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JUNE 2024 ISSN 1030-2662 06 9 771030 266001 $ 50* NZ $1390 12 INC GST INC GST ESR Test Tweezers USB-C Serial Adaptor Rosehill Gardens Sydney 19-20 June 2024 DC Supply Protectors Privacy Privac y Phones How important is your privacy when online? siliconchip.com.au Australia's electronics magazine June 2024  1 Fast and reliable temperature measurement. Digital Thermometers We stock a GREAT RANGE of thermometers, at GREAT VALUE, for domestic or commercial applications. MEASURE TEMPERATURES IN HOT, HAZARDOUS OR HARD TO REACH PLACES HELPS YOU AVOID FOOD FROM SPOILING FRIDGE/FREEZER THERMOMETER • -50°C to 70°C range • Min and max alarm function QM7209 JUST 44 $ Non-Contact Thermometer 95 • -50°C to 500°C range • 12:1 distance to spot ratio • Built-in laser pointer • Max, min, & auto data hold QM7410 JUST 6495 $ WATCH OVER THE TEMPS IN DIFFERENT ROOMS SUITABLE FOR THE LAB, WORKSHOP OR IN THE FIELD WIRELESS IN/OUT THERMOMETER/HYGROMETER • -45°C to 65°C (Outdoor), 0°C to 60°C (Indoor) range • 1% to 99% relative humidity range • Connect up to 3 sensors XC0322 JUST 5995 $ • -50°C to 750°C range • Built-in temperature sensor • K-type thermocouple input QM1602 RECORD AND STUDY TEMPS OVER TIME TEMPERATURE & HUMIDITY DATA LOGGER • -40°C to 70°C temp / 0-100% relative humidity range • 32,000 sample memory • Records at prescribed intervals • Easy USB interface QP6013 Shop at Jaycar for: Thermometer with K-Type Thermocouple • Thermometers & Thermocouples • Non-contact Thermometers • Probe/Stem Thermometers ONLY 129 $ JUST 5195 $ Includes Thermocouple • Digital Multimeters with Temperature • Desktop Temperature/Hygrometers • Weather Stations Explore our wide range of temperature measurement products, in stock at over 115 stores and 130 resellers or on our website. jaycar.com.au 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Contents Vol.37, No.06 June 2024 16 Privacy Phones Modern smartphones are invaluable, letting you look up information nearly anywhere, but the tradeoff is that your data is collected when using the phone and online services. So what can you do to reduce your ‘footprint’? By Dr David Maddison, VK3DSM Online privacy 32 Electronex 2024 Electronex – the Electronics Design and Assembly Expo – is being held at Rosehill Gardens Event Centre, Sydney, on the 19th & 20th of June this year in conjunction with the SMCBA Conference. Entry is free for all visitors. By Noel Gray (AEE) Electronics exhibition 64 MicroMag3 Magnetic Sensor The MicroMag3 measures the strength of a magnetic field in three axes (north-south, east-west and up-down). It can be used as a magnetic compass and inclinometer. By Jim Rowe Using electronic modules 46 Jaycar-sponsored Mini Projects This month’s set of Mini Projects includes a self toggling relay and an Arduino-based clap-activated switch that can be used to turn devices on or off remotely. Each project is designed so that anyone can build it. By Tim Blythman Mini projects 54 ESR Test Tweezers Privacy Phones Page 16 ElectroneX 2024 Rosehill Gardens, June 19-20 Page 32 Page 54 ESR TEST TWEEZERS Page 64 MicroMag3 3-axis Magnetic Sensor 2 Editorial Viewpoint 5 Mailbag 31 Subscriptions 90 Serviceman’s Log 96 Circuit Notebook 99 Vintage Radio 106 Online Shop 108 Ask Silicon Chip 82 WiFi DDS Function Generator, Pt2 111 Market Centre This Function Generator provides two wide-range, low distortion outputs and can be controlled from its touchscreen or remotely via a WiFi connection. In this final part of the series we detail building and operating it. By Richard Palmer Test equipment project 112 Advertising Index 112 Notes & Errata This new version of our Test Tweezers line has the handy capability of measuring capacitor ESR (equivalent series resistance) and capacitance. It can do all of this in a compact form factor using just a single 3V cell. By Tim Blythman Test equipment project 68 USB-C Serial Adaptor Despite being introduced nearly a decade ago, many USB serial adaptors with Type-C sockets do not properly adhere to the standard or have driver problems. So we’ve designed a simple project to give you a proper adaptor. By Tim Blythman Computer interface project 74 DC Supply Protectors We have designed three different DC Supply Protectors to help you protect equipment from malfunctioning or incorrect power supplies. They all feature protection from overvoltage and reverse polarity. By John Clarke Circuit protection project 1. USB serial data interceptor 2. NPN/PNP transistor tester 3. Bin reminder using an Arduino 4. Programming a Micromite over Bluetooth HeathKit GW-21A handheld transceivers 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): $70 12 issues (1 year): $127.50 24 issues (2 years): $240 Online subscription (Worldwide) 6 issues (6 months): $52.50 12 issues (1 year): $100 24 issues (2 years): $190 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 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Editorial Viewpoint Avoid cheap extension cords! My wife decided to mow the lawn one day while I was at work, and when I got home, she complained that the plug-in electric mower was not working. She said it just stopped. I was worried that the motor had failed and dreaded having to buy a new one. I took it out, found an extension cord, plugged it in and did a little mowing. It seemed to be working fine (whew!). Imagine my shock when my wife called me at work the next day, panicked because the extension cord had caught fire! When I got home, I found the cord in the state you see in the photo here. I don’t think there was any external damage to the cord. Instead, flexing the cord repetitively caused the internal insulation to break, allowing Active and Neutral to come in contact with each other, causing enough arcing to burn through the outer insulation. This could easily have caused an electric shock had someone come in contact with it in this state. Yes, we have RCDs, and they likely would have prevented serious harm in this case. Still, you can’t rely on an RCD. After all, their typical trip current is 30mA, while the lowest current that has been determined to stop a heart beating is 7mA for three seconds, less than one-quarter of the trip current! We have been using this mower for several years without any other incidents, so I think the fault lies with the cord more than anything else. We also have some thicker, yellow extension cords that hold up to this sort of use case a lot better. They have much thicker and more flexible insulation and probably finer wire strands. We’re only going to use those for mowing from now on. Even if you use the cheaper cords in more static situations, it’s entirely possible that over their life, they will eventually fail from being moved, furled, unfurled etc. Funnily enough, we have some ancient grey extension cords at the Silicon Chip office that are probably more than 30 years old and, except for the brass being a little tarnished, they still seem in reasonable condition and work fine. We have also had reports of cheap power boards and double adaptors failing, so I guess you need to think hard when buying mains accessories to determine if it’s worth the risk of buying the cheapest one you can find. I’m not saying you need to spend heaps on a high-end brand, but perhaps spending another $5 or $10 on that extension cord or power board will get you something a bit safer! by Nicholas Vinen Cover image source: Dan Nelson https://unsplash.com/photos/black-iphone-5-beside-brown-framed-eyeglasses-and-black-iphone-5-c-ah-HeguOe9k Australia's electronics magazine siliconchip.com.au The next discovery is at hand Unearth millions of components for your next design Although Montezuma's treasure remains nowhere to be found, you can find unlimited access to millions of electronic components, from well over a thousand leading brands engineers know and trust. For engineering design it’s pure gold. au.mouser.com 03 9253 9999 | australia<at>mouser.com 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”. Interest in Sputnik I have been catching up on Dr Hugo Holden’s Vintage Radio articles on his fascinating attempt at reconstructing a working replica of the Sputnik transmitter. In part 1 (November 2023, page 100), he explains the progression of events leading to the demise of transmissions. However, I would be interested to know what initiated Sputnik’s transmissions. Given the lead time for launch preparation, stacking, the inevitable weather delays etc, Sputnik must have been inert to avoid running the battery flat. So, what was the trigger that activated it? I can guess several possibilities, but perhaps Hugo can confirm this detail for the benefit of interested readers. Also in the same issue was Dr David Maddison’s continuing series on the History of Electronics, with several mentions of the development of tungsten filament lightbulbs. Readers might find this explanatory historical video of interest: https://youtu.be/ZuhapGSexyg Andre Rousseau, Auckland, New Zealand. Dr Hugo Holden comments: As far as I am aware, Sputnik1 had a switch that was physically deployed when the Satellite separated from the launch vehicle. I have not seen the schematic that includes this switch, the anatomy of the mechanism that deployed it or where it was placed in the satellite body. It was possibly wired in the battery’s common connections, in series with the battery supplies; it could have been a multi-pole switch. In any case, the transmitters were powered/activated (and one would assume the cooling fan battery circuit too) at separation from the rocket/ launch vehicle. Amateur radio is helpful in emergencies I was very pleased to read Dr David Maddison’s comprehensive feature on Amateur Radio in your April 2024 issue. Hopefully, many Silicon Chip readers will be inspired to explore all this great hobby has to offer! However, the section on “Using ham radio in emergencies” might lead some to think that nothing has happened in this regard since 2009. As a member of WICEN NSW Inc, a specialist support squad of VRA Rescue NSW, I have been active much more recently than that. For example, during the Black Summer fires of 20192020, WICEN was deployed around the state to assist the NSW Rural Fire Service (I worked in Bega and at RFS HQ in Homebush), and we supported a NSW Police land search on the Central Tablelands last year. WICEN has also provided communications support for the NSW State Emergency Service and other agencies at siliconchip.com.au various training operations and regularly supports community activities such as Dementia Australia’s Memory Walk and Jog events and so on. While communications technology has improved greatly in the last few years, there are still occasions when Amateur Radio can be usefully applied, as can our skills as communicators. I encourage readers to check out WICEN on Facebook (www.facebook.com/WICENNSW and www.facebook.com/ groups/124735400158) and on Twitter/X (https://twitter. com/wicennsw) to keep up with how Amateur Radio is assisting the broader community. Numerous YouTube channels focus on this aspect of our hobby; for example, Wavetalkers (www.youtube.com/<at> WaveTalkers) and The Tech Prepper (www.youtube.com/<at> TheTechPrepper). These days, it’s not just talking on the radio; digital technology is enhancing the ability of Radio Amateurs to assist in times of need. Richard Murnane, Hornsby, NSW. Comment: thanks for the update. Dr David Maddison got that information from the WIA website at www.wia.org. au/members/emcom/about but, for whatever reason, it doesn’t list any significant events after 2009 despite being updated in 2018. Double-height headers can simplify assembly Regarding the LC and ESR Meter project from the August 2023 issue of Silicon Chip (siliconchip.au/Article/15901), the meter board is fitted with a set of standard header pins, allowing it to be stacked onto the Arduino board’s header sockets. However, the spacing between the two boards with headers is such that the metallic USB Type-B socket on the Arduino board comes very close to soldered tracks on the underside of the meter board. The project’s designer recommends adjusting the headers by pushing the pins through the plastic carrier to give extra extension into the Arduino sockets and then holding the boards apart with spacers. Australia's electronics magazine June 2024  5 , 100% Australian Established 1930 ndard for quality “Setting the sta Owned M SAT. 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I found a better solution; I used a Samtec ‘board stacker’ from Mouser (part number EW-50-10-G-S-200; see the photo). It provides an extra 5mm of space between the boards with header pins that mate fully with the Arduino board. With this solution, the boards are firmly held together, and there’s no need for spacers to hold them apart at the correct distance. Paul Howson, Warwick, Queensland Comment: you can also put an insulating material like electrical tape on top of the USB socket; some sockets come with Kapton tape preapplied to avoid accidental shorting. Getting an Amateur Radio license is now much easier I have purchased Silicon Chip from the first issue (in 1987) and its predecessors from the days of Radio and Hobbies. It maintains such a high standard, although most articles are over my head these days. The articles by Dr David Maddison are first class, particularly the one on amateur radio. I had a licence back in the 1970s, and the hardest part was passing the Morse code test to qualify. I note from David’s article that this is no longer a requirement. Best wishes to you and your staff and keep up the good work. Alex Brown, Camberwell, Vic. An early instance of ‘fixing it in the firmware’ Back in the 1980s, JVC had moved to using microcontrollers in their VHS video machine mechanism controls and got rid of the 4000-series CMOS-based hard-wired logic controllers. In one of their machines, they had made a mechanical design error in the tape transport. The tape was too loose when it unlaced from the head and would sometimes jam in the cassette’s tape door when ejected from the machine, damaging the tape. They cured it with a firmware update that caused one of the reel motors to shuttle for a moment to tighten the tape before the cassette was ejected. This was the first case I know of (and the very thin end of a scary wedge) where firmware was used to mask a mechanical problem. As the years went by, these ‘kludges’ became much more frequent in many machines. The moral of the story is that you have to be familiar with the vagaries of a particular machine, especially if it has electromechanical components, before you can program a good controller. This makes the original code used in such devices even more precious. I doubt if much of the code used in those early microcontrollers still exists anywhere outside the chips, effectively making them irreplaceable. Dr Hugo Holden, Buddina, Qld. Technology hype and the ‘exponential trap’ I read in Popular Mechanics in the late 1950s that there would be flying cars in ten years – they had prototypes. Now, 60 years later, what do we have? Prototypes. Over the decades, there have been revolutions in 3D movies and video technology. Viewing would never be the same. Where is it? Then universal virtual reality was going to revolutionise our lives. Does anyone remember Facebook’s Metaverse? 8 Silicon Chip Five years ago, self-driving cars were on the verge of changing the world. After hype and billions invested, it is now quiet. Following limited trials and features, the problems became intractable. Electronics, sensors, communications, AI and algorithms cannot deal with all the varied conditions, contingencies and unexpected cases. Most companies have abandoned fully autonomous vehicles. There goes my chance to write a country and western hit about a sad bloke whose truck left him! Even Tesla almost admits its cars are not autonomous with the legal ‘cop-out’ that the driver must remain vigilant to take over in a split second when systems inevitably go wrong. There has been remarkable work with generative pretrained transformers (GPTs). Being trained on vast ingested libraries and with enormous processing power, they can do astonishing tricks. These will improve the efficiency of many tasks and potentially bring benefits (and detriment) to society. But calling this Artificial Intelligence (AI) is absolute hype. GPTs have no intellect, they are not cognitive, they lack emotional appreciation, they do not make judgements or build on their own experience, they have no ethics or morals, they do not know what truth is, and they do not understand when they are wrong. They don’t know what is inappropriate or offensive. They will guess but cannot innovate, analyse or create solutions for novel, unforeseen (untrained) scenarios. They do not have insights and cannot discover new concepts. They do not really ‘understand’ anything. GPTs and the other purported AI systems are just supercharged statistical models that happen to mostly give plausible answers. With these and other ‘out-there’ technologies, development gets exponentially more challenging as they proceed. They hit an ‘exponential trap’. Once significant progress has been made, the promise of profits, for example, from autonomous vehicles or ‘genuine’ intelligence, is tantalising. Hype kicks in. Looking backward, an exponential curve is a gentle rise, but looking forward, it is a brick wall. That is the trap. I believe autonomous vehicles have hit the wall. Flying cars, ubiquitous 3D video and virtual reality are struggling. Intelligence is out of reach (even though so-called AI systems have benefits). Recent scare talk of AI’s danger of becoming self-aware and eliminating humans is questionable hype by those who know better. It is a scam to boost publicity and suck in more investors. GPTs cannot become sentient or ‘decide’ they don’t need humans. Giving them nuclear launch codes would be humans, not AI, acting dangerously. However, the real danger from so-called AI is companies and governments that inhale the hype and use AI to do things it should never be used for. How would you like your insurance mysteriously rejected by AI? Nobody has any idea why. No human can follow its logic. Appealing is futile. Neal Krautz, Kedron, Qld. The days of linear TV are numbered I noted that Disney (which owns National Geographic) has retired several of its linear TV channels and variants globally. This has affected Foxtel, which shut down its cable network last year with a move towards streaming. Australia's electronics magazine siliconchip.com.au Introducing ATEM Mini Pro The compact television studio that lets you create presentation videos and live streams! Now you don’t need to use a webcam for important presentations or workshops. ATEM Mini is a tiny video switcher that’s similar to the professional gear broadcasters use to create television shows! Simply plug in multiple cameras and a computer for your slides, then cut between them at the push of a button! It even has a built in streaming engine for live streaming to YouTube! Live Stream to a Global Audience! Easy to Learn and Use! Includes Free ATEM Software Control Panel There’s never been a solution that’s professional but also easy to use. Simply press ATEM Mini is a full broadcast television switcher, so it has hidden power that’s any of the input buttons on the front panel to cut between video sources. You can unlocked using the free ATEM Software Control app. This means if you want to select from exciting transitions such as dissolve, or more dramatic effects such go further, you can start using features such as chroma keying for green screens, as dip to color, DVE squeeze and DVE push. You can even add a DVE for picture media players for graphics and the multiview for monitoring all cameras on a in picture effects with customized graphics. single monitor. There’s even a professional audio mixer! Use Any Software that Supports a USB Webcam! You can use any video software with ATEM Mini Pro because the USB connection will emulate a webcam! That guarantees full compatibility with any video software and in full resolution 1080HD quality. Imagine giving a presentation on your latest research from a laboratory to software such as Zoom, Microsoft Teams, ATEM Mini Pro has a built in hardware streaming engine for live streaming to a global audience! That means you can live stream lectures or educational workshops direct to scientists all over the world in better video quality with smoother motion. Streaming uses the Ethernet connection to the internet, or you can even connect a smartphone to use mobile data! ATEM Mini Pro $495 Skype or WebEx! Learn more at www.blackmagicdesign.com/au That aligns with consumers preferring the ‘on-demand’ model over linear TV. According to news reports, DirecTV has declared an end to new satellite launches; they and others have the opportunity to improve capacity and quality by phasing out certain older technologies on cable and satellite. They are noting the preference towards high-definition and are moving on-demand broadcasts, such as pay-per-view movies and sporting events, to online streaming. Several satellite Pay TV providers, such as SkyLife in South Korea, no longer use technologies older than MPEG4 and DVB-S2. That is in contrast to others, such as Foxtel, Sky UK, and DirecTV, who are still using older compression schemes. Most receivers that can only handle the older technologies are over 10 years old now. Bryce Cherry, via email. Home for unwanted Silicon Chip magazines About a year ago, I started reading Silicon Chip and have very much enjoyed it. I soon discovered that the local library had Silicon Chip magazines from 2022 and is still getting new ones. I borrowed all of them and have just about finished reading them. If anyone has Silicon Chip magazines to give away from January 1998 up to December 2021, please email Silicon Chip and ask them to pass the message on to me. Danni, “the inventor dude”, via email. PA equipment for sale My friend and I have a quantity of public address equipment for sale. It includes PA amplifiers, transformers, horn speakers, column speakers, a large quantity of cable, microphones and microphone cable rolls and stands, and an old telephone system. The lot can be had for $3000. If you are interested, email Silicon Chip, and they will forward your enquiry to me, or call Brian on 0411 791 991. Russell Soutar, via email. Details on how a thermocouple works In the article on the K-type Thermocouple/Thermostat in the November 2023 issue (siliconchip.au/Article/16013), you state that “A thermocouple works because the junction of two dissimilar metals produces a voltage that is dependant on temperature” (p51). I believe that is incorrect. According to Wikipedia (https://w.wiki/9vVo), “The Seebeck effect is the electromotive force (emf) that develops across two points of an electrically conducting material when there is a temperature difference between them.” The temperature difference between the ends of the wire generates the voltage, not the presence of a junction. The problem then arises of how to connect to both ends of the wire to measure the voltage without producing a similar voltage that exactly cancels the voltage you want to measure because the temperature difference between ends of the return wire will be about the same as that of the measurement wire. The solution is to use an alloy for the return wire that exhibits a Seebeck coefficient that tracks the temperature variations of the Seebeck effect of the measuring wire. Unfortunately, this scuppers my plans of patenting the tungsten-tungsten thermocouple for very high-­temperature measurements! 10 Silicon Chip 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+ $13.95 EA. BUY 4+ $12.45 EA. BUY 10+ $10.95 EA. 99.8% 300g Aerosol NA1067 BUY 1+ $15.95 EA. BUY 4+ $13.95 EA. BUY 10+ $12.45 EA. 70% 1 Litre Bottle NA1071 BUY 1+ $21.95 EA. BUY 4+ $19.45 EA. BUY 10+ $17.45 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+ $24.95 EA. BUY 4+ $22.45 EA. BUY 10+ $19.95 EA. 4 175g Aerosols Contact Cleaner Lubricant NA1012 Electronic Cleaning Solvent NA1004 BUY 1+ $13.95 EA. 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Jaycar reserves the right to change prices if and when required. 1800 022 888 I point this out because electronics magazines like yours were a significant source of my electrotechnical knowledge, including EA, ET, ETI, AEM, WW, EW+WW etc. Yes, I went to uni too (two, in fact) and spent years at tech. Still, magazines such as yours might have been about the greatest contributor to my technical knowledge, along with experience, and certainly to my enthusiasm for electronics. So, I would like to think that readers, especially electronics novices, don’t get misinformed, especially if they intend to apply that knowledge in the real world. Phil Denniss, Darlington, NSW. Possibly dangerous speed limit signs I have noticed that the variable speed limit signs used in Victoria, the type that looks like an electronic version of an ordinary speed limit sign with a red circle and numbers in the middle, have a failure mode in which they rapidly flash. This is not only annoying and distracting to motorists but potentially dangerous to the health of specific individuals. According to the Epilepsy Foundation in the United States (siliconchip.au/link/abv7), a light flashing between 5Hz and 30Hz can trigger a seizure in susceptible individuals. Efforts should be made to design circuitry so this failure mode does not occur. Editor’s note: according to Wikipedia, 1 in 4000 people are susceptible to light-induced seizures. One episode of the Pokemon cartoon shown on TV in Japan led to 685 children being hospitalised due to a red/blue flashing pattern at 12Hz. Symptoms included blurred vision, headaches, dizziness, nausea, seizures, temporary blindness, convulsions and unconsciousness – see https://w.wiki/9vUt On analog computers, repairability etc Please consider viewing the following videos about analog computers if you have not already seen them. Analog computers are being considered for operations that do not require high precision since they can have both greater speed and substantially lower power consumption than digital computers. If many of the current operations of digital computers are changed to analog operations, then significant power savings can be made. Derek Muller produced two YouTube videos about the return of analog computers, “The Most Powerful Computers You’ve Never Heard Of” at https://youtu.be/IgF3OX8nT0w and “Future Computers Will Be Radically Different (Analog Computing)” at https://youtu.be/GVsUOuSjvcg Battleships used to have mechanical computers to aim their guns, known as directors. They were also used for anti-aircraft guns as well, and similar devices were used for bomb aiming in aircraft (for example, the famous Norden Bombsight). If you thought that these devices were not as good as our modern digital computers, I suggest reading the article “Gears of war: When mechanical analog computers ruled the waves” at siliconchip.au/link/abv8 The “gods” of electronics and digital computing would be humbled if they existed. On another topic, I had an interesting problem charging a couple of Li-ion battery powered LED torches. Normally, the charge state would be displayed by four blue LEDs, with all four on when fully charged and the LEDs progressively 12 Silicon Chip Australia's electronics magazine siliconchip.com.au turning on and flashing as the cells charge from low to fully charged. However, the LEDs flashed erratically while charging from a 5V plugpack supply with a constantly lit power LED. My first thought was that the torches were faulty, but two torches malfunctioning simultaneously seemed strange. The power supply was plugged into a side-by-side double adaptor, so I plugged it directly into the wall socket instead, and the charging behaved correctly. There was something amiss with the double adaptor. When I opened it, I could see nothing wrong. Out of curiosity, I pushed the plugpack pins through the socket holes of the front plastic casing of the double adaptor, and then I saw the problem. The pins only protruded about 5mm past the plastic moulding and could only just touch the brass sockets in the double adaptor. I assumed that after many plug insertions, the little contact that was there when new had worn away. This is either planned obsolescence or just a bad design. Whatever the reason, I wonder what would have happened had they been owned by a non-technical person. I became curious about the cell arrangement in the battery packs of Tesla cars and found a web page with a good description. It is fascinating and, at the same time, a warning to anyone who thinks that they can reuse old Tesla batteries easily. The article can be viewed at siliconchip. au/link/abv9 Now I have a whinge. Why is there so much electronic kitsch in the world, particularly in Australia? Why are ordinary appliances ‘enhanced’ when there is no need; usually, the ‘enhancements’ are the addition of options that make the device more difficult to configure and use. I know that the answer from one of my mates would be, “because they can”. I just witnessed a perfect example with one of my elderly neighbours. She bought a 6kW air conditioning system and the day after its installation, it appeared not to be working. Luckily for her, I went to see the new A/C and found her almost in tears. She had asked the installers to set it up, but they were unable or unwilling to do that, and it was left running with unknown settings. The manufacturer of the A/C is a huge company that produces some of the best electronics in the world, yet they cannot produce a human-friendly remote control. It has many well-defined buttons but an LCD that is almost illegible. Haven’t they heard of e-paper displays? Then there is the user manual; I am sure it would win an award in a puzzle contest. Obviously, the operation of the A/C is a trade secret and must not be divulged in any form. Between tiny, almost illegible symbols on the Silicon Chip kcaBBack Issues $10.00 + post January 1997 to October 2021 $11.50 + post November 2021 to September 2023 $12.50 + post October 2023 onwards All back issues after February 2015 are in stock, while most from January 1997 to December 2014 are available. For a full list of all available issues, visit: siliconchip.com.au/Shop/2 PDF versions are available for all issues at siliconchip.com.au/Shop/12 We also sell photocopies of individual articles for those without a computer 14 Silicon Chip remote’s LCD and the lousy user manual, no wonder she was flummoxed. After some time, I was able to decipher the instructions and explain how to operate the basic controls to her. I did not even bother with the rest of the options – they would have only confused her! As I get older, I want things that are simple to use. I will not even consider anything that has a large number of options and/or extras. If I cannot buy what I want, I do without or make my own. For example, I was looking for a new van or ute. Except for some overseas models, everything I saw was loaded with electronics that were unnecessary for operating the vehicle. I would be paying for many things I do not need. The marketers would say that the extras are free. BS! Everything has a cost of manufacture, and everything costs money to service and repair. An example is the electric door lock on a car. They are not necessary but are convenient. One of my friend’s door locks failed; the replacement cost was $700! Thankfully, an imitation part could be made using a 3D printer at a fraction of the cost. If anyone wants to see what the future holds for Australia after being flooded with this rubbish, just look at the Russian/Ukrainian war. Ukraine has been supplied with very high-tech tanks that must be sent back to the donor countries because Ukrainians cannot repair or service them, even though they are tech-savvy. I wonder if anyone in the government or the various oversight organisations has ever considered the ramifications of this complex technology. There have already been documented cases where large militaries (eg, in the USA) cannot fix their own equipment and have to send it back to the manufacturer due to the use of ‘proprietary technology’. How would that work during wartime? That is described in the article at siliconchip.au/link/abva It has always been said that high technology would improve our lives, which is true in many cases, but little is said of the huge maintenance and repair costs accompanying it. George Ramsay, Holland Park, Qld. Vintage RTV&H Oscilloscope article enjoyed It was a pleasure to read Ian Batty’s article in the May 2024 issue on the 1963 Radio, TV & Hobbies 3in cathode-ray oscilloscope (CRO) design (siliconchip.au/Article/16259). I built one in the early 1970s as my first major project. The kit came from All Electronic Components in Melbourne’s CBD and cost just over $100. I used that oscilloscope until I bought a commercial 5-inch unit from Ellistronics late in the same decade. Sadly, neither of those excellent electronic retailers is with us anymore. My CRO is in very good physical condition and still sits proudly on a shelf in my workshop. It has one minor modification: I replaced the probe input socket with an RCA connector. It was in good working order when it was last switched on several decades ago. I would be happy to donate it to a good home, but it would need to be picked up in South East Melbourne as I’m not sure it would survive the rigours of transport by courier. [Editor’s note: email us at silicon<at>siliconchip.com.au if you are interested and we’ll forward it to Richard] Richard Palmer, Murrumbeena, Vic. SC Australia's electronics magazine siliconchip.com.au A selection of our best selling soldering irons and accessories at great Jaycar value! 25W Soldering Iron TS1465 $22.95 Build, repair or service with our Soldering Solutions. We stock a GREAT RANGE of gas and electric soldering irons, solder, service aids and workbench essentials. 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Jaycar reserves the right to change prices if and when required. 1800 022 888 Privacy Phones By Dr David Maddison, VK3DSM The modern smartphone can be very useful, allowing you to look up information just about anywhere, navigate to unknown places, take photos, watch videos, send and receive messages and more. It can also let all sorts of entities track you, from megacompanies like Google, Meta (Facebook), Microsoft and Apple to phone companies, the government & even criminals. What can you do about that? Image source: Dan Nelson – siliconchip.au/link/abv2 O ne of the things you can do is use a ‘privacy phone’, a smartphone designed to reduce the ability for third parties to track you. Note, though, that there’s no way of stopping phone companies or the government from tracking you if you have a mobile phone. Such devices are therefore mainly focused on preventing the harvesting of your personal information by ‘big tech’ (generally regarded as Google, Apple, Microsoft & Meta). It is possible to buy a privacy phone but you can also turn certain brands and models of Android phones into a privacy phone yourself. Information that ‘big tech’ gathers includes your location, how often and when you visit such places, what you search for, what videos you watch, who your contacts are, the contents of your text messages or emails and any other information that may be used to target you for particular types of advertising or services, or to sell to third parties for profit. 16 Silicon Chip Some information they harvest might also be passed onto the government in response to a warrant (or possibly without one, depending on their ethics or lack thereof). Have you ever used a popular search engine to search for a product or service and then found yourself bombarded with advertisements on social media, video platforms, or other search results for that product? It’s a commonly reported situation that demonstrates how much information is being collected. Before we get to the phones and software that can improve your privacy, let’s examine why that is a good idea. It’s important for us to state that while we do our best to make these articles comprehensive, we cannot cover every single edge case. What information is collected about you? Just about any information entered via your phone or computer is liable Australia's electronics magazine to be collected and used (or misused) by third parties. Apart from the examples mentioned above, that includes (but is not limited to): ● Name ● Email address ● Birth date ● Gender ● Phone number ● IP address(es) ● Places you visit ● Your interests, based on your web history, search history and the content of anything you post or even what is included in private emails ● Your political & other affiliations ● Websites you visit ● Videos you watch ● People you engage with ● Device information such as type, operating system (OS), type of browser and other apps ● Cookies stored by your web browser ● Which advertisements you watch or ignore siliconchip.com.au Are privacy phones liable for misuse? Any technology is open to abuse. Those with nefarious intentions certainly might benefit from phones (and other devices) that limit monitoring and eavesdropping. However, the main beneficiaries of privacy phones are intended to be normal, regular people. You don’t have to be an ‘interesting’ or high-profile person for your data to be routinely vacuumed up and stored, to be possibly used or misused in the future. In this article, we discuss the types of information that might be collected about you and what you can do to enhance your privacy. ● Which advertisements you click on ● The contents of messages, chats etc Where is your private data intercepted? Your data can be intercepted on the phone network, the web servers you access, or via apps you use, such as social media or search engines. A mobile phone connects to the world via two channels. One is the telephone network (via a mobile phone tower) for voice traffic and SMS (text messages). The other is via the internet (either via a tower or WiFi) – see Fig.1. It is possible for data to be intercepted over either network, although it more commonly occurs on the internet. Voice calls can be made over the mobile or PSTN (publicly switched telephone network) telephone network or using VoIP (voice over internet protocol), an application of SIP (session initiation protocol). The latter calls are made via the internet and do not require a mobile connection if WiFi is available. A VoIP phone on a private network can make calls to regular PSTN numbers using a SIP trunk provider. Big tech social media and search engines log your activities, which is probably the most common way your data is harvested. Note also that anything you say in a video that’s posted publicly (eg, on YouTube or Facebook) is also converted to text, which can be read by humans or artificially intelligent (AI) bots. Text in photos you post can also be converted to text and scanned. Photos you post or store ‘in the cloud’, or even those stored on your mobile device, can also have facial recognition applied, and they can figure out who the people are in your photos and thus form associations between you and others. siliconchip.com.au It isn’t just big tech that can intercept your data; state actors or malicious hackers can too. All phone call and text message ‘metadata’, such as who called whom, when, where, call duration and other parameters, are routinely collected. In Australia, it is a government requirement. The EU tried implementing similar data-gathering methods, but they were not well-received. The following 11-year-old video on the topic drew a lot of attention to phone privacy issues. It is named “Malte Spitz: Your phone company is watching” and can be viewed at https://youtu.be/Gv7Y 0W0xmYQ Why some apps are free Nothing is truly free and phone apps are no exception. Except for open-source software, if an app is free, that is probably because your data is being collected and sold through the app. Most private data that’s sold was actually handed over willingly by the subject, knowingly or unknowingly! Most apps downloaded via the Google Play Store or Apple App Store are required to show what data they collect. We do not deny that Google, Facebook and others offer valuable services. For many or even most people, the harvesting of your data is the price you pay for the services provided; some even appreciate the targeted advertising that results. These multi-billion-dollar companies have to earn an income somehow. Facebook We are not singling out Facebook but it is a widely used app that provides a good example of the sort of information of interest to social media businesses. Facebook uses machine learning to analyse your activities on Facebook and generate ads based upon such criteria as: ● What you have ‘liked’ ● Which ads you have clicked on ● Your activities on Instagram ● Age, gender, location and the devices you use to access Facebook ● Information that advertisers, their partners and marketing partners share with Facebook that they already have, like your email address and your activity on websites and apps off of Facebook If you wonder why you saw a particular ad on Facebook, you can click on the three dots and click on “Why am I seeing this ad?” to see why Facebook targeted it at you. For further information on this, see siliconchip. au/link/abv1 Facebook also analyses the content of your photos. For every photo a user uploads, it is said they identify people, objects, background scenes, the moods of people and their postures, animals (see Fig.2), location such as inside/outside, the geographic Fig.1: the basic configuration of a mobile (cellular) communications network. Original source: https://doi.org/10.3390/s23010352 (CC-BY-4.0). Australia's electronics magazine June 2024  17 Fig.2: examples of Facebook AI recognising animals in photos. Source: www. digitaltrends.com/web/facebook-ai-image-recognition/ location, activities such as relaxing by the pool. They store all the detected characteristics in an associated file (see siliconchip.au/link/abud). Facebook also uses its DeepFace facial recognition engine (Fig.3), which is said to be more accurate than the FBI’s. It can be used to tag friends in photos and can also detect if someone has stolen your profile photo, among other uses. Facebook uses AI to detect and delete inappropriate photos; they say they don’t use the phone’s microphone or text messages to generate ads. Facebook marketing tools allow the promotion of products according to: ● Region or population density ● Age, gender, marital status, family status and occupation ● Brand loyalty or user status ● Social status (eg, lower, middle or upper class) ● Interests, according to keywords used in searches ● Interests that intersect with the common pursuits of a chosen group That indicates the level of information being collected (see siliconchip. au/link/abus). Creating a social network map can also be valuable for marketers (see siliconchip.au/link/abuz). Google Again, we are not singling out any one company, but Google’s business model is based on harvesting data from users and selling it to advertisers. Google (and others) also harvest location data via SUPL (Secure User Plane Location) – see siliconchip.au/ link/abur Does big tech listen in on you for marketing purposes? Fig.3: Facebook’s DeepFace image recognition engine is said to be more accurate than the FBI’s. Source: www.facebook.com/photo?fbid=689135484598987 18 Silicon Chip Australia's electronics magazine Facebook and Instagram write: “We understand that sometimes ads can be so specific, it seems like we must be listening to your conversations through your microphone, but we’re not. We only use your microphone if you’ve given us permission and are actively using a feature that requires the microphone.” If you use Google Assistant, your phone is always listening and waiting for commands. However, Google says it does not listen to conversations to generate targeted advertisements. The Amazon Alexa is an example of a device that did use recordings to generate targeted adverts: siliconchip. au/link/abv0 siliconchip.com.au This is a contentious issue. Some people do not believe these denials. Others believe them and say that these companies know so much about you that their accurate predictive advertising makes it seem like you are being listened to. Apple While they have been criticised for various reasons (including by us in the past), Apple has pretty good privacy protections. They do not sell your data to advertisers, although they may use it internally. They offer end-to-end encryption on cloud services, do not embed trackers in third-party websites like Google, tracking between apps is ‘opt-in’, and they have many other privacy and security features (see siliconchip.au/link/abut). On the other hand, Apple’s phones are more expensive than many Android phones, and it seems they want you to replace them as often as possible (eg, by locking you into using their expensive replacement parts, including batteries). An iPhone can be de-Googled if you change the default browser to Safari and choose a privacy-focused search engine. If you use any app that uses Google for advertising, you will be connected to Google, although you can select “Ask App Not to Track”. Apple provides information about privacy and location services in iOS, iPadOS and watchOS at https:// support.apple.com/en-au/102515 For maximum privacy on Apple phones, it is important that you turn off settings that may compromise your privacy. Apple maintains that they have no ‘backdoor’ to decrypt data on an iPhone, not even in cases of national security: Apple has never created a backdoor or master key to any of our products or services. We have also never allowed any government direct access to Apple servers. And we never will – www. apple.com/privacy/governmentinformation-requests/ Security expert Rob Braxman has an alternative viewpoint. He says that Apple’s use of AI and ‘client-side scanning’ can reveal the contents of a phone before encryption. For example, a description of the content of certain photos might be generated by the phone, such as a person matching a particular description. siliconchip.com.au How much does privacy matter (to you)? Some people may be unconcerned with privacy issues and do not want a privacy phone or enhanced privacy on an ordinary phone. Everyone has their own opinion on such matters. After all, some people keep their windows covered at all times, while others leave the blinds open, even at night. Edward Snowden said, “Arguing that you don’t care about the right to privacy because you have nothing to hide is no different than saying you don’t care about free speech because you have nothing to say”. Most philosophers consider privacy a basic human right in a free society. Article 12 of the United Nations’ Universal Declaration of Human Rights states, “No one shall be subjected to arbitrary interference with his privacy...”. Even if you aren’t concerned about what big tech is doing with the data they gather on you, consider what would happen if they are hacked and the data makes its way onto the ‘dark web’ (as seems to happen often). The people who ultimately get a hold of that data may not have the best ethics or morals... In theory, that could be passed onto authorities, not necessarily benign ones, in the case of a dictatorial country. For more on this theory, see his video titled “Apple Now Has a Backdoor to Bypass Encryption!” at https:// youtu.be/Mg4HWEdar2Q Also see his video channels at: • www.youtube.com/<at> robbraxmantech • https://odysee.com/<at> RobBraxmanTech:6 • rumble.com/c/robbraxman Location tracking Your location is a valuable commodity to marketers. ‘Geofence marketing’ or geomarketing is a type of location-based marketing that targets consumers once they enter a particular geographically defined area (see Fig.4). You could receive advertisements via SMS, push notifications, Facebook advertisements or other advertisements describing promotions on offer in the area they have entered. The user’s location is tracked via a phone’s GPS, WiFi, Bluetooth or RFID. The consumer would (possibly unknowingly) have given permission for their location to be shared by various apps they use. Even after you have left a geofenced area, you may continue to receive advertisements because you have shown an interest in that area. This period may be up to 30 days (as per siliconchip.au/link/abuu). Google offers its customers a Geofencing API (application programming interface) to assist marketers in tracking customers. With a non-privacy phone, you are liable to give away location data that Fig.4: an example of geofence marketing by Propellant Media. Source: https:// propellant.media/geofencing-marketing-company-providers/ Australia's electronics magazine June 2024  19 Avoiding telemarketing calls and scams One way to enhance your privacy is to prevent telemarketers, scammers and others from getting your phone number. For some advice on how to achieve that, see www.acma.gov.au/make-your-phone-number-more-private can be used for marketing. Even if you turn location tracking off, your device can still be tracked by its IP address unless you use a VPN. If you use aeroplane mode, you can avoid being tracked, but you will also be unable to make or receive calls or use apps. In the USA, the FBI used geofencing to identify alleged rioters. Geofencing can also send notifications if a child with a device leaves a designated area. It can be used by home automation systems to turn appliances on or off when you arrive at home or leave. Certain car manufacturers such as BMW, Mercedes, Tesla and VW use geofencing to send the owner an alert if the car is moved. For more details, watch Naomi Brockwell’s video titled “You’re LEAKING Your LOCATION!” at https://youtu.be/A9DPDE0FZeQ reading, activities such as being at a gym or based on the videos you have been watching. Predictive advertising Privacy-respecting search engines ● Brave Search: https://search. brave.com/ ● Disconnect Search: https://search. disconnect.me/ ● DuckDuckGo: https://duckduckgo. com/ ● Gibiru: https://gibiru.com ● MetaGer: https://metager.org Google and Facebook generate ads according to your search history, browsing history and profile. They use machine learning to ‘know’ more about you the more you use the platforms by observing your behaviour and travels. They can target advertisements depending on what you are Enhancing your privacy Many people are fine with big tech collecting information about them, but what can you do if you don’t want to become a ‘data mine’? The main things you can do are to stop using certain apps, use a phone where the ability to harvest your data has been removed at the operating system level (a privacy phone) and use a VPN. Stop using certain apps Privacy experts say that the first step to privacy is to stop using Google services, any apps that use Google advertising services and Facebook. It is also essential to use privacy-focused search engines, email and browser apps. Fig.5: features of the privacy-focused Proton Mail service. 