Altium 365 Standard, with a limited number of roles available. Australia’s electronics magazine January 2021  37 Screen11: this feature was already available in Altium Designer 20, but we only just found out about it! A keypress (CTRL-W) will show you clearance outlines during interactive routing. Note how the gaps between the pins at lower-right are completely pinched off (but might open up if a narrower track is chosen). No more guessing whether or not a track will fit! Screen12: another new feature of Altium Designer 21 is single sign-on (SSO) support to streamline users logging in. This allows people to use their usual company credentials to log in to an existing Altium Live account (giving access to the company license to use the software) Cost Altium has a simple price model for Altium 365 Pro. It is $500 per year for each ‘seat’ that you have for Altium Designer. It can only be applied to all seats within a given license. Note that you could have more people than seats; the seat number sets the maximum number of people that can use the software simultaneously. There are servers located around the globe. Currently, Australian clients connect to a server in Singapore, although that might change in the future. We think that most Altium users could benefit from using Altium 365 Pro, but those who will get the most out of it will be larger organisations, who have the most to gain from the Pro features. Working from home Now with many people working from home (indeed, I’m writing this at home), a state of affairs that could continue for a while (or perhaps indefinitely), using tools like Altium 365 to keep teams working smoothly together makes a lot of sense. Even in our small team, we found that using Altium 365 was quicker and easier than trying to package and email projects or use a shared drive; the web interface works as intuitively as Altium Designer and the integration between the two is excellent. We are in the process of moving our library into the shared library in our Altium 365 workspace. That will allow us to synchronise added parts more smoothly than when we were working in the same office! Altium Designer 21 Many of the changes in Altium Designer 20 were intended to smooth the way for new features to appear in future releases. Some of these new features make an appearance in Altium Designer 21. One such feature is dynamic polygons. Instead of having to repour polygons (large copper areas) manually, the PCB editor will do it as needed. 38 Silicon Chip This might sound like a minor feature, but it will certainly make working on large PCBs with ground and power planes less of a hassle. Interactive routing will also check for signal integrity whilst routing is occurring. This is handy for those working with differential pairs and other high-speed designs. Around 50% of Altium users work on designs operating at or above 1GHz, and they stand to benefit the most from this feature. Also, length tuning options now include trombone and sawtooth patterns. Altium Designer 20 introduced an improved simulation engine, and AD21 makes better use of it. There is now a Simulation Dashboard which operates somewhat like a software wizard, stepping through the stages needed to set up and run simulations. AD21 also has a generic simulator library for many standard component types. Design Rules AD21 can define design rules on a per-object basis, and objects have rules as characteristics. This is in addition to the existing Design Rules window and can be found by switching to Document view or by adding a Design Rule to a selected object. Flex PCBs Support for flexible (and mixed rigid/flex) PCBs continues to improve. It’s still a bit more expensive to get these made than standard, rigid fibreglass PCBs, but Altium and many manufacturers are embracing the possibilities. With AD21, it is possible to add more complex bends to flexible PCB designs and then animate these in the 3D view (using the ‘5’ key shortcut). This is a great aid to visualising that flexible designs are correct. These different views can be captured and used in the Draftsman drawing creator to help others to understand the intended product. As we’ve heard Altium say before, this continuous improvement is necessary for them to stay competitive. We Australia’s electronics magazine siliconchip.com.au Helping to put you in Control RG-9 Optical Rain Sensor Hydreon RG-9 Solid State Rain Sensor is a rainfall sensing device intended to detect and communicate when a pre-selected rain intensity has been reached. SKU: HYS-005 Altium 365 currently integrates with three different mechanical CAD platforms. Changes can be made in MCAD and pushed back to Altium, for example if the mechanical team need to make changes to the board shape or mounting holes. Price: $99.00 ea + GST Solar Temperature Controller Designed for solar water heating applications. Two NTC-type temperature sensor inputs and two control output. 12 to 30 VDC Powered. SKU: CET-036 Price: $122.80 ea + GST look forward to using these new features. Large Temperature Display Another useful feature While investigating AD21, we also discovered some useful features introduced in AD20 that we didn’t know about. During interactive routing, it is possible to display clearance boundaries (CTRL-W key shortcut or as an option while routing is paused with TAB) – see Screen11. Large Temperature Indicator with range -19.9 to 99.0 °C. SKU: HNI-080 Price: $315.00 ea + GST Summary Altium 365 strikes a good balance for a cloud platform. The usual criticism is of losing control of one’s files, but Altium’s version control ensures that both local and cloud copies are synchronised and backed up. Indeed, simply having an automatic online backup of your local files is a handy feature. Many of the useful cloud features are available for free with the Viewer and Basic platforms, or at no extra cost (beyond licensing Altium Designer) for the Standard platform. For securely sharing (and keeping copies) of files and projects, the experience is quite seamless. We’ll definitely make good use of the shared component library, as this is one aspect of PCB design that can quickly become fragmented even within a small team. A single, shared library will be much easier to maintain, and will ensure that a consistent style is maintained between our designs. It will also mean that if one of us discovers an error and fixes it, it will be fixed for us all. With it becoming easier to import components from online sources, we expect to spend less time creating and managing components in the future. For those who don’t have an Altium licence, it’s now possible to try out many of its features at no cost with Altium 365 Viewer. We definitely recommend that anyone that uses Altium Designer have a look at Altium 365, given that they can take advantage of the features of the Standard version at no additional cost. A good way to start is to join one of the frequent webinars that are available to Altium license holders. For more information, visit http://365.altium.com/ Thanks to Altium for providing us with a trial of Altium SC 365 Pro for our review. siliconchip.com.au NEMA 42 Open-Loop Stepper Motor Large 20NM single shaft NEMA 42, 2 phase bipolar stepper motor with 20.0 N.m of holding torque. Rated at 6 A phase current, weighing 8.4 kg with 150 mm body length and 21.55 mm shaft diameter. SKU: MOT-176 Price: $307.30 ea + GST 1-Wire Digital Temperature Sensor DS18B20 Temperature Sensor with copper screw clip probe and a 3 metre cable. Connector is an option. SKU: GJS-006 Price: $23.95 ea + GST Wind Speed Sensor 0-10VDC Output Easy to use wind speed sensor up 60m/sec with 0 to 10VDC signal output and 1.5 meter cable. SKU: RKS-002 Price: $169.95 ea + GST Raw & Waste Water Level Sensor 0-10m with 20m Cable 2 wire 4 to 20 mA liquid level sensor 0-10m. Suitable for raw and waste water. Supplied with 20m cable. SKU: IBP-110 Price: $429.00 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine January 2021  39 THE MiniHEART: A Miniature Heartbeat Simulator Give a favourite soft toy a beating heart! With both soft sound and a real beat, it could relax a baby, puppy or kitten for sleeping, or even help you sleep better yourself. All are possible with the SILICON CHIP MiniHEART! M any newborns – human babies as well as pets – are unsettled when left alone to sleep. They miss their mum, and it’s lonely and frightening for them. Just being able to cuddle up to the sound of a heartbeat can help with their anxiety. The MiniHeart is a small gizmo that produces a low-level soothing heartbeat sound, mimicking that of a real heart. The beat rate can be adjusted so that it more accurately matches the rate of the heart it is to emulate, while a timer will shut off the heartbeat after a set time. The unit is switched on and off with a toggle switch with the actuating lever only protruding slightly outside the box. This is to prevent any injury to a baby. It is fully enclosed into a plastic case that clips together, and we have added extra screw supports to make sure it stays shut. That way, the two internal AAA cells will not be easily accessed to cause a choking hazard. We recommend enclosing the device into a cloth bag that is sewn or zippered shut. That provides an extra margin of choke hazard safety which is necessary when used with a baby. We should point out that the simulated heartbeat is not a loud sound – it is not meant to be. It is more like the subtle sound of a real beating heart; it needs to be placed close to the ear, and is felt more than heard. Think of it as a tiny heart, but in a rounded rectangular prism shape. A loud heartbeat sound would require a large loudspeaker properly baffled to produce bass along with an amplifier with a reasonable amount of power. Neither of these are a feature of the MiniHeart (but could be added externally). Heart sounds By John Clarke 40 Silicon Chip When listening to a heartbeat, you will hear two distinct, separate sounds, often called a “lub” and a “dub”. These two sounds are produced by the closing of heart valves required to pump blood efficiently. You’ve almost certainly seen the classic heartbeat waveform as shown on an electrocardiogram (ECG). These are the electrical signals sent to the heart muscles, and when monitored with electrodes on the skin, are useful for diagnosing heart problems. Electrode readings do not represent the sounds and vibrations made by the heart; heartbeat sounds are heard using a stethoscope. Australia’s electronics magazine siliconchip.com.au FEATURES AND SPECIFICATIONS • • • • • • • Fig.1: this block diagram shows that the MiniHeart is quite simple, using just a microcontroller and a Class-D amplifier chip to produce the sound. A basic RC low-pass filter turns the PWM output of the micro into an analog signal for the amp, while ferrite beads and capacitors reduce EMI from the Class-D drive to the speaker The MiniHeart block diagram is shown in Fig.1. Microcontroller IC1 produces a heartbeat waveform in the form of a pulse-width modulated (PWM) signal. The pulse rate is 31.25kHz, and the pulse width is varied to produce a smoothed lower-frequency waveform after passing through a low-pass filter. This removes the high-frequency signals so that only the heartbeat waveform remains. Fig.2 shows how a PWM signal is used to produce a lower-frequency, smooth waveform. The red waveform is the PWM output from the microcontroller, IC1, while the green waveform is its average value after filtering out the PWM pulse frequency. For convenience, we show a sinewave, although any wave shape could be generated. If the PWM signal has a 50% duty cycle, ie, an equal period of being high and low, then the filtered voltage will sit mid-way between the high and low voltage levels. To produce a higher voltage, the PWM signal duty cycle is altered so that the period while high is longer than the period when low (ie, duty cycle > 50%). Conversely, for a lower voltage, the PWM period is kept low for longer than it is high (duty cycle <50%). The green wave shows the signal that appears after the low-pass filter has removed all of the higher frequencies. Note that this PWM signal is a representation only – in reality, the frequency of the PWM signal is very much higher (around 700 times higher!) than the sine wave shown and cannot be reproduced to scale on the diagram. Overleaf, we show the various scope waveforms for the MiniHeart. Scope1-Scope3 show the general operation. Scope1 shows a few periods of the PWM signal at around 31kHz (25µs timebase). Scope2 and Scope3 (10ms timebase) are the ‘lub’ and ‘dub’ signals produced after filtering the PWM signal. Scope4 shows a single heartbeat with both the ‘lub’ and ‘dub’ waveforms, while Scope5 shows two heartbeats, with the pause between each heartbeat visible. The period between each heartbeat, the frequency of the ‘lub’ and ‘dub’ waveforms and the period between the ‘lub’ and ‘dub’ waveforms have a small amount of randomness added. This is to prevent the heartbeat from sounding too artificial. It simulates the variation in heartbeat rate and timing of a real heart. These waveforms are fed to a tiny Class-D (ie, switching) amplifier that’s usually used in mobile phones and it siliconchip.com.au • • • • • • Compact size Adjustable volume Adjustable timeout and heart rate Flashing LED synchronised with the heartbeat On/off power switch Power: two AAA cells (nominally 3V), operating down to below 2.5V Current draw: 10mA average during operation, 500nA standby (typical) Timeout: adjustable from two minutes to four hours Heartbeat rate: 42 to 114bpm Rate randomness: about 15% variation Sound frequency: 45Hz-51Hz (with a 2Hz randomness) Waveform generation method: PWM <at> 31.25kHz Waveform sampling rate: approximately 1kHz is designed to be highly efficient. It drives the small loudspeaker in bridge mode, to maximise the power output from the limited 3V DC supply. The loudspeaker is weighted, ie, the speaker cone has a weight attached to it. This is so that low-frequency vibrations will be heard and felt. Circuit details The full circuit is shown in Fig.3. At its heart (!) is a PIC12F617 microcontroller, IC1. Its master clear (MCLR) input, pin 4, is tied to the 3V supply rail via a 10kΩ resistor to provide a power-up reset function. IC1 applies 3V across adjustment trimpot VR1 via its GP5 digital output; this is only brought high when the trimpot position is monitored via IC1’s AN3 analog input (pin 3). After the GP5 output is brought high, to 3V, the voltage at AN3 is converted to a digital value via IC1’s internal analogto-digital converter (ADC). Once the value is read, the GP5 output goes low again (0V) to conserve power. Jumper link JP1 can be placed in one of two positions; position 1 where GP1 is pulled to 0V, or position 2 where GP1 is pulled to the 3V supply. When in position 1, trimpot VR1 adjusts the heartbeat rate. When in position 2, VR1 adjusts the timeout period. The heartbeat rate can be set from 42 to 114 beats per minute (BPM). The timeout can be set between two minutes and four hours. The heartbeat rate can be adjusted while the heartbeat is RED WAVEFORM = PWM (PULSE WIDTH MODULATION) SIGNAL GREEN WAVEFORM = SYNTHESISED SINEWAVE (AFTER LOW-PASS FILTERING) Fig.2: this shows how a high-frequency pulse-widthmodulated ‘square wave’ can be fed through a low-pass filter to produce a smoothly varying, lower-frequency arbitrary waveform (shown in green). The instantaneous voltage of the green waveform equals the average voltage of the red waveform. In reality, the pulse frequency would be much higher in comparison to the reconstructed waveform. Australia’s electronics magazine January 2021  41               SC  MINIHEART HEARTBEAT SIMULATOR  Fig.3: the full MiniHeart Simulator circuit is not much more complicated than the block diagram. Here you can see the detail of the second-order low-pass filter, the AC-coupling capacitors to the inputs of IC2 and the series resistors which set its gain. LED1 responds to the average voltage delivered to the speaker, so it starts to light once sound is being produced. being generated, but the timeout is only checked at powerup. So after charging timeout value via VR1, power must be switched off and on again for the new timeout to take effect. The heartbeat generation switches off after the set timeout period. This conserves power in case it is left switched on. If JP1 is removed then the pin 6 GP1 input is not held high or low. The voltage can float at a voltage anywhere between 0V and 3V. This can lead to high current consumption in IC1, reducing cell life, as digital inputs are supposed to be in one state or the other. So IC1 checks for this condition by changing GP1 to an output and setting it to a high level for 1ms. The 1kΩ resistor charges the 100nF capacitor to 3V. Then GP1 is changed to an input, and the level is checked. If the input voltage remains high, then there is either a jumper in position 2 pulling the input high, or there is no jumper, and the input IC1 uses its internal 8MHz oscillator to generate the 31.25kHz PWM signal at output pin 5. This is fed to a twostage RC low-pass filter. The first stage comprises a 10kΩ resistor and 100nF capacitor to give a -3dB roll-off at 159Hz. The second stage has the same roll-off frequency but uses a 100kΩ resistor with a 10nF capacitor. These components give an impedance which is 10 times that of the first stage filter, minimising the loading on the first stage due to the second stage. The filtered signal is fed to volume control Scope1: this shows just over seven periods of the ~32kHz PWM signal that is produced at pin 5 of IC1. The signal swing is 3V peak-to-peak, and the timebase is 25µs. Scope2: this ‘lub’ signal reproduces a a real heartbeat sound, produced by filtering the PWM waveform, measured at the wiper of VR2. Note the longer timebase used here (10ms/div). 42 Silicon Chip is held high via the charged 100nF capacitor. This test is repeated with a low output. If the level changed, then JP1 is inserted. To prevent the floating input condition, GP1 is changed to a low (0V) output and left like that, minimising power consumption. Heartbeat generation Australia’s electronics magazine siliconchip.com.au trimpot VR2 and then to the non-inverting input, pin 3, of amplifier IC2 via a VDD TO 1µF capacitor and 27kΩ resistor. INTERNAL BATTERY OSCILLATOR IC2 is a TPA2005D1 Class-D (ie, switching) amplifier in a tiny SMD package, measuring only 3 x 5mm. It is specifiIN – + cally designed for use in mobile phones VO+ where its high efficiency is crucial. The – block diagram of the TPA2005D1 is DIFFERENTIAL H-BRIDGE PWM INPUT shown in Fig.4. VO– + It has differential inputs to an internal IN + – amplifier that drives the PWM section at a switching frequency of 250kHz, set by the internal oscillator. The PWM section GND then feeds an H-bridge circuit for drivSHUTDOWN BIAS CIRCUITRY ing an external loudspeaker. The data sheet for the TPA2005 highTPA2005D1 lights two interesting points. The first is its high CMRR (common-mode rejection Fig.4: the internal block diagram of the TPA2005 Class-D audio amplifier chip. ratio) which supposedly eliminates the Its differential inputs go to a balanced analog amplifier and then onto a PWM need for input coupling capacitors. But modulator which drives a Mosfet H-bridge, and that in turn drives the speaker. this high CMRR only applies if the amThis provides high efficiency and plenty of power from a low supply voltage. plifier is used in balanced mode, with As shown, the chip can drive a speaker in Class-D mode without a filter. both inputs at the same DC level. In our circuit, we are using it in unbalanced mode, with ceramic capacitor close to IC2’s supply rails, and a 100nF the inverting input grounded (via the 1µF capacitor), so capacitor at IC1’s supply rails. we need to use two input capacitors. The 27kΩ resistor Diode D1 is included to protect against component damfor the non-inverting input, in conjunction with the inter- age if the cells are inserted with reversed polarity. In that nal 150kΩ feedback resistor, sets amplifier gain at about case, the diode will conduct and limit the negative voltage 5.5 times. Since the amplifier is a bridge type, the overall to the circuit. The disadvantage is that this will quickly gain is double that, ie, 11 times. drain the cells, but presumably, you would notice that the The second interesting point is that the TPA2005 can run device is not working and fix it straight away. without an output filter that would usually be required to The alternative protection method, with a diode in series remove the 250kHz switching signal. That is, provided the with the supply, drops too much voltage for this application. output leads are kept short. Even so, we use ferrite beads Even a Schottky type, with its lower forward voltage, would (FB1 and FB2) plus 1nF shunting capacitors to reduce elec- not be suitable and we can’t justify the cost of a Mosfet in tromagnetic interference (EMI). this role (which would have a lower voltage drop again). Power supply Indication Power is from two series AAA cells to provide a nominal 3V supply, switched on or off by power switch S1. A 100µF capacitor bypasses the switched supply with a 1µF LED1 lights simultaneously with the lub/dub sounds and is driven via the VO- output of IC2. With no signal, this output sits at an average of 1.5V. This is derived by an Scope3: this is the ‘dub’ signal measured identically to the ‘lub’ signal shown in Scope2. Again, it is a reproduction of a real heartbeat sound. Scope4: a single heartbeat sound with both the ‘lub’ and ‘dub’ waveform. You can see their slightly different shapes and amplitudes, and the delay between them. siliconchip.com.au Australia’s electronics magazine January 2021  43 Also, after the timeout period expires, microcontroller IC1 is placed in sleep mode and only draws about 150nA. Amplifier IC2 is also switched off by IC1 taking the GP0 output low, which connects to its SDWN (shutdown) input. IC2 then draws around 500nA. We measured a 500nA current for the whole heartbeat circuit when in shutdown on our prototype (half a microamp!). The cells should last for their shelf life with such a small current drain. Construction Scope5: two heartbeats as shown in Scope4. With this slower timebase, you can also see the delay between beats. RC low-pass filter (2.2kΩ/100nF) from the 250kHz square wave signal at pin 8 of IC2. It swings between 0V and 3V with a 50% duty cycle when idle. The LED lights when this voltage rises above the usual LED forward voltage of around 1.8V, and that happens when the duty cycle of the pin 8 output increases above 60%. Saving power Since the device is powered from AAA cells, we need to minimise power usage to conserve cell life. Typically, the circuit draws an average of 10mA when producing the heartbeat. However, once the timeout period has ended, the current needs to drop to a very low level until the unit is switched off. This is achieved in several ways. Firstly, as already mentioned, there is no voltage across VR1 most of the time. The MiniHeart Simulator is built on a double-sided, plated-through PCB coded 01109201 which measures 70 x 73mm. It is housed in an 80 x 80 x 20mm vented plastic enclosure. Fig.5 shows the PCB component overlays. Begin by fitting the SMD Class-D amplifier chip, IC2. It requires a very fine soldering iron tip and, ideally, a lit gooseneck or desktop magnifier (a good LED headband magnifier also works well). Identify its pin 1 dot under magnification, then orientate it as shown in Fig.5, with pin 1 towards the speaker hole. Add some flux paste to the middle of the central pad (or liquid flux, if you don’t have paste), position IC2 carefully over its pads, then tack-solder pin 4 to its pad. Check that the IC is still aligned with the PCB pads on both sides; remelt the solder if required. If all is OK, solder the remaining corner pins and then pins 2, 3, 6 and 7. Use solder wick to remove any solder that bridges between the IC pins. IC2 also has a ground pad that needs to be soldered to the PCB. This can be done by feeding solder from the underside of the PCB, through the hole positioned under the IC. Use minimal solder to prevent the solder from spreading out and shorting to the IC leads. The flux you added earlier will help this solder flow onto the pad on the underside of the IC. Now install the resistors and surface mount capacitors. Parts List – MiniHeart Heartbeat Simulator 1 double-sided, plated-through PCB coded 01109201, 70 x 73mm 1 Hammond 1151V4 vented enclosure, 80 x 80 x 20mm [Jaycar HB6118] 2 AAA PCB-mount cell holders 2 AAA alkaline cells 1 40mm diameter Mylar cone loudspeaker [Jaycar AS3004] 1 PCB-mount SPDT toggle switch (S1) [Altronics S1421] 1 8-pin DIL IC socket 2 ferrite beads, 4mm diameter & 5mm long (FB1,FB2) [Altronics L5250A, Jaycar LF1250] 1 3-way header, 2.54mm pitch with jumper shunt (JP1) 2 9mm-long M3 tapped spacers 2 M3 x 6mm panhead machine screws 4 No.4 self-tapping screws 2 M3 x 6mm Nylon machine screws (countersunk head preferred) 1 M8 marine-grade 316 stainless non-magnetic steel nut (6.35mm tall) 1 40mm length of 0.7mm diameter tinned copper wire (for FB1 and FB2) 1 100mm length of light-gauge hookup wire (or 2-way ribbon cable or figure-8) 1 small tube of neutral-cure silicone sealant (eg, roof and gutter silicone) 44 Silicon Chip Semiconductors 1 PIC12F617-I/P microcontroller programmed with 0110920A.hex (IC1) 1 TPA2005D1DGNRQ1 1.4W mono filter-free Class-D amplifier (IC2) 1 1N5404 3A diode (D1) 1 3mm high-brightness red LED (LED1) Capacitors 1 100µF 16V PC electrolytic 3 1µF 6.3V SMD M3216/1206 X7R# ceramic 4 100nF 50V SMD M3216/1206 X7R ceramic   1 10nF 50V SMD M3216/1206 X7R ceramic 2 1nF 50V SMD M3216/1206 X7R ceramic   Resistors (all 1% SMD M3216/1206) 1 100kW (code 1003 or 104) 2 27kW (code 2702 or 273) 2 10kW (code 1002 or 103) 1 2.2kW (code 2201 or 222) 1 1kW (code 1001 or 102) 1 10kW mini horizontal trimpot (VR1) 1 100kW mini horizontal trimpot (VR2) # a Y5V type was found to work in our prototype but X5R or X7R is a better choice Australia’s electronics magazine siliconchip.com.au Fig.5: these (and the matching photos below), show where components are mounted on both sides of the PCB. It’s generally best to fit all the SMDs to the top side (and possibly also the bottom side) before moving on to the through-hole components due to their small size and low height. Note how the speaker is orientated so that its terminals fit through the provided board cut-out, and also how the cell holder wires are bent to fit the PCB pads, fed in through the underside and soldered on top. IC1 is a normal 8-pin DIP . . . but IC2 (a TPA2005D1DGNRQ1) is TINY (it’s shown below about life size). A word of warning: don’t sneeze or turn a fan on if you ever want to see it again! These components are located on both sides of the PCB. The capacitors are usually unmarked except on their packaging. The resistors will probably be marked with a small code, as shown in the parts list. The first few digits indicate the resistance value, followed by the number of extra zeroes in the last position. So for example, a 1kΩ resistor will have the code 102 or 1001. That is a 10 followed by two zeros, or 100 followed by one zero. For 10kΩ, the code will be 103 or 1002 etc. Next, fit diode D1, taking care to orientate it correctly. Then mount ferrite beads FB1 and FB2 by first feeding tinned copper wire through the centre hole, then inserting and soldering these to the PCB pads. Keep the wire taught when soldering to prevent the beads from being loose. We used a socket for IC1 in case we ever want to remove it for reprogramming. Take care to orientate the socket correctly (notch toward the PCB edge). Trimpots VR1 and VR2 can be mounted now. Take care to place the 10kΩ trimpot in the VR1 position and the 100kΩ trimpot in the VR2 position. Then fit three-way header JP1 with the shorter ends of the pins through the PCB holes. Power switch (S1) is installed in the position shown. The switch we used differs slightly from the one in the parts list siliconchip.com.au in that the actuator is longer on the recommended switch. The positioning of the switch has therefore been moved further from the edge of the PCB. That way, the switch actuator will protrude from the case by the same amount as shown on our prototype. LED1 mounts with the anode (longer lead) in the hole marked ‘A’. Solder it so that the top of the lens is 11mm above the top edge of the PCB For the AAA cell holders, bend the wire terminals so that they stick out the sides of the holder, then bend them up to feed the leads through the holes on the PCB from the underside, and solder them on the top. The cell holders need to be orientated correctly, as shown on the overlay diagram. The base of the cell holders should be positioned so that they sit on the enclosure base when the PCB is seated on the four mounting posts. That means that the bottom of the cell holders will be lower than the bottom edge of the PCB. Next, fit the 100µF capacitor. Insert its leads with the longer lead through the hole marked +, then lie it over, so the capacitor body is between the LED and AAA cell holder. It must be no higher than 11mm above the top edge of the PCB. That will allow the lid to fit. The two PC stakes for the loudspeaker connections can Australia’s electronics magazine January 2021  45 i The Min HEART   SILICON CHIP Fig.6: this drilling diagram shows the locations of the 3mm LED hole, two 3mm lid attachment holes (along the bottom) and optional holes to access the adjustment trimpots without having to remove the lid. now be installed with the shorter end inserted into the PCB from the top side. At this stage, don’t plug in the PIC microprocessor (IC1). If you purchase your PICI2F617-I/P for this project from the SILICON CHIP ONLINE SHOP, it will already have the firmware (0110920A.hex) loaded. If you wish to do this yourself, the file can be downloaded from the SILICON CHIP website. Housing www.siliconchip.com.au Fig.7: the “front panel” artwork, which has a hole provided for the LED. See our website link in the text for ideas on how to print this out and attach it to the lid. You can download a PDF of this artwork from the SILICON CHIP website. the LED hole and the two trimpot adjustment access holes. The holes for the trimpots are optional; you can omit them if you’re happy to open the case if you need to make any adjustments. The lid panel artwork (Fig.7) is also available for download from our website. Details about printing and attaching panel artwork can be found at www.siliconchip.com. au/Help/FrontPanels Press the side clips into the case lid to release it from Testing the baseplate. Locating flanges insert into one edge of the Place a shorting link in JP1’s position 1 and connect two lid also secure it in place. wires, about 80mm long, to the two PC stakes under the The PCB is designed to be mounted onto the integral PCB in readiness to solder to the miniature 8-ohm speakstandoffs on the base of the case. There is only one correct er. We used two wires stripped from a length of rainbow orientation, and that is with the two notches along the top cable; mini figure-8 would also work well as well as sepaedge of the PCB fitting into the rate hookup wires. case lid locating flanges on the The loudspeaker mounts on base plate. The PCB is secured top of the PCB with the speaker with small self-tapping screws terminals in the cut-out area. The into the standoffs. wires connect to the speaker terWe attach two 9mm-long M3 minals from the underside of the tapped spacers to the PCB to alPCB. For the moment, the speaker low the lid to be screwed down. will be loose. This is in addition to the side Insert the two AAA cells and clips on the cover that hold it in switch on the power. Check there place. Two screws then go into is about 3V between pins 1 and 8 the standoffs from the outside of of IC1’s socket. the lid. Attach these spacers by Disconnect power and insert feeding short machine screws the programmed PIC in its sockthrough the underside of the et, making sure it is oriented corPCB into the two corner holes, rectly (the notch toward the edge then tighten the tapped spacers of the PCB). Reapply power and onto the screw shafts. the speaker should start to move This view shows how the PCB is secured to the case The template (Fig.6) shows in response to the ‘lub dub’ sound. lid but more importantly, shows the “damper” glued the position of the two holes re- to the mica speaker diaphragm (in this case, a stain- If not, make sure that VR2 is adjustquired for the securing screws. less steel nut). Don’t be tempted to use a mild steel ed at least partly clockwise. Adjust It also shows the locations for nut: they’re magnetic and will not work in this role. further clockwise for more sound. 