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MAY 2025 ISSN 1030-2662 05 9 771030 266001 $ 00* NZ $1390 13 INC GST INC GST 60 RGB LEDs that light different colours for the hour, minute and second Optional ‘subsecond’ hand chaser GPS module or NTP time via the internet using WiFi RGB LED ANALOG CLOCK Vers Ver satile siliconchip.com.au Battery Checker Australia's electronics magazine RNBD451 Bluetooth Module May 2025  1 MISS FLIPPING THROUGH OUR CATALOGUE? It’s Back—Digitally! The 596-page Engineering and Scientific Catalogue is back! Updated with the latest products and ready for you to browse online. View Online Now! Australia New Zealand IT’S BACK! Scan the QR Code or visit: catalogueflip.jaycar.com.au catalogueflip.jaycar.co.nz 2 Silicon Chip Australia's electronics magazine www.jaycar.com.au www.jaycar.com.au | www.jaycar.co.nz siliconchip.com.au Contents Vol.38, No.05 May 2025 12 Digital Scent and Taste Soon your smartphone might be able to detect smells for you, or let you sample the tastes of foods from a menu! These ‘electronic’ noses and tongues could be used like a “canary in a coal mine”. By Dr David Maddison, VK3DSM Science feature DIGITAL SCENT & TASTE 34 Electronex 2025 Electronex – the Electronics Design and Assembly Expo – will be held in the Melbourne Convention and Exhibition Centre on the 7th & 8th of May this year. Come and visit Australia’s largest electronics exhibition. By Noel Grey (AEE) Electronics exhibition 82 RNBD451 Bluetooth LE Module Microchip’s new RNBD451 Bluetooth module and its companion EV25F14A evaluation board provide a feature-rich way to add Bluetooth (including BLE) connectivity to your designs. Review By Tim Blythman Low-cost electronic modules 88 Precision Electronics, Part 7 After covering digital-to-analog converters, we take a look at the flipside: analog-to-digital converters (ADCs). Sampling analog values quickly and accurately is a little more tricky than producing them. By Andrew Levido Electronic design 24 Versatile Battery Checker Our newest Battery Checker works on all kinds of batteries like Li-ion, LiPo, lead-acid, 9V batteries and lower-voltage cells like C, AAA etc. It is compact, portable and can be powered by the battery under test or a 9V battery. By Tim Blythman Test equipment project 58 Tool Safety Timer If you have ever worried about leaving a tool on (like a soldering iron), this project is for you. It can switch a mains-powered device off after not being used for a set amount of time by detecting movement using an IR sensor. By Phil Prosser Power control project 66 RGB LED Analog Clock This colourful Clock uses a series of LEDs to imitate an analog clock. You can also enable a light chaser effect to have the LEDs circle around each second. The Clock supports a GPS module or NTP time to remain accurate. By Nicholas Vinen Clock project 78 USB Power Adaptor This simple and inexpensive project provides you with an easy way to add a USB socket to a 5V DC powered device. It uses less than a dozen parts, and you can fit either a USB Type-C or Type-B (mini or micro) socket to the PCB. By Nicholas Vinen Power adaptor project PAGE 12 Page 58 Tool Safety Timer USB Power Adaptors Page 78 2 Editorial Viewpoint 5 Mailbag 77 Online Shop 95 Subscriptions 96 Circuit Notebook 98 Serviceman’s Log 104 Vintage Radio 109 Ask Silicon Chip 111 Market Centre 112 Advertising Index 112 Notes & Errata 1. Digital voltmeter to ammeter conversion 2. Night alarm door checker 3. Automatic op amp offset nulling Emerson 888 mini-mantel set by Ian Batty SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff 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): $130 24 issues (2 years): $245 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: 9 Kendall Street, Granville NSW 2142 2 Silicon Chip Editorial Viewpoint Using WinCompose for typing special symbols In the November 2023 issue, I wrote about my frustration with the difficulty of typing common mathematical and other symbols on computers. For example, Greek letters are frequently used in mathematical formulae, and Unicode contains all of them, but there’s no easy way to type them on most computers. For a while, I was using copy-and-paste from a document I had created with these symbols. That was awkward. So was what I tried next, which was to use Google search to find symbols by name, then copy and paste them. Then, in the May 2024 issue, we published a simple Symbol Keyboard hardware device (siliconchip.au/Article/16250) that could solve this problem. But I thought there still had to be a better way. I know that there are ways to type symbols using their ASCII or Unicode codes, but who is going to memorise 50+ four-digit hexadecimal codes for typing these characters? I’m sure there are people who can, but I’m not one of them, and even if I were, it seems unnecessarily difficult. I subsequently found a free program called WinCompose (https://github. com/samhocevar/wincompose). It can be installed on Windows and acts as a kind of macro facility, converting multiple key presses into a single symbol. Importantly, its default set of codes is extremely intuitive, so learning them is very easy. It also provides a way to easily look up codes if you are not sure (although I find, more often than not, if I guess I get it right). You can also set a custom ‘compose’ key; the default is right Alt (which seems like a reasonable default) but I don’t have such a key on my ergonomic keyboard, so I changed it to another one I never really use. While you can set up custom sequences, I think it is very beneficial that the default settings work well. That way, you can install it on a computer and start using it. You don’t have to synchronise the settings between multiple computers (this is a problem I have with a lot of other software that needs to be customised to be usable). To give you an idea of how straightforward the sequences are to remember, I’ve listed some of the ones I use frequently below, along with the character that is generated. I find it so convenient now that I use it exclusively now for special character generation! Linux has ‘ComposeKey’ so I will have to figure out how to get it to work the same way. Sequence Character Compose x x → × Compose - - (space) → – Compose O / → Ø Compose + → ± Compose = / → ≠ Compose > = → ≥ Compose 1 / → 1/ Compose 3 4 → ¾ Compose 5 8 → ⅝ Compose * a → α Compose * b → β Compose * S → Σ Compose * m → μ Compose * V → Ω Compose C O → © Compose L → £ Compose E = → € Australia's electronics magazine by Nicholas Vinen siliconchip.com.au siliconchip.com.au Australia's electronics magazine May 2025  3 4 Silicon Chip Australia's electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd 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”. Magazines to give away I have a set of Silicon Chip magazines to give away from 1987 to 2023. I don’t expect any money for them, as long as you can pick them up. You can contact me via email at gdjmorr<at>tpg.com.au Geoff Orr, Sydney, NSW. Trio oscilloscopes were dependable When reading February’s Mailbag, I was happily surprised to see the photograph of the Trio CS-1577A CRO accompanying Dave Dobeson’s letter on page 6. I have one of these and, in September 2024, I encountered another in an action at the Model and Experimental Engineers’ Exhibition. If memory serves me correctly, I bought mine in about 1975 and, 50 years later, it’s still working as well as it did the day I bought it with never a problem along the way. I even have the box in which it was packaged, chiefly because it has provided splendid mobility protection. I mention this in the light of the miserable programmed obsolescence that is so often the chief undocumented feature of most of today’s electronic devices and about which so much has been said in the pages of Silicon Chip and its predecessor magazines. If my CRO is anything to go by, Trio wasn’t shy about bucking this trend back in the 1970s. It has served me very well indeed. George Clauscen, East Oakleigh, Vic. Clever way of converting 115V radios to 230V Regarding Ian Batty’s article on the Monarch five valve radio (January 2025; siliconchip.au/Article/17611), I noted with interest the existence of a 220V version of this radio. Ian mentioned the use of a capacitive dropper to allow what was normally a 110-120V set to operate on 220-240V mains. Although it’s possible to simply connect a suitable capacitor in series with the mains supply of the set to achieve this, there’s actually a bit more to it. Japanese manufacturers of AA5 sets used a clever circuit design for 220-240V export models that results in a smaller capacitor than would otherwise be expected. In the case of a midget set like the Monarch, the smaller the dropper capacitor, the better. Remember, it had to be a paper type, since electrolytics are unsuitable for constant AC use. The way the scheme works is that the heaters are connected in series, adding up to 120V in the usual way. The dropper capacitor of around 2μF is in series with the heaters. The capacitive reactance drops the additional 120V, so the heaters can be run on 240V mains. The ingenious part is that the AC input to the rectifier siliconchip.com.au is taken from across the dropper capacitor. Since there happens to be 120V across this, it suits the input to the 35W4 plate perfectly, and so the usual 120-odd HT volts are produced, which is what these valves are designed for. This means that the entire B+ current is also flowing through the valve heaters, and as a result, the reactance of the dropper capacitor does not have to be as low as if it were in series with the whole radio, in which case the capacitor would have to be typically around 3uF. Essentially, the heater and B+ supplies are in series with each other. The diagram above should make it easier to understand. It could also be imagined that this method also results in a ‘soft start’ for the valve heaters, since the full heater current does not flow until the set has warmed up and is drawing full B+ current. I describe this method of operation on my website at www.cool386.com/dropper/dropper4.html On the subject of the 3G shutdown, I totally agree with your editorial. It is interesting to reflect on times gone by when new technology was introduced. Take colour TV, for example. It is actually quite simple in its basic form, but the biggest challenge was largely to do with making it backwards-compatible with existing monochrome sets. Similarly, the design work that went into AM and FM stereo was to make it compatible with existing mono receivers. When DTMF dialling was introduced in telephone exchanges, the system was still compatible with the older decadic pulse dialling. This policy no longer exists in the modern day, and it’s basically a mountain of e-waste every time the powers that be decide we need to ‘upgrade’. So much for sustainability! John Hunter, Hazelbrook, NSW. More open-source software recommendations Thank you for your recent article on Open Source Software (February 2025; siliconchip.au/Article/17717). As someone who has extensively used FOSS for many decades, I was interested in David’s take on the range of software Australia's electronics magazine May 2025  5 that’s available – he mentioned several tools that look interesting but I was unaware of. While I accept it would be impossible to provide a comprehensive list of FOSS, I would have included the following: • Databases: SQLite (https://w.wiki/879g) is a serverless RDBMS. Thanks to the ease of embedding it in applications, it is the most widely deployed database engine. • Engineering & mathematical software: SageMath (https://w.wiki/DYsA) is a computer algebra system that is an alternative to Mathematica. • Operating Systems: BSD (https://w.wiki/DYsB) is a Unix-like OS that was developed within the University of California, Berkeley, by removing all the AT&T code from their distribution of Unix. The most popular variants are FreeBSD, NetBSD and OpenBSD and it forms the basis of macOS. • Wikis are collaborative software that are used to create websites. Mediawiki (https://w.wiki/M) runs one of the Web’s most popular websites. Peter Jeremy, Killarney Heights, NSW. Comment: some of those were in Dr Maddison’s original submission, but were cut for space as we simply couldn’t include everything. The article spanned 14 pages even without these extra entries! An interesting way to keep a battery pack balanced Thank you for continuing to publish Silicon Chip. It is always nice to read the magazine. I bought an electric scooter from a friend a few years ago with two spare battery packs. I bought it to get the Li-ion cells to make batteries of various voltages and sizes that I wanted. However, I wanted to avoid equalisation circuits and a controlling microprocessor. I considered a couple of ideas and eventually settled on treating the battery as a sequence of cells, each with its own charging circuit that is electrically isolated from the charging supply. I chose this method because it allows the use of cells of different capacities and, at the same time, avoids the problem of heat-generating equalisation circuits. I made a backup supply of 14.4V and approximately 17Ah capacity from some of the cells. They were arranged as blocks of six parallel cells with four blocks in series. As shown in the photo, the blocks were made using strips of 3M double side tape to hold the cells together and the terminals on each end were joined via hookup wire to a single sided PCB. Hookup wire was used to provide a simple fuse in case of catastrophic cell failure. Prior to completing a block, the cells were connected via resistors to allow them to equalise to the same voltage. I built the backup supply inside a second-hand enclosure. At the back is a Clipsal four-way power board with four Anko Wall Chargers from Kmart rated at 5V & 2.1A each. Each of these is connected to only one of four Li-ion charging modules I got from your Online Shop, thus providing four isolated charging circuits. Those are mounted on a piece of single-sided PCB behind a clear front window to allow the power and charging LEDs to be seen. Each charging module is then connected to a block of cells via fuses in both the positive and negative wires as a precaution against a catastrophic short-circuit in the charging module. The cell blocks are arranged in series from side to side across the enclosure with the negative wire going to the front connector and the positive wire going to three 7A polyswitches connected in parallel and then to the front connector. There is no temperature monitoring and no low-voltage monitoring. Six good Li-ion cells in parallel are capable of supplying up to 21A without overheating; it is intended that under-voltage protection would be handled by the connected equipment. George Ramsay, Holland Park, Qld. Surprised to see Smith charts again I never expected to be reacquainted with Smith Charts as I was in the February issue of Silicon Chip, in Roderick Walls’ article on “Antenna Analysis and Optimisation” (siliconchip.au/Series/434). I was introduced to Smith Charts in October 1966 when the Australian Army introduced the Radio Set AN/PRC 25, a US Army VHF FM man-portable radio. The 25 set and other similar US Army radio sets included Smith charts in the operator’s manual for the optimisation of antenna systems and transmission. Technicians in the telecommunications repair section of the Army field workshop in Vietnam knew about the charts. One technician took a particular interest in the function of the charts and was skilled in their use for improved operation of the radio sets. Still, there was no software back then to simplify matters. Peter Johnston, Merimbula, NSW. Metal boxes for Current & Differential Probes I contacted my local metal fabricator (Shearwater Marine Engineering) who agreed to use their NC milling machine to make me three metal boxes to house your recent Current Probe (January 2025; siliconchip.au/Article/17605) and Differential Probe (February 2025; siliconchip.au/ Article/17721) test equipment projects. If any other readers are interested in getting such boxes made, I could pass them on at my cost plus shipping. I thought other readers, like me, may not be too good at fiddly drilling stuff. I was going to change the height of the slide switch rectangle to 3.0mm (the difference is only the thickness of a sheet of paper each side) and, instead of right-angle corners, have a 1mm radius but I still need to confirm this with Shearwater. This shape will be easier to machine and will 6 Silicon Chip Australia's electronics magazine siliconchip.com.au FREE Download Now! Mac, Windows and Linux Edit and color correct using the same software used by Hollywood, for free! DaVinci Resolve is Hollywood’s most popular software! Now it’s easy to create feature film quality videos by using professional color correction, editing, audio and visual effects. Because DaVinci Resolve is free, you’re not locked into a cloud license so you won’t lose your work if you stop paying a monthly fee. There’s no monthly fee, no embedded ads and no user tracking. Creative Color Correction Editing, Color, Audio and Effects! 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Free DaVinci Resolve Micro Color Panel .............Only $809 DaVinci Resolve is perfect for editing sales or training videos! The familiar track layout makes it easy to learn, while being powerful enough for professional DaVinci Resolve’s color page is Hollywood’s most advanced color corrector and has been used on more feature films and television shows than any other system! It has exciting new features to make it easier to get amazing results, even while learning the more advanced color correction tools. There’s PowerWindows™, qualifiers, tracking, advanced HDR grading tools and more! editors. You also get a library full of hundreds of titles, transitions and effects that you can add and animate! Plus, DaVinci Resolve is used on high end work, Learn the basics for free then get more creative control with our accessories! so you are learning advanced skills used in TV and film. Learn more at www.blackmagicdesign.com/au siliconchip.com.au Australia's electronics magazine Download free on the DaVinci Resolve website May 2025  7 NO SUBSCRIPTIONS • NO ADS • NO USER TRACKING • NO AI TRAINING still provide enough clearance to accommodate the slide switch lever travel. Michael Vos, Taree, NSW. Windows’ built-in ‘cloud’ services are a problem I’ve pretty much given up any fight regarding the ongoing and relentless Windows upgrades. Perhaps I’m old but, for me, it’s just too hard to try to keep using old software. Soon enough, something will stop working and you have nowhere to go. So when my last home-built PC died, I bought a namebrand machine preloaded with Windows 11, and shelled out an additional one-time payment of a couple of hundred bucks for MS Word and Excel. In general, it has been pretty trouble free, with the only technical problem being that it went through a phase of dropping its desktop background, which is more annoying than it sounds. However, the default email client is completely lame, with no useful search facility, and it won’t read my old PST files. I do have a few complaints about Windows, mostly to do with the embedded cloud service OneDrive. In fact, my problems aren’t so much with OneDrive, but more that fact that it’s so deeply integrated into Windows. I get that OneDrive is probably great for people who travel a lot – they can access their data on whatever platform they’re using at the time, from wherever they are. But I work from home on a desktop machine, and don’t want or need any of it. Furthermore, I don’t want my data stored on a computer somewhere I don’t know about, with an unknown level of security. All that does is further expose me to malicious actors, who can then reach my data from anywhere in the world with an internet connection. I get tired of the endless warnings that my document isn’t backed up on OneDrive, or not being able find something because Windows decided I need to save it one OneDrive, not my local hard drive. I just don’t want it and wish that I could disable it. One day I’ll try Linux – I think it’s the real answer. Since KiCad and MPLAB X IDE both have Linux builds available, I think I should be able to do what I need. All I need is a little push; as soon as Microsoft force me into a subscription-­ based business model, I’m out. D.T., Sylvania, NSW. Older computers can be kept running This deliberate obsolescence with computers and phones etc is, to a point, a cynical exercise in making money. I keep a computer from 2000 running Windows XP. Of course, it gets no support from Microsoft, but one program it runs cannot be replaced. I do think some things are getting over complex. I have a radio scanner that I mainly use for bushfire info; it was built in 1992 and has never broken. The battery is a lead-acid gel cell (SLA) that charges from a three-terminal regulator, with a globe as a barretter (current limiter) should the battery be run down or flattened. Should the mains fail, a diode sees the battery cut in instantly, like a radio with just back-up batteries. The globe idea came from early Metz Flashguns, which used horrid NiCad batteries. These early ones had a habit ourPCB LOCAL SERVICE <at> OVERSEAS PRICES AUSTRALIA PCB Manufacturing Full Turnkey Assembly Wiring Harnesses Solder Paste Stencils small or large volume orders premium-grade wiring low cost PCB assembly laser-cut and electropolished Instant Online Buying of Prototype PCBs www.ourpcb.com.au 8 Silicon Chip Australia's electronics magazine 0417 264 974 siliconchip.com.au $ ONLY 329 $ QM1493 Specialty meters combined with multimeter functions. $ 119 TAKE EASY ENVIRONMENTAL MEASUREMENTS • MULTIMETER FUNCTIONS • SOUND LEVEL • LIGHT LEVEL • INDOOR TEMP • HUMIDITY TEST ALMOST ANYTHING! 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Jaycar reserves the right to change prices if and when required. of reversing polarity, so there was a Barretter to prevent the charger from being overloaded in case the battery presented as virtually a short circuit. Marcus Chick, Wangaratta, Vic. The cost of renewable electricity generation The article in March 2025 issue about the future of our power grid (siliconchip.au/Series/437) was an interesting read. I’m hoping future articles will discuss some of the subsidies/incentives that renewable energy receives. That includes the Australian Government Clean Energy Regulator Large-scale Renewable Energy Target (LRET), in which wind and solar farms receive Large-scale Generation Certificates (LGC) for each MWh exported to the grid. According to the Clean Energy Regulator website, these provide a financial incentive for electricity generated from renewable sources. Since the sale of LGCs is independent of the National Electricity Market, their actual cost isn’t reflected in the wholesale price of electricity, but is instead included in the retail price of electricity. Clean Energy Regulator posts on its website a quarterly report and states, “Future LGC prices for calendar years 2024 to 2026 fell in June 2024. However, the calendar year 2024 and 2025 forward prices remained at around $45.” With one LGC representing one MWh exported, this addition $45/MWh becomes a reasonably substantial incentive. The Clean Energy Regulator also reported that in 2024, they added 4272MW of new renewable generation to the scheme, bringing the total LGCs in the registry to 46,350,483. Clean Energy Regulator also runs the Small-scale Renewable Energy Scheme (SRES), which offers small-scale technology certificates (STCs) for solar installations less than 100kW with an annual electricity output less than 250MWh, or wind turbines smaller than 10kW with an annual electricity output less than 25MWh. Unlike LGCs, which are issued monthly, STCs are issued once, and calculated on the system potential renewable energy generation until 2030, when the SRES ends. If you have rooftop solar, part of the rebate you received would have been derived from the Small-scale Renewable Energy Scheme, which is also included in the retail price of electricity. On a slightly different topic, the cost of energy storage, if we look at NEM Open Electricity data for any given day, the Battery Discharge $/MWh spot market price is typically three times more expensive than wind or solar spot price, and double that of the ageing base-load generators. This suggests that energy derived from battery storage is quite expensive. To view the current $/MWh data, go to https:// openelectricity.org.au, scroll down and click View Tracker. In the AEMO 2024 integral system report, it states that Australia currently has 9GWh of battery storage, but will need 522GWh by 2034 for grid firming as we become more reliant on renewable generation. Sources below: • CER: siliconchip.au/link/ac5a • siliconchip.au/link/ac5b • siliconchip.au/link/ac5c • siliconchip.au/link/ac5d • siliconchip.au/link/ac5e • AEMO: siliconchip.au/link/ac5f Matthew Prentis, Port Augusta, SA. SC 10 Silicon Chip Australia's electronics magazine siliconchip.com.au CNC PLASMA ROBOT Portable powerful and easy to use. ArcDroid™ brings CNC plasma to your garage or workshop. ArcDroid™ combined with our custom operating system with Simple Trace™ can accurately reproduce your designs delivering fast, accurate and repeatable parts from your plasma cutter. 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All prices include GST and vild until 28.05.25 (08) 9373 9969 ay 2025  11 11 Valentine St, M Unit 11/20 Cheltenham Pde 03_SC_280425 View and purchase these items online: www.machineryhouse.com.au/SIC2405 DIGITAL SCENT & TASTE electronic noses and tongues Image source: www.pexels.com/ photo/girl-sitting-on-grasssmelling-white-petaledflower-1879288/ By Dr David Maddison, VK3DSM Computers can do a lot of things that humans can now, but taste and smell are still firmly in our domain. Or are they? It may not be too long before your smartphone can alert you to odours, or you can see an image of a dish someone has cooked and then find out for yourself how it tastes. W e have five primary senses: hearing, sight, smell, touch and taste. Electronics can already interface readily with vision, hearing and touch, but what about the other two primary senses, smell and taste? Actually, electronics interfacing with those senses goes back further than you might think. But they have proven more difficult than the others. By the way, our other senses include balance, temperature, pain, time, hunger, thirst & proprioception, for a total of 10-20, depending on how you define them. Imagine watching an online video, a movie at a theatre or playing a computer game and experiencing the smell of a field of flowers or the smoke of a disaster. The taste and smell of food or spices could even be reproduced for a cooking show. We could also have an “electronic nose” that analyses smells for various reasons. Those would include digitising and synthesising those smells to reproduce them at another location, 12 Silicon Chip to check food for signs of degradation, or to ensure that batches of coffee or wine were consistent. Electronic noses could even be (and are) used for smelling patients to determine disease; dogs have been successfully trained to smell cancer from the unique chemicals that it produces. Parkinson’s disease is also said to produce a unique smell. Incidentally, the idea of using smell to detect disease is not new. The Ancient Greeks had people known as uroscopists who would smell and taste urine to determine disease conditions. The taste of urine was also used to detect diabetes until about the 1840s, when other tests were developed. In Australia’s Northern Territory, electronic noses are being investigated for detecting diseases in plants (see siliconchip.au/link/ac4k). Other possible or actual applications of electronic noses include: • ensuring batch consistency in food or other production processes Australia's electronics magazine • detecting fake or adulterated food and drink • checking the quality and monitoring the degradation of meat • checking raw food ingredients for freshness and contamination • checking the efficiency of cleaning processes • comparing different recipes or food manufacturing processes • comparing a food product with a competitor’s • determining the effect of substitution of one ingredient of a food product with another • detection of bacteria or other pathogens • detecting drugs or explosives • detecting land mines (as animals are used now) • finding truffles • detecting pollutants in the air or soil Some of these jobs (like checking food) are currently done by humans, but different people have different abilities in this field and some people siliconchip.com.au Fig.1: the location of the olfactory system. 1) Olfactory bulb. 2) Mitral cells. 3) Bone. 4) Nasal epithelium. 5) Glomerulus. 6) Olfactory receptor cells. Source: https://w.wiki/Cw9K Fig.2: the olfactory system in a typical vertebrate. Each olfactory receptor neuron (ORN) is attached to cilia; their odour receptors (ORs) are sensitive to one particular type of odourant. Source: www.frontiersin.org/systems_ neuroscience/10.3389/fnsys.2011.00084/full can’t experience certain tastes or smells. So having electronic devices to do these jobs would provide a great deal of consistency, among other benefits. In the future, an electronic nose could be made into a consumer product to check for contamination or adulteration of food and drink, especially when travelling in foreign countries with poor hygiene standards. Odour localisation is another possible application, which involves finding the source of a specific problem odour when it is not obvious. An electronic nose could potentially be used to map an area (say in a large building) to help locate the source of a bad smell. All the above comes under the auspices of “digital scent technology”. For sensing or producing taste, there is “gustatory technology”. Challenges Arguably, emulating a sense of smell or taste is more difficult than emulating vision or sound. Vision fundamentally involves sensing just one type of thing (photons), while a microphone involves detecting sound pressure waves. siliconchip.com.au In contrast, sense of taste or smell involves sensing hundreds or thousands of different types of molecules, and both smell and taste cannot easily be objectively defined. To synthesise or analyse smells and tastes, it is important to understand how our natural systems of smell and taste work. The olfactory system The system for sensing smells is known as the olfactory system. It is located in the nose, with smell perception being processed in the brain (see Fig.1). When we smell something, we are actually sensing chemical molecules, either of one type or a mixture. These chemicals cause the stimulation of dedicated nerve cells high up inside the nose called olfactory sensory neurons (OSNs) or olfactory receptor neurons (ORNs) – see Fig.2. Each neuron is connected to cilia (hair-like extensions), which have odour receptors (ORs) that are sensitive to a specific chemical. They behave like a lock and key. There are about 500 different types of odour receptors. Australia's electronics magazine ORNs connect to glomeruli, which connect to mitral cells. Mitral cells process information before conveying it to the brain, via electrical signals, where the smell is interpreted in the brain according to past experience. Odour sensation depends on the concentration of the chemicals that are sensed and their combination and type. As there are many different types of odour receptors, the sensation depends on the specific combination of chemicals sensed, unless it is a simple odour comprising a single type of molecule (eg, bleach). Gustatory system The gustatory system is responsible for the sense of taste, which is mainly perceived by specialised taste receptor cells of the taste buds on the tongue. There is a persistent myth that different areas of the tongue sense different tastes, but this was due to a misinterpretation of a 1901 paper by German scientist David P. Hänig and it has since been debunked (see https://w. wiki/Cs$d). May 2025  13 Today, we know that taste receptors are distributed all over the tongue, soft palate and even the throat; they are not confined to specific regions. While some parts of the tongue might be slightly more sensitive to certain tastes, the differences are negligible. The five basic tastes (sweet, sour, salty, bitter and umami) can be detected wherever there are taste buds. In addition to the tongue, taste perception is influenced by other senses such as smell (which is why things taste different or not at all if you have a blocked nose), texture, temperature of the food and even pain receptors incidentally activated with particularly spicy foods or with ‘cool’ tastes like menthol. Primary smells Just as there are primary colours from which all colours (red, green & blue) can be made, and there are primary taste sensations (sweet, sour, salty, bitter & umami), numerous primary smells there have been identified, from which many others can be synthesised (at least in theory). The concept of primary smells is not universally accepted and different classification schemes exist. According to one classification scheme (siliconchip.au/link/ac4d), the primary smells the human nose can detect are as follows: • Chemical: usually smells of synthetic origin such as ammonia, bleach, gasoline, paint etc. • Fragrant: eg, floral smells or certain spices. • Fruit: eg, banana, lime and orange (lemon is a ‘fresh’ smell often used in cleaning products). • Minty: eg, eucalyptus, camphor, mint and peppermint. • Pungent: eg, blue cheese, sweat, onions, garlic, some fermented products. • Sickening and decaying: eg, rotting flesh, sewerage, burning rubber, mercaptans (the odourant in natural gas and butane). • Sweet: eg, chocolate, caramel and vanilla. • Toasted/nutty: eg, almonds, peanut butter and popcorn. • Woody and resinous: eg, timber and natural resin smells. According to another classification scheme (https://w.wiki/7AMo), the primary smells are: • Musky: eg, perfumes. • Putrid: eg, rotten eggs. • Pungent: eg, vinegar. • Camphoraceous: eg, mothballs. • Ethereal: eg, dry cleaning fluid. • Floral: eg, roses. • Pepperminty: eg, mint gum. Odour intensity There is a suggested scale of odour intensity: 0 – no odour 1 – very weak (detection threshold) 2 – weak 3 – distinct 4 – strong 5 – very strong 6 – intolerable Advanced smell classification There are more complex smell classification schemes, such as the Leffingwell Odor Dataset, which contains the Fig.3: a Principal Odour Map, analogous to a colour map but much more complicated. Source: https://research.google/blog/digitizing-smell-usingmolecular-maps-to-understand-odor/ 14 Silicon Chip Australia's electronics magazine smells of 3423 molecules, described by experts. These were combined with another data set, GoodScents, to create the SMILES (Simplified Molecular Input Line Entry System) odour data set, which includes the smells of 4983 molecules described using 138 descriptors (siliconchip.au/link/ac4e). Such data sets are used for research and the classification of different smells, as determined by large numbers of people (large numbers are needed because people perceive smells differently). Another way to classify smells is to generate a Principal Odour Map (POM). Such a map is analogous to a colour map showing hue and saturation, but it is vastly more complex because there are far more parameters describing smells than light wavelengths. A POM contains a vast database generated by people who rate various smells. A particular smell might be described statistically by many descriptors. With the use of a neural network, they can be reduced to two principal components representing by two axes on a graph, as shown in Fig.3. In that example, 400 different molecules were described using 55 different labels. Smells of individual molecules are depicted by the grey dots. These dots can be grouped together into similar types of smells. Based on the smells and mapping of known molecular structures, the Odour Map can be used to predict smells of unclassified and unsmelled molecular structures. Natural vs artificial smell recognition Fig.4 shows the analogies between natural and artificial smell recognition. In a human, first there are the odour receptors on the cilia, which connect to the glomeruli and then the mitral cells in the olfactory bulb. Mitral cells process information before conveying it to the brain, where the smell is interpreted. The equivalent processes in an electronic nose use a transducer as the receptor and a signal processor to convert the output of the transducer to useful information. This information is then processed by an algorithm and a neural network to interpret the smell, providing an identification. As it is very difficult to associate particular molecules with particular siliconchip.com.au Receptor an m Hu Mucous Cribiform plate Cilia Olfactory nerve Interaction E-n Olfactory bulb Signal generation os Vestibular cortex Volatile compound Sensor array: Transducer Somatosensory cortex Gustatory cortex (taste) Visual cortex Olfactory cortex Auditory cortex Signal processing Resistance (Ω) e Brain olfactory cortex Processed signal Input Identification Output Red wine Pattern recognition Fig.4: a comparison of human and electronic smell sensing processes. Source: Electronic noses and disease diagnostics – www.nature.com/articles/nrmicro823 smells, electronic noses need to be trained using machine learning and artificial intelligence (AI) to associate a particular smell or group of smells with the one that the operator is interested in detecting. In the rest of this article, we will look at the history of smell reproduction, electronic noses (for analysing smells), electronic tongues (for analysing tastes), and finally, taste reproduction. Smell reproduction in cinema To add extra sensations to movies, various attempts have been made to add a sense of smell as follows. Some are even in current use. 1868 The Alhambra Theatre of Variety in London sprayed scent into the audience during a live theatre performance. 1906 or 1908 At the Family Theatre in Forest City, Pennsylvania, the scent of rose oil was blown towards the audience using an electric fan during the display of a film, possibly about the Rose Parade in Pasadena, California. 1916 The Rivoli Theatre in New York was equipped with a system of vents to blow scents into the audience during the playing of the movie Story of the Flowers. 1929 During the showing of the film Lilac Time (https://youtu.be/ mmeXUJl_RMk), lilac perfume was poured into the ventilation system of the Fenway Theatre in Boston towards the beginning of the film. Also in that year, during the showing of The Broadway Melody (https://youtu.be/ siliconchip.com.au oYSOl0qYVE0), a theatre in New York sprayed perfume from the ceiling. 1933 A system was installed to deliver odours during a screening at Paramount’s Rialto Theater in Broadway, New York. All the above attempts to introduce odours into films or plays were by manual means; the timing of the delivery was not integrated electronically into a film soundtrack or other automatic signalling system. One problem was that the smells could linger for a long time, sometimes days. The human nose also can’t quickly transition to the next smell until a previous one has cleared. This suggests an alternative, more personal delivery means would be ideal. Small amounts of an odourant could ideally be delivered close to a person’s nose and quickly cleared. This strategy was used in some future systems. 1939 Scentovision was developed by Swiss inventor Hans Laube and introduced at the New York World’s Fair. This was later to be renamed Smell-O-Vision. Up 32 different smells could be delivered at individual seats by a system of pipes, and the delivery timing and amount was controlled by the projectionist using a control board. The first film produced using this technology was Mein Traum. The odours delivered included hay, peaches, roses and tar, corresponding to on-screen action. After the one and only screening at the World’s Fair, the technology was Australia's electronics magazine seized by police on the pretext that a similar system was already licensed for use in the United States (www. imdb.com/title/tt0151530/trivia). Investors took the matter to court, but it was futile, and the investors lost their investment. It is not clear what this alternative system was. 1951 Emery Stern of New York was granted US patent 2562959 for an Fig.5: Emery Stern’s 1951 US patent (2,562,959) for a scent distribution system for motion pictures. A perforated film, running in synchronicity with the movie film, was to be used to select scents. May 2025  15 Fig.6 (left): a newspaper clipping from 1960 showing produce Michael Todd Jr and inventor Hans Laube with their SmellO-Vision device. Hans Laube is shown pointing to the vials which each contain a different scent. Those scents would be selectively projected through tubes to every seat in the theatre. Source: https://cinematreasures.org/photos/258071 Fig.7 (right): an illustration from US Patent 2,905,049 for Smell-O-Vision. The smell is contained in the cells (12), part of a ‘train’, which is advanced according to signals on the movie reel, detected by a light beam (45) and sensor (46). “electromechanical scent distribution to accompany a motion-picture”. He envisaged a system of scent containers (item 54 near the centre of Fig.5) that are selected by a system comprising a perforated reel running synchronously with the film reel. Information on when to release scents was encoded by holes, which would be detected photoelectrically to trigger scent release or stop it. Unfortunately, at the time, there was a craze for 3D films and wide screens, so this scene system was left by the wayside. 1953 General Electric announced Smell-O-Rama, but it was never used to make a film and the technology was not pursued. It was demonstrated with a 3D image of a rose and scented puffs from an atomiser. The lack of commercialisation may also relate to the craze for 3D films and wide-screen at the time. 1959 Smell-O-Vision (called Scentovision on its invention in 1939 by Hans Laube) was patented in this year – see Fig.6. About 30 different odours could be triggered by signals on the movie soundtrack. It was first used in 1960; it was expensive to install and was said to work erratically. Individual odours were placed in 16 Silicon Chip containers on a reel, which were connected into a ‘train’ that moved according to signals on the movie track past an air distribution system, to collect and distribute the odours. The train was wound onto a take-up reel (see Fig.7). Scents were delivered to individual seats. 1959 AromaRama was used by theatre pioneer Walter Reade Jr for the screening of Behind the Great Wall, which was not made with the use of AromaRama in mind. It was in colour wide screen with four-channel sound and 31-72 smells including earth, firecrackers, horses, incense, grass, oranges, restaurants, smoke and tea. The system used for AromaRama was similar to the 1951 patent by Emery Stern, but the scent track was contained on the film print itself and not a separate reel. In preparation for the next smell, the previous smell was neutralised by an electrostatic device called the Statronic, which removed the scent particles from the air (although the patent says a neutralising agent was used). Fig.8: an advertisement from 1960 for a movie featuring Smell-O-Vision. Source: www. filmaffinity. com/en/ film478082. html Australia's electronics magazine siliconchip.com.au Fig.9: the configuration of conducting polymer sensor arrays for electronic and bioelectronic nose sensors. Source: www.researchgate.net/figure/ fig3_51824845 Fig.10: an electrochemical gas sensor. Source: www.baseapp.com/ nodesense/wireless-gas-sensors Supposedly, the previous scent could be cleared within two seconds, but some observers disagreed. You can read an unfavourable 1959 review of the experience at siliconchip.au/ link/ac4f 1960 Smell-O-Vision was featured in the movie Scent of Mystery, the only movie ever made with this technology in mind – see Fig.8. It was released just weeks after Behind the Great Wall. The competition between the two was called “the battle of the smellies” by Variety magazine. 2006 Japanese communications company NTT, in co-operation with a Japanese film distributor, released smells during the showing of The New World. They were released at three rows of theatre seats designated “Premium Aroma Seats”. The aromas were contained within plastic balls that were mixed and released at appropriate times during the showing, as commanded by a controller connected to a computer. 2009 4DX is a multi-sensory theatre special effects system that produces various sensations delivered to the individual viewer. These include rotating and vibrating seats, a ‘leg tickler’, airflow, hot air and water spray onto the viewer, plus scents. Theatre-­wide, special effects such as fog, flashes of light, snow, wind can also be produced. There are several 4DX cinemas in Australia: • Village Cinemas – siliconchip. au/link/ac4l • Monopoly Dreams – siliconchip. au/link/ac4m • Event Cinemas – siliconchip.au/ link/ac4n Intrinsically conducting polymers are used, typically polyaniline, polypyrrole, or polythiophene. They can pick up gas concentrations greater than 10ppm and, unlike MOS sensors, do not require heating. These sensors are relatively easy to make and it is also relatively easy to vary the composition. They are probably the second most common devices used in eNoses after MOS sensors. For more details on conducting polymers, see our article on Organic Electronics in the November 2015 issue (siliconchip.au/Article/9392). Electrochemical sensors are small electrochemical cells, similar to a battery, but generally with three electrodes instead of two. The extra electrode is used for reference purposes. As a gas enters the cell, which contains a liquid or gel electrolyte, it changes the electrochemical characteristics of the cell, which can be measured as a change in potential – see Fig.10. They are not sensitive to all gases. Metal-oxide semiconductor (MOS) sensors contain a chemoresistive metal oxide coating, which changes its resistance in response to a target gas of interest (Fig.11). An array of MOS devices with different coatings may be used to make a device sensitive to a variety of odours. These are among the most popular sensor devices in electronic noses. Electronic noses may be purely electronic or bio-electronic. The purely electronic sensors respond to a variety of odour molecules, while in bio-electronic noses, an attempt is made to more closely mimic the operation of biological noses. Proteins are cloned from biological receptor molecules that bind to specific odour molecules. This high level of specificity allows for extremely high sensitivity. An important aspect of electronic noses is that they should be relatively inexpensive. The gold standard for measuring any gas mixture is gas chromatography mass spectrometry (GCMS), which is accurate and reproducible but expensive, and not amenable to make into a miniaturised portable device. Electronic noses use much simpler and cheaper technology by comparison. They may not be as good as GC-MS for identifying substances, but they are suitable for the purposes for which they are intended. A variety of different types of sensors have been used or proposed. They include: Conducting polymer devices are chemoresistive, which means they change their resistance in response to a gas of interest. They are specially formulated to respond to particular gases. An array of different polymers or compositions may be used to make a device sensitive to a variety of odours (Fig.9). Electronic noses (eNoses) An electronic nose can detect smells (and according to some definitions, flavours). The basic elements of an electronic nose are an odour collection system (equivalent to a nose in a human), odour receptors, signal processing and pattern recognition. siliconchip.com.au Fig.11: the working principle of MOS electronic nose sensors. Source: www.researchgate.net/figure/ fig1_361874229 Australia's electronics magazine May 2025  17 Fig.12: the Cyranose 320 electronic nose. Source: www.sensigent.com/ cyranose-320.html Fig.13: the Sensigent MSEM 160 electronic nose. Source: www. sensigent.com/img/pdf/MSEM%20 160%20Datasheet.pdf 18 Silicon Chip It is possible to have multiple MOS sensors on one die. The detection threshold of commercial versions of these types of sensors is around 1-1000ppm. A disadvantage is their high operating temperature of 150400°C, requiring onboard heating and resulting in relatively high power consumption. Nanocomposite arrays are composite materials in which two or more phases are present, at least one of the phases having dimensions in the nanometre (one millionth of a millimetre) range. The components are designed to adsorb odours of interest, causing a change in impedance that can be measured. One such device that has been produced uses the conducting polymer polyaniline in a nanostructured composite to detect ammonia in human breath; a sign of kidney disease. Optical sensors for electronic noses rely on the fact that different gases absorb different wavelengths of light. By passing a gas between an optical light source and receiver, and measuring the absorption at different wavelengths, the type of gas can be determined. Piezoelectric sensors or quartz crystal microbalance sensors use piezoelectric quartz crystals with coatings that adsorb molecules of interest. As they do so, the resonant frequency of the crystal changes, and that can be measured. An array of several such devices can be used, each sensitive to different gases, to analyse mixtures of gases. Photoionisation sensors are used to detect low concentrations of volatile organic compounds (VOCs). These sensors work by using UV light to ionise the gases of interest, creating positively and negatively charge ions. These ions result in a current flow, which can be measured. Surface acoustic wave (SAW) sensors are a type of device in which acoustic waves travel along the surface. A coating or nanostructured surface can be used that is sensitive to a particular odour. As it is adsorbed, the acoustic velocity changes and that can be measured. An array with a variety of coatings can be constructed so that different odours can be sensed. Commercial & experimental eNoses The Cyranose 320 is a handheld Australia's electronics magazine device from Sensigent (www.sensigent.