20 Silicon Chip Australia's electronics magazine ● Mojeek: www.mojeek.com ● Qwant: www.qwant.com ● searX: https://searx.thegpm.org ● Startpage: www.startpage.com ● Swisscows: https://swisscows. com/en Be aware that search results from big tech search engines like Google typically have built-in biases and rank the search results accordingly, not necessarily in terms of the truth of answers (eg, they will put advertisers at the top of the results, even if they are less relevant to your search terms). Privacy-respecting email services ● ProtonMail: https://proton.me/ mail (free for small users; see Fig.5) ● Tuta: https://tuta.com (also free for small users) ● Posteo: https://posteo.de/en ● Private-Mail: https://privatemail. com ● StartMail: www.startmail.com ● CounterMail: https://countermail. com Note that if you send an email from one of these services to, say, Gmail, Google will still know its contents. Privacy-respecting browsers Some browsers, especially popular ones like Chrome, send information to websites you visit, including what hardware you use – see Fig.6. Cookies are downloaded by your browser when you visit a website. Notionally, they store preferences, login details etc, but they can also be used to track you across websites. Some browsers have settings to block ‘tracking cookies’ or will do it by default. Apple’s Safari browser (www. apple.com/au/safari/) is considered a privacy-­focused browser, but it is closed source and no longer available on Windows. Brave browser (https://brave.com/) is the best, according to Naomi Brockwell (www.youtube.com/<at>Naomi BrockwellTV & https://odysee.com/<at> NaomiBrockwell:4). You can watch her video titled “ESSENTIAL Privacy Tools” at https://youtu.be/V6yu0JN NtRw Firefox (www.mozilla.org/en-US/ firefox/new/) has features like cookie blocking, privacy extensions and settings, including a “Facebook container” to make it harder for Facebook to track users. There is also Tor (www.torproject. org), but it is slower than most normal siliconchip.com.au browsers. There are also many variants of existing browsers like Ungoogled Chromium, GNU IceCat etc. Privacy-respecting messaging apps Signal (https://signal.org) is regarded as a private and secure free messaging app. Alternatives include Telegram. Using a privacy phone The general consensus among privacy experts is that you should use a ‘de-Googled’ (privacy) phone and apps. They also say not to use social media apps; after all, the purpose of social media apps is to publicise you, not keep you private. A ‘de-Googled’ phone is usually an Android phone with Google services removed. The Android operating system was developed by Google and is based on Linux. It is available in two versions: the free and open-source Android Open Source Project (AOSP), or the non-open source version built into most phones, containing closedsource code such as Google Mobile Services. Google Mobile Services includes Google Search, Chrome, YouTube, Google Play, Google Drive, Gmail, Google Meet, Google Maps, Google Photos, Google TV, YouTube Music and Firebase Cloud Messaging. All of these apps are removed from privacy phones. Not all Android phones can be de-Googled. You need a phone where the existing operating system can be replaced with a non-Google version of Android. We will discuss that shortly. Fig.6: a comparison of web browser privacy features using the default settings. Source: https://brave.com Using a VPN Privacy phones A VPN (virtual private network) is a service through which you route your data instead of via your own ISP (internet service provider). Your data passes through an encrypted tunnel to the VPN server, so its contents are kept secret. It is then decrypted and routed through the internet from their end, then routed back to you through the same encrypted tunnel. VPNs are often used as a privacy measure as they obscure the source of the internet traffic. They can also allow you to access ‘geo-blocked’ content, like videos, that can’t be accessed from your country. Some people seem to think that using a VPN ensures your privacy, but really, it’s only a small part of the puzzle. VPNs have to be chosen well, as Some phones are manufactured as privacy phones, while others are standard phones with a new OS installed. One solution adopted by many users who want privacy is to use a ‘dumb phone’, much like the original mobile phones. One downside of not owning a smartphone is that it makes certain transactions impossible. For example, many shows or events now require the presentation of an electronic ticket. No paper ticket is offered, so you must possess a smartphone for entry. Your old dumb phone is not likely to be usable now as it probably used 1G, 2G (GSM) or 3G have limited or no support now. Examples of dumb phones that support 4G or 5G and are available for purchase in Australia siliconchip.com.au stated by Naomi Brockwell. She suggests using a Swiss-based VPN like ProtonVPN as they have strong privacy laws. Her video titled “The DARK side of VPNs” can be viewed at https:// youtu.be/8MHBMdTBlok Also see siliconchip.au/link/abux (PDF) and siliconchip.au/link/abuy (how to bypass geo-blocking for online shopping and streaming by Choice). Mullvad VPN (https://mullvad. net) can also be a good choice due to not requiring any details to make an account and being payable in cash. Australia's electronics magazine are the Nokia 8210 4G (Fig.7), Nokia 105 4G; Nokia 2660/2720/5710, Cat S22 Flip, Opel Mobile Lite (and similar models), Aspera F46/F48/R40 and Uniwa V202T. Purpose-built privacy smartphones Some phones that are purpose-built with privacy in mind include: ● The Bittium Tough Mobile 2C (Fig.8, siliconchip.au/link/abue) has Android 11 (the latest version is 14) with enhanced security, with or without Google Mobile Services, and data is strongly encrypted. It has a backup battery, so tampering can be detected even with a flat main battery, including Fig.7: the Nokia 8210 4G ‘dumb phone’. This classic design has been updated to support 4G networks. Source: https://w. wiki/9qRW (CC-BY-SA 4.0). June 2024  21 physical intrusion. The microphones, Bluetooth and camera can be disabled with a button press. ● The ClearPHONE (Fig.9, www. clearunited.com) runs the de-­Googled ClearOS, based on Android 10 but with a private key. There is more information in this video: siliconchip.au/ link/abuf ● The KryptAll K iPhone (Fig.10, www.kryptall.com) strongly encrypts voice calls and is said to be used by heads of state. It appears to be an Apple iPhone with modified firmware. ● The Purism Liberty Phone (Fig.11, https://puri.sm/) runs the de-Googled PureOS. They also make privacy-­ focused tablets and portable computers. ● The Murena 2 (Fig.12, siliconchip. au/link/abug) is a privacy smartphone that uses the de-Googled /e/OS. They write, “Murena aims to free people from the Big Tech control over our personal data.” ● Punkt (Fig.13, www.punkt.ch/ en/) makes the MP02, a “minimalist phone” reminiscent of a dumb phone. However, it can share a data connection with a laptop or other device and make encrypted VoIP voice calls using the Signal protocol. They also make the MC02 “smarter phone” (Fig.14), which resembles a traditional smartphone and uses the de-Googled Apostrophy OS or AphyOS. ● The UP Phone (Fig.15, www. unplugged.com) runs a proprietary version of the de-Googled LibertOS. It is to be released in May 2024. They write, “The company is on a mission to stem the tide against Big Tech and Big Government, by making privacy accessible and convenient for everyone”. Phones that can be turned into privacy phones While we know it is challenging to modify iPhones, many Android phones also cannot be easily altered. Generally, to make a phone into a privacy phone, it must have an unlocked bootloader. Some phone brands with that capability are easier to modify than others; see the list at https://w. wiki/9qQk Surprisingly, Pixel phones from Google are said to be the best for installing custom privacy-focused Android OSs, a process known as installing a custom ROM. Which phones can be de-Googled also depends on the version of the privacy OS that is to be used. Each operating system has a website with a list of compatible phones (see below). Buying a de-Googled phone If you don’t want to be involved in the (possibly) challenging process of installing custom firmware on a phone, many companies sell new phones, such as the Pixel, with the process already done for you (see Fig.16). If you are interested in that, try searching for “privacy phones Australia” (without quotes) via DuckDuckGo or Google. Three we found (but have not purchased from) are: • aussecurityproducts.com.au • privacyphone.com.au • threecats.com.au Privacy Android OSs Here are some options to consider if Fig.15: the UP Phone runs a proprietary version of LibertOS. you want to reflash your phone with a privacy OS. Before making any changes, make sure you research the consequences of doing so and back up all your important data beforehand! If something goes wrong when reflashing your OS, it may be possible to ‘brick’ your device. If that concerns you, buying a pre-made device is probably a better option. The following are all open-source and free to use: ● CalyxOS (https://calyxos.org) supports some Fairphone, Pixel and Motorola phones. It is open-source and free. ● Divestos (https://divestos.org) supports many devices; see https:// divestos.org/pages/devices ● /e/OS (https://e.foundation/eosphone-welcome) is a fork of LineageOS. It supports some Gigaset, Fairphone, Samsung, Pixel, OnePlus and Teracube phones. ● GrapheneOS (https://grapheneos. org) only officially supports Google Pixel devices. Figs.8-12 (from left-to-right): the Bittium Tough Mobile 2C privacy phone runs Android 11 with enhanced security; the ClearPHONE runs ClearOS, which is based on Android 10; the KryptAll K iPhone is unusual in that it appears to be an Apple iPhone with its firmware modified to improve privacy and security; the Purism Liberty Phone runs PureOS, which is based on Linux (Android is as well); the Murena 2 runs /e/OS, a fork of LineageOS which, in turn, is based on Android. 22 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.16: a deGoogled Pixel phone with Proton and other privacyrespecting apps. Source: https:// threecats.com.au/ degoogled-pixelgrapheneos-userguide Fig.17: a screen grab of the Magic Earth mapping and navigation software. ● Iodé (https://iode.tech/iodeos-en) is a fork of LineageOS. It supports a variety of phones. ● LineageOS (https://lineageos.org) is based on Android and supports a large number of devices, not just phones; see https://wiki.lineageos. org/devices/ ● PureOS (https://pureos.net) is a version of Linux, not Android ● Sailfish OS (https://sailfishos.org) is Linux-based and has some closedsource, non-free components ● Silent OS (siliconchip.au/link/ abui) is an Android-based OS that appears to be for enterprise users, but we could find little information on it. ● Ubuntu Touch (https://ubuntutouch.io) is a mobile version of Linux. It supports various devices, including some phones – see https://ubports. com/nl/supported-products The following are not open-source nor free: ● Apostrophy OS (or AphyOS) is based on GrapheneOS; the only phone that uses it is the Punkt. ● CopperheadOS (https://copper head.co/android/) supports Google Pixel devices. Fig.13: the Punkt MP02 is similar to a dumb phone, but it can communicate with a portable computer and make encrypted VoIP voice calls via Signal. Fig.14: also from Punkt, the MC02 “smarter phone” is a smartphone that runs Apostrophy OS. siliconchip.com.au Australia's electronics magazine Using a de-Googled phone The phone service is not affected in a de-Googled phone but no Google apps will be provided. You will still be able to use Google search via a web browser, or you can use the alternative search engines mentioned earlier. To replace the missing Google apps, you can use: ● Newpipe (https://newpipe.net) is an open-source client that can be used to watch YouTube videos, although you cannot upload videos or comment on them. It also supports certain other streaming platforms ● K-9 Mail (https://k9mail.app) is an open-source email client that can read Gmail emails or other services. ● Nextcloud (https://nextcloud. com) is an open-source content collaboration platform that can be used as a substitute for Google Drive, Contacts, Calendar, Photos etc. ● Google Maps can be used in a browser window, but it does not work as well as the app. ● GmapsWV (siliconchip.au/link/ abuj) loads the Google Maps web page in a WebView and doesn’t need any Google services on your phone. ● OpenStreetMap (www.open streetmap.org) uses crowd-sourced maps stored in your phone. ● Organic Maps (https://organic maps.app) also uses OpenStreetMap maps. ● Another option for mapping is Magic Earth (see Fig.17). Gmail and YouTube can still be used via a browser without an app on a de-Googled phone, although some other apps no longer allow a browser option. Waze works on a de-Googled phone. App stores Google Play Store is not present on de-Googled phones but Android apps do not have to be downloaded from Google. Alternative app stores like June 2024  23  : the privacy phone that was a trap We covered this story in our December 2021 article on “Big Brother Is Tracking You!” (siliconchip.au/Series/373), but it’s so relevant that we thought we’d mention it again. In 2021, an international consortium of police, including the FBI, European police agencies and the Australian Federal Police (AFP), arrested over 800 criminals in 16 countries in a sting. They managed to sell them supposedly anonymised phones with the encrypted “Anom” app. The phones and app were specifically marketed toward criminals and only criminals could buy the phones and app which required approval from other criminals. Anom was like a criminal version of WhatsApp. The app was written by Australian police and the FBI, enabling police to monitor and target organised crime, drug trafficking and money laundering activities worldwide. The criminals did not know that every single one of their messages on the app was fed back to law enforcement officials. The FBI’s name for the operation was Operation Trojan Shield, while Australian law enforcement called it Special Operation Ironside. About 50 such phones were sold in Australia, and 224 people were arrested. For more on Anom, see siliconchip. au/link/abuv and siliconchip.au/link/abuw F-Droid host privacy-focused apps, although they only have about 4,000 apps compared to Google’s 3.5 million. Perhaps 90% of Google apps can still be installed on a de-Googled phone. The Aurora Store acts as a proxy for the Google Play Store and allows you to obtain certain apps without the Play Store. MicroG is an open-source implementation of various proprietary Google libraries that allows some Google apps to work on a de-Googled phone while maintaining privacy. Some apps (perhaps 10%) will not work because they rely on external “Firebase” Google services. Apps that require payment, like Uber, will not work, although bookings can be made via their website (https://m.uber.com). De-Googled phones are reported to have dramatically improved battery life (as much as double!) because the phone is not constantly waking up and uploading and downloading data to and from Google, Facebook etc. identification. They discard or destroy them after use. In Australia, there are identification requirements for buying a SIM card, but that doesn’t completely prevent misuse. Phone calls made and received, SMS texts and data usage are logged when a phone is connected to the network. The Australian government mandates that such ‘metadata’ records must be kept for at least two years (siliconchip. au/link/abuk). Call eavesdropping & spoofing Early mobile phones’ 2G and 3G connectivity to the PSTN relied upon a signalling protocol known as SS7 (see Fig.18), which was developed in 1975 and introduced in 1984. It was adopted as an international standard in 1988. SS7 implements call setup and routing, call forwarding, automated voicemail, call waiting, conference calling, caller ID subscriber authentication and extended billing, toll-free calls, premium charged calls, SMS, roaming and tracking. SS7 has an associated internet protocol suite called SIGTRAN (Signal Transport). SS7 has security weaknesses that allow: Attackers to interconnect with the network for surveillance, location tracking and interception of short messaging system (SMS) codes for two-factor authentication ... Voice calls can also be intercepted via SS7 attacks, which ... are tricky to block – siliconchip.au/link/abul SS7 is vulnerable because it is based on trust, not user authentication. Anyone with access to a server or gateway can send a location or redirect request to a telco, and if they believe it to be legitimate, they will follow it. It is said to be difficult to distinguish a legitimate request from a hostile one. 4G & 5G use an improved signalling protocol called Diameter (see Fig.19), built on SS7 but with enhanced protections. However, it is still considered vulnerable. Unlike SS7, it is purely IP (Internet Protocol) based. There is little a phone user can do to avoid their calls being intercepted by attacks via SS7 or Diameter. Even though 4G and 5G calls are encrypted by the phone, the encryption key can be intercepted by an SS7 attacker. SMS short messages are sent unencrypted. What privacy phones won’t do Each phone has a unique identifier linked to the account holder, and any phone connected to a cellular communications network can be tracked via mobile phone tower triangulation. The phone location can be established within about 150-300m in urban areas, regardless of what phone functions are used. Even turning the phone off might not keep you from being tracked! Criminals use ‘burner phones’ that were stolen or purchased with false Fig.18: the architecture of the SS7 mobile phone communications network. The database keeps track of mobile phones on the network. Original source: www.techtarget.com/searchnetworking/definition/Signaling-System-7 24 Australia's electronics magazine Silicon Chip siliconchip.com.au Fig.19: how the proposed trueCall CIV (Caller ID Verification) system integrates into the modern heterogeneous communications network. SIP (session initiation protocol) is for voice, video and messaging, while VoIP is voice over IP. Original source: www.researchgate.net/figure/CIV-for-heterogeneous-telecommunication-networks_ fig2_371506513 (CC-BY-4.0). The Pico Gamer A PicoMite powered ‘retro’ game console packed with nine games including three inspired by Pac-Man, Space Invaders and Tetris. With its inbuilt rechargeable battery and colour 3.2-inch LCD screen, it will keep you entertained for many hours. SC6912 | $125 + post | complete kit with white resin case shown* Other Items for this project SC6911 | $85 + post | complete kit without any case* SC6913 | $140 + post | complete kit with a dark grey resin case* * LiPo battery is not included SC6909 | $10 + post | Pico Gamer PCB* See the article in the April 2024 issue for more details: siliconchip.au/Article/16207 The only practical measure to avoid eavesdropping is to make encrypted VOIP calls or use an encrypted messaging app (see siliconchip.au/link/abum & siliconchip.au/link/abun). In Australia, it is illegal for government agencies to record your voice calls without a valid court order. However, Australia is a member of the “Five Eyes” (Australia, Canada, New Zealand, UK & USA) ECHELON program (see https://w.wiki/9qSX), which monitors voice calls, emails and internet traffic for specific keywords of interest to intelligence agencies. Caller ID spoofing Callers can fake the number they are calling from, making it seem like they come from a legitimate number like a bank. STIR/SHAKEN (https://w.wiki/9hz$) is a set of protocols intended to combat such spoofing. However, they only work with IP-based systems like SIP (VoIP) and cannot be scaled globally. CIV is an alternative proposed system that also protects SS7 and Diameter-­ c onnected phones (see Fig.19 & siliconchip.au/link/abuo). IMEI and IMSI numbers The IMEI (international mobile equipment identity) number is a unique identifier allocated to each phone and printed somewhere on the phone or displayed on the screen. It can be changed for legitimate reasons, although that is not legal in some jurisdictions, as the IMEI can be used to block stolen phones. Phones without physical SIM cards have an IMSI (international mobile subscriber identity) number that works similarly, although it can move between devices. The IMEI is not authenticated and can be spoofed by criminals to clone phones. It should therefore be kept confidential to prevent misuse. If selling a phone, it has been suggested to only give the buyer the IMEI number after purchase as criminals have masqueraded as buyers to get an IMEI number, after which the seller loses the ability to use the phone. mobile phone towers and trick phones within range to connect to them rather than legitimate towers. They can log the presence of people in certain areas by recording their phone IMSI number, call metadata, the content of SMS messages and voice calls and data usage such as websites visited. They are used by law enforcement agencies as well as some criminals. Hackers are known to have used a fake mobile phone tower to send an SMS to users with a link convincing them to download banking malware onto Android phones (see siliconchip. au/link/abup). Tracking a powered-off phone Firstly, when a phone is “off”, the baseband processor (inside the radio chip) may still be active. It draws very little power in listening mode and can be remotely commanded to wake up the phone and do other things; in some cases, it can even enable the microphone! Then there is ultra-wideband (UWB) tracking. UWB is a low-energy, shortrange, high-bandwidth radio technology that can be used for precise device location. Radio signals are generated as pulses sent over a wide bandwidth at specific time shifts compared to a clock signal, with the time shift encoding information according to a predetermined coding scheme. The high bandwidth (>500MHz) allows the transmission of a large amount of energy while keeping within the regulatory limits of output power. The modulation technique is known as pulse position modulation (PPM), with clock-independent variations, such as differential pulse position modulation (DPPM; see Fig.20). This is in contrast to conventional digital radio, where the frequency, phase or a combination of both are varied over a small bandwidth to transmit information. UWB uses several techniques to establish location, such as time-offlight, time difference of arrival and two-way ranging. We will cover these in more detail in a later article. Phones and devices with a UWB chip include iPhones since the 11, Apple Watch since Series 6, Apple AirTags, Samsung Note 20 Ultra, Galaxy S21+, Galaxy S21 Ultra, Galaxy SmarTag+ and Xiaomi MIX 4. Chips in these devices can precisely locate other devices at short distances. The accuracy is around 10-50cm at a range of up to 200m using frequencies of 3.1-10.6GHz and data rates up to 27Mbps (see siliconchip.au/link/ abuq). The FiRa Consortium (www. firaconsortium.org) promotes interoperability of Ultra Wideband devices. Apple devices use the U1 ultra-wideband chip that is always powered even when the phone is ‘off’, as long as the battery is not completely flat. Incidentally, UWB technology is used in the US NFL football league to track the movement of players on SC the field. Fake mobile phone towers The Stingray was a product of Harris Corporation (now L3Harris Technologies) that has become a generic term. It refers to devices, also known as IMSI catchers, that masquerade as 26 Silicon Chip Fig.20: the Pulse Position Modulation (PPM) scheme. A clock-independent variation is Differential PPM or D-PPM. Original source: www.pcbheaven.com/ wikipages/Pulse_Position_Modulation/ Australia's electronics magazine siliconchip.com.au Mid Year SALE! Build It Yourself Electronics Centres® Don’t get stuck with a dud battery this winter! SAVE $40 199 $ M 8195B Great deals across the range, only until June 30th. Lithium-Ion Car Jump Starter Crank it up! Now with 15W charging! 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. 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To start your subscription go to siliconchip.com.au/Shop/Subscribe AB Chimie ● Adfweb ● ADM Instrument Engineering AFG ● AIM Training ● Akytec ● Altronic Distributors Amec Plastics Ampec Technologies Amtech ● AppVision Arno Fuchs ● Asscon ● ATI Pty Ltd Atop ● Chase Corporation Humiseal ● Chemtools CNS Precision Assembly Coiltek Electronics congatec Australia Control Devices Australia Curiosity Technology ● D3 Innovation Deutsch ● Dinkle ● Dyne Industries Echo Electronics Electro Harmonix ● element14 Entech Electronics Embedded Logic Solutions Emona Instruments Epoxy Technology ● Epson Singapore ESI Technology Ltd ● Europlacer Eurotherm ● Excelpoint Systems F&S Bondtec ● Fema ● Fluke ● Foxtam ● Frankonia ● Globalink Electronics Glyn Limited GPC Electronics GW Instek ● Hammond Electronics Hawker Richardson HW Technologies IMP Electronics Solutions Industry Update Inertec ● Ingenuity Design Group Interflux ● Inventec Performance Chemicals ● Japan Unix ● JBC ● JS Electronic Keysight Technologies KOH Young ● Kolb Cleaning Technology ● Komax Kabatec ● Labjack ● Leach (SZ) Co Ltd Leadshine ● Lintek LPKF Laser & Electronics ● Lumiloop ● Marque Magnetics Ltd B20 D13 B8 A32 D34 D13 A2 A35 A8 A12 A15 A12 A12 A20 D13 B20 D34 D10 A5 A16 B10 B8 A3 A2 A2 D30 D26 A2 D33 A28 A11 B2 B20 D31 B8 D18 B8 C9 B20 D13 A1 D13 A32 D26 A32 C36 A32 B33 B32 C26 D6 A12 A33 D18 B20 A12 D18 C22 A1 A12 A12 A12 D13 D32 D13 D6 A11 A32 C10 ● denotes – Co-Exhibitor Company/Brand Stand numbers are subject to change electronex.com.au 32 Silicon Chip Electrone Rosehill Gardens Event Centre, Sydney June 19-20 Electronex – the Electronics Design and Assembly Expo is being held at Rosehill Gardens Event Centre on the 19th & 20th of June, 2024. It will feature a vast array of new products and technology for companies using electronics in design, assembly, manufacture and service. T he event was first held in 2010; this year’s Expo will feature over 100 leading companies and suppliers with the latest innovations and solutions for a broad range of electronic applications. Trade visitors will be able to discuss their applications and talk to experts who can assist them in finding the right products and solutions for their business. Last year, 96% of visitors said the Expo was beneficial for their industry, 90% found new companies, while 85% discovered new products and technology they were previously unaware of. The SMCBA Electronics Design and Manufacture Conference will also be held in conjunction with Electronex. It will feature sessions and technical workshops from international and local experts (more details on that below). Electronex will feature a wide range of electronic components, surface mount and inspection equipment, test and measurement and related products and services. Visitors can discuss their specific requirements with contract manufacturers that can design and produce turnkey solutions. The show welcomes designers, engineers, managers, industry enthusiasts and other decision-makers involved in designing or manufacturing products that utilise electronics. Electronex is the only specialised event for the electronics industry in Australia. With many Australian manufacturers now focusing on niche products and high-tech applications, the event Australia's electronics magazine provides an important focal point for the industry in Australia. Free seminars A series of free seminars will be held on the show floor, with no pre-booking required. These sessions will provide insight into some of the latest product advancements and applications, plus case studies of successful onshoring manufacturing in Australia. See the full program on the show website (www.electronex.com.au/ free-seminars). Visitors to the expo can register for free at www.electronex.com.au The 35th SMCBA Annual Conference The 35th SMCBA (Surface Mount & Circuit Board Association) Annual Conference will be held in conjunction with Electronex 2024, at Rydges Parramatta Resort, Sydney on June 18th-20th. If you are designing or manufacturing electronics, the best opportunity in Australia to learn things that will help you do your job better is at the SMCBA Conference in Sydney on June 18th-20th. Presentations by global leaders in their fields will cover topics like implementing Industry 4.0 in electronics manufacturing, key aspects of PCB design, the evolution of the solder alloys and soldering processes. The SMCBA has a licensing agreement with the US-headquartered IPC to provide training and certification to that organisation’s internationally siliconchip.com.au neX 2024 recognised standards. It is therefore appropriate that the keynote speaker at this conference is the IPC’s Vice-­ President, Standards & Technology, David Bergman, whose topic is “Digitalization of Electronics Manufacturing – Towards Smart Factory Enabling Industry 4.0”. That will be complemented by further presentations by US-based PCB design experts Mike Creeden & Rick Hartley, plus Australian Design for Test (DFT) expert, Redback’s Chris Turner. Returning to the SMCBA Conference for the third time, Dave Hillman will share what he has learned in a lifetime on the front line of manufacturing and testing defence and aerospace electronics. Mike Creeden will highlight the importance of balancing the three sometimes-conflicting requirements that circuit designers must satisfy: high density, manufacturability and reliability in service. Rick Hartley will be addressing another of the challenges in circuit design, particularly as operating frequencies increase: dealing with Electromagnetic Interference (EMI). Chris Turner will explain the factors that need to be considered in the design process for testing to be efficient and effective. Dave Hillman will provide experience-based guidance on the factors that must be considered when dealing with the assembly challenges designers create. Dave’s guidance will be presented in the context of the continual evolution of circuit design, changes in siliconchip.com.au solder alloys from tin/lead to lead-free and then to high-reliability alloys, and finally to lower-temperature processes and the introduction of new assembly methods. Hand Soldering Competition For those wanting to get down to the basics, at the associated Electronex expo, the IPC and the SMCBA will be running the “Australasian Round” of the 2024 IPC Global Hand Soldering Competition. Anyone confident in their technique is welcome to compete, with the winner having the opportunity to represent Australasia in the international finals in Munich! For more details, visit the SMCBA website at www.smcba.asn.au Meet industry colleagues To provide an opportunity for delegates to catch up, there will be a reception at the end of the conference’s first day (Tuesday, June 18th). The event’s primary purpose is to catch up with colleagues and meet the speakers giving live presentations. A podium and microphone will also be available for anyone with thoughts they would like to share (the usual protocols apply). Keynote: David Bergman – Digitalization of Electronics Manufacturing Mike Creeden – circuit design Rick Hartley – dealing with EMI Chris Turner – efficient & effective testing Dave Hillman – assembly methods Australia's electronics magazine Mastercut Technologies MB Tech ● Mean Well ● Microchip Technology Australia Micron ● Midori ● Nihon Superior ● Ningbo Degson Electrical Ninghai Yingjiao Electrical Co Nordic Semiconductor ● Novis Automation NPA Pty Ltd NZFH Ltd Ocean Controls Okay Technologies ONBoard Solutions On-track Technology Oritech Oupiin ● Pacton Technologies Pendulum ● Phoenix Contact Pillarhouse International ● Power Parameters ● Powertran ● Precision Electronic Technologies QualiEco Circuits Quectel Wireless Solutions Quest Semiconductors Radytronic ● Rapid-Tech Raspberry Pi ● Redback Test Services Rehm Thermal Systems ● Re-Surface Technologies Rigol Technologies ● Rion ● Ritec ● Rohde & Schwarz (Australia) Rolec OKW - ANZ S C Manufacturing Solutions Salecom ● Scientific Devices Semikron Danfoss SIMCom Wireless Solutions Simex ● SMCBA Sonictron Ultrasonic Cleaning ● Stars Microelectronics Suba Engineering Successful Endeavours Sunon ● TDK Lambda ● Teledyne FLIR ● Thermaltronics ● Thermo Fisher ● Thousand Hundred Industrial UniMeasure ● Uni-T Instruments ● VGL - Allied Connectors Vicom Australia Viscom ● Whats New in Electronics Win-Source Electronics Wirepas ● Wurth Elektronik Xentronics Yamaha ● Yokogawa ● YSX Tech Co Ltd D12 B20 B8 C3 A2 B8 D34 B4 C16 A32 D13 A29 D25 D13 D34 C21 C23 D18 A2 D5 A1 A26 B20 A20 A2 D1 B1 B26 D36 A2 A1 D33 A10 B20 B32 B2 D13 A2 B16 D14 D28 A2 C3 B13 B20 D13 C20 B20 A6 A12 B22 A2 A32 A1 D34 B8 D9 B11 A1 C8 C14 B20 A36 C32 B22 B14 A9 B32 A1 A27 ● denotes – Co-Exhibitor Company/Brand Stand numbers are subject to change electronex.com.au June 2024  33 Altronic Distributors www.altronics.com.au stand A2 Altronics has added slimline DIN rail cradle relays to their range. This space-saving industrial design allows customers to use control panel space efficiently, fitting more parts without sacrificing performance. They clip to any standard 35mm DIN rail and provide 6A, 240V AC/DC or 24V DC switching at just 6.2mm wide! The 240V AC/DC model has a 60V DC coil, while the 24V DC model has a 24V DC coil. These relays boast exceptional durability and reliability even in the most demanding conditions. The design provides easy setup and maintenance and will seamlessly integrate into existing systems. Altronics also has new dual-colour SPST pushbutton switches, with a high level of vandal resistance for equipment like ticket and vending machines, industrial machinery, security systems and more. These IP65-rated switches are dusttight and water-­protected, making them suitable for indoor and outdoor applications. The dual LED colour adds a visually striking element to your control panel layout and provides users with clear feedback during use. ATI Pty Ltd co-exhibitors: Hioki & Power Parameters stand A20 Efficient power management is crucial to maximise EV ranges, so it is essential to measure power consumption and current leakage across the ECU and other components. Even with assembled vehicles, that can be easily achieved using our Hioki Memory Hilogger LR8450 data logger paired with the CT7812 & CT7822 alternating/direct current sensors. Our LR8450 data logger can simultaneously measure and record current consumption and leakage across multiple channels, making it the ideal choice for manufacturers and researchers. It can record up to 330 channels from both the battery and Controller Area Network (CAN) bus, allowing integrated analysis of vehicle states and current consumption profiles. For even more complex EV testing, you can utilise our LR8450-01 wireless measuring unit to reduce complex wiring and minimise data loss. Hioki has revolutionised high-frequency power measurement with its automatic phase shift function for current sensors, Power Spectrum Analysis (PSA) and a whole array of new/ improved features with its PW8001 Power Analyser V2. The increasing use of SiC and GaN power semiconductors leads to higher switching frequencies, so reducing power loss in the high-frequency domain is becoming critical. By intuitively and quantitatively assessing high-frequency power losses in ways that would be impossible with conventional harmonic analysis, the PW8001 is incredibly useful for optimising inverter control and motor magnetic design. Harmonic analysis is insufficient for reviewing the power-­ harmonic distribution in both the motor and inverter—PSA solves this problem. Using the PW8001 Power Spectrum Analysis function, you can accurately assess active power frequency distribution across a wide band. Chemtools stand D34 co-exhibitors: Okay Technologies, Thermaltronics, AIM AIM Training (a division of Chemtools) is a licensed IPC Training Centre and has led the way with IPC Training in Australia since 2007. AIM Training delivers comprehensive certifiable courses covering all areas of electronics. Along with a range of IPC Training Courses, their offerings include customised training courses for electronics throughhole and SMT production, master micro rework, repair and diagnostics for mobile devices and ESD Awareness. Courses can be conducted on customer premises or in Chemtools’ fully equipped training centre. Chemtools employs three full-time trainers who are all certified in electronics and provide IPC Training to many defence organisations in Australia, including Raytheon, Boeing, BAE Systems, Rheinmetall, SAAB, CEA Technologies, Thales, Lockheed Martin and Northrop Grumman, to name a few. They conduct IPC Training in all Australian states and New Zealand. Unlike typical Cartesian robots, the Thermaltronics TMTR8000S soldering robot is equipped with full vision to verify the procedure being undertaken; it does not simply follow a pre-determined program. It has an observation mode, a verification mode and decision-making capabilities. This ability to collect and utilise data for production processing is one of the most important factors for meeting Industry 4.0 standards. The Thermaltronics robot system is accurate, has highspeed operation, is repeatable and is durable. Programming is made simple by full image-merging and mapping techniques. Dynamic laser height measurement/adaptive control ensures precision soldering repeatability. A full vision mapping and matching system provides intelligent decision-making during operation. congatec Australia www.congatec.com stand A16 congatec’s new aReady.COMs (Computer-on-Modules) integrate a hypervisor, operating system and IIoT software configurations that customers can put together according to their requirements. Developers can boot these individually-configured COMs immediately and install their applications, reducing the complexity of the integration work. The first aReady.COMs are available with the ctrlX OS from Bosch Rexroth, with more products to follow. 34 Silicon Chip Australia's electronics magazine siliconchip.com.au The hypervisor, included in all our new x86 COMs, is implemented in firmware, lowering the barrier to system consolidation. It enables developers to run multiple operating systems (OSs) simultaneously on a single COM. Each OS is assigned to run on its own core or set of cores and I/Os (such as PCIe, Ethernet and USB) so they can run independently from each other. Booting or suspending the operation of any OS has no effect on any other. The hypervisor gives customers a software and hardware package that’s already qualified to support real-time applications. congatec is introducing four new high-end COM-HPCs based on 14th Generation Intel Core processors (Raptor Lake-S Refresh). They set new records for industrial workstations and edge computers in certain areas. Clock frequencies have been increased, resulting in performance gains across the range. The Intel Core i7-14700 based modules stand out, with four additional E-Cores compared to the i7-13700E variants, for 20 cores in total. Another new feature is the improved bandwidth of USB 3.2 Gen 2×2, up to 20Gb/s. The COM-HPC Size C form factor (120 × 160mm) suits applications that require outstanding multi-core and multi-thread performance, large caches, enormous memory, high bandwidths and advanced I/O. Target markets include industrial automation, medical, edge and network infrastructure applications. They all benefit from a hybrid architecture with up to eight performance and 16 efficiency cores. The new conga-TC700 COM Express Compact COMs with Intel Core Ultra processors (Meteor Lake) are among the most power-­efficient x86 client SoCs available. Up to 6 P-Cores, 8 E-Cores and 2 Low Power E-Cores support up to 22 threads. The integrated Intel Arc GPU with up to 8 Xe Cores and up to 128 EUs can handle stunning graphics up to 2x 8K resolution and ultra-fast GPU-based vision data processing. The integrated NPU Intel AI Boost executes machine learning algorithms and AI inferences particularly efficiently. Up to 96GB of DDR SO-DIMMs with in-band ECC at 5600MT/s is supported. congatec introduces six new, highly rugged COM Express Compact Computer-on-Modules based on 13th Gen Intel Core processors. They can operate over extreme temperatures ranging from -40°C to +85°C. With soldered RAM, the new COMs provide shock and vibration-­resistant operation up to the highest railway standards. Target OEM applications include manned and unmanned rail and off-road vehicles for mining, construction, agriculture, forestry and more. With up to 14 cores and 20 threads, seconded by ultra-fast LPDDR5x memory, the 13th Gen Intel Core processors deliver excellent parallel processing and multitasking options within optimised power budgets. The modules are supported by congatec’s high-performance ecosystem, which includes highly efficient active and passive siliconchip.com.au cooling solutions, plus optional conformal coating for protection against moisture, thermal shock, static, vibration and contamination. Schematics are available. Control Devices Australia Pty Ltd www.controldevices.com.au stand B10 Control Devices will be showcasing Seika Inclinometers and Accelerometers at Electronex 2024. Seika sensors are designed for most tilt measurement applications and are Safety Integrity Level 2 (SIL2) rated, suitable for any safety-related requirements. Sensor housing options are also available for advanced performance opportunities. Emona Instruments emona.com.au stand B2 Emona Instruments will be demonstrating the new Rigol DHO800 & DHO-900 series digital oscilloscopes. These are Rigol’s newest ultra-portable, high-performance 12-bit economical digital oscilloscopes. Weighing only 1.7kg and being just 78mm thick, these ultra-­ portable oscilloscopes do not compromise on performance. The series features 12-bit resolution, a capture rate of up to 1,000,000 waveforms per second (in UltraAcquire Mode), 25/50Mpts memory and a super-low noise floor. They also offer a large 7-inch 1024 × 600 pixel capacitive multi-touch screen. The brand new Flex Knob user interface, USB device & host ports, LAN and HDMI interfaces are all standard for all models in this series. The DHO-900 series also supports 16 digital channels. One instrument can analyse both analog and digital signals to meet the embedded design and test scenarios. At an affordable price, you can access automatic serial and parallel bus analysis, Bode plot analysis and other functions to meet test demands in R&D, education and scientific research. Epson Singapore www.epson.com.sg stand D31 Epson Micro Devices is a major supplier of quartz timing devices. Epson’s core technologies in crystal photolithography and timing IC IP enable a wide range of product offerings, from crystals to RTCs, SPXOs, VCXOs and TCXOs. Epson’s semiconductor focus is on low-power design and efficient graphical display technology. Epson’s product categories include display controllers, microcontrollers and ASICs. These enable interactive and user-friendly products such as smart watches, smart meters and automotive display solutions. Combining timing devices and semiconductors gives two small form factor products: inertial measurement units (IMUs) and accelerometers. These ultra-high-precision sensors are used in inertial navigation systems (INS), stabilisation and structural health monitoring (SHM). Led by the Japan-based Seiko Epson Corporation, the Epson Group comprises more than 73,000 employees in 91 companies worldwide. It is proud of its contributions to the communities Australia's electronics magazine June 2024  35 in which it operates and its ongoing efforts to reduce environmental impacts. One product Epson will be demonstrating this year is the S1C31D41 Cortex-M0+ MCU with dedicated sound hardware, which is available as part of a demonstration board. Globalink Electronics & Echo globalink-e.com stand D26 www.echo.com.hk With over two decades of experience, we are well-connected with global supply channels to assist customers in meeting their production deadlines. We ensure that all businesses enjoy competitive pricing without compromising on product quality. Globalink Electronics ventures into providing EMS services with fully integrated manufacturing facilities in China. Our services include design verification, sourcing and procurement, final assembly, testing and inspection. To keep pace with the rapid growth of the Electronics Industry, Globalink Electronics has been flexible. Time and money are always the two main challenges to the supply chain. To ensure the best quality of every part and product supplied, we scrutinise products with a strict checking process before any shipments are made to customers. Echo Electronics Company Limited (Echo) is a Hong Kong EMS company with a manufacturing facility in the PRC. With over 20 years of experience in the EMS industry, Echo Electronics has numerous electronic production certifications, including IS0 9001:2015 for designing and manufacturing electronic buzzers, magnetic switches and PCB assemblies. EMC certificates have also been issued to Echo for the alarms we manufacture. Our products and services include OEM/ODM product assembly, PCBA, through-hole, SMT and one-stop turnkey service. We produce magnetic buzzers, piezo buzzers and magnetic contact switches. Glyn High-Tech Distributions glyn.com.au stand A32 Glyn High-Tech Distributions is exhibiting the following products at their stand this year: Cincon has over 32 years of experience in power supply design. Their products include AC-DC power supplies and DC-DC power converters. They specialise in developing compact and high-power-density products with wide operating temperature ranges, excellent power conversion efficiency and high reliability. The LFM300S series of low-­ profile 300W AC-DC semi-potted power supplies have an input range of 85-264V AC and output voltages of 12V, 15V, 24V, 28V, 30V, 48V or 54V DC. The series meets Over Voltage Categories OVC II & OVC III and has efficiencies of up to 94%. The CQB150W14 series is a 150W quarter-­brick DC-DC converter with an ultra-wide 14:1 input range from 12V to 160V DC with output voltages of 5V, 12V, 15V, 24V, 28V or 54V DC. Efficiency is up to 90.5%. Sensirion is one of the world’s leading developers and manufacturers of sensors that improve efficiency, health, safety, and 36 Silicon Chip comfort. Founded in 1998, Sensirion now employs around 1,200 people at its headquarters in Stäfa, Switzerland. In line with Sensirion’s industry-proven humidity and temperature sensors, the SHT4x series of humidity/temperature sensors offers the best price-performance ratio on the market. They use the proven CMOSens technology to ensure high reliability and precision. The STS4x series offers low power consumption, minimal size and full calibration. Taken together, it achieves the greatest cost efficiency among comparable sensors on the market. The miniaturised SCD41 CO₂ sensor builds on the photoacoustic NDIR sensing principle and Sensirion’s patented PASens and CMOSens technologies to offer high accuracy at an unmatched price in the smallest form factor. SMD assembly allows cost- and space-effective integration combined with maximal design freedom. It has a specified CO₂ accuracy range up to 5000ppm. The SFC6000D is Sensirion’s next-generation mass flow controller, impressing with an unbeatable price-performance ratio and very attractive lead times. The SFC6000 is very small