Fullscreen HTML5Med Res (??MB)HTML4

NOVEMBER 2022 ISSN 1030-2662 11 9 771030 266001 The VERY BEST DIY Projects! $1150* NZ $1290 INC GST INC GST 28 | Tiny LED Icicle The perfect decoration for this Christmas 4 1 | LC Meter Mk3 An update to a crucial workbench tool 49 | Transient DC Supply Filter Protect your devices from harm 62 | Active Monitor Speakers A high-end sound system for your home All About Torches the history of the hand-held light siliconchip.com.au Australia's electronics magazine November 2022  1 Create highly detailed prints with Our Newest 4K 3D Printer The new Anycubic Photon Mono 4K resin printer is great value and perfect for any maker, from hobbyist to professional. • MAKE MODELS UP TO 165(H) X 132(W) X 80(D)mm • FAST 1.5 SEC LAYER CURE • 10-50µm LAYER HEIGHTS • 2.8" TOUCH SCREEN • RESIN FILL INDICATOR • REPLACEABLE ANTI-SCRATCH FILM • COMPATIBLE WITH PHOTON MONO FEP SHEETS • 6.23" 4K MONOCHROME LCD • 35µm XY RESOLUTION BRINGS VIVID DETAILS • 400:1 CONTRAST RATIO FOR SHARP & CLEAR EDGES JUST 599 $ • UV BLOCKING COVER • AUTO PAUSE IF COVER REMOVED MID-PRINT TL4419 10% OFF SELECTED RESIN TL4425 - TL4439 NOW FROM $39.95 Promotion Date: 02.11.22 – 13.11.22 Shop Jaycar for your 3D Printing needs: • 2 Models of Resin Printers, with over 45 types of resin • 8 Models of Filament Printers, with over 50 types of filament and counting! • Massive range of 3D Printer spare parts & accessories • In-stock at over 110 stores or 130 resellers nationwide Order yours today: www.jaycar.com.au/resinprinters Phone: 1800 022 888 TERMS & CONDITIONS: 10% OFF SELECTED RESIN applies to Anycubic Resin 500ml (TL4425-TL4429) & eSUN PLA Resin 1kg (TL4433-TL4439). Prices valid from 02/11/22 to 13/11/22. Company owned stores only. Contents Vol.35, No.11 November 2022 14 The Technology of Torches Page 41 Illumination has always been an important technology for humans, especially in a portable form for nighttime use. Once a stick with a fire on the end, modern torches are increasingly smaller and more powerful. By Dr David Maddison Handheld lighting feature 56 Raspberry Pi Pico W The Pico W is the newest Raspberry Pi module which now incorporates WiFi functionality, all for only a few dollars more! By Tim Blythman Microcontroller module review LC Meter Mk3 Raspberry Pi 76 WiFi-Synchronised Analog Clock Pico W If you can’t get reliable GPS signals, you can adapt the GPS-Synchronised Analog Clock (Sept 2022) to use a D1 Mini module to track time via WiFi. By Geoff Graham Timekeeping feature 78 Particulate Matter (PM) Sensors In the last article of this series on air quality sensors, we take a closer look at PM2.5 sensors, also called “dust” or “smoke” sensors. By Jim Rowe Using electronic modules Page 56 Page 62 28 Christmas LED Icicle Decoration This Tiny LED Icicle is simple to build with just a few components. It’s easy to join multiple together, making for a great holiday decoration. By Tim Blythman Christmas decoration project 41 LC Meter Mk3 This modernised LC Meter measures a wide range of capacitances from 1pF to more than 1200pF with 0.1pF resolution, and inductances from 100nH to 2.5mH. It uses three AA cells and has a battery life of ~72 hours. By Charles Kosina Test & measurement project 49 Transient DC Supply Filter This 12V DC Supply Filter helps prevent voltage spikes ruining your devices or supply noise messing with their performance. It can handle up to 5A (or 10A with different inductors), and fits in a compact UB5 Jiffy box. By John Clarke Power conditioning project 62 Active Monitor Speakers, Part 1 These high-quality Active Monitor Speakers create a superlative sound system to complement your living room. High-end Satori drivers are used throughout the project and can be combined with an optional subwoofer. By Phil Prosser Audio project 90 30V 2A Bench Supply, Part 2 To finish our new Bench Supply, we cover the construction details with extra attention to the mains wiring, testing and calibration procedures. By John Clarke Bench supply project Active Monitor Speakers with optional subwoofer 2 Editorial Viewpoint 4 Mailbag 30 Circuit Notebook 84 Vintage Radio 88 Online Shop 1. Digital preamp with tone controls 2. ESP32-Camera sentry with object detection Philips Minstrel radios by Assoc. Prof. Graham Parslow 100 Serviceman’s Log 108 Ask Silicon Chip 111 Market Centre 112 Advertising Index 112 Notes & Errata 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. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com 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 (Australia only) 6 issues (6 months): $65 12 issues (1 year): $120 24 issues (2 years): $230 Online subscription (Worldwide) 6 issues (6 months): $50 12 issues (1 year): $95 24 issues (2 years): $185 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. ISSN: 1030-2662 Printing and Distribution: 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Editorial Viewpoint Close-up vision: use it or lose it Like most people, as I am getting older, I have noticed that it’s becoming harder to focus on tiny objects close to my face. However, I think this has to do with more than just age. These days, due to my editorial duties, I spend a lot more time editing documents on the computer, answering e-mails and so on, and less time building PCBs and such. That means my vision is fixed at the same distance of around 30-50cm for much of the day. When I recently managed to get far enough ahead in my editing duties to work on some projects, I struggled working with parts that I had no difficulty with just a few years ago. But I noticed that over time, as I did more soldering and assembly work, much of my good close-up vision started to come back, and I was suffering less from eye strain and such. One of the reasons our vision deteriorates as we age is that the flexible lens in our eyes becomes less elastic over time, making it harder to focus on objects closer to our faces. But I wonder if that is accelerated if we are not using our close-up vision enough. I also suspect that the muscles that change the shape of the lens will weaken if they are not used, leading at the very least to increased eye strain when working with small objects or reading small type. Regardless of the mechanism, I think you are more likely to keep your close-up vision if you use it regularly. Having said that, it probably isn’t great to use it too much, either. We need to spend some time looking into the distance every day too, and many hours spent working with tiny details are likely to result in eye strain and headaches at the end of the day. Competition resulting in innovation It looks like the CPU market is heating up again (quite literally in some senses). After seemingly almost a decade of stagnation, AMD and Intel are finally working hard to leapfrog each other. The just-released Ryzen 7000 series runs at impressively high frequencies, up to around 6GHz in stock form, compared to around 5GHz for the previous generation AMD parts and current Intel CPUs. That frequency jump primarily comes down to the process node shrinking from 7nm in the previous generation to 5nm in the current generation (see our articles on IC Fabrication Technology in the June-August 2022 issues for details: siliconchip.au/Series/382). Along with efficiency improvements, the result is an approximately 30% improvement in single-threaded performance. That’s similar to the previous generation’s gain, so we’ve seen computer speeds jump nearly 70% in just a couple of years. Parallel processing users won’t be disappointed either, with the flagship AMD CPU (Ryzen 7950X) beating the Intel i9-12900K by 42%. And now, just after I wrote that, Intel announced their 13th-generation parts (that we knew were coming). They are certainly an improvement over the 12th-generation, increasing both the core count and maximum operating frequencies. But it looks like AMD is still in the lead in many workloads, at least for now, as Intel have not changed their node so radically. We don’t want the situation we had for most of the last decade where AMD was down (but not quite out), and Intel had no real competition. They would bring out a new generation of CPUs now and then with modest improvements, but it didn’t seem like they were really trying that hard. That laziness has cost them their technology lead, and now they are scrambling to catch up. Cover image source: https://unsplash.com/photos/BvAoCypqRXU Australia's electronics magazine by Nicholas Vinen 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 has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. Silicon Chip magazine giveaway I have about 20 years or more of Silicon Chip magazines and I need to start clearing out my stuff, for any readers who would find them useful. Bruce Dunlop, Ashburton, Vic. Comment: if you’re interested, send an e-mail to silicon<at> siliconchip.com.au and we’ll pass it on to Bruce. More on the topic of video displays I found the articles on Video Display Technologies (September & October 2022; siliconchip.au/Series/387) interesting. I wonder if anyone remembers that in 1954 the French company Laboratoires Derveaux developed a spiral scan television system that significantly reduced the flyback time by simply having one long spiral line per frame! It was roughly equivalent to 600 linear scan lines, but of course, the resolution was highest at the centre and progressively degraded towards the edges. The system was described in the January 1955 issue of Wireless World. Graham Lill, Lindisfarne, Tas. Spectral Sound project is working well I wrote to you a while ago asking for help getting the Spectral Sound MIDI Synthesiser project working (June 2022; siliconchip.au/Article/15338). One of the things that threw me off was the orientation of diode D2 being shown incorrectly in Fig.9, but your erratum in the August issue allowed me to fix that. After some more fiddling, I finally got it all working. I have had a fair amount of correspondence with Jeremy Leach (thanks for putting me in touch), and it has taken quite a bit of effort. One of the problems was with the way I was interfacing my keyboard to the synth. Purchasing a small MIDI controller and comparing voltages allowed me to sort that out. There was no issue with the optocoupler in the end, as I thought early on. We ran a few tests on the mixer micro and verified that it was working. Jeremy gave me a new build of the firmware (which should have been identical to the one you supplied), and many things started working better. I also reprogrammed the tone generator chips using firmware I got from him (which should be identical to the one you supplied), and it is now all working. I am very happy with the result and will work with Jeremy to enhance this project further, mainly focusing on using signal processing for creating models of new instruments from captured audio. Thanks for your help. By the way, if anyone wants to modify the Spectral Sound code, it’s vital to use the Microchip XC16 compiler 4 Silicon Chip for programming the Mixer (and Tone Processors) to get level 3 optimisations. These chips perform time-critical tasks, so optimisation is extremely important. Trying to use the free XC8 compiler just doesn’t work because the compiled code won’t run fast enough. Dan Amos, Macquarie Fields, NSW. DIY TV sets from the 1950s David Maddison’s articles on Display Technology brought to mind some of my distant past (siliconchip.au/Series/387). In the late 1950s, I built a TV set described in Radio, TV & Hobbies magazine using a 5BP1 (at school in “Leaving”, or year 11 in today’s vernacular). Here is a picture of the 5BP1s that I bought from Waltham’s in Melbourne. I believe they were from WW2 radar sets. Geoff Champion, Mount Dandenong, Vic. Solution for unreliable motion-triggered switch Back in February 2019, Silicon Chip published an article about a small vibration-triggered switch (siliconchip. au/Article/11410) that overcame the problem of permanently powered accessory sockets in cars that might allow a battery to be flattened by an accessory being left on. The switch turned off the power after a suitable delay if no motion was detected, ie, the car had stopped. The idea appealed to me as I had a car with this exact feature (problem!). I ordered a kit from Silicon Chip and duly built one but could never get it to work reliably. I often returned to the car to find that the amateur transceiver it powered was still on. Fast forward to 2022 and a new car with the same problem – unswitched accessory outlets! I decided to revisit your design and try again with a new kit, as I wanted to switch a low-power navigation device. However, I had the same problem: an unreliable switch-off. Even after purchasing new vibration sensors and very carefully installing them, in case I had done some damage to the originals, the problem persisted. Measurement of the voltage at the negative end of the 47µF capacitors to ground showed the correct 12V decreasing to less than 1V over the time-out period, at which point the circuit turned off. However, now and then, the voltage did not drop and stubbornly stayed at 12V. A good thump of the board and Australia's electronics magazine siliconchip.com.au the voltage would decrease, and the circuit turned off after the time delay. The sensor data sheet shows the contacts are rated at 20mA, and my thought is that the contacts were micro-welding themselves closed with the instantaneous short circuit current from the 47µF capacitors. I placed a 100Ω resistor in series with the contacts to limit the peak current, which has, so far, resulted in reliable operation of the switch. I tried using 680Ω as that would limit the current to the 20mA specification but the value was too high to properly discharge the capacitor, resulting in a shorter turn-off delay. I am not aware of any updates or errata for this project. Any thoughts? Thanks for a great magazine. Nigel Dudley, Ocean Beach, WA. Response: we think your diagnosis is spot on. We noticed that the prototypes would occasionally not switch off, but we thought it must have been due to the vibration sensor being damaged in testing. As you describe, we now realise that it was almost certainly contact welding. Your solution of inserting a series resistance is probably the simplest fix. Thank you for doing the work to figure this out. An alternative source for switch caps Regarding the WiFi DC Load project in September and October 2022 issues (siliconchip.au/Series/388), I found it somewhat difficult to procure the switch caps for the four pushbuttons on the control board. The switches are easy to obtain from Altronics or Jaycar, but when I went to order the caps, Altronics had no stock in any colour, and Jaycar doesn’t have anything suitable either. I found a compatible product, Omron B32-16x0. It is available in ivory, black, orange or yellow (1600, 1610, 1620, 1630). They are sold by the usual suspects (element14, RS, Mouser and Digi-Key) and some are in stock in Australia. I thought this information would be worth sharing with your readers. Erwin Bejsta, Wodonga, Vic. Fraud warning for too-cheap SSDs I am writing to inform you and your readers about an online SSD scam. One AliExpress vendor alone, “SSD HDD Wholesale Store”, has taken 3941 orders selling ‘multi-TB hard drives’ for pennies. Other stores have sold many thousands more. Now vendors are advertising up to 30TB drives for less than US$30. The feedback appears to show many happy customers. The drives show up on the operating system as a bunch of 2TB drives. In my case, four of them for an 8TB drive. You can write 2TB to each one. It will take around one whole day to write 2TB. Just don’t expect the data to be there when you read it. It won’t. It uses a USB 3.0 socket, but the control chips report they are USB 2.0. The write speed is around 6MB/s. It writes in small bursts with a long delay between each write. Presumably, this is so you will send good feedback for your apparently good purchase. 66% of the feedback is 5 stars, while almost 20% is 1 star. The actual memory chip, as reported by an SSD formatter, is either a 32GB or 64GB device. My 8TB drive had a mix. While this might be a good size for a thumb drive, it is less than 1% of what you expect. These drives have been faked. 6 Silicon Chip Australia's electronics magazine siliconchip.com.au PRECISION MADE EASY Next-generation oscilloscope for accelerated insight NEW R&S®MXO 4 The R&S®MXO 4 Series is the first of a new generation of oscilloscopes that excels in both performance and value. The instruments deliver a once-in-a-decade engineering breakthrough for accelerated insight. The R&S®MXO 4 Series oscilloscopes utilise leading-edge technologies to achieve fast and accurate results. Custom technology and innovative features in our oscilloscopes quickly boost your understanding of circuit behaviours. More at: www.rohde-schwarz.com/product/mxo4 Series oscilloscope Helping to put you in Control 1-Wire carbon dioxide sensor Monitor the fresh air level in a room or building, the TSM400-1-CP is a combined carbon dioxide and barometric pressure sensor with a 1-Wire interface. Power 4.5 to 26 VDC. SKU: TCS-016 Price: $340.95 ea Modbus carbon dioxide sensor TSM400-4-CP is a combined carbon dioxide and barometric pressure sensor with a Modbus RS485 interface. SKU: TCS-017 Price: $340.95 ea ToughSonic Chem 14 - 4.3 Meter Ultrasonic Sensor Senix new ultrasonic level sensor has been designed for demanding environments such as measurement of waste water and chemical liquids. It is built to IP68 and can be submerged. SKU: SNS-0810 Price: $1589.50 ea Din rail 4-20mA adjustable single generator Powered by 230VAC the output signal is an adjustable 4-20mA set via a front mounted potentiometer. Use for testing, VFD speed control. SKU: NTR-321 Price: $156.75 ea GBMA 0-10VDC Input 3 Digit Large Display Large three digit universal process indicator accepts 0-10VDC signal with configurable engineering units. 10cm High digits. 24V DC Powered. SKU: DBI-025 Price: $559.90 ea Climate Temperature and Humidity Sensor Wall mount RHT-Climate WM-485-LCD Temperature and Humidity Sensor with LCD display, RS485 Modbus Communications and 4 to 20mA/0-10VDC outputs. Powered by 12 to 30VDC. SKU: RHT-105 Price: $332.70 ea LabJack T7 Data Acquisition Module Is a USB/Ethernet based multifunction data acquisition and control device. It features high data acquisition rates together with a high resolution ADC. SKU: LAJ-045 Price: $902.00 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. 8 Silicon Chip There is no point asking for your money back. It would not be good PR for AliExpress to make so many refunds; they must think it’s best to ignore the situation and keep up the revenue. The store mentioned above seems to have no other products for sale. It has only been operating since Feb 23, 2022. The vendor has now sold out. It looks like it was set just for this scam. These drives are still being advertised on many other platforms: eBay, Amazon and Alibaba etc. If it seems too good to be true, it is too good to be true. I was lulled into a false sense of security by the positive feedback and the fact that so many vendors were selling these drives. The control card reader I used is “ChipGenius_ v4_19_0319.exe”. It tells you everything available to your operating system, except that the capacity is the real one. The SSD formatter sizes and formats the SSD memory chip itself. I used “FirstChip_MpTools_20200430_ FC1178_FC1179”. This is published by the control card manufacturer. Leave the password for Settings blank. Robin Fleet, Rockingham, WA Running 3-phase equipment from single-phase mains Regarding Andre Rousseau’s comment about running three-phase motors from single-phase AC (August 2022, page 12), I can confirm that the capacitor phase shift method does indeed work, probably somewhat better than you’d expect. About 40 years ago, a garage mechanic asked me if I knew any way to test some old three-phase machines he’d just bought, basically for scrap value. He just wanted to know if they were still electrically workable, if the bearings were OK and so on, to see if it was worth paying to have three-phase power installed. Starting with the bench grinder, I hooked up Active and Neutral to two of the phases and connected (from memory) a 6.5µF motor start capacitor to the other phase. I put it on a Variac, slowly cranked it up, and away it went. Not only did that confirm it was electrically and mechanically sound, but it seemed to be perfectly serviceable just like that! It wasn’t getting hot or showing any signs of distress. I subsequently hooked up the drill press, lathe and air compressor the same way, using larger capacitors. Holding a piece of hardwood against the chucks of the drill and lathe showed they still had plenty of torque. The compressor seemed to take a bit longer to fill the tank than we expected, but other than that, it was fine as well. He never actually got around to installing three-phase power; for his purposes, they were more than good enough as they were! Regarding Bruce Bowman’s letter about water-cooled amplifiers (August 2022, page 10), I remember reading in the 1940 edition of Donald Fink’s Principles of Television Engineering how the first generations of VHF TV transmitters used water-cooled triodes. The water was pumped into the anode heatsinks via copper tubes that also served as part of the transmission line to the antenna. Certain points on a transmission line are at zero RF voltage; one of those was where the cooling water was inserted and extracted. The best they could do then was about 12% efficiency at 50MHz, and the preferred option was to use a temperature-­ compensated LC oscillator to drive the output valves! Australia's electronics magazine siliconchip.com.au TRENDING Our dedication to provide you with products Excellence in Engineering New FOOT & PALM SWITCHES Product THERMAL SWITCHES WATERPROOF SWITCHES EC SERIES COMPACT E-STOP OTHER products LED INDICATORS LINEAR SENSORS ROTARY SENSORS TILT SENSORS TACTILE SWITCHES HAND CONTROLS INDUSTRIAL JOYSTICKS FINGERTIP JOYSTICKS USB DESKTOP JOYSTICKS CONTROL LEVERS PCB SWITCHES PANEL SWITCHES FOOT SWITCHES FOOT PEDALS ENCODERS FLEXIBLE COUPLINGS ACCELEROMETERS INCLINOMETERS GYROSCOPES AIR SWITCHES PRESSURE SWITCHES VACUUM SWITCHES INTERFACE MODULES DIGITAL PANEL METERS Anti-vandal Switches LED Indicators Push button Switches Miniature Joysticks Air Switches Rocker Switches Toggle Switches Switch Panels Pendant Control Stations Hand Controls ContaCt us FoR a QuotE toDaY CONTROL DEVICES Unit 13, 538 Gardeners Road ALEXANDRIA NSW 2015 www.controldevices.com.au siliconchip.com.au sales<at>controldevices.net Australia's electronics magazine 02 9330 1700 November 2022  9 Crystal-based harmonic generators were extremely difficult to design for those frequencies, at least using 1930sera components. Water-cooled CPU and GPU cards for computers are also ‘a thing’. Keith Walters, Riverstone, NSW. A different take on active crossovers I note the new 2/3-Way Stereo Crossover in the October issue (siliconchip.com.au/Series/371). A new version of the fully variable unit from a couple of years ago, more suited to experimental applications, is a good idea. It would seem to me that when employing active crossovers, they are best used in a modular manner with amplifiers at the speaker unit, requiring only two cables and giving optimum performance. Therefore, a single-channel PCB would be preferable. Each speaker unit can be calibrated using a simple sound level meter and signal source. From my experience, only a two-amplifier system is needed, one driving the power-hungry woofer and the other driving a conventional crossover for the midrange and tweeter. It also allows a woofer to be simply added to a quality bookshelf system, increasing performance. The main application which would definitely require the current unit is when a single subwoofer is used. Technically, this is a generic domestic trade name for an LFE (low-frequency effects) speaker for one of the cinema-­ based surround sound formats. The LFE is an entirely separate channel with a theoretical bandwidth of DC to 120Hz at +10dB to the main channels. LFE is used for audio support and creativity at the discretion of the movie directors/sound engineers. It is entirely separate from the main audio field, where each channel has a theoretical bandwidth of DC to 20kHz and are not meant to carry LFE. You can find a PDF of the entire history of LFE on the Dolby Laboratories website. The main channel speakers (all five in a 5.1 system, where the .1 is the LFE) are usually full-spectrum threeway drivers, although I think there are very expensive units that are two-way drivers. The Silicon Chip Senator speakers (May-June 2016; siliconchip.com.au/Series/300) also fall into this latter class, and might benefit from an active crossover treatment. Kelvin Jones, Kingston, Tas. Extra generator capacity needed for motor starting I was intrigued by the questions raised by George Ramsay in the Mailbag section of the July 2022 issue (pages 8 & 10). I have wondered about ‘pure’ sinewave output compared to ‘modified’; at what point does a switchmode power supply give up in trying to get the selected voltage from the modified waveform available? Now to the real question regarding getting a refrigerator up and running from a ‘genset’ power source. I have a Petters diesel-powered 4kVA genset. It uses about 1L/h at 3kVA output. Older electric motors were pretty easy to start as they only required a small amount of power to get them going (for instance, my oldish chest freezer and my old fridge/ freezer, now deceased). My replacement fridge/freezer won’t even consider starting. Questions to those in the know about these matters suggest I may need 8-10kVA output to have enough capacity to start it. As a case in point, my neighbour recently got skittled 10 Silicon Chip Australia's electronics magazine siliconchip.com.au Rack Equipment Ideal for IT Networking, Small Offices, Recording Studios, Sound & PA Equipment. GREAT VALUE and IN STOCK at your conveniently located stores nationwide. ALL cabinets feature: • Key lockable front, back & sides • Tempered glass doors • 60kg static loading capacity • Wall mount without brackets Swing frame SWINGS OPEN FOR EASY MAINTENANCE OR INSTALLATION 19" Rack Mount Cabinets 6U Flat Packed HB5170 / Assembled HB5171 12U Flat Packed HB5174 FROM 189 $ Swing Frame 19" Rack Mount Cabinets 6U Assembled HB5180 12U Assembled HB5182 FROM 279 $ Here's just some of our Rack Mount Accessories See our range in-store or online Patch Cables • Cat5e, Cat6a & Cat7 available YN8200-YN8299 FROM $3.45 24 Port Cat6 Patch Panel • Numbered ports • Labelling area • 1U rack height YN8048 JUST 79 $ 95 Patch Lead Management Panel • Keeps leads tidy JUST • Removable cover $ 95 • 1U rack height HB5434 29 Fixed Rack Shelves • Powder coated steel • Supports up to 20kg • 1U and 2U available HB5452 - HB5454 FROM 49 $ Professional 19" Rack Style Enclosures • Metal construction • Supplied flat pack • 1U, 2U and 3U available HB5120 - HB5130 Shop at Jaycar for your Computer Networking gear: • Computer Modems and Routers • Neworking Leads & Adaptors • Ethernet Switches • Keyboards & Mice • Networking Test Equipment • Storage, Docking & HDD Explore our full range of rack mount products, in stock at over 110 stores, or 130 resellers or on our website. jaycar.com.au/rack-mount 1800 022 888 FROM 9995 $ by a long-term power outage but needed an instant genset to get his farm water supply up and running. Stock aren’t happy about being thirsty. Since he was using a 1.7kVA pump, he was advised that he would need a genset with an output of 10-12kVA to get reliable starting. He got one, and it works well. On that happy note, I leave you. John Hardisty, Tewkesbury, UK. Comment: a possible ‘rule of thumb’ is that a motor starting on-load like a compressor or pump needs about ten times its rated power initially, and can draw more than its rated power until it gets up to speed, which can take a second or two. Generators can typically handle a small short-term overload, so your suggested ratio of 6-7 times rated power is a reasonable compromise between cost and capacity. Kind reader offering up his spare punctuation! I want to say how much I’m enjoying Silicon Chip these days, especially Leo’s articles about the magazine’s history (August & September 2022; siliconchip.au/Series/385). I was fascinated to finally know how it all happened. I may be one of your longest readers, being 75 and having been a reader of RTV&H, then EA and all the other mags since very early 1960 when my father bought me my first copy. Around 1967, I wrote a paper letter to EA saying it was the only magazine I read which lacked a Letters to the Editor section. Voila, the following month, the Letters section started. I’m not sure if my letter caused it, but I like to think it was. I started my career in broadcast TV engineering in 1966, so the recent articles on video recording were of great interest. I specialised in videotape and audio (and a lot else) at a Perth commercial TV station. The idea that high-definition video and audio can now be recorded on a tiny SD card with no moving parts at such low cost boggles my mind, considering the mechanical and electronic complexity of the machines I worked on. I clearly remember at an Ampex course being told that ordinary 625 line PAL required 270Mb/s, and that was impossible, so forget it. So much for that. I’m noticing the small changes you’re making and I strongly approve. I’m also noticing the degree letters after the names of many of your staff members. Congratulations. Although I moved to Perth, I visited Sydney many times. I wish I’d known, as I drove along Bassett St Mona Vale to my relatives’ house nearby, that your offices were there as I might have called in to say hello. Finally, I’m including a supply of !!!...!!! as you may be running short. Just ask, and I’ll send more!!!!!! Peter Croft, Butler, WA. DH30 MAX review feedback I was bemused by your article on the shortcomings of the DH30 MAX battery welder in the August 2022 issue (siliconchip.au/Article/15427). I am reminded of a definition from the 1980s: Marketing engineer: someone who takes a prototype, pulls out components one by one until it fails, then replaces the last one and signs off on it as plainly those other components were redundant and a waste of money. It certainly seems that’s what happened in this case. SC Dave Horsfall, North Gosford, NSW. Silvertone Electronics sells a range of Signal Hound spectrum analysers from 4.4GHz up to 43GHz. « This 4.4GHz spectrum analyser is yours from just $1677.50 This product and even more can be purchased from Silvertone's Online Store https://silvertoneelectronics.com/shop/ ► UAV & Communications Specialists 1/21 Nagle Street Wagga Wagga NSW 2650 Phone: (02) 6931 8252 https://silvertoneelectronics.com/ contact<at>silvertone.com.au Spike RF analysis software included for FREE with every Signal Hound analyser Silvertone is a reseller of these brands BitScope 12 Silicon Chip Australia's electronics magazine siliconchip.com.au A BOM tool with brains — it’s our Forte Check stock Part match Review lifecycles Forte The intelligent BOM tool® Authorized distributor of semiconductors and electronic components for design engineers. au.mouser.com/bomtool Save time All About Torches By Dr David Maddison Illumination so we can be active beyond daylight hours has always been an important technology. On foot, that usually means a torch. Once a stick with a fire on the end, modern torches (known elsewhere as “flashlights”) are almost always batterypowered. Image source: https://unsplash.com/photos/YK8Mvocj6yE P can also be gas or liquid-fuelled lanterns, or even chemical “glow sticks” that use chemiluminescence to create light. But this article will focus on electric torches. Until the introduction of LEDs, torches mainly used incandescent bulbs. Various types were available, described below. Batteries used were typically based on carbon-zinc 1.5V cells or, in later times, alkaline cells or nicad/NiMH rechargeables. By the time lithium-ion rechargeable batteries became commonly available, LEDs were the dominant lighting source. Some LED torches support multi-voltage operation, for example, being powered by a single AA alkaline cell at 1.5V or a 3.7V Li-ion rechargeable 14500 (same size as AA) cell. But that only works if the torch electronics are designed to handle the wide range of voltages. ortable lights Origin of the term “flashlight” In the UK and its former colonies, we use the term “torch”, but in the USA and Canada, the term is 14 Silicon Chip “flashlight”. The word “flash-light” predates the invention of battery-­ powered devices. It appeared in 1892 but referred to flash photography, where the flash came from chemicals. The Flashlight Museum (www. wordcraft.net/flashlight.html) says that the origin relates to early torches that had weak carbon-filament lamps and weak, low-powered cells with no switch to keep them on permanently, as extended operation would quickly drain the cells. The cells needed to ‘recover’ between uses. Electrical contact was made by pressing a spring-loaded contact to Fig.1: an “Ever Ready” flashlight from 1899. Note the momentary switch in the middle, hence “flashlight”. complete the circuit; hence, the light would flash. The first torch As we noted in our article All About Batteries (January 2022; siliconchip. com.au/Series/375), the D cell was invented in 1896 (and it’s still available today!). It was a dry cell; as there were no liquids to spill, it was suitable for portable use in any orientation. While not the first dry cell, it was the first that was mass-produced and led to the torch’s development. The first torch patent was assigned to British inventor David Missell who obtained US Patent 617,592 in 1899 (https://patents.google.com/patent/ US617592A/en and Figs.1 & 2). It used three D cells in a cardboard tube with a brass reflector and a carbon filament bulb. Some were donated to the New York City police, who liked them, but the torch was not generally popular because the batteries had a low capacity and the carbon filament bulb was not efficient or bright. At the time, torches were considered an expensive novelty. siliconchip.com.au Torches did not become popular until the development of the tungsten filament bulb (three times the efficiency of a carbon filament) in 1904 and the development of better batteries. By 1922, there were an estimated 10 million torch users in the United States. A range of devices was available, including tubular designs, lantern styles that could be set down, small pocket-size devices and large lights suitable for long-range use – see Fig.2. The first LED torch Who made the first LED torch is discussed in detail at siliconchip.au/link/ abfm – in summary: • Rockwell gave out promotional LED torches in the late 1970s to early 1980s • Edmund Scientific made a yellow LED torch in the late 1970s • Tekna made a red LED torch around 1980 • HDS Systems in Tucson, Arizona, USA made a torch with multiple LEDs in 1997 or 1998. • Arc Flashlight LLC (website – www.arcflashlight.com) was the first to sell high-power Luxeon Star LED torches around 2001 with the Arc LS model (see Fig.3). It was the first LED torch to rival incandescent torches. The company was in business from 2001 to 2004. Torch configurations The key elements of a torch are: 1) a light source and, if applicable, a reflector, lens and heatsink 2) driving electronics if the torch is not a direct-drive type 3) a battery 4) a switch Various other hardware is associated with the entire torch assembly, such as o-rings, clips, etc. Apart from the archetypal handheld model, traditionally about the diameter of a D cell, there are (continued overleaf): Fig.3: the first commercial LED torch (the Arc LS) that was competetive with incandescent torches. siliconchip.com.au Fig.2: early torches from the 25th MESCO (Manhattan Electrical Supply Co) catalog, circa 1910. Personal recollections on torches One of my earliest recollections of torches was my father walking me to a Cub Scout meeting through a dark park with a 3LR12 4.5V-battery powered light (see photo). They were often used on bicycles at the time but were easily removable for general use. Another time, I ascended Mt Bogong in Victoria and arrived at the campsite at night. I had decent lighting, but my walking companion had an inadequate incandescent torch powered by two AA cells which seemed nearly flat. That taught me several lessons: the importance of having at least one form of backup lighting and spare batteries when in the bush, and the extreme difficulty of setting up camp on a dark night without adequate lighting. Fortunately, having sufficient A vintage bicycle torch powered by lighting is rarely a problem these days a 3LR12 4.5V battery. By today’s with the ready availability, low cost, standards, the light was dim and low weight and high performance of battery life short, but they were still popular, especially for bicycles. LED lights. Australia's electronics magazine November 2022  15 • headlamps for applications such as caving or working hands-free • ‘lanterns’ designed to sit on a flat surface or hang from something to illuminate an area • torches with different light colours such as red to preserve night vision function for the military, hunters or astronomers • keychain lights • hand-cranked torches with a built-in generator for emergency applications • firearm mounted lights for hunters, law enforcement or the military • torches for scuba diving • lights for hazardous areas such as mines that are designed not to be an ignition source • inspection lights, with the light on a flexible mounting • infrared torches for use with night vision equipment • ‘shaker lights’, novelty items that produce light when shaken via a moving magnet (some are fake and have internal batteries) Apart from all those, most modern phones have a torch function. Light Sources In addition to incandescent globes and LEDs, there are other light sources such as HID lamps (high-­intensity discharge, less common now due to the availability of high-power LEDs) and the emerging technology of “laser” torches that use an LEP or laser-­ excited phosphor (siliconchip.au/ link/abfn). Incandescent bulbs Incandescent torch bulbs are mostly obsolete now but are still available. They are mainly defined by their Fig.4: a P13.5S base torch bulb, in this case, a Satco S6923 (0.63W, 2.33V). It has a “B3 1/2” shape, a C2-R filament and a rated life of 10 hours. 16 Silicon Chip Battery Warnings Lithium-ion batteries contain a lot of energy and can be hazardous. Also, keep button and coin cells away from children and animals as they are hazardous if swallowed. voltage rating, power rating, base configuration, glass bulb shape, gas filling and whether they flash (rare). Some bulbs are manufactured with LEDs as direct replacements for conventional incandescent globes. Incandescent bulbs can be small, or large sealed-beam units as used on older-style car headlights (eg, as used in the Big Jim torches, described later). Some higher-performance bulbs are filled with xenon or krypton gas, reducing the tendency of the tungsten filament to evaporate and allowing it to run at a higher temperature, making it brighter and more efficient. Halogen globes are filled with inert gas and a halogen substance such as iodine or bromine. A chemical reaction causes evaporated tungsten to be redeposited on the filament. Incandescent bulbs and LED bulbs that replace them (when made) are available in various base types. For each base type, various voltage and power ranges are available. Some common types include: ANSI P13.5S Also known as single contact (SC) miniature flange base (see Fig.4), this bulb has a flange with a maximum diameter of 13.5mm. The maximum distance from the base contact to the top of the metal barrel is 14mm. It is a common bulb for older torches. E10 This is also known as Miniature Edison Screw (MES). Fig.5: a G1.27 miniature bulb (1.27mm pin spacing). This 42005 bulb (1.35V, 0.32A) has a T-1 shape as used in AAA Maglites. Source: www.topbulb. com Australia's electronics magazine BA9S This base type is commonly used for older vehicle indicators but also by some torches and LED replacement bulbs. Miniature globes, eg, G1.27 base This bulb (Fig.5) has two pins protruding from the base. The number after the G indicates the centre-to-­ centre spacing between the pins in millimetres. Blinking bulb There were once bulbs that blinked, driven via a bimetallic strip inside the globe, which alternately heated and cooled, making and breaking electrical contact (Fig.6). They were available for 1.5V, 2.5V, 3.5V or 6V operation and were used in numerous toys in the 1960s as well as the Big Jim torch (see below) and even pinball machines. The base was typically an E10 and the current draw was 200mA with a 1Hz flash rate and 50% duty cycle – see siliconchip.au/link/abfo Fluorescent tubes Some torches use a miniature fluorescent tube – see Fig.7. They used to be somewhat common but are now rare as LED globes are superior. This style of torch remains in a specialised form to create UV or ‘black light’ to cause fluorescence in certain items such as currency, minerals, watermarks, biological contamination etc. Fig.6: a flashing globe from an old pinball machine with a BA9S base. Source: www.pinball.center siliconchip.com.au Fig.8: construction of a typical 3mm or 5mm LED as used in basic torches. LEDs LEDs (Figs.8-10) tend not to be removable like incandescent globes as they do not need routine replacement and are often an integral part of the torch. However, enthusiasts do change them for different types, power ratings, colour temperature tint or other desired characteristics. There are slight variations in LEDs coming from the same production line, so all LEDs are tested and ‘binned’ into types with similar characteristics, much like other semiconductors. Major LED manufacturers for torches are Cree, Luminus, Nichia, Osram, Philips Lumileds (Luxeon), Samsung and Seoul Semiconductor. LED emitters typically have no markings, so you have to know what they are or identify them from a chart such as at https://flashlightwiki.com/ LED_Gallery High-end LEDs used in torches typically have an efficiency of around 100lm/W (lumens per watt). Fig.9: a Cree XM-L2 T6 3B emitter attached to an MCPCB (metal core printed circuit board), used for the torch build described in the text. Fig.11: a 35W HID lamp (Philips CDM35/T6/830) with a two-pin G12 base, producing 3100 lumens. It is 103mm long and 20mm in diameter. The bases can be purchased without emitters to attach your own, or with the emitter already attached. runaway heating, so the current has to be limited using a ballast or other electronics. HID torches are still available but tend to be more expensive than others, and current high-power LED technology is competitive with them. High-intensity discharge lamps HID lamps work by establishing an electrical arc between two tungsten electrodes inside a quartz or alumina tube. The tube is filled with an inert gas (argon, neon, krypton and/or xenon) and a suitable metal or metal salts (eg, mercury, sodium or halides) – see Fig.11. When an arc is struck, the high-­ temperature plasma (ionised gas) generated causes the metal or salts to evaporate. Within any metal or metal salt at a high temperature, electrons jump between energy states, resulting in light generation. The light usually includes UV, which is filtered out. HID lamps are much more efficient than incandescent lamps but are more expensive due to the need for fairly complex control electronics. They have a negative resistance temperature coefficient, which could lead to A Phoebus Horizon HID 35W searchlight (shown below) with 3500 lumen intensity, 1370m throw and 2.5h runtime. Laser-excited phosphor (LEP) In an LEP torch, a blue laser beam is directed onto a special phosphor coating adhered to a metal plate (see Figs.12-14 and https://youtu. be/G0V3p8cc-3I). The laser causes the phosphor to fluoresce, emitting Fig.7: a UV torch with a fluorescent tube. Such ‘black lights’ have various scientific and law enforcement uses. Fig.10: how a LED emitter is attached to an MCPCB. siliconchip.com.au Australia's electronics magazine November 2022  17 broad-spectrum white light. The light emitted is not a laser beam but is laser-like. Classic laser light is monochromatic or close to it; the light from an LEP torch contains all colours. Note that ‘phosphor’ does not necessarily refer to the chemical element phosphorous but any substance that emits light when exposed to radiant energy. Typically, the blue light from the laser shines onto an yttrium aluminium garnet (YAG) phosphor, which absorbs the blue light and re-emits it as a combination of colours, making a white beam. This is similar to how white LEDs function; a blue or UV LED emits light onto a phosphor mix which re-emits it as white. The beam from an LEP torch is pencil-­like and the torch is very efficient. A blue laser is used because it is easier and more efficient for blue light to excite phosphors to produce the desired range of colours in the visible spectrum than other colours such as red or green. BMW uses LEP headlights in many of its vehicles, including the X7. The lights use less power, have longer range and enable a smaller headlight housing than LED lights. You can view a teardown and repair video on YouTube for a BMW laser headlight titled “Laser Headlight Teardown and How Fig.12: how a laser-enhanced phosphor (LEP) torch works. to Repair color change” at https:// youtu.be/a5mAdDl5pTA Power sources Power usually comes from a battery (rechargeable or disposable), which might be recharged via a solar panel or hand crank for emergencies (only some types). Supercapacitor-powered torches are sometimes seen. They don’t have the runtime of batteries but they can be charged very rapidly. You can easily make your own, and there are many online instructions; search the web for “supercapacitor torch”. You can find two examples at siliconchip.au/ link/abfp and siliconchip.au/link/abfq Consider that some rechargeable cells, such as certain protected 18650s, are too long to fit in some Fig.13: the Weltool W4Pro, an LEP torch. On high, it produces 560lm with a 2670m throw and two hour runtime. torch compartments. In this case, a non-­protected cell must be used, but make sure the torch has low-voltage shutdown to protect the cell. Also, some 18650s have flat tops that won’t make a good (or any) connection with the torch contacts. In that case, use button-top cells if they fit. LED drivers Most LED torches are not ‘direct drive’ and include an electronic driver to regulate the current and/or voltage delivered to the LED. The electronics might also provide multiple modes (eg, low/medium/high brightness), monitor the battery voltage and LED temperature, protect against reversed battery polarity, manage charging and possibly other tasks. Fig.14: a W4Pro beamshot. The narrow, pencil-look beam is typical of LEP torches. Fig.15: current vs voltage for differently-coloured low-power LEDs. The steep increase in current with voltage indicates why current regulation is preferred. 