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SEPTEMBER 2025 ISSN 1030-2662 09 The VERY BEST DIY Projects! 9 771030 266001 $14 00* NZ $14 90 INC GST INC GST AERIAL DRONES the latest hobby, commercial, military and passenger drones PICkit Basic Programmer Microchip’s new low-cost programmer & how to add a 3.3/5V power breakout board Pendant Speaker A high-performance hanging speaker with a 170mm woofer and 90W power rating HomeAssistant Run your own fully featured home automation system using a Raspberry Pi USB-C Power Monitor Measure voltage, current , power and energy for nearly all USB-C devices ALL NEW CATALOGUE! It’s Back & PRINTED Exciting news! The Jaycar Engineering & Scientific Catalogue has returned, and it’s our biggest issue yet, with 604 pages packed full of the latest products, components, and tools. ONLY 9 $ 95 ^ The catalogue will be available for purchase from our stores or online. Prefer digital? A convenient flipbook version will also be available online. www.jaycar.com.au | www.jaycar.co.nz Australia New Zealand BJ5000 $9.95 BJ5002: $11.90 Scan the QR Code or visit: AU: jaycar.com.au/p/BJ5000 NZ: jaycar.co.nz/p/BJ5002 Limited print run. Be quick before they sell out! ^Price Shown in AUD - NZ price is $11.90 Contents Vol.38, No.09 September 2025 16 Aerial Drones Drones are commonly used in commercial applications, like aerial photography. We cover the technological advances that drones have undergone, along with some of the latest types. By Dr David Maddison, VK3DSM Unmanned aerial vehicles PICkit Basic with Power Breakout 33 The MPLAB PICkit Basic Microchip’s MPLAB PICkit Basic is their newest programmer/debugger for use with version 6.25 of the MPLAB X IDE. It uses the familiar 8-pin connector and comes with an optional SWD (serial wire debug) adaptor. Review by Tim Blythman Microcontroller programmer/debugger 48 HomeAssistant, Part 1 Pages 33 & 38 Page 42 Here’s how to set up your own fully featured home automation system using a Raspberry Pi. By Richard Palmer Home automation 62 Amplifier Cooling, Part 2 For the second and final part of this series, we show you how we modified an existing amplifier design to improve its cooling. By Julian Edgar Electronic system design 38 Power Breakout for PICkit Basic Since the PICkit Basic programmer can’t provide power to a connected chip, you can build this handy adaptor board. It supplies 3.3V & 5V from a USB-C cable and connects inline with the programmer. By Tim Blythman Adaptor project 42 Pendant Speaker, Part 1 This high-performance speaker can be mounted up on a roof or ceiling and is built into a pre-made enclosure. It uses a 170mm woofer with dome tweeter and has a 90W continuous output rating. By Julian Edgar Audio project 54 HomeAssistant Satellite This companion project can be used to wirelessly connect different sensors, displays and more to a HomeAssistant-based system. By Richard Palmer Home automation project 68 Ducted Heat Transfer Controller Improve the energy efficiency of your home by transferring warm or cool air between rooms automatically using this smart controller. Part 2 by Julian Edgar & John Clarke Home automation project 78 USB-C Power Monitor, Part 2 Measure voltage, current, power and energy supplied to nearly all USB-C devices with readings up to 60V, ±5A, 300W and 999999J. By Tim Blythman Test & measurement project Pendant Speaker 2 Editorial Viewpoint 4 Mailbag 15 Subscriptions 76 Circuit Notebook 85 Online Shop 86 Serviceman’s Log 92 Vintage Radio 100 Ask Silicon Chip 103 Market Centre 104 Advertising Index 104 Notes & Errata 1. UV monitor using an ATtiny85 2. Emergency light using a supercap 3. Switching between 115V & 230V AC Pye PHA 520 “Colombo Plan” radio by Alby Thomas & Ian Batty SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $72.50 12 issues (1 year): $135 24 issues (2 years): $255 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 Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Editorial Viewpoint What is ferrite? My editorial in the April 2025 issue was titled “Ferrite beads are not inductors”. It explained that while ferrite is used in both inductor cores and beads, their functions are different. In it, I wrote: “Ferrite is a ceramic material that contains iron oxide.” This is true, but it’s a very simplified explanation. In response, a reader wrote in to say: “Ferrite beads are very rarely iron oxide. They are, in the main, MnZn and NiZn, with other exotics being used. Also, you can buy iron powder beads (not an oxide), which are in fact used for their inductance, among other things.” This comment makes a few interesting points worth examining. First, are ferrite beads “rarely iron oxide”, and are they really made of “MnZn” or “NiZn”? In my editorial, I didn’t claim that ferrite is iron oxide; only that it contains it. That distinction is important. Ferrite refers to a family of ceramic materials with a particular crystal structure – the spinel structure – which incorporates iron (Fe) and oxygen (O), along with other metal ions like manganese (Mn), nickel (Ni), zinc (Zn), or cobalt (Co). The only pure-iron spinel is magnetite (Fe3O4), but it’s unsuitable for most magnetic core applications due to its relatively low resistivity and poor high-­ frequency performance. Commercial ferrites, by contrast, are mixed-metal oxides; engineered ceramics with general formulas like (Mn1-×Zn×)Fe2O4 or (Ni1-×Zn×)Fe2O4, where x typically ranges from 0.2 to 0.6. These additional metal ions are not just incidental. First, the spinel structure doesn’t form correctly without them. Second, they profoundly affect the material’s magnetic and electrical properties: permeability, losses, Curie temperature, resistivity and more. That’s why ferrites are tailored for specific roles, from switchmode transformers to EMI suppression. You may have noticed ferrite cores labelled with codes like N27, N49, N87, N90, N97 (TDK/EPCOS), 3C90, 3C94, 4A11, 4C65 (Ferroxcube), or #31, #43, #61, #77 (Fair-Rite). These designations reflect specific ferrite formulations and performance characteristics. Some are optimised for low core losses at 100kHz, others for high resistivity and EMI suppression into the MHz range. Designers don’t always need to understand the chemistry, but they must choose the right material by referring to the datasheet. So, in a sense, the reader is correct: ferrite is not just one compound, nor is it just “iron oxide”. It’s a highly engineered family of materials. As for powdered iron “beads”, I didn’t mention them in the previous editorial because their function is fundamentally different. Powdered iron is a metallic material (not a ceramic), with much lower resistivity and different loss characteristics. These components are usually used as inductors, not EMI suppression beads. They are relatively uncommon; I’ve never knowingly encountered one in a circuit, or if I did, it was indeed labelled as an inductor, which is appropriate. The bottom line is that ferrite is a fascinating and versatile material, and many people who use it – whether in beads or transformer cores – may not be fully aware of how varied and finely tuned its properties can be. Cover image: https://pixabay.com/photos/dji-farming-agriculture-drone-4223416/ by Nicholas Vinen Subscription Prices, effective 01/09/2025 New Prices Print (AU) Printing and Distribution: 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Combined (AU) Print (NZ) Combined (NZ) RoW 6-month $72.50 $82.50 $85 $95 $105 12-month $135 $155 $160 $180 $200 24-month $255 $280 $300 $335 $390 Australia's electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. Short Circuits book PDFs are available for free In Ask Silicon Chip for July 2025, there was a query from R. K. in New Zealand regarding kit instructions for a design published in Jaycar’s Short Circuits book. It seems that Jaycar has, in recent times, made the Short Circuits books downloadable for free – see the bottom of the page at www.jaycar.com.au/short-circuits John Hunter, Hazelbrook, NSW. The Eddystone EC10 in Antarctica I was very interested to read the article on the Eddystone EC10 Receiver (July 2025; siliconchip.au/Article/18526). My experience with this receiver goes back to 1974, when I worked on a glaciology project on the permanent ice about 40km from Casey Station in Antarctica, near a place called Cape Folger. The receiver was housed in a sled-mounted caravan while we drilled two boreholes in the ice down to a depth of a little over 300m. My colleagues and I used the receiver to obtain time signals to keep our watches on time. This photo shows the EC10 sitting on a shelf above my amateur radio equipment (Yaesu FT101) and a transmitter power amplifier. There is another radio transceiver on the top shelf, covering the lower end of the HF band, used for communication back to the station. The photo was developed and printed at Casey Station. Keith Gooley, VK5OQ, Yattalunga, SA. 4 Silicon Chip EA & Silicon Chip magazine giveaway I have a complete set of Electronics Australia and Silicon Chip magazines from 1970 to 2017 to give away, all in good condition. If anyone is interested, they can email silicon<at> siliconchip.com.au and pass on their details. John Charlton, Middleton, Tas. Hints on EC10 alignment and fixing broken slugs I am very familiar with the Eddystone EC10 (Vintage Radio, July 2025); I have three. I spent some years perfecting their alignments and built test jigs to find the best possible replacement transistors for the tin-whisker-­affected original parts. There are some things about this radio, especially regarding its RF coils and slugs, that are not well understood. The first is that the slugs in the RF coils have two possible alignment positions at resonance. This is because the coupling coil is placed on one side of the resonant coil. Therefore, the coil can be set to resonance with two positions of the slug projecting from either side of the resonant coil. In one of the two cases, there is a higher degree of coupling to the coupling coil, which increases the drive energy to the next stage, thus increasing the gain, and lowers the bandwidth only a little. I don’t think the manufacturer stated which is the correct position, so most technicians assume that it is the first resonant peak as the slug is screwed in from the top. In reality, though, improved gain is achieved in the second position. So Ian Batty might be surprised at the changes in performance, depending on how the slugs are set. Also, if metal hex tools are used on these hollow slugs, they can fracture along their long axis. There is a specific method to remove these without damaging the coils. When the slug is cracked on the long axis, it won’t rotate because the tool forces the two fragments apart, and the sharp fractured thread edges bind into the threads in the former. It creates an extremely effective rotational brake. To get them out, it is best to cut down a wooden chopstick (by hand, with a scalpel) to make a timber hex tool. Then apply epoxy resin (eg, 24-hour Araldite) to it; not too much, just enough to glue the inner faces of the slug to the flat faces of the chopstick. If too much glue is used, it will migrate into the crack faces toward the thread; then it is game over. After it sets, the slug will unscrew because rotation of the chopstick tool cannot cause expansion of the slug halves or fragments away from each other because they are glued to it. I never use Teflon as a ferrite slug locker. The trouble is that it is not springy or elastic, and it does not provide a constant force. It is also difficult to get exactly the right Australia's electronics magazine siliconchip.com.au amount so that the slug is not too loose or too tight. An elastic locking method is preferable. To lock the slugs while still making them easy to adjust, it is better to place a very small diameter soft white rubber elastic cord beside the slug. This is actually what Eddystone had in the first place, but those original rubber cords perished over time. Thin rubber cord is readily available; you can get it by removing the cotton covering from shirring elastic, often used in the elastic bands on underwear etc. It is readily available as single cords, or taken from flat multi-cord elastic bands sold in the sewing shops or on eBay. Far and away the best transistor to replace the originals in the RF systems is the AF178. No circuit changes are required, and these parts generally have higher gain and lower noise than the originals, making it perform better, especially on the higher shortwave bands. Also, they look more the part, similar in size to the originals, rather than the AF125-AF127 series, which are smaller. I have a lot more information on these radios, including how to make a suitable buffer for the local oscillator to gain a feed for an external counter etc. I have also designed and built entire radios with the same design philosophy as the EC-10, because I really admire it as a radio. This is documented in the PDF at siliconchip.au/link/ac7u Dr Hugo Holden, Buddina, Qld. SSB Shortwave Radio project appreciated I want to thank you for publishing the fascinating SSB Receiver project (June & July 2025; siliconchip.au/ Series/441). The electronically switched receiving antenna tuner, in particular, was new to me. It is refreshing to see an amateur radio related project in your pages. Peter Marks, VK3TPM, Drummond, Vic. A lucky strike I was reading Charles Kosina’s water pump repair in the Serviceman’s Log column, July 2025, reminded me of an incident that happened over 55 years ago when I was still young and lived at home in NSW. Outside our house was a poser pole that had consumers’ mains connecting to our house and both the immediate neighbour’s houses. This pole was struck by lightning and the result was spectacular. The pole was blown to pieces, with the roadway and our front yard covered in pieces of the pole. Luckily, it was a dead-end street with very little traffic, so no cars were damaged in the incident. The power pole had to be replaced, and we had no power while this was happening. Surprisingly, not much electrical damage resulted from the strike. The neighbour on one side had their fridge blown up, the neighbour on the other side had their electricity meter blown up, and our TV was damaged. The TV was a monochrome valve HMV set and amazingly, the only damage that it suffered was the power switch on the front of the TV. My mother called the serviceman. He found the fault, and he was surprised that the set still worked. He did not have a new switch with him, as it was a push-on, push-off type with some special characteristic, so he had to order a new switch. ourPCB LOCAL SERVICE <at> OVERSEAS PRICES AUSTRALIA PCB Manufacturing Full Turnkey Assembly Wiring Harnesses Solder Paste Stencils small or large volume orders premium-grade wiring low cost PCB assembly laser-cut and electropolished Instant Online Buying of Prototype PCBs www.ourpcb.com.au 6 Silicon Chip Australia's electronics magazine 0417 264 974 siliconchip.com.au Travel Gear 4 Less. Get the latest gear before you go. 65W Go Anywhere Power Bank Jumbo 54Wh capacity! A handy 65W power delivery charger with 15W mag safe compatible wireless charging. Charges phones, laptops, tablets and more! Plus it comes with global mains travel adapters for recharging wherever you travel. All supplied in a handy zip up case. 54Wh / 15000mAh. ✅ Works in 180+ countries! ✅ 15W magnetic wireless charging pad. ✅ 65W PD output for laptops. ✅ Inbuilt USB C charging cable. ✅ Zip-up carry case. 129 $ SAVE $33 A0323 20W Go Anywhere Power Bank Magnetic wireless charging for your phone and watch, plus standard 20W USB power delivery (PD) output for fast charging anywhere you go. Plus it comes with global mains travel adapters for recharging wherever you travel. All supplied in a handy zip up case. 27Wh / 10000mAh. ✅ Works in 180+ countries! ✅ 15W magnetic wireless charging pad. ✅ 20W PD output for laptops. ✅ Inbuilt USB C charging cable. ✅ Zip-up carry case. A 0319A 79 $20 $ Outbound Travel Adapters Wireless Charging Stand Handy bedside charger - folds up for travel use. A powerful all in one charging stand for you to keep your watch, earbuds and phone charged up and ready to go when you need it. Why pay airport prices? Pick up all the power adapters you need for less than $10ea! A0304A AU to Japan/US A 0305A AU to US 3 pin A 0306A AU to Euro A 0307A AU to UK SAVE 9 $ .95 50 $ SAVE 15% D 2325A* Your electronics supplier since 1976. Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or shop online 24/7 <at> altronics.com.au Build It Yourself Electronics Centre® © Altronics 2025. E&OE. Prices stated herein are only valid until 30/9/25 or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. In the meantime, he bypassed the switch so that we could still use the TV by switching it on and off at the power point. He later returned and replaced the switch, and the TV was back to normal. It appears that the power pole itself took most of the impact from the lightning, most likely because it had been soaked by rain before the lightning hit it. Bruce Pierson, Dundathu, Qld. More details on the Silvertone AM/FM radio I read with interest Associate Professor Graham Parslow’s article on the Silvertone Model 18 AM/FM radio in the August 2025 issue (siliconchip.au/Article/18646). I noticed that the article did not describe the dual-passband design of the first FM IF amplifier (V4). This stage can amplify either a 455kHz AM IF signal or a 10.7MHz FM IF signal with no circuit switching. Filtering of the IF component is provided by C27/C28 (100pF), not C3 (4μF), which has such a high value that it would filter out all the signals, including the desired program audio. Also note that resistor R22 and capacitor C29 provide the de-emphasis function, as specified in the FM broadcast standard. For a complete description of the ratio detector and dual-passband IF strips, see my article in the August 2021 issue on the Bush VTR103 AM/FM radio (siliconchip.au/ Article/14999). Ian Batty, Rosebud, Vic. Automatic LQ Meter with current-limited supply I noticed that the switch-mode voltage regulator in the Automatic LQ Meter (July 2024 issue; siliconchip.au/ Article/16321) doesn’t like starting with a current-limited power supply. I set my power supply current limit to 100mA initially, and it just maxed out. It did the same at 200mA. I thought there was a short circuit on the board, but I couldn’t find anything. At 500mA, it started OK. My power also supply ramps up the voltage over about 50ms rather than applying it quickly, which probably doesn’t help. Hopefully, this information will assist if others experience behaviour. Mike Hammer, Mordialloc, Vic. Comment: it’s common for switch-mode converters, especially boost converters like the MCP1661 in this circuit, to fail to start and draw high currents if the supply is current-limited. It is because they increase their duty cycle in response to the input voltage dropping to try to regulate the output voltage. This creates a positive feedback loop – the output voltage initially doesn’t reach as its target, so it increases the duty cycle, drawing more current. The power supply reduces the supply voltage in response, to try to reduce the current drawn by the load, forcing the boost converter to increase its duty cycle further. It ends up at its maximum duty cycle, while failing to achieve the target voltage. A trick for loading USB serial drivers in Windows With regards to Geoff Coppa’s letter in June 2025’s Mailbag (Serial driver trick for Windows 7), I’ve seen a similar problem a few times now when connecting a piece of 8 Silicon Chip scientific equipment to a computer running Windows (also USB-to-serial adaptors). I was able to find an easy fix online and am wondering if the same solution might also apply to the Programmable Frequency Divider. Windows applications can access a USB device via either the D2XX DLL (allowing direct access to the device), or an emulated serial port, but not both. For devices requiring a serial port, the Virtual COM Port (VCP) driver is automatically loaded by Windows. But sometimes, the driver isn’t enabled as default. In this case, the device appears in the “Universal Serial Bus Controller” section of Device Manager instead of in the “Ports (COM & LPT)” section, and isn’t assigned a COM port. The fix is to locate the device in the “Universal Serial Bus Controller” section (if you’re unsure, unplug the physical device and see which item disappears). Rightclick the correct device and select “Properties”. Under the “Advanced” tab, you should see a configuration box that says “Load VCP”. Place a tick in the box to enable it, then press OK. Now when you unplug and replug the USB device, the correct VCP driver should load and a new COM port will appear under “Ports (COM & LPT)”. I don’t have a Programmable Frequency Divider to try out, but this simple procedure is worth a try in case the fault is caused by the same problem. Peter Ihnat, Wollongong, NSW. A long history of electronics enthusiasm I have been a subscriber to Radio & Hobbies, Electronics Australia, and Silicon Chip magazines since their inception and have enjoyed all of them. But I can no longer see to read them, so I must discontinue subscribing. I am the most appreciative owner of the following kits that I put together. They are still going (I have repaired them a few times each): • An 8+8 stereo amplifier from Radio & Hobbies. The output of this amp is accomplished by two sets of matched AD161/162 germanium transistors. • A Playmaster AM-FM Stereo Tuner/Clock. • A Silicon Chip LP Doctor (Dick Smith Electronics kit K5425). • A Mullard 10+10 valve stereo amp using 6GW8 valves. • Plus many, many other kits, CDI ignitions, signal generators, pulse generators etc. Once again folks, thanks for the enjoyment you all have given me. But I am too old now to appreciate the articles. Mick Olden, Wyndham, WA. Thumbs up to detailed project design descriptions I really enjoyed the SmartProbe article in the July 2025 issue (siliconchip.au/Article/18515). I am interested in voltage monitoring, particularly accurate, low-power monitoring of batteries. So, as well as wanting to build one or two of these probes, I am interested in using the circuit for battery monitoring. The fact that the article was very detailed is very useful in adapting it to other uses. I liked how it went into detail on how the goal of 27μA idle consumption was met and exceeded. Each section of the circuit was explained in terms of achieving low consumption, including how the software was used to change modes of pins when they were not in use and how the display and sounder units were limited to save power. 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(08) 9373 9969 07_SIC_280825 99 (G140) $ 132 (D065) I was also interested in the use of the accelerometer as an input device, and the novel combination of the boost power supply with battery power. The firmware was explained in broad terms. Initialising drivers each time the device wakes up was a novel way to save some more battery power. All in all, it was very detailed. I look forward to building them. I would be interested to know what software tools the author used to program the device, as I have not worked with STM32 before. Grant Muir, Christchurch, NZ. Andrew Levido responds: Thanks for the kind words – I am glad you enjoyed the article. I develop on a Mac, using the VSCode (Visual Studio Code) editor with the “STM32Cube for Visual Studio Code” plugin, although you can use these on Windows or Linux. This uses GCC, CMake and Cortex-Debug. All of these tools are free. There are plenty of tutorials online to get you up and running. I recommend purchasing an ST-Link/V2 or one of the low-cost clones for a programmer/debugger, as they are supported by the plugin ‘out of the box’. Watch out for fake 4G antennas In the hope of saving your readers from wasting their money and their non-refundable lifetime, let me share this cautionary tale about an LTE antenna I bought from a large and very well-known Chinese online seller. It was sold as a 700MHz LTE Band 28 Yagi antenna for around $20. Upon receipt of the antenna, which incidentally promised an integral ’signal booster’, I discovered (surprise!) no user instructions. So I took the cover off the grey terminal box to try to find what kind of DC voltage was necessary to power the ‘signal booster’. There was just a junction box with some curiously large brass tabs. Conspicuously, it lacked any connection between the coax output cable and any active part of the antenna. This led me to check the passive elements, which were too short by about 30%. The driven (active) element, at 65mm long in total, was way too short for the claimed frequency. Instead of having two electrically separate sections, it was simply a single piece of tube connected to the aluminium boom. No insulation or air gap between the two sides of the driven element and/or the antenna boom. In summary, this device was never a 700MHz Yagi. It remains a puzzle why making fake stuff like this can be a profitable enterprise for the seller. Why wouldn’t you spend the tiny bit more on manufacturing cost to make it fit for purpose? Peter Felton, Coolongolook, NSW. Speedometer source code appreciated I’d like to thank Tim Blythman for providing the MPLAB X C source code for the GPS Speedometer (Circuit Notebook, July 2025). The structure of the code is easy to read and follow, and it is broken down into separate files, similar to how I would have done it. The concept of sharing follows the base purpose of Silicon Chip: learning and experimenting. I was surprised to see the use of ‘bit banging’ for I2C when the PIC16F1455 has an MSSP I2C module, but there are 100 ways to skin a cat. The bit-banging code may come in useful one day. Each method is valid and has useful elements. Inclusion of the C code with the article has made me less cautious when sharing a build in the future. I have investigated Visual Studio for Python, where following structures into modules seems all ‘secret squirrel’ to eventually disappear into a compiled ‘nothing to see here’. Visual Studio Code with Arduino and ESP modules is so abstracted from the hardware by utilising structures and macros, and layering down into HAL levels through even more structures. I thought I may have been missing out on something where most of my microcontroller projects are coded in MPLAB X with C. I have looked over the fence, but have now returned to the home paddock with MPLAB X and C. Thanks, Tim! Michael Harvey, Albury, NSW. Clock radios are made cheaply Regarding the comment in the July issue Mailbag (p10) on flat batteries causing clocks to sometimes speed up, It is interesting that the most accurate timebase for a clock, other than a watch, was in a Yaesu FRG-7700 communications receiver run by three 1.5V batteries (no GPS reference). The worst timekeepers seem to be the bedside clock radios with battery backup. I have yet to see any of these that maintain accurate time when falling back on the 9V battery during a mains failure. It appears that the timebases are voltage-sensitive and, in the quest for cheapness, have no (or poor) regulation. Once the battery cuts in, accuracy immediately goes down the gurgler. Marc Chick, Wangaratta, Vic. Comment: we suspect they’re designed to be good enough that they still wake you up in the morning, so you don’t SC miss work, but that’s about all you can rely on! 10 Silicon Chip Australia's electronics magazine siliconchip.com.au TOP GIFTS FOR TECH-LOVIN’ DADS MARK YOUR CALENDAR: Wed 20th of Aug to Sun 7th of Sept, 2025 NOW FROM $ 299 BUILD VOLUME UP TO 153.36 X 77.76 X 175MM PRINTS EXTREMELY FINE DETAILS 7" 9K MONO LCD REMOVABLE DIVIDER SAVE<at>$170 PRINT SPEED UP TO 70MM/H NOW ONLY GH1640 $ 299 SAVE $50 36L, 50L & 60L Convertible Dual Zone Fridge/Freezers Mars 4 9K Resin 3D Printer GH1640 / GH1642 / GH1644 TL4824 ADD A COVER FROM ONLY $29.95 20 . 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PACK SERIOUS POWER IN A SMALL SPACE $ ONLY NEW PD100W 149 60,000mAh Power Bank MB3869 ^ALL PRICES SHOWN IN AUD - VISIT JAYCAR.CO.NZ FOR NZ PRICES Subscribe to AUGUST 2025 ISSN 1030-2662 08 The VERY BEST DIY Projects ! Mic th e Mouse 9 771030 266001 $13 00* NZ $13 90 INC GST INC GST Ducted Heat Transfer Controller RP2350B USB-C Power Monitor Pre-Assembled Development Board Australia’s top electronics magazine Measure current, voltage, power, Silicon Chip is one of the best DIY electronics magazines in the world. 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SpaceX; July-August 2025 Mic the Mouse; August 2025 RP2350B Development Board; August 2025 An online issue is perfect for those who don’t want too much clutter around the house and is the same price worldwide. Issues can be viewed online, or downloaded as a PDF. To start your subscription go to siliconchip.com.au/Shop/Subscribe siliconchip.com.au Australia's electronics magazine September 2025  15 DRONES By Dr David Maddison, VK3DSM Image source: https://unsplash.com/photos/black-droneon-air-over-cloudy-sky-at-daytime-JPAfSd_acI8 Drones are now commonly used for hobby purposes as well as commercial applications like aerial photography, and for military purposes. This is the result of numerous technological advances, such as satellite navigation for guidance, MEMS accelerometers, high-energy-density batteries and miniaturised control circuitry. T hree-dimensional (3D) printing has also helped to accelerate the proliferation of drones. They are so widespread that they are now often used for criminal purposes and even for terrorist attacks, hence the need for defence against drones. Terminology There are many names for what are popularly known as drones. This article is mostly about the type that fly. Terms for these include: • UAV (unmanned aerial vehicle) • UAS (unmanned aircraft system) • SUAS (small unmanned aerial system) – under 25kg • RPAS (remotely piloted aircraft system) • RPAV or RPV (remotely piloted [aerial] vehicle) • UAVS (unmanned aircraft vehicle system) • UCAV or CAV ([unmanned] combat aerial vehicle) – military types Other types of drones might be landbased and perform jobs such as mowing lawns, agricultural tasks, deliveries, military tasks (eg, reconnaissance or attack/defence) or inspections. Such 16 Silicon Chip devices are called unmanned ground vehicles (UGVs), ground drones or ground robots. Many such drones are used for agricultural purposes. We published an article on drones for agricultural uses in the June 2018 issue (siliconchip.au/Article/11097). There are also unmanned underwater vehicles (UUVs), also known as or autonomous underwater vehicles (AUVs). We covered these in their own article in the September 2015 issue (siliconchip.au/Article/9002). There are also drone ships, known as unmanned/uncrewed surface vehicles (USVs) or autonomous surface vessels (ASVs). Drone is a general, informal term for any of the above. For convenience, we will mostly use that term throughout the remainder of this article to refer to UAVs. Drone history Drones have been around for a surprisingly long time, at least in their more primitive forms. Perhaps unsurprisingly, early drones were mostly for military applications. However, the lack of precision navigation such as Australia's electronics magazine GPS meant that they were generally ineffective at hitting the desired targets or performing other precision tasks, unless they were remotely controlled by an operator within visual range. Some notable examples are as follows (this is not an exhaustive list): 1849 Arguably the first use of a drone-like device in warfare, the Austrian Army attacked Venice with balloon bombs set with half-hour fuses. It was not a success; the expression “own goal” aptly describes the outcome. 