and light, allowing customers to optimise their devices’ size and weight. It offers excellent repeatability, accuracy, control range and speed. The SFC6000 is highly integrated and has a very robust supply chain. Based on the thermal-mass measurement principle and using proven CMOSens MEMS technology, Sensirion builds radical mass flow controllers with best-in-class performance and speed. Unlike most other devices on the market, they do not drift or require in-service re-­ calibration. The SFM6000 is a valveless variant of the SFC6000, offering the same performance at an even lower price. Experience the future of air quality sensing with the compact and powerful SEN6x sensing platform. It combines multiple sensors in a never-before-seen form factor and can measure up to 10 environmental parameters: PM1, PM2.5, PM4, PM10, RH, T, VOC Index, NOx Index, CO₂ and HCHO. At the core of the SEN6x is a brand-new, miniaturised, MEMSbased particulate matter sensing component, the SPS6x. GPC Electronics www.gpcelectronics.com stand C36 GPC Electronics is Australia’s largest contract electronics manufacturer based in Sydney, with factories in Sydney (Australia), Christchurch (New Zealand) and Shenzhen (China). The company was founded in 1985 and now employs more than 400 professionals. Our experience and capacity, together with robust SAP MIIbased processes, continuous real-time quality monitoring, and highly trained professionals make GPC Electronics your ideal manufacturing partner. In today’s competitive market, customers expect fast turnaround, high yields and attractive pricing. GPC Electronics provides scalable solutions for high-value niche products through to high-volume products. Our services include NPI, Box Build, DfX, System Integration, printed circuit board assembly, cable harness assembly and testing. Our customers are in fields as diverse as aerospace, defence, automotive, renewables, agriculture, space, consumer goods and unmanned systems. Australia's electronics magazine siliconchip.com.au GPC Electronics is accredited with ISO 9001, ISO 14001, ISO 13485, IATF 16949, and AS 9100D. The company also holds a DISP accreditation. Hammond Electronics www.hammfg.com stand B33 Hammond Electronics has class-leading in-house modification capabilities, with many examples on show. Our standard products are low in cost, readily available and field-proven in many different applications, but they will always need to be configured to suit the project requirements. In-house modifications by the original manufacturer are the lowest cost option; Hammond will modify products for as few as 25 units. Hammond’s in-house modification capabilities include the precision CNC milling of holes, cutouts, pockets, tapping and countersinking; UV digital and silk screen printing; engraving of logos and text in both plastic and metal and pressed-in hardware – nuts, studs and standoffs. Subject to a minimum order quantity, ABS, flame retardant ABS and polycarbonate enclosures can be moulded in any custom colour. Plastic and metal enclosures can be powder coated in a smooth or textured finish to match a corporate colour. The stand will feature new products that were introduced since the last show. The flame-retardant ABS 1556 family, inspired by the IP68 1557 range, brings new rectangular sizes and the same versatility and features at a lower price point for general-purpose use. Additional sizes of many established product families will also be on the stand. Hawker Richardson hawkerrichardson.com.au stand B32 Visit Hawker Richardson’s stand to see the award-winning Mantis Microscope in action. The Mantis PIXO, Mantis ERGO, and Mantis IOTA all deliver high-quality 3D images in an easy-to-use ergonomic design. Unlike so many other binocular microscopes, the Mantis has been designed with an eyepiece-less viewer so you can wear prescription glasses! As you don’t have to align your eyes precisely, you can view the subject while moving your head. The Mantis also provides long working distances under 38 Silicon Chip lenses so you can do rework while looking at your subject under magnification, improving efficiency. The latest generation of entirely new models from the Mantis Classic range offers five-way illumination for maximum control over lighting for shadow-free inspection. The field of view is 10% larger for better movement control when working under the system. The PIXO and ERGO models have a three-lens turret, so you can scroll through magnifications quickly, increasing productivity with magnification up to 15 times. The integrated high-­ definition 5MP camera on the PIXO delivers superior image quality and greater colour reproduction. The video and image capture software lets users record, review and share resources for traceability, collaboration and training. All models accommodate the two new stands: the Stabila offers an extended range of improved focus travel from 55mm focus to 150mm, while the Verso arm has an increased reach over the previous models of 755mm. The Mantis is perfect for high-value, performance-critical micro-PCB work where you need to solder components onto a baseboard. You can get the maximum amount of space for tools without losing image quality. To take full advantage of the long working distance, the best setup is a PIXO or ERGO Mantis head with the multi-­turret lens fixture to allow for quick magnification changes. The PIXO and ERGO offer white/UV illumination for applications such as conformal coating validation on PCBs to ensure even coverage. Users can easily change from one light to another to view the coating. Improved hand-eye coordination and lower operator fatigue make tasks such as soldering, PCB inspection and rework easy for extended periods. Check out the Mantis PIXO with the integrated digital camera and Stabila stand and the compact Mantis IOTA with the Verso arm at the Hawker Richardson stand. Microchip Technology co-exhibitor: Scientific Devices stand C3 Microchip’s ATMXT2952TD 2.0 family of touch controllers offers cryptographic authentication and data encryption. The MXT2952TD 2.0 family is designed to encrypt touch data and cryptographically authenticate software updates to minimise risk and meet PCI certification compliance standards. In addition to EV chargers, the MXT2952TD 2.0 family is wellsuited for most unattended outdoor payment terminals such as parking meters, bus ticketing meters and other types of pointof-sale (POS) systems. The 2952TD 2.0 is optimised for 20-inch screen sizes, while its sister part, the MXT1664TD, is available for 15.6-inch screens. Microchip’s MCP998x family of 10 automotive-qualified remote temperature sensors is designed for 1°C accuracy over a wide operational temperature range. The device family includes five sensors with shutdown temperature setpoints designed not to be overwritten by software or maliciously disabled. With up to five channels of monitoring and several alert and shutdown options for security, this product family can support systems that supervise more than one thermal element. The remote sensors also integrate resistance error correction and beta compensation, eliminating the need for additional configuration for improved accuracy. Monitoring temperatures at multiple locations with a single, integrated temperature sensor reduces board complexity and size and simplifies design for a lowered bill of material (BOM). More accurate where it counts, designed for 2.5°C accuracy Australia's electronics magazine siliconchip.com.au up to 125°C, the MCP998x device family can be used at the high end of the traditional temperature range. This high-temperature tolerance makes them well-suited for applications where operating temperatures for electronics are a major factor. To enable easier design and development, the MCP998x family is supported by the new EV23P16A evaluation board. Microchip’s new PIC16F13145 family of MCUs is outfitted with a new Core Independent Peripheral (CIP)—the Configurable Logic Block (CLB) module. These MCUs enable the creation of hardware-based, custom combinational logic functions directly within the MCU. Because of its integration into the MCU, the CLB allows designers to optimise the speed and response time of embedded control systems, eliminating the need for external logic components and reducing Bill of Materials (BOM) cost and power consumption. The process is further simplified by a graphical interface tool, which helps synthesise custom logic designs using the CLB. The PIC16F13145 family is designed for applications utilising custom protocols, task sequencing or I/O control to manage realtime control systems in the industrial and automotive sectors. Since the CLB’s operation is not dependent on the CPU clock speed, it improves the system’s latency and provides a lowpower solution. The CLB can be used to make logical decisions while the CPU is in sleep mode, further reducing power consumption and software reliance. The PIC16F13145 MCUs also include a fast 10-bit ADC with built-in computation, an 8-bit DAC converter, fast comparators, 8- and 16-bit timers and serial communication modules (I2C and SPI) to allow many system-level tasks to be performed without the CPU. The family will be available in various packages from 8 to 20 pins. NPA www.npa.com.au stand A29 NPA is Australasia’s leading supplier of cabling, wiring accessories, Nylon fasteners and electronic interconnect hardware. It is a South Australian company with the same family ownership since its foundation in 1986. NPA is committed to excellence and is ISO9001 accredited. NPA is now located in modern purpose-built facilities in Kilkenny, SA. This investment in an office, warehouse and distribution centre has enabled NPA to strengthen its position as a preferred supplier to the electrical and electronic manufacturing industry. When everything is disposable, it’s refreshing to find a product that is designed to outlast its competition. Our new beaded cable ties do just that – they keep performing long after regular ties are buried in landfills. Their innovative beaded design allows for effortless adjustment and reusability, unlike conventional cable ties that require cutting and replacement upon removal. Beaded ties can be easily unfastened and adjusted, saving time and resources as well as reducing waste. They also keep wires from slipping or sliding due to pulling forces. Our beaded ties are constructed from polyethene to provide greater flexibility, allowing the tie to wrap more tightly around smaller diameters. Polyethene stays more flexible than Nylon, which can become rigid and brittle over time. There’s also no mechanical release mechanism that can break down or break off. Their one-piece construction provides consistent performance and reliability. Our new self-closing braided cable wrap is a popular cable management choice due to its outstanding versatility, siliconchip.com.au durability and ease of use. One of its key advantages is its self-closing mechanism, which allows for effortless installation and removal without additional tools or fasteners. The split-open design allows easy installation on cables that have already been assembled and additional cables can easily be added. The large expansion range of our braided mesh means it can accommodate a wide range of cable diameters, configurations and irregularities, providing a customised and snug fit for every application. This adaptability makes it ideal for organising and securing cables of different types and sizes, promoting tidiness and efficiency in any setup. Once in place, individual wires may be passed through the sleeving to allow for breakouts at any point along the harness. The polyester wrap has an operating temperature of -50°C to 150°C and is halogen-free, with a certified flammability rating of UL94 V-2. Ocean Controls www.oceancontrols.com.au stand D13 The KTA-382 offers a fresh and updated gateway replacement for the Davis weather stations, the Vantage Pro and the Vantage Pro 2. The updated model provides various new features for ease of operation and extra functionality. The base functions and dimensions of the KTA-282 and GWY-141 have been kept with the latest model, allowing for a seamless upgrade. New features include Wi-Fi capability, including a custom web page, Modbus TCP/IP over Wi-Fi or Ethernet, two independent serial ports with Modbus RTU (1x Db9/USB-C + 1x RS485), a data-logging variant with support for microSD cards, a PoE variant, direct cloud support for Weather Underground, a PC application for desktop monitoring/troubleshooting and two digital I/Os. The new KTA-396 is an updated and combined version of our KTA-296 and KTA-307. It is capable of relaying digital and analog I/Os over a span of 200m to 40km using ESP (200m), LoRa (1-2km) or RF Design (40km). The KTA-396 is also capable of mesh networking, allowing continuous transmission between multiple slave devices for easy expansion/remote control of your systems. The versatility of the KTA-396 makes it a powerful device across various industries like industrial automation, agriculture, environmental monitoring, aerospace and infrastructure management. The ability to wirelessly transmit digital and analog signals over considerable distances opens up many possibilities, including complex system control, relaying signals between distant PLCs and more. The KTA-396 can integrate with Programmable Logic Controllers (PLCs) or any other RS485-capable device. That means simplified installation, reduced maintenance costs and increased flexibility in system design. ONBoard Solutions and others onboardsolutions.com.au stand C21 ONBoard Solutions is an ISO 9001 credited supplier of production equipment for manufacturing, cleanroom products and advanced materials for the Australian & New Zealand markets. AB Chimie SND Cleaning and De-Fluxing Solvent is a fast-­ drying cleaning solvent that offers excellent removal of grease, Australia's electronics magazine June 2024  39 oil, flux residue and acrylic conformal coating from PCBs. This ozone-friendly solvent is designed to deliver superior performance. It efficiently removes coatings from PCBs and can dissolve acrylic varnish rapidly. Compatibility with various plastic materials enhances its versatility. The Sonictron VP 250/350 M vapour degreaser efficiently removes oil, grease, flux residue and particles. Fast, compact, scalable, and environmentally friendly, this compact vapour degreaser is perfect for small to medium production runs to remove contamination in short cycle times. It features two SUS 304 stainless steel tanks, heater control per tank, two ultrasonic power generators, a tank level sensor, a molecular water separator, a freeboard cooling coil and a 1 HP chiller. The low-surface-tension HFE solvent liquid has high penetration power, good cleaning and rinsing performance and high cleaning power. Rehm’s Protecto conformal coating solutions provide the highest quality, stability and productivity in automatic inline coating services. With up to four coating applicators, you can synchronise several modules in master-slave mode to apply the coating or directly apply up to four different materials without setup time. Up to two coating applicators can be used, giving a wide range of possibilities. The same nozzle can be used to switch between dispensing, spraying and jetting procedures on the fly. Parts that are tall or close together are easy to reach thanks to the slim nozzle design with a length of up to 100mm. If necessary, parts can be flushed from below using the patented Vario Coat nozzle. The Series 86 Battery Bonding System from F&S Bondtec is a heavy-wire version of the automatic wire bonders in our Series 86, featuring exchangeable bond heads. A fully automatic mode makes it ideally suited for medium-scale production. Parts to be bonded are fed manually by the operator, but the bonds are produced entirely without operator influence. Single bonds can be made within seconds, making the machine perfect for research and development, pilot manufacturing and middle-volume production. It offers a working area of up to 512 × 720mm. Special show offer: Receive a FREE product demonstration and a sample of AB Chimie SND Cleaning and De-Fluxing Solvent. Want to test AB Chimie SND Cleaning and De-Fluxing Solvent? Visit ONBoard Solutions at Elextronex with your dirty circuit board for a free demonstration and sample! Terms and conditions: Valid during Electronex Exhibition 2024. While stocks last. ONBoard Solutions reserves the right to change or rescind this offer at any time. Oritech www.oritech.com.au stand D18 The PSS Multiaxis Rotative PCB Support allows you to rotate and flip PCBs effortlessly without lifting them. It is ideal for repetitive soldering tasks. Set different heights to find your ideal position or adjust the distance between the PCB and the heating area of the PHSE Preheater. The support allows you to work continuously on the PCB without waiting for it to cool down. Connect the 40 Silicon Chip support to the ESD Common Grounding Point to protect your PCB from static electricity discharges. The JBC CDN High-Precision Soldering Station is designed for high-precision jobs in any micro-soldering application, offering maximum control working under the microscope. It provides all the advantages of JBC’s Most Efficient Soldering System in the smallest footprint. JBC Intelligent Heat Management provides the best soldering quality and, with Sleep & Hibernation Modes, extends tip life by five times. The Complete Tip Cleaning System, with exclusive Cartridge Exchanger, increases efficiency. It can connect to a Fume Extractor and Data Downloader for software updates and traceability. The Tagarno Zip is a simple digital microscope that might be small but don’t underestimate its power. Great for simple magnification tasks, it is user-friendly and lightweight. Unpack it, and you’re ready to go. The Tagarno Zip is used by companies worldwide for a reason. Its simple and user-friendly design makes it perfect for magnification tasks that do not require advanced features or software. Despite its sleek and simple appearance, the Tagarno Zip produces extremely sharp images at all magnification levels. Look at them and save them if needed. No maintenance is required with this microscope’s high-quality materials and surface treatments. The SQ3000 is an all-in-one solution that’s loaded with powerful tools that cover inspection and measurement for Automated Optical Inspection (AOI), Solder Paste Inspection (SPI) and coordinate measurement (CMM) applications. Attain highly accurate data with the industry-leading Multi-Reflection Suppression (MRS) sensor technology that meticulously identifies and rejects reflections caused by shiny components and reflective solder joints. High-speed inspection with the MRS sensor captures and transmits multiple images in parallel while advanced fusing algorithms merge the images, delivering microscopic image quality at production speed. Discover the excellence of Australian craftsmanship with our Interflux SAC305 DP5505 T4 88% Solder Paste, proudly made in Australia by Oritech. This high-quality solder paste is your go-to solution for seamless soldering applications. Experience superior soldering performance with our Interflux SN63 PB37 DP5505 T4 88.5% Solder Paste, proudly made in Australia by Oritech. It features the SN63 PB37 alloy, ensuring reliable and consistent results for your electronic projects. Precision Electronic Technologies precisionet.com stand D1 Precision Electronic Technologies is an ISO-certified contract electronic manufacturing organisation based in Melbourne, Australia. We are 100% Australian-owned and provide an extensive range of manufacturing services, including: • Printed circuit board assembly • Cable assembly • Wiring harnesses Australia's electronics magazine siliconchip.com.au R&S®ESSENTIALS NEXT-GENERATION OSCILLOSCOPE: EVOLVED FOR MORE CHALLENGES Precision made easy. The R&S®MXO 5 series delivers breakthrough oscilloscope technology to speed up your understanding and testing of electronic systems. With both four- and eight-channel models, the specifications of the R&S®MXO 5 series impress, making the instrument stand out above other industry choices. In addition, the R&S®MXO 5 series oscilloscopes are the epitome of cutting-edge technology by delivering quick and accurate results. With custom technology and game-changing features, these oscilloscopes are the perfect tools for understanding circuit behaviors. NEW R&S®MXO 5 Oscilloscope More at: www.rohde-schwarz.com/product/mxo5 siliconchip.com.au Australia's electronics magazine June 2024  41 • Stencils • Decals & membranes • Full turnkey box building assembly • Testing We provide a complete solution to our customers and have proven experience in volume supplies of circuit board assemblies, box builds and ancillary products. We provide engineering and manufacturing services to over 300 customers across various industries, including: • Medical/Health • Defence • Transport/Automotive • Telecommunications • Scientific • Utilities We pride ourselves in working with our customers’ technical and supply chain priorities and providing a solution that best fits their needs. We are known for our excellent customer service, technical knowledge, uncompromising quality, and timely delivery of all printed circuit board requirements. Led by some of Australia’s most experienced professionals, our manufacturing team ensures we deliver quality outcomes through our shared understanding and expertise of the electronics industry. Our current Customer Satisfaction (CSAT) score for 2023 is 94%. We have two large facilities in Melbourne and a branch in Hong Kong to manage our suppliers. QualiEco www.qualiecocircuits.com.au stand B1 QualiEco Circuits is now embarking on its 21st year of operation with great enthusiasm and momentum. In mid-2023, we proudly launched our Canada operation, extending our reach to serve the Canadian and North American markets. Since 2003, we have delivered standard and fast turnaround PCB manufacturing and assembly services to our valued customers in Australia and New Zealand. Our operations in all three countries – Australia, New Zealand, and Canada – are backed by ISO9001:2015 and ISO 13485:2016 (for medical devices) certifications, ensuring the highest standards of quality and reliability. The QualiEco Circuits Pty Ltd team is well known for providing excellent quality electronic manufacturing services and solutions. Customers have enjoyed excellent quality, low prices and on-time delivery for years. 42 Silicon Chip The company has customised delivery solutions for all customers at affordable prices. Customers can choose from the fastest to semi-fast and standard delivery options based on their budget and urgency. We take pride in our dynamic and growing company, where outstanding technical support and attention to detail are paramount. With over two decades of experience, we have established ourselves as a market leader in New Zealand, a testament to our dedication and expertise. As we celebrate our 12th successful year in Australia and venture into our inaugural year in Canada, we remain committed to delivering excellence and innovation in all we do. The technical team at QualiEco Circuits Pty Ltd has regularly prepared a guide on various technical aspects of PCB manufacturing and assembly. These technical guides are available at www.qualiecocircuits.co.nz/publications.htm Queensland Semiconductor Tech questsemi.com stand D36 Griffith University and Queensland Semiconductor Technology Pty Ltd (Questsemi), supported by Semefab Scotland and the Innovative Manufacturing CRC (IMCRC), are manufacturing high-performance silicon carbide (SiC) Schottky diodes, a key element in many power conversion systems. Due to their incredible thermal conductivity, high switching performance and efficiency, they are highly sought after for applications like solar inverters, motor drives, electric vehicle (EV) chargers and uninterruptible power supplies. Using SiC wafers, researchers at the Queensland Microtechnology Facility (QMF) of Queensland Micro and Nano­technology Centre (QMNC) at Griffith University have developed a new technology that allows for more efficient and low-cost fabrication of SiC diodes. As part of the research project, a pilot production facility will Australia's electronics magazine siliconchip.com.au be set up at QMF to support the commercialisation of the technology. Devices necessary for the initial commercial product supply will be manufactured there. Professor Sima Dimitrijev, who leads the research team, says the development and pilot manufacture of SiC diodes at QMF is an excellent example of advanced manufacturing collaboration. Rapid-Tech Equipment rapid-tech.com.au stand A1 Rapid-Tech Equipment is exhibiting the following products at their stand this year: Keysight Technologies’ latest Fieldfox N9912C RF Analyser is a lightweight, durable software-defined instrument for cable and antenna testing, vector network analysis and RF power measurement. Its features include real-time spectrum analysis, interference analysis, EMI pre-compliance and EMF measurements, AM/FM demodulation, 5G and LTE OTA analysis, mapping and more. All capabilities and options are software upgradeable. The frequency bands for each instrument (CAT, VNA, SA) can be upgraded separately as needed to 4, 6.5 or 10GHz. The new Pendulum Instruments CNT-102 Dual-channel Frequency Analyser is the world’s first dual-channel instrument supporting parallel and independent time/frequency measurements in a benchtop format. Key capabilities include simultaneous and gap-free Frequency, Period, Time Interval Error, Pulse Width, Rise/Fall time, Slew Rate, Totalise and Voltage measurements. The standard frequency range is up to 400MHz; the optional RF input extends it to 24GHz. The new multi-channel design enables parallel frequency measurements of two different test objects, or the comparison of pulse parameters between two parallel test points, without having to swap over test leads. The CNT-102 sets a new price/performance benchmark in the industry, with impressive 14ps time resolution, up to 13 digits/s frequency resolution and 1 million measurements/s at prices starting around $5000. Pendulum/Detectus SCN-500 EMC-Scanners are powerful and affordable pre-compliance tools for measuring and analysing electromagnetic interference and Immunity Testing. The SCN-series features repetitive high-resolution 4D scanning of radiation (3D movement plus rotation of the probe head), down to 100μm steps and up to 10GHz, with powerful scanning software for visualisation and documentation. Using the EMC-Scanner during the early stages of R&D enables you siliconchip.com.au to detect potential emission problems before they become expensive to correct. UNI-T Instruments has expanded its Arbitrary Waveform Generator portfolio with the new UTG9000T-series. With three models covering 350, 500 and 600MHz maximum output frequency, each instrument provides up to 64Mpts record length, 16 bits vertical resolution and four output channels. The nine basic waveshapes are sine, square, ramp, pulse and harmonic waveforms plus noise, PRBS (pseudo-random binary sequence), DC and arbitrary. Modulation includes AM, FM, PM, DSB-AM, QAM, ASK, FSK, 3FSK, 4FSK, PSK, BPSK, QPSK, OSK, PWM, SUM with linear, logarithmic, list frequency, stepping sweep, frequency sweep and burst output modes. SNR (signal-to-noise ratio) readings are available with a single click; digital protocol outputs include SPI, I2C and UART for interface testing. The new UTS3000B-series affordable spectrum analyser has a measurement range from 9kHz to 2.1/3.6/8.4GHz, with a three-year warranty at a very affordable price, to complement the UTS1000B-series (9kHz to 1.5/3.2GHz). The 10.1-inch multi-touch HD screen supports multiple gesture operations such as dragging, expanding, and zooming on the trace. The -161dBm DANL provides excellent sensitivity to test weaker signals, while the 1Hz to 3MHz RBW provides excellent selectivity. The UTS3000B-series provides up to 40,001 sweep points, giving higher frequency resolution, making it easier to capture signals that are difficult to detect with full amplitude accuracy <0.7dB. Options include analog demodulation & vector signal analysis. The EMI pre-compliance analysis option & near-field probes help you find and resolve EMI defects to shorten the development cycle. The advanced measurements option includes a range of RF power measurements, TOI & harmonics measurements, and a spectrogram for spectrum/interference analysis. Rohde & Schwarz www.rohde-schwarz.com/au stand B16 The R&S MXO5 Series breakthrough oscilloscope technology speeds up the understanding and testing of electronic systems with stand-out specifications, such as its impressive four- and eight-channel models. Why the MXO5? • Evolution in speed: Quick acquisitions with multiple channels, maths functions and seamless spectrum measurements for minimal blind time with a 21ns rearm delay. Australia's electronics magazine June 2024  43 • Unleash comprehensive spectrum analysis: Fast and pristine spectrum analysis and the ability to run up to four analyses simultaneously. • Extensive memory capacity: Benefit from the deepest standard memory and up to one million waveform segments. • Precise in-event detection: Our digital trigger is flawless at 18-bit HD resolution with adjustable sensitivity for accurate triggering. • Uncompromising performance: A low noise floor and the largest vertical offset range of ±5V at 0.5mV/div for exceptional signal fidelity. • Setting new sensitivity standards: the industry’s most sensitive triggering system, down to 0.0001div. • Leading trigger jitter performance: Best-in-class trigger jitter of less than 1ps. SC Manufacturing Solutions www.scmsau.com.au stand D28 SC Manufacturing is showcasing the L-4 8mm SMT Auto-Splicing System which has these features: • 8mm component tape width • Component tape thickness from 0.25-1.25mm • Handles deep pockets up to 2.5mm • Excellent FPY up to 98% • Comes standard with an intelligent vision system • Optional LCR verification for capacitors and resistors • Independent X/Y/Z axis design for LCR verification • Auto-adjusts LCR measurement probe for components size from 01005 (imperial) • Auto empty pocket detection with pre-cut stations and component pitch verification • Continuous operation for up to 12-16 hours once fully charged • MES integration with connectivity via Wi-Fi or direct network port The M2-900 Laser Marking System features include: • Generates high-quality 1D and 2D codes, text, logos, optical characters etc 44 Silicon Chip • Four types of laser (CO2, UV, Green & Fibre) are available for optimal performance • Supports top and bottom dual-head configuration for greater flexibility and throughput • Standard dual-camera configuration, simultaneous reading and marking to enhance throughput and quality • Equipped with fume detection • Safety enclosure with interlock switches that prevents pollution of the shop floor • Optional dual-conveyor configuration for higher throughput and greater flexibility • Optional Z-axis for additional flexibility in marking on different part heights • Separate dust collector comes standard • High efficiency • Creates high-quality marks • Easy to maintain The N-800A Vacuum Degassing System features include: • Inline configuration for easy integration into the production line • Single lane-single chamber configuration • Degassing using vacuum and heat • Adjustable vacuum profile • Maximum PCB size: 500 × 500mm • Easy to operate Würth Elektronik www.we-online.com stand B14 Würth Elektronik can supply free samples of the following products on request. Würth Elektronik’s new WPME-CDI (Capacitive Digital Isolator) SMT digital isolators come with or without an integrated power supply. They have a data rate of up to 150Mbps, UL 1577 approval and high immunity to system noise with CMTI (common mode transient immunity) of ±150kV/µs. Applications include isolating communication buses, industrial switch-mode power supplies and motor controllers, testing and measuring systems, battery management systems and photovoltaic inverters. The CDIS version, without a power supply, comes in two-channel SOIC-8NB (4.9 × 3.9 × 1.5mm) and four-channel SOIC-16WB (10.3 × 7.5 × 2.5mm) packages. In contrast, the CDIP (Powered) version is available with four channels and operates up to 100Mbps with up to 650mW of isolated power at 3.3V or 5V and an isolation voltage of 5kVRMS. Würth Elektronik’s new generation of connectors includes Australia's electronics magazine siliconchip.com.au the WR-CRD Micro SIM Card Connector with a push/push insert/eject mechanism. It has good kink resistance, high durability and easy card detection. The brass contacts are gold-plated and the package is made of tin-plated steel. The contact resistance is around 100mΩ, while the operating temperature range is -20 to +70°C. The new WPME-FISM ‘Fixed Isolated SIP/SMT Module’ from Würth Elektronik is rated for 1W output at 3.3V or 5V. The DC/DC voltage converter has a fixed output voltage and integrated switching power stage, transformer, input and output capacitance. It is 100% pin-to-pin compatible with the previous MagI³C-FISM but has improved properties: efficiency of up to 84%, the ambient temperature range has been increased to 105°C, and the isolation voltage is 3kV (for 60 seconds). Like some of its predecessors, this power module has continuous short-­ circuit protection. MagI³C FISM power modules require no external components. Applications include supplying voltages for interfaces and microcontrollers in test and measurement technology or industrial electronics. Its isolation helps prevent ground loops, ground shifts and interference in the signal path or sensor systems. The entire product range is UL 62368-1 recognised. The low level of conducted and radiated electromagnetic interference complies with the EN55032 Class B / CISPR-32 standard. Würth Elektronik’s very compact, cost-effective WSENHIDS series MEMS digital humidity sensors have a precision of ±1.8% RH in the 20-80% RH range. The DFN SMT package measures just 1.5 × 1.5 × 0.5 mm. The sensor draws only 0.4µA and can operate from 1.08V to 3.6V. It is ideally suited for distributed IoT sensor networks like those in smart farming applications. Its dielectric polymer interacts with water molecules to adjust the permeability of the capacitor structure depending on the relative humidity. A temperature sensor is also included. 16-bit measurement data is available via an I²C interface. The included heater has three heating levels that can be switched on temporarily as required. Würth Elektronik’s WR-COM USB 3.1 Type-C High-Rise SMT connector is a high-quality 24-pin SMT USB 3.1 Type-C connector with a high-rise design that allows complete visual control of soldering thanks to its two rows of twelve contacts. It is not only compatible with USB 3.2 Gen 1×2 signalling and USB Power Delivery standards but can also be used for alternative and accessory modes, including transmitting analog signals via the D+/D- pins. It is designed for at least 10,000 mating cycles and operating temperatures from -40 to +120°C. The pin contacts and outer retaining pins are gold-plated in the contact zone to ensure the best possible connection to the PCB. Würth Elektronik offers a complete range of connectors, EMC filters, components for ESD overvoltage protection and AC/DC to DC/DC power conversion for USB 3.1. These products are recommended in the USB Type-C reference designs from leading IC manufacturers. They include pulse-stable WE-MPSB SMD ferrites for hotplugin, high-efficiency pressed power inductors (WE-MAPI) for siliconchip.com.au Vbus filters, current-compensated data line filters (WE-CNSW HF) and the WE-TVS diode for ESD line protection. Würth Elektronik provides numerous Application Notes and reference designs for developing USB solutions. Würth Elektronik’s new WCAP-FTDB series film capacitors are designed for DC-Link applications. They have a voltage range from 500V to 1200V with high ripple current capability. This makes them particularly attractive for use in AC/DC and DC/DC converters for charging systems and power electronics in e-mobility or renewable energy solutions. The 24-model product family offers capacitance values from 1µF to 75µF. The operating temperature range is -40°C to 105°C; the voltage ratings apply up to 85°C. The metallised polypropylene film design gives them self-healing properties, making them significantly more durable than other capacitor types. The series is suitable for applications with long maintenance cycles, like wind turbines. Würth Elektronik’s WE-HEPC series is its smallest NiZn-­ ferrite-based self-shielded power inductor to date. Thanks to a new and completely automated manufacturing process, these inductors consistently provide very high quality and a higher saturation current than any previously known product. 15 models are available from 3.3μH to 100μH; and 1.3A to 3.3A in package sizes of 5030 (4.8 × 4.8 × 1.8mm) and 6030 (5.9 × 5.9 × 2.85mm). These inductors are suitable for DC/ DC converters, filter applications, embedded computers and other compact applications. They can also be used for some automobile applications. The operating temperature range is -40°C to +125°C. The WE-TORPFC inductor series has been expanded with 17 new parts. These toroidal inductors are suitable for continuous-­ conduction mode (CCM) boost converters up to several kW. Unlike traditional bobbin-wound power factor correction (PFC) inductors, this new series uses flat wire windings, resulting in lower winding losses and better cooling. The series is designed for elevated temperatures, up to 155°C, and can handle voltages up to 1kV DC. With multiple sizes available, inductances of 118-720µH and rated currents up to 48A, this new series is suitable for active power factor correction, industrial AC/DC, solar inverters and various other applications. The WSEN-PDUS family of differential pressure sensors from Würth Elektronik has also grown. The two new models run from 3.3 V, making them compatible with most microcontrollers supporting this supply voltage. The other models in the series require 5V. All sensors have high robustness and accuracy of up to ±0.25% FSS tolerance. A version is now also available with horizontal barbed nozzles. This new packaging design allows pneumatic hoses to be connected directly to the sensor nozzles, eliminating the need for an adaptor. Equipped with digital I²C and analog output interfaces, the sensors deliver fully-calibrated pressure data and optional temperature data. Different transfer functions from ±1mbar to +15bar are available. With an operating temperature range of -25°C to +85°C, these sensors can be used in various applications, from HVAC to monitoring filter status and detecting gas leaks, to inhalers. Würth Elektronik can also design individual application-­ specific sensor variants with customer-specific pressure ranges on request. SC Australia's electronics magazine June 2024  45 SILICON CHIP Mini Projects #005 – by Tim Blythman Self Toggling Relay Here’s a simple circuit, using just one relay and a handful of passive parts, that allows you to toggle or switch the relay off and on with just one pushbutton. It demonstrates some of the finer details of working with relays and can be used to control a wide range of devices. O ver the years, we have had several requests for simple circuits that allow a relay to be switched on and off by pushing a button. Some readers sent in suitable circuits, but they all involved multiple relays. This design achieves that goal using just one DPDT (double-pole, double-­ throw) relay, a common type. It provides a free set of ‘dry’ contacts, meaning they are not connected to any circuitry or a power source. You are free to do whatever you want with them, within the limits imposed by the relay’s ratings. It might be possible to build this circuit using a single-pole (SPST) relay if the thing you wanted to switch was completely independent of the relay’s power source. Still, DPDT relays are inexpensive, and using a free set of contacts is safer. The relay Our design relies on a property of relays that we can demonstrate with the circuit in Fig.1. A capacitor is connected across the relay’s coil and charged via a resistor fed from the normally closed (NC) contact. When power is applied, the capacitor charges until the relay’s armature pulls in. The contacts open, the capacitor discharges until the armature drops out, and the cycle continues. It forms a ‘relaxation oscillator’. Scope 1 shows the resulting waveform for the Jaycar SY4065 relay that we are using. The blue trace is the voltage across the coil, while the red trace shows Scope 1: the blue trace shows the voltage across the coil, which rises and falls between the must-release and must-operate voltages. The red trace shows the relay state changing as the voltage does (with quite a bit of contact bounce at the transitions, as is expected). 46 Silicon Chip Australia's electronics magazine the relay state changing. Although it is a 12V relay, the contacts open at around 1V and close at around 9V. The relay data sheet lists those as the ‘must release’ and ‘must operate’ voltages. As you can see from the scope grab, this circuit toggles at around 10 times per second, so this relay’s minimum 100,000-cycle operating life would be reached in about three hours! If you want to apply this design to another relay, we recommend checking its data sheet first. Our circuit Fig.2 shows the circuit for the Self Toggling Relay. RLY1’s coil has a resistance of around 160W, and when power is applied, it has around 6V across it. That is less than the must-­ operate voltage, so the relay remains off. The capacitor charges up via the relay’s NC and COM contacts, reaching close to 12V after a few seconds. Pressing S1 places the capacitor directly across the relay coil. Since it now has 12V across its coil, the relay pulls in and the contacts change over. When S1 is released, the coil voltage returns to around 6V, above the must-release voltage. The capacitor now discharges to 0V via the NO and COM contacts. This takes around a second, since it will have discharged slightly while S1 was pressed. If S1 is pressed again, the siliconchip.com.au Fig.1: this is the circuit we used to test our relay before building the prototype. Scope 1 shows the resulting waveform. We suggest you don’t build this as it will cause the relay to toggle rapidly, possibly wearing it out quickly. reverse happens and the relay drops out, returning to the earlier state. Effectively, we are using the hysteresis of the relay coil voltage (the difference between the must operate and must release voltages) to maintain its state and using the capacitor to change the state. The capacitor charging time sets the maximum toggling rate, about once per second for the chosen components. Since the relay is not operating at its full rated voltage, the contacts are not pulled in as tightly as they would otherwise be. This means the relay may be more susceptible to vibration and shocks and might drop out (or in!) if subjected to rough conditions. Also note that if power is removed, the relay will return to the released state almost immediately; this is a nice safety feature. Construction We have used a socketed relay to minimise the amount of soldering needed. The physical arrangement has been kept similar to the Fig.2 circuit diagram to make it easier to follow. You could use a smaller relay laying on its back and solder the other components to its leads, ‘dead bug style’. The circuit is also easy to assemble on a breadboard or prototyping board. Just be aware that other relays might have different pinouts or component requirements; we’ll discuss that later. siliconchip.com.au Fig.2: the Self-Toggling Relay circuit diagram, laid out similarly to our prototype. The component values have been chosen to work with the selected relay; different relays will likely require different values. The Parts List reflects what we have built, but several alternatives exist. See the photos for how the prototype was wired up. We used black wire for the two terminals connected to the negative end of the 12V supply, while the red wire connects to the positive of the 12V supply. Wire up the lower set of contacts first, as they will be hard to get to once the upper components (particularly the capacitor) are fitted. We’ve mostly made the other connections using the component leads, with some extra wire in some places. The blue and white wires connect to the switch terminals. Testing Hook up the 12V supply; nothing should happen right away. If the relay starts chattering, disconnect the power supply and check your wiring. You might have inadvertently made a circuit more like Fig.1 than Fig.2. A wrong value for the 1kW resistor might also cause chattering. Wait a few seconds, then press the pushbutton and confirm that the relay toggles. Wait another second and confirm that it toggles back when the pushbutton is pressed a second time. In that case, the circuit is working. You can use the second set of contacts as though they are an SPDT switch, or you can use either half (NO & COM or NC & COM) like an SPST switch, depending on whether you want it to default to open or closed when power is not applied. If you want to add an indicator light, a 12V globe or 12V LED could be connected between the COM and NC terminals. This will light up when the relay is pulled in. Similarly, a globe or LED connected between the COM and NO terminals will light up when the relay is off. Alternatives If you need another button that will always switch the circuit on or off, you could add another pushbutton, 1000μF capacitor and 1kW resistor and wire them up in almost the same fashion. In this case, instead of feeding the 1kW resistor from the relay’s COM contact, feed it from 12V for an ON switch or 0V (ground) for an OFF switch. That gives a circuit that can generate the necessary impulse, but it will always have the same effect instead of toggling. Keep in mind that pressing more than one switch simultaneously might connect capacitors charged to different voltages, possibly running high currents through the switch contacts and damaging them. Other relays The 150W resistor value was chosen to set the coil voltage between its must-­release and must-operate voltages. For other relays, a resistor with a similar resistance to the relay coil is a good starting point. By the voltage divider equation, this will put about Parts List – Self Toggling Relay (JMP005) 1 DPDT 12V relay (RLY1) [Jaycar SY4065] 1 relay socket base to suit RLY1 [Jaycar SY4064] 1 momentary SPST pushbutton switch (S1) [Jaycar SP0710] 1 1000μF 25V electrolytic capacitor [Jaycar RE6230] 1 1kW 1/2W resistor [Jaycar RR0572] 1 150W 1W resistor [Jaycar RR2554] 1 12V DC power supply various short pieces of stiff wire to make connections Australia's electronics magazine June 2024  47 This simple circuit is a proof of concept. Still, we think readers will find it handy when they need to toggle a relay using only a single momentary pushbutton. half the supply voltage on the coil. If the data sheet does not mention a figure, measure the coil resistance with a multimeter. Note that we used a 1W resistor here; you should check the power dissipation if making circuit changes. Your circuit should run from the voltage the relay is rated for. Don’t try to power a 5V relay from a 12V supply! An early prototype we built used a smaller relay and we found that a 100μF capacitor could provide enough impulse to toggle the relay. The exact value depends on the relay, so we advise experimentation to find a capacitor value that works consistently. The second resistor (1kW in our case) must have a high enough value to avoid substantially changing the coil voltage while the pushbutton is pressed. A value at least five times higher than the first resistor should work well. The combination of the 1kW resistor and 1000μF capacitor (as used in our circuit) dictates the maximum rate at which the pushbutton can toggle the relay. Larger values will mean a longer SC wait time between presses. 