­ com) that is designed to detect and identify complex chemical mixtures that constitute aromas, odours and fragrances (Fig.12). It can also be used to identify simple mixtures and individual chemical compounds. It uses an array of nanocomposite sensors as the sensing elements, which they call a “NoseChip”. Pattern recognition and training are used to teach the device to identify particular smells of interest to the user. According to the video at https:// youtu.be/r3jvpZPjcA4 the device can detect various pathogens and diseases in human breath. The MSEM 160 (Multi-Sensor Environmental Monitor) from Sensigent is a portable electronic nose that uses up to 30 different sensors, including nanocomposite sensors, electrochemical sensors, MOS sensors and photoionisation sensors (Fig.13). It is available with three different sensor configurations to detect: 1. Malodours like H2S (hydrogen sulfide), NH 3 (ammonia), CH 3SH (methyl mercaptan), organo-sulfur and organo-nitrogen compounds and mixtures. 2. Aromas like alcohols, aldehydes, terpenes and mixtures of volatile and semi-volatile organic compounds (VOCs). 3. Pollutants including CO, O3, NOx (nitrogen oxides), SOx (sulfur oxides) & other regulated gases and mixtures. It is also available in custom configurations. NTT Data (see https://nttdata-­ solutions.com/en/) is developing artificial nose technology controlled by artificial intelligence (AI). It is intended to determine questions such as should a public restroom facility be cleaned or not, what is the optimal expiry date for a food product, and quality control of coffee. The nose was entered in an SAP (a business analytics company) ‘hackathon’ competition and was tasked with smelling coffee samples. It used four sensors to measure various gas values, which became the unique ‘fingerprint’ of a smell. PEN3 is a portable electronic nose from Airsense Analytics (see https:// airsense.com/en) that uses ten different MOS sensors (Fig.14). Once trained for specific smells of interest, and with the use of its pattern matching algorithm, it is designed to give siliconchip.com.au Fig.14 (left): the PEN3 with the optional “enrichment and desorption unit (EDU)” under it. Source: https://airsense.com/en/ products/portable-electronic-nose Fig.15 (above): a smell.iX16 eNose chip. Source: https://smartnanotubes.com/products/ fast qualitative answers such as good/ bad or yes/no. Suggested uses are in process control, quality control and environmental monitoring. SmartNanotubes (see https:// smart-nanotubes.com) has developed a multi-channel electronic nose gas detector chip for the mass market. The chip, which is called the smell. iX16 (Fig.15) contains nanostructured materials that can detect multiple gases, smells and volatile organic compounds (VOCs). The chip uses just 1µW of power. These chips have been incorporated into a development kit with a device called the smell.Inspector, shown in Fig.16. AI-based software called smell. Annotator analyses detected odours from the smell.Inspector and provides information. The eNose Company (see www. enose-company.com) has developed an electronic nose specifically for detecting disease, shown in Fig.17. It uses a variety of sensors, including MOS, conducting polymer sensors and quartz crystal microbalance senors. The device has been certified to detect lung cancer, COVID-19 & colon cancer and is under investigation for the detection of tuberculosis, pulmonary embolism, colorectal cancer, Barrett’s oesophagus, thyroid carcinoma, multiple sclerosis and rheumatoid arthritis. You can watch a video on it at https://youtu.be/6KUwcWdUGpY In 2002, Australian scientists at the University of New South Wales were reported to have developed an electronic nose that can detect truffles, but we can find no further details or reference to this. Electronic tongues (e-tongues) IBM HyperTaste is an experimental system that uses both electrochemical and AI technology to taste and analyse fluids (Fig.18). Proposed examples of use include checking the authenticity of food and drink products, quality control of food and beverages (Fig.19) and monitoring water quality. It consists of sixteen conductive polymer electrochemical sensors. Signals from the sensors are sent to software in a mobile device like a smartphone, whereupon the raw data is uploaded to a cloud AI server, analysed and classified. Fig.16: the smell.Inspector development kit. It contains four iX16 chips, visible on the left. Source: https://smart-nanotubes.com/produkt/ smell-inspector-developer-kit/ Fig.17: an electronic nose for disease detection from The eNose Company. Source: www. enose-company.com/wp-content/ uploads/2022/10/1665128402161.jpg siliconchip.com.au Fig.18: IBM’s HyperTaste device ‘tasting’ liquid in a glass. In this case, it identified a certain authentic gin out of several fake alternatives. Source: IEEE Spectrum – siliconchip.au/link/ac4o Australia's electronics magazine May 2025  19 Fig.19: a classification of various fruit juices and wines by the HyperTaste. Source: https:// dataconomy. com/wp-content/ uploads/2022/06/ HyperTasteAI-based-etongue-analyzesthe-chemicalcomposition-ofliquids-3.jpg In tests, the device has been able to identify different types of bottled mineral water, identified fruit juices by fruit type, detected counterfeit alcoholic beverages, identified wines by brand and place of origin and determined the intensity of coffee. It has also been used on the autonomous ship Mayflower to sample seawater. Producing specific odours For research purposes, specific odours can be produced with an olfactometer. This is a device that produces particular odours at precise concentrations for subjects to smell. The purpose is usually scientific research, to test the ability to smell certain odours or to detect odours, or for market research to test new products. An example of a commercial olfactometer used for research is shown in Fig.20. It appears to be a Burghart Research Olfactometer OL023 (see siliconchip.au/link/ac4g). The smells are released through a plastic tube, and the response of a test subject’s brain can be measured in a functional MRI (fMRI) machine. Producing specific tastes The following devices can be used to synthesise tastes by electrical stimulation of the tongue or by the delivery of chemicals. Professor Yen Ching-Chiuan at KeioNUS CUTE Center, Smart Systems Institute of the National University of Singapore, has developed an experimental digital taste stimulator that stimulates tastes using both electrical and smell stimuli (Fig.21). “Electric salt” is a device developed by Professor Homei Miyashita with the purpose of enhancing the salty flavour of food. This is to allow Japanese people, who are said to consume too much salt, to reduce the intake of salt while maintaining the desired taste. The devices are in the form of a spoon and a bowl. A chopstick device has also been developed. The tongue is electrically stimulated with a waveform at 0.1-0.5mA with an undisclosed voltage and shape. The intensity of the current can be adjusted by the user. The devices are said to increase the perception of the saltiness of food by 1.5 times. A gustometer is a device used in scientific research to deliver to the tongue a predetermined concentration and volume of a substance for taste testing, over a specified period. It is named after the gustatory stimulus that arises from a chemical which activates the taste cells of the tongue, resulting in the perception of flavour. The liquid under study is delivered to the tongue via a plastic tube. The device is used for studies of taste perception in people and animals and functional MRI can be used to study the brain’s response to various taste stimuli. An example is shown in Fig.22 and a subject under test in an MRI machine can be viewed at www.wur.nl/en/ show/gustometer.htm Fig.20: a research olfactometer at Wageningen University & Research. Source: www.wur.nl/en/show/olfactometer.htm Fig.21: an experimental digital taste stimulator. Source: https://cutecenter. nus.edu.sg/projects/digital-flavor.html Australia's electronics magazine siliconchip.com.au 20 Silicon Chip The Norimaki Synthesiser was an experimental Japanese device, invented by Professor Homei Miyashita of Meiji University, that simulated tastes. A device was placed in contact with the tongue, which had agar gels containing the five basic tastes: sweet, umami, bitter, acidic and salty (see Fig.23). These tastes can be considered analogous to the primary colours of light. A voltage could be supplied to individual taste gels (see www.dailymail. co.uk/sciencetech/article-8359459/). With no voltage applied, a user would experience all five tastes. If a voltage is supplied to one or more individual tastes, the cations (positively charged atoms or molecules) move away from the tongue to the cathode side, so that taste is minimised. The intensity of the sensation depends on the voltage and current supplied via the control panel. The device is said to be able to simulate almost any taste, but not fragrances or spicy flavours. A Norimaki is a sushi roll wrapped in seaweed, which the device resembles. You can watch a video on this device at https://youtu. be/7HIm4LoAZxU NTT DOCOMO, a large Japanese telecommunications company, has developed a technology to share tastes online. A taste is first analysed and converted to 25 parameters defining the taste, then transmitted by digital means and recreated from a palette of the five basic tastes (sweet, sour, salty, bitter and umami) using 20 types of base liquid. A proprietary algorithm is used to take into account different individual’s taste perceptions. Taste the TV (TTTV) is a lickable TV screen that allows users to experience various tastes that are sprayed onto it from a carousel of ten canisters (Fig.24). A plastic film is rolled over the screen to allow new tastes to be experienced and also for hygienic reasons between users. It is proposed to be used for taste competitions, for the training of chefs and to experience the tastes presented in a movie. It was invented by Professor Homei Miyashita from Meiji University in Tokyo who also invented the Norimaki Synthesizer mentioned above. We are hoping that this idea will not be combined with a touchscreen! SC siliconchip.com.au Fig.22: a gustometer made using off-the-shelf modular pump system components: (1) Cetoni BASE 120 module with five low-pressure syringe pump modules, (2) clamp, (3) computer-controlled solenoid valves, (4a) syringe holders, (4b) syringe piston holders, (5) upright support structure, (6) highprecision glass syringes, (10) tubing connections, (11) ferrules for tubing. Source: https://edspace.american.edu/openbehavior/project/novel-gustometer/ Fig.23: the end of a cylinder which is placed against tongue. The colours (food dye) are just to distinguish the different gels. Source: www.dezeen. com/2020/05/28/norimaki-synthesizer-device-taste-technology Fig.24: Prof. Homei Miyashita’s TTTV device. There are ten spray canisters (right) to apply various taste chemicals to an LCD screen (left). A roll of plastic film advances between tastes or between different users. Australia's electronics magazine May 2025  21 NEED TO TOP-UP YOUR SERVICE AIDS AND ESSENTIALS? GREAT RANGE. GREAT VALUE. In-stock at your conveniently located stores nationwide. 4 2 1 3 5 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 4 1 Litre Bottle NA1070 BUY 1+ $15.95 EA. BUY 4+ $13.95 EA. BUY 10+ $12.45 EA. 3 Liquid Electrical Tape 28g Tube, Black, NM2836 BUY 1+ $29.95 EA. BUY 4+ $26.95 EA. 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Silicon Chip • Fasteners & Cable Ties • Ultrasonic Cleaners • Tools & Workbench Accessories jaycar.com.au - 1800 022 888 jaycar.co.nz - 0800 452 922 Australia's electronics magazine siliconchip.com.au Prices shown in $AUD and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Multi-coloured prints, uninterrupted Meet the K2 Plus CFS* Combo, the ultimate game-changer for 3D printing enthusiasts. 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Scan QR Code to learn more or visit: jaycar.com.au/p/TL4856 TL4856 Shop with confidence at Jaycar Backed by a trusted local team, nationwide stores for all your 3D printing needs, and expert support you can count on. siliconchip.com.au Australia's electronics magazine May 2025  23 All prices shown in $AUD and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. While Stock Lasts. Vers Ver satile Battery Checker Our previous Battery Condition Checker was designed specifically for lead-acid batteries and variants such as sealed lead-acid (SLA) types. This versatile tool allows you to check the condition of all manner of batteries, including Liion and LiPo types. It can also test 9V batteries and cells with a much lower voltage, so it can check C, D, AA and AAA cells too. Project by Tim Blythman V oltmeters (such as the ones built into multimeters) are a simple way to check the terminal voltage of a battery and can help to estimate its state of charge. However, voltmeters have a high input impedance, so they do not expose the battery to any significant load. Thus, a voltmeter reading does not indicate a battery’s internal resistance. Increasing internal resistance can be a sign of degradation and loss of capacity in a battery. We’ve seen batteries with a perfectly reasonable terminal voltage that completely ‘drop their bundle’ when exposed to any kind of load! Such a battery cannot be relied upon. So you really need a proper battery checker, like this one. Our Battery Condition Checker from the August 2009 issue (siliconchip.au/ Article/1535) worked with 6V, 12V and 24V lead-acid batteries. It applied a 15ms pulsed load to the battery, which could be 12A, 25A or 40A. The result was shown on a row of LEDs driven by the venerable LM3914 LED bargraph driver. Cleverly, it was powered by the 24 Silicon Chip battery being tested and performed its tests under the control of a 4017 decade counter. The circuit used four Mosfets to deliver the pulses, with circuitry controlling the Mosfet gate voltage based on the voltage across four current measuring shunts. This allowed the circuit to sink the desired current. Nowadays, we can use a modern microcontroller with an ADC (analog-­ to-digital converter) to control the sequencing of such a device. Its ADC can measure voltage and perform calculations to display results in an easyto-read text form. That makes for a much more compact instrument than the relatively large 2009 design. It also allows us to test batteries below 6V, such as the now very common ~3.7V lithium-ion, LiPo & LiFePO4 cells. It would also be handy to be able to test AA, AAA, C and D cells and such, as well as batteries made from them. That isn’t possible with the older design, since these cells do not provide enough voltage to run circuitry, so we have added the option of a separate battery to power the Checker. Australia's electronics magazine The Versatile Battery Checker is easy to use. You can set a voltage drop limit (specified in percent; we have set the default to 10%) and dial in the maximum test current. The test sequence starts at the press of a button, and the results are reported in about one second. The Checker runs 10 test pulses spread up to the maximum current limit. If at any time the test current is exceeded or the battery voltage drops too much, the remaining tests are cut short and the results of the completed pulses are reported. The Checker also monitors for conditions that might otherwise damage the hardware and cancels pending tests in such cases. Our Versatile Battery Checker Perhaps the best way to explain our new design is to examine the circuit diagram, Fig.1. The battery under test (BUT) connects between two binding posts, CON3 (positive) and CON4 (negative). The path for the test current is through diode D1, Mosfet Q1 and a 15mW current-measuring shunt. In the absence of any other signals, Q1 is held off by the 100kW resistor siliconchip.com.au connected to its gate via a 220W resistor. Diode D1 is for reverse-polarity protection, since Q1 would otherwise conduct excessive reverse current through its body diode if the connections were reversed. The circuit can run off the BUT, receiving power to its main V+ rail via diode D2. A 9V battery connected at CON2 can also supply power. Q5 is a PNP transistor arranged as a high-side switch that can source power to V+ via diode D3. From V+, PNP transistors Q2 and Q7 form a 600µA current-limited source that can be enabled by applying current to NPN transistor Q3’s base. This 600µA flows out of Q2’s collector and into Q1’s gate, tending to bias it on. A current source is used here so that the circuit’s operation is consistent even if the V+ voltage varies (and it likely will if running off the BUT). The section around NPN transistor Q4 provides the current control function. Assume for now that the line labelled CURCON is connected to circuit ground. As the current through the 15mW shunt rises, so does the voltage at Q4’s base. When the voltage across the shunt reaches about 0.73V, the divider can supply 0.6V to Q4’s base. This will switch on Q4 and shunt the current from Q2 away from Q1’s gate, reducing its gate bias voltage, and maintaining the current at a level that keeps this state. To achieve this, a nominal 48A needs to flow through the shunt. If we apply 3.3V to the CURCON line then, even if no current is flowing, Q4 has 0.6V at its base and the Mosfet is forced off. Between these two extremes, we can set a voltage that will approximately set the current that is flowing through the shunt and thus flowing out of the BUT. Of course, the voltage at Q4’s base will not strictly be 0.6V, and there are some variations in the other voltages, but the basic principle remains valid. Later, we’ll look at how this voltage is set. Since the shunt is on the low side (BAT−) of the circuit, the voltage developed across it (relative to circuit ground) is proportional to the actual current flowing, and the microcontroller can easily measure that. Power supply The control circuitry runs at a nominal 5V supplied from either REG1 or REG2. Only one of these regulators siliconchip.com.au Fig.1: key to this circuit’s operation is Mosfet Q1 being driven in constantcurrent mode with the target current set by the voltage on the CURCON line, produced by IC1’s internal DAC. The circuitry at upper left provides pushbutton power control using S5 and Q5. Two 100kW/10kW dividers allow the internal and external battery voltages to be sensed. should be fitted; the two parts are simply alternatives that perform the same role. The TLE4269G (REG2) can handle an input voltage up to 45V. We got a fairly large number of these nice chips inexpensively, so will supply them in kits. In case it becomes hard to find, an MCP1804 (REG1) can be used instead. This can handle up to 28V; that isn’t high enough to comfortably run from a fully charged 24V Australia's electronics magazine battery, which can reach nearly 30V. We’ll assume REG2 is fitted, since that is what we used on our prototype. It comes in the SOIC-8 package, with features not available on the 3-pin MCP1804 (the latter’s tab is connected to the middle pin). The connections to pins 2 and 3 of REG2 simply disable its extra features and pins 1, 5 and 8 provide the minimum input, ground and output connections needed. May 2025  25 When mounting the OLED module, it should be level with the surrounding plastic and the gaps will be covered by the panel. The two 10µF capacitors provide the necessary bypassing required by either regulator. Diodes D2 and D3, noted earlier, allow REG2 to be powered from either of the two sources. There is also a 100µF capacitor that holds up the V+ line during tests. This is important if the BUT is used to provide the supply current. Microcontroller IC1 is a PIC16F18146 8-bit microcontroller and it has a 100nF bypass capacitor fitted to its supply at pins 1 and 20 (ground). We make use of several of its internal peripherals. Importantly, it has an internal voltage reference that can be fed to an 8-bit DAC (digital-to-analog converter) with a buffered output at pin 17. The DAC is used to set the CURCON voltage and thus the BUT current. We use the 4.096V internal reference, so the DAC has an output resolution of 16mV, which maps to steps of ¼A for the BUT. The microcontroller connects to ICSP (in-circuit serial programming) header CON1 with its 5V supply rails, along with pins 4, 18 and 19. Pin 4 is pulled up to 5V to prevent inadvertent resets. We used CON1 for development, but it is does not need to be fitted unless IC1 needs to be programmed in-circuit. The remaining pins on IC1 are general-­purpose I/O pins (GPIOs) used for straightforward digital and analog input functions. Pins 2, 3, 7 and 8 connect to tactile switches S1-S4. These pins have an internal pullup current enabled, so they sit at a high level unless the switch is pressed, pulling it to ground and causing the digital input to change state. Pins 5 and 6 connect to OLED module MOD1, providing an I2C serial interface, along with the 5V supply rails. The switches and display form the user interface; we’ll delve into its details a bit later. Pins 9 and 12 connect to identical 100kW/10kW dividers supplemented by 100nF capacitors on their lower legs. These are used with IC1’s ADC peripheral to monitor the voltage at the 9V battery at CON2 and the BUT, respectively. The internal 4.096V internal reference is used for these measurements, giving a range of around 45V with a resolution of 11mV using the 12-bit ADC. Pin 14 is similarly used to monitor the voltage at the shunt and thus measure the current drawn by the BUT. The current measurements use a 1.024V reference, allowing currents up to 65A to be measured. The measured value of these internal references is written into the chip at manufacture, so we can use them without an extra calibration step. Measuring the change in BUT voltage due to various current loads is the essence of what the Checker does. These measurements also allow, for example, an internal resistance value to be calculated. We mentioned Q5 earlier, but not how it is controlled. Q5 can be switched on either by closing S5 or by raising the voltage on the POWERCON line (IC1’s pin 10), which switches on Q6. A typical sequence might involve pressing S5, which powers on the microcontroller. The micro then biases on Q6 to maintain power, and the button can be released. The micro can then switch itself off later by pulling POWERCON low, to 0V. This might be done under user control or after a timeout. The micro applies a pullup current to pin 11, allowing it to detect when S5 is pressed. D4 is used to prevent voltages above 5V from feeding back into the microcontroller, which could damage it. Pin 16, the TESTCON line, can be taken high to switch on Q3, which in turn activates the Q2 current source. This gives us two ways to ensure that Q1 is switched off between tests, since we can also put up to 4V on CURCON, V 2.0 1.6 1.2 0.8 0.4 0.0 -0.4 -0.05 seconds 0.05 0.15 0.25 0.35 0.45 0.55 0.65 0.75 0.85 Scope 1: eight pulses from a test sequence. Blue is TESTCON (which, at 5V peak, has exceeded the scale), red is the scaled battery voltage (BATSENSE), green is current (VSHUNT) and yellow is CURCON, offset for clarity (the peak level is nominally 4V). As CURCON drops, the VSHUNT curve indicates an increasing current and the battery voltage drops further. 26 Silicon Chip Australia's electronics magazine siliconchip.com.au V 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 -10.0 ms 0.0 10.0 forcing Q4 on and keeping Q1’s gate low. 20.0 Scope 3: this is like Scope 2 but with a closeup of a single pulse, except yellow is now the scaled battery voltage (BATSENSE). Note how Q1’s gate drive adjusts as the battery voltage sags. The firmware allows 10ms for the voltages to stabilise before taking several samples over a few more milliseconds. All the important voltages settle before sampling. test is stopped. Each sequence aims to run 10 tests up to the maximum, so even if the sequence is not completed, there should be a useful measurement amongst those taken. Before each pulse, the battery voltage is measured. The DAC is set to provide the requisite current, and the pulse is applied by taking TESTCON high and waiting for 10ms. This gives time for the test conditions to stabilise. The current and voltage are measured, and TESTCON is taken low to end the test. The DAC voltage is also increased to its maximum to ensure that Q1 is switched off. Scope 1 and Scope 2 show a sequence of eight test pulses. You can see the way the voltages change in the circuit as the test current is ramped up, from left to right. Scope 3 shows a single pulse and how the conditions Software overview The user interface for the Versatile Battery Checker is quite simple since there is not much to configure between tests. There is a single page that controls the test process. Initially, it shows the connected BUT voltage, and the buttons allows the test current to be set and the test started. Just like the earlier Battery Condition Checker, it runs several brief pulses, around 10 in this case. While the earlier project ran three tests at the same current, this Checker runs tests spread out from near zero up to the target current. If at any time the target current is exceeded, or the battery voltage drops by more than the specified amount, the Features & Specifications Compact handheld unit Handles batteries/cells from 1V to 30V Test current up to 30A Battery connects via a pair of binding posts Reports test current, unloaded & loaded battery voltage, percent voltage drop & internal resistance Wiring & terminal resistance can be calibrated out Runs 10 tests up to a configurable maximum current Results appear on an OLED screen Self-protection built into the software Runs from a 9V battery or the battery being tested (above 7V) Operating current: 30mA Battery life: 10 hours plus with a standard 9V battery settle before the voltages are sampled. The Checker displays the highest current reading that was made successfully, along with a measurement of the voltage drop and calculated internal resistance. You can also view the results of the other samples taken (at lower current levels), as long as the Checker deems them valid. It monitors for any conditions that V 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 -0.1seconds 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Scope 2: the blue trace is VSHUNT, red is Q1’s gate, green is Q4’s base and yellow is the CURCON line, all per the scale on the left. This shows the increased drive to Q1’s gate as the requested current increases and a fairly consistent voltage at Q4’s base despite CURCON being driven at different voltages. siliconchip.com.au Australia's electronics magazine May 2025  27 may need a reasonably powerful iron to solder them. There are a handful of through-hole parts to add, then some cutting and drilling for the enclosure. The panel PCB is a bezel for the entire front of the enclosure, so not much precision is required when making holes in the enclosure. Populating the PCB Fig.2: an annotated diagram from the SQM10250E data sheet; green shows the Mosfet’s safe operating area, while the red line marks out the limits that are enforced by the software. The white area inside the red lines cannot be reached because of the Mosfet’s minimum resistance. might be problematic before each test. For example, it checks that there is voltage on the BAT+ line before proceeding. There are also configuration pages to set some user preferences and calibration parameters. The software also compares the maximum test current, and the measured battery voltage, against the Mosfet’s safe operating area (SOA), shown in Fig.2. If the vertical line is exceeded, a “V too high” message is given. This can happen if the connected battery measures more than 30V. For the diagonal line, which corresponds to a VI product of 400W, the Checker reports an “SOA error” and the calculated VI product value. It also calculates a lower test current that would be inside the safe operating area, based on the measured BUT voltage. This means that for a fully charged 12V battery (at say 14.4V), the highest safe test current is around 27A, while a fully charged 24V battery can be tested up to about 13A. The horizontal line is enforced by not permitting the user to set the current over 30A. Between tests pulses, a 100ms delay is inserted and after a test has been run, the software enforces a further delay 28 Silicon Chip proportional to the test VI product before allowing another test to begin. This ensures that there is negligible chance of the components overheating. Since it is when the results are displayed, you might not even notice it. We’ll examine some of the finer details of the software operation, including setup, calibration and usage after assembly is complete. The most critical of the Checker’s calibration steps can be performed automatically, without any external test gear, and many of the others with just a multimeter. Construction The bulk of the construction involves populating the main PCB with surface-mounting parts, so the standard requirements for surface mounting gear apply. None of the parts are smaller than M3216/1206 or SOT23, and the PCB is fairly spacious, so it is not too difficult to build. You should ideally have a finetipped soldering iron (a medium tip should be OK), flux paste, a magnifier, tweezers and solder-wicking braid. Illumination and ventilation are also helpful. The power components sit on substantial copper areas, so you Australia's electronics magazine The main PCB is coded 11104251 and measures 70 × 76mm. Follow along with the overlay diagrams (Figs.3 & 4) and photos. Pay attention to the transistors, since both NPN and PNP types are used in the same package. Care should also be taken that the diodes are fitted with the correct polarity. All the SMD parts mount on the same side of the PCB. Start with IC1 and REG2, both in SOIC packages. If you have an MCP1804 (for REG1), then fit it instead of REG2. Apply flux to the pads on the PCB and rest the components in place. Both IC1 and REG2 have their pin 1 markers in the top left-hand corner. Clean your iron’s tip and add a small amount of fresh solder. Tack one lead and adjust the parts with the tweezers until all the leads are located above their pads and the parts are flat against the PCB. Carefully solder the remaining pins, cleaning the iron and adding solder as needed. If you bridge two pins, finish soldering the part before trying to fix the bridge. This will ensure it doesn’t move out of position. To remove a bridge, add a little flux paste, then press the braid against the bridge with your iron and allow it to draw up the excess solder. Go back and refresh any joins that you think might need it. Next, add a thin layer of flux paste and solder the three BC807 PNP transistors: Q2, Q5 & Q7. These parts are smaller, but you can use much the same strategy as for the ICs. Follow with the three BC817 NPN transistors: Q3, Q4 & Q6. That will be all the parts in SOT-23 packages fitted. Now fit the three 100nF capacitors, which should be thinner than the 10µF capacitors. They won’t be marked except on their packaging. The two 10µF capacitors can be installed next, near the regulator. Now solder in the three smaller diodes, D2-D4. Pay attention to the cathode stripes and siliconchip.com.au ensure they are placed closest to the ‘K’ markings on the PCB silkscreen. The 20 M3216/1206 size (3.2 × 1.6mm) resistors are the last of the smaller parts. Check the value of each using a multimeter (set to resistance) or by visually examining the resistance code and making sure it matches the value printed on the PCB silkscreen or overlay diagram. If your iron has adjustable temperature, you can now turn it up for soldering the three larger parts: D1, Q1 and the 15mW shunt. The strategy is much the same, although you might need to apply more heat, which could take more time. For Q1, the gate pin (at top left, above the Q1 silkscreen marking) will have less attached copper, so we recommend you tack it first. Also make sure you spread flux paste on all the pads before placing the part, so that solder will flow under it later. Q1 will only fit one way, but you should check the polarity of D1. D1’s pads and leads are also asymmetrical, so you can match the two smaller leads to the smaller pad on the PCB. The shunt resistor is not polarised. Once you have the components secured on all leads, you can check that there is no continuity between the BAT+ and BAT− pads in either direction. If this is low resistance or it shows a low voltage on a diode test, you may have the diode reversed. You should measure around 100kW due to the sensing divider. If all is well, you can add more solder to the exposed copper areas, which will enhance their current-carrying capacity (shown in grey near the top of Fig.4). Then use a flux solvent or isopropyl alcohol to clean up the PCB and allow it to dry fully. Check the PCB thoroughly for solder bridges and other defects and repair as needed. Programming IC1 The back of the Checker just before the rear panel is screwed on. The binding posts connect to the main PCB with short lengths of heavy-duty insulated wire, and the main current carrying path is supplemented with extra solder. At this stage, there is enough circuitry attached to IC1 that it can be programmed if that is required. If you have purchased a pre-programmed microcontroller from the Silicon Chip Shop, this will not be necessary. CON1 must be fitted to allow a programmer to connect. It goes on the same side as the SMD components, and can be left in after programming, since it won’t foul the case. You can see it in our photos, since we used CON1 quite a lot during development. You’ll need the Microchip IPE (integrated programming interface) software. This is a free download as part of the MPLAB X IDE from the Microchip website at www.microchip. com/en-us/tools-resources/develop/ mplab-x-ide Figs.3 & 4: all the SMD parts are on one side of the PCB and should be installed first. Only one of REG1 or REG2 should be fitted. The exposed traces in the highcurrent section of the circuit near the top can be supplemented with extra solder. The tactile switches are fitted to the other side of the PCB, as is the OLED screen. siliconchip.com.au Australia's electronics magazine May 2025  29 You’ll also need a programmer like a Snap, PICkit 4 or PICkit 5. If your programmer cannot supply power to the circuit, then the easiest way will be to rig up something to supply 6V or more to CON3 and CON4 (observing their respective polarity markings). A current-limited supply set to 50mA is ideal, since the circuit should not draw more than that when operating. Connect the programmer and, in the IPE software, select the PIC16F18146, open the HEX file and press the Program button. Check that the programming completes and the file is verified successfully. Nothing will happen after that, since there is no display connected. Disconnect the programmer and power supply before proceeding. Case cutting You’ll need to cut the holes to allow the OLED (MOD1) to be correctly located relative to the front panel. The front panel PCB can be used as a template for the holes. The seven round holes should match the front panel Parts List – Versatile Battery Checker 1 double-sided PCB coded 11104251 measuring 70 × 76mm 1 double-sided 0.8mm-thick black PCB coded 11104252 measuring 131 × 68mm (front panel) 1 Retex Betabox 33050552 145 × 80 × 34mm handheld enclosure with battery compartment 5 through-hole SPST tactile switches with stems 9mm above the PCB (S1-S5, 6mm actuator length) [Jaycar SP0603] 1 1.3in I2C OLED module (MOD1) [Silicon Chip SC6511 or SC5026] 1 9V battery and battery snap 1 5-pin header, 2.54mm pitch (CON1; optional, for ICSP) 1 2-way right-angle 2.54mm polarised header and matching plug (CON2; optional) 1 red binding post (CON3) 1 black binding post (CON4) 4 self-adhesive small rubber feet 1 piece of double-sided tape to secure battery 1 fresh AA cell and holder for setup and testing 1 5cm length of red 25A+ rated wire 1 5cm length of black 25A+ rated wire 1 small tube of neutral cure silicone or similar resilient glue Semiconductors 1 PIC16F18146-I/SO 8-bit microcontroller programmed with 1110425A.HEX, SOIC-20 (IC1) 1 MCP1804-5 5V low-dropout linear regulator, SOT-223 (REG1) OR 1 TLE4269G 5V low-dropout linear regulator, SOIC-8 (REG2) 1 SQM10250E 250V 65A N-channel automotive-grade Mosfet, D2PAK-3 (Q1) 3 BC807 50V 800mA PNP transistor, SOT-23 (Q2, Q5, Q7) 3 BC817 50V 800mA NPN transistor, SOT-23 (Q3, Q4, Q6) 1 SBRT15U50SP5 50V 15A schottky diode, POWERDI-5 (D1) 3 M4/GS1G/SM4004 400V 1A diodes, DO-214AC (D2-D4) Capacitors 1 100μF 50V radial electrolytic 2 10μF 50V SMD M3216/1206 size X5R ceramic 3 100nF 50V SMD M3216/1206 size X7R ceramic Resistors (all M3216/1206 size 1% ⅛W unless noted) 3 100kW 8 10kW 6 1kW 3 220W 1 15mW M6331/2512 size 1% 3W Versatile Battery Checker Kit (SC7465, $65 + postage): Includes everything in the parts list (and the case) except the optional components, batteries and glue. 30 Silicon Chip Australia's electronics magazine closely, while the square hole for the OLED will need to be cut larger on the case to allow the display to sit the directly behind the panel. Fig.5 shows the required cut-outs. This is shown from outside the case, as you will only be able to mark the case from the outside using the panel. It won’t matter too much if you the mark the case since the panel will cover it. None of the holes need to be cut with any accuracy since the panel PCB will hide any imperfections. Still, it is not hard to cut the round holes accurately, and they can be enlarged if needed. You can see the general layout in our photos. If things don’t quite line up as you are fitting the through-hole parts in the next step, you can adjust the case as long as the panel hasn’t been glued to it yet. Through-hole parts Solder the five tactile switches now, noting that they are on the opposite side of the PCB to the surface-mounting parts. Ensure that they are flat against the PCB so that they point straight up through the holes in the front panel. Fitting MOD1 requires a bit of precision, since it needs to be placed just behind the panel PCB for the best result. To align it, screw the main PCB into the case. The tactile switches should neatly pass through their respective holes without binding. If the header has not been soldered to the OLED module, do that now, keeping it as square as possible and ensuring it does not protrude above the front of the screen. Alternatively, if the header is already fitted, you might find that the pins protrude slightly above the screen. In that case, you can trim them back with some nippers. Slot the OLED module into place but do not solder it yet. Tape the front panel PCB temporarily in its location to allow the OLED module to be positioned correctly. We want to have the OLED sit just behind the panel and flat against it. You should be able to rest the assembly flat on its face and allow the OLED to rest against the back of the panel PCB. Tack one pin with your iron and check that it looks aligned from the front. It should be parallel to and just behind the panel. You can also check siliconchip.com.au Fig.5: the front panel PCB can be used as a template for the round holes. The OLED screen is smaller than the rectangular cutout, but it’s needed to allow the OLED to sit just behind the front panel. The Versatile Battery Checker is a handy tool for checking the condition of all manner of batteries. It can deliver test pulses up to 30A and handle batteries with up to 30V at the terminals. Internal resistance and percentage voltage drop are shown at the conclusion of each test. that it is square by comparing the OLED’s outline against its silkscreen markings on the main PCB. If all is well, solder the remaining leads and detach the PCB from the case. The 100µF capacitor can be fitted now. Bend its leads 90°, paying attention to the polarity markings, solder it to the PCB and trim the leads, keeping the offcuts. There are also two larger pads on the main PCB under the OLED. Thread the offcuts through the holes in the OLED module and solder the lower end to the large pad on the PCB. Then solder the tops of the offcuts to the OLED and trim them to a tidy length. If you are using the plug-and-socket siliconchip.com.au arrangement for CON2 (the 9V battery), these can be installed now too, with the battery snap wires crimped into the socket. Otherwise, thread the wires for the battery snap through the holes in the PCB (to give a degree of strain relief) and then solder them to their respective pads, observing the polarity. That is how we built the prototype. Binding posts You can perform a basic functional test of the Checker by connecting a 9V battery now. Nothing should happen until you press S5, the power button. The OLED should illuminate and show something like Screen 1 and then Screen 2. The UP and DOWN Australia's electronics magazine buttons should change the test current value on the third line. Disconnect the battery before continuing with assembly. Reattach the PCB to the case, then rest the front panel in place. It should locate itself fairly accurately within the boss around the edge of the enclosure. Spread a thin film of neutral-­cure silicone sealant around the lower half of the case and secure the top half of the panel with the binding posts. Make sure to fit the red binding post near CON3 and the black binding post near CON4. Solder the red and black wires to their respective pads on the PCB, then clamp the lower half of the May 2025  31 case to the panel until the silicone has cured. You can also apply some silicone to the 100µF capacitor so its leads don’t flex too much. Fit the 9V battery (if using it), affix it with the double-­ sided tape and screw the back onto the enclosure. Testing and calibration The operation of the Checker is shown in Screens 1-16. You can see that there are some parameters that can be calibrated, but only a few are absolutely necessary. A 1.5V cell such as a fresh alkaline AA type is used as our calibration BUT (a low-voltage battery with limited current capacity is less likely to cause damage if there is a problem). Connect the AA cell to CON3 and CON4 with the correct polarity. Press S5 (POWER) to switch on the Checker. The same button switches it off, although it might not respond right away if it is in the middle of a test or other operation. Hold S5 until “OFF” is shown, then release it. You should see something like Screen 2, but with the second line showing around 1.5V. The top line should be close to 9V. If these values are markedly different, there might be a problem. In that case, power off the Checker and examine the PCB for assembly errors. To calibrate the Checker, hold MODE for a second until the screen blanks, then release MODE. You will see Screen 6. With the AA cell attached to CON3 and CON4, press ENTER to run the calibration. This scans through the DAC settings to find the lowest value that will activate Q1 and sink 1A. You can also trim this manually with the UP and DOWN buttons. If you see a “Scan Failed Check Battery” message, make sure you have a fresh cell. It should be able to deliver 1A without dropping by more than 10%; we wouldn’t trust any modern AA cell that struggles with this! Any other battery that the Checker can test should work for the purposes of this calibration. Press MODE repeatedly until you return to Screen 2 and run a test at 1A by pressing ENTER. After about a second, you should see Screen 4. Scroll through the test results with the up and down buttons; there may only be one or a few. You should see a result 32 Silicon Chip Screen 1: you should see this splash screen when the Checker is powered on before it switches to the main operating screen (Screen 2 or 3). Screen 2: when running from the internal 9V battery, its voltage is shown at upper right. The down and up icons indicate that S1 and S2 can be used to adjust the test current. Screen 5: the no-load and loaded voltages, along with the calculated percentage drop, are shown on the second line. Below are the test current and calculated internal resistance. Screen 6: holding S4 for a second opens the setup menu. The first page shows the zero-current DAC setting level. Briefly pressing S4 again cycles through the remaining menu items. Screen 9: this value sets the nominal target current when the DAC is set to 0V. It is used to calibrate the target current setting during tests. Screen 10: this calibration sets the scaling for current measurements. All calibration and configuration values are saved to EEPROM and used immediately. Screen 13: this is the lowest voltage that will allow the Checker to operate tests; below this, the circuitry cannot guarantee that the Mosfet will be driven hard enough. Screen 14: if there are problems with the calibration and configuration values in EEPROM, they can be reset by pressing S1 and S2 simultaneously on this screen. showing a current around 1A or lower if the voltage has dropped over 10% at a lower current level. This indicates that the Checker is basically functional. You can try the Checker on other batteries if you like, to test the maximum current setting. If possible, run some tests at a higher current like 20A. One AA cell probably can not do this! Perhaps you could use a car battery, or a pack from a remote-controlled vehicle. A current-limited power supply can also be used to run the Checker through its paces. You’ll see that the top line shows the test number (0-9). If the maximum current is well calibrated, and the BUT can supply the test current without sagging more than 10%, then test #9/9 should be very close to the target test current. If not, you can trim the MAX I parameter to adjust this. Reduce it if the measured current is too high and increase if it is too low. Do this in small steps and run a few tests after each adjustment to get a feel for how much the results will vary. Even after making an adjustment, the Checker may overshoot the maximum current slightly, by less than an amp. This is due to the limited DAC resolution. If you prefer to avoid this, Australia's electronics magazine siliconchip.com.au Screen 3: when powered from a battery connected to CON3/CON4, the Checker shows “EXT” at top right. The right arrow icon above S3 starts a test cycle. Screen 4: the test results are shown after about a second, with the first line showing the number of successful tests. UP and DOWN can be used to cycle through the other test results. Screen 7: the timer for internal battery operation is set here with S1 and S2, and enabled or disabled with