18 Silicon Chip ► Australia's electronics magazine siliconchip.com.au Fig.16: one of the simplest possible LED torch circuits. Each type of LED has a maximum current and power rating. The voltage across the LED (Vf or forward voltage) varies depending on the colour and type. UV LEDs have the highest Vf at 3.1-4.4V; violet 2.8-4.0V; blue 2.5-3.7V; green 1.9-4.0V; yellow 2.12.2V; orange/amber 2.0-2.1V; red 1.62.0V; infrared 1.2-1.7V. White LEDs typically require around 3.0-3.6V (see Fig.15). LEDs are generally not driven with a fixed voltage because the current increases exponentially with voltage once Vf is exceeded, and they could experience thermal runaway. There are several ways to regulate LED power. These include direct drive, a linear regulator, pulse width modulation (PWM), boost or buck circuits, or a combination boost/buck circuit to drive the LED at the correct voltage, regardless of the input voltage. One of the simplest LED torch circuits is shown in Fig.16. It is a battery, LED and a resistor to limit the LED voltage and current. Direct drive In direct drive circuits, the voltage of the battery or power supply has to be no greater than the maximum Vf of the LED. They usually rely on the battery’s internal resistance or power supply to limit the maximum LED power. This is not an advanced method, but it can work. Fig.17: eight AMC7135 regulators plus a microcontroller fit on this small PCB to provide up to 3.04A (note that some AMC7135s are rated at 380mA rather than 350mA). The micro provides 12 group modes; this board was used for the torch build described in the panel at the end of the article. Taking Jaycar Cat ZD0196 as an example, Vf(typical) = 3.2V and Imax = 100mA. To drive that LED from a 9V battery, you could use a resistor of R = (9V – 3.2V) ÷ 0.1A = 58W (round up to 62W to be safe). That assumes Vf(min) is close to Vf(typical). For more on driving LEDs directly, including combinations of LEDs, see: • siliconchip.au/link/abfr • siliconchip.au/link/abfs • electronicsclub.info/leds.htm You can have fun buying a bag of 3mm or 5mm LEDs and a solderless breadboard and try connecting the LEDs in various series/parallel combinations. See the online calculator at siliconchip.au/link/abft The different series/parallel combinations give different voltages and currents for driving the same LEDs (the product of these, ie, the power will be mostly constant). For more information on this, see: • siliconchip.au/link/abfu • siliconchip.au/link/abfv Linear regulation The term linear regulator might refer Resistor current limiting The current to the LED can be limited using a series resistor, although the LED will dim as the battery discharges, and the resistor can dissipate a fair bit of power. If Vs(max) is the maximum supply voltage, Imax is the LED’s maximum current and Vf(min) is the minimum Vf at Imax, the resistor value required can be calculated as R = (Vs(max) − Vf(min)) ÷ Imax. siliconchip.com.au to either current or voltage regulation. Typically, LEDs are driven with a constant current. If the voltage supplied to the regulator is higher than Vf, energy is lost as heat. If the voltage drops below Vf, the current will be less than intended, but losses will be low. It is ideal to supply the regulator with as close to Vf as possible. A common current-regulating chip used in torches is the AMC7135 which can handle up to 350mA. Up to four can be placed on each side of a 17mm diameter driver board to give a total of 2.8A, which suits LEDs like the XP-L and XM-L2 in torches using 18650 Li-ion batteries (18mm diameter, 65mm long) – see Fig.17. A microcontroller can be combined with the linear regulator(s) to control brightness using PWM (see Fig.18). PWM (typically using a Mosfet) Instead of using a linear regulator, a Mosfet (or BJT) can be switched on and off by a microcontroller to control brightness using PWM as described above. The Mosfet acts as a low-­ resistance on/off switch. There is little voltage across the Mosfet when on, so it dissipates very little power. Some sort of current limiting is usually required. Still, it can be arranged to dissipate less power by operating it at a reduced duty cycle to achieve maximum brightness, so the overall efficiency is improved. Boost or buck circuit Fig.18: how PWM is used to vary duty cycle and thus control average current. Australia's electronics magazine An LED can be driven by either a boost or buck circuit that increases or decreases the supply voltage to that most appropriate for the LED. Some circuits can either boost or buck. These circuits are most efficient when the input voltage is close to the output drive voltage, but they are usually much more efficient than linear regulation regardless. November 2022  19 Fig.19: a flow chart for the generic Andúril 2 torch firmware – this is the ‘simple’ section! Source: https:// budgetlightforum. com/node/76941 Driver firmware Believe it or not, there are operating systems for torches (see Fig.19). Drivers with microcontrollers require firmware and such software can even be written or modified by the enthusiast. The firmware controls the user interface, eg, the program will advance the brightness every time the on-off button is quickly clicked. Popular firmwares include A6, Andúril, Biscotti, Bistro, Crescendo, NarsilMulti and RampingIOS. For a lot more information and links for flashing tools and software, see siliconchip. au/link/abfx There is a repository of flashlight firmware at siliconchip.au/link/abfy if you are interested in seeing what it looks like or developing your own. There is also extensive documentation for Andúril at siliconchip.au/link/abfz Example code for the Convoy S2+ torch is at siliconchip.au/link/abg0 Torches of note example is: siliconchip.au/link/abg1 We are aware of at least one modern torch that uses this battery. Unusually, it also uses a traditional incandescent globe. Big Jim The Big Jim torch was a large light from the 1960s and possibly earlier (there is very little documented history on these torches). It used a sealed beam headlamp, much like some former car headlights. It was made by Union Carbide or Eveready and used a large (125.4 × 132.5 × 73mm) 6V ANSI 918 battery, IEC 4R25-2, with a capacity of around 18Ah for zinc chloride (RS Pro) models to 33Ah for alkaline (Varta). Within these were 8 F-size cells. If buying one of these batteries, note there is a similar ► For a comprehensive list of LED drivers, see siliconchip.au/link/abfw 12V battery, Rayovac model 926D or ANSI 926 equivalent. Big Jim came in a variety of models. Some had just the sealed beam main light, while others also had a flashing red light, using a bi-metal strip as described earlier. Torches in this style are still available from the Big Beam Company near Chicago, USA – see siliconchip.au/ link/abg2 One of that company’s torches from the 1950s, the Big Beam No. 164, is remarkably similar to the Union Carbide Big Jim from my collection (see Figs.21 & 22). This light was subject to US Patent 2,861,174 of 1958 by Big Beam, so we assume Union Carbide licensed the design. For further information on this, see siliconchip. au/link/abg3 Fig.20: the Varta Palm Light is a modern European torch that uses a 3LR12 battery. It has a 3.5h battery life, a throw of 75m and 15lm brightness. It is a rare example of a modern torch with an incandescent globe. Source: www. varta-ag.com/en/consumer/product-categories/ lights/palm-light Some of the more prominent torches throughout history are listed below: The 3LR12 battery was (and is) more common in Europe and Russia than in other countries. Some torches still use this battery – see Fig.20. Adaptors are available for purchase or 3D printing to enable three AA cells to be used instead of a 3LR12 battery. One 20 Silicon Chip ► 3LR12 torches Fig.21: a Big Beam No. 164 from the 1950s. Source: Made in Chicago Museum Australia's electronics magazine siliconchip.com.au Fig.24: the current Dolphin LED torch. Fig.23: the author’s Convoy S2 torches. The one on the left has 365nm UV LEDs and 1.05A driver. In the middle is an S2+ with an SST20 4000K LED and 2.8A driver; on the right is an S2+ with SST40 5000K LED and 3.05A driver. was waterproof and could float, but This battery (IEC 4R25X or 4LR25X) Convoy S2+ it found acceptance in many applica- has spring terminals and typically The Convoy S2 and the later version, tions beyond boating. contains four F-size cells. Typical batthe S2+ are popular and inexpensive The Dolphin MK1 was known in the tery capacities are 8.5Ah for a Varta torches for buying, modifying or even USA as the “All American” or “No. “431” Zn-MnO2 (Zinc Chloride) type building from parts (described later) – 108”. The MK1 is the only one with or 11.9Ah for a Varta “4430” alkaline see Fig.23. They are not a ‘big brand’ metal retaining clips for the lens bezel type. Typical dimensions are 115mm but have better quality than their price in the Dolphin model range. × 68.31m × 68.31m. would suggest and many favourable The Dolphin used a 6V lantern batThere is a bit of confusion about the reviews. If buying one, make sure it is tery which gave it a good run time by date of the MK1 Dolphin. The Austrafrom a reputable seller and not a fake standards of the day, as typical torches lian Museum of Applied Arts & Sci(see the panel on page 27). from then ran from two D cells (3V). ences website (siliconchip.au/link/ That was before alkaline cells were abg4) lists the design date as 1965. The Eveready Dolphin torch widely available; standard cells of the However, Eveready (siliconchip.au/ Almost all Australians will be famil- time had poor capacity and current link/abg5) has design and manufaciar with the iconic Eveready Dolphin delivery. The Dolphin had a bright and ture dates of 1966. It also states that torch (Fig.24). It started life in the ‘throwy’ (long range) beam compared Dolphin torches “have been lighting USA in 1965 and was produced for to other torches. up the lives of Australian & New Zeasale around the world. Having a large battery back then land families since 1967, when the first The Dolphin was initially designed (the 1960s and early 1970s) was the MK1 lantern was launched”. for the boating community and thus only way to get a reasonable capacity. The second generation of the torch, Fig.22: the author’s collection of three Big Jim torches. The left-hand torch (model 100) is very similar to the Big Beam; the middle torch (model 101) lacks the red flashing light, while the one with the plastic head (model 101C) is Australian-made. siliconchip.com.au Australia's electronics magazine Two hand-cranked torches. The smaller Chinese-made one has a LED, while the larger one is incandescent and believed to be of Soviet origin. November 2022  21 Fig.25: a modern LED Maglite Solitaire, originally released with a G1.27 incandescent bulb. Source: https://maglite.com Fig.26: the base model PakLite torch on top of a 9V battery. Several other models are also available. Fig.27: the Photon Micro-Light II LED keychain torch. It is powered by a CR2032 coin cell, or two stacked CR2016s. the MK2, was a project of Eveready Australia. Eveready contracted the design to Paul Cockburn of Design Field Pty Ltd in 1972. It became the best-selling torch in the world in the 1970s and was manufactured by Eveready worldwide in various locations. The MK2 dispensed with the metal clips of the MK1 and featured a more streamlined look. The MK3 was released in 1988, according to www. dolphintorches.com/about/, but the Powerhouse Museum (siliconchip. au/link/abg6) states that the MK3 was designed by Paul Cockburn in 1989. The MK3 bezel screws on rather than clipping on. The MK4 was introduced in 1996, followed by the MK4.2 in 2000 and the MK5 in 2003, which featured a new reflector design, integral rubber mouldings for impact protection around the lens, an adjustable stand and better ergonomics. According to the Powerhouse Museum, the MK4 and MK5 were designed by “Design Resource in Crows Nest, NSW for the US-based Energizer company” (Energizer Holdings is a division of Eveready). The MK6 was released in 2007 and then the MK7 LED in 2012, the first Dolphin featuring an LED. Eveready states that 20 million Dolphins have been sold in Australia and New Zealand over 45 years (1967 to 2012). In 2016, a new LED Dolphin was introduced, which has no “MK” designation but is stated to have 200 lumens output, a beam throw of 250m and a battery life of 65h. above. In 2012, the LED version of the Solitaire was introduced, but there are DIY and commercial LED conversions for the earlier version. It is significant because it was a well-engineered miniature keychain light. Although the incandescent version was not particularly bright, it was enough to find a keyhole at night. Maglite Solitaire AAA The 1988 Maglite Solitaire AAA battery model (Fig.25) uses one of the smallest, if not the smallest incandescent globe to go into a commercial torch; see the G1.27 bulb section PakLite This novel torch (see Fig.26 and https://paklitegear.com/) sits on top of a 9V battery. It is produced by a family living off-grid in the mountains of Oregon. It is characterised by light weight, useful light output and extreme run time of up to 1200+ hours with a lithium battery on low, 80+ hours on high or 600+/30+ hours for regular alkaline batteries. It can even run on ‘exhausted’ 9V batteries from sources like smoke detectors, as it can run down to a very low voltage. There are many imitations of this light. Photon Micro-Light Fig.28: a classic Maglite six D-cell incandescent xenon torch. Maglite still sells these. It has a beam distance of 338m, 178 lumens and 28547cd peak intensity. It is 485mm long and weighs 1417g with a battery. Source: https://maglite.com This light (see Fig.27) is an extremely small key chain light with a stated minimum 4.5 lumens output and 18h run time, weighing 6.27. Depending upon which beam colour is chosen, it uses either two CR2016 or one CR2032 cell. Surefire P60 and other P60 hosts Fig.29: two Surefire-style torches and a selection of P6-modules, some Surefire, others after-market; some incandescent, others LED. Source: author’s collection 22 Silicon Chip Australia's electronics magazine Surefire introduced their 6 Series torches in 1988 (Fig.29). The 6C model produced 60 lumens from two CR123 batteries and was smaller and brighter than any comparable torch at the time. The 6P and 6R models were released in 1989 and featured a P60 incandescent xenon light ‘drop-in’ module of 65 lumens or a P61 module of 120 lumens. Today, many different P60-style modules with different light options are available for various Surefire 6 series style “host” lights. Examples siliconchip.com.au include the UltraFire WF501B, WF502B, WF503B, WF504B, WF502D (http://flashlightwiki.com/UltraFire) & Solarforce L2 (http://flashlightwiki. com/Solarforce). UltraTac K18 I use this outstanding AAA/10440 cell torch daily (see siliconchip.au/ link/abg7 and Fig.30). 10440 refers to a rechargeable Li-ion cell in AAA format. Fig.30: the UltraTac K18 AAA torch. It has a maximum brightness of up to 370 lumens (with a 10440 Li-ion cell) and a maximum run time of 40h at low brightness. Upgrading a vintage torch You can bring new life to a vintage or antique torch (100+ years). Some people make permanent modifications by adding LEDs and new battery systems, but this is regarded as unacceptable by some for rare lights. It’s possible to make non-­permanent modifications, such as changing the incandescent bulb for a ‘drop-in’ direct replacement, which can be readily purchased for most incandescent bulb types (see Fig.31). Battery replacements can be made with adaptors, given the lower battery capacity required for driving LEDs. For example, you can replace a D cell with an adaptor containing one, two or three AA cells. Fig.31: the author replaced the incandescent bulb in this vintage torch with a LED and replaced the D cells with AAs in adaptors. Performance standards for torches The ANSI/NEMA FL-1 standard is used for rating torches. It provides standard ways to measure light output, runtime, peak beam intensity, beam distance, water resistance and impact resistance. Measurement of light output Lumens (lm), lux (lx) and candela (cd) are the three most common units used to characterise lighting sources, although there are others – see Fig.32. Torch enthusiasts and manufacturers frequently wish to characterise torches in terms of overall light output or luminous flux, typically measured in lumens. Unlike lumens, which measures overall light output, lux takes into account the area over which luminous flux is distributed and is a measure of illuminance. Lux is lumens per square meter. Ten lumens over an area of one square meter would be ten lux, but ten lumens over ten square meters would be one lux. Foot-candle is the obsolete non-SI equivalent unit and is 1lm per square foot. siliconchip.com.au Fig.32: how candela, lumen and lux are measured. Lumens is the most critical measurement for torches. Australia's electronics magazine November 2022  23 Useful Links • Flashlight Museum: www.wordcraft.net/flashlight.html • TPAD Direct Thermal Path Technology for LEDs on MCPCBs for more efficient heat removal: www.cutter.com.au/tpad/ • MCPCBs for sale: https://led-mounting-bases.com/en/310-led-mcpcb • BudgetLightForum: https://budgetlightforum.com/ • Candle Power Forums: www.candlepowerforums.com • Flashlight Wiki: https://flashlightwiki.com/Main_Page Useful Videos • “Post Vietnam War Flashlight – History” https://youtu.be/UiTGRa6EikE • “1930s Flashlight Restoration-Niagara Searchlight – Kipkay Restored” https://youtu.be/VHlVQMbdayw • “I Bought EVERY Flashlight at Home Depot!” https://youtu.be/bdjHhVhUOWY • “Flashlight Museum is an illuminating experience (2005)” https://youtu.be/XdigO6-1MEY (sadly, it appears to have closed) The candela is a measure of luminous intensity and quantifies the perceived power per unit solid angle emitted by a point light source in a particular direction. It is a weighted measurement that takes into account the sensitivity of the human eye to various wavelengths (called the luminosity function). A beam from a 1lm light source distributed evenly within one steradian (the 3D equivalent to the 2D radian unit of angular measurement) has a luminous intensity of one candela. If the same beam were evenly focused into half a steradian, the luminous intensity would be 2cd. A typical wax candle measures around 1cd. ‘Candlepower’ is an obsolete term, but today is considered equivalent to the candela. Sometimes, a torch will be advertised with a candlepower rating in the millions (which sounds impressive) because it has a tightly focused beam, but its overall output in lumens might be low. Throw is a measurement of how far away a torch can usefully light up an area and can be calculated from its candela rating – see siliconchip.au/link/ abg8 and siliconchip.au/link/abg9 Measuring a torch’s brightness The most important measurement related to torches is lumens, which can be measured using an “integrating sphere” or “goniophotometer”. Unfortunately, professional equipment to measure lumens can be very expensive, but there are inexpensive solutions. To make this measurement, you (1) Fig.33: an inexpensive light meter that you can use to measure lumens. This Neewer meter shown can measure up to 200,000 lux. You can find a variety of these types of meters online, mostly sold at quite reasonable prices. 24 Silicon Chip Australia's electronics magazine Fig.34: a DIY lumen measurement with a hollow foam sphere, as described by run4jc. need a way to collect all the light coming from the torch, (2) a way to measure the illuminance and (3) a reference for calibration, such as a torch with a known accurate lumen rating from a reputable manufacturer. The illuminance can be measured using an inexpensive light meter; searching eBay for “lux meter” brings up many models under $50 (see Fig.33). The light collection device is ideally a sphere, but it can be a white foam box, a white foam sphere or even PVC plumbing fittings. Even a cardboard box with the inside painted white will work. The torch under test is shone into a hole in one side, and the collected light is measured (in lux) with a light meter inside the device. First, the reference torch is measured, and a conversion factor is calculated between the lux reading and the known number of lumens. This can then be used to measure unknown torches. Ideally, the calibration torch brightness is similar to the unknown device. You can get hollow foam spheres in Australia from Amazon and eBay; try Googling “hollow foam ball”. A method for making an integrating sphere from a hollow foam sphere is described at siliconchip.au/link/abga – see Fig.34. Another hollow sphere method is described at siliconchip. au/link/abgb Brooke Clarke describes the use of a professional integrating sphere for flashlight measurements with an accompanying video at siliconchip. au/link/abgc Also see the video by Matt Smith titled “DIY Lumen Measuring Device. Integrating Sphere and Lumen Tube” at https://youtu.be/xOE18kJ5WAU (refer to Figs.35 & 36). siliconchip.com.au Fig.35: a foam packing box can be used as the “integrating sphere” for lumen measurements. Source: Matt Smith video (https://youtu.be/xOE18kJ5WAU). These approaches will be acceptable for most non-professional purposes, but you can obtain surprisingly accurate results. Note that a large proportion of lumen ratings found on the internet are inflated, sometimes by a factor of 10 or more. See Matt Smith’s video titled “Internet Lumens vs Actual Lumens, and the 100 watt LED test” at https:// youtu.be/XIywzCfvunY Flood, throw and spill beams Torch light beams may be more ‘flood’, more ‘throw’ or a combination (see Figs.37 & 38). Flood beams are better for indoor and local area Fig.36: using PVC plumbing fittings as the “integrating sphere”, often called a “LumenToob”. Source: Matt Smith video. illumination, such as around a campsite. Throw beams are better for illuminating objects at a distance and tend to have a central ‘hotspot’. The spill beam is the light outside the central hotspot that comes directly from the emitter and not via the reflector. Reflectors and lenses Reflectors are important and, along with the nature of the bulb, determine the amount of flood or throw the light has. Some torches have reflectors with a variable focus to control this. Generally, smaller diameter torches have a more flood-like beam because of the smaller, shallower reflector and larger lights have more throw because of the deeper, larger reflector. Reflectors may be smooth or have an “orange peel” texture. Orange peel reflectors give a smoother beam; smooth ones give a better throw but have more visible beam artefacts. Lenses may be plastic or glass; better ones have an anti-reflection (AR) coating. TIR lenses are a special type of torch lens; TIR stands for “total internal reflection”. These are alternatives to reflector style lenses and are said to produce a better quality, fully collimated beam, unlike reflector optics. In a TIR lens, all light goes through the What is your EDC? EDC stands for “everyday carry” and refers to the torch you usually carry with you. It might be on a neck lanyard, a keyring, in a pouch or a pocket, and there might be more than one. EDC can also refer to other tools one might carry, such as a multi-tool, pocket knife, notebook, pen, watch, lighter, phone, charger pack etc. Fig.37: flood vs throw beams and a combination of both, directed by the reflector. Not shown here is the ‘spill beam’, light that comes directly from the light source and does not go via the reflector. Flood vs throw can be varied using a ‘zoom’ or variable focus feature. Fig.38: examples of a flood beam (left) and throw beam (right). Source: www.candlepowerforums.com/threads/spill-vs-flood.252751/ siliconchip.com.au Australia's electronics magazine An EDC organiser pouch, filled with various EDC items, including an Olight torch. Source: https:// everydaycarry.com/posts/35528/ trending-maxpedition-micropocket-organizer November 2022  25 lens, but in a reflector, not all light exits via the reflecting surface (see Fig.39). Guide to choosing a torch Fig.42: the components I purchased to build a Convoy S2+ torch. The parts that came as the ‘torch host’ are at the top, while the ‘pill’ is on the left side of the middle row. The optional lenses and lighted switch components are in the bottom row. When purchasing a torch, there are many factors to consider, including: ▢ Spend as little or as much as you want but remember that some inexpensive torches can be surprisingly good. Read reviews and watch review videos. An inexpensive torch we like is the Convoy S2+, described opposite. ▢ Try to ensure you are getting a genuine product, not a fake one. ▢ What size torch is required? ▢ What is the required lumen output and number of brightness settings? ▢ How much ‘flood’ or ‘throw’ beam or combination thereof do you need? ▢ If it has a rechargeable battery, is recharging convenient in your intended application or might disposable batteries be better? Some torches have a built-in USB charging port, so no dedicated charger is necessary. ▢ Do you want to use standard cells that can be purchased anywhere, such as AA, AAA or D, or a less common specialist type like the 18650? ▢ Does it have a long enough runtime at various power levels for its intended application, plus extra time for emergencies? My Convoy S2+ with an SST40 LED and eight AMC7135 drivers lasts around a week on the lowest brightness setting with a Sony VTC6 3000mA 18650 cell, perhaps longer. ▢ Some torches have a small parasitic battery drain, meaning the battery might be flat when you go to use it. Check for that. The tail cap can often be unscrewed to break the circuit for storage. ▢ Is the battery removable? If not, it could be a problem if it fails or you want to upgrade it. ▢ Does the torch use special custom batteries? For example, Olight uses product-specific batteries in some models. ▢ Is it multi-voltage; eg, can it use either alkaline or lithium batteries? ▢ Do you need a splash-resistant or waterproof torch? ▢ Is it shaped so it won’t roll away on an incline? ▢ Are there points to attach a lanyard? ▢ Does it have a crenulated bezel (Fig.40)? If the torch is set to a low setting and placed face-down on a flat Australia's electronics magazine siliconchip.com.au Fig.39: the difference between conventional reflector optics (left) and a TIR lens (right). Source: LEDiL Fig.40: a Nitecore SRT7 with a three-prong stainless steel crenulated bezel, an optional accessory on this discontinued model. 26 Silicon Chip Fig.41: a Lumintop FWAA torch with a two-way pocket clip that can be attached to the brim of a hat, into a pocket or onto a belt. surface, this allows a small amount of light to leak out, to provide a low level of illumination. In some cases, the bezel can even be used as a glass-­ breaking tool to rescue someone from a car or building. ▢ Can it tail stand? This can be useful to provide “ceiling bounce” light. ▢ What is the switch type, where is it and is it replaceable? Tail cap switches can be ‘forward’ (the torch will momentarily switched on if the switch is depressed halfway) or ‘reverse’ (momentarily switched off with a half-depression). ▢ Does it have a pocket clip, and is it one-way or two-way (Fig.41)? ▢ Does it have a magnet to attach to magnetic metal? ▢ Does it have a glow-in-the-dark (GITD) switch or o-ring? If not, GITD replacement O-rings can be purchased. ▢ How complicated is the user interface? Can you remember all its functions, or should you keep instructions with you? ▢ Can it be completely disassembled to modify or repair? ▢ Is there an active “modding” community? Is the torch easily modifiable? ▢ Are spare or other parts available? ▢ Check user reviews SC Building your own torch I purchased the parts shown in Fig.42 to build my own version of a Convoy S2+ from the “Convoy flashlight Store” on AliExpress (https://convoy.aliexpress. com). These parts can be purchased at many places, but they seem reliable. The parts are: Host body: Convoy S2+, which includes an orange peel reflector, pill, o-rings, glass, battery spring and lanyard for under $15 Driver: 7135 × 8, 17mm 3040mA 12-mode group driver with built-in temperature control, compatible with lighted switch, for under $9 LED: Cree XML2T6 3B LED for just over $5 Lenses: a range of TIR lenses with different illumination angles, compatible with XML and XML2 LEDs for about $4 (optional) Lighted switch: $4.95 (optional) Postage was a few dollars. Parts and tools I already had include an 18650 Li-ion cell and charger, thermal paste, solder and a soldering iron. The Cree XM-L2 T6 3B emitter came on an MCPCB (metal core printed circuit board) base. It handles up to a 3A and 10W and gives 1052lm output. T6 refers to which luminous flux group it is sorted into (280-300lm <at> 700mA), and 3B refers to its tint and colour temperature, 6200K cool white. Fig.43 shows how it is assembled into the pill and its relationship to the driver. Note solder pads for the emitter and other pads for + and – wires from the driver. Glossary of Terms Beamshot a picture of a torch beam, typically on a wall or in a natural environment and often used for comparisons between lights. Colour rendering index the ability of a light source to accurately render the colours of objects it is illuminating (also called CRI). A CRI of 100 is identical to daylight; lower numbers give worse colour rendition. Donut hole an undesirable dark spot in the centre of a torch beam. EDC everyday carry (see panel). GITD glow in the dark. HA hard anodised; a surface treatment applied to aluminium. Hotspot the centre part of the beam; a brighter hotspot provides better throw. Low voltage shutdown the torch shuts down if the battery voltage gets too low. Lithium-ion batteries can be ruined if their voltage goes too low; some such cells have their own low-voltage shutdown. Memory when the driver remembers the last mode it was in, eg, if you turned the light off at medium brightness, it would turn on again in that mode. Pill the part of the torch which is a mounting point and heatsink for the LED on one side and the driver on the other – see Fig.43. Fig.43: assembling the Convoy S2+ is pretty straightforward; this shows how the ‘pill’ goes together. The LED is on one side and the driver is on the other, held into the pill by a retaining ring. The driver wires must be trimmed and soldered to the LED PCB, and thermal paste should be added between the LED PCB and the pill. siliconchip.com.au Protected cell a cell with a small PCB to protect against over-charge, over-discharge and possibly over-current. Not all torches can accept protected lithium cells as they are several millimetres longer than standard cells. Unprotected cells can be safely used in torches with low voltage shutdown. Tactical flashlight military-style, but it essentially is a meaningless marketing term (some may disagree!). Thermal shutdown the torch will shut down if it gets too hot. The driver usually provides this function. UI user interface. Australia's electronics magazine November 2022  27 TINY LED ICICLE by Tim Blythman This miniature ‘icicle’ is perfect to match the look of a winter Christmas, despite the summer in Australia. This Icicle Ornament also has two power connections, making it easy to power a series of them on a single supply. I cicle-style Christmas lights are very popular. With vertical strings of lights that are often arranged in groups, they evoke the appearance of icicles hanging from eaves. The Tiny Xmas Ornaments from the November 2020 issue (siliconchip.au/ Article/14636) were a great hit, and we recently thought that an Icicle shape would be a great addition. So we’ve added an Icicle design to the cohort of tiny Ornaments you can create. The Icicle has a handy feature shared with the Reindeer Ornament published previously in that it has two power connections (as well as an onboard cell holder). That makes it easy to create a long chain and power it from a single power supply, such as a 2×AA battery holder. To keep things simple, we’ve laid out the LEDs in a simple top-to-­bottom order, the same as the existing Stocking Ornament. The firmware for the Stocking simply flashes the LEDs in order from top to bottom. The Icicle therefore reuses the existing code/HEX file from the Stocking. The resulting downward movement evokes water dripping from the Icicle. The circuit and parts list are thus the same as the Reindeer Ornament (except for a different PCB), and the firmware is the same as that for the Stocking. Easy! We tried a few different LED colours on our prototypes, and an assortment of colours looks quite good, but using all blue or white LEDs (or a mix) creates a striking effect. For more background, refer to the article from November 2020 or even the original Tiny Tree from November 2019 (siliconchip.au/Article/12086). The 2019 article explains how we Parts List – Tiny LED Icicle Wires go out one side of the Icicle PCB and into the other side of the next. Both are in parallel, so the battery holder can feed in at either end of the chain. 28 Silicon Chip Australia's electronics magazine 1 white double-sided PCB coded 16111192, 98.5 × 98.5mm (41 × 127mm upright) 1 PIC12F1571-I/SN (/1572-I/SN) or PIC16F15213-I/SN (/15214-I/SN) 8-bit microcontroller, SOIC-8, programmed with the appropriate version of 16111194.HEX (IC1) 12 SMD LEDs, M3216/1206 or SMA size, any colour (blue, cyan and/or white recommended) 1 SMD coin cell holder [BAT-HLD-001] 1 CR2032 or similar 3V coin cell, or 3V battery pack 1 10kΩ SMD resistor, M3216/1206 size 4 100Ω SMD resistors, M3216/1206 size 1 5-pin right-angle header (CON1; optional; for power/programming) 1 2-pin right-angle header (CON2; power) 1 length of light-duty figure-8 wire (if daisy chaining boards; eg, from ribbon cable) 1 M3 x 6mm Nylon screw 2 M3 nuts SC5579 Kit ($15) Choose from a variety of ornaments, each one is supplied with the parts above (except the coin cell, CON2 & figure-8 wire) and assorted LEDs to match. siliconchip.com.au control 12 LEDs from a tiny 8-pin microcontroller. We will be adding the Icicle to the list of Ornament kits available. You can order kits from siliconchip.au/ Shop/20/5579 – just be sure to select the correct colour and type of PCB (white only for the Icicle). Unlike the other Ornament kits, which come with 12 each green, red and white LEDs, the Icicle kits will come with 12 each blue, cyan and white LEDs. Construction is simple enough; refer to the older articles if you need more details. The main thing to check is that all the LED cathodes align with the markings on the PCB; they should all face the same way (to the left with it upright). The PIC is the only other polarised part, although you should be careful installing the cell holder, to be sure that it will allow the battery to be inserted; it only has an opening on one side. You don’t need to fit the cell holder if you are using a battery holder to power multiple Icicles but mind the polarity marked on the reverse of the PCB. We’ve used red and black wires to make it clear which is which, but you can use other colours as long as you don’t get them mixed up. Programming is not necessary if you have bought our kit, but if you have a blank PIC12F1571 or PIC12F1572 microcontroller, you can use a PICkit 3, PICkit 4 or Snap. The PICkit 3 is not compatible with the newer parts like the PIC16F15213 or PIC16F15214 (which are generally more available), so you’ll have to use a PICkit 4 or Snap for these parts. The Icicle should start flashing when programming is complete, although you might find some LEDs stuck on if the programmer is still connected. One pin is shared between the programmer and the LEDs. If you are building a chain of Icicles, test each individually before joining them together. They are all programmed to flash at the same rate, but minor variations in processor frequency mean they will quickly fall out of sync. Finally, secure the coin cell with a Nylon M3 × 6mm screw and two nuts against each other to lock them. SC CAUTION: Coin Cells Coin cells should be kept well away from children who may ingest them. Make sure the cell is secured firmly in place. siliconchip.com.au Fig.1: 12 LEDs are driven with just four microcontroller I/O pins using a scheme called Charlieplexing, explained in the November 2019 article. The Icicle is similar to the Reindeer as it has an extra connector for daisy-chaining power. Figs.2 & 3: there are parts on both sides of the PCB, but the front is clear of markings for a good presentation. Take care that the LEDs line up with their cathode markings, which are just visible. The LED cathodes all face to the left (when the Icicle is upright); there is a cathode mark on the PCB silkscreen. On the reverse, only microcontroller IC1 is polarised. Australia's electronics magazine November 2022  29 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. Digitally controlled preamp with tone controls The Sanyo LC75341 IC has great features with digital control for volume, balance, treble, bass, input gain and channel selection, all in a single package. It only needs a few external parts. There are four stereo inputs and signals are AC-coupled from them to pins on the LC75341 (IC2) using 1µF electrolytic capacitors (plastic film types could also be used). The selected signals are attenuated depending on the current volume setting and then fed to the Lout and Rout pins. These signals feed back to the Lbass and Rbass inputs via RC filters, allowing the chip to implement its bass tone control network. The resulting output signals are then fed to stereo output connector CON6 via two 2.2µF AC-coupling capacitors. The 2.7nF capacitors from the Ltre and Rtre pins to ground are required for the LC75341’s treble filter network to operate, giving control over the amount of treble in the output signals. The capacitors between Lin and Lselo and Rin and Rselo couple the signals from the input switching circuitry within IC2 to the preamp. This arrangement allows the signal to be intercepted and altered if desired, but in this case, we are just feeding the selected signals directly back into the preamp. Due to its widespread use, I decided on an ATmega328P for the controller. Five potentiometers are wired across the 5V supply rail (VR1-VR5); their wipers connect to analog inputs on microcontroller IC1, so it can use its internal analog-to-digital converter (ADC) to sense the positions of the pots. So if you rotate volume control pot VR1, IC1 senses this and sends a command to IC2 to change the current volume attenuation setting. Similarly, VR2 controls the left/right balance, VR3 the amount of treble, VR4 the amount of bass and VR5 the input gain. Four-position rotary switch S1 is connected to a resistor ladder network, so it has a voltage of around 0V, 1.67V, 3.33V or 5V on its common terminal. This is fed to the ADC4 input (pin 27) so IC1 can determine the position of the switch and send commands to IC2 to select the corresponding stereo input. The LC75341 is controlled over a Sanyo ‘CCB bus’, which has similarities to both the SPI and I2C serial buses. Like I2C, commands are sent to devices at a specific address. But like SPI, it has a chip select or chip enable line (CE) in addition to a data line (MOSI) and a clock signal (SCK). Addresses (eight bits) are sent with CE low, followed by data (32 bits) when CE is high. I used the Mikroelectronika mikroC compiler to generate the firmware. The ATmega328P’s SPI peripheral operates MSB-first (most significant bit; big endian) while Sanyo CCB requires LSB-first (least significant bit), so I am using a bit reverse routine to send the proper commands. There is a bit of a trick to implementing the balance control. When you turn the potentiometer anti-clockwise, you must adjust the right channel so that its volume fades while keeping the The photo at left shows the tone control single-sided PCB with a USBasp AVR programmer connected. The photo at right shows the same tone control board connected to a power amplifier. 30 Silicon Chip Australia's electronics magazine siliconchip.com.au left volume constant. Similarly, turning the potentiometer clockwise will reduce the left channel’s volume while holding the volume of the right channel steady. The power supply applies 6V AC to a bridge rectifier formed using diodes D1-D4 and filtered by a 1000µF capacitor to produce around 7-8V DC, which is regulated to 5V by linear regulator siliconchip.com.au REG1 to power IC1 and IC2. LED1 lights to show the presence of power at the input of the regulator, LED2 to show power at the output and LED3 flashes to show that microcontroller IC1 is operating. I designed a single-sided PCB for this project. You can download the PCB pattern along with the component layout, firmware HEX file and C source Australia's electronics magazine code for this project from siliconchip. com.au/Shop/6/60 After programming the chip, set the fuses to the following values: LFUSE 0x62, HFUSE 0xD9, EFUSE 0xFC. The performance of the prototype built using my PCB is good, with no observable hum or noise. Noel A. Rios, Manila, Philippines ($100). November 2022  31 ESP32-Camera sentry with object detection via TensorFlow The ESP32-Camera costs US$6 and includes a 2MP camera and a 2.4GHz WiFi interface that can operate at ranges of up to 200m. When connected to the internet, it can perform AI-­related jobs too. The ESP32-Camera takes and sends images to a remote computer via the internet. The remote computer uses AI (artificial intelligence) to analyse the image and determines the class of the object within. It sends that information back to the ESP32-Camera, which can then perform object-specific jobs. We want to use this for safety applications involving conveyor belts, where the belt must not operate with any people near it. For this, two cameras are focused across the 200m-long belt – one from the tail end and the other from the head end. The moment they detect any humans on its path, they will sound an alarm. If the ESP32-Camera detects a person in its view (from the front or back), it brings its GPIO14 pin high. The direct GPIO14 output of ESP32-Camera pulses due to continuous redrawing of the image boundary. Therefore, that input switches on NPN transistor Q1, pulling the trigger input (pin 2) of timer IC1 low. IC1 then switches on NPN transistor Q2 for up to 10 seconds, adjusted using trimpot VR1, activating the relay which triggers the alarm siren. In the software (which can be downloaded from siliconchip.com.au/ Shop/6/4529), the IP address for the ESP32-Camera module is fixed but can 32 Silicon Chip be changed by your requirements. The ESP32 continuously draws an object boundary over the image. If it finds two objects, it draws two boundaries and so on. The confidence level threshold can be from 0 to 100%. Other settings you can change are the image resolution, whether it is mirrored, whether the onboard LED is used as a ‘flash’, image quality, brightness and contrast. Note that the system will be extremely slow if you increase the image resolution from 320×240 to 1600×1200. It is better to leave the control at the default resolution first and change other settings. The ESP32-Camera board is a 3.3V device. The Li-ion or LiPo cell provides 3.7V to 4.1V which is reduced to 3.3V using an HT7333 regulator. It has a dropout voltage of only 90mV and a quiescent current of just 4μA. I have disabled brownout protection on the ESP32, so it will tolerate a marginally low voltage from the 3.3V regulator. The LMC555 will operate at a voltage as low as 1.5V, so the relay (3V / 5V DC coil) determines the operating voltage. To program the ESP32-Camera module, you need the latest version of the Arduino IDE (1.8 or above). The ESP32-Camera does not have an inbuilt USB interface. Therefore, one needs a USB-to-serial adaptor with its TX wired to the VOR pin (GPIO3), RX wired to the VOT pin (GPIO1) and GPIO0 connected to GND for the first few seconds of uploading after reset, then released. Australia's electronics magazine The coco-ssd model used in this project, implemented with TensorFlow, can detect a wide range of objects selected from the pull-down menu, varying from person to toothbrush. Whatever object is selected, the ESP32-Camera will look for the specified number of that type of object. If the number is exceeded, it will command the relay to switch on the alarm circuit. This type of collaborative AI model provides very fast detection. Other ideas for this circuit include: • A scarecrow, triggering the alarm in the presence of birds/dogs/ cats/cows/cars/etc. • A ‘magic eye’ for your front door, automatically raising the alarm when someone arrives. • A guest counter for a venue. • Other applications. Bera Somnath, Co-author: Sh S K Swain / Lara, North Karanpura, India. ($100) siliconchip.com.au November Build It Yourself Electronics Centres® Builder SAVE $100 399 $ BUYS! K 8600 The worlds best selling 3D printer! Over 800,000 sold worldwide. d. over the summer ahea Gear to keep you building ber 30th. Sale prices end Novem SAVE $26 99 $ T 2040 Creality® ‘Ender 3’ 3D Printer Learn coding! Have fun! Creality’s top selling 3D printer of all time! The Ender 3 is a compact 3D printer offering excellent print quality with a build volume of 22Wx22Dx25Hcm and is compatible with ABS, PLA and TPU filaments. Supplied mostly assembled and can be up and running within an hour. SAVE 14% Micron® 68W Compact Soldering Station This latest design benchtop soldering iron offers convenience and plenty of power for the enthusiast. Offers precise dial temperature control with temperature lock. In-built sleeper stand shuts down the unit when not in use saving on power costs. Includes a fine 1.2mm chisel tip, solder reel holder and tip sponge. SAVE 15% Requires Z 6439B micro:bit ($36.50). Tobbie II Hexapod Robot Kit Tobbie is back and he’s had an upgrade! Powered by the popular BBC micro:bit board, this version has unlimited scope for self programming. Front screen displays text & symbols. Great for teaching kids coding. Requires 4xAAA batteries & micro:bit board. Ages 8+ NEW! 19 T 2748A 5” Carbon Steel Side Cutters Tough carbon steel blades, stay sharp longer. Ideal for cutting solid core wires. 