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The USB also comes with its own case EACH BLOCK OF ISSUES COSTS $100 OR PAY $500 FOR ALL SIX (+POSTAGE) NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 JANUARY 2000 – DECEMBER 2004 JANUARY 2005 – DECEMBER 2009 JANUARY 2010 – DECEMBER 2014 JANUARY 2015 – DECEMBER 2019 WWW.SILICONCHIP.COM.AU/SHOP/DIGITAL_PDFS Ordering the USB also provides you with download access for the relevant PDFs, once your order has been processed 48 Silicon Chip Australia's electronics magazine siliconchip.com.au Mini Projects #006 – by Tim Blythman SILICON CHIP Arduino Clap Light Can’t find the remote control? Don’t worry! Clapping lets you switch devices on and off with this simple project. You may have seen it on TV; now you can build it yourself. T he “Clapper” is a sound-activated switch introduced in the USA in the 1980s. It is a box that plugs into a power point and allows two appliances to be connected. According to the motto, “Clap on! Clap off!”, you could simply clap to switch an attached device on or off. It toggled one appliance on or off when two claps were detected. Another appliance would respond to three claps. By some accounts, it could be too sensitive, reacting to other sounds or even people talking. Most people used it to control a light or lamp since they are unlikely to cause harm if switched on or off at the wrong time. This simple project provides a similar function. The Arduino Clap Light Such a device is easy to build using an Arduino Leonardo board and a module capable of detecting sound. To save ourselves from getting too close to mains voltages, we’ve added a 433MHz transmitter to provide remote control of a few different types of radio-controlled devices. This will allow you to control either a wireless power point such as Jaycar’s MS6148, or a commonly installed ceiling fan and light combination (sold under the ‘Brilliant’ brand), which incorporates an RF remote control. In both cases, the circuit transmits the same signal as the remote control, so the existing hand controller can still be used. Since we are providing the Arduino source code, you could adapt it to control another device, such as a relay module or even something simple like a light-emitting diode (LED) connected directly to the Leonardo board. Fig.1 shows the wiring diagram. You can also see how we have laid it out in the photos. We used Blu-Tack to attach the Leonardo to a breadboard, then fitted the modules to the breadboard and connected them with jumper wires. The Leonardo monitors the analog signal from the sound sensor module and then sends a digital signal to the wireless transmitter module at the appropriate time. Since the sound sensor module delivers an analog signal, we must Parts List – Clap Light (JMP006) 1 Arduino Leonardo [Jaycar XC4430] 1 Remote Controlled Mains Outlet (see text for options) [Jaycar MS6148] 1 Microphone Sound Sensor Module [Jaycar XC4438] 1 433MHz Wireless Transmitter Module [Jaycar ZW3100] 1 breadboard with jumper wires [Jaycar PB8819] 1 USB Type-A to micro Type-B cable to suit Leonardo [Jaycar WC7757] siliconchip.com.au Australia's electronics magazine perform some processing to distinguish claps. Scope 1 shows the analog signal presented by the sound sensor module in response to a clap; it is the positive half of the raw audio waveform. The negative half of the waveform is clipped to around 0V by a diode on the module. The Arduino sketch We can’t easily differentiate claps from other short, sharp sounds, such as knocks. Still, you might prefer to make a knocking sound to control it. We are basically trying to detect a sharp increase in volume. To detect claps, we need to smooth out the waveform to get a signal corresponding to volume (rather than instantaneous amplitude). We use ‘exponential smoothing’ because it is straightforward to implement. Adding an RC (resistor and capacitor) low-pass filter circuit would have the same effect, but we can do exponential smoothing in software without adding any parts. We then apply some thresholds to distinguish claps from other sounds. We detect the start of a clap when the smoothed value rises above a certain level and its end when the value falls below a different, lower level. This is called hysteresis and is another way to separate claps in a noisy environment. Once one clap is detected, a timer runs for one second and further claps within that second are counted. Thus, June 2024  49 Scope 1: the raw analog signal from the sound sensor module is the positive half of the audio waveform. It needs to be processed to allow claps to be detected. the software can detect multiple claps in close succession. The Leonardo’s onboard LED is also lit while each clap is detected. Scope 2 shows the Arduino Serial Plotter debugging data. The orange trace is the smoothed volume signal; each peak corresponds to what is seen in Scope 1. The green trace shows the claps being detected, while the yellow spike shows the one-second counter expiring, having detected two claps (indicated by the peak reaching 200 on the vertical scale). Note how the smaller orange peaks are ignored. The other two traces ensure that the plotter maintains a useful range. RF communication Scope 2: the Clap Light produces debugging data that can be displayed on the Arduino Serial Plotter. The green trace shows two claps being detected, while the yellow spike indicates when the processor acts on the claps. Other noises (the smaller orange peaks) are ignored. Wireless remote controls use different digital protocols; we have provided software libraries to encode the desired channel and function. We’ll delve into that a bit later during our setup and testing. The digital RF signals are pretty slow (compared to some digital protocols) and are simply ‘bitbanged’ with timed delays. During the period when the Arduino Leonardo is producing the digital RF transmission signal, it does not monitor or respond to a clap signal, but we don’t think that is a big deal, as you would usually not send a second command until you observed the original one being obeyed. The sketch also takes input on the Serial Monitor, so typing ‘1’ will have the same effect as making one clap, ‘2’ for two claps and so forth; this is handy for testing. We can handle cases up to five claps, since that was about the most we could achieve in one second. It wouldn’t be hard to update the code to deal with more if you wanted to. Construction Fig.1: use this wiring diagram to connect up the components for the Clap Light; the wire colours match the prototype. The wire that only connects at one end is the antenna; its other end can be plugged into an empty row on the breadboard. 50 Silicon Chip Australia's electronics magazine Wind the potentiometer on the sound sensor module fully clockwise; this is the highest gain and thus sensitivity setting. Referring to Fig.1, wire it up to the breadboard and Leonardo, but don’t connect the transmitter module. This will allow us to check the operation of the clap sensor. Connect the Leonardo to a computer and upload the Clap_Light sketch (available from siliconchip. au/Shop/6/418). If you open the serial plotter, you should see something like Scope 2. If the ‘L’ LED on the Leonardo flashes when you are not clapping, siliconchip.com.au Photo 1: we built our prototype on a breadboard with jumper wires, but this design could also be made into a custom shield, perhaps using the Jaycar XC4482 Prototyping Shield. turn the sound sensor module pot anti-clockwise until it settles down. If there is no response to claps, you can turn it clockwise. Find a level such that the LED flashes when you clap but not other times. There is also one LED on the sound sensor module that shows when it is powered, so if it isn’t on, there might be a problem. Other AVR main boards like the Uno, Nano and Mega should work, although we haven’t tested them. With that working, connect the transmitter module as per Fig.1. Note that one end of the ANT wire for the transmitter module plugs into an empty row on the breadboard, so the antenna wire doesn’t float around. Using the Jaycar MS6148 (or similar) wireless outlet requires a pairing step; you can also refer to the instruction manual. Power on the outlet and activate the ON function while its LED is flashing. The default sketch lets you do that using the ‘3’ command on the serial monitor. Then use ‘3’ and ‘4’ to check that the outlet switches on and off as expected. Finally, test the clap response while watching the serial plotter to confirm proper operation. The remote control for the MS6148 can control four separate outlets; the rfPowerPoint.h file shows the #defines you can use to emulate these different controls. You can also refer to the doThreeClaps() function in our sketch; the ppSend­RF() function is designed to work with these outlets. The ‘Brilliant’ fan and light controllers are typically hardwired by an electrician and have a remote control that looks like the one shown in Photo 2. Photo 3 shows the coding DIP switches inside the battery enclosure. You can see that this one is set to binary 0b1001 or 9, which is the channel number used in the sendCommand() function called by the doTwoClaps() function. If your remote control has a different coding, change the function to use that number instead of 9. ► Photo 2: if you have a fan and light with a remote control like this, the Clap Light should work with it. Other functions of the Brilliant remote control are listed in the rfFan.h file. There don’t appear to be distinct off or on functions for the light, but there is a code that will turn both the fan and light off together. Summary and more options The Clap Light is quite accurate, but we found it still occasionally reacted to other sounds. For this reason, we have avoided making it respond to single claps. We recommend you do the same and also be careful not to connect anything that might be dangerous if unexpectedly turned on or off. Some devices have integrated IR receivers, so they could be controlled by adding an IR transmitter. The sketch could easily be adapted to control low-voltage items via a relay module. Adding the Jaycar XC3730 LED Matrix Shield would allow you to add multi-coloured lights to the SC Clap Light. Photo 3: the DIP switches inside the remote control are set to match those in the fan/light, so change the sketch code to match its settings. In our case, ON-OFF-OFF-ON corresponds to binary 1001 or 9 in decimal. According to a sticker on the back, this is a Model No 99999 SII RF Transmitter. siliconchip.com.au Australia's electronics magazine June 2024  51 IDEAL FOR STUDENT OR HOBBYIST ON A BUDGET • DATA HOLD • SQUARE WAVE OUTPUT • BACKLIGHT • AUDIBLE CONTINUITY Don't pay 2-3 times as much for similar brand name models when you don't have to. 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ENTRY LEVEL * QM1500 QM1517 QM1527 MID LEVEL QM1529 QM1321 QM1020 QM1446 Display (Count) 2000 2000 2000 2000 4000 Analogue Security Category Cat II 500V Cat III 600V Cat III 500V Cat III 600V Cat III 1000V Cat II 1000V • • Autorange True RMS PROFESSIONAL QM1323 QM1552 2000 4000 2000 4000 4000 2000 4000 6000 4000 Cat III 600V Cat III 600V Cat IV 600V Cat III 600V Cat IV 600V Cat III 600V Cat IV 600V Cat IV 600V Cat III 1000V • • • • • • QM1551 QM1549 • • • • • XC5078 QM1594 QM1578 • Voltage 1000VDC/ 750VAC 500V AC/DC 500V AC/DC 600V AC/DC 1000VDC/ 750VAC 1000V AC/DC 1000VDC/ 700VAC 600V AC/DC 1000VDC/ 750VAC 600V AC/DC 1000V AC/DC 600V AC/DC 600V AC/DC 1000V AC/DC Current 10A DC 10A DC 10A DC 10A AC/DC 10A AC/DC 10A DC 10A AC/DC 10A AC/DC 10A AC/DC 10A AC/DC 10A AC/DC 200mA AC/DC 10A AC/DC 10A AC/DC Resistance 2MΩ 2MΩ 2MΩ 20MΩ 40MΩ 20MΩ 20MΩ Capacitance 100mF Frequency 10MHz Temperature Duty Cycle 20MΩ 40MΩ 200MΩ 40MΩ 40MΩ 40MΩ 60MΩ 100μF 100µF 100mF 100µF 100µF 100µF 6000µF 10MHz 10MHz 10MHz 10MHz 10MHz 10MHz 10kHz 1000°C 760°C 1000°C 760°C 750°C 760°C • • • • • • • • • • • • • • • • • • • Continuity • • • • • • Relative Min/Max/Hold • Non Contact Voltage • • • $33.95 $39.95 $59.95 Max Hold • • • $64.95 $87.95 $87.95 IP Rated Price • Max Hold • • $28.95 *Lifetime warranty excluded on models: QM1500/QM1517/QM1527 $35.95 $65.95 1000VDC/ 750VAC 4000MΩ • • • IP67 $16.95 QM1493 $119 IP67 $109 $179 $219 $329 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. TIM BLYTHMAN’S ESR TEST T EEZERS We have produced a few variants of our Test Tweezers since the original version in the October 2021 issue. Still, none has yet had the handy feature of measuring capacitor ESR (equivalent series resistance). Our new ESR Test Tweezers can measure ESR and capacitance while being significantly more compact than all our previous ESR meters! E SR (equivalent series resistance) is an inherent but undesirable property of capacitors that acts like a resistance in series with the capacitive element. Fig.1 shows this and the other factors that can be used to model a real capacitor, as opposed to an ideal, purely capacitive one. For good performance, especially at high currents (as in a switch-mode supply), a capacitor’s ESR and ESL (equivalent series inductance) should be low and the leakage resistance should be high. That combination best approximates an ideal capacitor. Generally, the ESL is relatively small and is often lumped together with ESR by specifying it at a known frequency, often 100-120Hz or 100kHz (the former being relevant when rectifying mains AC). The total series impedance can then be specified in ohms. If the ESR is high, the capacitor will dissipate a significant proportion of the energy that passes through it, Fig.1: the behaviour of real capacitors, especially electrolytic types, deviates from the ideal model of capacitors found in textbooks. ESR (equivalent series resistance) is one of the more prominent unwanted phenomena; capacitors often fail due to the ESR rising to unacceptable levels. 54 Silicon Chip unlike purely reactive elements such as ideal capacitors and inductors, which have no losses. It is well known that high-ESR electrolytic capacitors can cause problems, but they are not the only type of capacitor that can suffer from high ESR. Other types, such as plastic film, can be affected too. In a power supply, a high ESR manifests as a voltage drop due to the current flowing in and out of the capacitor. That will decrease the voltage available to the circuit and heat up the capacitor, sometimes to the point that its contents boil and spill out! Electrolytic capacitors depend on an electrolyte as the current path between the oxide dielectric layer and the cathode. If this electrolyte dries out, its resistance and thus the ESR will increase. Increasing ESR will also cause an increase in dissipation inside the capacitor, further heating and drying out the electrolyte. A high ESR capacitor will often cause mysterious or intermittent faults, as documented extensively in our Serviceman’s Log pages, where replacing the electrolytic capacitors usually fixes a power supply. The conductivity of the electrolyte can also change with temperature, leading to problems that appear or disappear as the capacitor heats up after the equipment is turned on. In audio circuits, the higher-than-­ expected ESR can change the frequency response of a circuit and may increase distortion. These are just Australia's electronics magazine some of the scenarios where a high ESR can cause problems. If you have a device that has failed or isn’t working correctly, after checking for obvious visual faults like burned components or failed solder joints, the next step is usually to test the electrolytic capacitors. If any are found to have a low capacitance, high leakage or high ESR, they may well be the culprits. Often, several are found to be on the way out. So, an ESR meter is a very valuable piece of equipment for making repairs and even checking new components to verify that they will perform as expected. Earlier ESR Meters we published include Bob Parker’s classic 2004 ESR Meter Mk2 (siliconchip.au/Series/99). That article goes into more detail on the construction of electrolytic capacitors and how they are affected by rising ESR. It also has numerous tips on troubleshooting capacitors. One frequently-seen piece of advice is a warning not to connect the ESR Meter to charged capacitors. We have included some protection circuitry, but large capacitors can pack enough of a punch to render that protection moot! The same advice applies to our ESR Test Tweezers. Like the ESR Meter Mk2, the ESR Test Tweezers is also well suited to measuring low resistances, such as current shunts. So they are sure to come in handy for other sorts of troubleshooting. siliconchip.com.au exact part number may not be known, so the earlier ESR Meters provided a table showing roughly acceptable values for a range of capacitors. Table 1 shows these values. Some data sheets might specify a dissipation factor or loss angle instead of an ESR value; page 63 has information about what those parameters mean and how to convert them to an ESR value. The ESR Test Tweezers are much smaller than the earlier devices, so we have not been able to include the table on the equipment, but you can download it, print it out and keep a copy handy. Features & Specifications ❎ Measures ESR/resistance from 0.01Ω to 1kΩ ❎ Measures capacitance from 100nF to 50μF ❎ Can perform in-circuit testing as long as capacitors are discharged ❎ Compact Tweezers format makes probing parts easy ❎ Runs from a single 3V lithium coin cell ❎ Will operate down to a cell voltage of 2.4V ❎ Displays results on a clearly visible OLED screen ❎ Typical accuracy better than 10% ❎ Adjustable sleep timeout and brightness ❎ Display can be rotated to suit left- and right-handed use ❎ Simple calibration of most parameters ❎ The standby cell life is close to the cell shelf life Design compromises ESR Test Tweezers Kit (SC6952, $50) This kit includes everything in the parts list except the coin cell & optional header CON1. The three resistors & one capacitor needed for calibration are included. The Arduino-based LC and ESR Meter from August 2023 (siliconchip. au/Article/15901) uses the same ‘frontend’ design as the ESR Meter Mk2 to measure ESR, but piggy-backs onto the Wide-range digital LC Meter from June 2018 (siliconchip.au/Article/11099), using its processor to drive the measurement circuitry and display the results. That was a popular project, but we reckoned we could simplify the all-­ important ESR sensing circuitry and fit it into a much more compact instrument that costs less to build. Measuring ESR Measuring ESR is not difficult in theory, although we must be able to separate the effects of the main capacitance and leakage resistance from the ESR (see Fig.1). As we noted, the ESR is often taken to include ESL at a specific frequency, so we don’t need to concern ourselves with ESL too much. The ESR Test Tweezers use the same philosophy as the other ESR Meters. Relatively low currents are briefly pulsed into the capacitor, and the voltage across the capacitor is measured. It is allowed to discharge between tests. The brief pulses do not have time to significantly charge the capacitor (assuming it is above 1μF); the capacitance acts like a short-circuit in this testing, so it does not affect the reading. Since the capacitor is practically always discharged, the leakage siliconchip.com.au resistance has no effect; the capacitance effectively short-circuits it. The pulses can also be considered analogous to an AC signal, so the capacitor’s impedance is low enough that the ESR dominates. Knowing the ESR is not enough to tell whether a capacitor is faulty. It’s a good idea to verify that its capacitance hasn’t dropped, and this Meter can do that, too, up to about 50μF. Beyond that, most DMMs will have a capacitance measurement mode that works up to a few thousand microfarads. Any decent capacitor will specify its expected ESR value (or equivalent) in the data sheet, and you can compare that value to the Meter’s reading. However, when servicing equipment, the This device is patterned on the very popular Advanced Test Tweezers from February & March 2023 (siliconchip. au/Series/396). They are a compact and elegant device with many useful functions. So we have kept the ESR Test Tweezers to much the same form factor, using differently-coloured PCBs to make the two tools easier to tell apart. We know that many readers will end up with both! The Advanced Test Tweezers performed most of the tests in software running on a microcontroller, so they needed relatively few external components. For testing ESR, we need more complicated circuitry, so we have had to use more components. They are the same M2012 (0805 imperial) SMD parts that measure 2.0 × 1.2mm along with a few other parts in small packages. Apart from there being more components, construction should not be any harder than for the Advanced SMD Tweezers. Table 1: typical ESR readings for good capacitors 25V 35V 63V 160V 250V 1μF 10V 5 4 6 10 20 2.2μF 2.5 3 4 9 14 4.7μF 6 3 2 6 5 1.6 1.5 1.7 2 3 6 10μF 16V 22μF 3 0.8 2 1 0.8 1.6 3 47μF 1 2 1 1 0.6 1 2 100μF 0.6 0.9 0.5 0.5 0.3 0.5 1 220μF 0.3 0.4 0.4 0.2 0.15 0.25 0.5 470μF 0.15 0.2 0.25 0.1 0.1 0.2 0.3 0.15 1000μF 0.1 0.1 0.1 0.04 0.04 4700μF 0.06 0.05 0.05 0.05 0.05 10mF 0.04 0.03 0.03 0.03 Australia's electronics magazine If your capacitor’s data sheet does not mention a typical or maximum ESR value, this table can be used as a guide. If your data sheet mentions a dissipation factor or loss angle, refer to our panel on page 63. This table can be downloaded from siliconchip.com. au/Shop/11/238 June 2024  55 The ESR Test Tweezers use simplified circuitry compared to the earlier ESR Meter designs. That’s partly to help us fit the parts on the board but also because we were able to reduce the parts count without compromising performance, saving on parts cost and assembly time. For example, the older designs feature a pulse injector with 11 parts and a pulse amplifier made from 17 parts. The corresponding sections of our circuit have only five and nine parts, respectively (50% less overall!). We are not using a voltage regulator either; instead, our software compensates for any variations in the supply voltage from the cell. The earlier designs used a compar- ator (built into the processor) alongside a voltage ramp to measure the pulse amplitude, requiring eight more parts. Our circuit uses the 12-bit ADC (analog-­ to-digital converter) peripheral built into the microcontroller and no external parts. Instead of a multiplexed LED display driven by a shift register IC, requiring several more parts, we are using the same graphical OLED display module as in the Advanced Test Tweezers (although it’s white this time rather than blue/cyan). It sits over the main PCB, occupying only the size of a four-pin header on the main PCB. The earlier ESR Meters could apply test pulses up to 50mA. Given that the ESR Test Tweezers are designed to run from a coin cell, we aimed to use lower amplitude pulses to avoid excessive drain from the cell. Despite all this, the ESR Test Tweezers can measure fairly accurately down to 10mW (just like our previous ESR meters) and will draw less than 1μA of current when in low-power mode; that’s low enough that the standby life of the cell will be close to its shelf life. We tested our prototype using our Coin Cell Emulator (December 2023; siliconchip.au/Article/16046). It reported a current of 0.0μA while the ESR Test Tweezers were sleeping, less than the 100nA minimum that the Coin Cell Emulator can display. Fig.2: the ESR Test Tweezers use a 16-bit, 28-pin PIC24 microcontroller to drive the measurement circuitry and a small OLED display. Different test currents are applied to the DUT via the 300W, 3kW and 30kW resistors, while Q2 amplifies the voltage across it for the micro to sense using its internal ADC. The diodes protect the micro in case the probed capacitor has some charge left. 56 Silicon Chip Australia's electronics magazine siliconchip.com.au The typical operating current is around 3.5mA with no components connected to the test leads, rising to 5mA when a component is being tested or settings are being modified. About half of that current is due to the OLED screen, which is set to near its lowest brightness setting by default. The current draw increases if you need to operate the OLED at a higher brightness, but we found that was not necessary for indoor use. Circuit details Fig.2 shows the full circuit diagram of the ESR Test Tweezers. Many components are common to the Advanced Test Tweezers: IC1, MOD1 and CON1 are much the same, with IC1 being the PIC24FJ256GA702 16-bit microcontroller. IC1 is powered by coin cell BAT1. The two 100nF capacitors bypass its two positive supply pins, while the 10μF capacitor provides bypassing for a 1.8V regulator internal to IC1. Practically nothing else is connected directly to the cell, meaning that IC1 has total control over what can draw current from it. The 22μF capacitor provides a reserve of power to assist the coin cell in delivering the test pulse current. This is about the highest value of capacitor commonly available in the M2012 size we are using for this project; it is sufficient for our needs. The highest pulse current is 10mA, applied for no more than 50μs. With a 22μF capacitor, the nominally 3V rail dips by about 0.02V, rather than the 0.2V expected without the capacitor. This also means that the coin cell is subjected to a lower average load; it does not see the heavy peaks that would otherwise shorten its useful life considerably. CON1 is the ICSP (in-circuit serial programming) header and the 10kW resistor on IC1’s pin 1 sets the micro to run normally unless a programmer is connected. We mainly included CON1 to simplify software development; you shouldn’t need it in regular operation, although it may be useful if we ever release a firmware update. MOD1 is an I2C OLED module powered at its Vcc pin by one of IC1’s I/O (input/output) pins. Pulling that pin low shuts off the display module completely. The other two connected I/O pins provide the I2C serial control interface. siliconchip.com.au The ESR Test Tweezers PCB (shown enlarged) looks similar to the Advanced Test Tweezers, but it has different capabilities. We used white PCBs to set them apart and will provide white arm PCBs to match. Tactile pushbuttons S1-S3 connect to three more I/O pins. Each is furnished with an internal pullup current from IC1, so their state can be easily detected without external parts. Debouncing is done by the software. The parts below MOD1 form the pulse injection circuitry. The 300W, 3kW and 30kW resistors allow nominal currents of 10mA, 1mA and 100μA to be generated from a 3V supply rail. IC1’s I/O pins can source 1mA with only a small (less than 0.1V) voltage drop. At 10mA, the drop would be around 0.6V, so the 300W resistor is provided with PNP transistor Q1 for switching; the second 3kW resistor provides the base current when Q1 is driven. The 22μF and 100nF capacitors in parallel are present to limit the amount of charge that can be injected if a large, charged capacitor is connected to the TP+ and TP− terminals. They act together as a low impedance when the pulses are applied. Silicon diodes D2 and D3 clamp any voltage from the capacitor being tested that exceeds their forward thresholds. The presence of D2 and D3 also means that the maximum pulse that can be applied is less than 1V. So even if you test a capacitor in reverse, the voltage should be low enough to avoid damaging it. IC1’s pins 21 and pin 22 are normally kept low, and pin 18 is kept high, turning Q1 off. The PULSE OUT line sits at 0V and the 22μF and 100nF capacitors are discharged via the 10kW resistor at bottom left. Any connected device is also discharged. Just before a pulse is applied, pins 21 and 22 are put in a high-impedance state by the processor. The appropriate Australia's electronics magazine pin is driven high (or low in the case of pin 18) to start the pulse. A measurement is then taken, and the pins revert to their idle state, ready for the next measurement. Sense amplifier The DUT (device under test), usually a capacitor or low-value resistor, connects between the TP+ and TP− pins. The test current applied to the PULSE OUT line induces a voltage at TP+ relative to circuit ground. The circuitry below IC1 amplifies the resulting voltage. When IC1’s pin 25 is low, this circuitry is powered off via the AMP POWER line, but it is brought high during testing. The 1MW/470kW divider ensures that Q2 is biased on slightly, as long as the supply is above about 2V. The 100nF capacitor at Q2’s base will have the bias voltage across it. Before a pulse is applied, the voltages at LOW ANALOG (pin 24, AN7) and AMP OUT (pin 23, AN8) can be sampled by IC1’s ADC to record a baseline voltage. The LOW ANALOG line will be close to 0V, and the AMP OUT pin will be close to the voltage provided by the AMP POWER line, which will be reduced slightly due to Q2 being biased on slightly. When a pulse is applied, the voltage rises at the TP+ pin, and the voltage at Q2’s base rises by a similar but slightly smaller amount. The reduction is due to the signal being attenuated by the surrounding components, such as the 10kW resistor and 1MW/470kW divider. Q2 behaves as an emitter follower, so its emitter will rise by much the same voltage, and the current through the 100W resistor will be proportional to the emitter voltage. June 2024  57 Since the collector current will match the emitter current (give or take the much smaller base current), the current through the 2.2kW resistor will be the same as that through the 100W resistor, meaning that the voltage across the 2.2kW resistor is 22 times that across the 100W resistor. The microcontroller then takes another sample to compare with the baseline values. In practice, the change at the AMP OUT pin is 10-15 times the change at the LOW ANALOG line. Of course, the AMP OUT line will fall during a pulse, while the LOW ANALOG line will rise, but it is simple enough to take the difference either way. The 1kW resistor and dual diode D1 provide another level of protection against external voltage sources (such as charged capacitors). While it appears that we effectively have six ranges to read (two analog inputs multiplied by three current sources), they overlap. We use four ranges: the 100μA source sensed at the LOW ANALOG input and all three test currents sensed at the AMP OUT input. Note that neither the LOW ANALOG or AMP OUT signals can swing rail-to-rail. Diode D1 clamps the LOW ANALOG level between AMP POWER and ground. Due to the 100W resistor, the AMP OUT signal cannot reach 0V, even if Q2 is saturated. Several calibration factors are programmed into the ESR Test Tweezers, including the levels at which the LOW ANALOG and AMP OUT signals are valid. Firmware The firmware driving the ESR Test Tweezers has much in common with the Advanced Test Tweezers since they use the same microcontroller. However, the ESR Test Tweezers do not have as many features. We have implemented three measurement modes, labelled ESR, RES Parts List – ESR Test Tweezers 1 double-sided main PCB coded 04105241, white solder mask, 36 × 28mm 2 double-sided arm PCBs coded 04106212, white solder mask, 100 × 8mm 1 double-sided back panel PCB coded 04105242, white solder mask, 36 × 28mm 1 0.96in 128×64 I2C OLED module, white (MOD1) 1 surface-mounting 32mm coin cell holder (BAT1) 3 SMD two-pin tactile switches (S1-S3) 1 3-pin gold-plated header, 2.54mm pitch (for tips and mounting MOD1) 1 4-pin header, 2.54mm pitch (to mount MOD1; usually comes with MOD1) 1 5-way header, 2.54mm pitch (CON1; optional, for ICSP) 1 M2 × 6mm Nylon panhead machine screw 2 M2 Nylon hex nuts 1 CR2032 or CR2025 lithium coin cell 1 small piece (eg, 2 × 2cm) of double-sided foam-core tape 2 100mm lengths of 10mm diameter clear heatshrink tubing Semiconductors 1 PIC24FJ256GA702-I/SS microcontroller programmed with 0410524A.HEX, SSOP-28 (IC1) 1 BC859 PNP transistor, SOT-23 (Q1; marking 4C) 1 BC817 NPN transistor, SOT-23 (Q2; marking 6C) 1 BAT54S dual schottky diode, SOT-23 (D1; marking KL4) 2 1N4007WS silicon diodes, SOD-323 (D2, D3) Capacitors (all SMD M2012/0805 size 6.3V+, X5R or X7R) 2 22μF 1 10μF 4 100nF 50V X7R extra 10μF (could be any type) for capacitance calibration Resistors (all SMD M2012/0805 size, 1/8W, 1% – codes in brackets) 1 1MW (105 or 1004) 2 10kW (103 or 1002) 1 1kW (102 or 1001) 1 470kW (474 or 4703) 2 3kW (302 or 3001) 1 300W (301 or 300R) 1 30kW (303 or 3002) 1 2.2kW (222 or 2201) 1 100W (101 or 100R) extra 10W, 100W and 1kW resistors for calibration 58 Silicon Chip Australia's electronics magazine and CAP. The ESR mode provides a function similar to our previous ESR meters. The main ESR testing mode uses the 100μA source and the LOW ANALOG input to detect if a component is present across TP+ and TP−. If so, it runs pulses from each of the 100μA, 1mA and 10mA sources, taking measurements using the AMP OUT signal from the pulse amplifier. If the 10mA pulse gives a valid AMP OUT reading, an ESR value is calculated using this data and a calibration factor. The 1mA pulse is checked next; if this is not valid, the ESR reading is taken from the 100μA pulse. You can tell which range has been used from the number of decimal places displayed. The 10mA pulse gives a result to two decimal places (0.01W), while the 1mA pulse gives a result to the nearest tenth of an ohm and so on. The RES mode (for resistance) is intended to measure the values of resistors, and it does so using only the 100μA source. That makes it a bit easier on the cell since there are no high-current pulses. The resolution of the RES mode is only around 10W; we expect it to be useful if you have many parts to sort through. The CAP mode gives a reading for both capacitance and ESR for the device under test. It also uses the 100μA source but applies it for long enough to charge up the capacitor, although this is somewhat limited by the 22μF capacitance in series with the DUT. It takes readings at 40μs, 400μs and 4ms from the start of the pulse. Our prototype gave us fairly accurate readings up to 50μF, so we’ve specified that as the maximum. The display will show dashes if the measured capacitance is higher than 50μF. The lower limit of 100nF is due to the resolution being about 10nF; the readings will tend to be inaccurate below 100nF. Since we have collected much the same data as the RES mode, an ESR reading is given too, with the same limitations as that mode. The firmware is also responsible for monitoring button presses and putting the processor to sleep when the device is not being used. There is a SETTINGS mode where preferences and calibration parameters can be changed, including the option to save the calibration and settings to flash memory. siliconchip.com.au We’ll delve into the calibration, setup & operation of the ESR Test Tweezers once construction is complete. Construction The SSOP-package microcontroller and M2012 parts mean assembly is not overly difficult, but it best suits constructors with some experience working with SMDs. If you have built the Advanced Test Tweezers, you should have little trouble with the ESR Test Tweezers. You will need a fine-tipped soldering iron, solder, flux paste and solder-­wicking braid. You should also have a magnifier, SMD tweezers and a means of holding the PCB in place, such as Blu-Tack. Good lighting is highly recommended, along with fume extraction (or work outdoors or near a large open window). Start by placing a little flux paste on the PCB pads for IC1 and rest it in place, checking that the pin 1 dot is in the correct position. Looking at the PCB with CON1 at the bottom, the text on the chip should be rightway-up. Check your build against the Fig.3 overlay diagram and accompanying photos. Note that our photos show CON1 fitted (which isn’t necessary unless you need to program the chip onboard). We also fitted a socket for MOD1 so we could remove the OLED if necessary; you can hard solder it using a standard pin header. Tack solder a couple of IC1’s leads and check that the other pins on both sides are correctly aligned. Adjust it if needed before carefully soldering the remaining pins. When finished, clean away any flux residue (eg, using alcohol) and closely inspect the soldering before proceeding, as it will be much easier to correct problems you find before more components are fitted. If you have bridged any of the pins of the IC, add a dab of flux paste on top and then use solder-wicking braid to clear it. Verify that all pins have had solder flow onto both the pin and the pad; if it’s just on the pin, it will not make a good connection to the PCB. Fit the three SOT-23 devices next, being careful not to mix them up. Dual diode D1 is near the top of the PCB, with PNP transistor Q1 near the bottom. Q2, the NPN transistor, is near IC1. If you aren’t sure which is which, they should have codes printed on the top. The parts list has likely codes siliconchip.com.au Fig.3: fit the components to both sides of the main PCB as shown here. Most of them are moderately easy to solder apart from IC1, which has closely spaced pins. Don’t mix up the different SOT-23 devices and note that D2 and D3 are connected in opposite directions. You don’t need to fit the headers for CON1 and MOD1; we did so to simplify the development process. These photos show a number of the important construction details. The arms attach to the main PCB with chunky solder fillets and are protected by heatshrink tubing. The white screw and nuts prevent the coin cell from being easily removed. A header pin soldered between the main PCB and the OLED PCB helps to reinforce the OLED mounting. A solder fillet mechanically secures the tips to the arms. Ensure that the solder surrounds one end of the header pin and flows into the holes in the arm PCB. (although they can vary by manufacturer). In each case, apply a little flux paste to the pads, tack one lead, then check that the other two leads are within their pads before soldering them. Australia's electronics magazine The two single diodes, D2 and D3, face in opposite directions, so check that the PCB’s cathode markings match the devices’ cathode stripes. Fit the capacitors next, being careful not to mix them up, as they are not June 2024  59 Screen 1: the default display at power-on. Touching the tips together will show a low readings in ohms. The cell voltage is displayed next to a countdown timer; when the timer expires, the Tweezers enter a lowpower sleep mode. Screen 2: the second operating mode uses the low-current range to measure resistance without unnecessarily loading the cell. If S1 is pressed in any operating mode, the timer is paused and dashes are displayed, as seen here. Screen 3: the third mode gives readings for capacitance (between 100nF and 50μF) and ESR using low-current pulses. A typical 10μF capacitor is connected here. Pressing S2 will resume the timer, as will changing modes with S3. marked. There are four 100nF capacitors on the front of the PCB plus one 10μF capacitor. One of the 22μF capacitors is on the front, while the other mounts on the back of the PCB. Now carefully work through the 11 resistors, matching the markings to the PCB silkscreen. The parts list shows the typical markings for the values we are using. Note that one of the 3kW parts is also on the back of the PCB. Next, solder the cell holder to the back of the PCB. Make sure that the opening faces towards the screw hole; you can compare it to our photos. Now thoroughly clean the flux residue off the PCB using a suitable solvent. Your flux might recommend one on its data sheet, but isopropyl alcohol is a good all-round alternative. Methylated spirits can be used, although it might leave residue. Allow the PCB to dry and inspect it again before proceeding. Next, solder the three tactile switches, S1-S3. We do this now to avoid getting solvent in their mechanisms. They are fitted in much the same way as the other surface mounting parts but are a bit larger and easier to manage. You can carefully clean up any flux residue from this step using a cotton tip or similar moistened by a small amount of solvent. available as part of the MPLAB X IDE download and can be installed on Windows, Mac and Linux computers. Choose the PIC24FJ256GA702 and open the 0410524A.HEX file in the IPE. Enable power from the programmer if you need it. To avoid permanently soldering the header to the PCB, you can push the 5-way header into the socket on your programmer while holding the other ends of the pins in place through the pads of CON1. It’s a bit of a juggle, but it will make the Tweezers easier to use later. Click the button to program the chip and check that the IPE verifies the program correctly. Programming the microcontroller You won’t need to perform this step if you have a pre-programmed microcontroller from the Silicon Chip Online Shop (including the one in our kit). If you have a blank micro, it’s best to program it now before the arms and display are fitted, as they might get in the way. You’ll need a Snap, PICkit 3, PICkit 4 or PICkit 5 programmer to program the PIC24FJ256GA702 microcontroller. The Snap cannot provide power, so you can temporarily fit the coin cell while programming occurs. We suggest using Microchip’s free MPLAB X IPE for programming. It’s Fitting the arms The arms are each formed from a long, thin PCB, with the tips using gold-plated header pins to offer a low-resistance contact surface that will not corrode. Tin each arm tip generously and remove the header pins from their shroud. The rear of the ESR Test Tweezers before the protective panel is attached. Coin Cell Precautions The ESR Test Tweezers make use of a coin cell. Even though we have added protections such as the locking screw, there is no reason for this device to be left anywhere that children could get hold of it. Also, the tips are pretty sharp and might cause injury if not used with care. 60 Silicon Chip Australia's electronics magazine siliconchip.com.au Screen 4: the Calibrate step takes readings with open and shorted tips and automatically sets the ADC saturation settings and probe (contact) resistance. Leave the tips open, press S1, then hold the tips together and press S1 again. Then release the tips. You can try again if you get an error. Screen 5: the bandgap voltage is the nominally 1.2V reference used by IC1 for voltage measurements. At the bottom is the calculated supply (cell) voltage; use S1 & S2 to trim the bandgap until the displayed voltage matches the cell voltage, measured using a multimeter or similar. Screen 6: the display can be rotated by 180° to suit left- or right-handed use. Press S1 to toggle it and the display will rotate immediately to the new setting. Like all the other settings here, these new values are used immediately but are not automatically saved to non-volatile flash memory. Using a pair of tweezers, solder a pin in position to the end of each arm, as shown in the photos. Try to line them up so they are centred. Note that the pins face inwards once the Tweezers are assembled. The arm PCBs slot over the larger pads in the corners of the main PCB. We recommend not fully pushing the main PCB into the slot; leave some room. Take care that the arms do not contact any other pads on the PCB. Fitting the arms is a bit like fitting the SMD components. Tack them roughly in place and check that they are aligned well, then add more solder to secure them firmly. Check the action and see that the tips meet correctly. Finally, add solid fillets of solder all-round to make them mechanically secure. Slide the heatshrink tubing over the arms, leaving the tips clear, then shrink it in place. Doing this now avoids damage to the OLED screen from excessive heat. We’ve taken some photos of the ends of the arms so you can see how the tips are attached and how the arms mount to the main PCB. prevent it from flexing and touching the main PCB. The back panel PCB can be soldered to the ground pins of MOD1 and CON1 or simply stuck to the back of the cell holder using double-sided tape. Ensure that the ESR TWEEZERS legend faces outwards (it’s a dual-use panel; the other side has the legend for the Advanced Test Tweezers). Finally, fit and secure the cell using the M2 Nylon screw and nuts. The nuts go on the same side as the cell, giving the depth needed to prevent the cell from being easily pulled out. The photos show how we have done that on our prototype. This is to prevent a child who might get hold of the Tweezers from removing the cell, which could be dangerous (it is hard to pull out regardless, but this is worthwhile extra security). The OLED screen The OLED is mounted next. You should be able to simply slot the fourway pin header into the pads of the MOD1 footprint on the PCB. We recommend temporarily placing a piece of card behind the OLED to prevent it from shorting the main PCB or arms. This will also help to add a small space between them. Tack one pin and check that the display is neat and square. Solder the remaining pins and remove the piece of card. You can fit the battery at this stage and check that everything works. You should see something like Screen 1 when it is first powered on. The reading should show a low value (under 0.1W) when the tips are shorted together. Remove the battery and solder a pin header or piece of solid wire to the top right corner of MOD1 and through to the main PCB underneath. This provides extra support for the OLED to Calibration and operation In regular operation, pushbutton S3 cycles between the modes, while S1 pauses the countdown timer. S2 The ESR Test Tweezers shown at actual size. It’s easy to read the screen while probing components. Most constructors do not need to solder the programming pin header. siliconchip.com.au Australia's electronics magazine June 2024  61 Screen 7: as with our other Tweezers, the OLED current draw is the single most significant drain on the cell. Setting the display brightness as low as possible (using S1 & S2) will prolong the cell life. The default level of 30 is the lowest usable setting; it can be changed in steps of five up to 255. Screen 8: the timer is displayed in the ESR, RES and CAP modes. The Tweezers go into a low-power sleep when it counts down to zero. The time can be set in multiples of five seconds up to 995 seconds (about 16 minutes). Since the timer can be paused, you might not need to change this setting. Screen 9: four screens like this calibrate the current pulse values. Connect the recommended resistor or capacitor value (100W here) across the probes and trim the value until the smaller text (99.90W) is close to the actual value connected. The default values are based on our prototype. (or any S3 mode change) will enable it again. The timer is shown at upper right and defaults to 10 seconds. When it expires, the low-power sleep mode is activated. Normal operation is resumed by pressing any button. Screen 2 shows the RES mode, with a 510W resistor connected. The three dashes at upper right indicate that the timer is paused. That means the ESR Test Tweezers will not go to sleep; it will probably drain the battery within a day or two if left like this. Screen 3 shows a 10μF capacitor connected in CAP mode; similarly, the timer has been paused to allow continuous readings to be made. All three operating modes also show the cell voltage at the top of the screen. Our prototype could function down to around 2V. This is about the point at which the PIC24 processor stops working. We specify 2.4V as the minimum supply voltage, as the accuracy of readings declines significantly below that. A long press of S3 (about two seconds) switches between operating and settings modes, with S3 then cycling through the various parameters and S1 and S2 adjusting them. The ESR Test Tweezers are usable without calibration, but the calibration steps are easy. There are also a couple of customisation preferences you can apply. Many calibration steps involve measuring a known value or voltage with the Tweezers and trimming the calibration factor until the displayed value is accurate, which is quite simple and intuitive. The suggested parts to use are 10W, 100W and 1kW resistors for calibrating ESR and a 10μF capacitor for calibrating capacitance. These values are near the top of their ranges, so they will provide the best resolution when performing the calibration. The calibration factors are shown in ohms because they are analogous to providing an exact value for the second resistor in a divider. However, because of the circuit’s complexity, they don’t correspond to any measurable resistance value. If you don’t have these exact value resistors, a lower value (preferably within that decade) will be adequate. Higher values might be outside the limit of their respective range, in which case the display will show “OPEN”. Remember that while resistors are readily available with 1% tolerance or better, capacitors could vary up to 20%. If possible, measure your capacitor with an accurate capacitance meter and use that instead of the nominal value. The panels above with Screens 4-12 detail the available calibration and setup options. Be sure to do the steps in the order listed, as some factors depend on others being set accurately beforehand. To return to normal operation from settings, press and hold S3 for about two seconds. Be aware that the sleep timer does not count down while in Settings mode, so you should return to operating mode immediately after changing the settings to avoid draining the battery. We designed this PCB to protect the back of the Test Tweezers. It can be attached to the cell holder with double-sided tape. It has markings on the opposite side so that it can also be used for the Advanced Test Tweezers. This blue version will be available on our website for users of the Advanced Test Tweezers, although a white version will be included in ESR Test Tweezers kits. 62 Silicon Chip Australia's electronics magazine Using the ESR Tweezers Connect the component to be tested between the tips of the probes and apply pressure to make sure they are making good contact. Polarised components should have their positive lead connected to the top (TP+) tip. However, the test voltage is low and should not cause damage if the component is reversed. Diagnosing capacitor problems due to high ESR is helpful for those in the power and audio fields. Now you can check that with a handy, compact tool that doesn’t cost much to build. The ESR Test Tweezers can measure ESR, resistance & capacitance (albeit over somewhat limited ranges), making them more valuable than the 2004 design and in a smaller package. SC siliconchip.com.au Screen 10: this is the last screen you should need to use for setup and calibration. Press S1 