46 Silicon Chip Australia’s electronics magazine siliconchip.com.au Note that the sound will have an approximate 1kHz background tone. That’s because, even though this tone is filtered out in the circuitry, the speaker is much more efficient at producing 1kHz compared to the approximately 47Hz ‘lub dub’ sounds. Also note that you won’t really hear the ‘lub dub’ sound, but you will feel it if you place a finger at the centre of the loudspeaker cone. The loudspeaker cone needs to be weighted to make the heartbeat audible and to prevent the reproduction of higher frequency tones. To do this, we use an M8 stainless steel (nonmagnetic) nut as a weight on the speaker cone. A non-magnetic nut must be used; otherwise, the speaker cone would be pressed against the magnet of the speaker by the nut. We get away with this because the speaker cone is made from Mylar and so it is quite strong. This means that the central speaker coil is still centred within the magnet gap even with extra mass. To attach the nut, apply a smear of neutral-cure silicone sealant (roof and gutter silicone is ideal) to one side of the nut and affix centrally on the speaker cone. Additional silicone is required to fill the inside of the nut, making sure it is filled down to the cone. Keep the silicone flush with the top face of the nut. Also apply a thin layer around the speaker cone. While you’re at it, it’s a good idea to secure the ferrite beads (FB1 and FB2) using some of the silicone to hold them to the PCB. Only a small amount is necessary. This will prevent them from rattling and adding obscure sounds to the heartbeat. The loudspeaker is also secured to the PCB with some silicone around the central magnet, where it fits into the PCB hole. Note that the speaker needs to be positioned correctly, with the wire entry points positioned over the PCB cutout and with the back of the speaker magnet resting on the base of the case. The PCB should be temporarily positioned on the integral standoffs in the case while the silicone cures. This way, the speaker will be at the correct height above the PCB. Using it Adjust the timeout period so that the heartbeat sound lasts for the length of time you require. This is done with JP1 in position 2. To do this, move JP1 into position 2 with the power off and set the required time. Full clockwise adjustment of VR1 gives a 4-hour timeout. The mid position is two hours and mid-way between fully anticlockwise and mid-way is about one hour. Set the timeout and then switch on the power. The timeout period will be recorded. Any further adjustment of VR1 with the power on will be ignored. It is only the setting of VR1 at power-up when JP1 is in position 2 that is recorded. The setting is stored in non-volatile flash memory and remembered for use next time. When jumper 1 is in position 1, the heartbeat rate can be adjusted. This can be changed with power on, from 42 to 114 beats per minute. The setting is also stored in flash memory, and the last setting will be used should the unit be powered up with JP1 in position 2. The volume is set using VR2. However, the drive to the loudspeaker will become distorted if VR2 is rotated too far clockwise, so a position less than halfway clockwise should SC be used. AUSTRALIA’S OWN MICROMITE TOUCHSCREEN Since its introduction in February 2016, Geoff Graham’s mighty Micromite BackPack has proved to be one of the most versatile, most economical and easiest-to-use systems available – not only here in Australia but around the world! Now there’s the V3 BackPack – it can be plugged straight into a computer USB for easy programming or re-programming – YES, you can use the Micromite over and over again, for published projects, or for you to develop your own masterpiece! The Micromite’s BackPack colour touchscreen can be programmed for any of the following SILICON CHIP projects: BACKPACK Many of the HARD-TO-GET PARTS for these projects are available from the SILICON CHIP Online Shop (siliconchip. com.au/shop) Poor Air Quality Monitor (Feb20 – siliconchip.com.au/Article/12337) FREE GPS-Synched Frequency Reference (Oct18 – siliconchip.com.au/Series/326) PROGRAMM Tariff Super Clock (Jul18 – siliconchip.com.au/Article11137) ING Buy either Altimeter & Weather Station (Dec17 – siliconchip.com.au/Article/10898) tell us whichV2 or V3 BackPack, pr oj ect you for and we’ll Radio IF Alignment (Sep17– siliconchip.com.au/Article/10799) program it fowant it r you, Deluxe eFuse (Jul17 – siliconchip.com.au/Series/315) FREE OF C HARGE! DDS Signal Generator (Apr17 – siliconchip.com.au/Article/10616) Voltage/Current Reference (Oct16 – siliconchip.com.au/Series/305) Energy Meter (Aug16 – siliconchip.com.au/Series/302) Micromite V3 BackPack: * Super Clock (Jul16 – siliconchip.com.au/Article/9887) JUST $7500 Boat Computer (Apr16 – siliconchip.com.au/Article/9977) See August 2019 (Article 11764) Ultrasonic Parking Assistant (Mar16 – siliconchip.com.au/Article/9848) P&P: Flat $10 PER ORDER (within Australia) *P Price is for the Micromite BackPack only; not for the projects listed. www.siliconchip.com.au/shop siliconchip.com.au Australia’s electronics magazine January 2021  47 Installing and using While Arduino software and hardware have made microcontroller projects accessible, many advanced users prefer to use MPLAB X, especially for PIC devices. Like the Arduino IDE, it is a free download. This article will step you through the process of creating your first MPLAB X project. T hose who have been dabbling with microproces- AVR parts (as described starting on page 88 of this issue). sors and microcontrollers for a long time may reMPLAB has evolved into MPLAB X, which is now Javamember a time when writing a program required based, and therefore runs on all major operating systems; intimate knowledge of instruction sets and memory maps. Windows, Mac and Linux. You had to hand-write assembly language or even machine For a long time, we’ve used this software and PICkit procode which would then have to be loaded into an EPROM. grammers to program microcontrollers for our projects, and Our early microprocessor projects, such as the 1989 Print- we see no reason to change that, especially with MPLAB er Buffer (siliconchip.com.au/Article/7380) or LED Message X now supporting AVR parts. Board (siliconchip.com.au/Series/255), There may be some out there also from 1989, used a Z80 microprofor whom microcontroller processor with separate RAM chips and gramming remains a mystery; an EPROM chip. perhaps you’re happy just buyAbout the same time came the first ing pre-programmed parts from PIC microcontrollers, with integrated the SILICON CHIP ONLINE SHOP, or program EPROM and in the next decyou just don’t have the need. But ade, flash memory. These were typicalyou may be interested in the proly programmed in assembly language, cess nonetheless. Or you might with the machine code created by an like to jump into the world of assembler program. microcontrollers. Flash-based devices such as the Rest assured that the process PIC16F84 meant it was finally possionly continues to get easier. In ble to quickly and easily update code this article, we’ll introduce and without having to manually erase an review the latest version of MiEEPROM under a UV lamp (or sunlight, crochip’s MPLAB X IDE. if you didn’t have a UV lamp). Once you’ve read through it, It was over ten years ago, in July you might also like to read the 2010, that we last gave an in-depth separate article on the new AVR ‘howto’ on programming PIC microDA family of microcontrollers controllers (siliconchip.com.au/Article/208). That article which are supported by MPLAB X. introduced the PICkit 3 programmer/debugger from MicroMPLAB X is not tied to that particular chip or developchip and their MPLAB software. ment board, but can be used with many Microchip microconMPLAB is a complete IDE (integrated development en- trollers, including virtually all PICs and many AVR MCUs. vironment). It’s integrated because it includes the ability to write programs in a high-level language (typically C) Microchip Technology and then compile, upload and even debug these programs. Microchip Technology is the company that makes PIC The PICkit 3 is still a handy device; we haven’t come microcontrollers. In 2016, they bought out Atmel, the makacross many PIC devices that it can’t program. But you will ers of 8-bit AVR microcontrollers (which are at the heart of probably have to switch to a PICkit 4 or Snap early Arduino boards such as the Uno). Atmel programmer if you want to work with the latest By Tim Blythman also made a range of 32-bit ARM-based micro48 Silicon Chip Australia’s electronics magazine siliconchip.com.au controllers (which are in some of the more recent Arduino boards). In a sense, these compete with Microchip’s MIPSbased PIC32 series. For a few years now, we have seen some crossover in features between the 8-bit PIC and AVR families. We described a then-new AVR part in January 2019, the ATtiny816 (siliconchip.com.au/Article/11372), and we’re following up with an article on the latest AVR DA parts this month (see page 88). Microchip Technology also produces the MPLAB X IDE software. It is available for free download, although some compiler optimisations (to produce smaller and faster code) are optional extras that you have to pay for. That said, you can get a lot done with the free version of the software. MPLAB X IDE MPLAB X IDE is an evolution of the earlier MPLAB IDE which dates back to 2001. The PICkit 2 programmer was introduced in 2005, and many people would have first come across MPLAB bundled onto a CD-ROM with their PICkit 2 purchase. MPLAB X was introduced in 2011 with support for the Mac and Linux platforms. Now, in 2020, the latest version of MPLAB X (version 5.40) is the first to drop support for 32-bit host processors (although it can, of course, program 32-bit microcontrollers). MPLAB X does not provide all features ‘out of the box’. Instead, compilers and other features are downloaded and added separately. In fact, it appears that in the future, new device support will be added using ‘Device Family Packs’ (DFPs – we speculated on the meaning of DFP in our ATtiny816 article!). What it does The User Guide for MPLAB X notes that it includes the following features: • a text editor (which also offers syntax highlighting and error checking) • a project manager • a software simulator Screen1: the default install directory includes the version number of MPLAB X, so it can be installed alongside earlier and later versions. This means you can try a new version before committing to it. siliconchip.com.au • a debugger engine offering breakpoints, single stepping and watch windows The following items can be added separately to the IDE: • compilers • programming frameworks (eg, Microchip’s Harmony series) • other tools As we noted earlier, programmers such as the PICkit devices are also needed to write firmware images to the microcontrollers. If you are experimenting with the AVR128DA48 Curiosity Nano board described in our article in this issue on the AVR DA family (or one of the other Curiosity Nano series), the programming function is built into the board, and no extra hardware is needed, apart from a USB cable. There is also the MPLAB Xpress Cloud-Based IDE, which runs in a browser. Installing MPLAB X Let’s get started with a basic introduction to the MPLAB X IDE. We’ll assume you’ve done some programming before, for example, using the Arduino IDE. The most basic steps involve writing code, compiling it and programming the resulting HEX file to the device. Under the Arduino IDE, the last two steps are combined in the function of the Upload button. The MPLAB X IDE can be downloaded from www. microchip.com/mplab/mplab-x-ide As we mentioned, the latest version at the time of writing (5.40) only supports 64-bit operating systems, so if you have a 32-bit processor, you may need to work with an older version instead. Legacy versions can be downloaded from www.microchip.com/development-tools/pic-and-dspicdownloads-archive There are minor differences with older versions, but you should be able to follow along; the big difference is that 5.40 is the first version to support the AVR128DA parts and thus is needed to work with the Curiosity Nano AVR128DA. Although MPLAB X supports other operating systems, much of the other software we use is still tied to Windows, so we will be using Windows 10 for our guide. But our Screen2: These options are new for version 5.40. There are separate options for the IDE (integrated development environment) and IPE (integrated programming environment). Choose the latter if you only wish to use MPLAB X for programming HEX files onto chips. The settings shown here are what we use, with support for 8-bit and 32-bit parts. Australia’s electronics magazine January 2021  49 Screen3: MPLAB X also installs drivers for devices such as programmers like the PICkit 4 and the programming interface on the Curiosity Nano AVR128DA. experience is that on Mac and Linux, it works in much the same way. The download for MPLAB X v5.40 is around 1GB and once installed, can take up to around 11GB. Installation is quite straightforward, and for the most part, the default options are fine (Screen1). It takes between about 10 minutes and an hour, depending on how fast your computer is. If you only wish to use MPLAB X for programming devices, then you might only want to install the IPE (integrated programming environment). There’s also the option to select whether you want support for 8-bit, 16-bit or 32bit devices; you will need 8-bit support for the AVR DA parts (see Screen2). The installer will also ask for permission to install some drivers (see Screen3). These are for devices such as programmers, so it’s a good idea to install them now too. When the MPLAB X installation is finished, you will also be prompted to install other items that you might typically need, such as a compiler – see Screen4. You will likely need to install at least one compiler, but if you want to install anything but the latest version, you’ll have to download them manually from siliconchip.com. au/link/ab4v The compilers are called XC8 (for 8-bit devices), XC16 and XC32 (for 32-bit devices like PIC32s). We currently use XC32 version v2.10 for our PIC32 projects, although some older projects use version v1.33. Also, the procedure for creating a “CFUNCTION” for a Micro- Screen5: the Free License for the XC8 Compiler works quite well. If you need the features of one of the Pro licenses (for example, more aggressive code optimisation), then it can be applied later. 50 Silicon Chip Screen4: to make proper use of MPLAB X, you need a compiler, so you should leave the top option checked. You can install compilers separately later, if required. mite only works with this older version. This is due to changes in the way some of the peripheral libraries work within the compiler. For 8-bit microcontrollers, we have previously used XC8 version v2.00. You might want to install one of these if you wish to modify some of our project code. The process here applies to version v2.20 of XC8, but other versions (and other compilers) should be fairly similar. If you want to build the code for the AVRDA family of chips, then you will need to install at least v2.20 of XC8. The first question you are asked when installing an XC compiler is about the licence type, as shown in Screen5. Initially, at least, the Free option is fine. A paid licence can be applied later if you need compiler optimisations (this means that, in general, your programs will be smaller and run faster). Then move onto the installation path; the default option is usually a good choice (Screen6), as the installer organises the different versions into folders, so it’s easy to check what versions are installed. The final step also relates to the licence. The Host ID (used for node-locked licences) is shown (see Screen7). Again, Screen6: the XC8 Compiler can be installed independently from MPLAB X, and different versions of it can be installed simultaneously. We sometimes use an older version of the XC32 compiler (for PIC32 parts) as it has a different set of libraries. Australia’s electronics magazine siliconchip.com.au Screen7: if you want to try the Pro license for XC8, there is a 60-day free trial. The easiest way to activate it is to rerun the installer and click the option shown here. for the free licence, you can simply click Next. At this stage, we have enough software installed to start compiling code, but let’s take a quick tour first. MPLAB X We’ll use the AVR128DA48 Curiosity Nano development board described in the accompanying article as an example. If you have one of these, plug it in now so that the software can recognise it. Open MPLAB X and choose New Project… from the File menu. The next step is to select a project type; we usually select “Standalone Project” (see Screen8). The other options are generally used to import existing projects from other programs. If you have installed the Harmony or MCC frameworks, then options for these will also appear. Harmony and the MPLAB Code Configurator (MCC) are the programming frameworks noted earlier; it is not necessary to install these to work with the AVR128DA48 Curiosity Nano. However, they may come in handy if you are working with some complex peripherals, especially USB. The next step is to choose the target part. For example, for the AVR128DA48 Curiosity Nano, the part will be AVR128DA48, because this board has the 48-pin variant. It’s possible to change this setting later (mid-project). For example, you may wish to port the code to a device from the same family with more pins, or even to a different device. Screen9: after creating a new project and adding a “main.c” file, you are presented with panels full of information. Project settings and properties can be found by right-clicking the project name at the top left and selecting “Properties”. siliconchip.com.au Screen8: as well as creating a Standalone project, you can also import Atmel Studio projects. If you have other frameworks (such as Harmony or MCC) installed, they appear as options here. On this tab, it’s also possible to select the programming tool. You should see the Curiosity Nano in the drop-down list. If you don’t have one of these, you can select “Simulator” or “No Tool”. The window will jump forward a few steps to allow a compiler to be chosen. Your only choice for the AVR128DA will be XC8 V2.20 or later (or its assembler, “pic-as”). Finally, you can choose a project name and location. We went with “AVR128DA48_blank”. The project is now created, but will (at a minimum) need to have at least one source code file. Right-click on the “Source Files” and click New -> avr-main.c. A file will appear in the main window and also at left. Your screen should now look like Screen9. Navigating the IDE The small window at top left allows you to navigate between projects and also individual files within a project. Below this, at the left, is the Dashboard. It shows important project information. Particularly handy are the Data and Program memory space bar graphs, which allow you to keep track of these resources as your code expands. At top right is the editor. If you have multiple files open, they will be shown by tabs along the top. The editor has the expected features like find and replace, but also syntax Screen10: the Project Properties window contains settings that are only changed rarely after the project is created. You might use the option at top right to modify a project to use a different part, for example, if you need more I/O pins and want to change to a larger member of the same family. Australia’s electronics magazine January 2021  51 highlighting and autocompletion. At lower right is the output window. Various stages of the development process are handled by different utilities (under the control of MPLAB X). For example, during compilation and upload, progress and warnings/errors (if any) are shown here. Of course, the windows can be moved around as needed, but we find that the defaults work quite well. The button with the green arrow coming out of the chip is for reading a device’s memory; typically this would be used to export the contents of flash memory to a HEX file, although this is usually not needed if you have compiled your own code. It might be handy, though, if your code writes data to flash (eg, its configuration) and you want to see what changes it has made. The button with the blue circular arrow is used to toggle the programmer’s device reset line, for example, if you wish to reset or disable the attached microcontroller during testing and debugging. The final button is used for hardware debugging. If you click this, your code is compiled with options allowing it to communicate with the programming tool, and is uploaded to the device. The MPLAB X IDE then switches to debugging mode, and some more buttons appear to control this. We explain the debugging process in more detail in the article on the AVR128DA, which starts on page 82. Handy hints MPLAB Xpress IDE Screen11: these buttons along the top of the MPLAB X window are for compiling and deploying your project to microcontroller hardware. The rightmost button initiates a debugging session. We can’t possibly detail all the features of MPLAB X, but we’ll briefly summarise those we use the most. It might pay to come back to this section while you’re working with the Curiosity Nano board. The main project properties can be opened by rightclicking on the project name in the Projects window (see Screen10). Many options from the initial project setup can be changed here. In fact, multiple configurations can be created, perhaps to target a variety of different processors or to help to port the project between compiler versions. The programmer can be changed too; it’s the first item under “Conf: [default]”. The “PKOB nano” is the programmer built into the Curiosity Nano (PKOB is short for PICkit On Board). You may have more need to tweak these settings when working with a standalone programmer. MPLAB X also includes an easy way to make a copy of a project. This can be handy if you don’t have some other form of version control in use, or you wish to use one project as the basis for another different project. Simply right-click on the project name in the Projects window and select “Copy...” Then supply a new name and click “Copy”. Just below the main menu items are commonly used tools, as shown in Screen11. The hammer icon builds (compiles) the project. Helpfully, the project name is shown, so you know which project you are building. This is handy if you have multiple projects open. The hammer and brush icon ‘cleans’ and builds. Usually, the build process only updates files that have changed since the last build. In contrast, a ‘clean and build’ ensures other changes like configuration settings changes are properly propagated through the compile process. For small projects, either process takes only a few seconds, so we find that we simply do a ‘clean and build’ most of the time. The next two buttons, labelled “Run” and “Make and Program Device”, perform the same function in most cases. The Run button can also be used to start the simulator for those devices that support it. Currently, this is only some PIC devices, so the AVR128DA is not supported by the simulator. 52 Silicon Chip It’s also worth noting that there is a cloud-based version of MPLAB X, called MPLAB Xpress IDE. It is not a replacement for the full IDE, but is a quick and easy way to have a look around at the platform’s features – see Screen 12. You can access it at the following link: https://www. microchip.com/mplab/mplab-xpress You can create a project, build it and even download a hex file. There’s also an option to export an MPLAB X project to work with the full IDE. Conclusion We’ve used MPLAB X for many years now, and it has improved over time. It’s especially handy that MPLAB X can now work with AVR parts as well as PICs, especially with in-circuit debugging (ICD). The latest version of the IDE doesn’t bring much in the way of new features for those that are familiar with using it to work with PIC microcontrollers. Indeed, many of the older versions are entirely adequate for coding, debugging and programming older PICs. But it is evolving to work with more microcontrollers, and SC these new AVR parts spread its reach even further. Screen12: the MPLAB Xpress IDE is an online IDE which allows you to export projects and compile HEX files. So it’s a good way to test out some of the features of MPLAB X without having to install it first. 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Universal T10/211/BA9S. 2.5W 260 Lumen ZD0585 $9.95 3.0W 310 Lumen ZD0587 $12.95 4.5W 450 Lumen ZD0589 $14.95 FROM 7 $ 95 WATERPROOF DEUTSCH 2-WAY CONNECTOR SET Perfect for connecting up sensors/ lights in the bay due to their superior corrosion protection. • 13A rated. 2-Way PP2150 $7.95 4-Way PP2149 $9.95 6-Way PP2148 $11.95 More ways to pay: FROM A range of 150 lumens ultra-bright white LED replacement globes for car interior lights. Compatible with modern "CANBus" sytems. 120° wide beam. 12VDC. 3 sizes available. ZD0750-54 NOW 2795 $ EA SAVE $5 FROM 89 $ 95 PR H4 HI/LO LED POWERED HEADLAMP KIT Bright and efficient. Equipped with advanced Luxeon Z ES LEDs. • 3800 lumens 40W NOW • 12/24VDC SL3524 WAS $169 JUST 6995 $ AUTOMOTIVE MULTI-FUNCTION CIRCUIT TESTER WITH LCD Designed to test the electrical system of an automotive vehicle running on 12V or 24V. Tests voltage and polarity of a circuit. Locates misfiring cylinders. • LED indicator QM1494 WAS $64.95 5995 SAVE $5 SAVE $20 AUTOMOTIVE DMM WITH DWELL & TACHO JUST EA HIGH GRADE CIGARETTE POWER SOCKETS For vehicle and marine use. Includes panel and surface mounts. 10A rating. Single PS2020 $16.95 Double PS2022 $21.95 Single with LED Voltmeter PS2024 $29.95 Single with Dual USB Charger PS2026 $29.95 JUST 19 $ 95 12V TO 5VDC CONVERTER WIRING KIT NOW $ 149 95 2 Diagnose your cars problem. Plugs into OBD-II port and transmits speed, RPM, fuel consumption, etc via Bluetooth® to your Smartphone. PP2145 1295 $ QC353 OBDII BLUETOOTH®4.0 ENGINE CODE READER $ 16 $ 4995 $ SAVE $20 Provides clean, crisp, natural and smooth balance sound. All models are paired with soft dome tweeters. Sold as a pair. 4" 40WRMS CS2400 $89.95 5" 50WRMS CS2401 $119 6.5" 75WRMS CS2402 $139 Car Lighting 995 249 COAXIAL SPEAKERS WITH SILK DOME TWEETER 4 DOOR REMOTE CONTROLLED CENTRAL LOCKING KIT WITH KILL SWITCH $ FROM $ Self-adhesive and easily moulded. Provides acoustic isolation and insulation for roof, firewall, floor, quarter panels, doors and under bonnets. 330mm wide. WAS $32.95 EA Butyl AX3687 Butyl/Foam Combo AX3689 95 FROM NOW SOUND DEADENER 94 $ 12V REVERSING CAMERAS ONLY Perfect for the workshop as an an engine analyser as well as basic DMM. Full dwell angle measurement and tacho. Max/ data hold and bright backlit LCD. • 2000 Display count • RPM x 10 QM1446 4995 $ Micro USB Plug (Mini USB adaptor included) Get rid of unsightly power cables floating around car dash that powers GPS, Dash Cam or mobile device. • 2.5A continuous current • Cable length 1.3m MP3675 IN-CAR BATTERY MONITOR AND TEMPERATURE DISPLAY Plugs into an available power socket to display system voltage and interior cabin temperature. Easy to read LED display. QP2222 ONLY 1995 $ 57 D E N I A T ENTER keep the kids AMAZING SELF-FLYING DRONE! 