130mm. Keep everything charged up in the car with this handy 36W dual USB charger. Stylish carbon fibre look finish. Flat jaws (no serrations), ideal for precision electronics work. 145mm. 15 339 $ M 8064 1000W 499 Rust free stainless steel! Stainless Steel Long Nose Pliers Rust Resistant - great for the tackle box or use in moisture prone environments. 130mm. Bluetooth® FM Audio Player $ 229 M 8062 600W M 8065 1500W T 2741A Flat Nose Carbon Steel Pliers SAVE $9.95 $ $ Super comfy handles Dual QC3.0 USB Car Charger Pure Sine Wave M 8060 300W $ T 2770B Superb build quality! $ 19.95 .95 $ 124 20% OFF THIS MONTH ONLY! NEW! 15 $ M 8630A 55 $ K 1150 Transmits bluetooth audio from your phone (music, routes phone calls etc) to your cars FM radio. Plus it’s also a QC3.0 & USB C charger. $ The ultimate in portable power. M 8067 2500W Housed in a rugged aluminium extrusion, this new range delivers robust reliability and unwavering performance - even under severe operating conditions. For peace of mind all models have been certified to Australian Standard AS/NZS 4763.2011. Ideal for tricky loads, such as laptops, TVs & game consoles. Perfect for 4WDs, campers, caravans & trade vans. Broken remote? No problem! Bluetooth® 3.5mm Jack NEW! 39.95 $ X 0604C 959 BlackMax Inverters. Instantly add wireless audio to any 3.5mm input - like your car, headphones or home amp. $ USB rechargeable for 4 hrs listening. AE1101 19.95 Dog ate your remote? This handy replacement has IR learning & preprogrammed codes for popular brands. A 1012A Your one-stop electronics shop since 1976. | Order online at altronics.com.au SAVE 20% 27 $ MAKE a better tool kit. T 2690A Iron Only T 2694A Kit SAVE $26 Iroda® Butane 4 Pack SAVE $40 99 165 $ $ Stock up the workbench with this value pack of quality double scrubbed butane. Doesn’t clog your tools like the cheap stuff! KIT VERSION INCLUDES: • Conical tip • Hot air blower • Hot knife/plastic finishing tip • USB cable • 1m solder • Tip sponge • Carry case *Solder not included. 19 30 $ Get a crisp close up view $ T 1302A Dual Solder Reel Holder Heavy weight base with solder guides. All metal construction. Adjustable 5x-7x magnifier with LED backlight. Great for reading fine print and hobbies etc. Includes case and batteries. 2 In 1 Torch & Lantern Super bright 3W LED with pop up lantern. X 0229 15 $ Perfect for the occasional soldering job or hobbyist on the go! Provides 70W of soldering power with accessories kit in a handy carry case. Includes hot knife, hot air blower, blow torch tips, plus solder and sponge. NEW! Not just for desoldering works great as a regular hot air gun! SAVE $40 X 0432A Iroda Solder Pro 70W Soldering Tool Kit T 2451 T 1289 119 $ 68 $ ® SAVE 14% 45 minute run time. 600°C max. Ideal for occasional soldering jobs or light duty repairs and field servicing. Recharge by USB power adaptor in your car or at home - or USB battery bank. Includes replaceable 18650 battery. SAVE 22% T 2596 24 30W Lithium ‘Go Anywhere’ Soldering Iron SAVE 25% SAVE 20% 3 for $ OVER $200 IN VALUE! view! Twist adjustable Scorching 1300°C blow torch & iron in one! 19.95 $ T 2488A The new pocket rocket! SMD Hot Air Re-Work Desoldering Gun BARGAIN! 29.95 $ T 2758A 5pc Plier & Cutter Set Iroda® Mini Jet Blowtorch Provides 300W of hot air for quick and easy desolder and re-work of surface mount boards. 200-500°C adjustable. Includes desk stand - plus narrow, medium and wide nozzles for different tasks. A must have for any electronics enthusiast. Includes: • Side cutters. • Flat long needle nose pliers. • Flat bent needle nose pliers. • Long nose pliers/ cutters. • Bull nose pliers/cutters Produces a powerful jet like flame - up to 1300°C! Refillable design is great for hobbyists. 10 Includes storage case. $ SAVE 20% SAVE 24% SAVE 28% T 2329 T 2282 9 $ .95 16 $ .95 The Pocket Hero is here! Tungsten Carbide PCB Drill Set This nifty 12 in 1 pocket saviour helps you fix life’s little problems. A set of 10 PCB drill bits in a handy plastic carry case. Sizes: 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2mm. SAVE $40 119 $ T 1295A 15.95 T 4018 $ T 2191A Magnetic Bowl Mini Ratchet Driver A handy 4” stainless steel bowl with magnetic base to keep screws from straying. Includes 7 driver bits stored inside the handle. SAVE 27% 29 $ T 2186A SAVE 20% SAVE 12% T 1461 40 $ Ultimate Flexible Helping Hands The ultimate in soldering helper hands! Includes magnifier to assist with those fiddly jobs. Arm length ≈30cm. 120mm long life high flow fan 27 $ T 1522 Desktop Fume Extractor 101 Piece Ratchet Driver Kit A must have for any soldering or 3D printing work space. Whisks away fumes and filters the air through active carbon filter pads (3 included). 115CFM air flow with low noise ball bearing fan. Features 95 security, philips, pozi and slotted bits made from tough S2 alloy. Includes ratchet handle with comfy rubber grip. See web for full contents list. Super Fast Wire Stripper Strips cable of insulation at the flick of the wrist. Our best selling cable stripper of all time! Your one-stop electronics shop since 1976. | Order online at altronics.com.au Soldering & Test Gear Savers Vacuum Desoldering Station Designed to desolder through hole componentry, removing molten solder quickly and easily from solder pads and components. In-handle reservoir is easily removed and cleaned. Includes three desoldering tip, nozzle cleaner and filter pads. 160°-480°C. SAVE $56 T 2065 Desolder parts in seconds! Super fast desoldering for quick repairs or recycling parts SAVE $80 T 2052 375 $ Soldering & Vacuum Desoldering Station Save space on your bench with this top performing 60W soldering iron and 90W vacuum desoldering station. Removes a 16 pin through hole IC in 30 seconds! Sucks molten solder away from components & pads in no time and is easily cleaned. 160° to 480°C adjustable. Includes 0.2mm soldering tip and three desoldering tips. 229 $ SAVE 24% T 2487A 50W Adjustable Temp. 30 $ SAVE 15% T 2483 80W 22 $ SAVE 22% SAVE 25% SAVE 20% 70 39 $ Q 1090 9999 Count True RMS Multimeter With in-built AC mains detection. Featuring a striking easy to read reverse backlit screen and a massive 9999 count readout. Auto ranging with easy push button operation. $ Q 1070A True RMS 20 Range Multimeter Price breakthrough for a True RMS multimeter! Packed with handy features like a 60MHz frequency counter, capacitance, non contact voltage detection, even a torch! T 2445 30W 15 $ SAVE 20% T 2440 60W 22 $ ement Affordable quality backed by a full range of replac spares by Altronics. Micron® Handheld Mains Soldering Irons An iron for every occasion! T 2440 and T 2445 are ideal for general purpose soldering. T 2483 is a heavy duty chisel iron for tinning large cable, terminals and joins. 19999 COUNT LCD! Includes bit types for latest phones & laptops TOP VALUE! To buy these separately would normally cost $154! SAVE 20% 40 $ T 2164A Jakemy Pro 72pc Servicing Tool Set ® Amazing value under $100 SAVE $19 70 $ Q 1135 19999 Count True RMS Multimeter Extended resolution to 4 digits! Offers everything the serious enthusiast could need with auto ranging, min/max/rel modes, frequency, duty cycle and non contact voltage detection. A premium finish aluminium driver handle with silent ball bearing ferrule top. Contains a huge variety of driver 4x28mm driver bits, double ended opening tools, spudger, curved tip tweezers and flexible drive extension. It makes servicing high tech devices easy! Q 1073A VALUE! 99 $ Top Spec True RMS DMM Our first multimeter with wireless USB charging in-built! Includes top spec features such as illuminated sockets, LED torch, desk stand, True RMS, non contact voltage detection, frequency meter and relative mode. SAVE 22% 70 $ T 2163 Get started in electronics with this handy 20pc kit. A jam packed starter kit including soldering iron, multimeter, solder sucker, wire stripper, cutters, pliers and more! Ideal for beginners & enthusiasts. Hands free, head worn magnifier. Thousands sold! Offers 1.5, 2.6 and 5.8x magnificatio with LED lamp. Requires 2xAAA batteries. SAVE 15% 30 $ T 2555 Order online at altronics.com.au | Sale pricing ends November 30th Get started in 3D Printing. SAVE $160 SAVE $100 899 369 $ $ K 8610 K 8620 ST! ONLY WHILE STOCKS LA Need help with 3D printing? L! INTRO SPECaiIA lable Hurry, only 20 ave. at this pric Ask our friendly staff in store for guidance on how to start, software, tips & tricks! Creality® Ender 3 S1 Pro 3D Printer The latest generation in the popular Ender 3 FDM 3D Printer - now with laser engraving compatability*. The Ender 3 S1 Pro is a compact 3D printer offering excellent print quality with a build volume of 22Wx22Dx27Hcm and is compatible with ABS, PLA, TPU, PETG, PA & wood filaments. Supplied mostly assembled and can be up and running within an hour. Creality® LD-002R Resin 3D Printer Get the Pro Ender 3 Upgrades: • Auto leveling with CR-Touch inbuilt • Up to 300°C nozzle temps for different filaments. • Change over the print head to a laser engraver. • 4.3” touchscreen control • Built in LED lighting • Silent stepper driver board Affordable entry level resin printer for fast, strong & smooth prints. Resin based 3D printers are rapidly becoming the go to tool for high resolution 3D prints. They offer a faster print process with excellent accuracy and a stronger finished product thanks to UV curing on each layer. The LD-002R can print objects up to 120 x 65 x 165mm. It is capable of printing up 20-30mm per hour, making it much faster than traditional FDM 3D filament printers. Creality® Premium PLA Filament Creality® UV Resin We’re now stocking Creality’s premium 1.75mm PLA designed for use in many brands of 3D printer on the market. Creality have focused on making top quality non toxic filaments with a tolerance of just 0.02mm. Each filament is 100% bubble free and offers excellent tensile strength & fluidity. This all adds up to more reliable prints and less waste! 1kg rolls. SAVE $10 Made from high quality materials for less brittle filament breakages. 39 $ n K 8387A Silver n K 8394A Purple n K 8388A Gold n K 8389A Pink n K 8391A Orange n K 8392A Green n K 8393A Yellow n K 8395A Blue n K 8396A Red n K 8397A Black n K 8398A Grey n K 8399A White High Temperature Polyimide Tape SAVE 15% Rare Earth Magnets Quality rare earth magnets. Great for building into 3D print designs. Model Type 2 FOR T 1464 25x5mm Countersunk T 1465 25 x 5mm Solid T 1466 10 x 3mm 4 pack T 1467 5 x 6mm 8 pack $18 $16 $14 $15 Great for 3D printing and other electronics applications. Leaves no residue in high temperature masking applications. Model Width NOW T 2971A 8mm T 2972A 12mm $9 $12 $13.50 $15 $17 $25 T 2973A 16mm T 2974A 19mm T 2975A 24mm T 2976A 36mm NEW! Quality UV curable resin for use with resin printers. Provides excellent grade finish and accuracy. Low shrinkage. 500ml bottles. SAVE 15% 32 $ K 8494 Translucent K 8495 Red K 8496 Blue K 8497 Black K 8498 Grey K 8499 White Or 2 for $60! T 2370 18 $ n n n n n n .50 Deburring Hand Tool Remove rough edges and neaten up prints with this comfort grip external chamfer tool. .75 SAVE 12% 15 $ 5 Piece Needle File Set T 2352 Accurate Digital Vernier Calipers Precision measuring with ease! 150mm length, suitable for measuring internal, external and depth dimensions. 0.01mm, 0.0005” and 1/128th” display. Fine edge files for smoothing 3D prints. Shop with us on eBay | www.ebay.com.au/str/altronicsaustralia SAVE 24% 44 $ T 2247A Handy Power Gear. Power your camping fridge without risk of draining your battery! SAVE 25% Commercial gr ade cells SAVE $189 749 $ SAVE $30 209 $ N 1130F S 2750 3 Way Breaker & Switch Panel 3 x 20A 12V DC rated switches with red illumination and 15A DC breakers. Size: 114W x 96H x 60Dmm. BONUS battery box for the first 20 customers! Includes canvas carry case. 130W Remote Power Folding Solar Panel Going bush? Have power wherever you go on your next 4WD/camping adventure. Includes 130W panel, solar regulator, battery connection cables and canvas carry case. 3 stage solar charger. Adjustable stand for best sun placement. Easily connects to the battery pack on right for a complete remote power solution. 664x631x75mm (folded). 44 $ with high disc harge! SL4576B + T 5098 Portable Battery Power Combo Deal Top quality LiFePO4 Lithium battery with 100Ah capacity, PLUS a bonus battery box valued at $139. Powers your whole campsite this summer - LED lighting, camping fridges, the lot! 19.95 $ P 7811 Anderson Style & Car Acc. Panel A handy connection for 4WD & campers. 60Wx75Hx42Dmm. Cutout: 40 x 61.5mm. Lithium-Ion Car Jump Starter Throw away your old jumper leads! SAVE $46 99 $ M 8534A 6/12V 4.5A Suits 12V battery vehicles. 20000mAh rated battery provides up to 2500A peak output when cranking. Three USB ports are provided for charging devices (like a giant battery bank!). It also has a super bright 1W LED torch in built. 192L x 90W x 36Dmm. SAVE $80 189 $ Now suits LiFePo4, lead acid & calcium type batteries! M 8536A 12V 10A Multi-Stage Vehicle Battery Chargers M 8195B Each model utilises a microprocessor to ensure your battery is maintained in tip-top condition whenever you need it. Helps to extend battery service life. Suitable for permanent connection. Great for caravans & seldom used vehicles. Weatherproof casing. $ 68 This dual input design connects to a solar panel and your cars alternator (12 or 24V) to provide charging for secondary batteries such as those used in campers, caravans and trades service vans/trailers. Suitable for Lead Acid, AGM and Lithium Fe PO4 batteries. Magnetic Battery Bank Charge your phone on the go with this MagSafe compatible wireless charging battery bank. 10,000mAh. 20W USB C PD in/out. *Shown with compatible Iphone 12 for illustration purposes. D 0515A* SAVE 20% 55 $ M 8627B SAVE $16 P 7784 2 x Anderson Style Socket Includes two SB50 style connector and crimp lugs. Size: 80x50x110mm. 72 $ SAVE $70 N 2089 40A 19.95 $ N 2087 20A 275 Includes SB50 style connector and crimp lugs. Size: 80x50x65mm. $ SAVE 30% 175 $ Anderson Style Socket 229 $ Powerhouse® Solar DC-DC Battery Chargers 14.95 $ NEW! SAVE $44 GREAT VALUE P 7783 24.95 $ Q 0594 LCD Battery Fuel Gauge Measures battery voltage, current, power, real capacity & remaining run time of your connected battery (8-120V input). Includes 50A shunt with 2m cable. 1% accuracy. Cut out: 53.5 x 37.5mm. 90W Car Laptop Charger Up to 90W power output for most laptops from your car accessory socket. Includes 9 laptop adaptors - see web for product compatibility list. P 7786 Anderson Style & Car Acc. Socket Includes SB50 style connector, crimp lugs and car accessory socket connection. Size: 80x50x110mm. Do-It-All Dual Battery Charger Recharge anywhere! SAVE 20% 63 $ D 0511B BIG QC3.0/USB C Power Bank With the latest QC 3.0 charging & 18W USB-C PD output, this enormous 20,000mAh power bank will keep your devices charged anywhere. Powered by USB, allowing you to stay powered up anywhere. Works with 10440 to 26650 size lithium and d AAAA to C size Charges: Li-Ion, Ni-Mh & Ni-C Ni-MH/Ni-Cd. SAVE 12% A 0289A 20 $ 34.95 $ P 7787 Anderson Style, Car Acc. Socket & USB Charging Panel Includes SB50 style connector, crimp lugs car accessory socket connection & dual USB charger. Size: 80x50x140mm. Order online at altronics.com.au | Sale pricing ends November 30th Build & have fun this Xmas. Z 6454 Cute Scurrying Hedgehog Kit 99 $ K 1152 This cute hedgehog toy kit bristles his spines when he hears a loud noise (such as a hand clap). He will even curl up and roll away if you scare him! Assembles in <2 hours, no special tools required. Requires 4 x AAA batteries. Ages 8+ + BONUS Hydraulic Cyborg Hand Kit BONUS! Z 6439B micro:bit board. Valued at $36.50 Build & code your own robot. STEM bot is an easy to program 2 wheel obstacle avoidance and line tracking robot. Coding your program is easy using the standard BBC Micro:bit software. Simple construction with easy to folow instructions. Can also be controlled via Bluetooth. Runs from 18650 rechargeable lithium cells (S 4736 $18.50). Ages 8+ K 2208 SAVE 22% SAVE $50 45 $ 109 $ Lab kits to suit any budget in store! SAVE 10% 49.95 Build your own full size hydraulic powered robotic hand. Fits over your own hand like a glove and simulates joint movements to pick up objects. No batteries. Left & right handed. 130 in 1 Electronics Learning Lab $ This comprehensive learning lab provides many hours of building and learning for electronic concepts - great for any young future engineer! Build a radio, broadcast station, organ, kitchen timer, logic circuits & more. Requires 6xAA batteries. Ages 10+ K 1141 TOP SELLER! Handheld Game Console Kit Build it 14 ways! This Arduino based kit allows you to download and play hundreds of open source games - or have a go at coding your own! Powered by an atmega32U4 chip with direct USB programming. 1.3” monochrome screen. SAVE 15% SAVE 40% 29 $ Z 6457 .95 55 35 18 $ SAVE $14 $ $ SAVE 18% .50 K 1097 K 1113 K 1138 Solar Powered Wild Boar Kit A basic solar DIY toy, it is ideal for a do-ityourself school holiday project with the bonus of being educational! Ages 6+ 14 Solar Kits In One! Tribo 3 in 1 Coding Robot A fun and educational kit designed to assemble 14 different ways to inspire your kids to learn about solar power. No soldering required. Requires no batteries. Ages 8+ An easy to build and program robot which uses keypad entry commands to program movements and actions. No PC required! Uses 4xAAA batteries. Ages 8+. SAVE $10 42 $ K 1149 VALUE! SAVE $10 45 $ K 1148 39.95 $ 12 In 1 Solar & Hydraulic Kit A huge parts kit which can be built and rebuilt into 12 different solar powered designs. Hours of fun for kids aged 8 or over (or younger with adult help). Features a central coding ring which tells the robot directions and when to perform actions. Can be built and re-built 5 ways. Teaches kids about coding with no computers required! Requires 1xAAA battery. Ages 8+ AM/FM Radio Kit A make-it-yourself AM/FM band radio which requires no soldering or special tools. Requires 9V battery. Ages 8+ 60 in 1 Electronics Lab 49 $ SAVE 22% 30 $ Keeps bored kids busy. Build a compass, a rain detector, electro magnet and more! Requires 9V & 2xAA batteries. SAVE 19% Ages 8+ SAVE 20% K 2204 20 $ K 1154 5 In 1 Smart ‘Coding’ Robot Kit A six legged robot kit designed to avoid objects or follow you around the room. Easy to build. Requires 4 x AAA batteries. Ages 8+ Contains everything you need to build a range of electronic projects to encourage learning about essential principles. Requires 2 x AA batteries. Ages 8+ SAVE $12 Build one robot up to 5 ways! Build it 12 ways! The Original Tobbie Robot Kit 30 in 1 Electronics Lab K 2212 Great intro to electronics 88 $ K 2200 10 in 1 Electronics Lab K 2206 Pique a younh engineers interest with 10 fun projects. Requires 9V battery. Ages 8+ Shop with us on eBay | www.ebay.com.au/str/altronicsaustralia Big savings on audio visual. Opus One® 140W Soundbar Wireless Subwoofer C 9021A SAVE $40 Our new premium finish soundbar offers rich, clear sound from it’s 6 high performance speaker drivers, plus a 8” subwoofer which can be placed anywhere in your lounge room thanks to wireless connectivity. Offers bluetooth audio streaming from your favourite devices, plus S/PDIF digital audio input for connection to your TV (cable included). 99 $ Soundbar: 97 x 8 x 7.5cm, Subwoofer: 30 x 25 x 30cm C 5059 Super Quiet Noise Cancelling Bluetooth® Headphones $90 299 SAVE $ FANTASTIC VALUE AT $99! Why pay $300 or more? No outside interference with world class noise reduction technology. Designed & engineered in Silicon Valley, USA. • Block out distractions while you work • Superb active noise cancelling • Bluetooth wireless • 12hrs of listening time. • USB rechargeable (includes cable) • Carry pouch. Amazing sound. You be the judge - try a pair in store! Handy kit to get started in online content creation! SAVE $64 D 0990 175 Pro grade condenser mic for a clear, crisp sound D 0980 $ SAVE $30 119 $ All-In-One Mini Audio Studio For Creators SAVE $40 199 $ Demo in store! The MaonoCaster Lite provides everything you need to get started in podcasting, live streaming, YouTube & Twitch. Get top quality audio from the included XLR cardioid pick up condenser mic, control all your device levels, effects and music using the mixer buttons. Includes mic, mixer console, USB C cable, tripod, windsock, 3 x TRRS jack cables and monitor earphones. Desk mount microphone arm to suit C 0506 $35.95. USB Podcast Mic A premium finish USB microphone with all metal case, stand and protective grille. Adds high clarity sound to your desktop for live streams & podcasts. C 5064 Opus One® Bluetooth Bookshelf System Want top notch sound for your games, hi-fi listening or home theatre? These new active bookshelf speakers need no amplifier, just plug them in & connect via Bluetooth, digital S/PDIF or stereo RCA. Amazing sound for their price with a sleek oak grain finish - looks great with grilles on or off! Size: 146 x 164 x 240mm. Plenty of bass! NEW! A 2696A Internet radio, digital radio & audio streaming in one. Wi-Fi Internet Radio System with DAB+, FM & Bluetooth. A stylish, easy to use receiver with access to over 26,000 global internet stations, plus DAB+ digital radio, FM frequencies and bluetooth streaming from your devices. Digital S/PDIF and analogue RCA outputs NEW! 19 $ SAVE 25% 22 $ i12 Bluetooth Earbuds ® C 9032A These affordable wireless Bluetooth 5.0 earbuds offer great sound for less! 2-3 hour listening time per charge. Compatible with iOS & Android devices. 389 $ .95 A 4201 Handy problem solver! SAVE $40 199 $ SAVE 20% 40 $ SAVE $50 109 C 9037B Top Value True Wireless Earbuds Bluetooth 5.0 offers superior range (up to 10m) & better audio quality. Sweat resistant design - great for exercise. 3-4hrs of listening time with battery bank case. $ L 2047 A 1116 Boost your TV signal! Add Bluetooth to your favourite speakers! Simple to install in-line booster for delivering added gain to your existing antenna. Great for fixing choppy reception issues. USB powered. Why buy new bluetooth speakers when you can add this module to existing speakers? 2 x 25W RMS output. Includes power supply. ® Bluetooth® 2x50W Amplifier Stream audio directly from your device to your speakers. 3.5mm and RCA inputs. Class D design. Internal headphone amplifier. Includes power supply, banana speaker plugs & 3.5mm to RCA cable. Your one-stop electronics shop since 1976. | Order online at altronics.com.au Top gadgets this month. SAVE $50 SAVE $15 SAVE $20 199 $ 60 $ 99 Boost your wireless audio range to 80m! $ A 1107A Music sensor can trigger lights to the beat! C 5160 Microphone for speeches & karaoke Active RGB LED lighting with beat triggering. X 3227* True Wireless Stereo (pairs to a second unit!) Bluetooth Boom Box & Wireless PA System Need instant sound for your next big get together? Not only is this a great sounding boom box for your party music, it also includes a wireless mic for speeches and karaoke! Offers up to 8 hours use from a single charge. You can even record speeches to USB. Size: 560H x 250D x 260Wmm. FIRE THE WEATHER MAN! Get live, local weather at home. 279 $ X 7063 With outdoor sensors & smartphone app! P 8149 D 2816 + A 0981 SAVE 24% 30 Great for uni students! X 0705A 79 $ Take high quality audio notes with ease! Record CD quality audio with excellent audio pick up for taking audio notes during lectures & recording interviews. 32GB on board memory with Micro SD slot. USB rechargeable. Build It Yourself Electronics Centres Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au $ SAVE $20 Wi-Fi Automation For Xmas Lighting. Switch appliances on or off remotely from anywhere in the world. Set schedules, monitor and control via the Tuya Android/ iOS app. Maximum 10A 2400W. Works with Google Home and Alexa. Western Australia Sale Ends November 30th 2022 39.95 $ 125 $ Make your TV even Smarter! Stream direct to your TV from streaming services, plus play games and connect to local media on your home network. Capable of streaming stunning 4K videos <at> 60fps! 4GB ram with 32GB on board storage. Requires 2A USB power supply. Includes FREE A 0981 trackpad/keyboard valued at $29.95. C 9034A SAVE $10 2 For SAVE $43.95 One box for all your entertainment. This kit includes 5m of RGB strip lighting, power supply, controller unit and IR remote control allowing you to create colourful lighting effects around your home. Music sensor input allows the lighting to trigger to music being played in the room. Works with Alexa and Google Assistant. 60 LEDs per metre. Transmit or receive Bluetooth 5.0 audio across distances up to 80m! Fitted with digital S/PDIF input and output for connection to the latest hi-fi equipment. Uses low latency technology so theres no lip sync issues! Powered by USB. Includes 3.5mm, S/PDIF, USB & RCA cables. This fantastic home weather station displays all your local weather data - great for boaties & gardeners. Bright & clear base station provides readings for indoor/outdoor temperature, humidity, air pressure, rainfall, wind speed and direction. Plus handy weather trends. You can even connect it to your home wi-fi to monitor readings & data with your smartphone. 100m sensor range. FREE! Wi-Fi RGB Strip Lighting Kit Long Range Bluetooth® Audio Transceiver » Perth: 174 Roe St » Joondalup: 2/182 Winton Rd » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd Great Bluetooth Sound For Less! The perfect every day commuter earphones with top notch wireless sound, compact folding design and up to 15 hours of listening between recharges ideal for longer flights. Bluetooth 5.0. 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 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 2022. 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. *All smartphone devices pictured in this catalogue are for illustration purposes only. Not included with product. B 0011 Find a local reseller at: altronics.com.au/storelocations/dealers/ LC Capacitance Range: 1pF to 1200pF+ with 0.1pF resolution Inductance Range: 100nH to 2500μH+ with 10nH resolution below 10μH Accuracy: typically better than 2% Power supply: 3 × AA cells, draws ~35mA during operation Battery Life: around 72 hours with fresh alkaline AAs; operates down to 0.6V per cell Display: 0.96-inch (24mm diagonal) OLED screen 3 Meter Mk This new LC (inductance/capacitance) Meter is a modernised version of a very old design - the Tektronix T130 from the 1950s. It can measure a wide range of capacitances and inductances, from less than 1pF to more than 1.2nF, and from less than 100nH to more than 2.5mH. It displays the results on an OLED screen. inspired to design this modIthewas ern LC Meter when I read about 1954 Tektronix Type 130 LC Meter in the series of Vintage Workbench articles by Alan Hampel from June to August 2020 (siliconchip.au/ Series/346). It was an impressive feat of engineering at the time, using all analog techniques. While there are many cheap LC meters available today, their main drawback is not being able to measure low values. RF filters often require accurate values less than 10µH or 10pF. The Tektronix design had a reference oscillator at 140kHz (Fref). The measurement oscillator (Ftest) was initially tuned to the same frequency. Then, by placing a capacitor across the tuned circuit, or an inductor in series with the inductor in the oscillator, the test oscillator frequency dropped. Mixing the two signals gave signal components at frequencies Fref + Ftest and Fref − Ftest. Selecting the latter using a low-pass filter, the T-130 used clever analog techniques to convert this to a capacitance or inductance value shown on a moving coil meter. Their design gave accurate measurements from 1–300pF or 1-300µH. It was all done using valves; transistors were not available back then. siliconchip.com.au My first LC Meter design emulated much of this principle and worked reasonably well, but that version had some deficiencies. It used two variable capacitors, a coarse and fine adjustment, to set the test frequency to the exact value before a capacitor or inductor was measured. This was time-­consuming and fiddly, so I added an ‘automatic zero’ on power-up. Also, its construction was complicated, using a large LCD, so I changed it to use the same OLED screen that I used for my AM-FM DDS Signal Generator (May 2022; siliconchip. au/Article/15306) and 0-110dB RF Attenuator (July 2022; siliconchip.au/ Article/15385). The OLED screen is cheaper and also consumes a lot less power. That allows the Meter to run for many hours on three AA cells and operate down to a total battery voltage of 1.8V (0.6V per cell) thanks to the use of a step-up regulator. That will save on battery costs. After making those changes, I had a Meter that worked well, but I felt it was still too complicated and used too many parts, some difficult to source. The auto-zero function took far too long, and the accuracy and resolution were worse than I would like. By Charles Kosina Australia's electronics magazine Calibration was problematic as well. I solved all those problems in my final design. It somewhat moves away from the original Tektronix concept in that it does not start at a particular frequency. The operating frequency is now of secondary importance as it gets cancelled out in the calculations. It is also self-calibrating, resulting in an accuracy of about 2% over the whole capacitance range. The capacitance range is now 1pF to more than 1200pF with a resolution of 0.1pF, while the inductance range is 100nH to more than 2500μH with a resolution of 10nH below 10µH. You might notice that this new auto-calibrating concept makes it somewhat similar in operation to our June 2017 Arduino-based Digital LC Meter (siliconchip.au/Article/10676), which was based on the earlier High-accuracy Digital LC Meter (May 2008; siliconchip.au/Article/1822). However, those designs use a comparator in the oscillator and that causes some problems and has limitations. As you will see when we get to the circuit, the implementation of this Meter is somewhat different. It uses a separate inverter-based oscillator and has self-calibration features to provide better accuracy over a wide range of component values. November 2022  41 Parts availability Sourcing components is always a problem these days, but I went to quite a bit of effort to ensure that everything was available from element14 at the time of writing. There are a few parts that are available from multiple AliExpress sellers at very low prices. However, for some of these, you may have to buy multiple quantities. Still, as the prices are so low, you will end up with plenty of spares. Of course, Murphy isn’t resting, and before this article was published, some of the critical parts ran out of stock. The good news is that we realised what was happening and snapped some up, so an almost complete kit is available (see the bottom of the parts list). So if you can’t source all the parts yourself or don’t want to, that’s an easy option. Performance One primary object of this design was to produce accurate readings for low-value inductors. VHF filters generally require inductors in the sub-1µH (ie, nanohenry) range. I possess an ancient Q-Meter, a Meguro MQ-160. The design dates Table 1 – inductance accuracy Meguro inductor Measured value 1.0μH 0.98μH Circuit details 2.5μH 2.53μH The circuit of the LC Meter is shown in Fig.1. It is based on a Franklin oscillator comprising two 74HC04 inverters, IC2a and IC2b. The 1MW resistor across the first inverter puts it into a linear mode, making it act like a very high gain inverting amplifier. The second inverter provides the phase shift, which feeds back into the tuned circuit. With the nominal onboard 330µH inductor (L1) and 220pF capacitor, the oscillation frequency is about 630kHz. It has a large operating range and will still oscillate reliably with more than 1200pF added across the tuned circuit or up to 2.5mH in series. One advantage of this arrangement is that the output of IC2b swings between the supply rails. This means that it does not need an additional fast op-amp to boost the signal into a range that a microcontroller can easily measure. Four transistors, Q1-Q4, switch additional capacitors across the tuned circuit. These capacitors are 1% tolerance types, and by using parallel 5.0μH 4.88μH  7.5μH 7.35μH 10μH 9.94μH  15μH 14.2μH 25μH 24.4μH  35μH 34.6μH 50μH 49.8μH  75μH 75.1μH 100μH 99.8μH  150μH 148μH 250μH 254μH  350μH 357μH 500μH 492μH  750μH  1000μH 750μH 1009μH 1250μH 1250μH 1500μH 1484μH 2500μH 2498μH made by connecting two coils in series (eg, 150μH = 100μH in series with 50μH)  42 back to the 1940s; the one I have was made in 1969. It still works quite well, as long as the valves inside keep functioning. The MQ-160 came with a box of 14 calibration inductors from 1µH to 25mH. They are all large air-cored coils and are really works of art. Their accuracy would not drift with time, so they continue to be a good standard. Using individual and series combinations of my standard Meguro inductors, I obtained the accuracy figures shown in Table 1. These assume that my test coils are accurate, as there is no specific information in the Meguro manual about their accuracy. The accuracy for capacitor values depends on how close the 1% calibration capacitors are, and can therefore be assumed to be no worse than ±2% (and probably closer to ±1%). At the measurement frequency of 600kHz or less, ferrite-cored inductors all read low as the ferrite permeability is reduced at lower frequencies. For example, a nominal 68µH inductor measured 58.5µH at 572kHz, but a 1µH inductor fared much better and measured 0.89µH at 630kHz. Air-cored inductor measurements will not vary significantly with frequency. Silicon Chip Australia's electronics magazine combinations, we get ten calibration points. The BFR92P transistors used here have very low collector-to-base and collector-to-emitter capacitances, typically 0.4pF and 0.23pF, respectively, so they will not detract from the accuracy. The base resistors for these transistors are 3.3kW, and with 5V applied, they drive the transistors well into saturation, providing low-impedance ground connections for the capacitors. We need to provide a ‘zero reference’ point for inductance measurement. This is done by connecting L1 to ground and measuring the oscillator frequency. My initial design used an NPN transistor for this, but once the inductance under test got close to 1000µH, the voltage across the switched-off transistor was such that its reverse-biased junction conducted and clipped the waveform. The solution was to substitute a small relay (RLY1). That allows the Meter to measure up to at least 2.5mH. DPDT switch S2 selects between capacitance (up) and inductance (down) measurements. For capacitance measurements, the DUT is placed across the tuned circuit, while the DUT is placed in series for inductance measurements. In both cases, the oscillation frequency will be reduced. The oscillation frequency is too high for the microcontroller to measure accurately, so a 74HC161 binary counter is used to reduce it to less than 100kHz. In the initial design stages, I was not sure how much division would be needed, so header JP1 gives the option to divide by 2, 4, 8 or 16. In the final design, a division ratio of eight is used. Microcontroller and display The processor used is the ATMega328P on the Arduino Nano module (MOD1). I chose it as it is cheap and readily available from multiple sources, including eBay and AliExpress. It also simplifies the construction substantially. Its INT0 interrupt pin (pin 20) is used to count the frequency from the oscillator. For capacitance measurements, a 250ms window is used to count pulses. However, this is increased to two seconds for inductance measurements to obtain enough resolution down to 10nH. The OLED screen is controlled over a two-wire I2C (inter-integrated circuit) siliconchip.com.au Fig.1: the primary oscillator is built from inverters IC2a & IC2b. Its frequency is affected by an external capacitor/ inductor at CON1, or onboard calibration capacitors switched by transistors Q1-Q4. Inductor L1 is used for measuring inductances, switched to ground by RLY1. The Arduino Nano controls and monitors the oscillator, computes the values and displays them on a small OLED screen. siliconchip.com.au Australia's electronics magazine November 2022  43 I always have a simplified RS-232 serial connection on my boards for debugging the firmware. In this case, the three unused 74HC04 inverters are used, with two in parallel for the TX pin to provide sufficient drive strength. The serial interface format is 38400,8,1,n and lots of debug information is transmitted, which I have left in, as it does not slow down the operation. Power supply The prototype lacks the relay and associated components at lower left, but otherwise is very similar to the final design. serial interface. Because this uses open-drain style signalling, no voltage translation is needed, just 15kW pull-up resistors to +3.3V. These values are higher than the usual 4.7kW to reduce power consumption further. With the short tracks, there is no problem with noise despite the lower bias current. One analog input on the micro is used to measure the battery voltage, while the other is used to sense the three-position function switch, S1. Momentary switch S3 is used for starting capacitance calibration or for inductance measurement. There is an optional output for a buzzer at CON4. This gives a beep when calibration is completed. As this is its only function, it may be safely omitted. The series diode is a safety feature as the connector is the same as for the battery input. Without the diode, if the battery was connected to the wrong socket, it could destroy the microcontroller! Fig.2: a plot of the oscillator frequency shift against external capacitance. Reading a frequency shift off this plot will tell you the connected capacitor value. This can be accurately approximated with a third-order polynomial, but linear interpolation between the points shown is close enough for our needs. Fig.3: the inductance vs frequency shift curve is similar to the capacitance curve shown in Fig.2, but it needs second-order curves over most of its segments to give a good enough approximation. The exception is the 0-10μH section, which is close enough to being linear. 44 Silicon Chip Australia's electronics magazine REG1 is an MCP1661 or MP1541 step-up voltage converter. It can operate with an input voltage below 2V and still provide the required 5V output. While two cells will provide enough voltage, by using 3 AA cells, the minimum voltage is less than 0.7V per cell. You can use up all those cells which no longer work in a mouse or other equipment to power the LC Meter, saving money. REG1 works by pulling its switch pin (pin 1) low, in pulses at 500kHz. When this pin goes low, current flows from the battery through inductor L2, to ground and back to the battery, charging up L2’s magnetic field. When the transistor pulling pin 1 low is switched off, current flows from the battery through L2 and schottky diode D4 into the 5V supply rail, powering the circuit and charging up the filter and bypass capacitors. As L2’s magnetic field collapses, the voltage at the anode of D4 rises above the battery voltage. Fig.4: a close-up of the 0-10μH section of Fig.3, comparing the actual curve to a linear approximation. The resulting errors are minor in comparison to other sources of uncertainty. siliconchip.com.au By controlling the duty cycle of the pulses, REG1 maintains the voltage at its Vfb (feedback) pin close to 1.227V. The division ratio of the 390kW and 120kW resistors causes this to be effectively multiplied at the top of the divider. This results in an output of 1.227V × (390kW + 120kW) ÷ 120kW = 5.215V. Measurement calculations The frequency of a tuned circuit is given by C = 1 ÷ ω2L and L = 1 ÷ ω2C, where ω = 2πf. For C in pF, L in µH and f in MHz, this simplifies to the useful equations C = 25330 ÷ f2L and L = 25330 ÷ f2C. If we know the inductance value by measuring the frequency, we can calculate the capacitance, but this method has two problems. Firstly, an accurate inductor is not available; the best we can get is ±5%. Secondly, suitable inductors are on a ferrite core and, as mentioned earlier, permeability varies substantially with frequency. It is impractical to use an air-cored inductor as it would be too large. This is where the calibration technique results in accurate measurement. On power-up, the oscillator frequency is measured first with transistors Q1 to Q4 off. This gives the frequency with no external capacitance. Then by switching on the transistors in different combinations, we get calibration points of 100pF, 220pF, 320pF, 470pF, 690pF, 790pF, 940pF, 1040pF, 1160pF and 1260pF. Fig.2 shows the curve derived from these calibration points with the frequency offset from 0pF. It is possible to describe this curve with a polynomial equation, but a third-order polynomial is needed to get good accuracy. This is of the form C(pF) = af3 + bf2 + cf + d (d = 0). The first cubed term (f3) results in huge numbers, well beyond 32-bit integer calculations. There are ways of getting around this by cleverly sequencing the calculations, but I chose a simpler method. There is not much of a curve between individual calibration points, and a linear interpolation gives acceptable accuracy. Capacitance readings are taken continuously at about half-second intervals. The resolution is 0.1pF for values below 200pF. Above this, only the integral part of the value is shown, as siliconchip.com.au the fraction is unlikely to have significant accuracy. Inductance measurements Inductance measurements are made a bit differently. We don’t have the privilege of built-in calibration inductors, as any accurate types would have to be air-cored and far too large. I measured the oscillator frequency with each of the calibration inductors that came with my Meguro Q-Meter, up to 2500µH, which is close to the practical limit of the Meter. This gave me a calibration curve similar to the one used for capacitance. This curve may also be approximated by a third-­ order polynomial L = 20-12 f3 − 50-8 f2 + 0.0045 f. With C in pF, L in µH and f in MHz Again, this makes 32-bit integer computation difficult, so I split it into several segments, some approximated by quadratics, as shown in Fig.3. I’ve included a spreadsheet in the download package for this project with the relevant calculations. The 0-10µH section of the curve is so close to a straight line that a linear equation is very accurate (Fig.4). From this, we can estimate the likely resolution for low inductance values. To get the required resolution, the oscillator must be stable in the measurement period of four seconds. The measurement readout is stable in practice, with the 10nH digit remaining constant between measurements. Note that this calibration curve depends on the actual inductance value of inductor L1, so we have to correct the difference. This requires a measure of the value of L1, which is performed as described in the “Onboard inductor value calculation” panel. By comparing the measured value with the one I used in my prototype, the offset frequency readings are modified for better accuracy. Firmware The firmware is written in BASCOM (BASIC for AVRs), which is easy to implement and easy to follow. It occupies just over half of the 32KB flash memory on the ATmega328 processor. If you want to know more about it, download and check out the source code. Case preparation The recommended enclosure is from Ritec (Altronics Cat H0324) and includes a clear lid. It has a slightly indented clear window measuring 98 × 76 mm. The drilling measurements shown in Fig.5 relate to this window. The transparent top is relatively brittle, so be careful if using a centre punch as it can crack the plastic. Likewise, use a low-speed drill to prevent damage to the top. A step drill gives the cleanest and most accurate results. As these holes have to be very Fig.5: the locations of the holes in the clear lid of the H0324 plastic box. You could copy this (or download it from the Silicon Chip website and print it out at actual size) and use it as a template. See the comment at the end of the body text explaining that one hole and switch could be omitted. Australia's electronics magazine November 2022  45 Onboard inductor value calculation As the value of inductor L1 will vary with the test frequency due to the permeability of the ferrite core varying, we cannot rely on its nominal value. To get a good estimate of the inductance in the oscillator circuit, we need to make some calculations. The capacitance across it is the 220pF plus the stray capacitance; call this C1. We know that L = 1 ÷ (ω12 × C1), where ω = 2πf (f = oscillator frequency). The resonant frequency will change if we add a capacitance C2 in parallel with C1. As long as it is not too different from the original frequency, the inductance value will be close enough to the same. The new equation becomes: L = 1 ÷ (ω22 × [C1 + C2]) Combining the above two equations, we get: ω22 × (C1 + C2) = ω12 × C1 This can be rearranged to: (C1 + C2) ÷ C1 = ω12 ÷ ω22 Further manipulation gives us: C1 = C2 ÷ (ω12 ÷ ω22 – 1) As the 2π factors in ω1 and ω2 cancel out, this becomes: C1 = C2 ÷ ([f1 ÷ f2]2 – 1) To more easily calculate this using 32-bit integer arithmetic, we multiply the numerator and denominator on the right-hand side by f22 to give the equivalent equation: C1 = f22 × C2 ÷ (f12 – f22) In our case, we know the added capacitance C2, and measuring f1 and f2 gives us the value of C1. From this, we can calculate L according to the first equation above, or the simpler version, L = 25330 ÷ f2 × C mentioned in the body text. This calculation is done during the calibration on power-up, with C2 being the 100pF calibration capacitor. The fact that the frequencies measured are divisions of the actual frequencies does not matter as the ratio remains constant. accurate, first locate the bottom-left hole 16mm from the window edges. Drill this to 3mm and attach the blank PCB with an M3 screw and nut. Position the PCB to be precisely square, then drill the other holes in the middle of the switches. Alternatively, use Fig.5 as a template to mark the four holes that need to be drilled, then enlarge the holes to 6.35mm (1/4in) or 6.5mm. The window has a moulding ‘bump’ in the centre that interferes with the OLED behind it. Drill this out as well, to 6.35mm or 6.5mm. Construction The LC Meter is built on a 91.5 × 63.5mm double-sided PCB coded CSE220503C. Components are mounted on both sides of the board, with the connectors and Arduino Nano module on the back, as shown in the overlay diagrams, Figs.6 & 7. The only fine-pitch SMD is the MPC1661 up-converter. As it is a fivepin device, the orientation is obvious. Solder it first, followed by the other ICs. Add a thin layer of flux paste onto its pads before placing it, tack one pin and then check carefully that the other pins are correctly aligned, ideally using a magnifier. If necessary, re-heat the tacked joint and nudge it into position. Then solder the other pins. Clean the flux off the board and inspect REG1 to verify that all its pins are soldered properly and none are bridged. If there are bridges, add a bit of flux paste and then remove them with a piece of solder wick. The remaining 14-pin and 16-pin chips are relatively easy to solder but make sure they are orientated correctly! Follow with the five transistors, four BJTs (Q1-Q4) and one Mosfet (Q5). They are all in three-pin SOT-23 packages, so don’t get them mixed up. The diodes are in two different package types: plastic SOT-123 (ZD1 & D4) and cylindrical glass Mini-MELF (D2, D5). In each case, start by identifying the striped (cathode) end. You might need a magnifier to see the stripe on ZD1 and D4. Then solder them in place, as shown in Fig.6. Now fit all the discrete resistors and capacitors. They are all M2012/0805 (2 × 1.2mm) or M3216/1206 (3.2 × 1.6mm) size, and none are polarised, but the resistors should have their codes marked on top. After that, solder the small SMD relay, taking care to orientate it correctly. That’s the last surface-mounting part. Now add the through-hole components, starting with the lowest-­profile axial devices and working your way up. The OLED screen plugs into a 4-pin socket strip. Carefully slide off the plastic on the OLED pins to reduce Figs.6 & 7: all the SMDs and most of the other parts are on the front of the board. The only one that’s a bit tricky to solder is REG1; make sure you scrutinise its solder joints before powering the board up. Also watch the orientations of the ICs, the Arduino Nano module (once it’s plugged in), the relay and the diodes. 