to save any altered settings to flash memory; S2 will load the defaults in case the saved data becomes corrupted. The defaults can also be loaded by holding S3 while powering up the Tweezers. Screen 11: after saving to or restoring from flash, you should get a message indicating it completed successfully. This is the last necessary step for setup and calibration; a long press of S3 will return to operating mode. As well as on the first use, you should recalibrate when a new cell is fitted. Screen 12: there are some screens after Save/Restore that should not need to be changed; they adjust the factors set by the Calibrate step shown in Screen 4. They include the probe contact resistance (shown here) and two pages with ADC limit values, used to check that readings are valid. Dissipation factor, loss angle and ESR Dissipation factor (DF) and loss angle (δ) measure the energy lost in an oscillating system. Many capacitor data sheets specify these instead of providing an ESR value. In our case, the dissipation factor and loss angle specifically refer to the losses in a capacitor due to ESR. These terms are also used in other contexts in electrical engineering, but we are looking specifically at capacitor ESR. We want to relate the capacitive reactance to the pure resistance due to ESR. Both can be plotted on the complex number plane, hence the references to angles. The loss angle is simply the inverse tangent function of the dissipation factor; thus, you might also see ‘tangent of loss angle’, which means the same as ‘dissipation factor’. Since the reactance changes with frequency, we need to focus on a specific frequency. For example, in a transformer-based mains power supply, the capacitors will be subjected to predominantly 100Hz (50Hz mains) or 120Hz (60Hz mains) ripple. Capacitors in audio circuits will be subjected to a broader range of frequencies, perhaps 20Hz to 20kHz. Capacitors in switchmode supplies will generally have ripple at 20kHz to 2MHz. Let’s take a concrete example of a capacitor, such as the 4700μF 50V electrolytics we have used in numerous projects, such as the Dual Hybrid Power Supply from February & March 2022 (siliconchip.au/Series/377). The Dual Hybrid Power Supply article specifies Nichicon UVZ1H472MRD capacitors to filter the rectified output of a mains transformer. Their data sheet lists a (maximum) tangent of loss angle of 0.2. That corresponds to a loss angle of 11.3° or 0.197 radians, ie, tan(11.3°) ≈ 0.2. Note that the loss angle (in radians) is very close to the dissipation factor for typical values. This is a well-known approximation for the tangent function at low values. Using the impedance equation for capacitors of Z = 1 ÷ (2πfC), we get an impedance value of 0.34W for a 4700μF capacitor at 100Hz. Multiplying this by the dissipation factor of 0.2 gives an ESR of 0.068W, close to the 0.05W noted in Table 1 for similar capacitors. If you measured an ESR siliconchip.com.au of 0.05W for such a capacitor, that would be acceptable, as it is below the specified maximum. The loss angle (δ) can be visualised with a diagram of the complex impedance (Fig.a), which shows the reactance due to capacitance in the imaginary plane (vertical) and the resistance due to ESR in the real plane (horizontal). The cosine of the loss angle relates to the proportion of energy transmitted by the capacitor (compared to that dissipated by the ESR). At low loss angles, the cosine of δ is close to unity, and there are no losses, although they rise sharply as the angle (and ESR) increases. These ideas are similar to concepts like power factor (and power angle), although, in AC power systems, the capacitive element is undesirable and a purely resistive load is preferred. You can also see from this how a high ESR would create a phase shift for audio signals, increasing distortion. Australia's electronics magazine Fig.a: this complex plot shows how a capacitor’s impedance (Z), ESR and loss angle (δ) are related. The dissipation factor (DF) is the ratio of the horizontal distance (ESR) to the vertical distance (Z), ie, DF = ESR ÷ Z = tan(δ). June 2024  63 Using Electronic Modules with Jim Rowe MicroMag3 3-axis Magnetic Sensor The MicroMag3 can measure the strength of a magnetic field in three orthogonal axes (eg, North-South, East-West and Up-Down). In effect, it combines the functions of a magnetic compass and an inclinometer. T he MicroMag3 can measure magnetic fields over a wide range of strengths with high resolution and operates from 3V DC, drawing less than 0.5µA of current. It has SPI (serial peripheral interface), so it can communicate with just about any microcontroller. As you can see from the photos, this module is quite small, measuring only 25.4 × 25.4 × 19mm, with the last dimension including both the Z-axis sensor mounted vertically on the top of the PCB and the two 7-pin headers under the sides of the PCB. Manufactured by US firm PNI Sensor Corporation based in Santa Rosa, California, it uses a patented technology called Magneto-Inductive Sensing. The module is specified as being able to measure magnetic fields over a wide range from -1100µT to +1100µT. 1T = 1 tesla = 10,000 gauss = 10,000G. So 1100µT = 1.1mT or 11.0G. The measurement resolution is specified as 0.015µT or 0.00015mG. The MicroMag3 and later versions using the same technology have found their way into a significant number of navigation devices for automotive, marine, aeronautical and even space vehicles. Before we delve deeper into how the MicroMag3 works and how it can be used, we should mention its availability. We bought a couple of the modules from Altronics, which, at the time of writing, has them available (Cat Z6300) for $5.90 each, plus delivery costs. It looks as if Altronics obtained them from the US firm SparkFun Electronics, but when you go to their website (www.sparkfun.com), they advise that the product has been ‘retired’ from their catalog and is no longer for sale. Then, if you go to the PNI Sensor Corporation’s website (www.pnicorp. com), they have dropped all references to the MicroMag3 and only provide data on later versions. You can still find the data sheet for the MicroMag3 on the SparkFun website if you go to www.sparkfun.com/ products/retired/244 So Altronics is the only current supplier of the MicroMag3 that we could find, suggesting that if you want to get hold of one, you may have to be quick! How it works 64 Silicon Chip Fig.1: the MicroMag3 sensor module uses a PNI 11096 ASIC (application-specific integrated circuit). The upper right-corner of the diagram shows how the sensors are orientated. Looking at the photos, you will see a single IC on the PCB, in a compact 28-pin SMD package. It is labelled PNI 11096 and is described in their data sheet as an ‘ASIC’ or application-­ specific IC. Apart from some SMD resistors and capacitors, the only other components on the PCB are the three tiny magneto-­ inductive sensors. Labelled MS1, MS2 and MS3, these each measure only 6.0 × 2.1 × 2.21mm. They are used to sense and measure the magnetic field in one of the three axes. Australia's electronics magazine siliconchip.com.au Fig.1 shows the circuit for the MicroMag3 module, with the PNI 11096 ASIC in the centre and the three magneto-inductive sensors to its right – each with a pair of biasing resistors. Along the bottom are the pins of the 7-pin header provided to allow control by and communication with an MCU (microcontroller unit). The first three pins (SCLK [serial clock], MISO [master-in, slave-out] and MOSI [master-out, slave-in]) are the SPI interface, while the other pins control the ASIC. Up the top are the pins of the second 7-pin header, with only two used to supply the ASIC with 3V DC power. At upper right in Fig.1 is a small diagram showing the way the three sensors are configured to measure the three magnetic axes. The MS1 sensor measures the field in the X or North-South axis, MS2 measures the field in the Y or East-West axis, while MS3 measures the field in the Z or up-down axis. According to the PNI data, the sensors are arranged in a south-west-down or ‘SWD’ configuration. We’ll explain the significance of that later on. Before we look at how the three magneto-inductive sensors measure surrounding magnetic fields, here’s a rundown of the basic measurement procedure, shown graphically in Fig.2. Bear in mind that the ASIC can only measure via one sensor at a time. First, the controlling device drops the voltage on the ASIC’s SS (slave select) pin to indicate that a measurement is to start, then it sends a short positive pulse (>100ns) to the RESET pin. After that, it sends an 8-bit command via the MOSI pin, specifying the sensor to be used (MS1, MS2 or MS3) and the measurement period. The measurement period specifies how many oscillator cycles should be used for the measurement, with choices ranging from 32 to 4096 cycles. The measurement resolution increases with the number of cycles, but 2048 cycles is usually sufficient. The next step involves the MCU either waiting for the ASIC to pull up the voltage on the DRDY (data ready) pin, or just waiting long enough for the ASIC to have made the measurement and have the data available. In either case, the MCU must then send out 16 clock pulses on the SCLK line, to receive the 16-bit measurement data via the MISO line. Finally, the MCU raises the voltage on the SS pin, to signal the end of that measurement sequence. Making measurements of the field intensity in all three axes requires three of these sequences to be completed, one for each axis. Magnetic sensing Now let’s look at how the magneto-­ inductive sensors are used to make the measurements. Each sensor consists of a solenoid coil wrapped around a very high-permeability magnetic core. As shown in Fig.1, each sensor coil has four connections to the ASIC. So the MS1 coil has direct connections to the APXIN and ANXIN pins, plus connections to the APXDRV and ANXDRV pins via the two 62W series resistors. The other two sensor coils are connected to the corresponding pins for the Y and Z axes. Inside the ASIC, each sensor’s coil is used in a simple L-R relaxation oscillator, with its inductance determining the oscillation frequency. As its inductance varies according to the The MicroMag3 module shown at twice actual size. magnetic field passing through its core, the external field can be measured by alternately driving a direct ‘bias’ current from one end of the coil to the other and then back the other way. When there is no external magnetic field, the sensor coil’s inductance will be identical when the bias current flows in either direction because the inductance will be swinging symmetrically on either side of the core’s ‘zero field’ peak. As a result, the oscillator frequency will be the same in both directions. But when there is an external magnetic field, the inductance and frequency will differ depending on the direction of bias current flow. This allows the PNI 11096 chip to measure the strength of the external field by measuring the time taken to complete a fixed number of oscillations in the ‘forward biased’ and ‘reverse biased’ directions, and taking the difference between the two. That is the principle of PNI’s magneto-­ i nductive sensing technology. Fig.2: the microcontroller sends a command byte on the SPI bus, then waits a certain period before reading back 16 bits of measurement data. siliconchip.com.au Australia's electronics magazine June 2024  65 If that explanation isn’t clear enough, there is a PNI ‘white paper’ called Magneto-Inductive Technology Overview, written by Andrew Leuzinger and Andrew Taylor, which you can download as a PDF file from several sources on the web. I found it at siliconchip.au/link/abs5 Connecting it to an Arduino Fig.3 shows how easily the module can be connected to an Arduino Uno. It should be just as straightforward to connect it to any other versions of the Arduino, including the new Uno R4 Minima, or many other microcontrollers such as the Micromite or Maximite. All you need to do is connect the module’s VDD and GND pins to the +3.3V and GND pins of the MCU, then connect its SCK, MISO and MOSI pins to IO13, IO12 and IO11 of the MCU. Those are the pins that the Arduino’s SPI library expects you to use for SPI communication. The only other connections required are those for the module’s SS, DRDY and RESET lines, which, as shown in Fig.3, connect to pins IO7, IO6 and IO5, respectively. Note, however, that if you use our sketch to control and communicate with the MicroMag3, you don’t need to connect the module’s DRDY pin to the Arduino’s IO6 pin. We found it easier to rely on a time delay before requesting the measurement data, as should become clear shortly. Software We need a sketch to use the MicroMag3 module with an Arduino, so I looked around the web to see if suitable sketches had already been written. I found a couple, but they both used a ‘bit-banging’ approach, rather than using the Arduino SPI library and the microcontroller’s built-in SPI peripheral. That seemed a bit clumsy, so I decided to see if I could come up with a more elegant solution. Producing a working sketch turned out to be more work than I anticipated. The main hurdle I encountered was in trying to use the module’s DRDY pin to sense when the module had measurement data available. That is the approach recommended in PNI’s data sheet, by the way. After many puzzling ‘hung sketch’ results, I tried analysing the module’s operation with a DSO. I discovered that the module’s DRDY did go high after each measurement, but only after about 36ms (milliseconds). That seemed to be too long of a wait. After discussing this with my Silicon Chip colleagues, Nicholas Vinen and Tim Blythman, we concluded that it would be better to forget about using the DRDY line and simply wait a little longer than the expected processing time before requesting the measurement data. Suddenly, the sketch sprang to life! The sketch then printed the field measurements for the three axes via the Arduino IDE’s Serial Monitor. Encouraged by this success, I added a section to work out the module’s ‘compass heading’ from the X-axis and Y-axis readings. It was clear that I would need an arctangent function to work out the compass heading from the X-axis and Y-axis readings, yet there seemed to be no such function listed in the Arduino Language Reference. Thinking I might have to include a special ‘maths’ library to get one, I went onto the Arduino forum to find the answer. I discovered that you didn’t need a special library because the existing library includes two such functions, even though they were not listed or even referred to in the Language Reference. The functions are atan() and atan2(), with the second able to work out angles in all four quadrants. Editor’s note – those are standard C library functions from the “math.h” include file, which might explain why they are available but not listed in the Arduino documentation. Arduino is built on C++, which is built on C, so you can access those underlying functions if necessary. Fig.3: how to connect the MicroMag3 module to an Arduino Uno or similar microcontroller. Note that if you’re using our example sketch, then the DRDY pin does not need to be connected. Fig.4: this is the orientation provided by our demo sketch. It could be changed with some extra calculations if required. 66 Silicon Chip Australia's electronics magazine siliconchip.com.au Once I understood that, it wasn’t too long before I could get the compass heading part of the sketch working. There was just one minor complication: the MicroMag3 module’s X axis is aligned with the white line with its arrowhead at upper right on the module PCB, which suggests that the sketch should read ‘true north’ when the module is facing north when pointed in the direction of the arrow. However, I could only get the heading function to work correctly once I reversed the module orientation so that the end of the PCB nearest the MS1 sensor and the ASIC is used as the ‘compass pointing’ end. I suspect this is because of the way the MicroMag3 is set up with the “SWD” scheme (south-west-down). It would be possible to fix that by adding 180° to the output of the arc­ tangent function, modulus 360. Still, I thought it was simple enough to use the module’s rear as the compass pointing end, as shown in Fig.4. Doing that produces the expected bearings without any additional mathematical steps. The resulting sketch file is named Screen 1: example sketch output 14:20:27.626 -> A sketch to communicate with the MicroMag3 14:20:29.781 -> X reading = 1112 14:20:29.781 -> Y reading = 17 14:20:29.781 -> Z reading = -1375 14:20:29.828 -> Heading = -0.02 radians or 0 in degrees 14:20:29.875 -> 14:20:40.045 -> X reading = 971 14:20:40.091 -> Y reading = -602 14:20:40.091 -> Z reading = -1472 14:20:40.138 -> Heading = 0.55 radians or 31 in degrees 14:20:40.138 -> 14:20:50.355 -> X reading = 826 14:20:50.355 -> Y reading = -764 14:20:50.401 -> Z reading = -1519 14:20:50.401 -> Heading = 0.76 radians or 42 in degrees 14:20:50.448 -> 14:21:05.820 -> X reading = 119 14:21:05.820 -> Y reading = 759 14:21:05.820 -> Z reading = -1576 14:21:05.867 -> Heading = -1.42 radians or -81 in degrees 14:21:05.913 -> “Silicon_Chip_MicroMag3_control_ sketch_V2.ino” and you can download it from siliconchip.au/Shop/6/330 Screen 1 shows a screen grab of the Serial Monitor listing when running my sketch, and first pointing north, then towards north-east (+31°, and +42°), and then towards the west (-81°). The sketch does not provide any readout of the magnetic field’s inclination, just the Z-axis reading. I will leave doing that as an exercise for our SC readers. PIC Programming Adaptor Our kit includes everything required to build the Programming Adaptor, including the Raspberry Pi Pico. The parts for the optional USB power supply are not included. Use the Adaptor with an in-circuit programmer such as the Microchip PICkit or Snap to directly program DIP microcontrollers. Supports most newer 8-bit PICs and most 16-bit & 32-bit PICs with 8-40 pins. Tested PICs include: 16F15213/4, 16F15323, 16F18146, 16F18857, 16F18877, 16(L)F1455, 16F1459, 16F1709, dsPIC33FJ256GP802, PIC24FJ256GA702, PIC32MX170F256B and PIC32MX270F256B Learn how to build it from the article in the September 2023 issue of Silicon Chip (siliconchip.au/Article/15943). And see our article in the October 2023 issue about different TFQP adaptors that can be used with the Programmer (siliconchip.au/Article/15977). Complete kit available from $55 + postage siliconchip.com.au/Shop/20/6774 – Catalog SC6774 siliconchip.com.au Australia's electronics magazine June 2024  67 Project by Tim Blythman USB C SERIAL ADAPTOR USB Type-C (USB-C) was introduced around 10 years ago and is now becoming standard. While USB-serial adaptors with Type-C sockets are available, many do not adhere to the USB-C standard and may also have Windows driver problems. Our design, presented here, has no such drawbacks and is relatively simple and compact. W e have started adding USB-C sockets to our projects as the necessary components have become available in a format that is easy to solder. Because almost all new smartphones and tablets have USB-C sockets, USB-C chargers and cables are becoming commonplace. Small electronic modules have been a great boon for many reasons. In parallel with the rise of Arduino, they have made it very easy to connect microcontrollers to other electronic components. We have a bit of a love/hate relationship with USB-serial adaptors. While they are incredibly useful and inexpensive, sometimes the chips used in them are clones. You might not have any idea of that until a Windows update causes the device to stop working. A clone chip can look identical to the real deal; sometimes, the only way to tell is to X-ray it! It isn’t just a single chip that suffers from this problem. Chips labelled FT232, PL2303 and CH340G have caused problems in the past. Others may be vulnerable too. Our design doesn’t have this problem because we use a PIC microcontroller programmed to act as a USB/ serial bridge, and it identifies as a generic CDC device, so there should be no way that the drivers can go wrong. Windows, Linux and macOS recognise it without needing any special drivers installed and should work immediately after being plugged in. We have used USB-serial adaptor modules based on the CP2102 chip in several projects. We covered this module with a dedicated article in the January 2017 issue (siliconchip. au/Article/10510). One advantage of Fig.1: a USB-C source provides pullup currents, while a sink has pulldown resistors. Both can monitor the voltage on the CC line to determine what has connected to the other end of the cable. The source applies different currents (Ip) depending on its capacity to supply current to VBUS, which the sink can detect as differing voltages on the CC line. Advanced modes, like power delivery (PD) and dual role (DRP), are negotiated through digital signalling on the CC lines. 68 Silicon Chip Australia's electronics magazine the CP2102 is that, like our design, it doesn’t require drivers to work with modern operating systems. Because of that, both the CP2102 module and our version will work if plugged into our Pico Digital Video Terminal from the March and April 2024 issues (siliconchip.au/ Series/413). The most common CP2102 module is a compact device with a micro-USB socket to connect to a computer and a six-pin header to provide 3.3V logic level UART (universal asynchronous receiver transmitter, ie, serial) signals. So we have patterned our designs on that one. USB-C advantages and challenges USB-C is becoming ubiquitous; even Apple products like the iPhone, which have long had proprietary connectors, have switched to using USB-C, starting with the iPhone 15 in 2023. The latest version of the Microchip PICkit debugger and programmer, the PICkit 5, also has a USB-C socket. We think that is an improvement over the micro-USB socket on its predecessor, the PICkit 4. We have reviewed the PICkit 5 in the November 2023 issue (siliconchip.au/Article/16016) Although only slightly larger, in our experience, USB-C plugs and sockets are more robust than the micro-USB and mini-USB parts that preceded them. USB-C plugs and sockets are also symmetrical, which means they are less fussy to use. USB-C to USB-C cables also exist, siliconchip.com.au USB-C Serial Adaptor Features & Specifications ● Drop-in replacement for compact CP2102-based USB-serial modules with the same connector pinout ● Uses the now standard USB-C socket instead of a micro-B USB socket ● Uses a low-cost PIC16F1455 microcontroller with a USB full-speed peripheral ● Moderate component size for hand construction ● Supports 8N1 format and a wide range of baud rates (47 baud to 3Mbaud) ● 3.3V, DTR, RX, TX, GND and 5V connections ● LED indicators for power, data reception and data transmission ● No concerns about Windows drivers refusing to work with it due to counterfeit blocking attempts USB-C Serial Adaptor Kits (SC6652, $20) Includes the PCB, programmed microcontroller and all other parts to build the module; see the parts list later in this article. in which case the cable ends are even interchangeable. They are certainly less bulky than the USB sockets and plugs that appeared over 20 years ago. So it is no surprise that USB-C is becoming popular. USB-C is also more complex than its predecessors and requires some knowledge to implement correctly. That has tripped up some engineers who don’t understand the requirements fully. Even the Raspberry Pi Foundation had trouble with this, as their first release of the Raspberry Pi 4 had a hardware bug that meant it would not work with some USB-C cables, specifically ‘smart’ e-marked (with embedded electronics) cables. Older, simpler legacy cables appeared to be immune. In simple terms, the signalling resistors used to determine the orientation and role of the cable (in combination with the CC wire in the cable) were not connected correctly. This meant that very early versions of the Raspberry Pi 4 boards were identified as audio adaptors instead of devices requesting a 5V power source and thus did not work. Legacy cables, such as USB-A to USB-C types, lack the CC wire in the cable and thus do not respond to the incorrect signalling and deliver power regardless. Fig.1 shows how the signalling should work. There is more background on this at siliconchip.au/ link/abu0 We’ve seen some versions of the CP2102 USB-serial modules that have replaced the micro-USB socket with siliconchip.com.au a USB-C socket but they completely omitted the signalling resistors. That means that these modules will not work in all cases. Such devices may appear to have intermittent faults, working with some cables or hosts but not others. At worst, they might not work at all. Our USB-C Serial Adaptor So, this USB-C Serial Adaptor is a drop-in substitute for the cheap but functional CP2102 USB-serial Module and it actually works reliably! Our Adaptor is a small PCB with a USB-C socket at one end and a sixway header at the other. Unlike the prebuilt modules you can buy, this is a constructional project you must assemble yourself. We have used some small parts, but it should be eminently doable for those with much experience in SMD soldering. It uses a PIC16F1455 microcontroller for its USB interface. The PIC16F145x family is one of the cheapest programmable chips with a USB peripheral. We’ve used the PIC16F1455 in several projects, most The USB-C Serial Adaptor is a minuscule 16×22mm and operates as a dropin replacement for the well-known CP2102 USB-serial Module. Its USB-C socket is more robust and modern than the micro-USB socket on typical USB-serial modules. The components are mostly M2012 (0805) size, but still can be hand-soldered. The USB-C socket is the finest-pitch part, so check its soldering thoroughly before applying power to the board. notably the Microbridge from May 2017 (siliconchip.au/Article/10648). The Microbridge provides a similar USB-serial function as our Adaptor but can also program PIC32 chips. However, the Microbridge doesn’t break out the DTR (data terminal ready) signal like the CP2102 module. The Microbridge also has a different connector pinout, meaning it is not a drop-in replacement for the Module. Circuit details One of the many types of CP2102based modules, which our USB-C Serial Adaptor is meant to replace. Fig.2 shows the circuit diagram of our new Adaptor. The USB socket, CON1, is a USB-C type that lacks the high-speed pairs. That means it only has one row of pins, making it easier to solder. The high-speed pairs are not needed for this design. We previously used a USB-C socket with those extra pins in the USB Cable Tester from the November and December 2021 issues (siliconchip.au/ Series/374). It had two rows of very fine pins and was very fiddly to solder; the variant used in this Adaptor is easier to work with. The SBU (sideband use) pins are present on the connector we’re using, but are not needed in this design and so are not connected. The two CC pins (configuration channel) are each connected to ground via 5.1kW resistors, signalling that the Adaptor is a power sink (ie, it consumes power rather than provides power). The remaining pins on CON1 are duplicated but are otherwise the same as used in standard USB 2.0 applications. The duplicated pins are simply Australia's electronics magazine June 2024  69 Unlike CP2102 modules, the USB-C Serial Adaptor (shown enlarged) has components on both sides, including a 1.27mm (0.05in) pitch 14-pin SOIC chip and a handful of passive components. connected together. They exist because the connector can be plugged in with two different orientations. CON2 is a six-way pin header matching that on the CP2102 modules. It provides a means to connect to the logic-level serial signals. 5V power and ground from CON1 are connected through to CON2, as well as supplying REG1, an MCP1700-3.3V regulator. It, and its two 1μF bypassing capacitors, provide the 3.3V supply to match that on the CP2102 module and so provide 3.3V logic levels. If you just wanted to get 5V and 3.3V from a USB-C cable, you could populate the Adaptor PCB with just the components mentioned so far. PIC16F1455 microcontroller IC1 is powered at pins 1 and 14 from the 3.3V rail. There is no separate bypass capacitor because the circuit is physically very small, and the 1μF capacitor on the 3.3V rail is close to the requisite pins on IC1. As an aside, the PIC16F1454 is much the same as the PIC16F1455, except it lacks the analog peripherals (such as the analog-to-digital converter [ADC]). We are not using any analog features, so the two chips are essentially interchangeable in this role. You should have no trouble using the PIC16F1454 if you have one on hand. Power indicator LED3 is fed from the 3.3V rail via a 1kW current-­limiting resistor. Serial data indicators LED1 (TX) and LED2 (RX) are driven via 1kW resistors from pins 9 and 10 of IC1 (digital outputs RC1 and RC0), respectively. Pin 11 of IC1 is connected to a 100nF capacitor that filters the output of a regulator internal to IC1’s USB peripheral. The USB D+ and D- signal lines (IC1’s pins 13 and 12) connect to the corresponding pins on USB socket CON1 to provide the USB data interface. Pins 5, 6 and 7 on IC1 are connected to CON2 via 220W resistors; these are the UART RX, TX and DTR signals, respectively. The 220W resistors protect the microcontroller by limiting the current that can flow through the pins. The 100kW resistor provides a weak pullup on the RX pin, preventing noise from being seen as data if that CON2 pin is left unconnected. The PIC16F1455 lacks an internal pullup on this pin, so we must provide this externally. Software The USB function is heavily dependent on software. We mentioned the Microbridge earlier; the Adaptor uses the same software library to provide the virtual USB serial port functions. The library enumerates IC1 as a CDC (communications device class) device. CDC encapsulates the features of devices like fax machines and modems that use a serial interface, so it is well suited to working as a virtual USB-serial port. The Adaptor software also configures pins 5 and 6 of IC1 as the UART (universal asynchronous receiver/ transmitter) RX (receive) and TX (transmit) pins. Unlike newer PIC chips, these functions cannot be allocated to other pins. Fig.2: aside from its basic functionality, the USB-C Serial Adaptor provides a few niceties, such as independently-driven TX and RX LEDs, series protection resistors for the data lines and a weak pullup on RX for noise rejection. 70 Silicon Chip Australia's electronics magazine siliconchip.com.au In theory, the Adaptor simply needs to check the current baud rate, take data at that rate from the UART RX pin and send it to the USB host, and from the USB host to the UART TX pin. In practice, a few other things need to happen to make it compatible with the CP2102 module. For a start, LED1 is switched on for about 50ms every time serial data is received from the USB host. Similarly, LED2 switches on whenever data is seen on the UART RX pin. Having separate lines to drive these LEDs means that the TX and RX lines are not loaded unnecessarily. We can also show a clearer indication that data is present by lighting the LED longer than it would be if driven directly by brief pulses on the serial lines. The DTR pin is held at a high idle level and then taken low whenever the virtual USB port is open; this means an application is actively connected to the CDC device. Also, the UART TX pin is set to a high-impedance state if a USB host is not connected. The utility of these functions may not be obvious, but they have specific uses in applications like the Arduino. Arguably, modules like the CP2102 USB-serial adaptor exist because of the Arduino ecosystem. In early Arduino boards (before the Uno!), the DTR pin on a separate USB-serial adaptor was used to reset the microcontroller and enter a bootloader. An RC circuit turns the high-low transition into a brief pulse for the micro’s reset pin, and the bootloader runs for the first second or so after reset. The circuit on the Uno R3 works similarly, although the USB-serial adaptor is incorporated into the board. Allowing the TX pin to float if there is no active connection means the corresponding RX pin on whatever is attached can be used for other purposes when not needed for programming since it is not being driven. USB data is passed in packets at times dictated by the driver in the USB host. Data is sent and received over the bus at 12Mbps (USB fullspeed) during these periods. If transmission and reception are both occurring, this data must be interleaved over the bus. Each direction has a 256-byte buffer to smooth the transition between the packetised USB data and the continuous UART data. The UART peripheral can also buffer a byte or two of siliconchip.com.au data before it gets moved to or from the main buffers. The software also monitors for packets requesting changes in the baud rate or to send a ‘break’ signal. A break is simply a condition where the TX line is held low for a time longer than one byte (the PIC16F1455 does this for 13 bit times). It is often used to synchronise transmission with the receiving device. When a request for a break signal is sent from the computer, the TX LED flashes for half a second. Limitations We have chosen the PIC16F1455 because it is inexpensive, but that is for a reason. An 8-bit microcontroller does not have much processing power, especially for handling the amount of data that USB can move around. As such, the Adaptor cannot do everything that a CP2102 module can. The UART peripheral on IC1 is limited to 8-bit or 9-bit data, and it does not natively support parity bits like the CP2102 chip. To keep things simple, we only support 8-bit mode. This helps with the throughput of the Adaptor too, as there is one less special case to handle. The current version of the software uses 92% of the 1024 bytes of available RAM, so there wouldn’t be space to store the 9th bit for both 256-byte buffers even if we wanted to. Still, it can handle all the typical use cases for a USB-serial adaptor, including very low and very high baud rates. Baud rates The PIC16F1455 has hardware that uses the USB host’s clock to tune its 48MHz internal oscillator; the available steps result in an oscillator error of up to 0.2%. The microcontroller can produce a wide range of baud rates, from 47 to 3,000,000 baud, from the 12MHz instruction clock. Our calculations show that the error in deriving the baud rate will be less than 0.2% for the standard rates shown in Table 1. Thus, the total error in the requested baud rate compared to the actual baud rate will be less than 0.4% for standard rates. Any arbitrary baud rate under 1Mbaud (1,000,000 baud) will have an error of less than 4%, which should be sufficient for most applications over short distances. Australia's electronics magazine Table 1 – baud rate accuracy Baud rate Max. error 110 0.20% 300 0.20% 600 0.20% 1200 0.20% 2400 0.20% 4800 0.20% 9600 0.20% 14,400 0.24% 19,200 0.20% 38,400 0.36% 57,600 0.36% 115,200 0.36% 230,400 0.36% 250,000 0.20% 460,800 0.36% 1,000,000 0.20% Typical error at standard baud rates (including 0.2% due to the internal oscillator). The throughput of a USB full-speed connection is 12 megabits per second; this will not be achieved in practice, as the USB connection is usually shared with other devices. Remember that this also includes data in both directions. In practice, the limit is much lower, primarily due to the drivers that limit the size of the packets that can be sent. We cannot easily change this, so we are somewhat stuck with that. So continuous transmission at higher baud rates is not possible, although we had no trouble sending and receiving bursts of data up to 3Mbaud and continuous reception up to 460,800 baud. Most of these concerns will not affect the common uses of these modules, such as acting as a programming interface for a microcontroller or handling user input (eg, on a Micromite) at baud rates between around 4800 and 115,200. Programming We have omitted a microcontroller programming header to keep the USB-C Serial Adaptor much the same size as the CP2102-based modules. Thus, unless you have a pre-­ programmed microcontroller, you should program it before soldering it to the PCB. If you purchase a kit from the Silicon Chip shop, IC1 will be programmed, so you won’t have to worry about it. June 2024  71 Our PIC Programming Adaptor project from September 2023 (siliconchip. au/Article/15943) has more information about the gear you might need to program an SMD chip. Note that you will also need a PICkit 3, 4 or 5 to do the programming. To allow us to quickly reprogram our prototype during development, we soldered fine wires directly to the PIC’s programming pins while it was mounted on the PCB. That is an option to consider if you only need to do this once for this project. We used the low-voltage programming pins (pins 12 and 13) since the other programming pins (pins 9 and 10) are loaded by the LEDs, which could interfere with programming. Of course, pins 12 and 13 are the USB pins, so you should not have a programmer connected at the same time anything is connected to the USB socket. Fig.3: use this diagram and the photos to ensure that the many small components are all fitted in the correct locations. Take care that IC1 is installed the proper way. If you look from the end of the chip, you should see the chamfered edge on the pin 1 side. a PCB, you might prefer a straight header. If you are adding the Adaptor to a low-power design, you could omit the LEDs to save on the current they would draw. In that case, you could also omit the 1kW resistors. The 100kW resistor could also be left off if you are sure that the RX pin will always be in a well-defined state. Construction options Construction We’ve specified a right-angled header for CON2 since that is what most CP2102-based modules are supplied with. If fitting the module to You’ll need all the standard gear for SMD work, including a good magnifier. This is one of the smaller projects we have created, and it packs the parts in fairly tightly. You might need a magnifier even to read the PCB’s silkscreen markings. Make sure you have solder flux (ideally as a paste), tweezers, a fine-tipped iron and a means of securing the board, such as Blu-Tack. Fume extraction (or working outside) will help remove flux smoke. You should also have a suitable solvent for cleaning up the PCB afterwards, and solder-wicking braid will be helpful in case a solder bridge forms. The USB-C Serial Adaptor is built on a double-sided PCB coded 24106241 that measures 16×22mm. We’ll refer Songbird An easy-to-build project that is perfect as a gift. SC6633 ($30 plus postage): Songbird Kit Choose from one of four colours for the PCB (purple, green, yellow or red). The kit includes nearly all parts, plus the piezo buzzer, 3D-printed piezo mount and switched battery box (base/stand not included). See the May 2023 issue for details: siliconchip.au/Article/15785 72 Silicon Chip Australia's electronics magazine siliconchip.com.au to the side with the USB-C socket as the top of the PCB, with microcontroller IC1 at the bottom. The overlay diagram, Fig.3, should help you place the small components. USB-C socket CON1 has the finest pin pitch of the parts used, so fit it first. Add a thin layer of flux to the PCB over its pads, then position the socket. There are holes to help align it, and you can add more flux to the top of the pins too. Tack the larger end-most pins and confirm that the other pins are aligned with their pads and that the socket is flat on the PCB. You can then solder the mounting pins to secure the location. Add flux to the tops of the mounting holes and apply the solder from below until it can be seen wicking up the pins to the top side. That way, you know this part is properly secured and won’t easily be torn off the PCB. Now solder the remaining pins of CON1. If you get a bridge between two pins, add a little more flux and use solder-wicking braid to draw it up. If you’re unsure about your soldering, clean up the flux to get a better view of the pins under magnification before proceeding. Solder REG1 in place next. This is on the same side of the PCB as CON1. Apply a little flux to the PCB pads and tack one lead, then check that the other leads are aligned before soldering them. That is the basic strategy needed for the remaining SMD parts. This side also has the three LEDs and their 1kW resistors. LED1 is blue and is fitted adjacent to the TX pin on CON2, while LED2 is red and is nearer to the RX pin. LED3 is green. While it wouldn’t be a tragedy if you mixed up the colours, we tried to make them easier to remember (eg, red and RX both start with the letter R). LED1 and LED2 have their cathodes towards the USB-C socket. The cathode is usually marked with a small green dot or something similar, but it’s best to check with a DMM set on diode test mode. When you touch the probes to the LED pads and it lights up, the red probe is on the anode, while the black probe is touching the cathode. LED3 faces the opposite direction. Next, solder the 1kW resistors and then one of the 1μF capacitors, which should be the last SMD part on this side of the PCB. Next, flip the PCB over and fit IC1. The technique is much the same, siliconchip.com.au Parts List – USB-C Serial Adaptor 1 double-sided PCB coded 24106241, 16×22mm 1 SMD USB Type-C socket with power & USB 2.0 data (CON1) [GCT USB4105 or equivalent] 1 6-way right-angle pin header (CON2) Semiconductors 1 PIC16F1455-I/SL microcontroller programmed with 2410624A.HEX, SOIC-14 (IC1) 1 blue SMD LED, M2012/0805 size (LED1) 1 red SMD LED, M2012/0805 size (LED2) 1 green SMD LED, M2012/0805 size (LED3) 1 MCP1700-3302 3.3V low-dropout linear regulator, SOT-23 (REG1) Capacitors (all M2012/0805 X7R, 10V or higher) 2 1μF 1 100nF Resistors (all SMD M2012/0805 size, 1/8W, 1%) 1 100kW 1 10kW 2 5.1kW 3 1kW 3 220W although its pins are smaller than those on the resistors and more closely spaced (although more widely spaced than the USB socket). Make sure you put it in the right way around, with pin 1 orientated as shown! Apply flux to the PCB, place the chip with tweezers and tack one lead. Check its alignment, then solder the other leads. It is best to fit the other 1μF capacitor next so that it doesn’t get mixed up with the 100nF capacitor that mounts next to it. The other seven parts are an assortment of resistors; ensure the correct values go in the right places, as shown in Fig.3. Now use a solvent to clean off any flux residue, allow the board to dry, then inspect it closely for bridges or dry solder joints. If everything looks good, you can solder your choice of CON2 and proceed with testing. Testing Try connecting the Adaptor to a USB supply. If you are not confident, don’t connect it to a computer, but use a USB power supply or something similar. You should see green LED3 illuminate within a second or so. If it does not, disconnect the Module and recheck the component placement and soldering. You could try flipping the USB-C cable to see if it makes any difference. If it does, that points to a problem with CON1 or the two 5.1kW resistors. While it is plugged into a power source, use a voltmeter to measure the 3.3V and 5V pins on CON2 relative to GND. A lack of 5V indicates a problem with CON1 or the 5.1kW resistors. Australia's electronics magazine If 5V is present but 3.3V is not, there could be a problem with the regulator, or perhaps another component is shorting the 3.3V rail. Once everything is working, connect the Adaptor to a computer and check that a new serial port is available. Use a program like TeraTerm or minicom to open the port and send some data by typing in the terminal window. You should see blue LED1 (next to TX) flash. If you connect the RX and TX pins on CON2 (eg, using a jumper cable) and send data, the red and blue LEDs should flash together as data is being looped back. Your terminal should echo the characters you are typing. If this is all as expected, the USB-C Serial Adaptor is working and can be deployed to your project. Using it The USB-C Serial Adaptor is generally a drop-in replacement for the CP2102 modules that it is intended to succeed. Like those modules, we use it to power and connect to projects for debugging purposes. We have also incorporated such modules into projects, such as the ESP32-CAM LCD BackPack (April 2024; siliconchip.au/Article/16212). You can use the USB-C Serial Adaptor instead of the micro-USB Type-B version specified in that project. Our Adaptor has some components on the bottom side, unlike the CP2102 modules, so it will need to be spaced away a little from the host PCB. The plastic insulation on standard pin headers should be sufficient for that purpose. SC June 2024  73 Project by John Clarke DC Supply Protectors Any one of these three simple, inexpensive circuits will protect your equipment from damage due to an incorrectly connected or malfunctioning power supply. They protect against a higher than expected voltage or a reverse polarity supply and have very little effect on the voltage applied to the device. M any devices are powered using a mains plugpack or power ‘brick’. All is well if you use the proper supply and it is wired correctly. However, damage can occur if the wrong supply is used or it is miswired, applying either the wrong polarity voltage or an excessively high voltage to the item to be powered. That is an especially big problem if you haven’t used the device for many years, have moved, if you’ve had to buy a replacement power supply (due to failure or loss), or someone else is using it who is not familiar with the correct supply. Our Supply Voltage Protectors prevent damage to equipment in the case of an incorrect input voltage. They switch off power to the equipment if the input voltage is too high and prevent current flow if the polarity is incorrect. A supply that produces more voltage than a piece of equipment expects can damage its internal components. Applying reverse polarity to a circuit can also irreparably damage parts, such as ICs and electrolytic capacitors unless the circuitry already includes reverse polarity protection. Such protection (eg, a diode) often reduces the voltage available to the device. However, the designs presented here are different, as they use a Mosfet instead that loses very little (basically no) voltage. Fig.1: the adjustable through-hole version of the circuit uses Mosfet Q1 for reverse-polarity protection and Mosfet Q2, controlled by the TL431 IC, for over-voltage protection. 