S3. If the timer is disabled, then the Checker will not automatically power off. Screen 8: the maximum voltage drop is set here, in percent. If the Checker detects a drop higher than this, it will stop the test, even if it hasn’t reached the maximum test current. Screen 11: use a multimeter to trim the calibration factor here so that the displayed value matches the voltage of the battery attached to CON3 and CON4. Screen 12: the VAUX calibration works much the same as the external battery calibration seen in Screen 11. If in doubt, you can use the same calibration factor. more details about the other configuration and calibration settings, but it will work quite well without much setup. Run a few tests with the Checker to try out its operation and you should become familiar with how it works. From the initial page, dial in the maximum desired test current and press ENTER to start the test. Wait for the results and use the UP and DOWN buttons to scroll through them, then press ENTER to return to the initial page. If you will only be using the Checker with 12V batteries or higher, the 9V battery can be left disconnected. The Checker will power up from CON3/ CON4 if it can, so you can simply hook it up to a BUT, run a test and then disconnect the battery. The target test current is saved in EEPROM and reloaded when the Checker starts up. We found normal internal resistance values fairly easy to find for reputable brands of batteries. For example, an alkaline AA cell should measure around 150mW. An 18650 lithium cell should be under 100mW. A 7Ah SLA battery like Jaycar’s SB2486 is specified at 25mW, while a car starting battery should be even lower (under 10mW). Naturally, if a battery or cell reads much higher than specified, it should be considered for replacement. Nulling the wiring resistance Screen 15: one of the error messages that might be seen when there is a problem. This will appear if you try to run a test without a battery connected to CON3 and CON4. Screen 16: the offset applied for the intrinsic resistance of the Checker and its wiring is set here. You can either use the value from the latest test or adjust it up and down manually. you can set the MAX I value even lower to be more conservative. BAT low”. That means it is definitely time to fit a new 9V battery. The “SOA ERROR” message should go away if you reduce the test current and try again. “I too high” probably means that the calibration is off and the Checker could not reach the target current using the settings it has. There is also an option to reload the default configuration from flash memory if they do somehow end up corrupted or unusable. You might see “SETTINGS ERROR” if the Checker thinks there is a problem with the configuration. Error messages You might see a few error messages when running tests. These are generally intuitive, although, for example, a “V too low” message can sometimes be fixed by trying a lower test current. This message means that even the lowest test current of the test set caused an excessive voltage drop. You could also check the calibration. If the 9V battery is getting flat, you will see the voltage dropping on the initial screen. When it drops below 7V, you might see a message reading “AUX/ siliconchip.com.au Usage The captions for the Screens give Australia's electronics magazine Some 12V lead-acid battery chargers estimate battery internal resistance (in mW) using the equation 3000/CCA (cold cranking amps). A reasonably large car battery will typically be rated at 600CCA, implying a 5mW internal resistance. The Checker has a calibration value for the intrinsic resistance of the Checker and its wiring; this is an offset in milliohms that is subtracted from all calculated internal resistance values. The default value is 0mW, so measurements will display unadjusted values unless you change this. Screen 16 shows how this can be edited. It can be manually trimmed up and down, or it can use the value of the most recent test that has occurred. Thus, a simple way to calibrate this value is to run a test on a large, known-good battery such as a car starter battery. After running the test, navigate to this page and press the ENTER button, then trim the value down by 5mW. SC May 2025  33 ADM Instrument Engineering AIM Solder Australia AIM Training Altronic Distributors Ampec Technologies Amtech ● AppVision Arno Fuchs ● Asscon ● BDTronic ● Braemac C-Prav Labs & Certifications Chemtools CNS Precision Assembly Coiltek Electronics Comtest Group congatec Australia Control Devices Australia Control Synergy Curiosity Technology ● D3 Innovation Davin Industries Deutsch ● Digilent Dinkle ● Displaytech ● Dyne Industries Echo Electronics Electro Harmonix ● element14 Embedded Logic Solutions Emona Instruments Entech Electronics Epson Singapore ESI Technology Ltd ● Europlacer Eurotherm ● Finenet Electronic Circuit Ltd Fluke ● FS Bondtec ● Globalink Electronics Glyn High-Tech Distribution GPC Electronics GW-Instek ● Hammond Electronics Hawker Richardson Hetech HIKMICRO ● Humiseal/Chase Corp ● HW Technologies IMP Electronics Solutions Inertec ● IntelliDesign Interflux ● Inventec ● Japan Unix ● JBC Soldering ● Keysight Technologies KOH Young ● Kolb Cleaning Technology ● Komax Kabatec ● Laser 3D Leach (SZ) Co Ltd Lintek Liquid Instruments LPKF Laser & Electronics ● Marque Magnetics Ltd Mastercut Technologies Masters & Young MB Tech ● MEAN WELL ● Mektronics Australia B1 A37 A37 B6 B24 C20 D5 C20 C20 C23 B10 A29 A37 D14 D28 B17 A10 C5 A12 B1 D20 A13 B6 D17 B6 A25 D12 B26 B6 A6 D2 A1 D23 A22 B1 D30 B1 A18 C1 C23 B26 C2 B30 C1 C34 A30 A15 C1 C23 D27 A25 C20 D26 D30 C23 C20 D30 C1 C20 C20 C20 A13 D22 A9 C27 D2 C6 D6 C30 C23 B1 A16 ● denotes – Co-Exhibitor Company/Brand Stand numbers are subject to change 34 Silicon Chip Electrone Melbourne Covention & Exhibition Centre (MCEC) May 7-8 Electronex – The Electronics Design and Assembly Expo & SMCBA Conference returns to the Melbourne Convention and Exhibition Centre on the 7th & 8th of May 2025. Electronex is Australia’s largest exhibition for companies using electronics in design, assembly, manufacture and service. E lectronex will be co-located with Australian Manufacturing Week, with trade visitors able to attend both events on the Wednesday and Thursday. Hundreds of exhibitors will be meeting face-to-face with thousands of trade visitors, creating the largest event for the manufacturing sector in Australia. Electronex focuses on the high-tech end of manufacturing. Visitors will see the entire spectrum of the latest products, technology and turnkey solutions for the electronics and manufacturing industries at the one venue. Electronex features a wide range of electronic components, surface mount and inspection equipment, test & measurement equipment, and related products and services. Discuss your requirements with contract manufacturers that can design and produce turnkey solutions for your products. Many companies will launch and demonstrate new products and technology at the event. Over 100 local and international companies will be represented at this year’s expo, making it the largest ever. With many Australian manufacturers now focusing on niche products and high-tech, the event provides an important focal point for the industry in Australia. Free seminars and contests A series of free seminars will also be held on the show floor, with visitors able to attend on the day (no Australia's electronics magazine pre-­booking required). Topics include: ● Reliability in Programmable Power Supplies ● Versatile Multifunction 12 in 1 Test & Measurement Devices Product Development ● Handling Complexity in PCB Manufacturing and Assembly ● Compliance and Regulatory Approval to Sell Your Products in Australia & Globally ● Microchip’s AI-Centric 64-Bit Processors ● Smart AI In Conformal Coating and Dispensing ● Software-defined Test: A More Efficient Way to Automate and Validate ● High Mix SMT Manufacturing ● Leveraging Strategic Partnerships to Transform Traditional Products into Smart Innovations ● Advancing Edge Computing with AMD ● Technology & Process Capabilities for SMT PCB Assembly in Australia ● Building a Product Test System the Right Way Visit the show website for times and session details. The SMCBA (Surface Mount & Circuit Board Association), with the support of IPC International, will once again be conducting the Australian Round of the IPC Hand Soldering Competition (HSC) and the Australian Round of the inaugural IPC/WHMA Wire Harness Competition (WHC)! siliconchip.com.au neX 2025 SMCBA conference Held in conjunction with Electronex, this exclusive three-day conference at the MCEC on 6-8 May brings together industry professionals, engineers, innovators and manufacturers to explore the latest advancements, trends and challenges in the ever-evolving electronics landscape. Whether you’re an industry veteran or an emerging entrepreneur, this conference is designed to equip you with valuable insights into quality and competitive design and manufacture of electronics. Tuesday 6th May: The Future of Advanced Manufacturing Following opening addresses from Nadia Court (CEO, Semiconductor Support Service Bureau) and Ben Kitcher (Executive Director, Advanced Manufacturing Readiness Facility on Australian advanced manufacturing), Jasbir Bath of Bath Consultancy LLC will share an in-depth review of the most recent INEMI Board Assembly Chapter Roadmap. He will detail some challenges the electronics assembly industry will face in the next 10 years and discuss potential solutions to those challenges, including component developments like larger BGAs and CPU sockets, press-fit technology, SMT printing, reflow and rework/repair of electronic assemblies and the developments needed for the assembly materials used. siliconchip.com.au Wednesday 7th May: Feeding the Hungry Lion Designs for devices with a high power draw require careful consideration of thermal management, power integrity and signal integrity. Chuck Corley of Speeding Edge will provide a course focused on the practical knowledge and design techniques needed for a power delivery system that supports the demands of modern power-­hungry ICs. Thursday 8th May: Invisible Terminations Bottom Termination Components present a unique set of challenges in modern electronics manufacturing. Dave Hillman of Hillman Electronic Assembly Solutions LLC will provide a workshop focused on the evolution and introduction of BTC and LGA components into the electronics industry. The SMCBA conference is the ultimate destination for professionals looking to stay ahead in the fast-paced world of electronics design and manufacture. Secure your spot today! Don’t miss out on this unparalleled opportunity to connect with local and global electronics experts. Register now and be part of the future of electronics. Registrations from only $585 ex GST (SMCBA Member discounted price). To see the full program and register, visit smcba.asn.au/conference Australia's electronics magazine Metcase ● Microchip Technology Micron ● Midori ● Mission 4 Nagarro Nano Components Nano Vacuum Next PCB Nihon Superior ● Nordic Semiconductor ● NPA Pty Ltd NZFH Ltd Ocean Vision Okay Technologies ONboard Solutions On-track Technology Oritech Oupiin ● Outerspace Pacton PCBWay Pendulum ● Phoenix Contact Pillarhouse ● POE Precision Electronics Powertran ● Precision Electronic Technologies QualiEco Circuits Quectel Wireless Solutions Radytronic ● Rapid-Tech Raspberry Pi ● Raytech Redback Test Services Rehm Thermal Systems ● Re-Surface Technologies Rigol Technologies ● Ritec ● Rohde & Schwarz (Australia) Rolec OKW - ANZ Salecom ● S C Manufacturing Solutions Semitech Semiconductor Shanghai Jingying Electronic Silvertone Electronics Skyzer SMCBA Stars Microelectronics Suba Engineering Successful Endeavours Sun Industries Sunon ● TCBEST LTD TDK Lambda ● Techal Solutions Tekt Industries Teledyne FLIR ● Thermaltronics ● Thermo Fisher ● Uni-T Instruments ● VGL - Allied Connectors Vicom Australia Viscom ● Whats New in Electronics Win-Source Electronics Wirepas ● Wurth Electronics Xentronics Xiamen Zettler Magnetics Yamaha ● Yokogawa ● A26 B19 B6 B1 B18 B11 B13 D4 B2 A37 C2 A29 B23 B27 A37 C23 B28 D30 B6 B25 D25 D11 C1 B24 C23 D8 B6 D9 A11 C15 B6 C1 A6 A25 D18 C23 A30 A1 B6 C16 A26 B6 A21 A5 C18 B16 D16 D35 A6 C20 A7 C31 B6 A23 C2 D24 D29 C1 A37 B1 C1 B21 C29 C23 C24 B7 A7 B20 D10 C28 A30 C1 electronex.com.au May 2025  35 C-Prav Labs & Certifications www.c-prav.com stand A29 C-PRAV (Compliance & Product Regulatory Approvals) specialises in product standards, regulations, testing and certifications (SRTC). With over 15 years of experience, we help global manufacturers navigate complex regulatory landscapes. Our expertise spans multiple regulatory regimes, including CE, FCC, ISED, BIS, TEC and ACMA, making us a trusted partner for businesses worldwide. We offer expert consultancy to help businesses develop and implement regulatory strategies, including product design compliance, regulatory advice, workshops, training and helping businesses through the journey of complex regulatory landscapes with expert advice and guidance on standards, regulations, testing & certifications. We provide state-of-the-art testing services at our Australian NATA accredited Lab to ensure product safety, compliance and market readiness. That includes safety testing, EMC testing, environmental testing and cybersecurity testing, including IT and telecom security compliance. We have advanced testing capabilities for regulatory compliance and product validation for global markets. Our advanced contract manufacturing capabilities allow us to assist with designing and producing components to your exact specifications. We work closely with our clients from concept to production, ensuring seamless integration and optimal performance of every component. With a reputation for quality craftsmanship backed by the ISO9001 certification and technical excellence, Coiltek Electronics is a solution for businesses that require custom, reliable, and innovative wire wound electronic components. Control Devices Australia www.controldevices.com.au The new APEM reinforced PBAK series (19mm in diameter) has been added to our range of piezo switches. This anti-vandal switch is designed with a stainless steel (316L) body and polycarbonate illumination ring for extended protection. It is sealed to IP69K and can withstand impacts of up to IK06 (equivalent to one joule), and delivers a very long-life expectancy, up to 50 million cycles. Featuring bright RGB illumination feedback for increased visibility in all types of conditions, the PBAK series is suitable for various outdoor applications such as bike sharing stations, emergency call boxes, or parking meters. It is also an ideal choice for applications that require impact resistance. Contact Control Devices today for more information or a quote. Comtest Group www.comtest.com.au We help businesses to obtain national and international product approvals with a seamless certification process. Over 60 countries are covered, including Australia, New Zealand, the USA, Canada, Europe, India, China, South Africa, Egypt, Brazil, Ethiopia, Chile, Saudi Arabia, Indonesia, Japan etc. Certifications offered include: • Telecom and wireless – FCC, CE, TEC, ISED, ACMA, RCM, NCC, CCC, ICASA etc • Product safety and EMC – CB Scheme, CSA, UL, BIS, BSMI, NRCS etc • Environmental and energy – RoHS, EPR, BEE, GEMS/E3, P-65 etc Coiltek Electronics https://coiltekelectronics.com.au stand D28 Coiltek Electronics specialises in delivering high-quality, custom solutions for a wide range of industries, including defence, aerospace, medical and mining. With over 25 years of expertise in coil winding, metal detector coils and bespoke wirewound components, we are a trusted partner for companies that demand precision and reliability. 36 Silicon Chip stand C5 stand B17 Comtest Laboratories Pty Ltd, established 1996, specialises in telecommunications, electrical testing and compliance for the Australian and New Zealand Markets. Our expertise covers product safety and energy efficiency testing across a wide range of electrical and communications devices, ensuring seamless market entry, product launch success and ongoing product lifecycle compliance. Comtest provides ongoing support in navigating Australia’s compliance regulations, keeping your compliance folders and documents up to date. Control Synergy / Exascend www.controlsynergy.com.au stand A12 The Exascend AS500 BGA SSD delivers fast, compact, ultra-­ reliable storage for connected vehicles, ADAS, infotainment systems, and autonomous driving applications. With a PCIe 3.0 NVMe 1.3 interface, the AS500 ensures blazing-fast data transfer and minimal latency, making it ideal for real-time, mission-­ critical automotive workloads. Built with automotive-grade 3D TLC NAND, the AS500 offers a wide temperature tolerance (-40°C to 105°C) and rugged durability. Advanced error correction, power loss protection, and intelligent thermal management guarantee data integrity and long-term reliability under continuous operation. It comes in an ultra-compact BGA form factor with storage capacities up to 1TB. Australia's electronics magazine siliconchip.com.au Unit 13, 538 Gardeners Road ALEXANDRIA NSW 2015 02 9330 1700 sales<at>controldevices.net MINIATURE JOYSTICKS PUSH BUTTON SWITCHES ANTI-VANDAL SWITCHES TOGGLE SWITCHES LED INDICATORS VISIT US 7 - 8 MAY 2025 PENDANT CONTROL STATIONS WATERPROOF SWITCHES TACTILE SWITCHES FOOT & PALM SWITCHES MELBOURNE (MCEC) STAND C5 MAKE YOUR NEW FAVOURITE E-STORE Enjoy a quick and easy, one stop shop,with a variety of competitively priced stock items and fast processing time. Find your switch, switch accessories, LED indicators, joysticks to audio parts today on SNS. WWW.CONTROLDEVICES.COM.AU siliconchip.com.au WWW.SWITCHESNSTUFF.SHOP Australia's electronics magazine May 2025  37 The Exascend EM500 eMMC Managed NAND is also designed for automotive applications. Built with high-quality 3D TLC NAND and advanced firmware, it ensures exceptional durability, seamless data integrity, and an extended product lifespan. It complies with the JEDEC eMMC 5.1 standards and comes in a compact BGA package, with capacities from 8GB to 256GB. The Exascend microSD500 series is designed for reliable in-vehicle storage in ADAS, dashcams, event data recorders (EDRs), infotainment systems, and telematics. Built with industrial-grade 3D TLC NAND, it delivers exceptional endurance, data integrity, and resistance to extreme conditions. With capacities up to 512GB, the microSD500 supports high-speed data recording for 4K video, real-time telemetry and AI-powered vehicle analytics. Its advanced error correction technology, wear levelling and firmware optimisations enhance long-term reliability. The Exascend PR4 Series is a radiation-hardened PCIe Gen 4 NVMe SSD engineered for aerospace and mission-critical applications. Available in U.2, E1.S, and M.2 form factors, it delivers exceptional resilience in extreme environments, making it ideal for satellites, avionics, autonomous systems and space missions. The PR4 Series mitigates the effects of radiation-induced data corruption, ensuring uncompromised performance in high-radiation and extreme-temperature conditions. Advanced error correction, power loss protection (PLP) and adaptive thermal management further enhance stability and endurance in zero-failure-tolerance environments. The Exascend PE4 Series is a PCIe Gen 4 NVMe SSD designed to meet the demanding storage requirements of data centres, enterprise servers, and cloud computing. The PE4 Series supports U.2, E1.S, and M.2 form factors with a capacity of up to 15.36TB. D3 Innovation www.d3innovation.com stand D20 D3 Innovation was founded in 2019 as an original design manufacturer (ODM) for customised IoT devices. D3 Innovation supports local and overseas customers to customise IoT devices in their own industries and ensure success for future developments, including big data analysis and AI. D3 Innovation has successfully delivered over 100,000 devices to local and overseas customers. The company also has its own manufacturing facility equipped with fully automated SMT lines, robotic soldering machines, 3D printers and more. Our services include: • Electronic circuit design of IoT products, including schematic design and PCB layout • Firmware development for IoT products • IoT framework and integration • High-precision SMT assembly • High-level assembly • Product outlook 3D development 38 Silicon Chip Davin Industries www.davin.co.nz stand A13 Since 1962, Davin Industries has been a trusted leader in precision sheet metal fabrication and contract batch manufacturing, specialising in high-quality sheet metal enclosures and components for the electronics and electrical industries. With decades of expertise, we provide end-to-end solutions, delivering durable, custom-engineered products that meet the highest industry standards. We combine cutting-edge technology with expert craftsmanship to ensure precision at every stage. Our comprehensive capabilities include design, laser cutting, punching and forming, folding, welding, powder coating, and assembly, allowing us to take projects from concept to completion with efficiency and accuracy. As a long-term supplier to the defence industry, we meet the stringent requirements of mission-critical applications, ensuring high performance and reliability in every product. We serve a diverse range of multinational customers, offering tailored manufacturing solutions to meet global demands. Our clients receive their products on time and in perfect condition. Our Christchurch facility is ISO9001-certified, reflecting our commitment to stringent quality management. Whether producing prototypes or high-volume production runs, Davin Industries is dedicated to precision, innovation, and reliability – delivering high-performance fabricated components that protect and enhance electronic, electrical and defence systems worldwide. Digilent Inc www.digilent.com stand D17 Digilent Inc (an NI company) is a leading electrical engineering products company, providing educational design tools to students and educational institutes all over the world. Since 2000, Digilent has created hardware and software to allow engineers, researchers and scientists flexibility to design rapidly and test the world around them. The new Analog Discovery 3 is a portable, pocket size, mobile USB-powered test and measurement device. It features a digital oscilloscope, logic analyser, waveform generator, pattern generator, and much more (it’s a 12-in-1 device). With our free WaveForms software, it can be used in the lab, in the field, or even at home. It is lightweight and small enough to fit in your pocket or backpack, so it becomes an exceptional companion for any engineer. It has a large buffer, allowing more data to be sent through the waveform generator and received through the mixed signal (analog and digital) oscilloscope. It also has an increased sampling rate of up to 125MS/s on all channels and a more potent power supply (up to 800mA). The Analog Discovery Pro (ADP2230) is a mixed-signal oscilloscope (MSO) for professional engineers. It features analog inputs, analog output and digital I/O, with deep memory buffers all operating at up to 125MS/s. Users can receive and generate digital signals to test and analyse data from various devices Australia's electronics magazine siliconchip.com.au The new Rigol MHO/DHO5000 series includes 8-­channel high-resolution digital oscilloscopes that are designed for the mainstream market to meet design, debugging and test demands. while simultaneously powering those systems with its robust power supply. The feature-packed design allows the ADP2230 to perform the functions of several test and measurement devices and can replace a stack of traditional instruments. The Analog Discovery Pro 5000 Series devices, the ADP5470 and ADP5490, are Digilent’s most ambitious MSOs to date, bringing higher sampling rates, wider bandwidth and more power to your benchtop. Each sports an integrated CAT II digital multimeter, three programmable power supplies, a dedicated trigger line and arbitrary waveform generator to complement the MSO. With 34 digital inputs operating at 1GS/s working in tandem with the analog system, the rugged 5000 Series devices provide a range of bandwidths and sample rates for analog inputs to fit your needs – from 100MHz at 1GS/s to 350MHz at 1.5GS/s or all the way up to 500MHz at 2GS/s. element14 https://au.element14.com stand A6 The Multicomp Pro MP013877 photovoltaic/solar connector is designed for use in solar power systems, ensuring secure and efficient connections between solar panels and other components within the PV system. The MC Dual Protection MOV is an integrated device with a PPTC resettable fuse and MOV. Combining overcurrent and overvoltage circuit protections, the PPTC is a direct current-sensing device, avoiding thermal runaway by limiting the overcurrent and maintain the MOV surface temperature. Benefits include extended MOV life and shorter response time. It is UL approved. The MCMOV series features a class-leading 600V rating, suitable for emerging telecom and industrial applications. They are fast reacting due to the thermal coupling effect of an integrated structure, resulting in faster and more accurate MOV protection. The PPTC and MOV elements provide synergistic circuit protection. Multicomp Pro high-performance PV fuses are specifically designed for photovoltaic systems; the fuses only isolate the faulty strings, leaving the rest of the PV system to generate power without interruption. These products are UL approved. Example applications include solar PV panels, DC combiner boxes, inverters, AC distribution boxes, battery systems and the power grid. Multicomp Pro Thermal Circuit Breakers are a cost-effective way to protect against overloads or short circuits. They are very compact and available in a manual reset version that leaves the circuit open until fault diagnosis is complete. Example applications include automation and process control, transformers and motor protection, and safety and system monitoring. Emona Instruments Pty Ltd www.emona.com.au stand A1 Established in 1979, Emona Instruments Pty Ltd has a head office in Sydney with branch offices in Melbourne, Brisbane, Adelaide and Perth. It is a high-tech engineering company specialising in electronics, electrical, education and additive manufacturing equipment. siliconchip.com.au Based on Rigol’s new Centaurus technical platform, they offer up to eight channels, 1GHz of bandwidth, 1,000,000 waveforms/second capture rate (in fast recording mode), 500Mpts memory depth, 12-bit resolution, an excellent noise floor and vertical measurement accuracy that can meet the demand for higher accuracy. The MHO/DHO5000 series support AFG, digital signal analysis, Bode plots and other functions. They can also be powered by a battery pack, offering convenient operation and control for complex test scenarios. The new Rigol DG70000 series are high-performance arbitrary waveform generators offering a 12GSa/s sampling rate (interpolated), 5GHz analog bandwidth and 1.5Gpts/channel (or 4Gpts for a single channel) waveform length. Additionally, the series provide 16-bit vertical resolution and -70dBc SFDR (spurious-free dynamic range) for cleaner and purer signal generation. The DG70000 are feature-rich systems, enabling the creation of advanced sequences for user-defined long complex waveforms. They support high-precision multi-channel synchronisation and produce high-bandwidth, low-jitter waveforms, making them ideal for applications in communications and research. On the Emona display at Electronex 2025, we will also feature RF test equipment, power supplies and EMC test equipment. That’s in addition to our range of 3D printers and additive manufacturing solutions, ranging from prototyping in composites through to production-scale printing in thermoplastics and metal. Epson Microdevices www.epson.com.sg/MicroDevice stand A22 Our philosophy is of efficient, compact, precise innovation. After all, bigger is not always better. We firmly believe that energy-saving solutions, space-saving innovation and ultrahigh precision help to protect the natural environment and enrich communities. Epson Microdevices has three key technologies: timing devices, semiconductors and sensing systems. Our new products include: • The SPXO SG2016CBN and SG2520CBN which have high stability and low jitter. They utilise Epson’s new low-noise IntegerN PLL technology. They can support high frequencies from Australia's electronics magazine May 2025  39 75MHz to 170MHz with a narrow frequency tolerance of ±15ppm, wide operating temperature range up to 125°C, and low jitter characteristics of 0.3ps typical. They are ideal for applications that require high-frequency, low-jitter clocks such as network equipment and image and/ or audio transmission. • The S1V3F351/352 is an LSI incorporating high compression and high-quality sound decoding functions, making it ideal for use in voice guidance products. An “Epson Voice Creation PC Tool” enables the generation of high-quality sound data from texts with ease without the bother of studio recording. All functions are controlled by commands over a serial interface. A stand-alone mode can be used to support existing systems without a processor. The S1V3F351/352 will shorten the time to market for products with voice guidance. • The M-G570PR is a high-precision, lownoise inertial measurement unit (IMU) enabled by multi-sensor technology. The IMU offers both high bias stability and environmental resistance with an IP67 rating for protection against dust and water. Finenet Electronic Circuit Ltd stand A18 www.finenetpcb.com.cn Founded in 2000, Finenet Electronic Circuit Ltd is one of the largest integrated solution providers in the high-tech printed circuit board (PCB) manufacturing industry. Finenet has a monthly production capacity of 500,000ft2 (46,500m2) and 60% of its products are exported. Its products include double-sided, multi-layer, HDI and metal base PCBs with different surface finishes such as leadfree HASL, ENIG, Chem Tin, OSP etc. Our customers come from different high-tech fields, and the products are exported to southeast-Asian countries, Australia, Europe and America. We service customers with a quality policy that includes customer satisfaction, win-win development, law-abiding, pollution prevention, energy saving, and sustainable development. Environmental protection is our social responsibility. The company strictly implements the RoHS management system in accordance with national environmental protection requirements and minimises the impact of the production process on the environment. Globalink Electronics / Echo Electronics www.globalink-e.com stand B26 With over two decades of experiences in the Electronics Industry, Globalink Electronics is a partner you can rely on and entrust. Globalink provides a one-stop solution for OEM/ODM services, including component sourcing. Let our professional 40 Silicon Chip team handle the hassle of monitoring the fluctuation of prices, factory lead time, meeting of production deadlines etc. Echo Electronics, founded in Hong Kong in 1989, has over 35 years of experience in the electronic manufacturing services (EMS) business. As a Hong Kong listed company, it is a trusted and reliable partner. The company manufactures a diverse range of products, including fishing alarms, beauty products, security products, hair removal products, buzzers and smoke detectors, along with other circuit boards. One of its unique strengths is its willingness to accept high mixture and low-volume orders, catering to various customer needs. Since obtaining ISO9001 certification in 1998, Echo Electronics has been supported by an experienced manufacturing and QA (quality assurance) team. Its self-owned production line includes SMT soldering, plastic injection and final product assembly. As Echo Electronics has its own factory and production lines, it can offer comprehensive services from material procurement to the production of complete products. It collaborates closely with customers throughout the product development and manufacturing process, aiming to optimise these processes and enhance product reliability. Glyn High-Tech Distribution www.glyn.com.au stand C2 The new ME910G1-NTN module seamlessly integrates non-­ terrestrial networks (NTN) with traditional cellular communication. Designed to enhance network reliability and application robustness, this next-generation module supports 2G, LTE-M, NB-IoT and satellite connectivity, ensuring continuous operation in remote locations. Built on the Qualcomm 9205S LTE modem, the module is optimised for IoT applications, including industrial sensors, agricultural equipment, utility meters, and transportation solutions. Attendees of Electronex 2025 can request to qualify for a global 5G data card sample. Our 5G data card portfolio enables commercial deployments for original equipment manufacturers (OEMs), system integrators, and service providers. These data cards support 4G/5G multimode operation, ensuring that new product concepts can be tested and deployed quickly. The industrial-grade M.2 form factor allows seamless migration from 3G and 4G solutions to 5G, making it ideal for enterprise routers and gateways, high-speed fixed wireless access modems, private LTE and 5G networks, video broadcasting, and security applications. The FN920C04 enables 5G mid-speed connectivity using the latest 3GPP Release 17 RedCap technology. It enhances performance and efficiency compared to LTE while offering a seamless transition to 5G. This industrial-grade, rugged module is designed for global deployment, featuring enhanced uplink performance, power-saving capabilities and LTE Cat 4 fallback. Australia's electronics magazine siliconchip.com.au The Monolithic Power Systems MP264x family Active Balancers are two-cell bi-directional active balancers that are interleavable for balancing many cells. They have 92.8% charge transfer efficiency at 3.3V and support cells from 2.4V to 4.35V with up to 2.5A of net balancing current. They have integrated MOSFETs and are powered from the battery stack. They have a low quiescent current and their extensive protections include over-current protection (OCP), over-voltage protection (OVP), under-voltage protection (UVP) and thermal shutdown. They come in a 4 × 4mm QFN-26 package. The MP279x family of Monitor and Protectors can monitor 4 to 16 cells in series. They have a cell voltage measurement error under 5mV, a current/coulomb counter error under 0.5% and an extensive set of configurable protections. They can also provide low-current balancing and come in a 4 × 4mm QFN-26 package. The MPF4279x family of Fuel Gauges include advanced estimations for two to 16 cells in series, including cell and pack state-of-charge (SOC), state-of-health (SOH), instantaneous available power, remaining runtime and charge time. They support Li-ion and LiFePO4 cells and can track cell equivalent series resistance (ESR). Thermal modelling is included for cell temperature rise. Applications for these parts include e-bikes and e-mobility devices, light electric vehicles (LEVs), energy storage systems (ESSs) and uninterruptible power supplies (UPSs). Hawker Richardson www.hawkerrichardson.com.au stand A30 Visit Hawker Richardson at stand A30 and see Yamaha’s YsUP software for SMT machinery. YsUP offers transformative benefits for PCB manufacturers of all sizes. Designed to meet the demands of Industry 4.0, Yamaha’s software suite empowers OEMs, CEMs and small operators to overcome the challenges of disconnected machinery and multi-vendor environments. It includes: • P Tools to program and schedule tasks, including data conversion and visual editing. • S Tools for production assistance and material management, including component setup verification. • T Tools for traceability, production history management and quality analysis support. With one smart, interconnected ecosystem, YsUP bridges the gap in non-machine-to-machine (M2M) environments, siliconchip.com.au providing manufacturers with a united M2M communication portal for traceability, control, and optimisation across many brands and suppliers. Key benefits include: • Enhanced productivity through streamlined workflows and predictive planning linking to existing factory MRP/ERP systems. • Improved quality with full-line control through AOI defect detection, allowing immediate actions such as halting the pick and place machine when a problem is identified. • Component management via links to SMT reel storage racks and towers. • Programming flexibility across many formats, including Gerber, CAD, ODB++, Fabmaster and more. • Industry 4.0 integration with full SMT line control is available through Hermes, Apco, and CFX. • Simplified line setup and control when using all Yamaha OEM-branded equipment. Meet the SMT production line experts at Hawker Richardson and see how YsUP can transform your PCB assembly process. IMP Electronics Solutions https://imppc.com.au stand A25 IMP Electronics Solutions is a trusted partner for engineers and manufacturers across Australia and New Zealand, providing high-performance components essential for developing and producing electronics. At Electronex, we’ll be showcasing a range of solutions designed to enhance your designs and streamline your supply chain, including: • Custom battery solutions • LCD screens • Printed circuit boards – standard, flexible & rigid-flex • Membrane switches • Decals and labels • Cable assemblies and wiring harnesses • Plastic injection moulded components • Precision metal components The DT050CTFT-IPS-SHB and -SHB-PTS are 5-inch colour IPS LCD modules with a wide form factor. Each comprises an LCD panel, display drivers, FPC display cable with RGB & SPI interface, and adjustable LED backlight unit. The display’s active area has a resolution of 800 × 480 pixels. The -PTS version is equipped with an additional capacitive touch panel. The DT035CTFT-IPS-SHB and -SHB-PTS are 3.5-inch colour IPS LCD modules with a wide form factor and a resolution of 320 × 480 pixels. Raystar’s range of e-paper displays (EPDs) provides energy-­ efficient, high-contrast, and ultra-wide viewing angle displays tailored for applications like electronic shelf labels (ESL), portable devices and more. Six models are available, from 1.54 inches to 2.9 inches, with low power consumption and crisp, high-­quality visuals. There are options for black, white, red, and yellow colour displays. Our EPD solutions cater to diverse require ments in fields such as smart retail, industrial control, and more. Australia's electronics magazine May 2025  41 Masters & Young www.masters-young.com.au stand C30 Our 150th RAPTR unit hits the ground running with Boeing Defence Australia! The RAPTR unit is set to revolutionise tactical operations and communications, pushing the boundaries of what’s possible in land force capabilities. In close collaboration with Boeing’s engineering team, Masters & Young has played a pivotal role in the production, assembly, and delivery of the RAPTR unit. We’re on track to fulfil our pledge of 400 units before the end of the financial year, demonstrating our unwavering dedication to precision, quality, and timely delivery in support of Boeing Defence Australia for Land 2072 Phase 2B commitments. If you’d like to learn more about how we’re shaping the future of defence technology, please contact us at info<at>­mastersyoung.com.au or visit our website www.masters-young.com. au to explore our cutting-edge solutions! Microchip Technology Inc www.microchip.com stand B19 As embedded systems continue to evolve, real-time and compute-­intensive applications, such as smart embedded vision and machine learning, demand more power efficiency, hardware-level security and high reliability at the edge. The new 64-bit PIC64 family addresses these requirements, offering a robust solution for various markets, from commercial to space applications. The PIC64-GX MPU family stands out with several key features designed to enhance performance and security: • Advanced processing capabilities – PIC64-GX MPUs feature a 64-bit RISC-V quad-core processor with Asymmetric Multi-Processing (AMP), capable of running Linux, a real-time OS and bare metal in a single processor cluster. This makes it ideal for mid-range intelligent edge computing needs. • High security and reliability including Athena F5200 TeraFire Crypto Processor; Cryptography Research Incorporated (CRI)-patented differential power analysis (DPA) protection; integrated dual Physically Unclonable Function (PUF), 56kiB of secure, non-volatile memory; built-in tamper detectors; and digest integrity check for sNVM and eNVM. • Wide range of applications 42 Silicon Chip – these MPUs are designed to serve industrial, automotive, communications, IoT, aerospace and defence segments, making them versatile for high-demand applications. • Support for multiple operating systems – the PIC64-GX family supports a wide range of operating systems, build systems and drivers/middleware, and is backed by both opensource and commercial tools. Our launch also includes the PIC64-HPSC (High-­Performance Spaceflight Computing) family, aimed at aerospace and defence applications. These space-grade, 64-bit multi-core RISC-V MPUs are designed to deliver over 100 times the computing performance of previous models while maintaining high levels of radiation and fault tolerance. For more information, visit siliconchip.au/link/ac57 and see the PIC64GX1000 data sheet at siliconchip.au/link/ac58 The configurable logic block (CLB) is a reconfigurable digital logic module, similar to a CPLD, that is integrated into the microcontroller (MCU) and performs hardware-based digital logic independent of the CPU. This results in fast and predictable response times for a diverse range of applications, including automotive and industrial. The CLB enables much larger hardware-based digital logic designs than previously possible on an MCU and is also capable of operating in sleep mode, allowing complex processing to occur with very low power consumption. The CLB can have up to 32 basic logic elements, including: • AND/OR/NAND/NOR gates • Buffer/inverting buffer • D flip-flop • JK flip-flop • Multiplexers • 4-input LUT Additional features include: • Dynamic configuration for on-the-fly logic changes • Tri-state logic • Input and output from software, I/O pins, and other PIC peripherals, such as an ADC, PWM, DAC and more • Less than 6ns Basic Logic Element (BLE) propagation delay at 5.5V (typical) • 20μA draw per BLE at 1.8V/1MHz (typical) For additional details, visit siliconchip.au/link/ac59 Nagarro www.nagarro.com stand B11 Nagarro is a full-service global digital engineering and consulting leader. We help our clients become human-centric, digital-­ first organisations, augmenting their ability to be responsive, efficient, intimate, creative and sustainable. Caring guides us as a global company. We have a long-standing international customer base, primarily in Europe and North America. This includes many global blue-chip companies, leading Independent Software Vendors (ISVs), market and industry leaders and public sector clients. At Nagarro, around 18,000 experts across 37 countries are helping our partners succeed today. Nagarro’s experience across industries allows us to create tailored, eco-friendly embedded systems. We serve multiple domains like automotive, life sciences, loT, I&A and many more. We can help with product strategy, quality assurance, product engineering, legacy support and modernisation. Our expertise is in Embedded C/C++, operating systems and drivers, hardware and firmware design and production & certifications. Australia's electronics magazine siliconchip.com.au siliconchip.com.au Australia's electronics magazine May 2025  43 NextPCB www.nextpcb.com/dfm stand B2 NextPCB is a subsidiary of Shenzhen Huaqiu Electronics Co Ltd, founded in 2011. Shenzhen Huaqiu (HQ) Electronics Co Ltd is the world’s leading industrial digital manufacturing platform for PCB manufacture, PCB assembly, component distribution and electronics design verification tools. Diligent PCB layout engineers will have Design Rule Checks (DRC) included in their workflows, but this alone is not enough to ensure manufacturability or catch costly mistakes. Commercial design for manufacture (DFM) and design for assembly (DFA) programs exist that cover manufacturability; however, they often can only be afforded by larger organisations. HQDFM by NextPCB is a free PCB design analysis program for DFM and DFA analysis of PCB production files. Developed using over a decade of in-house PCB manufacturing and assembly experience, HQDFM identifies real manufacturing and assembly problems and provides actionable insights to streamline production, improve reliability and reduce unnecessary costs. Its features are: • It checks for over 150 potential problems across 30+ DFM/ DFA categories. • Advanced footprint checker covering 6 million components and counting. • Tools covering manufacture and design such as panelisation, bulk impedance calculator, BOM checker and more. • An online Gerber Viewer version with the option to download a DFM report is also available. NPA Pty Ltd www.npa.com.au stand A29 Ensure the stability and safety of your PCB assemblies with NPA’s Teardrop Natural Nylon PCB Supports. Designed for durability and precision, these flame-resistant supports provide a secure and sturdy fit with a teardrop head, while the flat end allows for proper spacing and controlled mobility. Manufactured from high-quality UL 94V-0 rated Nylon, they offer exceptional strength, lightweight performance and consistent dimensional accuracy thanks to their one-piece moulded construction. NPA stocks a vast range of spacers and stand-offs, including cylindrical, hexagonal, threaded, swage, SMT, adhesive, slimline, snap lock and many more. These come in a variety of materials including Nylon, special Nylon blends, PVC, polyethylene, various metals and ceramics. With hundreds of high-quality PCB spacers, supports, and standoffs locally stocked, NPA ensures fast delivery – most orders arrive by the next business day. Need help finding the perfect component? NPA’s expert product specialists are ready to assist – simply give them a call to navigate the extensive range of options and find the ideal solution for your project. ONBoard Solutions Pty Ltd www.onboardsolutions.com stand C23 ONBoard Solutions is an ISO 9001 credited supplier of production equipment for manufacturing, cleanroom products and 44 Silicon Chip advanced materials to the Australia/New Zealand market. We provide ongoing support in the selection and subsequent use of our products to ensure products are used correctly in your applications. AB Chimie SND Cleaning and De-Fluxing Solvent is a fast-drying cleaning solvent offering excellent removal of grease, oil, flux residue, and acrylic conformal coating from PCBs. This ozone-friendly solvent delivers superior performance, making it a great tool for your cleaning needs. Want to test AB Chimie SND Cleaning and De-Fluxing Solvent? Visit ONBoard Solutions → at Electronex with your dirty circuit board for a free sample! HumiSeal 1B59 SEC is a synthetic rubber-based conformal coating designed to enhance sharp edge coverage while providing superior moisture and environmental protection. This latest formulation optimises edge retention, ensuring uniform thickness across complex geometries. Epoxy Technology Hybrid 353ND is an advanced UV- and heat-curable hybrid epoxy that delivers outstanding adhesion and mechanical performance. Ideal for bonding, sealing, and coating applications in electronic assembly, this hybrid epoxy offers exceptional flexibility and strength. It is a single-component, high-temperature hybrid epoxy for semiconductor, and fibre optic applications, designed to have similar cured performance to EPO-TEK 353ND, modified to allow for initial UV tacking. The BDTronic Mini Dis is a state-of-the-art micro dispensing device engineered for high-precision fluid applications. Designed to meet the demands of modern manufacturing, it offers ultra-accurate control for dispensing adhesives, sealants, and conductive materials. The MBTech N29 Automatic Stencil Cleaning Machine is a fully automated system designed for efficient and thorough cleaning of SMT stencils and misprinted circuit boards. Featuring advanced cleaning technology, it ensures superior contamination removal while minimising solvent usage. 