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AUGUST 2024 ISSN 1030-2662 08 The VERY BEST DIY Projects! 9 771030 266001 $ 50* NZ $1390 12 INC GST INC GST The Styloclone build your own instrument Tracking & Locating Devices How AirTags, emergency beacons & other trackers work Dual Mini LED Dice and much more in this month’s issue ONLY 329 $ QM1493 Specialty meters combined with multimeter functions. HIGH VOLTAGE INSULATION TESTING "MEGGER" • MULTIMETER FUNCTIONS • DIGITAL DISPLAY • ANALOGUE BARGRAPH • DATAHOLD ONLY TEST WIRING INSULATION 119 $ TAKE EASY ENVIRONMENTAL MEASUREMENTS • MULTIMETER FUNCTIONS • SOUND LEVEL • LIGHT LEVEL • INDOOR TEMP • HUMIDITY ONLY 179 $ QM1594 TEST ALMOST ANYTHING! 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Specialty Function Display (Count) QM1632 QM1493 XC5078 QM1594 Clamp Meter up to 600A AC/DC Insulation Test up to 4000MΩ LAN Cable Test with pinout indicator Sound, Light, Humidity & Temp 4000 4000 2000 4000 Security Category Cat III 600V Cat III 1000V Cat III 600V/Cat II 1000V Cat IV 600V/Cat III 1000V Voltage 600V AC/DC 750V AC / 1000V DC 600V AC / 600V DC 600V AC / 600V DC 40MΩ 4000MΩ 20MΩ True RMS • Current 600A AC/DC Capacitance 100mF Resistance Frequency • 200mA AC/DC 10A AC/DC 10MHz Temperature 1000°C Non Contact Voltage • Relative Measurement • 40MΩ 100µF 10MHz 750°C • • • Explore our great range of multimeters, in stock on our website, or at over 115 stores or 134 resellers nationwide. • www.jaycar.com.au 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Contents Vol.37, No.08 August 2024 12 Tracking and Locating Devices Modern tech makes it easy to track the location of people and property. These trackers can be used for locating children, pets or important belongings over potentially long distances. By Dr David Maddison, VK3DSM Location tracking Electronics Manufacturing in Australia Starting on page 38 38 Electronics Manufacturing in Oz Local electronics manufacturing has a long history in Australia, from garages to large factories. These companies included Astor, AWA, EMI, Pye, Philips and many more from the 1920s to 1970s. Part 1 by Kevin Poulter Historical feature 64 Altium Designer 24 The newest yearly release of Altium is here, so lets go over what has been added. We thought 3D-MID is an interesting new feature, which allows tracks and components to be placed on 3D objects. Review by Tim Blythman EDA software 27 The Styloclone Our Styloclone is a reinvention of the classic Stylophone musical instrument. It is a great introduction to both music & electronics. The whole project fits on a single board and can be mounted in a case or freeform. By Phil Prosser Musical instrument project 44 Dual Mini LED Dice Combining the old and new is this pocket-sized project which uses LEDs to display two six-sided dice. It runs from a coin cell and is controlled either by pressing a button or shaking it. By Nicholas Vinen Game project 55 Jaycar-sponsored Mini Projects This month, we have an ultrasonic garage door notifier which send updates via email, and can also tell you if there’s a car parked in the garage. Plus a stroboscope & tachometer project to measure rotation speed. By Tim Blythman Mini projects 70 Beer Can Filler This semi-automatic can filler is a great tool for a home brewer, and it’s not just limited to beer! You can build it in an afternoon for a fraction of the cost of a commercial product. By Brandon Speedie Brewing project 78 180-230V DC Motor Speed Controller This Speed Controller is intended for high-voltage DC motors like those in lathes, treadmills, conveyor belts and more. This article covers the assembly, testing and setup of the Controller. Part 2 by John Clarke Motor speed control project Altium Designer 24 REVIEW, PAGE 64 Beer Can Filler Project on page 70 2 Editorial Viewpoint 5 Mailbag 61 Circuit Notebook 87 Vintage Radio 92 Serviceman’s Log 98 Online Shop 100 Ask Silicon Chip 103 Market Centre 104 Advertising Index 104 Notes & Errata 1. Reading a BCD switch with one pin 2. Op amp-based guitar equaliser 3. Model railway tunnel timer HMV 42-71 receiver by Marcus Chick SILICON SILIC CHIP www.siliconchip.com.au Editorial Viewpoint Bringing Practical Electronics (PE) magazine into the fold Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Jim Rowe – B.A., B.Sc. Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $70 12 issues (1 year): $127.50 24 issues (2 years): $240 Online subscription (Worldwide) 6 issues (6 months): $52.50 12 issues (1 year): $100 24 issues (2 years): $190 For overseas rates, see our website or email silicon<at>siliconchip.com.au * recommended & maximum price only Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: You might have seen Practical Electronics magazine at the newsagent before. Based in the UK, it was established in 1964. Since the early 2000s, they have been licensing some of our content (mainly projects) for their magazine, alongside their locally-developed content. The owner of the current publisher, Electron Publishing, is now retiring and shutting down his business. Rather than ending the magazine’s 60-year run, we have agreed to take it over. The move made sense since PE already uses quite a bit of Silicon Chip content. They will remain essentially separate magazines, with PE continuing to have a significant amount of content originating from authors in the UK and Europe. PE will still republish our content because it has few native project article submissions. This should not affect Silicon Chip, except that we may occasionally elect to publish articles from PE authors that we think are particularly good and suitable for our readers. This is unlikely to replace any of our content (as we still have plenty!) but might augment it. For example, if we have enough articles for a 104-page issue, we might decide to add roughly eight pages of content from PE and turn it into a 112page issue. The biggest challenge in doing that is that many articles in PE are long-running series, making it difficult to just occasionally pick one to use. Even though this change is not likely to have much impact on Silicon Chip readers, I thought they would still like to be made aware of it. We have been having difficulty selling items to customers in the UK due to changes to their VAT (value-added tax) laws that occurred a couple of years ago (post-Brexit). We’re hoping to be able to solve that soon; while we do not have any physical UK presence, the fact that we’re doing some business there now might allow us to overcome that unfortunate problem. Minor price adjustments I had hoped to avoid increasing any prices this year. However, we’re still under pressure to do so. Australia Post recently increased their charges for mailing magazines quite substantially (letter rates went up 25% less than a year after the last price increase!) Still, I know that many people are under financial pressure due to the crazy cost-of-living expenses we are now suffering, so we can’t increase our prices too much and risk making the magazine unaffordable. We will only increase the cost of print and combined subscriptions by a small amount to partially cover the higher postage costs. The new prices are shown below. A 12-month print or combined subscription only increases by $2.50 per year, while six-month subscription prices remain the same (see the sidebar). If you renew before October 1st, you can take advantage of the existing, slightly lower prices. Online subscription prices are not changing. However, we will be rounding up the print magazine’s cover price to $13 starting with the October issue this year, to compensate for inflation. New Prices Print (AU) Combined (AU) Print (NZ) Combined (NZ) 12 months $130 $150 $155 $175 24 months $245 $280 $290 $325 Prices from October 1st, 2024; all prices are listed in Australian dollars (AUD). by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia's electronics magazine siliconchip.com.au The key to unrestricted access Explore millions of components for your next design While you can’t set foot on this protected aviary sanctuary, you can find refuge in the mouser.com tent, where you have access to millions of electronic components, from well over a thousand leading brands engineers know and trust. Let your designs take flight. au.mouser.com 03 9253 9999 | australia<at>mouser.com MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. Avoiding dodgy power boards Your Editorial Viewpoint regarding cheap extension leads in the June 2024 issue is spot on. My experience testing and tagging for a major aged care provider for ten years really opened my eyes. We never allowed double adaptors, both kinds, due to their flimsy fitting in power outlets when weighed down with leads, so we insisted on power boards. I’ve lost count of the enormous number of the cheaper power boards I’ve failed. Part of my tests was to wiggle the plugs in all the sockets; any break in contact was a failure, and the board was rejected. I discovered early on, after operating on and investigating the odd board that melted, that the cheaper boards seem to use a worse grade of brass for their socket contacts. The better-known power board brands use a brass alloy that maintains its tension and consequently, the pressure on the contacts of the plugs. As a result, the boards last a very long time. The cheaper brands seem to use cheaper brass for their socket contacts, which eventually lose their tension, causing the plug to develop a loose fitting within the socket. They eventually arc and melt and/or catch on fire. Hence, my wiggling of the plug during the test. After sharing my experience with new residents, I found that the cheaper boards had mostly disappeared. Whatever happened to Aussie standards? Jacob Westerhoff, Seaford Rise, SA. Outdoor power points must be the right type The June 2024 editorial about the cheap extension cord that caught fire reminded me that the outside power point used for our church coffee corner recently caught fire and was destroyed. As shown in the photo below, the wall was covered with black soot. I asked for it to be replaced, and it was. The indoor-style powerpoint that was installed outdoors. The original indoor-style power point was replaced with another good-quality indoor power point rather than a weatherproof IP53-rated outside type. I wonder how long the new one will last before it also catches fire! John Rajca, Mount Kuring-gai, NSW. Comment: it baffles us that an electrician would install an indoor power point in a location exposed to the weather. Outdoor power points are not that expensive! Even if they don’t catch fire, using an indoor power point in such a location risks tripping the RCD when wind-driven rain enters it and causes Earth leakage current to flow. Colour Maximite kit giveaway I want to give away an Altronics kit for the original Colour Maximite (September & October 2012; siliconchip. au/Series/22). It is free to a good home including postage (within Australia only). Ric Mabury, Melville, WA. Comment: please email us if you are interested in this kit. It is likely to go fast. Agreement on the cause of extension cord failure Regarding your June 2024 editorial, I don’t think the fault is entirely with the cord. It was probably due to the way it was folded. See the photo below of what happens when our cleaner folds up the cord on our steam mop! I also have a very old neoprene power cord (70 years old) that is still in good order. Also, regarding the first repair story in the Serviceman’s Log column in that issue, on capacitor problems in washing machines, he wrote, “The board AC power is fed from a 110V AC 60Hz transformer” using an external 240V to 110V stepdown transformer. That is a big no-no! 60Hz transformers have a lot less iron than 50Hz transformers. The result would be the core being partly saturated constantly, causing excess Right: the twisted power cable on this steam mop is due to it being rolled up too tight. siliconchip.com.au Australia's electronics magazine August 2024  5 heating and a distorted waveform. I think that could have been the real fault in the first place. John Chappell, Pelican Waters, Qld. If Richard Palmer would like a good home for his 1963 RTV&H CRO, count me in. Dean Cooper, Macquarie Park, NSW. Valve-based CRT oscilloscopes had sharp traces Praise for Blackmagic Design video equipment I’ve genuinely been enjoying reading Silicon Chip and have been spreading the word to all my jaded engineering mates who haven’t touched a piece of hardware for years. A recent experience with your sales team was well executed too. I had a bad display on a Coin Cell Emulator kit I’d purchased, and they replaced it for me free. I know not all readers are keen on historical articles, and to be honest, old broadcast-band radios aren’t my thing either. Still, I loved Ian Batty’s article on Jamieson ‘Jim’ Rowe’s Fully Calibrated Oscilloscope from RTV&H, 1963 (May 2024; siliconchip.au/Article/16259). What a great design! Ian didn’t fully put things in perspective though. Commercial ‘scopes were expensive. Indeed, everything other than the essentials for life were expensive in relative terms. A Tektronix 310 (4MHz single-trace three-inch [76mm] CRO), for example, sold for US$595 when it was released in 1955. That’s $10,500 in today’s money! In the June issue, Richard Palmer points out that his 1963 RTV&H scope kit cost just over AU$100. If he purchased it in 1966 after the transition to decimal currency, that would be $1558 today. Still not cheap! Today’s young electronics adventurers are incredibly lucky to have such a plethora of low-cost test equipment available to them. I have attached some photos with some 75% EBU bars that show just how good professional scopes of the era were. After all, six years later they helped put a couple of guys on the moon and gave us real-time images globally. I was very happy for you to see the Blackmagic Design ad in the latest edition of Silicon Chip. The number of rabbit holes you can now go down to explore the world of professional video & audio is almost limitless. When I started taking my own business more seriously, one of my first investments was a Blackmagic Design 4K Pocket Cinema Camera and an ATEM Mini Pro for more professional Teams meeting use. These exposed me to the world of LUTs, very large file formats, SDI etc. Although I would like to have the means to buy the entire BMD catalog to hang on my wall, I have only upgraded my camera recently to the Micro Studio Camera 4K G2, as it obscures less of my screen when in front of me. I often get comments on the clarity and quality of the image in a video call – often from wealthy people still using their dodgy laptop webcam! BMD being an Australian company is a bonus. Their website’s breakdown of product categories reads like a multiyear “What is” article series. I think their most interesting products are for the remote control and monitoring of broadcast cameras. Being able to set the focus, colour balance, focal depth etc from a desktop app via the network through the Mini Pro and HDMI to the cameras is pretty cool; many planets have to align to make it work as well as the BMD gear does. Finally, I would just like to say that I preferred when the Jaycar ads were published as a block rather than individually. That made it easier to look through the ads to see if there was anything I was interested in. Chris S., Brisbane, Qld. Keeping rodents away from tasty car wiring I read L. Ralph Barraclough’s cautionary warning on fake pest repellers (April 2024, Mailbag, p8). He has my sympathy; rats and mice are an absolute curse. In a post-­ nuclear-armageddon scenario, my money’s on the rodents! Although he didn’t mention it, these vermin are quite capable of wrecking your vehicle – they cost me one already! The fault was not necessarily the rodent(s) but rather my tardiness in implementing the solution I’d been meaning to get around to “one of these days...” The solution is simple, really; I just laid out a section of chicken-wire roofing mesh on the garage floor where I park the car and hooked it up to an electric fence driver... problem solved! I have not had a single problem with vermin damage ever since. It’s a concrete floor, so as long as it’s dry, it makes little noticeable difference to the fence ‘Zap’. If your parking space is bare earth, you might want to lay the mesh down onto a sheet of PVC/polythene cut slightly larger than the perimeter of the mesh. At the extremely high voltages that most electric fences operate at, there is so much leakage current they’ll still get a powerful enough zap. This solution isn’t just for rural dwellers, it’s also for city slickers. Electric fence units are available so cheaply off of the likes of AliExpress, Alibaba etc you’d need your head examined not to. They cost way less than losing your car insurance no-claims bonus! Mine cost about $85. 6 Silicon Chip Australia's electronics magazine siliconchip.com.au Introducing ATEM Mini Pro The compact television studio that lets you create presentation videos and live streams! Now you don’t need to use a webcam for important presentations or workshops. ATEM Mini is a tiny video switcher that’s similar to the professional gear broadcasters use to create television shows! Simply plug in multiple cameras and a computer for your slides, then cut between them at the push of a button! It even has a built in streaming engine for live streaming to YouTube! Live Stream to a Global Audience! Easy to Learn and Use! Includes Free ATEM Software Control Panel There’s never been a solution that’s professional but also easy to use. Simply press ATEM Mini is a full broadcast television switcher, so it has hidden power that’s any of the input buttons on the front panel to cut between video sources. You can unlocked using the free ATEM Software Control app. This means if you want to select from exciting transitions such as dissolve, or more dramatic effects such go further, you can start using features such as chroma keying for green screens, as dip to color, DVE squeeze and DVE push. You can even add a DVE for picture media players for graphics and the multiview for monitoring all cameras on a in picture effects with customized graphics. single monitor. There’s even a professional audio mixer! Use Any Software that Supports a USB Webcam! You can use any video software with ATEM Mini Pro because the USB connection will emulate a webcam! That guarantees full compatibility with any video software and in full resolution 1080HD quality. Imagine giving a presentation on your latest research from a laboratory to software such as Zoom, Microsoft Teams, ATEM Mini Pro has a built in hardware streaming engine for live streaming to a global audience! That means you can live stream lectures or educational workshops direct to scientists all over the world in better video quality with smoother motion. Streaming uses the Ethernet connection to the internet, or you can even connect a smartphone to use mobile data! ATEM Mini Pro $495 Skype or WebEx! www.blackmagicdesign.com/au Learn More! As far as rodent infestation inside the house is concerned, about 35 years ago, ETI published an electric shocker construction project intended for mice designed by the supremely talented Ian Thomas. Andre Rousseau, Auckland, New Zealand. More on 3.5-inch and 4-inch touchscreens with Micromite In response to the letter published in Ask Silicon Chip, June 2024, titled “Unable to Calibrate ILI9488 Display”, the 3.5-inch TFT ILI9488 display does work with the Micromite V5.05.05 firmware and the driver supplied with it. Installation details are in the Micromite manual. In my experience, the touch panel calibrates normally. However, the 4-inch IPS ILI9488 screen requires a modified driver as the colours are inverted. Also, the touch foil is reversed. A new universal ILI9488 diver is available on the Back Shed Forum here: siliconchip.au/link/abwe Importantly, the 4-inch IPS ILI9488 has no 3.3V regulator fitted (U1). Instead, it is bypassed by a link (R0), so it must only be supplied with 3.3V. Phil Petschel, Kinglake, Vic. The details of how thermocouples work Reading the June 2024 Mailbag, there seems to be a bit of confusion about how a thermocouple works. I will try to explain the facts as best as I can. For the record, I am an instrument engineer and used thermocouples for over 30 years. In my courses at RMIT on instrument technology, the electronics was not taught in great detail. We only learned the basic principles. In practice, we just use standard tables and select thermocouples based on the application. My references are: 1. Instrument Technology Vol.1 by E. B. Jones, 2nd Ed. 1965, chapter 3.1.3 2. Process Instruments and Controls Handbook by Douglas M. Considine, 3rd Ed. 1985 (ISBN 0-07012436-1), chapter 2.17 The thermocouple effect was first discovered by Volta and rediscovered by Seebeck in 1821. He discovered the existence of thermoelectric currents while observing electromagnetic effects associated with bismuth-copper and bismuth-antimony circuits. This experiment showed that a closed circuit of two dissimilar metals exposed to different temperatures generated a new thermal electromotive force, creating a current flow. Under zero current conditions, this Seebeck voltage depends on the temperature difference and the metals involved. He also arranged 35 metals in order of their thermoelectric properties (25 are listed in reference 1), with current flowing from the first to second at the hot junction. Ni, Pt, Cu, Pb, Au, W and Fe are included in the list. In 1834, Peltier discovered that when a current flows across the junction of two metals, heat is absorbed or liberated depending on the direction. This is not the same as the Joule heating effect. The junction was found to be the source of the EMF; the direction and value depend on the metal and the temperature difference between hot and cold junctions. In 1856, Thomson (later Lord Kelvin) found that heat is liberated when current flows from a hot part of a wire to a cold part. It is absorbed if current flows in the opposite direction. This is known as the Thomson effect, defined 8 Silicon Chip Australia's electronics magazine siliconchip.com.au siliconchip.com.au Australia's electronics magazine August 2024  9 as the change in the heat content of a single conductor of unit cross section when a unit of electricity flows through it along a specific temperature gradient. It also gives rise to an EMF. The Seebeck EMF is the sum of the Peltier & Thomson EMFs and thus proves that the thermocouple is working due to two junctions (hot and cold) of dissimilar metals. The Thomson effect also gives rise to the neutral temperature for the thermocouple (TC). For the B type, it is at 20°C, while for Cu-Fe, it is about 275°C. The Cu-Fe thermocouple is not one of the ANSI types used in industry. The neutral temperature occurs where the lines cross in the thermocouple-electric diagram for the metals concerned and is seen where the EMF reverses the gradient (peak EMF is reached) as the temperature rises further. The general formula for the thermocouple EMF is EMF = a + b × (T2 − T1) + c × (T22 − T12), where T2 > T1. Constants a, b & c are determined by the TC metals using three reference temperatures. Regarding the W (tungsten) based thermocouples mentioned in the June issue, three variants are listed (types G, C and D) but are not part of the ANSI set. They are used only above 1200°C and must be in a vacuum, hydrogen or other inert gas for protection. They were discovered before 1957 because they were already listed in the first edition of reference #2. The gold thermocouple I found was only used inside a dual-beam IR spectrophotometer. It was inside a sealed TC enclosure behind an IR transparent window (not glass). The spectral response of the TC would be flatter, with a greater range than modern IR photodiodes. The current ANSI thermocouples available, as of 1983, are types S, R, B, J, K, T, E and N. I hope this clarifies that the thermocouple works because of the junction of two dissimilar metals. Wolf-Dieter Kuenne, Bayswater, Vic. More on thermocouples The letter on thermocouples in the June 2024 issue got me thinking a bit more about how these devices function. I believe many of your readers will also be interested in an 10 Silicon Chip expanded explanation. I found a well-written article online by an organisation called Creative Design Network. I have summarised it as follows. In the 1800s, it was discovered that heating one end of a piece of metal would create a measurable voltage difference due to the valence electrons in the metal atoms becoming agitated and spaced out when the heat was applied. That allowed these valence electrons to migrate to the cooler end of the metal. Since electrons are lost at the heated end, a positive charge results, while at the cooler end, a negative charge occurs. A thermocouple is formed by two wires electrically joined at the end to be heated. An equal charge is developed if the two wires are of the same metal, giving a net zero potential across the cool ends. However, if the metals differ, the valence electrons will disperse differently. For example, if wire “A” has an electrical charge difference of 0 hot and -5 cold whilst wire “B” has 0 hot and -3 cold, the net difference between wires “A” and “B” will be (-5) − (-3) = -2. This is called the “Seebeck Effect”. The cool ends of the wires need to be at the same temperature. The full article with illustrations can be found at www.cdn-inc.com/thermocouples Terry Ives, Penguin, Tas. New Blue Mountains amateur TV repeater wanted Sydney has had an amateur television repeater in the Blue Mountains since the early 1980s, but the site was lost just over a year ago. Sending and receiving amateur TV (ATV) signals is very challenging as the range of wideband signals is limited, and Sydney’s hilly terrain makes it difficult or impossible to exchange TV pictures. An ATV repeater makes it much easier to get started, as it transmits a signal using the same standard used by terrestrial broadcast stations so that it can be picked up on various readily available receivers. Like many voice repeaters, an ATV repeater provides a focal point. It allows a weekly net to occur that otherwise would be impossible due to direct signal paths not existing between participants. ATV is one of the few activities that requires home construction, as no commercial equipment is available for digital ATV. This encourages skill-building in hardware and software, video and audio processing and using RF and antennas. This is the challenge that ATV operators enjoy, as opposed to simply streaming video on the internet, which anyone can do. An ATV repeater can also transmit on-demand educational videos to benefit all amateurs who can receive them. As an ATV repeater encourages activity on 70cm and 23cm, the wideband ATV signals make good use of the available spectrum, helping to justify the allocations for amateur radio (use it or lose it!). Sydney is now lagging well behind other major cities which have ATV repeaters. We have the equipment and are ready to provide the technical support to any club, group or organisation that could provide an elevated site, ideally on the Sydney metropolitan edge due to directional antenna requirements. Please consider our request; don’t let Sydney fall behind! John O’Shea, on behalf of the Sydney ATV Group, Revesby, NSW. SC Australia's electronics magazine siliconchip.com.au The world’s first desktop waterjet CNC - WATERJET CUTTING WAZER is the first desktop water jet that cuts any hard or soft material with digital precision. 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For a list of example materials please visit our website 2 x 240VAC 10amp plugs Order Code PRICE PRICE COPPER Desktop W08720 Standup W08720S $14,650 $16,250 $16,115 $17,875 ex GST inc GST GLASS STEEL standup. desktop. View and purchase these items online: www.machineryhouse.com.au/SIC2407 siliconchip.com.au ALUMINIUM SYDNEY (02) 9890 9111 BRISBANE (07) 3715 2200 Australia's electronics magazine 1/2 Windsor Rd, 625 Boundary Rd, Northmead Coopers Plains Specifications and prices are subject to change without notification. All prices include GST and vild until 29.08.24 NOW OPEN MELBOURNE PERTH (03) 9212 4422 (08) 9373 9999 4 Abbotts Rd, Dandenong Kewdale ADELAIDE (08) 9373 9969 August 2024  11 Unit 11/20 Cheltenham 11 Valentine St, Parade Woodville SA 5011 06_SC_290724 Now cut anything with digital precision using high-pressure water WAZER WAM Tracking & Locating Devices Apple AirTags, Car Keys and more Source image: https://unsplash.com/photos/a-cell-phone-sitting-on-top-of-a-moss-covered-ground-ReQq6kUYjLI Modern technology has made it relatively easy to track the location of people or property for safety, security or other purposes. Trackers can be used to locate children, pets, your mobile phone, computer, baggage, products in transit, machinery, cars, boats, planes or just about any other movable object. By Dr David Maddison, VK3DSM T racking devices operate over various distances, from short to long ranges. Some can provide an absolute position fix, such as latitude and longitude coordinates, while others give a relative position, such as an approximate distance and direction from your current location. Modern GPS/GNSS receivers are small enough and have low enough power consumption to make them practical for use in portable devices. More recent technologies used for tracking include ‘multilateration’ (triangulation) with radio beams and ‘ultra-wideband’ (UWB) chips. This article will cover tracking 12 Silicon Chip techniques, technologies and methods and then give examples of common or interesting tracking devices. As mentioned in our June 2024 article on Privacy Phones (siliconchip.au/ Article/16280), it is generally possible for anyone carrying a mobile phone to be tracked even without their permission. Tracking techniques and technologies Satellite positioning systems, including GPS, Galileo, BeiDou and GLONASS, are collectively known as GNSS (global navigation satellite systems). Many trackers will locate Australia's electronics magazine themselves using GNSS and then transmit that location via WiFi, Bluetooth, 4G/5G or radio. Non-GNSS tracking devices typically emit a radio signal, either via Bluetooth, UWB or WiFi, which is then processed to extract positional data such as via one of the techniques described below: AoA, Multilateration, NFER, ToA, TdoA or ToF. One advantage of those systems is that they can work in places where GNSS signals are too weak or blocked, such as indoors or underground. Angle of arrival (AoA) The direction of a transmitter can siliconchip.com.au be determined by measuring the AoA of a radio signal using an antenna array and measuring the phase shift of a received signal between each of multiple antennas – see Fig.1. A second angle measurement from a second antenna array allows the location to be established at the intersection of the two directional vectors. Multilateration (see below) needs a minimum of three sensors, while this technique requires two. However, using more sensors generally provides better accuracy. Bluetooth This is a popular short-range wireless communications protocol for functions such as connecting wireless headsets to a phone or computer, connecting a phone to a car, printing, remote control etc. It has other applications, including locating and tracking objects. Its operating range extends to about 10m for basic Bluetooth and up to about 240m for Bluetooth 5.3 (depending on the amount of clutter). Bluetooth Low Energy (BLE) beacons are commonly used for tracking. One method of localisation for these beacons is multilateration, using three fixed beacons or ‘anchors’ to measure the distance to a movable device. Even with a single device, the distance can be roughly determined by measuring signal strength. A Bluetooth Distance Measurement API uses the Bluetooth RSSI (Received Signal Strength Indicator); the direction can be determined using antennas on multiple devices. Fig.1: the angle-of-arrival locating method using an antenna array, such as a WiFi router with multiple antennas. A second router is needed to establish the position (one just gives you an angle). Fig.2: the principle of multilateration using three fixed devices at the centre of circles with radiuses r1, r2 and r3; the tracked device is at the point (x,y). Multilateration This is also known as hyperbolic positioning or trilateration; it is the process of determining the position of an object by measuring the distance between three or more known locations and one unknown location – see Fig.2. The distance may be established by the time difference of arrival (TdoA) of radio signals, relative signal strength or other means. Near-field electromagnetic ranging Near-field electromagnetic ranging (NFER) is an emerging ranging technique not yet commonly used for tracking. A radio transmission’s ‘near field’ is the electromagnetic field close to the antenna (see Fig.3). Its properties differ from the electromagnetic field further away, the ‘far field’. Fig.3: radio transmissions differ in how they behave in ‘near fields’ (close to the transmitter) & ‘far fields’ (further away). Original author: Goran M Djuknic siliconchip.com.au Australia's electronics magazine August 2024  13 Close to a small antenna or emitter, in the near field, the electric (E) and magnetic (H) components of an electromagnetic (EM) wave are up to 90° out of phase. In the far field, the pattern of electromagnetic radiation is more conventional. The phase difference between the EM wave’s electric and magnetic field components in the far field is zero; they are in phase. Between those two extremes, the phase difference is less than 90°, so if the phase difference is measured, it can indicate distance. NFER uses frequencies below about 30MHz. As an example, for a 1MHz signal, Fig.4: the phase versus range relationships near an electric dipole. The phase angle (labelled “Phase Delta”) can be used to determine the distance in terms of wavelength. Original source: www.researchgate.net/publication/276919686 Fig.5: indoor WiFi positioning in an office environment using three routers with Received Signal Strength Indicators (RSSI). Original source: https:// github.com/sankalpchauhan-me/ IndoorPositioning Fig.6: how time-of-flight (ToF) is calculated in principle. δ is the delay in response from the target device, T_P is the signal propagation time, T_ACK is the time needed for acknowledgement and the ToF used in the calculated distance is T_MEASURED. Original source: https://w.wiki/AMEk 14 Silicon Chip Australia's electronics magazine the phase difference between the electric and magnetic field varies from 75° to 25° over the more linear region between 30m and 60m from the source (see Fig.4). With a delta of 50° over 30m, if the phase different were measured with a 1° accuracy, that would give a resolution of 1/50th of 30m, ie, around 60cm. NFER operates within about half a wavelength of the signal used. A 1MHz signal has a wavelength of 300m, so a range up to about 150m could be measured. NFER is suitable for indoor use where GPS signals can’t be received (for example). One disadvantage is that, due to the low frequencies required, efficient antennas are large. Possible solutions include fractal antennas, loop antennas or ferrite rod antennas (as used in small radios). US patent 2014/0062792A1 describes a way to use commercial AM broadcast signals as ‘signals of opportunity’ for NFER. Usually, they will be in the far field. Still, when such signals interact with structures like power lines, they can resonate within them, introducing near-field components as though that structure was an emitting antenna and enabling the signal to be used for NFER. For more on near fields and far fields, see these videos: ● “EEVblog #1273 - EMC Near Field vs Far Field Explained” (https://youtu. be/lYmfVMWbIHQ) ● “EEVblog #1178 - Build a $10 DIY EMC Probe” (https://youtu. be/2xy3Hm1_ZqI) ● “#234: Basics of Near Field RF Probes | E-Field & H-Field | How-to use” (https://youtu.be/ctynv2klT6Q) RSSI Fingerprinting Received Signal Strength Indicator (RSSI) Fingerprinting is a positioning method using WiFi where a database is created and constantly updated to record the locations and signal strengths of many WiFi access points from various known positions. This enables an unknown location to be quickly determined by comparing the WiFi signal strengths to signatures in the database, with a median accuracy of 0.6m. RSSI Multilateration Received Signal Strength Indicator Multilateration uses the relative strengths of signals as a proxy for the siliconchip.com.au distance between devices. An example of this method applied to WiFi routers is shown in Fig.5. Time of arrival (ToA) While not tracking techniques, ToA & TDoA (time difference of arrival) are used in other techniques described here. ToA is defined as the absolute time when a radio signal emanating from a transmitter reaches a remote receiver. TDoA is the difference between ToAs. Time of flight (ToF) Time of flight (ToF) is a WiFi-based position measurement technique, although the principle can be applied to other types of signals. It involves measuring the time taken for a radio signal to travel (at the speed of light) between a measuring station (in this case, a WiFi access point) and a target device (eg, a smartphone) – see Fig.6. The time taken to return is also measured, allowing for a delay due to response time. The distance between devices can be calculated, and in conjunction with the time taken to other measuring stations, the location can be determined. The system is accurate, but devices must be synchronised to a master clock. Ultra-wideband (UWB) UWB was briefly mentioned in our June 2024 article on Privacy Phones (siliconchip.au/Article/16280). This technology is incorporated into various devices, including some iPhones and certain Samsung and Google Pixel model phones (more on that later). UWB is a short-range radio protocol that operates between 3.1GHz and 10.4GHz. Radio energy is sent over a very wide bandwidth, around 500MHz or more, to allow the transmission of a relatively large amount of energy without exceeding regulatory limits for certain frequency bands or causing interference (see Fig.7). UWB utilises extremely short pulses of one or two nanoseconds. Positioning using UWB is capable of very high accuracy, with errors as little as 10-50cm or even down to centimetre-­level accuracy (see “Athlete trackers” below). UWB positioning or tracking systems ideally utilise three fixed receivers or anchors. Techniques such as ToA, ToF or TDoA are used to establish siliconchip.com.au Fig.7: the frequency range and spectral power density of UWB compared with other radio technologies. Source: www.rtsmartdata.com/technology/uwb Fig.8: one variation of the Pulse Position Modulation (PPM) scheme used in UWB communications. Source: www.rescueswag.com.au/products/rescueme-plb1 the distance between the UWB tag or device and the receivers; the position of the receiver is then established by multilateration. Unlike conventional radio, in which information is transmitted via variations in frequency, phase or power, with UWB, information is encoded as pulses with specific time shifts in a scheme known as Pulse Position Modulation (PPM) – see Fig.8. UWB can transmit data at a high rate (~100Mbit/s), with transmissions over 1Gbit/s having been demonstrated. UWB is relatively energy-efficient compared to other methods, and signals can pass through many obstacles, including certain types of walls and people in crowds. Information sent from a UWB device Australia's electronics magazine usually contains its ID, ToF and timestamp data. UWB is governed by the IEEE 802.15.4a/z standard. UWB chips are fitted to the following devices: • the Apple iPhone 11 and later, excluding the iPhone SE (2nd and 3rd generation) • the Apple Watch Series 6 and later • some other Apple devices • various Samsung Galaxy models (including the Galaxy Buds Pro 2) • the Google Pixel 8 (and some other phones from Google) • the Xiaomi MIX4 • the Motorola Edge 50 Some devices, such as the iPhones with UWB, always have power to the UWB chip even when the phone is ‘off’ so it can be used to find them. August 2024  15 Wireless LAN (local area network) WLAN/WiFi can be used for location and tracking. Google uses publicly broadcast data from WiFi routers that have been scanned as they drive around in their Street View vehicles. Their locations are recorded (siliconchip.au/link/ ab9n) to enhance the accuracy and speed of location in conjunction with GPS (or to provide location even without GPS). This is used by any tracking app or hardware that uses Google Location Services. In smaller areas with access to a WiFi network, devices can be located using techniques such as RSSI Multilateration, RSSI Fingerprinting, ToF and AoA. Examples of tracking devices Here are some example of commonly found tracking devices, listed in alphabetical order. Note that this is not meant to be a comprehensive list. Aircraft tracking Commercial and many other aircraft are routinely tracked via a variety of methods, including Aircraft Communications Addressing and Reporting System (ACARS), Automatic Dependent Surveillance–Broadcast (ADSB) and FANS (Future Air Navigation System). ACARS communicates aircraft events, including equipment and sensor status, via VHF and ground stations when near land (line-of-sight, within about 370km) or via satellite receivers for almost global coverage. ACARS does not usually send position coordinates but does send speed and altitude. ADS-B broadcasts an aircraft’s callsign, position, altitude, velocity and other data twice per second. That information is sent to air traffic controllers via ground stations or satellites. Positional information is obtained via GNSS. Air Services Australia operates 61 ground stations for ADS-B. ADS-B is mandatory in Australia for aircraft flying under instrument flight rules (IFR); other countries have similar rules. FANS is a system that provides a data link between an aircraft and aircraft traffic controllers, including information concerning air traffic control clearances, pilot requests and position reporting. Communication is via ground stations or satellite. In 1995, a Qantas Boeing 747-400 (VH-OJQ) became the first aircraft to use the Rolls-Royce FANS-1 package, and Air New Zealand soon followed with a package from General Electric. Ankle bracelets Courts order police to fit some criminals or suspects with a GPS ankle (or wrist) bracelet for tracking them. These can be used to restrict them to a particular zone (such as a home) or prevent them from entering designated prohibited areas (such as where a victim might live or work, airports, schools, shopping centres etc). Alerts for violations are issued via the mobile phone network. These devices are waterproof, are designed to detect tampering and will periodically ‘check in’, generating an Fig.9: internal and external views of an ElmoTech TRXL-830 ankle monitor. Source: https://fccid.io/LSQ-TRXL-830/Internal-Photos/InternalPhotos-1338485.pdf 16 Silicon Chip Australia's electronics magazine alert if they are not functioning. As the ankle monitor is offered as a ‘service’ to the recipient to allow some freedom of movement, tampering is regarded as a very serious matter and will likely result in them being sent to jail instead of having a small amount of freedom. Similar tracking devices can also be used for people with mental impairments (eg, dementia) who may wander away from institutional care facilities. These devices can determine their location via GPS, LBS (location-based service, using mobile phone towers) or indoor beacons using BLE when no GPS or LBS signal is available. One example is the ElmoTech TRXL-830 (see Fig.9), designed to enforce curfews. It has a receiver unit that logs the presence or absence of a ‘client’ wearing one of these devices and compares that with a stored schedule of curfew hours the person has to conform to. If they are not present, the receiver unit reports the violation. Bracelets with alcohol monitoring The SCRAM Continuous Alcohol Monitoring (CAM) bracelet (Fig.10; siliconchip.au/link/abwj) is for certain classes of criminals, such as habitual drunk drivers or domestic violence offenders. It samples the wearer’s sweat for alcohol every 30 minutes and reports the result. Alcohol in sweat is detected with an electrochemical fuel cell. The bracelet must be worn in contact with the skin. The SCRAM CAM does not include tracking but can be used in conjunction Fig.10: the SCRAM Continuous Alcohol Monitoring (CAM) bracelet detects the wearer’s blood alcohol level via their sweat. Source: https://go.scramsystems. com/l/149911/2016-05-02/ tmlc/149911/1614372926rk0W3lb1/ scram_cam_product_brochure.pdf siliconchip.com.au with a tracking bracelet on the other ankle. Apple’s AirTag T h e A i r Ta g (shown here and in Fig.11) is a small disc-like token designed to find and track keys, luggage, computers, cars and any other object they are attached to, including people. AirTags use the proprietary Apple “Find My” network, a crowdsourced mesh network that uses an estimated one billion Apple devices. It requires an iCloud account and uses both Bluetooth and ultra-wideband (UWB) technology. The AirTag transmits a Bluetooth ‘beacon signal’ that is anonymously received and retransmitted by other Apple devices without alerting the other device’s owner. iPhone 11 or later users can also utilise the phone’s U1 UWB chip (or U2 in the iPhone 15 and later) to locate the AirTag more precisely. The U1 has an approximate range of 20m, while the U2 has a range of up to 60m, although estimates vary and it depends on conditions. Some reports claim AirTags can be detected at up to 250m outdoors. Despite the relatively short ranges, you or your AirTag are never likely to be far from an iPhone in an urban area. Some people have mailed packages with AirTags to follow their route and have had numerous ‘pings’ at airports, warehouses and similar facilities. Details on the impressive internals Fig.13: a Playertek GPS device weighing 42g (top right) with a screen showing the Playertek athlete monitoring tracker software. It depicts various parameters and a heat map to show the location of athletes on the field. Source: https:// performbetter.co.uk/products/playertek of the AirTag can be seen at https:// adamcatley.com/AirTag Athlete trackers Athletes’ activities can be monitored by GPS or UWB (ultra-wideband) tracking devices worn within their clothing, with the goal of improving performance. The Playertek (Fig.13) is an example of an athlete tracker that uses GPS. In the USA, the National Football League (NFL) uses UWB trackers from Zebra Technologies (www.zebra.com) to monitor athletes and the ball. The data collected includes the ball altitude, velocity, rotation, player speed, passing rates, rushing attempt in yards, pass completion, receiver separation and more. They call this “Next Gen Fig.11: the internals of an Apple AirTag (both sides). Onboard devices include the Bosch Sensortec BMA28x 3-axis accelerometer, Apple U1 ultra-wideband transceiver, Nordic Semiconductor nRF52832 Bluetooth low-energy SoC w/NFC controller and various memory, audio and power supply components. Source: www.ifixit.com/News/50145/airtag-teardown-part-one-yeah-this-tracks (CC-BY-NC-SA) siliconchip.com.au Australia's electronics magazine Stats”; see https://nextgenstats.nfl. com/glossary Each NFL stadium has 20-30 UWB receivers, two or three trackers in each player’s shoulder pads (to ensure better tracking when close to the ground), trackers on officials and other items. They collect around 1000 data points per second with centimetre accuracy. A total of around 250 trackers are used for each game. A game can be replayed in animated form in various apps using the data (see siliconchip. au/link/abx1). Boats Trackers for boats use the mobile phone network or NB-IoT networks close to shore, or a satellite service if further out to sea (see Fig.12). Some Fig.12: the Keep Track G120 Cellular and Satellite GPS Tracker showing the optional Iridium satellite module. It can be used to track other assets apart from boats. Source: Keep Track GPS – siliconchip.au/link/abx2 August 2024  17 use both mobile and satellite links. NB-IoT stands for ‘narrowband Internet of Things’ and is part of the mobile network. Telstra’s NB-IoT coverage is shown at siliconchip.au/link/abwk Child trackers Various child-tracking devices are available. These are similar to devices used for tracking adults but with the style and functions tailored for children and their carers. The Jiobit (www.jiobit.com) is a highly-rated pendant-type device for tracking children, but it is not supported in Australia. There are many watch-style devices, some of which are also suitable for adults. For example, the Apple Watch SE is not designed to track children but can be set up for such use. Two other examples (of many) include the Kids Buddy Watch (see siliconchip.au/link/abwl) and the Garmin Bounce (siliconchip.au/link/ abwm) – see Fig.14. JB HiFi sells a range of these devices, as shown at siliconchip.au/link/abwn Cube Shadow The Cube Shadow (https:// cubetracker.com/) is a subscription GPS tracker device and service that connects via the mobile phone network. It is advertised for tracking vehicles, assets, fleets, the elderly and pets. Although it is advertised as a global service, the website states, “We currently do not offer shipping outside the USA”. Chipolo ONE Spot and CARD Spot These AirTag alternatives work with Google Find My Device (see Fig.15), although they do not support UWB. See siliconchip.au/link/abwo Digital Car Keys This type of virtual car key is powered by a smartphone or watch (Fig.16). While not a tracker, it uses similar technologies, including UWB. The The misuse of trackers and the Tracker Detect app Unfortunately, criminals have been known to use tracking devices to stalk, harass and track victims. Apart from the Tracker Detect app, there is no universal or practical way to detect or disable them. Blocking GPS or phone signals is illegal, so if you think you are being stalked, contact your local police. Apple AirTags have been alleged to be misused in this way, although no doubt others have been too. If you have an Apple device with iOS 14.5 or later, it will alert you to the presence of an AirTag that is not yours and is moving with you. For further details on that, see siliconchip.au/ link/abwv You can detect the presence of Apple AirTags using an Android phone by using a free Apple app called Tracker Detect. If an AirTag has been tracking you for more than ten minutes, the App will allow you to play a sound on the AirTag to help you find it. Android versions since v6.0 (basically any modern version) can also provide alerts for unknown trackers; see siliconchip.au/link/ abww What about GPS trackers that transmit location data via the mobile An unknown tracker alert from a phone network? Presumably, devices recent version of Android. Source: that detect mobile phone activity can https://support.google.com/android/ detect such trackers. We came across answer/13658562?hl=en two covert mobile detector devices: the PocketHound (siliconchip.au/link/ abwx) and the WG Portable Mobile Phone Detector (siliconchip.au/link/abwy). If an active tracker does not use the mobile network, it would be difficult to detect, especially if the radio link uses spread spectrum techniques or extremely low power transmission like LoRa. For further information, see the article at siliconchip.au/link/abwz and the video titled “How Apple AirTags are being used by criminals” at https://youtu. be/OfXyRUwvQ8Q 18 Silicon Chip Australia's electronics magazine Fig.14: a Garmin Bounce tracking watch for children, with a screen showing the child’s location. Source: www.garmin.com/en-AU/ p/714945#overview Fig.15: a Chipolo ONE point tracking device in use. We would keep the tag inside the suitcase rather than on the outside (as long as the case is not metallic). Source: https://chipolo.net/ en/products/chipolo-one-point siliconchip.com.au Car Connectivity Consortium (CCC) maintains the specification. Car manufacturers who support the standard include AITO, BMW, BYD, Genesis, Gogoro, Hyundai, Kia, Lotus, Mercedes Benz, MINI, RAM, Škoda & Volvo. The keys are stored in mobile digital wallets such as Google Wallet, Samsung Wallet, Huawei Wallet and Apple Wallet for iOS and watchOS. Communication occurs via NFC (near-field communication) at very short ranges or UWB at longer ranges. Emergency locator transmitter (ELT) ELTs signal aircraft distress. They operate similarly to EPIRBs and transmit on 406MHz and 121.5MHz. Emergency position-indicating radiobeacon (EPIRB) An EPIRB (Fig.17) is used by boats or ships to communicate a request for immediate assistance, for example, if the vessel is sinking or there is a medical emergency. The device sends a 406MHz distress signal to a Cospas-Sarsat satellite (www.cospas-sarsat.int/en/), which then reports the position indicated by the EPIRB device (obtained via GPS or other satellite navigation system). It then reports the emergency to appropriate search and rescue (SAR) authorities for that area. If a position was not transmitted, it calculates the approximate position by analysing the signal. When SAR are close to the reported position, they can home Fig.16: opening a Kia car with a digital key via UWB. Source: www.kia.com/mu/owners/ owner-resources/quick-tips/ connectivity/setting-kia-digitalkey2-touch-smartphone.html in using radio direction finding with the EPIRB’s 121.5MHz homing signal, strobe lights on the device or the AIS (automatic identification signal) on newer devices. An EPIRB is activated either by contact with water or by manual activation; many are activated automatically and ‘float free’ if a vessel sinks. If using one of these devices, note that it is a free service but it is essential to register it correctly. They are mandatory in certain jurisdictions for certain types of vessels, but in any case, they are recommended for whatever vessel you use. Note that 121.5MHz is no longer monitored by satellites (as with older EPIRBs), but it is still used for homing purposes and is also the International Air Distress frequency. Google Find My Device This relatively new network will Fig.17: a typical EPIRB; this one is a GME MT600G. Source: www.gme.net.au/au/ emergency-safety/mt600g Fig.18: an example of items tracked using Google’s Find My Device network and an Android phone. Source: https://blog.google/ products/android/androidfind-my-device siliconchip.com.au Australia's electronics magazine work with all Android devices (about three billion of them) – see Fig.18. It is intended to be equivalent to Apple’s “Find My” network. Until recently, only Apple users have enjoyed the ability to utilise a huge number of devices that form a mesh network to find an AirTag. Now that ability has come to Android devices (running Android version 9 ‘Pie’ or later) via an upgraded Google Find My Device network, which started to be rolled out worldwide on April 9th this year – see siliconchip. au/link/abwp The rollout appears to have reached Australia in late May/early June. Like the Apple Find My network, the Google/Android Find My Device network utilises a vast network of Android devices as part of a crowd-sourced mesh network to communicate the encrypted location of a tracked device without needing the knowledge or permission of the other Android users. As with Apple, the connection is made to the mesh network via Bluetooth. Google says that all communications via the Find My Device network are end-to-end encrypted, and the location of devices participating in communicating data via the mesh network is not known to Google or anyone else. There are said to be numerous privacy safeguards. Security alerts will be provided to users if any unwanted Find My (iOS) or Find My Device (Android) compatible tags are tracking them. Like late-model Apple iPhones, Google Pixel 8 and 8 Pro phones can be tracked even if they are ‘off’ due to the ultra-wideband chip being constantly powered. August 2024  19 Is it possible to defeat GPS trackers? Sadly, criminals can detect and defeat GPS trackers attached to protected equipment. Methods used include GPS jammers, scanning for RF emissions, visual inspection, blocking devices (such as wrapping them in aluminium foil), physical removal or destruction of trackers and the use of a GPS signal spoofer to make the device appear to be in a different location than it really is. The HHD S7 tracker (siliconchip.au/link/abx0) is an example of an assettracking device that is said to be detection and jammer resistant. The device is sold as a subscription rather than a one-time purchase. Third-party trackers designed for the Find My Device network include Chipolo and Pebblebee, with devices yet to be released from Eufy, Jio and Motorola. Find My Device seems not to work on a locked-down privacy phone, as enabling it would defeat many of the privacy functions of such a phone. However, some options and apps are discussed for the privacy-focused GrapheneOS at siliconchip.au/link/ abwq Mobile personal alarms Elderly people typically use these devices, which generally are in the form of a pendant or wristband with a ‘panic button’. One model we are familiar with is the LiveLife Mobile Alarm (https://livelifealarms.com.au) shown in Fig.19. When the button is pressed, it calls a series of nominated contacts, sends the user’s location via text message and establishes hands-free two-way voice communications. It will also detect calls and issue an alert. The location is established via GPS, WiFi and Google Maps, with communications via the Telstra 4GX mobile network. 4GX is a Telstra marketing term for the 4G 700MHz (Band 28) network, which works at longer ranges than other parts of the 4G spectrum. Periodic testing of such life-­saving devices is highly recommended. Another similar product we saw was the Adult Buddy Watch (siliconchip. au/link/abwr) – see Fig.20. Mobile phone tracking apps You can install these apps on your phone and those of willing friends and family members, including children, to enable you to see where they are. Such apps include: • Familo (available on Android and iOS) – www.familo.net/en/ • Family Locator (Android and iOS) – https://family-locator.com • Find My (iOS) – www.apple.com/ au/icloud/find-my • iSharing (Android and iOS) – https://isharingsoft.com • Life360 (Android and iOS) – www.life360.com/au/ Pebblebee These Bluetooth trackers will soon be offered in versions for both iOS and Android. The Android version supports Google’s Find My Device network. They do not use UWB. Pet RFID implants These RFID devices are about the size of a large grain of rice and are used to identify a pet (eg, if they are lost). Some have considered whether such a device can be used to track an animal, but it is very short range only and can’t be sensed more than about 10cm away. Pet finders These use various tracking methods. For short ranges, up to 100m or so, Bluetooth or WiFi can be used to track a pet. The location might be provided as a range with no specific location or, if the tracker is equipped with GPS, a location if a GPS signal is available. For longer ranges, a tracker con- Personal locator beacons (PLBs) PLBs are similar to EPIRBs but are intended for land-based use, such as by bushwalkers and outback adventurers – see Fig.21. They are typically smaller than EPIRBs and don’t usually have strobe lights or water activation. If you intend to use one, make sure it’s registered correctly. Fig.19: a LiveLife mobile personal alarm. Source: https://livelifealarms. com.au/product/order4GX-mobile-alarm Fig.20: the “Adult Buddy Watch” from Buddy Gard. Source: https:// mybuddygard.com.au/ pages/adult-buddy 20 Silicon Chip nected to a mobile phone network can transmit GPS coordinates provided there is network coverage. Devices that connect to the mobile phone network typically require a subscription to function. When phone network coverage is unavailable, there is also the Aorkuler dog GPS tracker (https://aorkuler. com). It has its own radio transmitter and receiver rather than using a mobile phone, transmitting a GPS location to the receiver up to 5.6km away, depending on terrain, according to the manufacturer. We could not find out what frequency or certification it uses, so we are uncertain if this device would be legal to use in Australia or New Zealand. Some trackers enable ‘geofenced’ boundaries to be established, so an alert is issued if a pet wanders outside those boundaries. Pet trackers, like others, require regular battery replacement or recharging, as they can use a reasonable amount of power. They typically need to be charged every few days. Australia's electronics magazine Fig.21: a miniature PLB (emergency beacon) suitable for bushwalkers. This is the RescueME PLB1; it weighs 65g. Source: www. rescueswag.com. au/products/ rescueme-plb1 siliconchip.com.au Q-TRACK Q-TRACK produced a range of devices using near-field electromagnetic ranging (NFER). The company has since been acquired by GaN Corporation, and the products appear to no longer be available. NFER is an emerging technology. Radio-based key finders These are always listening for a signal from a dedicated transmitter and will sound if the transmitter is activated. One example is the “REDPINGUO Wireless RF Item Locator”. The range is said to be about 30-40m and it operates at 433.92MHz. Fleet vehicle trackers Rental cars, other rented assets and vehicle fleets are often tracked by GNSS-based devices to ensure they are used according to usage agreements, to prevent theft and for general management purposes. Highly-valued private cars may use these devices. Netstar (www.netstaraustralia.com. au) is an example of an Australian company that advertises its products and services for such devices. Radio Frequency ID (RFID) RFID tags are attached to objects to identify them or track their location, such as the progress of an item down an assembly line or through a delivery network like a postal service. RFID tags may be passive or active. Short-range passive tags contain circuitry that is activated by energy from an interrogating radio beam, while active tags contain a battery and work at much longer ranges. Cited ranges for readability of the tags vary considerably according to the model and technology used. Still, typical figures quote up to 1m for a passive tag at 13.56MHz, up to 100m or more for an active tag operating at 433MHz or 2.45GHz and 200m or Fig.24: the Lars Thrane LT-3100S GMDSS (Global Maritime Distress and Safety System) for SSAS and other forms of ship-to-shore voice and data communications via the Iridium satellite system. Source: www.prnewswire. com/news-releases/new-era-for-safety-at-sea-as-first-ever-iridium-gmdssterminal-is-unveiled-300861105.html higher in other frequency bands. Common examples of RFID devices are pet ID implants, inventory tags in stores, access control devices, trackers for railway rolling stock, trackers for shipping containers, some passports (including Australia’s), books in some libraries, toll collection devices and many others. The devices are generally very cheap. We published a DIY RFID tag design in the July 2023 issue (siliconchip.au/ Article/15860). Samsung SmartTag2 The SmartTag2 (Fig.22) uses Bluetooth and UWB for tracking and has a range of up to 120m from the nearest phone. It does not support Google’s Find My Device network and only works with Samsung Galaxy devices. Nevertheless, it has received favourable reviews, such as siliconchip.au/ link/abws It has a claimed battery life of 500 days, or 700 days in power-saving mode. Shipping container tracking Shipping containers are tracked using various technologies and sensors, such as GPS with connectivity provided by Bluetooth, LPWAN (Low Power Wide Area Network), mobile IoT and satellite. Some also include door and movement sensors, temperature sensors and weight sensors. One example is the Vimel VIM4GCONT (Fig.23). It has a five-year battery life with daily location updates, stores location data if out of network coverage and more (see siliconchip. au/link/abx3). Ship security alert system (SSAS) The SSAS alerts authorities that a ship is under attack by pirates or terrorists – see Fig.24. An SSAS report contains the ship name, unique identification numbers like MMSI (Maritime Mobile Service Identity), IMO (International Maritime Organisation) number and call sign, the date and time, the ship’s current position, speed and course. Fig.23: the Vimel VIM-4GCONT is a shipping container tracker. Source: Security Lab – siliconchip.au/link/ abx3 Fig.22: typical use cases for a Samsung SmartTag2. Source: www.samsung. com/au/mobile-accessories/galaxy-smarttag2-black-ei-t5600bbegau siliconchip.com.au Australia's electronics magazine August 2024  21 Figs.25 & 26: the mOOvement GPS ear tag (www.moovement.com.au) for domestic cattle (left). This model has a long battery life due to onboard solar cells for charging. As one use example, data from the device can be used to create a heat map of grazing patterns (right). Sound-based devices Examples of these devices are early key finders that require you to whistle or clap your hands to activate a tone. You could then ‘home in’ on the tone using your ears. However, they were generally unreliable and are now largely obsolete. Tile Tile trackers (www.tile.com/en-au) are Bluetooth-based tracking devices for keys, wallets, luggage and other objects. If a tagged item is lost, a smartphone app can make the Tile device make a noise, and the last known location will be shown on a map. A lost phone can also be made to make a sound by double-clicking on a Tile tracker. orbit at 850km altitude, orbiting about every 100 minutes. A message length of 3-31 bytes is allowed per satellite pass. From there, data is transmitted to a ground station. Wildlife is also tracked using mobile telephone networks. When the animal is out of range, tracking data can be cached. VHF, UHF or LoRa can be used for shorter-range communications. There is a free worldwide animal tracking database where researchers, journalists, students or developers can access animal tracking data. It is called Movebank (siliconchip.au/ link/abwt). There is a free app for members of the public to track various animals; see siliconchip.au/link/abwu and the YouTube video titled “Animal Tracker App” which you can view at: https:// SC youtu.be/wdG99OdwpWE Animal tracking Depending on the species, wildlife and farm animals can be tracked with GPS tags or collars. For domestic livestock such as cows, a GPS ear tag can be attached (see Figs.25 & 26). In that example, GPS location data from the tag is relayed via a low-cost LoRaWAN (Long Range Wide Area Network) network on the farmer’s property, with a range of about 8km. For more information on LoRa, see page 21 of our Digital Radio Modes article from May 2021 (siliconchip.au/ Article/14848). In the case of wildlife that travels a long distance, tracking can be performed via the Argos satellite system (www.argos-system.org) with its uplink at 401.65MHz (see Fig.27). This system has seven satellites in polar 22 Silicon Chip Fig.27: a wild animal (a female elk) with a North Star GPS tracking collar. Source: www.northstarst.com/tracking-wildlife/wild-animals Advice for tracking pets If you use a tracker for your pet, you should familiarise yourself with its operation, capabilities and limitations before it is needed. That includes replacing or charging the battery when necessary. I know of someone who did not do this, and when their pet wandered off, the device (which they had never tested) did not work! Fortunately, the pet was found the old-fashioned way, with a person who found it calling the phone number on the collar. Australia's electronics magazine siliconchip.com.au Gadgets & Gear SALE Pick up a great deal this d AV. month on tech, tools an st. 31 Prices end August Build It Yourself Electronics Centres® Easy to set up anywhere! 159 $ SAVE $30 A 3615 Mini Wi-Fi LED Projector Great for movie nights with friends and family! 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Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. Project by Phil Prosser The Styloclone musical instrument This reinvention and homage to a musical classic is an excellent project for starters. It’s also lots of fun for the musically inclined, especially those interested in old-school instruments. The whole project fits on one easy-to-build circuit board that can be mounted in a case or built as a free-standing project! T his project is simple enough to be ideal for people learning electronics, but useful enough to be fun for all ages. A Stylophone is a very simple musical instrument that can play a single note at a time, driven by a stylus (or pen). A unique feature of a Stylophone is that it uses tracks on the PCB to form the instrument’s keys. The original Dubreq Stylophone was released in 1968. While it has never become as popular as, say, the electric guitar, it definitely made a mark on popular music! Notable uses of a Stylophone are at the start of David Bowie’s “Space Oddity” and throughout the Tornados’ instrumental, “Telstar”. So, while simple, the distinctive sound of this instrument has a real place in music. The name “Styloclone” indicates siliconchip.com.au it is not a real Stylophone; it is more an homage to the original instrument, drawing inspiration from it. Our version draws a lot from the 1970s design of the Stylophone, and keeps the essentials such as the PCB tracks forming the keyboard. As an engineer, my immediate reaction to this project was to ‘gold plate’ it, allowing it to do things that no sensible person would want. However, that would miss the essence of the Stylophone. We could have based it on a microcontroller, allowing all manner of clever stuff, including fancy waveforms and effects. Alternatively, we could ‘keep the purity’, as local Sydney musician Blair “Moog” Joscelyne would say (www.blairjoscelyne.com). [He is talented – Editor] Australia's electronics magazine Ultimately, we decided to use the KISS principle (“keep it simple, stupid”) and, if people enjoy the oldschool goodness of our take on a Stylophone, we could develop a new-­ fangled version later. Our Styloclone comprises a PCB, a stylus and an optional case, as shown in the photos. The original Sylophone circuit has two main parts. The first is a simple oscillator in which the stylus changes the RC time constant to play the notes. The secondary vibrato oscillator causes the note frequency to vary slightly but rapidly, making the sound more interesting. You may recognise the concept of vibrato as it is applied to many instruments, including the human voice. Early Stylophones used a unijunction transistor for the note oscillator August 2024  27 Fig.1: the Styloclone circuit uses just two ICs and one transistor. IC1 is the main oscillator that produces a note when the stylus wired to CON3 touches one of the keypads, shorting a point in the resistor string to ground. The vibrato oscillator is based on transistor Q1; it varies the voltage at pin 5 of IC1, modulating the frequency at around 7Hz. VR1 is for calibration, VR2 for tuning and VR3 for volume control. but those are rare these days. Later versions used a 555 timer IC, which remains super common today, so we have also used one. The original approach is a masterclass in squeezing as much as possible from the minimum number of parts. We kept the essence and added a few new parts to make a modern, buildable project. That includes a simple output amplifier, allowing us to use a standard 8W speaker. The original circuit used a high-impedance speaker, which is now difficult to obtain. We are using an LM386 amplifier, which is hardly dragging the 28 Silicon Chip Stylophone into the 21st century, as that part has been around since the mid-1970s. The LM386 itself has some fame in the musical domain as a very common IC in guitar practice amplifiers and distortion boxes, so it is a fitting choice. You can hear some audio clips of the prototype Styloclone at siliconchip. au/Shop/6/432 but remember that I am more of an engineer than a musician, so don’t expect the Brandenburg Symphony! Still, they should give you an idea of the tone it produces if built as described here. It’s possible to make some simple modifications to change Australia's electronics magazine the tone, some of which will be mentioned later. Circuit details The resulting circuit is shown in Fig.1. There are two oscillators, one for vibrato and the second to generate the notes. The vibrato oscillator is built around BC549 transistor Q1, with 100nF capacitors and 68kW resistors forming a feedback network. The result is a very simple phase-shift oscillator. Early Stylophones used a 10MW pull-up resistor on the base of Q1 to bias this amplifier, which is effective but subject to significant variation. We siliconchip.com.au Scopes 1 & 2: the left scope shows the 1µF capacitor being charged and discharged by the 555 timer (cyan) and the output voltage being delivered to the speaker for a 440Hz A note (yellow). The control voltage (mauve) is about 5.3VDC in this case, although there is about 50mV AC superimposed on it from the output. The right scope shows the same signals as in Scope 1 but with a faster timebase and with vibrato enabled, visible as a periodic shifting of the waveform. have used a slightly more complex arrangement that ensures a defined setpoint for the vibrato oscillator. It should work for any high-gain NPN transistor similar to the BC549. The vibrato can be switched on and off using S2, which shorts the collector of Q1 to ground. This is a brutal but effective way of stopping this oscillator. We will discuss how the vibrato works as we describe the main oscillator. The main oscillator in the original Stylophone used a programmable unijunction transistor in the main oscillator, although early updates replaced that with the NE555 timer IC, which came out in about 1972. The 555 is set up as an astable multi-vibrator, which is a fancy way of saying that it oscillates continuously. For now, let’s look at it with the vibrato switched off and the tuning potentiometer at its midpoint. Note that the 555 will work just fine without the tuning potentiometer but without the ability to adjust the tuning. In this case, with the pen not touching any of the keyboard pads, both the trigger and threshold inputs are pulled to ground via trimpot VR1 and the long string of series resistors that ultimately connects to 0V. Referring to Fig.2, the output of Comparator C goes low, while Comparator T’s goes high. The RS flip-flop is reset, so OUT goes low. The output buffer inverts this, so the 555 output goes high. It remains in this state while no note is selected. When the stylus touches the keyboard, it connects the 555 output to part of the resistor string that defines each note. The 1µF timing capacitor charges via these resistors, siliconchip.com.au with the charge rate determined by the resistance in the string (ie, the note selected). It continues to charge until the voltage on the Threshold pin exceeds the Control voltage and the Comparator C output goes high. The RS flip-flop is reset, and the OUT pin goes high, so the 555 output pin goes low. The 1µF capacitor starts to discharge via the resistor string. Once the voltage goes below the Comparator T positive input reference voltage, the Comparator T output goes high again, setting the RS flip flop. This drives the output high, and the whole process repeats. The resulting oscillation is demonstrated in Scope 1. There are a few tweaks to the operation of the 555 IC in a Stylophone. The first is that the control voltage (CV) pin is connected to the wiper of a potentiometer. This varies the control voltage, which changes the voltage over which the 1µF capacitor must charge over the oscillation cycle, allowing the Styloclone to be tuned. We have selected resistors for each note that are in tune with middle A at 440Hz, as long as the 1µF capacitor is reasonably accurate. The tuning works well, but this is a very simple circuit, so if you set the tuning pot very high or low, you will find the octave is a bit off. We have selected values for the keyboard resistor string that give very close to in-tune notes. The second tweak is that the vibrato oscillator is capacitively coupled to the 555’s control voltage input. This adds an AC component to the control voltage and modulates the charge/ Fig.2: the 555 timer generates two reference voltages at 1/3 and 2/3 of its supply voltage, which are fed to the inputs of two comparators. The outputs of those comparators control a flip-flop, which in turn controls the output voltage. The discharge transistor switches on when the output is low. Australia's electronics magazine August 2024  29 The desktop version of our Styloclone doesn’t need a case, keeping it simple and pure! It uses four standoffs in the corners for feet. discharge range required for the 1µF capacitor, as seen in Scope 2. Tuning calculations Getting the notes right took a lot of work. The standard formula for oscillation frequency for a 555 timer is f = 1.44 ÷ (C × [Ra + 2 × Rb]). With the tweaks to the circuit, such as not using the discharge circuit, we found we needed to use f = 0.5823 ÷ (R × C). This is because we are not charging from Vcc and discharging to ground but instead using the 555 output as the charge/discharge source. Even then, there was non-linearity across the scale; we were able to use this formula to get close to the right resistances, but then we had to handtune the values. We were conscious that this might introduce variation in behaviour for chips from different suppliers, which may have differing high and low output voltages. To test this theory, we drove around town and bought five different chips from various suppliers and batches. We verified that the resistances we chose worked for all of these with only minor variations. The fact that Stylophones have been made this way for years should have told us that we were jumping at shadows. 