46 Silicon Chip Australia's electronics magazine siliconchip.com.au the height above the board. It is then secured by two M2.5 or M2 screws with 8mm untapped spacers. The Arduino Nano and connectors are on the opposite side of the board. I also used socket strips for the Nano, but that is optional. The Nano has 15 pins on each side, so ideally, you’d use 15-pin strips, but they are not easy to find. You can use 14-pin headers inserted towards the top edge of the board, as the lowest pin on each side is not electrically connected, or cut down longer sockets. The other components on the back of the board are headers CON2 & CON4, the optional debugging header (CON3) and the BNC socket (CON1). All the switches mount on the front, and are best fitted last. We’ve specified solder-lug switches rather than PCB-mounting types, and provided sufficiently large slots to solder in the lugs. This is because the solder lug style switches are more widely available, especially in the wide variety needed here. Make sure they’re perpendicular to the board before soldering all the lugs. Clean the board with circuit board cleaner and inspect all the soldered joints for any that may have been missed, and check for shorts between pins. Finally, place the jumper on JP1 in the position shown in Fig.6. Assembling it into the case Presumably, you followed the earlier instructions to prepare the lid with the aid of the blank PCB. If not, you’ll have to go back and use a template made from Fig.5 instead. Then you can print and prepare the front panel label, shown in Fig.8. Print this label on photographic paper. I placed a transparent 1mm thick sheet of polycarbonate on top of the label to protect it, although you could laminate it instead. Although the PCB has mounting holes, the toggle switches are adequate to bolt the unit onto the panel. The battery holder for the three AA cells (BAT1) should be attached to the bottom of the case with double-sided adhesive tape. While you could solder its leads directly to the PCB pads for CON2, that would make disassembly somewhat tricky. So we’ve specified a polarised header for CON2 and a matching plug. Crimp and/or solder the plug to the battery leads, ensuring they are not reversed. siliconchip.com.au Parts List – LC Meter Mk3 1 double-sided PCB coded CSE220503C, 91.5 × 63.5mm 1 125 × 85 × 55mm IP65 sealed ABS enclosure (clear lid) [Altronics H0324] 1 panel label, 98 × 76mm 1 Arduino Nano microcontroller board (MOD1) 1 0.96-inch OLED display module with I2C interface and SSD1306 controller (OLED1) [SC6176 (cyan)] 1 Omron G6K-2F-Y-DC5V SMD relay (RLY1) 1 330μH axial RF inductor (L1) 1 3.3μH axial RF inductor (L2) 1 PCB-mount miniature SPDT centre-off toggle switch (S1) [Altronics S1330; S1332 is PCB-mounting equivalent] 1 PCB-mount miniature DPDT on-on toggle switch (S2) [Altronics S1345; S1350 is PCB-mounting equivalent] 1 PCB-mount miniature SPDT centre-off momentary toggle switch (S3) [Altronics S1340; S1333 is PCB-mounting equivalent] 1 PCB-mount miniature SPDT on-on toggle switch (S4) [Altronics S1310; S1315 is PCB-mounting equivalent] 1 PCB-mount right-angle BNC connector (CON1) [Altronics P0529] 2 2-way polarised vertical pin headers with matching plugs (CON2, CON4) 1 3-way polarised vertical pin header (CON3; optional, for debugging) 1 4-way header socket (for OLED) 2 14-pin or 15-pin header sockets (optional, for mounting Nano) 1 2×4-pin header, 2.54mm pitch (JP1) 1 jumper shunt (JP1) 2 8mm untapped spacers (for mounting OLED) 2 M2 × 12-16mm panhead machine screws and nuts (for mounting OLED) 1 3 x AA battery holder with flying leads (BAT1) 3 AA cells (ideally alkaline) 1 200mm length of foam-core double-sided tape (to attach battery holder) 1 BNC to screw terminal adaptor (optional, to measure components) 1 chassis-mount piezo buzzer (optional) [Altronics S6109, Jaycar AB3462] Semiconductors 1 74HC161D or 74AC161D synchronous binary counter, SOIC-16 (IC1) 1 74HC04D or 74AC04D hex inverter, SOIC-14 (IC2) 1 MCP1661T-E/OT integrated high-voltage boost regulator (or MP1541DJ-LF-P boost converter), SOT-23-5 (REG1) 4 BFR92P low-capacitance NPN transistors, SOT-23 (Q1-Q4) 1 2N7002 60V 115mA N-channel Mosfet, SOT-23 (Q5) 1 BZT52C4V7 4.7V 500mW zener diode, SOD-123 (ZD1; optional) 2 LL4148 75V 500mA small signal diodes, SOD-80 (D2, D5) 1 MBR0540 50V 500mA schottky diode, SOD-123 (D4) Capacitors (all SMD M2012/0805 ceramic) 2 10μF 16V X5R 3 100nF 50V X7R 1 470pF 50V NP0/C0G 1% 1 330pF 50V NP0/C0G 1% 2 220pF 50V NP0/C0G 1% 2 120pF 50V NP0/C0G 5% 1 100pF 50V NP0/C0G 1% Resistors (all SMD M2012/0805 1%) 1 1MW 1 390kW 1 120kW 6 15kW 2 10kW 4 3.3kW Optional Adaptor Board 1 double-sided PCB coded CSE200603, 33 × 20.5mm This optional adaptor 1 SMA edge connector board makes it easier 1 6-pin header socket to test components. 1 short SMA to BNC cable KIT (SC6544 SC6544) – $65 + P&P: includes everything in the parts list above that isn't optional except for the case, AA cells and front panel label. Australia's electronics magazine November 2022  47 The battery holder and piezo buzzer are located in the case so that they don't interfere with the PCB when the lid is attached. Note the position of the hole in the side for the BNC socket. Before plugging the battery in, very carefully check that polarity as the PCB does not have reverse polarity protection. Using it The BNC connector by itself is not ideal for connecting to separate components. The simplest solution is to use a BNC plug with screw terminals and a couple of clip leads to connect to leaded components. You can connect some parts directly to the screw terminal. With care, the clip leads may also connect to M3216/1206 and M2012/0805 size SMDs. Depending on the length of leads, these will add about 100nH to measured inductances. This can be measured by shorting the leads together; then, you can subtract this from the inductance reading. That will only be necessary for values below about 5µH. An alternative is a small PCB I designed (coded CSE200603) connected by a short coax cable, BNC to SMA – see the end of the parts list. This allows more device options and includes pads for SMD capacitors. M3216 and M2012 chip capacitors can be accurately measured by carefully holding them down on the pads with a non-conducting stylus. The added capacitance of the coax cable is about 15pF, so it is necessary to run calibration with the adaptor connected, cancelling it out. Calibration runs automatically at power-up, but it can also be triggered manually by pressing the CAL/START switch. This requires the L/C switch to be in 48 Silicon Chip Some example screengrabs when operating the LC Meter Mk3. the C position and no external component connected. To make inductance measurements, switch to the L position, connect the unknown coil and press CAL/START. This will power relay RLY1 for two seconds to give a reference zero offset. After that, RLY1 is switched off, placing the unknown in series with L1. A lower frequency will be measured and subtracted from the “zero” point to give an offset frequency. The inductance is then calculated from this offset. The inductance will continue to be measured from then on, each reading taking about four seconds. If no inductor is connected, the display will show “Reading Error”. In any case, it’s best to take several readings to get a consistent result. The calibration is accurate up to 2,500µH (2.5mH). It will measure values higher than that, but the precision of such readings is unknown. Future enhancements The onboard three-position toggle switch (S1) provides Option 1 and Option 2 for possible enhancements in the future. One option I tried was to double the measurement window for improved resolution but, in practice, there was no significant difference, so I discarded it. That switch may be omitted to reduce the construction cost slightly, and the label modified to remove the options. Finally, I would like to acknowledge another regular contributor to Silicon Chip, Andrew Woodfield, for his helpful suggestions. It was largely his desire for measuring sub-1µH inductors that I was pressed to improve my SC earlier designs. LC METER MK3 CAL / START OPTION 1 C L NORMAL OPTION 2 Australia's electronics magazine ON Fig.8: the front panel label can be downloaded from the Silicon Chip website and printed on photo paper. There are two versions available, one with the OPTION switch at lower left (shown here) and one without it. siliconchip.com.au Handles 12V <at> 5A (or 10A with alternative inductors) by John Clarke Easy to build and store in a compact UB5 Jiffy box Effective noise and transient suppression Low standby current under 5mA Transient voltage clamping Low-pass filtering Fused supply DC Supply Filter for vehicles Many devices will run off 12V DC, so it’s pretty tempting just to plug them into a vehicle supply (via a cigarette lighter socket or similar), and away you go. But you’re likely to run into two significant problems with that: supply noise messing with the device’s performance and voltage spikes possibly frying it. This Filter solves both those problems. P rotect your 12V equipment from voltage transients that could cause irreparable damage using this Vehicle DC Supply Filter. It connects inline with the DC supply to clamp and filter transient voltage excursions. It’s especially useful for audio gear as it reduces that horrible ignition system whine that can pass through the vehicle’s electrical system. While many 12V supplies are transient and noise-free, some are not. That’s especially true of the 12V (or 24V) supply from a vehicle with the engine running. In particular, heavy load switching such as electric radiator fans or air conditioner compressors switching on or off can produce voltage transients on top of the theoretically smooth 12V DC supply. Other noise and transient sources include the vehicle’s alternator, where alternator brushes produce electrical noise, and the ignition system with frequent pulses delivered to the coils and spark plugs. siliconchip.com.au It isn’t just for vehicles, either. Mains switchmode power supplies can also have transients on their output, as well as noise. These typically have high-frequency noise due to the switching nature of the supply and can produce transients when the load is abruptly changed from full load to a lesser current. We have found on multiple occasions that modern switchmode plugpacks are unsuitable for powering sensitive circuits, including signal generators, preamplifiers and theremins. While some equipment powered from such sources can survive damage, others are more sensitive. The device may fail quickly due to voltage transients exceeding the internal electronics ratings, or it could fail over an extended period as sensitive electronic components accumulate damage with each voltage transient. Transients and noise can be reduced with a low-pass filter, and a transient Australia's electronics magazine voltage suppressor can absorb harmful spikes. The Filter effectively removes high-frequency signals from the DC supply. The result is a supply with much lower noise, less high-frequency ripple and more minor voltage transients. Filtering can go a long way to protecting your valuable equipment from damage. Our DC Supply Filter is quite compact and can be housed in a small Jiffy box. Heavy-duty screw terminals are provided for the input and output connections, plus there is an onboard fuse and a power-on indicator LED. Filter design The circuitry for the Filter is relatively straightforward, as shown in Fig.1. It uses two inductors and several capacitors. A transient voltage suppressor (TVS) is included to absorb excessive voltage spikes. The TVS specified begins to conduct at its Vbr (reverse breakdown voltage) of 14.4V and provides full voltage November 2022  49 Fig.1: the Filter has two main roles: to reduce high-frequency noise and absorb large spikes. Noise is attenuated by two cascaded LC filters (47μH/101.1μF) while the TVS between the two shunts to ground any particularly large voltage spikes that make it past the first filter stage. clamping at 23.5V, although it would have to be a mighty spike for it to allow the voltage to rise much above 16V. Note that a TVS will conduct a small leakage current at voltages below its reverse breakdown voltage. As it turns out, about half the quiescent current of this Filter is due to the TVS. But we need it to protect the downstream equipment from the worst spikes such as ‘load dumps’. If you want to use the Filter at a higher voltage, like 24V, you will need to change the TVS to one with a suitable Vbr rating, plus the two electrolytic capacitor working voltages will need to be increased (to 35V or 50V for a 24V supply). For the particular TVS we used, we measured a leakage current of about 2.6mA from 12V up to 15.6V, at which point the current increases as it begins to clamp the voltage. The leakage current through the TVS is something to The assembled PCB for the 5A version mounts within the UB5 enclosure on the flanged lid using TO-220 insulating bushes as standoffs. 50 Silicon Chip Australia's electronics magazine consider if this is going to be the cause of battery discharge over time. An extra 2mA (approximately) is drawn by the power indicator LED. Typically, when used on a vehicle supply, the overall 4.6mA current should not discharge the battery except over a long time. Returning to the Fig.1 circuit, power is applied at CON1, and current flows through the fuse (F1) to a small bypass capacitor, then the inductor L1, rated at 47μH and 5A. Following this are three paralleled capacitors: a 100μF low-ESR electrolytic, 1μF multi-layer ceramic and 100nF MKT polyester. These bypass ripple, noise and transients to ground. The TVS is connected in parallel with these capacitors to clamp over-voltage spikes. We use a mix of capacitors to improve the filtering action over a wide range of frequencies. The non-electrolytic capacitors function better at higher frequencies, while the electrolytic capacitor provides reasonable filtering below 100kHz and better still below 10kHz. A second identical LC (inductor/ capacitor) low-pass filter follows, forming a second stage to reduce noise and ripple going to the output at CON2. Note that a radio signal filter design would likely not include the capacitors across CON2 because they expect 50W source and load impedances. With our Filter, we expect the source impedance will be close to 0W, and the output impedance can be anywhere from about 1kW down to as low as 2.9W for a 5A load with a 14.4V supply. The capacitance across the output of the Filter at CON2 gives an effective frequency roll-off that is relatively independent of the external load siliconchip.com.au Fig.2: the measured performance of the prototype is quite a bit better than what was predicted by simulation, with noise and ripple attenuation starting below 1kHz and already below -20dB by 2kHz. -55dB is reached just above 5kHz. connected to the output. In effect, the capacitors provide a low impedance down to below 10Hz. The LED indicator (LED1) is driven from the 12V supply via a 4.7kW resistor. The LED does not light if the unit is not powered or the fuse has blown. would have made the details of the transient harder to see. We also plotted the Filter’s frequency response using the LTspice simulator and by measurement in Fig.2. The measurement was checked down to -55dB at 6kHz, and the expected roll-off above this frequency continues as an extrapolation of the measured roll-off rate. Testing the Filter We conducted a test to see how effectively the Filter reduces voltage transients using two power supplies. One supply was set to provide 14.4V DC and the other 50V DC. The 14.4V was fed to the filter input via a large inductor to isolate this from the transient voltage derived from the 50V supply. The transient was created by charging up a 100nF 100V capacitor that was subsequently switched over to connect to the Filter’s input momentarily. The result can be seen in Scope 1. The top yellow trace shows the input voltage transient with a peak 26.4V above the steady 14.4V DC supply. At the output of the Filter, shown on the lower cyan trace, there was only a 600mV increase; that’s a reduction Scope 1: a demonstration of the effectiveness of the Filter. We purposefully created a 26V spike on top of a 12V supply, causing some ongoing oscillations at the Filter’s input. The voltage at the Filter’s output peaked at only 0.6V above the DC level. in transient amplitude by a factor of 44 times. Note that the oscilloscope traces were AC-coupled, so the 14.4V DC applied to the Filter is not seen on the oscilloscope traces. If we had DC coupled the traces, the sensitivity (volts per division) would have needed to be much higher to prevent the traces from going off-screen at the top. That Construction The Filter is built on a double-sided, plated-through PCB coded 08108221 that measures 77 × 46mm. The 5A version fits in a standard UB5 plastic Jiffy box. If you wish to make a 10A version, you will need a larger UB3 box. The part changes required are shown in the parts list, including the use of a 10A fuse instead of 5A. See the separate panel on winding and mounting the inductors. Refer to the overlay diagram, Fig.3, as a guide to construction. Begin by soldering the 4.7kW resistor and low-profile parts such as the TVS and capacitors. The TVS needs to be orientated correctly, with the striped Fig.3: the Filter assembly is straightforward; the components shown here are for the 5A version. Only the TVS, LED and electrolytic capacitors are polarised. For the 10A version, the inductors will be larger and must be mounted above the other components on longer leads. siliconchip.com.au Australia's electronics magazine November 2022  51 Parts List – DC Transient Filter (12V, 5A version) 1 double-sided, plated-through PCB coded 08108221, 77 × 46mm 1 panel label, 80 × 47mm (optional) 1 UB5 Jiffy box with flanged lid [Altronics HF0155, Jaycar HB6016] 2 15A 2-way PCB-mount screw terminals (CON1, CON2) [Altronics P2101] 2 47μH 5A chokes (L1, L2) [Altronics L6617, Jaycar LF1274] 1 30A blade fuse holder [Altronics S6040] 1 5A blade fuse (F1) 2 cable glands to suit 4-8mm cable diameter 4 M3 × 10mm countersunk head (CSK) screws 4 M4 hex nuts 4 TO-220 insulating bushes 2 100mm cable ties (5A version only) 1 transient voltage suppressor rated at 1500W with a Vbr of 14.4-15V (TVS1) [Jaycar ZR1170] 1 3mm LED, any colour (LED1) 2 100nF 63V MKT capacitors 2 1μF 50V multi-layer ceramic capacitors 2 100μF 25V low-ESR electrolytic capacitors 1 4.7kW 1/2W resistor 10A version changes 1 UB3 Jiffy box [Altronics HF0203, Jaycar HB6014] (instead of UB5 Jiffy box) 2 powdered iron toroidal cores (L1, L2) [Jaycar LO1244] (instead of 47μF 5A chokes) 1 2m length of 1.25mm enamelled copper wire (for winding L1 & L2) 1 10A blade fuse (F1) (instead of 5A fuse) Winding L1 and L2 for 10A use The ratings of pre-wound inductors L1 & L2 limit the standard version of the Filter to 5A. The circuit can supply up to 10A by using hand-wound inductors instead. In this case, L1 and L2 are made by winding 24 turns of 1.25mm diameter enamelled copper wire on the specified toroidal core. The ends of the wire will need to be stripped of insulation using a sharp craft knife before soldering. Keep the ends long enough so the inductors can mount raised off the PCB, as they will not fit in the space allocated for the 5A inductors. Ideally, these inductors should be secured high enough to clear the other PCB-mounted components, but low enough to allow the assembled PCB to fit inside the enclosure. A horizontal mounting will give the best clearance; the inductor leads may need extending if they aren’t left sufficiently long. You can use neutral-cure silicone sealant to secure the inductors to the PCB and adjacent components. Fig.4: you can attach this panel label to the box lid, so its contents aren’t a mystery. The insulating bushes for the PCB should be trimmed to fit the lid. This filter is suitable for use with the Multi-Stage Buck/Boost Charger (October 2022) for battery charging from a vehicle power supply. 52 Silicon Chip Australia's electronics magazine end to the top. The two electrolytic capacitors must have their striped (negative) side toward the bottom, with the longer positive leads to the pads marked with a plus sign on the PCB, towards the top. The fuse holder, CON1 and CON2 can be fitted now. Inductors L1 and L2 are installed upright, with the leads entering the smaller holes adjacent to each side of the inductors on the PCB. The cores are held using a cable tie through each core and around under the PCB via the larger holes. Ensure the cable tie joint is on the top side of the PCB rather than on the underside, as the PCB needs to sit low in the Jiffy box to fit. Depending on your preference, the LED should be installed either down close to the PCB or with long enough leads to protrude through the enclosure. Mounting it in the enclosure If using the UB5 Jiffy box, mount the PCB to the inside of the flanged lid using countersunk head screws from the outside, with the PCB raised off the base with insulating bushes. These are the type usually used to isolate a TO-220 transistor (or similar) from its mounting screw. Cut a section of the round washer portion of the bush with side cutters to allow it to fit on the flanged lid, adjacent to the corner mount mouldings, as shown in the photo at the bottom of this page. Holes at each end of the enclosure are required for the cable glands. The PCB has cut-outs to make room for the gland nuts, so ensure the holes are centred on the enclosure sides. The input and output wires pass through the cable glands at each end and are terminated at the screw terminals. Make sure the wiring polarity is correct, as the fuse will blow if connected incorrectly to the input. Draw the wires out through the glands as the PCB is inserted into the enclosure, then tighten the gland nuts to prevent the wires from being pulled out. We have designed a panel label that can be printed and affixed to the enclosure, as shown in Fig.4. A PDF file of this label can be downloaded from: siliconchip.au/Shop/11/34 Information on how you can make labels is available at siliconchip.au/ Help/FrontPanels SC siliconchip.com.au Huge Range of 12/24V Switches Control power to your lighting and other devices in your car, 4WD, RV or boat. SAME GREAT RANGE AT SAME GREAT PRICE. TRANSLUCENT PROTECTIVE COVERS ONLY 2995 $ IP67 RATED FOR USE IN DUSTY OR WET CONDITIONS SZ1925 FROM 22 95 $ SP0798 Illuminated DPDT Dust & Waterproof Pushbuttons • 12V LED illumination • On/Off or momentary options available with red, green and blue illumination. SP0791-SP0798 4 Gang Switch Bank with Circuit Breakers • Illuminated 16A circuit breaker rocker switches • Supplied with 45 labels PRE-WIRED FOR EASY INSTALL SZ1926 SZ1925 EA WEATHERPROOF FOR MARINE OR AUTOMOTIVE USE Illuminated Rocker Switch Panels • Dimmer supported blue LEDs • 12V/20A 24V/10A rated switches • 45A max. rated panel SZ1923-SZ1925 Shop at Jaycar for: • Micro Switches • Toggle Switches • Slide Switches 95 DC Rocker Switches • 12V/20A 24V/10A rated switches • SPDT On/Off • White, red, blue and amber LED options • Supplied with range of vehicle-related decals SK0910-SK0916 FROM 3995 SK0912 ONLY 15 $ EASY INSTALLATION & WIRING $ CONTROL POWER TO LIGHTS, AND OTHER 12/24V DEVICES • Tactile Switches • DIP Switches • Rotary Switches ONLY 14 95 $ SZ1923 Sealed Toggle Switch • SPST On/Off • Up to 24V 15A rated ST0574 • Foot Switches • Tamper Switches • IP Rated Switches Explore our great switch range with discounts for bulk purchases, in stock on our website, or at over 110 stores or 130 resellers nationwide. jaycar.com.au/switches 1800 022 888 Don't pay 2-3 times as much for similar brand name models when you don't have to. IDEAL ENTRY LEVEL STATION GREAT FOR ENTHUSIAST'S WEEKEND PROJECTS ONLY 5995 $ 119 $ TS1620 TS1564 LIGHTWEIGHT IRON WITH ADJUSTABLE TEMPERATURE • 48 WATT • SLIMLINE DESIGN OUR MOST POPULAR STATION FOR HOBBYISTS • 48 WATT • ANALOGUE TEMP ADJUSTMENT MAINTAINS HEAT SETTING WITH A HIGH DEGREE OF ACCURACY • 65 WATT IRON • FAST HEAT TRANSFER • RAPID TEMP RECOVERY • ESD SAFE • MADE IN JAPAN GREAT FOR EVERYDAY ELECTRONICS ENTHUSIASTS ONLY 159 $ TS1640 54 ONLY RELIABLE OPERATION WITH EXCELLENT TEMPERATURE STABILITY • 65 WATT • DIGITAL TEMP ADJUSTMENT • ESD SAFE • INCLUDES FULL SET OF SPARES INCLUDING REPLACEABLE PENCIL ONLY 329 $ TS1440 PERFECT FOR TECHNICIANS OR ADVANCED HOBBYISTS Explore our great range of soldering stations, in stock on our website, or at over 110 stores or 130 resellers nationwide. Silicon Chip Australia's electronics magazine jaycar.com.au/solderstation 1800 022 888siliconchip.com.au Soldering Stations Soldering made easy with our BEST RANGE of soldering stations at the BEST VALUE, to suit hobbyists and professionals alike. SOLDER OR DESOLDER SURFACE MOUNT COMPONENTS ONLY 249 $ TS1648 COMPLETE SOLDER/DESOLDER STATION • 60 WATT IRON • 300W HOT AIR PUMP • RAPID TEMP RECOVERY • DUAL DIGITAL DISPLAY • ADJUSTABLE TEMPERATURE • ESD SAFE Use this colour coded selection guide to pick the soldering stationthat best suits your needs. GREEN labelled products suit hobbyists and those on a budget. BLUE suit makers who use a soldering station regularly and need ESD protection. For advanced hobbyists or technicians, choose from the ORANGE professional range. ENTRY LEVEL MID LEVEL PROFESSIONAL TS1610 TS1620 TS1564 TS1640 TS1648 TS1440 Key Feature Compact Design Slimline Ceramic Element Digital Display Soldering & Hot Air Excellent Temp Stability & Rapid Heat Recovery Power (Watts) 10W 48W 48W 60W 300W 65W Temp. Range 100-450°C 150-450°C 150-450°C 160-480°C 50-480°C Soldering 100-500°C Hot Air 200-480°C Display Digital Digital Digital ESD Safe • • • $159 $249 $329 Price $34.95 $59.95 $119 *Temperature rating is set by the soldering iron tip. ESD means Electro Static Discharge Shop Jaycar for your soldering essentials: • 6 Soldering stations • 12 Electric handheld irons • Over 12 gas powered irons siliconchip.com.au Australia's • Classic 60/40, lead-free, silver & paste solder options • Multiple desolder braid and tools • Wide range of stands, cleaners and PCB holders November electronics magazine 2022  55 Raspberry Pi Pic W Review by Tim Blythman The Raspberry Pi Foundation has a habit of making surprise announcements of new hardware. Although created with education in mind, their low pricing has made the various single-board computers and microcontroller boards extremely popular in all sorts of applications. Adding WiFi support can only increase that popularity! A fter nearly ten years of their range of single-board computers, the Raspberry Pi Foundation surprised everyone last year with the release of its first microcontroller, the RP2040, and its own microcontroller board, the Pico. Now the Pico W is available, building on the already very handy Pico board, adding all-important WiFi capability. Background The RP2040 is a dual-core ARM Cortex M0+ processor with 264kiB of RAM, a 16kiB boot ROM that provides a USB bootloader, plus some other handy functions. Like many such 32-bit devices, it runs from 3.3V. The Pico is a fairly minimal board implementation that adds a 4MB flash memory chip and a 3.3V voltage regulator. It breaks out 26 of the RP2040’s I/O pins into a compact board suitable for breadboarding or even surface-­ mounting on another PCB. Its target launch price was $6, and incredibly it is still in stock from multiple vendors at about that price. While the board is minimal, it is very capable (especially considering the price) and could be programmed in C or MicroPython from launch. Arduino support appeared very quickly after its debut. Raspberry Pi is a trademark of the Raspberry Pi Foundation It’s the same size as the Pico and costs only a few dollars more. We can see the Pico W challenging other WiFi boards like those based on the ESP32 and ESP8266 due to its low price and excellent support. 56 Silicon Chip Australia's electronics magazine The RP2040 microcontroller was also available in good numbers and at a good price (under $2 in single quantities). It was quickly taken up by other companies who created their own spin on the Pico, including variants such as the Arduino Nano RP2040 Connect, one of the many boards that includes WiFi. We reviewed the Pico in December 2021 (siliconchip.au/Article/15125) and found that it is a well-designed board with a nimble microcontroller that has a very useful set of features. With the work of Geoff Graham and Peter Mather, it was soon possible to program the Pico in BASIC. This is the so-called PicoMite (January 2022; siliconchip.au/Article/15177). The PicoMite has much in common with the Micromite, including the ability to drive an LCD touchscreen. That led us to create the Pico BackPack in March 2022 (siliconchip. au/Article/15236). The BackPack is designed to connect to an LCD touchscreen and includes an RTC (realtime clock) chip, IR receiver, stereo line-level audio output and a micro SD card slot. We also showed how to program the Pico BackPack in four different languages. The very popular VGA PicoMite followed that in July 2022 (siliconchip. au/Article/15382). The addition of a VGA output and a keyboard input means that the VGA PicoMite is more siliconchip.com.au Table 1: GPIO differences between Pico and Pico W Function Pico Pico W Notes PSU PS pin GPIO23 WL_GPIO1 Has 100kΩ pulldown, low is PFM mode, high is PWM mode USB Vbus sense GPIO24 WL_GPIO2 Digital input with pulldown LED GPIO25 WL_GPIO0 Also broken out to TP5 downstream of resistor Vsys/3 GPIO29 GPIO29 For Pico W, only when enabled by GPIO25 being high WiFi CLK – GPIO29 WiFi CS – GPIO25 Also connected to Mosfet on Pico W to enable ADC readings on GPIO29 WiFi MISO/MOSI – GPIO24 Connects to four SDIO pins of CYW43439 WiFi EN – GPIO23 Connects to both WL_REG_ON and BT_REG_ON of CYW43439 like a Maximite than a Micromite and is reminiscent of the computers of yore, like the Commodore 64. Enter the Pico W The Pico W, as you might guess, is an RP2040-based microcontroller board to which a WiFi module has been added. Its target price is $9. It’s the same size and has much the same pinout as a Pico, but with a small metal can at the end opposite the micro USB socket. That can contains the WiFi chip. The three-pin SWD (serial wire debug) header has been moved to make way for the WiFi antenna. The Pico W is not the first RP2040 board with WiFi, but given the Raspberry Pi Foundation’s aggressive pricing, it is among the cheapest. It’s similar in price to ‘off-brand’ boards with ESP8266 or ESP32 microcontrollers, which also have a similar set of features. The WiFi module is based on an Infineon CYW43439 chip, which boasts 802.11n (2.4GHz) WiFi support and Bluetooth 5.2. However, there doesn’t appear to be any software support for Bluetooth on the Pico W at this stage. The CYW43439 chip has separate WiFi and Bluetooth subsystems which each have their own ARM microcontroller core. There are several ways to communicate with the WiFi Chip but, importantly, the common SPI interface has been used on the Pico W. That means that Bluetooth could be supported on the Pico W in the future. Design evolution Having another chip interfaced to the RP2040 inevitably leads to the question of what has been sacrificed, since some resources will at least need to be shared if not given up entirely. The first clue is that all the exposed siliconchip.com.au pins are marked the same as the original Pico. The WiFi interface happens through four GPIO pins that are not broken out on either board. These are GPIO23, GPIO24, GPIO25 and GPIO29. On the original Pico, these all had various internal functions. The Pico W now uses these to communicate with the WiFi chip. Some of the original functions are kept, while others are delegated to GPIO pins on the WiFi chip. Table 1 summarises these differences. There are other subtle differences. The original Pico uses an RT6150 buck/boost regulator to provide the 3.3V rail. This is rated to 800mA and can work with an input between 1.8V and 5.5V. The Pico W uses an RT6154, which has a similar input voltage range but can deliver over 2A. Some extra current will be necessary to drive the WiFi chip; this extra capacity will surely come in handy elsewhere. Apart from the pin changes noted in Table 1, the interfaces to the power supply are much the same despite the pin changes. One I/O pin monitors Vbus to detect the presence of USB power. At the same time, another is used to select between the more efficient PFM (pulse frequency modulation) and lower ripple PWM (pulse width modulation) modes. In practice, the biggest difference is how the onboard LED is driven, since the Pico W uses one of the CYW43439’s I/O pins to drive it. On paper, the Pico W appears to be a mostly compatible and painless upgrade to the Pico. Some functions have changed locations, but that is to be expected. Hands-on testing The Pico W was unavailable in Australia until August this year due to Australia's electronics magazine delays in the Raspberry Pi Foundation getting RCM (Regulatory Compliance Mark) approval. As soon as we could get one, we tried it out. We built a Pico BackPack and fitted it with female headers, allowing us to change out the two different boards (fitted with male headers) quickly for testing. This arrangement also helps keep the Pico W’s WiFi antenna clear of the solid copper pours on the BackPack PCB and LCD module. We used stacked spacers for testing the WiFi capabilities of the Pico W. We loaded each of the four UF2 test files provided for the original Pico BackPack article onto both the Pico and Pico W in turn and checked their operation. The only difference we noted was that the Pico W does not flash its LED when using the PicoMite example firmware, which was expected due to pin 25 being used for the WiFi module instead of the LED. Otherwise, all the test programs worked identically between the two boards. So if you can afford the premium of an upgrade from the Pico to a Pico W, there aren’t really any downsides. Next, we decided to see what could be done with the Pico W’s WiFi. Using WiFi The Raspberry Pi Foundation does a great job of making it easy to get started; perhaps that is not surprising, given their educational focus. They have published online numerous data sheets, user guides and other resources such as the full circuit diagrams for both boards. Among these documents is a guide on connecting to the internet with the Pico W. You can find it at siliconchip. au/link/abgv We made good use of that information during our testing. Although the November 2022  57 WiFi chip on the Pico W uses SPI, it is in half-duplex mode, using the same data pin for communication in both directions. According to the official C SDK (software development kit) for the Pico and Pico W, the SPI peripheral is actually implemented in one of the PIO blocks. As we mentioned in our original article on the Pico, PIO blocks are I/O-orientated state machines that can run a small program and thus emulate communication peripherals like SPI or UART. There are even DVI implementations that can generate signals that work on HDMI displays. This means that existing designs that use the PIO state machines may need to be modified to work with the Pico W but presumably, only if the WiFi features are actually used. Unfortunately, it looks like the PicoMite (MMBasic) firmware will not be updated to include support for the WiFi chip, as explained at www. thebackshed.com/forum/ViewTopic. php?TID=14977 That’s because the WiFi chip on the Pico W needs a firmware image to be loaded at runtime, and that alone consumes around 300kB of flash memory, plus RAM at runtime. It would also require a framework and commands to provide a way to control the WiFi module through the BASIC language. We can see that this would be a lot of work and perhaps isn’t justified, especially as it is so easy to interface to an ESP8266 loaded with an AT command firmware. Regardless of the language used, any project that is updated to use the WiFi feature will undergo considerable changes anyway. MicroPython support There are two ways of programming the Pico W (and the Pico) provided by the Raspberry Pi Foundation: the C SDK and MicroPython, a port of the Python language optimised for microcontrollers. The Pico W’s MicroPython port supports WiFi out of the box. It is not the first microcontroller with WiFi to work with MicroPython; MicroPython has long had support for WiFi on the ESP8266 and ESP32. There is a prebuilt UF2 image of MicroPython for the Pico W available. Once uploaded, the following commands initialise the WiFi chip and print out a scan of nearby WiFi networks: import network wlan = network. WLAN(network.STA_IF) wlan.active(True) print(wlan.scan()) The Connecting to the Internet guide mentioned earlier has chapters on using MicroPython to connect to networks, make HTTP requests and build HTTP servers, including controlling Besides the added WiFi (the metal can), the PCB trace WiFi antenna has necessitated the SWD (serial wire debug) header being moved to a different location. Otherwise, the pins are in much the same locations as the original Pico. The back of the Pico W has pin markings that are identical to those on the Pico. The six test points all remain in the same locations. Like the Pico, the Pico W comes without headers; the H and WH variants cost more but have presoldered headers. the onboard LED from a web page. The guide includes source code for performing those tasks. C SDK Similarly, the Connecting to the Internet guide has a chapter on using the WiFi features under the C SDK, although these depend heavily on downloadable example projects. We had previously installed the C SDK, so we simply had to perform an update at the command prompt to get access to the new libraries and examples. New installs of the C SDK should already include the most up-todate files. There are a few command line switches that need to be used in the “cmake” command for WiFi support: -DPICO_BOARD=pico_w -DWIFI_SSID=“Network Name” -DWIFI_PASSWORD=“Password” The first of these sets the board to be a Pico W; we had not needed to use a switch previously as the Pico was the default. If you wish to eliminate confusion, the switch argument for a Pico is simply “pico”. The other switches set the SSID and password parameters for a WiFi network. Doing it this way is much easier than manually updating many source files. It also avoids having to store these credentials in a source file that might need to be distributed to others. The release notes for version 1.4.0 of the C SDK describe the updates that coincided with the release of the Pico W. You can find them at https://github. com/raspberrypi/pico-sdk/releases As for the Pico, the Raspberry Pi Foundation’s guides assume that you are using a Raspberry Pi computer to compile for the Pico W. While not the quickest way to compile code, the instructions are clear and work well in that case. There is also Pico Setup for Windows, which installs all the programs needed to compile for the Pico and Pico W using the C SDK. It can be downloaded from https://github.com/ ndabas/pico-setup-windows/releases Although the most recent version of that software predates the Pico W, the installer can download more recent SDK files. Using the Arduino IDE We tried two different board profiles for the Pico in our review from last 58 Silicon Chip Australia's electronics magazine siliconchip.com.au year. There is an ‘official’ board profile that uses Mbed OS and another profile (Arduino-Pico) that uses the C SDK. The first is included as one of the default options that can be installed by the Arduino Boards Manager, while the other needs a link to be added to the Additional Board Manager URL field under Preferences. We found that the latter was actually the first to support the Pico W, although this is perhaps not surprising as it uses the C SDK from the Raspberry Pi Foundation itself. At the time of writing, we have not seen an official Arduino core for the Pico W. So all our tests with the Arduino IDE for the Pico W have been with the Arduino-Pico core: https://github.com/ earlephilhower/arduino-pico That link includes instructions on how to install this core into the IDE. Using the Arduino IDE for the Pico W was as simple as it gets. After updating or downloading the Board Profile, we set the board to “Raspberry Pi Pico W” and uploaded the “ScanNetworks” example sketch. It then produced a list of nearby WiFi networks on the Serial Monitor (see Screen 1). As a test, we tried the Pico W sandwiched between the BackPack and LCD PCBs, as well as sitting loose on our workbench. Most networks showed a decrease of around 10dB in the indicated RSSI level compared to when the Pico W was loose and unshielded by other boards. That’s probably not critical for most applications. Still, it’s worth noting that using the BackPack and accompanying LCD with the Pico W attached directly will likely reduce the range or performance of the WiFi chip. Comparing WiFi boards The release of the WiFi-capable ESP8266 almost a decade ago and support for it being added to the Arduino IDE suddenly made hobbyist WiFi projects both cheap and straightforward. At that time, many boards under $10 appeared on the market. The Pico W is in the same league as the ESP8266. The newer ESP32 is better-equipped and offers the promise of more I/O pins. We made a comparison with these in our original Pico review. The Arduino IDE does a great job of using consistent language across different hardware, making it easy to try other devices if you are already siliconchip.com.au Screen 1: With excellent support for the Pico W in the Arduino IDE via the Arduino-Pico core, the example sketch to scan for nearby WiFi networks was easy to compile and run, producing the expected results. familiar with the ESP8266 or ESP32. Those using MicroPython should have little trouble moving across, too. In the short term, we expect the Pico W’s documentation to be its strength compared to other WiFi-equipped boards, perhaps drawing in a greater share of novices. The continuing parts shortages may give the upper hand to any board which is simply available (as long as pricing remains reasonable), and the Raspberry Pi Foundation appears to have ample supplies of the RP2040 chips; however, the early supply of the Pico W is patchy. In the long term, we think the different boards will find their own niches. For example, the RP2040’s PIO appears to have a lot of untapped potential. The RP2040 also has two cores, although some devices in the ESP32 family also do. We will also keep a close eye on when Bluetooth becomes usable on the Pico W. Conclusion It’s still relatively early days, and we expect that there will be some refinement to the various libraries and other software for the Pico W. There are hints on some forums that the Bluetooth Australia's electronics magazine capabilities of the CYW43439 chip will be put to use. Devices like the ESP32 (which is similarly supported by MicroPython and the Arduino IDE) already offer various Bluetooth capabilities, such as serial and audio over Bluetooth and also Bluetooth Low Energy (BLE). Hopefully, the Pico W will gain similar features. We didn’t run into any problems using the Pico W on our BackPack with an LCD touch panel, although the other PCBs in proximity did seem to attenuate the WiFi signals slightly. With MicroPython and the Arduino IDE long having had support for WiFi and Bluetooth, it won’t be long before we see projects using the Pico W in place of other boards using ESP8266 and ESP32 chips, especially at current prices. At the time of writing, the Pico W was available from: ∎ Digi-Key Electronics (SC0918) siliconchip.au/link/abgw ∎ Core Electronics (CSE08703) siliconchip.au/link/abgx Other retailers we expect might stock the Pico W when it becomes available in volume include Altronics, element14, Mouser and Little Bird Electronics. SC November 2022  59 Multi-function Weather Stations GREAT RANGE. GREAT VALUE. In-stock at your conveniently located stores nationwide. FROM 7495 $ • Indoor & outdoor temperature • Temperature alert alarm • 12 Hour weather forecast XC0366 $74.95 A GREAT PRICE FOR A 7 MODELS PRINTER / ENGRAVER / GREAT VALUE! LASER ETCHER RECEIVE ALERTS AND CHECK TEMP & HUMIDITY IN REAL-TIME ON YOUR SMARTPHONE • Monitors temperature & humidity • Upload data via Wi-Fi using Tuya app • Long range 150m wireless sensor • Additional soil & temperature sensors available (XC0439 $19.95) XC0442 $129 • Indoor & outdoor temp • Wind speed with direction • Dew point & heat index • Rain gauge with rate • 12 Hour weather forecast XC0432 $199 Our stylish weather stations are feature rich with useful atmospheric measurements such as temperature, humidity, barometic pressure, moon phase, rainfall plus data logging, alarms, time, calendar and more. T GRE A GIEFATS! ID From simple forecast displays to detailed modelling we have a model to suit any budget. Shop Jaycar for environmental meters: • Desktop Thermometers • Light, Wind and Sound Meters • Digital Multimeters & Data Loggers AUTOMATICALLY UPLOADS WEATHER DATA TO ONLINE WEATHER SERVICES ALL OF THE WEATHER DATA AT THE BUDDING METEOROLOGIST'S FINGERTIPS 5.4" Colour Screen & Wi-Fi 7" Colour Touchscreen with separate Temp/Humity Sensor with 5-Way Long Range Transmitter • Indoor & outdoor temperature • Wind speed with direction and chill • Dew point & heat index • Rain gauge with rate • 12 Hour weather forecast JUST 299 $ XC0434 Model Comparison • Indoor & outdoor temperature • Wind speed with direction and chill • Dew point & heat index • Rain gauge with rate • Upload data via Wi-Fi to Weather Underground & Weather Cloud 349 $ XC0440 ENTRY LEVEL MID JUST PROFESSIONAL XC0366 XC0412 XC0400 XC0442 XC0432 XC0434 XC0440 Indoor Thermometer √ √ √ √ √ √ √ Outdoor Thermometer √ √ √ √ √ √ √ Min/Max Records √ √ √ √ √ √ √ Hygrometer √ √ √ √ Touchscreen √ √ √ √ Wind Speed √ √ √ √ Wind Direction √ √ √ √ Wind Chill √ √ Dew Point √ √ √ √ Rain Gauge √ √ √ √ Rain Rate √ √ √ √ √ √ √ √ √ √ √ √ √ Barometric Pressure √ √ √ √ Time/Date Display √ √ √ √ √ √ √ √ √ Transmitter Power 2 x AAA 2 x AA 2 x AA 2 x AA 3 x AA 3 x AA 7 x AA √ √ Transmission Range 30m 30m 100m 150m 150m 150m 150m $74.95 $99.95 $149 $129 $199 $299 $349 Moon Phase High/Low Alarms Colour Screen Price √ √ √ √ √ √ Explore our full range of weather stations, in stock at over 110 stores, or 130 resellers or on our website. jaycar.com.au/weather-stations 1800 022 888 High-end Part 1: By Phil Prosser Active Monitor Speakers With Subwoofer This hifi system takes a ‘no compromise’ approach to build a truly superlative sound system that will be at home in a modern living room. We are utilising high-end components that are readily available while avoiding falling into the abyss of overly expensive, gold-plated parts. The parts used are not cheap but this system will still be within reach for many people. T his new high-end hifi system will be presented in three parts. This first part details the design and construction of the relatively compact main (left & right) speakers that provide excellent sound quality without being overly obtrusive. Because these are active speakers, they need an amplification solution that integrates an electronic crossover, which will be the focus of the second article. The electronics are housed in an attractive two rack unit (2RU) black rack-mount case, including all the amplification, signal conditioning and power supply circuitry. The third article will present a very high-quality Active Subwoofer to round out the system. It is ideal to combine with the speakers presented here, giving a full-range sound system. However, nothing locks the subwoofer into use with these particular speakers; it would be a fine addition to almost any sound system. While you could build these speakers without the sub, I reckon almost anyone going to the trouble of building these will want to extend the bass all the way down to 20Hz. So basically, all three parts are intended to be combined into one excellent sound system. Still, I have taken a modular approach, allowing you to choose which parts to build. I was a bit cheeky in the intro when I said there were no compromises. There are always compromises – in this case, one of them is that the system is a little on the expensive side. While most of our recent loudspeaker systems have aimed to be ‘good value’ systems with excellent sound quality, this one erred more on the side of ultimate fidelity without worrying too much about the bottom line. Still, we aren’t talking sheep stations. The four drivers for the Active Monitor speakers total just under $1000, while the subwoofer driver is another $339. Add in all the other bits and pieces and you can probably build the speakers for a little over $1500. Factor in the electronics, and you’re looking at perhaps a little over $2000; that’s far from outrageous for a highend speaker and amplifier system. Another compromise we often make in our loudspeaker systems is to prefer larger enclosures. That helps us achieve excellent sound quality at a reasonable price. But for this system, I decided that many people these days do not want huge loudspeakers in their living spaces. So I have tried to keep with the modern principle of keeping the speakers as small as possible without ruining the sound quality. That is part of the reason they are a bit more expensive. It does have the significant advantage that they are far less likely to be vetoed by any people who might have the power to say “no”! Photos 1 & 2: the SB Acoustics tweeter (left) and mid-bass woofer (right) used in the Active Monitor speakers. They are quality units with a broad range of frequencies at which they can both operate, giving us many choices for the crossover frequency and slope. Note that these photos are not to scale. 