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 are fed manually by the operator, but the bonds are produced without operator influence, using pattern recognition. Single bonds can be made within seconds, making the machine perfect for research and development, pilot manufacturing and middle-volume production. The Viscom iS6059 3D AOI PCB Inspection Plus is a high-­performance automated optical inspection (AOI) system designed for precise and highspeed PCB quality control. It Australia's electronics magazine R&S®ZNB3000 Vector Network Analyzer FAST FORWARD TO RESULTS The R&S®ZNB3000 is the instrument you need for RF component production. This latest addition to the Rohde & Schwarz network analyzer portfolio offers best-in-class RF performance, combining high measurement accuracy with exceptional speed. With its high throughput rate, it is especially suitable for high-volume production and short ramp-up time environments. For more information visit: www.rohde-schwarz.com/solution/ZNB3000 siliconchip.com.au Australia's electronics magazine May 2025  45 combines advanced 3D imaging, AI-driven defect detection and seamless SMT line integration, making it ideal for zero-defect production environments. It is ideal for automotive, aerospace, medical devices, and industrial electronics, where precision and compliance with IPC standards are critical. PCBWay www.pcbway.com stand D11 At PCBWay, we are dedicated to providing a comprehensive range of PCB manufacturing services tailored to meet the diverse needs of our customers. With years of industry experience, we specialise in high-quality PCB prototyping, assembly and custom services. Our key offerings include: • Standard PCB Manufacturing: high-quality printed circuit boards with specifications to suit your design requirements. • PCB Assembly: full-service assembly, including surface mount technology (SMT) and through-hole assembly. • Flexible PCB: solutions for applications where space and weight are critical, offering durability and versatility. • Advanced Testing Services: comprehensive testing solutions to ensure the reliability and performance of your PCBs. • CNC Machining and 3D Printing: advanced services for precise fabrication and custom designs. We are excited to showcase our latest offering, the multi-­ colour PCB Printing Service, designed to meet the growing demand for aesthetically pleasing circuit boards. • Advanced UV Printing Technology: our UV-curable inks produce stunning images on various materials, including fibreglass, metal, ceramic, flexible, and rigid-flex boards, ensuring durability and resistance to fading. • High Precision and Customisation: utilising industrial-­ grade UV printers, we deliver exquisite, tailored results that accommodate intricate designs and bold graphics in a wide range of styles and colours. • Instant Drying for Enhanced Efficiency: our UV-LED lamp curing process allows for quick production without compromising quality. • Environmentally Friendly: our UV printing process is free of volatile organic compounds, promoting a safer and healthier environment for our team and clients. Phoenix Contact www.phoenixcontact.com/en-au/ stand B24 With our innovative products and solutions, we are paving the way to a climate-neutral and sustainable world. Phoenix Contact develops innovative products for electrical connection and automation technology. Our GameChangers will bring your applications to the next level of success. Connect cables easily and flexibly with our installation connectors. Depending on the application, choose between simple cable connections, convenient power distribution, or compact 46 Silicon Chip device connections. Robust housings and high degrees of protection up to IP69K enable reliable power transmission outdoors and in wet environments. Push-in connection technology enables the direct and toolfree contacting of conductors from 0.25mm2. The special contact spring enables low insertion forces, high conductor pullout forces, and impresses with its high contact quality. Industrial connectors from the HEAVYCON complete series protect your interfaces and ensure the reliable transmission of power, data, and signals even under the harshest conditions. The industrial connectors are resistant to dirt, water, vibrations, and high levels of mechanical strain. The heavy-duty connectors have a seal rating of up to IP69K. With innovative technologies like SFB (Selective Fuse Breaking) Technology, ACB (Auto Current Balancing) Technology, and IQ Technology, our power supply solutions ensure superior system availability. More compact than ever before. The limited space of your devices makes the performance of our GameChangers even more convincing. Extract more speed, flexibility, functional density, and safety from every millimeter. More powerful than ever before. No matter how high the requirements are, our GameChangers provide full power for the most demanding applications. Increase your power with superior technology. QualiEco Circuits Pty Ltd www.qualiecocircuits.com.au stand A11 QualiEco Circuits is now embarking on its 22nd year of operation with great enthusiasm and momentum. Since 2003, we have been delivering 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 (since 2023) Canada – are backed by ISO9001:2015 and ISO 13485:2016 (for medical devices) certifications, ensuring the highest standards of quality and reliability. Our customers have been enjoying excellent quality, low prices and on-time delivery for years. Fast, semi-fast and standard delivery options are available to suit your budget and urgency. 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 on the company’s website: www.qualiecocircuits.co.nz/publications.htm Please visit us at stand A11. We would love to talk to you! Rapid-Tech https://rapid-tech.com.au stand C1 The UNI-T MSO7000X-series is a new mixed-signal oscilloscope with a bandwidth up to 2GHz and sampling rate up to Australia's electronics magazine siliconchip.com.au siliconchip.com.au Australia's electronics magazine May 2025  47 10GSa/s. Its unique UltraAcq technology provides a capture rate up to 800,000wfms/s, with advanced measurement and analysis functions. The 15.6-inch high-definition capacitive touchscreen supports multi-window split-screen display and multi-gesture touch control. For wireless applications, the recently released UTS5000A-­ series of spectrum and/or signal analysers with frequency coverage up to 26.5GHz offers numerous standard features plus EMI, Vector Signal and I/Q analysis options that complement the existing UTS1000B and UTS3000A models. The new USG3000M and USG5000M RF signal generators offer exciting features and value up to 6.5GHz and 22GHz, respectively. Keysight Technologies expands its portfolio with two new analog signal generators in the AP5000 family. These tools are essential for producing RF test signals during design, installation and maintenance. Keysight Technologies recently introduced the InfiniiVision HD3-series of native 14-bit, 200MHz to 1GHz oscilloscopes. Software licensing provides immediate bandwidth, memory and feature upgrades, enabling users to purchase options they need now and upgrade as their designs evolve. The PathWave Advanced Power Application Suite (PW9254A) from Keysight Technologies is a software platform for accelerating battery testing and design. The platform consolidates PathWave’s IV Curve Measurement software, Advanced Power Control and Analysis, as well as Advanced Battery Test and Emulation into a single comprehensive test environment. The CNT-104R is the third instrument in its series, supporting parallel and independent time and/or frequency measurements in a bench-top format. It inherits all key capabilities from the CNT-104S, including simultaneous and gap-free measurements of frequency, period, time interval error, pulse width, rise and fall time, slew rate and voltage measurements. New in the CNT-104R is a built-in Rubidium atomic clock and an optional GNSS receiver for disciplining it, eliminating all frequency drift. The standard input frequency range is up 48 Silicon Chip to 400MHz and an optional RF input extends bandwidth up to 24GHz. Pendulum’s FTR-210R GNSS-disciplined rubidium frequency and time reference provides Cesium-type stability thanks to GNSS based disciplining. Its optional integrated frequency calibrator guarantees true traceability to NIST & GPS-time scale and is the innovation which sets the unit apart from any other frequency reference available today. The FTR-210R also provides traceable calibration data available for reporting purposes. Rohde & Schwarz www.rohde-schwarz.com stand C16 We are thrilled to announce the launch of the R&S ZNB3000, the latest addition to our network analyser portfolio. With over 70 years of expertise in vector network analysis, Rohde & Schwarz continues to push the boundaries of technology. The R&S ZNB3000 vector network analyser sets the standard for speed, precision and versatility in RF testing. With industry-­ leading dynamic range, fast measurement speeds and scalable upgrades, it can tackle your most demanding applications. Fast forward to results with the ZNB3000 – the instrument you need for RF component production. Its features include: • Maximised throughput with extremely fast measurement cycles for reduced testing costs and faster time to market. • Flexible upgrades to support fast scale-up requirements. • Highest dynamic range in class combined with exceptionally low trace noise. • Highest output power in class. • Future-ready performance with support for next-­generation technologies, such as 6G. Discover how the R&S ZNB3000 can transform your test and verification processes. For more information, visit our website to learn more and stay tuned for updates. ROLEC OKW www.okw.com.au stand A26 METCASE has new TECHNOMET-CONTROL aluminium enclosures for electronic control systems, panel PCs and HMI electronics. They are designed for mounting on standard VESA brackets/arms, walls, machines and round poles. This series is ideal for indoor applications such as industrial machine control, factory processing, security systems, test and measurement, point-of-sale, IoT and detection equipment. It is suitable specifically for Siemens TP displays (sizes KTP400 to TP1200), but can also house touchscreens and displays by other manufacturers, including Beckhoff and B&R. These cases is available in four sizes from 230 × 180mm to 420 × 300mm, with a slim profile that is just 95mm deep. Custom colours are available on request. ...continued on page 57 Australia's electronics magazine siliconchip.com.au Mega May SALE altronics.com.au Includes travel adapters 99 BONUS! 129 $ T 1345 Ultra High Speed Mini Jet Blower Vac T1346 FREE vacuum accessory valued at $14.95 High speed jet fan with up to 1.5 hours use per charge. USB C rechargeable. All metal design. If you use a few cans of air duster a year, it pays for itself in no time! Open Ear BT Earphones 100W USB PD Charger Hub A0319A 20W 10000mAH Introducing our new global travel power banks. Available in either 20W or 65W power delivery with in-built mag safe compatible wireless charging they come with travel adaptors for travel all over the world. All supplied in a handy zip up case. Save $$$ chasing car issues! This handy analyser suits OBDII equipped vehicles (most brands post 2005). Detects general and vehicle specific codes and provides diagnostics. Also tests battery charging & cranking. C 9038A 69 30 $ A 0329 Great travel accessory! M 8865 SAVE $26 99 $ D 2364 USB-C Multi Port Hub 4 x USB 3.0 type A ports, USB C port, 2 x HDMI ports, SD/microSD card slot, 3.5mm out, ethernet and VGA. SAVE 25% 40 Never change batteries again! Kinetic action with wireless chime unit. 58 ring tones. 150m range. 50 85 $ X 0226 Battery Free Door Bell $ SAVE $14 Compact and USB rechargeable! Standard torch PLUS 5W LED flood light in one convenient folding design. SAVE 24% SAVE $9.95 X 6017 A light for camping, fishing, anything! $ This handy hub turns a single USB type C PD port into 5 x 20W charging ports! A0323 65W 15000mAH Recharge anywhere you go! SAVE $30 Latest design in over ear wireless stereo (OWS) headphones - drivers sit on your ear rather than in your ear canal for all day comfort. Includes charging case for up to 8 hours use per charge. $ Powerful OBDII Car Analyser BACK IN STOCK! This high power rechargeable fan/ vacuum is great for servicing computer equipment, cleaning keyboards - even inflating air mattresses for camping. 159 $ Tech savings across the range. Only until May 31st. 2 for $ Stay charged. Stay on time! A stylish bedside alarm clock with 15W wireless charging for your phone & FM radio. Display also shows calendar & temperature. SAVE 10% 49 $ D 2321 Your electronics supplier since 1976. Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Sale ends May 31st 2025. siliconchip.com.au Australia's electronics magazine Build It Yourself Electronics Centre® May 2025  49 Power it up. 140W USB Car Charger NEW! Power up all your devices while on the camping or just on the open road! Provides 140W USB C Power Delivery (PD3.0/3.1). In addition it also features a secondary 20W USB-C PD port for charging phones, watches etc. Fitted with a 2m cable allowing you to run it from your battery into your tent or camper. SAVE $30 149 $ 129 $ M 8867 M 8196 Getaway Power Generator & Light With powerful LED lantern, torch & emergency dynamo! This compact portable charging solution keeps your devices powered up. 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Huge 30W PD output from a tiny car charger! QC3.0 plus USB type C power delivery. SAVE 40% 19.95 $ M 8632A Like our service? Review your store on Google. Every review helps us serve you better. Australia's electronics magazine siliconchip.com.au Solar savers. N 1114A 100W SAVE $104 245 Solar Panels for DIY remote & mobile power projects. $ N 1117A 200W Sourced from one of the worlds leading solar manufacturers. Aluminium frames, waterproof junctions, tempered glass panels. 25 year output warranty. 5 year workmanship warranty. SAVE $204 445 $ Note: Online orders or click and collect only. Heavy Duty Solar Blankets Premium quality solar charging for your remote power system. Provide portable charging power for your campsite set up. Double stitched panels, durable webbing straps and metal hanging loops and zippered cable pocket. 200W version has folding legs which allow the panel to be used freestanding. Folds up and secures with velcro for a fast getaway! 5m Anderson cable connection. 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SAVE $20 SAVE 26% 8 $ SAVE 24% 15 H 1782 M6 H 1783 M8 $ P 8064 Grey P 8057 Black /pr SAE Battery Posts Screw in for M6 or M8 battery terminals. Sealed Cable Entry Points Provides a weatherproof cable entry for your caravan or camper. SCAN TO FOLLOW US! Stay up to date on latest releases, exclusive specials and news on our socials. siliconchip.com.au 99 SAVE $40 159 $ $ M 8534B 4.5A M 8536B 10A Suits lead acid, AGM & LiFePO4 batteries 6V/12V Battery Chargers & Maintainers Utilises a microprocessor to ensure your battery is maintained in tip-top condition whenever you need it. Helps to extend battery service life. Suitable for permanent connection for battery maintenance. Great for caravans & seldom used vehicles. Weather resistant IP65 casing. Like our service? Review your store on Google. Every review helps us serve you better. Australia's electronics magazine May 2025  51 C 5162 SAVE $59 220 $ Audio Visual. 14” Go-Anywhere Portable Digital TV C 5161 SAVE $40 SAVE $60 229 Perfect for the car or caravan! Powered off internal rechargeable battery, your vehicle battery or mains plugpack. Also fitted with USB connection for recording TV. 149 $ $ With internal battery - use it anywhere! S 8864A Why pay $300 or more? SAVE $35 145 $ Boom Box & Wireless PA Systems Need instant sound for your next big get together? Pick up a new Bluetooth entertainer box - available in small or large systems. They not only sound great, but offer a wireless micro phone for PA use, plus TWS pairing to a second unit (of the same type) for added volume. Offers up to 3-8 hours use from a single charge (depending on volume). H 8126C A 2696A SAVE $40 349 $ Internet radio, digital radio & audio streaming in one. Wi-Fi Internet Radio System with DAB+, FM & Bluetooth. A stylish, easy to use receiver with access to over 26,000 global internet stations, plus DAB+ digital radio, FM frequencies and bluetooth streaming from your devices. Digital S/PDIF and analogue RCA outputs. 299 $ Cantilever Arm TV Bracket Silky smooth cantilever adjustment, stays just where you want it to. It even has 15° of tilt adjustment. Engineered for flat screens up to 90” using 800 x 400mm VESA. Max weight, 60kg. SAVE $70 A 4860 2x50W Stereo Bluetooth Amplifier A compact bluetooth stereo amplifier for home and commercial sound systems. Features a high spec Class-D 2x50W RMS amplifier and optical input for connection to digital audio sources. Pairs well with the A4861 200W subwoofer amplifier ($520). SAVE $50 SAVE $40 249 $ SAVE $60 99 $ 89 $ A 2548 A 2651 D 0980 Pro grade condenser mic. Clear, crisp sound HOT DEAL! 4 Ch. USB Mixer With EQ & FX 6 Ch. Mixer With USB Audio Player Want to get into recording podcasts, voice overs or making your own audio samples? This mini USB mixer connects directly to your PC or Mac and is powered directly from USB. A great small venue audio mixer! Featuring USB/SD card playback with easy to use controls. All channels feature balanced XLR, unbalanced 6.35mm, insert inputs, high/mid/low adjustment, pan & gain level. Premium USB Desktop Mic A premium finish USB microphone with all metal case and stand. Adds high clarity sound to your desktop for live streams & podcasts. NO STRESS 30 DAY RETURNS! GOT A QUESTION? Not satisfied or not suitable? No worries! Return it in original condition within 30 days and get a refund. Ask us! Email us any time at: customerservice<at>altronics.com.au Conditions apply - see website. 52 Silicon Chip Australia's electronics magazine siliconchip.com.au 3 preset channels for quick temp selection. T 2460A Tools & more. SAVE 20% 50 $ High Power Blow Torch T 2168A SAVE $120 Features 1/4” and 4mm drive handles 319 $ Micron® Touchscreen Soldering Station A sturdy 100W benchtop soldering station featuring an all aluminium case and 2.8” touchscreen for quick temperature and preset selection. 100-500°C temp range with slimline handle featuring burn resistant cable. ESD safe design. Fast heat up and recovery. Works with SMD tweezer handle T 2461A ($219). 69 Pc Dual Ratchet Driver Kit Superb quality ratchet driver with a wide selection of bits for most electronic jobs. Includes both a 1/4” adjustable angle (<90°) ratchet handle and a smaller 4mm ratchet handle. Great for the home handyman or enthusiast. SAVE $40 NEW! 129 $ Trade quality! Super hot 1350°C flame! Handheld or self standing design for heatshrinking, model making, silver soldering! Easily refilled. All aluminium design. SAVE $17 66 Add gas for $9.50 (T 2451) $ T 2494 99 $ Q 1058 X 0109 SAVE $30 Great for cleaning jewellery & more!! 99 $ Packed with features! Clean & rejuvenate tiny parts Uses water, detergent and ultrasonic waves to remove gunk from small parts, spectacles, jewellery, DVDs, even 3D prints! No solvents required. Stainless steel 18x8x6cm water tank. Folding Auto Ranging Multimeter Provides in depth functionality for technicians. Folding design stays put on any surface while testing, making it great for auto electrical work. Q 1089 SAVE 12% 69 $ T 2130 This Jakemy® electronic screwdriver set is great for device repairs and other maintenance tasks. Driver offers three-speed torque options with automatic power save mode. Unique folding case houses all 180 bits and accessories. NEW! Autoranging True RMS Digital Multimeter Push button design simplifies operation and test jack indicators ensure you never plug a cable in wrong! With frequency & temperature ranges, plus in-built torch! 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A handy 40cm sensor light with in-built USB rechargeable battery. Great for wardrobes. 30s on time. Detaches for recharging. X 2384 22 $ X 2386 4W 500 Lumen X 2387 7W 800 Lumen LED Solar Sensor Lights Add instant security to your place with these weather resistant solar lights! Shed some light on pathways, driveways, gardens and patios. Require no wiring and are IP54 rated for use outdoors - plus stainless steel rust resistant hardware. 3 dusk activated lighting modes. Great night light for kids! 39.95 $ Lights up to 80sq/m with this powerful multi panel 600 lumen LED light which requires no wiring and is powered by the sun! IP65 rated. 30 $ SAVE $10 Super Bright Cable Free Solar Security Light SAVE 24% X 2396 X 2388 SAVE 17% SAVE 26% 2 for $ 2 for $ 66 X 0213 SAVE $9.95 40 $ 25 X 2390 X 2385 39 $ SAVE 26% SAVE 18% SAVE 30% Wall Mountable 2 for $ 2 for $ 22 44 6W Solar Outdoor Light This powerful solar light needs no wiring. Ground spike or wall mount. Flood/spot modes. 6-7hr run time. IP67 rated. Handy 3 in 1 Torch & USB Battery Bank X 2389 X 2391 Caravan Oyster Lights Weather resistant 12V input LED lights. Pure white 5500K. X2390: 180mm. X2391: 125mm with switch. Outdoor Solar Lights Ideal for camping, roadside emergencies and a variety of uses around the home. It can be used as an LED lantern, torch, emergency light and USB battery bank for keeping devices charged when camping. 4800mAh internal battery. Provides low level lighting for steps, paths and decks. Turns on automatically at night. X2388: 109Øx22mm. X2389: 100x88x50mm. 20% OFF Neon Flex Rope Lighting. Use it in long lengths for stunning coloured lighting effects or cut and shape into your own custom “neon” signs. Super flex design for tight radius bends, IP65 weather resistant. See web for full range and pricing. SAVE 24% SAVE 15% 15 25 $ X 0203 $ X 0204 X 3229 X 0212A SAVE 15% SAVE 20% 2 for $ 33 USB Dual LED Head Torch Weather resistant, USB rechargeable, & 120 lumens for JUST $15! Why pay $50 or more? 29 $ Wardrobe Sensor Light Kit Aluminium USB Torch Genlamp® Pro Head Torch At less than $20 you can afford to put these 4xAAA battery powered sensor lights in every cupboard! 1m length. Durable all metal 5 Watt USB rechargeable torch. Can be used as an emergency power battery bank. 182mm long. A camping essential! 280 lumen spot + 220 lumen flood beam. USB C recharging. SCAN TO FOLLOW US! Stay up to date on latest releases, exclusive specials and news on our socials. 54 Silicon Chip Like our service? Review your store on Google. Every review helps us serve you better. Australia's electronics magazine siliconchip.com.au Maker parts. Z 6240A UNO R4 30 SAVE $20 $ 99 $ Top seller! Z 6315A SAVE 24% Includes UNO R3 25 $ Z 6385A ESP32 Wi-Fi & Bluetooth Board 165 Piece Arduino Parts Pack Includes a huge selection of sensor boards, LEDs, pots, jumper wires, a breadboard, LCD screen and much more! Plus a UNO R3 compatible board to get you designing fast. A handy storage case keeps it neat when you’re finished. ZW6240A UNO R4 WiFi 49.95 $ New UNO R4 Compatible Boards A development board integrating 802.11b/g/n WiFi, Bluetooth 4.2 and BLE. Fully Arduino compatible and perfect for wireless projects. Get designing on the latest UNO R4 compatible development boards - same form factor as earlier Arduinos for maximum shield compatibility, but with expanded memory and faster clock speed. Z 6497 Z 6317 NEW! 19.95 $ Temperature & Humidity Controller A 2 channel board which activates a connected load at preset temperature (-20 to 60°C) or humidity (0-100%). Runs off 12V DC with 10A relay outputs. Z 6319 NEW! NEW! 29.95 $ .95 9 $ Digital Temperature Controller The STC-1000 controller is a 12V DC heating/ cooling controller allowing you to activate or deactivate loads up to 10A. Includes 1m sensor. Precision Temperature Controller 12V input with single 10A relay for on/off control. Waterproof sensor with -30 to +110°C range and 0.1°C accuracy. In-built 3 digit display. SAVE 22% 14 $ Z 6494 Z 6316 NEW! 27.95 $ Z 6489 NEW! 19.95 $ Bluetooth Relay Board 60W Digital Power Amp Dual 12V 10A relay and control board with the ability to switch on and off loads using eWeLink app on your phone. A high-performance audio amplifier designed for applications requiring compact size, low resistance, and high power output. TPA3118 chip. Z 6427 Wi-Fi ESP8266 Relay Module A handy Wi-Fi activated 3A relay module for wireless switching applications. 3.3V input. Z 6334 NEW! SAVE 24% 9 $ ea 6 $ .95 Turn a USB charger into a power supply. Allows you to connect to a USB PD power supply and output 5, 9, 12, 15 or 20 Volts. DC-DC Buck Module Generate a lower voltage output from a higher supply. 3-40V DC in, 1.5-35V DC out. 3A max. NO STRESS 30 DAY RETURNS! GOT A QUESTION? Not satisfied or not suitable? No worries! Return it in original condition within 30 days and get a refund. Ask us! Email us any time at: customerservice<at>altronics.com.au Conditions apply - see website. siliconchip.com.au Australia's electronics magazine May 2025  55 Clearance Buys. Soundbar Wireless Subwoofer X 7063 SAVE $80 199 $ LIVE & LOCAL WEATHER. Wireless Weather Monitoring Station. With outdoor sensors & smartphone app! Our premium finish soundbar offers rich, clear sound from it’s 6 high performance sound bar drivers, plus a 8” subwoofer which has wireless connectivity. It even offers Bluetooth audio streaming from your favourite devices, plus S/PDIF digital audio input for connection to your TV (cable included). SAVE $190 199 $ C 5059 This fantastic weather station displays your local weather data - great for boaties & gardeners. Bright & clear base station provides readings for indoor/outdoor temperature, humidity, air pressure, rainfall, wind speed and direction. Plus handy weather trends. You can even connect it to wi-fi for monitoring readings & data with your phone. 100m sensor range. Iroda® Solderpro 180 Portable Gas Tool SAVE $66 99 $ 185W of power for both blow torch and soldering work. Powered by refillable butane cartridges (2 included). Provides 500°C soldering & 1300°C blow torch. Kit includes tips, solder sucker, flux, cutters & solder. 4K video or 30MP still shot resolution. 249 $ SAVE $50 109 $ Great for monitoring in remote locations, temporary CCTV monitoring etc. Solar panel & internal battery makes it quick & easy to set up. Weatherproof case with LCD screen. Requires SD card, DA0330A 64GB $27. 169 SAVE 20% 40 $ Need an extra laptop charger? Answer the door when you’re not home! 4K video surveillance anywhere you need it! SAVE $40 $ S 9445 SAVE $100 T 2651 Tool Kit T 2650 Iron Only. S 9455A M 8868A This 65W USB-C power delivery (PD) charger offers recharging for MacBooks, Nintendo Switch and other type C equipped devices. Record anywhere! D2324* Record videos anywhere with this handy flexible tripod for phones, GoPro cameras and small cameras. $ SAVE 22% 25 D 2358B SAVE $30 25 D 2212* SAVE 20% 69 27.95 $ $ P 0696A SAVE 28% $ This stylish doorbell connects to your wi-fi and notifies your mobile phone when a person arrives at your doorstep. Great for telling the postie where to put packages. Security camera mode. Motion detect notification. See messages while you charge. 15W charging. Requires QC3.0 USB wall charger. USB C Multi Hub Provides HDMI (4K <at> 30Hz), wired ethernet, plus three USB 3.0 ports, SD/Micro SD and 60W power pass. USB 18W PD Socket & Voltmeter Includes QC3.0 3A output, plus 18W USB C PD. 29mm mounting. Sale Ends May 31st 2025 Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or find a local reseller at: altronics.com.au/storelocations/dealers/ 56 Silicon Chip Shop online 24/7 <at> altronics.com.au Australia's electronics magazine B 0005 siliconchip.com.au © Altronics 2025. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. METCASE’s premium TECHNOMET desktop instrument enclosures can be specified without a handle, or with recessed side handles or a tilt/swivel carry handlebar. The handle options makes these enclosures readily portable. Applications include medical/wellness, test and measurement equipment, industrial control, peripheral devices and interfaces, switchboxes, communications and laboratory equipment. The range is available in 11 sizes from 225 × 200 × 75mm to 350 × 320 × 150mm, including three versions with a sloping front bezel. The CARRYTEC enclosure features a functional handle and large surfaces ideal for user interfaces, making it perfect for quickly aligning and positioning displays and operating surfaces, as well as ensuring clean cable routing. The slightly smaller INTERFACE-TERMINAL stands out as a multifunctional electronics enclosure with numerous design options, a wide range of accessories, and optional IP54 protection. For added robustness, the SMART-TERMINAL aluminium profile enclosure, with its recessed control panel for installing and protecting displays, membrane keypads, and control elements, is also an excellent choice. OKW’s product portfolio includes a large number of plastic enclosures up to IP67, with impact protection up to IK08. They are suitable for a wide variety of applications, including HVAC, machine and plant engineering, measurement and control technology, electrical installation, agriculture or factory use. Shanghai Jingying Electronic www.sh-jycrystal.com/en stand C18 Shanghai Jingying Electronic Co Ltd (JY), established in 2000, is a professional quartz crystal based frequency control & timing component and oscillator device manufacturer, headquartered in Shanghai, China (see photos below). siliconchip.com.au Our manufacturing facility in Suzhou City has a complete production line for all types of quartz crystal products (kHz and MHz). It is a high-tech plant with advanced test equipment and an output of over 200 million units per year. We offer guaranteed quality, customised production, professional service, competitive cost and short lead times. We supply clients in industries such as consumer electronics, industrial meters, telecom equipment, IoT, computers, clocks and controllers. JY has become one of the largest quartz crystal resonator and oscillator device manufacturers and exporters in China. The OCK-3225 and miniature OCK-2520 32.768kHz oscillators achieve superb stability over a broad range of operating conditions as well as tight tolerance requirements. A tri-state function is available for power saving, and an extended working temperature range is optional. Supply voltage is from 1.8V to 3.3V. The seam-sealed ceramic surface-mount package assures reliability and ease of use. RTC-3225 is a standard real-time clock IC module with an I2C interface, built-in 32.768kHz TCXO and low current consumption (<1.0μA), tight frequency tolerance (±2 PPM from -40°C to 85°C) as well as automatic backup power switching. TCM-2520 and miniature TCM-2016 are the standard solution for temperature-compensated oscillators, achieving superb frequency stability over a broad range of operating conditions. The supply voltage is from 1.8V to 3.3V. They also come in a seam-sealed ceramic surface-mount package. Techal Solutions www.techalsolutions.com stand D24 Based in Melbourne, Australia, Techal Solutions specialises in providing state-of-the-art SMT production equipment, assembly automation solutions, as well as spares, consumables, and accessories. We are committed to delivering comprehensive solutions tailored to meet the evolving needs of the electronics manufacturing industry. We supply equipment for: • Surface-mount assembly • Assembly line integration • Automated inspection • X-Ray inspection and testing • Pneumatic and electric screwdrivers • Torque-measuring devices • Automatic screw feeders • Complete assembly automation systems • Air tools and air motors SC • Comprehensive spares and consumables Australia's electronics magazine May 2025  57 PROJECT BY PHIL PROSSER Tool Safety Timer Have you ever accidentally left your soldering iron switched on? This project will help allay your fears. It’s also a great idea for fitting to a hot air rework system or other mains-powered tools. » Switches a mains-powered device off after a period of inactivity » Activity of user movement sensed using a PIR (passive infrared) sensor » Selectable timeout of 10, 20, 30 or 60 minutes » Pushbutton to switch tool back on again after timeout » Indicator LED shows when PIR is picking up motion » Power supply: 12-20V DC, 9-15V AC <at> 200mA maximum with the device handling up to 10A/2.3kW T he hot air gun we use is one of those ubiquitous ones sold under many different brands. These tools are quite low in cost but function surprisingly well. To operate them, you lift the handpiece and the heater and fan start automatically. They run until you place the handpiece back in the cradle, which is sensed by a magnet in the cradle and everything cools down. The hot air gun is often set well in excess of 300°C and is therefore fully capable of igniting combustible material. Unfortunately, this author is really forgetful and often comes back hours later to find the hot air gun ready to go. If, for example, a mischievous cat brushes against it, or a child decides to play with it, the hot air gun may fall from its cradle with nobody around to avert disaster. This has the real potential to set the house on fire, which is the one thing about this tool that we really dislike. It should shut itself down after a period of being idle. On a somewhat less dramatic note, our soldering iron is left on more often than not. The one in our lab does not have an automatic shutdown, and we have found it running at full temperature after many days. This is much less likely to cause a fire, but we have replaced many more tips than necessary (and wasted expensive electricity too). My modified hot air gun. We mounted the PCB to the inside of the lid, a transformer to the base and the sensor and start switch to the side. This has proven to be very effective. Yes, our hot air gun has seen some use. 58 Silicon Chip Australia's electronics magazine This project is to provide a very simple and convenient approach to automatically switching these tools off. You run your tool from a switched mains source with a timer you can set. If you are present and moving the tool around, or moving around yourself, the timer will be reset. If you leave the room, when the timer expires, your tool is switched off. When you come back later, you just need to press a button on the box to restart it. You might be sitting there for an hour or two and the tool might run for this time, but our theory is that if you are present, you would catch any significant hazard. Once you leave, the system will ‘time out’ and protect you and your tools. Our tests have shown that with the sensor on the desk near the user and tool, it will easily detect the user’s hand, and especially a hot soldering iron or hot air gun. We recommended the PIR is pointed in the direction of your tool stand, ideally away from yourself and definitely away from thoroughfares. This way, it can detect when you stop using the tool or when you leave the desk. In practice, this works as long as there is a line-of-sight from the sensor to you or the tool when you place it in its stand. We considered two ways to use the Tool Timer. The first is to mount it in a UB1 ABS plastic case and power it from an external 12V DC plugpack. The second is to embed this in a tool, siliconchip.com.au Fig.1: the circuit is based around microcontroller IC1 and the PIR sensor. When the sensor’s output goes high, meaning it has detected movement, the timer is reset. Once the time period has elapsed, the relay is de-energised, switching off the tool. It can be switched on again by pressing S1. like our hot air gun. We will describe how to package it in the UB1 case in detail. Because we do not know the specifics of your tools, we can’t go into great detail on how to fit it inside a tool. However, we will provide notes and advice on this. If you are not completely confident and comfortable analysing and understanding how your specific tool operates, we recommend you stick to the UB1-packaged version. Circuit details The Tool Timer circuit is shown in Fig.1. Switching of the tool power is via a 10A mains-rated relay. The recommended relay can actually carry and break 16A, which is more than enough. We have heavy tracks on both sides of the PCB so it can handle 10A continuously. The Tool Timer switches the Active line only. Never assume that a device that is disabled by it is isolated from the mains. We use an IEC plug/socket combo for the mains input and output. This has the Earth link integrated. We link Neutral to Neutral directly on this part, siliconchip.com.au and wire the Active input through our PCB to the Active output. It does not matter which pins of CON2 are used as the input and output. For the PIR sensor, we chose the Altronics Z6382A. This can operate from a wide range of voltages, up to 20V DC, and provides a 3.3V logic high level on the middle pin when an object is detected. We have included a test point on the PCB to which you could connect another LED with a series resistor to indicate when an object is being detected by the PIR. This is labelled “PIR”. This PIR signal is fed to the PIC and, if movement is detected before the Tool Timer has switched the load off, it will reset the timer. This means that if you use a soldering iron or heat gun, taking the tool from its holder and replacing it, the PIR will sense this and reset the timer. So it will never time out while you are actively working. The PIC has two jumpers, JP1 and JP2, that allow you to program a timeout period of 10, 20, 30 or 60 minutes. The timer starts when the PIC is powered up, and the relay is switched on while the timer is counting down. Australia's electronics magazine In practice, it won’t expire if you are using the tool; there is even time to get a cup of coffee, even from the shop, if you are using 30 or 60 minute timeout! Once the timer expires, the relay switches off, and will only switch on again if you press the START button on the front panel (S1). That is really all there is to this project. Other uses of the Tool Timer are quite varied. It could be used as a night light that times out after 60 minutes and after people stop moving in the room. Another potential use is as a timer for kitchen equipment, such as coffee makers, toaster ovens etc. You can start the device by pressing the button and it will continue to run while people are around and for a set period thereafter. This will help avoid that burned coffee smell when the pot is left running too long, or that toasty maker sitting there running forever, waiting to burn unsuspecting fingers. Power supply The power supply includes provision to mount a bridge rectifier, which might seem odd. The intent is that if May 2025  59 you are integrating this into an existing piece of equipment, it may be easier to power it from AC. Our heat gun, for example, has 9V AC accessible. With the bridge rectifier, this works just fine. Of course, you can run DC via the bridge rectifier, provided you have at least 12V available for driving the relay. We use an LM317 regulator to generate 3.3V for the PIC, but we operate the PIR from the raw DC. The recommended PIR has its own regulator and can accept 5-20V DC. This same PIR sensor module is widely available from various suppliers on the internet, so it should not be difficult to get. Table 1 – R1 values for a DC supply (BR1 linked out) Table 2 – R1 values for an AC supply (BR1 loaded) Supply R1 value Supply R1 value 12V 0W (wire link) 9V 0W (wire link) 14V 33W ¼W 11V 39W ¼W 16V 68W ½W 13V 82W ½W 18V 100W 1W 15V 150W 1W 20V 150W 1W OU T D4 4148 START CON7 330W PIR 560W REG1 LM317T Q1 BC338 GND A K CON8 LED 4.7kW 4.7kW 4.7kW 4.7kW R1 Tool Timer v12 Nov 2024 60 Silicon Chip CAUTION 230V AC 4.7kW 4148 + PIR CON6 10mF RLY1 250V AC 10A 12V DC COIL 4.7kW CON5 ICSP ~ – + ~ 12-20V DC/AC +3.3V 4.7kW 4.7kW wire links in its place, as shown on the PCB and in Fig.2. In our testing, using a 12V DC plugpack, the relay operates just fine with this bridge in place, but it is not necessary. Double-check that you are inserting it the right way around (pay attention PCB design to the markings on the device and We have added slots in the PCB to the board), as these are really fiddly ensure isolation between the mains to remove from the PCB if installed and low-voltage sections of the board. incorrectly. They will make certain that whatever Follow by fitting the fuse clips (with load you connect won’t cause arcing the retention tabs on the outside) and across the relay tracks. all the capacitors, watching the polarity of the electrolytics. Next, mount the Construction headers and screw terminal. The screw The Tool Timer is built on a double-­ terminal specified is rated to 300V sided board coded 10104251 that mea- AC and 16A. This part has a standard sures 71 × 88mm. Assembly is fairly 5.08mm lead spacing; if you substieasy as all the parts are through-hole tute it, make sure the part is rated for types and the board is not tightly at least 250V AC and the current you packed. Start with the resistors; fit all are switching. the 4.7kW parts, then the others. Next, Now mount the transistor, relay and mount the three 1N4148 diodes, mak- regulator. The relay has a very staning sure they face as shown in the PCB dard footprint and you will find many overlay diagram, Fig.2. options. If you substitute this part, We have specified a W02/W04 (or again you need to pay attention first similar) diode bridge. If you are run- to the voltage and current ratings, as ning this from DC, you could install well as the coil voltage rating. We have wired the relay to JP1 IN, JP2 IN → 10min FIT RED WIRE operate from the input supply. JP1 IN, JP2 OUT → 20min LINKS INSTEAD JP2 JP1 OUT, JP2 IN → 30min If this is a 12V DC plugpack, OF BR1 FOR DC JP1 OUT, JP2 OUT → 60min JP1 we want this to power the F1 1A relay directly. In this case, R1 B R1 is a wire link (ie, 0W). If your W02/W04(M) CON2 DC supply is more than 12V, IC1 TO LOAD + PIC16F15214 we want to drop this back to 12V with a resistor. 470mF This dropper does not need 100nF D3 to be very accurate. If the relay CON1 100nF Power 100nF gets a supply within a volt or COIL 4148 D2 Fig.2: there is nothing terribly difficult about assembling this PCB. We don’t recommend using a socket for IC1, as it could fall out and cause a safety hazard. Watch the orientation of the bridge rectifier, electrolytic capacitors, regulator, diode and IC and note the three safety clearance slots. Australia's electronics magazine two of 12V, it will be OK. Table 1 provides values for R1 if your DC supply us higher than 12V, while Table 2 provides various R1 values for AC supplies. If using an AC supply, it must not exceed 15V. With all the parts aside from the PIC loaded, apply power to your board using a plugpack or bench supply and measure the voltage between pins 1 and 8 of IC1’s pads. The reading should be 3.3V ±0.2V. If this is not right, check that the bridge is in the right way around and that the regulator is mounted correctly. Also check the 330W and 560W resistors and diodes. With the power supply operating OK, disconnect the power supply and fit the PIC. Double-check its orientation before soldering it. If yours is pre-programmed, you can move onto the Packaging section. There is a programming header on the PCB (CON5); this uses the standard Microchip pinout so a SNAP or PIC kit can be plugged straight in. You can download the required firmware from siliconchip. au/Shop/6/1825 Packaging A UB1 Jiffy box is a good match for this board and associated parts. Figs.3 & 4 show the holes and cutouts that are required. Mark and drill the round holes first. We used a stepped drill for the PIR hole. If you have never used one of these, we reckon you should try one – they are awesome for making larger holes in plastic and aluminium. There are a couple of locations where you will need to trim back the PCB guide rails on the inside of the case using a sharp knife or chisel. For the holes in the base for the PCB, a quick cheat is to drop the board into the case and mark through the mounting holes. We wanted the PCB on the opposite side of the box from the PIR to allow room for connectors, and we suggest you do the same. We used an oscillating multi-tool for the rectangular cutout, which made a siliconchip.com.au Figs.3 & 4: just four holes are required in the base – you can use the PCB as a template to mark their positions before drilling. Make the holes as shown here (and in Fig.6 overleaf) to verify how they relate to each other. You can use a multitool or rotary tool to cut the rectangular opening, or drill a series of small holes inside its perimeter and then file it to shape. Fig.5: the label for the Tool Safety Timer is shown here at 50% actual size. You can download it from siliconchip.au/Shop/11/1827 May 2025  61 Fig.6: here is how to run the wiring. While you could solder most of the wires to the PCB, the headers and plugs make it much easier to disassemble it should you need to. Don’t omit the cable ties and make sure the mains wires are correctly rated, the right colours and routed to the appropriate terminals (they are usually marked A, N & E on the connector). somewhat fiddly job easy. So if you have one, crack it out for this part of the job. The recommended case is made of ABS plastic, which is not hard, so you can easily use a small hand saw for this. Make sure this hole starts smaller than needed and file it to the final size. Lastly, you should add a 1.6mm thickness (or more) piece of insulating material like fibreglass between the IEC socket and PCB. The insulation material should be cut to fit the UB1 case (89 × 48mm), and you will need to use a sharp knife to cut a small hole to allow wiring to pass through. Setup and wiring With the box ready, we can now start pulling it all together. Use the wiring diagram, Fig.6, and photo opposite as guides while you read the following steps. Headers JP1 and JP2 set the timeout period to 10, 20, 30 or 60 minutes. We are using jumpers since our experience is that once you settle on a workable period, you don’t need to change it. It is possible to wire these to a switch or switches if you have an application in which this is necessary. Refer to the circuit diagram (Fig.1) to determine whether to place shunts on JP1 and/or JP2 for your preferred timeout and set that up now. We have used a 33W resistor for the relay, as our DC supply is 14V. You need to select the right value for your application. 