1898 Nikola Tesla demonstrated a radio-controlled boat (described in some detail on page 15 of our November 2024 issue; siliconchip.com.au/ Series/427). 1914 The Royal Aircraft Factory in Britain designed an RPV, which they called an Aerial Target (AT) to fool their enemies into thinking it was a test target vehicle. Its true purpose was to attack German airships and as a flying bomb. It was designed by Henry P. Folland, with radio equipment designed by Archibald M. Low. It was first built in 1916 – see Fig.1. It carried around 40kg of explosives and was designed to be controlled siliconchip.com.au either from a ground station or another plane. It was a high-wing monoplane weighing 227kg, launched by catapult and landed on skids. Flight tests in 1917 were unsuccessful, but the feasibility of RPVs was proven. The AT Mark II (Fig.2) was probably built by Sopwith. It was designed to carry 23kg of explosives, but was never tested. 1917 The Hewitt-Sperry Automatic Airplane was first tested by the US Navy; it is considered by some to be the first cruise missile. It was stabilised by Sperry gyroscopes and flew a preset course. However, it was not adopted by the Navy, partly because it had insufficient accuracy to hit a ship. 1918 The Kettering Bug was an experimental unmanned aerial torpedo developed for the US Army that could strike targets at a range of 121km. It was never used in combat. 1935 The DH.82B Queen Bee was a radio-controlled variant of the Tiger Moth, used as a target drone for training antiaircraft gunners. About 470 were built in total. The term drone apparently came into use at this time as a reference to the male bee seeking the queen bee in one fatal flight. 1937 US Navy Curtiss Fledgling trainer aircraft were modified to make radio-controlled target practice drones, designated A3. In 1938, it was also experimentally rammed into a ship; a forerunner of guided weapons. 1939 The Radioplane Company made a variety of radio-controlled target practice drones for the US military, manufacturing them by the thousands. Models included the OQ-1 (RP-4), OQ-2 (RP-5) and OQ-3, among others – see Figs.3, 4 & 5. 1944 (June) The German V-1 flying bomb was the first mass-produced, operational cruise missile. Like the Hewitt-Sperry device, it followed a preset course using gyroscopes and autopilot controls, but unlike its American predecessor, the V-1 was used in combat. Over 9,000 were launched against London alone (more than 30,000 in total), causing substantial damage, injuring and killing many people. Its distinctive buzzing pulse-jet engine earned it the nickname “buzz bomb”. Its success marked a turning point in the military potential of unmanned aircraft. 1944 (August) The United States, under the Army Air Force’s Aphrodite siliconchip.com.au Fig.1: the Aerial Target RPV, built in 1916. Source: https://shvachko.net/?p=1378 Fig.2: the British Aerial Target Mark II RPV, likely built by Sopwith. Source: https://w.wiki/EDQ7 Fig.3: Norma Jeane Dougherty, later known as Marilyn Monroe, assembles an RP-5 (OQ-2) drone in 1944 or 1945. Source: https://w.wiki/EDQ8 Fig.4: a Radioplane OQ-3 target drone in 1945, ready for launch. Source: https://w.wiki/EDQ9 Fig.5: the OQ-2A aerial target of 1941. Source: www.nationalmuseum.af.mil/Upcoming/Photos/igphoto/2001562776 Australia's electronics magazine September 2025  17 and Navy’s Anvil programs, modified worn out B-17, B-24 and PBY4-1 bombers to operate under remote control from another ‘mothership’ aircraft, filled them with explosives and flew them into heavily defended German targets. Television pictures of the controlled aircraft’s instrument panel were relayed to the mothership. However, the program was a huge failure. 1951 The Ryan Firebee series of target drones led to the development of the highly successful Ryan Model 147 “Lightning Bug” reconnaissance drone series, which were used from 1962, including in the Vietnam war. Archibald Montgomery Low, 1888-1956 Archibald is known as the “father of radio guidance systems”. He designed the control system for the first drone, the British “Aerial Target”, as well as guided rockets and torpedoes. He was a prolific inventor, author and futurist and was also involved in the early development of television. 1962 The SDI Surveillance System was used by the British Royal Artillery for observation over the battlefield, and to locate targets, although there is little information available about it. 1969 Israel used a drone to photograph enemy positions on the 7th of July 1969. Conventional aircraft were useless because they had to fly too high to avoid ground-to-air missiles, so the photos showed little. An officer called Shabtai Brill conceived the idea of using a radio-controlled aircraft purchased in a toy store that he fitted with a 35mm film camera, with a timer to take pictures every ten seconds. The mission was a huge success, but it was forgotten until after the 1973 Yom Kippur war. That led to Israel becoming a dominant player in the drone industry; it still is today. 2001 After the September 11th terrorist attacks, the United States General Atomics MQ-1 Predator saw widespread (and heavily publicised) use in Afghanistan, bombing enemy positions. 2013 Jeff Bezos announced that Amazon was considering using drones as a package delivery method. 2022 Russia’s invasion of Ukraine marked the first large-scale conflict with widespread use of both purpose-­ built military and improvised civilian drones. Ukraine used consumer-grade quadcopters for reconnaissance and artillery spotting, while both sides deployed loitering munitions, kamikaze drones and electronic warfare systems. The war demonstrated how lowcost drones could be highly effective in modern combat, revolutionising battlefield tactics. Thousands of expensive military targets have been destroyed by drones to date in this war, including numerous tanks, surface-­ to-air missile systems, ammunition depots and more. Drone types Drones come in a variety of sizes, from the size of an insect to full-size fighter jets and bombers. They include the following: ● Tricopter – a relatively rare type of drone with three rotors. ● Quadcopter – an aircraft with four rotors, designed for vertical take-off and landing (VTOL). ● Multirotor – similar to a quadcopter but with more than four rotors. These include hexacopters (with six rotors) and octocopters (eight rotors). ● Fixed-wing – similar to a conventional aircraft. ● Hybrid-VTOL – these can take off and land vertically but fly horizontally, like a conventional aircraft. They may or may not have tilting rotors. ● Balloon drones – these use hydrogen or helium for buoyancy. They may float with the wind, or have guidance using propellers. An example is the “h-aero” (more on that later). ● Passenger drones – also known as autonomous aerial vehicles (AAVs), they are pilotless and designed to carry passengers short or medium distances, such as from an airport to a city centre. ● Ground drones with wheels or tracks. ● Sea drones in the form of a boat or submarine. While most drones are intended to be reused, some drones are regarded as expendable, especially some used in military applications. Drone categories and uses The US Department of Defense categorises drones according to the scheme shown in Table 1. The higher the group number, the more capable the drone is. Among the many uses of drones are recreation, aerial photography (eg, real estate & sports events), surveillance, Fig.6: a few possible examples of civilian uses for drones. Source: www.gao.gov/drone-operations 18 Silicon Chip Australia's electronics magazine siliconchip.com.au package delivery, search & rescue, rail inspection, power line inspection, agricultural inspection & spraying, maintenance (eg, washing buildings, solar panels or mowing lawns), military and others uses. Fig.6 depicts some of these applications. Drone navigation More basic drones, such as toys and early models, are guided by a human operator who can observe the vehicle directly or via a video link. More advanced drones can be programmed with a flight path, which the drone follows using satellite navigation (GNSS; eg, GPS). Most drones also use inertial measurement units (IMUs) to ensure they are orientated correctly. Advanced drones may include altimeters (usually based on air pressure) and electronic compasses (often integrated into the IMU). As drones can be disabled by disruption of their data links or GNSS (global navigation satellite system) signals, more advanced drones, especially military ones, can be autonomous, using artificial intelligence (AI) to guide them. They may also use sensors like LiDAR (light detection and ranging), cameras, radar and other inputs. Optical flow sensors can be used; these analyse images from the drone camera to determine its movement over time. They can also use a system called SLAM (simultaneous location and mapping) to determine their position and movement. Data from LiDAR and IMUs is used in this type of navigation, among other inputs. SLAM is also used Table 1 – US DoD drone categories Group Maximum weight Typical altitude Speed 1 0-9kg <366m (1200ft) <185km/h 2 9.5-25kg <1067m (3500ft) <463km/h 3 <599kg <5486m (18,000ft) <463km/h 4 >599kg <5486m (18,000ft) Any 5 >599kg >5486km (18,000ft) Any in self-driving cars and even robotic vacuum cleaners. Some drones, which we will discuss later, have fibre optic data links to enable them to operate without wireless data links or GPS/GNSS, and without needing to be autonomous. For hobbyist drones, there are many navigation systems to choose from, including open-source software like ArduPilot (https://ardupilot.org) and flight controller hardware like that shown in Figs.8 & 7. Even though ArduPilot was developed by hobbyists, it can control some very advanced drones and is used commercially. Even Boeing has used it for experimental cargo delivery drones. Apart from UAVs, it can also control UGVs (ground), USVs (water) and UUVs (underwater). Power sources Drones can be powered by a variety of sources: ● Batteries, typically rechargeable lithium-ion/LiPo types. These are the norm for hobby drones. For a non-fixed-wing (VTOL) drone, a typical flight duration is up to 10 minutes, although military or commercial drones can last 30-60 minutes. A fixed-wing electric drone may have an endurance of several hours. These drones are relatively quiet and have low maintenance requirements. ● Internal combustion engine (ICE) drones use a fuel like petrol, diesel or kerosene. They have much longer flight durations due to the higher energy density of liquid fuels compared to batteries, but may be noisier and require more maintenance. Their flight duration can be up to around 16 hours for a fixed-wing type or eight hours for a VTOL type, like the IAI APUS 25 (siliconchip.au/link/ac6x). ● External combustion engine drones use a turbojet engine. They are fast but have high fuel consumption compared to ICE drones. An example is the Boeing MQ-28 Fox Bat being developed for the RAAF. ● Fuel cell powered drones are relatively new and experimental. They may have better endurance than battery types. They can use hydrogen as the fuel, kept as a gas in high-­pressure cylinders. Storage of hydrogen as a cryogenic fluid is possible but requires a lot of infrastructure and management. Australian company Stralis has developed a hydrogen fuel cell they Fig.7: drone mission planner software. Source: www.ardupilot. co.uk Fig.8: an ArduPilot Mega (APM) flight controller. Source: www.ardupilot.co.uk siliconchip.com.au Australia's electronics magazine September 2025  19 say can power a hydrogen-electric aircraft for ten times longer than batteries. ● Hybrid drones operate much like hybrid cars, with an ICE to produce power, driving electric motors and/ or recharging batteries. An unusual implementation of a hybrid commercial/military drone is the Jabiru JCQ50 “Donkey”, which has coaxial rotors for vertical lift directly driven by an ICE, plus electric motors for directional control. ● Solar power – some specialised fixed-wing drones are solar-powered but they have to be high-efficiency, lightweight drones designed for long endurance. The solar cells can charge batteries and drive propellers during the day, while batteries drive the propellers at night. ● Nuclear – a nuclear power source will be used to power the Dragonfly drone to explore Saturn’s moon Titan (more on that later). Such systems are not considered suitable for use on Earth for several reasons. ● Balloon drones require no power to provide lift; it is provided by a lifting gas like helium or hydrogen. So they have an almost indefinite flight duration, until the gas eventually leaks out (no lightweight material can hold these gases indefinitely). Control for onboard electronics or propellers for station-keeping can be provided by solar panels. Example drones Some notable examples of drones are as follows: drones (see Fig.11). It operates in the Tolleson, Arizona area and can deliver packages of around 2.3kg within an hour of placing an order. The drone was designed for package delivery, with redundant systems, including a second flight controller. This ensures there is no single point of failure that will allow loss of control of the drone. It has also been designed to minimise noise. It has a camera and uses machine learning to identify obstacles such as clotheslines, trampolines, humans, animals and other aircraft which may not show up in satellite imagery. It has received regulatory certification with the US FAA for beyond-line-of-sight operations. Fig.9: an anti-drone gun at the Pope’s funeral. Source: https://x.com/ma777hew/ status/1916067221488480319/photo/1 300 (www.avinc.com/lms/switchblade) or so-called kamikaze drone is used by the Australian military – see Fig.10. Its procurement was announced in 2024. It is a precision loitering drone; it can fly to an area and a decision can be made whether to engage a target or call off the mission. It weighs 1.7kg, has a range of 30km or a loitering time of 20 minutes, flies at up to 150m altitude and has a loiter speed of 101km/h. It is launched from a tube, after which its wings fold out. Anti-drone device On a news item about the Pope’s funeral, we saw a security official holding an apparent anti-drone device (Fig.9). It is the CPM-­ WATSONPLUS by CPM Elettronica (www. cpmelettronica.com). Australia Post parcel delivery Australia Post is looking at concepts of future mail and parcel delivery via drones. One idea is a ground drone (Fig.12). Another is a UAV (see https://x.com/auspost/­ status/720786994511491072). Balloon drones Balloon drones have the advantage of extremely long flight times as their lift comes from a gas like helium or hydrogen. They can be stationed in the upper atmosphere, where wind is minimal, so they can stay on station using small amounts of solar power and AeroVironment Switchblade The AeroVironment Switchblade Amazon delivery drones In November 2024, Amazon released its MK30 delivery drone, with twice the range of its previous delivery Fig.10: the launch of a SwitchBlade 300 drone, used by the Australian Army. Source: https://w.wiki/EDQA Fig.11: an Amazon MK30 delivery drone, now in service in Arizona, USA. Source: www.aboutamazon.com/news/operations/mk30-drone-amazondelivery-packages 20 Silicon Chip Australia's electronics magazine siliconchip.com.au propellers. This was covered in detail in our August 2023 article on High-­ Altitude Aerial Platforms (HAAPs; siliconchip.au/Article/15894). These drones can be used for tasks like bushfire surveillance (or other types of surveillance), radio relays, and scientific research. In our June 2025 Airshow article (siliconchip.au/Article/18303) we mentioned that the Australian company Stratoship (https://stratoship.au) is developing balloon drones. Another company that produces balloon drones for lower altitude use is h-aero (https:// h-aero.com/en) – see Fig.13. Black Hornet 4 nano drone The Black Hornet 4 (Fig.14) is a miniature drone built by Teledyne (www.flir.com) with thermal imaging and optical cameras, the latter having low-light capability. It is tolerant of wind, flies at up to 36km/h, has obstacle avoidance capabilities, weighs 70g and can fly for 30 minutes. Most other specifications of this model are not published, but earlier models had a transmission range of 1km. These are used by numerous militaries, including Australia’s. According to Wikipedia, in 2015, the original model cost US$195,000 each. A recent video claims the cost as US$40,000. Such is the cost of military procurement. You can buy a similar-looking one for $100-200 online, but perhaps with a little less capability. For more information, see the video at https:// youtu.be/DMJgq2tpNJA Boeing MQ-28 Ghost Bat Boeing Australia is developing the MQ-28 Ghost Bat for the RAAF. We reported on this vehicle in our article on the Avalon Airshow (June 2025; siliconchip.au/Article/18303). It is a stealthy, multi-role UCAV. Fig.12: Australia Post’s idea of using a ground-based drone to deliver mail and parcels in the future, compared with a traditional postie on a motorcycle. Source: https://auspost.com.au/content/dam/corp/startrack-insights/customerexperience/photo-robot-delivery-machine.jpg Fig.13: the h-aero balloon drone. Source: https://cloud.aicanfly.de/index.php/s/xfnayzmeKJzPs8P Building maintenance drones Drones can be used to wash buildings or solar panels. An example is the Joyance JTC30T (https://joyance.tech), shown washing solar panels in Fig.15. DefendTex D40 The DefendTex D40 is an Australian-­ made drone for military purposes (see Fig.16). The manufacturer states it can be launched from a standard 40mm grenade launcher; it is low in cost, can carry an intelligence gathering payload, can swarm with other drones, siliconchip.com.au Fig.14: the Black Hornet Nano drone. Source: www.techeblog.com/teledyne-flir-black-hornet-4-nano-drone Australia's electronics magazine September 2025  21 Fig.15 (left): Joyance’s JTC30T cleaning drone. Source: www.spreaderdrone.com/Solar-panel-washing-drone-roofcleaning-drone-in-USA-pd524419658.html Fig.16: the DefendTex D40. Source: www.defendtex.com/uav can perform autonomous flight and is waterproof. Little else about it is known. De-icing wind turbines A Latvian company, Aerones (https://aerones.com), has developed a drone for deicing wind turbine blades (Fig.17). This can be a problem in North America and Europe. The drone is supplied with electricity from a cable, and hot water or deicing fluid via a hose to clean the turbine blades. It has multiple redundancy and safety features, such as onboard batteries, so that the drone can land safely in the event of a power failure. For more details, see the video at https://youtu. be/mP5LZYpFggM Dragonfly drone Dragonfly (https://dragonfly.jhuapl. edu), shown in Fig.18, is a multi-rotor drone that will be used to explore one of Saturn’s moons, Titan. It is planned to be launched in 2028 and will land in 2034. It will use a nuclear power source, a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), like the Curiosity rover on Mars. The nuclear power source is too weak to power the drone in real-time. Therefore, the plan is for the MMRTG to charge a lithium-ion battery, which will power it in flight, up to a distance of 16km with a duration of 30 minutes on each battery charge. When Dragonfly lands, the 134Ah battery will be recharged. Dragonfly will carry various scientific instruments. It is surprisingly large, weighing 450kg, and each of its eight rotors is 1.35m in diameter. Each ‘corner’ of the quadcopter will have two rotors and two motors; the 22 Silicon Chip aircraft is designed to be able to tolerate the loss of one rotor and/or one motor. It will be launched on a SpaceX Falcon Heavy. Dragonfly will navigate using an optical system to recognise visual landmarks as a reference; LiDAR to detect hazards; inertial measurement units (IMUs) to track the drone’s orientation, velocity, and acceleration; plus pressure and wind sensors. It will make autonomous flight and landing decisions. Delivery drones Apart from the Australia Post and Amazon delivery drones mentioned above, we covered the Australian Quickstep Brolga (www.quickstep. com.au) and Jabiru’s JCQ50 “Donkey” cargo drone (https://jabiru.aero/jcq50) in our most recent Airshow article. Domestic ground drones Common domestic ground drones include robotic lawn mowers, robotic vacuums and mops. Energy-harvesting drone Danish researchers at the University of Southern Denmark have developed a self-charging drone that finds and attaches to high voltage power cables using millimetre-wave radar and then inductively charges its onboard batteries. The purpose of these drones is to inspect the same cables they harvest energy from. See Fig.19, siliconchip.au/link/ac66 and the video at https://youtu.be/C-uekD6VTIQ for more details. Fibre-optic guided drones In the Russia-Ukraine war, both sides are actively developing and using drones that are controlled via optical fibres. According to Forbes (siliconchip.au/link/ac67), the Kalashnikov subsidiary company ZALA makes “Product 55”, an unjammable quadcopter. Such a drone was discovered by the Ukrainian military blogger Serhii, who asked what the ‘egg-shaped’ Fig.19: a Danish energy-harvesting power line inspection drone attached to a power line to recharge. Source: https://youtu.be/C-uekD6VTIQ Australia's electronics magazine siliconchip.com.au Fig.17: Aerones’ wind turbine deicing drone. Source: https://wonderfulengineering.com/this-giant-drone-cande-ice-wind-turbines-in-few-minutes contraption was (see Fig.20). It turned out to be a spool of optical fibre for data and control, which held over 10km of cable! This is necessary as both sides field extensive RF and GNSS jamming technology to make the other sides’ use of drones difficult or impossible. There is actually a long history of guiding torpedoes and missiles with wire or optical fibre like this. For example, the Germans experimented with wire guidance for missiles in 1944, and US TOW (tube-launched, optically tracked, wire-guided) antitank missiles are in common use, even today. Fishing drones Drone fishing is a style of fishing where a drone is used to deliver the rig and bait far further than it can be manually cast. Distances of up to 500m are possible. This enables the fisher to get access to deeper water, and perhaps a different species of fish. According to the August 2013 issue Fig.18: a rendering of Dragonfly drone to be used on Saturn’s moon, Titan. Source: https://science.nasa.gov/wp-content/ uploads/2024/04/dragonfly-inflight.jpg of Popular Mechanics, the first person to catch a fish with a drone was Dave Darg, in 2013. Drones also allow visual examination of a proposed fishing area. Some drone fishers hang the line and bait directly from the drone rather than using the drone to haul the line out from a rod and reel. Considerations are the line release mechanism and whether to purchase a water-resistant drone. Various companies sell drones and accessories for fishing; try searching for “fishing drones”. If in Australia, make sure to follow CASA’s rules. Floor-cleaning drones Many commercial operations such as airports, hospitals and supermarkets now have their floors cleaned by drones. An example is the Gausium Phantas; see https://gausium.com Ingenuity helicopter The Ingenuity helicopter (Fig.21) was the first flying vehicle on another planet. It was delivered as part of the Mars 2020 mission, along with the Perseverance ground rover. It was intended to last only five flights, but completed 72 flights before a rotor blade failure. The failure was attributed to a blade strike on the ground due to the inability of the navigation system to cope with an area of featureless terrain. It weighed 1.4kg, had a motor power of 350W and used the Zigbee protocol for communications back to the rover. It was powered by six Sony/Murata US18650VTC4 lithium-ion batteries (which anyone can buy), which were recharged by a solar panel between flights. Its cumulative flight time was just over two hours, and it covered 17km. Due to the extremely low air pressure on Mars, the rotor blades had to spin extremely fast; between 2400 and 2900 RPM despite their large diameter of 1.2m. Surprisingly, this is comparable with small model helicopters on Earth, such as the Blade Fusion 480, which Fig.20 (left): Serhii’s photo of a Russian optic-fibre guided drone found in Ukraine. The optical fibre spool is outlined. Source: https://t.me/serhii_flash/2413 Fig.21 (above): the Ingenuity helicopter drone on Mars. Source: NASA siliconchip.com.au Australia's electronics magazine September 2025  23 has a 1.1m rotor diameter with rotor speeds up to 3000 RPM. General Atomics MQ-1 Predator This US drone became famous for its use in 2001 in Afghanistan, with other appearances in Bosnia, Iraq, Libya, Pakistan, Somalia, Syria, Yemen and Yugoslavia – see Fig.22. It was in production from 1995 to 2018, and could be used for either reconnaissance or attack. It had a cruise speed of 130km/h, a 24 hour endurance, a range of 1250km, a service ceiling of 7600m and an 86kW Rotax four-cylinder air-cooled turbocharged engine. Fig.22: an MQ-1 Predator surveillance/attack drone. Source: https://w.wiki/EDQG Fig.23: an artist’s impression of the Lockheed Martin RQ-170 Sentinel stealth drone. Source: https://w.wiki/EDQH Lockheed Martin RQ-170 Sentinel The RQ-170 (Fig.23) is a stealth reconnaissance drone introduced in 2007. Very little is known about it. It is a flying wing design, somewhat like the Northrop B-2 Spirit; about 20-30 are believed to be in service. It was produced at the famous Skunkworks facilities, where America’s most advanced and secret aerospace projects are developed. It has a wingspan of 11.6m and a length of 4.5m. It is powered by a turbofan engine and is thought to have an endurance of 5-6 hours and a service ceiling of 15,000m (49,000ft). Long-range consumer drones We saw a quadcopter drone available in Australia at https://au.aeroodrones. com/products/aeroo-pro that is stated to be able to deliver a 1kg payload with a flight time up to 45 minutes and a 10km range (note CASA rules, see below, when considering the flight range). Lunar drones We mentioned the Australian-made lunar rover Roo-ver in our article on the 2025 Airshow. Another interesting lunar drone is the Micro Nova “Grace”, a unique hopping drone that uses a rocket engine to move about – see Fig.25. It landed on the moon on the 6th of March 2025, as part of the IM-2 mission. Unfortunately, the lander carrying it fell over and the mission failed. Fig.24: an ornithopter drone. Source: www.hackster.io/news/swifts-provideinspiration-for-lightweight-quiet-and-maneuverable-ornithopter-droned0e2f8a0785c Medical drones Some drones are used to deliver medical supplies or equipment, such as defibrillators. These are designed so non-specialists can use them to Australia's electronics magazine siliconchip.com.au 24 Silicon Chip provide first aid before emergency services arrive. Ornithopter drones Ornithopters are aircraft that fly by flapping wings like birds, bats and insects. Researchers at Nanyang Technological University, the Defence Science and Technology Group, Qingdao University of Technology, the University of South Australia and National Chiao Tung University developed a 26g, 200mm-long ornithopter flapping wing drone (see Fig.24). It is quiet and energy efficient, consuming 40% less energy than the production of equivalent thrust from a propeller. Passenger drones Companies that are developing unpiloted drones to convey passengers as air taxis include: ● Archer Aviation (https://archer. com) ● Boeing (https://wisk.aero) ● CityAirbus (siliconchip.au/link/ ac6a) ● Ehang (www.ehang.com) ● Joby Aviation (www.jobyaviation.