30 Silicon Chip Our choice of a 1µF timing capacitor in the oscillator defined the resistances required for each note. Some rather odd resistances are required. Table 1 shows each note’s ‘ideal’ frequencies and incremental resistances. Because the resistance is in a string, we have worked out the best-fit values from the E24 resistance range. As expected, there are minor errors. While these errors are not huge, they indicate there is no benefit in being overly anxious about achieving the exact modelled resistances. So, you can use 1% E24 resistors of the specified values; there is no need for more precision than that. We considered having one potentiometer per note, but even the cheapest trimpots would have cost more than 10 times that of simple resistors. It would have also made tuning very complicated! If you choose to fine-tune your Styloclone by varying the resistor values, remember to set the tuning control to your ‘zero point’ and keep it there while you select new resistors. You must start with the highest note and then work down the scale. All the tuning resistors add up, so if you go back and change a higher note, you need to retune all the lower notes. We have lined all these resistors Australia's electronics magazine up alongside each note on the board. Make sure you check each value as you go and don’t put any in the wrong spot, or the tuning will end up all wonky. The original Sytlophone used a high-impedance speaker. We have added an amplifier and optional line output in case you want to record a hit song with your Styloclone. The circuit around the LM386 is bog standard, and the only part warranting comment is the 1µF capacitor from its pin 3 to ground that rolls off the high-frequency response. The resulting filter has a pretty brutal corner frequency of around 190Hz. The resistance of the RC circuit is formed by the 1kW resistor in parallel with the 4.7kW resistor from the volume control plus the volume control’s resistance. This filter tones down the harshness of the square wave output a lot. If you want a brighter sound, reducing this 1µF capacitor will give you that. We have used a simple 57mm speaker for this device; they are cheap and rugged. This speaker can produce plenty of output, but if more sound is required, you can certainly plug it into your Marshall Stack via the mono 3.5mm jack. The stylus We have used yet another Biro (ballpoint pen) case as the stylus handle in this project. This seems to be something of a tradition in the making! As the tip, we used a 4mm Posidriv machine screw (Altronics H3310; Phillips head would also be fine), to which we soldered the stylus lead. We then glued it into the tip of that obligatory Biro case using Araldite epoxy – see the photo below. You might find another way of doing this. For example, you could simply place a small diameter heatshrink tubing around a stiff piece of wire and bend the end back so it isn’t sharp. However, if you use an alternative approach, ensure that the player is insulated from the stylus tip, as The stylus is made from a Biro (ballpoint pen) case, an M4 machine screw and siliconeinsulated wire soldered to the end of the screw. siliconchip.com.au otherwise, skin resistance and body capacitance could interfere with its operation. Our goal was to make a conductive stylus tip that did not have sharp edges that would scratch and wear the PCB ‘keys’. For the stylus wire, we used super-flexible silicone-insulated wire on the assumption that the lead will be waved around a lot. We don’t want the lead breaking! The Altronics W2400-W2407 wire (the last digit determines the colour) has 95 strands with silicone insulation and is made for this sort of application (well, meter leads etc). The large number of thin wires in the wire will make this very tolerant of flexing and maximises the fatigue life. The length of the stylus lead can be tweaked, but 600mm feels about right to us. To attach the wire to the screw, we held the screw in a vise, applied flux to end top of the screw and tinned it. We then soldered the flexible wire to the end of the screw. We have included two 4mm holes in the PCB to secure the stylus lead using a zip/cable tie in front of the stylus connector. This allows you to run the stylus lead through a simple hole you drill in the side of the case without the risk of it being pulled too hard and damaged. We recommend you select a side to suit your right- or left-handed preference. perhaps mount it onto a piece of timber or other board. You need to decide which version you want to build before starting construction since the circuits are identical but the board layouts are quite different. Case preparation For the case-mounting version, we have put in some effort so that mounting the board is easy. The hardest part is neatly cutting the rectangular hole in the case to access the keys. We’ll describe how to prepare the case before assembling the PCB, as it might be easier to do it first. You can skip this section if you are building the version without the case. The best approach to cutting the large hole is to mark its outline on the case, then drill 6mm holes in each corner 3mm inside the actual corner junction, so the edges of the holes align with the cutout. Next, use a hand saw or rotary tool to cut just inside the lines. You can then file the hole to size. ABS plastic works very easily and does not clog files too severely, so tidying up the hole is a lot easier than you might expect. The drawing for the front panel cutout and drilling is in Fig.3. I used a really sharp knife and ruler to score each line, but you have to be very careful not to slip and cut your fingers while doing that! If you cut like this repeatedly, you can actually go all the way through the plastic. If you decide to do that, we suggest you wear chainmail (mesh) gloves. We are not making this up; chefs use them to avoid cutting their fingers. They are readily available, not too expensive, and surprisingly flexible. Search for “cut-resistant gloves” or “chef’s gloves” to find them. The remainder of the case preparation is drilling the speaker holes on the top panel, plus the switch and potentiometer holes in the rear panel. We found it kind of fiddly to get the measurements right for the rear panel, which is at an angle to the front panel and has rounded edges. So be Table 1 – Styloclone note ideal frequencies, resistors & actual frequencies Note Ideal Resistor Running total Measured Error Error (%) B 493.9Hz 68Ω 1179Ω 493Hz -0.9Hz -0.3 to -0.1 A♯ 466.2Hz 68Ω 1247Ω 466Hz -0.2Hz -0.2 to +0.1 A 440.0Hz 75Ω 1322Ω 440Hz 0.0Hz -0.1 to +0.1 G♯ 415.3Hz 82Ω 1404Ω 416Hz 0.7Hz +0.0 to +0.3 G 392.0Hz 82Ω 1486Ω 394Hz 2.0Hz +0.4 to +0.6 F♯ 370.0Hz 91Ω 1577Ω 371Hz 1.0Hz +0.1 to +0.4 Case options F 349.2Hz 91Ω 1668Ω 351Hz 1.8Hz +0.4 to +0.7 We have produced two slightly different PCB designs. The first, coded 23106241, fits into an Altronics H0400 case sloped instrument case and allows you to mount the board to the front panel using the inbuilt mounting holes. It gives a neat finish and delivers a neatly packaged product. The way this board mounts requires all the components to be placed on the back of the board, with the ‘keys’ on the front of the board so they can be presented to the user through a large rectangular hole in the case. However, we recognise that the case costs more than all the electronic components, and it isn’t strictly required. So the other PCB option, coded 23106242, has all the components on the top side of a rectangular board, with holes in the corners to use 10mm Nylon standoffs as feet. This way, you can set it on a flat surface to play it or E 329.6Hz 100Ω 1768Ω 332Hz 2.4Hz +0.6 to +0.9 D♯ 311.1Hz 120Ω 1888Ω 312Hz 0.9Hz +0.1 to +0.5 D 293.7Hz 120Ω 2008Ω 294Hz 0.3Hz -0.1 to +0.3 C♯ 277.2Hz 120Ω 2128Ω 278Hz 0.8Hz +0.1 to +0.5 C 261.6Hz 120Ω 2248Ω 264Hz 2.4Hz +0.7 to +1.1 B 246.9Hz 130Ω 2378Ω 251Hz 4.1Hz +1.5 to +1.9 A♯ 233.1Hz 150Ω 2528Ω 236Hz 2.9Hz +1.0 to +1.5 A 220.0Hz 150Ω 2678Ω 223Hz 3.0Hz +1.1 to +1.6 G♯ 207.7Hz 180Ω 2858Ω 210Hz 2.3Hz +0.9 to +1.3 G 196.0Hz 180Ω 3038Ω 198Hz 2.0Hz +0.8 to +1.3 F♯ 185.0Hz 200Ω 3238Ω 186Hz 1.0Hz +0.3 to +0.8 F 174.6Hz 200Ω 3438Ω 175Hz 0.4Hz -0.1 to +0.5 E 164.8Hz 200Ω 3638Ω 164Hz -0.8Hz -0.8 to -0.2 D♯ 155.6Hz 200Ω 3838Ω 155Hz -0.6Hz -0.7 to -0.1 D 146.8Hz 220Ω 4058Ω 147Hz 0.2Hz -0.2 to +0.5 C♯ 138.6Hz 220Ω 4278Ω 139Hz 0.4Hz -0.1 to +0.6 C 130.8Hz 240Ω 4518Ω 131Hz The Error column has an uncertainty of ±0.5Hz. 0.2Hz -0.2 to +0.5 siliconchip.com.au August 2024  31 cautious with this; perhaps start with smaller holes than required and be prepared to file them to a final size. Fig.4 shows the drilling details for the rear panel. Regarding labelling, we were on a roll with the retro feel of this project and had just purchased a 3D printer for the young enthusiast. So we got out the 3D modelling software and made a cool label for the project. We reckon it looks pretty good. The STL file is available from siliconchip.au/Shop/11/434 Note that it needs to be printed at a 5% scale, a simple selection in the Cura slicer program. You could probably use super glue to attach the PLA 3D-printed parts to the ABS plastic case, but we read that you can melt ABS plastic in acetone to make “ABS glue”. We picked up some of the swarf from drilling the front panel, put it in a teaspoon of acetone and mixed until we had a thick, sticky liquid. We dabbed it onto the back of the PLA labelling and carefully placed it on the front panel, where it stuck perfectly. Get it in the right spot when you put it down and do not move it. PCB assembly Building the Styloclone electronics is pretty straightforward. All parts are through-hole types, and we have used larger pads where possible to facilitate soldering. First, check that you have the correct PCB, either the one coded 23106241 that measures 179 × 123mm for the case-mounting version or the standalone board that’s coded 23106242 and measures 207 × 124.5mm. Figs.5 & 6 are the PCB overlay diagrams for the two versions that show where all the components go. The best place to start is with the resistors. We have had to use several E24 resistors with less-familiar values like 91W, 200W etc. These are used to get the tuning right for each note, so you really need the specified parts. Altronics and Jaycar stock these E24 values, and the larger online suppliers like Mouser, DigiKey, RS and element14 have them too. When fitting these, we recommend measuring each part’s resistance as you go since the colour codes can be tricky to read sometimes. If you get a part in the wrong spot, you will find that some of the notes are out of tune. Once all the resistors are in place, add 1N5819 schottky diode D1 (taking care to match its orientation to the overlay) and the 200W trimpot. At this point, it is convenient to mount the 555 and LM386 ICs. Do this before the capacitors, as it will give Fig.3: cutting the large rectangular hole is the fiddliest part of the project. We used a Dremel cutting tool and file for ours. The easiest way is to mark and drill the corner holes for the cutout from the inside, then do the remainder of cutting and drilling from the outside. If you need an inside template, you can print this out mirrored. Regardless, double-check which side you drill the speaker holes on. All dimensions in this diagram are in millimetres. 32 Silicon Chip Australia's electronics magazine siliconchip.com.au Shown at left is a view of the case-mounting version inside the case, from the underside, where the components live. The keyboard is accessible through a cutout on the other side. The finished Styloclone is shown above in its case. This version in a box gives much richer sound than the free standing version. you more room to get them in place. The 555 and LM386 look the same, so you will need to check the part numbers and ensure they are both the right way around. The dot or indent on the chips goes to the top of the board, and the PCB silkscreen has dots in nearby positions to help you. It is then time to install the capacitors. Make sure you use film capacitors for values up to 1µF; either MKT or greencaps will work fine, although greencaps may need their leads bent to fit the pads. Do not use ceramic capacitors, as they have a huge temperature coefficient and large values can even be microphonic. The 1µF capacitor on pin 2 of the 555 is particularly critical; it must be close to 1µF, so use a part with a decent tolerance (5% if possible; failing that, 10%). After that, you can add the electrolytic capacitors. Make sure each one is the right way around, with the longer positive lead on the side with the + symbol. The stripe on the can indicates the negative side, so it should be opposite the + symbol in each case. To make this process easier, all capacitors are orientated in the same direction. Next come the two 5mm screw terminals and the battery clip. We like to make connections to offboard components using terminals as it makes it easy to service, but you could simply solder flying leads to the board if that suits you. Put a dab of neutral-cure silicone sealant under the battery clip before you solder it to the board, as that will keep it secure when the Styloclone is in use. We have added two 4mm holes on either side of the battery, allowing you to ‘zip tie’ it to the board so it can’t come out during transport. Now fit the two switches. We have used PCB-mounting switches from Altronics. Similar switches are available from Mouser and other larger suppliers; you could run flying leads from the PCB pads to panel-mounted switches in a pinch. Two similar but not identical types of potentiometers are used: a 5kW linear type for the tuning control and a 5kW logarithmic type for the volume control. Both are standard 16mm-size devices. The volume pot will be labelled A5K, where A Fig.4: the drilling details for the Styloclone’s rear panel. This is the top of the case; the front panel is at the bottom in this drawing. All measurements are referenced to the top of the fixing post on the left. siliconchip.com.au Australia's electronics magazine August 2024  33 MINI SPEAKER E A# G# F G D2# C2# B A C2 G2# F2# D2 E2 3.3kW D C F# D# C# TUNE F2 G2 A2# A2 B2 VOLUME VR3 5kW log. + 1kW 10kW 100nF REAR OF MINI SPEAKER 100nF 68kW 100nF 68kW 100nF 4.7kW Q1 BC549 + 100mF FINE CON2 TUNE SPEAKER 240W 220W 220W 200W 200W 200W 200W 180W 270kW 180W 130W STYLUS TP2 100W 91 W 91W 82W 82 W 75 W 68W 68W 100nF 1kW 100nF TP1 VR1 200W CON3 120W + 2.7W TO STYLUS 470mF 120W + 220mF 1m F 120W 100nF IC1 555 120W IC2 LM386N 1kW 5819 D1 150W BAT1 9V BATTERY HOLDER VR2 5kW lin. 4.7kW 1kW 120kW 47kW 10 m F 4.7kW 100nF 1mF S2 150W S1 CON1 VIBRATO POWER OUTPUT FRONT OF BOARD C B2 UNDERSIDE OF BOARD (TRUNCATED) 34 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.5: here is where to fit all the components for the case-mounting version of the Styloclone. In this version, all parts mount on the bottom while the ‘keys’ are on the top. Take care with the orientations of the diode, ICs and electrolytic capacitors and make sure you don’t mix up all the different-value resistors! 240W C C# D# E MINI SPEAKER 200W 200W F# 200W 270kW 200W F 3.3kW 180W 4.7kW 150W + A# B 150W GND 1kW 100nF 130W FINE TUNE 120W 120W VR1 200W VOLUME 100nF CON3 STYLUS 1mF IC1 555 100nF E2 120W 100W TP1 OUTPUT 1m F IC2 LM386N 220mF VR3 5kW log. + 470mF 1kW D2# 10mF 100nF 120W D2 S2 VIBRATO 68kW C2 C2# 100nF 68kW VR2 5kW lin. 1kW A Q1 100nF BC549 4.7kW 47kW 100mF 120kW SPEAKER 4.7kW 180W 1kW G# TUNING 10kW G + 100nF CON1 91W F2 82W G2 G2# 82W 100nF BAT1 TP2 9V BATTERY HOLDER + 75W A2 D1 A2# 5819 68 W POWER 68W S1 ► B2 91W – F2# 2.7W ► siliconchip.com.au 220W D Testing your Styloclone Once all the parts are in, insert a fresh battery and measure the voltage across it. It should be near 9V. If the voltage is low, look for parts getting hot; if none are, pull the battery out and check that it is fresh. With the voltage rail all good, set the volume and tuning controls to midrange and touch the stylus to one of the key pads. You should hear a tone. Run up and down the keys and you should get a reasonable set of notes. If you get nothing: 220W + indicates “Audio Taper”, while the tuning pot is linear and will be labelled “B5K”. Do not get these mixed up. If you intend to plug the Styloclone into an amplifier or recorder, mount the 3.5mm socket now. If you will never use it, you can save yourself a bit of money and leave it off. We used a thin bead of neutral-cure silicone sealant around the hole in the PCB to attach the speaker. After applying the sealant, gently push the speaker into place. An alternative is to use 5-minute Araldite (or another epoxy glue), which works a treat and is pretty permanent. The speaker must go in so that the cone is visible from the same side as the tin-plated ‘keys’. If building the board designed to mount in the case, the speaker will be inserted from the opposite side of the board to the majority of the components, so the magnet comes through to the same side as the components and the cone can present through the front panel. If you are building the standalone board, the speaker is inserted from the same side as the components, and the magnet will be on the underside of the board. Once you glue the speaker in, take a break and ensure your glue cures. Once that silicone cures, the speaker will never fall out, but until then, it will fall out and make a mess of everything near it. Don’t ask me how I know! Solder wires to the speaker terminal and screw them into the speaker header; it doesn’t matter which way around they go. Also connect a wire to the stylus connector for testing. Depending on whether you are left- or right-handed, drill a 3mm hole for your stylus wire to go through in one side of the case. This should be on the top half of the case, about halfway down the length. Fig.6: for the standalone (non-case) version of the Stylophone, all parts mount on the top side, which also has the keyboard. All the same parts are used in both versions. Again, watch the orientations of the diode, ICs and electrolytic capacitors and make sure you don’t mix up all the different-value resistors. Australia's electronics magazine August 2024  35 T Check the voltage on pin 8 of IC1, the 555 timer. It should be more than 8V. If not, then something is wrong with the power supply. Is it on? Is diode D1 the right way around? T Is IC1 indeed a 555 and is it the right way around? T Check that pin 5 of IC1 is between 4V and 6V. The tuning pot sets this, so try adjusting that. It does not need to be exact, but it should not be pegged to one of the rails. T Check for an AC voltage on pin 3 of IC1. This will be a square wave. T If there is a voltage there, trace through the 10µF capacitor to the clockwise terminal of volume control VR3, then to its wiper and on to pin 3 of IC2, the LM386. Try turning the volume up if you lose the signal at the wiper of VR3. T Check pin 6 of IC2 for 8-9V DC. If this is not present, track back to the battery again. T Check pin 5 of IC2 for an AC voltage. If this is present, is the output capacitor the right way around, and is the speaker wired up properly? Are its terminals shorted? If the notes are all wrong: T Check that 200W trimpot VR1 on the board is set to around 110W. You should measure close to 1110W across test points TP1 and TP2, which are just below the battery (this measures VR1 and a 1kW series resistor). T Check that the correct values have been used for the row of resistors near the keys. T Set the tuning potentiometer, VR2, to about 2/3 scale. Turn the Styloclone on and measure the voltage at pin 5 of the 555 timer. This should be about 5.3V. If not, adjust the trimpot and see if it can be set to about 5.3V. Check that you have not swapped the linear and log pots. T Touch the stylus to the high B. You should get a reasonably high note at around 494Hz. If this is way off, check the value of the 1µF timing capacitor. If this note is wrong, every other note will also be wrong. T Assuming the high B is OK, run along the notes going down the scale. If you find a wrong note, check the associated resistor and correct the problem. Repeat until they are all correct. T Remember that all lower notes are built on the preceding notes, so you should only fix a resistor associated 36 Silicon Chip Parts List – Styloclone 1 134 × 189 × 55mm sloping ABS desktop instrument case [Altronics H0400] OR 4 M3 × 10mm tapped Nylon spacers 1 double-sided PCB coded 23106241 (case version), 179 × 123mm OR 1 double-sided PCB coded 23106242 (standalone version), 207 × 124.5mm 1 57mm diameter 8Ω 700mW loudspeaker (SPK1) [Altronics C0610] 2 PCB-mount right-angle miniature SPDT toggle switches (S1, S2) [Altronics S1320] 1 200Ω top-adjust mini trimpot (VR1) 1 5kΩ 16mm single-gang linear (B5K) potentiometer (VR2) 1 5kΩ 16mm single-gang logarithmic (A5K) potentiometer (VR3) 1 PCB-mount 9V battery holder (BAT1) [Altronics S5048] 1 PCB-mount 3.5mm SPST chassis-mount mono jack socket (CON1; optional) [Altronics P0090] 2 2-way 5mm/5.08 miniature PCB-mounting terminal blocks (CON2, CON3) 4 M3 × 6mm panhead machine screws 4 M3 shakeproof (star) washers 1 ballpoint pen case 1 short M4 panhead machine screw 1 9V battery 2 short 2.5mm- or 3.5mm-wide cable ties (‘zip ties’) 1 60cm length of white silicone-insulated hookup wire (outside diameter ~2.5mm) [Altronics W2407] Semiconductors 1 555 timer IC, DIP-8 (IC1) 1 LM386N mono amplifier IC, DIP-8 (IC2) 1 BC549 30V 100mA NPN transistor, TO-92 (Q1) 1 1N5819 40V 1A schottky diode (D1) Capacitors (16V electrolytic unless noted) 1 470μF 1 10μF 50V electrolytic 1 220μF 2 1μF ±5% 63V/100V MKT 1 100μF 8 100nF 63V/100V MKT Resistors (all 1/4W 1% axial unless noted) 1 270kΩ 4 1kΩ 4 120Ω 1 120kΩ 1 240Ω 1 100Ω 2 68kΩ 2 220Ω 2 91Ω 1 47kΩ 4 200Ω 2 82Ω 1 10kΩ 2 180Ω 1 75Ω 3 4.7kΩ 2 150Ω 2 68Ω 1 3.3kΩ 1 130Ω 1 2.7Ω (5% OK) with a wrong note if all the notes above it are correct. Switch on the vibrato using switch S2 and check that you get a warbling effect. Now you should have a working Styloclone. We used VR1 and VR2 to tune the upper A on our unit to 440Hz. At this frequency, the resistors we selected have pretty much the whole range of notes in tune (just as importantly, you’ll be in tune with a concert grand piano). The tuning process is: 1. Using a DMM, adjust trimpot VR1 to achieve 1110W between TP1 and TP2. 2. Adjust tuning potentiometer VR2 to get 440Hz at pin 3 of IC1 when the Australia's electronics magazine upper A is played. If you have a frequency meter, probe the speaker output. 3. Check that the other notes are in tune. If they are not, use a DMM to check the associated resistor values. How long will the battery last? That depends on how loud you play it. When switched on but not playing a note, ours drew 8.5mA. A typical 9V battery would idle for about 50 hours before going flat. At moderate volumes, the current draw increases to about 60mA, which means it should provide about 3-6 hours of playing time. You should now be set to go and create your masterpiece! SC siliconchip.com.au The Melbourne Society of Model & Experimental Engineers presents the “Let’s Make It” Exhibition 21st September 2024 • Saturday 10am - 5Pm South Oakleigh College, Bakers Rd, South Oakleigh, Victoria, Australia See model steam and petrol engines running, home-built clocks ticking, robotics whirring, electronics zapping then view creative dioramas and textile displays – the Melbourne Society of Model and Experimental Engineer’s “Let’s Make It” Exhibition will inspire everyone to make stuff. For further information contact Bruce Rodda via email brucerodda<at>yahoo.com Electronics Manufacturing in Australia Australia has a long history in local electronics manufacturing, from garages to vast factories employing hundreds of people. Many products were designed and built here by brands including Astor, AWA, EMI, Pye, Philips, Malvern Star (they made pushbikes too!), Hot Point, Whirlpool and many more. Part 1 by Kevin Poulter S ome of the biggest brands like Pye, Philips and AWA (through connections to Marconi) had the advantage of having links to European or American radio manufacturers. So many early radios sold under those brands were imported or arrived as kits for assembly here. Soon, that evolved into local design and production. This first part of the series will cover manufacturing by Pye Telecommunications Ltd, where I had considerable experience. Part two will cover radio and TV manufacturers including AWA, Astor and EMI/HMV. Pye’s UK heritage Pye was founded by W G Pye in Cambridge, England as a supplier of 38 Silicon Chip scientific instruments to Cambridge University. In 1925, he hired Charles Orr Stanley to lead their domestic radio production. Pye initially struggled in this sector, as they were arguably the best in their field and met the stringent rules to avoid signal radiation. That resulted in high selling prices and poor sensitivity, both disasters in the open consumer market. Pye noted that other brands made cheaper, better-­ performing radios due to less strict compliance with emissions rules, so they took that path. Soon, Pye was a popular brand and its radios could receive a host of stations, even those in mainland Europe. Australian Pye domestic receiver and commercial telecommunications production started in 1949 at Abbotsford, Victoria, near Melbourne. Imports from the UK supplemented those sets. Despite local competitors, the Telecommunications division was very successful and Pye built a huge Captions; top left: manufacturing Base Stations like the F60 in the 1960s. Top right: the assembly line for UHF transceivers. The line on the far right is winding coils. Bottom two: the crystal clean room, for assembling frequency control crystals, around 1970. Australia's electronics magazine siliconchip.com.au purpose-built Telecommunications plant in Clarinda, near Clayton, in Melbourne’s southeast. It was vast, capable of accommodating about 200 staff. The managers included some from the UK, who brought over their extensive production experience. The Australian demand for two-way radios was vital to the success of this factory, as mobile phones were just a “Dick Tracy” fantasy at that time. Locally-made parts Each Australian manufacturer that made products independently of overseas (sometimes parent) companies decided how much would be made in-house. AWA and Philips made nearly every component locally, including valves and transistor components, while Pye’s model was to buy those parts, including Rola speakers. Regardless, Pye Telecommunications made nearly every part of their transceivers, including all the metalwork, stamping out chassis, coils, wafer switches, screen-printing/etching printed circuit boards, tag strips, some transformers, relays, cavity resonators and quartz crystals. The massive metal stamping equipment in the open-plan building ensured the factory was not silent! The military demanded high-­ quality parts and tropical jungle-safe techniques like encapsulating parts and assemblies (sealing them with a varnish-­like coating). There, I learned how to gold-plate copper on circuit boards, which looked just like a basic science experiment. The military sent inspectors to check items during production and witness testing procedures, which were more involved than those of any civilian customer. Much of the factory was abuzz before the inspectors arrived, taking special care to select above-average products and ensure that all areas were neat and tidy. The Special Projects room developed, built and/or adapted products outside the normal Pye product range so that large contracts could be supplied. A Pye Overland F10 type FM706 D/V/12 on top of a PS728 power supply. The mains unit (pictured) and a Tulip (Lily) microphone enabled a mobile two-way to be a compact base station. This was one of the power supplies that blew up upon testing. Circa 1970s. The all-valve Pye PTC 116 Reporter, in radio-telephone mode, from the 1959 range made at Pye Abbotsford, Vic. It was used in Australian taxis, fire engines, ambulances, for ship-to-shore communications and many other applications. The big Philips takeover Pye Tulip microphones were iconic accessories for decades. There were two main components: an electromagnetic dynamic microphone and a push-totalk microswitch. In 1967, Philips took over Pye worldwide, although it was not until 1970 that Philips and Pye Telecommunications merged manufacturing. Most of the facts in this article apply equally siliconchip.com.au Australia's electronics magazine August 2024  39 A UHF Transceiver developed by Pye for the Department of Civil Aviation, seen here in September 1964. It was fitted in a 19-inch rack and similar units were supplied to the RAAF. Cavity resonators are visible; they were used to peak the tuning. to Philips’ situation after the takeover. Pye Clayton staff were relieved to find that nearly all their staff remained; only a few Philips staff merged into key positions. The Philips Telecommunications Manufacturing Company Limited (Philips-TMC for short), Radio Communication Division, head office and factory were at Clarinda Road, Clayton in Melbourne. Philips-TMC combined the experience and technical know-how of the global Philips and Pye companies to create the largest and most experienced manufacturer of two-way radio equipment in Australia. They marketed two-way radios throughout Australia and 40 other countries. The company maintained Australia’s largest, best-equipped after-sales service organisation, with branches in all mainland capital cities and 97 authorised distributors nationwide. Philips-TMC was represented in Fiji, the Philippines, Hong Kong, Singapore, Malaysia, Taiwan, Papua New Guinea, Thailand and Indonesia, among other countries. Two-way radios were also assembled in Indonesia for local supply. Pye products were still available for a while, with many being simply re-branded Philips designs. Eventually, the Philips 1680 became the main mobile two-way radio product. At the production level, very few changes were noted, other than a visit by the director of Philips. If a client wanted a limited number of transceivers that were outside the standard product range, two-way radios like the Pye Cambridge were imported from the UK. Many mobiles and rack-mounted equipment were exported to Pacific islands and Asian countries. In a surprising turn of events, Philips Melbourne received a large order for Australian model 1680 mobiles from the Dutch Police! Manufacturing structure Pye played a leading role at the 1956 Olympics in Melbourne, providing twoway radios, loudhailers, television cameras and domestic TVs used as monitors. This technical room was used to monitor and service all their equipment. 40 Silicon Chip Australia's electronics magazine Factory sections included Assembly, Accounting, Testing, Metal Fabrication, Special Projects, Parts Store, Printed Circuit boards, Coils, Design, Sales, Purchasing, Promotion, Crystal Production, Order Processing, Canteen, Export and Despatch. Challenges abound when competitors exist, so Pye had local and export Sales Teams. Customers included a siliconchip.com.au host of Australian companies, especially those with fleets of vans for, say, TV repairs, CFA (Country Fire Authority), city fire brigades, government, military, taxis, police, DCA (Department of Civil Aviation), the Flying Doctors and much more. A highlight from the early days was the 1956 Olympics in Melbourne, with Pye supplying ship-to-shore communications from the Royal Yacht Britannia to the Royal vehicles for the Duke of Edinburgh, and televisions to monitor the games. A large quartz crystal plant was built next to the Pye plant, arguably the best in Australia. Natural Brazilian quartz was imported and X-rayed for the best cutting angle. Calculations were sent by landline overnight to the Monash University large computer. Those calculations could be done now in seconds on a laptop, but it was the best procedure available at the time. When the Pye technician arrived in the morning, he hoped there had not been any glitch in the transmission, or it was back to square one, redoing it the following night. Pye experimented with new techniques for quicker and more reliable production of products such as crystals. During the normal process, a finished crystal wafer was gold-plated and mounted on two delicate wire connectors. The base and top cover were then soldered together and evacuated during the final sealing. Since soldering creates high temperatures, engineering thought: why not use cold welding? It seemed like a winwin: fewer staff would be required, and there would be little heat in the process. Initially, there were many failures in getting the correct settings without contamination. However, they made it work in the end. Another bright idea occurred for optimising the production of twoway radios. The plan was to push all the parts onto the main circuit board, bend the component tails for more grip on the copper tracks, then cut off the excess leads. Next, a conveyor belt took the completed board into a molten solder bath, with a speed control to adjust the time the parts were exposed to the solder. It was soon discovered that running the conveyor too quickly resulted in many dry joints while running it too siliconchip.com.au A Pye microphone and earphone in a handset for a telephone-like experience. They were re-branded as Philips by this time in the 1970s. The Pye Victor, one of the last valve-based two-way radios made in Australia. All products are from Kevin Poulter’s collection and were photographed by him using a Nikon P900 and in-camera flash. Manufacturing and testing Pye Overland two-way radios. The test gear seen here, like the Marconi signal generator and AVO meter, will be known to many readers. Australia's electronics magazine August 2024  41 Top: Ian Hyde (in white overalls) arriving at the docks to service Pye gear in a Navy ship. Left: Marlene checking the cut angle of a quartz wafer using diffraction X-ray equipment, c1970. Bottom: servicing a Pye mobile PTC116 mobile telephone in a Navy ship in the 1950s. 42 Silicon Chip Australia's electronics magazine slowly resulted in ‘cooked’ components. It is now a standard soldering technique used for many products that still use through-hole components, called “wave soldering”. It could be said that, next to sales and design, the company’s backbone was the mums who sat on the production line, each assembling just a small portion of the mobile radio. Provided the supervisor was not watching, they chatted about family matters as they added their quota of parts to the radio. Usually, this worked very well. One of the items assembled on the line was a rugged 12V power supply that enabled a mobile radio to operate on mains and thus become a small base station. The lady on assembly soldered the massive filter capacitors in place, then the finished unit went to test. With considerable confidence, the test technician flicked the on switch, and there was instantaneously an unearthly “BANG”, not unlike a shotgun, and the factory filled with smoke. The lady had wired the part in with reversed polarity! I recently met the test technician, who was rather rattled by the explosion but uninjured. Parts anyone? One of the biggest challenges was to make a list of parts for a new product so that they could be made or ordered with enough time to supply the production process. Halting the assembly line to wait for parts was a ‘must avoid at all costs’ situation. Some parts needed multiple steps, like metal stamping and cadmium plating (passivation), painting, captive nuts machined in place, or parts like feedthroughs. The latter was a plated nail surrounded by an insulator. When pressed into a small hole in the chassis, the feedthrough enabled a wire to be soldered on the top and bottom of the nail, thus enabling voltage to be transferred from the top of the chassis to underneath. Parts were ordered with around 10% excess to cover failures, damage and shortfalls. Potential losses occurred when parts were dropped to the floor by assembly ladies or staff who used components to make their own projects (‘foreign orders’). Faced with considerable production delays when some parts ran out, management asked the ladies to be siliconchip.com.au careful not to drop parts like resistors. All parts in stock were housed in a cyclone-caged store. Parts could only be obtained internally with a requisition slip signed by a senior staff member. The order processing department was the link between sales and production or, in the case of crystals, between the client and production. Products were ordered from the factory using a form with key data like the customer name, the required delivery dates, model numbers, transmission frequencies and ordering codes. A Philips FM320, made in the ex-Pye factory. Competition Competitors like AWA and Pye tolerated each other; for example, AWA used Pye crystals. Some readers may identify AWA, Marconi, and Eddystone test equipment in the photographs. Pye had no reservations about using competitor’s test equipment. AWA also made components branded MSP (Manufacturer’s Special Products) so that competitors could use them without having an AWA logo on their gear. The Golden Era ends The two-way radio businesses boomed as so many Australians needed wireless communications. Two-way radios in ambulances and fire engines helped save lives. Thousands of Australians benefited, through employment at the parent company or at the suppliers. Like so many products, the industry’s demise was due to politics, the introduction of the mobile phone and overseas competition. Philips Two-way Radio in Australia closed decades ago, with some staff moving to Simoco. Today, a small number of Australian speciality companies survive in the world electronics market by making unique items, such as modules for space vehicles and sensors for food production. An internal view of the Philips FM320. The components and construction techniques used would be familiar to many of our readers. Conclusion & future articles For more information on Pye Telecommunications Australia in the 1950s, please visit siliconchip.au/ link/abvb The second article in this series will cover other brands that manufactured electronics in Australia, especially televisions and radiograms. The brands featured will include EMI/ HMV and AWA. SC siliconchip.com.au PYE Australia Quartz Crystal frequency control products, circa 1970. The plain silver box is a TCXO (temperature compensated crystal oscillator). Top left is the outside and inside of a crystal filter. Australia's electronics magazine August 2024  43 Dual Mini LED Dice This article is a blend of the old and the new. It’s similar to our May 1994 Dual LED Dice design but has been updated to use more modern parts (still with discrete logic) and runs from a 3V coin cell. As we have used mostly SMDs (on the larger side), it will easily fit in your pocket. Project by Nicholas Vinen T his small board ‘rolls’ two sixsided ‘dice’ each time you activate it, giving you a pair of random numbers in two different colours. It’s small and light at just 60 × 28 × 15mm so it’s convenient to use. You could even build two or three for games that require more than two dice to be rolled. I am sure there are plenty of dice apps on smartphones these days, but there’s something pleasing about a design based on old-fashioned discrete logic with Das Blinkenlights (in this case, 14 LEDs). I also think it’s interesting to have such simple circuitry that does a useful job and only draws a few milliamps. It even switches itself off automatically, so the small coin cell should last a long time. One thing I did to make it a little more interesting is add the option of triggering the dice roll with a vibration sensor. That way, you can shake it to roll! That part is optional, but it’s pretty fun as you can just pick it up and quickly get some random numbers. Coming up snake eyes My original plan was to shamelessly copy borrow the May 1994 project circuit by Darren Yates, change the parts to make it run from a lower voltage and redesign the PCB to be smaller. However, I quickly ran into a problem. He had used four 4000-series logic ICs: two 4015 dual 4-bit shift registers and two 4093 quad schmitt-trigger NAND gates. The shift registers kept track of the state of the dice and also did some of the ‘decoding’ to drive the LEDs (more on that later). The NAND gates formed the oscillators to ‘roll’ the dice & performed some logic to always keep the shift registers in valid states. There are direct equivalent 74-series logic chips to the 4093 NAND gates, such as the 74HC132, which would run from a 3V supply. However, I could not find any such equivalent of the 4015 dual 4-bit shift registers, at least, not at a reasonable price. There are 74-series shift registers but single eight-bit shift registers seem to be much more common/popular than dual 4-bit types. So, while it might be possible to base a new circuit off the old one, it would make building it quite expensive, which I thought was against the spirit of the project. I wanted to have cheap kits, under $20 each, to make it a fun device that you can build several of if you are so inclined. So, back to the drawing board then, to come up with an equivalent circuit using more modern (readily available and inexpensive) parts. While I was revising the design, I thought I would see if I could come up with a way to do it with fewer chips. Spoiler: my design uses just three to do the same job (with two spare logic gates!). But before we get to that, let’s look at the problem I had to solve. Of course, I considered using a PIC to do this, but what’s the fun in that? The software would be trivial and the resulting board would be tiny and pretty cheap to build, but it would be a ‘black box’. Keeping with the discrete logic means that anyone can understand how the circuit works. Rolling the bones There are basically four things a battery-powered circuit needs to do to emulate rolling two dice: 1. Switch on when the button is pressed (and switch itself off some time later, so you can’t forget) 2. Trigger two oscillators when the button is pressed, each The SMD and through-hole LED prototypes. Both versions have the option of a white or black PCB. The black PCB is showing the dice rolls four & three, while the white PCB shows six & one (although it’s only faintly visible due to the camera flash). 