62 Silicon Chip Australia's electronics magazine Next, complete the wiring to the panel-­ mounting LED, start button, PIR sensor and power input connector. You need these installed in the case and secured with the appropriate washers and nuts before you connect the headers to their connecting wires, as the headers will not fit through the holes in the case. Assuming your DC supply is from a plugpack and you’ll be using a barrel socket, wire it to the board using two 90mm lengths of light-duty hookup wire. We used red and black, with the red wire going to the positive middle pin on our 2.1mm inner diameter barrel socket. For a DC supply, make sure that your positive wire goes to the pin of CON1 marked +. If you don’t have the crimping tool for the plug, you can use a pair of side cutters or needle-­ nose pliers to crimp the wire in. This crimp will not be great, so solder over your temporary crimp, and it will be secure. Just don’t add a lot of solder or you won’t be able to insert the pin into the plastic block. For the PIR, use 70mm of light-duty wire. We used a ribbon cable offcut as this helps keep the wiring tidy. You need to ensure that the headers are wired correctly, ie, the + pin on the siliconchip.com.au PCB goes to the positive supply on the module, the – pin goes to the negative supply and the centre pin goes to the PIR output. For the LED, use two 90mm lengths of light-duty hookup wire or another ribbon cable offcut. You need to make sure you get the anode and cathode to the right pins. The cathode has a chamfer on the side of the LED and a shorter pin (it goes to the pad marked K). For the start button, use another two 90mm lengths of light-duty hookup wire or a ribbon cable offcut. Any colour will do. The button is not polarised, so connect the button to the twoway plug however you want. Testing With the timer set to 10 minutes (JP1 & JP2 in), apply power. Put something over the PIR sensor so it cannot detect your presence; a sheet of paper will do the trick. The LED should light and stay lit for pretty close to 10 minutes, then it should switch off. You should hear the relay switching along with the LED. If the LED stays on permanently, check that you have the PIR covered and that it is not detecting you move around, as it will reset the timer and the LED won’t go off. Also check that the voltages on the PIR are right. You should be able to monitor the PIR output using a DVM on the PCB test point, and see the PIR detecting your hand if you wave it in front of the PIR. If it still isn’t working, check for short circuits on the PCB around the PIC and the PIR header, and verify that the transistor is in the right way around and that you have used an NPN type (BC337 or BC338). Once it has timed out, press the start button. The relay should switch and the LED should come on again for a further 10 minutes. Finally, run the same test with the PIR pointing in your general direction and wait the 10 minutes. Unless you sit statue still, the PIR will sense you and the LED and relay should stay on. Final assembly We can now assemble this lot into the enclosure. Install the standoffs using shakeproof washers and machine screws, then mount the PCB into the enclosure. If you haven’t already, plug the power, start, PIR and LED headers onto the board. siliconchip.com.au The wiring for the Tool Safety Timer in the recommended UB1 enclosure. Use 10A mains-rated wire for the connections to the IEC connector. Now you can zip tie both the PIR and power wires to the PCB using the two holes provided next to the power connectors. Similarly, zip tie the start button and LED wires using the lower set of 3mm holes provided on the PCB. We recommend applying a drop Australia's electronics magazine of Loctite or similar glue to the connectors to secure them to the board. Now install the IEC connector into the enclosure. Ensure it is secure and the mounting snap-in tabs hold it in place. If it is not totally secure, fix that before proceeding. May 2025  63 Parts List – Tool Safety Timer 1 double-sided PCB coded 10104251, 71 × 88mm 1 UB1 Jiffy box, 158 × 95 × 53mm 1 1.6mm-thick insulation material cut to 89 × 48mm (fibreglass, acrylic, Presspahn or similar) [Jaycar HP9512] 1 12V DC 200mA+ power supply (eg, plugpack) 1 12V DC coil 250VAC/10A+ SPST PCB-mount relay (RLY1) [Altronics SA4198 or equivalent] 1 PIR motion sensor module (MOD1) [Altronics Z6382A or equivalent] 2 M205 PCB-mounting fuse clips (F1) 1 M205 1A fast-blow fuse (F1) 1 SPST red panel-mount pushbutton switch (S1) 2 2-way headers, 2.54mm pitch (JP1, JP2) 2 jumper shunts (JP1, JP2) Connectors 3 2-pin polarised headers with matching plugs and pins (CON1, CON7 & CON8) [Altronics P5472 + P5492 + P5470A] 1 2-way mini terminal block, 5/5.08mm pitch (CON2) [Altronics P2032B] 1 chassis-mounting barrel socket (to suit power supply) (CON3) 1 10A 250V IEC mains power input (C13) & output (C14) socket combination (CON4) [Altronics P8330A] 1 5-pin header, 2.54mm pitch (CON5; optional – for ICSP) 1 3-pin polarised header with matching plug and pins (CON6) [Altronics P5473 + P5493 + P5470A] Hardware, cable & wire 8 M3 × 6mm panhead machine screws 8 M3 shakeproof washers 4 M3 × 10mm tapped spacers 7 100 × 2.5mm Nylon cable ties 1 100mm length of 5mm diameter black heatshrink tubing 1 100mm length of light blue 10A mains-rated wire 1 300mm length of brown 10A mains-rated wire 1 IEC C13-C14 mains extension cable [Altronics P8422] 4 stick-on rubber feet Semiconductors 1 PIC16F15214-I/P programmed with 1010425A.HEX, DIP-8 (IC1) 1 LM317T 1A adjustable regulator, TO-220 (REG1) 1 BC337 or BC338 25V 800mA NPN transistor, TO-92 (Q1) 1 red 5mm LED with bezel (LED1) [Altronics Z0210] 1 W02(M) or W04(M) 1.2A bridge rectifier (BR1) 3 1N4148 75V 200mA signal diodes (D2-D4) Capacitors 1 470μF 35V electrolytic 1 10μF 50V electrolytic 3 100nF 63V MKT Resistors (all ¼W 1% axial unless noted) 8 4.7kW 1 330W 1 560W 1 0-150W 0.25-1W resistor (R1; see Table 1 & text) Check that the Earth link is good. It is part of the connector and it’s critical for safety, so we want to make sure it is OK. You will need to solder the Earth link on the back of the IEC connector as its fixing assumes a wire will be soldered to it. Now connect a short length of 10A light blue mains-rated wire between the terminals labelled N on the rear of the connector. 64 Silicon Chip Use two pieces of 5mm diameter heatshrink tubing to insulate the connections of this wire to the IEC connector tabs. Note that this wire will cross over the Earth strap. Now take two 150mm lengths of brown 10A mains-rated wire and connect them to the Active terminals on the IEC connector. Insulate these with 5mm heatshrink tubing too. Run a 2.5mm cable tie around the Active Australia's electronics magazine and Neutral wires, under the ground strap, and secure them together. With the PCB in the case, trim the length of the two brown Active wires so they neatly present to the load switch connector, CON2, on the PCB. Once wired to the terminal, secure it to the PCB using a cable tie. Stick on four rubber feet onto the case so you don’t scratch your desk, and the Tool Timer is complete. Finally, you can attach a label to the lid. This is a simple and cheap way of making this utilitarian project that little bit neater. The label can be downloaded from siliconchip. au/Shop/11/1827 and you can find instructions for printing and attaching it at siliconchip.com.au/Help/ FrontPanels We used an Altronics P8422 0.75m IEC extension cable to connect our soldering station to the tool timer. In operation, you can simply press “Start” on the tool timer and, while you are around and moving, your tool will stay on. When you wander off, it will switch itself off. Simple! We will not go into detail regarding how the tool timer can be installed inside a heat gun as there are too many inconsistencies in how these are built for instructions to be safe. Only attempt this if you thoroughly understand what you are doing. After reverse engineering our hot air gun, we concluded the safest approach would be to shut down the entire controller after the timeout. We chose to install a small 12.6V transformer in the case alongside the main transformer to power the Timer. We then used the Timer’s onboard relay to disable the main transformer that ran the hot air gun controller. Now I am less worried about my thoughtless cat setting my house on fire! Modifications If you want a timeout period different from the four options we have provided, the source code for the PIC firmware is available to download from siliconchip.com.au/Shop/6/1825 The definitions for the timeout period are in the header file “util.h”, defined in four lines (starting with #define Time_10Min_Runtime). The timer counts in tenth of a second intervals, so 10 minutes is 6000 counts. Hence, each value is the required number of seconds multiplied by ten. SC siliconchip.com.au Need to protect your project from heatstroke? 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Check stores for stock • Metal & plastic with dust filter options • Available in 3 sizes YX2511 - YX2554 FROM • Nanoflux magnetic levitation • 80, 90 & 120mm models • Tacho output 395 $ Shop at Jaycar for: • Wide range of ventilation fans • Fan guards and dust filters • Great range of project enclosures • Power leads and wiring • Mounting hardware • Heatsinks and thermal protection Explore our full range of ventilation fans, in stock on our website, or at over 121 stores or 130 resellers nationwide. siliconchip.com.au jaycar.co.nz 0800 452 922 1800 022 888 Australia's electronicsjaycar.com.au magazine May 2025  65 All prices shown in $AUD and correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. RGB LED ‘ANA This colourful and unique clock tells the time with LEDs arranged in a circle that light up in different colours to represent the hour, minute and second ‘hands’. There’s even a light chaser effect you can optionally enable that has the LEDs racing around each second. It’s a straightforward build that looks great when finished. By Nicholas Vinen T his RGB LED Clock is simple and stunning, using very few components outside the LEDs. I came up with the idea of this clock being vaguely aware of the somewhat similar “Mesmeriser” clock by Grantronics that was published in the June 2005 issue and available as a Jaycar kit at the time. I knew it used single-colour LEDs; I thought it’d be much nicer to make my Clock from multi-coloured RGB LEDs. This is a hybrid digital/analog clock. All the principles involved in timekeeping and the display are digital, but it mimics an analog clock in how it shows the time. Rather than two or three physical hands that rotate about the centre, pointing to the numbers, 60 LEDs are arranged around the outside of the face. They light up where an analog clock’s hands would point. A real analog clock uses different hand sizes to distinguish the hours, minute and second hands. Instead, this clock lights up the LEDs in different colours. If they ‘overlap’, the colour is a mixture! For example, if the hour hand is red and the minute hand is green, when they point to the same number, the LED lights yellow (which is what you get if you combine red & green light). Funnily enough, if you are familiar with that clock, you will see that I’ve had some similar ideas to its designers, the main one being that it incorporates an optional ‘chaser’ that runs around the clock face once per second. It’s very eye-catching and also serves to indicate to the beholder the passage of each second. Having said that it’s similar to the Mesmeriser, my chaser does operate a bit differently. You can see a video of the clock in operation with this feature enabled at siliconchip.au/Videos/ RGB+Clock If you don’t like or want the chaser, it’s easy to turn off with a button press. Includes all the parts in the parts list except the power supply. The microcontroller is pre-programmed. Choose a BZ-121 GPS module or Pico W (that you need to program) for the time source. One major difference from the Mesmeriser is in terms of complexity. I wanted this clock to be as simple as possible (“keep it simple, stupid!”). So besides the LEDs, there’s just one microcontroller, 20 resistors and a few other bits and pieces. That earlier design used way more parts and would have been a lot of work to build. I would say this one is elegant in its simplicity. I also wanted to keep the parts relatively cheap so that it could be made into an affordable kit. I considered using SMD RGB LEDs, but the 5mm through-hole types I ended up using work extremely well and are quite inexpensive in bulk. The only expensive part is the PCB because it’s quite large at 200mm in diameter. Still, you wouldn’t want a wall clock much smaller than that. I think the KISS (keep it simple, stupid) principle worked out quite well because this design is considerably easier to build than the almost 20-year-old Mesmeriser design. That one had a digital display as well, but I thought most people would want either a digital or analog like readout, not both. One concession I made to Australia's electronics magazine siliconchip.com.au RGB LED Analog Clock Complete Kit (SC7416, $65.00) 66 Silicon Chip ALOG’ CLOCK ● 200mm black clock face with 60 RGB LEDs that light different colours for the hour, minute and second ● 12 different colour schemes to choose from ● Optional ‘subsecond’ hand chaser ● Adjustable, automatic PWM-based dimming using an LDR to sense the ambient light level ● Two optional single-colour LEDs (any colours) to indicate AM or PM ● Time source: GPS module or NTP time via the internet using WiFi ● Accuracy: typically within one second ● Time zone: from GMT−14 hours to GMT+14 hours in 15 minute increments ● Daylight saving: manual one hour toggle ● Power supply: 5-12V DC <at> 50mA from plugpack or USB ● Time source baud rate options: 4800, 9600, 19200, 38400, 57600, 115200 digital clocks is to add optional AM/ PM indicator LEDs to make the time unambiguous. While I think this clock is nicer than the Mesmeriser, the kit is less than half the cost (even less if you consider 20 years worth of inflation!). It is also a bit larger than the Mesmeriser, and since the LEDs are right at the edge, the display is larger again. I didn’t think it was realistic to power a clock that uses LEDs for time display from a battery, so it’s simply powered from a DC supply between 5V and 12V (ideally in the range of 6-9V). That could mean a plugpack or USB supply. The simplest way to connect it is to have a thin figure-8 wire hanging down from the bottom of the clock to the nearest power point. If you really wanted to power it from a battery, with the average current draw of around 25mA for our prototype, you could expect four AAs to power it for around five days. So you’d want to use high-capacity rechargeable (eg, NiMH) cells to avoid spending a fortune on alkaline cells. In terms of timekeeping, I have offloaded that to your choice of either a GPS module or a WiFi module that siliconchip.com.au fetches NTP time via the internet and your WiFi network. That makes the clock extremely accurate, with no drift, while also helping to keep the circuit simple. The Clock is designed to hang on the wall as a PCB assembly. It might get a bit dusty, but you don’t normally touch clocks often, so it doesn’t strictly need a case. If you want to put it in a case, you can likely find a suitable one. The easiest solution is probably to buy a cheap clock in a plastic case that’s large enough, gut it and install this PCB in that case. Just make sure it’ll fit first! Circuit description The full circuit is shown in Fig.1. The key to keeping it simple is the use of Charlieplexing to allow all 60 RGB LEDs, containing a total of 180 junctions (plus the two optional AM/PM LEDs) to be driven from a 20-pin IC. This technique involves keeping most of the pins connected to the LEDs in a high-impedance state (eg, configuring them as digital inputs). One output is driven high (to +5V) and the other is pulled low (to 0V). A different LED junction is connected across each possible pair of pins, so depending on Australia's electronics magazine which pin is high and which is low, only one lights. Due to the way the connections are arranged, we can actually light any combination of the red/green/blue junctions in a single LED at any time. By multiplexing them (switching quickly between different states), we can make it appear that multiple LEDs are lit at once. In the case of this clock, we need to light up to five LEDs at once: for the hour ‘hand’, minute ‘hand’, second ‘hand’, the optional ‘subsecond hand’ (which goes around the face once per second) and the optional AM or PM LED. That means each LED is lit for a maximum of 20% of the time. To compensate for that, we drive them pretty hard, so they still look quite bright. By lowering the amount of time they are lit for (ie, having all LEDs off sometimes), we can control the brightness, too. The formula for the number of LEDs (ℓ) that can be driven by a Charlieplexed arrangement for a certain number of pins, n, is ℓ = 2(n−1) + 2(n−2) + 2(n−3) + ... + 2, which can be simplified to ℓ = n(n−1). This is a quadratic equation, so we can solve it for n and get the formula n = (1 + √1 + 4ℓ) ÷ 2. May 2025  67 Plugging in our value of ℓ = 182, we can determine we can do it with exactly 14 I/O pins. However, our circuit uses 15 because that allows us to use a much simpler arrangement where figuring out which pins to drive high and low to light any given LED is trivial. You can see the arrangement we used in the circuit diagram. The RGB LEDs are grouped in sequential sets of four, having their common anodes all tied together and connected in turn to I/O A (LED1LED4), B (LED5-LED9) etc, up to the 15th I/O, O (LED57-LED60). For the first group with their anodes driven by I/O A, the cathodes are driven by B, C, D, ... K, L and M. For the second group with the anodes driven by I/O B, the cathodes are driven by C, D, E, ... L, M and N. After the third group, which ends with the final cathode being driven by the 15th I/O, O, it wraps around to A again. The critical thing is that no I/O pin appears twice in the same group. The AM and PM LEDs are connected to spare combinations of pins that are not used for any of the RGB LEDs. To light one LED, all we have to do is figure out which group it is in and drive the corresponding shared anode pin high. We then pull one, two or three of the cathode pins connected to that LED low to light it with a particular colour. The nets designated A through O connect to pins on microcontroller IC1 via 68W current-limiting resistors. These were calculated with the microcontroller’s absolute maximum current limit per pin of ±25mA, as well as the typical limit for an LED being 20mA (although, with duty cycle always being under 50%, it isn’t really a concern). Each LED will have two resistors in series when it is lit, one in the anode circuit and one in the cathode circuit. Assuming the lowest LED forward voltage at 20mA is 1.8V and the supply is exactly 5V, that means there will be 3.2V across the resistors, allowing a maximum of 23.5mA to flow (3.2V ÷ [68W × 2]). However, the microcontroller’s output transistors also have an inherent resistance that we can calculate as being close to 68W from information in the data sheet. This means that the series resistance for each LED is effectively around 200W, so the actual current limit is closer to 16mA, comfortably under the 25mA limit. 68 Silicon Chip Brightness adjustment We want the LEDs in the clock to be bright in a well-lit room but not so bright at night so they don’t sear your eyeballs. Thus, there is a light-­ dependent resistor (LDR) near the middle of the clock face that senses the ambient light level. It forms a divider with the 100kW resistor in series wtih it, across the 5V supply rail. At higher light levels, the LDR’s resistance is low, so the RA5 analog input of IC1 will be close to 5V (probably around 4.5V). As the light level drops, its resistance will increase to 100kW and above, so that voltage will drop to 2.5V and lower. The microcontroller can thus use its analog-to-digital converter (ADC) to read the voltage on that pin and adjust the LED brightness. That is done using pulse-width modulation (PWM). We’ll explain how it’s implemented in the software section. Cheekily, we also use pin 2 of IC1 to sense presses of pushbutton switches S1 and S2. They are used to change the clock’s configuration, set the time zone, compensate for daylight saving, adjust the LDR sensitivity and so on. When one is pressed, it pulls pin 2 either almost all the way up to 5V or all the way down to 0V. The LDR’s resistance doesn’t vary enough to allow the voltage to get that close to either rail, so the microcontroller knows a button has been pressed. The 220W series resistors are low enough not to interfere with that, but high enough to avoid damage in case both buttons are pressed (an invalid condition). Timekeeping While IC1 has an internal oscillator, it isn’t super accurate, so it’s only used for timekeeping from second-to-­ second. For longer intervals, we rely on the time source: either a GNSS (eg, GPS) module, which gets its time from atomic clocks in satellites, or a module that fetches the time via internet NTP servers using a WiFi network. Either way, we’re relying on that module to have a crystal for reliable timekeeping, and we simply get its updates (once per second or more frequently) and display whatever time it gives us. The GNSS or NTP module is connected via six-pin header CON3. Some modules have four or five wires, in which case some of these pins are not connected. Actually, only three are required: Vcc (5V) and GND (0V) to Australia's electronics magazine supply the module with power, and TX, which is the pin it uses to send serial data to our microcontroller that includes the time. We provide a pad for soldering the module’s RX wire that pulls it high via a 10kW resistor so that the module doesn’t get spurious serial data due to EMI. We never actually need to send it data. The 1PPS pad is provided as a place to anchor a 1PPS wire if the module has one; we don’t need that either. The EN pad will pull up the module’s EN wire, if it has one, to enable it. Remaining circuitry IC1 has a 100nF supply bypass capacitor for stability, plus a 10kW pull-up resistor on its MCLR (reset) pin to prevent spurious resets. Optional in-circuit serial programming (ICSP) header CON2 provides a way to reprogram IC1. While some LEDs will light dimly while doing this (as pins 18 & 19 of IC1 are used for both programming and driving LEDs), we didn’t find this interfered with programming the chip. All that remains is the simple linear power supply. REG1 is a low-dropout 5V regulator that allows you to feed in a higher voltage (6-12V DC) and it will provide a nice, stable output to run the clock. As the current draw is usually less than 50mA, it will only dissipate 350mW at most ([12V – 5V] × 0.05A). It’s in a medium-sized SOT223 package soldered to the board, so it will handle that easily. The AMS1117 regulator requires a 1µF ceramic capacitor on its output, plus an input bypass capacitor of at least 100nF, so we have provided those. They are both 1µF to simplify construction. Mosfet Q1 provides reverse polarity protection, as the power input is via a simple two-pin header or soldered wires. If the supply polarity is connected correctly, Q1’s gate is pulled up, and it switches on, connecting the supply negative wire to circuit ground. If the supply wires are swapped, Q1’s gate is pulled down and its body diode is reverse-biased, so no current will flow. ZD1 protects Q1’s gate in case a negative voltage exceeding 16V is applied to the board, however unlikely that is. Options While we are specifying common-­ anode RGB LEDs, it will actually work siliconchip.com.au Fig.1: the circuit is dominated by the 60 RGB LEDs that connect to microcontroller IC1 via fifteen 68W series resistors. The micro can light any element of those LEDs (or the two extra ones) by bringing one of the connected pins high and the other low, while the remainder are kept as high-impedance digital inputs. siliconchip.com.au Australia's electronics magazine May 2025  69 with common-cathode RGB LEDs too. All that needs to change if CC LEDs are used is for the drive polarity to be reversed, ie, instead of pulling a pin high, it is pulled low, and vice versa. The only catch is that if you fit the AM & PM LEDs (LED61 & LED62) and are using common-cathode RGB LEDs, they need to be reversed (rotated by 180°) so that their polarities match the other LEDs. PCB layout You would think with all these LED connections, the PCB layout would be a nightmare, but actually, it was straightforward. We have kept it as neat as possible, and quite symmetrical, since the PCB also forms the clock’s face – see Fig.2. We could have hidden most of the circuitry on the back, but we thought it’d be more Fig.2: the 200mm diameter PCB forms the clock face, with the 60 RGB LEDs arranged in 6° increments around the outer edge. interesting to have some on the front! The microcontroller, IC1, is right at the centre of the face, which seems appropriate since it’s also logically at the centre of the circuit. Most of the resistors are to its left and right. The bypass capacitor is above it, while the LDR is centred below it. The pushbuttons are on the left and right sides, lined up with IC1. The power supply components mount on the back of the PCB, towards the bottom. We initially thought of using the auto-router to make the 244-odd connections to the LEDs, but came up with a better (and much neater!) idea. The 15 I/O lines (labelled A through O on the circuit diagram) are assigned to 15 bottom-layer circular tracks that run at fixed intervals inside the circle of RGB LEDs. Top-layer radial linear tracks run from each RGB LED pad partway towards the centre of the PCB, all terminating just above the innermost bottom-layer ring track. With this arrangement, all we needed to do was place one via on each of those radial tracks at the appropriate location to join it to the correct circular track (A-O). One of each of the radial tracks connected to the A-O lines is then routed to the series resistor that connects to the appropriate microcontroller pin. (Thanks to Tim Blythman for his help in suggesting this neat arrangement!) While there are pads for the three connectors to be inserted from the front side of the board, we siliconchip.com.au thought it would be a bit ugly having them stick out. These pads don’t have exposed copper on the front of the board, to keep it looking clean, but it is still possible to solder vertical or (ideally) right-angle headers on the back side. Most constructors would not need to fit the ICSP header. Since GPS modules usually come with plug-in wire assemblies, there’s no real need to fit a header for CON3. Instead, we suggest you simply solder the wires to those pads on the back, as we did. We stuck the GPS module on the back of the PCB with double-sided tape to hide it, as otherwise the wiring will look a little messy. That just leaves the power input, CON1. You have a few options there. You could solder a right-angle polarised header to the back of the board and use a plug to connect it. You could also just solder bare wires (either directly from a plugpack, or to an inline barrel socket) to those pads. There’s also the option of using a small, separate board we developed that can be soldered to the main board using a pin header, which has an onboard USB socket. You can then use a 5V USB supply to power the clock. While that will probably mean REG1 will be in dropout and not regulating, and the LEDs might not be quite as bright, we haven’t found it to make that much difference. That small add-on board will be useful in many applications, so we’re presenting it as a separate project. Software The software is simple in principle, although it is actually quite involved when examined in detail. The microcontroller runs with a 16MHz main clock (‘Fosc’) that results in a 4MHz instruction clock. Three hardware timers are used: TMR0, TMR1 and TMR2. The other peripherals we need are the analog-to-digital converter and the UART for serial reception. TMR1 is used for timekeeping and to control the main loop rate. It is a 16-bit timer running from Fosc ÷ 4, and it uses a 1:1 prescaler, meaning it overflows at a rate of 61.035Hz (16MHz ÷ 4 ÷ 65536). Happily, this is almost exactly what we want. Assuming the subsecond hand/chaser is enabled (and it looks cool, so why wouldn’t you?), the subsecond hand makes 61 steps each siliconchip.com.au second. That’s because it has to go around the clock face once (60 LEDs) plus advance one step with the second hand (plus one LED). This is pure coincidence, but it works out really well! While we advance the clock to the next second after 999.4ms (61 ÷ 61.035), we expect the GPS/NTP module to give us a time update after exactly 1000ms, so that event is used to reset the timer. That way, as long as we are getting time updates every second, there are no glitches in the time display. TMR0 and TMR2 are used for LED multiplexing and PWM, respectively. They are both 8-bit timers that run from Fosc ÷ 4, using a 4:1 prescaler, so they run at 3.906kHz (16MHz ÷ 4 ÷ 4 ÷ 256). Each time TMR0 overflows, it triggers an interrupt routine that switches to lighting the next LED (using port masks precalculated by the main loop). That means each LED is lit for 51μs at a time, giving a duty cycle of approximately 20% at full brightness. TMR0 and TMR2 run in lockstep. At full brightness, TMR2 never triggers. The PR2 register controls how soon the TMR2 interrupt occurs after TMR0 overflows. As the value in PR2 is reduced, the TMR2 interrupt occurs earlier and when its interrupt service routine (ISR) is called, it simply switches all LEDs off. The earlier that happens after switching on, the dimmer the display becomes. This means we can use the PR2 register as an 8-bit PWM control for all LEDs, since it occurs at the same interval after each multiplexing step. Besides calculating which LEDs to light based on the current mode and time, the main loop also receives serial data from the GPS/NTP module, decodes it and uses it to update the current time. After getting the UTC/ GMT time, the configured timezone offset and DST offset (if enabled) is applied before updating the clock face. It reads the voltage from the LDR divider on each run through of the loop, filters it, and uses it to calculate the new brightness level. It also checks if button S1 or S2 has been pressed, performs debouncing, looks for long or short presses and changes the mode as appropriate. Construction The RGB LED Clock is built on a large circular PCB measuring 200×200mm (ie, 200mm in diameter) with a black Australia's electronics magazine solder mask, coded 19101251. We recommend you start by fitting the topside SMDs, with IC1 being the first. You should have a temperature-­ controlled soldering iron, fine-tipped tweezers, solder wire, a syringe of flux paste and a roll of solder-­wicking braid on hand. Work in a well-ventilated area, either using a fan, next to an open window or outdoors as flux smoke is not good for you if you inhale it. If you bought a kit or programmed microcontroller from the Silicon Chip Online Shop, your chip will already be programmed and you can just solder it to the board. If you have a blank chip and the ability to program it offboard, do so now. We described how to do that in our article on the PIC Programming Adaptor from the September 2023 issue (siliconchip.au/ Article/15943). If you don’t have such a programming rig and your chip is blank, solder it now and you can use CON2 to program it later. Before soldering it, make sure you identify pin 1 and line it up with the markings on the board and in the top-side component overlay diagram, Fig.2. Fixing a reversed SMD chip is not fun! Tack one pin to the board using a little solder, then inspect the leads to verify they are all over their pads. If not, remelt that solder and gently nudge the chip into position. Verify again that the IC is orientated correctly, then solder the diagonally opposite pin. Apply flux paste down the pins on both sides, then solder all the remaining pins. You can do it individually, by adding a little solder to the iron tip and touching it to the junction of the pin and pad, or you can drag-solder them several at a time. If any bridges form (which is likely with drag soldering), add a little flux paste and then use solder-wicking braid to remove the excess solder. Inspect all the solder joints and pins under magnification to ensure all pins have been soldered to their pads with good fillets and no bridge remain, then move onto the passives, using Fig.2 as a guide. It’s best to fit the 220W, 10kW and 100kW resistors first, since all the remaining resistors will be the same value (68W). The sole capacitor on this side is the 100nF type. You can use a similar technique as for the IC: tack the part to one pad, check its orientation, adjust if necessary, then solder the other pad. Add a May 2025  71 tiny bit of flux paste to the first one and heat it with the iron to reflow the joint. With all these parts in place, clean the flux residue off the board using alcohol or a flux solvent. It’s much easier to clean the board before any through-hole parts are in place. This will be the clock face, so you want it to be nice and presentable! You’ll probably have to clean it two or three times, using a fresh section of lint-free cloth each time, to get it looking nice. Now solder the two tactile switches using the same technique. This will probably leave a little flux residue, but we don’t want to soak the switches in solvent as it can damage them, so apply Fig.3: there aren’t too many components on the back – six SMDs for the power supply near the bottom, up to three connectors (depending on your preference), the time source (a GNSS module shown here) and... some wires to hang it on the wall. The wiring shown suits the BZ-121 module we used but virtually any 5V-powered TTL module should work. You can also use a Pico (2) W programmed as an NTP Time Source. a little solvent to a section of the lintfree cloth and wipe off the flux residue using that. Flip the board over (rest it on a cloth so its face doesn’t get dirty or scratched), then solder the parts on the reverse side, as shown in Fig.3. Don’t get Q1 (possibly coded XORB) and ZD1 (likely coded T12 or Z3) mixed up, as they are in the same type of package. When finished, clean up the flux residue, although thoroughness is less crucial since it will be against the wall later. You can now solder the LDR on the front side; you may need to bend its leads in to make them fit the pad pattern. Make sure it’s straight and close to the board so that it looks nice. Soldering the LEDs Now for the big job. This will probably take you at least a couple of hours. Don’t rush it as it’s harder to fix problems like bridged pads than it is to do them right the first time. Make sure you fit each of the 60 RGB LEDs the right way around. Pay attention to the orientations of the flat faces on the PCB silkscreen and in Fig.2. For each LED, insert it and then rest the board on your work surface such that the weight is on that LED, so it’s pushed into the board. You could place something like an eraser between the lens of the LED you’re soldering and your bench to ensure that. Then solder one of the outer leads, with the soldering iron on the outside, using a minimal amount of solder. siliconchip.com.au Don’t use too little; you need to be able to see that a fillet has formed. Still, you should use just enough solder to get that fillet. Next, check if the LED is flat and straight. If not, you still have a chance to push it into the PCB with your finger while you remelt that initial solder joint. Once you’re satisfied, solder the opposite lead, again with the iron coming in from the outside. The critical part here is that the pads are very close together, with large holes and thick leads, so it’s quite easy to bridge the pads and somewhat difficult to fix it if a bridge forms. For the two remaining leads, bring in the soldering iron from the middle or outside of the board so it touches the pad and lead, then feed in a minimal amount of solder from the outside until it melts, as shown in Fig.4. Again, use just enough to form a fillet. Repeat for the final lead/pad, then use sharp side-cutters to trim all four leads reasonably close to the PCB and evenly. When trimming, use eye protection and/or hold onto the leads so they don’t fly into your eye! They can attain quite a high velocity when cut through. Now check to make sure the pads have not been bridged. If you have followed our instructions carefully, they should not be. If they are, add some flux paste and use solder-­wicking braid to remove the excess solder until the bridge is clear. You can then add a tiny bit of solder back to the pads to ensure there’s enough. Repeat until you have soldered 5-10 of the LEDs. Testing the LEDs It’s best to test the LEDs as you go, because a short circuit at any point on the board can cause the whole display to go haywire (after all, there are only 15 separate tracks connecting to all 60 LEDs). When first powered up, the firmware runs a display test where LED1-LED62 are lit up white in sequence at about 4Hz. This should allow you to quickly spot problems. I found the easiest way to power the board was to get a regulated 5V supply (eg, a bench supply) and use clip leads to attach two male-male jumper wires to its outputs. With the clock face towards you, right-side up, rest the black (negative) wire in the right-most terminal of CON1 (the one labelled GND in Fig.2). The weight of siliconchip.com.au Fig.4: no doubt there are many ways to solder the RGB LEDs without accidentally bridging the very closely-spaced pads, but this is what we found worked best. The soldering iron tip and solder should come in from 180° opposite positions along the long axis of the pads. That minimises the chances of accidental bridges, which are difficult to clear. The final PCB will feature more widely spaced pads to make this a little less tricky than our prototype (although we managed to do it). the cable will bring it contact with the plated through-hole. Similarly, insert the positive jumper wire into the side of CON1 labelled + and ensure the two wires are not shorted, then switch the supply on. Ideally, it should be current-limited to around 50mA (the board will draw less than 20mA in this configuration). Power it up and check that LED1 lights, then LED2 etc. If you don’t have a current-limited supply, you could use a fixed-voltage DC supply with a series resistor to prevent damage in case there is a fault. For example, a 12V supply with a 150W 1W series resistor would easily deliver the ~20mA needed to power the circuit for testing but would be limited to 80mA in case of a fault (with the resistor dissipating just under 1W). When powered, if any of the LEDs don’t light up white, or they light at the wrong time, switch it off and check the most recent LEDs you’ve soldered for bridges or bad joints. Once they all light up OK, go back and solder a few more LEDs. Keep testing until all 60 are fitted and they are lighting up nicely. You can then solder LED61 and LED62 if you are going to use them. Remember to reverse them if you used common-cathode RGB LEDs. They will light up individually during the test, after all 60 of the RGB LEDs. While the LED solder joints are on the back of the board, if you have a lot of flux residue left behind, you may want to clean it up to avoid getting sticky hands when handling the clock. A proper flux remover is better than alcohol here, as alcohol dries fast, but you can use it if that’s all you have. Because of the sharp leads, you will have to dab it off, rather than wipe it off. Australia's electronics magazine It took a little while, but we cleaned this flux residue up. Try not to let any get onto the face (ie, the opposite side of the PCB), or you’ll have to clean it again so it looks nice. Final assembly There isn’t much left to complete the clock. If you’re using CON2, fit it now; most constructors will not need it. We suggest you stick the GNSS or NTP module to the back of the clock using double-sided foam-cored tape. Cut it to size and stick it on. The GPS module will usually have a flat, non-­ conductive ceramic antenna that you can stick somewhere without too many tracks. The NTP module has conductive parts on the back, so make sure none of them can short to the PCB. Most of the back of the Clock PCB is covered with a solder mask, so short-circuits are unlikely, but you should still check. If you’re using an NTP module like the WiFi Time Source for GPS Clocks (June 2023; siliconchip.au/Article/ 15823), you will need to configure it so it can connect to your WiFi network. That is usually best done before wiring it up; refer to that article for instructions. Now wire the GPS or NTP module to CON3. You can use a header and plug(s), if you want, but we think soldering wires directly to the pads is fine. As mentioned earlier, you won’t necessarily have all six wires to connect to CON3. It doesn’t matter; the vital ones are VCC, GND and the TX signal from the module (which goes to the pad marked TX, not RX; ie, the labels are from the module’s point of view). If your module has an EN wire, check that it’s active high. If so, you May 2025  73 There’s nowhere suitable on the PCB to mount a USB connector, so if you want to use USB power, you can attach the add-on board like this. can solder it to the EN pad. Otherwise, solder it to GND. Most modules will have an RX pin, which should be soldered to the RX pad, pulling it high to disable it. Power supply For power, you can solder a lightduty figure-8 lead to the pads for CON1 on the rear of the board and either hard-wire it to a 6-12V DC plugpack or similar, or have an inline barrel socket or other connector at the end of that wire to connect a DC supply. Try to get the polarity correct (refer to Figs.2 & 3), although the board should not be damaged if you do accidentally reverse it. Another option is to build our USB Power Breakout Board, described in the accompanying short article. This is a small PCB that can accept a USB Type-C or USB Type-B Micro/Mini socket and a pin header. It supplies ~5V DC to that pin header when a USB supply is connected. This may not run the clock at full brightness, but it won’t be far off, and USB supplies are common and convenient. We didn’t put pads for a USB socket on the clock PCB itself because there was no room to do it along the edge (the whole edge is filled with LEDs).If the socket wasn’t near the edge, there wouldn’t be room for a cable to plug in, so the PCB would need an ugly cut-out. Spacing this small PCB off the back of the clock PCB on a header provides enough room for the cable to plug in. The only components you need on 74 Silicon Chip that PCB are the USB socket, a 0W SMD M3216/1206 resistor and the pin header. Once that’s assembled, you can then solder it to the back of the Clock PCB as shown in the photo above. Note how the USB Power Breakout Board PCB has four through-hole pads; this allows a two-way pin header to be fitted with multiple different polarities. The header position shown in Photo 1 is required to match the polarity of CON1. If you’re unsure, refer to the separate article and its PCB overlays to see how the header position affects the polarity. Finally, you will have noticed several large rectangular pads on the back of the Clock PCB. These are provided to solder a loop of wire for hanging the clock, with other pads near the bottom to solder wire loops so it hangs vertically on the wall. The photo overleaf shows how we attached the wires to our Clock for hanging; you can use a similar arrangement. You can bend the wires into different positions to suit your hanger (whether it’s a nail, screw, hook or whatever). If possible, do that before soldering the wires to avoid stress on the soldered joints. Final testing Presumably if you’ve gotten to this point, the LED testing went well, so the microcontroller and LEDs are working. There isn’t much else to go wrong, apart from the GPS/NTP module wiring and the power supply itself. We suggest you use the same Australia's electronics magazine procedure you used for testing the LEDs and check that the current draw is under 100mA. With the BZ-121 module we used, our Clock drew around 45mA. If that’s the case, it’s unlikely you have anything really wrong. You can test the LDR-based dimming now. Place a small opaque object like a credit card over the LDR and observe the LEDs. They should dim when you block the light to the LDR and brighten again when you remove the obstruction. You will have to cover the LDR thoroughly, as even a bit of light leading around its edges is enough to make the LEDs quite bright. If that doesn’t work, you probably have a soldering problem with the LDR or its series resistor, a button is stuck down or the LDR is the wrong type. If you’re using a GPS module, we suggest you put the clock near a window and set the baud rate to the correct one for your module, as described below. Leave it powered for around 30 minutes, then come back and check if it’s showing the correct time for London (ie, GMT). If so, that means it has acquired the signal and is decoding the data properly. You can then complete testing by setting it up. If using an NTP module, you should have set it up earlier, so once you have set the correct baud rate (as explained below), it should connect and show you UK time within a few seconds. In that case, proceed to the following section. Setting it up The first setting is the baud rate. This can only be changed after power-­ up when the initial LED test has completed and the spinning chaser (at roughly one ‘rotation’ per second) is operating, to indicate it’s waiting for GPS/NTP data. If you see a clock face instead, it’s likely the initial baud rate was already correct and it’s getting data, so you can skip this bit. The chaser will initially be red if it isn’t getting any valid data, changing to green if there is data but no valid time yet. Once it’s green, it’s usually just a matter of time before it switches to telling the time (assuming you have a strong enough GPS or WiFi signal). During this time, one of the digits 1-6 will be lit blue, indicating the baud rate: 1. 4800 baud 2. 9600 baud 3. 19,200 baud siliconchip.com.au 4. 38,400 baud 5. 57,600 baud 6. 115,200 baud (default) Pressing A will go to the next lower baud rate, while pressing B will go to the next higher one. If you don’t know the correct baud rate, try each one for a few seconds until the chaser changes to green. If it doesn’t for any baud rate, switch off and check your wiring. Remember that TX from the module should go to the TX pad on the PCB. All settings, including the baud rate, are stored in EEPROM, so you shouldn’t have to do this again. The remaining settings that can be accessed in time display mode are: 1. the time zone offset and optional DST (+ 1 hour when activated) 2. the colour scheme 3. the second and sub-second hand modes 4. the LED dimming calibration (minimum & maximum brightness) Once you’re in clock mode and the time has been acquired, you can set the time zone offset. Hold down the A button for a second and release it. The time display should remain, but it will now flash at 1Hz with a 50% duty cycle. If daylight saving is active in your area, hold down B for one second to enable DST mode. A short press of the A button will make the time 15 minutes earlier, while the B button will make it 15 minutes later. Use this to set the correct local time, then hold down the A button to return to the normal display. The time zone you set will be stored in EEPROM. After this, if your area has DST and the time changes, you just need to go into this mode and hold down B for one second, then hold down A for one second to switch between DST and non-DST. Alternatively, you could just change the time zone offset until the time is correct. the second ‘hand’ visible, plus the ‘sub-second hand’ in the same colour. The sub-second hand is a chaser that runs around the clock face each second. It starts where the second hand is, goes all the way around, and ‘pushes’ it over to the next second on the tick. A short press of B will cycle through the four possible second-hand modes: 1. the second hand and sub-second hand are visible and matching colours (the default) 2. the same as #1 but with a dimmer sub-second hand 3. the second hand and sub-second hand are visible, with the sub-second hand being white 4. the same as #3 but with a dimmer sub-second hand 5. the second hand is visible but the sub-second hand is not 6. there is no second hand, only the hour and minute hands Dimming adjustments A long press on the B button in time display mode will switch to the brightness/dimming adjustment mode. In this mode, you can control both the maximum brightness and how the brightness reduces at lower ambient light levels. By default, the maximum brightness is 100%, reducing to a low level, but not the lowest possible, in total darkness. Upon entering this mode, you are adjusting the maximum possible brightness. Pressing A will reduce the maximum brightness and you will see the display dim. Pressing B will increase it (if it is not at its maximum). While making this adjustment, the LDR reading is ignored; you are seeing the brightness level that will be used at the highest possible ambient light level. Keep in mind that, depending on where your clock is positioned, it may not normally ‘see’ a very high ambient light level. For this reason, you can actually set the maximum brightness above 100%. This will not make the display brighter, but it will mean that the ambient light level has to drop further before the brightness starts reducing. The clock face shows a continuous chaser in this mode to help you see the brightness level you’ve set, which spans a portion of the clock face related to the possible brightness range. The portion from six o’clock to twelve o’clock shows the maximum brightness setting, so the chaser gets Parts List – RGB LED Analog Clock In time display mode, short presses of the A button will cycle through the six possible colour schemes for the hour, minute and second hands. Each can be red, green or blue, but they must all be different. Use whatever scheme is easiest for you to remember. The default is blue for the hour ‘hand’, green for minutes and red for seconds. A short press of the B button will cycle through the six possible second-­ hand modes. The default is to have 1 black double-sided PCB coded 19101251, 200×200mm 1 5-12V DC 100mA power supply (6-9V DC recommended) 1 2-pin vertical or right-angle header (CON1; for power – see text) 1 5-pin right-angle header (CON2; optional – for ICSP) 1 6-pin right-angle header (CON3; optional – for GPS module) 1 5V GPS module or compatible NTP time source (MOD1) [BZ-121 GPS module recommended, Silicon Chip SC7414] 2 2-pin SMD black tactile pushbutton switches (S1, S2) 1 20×20mm piece of foam-cored double-sided tape (to affix GPS module) 1 200mm length of tinned copper wire (to make hanger/standoffs) 1 USB power supply module (optional; see text and accompanying article) Semiconductors 1 PIC16F18146-I/SO micro with 1910125A.HEX, wide SOIC-20 (IC1) 1 AMS1117-5.0 15V input low-dropout linear regulator, SOT-223 (REG1) 1 AO3400 or equivalent logic-level N-channel Mosfet, SOT-23 (Q1) 1 BZX84B5V6 or BZX84C5V6 5.6V zener diode, SOT-23 (ZD1) 60 frosted-lens 5mm RGB LEDs (LED1-LED60) * 2 5mm high-brightness LEDs with diffused lens of various colours (LED61 & LED62; optional AM & PM indicators) * the kit will come with common anode LEDs but common cathode types can also be used Capacitors (all SMD M3216/1206 size 50V X7R) 2 1μF 1 100nF Resistors (all SMD M3216/1206 size unless noted) 1 100kW light-dependent resistor (LDR1) [GL5528] 2 100kW 2 10kW 2 220W 15 68W siliconchip.com.au Australia's electronics magazine Colour scheme May 2025  75 shorter as you reduce it and longer as you increase it. A long press of A will return to the time display, while a long press of B in this mode will switch to adjusting the other end of the range, ie, how much it will dim at low light levels. Similar to the maximum brightness setting, you have a fairly wide range of adjustment here, as you may wish the clock to fully dim before it is in total darkness. Or you may wish for it to never go to minimum brightness, even when the LDR sees no light. The default is somewhere between those two extremes. While making this adjustment, the LDR is active and the display will dim based on the current ambient light level and the current setting so you can see its effect. To simulate the clock being in darkness, you will need to cover the LDR with something opaque, like a credit card. Small objects can easily have light leak around the edges, so make sure the object is touching the whole face of the LDR and extends beyond it in all directions if you want to simulate total darkness. Being in a dimly lit room for this adjustment will help. In this mode, a long press of button A will return to time display mode, while a long press of button B will go back to adjusting the maximum brightness, as described above. Using it We attached thick wire to these solder pads on the rear of the Clock, so that it can be hung on a wall. The clock face is designed so it doesn’t take attention away from the LEDs. 76 Silicon Chip Australia's electronics magazine Once you have set your time zone offset, confirmed that your time source is working, adjusted the brightness levels and chosen your preferred colour scheme and mode, the clock is set up and ready for use. If it loses power, when it regains it later, it will go back into exactly the same mode. It just might take a while for your time source to resume, especially if it’s a GNSS/ GPS module. All that remains is to hang it on the wall and connect the permanent power supply arrangement. We recommend soldering an inverted-U-shaped piece of tinned copper wire between one pair of pads on either side at the top of the clock. Bend it so that it will comfortably hook around the head of a screw in your wall, or a wall hook. A couple of smaller loops soldered across the two pairs of pads near the bottom of the clock will stop the bottom of the clock from touching the wall. However, you may wish to have it angled down, as it could make it easier to read. So you could omit those loops, or make them stick out less than the upper one. If there is no power source under where you want to hang the clock, you could run a thin figure-8 cable from CON1 up behind the clock, then along the wall and then down to a more convenient location. The wire will be less visible if it’s the same colour as the wall (you could paint it). While few homes have picture rails on the walls anymore, if you’re lucky enough to have them, they are an excellent way to hide such wire runs! SC siliconchip.com.au 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. 