62 Silicon Chip Australia's electronics magazine siliconchip.com.au Features & Specifications ∎ Modestly-sized bi-amplified monitor speakers plus a subwoofer ∎ Frequency response: 25Hz-20kHz, ±3dB (20Hz-20kHz, +3,-12dB; see Fig.8 and the following article on the Active Subwoofer) ∎ Distortion: <1%, 20Hz-10kHz (typically <0.3% for normal levels; see Fig.9) ∎ Over 400W total power (2×50W tweeters + 2×50W woofers + 1×200W subwoofer) ∎ Active crossover <at> 2.7kHz (woofer/tweeter) & 90Hz (subwoofer/woofer) ∎ High-end Satori drivers used throughout ∎ Good time alignment between woofers and tweeters ∎ Excellent off-axis response Driver lineup For this system, I have chosen drivers from the SB Acoustics Satori series, their premium product line. The ‘Active Monitor’ speakers utilise: Satori MW16P-8 bass mid-range: a 165mm (6.5in) driver utilising papyrus fibres in the cone with a rubber surround and a copper sleeve on the pole piece. That sleeve helps to reduce inductance change with cone position and reduces flux modulation and distortion. In this design, it operates down to 90Hz in the active implementation and ~40Hz without the subwoofer. Satori TW29R-B tweeter: a 29mm ring radiator with a frequency response within ±2dB over 1-20kHz. It has a low resonant frequency of 600Hz and a very well-behaved impedance. Distortion over the frequency range of interest is very low indeed. Does that sound good? Wait a moment; a whole octave is missing from this equation, but it is delivered by the active subwoofer using the SB34SWNRX-S75-6. It is a 12-inch driver, although it is actually 346mm in diameter, with a 3in (75mm) voice coil, one of the real measures of continuous power handling of a driver. It has a resonant frequency of 19Hz and a 22mm peak-to-peak linear cone excursion. In an 80-litre enclosure tuned to 25Hz, this driver will deliver solid bass to 25Hz (-3dB) and operate in its linear region right down to 20Hz at up to 200W. The parts combine to form a stereo system of the highest quality. Both my measurements and listening tests reflect that. The electronic configuration of this system is shown in Fig.1. Once built, you just need to plug it into your preamp and away you go. Let’s now turn our attention to the Active Monitor speakers that are the subject of this article. They are a ‘pigeon pair’ with the Active Crossover Amplifier that will be presented next month. Being active speakers, we dispense with the cost and complexity of passive crossover components. We also benefit from an amplifier directly driving each driver and the control that provides. If you use the Active Monitor speakers without the intended subwoofer, you can achieve a low-frequency cutoff The finished speakers shown with subwoofer and Philips CD player. The speakers can be mounted on top of 800mm tall stands, as shown here, bringing them to about ear height when seated (see the parts list). siliconchip.com.au Australia's electronics magazine November 2022  63 Projects used in a stereo Active Monitor Speaker system 4 x Hummingbird Amplifier – December 2021; siliconchip.au/Article/15126 3-Way Active Crossover – October-November 2021; siliconchip.au/Series/371 Multi-Channel Speaker Protector (4-CH) – January 2022; siliconchip.au/Article/15171 Power Supply – to be described next month Projects used in the Optional Subwoofer Ultra-LD Amplifier Mk3 Amplifier – March-May 2012; siliconchip.au/Series/27 OR Ultra-LD Amplifier Mk4 – August-October 2015; siliconchip.au/Series/289 Multi-Channel Speaker Protector (4-CH) – January 2022 Power Supply – to be described in two months of about 45Hz, but note that you will have to adjust the active crossover for that. 45Hz is OK, but by adding the active subwoofer, you will experience the entire audible spectrum from about 20Hz to 20kHz. Few speakers can deliver that, especially with low distortion. The drivers are very high-quality units and, as you will see, their performance is outstanding. While their price is not stratospheric, the quality of these components does mean the cost of building this system is relatively high. The drivers used have excellent frequency responses and are well regarded for their subjective performance. See the panel titled “Subjective vs objective performance” for some insight into how I approached this design. Working on a speaker system that costs thousands of dollars to build, I feel that I am obliged to bring both a scientific and analytic approach. But I also need to use a somewhat subjective and emotional assessment to tune the final result. Both approaches have a place in this exercise. Photos 1 & 2 show the two drivers used in the Active Monitor speakers, while Figs.2 & 3 are plots of their individual frequency responses in a sealed box at 1m. Those figures show that, in terms of simple frequency response, there is a very wide crossover region throughout which both the woofer and tweeter have a flat response and do not exhibit unwanted behaviour such as breaking up, unmanageable resonances, glitches and the likes. From this measure, these drivers are a good match. The 30° off-axis measurement provided by the factory shows that for a 2-3kHz crossover point, both drivers remain well-matched and provide good off-axis coverage. Editor’s note: a good off-axis response is an essential feature of a hifi loudspeaker unless you only ever listen from a single point in a room! The ‘woofer’ actually performs extremely well out to 10kHz looking at amplitude alone, but does show signs of breaking up in the 4.5-5kHz region. Fig.1: this block diagram shows the configuration of the speaker system. A single rack-mount case houses the power supply, four amplifiers for the Active Monitors, the speaker protector and the active crossover. The line-level subwoofer output drives the active subwoofer, which has an internal power supply and amplifier. 64 Silicon Chip Australia's electronics magazine siliconchip.com.au These drivers are a paper cone type with Neodymium magnets and the build quality is excellent. That is evident in the comparison of two drivers shown opposite in Fig.4. Modelling this driver indicates that a 21L enclosure tuned between 29Hz and 35Hz covers Butterworth-Chebyshev alignments. (Butterworth is a response with a ripple-­free passband, while Chebyshev allows a little passband ripple for a faster roll-off). Reducing this volume a touch to 18L and stuffing it well allows us to keep the size of the enclosure under control at the cost of the -3dB point moving up a few hertz, to 44Hz. Given that we are designing the system to have a subwoofer, this is a moot point. This slight reduction in volume means we can keep the depth of the enclosure within reasonable limits. Driver alignment The relative placement of the tweeter and woofer is critical to the operation of the speaker, especially through the crossover region. Aside from the obvious function of filtering signals for each driver, the crossover needs to do this in a manner that results in a flat frequency response through the crossover region. There is a critical interplay between driver placement and the operation of the crossover, shown in Fig.5. The result of this misalignment of the acoustic centre of the tweeter and woofer is a skewing of the beam pattern of the speaker downwards (about 5° in our case) and a null at the crossover frequency about 5° above horizontal. These effects occur for signal frequencies in the crossover region and result in a dip in the speaker’s frequency response. If you are not aware siliconchip.com.au Amplitude (dB) -10 -20 -30 -40 100 200 500 1K 2K 5K Frequency (Hz) 10K 20K Fig.2: the SB Acoustics tweeter’s frequency response, measured 1m away. The top-end roll-off is almost entirely due to filtering on the front end of the ADC used to make these measurements. 0 -10 Amplitude (dB) The MW16P-8 woofer 0 -20 -30 -40 50 50 100 200 500 1K Frequency (Hz) 2K 5K 10K 20K Fig.3: the SB Acoustics mid-bass woofer’s frequency response in a sealed box, measured 1m away. The top end above about 5kHz looks good, but there is breakup occurring in this region. The roll-off below about 200Hz is due to the enclosure, while the ripple in the low end is due to room modes. No effort has been made to make the plot pretty or smooth. The response over the 200Hz3kHz region is excellent. 10 0 -10 Amplitude (dB) The tweeter response extends well beyond 20kHz. Cone breakup is not evident until above 20kHz, and is well-controlled. So crossing from the woofer to the tweeter in the 2-3kHz region will: 1 - Provide a fairly continuous horizontal coverage from the speaker 2 - Have the potential to have a very flat frequency response 3 - Not excite breakup modes in the woofer 4 - Operate the tweeter several octaves above its resonance (600Hz) -20 -30 -40 -50 -60 1K 2K 3K 4K 5K 6K 7K 8K 9K 10k 12K 14K 16K 18K 20K Frequency (Hz) Fig.4: a frequency response plot comparing two woofers. I suspect that some of that difference is me standing a little too close to the measurement system! It is also very pleasing to note that the response is extremely smooth and flat. The ripple visible below about 1kHz is entirely room modes. of this, it can make designing a crossover very confusing! There are a few ways designers tackle this problem. The most direct manner is to increase the output in Australia's electronics magazine this crossover region by playing with crossover frequencies and shifting the phase at crossover by pushing the tweeter crossover frequency down. That approach can work but has the November 2022  65 effect of putting more energy into the room at off-axis angles. Editor’s note: I reiterate my earlier point that little change in sound quality or frequency response off-axis is very desirable. Another approach is to offset the drivers. There are several ways to approach this; a famous example is the Duntech speakers from the nineties, which used stepped baffles and acoustic treatment to reduce diffraction from the edges. My solution is a bit of a mix of the two approaches. If this sounds like I am hedging my bets, I kind of am. I have opted for a gently-sloped baffle that somewhat offsets the tweeter back from the woofer (see Fig.6). I have also recessed the tweeter, which is good for avoiding diffraction around the transition of the tweeter face plate to the front panel. The woofer is not recessed; I simply applied felt around it to help reduce the visual and acoustic impact of this choice. It would have otherwise been Fig.5: the drivers have different depths, so their ‘acoustic centres’ are not aligned when installed on a flat panel. Around the crossover frequency, both drivers are producing signals, and the phase shift due to this misalignment causes undesirable reinforcement and cancellation at different locations in the room. necessary to slope the front panel back by 8° to get the offset between tweeter and woofer perfect. My tests show that the result is quite good. By recessing the tweeter, we get away with a modest 5° tilt on the front panel while keeping the drivers in time alignment. To my eye, the sloped front makes a pleasing change from a rectangular cube for a speaker. Still, the effect is subtle enough that you won’t even spot the front panel tilt in many of the photos. The crossover I have set the crossover frequency to 2.7kHz, implemented by an active crossover in the amplifier. I have also implemented ‘baffle step correction’ in the amplifier. This accounts for the effect of acoustic radiation from the speaker transitioning from omni-­ directional at low frequencies to directional at high frequencies. The transition frequency is a function of the driver and its location on the front panel. The step can be as much as 6dB, but in our case, a boost of 3dB at frequencies below 250Hz works well. As the speakers are bi-amplified, each driver is powered directly from its own amplifier. However, I have included a large 100μF DC blocking capacitor (Jaycar Cat RY6920) in series with the tweeters as the last line of defence against faults or crossed wiring. This capacitor has no effect in regular operation but will save your bacon should LF or DC signals somehow make their way to the tweeters. If substituting this part, make sure you use a high-voltage, high-current capacitor; many small 50V-rated bipolar capacitors do not have the ripple current rating for use in loudspeakers. Performance Fig.6: by tilting the front panel and using some other tricks, we bring the ‘acoustic centres’ into horizontal alignment, so the signals around the crossover frequency coincide, and we avoid constructive and destructive interference. 66 Silicon Chip Australia's electronics magazine Measuring the system’s overall frequency response was an exercise to minimise room reflections. The final plot (Fig.7) is a composite showing two measurements, one with the speaker on a stand and measured at 1m, the second plot with the speaker facing upwards. Both plots are smoothed one-third octave to eliminate the usual ‘fuzz’ you get on these plots. It might look a bit lumpy, but loudspeaker systems are notoriously difficult to characterise in this way. As speakers go, this is actually remarkably siliconchip.com.au flat when measured indoors, on average from around 25Hz up to 20kHz. Fig.8 is a frequency plot measurement made outside over grass near the shed. For a stand 80cm tall and 1m from the microphone (with the speaker cone at about 0.9m), the “bounce path” is 2.06m (2 × √0.9m2 + 0.5m2). The direct path is 1.0m, the difference being 1.05m. Because it’s measured outdoors the -3dB point is shown at 35Hz rather than 25Hz quoted above. Subjective vs objective performance The engineer in me always thinks, “if you can’t measure it, then you can’t hear it”. Ultimately, this is true. But the question is: what exactly do we need to measure to determine what makes one speaker sound better than another? I have run tests to see what I can hear compared to what I can measure. I have been surprised at the results, concluding that the ‘character’ of a speaker comprises not only the gross frequency response but is also influenced by less overt parameters such as the stored energy in the driver, its breakup modes and distortion profile. The lessons my experience brings to the Active Monitor speakers are: ■ We should operate the drivers well within their linear regions ■ I took note of trusted reviewers’ opinions of the drivers ■ I considered the stored energy (waterfall plots) of the drivers ■ I sought to match the beam patterns of the drivers via the crossover ■ I prefer higher crossover rates where practical ■ I stuck to drivers with few breakup modes and definitely avoided exciting them ■ After designing the system using proper engineering principles, I still needed to listen to the result and then tune or tweak it until I was happy with the sound ■ I shouldn’t be afraid to tune a speaker, but I should consider why I am making any given change siliconchip.com.au Amplitude (dB) The cabinet material you choose comes down to the finish you want, your skill at woodworking and cost. I recommend you use MDF, plywood or chipboard. All these materials will work fine for the Active Monitor Speakers. I prefer MDF over ply. MDF is denser and has a reputation as a “deader” material than chipboard. But be warned, it is also heavier and makes an extraordinary amount of dust when cut and routed. Wear a mask while working with it; breathing this dust can be harmful to your health. My woodworking skill is modest, and in building the prototypes, I have intentionally stuck to tools that most people would have. The tools I recommend using are: 1 – Circular saw with the cut angle adjustable to 5° I used a cordless circular saw and it worked great. My old mains-powered unit would also have been fine for the job. A younger or skilled person could possibly make these cuts with a hand saw, but they would be nowhere near as clean or accurate. 2 – Jigsaw Used for a couple of cuts, especially 180 120 0 60 -10 0 -20 -60 -30 -120 -40 20 50 100 200 500 1K Frequency (Hz) 2K 5K 10K -180 20K Fig.7: two frequency response plots of the overall system. Depending on where and how the speaker is located, we can move the low-frequency dip around and usually work out what is causing it. The only way to avoid it entirely would be to stick the speaker up a tall ladder, but that’s a bit awkward! So it’s best to ignore the very bottom of the frequency response as it was taken outdoors. 10 0 Amplitude (dB) Building the Active Monitor speakers 10 Phase (deg) For sound travelling at 343m/s or so, the half wavelength frequency is 163Hz, which is pretty close to the dip in that figure. That shows this is a test setup phenomenon, not the speakers. -10 -20 -30 -40 20 50 100 200 500 1K Frequency (Hz) 2K 5K 10K 20K Fig.8: a frequency response measurement of the speaker system in a relatively open grassy area. That dip at 159Hz is because the measurements were taken outside with the sub arbitrarily placed. Australia's electronics magazine November 2022  67 in the braces. You could use a small handsaw instead, but it would be a miserable task. 3 – Cordless drill/screwdriver You will also need various drill bits and a Philips No.2 driver bit for the screws. 4 – Router and bits plus a circle jig You will need a 10mm round over bit (or similar size), a 6mm round over bit (or similar size) and a 16mm straight cut bit. 5 – Sash clamps You’ll need at least two; many more if you choose to glue the enclosures only (not glue & screw). 6 – Sanding disc with 120 grit paper This will be used to smooth the edges before routing. It is possible to do this by hand if your assembly is clean. 7 – 120-400 grit sandpaper and block Buy lots of 120, 240 and 400 grit sandpaper (you can buy it as 5m rolls). Change paper frequently to reduce the amount of elbow grease required. 8 – Builders’ bog To smooth over gaps. 9 – 100mm roller, short nap For applying the acrylic primer. Assembly tips If possible, attach your vacuum cleaner to your router. If you don’t do this, don’t say I didn’t warn you! It’s also important to work in a well-­ ventilated area to help prevent inhalation of sawdust. Work out what final finish you are aiming for before you start. This will affect your construction method and Fig.9: a distortion plot for the overall system. These levels are very low for a loudspeaker system, where 0.5% is considered good. It is excellent between 50Hz and 1kHz, with the distortion generally below 0.33%. The distortion is primarily second harmonic; the third harmonic is very low, which is why these speakers sound so good. planning. I chose to go for a smooth, painted finish. This choice was driven by cost, my existing décor, and to allow me to demonstrate that you can produce a good speaker finish at home with no special tools. I have laid out the design with rebated joints, allowing you to glue and clamp or glue and screw the enclosure together. It requires some precision in routing, but once your jig has been set up, that is reasonably easy to achieve. If you do not have a router, fear not. Rejig the panel sizes to use butt joints and screw them on the end grain (with pre-drilled holes!). Fig.10 shows the cuts for a 2400mm x 1200mm sheet of 16mm-thick MDF (or two or three smaller sheets). I could have brought the sheet home in a ute and made all the cuts myself, but instead, I asked the nice people at my Photo 3: my simple jig allows quick and repeatable 90° (and angled) cuts and routed lines to be made. This saved hours of fiddling with clamps at the cost of a few timber off-cuts. You can use this with a saw or router but be prepared to throw away your ‘alignment edge’ every time you change the angle. 68 Silicon Chip Australia's electronics magazine local hardware store to cut two vertical strips 188mm wide, two 210mm wide and two 358mm wide. I took the extra as an off-cut. That lot slid easily into a VW golf hatchback, and everything, including cutting, was $50 – the cuts came free. There aren’t many free things in life, so you might as well take what you can get! Figs.11, 12 & 13 show the details of the various panels that make up the enclosures for the Active Monitor speakers. Cutting the panels from the strips is relatively straightforward; just note that accuracy here will pay dividends in final assembly. Some things to keep in mind are: • The front panel and the internal brace are sloped back by 5°. I set my circular saw to an angle of 5° and admit to using some bog to smooth these joins in my assembly. • All rebates are routed to a depth of 5mm. Do a test cut or two and get this right; do not cut too deep, or your panels will need trimming to fit. • If you need to trim a panel, plane or use a disc sander – you do not want to lop off large chunks of timber. • Keep track of your left and right panels as they have the routing on opposite sides! I used an extremely simple jig to allow simple right-angle and 5° cuts and routed lines to be made, as shown in Photo 3. Once you have cut the panels to size, mark and route the rebate for the tweeter, which is 104mm in diameter and 5mm deep. Check that the tweeter fits your circle by routing an off-cut. Next, cut the tweeter and woofer holes, noting that there are two notches siliconchip.com.au Making circular rebates for the tweeters You need a router circle jig to make neat rebates for the tweeters, as they will be visible. You can buy a circle jig for most brands of routers, but you can also make one. Get a flat sheet of aluminium about 100mm wide and 250mm long and drill a hole near one end that’s larger than your biggest router bit. Measure and drill mounting holes for the router relative to that and countersink them so the screws will not scratch the timber. Next, drill a series of 3mm holes to provide various radii from the router bit and countersink them from the top. Attach the jig to a centre hole on your workpiece using a countersunk M3 machine screw with an extra nut between the jig and the workpiece to keep it stable, and voila, you have a circle jig. Just make sure to test it on offcuts to select the ideal hole in the jig before doing the final rebate. Fig.10: here’s how to cut the full set of Active Monitor panels from one or two MDF sheets. Smaller sheets could be used, or as described in the text, take advantage of the free cutting service offered by many hardware stores. Cut these as accurately as possible, then route and cut the indicated holes in the panels for the drivers, ports and holes in the brace. siliconchip.com.au Australia's electronics magazine November 2022  69 in the tweeter cutout to accommodate the connection terminals. Once the front panel is finished, you can cut the holes in the brace. I marked these and then used a jigsaw. There is nothing terribly special about the dimensions on these cutouts, but you want to leave sufficient material to strengthen the enclosure. Finally, cut out the speaker terminal hole. Again, a jigsaw is handy but not essential. Also make the cutouts for the input terminals and speaker port on the rear panel. Now route all the rebates. I recommend setting up a jig as this will save you a lot of time and give you consistent route line locations. Cabinet assembly Whether you plan to simply glue and clamp or glue and screw the enclosures, do a dry assembly to check that all the joints are neat and fit correctly. Make any adjustments now, so that everything sits flush. If you are planning to screw the panels together, be prepared to drill 2.5mm pilot holes for your screws and countersink the heads. If your timberwork is neat and achieves a clean and tight fit together on dry assembly, simply gluing the enclosures together is something you could consider. Apply a generous layer of glue to both surfaces and use masking tape to hold panels in place if you find yourself looking for an extra hand. Wipe away excess glue as you assemble them, keeping everything relatively clean. With the rebates and internal brace, which sit horizontally between the front and rear panels, the boxes should fit nicely together. Jiggle the panels into their final places and add sash clamps to hold the lot together while the glue sets. To ‘clamp’ the top and Fig.11: details of the Active Monitor front and rear panels. Note the notches for the tweeter terminals, the rebate to recess the tweeter and the rectangular areas routed out of the inside for the internal brace. 70 Silicon Chip Australia's electronics magazine siliconchip.com.au bottom panels down, I sat the assembled speaker on the floor and put some bricks and a hefty box of transformers on top of it, as shown in Photo 4. Once clamped, take a damp cloth and wipe all excess glue from the joints. This is an essential step as sanding PVA glue is extremely difficult. Applying the finish No matter how you choose to finish your speakers, the most important thing is preparation. Once the glue had set, I used a sanding disc to sand back all external joints to flush. I then used ‘bog’ to fill any gaps between joints, being extremely careful not to overfill. The sand-and-fill process was Fig.12: details of the top and bottom panels, and the internal brace. The brace fits horizontally between the drivers and ensures good rigidity. The bottom panel is larger than the top due to the angled front. Fig.13: details of the side panels, which are trapezoidal to fit the tilted front panel. The routed areas are where the front and rear panels attach as well as the horizontal internal brace. siliconchip.com.au Australia's electronics magazine November 2022  71 Photo 4: one Active Monitor speaker box, glued and clamped, waiting to dry. This sat for 24 hours before further work was undertaken. repeated, moving through 120 grit to 240 grit sandpaper until the boxes were totally smooth. You will see in the photos that I rounded the speakers’ edges. The front edges have a 10mm radius curve to the edge, while the sides have a 6mm radius. The front edges are rounded to reduce diffraction, although if your finish demands a square edge, that will be OK. My earlier prototypes had square edges and did not show significant refraction-related problems. Next, I used a roller and acrylic primer to seal the timber, paying particular attention to the end grain. We need this sealed; otherwise, it will absorb paint and be visible through the top coat. The primer had an orange-peel effect which required yet more sanding with 240 grit paper to make the finish smooth, as can be seen in Photo 5. After the acrylic primer had been sanded totally smooth, I applied a spray primer. This sealed any patches of MDF showing through. I sanded that again using 400 grit paper and then applied two top coats with a light sanding using 400 grit paper in between. I used “satin black”, which is more matte than gloss. Gloss is the worst case for showing any flaws. Luckily, the results were excellent. Photo 6 shows the least flattering aspect of the speaker, with a slight imperfection along the top rebate joint at the rear. I almost filled and re-coated this to make them perfect, but the reality is this is only visible from this angle, so I considered the extra effort unwarranted. Installing the drivers Set the speaker port to 100-110mm in length. This does not need to be super exact; a 90 to 115mm range is acceptable. The specified Altronics port is 110mm long with the adjustable extension removed. Install and screw the port in, as shown in Photo 7. The connector is the ideal place to mount the protection capacitor for the tweeter. The 100μF capacitor will protect against the application of DC and provide a small measure of protection against modest levels of fullrange signal. However, it will not protect against prolonged high-level low-­ frequency material. To prepare the connector, you must take the bridging straps off before soldering anything to the tabs. I hot-melt glued the capacitor to the input connector and wired it directly in series with the tweeter wire. I used 1mm2 (17AWG) heavy-duty speaker cable for the tweeter and woofer connection. Make sure you cut these long enough that you can solder them to the drivers when you install them. I started with 600mm lengths, soldered them to the input terminals and trimmed them to length when I connected the drivers – see Photo 8. Mark the woofer and tweeter connections so Photo 5: the primed Active Monitor speakers drying in front of the air conditioner. These were later sanded smooth before applying spray primer, then sanded again before the top coat. Photo 6: the ultimate finish, shown at the least flattering angle (see the top rear). A final smear of filler and a couple of top coats would resolve this, but I figured it wouldn’t be visible in the listening room. 72 Australia's electronics magazine you do not get them confused. I also suggest labelling the connectors on the exterior of the box so that in the future, when you have forgotten how you built these, the connections are clear. Poke the speaker wires into the enclosure, put foam tape around the terminal cutout, then screw it down with four wood screws. Next, cut two strips of thick wadding about 1m long, fold one and stuff it above the brace, then the second one below it. The aim is to loosely fill the enclosure with wadding to damp rear radiation into the enclosure. The drivers have pre-installed foam gaskets. Solder the tweeter wires to the tweeter, being careful to get the phasing correct. Now screw the tweeter in and follow by installing the woofer. Secure the drivers with 16mm screws. Finally, I installed the felt. It is best to cut the circles after it has been stuck to the front panel but cut the straight lines using a ruler and sharp knife before installing. The pattern I used is shown in Fig.14. This is required as we are mounting the woofer flush to the front panel; the felt neatens the appearance and allows the woofer to be moved forward, improving time alignment and reducing diffraction. Depending on the felt you can source, you might need two layers. Ultimately, you want the felt flush with the woofer frame. Parts List – Active Monitor Speakers (per pair) 1 Amplifier/Crossover (to be described next month) 1 active subwoofer (optional; but recommended; described next month) 2 SB Acoustics Satori MW16P-8 165mm mid-woofers [Wagner Electronics – siliconchip.au/link/abfi] 2 SB Acoustics Satori TW29R-B 29mm ring tweeters ➊ [Wagner Electronics – siliconchip.au/link/abfj] 2 100μF 100V bipolar crossover capacitors [Jaycar RY6920] ➋ 2 35mm adjustable speaker ports [Altronics C3638] 2 bi-wire speaker terminals with two independent inputs [Altronics P2019] 1 2400 × 1200 × 16mm sheet of MDF or similar, cut as per Fig.10 30 16mm-long 8G wood screws 1 2m length of 1mm2 (17AWG) figure-8 speaker [Altronics W1936] 2 5mm-thick sheets of dark felt, 300 × 200mm 1 5m length of 5-10mm wide soft foam sealing tape (for sealing driver and terminal holes) 1 2m × 1m acoustic wadding blanket [Lincraft “king size thick wadding”] 1 300mL tube of PVA glue 1 500mL tin of acrylic primer paint 2 350g cans of spray primer paint 2 350g cans of spray paint (for two or more top coats) ➊ If you’re ordering the drivers from Wagner and want to build the subwoofer, you can get the SB34SWNRX-S75-6 subwoofer driver at the same time (siliconchip.au/link/abfk). ➋ Increasing the value up to 220μF is beneficial but not required. Make sure the capacitors can handle the currents involved. Parts for optional stands (per pair, 800mm tall) 2 2m lengths of 120 × 19mm DAR pine 2 300 × 300 × 16mm sheets of MDF or similar 2 200 × 140 × 16mm sheets of MDF or similar 8 75mm-long 10G wood screws 8 50mm-long 10G wood screws 1 250mL tin of acrylic primer paint 1 350g can of spray primer paint 1 350g can of spray paint (for two or more top coats) Fig.14: cut the felt to this shape and glue it to the front of the speaker. It serves two purposes: to prevent sound from refracting from the edges of the drivers and to hide the difference in the mounting styles of the two drivers. Photo 7: the rear of the speaker, showing the texture you get if you don’t sand the undercoat. This also gives you a good view of the vent and the terminals. siliconchip.com.au Australia's electronics magazine November 2022  73 Speaker stands Where and how you use your Active Monitor speakers is a personal choice. That said, positioning is important; having them at ear level is a good idea. My speakers are in a listening room and I wanted some stands to set them at the right height. I made suitable speaker stands from off-cuts of MDF and 120 × 19mm DAR pine timber. I used angled braces to make them both stronger and more visually interesting. Fig.15 shows how you can make some of these simply and cheaply. I cut the timber as shown, primed, sanded and applied a top coat in a similar manner to the Active Monitor speakers. The overall height of the stands as specified is 800mm; you can tweak the height to suit your needs. Testing We’re getting a bit ahead of ourselves Fig.15: the details of the low-cost but sturdy and attractive stands I designed for the Active Monitor speakers. You can probably cut the base and top plates from off-cuts of the material used to make the speakers. 74 Silicon Chip Australia's electronics magazine siliconchip.com.au -27 150 -30 100 -33 50 -36 0 -39 -50 -42 -100 -45 1.0K 1.5k 2.0k 2.5k 3.0k 3.5k Frequency (Hz) 4.0k 4.5k 5.0k 5.5k 6.0k 6.5k 7.0k 7.5k 8.0k 8.5k 9.0k 9.5k Phase (deg) Amplitude (dB) here because you’ll need to build the amplifier/crossover system described in the article next month to test your new speakers properly. Still, this is an appropriate place to discuss how to check that everything has gone together properly, so let’s proceed on the assumption that you have already built the electronics. A good test for a crossover and speaker alignment is to invert the tweeter phase and see if there is a dip at the crossover frequency. Fig.16 shows a 10dB dip in the response at the crossover frequency when I invert the phase of the tweeter. This indicates that the time alignment is correct and that everything in the system is working as planned. -150 Fig.16: a major dip is seen in the frequency response when the tweeter phase is inverted. This sound cancellation shows that everything is well aligned and working as expected. Calibration and use Assuming you are setting the output level controls on the 3-Way Active Crossover, I recommend you use an oscillator and AC voltmeter. The oscillator could be your PC audio output. Be a little cautious using DVMs as an AC voltmeter as some do not respond to signals above 400Hz, so check you get sensible readings. The steps are: 1 - Unplug your Active Monitor speakers from the Active Crossover Amplifier. 2 - Set the woofer level to maximum. 3 - Set your oscillator to generate 400Hz at 1V RMS. 4 - Measure the woofer output of the active crossover or amplifier. These should be 0.65V/12.6V RMS respectively; ±1dB precision on these is 0.580.73V & 11.2-14.1V. 5 - Now set your oscillator to 5kHz. Check that your meter still reads 1V RMS at the input to the Active Crossover Amplifier. 6 - Adjust the tweeter volume control to get 0.24V/4.7V RMS on the active crossover or amplifier’s tweeter output; ±1dB precision on these is 0.21-0.27V/4.17-5.25V. 7 - Set your oscillator to 40Hz and check that your meter still reads 1V RMS at the input to the Active Crossover Amplifier. 