44 Silicon Chip Australia's electronics magazine siliconchip.com.au of which increments the number on a die, going through the sequence 1, 2, 3, 4, 5, 6, 1... with decreasing frequency, so it eventually stops on two numbers. 3. Keep track of what number each die is currently showing. 4. Convert that number (1-6) into a pattern of LEDs akin to the dots on the face of a traditional die. For #1, I decided on a trick we’ve used a few times in previous projects: a Mosfet with a capacitor and parallel resistor between gate and source, plus a second resistor (and in this case, diode) to pull the gate up when the button is pressed. The RC time constant of the first two components sets the maximum time the Mosfet will remain on, powering the circuit, before switching itself off. The advantage of this approach is its simplicity and low cost, requiring just one small Mosfet (as the circuit’s current requirements are low) and a few passives. The disadvantage is that it switches off by slowly lowering the supply voltage. That means the dice LEDs fade out rather than just switching off, but I can’t see the harm in that. That gives you a bit of warning that it’s going to switch off! For #2, I copied the design from the May 1994 circuit, where the same button that switches the unit on also charges up a pair of capacitors that control two oscillators using schmitt-trigger NAND gates as inverters. The voltage on the capacitor affects the oscillator rate, so they slow down and then stop when you release the button. I made one change here; the original circuit used two capacitors of identical values and relied on the fact that no two capacitors will be exactly the same value to cause the oscillators to desynchronise, so you don’t get the same numbers on each die. I found that did not work too well – in one test, I had 20 rolls in a row where both dice gave the same number! I think this was because the oscillators were close enough that feedback through the power supply was locking them together. Using two different values for the capacitors fixed that, and I think it’s more pleasing that the ‘dice’ stop at different times; just like real ones. #3 and #4 are where the designs really differ, and this is where I was able to save one IC. Unlike the 1994 design, where state-keeping and decoding were somewhat muddled siliconchip.com.au together, my design keeps them mostly separate. To keep track of the state of each die, instead of using shift registers, I am using the registers in a dual 4-bit counter IC, the common 74HC393. Normally each counter will go from 0 to 15 and then back to 0, repeating forever, with the counter incrementing on each clock pulse. However, we want it to roll back to zero after five, so it has six discrete states. We achieve that by creating a ‘crude’ AND gate for each counter out of a dual common anode schottky diode. We connect the cathodes to the O1 and O2 outputs, the anode to the CLR input and pull the CLR input up with a resistor. Fig.1 shows how the O1 and O2 outputs both go high for the first time when the counter reaches 6. It is at this point that the diode stops conducting, allowing the pull-up resistor to assert the clear input, causing the counter to reset to zero. When it resets, O1 and O2 go low, so clear is immediately de-­ asserted. This causes the counter to go 0, 1, 2, 3, 4, 5, 0, 1, 2, 3... LED driving So we have our die states and we can roll them, but how do we drive the LEDs? I spent a couple of hours pondering how to convert the O0-O2 outputs of each counter to the six required LED states that are shown in Fig.1, trying to find the absolute minimum of low-cost logic to do it. The logic required can be minimised by driving some LEDs from one end, with others driven at both ends. By driving the LED from both ends, we effectively get a ‘free gate’, because it will only light in one of the four possible states of a pair of digital outputs. It will light with the anode pulled high and the cathode low. In two other states (low/low and high/high), there is no voltage across the LED. In the fourth, it is reverse-biased and will not conduct (at least, not with the meagre 3V we are applying). Complicating things a bit is the fact that our counter doesn’t go from 1 to 6, but from 0 to 5. I considered that we don’t necessarily need the numbers to come in order; as long as all are present and equally likely. However, I figured out a way for them to occur in order, so I kept it that way. The problem with mapping counter values of 0-5 to die face numbers of 1-6 Australia's electronics magazine is that the O1 and O2 outputs change on the counter transitions from 1 to 2, 3 to 4 and 5 to 0 on the counter. That would correspond to die face values of 2 & 3, 4 & 5 and 6 & 1, when those are actually the most similar states (two of them differing only by the state of the middle LED). Instead, I decided that a counter value of zero should show six on the die face, with the other five values (1-5) mapping to those same values on the die face. That makes decoding much easier, but keeps the numbers in sequence (6, 1, 2, 3, 4, 5, 6, 1, 2...). Circuit details Having decided on that, we can immediately sort out the central LED. It is always lit for odd numbers but never for even numbers. As shown in Fig.1, O0 is always high for odd die case numbers and low for even ones, so we just need to connect the O0 output to the middle LED’s anode (via a resistor) and connect its cathode to ground, as shown in Fig.2, and it will light at the right times. Next, let’s consider the two diagonal LEDs that will light initially to show two, then three, remaining on for four, five and six. We could chose either diagonal pair but I have opted for LED2 (upper left) and LED3 (lower right), as per Fig.1. The only die face number Fig.1: how the three binary counter outputs O0-O2 correspond to the counter value and die faces. August 2024  45 where they are off is one; they are on for the five remaining possibilities. The logic required to detect a one from the O0-O2 outputs is O0 AND NOT (O1 OR O2), which gives 1 for a die face of one and 0 for everything else. That can be rewritten as O0 AND (O1 NOR O2). NAND ICs are more common than AND, but that’s OK because using one instead just inverts the result, meaning we get a result of 0 for a die face of one from IC2b/IC1c. We therefore connect this gate output (pin 8 of IC1c) to the anodes of LED2 & LED3, connect their cathodes to ground, and they will light for any die face state but one. So far, besides the counter IC, we just need two NOR gates and two NAND gates for both dice. Two-input logic ICs usually have four gates each, so with one NOR and one NAND IC, we have two of each gate type left. We want to use two NAND gates for our oscillators, leaving us with just two NOR gates. Is that enough to drive the remaining four LEDs? Actually, we don’t need any more logic gates; we’ve already performed all the logic we need! The other two diagonal LEDs, LED6 & LED7, need to light for die face states of four, five and six. That’s the same set of states as for LED2 & LED3, except the ones where the O1 output is high (two and three). Therefore, all we need to do is connect the anodes of LED6 & LED7 to the same point as LED2 and LED3 and connect their cathodes to the O1 output. LED6 and LED7 will therefore light when LED2 and LED3 are, except when the O1 output is high. In that case, both ends of LED6 & LED7 will be at the same voltage. Therefore, LED6 and LED7 are off for values of 1, 2 & 3 and on for 4-6. Finally, we have the middle LEDs on either side, LED4 & LED5. They only come on to show six, when all three digital outputs of the counter, O0-O2, are low. We already have a NOR gate (IC2b) combining outputs O1 and O2; its output will be high only for two die face values, one and six. So all we need to do is eliminate one. So we connect the NOR gate output (pin 4 of IC2b) to the anodes of LED4 Fig.2: the circuit is based on one dual 4-bit counter, four schmit-trigger NAND gates, two NOR gates and a few other bits. 46 Silicon Chip Australia's electronics magazine siliconchip.com.au & LED5, and join their cathodes to the O0 output. They will only light when the anode is high (states one & six) and cathode is low (states two, four and six). Therefore, they only light up for six. That’s it – all LEDs are lit at the appropriate times, and we have two NOR gates to spare! I couldn’t think of anything useful to do with them; I suppose they could have been used to buffer some LEDs, so the NAND gate didn’t need to drive so many, but I found it easier to leave them unused and tie their inputs to GND. Power supply and oscillators 22μF capacitor C6 is usually charged up to the full cell voltage, so Q1’s gatesource voltage is 0V and it remains off. The circuit’s ground is therefore disconnected from the bottom end of the cell, and the circuit is not powered. In case of any leakage, C6 is kept charged by the 10MW resistor between Q1’s gate and source terminals. When the contacts of S1 (tactile pushbutton) or S2 (vibration switch) close, current can flow from the positive terminal of the 3V cell via the two schottky diodes in D5 to two places. One of those current paths flows through a 1kW resistor to discharge C6, raising Q1’s gate voltage to around 3V and switching it (and thus the rest of the circuit) on. Once the switch is released, the 10MW resistor slowly recharges C6, eventually switching Q1 and the rest of the circuit off after about a minute. 22μF capacitor C7 is discharged at the same time, via a second 1kW resistor, but this one charges more quickly, via a 100kW resistor to ground. This produces the voltage that varies the oscillator speed from fast to slow, then stopped, to simulate the dice roll. That voltage starts high when the switch is pressed and then drops. It is applied to the inputs of both schmitt-trigger inverters (IC1a and IC1d) via 1MW resistors, charging up the 47nF & 68nF capacitors from those points to ground. Once those capacitors charge to a certain point, the output of the inverter goes low, discharging the capacitor quickly via D3 or D4. The cycle then repeats. We only use parallel diodes for D3 and D4 so that we can use identical diode parts throughout the circuit, making component sourcing and construction easier. siliconchip.com.au As the ‘dice roll’ voltage drops, the charge current through 1MW resistor drops, so it takes more and more time for the oscillator cycle to complete. When the voltage from C7 drops below the negative-going threshold of schmitt-trigger inverters IC1a and IC1d, they can no longer oscillate, and the dice display remains static until a switch contact closes or the unit powers down. The reason we have both C6 and C7 is that we want C6 to charge more slowly, so the unit stays on for a while, but C7 charges fast so the dice roll completes within a couple of seconds. There is a 22μF capacitor across the coin cell to improve its surge current capability, plus a 22μF bypass capacitor for IC1 and 100nF bypasses for IC2 and IC3. A high-value bypass capacitor is used for IC1 because we don’t want voltage variations due to different LEDs lighting to affect the oscillators too much, or that could bias the dice rolls (increasing the chance of them stopping on certain numbers). The different value oscillator capacitors (47nF & 68nF) ensure the oscillators run at different rates, so there is no relationship between the number shown on the two dice. LED colours You could use the same colour of LED for both die faces but we think it’s helpful to have them be different colours. For example, if two people need to roll one die, you can assign them each a colour and roll them together. Still, it’s up to you. We chose blue and red because they both have a high efficiency and give similar brightness with 1kW current-limiting resistors running from a 3V supply. The red LEDs do draw a little more current, as they have a lower forward voltage, but both are pretty economical on power. The blue LEDs are quite bright at about 0.5mA while the red LEDs are similar at around 1.2mA. We tried green LEDs and they barely lit up with the 1kW series resistors running from 3V. We considered lower resistor values but that would put quite a strain on the button cell. Another colour that could work well is white. Yellow or amber LEDs might work well if they are high-efficiency types. A note on vibration sensors One of the biggest challenges during Australia's electronics magazine the development of this project was finding vibration sensors that actually worked! One of the most common such devices is the SW-18010P, which we have used before. However, it turns out that there a lot of dud/fake/counterfeit/ badly made devices around sold under the name SW-18010P. So you have to make sure you get them from a reputable supplier. The first lot of SW-18010Ps we got were complete duds, despite getting them from a supplier who had sent us good parts previously. They have tiny writing on the black body, as shown below. While they showed some signs of life, you had to shake them at Earthquake Magnitude 10 level to get any sort of switch closure and it seemed very inconsistent. So in the bin they went. Thinking that maybe the SW-18010P was not a good part to use, we looked for alternatives and found several likely ones: the SW-200D, SW-420D and SW-520D, all described as “highly sensitive vibration switches”. We duly purchased some of each, and were shocked upon receiving them to find that they were all tilt sensors, not vibration sensors! It’s easy to tell that because you can hear a ball rolling inside them when you tip them, and they have a high resistance in some orientations and a low resistance in others, even when static. So they clearly were not suitable. Finally, we found a seller online who actually supplied us with SW-18010P sensors that worked. As you can see in the photo, they have a slightly lighter body and larger writing. DigiKey also sells the AdaFruit version of this part (Cat 1528-2158ND) which would be a good option if you need to buy it yourself. Still, our kits will come with parts that we’ve checked and found to be working, so if you build this from a kit, Two different SW-18010P vibration sensors we purchased. We found that the ones with smaller writing on the side were highly unreliable! The ones shown at the top work much better. August 2024  47 The underside of the SMD (left) and through-hole (right) versions of the Dual Mini LED Dice use the same components. There is also a Nylon screw used to secure the coin cell, to reduce the risk of a child getting a hold of it. you shouldn’t have to worry too much about the sensor being functional. By the way, the less-sensitive SW-18015 and SW-18020 devices are probably no good because even the SW-18010P is barely sensitive enough (you have to give it a pretty firm shake to activate it). While the vibration sensor makes it a very fun device to use, it it is a bit of a gimmick. Even though you have to shake it fairly hard to get a good roll, accidental triggering is still a problem. For example, if you transport it in a car, it will roll the dice if you go over a pothole or big bump in the road. If you keep it in a pocket, it could be triggered while you walk, wearing down the battery. If you’re playing a game and depend on a good roll, we suggest you use the pushbutton to roll the dice as it seems to give better randomisation. Still, as long as you make sure you give it a good shake, it seems to work well enough, and it certainly will wake it up from sleep reliably. Construction Despite the design being mostly SMD based, we’ve chosen to use 3mm through-hole LEDs as we think they look more like the coloured dimples on a die face and, as their lenses project above the tops of the SMDs, they stop the other components on the board from detracting from the LED display. We have produced an alternative PCB (coded 08103242) that uses SMA/ M3216/1206 (imperial) sized SMD LEDs instead, for any constructors who might prefer the slimmer result. We could have designed a PCB to accept both but then we think it wouldn’t have looked as good when using the 3mm through-hole LEDs. Both PCBs measure 59.5 × 26mm and the overlay diagrams are shown in Figs.3 & 4. Components mount on both sides of the PCB. The top side mainly has the LEDs and their current-­limiting 48 Silicon Chip resistors, while all the ICs and the battery are on the other side. Once assembled, the whole thing can be encapsulated in a length of clear heatshrink tubing for protection. We recommend that you start by mounting all the SMDs on the side of the PCB with the LEDs (the ‘front’). The resistors will be labelled with codes like those shown in the parts list; you may need a magnifier to see them. The capacitors will not be labelled so don’t get them mixed up once you remove them from their packages. There are various ways to solder these components but the way we assembled the prototype was to put a little solder on one pad then, holding the part with tweezers, slide it into place while heating that solder. We removed the iron and let it solidify once the part was centred on its pads. We then checked its alignment and, if it was off, reheated the solder and gently repositioned the part with tweezers. Once it was nicely centred and flat on the board, we soldered the opposite pad, ensuring we added enough solder for it to flow onto and adhere to both the pad and part. We then waited for that to solidify, added a tiny bit of flux paste to the initial joint and heated it with the iron tip to reflow it. Repeat until all the passives are in place on the top side. Next, mount Mosfet Q1 (SOT-23) towards lower left. Use a similar technique but this time there are three pins to solder. Follow with the other SOT23 package devices on the top side, diodes D3 through D5. If you are building the board with SMD LEDs, fit them next. Don’t get the different colours mixed up or it will look odd; use all the same colour LEDs for each die face. Ensure the cathodes are orientated as shown for LED1 in Fig.4. You can check this with a DMM set on diode test mode. Carefully touch the probes to the LED leads. When it lights up, the red probe is on the anode and the black probe on the cathode. Now is a good time to clean any flux residue off this side of the board with isopropyl alcohol, methylated spirits or (ideally) a specialised flux cleaning formula. After that, flip the board over. Parts on the other side The three ICs mount on this side. All three are in similar 14-pin SOIC packages, so don’t get them mixed up, and make very sure that you identify pin 1 and locate it as shown on the underside overlay. It’s difficult to remove and refit an SMD IC unless you have a hot air station! Use a similar technique as before, tacking one pin in place and checking that all the pins are aligned over their pads before soldering the other corner pins, then the remainder. You can add a little flux paste along both rows of pins and drag solder them, or just touch a soldering iron loaded with a little solder to each pin and the flux should draw it onto the pin and pad. Don’t be too concerned if you accidentally bridge two pins. Once all pins are soldered, check for bridges and, if you find any, add more flux paste to those pins and use a piece of Both versions of the LED Dice (shown at actual size) can be covered with heatshrink for protection. You can then use it via the pushbutton, or by shaking it (if you have mounted the vibration sensor). Australia's electronics magazine siliconchip.com.au solder-wicking braid to draw off the excess solder. Once all three ICs have been soldered, clean off the flux residue and check that all the solder joints are good with a magnifier, and verify there are no bridges. You can then fit the two remaining diodes on this side, then the three 100nF capacitors and two 100kW resistors. Clean off any new flux residue, then flip the board back over and solder the tactile pushbutton in place. Try to get it straight so it looks neat. If using the through-hole LEDs, now is a good time to solder them in. With the board right-side up (the side that the LEDs sit on), the anodes (longer leads) all go towards the top, and the flat side of the lenses to the bottom. Insert each LED fully, then solder and trim the leads once you are sure it is sitting flat on the PCB. Return to the underside of the board and tin one of the rectangular cell holder pads near the edge. Add a smear of flux paste onto both of those rectangular pads. Rest the cell holder in place and make sure the entry side is facing the edge of the board (if you’re unsure of the correct orientation, consult our photos). Add a bit more flux paste on top of the two tabs that rest on the PCB. Once you’re sure it’s lined up correctly, gently press it down and feed solder onto one of the tabs. You may need to turn your iron up due to the thermal mass of the metal holder. If you will be using the vibration switch, leave it off for now as it’s easier to test the circuit without it. Testing If you have a current-limited bench supply, you can set it to 3V/50mA and connect it using clip leads. Clamp the red alligator clip to the metal shell of the cell holder but make sure it isn’t touching any other components or tracks on the PCB. Carefully clip the black one to the edge of the PCB near the cell holder so it contacts the round pad under the holder but nothing else. Switch the supply on. If you don’t have that, you can just use a lithium coin cell. They can’t deliver a lot of current and it’s easy to temporarily slip one into the side of the cell holder, making enough contact to power the circuit but allowing you to quickly pull it out if something seems wrong. Note that if you use a coin cell, the siliconchip.com.au Figs.3 & 4: we didn’t find the coin cell shorted the adjacent LED leads, but make sure you trim them close to the PCB. For the SMD version, the LED cathodes all go towards the bottom of the PCB. circuit will take a little while (probably 60s) to settle. The LEDs may be dim at first but should get brighter, assuming you are using a fresh cell. When power is applied, you should Australia's electronics magazine see the LEDs immediately light up and the dice roll. If that doesn’t happen, or the circuit draws more than 20mA, switch it off check for incorrectly placed or soldered components. August 2024  49 Parts List – Mini LED Dice 1 double-sided PCB coded 08103241, 59.5 × 26mm ● 1 SMD 20mm coin cell holder (BAT1) 1 CR2032 lithium coin cell 1 2-pin SMD tactile pushbutton (S1) 1 SW-18010P vibration sensing switch (S2) (optional) 1 75mm length of 30-40mm diameter clear heatshrink tubing 1 M2 × 6mm Nylon panhead machine screw 1 M2 Nylon hex nut Semiconductors 1 74HC132 schmitt-trigger quad 2-input NAND gate CMOS IC, SOIC-14 (IC1) 1 74HC02 quad 2-input NOR gate CMOS IC, SOIC-14 (IC2) 1 74HC393 dual 4-bit binary counter CMOS IC, SOIC-14 (IC3) 1 AO3400 30V 5.8A N-channel logic-level Mosfet or equivalent, SOT-23 (Q1) 7 blue 3mm high-brightness diffused lens LEDs (LED1-LED7) ● 7 red 3mm high-brightness diffused lens LEDs (LED11-LED17) ● 5 BAT54A dual common-anode schottky diodes, SOT-23 (D1-D5) Capacitors (all SMD M3216/1206 size 50V X7R unless noted) 4 22μF 6.3V 2 100nF 1 68nF 1 47nF Resistors (all SMD M3216/1206 size 1% unless noted) 1 10MW (code 106 or 1005) 2 10kW (code 103 or 1002) 2 1MW (code 105 or 1004) 16 1kW (code 102 or 1001) 3 100kW (code 104 or 1003) Substitutions for SMD LED version (replaces the parts marked with ●) 1 double-sided PCB coded 08103242, 59.5 × 26mm (instead of PCB coded 08103241) 7 blue 3mm high-brightness SMD M3216/1206/SMA size LEDs (LED1-LED7) 7 red 3mm high-brightness SMD M3216/1206/SMA size LEDs (LED11-LED17) 1 Mini LED Dice kit with through-hole LEDs (SC6849; $17.50) 2 Mini LED Dice kit with SMD LEDs (SC6961; $17.50) Each kit includes everything in the parts list, except the cell. Price does not include postage. A common cause of faults is a bridge between IC pins that’s near the body of the IC, making it hard to spot. Assuming it’s working, check that both dice show valid numbers (refer to Fig.1). Press S1 and roll the dice, then check again that the states are valid. Repeat until you have seen all six numbers on both dice. If any of the dice don’t look right, check if it’s because one or more LEDs are not lighting. If so, they might be connected backwards, have bad solder joins or (in rare cases) be duds. If all the LEDs are lighting but some of the patterns are wrong, check for solder bridges between IC pins or between components. About 30 seconds after pressing S1, you should notice the LEDs fading out. Typically the blue ones will fade out and switch off before the red ones due to their higher forward voltages. After about 90 seconds, the LEDs should be off and the circuit is in a low-power state. Pressing S1 should switch it back on and roll the dice again. 50 Silicon Chip Note that it’s possible to get a short roll with a short press of S1. The results should still be random, but if you want to be sure, hold it down for a half a second or so rather than just pressing it. Final assembly If you are fitting the vibration sensor, remove the cell and bend its leads at right-angles to fit the PCB pads. We suggest doing this with two pairs of fine-nosed pliers to avoid damaging the sensor by applying too much force to the lead where it enters the sensor body. Lay it over the rectangle in the top-left corner of the board, solder it in place and trim the leads. Now reinsert the cell and shake the board. It should switch on and roll the dice. They should roll every time you shake it. Insert a short Nylon M2 machine screw through the small hole in the PCB, with the head next to the coin cell, and add a Nylon hex nut on the back. Do it up tightly, then trim off the Australia's electronics magazine excess screw shaft length with side cutters. While it is almost impossible for children to remove the coin cell (due to the holder’s tightness), it provides an extra layer of safety against especially keen toddlers. Finally, slip a length of ~35mm diameter clear heatshrink tubing over the whole assembly, shrink it down (try to spread the heat out, rather than heating just one area) and trim the ends. That will protect it from moisture, dust, shorting against anything metal etc. To change the cell, cut it off and shrink on a new piece. You can use the board without the heatshrink tubing but be aware that, as parts of the circuit operate at fairly high impedances to improve the battery life, your skin resistance (which can be well under 100kW) can mess with its operation. So it’s better to sleeve it. I noticed when I encapsulated the prototype, because the board got quite hot, it activated and the dice started rolling really fast. It went back to normal when it cooled down. I put this down to increased leakage through the Mosfet due to heat, providing enough current for the circuit to run, along with changes to the schmitt-­ trigger thresholds affecting the oscillator speed. Also, if you are using the vibration sensor, its operation could be affected if it is squeezed too tight. I noticed a slight reduction in sensitivity but that could probably be fixed by adding a small slit in the tubing near the sensor to relieve the pressure on it. Alternatively, try to avoid shrinking the tubing fully in that area. Conclusion We aren’t sure whether the randomness of our Dual SMD LED Dice is sufficiently good to run a tournament, but it should be fine for casual game playing and it’s a conversation piece compared to regular dice. It also demonstrates what you can achieve with some very simple digital logic! If using the vibration sensor, it probably isn’t a good idea to keep it in a bag, a pocket or a vehicle as it might use up its battery quite quickly. SC Coin Cell Precautions Even though we have added protections such as the locking screw, it is best to make sure that children do not use this device unattended. siliconchip.com.au Great Dad-Approved Gifts ON SALE WED 14.08.2024 - SUN 01.09.2024 SPECIAL OFFERS*, LIMITED STOCK Limited to 2 of each item per customer • DRINK HOLDERS & RULER • REVERSIBLE LID • DIGITAL CONTROLS 7995 $ NOW 239 $ HOT PRICE SAVE $110 V6 & V8 Engine Style Can Coolers 30L Portable Fridge/Freezer 34 Great compact, robust and reliable fridge/freezer that fits perfectly in your car, ute, or 4WD. 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MB3763 FOLDS AWAY & FITS IN YOUR POCKET RC Foldable Mini Drone with 1080p Camera Auto lift-off, landing & hover. Headless & altitude hold modes & more. Ages 14+. GT4900 Smartphone not included. SALE ENDS SUNDAY 01.09.2024 Scan QR Code for your nearest store & opening hours 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE Rhodes Corporate Park, Building F, Suite 1.01 1 Homebush Bay Drive, Rhodes NSW 2138 Ph: (02) 8832 3100 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Mini Projects #007 – by Tim Blythman SILICON CHIP Ultrasonic Garage Door Notifier If you’re like us, there will have been times you’ve left home and couldn’t remember if you shut the garage door. Wonder no more with this device, which emails you hourly, telling you whether it’s open or closed. It will also tell you if there’s a car parked in the garage or not. Since the emails come on the hour, you will know if the device is offline. T he Garage Door Notifier monitors the status of your car and garage (see Fig.1). It has an ultrasonic distance sensor that, with the correct placement, can detect a few different states. If the garage door is open, the sensor detects the door at a close distance. If the door is closed, the sensor can monitor the distance to whatever is in the garage. If a car is present, the distance it measures will be lower. It sends an email every hour, reporting its status. We had that application in mind when designing this circuit, but we think our readers will come up with many other uses. For example, distance sensors can also measure the liquid level in a tank, so you could adapt it to monitor the amount of water in a rainwater tank. Fig.2 shows the circuit diagram of the Notifier. It’s basically just a WiFi Mini ESP8266 Main Board connected to an Ultrasonic Distance Sensor. The ESP8266 processor on the board connects to a WiFi network and uses NTP (network time protocol) to get the current time. When it is due to report, on the hour, it activates the sensor to measure the distance. It then assembles a report and fires off an email. If you don’t see the email when it is due, you know something is amiss, like a power outage. Circuit details We previously covered the operation of the Ultrasonic Distance Sensor in the December 2016 issue of Silicon Chip (siliconchip.au/Article/10470) as part of our series on electronic modules. This sensor must be powered from 5V. When a high pulse is sent to its TRIG pin, it emits a ping from one of its ultrasonic transducers, which reflects off a nearby surface. When the other ultrasonic transducer receives the reflected ping, the sensor produces a high pulse on the ECHO pin. The time between the pulses depends on the distance (and speed of sound); thus, the distance can be inferred from the delay. The WiFi Mini (also known as the D1 Mini) is a small module integrating an ESP8266 processor with WiFi, plus a USB-serial converter. It’s one of the most compact WiFi boards that does not require any external parts to program. We previously used these modules in Silicon Chip projects like the Clayton’s GPS Time Source from April 2018 (siliconchip.au/Article/11039) and the Smart Tariff Super Clock from July 2018 (siliconchip.au/Article/11137). The ESP8266 processor has 3.3V I/O pins but the sensor must be powered from 5V. The TRIG pin on the sensor will respond to a 3.3V signal, so we can directly connect the ESP8266’s D2 digital output on the WiFi Mini to the TRIG pin on the sensor. We have placed a 10kW resistor between the 5V ECHO output on the ultrasonic module and the D1 digital input pin on the WiFi Mini out of caution. There are widespread reports that the ESP8266’s I/O pins are tolerant of 5V, but the resistor is cheap insurance Fig.1: this shows how the Garage Door Notifier can detect both the position of the garage door and the presence of a car inside the garage by measuring a distance. This assumes you have a tilting or segmented door; the position of a roller door could be sensed with a different arrangement but it probably couldn’t detect the car at the same time. We expect readers will think of other applications for this device. siliconchip.com.au Australia's electronics magazine August 2024  55 Screen 1: this shows how you add an SMTP user to your SMTP2GO account. The SMTP settings shown here will already be set in the sketch. and limits the current into that input pin should it be clamped at 3.3V by an internal diode. Software The software is written for the Arduino IDE and does not require any external files beyond those included with the ESP8266 board profile. The sketch connects to a WiFi network and uses NTP to get the time. If a WiFi network is connected and the time has been correctly set, the onboard LED lights. The software checks the time, and when it detects that the hour has rolled over, it takes a measurement and uses the SMTP2GO service to send an email. The internal time is rechecked daily using NTP to avoid any drift that might occur long-term due to crystal tolerances. The sketch is divided into several smaller helper functions, simplifying the main program We bridged adjacent pads, as shown here, to connect the wires to the ultrasonic sensor. Check that the header pins are attached and the shield is orientated correctly. 