­ com) ● Volocopter (www.volocopter. com/en) The VoloCity by Volocopter (Fig.26) may be furthest down the certification pathway, and will commence operations with a pilot soon. It is intended to be pilotless in the future. It has two seats, 18 rotors, nine swappable batteries for a fast turnaround, a maximum takeoff weight of 1000kg, a range of 20km and a cruise speed of 90km/h. It has undergone 2000 test flights to date. Power line inspection Drones can be equipped with UV cameras for inspecting of power lines. Ultraviolet light emanates from a corona discharge, which can indicate a faulty power line. Solar-powered micro drones Researchers at Beihang University have produced a tiny solar powered drone weighing just 4.21g with a diameter of 20cm (see Fig.27). The vehicle is called the CoulombFly and uses an electrostatic motor rather than a traditional AC or DC motor. An electrostatic motor utilises the attraction and siliconchip.com.au repulsion of electric charges rather than magnetic fields. Electrostatic motors require high voltages to operate, so the CoulombFly contains a boost converter to boost less than 100V from the solar cells to over 9kV. This prototype device does not carry a payload. Solar surveillance drone Some drones using solar panels have an especially long flight time. The Zephyr High Altitude Platform Station (HAPS) is a high-persistence solar-powered surveillance drone that has been developed by Airbus subsidiary AALTO (www.aaltohaps.com). It has a 25m wingspan, weighs 75kg, operates above 18km (59,000ft) and runs on batteries that are charged by solar panels during the day. It has a potential mission duration of many months. See our August 2023 article on High-Altitude Aerial Platforms (HAPS; siliconchip.au/Article/15894). Stealthy drones Is it a bird? Is it a plane? Guard from Above (https://guardfromabove.com) have developed the Evolution Eagle UAS for covert surveillance. It blends into the natural environment – that’s a fancy way of saying it looks like a bird ( s e e the photo on the left). Its suggested uses are intelligence, border patrol, public safety, wildlife control and detection of poachers. Swarming drones Swarming drones act in groups and can have either military or civilian applications. A robotic swarm is a group of robots that behave in a swarm-like manner (like a flock of birds or swarm of insects) without centralised control (except perhaps overall direction). The members interact with other members of the swarm and the environment at large. Robotic swarms can exhibit complex behaviour, but are governed by a small set of principles as follows: maintain separation to avoid collisions, coordinate movement to maintain the average heading of neighbours (alignment), and keep the group together as a whole by maintaining a group ‘centre of mass’. To accomplish this, there may be many simple robots of limited ability Australia's electronics magazine Fig.25: the Micro Nova “Grace” lunar hopping drone. Source: www. intuitivemachines.com/micro-nova Fig.26: VoloCity is said to be quieter than a helicopter. Source: www. volocopter.com/en/newsroom/vc-jetsystems Fig.27: the prototype solar-powered CoulombFly drone, which uses an electrostatic motor. Source: Xinhua News – siliconchip.au/link/ac6d September 2025  25 that can communicate with all the others to follow the above principles. These principles apply to swarming animals too. Robotic swarms have some benefits: ● Fault tolerance; the failure of one device does not have a major impact. ● The swarm can be scaled up or down in size as required. ● A swarm is flexible and can be programmed to perform many different tasks. ● The swarm may be more cost-­ effective than a few more expensive drones. Military applications include surveillance and/or attack. Civilian applications include drone shows (see Fig.28). the event the cable is severed. Typical altitudes achieved by tethered drones are 60-120m, or even as high as 200m, depending on regulatory limits. Various hobby or professional drones can be converted to tethered operation with appropriate accessories. Example accessories to convert some DJI drones to tethered operation can be seen at siliconchip.au/ link/ac6b WASP The WASP AE, built by AeroVironment (https://avinc.com), was introduced in 2012 and is used by the US military and Australian Army, among others – see Fig.29. It is in the process of being phased out. It weighs 430g, has an endurance of 45 minutes, a Tethered drones range of 5km, an altitude of up to 300m These are like conventional free-­ (1000ft) and a top speed up to 65km/h. flying drones, but they have a wire connecting them to the ground, over Drones in warfare which power and data can be transMilitary drones need no longer be mitted. This theoretically gives them multi-million-dollar machines used an indefinite flight duration; or at least by well-funded militaries; cheap conuntil the motors or other components sumer or home-made drones can be need maintenance or wear out. easily adapted or constructed for miliThere are obvious limitations on the tary purposes. Hobby drones are plenlength of wire that can be supported tiful, cheap, easy to transport and easy (but also see the section on drones with to set up. The cost benefit is hugely optical fibre data links). Advantages asymmetrical. include relative ease of operation; no As an example, a properly equipped RF emissions (making them stealthy); $300 drone can destroy a $30 million imperviousness to jamming; the abil- asset like a parked aircraft or tank. For ity to perform persistent surveillance; example, see the video about Ukraine’s and the ability to be attached to a mov- use of hobby drones at https://youtu. ing vehicle. be/hWxUt41DlB4 One application is as a self-­ Ukraine has developed its own contained radio relay, like the MPU5 indigenous drone capability and Mobile Ad Hoc Networking (MANET) makes its own drones without reliance radio (www.persistentsystems.com/ on imported components, or at least mpu5). Tethered drones usually have can use generic imported components a backup battery to return home in with no reliance on just one or a few suppliers (https://en.victory-drones. com). Ukraine has also converted conventional aircraft such as small Cessnas into drones. Australia also supplies cardboard ‘flat pack’ drones to Ukraine (www. sypaq.com.au). In Ukraine, inexpensive ground and sea-based drones are also being used for military purposes. Drone rules The rules for usage of recreation and other drones are constantly evolving. Notably, for recreational use, there are height restrictions, highly restricted or prohibited usage in public parks and national parks, a ban on beyond-­ visual-range flying, transmitter power and frequency limits, and many other restrictions. If you plan to fly a drone in Australia, familiarise yourself with the rules and regulations. There is information at www.casa.gov.au/drones and www. casa.gov.au/drones/drone-rules Commercial drone operators need to be licensed. Also, in Australia, any drone used for commercial purposes needs to be registered. There was a proposal for hobbyist drones over 250g to be registered, but this has been delayed. At the time of writing, the CASA website states, “In some cases, you don’t need to register your drone, such as when: … you don’t intend to fly it … you’re only flying for sport or recreation, including at CASA-approved model airfields”. Approved commercial drone delivery services in Australia include the Australian company Swoop Aero, now called Kite Aero (https://kite.aero) and Wing Aviation (https://wing.com). Kite Aero’s drone can deliver a 3kg payload Fig.28: a drone show made using Skybrush. Fig.29: soldiers from the Australian Army with a WASP AE drone on left and a PD-100 Black Hornet drone on right. Source: Sgt. Janine Fabre, Australian Defence 26 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.30 (left): the R&S Ardronis protection package. Depending on the model, it can detect the radio signal from a drone, even before it is launched; can determine the position of the drone; and can disrupt radio signals from the drone. Source: www.rohde-schwarz.com/de/unternehmen/magazine/drohnenabwehr_251858.html Fig.31 (right): the Discovair CUAS acoustic detection sensor. Source: www.sqhead.com/drone-detection over 175km at a speed of 122km/h (see Fig.32). Wing’s drone can deliver a 2.3kg payload over 10km at a speed of 105km/h. Kite Aero is approved to deliver goods in Toowoomba & Goondiwindi (Qld), while Wing Aviation (owned by the parent company of Google) is approved to deliver goods in areas of East Melbourne (Vic), North Canberra (ACT) and Logan (Qld). Defending against drones Defence against hostile drones can be either active or passive. The best approach depends on whether the drone is using radio control and satellite navigation (GPS or other GNSS) or is fully autonomous. An autonomous drone cannot be disabled by disrupting radio signals, as it does not use any. Active approaches for drones under external control and navigation include disruption or jamming of radio signals or navigation signals, causing the drone to crash; or spoofing of GNSS to make the drone think it is somewhere other than the intended place. Another approach is to ‘hack’ into the drone to assume control of it (see D-Fend Solutions; https://dfendsolutions.com). Other defences involve the destruction of the drone using a laser or projectiles. The ‘obsolete’ German Flakpanzer Gepard anti-aircraft system has been found to be especially effective at destroying at ranges of up to 4km. High-power microwave beams or electromagnetic pulses can also be directed at a drone to destroy the device’s electronics, assuming they aren’t shielded. Systems exist that ‘fry’ drone electronics using focused beams of radio-frequency energy. These directed energy weapons (DEWs) or high-powered microwave (HPM) systems typically only work over a range of a few hundred metres, though, so they are best for point defence of critical infrastructure. Physical barriers are another option. Fig.32: the Kite Aero Kite delivery drone. Source: https://kite.aero/technology/kite/ siliconchip.com.au Australia's electronics magazine In some cases, such as jails, netting is reported to be used to prevent drone landings. Devices that fire a net at a drone are also available. An unusual approach is the use of a trained predatory bird to attack drones. Passive approaches include detecting drones using sensors like radar, cameras and microphones. RF analysers can also detect control signals, if present, and reveal the make and model of drone. In some cases, it’s possible to use triangulation to locate the drone with multiple RF receivers, to provide an early warning of an approaching drone. All of these approaches have advantages and disadvantages; it is best to use a combination of them. Commercial anti-drone systems The Rohde & Schwarz Ardronis (see www.rohde-schwarz.com/au/ home_48230.html) is a drone protection package which, depending on the model, can detect the radio signal from a drone and identify the model, even before it is launched – see Fig.30. It can also determine the position of the drone and disrupt radio signals. The Squarehead Technology Discovair CUAS detection sensor (www. sqhead.com) is an acoustic array that uses machine learning to acoustically detect drones – see Fig.31. Multiple sensors can be coupled together to provide more extensive coverage and triangulation of the position. The CPM-WATSON-PLUS is a device to disrupt drone control and GNSS navigation signals (see Fig.9). DIEHL Defence (www.diehl.com/ defence/en) makes the HPEM (HighPower Electro-Magnetics) Skywolf, September 2025  27 which produces high-power electromagnetic pulses directed at a drone to disrupt its electronics – see Fig.33. Dutch firm Guard From Above (https://guardfromabove.com) trains eagles to attack drones – see Fig.34. Fig.35 shows a system from Rafael (https://rafael.co.il) for a kinetic means to destroy drones, especially autonomous ones that don’t use a data or navigation link. Australian company RedTail Technology (www.redtailtech.com.au) has developed a range of directed-­energy laser weapons to combat unfriendly drones, especially autonomous types. Fig.33: the Diehl Defence HPEM Skywolf produces high-power electromagnetic pulses to disrupt drone electronics. Source: www.diehl.com/defence/en/ products/reconnaissance-and-protection Drone shows & sports Skybrush (https://skybrush.io) is open-source drone show software. It can be used to create spectacular shows with groups of swarming drones, as previously shown in Fig.28. Drone racing is a sport governed internationally by the Fédération Aéronautique Internationale. The drones used are typically small, high-powered quadcopter-style aircraft with an FPV (first person view) camera. This allows the operator to view the live video feed on a headmounted display. The first FPV drone races were held in Australia and New Zealand in 2014, but drone racing without FPV equipment was first held in Germany in 2011 (siliconchip.au/link/ac68). Normally, humans race each other, but you can see a human-vs-AI race at siliconchip. au/link/ac6e The AI drone taught itself a faster way through the course than the human. For more details, see www. droneracingaustralia.com.au and www.droneracing.nz Future concerns Fig.34: a trained eagle attacks a drone. Existing and future airspace management concerns include how to integrate drone operations, such as deliveries, with existing air traffic control. It’s also necessary to protect against the use of drones by terrorist groups, requiring the development and use of counter-drone technology. Hobbyists and experimenters should also not be unnecessarily restricted by such considerations. Accidents During the recent Los Angeles wildfires, one plane was hit by a drone. Fortunately, the damage was not severe and no-one was hurt. This is why strict rules against flying hobby drones near airports and in controlled airspace need to be observed. Further reading/viewing Fig.35: Raphael Typhoon 30 for defence against drones, at a test site. The projectile is fired from the barrel on the left; the tower hosts the sensors. 28 Silicon Chip Australia's electronics magazine ● More information about the US Army Air Force’s Aphrodite and the US Navy’s Anvil programs is at siliconchip.au/link/ac6c ● How Ukraine’s grenade-­dropping drones changed war (Daily Mail): https://youtu.be/qtF2dOic0Y4 ● How Ukraine tries to change the battlefield with ground drones: https:// SC youtu.be/NXqt9dRfqQM siliconchip.com.au Spring Power Up’s altronics.com.au 240V power from a lithium battery! Sale prices end September 30th. GREAT VALUE! SAVE $30 34.95 $ 30 $ X 7014 T 2555 Keep an eye on the weather Hands free, head worn magnifier. Thousands sold! Offers 1.5x, 3x, 8.5x,10x magnification with LED lamp. Requires 2xAAA batteries. This handy indoor/outdoor weather monitor provides temperture, humidity, clock & calendar in one handy jumbo readout. Includes wireless sensor. SAVE $19 M 8199B Portable power for any adventure. 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It requires the latest version 6.25 of the MPLAB X IDE software, so we decided to see what new features are available. We’ll also mention some other recent announcements from Microchip. Review by Tim Blythman W e’ve seen a number of interesting announcements from Microchip Technology lately, so we thought that this article would be a good place to wrap up the latest news. While we don’t exclusively use their microcontrollers in our projects, we do use them quite frequently, so we take an interest in new tools, parts and software they offer. Readers often ask about the best programmer to get; many need to program just a single chip to get their project working. So it’s often the case that the cheapest thing that will do the job is the best. Thus, the cost-effective PICkit Basic programmer/debugger caught our attention. The related MPLAB X IDE software includes features such as an editor, compiler and programmer interface to integrate all the steps needed to develop software for microcontrollers. The release notes for MPLAB X IDE version 6.25 mention support for the new PIC32A and dsPIC33A families of processors, so we’ll look at what they offer. We’ve also designed a small USB power PCB to enhance the PICkit Basic. We describe its purpose, construction and use in an separate, accompanying article. Previous programmers Before getting to the details of the PICkit Basic, let’s take a quick look at what led up to it and some related concepts and articles. We reviewed the PICkit 5 programmer and debugger in November 2023 (siliconchip.au/Article/16016). Externally, it looks quite similar to its PICkit 4 predecessor, although it has a modern USB-C socket instead of the 4’s micro-USB socket. That article also covered the new features of the MPLAB X IDE v6.x, which had just been released then. The PICkit 5 has a Bluetooth module and can communicate wirelessly with a Microchip smartphone app, allowing a PICkit 5 to use its PTG (programmer to go) features without needing to be connected to a computer. This provides full galvanic isolation whilst using the PTG feature, since the PICkit 5 can also be powered from its target circuit. The PICkit Basic comes with more accessories than the more expensive PICkit 5. The serial wire debug (SWD) adaptor and cable will be handy for those working with ARM chips, while the eight-way connector with colour-coded extension wires are suitable for all processor types. siliconchip.com.au Australia's electronics magazine In case you are not aware, a programmer is used (among other things) to load a program file onto a microcontroller platform. For modern systems, that typically means writing to the micro’s internal flash memory. A debugger can be used to monitor and control a running microcontroller so that its operation can be checked. As the name suggests, this can help to find bugs (ie, faults in the software). You might hear it called in-circuit debugging (ICD) to emphasise the fact that you can debug the microcontroller while it is connected to a working circuit. Devices like the PICkit 5 can pause the microcontroller’s operation and even read and write its memory. ‘Breakpoints’ make it pause when the program reaches a certain point. All the currently supported Microchip programmers also incorporate comprehensive debugging features for the PIC microcontrollers that we use, so we will simply refer to them as programmers. Our review of the PICkit 4 included a panel about debugging if you want to read more about this process using the MPLAB X IDE (September 2018; siliconchip.au/Article/11237). The Snap programmer was released September 2025  33 The pin markings on the top of the PICkit Basic’s case are a very nice touch. The colour codes match those on the eight-way connector cable. The slot at lower left gives access to a pushbutton that can be used to hard-reset the programmer. not long after the PICkit 4. We reviewed it in May 2019 (siliconchip. au/Article/11628) and found it to be a cut-down (and thus cheaper) version of the PICkit 4. While it lacks some features, we have been using the Snap for most of our programming and debugging needs over the last five years. Other articles that might be helpful include our feature from January 2021 about installing and using the MPLAB X IDE (siliconchip.au/Article/14707). Also, the PIC Programming Helper project (June 2021; siliconchip.au/ Article/14889) still works with recent, small (eight- to 20-pin) 8-bit PIC microcontrollers. The PIC Programming Adaptor (September 2023; siliconchip.au/ Article/15943) is designed to ease the process of programming micros outof-circuit. We use this frequently to program DIP chips for sale in the Silicon Chip Shop. It can handle just about all the through-hole PIC micros we sell that have no more than 40 pins. For programming microcontrollers in SOIC and SSOP SMD packages, we use commercially available SMD-toDIP adaptors, which are discussed on the last page of the Adaptor article. For larger parts in the TQFP (thin quad flat pack) form factor, there is the option of using the TQFP Programming Adaptors project (October 2023; siliconchip. au/Article/15977). The PICkit Basic The PICkit Basic appears to be a lowcost variant of the PICkit 5, much like the Snap was for the PICkit 4. Like the Snap, it cannot power the target microcontroller or perform ‘high-­ voltage programming’. The Snap programmer shares a close resemblance to the PICkit Basic. They both boast a SAME70 processor and are very similar in size and layout. The PICkit Basic rounds out the product range neatly, with it being the low-cost version of the PICkit 5. Similarly, the PICkit 4 was followed by the low-cost Snap programmer. 34 Silicon Chip Australia's electronics magazine Target power is definitely a handy feature, especially when chips are being programmed out of circuit, but it is by no means essential. Our PIC Programming Helper project noted a small modification that can be made to the Snap to allow it to provide 5V or 3.3V target power. High-voltage programming (HVP) uses a voltage much higher than the chip’s normal supply voltage to signal entry to programming mode; 9V or higher is typical. Earlier parts like the PIC16F84 required HVP, but newer parts from most families now have a low-voltage programming (LVP) mode. HVP is not so easy to simulate, since the high-voltage pulses have to be delivered with the correct timing and in synchronisation with the programmer’s actions. Some of the newer AVR chips can be reset to LVP mode by a single high-voltage pulse to the right pin, but it is more typical that the HVP and LVP protocols are completely separate. Some microcontroller features can only be accessed with HVP. This usually allows an extra pin to be used as a digital input; a minor advantage compared with the ability to use a much cheaper programmer. So for the most part, we prefer to design our projects to use LVP and thus transparently allow use of cheaper programmers like the Snap and PICkit Basic. The PICkit Basic has the eight-pin header that was introduced with the PICkit 4. This was around the time that Microchip took over Atmel, and started adding support for the protocols of the various AVR and SAM chips produced by Atmel. Since they make up the bulk of the micros that we use, our review will focus on using the PICkit Basic with PIC microcontrollers. But it will work with many of the other microcontroller families that are offered by Microchip. There is no microSD card slot on the PICkit Basic, and no Bluetooth module, so there is no PTG (programmer to go) feature or app connectivity. The PICkit 5 also has a hidden pushbutton switch actuated by pushing on the top of the unit that the PICkit Basic lacks. The status of the PICkit 4 or 5 is shown through a stripe-shaped light guide on the top of the case, while the Basic has two small round holes siliconchip.com.au through which LEDs are visible. There are two larger holes in the top of the case, one of which allows access to an emergency recovery pushbutton. The Snap only offers a pair of pads that can be shorted to provide this function! Unlike the Snap’s bare PCB or even the fully-featured PICkit 5, the PICkit Basic has a plastic case marked with a pin connection guide for six different microcontroller families. So our initial perception is that the PICkit Basic is similarly featured to the Snap, but with a number of niceties, like the case and a USB-C connector. These make it a better tool overall. Accessories The PICkit 5’s only supplied accessory was a USB-A to USB-C cable, while the PICkit Basic comes with a USB-C to USB-C cable. Also supplied is an eight-pin SIL connector with colour-coded wires; the coding matches the main unit. The colours are the same as resistor colour codes, except that brown and orange (for one and three) are swapped! Presumably, this is to keep us on our toes. An ARM SWD (serial wire debug) adaptor is also supplied, adapting the 8-pin 2.54mm (0.1in) pitch to a 10-pin 1.27mm (0.05in) box header. It comes with a matching ten-pin IDC cable with socket headers at both ends. These suit the SWD headers found on many ARM development boards. SWD is an implementation of the JTAG (Joint Test Action Group) standard designed for use with ARM processors. It performs much the same role as ICSP (in-circuit serial programming) on PIC microcontrollers, and can be used for programming and debugging. You can see the SWD and JTAG pinouts marked on the top of the PICkit Basic. The eight-pin SIL header suits just about all of our PIC projects that incorporate an ICSP header. Typically, only Screen 1; the ‘data stream interface’ is a USB-serial port that is connected to pins 7 and 8 of the PICkit Basic’s headers. It can be used independently of the ICSP programming pins (refer to Table 1). five of the eight connections need to be made for PICs. The package also includes a sticker sheet with two MPLAB PICkit Basic stickers. Table 1 shows the pinouts for the various supported interfaces, as listed on the PICkit Basic’s label (plus the AVR ISP pinout, which many readers might find handy). The rightmost column shows the pinouts for the so-called data stream interface. This is effectively a USB-­ serial adaptor built into the programmer; it appears as a virtual serial port on our computer. Internals We popped the PICkit Basic out of its case to see what’s inside; the photos overleaf show the PICkit Basic’s red PCB. The family resemblance to the Snap is striking, with a SAME70 processor dominating both boards. Much of the remaining circuitry looks almost identical to the Snap, with the emergency recovery pushbutton labelled SW1 and two larger LEDs being the most obvious differences. Hands-on testing The PICkit Basic is not supported by versions of the MPLAB X IDE prior to 6.25, so we had to install the latest version before using the programmer. From there, operation of the PICkit Basic was quite seamless. We selected the new programmer in our current PIC project and, after a brief delay to Pin Colour ICSP MIPS EJTAG SWD JTAG 1 Orange MCLR MCLR RESET 2 Red VDD VDD VDD VTG VTG 3 Brown GND GND GND GND GND 4 Yellow DAT TDO SWO TDO 5 Green CLK TCK SWCLK TCK 6 Blue 7 Purple TDI 8 Grey TMS Table 1 – PICkit pin mappings debugWIRE UPDI AVR ISP UART VTG VTG VTG GND GND GND DAT MISO RESET RESET CLK RESET TDI SWDIO update the firmware in the programmer, everything simply worked. Fortunately, the project we used to test this has an internal power source, so the lack of target power was not a problem. We then tried out the data stream interface. On Windows, we did not need to install any drivers, but were greeted with a new COM port named “PICkit Basic Virtual COM port” (see Screen 1). We could open this port in the TeraTerm terminal emulator, even while programming a PIC using the IDE. It’s as though they are two completely separate hardware devices. Of course, some of the other available device types require the data stream interface pins, so this feature will not be available when the PICkit Basic is configured for other devices. We’ve taken our Snap programmer for granted for a while now, and its micro-USB socket is starting to misbehave with wear and tear. The PICkit Basic has come along at a good time and it has quietly replaced its predecessor without any fuss. So there really isn’t much more to say; the PICkit Basic offers much the same experience as the Snap, but with a case and a USB-C socket, it’s sure to be a more robust tool. There is a user guide, but we imagine that anyone that has used a Snap will not even need that. We noted in the PICkit 5 review that the PICkit 4 was quietly relegated to the status of ‘not recommended for new designs’. We would not be TMS Australia's electronics magazine RESET MOSI TX RX September 2025  35 Screen 2: the note at the bottom of the MPLAB X v6.25 installer marks the dropping of support for the PICkit 3, among other older development tools. surprised if something similar occurs with the Snap programmer. At the time of writing, some retailers are listing the Snap quite cheaply, but many also have them on back-order. The Snap may be hard to buy in the future. We purchased our PICkit Basic for just over $50 from Mouser Electronics; it is listed for much the same price at DigiKey. Both these stockists have free shipping for orders over $60. By adding a few extra parts to our order, we were able to get our PICkit Basic shipped for no extra cost. Its Microchip part number is PG164110, so a web search for that should find other suppliers. The installation process of MPLAB X version 6.25 shows this (Screen 2). Older versions of the IDE are still available for download from the MPLAB archive at siliconchip.au/link/abpn Like the transition from the Snap to the PICkit Basic, the new version of the MPLAB X IDE works in much the same fashion as its predecessor. The older versions would occasionally fail to compile a project, apparently for no reason, since the compilation would complete without problems when started a second time. We’ve seen less of these sorts of difficulties with version 6.25. MPLAB X 6.25 IDE software This version of the MPLAB X IDE is the first to offer support for the PIC32A and dsPIC33A families of parts. For a long time, we have used the PIC32M series of microcontrollers, such as the PIC32MX parts used in the many Micromite variants. These have a MIPS (Microprocessor without Interlocked Pipelined Stages) processor core. MIPS is a type of RISC (reduced instruction set computer) processor and is typically contrasted with CISC (complex instruction set computer) processors of which the x86 and x64 families are probably the most widely-­ known. The PIC32C family is based on the ARM RISC architecture, while the The MPLAB family of programs goes back over 20 years, with the MPLAB X variants appearing around 12 years ago. The latest versions are highly modular, with separate compiler programs and loadable device family packs for different processor families. There are add-ons such as MPLAB Harmony that can be used to simplify device configuration. The previous version (6.20) was the last to support the venerable PICkit 3. The PICkit 3 was released in 2009 and has now been copied so much that if you were to try to buy a PICkit 3 today, it would likely be a clone instead of the real thing. 