9995 $4995 LASER GUN & DRONE SET REMOTE CONTROLLED 2-IN-1 TANK CONSTRUCTION KIT 4995 Build your own 'marble' roller coaster. The spiral "elevator" lifts the marbles to the top of the rail, and gravity takes care of the rest. 170 piece. Requires 1 x C battery (sold separately). Ages 15+. KJ9004 2 PK C Batteries SB2416 $4.50 TOBBIE THE ROBOT - HEXAPOD KIT A 6-legged robot that you can build. Walks and spins in any direction and will beep and flash its eyes. Ages 8+. KJ9031 Assembled into two different tanks. Drive around on caterpillar tracks and raise/lower the turret. Equipped with gunfire sounds. 759 pieces. Ages 6+. Requires 3 x AAA and 6 x AA batteries (sold separately). KR9242 4 PK AAA Batteries SB2413 $3.25 12 PK AA Batteries SB2333 $7.95 JUST 2995 $ VIDEO ONLINE JUST Runs on potatoes or with tomatoes, lemons, apples, even soft drink or beer! Safe and highly educational. Ages 10+. KJ8937 95 NOW 1995 SAVE $3 4995 $ ANYWHERE TABLE TENNIS • Collapsible net • Spring-clamp net support posts • Includes 2 x paddles & 2 x ball GH1162 WAS $22.95 NOW 95 POTATO CLOCK KIT Interchangeable 4WD tyres for speed and caterpillar tracks for rough terrain. Speeds up to 10km/h. 2.4GHz remote requires 2 x AA batteries (sold separately). Ages 8+. GT4247 2 PK AA Batteries SB2424 $1.95 JUST Simulates the movements of human hand/ fingers, using hydraulic power. It allows every finger joint to adjust at different angles for close-fist/or open-palm precisely. Ages 10+. KR9266 12 $ REMOTE CONTROLLED 2-IN-1 ROCK & DIRT CRAWLER $ HYDRAULIC CYBORG HAND KIT 49 $ JUST $ SPACE RAIL CONSTRUCTION KIT JUST JUST JUST $ Launch this amazing 'obstacle avoidance & self-flying drone and watch it fly, then pull out the gun, take aim - shoot! Hit the drone and it shudders, strike it 3 times and it falls safely to ground. Warning - The drone shoots back. Full colour lighting and multiple sound effects. Add up to 3 drones. Ages 8+. GT4082 See website or in-store for details. Additional Drone to Suit GT4082 GT4084 $24.95 Due early January. ...at home FROM 995 $ KJ89 70 SNAP-ON ELECTRONIC KITS All in bright coloured pieces. Parts simply snap together without any screws or soldering. Ages 6+. KJ8970-KJ8985 Full range available in store or online. 1495 $ SAVE $2 MAKE YOUR OWN: CLOCK KIT Easy to assemble. No batteries required. 31 pieces. Ages 6+. KJ8996 WAS $16.95 80W 240V Soldering Iron TS1485 $24.95 WEARABLE BADGES & ELECTRONIC DICE KITS These kits are a great way for your kids and grand kids to start soldering and pick up some electronics on the way. They will also learn about how various components work including LEDs, transistors, integrated circuits and more. Each kit requires a CR2032 battery (SB2522 $3.25 sold separately). $19.95 EA 6 DIFFERENT KITS AVAILABLE: 1. Skull Badge 2. Owl Badge 3. Rocket Badge 4. Pirate Badge 5. Robot Badge 6. Electronic Dice with Alternating Flashing LEDs with Touch Sensitive LEDs with Flashing LEDs with Flashing LED Eye with Touch Sensitive LEDs & Buzzer with Flashing LEDs 58 5 40 3 $ 6 SAVE $19.85 In the Car RETRO STYLE HANDHELD GAME CONSOLE WITH 256 GAMES Hours of entertainment to keep you and the kids entertained. Features a 2.8" colour screen, built in speaker and a 3.5mm to RCA and USB recharge cable. Available in Black or Red. Ages 15+. GT4280 Due early January. KM1090 KM1092 KM1094 KM1096 KM1098 KM1099 ANY 3 KITS FOR JUST CONNECT IT TO YOUR TV 29 $ click & collect ONLY 95 129 7" TFT LCD WIDESCREEN COLOUR MONITOR WITH IR REMOTE $ Wireless Headphones Suitable for in-car and home entertainment, use it to watch video AA2047 RRP $39.95 from any composite source such as a DVD player or game console. QM3752 Buy online & collect in store JUST 3995 $ bonus free gift WIRELESS INFRARED STEREO HEADPHONES Add these wireless headphones to the monitor on the left and enjoy automotive bliss! Soft cushioned pads. AA2047 ON SALE 27.12.2020 - 23.01.2021 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. AUDIO & VISUAL SECURITY Cat. No WAS NOW SAVE 150m 1080p HDMI Cat5e/6 Extender with Infrared HOT PRICE AC1746 $219 $169 $50 1080p AHD Dome Camera with IR HOT PRICE AM4201 $69.95 $39.95 $30 1080p Wi-Fi IP Camera with Pan/Tilt 2 Way DisplayPort Splitter AC1755 $49.95 $39.95 $10 12V AC/DC Door Strike release 2 Way DisplayPort Switcher AC1757 $49.95 $39.95 $10 15m CCD Camera Extension Cable 2 x 15 WRMS Portable Stereo Amplifier AA0504 $69.95 $49.95 $20 4 Door RFID Access Controller 2 x HDMI to VGA/Component & Analogue/Digital Audio Converter AC1721 $99 $20 720p AHD Dome Camera with IR 3.5mm Plug to Socket Cable with Microphone and Volume Control - 0.5m WA7120 $14.95 $9.95 $5 720p AHD Wireless Receiver & Camera Kit QC8663 $99 $89 $10 4 Way Digital Audio Switcher AC1723 $39.95 $34.95 $5 720p Outdoor Trail Camera QC8041 $149 $129 $20 6 Way Speaker Selector with Internal Protection AC1683 $129 $99 $30 Ceiling Mount Alarm with Remote Control 6.5" Rechargeable Cube Speaker with Bluetooth® Technology CS2489 $119 $89 $30 Concord 8 Ch. 4K DVR Package - 4x5MP Cameras HOT PRICE QV5100 $299 $249 HOT PRICE QV5602 $1,299 $1,099 2 Channel Mixer with Microphone Preamp $119 Cat. No WAS NOW HOT PRICE QC8687 $129 $89 HOT PRICE SAVE $40 QC3858 $89.95 $69.95 $20 LA5078 $49.95 $29.95 $20 WQ7277 $49.95 $39.95 $10 LA5359 $199 $149 QC8639 $99.95 $69.95 LA5215 $34.95 $24.95 $799 $699 $50 $30 $10 $100 $50 Concord 8 Ch. 4K NVR Package - 6x5MP Cameras Economy UHF/VHF Masthead Amplifier LT3276 $49.95 $34.95 $15 Motion Sensor Camera recorder with 38 IR LEDs QC8027 HDMI 4K Repeater AC1717 $34.95 $24.95 $10 Non-Contact Infrared Door Exit Switch LA5187 $74.95 $49.95 $25 Rechargeable Solar Sensor Light SL3239 $69.95 $54.95 $15 Concord 50m 4K HDMI Fibre Optic Cable Portable 5.8GHz Wireless 1080p HDMI AV Sender HOT PRICE WQ7496 HOT PRICE AR1901 $229 $179 $50 Cat. No WAS NOW SAVE POWER $89 $79 $200 $10 IT & COMMS 125A Dual Battery Isolator (VSR) MB3687 $49.95 $39.95 $10 0.5W 80 Ch UHF Transceivers 12V 8.5A Desktop Power Supply HOT PRICE MP3258 $99.95 $69.95 $30 3W UHF CB Radio Tradies Pack - Pair 5W UHF CB Radio Tradies Pack IP67 $5 Cat. No WAS NOW DC1027 $69 $59 $10 HOT PRICE DC1076 $329 $229 $100 HOT PRICE DC1069 $449 $349 $100 18W USB Type-C Mains Power Adaptor with Power Delivery MP3410 $24.95 $19.95 240VAC Aluminium 48 LED Light Strip with Switch ST3946 $59.95 $49.95 $10 Advanced 2 Watt 80 Channel UHF Transceiver with CTCSS DC1049 $69.95 $59.95 240VAC Aluminium 72 LED Light Strip with Switch ST3948 $69.95 $59.95 $10 Ethernet Over Power N300 Wi-Fi Access Point YN8357 $149 $129 SAVE $10 $20 $99 $30 Ethernet-Over-Power Kit YN8355 $99.95 $89.95 $10 2600mAh Metallic Power Bank Rose Gold MB3794 $14.95 $9.95 $5 VGA To Composite & S-Video Converter XC4907 $49.95 $39.95 $10 2600mAh Metallic Power Bank Silver MB3792 $14.95 $9.95 $5 Waterproof Floating 80 Channel 3W UHF CB Transceiver DC1074 $129 $99 $30 2600mAh Metallic Power Bank Space Grey MB3793 $14.95 $9.95 $5 ST3487 $4.95 2500 Lumen Rechargeable LED Torch 3 x Oslon Osram LED Torch HOT PRICE 1/2 PRICE! ST3499 $129 $9.95 $5 30W 5V 6A Encapsulated Mini Power Supply MP3301 $42.95 $29.95 $13 5VDC 1A USB Mains Adaptor with Micro-B Cable MP3544 $19.95 $14.95 $5 6300 Lumen 6.5 Inch Solid LED Driving Light SL3920 $149 $129 $20 EDUCATIONAL KITS & GADGETS AUTO & OUTDOORS 1080p Wi-Fi Dash Camera with GPS 3G GPS Vehicle Tracker HOT PRICE Cat. No WAS NOW SAVE QV3865 $189 $169 $20 LA9026 $199 $149 $50 Bluetooth® In-Car Earpiece with USB Charger AR3135 $19.95 $14.95 FM Transmitter with USB & SD Playback AR3136 $14.95 $9.95 $5 $5 Cat. No NOW SAVE Cat. No WAS NOW SAVE Circuit Scribe Maker Kit KJ9310 $89 $69 $20 Crookes Radiometer GG2108 $59.95 $39.95 $20 Draw Circuits Circuit Scribe Basic Kit KJ9340 $69.95 $59.95 $10 30 Piece Tool Kit with Case TD2166 $29.95 $19.95 $10 QM1568 $49.95 $39.95 $10 HARDCORE KJ9300 $149 $109 $40 3000A True RMS AC High Current Clamp Meter Makeblock mBot Blue Robot Kit KR9200 $199 $169 $30 300W Hot Air SMD Rework Station MakeBlock Neuron Inventor Kit KJ9190 $99 $79 $20 8 Piece 1000v VDE Set Draw Circuits Circuit Scribe Ultimate Kit HOT PRICE HOT PRICE TS1645 WAS $159 $129 TD2031 $59.95 $39.95 MeetEdison Robot Kit KR9210 $99.95 $79.95 $20 Benchtop 16-Bin Storage Organiser HB6341 $49.95 $34.95 Motion Drone GT4224 $34.95 $24.95 $10 2 Bay USB 3.0 SATA HDD RAID Enclosure XC4688 Portable 14L 12V Cooler / Warmer Puppy Go AI Smart Dog HOT PRICE $89 GH1373 $119 $89 $30 Arduino Compatible 16x16 LED Dot Matrix Module XC4607 $24.95 $19.95 KR9234 $169 $129 $40 Arduino Compatible 3W 200 Lumen LED Module XC4468 $10.95 $49.95 $39.95 Space Rail Construction Kit - Glow in the Dark KJ9001 Squishy Circuits Deluxe Kit KJ9352 Vinyl Record Carry Case GE4101 $39.95 $29.95 More ways to pay: $99 $129 $99 $6.95 $10 Arduino Compatible Ultraviolet Sensor Module XC4518 $29.95 $24.95 $30 Long Range LoRa IP Gateway XC4394 $10 USB Port Voltage Checker Kit KC5522 $33.95 $19.95 $99 $79 $30 $20 $15 $10 $5 $4 $5 $20 $14 59 HOT OFFERS: THREE FILAMENT 3D PRINTER SAVE $200 COLOUR MIXING TECHNOLOGY DESKTOP 3D SCANNER V2 WITH SOFTWARE Watch real life objects become digitized • CAPTURES before your eyes. Scans up to 250 x GEOMETRY IN 180mm. Sleek, foldable design for AS FAST AS workspace storage. Comes packed with 1 MINUTE! MFStudio software with +Quickscan. • SCAN OBJECTS • Scans up to 250(H) x 180(D)mm WITH AN TL4420 WAS $1499 ACCURACY See website for details. WITHIN +/- 0.1MM NOW RESOLUTION. MOOZ-3Z TRIPLE FILAMENT 3D PRINTER • Equipped with a three-color print head for colour mixing • Easy-to-use controller and mobile app • Featured with 3.5" LCD touch pad, Wi-Fi USB connectivity, magnetic heat bed and more • Supplied with a roll each of cyan, magenta and yellow filament to get you started. • Prints up to: 100(H) x 100(Dia.)mm TL4412 WAS $1499 1299 $ SAVE $200 Stream music from your Smartphone or Tablet via Bluetooth® in true stereo, or connect via 3.5mm Aux input. • IPX5 Water resistant • Bluetooth® Wireless Technology • True Wireless Stereo (TWS) • Google Assistant & Siri® Support CS2499 WAS $149 NOW 5 PORT USB CHARGING STATION WITH STORAGE COMPARTMENT • Charge up to 5 USB devices at the same! • Maximum power output of 2.4A per port. • Includes 6 dividers and a 12VDC, 4A power supply. WC7766 WAS $59.95 NOW 119 $ SAVE $30 2 FOR 70 SAVE $49.90 15,000MAH PORTABLE POWER BANK • 4 x LEDs show charge status • Dual USB Type-A ports & 1 x USB Type-C port • Up to 3A total power output MB3806 $59.95 EA. Modern touch sensitive monitor with clear vision to idenitfy visitors. Provides electronic door strike and gate control, as well as full talk-back to the outdoor unit. QC3884 WAS $399 • 2-way audio intercom • Various melodies • IP44 rated 329 $ 95 SAVE $70 SAVE $20 $ 7" LCD WIRELESS 2.4GHZ VIDEO DOORPHONE NOW 39 $ SAVE $200 LOTS OF FILAMENT COLOURS & STYLES AVAILABLE PRICE FROM $19.95 See website for details. PORTABLE BOOM BOX SPEAKER NOW 1299 $ WIRELESS TWS SPORT EARPHONES WITH BLUETOOTH® WI-FI IP CAMERAS WITH INFRARED LEDS R/C MOTORISED ROBOT ARM KIT Suitable for night time use. 720P QC3849 WAS $69.95 NOW $49.95 (Shown) 1080P QC3862 WAS $79.95 NOW $59.95 Ideal for anyone interested in robotic construction. 100g lift capacity. Supplied as a kit of parts with detailed instructions. Requires 4xD batteries (SB2321 $8.95 sold separately). Ages 12+. KJ8995 WAS $139 NOW NOW FROM NOW Fits comfortably and pairs very easily. Up to 3hrs play/talk time. • Bluetooth® 5.0 • True Wireless Stereo (TWS) • Built-in Microphone AA2147 WAS $69.95 5995 $ SAVE $10 4995 $ SAVE $20 99 $ SAVE $40 TERMS AND CONDITIONS: REWARDS / CLUB MEMBERS FREE GIFT, % SAVING DEALS, & 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 1: 10% OFF Flashforge Filament applies to all colours and sizes. FREE GIFT: Buy Dash Cam (QV3849) and get 32GB microSD card (XC4992) FREE. 15% OFF TV Mounting Brackets apply to CW2805, CW2811, CW2819, CW2834, CW2840, CW2851-53-59, CW2864-66-67-68-69, CW2874-75-78, CW2880-82-83. Page 3: Buy 1 x QC3890 + 1 x QC3896 for $249. MULTIBUYS: 2 x MS6106 for $30. 2 x MS6104 for $50. 3 x LA5046 for $99. Page 4: Buy 1 x MP3741 + 1 x MP3746 for $219. Page 6: MULTIBUYS: Buy ANY 3 KITS for $40 applies to KM1090, KM1092, KM1094, KM1096, KM1098, KM1099, KM1097 & XC3758 or any combination. FREE GIFT: Buy In-car Monitor (QM3752) and get Headphones (AA2047) FREE. Page 8: MULTIBUYS: 2 x MB3806 for $70. SUPPLY CHAIN DISRUPTION. We apologise for factors out of control which may result in some items may not being available on the advertised on-sale date of the catalogue. For your nearest store & opening hours: H NY BA AL Y W Maddington Unit 1A/1808 Albany Hwy Kenwick, WA 6107 (08) 9493 4300 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide 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 27.12.2020 - 23.01.2021. SERVICEMAN'S LOG One good turn deserves another Dave Thompson A client turned up at the workshop the other day with what I would consider the perfect job for me. This bloke is a known audio ‘nut’ in my old circle of friends. Although I hadn’t heard from him for many years, he had tracked me down because he finally decided to fix up a few of the ‘vintage’ items in his vast collection of 70s and 80s audio gear. I say ‘my circle of friends’, but I didn’t really know him; I had met him briefly, and knew of him by reputation back when I was a young jobbing musician. He played bass guitar in one of the many bands I used to cross paths with while grinding out gigs on the local pub circuit. He was known for being right into his audio gear, so in lieu of any real information available to us at the time (no internet in those days), we often bowed to his supposedly superior knowledge in subjects related to sound reinforcement and instrument amplification. For better or worse, he was a fount of knowledge at the time; I had to learn this stuff somewhere, right? For those intent on writing off my experiences, put those burning torches and pitchforks down; I admit I was never a ‘rock star’ but I did play in touring bands for many years, and one picks up pertinent knowledge along the way. While I might not know what amplifier and speaker combination works best in your man-cave/ lounge room, I could suggest what sound reinforcement hardware you would choose if you wanted to sonically light up a 500-seat theatre! My point is that we all knew this bloke as an audio purist, and while we somewhat blundered on with our typically low-fi stage gear, he was the one who was really into the specifications and minutiae of the speakers and amplification that were being used back then. While I hesitate to label anyone I’ve ever known as an ‘audiophile’, he was probably as close as I ever came to meeting one. Not that he was in any way one of siliconchip.com.au these guys who proclaims that those $500-per-metre, plutonium-enriched gold and copper alloy speaker cables as the only thing to use for a home stereo setup. Or that one had to have thousands of dollars’ worth of audio hardware to have a good sound; he was just really into his audio hardware. Many of us likely know (or have known) someone like this, to varying degrees. I’ve met guys over the years who insist that speaker cabinets need to be mounted on Kryptonium-alloy Australia’s electronics magazine Items Covered This Month • • • Acoustic research turntables PA system repair HP5100 frequency synthesiser repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz January 2021  61 needles embedded into unicorn-horn substrate on an isolated, rubber-floored room to really appreciate the sound of their stereos. And all this will have to be powered through some rare and obscure Class ABCDEFGHIJK+ amplifier that costs more than a small house. The marketing bumf of the time laid it on pretty thick, having us believe that unless one has this type of system, it simply wasn’t worth even firing up the turntable. This is obviously not the case, but I gave up trying to convince anyone of this a long time ago. To me, whatever sounds good to me is the best system, regardless of specs and cost. It seems my old friend has mellowed a bit; maybe because of age and wisdom, but likely also because his now-wife doesn’t share his passion for spending money on expensive audio gear. That said, he still uses and swears by his many 70s and 80s highend amplifiers and turntables. I only mention this because when he called the other day, and after the usual 30-minute, three-decade catchup conversation, he arranged to bring in a couple of his Acoustic Research (AR) turntables for me to have a look at and see what I could do with. After that is the promise of some more juicy gear to work on. Life could be worse! You turn me right ’round Most people realise that anything with words like ‘research’ or ‘labs’ in the brand name must be excellent, and therefore expensive; and back in the day, in New Zealand, these Acoustic Research ES-1s were. They weren’t insanely expensive, like the Mitchell Transcriptor turntable (featured in the movie A Clockwork Orange), or the Oracle Delphi MK1, both of which could be had here for the price of a small car (minus tonearm, of course, which they assumed you would want to add yourself anyway). But they were still relatively pricey none-the-less. The customer duly arrived with a couple of banana boxes full of bits and pieces, and I could see my work would be cut out for me. One box contained one AR ES-1 turntable, which was the most complete, but this had a damaged drive motor and spindle assembly, which made the drive spool wobble like crazy when powered up. Even if I could get a belt to hang 62 Silicon Chip onto it, playing any records would be pointless and sound reproduction would suffer badly. The second box contained a turntable identical to the first, but which had seen better days. While it still powered on and the motor ran, the veneered timber case was in a very sorry state, and the power indicator lamp was not working. This one was also missing several pieces, such as a tonearm, the tonearm mounting plate and most alarmingly, the rectangular clear Perspex cover. The cover hinges were still attached to the base, but the cover was nowhere to be found. It transpired that this particular table had been bequeathed to the current owner after the previous owner had passed away; a sorry situation to be sure, but at least the turntable wasn’t just thrown into the garbage by the grieving family. So, in summary, I had to repair two Acoustic Research ES-1 turntables; one was complete but had a wobbly drive capstan, and the other was minus a lid, tonearm and altogether incomplete and to be honest, a bit of a mess. This was no problem for a serviceman like me, though! If he wanted to pay me to restore these two beautiful machines, I’d be more than happy to oblige. However, I’m sure you see the predicament; often, when servicemen start talking about the money involved, getting vintage devices back to rude health can suddenly become a lot less urgent! I quoted the guy, and he was more than happy to pay. Darn! I knew I should have charged more! Australia’s electronics magazine Suspect #1 I tackled the most complete one first. That entailed removing the platen, which is simply held in by gravity, the drive belt, and the eight screws that held the cast metal plate to the timber chassis, the fibre-board floor underneath the turntable (which is held on with the four rubber feet screws) and desoldering the wires that go from the drive motor to the small circuit board. The tonearm cables just go straight through the mounting plate and out through a cut-out in the fibre-board floor to the amp, with just one small plastic cable clip holding them in place inside the box. Once these items are removed, the whole mechanical assembly lifts clear, leaving what is essentially a timber box with a circuit board and mains cable mounted to it. Simple, to be sure, but very effective. The only problem with this one was the bent drive shaft. God knows how this happened, but it was severely eccentric when running. Fortunately, the customer had purchased a replacement motor from an internet auction site, but hadn’t fitted it because he couldn’t get the drive pulley off the bent shaft. This proved no real problem for me, as I have the right tools for the job (woohoo!). After removing the motor (which required desoldering the two motor power leads), I mounted it in some jaws under my bench press and gently pushed the pulley free. I had to be careful because these pulleys are typically a cast alloy and are very soft. It separated from the motor shaft quite readily though, and I ran it siliconchip.com.au on a temporary mandrel in my cordless drill to check its concentricity. The pulley itself was fine. I simply mounted it onto the replacement motor with some Loctite and replaced and re-soldered it back to the drive plate. On switch-on, it ran almost perfectly, although it required a few light taps on the high side with a small rubber mallet to get it running dead true. Another problem with this turntable was the drive spindle on the platen itself. The heavy platen sits and runs in what appears to be a phosphor-bronze bearing. It had excessive play, and I suspected this to be due to the bearing drying out. These types of bearings are usually pressure- or vacuum-infused with oil when manufactured, and last for years, but this one was bone dry. I don’t have a vacuum chamber (I know, I know), so all I could do was fill the bearing with oil and leave it standing for a few days before removing the excess and trying the fit again. This time it was better, and operation was smooth and steady, but since I had no instruments to measure wow and flutter (I know, I know), I’d have to go with what I had. The owner would either have to get that bushing replaced, or re-oiled, or do some regular lubricating maintenance on it in the future; he didn’t seem too worried about this prospect when I mentioned it to him. Suspect #2 That brought me to the next pile of bits. It’s always nice to have a fullyfunctional version to compare with when assembling parts, and this time was no different. I put all the metalwork back together and laid everything out in the case, and the only part missing was the tonearm mount. I took some measurements from the working version. The plate appeared to have been made from some kind of painted hardwood, so I fabricated one from an oak offcut I had in my timber bins. I bored the four countersunk mounting holes around the periphery, but left the rest undrilled; how and where the other holes go would depend on what tonearm he wanted to use. I offered to do that for him when the time comes, and said he would let me know. After filling, sanding and painting it with a semi-gloss black lacquer, it looked almost the same (and as good) as the original. siliconchip.com.au The same couldn’t be said for the timber turntable case, though. It looked like it had been left exposed to the sun for many years, and all the dark external veneer had peeled and flaked, exposing the lighter timber beneath. The only way to solve this was to strip the veneer off and re-finish the timber below. I used a coarse belt on my belt sander to rip the old finish off. While messy, it came off easily; the trick is not taking any of the solid timber underneath! I then used progressively finer paper on my recentlyrepaired 1/3-sheet sander to smooth everything off. A few coats of Danish oil brought out the grain, and five coats of clear lacquer resulted in a beautiful finish which was (luckily!) very close in shade to the original model, so I was happy with it. The customer was too, when he saw it. I didn’t have a Perspex cover for it though, and couldn’t find one online. I contemplated making one from scratch, but I didn’t have any plastic heater/former/folder gear with which to do it (I know, I know). Dad had all that stuff, but I don’t know what happened to it. The customer wasn’t too bothered; he planned on putting the turntable in a rack that had a top cover anyway, so with his agreement I removed the original lid hinges and plugged and filled the holes left behind. I used plugs of similar-coloured timber so it wasn’t too obvious that it had been done, though of course, if you looked closely you could see it. However, it was on the rear of the case so the repair would be out of view for the most part. The next challenge was the indicator light. These turntables have a simple on/off switch mounted on the top (under the plastic hood) that switches the motor, well, on and off. When on, a pinpoint of orange light shows through about halfway down the front of the case and directly underneath the power switch. It is quite bright, so I wasn’t sure exactly what was being used. Whatever it was had been glued or embedded into the timber on the inside of the case, and someone in the past had tried to remove it by simply pulling on the connecting wires. They had parted company, and I could see what looked like the bottom of a peanut bulb stuck in the hole. Australia’s electronics magazine Cautious use of a dental pick from the inside of the case soon had the lamp out, and it turned out to be a peculiarly-shaped neon bulb with a pinpoint at the tip, which is the part of it I could see from the outside. I have a good selection of neons collected over the years, but I didn’t have anything like this. I decided to use a light-emitting diode instead, and the customer was OK with this. The problem was that the neon ran from a 160V AC feed from the circuit board (as measured across the broken-off leads), and I think that’s a little high for LEDs, and they prefer DC too. I installed a high-voltage full bridge rectifier across the circuit board contacts which gave me a DC voltage I could use for the LED. I calculated I’d need a resistor of around 15kW to drive the LED from this supply without blowing it. After installing the LED into the hole and soldering everything up, I tentatively plugged it in and switched on. The LED was a little dim, so I dropped the resistance to 13kW, and that did the trick. After running it for half an hour on the bench, nothing became overly hot or emitted smoke. The effect from the outside of the case was almost the same as the neon, so I was happy with it. After insulating everything with heatshrink tubing and tacking the LED into the chassis with a small dot of epoxy, I assembled everything into the case and buttoned it up with new rubber feet. This turntable suffered the same problem of excessive play in the platen spindle, so I did the oil bath trick again, and that sorted it out. After fitting a new belt the customer had supplied, and trying out the drive system, I was happy with the way it was running. The final job was to re-attach the AR badge lying in the bottom of the box to the correct location on the front of the case, and it was the job done! PA system repair R. J., of Laingholm, NZ found out what happens when amateurs and barely competent ‘professionals’ have a go at installing or fixing a large PA system. The result wasn’t pretty, so he had to spend some time cleaning up the mess... My main focus is in broadcast studios, but I do get to work at theatres and festivals and have a fair bit of January 2021  63 equipment that needs maintaining, so service jobs are part of the portfolio. In the ‘good old days’, a band or performer would turn up at a venue with a sound system of variable quality and crank it up to 11. But times have changed, and most venues now have good sound systems and some control over the volume. Bands have been replaced in some places by a DJ who can play any one of several thousand songs, making it even more important to have a quality sound system. I have an acquaintance who runs a performing artist booking business, and before he books performers, he checks out each venue. At one venue, he found the system to be terrible. The owner who recently purchased the business claims the system cannot be that bad because it cost $50,000; that was its value on the books when he took over the business. So I was called in. It was a restaurant/sports bar/dance floor and verandah in an industrial area building which looked like it had been a warehouse or a workshop. The restaurant and bar fit-outs were well done. The stage is bigger than most, and at one time, the venue had been fitted with an excellent system which was well worth the stated value when new. The only fault I could see in the layout was the positioning of the speakers above the stage. They are mounted behind the front line and close enough to a back wall to cause feedback problems. The shock came when I was shown the equipment rack, in a nonventilated office at the back. It seems that the venue had some sort of problem with the system which caused a number of the original amplifiers to fail. The cost to have someone come and fix it was deemed too much. It seems one of the regular clients of the bar said he could fix these things. He got it going again by taking out the non-performing amplifiers and replacing them with domestic stereo amplifiers! The original amplifiers disappeared, along with that patron... The system was in a state of chaos and disrepair. The owner wanted to stage the repair process because his venue had fallen on hard times, and costs have to be managed as the owner re-invents the place to meet the current market. This suited me as I could do it as a fill-in job. 64 Silicon Chip This system has a DBX Zone Pro controller which can switch any one of six sources to one of six zones. It was not switching as expected, and randomly dropping the level to various outputs. Fortunately, the agent is Jands who have a local office and some very competent people. There is no field service. The DBX needs to be assessed on a test bench, so I took it over. Next day they phoned to report that they’ve found the fault and that it is fixable at a reasonable price. I have it back in a day, armed with a warning that the problem is definitely heatrelated. Not only is the rack in the least ventilated part of a building, but there is also a kitchen adjacent, so the ambient temperature is warm. The rack is well-made and has four fans in the top, none of which work. We agreed this was an urgent matter, so I sourced four fans. The mounting screws were different, but with some assistance from a specialist, the replacements went in. The original fans seemed to have failed due to debris falling through the vents. I put the DBX back in with an air gap above and below, and a warning to