05/25 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 ATmega328P ATtiny45-20PU PIC10LF322-I/OT PIC12F617-I/P 110dB RF Attenuator (Jul22), Basic RF Signal Generator (Jun23) ATSAML10E16A-AUT High-Current Battery Balancer (Mar21) 2m VHF CW/FM Test Generator (Oct23) PIC16F1847-I/P Digital Capacitance Meter (Jan25) Range Extender IR-to-UHF (Jan22) PIC16F18877-I/P USB Cable Tester (Nov21) Active Mains Soft Starter (Feb23), Model Railway Uncoupler (Jul23) PIC16F18877-I/PT Dual-Channel Breadboard PSU Display Adaptor (Dec22) Battery-Powered Model Railway Transmitter (Jan25) Wideband Fuel Mixture Display (WFMD; Apr23) PIC12F675-I/P Train Chuff Sound Generator (Oct22) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC16F1455-I/P Railway Points Controller Transmitter / Receiver (2 versions; Feb24) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23) Battery-Powered Model Railway TH Receiver (Jan25) ESR Test Tweezers (Jun24) PIC16F1455-I/SL Battery Multi Logger (Feb21), USB-C Serial Adaptor (Jun24) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) Battery-Powered Model Railway SMD Receiver (Jan25) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) USB Programmable Frequency Divider (Feb25) Advanced GPS Computer (Jun21), Touchscreen Digital Preamp (Sep21) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC16F1459-I/P K-Type Thermostat (Nov23), Secure Remote Switch (RX, Dec23) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) Mains Power-Up Sequencer (Feb24 | repurposed firmware Jul24) $20 MICROS 8-Channel Learning IR Remote (Oct24) ATmega32U4 Wii Nunchuk RGB Light Driver (Mar24) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) AM-FM DDS Signal Generator (May22) PIC16F15214-I/SN Digital Volume Control Pot (SMD; Mar23), Silicon Chirp Cricket (Apr23) ATmega644PA-AU PIC32MK0128MCA048 Power LCR Meter (Mar25) PIC16F15214-I/P Digital Volume Control Pot (TH; Mar23), Filament Dryer (Oct24) Tool Safety Timer (May25) $25 MICROS PIC16F15224-I/SL Multi-Channel Volume Control (OLED Module; Dec23) PIC32MX170F256B-50I/SO + PIC16F1455-I/SL Micromite Explore-40 (SC5157, Oct24) NFC IR Keyfob Transmitter (Feb25), Rotating Light (Apr25) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC16F18146-I/SO Volume Control (Control Module, Dec23), Coin Cell Emulator (Dec23) PIC32MX470F512L-120/PT Micromite Explore 100 (Sep16) Compact OLED Clock & Timer (Sep24), Flexidice (Nov24) $30 MICROS Versatile Battery Checker (May25), RGB LED ‘Analog’ Clock (May25) PIC16LF15323-I/SL Remote Mains Switch (TX, Jul22), Secure Remote Switch (TX, Dec23) PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) STM32G030K6T6 Variable Speed Drive Mk2 (Nov24) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) W27C020 Noughts & Crosses Computer (Jan23) KITS, SPECIALISED COMPONENTS ETC VERSATILE BATTERY CHECKER KIT (SC7465) (MAY 25) Includes everything in the parts list (including the case), except the optional components, batteries and glue (see p30, May25) RGB LED ‘ANALOG’ CLOCK KIT (SC7416) $65.00 (MAY 25) Includes all the parts except the power supply. When buying the kit select either a BZ-121 GPS module or Pico W (unprogrammed) for the time source (see p66, May25) $65.00 USB POWER ADAPTOR COMPLETE KIT (SC7433) (MAY 25) Includes everything in the parts list and a choice of one USB socket: USB-C power only; USB-C power+data; Type-B mini; or Type-B micro (see p80, May25) $10.00 PICO/2/COMPUTER (SC7468) (APR 25) siliconchip.com.au/Shop/ COMPACT HIFI HEADPHONE AMP (SC6885) (DEC 24) CAPACITOR DISCHARGER KIT (SC7404) (DEC 24) FLEXIDICE COMPLETE KIT (SC7361) (NOV 24) MICROMITE EXPLORE-40 KIT (SC6991) (OCT 24) Complete kit: includes everything except the power supply (see p47, Dec24) Includes the PCB and all components that mount on it, the mounting hardware (without heatsink) and banana sockets (see p36, Dec24) Includes all required parts except the coin cell (see p71, Nov24) Includes all required parts (see p83, Oct24) $70.00 $30.00 $30.00 $35.00 (OCT 24) Includes an assembled PCB, separate Raspberry Pi Pico 2 and front/rear panels $120.00 DUAL-RAIL LOAD PROTECTOR (SC7366) Hard-to-get parts: includes the PCB and all semiconductors except the ROTATING LIGHT FOR MODELS KIT (APR 25) optional/variable diodes (see p73, Oct24) $35.00 Complete kit which includes the PCB and all onboard components (see p60, Apr25): (SEP 24) - SMD LEDs (SC7462) $20.00 PicoMSA PARTS (SC7323) - Through-hole LEDs (SC7463) $20.00 433MHz TRANSMITTER KIT (SC7430) (APR 25) PICO 2 AUDIO ANALYSER SHORT-FORM KIT (SC6772) (MAR 25) USB PROGRAMMABLE FREQUENCY DIVIDER (SC6959) (FEB 25) NFC PROGRAMMABLE IR KEYFOB (SC7421) (FEB 25) PICO COMPUTER (DEC 24) Includes the PCB and all onboard parts (see p75, Apr25) The Pico Audio Analyser kit from Nov23, but with an unprogrammed Pico 2 Complete kit: includes all components (see p85, Feb25) Complete kit: includes all required items, except the cell (see p67, Feb25) Hard-to-get parts: includes the PCB, Raspberry Pi Pico (unprogrammed), plus all semiconductors, capacitors and resistors (see p63, Sep24) $50.00 $20.00 COMPACT OLED CLOCK & TIMER KIT (SC6979) (SEP 24) $50.00 DISCRETE IDEAL BRIDGE RECTIFIER (SEP 24) DUAL MINI LED DICE (AUG 24) $60.00 $25.00 Includes everything except the case & Li-ion cell (see p34, Sep24) $45.00 Both kits include the PCB and everything that mounts to it (see page 83, Sep24) - All through-hole (TH) kit (SC6987) $30.00 - SMD kit (SC6988) $27.50 Complete kit: choice of white or black PCB solder mask (see page 50, August 2024) - Through-hole LEDs kit (SC6849) $17.50 - SMD LEDs kit (SC6961) $17.50 For full functionality both the Pico Computer Board and Digital Video Terminal kits are AUTOMATIC LQ METER KIT (SC6939) (JUL 24) required. Items shown unbolded are optional (see p71, Dec24) - Pico Computer Board kit (SC7374) $40.00 Includes everything except the case & debugging interface (see p33, July24) $100.00 - Pico Digital Video Terminal kit (SC6917) $65.00 - Rotary encoder with integral pushbutton (available separately, SC5601) $3.00 - PWM Audio Module kit (SC7376) $10.00 ESR TEST TWEEZERS COMPLETE KIT (SC6952) (JUN 24) - ESP-PSRAM64H 64Mb SPI PSRAM chip (SC7377) $5.00 Includes all parts and OLED, except the coin cell and optional header $50.00 - DS3231 real-time clock SOIC-16 IC (SC5103) $7.50 MSC6936) ay 2025  77 siliconchip.com.au Australia's$10.00 electronics - 0.96inmagazine white OLED with SSD1306 controller (also sold separately, $10.00 - DS3231MZ real-time clock SOIC-8 IC (SC5779) *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. USB Power Adaptor Project by Nicholas Vinen This simple and cheap PCB provides an easy way to add a USB socket to a 5V DC powered device. It accepts a Type-C or mini/micro Type-B socket and provides optional reverse power flow/reverse polarity protection and LED power indication. I wanted to add a USB socket to my RGB LED Clock (the article just before this one) for power, but I couldn’t fit one near the PCB edge as it is totally occupied with LEDs. Horizontal USB connectors won’t work if placed in the middle of the board. Tim Blythman suggested I mount the socket on a small, separate PCB and suggested that it could have other uses. Hence this project. To make the board as flexible as possible, I have placed four different USB socket footprints on this tiny 12.7 × 26.5mm board. You can attach the very common SMD mini Type-B socket, one of two readily available micro Type-B sockets or one of two fairly standard Type-C sockets. Use whichever suits your needs. The resulting 5V DC is available on a set of four pads in the middle of the PCB. These allow a two-way pin header to be fitted in eight orientation and polarity combinations. This is especially handy if you’re mounting this PCB to another one via a pin header, as you can choose which direction the USB socket will face (north, south, east or west) regardless of the header polarity. You don’t have to attach this board to another one; you can solder a pair of wires, or a header and use jumper wires. In fact, it’d be a convenient way to feed 5V to a breadboard from a computer or USB charger. If using a micro Type-B socket, you can choose one with or without through-hole mounting pins; the PCB will accept either. Having said that, we’ve specified the type with pins in the parts list as it is easier to mount and more secure once soldered. Similarly, for USB Type-C, you can use a six-pin power-only socket or a 12-pin power-plus-data socket (the data pins are not connected). The circuit is very simple, as shown 78 Silicon Chip in Fig.1. You can use a 1A or 3A schottky diode for D1, or a 0W resistor (shown as a dashed link shorting D1 out). USB connectors are polarised, so in theory, you don’t need D1 for reverse-polarity protection. Its main purpose is to prevent power from feeding back into the USB power source if the target board is separately powered. So whether you fit D1 or a 0W resistor will depend on whether that is possible in your application. If you’re wiring up the USB cable yourself, or if its forward voltage is irrelevant (eg, the target board immediately reduces it to 3.3V with a low-dropout regulator), you may still want to fit D1 for reverse polarity protection. You don’t need to fit the LED and its series resistor if you don’t need a power-on indicator. As for the other two resistors, they are only required if you are fitting a USB Type-C socket, to signal to the power source to supply 5V. For Type-B sockets, you can just leave them off. Construction Depending on which socket you are using, follow the relevant overlay diagram: Fig.2(a) for USB-C power only, Fig.2(b) for USB-C power and data, Fig.2(c) for mini-B or Fig.2(d) for micro-B. All other required or optional components are shown fitted. If you don’t need LED1, leave it and the resistor on the opposite side of the board off. If you don’t need D1, replace it with the 0W resistor. Start by fitting the USB socket. It will make soldering easier if you spread a thin layer of flux paste over all the pads for your particular socket before you place it on the board. Only the USB-C power-only socket lacks locating posts; the others should snap into place and you can then tack one pin and check that all the pins are Australia's electronics magazine Fig.1: the four possible USB sockets are wired in parallel and it has provision for the two 5.1kW pull-down resistors needed for a Type-C socket to receive 5V. D1 prevents power flowing back into the USB socket, while LED1 provides power-on indication. siliconchip.com.au From left-toright: the Mini USB, USB-C & Micro USB versions. aligned. For the USB-C power-only socket, you’ll have to position it by eye initially. Remelt that initial solder joint and nudge it until its six relatively large leads are over their pads. Add a bit more flux paste over the remaining leads and then solder them. Once those leads have been soldered, you can solder the mechanical mounting pins or tabs. The USB-C power+ data socket is designed for 1mm-thick PCBs, which is why we’ve specified this board that way. Otherwise, its mounting tabs won’t go all the way through the board. You may need to turn your iron up a bit while soldering the mechanical mounting tabs as the USB socket case will draw heat away from them. Turn it back down when you’ve finished. Most sockets have pins that are closely spaced, so it’s likely you will have some bridges between them now. If you do, add some more flux paste and then press solder-wicking braid down on them with the tip of your soldering iron. Wait for the solder to flow, then slide the braid away from the pins. It should remove the excess solder and leave behind nice-­looking joints. Now is a good time to clean off any flux residue, either with a specialised flux remover, isopropyl alcohol or methylated spirits. Then inspect the board under magnification and good light. Verify that all the USB socket solder joints are good. If not, add some more flux paste and rework them, either by adding more solder or removing excess solder with the wicking braid. If you fitted either of the USB-C sockets, you’ll now need to install the two side-by-side 5.1kW resistors. Without them, you may not get power. Now move on to diode D1. If fitting it, make sure it’s orientated as shown. Otherwise, replace it with the siliconchip.com.au 0W resistor, so there is a path for current to flow from the USB socket to CON3/CON4. If you want the power indicator LED, solder it now. It is also polarised. The best way to do this is to use a DMM set on diode test mode to probe the ends of the LED until it lights up. The black probe will be touching the cathode when it does, so that is the side you solder to the pad marked K on the PCB. If fitting this LED, don’t forget its series resistor; otherwise, it can be left off. That just leaves pin header CON3/ CON4. There are two + symbols shown in two corners; the other corner pads are ground (ie, negative). There are four possible positions that you can solder a two-pin header here, on either side of the board. Whichever one you choose, one of its pins will go to a pad marked with a + symbol. So choose the location that gives your required polarity (if it matters). Fig.2 shows four of the possible locations for that header. Alternatively, Fig.2: follow the appropriate overlay diagram for the socket you are using. All show D1 and LED1 fitted but you can replace the former with a 0# resistor or wire link, or omit the latter, if you want. The presence and location of CON3/ CON4 will also depend on your requirements. Australia's electronics magazine May 2025  79 Parts List – USB Power Adaptor 1 1mm-thick black double-sided PCB coded 18101251, 12.7 × 26.5mm 2 5.1kW M3216/1206 SMD resistors (only required for Type-C USB sockets) 1 0W M3216/1206 SMD resistor/link Pick one of these sockets: 1 SMD Type-C USB power-only socket (CON1) [GCT USB4135 or equivalent] 1 SMD Type-C USB 2.0 socket (CON2) [GCT USB4105 or equivalent] 1 SMD mini Type-B socket (CON5) [Molex 0675031020 or equivalent] 1 SMD micro Type-B socket (CON6) [GCT USB3080-30-01-A or equivalent] Optional parts 1 2-pin header (CON3/CON4) 1 SS14 (1A), SS34 (3A) or equivalent schottky diode, DO-214AC (D1) 1 M3216/1206/SMA SMD LED plus 5.1kW M3216/1206 SMD resistor (LED1) simply solder two wires to these pads, one to a pad marked + and the other to an unmarked (ground) pad. The accompanying photo shows the USB Power Adaptor fitted with a Type-C socket mounted on our RGB LED Analog Clock (presented earlier in this issue) using CON3. That position was chosen as it matched the polarity of the power header on the Clock PCB. Testing Plug your assembled board into a USB power supply and use a DVM to check the output at CON3/CON4. If you connect the red probe to a + pad and the black probe to one of the other two, you should get a reading of about +5V, or +4.7V if you fitted D1 rather than a 0W resistor or wire link. If you get nothing, check that your supply is on and that diode D1 is orientated correctly or linked out. If you fitted LED1, it should light up. If you can measure voltage but it isn’t on, it may be backwards or have a bad solder joint. Also check the series resistor’s solder joints. All that’s left is to wire this up or solder it to your target board, apply power and check that it works. Make sure you get the output connection polarity right! Note that the final version of the PCB fixes a couple of minor problems with the prototype ones shown in the photos. It’s a little bit shorter so the plugs can reach the sockets more easily, the USB-C 2.0 connector has four solder pads to secure the shell rather than two, and the micro-B footprint was improved to make it easier to solder and more secure. The power + data version of the USB-C Power Adaptor. We didn’t have a 0W resistor on hand so used a piece of wire instead. Using it Besides the RGB LED Analog Clock, some of our recent projects that this board could potentially be used with include: • Coin Cell Emulator (December 2023; siliconchip.au/Article/16046) • TQFP Programming Adaptors (October 2023; siliconchip.au/Article/ 15977) • Eight Small LED Christmas Ornaments (November 2020; siliconchip. au/Article/14636) • Dual-Channel Breadboard PSU (December 2022; siliconchip.au/ Series/401) In some cases, the connection would be made via the ICSP (in-­ circuit serial programming) header, which has VDD and GND pins next to each other, suitable for connection SC to CON3/CON4 on this board. One of the USB-C versions of the Power Adaptor attached to our new RGB LED Clock. USB Power Adaptor Kit (SC7433, $10.00) Includes everything in the parts list – and a choice of one USB socket from: 1. USB-C power only 2. USB-C power+data 3. mini Type-B 4. micro Type-B. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT 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) 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 CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION 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) 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 DATE 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 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 JAN24 JAN24 JAN24 JAN24 PCB CODE 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 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 04106181 04106182 15110231 01108231 01108232 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 Price $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 $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 $2.50 $2.50 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 $10.00 $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 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT 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 SKILL TESTER 9000 PICO GAMER ESP32-CAM BACKPACK WIFI DDS FUNCTION GENERATOR 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (BLUE) FAN SPEED CONTROLLER MK2 ESR TEST TWEEZERS (SET OF FOUR, WHITE) DC SUPPLY PROTECTOR (ADJUSTABLE SMD) ↳ ADJUSTABLE THROUGH-HOLE ↳ FIXED THROUGH-HOLE USB-C SERIAL ADAPTOR (BLACK) AUTOMATIC LQ METER MAIN AUTOMATIC LQ METER FRONT PANEL (BLACK) 180-230V DC MOTOR SPEED CONTROLLER STYLOCLONE (CASE VERSION) ↳ STANDALONE VERSION DUAL MINI LED DICE (THROUGH-HOLE LEDs) ↳ SMD LEDs GUITAR PICKGUARD (FENDER JAZZ BASS) ↳ J&D T-STYLE BASS ↳ MUSIC MAN STINGRAY BASS ↳ FENDER TELECASTER COMPACT OLED CLOCK & TIMER USB MIXED-SIGNAL LOGIC ANALYSER (PicoMSA) DISCRETE IDEAL BRIDGE RECTIFIER (TH) ↳ SMD VERSION MICROMITE EXPLORE-40 (BLUE) PICO BACKPACK AUDIO BREAKOUT (with conns.) 8-CHANNEL LEARNING IR REMOTE (BLUE) 3D PRINTER FILAMENT DRYER DUAL-RAIL LOAD PROTECTOR VARIABLE SPEED DRIVE Mk2 (BLACK) FLEXIDICE (RED, PAIR OF PCBs) SURF SOUND SIMULATOR (BLUE) COMPACT HIFI HEADPHONE AMP (BLUE) CAPACITOR DISCHARGER PICO COMPUTER ↳ FRONT PANEL (BLACK) ↳ PWM AUDIO MODULE DIGITAL CAPACITANCE METER BATTERY MODEL RAILWAY TRANSMITTER ↳ THROUGH-HOLE (TH) RECEIVER ↳ SMD RECEIVER ↳ CHARGER 5MHZ 40A CURRENT PROBE (BLACK) USB PROGRAMMABLE FREQUENCY DIVIDER HIGH-BANDWIDTH DIFFERENTIAL PROBE NFC IR KEYFOB TRANSMITTER POWER LCR METER WAVEFORM GENERATOR PICO 2 AUDIO ANALYSER (BLACK) PICO/2/COMPUTER ↳ FRONT & REAR PANELS (BLACK) ROTATING LIGHT (BLACK) 433MHZ TRANSMITTER DATE FEB24 FEB24 FEB24 FEB24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 APR24 APR24 APR24 MAY24 MAY24 MAY24 JUN24 JUN24 JUN24 JUN24 JUN24 JUL24 JUL24 JUL24 AUG24 AUG24 AUG24 AUG24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 OCT24 OCT24 OCT24 OCT24 OCT24 NOV24 NOV24 NOV24 DEC24 DEC24 DEC24 DEC24 DEC24 JAN25 JAN25 JAN25 JAN25 JAN25 JAN25 FEB25 FEB25 FEB25 MAR25 MAR25 MAR25 APR25 APR25 APR25 APR25 PCB CODE 01110231 01110232 09101241 09101242 16102241 16102242 07112231 07112232 07112233 16103241 SC6903 SC6904 08101241 08104241 07102241 04104241 04112231 10104241 SC6963 08106241 08106242 08106243 24106241 CSE240203A CSE240204A 11104241 23106241 23106242 08103241 08103242 23109241 23109242 23109243 23109244 19101231 04109241 18108241 18108242 07106241 07101222 15108241 28110241 18109241 11111241 08107241/2 01111241 01103241 9047-01 07112234 07112235 07112238 04111241 09110241 09110242 09110243 09110244 9049-01 04108241 9015-D 15109231 04103251 04104251 04107231 07104251 07104252/3 09101251 15103251 Price $7.50 $7.50 $5.00 $2.50 $5.00 $2.50 $5.00 $2.50 $2.50 $20.00 $20.00 $7.50 $15.00 $10.00 $5.00 $10.00 $2.50 $5.00 $10.00 $2.50 $2.50 $2.50 $2.50 $5.00 $5.00 $15.00 $10.00 $12.50 $2.50 $2.50 $10.00 $10.00 $10.00 $5.00 $5.00 $7.50 $5.00 $2.50 $2.50 $2.50 $7.50 $7.50 $5.00 $15.00 $5.00 $10.00 $7.50 $5.00 $5.00 $2.50 $2.50 $5.00 $2.50 $2.50 $2.50 $2.50 $5.00 $5.00 $5.00 $2.50 $10.00 $5.00 $5.00 $5.00 $10.00 $2.50 $2.50 VERSATILE BATTERY CHECKER ↳ FRONT PANEL (BLACK, 0.8mm) TOOL SAFETY TIMER RGB LED ANALOG CLOCK (BLACK) USB POWER ADAPTOR (BLACK, 1mm) MAY25 MAY25 MAY25 MAY25 MAY25 11104251 11104252 10104251 19101251 18101251 $5.00 $7.50 $5.00 $15.00 $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 Microchip’s RNBD451 Bluetooth Module and EV25F14A Evaluation Board There are a few different ways to connect to your device via Bluetooth, including the wellknown HC-05 and HC-06 modules. Microchip’s RNBD451 Bluetooth module is another option that offers many more features. Review by Tim Blythman B luetooth technology has been around for about 20 years and is incorporated into many modern devices. It uses the 2.4GHz ISM (industrial, scientific and medical) license-free radio band and is well suited to use over short distances; up to 10m is the typical range. ‘Classic Bluetooth’ supports several ‘profiles’ that encapsulate the needs of a specific interface. For example, the handset profile (HSP) allows an external Bluetooth headset to communicate via the voice channel of a mobile phone, while the serial port profile (SPP) provides a serial link. Hobbyists have had access to Bluetooth modules for a while now. One of the better-known implementations of the serial port profile is the HC-05 module, based on a Cambridge Silicon Radio chip loaded with a custom firmware. That allows these modules to behave as a UART (universal asynchronous receiver/transmitter) bridge. They have an AT-command interface so they can be configured over the serial port, The RNBD451 module is a small PCB (shown adjacent at actual size) with a metal shield covering just about everything except a PCB trace antenna. Connections are made via pads on the underside of the board. The WBZ451 marking indicates the part on which this module is based. 82 Silicon Chip allowing custom device names, baud rates and security settings. The RNBD451 Bluetooth module is similar in that it can emulate a serial port, but it has quite a few other features too. In particular, it uses lowpower BLE (Bluetooth Low Energy) technology. RNBD451 Bluetooth module The RNBD451 is a compact module at 15.5 × 20.7mm. It is in the form of a PCB with trace antenna and a metal can housing the RF components. Connections are made via SMT pads on the underside of the module. It is currently available for just over $10, so it is on par with prices for similar modules. It is based on Microchip’s PIC32CX-BZ2 BLE SoC (Bluetooth Low Energy System on a Chip), a 32-bit ARM processor with an integrated 2.4GHz RF transceiver. Like the HC-05 modules, the processor has integrated flash memory that is loaded with a program to provide its features. Fig.1 shows the block diagram of the RNBD451 module. Although not supported in this module, the PIC32CX-BZ2 SoC can also work with other protocols that operate in the 2.4GHz ISM radio band, like Zigbee and Thread. Unlike the sparse and sometimes inaccurate documentation that exists for the HC-05 modules, the RNBD451 has a 200-page user guide fully describing its many features, which easily surpass those of the HC-05. We initially took an interest in the RNBD451 as a replacement for HC-05 modules. In most cases, they are permanently connected to a microcontroller and translate a logic-level UART serial data link wirelessly using Bluetooth. The Bluetooth link replaces a hard-wired connection, turning a wired connection into a wireless one. An example of this is the “Micromite to a Smartphone via Bluetooth” project (September 2021; siliconchip. au/Article/15031). It explains how the HC-05 can allow a Micromite to communicate with a mobile device. You can use such a wireless link to program the Micromite, send Fig.1: as well as a 32-bit ARM processor, the RNBD451 has power, oscillator and RF blocks, among others. The power stage at upper left can be switched between a buck (step-down) or LDO (linear) regulator by sending the appropriate command. Australia's electronics magazine siliconchip.com.au commands to it, receive data from it, or even modify the program in place using the Micromite’s fullscreen editor. In this article, we will similarly explain what is involved in configuring the RNBD451 modules to work with devices that expect a serial connection. It’s also possible to pair two RNBD451 modules to completely replace a wired serial link with a wireless Bluetooth link. Fig.2 shows a few of these scenarios. We’ll also cover some of the numerous options and settings that the module offers, plus some other Bluetooth features. As the RNBD451 modules use the newer BLE (Bluetooth Low Energy) standards, they should use less power to achieve similar range. BLE does not support the traditional serial port profile, so this device will not necessarily be a drop-in replacement for the HC-05 or other SPP devices. Instead, like many BLE devices, it uses the so-called Generic ATTribute profile (GATT) to pass serial data. Three GATT ‘characteristics’ are provided, each of which has an associated 128-bit UUID (universally unique identifier). The three GATT characteristics provide a serial transmit channel, a serial receive channel and a control channel. Each characteristic can only pass 20 bytes at a time, so the data is effectively sent in 20-byte packets. Other devices communicating with the RNBD451 modules must conform to the specific service characteristics that it provides. A second RNBD451 is one of the ways to achieve that. Interestingly, the so-called HM-10 serial Bluetooth modules use much the same scheme, although they use different services and characteristics. That explains why they are less widely used than the HC-05 modules; they do not support the classic Bluetooth serial port profile that the HC-05 does. App support Programs on other devices can also interoperate with the RNBD451’s service characteristics. Microchip provides the Microchip Bluetooth Data app for Android and iOS, which has a serial terminal program for communicating with the RNBD451 modules. This app can also be used to test various BLE features as well as perform firmware updates on modules. OTA (over the air) updates for the module are sent via the Bluetooth link. siliconchip.com.au Fig.2: Bluetooth allows wireless communication in several different scenarios. Using a Bluetooth serial device like the RNBD451 module adds the possibility of using Bluetooth with a device that might not be natively equipped. We were also able to use the Serial Bluetooth Terminal Android app (by Kai Morich) to communicate with the RNBD451 modules. This is an app we previously used with HC-05 modules. Like the Microchip app, it identifies that the connected BLE device provides the specific service characteristics and communicates through them. EV25F14A Evaluation Board The EV25F14A Evaluation Board contains an RNBD451 module plus some extra circuitry to allow you to easily test it out and communicate with it. It is also described as an RNBD451 Add-on Board. There is an MCP1727 LDO (low dropout) regulator for 3.3V and an MCP2200 USB-serial chip to connect to the serial interface. The MCP2200 thus provides a virtual serial port at the operating system level (eg, a COM port on Windows or /TTY device on Linux) so it can be accessed by a serial terminal emulator, like TeraTerm, the Arduino IDE serial monitor or the MMEdit console. There are some onboard indicator LEDs and a few breakout headers, including a ‘mikroBUS Click’ header. The Click header provides two 8-pin 2.54mm pitch headers, suitable for plugging into a breadboard or matching socket header on a project PCB. While the Click standard can work with SPI and I2C, the Click header on the EV25F14A only breaks out power, the serial bus (including flow control lines) and some digital status & control Australia's electronics magazine The EV25F14A Evaluation Board (shown at twice actual size) contains an RNBD451 module and a USB-serial adaptor to allow the module’s features to be easily tested from a computer. A 16-pin ‘Click’ header can plug into a breadboard or PCB, while the jumper shunt selects the power source (from the Click header or USB power regulated down to 3.3V). May 2025  83 pins. All logic levels are 3.3V and its pinout (from above) is shown in Fig.3. Testing Fig.3: the ‘Click’ header on the EV25F14A Evaluation Board follows a standard layout, allowing Click modules and boards to easily interoperate. Other Click boards include SPI or I2C on the pins that the EV25F14A uses for serial ancillary functions. The header could be used to connect this board to another PCB, while the wiring here shows how it could be connected to another serial device. The underside of the EV25F14A Evaluation Board (shown at twice actual size). 84 Silicon Chip Using the USB-serial converter built in to the EV25F14A allowed us to easily check the operation of the RNBD451 module in a serial terminal program. We used TeraTerm under Windows, but any program that can connect to a virtual USB-serial port should work. The default settings for the serial port are 115,200 baud, eight bits, no parity and one stop bit; in TeraTerm we just needed to change the baud rate. The commands expect CR (carriage return) only as their line ending. The RNBD451 uses a scheme similar to the old Hayes-compatible dial-up modems to switch between data and command mode. In command mode, the serial data is treated as commands, while in data mode, the serial data is passed to the remote device. The string ‘$$$’ switches to command mode. The commands are similar to those of the Hayes modems, being a short sequence followed by parameters separated by commas if they are needed, although the RNBD451 command set has different needs to that of a modem. The sequence shown in Screen 1 was sufficient to pair with a second EV25F14A on another serial port. The yellow text is entered into the terminal window, while the white text is produced by the EV25F14A. Entering the sequences “$$$” followed by “D<CR>” switches the module to command mode and shows the six lines of local status information. The command “SR,0001<CR>” enables the Bluetooth status LED on the EV25F14A; the AOK response is the typical for successful command execution. Many ‘set’ commands, like “SR<CR>” have a corresponding ‘get’ command with a ‘G’ prefix; “GR<CR>” will report back the results of using the “SR<CR>” command. This command requires a reboot to take effect, so “R,1<CR>” is entered, followed by another “$$$” to re-enter command mode after the reboot. The command “C,0,9C956E4426C4<CR>” connects to the device with that specific hardware address. You could find the hardware address by running the “D<CR>” command Australia's electronics magazine on the remote device or running the scan command, “F<CR>”, locally. Both terminals then show a flurry of activity, with responses bracketed by % characters. With the %STREAM_OPEN% response, the EV25F14A reverts to data mode. You would not know that, except by seeing that data is sent to the remote device instead of being taken as a command. Another “$$$”, followed by “B<CR>”, bonds to the remote device. You can see the remote device’s actions in the lower terminal window. The command to exit command mode is “---<CR>” (three dashes). At this stage, the two modules are paired and will behave as a transparent serial link. With the intended role of the RNBD451 module being to connect with a microcontroller, such a microcontroller would have to send these commands, plus perhaps a few more, to the module in order to control it. Fewer commands would be required if the modules were permanently paired to a single device. There are also commands to manually connect and disconnect from remote devices. They could be handy if you are using one device to communicate with several others. Up to eight devices can be paired, but only one can be connected at a time. There are also modes to modify the security and visibility of the modules; they might need to be appropriately set to ensure that unauthorised access is not possible. There are commands to change the command and data delimiters (eg, ‘$’, ‘-’ and ‘%’) so that they don’t conflict with any data format you might be using. Many more commands exist; the complete reference is available online at siliconchip.au/link/ac07 The delimiters can also be cleared, which means that many of the status strings will be disabled. That may be preferable for simple applications. The SR options command can also configure one of the I/O pins to be used to switch between command data modes. Another option for setting up multiple devices is the remote control mode, which allows remote commands to be sent over the Bluetooth link between two RNBD451 modules. Like the HC-05 modules, there are commands to change the baud rate, serial data format, device name, PIN siliconchip.com.au Screen 1: with two EV25F14A Evaluation Boards connected to serial terminals, we can observe the process of pairing and connecting. The yellow text marks commands entered into the terminal window, while the white text is their output. No action is needed on the second module. Screen 2: the main ◀ page of the Microchip Bluetooth Data app has numerous options. This app is intended to be used with a wide range of Microchip’s Bluetooth equipped devices. access code and so forth. The syntax is a bit different, but simple enough. We made good use of the factory reset command (“SF,2<CR>”) during testing. One handy command allows the device name to be set using the last four nybbles (half-bytes) of the device MAC address as a suffix. This means that numerous devices could be easily set to have unique names based on the same prefix. We also tested wiring a CP2102based USB-serial converter to the EV25F14A (instead of its onboard USB-serial chip) and the connections we used are shown in Fig.3. Note that the jumper shunt on the EV25F14A needs to be changed over to take power from the Click header. These minimal connections might be all that is needed to add the evaluation board to a project to give it a wireless serial link, and would be much easier than soldering the tiny RNBD451 module. Using the apps The mobile device apps can be used to connect to the RNBD451 or EV25F14A. This could make things simpler, since pairing and configuration can be done on the mobile device. We started with the Microchip Bluetooth Data app, shown in Screen 2. We tested this on Android but expect the iOS version to be similar. Next, we selected the BLE UART option, siliconchip.com.au followed by the PIC32CXBZ option seen in Screen 3. Running a SCAN (Screen 4) showed the compatible devices that were in range. Tapping on a device will bring you to Screen 5. If the remote device is an EV25F14A connected to a serial terminal program, you should see the connection status reports as the app connects to the remote device. Screen 5 shows the results of a Burst Mode test, which sends a 100kiB file over the BLE link to test its speed. The resulting 11.38kiB/s is consistent with the 115,200 baud limit on the downstream serial port. The Text Mode button provides a simple serial terminal interface for text communication with the remote device. This could be used, for example, to connect to a device and interact with it, running commands or reading status information, as you might with a wired serial connection. This is not a fully-featured terminal program like TeraTerm; it is a simple line terminal, sending and receiving plain text. It does not provide features like VT100 terminal emulation that some devices require, such as the Micromite’s fullscreen editor facility. Other Microchip app features The BLE Smart menu option (seen in Screen 2) simply provides a scan of nearby BLE devices, as shown in Screen 6. Selecting one of the Australia's electronics magazine Screen 3: with the RNBD451 module being based on the PIC32CX-BZ2 processor, this is the option that should be chosen from the BLE UART screen. Screen 4: a scan shows the hardware (MAC) address of nearby compatible devices and the corresponding RSSI (received signal strength indicator) readings. May 2025  85 EV25F14A boards and connecting to it provides further information about the services provided. The BLE Connect option offers a similar scan and report about nearby devices. The serial command interface of the RNBD451 can also conduct a scan and get a response in text format about nearby devices. We mentioned the OTA DFU (over the air device firmware update) option earlier, which can be seen in Screen 8. We didn’t see any need to try it out, but it could be helpful if newer features become available in the future. It’s also possible to apply firmware updates over the serial connection. It is apparent that the Microchip app can work with many more devices that just the RNBD451 and EV25F14A. Microchip also has some software examples and libraries available at https://github.com/MicrochipTech A search for RNBD451 finds an Arduino library and sample projects for interfacing with the RNBD451. The source code for the Android and iOS apps is also available. Serial Bluetooth Terminal Screen 5: the burst data transmission test runs practically at the limit of the 115,200 baud hardware serial link. Screen 7: selecting a device from the BLE Devices scan shows the services and characteristics it provides. Some of these are used to implement the serial communication interface of the RNBD451. We have used this app on Android devices for many years, and it even works with devices like the HM-10 and HC-05. Screen 9 shows how a device can be selected for connection. Note that there are separate tabs for Bluetooth Classic (eg HC-05 devices) and BLE devices (most others). Screen 10 shows the terminal window; like the Microchip app, it does not provide all the terminal emulation features that you would have on programs like TeraTerm. Computer applications Screen 6: the BLE Devices option in the Microchip Bluetooth Data app can scan for all nearby Bluetooth devices. 86 Silicon Chip Screen 8: an OTA DFU (over the air device firmware update) can be performed from the Microchip Bluetooth Data app using the Bluetooth link. Australia's electronics magazine The one thing that stands out from all this is the lack of a fully-featured terminal program that can interact with devices that offer terminal emulation facilities, like the fullscreen editor of the Micromite. Under Windows, it is possible to create a virtual serial port to connect to a traditional Bluetooth SPP device. However, that does not appear to be the case for devices using custom BLE services. We found a project that appears to bridge this gap at https://github.com/ Jakeler/ble-serial although it’s not clear if it supports the characteristics used by Microchip, and it is still not as straightforward as for SPP devices. siliconchip.com.au The simplest way we found to get around this was to use the USB-serial adaptor of the EV25F14A board and connect to it using TeraTerm on Windows. Any other terminal program that can communicate with virtual USB-serial ports should work with the EV25F14A. In this case, connecting to devices and pairing must be done through the terminal interface, rather than a menu on the computer. However, that is easy enough when you become familiar with a few basic commands. to near 18mA during long periods of transmission. Internally, the module can use a buck or LDO regulator; the LDO is used by default. We found that the buck regulator saves around 5mA, although the module is only rated to operate down to 2.4V when using the buck regulator. There are several power-saving modes that can be activated through the command interface. Some modes will automatically wake up at intervals, or the device can be woken by a signal on one of the I/O pins. Other features GPIO pin control The hardware data sheet for the module (siliconchip.au/link/ac0a) and the data sheet for the EV25F14A Evaluation Board (siliconchip.au/link/ ac09) relate to the hardware and such things as pinouts. You can also find circuit diagrams for parts of the EV25F14A Evaluation Board, which will be very handy for creating a design which similarly incorporates the RNBD451 module. The user guide for the RNBD451 module stretches to over 200 pages (siliconchip.au/link/ac08). This is where you will find information about the command interface and software operation of the module (and thus the evaluation board). This document describes (in chapter 7) the ability to set up custom GATT services and characteristics. That may suit a simple application that needs to exchange infrequently changing status information. It might also be possible to emulate other existing BLE devices by mimicking their characteristics. The RNBD451 can also be configured to offer lowpower beacon advertisements. There are many ways to use BLE devices to create a positioning system (say, like GPS, but indoors), using relative signal strength (RSSI) as a proxy for distance. The RSSI of remote or scanned devices can be read through the command interface. The RNBD451 module has many more pins than are needed for a simple serial interface, so some can be configured as GPIO (general purpose input/output) pins. Using commands over the serial data link, pins can be set high or low or their status read back. One pin is also connected to an ADC (analog-to-digital converter), so an analog level, such as a battery voltage, can be read too. Some pins can be configured to change state if serial data arrives, allowing the main microcontroller to remain in a low-power sleep mode. It can be woken up before the RNBD451 module sends the data it has received. Power supply The RNBD451 datasheet notes it can operate between 1.9V and 3.6V, so it would be well-suited to use in battery-powered scenarios with a 3V supply, or taking power from a lithium battery via a low-dropout regulator. Operating from a 3.3V supply, we found that a bare RNBD451 module consumed around 13mA, jumping up siliconchip.com.au Screen 9: the Serial Bluetooth Terminal app can scan for and connect to a number of BLE and Bluetooth Classic devices. Conclusion The RNBD451 module is not quite a drop-in replacement for the likes of the HC-05 Bluetooth serial modules, but can be configured to provide most of the same features and more. The modules don’t have native Bluetooth support under Windows (as virtual COM ports), so we recommend using an EV25F14A as a bridge to allow communication with fully featured serial terminal emulators like TeraTerm. The remote control and configuration features of the RNBD451 module are very handy when they are used in pairs. With the ability to configure custom services and characteristics, the RNBD451 can be used for many other tasks beyond simple serial communication. The RNBD451 module and EV25F14A Evaluation Board are available from DigiKey and Mouser: • DigiKey 150-RNBD451PEI110-ND • DigiKey 150-EV25F14A-ND • Mouser 579-RNBD451PE-I110 • Mouser 579-EV25F14A SC Australia's electronics magazine Screen 10: the Serial Bluetooth Terminal app provides a simple linebased means of sending and receiving data from a remote device. May 2025  87 By Andrew Levido Precision Electronics Part 7: Analog-to-Digital Conversion Last month, in the sixth instalment in this series, we covered the various sources of analog-to-digital and digital-to-analog conversion errors. We also looked at digitalto-analog converters (DACs) in detail. This month, we will focus on analog-to-digital converters (ADCs) and, as usual, that will include a practical example. J ust as a quick recap, we saw that all converters exhibit quantisation errors due to the discrete way numbers are represented in digital systems. Quantisation error is directly related to the number of bits (the resolution) of the converter. We saw that this can cause quantisation noise if we are dealing with AC signals. On top of quantisation errors, we saw that there are usually offset, gain and non-linearity errors associated with conversion and that these can be combined to give a total unadjusted error (TUE) figure that can be used in error calculations. All of this applies equally to DACs and ADCs. Sampling and aliasing In contrast to DACs, which convert discrete digital codes to discrete voltage levels, ADCs have to convert an infinitely variable (and maybe varying) voltage level to discrete digital codes. We therefore have to ‘sample’ the analog voltage at some instant in time and convert that value to the appropriate (nearest) digital code. Because the conversion takes a finite amount of time, in most instances, we want to take a ‘snapshot’ of the input voltage so that the entire conversion process takes place with a fixed input value. For this reason, many converters (but not all, as we shall see below) are preceded by a ‘sample-and-hold’ circuit similar to that shown in Fig.1. The output of the sample-and-hold buffer follows the input during the sampling period, when the switch is closed. It is held constant by the capacitor during the hold period, while the switch is open. The conversion takes place during the hold period while the value is stable. In Fig.1, I have shown the sample and hold’s output (red trace) instantaneously snapping back to track the input voltage when the switch is closed. In reality, the capacitor takes a finite time to charge or discharge. If your ADC has a sample-and-hold system, you need to make sure the sampling time is long enough for the capacitor to fully charge to the signal voltage through the signal’s source impedance. This source impedance can include the sample-and-hold switch on-­resistance, the on-­resistance of any analog multiplexer, and the external source impedance. Values in the kilohms range are not unusual. The sampling time should be long enough for the capacitor voltage to Fig.1: the output of a sample-and-hold circuit follows the input while the switch is closed, but ‘freezes’ the value while it is open. This allows the analog-to-digital conversion process to occur with a steady input voltage. 