36 Silicon Chip The PIC32A and dsPIC33A Australia's electronics magazine PIC32A and dsPIC33A families are a 32-bit evolution of the familiar 8-bit and 16-bit PIC processor cores. Users of the 16-bit PIC24 and dsPIC33F parts will note a similarity in the architecture and instruction set. We’ve had a look at the data sheets for these parts and there is lot of similarity with the PIC24 family. The instruction set is quite similar. So we anticipate that they will be of interest to those who work with PIC assembly language. The register set and status bits are also quite familiar. The new family also features a 64-bit floating point unit, and two 72-bit multiply-­ accumulate units. Those latter features may sound pretty straightforward but they represent a very large increase in number-­ crunching computing power compared to chips that lack such dedicated hardware. We’ve seen these new parts being pitched as low-cost, and a search on the likes of DigiKey and Mouser suggests they are available for around $3 in single quantities (and, of course, somewhat cheaper if you buy many). The dsPIC33AK128MC102 is a 28-pin part in a SSOP package. Another example we found is the PIC32AK3208GC41048, available in a 48-pin TQFP package. The PIC32AK3208GC41048 is no slouch, with a 200MHz clock speed, 32kiB of program (flash) memory and 8kiB of SRAM. The usual digital peripherals such as PWM, UART, I2C and SPI are present. The analog peripherals are impressive, with two 12-bit, 40MSa/s ADCs. There are also onboard comparators, op amps and three 12-bit DACs. Internal peripherals include peripheral pin select (PPS), which allows remapping of many digital peripherals to different pins. There are also four CLC (configurable logic cell) instances. The CLC can be used as internal ‘glue’ logic between peripherals. We previously used the CLC in an 8-bit PIC16F18146 to combine the comparator and PWM features to implement a simple but effective voltage boost controller. This was documented in the Digital Boost Regulator project (December 2022; siliconchip. au/Article/15588). So there is a lot of commonality for those accustomed to other PIC families. Even the configuration bits have familiar names and behaviours. These siliconchip.com.au chips also have a security module to allow secure booting and code protection. The dsPIC33A family, like other dsPIC families, is clearly aimed at real-time digital signal processing applications. This also includes machine learning algorithms, as well as the more traditional DSP applications, like audio and image processing. These are capable chips at a good price, and with their PIC pedigree, should be easy to work with for those who are familiar with other PICs. The fast ADC alone may make it the part of choice for certain projects. Other news There is also a 64-bit PIC family, the PIC64GX, which has four RISC-V cores. RISC-V is an open-source RISC architecture, so manufacturers are not encumbered by license fees as they might be with other architectures. The PIC64GX family is capable of running Linux, so it appears to be suited to a general-purpose computing role. The writing of this article coincided with the Electronex trade show, and we had the opportunity to talk to the staff at Microchip as well as see a presentation on the PIC64GX family. We learned that there are other PIC64 RISC-V families planned for launch later in 2025. The Microchip engineers spoke about how the PIC64GX offers true asymmetric multi-processing. This allows one of the processor cores to be dedicated to real-time applications, such as motor control, while the remaining cores can run operating system or application software. We have also read that there is now a Microchip MPLAB extension for the Visual Studio Code IDE (VS Code). We previously noted that the official Raspberry Pi SDK (software development kit) for the Pico family of processors has now moved to use VS Code; see the article about Transitioning to the Pico 2 from (March 2025; siliconchip. au/Article/17796). To get started with the Microchip MPLAB extension, search for “MPLAB” in the VS Code Extensions Marketplace and install the MPLAB Extension Pack. This should also install other features like project import and toolchain support. As with the MPLAB X IDE, compilers are installed separately. There is also an AI coding assistant, which we plan to test out in the near future. Where to buy it Our Snap programmer has seen six years of good use and the PICkit Basic has come along at a good time. It has quietly and seamlessly replaced the Snap and we expect it should be good for many more years, since its case and USB-C socket will make it a more robust tool. It just works! There have been no real surprises in the new version of the MPLAB X IDE. We will pay close attention to the Microchip MPLAB extension for the VS Code IDE, especially given that we can also use that IDE for development of projects for the Raspberry Pi RP2xxx processors used in the Pico and Pico 2 boards. The new processor families being released look very promising to us, so we’ll monitor developments with the new PIC32A, dsPIC33A and PIC64 parts that are now available. For more information on the PICkit Basic, see www.microchip.com/en-us/ development-tool/pg164110 Buy the PICkit Basic from Microchip Direct: www.microchipdirect. com/dev-tools/PG164110 DigiKey: www.digikey.com.au/en/ products/detail/PG164110/25965142 Mouser: https://au.mouser.com/ SC ProductDetail/579-PG164110 We removed the PICkit Basic’s plastic case to get these photos of the top and bottom of the PCB. Readers who have a Snap programmer will see the similarities. siliconchip.com.au Australia's electronics magazine September 2025  37 Project by Tim Blythman PICkit Basic Power Breakout Board The PICkit BASIC programmer/debugger is compact, robust and works with most modern PIC chips. But it could really use the ability to provide power to the chip being programmed. This small PCB fixes that! Compact inline unit Makes 5V & 3.3V available from a USB-C cable Passes USB 2.0 data through, allowing a PICkit Basic to be connected A s we noted in our review of the PICkit Basic, starting on page 33 of this issue, it appears to be an updated version of the Snap programmer. Two of the most obvious improvements are the plastic case and a USB-C socket. Like the Snap, it does not offer high-voltage programming (HVP). HVP involves applying 9-13V to one of the microcontroller pins to enter its programming mode. This was the only way to program older chips like the PIC16F84. Later chips still support HVP, but many parts now support LVP (low-voltage programming). So you can use the PICkit Basic to program most PICs we have used in our projects over the last few years (plus some other non-PIC chips). The feature that’s most notably absent is the ability to provide ‘target power’, to run the chip being programmed (the target). Neither the Snap nor PICkit Basic can do this. Both these programmers still have a power pin. On the PICkit Basic, it is labelled as Vdd or Vtg. The programmer uses this to check for the presence of a suitable supply LED indicators for 5V & 3.3V presence Jumper wire for voltage selection voltage for the selected microcontroller before communicating with it. Programming parts out-of-circuit, like we do for the programmed chips we sell, can be done using a device like our TQFP Programming Adaptors (siliconchip.au/Article/15977). These adaptors have separate terminals that can be used to provide power, so it’s not necessary for the programmer to offer target power, although it is still convenient that you don’t need a separate power supply. For in-circuit programming, such as during a project’s development or for a part that cannot be easily programmed out-of-circuit, it might be possible to use the onboard power supply. However, that might not be feasible for projects powered by high voltages, such as from the mains. At the other extreme, some circuits use batteries or coin cells for power. For those cases, it makes sense to use an external power supply to avoid discharging the battery during development. Thus, it often makes sense to supply power via the programming header. So we need a way of injecting an appropriate voltage into the Vdd/Vtg pin. Most modern micros will happily work at 3.3V, including just about all the parts we use these days. So we have chosen that as one of the available voltages. The USB cable also means that 5V is available. The Breakout Board replicates a handy feature we added to our Snap programmer. The yellow wire extracts 5V or 3.3V from suitable points on the Snap and feeds it to the Vdd/Vtg pin of the Snap’s programming headers, supplying power to the connected circuit. 38 Silicon Chip Australia's electronics magazine In our PIC Programming Helper project, we noted that the Snap has pads that expose 5V and 3.3V rails. We modified our Snap to add a threeway header socket so that these rails can be easily accessed (June 2021; siliconchip.au/Article/14889). The third position of the header is not connected to anything and provides a location for a wire in cases where a voltage is not required. The photo at lower left shows our modified Snap, with one end of a jumper wire soldered to the Snap’s Vdd/Vtg pin. Of course, the PICkit Basic’s plastic case makes direct access to its PCB more difficult. It does have marked internal pads for 5V and 3.3V, but they are not as conveniently arranged as on the Snap. So the intent of the Power Adaptor is to provide these power breakouts without needing to modify the PICkit Basic. USB 2.0 The PICkit Basic uses only USB full-speed (USB 2.0) communications, although it is fitted with a USB-C connector. It makes sense to fit the Power Breakout with a USB-C plug and socket so that it can be connected inline, without needing an extra USB lead. USB-C brings along with it the delightful possibility of up to 48V being present if a USB-PD (power delivery) device is connected. To avoid that, we have designed the circuitry so that the USB-PD control lines are not carried through. The Power Breakout makes it appear that the upstream source is a USB 2.0 legacy 5V host by taking over the USB-PD control lines. This means that the Power Breakout siliconchip.com.au ◀ Fig.1: the circuit requests and offers a 5V legacy power source, turning a fully featured USB-C connection into a basic 5V USB-2.0 connection. The regulator and capacitors derive 3.3V from the USB 5V supply, while the LEDs and resistors act as power indicators. Fig.2: after soldering the USB socket and plug, the remaining parts are easy. has a second use: if you have a non-­ compliant device with a USB-C port that does not get 5V power when connected via a USB-C to USB-C cable, inserting the Power Breakout inline will fix this. Blocking USB-PD might seem a bit overly cautious, but we suspect that constructors might find other uses in situations where devices don’t play well with the newer features of USB-C and power delivery. Circuit details Fig.1 shows the circuit; CON1 is a USB-C receptacle. This variant sports 12 pins and breaks out power, USB 2.0 data, the CC (configuration channel) and SBU (sideband use) pins. CON2 is the corresponding plug, allowing the Power Adaptor to be fitted inline. It is a nine-pin part, providing access to power, USB 2.0 data, one SS (‘Superspeed’) pair and one CC pin. Only one CC pin is needed, since this is the point at which the cable orientation is detected in a USB-C cable arrangement. CON1’s CC pins are connected to separate 5.1kW resistors to ground, in the well-known legacy arrangement that marks this as a power sink. This means only 5V is requested from the power source. CON2’s CC pin implements the corresponding source arrangement, with a 56kW resistor connecting it to Vusb. Technically, arrangements like this are not strictly allowed by the USB-C specification. But since we are not interested in higher voltages, currents or USB data speeds, it is very unlikely to cause any problems. The remainder of the circuit is straightforward. REG1 and its two siliconchip.com.au bypass capacitors derive 3.3V from the nominal 5V Vusb rail. LED1 & LED2 are connected (with dropping resistors) to indicate that the two rails are present. CON3 is a three-way header that provides the same connections as our modified Snap. One position has 5V, one 3.3V, and the last is not connected. CON4 is a similar three-way header, but all pin positions are connected to ground, in case grounds are needed. We used a stackable header to intercept the connections for connecting the Power Breakout to the PICkit Basic. A jumper wire soldered to the appropriate pin allows power to be injected when the other end of the jumper wire is plugged into CON3. You can see this in our photos overleaf. If you just need 5V or 3.3V from a USB-C cable, you could assemble the Power Adaptor without CON2 and break out the requisite voltages from the pins of CON3 and CON4. Construction The main assembly is a PCB fitted with small surface-mounting parts and some fine-pitch USB connectors, as shown in the overlay diagram, Fig.2. The layout is fairly simple, so you might get by using the PCB silkscreen markings. The pin pitch is around 0.5mm on CON1, so you’ll need surface-mount soldering tools and gear, including a good magnifier. Flux paste and solder-­wicking braid are highly recommended, too. Add a thin layer of flux to the component pads on the PCB as you go. Start by soldering CON1; it shouldn’t be too hard to align correctly, since it has locating pins. Tack one of these in place and confirm that the leads are centred on the pads and that the part is flat against the PCB. Add flux to the pads and solder the pins. We’ve extended the pads slightly, so you should be able to touch the iron to the pads and see the solder flow onto the leads. Solder the remaining locating pins and check for solder bridges between the pins. CON2 should be similarly easy to locate. It has a slightly wider 0.65mm Parts List – PICkit Basic Power Breakout 1 double-sided 42 × 14mm PCB coded 18106251 1 MCP1700T-3302E/TT 3.3V LDO regulator, SOT-23 (REG1) 2 red SMD LEDs, M2012/0805 size (LED1, LED2) 2 1μF 50V X7R M2012/0805-size SMD MLCC capacitors 1 USB 2.0 type-C receptacle (CON1) [GCT USB4105-GF-A] 1 edge-mounting USB 2.0 type-C plug (CON2) 1-2 3-way 2.54mm/0.1in pitch socket headers (CON3, CON4; optional) 1 8-way stackable header strip 1 jumper wire or similar pluggable arrangement to suit CON3 1 4cm length of 20-25mm diameter clear heatshrink tubing a small amount of neutral-cure silicone sealant or thick glue Resistors (all SMD M2012/0805 size, ±1% ⅛W) 1 56kW 2 5.1kW 1 1kW 1 470W SC7512 Kit ($20 + P&P): includes all parts except the jumper wire and glue We built some cables like this, with five-way plug and socket headers, to provide a flexible connection between our Snap and boards that we have been developing. Soldering an extra wire allows the connection to be made to the Power Breakout. ◀ pin pitch and fewer pins, so you can folThis header simply low much the same has half a jumper wire soldered to the second process. pin of a stackable header. The Breakout Fit REG1 next, notBoard sits upstream of the programmer, ing the correct orienwhile the stackable header connects tation. Tack one lead, downstream, to the ICSP header. confirm the part is flat and square and then dry. Inspect it under a magnifier and fix solder the remaining any bridges or dry joints that you see. leads. The two LEDs Testing and completion should be aligned with their cathodes towards The PCB can now be tested by plugthe ‘K’ marks on the ging CON1 into a USB power source. PCB. The cathode is You should see LED1 and LED2 illuoften marked with a minate. If you have a multimeter, you small green dot, although should measure close to 5V or 3.3V at we have seen some parts the marked pins on CON3. You can use where the anode is any pin of CON4 or the USB connecmarked instead. tor shells for ground. The remaining parts You can also double-check that a are not polarised. The device can be connected downstream, capacitors will not be marked, but forto CON2. Any USB 2.0 device should tunately, only one value is used in this work just as well as if it had been conproject, on either side of REG1. Fit the nected directly with a USB-C cable. resistors next, matching the values to Any problems here point to a soldering the silkscreen. problem with CON1 or CON2. That completes the SMD parts, so Next, solder CON3 in place. We clean any excess flux using an approdon’t plan to use CON4, so we left that priate solvent and allow the PCB to off our prototype. Cut the heatshrink 40 Silicon Chip Australia's electronics magazine into a piece 1cm long and another piece 3cm long and shrink in place on either side of CON3. Make sure to cover CON3’s pins on the underside. That completes the unit. You can see from our photos that we used a stackable header to feed power into the downstream target. Half a jumper wire is used to provide a pluggable connection to CON3. Solder the jumper wire to the second position on the stackable header. This needs to align with the red Vdd/ Vtg markings on the PICkit BASIC, so a red jumper wire is preferred. Follow by adding some glue to the pins where they join the housing of the header. Run the glue up on the insulation of the jumper wire as well and allow the glue to cure. We recommend a fairly thick geltype glue or silicone sealant, since a thinner glue may flow into the header housing and gum it up. This happened to one of our prototypes. The glue has two purposes. Since the pins are only a press-fit into the housing, this will stop them from coming loose. The glue on the jumper wire will also offer some strain relief and prevent the wire breaking at the solder joint. You might also like to mark the heatshrink with the 5V and 3.3V markings if they aren’t otherwise visible. Using it Plug the header and PCB into the PICkit Basic as shown in the photos, aligning the wire with the Vdd/Vtg markings. Plug the jumper wire into the 5V or 3.3V position, depending on your needs. Most newer PIC micros can be programmed with a 3.3V supply, so that is a fairly safe option. Connect the header socket to the ICSP header of the target board and plug a USB-C cable into the PICkit Basic. The photos show another arrangement we tried. For a while now, we have used a short, flexible five-way lead to provide a degree of strain relief between our Snap programmer and target. It’s a bit less precarious than plugging the programmer directly into the PCB and having it balance vertically. By adding an extra orange power wire to the assembly, we can avoid the need to rig up the header socket. It’s frustrating when a loose or intermittent connection causes problems, so this eliminates a potential point SC of failure. siliconchip.com.au Q 1135 Q 1089 NEW! SAVE $19 79 $ Extended resolution 19999 count Q 0102 SAVE $130 70 $ Autoranging True RMS DMM This compact true RMS meter provides in depth functionality for technicians troubleshooting circuits. Push button design simplifies operation and test jack indicators ensure you never plug a cable in wrong! 299 $ True RMS 19999 Count DMM Handheld 40MHz Oscilloscope Extended resolution to 4 digits! Offers everything the serious enthusiast could need with auto ranging, min/max/rel modes, frequency, duty cycle and non contact voltage detection. This compact digital storage oscilloscope and digital multimeter makes field testing easy. Offers 2 channels with real time sampling of 125MSa/s per channel with waveform comparison tools and more. Test. Measure. Repair. G r e a t v a l u e w o r k b e n c h g e a r. SAVE $54 M 8254 145 $ M 8303 3A SAVE $40 SAVE $22 119 $ T 2098 Low Current Lab Power Supply 13.8V 20A Bench Power Supply Great for servicing, repair and design of electronics. Low noise switchmode design. Fine & coarse voltage and current controls. 3A max. Size: 85Wx160Hx205Dmm. A fixed voltage output power supply designed for powering automotive, marine and communications equipment. Low noise and ripple design (<100mV). M 8213 SAVE $130 499 $ 20A Benchtop Power Supply A compact 1-30V DC power supply with 3 programmable preset outputs. Fixed 5A aux output also available from front panel. High efficiency design with low noise and ripple for reliable use in electronic servicing. 200 x 90 x 215mm 88 $ Micron® 300W Adjustable Solder Pot Tin multiple stranded hookup wires or remove multi-pin connectors from boards quickly and easily. Takes up to 1350g of solder. Stable temperature control: 200-480°C. Suitable for lead free and leaded work. Hot Air Re-Work Desoldering Iron Provides 300W of hot air for quick and easy desolder and re-work of surface mount boards. 200-500°C adjustable. Also makes a great hot air gun. T 1289 SAVE $50 119 $ Your electronics supplier since 1976. Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or shop online 24/7 <at> altronics.com.au Build It Yourself Electronics Centre® © Altronics 2025. E&OE. Prices stated herein are only valid until 30/9/25 or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. This speaker hangs from a high roof or ceiling and provides excellent quality sound – especially considering how little it costs to build. Its features include: Easy to assemble, with a largely pre-built enclosure Multiple configurations for different applications Excellent quality sound for a pendant speaker Uses a 6.5-inch (170mm) woofer and a dome tweeter Low-cost drivers and crossover 90W rating on normal program material Optional low-cost speaker protection Impedance: 4W (minimum, 20Hz-20kHz) 44cm wide, 40cm high and 7kg in weight High-Performance Pendant Speaker Part 1 by Julian Edgar T his pendant speaker is easy to build, cost-effective and has good performance. It is also an excellent complement to the Outdoor Subwoofer (June 2025; siliconchip.au/ Article/18313). But first, what is a pendant speaker, and why would you want to build one (or more)? Pendant speakers hang from a high roof or ceiling. They are used where floor speakers would be inconvenient or get in the way and in-ceiling speakers cannot be used because there is no ceiling (eg, in a shed or workshop), the ceiling is made of concrete (eg, the ceiling is the underside of the floor above), or there is no space. As they can be placed high, out of reach, pendant speakers are also useful in areas subject to vandalism or interference. Our readers could use them for playing music in home workshops and sheds, but they can also be used for music in large rooms with raked ceilings and in undercover outdoor areas with high roofs. They work well in shops with high ceilings. Finally, they can also be used in public address roles. In fact, we have a specific enclosure variation for when they will be primarily used for voice. Design challenges A pendant speaker is much more challenging to design than a conventional speaker for two reasons. The first is aesthetics. A box-shaped speaker enclosure hanging from the ceiling will look plain weird; instead, what is needed is a curved shape – like a pendant. However, unlike the jewellery, a pendant speaker needs to be three-dimensionally curved. That A single Visaton 170mm (6.5in) WS 17 E woofer/ midrange driver is used. Source: Visaton The tweeter is a 25mm (1in) soft dome unit. They are available inexpensively in pairs. 42 Silicon Chip Australia's electronics magazine normally makes home construction very difficult, but we have a trick that overcomes that difficulty. The second design problem is acoustic. Loudspeakers work by propagating pressure waves in the air; to do that, the moving cone needs to connect with the air. The ability of the cone to transmit energy to the air depends on the acoustic impedance of the system, that is, the opposition that the system presents to the acoustic flow. To put that more simply, the air needs to load the cone, or no energy exchange will occur. This effect is greatest at low frequencies (ie, bass). Acoustic horns load the speaker cone strongly, giving the horn its characteristic high efficiency. A similar increased loading occurs if you put a conventional speaker enclosure at the junction of a floor and wall, and even more loading occurs if you put the enclosure in a corner comprising two walls and the floor (or ceiling). This is why bass response improves at these speaker locations. Now think of a pendant speaker. It’s suspended in mid-air and so cannot benefit from any of those loadings! If we want good bass response, we cannot use a horn, as it would need to be enormous. siliconchip.com.au ◀ The High Performance Pendant Speaker has been tuned to give good performance when hanging in midair. We chose to use an open grille, but alternative grilles with smaller openings can also be used. The tweeters come with two different mounts, cables and crossover capacitors (in the boxes). However, we don’t use these capacitors. The enclosure design we have developed has an option to increase its output at low frequencies. That helps offset the lack of bass augmentation because it’s not positioned near any flat surfaces. However, if you want strong bass, it’s likely you will need to add a subwoofer – for example, the Outdoor Subwoofer we described previously. That will take up floor space, but it’s only one small speaker compared to using multiple large floor speakers. Overall, the pendant speaker design presented here gives excellent sound quality for this type of enclosure. Design approaches A key aspect of the design that makes it cheap and easy to build is the use of a pre-formed speaker enclosure. It is made from recycled plastic and has reasonably thick, acoustically dead walls. In fact, it’s a pot available from Bunnings! To turn it into a pendant speaker, all we do is make a baffle from particleboard and glue and screw it into place. Then we add a woofer/midrange driver, a dome tweeter and a simple crossover. The woofer and tweeter are quite inexpensive (we already met the woofer in the Outdoor Subwoofer project) and the rest of the hardware – including the grille – is also cheap. Depending on the application, the enclosure can be built as a ported (bass reflex) or a sealed design. More on those options in a moment. siliconchip.com.au The bass/midrange driver (I’ll just call it the woofer from now on) is a single 170mm (6.5-inch) WS 17 E unit made by Visaton. This driver is available in 4W or 8W versions and, in this design, we use the 4W driver. These speakers are available worldwide – a web search will find your nearest stockist. We bought ours from Soundlabs Group, and it cost $54 plus postage. For its low cost, this is an excellent speaker that, in addition to providing good bass response, is quite capable in the midrange. When we used this driver in 8W form in our Outdoor Subwoofer, the measured Thiele-Small specifications differed a little from the advertised specs. The 4W drivers we bought this time were also a bit different from their stated specifications, as shown in Table 1. The bass response of the enclosure was modelled using the freely available WinISD speaker enclosure design software (www.linearteam.org). In this modelling, we used the average of the two sets of Thiele-Small test results. The tweeter we have selected is a 4W “Alpine” DDT-S30 one-inch (25mm) soft dome design that is available online for $30 a pair, including delivery. I’ve put Alpine in inverted commas because it is very likely that these are not genuine Alpine products. The tweeters come with crossover boxes. However, they contain just a single non-polarised capacitor. That is the simplest possible way of preventing bass frequencies reaching the tweeter. By the way, the measured impedance of the finished speaker never drops below 4W. Different enclosure options Two different enclosure designs can be built. The first is used for playing music, while the second is for voice applications. Both designs are quite Table 1: driver measurements vs specifications Specification Listed Tested speaker A Tested speaker B DC resistance 3.2W 3.4W 3.3W 85.5dB 86dB Resonant frequency 45Hz Sensitivity 88dB 44Hz 46Hz Qms 2.35 3.30 3.40 Qes 0.90 0.93 0.89 Qts 0.65 0.71 0.71 Vas 22.0L 24.9L 22.7L Australia's electronics magazine September 2025  43 straightforward to build – the one for playing music uses a ported enclosure, or for voice, a sealed enclosure. A ported enclosure can become sealed just by blocking the port, so if you’re not sure which approach will suit your application, test the ported design first. The ported design has a modelled frequency response that smoothly rises to a peak at +8.5dB at 78Hz (see Fig.1). To put this a different way, on some amplifiers, this is the equivalent of turning the bass control up by about two-thirds. Remember, though, that the pendant speaker isn’t getting any of the bass boost that normally occurs because of the presence of the walls and floor. In this form, its -3dB point is 48Hz. That modelled response is achieved with a port that is 86mm in internal diameter (so quite big) and 100mm long. If you want a peakier or smoother bass response, we will cover that in the section on tuning next month. The sealed design that is better for voice has a bottom end modelled as being only 1dB up by 94Hz, with a -3dB point of 51Hz. What is not generally realised is that speaker simulation and design packages assume that the speaker enclosure is working into ‘half space’, that is, it’s placed in the middle of an infinitely large wall. Therefore, the simulation graphs shown in this article are for a speaker positioned like that, not for one hanging in free air. If you are looking in horror at the ported enclosure’s modelled frequency response, that is very important to The metal grille can be made from open mesh (left) or mesh with small perforations (right). In fact, any metal grille can be used. Source: Bunnings keep in mind! When it is suspended in free air, the design sounds nothing like the modelled response curve; instead, its bass is smooth and effective. Before going any further, why can’t you use the ported design for voice, or the sealed design for music? You can, but there are some disadvantages. With the ported design, on some voices (eg, a man’s deep voice), the speaker may sound too chesty, especially if the source also has bass boost applied to the signal. More importantly, it will be harder to work out what the person is saying – intelligibility will be worse. Conversely, the sealed design on Fig.1: the modelled bass response of the 27L ported (green) and sealed (blue) enclosure versions. The response of the sealed enclosure has been designed to strongly augment bass, compensating for the lack of cone loading caused by the absence of flat surfaces near the hanging speaker. The ported enclosure design is best for music, while the sealed version is best for voice applications. 