the owner that if the temperature goes up, we will have problems. I also purchased an external fan to assist with airflow, and removed most of the junk on top of the rack, which was blocking the airflow. Reprogramming the DBX with the supplied software was easy. Working through the amplifier levels, I found that they were nowhere near what the venue needs. The monster amplifier in the rack used for driving the subs had failed. It was a brand no one knows and uses components we can’t find. It seems to have been a short-lived European import brand. I contacted the company who did the original install, but they were not helpful. One good thing about this system was the speakers. They were a wellknown European brand, and they all functioned properly. They all had power-handling capabilities well above anything we could deliver. There were two line-level XLR leads from the stage back to the DBX. Whenever someone plugged into them, there was a huge hum. I was told that it had been like this since the system was put in. On the stage, a mixer of indeterminate parentage was feeding audio to Australia’s electronics magazine the DBX. Replacing this with a small Alesis ‘fixed’ the problem; the Alesis line out is isolated from the local Earth. But 99% of the visiting equipment is not such a good design, so I would have to come up with a better solution. I located a couple of 600W:600W transformers which have good audio bandwidth. Don’t be fooled by the cheap ones; they only go to 4kHz, and the proper ones are not cheap. The wall box on which the XLR sockets are mounted has enough room for a small PCB and the transformers, suitably wired and insulated. Now anyone can plug into the house and get clean audio. So the main job left was to upgrade the amplifiers. We settled on a Class-D Talon amplifier, which claims to deliver 2 x 450W. One was purchased to see how it performs, and the result was stunning. It has XLR inputs and can be run in bridged mono mode. There are two fans, and the unit is quiet and runs relatively cool. The owner was impressed and some time later called me in, and we ordered several more. Another afternoon’s work, and we had a system which was performing as well as ever. I can’t believe the domestic stereo amps lasted as long as they did. At least one was cutting in and out on one channel; likely, its power supply was not up to 5+ years of 12 hours of daily use. The other just had trouble making steam. The two originally installed Aussie-made amplifiers are still working. But there was one last problem remaining. The venue has an AMS music system which streams music and video to each client over a proprietary system via an HP laptop computer. When this system was installed, a ‘contractor’ was booked by AMS to run the cabling. The cabling is not part of the rented system, so its maintenance is the venue’s responsibility. From what I could see, it had not been done properly. One was run over Cat5 via a balun which has one coaxial wire and a pair of wires originally intended for feeding DC. There was another balun at the end of the 40m cable with some RCA connectors that had been grafted in place of the original BNC connectors. That it worked was more by chance than design. The baluns were not designed for audio, resulting in significant losses of both low and high audio frequencies. Cat5 has varying twists on siliconchip.com.au its four pairs, and the only pair suitable for audio is blue/white (pins 4 & 5). Replacing this cabling was not an option given the cost. I tried to source some Cat5 audio baluns but had difficulty finding them. I eventually got hold of some suitable RJ45 termination. An hour or so and we have an ‘improved’ cabling system which delivers audio at high quality over Cat5. Just why this was never run with proper audio cable and terminated with XLRs or TRS jacks will never be answered. The venue now has a grunty music system which was well tested over the next weekend, and a reliable pub quiz system which fills the place on Tuesday nights. HP5100 frequency synthesiser repair R. F., of McCrae, Vic wrote in to tell us a little bit about how he got into electronics (see the Mailbag section in this issue). In that letter, he mentioned that he was fixing up an HP5100 frequency synthesiser. Here are the details of what was wrong with it, and how he fixed it… My earliest recollection of a “fabulous” electronics device was on display at an open day for prospective students in the old cream brick Electronic Engineering School at the UoM. It was an HP524A digital counter set up to measure the speed of a rotating shaft. It could measure frequencies up to 220MHz and weighed a massive 55kg. It had digital readout columns of 10 digits per decade. Somehow, it was very cool; one of my clock-building friends still has one. Years later, as engineering students, we keenly appreciated the precision and superb construction of the Tektronix 547 oscilloscope – one of the most sought-after instruments in our laboratory sessions. Hewlett Packard made a nice range of ‘scopes, but was more renowned for their general and specialised test equipment, which brings us to the devices needing repair. Back when I was home-brewing amateur radio linear amplifiers for HF and two-metre operation, I decided that I needed an accurate, high-resolution signal generator. I heard of an HP5100A synthesiser available at a give-away price, so I bought it. However, it needed an HP5110B synthesiser driver, and despite an exsiliconchip.com.au haustive search via eBay and other channels, I could only find the driver as part of a pair; the other part was a J02 HP5100B synthesiser. The HP5100A could generate signals in 0.01Hz steps from 0.01Hz to 49.99999999MHz, whereas the J02 HP5100B generated signals in 1Hz steps from 1Hz to 29.999999MHz. Fortunately, the HP5110B could simultaneously drive both synthesisers. So I bought the second synthesiser and driver as a package. To cut a long story short, I installed the two synthesisers, the driver, a Australia’s electronics magazine modified HP5061A caesium-beam frequency standard, an HP5245L electronic counter and an HP6263B DC power supply into – you guessed it – a Hewlett Packard Systems equipment rack. This massive collection of boatanchors weighs over 170 kg. The caesium beam tube of the HP5061A was unserviceable when I bought the unit for $100 about 15 years ago, but the unit had a highly-accurate 5MHz crystal oscillator in a temperature-regulated oven. So I stripped out the caesium beam assembly and related parts and replaced them with a January 2021  65 erating techniques all combine to produce exceptional performance. But inevitably, a small proportion of components do fail. Over the past few years, the performance of my units slowly deteriorated until I had no choice but to delve into them. Repairing the behemoths modern GPS receiver and controller to synchronise the oscillator. The very stable 1MHz output from the HP5061A is connected to the synthesisers, driver and counter to provide GPS-accurate synchronisation, and consequently extremely accurate and stable frequency synthesis and measurement. It still seems like a small miracle that all this stuff can work so reliably as a total package. There are thousands of components in the fully solid-state system, hundreds of discrete transis66 Silicon Chip tors, and just a few integrated circuits. Fortunately, the total power consumed with all devices on-line is just over 200W, so heat – the enemy of long-term reliability – is at a minimum. Clearly, the original HP designers realised that component quality and assembly workmanship had to be of the highest order to ensure a high MTBF rating, and this is part of the ‘wow factor’ associated with these early behemoths. Gold plated circuit board traces and pins, beautifully loomed cables, modular construction and simple opAustralia’s electronics magazine The front panel of the HP5100A synthesiser has an array of 103 pushbuttons to select the desired frequency. At the rear, it has 46 coax cables going to the HP5110B driver. A harmonic generator takes the output of the 1MHz master oscillator and feeds them through a series of filters. These produce signals with discrete frequencies of 30-39 MHz (in steps of 1MHz), which are fed to 10 of the BNC sockets on the rear panel. Each of these signals is also divided in decade dividers to produce 3.0-3.9 MHz signals which also go to rearpanel BNC sockets. A further three signals at 1.0, 3.0, and 24.0 MHz are generated as driver outputs. All output signals are extraordinarily stable and spectrally pure. An elaborate power supply produces voltages of +6.3V DC and -12.6V DC, and is always on to supply the temperature-controlled oven of the 1MHz master oscillator and the oscillator circuitry. A DPDT toggle switch with Standby and Operate positions supplies the rest of the driver electronics. I discovered that this switch was faulty, with a defect that I hadn’t previously encountered. The switch toggle operated and felt completely normal, but only one of its poles was actually switching, thereby leaving the -12.6V supply disconnected from the instrument in both standby and operate modes. A replacement switch brought the driver back to life. With the HP5110B driver working again, the HP5100A synthesiser performed well, but the J02 HP5100B stubbornly refused to generate an output signal. This near-twin of the HP5100A is not quite as complicated, having a reduced frequency range and lower resolution. “Only” 73 push-buttons are required to cover this range and resolution. The output frequencies from the synthesiser are all derived from the single 1MHz precision oscillator in the driver, and its 23 output signals. The synthesiser outputs are produced through the processes of fresiliconchip.com.au quency addition, subtraction, multiplication and division. The array of 73 push-button switches supply -12.6V to a matrix of diode switches. Each diode switch comprises one silicon and two germanium diodes, normally biased off by 6.3V applied to the silicon device. The -12.6V overrides the 6.3V through a resistive network and turns on the germanium diodes, allowing an RF signal to pass through the matrix with low loss and negligible delay. A full description of the synthesiser is beyond the scope of this article, but through an extremely ingenious combination of mixers, multipliers and dividers, the signals from the driver can be synthesised into any frequency between 1Hz and 29.999999MHz. The synthesiser function is implemented by a low-frequency section (3.0 to 39.0MHz) and a UHF section (370 to 390MHz). The latter section is mounted on an internal sub-frame which swings outwards from the instrument, to provide access to the various modules and their interconnecting cables. All told, there are 25 modules, many of them plug-ins, and 125 germanium PNP transistors. Despite its complexity, troubleshooting the synthesiser is relatively straightforward. If a single module fails, the device produces no output signal. Locating the faulty module, and confirming it is indeed at fault, is difficult; but access is easy, and all the modules contain discrete components (1964 was before ICs had hit the market). I reflected that even the transistor had only been invented 15 years beforehand, yet the mainly germanium transistors in the instrument were capable of reliable operation up to 390MHz. That led me to the 39 to 390MHz multiplier module, which indeed was faulty. I found that a 2N2402 transistor had failed. This PNP Ge device was rated at 18V maximum between emitter, base or collector and had a transition frequency of 220MHz. The nearest equivalent in my parts bin was a 2N3906 Si device, rated at 60V and with a transition frequency of 250MHz. It seemed to be operating as a ClassC amplifier, and biasing differences between germanium and silicon devices proved to be unimportant when its replacement with the 2N3906 brought the module and the entire instrument back to life. SC siliconchip.com.au Australia’s electronics magazine January 2021  67 A 2021 variation on an old theme . . . The Bass Block If you’re building a home theatre system, or want to listen to music with small monitor or tower speakers (because you don’t have room for huge ones, perhaps), then this subwoofer is for you. It’s compact and easy to build, but it pumps out plenty of bass to fill in the gaps left by smaller speaker systems. Virtually all music and movies can benefit from a healthy dollop of low-end sound! S ubwoofers have become collisions. So ideally, you want a commonplace in recent Features & specifications sound system which doesn’t just Frequency response: 40-100Hz, ±3dB; decades. There are sevdie off below 50Hz. 25-150Hz, ±5dB eral reasons for this: One is the Impedance: Traditional speaker designs nominally 4Ω Ω popularity of home theatre sys- Dimensions: (whether sealed or bass reflex 240 x 272 x 396mm tems with 5.1 surround sound Material: boxes, or more exotic designs 16mm thick MDF (where the .1 refers to the sublike horn-loaded or transmission woofer). Another is the increaslines) all have similar difficulty ing trend towards small speakers which are less obtrusive in reproducing this bottom octave without large drivers in a home setting. and enclosures. This is especially true where high sound Compact speaker systems (and many larger ones) tend pressure levels (SPL) are needed. to have a bottom end roll-off in the region of 50Hz. While Speaker manufacturers have responded by developing much of the satisfying bass components of music is in the drivers with extremely long excursions to “move more 50-60Hz range, there is still plenty below this level. For air”. Unfortunately, these drivers still tend to be large and example, the bottom A on an 88-key piano with modern expensive. tuning has a fundamental frequency of 27.5Hz. In recent decades, mathematicians and audio/acoustic For speakers with a -3dB point of 50Hz, at least half an engineers have developed new speaker enclosure configentire octave will be severely diminished, and the funda- urations which enable these bass frequencies to be repromental of the bottom note perhaps not heard at all; only duced in much smaller physical volumes. the overtones and harmonics. One such design, implemented by Julian Edgar, was the It isn’t just classical or piano music either; other types of “Bass Barrel”, presented in the August 1997 issue of SILImusic which have a lot of content in the 20-50Hz range in- CON CHIP – (see siliconchip.com.au/Article/4846). clude reggae, hip-hop, rap, rock and pop. And action movIt used a “Compound Isobaric 6th Order (A) Bandpass ies make good use of the lowest octave, Double Vent” enclosure. This type of cabBy Nicholas Dunand inet employs two drivers mounted faceto reproduce sounds like explosions and 68 Silicon Chip Australia’s electronics magazine siliconchip.com.au Behold the Bass Block, in all of its blocky magnificence! It is made from MDF, which you could just leave “natural”, but if you rout the edges and corners and paint it like this one, it looks a whole lot better. You could also glue speaker carpet to the outside (as was done with ye olde Bass Barrel). Read on for more details on how I achieved the finish shown. to-face in a ‘push/pull’ (out of phase) configuration, with each driver working into separate volumes with different vented tunings. The net effect of the chambers interacting is an acoustic bandpass response, where the upper roll-off, lower rolloff and passband frequency response can be manipulated. This is particularly useful for subwoofers. The Bass Barrel design has some advantages; chiefly, it is small and cheap to build. It used a novel construction technique that made building it much easier for people with limited facilities. I built a couple of these subwoofers (as conventional rectangular MDF boxes) for two small sound systems, and they were very effective. Fig.1: the predicted response of the subwoofer design, produced by “Speaker Box Lite”. The goal was to design a small sub with a useful response up to at least 100Hz, and down to as close to 20Hz as possible. With a free version of the iPad speaker design app “Speaker Box Lite”, and using the original design as a starting point, I set about investigating the substitution of these new C3055 drivers. The design goals were: 1. Keep the boxes as small and unobtrusive as practical, with the smallest footprint. 2. Obtain the lowest possible bass extension. 3. Cross the subs over at around 90-100Hz to relieve the Tannoys of some of the bass demands. 4. Be able to take advantage of “room gain”, managed with equalisation and via the crossover. Initially, I plugged the Thiele-Small parameters of the new drivers and the original enclosure dimensions into the software. The predicted response was not a beautiful thing, so I started experimenting with different chamber volumes and ports. After many iterations using common sizes of PVC pipe for the ports, I settled on the following design. The total internal volume is 20L in two chambers: one of 15L, with a 210mm length of 32mm inner diameter electrical conduit for the port, and one of 5L, using a 180mm length of 63mm internal diameter plumber’s pipe for the port. The box is made of 16mm MDF with both ports facing forward. In the course of testing, I ran simulations on larger box sizes. One design produced predicted bottom-end extension flat within ±1dB down to the mid-20Hz region. I built a test box, and the measured response proved that it was delivering well down in the predicted region. The internal volume of this design was 36 litres, but in the end, I rejected it as simply being too large for me. The predicted response from the software for the configuration I selected is shown in Fig.1. After building a test box and measuring in a ‘free-air’ environment, the measured response is shown in Fig.2. It isn’t precisely as predicted, but close. Note that this measured response has 1/6 Fig.2: the actual ‘free-air’ response of the test sub built to the specifications used to produce Fig.1. While not an exact match, it’s pretty close and certainly meets the design goals. The response changes somewhat when the sub is placed within a room. Fig.3: here is the room response, and by comparing it to Fig.2, you can see the standing waves created at certain frequencies by sound waves reflecting off hard surfaces. This results in a faster high-end roll-off but also a useful amount of low-end boost. Updated version Having recently acquired a pair of Tannoy ‘bookshelf’ studio monitors for another system, I decided to make another pair of stereo subs to go with them, to fill out the missing bottom octave. Referring to Altronics catalogue for the original drivers used in the Bass Barrel (“Redback 6.5-inch woofers”, Cat C3086), I found they were no longer available. There is, however, a ‘replacement’ driver, the 165mm (6.5”) 30W Woofer / Midrange Polypropylene Speaker (Cat C3055). This driver has advantages and disadvantages compared to the original. It has a reduced power handling capacity, so the maximum possible SPL is lower. If you want to build a subwoofer for a large home theatre set up, and have the plasterboard crack whenever a Star Destroyer rumbles overhead, this may not be for you. On the other hand, the driver parameters are more suited to this application, allowing a deeper bottom end extension than the original design. So it’s not that this design is bad for home theatre use; in fact, it is very well suited, just at more moderate levels. (Your neighbours can thank us later!) Design process siliconchip.com.au Australia’s electronics magazine January 2021  69 Fig.4: here, the response from the two ports is shown, along with the overall response of the subwoofer. This gives you an idea of how the two separate cavities and ports contribute to the extended flat response of the subwoofer. Fig.5: the response that’s possible from this subwoofer with equalisation applied. It is now mostly flat from 24Hz up to just over 100Hz; an excellent result for a sub this small! octave smoothing applied. This is a nice, clean response. On the face of it, the response is not ideal due to the gradual and increasing roll-off at the bottom end. However, it is only down by 6dB at 30Hz and about 9dB at 25Hz. This is less of a problem than it appears. the order of +6dB of ‘room gain’ at 25Hz, which effectively enhances the raw bass performance of speakers. Unfortunately, the same reflections which can enhance the bass also interact with the direct sound coming from the speakers, producing what are commonly (probably incorrectly) referred to as “nodes”, where the amplitude of the sound waves add, and “nulls” where they cancel out. The actual result is entirely dependent on the speaker, its placement, the room size and shape and the types of surface treatments (eg, carpet, timber or tiles). The result is that it is often difficult to predict and control the room nodes. I placed the stereo subs in my room and measured the response at the listening position, which is shown in Fig.3. Again, this measurement has 1/6 octave smoothing applied, and all the good and bad results of room effects are plain to see. While room nodes at 40Hz and 60Hz are a problem, the worst peak is only +6dB. Moving the speakers would likely change the response considerably. Depending on the phase relationships at these points, it may be possible to cancel out the nodes. Room gain At mid-to-high frequencies, the propagation of sound from speakers is increasingly directional. This is commonly referred to as a “two pi” response. However, at lower frequencies, the sound propagation becomes more omnidirectional or spherical, referred to as a “four pi” response. There are several consequences of this characteristic. The first is that it becomes less apparent where the sound is coming from, and the speaker placement becomes less critical for the stereo image. The second is that the very long wavelengths at these frequencies pressurise the room to a certain extent, and interact with the room boundaries (especially the floor, where subs are typically placed). The net effect of this is bass boost, which increases as the frequency drops. It’s fairly typical to get something in 396 396 272 240 272 240 240 240 240 396 240 396 240 900 x 9 00 SHEET FOR A SINGLE UNIT 240 Fig.6: the easiest way to cut the 16mm panels for the subwoofer(s) is to cut three strips from a 900x900mm (or 900x1800mm for two subs) sheet of MDF, then cut the strips into the lengths shown. 70 Silicon Chip Fig.7: the basic layout and dimensions of the subwoofer. The hole which is used for mounting both drivers is 148mm in diameter and comes within 18mm of the edge. The upper port hole is approximately 68mm in diameter while the lower port hole is 40mm in diameter (if using the recommended pipes). Australia’s electronics magazine siliconchip.com.au Fig.8: start by glueing and screwing (or nailing) the first three panels together like this. Fig.9: next, add the inner baffle and base panel. On the plus side, the room gain has raised the measured response so that it is now only about -4dB at 25Hz. Subjective listening tests bear this out. Observing a Spectrum Analyser while listening to music will reveal that not a lot of recorded music actually has much full-level content in the range from 20Hz to 25Hz. However, deep bass from 25-50Hz is often present in rock, dance and reggae music. Where it is, the boxes produce a satisfying level of tight and clean deep bass at any volume level that I listen to, and when integrated with the main speakers, the overall full range response is rich and smooth. When the boxes were driven with higher levels of pure low-frequency sinewaves, there was some “chuffing” or port noise coming from the small diameter port, but in real-life use (eg, listening to music), it was inaudible to me. More for interest than anything else, I measured the output from each port separately. This is shown in Fig.4. As expected, the low-frequency response from the larger chamber with the small port, while the higher frequencies come from the smaller chamber with the large port. Crossover and equalisation Although acoustic bandpass designs like this have an inherent high-frequency roll-off, this is not good enough to use as the crossover. These drivers have a rated response up to 4kHz. Without a crossover, these higher frequencies are audible from the finished sub. This would lead to undesirable interaction with the main speakers, so signals at these frequencies need to be removed. My Tannoys have a response down to around 50Hz, but I wanted to relieve them of some of the bottom end effort, so I aimed to cross them over at about 90Hz. So the subs had to reproduce up to at least that frequency. As mentioned earlier, the directionality of low-frequency sounds is less apparent than higher frequencies, but at 90Hz, this effect is certainly not absolute. Directional information in the music content is audible at 90Hz. So for hifi use, I needed a stereo pair of subs. The cost of these drivers is so modest that it hardly broke the bank, and the upside is a doubling in the sound output enables higher ultimate SPLs without overdriving the subs. I am using miniDSP signal processors to cross over the subs to the main speakers, and also to equalise the speaksiliconchip.com.au ers and the room. There are two versions of this device, the standard miniDSP (siliconchip.com.au/link/ab4c) and the HD miniDSP (siliconchip.com.au/link/ab4d). You could also use our DSP Active Crossover and Equaliser (May-July 2019; siliconchip.com.au/Series/335) or the 3-way Active Crossover for Speakers (September & October 2017; siliconchip.com.au/Series/318). The miniDSP units provide many options for crossing over and parametric equalisation of both its inputs and outputs, to help manage speaker and room idiosyncrasies. Applying a modest amount of correction with these units can easily yield a corrected free air response like that shown in Fig.5. This is an advantage of a design with a long shallow roll-off rather than one which is initially deeper, but drops off steeply. Construction Refer to the parts list to gather the required supplies. Fig.6 shows a cutting diagram to help you cut the panels required. The 240 x 240mm sheets are for the top and bottom of the enclosure, plus the internal baffle. The sides are 240 x 396mm while the front and back pieces are 272 x 396mm. If you haven’t already, cut the conduit and pipe to length. Fig.7 shows what we are aiming to build. The small port dimensions I chose were optimised to Parts list (to make one subwoofer) 1 900 x 900mm sheet of 16mm thick MDF 1 210mm length of 32mm internal diameter electrical conduit (40mm outer diameter) 1 180mm length of 63mm internal diameter PVC (plumber’s) pipe 2 165mm (6.5in) 30W polypropylene woofers [Altronics Cat C3055] 1 pair of panel-mounting speaker terminals 1 1m length of twin conductor speaker wire 4 spade crimp terminals, to suit speaker wire thickness 1 roll of acrylic speaker dampening material [Jaycar Cat AX3694] Nails, wood screws, construction adhesive, paint as required Australia’s electronics magazine January 2021  71 Fig.10: then add the side panel and glue in the port pipes (if you haven’t already). Make sure the joints are well sealed. provide the long, shallow roll-off I was pursuing. I made the ports from thick-wall 40mm outer diameter electrical conduit. Although it is quite cheap, it is typically sold in 4m lengths (for around $9), leaving a lot left over. An alternative is to use 40mm plumber’s PVC pipe with an inner diameter of 38mm. This has the advantage of being available in short lengths from hardware stores, and the larger diameter would likely reduce the risk of port noise. However, this small difference in diameter produces a notable difference in response, with a flatter initial (higher frequency) curve, but a steeper roll-off. Taking into account room gain, this would likely result in a peak at around 30-40Hz, which is not so good for HiFi use, but may well suit a home theatre application. Another option is to use PVC pressure pipe with an inner diameter of 30mm. This produces a predicted response closer to my chosen solution, but the smaller diameter of the pipe risks increasing port noise under higher SPLs. I chose the dimensions of the box to provide both a small footprint and to simplify cutting. The pieces come from three MDF strips. After cutting the strips, you can then cut the individual pieces to length. If you have limited facilities for cutting straight lines, cabinetmakers and even timber suppliers will sometimes cut pieces to order, or perhaps just the strips if you have a drop or slide saw to cut the lengths. The sheet sizes specified are commonly available at hardware stores, and there will be a little left over, but not much. The general construction procedure is: 1. Cut the individual rectangular pieces. 2. Use a jigsaw to cut the 148mm driver hole offset in the baffle, the port holes (note: not portholes!) in the front panel and (if appropriate), a hole for the speaker terminal in the back panel. 3. Drill the holes for the speaker mounting bolts in the baffle. 4. Cut the port tubes to length, glue them into the front panel with construction adhesive and put it aside to cure. 5. Starting at one end, glue and screw the first three pieces together flush, as shown in Fig.8. If you have a small 72 Silicon Chip nail gun, putting a couple of tacks in first will hold everything in place until the screws go in. 6. Fix the baffle in place, then the other end piece (see Fig.9). Remember to mount the baffle with the offset driver cutout closest to the still-open side 7. Mount the drivers and wire them up to each other (out of phase) and to the speaker terminals. I recommend applying a small amount of sealant to the rims of the speaker and around the mounting holes, as well as the hole where the lead passes through the baffle. You can wait until the facepiece is mounted to do this, but it’s easier now. 8. Fix the face panel (see Fig.10). 9. Place some polyester wadding around the inside surfaces of the two chambers. 