56 Silicon Chip loop. The Notifier sends a lot of debugging data to the serial port at 115,200 baud and can also be manually triggered (for testing) through that serial port. SMTP2GO We previously used the SMTP2GO service (www.smtp2go.com) for the WebMite-based Watering System Controller from Silicon Chip, August 2023 (siliconchip.au/Article/15899). SMTP­ 2GO is an online service that makes sending emails easy from less-capable devices like microcontrollers. SMTP stands for Simple Mail Transfer Protocol. It is the internet protocol that is used for sending email. SMTP2GO has a free tier that allows 1000 emails per month; an email per hour works out at under 800 emails in We used short lengths of insulated wire and one 10kW resistor to connect the ultrasonic sensor’s pins to the correct pins of the WiFi Mini and its prototyping shield. Take care that this is correct as some wires carry 5V and some 3.3V. a month, so that should be sufficient. There are paid tiers if you need to send more frequent emails. To use SMTP2GO, you need to set up an account using an existing email address. We have heard that some ‘free’ email providers, such as Gmail, are not allowed, so we recommend checking if you can set up an account before starting your build. Once you have registered, you must set up an SMTP user (Dashboard → Sending → SMTP Users → Add SMTP User; see Screen 1). The SMTP username and password need to be placed in the sketch and authenticated as part of the sending process, so make sure to record them when you create the SMTP user. The SMTP user account differs from the main SMTP2GO account; multiple Fig.2: the circuit is simple. If you didn’t want it permanently soldered, you could probably rig this up with jumper wires in a few minutes. Australia's electronics magazine siliconchip.com.au SMTP users could be created under the same SMTP2GO account if you have multiple Notifiers. Testing SMTP You can test the SMTP2GO account using the WiFi Mini on its own. You will need to install the ESP8266 board profile into the Arduino IDE. If you don’t already have the IDE, it is a free download from www.arduino.cc/en/ software/ To install the board profile, add https://arduino.esp8266.com/stable/ package_esp8266com_index.json to the Additional Board Manager URLs field of the Arduino Preferences window. The “ESP8266 by ESP8266 Community” board profile can then be installed from the Board Profiles window – we used version 3.1.2. Choose “WeMos D1 R2 and Mini” as the board type and select its serial port. Drivers can be downloaded from the Jaycar XC3802 product web page if needed. Now download the sketch from siliconchip.au/Shop/6/428 and open it in the IDE. Six #defines near the start of the sketch must be customised. STASSID and STAPSK correspond to the WiFi network name and password; set them to correspond to your home network. SMTPUSER and SMTPPASS correspond to the SMTP user account you set up earlier. The SMTPFROM field must be the same as the email address used to set up the SMTP2GO account. The SMTPTO field is the intended recipient; we set this to be the same as the SMTPFROM field. The default SMTPHOST and SMTPPORT values should work, but if you run into problems, check that they match those shown in Screen 1. Now upload the sketch and open the Serial Port Monitor in the IDE at 115,200 baud. Within the first minute, you should see the first eight lines of Screen 2 appear, and the blue LED on the WiFi Mini should light up. If the WiFi network doesn’t connect, check that the STASSID and STAPSK values are correct. Typing ‘~’ on the serial monitor will trigger an email, even if the sensor is not connected. If everything is working, you will see something like the remainder of Screen 2. The three-digit codes are SMTP status codes. Those in the range 2xx and 3xx indicate that no error has occurred. siliconchip.com.au Parts List – Garage Door Notifier (JMP007) 1 WiFi Mini ESP8266 Main Board [Jaycar XC3802] 1 Ultrasonic Distance Sensor [Jaycar XC4442] 1 WiFi Mini Prototyping Shield [Jaycar XC3850] 1 10kW ½W axial resistor [Jaycar RR0596] 1 micro-USB cable for power [Jaycar WC7723] Assorted short pieces of insulated wire Screen 2: the serial port output of a working Notifier should look like this; the three-digit SMTP codes at bottom left will help diagnose problems with email transmission. A 4xx is likely a server error; you should retry. Codes in the 5xx range mean that there is a client (Notifier) problem with the SMTPUSER, SMTPPASS, or SMTP­ FROM fields. Check and edit these, then upload the sketch again. Construction We assembled this project with a prototyping shield, although it is simple enough to be done on a breadboard or even directly soldered. See the photos for the layout we used; refer to the circuit diagram, Fig.2, to check your wiring. Remember the 10kW resistor for the ECHO pin. We poked the wires through the shield to solder to the sensor pins on the underside. You may also need to attach header pins or sockets to the WiFi Mini or shield. Power up the assembled Notifier and check that it works as before. You can use the ‘t’ command on the serial Australia's electronics magazine console to test the sensor; this will generate a report but not email it. Check that the sensor reports distances correctly; if so, then all is working. Customisation Changing the doReport() and getStatus() functions is the easiest way to modify the contents of the emails that are sent. To send daily emails, move the doReport() function call down into the section that checks for the day changing, about seven lines lower. If you are skilled with Arduino, you should have no trouble using our helper functions to create your own Notifier, produce custom reports and perhaps monitor other sensors. You will have to work out the power and mounting options; a USB power supply and micro-USB cable should be sufficient for power delivery. Fig.1 should give you an idea of where to mount the unit. SC August 2024  57 Mini Projects #009 – by Tim Blythman SILICON CHIP Stroboscope and Tachometer Stroboscopes and Tachometers are handy tools for measuring how fast an object like a flywheel is spinning. This Stroboscope/Tachometer is easy to build from a few Arduino modules and other parts. Warning: flashing lights, particularly in the lower frequency range from about 5Hz (300RPM) upward can induce seizures in people subject to photosensitive epilepsy. Flashing lights can also trigger a migraine attack. We recommend that people prone to these effects avoid stroboscopic lights. S troboscopes are devices that use a rapidly flashing light source to help observe a rotating object. If a light is flashed at the same rate as the object is rotating, the object is lit at the same location on each rotation. In this case, human persistence of vision means that the object appears stationary. This lets you observe something spinning too fast to see. Also, if you know the flash rate when the object appears stationary, you can estimate the rotation rate. Another way to measure rotation speed is with a fixed light source and a light sensor. The light sensor detects the light changes as the object rotates; a reflective sticker is often applied to assist this detection. Measuring the time between rotations allows the rotational speed to be calculated. Such a device is called a Tachometer. This project combines a Stroboscope and a Tachometer into one simple device. As it is based on an Arduino Uno, it is easy to modify and experiment with. We published a more advanced version of this device in the August and September 2008 issues of Silicon Chip (siliconchip.au/Series/52). We also produced a Strobe to check the speed of record turntables in December 2015 (siliconchip.au/Article/9640). This simpler design could perform many of the same jobs. Hardware We built our prototype using an Arduino Uno mainboard and a Jaycar XC4454 LCD Shield. Since the shield has pads to break out unused I/O pins, we simply soldered the required components to those pads on the shield. Parts List – Stroboscope (JMP009) 1 Arduino Uno R3 main board [Jaycar XC4410] 1 Uno-compatible LCD Keypad shield [Jaycar XC4454] 1 5mm white LED [Jaycar ZD0290] 1 3mm infrared (IR) LED [Jaycar ZD1946] 1 IR photodiode [Jaycar ZD1948] 1 100kW ½W 1% metal film axial resistor [Jaycar RR0620] 2 220W ½W 1% metal film axial resistor [Jaycar RR0556] 5cm length of 5mm diameter heatshrink tubing [Jaycar WH5553] 1 USB cable to suit the Arduino Uno [Jaycar WC7701] 58 Silicon Chip Australia's electronics magazine The LCD Shield also includes several tactile pushbuttons, so we have everything we need for a complete user interface. The character (alphanumeric) LCD on the shield is driven in four-bit mode by pins D4-D7 of the Uno, with D8 and D9 providing the RS and E signals, respectively. The pushbuttons are connected to a resistor chain that sends a different voltage to the A0 analog input, depending on which buttons are pressed. Fig.1 shows how to wire up the external components. At the top, the white LED connects between D12 and D11 with a 220W resistor in series. This makes up the Stroboscope, with the processor driving D12 to control the flash rate. D11 is permanently held low to create a convenient alternative to a ground connection. The IR LED is powered by the 5V and GND pins, so it is always on. Its job is to provide an IR light source for the IR photodiode to detect. With the arrangement we are using, the photodiode behaves somewhat like a solar cell, generating a voltage on its anode relative to the cathode. Since the photodiode behaves more like a current source than a voltage source, a parallel resistor is siliconchip.com.au provided to turn the current into a voltage that the ADC peripheral of the Uno can measure. We use a photodiode as they can respond faster than devices like LDRs. For this project, we have used an Arduino Uno R3 as other processor boards like the Arduino Leonardo use their processor to handle their USB interface. Since the Uno has a separate USB interface chip, it has fewer interruptions, making it better at managing the precise timing needed in this project. Fig.1: practically all the wiring is done by soldering components directly to the LCD Shield. You can also see the connections we’ve made in the photos. Software The software consists of an Arduino sketch and two libraries. The library to drive the LCD panel is included with the Arduino IDE, while an external ‘TimerOne’ library is used to manage the strobe timing. The sketch sets up a timer interrupt to drive the white LED with a duty cycle of 10% (ie, off for nine times longer than it’s on) at a rate you can control. The strobe can also be switched off. Professional strobes use a much lower duty cycle at a higher power level to more accurately ‘freeze’ the view. The sketch also samples the photodiode voltage at 10ms intervals (100 times per second), then calculates and displays a rate based on the time between detected pulses. The display can be set to RPM (revolutions per minute) or Hz (revolutions per second) for both the Strobe and Tachometer. The Stroboscope/ Tachometer uses a white LED for the Stroboscope; the strobe rate can be set by pushbuttons. The Tachometer consists of an IR LED and photodiode to sense changing light reflection due to rotation. Assembly Start by soldering the LEDs to their 220W resistors by cutting each anode (longer) lead short. Cut down one lead of each 220W resistor to a similar length. Solder the resistor to the LED and use a few centimetres of heatshrink tubing to cover the resistor. You can then solder the LED assemblies to the LCD shield as shown. The white LED connects between the second and third pads at the top of the shield, with the cathode on the third pad. The IR LED (which is blue) is wired between 5V and GND, with its cathode to GND. Trim any excess lead length from these components. Solder the 100kW resistor between the other GND pin and A1; it should be a comfortable fit. The longer anode lead of the photodiode is also soldered siliconchip.com.au Australia's electronics magazine August 2024  59 to A1, with the cathode going to GND. The active area of the photodiode is the curved lens, so bend its leads to point the lens in the same direction as the IR LED. Finally, plug the LCD shield into the top of the Uno and hook it up to your computer for programming. You should see the power LED on the LCD shield light up. Programming You can download the Arduino sketch for this project (siliconchip. au/Shop/6/448). We have included a copy of the Timer­One library with the sketch download, but it can also be installed by searching for “timerone” in the Arduino Library Manager. Use the Arduino IDE (download from www.arduino.cc/en/software) to upload the sketch to the Uno, being sure to select the correct port and use the Uno board profile. Screens 1, 2 & 3 show some of the typical displays. Using it Screen 1: this help screen can be seen when the SEL button is held down. The SEL button also toggles between the RPM and Hz displays, shown in Screen 2 and Screen 3, respectively. Screen 2: pressing the LEFT button should cause the white LED to start flickering. You can change the rate with the UP and DOWN buttons. Screen 3: the RIGHT button will change the steps by which the rate is changed. This is always shown in RPM, even if Hz is selected as the unit. To use it as a Stroboscope, shine the white LED at a rotating object and adjust the rate until the object appears stationary. Remember that the object will also appear stationary if the rate is a fraction (eg, 1/2 or 1/3) of the rotation speed. The correct rate is the highest rate at which the object appears stationary. When using the Stroboscope, remember that the object that appears stationary might not be! This can be dangerous if that object is machinery, as you might be tempted to touch it. So take great care when using the Stroboscope near running machinery. The Tachometer is used by aiming the IR LED and photodiode at a rotating object and reading out the value in the lower-right corner of the LCD screen. You should be able to get a reading of a few Hz or a few hundred RPM by waving your hand a few centimetres in front of the LED/photodiode. If you don’t get a good reading, check that the IR LED is emitting by pointing a mobile phone camera at it. The camera should show a red or purple glow that isn’t visible to human eyes. Other IR emitting sources (eg, remote controls) might cause interference, so keep the unit away from them. Remember that objects like fans with multiple blades will cause multiple events per revolution, so you may have to account for this in your calculations. One way around this is to place a piece of reflective tape on the object so that you can easily pick up one event per revolution. Summary Assembly of the Stroboscope involves plugging the modified LCD Keypad shield into an Arduino Uno (shown above). 60 Silicon Chip Australia's electronics magazine The Stroboscope/Tachometer is a simple and handy tool for checking the speed of rotating objects. It may not be the best tool for calibrating heavy machinery, but we think it would be a convenient way to check if your record turntable is spinning at the correct rate, for example. To check a turntable rotation speed, you also need a separate strobe disc with markings. SC siliconchip.com.au CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. Reading a BCD switch using one micro pin I devised this circuit to easily interface a BCD wheel or hex switch to any microcontroller with an analog input, using just one pin. With all the internal BCD switches off, the 1kW resistor pulls the analog input pin down to 0V. When one or more switches are closed, the connected resistors result in a unique voltage at that input pin. After using the microcontroller’s internal analog-to-digital converter (ADC) to convert that voltage into a number, refer to the accompanying table that shows the ranges to translate into each possible switch state. Those are for a 10-bit ADC that gives values between 0 (0V) and 1023 (Vcc). For a 12-bit ADC, multiply the values by four; for an 8-bit ADC, divide them by four. The actual value read should be close to the middle of the range, but using ranges allows for accurately sensing the switch position regardless of electrical noise or resistor tolerances. The values will be the same irrespective of whether Vcc is 5V, 3.3V or something else as long as the four lower resistors connect to the same voltage that the ADC uses as its reference. Geoffrey Younger, Woodvale, WA. ($60) TEST MANY COMPONENTS ESR TEST T Measures ESR/resistance from 0.01Ω to 1kΩ Measures capacitance from 100nF to 50μF Can perform in-circuit testing as long as capacitors are discharged Compact Tweezers format makes probing parts easy ITH OUR EEZERS Runs from a single 3V lithium coin cell Will operate down to a cell voltage of 2.4V Displays results on a clearly visible OLED screen Typical accuracy better than 10% Adjustable sleep timeout and brightness Display can be rotated to suit left- and right-handed use Simple calibration of most parameters The standby cell life is close to the cell shelf life Complete kit for $50 (SC6952; siliconchip.com.au/Shop/20/6952) The kit includes everything pictured, except the lithium coin cell and optional programming header (CON1). The three resistors and single capacitor needed for calibration are included. See the article in the June 2024 issue for more details (siliconchip.au/Article/16289). For testing other components like capacitors and diodes, check out our Advanced SMD Test Tweezers from the February & March 2023 issues (siliconchip.com.au/Series/396). We sell a kit for those Tweezers for $45 (SC6631). siliconchip.com.au Australia's electronics magazine August 2024  61 Op amp based Guitar Equaliser Many Fender, Marshall, VOX (collectively known as FMV) and similar guitar amplifiers use much the same, simple tone control system (Lo, Mid, Hi). The mid-frequencies are fixed in some amps like the VOX AC-30, but the bass and treble controls are similar to the three-band system in those. The system, and variations thereof, first appeared in the 1950s and was incorporated into most amps being built by Fender, Marshall and others at the time. While the system was simple and cheap, it had some problems. Control is difficult as it is somewhat non-linear, being very sensitive in some areas and not in others. The controls have a high degree of interaction. Also, due to component tolerances, the same amplifier model can give rather different responses at the same settings. Finally, frequency adjustment (controlled shift) is nonexistent. Generally, when all the controls are in the centre (12 o’clock) position, there is a ‘scooped’ response, which provides 5-10dB of cut to the mid frequencies centred somewhere between 400Hz and 800Hz, depending on the amp model. The bass control provides 10dB of boost or cut at 50-100Hz, sometimes rolling off steeply below that point. 62 Silicon Chip Mid provides around 10dB of cut (only). The exact frequency at which this occurs varies with models and is affected by the Bass and Treble control settings. Treble provides around 6dB of boost or cut at 10kHz relative to its centre position and, in some instances, affects the Mid adjustment. I have designed a tone control system with none of these drawbacks. It uses four switches and five pots and has a parametric mid-range EQ. Two of the switches set the mid frequencies for bass and treble adjustments (40/100Hz and 1/4kHz), while the other two, labelled DEEP and BRIGHT, provide overall adjustments. With all controls in neutral (12 o’clock) positions, the frequency response is relatively flat, with -3dB points at around 20Hz and 9kHz. The DEEP switch provides about 12dB of boost around very low frequencies, peaking at around 50-60Hz. Similarly, BRIGHT provides approximately 12dB of boost to very high frequencies, around 8-10kHz. The BASS switch and knob work together to provide up to 12dB of cut or boost around the selected frequency (40Hz or 100Hz). Similarly, the TREBLE switch and knob provide at most 12dB of cut or boost around either 1kHz or 4kHz. These controls don’t interact with each other, the DEEP and BRIGHT switches or the mid controls, other than their effects being cumulative. The MID parametric equaliser is the most versatile and potentially most useful section. The WIDTH (Q) knob adjusts the breadth of the frequency response over a range of approximately ½ to 2-3 octaves centred on the mid-frequency that has been set. The MID knob, like other tone controls, provides a controllable amount of boost or cut within the range of around ±12dB. The FREQUENCY knob adjusts the centre frequency of the MID response over the range of about 100Hz to 1kHz. The circuit consists of three primary blocks. The first is the BRIGHT/DEEP control based around op amp IC1a and its associated frequency and gain-­ determining components. A similar system, or a simplified version thereof, is used in some guitar amplifiers. The second is a Baxandall-style bass/treble filter using IC1b and its associated components, including switches that allow the centre frequency of both the bass and treble response to be lowered by an octave or two. Most general-purpose amplifiers use a centre frequency of around S3 Treble frequency S4 Bass frequency Open 4kHz Open 100Hz Closed 1kHz Closed 40Hz 1kHz, but that is somewhat high for guitar applications. This is the classic tone control used in many amplifiers – both for guitar and general use. It was initially designed by Peter Baxandall in the 1950s (although it did not use op amps back then), and is just one of Peter’s many significant contributions to designing audio equipment and systems. The third section is a ‘state variable filter’ that provides the mid-band functions. These are often used in more upmarket audio devices, such as audio mixers and outboard attachments. Like other parts of this circuit, it has been tuned to suit guitar use. Note that the two 12kW resistors connected between pairs of terminals of VR4a and VR4b have also been chosen to linearise the frequency control provided by this potentiometer. Their values may need to be adjusted slightly depending on the actual values and linearity of the pots. In practice, they make VR4 a ‘reverse-log’ pot, as is needed for linear frequency control. The input impedance to this filter circuit is relatively low, so it should be driven from a low-impedance source. While no power supply is shown on the circuit diagram, all the op amps should be powered from a split ±15V supply with a single bypass capacitor between their positive and negative supply pins (eg, one 100nF each plus a 10μF bulk bypass capacitor shared by all of them). You might get away with slightly lower supply rails depending on the signal levels or by using rail-torail op amps. Graham Bowman, Duncraig, WA. ($120) Tunnel timer for model railways Most model railways have a tunnel. Its portals usually enter a mountain, giving the impression that they extend underground for a long distance. In reality, the model track in the tunnel is no more than a metre long, so the time taken for a train to pass through is only a few seconds. To make the travel time more realistic, a simple timer can be added that stops the train inside the tunnel for a preset time while it is out of view, giving the impression that the tunnel is much longer. A small rare earth magnet is mounted on the train engine, and when it passes over a reed switch on the track inside the tunnel, the timer opens a relay contact that cuts power to the train. When the delay period ends, the relay switches off, closing the contacts that supply power to the train, and it exits the tunnel. The timer circuit is shown here, and I have designed a 46 x 53mm siliconchip.com.au single-­ sided PCB for it (see the photo). You can download the Gerber files for making that PCB from siliconchip.au/Shop/10/420 (along with the software). When the magnet on the front of the train passes over the reed switch, its contacts close, taking the GP2 digital input of microcontroller IC1 high. That triggers an interrupt routine in the software that takes the GP0 digital output high, biasing the BC547 transistor on and opening the relay contacts. LED1 lights to show that the relay coil is powered. At the same time, the software starts a timer. The train’s stopped time is set by the 5kW trimpot VR1 between 0 seconds and 10 seconds. Turning the potentiometer clockwise increases the time. The micro calculates the time by measuring the potentiometer wiper voltage via its analog input GP4 and internal analog-to-digital converter (ADC). Australia's electronics magazine When the timer expires, Q1 is switched off, and the relay contacts close, restarting the train. The 1N4004 diode quenches the backEMF the relay coil generates at switch-off. Les Kerr, Ashby, NSW. ($80) August 2024  63 Altium Designer 24 Review by Tim Blythman Each year brings a new version of Altium Designer. We have spent a while trying out Altium Designer 24 and exploring its latest features. This review covers our findings and includes support for the exciting new 3D-MID technology. A ltium Designer 24 is the latest version of the Altium Designer EDA (electronic design automation) software, released late last year. We use Altium Designer to create practically all our PCB designs, so we are pretty familiar with it. We tested version 24.0.1 for this review. As has been the case for a few years, incremental updates have been released for Altium Designer on a monthly basis. Sometimes, very new and upcoming features can be enabled for trial (‘beta’) by enabling an option in the Advanced Settings dialog. Some of the new features we tested may have been available for a while, even appearing in versions of Altium Designer from late last year. We always seem to find some new tools or options that are handy and helpful. The web page at www.altium.com/ altium-designer/whats-new lists changes by version. You can also see planned future features at www. altium.com/altium-designer/coming-­ soon Depending on your beta settings, product access level and installed version, some of these features may or may not be available. More information about features and their corresponding subscription requirements can be found at www.altium.com/ altium-designer/subscription We quite like the simplified Gerber export dialog box that we noted in our review of Altium Designer 23 (March 2023; siliconchip.au/Article/15697). There is now also a simplified License Management page, shown in Screen 1 below. It includes only the most relevant information, and the option to hide expired licenses means there aren’t any unnecessary items that you have to scroll past. It’s a small change, but making the simple tasks easy is always helpful. PCB CoDesign Many of our projects use Altium Designer for the basic steps of ‘schematic capture’ (drawing a circuit diagram on a computer), PCB layout and Gerber export. Gerber files are what PCB manufacturers use to produce circuit boards. Nearly all of our designs are handled by one person from concept to completion due to their relative simplicity. However, more complex designs might require a large team working together to complete a PCB. Screen 1: the License Management screen has been simplified to make the most useful buttons and data visible. Expired licenses can be hidden, and essential status information is displayed clearly. 64 Silicon Chip Australia's electronics magazine siliconchip.com.au Screen 3: it’s easy to import a STEP file into Altium Designer to visualise how a 3D model of a mechanical part, such as an enclosure, will fit the PCB. The 3D view can even detect conflicts and collisions. Keeping the efforts of many workers synchronised is not a simple task, and Altium has released tools over the last few years to keep things such as component libraries consistent and up to date. The Altium 365 Workspace is one example. PCB CoDesign allows multiple people to work on the same PCB without causing conflicts, by resolving and handling differences within the Workspace (see Screen 2). Electronic design automation You might think that Altium Designer is just about PCB design, but it can do much more than that, even if that is what we usually use it for. The concept of electronic design automation (EDA) stretches beyond just PCB design, and Altium Designer incorporates several features in addition to designing circuit diagrams and circuit boards. For electronic engineers, mechanical computer-aided design (MCAD) typically encompasses mechanical parts like enclosures and heatsinks. MCAD is well-covered by other programs. Our review of Altium Designer 21 (January 2021, siliconchip.au/­ Article/14705) noted software plugins that allow the integration of mechanical designs into Altium projects. Supported MCAD tools include Solidworks, PTC Creo, Autodesk Inventor, Autodesk Fusion 360 and Siemens NX. These plugins work both ways, allowing electronic and mechanical engineers to see how their respective designs mesh together. The siliconchip.com.au Screen 4: a STEP file representing the PCB can be exported for use in 3D modelling programs, in this case a populated Breadboard PSU PCB with all components present. You can also export the PCB without 3D components. plugins allow changes to be easily seen and acted upon. Even if you aren’t a user of one of the fully-featured MCAD programs Altium Designer supports, you can still do simple things like importing and exporting 3D models to see if they mechanically align with the PCB. With many parts suppliers now providing 3D models of their offerings, it’s easy to validate a design’s complete assembly without having to buy all the parts first. 3D printers are now commonplace, so this feature will simplify the checking of custom parts before they are even 3D printed. If you have a STEP file, checking it is as easy as using the Place → 3D Body menu selection. The object can be positioned and rotated to check its alignment with other parts. You can even change the colour or transparency to help visualise how the parts combine. Screen 3 shows our Pico Analyser PCB being aligned with a model of its Jiffy box in the Altium Designer 3D viewer. Conversely, you can export a 3D model of the PCB itself; this can include or exclude 3D component bodies, which would be much the same as Screen 2: an example of the PCB CoDesign interface from Altium. Australia's electronics magazine August 2024  65 the model being either a populated or unpopulated PCB. This can be handy if you want to design an enclosure around an existing PCB design or test a PCB’s fit into an enclosure. Screen 4 shows an exported STEP file placed into a 3D printing program, with all components included. We’ve even heard of people 3D-printing the shape of the PCB so that they can test its fit into an enclosure before the fabricated PCB arrives! Many electronics products rely on wiring harnesses as part of their construction, and now Altium Designer can be used to design and lay out wiring harnesses. Harnesses can also be incorporated into a multi-board design. We’ll discuss the Harness Designer feature of Altium Designer 24 later. Another emerging technology in the EDA field is 3D-MID, a 3D fabrication technique that blurs the line between PCB and enclosure. 3D-MID Our 2021 review also covered Altium Designer’s support for flexible and mixed (combining rigid and flexible) PCBs. Many PCB manufacturers (including those accessible to hobbyists) can now produce flexible PCBs, and they are clearly useful when space in an enclosure is tight or a rigid PCB is not feasible. Altium Designer 24 introduces support for 3D-MID (three-dimensional mechatronic integrated device) technology. At the time of writing, the 3D-MID feature is at the beta stage and must be specifically enabled as a beta feature. With a 3D-MID design, the substrate to which components are fitted is a 3D plastic part instead of a flat or flexible PCB. The part could be 3D printed (in the case of a prototype) or made by injection moulding for mass production. The traces are added directly to the part using a technique known as laser direct structuring (LDS). In LDS, the plastic contains additives that are activated by a laser, which scans over the part after it has been formed. The activated regions can then be selectively plated with a conductive trace material such as copper, nickel or gold. Solder paste is applied, and components are mounted to the traces using traditional solder reflow technology, supplemented by adhesives as needed. The substrate material is chosen to work with the required temperatures for reflow. Effectively, the enclosure or other mechanical part replaces or supplements the PCB. This sort of technology is already used to embed simple PCB-trace circuitry like antennas and touch sensors into devices like mobile phones. Still, we expect more complex applications will be developed. Altium Designer 24’s 3D-MID design process is not too different from that needed for standard 2D PCB designs. A circuit diagram is drawn, and component footprints and packages are selected, just as in a design intended for a PCB. But instead of a layer stackup, a 3D STEP or IGES file is imported and used as the substrate. Like a 2D design, the following steps are to place the components, connect them with traces and validate the layout with a design rules check, although we anticipate there will be new factors and design constraints to be considered. For example, the component’s orientation in 3D space must be considered as it definitely affects the placement step. We expect that simulation of the RF and emissions performance would Screen 5: 3D-MID is a new technology that allows customised 3D parts to be used in place of standard PCB substrates, including flexible and mixed substrates. Altium Designer’s 3D-MID tool allows a circuit to be translated into a 3D-MID design, which can be exported for use in the LDS process that creates conductive traces on the surface of a plastic part. Screen 6: the View Options tab of the View Configuration panel allows the 2D and 3D views of a PCB design to be customised. This makes it easier to visually check the design and see what it would look like with different solder mask and silkscreen printing colours. 66 Silicon Chip Australia's electronics magazine siliconchip.com.au need to happen during the design of the 3D part, and possibly again once the components and traces have been laid out. Once the layout is finalised, production files are produced. Instead of Gerber files, the output is a file that can be used by the LDS process. Screen 5 is a sample 3D-MID design from the Altium website. Support for features like vias appears to be limited at this stage. Still, we expect this concept will be a rapidly evolving aspect of EDA and look forward to a time when custom-­ metallised 3D parts are as cheap and accessible as PCBs are. Viewing options Even if you don’t have the means to undertake a 3D-MID design, there are some enhancements to the 3D PCB viewer that make it easier to understand how a standard PCB fits together in both 2D and 3D space. In the View Configuration panel (accessible from the Panels menu), the View Options tab has options to customise both 2D and 3D views. Various colour schemes can be chosen so you can see how your PCB looks with different silkscreen and solder mask colours. Screen 6 shows the View Options tab. You can tweak the transparency to see how the various layers align, seeing things that would typically not be visible in a regular 3D perspective. Similar options also apply to 2D views. Section View You can also use the Section View (View → Toggle Section View when in 3D mode) to look at cross-sections, achieving views that would not otherwise be visible. Screen 7 shows the PCB from our ESR Test Tweezers using Section View. The view can also be customised from the Section View tab of the View Configuration panel. The sectioning planes are changed by simply dragging the arrows in the viewport. Harness Designer Altium often presents webinars aimed at demonstrating new and upcoming features, including those available through the beta program. A webinar we saw during our review of Altium Designer 23 noted the then-upcoming Harness Designer siliconchip.com.au Screen 7: Section View allows further inspection of a PCB design by allowing sections to be ‘cut’ through a design. The View Configuration panel also offers a Section View tab for customising that view. feature. Wiring harnesses are another facet of EDA, and the Harness Designer allows harnesses to be created as a standalone project or as part of a multiboard assembly. Altium Designer 24 allows the creation of a harness design project as a PrjHar file. Just as a PCB project typically contains a schematic file (SchDoc) and a PCB file (PcbDoc), the harness project has a wiring diagram (WirDoc file) and a layout drawing (LdrDoc file), with roughly analogous roles to the schematic and PCB files. Altium Designer Draftsman can then create views, bills of materials (BoMs) and engineering drawings (HarDwf file) of a harness. Screen 8 shows these stages of a harness design project. Draftsman can create engineering drawings for PCBs, too, and we covered that feature in the June 2022 review of Altium Designer 22 (siliconchip.au/Article/15348). Draftsman drawings of PCBs can include elements such as tables, 2D and 3D views, layer stackups and bills of materials. If there is the need to revise the documents (such as PCB or harness layout) used to create the drawings, the Draftsman document can be updated by simply selecting Tools → Import Changes. Layout Replication We mentioned Reuse Blocks in the Altium Designer 23 Review. Reuse Australia's electronics magazine Blocks are circuit snippets, usually with circuit and PCB elements. The block encapsulates the component wiring and also the PCB trace layout. It’s ideal if you use a similar component block in multiple projects. Layout Replication is a similar concept. However, it is better suited to laying out repeated component blocks on the same PCB rather than maintaining a block for later use in another design. Thus, it is accessed from within the PCB editor. With many designs having some repeated elements, this feature is bound to take some of the tedium out of PCB layouts. Effectively, it allows you to transfer a layout from one group of components to another group of the same components. Importantly, Altium Designer looks for the same connectivity between the same components, so if you have copied and pasted part of a circuit diagram, layout replication is likely to be helpful in duplicating the layout of those parts between the copies. You can choose how much of the layout (such as internal and external routing) is copied. Naturally, you can tweak the layout afterwards if identical layouts are not appropriate due to space or other design constraints. A block can also duplicate the layout of items like component designators. Screen 9 shows the PCB Layout Replication dialog box, opened from the August 2024  67 Tools menu. We used it to place and route the components shown at upper right, so they matched those at upper left. We just had to select Target Block 1 and press the Replicate button! We found it very easy to use and it saved a lot of time. It can even process multiple target groups at the same time, and the results are consistent and tidy. This is a feature we will undoubtedly use in laying out future designs. series of videos, each focusing on a specific aspect of using Altium Designer. The videos can also be found on the Altium Academy YouTube channel at www.youtube.com/<at> AltiumAcademy The Certificates section opens a web page explaining Altium’s paid training courses. Even if you aren’t an Altium subscriber, you can access much of the free content from https:// my.altium.com/ Education Product access The Home page of the Altium Designer program presents various educational and learning opportunities, as shown in Screen 10. It’s clear that Altium wants its users to be able to make the best use of the program’s features. The Design Secrets category is a While researching this article, we noticed that much of the online documentation states that some features are only available at certain product access levels. It may be the case that certain features that we’ve described will not be available to all users. As we mentioned earlier, this will depend on your beta settings, product access level and installed version. Access to beta features is controlled from within the Advanced Settings window of System Preferences. Free stuff Some Altium content can be accessed online for free. Videos like those from the Altium Academy mentioned earlier can be seen on YouTube. Altium 365 also has a free online file viewer at www.altium.com/viewer There is even the option of a free trial of the Altium Designer software. You can find out more about that at www.altium.com/altium-designer/ free-trial If you’re a hobbyist, Altium’s CircuitMaker software (https://­circuitmaker. com) can be used at no cost. We reviewed it in the January 2019 issue (siliconchip.au/Article/11378). CircuitMaker has a similar feel to Altium Designer and allows designs to be easily shared with others. You can see projects that other people have created at https://circuitmaker. com/Projects Summary Screen 8: this shows the order of the different stages of a Harness Design in Altium Designer, from top to bottom. The top shows the wiring diagram to which you can connect wires, connectors and splices. The second document shows the layout drawing, while the final products are the engineering drawings that can be created by Draftsman for production. 