44 Silicon Chip Australia's electronics magazine music will sound tinny, especially if being fed a flat signal (with the bass control on the amplifier set for zero boost). Remember, all these comments apply only when the speaker is being dangled in midair! We chose a welded steel mesh for the grille. It has openings that are 12.7mm square and it is available from Bunnings (I/N: 0082424). This grille allows you to clearly see the woofer, tweeter, port and (optional) speaker protection lamp, and gives the speaker an ‘industrial’ look. If you want a more conventional grille, Bunnings also sells steel mesh sheets with much smaller openings One of the prototype speakers deliberately being over-driven. Note the glowing protection lamp that is limiting the power. siliconchip.com.au (eg, I/N 0647223 has 3.2mm round holes). Optional speaker protection In our previous Outdoor Subwoofer project, we used a specific halogen lamp as a speaker protection mechanism. The lamp was wired in series with the speaker and, as current through the lamp increased, so rapidly did its resistance, limiting the power that reached the speaker. In that design, the protection was needed as it was easy to over-drive the subwoofer without realising it. With the full-range pendant speaker presented here, the situation is somewhat different. If the speaker is overdriven, it is easier to hear distortion than in the subwoofer. However, a good outcome requires that the listener knows what distortion sounds like and then immediately turns the amplifier power down! The nominal peak power rating of the speaker is 90W, but if there’s any possibility of the speaker being overdriven, we recommend that a protection lamp be installed. The lamp mounts on a bracket behind the grille, so it’s visible when the speaker is hung in position. If the speaker is constantly over-driven, it is possible for the lamp to become very hot. Because of this, the lamp needs to be spaced away from the baffle, and a metal grille (rather than cloth grille) should be used. The suggested protection lamp is a Narva 24V 55W bulb, part number 48701. At around $10, it is cheap insurance. A halogen incandescent light bulb is used as the optional speaker protector. It rapidly rises in resistance as its current flow increases, limiting the maximum speaker power. Source: Narva siliconchip.com.au The simple crossover can be built on a piece of plain punched laminate. In our tests, using a 50W amplifier to drive the pendant speaker, the lamp did not light at all on any program material, even at full volume. This is what you would expect to see in normal use – the lamp filament not glowing at all. Using a much more powerful amplifier, the light would glow dimly on some passages at about 70% volume; at 80%, it would glow more brightly on bass passages. At volume settings above that, it would glow very brightly. No distortion was audible and the speaker was not damaged – so the simple lamp protection mechanism works very well! Finally, while testing the speaker, I made an interesting mistake. I was swapping line level inputs to the amplifier, not realising the amp was still switched on and at full volume! As I pulled an RCA plug, a huge 50Hz hum was fed to the speaker, but the protection lamp immediately lit, and no damage was done. Performance I have built many speakers over the decades, and normally, you test them sitting on the floor. Depending on their application, it might be a big room or a little room, but they’re always on the floor (or sometimes on short stands). However, in the case of the pendant speaker, I had to test it 4m above the ground. Two different testing venues were used. The first was in a partially built house with a 10 × 6m room with a raked roof peaking at 6m high. The second test location was a large shed, 24 × 8m, again with a 6m peaked roof. In both cases, the speaker was positioned 4m from the ground. As described earlier, this position is a tough test for a speaker’s bass response, and developing adequate Using the Pendant Speaker with the Outdoor Subwoofer In the June 2025 issue of SILICON CHIP, we introduced the Outdoor Subwoofer. This uses a fibre-cement stool as the ported enclosure, with two Visaton WS 17 E 8W drivers mounted in an isobaric (face-to-face) configuration. As its name suggests, the sub is designed primarily for outside use. Still, it can also be used indoors, especially in large spaces. The Pendant Speaker works very well in combination with this subwoofer. We performed some testing using the pendant speaker and the subwoofer in the previously described 10 × 6m room with a 6m roof. Using a 100Hz electronic crossover, we found the sub’s input power needed to be less than the pendant speaker’s. In other words, with equal amplifier power to the pendant and sub, the bass was too strong. However, with the sub pulled back, the sound quality on music was excellent. That led to another thought. This combination of the pendant speaker and sub is likely to give excellent sound quality in large shops, especially those without suspended ceilings, where the room volume is very great. Certainly, we’d back the system over the small cube speakers and subwoofers often seen (and heard) in such environments. In that application, we suggest fitting protection bulbs to both the sub and pendant speakers. Australia's electronics magazine September 2025  45 sound output in such large room volumes is also a difficult task. However, it also reflects how the speaker will likely be used. I also purchased a commercial pendant speaker for a similar price, allowing direct comparisons during development. The commercial speaker used a 6.5inch coaxial (two-way) driver, a complex crossover and a small enclosure. My aim was to get a much better result with our project than the commercial speaker – and that was achieved in spades. In comparison to our final design, the commercial speaker had very poor bass, with a rapidly falling response below about 150Hz, accompanied by a buzz. Furthermore, there were clear resonances at 260Hz, 210Hz, 170Hz and 120Hz. In comparison, our project speaker had no loud resonances at all. Also, there was no bass buzz in our speaker and our speaker has an audible response down to 45Hz. The mid-range of the commercial speaker was also overly bright – but perhaps that was intentional, for better voice intelligibility. On the other side of the ledger, the commercial design was quite sensitive, being louder than our project speaker on the same Fig.2: the simple crossover circuit uses a non-polarised 4.7μF capacitor and two 5W resistors. volume control setting, despite the commercial speaker having a higher impedance (8W versus our 4W). The treble of the commercial speaker was initially better than our project speaker, but development of the crossover (covered next) gave treble in our design that matched the commercial speaker. Again, these comments apply when the speakers are tested in mid-air. The crossover During testing and development, the wiring for the woofer and tweeter were run outside the enclosure so that external tuning changes to the crossover could be easily made. In the final version, the crossover components are mounted inside the enclosure on the back of the baffle. The “Alpine” tweeter comes with a simple 6dB/octave high-pass crossover: a single 3.3μF non-­polarised capacitor. This gives a nominal crossover point of 12kHz. That’s a bit high for the 6.5-inch woofer, which has specifications showing it has a good response only until about 7kHz. Using a 4.7μF capacitor drops the nominal crossover frequency to 8.4kHz. However, the tweeter was then a little bright, so it was pulled back by about 3dB by using an L-pad comprising a series 1W resistor and a 10W parallel resistor. The final crossover circuit is shown in Fig.2. The crossover is built on a piece of bare punched laminate board. We chose to use input and output terminal blocks, but you could solder directly to the components on the board for these connections, then fasten the flying leads in place with cable ties. If you don’t have any punched laminate board, you could glue the three large components to a piece of board and then wire them together. Next month That’s all the space we have for this month. In the second and final part next month, we will show you how to build the speaker, test it and (optionally) tune its performance to suit your taste and listening environment. SC Parts List – Pendant Speaker 1 Eden 44cm Black Faux Planter pot [Bunnings I/N 0118235] 1 Visaton 170mm (6.5-inch) WS 17 E 4W woofer [Soundlabs etc] 1 pair of “Alpine” DDT-S30 1-inch soft dome tweeters [eBay etc] 1 4.7μF 100V non-polarised crossover capacitor [Jaycar RY6904] 1 10W 5W ±5% wirewound resistor 1 1W 5W ±5% wirewound resistor 1 80 × 70mm piece of plain punched laminated board 1 1000 × 500mm piece of 18-22mm thick particleboard (or two 500 × 500mm pieces) 1 600 × 900mm piece of steel mesh with 12.7mm square openings [Bunnings I/N 0082424] 1 1.5 × 1m piece of 150 GSM quilt wadding [Spotlight] 1 500mm length of thin-walled 90mm OD PVC stormwater pipe 1 can of black spray paint 1 Narva 24V 55W bulb, part number 48701 (optional) [auto parts store] 2 cartridges of Liquid Nails water clean-up building adhesive [Bunnings] 1 40mm saddle clamp or 8mm eye bolt Assorted hardware, eg, 40mm particleboard screws, spacers & solder tags Machine screws, bolts, washers and Nyloc nuts Assorted lengths and colours of hookup wire double all quantities except these for two speakers this may only be available in large sheets. You can buy a large sheet and have the store cut it into manageable pieces. If new homes are being built where you live, approach a carpenter and see if they have any offcuts of particleboard flooring to give away. Testing a pair of the pendant speakers during development. The stepladder is 3.7m high. Australia's electronics magazine siliconchip.com.au 🔸 ▪ 🔸 🔸 🔸 🔸 ▪ 46 Silicon Chip Two of the pendant speakers hanging in a shed converted to a living space. Using different sized enclosures After considering many different sizes, we chose to make the High-­Performance Pendant Speaker quite large. The enclosure volume is nominally 27L, while the enclosure as a whole has a volume of about 35L. Selecting a relatively large enclosure has benefits, especially in bass response. Because it is hanging in mid-air, so not taking up any floor space, the downsides of going large are minimal. But what if you want to use a smaller enclosure? In addition to modelling the 27L enclosure, we also modelled two smaller enclosures in both sealed and ported designs. Table 2 shows the results, with the ported designs tuned to give a strong lower end bass boost, as needed in a pendant speaker. Table 3 shows the length and diameter of the port needed with each smaller enclosure, and the frequency each enclosure has been tuned to. 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 Enclosure Vol. Sealed -3dB Sealed peak Ported -3dB Ported peak JANUARY 2000 – DECEMBER 2004 27L 51Hz +1dB <at> 94Hz 48Hz +8.5dB <at> 78Hz JANUARY 2005 – DECEMBER 2009 20L 54Hz +1.5dB <at> 90Hz 52Hz +8.5dB <at> 85Hz JANUARY 2010 – DECEMBER 2014 15L 56Hz +2dB <at> 96Hz +8.5dB <at> 94Hz JANUARY 2015 – DECEMBER 2019 59Hz Table 2: bass performance with reduced enclosure volume OUR NEWEST BLOCK COSTS $150 JANUARY 2020 – DECEMBER 2024 Enclosure Vol. Port diameter Port length Tuned frequency (modelled) 27L 90mm 100mm 63Hz (55Hz measured) OR PAY $650 FOR THEM ALL (+ POST) 20L 75mm 100mm 66Hz 15L 50mm 45mm 69Hz WWW.SILICONCHIP.COM. AU/SHOP/DIGITAL_PDFS Table 3: port tuning September 2025  47 Part 1 by Richard palmer HOME ASSISTANT R P with a aspberry i There are many situations around the home and on the workbench where remote sensing and control can improve our lives. T his short series will explore the world of home automation and create the core of a system that interfaces with a broad range of commercial smart home devices, plus hundreds of DIY sensors and remote-control interfaces. That will include everything from sprinklers to music systems, pet tags to air conditioners. Home automation has matured to the point where do-it-yourself installations can be achieved without needing to write code. Readily available sensors and controls can be wirelessly connected to a central hub and added to the system with just a little configuration information. This month, we will review community-­supported home automation platforms. We’ll also discuss our simple project (in this issue) that can connect sensing and control devices to a central home automation hub using a WiFi network. A follow-up article next month will have information on more advanced matters, such as remote access, customised dashboards and cameras. Smart homes & IoT IoT (the Internet of Things) connects the physical and virtual worlds using sensors and controls connected to monitoring and automation software via communication networks. Home automation is a subset of IoT focused on the domestic environment. 48 Silicon Chip Home automation begins with sensing something in the environment, such as time, temperature, light intensity, the presence of smoke, or movement. A set of rules is applied to automate actions, such as switching a light on or off, or sending a notification based on sensed changes. A typical home automation system includes an in-home server (the ‘hub’), and a range of ‘satellite’ devices distributed around the property, communicating using some form of wireless link. That link could be a local WiFi network, Bluetooth or a Zigbee mesh. The hub is either a stand-alone device, or connects to a cloud-based platform which enables remote access – see Fig.1. Dr David Maddison’s review of home automation in the January 2024 edition of Silicon Chip (siliconchip. au/Article/16082) describes many of the available technologies and protocols used. There are a multitude of commercially available devices that can directly interact with home automation services. A quick internet search turned up eleven pages of smart home products at Officeworks and 740 products at JB Hi-Fi, covering lighting, gardens, security and even smart pet-tech. Similar searches via AliExpress and eBay each returned more than fifty pages of results. Where devices are not designed to be directly controlled by such a system, automated control can often be implemented by switching their power on and off, or mimicking an existing control capability, such as an infrared (IR) remote. For devices with no remote control capabilities, there are Fig.1: the HomeAssistant ecosystem comprises a local hub with satellites that host sensors & controls. Satellites may be microcontroller-based, using ESPHome, or be fully integrated units such as IP cameras. Communication between elements commonly uses WiFi, Bluetooth or Zigbee. Remote access to the system can be provided by a VPN or cloud service. Australia's electronics magazine siliconchip.com.au There are excellent and easy-to-use commercial integration platforms such as Google Assistant, Amazon Alexa, Apple HomeKit, Philips Hue and Samsung SmartThings. Each has its pros and cons. However, these platforms are largely devoid of features that support DIY. Almost all require a commercial in-home hub and an online account. Mix-and-match integration of various vendor’s ‘ecospheres’ into one master platform can be a frustrating and sometimes-unattainable goal. Fortunately, there are several groups of enthusiasts that have created opensource home automation ecosystems that can integrate with a range of commercial hardware and also support DIY applications. Two enthusiast-­ friendly platforms stood out as I began researching this series: openHAB and HomeAssistant. They both offer a fully featured hub, integrations with a wide range of DIY and commercial home automation products, remote access and integrated cloud services. Both host their hubs on the Raspberry Pi platform using customised operating systems. They both offer voice control via integration with smart home assistants such as Google Assistant, Siri or Alexa. For DIY projects, HomeAssistant (HA) stood out. From the hub’s browser interface, you can configure and manage remote sensors and controllers based on WiFi-capable microcontrollers such as the Raspberry Pi Pico W and Espressif Systems wireless microcontrollers (eg, the ESP8266 & ESP32) using HA’s ESPHome firmware. More than a hundred sensors and control interfaces are pre-­ integrated. While HomeAssistant’s cloud service costs around $10/month, remote access can be configured at no cost using one of several free VPN services. openHAB also has a very wide range of integrations with commercial home automation devices; however, integrating DIY projects is more Fig.2: the HomeAssistant platform has three layers: a basic Linux operating system, a Supervisor layer and the HA Core. Source: https://developers.homeassistant.io/docs/architecture_index The HomeAssistant Overview dashboard with the ESPHome satellite and a USB webcam installed. » Fully-featured DIY home automation system using a Raspberry Pi » Integrates with a wide range of commercial & DIY equipment » Remote access via smartphone, tablet or computer » Broad open-source community support ‘fingerbots’ that can press a button on command! Choosing a platform siliconchip.com.au Australia's electronics magazine complex. Its cloud platform, myopenHAB, is free. While openHAB’s free cloud service was very tempting, we selected HomeAssistant for this series based on its flexible DIY device capabilities. Installation on a Raspberry Pi 3B, 4 or 5 is straightforward, or it comes pre-installed on HA’s Yellow or Green platforms. HomeAssistant HomeAssistant has three layers: a basic Linux operating system, the HA Core that interacts with users, devices and services and the Supervisor, which orchestrates the various HA components and manages backups and updates – see Fig.2. Home Assistant’s language can be confusing at first. A few key definitions may be helpful: • An ‘entity’ is the basic building block of home automation. It represents a single sensor, control element or function. Entities have ‘states’, which may be binary or a range of values. • A ‘device’ may host a single entity, such as a switch or a light sensor, or several entities, such as temperature, pressure and humidity sensors. • An ‘area’ is a logical grouping of entities and devices, often representing a geographic location, such as a kitchen. Areas can be assigned to ‘floors’. • An ‘integration’ is the software that connects HomeAssistant to a compatible device, such as an ESPHome September 2025  49 Another practical application While writing this article, a local community radio station needed to improve the monitoring and control of the equipment at its transmitter site from the studios, or remotely using the engineering team’s laptops or phones. The station’s two transmitters, uninterruptible power supply (UPS), studio-­ transmitter link and backup program links have a range of digital and analog inputs and outputs for monitoring and control. HomeAssistant and ESPHome seemed a good solution to their problem. Pico-based satellite hardware like that described in the accompanying project article was used for the thirty-odd digital and analog values to be monitored and drive relay and opto-isolated outputs. It only took a few hours to integrate the hardware into ESPHome and create the required sensors and controls in HomeAssistant. No custom code was required, saving weeks of programming and improving reliability. satellite or a webcam, or another home automation or service platform such as email or the HomeAssistant Cloud. • ‘Automations’ are sets of repeatable actions that can run automatically. They comprise ‘trigger’ events, tests for ‘conditions’ on those events and resulting ‘actions’. You can find a more detailed discussion of these concepts at siliconchip. au/link/abr3 The Home Assistant hub We chose to create our own hub using a Raspberry Pi. Any Raspberry Pi, from the Model 3B onwards, will do. All that is required besides the Pi is a 32GB Class A2 microSD card for the custom HAOS operating system. An existing Raspbian SD card can be overwritten with the new OS. Details of the requirements and options are available on the HomeAssistant website (siliconchip.au/ link/ac5w). While many home automation needs can be satisfied with off-theshelf commercial components, there are still situations where it is more practical and less expensive to create a DIY solution. There are also situations where a compatible remote control device isn’t available commercially, but the communication protocol is well-­ documented. TVs and air conditioners are a case in point. To assist with these needs, we have developed a small PCB that can connect to a wide range of digital, analog and I2C sensors, as well as controlling devices via an IR signal or relay. It is Screen 1: when preparing the SD card, select Home Assistant OS in the Raspberry Pi Imager app. 50 Silicon Chip Australia's electronics magazine This fingerbot can press a button on any device as a simple remote control. presented as a separate project in this issue, starting on page 54. Setting up HomeAssistant For the purposes of this tutorial, we will use a Raspberry Pi Model 5 as the hub. However, the process is similar for other platforms. Detailed instructions are available at siliconchip.au/ link/ac5w When procuring a case for the Raspberry Pi, avoid those made entirely of metal as they tend to reduce the WiFi range significantly. The official redand-white plastic case or a clear acrylic case are solid choices. The active cooler kit is also a good investment and fits neatly into the acrylic case. The HomeAssistant and ESPHome communities are very active, producing updates several times a month. For this reason, some of the instructions below may be out of date by the time this series is in print. Don’t despair if this happens; the documentation is kept up to date and help is available via the very responsive HomeAssistant user community (https://community. home-assistant.io). If you don’t want to build your own hub, the pre-configured HomeAssistant Green hub is readily available for around the same price as a well-­ configured Raspberry Pi 5 and case. Preparing the Pi is straightforward. If it came in kit form, just fit the motherboard into its case and mount the cooler’s heatsink. The fan cable goes into the connector behind the outside-­ edge USB connectors. There is no need to load or configure the Raspbian OS, as it will be replaced by HA’s HAOS operating system. Install and run Raspberry Pi’s Imager software on a Windows, Mac or Linux PC – see Screen 1. Select your siliconchip.com.au Raspberry Pi board from the list in the first box, then choose the required operating system in the second box, by selecting “Other specific-purpose OS”, then “Home Assistants and Home Automation”, then “Home Assistant” and the blue-logo version from the drop-down menus. Plug in an SD card adaptor with the microSD card installed (or, if your computer/monitor has an integrated SD card socket, use that). Select that card in the final Imager box. Click NEXT, and the card will be programmed over several minutes after an erasure warning box is displayed. Installing the OS There is no need for a screen, keyboard and mouse for the Pi as the installation is ‘headless’. Wired Ethernet is mandatory for the initial installation process, but it can be replaced by WiFi once HA is configured. Insert the SD card into the Pi and an Ethernet cable between the Pi and your WiFi router. Connect the power adaptor and press the power button on the Pi if it remains red after connection. Wait for 4-5 minutes for HAOS to initialise. The green power LED will flash intermittently during this time. The final configuration steps are completed via a browser on your PC; enter “http://homeassistant. local:8123/” in the URL bar. Refresh the URL regularly until the Home­ Assistant welcome page loads. Click on the “Create my smart home” button. The Name field is used for display, while the Username is used for logging in. They can be the same name. Add your location, which will be used for the weather displays and proximity mapping of any devices you choose to track. Select what information you wish to share with HomeAssistant’s developers. A screen of compatible devices that HomeAssistant has located on your network completes the basic installation process. The HomeAssistant Overview screen should then appear, as shown in Screen 2. Click on the Settings menu item and then Network. Under “Configure network interfaces”, click on WLAN0 and SEARCH NETWORKS. Select your WiFi network from the list, choose the appropriate security scheme, and enter your WiFi password. Click the SAVE button at the bottom of the block, not the one at the bottom of the page. siliconchip.com.au HomeAssistant-compatible cameras Several types of cameras can be added to HomeAssistant. The simplest is a USB webcam connected directly to the hub. Most commercial USB webcams should be compatible. If a remote camera is required, ESP32-based ESP-CAMs are available at very low cost and with acceptable picture quality. A USB-CAM with the standard OV2640 camera, including the USB adaptor board, costs less than $10 on AliExpress (eg, AliExpress 1005006501528278). While the OV5640 version provides a higher resolution image, plus autofocus on models with the silver lens surround, I do not recommend it. The one we tested had marginal low-light performance and tended to overheat, reaching temperatures of 70°C within a few minutes. A heatsink attached to the back of the sensor reduced the temperature to 40°C. Commercial WiFi cameras offer more advanced features such as pan and tilt, automatic IR illumination at low light levels, motion tracking and substantially better images. However, they are the most difficult to integrate due to a wide variety of firmware platforms being used. Of the WiFi cameras I tested, those using the V380 or V380 Pro configuration apps and marked ONVIF compliant in their specifications were the most likely to be compatible. We’ll have more on using cameras with HomeAssistant in the follow-up article next month. This $10 USB webcam produced very acceptable images. Screen 2: the Overview dashboard after the system has been initialised. The auto-discovery process located a Google home device; local weather is displayed by default. Parts List – Home Assistant 1 Raspberry Pi Model 3B or greater, with at least 4GB of RAM [Core Electronics CE09785] 1 Power supply for the Raspberry Pi [Core Electronics CE09787] 1 non-metallic case [Core Electronics WS-26089 or CE09789] 1 active cooler kit for the Raspberry Pi [Core Electronics CE09791] 1 32GB Class A2 microSD card 1 USB microSD card reader/writer (if your computer doesn’t have one) 1 Ethernet cable (for installation) Australia's electronics magazine September 2025  51 Left: a $10 ESP32-CAM with an OV2640 sensor. Right: a $50 WiFi camera with pan and tilt functions and IR-illuminated night vision. ONVIF compliance is essential for HA compatibility. Screen 3: HomeAssistant automatically scans the network for compatible devices. Now that your WiFi credentials have been entered, the unit no longer requires a wired connection. The username and password you set may also be used for smartphone, tablet and remote browser access. It is a good idea to use credentials without full administrator privileges whenever possible to reduce the possibility of accidental misconfiguration, and to increase remote access security. The basic installation is now complete, and you can start configuring your smart home. Before adding any new devices, it is useful to clean up the devices that have been auto-­ discovered. Select Settings near the bottom of the left-hand menu and click on Devices & services. A screen of discovered devices will appear, like in Screen 3. Devices like wireless-­capable printers and set-top boxes will be included. Click IGNORE on all except the iBeacon Tracker and perhaps a printer. They will clutter up the screen and can be easily re-discovered later. Further down the screen is a list of configured services (see Screen 4). There are some generic services, such as Bluetooth and the Home Assistant Supervisor, as well as some applications like a live-streamed radio channel browser and a weather service from the Norwegian Meteorological Institute. I clicked on “Shopping list”, then the three dots at the side of the “Integration entries” panel and then Disable to hide that service. The sidebar menu Screen 4: some services are enabled by default. Screen 5: the simplified HA menu after hiding some items. 52 Silicon Chip Australia's electronics magazine The sidebar menu has some items you may rarely use. To customise what’s displayed, click on your username at the bottom of the sidebar. Scroll down to the “Browser settings” block and click EDIT to change the order and hide items from the sidebar. Click on the X next to the items you don’t want to appear. The order can be changed by sliding the items to your desired location. Click DONE at the top of the main menu bar when you are finished. Initially, I hid all the optional items other than the Overview dashboard and the Logbook – see Screen 5. The “ESPHome” add-on will be needed to add the satellite device that’s described in the separate project article in this issue (it won’t hurt to add it regardless). Go to Settings siliconchip.com.au Screen 6: configuring the ESPHome Device Builder. Screen 7: a custom HomeAssistant dashboard showing the satellite’s sensors and controls, an IP camera’s image and a thermostat automation. The spikes in the temperature reading are from a finger being placed on the sensor. The thermostat temperature was raised during the second spike. then Add-ons, click on the ADD-ON STORE button at the bottom right, search for “ESPHome”. Select it and click the INSTALL link at the bottom of the tile, and then START once the installation is complete. Before exiting the installation menu, enable the “Show in sidebar” and “Watchdog” options – see Screen 6. ESPHome Builder should now appear in the left sidebar menu. Select it. Click on the SECRETS button at the top right-hand corner of the ESPHome tab. The edit window should contain something like the following: siliconchip.com.au ## secrets.yaml wifi_ssid: “your wifi ssid” wifi_password: “your wifi password” Fill in your network credentials and save them. This will allow new ESPHome devices to be automatically configured for your network. Click on the X next to the file name to close the edit window. Conclusion A separate project in this issue Australia's electronics magazine covers the construction of a satellite board based on a Pico W. Among other things, it supports temperature, humidity and motion sensors and an OLED display. That article will describe how to use it to create a simple thermostat, demonstrating HomeAssistant’s automation capabilities. Next month, in a follow-up article, we’ll add some more advanced features such as custom dashboards, remote access from a mobile phone or tablet, IR remote control, notifications SC and a camera or cameras. September 2025  53 Project by Richard Palmer HomeAssistant Satellite using a Raspberry Pi Pico W » Analog and digital inputs and outputs » Can transmit infrared remote control codes » Includes a relay/LED driver » ESPHome supports hundreds of sensors and controls » Includes an I2C bus connector compatible with 2QWIIC, STEMMA QT, GROVE & PiicoDev » Remote configuration and management This simple board lets you connect lots of different kinds of sensors, displays and other things wirelessly to a HomeAssistant based Home Automation system. n a Home Automation system, sensors and actuators CON9, a 4-pin JST-SH connector that is compatible with Itions attach to ‘satellites’, which can be placed at different loca- QWIIC, Stemma QT, Grove and PiicoDev devices. CON8 around the home. Each can support multiple attached also provides access to the I2C0 bus, allowing the connec- devices communicating with the hub over the household tion of a small OLED screen. If two devices with the same I2C address need to be WiFi network. Our Satellite uses a Pico W microcontroller module pro- connected, a second I2C bus is available at several locagrammed with the ESPHome firmware. While the newer tions on the expansion connector, CON4. However, note Pico 2 W may be used, it costs a little more and the extra that pull-up resistors will need to be added if the second power is not required for this application. I2C1 bus is used. A small PCB hosts the Satellite’s The adjacent table lists the functions CON4 expansion header pinout basic components and makes it easy to available on the expansion connector. connect to a wide range of supported Pin Signals Separate pads for the 5V and 3.3V supdevices. You can see a list of the sup- 1 plies and ground are provided at CON1GP15, I2C1, SPI1 ported sensors at https://esphome.io/ CON3. 2 GP14, I2C1, SPI1 components For remote control, IR LED1 is driven 3 GP13, SPI1, UART0 by Q1, a BC817 or similar NPN transistor, Circuit description from the 5V supply. Its 40mA operating 4 GP12, SPI1, UART0 Fig.1 shows the Satellite circuit. current is higher than can comfortably GP11, I2C1, SPI1 As you can see, there isn’t a lot to it 5 be supplied directly by a digital output besides the Raspberry Pi Pico W mod- 6 pin on the Pico module. GP10, I2C1, SPI1 ule shown in the middle. Transistor Q2 can drive an off-board 7 GP9, SPI1, UART1 Most sensors and many control 5V relay or solid-state relay (SSR). LED2 GP8, SPI1, UART1 devices will connect to the Satellite 8 lights when the relay is operating, while via a two-wire I2C serial bus. I2C0’s 9 diode D1 protects the transistor against GP7, I2C1, SPI0 SDA (I2C data) and SCL (I2C clock) back-EMF when a traditional relay GP6, I2C1, SPI0 functions are connected to GPIO pins 10 switches off. GP28, ADC0 20 and 21, with pull-up resistors to 11 The 64kHz PWM signal at GP16 is the 3.3V rail as required for I2C com- 12 smoothed by an RC low-pass filter formed GP27, ADC1 munications. by a 10μF capacitor and 470W resistor, GP26, ADC2 Access to the I2C bus is provided by 13 giving a -3dB frequency of approximately 54 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.1: the Raspberry Pi Pico W module drives the IR LED (LED1) and relay through transistors Q1 and Q2. Digital and analog I/O is via CON4, with power available from CON1-3. CON9 is a QWIIC, Grove and PiicoDev compatible I2C connector. The I2C OLED display connects via CON8. 