10. Fix the last side in place or, if you want to make it removable as with my test boxes, apply some thin foam as a gasket and screw the side on without glue. Aesthetics There are various options for finishing the boxes. Automotive type carpet was particularly practical for the original Bass Barrel because the cylindrical shape was relatively This test speaker was built with a thick piece of acrylic in place of one of the MDF side panels. I did this so that I could observe the driver excursion, to make sure it was not excessive. I don’t recommend that you do this, but you could if you really want to. Australia’s electronics magazine siliconchip.com.au Panel: Making the measurements The software I used for measuring the subs’ actual response is Room Eq Wizard (REW). This excellent, comprehensive software produces a sinewave swept from 15Hz up to 20kHz and samples the response picked up by a microphone (or sound level meter). It can then apply many analytic processes to the measured result, not just frequency-domain measurements. The process involves first measuring the ‘native’ response of the speakers, then measuring the whole system response in a real-world room setting. The native response shows what the speakers would produce in a completely neutral environment, but in real life, of course, this never exists. Acoustic engineers make these measurements in an anechoic chamber where all reflections and external interference can be effectively eliminated. Without an anechoic chamber, the unwanted influences can be reduced in a couple of ways. One is to make the measurements in the most open environment possible. Making the measurements outside in the middle of a sports field would go a long way to eliminating the effects of room interference, but is hardly practical. Many of the response graphs in this article were made in a very large empty workshop, with the speakers about 2m above the ground. These are the measurements I have referred to (perhaps erroneously) as ‘free air’. Although it is certainly not equivalent to an anechoic chamber, it is as near as I can come for practical purposes. Another way to reduce unwanted interference is to make measurements ‘nearfield’. This involves placing the microphone quite close to the speakers and making the measurements at modest SPLs. In a nearfield position, the relative SPL coming from the speaker is much higher than that of the reflections coming from the environment. Consequently, impingement of the interference on the measurement is largely reduced. For these measurements, I used a calibrated microphone from miniDSP (siliconchip.com.au/link/ab4e). Unlike professional microphones costing many hundreds or thousands of dollars, these USB microphones are cheap! The microphones don’t need to be fancy (or accurate for that matter), they just need to be able to sample the full spectrum of audible sound, and be themselves measured. Each microphone is supplied with a siliconchip.com.au matching calibration file, which is then loaded into the measurement software, to adjust the incoming measurements accordingly. Note that in all the response plots, you can disregard the varying absolute amplitude measurements on the left Y-axis of the graph. These simply reflect different measurement volumes at various locations and points in the room. What we are really interested in is the relative flatness and smoothness of the response. The small-scale variations in the curve are dependent on the measured frequency response, of course, but also the ‘smoothing’ applied to the response graph. Speakers never reproduce all frequencies equally, and room effects produce responses similar to comb filtering, where nodes and nulls cancel or enhance particular narrow frequency bands. These can easily be heard if you put a sine wave generator with uniform amplitude into the system and very slowly sweep through the frequencies. Many dips and peaks can easily be heard as changes in volume as the frequency changes. In many cases, though, these narrow bands are never heard in real-world listening to music. REW can take up to one million samples per sweep of the audio spectrum (although I settle on 512,000). This means that it can resolve tiny frequency band variations which might not be at all audible. For practical use, the response plots can be ‘smoothed’ for different purposes. The software offers smoothing options from one octave (which produces a curve that manufacturers might like to present to customers) through to 1/48th of an octave, which reveals many artefacts which might not be audible. There are also specialised options like “psychoacoustic smoothing”. Plots of the sub’s response with various smoothing options are shown in Figs.a-e. Throughout the article, I’ve used 1/6 octave smoothing, which reveals plenty of detail without showing extraneous information which is probably not relevant. The 1/6 octave smoothing comes out looking much like the psychoacoustic option. Note that the psychoacoustic smoothing reduces some of the low-frequency peaks and troughs visible with 1/6th octave smoothing, and accentuates some in the higher frequencies. Without knowing the algorithm used to make this smoothing, it’s probably fair to say this is intended to provide a more accurate representation of what the human ear would perceive. Australia’s electronics magazine Fig.a: one-octave smoothing gives an almost useless result – it’s just too smooth! Fig.b: 1/6th-octave smoothing is about right. You can see the details of the response, including standing wave peaks and troughs, and accurately gauge the turnover points and roll-off steepness. Fig.c: 1/48th-octave smoothing also gives a reasonably good result, although it’s questionable whether the extra detail is helpful. In some cases, such as when optimising edge diffraction, it could be. Fig.d: without smoothing, the result is similar to 1/48th octave smoothing over most of the portion of interest, but gets very noisy above 200Hz, mainly because the sub isn’t producing much (if any) output at those frequencies. Fig.e: psychoacoustic smoothing is an interesting option as it appears to give a useful curve that supposedly compensates for the properties of human hearing. January 2021  73 easy to wrap, and trim out with edging. The block shape here would make the trimming a bit more of a fiddle to get a neat finish. An alternative is polish over iron-on timber veneer, or a laminate finish or, as I did, a paint finish. I began by rounding over all the edges with the router (making sure all the nail and screw heads were well down so the router didn’t hit them). I also rounded over the port openings. Theoretically this smoothes the passage of the air as it pumps in and out of the ports and reduces the likelihood of chuffing. I couldn’t hear any difference, but I liked the appearance better. After routing, I filled and sanded all the holes and applied a general primer to seal the MDF. It takes quite a lot of work of filling and sanding to completely hide the joins in MDF boxes – they can stubbornly show even after several coats of automotive spray putty. I used a pressure pack can of “Granite Effect” paint to create the texture. This paint comes out as splatters of different greys to simulate granite. I didn’t want the light/ medium grey colour of the paint, but I used it to create the base texture surface. The top coat was a satin dark “charcoal” colour. But this material is expensive, difficult to work with, and certainly not needed for the functioning of the box. You can also see that the boxes are “empty”. It is common practice to put damping material inside speakers, which can provide various benefits. I tested the boxes with differing amounts of stuffing, but the frequency response didn’t change at all. That does not mean that it serves no function. I didn’t test impulse response, for example, and damping material may well help in this respect. In the end, I left some in on the surface opposite the drivers. SC What about a barrel? The design presented here is not particularly suited to the PVC pipe construction used in the original “Bass Barrel” article because of the port lengths. But it is possible to tweak the design so you can build it that way – see Fig.11. The material for the baffle and the ends is 16mm MDF again. In this case, the 63mm inner diameter pipe is 200mm long instead of 180mm. The 32mm inner diameter pipe is still 210mm long. This results in a predicted response as shown in Fig.12. The response is similar to my original design with a 38mm diameter small port: the overall response is flatted, but it has a steeper roll-off, which when room gain is taken into consideration, might produce a less ‘manageable’ result. Using this design with the 38mm port accentuates this characteristic, with a further raising and straightening of the initial curve and a steeper low-end roll-off. I was not personally interested in this construction method, so I did not build and measure a test speaker. Most likely, further tweaking could produce alternative (possibly enhanced) variations for this construction method. Speaker Box Lite (and similar) software enables many different configurations of drivers and enclosures to be investigated easily. TUBE 68 DIAMETER 168 ~300mm (eg STORM WATER PIPE) Fig.11: if you want to make a “Bass Barrel” as per the August 1997 article, but with currently available drivers, here are the dimensions. If you don’t have an anechoic chamber but want to characterise speaker response accurately, you either need to do it in a wide-open space, or else perform ‘nearfield’ measurements, as shown here. This involves placing the microphone very close to the speaker, so that reflected sound waves are at very low levels compared to the direct sound being measured, and thus do not unduly affect the results. This test was done prior to the final box coating. 74 Silicon Chip Fig.12: the predicted response of the barrel version of the subwoofer is very close to the rectangular version. Australia’s electronics magazine siliconchip.com.au 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. A reliable solar lighting system The steps to my shed do not all have the same tread depth and riser height. I am used to them, but I still have some difficulty on moonless nights. A few years ago, when solar-powered garden lights became available cheaply, I bought a few of them and poked them into the ground alongside the steps, and I could finally see the steps at night. The problem is, these things are only made to have a life of about 12 months if you’re lucky, and soon they needed repair or replacement. After going through a couple of repair/replacement iterations, I decided that I needed a more permanent solution. I had collected a few 18650-size Li-ion cells which still seemed to have some life left, so I decided to use these in a lighting system for the steps. I needed to mount the actual lights on something solid so they wouldn’t be destroyed by a brush-cutter. I mounted the LEDs in a length of rectangular steel tube from a discarded swing set. I mounted this so that it also formed a handrail for the steps using tubular steel supports concreted into the ground with welded brackets. The four LEDs came from a defunct garden light. Once they were mounted siliconchip.com.au to the underside of the handrail, I ran a cable into the shed. The accompanying circuit diagram shows the solar panel, battery charger and battery manager for the lights. The circuit switches on the lights at nighttime but switches them off once the battery is flat. The solar panel is a 10W, 12V type left over from a previous project, already mounted on the shed roof. The XL6009 buck-boost regulator module reduces the voltage from the solar panel to the 5V required to run the TP4056-based Li-ion battery charger. The low voltage cut-off circuit below prevents damage to the Li-ion cells from over-discharge. Op amp IC1a acts as a voltage comparator with the reference coming from VREF1, an LM385BZ. This device only requires tens of microamps to operate and produces an accurate 1.2V which is fed to pin 2 of IC1a. Its other input pin samples the battery voltage via a 120kW/100kW divider. When the battery voltage falls to 2.7V, the output of IC1a goes low and so NPN transistor Q2 switches off. The gate of Mosfet Q1 is then pulled up to its source voltage by the 100kW resis- Australia’s electronics magazine tor, so Q1 turns off, preventing current from flowing from the battery to the LEDs. About 200mV of hysteresis is built into the switching point by the 560kW positive feedback resistor. The LEDs are also switched off during the day due to the action of NPN transistor Q3. When the solar panel voltage rises above about 1.2V, Q3’s base-emitter junction is forwardbiased, and so it switches on, pulling the battery-related voltage at pin 3 of IC1a low, close to 0V. This is sensed by IC1a as if the battery is flat, so again it switches the LEDs off. The rest of the time (ie, when the battery is above 2.7V and the solar panel is in darkness), the LEDs are connected across the battery and so they light up. The garden light LED modules incorporate current-limiting resistors to prevent them burning out with a fully charged (4.2V) battery, not shown on the circuit diagram. Note that Q1 was chosen so that it would present a low channel resistance with its gate at -2.7V compared to its source, ie, just before the low-battery cutout activates. It must also have a sufficiently low on-resistance to avoid getting too hot (~20mW in this case). K. G., One Tree Hill, SA. ($80) January 2021  75 Converting a cheap welder to a high-current battery charger I modified a low-cost Kenstar 200A IGBT inverter welder so that it can be used as a welder or a battery charger. An added switch and relay allows either of the two functions to be selected. The circuit uses the common UC3846 switchmode controller chip. Its output voltage can be varied from 11-22V, with the typically ~14.4V charging voltage for 12V lead-acid batteries well within this range. Generic IGBT or Mosfet welders are cheap to buy and usually easy to repair or modify. If they fail, it is often the auxiliary ±24V power supply module that is faulty. I bought my welder for $7 in a nonworking condition and repaired it for a few dollars. For any engineer used to working on mains-powered equipment, it is easy to modify it to charge a car battery. The high-voltage side does not have to be changed – only the lowvoltage control board. I purchased a low-cost LED voltage/ current meter online to display the battery voltage and charging current (see our article on these meters in the De- cember 2020 and this issue on p102; siliconchip.com.au/Series/306). It is necessary to add a current shunt resistor to sense and display the charge current; most meters come with the shunt. Both are shown in my circuit diagram. The modifications for switching between charging and welding are as follows. I added a 12V regulator on the +24V rail which generates a voltage to switch the coil of the added relay via the charge/weld switch. I cut the connection between pins The modifications marked on the welder – remember to be careful when working on mains-powered equipment. Radiating test antenna for AM radios Most transistor radios, and many later valve models, use ferrite rod antennas. While some of these provide external antenna/Earth connections, most don’t. While it is possible to connect a signal generator directly to sets that do have antenna connections, proper alignment demands the use of a ‘dummy’ antenna to mimic the capacitive nature of the few metres of wire typically used. This radiating antenna solves several problems. It will work with all sets using ferrite rod or wire loop antenna circuits, needs no electrical connections to the set being tested and, for ferrite rod antennas, gives an actual 76 Silicon Chip sensitivity calibration in microvolts per metre (µV/m). The antenna uses an ordinary 200 x 9.5mm ferrite rod. The coil is seventeen turns of wire, 0.4-0.65mm diameter (22~26 B&S gauge), spaced over 100mm. The two resistors, 100W and 82W, are carbon types. The antenna can sit in a simple non-metallic cradle of timber or plastic. Placed close to the set under test, it’s possible to inject IF signals at a high enough level for IF alignment, even for the low-sensitivity Regency TR-1 with its unusual intermediate frequency of 262kHz. This eliminates the difficulties of injecting to the converter base in compact sets. Australia's Australia’s electronics magazine For broadcast alignment, set the radiating antenna 600mm from the receiver’s antenna and parallel to it, and align at the usual frequencies of 1610kHz for the oscillator trimmer, 600kHz for the local oscillator coil and antenna and 1400kHz for the antenna trimmer. Once you have completed alignment, you can easily determine your set’s sensitivity for 50mW output. With the radiating antenna 600mm from the set’s antenna rod, divide the generator output by 20 to get the field strength at the receiver. For example, a signal generator output of 20mV RMS gives a field strength of 1mV/m at the receiver. The radiating loop gives useful results on sets with frame antenna loops, but the radiating loop must be aimed perpendicularly at the frame antenna for measurement results. This design is based on information in Mingay’s Electrical Weekly, October 18, 1963: Pye Caddy Transistor Portable Receiver Service Data Sheet. Ian Batty, Rosebud, Vic. ($80) siliconchip.com.au 6 and 7 of IC2, the UC3846, and I also cut the connection between output pin 1 of op amp IC1a and input pin 12 of op amp IC1d. Both of these broken connections are re-connected via the added relay contacts when it is energised (ie, when the switch is in the WELD position), hence the circuit works as it did before. The switchmode controller operates to regulate current while in welding mode, and voltage in charging mode. Current feedback to IC2 is usually via IC1a and IC1d as mentioned above, but when in charging mode, I instead feed the 5V reference voltage from pin 2 of IC2 back to pin 12 of IC1d via one of the relay’s normally-closed contacts, disabling current regulation. siliconchip.com.au In the case of pins 6 & 7 of IC2, these are also disconnected when in CHARGE mode, and there is instead a 12kW resistor connected between these pins (it’s shorted out when the relay contacts close). This changes the compensation in the feedback loop of the switchmode controller, which is necessary for stable operation in the 11-22V range. When in CHARGE mode, the output voltage is set by potentiometer VR1 which is connected across the output terminals with 12kW padder resistors at either end (to limit the adjustment range to be within the capabilities of the controller) and an added 10,000µF 25V filter capacitor. The 12V zener diode is to protect IC2 Australia’s electronics magazine from excessive feedback voltages. The feedback voltage from the wiper of VR1 goes to pin 6 of IC2 (EA-) via one of the normally closed relay contacts. This switches the controller into voltage regulation mode for battery charging. Now, when my car battery is a bit flat, two minutes charging at 20A will get the car started. Please see my YouTube video on making these changes at https://youtu.be/a2G7hFAv02k Warning – working on mains-powered equipment can be dangerous. Do not attempt these modifications unless you are an experienced engineer. It is not for beginners! John Russull, Cambodia ($120). January 2021  77 For those times when you DON’T want to be interrupted . . . I’m busy. Go away! OK, it’s a bit tongue-in-cheek . . . but it could have other, more serious, uses. The Busy Dunny Door Warning flashes a bright LED light on the door when you, ahem, don’t want someone barging in. When you leave and open the door the light goes out! It’s a simple idea with a real simple circuit – but it makes a superb beginner’s project . . . T he idea for this little project came about when avid SILICON CHIP reader John Chappell was sitting, reading his latest copy . . . and the dunny door burst open, with obvious embarrasement all around. So maybe he had taken a bit longer than normal; maybe he was so engrossed in the magazine that he didn’t hear anyone yelling out . . . but it started him thinking how to avoid the delicate situation in the future. One problem was that the door lock, umm, didn’t. So without replacing the lock, how 78 Silicon Chip to let others know that the best seat in the house was, umm, occupied – without the embarrasement! Light bulb LED moment Of course, that was the answer: a bright, flashing LED that would let others know not to barge in. If it was made somewhat automatic – ie, it turned off when the outhouse door opened to let him out, so much the better. And this really simple circuit is the outcome. Original by John Chappell Australia’s electronics magazine When the pushbutton (S1) is pressed, both the LED mounted on the door and the internal LED start flashing. Why two LEDs? One is the ultrabright warning LED mounted on (or through) the dunny door to warn others that it is occupied. The second (internal) LED merely confirms that the circuit is operating. Overkill? Perhaps - but at the cost of a 10c LED and a 5c resistor, it doesn’t add much cost to the project. When the dunny door is opened, a magnetic reed switch resets the cirsiliconchip.com.au You’re looking at the entire project! On the left is a reed switch and magnet which turn the LED off when the door is opened. At right is the door-mounted ultrabright LED, while the internal LED in this case is integrated with the pushbutton “start” switch cuit and the LEDs turn off. It really is that simple! As we said earlier, it makes a great beginner’s project. Parts are as cheap as chips; it’s battery operated (and the battery will last for yonks) and it doesn’t use any of those pesky surfacemount devices that beginners have so much difficulty soldering. Total assembly time shouldn’t be much more than an hour. The circuit It’s shown in Fig.1 – and as you can see, there’s not much to it! It’s based on a 4093B CMOS quad 2-input Schmitt trigger NAND gate chip (IC1). Now if all those words scare you, don’t worry: see the panel “What is a NAND gate?” and all will be revealed. The four NAND gates are configured in different ways. IC1a is an inverter: when its inputs are low, the output is high (and vice versa). With the door closed, the magnet pulls the “normally open” reed switch closed, which in turn means IC1a’s inputs are both low – so the output is high. IC1b and IC1d form a latch with the inputs to IC1d normally high. Think of a latch just like a door latch: it’s normally at rest but needs someone to actuate it. In this case, when the push button siliconchip.com.au (“Start”) switch is pressed, the latch is reset by forcing pin 12 of IC1d low which forces the output, pin 11, high. This also enables IC1c, with its 47kΩ resistor and 10µF capacitor, to start oscillating, with its output going high and low at a rate set set by the time it takes the tantalum capacitor to charge and discharge – in this case the rate is about one second. As it goes low, the two LEDs connected in series between its pin 10 output and +9V become forward biased and therefore light up. Incidentally, you can change the flash rate by changing the resistor and/ or capacitor. Increasing either (or both) will slow the rate down and, as you would expect, decreasing will speed the rate up. When the door is opened, the reed switch opens (when the magnet moves away), IC1a inputs go positive because of the 100k resistor connected to 9V and the circuit reverts to its dormant state. Power The circuit is powered by a single 9V battery which, due to the intermittent drain, should last for almost as long as its shelf life. For the same reason, no on/off switch is provided or needed. (Of course, if you decide to read War and Peace during your “visits” you might not get quite that life). l l Fig.1: the circuit consists of one quad Schmitt NAND gate, designed to flash an ultrabright LED mounted on the door. It is actuated by S1, the “Start” switch and automatically turned off when the door is opened. Australia’s electronics magazine January 2021  79 Fig.2: the PCB component overlay will help you place the components in the right positions. Watch the polarity of IC1, the diode and LED and both of the capacitors. This PCB is different from the photo at right in that it has “extensions” on it to allow it to snap into place in the Jiffy box. These can be cut off if not needed. The battery snap leads can connect to a header set, or feed under the board and up through the hole at bottom left before soldering to their respective pads from the board top. This gives some strain relief to prevent the rather thin leads breaking off. A 1N4004 silicon diode is included in series with the battery to prevent damage if you try to connect the battery back-to-front (surprisingly easy to do!) A single 10µF capacitor bypasses (or filters) the 9V supply. While a tantalum capacitor is specified in the parts list, you will probably note from the photos that a standard 10µF 16V electrolytic was used. Either is fine – but the other 10µF capacitor (on pin8 of IC1c) should be a tantalum. Construction There are only ten components to solder to the PCB and only five of these are polarised: the 4093B IC, of course, the on-board LED, the 1N4004 diode and the two capacitors. Fit the resistors first – as well as reading the colour codes in the parts list, use your multimeter to confirm their value. In the case of the tantalum capaci- The PCB photo is reproduced larger than life size. It is of an early prototype and there are some differences between the overlay and this board – for example, S1 and LED1 are both housed in the same bezel (you can use this type or a separate LED and switch). Also in this case, the battery connector is “hard wired” to pads on the board and using the hole at lower left for strain relief. tors, the + marked on their body goes to the + mark on the PCB. (“Ordinary” electros have the – leg marked; this of course goes to the – mark on the PCB). Similarly, make sure the stripe on the diode aligns with the stripe on the PCB. Finally, note the notch on the end of the quad gate IC: it goes closest to the right edge of the board. The anode of the internal LED is the longer of the two leads – again, it goes to the “A” marked on the PCB. S1, the “start” switch, should be soldered direct to the PCB. The reed switch and external LED both connect via thin insulated wires to their respective screw terminals on the PCB (reed switch to CON1; LED to CON2). Watch the LED polarity – make sure the anode connects to the A marking on CON2. Before drilling the case and mounting the completed PCB, connect the 9V battery and check operation. Hold the door magnet close to the reed switch, then press S1. Both LEDs should start flashing; move the magnet away from the reed switch and they should stop flashing. If none of this happens, check your The battery snap wires are quite thin, so they go through a strain-relief hole in the PCB before soldering to their respective pads. As mentioned in the text, the capacitor at lower right is specified in the parts list as tantalum but here, a standard electro is adequate. The other capacitor (the yellow component) should be tantalum due to their lower leakage. 