88 Silicon Chip Australia's electronics magazine charge or discharge to within ½LSB (least significant bit) of the signal voltage to avoid adding error to the conversion. Many ADCs allow the user to control the sampling time for this purpose. Assuming we want to perform the analog-to-digital conversion on an ongoing basis, we need to sample and convert the input signal at regular intervals. We call these intervals the sampling rate. The Nyquist-Shannon sampling theorem states that an AC signal can be fully reconstructed (without any loss whatsoever) so long as the sampling rate, fsamp, is at least twice the highest frequency component present in the signal (fmax). The particular sampling rate that is exactly twice fmax is the known as the Nyquist frequency, fn. If we sample at a higher rate than strictly necessary (fsamp > fn), we are said to be oversampling, while if we sample at a lower rate (fsamp < fn), we are undersampling. We often want or need to oversample, but we generally try to avoid undersampling as it can lead to a phenomenon called aliasing, which can give rise to significant errors. Fig.2 shows what can happen if we Fig.2: here a 1kHz signal is sampled at 1.25ksps, lower than the Nyquist limit of 2ksps. This results in the ADC measuring a 250Hz alias signal instead of the expected 1kHz signal. siliconchip.com.au undersample a signal. Here, a 1kHz sinewave (shown in blue) is sampled at about 1.25ksps – lower than the Nyquist frequency of 2ksps. The sample points (red dots) trace out a false ‘alias’ signal with a frequency of 250Hz. Within the digital system, we will have no idea that the true signal includes a 1kHz component and that the 250Hz signal is an alias – all we will measure is the 250Hz sinewave. To avoid aliasing, we must ensure that there is no content in the sampled signal with a frequency higher than ½fsamp. This can be achieved by limiting the bandwidth of our signal with a filter, or by using a high enough sampling rate. In practice, we often need to do both. For wideband signals, it can be difficult or impossible to totally eliminate aliasing since perfect ‘brick wall’ filters are hard to come by! Instead, we have to be satisfied with reducing the amplitude of the worst possible alias to something we can live with. It is easiest to understand this in the frequency domain, as shown in Fig.3. In each diagram, the vertical axis is the relative amplitude of the signal in decibels (dB), while the horizontal axis is the frequency on a linear scale. We are interested in digitising a broadband signal within the band of interest shown shaded in blue. Because the signal is broadband, we apply some low-pass filtering with corner frequency fc, shown by the solid curve. The dotted lines represent the magnitude of the alias signals obtained by reflecting the filter roll off about the Nyquist limit (½fsamp). If the filter had a ‘brick wall’ cutoff, there would be no aliasing. Silicon Chip kcaBBack Issues $10.00 + post $11.50 + post $12.50 + post $13.00 + post January 1997 to October 2021 November 2021 to September 2023 October 2023 to September 2024 October 2024 onwards In the first diagram, we try to eliminate aliasing by adding a second-­ order low-pass filter, with its corner frequency set at the upper end of the bandwidth of interest, and by oversampling by 50% (the Nyquist limit is set 50% higher than the upper limit of the band of interest). You might think that this would be enough to eliminate aliasing, but unfortunately, it is not. The dotted line shows that there will still be an alias component within the band of interest, although it will be 6dB or more below the level of the signal of interest. This happens because there is still content in the low-pass filtered signal with frequency components above the Nyquist limit, albeit at a low level. The second chart shows that using a fourth-order filter, with its steeper roll-off, helps by shifting the alias signal down to -16dB or lower. We could improve this even further by using a sixth- or eighth-order filter, at the expense of complexity. The final chart shows what happens if we retain the fourth-order filter but increase the sampling rate to oversample at 100%, rather than the 50% in the first two cases. The alias signal is now down by 30dB or more. The long and short of this is that if you are digitising signals with a broadband AC component, you need to choose your sampling rate and filter 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 configuration carefully to ensure you don’t introduce errors due to aliasing. You don’t have to eliminate the aliases entirely – you just need to get them down to a level where the errors from them are manageable. You may not need an anti-aliasing filter or oversampling if your signal is band-limited by its very nature. If your signal is nominally DC (or at least very slowly changing), you can be even more relaxed about choosing the sampling rating and anti-aliasing filter. Flash ADCs With anti-aliasing taken care of, and a sample-and-hold system keeping our ADC’s input constant while sampling, we are ready to actually convert our analog signal to a digital one. The most straightforward way to do this is the ‘flash’ or parallel ADC, a simple threebit example of which is shown overleaf in Fig.4 (this is not directly related to flash memory). A resistor string establishes a series of threshold voltages representing the transition voltages between each code. The input voltage is simultaneously compared to all of these thresholds. A comparator output will be asserted low if the input voltage exceeds the respective transition threshold. A priority encoder outputs the code associated with the highest-­value input that is asserted. Fig.3: using a higher-order low-pass filter and increasing the sampling rate can both help reduce aliasing when digitising broadband signals. siliconchip.com.au Australia's electronics magazine May 2025  89 True flash converters require 2n matched resistors and the same number of comparators (where n is the resolution in bits), so they are usually limited to about 16 bits, but they are very fast. They can make a conversion every clock cycle, so they can reach sampling rates in the Gsps (gigasamples per second or 1,000,000,000+ samples per second) range. Many modern flash ADCs use a multistage architecture with a series of lower bit-count flash conversions of increasing precision. These ‘pipelined’ flash converters can have a latency of several tens of clock cycles, but maintain conversion rates in the Gsps range, since sequential samples are being processed in each stage. Several flash ADCs can be interleaved to achieve even higher sampling rates. If you have a digital oscilloscope (DSO), it most likely uses a pipelined flash converter with eight, 10 or 12 bits of resolution and a multiGsps sampling rate. Successive approximation Successive approximation analog-­ to-digital conversion uses a binary search strategy to find the digital code corresponding to the analog input. A simplified three-bit successive approximation converter is illustrated in Fig.5. At the start of the conversion cycle, the controller clears the successive approximation register and sets its MSB to one. The output of the DAC will therefore be a voltage that is 50% of the full scale. The comparator checks if the input voltage is above or below this threshold. If it is above 50% (comparator output high), the MSB in the SAR remains set; otherwise, it is cleared. The controller then sets the next most significant bit so the DAC and comparator can check if the input voltage lies in the upper or lower part of the appropriate sub-range. Again, the bit remains set or is cleared based on the comparator output. This process continues bit-by-bit until the value of the least significant bit is confirmed. At this point, the controller latches the SAR contents through to the converter output, and the cycle can begin again. This binary search process is shown graphically on the right side of Fig.5. Starting with the MSB, each bit is set or cleared successively until the output code is complete. This iterative approach means that the conversion takes at least one clock cycle for each bit, so SAR converters are generally slower than flash converters, with conversion rates typically limited to the Msps (megasamples) range. This is the type of converter you will usually find in microcontrollers and many low-cost serial interface ADC chips. Integrating converters Fig.4: a ‘flash’ ADC compares the input signal to each threshold voltage simultaneously. The output is the digital code associated with the highest threshold the input signal reaches. 90 Silicon Chip You can see why a sample-and-hold system is important if you are using a successive approximation ADC. If the value of the input were to change mid-conversion, the result could be a wrongly set bit and therefore a potentially significant error. However, there is a class of converter – the integrating converter – that can accommodate a changing input during the conversion cycle. In fact, we can use this characteristic to our advantage. Australia's electronics magazine The simplest integrating converter is the single-slope variant shown in Fig.6. When the start signal is pulsed, the flip-flop is set, the transistor is switched off and capacitor C begins to charge linearly at a rate determined by the value of the current source. Simultaneously, the clock is gated through to the counter, which begins counting up. When the voltage on the capacitor rises to Vin, the comparator resets the flip-flop and stops the counter, which holds a number proportional to the time taken to charge the capacitor to Vin. The count time is given by Tcount = C × Vin ÷ I and the count value will be N = (C × Vin) ÷ (I × Tclk), where Tclk is the clock period. The output count is therefore dependent not only on Vin and the current I but also on the capacitor value and the precision of the clock frequency. The latter two are a bit of a problem, since tight tolerance capacitors are rare and expensive, and very precise and stable clocks are not easy to create. Fortunately, a variation on this scheme – the dual-slope converter – solves these problems very elegantly. Fig.7 shows how it works. This time, the controller first charges the capacitor up for a fixed period (Tcharge) with a current proportional to the input voltage. The capacitor is then discharged by a fixed current of Idis, and the time taken for the capacitor voltage to ramp down to zero (Tcount) is measured by the counter. If we allow the capacitor to charge for M clock cycles, its voltage will reach Vcap = Iin × M × Tclk ÷ C. The count required for the capacitor to discharge from Vcap to 0V will be N = C × Vcap ÷ (Idis × Tclk). As Vcap is the same for both charge and discharge phases, we can substitute the first equation into the second. The capacitor value and the clock period cancel out, and we are left with N = M (Iin ÷ Idis). Recalling that Iin is proportional to Vin, we can see the count N is proportional to Vin, Idis and some constants. The conversion precision is therefore not dependent on the capacitor’s value or the clock frequency. As a bonus, any offset error in the comparator is also eliminated since the charge-discharge cycle will start and end at the same voltage, even if it is not precisely zero. siliconchip.com.au Fig.5: a successive approximation ADC uses a binary search algorithm to determine the state of each successive bit, starting with the MSB (most significant bit). Fig.6: a single-slope integrating ADC measures the time taken to charge a capacitor up to the input voltage using a known current. Achieving high precision requires a stable clock and a precise capacitor value. The only requirement is to use precision current sources and a capacitor with low dielectric absorption (a polypropylene dielectric is a good choice). Dielectric absorption is the mechanism responsible for the ‘memory effect’ in capacitors, where a recently discharged capacitor recovers some voltage over time after being discharged. This would obviously lead to errors in the dual-slope converter. The ‘integrating’ nature of the charge cycle explains why dual-slope ADCs don’t generally need a sample-andhold circuit. Any changes in input voltage are averaged out over the capacitor charge period. This means integrating converters are inherently low-pass filters, so they work best with DC or very low-frequency signals. An anti-aliasing filter is not normally required for the same reason. You can take advantage of this averaging to very effectively reject any mains-frequency interference that might be present on your signal. By setting the charge time to an integer multiple of the mains cycle period (20ms for 50Hz mains), any mains component present at the input will be averaged to zero over one or more full cycles. Being counter-based, integrating ADCs are quite slow, but with resolutions of 20 or more bits (better than 1ppm resolution), and the ability to effectively reject mains interference, they are widely used in test and measurement equipment like digital multimeters (DMMs). Very high-end test equipment (6½ or 7½ digit multimeters, for example) use more advanced variants known generically as multi-slope converters. Each manufacturer has their own proprietary flavour, but they all rely on the same charge-balancing principle. Delta-Sigma ADCs Another type of ADC that has come to the fore in recent years is the delta-­ sigma converter. A delta-sigma ADC consists of an analog modulator that produces a single bit stream, followed by a complicated digital filter. The inner workings of delta-sigma ADCs are not easy to describe or understand – so bear with me as I give it a shot. We will start with the modulator, which is where the magic happens. The upper part of Fig.8 shows a simplified first-order modulator. Practical ADCs use higher-order modulators, but the principles remain the same. The input is an analog voltage in the range ±V with a maximum frequency Fig.7: the dual-slope integrating ADC has the advantages of not being dependent on either a precise capacitor value or clock frequency. Its integrating nature also allows it to be configured to reject mains interference. siliconchip.com.au Australia's electronics magazine May 2025  91 Fig.8: the delta-sigma ADC consists of a modulator that produces an oversampled bit stream followed by a complex digital filter. These ADCs can have up to 32 bits of resolution and sampling rates in the Msps range (although not at the same time). component of fmax. The modulator is clocked at a rate higher than 2fmax by an oversampling rate factor (OSR). We will assume the OSR is 128 for the purposes of this example. The clock frequency is therefore 256fmax. The output of the modulator is a stream of 1s and 0s at the clock frequency, where a 1 code corresponds to V+ and a 0 code corresponds to V–. The average value of this bit stream over many cycles is equal to Vin. For example, a zero-volt input would be represented as a string of alternating 1s and 0s corresponding to alternating V+ and V– voltages, averaging to 0V. The example waveforms to the right of the figure show what happens with an input voltage of ¼V+. In the initial clock cycle, the bit stream value is zero, and the switch directs a voltage of V– to the summing junction, where it is subtracted from the input voltage. The resulting voltage (5/4V) represents the ‘error’ between the input and the reconstructed modulator output (this is the ‘delta’ part of the delta-sigma converter). This error is integrated (the ‘sigma’ part) and the comparator determines if the result is positive or negative. In our example, the result transitions from negative to positive about ¼ of the way through the clock cycle. On the next clock edge, a one is latched into the bit stream. The error voltage swings to -3/4V, and the 92 Silicon Chip integrator starts to ramp down. The result is still positive at the end of this cycle, so the comparator output stays high and the third bit in the stream is also a 1. This process continues indefinitely, producing a bit stream with five 1s and three 0s for every eight bits, as shown. Since we want to provide an output code at the sampling frequency (2fmax), we have to do it every 128 clock cycles. There can therefore only be 128 possible discrete values in the bit stream for each sample (128 zeros to 128 ones). If this was all there is to it, we would have created a 7-bit converter, which is pretty unexciting. However, the delta-­ sigma converter has a trick or two up its sleeve. The filter component of the ADC is a digital filter called a Finite Impulse Response (FIR) filter. We could write a whole series of articles on digital filters, but for a one-bit input this just consists of a long shift register with each output enabling or disabling a coefficient (a carefully chosen number) depending on whether it is a one or a zero. All the coefficients are summed on each clock cycle to produce a digital output code. The coefficients are chosen to produce a very steep low-pass filter, with a cutoff frequency of fmax. The output is decimated so that the resulting number changes only once for each sampling period. Decimation in our example just means each 128th Australia's electronics magazine sample is sent to the output and the other 127 are thrown away. The filter coefficients have a resolution much higher than seven bits, and there may be many hundreds or even thousands of coefficients in the filter. This means each output code can take significantly more than 128 different values and, therefore, it has much more than seven bits of resolution. If you find this last part hard to grasp, you are not alone. The mathematics behind it is complex, and some of the explanations you will find are confusing. Another way to look at it is to think of the modulator as a ‘perfect’ ADC with significant quantisation noise superimposed on it. The oversampling nature of the modulator is such that this noise is ‘shaped’ (pushed up) to frequencies well above the sampling rate. The low-pass filter then blocks most of this noise, leaving a level of quantisation noise corresponding to many more bits of resolution than the oversampling rate would suggest. Delta-sigma ADCs offer excellent performance at reasonable prices. Audio ADCs can easily have 24-bit resolution and sampling rates of 96kbps or 192kbps, with extremely low distortion. Precision DC-accurate delta-­ sigma converters with up to 32 bits of resolution are available (at a price). Delta-sigma ADCs are available with sampling rates up to 20Mbps. One of siliconchip.com.au the big advantages of delta-sigma converters is their inherently high oversampling rate means that anti-aliasing filtering is made easier. chip bandgap reference with a nominal 1.2V value and ±100ppm/°C tempco. At manufacture, the value of this internal reference is read by the ADC while the chip is supplied with a preA practical example cise supply voltage (3.0 ±0.01V). The I am developing a project that uses a resulting code is burned into non-­ low-cost microcontroller with a 12-bit volatile memory on the chip. You can successive approximation ADC to use this to convert a supply-referenced measure a ±6V analog signal. We will ADC reading to an absolute voltage use this example to see what kind of with known precision. performance we can expect from this The ADC also includes an auto-­ pretty common scenario. calibration feature that automatically The microcontroller I have chosen performs a zero calibration. This only is the STM32L031, a low-power, low- works to eliminate on-chip offset pin-count unit with a Cortex M0+ CPU errors, such as those related to the anacore. It has a built-in 12-bit ADC with log multiplexer, the sample-and-hold a maximum sample rate of 1.1Msps system and the ADC itself. If you want that uses the microcontroller’s power to eliminate off-chip offset errors, you rail as its reference. need to provide the hardware and do The ADC’s headline specifica- this yourself, as we discussed in the tions are modest, with a worst-case third article in this series. offset error of ±2.5LSB, a worst-case In addition, the ADC includes an gain error of ±2.0LSB and an INL of oversampler that automatically makes ±2.5LSB for a TUE of just over ±4LSB. several sequential conversions (up to Data sheet typical values are about half 256), sums the result, then scales the of these figures, but you already know result back by some factor to get an how I feel about typical values. averaged result. Of course, you could This would mean that the lower do this in firmware, but the hardware two bits of the result probably should oversampler does everything in the not be trusted, making this effectively background for you. a 10-bit converter, unless we can do This technique can actually improve something to improve its performance. the precision of ADC measurements in The ADC does have some nice fea- the presence of noise. This means that tures. One of the downsides of micro- a 12-bit ADC could appear to have 13 controller ADCs is that they use the or more bits of precision. power rail (or, if you are lucky, a dedThe reason this works is shown in icated analog supply pin) as the full- Fig.9. Here, we have a noisy signal scale voltage reference. Since I am with an average value between the powering this device from a 3V coin nth and nth+1 thresholds of an ADC. cell and boost converter, the power rail If we were to take just one sample, we is neither very precise nor very stable. could get either result. In fact, it is posThe STM32L031 includes an on-­ sible we could get a result one more bit higher and lower if we are unlucky with our sampling. If we make many measurements, however, some will be high and some low, but their average will lie somewhere between the two thresholds. We could say the resulting measurement is at the nth+½ threshold, effectively giving us an extra bit of resolution. This only works if the noise has an average value of zero and is uncorrelated with the sampling rate, and the noise has to have sufficient magnitude. Sometimes, a designer will deliberately introduce noise or some other form of ‘dither’ to a signal to increase the resolution when oversampling. Design decisions The relevant part of the test circuit I built is shown in Fig.10. The challenge is to digitise a bipolar (in this case, ±6V) signal with a single-ended ADC and a single 3.3V supply. The input signal is coupled to the ADC by a difference amplifier with a gain of 0.25, reducing the 12V input span to 3V, within the ADC input range. Using a difference amp here allows the input voltage to extend well beyond the supply rails without getting into problems with an op amp’s common-mode input range. The reference input of the difference amplifier is connected to the mid-point of the power supply derived from a voltage divider and buffer op amp. The output of the difference amplifier will therefore Vout = 0.25 (Vin+ – Vin–) + 1.65V. This means the voltage applied to the ADC will be in the range 1.65 ±1.5V (0.1V to 3.2V) over the ±6V input span, Fig.9: it is possible to increase the effective resolution of an ADC for slowly changing signals by averaging many samples of a noisy signal. Fig.10: the test circuit digitises a ±6V input using a difference amplifier with a gain of 0.25 and an offset of about 1.65V. The latter value is not critical, since this voltage is also digitised and the measured value is used to reconstruct the input voltage. siliconchip.com.au Australia's electronics magazine May 2025  93 avoiding the ends of the ADC input range near the supply rails where we know errors may lie. I have used lowcost TP5534 zero-drift op amps and 0.1% gain setting resistors to keep the analog errors down. The error budget table (Table 1) shows the analog error (line 5) is around ±0.2% in the worst case – almost all down to the gain resistor tolerance. The offset errors in lines 1 and 2 of the table are very low, so the internal zero calibration should be sufficient for our purposes. It is probably not worth using higher precision resistors here, since the ADC and calibration errors are of a similar magnitude. The ADC TUE of ±4LSB corresponds to a relative error of just over 0.1% and an absolute error of ±3.2mV. The relative error is easy to calculate from the TUE and the ADC precision: 100% × TUE ÷ (2n – 1), where n is the ADC precision in bits. We don’t need to use precision resistors to create the mid-supply voltage since we also digitise this voltage and subtract it in firmware. The absolute value of the mid-point voltage therefore does not matter – it just has to be close to half the supply voltage. I set the ADC up with an 8MHz clock giving a cycle time of 125ns. A single conversion consists of a sampling period, which is programmable, and a conversion time of 12.5 clock cycles. I chose a sampling time of 19.5 cycles (about 2.5µs) to be 10 or more times longer than the time constant of the external RC filter, and that of the internal filter made up of the 8pF sampling capacitor and the 1kW resistance of the analog multiplexer and sampleand-hold switches. I configured the oversampler to take 256 samples and to divide the resulting sum by 256 to restore 12 bits of resolution. There is no point in going for higher resolution, since the analog errors and the ADC TUE are already at this level of precision. No amount of oversampling will compensate for errors that affect every sample to the same extent. We use the same oversampling on all three ADC conversions: the main input, the mid-supply offset and the internal voltage reference. I also performed an internal zero-calibration on initialising the ADC to make sure any offset errors in the input multiplexer and sample and hold were minimised. Scaling the ADC results The relationship between the ADC code N and the absolute voltage on an ADC pin is Vin = Vdd (N ÷ 4095), where Vdd is the microcontroller’s power supply voltage. We don’t know this voltage precisely, but we can work it out by using the ADC to read the internal reference (NIREF) and the stored ADC code (NCAL) that was converted with a known supply voltage: Vdd = 3.0 × (NCAL ÷ NIREF) Having calculated the absolute voltage of the input and the midpoint offset voltage (in millivolts, since we are dealing with integers), we can use these, plus the nominal differential amp gain, to calculate the overall circuit input voltage. I did all of this and measured the input voltage, the ADC channel input voltage and read out the digital result. The results are pretty impressive – the measured error is better than ±0.05%, corresponding to ±3mV on the fullscale ±6V input range. This is 1 part in 2000, or about 11 bits of effective resolution. The transfer function of the ADC turned out to be f(x) = 0.9995x – 0.0002 with an R2 of 1.000. The line-of-bestfit gain error is less than ±0.01% and the offset error is less than 1mV. The worst individual sample error was better than ±0.05%. These results are an order of magnitude better than the 0.6% error calculated in the error budget. To some extent, this is to be expected (the odds are low that we will have the worstcase errors everywhere), but it is worth a bit of a closer look at why it performs better than expected. First, the calculated analog gain error is almost all due to the resistor tolerances, which would have to all be at the extremes of their tolerance band – that is unlikely in practice (but possible, of course). Second, the calculated TUE includes offset error, which is nulled out through the zero-calibration process. And finally, the 0.3% error on the supply voltage for the factory calibration seems to me to be a very conservative figure. I would be surprised if the supply voltage was not regulated more tightly than ±10mV during this step, so will probably be better than specified by an order of magnitude. So, in conclusion, the typical 10to 12-bit ADCs used in microcontrollers are really useful, but they have some limitations – especially if you are using the power supply voltage as the reference. Read the data carefully, since they will likely have fewer bits of effective resolution once the TUE is taken into account. To most effectively use the bits at your disposal, you should think seriously about averaging many samples if your microcontroller has the time to do so. That depends on how quickly your input is changing, how fast your ADC is, how many measurements you have to make, how often and so on. As I have mentioned before, in precision applications, you should also avoid using the very ends of the ADC SC span. Table 1: ADC (analog-to-digital converter) error budget Error Source (25˚C) Nominal Value Absolute Error Relative Error 1 Op Amp Offset Voltage (±20µV, 0.05µV/˚C) 0V 20μV 0.000% 2 Voltage due to Op Amp Offset Current (±100pA, 300kW || 1.2MW) 0V 24μV 0.000% 3 Total error at Op Amp Input (Line 1 + Line 2) 0V 44μV 0.001% 4 Op Amp Gain Error (0.1% resistors) 1.25 5 Voltage error at ADC Input (Line 3 × Line 4) 0V 12mV 0.201% 6 ADC (TUE ±4LSB – least significant bits) 0V 3.2mV 0.107% 7 Total error in ADC code (Line 5 × Line 6) 0V 10.2mV 0.308% 8 Error in internal Vref calibration (<at>3.0±0.01V) 0V 10mV 0.303% 9 Total error (Line 7 × Line 8) 0V 20.2mV 0.611% 94 Silicon Chip Australia's electronics magazine 0.200% siliconchip.com.au Subscribe to APRIL 2025 ISSN 1030-2662 04 The VERY BEST DIY Projects ! 9 771030 266001 $13 00* NZ $13 90 INC GST HDMI video up to 1280 x 720 Four USB Type-A connectors 3.5-inch audio socket Programmable using MMBas ic DS3231 real-time clock - PICO/2/COMPUTER 433MHz Transmitter Module » drop-in replacement for commercia l equivalents » easy-to-build, with just a few parts » good for short range communic ations Australia’s top electronics magazine Rotating Lights for Models adjustable rotation speed, direction Silicon Chip is one of the best DIY electronics magazines in the world. 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Pico/2/Computer; April 2025 The Future of the Grid; March & April 2025 High-Bandwidth Differential Probe; February 2025 An online issue is perfect for those who don’t want too much clutter around the house and is the same price worldwide. Issues can be viewed online, or downloaded as a PDF. To start your subscription go to siliconchip.com.au/Shop/Subscribe siliconchip.com.au Australia's electronics magazine May 2025  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. Digital voltmeter to ammeter conversion This is a simple project suitable for younger electronics enthusiasts. Small, bright, multi-colour three-wire, four-digit digital voltmeters (DVM) abound on the internet for a mere song. They are very useful for a variety of voltage measurement activities. Their power requirements are flexible, usually needing around 8-30V DC <at> 9-12mA. They can measure up to a 100V with average to reasonable accuracy on a 1.999-count display, refreshed about three times per second. There is usually a calibration pot on the back. You probably have a few hiding or collecting dust in the toolbox already. Similar ammeters are not so easy to obtain. The equivalent is much more expensive and they may have an unsuitable range for your application. But you can convert an existing DVM to a 0-999mA range digital ammeter (DAM) using this circuit. An ideal application would be to monitor the continuous current output of a 5-20W solar panel. The DAM is not particularly accurate at its range limits, but is reasonable for such an application. The 7808 or 7809 regulator is important for providing a stable voltage to supply the DVM. Choose a 1W 5W shunt resistor that measures slightly over 1W. That allows a simple parallel configuration for the 1W trimmer resistor, Rt. It usually just needs to be a few ohms, selected by trial and error. The value of the final combination should be as close to 1W as practical. D1 is only required if the final load is to be a battery under charge. For calibration, upon powering it up, unloaded, the DVM will read a nonsensical value. Wind VR1 anti-clockwise until the DVM reads as close to 1.000 as possible. Using black masking tape, cover the “1.” digit permanently, leaving the remaining “000” observable. This becomes your baseline 0mA reading. Now series-connect a high-wattage 100W load resistor and an accurate Night alarm to check if a door is open There have been times that one of our children wakes up at night and opens the balcony door, letting cold air in. Possibly worse things could happen! One solution is to install an electronic alarm to alert you if a child opens the door. Those who have basic electronics knowledge can build a tailor-­made circuit to their needs. This circuit is a simple and flexible custom solution. The audible alarm is triggered at night if the door remains open. The beep is repeated every minute. This alarm function is disabled during the day, although you can keep it enabled day and night if you remove 96 Silicon Chip the LDR. The software for this circuit is at siliconchip.com.au/Shop/6/1842 In brief, the PIC microcontroller (a baseline PIC10F222) is powered by a small battery between 2.0V and 5.5V (a Li-ion, LiPo or lithium primary cell would be suitable). I measured the average current consumption with a 3.6V supply at 8.6µA in run mode for 10.7ms (no alarm), followed by 3.5µA for 2.5s in sleep mode. This averages out to around 3.6µA. Even using a CR2032 coin cell (225mAh), the maximum functional life of this circuit would be 64,285 hours (225mAh ÷ 0.0035mA), which is Australia's electronics magazine DMM set on the A/mA range. This should draw approximately 120mA from the 12V battery or panel. The DMM and the new DAM readings (directly read) will be hopefully similar, due to Ohm’s law. The DMM burden voltage will be a small factor to consider besides the DVM’s accuracy. Now the fun begins, trying to find the best compromise between varying the values of Rt and the setting of VR1. It’s best to start by varying Rt. The ultimate target is to get the DAM and the DMM readings to coincide. While the DAM accuracy might not be perfect, for any given range, it is reasonably reproducible. It is a good idea to mount the DAM in an enclosure on the back of the solar panel. Colin O’Donnell, Adelaide, SA. ($80) 2678.5 days or more than seven years!. I used a Nordic Semiconductor Power Profiler kit to make these measurements (siliconchip.au/link/ac40). The Coin Cell Emulator (December 2023; siliconchip.au/Article/16046) is also designed to make such measurements. When the alarm sounds, the piezo buzzer produces six successive ‘bips’ at 2kHz and 4kHz. The peak current draw reaches 100mA. Since a coin cell can only deliver about 10mA safely, the 10μF bypass capacitor provides the current during these brief pulses. We need to use only three GPIO pins on the PIC microcontroller. GP0 is configured as an analog input to measure the variation in resistance of the LDR, siliconchip.com.au Automatic op amp offset nulling This circuit implements an op amp with automatically nulled input offset voltage. Readers might like to compare this circuit to the one in Part 2 of Andrew Levido’s article on Precision Electronics (page 41 of December 2024; siliconchip.au/ Article/17311), which uses op amps that have inbuilt nulling. This circuit uses ordinary op amps instead. Capacitors C1, C2 & C3 are used to cancel the input offset voltages of op amps IC1/IC4; IC2/IC5; and IC3, respectively. The clock driving the Φ1 and Φ2 control inputs to the CMOS switches is a two-phase non-overlapping clock. IC1 is the main amplifier, and its output Vout is always valid. IC2 is used as a mirror of IC1. During clock phase Φ1, the IC2/IC5 op amp offsets are nulled by charging C2 to the difference between the input offset voltages of IC2 and IC5. Similarly, IC3 is nulled by charging C3 to IC3’s input offset voltage during clock phase Φ1. During clock phase Φ2, the nownulled IC3 compares the outputs of IC1 and IC2 and corrects the voltage on C1 so that the output of IC1 exactly matches that of the nownulled IC2. This is equivalent to nulling the IC1/IC4 op amp pair. Capacitor C1 maintains the offset adjustment of IC1/IC4 while IC2/IC5 and IC3 are taken out of service to be nulled in clock phase Φ1. Buffer IC4 ensures that enough current can flow in C1 during phase Φ2. It can be omitted (replaced by a direct connection from -IN to the left end of C1) if the -IN signal is supplied from a reasonably low impedance. Similarly, buffer IC5 ensures that enough current can flow in C2 during phase Φ1. It can be omitted (replaced by a direct connection from the junction of the leftmost Φ1 and Φ2 switches and the left end of C2) if the +IN signal has a reasonably low source impedance. Because there are no switches in the signal path from +IN and -IN to Vout, the frequency and period of the clock signal and the values of capacitors C1, C2 and C3 do not affect the bandwidth of the circuit. All three capacitors should have the same nominal value. They need to be sufficiently large that the drift in the capacitor voltage caused by the maximum specified input current of the op amps during the off-duration of the clock phases does not exceed the maximum tolerable offset error. Andrew Partridge, Launceston, Tas. ($100) Comment: the two phase non overlapping clock could come from a TL494 set for push-pull operation. which produces a low voltage on GP0 when illuminated, and higher voltages in darkness. Use an LDR that measures less than 10kW when illuminated and over 100kW in darkness. The necessary 560kW pull-up resistor for LDR1 is driven by GP1, configured as output that’s driven high during periodic measurements, then reconfigured as a high-impedance input the rest of the time, to save on power. GP2 is configured as a permanent output to drive the alarm via Nchannel Mosfet Q1. It has a 56kW gate pull-down resistor, so no current flows through it when the micro is not actively driving GP2 (eg, during programming). Autotransformer L1 siliconchip.com.au allows the piezo to produce a loud sound even with a low supply voltage. The second N-channel Mosfet, Q2, has a gate pull-up resistor. This means it is switched on when the door is open. When the door is closed, it short-circuits Q2’s gate to its source, switching it and the rest of the circuit off. The high value of the 1MW resistor means that the current is low with the door closed (1μA per battery volt). A higher resistor value, like 10MW, could probably be used to reduce the quiescent current even further. Hichem Benabadji, Oran, Algeria. ($75) SERVICEMAN’S LOG A bang in the night! Dave Thompson Dave Thompson is currently busy trying to break the world record for the most Kiwi birds juggled while singing Aotearoa atop a ride-on lawnmower. So instead of his usual column we have a collection of stories from readers. In the 1970s, I worked as an Electronics Technician at Whenever an HF transmitter was re-tuned to a differthe National Broadcasting Service transmitter site at Wan- ent operating frequency, a spot distortion and noise check neroo Road in Hamersley, WA. During one evening shift, would also be conducted. a fault developed in the 50kW HF transmitter that eluded One night, towards the end of our evening shift, we were several maintenance staff. getting ready for the shift change at midnight. All was quiet The site was operated on a 24/7 basis by three eight- except for the transmission monitoring speakers operathour shifts. The day shift was from 8am to 4pm, followed ing in the transmission hall. Just after 11pm, we heard an by an evening shift from 4pm to midnight, and the night almighty bang from the transmitter hall, followed by the shift was from midnight until 8am. sound of HF3 cycling back up. The ABC Radio services transmitted from the site at A check of the transmission output using the monitorthat time were the local AM transmitters for 6WF (55kW ing speaker did not indicate a significant problem with the <at> 720kHz) and 6WN (10kW <at> 810kHz), along with the transmission (with hindsight and tuning a critical ear to three high-frequency shortwave transmitters for the VLW the monitor output, one may have been able to glean an Service, which transmitted to north-western WA. idea of what the problem was). 6WF would commence transmission at 0500 hours and We then proceeded to check the meter readings against would continue until midnight. 