34Hz, reducing the ripple of a 50% duty cycle output to around 10mV peak-to-peak. While the Pico is capable of much higher PWM frequencies, which would result in even lower ripple, there is a trade-off between frequency and bit depth (resolution), which is 10 bits at this frequency. The smoothed output is presented at CON6, forming a basic kind of digital-to-­ analog converter (DAC). The board’s 5V supply is powered either via a microUSB cable plugged into the Pico W, or from CON5. In most cases, a 5V 500mA supply should be adequate, as the Pico W draws less than 100mA and the IR transmitter requires 20mA on average. However, the supply must also be able to support the needs of any connected devices. For instance, 5V relays commonly draw 75mA or more when energised. The Pico W module has an onboard 3.3V regulator capable of supplying 250mA to auxiliary devices. If more than this is required, an additional 3.3V supply will be needed. Construction The Satellite is built on a double-­ sided PCB coded 15104251 that measures 51 × 54mm. Start by soldering the SMD components in the locations shown in Fig.2. The band on the diode must point toward the power header. Next, add the two 20-pin female headers for the Pico, the JST-ST connector (CON9) and the two LEDs. Leave CON1CON8 off at this stage. Solder headers to the Pico W, if they weren’t already fitted, and plug it in with the USB socket at the top of the board. You can use the sockets on the board as a jig to hold the headers while soldering them to the Pico W. Now plug the USB cable into a port on your PC. 5V should appear on CON1 and 3.3V at CON3. Disconnect it after checking those supply rails. siliconchip.com.au Configuration If you have difficulty with any of the configuration steps below, there is documentation at ESPHome’s website (https://esphome.io) and a helpful user community at https://community.home-assistant.io Load the ESPHome firmware next. Go to the ESPHome Builder tab in HA, click on the + NEW DEVICE button and CONTINUE. You can name your device “myHome” (or something else if you prefer). Select Raspberry Pi Pico W as the platform, then click INSTALL. A copy of the encryption key will be saved in the configuration file. Select the “Manual download” option when the pop-up window appears – see Screen 1. It will take a minute or more for HA to compile customised code for the new device. When the wheel stops spinning, select Download project and UF2 factory format, then close the pop-up window. You may need to approve the download in your browser (“Keep” in Chrome) as it’s coming from an unsecured host. Hold down the BOOTSEL button on the Pico while plugging its USB cable into your computer. Copy the downloaded UF2 file across to the “RP1-RP2” drive that has appeared in the PC’s file manager and close the pop-up window. Fig.2: all components are on the top of the PCB; mount the SMD components before the through-hole items. Australia's electronics magazine September 2025  55 The block with your Pico’s name should become ONLINE in the ESPHome Builder tab, after a 30 second delay (Screen 2). This is a basic ESPHome device, with no sensors or outputs configured. Click on the EDIT link on the myHome card and the configuration file will be displayed. Additional configuration lines for sensors and controls will be added below this code – see Screen 3. Screen 1: the “New device” screen while the code is being compiled. Each YAML block starts with an identifier, usually the item’s type. Values are indented and the number of leading spaces is significant (usually two per level). Each level’s information is terminated when a less indented item is encountered. Comments begin with a “#” and continue to the end of line. Close the editing window by clicking the X at the top left corner and click on the LOGS link in the myHome card. A window will open with the history of the device since it was last booted. In this case, most of the information is in purple, describing the WiFi connection process. Close the window. The Satellite is now ready and the final step is to tell the HA Core that it exists. Go to Settings then Devices & services and +ADD INTEGRATION. Search for “ESPHome” and click SUBMIT. The Satellite should pop up as a discovered device. If not, type “myHome.local” (or prefixed with whatever name you gave it) into the “Host” field and click SUBMIT. If you had to enter the host name, the installer will ask for the encryption key from the myHome.yaml configuration file. Click SUBMIT after that. The Area field may be left blank on the next screen. Approve the request for the device to perform HomeAssistant actions, then click FINISH to make the Satellite active. The Satellite may not appear on the Overview dashboard at this stage, as it has no sensors or controls defined. Adding a sensor Unplug the USB cable, connect an SHT40 temperature sensor to the I2C port and plug the USB cable back in. Re-open the editor and add the following code at the bottom of the myHome.yaml file. Screen 2: the initialised Pico W Satellite’s card in the ESPHome builder tab. ## Temperature.yaml ## Temperature & Humidity sensor ## Pico W I2C0 bus i2c: sda: 20 scl: 21 scan: true frequency: 400kHz ## SHT40 sensor sensor: - platform: sht4x update_interval: 10s humidity: name: “Humidity” id: humidity temperature: name: “Temperature” id: temperature Screen 3: the myHome device’s initial configuration file. 56 Silicon Chip Rather than typing this in, you can copy and paste this from the file named “Part2.yaml” in the download package for this series (siliconchip.au/Shop/6/2482). That will not only save time but ensure you get the correct formatting for it to work. The first section defines the I2C bus that will be shared by other connected devices. The sht4x ‘platform’ uses the defined I2C bus by default. The “name:” field is used when displaying the entity, while the “id:” field is required if the entity is to be referenced by code. Australia's electronics magazine siliconchip.com.au In the SHT40 section, humidity and temperature sensors are defined, and the interval between readings is shortened from the default value of 60 seconds to 10. After adding the code, click SAVE and INSTALL (in the top right-hand corner) and select the Wirelessly option in the pop up. Depending on your HA setup, compiling the code may take a minute or more. You will know it has finished when the green SUCCESS message appears in the log. The code will then attempt to upload to the Pico and, after a delay of thirty or more seconds; the screen will show the Pico’s boot log. At the bottom should be light blue text indicating that temperature and humidity readings are being sent to the HA hub. If your configuration won’t compile, it may be due to incorrect indentation or code in the wrong location. The window may be closed by clicking STOP at any time after the download has completed. While STOP may appear a strange command to close the window, HA has launched a virtual Docker machine to do this work, and stopping the virtual machine when it is no longer needed closes the window. Close the myHome.yaml edit window, then go to HA’s Overview dashboard. After a minute or so, the myHome card should appear, showing the temperature and humidity. If it doesn’t, try reloading the web page. Screen 4: the myHome dashboard card with the Relay LED. The SSD1306 display showing temperature, humidity and the state of the Relay LED. Controlling the relay and LED Only a few extra configuration lines are needed to map the relay driver’s GPIO pin as a switch output. They are added to the Satellite system’s myHome.yaml configuration file below the SHT40 sensor definitions. The “switch:” component indicates that this is a binary output. The GPIO platform then maps the function to a microcontroller pin: ## Relay_LED.yaml ## Pico Relay and LED switch: - platform: gpio pin: 22 name: “Relay LED” id: led Save and install the updated configuration. After a minute or so, the myHome tab on the Overview dashboard should include a switch for the Relay LED – see Screen 4. Toggling the switch should cause the LED to come on. The completed Satellite board with and without the Pico W. All components are mounted on the top of the doublesided PCB. The optional header pins at CON8 allow easy disconnection of the OLED display. Adding a display ESPHome supports a wide range of displays. The SSD1306 OLED used in this project has an I2C interface and we can use it to show the current temperature and humidity, along with the LED/relay state and a graph of temperature over time. The display can be daisy-chained with the temperature sensor or connected via CON8. When wiring it up, take care with the pinouts as they tend to vary between display manufacturers. The I2C bus is already defined, so all that is needed is to declare the OLED display and add some lines of code to run regularly that write to the display. The OLED screen is set to the standard I2C address for 128×64 pixel mode. As the built-in font is blocky, we can use some Google fonts instead. In the display section of the code below, there is a portion siliconchip.com.au Australia's electronics magazine September 2025  57 Parts List – Home Assistant Satellite 1 double-sided PCB coded 15104251, 51 × 54mm 1 Raspberry Pi Pico W module with two 20-pin headers (MOD1) 1 micro-B USB cable 2 20-pin single-row female header sockets 4 3-pin headers (CON1-CON3, CON7) (optional) 1 13-pin header (CON4) (optional) 2 2-pin headers (CON5, CON6) (optional) 1 4-pin header (CON8) (optional) 1 4-pin JST-SH 1mm-pitch socket (CON9) [Core Electronics PRT-14417] Semiconductors 2 BC817 NPN transistors, SOT-23 package (Q1, Q2) 1 5mm 50mA IR LED (LED1) [Altronics Z0880A, Jaycar ZD1945, Core Electronics ADA387] 1 3mm red, yellow, amber or green LED (LED2) 1 SS14 or similar 1A schottky diode, DO-214AC/SMA [Altronics Y0084] Capacitors 4 10μF M2012/0805 16V X7R Resistors (all SMD M2012/0805 size 1%) 3 2.2kW 2 1kW 1 470W 1 100W Add-on sensors & display used in this article 1 SHT4x QWIIC temperature and humidity sensor [Core Electronics ADA4885 or ADA5776] 1 QWIIC cable [Core Electronics CE07773, Altronics Z6596 or Z6597] 1 AM312/AS312 PIR sensor module [Altronics Z6382A, Jaycar XC4444, Core Electronics CE05786] 1 SSD1306 I2C OLED display [Altronics Z6525, Jaycar XC3728, Core Electronics CE09493] marked “lambda”. Any code following the lambda marker is passed to a command interpreter for execution at runtime. Lambda code is written in the C language. Add the code to myHome.yaml below the relay’s “switch:” definition block: ## OLED_display.yaml ## define the fonts font: - file: “gfonts://Roboto” id: roboto_12 size: 12 - file: “gfonts://Roboto” id: roboto_16 size: 16 ## graph configuration graph: - id: temp_graph sensor: temperature ## sliding time window duration: 60min width: 106 ## half display height height: 32 border: True max_value: 40 min_value: 10 y_grid: 10 ## SSD1306 display display: - platform: ssd1306_i2c model: “SSD1306 128x64” address: 0x3C ## Print the text and graph lambda: |it.printf(0, 0, id(roboto_16), “%.1f°C %.0f%%”, id(temperature).state, id(humidity).state); if (id(led).state) { it.print(0, 14, id(roboto_16), “ON”); it.filled_circle(44, 22, 6); } else { it.print(0,14, id(roboto_16), “OFF”); it.circle(44, 22, 6); } it.print(110, 30, id(roboto_12), “40”); it.print(110, 52, id(roboto_12), “10”); it.graph(0, 32, id(temp_graph)); As with other YAML code, the lambda block ends when less indented text is found. The version in the download pack is easier to read, as the lines haven’t been wrapped to fit into a magazine column. The lambda code prints temperature and humidity on the first line, with the state of the LED and a circular on/ 58 Silicon Chip Australia's electronics magazine siliconchip.com.au Screen 5: the Traces screen for the “AC off” automation. off indicator on the second line. The bottom half of the screen displays a graph of the temperature over the past 60 minutes, between 10°C and 40°C, with horizontal grid lines every 10°C. The state of the relay LED slider on the dashboard (Screen 4) should be reflected in the OFF/ON text and indicator on the display. A simple thermostat Automations use the output of a sensor or other input condition, such as the time of day, to trigger an action. We will create a simple air conditioner thermostat that switches on the relay/LED when the temperature rises above 28°C and off again when the temperature falls below 27°C. These settings are convenient for testing with a finger on the temperature sensor. To implement the thermostat, the temperature reading is connected to the Relay/LED using two automations. On the HomeAssistant screen, go to Settings then Automations & scenes. Click on + CREATE AUTOMATION at the bottom right corner of the screen and Select “Create new automation” from the pop-up menu. Under “When”, click on + ADD TRIGGER. Select Device and choose “myHome” from the drop-down list. Select “myHome temperature changes” from the Trigger dropdown. Enter 28 into the Above field. The Below and Duration fields should be left blank. Under “Then do”, click ADD ACTION. Select Device and “myHome” as before. The Action is “Turn on myHome Relay LED”. Save the automation as “AC On”. Click the back arrow at the top of the screen to return to the “Automations” menu and create a second automation to turn the AC off. Under “When”, click on + ADD TRIGGER. Select Device and then myHome from the drop-down list. Select “myHome temperature changes” from the Trigger dropdown. Enter “27” into the Below field. Under “Then do”, click ADD ACTION. Select the Device myHome as before. The Action is “Turn off myHome Relay LED”. Save the automation as “AC Off”. The two automations will automatically activate within a minute. Go back to the Overview dashboard and hold a finger to the temperature sensor. The LED should light once the temperature rises above 28°C. The indicator on the dashboard should change, the relay LED should light, and the OLED display should indicate that the virtual AC is on. siliconchip.com.au When the temperature is allowed to fall, the relay LED should switch off below 27°C. Go back to the Automations & scenes menu and select “AC off”. Click on TRACES at the top right corner. The Trace Timeline tab should produce a screen very much like Screen 5; this view is useful when debugging more complex automations. We’ll have a follow-up article next month that describes how to use IR remote control to switch a split-system air conditioner on and off, a more realistic control method. Analog outputs We can set up GP16 to generate a 64kHz PWM signal that is smoothed by a simple RC filter and presented at CON6. The result is a voltage that’s proportional to the temperature, with the output scaled to a maximum of 3.3V at 33°C. The “monochromatic light” platform component is used as it provides a straightforward conversion from an input value to a brightness output. However, the conversion isn’t linear by default; the gamma value must be explicitly set to 1. Edit the configuration file’s “sensor:” block to add the on_value clause immediately after the “id: temperature” statement, then add a new “output:” block for the PWM at the end of sensor clause: ## PWM_temp.yaml ## PWM set by temperature ## Replaces existing temperature ## and humidity sensor code ## sensor: - platform: sht4x update_interval: 10s humidity: name: “Humidity” id: humidity temperature: name: “Temperature” id: temperature on_value: then: - light.turn_on: id: pwm_lamp ## 10 degrees/volt brightness: !lambda “return x/33;” Australia's electronics magazine September 2025  59 Screen 6: the myHome dashboard card with the PIR sensor. Also add the following after the sensor block: ## PWM_output.yaml output: - platform: rp2040_pwm pin: 16 id: PWM_16 frequency: 64000Hz light: - platform: monochromatic output: PWM_16 ## straight line temp:pwm gamma_correct: 1.0 name: “PWM lamp” id: pwm_lamp When the code is installed, the PWM output voltage at CON6 will track the measured temperature. PIR motion detection Connect a PIR sensor to the GP15 input at pin 1 on CON4, with 5V power and ground to CON1 and CON2, respectively. The required connections are shown in Fig.3. The sensor produces a binary value, so the code sits in a separate block to sensors that produce numeric values. Add the following code to your device in ESPHome Builder after the “sensor:” block, then save and install the changed configuration: ## PIR.yaml binary_sensor: - platform: gpio pin: 15 name: “PIR” device_class: motion id: PIR The MyHome card on the Overview dashboard should SC now look something like Screen 6. Fig.3: wiring for the PIR sensor is simple. In this example, Vout goes to GPIO GP15 (pin 1 on CON4), while 5V power comes from any combination of pins on CON1 & CON2. 60 Silicon Chip Australia's electronics magazine siliconchip.com.au SOnline ilicon Chip Shop Kits, parts and much more www.siliconchip.com.au/Shop/ Rotating Lights April 2025 USB-C Power Monitor August-September 2025 USB Power Adaptors May 2025 SMD LED Complete Kit SC7462: $20 TH LED Complete Kit SC7463: $20 Short-Form Kit SC7489: $60 siliconchip.au/Article/17930 siliconchip.au/Series/445 siliconchip.au/Article/18112 This kit includes everything needed to build the Rotating Light for Models, except for a power supply and wire. This kit includes all non-optional parts, except the case, lithium-ion cell and glue. It does include the FFC (flat flexible cable) PCB. You can choose from one of four USB sockets (USB-C power only, USB-C power+data, mini-B or micro-B). The kit includes all other parts. Compact HiFi Headphone Amplifier Complete Kit SC6885: $70 Complete Kit with choice of USB socket SC7433: $10 Capacitor Discharger December 2024 December 2024 & January 2025 siliconchip.au/Series/432 This kit includes everything required to build the Compact HiFi Headphone Amplifier. The case is included, but you will need your own power supply. Programmable Frequency Divider Complete Kit SC6959: $60 Feb25: siliconchip.au/Article/17733 Includes all onboard components, except for a power supply and the optional programming header. Short-Form Kit SC7404: $30 siliconchip.au/Article/17310 Includes the PCB, resistors, semis, mounting hardware and banana sockets. Case, heatsink, thermal switch and wiring are not supplied. → Subscribers receive a 10% discount on all purchases, except for subscriptions (postage is not discounted). → Prices listed do not include postage. Postage rates within Australia start at $12, rates are calculated at the checkout. Last month, we looked at some ways to improve amplifier cooling, either in an amplifier you are building or an existing one that is running too hot. This month, we go into the details of modifying a specific amplifier to improve its fan cooling. Part 2 by Julian Edgar Cooling Audio Amplifiers A fter ‘cooking’ two hard-working amplifiers in a hot roof space, I resolved that any further amplifiers put to this torture test would need to be commercial (rather than domestic) designs – and preferably fan-cooled. My budget didn’t extend to new amplifiers, so I looked for second-hand ones. After an extensive search, I found two LD Systems amplifiers – the XS-400 and XS-700. The XS-400 has an output of 2 × 200W into 4W, while the XS-700 develops 2 × 350W into 4W. Both are Class-D amplifiers that have a maximum distortion of less than 0.1%. Not hifi, but good enough for a wholeof-house sound system. I bought the XS-700 first and tested it extensively, using it to power two 15-inch (380mm) subwoofers, also located in the roof space. The testing showed two things. First, the amplifier worked well, and second, despite the fan cooling, certain internal components ran quite hot. I’ll concentrate on the XS-700 in this article, but I modified both amplifiers in the same way. Airflow will take the path of least resistance, and the inner surface of the top amplifier panel is often the smoothest, least obstructed path. Therefore, with air inlets in the front panel and an outlet fan in the back panel, unless it is prevented from doing so, a lot of air will flow along the underside of the top panel, completely missing all the components it is meant to cool! these initial temperatures were measured in 20°C ambient conditions). The heatsink in the audio section of the amplifier was noticeably hotter – about 45°C. What really concerned me were two voltage regulators positioned in the middle of the PCB. These were running at 60°C – and in hot ambient conditions, I saw 75°C! See Photos 2 & 3. The data sheets for these KA7815 and KA7915 regulators showed a specified operating range of 0-125°C. However, that’s the junction temperature, which is likely to be a fair bit higher than the external temperature (to calculate how much, we’d need to know their dissipation and multiply it by the junction-to-case figure in the data sheet). Still, they are likely well within their specifications. However, running 40°C above ambient seems pretty darn hot to me! Perhaps more worryingly, they’re located very close to two large electrolytic capacitors, which are known for not liking heat. Australia's electronics magazine siliconchip.com.au Initial temperature testing The amplifier uses two major heatsinks: one located in the audio amplification section, with the other for the switch-mode power supply (see Photo 1). Measurements from an infrared thermometer showed that the power supply heatsink was typically running relatively cool, for example, 37°C (all Air can be sneaky sometimes 62 Silicon Chip Photos 1-3: this LD Systems 350W × 2 Class-D amplifier has a single rear fan that draws air through two grilles in the front panel. The large heatsink on the right is for the power supply; the one on the left is for the audio amplifier. The thermal camera view inside the amplifier shows the hottest parts to be two voltage regulators – they’re nearly 39°C in 20°C ambient conditions after only a few minutes. Once more time has passed, those two regulators (circled) are over 60°C. While within their specifications, they are next to two large electrolytic capacitors. Such capacitors don’t like heat. For cooling, the amplifier uses two front grilles and a 35mm fan located more or less centrally on the rear panel (Photos 4 & 5). The two front grilles are internally covered with a dust filter (Photo 6). The fan operates at two speeds; it appears the increased speed is triggered when the audio heatsink is above 55°C. An airflow baffle made of PCB laminate is positioned transversely near the front of the amplifier, between the two main heatsinks, with some small holes in it. No airflow baffles are provided outboard of the two major heatsinks. So where was the air going inside the amplifier? I removed the upper panel of the enclosure and temporarily replaced it with a sheet of clear acrylic. I then used the smoke from an incense stick to carefully observe It is difficult to concentrate when an amplifier is belting out at full volume, so it’s best to use a dummy load when doing high-load testing. People in your household (and possibly your neighbours, and their neighbours) will thank you. The load comprises resistors of an appropriate value to emulate the speakers you are using – for example, 4W or 8W. Very high power resistors are expensive, but there’s a cheap and easy way to create your own load. Two approaches can be taken. In the first, buy two electric jug elements of the sort that have an exposed winding on a ceramic base. Unwind sufficient length from each so that you create a load with the appropriate resistance. For example, configure each as an 8W load and wire them in parallel to give a 4W load (see Photo 7). Or, since this type of jug element is now becoming more expensive Photo 4: a standard baffle is located between the two main heatsinks to prevent air flowing directly from the front vents to the rear extracting fan. However, testing with smoke showed quite a lot of air passed straight over the top! Photo 5: the rear-mounted fan has two speeds, with the slower of the two being inaudible. siliconchip.com.au the pattern of the airflow within the working amplifier. As always, when doing this type of flow testing, things were not as expected! There were three main paths that the air took between the inlet grills and the outlet fan – bypassing the audio heatsink to the left, bypassing the power supply heatsink to the right, and flowing over the top of the central baffle in the gap between the baffle and the lid! That is, none of the heatsinks had much airflow passing along their fins, and the two very hot voltage regulators were largely in static air, although they got a small amount of flow. Before doing any further testing, I decided to connect a dummy load. Dummy loads Australia's electronics magazine September 2025  63 and harder to find, buy some 5W, 1W wire-wound resistors and wire them in series to get the required resistance. Use thick cable to connect the loads to the amplifier’s speaker terminals – one load for each channel. Then fill a Pyrex (or ceramic) container with water and place the loads in it. Ensure that the resistors and connecting cables cannot short out and be aware that the water can become hot enough to burn. Make sure that neither you nor anyone else can come into contact with the water. I used eight 1W 5W resistors, wired in series to form two 4W loads, placed each side in a double ceramic cooking dish. The dish contained about one litre of water (Photo 8). It took about an hour of testing for the water to get really hot. One problem with using a dummy load for an extended period of testing is that, should your input signal fail, you may be unaware of that. To overcome this, wire a speaker to one channel of the amplifier through a 150W 5W series resistor. This will allow you to hear the input signal at a low volume, even when the amplifier is working hard. If the speaker is still too loud, increase the resistance. The monitoring speaker will also let you know if you have cranked up the amplifier high enough that it clips (the sound will distort), so you can turn it down a bit. While most amplifier testing uses a sinewave input, I suggest that for this testing, you use normal music of the This will allow the heatsinks to heatsoak and so be forced to work as heat exchangers. This test also allows you to monitor your dummy load, to ensure that the water doesn’t become too hot. If it does, switch the amplifier off and then carefully replace the water at appropriate intervals, or use a larger container. If you are unsure whether the amplifier has an automatic temperature-­based shutdown, monitor internal temperatures during this initial run-in period. Testing with the dummy load Photo 6: the front air inlet grilles had this filter placed over them. I removed it to achieve better flow. sort you listen to. A sinewave input will work the amplifier extremely hard, and unless you habitually listen to sinewaves for recreation, it’s also not indicative of the conditions under which the amplifier will actually be working. To set the input level correctly, take note of the volume control’s position when your normal speakers and source are connected and you are playing music as loudly as you ever will. Then, with the dummy load and monitoring speaker connected, replicate that level on the control. When testing, start by running the amplifier at full power (below clipping, remember) for 15-20 minutes. With the dummy load connected and the clear acrylic lid in place, I could fully test the XS-700 amplifier. My first concern was with the very hot voltage regulators. Their heatsinks were small, had vertical fins (whereas the airflow through the amplifier enclosure is horizontal) and furthermore, the two heatsinks were positioned at right-angles to each other. Editor’s note: those small blocky heatsinks are better than no heatsink but otherwise are mostly useless. Even a small flag heatsink will generally outperform them. Flag heatsinks have gaps in the fins, so airflow in virtually any direction will help them dissipate heat. Replacing these heatsinks with a much larger, horizontally aligned design seemed to be a good first step – but there was a snag. To remove the existing heatsinks would be very difficult; the main PCB would need to be removed from the case, and even then, Photos 7 & 8: a dummy load can be made by rewiring electric jug elements or using series wire-wound resistors. In both cases, match the impedance of the speakers you are using (eg, 4W). The load is then placed in a ceramic (or Pyrex) dish that has been filled with water. Warning: the water can become hot enough to scald; and both resistive loads for each channel should be kept separate as contact between them could damage the amplifier. 