80 Silicon Chip Australia’s electronics magazine component placement, orientation and soldering. With so few components, there is very little else that could go wrong. If all else fails, measure the battery voltage when the circuit should be on. It should be at or very close to 9V. Mounting the PCB The board sits upside-down in the Parts List – Dunny Busy Warning 1 PCB, 38.5 x 49mm; code 16112201 1 UB5 Jiffy case, 83 x 54 x 31mm [eg, Jaycar HB6025] 1 reed switch set (reed switch & magnet - often sold for alarm systems – eg, Jaycar LA5027) 1 small momentary contact pushbutton switch (S1) # 2 mini PCB mount connectors 1 4093 quad Schmitt NAND gate (IC1) 1 1N4004 diode (D1) 1 ultrabright red LED [eg, Jaycar ZD0102] 1 standard red LED # Suitable mounting for internal and external LED 1 9V battery snap 1 9V battery Capacitors 2 10µF 16V tantalum Resistors (0.25W, 1%) 2 100kW (brown black yellow brown) 1 47kW (orange violet orange brown) 1 1kW (brown black red brown) # we used a pushbutton switch with an integrated LED; provision is made on the PCB for this or for separate switch and LED. siliconchip.com.au Fig.2: the PCB mounts upside-down in the case, held in place by the notches in the case edge. The component at left (on the red/black wires) is the ultrabright LED which mounts on the door. jiffy box – the board is designed to snap into the captive guides on the box sides. You’ll need to drill holes in the bottom of the case (which becomes the top!) for “start” switch (and internal LED). If the start switch is soldered directly to the PCB, you need to be quite accurate with the hole placement. Another hole is needed in the top of the case (which becomes the bottom!) for the wires to go off to the reed switch and to the door LED. Mounting the door hardware The exact location of the warning LED is entirely up to you – whatever gives the best visibility. That might be actually through the door . . . or it could be on the door jamb. A wide variety of LED bezels is available, some of which are designed to work through a door or jamb. Or you might simply glue the flat base of an ultrabright LED to the outside of the door, with a couple of fine holes for its leads/wires. The reed switch and its magnet need to be placed so that when the door is closed, the magnet comes very close to the reed switch (without hitting it!). It’s probably best to have the reed switch on the door jamb and the magnet on the door. What is a NAND gate? There are handy reed switch sets which come in plastic holders with screw holes, intended for alarm systems (eg, Jaycar LA5027). There are others which are intended for completely concealed mounting – the reed is recessed into the jamb and the magnet mounts inside the door. (eg Jaycar LA5075). Using it That is simplicity itself! When you go into the dunny, you press the momentary action (ie, normally open) “Start” switch (S1). This starts both LEDs flashing (the internal LED to assure you that you don’t have a flat battery). It stays that way until you open the door to leave. As the magnet moves away from the reed switch (S2) it opens, turning off the circuit, ready for the next occupant. The “automatic” reed switch turnoff is included because of the high likelihood that someone will forget to manually turn it off, resulting in a queue at the door of an unoccupied dunny! We could have made it fully automatic (ie, LEDs start flashing as soon as you entered) but deemed the extra complication not worthwhile. But for experimenters, it wouldn’t be hard SC to do. Two types of reed switch, both suitable for this application. The type at left (Jaycar LA5072) is designed for surface mounting (hence the mounting holes) while the type above (Jaycar LA5075) is fully concealed, mounting in holes drilled in a wooden door (or window) frame. There are two halves – the reed switch itself (on the right in both cases) and the actuating magnet. The switch is normally open, closing when the magnet is brought into close proximity. siliconchip.com.au Inside the 4093B chip there are four identical gates, each one operating completely independently of the others (but with a single power supply). That’s why it’s called a “quad”. First, we’ll look at an AND gate. Think of a gate as you would a gate in a fence. It can be either open or closed. With two gates, BOTH have to be in the same state, open or closed, to have any effect. With an AND gate, if both inputs are high, the output will be high. If either is low, the output will be low. That’s why it’s called an AND gate. But the 4093 has extra circuitry in each gate which “inverts” the output. So instead of both inputs going “high” resulting in a “high” at the output, both inputs going high result in a “low” at the output (and vice versa). This makes it a NAND gate, an abbreviation for NOT AND. The little circle at the gate output tells you that it is a NAND gate (an AND gate won’t have the circle). Australia’s electronics magazine Before we leave the AND/NAND gate, you’ll often see another type of simple gate, the OR/NOR. With this gate, as its name implies, either input – one OR the other – can be high to bring the output high. But if it’s a NOR gate, as distinct from an OR gate, the output will be inverted (just like the difference between NAND and AND gates). Finally, where does the “Schmitt Trigger” part come from? In most gates, the transition between the high and low states is fairly wide – it needs to be below a certain voltage to be low (close to 0V) and above a certain voltage to be high (much closer to the supply voltage). Voltages between the low and high states are not defined. However, this is often undesirable, so circuitry is included inside the gate which makes the transition from low to high or high to low much more defined due to hysteresis. This is called a Schmitt Trigger. January 2021  81 The AVR128DA48 and the Curiosity Nano evaluation board By Tim Blythman The AVR DA Curiosity Nano Evaluation Kit demonstrates Microchip’s new range of AVR128DA microcontrollers. These have several very significant advantages over commonly used AVRs, such as much more flash memory and RAM, a higher operating speed, 12-bit ADC channels and a 10-bit DAC. Despite all this, they actually cost less than the ATmega328P! W hen we saw that the new AVR DA family AVR chips were available, we had to try them out. They cost around $2.50 even in single quantities, slightly less than an ATmega328P. But they have four times the flash memory, eight times the RAM and greatly enhanced peripherals. If you’re designing a new circuit around an AVR, it would be silly not to use one of these. While some micros have cryptic part numbers, the AVR128DA series is quite straightforward. The “AVR” means that it is an AVR processor (originally from Atmel, now part of Microchip). The “128” means that it has 128kB of program (flash) memory and the “DA” refers to this particular AVR family. There are also AVR32DA and AVR64DA parts with 32kB and 64kB of flash memory, respectively. The two digits following the “DA” are simply the number of pins that the part has. The parts in this series are AVR82 Silicon Chip 128DA28, AVR128DA32, AVR128DA48 and AVR128DA64. These are available in various packages and footprints, which are described by further suffixes. When we looked at the ATtiny816 in January 2019 (siliconchip.com.au/Article/11372), we thought it looked like a fair competitor to the ATmega328 (as found in the Arduino Uno board). In fact, with more ADC (analog-todigital converter) channels, it was an tinyAVR series chip that could put its bigger (megaAVR) sibling to shame. The AVR DA family is even more impressive – see Table 1. Like the ATtiny816, the AVR128DA series has Event System and Configurable Custom Logic (CCL) hardware. These two peripherals handle in hardware what would have previously been done with software, freeing up processor time. The comparators and 10-bit DAC allow arbitrary trigger voltage thresholds to be set for external signals. One example of the benefits of the Event System is that, Australia’s electronics magazine siliconchip.com.au instead of a timer triggering an interATmega328 ATtiny816 AVR128DA28 AVR128DA48 rupt which then starts the ADC sam# pins 28 20 28 48 pling, it’s possible to configure the SRAM 2k 512b 16k 16k timer event to trigger the ADC directly, reducing latency and procesFlash 32k 8k 128k 128k sor overhead. EEPROM 1k 128b 512b 512b Clearly, these chips are even more Max. clock 20MHz 20MHz 24MHz 24MHz potent than their predecessors. With # ADC 6 x 10-bit 12 x 10-bit 10 x 12-bit 18 x 12-bit substantial RAM and flash memory, they put the ATmega328 from the Ar# GPIOs 21 18 23 41 duino Uno to shame. # timers 3 4 6 8 While the amount of EEPROM is # DACs 0 1 x 8-bit 1 x 10-bit 1 x 10-bit reduced, like many AVR parts, they are also capable of writing directly to # USARTs 1 1 3 5 their flash memory. Thus the reduced # HW SPI 1 1 2 2 EEPROM is more than offset by the # HW TWI 1 1 1 2 substantial increase in flash memory Programming ISP UPDI UPDI UPDI that is available for storing data. Also of note are the numerous 12Table 1 – comparison of four AVR micros. bit ADC channels and the UPDI programming interface. Since the UPDI interface only uses one pin, no GPIO ports are comproOther settings can be changed by copying simple text mised by being connected to the programming interface. files with a specific format and content. You can download a complete datasheet for these deThe AVR128DA48 itself (U200) has nearly the bare minivices from http://ww1.microchip.com/downloads/en/ mum of surrounding components. A 2.2µF capacitor proDeviceDoc/40002183A.pdf vides bulk bypassing. Three 100nF capacitors locally bypass the supply (two on digital VDD and one on analog VDD). Available packages The analog supply is fed via an inductor for extra filtering. While the device fitted to the AVR128DA Curiosity Nano A 32kHz crystal and its accompanying capacitors are board is the 48-pin TQFP (thin quad flat pack) version, there connected to supply a reference frequency for the RTC (reis also a 28-pin version available in a DIP package. We’ll al-time clock) peripheral. The internal oscillator can clock detail both below in our comparison with other AVR parts. the processor at 24MHz and a PLL allows peripherals to We’ll describe how to build a circuit around a bare AVR- run at 48MHz, across the full supply range down to 1.8V. 128DA28 chip later; the DIP version is an obvious candidate for breadboarding. The AVR128DA48 Curiosity Nano Evaluation Kit comprises the AVR128DA48 noted earlier, surrounded by a small number of extra components – see its complete circuit, shown in Fig.1. The PCB also includes an ATSAMD21E18A 32-bit ARM processor (U100), accompanied by its own entourage of components at one end of the PCB (U103-U107). The ATSAMD21E18A provides the PKOB Nano (PICkit On Board) programmer function, and is connected to a micro-USB socket to interface to the host computer. Interestingly, there is a fairly clear line on the Curiosity Nano’s PCB that separates the programmer and its target. There are even jumper pads on the PCB underside so that the connection between them can be broken if needed (J101, J201, J203, J205 & J206). We won’t delve into the details of the programmer; suffice to say that it includes an adjustable voltage regulator and five tiny level converter ICs, which bring three debug signals and a UART (TX/RX) pair back to the programmer for communication. As well as the PKOB function, it also provides a virtual COM port (to communicate with the UART on the AVR128DA) and emulates a USB flash drive too – see Fig.2. The USB drive is only ‘virtual’ and doesn’t work like a portable flash drive. The files that are present can be opened to show status information, but can’t be edited. One of the more interesting features is that you can flash A block diagram of the AVR128DA family from the datathe AVR128DA48 on the Nano by copying a HEX file to sheet. Note how the Event System Bus runs in parallel with the main Data Bus, connecting most peripherals. the virtual drive. siliconchip.com.au Australia’s electronics magazine January 2021  83                    SC  AVR128DA48 CURIOSITY NANO EVALUATION MODULE Fig.1: like the PCB itself, the circuit for the Curiosity Nano AVR128DA is clearly divided between the programmer and power supply at left, and the target device at right. Solder jumpers J101, J201, J203, J205 and J206 can be used to disconnect the two halves. 84 Silicon Chip Australia’s electronics magazine siliconchip.com.au     siliconchip.com.au Australia’s electronics magazine January 2021  85 parts if you already have a PICkit4. Programming the Curiosity Nano Fig.2: five files appear on the virtual USB drive that the Curiosity Nano AVR128DA presents; they can be dragged and dropped to change settings. It’s even possible to upload a HEX file to the AVR128DA48 by copying it to the virtual drive. Talk about easy to program! A user pushbutton and LED are also connected via 1kΩ resistors. These connect to GPIO pins PC7 and PC6, respectively. It’s not much, but allows some basic code to be tested without needing to connect any external hardware. In any case, the narrow PCB shape is perfect for fitting to a breadboard. The edge of the PCB is ringed by a series of pads which allow a row of pin headers to be friction fitted, although we found that they were a very tight fit. The pads are also duplicated as castellated half-holes, making it possible to solder the headers in place, or even to solder the board to a matching set of pads on another board (ie, treating the whole Curiosity Nano as an SMD). The pads at the end of the board closest to the USB socket duplicate those pins used by the programmer. AVR128DA28 in DIP To do this, you will need the free Microchip MPLAB X software; see our article on installing and using that software starting on page 48 of this issue. The basic steps are to write the code, compile it and then program to the device. We suggest starting with our sample project (available for download from the SILICON CHIP website) if you haven’t worked with MPLAB X before. Open that project, expand the “Source Files” to see “main.c” and double-click to open it. We’ll quickly walk through this example. The first #define for F_CPU lets the code know how fast the instruction clock is. By default, these parts start up with a 4MHz primary clock frequency, which can be later changed in software. There is no need to change this for our simple examples. The blink() function is called by main(), and it sets pins PA7 and PC6 as outputs (setting the DIRSET register). Then, it goes into an infinite loop, cycling between setting these pins high (OUTSET) and low (OUTCLR), separated by onesecond delays. With the project open, click “Clean and Build” (hammer and brush icon). You should get a “BUILD SUCCESSFUL” message. AVR devices require the fuse bits to be read before programming. These are the same as configuration bits on PIC devices, and the MPLAB X software calls them configuration bits for consistency. This can be done by clicking the Window-> Target Memory Views -> Configuration Bits menu item. The top-most icon with the green arrow facing up is “Read Configuration Bits”. Click this and allow the process to complete (see Fig.5). You may need to select the programming tool if you are using something different, but if this read occurs successfully, then Programmer communication is working fine. We also tried working with an AVR128DA28 on a breadboard. Our minimal setup is shown in Fig.3, and the corresponding circuit in Fig.4. The two supply pins, 20 (VDD) and 14 (AVDD) are bypassed to nearby GND pins (21 and 15) by 100nF capacitors. A 10kΩ l resistor pulls up the RST pin (18) to VDD. This is about the minimum needed for normal operation. For programming, we connected pins 2, 3 and 4 (VDD, GND & UPDI) of a PICkit4 to pins 20, 21 and 19 of the AVR128DA28 via a six-pin SIL header. Because the PICkit4 cannot supply power to the target in UPDI mode (as it can with some PICs in ICSP mode), external power must be supplied to the VDD and GND rails. We also fitted a LED and 1.1kΩ resistor between pin 1 (PA7) and GND, to provide the hardware equivalent of a “hello world” program (a blinkenlight!). Since the PC6 and PC7 pins (as used for the button and LED on the Curiosity Nano) are not present on the 28-pin variant, we did Fig.3: this minimal breadboard circuit for the AVR128DA28 needs only not do much more than verify that we could a handful of passive parts as, by default, the device is clocked from an flash the LED successfully. Still, this is an even internal oscillator. The LED and resistor are optional but are useful to cheaper way to experiment with these new AVR test that it is working as expected. 86 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.6: these debugging buttons are only visible after a debugging session has started. Most of these buttons also have keyboard shortcuts assigned to them, which is handy for quickly stepping through code while debugging it. Fig.5: the small button at upper left in the Configuration Bits window reads the device’s configuration bits (or fuses in AVR parlance). Then the fuse settings can be changed and exported by using the Generate Source Code button at the bottom. We would advise not changing anything here, even if you are familiar with PIC configuration bits. Unlike PIC programming, some AVR fuse bits (particularly some clock settings) can prevent the device from being programmed. You should now be able to press the “Run” button to program the Curiosity Nano. When this completes, you should see the LED on the Nano flashing at around 0.5Hz. Debugging One of the great features of MPLAB X is the ability to debug a project as it runs. If you’ve worked with BASIC programs or the Arduino IDE, you’re probably familiar with the use of PRINT statements to display the internal program state and determine why it isn’t doing what it should. This can be very helpful and can often give enough information to get to the bottom of a problem. But it can also interfere with program operation, and you cannot pause the running program to allow it to be examined in depth. The debugging feature of MPLAB X operates quite seamlessly and can halt the running program to inspect its internal state. You can even set ‘breakpoints’ to allow the program to pause operation at a certain point in its operation automatically. You might hear it referred to as ICD (in-circuit debugging) to emphasise the fact that you can debug the actual circuit operation, with all hardware attached and working. Another handy resource to use during debugging is the disassembly listing. It can be found under the Window -> Debugging -> Output -> Disassembly Listing File menu. The “Load symbols” option needs to be set to allow this. It can be found under the Properties window, but our example project already has this set. MPLAB X will show you where to set this if it is not. The disassembly listing contains both the source code and also the specific machine instructions and their locations in program memory. It can be a handy tool to use on its own, even without the debugger. A debugging session is started by clicking the “Debug Project” button, just below the main menu bar. Then, the buttons in the Debugging bar (Fig.6) become available. These buttons should give you a good idea of how handy the MPLAB X debugger can be. From left to right, the first button is Stop, which ends the current debugging session. This is followed by Pause, Reset and Continue. The remaining buttons provide different Step options, allowing the program to run until, for example, the next statement (Step Over) or until the current function ends (Step Out). Hence, the importance of the disassembly listing; the debugger needs to know what point in program flash memory corresponds to what line of code to be able to highlight where it stops. A good example of stepping would be to see what course a program takes on an if statement or switch statement. After starting a debugging session, click Pause and you should see the editor window highlight a line of the source code in green (it’ll probably be a line from “delay.h”, as that is where the program spends most of its time). In the bottom right window, there should be a “Variables” tab. Build the world’s most popular D-I-Y computer! 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Subscriber’s price is just $ 14000 10%! $ 12600 Plus $10.00 p&p in Aust Waveshare CPU module pre-loaded with MMBasic the PCB – high quality board with silk screening component ID SILICON CHIP Subscribers: front & rear panels – already drilled/punched so you don’t have to! $AVE and all other components required to build the Colour Maximite 2 Fig.4: a protoboard mockup of the circuit opposite. Obviously this layout is not sacrosanct – but if you’re not familiar with breadboards, follow this one to avoid mistakes. siliconchip.com.au + p&p Order now (or more information) at www.siliconchip.com.au/shop/20/5508 Australia’s electronics magazine January 2021  87 Click this and then click on “<Enter new watch>”. A watch is a variable which the debugger can read and display. It isn’t updated in real-time, but can be inspected any time that the program is paused and is highlighted in red if it has changed. While variables only exist as bytes in RAM, the debugger knows what type it is (eg, int, char or pointer) and can display other appropriate information. For example, the value of a pointer’s target can be resolved and displayed, or a character array can be displayed as a text string. One interesting value to display is “PC”, the program counter, which is effectively one of the program’s internal variables. You can pause the program and check that the value of PC matches the line of code as shown in the assembly listing. Of course, our example program is elementary. But also, modern compilers are very good at optimising code, which sometimes means that even the debugger can have trouble mapping the source code to the program memory. One more useful tool that the debugger provides is called a breakpoint. This is a point in the source code which will automatically pause the program when it is reached. Cleverly setting breakpoints can help pin down where a problem might be occurring. For example, you could set a breakpoint just before a switch statement, then step through the switch statement to check the logic and values of critical variables to ensure that the correct branch is taken. When we reviewed the PICkit 4 in September 2018 (siliconchip.com.au/Article/11237), we also gave a brief overview of in-circuit debugging (ICD). We noted, amongst other things, that the PICkit 4 was much more responsive than the PICKit 3 during debugging. We found that the PKOB debugger on the Curiosity Nano was similarly fast. Example code Microchip has provided some sample code for these processors at siliconchip.com.au/link/ab4m These are actually Microchip Studio (previously known as Atmel Studio) projects, but they contain a “main.c” file which can be added to a blank MPLAB X project. We tested this with the “AVR-DA_LED_dimming_PWM” example, and it worked with no changes to the code. Examples like these are great resources for getting started with microcontroller peripherals. Typically, you would have little more than a list of registers from a data sheet. The examples provide working code that can be used directly. This even helps with subtle things like checking the correct syntax for manipulating the correct registers. Conclusion The AVR DA family of microcontrollers is an impressive update to the AVR roadmap, while the AVR128DA48 Curiosity Nano Development Board provides a simple and economical way to try out the new features. You can get these parts from: Digi-Key: https://www.digikey.com.au Mouser: https://au.mouser.com Microchip Direct: https://www.microchipdirect.com Microchip’s part number for the Curiosity board is DM164151, and the current price is around AU $25, excluding delivery costs. SC Subscribe to SILICON CHIP and you’ll not only $AVE MONEY but we GUARANTEE you’ll get your copy! When you subscribe to SILICON CHIP (printed edition) in Australia we GUARANTEE you’ll never miss an issue! 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K 9640 SAVE 12% 30 $ Victoria 08 9428 2188 08 9428 2166 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St 02 8748 5388 Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd 08 8164 3466 Find a local reseller at: altronics.com.au/storelocations/dealers/ 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. © Altronics 2020. 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 $ NEW! PRODUCT SHOWCASE New microcontrollers from Microchip help with analog system design Sensor-based Internet of Things (IoT) applications rely on a combination of analog functionality and digital control capability to meet a list of requirements including cost, size, performance and power usage. Addressing this through a focus on increased microcontroller (MCU) integration, Microchip Technology announced the PIC18-Q41 and AVR DB MCU families (as seen on page 82 of this issue). These are the first to com- bine advanced analog peripherals and multi-voltage operation with interperipheral connections for increased system integration and reduced signal acquisition times. To address the need for signal conditioning in space-constrained sensing and measuring applications (such as IoT end nodes and industrial, medical devices, wearables, automotive and lighting systems), the PIC18-Q41 MCU has a configurable operational ampli- Microchip Technology Inc. Unit 32, 41 Rawson Street Epping 2121 NSW Tel: (02) 9868 6733 www.microchip.com New NP400 low-cost pressure sensors from Ocean Controls Digi-Key releases 1.5 million SnapEDA CAD models Digi-Key Electronics announced its collaboration with SnapEDA, providing over 1.5 million high-quality symbols, footprints, and 3D models for Digi-Key parts. These can now be downloaded from digikey.com With this collaboration, engineers can access SnapEDA’s high-quality CAD models directly on Digi-Key’s website, further streamlining their design flow. To start downloading EDA and CAD parts from Digi-Key, go to a part detail page, look for the row labelled "EDA / CAD Models" and click on Download from SnapEDA. Supported formats include Altium, Eagle, KiCad, OrCad, Allegro, PADS, and DXDesigner. Novus NP400 two-wire pressure sensors break the $100 barrier. These compact sensors are ideal for air and water applications. They feature a wide power supply range of 11-33V DC, ±0.5% accuracy, an overpressure range (twice the maximum range) and rupture pressure (triple the pressure range upper value). Process connections: external thread ¼ NPT, ¼ G, ½ NPT or ½ BSP. ► siliconchip.com.au fier, analog-to-digital (ADC) & digitalto-analog converters (DAC). It is particularly well-suited for IoT and large-scale artificial intelligence (AI), including predictive maintenance edge nodes in a smart factory. Offered in compact 14- and 20-pin packages, the PIC18-Q41 MCU also makes a good companion to Microchip’s 32-bit MCUs and other controllers that require analog integration. Mixed-signal IoT systems often include multiple power domains, and the AVR DB MCU simplifies these designs while reducing cost by integrating true bi-directional level shifters. This feature lowers cost in a wide range of applications such as automotive, HVAC and liquid measurement. The addition of three independent and highly configurable op amps, a 12-bit differential ADC, 10-bit DAC, three zero cross detectors and core independent peripherals (CIPs) makes the AVR DB MCU ideal for virtually any application involving analog signal conditioning and processing functions. SnapEDA adds millions of parts to its library each year, aided by its computer vision technology such as InstaBuild, and other automation tools. Supported suppliers on SnapEDA include Recom, CUI, Samtec, TE Connectivity, I-PEX, GCT, CUI Devices, Bel Fuse, Murata, Texas Instruments, ECS, Triad Magnetics, Quectel, Infineon and many more. SnapEDA is on a mission to help engineers innovate faster by removing barriers. They help over one million engineers find CAD models for their electronics designs each year. Their community of professional engineers are making everything from medical devices to electric airplanes. Ocean Controls Digi-Key Electronics 44 Frankstown Gardens Drive Carrum Downs 3201 VIC Phone: (03) 9708 2390 Website: oceancontrols.com.au Thief River Falls Minnesota, USA Phone: 1800 285 719 Website: www.digikey.com Australia’s electronics magazine January 2021  93 Vintage Radio Philips Philips 1963 1963 “Musicmaker” “Musicmaker” MM1 MM1 mantel mantel radio radio By Associate Professor Graham Parslow Philips valve radios from the 1960s had excellent sound, came in a variety of interesting colours and were quite affordable at the time. This article covers three different models: the model 224, MM1 and MM1/01, as they look similar. Their performance is indistinguishable because they all use the same circuit and components. The design of valve-based superhets was fully mature by the 1960s. By then, they were pretty much all using tried and tested components and circuitry. The competing Kriesler range of valve mantels were comparable and sold in greater numbers, as judged by the number of remaining units held by collectors. The Philips radios had a more conservative style, and that may have been advantageous for a kitchen radio where function was the prime consideration. Philips also made other valve radios in the 1960s, notably the mantel model 172 using inductive (permeability) tuning, as well as valve radiograms. But the biggest competitors to these radios were the then-new transistor types. Philips made a good range of transistor sets, both for battery and mains operation, at prices comparable to the valve radios. Their transistor models included the Philadelphia model MM2, the Metropolitan model MT7 and the Leisuremate model RB290, all are pictured at the end of the article. The downside to these transistor radios was an audio output of only about 300mW before distortion became severe. Australian Philips valve and transistor radios were manufactured at Hendon in South Australia. Local production ceased in the early 1970s when tariff protection was lifted and imported radios took the market. Those imported radios usually cost less than just the local cost of the components! 