8 - Adjust the subwoofer volume control to get 0.59V RMS on the subwoofer output; ±1dB precision on this is 0.48-0.61V. It is probably best to set the subwoofer output by ear as there can be huge differences between listening rooms. Adjust the level up until it siliconchip.com.au Photo 8: I used hot melt glue to attach the DC block capacitor for the tweeter to the back of the speaker terminal. I then soldered 600mm of heavy-duty speaker wire to the terminals, ready for attachment to the drivers. sounds ‘bassy’, then back it off until the sound is dry. The right level is in between those settings. If you have an SPL meter, use it, just be aware that your room will create all sorts of interesting peaks and dips. Some say that two subs can help fill these, but it is an expensive proposition. Still, there’s absolutely nothing stopping you using both subwoofer outputs from the Active Crossover Amplifier to drive one sub each. In that case, you’ll initially want to set the subwoofer output closer to 0.4V RMS. I adjusted the baffle step correction to achieve optimal subjective sound quality in my listening room. You might wish to tweak this to suit your room. This is because the baffle step corrects how much sound is heard at the listening spot – but remember that diffraction merely redirects the sound off Australia's electronics magazine to the side, and the sound is still in the listening room. So each room may demand a different correction. Increasing the 2.2kW resistor will reduce the amount of baffle step correction (and reduce the frequency at which the correction kicks in). The recommended value should be correct in many situations, but you may like to experiment with it. I trust that you will enjoy building and tweaking, then listening to these very high-quality speakers and possibly making your own version inspired by some of these ideas. Next month The second article next month will describe the Active Crossover Amplifier system for driving the Active Monitor speakers. After that, we’ll have an article on building the matching High Performance Subwoofer. SC November 2022  75 Using WiFi with the GPS-Synchronised Analog Clock By Geoff Graham ur new GPS-Synchronised Analog O Clock Driver featured in the September issue has been a great success, it with the new GPS Synchronised Clock. If you want the full details, read the original article at siliconchip.au/ Article/15466 The recommended WeMos D1 Mini WiFi module is available from many sources, including Altronics (Cat Z6441) and Jaycar (Cat XC3802), as well as on eBay, AliExpress etc. The original module is made by a Chinese company called Lolin, but many clones exist. While they may look different, they have the same form-factor and pinout and work just as well. When buying the module, make sure it is the D1 Mini version. There are other variations called D1 but without the Mini suffix; they are much larger and will not fit in the space reserved for the GPS module. with hundreds built. It was so popular that there was a two-week backlog of kits until early October (kits are now back in stock). However, some constructors have reported difficulties with the GPS module being unable to get a signal. This is usually because the GPS signal is blocked or heavily attenuated when used in a multi-level house or building, a building with a steel roof or even heavy rain. The solution is Tim Blythman’s “Clayton’s GPS”, described in the April 2018 issue (siliconchip.au/Article/ 11039). This is a WiFi module that emulates a GPS module, but it gets the time from a public time server on the internet using the network time protocol (NTP). Besides the WiFi module, it does not require any extra components and is a drop-in replacement for the GPS module specified in the September article. You could swap back and forth between the two, and the clock would not notice the difference. This article briefly describes how to set up the WiFi module and use Loading the firmware To make the D1 Mini emulate a GPS module, you need to load the appropriate firmware, which can be downloaded from siliconchip.com. au/Shop/6/52 The following description is based on the Windows operating system. You can load the firmware using other operating systems, but that will require the Arduino IDE software. That process is described in the original Clayton’s GPS article from April 2018. First, plug the D1 Mini into a USB port on your Windows computer. It will connect as a serial-over-USB device. No device driver is required for Windows 10 or 11. Open Device Manager and you should see it listed as “USB-SERIAL CH340” – see Fig 1. Note the COM port number, which is COM23 in this example. Next, run the program file named “ESP8266Flasher.exe”, which is included in the firmware download. This is an easy-to-use programmer for ESP8266 devices developed by www. nodemcu.com When you start the programmer, it will guess the COM port number (see Fig.2), so the first thing that you should do is check that it has selected the correct number for the D1 Mini. Then you need to click on the Config tab and enter the path to the firmware file, “ NTP_client_for_ESP8266_GPS_ OUTV12.bin”. Leave the starting address at 0x00000 (hexadecimal value) and do not change any of the settings in the Advanced tab. Finally, return to the Fig.1: when you plug the D1 Mini into a computer running Windows, Device Manager will show the COM port allocated to it. ► Fig.2: ESP8266Flasher.exe is an easy-to-use programmer for the D1 Mini. It has correctly guessed the module COM port here, but you should still check it. 76 Silicon Chip Australia's electronics magazine siliconchip.com.au Operation tab and click the Flash(F) button. The programmer will load the firmware. While that is happening, the blue LED on the D1 Mini should flicker rapidly. When the programmer has finished, it should show a green tick on the bottom left corner of the program, indicating that it was successful. If you do not see that, click on the Log tab and scroll to the end of the log to view any error messages. NTP GPS Source Setup: Current Baudrate:9600 1.Set 4800 Baudrate 2.Set 9600 Baudrate 3.Set SSID. Current:SSID 4.Set Password. Current:PASSWORD 5.Set NTP Server. Current:pool.ntp.org 6.Set Dummy Coords. Current:3351.000,S,15112.000,E 9.Exit and save Enter a number: ❚ Fig.4: the WiFi module fits neatly in the space usually occupied by the GPS module, and only three connections are required. Configuring the firmware After successfully loading the firmware, disconnect and then reconnect the USB cable. That will reboot the module, and the blue LED on the top of the module should illuminate and stay on. Open a terminal emulator like Tera Term (https://tera-term.en.lo4d.com), set the baud rate to 9600 and connect to the COM port used by the D1 Mini. You will see the output of the module, which will be emulating a GPS module that cannot find a signal. Using the terminal emulator, enter the tilde (~) character on your keyboard and you should see the setup menu as shown in Fig.3. Change the SSID and Password to suit your network, then save and exit the configuration menu by pressing 9. None of the other settings need to be changed. Finally, disconnect and reconnect the USB cable, and the D1 Mini module should start up with the blue LED coming on solidly. That indicates the firmware is connecting to your WiFi network, accessing the internet and contacting a public time server. The blue LED will change to a brief flash every second when the firmware has received the current time. If you reconnect with your terminal emulator, you will see that the module is now producing GPS-­compatible messages indicating the correct (UTC) time. Installing the module The module fits neatly into the space reserved for the GPS module on the clock controller PCB, as shown in Fig.4. Only three wires are needed: the pin labelled 5V on the module connects to the solder pad labelled “RE” on the controller board; pin G on the module to pad “BK” on the main PCB; Inductor part code mix-up The 10 × 10mm inductor (L1) used to build the prototype, RS Components 496-0401, fit the PCB nicely and worked well. As such, we provided the part code from that item’s description in the parts list (EPCOS B82462-A4). We now know that the correct part code is B82464-A4 (that code appears on the RS page, just further down). By the time customers clued us in, we had supplied hundreds of EPCOS B82462-A4 inductors in kits from another supplier. They are electrically compatible, just smaller at 6 × 6mm. If ordering that part from RS, you will need to use the part code we gave in the parts list, as that is what they use, but from any other supplier, use the correct part code (B82464-A4-472M). If you already have the part (eg, you got it as part of a kit), we recommend you solder one side to a pad on the PCB, then use a component lead off-cut to bridge the gap between the other side and the opposite PCB pad. Many constructors have successfully built the kit that way. To make construction easier, we will be supplying a redesigned PCB that will accept either size of inductor. Those new PCBs should be available by the time you are reading this and will be included in future kits. siliconchip.com.au Fig.3: this is the configuration menu for the module. You need to change the SSID and Password entries, but the remainder of the settings can be left as they are. Australia's electronics magazine and pin TX on the module to pad “BU” on the PCB. Finally, attach the D1 Mini to the controller board using double-sided tape. When you insert cells into the clock, you should see the module’s blue LED illuminate for a few seconds while it accesses the internet, changing to a flash when it gets the correct time. Almost immediately, the clock controller’s microcontroller will power down the module (because it has the correct time) and the LED on the controller board will start a long flash every second. That indicates that it is waiting for the next hour or half-hour to start the clock running. That’s it! You can hang your clock on the wall, and it will keep accurate time for as long as it can reach the internet via your WiFi network. Incidentally, your clock will keep going even if you turn off your WiFi (for example, if you go on holiday). Then, when you re-enable your WiFi, the clock will get the correct time when it next tries to synchronise (within 24 hours) and immediately correct any error that accumulated while you were away. D1 Mini module kit (SC6472) We will be offering the D1 Mini as an option for the current kits instead of the GPS module – note that the D1 Mini will require programming. SC November 2022  77 Using Electronic Modules with Jim Rowe PM (particulate matter) “Dust” Sensors In this last article on low-cost air quality sensors, we look more closely at particulate matter (PM) sensors, also called “dust” or “smoke” sensors. A s mentioned in the first of these articles, PM sensors fall into three groups based on the size of the particles they are designed to detect: less than 10μm (PM10), less than 2.5μm (PM2.5) and less than 1μm (PM1.0). Currently, PM2.5 types are the most common in the low-cost section of the market, so we’ll concentrate on modules that support it. The basic principle of the most common type of PM sensor is shown in Fig.1. This was described in the first article but we’ll briefly go over it again. A small fan pulls air from the surrounding environment into a channel which passes through a sensing chamber. A laser sends a focused beam of light through the chamber, and any particles in the air scatter the light towards the sides of the chamber. One or more photodiodes detect this scattered light on the sides of the chamber. Any light not scattered by particles passes through the chamber to be absorbed by the ‘beam dump’. By controlling the fan speed and thus moving the air through the sensing chamber at a known rate of volume and measuring the photodiodes’ output, the concentration of particles in the air can be calculated. The result is in terms of μg/m3 (micrograms per cubic metre), because the traditional and most accurate way of measuring PM is the ‘gravimetric’ method. This involves using a preweighed clean filter to collect particles from the air over a 24-hour sampling period, then weighing the filter again to determine the total mass of the accumulated particles in micrograms. The concentration is then obtained by dividing this figure by the total volume of air that passed through the filter during the 24-hour sampling period. Available PM modules There are several low-cost PM sensors currently available, including the Grove-Laser Sensor module, based on the Seeed Studio HM3301 sensor from Shenzhen, China, and the SN-GCJA5 sensor made by Panasonic Photo and Lighting Co in Osaka, Japan. The first is a fan-type sensor, as shown in Fig.1. But other types of PM sensor modules do not have an internal fan, including the Panasonic SN-GCJA5 and the XC3780 from Jaycar, The Grove-Laser air sensor module is based on the Seeed HM3301 particulate matter sensor. The sensor itself measures 38 x 40 x 15mm and the module comes with a suitable cable. Fig.1: the basic operating principle of a particular matter (PM) sensor. Air is drawn through a chamber with a laser beam, and any laser light scattered by particles in the air is picked up by one or more photodiodes. 78 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.2: the components of the HM3301 sensor. The part at left is basically identical to what’s shown in Fig.1, while the section at right shows the electronics that pick up the scattered light level and turn it into a digital measurement. based on the Sharp GP2Y1010AU sensor. We will look at all three of these sensor modules in this article. The Grove-Laser module The Seeed Studio HM3301 sensor comes inside a compact plastic and metal case measuring 38 × 40 × 15mm. In addition to the fan, laser and photodiodes, it has built-in electronics that provide fan control, photodiode signal amplification, filtering, multi-channel data acquisition and an MCU (microcontroller unit) for data processing. The output is via a two-wire I2C serial interface. In the Grove-Laser module, the HM3301 sensor is mounted on a PCB measuring 80 × 40mm, with a four-pin connector at one end for connections to a 3.3-5V power supply and the I2C lines for connection to a PC or an external MCU. The effective PM2.5 measuring range of the module is 1-500μg/m3, although it can measure up to a maximum level of 1000μg/m3. This module is available from Australian distributor Pakronics in Rosanna, Vic for $46.06 plus shipping and GST, totalling $62.07. Fig.2 shows a functional block diagram of what’s inside the HM3301 sensor. The actual PM measuring section with the fan, laser, detection chamber, and photodiode detector is on the left. On the right is the electronics section with its filter/amplifier, multi-channel acquisition and internal MCU for digital signal processing and the I2C data communication interface. Since the HM3301 sensor operates from a 3.3-5V DC supply and has a standard I2C interface, connecting the module to an Arduino module or similar is relatively straightforward. A sample connection scheme is shown in Fig.3. Note that although the HM3301 sensor itself has no internal pull-up resistors on the SDA or SCL lines, the Grove-Laser module provides pull-up resistors plus logic-level converters on its PCB. That’s why the connections shown in Fig.3 are so straightforward. Of course, wiring the module up is only part of the story. You also need software that can communicate with it and display the results. So if you want to use it with an Arduino, you’ll need both a matching library and a sketch designed to communicate with the HM3301 sensor using it. When I went to the “Reference” section of the Arduino website and scrolled down through the Libraries/ Sensors list, I found a library that had clearly been produced to do the job: “grove-laser-pm2.5-sensor-hm3301”. And when I clicked on “Read the documentation” on its page, it took me to GitHub, where I found both the documentation and a link to download the library (v1.0.2). After downloading and installing the library, I found that it came with an example program called “basic_demo. ino”. After verifying and uploading that program ‘sketch’ to an Arduino Uno connected to the Grove-Laser Fig.3: connecting the Grove HM3301 module to an Arduino is simple. All it needs is a ground connection, a 5V DC supply and the SDA and SCL pins connected to an I2C bus. Fig.4: HM3301 sample output siliconchip.com.au 08:46:39.046 -> sensor num: 0 08:46:39.046 -> PM1.0 concentration(CF=1,Standard particulate matter, unit:ug/m3): 404 08:46:39.046 -> PM2.5 concentration(CF=1,Standard particulate matter, unit:ug/m3): 850 08:46:39.046 -> PM10 concentration(CF=1,Standard particulate matter, unit:ug/m3): 1356 08:46:39.046 -> PM1.0 concentration(Atmospheric environment,unit:ug/m3): 266 08:46:39.046 -> PM2.5 concentration(Atmospheric environment,unit:ug/m3): 524 08:46:39.046 -> PM10 concentration(Atmospheric environment,unit:ug/m3): 776 module as per Fig.3, the Arduino IDE’s Serial Monitor (set to a baud rate of 115,200) sprang into life. I immediately saw the text shown in Fig.4, with two sets of PM1.0, PM2.5 and PM10 measurements appearing every five seconds. The example output shown in Fig.4 is higher than normal (it should be just above zero). That’s because I struck a match and blew it out just before that, blowing the smoke towards the HM3301 sensor. The readings jumped up quite quickly but went back to normal after about 10 seconds. So while it’s not particularly low in cost, the Grove-Laser PM module is easy to use and seems quite sensitive. Panasonic SN-GCJA5 sensor similar to the HM3301 sensor innards shown in Fig.2, apart from not having any internal fan to move the air through the detection chamber. Since it has an I2C interface, it connects to an MCU like the Arduino in much the same way as the Grove-Laser module, as shown in Fig.6. But there’s one small but significant problem: connections to the SN-GCJA5 sensor are all made via a tiny 5-pin ‘pico’ connector at one end, but a connection cable with a matching plug is not supplied with it. So if you want to use – or even try out – the sensor, you first need to obtain a matching cable. Panasonic’s data sheet for the SN-GCJA5 sensor states that its connector is made by JST (Japan Solderless Terminals) Manufacturing Company, and has the type number SM05B-GHS-TB(LF)(SN). I had a lot of trouble finding any compatible cables – most cables I found with similar connectors turned out to have pins either 1.0mm or 1.5mm apart, not the 1.25mm of the JST SM05B-GHSTB(LF)(SN). Just as I was on the brink of concluding that I would not be able to try out the SN-GCJA5 sensor, Silicon Chip’s Editor emailed me to say that he believed he had found a supplier of compatible cables on AliExpress (www.aliexpress.com/ item/33005797784.html). I quickly checked them out and then ordered a pack of 10 (the smallest quantity). These cost $18.20 including postage and GST, and they took quite a few weeks to arrive. But they did finally arrive, and I used one (or half of one, to be precise) to hook up the sensor to an Arduino and try it out. It was again necessary to find a suitable Arduino library to communicate with the SN-GCJA5. Luckily, I found one in the Reference section on the Arduino website, under siliconchip. au/link/abep When I downloaded this library and installed it, I found that it again included some example sketches. The first of these was called “Example1_ BasicReadings.ino”. When I verified and uploaded this sketch to the Arduino Uno connected to the SN-GCJA5 sensor, as shown in Fig.6, it finally sprang into life. Once again, I had to set the Arduino IDE Serial Monitor to 115,200 baud. You can see the output of the sketch ► The Panasonic SN-GCJA5 sensor is again mounted inside a compact moulded plastic box that measures 37 × 37 × 12mm and weighs 13g. As with the HM3301 sensor, it includes electronics to control the laser and amplify and filter the signals from the photodiodes, plus an MCU for data processing. The output is via either an I2C or a UART TX terminal. The effective measuring range of this module is 0-2000μg/m3. The Panasonic SN-GCJA5 sensor is currently available in Australia from element14 for $33.56 plus delivery and GST, giving a total of $53.42 (less if you buy it along with enough other stuff, such as a second sensor, to get free delivery). Fig.5 shows what is inside the SN-GCJA5 sensor. As you can see, it’s External connections to the SN-GCJA5 sensor are via a tiny 5-way JST connector with 1.25mm pin spacing. No matching cable is supplied, which is a bit of a problem as they are hard to find! Fig.5: the Panasonic SN-GCJA5-PM sensor does not use a fan. It instead relies on passive diffusion of air through its sensing channel. Otherwise, its structure is similar to the HM3301 shown in Fig.2. The Panasonic SN-GCJA5 particulate matter sensor is in a small moulded plastic case measuring 37 x 37 x 12mm. In addition to the laser and photodetector, it contains all of the electronics and provides both I2C and UART digital outputs. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.6: connecting the Panasonic SN-GCJA5 module to an Arduino is again simple. All you need to do is connect a 5V DC supply, a ground connection and the I2C bus via the SCL and SDA pins. Pin 1 isn’t used for anything, nor does it have any function. Fig.7: SN-GCJA5 sample output 08:03:23.189 08:03:23.189 08:03:23.189 7.5, 10, 08:03:23.236 08:04:18.209 08:04:28.238 146,4, 08:04:48.249 08:05:58.231 in Fig.7. It gives three PM readings (1.0, 2.5 and 10) at the start of each sample line, followed by six Count figures (labelled 0.5, 1, 2.5, 5, 7.5 and 10). The first three figures are the ‘mass densities’ for the three main particle categories, while the later figures are ‘particle counts’ for all six particle size categories. Looking at Fig.7, the first values outputted are pretty low, they then shoot up to much higher levels after I lit a match about 150mm from the sensor and then blew it out, blowing the smoke towards the sensor. So the Panasonic SN-GCJA5 sensor does work, and even works quite well, once you manage to find a suitable cable to connect to it. It would be -> Panaosnic SN-GCJA5 Example -> Sensor started -> PM:1.0, 2.5, 10, Counts: 0.5, 1, 2.5, 5, -> 2.79,3.12,3.50,5,32,4,0,0,0, -> 57.99,135.45,448.29,39,598,801,13,71,2, -> 1370.39,1730.99,2392,60,440,3824,3759,37, -> 139.76,154.51,173.83,513,1210,153,1,2,0, -> 62.35,73.86,83.09,200,591,120,1,0,0, a lot easier if they supplied a matching cable! The Jaycar XC3780 sensor As mentioned earlier, Jaycar’s XC3780 dust sensor module is based on the Sharp GP2Y1010AU fanless sensor. The sensor itself is pretty compact, measuring 46 × 30 × 17.5mm, and the XC3780 module is only a little larger, at 62 × 35 × 19mm. 7.5mm diameter holes in the top and bottom of the sensor (and the PCB) allow air containing any particulate matter, dust or smoke to diffuse through the sensor. At the time of writing, the XC3780 module is available from Jaycar stores for $23.95 or their online Techstore for $31.95, including delivery. Because the sensor’s mini six-pin SIL connector is on the top of the case, the XC3780 module comes with a short six-wire cable connecting it to a matching mini SIL connector on the end of the module’s PCB. There are some passive components at the same end of the board plus a four-pin SIL header with standard 0.1in/2.54mm spacing, to simplify connection to an external MCU. Fig.8 shows the components inside the GP2Y1010AU sensor itself, and as you can see, it’s similar to Fig.5 apart from not having a microcontroller to digitise and process the output signal. In this case, the analog output signal “VO” is simply made available at pin 5. Note that the centre amplifier The Jaycar XC3780 module is based on the Sharp GP2Y1010AU dust sensor. Being fanless, it relies on air diffusing through 7.5mm diameter holes in the top and bottom of the sensor’s case. It has a varying DC voltage output rather than digital outputs, so conversion into a dust density figure is done by software running on the controlling MCU. siliconchip.com.au Australia's electronics magazine November 2022  81 Fig.8: the main difference between this GP2Y1010AU ‘dust’ sensor and the Panasonic sensor shown in Fig.5 is that this one lacks any digital control electronics; it only includes analog signal processing. Therefore, the driving microcontroller module must power the LED via pins 1-3, measure the voltage at output pin 5 and convert that into a particle level. Fig.9: this curve shows the transfer function between the output voltage of the GP2Y1010AU sensor and the corresponding dust density in mg/m3. A table (or similar) representing the points in this plot needs to be loaded into the microcontroller to perform this conversion. Fig.10: there aren’t many components on the Jaycar XC3780 module besides the Sharp sensor. All they do is filter the power supply to the module, provide a power-on indication via LED1 and route the necessary signals to a standard four-pin header for connection to an MCU. 82 Silicon Chip Australia's electronics magazine section has a small adjustable resistor or trimpot to adjust the sensor’s effective sensitivity. But the Sharp data sheet for the GP2Y1010AU sensor warns that this trimpot is set to make the sensor conform to its specification before shipment. As a result, they advise against further adjustment of the trimpot. This specification is summarised in Fig.9, which shows how the output voltage (VO) varies with dust density. VO is close to 0.9V with zero dust in the air, rising relatively linearly to about 3.25V at a dust density of 0.4mg/ m3 before flattening off at about 3.55V for a dust density of 0.53mg/m3. It then rises very slowly to about 3.6V for a dust density of 0.8mg/m3. Note that 1mg = 1000μg. The complete circuit of the XC3780 module is shown in Fig.10, and there are only a few passive components on the PCB apart from the GP2Y1010AU sensor itself. The 150W resistor and 220μF capacitor provide decoupling and smoothing for the supply to the sensor’s internal LED, while the 1kW resistor and LED1 indicate when the module is powered up. Connecting the XC3780 module to an Arduino is quite straightforward, as shown in Fig.11. The GND and VCC pins of the module can be connected to the GND and +5V pins of the Arduino. The LED pin should be connected to the IO3 (D3) pin of the Arduino while the VO/OUT pin goes to the Arduino’s ADC0 (A0) input. These are the connections needed to ensure that the XC3780 module works correctly when a specific sketch runs on the Arduino. That sketch uses a particular library to control the LED inside the GP2Y1010AU and convert its DC output voltage into the equivalent dust density. I found this library on the Arduino website in the reference → libraries → sensors section. Called PMsensor, it was written by JongHyun Woo, and the latest version is 1.1.0. When I downloaded this library (“PMsensor-­ master.zip”) and installed it in my Arduino IDE, I found that it came with an example sketch called “PMsensor_ demo.ino”. This sketch provides almost no information on the correct connections for the sensor’s LED and VOUT lines, or the correct baud rate to use for the Arduino link back to the PC. However, after examining the code in the sketch, siliconchip.com.au I determined that the proper connections were those shown in Fig.11, and the correct baud rate was 9600 baud. I then powered it up and got the result shown in Fig.12. I decided to adapt JongHyun Woo’s sketch into one with more helpful information in a ‘header’ section. I called this new sketch “SC_PMsensor_­ demo.ino” and it is available to download for free from siliconchip.com.au/ Shop/6/62 As you can see from Fig.12, this sketch simply pulses the sensor’s internal LED once per second, then reads its output voltage and converts it into an equivalent dust density reading. This is then printed in the lines reading “Filter : XXX.XX”. You may have noticed in Fig.12 that at the top of the listing, the readings are low. But then they started rising because I struck a match and blew it out with the smoke passing over the top of the sensor. Precisely what these figures mean is not too clear, though. They could represent the dust density in μg/m3 (micrograms per cubic metre), or they might not. So the XC3780 dust sensor can be connected fairly easily to an MCU like an Arduino, and it does work using JongHyun Woo’s library and demo sketch. But the accuracy and significance of its readings are a tad indeterminate. The bottom line Overall, I prefer the Grove-Laser module based on the HM3301 fan sensor. It is the most expensive of the three, but not unreasonably so, considering its ease of use and the apparent accuracy of its readings. I would have to rate the Panasonic SN-GCJA5 sensor as the next best; although it seems to give fairly accurate readings, it lacks a fan and also has the disadvantage of not coming with a matching cable. The Jaycar XC3780 module is only about half the cost of the other two modules/sensors and is the easiest to get. But the fact that it needs software running in the Arduino to convert its DC output voltage into dust density makes me a little less confident in the accuracy of its readings. Still, it would be fine if all you needed were relative readings, eg, to use it as a kind of smoke alarm. SC siliconchip.com.au Fig.11: connecting the Jaycar XC3780 module to an MCU is straightforward. Various pin connections could be used, but this is the routing needed for the test sketch to work. It uses one digital pin (to control its internal LED) and one analog pin (for sensing the output voltage). Fig.12: XC3780 sample output 15:15:25.825 15:15:25.825 15:15:26.762 15:15:26.809 15:15:26.809 15:15:27.793 15:15:27.840 15:15:27.840 15:15:28.824 15:15:28.824 15:15:28.871 15:15:29.808 15:15:32.854 15:15:32.901 15:15:33.839 15:15:40.962 15:15:40.962 15:15:41.946 -> -> -> -> -> -> -> -> -> -> -> -> -> -> -> -> -> -> Read PM2.5 Filter: 11.15 ========================= Read PM2.5 Filter: 30.79 ========================= Read PM2.5 Filter: 78.10 ========================= Read PM2.5 Filter: 120.76 ========================= Read PM2.5 Filter: 253.01 ========================= Read PM2.5 Filter: 396.47 ========================= We assume the readings are in μg/m3 but the documentation is a bit vague Useful links Suppliers: • www.pakronics.com.au • https://au.element14.com/3523840 • www.jaycar.com.au Software libraries: • www.arduino.cc/reference/en/libraries/grove-laser-pm2.5sensor-hm3301 • https://github.com/Seeed-Studio/Seeed_PM2_5_sensor_HM3301 • www.arduino.cc/reference/en/libraries/pmsensor/ • https://github.com/ekkai/PMsensor • https://github.com/sparkfun/SparkFun_Particle_Sensor_SN-GCJA5_ Arduino_Library Panasonic SN-GCJA5 data sheet: siliconchip.au/link/aber Sharp dust sensor application note: siliconchip.au/link/abeq Australia's electronics magazine November 2022  83 Vintage Radio Philips Minstrel radios By Assoc. Prof. Graham Parslow The Minstrel series of radios from Philips in the early 1950s was intended to be affordable and cheerful. Comparable kitchen radios are the Astor Mickey, HMV Little Nipper, AWA model 467MA and Healing model 404. The Philips Minstrel cost £21, similar to its four-valve competitors. 84 Silicon Chip Australia's electronics magazine I managed to get a copy of the original advertisement showing the nine beautiful colours that the cabinet came in via Glen Oriss, a member of the Facebook group The Real Bakelite and Antique Radio Page. As well as the models noted in the introduction, Philips also competed against themselves with the Jubilee model 122. But this comparable fourvalve radio was much more conservatively styled in dark Bakelite. The performance of these radios is excellent on local stations due to the progressive refinement of the three valves in the radio circuit (the fourth valve is the high-tension rectifier). More expensive five-valve sets added audio preamplification and are usually indistinguishable in performance for city locations. The Minstrel radios were moulded from solid-colour plastics. These new polymers were used in many items in the 1950s when plastic was fantastic. Before these plastics, light colours were often produced as factory-­ painted Bakelite. The standard Minstrel is the model 138. When they added a clock, it became the Chronoradio model 145. The circuit and construction of the two models are otherwise almost identical; the clock radio has an additional socket on the chassis that allows the synchronous-motor clock to connect to the 240V 50Hz mains and switch the radio on at set times. The clock radio has a low profile 4-inch speaker (100mm) mounted at the top and delivers sound through a grille moulded into the top of the case. This produces reasonable sound, but not as good as the 5-inch (125mm) speaker mounted at the front of model 138. The station markings on the dial depended on the target states for sale. The blue radio pictured opposite features WA and SA stations. The clock radio included at the end of the article has all states on the one dial. Circuit details The original circuit for the model 138 clock radio is shown in Fig.1. The aerial coils of the 1950s were well-evolved to make the best of whatever aerial was connected. The Radiotron Designer’s Handbook 4th Edition from 1957 says, in the summary of design for aerial coils: “It can be seen that the common siliconchip.com.au Fig.1: the circuit for the Philips Minstrel Four 138 radio is nearly identical to the model 145. The 145 has one less tap on the secondary of the power transformer (L14 is removed) and some of the resistors have been changed by ~10% in value. An excerpt from the model 145 circuit showing the clock portion is shown on the left-side with a grey fill. loose coupled primary and secondary for MW radios is most satisfactory because it readily lends itself, with minor modifications, to applications using balanced or unbalanced aerial systems.” Random lengths of wire connected to a domestic radio certainly fit into the unbalanced category. In looking at the aerial coil circuit for this radio, I was motivated to dig a bit deeper to work out what the hook shape at the top of pin 2 indicates. Whatever it is, it was logical that it would be equivalent to many other front-ends that connect a 15pF capacitor between pins 2 and 3. C1 (100pF) makes a resonant circuit with L1, and ideally, that resonant frequency will be below 550kHz at the bottom of the MW band. This avoids an impedance peak in the MW band that would give uneven matching between primary and secondary over the span of the band. Even so, the signal coupling will deteriorate as tuning goes from 550kHz to 1600kHz. Adding a small capacitor between pins 2 and 3 boosts the signal at higher frequencies to even out the sensitivity over the MW band. I went to my salvage shelf and found another Philips radio with the same siliconchip.com.au aerial coil and removed it. I melted off the protective wax covering using a heat gun to reveal the wire connections shown in Fig.2. The primary of this transformer measured 25W and the secondary 2W. At first, this seems a paradox until looking at the wire gauge in the different coils. The primary has many more turns of fine-gauge wire, giving a higher inductance than the secondary, so its resonance with a 100pF capacitor (C1) is below 550kHz. The separation between the primary and secondaries (loose coupling) makes the tuning characteristics more robust to whatever aerial is connected to the primary. This Minstrel is originally blue; the colour is solid through the case. Re-sprayed radios can usually be detected by having a different colour inside the case. Australia's electronics magazine November 2022  85 100pF 3 4 4 2 Aerial coil with wax coating Secondary To pin 1 Primary 3 Loop of gimmick wire between secondary coils connects to pin 2 To pin 2 Connection between loops of the secondary Fig.2: an aerial coil taken from another Philips radio. The protective wax coating was melted off to reveal the connections shown above. At last, the nature of that hooked line (a gimmick) on the circuit diagram from pin 2 to 3 was revealed. It is a loop of wire sandwiched between the secondary coils and provides capacitive coupling to augment the higher MW band frequencies. Valve lineup V1, the mixer valve, is a 6AN7, possibly the most common valve for this application through the 1950s. Philips released this 9-pin miniature triode-hexode valve in 1949, so it was new technology for the Minstrel. The local oscillator (L3 and L4) is an Armstrong type with feedback from the triode anode to sustain oscillation. The double-gang tuning capacitor is the compact brass-plate type introduced by Philips in the early 1950s and used right up to the early Philips transistor radios. The compact IF coils in the Minstrel were another new standard for Philips radios that would span the 1950s. These IF transformers are configured to tune both the primary and secondary with slugs adjusted at the top. They are a cause for some apprehension because the IF coils are set in resin, so the common occurrence of open circuits due to spot corrosion condemns them to the bin. V2, the pentode IF amplifier and twin diode detector, is a 6N8. This is also a Philips-designed valve, released in 1949. The 6N8 is not reflexed as an audio amplifier, so the detected signal is passed directly to the 6M5 output pentode via potentiometer R7 (0.5MW). Unsurprisingly, the 6M5 (V3) is another Philips design released in 1949. At the anode voltage of around 210V used in the Minstrel, the audio output from the 6M5 is comfortably 2W. This is a fair match to the 5-inch (125mm) round speaker made by Philips that fits snugly into the moulding in the case. R13 (160W) generates a negative bias for the 6M5 of -6.5V. R13 also serves to generate a negative grid bias voltage for the 6AN7 and 6N8. The first two valves additionally receive negative feedback (AGC) from the audio detector. Follow the circuit from the intersection of R4 and R5 to trace the AGC. Because of R13, the AGC does not work on weak signals and comes into The front of the model 138 chassis, with the power transformer visible on top. 86 Silicon Chip Australia's electronics magazine effect as signal strength increases (ie, this set has delayed AGC). The high-tension (HT) circuit is conventional using a 6V4 valve (V4). The Minstrels were assembled at Hendon in Adelaide, and the components were largely Australian-made (including valves) with occasional European imported stock. A European-made EZ82, equivalent to the 6V4, can also be found in these sets. Interestingly, the indirectly-­ heated 6V4 valve has the heater powered by its own 6.3V transformer winding. This allows the heater and cathode to be connected to avoid any high tension arc-over between these elements. Later Minstrels had an alternative transformer with only one 6.3V winding and no connection between the cathode and heater. There is no tone control and no feedback from the speaker to modify the tone and maintain stability. Even so, the sound is cheerful. The radios typically consume 28-30W; included in that figure is the power for a single dial lamp. The hardware Disassembling a Philips radio is invariably a challenge. A minor nuisance with the Minstrel is that the captive speaker obliges the connecting wires to be desoldered. A trap for the unwary is to overlook disconnecting the dial cursor from the dial string before pulling the chassis out. Forcing the chassis out breaks the dial string, and restringing these radios is one of life’s greater challenges, particularly without the stringing diagram. The underside of the model 138 chassis, showing the output transformer. siliconchip.com.au When the chassis is out, these units are relatively easy to work on because they are happy to stand up resting on the power transformer at the bottom. The filter electrolytics (2 x 24μF) are both mounted in a single can. With the original paper capacitors in place, the 6N8 and 6M5 bases are inaccessible. Fortunately, it is only a minor chore to replace the old units with small modern capacitors and continue with a complete re-cap. Two Minstrel radios I have worked on had C10 measuring negligible capacitance, preventing the frontend tuning circuit from functioning. C10 is an Earth return from pin 4 of the aerial coil. It is soldered into a cramped position with one lead tightly folded back, probably pulling an endcap away from the internal foil with time and heat. Case restoration One Minstrel that I acquired on eBay was apparently posted via the post office branch that assesses survivability after ‘robust’ handling. It was packed in a cardboard carton with only crumpled newspaper pages for padding. The outcome was instructive (or should that be ‘destructive’?). Fortunately, I was able to glue the shards of the case back in place reasonably well with thin-CA (cyanoacrylate) glue. After that, I applied a twopart epoxy body filler, then abraded it back to a smooth finish. I then sprayed it with an undercoat, sanded it back and repeated. I needed to make four applications before I was happy with the adhesion and quality of the surface. I then finished the radio in powder While the case arrived cracked, it glued back together quite well. blue, a slightly lighter shade than the original Philips blue. In the end, there was no external hint of the distress suffered by the case. The inside of the case was left cream so that it could not be passed off at a future time as an original blue radio. The clock radio All major manufacturers offered a clock variant of their low-end models so that they could serve as a kitchen or bedroom set. The clock radio shown below did not work when I received it, due to a faulty capacitor C10, which was not a surprise. However, another unexpected fault was a 27kW resistor installed as a replacement for two 50kW resistors in parallel (R2 and R3). This determines the screen voltage to the 6AN7 and 6N8, and the screens should be 55V. On this radio, it measured only 40V. Replacing it with an 18kW resistor restored the correct screen voltage. The clock is accommodated by moving the speaker to the top and using a low-profile clock. There are no markings to indicate where those clocks were sourced or made. Most Australian clock radios use a Smiths synchronous movement that is too bulky for the limited space at the front of this radio. The 4-inch Alnico speaker in the clock radio was carefully chosen to fit between the chassis and clock at the top of the case. To be fair, the installed speaker did an adequate job for kitchen or bedroom listening. I tried replacing the original speaker with others that had better specifications, but they fouled the clock. The conservative Minstrel case was utterly compliant with the norm at the time – a rectangular shape with rounded edges. The distinctive niche of the Minstrel radios was to introduce the world of coloured plastics to radios SC made by Philips in Australia. The Philips model 145 radio also includes a clock on the dial. siliconchip.com.au Australia's electronics magazine November 2022  87 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 139, COLLAROY, NSW 2097 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 11/22 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS $15 MICROS 24LC32A-I/SN ATmega328P ATmega328P-AUR ATtiny85V-10PU ATtiny816 PIC10F202-E/OT PIC10LF322-I/OT PIC12F1572-I/SN PIC12F617-I/P Digital FX Unit (Apr21) Si473x FM/AM/SW Digital Radio (Jul21), 110dB RF Attenuator (Jul22) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) Range Extender IR-to-UHF (Jan22) LED Christmas Ornaments (Nov20; versions), Nano TV Pong (Aug21) Model Railway Level Crossing (two required – $15/pair) (Jul21) Range Extender UHF-to-IR (Jan22) PIC12F617-I/SN Model Railway Carriage Lights (Nov21) PIC12F675-I/P Heater Controller (Apr18), Useless Box IC3 (Dec18) Train Chuff Sound Generator (Oct22) PIC12F675-I/SN Tiny LED Xmas Tree (Nov19) PIC16F1455-I/P Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller Slave (Dec20), Auto Train Controller (Oct22) PIC16F1455-I/SL Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P 20A DC Motor Speed Controller (Jul21) Fan Controller & Loudspeaker Protector (Feb22) Secure Remote Mains Switch Receiver (Jul22) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Improved SMD Test Tweezers (Apr22), Tiny LED Icicle (Nov22) PIC16F1705-I/P Flexible Digital Lighting Controller (Oct20) Digital Lighting Controller Translator (Dec21) PIC16LF15323-I/SL Secure Remote Mains Switch Transmitter (Jul22) ATSAML10E16A-AUT PIC16F18877-I/P PIC16F88-I/P High-Current Battery Balancer (Mar21) USB Cable Tester (Nov21) UHF Repeater (May19), Six Input Audio Selector (Sep19) Battery Charge Controller (Dec19 / Jun22) Railway Semaphore (Apr22) PIC24FJ256GA702-I/SS Wide-Range Ohmmeter (Aug22) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) Advanced GPS Computer (Jun21), Touchscreen Digital Preamp (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS ATmega644PA-AU PIC32MX470F512H-I/PT PIC32MX470F512H-120/PT PIC32MX470F512L-120/PT PIC32MX795F512H-80I/PT AM-FM DDS Signal Generator (May22) Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Micromite Explore 100 (Sep16) Touchscreen Audio Recorder (Jun14) dsPIC33FJ64MC802-E/SP dsPIC33FJ128GP306-I/PT 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb13) $25 MICROS $30 MICROS PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC VARIOUS MODULES & PARTS siliconchip.com.au/Shop/ WIDE-RANGE OHMMETER (CAT SC4663) (AUG 22) VGA PICOMITE KIT (CAT SC6417) (JUL 22) MULTIMETER CALIBRATOR KIT (CAT SC6406) (JUL 22) 110dB RF ATTENUATOR SHORT-FORM KIT (CAT SC6420) (JUL 22) Specify the Icicle style – comes with 12 white, cyan & blue LEDs and all required components (except the coin cell, CON2 & figure-8 wire for daisy chaining) $15.00 BUCK-BOOST LED DRIVER KIT (CAT SC6292) (JUN 22) NEW GPS(/WIFI)-SYNCHRONISED ANALOG CLOCK SPECTRAL SOUND MIDI SYNTH KIT (CAT SC6261) (JUN 22) IMPROVED SMD TEST TWEEZERS KIT (CAT SC5934) (APR 22) RASPBERRY PI PICO BACKPACK KIT (CAT SC6075) (MAR 22) 500W AMPLIFIER HARD-TO-GET PARTS (CAT SC6019) (APR 22) CAPACITOR DISCHARGE WELDER (MAR 22) - INA282AIDR + 20mW shunt (30V 2A Bench Supply, Oct22, SC6578) - ISD1820-based recording module (Auto Train Controller, Oct22, SC5081) - 70W LED panel (cool white, SC6307 | warm white, SC6308) - 0.96in SSD1306-based yellow/blue OLED (AM-FM DDS, May22, SC6421) - Pulse-type rotary encoder (AM-FM DDS, May22, SC5601) - DS3231 real-time clock SOIC-16 IC (Pico BackPack, Mar22) LC METER MK3 (NOV 22) Short Form Kit: includes the PCB and all non-optional onboard parts, except the case, front panel label and power supply (Cat SC6544; see page 47) - Cyan/blue 0.96-inch OLED (Cat SC6176) TINY LED ICICLE KIT (CAT SC5579) $10.00 $7.50 $19.50 $10.00 $3.00 $7.50 $65.00 $10.00 (SEP & NOV 22) (OCT 22) Includes everything in the parts list (see page 64) except the Buck/Boost LED Driver (see adjacent; Cat SC6292) $40.00 - laser-cut acrylic cover panel (SC6567) $2.50 - cyan/blue 1.3-inch OLED (SC5026) $15.00 - white 1.3-inch OLED (SC6511) $15.00 MINI LED DRIVER (SEP 22) Complete Kit: includes everything in the parts list (Cat SC6405; see page 81) - XL6009 4A DC-DC boost module (Cat SC6546; red PCB) WiFi PROGRAMMABLE DC LOAD $25.00 $6.00 (SEP 22) Short Form Kit: includes all SMDs, the power Mosfets, four 0.02W 3W resistors and the VXO7805 regulator module (Cat SC6399; see page 39) - laser-cut 3mm clear acrylic side panel (SC6514) - 3.5-inch TFT LCD touchscreen (Cat SC5062) Complete kit with everything needed to assemble the board, you just require a few external parts such as a power supply, keyboard and monitor $35.00 Complete kit with everything needed to assemble the board Includes the PCB, programmed micro, OLED and all other on-board parts (NOV 22) GPS-Version Kit: includes everything in the parts list with the VK2828 GPS module (Cat SC6472; see Sep22 p63) $55.00 WiFi-Version Kit: includes everything in the parts list with the D1 Mini module instead (Cat SC6472; D1 Mini is supplied not programmed, see Nov22 p76) $55.00 - VK2828U7G5LF GPS module with antenna and cable (Cat SC3362) $25.00 BUCK/BOOST CHARGER ADAPTOR KIT (CAT SC6512) Partial Kit: includes the PCB, programmed micro, all SMDs, most semiconductors, PPS capacitors and calibration resistors $75.00 - 16x2 alphanumeric LCD with blue backlighting (Cat 5759) $10.00 $85.00 $7.50 $35.00 Complete kit with everything needed to assemble the board Complete kit including all programmed PICs (no case or power supply) $45.00 $75.00 $80.00 $200.00 Complete kit with PCBs, all onboard parts, new microcontroller and gold-plated header pins to use for the tips. Does not include a lithium coin cell $35.00 Complete kit, includes all parts except the optional DS3231 IC $80.00 All the parts marked with a red dot in the parts list, including the 12 output transistors, driver transistors, VAS transistors, input pair (2SA1312), BAV21 & UF4003 diodes, TL431 ICs, 75pF capacitor, E96 series resistors and 10kW 1W resistor $200.00 Parts for the Power Supply – includes the power supply PCB, IC1-3, D1, the 1W shunt and sole SMD capacitor (Cat SC6224) Parts for the ESM – includes one ESM PCB, IC8, Q3 & Q4 (IRFB7434G), D9 plus the SMD capacitors and resistors (Cat SC6225) → 8-14 sets typically needed SMD TRAINER COMPLETE KIT (CAT SC5260) (DEC 21) Includes PCB & all on-board components, except for a TQFP-64 footprint device $25.00 $20.00 $20.00 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # P&P prices are within Australia. Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT TINY LED XMAS TREE (GREEN/RED/WHITE) HIGH POWER LINEAR BENCH SUPPLY ↳ HEATSINK SPACER (BLACK) DIGITAL PANEL METER / USB DISPLAY ↳ ACRYLIC BEZEL (BLACK) BOOKSHELF SPEAKER PASSIVE CROSSOVER ↳ SUBWOOFER ACTIVE CROSSOVER ARDUINO DCC BASE STATION NUTUBE VALVE PREAMPLIFIER TUNEABLE HF PREAMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) NUTUBE GUITAR DISTORTION / OVERDRIVE PEDAL THERMAL REGULATOR INTERFACE SHIELD ↳ PELTIER DRIVER SHIELD DIY REFLOW OVEN CONTROLLER (SET OF 3 PCBS) 7-BAND MONO EQUALISER ↳ STEREO EQUALISER REFERENCE SIGNAL DISTRIBUTOR H-FIELD TRANSANALYSER 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 ↳ BALANCED ATTENUATOR SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE 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) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE BK1198 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG Si473x FM/AM/SW DIGITAL RADIO 20A DC MOTOR SPEED CONTROLLER DATE NOV19 NOV19 NOV19 NOV19 NOV19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 APR20 APR20 APR20 APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 NOV20 AUG20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 JUN21 JUN21 JUN21 JUN21 JUL21 JUL21 PCB CODE Price 16111191 $2.50 18111181 $10.00 SC5168 $5.00 18111182 $2.50 SC5167 $2.50 01101201 $10.00 01101202 $7.50 09207181 $5.00 01112191 $10.00 06110191 $2.50 27111191 $5.00 01106192-6 $20.00 01102201 $7.50 21109181 $5.00 21109182 $5.00 01106193/5/6 $12.50 01104201 $7.50 01104202 $7.50 CSE200103 $7.50 06102201 $10.00 05105201 $5.00 04104201 $7.50 04104202 $7.50 01005201 $2.50 01005202 $5.00 07107201 $10.00 SC5500 $10.00 19104201 $5.00 SC5448 $7.50 15005201 $5.00 15005202 $5.00 01106201 $12.50 01106202 $7.50 18105201 $2.50 04106201 $5.00 04105201 $7.50 04105202 $5.00 08110201 $5.00 01110201 $2.50 01110202 $1.50 24106121 $5.00 16110202 $20.00 16110203 $20.00 16111191-9 $3.00 16109201 $12.50 16109202 $12.50 16110201 $5.00 16110204 $2.50 11111201 $7.50 11111202 $2.50 16110205 $5.00 CSE200902A $10.00 01109201 $5.00 16112201 $2.50 11106201 $5.00 23011201 $10.00 18106201 $5.00 14102211 $12.50 24102211 $2.50 10102211 $7.50 01102211 $7.50 01102212 $7.50 23101211 $5.00 23101212 $10.00 18104211 $10.00 18104212 $7.50 10103211 $7.50 05102211 $7.50 24106211 $5.00 24106212 $7.50 08105211 $35.00 CSE210301C $7.50 11006211 $7.50 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT MODEL RAILWAY LEVEL CROSSING COLOUR MAXIMITE 2 GEN2 (4 LAYERS) BATTERY MANAGER SWITCH MODULE ↳ I/O EXPANDER NANO TV PONG LINEAR MIDI KEYBOARD (8 KEYS) + 2 JOINERS ↳ JOINER ONLY (1pc) TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM SMD TEST TWEEZERS (3 PCB SET) USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS HUMMINGBIRD AMPLIFIER DIGITAL LIGHTING CONTROLLER TRANSLATOR SMD TRAINER 8-LED METRONOME 10-LED METRONOME REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL FAN CONTROLLER & LOUDSPEAKER PROTECTOR SOLID STATE TESLA COIL (SET OF 2 PCBs) REMOTE GATE CONTROLLER DUAL HYBRID POWER SUPPLY SET (2 REGULATORS) ↳ REGULATOR ↳ FRONT PANEL ↳ CPU ↳ LCD ADAPTOR ↳ ACRYLIC LCD BEZEL RASPBERRY PI PICO BACKPACK AMPLIFIER CLIPPING DETECTOR CAPACITOR DISCHARGE WELDER POWER SUPPLY ↳ CONTROL PCB ↳ ENERGY STORAGE MODULE (ESM) PCB 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) AM-FM DDS SIGNAL GENERATOR SLOT MACHINE HIGH-POWER BUCK-BOOST LED DRIVER ARDUINO PROGRAMMABLE LOAD SPECTRAL SOUND MIDI SYNTHESISER REV. UNIVERSAL BATTERY CHARGE CONTROLLER VGA PICOMITE SECURE REMOTE MAINS SWITCH RECEIVER ↳ TRANSMITTER (1.0MM THICKNESS) MULTIMETER CALIBRATOR 110dB RF ATTENUATOR WIDE-RANGE OHMMETER WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD MINI LED DRIVER NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD DATE JUL21 AUG21 AUG21 AUG21 AUG21 AUG21 AUG21 SEP21 SEP21 OCT21 OCT21 OCT21 NOV21 NOV21 NOV21 DEC21 DEC21 DEC21 JAN22 JAN22 JAN22 JAN22 JAN22 JAN22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 MAR22 MAR22 MAR22 MAR22 MAR22 APR22 APR22 APR22 MAY22 MAY22 JUN22 JUN22 JUN22 JUN22 JUL22 JUL22 JUL22 JUL22 JUL22 AUG22 SEP22 SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 PCB CODE 09108211 07108211 11104211 11104212 08105212 23101213 23101214 01103191 01103192 01109211 12110121 04106211/2 04108211 04108212 09109211 01111211 16110206 29106211 23111211 23111212 15109211 15109212 01101221 01101222 01102221 26112211/2 11009121 SC6204 18107211 18107212 01106193 01106196 SC6309 07101221 01112211 29103221 29103222 29103223 01107021 09103221 09103222 CSE211002 08105221 16103221 04105221 01106221 04107192 07107221 10109211 10109212 04107221 CSE211003 04109221 04108221 04108222 18104212 16106221 19109221 14108221 04105221 04105222 09109221 09109222 24110222 24110225 24110223 Price $5.00 $15.00 $5.00 $2.50 $2.50 $5.00 $1.00 $12.50 $2.50 $15.00 $30.00 $10.00 $7.50 $5.00 $2.50 $5.00 $5.00 $5.00 $5.00 $7.50 $2.50 $2.50 $7.50 $5.00 $5.00 $7.50 $20.00 $25.00 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $2.50 $5.00 $5.00 $5.00 $25.00 $2.50 $2.50 $7.50 $5.00 $5.00 $5.00 $7.50 $7.50 $5.00 $7.50 $2.50 $5.00 $5.00 $7.50 $7.50 $5.00 $10.00 $2.50 $5.00 $5.00 $7.50 $2.50 $2.50 $2.50 $2.50 $2.50 $2.50 LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) AUDIO/RF SIGNAL TRACER HEAVY-DUTY 240VAC MOTOR SPEED CONTROLLER NOV22 NOV22 NOV22 NOV22 JUN97 NOV97 CSE220503C CSE200603 08108221 16111192 04106971 10311971 $7.50 $2.50 $5.00 $2.50 $5.00 $7.50 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 0-30V 0-2A Part 2 by John Clarke bench supply This new Bench Supply, introduced last month, is basic yet feature-packed, including full onboard metering and an adjustable current limit. It’s pretty easy and cheap to build, so it is suitable for relative beginners. You will find it handy for various purposes, including powering circuits for testing or development. It also fits neatly into a compact and attractive instrument case. So let’s get to building it. P art of the reason for the 30V and 2A limits is that they allow us to use an inexpensive and modestly-sized transformer that fits neatly alongside the regulator board in a compact 160 × 180 × 70mm benchtop instrument case. It’s small enough to stay out of your way but powerful enough for many jobs. You could even stack two or three to have a few different voltages available or connect two in series to form a split supply. Just keep in mind that their current limits will be enforced separately, so if there is a fault, it’s possible that one Supply would go into current limiting while the other(s) wouldn’t. While this is a mains-based project, anyone who is good at following instructions and with reasonable soldering skills should be able to build it safely. Just make sure you perform all the wiring as described using correctly rated wire, and don’t skip any of the required insulation or cable ties. 90 Silicon Chip Before we get to construction, a word about the metering. We tested some low-cost volt/ammeters from eBay but found that they were too inaccurate, which is why we specified the part from Core Electronics. Use caution if you want to substitute another meter, as its readings could be way off. As with many projects, the first step in construction is soldering the majority of the components to the printed circuit boards. Construction Most of the parts for the Supply mount on two PCBs. The main 76 × 140mm PCB is coded 04105221 and includes most of the components, while the smaller 56 × 61mm PCB coded 04105222 has the front panel parts such as voltage and current setting potentiometers, indicator LEDs and load switch. A 14-way ribbon cable fitted with insulation displacement connectors (IDCs) connects the two PCBs. Australia's electronics magazine As explained last month, there is the option to use a single 2.5kW multi-turn potentiometer for VR1 or a standard single-turn 5kW potentiometer in conjunction with a 5kW multi-turn trimpot (VR2). If you are using the 2.5kW multi-turn potentiometer, VR2 is not used and must be left off the PCB. During the following process, refer to the PCB overlay diagrams (Figs.5 & 6) to see which parts go where. Begin construction with the main PCB by fitting the two surface-mount components. These are the INA282 shunt monitor (IC2) and the 20mW resistor. For the resistor, we have made provision on the PCB for either two 10mW resistors in series or a single 20mW resistor. Both the resistor and IC are relatively easy to solder. Find the pin 1 orientation marker on the INA282. This can be a dot on the top face, a notch at the pin 1 end of the device, or a chamfer along the pin 1 to 4 edge of the package. Position the IC over the pads and siliconchip.com.au Fig.5: fit the components to the main PCB as shown here, watching the orientations of the polarised parts. VR2 is not shown as it is only needed if VR1 is 5kW; in that case, install it with the adjustment screw towards the top of the board like the other trimpots. Leave Q1 and REG1 off until the case has been prepared (see text). Ensure the sockets for CON1 and CON2 are rotated so the wires exit on the correct side per the photos. Figs.6(a) & (b): this board carries the front panel controls and indicator LEDs. Potentiometer VR3 is held to the board using PCB pins, and its terminals are also connected via PCB pins. VR1 is attached using brackets on either side of its body and connected to its three pads (labelled “Anti CW”, “Wiper” and “CW”) via short lengths of wire. solder a corner pin using a fine-tipped soldering iron. Once soldered, check the alignment against the remaining IC pin leads and PCB pads. Remelt the solder and realign the IC if necessary until each pin aligns with its pad, then solder the remaining pins to the PCB. Any solder bridges can be fixed using solder wick with flux paste to draw up the excess solder. The surface-mounting resistor can be soldered similarly, one end at a time. Straighten the resistor by remelting the solder and nudging it after the first end is soldered should it be skewed. The next components to be installed are the through-hole (axial) resistors. The resistors have colour bands, but it is a good idea to check the values using a multimeter too. Leave the larger 1W resistor for last. Fit the four types of diodes next. They are all polarised and must be oriented as shown in Fig.5 and the screen printing on the PCB. Use the smaller siliconchip.com.au glass-encapsulated 1N4148 diodes for D5, D6 and D9. D1, D3, D4, D7, D8 and D10 are the larger 1N4004 devices, while D2 is a larger still 1N5404 diode. The three remaining diodes are zener diodes ZD1, ZD2 and ZD3, which are in larger glass packages. ZD1 is 33V (1N4752) while ZD2 and ZD3 are 12V (1N4742) types. Ensure each is installed in the correct position. Operational amplifier (op amp) IC1 can now be installed, taking care to orientate it correctly. This can be mounted using a socket or directly on the PCB. Follow with transistors Q2-Q6 and REG2. These all are in TO-92 plastic packages, so be sure the correct device is installed in each location. Q2 is a 2N7000 while Q3-Q5 are BC547s and Q6 is a BC327. REG2 is the LM336-2.5. Mount the trimpots next. These are top-adjust multi-turn types; two are 10kW (VR6 and VR7), one or two are 5kW (VR2 and VR4), while VR5 is 100W. The 10kW trimpots might be Australia's electronics magazine labelled 103, the 5kW trimpots as 502 and the 100W trimpot as 101. Be sure to orientate these with the adjustment screws as shown in Fig.5. Note that if using a 2.5kW multi-turn pot for VR1, VR2 is not fitted. Now install rectifier bridge BR1; the diagonally cut corner is the positive side, so make sure that faces as shown. You can install the four-way pluggable terminals for CON1 and CON2 now. Ensure these are oriented correctly by inserting the plugs into the sockets first, then rotating them so that CON1’s screw heads face toward the edge of the PCB and CON2’s screw heads are toward CON3. Then solder the terminals in place, followed by box header CON3, orientated as shown. There are 12 test points located around the PCB. You can fit PC stakes/ pins in each or leave them bare and use your multimeter probe directly onto the PCB pad instead. It is easier to have a PC stake at TP GND so that you can use an alligator or crocodile November 2022  91 The main and both sides of the front panel PCB are shown here at 75% of actual size. Shown opposite is an internal photo of the completed Supply minus both PCBs, so you can more clearly see where the various other parts mount and how the wiring is run. Note the locations of the three plugs in the lower portion, ready to plug into the main PCB. clip for measurements with respect to 0V. If fitting the PC pins, do that now. Mount the capacitors next. The 100nF, 10nF and 1μF ceramic types can be installed either way, but most of the electrolytic capacitors are polarised and must be inserted with the polarity shown. The positive side usually has a longer lead, while there is a stripe on the negative side of the can. The 10μF capacitor marked NP is non-polarised and can insert either way around. Now mount relay RLY1 and two-way header CON7. Leave Q1 and REG1 off for now. Front panel PCB assembly The front panel PCB has components mounted on both sides. The potentiometers, switch and LEDs are on the top, while CON4-CON6 are mounted on the underside. It is easier to solder in the 14-way box header (CON4) first so that you have full access to solder its pins on the top side of the PCB. It is installed on the underside of the PCB; ensure it is oriented correctly, as shown in Fig.6(b), before soldering it in place. Next, install the six PC stakes for VR1 and the three for VR2. Then fit CON5 on the underside of the PCB, with its wire entries towards the nearest PCB edge. 92 Silicon Chip Mount switch S2 on the top side of the PCB. This sets the height position for the potentiometers and LEDs; however, LED1 and LED2 are mounted after the front panel holes are drilled and LED bezels are inserted. Fit VR2 next, but first cut its shaft so that the length from the top of the threaded mounting boss to the end of the shaft is 15mm. VR2 is supported by PC stakes soldered to the potentiometer body. You need to scrape off the passivation coating in the area where the PC stakes will be soldered so that the solder will adhere. Solder it so that the top of the threaded section matches that of switch S2. Once it is in place, make the electrical connections to the potentiometer using PC stakes. Mounting VR1 The mounting method for VR1 depends on whether you are using a single-turn or multi-turn pot. The circular cut-out allows the multi-turn potentiometer to pass through the hole. Solder right-angle brackets to the back of the PCB and use a cable tie to position the pot as shown above. Connect short wires from the pot terminals to the wiper, anticlockwise and clockwise terminals on the PCB. Australia's electronics magazine Similarly, if using a single-turn pot, it is held in position by right-angle brackets soldered to the pot body and the PCB. The brackets need to be soldered to the PCB such that they reach the pot body and there is some overhang from the cut-out. Again, you will have to scrape off the passivation coating from the pot body where you will solder the brackets. For a single-turn pot, solder its terminals directly to the PC stake connection points. Making the ribbon cable Fig.7 shows how the IDC line sockets are attached to the ribbon cable. Ensure the 14-way wire and sockets are oriented correctly, with the notches positioned as shown, before compressing the connectors. You can do this by placing a small piece of soft timber (such as radiata pine) over each side of the connector and compressing it with a G clamp or bench vice. Alternatively, you can buy a specialised IDC crimping tool. Metalwork Now it’s time to drill and shape holes in the baseplate of the enclosure and the heatsink, as shown in Fig.8. Rectangular and similarly-shaped cut-outs can be made by drilling a siliconchip.com.au series of small holes around the inside perimeter, then knocking out the centre piece and filing the job to a smooth straight finish. The power switch hole must be sized so that it stays clipped in when inserted into the cut-out, so take care when shaping it. The banana sockets have ovalshaped holes (“F”) that can be made by first drilling round holes and then using a round file to elongate them. There are four holes for mounting the regulator, power transistor and thermal switch on the rear panel; these are the holes marked “A” not near the mains input socket. After drilling them, clean them up around the edges on both sides with a deburring tool or a larger drill bit, so there are no sharp edges around the rims. This will avoid puncturing the insulation pads for the regulator and transistor and allow the heatsink to sit flat against the rear panel for maximum heat transfer. It would give even better heat transfer to the heatsink if you cut out a rectangular hole for the transistor, so the transistor and its insulating pad can be mounted directly against the heatsink instead of the rear panel of the case. However, we found that mounting onto the rear panel provided sufficient heat transfer to the heatsink, satisfactory for most Supply use cases. Still, if you require a high current at low voltages for an extended period, having this cut-out will reduce the transistor temperature. Once the drilling and cutting are finished, temporarily install the mains IEC input connector and then place the heatsink against the back panel with its side about 1mm away from the IEC connector and the top edge in line with the top edge of the rear panel. Mark out the positions for the transistor, regulator and thermal switch holes on the heatsink through those already in the back panel. Make sure all the holes will be within the central mounting area of the heatsink and not through the fins, or the screws won’t fit. Once you’ve Fig.7: fit the IDC line sockets to the cable as shown here. This way, pin 1 is correct on both sockets but having them on opposite sides makes routing the cable easier once everything is in the case. Note that some sockets don’t come with the third locking bar over the top, in which case the ribbon cable isn’t looped. siliconchip.com.au Australia's electronics magazine November 2022  93 Fig.8: the shapes and sizes of some of the cut-outs are critical, so file them to shape carefully and periodically test to see if the parts fit in the holes. For example, the panel meter will fall out if its hole is too large, as will the rocker switch. For the binding posts (marked “F”), drill round holes, then elongate them to ovals using a round file. checked that, drill them in the heatsink, then deburr them for a smooth finish on the heatsink. Case assembly Attach the four 6.3mm-long M3-tapped spacers to the corners of the main PCB using 5mm M3 machine screws. Next, insert the power transistor and the regulator leads into their allocated holes in the PCB. Slide the PCB so the transistor and regulator can later be attached to the rear panel via the pre-drilled holes using machine screws (temporarily secure the transistor and regulator to the rear panel with M3 screws and nuts). Adjust the leads so that the device tabs sit flat against the rear of the case then, making sure the PCB is straight and not skewed in the case and the standoffs are directly on the base, 94 Silicon Chip solder the leads to the PCB on the top side. Next, mark out the locations for the standoff mounting holes in the base of the case. Also mark out the mounting holes for the transformer. This sits between the left edge of the PCB and the left edge of the case, leaving equal clearance on both sides. The transformer is also positioned centrally between the front and rear of the case. Once that is done, remove the transistor and regulator mounting screws. Solder the transistor and regulator leads on the underside of the PCB. Now drill out the holes for the PCB and transformer (see Fig.9 for the component layout in the case). Also, drill the Earth lug holes in the base and scrape away the paint from around the holes so the Earth connections will be against the metal, not the paint. Australia's electronics magazine Attaching the heatsink The heatsink is a little taller than the enclosure. There are two ways of preventing the heatsink from touching the workbench, as the enclosure mounting feet are not tall enough to prevent this from happening. One option is to add extra spacers between the feet and the case, such as two M3 Nylon washers under each foot to raise the enclosure a little. This prevents the heatsink from touching the bench. Use the longer self-tapping screws supplied with the enclosure to secure the mounting feet. The second method is to cut the bottom of the heatsink off, so it is 67mm tall. That can be done with a hacksaw or a metal cutting saw. After you’ve sorted that out, apply a smear of heatsink compound to the rear of the heatsink. Press it onto siliconchip.com.au the rear panel in its correct position and install the thermal cut-out using 15mm-long M3 machine screw and nuts. Leave the screws loose for the moment, so there is movement to adjust the mounting. Insert the 20mm screws for the transistor and regulator through the heatsink, then feed them through the rear panel. Place the TO-3P silicone washer for Q1 and TO-220 washer for the regulator onto the screw ends. Now you can re-mount the PCB, with the mounting screws for the regulator and transistor passing through the device holes. Push the insulation bush into the regulator mounting hole before attaching it with a hex nut. For the transistor, add a steel washer against the device before attaching the nut. Secure the PCB to the base with M3 × 5mm screws and then tighten up the screws for the thermal cut-out, transistor and regulator, ensuring the heatsink stays square against the rear panel. The main PCB is attached to the base using four M3 × 5mm screws with Nylon washers. The washers allow the screws to tighten into the standoffs without touching the screws that enter from the top. Front panel label The panel label (see Fig.10) can be made using overhead projector film, printed as a mirror image so the ink/ toner will be between the enclosure and film when affixed. Use projector film that is suitable for your printer (either inkjet or laser) and affix it using clear neutral-cure silicone sealant. Roof and gutter silicone is suitable. Squeegee out the lumps and air bubbles before it cures. Once cured, cut out the holes through the film with a hobby or craft knife. For other options and more detail on making labels, see the page on our website: siliconchip.au/Help/FrontPanels Insert the two LED bezels for the Fig.9: the internal case layout and wiring. Take care that your unit is wired up exactly as shown here, especially the mains wiring, and don’t skimp on the cable ties, insulation or Earthing. See the notes in the text about the transformer secondaries; they might be labelled backwards, in which case you’ll have to reverse the connections. The transformer is shown here closer to the front of the case than in reality. siliconchip.com.au Australia's electronics magazine November 2022  95 LEDs into the front panel and place the LEDs into the holes from the top side of the PCB, taking care to orientate them with the longer lead to the anode (“A”) side. Push the LEDs down onto the PCB but do not solder the leads yet. Break off the locating spigot on potentiometer VR3 (and single-turn potentiometer VR1, if used) and mount them onto the front panel with the washer on the pot side and nut on the outside. Then mount the on/off switch with one nut on first, to set the depth that the panel sits into the threaded section, then place the second nut on the outside to hold it in place. Move the LEDs off the PCB, insert them into the bezels and solder the LEDs in place. The front panel PCB is held in position by the switches and potentiometers; there is no need for extra support. If you wish, you can add 15mm-long standoffs at a couple of the corners. Now attach the pot knobs. For VR2, ensure the pointer is correctly positioned so it points to the end stops on the front panel label at both rotation extremes. Remaining parts Mount the IEC connector to the rear panel using M3 × 15mm screws and nuts, and the transformer to the base using M4 × 10mm screws, star washers and nuts. The panel meter can be installed next. This is intended to slide and clip into the panel cut-out, but the top and bottom clips will not compress because they impinge on the seven-segment displays. The solution is to lever out the side clips to allow the internal PCB and displays to come out of the surround, then insert the surround through the front panel. The top and bottom clips can now be compressed so the meter can sit in the front panel. Once it’s in place, reinstall the meter internals. Mains wiring All mains wiring must be done using mains-rated cable. Be sure that brown wire is used for Active while the blue wire is used for Neutral. The green/yellow-striped wire is for the Earth wiring only (see the wiring diagram, Fig.9). Connect up the mains leads to the IEC connector and use a cable tie to secure the wires together and insulate using the rubber boot after it is cut so that the main section is 30mm long. This is so there is room for the transformer. Pass the wires through the boot before fitting it. The Earth wire from the IEC connector must go straight to the Earth mounting point on the case. This is attached using a crimp eyelet secured to the base with a 10mm M4 screw, star washer and two M4 nuts. If you haven’t already done so, you must scrape the paint away from around the hole to ensure the Earth connects to the metal of the case and not just the paint. The wires connect to the mains switch using female spade crimp connectors. Be sure to cable tie the wires together to prevent any broken wires from coming adrift. Additionally, cover the spade connections with 25mm diameter heatshrink tubing. Connect the transformer secondaries to CON1 using 7.5A-rated wire. Note that there is an anomaly for the transformer secondary outputs. The photos shown for the transformer on Fig.10: this front panel label can be downloaded as a PDF from the Silicon Chip website and printed out to form a label for the case. There is an alternative label without voltage markings to suit a multi-turn potentiometer. 96 Silicon Chip Australia's electronics magazine siliconchip.com.au These four close-up views show how the panel meter, mains switch, mains input socket and thermal switch are wired up and insulated. the Jaycar website have the terminals for the 0, 9, 12, 15, 18, 21, 24 and 30V as shown in our wiring diagram. But on our sample transformer from Jaycar, the windings only produced the expected AC voltages when the order of the taps (including the 0V and 30V ends) were reversed. The discrepancy wouldn’t matter if the taps were symmetrical, but they are not, and the resulting voltages are quite different depending on which end is defined as the 0V tap. It is important to have the 0V tap correct to get the required sequence of 0, 9, 12, 15, 18, 21, 24 and 30V. Otherwise, you will get 0, 6, 9, 12, 15, 18, 21 & 30V. To make sure you have the correct windings, use a multimeter set to measure AC volts to probe the secondaries and carefully check their voltages with power applied. Apply power by connecting the IEC plug to the mains with the IEC plug inserted into the IEC connector at the rear of the power supply. The fuse will need to be installed in the IEC connector. Check that the neon lamp in the switch lights up when the power switch is on. Find the two ends of the windings first; that should give the full 30V AC. Then check the secondary taps off each end to find the following voltage. It should be 9V AC at the 0V end and 6V AC at the 30V end. These voltages may be around 10% higher due to mains voltage variations and the fact that the transformer is unloaded. Once you’ve verified which is the 0V end, switch off power and wire up the secondaries as per Fig.9. The Supply should look like this once you have finished fitting all the parts and wiring them up. After checking it works, all that remains is to attach the lid using two of the supplied screws on either side. siliconchip.com.au Australia's electronics magazine November 2022  97 Next, connect the IDC cable between the two boards and wire up the meter. The supply ground for the meter is not connected and can be either cut short or connected to the NC terminal at the centre of CON5. That centre terminal is used as a wire keeper; it makes no electrical connection. Attach the banana sockets to the front panel, wire them up to CON2 (black for negative, red for positive) and connect the Earth terminal to the chassis. Testing and calibration Before applying power, check your wiring carefully and ensure all mains connections are correct. If you are using a socket for IC1, insert it now with the proper orientation. Take care that none of its leads fold under its body during insertion. Wind VR1 fully anti-clockwise and VR3 a little clockwise from fully anti-clockwise. This sets the Supply to its minimum output voltage at a low current. Wind VR6 fully clockwise by turning it until a faint click is heard, or if you don’t hear a click, wind for 20 turns in the clockwise direction. This prevents the regulator output voltage from going negative initially before being set up correctly. Switch power on, and the voltmeter should show around 1.2-1.3 V. Check that you can increase the output Summary of test points TP1 is the negative voltage applied to REG1 via VR1 and VR2. It is measured with respect to GND (or V- at CON2) and can range from -1.2V to -1.3V. VR6 is adjusted to provide a 0V output at V+ on CON2 when VR1 is fully anti-clockwise. TP2 is the -2.49V reference. It is measured with respect to GND (or V- at CON2) and adjusted via VR7. TP3 is the current limit setting, measured between TP3 and TP10 at CON6, that ranges from 0V to 2V when correctly adjusted. The upper and lower thresholds are adjusted by VR4 and VR5, respectively. CON6 allows the current limit setting of VR2 to be measured using a multimeter or other floating voltmeter. TP4 is the raw negative supply and should read around -8V to -9V relative to GND. TP5 is the output of current monitor IC2, giving 1V per amp of load current, measured with respect to TP2 (-2.490V). TP6 is the negative voltage applied to IC1a. TP1, the output of IC1a, should be within a few millivolts of TP6. See above for the significance of TP1. TP7 should be near 0V, rising toward 0.6V when power is switched off, measured with respect to GND. This is the AC detection voltage for the relay switching. 0V = AC detected, 0.6V = no AC detected. TP8 should rise from 0V to 13.6V with respect to GND over several seconds when power is first applied and drop quickly to near 0V when power is switched off. The time the voltage takes to rise from 0V to 13.6V is the switch-on delay. TP9 should be at about 12V with respect to GND, generated by zener diode ZD2. TP10 is the current setting offset to compensate current readings at TP5 (see TP3 above). TP 25V is the positive supply and should measure around 25V with respect to GND. 98 Silicon Chip Australia's electronics magazine voltage by rotating VR1 clockwise. Take care not to increase the output above 35V as the output capacitor is only rated to handle 35V. If the Supply does not appear to be working at this stage, recheck your construction. In particular, check that there is about -8V (or similar) at TP4 and about 25V at TP25V. Check that TP1 is around 0V. Once the voltages appear correct, it is time to make adjustments. Firstly, the precision reference needs to be set. Measure the voltage between TP GND (or the negative output terminal on the front panel) and TP2, and adjust VR7 for a reading of -2.490V. Once adjusted, the regulator can be set to produce a minimum of 0V. This is done by initially winding VR1 fully anti-clockwise and measuring between the Supply’s output terminals. Adjust VR6 anti-clockwise until the reading just reaches 0V. Next, we set the maximum 30V output range. This is only if you are using a single-turn potentiometer for VR1. For the multi-turn potentiometer, ignore this step since VR2 is not fitted. For the multi-turn pot, the maximum voltage will be close to 30V when VR1 is wound fully clockwise, possibly a little more. Carefully adjust VR1 clockwise and stop where the voltage is 30V or when the pot is fully clockwise, whichever comes first. If the pot has reached full clockwise rotation and the voltage is less than 30V, adjust VR2 clockwise until you get a 30V output. If 30V is reached before full rotation, adjust VR2 anti-clockwise and VR1 clockwise a little each time until 30V is reached with VR1 fully clockwise. The current limit range is adjusted by rotating VR3 fully clockwise and measuring between TP2 and TP3. Adjust VR4 to obtain 2V. That sets the maximum current to 2A. The minimum current setting alters the lower end of VR3 to cancel out the offset voltage of IC2. To set this, rotate VR3 fully anti-clockwise, then measure between TP5 and TP10 and adjust VR5 for 0V. It shouldn’t be necessary to readjust VR4 again for the maximum current limit as the voltage adjustment made with VR5 will only change the maximum current setting by about 20mV, which is insignificant compared to the original setting at 2A. But you could tweak it again if you want to. SC siliconchip.com.au Laboratory Power Supplies A GREAT RANGE of fixed and variable output power supplies at GREAT PRICES for hobbyist or industrial workbenches. CLUB OFFER 15% OFF LAB POWER SUPPLIES Not a member yet? Sign up in-store or visit: jaycar.com.au/member-access MP3078 - MP3842 Promotion Date: 01.11.22 – 23.11.22 AFFORDABLE PRECISE VOLTAGE SOLUTION AFFORDABLE HIGH CURRENT SOLUTION Variable Voltage & Current Precise voltage level and current limiting. • Adjustable 0 to 30VDC • Adjustable 0 to 5A • <1mVRMS Ripple Voltage MP3840 CLUB OFFER NOW JUST 177 $ SAVE 15% POWER TWO CIRCUITS SIMULTANEOUSLY Variable Voltage & High Current High current range with current limiting. • Adjustable 0 to 15VDC • Adjustable 0 to 40A • 100mV Peak-Peak Ripple MP3091 ENTRY LEVEL 339 $ MP3079 MP3078 MP3089 MP3096 MP3097 Type Fixed Fixed Fixed Fixed Fixed Output Single Single Single Single Single Single Voltage DC 13.8V 13.8V 13.8V 13.8V 13.8V Current 12A 20A 40A 5A 10A MP3800 SAVE 15% MP3802 $119 $219 $129 $169 SAVE 15% MP3098 MP3842 MP3840 MP3091 MP3087 Fixed Variable Variable Variable Variable Single Single Single 0 to 24V 0 to 16V 13.8V 15A 25A 20A Variable Variable Backlit Backlit Analogue Analogue $79.95 369 $ PROFESSIONAL Current Limiting Display CLUB OFFER NOW JUST Automatic constant-voltage/ constant-current. • 2 x 0 to 30VDC, 2 x 0 to 3A • Independent outputs & displays • <1mVRMS Ripple Voltage MP3087 MID LEVEL Model no. Recommended Retail Price (RRP) Dual Output, Dual Tracking CLUB OFFER NOW JUST $179 $239 $249 Single Single 0 to 30V 0 to 15V 2 x 0 to 32V 0 to 16V 0 to 5A 0 to 27V 0 to 3A 0 to 36V 0 to 2.2A 0 to 5A 0 to 40A 2 x 0 to 3A • • • • Backlit LCD LED Backlit LCD Backlit LCD $169 $209 $399 $439 Shop at Jaycar for: • Isolated Stepdown Transformers • AC/DC Power Supplies • Auto Transformer (VARIAC) • Plugpacks & Desktop • Power Leads & Boards Power Supplies Explore our full range of power supplies, in stock at over 110 stores or 130 resellers or on our website. Dual jaycar.com.au/laboratory-psu 1800 022 888 SERVICEMAN’S LOG Toys with a serious purpose Dave Thompson You might think I’m running out of things to repair because I’m working on toys again. But actually, while this device appears to be made of child’s toys, it has a serious medical use. It is used to check the hearing of young children who can’t yet talk (or don’t like to) but this particular example didn’t survive the tender mercies of one particular delivery service... It will come as no surprise to many that I sometimes get weird and wonderful devices through my humble workshop. Word somehow leaks out through the concrete-­jungle telegraph that I am willing to look at anything, always with a view to (hopefully) repair it. A few weeks ago, a long-time Silicon Chip reader from another part of the country contacted me about a device he had designed and built many moons ago that needed some electronics-based love and attention. Darryl was an audiologist in one chapter of his life, and as an electronics enthusiast, he had designed and built several VRA (visual reinforcement audiometry) devices to assist with testing very young children’s hearing. The usual traditional tone-testing we all know as adults is not so easily performed on toddlers. These so-called ‘puppet boxes’ are utilised as an audio-­ visual testing aid. In this case, the ‘box’ itself is in the form of a large, round, carpet-covered timber tube about 1.8m high and 50cm in diameter. The front ‘face’ of the tube is covered by a dark Perspex cover almost to the bottom, where there is a panel covering the electronics. 100 Silicon Chip There are three levels to this box, all isolated and separated from each other. In each of the levels is a different animatronic ‘toy’ which, when activated, is illuminated by an LED spotlight in the top-left corner of that section. A hand controller – a jiffy-type box with three press-tomake, release-to-break switches on a long lead activates each of the toys. The ant, the gorilla and the elephant In this box, starting in the top section, is a large ant in a forest-type setting. He speaks a phrase and his bug-eyes move and blink when the appropriate button on the hand controller is pressed. The animation and light activates for about 15 seconds before going dark again. The middle level contains a furry gorilla toy, set in a yachting scene; this toy dances and his mouth opens and closes along (roughly) to a popular 90s novelty song. The bottom section has a pink plush elephant, which animates with its legs moving in time to a typical child’s ‘crawling song’. In practice, I suppose it doesn’t really matter what toys are there and what they do; they are just something to grab the attention of the child. I was certainly entertained and admit to pressing those buttons a lot – once I’d fixed it. I now know the lyrics to a crawling song, so life is full of surprises! In use, a child being tested is ‘trained’ to respond to a test tone they hear through headphones by watching a visual stimulus every time they hear the tone. The audiologist plays a tone and activates the puppet box at the same time. The child looks at the animated toy and ‘learns’ that when they hear the tone, they’ll see the toy light up and move. As the audiologist changes the tone frequency and the volume level, they can build a picture of that child’s hearing and diagnose accordingly. It’s a time-honoured method of testing children’s hearing. The idea of the puppet box is relatively simple, and the implementation in this case very clever; I suppose any animated toy could do the job, and all we need is a suitable power supply, some lights and a timer board to control it all. The majority of us would likely never see such a thing, unless we had a very young child in need of having their hearing tested. I’ve certainly never seen one before, even though I’ve had many hearing tests over the years, so all this has been an education for me. Australia's electronics magazine siliconchip.com.au The VRA in my workshop is a classic example of someone with electronics knowledge and the vision to create something practical and useful using that knowledge. These things should have become an industry standard. They might very well be, for all I know – no doubt some company makes and sells them for exorbitant amounts of money. Still, for whatever reason, this box, and several others like it Darryl made, have stayed a relatively ‘local’ solution to this problem. Damaged in transit The problems with this unit started when the puppet box was shipped from ‘up north’ to ‘down south’. When it arrived, it no longer worked. According to the people involved, the packaging showed no signs of trauma, and the unit was intact, but there was obviously something quite wrong with it. The sections lit up with the button press, but the only toy moving was the elephant. While I got audio from the others, the ant and the gorilla were not animating at all, though their LED spot lights did activate. The recipient of the box got in touch with Darryl and then he got hold of me. Me being in the same town down here as the customer likely sweetened the deal. He asked me if I could take a look at it, rather than ship it all the way back ‘up north’. Of course, I said yes, and really, what else could I do? The chance to work on something new and unique is many a serviceman’s dream (well, it is mine anyway). The box arrived at the workshop nicely bound up in a woollen rug, although that was not the original shipping material. After unwrapping, it seemed intact and undamaged when viewed from the outside. However, after plugging it in, connecting the hand controller and trying it, there was obviously something wrong. The ant and the gorilla toys looked to be sprawled on the floor of their respective compartments, and there was no movement at all visible when the compartment lights came on. The elephant at the bottom also looked a bit skewed, but it did at least have some music and motion when the relevant button was pushed. The first thing to do was remove the smoked black Perspex cover, exposing the toys. It was held on with standard super-screws, countersunk into the plastic. Some kind of sealant had been applied around the bevelled edges of the screen, perhaps to remove any sharp machining edges that might catch a small hand. With the screen off, I could see what was going on. The ant was meant to siliconchip.com.au Items Covered This Month • • • • • Toys with a serious purpose A Sony tuner with a side of gum Washing machine and mixer repair Repairing a Toyota wheelchair lift Restoring a Porsche 928 Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com be standing upright and be glued to the back of the compartment, while his ‘feet’ were fixed to the timber ‘floor’ of the section to hold it into position. The glue holding it upright had torn away from the wrap-around cardboard picture background, so the toy was just folded up headfirst like a rag-doll on the floor. I unwound him and stood him up and pressed the button. This time, his eyes rolled and blinked and he said his lines quite happily. A simple fix for this one then; all I had to do was clean him up and glue his backpack back into place on the background to secure him in the right place. One sick gorilla The gorilla section was a bit different. He’d come well adrift and was crumpled onto the floor. He’d been tacked/ glued in three places to hold him upright – all these points had been torn away, as evidenced by the paper stuck to the glued areas. The box had evidently suffered quite an impact – at least enough to knock these guys free. The gorilla didn’t move at all, so something electrical had gone wrong. He did, however, emit the opening notes of that novelty song, but it sounded like a stuck record, playing the same sound-bite over and over. A check with Darryl confirmed that it should play the whole song for the allotted time, while the gorilla would usually dance and ‘mouth’ the words. Apparently, something else was amiss here. All the toys were originally battery-­ powered. Power for this box – and the toys and lights – was derived from a battery charger mounted into the cavity in the base of the unit. Australia's electronics magazine November 2022  101 Switched permanently to the 6V setting, the charger was working because all the compartment LED lights activated on the press of the button. Two of the toys moved, however weirdly, so the juice was making it through to all but the ape. The lights and animation were all controlled by a common timer, so they all operated for the same duration. It was mounted on top of the charger. The ammeter on the charger indicated when the toys were powered – again, except for the gorilla, which was not surprising as it seemed to be the most affected by the drop. The toy was easy enough to remove – one foot was still glued to the base, so I carefully got a box-cutter style knife blade in between the glue and card and gently separated the two. Once free of that, I then had to desolder the power leads, which went directly to the battery compartment and were soldered to the contacts there. With the toy removed, I pressed the button and my trusty multimeter showed roughly 6V getting to the now-bare wires, so whatever was wrong was inside the toy. Fortunately, the manufacturer had installed a zip in the bottom of the plush, and when opened, this revealed the internal mechanism. A large torso-shaped plastic clamshell box was held together with four screws, and with these removed, the two halves came away easily. Access was very tight – the plush would only pull back a limited amount, as a cable tie secured the neck area to the actuator case. I had to cut and remove that tie to allow deeper access, and as there were linkages to the arms, the head and the mouth, I had to be careful I didn’t damage those. More damage inside Inside the actuator was the sound and movement controller module. This was made from two small PCBs joined at right angles, screwed to the plastic case, with one containing a COB (chip-on-board) IC that likely had the song programmed into it. There were a few other surface-mounted components which I assumed controlled the animatronics. The bottom half of the case also contained a reasonably complex plastic gearbox and an electric motor. The motor is a typical small DC motor that powers countless toys. Its 102 Silicon Chip leads were adrift, explaining why there was no movement. I applied a bench power supply at 5V to that motor directly and sure enough, it fired into action, so that was the likely problem. A suppressor capacitor was also connected across the motor’s terminals – this had broken away on one side, so a quick hunt through my spares box had that replaced and the connections remade and solidly soldered in place. A press of the button proved the gorilla now jiggled and animated, but his mouth didn’t move (it should) and that song was still just a machine-gun-style delivery of one note. I didn’t think I’d be able to do anything about the lack of music, but I could look into that gearbox and see why the mouth didn’t articulate. After stripping the gearbox assembly from the toy (which meant pressing a few pin-hinges out), I could see an actuator shaft that should have operated the mouth had snapped at a join in the neck area. It was a clean break and there was plenty of meat there for a glue job, so I hunted through my adhesives collection for some plastic-welding cement. This material is standard PVC or similar, and a test drop of glue onto an open area confirmed that it would indeed weld those bits together. Once glued and held for a few minutes (nothing seems to go on as long as waiting for glue to harden), I carefully reassembled the gearbox, motor and linkages and left it overnight before powering it up. The next morning, I held the gorilla roughly in place and pressed the button. Success! He did a little dance, and his mouth snapped open and closed. The ‘music’ wasn’t happening properly, but Darryl mentioned that as long as there was some noise, it would suffice for the purpose. I suppose we could have sourced another toy, or even grabbed a sound module from a charity shop talking toy, but a quick look showed that animated toys are really expensive these days. I learned over the phone that most donated toys go pretty quickly from the Salvos and Vinnies stores. Shaving the gorilla (no, really!) After zipping him back up, I cleaned off as much of the old hot-melt glue originally used to hold the gorilla in from his fur coat as I could. I wouldn’t like to have to get this glue out of a real coat, because it makes a nasty mess! Shaving it partially was the only way to remove the bulk of it. I used the rest of the glue as a template to fit the limbs back into their original positions, which were pretty obvious due to the torn-away card. I also used the same glue to reattach the elephant toy to the bottom, which was a little askew on its mounts, but still working as intended. After a bit of tidying up of wire runs and the dog-eared and torn panoramic picture backgrounds, I was satisfied it was all working as well as it ever would. Due to the extra dollops of glue liberally applied to the toys, I’m reasonably sure they won’t be coming loose again. [I’m sure the post office would accept your challenge – Editor]. If they do, I think we’ll have bigger problems! The only thing left to do was to replace the front cover and give the box a good workout. As it has been in the workshop for a couple of weeks, all my visiting customers see it and, of course, ask what it is and how it works. I pass them the hand controller and everyone seems to have fun making the toys animate; it makes for a good conversation piece. Australia's electronics magazine siliconchip.com.au Keep your electronics clean, lubricated and protected. Service Aids & Essentials. GREAT RANGE. GREAT VALUE. In-stock at your conveniently located stores nationwide. 