64 Silicon Chip Australia's electronics magazine siliconchip.com.au gaining access to the screws that held the heatsinks to the regulators would be difficult. Obviously, these components were installed early in the build process. Could the heatsinks be retained and airflow better directed at them? I created a smooth channel between the fan and the two regulators from two thin strips of cardboard. In effect, nearly all the fan’s air was then being channelled through the voltage regulators’ heatsinks. Doing this showed a dramatic drop in the regulator temperatures – from running at 60°C to 49°C. However, as you would then expect, the airflow pattern within the enclosure was altered – testing with smoke showed that the audio amplifier heatsink was getting much less airflow past it, and the infrared thermometer showed a commensurate increase in heatsink temperature. I then cut a small opening in the wall of the baffle closest to the audio heatsink, allowing the fan to draw some air from that direction. Smoke testing showed this was indeed happening, and the audio heatsink dropped in temperature (see Photo 10). But what about the other end of the amplifier – the power supply section? That heatsink had never run particularly warm, and yet a lot of airflow was passing around it – a waste of flow, if you like. I then extended the standard central baffle in that direction, reducing the flow around this heatsink. As expected, the heatsink’s temperature then rose a little – but it was Measuring temperatures For reasons of safety, convenience and speed, infrared temperature sensing is the best way to check the amplifier’s temperature during testing. An infrared thermometer measures the amount of infrared energy given off by an object. The amount of infrared energy coming from an object depends on its temperature and emissivity. The emissivity of a perfect radiator of infrared energy, called a blackbody, is 1. However, many objects have emissivities that are less than 1, and if a correction isn’t made for this, the temperature measurement will be wrong. If the object either reflects or transmits infrared energy, the emissivity value will be less than 1. Shiny polished surfaces, such as aluminium, are so reflective of infrared energy that accurate temperature measurements of those surfaces may not be possible without modifying them. Some infrared thermometers can be programmed for the emissivity of the surface you are measuring, but many just use a default value of 0.95 – the emissivity of lamp black or candle soot. If you are making only comparative measurements (has the temperature gone up or down with your modifications?), the emissivity won’t matter much, but if you want accurate values and you are measuring a shiny surface, you may want to colour it black with a marker, or on a large shiny heatsink, stick a thin piece of black electrical tape onto it. A thermal camera, while more expensive than a digital infrared thermometer, can also be very useful. Like an infrared thermometer, thermal imaging cameras (sometimes also called thermographic cameras) measure infrared radiation. However, unlike the thermometer, they then render that as a visible light image on a colour LCD. Typically, the ‘hotter’ the colour on the display colour, the higher the temperature of that area. The biggest advantage of a thermal camera over an infrared thermometer is that you can quickly scan whole areas – just point the camera at the open amplifier and you can immediately see the hot spots. Another advantage is that thermal imaging cameras automatically adjust the scale that they are using, depending on the variation in temperature. Therefore, quite subtle variations in temperature, that you would take a long time to find with the infrared thermometer, are immediately visible. However, unless you have other uses for a thermal camera (I have found that there are plenty), the infrared thermometer should be good enough for amplifier temperature measurement. Photo 9: it doesn’t photograph well, but it’s easy to see the smoke flow from an incense stick being drawn through the case. The top cover has been replaced by a sheet of clear acrylic. A temporary cardboard baffle (under the brown wiring) is reducing the flow that bypasses the power supply heatsink. Photo 10: a close-view of the temporary cardboard baffles. The cutout in the baffle nearest the camera allows airflow from the front inlets past the audio heatsink (left, out of view). This tiny cutout made a dramatic change to the measured flow past that heatsink. siliconchip.com.au Australia's electronics magazine September 2025  65 2 3 1 Photo 11: the temperature and flow testing setup. (1) Temporary baffles linking the voltage regulators to the fan. (2) Strip prevent air flowing over the top of the standard baffle. (3) Baffle to prevent flow bypassing the lower power supply heatsink. Table 1 – amp modifications Heatsink Standard Modified Power supply 37°C 39°C Voltage regulators 60°C 49°C Audio 55°C 52°C Photo 12: the final airflow baffles and guides can be made from insulating paper such Presspahn or this fibroid fish paper. The baffles and guides can be held in place with small dabs of silicone sealant. 66 Silicon Chip still the coolest major heatsink in the amplifier. Time for some more smoke testing. With the voltage regulator cooling tunnel in place, complete with the cutout in the wall to promote some flow around the audio heatsink, and the baffle preventing a lot of wasted airflow past the power supply heatsink, the interior airflow pattern of the amplifier had greatly changed. With some of the previous free-flow channels now blocked, a lot of airflow was passing over the top of the standard front baffle. I then added a cardboard strip to block this flow (Photo 11). Interestingly, the fan could now be heard working harder – it was drawing air past the components it was meant to cool, rather than happily bypassing most of them! Table 1 shows the results. They were measured just below clipping on music material, working as a subwoofer amplifier crossed over at 90Hz, in a 20°C ambient environment, with the fan operating at a low speed. As can be seen, at full load, the altered airflow has caused a slight increase in the power supply heatsink temperature, a reduction in the audio heatsink temperature and a major reduction in the voltage regulator temperature. In fact, many hours of testing showed that the voltage regulator Australia's electronics magazine temperatures were reduced by as much as 25°C in some conditions! Installing the baffles Rather than use cardboard to form baffles and guides, it is better to use an insulating product such as Presspahn. However, I found it difficult to get cheaply in small quantities, so I used fibroid fish paper, which is available from Rockby Electronics. It comes in a tight roll and needs to be flattened before it can be used. This can be achieved by rolling it in the other direction and/or using an iron. The paper can then be cut to size and inserted where the cardboard trial baffle and guides were. A few dabs of silicone sealant hold them in place. To seal the baffle (the one that had plenty of airflow over the top), I used a strip of soft foam rubber cut from a larger sheet. Again, this was held in place with some silicone. When the lid is replaced, it seals against this foam. Conclusion Whether it’s thermally connecting panels to act as heatsinks, re-­orientating heatsinks to allow better convectional flow, adding fans or altering airflow patterns within the enclosure by using guides and baffles, improving amplifier cooling can make a major difference to SC internal temperatures. siliconchip.com.au Photo 13: the finished modifications. They cost very little but give major reductions in the temperature of the hottest components. Versatile Battery Checker This tool lets you check the condition of most common batteries, such as Li-ion, LiPo, SLA, 9V batteries, AA, AAA, C & D cells; the list goes on. It’s simple to use – just connect the battery to the terminals and its details will be displayed on the OLED readout. Versatile Battery Checker Complete Kit (SC7465, $65+post) Includes all parts and the case required to build the Versatile Battery Checker, except the optional programming header, batteries and glue See the article in the May 2025 issue for more details: siliconchip.au/Article/18121 siliconchip.com.au Australia's electronics magazine September 2025  67 Part 2 by Julian Edgar & John Clarke This smart controller can improve the energy efficiency of your home. It can transfer warm or cool air between rooms automatically when needed. Ducted Heat Transfer Controller L ast month, we introduced the Ducted Heat Transfer Controller that switches a fan used to move heat between rooms that are at different temperatures. This month, we describe how to build it and set it up. We will also show an example installation in detail. Device layout The Ducted Heat Transfer Controller is made using three different PCBs. The main PCB holds most of the components and is installed within a 171 × 121 × 55mm polycarbonate IP65 waterproof enclosure. The second PCB is for the control panel. This mounts at the rear of a Clipsal rocker switch plate and hosts the switch, LED and piezo buzzer. The final PCB is for the temperature sensor. You will need two of these – one for each sensor. This PCB simply provides a connection between the 8P8C (RJ45) socket and the DS18B20 temperature sensor. These boards can be housed within small vented enclosures, such as Jaycar’s HB6116, which has room for the sensor end of the PCB. The larger HB6114 allows the whole PCB to fit. Alternatively, you can use the probe version of the DS18B20 and install the PCB within the wall cavity, with the probe exposed to the room air. Both the control panel and the 68 Silicon Chip temperature sensor boards connect to the main PCB using 8P8C (RJ45) plug-terminated Cat 5, Cat 5E or Cat 6 cables. You can also have two control panels, with one in each room. In this case, they connect to the main PCB using an 8P8C (RJ45) double adaptor and extra Cat 5/5E/6 leads. You can use pre-made Cat 5/5E/6 cables in fixed lengths with connectors already fitted at each end, or make your own using suitable cable, connectors and a crimping tool. Main PCB construction The main PCB is coded 17101251 and measures 151 × 112mm. Fig.4 shows the parts layout on this board. Begin by installing the resistors. Their colour codes were shown in the parts list last month, but you should also use a digital multimeter to check each resistor before mounting it in position (sometimes the colour bands are hard to distinguish). Diodes D1-D19 are next on the list. Make sure these are orientated correctly and that the correct diodes are installed at the right location before soldering their leads. D1-D16 are the smaller 1N4148 signal diodes, while D17-D19 are larger 1N4004 power diodes. In each case, the cathode end is indicated by a band, so match those up to the PCB silkscreen and Fig.4. Bridge rectifier BR1 (containing four Australia's electronics magazine power diodes) can then be installed, taking care to orientate it with the correct polarity. We used a socket for IC1. However, this IC could be soldered in place, assuming it has already been programmed with the Ducted Heat Transfer Controller firmware (it’s available as a download from siliconchip.au/ Shop/6/1835). As mentioned last month, the PCB is designed to use either BCD switches for BCD1 to BCD4, or alternatively, a 2×8-pin header instead of each switch. Install the BCD switches or the DIL headers that go in the middle of their footprints, depending on which you prefer. Also fit the two-pin header for JP1 now. The capacitors can now be fitted. Two types are used: electrolytic and MKT (polyester). The electrolytic capacitors need to be orientated correctly since they are polarised (the longer leads are positive), while the MKT capacitors can be installed either way around. REG1 is installed horizontally and secured with an M3 screw and nut. Bend the leads to insert them into the pads before soldering the leads in place. Q1-Q3 can also be installed now; they are all the same type and orientated identically. Connectors CON1 through to CON4 can now be installed. Note that the siliconchip.com.au Fig.4: the main PCB is straightforward to assemble. If you don’t want to install the BCD switches, instead solder a 2×4 pin header into the eight pads in the centre of the switch locations and use jumpers. Watch the orientations of IC1, the diodes, BR1, electrolytic capacitors and BCD switches. wire entry for CON3 is toward REG1, while for CON4, it is towards the nearest edge of the PCB. Then fit the three 8P8C RJ45 connectors (CON5CON7). The next step is to mount relay RLY1 on the PCB with its coil terminals toward CON3. The relay is secured in position using M4 screws and nuts, with each screw inserted from the underside of the PCB. RLY2 is soldered directly to the PCB. Transformer T1 is a PCB-mounting type. A cable tie that wraps around the transformer and is tied to the PCB by passing it through the slots provided. The cable tie is necessary to prevent the transformer body from being pulled off the PCB when only supported via the soldered pins, so make sure it’s tight. Once it’s firmly anchored, solder its leads. Case preparation The main PCB is secured to the enclosure base using M3 screws into the integral brass inserts. However, before attaching the PCB, you will need to make cutouts for the IEC connector at one end of the enclosure and the 8P8C sockets at the other, as shown in Fig.5. You also need to drill and shape holes for the GPO socket in the lid. 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 edges to a smooth finish. Alternatively, use a speed bore drill to remove the bulk of the area before filing it to shape. If you are using the Fire Alarm function, you will also need a hole for a cable gland to allow wiring to pass through and connect to RLY2 via CON4. Once the drilling and filing is complete, move on to the IEC connector. Cover the Active busbar metal strip on the rear with a layer of neutral-cure Fig.5: use these diagrams to mark and then cut out the required holes in the enclosure. siliconchip.com.au Australia's electronics magazine September 2025  69 Fig.6: these labels can be printed out and stuck on the switch plate and main enclosure. If you choose not to use the labels, ensure you mark the sockets for the switch plate and two temperature sensors. silicone sealant (eg, roof and gutter silicone) to prevent it from being a shock hazard, then mount the connector to the case. The IEC connector must be attached using 10mm-long nylon M3 screws, although metal nuts can be used. Using nylon screws means they cannot become live should a mains wire inside the enclosure come adrift and contact the screw. The PCB can then be placed inside without securing it into the integral brass inserts just yet. You can download the panel label artwork shown in Fig.6 (siliconchip. au/Shop/11/1844) and print it out at actual size to make the panel labels. Details on making an adhesive front panel can be found on our website at siliconchip.au/Help/FrontPanels Now wire it up as shown in Fig.7. All wiring must be run using mainsrated cable. Be sure to use 10A cable for all connections except those to CON3 or CON4, where you can use either 10A or 7.5A mains-rated wire. Note that brown wire is used for the Active wiring, while blue (ideally light blue) is used for the Neutral leads. The green/yellow-striped wire must be used for Earth wiring (only), and the Earth lead from the IEC connector goes straight to the GPO. Be sure to insulate all the connections with heatshrink tubing for safety, and cable tie the wires where shown to prevent any wire breakages coming adrift. The Active and Neutral leads are secured to the GPO using a cable tie that passes through the hole in its moulding. 70 Silicon Chip 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 is marked A or L for Active or Live, the Neutral terminal is marked N and the Earth terminal E. Do the screws up tightly so that the leads are held securely. Similarly, make sure that the leads to the screw terminals are firmly secured. Control Panel assembly The Control Panel PCB is coded 17101253 and measures 51 × 67mm, as shown in Fig.8. Solder the vertical 8P8C connector, polarised header and terminal block on the top side. Make The temperature sensor PCB is placed through a hole suitably drilled and filed in the rear wall of the enclosure. The RJ45 socket in accessible from the rear. In use, the socket and cable protrude into the wall cavity. Australia's electronics magazine sure the terminal block wire entries face away from CON11. The piezo buzzer can then be soldered on the other side, with its + terminal orientated as shown. The LED will be supplied already wired with current limiting resistors and a diode suitable for being powered via the mains voltage, with all exposed connections heatshrink wrapped – see the photo at the bottom right corner of the page. Slit the heatshrink tubing down one side and remove it to expose the two LED leads. Remove and discard the original diode and resistor. Solder short lengths of hookup wire to the LED and cover the joints with 1mm diameter heatshrink tubing. These wires can then be crimped to pins and inserted into the plastic block to plug into 2-way header CON11. Two wires are also required for the switch terminals to CON12. Make those connections using 7.5A mains-rated wire or similar. This wire size works best for the switch terminals that are designed for heaver gauge wire compared to light-duty hookup wire. A 14mm hole needs to be drilled in the 3041G single Gang Switch Grid Plate for the piezo buzzer, while a 2mm hole should be drilled in the 3041C-VW cover plate for the buzzer sound to exit. Temperature sensors The temperature sensor adaptor PCB is coded 17101252 and measures 20 × 37.5mm. It is shown in Fig.9. Assembling the temperature sensor PCBs involves installing the siliconchip.com.au WARNING: Mains Voltage This Direct Heat Transfer 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. Fig.7: take care when doing the mains wiring. Use the correctly coloured and current-rated wire and secure the wiring with cable ties as shown. temperature sensor and the 8P8C socket on each PCB. If you are using the temperature probe package version of the sensor, instead of the TO-92 package version, then be sure to connect the wires to the correct GND, DQ and Vcc terminals. The wire colours are black for ground (GND), yellow for data (DQ) and red for 5V Power (Vdd). In this case, we suggest you cable tie the leads to the PCB using one of the PCB corner mounting holes as an anchor point for strain relief. indication at power-up, or when a sensor is disconnected while the system is powered. One beep means TS1 is disconnected, while two beeps mean TS2 is disconnected. If both are disconnected, both sound indications will occur, one after the other. This indication will occur once only for each sensor. ◀ Fig.8: there are only four parts on the Control Panel PCB so it’s easy and quick to assemble. Testing Fig.9: the temperature sensor PCB is even simpler, with only two parts. Thoroughly test the system before installing it. Do this by first selecting the four BCD switch positions that give the mode, temperature difference and hysteresis you will likely require (see Table 2 from last month). Re-secure the lid and plug in the two temperature sensors and the wall plate control switch. For this testing, you can use short Cat 5/5E/6 leads if you have them. If one of the temperature sensors is not connected, there will be an siliconchip.com.au The Ducted Heat Transfer Controller can still be used without temperature sensors; however, without the temperature readings, the unit can only be used in modes 0 or 1, and without the fire alarm or LED temperature monitoring features. If the fire alarm sounds, a quick press of S1 will silence the buzzer, but the LED will continue to flash at 5Hz. The LED provided with the switch plate is wired for mains power. In our application, it is driven from a low voltage, so both the resistor and diode need to be removed. Australia's electronics magazine September 2025  71 A long press will clear the fire alarm. The fire alarm will sound again if the temperature rise of either temperature sensor is >8°C/min or if 70°C is exceeded. Plug a mains load (eg, a lamp) into the GPO and then connect power via the IEC socket. Warm one of the sensors (your fingers can do this if you’ve set the setpoint and hysteresis values fairly low) and check that the lamp activates as you’d expect. Also check that the wall plate control switch works correctly for the mode you’ve selected, and that the LED flashes appropriately. Table 1 last month showed the modes and other switch settings. You can also refer to the sections titled “Operating modes” and “Monitoring LED and beeper” in that article for a description of how the fan, switch and LED should behave in each mode. If you wish to check other modes, you can disconnect the power, open the lid and then alter the BCD switches appropriately. However, if the system works in one mode, it should also work in the others. If you have the fire alarm link in place, check that if you rapidly heat one of the temperature sensors (eg, using a hot air gun) that the LED and buzzer pulse quickly. If you find any problems, first disconnect power and then very carefully check your wiring, parts locations, parts orientations and soldering. doesn’t matter which sensor goes in which room. The wall plate switch also connects to the controller via Cat 5/5E/6 cables and plugs. Such cables are available readymade in a variety of lengths, or you can buy the cable, plugs and a suitable tool and make your own with custom lengths. The controller plugs into mains power via an IEC cable and the duct fan plugs into the GPO socket on the controller. All the cables should be laid without any kinks or being stretched and should be fastened into place with cable ties and/or wiring clips. Installation Temperature sensor locations The controller needs two temperature inputs, one in the source room and the other in the destination room. These connections are made by Cat 5/5E/6 cables with RJ45 plugs. It The locations of the two temperature sensors are important. When using the system to transfer heated air, in the room providing the heat Insulate the ducts! Many commercial heat transfer ducts use uninsulated ducts, but that is a poor idea. The heat transfer duct comprises four main parts: • An intake grille in the ceiling of the warm room • An outlet grille in the ceiling of the room to be warmed • A duct in the ceiling connecting the two • One or more fans located in the duct All these components are in the ceiling space, which is typically poorly insulated and so is a similar temperature to the outside air. In modern houses, a roof blanket is often using to insulate the roof and so the ceiling space, but this is usually much less effective than the ceiling insulation. The roof blanket also doesn’t cover the eaves. So we have a duct that draws warm air in, and in the transfer to the other room, potentially loses a lot of that heat to the roof space. Furthermore, even when the fan is not operating, major heat loss can occur through the duct. So instead of making your home more energy efficient, you’ve made it less! The answer to this problem is to use an insulated duct. Flexible ducts suitable for heat transfer are available in a range of insulation values, where the higher the R value, the better the insulation. Ducts can be bought with R1, R1.5 and R2 insulation. I could not find any ducts better insulated than R2 – in fact, I only saw one example of R2 insulated ducts. These are made by Bradflo and are available in a variety of diameters. The Bradflo R2 duct is available by special order through Metalflex (a sister company to Reece Plumbing). Of course, you can buy uninsulated ducts and insulate them yourself, or if using insulated ducts, add to the insulation that is already there. The neatest and easiest way of achieving this is to use roof blanket insulation, which comprises aluminium foil and a thin layer of fibreglass insulation. This can be wrapped around the duct, aluminium foil outwards, with the joins made with tape. Roof blankets are rated at R1.3. The insulation value rises with thickness, so if you added two wraps of roof blanket (offset the joins) to an uninsulated duct, you’d have a total value of about R2.6 (probably a bit less because the foil doesn’t add up in the same way as the fibreglass). Flexible ducts will lose a lot of their flexibility when wrapped in this way, so it is best to position the duct in the ceiling before wrapping it. Note that the same potential for heat loss occurs even if the duct is placed under the floor. 72 Silicon Chip Australia's electronics magazine siliconchip.com.au (the source room), the sensor should be placed high in the room – near the ceiling. This is because hot air rises, and so once warm air is available for transfer, the controller should be able to measure it. Conversely, in the room receiving the heat (the destination room), the sensor should be placed closer to shoulder height – that is, measuring the temperature of the air that the occupants will feel. Where the system is being used to transfer cool air, or warm air in winter and cool air in summer, both sensors should ideally be at shoulder height. In all cases, the sensors should not be placed close to the duct openings – the flow through the ducts will affect local temperature readings. The enclosures in which the temperature sensors are placed should be a light colour. If they are painted a dark colour, they will absorb radiant heat, especially if exposed to direct sunlight, so the temperature reading may not reflect the true air temperature. Setting the temperature difference Setting the temperature difference to a low value will cause the fan to operate earlier as the room providing the heat warms up. However, if this value is set too low, the air may not have sufficient heat in it when it reaches the destination room. This is because even if they are insulated, all ducts will lose some heat (see the panel on insulating the ducts). For a given level of insulation, the longer the duct, the more heat loss that will occur. To put this a different way, if the temperature difference is set too low, the duct may blow cold air into the destination room! The temperature difference at which the fan will turn off is called the hysteresis. If the fan switches on and off a lot, increase the hysteresis. Conversely, if the temperature in either room varies up and down noticeably, decrease the hysteresis. Conclusion Using a heat transfer duct with our automatic controller can improve your home’s energy efficiency, comfort levels and, especially if using passive solar heating, reduce heating costs. Our controller has sufficient versatility to work in nearly all situations where heat transfer is needed and can be used in either a new house or where a heat transfer duct is being retrofitted. See overleaf for a panel on how Julian Edgar installed the Ducted Heat Transfer Controller in his house. The transformer is held in place with a cable tie. The mains power connections are insulated with heatshrink and silicone sealant is used to insulate the exposed terminals on the IEC connector. This board uses the BCD switch option. ◀ Shown to the left is one of the temperature sensor PCBs. Up to two of them can be connected to the Controller PCB. siliconchip.com.au The rear of the switch plate in assembled form (shown above). There is a hole drilled in the rear plate for the buzzer to protrude through, and a smaller hole drilled in the faceplate to allow the sound to come out. This PCB is a snug fit around the switch mechanism; it can be held in place with a little silicone. September 2025  73 The details of our installation Photo 1: Bradflo 250mm ducting, insulated to R2.0. Photo 2: another layer of insulation was wrapped around the outside of the duct. Photo 3: two Papst 24V 250mm brushless fans were used. Photo 4: one of the Papst fans taped to the inner flexible ducting. 