68 Silicon Chip Australia's electronics magazine Altium continues to add useful features to the Altium Designer software and provides great support to educate current and potential users. Many of the new features target advanced users who create multilayer PCB designs with high-speed requirements and advanced constraints. That’s often very different to our own PCBs, which are nearly always straightforward two-layer affairs. But we always find something useful to us in new Altium Designer releases. Layout Replication is a tool we are sure we will use in the future. The numerous 3D import and export options, tools and viewers are very handy for checking, visualising and validating a design as it develops. The concept of 3D-MID is fascinating, and we imagine it will find many novel and interesting applications. The availability of cheap, custom PCB designs has made electronics very accessible, and we look forward to a time when 3D-MID technology is available to the likes of hobbyists as well. Visit www.altium.com/altium-­ designer for more information on Altium Designer 24. SC siliconchip.com.au Screen 9: we found Layout Replication a handy tool for laying out and routing repeated groups of components. It is easy to use, and multiple target blocks can be processed with different options. It’s now easy to produce neat PCB layouts with repeated elements. Screen 10: Altium Designer’s Home tab provides links to numerous educational videos and webinars. Even if you don’t have an Altium license or subscription, much of the material is freely available online. siliconchip.com.au Australia's electronics magazine August 2024  69 Beer Can Filler A ny brewer will attest that the tedious process of bottling or canning the product can quickly erode the joy of producing your own beer. Commercial canning machines are available, but even simple entry-level units can go for thousands of dollars, and fully automated machines cost hundreds of thousands. By contrast, this DIY version can be built for a few hundred dollars using commonly available parts from your local hardware store and some online electronics suppliers. It has proven a reliable design for a craft brewery in Melbourne’s south-east, where it has successfully filled some 50,000 cans over the last few years. It even recently came to the rescue of another craft brewery that faced spoiling an entire brew when their newly-­ ordered commercial unit didn’t work! Overview This semi-automatic can filler is a valuable tool for any home brewer. It can be built in an afternoon for a fraction of the cost of a commercial offering! 70 The key to reliable and repeatable beer storage is to ensure there is no oxygen inside the package when it is sealed up. This canner works by displacing the oxygen using an inert gas, typically carbon dioxide, which the yeast in beer also produces naturally. Most food-grade CO2 sold is the excess produced by breweries. The fill process is thus: 1. Gas purge (around five seconds) 2. Pause (100ms) 3. Beer fill (around 20 seconds) 4. Pause (100ms) 5. Final Gas Purge (one second) This is also shown in the state machine diagram, Fig.1. Each state has adjustable timers so that the machine can be tuned for process variations due to ambient temperature, gas pressure, beer viscosity etc. Two connections need to be made to the machine, one to the carbon dioxide bottle and the other to the beer keg. This design fills two cans at a time, so each connection splits off at a tee and runs to its own solenoid. We therefore need to control four solenoids: left gas, right gas, left beer and right beer. The solenoids feed a pipe downstream that extends partway into the can to administer the gas or beer, as shown in the photos. Circuit description Project by Brandon Speedie The brains of the operation is a “smart relay”, which is essentially a simple, low-cost PLC (programmable logic controller). It is well-suited Australia's electronics magazine siliconchip.com.au Silicon Chip Fig.1: the operation of the Beer Can Filler is straightforward, as shown in this flowchart/state machine diagram. It is implemented using a basic form of programmable logic controller (PLC), a microcontrollerbased module used widely for industrial applications. to this application given its rugged industrial build quality, a decent array of inputs and outputs, and an LCD screen. The relay outputs control the solenoids simply by switching the 24V DC power supply. Freewheeling diodes such as 1N4004s can be used to protect against inductive voltage spikes, although the relays are pretty beefy, being rated at 265V AC/30V DC and 8A, so I didn’t bother. The six digital inputs are wired to 22mm pushbuttons and switches for user input. Digital Inputs 1, 2 and 3 are start buttons to begin a fill cycle. siliconchip.com.au Photo 1: the back of the Beer Can Filler, showing how the flexible tubes enter the rear of the bulkhead fittings that lead to the pouring spouts. You can see the four solenoids, plus the optional gas pressure regulator. DI1 will fill the left can only, DI3 the right can, while DI2 will fill both cans. DI2 is also wired to a footswitch in our application, as the operator usually has their hands full with cans. DI4 cycles through different timer settings on the LCD. DI5 and DI6 are used to adjust those timers up or down, respectively. Power is derived from a mains switch-mode power supply rated at 24V DC 1.5A. Software The smart relay is programmed in “ladder logic”, a graphical language Australia's electronics magazine widely used in industrial automation. Inputs and outputs are linked to form “rungs”, like in an electrical drawing. Given its similarity to a schematic, it is a popular language among practically-­ minded people and a great way to get into programming if text-based languages put you off. The “code” is read from left to right. Output elements called “coils” are placed on the right side of a rung. The coil will be energised if a connection is established from the left side (a binary “1”). Input elements called “contacts” can be placed in line with the rung to build up program logic. Series contacts August 2024  71 Screen 1: the “Idle” state ladder logic. Contacts M01 & M11 are closed on program startup. Should the user press a start button, contact N01 (left fill), N03 (right fill), or N02 (both fill) closes, which latches M01/ M11 off and M02/M12 on. This transitions the code to the next state. Rungs 17-22 are the “Purge” state code. Contacts M02/M12 are closed when transitioning from the Idle mode, enabling Timer 01. When the timer elapses (after five seconds, user configurable), contact T01 will close, which latches M02/M12 off and M03/M13 on, transitioning to the next mode. Screen 2: the gas and beer solenoid outputs. When in either purge mode (M02/M06 & M12/ M16), relay outputs Q1 & Q2 are closed, energising the solenoids and begins the flow of gas. When in beer fill mode (M04 & M14), the same occurs for Q03 & Q04. Screen 3: these rungs allow the timer periods to be adjusted via the buttons connected to inputs I5 & I6 (N5 & N6). T05 is used so that if you hold down one of the buttons, the timer continuously increments or decrements. The “rung” numbers are referring to the software. 72 Silicon Chip Australia's electronics magazine are a Boolean AND operation, while parallel contacts are Boolean OR. When the program starts, contacts M01 and M11 are latched on. This is the idle state, waiting for user input to start the sequence. In the program, the digital inputs are represented as I01 through I06. If the user presses the left start button, contact I01 is closed, turning on coil N01 (rung 5). M01 and N01 would then both be closed, which latches M01 off and M02 on (rungs 12 & 13), beginning the fill cycle – see Screen 1. M02 is the purge mode, turning on relay 1 (Q01 in the program) to begin the flow of carbon dioxide (rung 65). While in purge mode, timer T01 begins counting (rung 17). Once the timer has elapsed, purging is complete. Contact T01 will close, which latches M02 off and M03 on. M03 is the pause mode, which turns off the purge solenoid and waits for timer T02 to elapse before latching M04 and unlatching M03 to move to the fill mode (rungs 26-27). M04 turns on the beer-fill solenoid Q3 (rung 69). Beer will begin to flow from the keg into the can until timer T03 has elapsed, which latches M04 off and M05 on to transition to the second pause mode (rungs 32 & 33). M05 is the second pause mode, waiting for timer T06 to elapse before latching M05 off and M06 on (rungs 38-40). M06 is the final gas purge mode. Gas solenoid Q01 is activated to provide the final short blast of carbon dioxide before the package is sealed (rung 66 on Screen 2). When timer T07 elapses, M06 latches off, and M01 latches on, at which point the program returns to idle mode and waits for the user to trigger the next can. A similar process operates on the right side using timers and contacts M11/12/13/14/15/16 and T11/12/13/14 etc. Minor differences will exist between the flow rates into each can, so different fill times can be applied to the left and right sides. The timers can be adjusted using I05 and I06 (digital inputs 5 and 6), which increment or decrement counters C02, C03, C04, C05 and C06 for purge time, left fill time, right fill time, left post purge, and right post purge, respectively (rungs 97-101) – see Screen 3. Acceleration is provided via timers T04 and T05 (rungs 104-106) so that the time will automatically increment or decrement if the button is siliconchip.com.au Fig.2: the platform and support structure for the Beer Can Filler were made from 19mm-thick plastic, although the home brewer could also use timber (like MDF or plywood). The angle bracket is for the beer cans to rest on; the holes above that are for the spouts. held down. These counters/timers are saved to non-volatile memory, so settings will be preserved between power downs. The LCD screen will cycle through individual pages for purge, break, fill and post-purge as the sequence is executed. Timers are displayed to give user feedback. When in idle mode, the timers can be adjusted for purge, left fill, right fill, left post purge, and right post purge by cycling through the setting page using DI4 (rung 72). I have saved the whole program in a file called “Can_FillerV2.gen”, which is available for download from the Silicon Chip website (siliconchip.au/ Shop/6/414). You can upload that to the PLC using the programming cable specified in the parts list. Mechanical construction Begin by cutting out the plastic sheet siliconchip.com.au per the dimensions in Fig.2. We used food-grade HDPE, as this device is used in a commercial setting, but the home brewer could substitute a plastic cutting board or timber. Glue and screw the joints together using the drill pattern. The aluminium angle piece can be fastened in the same fashion. Drill 13mm (or ½in) holes for the pouring spouts on the front fascia. This design has separate pipes for the gas and beer. They were originally combined using a tee piece to give a single manifold to extend into the can, but the pour is marginally smoother with separate manifolds. Still, a single pipe is less cumbersome for the operator. See Figs.3 & 4 for the two hydraulic circuits, depending on whether you use single- or double-outlet pipes. Begin assembling the pipework by fitting the pouring spouts through the Australia's electronics magazine Photo 2: the LCD screen shows the current state of the process, including the duration of any timer that is currently in use. August 2024  73 Fig.3: I built the unit shown here with separate outlets for CO2 gas and beer, as I found it gave smoother pouring. However, it is a bit more fiddly to use and requires extra pipes. Fig.4: alternatively, use tee pieces to combine the beer and gas pipes into single outlets. That means you only have to insert one pipe into each can but I feel that it doesn’t do quite as good a job. drilled holes using the bulkhead connectors. The pipe extends through the solenoids and back to the main fitting: a keg attachment for the beer & gas fitting for the CO2. This design also includes a local gas regulator, which gives more consistent results as the canister runs down, but isn’t strictly necessary. The enclosure to house the electronics needs 22mm holes drilled for the buttons and switches, as shown in Fig.5. Also drill holes on the side of the enclosure to fit the cable glands. These are the penetrations for the wiring, so they can be positioned wherever is convenient. This design has two on the bottom of the enclosure and one on the side. Now would also be a good time to drill a small hole in the side to mount a DC input socket and fasten it into that hole. Drill 3mm holes in the centre of the baseplate and thread 3mm fasteners and washer through to secure the length of DIN rail. The smart relay and screw terminals can now be clipped onto the DIN rail. Mount the selector switch and buttons to the front fascia by threading through the 22mm holes, tightening the plastic nut and clipping the carrier on the back. The enclosure can be secured to the top of the assembly using glue or some screws. Electrical wiring Fig.5: these five 22mm holes in the electronics enclosure lid are for the controls: four momentary pushbuttons and one three-position selector switch. Holes are also required on the side for cable glands to pass the wiring through; refer to the vendor for the appropriate size and our photos for their approximate locations. All dimensions are in millimetres. The schematic/circuit diagram, Fig.6, shows the required wiring. Colour-code the wires red for +24V, black for GND and white (or other colours) for signals. Any cables with a single termination should be crimped with 0.75mm ferrules, while double joins should be made with a double ferrule. This isn’t strictly necessary but does make for a neater job. Begin by running a red wire from +24V on the power supply input connector to each selector switch. Double ferrules can be used to jump between each switch. These switches wire to the ‘normally open’ contacts on each selector, which is the terminal pair closest to the switch itself. A multimeter can be used to buzz out which contacts are normally open and which are normally closed if you are unsure. White cable can then be used to hook up each switch to its corresponding digital input on the smart relay. DI1, DI2 & DI3 go to the three green buttons at the bottom, while DI4 is for the top button. DI5 and DI6 are for the Australia's electronics magazine siliconchip.com.au 74 Silicon Chip Fig.6: connect the switches, solenoids and power supply as per this diagram. The Remote HMI is optional and not described here, as you don’t need it. The foot switch is also optional. Use the DIN rail terminals where you have to join multiple wires together, eg, for the common +24V & 0V connections. Photos 3 & 4: while my unit has an internal power supply, you should build it with an external DC supply to ensure live mains wires cannot coming in contact with anything else; that would be a major hazard. This can be done by drilling a small hole in the side to mount a DC input socket and fasten it into that hole. selector switch, which has two connections (up and down). If a footswitch is to be used, it can be wired in parallel with the middle button (digital input DI2). The baseplate can now be placed siliconchip.com.au into the enclosure, but it is best not to screw it in with the supplied self-­ tappers until all the wiring is complete. Continue with the red cable by connecting from +24V to one side of each Australia's electronics magazine relay output. The other side of each relay runs to each of the four solenoids: Q1 for left gas, Q2 for right gas, Q3 for left beer and Q4 for right beer. Complete the solenoid connections by running a black GND wire to each. August 2024  75 Photo 5: make the wiring to the front panel switches long enough that you can swing it out like this. These industrial switches are waterproof and making connections to them is easy thanks to the screw terminals. Photo 6: a closeup of the pipework on the rear of the unit. The solenoids I used for beer (below) are larger than the ones for gas (above) but you can use four of the same type. Just make sure the beer valves have orifices at least 4mm in diameter to avoid the beer fizzing up as it passes through. 76 Silicon Chip Australia's electronics magazine The DIN rail screw terminals can be fitted with internal jumpers and used as a busbar for multiple GND connections, including for the DC input socket. Programming and testing Plug in the power supply and switch it on. You should see the LCD on the smart relay glow green and boot up into a menu. Download the smart relay software (SG2 Client) from https://oceancontrols. com.au/TEC-005.html, install it and run it. Download the source code (from siliconchip.au/Shop/6/414), unzip it and open it using the software. Plug the programming cable into your computer via the USB to RS-232 adaptor. Give Windows a few minutes to install drivers, at which point the programming cable will appear as a virtual serial port. You can check progress using Windows Device Manager, which will display the serial port as a COM port under Ports (COM & LPT). The other end of the programming cable can now be plugged into the smart relay. A small cover below the keypad obscures the programming port, but it can be removed with a flatblade screwdriver. This will expose a four-way header, which accepts the other end of the programming cable. Back in the software, a connection to the smart relay can be established via Operation → Link Com Port. Enter the COM port name as shown in Device Manager. You should get a “link successful” dialog box after pressing OK. The source code can now be uploaded to the smart relay using the “write” button on the toolbar. Once the progress bar is complete, the smart relay should be ready. Briefly power cycle the relay after programming to place it into run mode, or that can be manually selected using the keypad buttons and LCD. Once the program is running, you will see a screen similar to Photo 2 on your LCD. You can now test the sequence by pressing one of the run buttons (DI1 for left, DI2 for both or DI3 for right). The solenoids should click on in sequence. The run timers can be adjusted by cycling through the menu using the top button and changing parameters using the selector switch. Finish the build by removing the programming cable and securing the lid to the enclosure using the provided fasteners. Happy brewing! SC siliconchip.com.au Parts List – Beer Can Filler 1 TECO SG2-12HR-D programmable logic relay [Ocean Controls TEC-005] 1 TECO SG2 series PL01 programming cable [Ocean Controls TEC-200] 1 TECO OP10N 4.3in 192 × 64 pixel graphic panel (optional) [Ocean Controls TEI-001] 3 green momentary pushbuttons [Ocean Controls HNR-200G] 1 white momentary pushbutton [Ocean Controls HNR-200W] 1 3-position momentary selector switch [Ocean Controls HNR-232] 1 24V DC 1.5A+ external power supply [Altronics M9393B] 1 175 × 35 × 7.5mm top hat DIN rail strip [Altronics HA8572] 5 25A 2.5mm DIN rail screw terminals [Altronics P2400] 1 shorting link for 25A 2.5mm DIN rail terminals [Altronics P2460] 1 220 × 160 × 80mm IP65 sealed ABS enclosure [Altronics H0333] 1 aluminium baseplate to suit Altronics H0333 [Altronics HA0312A] 1 USB to RS-232 converter [Altronics D2340B] 1 chassis mount DC barrel socket (to suit power supply) [Altronics P0622] Cable & hardware 1 370 × 300 × 19mm plastic or timber sheet (for example Delrin, HDPE, MDF, plywood) 1 320 × 300 × 19mm plastic or timber sheet (for example Delrin, HDPE, MDF, plywood) 1 300 × 100 × 19mm plastic or timber sheet (for example Delrin, HDPE, MDF, plywood) 1 300mm length of 50 × 50 × 1.6mm aluminium angle 25 M3 × 10mm panhead machine screws, nuts and flat washers 3 cable glands to suit 5-10mm cable [Altronics H4315A] 1 7.5A mains cable terminated with bare wires (not required if using an external 24V supply) [Altronics P8400C] 1 5m length of red heavy-duty hookup wire [Altronics W2270] 1 5m length of white heavy-duty hookup wire [Altronics W2271] 1 5m length of black heavy-duty hookup wire [Altronics W2272] 1 pack of 0.75mm single ferrule terminals (optional) [Altronics H2425B] 1 pack of 0.75mm double ferrule terminals (optional) [Altronics H2488B] 1 ferrule crimp tool (optional) [Altronics T1547A] Gas/liquid handling 1 beer keg 1 keg coupler [KegLand KL06903] 1 carbon dioxide (CO2) tank 1 gas fitting to suit the CO2 tank 1 adjustable gas pressure regulator (optional) [KegLand KL15035] ◾ 1 12m length of food-grade 8mm OD flexible gas-tight tubing [KegLand KL06224] 4 24V DC normally-closed solenoid valves, 2 × ½in BSP male threads 🔷 [AliExpress 1005005244510404] 8 ½-inch female BSP to 8mm push-fit adaptors [KegLand KL18753] 1 8mm diameter, 200mm long & 1mm thick stainless steel tube (304 grade) 2 8mm push-fit tees [KegLand KL02387] 4-5 8mm push-fit elbows [KegLand KL02400] 🔴 4 8mm push-fit bulkhead fittings [KegLand KL21036] 1 small roll of gas-tight (blue) Teflon tape AliExpress 32926145983 is a cheaper alternative, but you will also need one ¼in male BSP to 8mm push-fit adaptor plus one ¼in female BSP to 8mm push-fit adaptor these are not food grade but we think they are suitable for home use if cleaned. We used (much more expensive) food-grade alternatives in our unit; see www.valvesonline.com.au/stainless-steel-general-purposedirect-acting-norm (4-inch male BSP adaptors are required instead of ½-inch female) one extra elbow can result in neater hose routing but is not strictly required Silicon Chip PDFs on USB ¯ A treasure trove of Silicon Chip magazines on a 32GB custom-made USB. ¯ Each USB is filled with a set of issues as PDFs – fully searchable and with a separate index – you just need a PDF viewer. ¯ Ordering the USB also provides you with download access for the relevant PDFs, once your order has been processed ¯ 10% off your order (not including postage cost) if you are currently subscribed to the magazine. ¯ Receive an extra discount If you already own digital copies of the magazine (in the block you are ordering). EACH BLOCK OF ISSUES COSTS $100 NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 ◾ JANUARY 2000 – DECEMBER 2004 🔷 JANUARY 2010 – DECEMBER 2014 🔴 siliconchip.com.au Australia's electronics magazine JANUARY 2005 – DECEMBER 2009 JANUARY 2015 – DECEMBER 2019 OR PAY $500 FOR ALL SIX (+ POST) WWW.SILICONCHIP.COM. AU/SHOP/DIGITAL_PDFS August 2024  77 180-230V DC Moto Controls 180-230V DC motors rated from 1A to 10A (¼HP to 2.5HP) Controlled by four common op amp ICs with one opto-coupler and three linear regulators Zero to full speed control Safe startup procedure Emergency cut-out switch facility Automatic over-current switch-off Optional reversing switch capability PWM, Live and Power indicator LEDs Rugged diecast aluminium enclosure Current and back-EMF monitoring for speed regulation under load Initial setup adjustments can be done with a low-voltage supply M otors rated at between 180V and 230V DC are supported; they are driven by PWM-chopped rectified mains. Motor load/speed feedback is via current and back-EMF monitoring. The circuit is based on analog techniques and is designed to be robust and easily adjustable. Most of the active devices are common types of operational amplifiers (op amps). The motor speed is controlled by a rugged IGBT (insulated gate bipolar transistor). Most parts are throughhole types except for a few resistors and the opto-isolated IGBT driver. It all fits in a convenient diecast aluminium case. Having already described the overall design and how the circuit works in the first article published last month, let’s move on to building it. Construction Most of the parts are mounted on a double-sided, plated-through PCB coded 11104241 that measures Warning: Mains Voltage This Speed Controller operates directly from the 230V AC mains supply; contact with any live component is potentially lethal. Do not build it unless you are experienced working with mains voltages. 78 Silicon Chip 201×134mm, which fits in a 222 × 146 × 55mm diecast aluminium enclosure. The only off-board parts are the GPO socket for the motor, the speed potentiometer and the IEC mains input socket. Some of the PCB tracks connecting to Q1, BR1 and CON1 on both sides of the PCB are tin-plated so they can handle more current. Before installing any parts, they should be covered with a layer of solder to thicken the tracks and further reduce their resistance (shown in red in Figs.3 & 4). However, be careful to avoid getting solder in the component through-holes when doing so. Fig.3 shows the layout of the topside parts on the PCB, which you can use as a guide during assembly. Begin by fitting the surface-mounting opto-coupled Mosfet driver (IC5). You will need a soldering iron with a fine or medium tip, a magnifier and good lighting. It’s also a good idea to have a syringe of flux paste and some solder-­ wicking braid on hand. Solder IC5 to the PCB pads by first placing it with its pin 1 locating dot to the top left and the IC leads aligned with the pads. Solder a corner pin and check that the IC is still aligned correctly. Soldering the small leads will be easier if you apply a small amount of flux paste on top first. If it needs to be realigned, remelt the solder and gently nudge the IC into Australia's electronics magazine alignment. When correct, solder all the IC pins. Any solder that runs between and bridges them can be removed with solder wick. Following that, mount diodes D2-D10 and zener diodes ZD1-ZD3. Ensure each is orientated correctly and that the correct diode or zener diode is installed in each location before soldering their leads. Diodes D2 and D6-D8 are 1N4004 types, while the remainder (except for the zeners) are 1N4148 types. ZD3 has a different voltage rating from ZD1 and ZD2, so don’t get them mixed up. TVS1 can also be installed now; it is bi-directional, so it can go in either way around. Follow by soldering the SMD resistors in place. These mount on the underside of the PCB, as shown in Fig.4. They are the 10kW resistor under IC5 and the four 0.022W resistors under inductor L1. If you are building the speed controller for a motor rated at 5A or less, see Table 1 for the required number and value of these shunt resistors. Otherwise, fit all four. Install these by soldering one end first, then the other after you’ve checked that the part is aligned correctly and the first solder joint has solidified. The low-wattage (½W) throughhole axial resistors can be fitted now. siliconchip.com.au or Speed Controller Our new High-voltage DC Motor Speed Controller, revealed last month, can control motors commonly used in lathes and treadmills. It can operate such a motor from stopped up to full speed and maintains a constant speed even with a varying load. This article covers the assembly, testing and setup of the Speed Controller. They have colour-coded bands and the codes were shown in the parts list last month. However, you should also use a digital multimeter to check each resistor before soldering it, as the colour bands can be difficult to distinguish (especially brown, red and orange). The remaining ICs can now be installed, taking care to get the correct one in each place and with pin 1 in the proper location (double check that!). Sockets can be used for each of the ICs, although they can also be soldered directly to the PCB, which is likely to give better long-term reliability. The 1W and 5W resistors can be mounted next. When fitting the 5W resistors, leave a gap of around 1mm between the body and the PCB to allow air to circulate. Regulators REG1-REG3 mount horizontally with their leads bent by 90° to fit into the allocated holes in the PCB. Each Part 2 by John Clarke regulator is secured to the board using a 6mm-long M3 screw and nut before the leads are soldered. Make sure you don’t mix up the three different regulator types. Diode D1 is mounted horizontally with its leads bent by 90° so you can insert them into the PCB holes. Secure it with an M3 screw, washer and nut before soldering. The capacitors can now be installed. There are four types used. The 630V-rated 47nF capacitors operate at rectified mains voltage, so make sure the correct types are used in the upperleft corner of the PCB. The other types are ceramic, MKT polyester and electrolytic. The 100nF and 1μF ceramic capacitors are placed near IC5. The electrolytic capacitors need to be orientated correctly since they are polarised. The longer lead indicates the positive side, while the negative stripe down one side of the capacitor indicates the negative side. One 100μF (just above IC3) and 10uF capacitor (above D4) is rated at 25V, so ensure it is located correctly, or it will be damaged when power is applied. For the MKT and ceramic capacitors, the 10nF capacitor is likely to be marked 103, the 100nF capacitors marked 104, the 220nF capacitor marked 224, and the 1μF capacitor marked 105. Solder in the three PCB-mounting spade connectors (CON5-CON7), then bridge rectifiers BR1 and BR2, ensuring correct orientation. BR1’s positive lead is spaced further from the others, so it will only fit in one way. Mount it so there is about 1mm of lead length below the PCB for soldering. For BR2, the longer lead is positive. The AC and + terminals will also be marked on the package. LED1-LED5 can be fitted now. Be sure they are correctly orientated with the longer lead placed into the anode (A) hole in each case. The power LED, Table 1 – shunt resistor values depending on motor rating HP ¼ ½ ¾ 1 1¼ 1½ 1¾ 2 2¼ 2½ kW 0.18 0.36 0.54 0.72 0.9 1.08 1.26 1.44 1.62 1.8 A 1 2 3 4 5 6 7 8 9 10 2S* 3 3 3 4 4 4 4 4 913W 764W 645W 0.022W W shunts 2S* VR2 value (R1) 4.95kW 2.25kW 1.95kW 1.36kW 1.47kW 1.36kW 1.1kW IC1b gain 12.5 siliconchip.com.au 6.25 5.55 4.16 3.33 4.16 3.57 Australia's electronics magazine 3.125 2.77 2.5 * S = in series. Alternatively, you can use two 0.05W resistors in series and set R1 to 1.93kW (¼HP) for a gain of 5.5 or 752W (½HP) for a gain of 2.75 August 2024  79 Fig.3: most components mount on the top side of the PCB. T1 and L1 are heavy, so both are secured to the PCB using cable ties. The large relay, RLY3, is attached to the board using screws and nuts, and will later be wired to CON1 and CON3. This diagram and Fig.4 are both shown at 90% of actual size. The red areas are where extra solder is added. LED2, is green while the remainder are red. LED1 and LED3 can be mounted vertically with 5mm of the leads projecting above the top PCB surface. LED2, LED4 and LED5 display the Power, Reset and Run status on the front lid via fibre-optic light transporters. Before soldering each LED, clip the LED bezel end piece for the fibre optic connection onto the LED, then solder it in place with the clip touching the PCB surface. CON1 to CON3 can be fitted now. CON1 can be installed either way around, but CON2 and CON3 must be orientated correctly. That is most easily done by plugging the screw terminal plug into each socket before mounting it to the PCB. For the 3-way terminal, CON2, the wire entry faces toward diode D5. For the 2-way terminal, CON3, the wire entry faces away from diodes D7 and D3. The next step is to install the relays. RLY1 and RLY2 directly mount onto the PCB, while RLY3 is held to it using M3 screws, washers and nuts, with 80 Silicon Chip each screw inserted from the underside of the PCB. The washers go under the nuts on top of the relay’s mounting feet. T1 can now be mounted onto the PCB. Its pins hold it in place, but we use a large cable tie to ensure it cannot move and break the transformer pins if it is dropped. There are slots in the PCB to accommodate the cable tie, to wrap around the transformer body and under the PCB after soldering it in place. Winding inductor L1 L1 is made using two powdered iron cores side-by-side. Use epoxy resin to glue the two cores together. Once the glue has set, wind on seven turns of 1.25mm-diameter enamelled copper wire. The winding direction is not important. The finished winding and core are mounted on the PCB with a cable tie securing the toroid to the PCB. This tie is fed through the slots in the PCB to wrap around through the centre hole of the core and under the PCB. Australia's electronics magazine Trim the wires to sufficient lengths to solder to the PCB pads, then strip the insulation off the ends of the enamelled wire. It’s generally best to do that with a sharp hobby knife (be careful not to cut your fingers!) or emery paper. Depending on the enamel used, you may be able to burn it off by holding a blob of molten solder over the wire ends. Make sure the enamel is entirely removed so you can make a good solder joint, then solder the wire ends to the pads for L1. Q1 can be installed now. Stand it above the PCB so there is about 1mm of lead projecting below the PCB to allow soldering. Because the PCB tracks near the IGBT are thin, the exposed, tinned PCB tracks at the emitter and collector should be built up with solder to lower the resistance. Final assembly The PCB is secured inside the enclosure base using M3.5 screws into the integral standoffs in the base. However, before attaching the PCB, the IEC siliconchip.com.au Fig.4: if all four 0.022W shunt resistors are soldered to the board, as shown here, the Controller will suit motors rated at 6-10A (1.5HP+, 1.08kW+). For lower-powered motors, fewer resistors are fitted, as per Table 1. For ¼HP and ½HP motors, make sure the two resistors are in series, not parallel. If three resistors are required, any three can be fitted. connector cutout will need to be made in the side of the enclosure. You will need to drill and shape holes in one end of the case for the IEC connector and Earthing screw. You might as well prepare the lid at the same time, which needs holes made for the GPO socket, Earthing screw and speed control potentiometer. Fig.5 is a guide for the required cutouts; it can be copied or downloaded and used as a template. The large cutouts for the mains GPO and IEC connector can be made by drilling a series of small holes around the inside perimeter, then knocking out the centre piece and filing the job to a smooth finish. Alternatively, you can use a speed bore drill to remove a large portion of the required area and then file it to the final shape. The Earth screw positions are not critical. Use the wiring diagram (Fig.6) to decide where to place the holes. One 4mm hole is required on the lid, and one in the enclosure base. Two 3mm holes are needed to secure the IGBT (Q1) and BR1 against the side of the siliconchip.com.au The underside of the Motor Speed Controller’s PCB. There are five components that are soldered to this side, the four 0.022W shunts (shown in the left insert) and the 10kW resistor (shown at right). The extra through-hole resistor shown at the bottom of the PCB was only for our prototype, and is fitted on the topside with the final PCB. Australia's electronics magazine August 2024  81 Fig.5: the required holes in the lid and base of the diecast aluminium case. Ensure the IEC and GPO socket holes are shaped correctly (filed carefully to size) so they are not loose. The exact Earth screw positions are not critical, so they are not marked. enclosure. Temporarily place the PCB into the enclosure and mark where the holes for Q1 and BR1 are needed. The holes for Q1 and BR1 need to be slightly countersunk on the inside of the enclosure to provide a flat mounting surface. There must not be any sharp edges around the hole or any remaining swarf that could puncture the silicone insulating washer. 