4 2 1 5 3 BUY IN BULK & SAVE!!! 1 Isopropyl Alcohol 99.8% 250ml Spray NA1066 BUY 1+ $7.95 EA. BUY 4+ $7.15 EA. BUY 10+ $6.35 EA. 99.8% 300g Aerosol NA1067 BUY 1+ $11.95 EA. BUY 4+ $10.45 EA. BUY 10+ $9.45 EA. 70% 1 Litre Bottle NA1071 BUY 1+ $19.95 EA. BUY 4+ $17.95 EA. BUY 10+ $15.95 EA. 2 Electronic Parts Cleaning Solution 1 Litre Bottle NA1070 BUY 1+ $15.95 EA. BUY 4+ $13.95 EA. BUY 10+ $12.45 EA. 3 Liquid Electrical Tape 28g Tubes, Red or Black NM2836-NM2838 BUY 1+ $19.95 EA. BUY 4+ $17.95 EA. BUY 10+ $15.95 EA. 4 175g Aerosols Contact Cleaner Lubricant NA1012 Electronic Cleaning Solvent NA1004 BUY 1+ $12.95 EA. BUY 4+ $11.45 EA. BOX OF 12 JUST $119.40 PTFE Dry Lubricant NA1013 BUY 1+ $15.95 EA. BUY 4+ $13.95 EA. BOX OF 12 JUST $149.40 5 J-B Weld Products J-B Weld Epoxy 28g NA1518 BUY 1+ $17.95 EA. BUY 4+ $15.95 EA. BUY 10+ $13.95 EA. SuperWeld Extreme 15g NA1539 BUY 1+ $14.95 EA. BUY 4+ $13.45 EA. WaterWeld 57g NA1532 BUY 1+ $23.95 EA. BUY 4+ $21.45 EA. BUY 10+ $18.95 EA. Shop at Jaycar for even more service aids & essentials: • Adhesives & Insulation Tapes • Solder & Soldering Aids • Wire & Heatshrink Tubing Explore our full range of service aids, in stock at over 110 stores, or 130 resellers or on our website. • Fasteners & Cable Ties • Ultrasonic Cleaners • Tools & Workbench Accessories jaycar.com.au/serviceaids 1800 022 888 It would have gone back by now, but the designer and the customer are talking about modding it for use with foot-­ operated switches as well. That would require finding some single-pole press-to-make, release-to-break stomp-box type switches (sometimes called momentary switches), some of which I think Darryl has already sourced. I initially thought readily-available musicians’ foot switches would be ideal, as they are designed to be trodden on. However, they are usually quite expensive and are typically multi-pole, press-to-make, press-to-break types used for switching effects in and out of the signal chain. Anyway, with the right switches in hand, it will be a relatively simple matter of taking off the power supply cover again and adding another paralleled multi-pin plug to the existing facia. As the audiologist may want to have the switches in a different room to the box (usually, they are in the same room), we’ll have to find a way to utilise jack panels on the walls. Still, that’s for another day – at least now, the box can be returned to normal service and delight kids of all ages. One Sony tuner with a side of gum B. H., of Little Mountain, Qld ran into one of those situations where, while diagnosing a fault, the measurements didn’t seem to make sense. Luckily, he managed to figure out the reason for those discrepancies... I inherited a Sony tuner that played for many years, but within the span of one week, its FM output diminished to zero. I thought the most likely culprit was the first RF transistor. This unit is beautifully made and is of the PLL type, which was very novel back in 1981. After googling for many days, I could not find a schematic, so I started from the beginning. This unit is not unusual; the RF input stage is followed by the mixer/oscillator, then a dual transistorised IF stage, followed by an IC that turned out to be the PLL FM IF decoder, which includes another six stages of IF amplification. Three ceramic filters are associated with the transistor amplifiers. However, I couldn’t find a bias voltage at the base or emitter of either transistor. I also checked the voltages on the connected resistors. They had used red gum to stop some flying leads from interfering with the station pointer dial mechanism. This blob covered a resistor and solder joint. I removed the red gum to access the resistor, which I believed to be the bias provider. The resistor had the correct value on the component side, but the solder joint on the copper side was peculiar. I could measure a positive Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. 104 Silicon Chip voltage on the resistor lead, but the surrounding solder tested 0V, suggesting a dry joint. Re-soldering it made no difference; the pad and resistor wire were still 14V apart. It all looked proper on closer inspection; the wire was surrounded by solder with the correct colour. But I could not find any continuity between the wire and the solder. I think the gum from the PCB component side must have corroded the tin coating of the resistor wire all the way down into the solder joint, isolating the resistor from the solder. Replacing the resistor with one soldered on the copper side of the PCB fixed it. Washing machine and mixer repair P. M., of Christchurch, New Zealand made three successful repairs on very different pieces of equipment lately... The first was my washing machine, which has been reliable for more than ten years. Recently, I switched it on and instead of the usual bright display of LEDs showing the wash program and time, the LEDs were dull and flashing slowly. Switching it off and on again didn’t help. A Google search first turned up some unhelpful suggestions, but then there was one that seemed to be on the right track. The post mentioned a faulty 10µF 450V electrolytic capacitor on the main board and that person had found a replacement at Jaycar. I was planning to go to Jaycar later that day, so I added the capacitor to my list. The post also mentioned cutting a hole through some plastic with a hole saw to get to the part, which sounded a bit extreme to me at first. The machine’s top must be removed to get to the main board. Once away from the wall, after removing a few screws and some plugs, out comes the main board. The board sits in a plastic tray filled with clear sealant covering most of the components. The capacitor was visible in the middle of the board and was obviously faulty as the top had bulged open. The problem was that the solder side of the board was face-down in the plastic tray, and I didn’t want to disturb the sealant holding it all there. The hole saw was starting to make sense now, but still seemed a little risky. Instead, I drilled a series of small holes to make a circle that I could nibble out to make a hole to access the solder joints of the capacitor. I was glad I did this as there were more components on the solder side of the board, and hitting any of them with the hole saw would not end well. I could now replace the capacitor and used silicone sealant to refit the plastic piece I had removed. As I was putting it all back together, I remembered the original poster had said to be careful not to pinch the rubber hose at the back of the machine when refitting the top cover. This was valuable advice, as when I looked at the hose, it was indeed pinched under the top. This hose is part of the water level sensor, and if I had not freed it, the machine would have overflowed the first time it was used. Unsurprisingly, when I fired it back up, it was working correctly again. Secondly, I repair a lot of analog audio mixers of various sizes; some of the most common problems are faulty faders. Those slots in the panel for the faders allow ingress of all manner of dirt and liquid spills. In most of these units, everything is mounted on one large circuit board, including Australia's electronics magazine siliconchip.com.au the faders, so access means removing all the knobs, nuts and screws to get the board out. I have found that in many cases, there is sufficient space at the front edge of the board to wiggle the fader out once it has been desoldered, and a new one can be refitted the same way. The mixer I worked on recently did not have this space, but I still managed to get the faulty fader out. Getting the replacement in would be a different story until I had an idea. I fed a piece of fine wire through the fader slot from the top of the panel and wiggled it around until I got it past the PCB. I then tied the wire to the fader’s shaft and used it to slowly guide the fader to its location, where I could then push it back into the holes in the board, resolder it and test it. That saved me a lot of work. Thirdly, a friend sent me his large stereo amplifier that had stopped working after a heavy session. After a bit of probing, I discovered the power transformer’s primary winding was open circuit. It is not uncommon for Japanese-­ manufactured equipment to have a thermal fuse inside the power transformer in series with the primary winding. These fuses are non-resetting, so the unit will no longer work after they trip. At first, I could not see the fuse; they are often buried inside the bobbin that holds the windings. After snipping away some small pieces of the bobbin, I could just see the fuse at the bottom of a slot roughly 5mm wide and 40mm deep. With a suitable probe, I could determine that this was where I needed to connect to the winding, but how could I connect to it when my soldering iron would not fit in the slot without melting everything around it? Then I remembered that my soldering gun uses a piece of looped copper wire as an element and it is not very wide. I dropped a small grain-of-wheat lamp into the slot and powered it from my bench power supply so I could see. I was then able to solder a wire to the fuse to complete the circuit. That got it back into business, but as I had defeated the thermal fuse, I checked to ensure a conventional suitably-­ rated fuse was in line with the transformer. The thermal fuse is an extra line of defence, but there are millions of power transformers out there that do not have one. I have even seen some transformers with an extra wire to bypass the thermal fuse should it fail. Repairing a wheelchair lift inside a car J. W., of Hillarys, WA is another regular contributor to this column. His latest entry involves repairing a wheelchair lift built into a Toyota Regius van... A friend rang recently and asked if I could have a look at his daughter’s wheelchair lift. He said that the lift was not going back to the home position in the back of the van. He had contacted several local auto electricians, but they were not interested in looking at it, as it was a Japanese import with no service information available. So I went around to have a look. The system was a genuine Toyota accessory and seemed well-built (much like their cars). If the carriage was taken too low, it would start to lift the van! The lift has large motor driving screws that lower and raise the platform, and that part was working as it should (see the photo at upper right). siliconchip.com.au The wheelchair lift attached to a Toyota Regius van. Once the platform was back at the level of the van floor, two smaller motors and a second set of screws was supposed to drive it into the home position. This was not happening. The system was all-electric and controlled by four relays & four microswitches. The main control assembly was easy to unbolt and inspect. It had three large onboard relays plus a smaller one. The large ones were not enclosed, so I could see them operating; they seemed to be working OK. I unplugged and tested the small relay, and it was also functional. Next, I decided to start checking the microswitches. Two were easy to access and tested OK. The other two, which switched power from the large motor to the smaller motors and stopped the platform in the home position, were challenging to access. After some deliberation and standing on my head in the back of the van, my friend figured out that we needed to take off the runner plate as that would let me access the microswitches and wiring. After that, I tested the final two switches, which were fine. I then lay on the van’s floor and used a torch to look at the wiring to the platform, which was hidden in part of the frame. It was encased in black plastic cable chain. Sticking out of the cable chain was a broken wire. I managed to effect a repair by joining the broken ends using a small section of new wire. The break had occurred because the plastic cable chain had broken at one end, so the wiring was not supported. I managed to cut some flexible conduit and fit it over the broken section, which did not actually need to be flexible. We then put the whole system back together, and it worked as it should. The whole process took many hours over several days. My friend and I were relieved finally to have the lift back in the van and working again. Restoration of a Porsche 928 (Central Warning System) D. T., of Sylvania Southgate, NSW previously wrote about repairing a Porsche 928 demister control relay (February 2022, pages 88-90). He’s still working on restoring that car, but this time, it’s the warning system that’s on the fritz... Australia's electronics magazine November 2022  105 During my restoration of a 1982 Porsche 928, I came to the Central Warning System (CWS). In addition to all the usual warning lights in the instrument cluster, the 928 CWS integrates all the warnings that the car generates into one central warning light, also in the instrument cluster. As well as illuminating this light if there is a major problem like oil pressure, high temperature or low fuel, it will also light up with less common things like a low washer bottle level or worn brake pads. This warning light repeatedly flashes a specific number of times, with the number indicating what the problem is. Low-importance warnings can be cleared by pressing a button, but high-importance warnings can’t. The central warning light is also duplicated in the centre console – the two lights are connected in parallel. I guess that way, if the driver doesn’t notice it, the passenger might. Finally, the CWS also turns all the instrument cluster warning lights on each time you start the car, so you can verify they’re working correctly. Electrically, the CWS sits between the sensors and the dashboard warning lights. The less-expensive model of the car had a simple adaptor fitted in place of the CWS that connected the sensors directly to the dash warning lights in the traditional way. With it plugged in, there was no response from any of the instrument cluster warning lights or the light in the centre console. I found that the light in the centre console was shorted out with a piece of wire deliberately soldered across it – I guess at some stage in the past, the CWS has failed, and this was the easiest way to eliminate the warnings! The indicator panel cleaned up with the short removed, but I wasn’t surprised when it didn’t change anything – with a short across the lamp, the driver was probably toast. The next step was to open the CWS unit. I’ve found the Porsche 928 modules to be quite serviceable in the past, and this one was no exception. After I bent a few tabs, the internals slid out of the aluminium housing to reveal a sandwiched pair of PCBs with plenty of parts – all through-hole, and all discretes except for one 14-pin DIP IC. The IC was an SN8400 with a TI logo, but I couldn’t find any data on it. I decided it’s nothing like an embedded microprocessor – this car was designed in the mid-1970s, and they didn’t exist then. There were plenty of transistors onboard, of seven or eight different types, with all but two being in TO-92 plastic packages. Some I could find data on, but most not. When I tipped the housing over, a blackened 1W resistor fell out. It only took a minute to figure out where on the board the resistor came from, and tracing showed it drove the two central warning lights – no doubt it overheated and melted the solder because of the external short. The driver transistor connected to it also had a crack in it. I didn’t recognise the number on the transistor and couldn’t find any data on it, but I measured a few others with the same marking and decided a BC547 would probably do. Having fixed those two items, I now had the central warning lights stuck on, but no instrument cluster warning lights. Next, I looked at the electros. There were some standard-­ looking aluminium electros which all looked OK, but there were also some plastic-cased 22μF units that had brown residue around the top. Brown residue is never good on electros. Funnily enough, it wasn’t anywhere near any 106 Silicon Chip seam in the case, but all the plastic-cased electros had it to some degree. I tried measuring them in-circuit with my Fluke, but I haven’t really used the capacitance measurement facility on the meter before and was dubious about it, especially since I was measuring in-circuit. I wasn’t surprised when I measured something other than the marked value. I decided to remove one and measure it out of circuit and it measured low – about 8μF. Not really being sure how they were used, I thought I might as well replace them all. I now had a flashing central warning light, but the flashing was inconsistent, bordering on gibberish. I thought it might be because multiple valid warnings were present (for example, the fuel tank and washer fluid were both empty). However, posts on a Porsche forum said that it managed this OK when it was working correctly. The next step was to check all the transistor junctions using the Fluke’s diode tester. I felt more confident about this than I did with the capacitors – the voltage across a PN junction should never exceed about 0.7V at low currents. Plus, there were enough of each type of transistor on the boards, so I could guess what was normal and what wasn’t. Some types gave high base-emitter readings of about 1.3V. I decided these were Darlingtons with two diode drops between the base and emitter. I found two transistors I didn’t like. One I replaced with a BC547, but the other was one of these Darlingtons. I spent a bit of time looking around to try to find something to replace it with, but TO-92 Darlingtons aren’t that common even when there isn’t a silicon shortage, so in the end, I replaced that device with a pair of BC547s connected as a Darlington. After that, I had a consistent flash indicating I had no petrol, and the instrument cluster lights started working. Afterwards, I measured the aluminium electros I’d replaced on the bench and saw a range of values, some very low, under 1μF. Interestingly, when I measured the new ones in-circuit, they all measured about 22μF – chalk another one up for the Fluke. Editor’s note: the SN8400 is likely a quad NAND gate like the SN7400 but with a different (possibly wider) operating SC temperature range to better suit vehicular use. Australia's electronics magazine siliconchip.com.au Established 1930, ard for quality and “Setting the stand 100% Australian Ow ned value” R E B M E V NO 3PM SATURDAY TENDED TRADING TILL EX 19th NOVEMBER! 70-605 - Measuring Box set • • • • DB-180 Digital Bevel Box 35-2041-IP 65 Digital Protractor Measuring Kit 4 Piece • • • • • • 0 - 25mm micrometer 150mm / 6" rule 150mm / 6" vernier 100 x 70mm square • • • • Full 360° range (90° x 4) 0.05° resolution ±0.15º accuracy IP-65 waterproof rating Large back light LCD screen Magnetic base • CNC Machined for high accuracy • Ground measuring face • Black anodized coating for a protective anti rust coating • Precision Laser Engraved Markings Digital Height Gauge 4 x 90º range Auto shut off Magnetic base 0.1º resolution • Dual imperial/ metric scale • Fine adjustment • Pre-sets and memory 12"/300mm capacity METRIC S ATION GRADU ECARBIDD TIPPE R SCRIBE Order Code: M012 Order Code: Q2041 55 Order Code: M977 140 $ SAVE $11 off RRP SAVE $25 off RRP 0-25mm/0-1" range ±0.001mm accuracy Friction thimble design Large LCD for easy reading Carbide measuring faces • • • • • Order Code: Q124 Order Code: Q1242 112 0-25mm/0-1" range ±0.001mm accuracy Protected to IP65 specifications Large LCD for easy reading Carbide measuring faces Order Code: Q1245 140 $ 187 $ $ • • • • • 150mm / 6" IP67 coolant proof Large clear screen display Metric/Imperial conversions Four way measurement 33-244 Inside Caliper Gauge 33-239 Outside Caliper Gauge 34-221 Digital Indicator 36-2105 Digital Height Gauge 308 $ SAVE $55 off RRP Order Code: Q239 308 $ SAVE $55 off RRP Order Code: Q221 299 $ SAVE $53 off RRP 200mm / 8" IP67 coolant proof Large clear screen display Metric/Imperial conversions Four way measurement Order Code: Q1861 205 SAVE $37 off RRP Order Code: Q244 • • • • • 233 $ SAVE $33 off RRP • Zero setting at any position • Metric/Imperial system conversion at any position • Max speed 1.5m/ sec 31-1861- Digital Caliper Coolant Proof Order Code: Q1851 SAVE $25 off RRP • LCD display Metric/Imperial conversion • Accuracy 0.03mm • Auto power off • Remembers the data of Max. and Min. or hold data SAVE $22 off RRP 31-1851 - Digital Caliper Coolant Proof SAVE $20 off RRP • LCD display Metric/Imperial conversion • Accuracy 0.03mm • Auto power off • Remembers the data of Max. and Min. or hold data $ SAVE $44 off RRP 10-1245 - Digital Outside Micrometer • • • • • 77 $ SAVE $22 off RRP 25 - 50mm / 1 - 2" range ±0.002mm accuracy Friction thimble design Large LCD for easy reading Carbide measuring faces Order Code: Q605 198 $ 10-124 10-1242 - Digital Digital Outside Micrometer Outside Micrometer • • • • • Order Code: M704 49 $ $ SAVE $42 off RRP • 0-300mm / 12" range • Carbide tipped scriber • Metric/imperial conversion • 0.01mm/0.001" resolution • ±0.04mm accuracy Order Code: Q2105 589 $ SAVE $104 off RRP www.machineryhouse.com.au SYDNEY BRISBANE MELBOURNE PERTH (02) 9890 9111 (07) 3715 2200 (03) 9212 4422 (08) 9373 9999 Specifications & Prices are subject to change without notification. All prices include GST and valid until 30-11-22 UNIQUE PROMO CODE SIC2210 ONLINE OR INSTORE! 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 Suitable parts for the WiFi DC Load Thanks to Richard Palmer for the WiFi DC Load project (September & October 2022; siliconchip.au/ Series/388) and thanks for all the component links you supplied. I have some questions about the remaining parts. The case is described as metal. Is it actually all metal, or are the front panels plastic? I’ve found cases on eBay described as “270mm x 210mm x 140mm Blue Metal Enclosure” with the material described as ‘metal & plastic’ listed for $45.47 with free delivery. There’s another similar one available, also ‘metal & plastic’. The seller is “silaluna88” and the brand “Uxcell”. Are those the right items? From the text, I take it that the relay is chassis mounted, with a contact rating of at least 30A. I assume a minimum contactor operating voltage of 150V DC with a suggested opening time of no more than 10ms and a 5V or 12V coil. I can source a PTRH-1C-12ST5-X relay that seems suitable, except the coil operating power is 0.9W. The following components are not available until 2023: MCP4725A0T-E/ CH and ADS1115IDGSR. What about the wirewound resistors – can I substitute MSR3-0R02F1 with better specs? (B. P.) ● Those are suitable enclosures; the front panel is metal. The relay current is determined by the BC817 driving transistor’s 500mA limit. That should be plenty to drive your suggested relay coil. Its mounting lugs would be an improvement on the one I used in the prototype, a 30A “Arduino module” with an onboard driver transistor found on eBay (siliconchip.au/link/ abh6 or siliconchip.au/link/abh7). The relay operating time is a secondary concern for short-circuit protection as the software detects over-­ current within around 1ms, switching the Mosfets off in less than 2ms. The relay is most useful for reverse voltage protection, where the Mosfets can 108 Silicon Chip conduct more than 100A each when reverse-biased, as well as over-voltage protection. In both cases, the load’s design is conservative and should easily survive the 10ms relay operating time. Both the ADS1115 and MCP4725 are available as part of Arduino modules on eBay. I have successfully floated devices off these modules in the prototype when unable to source them from other suppliers. Sometimes the ADC module actually contains an ADS1015, but the loss of accuracy is manageable in this application. Alternatively, you can get those two parts along with all the other SMDs and some other useful parts in the Silicon Chip kit (siliconchip.au/ Shop/20/6399). Tweeter and subwoofer drivers for isoundBar Concerning the tweeter part number specified for the isoundBar (August 2022; siliconchip.au/Article/15426), I have conducted an exhaustive search of the Vifa/Peerless (Tymphany) catalogue, and the model BC25SC55-04 is the only one to be found. I believe the 4Ω tweeter will work perfectly well in this instance. This tweeter is also stocked by Altronics (Cat C3019). Further to the tweeter in-cabinet placement, I have reviewed the quoted published axial response diagrams. In my view, the high-frequency response would be disappointing unless the room in which the soundbar is to be used has side walls fairly close to the position of the television and soundbar. My solution would be to modify the arrangement of the midrange speakers so that the tweeters could be positioned facing the front and the outer midrange speaker be relocated inboard. I would flip the second midrange speaker 180° on the designated panel. The associated port for this isobaric subsystem would need to be relocated adjacent to the repositioned front-facing tweeter. Australia's electronics magazine As for the subwoofer option, I’m afraid that Ryda states it to be obsolete/ discontinued. Only US eBay sellers appear to be offering it, so cost-plus freight makes it unaffordable. (R. K., Cessnock, NSW) ● Allan Linton-Smith responds: you are right; I used the BC25SC55-04 tweeters, not -06. The so-called ‘mid-range’ front-­ facing speakers are actually full-range and have an excellent frequency response up to 20kHz. All the frequency response measurements published in the article were taken with the microphones positioned directly in front of the isoundBar. There is no need to add tweeters for more front-firing high-frequency sound, so I do not recommend you place the tweeters on the front panel. Otherwise, the sound will be very ‘bright’ and higher frequencies will predominate. The tweeters are deliberately positioned at each end to give a ‘spacedout’ effect. Most TVs are located in rooms with adjacent walls, and some high-frequency sound waves will be reflected off the back wall, ceiling etc. This helps to avoid a muted off-axis response. Even in the large, open Silicon Chip office, this spatial effect was noticeable, and it was tuneable by using the tweeter level control to suit personal preferences. Unfortunately, the JBL subwoofer has been enormously popular and is now difficult to get. We have obtained a sub with almost identical specifications from a local eBay supplier named “Boss Audio D10F” for $130 (eBay: siliconchip.au/link/abh8). You will probably have to be quick! Questions for the isoundBar project I am considering building the isoundBar project (siliconchip.au/ Article/15426), but I have a few questions. How do you control the overall volume without having to climb siliconchip.com.au Does winding wire diameter affect inductance? Thank you very much for your response to my question regarding the diameter of enamelled wire for winding T1 and L6 for the Super-9 FM Radio Receiver. I wasn’t aware of the errata feature on your website (siliconchip.au/Articles/Errata). As I am ignorant of the physics underlying RF transformers and inductors, I’d like to ask a question on this subject regarding the selection of wire diameters for T1 and L6 in the radio. It appears that the diameter of the wire is not a critical factor in the electromagnetic equation regarding RF; instead, the number of turns is the relevant factor, notwithstanding the physical limitations that need to be considered. After an extensive internet search, I could not find enamelled wire of 0.125mm diameter in small enough quantity to make it realistically affordable. Still, I found 0.12mm and 0.13mm diameter wires readily available. Given what I understand now, I assume that either of those two diameters would work OK. As an alternative, I have an assortment of enamelled wire I have salvaged from transformers, so would the principle of ‘close enough is good enough’ apply to the subject inductors? Thank you in advance for any advice you can give me regarding my questions above. (C. B., Bonville, NSW) ● Yes, 0.12mm or 0.13mm are within manufacturing tolerance of 0.125mm diameter, so either would be expected to give identical results. The diameter has a small effect on inductor properties as it determines how thick the windings become and therefore, the exact diameter of the turns (especially towards the outside if there are multiple layers). Still, you are correct that the number of turns is the primary concern, along with the resistance and current-carrying capacity of the wire (neither being terribly important in this case). In this case, the properties of the inductor are not critical, so you can get away with using a range of different wire diameters. The erratum we published doesn’t say that you need to change the number of turns depending on whether you are using 0.125mm and 0.25mm diameter wire, so you can almost certainly use anything between those values with satisfactory results. around the back of the unit? Many TVs are mounted on a plinth and, in our case, I would have to put the TV on top of the soundbar. I am considering making an extension so that the soundbar has larger dimensions to allow the top-mounted bass unit to be clear of the TV plinth. Where does the amplifier control panel mount? On the outside or inside of the enclosure? It is not clear from the article. Are the ports covered with speaker cloth? Finally, the parts list calls for a sheet of 4mm plywood. Could I use MDF instead? (J. C., Pelican Waters, Qld) ● Allan Linton-Smith replies: I usually plug the sound bar into the 3.5mm headphone socket on the TV and then use the TV remote for volume control after setting up the balance between treble, L & R and woofers. You can also pair it with your TV with Bluetooth if it recognises it (mine doesn’t). Yes, you could make it larger externally but be careful; if your TV is heavy, it could warp the top. If the woofer is blocked, it might be best to use the external subwoofer. The control panel is mounted internally and I used 3mm machine screws siliconchip.com.au and nuts to secure it. The picture on p58 shows the little screws but they are not obvious, as you noted. Yes, I covered the whole thing with speaker cloth so it would not stick out visually. I initially used 3mm MDF but had problems because the panels got mouldy during our wet period and I had to throw them away. They also proved very weak and vibrated occasionally. The 4mm plywood feels and sounds a lot better. Incorrect isoundBar timber length When reading the isoundBar project (siliconchip.au/Article/15426), I thought it was just what I needed, so I have ordered the speakers and amplifier as specified. On reading the parts list and looking at the dimensions of the cut-outs, though, there appear to be some inconsistencies. The diagram on page 51 shows the front and rear panels to be 1240mm wide, yet the parts list includes three lengths of 1200mm pine. The plan view of the construction on page 53 shows that the front and Australia's electronics magazine rear panels need to be 1240mm long. An alternative would be to have the end panels be 200mm long and mount them outside the front and rear panels. That would then tie in with the front and rear panels being 1200mm wide, adding the two 20mm thicknesses of the end panels of 20mm for a total width of 1240mm. Could you advise the correct dimensions, or have they been corrected in the next issue? (C. G., Beckenham, WA) ● Allan Linton-Smith replies: you will have seen the erratum stating that those lengths of timber should be 1.24m, not 1.2m, as you have surmised. It is a good idea to adjust the side panels for those who may have already purchased the 1.2m lengths. The original idea was to have a soundbar the same width as several common sizes of TV, but I settled on making it as wide as a 55-inch TV, typically 1232mm. You can make the soundbar bigger to look better with wider TVs, but not smaller because the performance will be compromised. For a 65-inch TV, make it 1454mm wide (or a bit more), and for 75 inches, use a width of at least 1677mm. Limited VGA PicoMite colour resolution I am building the VGA PicoMite project (July 2022; siliconchip.au/ Article/15382) and I like that it is a low-cost computer with many useful features. However, I noticed that when switched to colour mode, the VGA resolution drops from 640 × 480 to 320 × 240. I guess the 640 x 480 monochrome frame buffer takes up 640 × 480 ÷ 8 = 37.5kiB and the 320 × 240 4-bit frame buffer also takes up 320 × 240 ÷ 2 = 37.5kiB. Still, with 262kiB of RAM, the Pi Pico should have enough RAM for a 640 × 480 colour framebuffer (150kiB) with more than 100kiB left. Is there a reason that a 640 × 480 colour mode is not possible? (P. B., Turramurra, NSW) ● Geoff Graham responds: I asked this of Peter Mather, who ported MMBasic to the RP2040 chip. A lot of RAM was needed to improve performance, so there was a trade-off with the RAM needed to buffer the video. Another hurdle is the banked RAM architecture. The RP2040 processor does not have flash memory on the chip, so the November 2022  109 firmware and the BASIC program must be accessed over a quad SPI bus (very slow). To alleviate this, the core components of MMBasic are loaded into RAM and executed from there. Other tricks were used to get the performance up such as a RAM based hash table for indexing BASIC variables. The result is that the performance (per MHz clock) is about the same as the other implementations of MMBasic, despite the slow access to the flash memory. However, a significant portion of the Pico’s RAM is therefore unavailable for other uses. This is the RAM budget used in the final version: 44kB of memory-buffered firmware 38kB of video memory 32kB of variable hash table 4kB of stack for the 1st core 4kB of stack for the 2nd core 2kB for the main heap 32kB for general variables including function hash buffer 100kB for the MMBasic heap 8kB for miscellaneous uses SMD Test Tweezers display cut off I have recently built the Improved SMD Test Tweezers (April 2022 issue; siliconchip.au/Article/15276) and find them extremely useful and practical, especially with the increasing usage of small SMD components in projects today. My only problem is that the right-most character on the screen is cut off. Is it possible to reduce the font size and move the displayed text to the left? (J. A., Townsville, Qld) ● We’ve had reports of this occurring for some other users but did not see it with any of our prototypes. We suspect there may be some OLED modules that map their columns differently, meaning that there is not a universal fix. OLED modules with and without this problem may not be easily distinguishable, either. We’re working on another update of the Tweezers using a larger display (which will not have this problem as it maps all rows and columns), and it will also have a better power-saving mode as it will completely shut down the OLED at its supply. With a more capable microcontroller, we plan to give the next version a better set of test routines as well as extra buttons to simplify control and calibration. 110 Silicon Chip Readers wishing to experiment could try changing the value of OLED_X_OFFSET in the oled.h file and then recompiling the code. Control pot values for Hybrid Power Supply Thank you for your fine efforts in producing the Intelligent Hybrid Power Supply (February & March 2022; siliconchip.au/Series/377). The regulator PCB is a work of art in itself. I intend to create one manual board only for the simplicity of my needs. I have a couple of points that need clarification. Please nominate the value of the two panel-mounted pots connected to CON5 and CON6, as there is no reference to their values in the text. I intend to connect a multi-turn pot to V-Set, but they are not cheap. Secondly, there appears to be a ghost component in Fig.10 on page 85 of the March 2022 issue. Below REG4 is a polarised 10µF capacitor as per the circuit diagram. To its immediate right appears another spurious 10µF capacitor with its designation written vertically. There is no provision for this capacitor on the PCB I bought. Lastly, in the circuit diagram (Fig.7), I am wondering about the function of transistors Q8, Q10 and Q11. I could find no reference to them in the text. They appear to provide some Darlington-­ based constant current load to the pre-regulator IC, but there must be more to it than that. Thanks once again for your fine efforts, and those of your colleagues from this 75-year-young hobbyist. (C. D., Glenside, SA) ● Phil Prosser responds: the potentiometers I used when running in ‘manual’ mode were 1kΩ types. This results in a 5mA current through them and 25mW dissipation. Other values could be used, but 1kΩ seems safe. Multi-turn pots are very expensive. I suggest that you start with a single-­ turn pot, as the old-school power supply I have been using for years has a single-turn pot, and I have never had trouble with it. The ‘ghost cap’ is left over from an earlier version of this board. When the diagram was revised, with a new copper track layout and some changed component locations, it appears that redundant capacitor was not removed. Australia's electronics magazine There is no more to the circuit block involving Q8, Q10 & Q11 than a simple load for the switchmode regulator. If the circuit was built without them, I suspect it would work, but having them there ensures that the minimal load specification is always met. Battery Condition Checker running at 48V Some years ago, I built your LeadAcid/SLA Battery Condition Checker (August 2009 issue; siliconchip.au/ Article/1535). It’s an awesome tool; I still use it today. I am wondering how difficult it would be to change the 24V setting to 48V. (Ian, via email) ● For 48V operation, change the 220Ω resistor at the bottom of the divider chain connected to switch S3a to two 110Ω resistors in series. The middle tap of the 110Ω resistors can then be connected to the common terminal of S3a for use with a 48V battery. Another change you’ll need to make is to add a 24V zener diode in series with D11 at the input to the LM2940 regulator (REG1) with its anode to D11’s anode, to reduce the input voltage to a safer level for the regulator. That added zener diode will need to be shorted out for 6-24V operation. You could add a DPDT switch so that it shorts out that zener diode in one position, while connecting the common terminal of S3a to pin 2 of IC4. In the other position, it would remove the short across the zener diode, disconnect S3a’s common terminal and instead, connect pin 2 of IC4 to the junction of the 110Ω resistors. That switch will then select between 6-24V operation and 48V mode. Depending on the Mosfets used for Q4-Q7, consider using higher voltage rated types at, say, 100V. You might get away with the 55V types specified, provided the 48V battery terminal voltage will never exceed 54V during testing (a freshly charged 48V battery might be above 54V for a short period after charging). Capacitor Discharge Ignition questions I have obtained copies of High Energy Multi-Spark CDI series (December 2014 & January 2015; siliconchip. au/Series/279). continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE FOR SALE DAV E T H O M P S O N (the Serviceman from Silicon Chip) 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 LEDsales SILICON CHIP LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. Some of the books may have already been sold, but most are still available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip. com.au/link/aawx KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com LEDs and accessories for the DIY enthusiast VISIT THE NEW TRONIXLABS parts clearance store for real savings on new parts at clearance prices, with flat rate express delivery Australia-wide – go to https://tronixlabs.com Lazer Security PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au For Quality That Counts... QUALITY COMPONENTS + MORE The parts clearance sale continues, but stock is limited, this month check out the freebies – go to lazer.com.au Email for a postage quote, quote the number directly below the photo when referring to a book: silicon<at>siliconchip.com.au Keep your copies safe with these handy binders REAL VALUE A T $21.50 PLU S P&P Order online or call (02) 9939 3295 www.siliconchip.com.au/Shop/4 ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia's electronics magazine November 2022  111 The design seems very good but would require considerable effort (and probably extra cost) for little benefit for my circumstances. All that I need is a simple, reliable spark. I know that I will have to buy a 12V coil and battery; I just need the electronics to control the spark. I can use the existing trigger but will need circuitry to couple it to the control module. My questions are: 1. Is a PCB available for the December 2005 Universal High Energy Electronic System, code 05112051? 2. Is there a kit available for that project, or would I have to buy components separately? 3. Is a PCB available for the reluctor circuit? 4. Are there any components that are not available now. If so, what are the alternatives? 5. Are the above all available from your Shop? (T. H., Wallington, Vic) ● We do not recommend building the 2005/6 version of the High Energy Ignition system as there are no longer any kits or PCBs available. However, a Advertising Index Altronics.................................33-40 Control Devices............................. 9 Dave Thompson........................ 111 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Hare & Forbes........................... 107 Jaycar.......................IFC, 11, 53-55, ..................................60-61, 99, 103 Keith Rippon Kit Assembly....... 111 revised version of that project was published in the November & December 2012 issues (siliconchip.au/Series/18), and the PCB is still available; see siliconchip.au/Shop/?article=464 Kits for that project may also still be available. Check with Jaycar regarding their kit KC5513; their website currently says “Limited quantities available in store”, and if available, it is on sale at $19.80. As well as the PCB, we sell the hardto-get parts such as IGBT and programmed PIC, available via the link above. The other parts are commonly available. The reluctor circuitry is catered for on the PCB supplied. Replacement SOT-223 LDO regulators I am in the process of making the PIC/AVR Programming Adaptor Board (May & June 2012; siliconchip.au/ Series/24), but I can’t seem to find any AP1117E33 3.3V low-dropout linear regulators. Can I use an MCP17993302H/DB or LDI1117-3.3H instead? (L. P., Sydenham, NSW) ● There are many different kinds of compatible LDO regulators in SOT-223 packages with 1117 in their part code. The 3.3V version of the LDI1117 you mentioned should work. Another common compatible type is the AMS1117. The MCP1799 will not work without modifying the PCB because it has a different pinout (Vin, GND, Vout rather than GND, Vout, Vin). About power supply in Circuit Notebook I want to build the “Fully adjustable power supply” circuit published in the Circuit Notebook column, March 2004 (siliconchip.au/Article/3427). I assume the 33Ω resistor needs to be rated at 5W. I do not have an 18V supply at 5A. Can I use a transformer secondary rated at 15V 6A, giving approximately 21V when rectified? I could use a 1W 18V zener and dropping resistor to power the TL071. Is there any erratum for this circuit? (R. M., Melville, WA) ● The 33Ω resistor can be a 1/2W or even 1/4W type as its dissipation will be less than 30mW. There will only be a maximum of about 0.7V across it (the base-emitter forward voltage of transistor Q1). Yes, you can use your proposed 20V DC supply to power that circuit. The TL071 can run from a supply of up to 30V, so no extra zener clamp is required. Replacing components on a failed Turbo Timer I have a burnt-out resistor on my Turbo Timer circuit board (November 1998; siliconchip.au/Article/4649). It is labelled “33R [680R]”. Can you please confirm the value of the resistor I have to replace it with? (S. M., via email) ● The resistor should be 33Ω 1/2W. However, zener diode ZD1 and the 555 timer IC are possibly destroyed as well. The burned-out resistor would have been caused by a voltage transient that shorted the zener diode and possibly harmed the 555 timer. Check if there is a short circuit across ZD1. We suspect that it will measure near 0Ω with a multimeter. All three components should be replaced. SC Lazer Security........................... 111 LD Electronics........................... 111 Microchip Technology......... 5, OBC Mouser Electronics..................... 13 Ocean Controls............................. 8 Rohde & Schwarz.......................... 7 Silicon Chip Shop.................88-89 Silvertone.................................... 12 The Loudspeaker Kit.com.......... 10 Tronixlabs.................................. 111 Wagner Electronics....................... 6 112 Silicon Chip Errata and Next Issue LEDsales................................... 111 isoundBar with Built-in Woofer, August 2022: the part code given for the Peerless tweeters should have been BC25SC55-04 instead of BC25SC55-06. Also, the sheet of 19-20mm thick plywood in the parts list is arguably not required as all the pieces can be cut from the DAR pine lengths. Motion-sensing 12V Power Switch, February 2019: it has been reported that the vibration switches can become unreliable (stuck ‘on’) due to contact welding when it closes. To solve this, solder a 100Ω resistor in series with one of the sensor leads (we suggest the thinner one). This value seems to work well but note that it is a compromise as it must be low enough to discharge the capacitor quickly but high enough to avoid contact welding. Next Issue: the December 2022 issue is due on sale in newsagents by Monday, November 28th. Expect postal delivery of subscription copies in Australia between November 28th and December 12th. Australia's electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! Ex GST RIGOL DS-1000E Series RIGOL DS-1000Z/E - FREE OPTIONS RIGOL MSO-5000 Series 450MHz & 100MHz, 2 Ch 41GS/s Real Time Sampling 4USB Device, USB Host & PictBridge 450MHz to 100MHz, 4 Ch; 200MHz, 2CH 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 429 FROM $ ex GST 649 FROM $ ex GST 1,569 ex GST Multimeters Function/Arbitrary Function Generators New Product! RIGOL DG-800 Series RIGOL DG-1000Z Series RIGOL DM-3058E 410MHz to 35MHz 41 & 2 Output Channels 416Bit, 125MS/s, 2M Memory Depth 425MHz, 30MHz & 60MHz 42 Output Channels 4160 In-Built Waveforms 45 1/2 Digit 49 Functions 4USB & RS232 FROM $ 479 FROM $ ex GST Power Supplies 725 ONLY $ ex GST Spectrum Analysers 789 ex GST Real-Time Analysers New Product! 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