6WN would commence those that were recorded earlier in the night at 10pm but transmission at 0600 hours and would continue until 0100 could not find any significant differences. At that point, it hours. The three VLW services were transmitted at 6140kHz was decided to leave it as-is and wait until service close (VLW6), 9610kHz (VLW9) and 15,425kHz (VLW15). The at midnight. The night shift could follow it up, rather than time of day for these transmissions varied due to iono- losing the service altogether for the short duration before spheric propagation. closing time. VLW6 operated from 0500 hours until 0900 hours and The next day, when we reported for duty at 4pm, we then from 1725 hours until midnight. VLW9 operated all found that the HF3 transmitter was out of service (and had day, from 0500 hours until midnight. VLW15 operated from been all day), with various transmitter parts being placed 0700 hours to 1730 hours. on the transmitter hall floor adjacent to HF3. Two of the HF transmitters (HF1 & HF2) were 10kW STC The night shift had measured unusually high distortion 4SU48B units. These could operate on any of the three fre- and noise figures when they checked the transmitter after quencies used by the VLW service. Normally, HF1 would re-tuning it to the daytime operating frequency (15,425kHz). operate at 6140kHz and HF2 would operate at 9610kHz. They had commenced fault-finding unsuccessfully and HF3 was capable of 50kW, with an STC 4SU48B front end had passed it onto the following day shift. Day shift confollowed by a 50kW power amplifier section and an asso- tinued the fault-finding unsuccessfully until we arrived ciated 25kW audio modulator. for our shift at 4pm. HF3 was used to transmit the VLW15 service from The first thing I did was look around the transmitter to 0700 hours until 1730 hours. It would then be re-tuned to see if I could find the source of the loud bang we had heard 9610kHz and took over transthe previous evening. Those mitting the VLW9 service at high-power transmitters tend 1741 hours until midnight. to leave tell-tale marks (burnt • A transmitter at Radio National (Radio 2) All three of the HF transor otherwise) when a large mitters were built in Australia amount of energy is dissi• Another MIG welder for the pile by Standard Telephones and pated quickly, as indicated • Cleaning up cabling Cables (STC). by the loud noise. Opening it is half the battle • When preparing the transWithin five minutes, I had • Repairing a toy skating pond mitters for service, the usual located the cause. Inside • A fault in a car antenna procedure was to conduct the left-hand access door, Dave Thompson runs PC Anytime in Christchurch, NZ. spot (400Hz) distortion and there were six high-voltage noise checks on all transcapacitors used to filter the Website: www.pcanytime.co.nz mitters (both MF and HF) to high-voltage supply for the Email: dave<at>pcanytime.co.nz ensure that they were ready large vacuum tubes used in Cartoonist – Louis Decrevel Website: loueee.com to go. the 50kW power amplifier Items Covered This Month 98 Silicon Chip Australia's electronics magazine siliconchip.com.au and audio modulator sections. These capacitors were protected by inline fuses. The fuses are mechanically designed so that when the fuse blows, a metal lever (held up by a length of fuse wire) drops down to short out the capacitor; no bleeder resistors were used. This prevents the capacitor retaining a high amount of stored energy when the fuse fails, which would pose an electrical shock hazard to the servicing staff. I can only assume that one fuse had failed first, and that caused the next one to fail due to the extra loading, and so on until all six fuses failed in quick succession. That large amount of energy being discharged very quickly would have been the cause of the loud bang we had heard. After replacing the fuses and restoring the transmitter parts that had been removed, distortion and noise checks produced normal figures. The transmitter was returned to service. Finding the fault quickly was a feather in my cap and a memory that has stayed with me over the years. I received a considerable number of jibes from the other shift members who were involved in the fault finding, along the lines of, “That young upstart showing us up!” Looking back with hindsight, I think that the night shift had not investigated the cause for the loud bang we told them about, and just continued with the normal routine of re-tuning the transmitter for the day’s operation. With ABC radio and television services being distributed via AUSSAT, the VLW services were no longer required and were shut down in the late 1980s. I believe the HF transmitters were broken down for scrap. L. H., Geraldton, WA. A Workzone MIG welder repair Mk2 I was welding a frame to make a small table with my Workzone flux-core MIG (metal inert gas) welder when it suddenly went haywire, shooting the wire out at high speed, making it impossible to make any welds. I had this same thing happen to my smaller SIP MIG welder that I used before getting this welder from Aldi Special Buys a few years ago. In the case of the SIP MIG welder, it was dry joints on the circuit board that were easily fixed by re-soldering. A few months back, I had to repair this Workzone welder when the wire for the trigger broke and I had to run a new wire through the sheath. That repair was described in the October 2024 issue, starting on page 92. Now it had another problem. I wondered if it might be the same thing that happened with the SIP MIG; there was one way to find out. I removed the front panel from the welder, and the problem was obvious. One of the wires going to the circuit board plug had broken. I don’t know how that could have happened. It is a very unusual fault in my experience. I didn’t have much room to move with the front panel still attached to the welder, so I removed all the plugs from the circuit board. That let me get the front panel out of the way, so I would have room to repair the broken wire. Some of the plugs were a bit difficult to remove, but I got them all out and put the front panel aside for now. The next problem was how to affect a repair so that I could get the welder back in working order and finish the job at hand. My quick solution was to cut a nick in the plug to provide access to the pin that the wire used to be connected to and solder it back on. icomretail.com.au       siliconchip.com.au Australia's electronics magazine May 2025  99 Making a small cut in the plug plastic gave me access to the pin to reconnect the wire. Two unrelated cable faults within a week, in a system that had been running reliably for nearly 20 years? Unlikely! Had someone or something disturbed the cabling? If so, we were likely to see more faults in the near future. Out came our trusty PMG cable tracer. It was made by Melbourne company Aegis back in the 1970s, back when we still had a strong electronics manufacturing sector in Australia. We traced the cable from the meeting room RJ-45 port up into the false ceiling, across the building and back to the computer rack. It had a patch bay across to one of the audio racks, where the clock signals originated. The signal I got my 20W soldering iron and plugged it in to heat up ended at the computer rack. while I prepared the plug by trimming out a small piece On closer examination, we noticed a patch cable going with a utility knife. This was the easiest and quickest way to a port that we knew was unterminated, and another port of repairing it, rather than going to the trouble of extract- that should have been patched that wasn’t. That explained ing the pin. the faults, but who was the culprit? I plugged the plugs back into the circuit board and reasIt turned out that our contracted IT support guy had sembled the welder. I then made a couple of test welds on been in and ‘tidied up’ the IT cabling. Yes, you guessed it, some scrap steel, and the welder was back in working order human intervention had caused the problem. We re-patched again. I could now finish making the table frame. Some- it, stripped out the temporary Cat 5 cable and restored the times, a very simple fault can put a device out of action, original one. but a simple fix gets it back in working order again. At one level we were annoyed that the IT guy had disB. P., Dundathu, Qld. turbed the audio patching, which was none of his business (then again, maybe he didn’t realise it was even there). At Studio signals suspiciously stopped another, we were pleased that we weren’t facing a bigger At my local community radio station, the GPS-­ problem. synchronised clocks and open-mic indicator went offline R.P., Melbourne, Vic. in one of the three on-air studios. We quickly substituted Sometimes opening it is half the battle a spare clock to make sure that wasn’t the problem. Breaking out the RJ-45 connector in the studio verified I was asked by a friend to look at a radio, as the volume that no signals were present. As both signals are supplied control did nothing, but they liked the sound quality when via a single Cat 5 cable from a rack in the control room, it was working. and similar services in the other studios were unaffected, When I accepted the radio, I got a shock. I am in my the basic problem was clear: the cable was broken some- eighties and from the analog age, so I had anticipated a where between the Krone block in the control room rack loose wire broken off the potentiometer. But this radio was and the RJ-45 connectors in the studio. a modern digital one. The volume control was not a pot, it Since the studio was booked for use within the next few was a rotary encoder. It was used to not only set the volume hours, we simply patched in a new cable. Problem solved? but also select the input, set the clock and everything else. Not quite. How to dismantle A few days later, the open-mic indicator in the same it? There were studio came on permanently and the synchronised clock no screws in the meeting room stopped working. The meeting room v i s i b l e ; fault also revealed that no signals were arriving at the clock, the first despite being present at the control room end of the cable. place to 100 Silicon Chip Australia's electronics magazine siliconchip.com.au look was under the felt feet in their recessed hole, but still no screws. I asked a friend, who looked online for that model but didn’t find anything helpful. Finally, in desperation, we prized off one end plate. That broke some plastic mounts, but revealed that the screws were under the metallic face plate that was glued to the front. We were able to remove the faceplate, take out the screws and open the radio. That exposed the top panel that the PCB was attached to. There was a rotary encoder with a push switch, plus a further eight tactile switches to set up and operate the radio. In my days, this would have needed up to twelve wires to operate, but to my surprise, only three wires were needed! This PCB contained only two capacitors and twelve resistors, eight tactile switches, and the encoder, all surface-­ mounted. All was revealed once the board was in a suitable lighted area: liquid had been spilt over part of the board. The owner confessed later that this would have been wine. I wiped off as much as possible, but found that one switch had sticky residue under it and did not work, so I removed it and left the board soaking overnight in isopropyl alcohol. Our local Jaycar did not have a suitable switch, but a colleague had one, which was gratefully accepted. Still, it would be three weeks before I received it. Unfortunately, I found it to be unsuitable; the protruding stem was too long, the one required would have been about 1mm long. Since the delays were increasing, I spoke to the owner to explain the problem of finding a suitable replacement. It transpired that the radio was never used as a clock or even as an alarm clock. The ‘snooze’ button (a long bar) had a switch at both ends, wired in parallel, so I borrowed one and replaced the faulty one. I packed the end of the bar with a small piece of foam to make it horizontal and look good. The snooze function would still work, but only if pressed at one end! Reassembling the radio was a bit of a challenge due to the broken lugs, but I finally got it together, and had a happy friend with a now-working radio. The second item I repaired was a small battery-­operated audio amplifier. The complaint was that there was no sound and it had a rattle from the enclosure; something had obviously come loose. After removing five screws, the cabinet would not come apart, so based on the earlier repair, I decided to remove the metal grille in front of the speaker. This revealed eight more screws (the manufacturer did not want the speaker to get out!). The photo shows that the rattle was the magnet. It had detached from the speaker housing; all four rivets had given away. I wonder what sort of handling could cause this? As the complete unit was only worth about $120.00, a new speaker and my time made the unit an uneconomical repair. R. R., Morrinsville, New Zealand. Skating Pond toy repair My daughter presented me with a Lemax Village Skating Pond from one of her friends. It was not working. I have been fixing faulty electronic equipment for many years and this is just another one of those challenges for me. These Chinese-manufactured devices usually come out at Christmas time to amaze the children. It is designed to have miniature figures skating around the table-top pond siliconchip.com.au Australia's electronics magazine May 2025  101 to the sound of a crowd and carousel type music. There is a magnet connection through the pond surface from the mechanism to the skating figures. This one had working sound but no movement on the pond. I took it apart and was presented with the motor and belt driven mechanism. After powering it up again, I spun the motor shaft with my fingers and the mechanism ran, but the beautiful sound deteriorated to a horrible noise, which I worked out later was commutator hash. I then measured the voltage going to the motor and found they were feeding the red and the black wires on the PCB motor socket with reversed polarity. The motor is a model RF-300CA 11440, which provides clockwise rotation looking at the motor drive end. It appears they worked out the mechanism design and then added a motor and found that the motor style that was chosen rotated the wrong way – so they just reversed the connection to it! The mechanism design would not work if the motor rotated in its intended direction. [The initial design probably used a different motor, but they subsequently changed it due to availability or price – Editor.] I switched the unit off to work on it and removed the belt. I then reversed the motor wiring to correct the polarity. Leaving the belt off, I powered up the unit and found that the motor started by itself and the sound coming out was normal – very pleasant. I then searched the internet for a motor of this style, approximately 25mm diameter with 16.5mm screw mounting, running in an anti-clockwise direction (looking at the motor drive end). However, I came up with nothing. It appears that most cheap DC motors have commutators designed to go best in one direction. Some of the better brands, such as Mabuchi, say that the direction can be reversed by reversing the wiring polarity. They are probably built to work that way. Unfortunately, Mabuchi did not have an equivalent motor that would fit. So I had to work with this motor and somehow change something to make the mechanism work with the motor rotating in the opposite direction. I thought of changing the drive to a figure-8 belt drive, which worked OK, but there was rubber wear where the belt crossed over. I then thought of placing a slippery sheet of something between the belt crossover. What I used was part of an antistatic bag (that was on my desk at the time), with a couple of subtle bends. This was held under one of the motor board mounting screws. That fixed it – the unit was put back together and is still working to this day. Looking at reviews for this unit, many people had problems with it only working for so many hours and then stopping, or it working for one Christmas and not working at the next. I suspect this all comes down to the use of an unsuitable motor. E. R., Marion, SA. Car antenna fault Around a year ago, I started to experience poor FM reception on my 2009 Ford Ranger car radio. It has a telescoping type antenna on the right-hand roof support pillar. The antenna was looking worse for wear, with a fair amount of dirt and corrosion. I found a suitable replacement on eBay and set about fitting it. Disconnecting the cable from the back of the car stereo and pulling the cable over to the driver’s side of the vehicle was fairly easy, but threading the new antenna cable down the support pillar would not be an easy task. I pulled the old antenna cable with a draw wire and fed Australia's electronics magazine siliconchip.com.au the cable up while my wife slowly removed the antenna from the top of the car. I then taped the new antenna cable to the draw wire and pulled it back into the vehicle and to the back of the stereo as my wife fed the cable in from the top. Once the antenna was screwed down, I tried it, and everything seemed to be working. That was until I got about 2km out of town and the reception dropped out. Naughty words were said! I removed the stereo (it is the stock Ford system) at the next opportunity and resoldered the antenna socket in case there was a bad solder joint. I also looked over the rest of the circuit board but could not see any problems. The circuit board is full of SMD components, and I have no circuit diagram anyway. I reinstalled the stereo and it made no difference. I sourced a replacement stereo from the local wrecker and installed it. Guess what? More naughty words were uttered. It was time to get scientific. I hadn’t noticed before, but I tried scanning the AM band and was surprised to find nothing. Usually you will pick up something up due to the long distances AM will travel. I set my signal generator to 639kHz (2HC Coffs Harbour) amplitude modulated at 1kHz. I draped the insulated signal generator lead around the car antenna and tuned to 639kHz. Total silence. I had the signal level full bore (5V peak-to-peak) on the generator. At least I had a clue now. If I touched the antenna with the bare end of the signal generator lead, a loud and clear 1kHz tone came through the radio, but still nothing if I draped the insulated wire over it. I unscrewed the antenna and slowly pulled it out of the pillar while listening, and bingo. A 1kHz tone was heard loud and clear. I slowly lowered the antenna back down the pillar and the signal dropped out again. OK, there must be some insulation damage. I tested with a multimeter set to measure resistance and there were no shorts between the screen and centre pin of the antenna lead. There was also no short to the frame of the car. The base of the antenna was grounded to the body of the car. You can’t test continuity of the antenna to the centre pin, as the car service manual states that the antenna is AC-coupled via a capacitor. Of course, no value for this capacitor is given. I tested with a capacitance meter and found it to be about 6.5nF, which would have a reactance of about 46W at the lower end of the AM band. Does this seem right? I’m not sure. Maybe a radio guru could comment. This was frustrating, as I had to reattach a draw wire and again pull the antenna out to inspect the coax and the telescoping part of the antenna itself. A visual inspection of the coax and antenna body revealed nothing. This was crazy! Maybe there was some sort of capacitance to the frame of the car. In desperation, I wrapped the whole antenna telescope body and about a metre of the coax with two layers of insulation tape, and slowly lowered it back down the pillar as before while listening to the 1kHz tone. It all went back together, with no break in the signal this time. When I switched the signal generator off, I was greeted with 2HC Coffs Harbour. I don’t know the true cause, but after much frustration, the antenna and radio work on both AM and FM as they should. G. C., Toormina, NSW. SC siliconchip.com.au Australia's electronics magazine May 2025  103 Vintage Radio The Emerson 888 mini-mantel set (UK Version) By Ian Batty Emerson’s 888 radio was dubbed Vanguard in its US release, with a stylised rocket as part of the logo, overlaid by the word VANGUARD. From left-to-right, Regency’s TR-7, Zenith’s Royal 500, the Emerson 888, Toshiba’s 9TM-40 “robot” and Admiral’s 7M1. V anguard was the name of the US rocket that placed their second satellite into Earth orbit. It was intended to be the first, but when the Soviet Union successfully launched Sputnik I on the 4th of October 1957, they scrambled to respond. After the failure of the Vanguard TV-3 launch, they decided to quickly get the Explorer 1 satellite into orbit using a Juno I rocket. That was followed by Vanguard 1, making it the second successful US orbital launch of a satellite. The satellite launched on that rocket was retrospectively named Vanguard 1. Vanguard 1 continued to make useful contributions to space science until 1964. It, and its third launch stage, are the oldest artificial objects in orbit around the Earth, with an expected lifetime of some 185 years to run. The British release of this radio lacked the VANGUARD label, perhaps because “Vanguard” failed to resonate in the same way in the UK. A history of Emerson Victor Hugo Emerson (an early recording engineer and executive) started Emerson Radio Corporation in 1915 as Emerson Phonograph Co., based in New York City. Although Emerson introduced the first radio-phonograph combination sold in the USA, the company remained in obscurity until 1932, when, during the Great Depression, it introduced the “Peewee” radio. It sold like hotcakes, becoming ‘the’ radio to have. Emerson Radio & Phonograph converted to military 104 Silicon Chip production for World War II in 1942, when it held one-sixth of the US radio market. In 1947, among its first post-war products, Emerson offered a television set with a 10-inch (25cm) tube. Between fiscal years 1948 and 1950, the high demand for television allowed Emerson to more than double its sales. In 1953, Emerson Radio and Phonograph purchased Quiet Heet Corporation, which entered the company into the air conditioning market. Although radio represented only 15% of Emerson’s revenue by 1954, the company credited itself as creating the firsts of the clock radio, the solar-powered radio, and the hybrid pocket radio – the 838, reviewed in the October 2018 issue (siliconchip.au/Article/11276). They started producing tape recorders in 1955. Emerson Radio and Phonograph purchased the consumer products division of Allen B. DuMont Laboratories Inc in 1958. With this acquisition, a higher-priced line of television sets, phonographs and high-fidelity and stereo instruments, along with the DuMont trademark, were added to Emerson’s products. Unfortunately, by this time, almost every US household that wanted a TV set already had one, and many customers who were in need of another set were waiting for colour television instead of buying a replacement monochrome set. Emerson would be acquired by National Electric Corporation (NEC), ending some fifty years as an independent manufacturer. Emerson-branded products were finally discontinued in 1972 (see https://w.wiki/D6fJ for more details). Australia's electronics magazine siliconchip.com.au The Emerson 888 Regency’s TR-1 wasn’t a pocket set unless you had a large coat pocket. But it looked a bit lost on a shelf, so the ‘trannie’ would need to either become smaller, such as Sony’s TR-63, or larger. You could offer a full-sized mantel, as many manufacturers did, but mantels lose the cachet of portability. What about a ‘mini-mantel’ set? Released in 1958, Emerson’s 888 model is a convenient size, with a fold-back handle that allows it to sit safely at an angle. Similar sets include Regency’s TR-7, Zenith’s Royal 500, Toshiba’s 9TM-40 ‘robot’ and Admiral’s 7M1 (see the lead photo). In the hand, Emerson’s 888 is a simple brick with a thumb-wheel dial at the top. The volume control, fitted with a decorative key tab, demands that you hold the set in one hand and adjust the volume with the other – reminiscent of Regency’s TR-1, and less ergonomic than Sony’s TR-63. The dial is calibrated in metres rather than kilocycles (as would have been used back then). The tuning range is 550~200m (545~1500kHz) for medium-wave, with an original fixed long-wave frequency of 200kHz. There’s no separate band-change switch; long-wave is selected by tuning past the top end of the broadcast band to actuate an internal switch. Circuit description This radio follows the design that had stabilised by the mid-1960s. This UK release is the familiar six-transistor superhet, a scaled-down version of the eight-transistor US releases (Fig.1). The US releases featured an unusual direct-coupled two-stage second intermediate frequency (IF) amplifier and an audio preamplifier. Converter transistor TR1 is the familiar OC44. Both it and the similar OC45 use alloyed-junction construction, with the main difference being their cutoff frequency; over 7.5MHz for the OC44 or greater than 3MHz for the OC45. The circuit uses collector-emitter feedback, typical of European/US/Australian designs. While this gives similar performance to the collector-base feedback used in many Japanese designs, it has the advantage that you can inject a signal directly to the converter base without stopping the local oscillator (LO). Historically, collector-emitter feedback was used in the first transistor set, Regency’s TR-1. That ensured its grown-junction converter, with its limited high-frequency specification, would operate reliably over the broadcast band. This set’s LO tuning capacitor section has a cut-plate design. As this naturally forces the LO to track at 470kHz above the incoming signal frequency, no padder capacitor is needed on the broadcast band. It’s unusual to see cut-plate tuning capacitors in multiband sets, as the cut-plate construction can only give correct tracking over one band. But the 888’s long-wave band uses fixed tuning, so the cut plate’s LO offset has no effect on it. For the broadcast band, the ferrite antenna rod’s L1 primary is tuned over the range of 545~1500kHz by tuning siliconchip.com.au Fig.1: this cut-down set uses six transistors: TR1 (mixer/oscillator), TR2 (first IF amplifier), TR3 (second IF amplifier), TR4 (audio preamplifier) and TR5/TR6 (Class-B push-pull audio output). The demodulator is a single OA70 diode. There are also three IF transformers, one oscillator transformer and two audio transformers (phase splitter and speaker matching). In the UK, Cockburn & Gunn Ltd, operating from 1958, imported Emerson products from the USA. They became Emerson Electronics Ltd in 1962. capacitor VC1, with top-end trimming by TC2. Tuning the 888 to the very top of the broadcast band activates bandchange switch S1a/S1b. The antenna section, S1a, connects long-wave trimmer TC1 and 1100pF band-change capacitor C1 to antenna coil L1, thus pulling its resonant frequency down to 200kHz. C1’s high value of 1100pF ensures that broadcast trimmer TC2’s setting has virtually no effect on long-wave antenna tuning. Note that the C1 and C6 band-change capacitors are both ±2% tight-tolerance types. Broadcast LO tuning is by cut plate section VC2, trimmed by TC3. For long-wave, trimmer TC4 and 100pF bandchange capacitor C6 bring the LO frequency down to the required 670kHz. As C6 has a much smaller value than the antenna circuit’s C1, LO trimmer TC4 has a much wider adjustment range than antenna circuit trimmer TC1. In practice, in long-wave mode, it is designed to tune only to 200kHz, or close to that frequency. In common with other transistor converters, whether autodyne or separately excited, TR1 appears to work with almost zero bias. This implies that it’s working close to Class-B, as we’d expect with a self-oscillating converter stage. TR1 feeds the tuned, tapped primary of T2. This first IF transformer is permeability tuned by an adjustable ferrite slug. T2’s secondary feeds the base of the first IF amplifier transistor, TR2, an OC45. As this has an automatic gain control (AGC) voltage applied, its base resistor (R4) has a high value of 68kW. This allows the AGC control voltage to significantly reduce TR2’s bias on strong signals, thus reducing the stage gain and helping keep the audio output constant with stronger or weaker stations. The ‘cold’ side of T2’s secondary is bypassed to ground by an 8μF electrolytic capacitor, C7. This is not regarded as good practice, as electrolytics do not perform well above audio frequencies. That said, it worked just fine, even without a better-performing capacitor in parallel. TR2, like all alloyed-junction types, has considerable collector-base feedback capacitance. It uses R6 and C10 to cancel the feedback capacitance. As this circuit uses resistance and capacitance, it’s unilateralisation rather than simple neutralisation. TR2 feeds the tuned, tapped primary of second IF transformer T3. T3’s untuned, untapped secondary feeds the base of the second IF amplifier, TR3. TR3 works with fixed bias, having its own bias divider (R8/R9), and working at fixed gain. It’s also unilateralised, by R10/C14. Both networks (R6/C10 and R10/C14) use tight-tolerance type capacitors (±2%) and resistors (±5%). TR3 feeds the tuned, tapped primary of third IF transformer T4. T4’s secondary feeds demodulator diode D1. This, in turn, feeds 5kW volume control potentiometer VR1 as its load, with 10nF capacitor C15 filtering out all but the audio signal. The DC voltage developed across VR1 is fed, as the AGC voltage, back to the bias circuit of the first IF amplifier transistor, TR2, via 8.2kW resistor R5. TR2’s biasing from 68kW resistor R4 puts D1 weakly into forward conduction, improving the radio’s sensitivity. The audio developed across VR1 goes to the base circuit of audio driver TR4, an OC71, via 8μF capacitor C16. Using combination bias, TR4 feeds the primary of phase-splitter transformer T5. The output pair of transistors, TR5/TR6 (both OC72s), operate in Class-B mode. Their bias is derived from divider R17/R18. This circuit lacks temperature compensation, and this appears to be more common in English-designed sets. Australian designs, starting with our first transistor set (AWA’s 879P), incorporated thermistor compensation from the beginning. I’ve seen European equipment – which probably worked just fine in Europe – either go out of alignment, or just die, when exposed to our wider range of environmental temperatures. Top-cut is applied by 40nF capacitor C20. Local feedback is provided by 10W common emitter resistor R20, and there A top view of the Emerson 888 radio’s PCB with some of the important components labelled. You can see the battery holder attached to the volume control at the bottom. Converter Oscillator Coil 1st IF Transformer 1st IF 2nd IF Transformer Driver Transformer Outputs Output Transformer 2nd IF 3rd IF Transformer 1st Audio Demodulator Diode Volume Control 106 Silicon Chip Australia's electronics magazine siliconchip.com.au is overall feedback from T6’s secondary, via R19 (1.5kW), to T4’s unbypassed emitter resistor, R16 (10W). TR5/TR6 drive output transformer T6, and its secondary drives the internal speaker, or an earphone plugged in to the earphone socket. The set runs from a 6V supply made up of four AA-sized cells in a carrier. Restoration The review set was in good cosmetic condition, so a light clean had it looking just fine. Turning it on produced nothing. Usually, this points to a dead set, but I was able to inject a few millivolts of audio into the volume control and get an output. Further testing showed the RF/IF section was as dead as the dodo. Injecting a 470kHz signal into the demodulator produced nothing, and the cause was an open-circuit demodulator diode, D1. This was a reminder that, really, you need to be alert to any possible fault, no matter how unlikely. D1, the famous OA70 we probably used in crystal sets, is in a low-stress part of the circuit, never getting more than a few hundred millivolts compared to its maximum reverse rating of 22.5V. But there it was – as open a circuit as just leaving the multimeter leads lying on the test bench. Replacing D1 (with a near-equivalent OA81) brought the set to life, and it was just a matter of checking voltages, aligning it and putting it through its paces. Be aware that, in common with many British designs, this uses a 470kHz IF, with their other common frequency being 465kHz. If you’re unsure, get the manufacturer’s data or service sheets. Performance results It’s on a par with other six-­transistor sets of the day. I was puzzled at first, as it didn’t emit the usual front-end noise when turned up to full volume, but its specifications appear to be about right. In detail, for 50mW output, it needed just on 1000μV/m at 198kHz, 275μV/m at 600kHz and 225μV/m at 1400kHz, with signal+noise to noise (S+N/N) figures exceeding 20dB. The relatively poor long-wave sensitivity may have been due to my radiating test ferrite rod, as it was only ever specified for the 535~1605kHz broadcast band. My on-air weak station reference, Warrnambool’s 594kHz 3WV, rocked in at full volume. Regrettably, there are no local long-wave transmissions in the Geneva Frequency Plan of 1975, specifying band coverage of 153kHz to 279kHz. Non-directional beacons (NDBs), used in air navigation, are located at higher frequencies, just at the lower end of the 300kHz~3MHz medium-wave band. The closest NDB to me here on the Mornington Peninsula is the Moorabbin NDB at 398kHz. Using the European/US converter design of emitter feedback allowed me to inject a test signal at the converter base, and the levels there are consistent with the pickup effectiveness of the 888’s short ferrite rod. Its IF bandwidth is 1.25kHz for -3dB and 22.5kHz for -60dB. The AGC allows about a 6dB rise for a 28dB signal increase. That’s about as good as you’ll get with the single-stage AGC siliconchip.com.au The band-change switch is circled in yellow; the LW trimmers are also visible in this photo. The underside of the Emerson 888 PCB. Note that the volume control pot is secured with three screws. Australia's electronics magazine May 2025  107 The Emerson 888 has a distinctive volume control knob, resembling a door knob. The tuning dial is made from plastic with the “LW” setting just past the “200” mark. used in the 888. The audio response from antenna to speaker was 180Hz to 2000Hz for -3dB. From volume control to speaker, it’s around 180Hz to 7.8kHz. At 50mW, total harmonic distortion (THD) was 4.2%, with clipping at 70mW, giving a THD of 10%. That seems like a low maximum output power, but the clipping was symmetrical, which it would not have been with one faulty output transistor. At 10mW output, the THD was 4.6%. Low-battery performance was good: with a 4.7V supply, it managed a useful 35mW at clipping, albeit with visible crossover distortion due to the voltage-divider bias circuit. Is it worth buying? I think it’s worth having as an example of a major American manufacturer customising their design to suit an export market. It’s unusual in having the fixed-tuned long-wave provision. Any long-wave provision – even a fixed-tuned design – appears an oddity, given that long-wave was in decline when the 888 was released. The BBC, however, maintains its 500kW 198kHz Droitwich service, as its transmissions cover most of England and Wales, plus much of the Republic of Ireland. Its rubidium frequency synthesiser-controlled broadcasts are readily 108 Silicon Chip available as a frequency standard reference (see https://w. wiki/D8fu for more details). Special handling The tuning dial is secured by a central screw with a knurled head that is easily removed. The volume control knob is a press-fit onto a chamfered shaft – be careful when withdrawing the knob, as it is plastic and is easily damaged by injudicious levering-off. The board is secured to the case by one large nut and two small ones. Emerson states that you must include fibre insulating washers between the nuts and the circuit board. At least one nut would otherwise short out a circuit board track. Be aware that the medium-wave band is specified for a maximum frequency of 200 metres (1500kHz). I did try tuning up to the standard 1605kHz. While the LO would tune correctly, the antenna trimmer, even when wide open, would not bring the antenna circuit into tune. It did work perfectly well for a maximum of 1500kHz. The long-wave tuning is intended for 200kHz (198kHz for the major remaining UK station). While the LO will tune more broadly, the 1100pF antenna circuit padder (TC1) severely limits the authority of the long-wave antenna trimmer, TC3. For more info on this set, see siliconchip.au/link/ac4q SC Australia's electronics magazine siliconchip.com.au ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Changing Continuity Tester resistor value In the Continuity Tester Mini Project #023 (March 2025; siliconchip.au/ Article/17791), you mention that you can use a 9V supply but the 1.5kW resistor value should change. What should I change it to? (R. M., Melville, WA) ● We suggest you use 3kW or 3.3kW. This is calculated by subtracting 1.2V from the supply voltage, then dividing by 2.5mA (0.0025A), which gives 3120W. 3kW is the nearest E24 series value but 3.3kW (E12 series) is close enough in case that’s easier to obtain. Sourcing the cell used in the Current Probe I have built three of the 40A Current Probes from the January 2025 issue (siliconchip.au/Article/17605). They are complete except for the 14500size Li-ion PCB-mounting cell. I have been unable to find anywhere with it in stock. I tried Jaycar, Altronics and a few online stores. I even placed an order online with Bourne Electronics, only to have it cancelled three weeks later. Some sellers on eBay have them at around $25 per battery; I need three, so that’s a bit expensive. Do you have any suggestions on where I could purchase them? (P. H., Cranbourne, Vic) ● We bought our cells from Altronics late last year and they were in stock at that time. As you suggest, it looks like the PCB-mounting version is out of stock at present. We can think of two alternatives: 1. You might be able to squeeze in a PC-mount AA cell holder like Altronics’ S5029 and use their S4979 cell, which is just a normal AA style Li-ion rechargeable. We have not tried this, so have not confirmed it will fit in the case. You will probably have to bend the leads somewhat to make them line up with the holes. 2. You could use the version with solder tags (Altronics S4980), although it obviously can’t be mounted in the siliconchip.com.au usual way. You could probably fasten it to the board with hot-melt glue (or a couple of judiciously placed holes and a cable tie) and connect it with short lengths of hookup wire. Be careful to get it the right way around, and insulate the terminals carefully in case something comes adrift. Errors in Surf Sound circuit and text There seems to be an error in the Surf Sound Simulator circuit diagram (November 2024, page 90; siliconchip. au/Article/17018). I have breadboarded this circuit and couldn’t get it to work – there was no sound output. I think I have traced the error to the position of the 56nF capacitor connected to pin 9 of IC2c. I believe it should connect from the anode of D5/68kW resistor to pin 9 of IC2c. The two 120nF and one 470nF capacitors connect directly to pin 9, rather than via the 56nF capacitor. With those changes, the circuit worked as expected. Also, in the Triangle Wave Generation panel on page 51, pin 8 of IC1d is referenced twice, once in the text and once in the Scope 1 description. Both references should be to pin 14 of IC1d. (M. H., Waiuku, New Zealand) ● You are correct. Thank you for pointing these errors out. Turning car alternators into brushless motors You recently published a Variable Speed Drive (November-December 2024; siliconchip.au/Series/430). I am converting old car alternators into “brushless” motors and am wondering how hard it would be to make a low-voltage version (12-24V) that could deliver output waveforms up to 400Hz or more. (R. S., Huntly, Vic) ● Converting a car alternator into a motor requires a three-phase supply to drive the stator windings and a DC source for rotor field excitation. Adapting the Variable Speed Drive for Australia's electronics magazine Induction Motors for this application would not be practical; so much of the circuit would need modification that it would become an entirely new project. It would also not be an economical solution given the low cost of offthe-shelf electronic speed controllers (ESCs) intended for electric bicycles and the like. Just make sure to select one that has the option of operating without the Hall-effect position sensors. You would still need to provide the field excitation supply separately. Secure Remote Switch worked, then didn’t I have built the Secure Remote Switch from the December 2023 and January 2024 issues (siliconchip.au/ Series/408). It worked fine first time, but the next day I switched it on to make some adjustments and, when pressing remote buttons, I get an acknowledgement from the Receiver board but the relay does not operate. Also, if I want to increase the length of the receiver antenna, should it be a multiple of the carrier wavelength? (F. C., Maroubra, NSW) ● Check that the identities for both the transmitter and receiver are set the same. There could be a solder joint that has gone dry, causing a poor connection. Also check the supply used for powering the relay. There is the option of 12V or 24V depending on the relay used. There shouldn’t be too much wrong if the project already worked. As a last resort, if you can’t find any other problems, make it re-learn the remote control. It’s best to stick with a ¼ wavelength antenna as other lengths will have different chacteristic impedances. GPS Analog Clock is gaining time I built the recent GPS-Synchronised Analog Clock (September 2022 issue; siliconchip.au/Article/15466). My version is the continuous sweep one. It works very well, except for one quirk. May 2025  109 It is accurate for many months, then it starts gaining time; about 90 seconds per day! By the way, we do not have daylight saving in WA. The first time it happened, I changed the C batteries without checking their voltage. It returned to accurate timekeeping for many months. The next time it started gaining time again, I thought to check the voltage of the batteries and found they were down to about 1.1V each. I notice Geoff has a low battery mode to extend the time the movement will work. I suspect the low voltage might be causing this behaviour. Do you know what is going on? Should I change the movement? (D. L., Perth, WA) ● Geoff Graham responds: You have an interesting fault. There are many possible reasons why the clock can slow down (faulty movement, flat batteries etc) but it is difficult to think of anything that would cause it to speed up. It is certainly not a faulty movement. I believe that the clue is in the fact you changed the C batteries and then, after “many months”, their voltage dropped to a very low 1.1V. C cells should last for years driving a clock like this, not months. I suspect that, at some point, the clock controller is unable to get the time and that this failure has lasted for a while (weeks or months). This could be because the GPS module cannot get a signal or the WiFi module is unable to reach the internet. In that event, the clock would try to get the time for an hour before giving up, then retry again in 24 hours and keep repeating. If that continued for long enough, it would flatten the battery quite quickly. It would also mean that the clock would not be synchronised for a long time, so a slight error in the crystal frequency would show up as it running fast or slow. It would be worth checking the controller board as, during this period, the LED on it will flash once a second as a warning that the time source could not be accessed. If you are using a GPS module, you could switch to a WiFi module for getting the time. Another possibility is to remove the module from the PCB and extend its wires so that you can place the module in a location with a better GPS signal, or use a GPS module with an external antenna. If you are using a WiFi module, you will need to investigate why it cannot access the internet periodically. Troubleshooting the Hummingbird Amp I’ve been building the Hummingbird Amplifier and I must have made a big mistake somewhere (December 2021; siliconchip.au/Article/15126). I built the Altronics kit and tonight I tried to test it without the heatsink with a ±20V DC supply from a power supply I made from a 15V AC transformer, bridge rectifier and capacitor bank. I was getting about ±20.5V at the amplifier supply inputs, so I think the power supply was OK. On connecting power, I connected a multimeter on the positive output connector to the ground on the capacitor bank and I was getting 2.6V. Not good, obviously. Then, on the positive rail, the 47W resistor started to smoke and burned up. I think I made a small mistake as I made up the safety resistors with the 200mA fuses but I didn’t pre-blow the 200mA fuse, but I wouldn’t have thought that would matter. Any ideas on what I might have done wrong? (E. M., Hawthorn, Vic) Reason for resistors between signal grounds in preamp I am currently building the Ultra-low-noise Remote Controlled Stereo Preamp (March & April 2019 issues; siliconchip.au/Series/333). The signal inputs have a 10W resistor to ground, marked as “see text”. I have scanned both issues multiple times but can’t find any text reference to these resistors. Also, the microcontroller uses a 4MHz crystal but my local Jaycar store only stocks 3.5MHz and 4.4MHz. Can either of them be used or does the software rely on 4MHz for timing? (J. B., Hataitai, New Zealand) ● The explanation for those resistors was left out of the article. They are to reduce ground current (hum loops) that can cause hum in the sound. A 4MHz crystal must be used to ensure the infrared remote control works correctly. Otherwise, it won’t be able to decode the messages due to a mismatch between the expected and actual pulse timings. You should be able to ask your local Jaycar store to get the 4MHz crystal in for you (Cat RQ5274). 110 Silicon Chip Australia's electronics magazine ● Phil Prosser responds: your voltage rails sound fine. If that resistor was overloaded, something in the front end is drawing a lot of current. The fact that the 47W resistor smoked but not the 82W resistor in the VAS stage, nor the constant current devices, is unusual. Check the current source transistors and that 82W resistor with power applied. Are they hot? We wonder if you have the electrolytic capacitor just downstream of the 47W resistor in the wrong way around. If you have an oscilloscope, is the amplifier actually amplifying, or is it oscillating? Current transformer for Motor Controller I am keen to build your Refined Full-Wave Motor Speed Controller (April 2021; siliconchip.au/Article/ 14814) and I have begun to collect the parts. I will place an order with your Online Shop for the PCB, the PIC micro, and any other parts that you are able to supply. I would have ordinarily bought the current transformer from RS, but they appear to have nil stock of them at the moment. Do you stock this part? I think I can buy most of the other parts locally that I don’t already have. (P. W., Pukekohe, New Zealand) ● Yes, we can supply the current transformer as part of a set of ‘hard-toget parts’ (SC6503) that also includes the PCB, programmed microcontroller, Triac and more. See siliconchip. au/Shop/?article=14814 for all items we sell associated with that project. Motor speed controller soft start doesn’t work I finally go around to putting together the Refined Full-Wave Motor Speed Controller (April 2021), the speed control works fine but the soft start doesn’t work; the motor seems to want to start but doesn’t. Any thoughts on how to fix this problem? (D. Q., Charlestown, NSW) ● Ensure that the mains lead is disconnected, then check all the wiring and verify the correct placement of all components. Also examine all soldered joints for a good connection. Next, check the operation of the soft start switch, S1. Using a multimeter set to read resistance, check that pin 4 of 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. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au Mains Power-Up Sequencer February-March 2024 LEDS, BRAND NAME AND GENERIC LEDs, filament LEDs, LED drivers, heatsinks, power supplies, kits and modules, components, breadboards, hardware, magnets. Please visit www. ledsales.com.au PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. Hard-To-Get Parts SC6871: $95 siliconchip.au/Series/412 The critical components required to build the Sequencer such as the PCB, micro etc. Other components need to be sourced separately. Lazer.Security WE OFFER KITS, LEDs, LED assemblies and all sorts of quality electronic components, through-hole and SMD, at very competitive prices. Check out the latest deals at www.lazer.com.au 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 May 2025  111 Advertising Index Altronics.................................49-56 Blackmagic Design....................... 7 Control Devices........................... 37 Dave Thompson........................ 111 DigiKey Electronics....................... 3 Electronex................................OBC Emona Instruments.................. IBC Hare & Forbes............................. 11 Icom Australia............................. 99 Jaycar....................IFC, 9, 22-23, 65 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology................ 43 Mouser Electronics....................... 4 OurPCB Australia.......................... 8 PCBWay....................................... 47 PMD Way................................... 111 Rohde & Schwarz........................ 45 Silicon Chip Shop................ 77, 81 Silicon Chip Subscriptions........ 95 The Loudspeaker Kit.com.......... 10 Wagner Electronics................... 103 Notes and Errata Pico/2/Computer, April 2025: boards with CH334F chips marked 13122E20 will not work unless resistors R54 and R55 are removed. Boards we sell with matching chips will come with those resistors removed so they function correctly. CH334F chips with batch code 1163FD43 are not affected and will work with the resistors in place. Surf Sound Simulator, November 2024: in the circuit diagram (Fig.2), the 56nF capacitor connected to pin 9 of IC2c should instead be connected from the anode of D5 to pin 9 of IC2c. The overlay diagram and PCB is correct. In the panel on p51, the two references to pin 8 of IC1d should say pin 14. Next Issue: the June 2025 issue is due on sale in newsagents by Thursday, May 29th. Expect postal delivery of subscription copies in Australia between May 26th and June 16th. 112 Silicon Chip IC1 is connected to the 0V supply via 100W when S1 is switched to the soft start position and that pin 4 is tied to the +5V supply rail via a 47kW resistance when S1 is open (soft start is off). Also check that pin 4 of IC1 is properly inserted into the socket and not bent under the package. LC Meter relays not switching I am testing the Digital Wide Range LC Meter (June 2018; siliconchip.au/ Article/11099) but I am encountering problems as the instrument does not indicate any values of either capacitors or inductances. I think the problem is the reed relays not switching. I have verified that the output voltage from the Arduino pins drops to 0.8V, but I cannot verify the reed contact closure. I have checked the coil current is 12mA, which seems normal. The firmware on the micro is OK. The problem could also be the comparator; I will check its output with an oscilloscope. (M. F., Scandicci, Italy) ● We don’t think the output voltage from the pins should drop that low; it should stay fairly close to 5V when the relays are being driven. We suspect your reed relays have an intrinsic diode that is shunting the current away from the coil. The circuit was designed to use relays without diodes, but similar relays are available with such diodes. If this is the case, you are not the first to have had this problem. A significant proportion of the problems reported with the LC Meter have been due to the incorrect relays being used, and changing to different relays fixed the problem. It would help if you could send some photos of your construction, including the part numbers on the relays. That will also allow us to see if there are any other potential problems. Universal Loudspeaker Protector resistor value I am currently building the Universal Loudspeaker Protector Mk3 (November 2015 issue; siliconchip. au/Article/9398). The parts list and the SMD parts set I bought from the Silicon Chip Online Shop (SC3217) includes a 5.6kW M3216/1206 SMD resistor. However, the circuit shows a 6.8kW resistor between pins 5 and 9 Australia's electronics magazine of the LM339, and the PCB mask also has 6.8kW. Is it OK to use the 5.6kW resistor instead? (J. B., Hataitai, New Zealand) ● According to the text in the righthand column on p67, 5.6kW is the correct value and gives fan-on/overheat thresholds of 65°C/75°C. Using a 6.8kW resistor gives slightly lower fan-on/ overheat thresholds of 60°C/70°C, but in that case, the 15kW resistor should be changed to 18kW. The value was changed to 6.8kW at the last minute and the 15kW resistor was changed correctly but we missed changing the 5.6kW resistor in a couple of places. WiFi Weather Logger Arduino compiler error While compiling the firmware for the WiFi Weather Logger (December 2024; siliconchip.au/Article/17315), I got some errors from the Arduino IDE. I fixed them by changing D8 to 15 and D4 to 2 on lines 10 and 15 of the code. Otherwise it worked ‘out of the box’. (R. L., Wareemba, NSW) ● We tried to replicate your error but were unable to, using the latest version (3.1.2) of the ESP8266 board profile, version 2.3.3 of the Arduino IDE and the “LOLIN(WEMOS) D1 R2 and Mini” board definition as per the article. If we change the board definition to something like the Generic ESP8266 Module, then we get these errors (amongst others): WIFI_WEATHER_LOGGER.ino:11:17: error: ‘D4’ was not declared in this scope WIFI_WEATHER_LOGGER.ino:10:19: error: ‘D8’ was not declared in this scope; did you mean ‘s8’? So we think you may be using the wrong board definition or the board definition is corrupted on your computer. You can find these pins definitions on Windows in “[user directory]\AppData\Local\Arduino15\ packages\esp8266\hardware\ esp8266\3.1.2\variants\d1_mini\ pins_arduino.h” and they are set as follows: static const uint8_t D4 = 2; static const uint8_t D8 = 15; If this file is missing/corrupted, that may be the cause of your errors. 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