3.5mm diameter holes are needed for the fibre-optic LED bezels on the front panel. These are not directly above the LED position on the PCB to give the fibre optic cables room to flex in an ‘S’ shape when the lid is attached. Once the drilling and filing is complete, install the IEC connector using countersunk head 10mm-long M3 machine screws and nuts. The PCB can then be placed inside the case but wait to secure it to the corner posts. Q1 needs to be insulated from the enclosure using a TO-247-sized silicone insulating washer. Its package has an insulated hole, so no insulating bush is required to insulate the package from the screw. A 12mm-long M3 screw and M3 nut can be used to secure Q1 to the side of the enclosure. Check that the enclosure is insulated from all three of Q1’s leads by measuring the resistance between each lead and the enclosure. There should be high resistance reading in each case, in the megohms region. BR1 does not require an insulating washer since the metal tab on the back of the package is insulated from the internal diodes. Before attaching the mains GPO, you can print out the front panel label (Fig.7), available to download from our website at siliconchip.au/ Shop/11/436 Details on making a front panel are found at: siliconchip.au/ Help/FrontPanels Now wire everything up per Fig.6. All wiring must be run using mainsrated cable. Be sure to use 10A cable where indicated, and note that brown wire is used for the Active wiring and blue for Neutral. Green/yellow-striped wire must be used for the Earth wiring only, and the Earth lead from the IEC connector is attached via a crimp eyelet to the enclosure Earth. The wiring not marked as 10A can be lighter-duty 7.5A mains wire, such as for the speed potentiometer VR1, or use 10A wiring throughout. The IEC socket and Earth screw are on the lefthand side of the case. 82 Silicon Chip Australia's electronics magazine The terminals on relay RLY3 will be too tall for the lid to fit, so they need to be cut down, with the wires soldered directly to the shortened terminals and covered in heatshrink insulation. These terminals are brittle, so hold the lower part of the terminal with small flat-nosed pliers while you break off the top part with another set of pliers. The terminals will break at the wire hole location. Be sure to insulate all the connections with heatshrink tubing for safety, and cable tie the wires to prevent any wire breakages coming adrift, as shown in Fig.6. The Active and Neutral leads are secured to the GPO using cable ties that pass through the holes in its moulding. Use neutral-cure silicone sealant (eg, Roof and Gutter silicone) to cover the Active bus piece that connects the Active pin to the fuse at the rear of the IEC connector. Take great care when making the connections to the mains socket (GPO). In particular, be sure to run the leads to their correct terminals; the GPO has the A, N and E clearly labelled. Do the screws up tightly so that the leads are held securely. Similarly, make sure that the leads to CON1’s screw terminals are firmly secured. Warnings Almost all of the circuitry operates at mains potential, so it is dangerous to make contact with any part of the circuit when it is powered. The speed potentiometer connections are also at mains potential. siliconchip.com.au Fig.6: all wires must be mains-rated; the wires marked with an * need to handle 10A, while the others can be rated at 10A or 7.5A. Some adjustments can be made more safely by disconnecting the mains supply from some parts of the circuit. This leaves the circuit floating at mains Neutral potential instead of Active. You still need to be very careful, but the risk of electrocution should you touch the circuitry is much lower. Some adjustments will need to be made when the circuit is live. We recommend using a 1000V-rated screwdriver with a 0.4mm-thick, 2.5mm-wide flat tip. That size of screwdriver suits the trimpot adjustment screws and has a sufficient voltage rating to protect against electrical shocks. We used a Wiha 1000V screwdriver that has an insulated shank. Similarly, when measuring voltages in the circuit, use a 600V CAT III (or higher, eg, CAT IV) rated multimeter and probes. We provide indicator LEDs that show when the circuit is powered and live. So don’t touch the circuit when any LED is lit, and always unplug it siliconchip.com.au from the mains before working on it (except during the part of the setup where it needs to be operating). Another LED shows the PWM duty cycle by varying brightness with PWM duty. A separate LED shows when the speed potentiometer is rotated fully anti-clockwise. Finally, there is one LED that shows when the motor can be started. Testing Ensure that the mains power point you connect to when testing and adjusting the 180V DC Motor Controller is connected to an Earth-­leakage core balanced relay, also known as a Residual Current Device (RCD) or mains safety switch. This can be installed in the fusebox, as a separate unit within the power point or as a plug-in device. The RCD is designed to cut the power should you receive an electric shock that passes through your body to Earth. However, an RCD will not Australia's electronics magazine Errata: in Fig.2 last month, the labels for REG1 and REG2 were transposed. The top regulator should be REG2 (7815), while the middle one should be REG1 (7812). protect you if current flows through your body from Active to Neutral (eg, by touching two points in the circuit with different hands). Thus, it is a good idea to use one hand only when there is any possibility of making contact with the live circuitry within the Motor Controller. If you are building the Controller in a different arrangement than the one we described, eg, with the motor hardwired to it, any wiring that goes outside the enclosure must be run in sheathed mains-rated cable that is secured to the enclosure with cordgrip grommets. This includes the safety/ emergency stop switch wires. The safety/emergency stop switch must be mains-rated and enclosed in an Earthed enclosure with its contacts covered in heatshrink tubing and the wiring cable tied together. Treat all connections to it as if they are live! Additionally, the wires from the safety switch need to be secured to its enclosure with a cordgrip grommet. August 2024  83 Fig.7: this panel label is also available as a PDF download from the Silicon Chip website. It can be printed, laminated and attached to the lid. This panel is shown at 83.3% actual size, and so needs to be enlarged by exactly 20%. Initial settings that can be made with the power off include setting the torque trimpot to near 0W. This resistance can be measured between the Vt and Rt test points. IC1b’s gain is set by varying VR2’s resistance (referred to as R1) to provide the required current measurement output voltage at the rated current of the motor that’s used. Table 1 shows the resistance setting for R1 versus motor ratings and shunt resistances. We show values based on ¼HP increments from ¼HP through to 2½HP. This closely corresponds to 1A to 10A motor ratings in 1A steps. That’s because, for a 180V DC motor, each amp is 180W. Since 1HP is 746W, 180W is 0.24HP or near enough to 0.25HP. resistors in series to form a 0.1W shunt instead of the 0.022W shunts used for other ratings; in that case, less gain is required from IC1b. The gain for IC1b is set so that, at the full rated motor current, its output sits at 0.55V. For example, when the current shunt is 0.022W, and the motor is rated at 10A, the voltage across the shunt will be 0.22V at 10A. IC1b needs to amplify this to give the 550mV output, meaning a gain of 2.5. The formula for the required R1 resistance is (gain – 1) × 430W. That works out to 645W in this example. With the power off, connect your multimeter probes to the two R1 test points on the PCB and adjust VR2 for the value required for R1. Now insert IC1 and the remaining ICs in their sockets if you have not already done so. Shunt values Overload setting Note that the shunt resistance comprises series and parallel resistors to provide the required overall shunt resistance. For the 1A and 2A rated motors, you can use two 0.05W At the motor’s rated current, IC1b’s output delivers 0.55V. IC3d amplifies this by 4.68, giving a 2.57V output. VR6 provides adjustment of the current threshold (It) for motor Setting IC1b’s gain 84 Silicon Chip Australia's electronics magazine overload. To set the motor overload to 1.6 times the rated current, the ‘It’ setting should be 1.6 × 2.57V = 4.1V. This value assumes that the Vovl offset output from IC3d is set to 0V using VR5, which we will do later. The overload trip voltage needs to be set with the power on. Before applying power: 1. Check your wiring carefully and ensure all mains connections are covered in heatshrink tubing and the wiring is cable-tied. 2. Check the Earth connection between the enclosure and the Earth pin on the IEC connector. The reading should be steady and under 1W. 3. Install the fuse inside the fuse holder. Testing The initial testing and setting up can be done more safely by disconnecting the Active wire to BR1. This is done at CON1, by removing the wire between terminals 4 and 5 and only connecting the Active wire to terminal 5. Also disconnect the spade connector wire loop between CON5 and CON7. siliconchip.com.au The large relay’s terminals are cut down and the wires soldered and covered with heatshrink so the lid will fit. Because the circuit operates at mains potential, it is unsafe to make contact with any part of the circuit, including the terminals of VR1, when it is switched on, despite the above measures. Do not touch any part of the circuit except with the multimeter probes and 1000V-rated screwdriver. Attach the enclosure lid before switching on power for the first time. That will make it safer if something is wrong, such as a reverse-connected electrolytic capacitor or if a 16V capacitor is installed in a 25V position. Still, check those aspects again before fitting the lid and applying power. If all is quiet when power is applied (except for relays clicking), switch off the power and open the lid. Wearing safety glasses, switch on the power again and measure the AC voltage between Neutral (at terminal 3 of CON1) and the mains Earth connection to the enclosure. The reading should be no more than a few volts. You should read close to 230V AC between Earth and terminal 5 of CON1. If the Neutral reading is instead close to 230V AC, check that you have siliconchip.com.au wired up the IEC connector correctly. If the wiring is correct, your mains supply may have the Active and Neutral wires transposed. Have this corrected by an electrician before proceeding with testing the motor controller. Switching on power again, you should be greeted with power LED2 lighting to show that the +12 and -12V supplies are up. Check the regulators for the correct output voltages. There should be +12V between the 0V and +12V test points. Similarly, there should be +15V at the +15V test point and -12V at the -12V test point. These voltages should be within 5% of the designated voltages. That means between 11.4V and 12.6V for 12V, -11.4V to -12.6V for -12V and between 14.25V and 15.75V for +15V. Verify that when VR1 is fully anti-clockwise, LED4 is off and only switches on once the speed pot (VR1) is rotated clockwise slightly. It is important to test the Controller Australia's electronics magazine initially using a filament light bulb. A halogen 25-100W bulb is sufficient, eg, in a table lamp. This way, nothing bad will happen if the ‘motor speed’ oscillates; any changes in ‘speed’ can be seen by observing the lamp brightness. Setup and adjustment With the lamp connected, perform the following tests and adjustments. All voltage measurements below are with respect to the 0V test point. 1. Adjust VR3 for -7V at Vt. 2. Adjust VR1 for 0.5V at Vc. 3. Adjust VR7 so that LED3 is just lit, then back off anti-clockwise until the LED is off. Vs should measure 0.4-1.0V. 4. Adjust VR5 for a reading at Vovl as close to 0V as you can manage. 5. Adjust VR6 for 4.1V at ‘It’. This sets the motor overload threshold to 1.6 times its rating. Now switch off the power, unplug the unit and restore the Active connection between terminals 4 and 5 of August 2024  85 The assembled module, ready for mounting in the case. CON1. Also reconnect the crimp spade lead from CON5 to CON7. Make sure VR1 is set fully anti-clockwise and connect the lamp. Apply power and wait for RLY1 to switch off (indicated by LED4 switching off). Check that the lamp begins to glow at low speed settings and reaches full brightness with the potentiometer fully clockwise. Once the operation is successful with the lamp, switch off the power and test it with the motor. Verify that the motor speed can be controlled, noting that the motor will not start unless the speed potentiometer is rotated fully anti-clockwise first (LED4 off). Wait for RLY3 to be powered (LED5 lit) before bringing it up to speed. Test the motor under load at around 25-50% of full speed and adjust the Torque trimpot, VR4, so that the motor does not drop markedly in speed when a load is applied. Anti-clockwise rotation of VR4 increases the feedback control, meaning that more torque will be applied when the motor is under load. Too much speed compensation can cause the motor to speed up under load, so minor adjustments between tests are necessary to get it right. Note also that the torque adjustment will affect the Vs value set with VR7, which ensures the PWM output is zero when the speed potentiometer is brought fully anti-clockwise. Check this by repeating steps 2 and 3 above after adjusting VR4. Suppose the motor drops in speed too much under load even with 86 Silicon Chip maximum torque adjustment. In that case, the output from IC1b (current feedback) can be boosted by increasing the gain of this amplifier via clockwise adjustment of VR2. Again, make small adjustments between load tests. Increasing the gain of IC1b will also require increasing the overload threshold (It) using VR6 by the same percentage. Adding a reversing switch If you need a motor reversing switch, you can use a 3PDT switch, as shown in Fig.8. One suitable switch is the “Lovato 3PDT 3 Position 60° Motor Reversing Cam Switch”, rated at 20A. It has a knob actuator and is available from RS Components (Cat 8405624). Two poles of the switch are used to reverse the motor polarity. The third switch pole ensures the motor is disconnected from power during the switching. It does this by opening the safety switch connection at terminals 7 and 8 of CON1. This prevents the motor from being switched into reverse while the motor is running. After reversing, the motor can only be started once the speed pot is returned to its anti-clockwise position. If a safety/emergency stop switch is also used, this will need to connect in series with the reversing switch pole at terminal 8 of CON1. There is insufficient room inside the enclosure to install a reversing switch. Consequently, mains wiring for the motor connections and safety/ emergency stop switch will need to run outside the enclosure using 10A sheathed mains cable, with the cables secured to the enclosure using cordgrip grommets. The reversing switch must also be enclosed in an Earthed metal enclosure with cables secured using cordgrip grommets. Altronics H4280 grommets are suitable. Note that if you have an on/off switch in series with the motor wiring, the switch needs to be a double-pole, double-throw type (DPDT) so that one pole connects or disconnects the power to the motor, with the second pole connected in the same way as shown for the third pole in the reversing switch. That way, the motor can’t suddenly be reconnected, which could SC damage the Speed Controller. Fig.8: a 3PDT or 3P3T switch can be used to reverse the motor. The third pole (terminals 9-12) is used to shut down the Controller when the direction is changed. The speed pot needs to be reset to zero each time the switch is thrown before the motor will be powered again. Australia's electronics magazine siliconchip.com.au Vintage Radio HMV 42-71 dual-wave superhet receiver By Marcus Chick This radio by His Master’s Voice was made in Australia from 1954 to 1959, using HMV’s type 42 chassis. It’s a mostly standard mains-powered set with MW and SW reception, but a few surprises are hiding within. T his set came to me due to an acquaintance downsizing and moving into a retirement village. It was described to me as a 6V radio. However, on collecting it, it was apparent that it was mains-powered. Editor’s note: this set was previously reviewed by Rodney Champness in the August 2003 issue (siliconchip.au/ Article/5648). You can read that article for a more detailed breakdown of the model 42-71’s circuit. The model 42-71 is a typical Bakelite table radio of the day, featuring the then-recently-introduced miniature valves. For a multi-band set, it siliconchip.com.au is unusual as this set is in the higher price range. While it is designed as what the Americans called “farm radios”, it does not have the usual RF amplification valve preceding the frequency-­changer valve. Nonetheless, it is an attractive piece. Not uncommon for the era, the set shared its chassis with other cabinet shapes to become ‘different models’. After all, why reinvent the wheel? In this case, the chassis is type number 42. You can get the service manual for that chassis from Kevin Chant’s website at www.kevinchant.com/ hmv3.html Australia's electronics magazine Uniquely to HMV, it uses 457.5kHz for its intermediate frequency (IF), whereas most in that era used 455kHz. There was sound logic behind that. The objective was to ensure that none of the sub-multiple frequencies produced by the oscillator fell on a radio station, especially the one you were trying to listen to. There were plenty of national and international radio broadcasters back then. To accommodate that, there were three shortwave (SW) bands because changes in the time of day, sunspot activity and weather all conspired to render some bands inoperable. August 2024  87 SW1 covered 14.2 to 18.4MHz, SW2 covered 24.79 to 31.92MHz and SW3 covered 5.9 to 7.5MHz. SW3 is ‘band spread’, so fewer station frequencies are over a larger area of the dial. Then we have the broadcast band of 540–1600kHz, which had its station spacing reduced from 10kHz to 9kHz in 1978. That is why only 3SR and 2AY are anywhere near their original positions. Circuit details Fig.1 shows the set’s circuit, which follows the general plan for a superheterodyne radio of the day. V1 (6AN7), the ‘frequency changer’, is actually two valves in the same envelope. This was a 88 Silicon Chip step forward as the triode in the 6AN7 complements its hexode by becoming a separate exciter for the oscillator. Valves of this type were used in shortwave sets as they provided better modulation (and thus better performance) at higher frequencies. Restoration A cable with a mains plug is no guarantee of its actual operating voltage, so I needed to assess it first. I never plug a set in to see if it works; I cannot viably repair some sets when they self-destruct after being plugged in like this. Many of these sets were abandoned after they broke down, and as we who fix know all too well, Australia's electronics magazine certain bits deteriorate when the set is not used for a long time. I concluded that the incorrect description came from the fact that the visible valves have sixes written on them. In other words, the heaters ran from 6V, not the whole set. The set only had one knob attached, which was not entirely unusual, as they were the long-shanked plastic types with a clamp. Most of those were bad news. Rigid plastic and movement were never a successful combination, and that plastic does decompose and go brittle. Under the dirt, there appeared to be an almost-mint Bakelite cabinet. So, after separating it from the chassis siliconchip.com.au ◀ Fig.1: the circuit diagram for the HMV 42-71. Its most notable features are the multiple wafer switches for selecting between the MW, SW1, SW2 and SW3 bands and the somewhat unusual 457.5kHz intermediate frequency. Unlike some similar sets, this one lacks an RF amplification stage. The chassis diagram for the set is shown at lower left. and giving it a shower to get the dust off, I decided it was in better condition than I first thought. The chassis (which had not been showered) was also in reasonable condition. I took a good look at the chassis and noticed several waxed paper capacitors as well as obvious heat damage to the transformer wires. There were also three aged Ducon electrolytic caps, plus the mains cable didn’t seem to be in great condition. There was no way I was going to power it up in this state. General restoration advice I have no tolerance for wax paper and some oil-filled caps; they inevitably become electrically leaky. I do not siliconchip.com.au bother testing wax paper caps; finding one good one in probably five hundred is not efficient, so I replaced them all. My “Honor” (Lafayette) RC Tester manual quotes a non-polarised capacitor with a leakage resistance below 50MW (at valve working voltages) as unsuitable for screen decoupling, and less than 200MW unsuitable for coupling. Therefore, I will not tolerate a leaky non-polarised capacitor, regardless of whether it can be made to function. Consider that in a set like this, the grids will draw next to no current. So any positive voltage applied to the control grid will destroy its bias and can, or will, damage the valve. Even if Australia's electronics magazine it doesn’t, it will ruin its performance. I usually touch a battery across the output transformer’s primary to ensure it is working and then perform resistance checks on primaries and secondaries. That eliminates a lot of time-wasting and potentially damaging rework later. Most Australian mica caps from the late thirties are reliable, and they should not touched, unless one end is out of the circuit. If one of its wires is out of circuit, I perform an insulation test to ensure there is no leakage. I absolutely do not perform this test on any capacitors that are across tuning coils etc (the coils and gang are a matched set). Since the mica capacitors are installed during manufacture, tampering with them is liable to cause the set to not work properly. The coils and gang are a matched set. They have mica caps installed during manufacturing to meet their specifications and tampering with them can have catastrophic results. Amazingly, there was one early modern type capacitor in this set. It stayed while the rest went. I was surprised to find no resistors worth changing as I went through the caps. As the transformer wires had succumbed to the heat of the rectifier and output valves, I cut the wires short and spliced in new lengths. Adding some heat shielding I cut out a piece of spare sheet metal from some shed doors to make a heat shield to fit between the 6N8, 6M5 & 6V4 valves and the transformer, protecting the new transformer wires. You can see it in place in the photo of the rear of the chassis. The mains cable had also been affected by the heat from the rectifier, so I took the opportunity to cut off the supply wires to the gramophone socket and, as there was room, reroute the new Earthed mains cable along the side of the chassis with clamps (you can also see this new arrangement in that chassis photo). August 2024  89 90 Silicon Chip Australia's electronics magazine siliconchip.com.au These three photos show the HMV 42-71 set after cleaning it, replacing all the old paper capacitors and some of the resistors. The mains cable was also replaced, as the previous one was too degraded, and lastly you can see the heat shield behind the 6N8, 6M5 & 6V4 valves in the photo at lower left. The P-clamp that holds the mains cable is too large, and uses a ‘not-to-standard’ cable tie to prevent it from pulling out. Best practice would be to use an appropriately-sized P-clamp to hold the cable securely. This was also the point that I decided that I needed to find out what model the set actually was, to ascertain the IF. As mentioned earlier, it is actually 457.5kHz, rather than the common 455kHz of most sets of that era. I noted that the circuit required R11, R12 & R13 to be three 10kW resistors in parallel. Interestingly, this set only had two. I left it as was. After completing a refit, I attached an analog meter across the B supply to monitor it and powered up the set via an isolation transformer with a kill switch. I also have neon lamps in bezels to the primary and secondary of the isolation transformer so I can quickly see if voltage is present, along with fuses on both primary and secondary to protect the transformer itself. Powering it up The start-up was perplexing. There were no dial lights; the heaters were glowing, but there was no HT. Blown dial lights are typical, so I fitted new globes. There was power on the rectifier, but nothing coming out of it. I hunted down another 6V4, as my “Knight” tester will not check a 6V4. With the new valve, I got a reading siliconchip.com.au on the B voltage, although it was low. That was obviously due to the missing 10kW resistor, so I replaced the two in the set with three new ones in parallel. Calibration It quickly became clear that someone had been playing with all the adjusting screws. Initially, the calibration did not go well; a symphony orchestra of various noises was getting in via the 36m antenna. A new G10 LED light was sending out a mass of RFI. Like the other noisy LED lights I’ve purchased, I returned it for a refund. That is why I use a halogen desk light. The computer’s UPS was also chipping into the EMI cacophony. Clearly, regulations around RFI no longer exist or are being ignored. AM radio is being pushed out to hide the fact that RFI is out of control. After killing power to all the noisy lights, plugpacks and such, I managed to get the calibration done. That improved things immensely. I did it with an entry-level signal generator, calibrated with a Fluke frequency counter and an oscilloscope as the meter. The ‘scope is also helpful for Australia's electronics magazine checking for gross distortion and, if present, helping to find its source. The signal generator must not be calibrated with the modulation tone on. My oscilloscope, counter and signal generator are coupled via a dedicated attenuator box in a shielded metal housing. Naturally, there was that annoying hissy crackle of a bad connection audible on start-up, which I quickly traced to pin 3 of the 6M5 socket. After sorting that and burn-in testing the chassis, I treated the cabinet with a beeswax furniture polish and put the set back together. It does pay to remove and replace valves and to scrape any oxidation from the pins. They should also be tested before putting them back in. Note that the knobs shown in the photos are from HMV but are not correct for the model. Conclusion This is an attractive radio that cleaned up well. You have to be wary of people having messed with the set previously and introduced faults. Most importantly, if the condition of the set is unknown to you, make sure it’s safe to power up before doing so! SC August 2024  91 SERVICEMAN’S LOG Use the force, Dave Dave Thompson Over the years, I have built and repaired some weird and wonderful things. These items are not necessarily electronics-related, either. But none of that prepared me for what showed up on my workbench this month. F or example, I have built a car from the ground up. I have made my own furniture, musical instruments (many, many guitars, mandolins and violins) and solid-state and valve amplifiers to make the instruments louder. I have made my own microphones, bugs, radios, computers, Theremins and myriad other hobby electronics projects in between, mainly described by the likes of Electronics Australia, Silicon Chip, Electronics Today International and all the British magazines of the 1970s and 1980s. I have also repaired hundreds, if not thousands, of devices, from mechanical repairs to purely electronic fixes. As you can imagine, this has been far more rewarding than merely being an IT guy, though that business has allowed me to indulge in all those other things. I have repaired TVs and VCRs in Australia (which gives you an indication of when I was there last!) and computers and various other devices in England, Austria and Croatia. Still, in all my years of doing this work, I have never repaired a lightsabre! I know. I can hear your gasps of excitement from here! But, full disclaimer, and somewhat sadly, I must advise that these are not ‘real’ lightsabres. I can hear your groans of disappointment from here. Real lightsabres are 92 Silicon Chip military-grade, highly classified and, as such, are very closely monitored by the government because those things can be really dangerous! If one isn’t careful, someone could lose a hand! The purple ones are especially hazardous and must be treated with great caution. These two in the workshop are just civilian-level lightsabres. Even if modified (which I would never do, of course), they will not take a leg off, cut burning swathes through spaceship hulls or slice open the belly of a tauntaun on the frigid surface of ice planet Hoth. I know this is disappointing to many, but they are only for training purposes, and are designed to avoid the catastrophic injuries typically associated with the real ones. Toys vs the real deal Many of you will have seen these toys in the stores and may have even bought some for the grandkids. Generally, they are nasty, lightweight, cheap plastic things. The best they do is flash a few LEDs down the soft translucent plastic tube that is supposed to be the ‘sabre’ part of the device. A few even make it look as if the blade ‘grows’ longer by using strip lights, an effect that usually only works in complete darkness and with a lot of imagination thrown in. Typically, kids have these things bent and broken in minutes because it is almost impossible to resist the urge to smash them against each other (if two are available) or into household furnishings. This generally destroys them pretty quickly, because they are not designed for that sort of action (even though it’s the first and only thing a kid will want to do when they get hold of one). I remember being in a play at primary school wherein I was cast as a pirate. Dad made me a sheet aluminium ‘cutlass’ style sword with a timber dowel and insulation-tape handle to use as a prop. He warned me that it was pretty weak around the tang (he used the word handle), so I shouldn’t hit anything with it. You already know what I did, the first chance I got. In my defence, it’s a natural human reaction. Of course, I hit something and sheared off the blade from the handle on the first strike. He wouldn’t make me another one, so I learned a lesson that day. I did the play with a plastic one, and keenly felt the difference and his disappointment! So, there’s a massive difference between the lightsabres on the market. Some are for kids and don’t/won’t last, while others are a little more adult, better thought out and might actually make the grade. Australia's electronics magazine siliconchip.com.au Items Covered This Month • Stress testing your electronics • Shining a light on an intermittent LED magnifier • The beeping and oscillating fan • Repairing a gifted extension lead Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com Nicely made but not robust The two that turned up in my workshop recently were of the latter variety. These devices were heavy-duty and very well made, the best I have ever seen. They hailed from China (where else) and were not overly expensive, given their build quality. The handles were substantial and hefty, about 200mm long and 25mm in diameter. They were made from beautifully turned thick aluminium stock, anodised in black. A small speaker was mounted within the tube handle right at the bottom, protected by a fine steel mesh. If you can recall those ultrasonic transducers we used to experiment with back in the 80s, you’ll be able to picture what this speaker looks like from the bottom. At the other end, a very shiny parabolic-shaped reflector is embedded in the top end of the handle. This contains a super-bright LED array, in monolithic form, mounted right in the centre. Along the top of the handle, where your thumb would naturally sit, is a solid push button, which switches the device on and off. Just below that is a charging port, a standard barrel connector that uses a lead (which comes with the devices) that plugs into a suitable USB phone wall charger. These sabres have heft and certainly looked the part! I didn’t see the extended polycarbonate translucent ‘blade’ part, as the client had already removed those for easier transport. In my opinion, that is the hardest part about replicating a lightsabre. Most just don’t look right. The typical frosted plastic ‘blades’ are not convincing, and some of the toy versions I have seen even have an extendable blade system (like an old transistor radio aerial) that is supposed to mimic the blade ‘growing’ out of the handle. They are usually inherently weak and next to useless. My customer reported that his son, who owned these sabres, also practises kung fu. Kung fu features all manner of blade work; it’s basically an umbrella term for any Chinese martial art. It seems the son and his friend had staged some full-contact combat using these toys, and suddenly, both had stopped working. Yikes! I guess somewhere in the Chinese instructions, they advise against hitting anything at all with them, but the very solid construction likely gave the guys a false sense of security as to how far they could push their swordplay. I know the feeling; after 25 years of Aikido, I was pretty tough on my timber training swords, requiring me to replace them every few years because splinters can really hurt! siliconchip.com.au Because the acrylic ‘blade’ parts had been removed, it was a lot easier to work with them on the bench. My bench looks like a grenade has gone off anyway, so not having to deal with anything but the handle part of it was a relief. Getting them apart Small grub screws held everything in, and it was clear that someone had had these apart before. Several of the screws had their threads stripped in the aluminium housing, so they just spun and wouldn’t come out. One had been cranked in so tightly that it had distorted the speaker casing. It’s never good to get things in for repair that someone has already had a go at. Never mind, there was nothing that couldn’t be undone, so far anyway. The button and charging port on the handle had a couple of domed Allen screws holding it into the handle. I guessed there would be a PCB in there that held all the electronic components. I took out the grub screws holding the speaker and those holding the LED lens assembly completely, and when the button screws were removed, I could slide the whole caboodle out of the case. I was impressed with the build quality of everything I saw – someone had put some real effort into designing this ‘toy’. Once I had all the gubbins clear of the case, I could also appreciate how much they’d managed to cram into it. It all came out as one ‘string’ of components, with the LED assembly at the top end, then the PCB, then the battery and finally the speaker. Everything was inter-wired and taped together. It was very well made. My first port of call was the battery. I know some of these rechargeable 18650 cells can be a little shonky in Chinese gear, so it was out with the multimeter to see what was going on with it. Sure enough, it was flat, reading just under 1V – very low. The customer said they might have been sitting around a while, so I broke out my bench power supply to give it a nudge. As soon as I connected the ad-hoc charging cable I’d made up for it, I was rewarded with a bright green light from the LED, which I guessed was a charging indicator light. That was a good sign. After a few hours of pumping 5V at 250mA Australia's electronics magazine August 2024  93 into it, I pressed the button and was rewarded with a screeching sound from the speaker and a bright light from the other end. I suspect that sound is the sampled sound of a lightsabre firing up. As you can tell, I don’t watch many Star Wars movies! Pressing the button sequentially changed the LED colour and a few of the sounds. I think that when the acrylic ‘blade’ was attached, this would look quite cool with all the different colours and levels. The LEDs used dimming effects, going brighter and darker to simulate starting up and shutting down; that’s quite clever, and when you include the sounds, the experience is quite immersive. I have to say, while these LEDs were not lasers, they were exceptionally bright. I couldn’t look directly at them – a mistake I made just once. I don’t know whether they had some tricky circuitry on the board to boost the battery’s output, but overall, the single 1800mAh cell did a pretty good job of making this thing shine. So, the battery was flat on light sabre number one. Hopefully, number two would be just as simple. A tougher nut to crack While I charged number one’s battery, I disassembled number two. This was the one with a distorted speaker housing and a few stripped grub screws. I plugged my second power supply into the charging port (using crocodile clips as my charging lead was already in use) and initially got... nothing. Hmm. The battery measured less than 0.3V and was likely too far gone even to be chargeable now. The critical level is usually around 2V. I unplugged it – the batteries on these devices are connected using those typical little white twopin connectors we often see, usually called JST connectors. This makes it easy to swap things over. 94 Silicon Chip I sat number one alongside number two and plugged the battery from one into two but still nothing happened. Obviously, there was something else going on with number two. I placed number one’s battery into its chain and set it aside to let it continue charging – hopefully, that one would return to its normal capacity with a little love. I ‘zapped’ the battery in number two just to see if I could resurrect it. I also ordered a new one in case I needed it. However, despite my best efforts, I could not get much life from this battery. I could bring it up to voltage, but I just couldn’t get any capacity out of it. Swapping things around the other way, battery two in handle one, it would fire up, but it would be flat in a minute. The number two sabre itself still didn’t work. It lit up with a flickering green charging light with the power supply at a very specific voltage, but it just wouldn’t do anything otherwise; pressing the button had no effect. I tried bridging the switch connections on the PCB, in case the actual switch had failed, but to no avail. Hmm... I went over it under the microscope, looking for cracks in the printed circuit board or other physical damage, but I could see none. It is a wafer-thin multi-layer board; I guess they don’t want to waste any more material than they absolutely have to. Given the complexity of the board, there could be any number of problems with it. The PCB is packed with SMDs and all the part codes had been ground off the chips, which is so typical of this type of product. siliconchip.com.au I couldn’t see anything inside that might be affected by impact damage. There were no apparent cracks, components fallen off or wires disconnected. It just didn’t work. I suppose that, given time, I could have swapped PCBs and other ancillary components between the two, even at a board level, but I had to accept that number two was dead. I did swap speakers to check that the bent one still worked. Once I confirmed it was working, I used a pair of vice-grips (suitably taped up to avoid leaving any marks) to gently squeeze the speaker back into a rounder shape. It seemed a moot thing to do, given that the sabre itself didn’t work, but it needed doing, so I did it. Fix or do not fix, there is no try Sadly, with no circuits, no information online or even any idea what the ICs were, there was not much I could do except make sure the first one’s battery was up to spec (which it seemed to be) and to chat with the client about charging them up. The charging lead came with the sabres, and it is designed to be used with a phone charger. The problem is, as I’m sure you can all see, is that there are several flavours of phone chargers. The one the customer was using was a little weenie, but he did have one that stated 2A output, so I advised him to use that one. The smaller one may have eventually charged the batteries, given time, but when it comes to playing with swords, especially ones that make noise and flash when you hit them, there is no time like right now! I reassembled the electronics into the handles, once again marvelling at the attention to detail. For example, the speaker had an O-ring, which sat in a groove around the circumference and not only isolated it acoustically but likely physically as well. I doubt it was for water-proofing – civilian-level light sabres do not work under water – so it must be there to provide some damping from whatever vibrations or shock might befall it during use. So, mixed results then. One is up and running; the likely problem was that the charger being used wasn’t supplying enough juice to keep the battery charged. However, with the second one, my guess is that it’s an internally cracked board. Some of it seemed to work (for example, the battery charging circuitry), but something prevented the rest from powering up. Sadly, that was about as far as I could go without exceeding the cost of simply buying another one. Nobody wants to pay hundreds to fix a $50 device. Still, at least he still has one very cool, working lightsabre! Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. However, it has been playing up for the last year or two. After switching it on, it would work normally, but after a few minutes, the light would dim or go out. Switching it off and on would sometimes result in it ‘resetting’ and working fine for a bit longer, only for it to go out again shortly after. This intermittent fault had long puzzled me because my initial diagnosis of it being an overheating component was not supported by the fact that it would sometimes immediately reset once power cycled. A hot component does not immediately cool down when the power is switched off. In any case, after putting it off for way too long, I decided to take a look and pulled it apart, still mounted to the bench but rotated by 180°. It is a 90 LED unit with three curved boards of 30 surface-mount LEDs, each surrounding the magnifier lens, mounted on a removable plastic sub-frame. The three LED boards are connected in series by hard wire jumpers. My initial assumption was that the fault was in the LED driver board. Without the benefit of the magnifier (I later realised I could’ve just popped the lens out and held it!), I checked for obviously faulty joints, but everything seemed in order. Noting carefully which end of the board was at mains potential and which was low voltage, I gingerly felt the back of the board for hot spots. I didn’t feel any, but I must have bridged two wires that shouldn’t have been bridged because the lights went out and refused to come on again! I thought I had really ‘blown’ Jaycar QM3546 LED magnifier repair I hate to throw something away that could be fixed, so I often give it a go, whether it is mechanical or electrical. I am an electronic repairer wannabe with a very mixed hit rate. Needless to say, my favourite column in Silicon Chip is Serviceman’s Log. My Jaycar QM3546 desk-mounting LED magnifier has been a great investment as birthdays flit by and vision becomes more challenging. It was an essential item in my fiddliest repair ever – my mother’s old pot plant moisture meter in which the hairspring had come off. That required the pointiest of soldering irons, the steadiest of hands and the magnifiest of magnifiers. siliconchip.com.au An internal view of the Jaycar QM3546 LED magnifier. The fault seemed to be temperature-related. Australia's electronics magazine August 2024  95 it this time. But after leaving it and coming back later, the lights came on, bright at first, then dim. After unscrewing the PCB, I noted that the one large 100V 100μF electrolytic capacitor was not bulged or leaking. I considered desoldering a leg to test its capacitance and ESR, but first, I looked online to see if I could buy a replacement if it was a dud. Dishearteningly, I couldn’t find an exact replacement. It was time to remove it from the desk to do some proper checks. After crawling under the desk to remove the clamp and give a contortionist a run for their money, I discovered that I need not have, as the lamp simply lifts out of its clamped socket. Dang. On a spare table, and with the LED sub-board flipped over so as not to blind me, I switched it on and it came on dim. I measured the output voltage at around 47V. I assumed that the voltage must be higher for it to work correctly. As a better test for overheating components, I added a spray nozzle to a can of butane, ensured no ignition sources were nearby, inverted the can, and sprayed the board. The board got cold, but nothing changed; the lights remained dim. Getting the lights to shine brightly so I could measure the output voltage in that condition was problematic and took some time and fiddling. When they finally did, I quickly measured the output voltage, expecting it to be much higher than before – it was the same! If there was no difference in the output voltage as the brightness changed, the fault must be with the LED boards. After switching the lights off and reinstalling the PCB, I flipped the LED sub-frame over and examined them. One LED had brown stains at each end, but after testing it, I found it wasn’t blown and seemed to work normally. I checked it while wearing a pair of welding goggles! I started noticing that the more I handled the sub-frame, the more the lights flickered. I checked and wiggled the main power input wires, but they seemed securely fastened. Each LED sub-board was held in place with three screws, and I removed them now. Since the jumpers were not flexible multi-strand wires, I felt sure that lifting the light boards out of their little cradle would result in breakage, and I would inevitably end up re-soldering something. As I began to raise them, one joint broke almost immediately. Reseating them in the cradle and using a screwdriver to re-make the connection resulted in the lights shining brightly. I screwed the boards back down to prevent relative movement and re-soldered this joint. I deeply suspected that this was the fault all along and not merely the outcome of my disassembly. That was confirmed when the lights came on immediately and powerfully, in contrast to before, when the lights would take time to ramp up and were not fully bright. In the accompanying photo (on page 95), the screwdriver points to the initially faulty connection. After beginning to reassemble it and almost forgetting to include the diffuser/lens-holder, I got it all back together and working nicely above my desk. There were many times I toyed with the idea of discarding this lamp and buying one of the sexy new ones with interchangeable lenses, but I knew that this one would continue to haunt me if I didn’t at least try to fix it, a fix that turned out to be relatively simple. It’s always about giving it a go, taking it slowly, trying to think as logically as possible, eliminating what it isn’t, leading you to what it is. T. M., Capel, WA Lucci Breeze model 213128 fan repair A friend rang and asked me if I could come over and look at her oscillating fan, which was making beeping noises when switched on. The fan was bolted to the wall and could be operated by an infrared remote control. She was correct; when I switched on the power, the fan made beeping noises but did nothing else. So I unbolted it and took it back to examine it on the bench. The fan was relatively easy to get apart, and I was soon looking at a circuit board with a capacitive power supply that had a 1μF X2 capacitor in series with the mains. The capacitor drops most of the mains voltage and dissipates little to no power because the current and voltage are out of phase. Above: the main PCB for the Lucci Breeze fan (shown adjacent) with the 1μF capacitor removed. Keen eyed readers might be able to see that the PCB silkscreen labels that capacitor as 0.1μF. 96 Silicon Chip Australia's electronics magazine siliconchip.com.au This type of circuit is dangerous to work on, as the whole electronics board is at mains potential. So I plugged it into my mains isolating transformer to be on the safe side. It no longer beeped when I turned it on, so I thought it could be an intermittent fault. I measured +5V across a large filter capacitor, so all seemed OK. But when I tried to operate the fan, the +5V dropped to +3V. I have seen this fault many times before where the X2 capacitor has dropped in value, so the reactance becomes too high for the circuit to work properly. I removed the capacitor and found it to be only 170nF instead of the specified 1μF (1000nF). A typical tolerance of such a part is 20%, so it was way out of spec. I had a replacement class-X2 capacitor in my range of spares, but it was physically a bit larger and would not fit under the circuit board where the original was. I had to make flying leads and attach the capacitor to the plastic case around the circuit board, ensuring the system was still well insulated. The fan worked as intended when powered on, with the remote controlling the speed and oscillation. After reassembling it, I returned the fan and reattached it to the wall. My friend was very happy to have her cooling fan going again, as summer was just around the corner. Editor’s note: we often find that replacement X2 capacitors are physically larger than the failed ones. We wonder why! J. W., Hillarys, WA Extension lead repair I was sorting through some items in a box given to me years ago that I hadn’t gotten around to checking when I found a short extension lead. I noticed that the cord-grip nut was missing from both the plug and the socket, so I would have to repair it before I could put it with our other extension leads. I started at the plug end and immediately noticed that the plug was on the wrong end of the cable because the Active and Neutral wires crossed over instead of going straight to their respective terminals. That meant I would have to remove the plug and the socket and swap them. I turned my attention to the socket end and could see that the Active and Neutral wires did not cross over but were connected to each other’s terminals! I don’t know who made this extension lead, but they obviously did not know what they were doing. With both the plug and the socket removed, I fitted them to the correct ends of the cable, along with cord-grip nuts, ensuring that the Active and Neutral wires connected to their correct terminals. I then tested the lead with my multimeter, and all was good. Whenever I encounter an extension lead that is not ours, I always check it to verify that it’s in good condition and wired correctly. This particular lead could have been dangerous in certain circumstances, for example, if some idiot used the ‘black is Earth’ idea (a common vehicle terminology, which isn’t correct either). I remember reading a Serviceman’s entry in Electronics Australia decades ago, where a similar situation existed with a live PA system. If you don’t know what you are doing with mains wiring, it’s best to leave it to someone who does. B. P., Dundathu, Qld SC siliconchip.com.au Australia's electronics magazine August 2024  97 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. 08/24 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. 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The included Pico W is not programmed (SC6942) - Optional laser-cut acrylic stand pieces (SC6932) - 3.5in LCD touchscreen: also available separately (SC5062) 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (SC6881) $100.00 $3.00 (JUN 24) All kits come with the PCB and all onboard components (see page 81, June24) - Adjustable SMD kit (SC6948) - Adjustable TH kit (SC6949) - Fixed TH kit – ZD3 & R1-R7 vary so are not included (SC6950) (APR 24) - SC6911: everything except the case & battery; RP2040+ is pre-programmed - SC6912: the SC6911 kit, plus the LEDO 6060 resin case - SC6913: the SC6911 kit, plus a dark grey/black resin case - 3.2in LCD touchscreen: also available separately (SC6910) siliconchip.com.au/Shop/ $42.50 $85.00 $125.00 $140.00 $30.00 Short-form kit: includes everything except the case; choice of front panel PCB for Altronics H0190 or H0191. Picos are not programmed (see page 46, Mar24) $65.00 Hard-to-get parts: includes the PCB, programmed micro, all other semiconductors and the Fresnel lens bezels (SC6871) $95.00 Current detection add-on: includes the AC-1010 current transformer, (P)4KE15CA TVS and MCP6272-E/P op amp (SC6902) $20.00 Includes the standard PCB (01110231) plus all onboard parts, as well as the switches and mounting hardware. All that’s needed is a case, XLR connectors, bezel LED and wiring (see page 35, Feb24) - VGA PicoMite Version Kit: see page 52, January 2024 (SC6861) - ps2x2pico Version Kit: see page 52, January 2024 (SC6864) - 6-pin mini-DIN to mini-DIN cable, ~1m long. Two cables are required if adapting both the keyboard and mouse (SC6869) - Control Module kit: see page 68, December 2023 (SC6793) - Volume Module kit: see page 69, December 2023 (SC6794) - OLED Module kit: see page 69, December 2023 (SC6795) - 0.96in SSD1306 cyan OLED (SC6176) *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. $30.00 $32.50 $10.00 - Receiver short-form kit: see page 43, December 2023 (SC6835) - Discrete transmitter complete kit: see page 43, December 2023 (SC6836) - Module transmitter short-form kit: see page 43, December 2023 (SC6837) - 28mm square spade: see page 35, December 2023 (SC6850) - 21mm square pin: see page 35, December 2023 (SC6851) - 5mm pitch SIL: see page 35, December 2023 (SC6852) - Mini SOT-23: see page 35, December 2023 (SC6853) - D2PAK SMD: see page 35, December 2023 (SC6854) - TO-220 through-hole: see page 35, December 2023 (SC6855) $70.00 $50.00 $55.00 $25.00 $10.00 $35.00 $20.00 $15.00 $30.00 $30.00 $30.00 $25.00 $35.00 $45.00 PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL FAN CONTROLLER & LOUDSPEAKER PROTECTOR DUAL HYBRID POWER SUPPLY SET (2 REGULATORS) ↳ REGULATOR ↳ FRONT PANEL ↳ CPU ↳ LCD ADAPTOR ↳ ACRYLIC LCD BEZEL RASPBERRY PI PICO BACKPACK AMPLIFIER CLIPPING DETECTOR CAPACITOR DISCHARGE WELDER POWER SUPPLY ↳ CONTROL PCB ↳ ENERGY STORAGE MODULE (ESM) PCB 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) AM-FM DDS SIGNAL GENERATOR SLOT MACHINE HIGH-POWER BUCK-BOOST LED DRIVER ARDUINO PROGRAMMABLE LOAD SPECTRAL SOUND MIDI SYNTHESISER REV. UNIVERSAL BATTERY CHARGE CONTROLLER VGA PICOMITE SECURE REMOTE MAINS SWITCH RECEIVER ↳ TRANSMITTER (1.0MM THICKNESS) MULTIMETER CALIBRATOR 110dB RF ATTENUATOR WIDE-RANGE OHMMETER WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD MINI LED DRIVER NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) 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) DATE JAN22 JAN22 JAN22 JAN22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 MAR22 MAR22 MAR22 MAR22 MAR22 APR22 APR22 APR22 MAY22 MAY22 JUN22 JUN22 JUN22 JUN22 JUL22 JUL22 JUL22 JUL22 JUL22 AUG22 SEP22 SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 PCB CODE 15109211 15109212 01101221 01101222 01102221 SC6204 18107211 18107212 01106193 01106196 SC6309 07101221 01112211 29103221 29103222 29103223 01107021 09103221 09103222 CSE211002 08105221 16103221 04105221 01106221 04107192 07107221 10109211 10109212 04107221 CSE211003 04109221 04108221 04108222 18104212 16106221 19109221 14108221 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 SC6658 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 Price $2.50 $2.50 $7.50 $5.00 $5.00 $25.00 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $2.50 $5.00 $5.00 $5.00 $25.00 $2.50 $2.50 $7.50 $5.00 $5.00 $5.00 $7.50 $7.50 $5.00 $7.50 $2.50 $5.00 $5.00 $7.50 $7.50 $5.00 $10.00 $2.50 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 $12.50 $5.00 $5.00 $5.00 $1.50 $4.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT 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) PICO AUDIO ANALYSER (BLACK) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION MULTI-CHANNEL VOLUME CONTROL: VOLUME PCB ↳ CONTROL PCB ↳ OLED PCB SECURE REMOTE SWITCH RECEIVER ↳ TRANSMITTER (MODULE VERSION) ↳ TRANSMITTER (DISCRETE VERSION COIN CELL EMULATOR (BLACK) IDEAL BRIDGE RECTIFIER, 28mm SQUARE SPADE ↳ 21mm SQUARE PIN ↳ 5mm PITCH SIL ↳ MINI SOT-23 ↳ STANDALONE D2PAK SMD ↳ STANDALONE TO-220 (70μm COPPER) RASPBERRY PI CLOCK RADIO MAIN PCB ↳ DISPLAY PCB KEYBOARD ADAPTOR (VGA PICOMITE) ↳ PS2X2PICO VERSION 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 DATE JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 JAN24 JAN24 JAN24 JAN24 FEB24 FEB24 FEB24 FEB24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 APR24 APR24 APR24 MAY24 MAY24 MAY24 JUN24 JUN24 JUN24 JUN24 JUN24 JUL24 JUL24 JUL24 PCB CODE CSE230101C CSE230102 04105231 09105231 18106231 04106181 04106182 15110231 01108231 01108232 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 04107231 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 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 Price $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 $5.00 $2.50 $2.50 $5.00 $5.00 $5.00 $3.00 $5.00 $2.50 $2.50 $5.00 $2.00 $2.00 $2.00 $1.00 $3.00 $5.00 $12.50 $7.50 $2.50 $2.50 $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 STYLOCLONE (CASE VERSION) ↳ STANDALONE VERSION DUAL MINI LED DICE (THROUGH-HOLE LEDs) ↳ SMD LEDs AUG24 AUG24 AUG24 AUG24 23106241 23106242 08103241 08103242 $10.00 $12.50 $2.50 $2.50 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Pico Gamer did not work due to faulty part I am building the Pico Gamer (April 2024; siliconchip.au/Article/16207) as a present for my grandson on his birthday this Sunday. I purchased the PCB from you but sourced the other parts myself. When I try to load the firmware, there is no response from Windows when plugging the cable in; no virtual USB drive appears. I tried holding down the BOOT button while plugging it in. I plugged in an old Pico, and a window opened. I’m using the cable I use to back up my phone. I tried a different cable, but no go. I ordered another RP2040-Plus to try. (J. R., Norco, California, USA) ● We got the RP2040-Plus modules for our kits directly from Waveshare, and they all worked fine straight away when we programmed them for the kits. It does seem like the RP2040-Plus is faulty unless you have it plugged into the Pico Gamer board and there is a short on that board that prevents it powering up. Note: the reader got back to us a few days later, stating: Success! After our last email, I bought a cheap hot air rework station from Amazon that was delivered overnight. I also purchased a new RP2040-Plus. I got up early Sunday, desoldered and replaced the Pico, transferred the firmware, and was in business at noon for the birthday party. Substituting Bench Supply transformer In the parts list of the 30V 2A Bench Supply (September & October 2023; siliconchip.au/Series/403), you listed a transformer from a store in Australia, but I live in New Zealand. I think I have found a similar product available at Jaycar: MM2014. Is this a suitable replacement for the transformer? Also, can the output current be increased? The new transformer states 5A output, although the other one says 2.5A in the configuration described in the issue. Thanks in advance. (J. N., via email) ● The Jaycar MM2014 has the same ratings as the specified Altronics transformer in a slightly smaller physical size. You could use it. Regarding transformer ratings, the VA specification determines the current available. With a 60VA rating, the MM2014 can provide 5A if the two 12V windings are in parallel or 2.5A when the windings are in series. Since we are using the transformer to provide 24V with the series windings in this power supply, the available current is 2.5A. Increasing the Bench Supply’s output above its design figure of 2A would require a larger transformer and possibly some changes to the circuit, such as more or larger filter capacitors and an adjustment to the current-­limiting threshold. These changes would also mean a larger enclosure. Substituting LM1085 regulator in GPSDO I am building the GPS Disciplined Oscillator project (GPSDO, May 2023; siliconchip.au/Article/15781) but am having problems finding the LM10855.0 regulators. I found a data sheet for the OSC5A2B02 OCXO, which 100 Silicon Chip Australia's electronics magazine specifies <600mA warm-up current and <250mA ‘running’ current, so I think an LM7805 (rated at 1A) could be used. Can I replace the LM1085-5.0 regulators above with a standard LM7805 and fit an LM7808 device instead of the 7.5V buck converter? That should give enough headroom for the LM7805s to operate correctly. (G. P., Narre Warren, Vic) ● It will probably work with 7805s instead of the LM1085s. You could keep the buck regulator for better efficiency. We think the LM1085 was chosen because it has better regulation and a less noisy output than the 7805. LM1085s are available on websites like eBay and AliExpress. Also, Altronics has the LM1084IT-5 (Cat Z0580), which is similar to the LM1085-5.0. Blender vs OpenSCAD software I noticed that Geoff Graham decided to use Blender to design the case for his Pico Gamer project from April 2024. I have been using OpenSCAD for similar jobs, and I quite like it, but it sometimes gets a bit of a chore, so I wondered if Blender might be better. I started by reading the documentation. Wow! I can’t believe so much could be free. However, I couldn’t work out how to use Blender to make anything simple, like a basic case. Fortunately, you recommended this video https://youtu.be/rN-HMVTB7nk – I would have been lost without that. The video is very good, verging on essential, and persuaded me that Blender is an excellent product. Modern software like Photoshop, Altium Designer, and Blender seem intended for experts who use them often and love shortcuts. For me, this sort of interface is not the least bit ergonomic, and I feel I’m playing a ‘discover where the elf hid the goblet’ video game. The feature I want is under some icon somewhere, but ‘somewhere’ is a very big place. siliconchip.com.au Worse, despite clever undo capabilities, many buttons open and close windows and panels that persist even after closing the program and opening it again. I’ll use Photoshop as a suitably neutral example. I’d obviously touched some hotkey I wasn’t aware of, and the up/down scroll bar became unavailable for several days. Although I eventually discovered how to fix the problem, the solution was obscure! Blender seems to have a similarly clever interface, and I anticipate it will be fraught with similar irritations. Consequently, I think I’ll persevere with OpenSCAD and its seemingly old-fashioned interface where I type words that the software and I both understand. I can include lots of comments, too, especially for myself tomorrow. Do you have any preference for one or the other? (K. A., Kingston, Tas) ● Geoff Graham documents his use of Blender (for the Pico Gamer case) on his website at https://geoffg.net/3D_ Printed_Cases.html Our preference is for OpenSCAD. If designing the case for the Pico Gamer, we suspect that our OpenSCAD version would end up being a bit less stylish than Geoff’s! That said, we are impressed by what Blender can achieve. We have even used both tools for the same design, eg, exporting an STL from Blender into OpenSCAD and modifying it further. It’s certainly possible to start a design in OpenSCAD and add some embellishments in Blender. At its simplest, we would say that OpenSCAD is better for precise, engineering-­type applications, while Blender is better for animations and more organic objects. Like you, we also like the code-­ programming interface, especially for its ‘non-linear undo’ capabilities. You might also want to look at FreeCAD (www.freecad.org), which falls between OpenSCAD and Blender in terms of complexity. It really comes down to ‘different strokes for different folks’ and using what works for you. And yes, we have the same UI frustrations as you: we’ll accidentally press some key combination, and something critical will disappear, with no obvious way to get it back. Let’s just say that modern graphical user interface design leaves a lot to be desired. Customisation is nice, but it shouldn’t be required to make the program remotely usable. Also, there’s no reason you can’t have plenty of keyboard shortcuts but still have the same functions available graphically. More questions on the SC200 amplifier Thanks for your advice in the July 2024 issue (“SC200 amplifier assembly questions”, p102). I am building the SC200 as a dual-mono setup. I will need two Loudspeaker Protection kits, as I need to connect one to each channel for the separate ‘AC Sense’ signals from the two power supplies. Is that correct? Also, each protection module’s ‘AC Sense’ signal comes from the two AC terminals on the 35A diode bridge used in that channel’s power supply. With the 35V-0-35V transformers I am using, this AC sense voltage will be about 70V AC. Is that correct? I ‘plugged’ both amp modules into one of the power supplies with protection resistors but both the red and green LEDs illuminated during initial testing. There is a 1V drop across the The Pico Gamer A PicoMite powered ‘retro’ game console packed with nine games including three inspired by Pac-Man, Space Invaders and Tetris. With its inbuilt rechargeable battery and colour 3.2-inch LCD screen, it will keep you entertained for many hours. SC6912 | $125 + post | complete kit with white resin case* Other Items for this project SC6911 | $85 + post | complete kit without any case* SC6913 | $140 + post | complete kit with a dark grey resin case* * LiPo battery is not included SC6909 | $10 + post | Pico Gamer PCB* See the article in the April 2024 issue for more details: siliconchip.au/Article/16207 siliconchip.com.au Australia's electronics magazine August 2024  101 Micromite LCD BackPack has started randomly rebooting My Micromite-based Superhet IF Alignment device (September 2017; siliconchip. au/Article/10799) has developed problems. No matter how it is set up or what screen it is left on, it will eventually default to the sweep output screen with a range of 450-455-460kHz and a level of 20 after one minute. In the sweep output screen with frequencies other than the default (before the minute is up), attempts to change any parameters by pressing the sweep screen will cause a reboot. When it returns to the sweep output screen, the on-screen controls are inactive, apart from the sine/triangle/square wave and sweep buttons at the bottom of the screen. Sinewave parameters can be set and will be reflected in the sweep output screen until it ‘reboots’. Triangle wave parameters can be set, but the level resets to 20 and frequency resets to 455kHz after the ‘reboot’. The square wave level cannot be changed, but the frequency resets to 455kHz after the default to sweep the output screen. The sweep parameters can be changed. The individual mode functions are on frequency and perform normally until it ‘reboots’. I have checked all of the connections and they appear secure. The problem does not vary with different USB power supplies. I wonder if I have zapped it somehow. Can you please suggest which module and/or component of the unit may be responsible? (G. B., Corrimal, NSW) ● It sounds like the microcontroller is randomly rebooting. We suggest you check the soldering of the three higher-value (10μF+) capacitors plus the two 100nF capacitors closest to IC1. Also check the soldering of REG1 and IC1. If IC1 is socketed, try unplugging it (careful not to bend the pins) and then re-inserting it in case the contacts have become oxidised. If the soldering looks OK, replace the capacitor typically marked as 47μF (it may be a lower value like 22μF or 10μF). That capacitor is critical to the stability of the microcontroller. If that doesn’t help, replace the other two 10μF capacitors. If it’s still acting up, it seems likely that IC1 has been damaged and will need to be replaced. 68W resistors on the positive rails of both amp boards and an approximate 700mV drop across the resistors on the negative rails. Does that seem OK? As no smoke or heat was coming from the modules, I forged ahead. With the fuses and safety resistors still attached, only the green LEDs illuminated, as expected. Rotating VR1 clockwise does cause a rise in voltage across the resistors, but very slowly. Adjusting VR2, I got the offset voltage across the outputs very close to 0mV. From this, I feel that the modules are working correctly. Not being an electronics engineer, I thought the substituted transistors (TTA004B for KSA1220 and TTC004B for KSC2690) might have caused the slightly different behaviour. I am only measuring a 70mV drop across the 68W resistors in place of the fuses. The article says to expect just under a 1V drop, like when the resistors are in the power rails (I did get that). When I turned VR1 clockwise, the voltage drop increased, but only to 100mV after a few turns. There are no smells, smoke or heat, though. I realise the output transistors are not matched, so I expect a variance between their sharing of the load current. My test results for both boards are shown below. Do you see any problem with them? It is mentioned in the article that if the reading between TP7/ TP5 is above 5mV, readjust it to bring it back ‘below this figure’. As you can see, both boards are at 4.4mV between TP7/TP5 and very close between TP7/TP3. However, the readings are slightly higher for the PNP output transistors at 5.1-5.3mV. Should I try to lower these values? (S. W., via email) Left Right TP3 4.7mV 4.3mV TP4 5.2mV 5.1mV TP5 4.4mV 4.4mV TP6 5.3mV 5.1mV ● Yes, if you have separate power supplies with separate mains switches, you will need two speaker protectors. We are unsure which speaker protector design you are using, but the November 2015 article on the Universal Loudspeaker Protector has a wiring diagram on page 69 (siliconchip. au/Article/9398). You only wire the AC Sense terminal to one of the transformer secondaries, so it will have 35V AC applied, not 70V AC. With the fuses out, the only path for current to flow to the output stage will be via the red LEDs, so they will light. That small current will probably be enough to raise the output stage supply rails by a few volts, lighting the green LEDs. So you are right that both will likely light with the fuses out. With the fuses or safety resistors in, we expect only the green LEDs to light. 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. 102 Silicon Chip Australia's electronics magazine 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 FOR SALE LEDs and accessories for the DIY enthusiast 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. PCB PRODUCTION Lazer Security 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 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 For Quality That Counts... 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. Your 0.7-1.0V readings across the safety resistors is good, as is the fact that it increases slowly as you rotate VR1 clockwise. That, combined with the low output offset voltage, makes it very likely that the modules are working correctly. Those substitute transistors have specifications that are very close to the originals and should not cause any problems. The substitution was necessary as one of the originals is no longer made/available. Once the resistors are moved to the fuse locations, the voltage drop across them only depends on the output stage current, not the total module current. Since the initial bias is so low, the output stage is drawing almost no current, hence the low voltage drop readings at first. That probably should have been explained in the article. siliconchip.com.au Yes, there will be a slight variation in the current sharing. That’s part of the reason for the emitter resistors; they help to reduce the variation. Your measurements are fine, and we would not bother to make any further adjustments as long as the bias currents don’t keep increasing over time as the module warms up (thermal feedback). With the readings between 4mV and 6mV, you should get performance pretty much identical to the published graphs, and as long as the voltages are not creeping up, there is no risk of thermal runaway. Appliance Energy Meter voltage is wrong I built the Appliance Energy Meter (August-October 2016; siliconchip.au/ Series/302) and much of it works fine. Australia's electronics magazine The Micromite display comes on and I can set clock time. At first, I could calibrate the AC voltage readings to match the mains, but now I am unable to do that. I have checked voltages at various points as given on the circuit diagram and all check out except some around IC4 (the ACS718). I measure 4.87V at pin 10, 2.47V at pin 12 and 0V at pin 15. Pin 15 is shown as Vcc and should give 5V. I can measure 5V up to the 56kW resistor but not beyond. I can see the PCB track from pin 15 connecting to Earth at the end of the 2.2kW resistor. What am I missing here? Is the PCB faulty? If the 5V rail connected to Earth, I would think none of the other positive rail points would show a voltage. I have built many projects over many decades (back to Radio, TV continued on page 104 August 2024  103 Advertising Index Altronics.................................23-26 Blackmagic Design....................... 7 Dave Thompson........................ 103 DigiKey Electronics....................... 3 Emona Instruments.................. IBC Hare & Forbes............................. 11 Jaycar............................. IFC, 51-54 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Melbourne Society of Model & Experimental Engineers............. 37 Microchip Technology.............OBC Mouser Electronics....................... 4 PCBWay......................................... 9 PMD Way................................... 103 Silicon Chip ESR Tweezers....... 61 Silicon Chip PDFs on USB......... 77 Silicon Chip Pico Gamer......... 101 Silicon Chip Shop.................98-99 The Loudspeaker Kit.com.......... 97 Wagner Electronics....................... 8 Notes and Errata WiFi DDS Function Generator, May & June 2024: errors on the PCB cause Button A to start channel B and Button B to have no effect, while LED T/Trig Out is shorted to ground. The two tracks currently going to pins 22 and 23 (GP17 and GND) of MOD1 should be cut and re-routed to pins 21 & 22 (GP16 and GP17), respectively. Also, both tracks currently going to pin 33 (AGND) need to be re-routed to pin 32 (GP27). Finally, in the parts list, diode D2 should be listed as a 1N5819, not 1N5189 (the diode supplied in the kit is correct). Next Issue: the September 2024 issue is due on sale in newsagents by Thursday, August 29th. Expect postal delivery of subscription copies in Australia between August 26th and September 13th. 104 Silicon Chip & Hobbies) but I admit this is one of the technically most complex I have done even though the construction was straightforward. (E. G., St Kilda, Vic) ● We are not sure how this happened but the revised circuit diagram is wrong. According to the data sheet, pin 15 of the ACS718 should be connected to GND. Vcc is pin 10; there is no FILTER pin on this part. So the PCB connections are correct. The ACS718 is not involved in voltage measurements anyway, only current measurements. We have corrected the circuit in the online edition. The mains voltage is monitored via transformer T1, op amp IC3a and ADC IC2. The output from T1 should be approximately 12V AC. The junction of the 22kW/2.2kW divider should be just above 1V AC, and pin 3 of IC3a should measure a similar AC voltage but with a 2.5V DC bias. If measuring these with mains power applied, please be very careful to keep away from all the other components and mains wiring and use a multimeter with insulated probes and a suitable voltage rating. Alternative for FR607 fast recovery diode I’m hoping you can suggest a replacement for FR607 6A 1000V fast recovery diode used in Li’l Pulser Mk.2 (July 2013; siliconchip.au/Series/178). I did some research but couldn’t find one with similar specs. Jaycar sells a pack of 10 FR607s but I only need one. (P. C., Croydon, Vic) ● You could use the MBR20100CT (Jaycar ZR1039, available separately rather than in a pack of 10). It is a different package (TO220 instead of the DO-201 axial leaded FR607). You could wire it up using tinned copper wire with the two outside pins joined as the anode and the centre pin or tab as the cathode. Ensure the device is mounted so it can’t short to other components. Covering in heatshrink tubing or securing it with neutral-cure silicone would achieve that. Alternative to 10-turn potentiometers Is there any way to make a single-turn potentiometer act like a 10-turn pot? Also, Jaycar has discontinued the Australia's electronics magazine MCP1703T-5002E/CB regulator you used in the Versatimer/Switch (June 2011; siliconchip.au/Article/1038). Is it possible to bypass the regulator and use a 7805 or 78L05? I understand the current draw will increase. Keep up the good work with the magazine. (R. M., Melville, WA) ● 6:1 reduction drives are available but it is almost certainly cheaper and easier to just use a 10-turn pot. See www.nationalrf.com/reduction.htm Yes you could use a different 5V regulator for the Versatimer/Switch as long as you take care connecting it correctly to the PCB for the input, GND and output connections. Yes, the low standby current feature will be lost if using one of those regulators. Different regulators may require extra capacitance at the input and or output. Check the data sheet for the regulator you use. Using Touch Lamp Dimmer with LED bulbs I built the Touch Lamp Dimmer from the June 1989 issue (siliconchip.au/ Article/7459) for both my bedroom and lounge. When suitable LED lamps became available, I was able to continue using the Dimmer in on/off only mode by retaining two 28W halogen bulbs in each room. Replacing the halogen bulbs is becoming a bit tedious, so I wanted to use a fixed capacitive or resistive load instead. I searched the internet, but it appears no one has published instructions on calculating the required load. The 5.5W LED lamps draw 22.4mA, while the 28W halogen lamps draw 123.8mA each. There are two halogens in each of the 12 lamps in the lounge and the 7 in the bedroom. Many thanks for your help. I have been collecting and reading your magazine since the beginning. ● It is not terribly practical to use resistors since the value required to draw the same current as one halogen bulb is 1.8kW, resulting in a dissipation of 32W. So, a 50W-rated resistor would be required, mounted on a large heatsink. You might consider instead replacing the dimmer with the Versatile Trailing Edge Dimmer with Touch Plate & IR (February & March 2019; siliconchip.au/Series/332), as it is compatible with LED lamps. 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