74 Silicon Chip Australia's electronics magazine siliconchip.com.au These Protectors can be built as standalone devices. Still, as they are relatively compact and inexpensive, they should ideally be installed within existing equipment. That way, nothing bad should happen unless you connect a supply that’s outside the usual ratings. We are presenting three versions of the circuit. Two have a trimpot adjustment to set the overvoltage protection threshold; both can be used with plugpacks that produce up to 27V DC. One of those two versions uses surface-­mounting parts, so it is smaller than the other versions and can be squeezed into tighter spaces. It is rated to handle up to 3A. This version can have the overvoltage set as low as 3V. The through-hole equivalent can handle more current, up to 7A. However, it needs at least 5V to operate. The third version is slightly cheaper to build but can only be adjusted in voltage steps determined by zener diode reverse breakdown or avalanche values. It can handle up to 50V. One advantage of this version is that it doesn’t require a setup procedure; you simply build it, install it and away you go. Its minimum overvoltage protection setting is 7.5V. is the same for the TH (Fig.1) and SMD (Fig.2) versions of the board, except that some parts have different codes/ packages and some ½W TH resistors are replaced with two parallel ¼W SMD resistors (where a higher power rating is required). This overvoltage protection circuitry comprises N-channel Mosfet Q2, shunt regulator IC REF1 and bipolar transistors Q3 & Q4. Q2 is usually held on via gate voltage applied through the 10kW resistor from the positive supply. In this case, it has a low resistance between its drain and source, connecting the ground terminal of CON1 to the negative side of CON2, so current can flow between the load and supply. Zener diode ZD2 protects the gate of Q2 from excessive voltage. A 10V zener is used for the SMD version, while a 13V zener diode is used for the TH version, reflecting the ratings of the selected Mosfet types. Power indicator LED1 is lit by current flow through the 2.2kW resistor to the negative side of the supply. For the SMD version, the 2.2kW resistor is instead two 4.7kW resistors in parallel, in case the supply voltage is at the higher end of the allowable range. The TL431 adjustable shunt voltage Circuit details reference IC, REF1, detects an overFigs.1-3 show the circuits of all three voltage condition from the input supversions. They all provide reverse-­ ply. Fig.4 shows the circuitry within polarity protection using P-channel the TL431, which includes a 2.5V refMosfet Q1. With a correct polarity erence, an op amp, an output transisconnection, Q1 conducts initially via tor and a protection diode. the intrinsic diode within the Mosfet, When used as a voltage reference, allowing current to flow and voltage the REF input connects to the cathto appear at the source. ode, placing the TL431 in a negative The 10kW resistor then pulls the gate feedback configuration, where it regto ground, so Q1’s channel is switched ulates its ‘cathode’ voltage to match on. This allows current to bypass the its internal reference voltage. If you intrinsic diode, greatly reducing the want a higher cathode voltage, a voltvoltage across it. Zener diode ZD1 age divider is included between the prevents the gate-to-source voltage cathode and anode, with the divided from exceeding the maximum speci- voltage applied to the REF input. fication of 10V for the surface-mount For our circuit, we instead apply a device (SMD) version and 15V for the voltage to the REF terminal via a resisthrough-hole (TH) version. tance. In this case, the TL431 operates On the other hand, if the polarity in open-loop mode without any feedof the input supply is reversed, Q1’s back to maintain the reference voltage. intrinsic diode is reverse-biased and This arrangement uses the internal op the gate voltage is the same as the amp as a comparator, switching the source. So the Mosfet remains off, and output transistor off if the input voltno current flows to the load. age (Vin) is lower than the reference voltage, or on otherwise. Adjustable over-voltage When the transistor is off, the cathprotector circuit ode connection is pulled to the supFigs.1 & 2 are the adjustable over- ply voltage via Rsupply. In contrast, voltage protector circuits. The circuit when the transistor is switched on, siliconchip.com.au Australia's electronics magazine Features & Specifications Adjustable through-hole version ● Overvoltage protection threshold: 5-27V (3-27V if SMD TL431 is used) ● Input voltage range: 5-27V ● Maximum current: 7A Adjustable SMD version ● Overvoltage protection threshold: 3-27V ● Input voltage range: 3-27V ● Maximum current: 3A Fixed through-hole version ● Overvoltage protection threshold: 7.5-47.7V ● Input voltage range: 5-50V ● Maximum current: 7A DC Supply Protector Kits Adjustable SMD Version (SC6948, $17.50): includes the PCB and all onboard parts. Adjustable TH Version (SC6949, $22.50): includes the PCB and all onboard parts with both SOT-23 & TO92 TL431 ICs. Fixed TH Version (SC6950, $20.00): comes with the PCB and all onboard parts except ZD3 and R1-R7. June 2024  75 Fig.2: the SMD adjustable version of the circuit is very similar to the one shown in Fig.1. The main differences are the use of alternative devices and the doubling of some resistors for increased power handling. the cathode connection is held close to the anode voltage of 0V. The state of the output, whether high or low, depends on the voltage applied to the REF input. In our circuit (Fig.1 or Fig.2), this voltage is from the divider connected across the input supply formed by trimpot VR1 and a 3.9kW fixed resistor (or two 7.5kW resistors in parallel, giving 3.75kW). When this divided (reduced) voltage is below the 2.5V reference, the cathode of REF1 is pulled high. When the divided voltage is above 2.5V, the cathode is pulled low, near to ground potential. Trimpot VR1, in conjunction with the 3.9kW resistor, sets the overvoltage threshold. When the threshold is reached, the cathode of REF1 goes low, so transistor Q3 switches on. It in turn switches on transistor Q4, which pulls the gate of Mosfet Q2 low to switch it off. In this condition, the high collector voltage of Q3 pulls the adjust terminal of REF1 higher again via diode D1 and the 10kW resistor. This provides voltage hysteresis, ensuring that REF1’s cathode remains low until the supply voltage drops significantly below the overvoltage setting. The 100nF capacitor between the base and emitter of Q3 is included to prevent the circuit from initially latching into a voltage overload state at power-up. Immediately after power is applied to CON1, REF1 would momentarily conduct current that would otherwise switch on Q3 and latch REF1 on if it were not for the capacitor momentarily holding Q3 off. LED2 is the overvoltage indicator and it lights under two conditions. If the input supply exceeds ZD2’s breakdown voltage, current will flow through LED2, its 2.2kW series resistor and ZD2. However, if the overvoltage threshold is set below ZD2’s An enlarged photo of the underside of the Adjustable SMD version of the DC Supply Protector. Compared to the other versions, this one has components mounted on both sides of the PCB. 76 Silicon Chip Australia's electronics magazine breakdown voltage, LED2 will only light when there is an overvoltage shutdown, via NPN transistor Q4. Overvoltage shutdown is indicated when LED2 is on and LED1 is off. When reverse polarity protection is active, both LEDs will be off despite the input power supply being switched on. TL431 limitations One thing to note when using the TL431 in the TO-92 through-hole package is that the threshold between switching high or low is closer to 2V than 2.5V. The likely reason is that the reference requires a minimum current to produce the 2.5V reference, which is only available in closed-loop mode. In open-loop mode, the reference is operating further down the threshold knee of the voltage versus current curve. This threshold also varies with temperature, although provided the temperature does not vary over a wide range, the resulting accuracy will be satisfactory. For more information on using the TL431 in open-loop mode for undervoltage and overvoltage detection, see the Texas Instruments Application Report SLVA987A PDF at www. ti.com/lit/pdf/slva987 The SMD version of the TL431 does not appear to suffer the same problem, as it shows a very sharp voltage-­versuscurrent threshold voltage curve even at very low currents. For this reason, the TH PCB has provision for using siliconchip.com.au Fig.3: the fixed overvoltage version requires you to select values for resistors R1-R7 depending on the threshold voltage you want; see Table 1 overleaf. It uses an SCR and zener diode for the over-voltage function rather than a TL431. the surface-mount version instead of the TO-92 package version. Fixed overvoltage protector circuit Fig.3 is the fixed overvoltage protector circuit. This circuit includes reverse polarity protection using P-channel Mosfet Q1 in the same way as Figs.1 & 2. The overvoltage protection also uses N-channel Mosfet Q2, although Q2 is controlled differently in this circuit. Instead of an adjustable overvoltage threshold controlled by a TL431 shunt reference IC and trimpot, the threshold is set and detected by zener diode ZD3. If the voltage applied to the zener is above the overvoltage threshold and it conducts, silicon-controlled rectifier SCR1 is triggered to switch off Mosfet Q2. A 10nF capacitor is included across the SCR to prevent it from latching on due to a rapid rise in voltage (dV/dt) as power is initially applied to CON1. Any voltage rise faster than 8V/μs will likely switch the SCR on. The 10nF capacitor slows down the voltage rise. Mosfet Q2 is normally held on via the gate voltage applied by the 10kW gate resistor and paralleled resistors R3-R6. Zener diode ZD2 protects the gate from excessive voltage. With Q2 on, a low-resistance connection exists between the drain and source, connecting the ground of CON1 to the negative side of CON2. siliconchip.com.au In that case, the power LED (LED1) lights due to the current flow through R7 to the negative side of the supply. Transistor Q3 is typically switched on by the bias current from the positive supply via resistors R3-R6 and R1. With Q3 on, current can flow through ZD3 at its collector and the 150W resistor at its emitter, but only if the supply voltage exceeds ZD3’s breakdown voltage. 4mA needs to flow through ZD3 before the voltage across the 150W resistor reaches 0.6V, which is just sufficient to trigger SCR1 via its 470W gate resistance. Thus, when the SCR switches on and disconnects the load, the supply voltage is ZD3’s rated breakdown voltage plus the 0.6V required across the 150W resistor. When SCR1 latches on, there is about 1V between its anode (A) and cathode (k), so Q3 switches off. With SCR1 on, the low voltage at Q2’s gate switches it off, disconnecting the ground supply at CON2. LED1 is now off, while the low voltage across SCR1 causes LED2 to light, with current flowing through the 9.1kW resistor to the switched-on SCR. Note that LED2 will also light when the voltage across ZD2 reaches its breakdown of 13V. As the supply voltage rises, LED2 brightens as more current flows through the LED via the 9.1kW resistor and ZD2. Overvoltage shutdown is indicated when LED2 is lit but LED1 is off. The voltage divider formed with R1 and R2 ensures that Q3’s base is well below 0.6V, keeping Q3 off when SCR1 is on. With Q3 off, the gate drive to SCR1 is off, but the SCR remains latched on due to the current flowing through it. Resistors R3 to R6 provide the required 5mA latching and holding current to ensure it stays on in this condition. Fig.4: the basic circuitry within a TL431 voltage reference. Usually, the REF terminal is connected to a divider between the anode and cathode (closed-loop mode). Here, we are using it in open-loop mode, as a voltage detector. Australia's electronics magazine June 2024  77 Table 1 – resistance values for fixed TH version ZD3 Vovl R1 R2 R3 R4 R5 R6 R7 47V 47.7V 130kΩ 13kΩ 18kΩ 18kΩ × × 8.2kΩ 43V 43.7V 110kΩ 13kΩ 16kΩ 16kΩ × × 6.8kΩ 39V 39.7V 100kΩ 13kΩ 15kΩ 15kΩ × × 5.6kΩ 36V 36.7V 91kΩ 13kΩ 16kΩ 13kΩ × × 4.3kΩ 30V 30.7V 75kΩ 13kΩ 12kΩ 12kΩ × × 3.0kΩ 27V 27.7V 68kΩ 13kΩ 5.6kΩ × × × 2.4kΩ 24V 24.7V 62kΩ 13kΩ 4.7kΩ × × × 2.2kΩ 22V 22.7V 56kΩ 13kΩ 8.2kΩ 10kΩ × × 2.0kΩ 20V 20.7V 51kΩ 13kΩ 8.2kΩ 8.2kΩ × × 1.8kΩ 16V 16.7V 36kΩ 10kΩ 10kΩ 10kΩ 8.2kΩ × 1.3kΩ 15V 15.7V 33kΩ 10kΩ 10kΩ 8.2kΩ 8.2kΩ × 1.3kΩ 13V 13.7V 30kΩ 10kΩ 8.2kΩ 8.2kΩ 6.8kΩ × 1.2kΩ If you are wondering why we need Q3 instead of ZD3 connecting directly in series with the 150W resistor, it is because ZD3 could be damaged by excessive current as the supply voltage rises well above its breakdown voltage. For example, if ZD3 is a 12V zener diode, it will conduct 4mA when the supply is at 12.6V but 186mA at 40V. In that case, it would be running well above its power rating. Additionally, the 150W resistor would be dissipating just over 5W. Having transistor Q3 means that all this current stops once the overvoltage threshold is reached, preventing high dissipation in ZD3 and the 150W resistor. 12V 12.7V 27kΩ 8.2kΩ 6.8kΩ 6.8kΩ 6.8kΩ × 1kΩ 11V 11.7V 24kΩ 8.2kΩ 5.6kΩ 6.8kΩ 6.8kΩ × 1kΩ Zener diode biasing 10V 10.7V 18kΩ 6.2kΩ 6.8kΩ 5.6kΩ 5.6kΩ × 910Ω 9.1V 9.8V 15kΩ 4.3kΩ 5.6kΩ 5.6kΩ 5.6kΩ × 820Ω 8.2V 8.9V 12kΩ 4.3kΩ 4.7kΩ 4.7kΩ 4.7kΩ × 750Ω 7.5V 8.2V 7.5kΩ 2.4kΩ 5.6kΩ 5.6kΩ 5.6kΩ 5.6kΩ 620Ω 6.8V 7.5V 3.6kΩ 1.2kΩ 4.7kΩ 4.7kΩ 5.6kΩ 5.6kΩ 560Ω White = ½W, yellow = 1W, × = not fitted Fig.5: a typical V/I curve for a zener diode. 78 Silicon Chip Australia's electronics magazine The 150W resistor could be increased in value, but that would mean that the overvoltage threshold would occur at a much lower voltage than the zener diode breakdown voltage. This would be less consistent than using the zener at the steeper region of its conduction curve. Fig.5 shows a typical zener diode V/I curve. In the forward direction (current flowing from anode to cathode), it acts like a regular diode, conducting current with 0.6-0.7V voltage across it. In the reverse direction, the zener initially acts like a diode, blocking current with minimal leakage current. However, beyond a certain voltage, the ‘leakage’ current increases and then it begins conducting significant reverse current. This is the reverse breakdown mode, which provides a relatively steep VI curve beyond the knee region. Each zener diode is characterised at a particular current for its zener voltage. If the zener diode is operated at a current much less than that, the voltage across it will also be lower. For our circuit, we want the zener diode operating more in the linear region, where the V/I curve is steep, rather than in the knee region and preferably near to the reference current for the zener. The recommended BZX79Cxx series of zener diodes for our circuit are characterised for a 5mA reference current between 2.4V to 24V, or 2mA above that. The 4mA current for the zener diode in our circuit is a reasonable compromise between those. siliconchip.com.au Resistance value calculations The resistance values required for resistors R1 to R7 depend on the overload voltage (Vovl), the maximum input voltage (Vmax) and the latching and holding current for SCR1. Resistor power ratings, LED currents, transistor Q3’s base current and ZD3’s current need to be considered. Table 1 shows the resistor values and wattage ratings for various overvoltage thresholds and a 50V maximum applied input voltage. A panel describes the calculations used to formulate that table in more detail. SMD adjustable version The SMD adjustable version is built using a double-sided plated-through PCB coded 08106241 that measures 51 × 23mm. As shown in the overlay diagrams (Fig.6), all the SMD parts except the two LEDs mount on one side of the PCB, with the through-hole parts such as the two screw terminals and trimpot on the other side. Begin by soldering the SMDs. That can be done by soldering one lead of the component first, holding it in place with tweezers. Once it is aligned and positioned correctly (by remelting the solder if necessary), the remaining lead(s) are then soldered. A good light and a magnifying glass are very useful for this task. You will need to identify the parts first. The resistors are marked with three or four digit codes as shown in the parts list. The 100nF capacitor will not be marked. The smaller semiconductors in SOT-23 packages also have component markings, as per the parts list (although they can vary). The 10V zener diodes are cylindrical with blue markings at the cathode (k) end. Diode D1 also has a polarity stripe at the cathode end. Note that the TL431 can have alternative pinouts, with the standard pinout having the cathode at left and reference at right when the anode pin is at the top. The mirrored pinout has the cathode and reference pins transposed. We have provided for both orientations on the PCB by having a 6-pad footprint instead of just the three required for one pinout of the device. The TL431 must be orientated according to the pinout of the device used. We have marked the pins on the PCB overlay showing the anode, cathode and reference pads. The parts supplied in our kit should be the mirror pin version. The way to check this is to use a multimeter on its diode test across the cathode and reference pins. You should get a reading of one diode drop (around 0.7V) when the red probe is on the REF pin and the black probe on the cathode pin. You can then orientate it correctly on the PCB and solder it in place. While doing that, be careful not to let solder bridge the used and unused pads. If that happens, use a bit of solder wicking braid can be used to remove the excess solder (adding flux paste will make it easier). When installing the diodes, make sure these are orientated correctly. The anode (A) and cathode (k) orientations are marked on the PCB overlay. Once all the surface mount parts have been soldered in place on the one side, flip it over and fit the LEDs, taking care to place each with its correct orientation (checked as mentioned earlier) and in the correct position with regard to colour. These are green for power and red for overvoltage, although you are free to customise the colours if desired. Ideally, the surface mount LEDs should be tested using the diode test mode of a multimeter. With the red probe on the anode and black lead on the cathode, the LED should light and show its colour. We used green for power and red for overload. There is often a stripe or dot on the cathode but we have seen LEDs with a marking on the anode, so it’s better to test them. The trimpot is installed with the top screw adjustment orientated as shown. This provides an increasing overvoltage threshold with clockwise rotation. The two screw terminals should be mounted with the wire entry toward the outside of the PCB at each end. TH adjustable version The through-hole adjustable version is built on a double-sided plated-­ through PCB that’s 08106242 and measures 70.5 × 35.5mm. Refer to Fig.7, the PCB overlay diagram, during the assembly process. If you are using the SMD TL431 version, install it first, but be careful as they can have alternative pinouts with the reference and cathode transposed. See the instructions a few paragraphs above on determining which pinout you have, aligning it with the PCB markings and soldering it. The zener diodes and diode D1 can be fitted next. ZD1 is a 15V type, while ZD2 is rated at 13V. These each need to be orientated as shown in Fig.7, Fig.6 (left): the overlay diagrams for the SMD adjustable version of the Supply Protector (shown at 150% actual size). Fig.7 (upper right): the PCB overlay diagram for the through-hole adjustable version. Fig.8 (lower right): the PCB overlay diagram for the through-hole fixed overvoltage version. siliconchip.com.au Australia's electronics magazine June 2024  79 Resistance value calculations Table 1 shows the required resistance values and power ratings for the Fixed Protector for overvoltage thresholds from 7.5V to 47.7V with a maximum input voltage of 50V. There are no satisfactory resistance values to meet all requirements for overvoltage thresholds below 7.5V, so if you require a threshold that low, build one of the other versions. R3 to R6 calculations The total resistance for R3 to R6 is calculated first. This resistance provides current for SCR1 and the base of transistor Q3 via R1. Up to four resistors can be paralleled for a sufficient power rating and to achieve the required resistance. The latching and holding current required for SCR1 to remain in conduction is 5mA. This satisfies the worst-case latching current and the worst-case holding current at 25°C. The total resistance, R, required is the overload voltage threshold (Vovl) minus one volt (the SCR anode-to-cathode on-voltage), divided by 5mA, ie, R = (Vovl − 1V) ÷ 5mA. The total power rating required is the maximum operating voltage for the circuit (eg, 50V) minus 1V squared and then divided by the resistance, ie, (Vmax − 1V)2 ÷ R. The required power rating can be reduced by spreading it between two to four resistors in parallel. If all those resistors have the same value, they share the dissipation equally. If different, each resistor will need to be assessed for its share of the dissipation. R1 & R2 value calculations Resistor R1 drives the base of Q3, which must saturate when conducting 4mA. This 4mA is the current that flows through ZD3, Q3 and the 150Ω resistor at the overvoltage threshold. We drive Q3’s base with 250μA (1/16th the collector current) or more to ensure Q3 goes into saturation. Resistor R2, between the base of Q3 and ground, is necessary since it reduces the base voltage to less than 0.3V due to divider action with R1 once SCR1 is latched. Typically, SCR1 will have about 1V across, so provided that R1 is at least triple R2’s value, that will be reduced to 250mV or less. That prevents Q3 from conducting through ZD3 once overvoltage has been detected and SCR1 latches on. For overvoltage settings of 20.7V and above, we set R2 so 100μA flows through it at the overload voltage threshold. At this threshold, there will be 0.66V between the base and emitter of Q3 and 0.6V at the emitter of Q3, giving a total of 1.26V across R2. For an approximate 100μA current, R2 needs to be 12.6kΩ (13kΩ is the closest E24 value). 13kΩ gives 96.9μA, close enough to 100μA. When calculating the value for R1, this 100μA needs to be included since this bypasses the current from Q3’s base. So, instead of R1 supplying 250μA to Q3’s base, it needs to supply 350μA in total. R1 is calculated as the overload voltage threshold (Vovl) minus the 1.26V at Q3’s base, divided by 350μA. Since R1 is in series with the R3-R6, the parallel value of R3-R6 is then subtracted from this to get R1’s value, ie, R1 = (Vovl − 1.26V) ÷ 350μA − (R3 || R4 || R5 || R6). If the calculated value for R1 is less than three times the value of R2, the current through R2 needs to be increased and the equations reworked. For example, to get 200μA through R2, R2 = 1.26V ÷ 200μA = 6.3kΩ (use 6.2kΩ). Then R1 = (Vovl − 1.26V) ÷ 450μA, where 450μA is the 200μA R2 current plus the 250μA required for Q3’s base. with the cathode band toward the top. The resistors can be mounted next; check each value with a multimeter to be sure the correct value is installed in each place. The two LEDs are installed with the tops of their domes about 12mm above the top of the PCB. Check which colour the diode is before installing it, using the diode test mode on a multimeter if the lenses aren’t tinted. We used a green LED for power (LED1) and red for overvolage (LED2). In each case, the longer lead is the anode. Next, fit transistors Q1-Q4, being careful that each is placed in the correct position (check their part codes against Fig.7 and the PCB overlay). If using the TO-92 package version of the TL431 (REF1), you can also fit it now. Follow by mounting the 100nF capacitor. The trimpot is installed with the screw adjustment orientated as shown, providing an increasing overvoltage threshold with clockwise rotation. The two screw terminals are mounted with the wire entry toward the outside of the PCB at each end. TH fixed overvoltage version LED current LED1 switches off above the overvoltage threshold, so the maximum LED current will occur with the supply at the overvoltage setting. Assuming 10mA is a suitable maximum current, the value for R7 is the overload voltage minus the 2V across the LED, divided by 10mA, ie, R7 = (Vovl − 2V) ÷ 10mA. The power rating for R7 also needs to be considered, so its value needs to be greater than (Vovl − 2V)2 ÷ 250mW, where 250mW is a conservative derating for a 500mW resistor. If this calculation gives a higher value than the above, the maximum LED current will be below 10mA to avoid overheating the current-limiting resistor. The overvoltage LED (LED2) series resistor value is calculated similarly; only this time, the maximum input supply voltage is used in the calculation. That’s because LED2 will light from the overvoltage threshold to the maximum input supply voltage, Vmax. So the calculation is Vmax minus the voltage across LED2 and SCR1, divided by 10mA, ie, R = (Vmax − 3V) ÷ 10mA. Similarly, the minimum value, considering the resistor power rating, is (Vmax − 3V)2 ÷ 250mW. We selected a 9.1kΩ 1/2W resistor for a Vmax of 50V. The through-hole fixed overvoltage version is built on a double-sided, plated-through PCB coded 08106243 that measures 70.5 × 35.5mm. The PCB overlay diagram for this version is Fig.8. First, the values for resistors R1-R7 need to be selected using Table 1, based on the required overvoltage threshold. The required voltage rating for ZD3 is also listed in that table. Note that resistors R3-R6 may need to be 1W types (if shown in yellow in Table 1), and not all four of these resistors are necessarily used for all possible threshold voltages. The zener diodes and diode D1 can be fitted now. ZD1 is rated at 15V, ZD2 is a 13V type, while ZD3 is as per Table 1. These each need to be orientated as shown in Fig.8, with the cathode band toward the top. The resistors can be mounted next; check each value with a multimeter to be sure the correct value is used in each location. The two LEDs are installed with the tops of their domes about 12mm above the top of the PCB. Check which colour the diode is before installing it, using the diode test on a multimeter if the lenses aren’t tinted. We used green Australia's electronics magazine siliconchip.com.au 80 Silicon Chip for the power LED (LED1) and red for overvoltage (LED2). In each case, the longer lead is the anode. Be sure when mounting Q1 to Q3 that each is placed in the correct position and orientation. The SCR goes in with the metal tab side towards R3-R6. The trimpot should be installed with the screw adjustment orientated as shown, providing an increasing overvoltage threshold with clockwise rotation. The two screw terminals are mounted with the wire entry toward the outside of the PCB at each end. Testing If you have an adjustable power supply, you can apply power to the input and check that the power LED lights and the overvoltage switch-off function operates at the desired voltage. This is preset with the fixed version or can be changed using VR1 for the adjustable versions. Once the overvoltage threshold has been reached, the power LED goes off and the overvoltage LED lights up.The supply will need to be switched off or significantly reduced before power is restored to the output. Also remember that the overvoltage LED may light once the supply voltage exceeds ZD2’s breakdown voltage. Overvoltage shutdown is indicated when the power LED (LED1) is off and the overvoltage LED (LED2) is lit, but not when both LEDs are alight. For the adjustable versions, you can set the overvoltage threshold approximately by measuring the resistance across VR1 when the power is off. Divide the VR1 resistance by 3.9kW, add one, then multiply by 2V if you used a TO-92 TL431 or 2.5V if you used the SMD version. The formula is Vovl = (R(VR1) ÷ 3.75kW + 1) × Vref. That will tell you roughly what voltage it will cut out at, within about 1V. For the reverse calculation, to determine what resistance you need across VR1 for an approximate voltage threshold, divide the desired threshold by 2V (TO-92 TL431) or 2.5V (SMD TL431), then subtract one and multiply by 3.9kW (3.75kW for the SMD version) The formula is R(VR1) = (Vovl ÷ Vref − 1) × 3.9kW. To set it more accurately, you will need an adjustable power supply or make a basic one using a wirewound 1kW potentiometer connected across a fixed supply (but be careful not to exceed its power rating). SC siliconchip.com.au Parts List – DC Supply Protectors Common between all versions 2 2-way PCB mount screw terminals with 5mm or 5.08mm spacing (CON1, CON2) SMD Adjustable Version 1 double-sided, plated-through PCB coded 08106241, 51 × 23mm 1 100nF 50V X7R ceramic capacitor, SMD 3216/1206 size 1 50kΩ multiturn top-adjust trimpot, Bourns 3296W style (VR1) Semiconductors 1 AO3401(A) 30V 4A P-channel logic-level Mosfet, SOT-23 (Q1; marking: X15V) 1 AO3400 30V 5.8A N-channel logic-level Mosfet, SOT-23 (Q2; marking: XORB) 1 BC856C 65V 100mA PNP transistor, SOT-23 (Q3; marking: 9AC) 1 BC846C 65V 100mA NPN transistor, SOT-23 (Q4; marking: 1C) 1 TL431 adjustable shunt voltage reference, SOT-23 (REF1; marking: 431) 🔴 1 1N4148WS 75V 150mA switching diode, SOD-323 (D1) 2 BZV55-C10 10V 500mW zener diodes, SOD-80C (ZD1, ZD2) 1 green SMD LED, M3216/1206 size (LED1) 1 red SMD LED, M3216/1206 (LED2) Resistors (all M3216/1206 size 1/4W 1% SMD) 7 10kΩ (code 1002 or 103) 4 7.5kΩ (code 7501 or 752) 4 4.7kΩ (code 4701 or 472) Through-Hole Adjustable Version 1 double-sided, plated-through PCB coded 08106242, 70.5 × 35.5mm 1 100nF 63V/100V MKT polyester capacitor 1 50kΩ multiturn top-adjust trimpot, Bourns 3296W style (VR1) Semiconductors 1 SPP15P10PL-H 100V 15A P-channel logic-level Mosfet, TO-220 (Q1) 1 CSD18534KCS or IPP80N06S4L 60V N-channel logic level Mosfet, TO-220 (Q2) 1 BC556 65V 100mA PNP transistor, TO-92 (Q3) 1 BC546 65V 100mA NPN transistor, TO-92 (Q4) 1 TL431 adjustable shunt voltage reference, TO-92 (REF1) OR 1 TL431 adjustable shunt voltage reference, SOT-23 (REF1; marking: 431) 🔴 1 1N4148 75V 200mA signal diode (D1) 1 15V 500mW or 1W zener diode (ZD1) 1 13V 500mW or 1W zener diode (ZD2) 1 3mm green LED (LED1) 1 3mm red LED (LED2) Resistors (all ½W metal film, 1%) 7 10kΩ 2 3.9kΩ 2 2.2kΩ Through-Hole Fixed Overvoltage Version 1 double-sided, plated-through PCB coded 08106243, 70.5 × 35.5mm 1 10nF 63V/100V MKT polyester capacitor Semiconductors 1 SPP15P10PL-H 100V 15A P-channel logic-level Mosfet, TO-220 (Q1) 1 CSD18534KCS or IPP80N06S4L 60V N-channel logic level Mosfet, TO-220 (Q2) 1 BC546 65V 100mA NPN transistor, TO-92 (Q3) 1 C106B 200V or C106D 400V 4A SCR, TO-126/TO-225AA (SCR1) 1 15V 500mW or 1W zener diode (ZD1) 1 13V 500mW or 1W zener diode (ZD2) 1 BZX79Cxx 500mW (2mA or 5mA reference current) zener diode (ZD3) [See Table 1 for voltage rating] 1 3mm green LED (LED1) 1 3mm red LED (LED2) Resistors (all ½W metal film, 1%) 2 10kΩ 1 9.1kΩ 1 470Ω 1 150Ω R1-R7: see Table 1 🔴 TL431QDBZR, TL431FDT or TL431SDT have the standard pinout; TL431MFDT or TL431MSDT have the mirrored pinout Australia's electronics magazine June 2024  81 Part 2 by Richard Palmer WiFi DDS Function Generator This flexible function generator, introduced last month, has seven different output modes and numerous other useful settings like burst and sweep modes. It can be controlled via an onboard touchscreen, a remote web interface via WiFi, or SCPI commands via WiFi from a computer. D espite its substantial feature set, the LCD touchscreen interface makes it simple to use. The unit can also be controlled from a computer, tablet or mobile phone via its web browser interface. This second and final part of this series of articles focuses on constructing, commissioning and operating the unit. As with the other test bench instruments I have designed (Bench Supply, Programmable Load and ‘Swiss Army Knife’), SCPI commands are also supported. The device fits neatly into a snap-­ together instrument enclosure, with a single PCB accommodating all the components, LCD screen, controls and connectors. The Raspberry Pi Pico W microcontroller has a much simpler ‘drag and drop’ programming method than the ESP32 processors I used in the earlier instruments in this series, making programming simple. Construction Because a generous PCB is required to accommodate the switches, rotary 82 Silicon Chip encoder and various connectors, there is ample space to use through-hole components almost exclusively in this project. As shown in Fig.8, the Pico and PCM5102A modules mount on one side of the PCB, with all the passives, while the LCD, LEDs and switches are on the other. Two footprints are provided for the PCM5102A module, to suit the two most common versions available online. It is best to start by fitting all of the parts on the Pico side of the PCB first, doing some testing, then moving to the other side of the board. That’s because the LCD screen obscures the pads of several components. The screen is mounted on 6mm spacers to align its face with the front panel, rotary encoder and pushbuttons. Refer to the overlay diagram, Fig.8, as you mount the parts on the PCB. You can also check the PCB photos (from part one) to see how it should look. Start with the only surface-mounting device, diode D1. Tack-solder one lead Australia's electronics magazine to its pad (making sure the leads bend down towards the PCB, not up in the air like a dead bug), then check its alignment with the other pads. If it’s misaligned, remelt the solder and nudge it gently into position, then solder the other leads and refresh the first one. You can do that by adding a little extra solder or, even better, adding a tiny bit of flux paste and then heating it with a clean soldering iron tip. Follow with the resistors. Ideally, you should check each batch with a multimeter to verify they have the correct resistance (the colour-coded bands can sometimes be hard to distinguish). After that, fit diode D2, the only through-hole (axial) diode, with its cathode stripe to the left as shown in Fig.8. If you are using IC sockets, mount them so that the notched ends face in the correct directions (IC2 faces down, the others face up), then plug REG3 into its socket, with pin 1 at upper left. If not using sockets, solder REG3 in place, also being careful siliconchip.com.au 4 37 MOD2b 5 36 35 7 RASPBERRY 34 PI Pico W 33 10 11 12 29 13 28 14 27 15 26 16 25 18 WIFI MODULE 23 22 20 21 OUT A 5.6kW 2.2kW PCM5102A MOD2 24 19 220pF 100nF 2.2kW 31 30 220pF 5.6kW 32 RP2040 MCU 2.2kW 2.2kW L IC2 24C256 10kW 10kW 10kW 9 100nF 2.2kW 2.2kW 2.2kW 6 100nF 220mF IC1 NE5532 100nF 17 100nF 10W 38 220pF 220pF G R G 10kW 2.2kW 1kW 2.2kW + 100nF 39 3 8 2.2kW 40 10W D1 BAT54S SCK BCK DIN LRCK GND VIN 100nF 1 2 MICRO USB–B PORT 5819 10W 10mF 10mF K 100nF 220mF D2 MOD2a + MOD1 100pF CON5 10W 4.7kW 4.7kW REG3 MAX1044 220mF CON4 CON1 + 100nF REG1 7809 O UT B TRIG IN TRIG OUT CON3 CON2 + 100nF +12V + REG2 7805 PCM5102_MOD 4.7kW 100nF 4.7kW 2GER 5087 LED1 LEDW A K 3GER 4401XAM S1 LED2 LEDT K A LED4 LEDA LED3 LEDB K K A A 3.5" SPI TOUCH SCREEN LCD MODULE WITH 480 x 320 PIXEL RESOLUTION (ILI9488 CONTROLLER, LCD1) ROTARY ENCODER S5 S4 S3 S2 A ON B ON L BUT R BUT siliconchip.com.au Australia's electronics magazine Figs.8 & 9: fit the components on both sides of the PCB as shown here. It’s best to solder the top side components first (starting with the sole SMD, then the axial components) and only fit the switches, LCD screen etc to the underside once all the components on the other side have been mounted and tested. Errors on the PCB cause Button A to start channel B and Button B to have no effect, while LED T/Trig Out is shorted to ground. The two tracks currently going to pins 22 and 23 (GP17 and GND) of MOD1 should be cut and re-routed to pins 21 & 22 (GP16 and GP17), respectively. Also, both tracks currently going to pin 33 (AGND) need to be re-routed to pin 32 (GP27). June 2024  83 Screen 1: the Function Generator provides this web page so it can be controlled remotely via WiFi. to orientate it correctly. Leave IC1 and IC2 off for now. After that, mount REG1 and REG2. While they do not generate substantial amounts of heat, it is worth mounting them with a thin smear of thermal paste between the tabs and PCB. Start by bending their leads down by 90° just after the end of the thick part, insert them into their pads, attach the tab with a machine screw and nut, then solder and trim the leads. Don’t get REG1 & REG2 mixed up, as they have different output voltages but come in the same package type. Now solder all the ceramic capacitors in place. They are not polarised, so their orientations are not critical. Many are 100nF types, but there are other values, so don’t confuse them. Follow with the electrolytic capacitors, which are polarised; in each case, the longer lead should be inserted into the pad nearest the + symbol on the PCB. Fit the DC socket, ensuring it is pushed down fully before soldering its tabs, and you are ready for initial testing. Apply 12V DC to the input and use a DMM set to measure DC volts to check the +5V, +9V and -9V rails. You can use one of the regulator tabs as a convenient ground (negative) reference and probe the Pico’s pin 40 pad (+5V), IC1’s pin 8 (+9V) and IC1’s pin 4 (-9V). Each should be within half a volt of the expected reading. If not, switch off the power and check for incorrectly placed, orientated or poorly soldered components. Assuming all is well, solder or plug in IC1 and IC2, ensuring that pin 1 is 84 Silicon Chip in the correct location in each case. Next, solder in the sockets for the Pico W and PCM5102A modules. The 20-pin sockets for the Pico W and the 6-pin socket for the DAC module may be available pre-made. If not, you can cut them down from longer sockets. The 9-pin socket for the DAC module will probably have to be cut from a socket with at least 10 pins. Cut in the middle of a pin to ensure a clean break. The four RCA connectors are the final components to mount on this side of the board. Ensure they are fully pushed down before soldering their pins. Now move on to the other side of the PCB. Mount the switches and encoder on the rear of the board, as shown in Fig.9. The switches need to have the flats orientated as shown, or they might not work. We will add the LEDs and LCD screen at a later stage. Programming the Pico W Loading software to the Raspberry Pi Pico W is very straightforward. It does not need to be mounted on the PCB for this process. Plug it into any computer (Windows, Linux or Mac) using a suitable USB cable. It will appear as a virtual drive on the system called “RPI-RP2”. If the virtual drive doesn’t appear, unplug the Pico and hold down the white BOOTSEL button while plugging it back in. Copy the 0410421A.uf2 binary file (download at siliconchip.au/ Shop/6/398) onto that drive using the computer’s regular file management tool. The Pico will automatically Australia's electronics magazine reboot and run the uploaded code as soon as the file is transferred. After programming has finished, the Pico will reboot and the drive on your computer will disconnect, at which point you can unplug it. Uploading that file actually did two things: it loaded the software onto the Pico and also some files that are used to generate the web page for remote control (stored in a ‘LittleFS’ file system). We have combined them into a single file to make programming as easy as possible. There is a file in the download package linked earlier called “Pico Production Programming.pdf” that explains how the files can be loaded separately if you are interested. Further testing The main functions can now be tested by plugging the programmed Pico W and PCM5102A module into the board and powering it up. Solder the headers to them if they are not already attached; you can use the sockets on the main PCB as a jig to hold them in place while you do so. Clicking the channel A and B switches should start the Generator producing a 1kHz sinewave at 1V peak-to-peak on channel A and 500Hz at 1V peak-to-peak on channel B. Both signals should have no significant DC offset. A 3.3V 1kHz square wave should also appear at Trig Out. The LCD screen can now be mounted on 6mm spacers. While I used tapped metal spacers in the prototype, plastic or untapped spacers can be used with 12mm countersunk head machine screws and nuts. If your LCD screen has a four-pin header mounted at the SD card holder end of the module, cut the pins off flush with the plastic retaining strip to prevent them from binding on the PCB and RCA sockets. The LCD screen’s pins are only just long enough to reach the PCB pads, so they should be soldered on both sides of the board to ensure good connections. Powering up the unit should now produce the operating display on the LCD. If the screen orientation isn’t correct or it responds to touches erratically, use the touchscreen calibration process described in the PDF manual included in the download package. That should correct any screen rotation and touchscreen alignment problems. siliconchip.com.au Setting up WiFi If desired, the following steps to enable the WiFi functions can be performed later. Edit your WiFi credentials using the touchscreen interface (see Screens 6 & 7) and click the AC button to enable WiFi. When a connection is made to the WiFi LAN, the red LED will change from flashing to constantly on. Don’t switch off the unit for 30 seconds after setting the WiFi credentials to ensure they have been saved to EEPROM. The unit may now be accessed from a web browser at http://dds.local If the firmware program and files have been loaded correctly, the display should look like Screen 1, and the values should update to match those on the LCD screen after a second or so. If not, try a hard reload of the web page by holding down the Shift key while refreshing the page. Apart from the optional calibration step, the unit should now be fully functional. Preparing the case The main depression on the underside of the case is slightly larger than the one on the top, and clearance around the LCD screen is at a premium. So, we use the case upside down, with the four small circular dimples beside the rounded rectangular depression on top. Fig.10 shows the case drilling details; it is also available as a PDF download (siliconchip.au/Shop/11/400). If you print that PDF, ensuring that you do it at “actual size” or 1:1 (not “shrink” or “fit to page”), you can use it as a drilling template. Carefully trim the templates to size, but don’t cut out any holes. Lay the top template on top of the case and prick through the centre of the four LEDs, four switches, four PCB mounting holes, the encoder mounting hole and the corners of the LCD cutout. Next, drill all the holes: 3.5mm diameter for the LEDs and PCB mounting holes and 10mm diameter for all others. After that, make the LCD cutout. Probably the easiest way to do that is to drill a series of small (~3.5mm) holes around the inside of the perimeter, knock the centre piece out, then file the edges smooth. The LCD cutout is intentionally a millimetre or so larger all-round than the actual screen; the decal will cover any gaps. siliconchip.com.au Fig.10: you can mark the case using the dimensions shown on this drilling diagram, or print/copy it at actual size and use it as a template that can be temporarily attached to the case. If using it as a template, prick or drill small holes through the centres of each hole to locate them before drilling. Fig.11: you can download the artwork for these labels from our website, print them at ‘actual size’, laminate them, cut them out and stick them to the case. Australia's electronics magazine June 2024  85 Countersink the four PCB mounting holes so that the tops of the screw heads are flush with the surface of the case. Test-mount the PCB on 10mm spacers. If required, ream out the switch holes in the top of the case to stop them from binding. Once the cover fits neatly with a little clearance around the switches, encoder and LCD, colour around and inside the switch and LED holes, plus the LCD cutout with a black permanent marker. That will stop the grey plastic from being visible through the holes in the decal. Assemble the PCB to the top cover on 10mm spacers. If the LCD mounting screws bind on the inside top of the cover, either drill clearance holes in the cover or gently countersink the screw holes in the LCD’s PCB. Test the LEDs against the inside top of the case. Their tops should protrude by about 1mm. It may be necessary to lightly countersink the backs of the holes in the top of the case if the LEDs don’t protrude far enough. Insert but do not solder the LEDs. The two white LEDs fit above the channel A and B buttons, the blue one (trigger) above them and the red one (WiFi) near the 5V regulator. Mount the PCB into the top of the case and solder in the LEDs. ensuring the flats on the lenses face as shown in Fig.9. If you choose different coloured LEDs, the current limiting resistor values may need to be changed to equalise their brightness. In development, 2.2kW resistors provided adequate brightness for the red and blue LEDs, but the white LEDs needed 4.7kW resistors to reduce their brightness to match the others. Print and laminate the decals (Fig.11), also available as a download at the link above, again ensuring that they are printed at 1:1 scale. Carefully trim their outsides to size. Cut a hole in the main decal for the encoder. A 10mm wad punch does the job neatly. The LED holes can be cut with a 3mm plier punch. Cut the switch holes with an 8mm wad punch to allow for adjustments if the switches are not perfectly centred. You can use a sharp hobby knife if you don’t have punches. Lay the decal in position and check that all the holes align. Make any switch centring adjustments on the decal and punch/cut them to 10mm. If the LED holes in the decal are slightly out of position, make the hole in the case top marginally larger. The decal will cover any scars. Finally, check the LCD screen alignment by feeling for its corners through the decal. Prick the corners of the LCD screen on the decal and remove the unwanted section with a sharp knife. Repeat the process for the rear panel, noting that the exact height of the RCA connectors will vary slightly depending on which version you have used. Prick all the holes through the decal and drill 3mm holes for the power socket and one RCA socket. Loosely fit the back shell and place the unit on the bench, then slide the connector panel up to the RCA connectors and check the alignment of the pilot holes. Make any adjustments to their positions and drill all five holes to 10mm, allowing adequate clearance for the RCA plug shells and the coaxial power plug. Now lay the trimmed decal in its cutout on the rear panel. Holding the assembly up to the light should enable you to establish the correct position of the holes in the decal. Punch the holes with a 10mm wad punch. Colour in and around the holes in the connector cover with a black marker to hide any grey plastic behind the decal. The decals may now be affixed with thin double-sided tape and the encoder knob attached. Stick the small rubber feet onto the bottom of the case. If using the optional acrylic stand, assemble it and place the Generator into the stand to ensure everything is square. Turn the assembly over and Screen 2: a sample of the Function Generator’s display on the 3.5in LCD touchscreen. This one sets the Pulse waveform output parameters. Screen 3: the sweep menu is accessed via the “Swp” button on the main screen. Screen 4: the burst menu lets you set up a channel to switch its signal output on and off at intervals, or have the signal switch between the two channels (the “B alt A” setting). 