94 Silicon Chip Three similar models The model 224 was introduced in 1961 at £27, and was marketed with the title “Futura Five”. It came in one of six colours: ember red, flamingo, charcoal, turquoise, grey and primrose. The escutcheon at the sides of the dial had a two-tone colour scheme, with one section usually being metallic chrome or gold. The other section was usually black, but sometimes colour-matched to the case. The knobs were cream with eight raised flutes. The volume and tone knobs at the left drove concentric pots, with a DPDT on/off switch linked to the tone control. The tuning knob used the same two segments to duplicate the appearance of the left-hand knob, but it was mounted onto a single shaft with stepped diameters to lock the sections together. The easiest way to identify the model is to look at the paper label pasted under the case. However, these labels are easily damaged and sometimes missing. An example of the label from an MM1 radio is shown at the end of the article. The model MM1, marketed as the The Philips model MM1 (1963) is nearly identical to the Futura Five 224, except it has provision for an external pick-up. Sadly, this particular example has a crack in the top of its case. Australia’s electronics magazine siliconchip.com.au easily when subjected to trauma. The mauve-coloured case shown here was particularly badly affected by heat. The last of the line was the model MM1/01, which was an entirely cosmetic change. The knobs were made more conical in shape, with more flutes, and the escutcheons were black in all sections. Circuit details Why add the pick-up facility to this mature product line? Possibly, it was to compete with the better-selling Kriesler radios that had such an input. Another reason may have been to promote the low-end phono turntables made by Philips that sold for around £5 at the time (see the accompanying advertisment from National Radio Supplies Sydney, originally in RTV&H, December 1963 on p114). These sets draw around 30-32W in use. Unfortunately, the thermo-mouldable plastic case is easily damaged by heat, including the internal heat generated by the valves. The cases also crack Referring now to the original circuit diagram, reproduced overleaf, L1 is an RF choke wound around a 6.8kW resistor, and is described as a loading coil. Loading coils are added to achieve more efficient coupling of RF to a tuned circuit from a short external aerial. The external aerial coupling coil, L2, is three turns around the 6.5inch (165mm) long ferrite rod, spaced 20mm away from L3. The circuitry around mixer/oscillator valve V1 is conventional, with L3C1 for tuning and C4-L4 to set the local oscillator frequency. Oscillation is sustained by feedback from L5. In all these Philips radios, the circuit data specifies a 6AN7 for V1, but the later radios had 6AN7As installed. The nine-pin 6AN7 mixer valve was released in 1948 and became widely used throughout the 1950s. The joint release of the 6AN7 and 6M5 by Philips is described in Radio and Hobbies magazine, January 1950, page 67 (a recommended read). The Philips MM1/01 (1965) is the same as the MM1 with changes only to its external appearance, such as the conical knobs, dial, escutcheon, grille and case colour. This extract of the RTV&H advert from National Radio Supplies Sydney, shows contemporary turntables for sale. The Philips Futura Five 224 (1961) is a 5-valve superhet mantel radio enclosed in a plastic case. “Musicmaker”, was introduced in 1965 and added a pick-up input to the circuit. The way this connected can be seen from the pseudo-3D chassis layout on the MM1 label. The almost identical model 224 label had a simpler 2D chassis diagram because it did not have a pick-up input. This offers another way of recognising the earlier model 224, because the 224 case has only one lower slot at the rear, positioned to view the chassis serial number. The MM1 radios have an additional narrow slot for pick-up access, as seen at the bottom of the mauve case on page 97. siliconchip.com.au Australia’s electronics magazine January 2021  95 The 6AN7 draws 0.23A of filament current at 6.3V. The slightly more efficient, but otherwise identical, 6AN7A valve was released in 1961. It had better cathode emission and required 0.3A for the filament. In a radio with parallel filaments supplied with 6.3V, there is no problem with interchanging the two valve types. However, farm radios powered by 32V DC often connected the filaments of five valves in series, with equalising resistors to regulate the 6AN7 filaments to 0.23A. If a 6AN7A is used as a replacement in these 32V radios, the equalising resistors should be altered to maintain correct filament voltage and current. The IF signal created by the mixer enters the first IF transformer from the plate of the 6AN7. IF amplification is carried out by a 6BH5 pentode. The 9-pin 6BH5 was released in 1952. This Philips-made valve was only built for the Australian market, and is uncommon in non-Philips radios. The amplified IF signal is detected by the diode connected to pin 6 of the 9-pin 6BD7. The 6BD7 triode-double diode is a commonly encountered valve dating from 1950. The IF transformers are the thin rectangular types that Philips introduced in the early 1950s. With age, some of these transformers have gone open-circuit. As the internals are set in resin, sadly they cannot be repaired. Fortunately, none of the IF transformers in the sets described in this article had failed. The bottom end of the second IF transformer secondary (L9) is grounded for the 455kHz IF signal by mica capacitor C15 (220pF). C15 has no effect on audio frequencies, so demodulated audio passes across R7 (47kW), superimposed on the negative DC output from the diode. The AGC circuit passes a negative bias to the preceding 6AN7 and 6BH5 grids via R6 (3.3MW). Delayed AGC is achieved by 47W resistor R14 between the centre tap 96 Silicon Chip Australia’s electronics magazine siliconchip.com.au This photo of an MM1 was taken before restoration, as can be seen by the dust and other debris on the underside of the chassis. The external links to a pick-up can be seen at the top of the photo with shielded cable to connect to the audio amplification section. of the power transformer and ground, with the low-signal grid bias for the 6AN7 and 6BH5 being derived from the transformer end of R14. This means that a higher AGC voltage is required before the gains of those valves are reduced. To listen to the radio, the A-B jumper link in the pickup connector needs to be in place. The demodulated audio signal is then fed to the 500kW volume control (R8). The link has a pull-string accessible through its cabinet slot. A ceramic or crystal phono cartridge can instead be connected between B and C on the linking socket. The audio signal from the cartridge is then amplified by the 6BD7 triode and conventionally passed to the 6M5 grid via 10nF coupling capacitor C18. Many radios have top-cut tone controls acting at a point of high voltage that compromises the reliability of the components. This circuit sensibly places R13 (a 250kW pot) and C19 in a position that is nominally at 0V DC. The 6M5 output pentode has 6.5V of grid bias, generated by R17 (220W). Unusually, there is no cathode bypass electrolytic across R17. A bypass capacitor here would provide a low-impedance path for audio, thereby maximising the amplified output from the pentode. This gave me a chance to see how critical, or otherwise, that conventional bypass electrolytic is. I found that adding a 22µF capacitor across R17 made no audible difference, so It’s a bit hard to see from this angle, but the connection for the pick-up is at the bottom rear of the chassis (circled in red). Here it has been fitted with a wire-link between points “A” and “B” for normal radio operation. siliconchip.com.au Australia’s electronics magazine January 2021  97 The Philips MM1 label originally had a red background, but it has been changed here to white for clarity. Philips did not make an unreasonable omission. There is no convenient place to mount the speaker transformer on the top of the chassis, so it is mounted below. The resulting ‘spare space’ above the chassis is occupied by the aluminium cans for filter electrolytics C16 and C17. There is no filter choke in the HT supply. The 4 x 5.5-inch (100 x 140mm) elliptical Rola speaker has the 1960s rounded edge magnet profile. This replaced the plain cylindrical profile that Rola used for magnets in the 1950s. The baked enamel frames of these speakers resist rusting, but the magnets often show rust. The Rola speakers mounted in these radios sound surprisingly good for their modest dimensions. Faults and troubleshooting Although these radios are ‘modern’, they are still over 50 years old. Most of the original Ducon paper capaci- tors remain serviceable. Nevertheless, in three of these radios, I found C18 was leaky and compromised the 6M5 grid bias. Editor’s note: some restorers prefer to replace paper capacitors regardless, as they will fail eventually. I selected a model 224 to listen to as a shed radio after replacing only C18. For some days, it behaved well, but then failed completely. Rocking the valves in their sockets revealed the problem. The fix at this time was cleaning the pins of the 6AN7 and 6BH5. After a few more days, it developed a crackle. Suspicion immediately fell on the two mica capacitors, C7 and C15. Against optimistic expectations, their replacement did nothing to help alleviate the crackle. The next step was to begin replacing the paper capacitors, starting with C20 across the output transformer. The crackle stopped after this single replacement, so the radio went back into service. The back of another MM1 radio which is badly deformed from the heat of the valves during operation (likely with high ambient temperature and poor ventilation). 98 Silicon Chip Australia’s electronics magazine However, the crackle soon started again, so it was back to the bench for a systematic replacement of all paper capacitors. After every capacitor was replaced, the radio still produced abundant crackle. Worse still, only strong stations now tuned in weakly and turning up the volume drove the set into audio oscillation at around 2kHz. All resistors checked as true to value, except R2 and R4, which had gone significantly high in value. Replacing them did not change anything. If the problem cannot be found below the chassis, then it might be above. As soon as I looked at the tuning capacitor, I saw that trimmer C2 had broken away minutely from the solder joint to Earth. Repairing that changed nothing, so it was back to looking below. It then became clear how I had compromised the set by a simple mistake. The original, large capacitor C6 was soldered into a cramped space and the more compact polyester replacement allowed me to connect it to a more convenient Earth point. The problem was that the free tag I used was above an Earthing solder point on the chassis, but the tag was not connected to it, so C6 was floating. A simple Earth link brought the radio back to full function, complete with crackle. Back on the top of the chassis, removing the mixer valve did not affect the crackle, so I determined that it was being introduced at a later stage. Removing the 6BH5 IF amplifier valve produced blissful silence. I had not previously run into a crackling valve, but a replacement 6BH5 was indeed the answer. Since replacing the 6BH5, the radio has been perfectly reliable. SC siliconchip.com.au These three Philips transistor radios were contemporaries of the MM1 radios in the 1960s. From top-tobottom: Metropolitan MT7 mantel; Philadelphia MM2 mantel; and Leisuremate RB290 portable. siliconchip.com.au Australia’s electronics magazine January 2021  99 SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS H-FIELD TRANSANALYSER MAY20 CAR ALTIMETER RCL BOX RESISTOR BOARD ↳ CAPACITOR / INDUCTOR BOARD ROADIES’ TEST GENERATOR SMD VERSION ↳ THROUGH-HOLE VERSION COLOUR MAXIMITE 2 PCB (BLUE) ↳ FRONT & REAR PANELS (BLACK) OL’ TIMER II PCB (RED, BLUE OR BLACK) ↳ ACRYLIC CASE PIECES / SPACER (BLACK) IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION USB SUPERCODEC SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 AUG20 AUG20 SEP20 SEP20 SEP20 06102201 $10.00 05105201 04104201 04104202 01005201 01005202 07107201 SC5500 19104201 SC5448 15005201 15005202 01106201 18105201 04106201 04105201 04105202 08110201 $5.00 $7.50 $7.50 $2.50 $5.00 $10.00 $10.00 $5.00 $7.50 $5.00 $5.00 $12.50 $2.50 $5.00 $7.50 $5.00 $5.00 Subscribers get a 10% discount on all orders for parts SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) SUPERCODEC BALANCED ATTENUATOR DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 01110201 01110202 24106121 16110202 16110203 SEE P31 16109201 16109202 01106202 16110201 16110204 11111201 11111202 16110205 $2.50 $1.50 $5.00 $20.00 $20.00 $3.00ea $12.50 $12.50 $7.50 $5.00 $2.50 $7.50 $2.50 $5.00 JAN21 JAN21 JAN21 CSE200902A $10.00 01109201 $5.00 16112201 $2.50 NEW PCBs AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) PRE-PROGRAMMED MICROS As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS ATmega328P-PU ATmega328P-AUR ATtiny85V-10PU PIC10F202-E/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-I/P $15 MICROS RF Signal Generator (Jun19) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) LED Christmas Ornaments (Nov20; specify variant) Door Alarm (Aug18), Steam Whistle (Sept18), White Noise (Sept18) Trailing Edge Dimmer (Feb19), Steering Wheel to IR Adaptor (Jun19) Car Radio Dimmer Adaptor (Aug19), MiniHeart (Jan21) Tiny LED Xmas Tree (Nov19) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) Ol’ Timer II (Jul20) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20) Flexible Digital Lighting Controller Slave (Oct20) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC16F877A-I/P 6-Digit GPS Clock (May09), 16-bit Digital Pot (Jul10), Semtest (Feb12) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS, SPECIALISED COMPONENTS ETC MINIHEART HEARTBEAT SIMULATOR (CAT SC5732) AM/FM/SW RADIO $5.00 (JAN 21) $2.50 $3.00 $7.50 - PCB-mount right-angle SMA socket (SC4918) - Pulse-type rotary encoder with integral pushbutton (SC5601) - 16x2 LCD module (does not use I2C module) (SC4198) LED CHRISTMAS ORNAMENTS (CAT SC5579) (NOV 20) $14.00 Complete kit including micro but no coin cell (specify PCB shape & colour) RGB STACKABLE LED CHRISTMAS STAR (CAT SC5525) (NOV 20) $38.50 Complete kit including PCB, micro, diffused RGB LEDs and other parts D1 MINI LCD WIFI BACKPACK KIT (OCT 20) $70.00 Complete kit including 3.5-inch touchscreen, PCB and ESP8266-based module SHIRT POCKET AUDIO OSCILLATOR (SEP 20) Kit: including 3D-printed case, and everything else except the battery and wiring - 64x32 pixel white OLED (0.49-inch/12.5mm diagonal) - Pulse-type rotary encoder with integral pushbutton COLOUR MAXIMITE 2 in stock now Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (Cat SC5478) Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (Cat SC5508) MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) (JAN 21) All SMD parts, including IC2 – does not include PCB $40.00 $10.00 $3.00 (JUL 20) $80.00 $140.00 (AUG 19) Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $30.00 - DHT22 temp/humidity sensor (Cat SC4150) $7.50 - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor $5.00 - BME280 temperature/pressure/humidity sensor (Cat SC4608) $10.00 - DS3231 real-time clock SOIC-16 IC (Cat SC5103) $3.00 - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) $5.00 - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) $1.50 - 10µF 16V X7R through-hole capacitor (Cat SC5106) $2.00 VARIOUS MODULES & PARTS - Pair of CSD18534 (Vintage Radio Supply, Dec20) - IPP80P03P4L04 (Dual Battery Lifesaver / Vintage Radio Supply, Dec20) - 16x2 I2C LCD (Digital RF Power Meter, Aug20) - DS3231 real-time clock SMD IC (Ol’ Timer II, Jul20) - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) - MAX038 function generator IC (H-Field Transanalyser, May20) - MC1496P double-balanced mixer (H-Field Transanalyser, May20) - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 - SMD 1206 LEDs, packets of 10 unless stated otherwise (Tiny LED Xmas Tree, Nov19): yellow – $0.70 ¦ amber – $0.70 ¦ blue – $0.70 ¦ cyan – $1.00 ¦ pink (1 only) – $0.20 $6.00 $5.00 $7.50 $3.00 $15.00 $25.00 $2.50 $10.00 $5.00 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. PAYPAL (24/7) INTERNET (24/7) MAIL (24/7) PHONE – (9-5:00, Mon-Fri) eMAIL (24/7) To Use your PayPal account siliconchip.com.au/Shop Your order to PO Box 139 Call (02) 9939 3295 with silicon<at>siliconchip.com.au Place silicon<at>siliconchip.com.au Collaroy NSW 2097 with order & credit card details Your You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. 01/21 Order: “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! 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RIGOL DP-832 RIGOL DSA Series RIGOL RSA Series 4Triple Output 30V/3A & 5V/3A 4Large 3.5 inch TFT Display 4USB Device, USB Host, LAN & RS232 4500MHz to 7.5GHz 4RBW settable down to 10 Hz 4Optional Tracking Generator 41.5GHz to 6.5GHz 4Modes: Real Time, Swept, VSA & EMI 4Optional Tracking Generator ONLY $ 749 FROM $ ex GST 1,321 FROM $ ex GST 3,210 ex GST Buy on-line at www.emona.com.au/rigol Sydney Tel 02 9519 3933 Fax 02 9550 1378 Melbourne Tel 03 9889 0427 Fax 03 9889 0715 email testinst<at>emona.com.au Brisbane Tel 07 3392 7170 Fax 07 3848 9046 Adelaide Tel 08 8363 5733 Fax 08 83635799 Perth Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA Using Cheap Asian Electronic Modules By Jim Rowe Mini Digital AC Panel Meters In this follow-up article on low-cost digital panel meters, we’re looking at meters designed to measure AC voltages and currents. Some of them can even calculate and display power, energy consumption and frequency. As usual, we’ll give you an idea of how they work, how they perform and how easy they are to use. A s promised last month, this second article describes some small meters designed to measure AC voltages and currents. The AC models are even more interesting than those we described last time. For a start, they vary more significantly in both size and price. Like the DC meters we looked at in the first article, these AC meters are all designed to be powered from the same source used for voltage measurements. So no separate power source is needed. It’s important to make sure all connections are properly insulated when taking measurements. As explained last month, DC meters measure currents by measuring the voltage drop across a very low resistance current shunt. In contrast, AC meters typically measure currents by using a special kind of transformer: a current transformer or ‘CT’. This steps down the current to a much lower level, as well as providing galvanic isolation for improved safety. compared with DC, as Nikola Tesla and George Westinghouse stressed over 120 years ago, is that with AC you can use transformers to step the voltage up or down to whatever level best suits your purposes. This means that AC power can be stepped up to hundreds of thousands of volts to reduce losses when conveyed over long distances, then stepped down to much lower voltages like 230V or 115V, for somewhat more safe use in houses, factories and offices. Of course, when a transformer steps up the voltage, it also steps down the current, and vice versa. This is due Fig.1: how the current transformer (CT) operates. The CT secondary should be terminated with a low impedance, otherwise it will generate a very high voltage if any significant AC current is flowing in the primary. Make sure to connect the secondary leads of the CT to the panel meter before any current is allowed to flow through the primary. Current transformer basics One of the big advantages of AC 102 Silicon Chip to the conservation of energy (ie, the product of voltage and current at the output must be similar to that at the input). So if the voltage is stepped up by a factor N, the current is stepped down by the same factor, and if the voltage is stepped down by N, the current is stepped up by the same factor. This is much harder to do with DC; generally, this means converting the DC voltage to AC, stepping it up or down, then rectifying and filtering it to turn it back into DC. That is not easy to do efficiently! The current transformer works on the same principle, as shown in Fig.1. It consists of a toroidal magnetic core, Australia’s electronics magazine siliconchip.com.au So for example, if the CT has a secondary winding of 1000 turns and the current flowing in the primary wire is 50A, the secondary current will be 50mA (50A ÷ 1000). The advantages of using a CT includes a stable transformation ratio, which helps ensure measurement accuracy, as well as a high degree of electrical isolation. The main disadvantage that the ‘primary’ wire must be passed through the centre of the transformer core. One way around this is to have the core in two halves. But this adds significantly to the cost, as well as reducing its conversion efficiency a little (due to the inevitable air gaps). The AD16-22FVA is the smallest AC panel meter out of the three but has the highest measurement range of 60-500V. The current transformer (CT) is shown adjacent and is rated at 0-100A. The AD16-22FVA meter shown at actual size. usually made from either silicon steel or ferrite, through which passes the wire carrying the current to be measured. The wire effectively forms the transformer’s single-turn primary ‘winding’. Many turns of much lighter wire are wound around the toroidal core to form the transformer’s secondary winding. So the turns ratio is 1:N, where N is the number of secondary turns. When a relatively heavy alternating current is flowing through the wire forming the CT’s primary, this produces an alternating magnetic field in its core. And as a result, an AC voltage is induced in the CT’s secondary winding, which can provide an alternating current N times smaller than that flowing through the single-turn primary (assuming that it’s connected to a low-impedance load or ‘burden’). This is illustrated by the expression at upper right in Fig.1, relating secondary current IS to primary current IP . Fig.2: the AD16-22FVA meter is easy to use. One of the power leads from the AC source to the load passes through the CT (polarity connections do not matter), while the other two leads connect across the source. siliconchip.com.au Australia’s electronics magazine The AD16-22FVA meter The AD16-22FVA is both the physically smallest meter that we will describe in this article, and also the lowest in cost. As you can see from the photos, it’s quite tiny, measuring only 31mm wide, 31mm high and 56mm deep. Behind the front square display section, the body is cylindrical so it can pass through a 22mm diameter hole in the panel. It comes with a matching plastic ‘nut’ which allows the meter to be attached firmly to the panel. The CT is separate and is connected to the meter via a light two-wire lead. The CT lead is close to 180mm long, while the meter’s own lead is 100mm long. The AD16-22FVA has two 3-digit 7-segment LED displays, one above the other, with both sets of digits 7mm high. And the meter is available in five versions, with red, blue, green, yellow or white displays. It’s hard to be sure, but I suspect that all these versions differ only by having different colour filters in front of the same white LED displays. The voltage measurement range of all versions is 60-500V AC, while their current range is 0-100A. The AD16-22FVA meter is very easy to set up and use, as you can see from Fig.2. All you have to do is pass one of the load power leads through the centre of the CT, and then connect the power terminals of the meter to the same source of AC power. I found the AD16-22FVA advertised on AliExpress by the supplier Sevenstar Tools at $4.58 plus 78¢ for delivery (including the CT). The ‘white display’ version I ordered arrived about 30 days later, in good condition. January 2021  103 I checked its performance with my reference instruments, using a finned oil heater as the load. It gave voltage readings that were 0.2% low and current readings that were 0.94% low, compared with my Agilent U1251B DMM. So the AD16-22FVA may be tiny, but its performance is quite respectable. I admit that I found the small 3-digit displays a little hard to read. But for less than $5.50, it still represents excellent value. The DL69-2042, shown at actual size, looks nearly identical to the DSN-VC288 shown in the last article. The DL69-2042 meter Apart from the separate CT, the DL69-2042 AC meter looks almost identical to the DSN-VC288 DC meter we checked out in the last article. It’s somewhat larger than the AD1622FVA at 80mm wide, 42mm high and 48mm deep. It clips into a 75 x 39mm rectangular hole in a panel. The DL69-2042 sports two 4-digit 7-segment LED displays, both with digits 10mm high. The volts display is at the top, with a red filter, while the current display is below with a green filter. This meter has a voltage range of 80300V, although it is also available with a range of 200-450V. In both cases, the current range is 0-100A. The rated accuracy is ±1%, ±2 digits for both voltage and current. I found the DL69-2042 advertised on the Banggood website for $17.00 plus $3.73 air parcel shipping (again, including the CT), ie, about four times the price of the AD16-22FVA. It too arrived safely about 30 days later. When I checked it out using the same test setup as before, the voltage readings were only 0.2% high while the current readings were 2% high. This was just within spec at the current level concerned (about 6A). Like the AD16-22FVA, the DL692042 is quite easy to use, as you can see from Fig.3. Again all you need to do is thread one of the wires connecting to the load through the centre of the CT core, then connect the meter’s voltage input terminals to the same source of AC power. Both the CT and Vin terminal blocks are on the rear of the meter’s case; they’re only shown on the front in Fig.3 for clarity. The larger digits make the DL692042 significantly easier to read than the AD16-22FVA, while the 4-digit displays provide higher resolution. 104 Silicon Chip The DL69-2042 has a measurement range of 80-300V and 0-100A. There are also some versions with a voltage range of 200-450V. You can even buy it online from the Dick Smith website which is owned by Kogan. Fig.3: as you might expect, like all the other panel meters described in this article, the DL69-2042 is very simple to operate. So this meter is good value for money even at its higher price. If you only need readings for both voltage and current, it is a good choice. The PZEM-061 meter If the PZEM-061 AC meter looks a bit familiar, that’s because apart from the accompanying CT, it looks almost Australia’s electronics magazine identical to the PZEM-051 DC meter module we described last month. That’s because it is manufactured by the same firm, Ningbo Peacefair Electronic Technology, in China’s Zhejiang province. Like the Peacefair DC meter, it comes in a rectangular case measuring 90mm wide, 50mm high and 25mm siliconchip.com.au The rear and internals of the PZEM-061. It has a measurement range of 80-260V and 0-100A in addition to reading power levels from 0-22kW (power factor is taken into account). The front of the meter is pictured on page 102 and has a bright blue backlight. Fig.4: how to set up the PZEM-061 for measurement. ing as 1000-9999W and readings for power levels above 10kW showing as 10.0-22.0kW. The energy consumed range is 0-9999kWh (kilowatt-hours), with readings below 10kWh showing as 0-9999Wh and readings above 10kWh showing as 10-9999kWh. It has a small recessed button at centre right on the front panel, allowing you to switch the backlighting on or off, reset the energy consumption level to zero to start a new set of measurements, or set a power level alarm threshold to a level between 0.0 and 22.0kW. The PZEM-061 is again quite easy to use, as you can see from Fig.4. You simply need to pass one of the load power leads through the centre of the CT, and then connect the meter’s own power leads to the same source of power. The four-way terminal block is at the rear of the meter, but is shown in Fig.4 at the front, for clarity. I found the PZEM-061 advertised on the Banggood website for $19.22 plus $3.73 for air parcel delivery. Again, it arrived about 30 days after I ordered it. The rated measurement accuracy of the PZEM-061 is ±1%, and when I checked it out, I found the voltage readings to be 0.21% high while the current readings were 0.05% high. That is not only well within spec, but quite respectable. The power and energy readings were accurate too; not surprising as these are calculated from the measured voltage and current. Although the display digits are only 6.5mm high, the blue LED backlighting makes them quite easy to read. So all in all, the PZEM-061 represents excellent value for money. The D69-2058 meter deep, designed to clip inside a rectangular panel opening 87 x 46mm. Like the DC meter, it also features an LCD window measuring 50 x 30mm with blue LED backlighting, the main digits being about 6.5mm high. In addition to the voltage and current readings, it also shows the corresponding power level and energy siliconchip.com.au consumed. All of these parameters are displayed using four digits (see the left-hand photo on page 102). The voltage measurement range is 80-260V and the current range 0-100A. The power range is 0-22kW, with readings for power levels below 1kW showing as 0.0-999.9W, readings for power levels between 1kW and 10kW showAustralia’s electronics magazine The last AC meter we’re describing is the D69-2058 multi-function meter. This one is slightly smaller than the PZEM-061 at 80mm wide, 42mm high and 47mm deep, but it displays a total of six measurement parameters: voltage, current, power, mains frequency, energy consumption and power factor (see the right-hand photo on page 102). The D69-2058 has an LCD screen with digits about 6.5mm high, and it is quite bright, so all the parameters are easy to read. The voltage display has four digits and covers the range of 80-300V (although the meter can alternatively be ordered with a range of 200-450V). January 2021  105 Silicon Chip Binders REAL VALUE AT $19.50 * PLUS P &P Are your copies of SILICON CHIP getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? Shown above are the internals of the D69-2058 AC panel meter. Compared to the previous three meters, this one offers a lot more features displaying voltage, current, power, mains frequency, energy consumption and power factor. The front view can be seen on page 102. Fig.5: how to use the D69-2058 meter. Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of SILICON CHIP. They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. H 80mm internal width H SILICON CHIP logo printed in gold-coloured lettering on spine & cover Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Order online from www. siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *See website for delivery prices. 