86 Silicon Chip Australia's electronics magazine siliconchip.com.au Scope 9: when “B alt A” is enabled for burst waveforms, the signal alternates between channels B and A. The idle value for the currently inactive channel is the DC offset for sinewaves, or V Low for other waveforms. put a small drop of superglue at each join. Stick the rubber feet to the crossing points of the stand. The unit is now complete. Operation Basic operation is very straightforward: supply power to the unit and click the channel on/off button to start generating the selected waveform. The white status LED lights when a channel is active. Changing settings is achieved by Screen 5: the Control menu lets you set the phase difference between channels, enable the external trigger input and set the trigger input/output signal polarities. siliconchip.com.au Scope 10: channel A’s signal is inverted in channel B (blue trace) when coupling is enabled and the phase lag is set to more than 0° for step and pulse waveforms. touching the value on the screen and winding the encoder knob. The highlighted digit is changed with the white ‘number position’ buttons under the knob. The left button will move the highlight to a more significant digit, and the right button to a less significant digit. Channel A and B settings are accessed by touching the A or B at the top of the screen (see Screen 2). The selected channel button is highlighted. To change the waveform, touch the waveform label at the top of the screen and select the required function from the drop-down list. Due to its computation requirements, the IMD waveform is only available on channel A. It is possible to set some parameter combinations that are not legitimate; for instance, a sinewave with an amplitude of 10V and a DC offset of +5V. Erroneous parameter combinations are flagged at the bottom of the LCD and web page. Where the combination will cause the unit to clip or Screen 6: the Settings menu lets you calibrate the output levels and provides access to the touchscreen calibration and WiFi settings screens. Screen 7: the communications settings menu (“COMMS”) is accessed via the settings menu by pressing the SET button on the main screen. Australia's electronics magazine June 2024  87 otherwise generate a distorted waveform, the software ensures that the settings are compatible. In the case above, the sinewave’s amplitude value is automatically reduced to prevent clipping. Further details of the handling of problematic setting combinations are provided in the PDF user manual included in the software download package. Across the bottom of the screen are the menu buttons that give access to the sub-menus shown in Screens 3-7. In the sweep (Swp) menu (Screen 3), setting the V/F/D value determines whether channel A waveform’s amplitude, frequency or duty cycle is swept. The Initial and Final values of the swept parameter can then be set. Sweeps can be one-shot or continuously repeated and have linear or logarithmic steps. Logarithms can only be calculated for positive values, so for log sweeps, a value of 0.01 is used when the initial value is set to zero or less. Touching the Sweep button at the top of the LCD screen or clicking the encoder button will start the sequence, as will an external trigger pulse if that function has been enabled in the control menu. Sweep parameters are stored separately for each waveform and V/F/D combination. The “X” button at the bottom right exits the menu and returns to the channel A waveform display. For bursts (Screen 4), set the number of cycles for the channel A signal to be active and idle. Clicking on the Burst button at the top of the LCD screen or clicking the encoder knob will start the burst sequence. One-shot or continuous burst cycles can be generated. Channel B can also be set to alternate with channel A. When the “B alt A” feature is selected, channel B uses channel A’s waveform settings (Scope 9). This setting overrides the value of the Control menu B=A setting. The Con (Control) menu (Screen 5) sets B-to-A channel signal coupling, phase, and trigger input and output functions. For most waveforms, channel B’s output can be set to follow channel A using the B=A setting in the Control menu. For sine, square and triangle pulses, a phase offset from 0-359.99° can be set. For step and pulse waveforms, any phase setting above 0° results in an inverted waveform on channel B (Scope 10). The Set (settings) menu (Screen 6) provides output voltage and touch screen calibration, communication settings, and a factory reset button. To set your WiFi parameters, enter the Com (communications) sub-menu (Screen 7). Replace “mySSID” and “myPass” with your WiFi network’s credentials using the on-screen keyboard and click the AC button to enable the unit to auto-connect to your local WiFi network. The connection process can take several seconds, during which the WiFi LED will flash. Multiple WiFi networks can be stored – instructions for doing that are in the PDF user manual. All parameters are saved to EEPROM within 30 seconds of the last value change. The red WiFi LED will change state for two seconds to indicate an EEPROM save has occurred. accessible via http://dds.local once your WiFi credentials have been entered and activated in the Com submenu. Both channels, the Control and the Burst/Sweep menus are all displayed side by side on the screen. Operation is similar to the LCD screen: click on the value to be changed and wind the virtual knob. The radio buttons below the knob indicate which digit will be changed. Changing true/false or +/- parameters is best accomplished with the units radio button selected (just to the left of the decimal point). More detailed information on the web interface is in the PDF user manual. SCPI remote Control Screen 8: adding the Function Generator to the TestController software is straightforward; select the unit from the drop-down list and add its hostname. Almost all settings and functions can be set and read using SCPI commands. The results of the power on self-test (POST) and the last error message can also be read remotely via the Pico’s serial interface or TCP port 5025 using http://dds.local as the address. The user manual explains the SCPI commands, parameters and results in detail. Using a program such as TestController (siliconchip.au/link/abev) enables automated and repeated testing using one or more remotely controllable instruments. While more complete instructions are available in the user manual, connecting the Function Generator to TestController is as simple as copying two files from the download pack and registering the device on the TestController Load Devices menu (Screen 8). To illustrate the power of automated tests, I have included the script used to test the frequency response of the DAC’s sinewave (Listing 1). It cycles through the DDS frequency range at a set output voltage. After waiting several seconds for the reading to settle at each point, the script reads the value from my Bluetooth-­enabled Owon B41T multimeter and XDS3000 digital oscilloscope, puts the frequency and voltage values into the logging table and proceeds to the next value. The table of readings was exported to Excel for analysis, though it could also have been performed in TestController. These values were used to produce the Fig.3 frequency response plot published last month (after correcting for the B41T’s frequency response). Australia's electronics magazine siliconchip.com.au 88 Silicon Chip Web interface The web interface (Screen 1) is The finished WiFi DDS Function Generator. The touchscreen is used to select functions, while the knobs and buttons let you set values and turn the channels on or off independently. After each tweaking of the settings, the automated tests ran in the background, saving hours manually adjusting the frequency and jotting down the results. With a little more effort, I could have used the ‘math’ functions in TestController to plot the final response curve. Further information on using TestController can be found in my April 2023 article on that software, see: siliconchip.au/Article/15740 Calibration Uncalibrated, the unit’s output voltages should be accurate to within 1%, with any error due to resistor tolerances in the buffer amp. If greater accuracy is required, set both channels to PULSE mode and set both V High and V Low to 5.00V. At least one of the time values should have a nonzero value. Start both channels and enter the LCD touch screen Set menu (Screen 6). Enter the voltages measured on the output pins in the respective fields, then touch Save and restart each channel’s output. The output voltages will now reflect the new calibration settings. Wait 30 seconds before turning siliconchip.com.au the unit off to ensure the settings are permanently saved. Conclusion The use of modules simplified the design and construction of what could otherwise been a substantially more challenging project. The PCM5102A module avoids soldering the DAC chip’s finely spaced pins and allows optimum component placement around the main DAC chip. Similarly, the Raspberry Pi Pico W is an inexpensive, highly functional WiFi-capable microcontroller that is much simpler to program than the ESP32 used in earlier instruments in this series. Using these two modules allowed the project to almost avoid soldering surface-mounting components altogether. This may bring the project within reach of those who don’t have easy access to, or confidence with, SMD components. Providing remote control capability extends the usefulness of the unit where access to the LCD screen controls is difficult. Importantly, it also allows it to be teamed up with other test instruments for automated SC testing. TestController sinewave frequency response script ; DDS to B41T multimeter and DSO =var sVal=20 ; create a control variable #log 4 ; log readings every 4 seconds #while (sVal<70000) PlatyDDS:::SINE:FREQ (sVal) #hasLogged ; wait for the log delay to expire =sVal=(sVal*1.2) ; exponential frequency increment #endwhile #log 0 ; stop logging Listing 1: this TestController script geometrically steps the unit’s output frequency from 20Hz to 70kHz while logging the output levels via separate instruments. Australia's electronics magazine June 2024  89 SERVICEMAN’S LOG Another mixed bag of servicing stories Dave Thompson has returned from his arduous trek, which he made to pay respect to the most revered authority in New Zealand: the national Rugby Union team. We have some reader-contributed servicing stories while he is recovering. Regular service will resume next month! Common capacitor problems in appliances N. B., of Taylors Lakes, Vic repairs commercial laundry equipment and, given the constant use (and no doubt abuse) they receive, he is not short of work. Here are some of the more memorable repairs he’s made lately... I have repaired many Maytag coin-operated washers and dryers that use the power supply board shown in the accompanying photo, including models like the MHN33, MH30, MD20, MDA20 and the Neptune range (shown here). The fault is that the coin mechanism sometimes won’t count the coins. The display remains in the idle state. A significant ripple voltage is present on the +24V supply rail. Visually inspecting the board, it is apparent that the 5V rail filter capacitor has failed, but that was actually caused by the less obvious failure of the larger 24V rail filter capacitor. Generally, I replace them with a 2200µF 35V capacitor for the 24V rail and 470µF 35V for the 5V rail, and everything then operates correctly. Sometimes it doesn’t because significant ripple is still present on the +24V rail. The power supply arrangement in this machine is unusual. The board AC power is fed from a 110V AC 60Hz transformer. A 240V AC to 110V AC step-down transformer drives the primary of the isolating transformer that supplies power to the PCB. I don’t know why they didn’t use a dual primary transformer instead, with them in series for 230V AC countries and parallel for 110V AC. I thought the 2200μF capacitor might be drawing too high an impulse current, causing saturation of the magnetic circuit of one or both of the transformers, causing that ripple. 90 Silicon Chip To prove this, I disconnected the 2200μF capacitor and soldered two 1000μF capacitors in parallel in its place via flying leads. That worked, but I didn’t want capacitors hanging around off the PCB, so I decided instead to reconnect the 2200μF capacitor, adding two clip-on ferrite filters onto the wires from the PCB to the 20V AC output of the transformer. To my surprise, that worked too. Now the only problem is ensuring the technician installing the repaired PCB reads my notes and follows them! I also received a few Speed Queen (Alliance) Quantum dryer power supply PCBs (Alliance also makes Primus and Ipso brand machines). The machines were showing an “EHT” error on their displays, and the customer note said the dryer stopped working and only came good when the power was cycled off and on. Searching for that error code online told me the dryers were not reaching their drying temperature within the maximum allowed time. This happens if the flue is clogged with lint, the fan is going in the wrong direction, the heater has failed, or the dryer is too full of wet clothes. Finding no errors with the PCB, after finding out it was a very intermittent fault, I suggested that the customer should change the customer programmable “heat fault” setting to off. I would not suggest this if the dryers were gas-powered, but I knew all his machines were electrically heated, so the possibility of a fire is much lower than for gas machines, and the site is well supervised. Two other PCBs that came with that batch had the fault described as “no power”. Australia's electronics magazine siliconchip.com.au Items Covered This Month • Maytag coin-operated washers and more • Repairing a Seiko S451 watch pressure tester • Failed Li-ion battery packs in leaf blowers • Fixing the Silicon Chip 20W Class-A Amplifier • Poorly timed failure of a USB sound card • Microwave oven repairs 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 I first looked up the chip descriptions on the internet for the ICs most likely to be power regulators. The first one closest to the rectifier and large 350V-rated electrolytic was a TOP256. With the 50-page data manual downloaded, I read the brief description and viewed the simplified circuit for that part. When I got to the paragraph titled “Soft start”, I found a brief description of the soft start circuit. The chip’s internal Mosfet is off at power-up; the rectified/filtered mains (now in the region of 350V DC) is applied to pin 4, where it is bled via an internal high-voltage current source to pin 2, the DC low-voltage input for the chip’s internal control and workings. On this pin is a 47μF 35V electrolytic filter capacitor (C9 in the sample circuit), which must be charged to 5.8V before the chip comes alive. A set of well-insulated flying leads to a voltmeter indicated that this voltage was never reached when the board was connected to a mains supply. A quick change of this capacitor got the supply running beautifully. Editor’s note: this is a fairly common fault in switchmode supplies where an electrolytic capacitor’s leakage increases to the point that the initial ‘trickle’ current is no longer enough to ‘bootstrap’ the circuit. The red arrow indicates the faulty capacitor, while the yellow arrow points to the TOP256GW IC. You can tell this PCB came from a dryer as it’s covered in lint! Note the conformal coating on the board that stops anything that might be conductive (eg, moist lint) from causing problems. The other PCB didn’t have this same capacitor problem; the starting voltage was correct, but the TOP256 IC had obviously failed, since it came alive after I replaced that. Seiko watch pressure tester repairs B. T., of Mudgeeraba, Qld writes: in the October 2023 Serviceman’s Log column (siliconchip.au/Article/15983), when recounting his adventures with his watch, Dave Thompson mentioned that he didn’t know how it was pressure tested. I may just be able to enlighten him! For many years, I repaired Seiko S451 watch pressure testers for jewellers and Seiko. The tester consists of a small pressure chamber surrounded by four PCBs and a separate air pump, similar to those used to inflate car tyres. The watch is placed face-up on a small holder inside the pressure chamber, and a very light lever rests in the middle of the watch’s glass face (crystal). A somewhat fiddly adjustment positions the watch until a front panel LED is illuminated. When the start switch is operated, the compressor pressurises the chamber to about three bar. This causes a good sealed watch to deform slightly; the crystal domes inward a little. A leaky watch does not deform; if it does, it will not maintain the deformation as the pressure inside the watch equalises with the pressure outside. The deformation is sensed by a phototransistor illuminated by a light-emitting diode. The lever resting on the crystal controls the amount of light the phototransistor receives. The electronics notes the position of the lever at the start of the test and compares this reading with that obtained when the chamber is pressurised and again after a delay of a minute or so. If it passes all the tests, the watch is declared “Acceptable”; otherwise, it is “Not Acceptable”. Most of the faults in these units were pressure leakage due to worn hinges or locks on the chamber door, poorly adjusted pressure switches that control the compressor, problems with the watch supporting platform etc. Occasionally, there was an electronic fault, but it was not common. One especially common fault was a blown-up compressor. This was caused by the fact that the unit had a power transformer that allowed it to operate from 100-110V AC (Japan/USA) or 220-240V AC (Europe/Australia). Unfortunately, the unit came with a US-type mains plug; most people used an adaptor to connect to our power. Left (p90): a PSU from a Maytag Neptune appliance. Left (p91): the faulty capacitor (red arrow) plus TOP256GW IC (yellow arrow) on the Speed Queen dryer power supply PCBs. Above: the Seiko S451 air pressure and water resistance tester. siliconchip.com.au Australia's electronics magazine June 2024  91 However, the compressor ran from 100V supplied by an internal transformer and fed to the compressor via a US-type three-pin socket on the back of the unit. It was therefore very easy to put the adaptor plug on the compressor cable and plug it into the 230-240V mains. The result was a spectacularly killed compressor. The compressor motor was a brush-type universal motor with a bridge rectifier in series with the 100V mains supply. That rectifier often saved the motor, as the bridge would rapidly spread itself over the inside of the case, and the motor often got off with just burn marks on the commutator and could be repaired. These units were very popular with jewellers for many years, long after Seiko stopped supporting them, but I haven’t heard of them for some time now. So I imagine the march of time has caught up with them. Repairing failed Li-ion battery packs B. P., of Dundathu, Qld writes: several years ago, my wife asked me to get her a battery-powered leaf blower to blow the leaves off the verandah instead of sweeping them. I purchased a 20V leaf blower on eBay for a reasonable price. It worked well for the purpose, but my wife asked me if I could get another battery for it so that she could use one while the other was on charge. A spare battery cost almost as much as the leaf blower, so I just bought another leaf blower. That way, once the original leaf blower reached the end of its life, we’d have another one to use in its place. That proved to be a good move, as some time later, the wire on the charger’s plug broke and I didn’t have a plug of the correct size to replace it. I ordered some plugs on eBay and we used the spare charger while waiting for it to arrive. Once the plugs arrived, I fitted one to the original charger and returned it to service. All went well for a few years until one of the batteries died. Removing four screws let me open it up. I checked the five 18650 cells and found that one was dead. I looked on eBay for a new battery, but they were no longer available. Replacement 18650 cells were very expensive, with five cells costing as much as the original price of the leaf blower. I remembered that I had a dead laptop battery that used 18650 cells, so I checked the cells in it, finding three that 92 Silicon Chip still had good voltages. I removed one of those cells and fitted it to the leaf blower battery. Once it had fully charged, my wife tried using the leaf blower with this battery, but she said it only lasted a minute and then stopped, so the replacement cell was no good. It was back to one battery again, but this situation only lasted a few months, until the second battery died. I dismantled the battery and found that one cell was dead again. Then I had an idea. I took one of the good cells from the first dead battery and fitted it to the second dead battery in place of the dead cell. This got the second battery working again, but it still meant we only had one good battery. I looked on AliExpress and found 18650 cells a lot cheaper than eBay, so I ordered 10. I also ordered some nickel strips on eBay so that I’d be able to fit the new cells when they arrived. The nickel strips arrived, but the cells did not. I followed the tracking for the cells, which showed they had been delivered in Sydney. How was that possible when we live in Queensland? My son said there is an almost identical address there, so someone couldn’t read the postcode! I got a refund, then ordered another 10 cells from a different seller at a slightly higher price. Unfortunately, in this case, the tracking number did nothing. I was getting concerned, but the cells arrived after 13 weeks. I used my 80W soldering iron to solder the new cells in place, then reassembled the battery and put it back into use. Unfortunately, the replacement cells were junk, and the leaf blower would only work for 20 seconds on high speed. It still worked on low speed, though. So we had one reasonably good battery and one that was of very limited use. Sometime later, another cell died in the ‘good’ battery, so I again replaced it with one of the leftover good cells from the second battery. Not long after, my wife said that both batteries were dead and the leaf blower no longer worked. I searched again for some decent 18650 cells and came across Tinker brand 3400mAh cells. I’d never heard of this brand, but the specifications suggested they should be good, as their weight was about the same as the original 2200mAh cells from the leaf blower battery. There were several five-star reviews on them, and some of the reviewers had done discharge tests and confirmed that the cells were what they claimed to be. Australia's electronics magazine siliconchip.com.au The leaf blower’s battery pack had died, so some replacements were sourced, which can be seen in the adjacent photo. They were rated higher than the originals (at 3400mAh) and worked well. These cells are available in Australia and come with a satisfaction guarantee or a refund. Had I finally found some good 18650 cells at a reasonable price? There was only one way to find out. They cost $7.55 each, with a 10% discount for buying 10 cells. I decided to order 10 cells, and they arrived quickly. I once again repacked the battery. Before charging it, I did a quick test by fitting it to the leaf blower to ensure the battery was in working order. I switched on the leaf blower and nothing happened. I got the other battery, and again, nothing happened. I got out the spare leaf blower, and both batteries worked in it. So now the original leaf blower no longer worked. I put the newly repacked battery on charge and, while it was charging, decided to dismantle the original leaf blower to see what was wrong with it and if it could be repaired. I removed the screws and split the case apart. It was apparent why the leaf blower no longer worked, as one of the wires had come off the switch. I got my 20W soldering iron out, soldered the wire back onto the switch and reassembled the leaf blower. Sometime later, the newly repacked battery was charged, and the repaired leaf blower was ready to use with the ‘new’ battery. I asked my wife to evaluate the performance of the leaf blower with the siliconchip.com.au replacement cells and see how it went and how long it lasted. She reported that the leaf blower now worked better than when it was new and the battery lasted at least 50% longer than it had done initially! That was an excellent result and it worked out at just under $37 per repaired battery. We also have a Hoover Linx vacuum cleaner. Last year, the battery died and I purchased a replacement battery on eBay for $57, but we still had the old battery. I took the old battery apart and, sure enough, it uses five 18650 cells. Unfortunately, I hadn’t thought of this old battery when I ordered the cells for the leaf blower, or I would have ordered 15 cells. But that is another job for another time. 20W Class-A Amplifier repair The Silicon Chip Class-A amplifier module first appeared in the July & August 1998 issues as a 15W module (siliconchip.au/Series/140). In May-August 2007, a 20W version was described (siliconchip.au/Series/58), and in September 2007, instructions for a complete stereo amplifier were published. J. G. of Bendigo, Vic built the 20W stereo amplifier from an Altronics kit... I modified it slightly in 2011 based on changes made in the later Ultra Low Distortion (Ultra-LD) Mk2 and Mk3 amplifiers, and it has performed outstandingly. However, when I powered it on recently, there was no sound from either speaker. The speaker protection relay did not appear to operate at power-on or power-off. The likely problem was a DC offset on the output of one channel of over 2V, triggering the DC offset protection. I removed the lid, powered it up and checked the module outputs with the power on. One channel settled quickly to around 40mV, while the other started at around +9V, dropping rapidly to +4V and slowly reduced to around +3V. I checked the DC voltages on the amplifier PCB against the published figures. The supply voltage is ±21V, not the ±22V of the original design, as a choke filter was installed in the power supply to reduce transformer buzz. This increases the time the diodes are conducting by storing energy in the choke, reducing the peak current drawn from the transformer. The downside is that the maximum output power is slightly decreased. Australia's electronics magazine June 2024  93 All the measurements I made were close to the published figures. The bad channel was amplifying a sinewave cleanly but clipping on the positive cycles. Given that the amplifier was working, the problem appeared to be a voltage mismatch in the input circuitry, with the output voltage offset developing to compensate for it. I disconnected the bad channel PCB to check the input transistors (Q1 & Q2) as I suspected a fault in those. Testing them out of circuit with a Peak DCA75, the Vbe figures were almost identical, and the gains were very close at 225 and 236. It was good to see they were closely matched after many years; however, they were clearly not the problem. Bizarrely, I found that the output voltage of the bad module was -0.45V with no power applied, while the good channel measured 0V as expected. The voltage was originating from the capacitor connecting the 510W resistor to the base of Q2, which ironically exists to reduce the amplifier’s DC offset. It is nominally 220µF but was replaced with a 1000µF capacitor as part of the 2011 changes. Compared with the same capacitor in the good channel, the top was raised slightly, a symptom of faulty capacitors manufactured from 1999-2003 (‘capacitor plague’). This capacitor was from my junk box and could have been manufactured at any time. It seemed to be suffering from a chemical reaction, causing pressure in the can and making it act as a battery. The voltage across it measures -0.5V with no load. With around -0.4V on the base of Q2, the output voltage had to go positive to compensate and drive the base voltage to +0.1V, to match the input signal. With the amplifier gain of around 20 times (20kW/510W), that -0.5V difference was amplified to about 10V. After reinstalling Q1 and Q2 and replacing the faulty 1000µF capacitor (as well as the same type in the other channel), both outputs were back to <50mV DC offset, and the amplifier is working well. USB sound card micro repair P. P., of Prospect, SA had to dive into a repair at precisely the wrong time, when he had lots of work to do, but couldn’t because his measurement device was broken... Isn’t it strange how things break exactly when you want to use them? It seems to be a rule of nature, similar to how, when you are searching for something, it is always in the last place you look. The logical inevitability of these sayings is of little comfort when you are in the middle of such a disaster. I was about to make a bunch of measurements using my audio test system and, well, nothing was working. This system uses the Silicon Chip USB SuperCodec (August-October 2020; siliconchip.au/Series/349), which has a tiny USB-toI2S (digital audio) converter embedded in it. The PC this plugs into was not finding the interface card, which foiled any hope of making the tests. I was in a hurry and had an extensive list of other tasks to get to, and here I was with the first task foiled. Because this was a PC-based test system, the logical assumption was that a Windows update had broken something, so I needed to reboot and check the drivers. One reboot later and the PC still sat there telling me that nothing was plugged in. After a few minutes of futile plugging and unplugging, I conceded that this laptop would never find the Codec. So I packed the whole lot up and moved to another computer, but it still wasn’t detected, confirming that the problem was the Codec. This was not good news, as I didn’t have a spare one; the I2S interface costs $140 and takes a week to arrive. My stress levels were increasing as I really wanted to get these measurements done. There was no option but to pull the thing out and look for obvious faults. The problem is that this card is tiny and loaded with M1608/0603 parts (1.6 × 0.8mm!) and a 0.5mm pitch IC with many pins. With repeated plugging and unplugging, I noticed one occasion where the PC complained that the USB device had failed. I took this as good news, as it meant that something was working sometimes. But what was causing this intermittent behaviour? As many of us have, I sat there looking disconsolately at a PCB loaded with hundreds of bits that I could only guess the purpose of, wondering where to start. I drank some coffee and had a think. My logic was that the computer only needs to talk to the processor (an XMOS IC) on this card for it to be registered in Windows, so I should check the USB cable, connector and any bits between that The audio interface board plus a close-up photo near the USB Type-B connector (marked with a red arrow on the lefthand photo). That marked transformer had a dodgy solder joint that was not clearly visible at a glance. 94 Silicon Chip Australia's electronics magazine siliconchip.com.au and the XMOS IC. The occasion where it almost worked convinced me that the fault was not catastrophic. Swapping USB cables took that as a cause off the table. Poking with a meter showed that the USB connector was fine, and I could get conductivity to the IC. I moved my attention to the soldering of the XMOS IC to the PCB, as some leads looked less than perfect. My usual check is to poke each lead with the tip of a sharp knife. Bad connections are really obvious as the leads bend very easily. While no leads appeared to have completely failed, some leads were clearly just soldered. So out with the iron, and with liberal amounts of flux, I reflowed all the pins on the XMOS IC. As a tip for those new to the service game, running a sharp knife along a row of SMD leads is a great way to find unsoldered/dry joints; the leads ‘jump’ as you go over them. I plugged the board back into the PC with its freshly soldered XMOS IC. The PC’s insistence that the board still didn’t exist increased my stress to the ‘muttering curses’ level. At this point, I purchased a new USB to I2S card, figuring that the sooner I ordered it, the sooner it would turn up. Just before I threw the presumably dead part in the bin, I took a peek through a microscope and noticed something a little less than perfect on the USB data line transformer (between the IC and USB socket). This is the only connection between the USB connector and the XMOS IC. I should have started there, as it is a really critical part of this device and not in a great spot for reflow soldering given that lumbering great connector near it. I gave it a squirt of freezer spray while the board was plugged in; nothing happened. I was one second from unplugging things and binning it, but as a last gesture, I poked the soldering iron on it (yes, while it was plugged in and powered on, which is bad form indeed). The PC found the card and a blue light came on! I sprayed it with freezer spray and it disappeared. Two minutes later, I had rather brutally reflowed the joints on that tiny transformer. Dodgy SMD joints can be really hard to find, not least because they are small but also because it is fiddly to rework them, and the actual fault can be underneath a component. I could not see the cracked joint, but I was able to demonstrate its presence, which was enough for me. Now I could freeze and heat the board, and it remained connected to my computer. So, a couple of hours later than planned, I had the Codec running again and was off to make the measurements I needed. My blood pressure was also coming down, and I was speaking English again. I also have a $140 spare card on its way as a lesson not to buy expensive spares until all reasonable courses of action have been taken! The internal temperature in the oven can be quite high due to heat from the magnetron (at 70% efficiency, 300W is dissipated). The capacitor also heats up due to its internal resistance. The capacitor is rated to 85°C; its polypropylene dielectric insulation resistance drops significantly with temperature. Measuring the voltage across the capacitor with an oscilloscope shows peak voltages exceeding 3000V during operation, so the capacitor is stressed by both voltage and temperature. The capacitors that failed were all made by BiCai in Ningbo, China. They use polypropylene insulation, and the volume price of the capacitors is about US$2 each. One solution is to limit the cooking time in summer. Alternatively, you can buy a 3000V AC capacitor at a higher price from the USA. Another microwave, a Sharp R395Y inverter oven, was tripping the mains supply circuit breaker during operation. I replaced the inverter’s insulated gate bipolar transistor (IGBT), type 40T321 (40A, 1500V), along with the protective gate-to-emitter zener diode and resistor. When the oven was tried again, the inverter failed again, indicating a faulty 2M368H(L) magnetron. With a new IGBT and another magnetron (I had a 2M319 on hand), the oven would still not heat. I then tried yet another magnetron (2M339) and finally achieved success. I measured the magnetron voltage at 6kV (magnetron disconnected) and 3.7kV with the oven at full power. So the faulty 2M368H(L) magnetron caused the inverter failure. I also had a faulty 2M319 magnetron. The mounting holes are different for the 2M368H(L) versus the other magnetrons, so I had to drill some new holes. I will now get a replacement magnetron of the right type for the oven. What is the difference between the magnetrons for inverter versus non-inverter ovens? Many magnetrons are similar. I tested the 2M386H(L) with a Megger and it broke down at 1000V. The cost of a new magnetron exceeds $300 and the inverter cost is similar. You can buy the magnetron on eBay for about $100 but not the inverter. Buying a new oven is cheaper than replacing both parts; an example of planned SC obsolescence. Microwave oven repairs R. S., of Fig Tree Pocket, Qld has repaired many microwaves and is familiar with many of the more common failure modes... This Breville BM0735 BSSANZ microwave oven (non-­ inverter type) has a voltage doubler circuit using a 1µF 2100V AC capacitor. If the oven is run for 10 minutes or more in summer (ambient temperature of at least 28°C), the capacitor can short-circuit, blowing the high-­voltage fuse. siliconchip.com.au During summer these HV 1μF capacitors were shorting in my microwave oven after extended use. Australia's electronics magazine June 2024  95 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. USB-serial data interceptor This interceptor behaves as a USB host and attempts to enumerate a USB-serial device connected to it. It also appears to an upstream host to be a commonplace type of CDC USB-serial device that does not require any drivers to work on modern operating systems. Data is passed between the upstream and downstream USB buses. Settings such as baud rate are also passed between the two busses. As far as the host is concerned, communication with the downstream device occurs as usual. However, the Pico running as the interceptor could log and possibly modify the data between the two devices. The hardware comprises a partially-­ populated PCB for the USB to PS/2 Keyboard Adaptor (January 2024; siliconchip.au/Article/16090). The only parts fitted are one of the USB sockets (eg, CON1), the two 22W resistors, the 1kW resistor, the LED and the Raspberry Pi Pico module. The resulting circuit is shown here. The software configures the Pico’s PIO (programmable input/output) peripheral to work as a USB host, using the USB socket and 22W resistors. The LED lights if the Pico detects a compatible USB-serial device attached. The Pico’s inbuilt USB peripheral performs the role of the USB-serial device, so the whole circuit simply appears to a computer as a USB-serial device. Note that there are certain unusual types of USB-serial adaptors that this device can’t recognise, such as those that use the fairly old PL2303HXA chip. It might be handy in cases where Windows does not recognise the USB-serial device, but the Pico does. An example might be locked down systems that do not allow driver installs. The LED will quickly show if the Pico can recognise an attached device. The brief sketch is modified from the example “serial_host_bridge” sketch to act as a basic bridge without injecting extraneous data into the upstream or downstream port. It has also been modified to use the Pico’s PIO USB host implementation. If you want to inject (or remove or transform) any data, that can be done by modifying the sketch. We also include a precompiled UF2 file in the download package that can be easily copied onto the Pico’s bootloader drive and accessed by holding the bootloader button while plugging in the Pico. The “forward_serial” function handles passing data between the upstream or downstream ports. One possible way to use this hardware could involve adding code to infiltrate or exfiltrate data as it travels between the ports. Quick NPN/PNP transistor tester This small circuit allows you to make a quick good/bad check of both NPN and PNP bipolar transistors. If the transistor under test is a working NPN, the green LED will flash, while the red LED will flash for a functional PNP device. If the transistor is shorted, both LEDs will flash; if it is open-circuit, both LEDs will stay off. It is based on a 4011 quad NAND 96 Silicon Chip gate chip. IC1a and IC1b, together with the 1MW resistors and 220nF capacitor, form an oscillator that generates a low-frequency square wave at pin 4. This is applied to both the emitter of the transistor under test and IC1c, configured as an inverter. The inverted square wave from IC1c and the oscillator output drive the test circuit (two LEDs and two 1kW resistors) differentially, so the polarity Australia's electronics magazine That could involve adding code to deliver the serial data on a hardware serial line on one of the Pico’s pins, allowing eavesdropping. That could be handy in cases where the downstream device implements a virtual serial device and does not expose a hardware serial UART. The interceptor could also be used as an active USB cable extender, working around the 3m limit for USB 2.0 hardware. Of course, it’s limited to work with USB-serial devices, but that might be useful in some cases. The Pico software for this design can be downloaded from siliconchip. au/Shop/6/350 Tim Blythman, Silicon Chip. across that part of the circuit is repeatedly swapped. If an NPN transistor is being tested, when pin 10 is high and pin 4 is low, current flows through LED1 and the forward-biased transistor, but no current will flow when pin 10 is low and pin 4 high since the transistor is then reverse-biased. Green LED1 will therefore flash at the oscillator rate. As you would expect, a PNP transistor will be forward-biased when pin 10 is low and pin 4 high, so current then siliconchip.com.au Arduino bin reminder This simple project came about when one person in our street put out the wrong coloured bin. This created confusion in the street as most people copied what bin the earlier neighbour had put out, including yours truly. I decided to check the council website for the bin timetable. After wasting about half an hour, I found that the council, in its wisdom, had put the 2024 calendar up and deleted the 2023 timetable before the end of the year! I remembered Silicon Chip published a bin reminder project some years ago (January 2013; siliconchip. au/Article/1315). While it is an excellent design with many great features, I wanted something very simple with no buttons for anyone to fiddle with. The circuit presented here is straightforward, using little more than a real-time clock module and an Arduino Uno. All of the programming is done in the sketch code rather than using buttons. I have commented the sketch so it is easy to set your bin colour LEDs and their timing. If, when the Arduino is powered up, it detects that the real-time clock module does not have a valid date and time, it sets them to the date and time that the sketch was compiled and uploaded, which should be just a few seconds earlier. That slight time difference will be inconsequential to the device’s job. The sketch changes the display over at 1:30am every Sunday morning, to tell the user what the bin colours are for the week. When the circuit boots up, the LEDs for the current week will be displayed. The reminder will then change to your setting for the alternate week the following Sunday morning. The Sunday after that, the LEDs will swap back again. This cycle continues while power is applied. The unit must be kept powered up continuously (do not press the Arduino reset once programmed). As shown in the circuit diagram, I achieved that with a trickle-charged 9V NiMH battery. The software sketch for this project can be downloaded from: siliconchip.au/Shop/6/352 Geoff Coppa, Toormina, NSW. ($80) flows through LED2 (red). The 5V supply rail is chosen carefully because it needs to be sufficient to light the LEDs but not so high that it could cause reverse breakdown in the transistor or LEDs, which could cause both an erroneous result and possibly damage the transistor. The fourth section of the chip (IC1d) is not used, so its inputs are tied to the 0V rail. Raj K. Gorkhali, Hetauda, Nepal ($50). siliconchip.com.au Australia's electronics magazine June 2024  97 Programming a Micromite over Bluetooth In the September 2021 issue, Tom Hartley described how to connect an HC-05 device to a Micromite using an Android phone (siliconchip.au/ Article/15031). Tom's article made me realise that if I could get an HC-05 to work under TeraTerm, I could change my programs wirelessly. Many computers these days have built-in WiFi (including many desktops and virtually all portable computers). If they do, they usually have Bluetooth support as well. If not, you can get a USB Bluetooth adaptor for just a few dollars. Once you have a Windows computer with Bluetooth, you just need an HC-05 adaptor to program Micromites remotely! Under Windows 10, when an HC-05 Bluetooth device is detected, it creates two virtual COM ports. Windows 10 has drivers for the HC-05, so no drivers need to be installed. The great thing is that TeraTerm does not know the difference between virtual and real COM ports, so it works as if wires were connected. In Tom's article from September 2021, he describes how to attach the HC-05 to a USB-TTL serial converter to set it up. He mentioned that some HC-05 devices come without an enable button, but these may be set up to a baud rate of 38,400, so they may work without being set up. The devices I received had the enable button; they were set to 38,400 baud, but they still did not work without the setup procedure. Try to get the HC-05 that looks the same as the picture in Tom's article, with the tiny button on one side of the board close to the EN pin. Another thing to check is that there are six pins on the module. Setting up the module Set up the module using Tom's 98 Silicon Chip excellent instructions. He suggested powering the module from a 4.5V battery pack via a switch, but I used 3.3V from a CP2102 USB-TTL serial converter (Jaycar XC4464) via jumper wires. Plugging and unplugging the 3.3V jumper wire acts as a switch. We are not using USB to connect to the Micromite; the HC-05 has a serial output and connects directly to the serial input of the Micromite. If the Micromite has a USB connection, it must be disabled. For example, a Micromite LCD Backpack V3 can be configured for straight serial by removing the PIC16F1455 chip and connecting via the 5V/TX/RX/ GND header. Once you have followed Tom’s instructions to set up the HC-05, unplug it from the CP210x USB-toTTL serial converter and remove the CP210x from the computer USB port. Connect the HC-05 Tx pin to the Micromite’s Rx pin and vice versa. Connect the two GNDs together and the HC-05 Vcc to the Micromite’s 5V pin. Don’t connect the STATE or EN pins on the HC-05 module. The Micromite may be powered from any 5V source. The Micromite can now be several meters away from the Windows 10 computer, with no wires connected between them. Once the HC-05 is powered up (no need to press the button this time), go to the computer’s Bluetooth settings to pair with the HC-05. You should see a Bluetooth symbol next to the computer’s system clock, at the right end of the taskbar. If you can't see it, try pressing the ^ symbol. Click on the Bluetooth symbol and choose “Add a Bluetooth Device”. On the screen that pops up, click on the plus button next to “Add Bluetooth or other device” near the top of the window. You will get a menu Australia's electronics magazine titled “Add a device”. Choose the top option: “Bluetooth (Mice, keyboards, pens, or audio and other kinds of Bluetooth devices)”. You might see “HC-05” or “unknown device” appear, then the name should change to the name you gave it during set-up. Click on that and type 1234 in the password box that pops up. When the ‘paired’ notification pops up, click Done. Open Device Manager again and look under ports. You should see two new serial ports; mine were COM3 and COM6. I used the first one, COM3. In TeraTerm, use the File → New Connection menu option, set the Serial Port to COM3 (or whatever the first port in Device Manager was), then click OK. Set the terminal settings to how they should be to talk to a Micromite (in the Setup menu, click Terminal). That is, Local Echo off, Receive set to CR and Transmit set to CR. Now you are all set to program your Micromite. To test the connection, press Enter, and you should see the ">" prompt. You can type EDIT to access the full-screen editor or LIST to view the program. Note that if you have more than one HC-05, you have to remove one HC-05 from the Bluetooth setup window before you can communicate with the next one; at least, that was my experience. Now we have an HC-05 programmed to talk to the Micromite at 38,400 baud with the correct parity settings. It can be left attached to the Micromite board. You could put it in a project anywhere nearby and blissfully program away with nothing cluttering up the place except your computer! Grant Muir, Sockburn, New Zealand. ($75) siliconchip.com.au Vintage Radio HeathKit GW-21A handheld transceivers By Dr Hugo Holden Screen 1: a frame from Voyage to the Bottom of the Sea. In the early 1960s, manufacturers such as HeathKit started to lift their game in mobile transceiver design. The clear choice was the single-conversion superhet format, keeping it as simple as possible but not too simple. B y the early 1960s, many germanium transistor radios had been produced, with some capable of excellent high-frequency performance. In Europe, the typical transistors used were the OC169, OC170 and OC171. The similar AF114 to AF117 were ultimately replaced by the AF124 to AF127 series, the former parts all being affected by tin whisker disease. In the USA, various 2N prefix types, such as the 2N2084 made by Amperex, had similar performance to the AF124. The RF-capable transistor types were characterised by having very high transition frequencies and very low collector-­ to-base feedback (Miller) capacitances. That also allowed them siliconchip.com.au to be used in IF amplifier chains without neutralisation. As one example, the AF124, in a grounded base circuit, had a useful power gain of 14dB at 100MHz and was used in the front-end of FM broadcast-band radios operating from 87MHz to 101MHz. In the years that followed, into the 1970s, very advanced germanium types appeared that would work in VHF and UHF TV tuners, such as the AF239 and AF240. These worked in mixer and oscillator circuits up to an astonishing 890MHz. Back in the early 1960s, transistor radios of many kinds were coming to dominate the radio world. These Australia's electronics magazine pushed the older valve (vacuum tube) designs into the background, ultimately making them obsolete. This process was accelerated by the development of temperature-stable, lower-­ noise, higher-power-rated silicon transistors, which generally outperformed their germanium ancestors. Germanium-transistor-based handheld compact transistor transceivers, like the HeathKit GW-21A, started to appear in stores and in popular culture, on the TV and in movies too. Screen 1 (shown above) is a frame cut from an early 1960s TV show, Voyage to the Bottom of the Sea, where a HeathKit GW-21 transceiver was used to save the day. June 2024  99 These 2N2804 transistors were used to replace the MM1056 transistors. They have similar performance to the AF124. Simple super-regenerative transceivers or “walky-talky” designs for children had appeared in toy stores in the 1960s, typically powered by a 9V battery. These ‘toy’ units often used a single transistor stage as an oscillator in transmit mode. A small audio amplifier would amplitude-modulate it. The same transistor oscillator stage then behaved as a super-­regenerative receiver, with the audio amplifier redeployed to drive the speaker in receive mode. Therefore, most of the circuitry in the unit is deployed in both transmit and receive modes, hence the term ‘transceiver’, as the circuitry transforms and reconfigures itself for the two modes of operation. These early transistor-based super-­ regenerative units usually operated in the citizen’s band (CB) around 27MHz. The receiver section was typically quite noisy (as super-regenerative receivers are), and the transmission range was limited. Sometimes the results even disappointed the children as well as the adults playing with them. Transistor superhet receivers of the time were already known to have high gain, low noise and good selectivity in the medium-wave and short-wave bands, up to and above 30MHz. Ideally, the transmitter would also have an independent RF output stage, amplitude-modulated by an audio amplifier, and a separate, stable crystal oscillator would drive that output stage. This two-stage design limits any frequency-modulating effects on the transmit oscillator. Again, the audio amplifier in the transceiver would perform two roles: as a modulator in transmit mode and an audio amplifier in receive mode. This type of design appeared in the HeathKit GW-21 and GW-21A transceivers. They are apparently identical units, except for the transistor types used. Recently, I came across a pair of HeathKit GW-21As on eBay. I had seen them on TV during my childhood and 100 Silicon Chip always wanted them. So, for nostalgia’s sake, I decided to buy them and restore them. Then I could put them through their paces and find out how well they worked. AGC voltage, which is filtered and fed back to Q3 and Q1. It is worth noting that, in a set with PNP transistors, the AGC voltage becomes more positive with increasing signal strength. This tends to take General description the transistors to which the AGC is The GW-21 appeared in the time applied out of conduction, shifting window of 1964 to 1969. The price towards a lower gain condition with per unit at that time was $39.95. In increasing received signal strength. today’s dollars, that is about $380.00 Essentially, the AGC system is a long each; it’s no wonder I did not have time constant negative feedback loop. one back then! The AGC’s time constant & circuit They boasted nine transistors, two resistances are set by the value of 10µF diodes and a single-channel crystal-­ electrolytic capacitor C12 and resistor controlled system using two crystals R14. Note that, with very high signal per unit. Separate crystals were used levels, the voltage on a transistor radio’s for the receiving and transmitting AGC capacitor can reverse polarity, so oscillators. They had an on/off/vol- generally, I replace the AGC capacitor ume control, squelch control, push- with a bipolar or film type. to-talk (PTT) button, an earphone jack, The recovered modulation (audio an external antenna jack and an inte- signal) then passes via “squelch diode” gral whip antenna. A single 9V battery D2 to the volume control. D2 is set up powered the whole thing. with a variable DC voltage applied to The circuit of the GW-21A is shown its cathode from the squelch control. in Fig.1. On the receiver side, the This allows the diode to be cut off, prodesign is of a conventional super- gressively uncoupling the audio feed to het with an RF stage designed for the volume control unless the dynamic single-frequency reception. The RF signal peaks are large enough to overinput from the antenna is passed, after come the diode’s forward voltage drop. appropriate impedance matching, Testing shows that the diode to Q1, the RF amplifier. The crystal-­ has a 0.43V forward bias in the controlled local oscillator (Q2), called ‘unsquelched’ condition. That is more an Autodyne Converter or mixer-­ than enough for the germanium diode oscillator, runs above the received to be in full conduction. With the frequency. knob in the full squelched condition, The oscillator stage receives the sig- the applied forward bias is very close nal from the RF amplifier and the mix- to 0V, so the recovered audio signal ing products appear in Q2’s collector from the detector has to overcome the circuit. The sum and difference fre- diode’s entire forward voltage to pass quencies of the incoming carrier wave through to the audio amplifier. and the oscillator wave appear because The audio is then passed via the the non-linear mixing results in prod- press-to-talk switch (in its unpressed ucts of these two waves. or listen condition) to the input of the The first IF transformer, T1, effec- audio amplifier stages. tively filters off the difference freThe audio amplifier design is typquency of 455kHz and feeds this to ical of the era: a Class-A driver stage transistor Q3, the first intermediate driving the bases of two output transisfrequency (IF) transistor. tors in Class-B. The output transistors Typically, in most superhet radios have just enough initial bias to avoid with a 455kHz IF channel, the receiver crossover distortion. oscillator frequency runs 455kHz These simple amplifiers are energy-­ higher than the incoming carrier wave. efficient, have a low quiescent curIn my GW-21A radios, the transmit rent and are generally suited to batcrystal frequency is 27.085MHz (CB tery operation. The only difference channel 11), while the receive oscil- here is that the output transformer lator crystal in the converter stage is has an additional winding to ampli27.540MHz. tude modulate the power supply to From Q3, the IF signal passes via the RF output stage when the unit is T2, Q4, then T3 in the IF amplifier in transmit mode. to the detector diode D1, where the amplitude modulation is recovered. Restoration In addition, the detector generates an Both the units arrived in good Australia's electronics magazine siliconchip.com.au Fig.1: this is the circuit for the GW-21A. The GW-21 (non-A) version used the following transistors. Q1: 2N1726, Q2: 2N1727, Q3 & Q4: 2N1108, Q5-Q7: 2N185, Q8: R425, Q9: R424. Otherwise, they were mostly identical. June 2024  101 Australia's electronics magazine siliconchip.com.au Because one of the 10µF electrolytic capacitors read high at ~38µF, I decided to replace all of them. I also replaced the 100W resistors in the emitter circuits of the oscillator and RF output transistors. condition, and fortunately, there was no evidence of previous repairs or modifications. Having worked on several items of this vintage with germanium transistors, I decided to start with a standard protocol, checking the electrolytic capacitors and replacing them where required. I removed seven electrolytic capacitors in each unit for inspection and detailed testing. There were some abnormalities. All had leakage values over 100 times higher than a new electrolytic of the same value. Interestingly, the ESR of all of them was within normal limits. The capacitance values were reasonable, except for the axial 10µF electrolytics, which interestingly read around 38µF. Due to the high leakage values, I replaced them all. I also quickly determined that the 100W resistors in the emitter circuits of the oscillator and RF output transistors were out of spec at 135W each, so I replaced them too. All the other resistors were in good order and within the expected ranges. One of the units had a cracked section on the lower corner of the phenolic PCB. I strengthened it with a small 2mm-thick brass plate tapped with threaded holes for 1.6mm brass screws to secure it. I cleaned the potentiometres, transistor sockets and PTT switch with CRC’s CO contact cleaner and then lubricated them with Inox’s MX3, which I have found better than using a combined cleaner-lubricant product. Inox MX3 is a very high-­purity oil; I have subjected it to several experiments on various metals, and it is my preferred lubricant for restoration work. Before attempting testing and alignment, I have a standardised approach when transistor sockets are present for checking the transistors for gain and noise. I check the audio transistors in-­ circuit, though. I replaced the speaker with a 10W dummy load (the original speaker is a 10W type). I then connected my oscilloscope across that dummy load and fed a test sinewave signal from a generator to the input of the audio stage (in the driver transistor/volume control area). It is easy to see if the audio transistors are OK in this sort of amplifier. If either output transistor is unwell, it unbalances the output, and the sinewave becomes asymmetric. Also, the Fig.2: the circuit I used to test for defective transistors. 