106 Silicon Chip The current range covers 0-99.99A, with a minimum resolution of 0.01A. Power can be displayed over the range 0-9999.9W, with a claimed accuracy of 0.1W. Mains frequency can be displayed over the range 45-65Hz, which should cover all countries outside of odd situations. Energy consumption can be calculated and displayed over the range from 0-999999kWh, with a resolution of 0.01kWh for values below 1000kWh, a resolution of 0.1kWh for values up to 9999.9kWh, and 1kWh for values up to 999,999kWh. Finally, the power factor is shown as 0.00-1.00. The rated accuracy of the D69-2058 for voltage and current is ±1%, ±2 LSDs (least-significant digits). I found the D69-2058 on offer at AliExpress from a supplier called Cooperate Electric Store, for $19.65 plus 81¢ for airmail shipping. It arrived in good condition about 40 days later. The D69-2058 is just as easy to use as Australia’s electronics magazine each of the other AC meters, as you can see from Fig.5. I found that the voltage readings were 0.22% high, while the current readings were 0.22% low. So the power readings should be very close to spot-on. Summary All of these AC panel meters work well and offer excellent value for money. But I think the one that impressed me most of all was the D69-2058, which not only has the largest number of measurement parameters, but also the most readable display. So if you need a multi-function AC meter for checking the operation of household appliances or workshop machines, it would make an excellent choice. It’s important to make sure that, regardless of what meter you use, all your mains wiring is properly insulated, and the meter is housed in an appropriate, sturdy case! SC siliconchip.com.au 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 Dual Battery Lifesaver mods for 24V Silicon Chip is a great magazine. What changes would be necessary to use the Dual Battery Lifesaver from the December 2020 issue (siliconchip. com.au/Article/14673) with a 24V battery? (J. O’G, Allambee, Vic) • You would need to use a different regulator as the S-812C33 is only rated for 16V at its input. The only suitable regulator we can find in a TO-92 package is the AP7381-33V-A, but it has a different pinout from the S-812C33. It could be adapted to the PCB footprint with a bit of lead-bending. The capacitor ratings would also need to be increased to 50V. The Mosfet ratings are 30V, so they should be just adequate. Other than the above, you would just need to change the dividers to suit the higher thresholds. Isolation transformer no good for fast signals In the November 2020 issue (p110), a reader inquired about “Adjusting Mosfet dead time with a scope”. Could this be done by inserting a step-up transformer in place of the shunt resistor? Alternatively, could a ferrite clamp transformer be used to measure the dead time current magnitude and shape? The current meter style clamp I bought at Jaycar has a voltage-to-current conversion table printed on it. This meter does not seem to be available any more; perhaps you could publish a project to build one. (N. B., Taylors Lakes, Vic) • A transformer in that role would affect the measured signal phase, and would be unlikely to have enough bandwidth to accurately reproduce the signal, which has fast rise and fall times. So a transformer probably couldn’t be used to measure the Mosfet dead time accurately. Ferrite current clamp meters have the same problem, whereas a resistive shunt does not cause a phase shift and siliconchip.com.au will not affect the rise and fall times, even at low levels. The measurement limitation then becomes the scope’s bandwidth and sensitivity, with many scopes being fast enough and sensitive enough to make this sort of measurement. As for your idea of a DIY Clamp Meter, we published such an article in the September 2003 issue (siliconchip. com.au/Article/3884). That design is still valid and all the parts used are still available, although you will have to find another source of the 50A alligator clip as the original DSE is no longer around. Questions about AWA ribbon mics I have a pair of AWA ribbon microphones that are identical in every respect to RCA 44BX models, and I’d like to know if they were made under licence by AWA or someone else or just rebadged. I’ve corresponded with a guy in the USA who reconditions these; apparently, his father worked for RCA and designed the 44BX. He’s fairly sure they’re just rebadged. I recall them being advertised in Electronics Australia in the mid-70s when 4VL was selling off some surplus studio gear. It stuck in my mind as my brother was an announcer there around that time. Years later, a friend told me he bought them from that ad and subsequently gave them to me. I’ve loaned them out a couple of times as stage props, but on both occasions, they were used as live mics. My brother worked at QTQ9 for a period and had their techs check them out, and they considered they were still up to broadcast specs. I have no use for them and would like them to be used by someone who does. The price will be enhanced if someone can confirm that RCA built them, so I hope someone can fill in the gaps. (B. M., North Ryde, NSW) • We don’t know the answer to this, but maybe one of our readers does. Australia’s electronics magazine Using D1 Mini BackPack with 2.8in screen I happen to have a 2.8-inch TFT touchscreen on hand, so I am using it to build the D1 Mini BackPack project (October 2020; siliconchip.com.au/ Article/14599). I have wired it all up and loaded the code etc. Only part of the screen has a display, and the keyboard buttons respond but they are not aligned. For example, if I press “s” I get a “c” etc. Are there other software settings and changes I need to do to get a 2.8-inch screen working with this project? (S. O., Sydney, NSW) • As we said in the article, our software is designed for the 3.5in display, which uses a different driver and has a different resolution to the 2.8in display (480x360 compared to 320x240). If it was simple to make the software work with both displays, we would have done so, but it is not, and it will involve more than just changing settings. The driver and initialisation code will have to be changed to suit the ILI9341 controller that is used in the 2.8in display. Also, all the graphics, touch and user interface will have to be adjusted to work at the lower display resolution. That means numerous changes throughout the code. We are sure that it is possible to get it to work, but it will involve significant changes to the demonstration sketch. D1 Mini BackPack not showing weather info I am building the D1 Mini BackPack; thanks for an interesting project. I have gone through the software installation, and everything seemed OK until I got to the OpenWeather part. I made a free account and got the API key straight away. I entered that into the script and loaded it into the ESP8266. When I switched it on, the screen came to life, and I entered my WiFi info and then selected my location. But all I get on the screen is my area, WiFi IP address and signal January 2021  107 strength stating OK (green), plus the local time. But no weather information ever comes up. I am wondering if anybody has had the same problem. (R. S., Epping, Vic) • If it is showing the current time, that means that it is connecting to your WiFi OK and has internet access. We don’t know why it isn’t connecting to OpenWeatherMap. There’s a lot more information available through the Serial Monitor, so we suggest that you open that and check what messages appear. Your API key should be enough for the weather function to work. Vintage Radio cabinet restoration I always enjoy reading the Vintage Radio section of your magazine. Associate Professor Graham Parslow and Ian Batty do a great job presenting the details of the restoration process. The October 2020 edition depicts a marvellous 1940 AWA Radiola, and it made me wonder about how the cabinet is restored to such fine condition. Have you ever published details on that subject? (T. V., Ivanhoe East, Vic) • We do sometimes have descriptions of cabinet restoration in Vintage Radio articles, but not that often. One recent example is the article on restoring a 1946 STC model 512 radio in the August 2017 issue (siliconchip.com. au/Article/10764), also by Graham Parslow. That article had around ten paragraphs describing the cabinet restoration. More recently, there was the Vogue radio restomod by Fred Lever (November 2019; siliconchip.com.au/ Article/12101). Sometimes the cabinet does not require extensive restoration; it might have been restored before it came into the writer’s possession. And sometimes they simply don’t cover the restoration in any great detail. Pocket Oscillator resets on input selections I purchased your Shirt Pocket Oscillator kit (September 2020; siliconchip. com.au/Article/14563) and put it together over a day or two. When I finished it, I powered it up only to be presented with a blank screen. I could see that the chip was getting power, so I tried reprogramming it and it came up with the welcome screen, then 1000 appeared on the screen. 108 Silicon Chip But when I try to change the frequency or use the rotary encoder, the ATtiny85 resets and returns to the welcome screen. The output from the Oscillator looks OK on my DSO, as does the signal from the rotary encoder. Did I receive an ATtiny chip that wasn’t programmed? Or do I have something weird going on with my unit? I have carefully checked my construction and it appears to be all correct. I wonder if you have struck this problem and if there is an obvious fix for it. (T. MacC., Bathurst, NSW) • It does sound like you received an unprogrammed chip, but we are mystified how that could happen. We checked all of our programmed chips in stock and they appear to all have been programmed correctly. We think this was an isolated incident as we have not received any other similar complaints. As for it resetting after you have programmed the chip, the designer (Andrew Woodfield) replies: It is almost certainly due to a failure to program the fuse bits, and in particular, the high fuse bit 7. If it is possible to verify the chip after programming, then that bit was definitely not programmed correctly. In the Pocket Oscillator design, the RSTDISBL bit must be set to 0. The default for this fuse bit is 1, in which case, any high-to-low transition on the RST pin (pin 1), where the rotary encoder is connected, will reset the chip. The fix is easy: program the fuse bit as described in the article, using any normal Atmel/Microchip programmer such as one of the super cheap USBASP programmers. Once this has been done, you can no longer reprogram the chip because the chip will not respond to the reset signal from the programmer at the start of programming. The only way to program a chip once it has been flashed with RSTDISBL=0 (or with an incorrectly configured clock source) is to use a high-voltage programmer. cycle lead-acid battery that cost over $200, and I want to keep it on float charge most of the time and use it for an electric outboard motor. Would your Universal Battery Charge Controller (December 2019; siliconchip.com.au/Article/12159) be the way to go? I note that you had a Deep Cycle Charger (November 2004; siliconchip.com.au/Series/102), but thought that might be a bit dated by now. (G. C., Toormina, NSW) • Yes, the December 2019 Charge Controller is suitable for float charging. The November 2004 charger would also work, but you might find it hard to source some of the parts now. I recently had a deep-cycle battery that gets infrequent use, fail while being kept on float charge. That was with a standard battery charger and a regulator added on to maintain the float voltage. I have purchased another deep December 2019; siliconchip.com.au/ Series/339) and testing it set to 0V with all pots turned low, I measure -0.417V at the output. The article says if it is not 0V, to check for faults and I’m wondering How to use Silicon Chip short links At the bottom of page 13 in your November 2019 issue, there is a reference to an article numbered 8124. How do I find this from your home page? (B. H., Pacific Pines, Qld) • It took me a while to figure out which page of which issue you are referring to. I think it is the web link at the bottom of page 13 in the November 2019 issue (siliconchip.com.au/ Article/8124). All you need to do is type the link address (in this case, “siliconchip. com.au/Article/8124”) into the address bar on a web browser and press Enter. It will then take you to the appropriate page. The situation is the same with our short links to external websites, which are formatted like siliconchip.com.au/link/abcd The links will also work with a www. in front, but we leave that part out to keep the links as short as possible. That’s also why we don’t prefix the links with http:// or https://, which is technically required to make them proper URLs. But most web browsers default to assuming the HTTP protocol, so we don’t include that part of the links either. Bench supply output slightly negative Using Charge Controller sits I’m at the point of final testing of the for float charging 45V 8A Linear Power Supply (October- Australia’s electronics magazine siliconchip.com.au where to look. I also think the temperature reading is a couple of degrees higher than actual and I’m wondering if there’s a way to calibrate that. (S. B., Banyo, Qld) • Assuming that you haven’t reversed the output terminals, the schottky diode should clamp any negative voltage at the output near the output terminals (the one that was confusingly marked D5 or D6 in different places). A non-zero positive reading could indicate a circuit fault, but that diode is the only thing that could cause a negative voltage to slip through. We suspect that it will go away once you complete the calibration. The displayed temperature simply comes from a table in the file “thermistor.h”, so to fully recalibrate the temperature readings, you would need to alter that table and recompile the software. Otherwise, try changing the value of the 9.1kW resistor between pin 1 of CON7 and the +12V rail. That will only allow you to shift the temperature at one point, so it might become inaccurate in other places, and it might also affect how the fans respond and the thermal shutdown point. Trouble with touchscreen on Arduino I purchased the PCB to adapt the 3.5in LCD touchscreen to an Arduino in the May 2019 issue (siliconchip. com.au/Article/11629) along with an ILI9488-based 3.5in screen. The graphics test and SPI display demo sketches work correctly. However, the SPI touch calibration loads the serial monitor display correctly, then blanks the screen and doesn’t respond to serial inputs or screen touches. Also, the SPI shield demo with touch failed to verify (compile) giving the error message “cannot declare variable ‘c’...” from line 11. All of these sketches place a lot of technical bookkeeping in the main program. Any suggestions to get these programs running would be appreciated. Silicon Chip magazine is always a great read! (D. H., Nelson, NZ) • The only difference we can see between our setup and yours is that you are using the older Arduino 1.6.13, while we are using 1.8.5. We are sure that this is the cause of the “cannot declare variable ‘c’...” error, and probably the other failures as well. Please siliconchip.com.au upgrade your Arduino IDE to version 1.8.5 and then try again. The reason we put everything in the main program is to make it easier for people to modify the software and see how it works. Wide-range LC Meter pitfalls I recently built the Wide Range Arduino based LC meter (June 2018; siliconchip.com.au/Article/11099). I am having some difficulty getting it to work, and wanted to ask if there was any errata published for this project which might help me work out what is wrong. (B. C., UK) • There are no known problems with the article or the design, but there are a few common pitfalls which can prevent it from working, and can be frustrating to track down. The two biggest problems that we have seen from constructors are: 1) Using a relay which has a different pinout, coil voltage or integral diode compared to the one we used. Partly this is because our suggested sources (Jaycar/Altronics) theoretically sell only suitable relays of the type we specified. Still, other types are available elsewhere, and it is easy to get them mixed up. Suppliers might sometimes have 12V relays in their 5V bins, so you need to check! The usual symptom of incorrect relays is that the display will work, but the results will be wrong, or the unit won’t calibrate correctly. If all the relays are heard to be clicking when operating the device, then there’s a good chance that is not the problem. 2) Variants of the I2C LCD controller having a different address. The code notes (at line 14) that the controller could be in the range 0x20-0x27, but there are variants which have addresses from 0x38-0x3F. If the default address of 0x27 doesn’t work, try changing it to 0x3F. If the display is not working, there’s a good chance this is the reason. This was noted in an erratum that we published in September 2018. Any number of other construction errors could also show either of these symptoms, but it is worth checking the above first. Finally, we note that one constructor reported that the unit started working after changing the comparator IC for another one. Australia’s electronics magazine Maximite or Micromite? I just bought the “Maximite BackPack” and have assembled it and have tried it on a terminal. It will connect and give answers to print 1/7 etc and the LCD screen lights brightly. But it will not run the OPTION LCD command; it just says “command not recognised”. Can you suggest anything to help? I thought of reflashing the HEX file but am not really sure how. (R. M., Ilkley, Qld) • We haven’t published a Maximite BackPack. Are you sure it is a Maximite and not a Micromite? Please send us a copy of the terminal text (commands and responses) so that we can check them. Also send the results of this command (which prints the software version): PRINT MM.VER The Micromite has no OPTION LCD command, only OPTION LCDPANEL so perhaps this is the root of your problems. By default, the screen will light up white if it is not initialised. If you want to try reflashing the HEX file, refer to the Microbridge article from May 2017 (siliconchip.com.au/ Article/10648). Running SC200 amplifier from ±63V Can I power the SC200 amplifier (January-March 2017; siliconchip. com.au/Series/308) from a ±63V DC supply? (R. R., Melbourne, Vic) • We definitely don’t recommend doing that if you are going to drive 4W speakers, as you are likely to blow the output transistors at high output levels. We still don’t think it’s a great idea with 8W speakers, but you might get away with it. Check your speaker impedance curves (if you have access to them) to verify that their lowest impedance is not too low at any given frequency (ideally, no lower than about 6W). Hopefully, that will keep the output transistors within their safe operating areas. You will have to change the 63Vrated capacitors to 80V or 100V types, as your supply is likely to have peaks above 63V. We don’t think any of the other parts would need to change. So basically, if you are willing to risk the output transistors and have 8W January 2021  109 speakers without any very low impedance dips, you could consider trying it. But we cannot guarantee that it will work as the design was not verified with supply voltages above 60V DC. Speed Controller cuts out at higher currents A few months, I built the High Power DC Motor Speed Controller (January & February 2017; siliconchip.com.au/ Series/309) with some modifications. I raised the switching frequency because the motor was too noisy. I am using this controller for one Minn Kota 12V trolling motor. I have used the motor on my fishing boat with this speed controller, and I’m happy with it. But I have one problem that I can’t solve. Without load, I can adjust the speed from minimum to maximum without a problem. When loaded, once the speed potentiometer is halfway and the current reaches around 16A, the motor suddenly stops for one second and then runs again, then stops again. If I reduce the speed a little bit, the motor runs normally. When it stops for a fraction of a second, it also lights up the red LED. My battery is a 100Ah lithium type and can provide more than 50A without problems. I assumed the back-EMF was the problem but adjusting the trimmers does not solve it. (A. D., via email) • This is probably due to the lowvoltage shutdown setting. At 16A, the battery voltage drops below the low voltage threshold, and the voltage increases when the motor is switched off or the speed is reduced. Adjust low-voltage threshold trimpot VR3 for a slightly lower cut-out voltage, so that the battery does not reach the cut-out voltage during normal operation when charged. Uses for ‘electronic transformers’ Has Silicon Chip magazine ever published any applications for the ubiquitous electronic transformer? Are they suitable and safe for inclusion into various power supply projects? I have been one of your keen readers for many years; I used to read Electronics Australia since the 1960s and made many of the kits. (E. U., Castle Hill, NSW) 110 Silicon Chip • We haven’t used the switchmode 12V AC output ‘transformers’ in any projects (typically used for driving halogen or LED downlights). However, we used the older style 12V AC halogen transformers in a battery charger project in April 2013 (siliconchip.com. au/Article/3759). We would not recommend using the switchmode transformers in this application, as they were connected in parallel for more current, and the electronic versions may be damaged when paralleled. Electronic transformers can usually be used as a 12V AC supply. They may fail or shutdown if connected to a bridge rectifier and filter capacitor to derive a DC supply. They are mainly suitable for the purpose they were designed for, ie, supplying 12V AC to a resistive load such as for LED lighting. CDI module needed for use in jet skis I want to rebuild some retro 1980s & 1990s stand-up jet skis with Kawasaki JS550 twin-cylinder, two-stroke engines. These all had CDI systems originally, but it is difficult and expensive to get original parts, so I am thinking of building replacement CDI systems for them. As I understand it, they have a wasted spark arrangement, where both plugs are both fired every half revolution. On the later models, they realised that a rev limiter was needed for when the impeller cavitates and the engine spins on no load, so that would be a good feature to add. I am considering your Replacement CDI Module For Small Petrol Motors from May 2008 (siliconchip.com.au/ Article/1820), but I see that you have also published other ignition systems, including a Multi-Spark CDI in December 2014 & January 2015 (siliconchip. com.au/Series/279). Can you recommend which option is best for me, and what smart/programmable controls could be added to such as a rev limiter, multi-spark, timing advance etc. As the HV coils and CDI were all sealed inside a single factory original unit, what is your recommended coil arrangement? There seem to be several aftermarket twin coils for sale online, but how would I choose? Their Australia’s electronics magazine only specifications are primary and secondary impedance values. (L. C., Donvale, Vic) • The Kawasaki magneto ignition includes a high-voltage generator coil to produce around 300V to charge the capacitor in the CDI, and another trigger coil to fire the ignition. The May 2008 replacement CDI unit should be suitable. This CDI will work with many ignition coils, so the choice is not critical, and ideally, you should use the two high-tension outputs to drive both spark plugs. We don’t recommend that you use so-called “sports coils” as these can develop very high voltages and could break down when used with a CDI. The primary resistance of the coil is an indication of whether the coil is suitable. Choose one rated at 3W or more (for a 12V coil). That means that the charged (or saturation) coil current would be less than 5A (assuming a 14.4V supply from the battery). Many sports coils have a much higher charging current. The multi-spark CDI is more for converting a standard ignition that has conventional triggers such as reluctor, Hall effect or optical and powered via a battery supply. We have published two rev limiter designs which you could use, one in April 1999 (siliconchip.com.au/ Article/4589) and one February 2008 (siliconchip.com.au/Article/1753). Substituting amplifier output transistors I am building a pair of 500W Power Amplifier modules (August-October 1997; siliconchip.com.au/Series/146), the article specifies 12 MJL21193/4 output transistors. I have been looking around and found the MJL1302/ MJL3281 which have almost identical specifications. Their safe operating area (SOA) is the same, but the 1302/3281 maximum collector voltage is slightly less at 200V compared to 250V; the maximum collector current is 15A vs 16A. The gain-bandwidth products of these transistors are quite different 4MHz vs 30MHz. Can I substitute the MJL1302/3281s or should I spend more and buy the MJL21193/4? If they can be substituted, are any modifications required? (L. K., Wanganui, NZ) continued on page 112 siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP PCB PRODUCTION KIT ASSEMBLY & REPAIR 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 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 FOR SALE GREAT VALUE PARTS and more are found in the Tronixlabs eBay store via tronixlabs.com.au – for enquiries or support please email support<at> tronixlabs.com LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote, quote photo numbers when referring to a book: silicon<at>siliconchip.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 Every article in every issue of YOURS FOREVER IN N DIGITAL (PDF) FORMA MA A Can now be yours forever in digital (PDF) format - Storing 30+ years of SILICON CHIP magazines takes up a lot of space. Now save all that space and still have every issue available. Or maybe you simply want the convenience of searchable files plus index –-so you can find a feature or article you want without trawling through back issues! The digital edition PDFs are supplied on a quality metal 32 or 64GB USB flash drive, each five-year block (60 issues), covering: Nov 87 - Dec 94 Jan 00 - Dec 04 Jan 10 - Dec 14 Jan 95 - Dec 99 Jan 05 - Dec 09 Jan 15 - Dec 19 Each five-year block is priced at just $100, and yes, current subscribers receive the normal 10% discount. If you order the entire collection, the 6th block is FREE (ie, pay for five, the sixth is a bonus!). All PDFs are high resolution (some early editions excepted). Save the files to your PC hard disk, and the USB Flash Drive can be used over and over! For more information, or to place an order, visit www.siliconchip.com.au/ shop/digital_pdfs 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, ad­ dress & 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 2021  111 • While the MJL21193/94 transistors from ON Semiconductor are recommended, they are now obsolete and difficult to get. We recommend the ON Semiconductor NJW21193/94 transistors instead. You could use MJL1302/MJL3281. As you mention, they have a higher cut off frequency. This might or might not be a problem. They may give better performance, but it’s also possible that the amplifiers could oscillate. If you find the DC fuses are blowing for no reason, try increasing the value of the 100pF 500V compensation capacitor. However, as that value is quite high, it should be OK. According to the circuit, you need seven of each type of transistor, regardless of which types you use. Power supply cable stripe polarity I use figure-8 speaker cable (eg, Jaycar WB1703) in many projects. Should the black stripe for polarity identification be used for positive or negative? I originally thought black indicates negative, but then I noticed that most plugpacks have the striped side of the wire indicating positive. Now I’m thinking that as positive is the wire I want to be identified, perhaps I should always use the black striped wire for positive. I use the wire for motors and Arduino projects, but if anyone was connecting speaker wire to the black and red terminals on a speaker box, surely the wire with the black stripe would go to the black terminal. Is there a standard for this? (J. B., Benalla, Vic) • If you have red and black wires, then usually red would be positive and black would be negative. But it’s a bit more tricky when you have a stripe. Sometimes you have a white stripe, sometimes a red stripe and sometimes a black stripe (and possibly other colours). Usually, the stripe is used to indicate positive, but that certainly is confusing when the stripe is black. Ultimately, it doesn’t matter as long as you are consistent so that there is no confusion. As you say, plugpacks tend to use the stripe for positive (usually a white stripe, though), so it would make sense to follow that convention. Probably the best solution would be to use Jaycar Cat WH3057, WH3087 or similar cable which has red and black insulation for the two wires in the cable. Flashing lights wanted for model railway I am trying to find a railway crossing flashing light kit, or at least a PCB for it. I am sure I have seen something like it in past magazine issues. I have searched your site without success. Could someone point me in the right direction? (P. C., via email) • We published a two-lamp flasher circuit (January 1998; siliconchip. com.au/Article/4748). You can download its PCB pattern from the following page: siliconchip.com.au/ Shop/10/2362 Jaycar also sells a kit for that project, Cat KJ8070. This design runs from 12V and so is suitable for 12V SC lamps. Advertising Index Altronics...............................89-92 Ampec Technologies................. 19 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. 101 Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.............. IBC Mouser Electronics...................... 7 Ocean Controls......................... 39 Rohde & Schwarz.................. OBC SC Micromite BackPack............ 47 Silicon Chip Binders............... 106 Silicon Chip PDFs on USB..... 111 Silicon Chip Shop.................. 100 Silicon Chip Subscriptions....... 88 The Loudspeaker Kit.com......... 99 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics..................... 5 Notes & Errata Balanced Input Attenuator for the USB SuperCodec, November-December 2020: the photo shown halfway down the lefthand column on page 71 of the December 2020 issue, showing the wiring to the power connector, is incorrect. The positive (red) wire should be shown going to the bottom-most pin in the socket, with the black (negative) wire to the top. Also, in the circuit diagram on pages 50 & 51 of the November 2020 issue, the centre (ground) pin of CON3 at upper right should only be connected to the junction of the two zener diodes, the negative end of the 100µF capacitor next to switch S1 and the negative ends of all relay coils. The junction between this ground and the other grounds in the circuit is on the main SuperCodec board. Two LED Christmas Stars, November 2020: in the parts lists on page 41, there is no such part as a 75HC595. It should read 74HC595 instead. D1 Mini LCD BackPack with WiFi, October 2020: in the circuit diagram (Fig.1), the connections to pins 7 & 8 on the LCD module via CON1 are swapped. The drain of Q1 should go to pin 8 (LED) while pin 7 is the display SCK line and also connects to pin 10 on the LCD module and on to the D5 pin of MOD1. The February 2021 issue is due on sale in newsagents by Thursday, January 28th. Expect postal delivery of subscription copies in Australia between January 27th and February 12th. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au