102 Silicon Chip Australia's electronics magazine driver transistor can easily be checked against a known-good germanium PNP audio driver transistor like an AC126. The output transistors can be verified against known-good AC128 types. One final check is to compare the audio amplifier sections between the two units for gain and power output. I was satisfied that both units’ audio stages were normal and that all the original audio transistors, RCA 2N407 types, were perfectly operational. The radio-frequency transistors are a different matter. I check them out of the radio in a test jig with a socket, to examine their gain and frequency response up to 100MHz. Its circuit is shown in Fig.2. This is a way of screening out defective transistors. I use a Philips PM5326 RF generator, which has a 75W output resistance, and a Tektronix 2465B ‘scope, set on its 50W input resistance option. The transistors are placed in the socket of the simple test jig to evaluate their basic performance and compare them to some excellent AF178, 2N2084 and AF124 transistors that I have, as well as comparing the same types from the two units with each other. The test circuit quickly screens out noisy and weak transistors. On testing, the 2N1525 IF transistors all had similar properties, with nearly identical gain to an AF124 reference transistor below 1MHz. Unlike the AF124, where the output amplitude in my test jig drops by 50% at 70MHz, the 2N1525’s output reduces by 50% at about 10MHz. The 2N1525 transistors are just satisfactory enough (low enough collector to base feedback capacitance) to work in an IF amplifier without neutralisation. You will notice from the GW-21A siliconchip.com.au The phenolic PCBs for the HeathKit GW-21A transceivers. An original PCB is shown at left; the adjacent PCB has new electrolytic capacitors and a crack repair in the lower left corner. circuit that it has a non-­neutralised 455kHz IF. The A1384 transistors in the RF, converter, and transmitter oscillator stages were all good in both units. These are not 2SA1384s; they are an Amperex part. In the test jig, their output drops to 50% at around 50MHz. They are higher-frequency capable than the 2N1525 transistors used in the IF amplifier, as they have to be for the role they play operating in the 27MHz stages. Then there were the two RF output transistors to test for each unit, the somewhat mysterious Motorola MM1056. I could not find the original Motorola data sheet for them, so I didn’t know the expected transition frequency. Some basic data I found online suggested they were similar to the AF124. I also posted on the Antique Radio forums but had no luck finding the original Motorola data sheet. The logical place to find it would be in an early 1960s vintage Motorola transistor data book. siliconchip.com.au One of these transistors was defective, and its leads had been cut by someone in the past. The junction was damaged and badly leaking. The transistor from the other GW-21A unit was good. Testing the good one in the test jig, it was clearly capable of very high-frequency performance, being very similar to the AF178, with its output dropping to 50% by about 110MHz. However, during alignment and testing of the transmitter section of the radios, I elected to replace the MM1056 transistor in both units with Amperex 2N2084s, as they gave more stable results with slightly higher output. I also found some capacitive coupling effects on the transistor body. In these HeathKit radios, all of the transistor sockets have three pins; there is no shield connection. The quick solution for the 2N2084 was simply connecting its shield (case) to its emitter wire (which is at RF common). That solved the problems of higher frequency parasitic oscillation I Australia's electronics magazine observed with the original MM1056 transistor and the Amperex 2N2084, when the body of the transistor was floating in both cases. After aligning L5 & L6 in the transmitter section, Scope 1 shows the output of the transmitter with the antenna retracted into the unit and the scope connected to the base of the whip. The measured voltage was about 16V peak-to-peak. With the antenna up, the amplitude drops to about 8V peakto-peak. Of note, if L5 is peaked for maximum Scope 1: the transmitter output with the antenna retracted. June 2024  103 The underside of the GW-21A PCB. Note the modified AAA cell holders; I did that because the battery compartment was too large for a typical 9V battery. This time, the repaired PCB is shown on the left, although both have new capacitors. power output and then the slug is unscrewed further, the oscillator can drop out or fail to start when the pushto-talk button is pushed. So it is best to adjust it just a little on the opposite side of the peak, with the slug a little further into the former. With the speaker replaced by a 10W dummy load, I couldn’t talk into the speaker to test the transmitter, so I applied a 1kHz sinewave modulation signal from a signal generator. I set the generator output to 0.5V peak or about 350mV RMS and used a 3.3kW series resistor to deliver the signal across the 10W dummy speaker resistance. That corresponds to only about 1mV RMS of signal to the input of the audio amplifier. The result is shown in Scope 2, with the carrier at the antenna base now at about 28V peak-to-peak on the modulation crests. Increasing the modulation signal level from the generator, the RF output stage clipped fairly softly, and the 104 Silicon Chip carrier was not modulated to zero, as shown in Scope 3. This occurred before clipping in the audio amplifier. I was pretty impressed by the reasonably soft carrier clipping and residual carrier signal. RF output power I read on the internet that the output power of this radio was 100mW, but I wanted to check it for myself. After working on these radios for some time, I noticed that the 9V batteries I had been using, which had seen some use before, had dropped to 8V. So I repeated the carrier output test with fresh batteries and got the result shown in Scope 4. With a fresh battery, the RF output at the antenna base (with the antenna retracted) comes up to 12V peak or 24V peak-to-peak and about double that at 100% modulation. Raising the whip antenna caused the voltage to fall approximately 50%. That suggests Australia's electronics magazine the antenna impedance has been well matched with its loading coil to the RF output stage. I decided to test with various load resistors at the antenna’s base, with the antenna retracted, to find which resistance also lowered the RF level to 50% to estimate the antenna’s impedance at its full extended length. A 680W resistor resulted in the level dropping by 50%, much as extending the antenna does. With no modulation, the voltage developed across the 680W load was 6V peak or 4.24V RMS, and at full modulation, it was about 8.48V RMS. Therefore, the peak envelope power (PEP) delivered to the 680W dummy load resistor (or the fully extended antenna) is approximately 106mW (8.48V2 ÷ 680W) at full modulation. With zero carrier modulation, the RF output power is ¼ of that, about 26mW. So, the suggestion that these GW-21A radios had a 100mW RF siliconchip.com.au output probably referred to a PEP measurement, not an unmodulated carrier wave power, which is ¼ of the PEP. In another attempt to estimate the RF power output, I tested the signal out of the external antenna jack. The output impedance here appears very low. Unloaded and unmodulated, it delivers a signal of about 4V peak-to-peak. Loaded with a 15W resistor, it drops to 2V peak-to-peak (0.7V RMS), corresponding to around 32mW (unmodulated) into 15W. I made a 1:2 turn ratio (1:4 impedance ratio) ferrite RF impedance matching transformer and found, unmodulated, it could deliver 28mW into a 50W load, or around 112mW PEP at full modulation. Receiver alignment The receiver alignment was pretty straightforward. First, I aligned the IF by connecting the ‘scope across the 10W dummy speaker load resistor and applying a signal to the antenna connection from a Philips PM5326 RF generator. I set the generator for precisely 455kHz at a carrier modulation level of 30% and the volume control to maximum. I unplugged receiver crystal X1 to disable the converter. Enough level was provided so the recovered signal was visible just before significant AGC activation, and I peaked IF transformers T1, T2 and T3. After that, I plugged the receive crystal back in and set the generator for 27.085MHz, then aligned the receiver for maximum gain by adjusting L1 and L2. I then disconnected the generator, attached a small antenna to the generator output and adjusted L1 and L2 again, with the GW-21A’s antenna extended a few metres from the generator. I did that in case the attachment of the generator had caused some Scope 2: the amplitude-modulated output with a 1mV signal injected. siliconchip.com.au detuning effects, but it turned out that the slugs of L1 and L2 were already in the correct positions. The signal was audible above the noise floor when the generator’s variable attenuator was in the region of -70dB to -80dB. With noise and signal about equal to the ear, the attenuator was on -75dB. The PM5326 generator on 0dB applies 50mV RMS into 75W and about double that to a high-Z load. This suggests the receiver can resolve a signal of about 17µV from the noise floor. Once the receivers were aligned, it was time to try them out. In practice, at full volume, there is moderate audible noise; nothing as severe as a super-­regenerative radio, though. The squelch control works well, unlike a typical squelch that suddenly kills the noise; its effect is more gradual. I could hear intermittent transmissions of people speaking at times, with American accents, making me wonder if that was some sporadic short-wave transmission on CH11 from overseas. In any case, the receiver appears very sensitive indeed. So far, I have tried these radios with about 100m separation with very good results. I am going to perform a maximum line-of-sight test on them soon. so the batteries would fit snugly. The final photo shows the two restored units with the batteries fitted. While many HeathKit radios were sold as kits, the quality of the construction makes me think these two were factory assembled. Summary The battery compartment is a little large for a typical 9V battery, so I modified some six-AAA cell holders and fitted them with a 9V battery power clip. That gives a much higher capacity battery at a lower cost. With these holders, it pays to tape the batteries in. I use Scotch 27 fibreglass tape as it can be reused a few times, and it stops the holders from sliding around, too. The photos show the relative size. It was necessary to add some soft packing into the battery compartment The GW-21A is a remarkable early germanium transistor handheld transceiver. While it does not have a spectacular RF output power compared to modern transceivers, only 100mW PEP, it makes up for that by having a very sensitive superhet receiver. The GW-21(A) is far from a toy radio. It would have been a dream to have owned a pair of these as a boy, back in the 1960s, when most transceivers children could get their hands on were poorly performing noisy super-­ regenerative types. These sorts of transceivers make an interesting restoration project, and replacement or equivalent germanium transistors are SC still available if required. Scope 3: the amplitude-modulated output with maximum modulation. Scope 4: the carrier output test signal with new batteries. Australia's electronics magazine June 2024  105 Batteries 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 194, MATRAVILLE, NSW 2036 (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. 06/24 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 ATtiny45-20PU ATtiny85V-10PU PIC10LF322-I/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F617-I/SN PIC12F675-I/P PIC16F1455-I/P Digital FX Unit (Apr21) 110dB RF Attenuator (Jul22), Basic RF Signal Generator (Jun23) RGB Stackable LED Christmas Star (Nov20) 2m VHF CW/FM Test Generator (Oct23) Shirt Pocket Audio Oscillator (Sep20) Range Extender IR-to-UHF (Jan22) LED Christmas Ornaments (Nov20; versions), Nano TV Pong (Aug21) Active Mains Soft Starter (Feb23), Model Railway Uncoupler (Jul23) Model Railway Carriage Lights (Nov21) Train Chuff Sound Generator (Oct22) Auto Train Controller (Oct22), GPS Disciplined Oscillator (May23) Railway Points Controller Transmitter / Receiver (2 versions; Feb24) PIC16F1455-I/SL Battery Multi Logger (Feb21), USB-C Serial Adaptor (Jun24) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P Cooling Fan Controller (Feb22), Remote Mains Switch (RX, Jul22) K-Type Thermostat (Nov23), Secure Remote Switch (RX, Dec23) Mains Power-Up Sequencer (Feb24) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Tiny LED Icicle (Nov22), Digital Volume Control Pot (SMD; Mar23) Silicon Chirp Cricket (Apr23) PIC16F15214-I/P Digital Volume Control Pot (through-hole; Mar23) PIC16F15224-I/SL Multi-Channel Volume Control (OLED Module; Dec23) PIC16F1705-I/P Digital Lighting Controller Translator (Dec21) PIC16F18146-I/SO Volume Control (Control Module, Dec23), Coin Cell Emulator (Dec23) PIC16LF15323-I/SL Remote Mains Switch (TX, Jul22), Secure Remote Switch (TX, Dec23) W27C020 Noughts & Crosses Computer (Jan23) ATSAML10E16A-AUT PIC16F18877-I/P PIC16F18877-I/PT High-Current Battery Balancer (Mar21) USB Cable Tester (Nov21) Dual-Channel Breadboard PSU Display Adaptor (Dec22) Wideband Fuel Mixture Display (WFMD; Apr23) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23), ESR Test Tweezers (Jun24) 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) 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 ATmega32U4 ATmega644PA-AU Wii Nunchuk RGB Light Driver (Mar24) AM-FM DDS Signal Generator (May22) $25 MICROS dsPIC33FJ64MC802-E/SP 1.5kW Induction Motor Speed Controller (Aug13) PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sep16) $30 MICROS PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC ESR TEST TWEEZERS COMPLETE KIT (SC6952) (JUN 24) Includes all parts and OLED, except the coin cell and optional header - 0.96in white OLED with SSD1306 controller (also sold separately, SC6936) DC SUPPLY PROTECTOR (JUN 24) All kits come with the PCB and all onboard components (see page 81, June24) - Adjustable SMD kit (SC6948) - Adjustable TH kit (SC6949) - Fixed TH kit – ZD3 & R1-R7 vary so are not included (SC6950) USB-C SERIAL ADAPTOR COMPLETE KIT (SC6652) (JUN 24) WIFI DDS FUNCTION GENERATOR (MAY 24) Includes the PCB, programmed micro and all other required parts Short-form kit: includes everything except the case, USB cable, power supply, labels and optional stand. The included Pico W is not programmed (SC6942) - Optional laser-cut acrylic stand pieces (SC6932) - 3.5in LCD touchscreen: also available separately (SC5062) 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (SC6881) (MAY 24) PICO GAMER KITS (APR 24) Complete kit: Includes the PCB and everything that mounts to it, including the 49.9Ω and 75Ω resistors (see page 38, May24) $50.00 $10.00 $17.50 $22.50 $20.00 $20.00 $95.00 $7.50 $35.00 $40.00 - SC6911: everything except the case & battery; RP2040+ is pre-programmed - SC6912: the SC6911 kit, plus the LEDO 6060 resin case - SC6913: the SC6911 kit, plus a dark grey/black resin case - 3.2in LCD touchscreen: also available separately (SC6910) ESP-32CAM BACKPACK KIT (SC6886) (APR 24) PICO DIGITAL VIDEO TERMINAL (SC6917) (MAR 24) MAINS POWER-UP SEQUENCER (FEB 24) Includes everything to build the BackPack, except the ESP32-CAM module - 3.5in LCD touchscreen: also available separately (SC5062) $85.00 $125.00 $140.00 $30.00 $42.50 $35.00 Short-form kit: includes everything except the case; choice of front panel PCB for Altronics H0190 or H0191. Picos are not programmed (see page 46, Mar24) $65.00 Hard-to-get parts: includes the PCB, programmed micro, all other semiconductors and the Fresnel lens bezels (SC6871) $95.00 siliconchip.com.au/Shop/ Current detection add-on: includes the AC-1010 current transformer, (P)4KE15CA TVS and MCP6272-E/P op amp (SC6902) $20.00 MICROPHONE PREAMPLIFIER KIT (SC6784) (FEB 24) USB TO PS/2 KEYBOARD & MOUSE ADAPTOR (JAN 24) COIN CELL EMULATOR (SC6823) (DEC 23) MULTI-CHANNEL VOLUME CONTROL (DEC 23) SECURE REMOTE SWITCH (DEC 23) IDEAL DIODE BRIDGE RECTIFIER (DEC 23) MODEM / ROUTER WATCHDOG (SC6827) (NOV 23) Includes the standard PCB (01110231) plus all onboard parts, as well as the switches and mounting hardware. All that’s needed is a case, XLR connectors, bezel LED and wiring (see page 35, Feb24) - VGA PicoMite Version Kit: see page 52, January 2024 (SC6861) - ps2x2pico Version Kit: see page 52, January 2024 (SC6864) - 6-pin mini-DIN to mini-DIN cable, ~1m long. Two cables are required if adapting both the keyboard and mouse (SC6869) - Receiver short-form kit: see page 43, December 2023 (SC6835) - Discrete transmitter complete kit: see page 43, December 2023 (SC6836) - Module transmitter short-form kit: see page 43, December 2023 (SC6837) - 28mm square spade: see page 35, December 2023 (SC6850) - 21mm square pin: see page 35, December 2023 (SC6851) - 5mm pitch SIL: see page 35, December 2023 (SC6852) - Mini SOT-23: see page 35, December 2023 (SC6853) - D2PAK SMD: see page 35, December 2023 (SC6854) - TO-220 through-hole: see page 35, December 2023 (SC6855) $30.00 $32.50 $10.00 - Kit: Contains all parts and the optional 5-pin header (see page 77, Dec23) - 1.3in blue OLED (SC5026) - Control Module kit: see page 68, December 2023 (SC6793) - Volume Module kit: see page 69, December 2023 (SC6794) - OLED Module kit: see page 69, December 2023 (SC6795) - 0.96in SSD1306 cyan OLED (SC6176) $70.00 $30.00 $15.00 $50.00 $55.00 $25.00 $10.00 $35.00 $20.00 $15.00 $30.00 $30.00 $30.00 $25.00 $35.00 $45.00 Short-form kit: includes all non-optional parts, plus a 12V relay and unprogrammed Pi Pico. Does not include a case (see page 71, Nov23) $35.00 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT HUMMINGBIRD AMPLIFIER 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 AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) DATE 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 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 PCB CODE 01111211 29106211 23111211 23111212 15109211 15109212 01101221 01101222 01102221 SC6244 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 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 SC6658 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A Price $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 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT LOUDSPEAKER TESTING JIG BASIC RF SIGNAL GENERATOR (AD9834) ↳ FRONT PANEL V6295 VIBRATOR REPLACEMENT PCB SET DYNAMIC RFID / NFC TAG (SMALL, PURPLE) ↳ NFC TAG (LARGE, BLACK) RECIPROCAL FREQUENCY COUNTER MAIN PCB ↳ FRONT PANEL (BLACK) PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT ARDUINO ESR METER (STANDALONE VERSION) ↳ COMBINED VERSION WITH LC METER WATERING SYSTEM CONTROLLER SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER 2M VHF CW/FM TEST GENERATOR TQFP-32 PROGRAMMING ADAPTOR ↳ TQFP-44 ↳ TQFP-48 ↳ TQFP-64 K-TYPE THERMOMETER / THERMOSTAT (SET; RED) PICO AUDIO ANALYSER (BLACK) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION MULTI-CHANNEL VOLUME CONTROL: VOLUME PCB ↳ CONTROL PCB ↳ OLED PCB SECURE REMOTE SWITCH RECEIVER ↳ TRANSMITTER (MODULE VERSION) ↳ TRANSMITTER (DISCRETE VERSION COIN CELL EMULATOR (BLACK) IDEAL BRIDGE RECTIFIER, 28mm SQUARE SPADE ↳ 21mm SQUARE PIN ↳ 5mm PITCH SIL ↳ MINI SOT-23 ↳ STANDALONE D2PAK SMD ↳ STANDALONE TO-220 (70μm COPPER) RASPBERRY PI CLOCK RADIO MAIN PCB ↳ DISPLAY PCB KEYBOARD ADAPTOR (VGA PICOMITE) ↳ PS2X2PICO VERSION MAINS POWER-UP SEQUENCER MICROPHONE PREAMPLIFIER ↳ EMBEDDED VERSION RAILWAY POINTS CONTROLLER TRANSMITTER ↳ RECEIVER LASER COMMUNICATOR TRANSMITTER ↳ RECEIVER PICO DIGITAL VIDEO TERMINAL ↳ FRONT PANEL FOR ALTRONICS H0190 (BLACK) ↳ FRONT PANEL FOR ALTRONICS H0191 (BLACK) WII NUNCHUK RGB LIGHT DRIVER (BLACK) ARDUINO FOR ARDUINIANS (PACK OF SIX PCBS) ↳ PROJECT 27 PCB CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION SKILL TESTER 9000 PICO GAMER ESP32-CAM BACKPACK WIFI DDS FUNCTION GENERATOR 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (BLUE) FAN SPEED CONTROLLER MK2 DATE JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 JAN24 JAN24 JAN24 JAN24 FEB24 FEB24 FEB24 FEB24 FEB24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 AUG23 AUG23 APR24 APR24 APR24 MAY24 MAY24 MAY24 PCB CODE 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 04106181 04106182 15110231 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 04107231 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 10108231 01110231 01110232 09101241 09101242 16102241 16102242 07112231 07112232 07112233 16103241 SC6903 SC6904 01108231 01108232 08101241 08104241 07102241 04104241 04112231 10104241 Price $12.50 $5.00 $5.00 $5.00 $1.50 $4.00 $5.00 $5.00 $5.00 $2.50 $2.50 $5.00 $7.50 $12.50 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 $10.00 $5.00 $2.50 $2.50 $5.00 $5.00 $5.00 $3.00 $5.00 $2.50 $2.50 $5.00 $2.00 $2.00 $2.00 $1.00 $3.00 $5.00 $12.50 $7.50 $2.50 $2.50 $12.50 $7.50 $7.50 $5.00 $2.50 $5.00 $2.50 $5.00 $2.50 $2.50 $20.00 $20.00 $7.50 $2.50 $2.50 $15.00 $10.00 $5.00 $10.00 $2.50 $5.00 ESR TEST TWEEZERS (SET OF FOUR, WHITE) DC SUPPLY PROTECTOR (ADJUSTABLE SMD) ↳ ADJUSTABLE THROUGH-HOLE ↳ FIXED THROUGH-HOLE USB-C SERIAL ADAPTOR (BLACK) JUN24 JUN24 JUN24 JUN24 JUN24 SC6963 08106241 08106242 08106243 24106241 $10.00 $2.50 $2.50 $2.50 $2.50 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 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 How does “Fender shimmer” work? I enjoyed Brandon Speedie’s article on the Fender Bassman guitar amplifier (April 2024 issue; siliconchip.au/ Article/16218). It was music and a fascination with circuits that got me into electronics in the first place. However, I am perplexed by the description of the Fender “Tone Stack”, in particular, how a linear circuit could produce non-linear distortion (“The resulting harmonics and intermodulation...”). I suppose it is possible that at some settings, the impedance of the Tone Stack overloads the preceding stage, but I’m not in a position to analyse it. Perhaps Brandon could elaborate. (P. D., Darlington, NSW) ● Brandon responds: you make a good point. The “Fender shimmer” effect is anecdotal, and I’ve never actually questioned its inner workings. As you say, the Tone Stack itself won’t be able to introduce distortion (aside from the non-linearity of the capacitors). I agree that it is probably an interaction between the filtering and the adjacent gain stages, or perhaps the subjective effect of filtering on the existing distortions. However, as is often the case in vintage audio, it might just be a figment of imagination. I’m pleased you enjoyed the article. I, too, was led to electronics from an earlier love of music. You may also enjoy my upcoming piece on foot pedal effects units from the 1960s. Using Remote Switch with a one-button door If I use the Secure Remote Switch (December 2023 & January 2024 issues; siliconchip.au/Series/408) to open my gate, how can it close the gate without another relay? My garage door uses a single switch for opening and closing. (B. B., Palmerston, NT) ● Use the momentary selection and set the on-time between 200ms 108 Silicon Chip and 500ms. The common (COM) and Normally open (NO) contacts can then replace or parallel the existing switch, allowing you to open or close the door remotely. Problems running BIN file for WiFi DC Load I built the WiFi Programmable DC Load controller (September & October 2022; siliconchip.au/Series/388) but encountered a problem trying to get the supplied firmware to work. I am using the ESP32_Devkitc_V4 with WROOM32D WiFi MCU (and ESP32-DOWD-V3 rev 3.1 core) for this project. I can load the supplied DC_ Load_3-5.ino.bin file via OTA without any initial problems. After the binary file loads via OTA, the ESP32 boots and runs the code as expected. All seems well, but the problem arises when I cycle the power – the LCD screen simply displays a white background and does not boot into the main program. Booting the program also fails if I press the reset button on the ESP32. I tested the ESP32 with a WiFi-based weather app (from the internet, as I couldn’t find the test weather app in the supplied zip file). The weather app works with no problems. I then set up the Arduino IDE v1.8.19 with the Load Controller source code (from https://github.com/palmerr23/ ESP32-DCLOAD) and recompiled and loaded the ESP32 from the IDE with the following settings: Partition Scheme: Minimal SPIFFS(1.9MB App with OTA/190KB SPIFFS) Both Arduino and Events running on Core 1 The program reboots without any problems, including after power cycling and testing, indicating everything works fine. Loading the compiled BIN file via OTA also works fine. The readme.md file states: Use “Arduino Runs On Core 0” and “Events Run On Core 1”. Running both Australia's electronics magazine on the same CPU results in lost ADS ADC interrupts. However, with these settings, I found that while the program boots without any problems, it repeatedly reboots within seconds once the program has started. Hence, I have reverted to using the same core for both Arduino and Events. I haven’t noticed any problems with the potential loss of ADS ADC interrupts, but I welcome any comments. So, it appears the BIN file on the Silicon Chip website (and the GitHub repository) does not work correctly with these ESP32 modules. While everything appears to be working now, the only minor issue I noticed was that the yellow “E” to indicate a pending EEPROM update does not appear when changing settings. However, I know that the EEPROM has been updated since the values are retained after powering it off and back on. Other than that, the finished project works well and is a great piece of test gear! I had problems finding the Hyper 103 coolers anywhere (out of stock) but instead used the DeepCool AG300 Compact Single-Tower CPU Cooler available from mwave (SKU AC60889; siliconchip.au/link/abv6) if one doesn’t mind foregoing the LED lighting. This cooler gives ample room to drill and tap the Mosfet mounting holes. Do you know why I encountered problems with the precompiled BIN file? (S. M., Valdora, Qld) ● Richard Palmer responds: I’m sorry you ran into difficulties with the original BIN file. Did you try the DC_ Load3.5v3.ino.bin file in the repository code folder? The reboots are probably due to watchdog timeouts, which are common on the ESP32 unless explicit measures are taken to feed it. I thought I had sufficient calls to yield() and feedLoopWDT() to prevent this. The resets may be coming from the non-­Arduino core, though I hadn’t experienced them for some time on the prototype. siliconchip.com.au Other than both Arduino and events running on core 1, your compile setup looks normal. The only downside that might occur from running everything on a single core is that the responsiveness to overload conditions could be a little slower, particularly if an EEPROM write, screen rewrite, or web page reload is occurring simultaneously. By the time Silicon Chip published the article (it takes a few months for editorial, layout and production), the Hyper 103 coolers were becoming rare. The replacements you chose look fine; all the three-heat-pipe CPU coolers I tested performed well at full load, and I selected the one with the most straightforward mounting arrangements. I’m unaware of the problem with the ‘E’ flag not changing colour, so I’ll look into it. I also have some improvements to the battery testing code proposed by another constructor, which I intend to incorporate into the code when I have time. By the way, if you are using the Kelvin voltage sensing arrangement (or plan to), please read my note published on pages 5 & 6 of the May 2023 issue. There is a potential problem with that part of the circuit that can be mitigated with some simple changes. GPS-synched Clock has become inaccurate My GPS-synchronised Clock with a stepping movement is 24 seconds slow (September 2022; siliconchip. au/Article/15466). I last checked it when daylight saving ended (April 7th), and it was two seconds fast. The two AA cells measure 1.29V each. I expected the clock to remain accurate until the cells reached approximately 1V each. They are Eveready Gold types and have been in the clock for 19 months. The clock ran about 30 seconds slow once last year, which I corrected by pressing the switch repeatedly, as described in the magazine article. Any suggestions would be appreciated. (J. B., Blackwood, SA) ● We asked Geoff Graham, and he responded: I don’t think this is caused by a poor GPS signal because, at one point, you corrected the error, which would have resulted in the clock being way too fast when the GPS signal was eventually reacquired. Almost certainly, the fault is caused by too much friction in the clock’s movement/motor, causing the motor to stall. My guess is that a bit of rubbish has become stuck in the movement’s gears. You could try cleaning the movement, but the best solution would be to replace it, taking care not to damage the new movement’s gears and keeping them free of debris. PCB silkscreen differs from overlay in article I purchased four Cooling Fan & Loudspeaker Controller PCBs (February 2022 issue; PCB code 01102221; siliconchip.au/Article/15195). Upon assembly, I noticed a few discrepancies in the screen printing, which I was hoping you could clarify. The circuit and PCB overlays published in the article match, but the PCB silkscreen shows two 2.2kW resistors as 100W, ZD1 & ZD3 as 4.7V rather than 15V and D1-D3 as 1N4004 diodes instead of 1N5819. Has the circuit changed, or is the silkscreen wrong? By the way, I have been a reader of the magazine for 30 GPS-Synchronised Analog Clock with long battery life ➡ Convert an ordinary wall clock into a highlyaccurate time keeping device (within seconds). ➡ Nearly eight years of battery life with a pair of C cells! ➡ Automatically adjusts for daylight saving time. ➡ Track time with a VK2828U7G5LF GPS or D1 Mini WiFi module (select one as an option with the kit; D1 Mini requires programming). ➡ Learn how to build it from the article in the September 2022 issue of Silicon Chip (siliconchip. au/Article/15466). Check out the article in the November 2022 issue for how to use the D1 Mini WiFi module with the Driver (siliconchip.au/Article/15550). Complete kit available from $55 + postage (batteries & clock not included) siliconchip.com.au/Shop/20/6472 – Catalog SC6472 siliconchip.com.au Australia's electronics magazine June 2024  109 years and would like to thank everyone for their contributions. I hope the magazine is around for years to come. (D. Z., Croydon, Vic) ● Sometimes the PCB silkscreen is not updated to reflect the final design when just component values change, as is the case here. The PCB overlay diagram published in the magazine should be considered final and correct unless any errata is published to state otherwise. The circuit should work with either the 4.7V zeners and 100W resistors, as printed on the PCB, or the 15V zeners and 2.2kW resistors, as in the magazine. However, the 15V zener diode option is preferred as it prevents the half-supply offset described in the first couple of paragraphs of text on page 49 of the February 2022 issue. D1-D3 could be 1N4004 types, although the fans will run slightly slower. So, while the values and types marked on the PCB are workable, we recommend sticking with what’s shown in the article. Unable to calibrate Battery Multi Logger I recently finished building the Battery Multi Logger (February & March 2021; siliconchip.au/Series/355). Everything appeared to work OK, except that I had to recalibrate the touch panel because even though touch worked, it was as if the buttons were mirrored. For example, touching the panel at upper left activated a button on the lower right. I ran the GUI CALIBRATE command and got an out-of-bounds warning, but it still fixed the touch problem. I was able to calibrate the voltage as per instructions, and it is accurate for voltages applied to CON1. However, when attempting current calibration for CON2-CON4, any value I enter other than zero locks up the display, and upon rebooting it, the value has not been updated. I am using the onboard 15mW current shunts, but the display shows milliamp values and will go negative if some current passes through the above ports. Thanks in advance for any hints as to why I cannot enter values for current calibration. (J. M., Cohuna, Vic) ● It is not uncommon to need to recalibrate the display since the touch panel orientation varies between v1.1 110 Silicon Chip Increasing current handling of Brownout Protector I have a query regarding the Brownout Protection circuit (July 2016; siliconchip. au/Article/10000). I want to use a circuit like this for my ducted air conditioner. Am I correct in thinking the 10A limitation of the circuit is due only to the 10A plug, socket and fuse? My aircon can draw up to 4.46kW on startup and up to 3kW continuous. I would hard-wire the input and output and move the fuse to be inline with the circuit but not the load. Would that work, and would I also need a larger relay? (P. H., via email) ● Yes, the 10A limit is due to the wiring, fuse, plug and socket. The relay contacts are rated at 30A and should be suitable for the air conditioner. If you use suitably rated wire and connect it as you suggest, with the circuitry via a fuse (say, 1A) and the air conditioner power bypassing the fuse, that should work. You may wish to add a suitable mains-rated fuse or circuit breaker for the air conditioner, although there should already be one in the house fuse box. Note that modifying fixed wiring might require an electrician’s license, depending on where you live. and v1.2 displays. They are rotated relative to each other, so depending on which type you get, it might not match the preexisting calibration data. The GUI CALIBRATE command will fix it if it’s wrong. We have investigated some potential solutions, but the software cannot easily tell them apart, so re-calibration is the quickest and easiest fix. The default current calibration should work ‘out-of-the-box’ with the specified 15mW shunts. It shouldn’t need changing unless you are using different shunt values. What value are you trying to change the calibration to? We have not seen the software lock up in that way. There is a workaround that might get your unit working. It involves manually editing the I_CAL() array values. Stop the running program by pressing Ctrl-C at the Micromite serial terminal and enter a command to change the values: ‘change Current 1 shunt to 0.0149W I_CAL(2) = -67 Where the -67 is replaced with the shunt value in ohms multiplied by 4500. Next, use the command: VAR SAVE I_CAL() To save the values to flash. Following that, use the RUN to restart the program. Exporting data from the Diode Curve Plotter I built the Multi Diode Curve Plotter (March 2019 issue; siliconchip. au/Article/11447) and would like to export and save the test data. Your article states, “The plot data can also Australia's electronics magazine optionally be sent to a connected computer as rows of CSV (comma-­ separated value) data, allowing plots to be stored and analysed further if necessary.” Can you tell me what I need to do? (W. F., Atherton, Qld) ● The dumpData() function prints the current set of samples via the serial port. You will need a serial terminal program (the Arduino serial monitor should work) to capture the serial data, which can then be copied and pasted into a spreadsheet program. The dumpData() function is called whenever the I/V Test or Reverse buttons are pressed on the graph page (eg, Screen 2 or Screen 3 on page 65 of the article). So you will get a report to the serial port any time you press either of those buttons. The code actually uses tabs as the column separators (rather than commas), but most spreadsheet programs should allow data to be imported with a tab separator. You might need to use Paste Special to force the data to be interpreted as rows and columns. Alternatively, the code can be changed to produce commas instead by replacing the instances of ‘\t’ in the dumpData() function with a comma and then re-uploading the sketch. Confusion over NEC IR repeat codes I am putting together the “Control your computer with an IR Remote control” project from August 2018 (siliconchip.au/Article/11195) and I am using the recommended XC3718 remote. I tested the codes it was emitting, but whatever button I pressed, it was “0xFFFFFFFF”. I see that there continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE DAVE THOMPSON (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, New Zealand, but service available Australia/NZ wide. Email dave<at>davethompson.co.nz LEDsales KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. 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Silicon Chip Kits (Jun24) DC Supply Protector Adjustable SMD Version (SC6948, $17.50) DC Supply Protector Adjustable through-hole (TH) Version (SC6949, $22.50) DC Supply Protector Fixed TH Version (SC6950, $20.00) – ZD3 & R1-R7 are not included ESR Test Tweezers Complete Kit (SC6952, $50.00) – LiPo cell is not included USB-C Serial Adaptor Complete Kit (SC6652, $20.00) 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 (02) 9939 3295. 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 June 2024  111 Advertising Index Altronics.................................27-30 Blackmagic Design....................... 9 Dave Thompson........................ 111 DigiKey Electronics....................... 3 Electronex................................OBC Emona Instruments.................. IBC Hare & Forbes............................ 6-7 Jaycar..................IFC, 11, 15, 52-53 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology................ 37 Mouser Electronics....................... 4 PCBWay....................................... 13 PMD Way................................... 111 Rohde & Schwarz........................ 41 SC GPS Analog Clock............... 109 SC Programming Adaptor.......... 67 Silicon Chip Back Issues........... 14 Silicon Chip Binders................ 111 Silicon Chip PDFs on USB......... 48 Silicon Chip Pico Gamer........... 25 Silicon Chip Shop............ 106-107 Silicon Chip Songbird................ 72 Silicon Chip Subscriptions........ 31 The Loudspeaker Kit.com.......... 10 Wagner Electronics..................... 12 Notes and Errata Skill Tester 9000, April & May 2024: in Fig.2 on p64 of the April issue, IC6 at lower left (NE555) is incorrectly labelled IC2. In Fig.3 on p69, the V+ and RS labels for pins 4 & 8 of IC9 and IC14 are swapped (pin 4 is RS, pin 8 is V+ in each case). In the text on p70, the 33nF, 470nF & 1μF values mentioned in the third paragraph of the righthand column should be 10μF and 22μF instead. Finally, on p71, the 470nF value mentioned in the fourth line of the left-hand column should instead read 33nF. Next Issue: the July 2024 issue is due on sale in newsagents by Thursday, June 27th. Expect postal delivery of subscription copies in Australia between June 26th and July 12th. 112 Silicon Chip is code that deals with this “NEC encoding”. After I compiled and uploaded the code, nothing happened when I pressed any button. Can you help? (F. C., Maroubra, NSW) ● The 0xFFFFFFFF code means that the IR receiver is seeing an NEC repeat code. When a button is first pressed, the remote sends a code related to the key; then, if the button continues to be held down, the repeat code is sent after a delay (repetitively until you release the button). For example, pressing “2/up” and holding it down should see the sketch receive a code like 0xFF18E7, followed by a sequence of 0xFFFFFFFF for as long as the button is held down. This is handled with the line: if (code==0xFFFFFFFF) {code=lastcode;} Which simply repeats the last command if 0xFFFFFFFF is received. So it’s quite common to see 0xFFFFFFFF, but it should only follow another code if a button is held down. It seems like the hardware is working because you are seeing something being received. It would help to know which sketch you are compiling (IR_ Code_Typer_and_Serial.ino?) and the output from the bottom window of the Arduino IDE when you compile it. More information about your setup (computer/PC, Arduino hardware) could also be helpful. Unable to calibrate ILI9488-based display Some time ago, I built the V3 Backpack with the latest firmware (V5.0505) and have been using it with the 2.8in ILI9341 display. I also have two 3.5in and one 4in ILI9488 display. I wanted to use a larger screen, so I loaded the ILI9488 driver as per the instructions and restarted the processor. However, all three ILI9488-based displays I have will not calibrate. After I touch the first two targets, I get a Touch Hardware Error, but they all calibrate OK on a PicoMite. (P. C., Balgal Beach, Qld) ● This is a new one for us as we have built many BackPacks with ILI9488based displays and have not had trouble calibrating the touch sensors. Many of our readers have also built designs combining the two without reporting such problems. Australia's electronics magazine The fact that they are working with the PicoMite suggests that the problem does not lie with the LCDs, and that the V3 BackPack is working with the 2.8in panels suggests it’s also fine. Please send us the output of the OPTION LIST command so we can check that the touchscreens have been set up correctly. Try comparing the result to the OPTION LIST from the PicoMite. The Micromite firmware version 5.05.05 was released after we designed the V3 BackPack; it could be that the newer version has some incompatibility that we have not seen before. Still, we would be surprised if nobody else had reported that by now if that was the case. It might be worth trying V5.05.01, as that is what we used for testing. You can find older versions of the Micromite firmware at https://geoffg. net/Downloads/Micromite/Archives/ Can eFuse be used with AC for DCC? I’m building an N-gauge model railway and considering how to manage the power regions in my layout. I was wondering if it is possible to adapt the eFuse featured in the April 2017 issue (siliconchip.au/Article/10611) for power region protection. It would be easy if I were planning on using a DC layout, but I will be using DCC. As you will know, DCC is a modulated AC signal at around 4-6kHz. I propose interposing the eFuse in the DC load side of a full bridge rectifier, using schottky diodes, in one leg of my DCC supply. Your thoughts on this plan would be appreciated. (B. P., Jeir, NSW) ● It should work if you place the eFuse within a schottky diode bridge so that only a DC voltage is applied to it. The rectified DCC would need to be filtered using a capacitor to remove the modulation; the result should be around 15V DC. That’s suitable for powering the NIS5112 ICs used in the eFuse project. The DCC supply must be able to charge the filter capacitor within the diode bridge without significantly rounding the DCC square wave. Each eFuse IC draws around 2mA, for a total of 4mA. A 1μF MKT polyester capacitor should be suitable as the supply filter capacitor. The resulting ripple would be around 1V when powering the two NIS5112 ICs. 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