74 Silicon Chip In our installation, a long, straight duct was used to link the two end rooms in a rectangular-shaped house that is currently being built. Each of the two end rooms has a cathedral (raked) ceiling, meaning that each has an interior wall that adjoins the roof space. The duct joins vents in each of these walls. We used Bradflo 250mm R2.0 insulated ducting. This had a further layer of R1.3 foil and fibreglass insulation wrapped around it. The joins were made using 75mm-wide ProctorPassive YouRippa tape, which has excellent adhesion and is airtight. That’s in contrast to the aluminium flashing tape I used first, which did not adhere well enough to remain sealed. The duct is 14m long, so two fans have been used. They are Papst units from a Bradford Ecofan Subfloor Ventilation system. I chose them because of the brand quality, their brushless DC design and the fact they work from 24V plugpacks, removing the need for mains wiring connections to the duct. The retail price for the Ecofan Subfloor Ventilation varies a lot, so if you decide to use the same fans as I did, it pays to shop around. These fans come with control boxes that allow the selection of three fan speeds. They are usually screwed to grilles, but in our application, we want to insert the fans within the ducting so I removed the grilles. To minimise noise, the fans were placed within the duct, about 1m from each end. The fans are light enough to be supported by the ducting, and the fan shroud’s diameter and circular shape means the inner ducting can be pulled over the shroud and taped into place. Once the fan was inserted into the duct, the area was re-insulated with standard Bradflo duct insulation and the additional layer of R1.3 insulation. The metre of ducting between the fans and the vents reduces aerodynamic noise, and the double layer of insulation around the fans reduces vibration (and so noise) transmission to the house’s framework. When running, the fans are inaudible on the slowest speed setting, just audible on the medium setting and can be heard (but not at an objectionable level) on their fastest speed. If you choose a duct that’s large enough, you shouldn’t need to run them at maximum speed for sufficient heat transfer. It is difficult to work out ahead of time how much airflow will be needed to heat the destination room. Therefore, in this new house build, provision was left for the installation of a second parallel duct, should it be needed. If you find you do need to run the fans at full speed, you could consider a second duct, allowing them to run them slower for similar aiflow. The original grilles from the Bradford ventilation system were not used. Instead, 250mm cone diffusers were placed at each end of the duct. These likely provide less restriction that the more intricate Bradford grilles, and were also chosen to be a styling match for additional grilles used for other purposes. The Heat Transfer Duct Fan Controller was located in the roof space near to one of the fans. The controller is accessible in this location from a loft space. The second fan’s plugpack is fed by a long extension cable that uses a male/ female plug, allowing the cable and the first fan’s plugpack to both plug into the controller’s GPO. The temperature sensor in the source room was placed high on the wall, with the other in the destination room at shoulder height. The wall plate with the LED, buzzer and rocker switch was placed in the source room – just one Control Panel was used. Editor’s note: we have been pleased with inexpensive mains-­powered axial flow fans we purchased from AliExpress (we used one for our laser cutter exhaust). Search AliExpress for “axial fan hydroponics”. Similar fans are availSC able on eBay. Australia's electronics magazine siliconchip.com.au Photo 5: the white tape and cable show the location of the inserted fan. Another two layers of insulation were wrapped around this spot, reducing heat loss from this area and making the fan quieter. Photo 6: the duct is 14m long and rests on two added longitudinal timbers. It is stiff enough that it could probably have just been draped across the ceiling joists. Photos 7 & 8: one of the 250mm grilles, called a ‘cone diffuser’ in ventilation circles, prior to plasterboard installation. My vents are in the walls rather than the ceiling. Photo 9: one of the temperature sensors out of its box. This one is located high on a wall on a sheet of bracing plywood. Photo 10: the switch plate temporarily installed before the addition of plasterboard. Photos 11 & 12: the installed Ducted Heat Transfer Controller with the insulated duct visible behind. siliconchip.com.au Australia's electronics magazine September 2025  75 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. UV Monitor using an ATtiny85 This project was inspired by Jim Rowe’s article on the “UVM-30A Module Ultraviolet Light Sensor” in the May 2023 issue (siliconchip.au/ Article/15776). I had used a Digispark ATtiny85 microcontroller board with the Tiny4kOLED library in a freezer alarm project, so I decided to use the same combination in this design. The Tiny4kOLED library is very memory efficient. This is important because the ATtiny85 has only about 6kiB of memory available. Also, the oled.fillLength() command proved to be useful. Two segment linear approximation provides a close fit to the UV sensor module characteristic graph included in Jim Rowe’s article: UVI = Vout ÷ 240 when Vout < 200mV UVI = (Vout – 100) ÷ 100 when Vout > 200mV In calculating the integer UV Index Number, I added half a step value to Vout to compensate for truncation so that the readings fall to the mid-step (in other words, this is necessary to achieve correct rounding). The oled.fillLength() function makes it easy to display a bar graph. The OLED display contents are stored in the display memory. Therefore, when Vout decreases, the old display needs to be erased. Using the Clear Screen command results in flicker. To avoid this, I used oled.fillLength() to blank out the top end of the bar. For this reason, the bar graph is limited to a maximum value, although the numeric index value is not limited. Rather than displaying Vout , I decided that UV irradiation readings would be more interesting. Irradiation power (Pirr) is calculated from Vout as follows: Pirr (in mW/m2) = Vout ÷ 10 when Vout < 200mV Pirr (in mW/m2) = (Vout – 100) ÷ 4 when Vout > 200mV I added an alarm option to this monitoring device. The trigger level is currently set at 200mW/m2 (the beginning of the VERY HIGH range). During testing, it became clear that some filtering of the input signal was desirable, so I applied a running average (over ten samples) to the input. The resulting display has a twin bar UV level inductor with a 0-10 graduated scale. It shows the UV index and UV irradiation level in mW/m2. The audible alarm trigger level can be adjusted in the software. Even though OLED displays are self-illuminated, they are not easy to read in sunlight. Therefore I decided it was useful to be able to freeze the The UV Monitor can be wired up using flying leads. display so it can be viewed away from bright lights without the readings changing. To achieve this, I added in a switch (S1) to connect RESET to GND. The microcontroller stops processing and the screen is frozen. It is then possible to read the captured image in the shade. Releasing the RESET button returns the microcontroller to normal operation. Mauri Lampi, Glenroy, Vic. ($90) Circuit Ideas Wanted Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, credit or direct to your PayPal account. Or you can use the funds to purchase anything from the Silicon Chip Online Store. Email your circuit and descriptive text to editor<at> siliconchip.com.au 76 Silicon Chip Australia's electronics magazine siliconchip.com.au Emergency light using a supercap It’s very convenient to have a light that will switch on and keep going during a blackout. One can build a reliable and simplified emergency light circuit with energy-efficient LEDs, using supercapacitors or ultracapacitors instead of rechargeable batteries for longer life, quicker charging and deeper discharging. Supercapacitors typically do not need trickle charging; they can be completely discharged and constantly topped off (www.ti.com/lit/ an/sluaao7/sluaao7.pdf) and they do not degrade significantly from this approach. Unfortunately, supercapacitors do tend to have significantly higher self-discharge rates that are temperature dependent (siliconchip. au/link/ac5g). This circuit uses a standard 5V DC plugpack to keep a supercapacitor (or bank of supercapacitors) constantly charged to around 4.7V. A 6V DC plugpack would be even better, with D1 & D2 replaced with standard 1N4004 diodes, to keep the supercap charged to around 5.4V, just below its upper limit (this will allow it to store more energy). Diode D2 keeps the capacitor at the base of Q1 charged to the same voltage as its emitter, so Q1 remains off while mains power is available. If mains power is lost, the 1μF capacitor quickly discharges and Q1 switches on, powering the white LED. The initial maximum LED current is 20mA, but this decreases over time, with a slowly fading brightness. Using a 4F supercapacitor and a high-­brightness white LED, it will last around 40 minutes. If constant brightness and a longer on-time is needed, the classic “Joule Thief” circuit shown below can be inserted between the collector of Q1 and the LED. Voltage regulation is achieved by N-channel Mosfet Q3, which is used as feedback to switch off Q2 when the output reaches its gate threshold voltage. The body diode of Q3 also protects the base-emitter of Q2 against periodic negative spikes. This extra circuity means that not only will the LED brightness remain essentially constant until the supercapacitor(s) have discharged but also that almost the full charge of the caps can be used, extending the on-time by about 50%. That’s in contrast to the LED switching off once the capacitor(s) have discharged below the 3V or so needed to forward-bias the LED. Mohammed Salim Benabadji, Oran, Algeria. ($75) Switching between 115V & 230V AC I discovered this trick in the IBM 5155 Computer power supply circuit. It allows a single SPST switch to select between 115V AC and 230V AC input while providing the same DC bus voltage. In 230V AC input mode, the arrangement is that of a full-wave bridge rectifier. In 115V AC mode, it becomes a half-wave voltage doubler, and D3 & D4 no longer conduct. Note how it is possible to connect a transformer (T5) with a 115V AC primary that will produce the same output regardless of whether the line voltage is 115V AC or 230V AC. This is possible because the bridge rectifier & filter capacitors create what amounts to a low-impedance artificial centre tap (or virtual zero) on the incoming 230V line voltage. The reactance of the filter capacitors at mains frequencies is very low. siliconchip.com.au In the IBM 5155 supply, transformer T5 has a 12V secondary that powers most of the electronics in the switch-mode power supply for bootstrapping. Once the switch-mode supply is up and running, its 12V output can take T5 over powering this D1 PRIMARY circuitry (this makes ~ the supply less sensitive to brown-outs). 230V D2 The resistors across AC the electrolytic capacitors ensure that the charge is split evenly across them; their valT5 D1 ues will depend on PRIMARY the maximum capac~ itor leakage currents 115V and load symmeD2 AC try. In the IBM 5155 power supply, the top Australia's electronics magazine one is 55kW (two 110kW resistors in parallel), while the lower one is 27kW. They dissipate up to 0.56W and 1.13W, respectively. Dr Hugo Holden, Buddina, Qld. ($100) + D3 ~ – D4 470mF S1 20 0V 4.7nF 470mF 325V DC 20 0V SC Ó2025 + D3 ~ – D4 470mF S1 20 0V 4.7nF 470mF 325V DC 20 0V September 2025  77 USB--C USB Part 2 by Tim Blythman Power Monitor This compact device lets you monitor the voltage, current, power and energy supplied to a USB-C device. The first article last month covered some background information, the circuit details and reasons for the design choices. Now we’ll describe the construction and usage of this handy tool. T he USB-C Power Monitor can measure the Vbus voltage and current flowing between two devices; using this information, it can also calculate power and energy. That makes it similar to our USB Power Monitor (December 2012 issue; siliconchip.au/ Article/460) but with USB-C connectors, a more comprehensive display and extra capabilities. Since USB-C allows current to flow in either direction, the new Monitor must handle that, as well as USB-C’s higher voltage and current capabilities, up to 48V and 5A. It has an internal rechargeable battery to avoid loading the USB host. The Monitor also tests the state of the configuration channel (CC) lines, which are also new to USB-C. It has an OLED display module and three tactile switches for control. All these features are packed into a compact 80mm × 40mm enclosure. Construction The two PCBs are connected by soldered wire, ribbon cable or FFC (flat flexible cable) connections. That’s because pluggable connections have variable resistance and will interfere with the correct operation of the current shunt monitor. The smaller PCB has the USB-C plug and socket. We will build this first, since it is easy to test. The second PCB carries most of the parts and also forms the front panel of the completed unit. This PCB can operate by itself, without a battery, so the second PCB can also be tested for basic functionality before everything is joined. The case we have chosen requires three cutouts to be made. These are not too tricky, and they can also be tested for fit before the final assembly step. As you can see from our photos, the completed unit is compact and neat. Both PCBs are 0.8mm thick and feature surface-mounting parts, so you will need the usual SMT gear; a finetipped soldering iron (or medium/ chisel tip, if you prefer), solder, flux paste, tweezers, a magnifier and good lighting. Solder wicking braid will come in handy, too. Work outside or with good ventilation to avoid inhaling smoke from the flux. Connector PCB You might not need them, but Fig.4 shows the overlay diagrams for this PCB, which is coded 04102251 and measures 78 × 11mm (it’s 0.8mm thick). There aren’t many parts on it, but we think it’s the most tricky to solder because of the fully featured USB-C connectors and their fine pin pitch. We found socket CON2 to be most challenging, so we recommend starting with that. We haven’t tried it, but if you have a hot-air station and solder paste and are familiar with using them, then you might like to use them to assemble the connector PCB. This process would be closer to the reflow process used for commercial soldering of these parts. CON2 is much the same part that we used in the USB Cable Tester (November & December 2021; siliconchip. com.au/Series/374), although this time we are using a variant with shorter through-hole pins since the PCB is thinner. These pins are very fine and can easily bend if they are bumped; this could lead to short circuits with other pins, so be gentle. Place CON2 on the PCB and tack one of the larger shell pins, then confirm that the SMT pins on the top of the PCB are aligned and flat against the PCB. This should avoid the possibility Short-form Kit (SC7489, $60): this kit includes all the non-optional parts listed except the case, lithium-ion cell and glue. It will also include the FFC (flat flexible cable PCB) for joining the two PCBs. 78 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.4: there aren’t many components on this PCB; it does little more than pass all USB-C signals through and break out a few of them for connection to the main PCB. Soldering CON1 and CON2 will probably be the trickiest part of this project. of the part moving while you are trying to solder it. Clean the iron and add a small amount of fresh solder. Carefully add flux to the smaller pins and solder them. We’ve extended these pads where possible, as this will allow you to touch the iron to the pad and see that the solder has flowed and melted onto the pin. Flip the PCB over and solder the through-hole pins, including the four larger shell pins. If you think you have a bridge between pins, carefully use the braid and a little more flux paste to draw the excess solder away. The solder’s surface tension should hold enough solder behind to make a solid joint. If in doubt, add a little more, with some more flux to ensure it flows smoothly. The USB-C plug (CON1) is a straddle-­ mount part that clips over the edge of the PCB. This helps to lock it into place so it’s not likely to move during soldering. Its pins are also fine, and if they are bent at all, particularly sideways, then they may bridge to other pins. If it has a protective cap, leave it in place for now. Place the plug over the edge of the PCB and check that it is flat against the PCB and all the pins on both sides align with their pads. Carefully slide it sideways if needed. It should be parallel to the edge of the PCB, too. Add flux to all the pins and touch the iron to the end of each pad in turn until the solder flows onto the respective pin. The shell can also be soldered to the larger pads on the outside edge of the PCB; this will add mechanical strength. Check for solder bridges and use the braid with extra flux paste as needed. Once you are happy with it, fit the three resistors to this PCB. The larger part is the 15mW shunt; the other two are 220W. Clean up the excess flux on the PCB using the solvent of your choice. Some fluxes recommend specific chemicals, but we find that isopropyl alcohol is a good alternative. siliconchip.com.au Allow this PCB to dry and give it another inspection. If there is a short circuit between any pins, it will not work as designed. Remove the cap on CON1. At this stage, this PCB should be functional as a USB-C extension, so you can test it by connecting a fully featured USB-C cable (with plug) to CON2. Be sure to rotate the connector 180° to test both configurations. Ideally, our USB Cable Tester should be used for initial tests, since this will not cause or suffer any damage if there is a fault. The extended cable should give exactly the same results as the cable on its own, since all the lines are taken straight through. There may be a slightly higher cable resistance due to the extra cable junctions. Lacking that, connect a USB-C device you don’t care about too much to a computer through this extension and check that it works normally. We also used a USB-PD power supply connected to a USB-PD trigger device to test this PCB, since they are fairly cheap and will exercise the power and CC (configuration channel) wires. See the end of this article for an example of the boards we used for testing. If the tests work as expected, then test out the data wires using a computer or similar. Be sure to use it with a USB 3.x device so that you know that all the USB data circuits are functional. As before, the extended cable should give the same results as the cable on its own. If you run into any problems, go back and rectify them before using this PCB. Main PCB While the second PCB, coded 04102252 and measuring 80 × 40mm, has a few smaller parts, in comparison, it should be relatively straightforward (see Fig.5). Start with the smaller ICs and the regulator. IC3 is the AD8541 op amp (or similar) and should be labelled with the code A4A or A12, while IC4 is the MCP73831 charge controller and should be labelled KD, followed by a two-character lot code. They are both in SOT-23-5 (five lead) packages. Note that the pads for IC3 have been modified to allow either an SOT-23-5 or slightly smaller SC-70-5 part to be fitted since we will supply SC-70-5 parts in our kits. They are The main PCB (shown enlarged) has numerous SMDs, plus a through-hole LED that shines through a hole in the PCB solder mask. The OLED module is also mounted to be visible through a cutout in the PCB. A row of header pins can be fitted to CON5 if in-circuit programming of IC1 is required. Australia's electronics magazine September 2025  79 marginally smaller, so not too much more difficult to solder. If you’re sourcing the parts yourself and prefer to use an SOT-23-5 part, it should fit the same pads just fine (it’s a dual footprint). REG1, the MCP16252, is similarly small in a six-lead SOT-23-6 package and marked with the code MC and a two-character lot code. Be sure to check the orientation on this one, since it is symmetrical, unlike the fivelead parts. The alignment dot is below and to the left of the MC code; in other words, pin 1 is at lower left when the text is upright. Double-check its orientation before soldering more than one pin as it’s tricky to fix if you get it wrong! Follow with IC1 and IC2, the two SOIC parts; these should be a breeze after the smaller parts, but you still need to pay careful attention to their orientations. Diode D1 is quite small, but should be easy enough to manage. CON5, the third USB-C connector should be aligned flush with the edge of the PCB as much as possible. After the resistors, capacitors and sole inductor are fitted, this PCB will be fairly complete. There are only two different capacitor values; the five 10μF parts might be thicker than the five 100nF parts. They will be unmarked, though, so be sure not to mix them up. There are several different resistor values, so match the markings to the silkscreen or use a multimeter if you are unsure. On the PCB, the silkscreen values are generally below or to the right of the part when they are in a row, to avoid ambiguity. You can also check against the overlay diagram (Fig.5) and photos. You can also solder in the 3mm LED now. We’re using a through-hole part here, since two-lead SMD bicolour LEDs are not widely available. The K marking on the PCB corresponds to the cathode of the green LED in the package. Bend the leads as shown in the photos and solder it to the PCB. Keep the lead offcuts for later. Now is a good time to clean up the flux residue on the PCB, before the OLED and tactile pushbuttons are fitted; these parts will not appreciate being immersed in solvent. Allow it to dry and inspect the soldering for Fig.5: this PCB hosts most of the parts. Don’t mix up the various SOT-23/SC-70 parts (in 3-pin, 5-pin & 6-pin variants). Fortunately, there is a fair amount of space on the PCB, so the silkscreen markings should be easy to follow. Fig.6: the partially assembled main PCB – you can testfit the boards before they are turned into a single assembly. We recommend you take your time and ensure that they are a good fit individually before joining them together. 80 Silicon Chip Australia's electronics magazine any poor connections or bridges and rectify them if needed. Fig.6 shows the state of the PCB at this point. Finishing the main PCB You can now fit the OLED module and tactile switches to the main PCB. For the OLED module, desolder any header that has been attached to it and clean up the four pads. The easiest way to do this is to add solder to the pins so that they are all covered in a single, large blob of solder and then heat that while pulling the pins with pliers until they slide out of the board. After that, use a solder sucker to remove the excess solder bridging the pads. Now solder short wire offcuts to the four pads on the main PCB. These should point straight up and align with the holes in the OLED when it is overlaid. The best way to do this is to bend short pieces of wire into an ‘L’ shape and use the extended pad to secure them better. It’s a bit fiddly, but we think it leads to a very tidy result. Remove the OLED’s protective film and slot the OLED over the offcuts, then solder the OLED module to them. Be sure that the OLED is not too close to the edge of the PCB; otherwise, it could foul the enclosure. Another piece of wire can be soldered to the long pad near LED1 and bent over the OLED module. This will provide support to the other end of the OLED. Fit the pushbutton switches next. Their stems poke through the PCB to face outwards, so you may need to sit the PCB up using spacers or a PCB holder. Tack one lead and adjust the switches so that their stems are centred in the holes. This will look better and eliminate the chance of the switches binding. Once you are satisfied with the positions, solder the remaining leads. You can tidy up with a cotton-tipped swab or similar. Dip it in some solvent and wipe up any excess flux. Programming IC1 Chips purchased from the Silicon Chip Online Shop (including those in the kit) will be supplied in a programmed state, so will not need programming. You can skip to the next section if you have such a chip. To program IC1, you can fit a header to CON3. For our prototype, we just used a standard through-hole header strip and soldered it as though it were siliconchip.com.au The USB-C Power Monitor runs from an internal Li-ion rechargeable battery and can measure up to 60V and 5A. The loop in the FFC goes over the OLED module so that the cell will fit into the space above IC2 when the case is closed. With the cell stuck down using foam-cored tape, the main PCB should rest in place as a snug fit. This PCB becomes the lid and is attached using the screws included with the case. a surface-mounting part. It can stay in place since it will not foul the enclosure if installed squarely. You can see it in the photo of the completed assembly above. You can apply power to the PCB through CON5 (the USB-C power-­ only socket on the main PCB), if this is needed. Use a Snap, PICkit 4, PICkit 5 or PICkit Basic and choose the PIC16F18146 from the MPLAB IPE. Open the 0410225A.HEX file, use it to program the chip and confirm that the verification is successful. You should also see the OLED illuminate and display the main screen; the readings will be nonsensical, since there is no connection to the second PCB. Pressing S3 (>) should cause the screens to cycle. If this is the case, then all is well. If not, double-check your soldering before continuing. Enclosure It’s a good idea to prepare the case next, as that will allow the two PCBs to be checked before they are joined together. Note that the cutting here matches our prototype as built, with the USB-C socket (CON2) on the left and the plug (CON1) on the right. In other words, the CON5 USB-C power-­ only socket is on the same end as CON2. Because the assembled PCB with CON1 & CON2 is longer than the case, the final assembly step will involve passing CON2 fully through its hole (and out the side of the case) so the CON1 end of the PCB can be dropped into place. The PCB is then slid back so that the two connectors are in their final locations. siliconchip.com.au Because of the extra room needed for these manoeuvres, the holes will be slightly oversized. As such, the lower PCB will need to be secured with glue (but not just yet!). This will also provide reinforcement against wear and tear on the connectors. Fig.7 shows the cutting diagram, but you can also use the two PCBs to mark out the cuts as you go. For example, you can rest the main PCB on top of the case and mark the sides of CON5, rather than trying to measure out the dimensions with a ruler. The bottom of the holes for CON1 and CON2 should be level with the floor of the case, which is 2mm thick. Since the CON5 cutout is a notch at the top edge of the enclosure, you could use a sharp hobby knife or fine hacksaw to make the vertical cuts. Make a score mark at the base of the tab and carefully flex it with pliers until it snaps off. Then tidy the edges and make sure that the main PCB can sit flat on the top of the case. The other holes should be started with a drill at their outer edges. Make further drill holes along the length and use a file or knife to join those holes. Then enlarge the holes until the smaller PCB can be inserted and check that the lower PCB can slide freely and can be slotted into place from above. long, so wire, if used, should be the same length. This will neatly loop to one side of the case without bunching up. The loop provides space for the lithium cell. Pay careful attention to the orientation of the two boards in our photos. You can see that CON2 is at the same end as CON5 to match our cutting diagram and prototype. Start by soldering the FFC to the main PCB. We have aligned the striped conductor with the square pads on the PCB; this is pin 1. The FFC does not need to sit flat, but can pass at an angle just enough to clear the OLED module. Just like an SMT part, you can tack one lead and confirm that the FFC is square and aligned to the main PCB. You shouldn’t need to use flux since you will need to use a generous amount of solder. Tack the lead at Connecting the PCBs The two PCBs are ideally connected by a flat flexible cable (FFC), which is effectively a flexible PCB with the code 04102253. An alternative is to simply use light-gauge insulated wiring or ribbon cable. The FFC is 4cm Australia's electronics magazine Fig.7: the recommended cut-outs. You will need to swap the CON1 & CON2 cut-outs if you plan to fit the smaller board in the opposite orientation than we are recommending. September 2025  81 the other end and if everything looks correct, solder the remaining leads to their pads. Follow the same process to connect it to the second PCB. The FFC connects to the side opposite the resistors, so it can sit flat against the PCB. You can see the arrangement in the photo on page 81. Once this is done, take care with the assembly. The FFC is reasonably robust, but will not stand up to repeated flexing. It could tear if subjected to excessive force, or be kinked if it is bent too hard. Completion Now that the PCBs are connected, you could power up the unit (at CON5) and see that it is showing reasonable readings, close to 0V and 0A. Without a battery connected, our LED flashed red, then green and then switched off; if yours flashes green then red, the LED may be reversed, and it is best to correct that now. You can jump ahead to the setup and usage section if you’d like to run some further checks before gluing the PCBs down and closing everything up. Since the next step involves soldering the battery to the PCB, you should disconnect power. Take great care whilst working with the battery, since the lithium-ion cell will not take kindly to being short-circuited. Everything will be live (at up to 5V) from now on. Carefully prepare the leads for soldering. Our battery had a connector that we needed to cut off. Only cut one lead at a time to avoid shorting them with the cutters. Use tape to cover the ends so that only one is exposed at a time. Solder the leads to the terminals marked BAT1 on the PCB, observing the polarity seen in the photos and on the silkscreen. The Monitor should switch on. You can place it in a low-power sleep mode by pressing and holding S3 (>) until Screen 2 is seen. Then press S1 (down) to enter sleep; the text SLEEPING will appear before the screen blanks. Apply glue (neutral cure silicone) to the battery terminals on the PCB and cover any bare metal. This will add some extra strain relief and also insulate the bare ends of the wires. Now you can slot CON1 and CON2 into the case. Ideally, CON2 should protrude slightly from its end, with the lower PCB resting against that end wall of the enclosure. Add glue to secure the PCB in place and take care not to allow any to seep inside the connectors, especially the holes on the top of CON2. For now, apply just enough glue to make sure that the PCBs are mechanically secure. If needed, you can tidy up the external appearance by filling in the gaps in the case around CON1 and CON2 later. Now you should wait until the glue has fully cured to ensure that nothing breaks loose during the final stage. While waiting for the glue to cure, you can charge the battery via the CON5 USB-C socket. The LED should light up red and then change to green when charging is complete. Closing it up Use foam-cored double-sided tape to secure the battery to the inside of the case. It should sit against the lower wall, near the middle of the case. Resting it against the internal boss should ensure that it is clear of CON3 if fitted. LED1 is the other component that might conflict, but that should not be a problem if you use the same size cell we did. The main PCB is now placed on top of the case. Check that there aren’t any internal collisions with the battery. If all is well, secure the lid with the two screws included with the case hardware. They will sit slightly above the surface of the PCB. Don’t screw them down too firmly; the thin PCB is flexible and will be somewhat susceptible to cracking if stressed. Setup and usage Screens 1-4: there are four main operating screens and nine configuration screens. These operating screens are described in detail in the text. Screen 5: the brightness of the OLED screen can be adjusted here; the default value of 130 is near the midpoint of the adjustment range. Higher values will flatten the battery faster. Screen 6: the displayed energy units on the main page can be set to either Joules (J) or Watt-hours (Wh). This can be changed at any time without affecting readings. Screen 7: the TRIM factor on this screen sets the multiplier for voltage readings. Use a multimeter to compare the measured value against the displayed value. Screen 8: the current ranges are trimmed in similar fashion to Screen 7. For the high current range, apply and measure a load of at least 1A to ensure accuracy across the range. 82 Silicon Chip Australia's electronics magazine When the screen is blank, pressing any of the buttons should end the sleep mode. The unit returns to Screen 1 when this happens. A brief press of S3 (>) will cycle between the operating screens (Screens 1-4). A long press of S3 will enter the settings and configuration screens; there are nine of these, shown in Screens 5-13. You can exit the settings screens by another long press on S3. The main screen (Screen 1) shows the measured voltage, current and power as well as accumulated energy. Below the current is a timer that can run up to 99 hours. On this screen, the up and down buttons control the timer and energy counter. The state shown here has the timer stopped; the time display will alternate with ∧ START. Pressing ∧ will start the timer and the energy counter siliconchip.com.au will integrate the power value. You can always calculate an average power by dividing the energy by the time. Pressing ∨ will pause the timer (and energy counter) if it is running. Pressing it while paused will reset both values. The current display will show units of mA (to two decimal places) if the low current range is being used. The display will be in A (to three decimal places) when the higher range is in use. The arrow on the first line shows the direction of current flow (source to sink). Right to left corresponds to a positive value of power and energy. Since the power will always be the same sign as the current, this should be unambiguous. There is also a timeout that is only active on this screen. It is reset any time the Vbus voltage is above 1V, if the timer is running or any time a button is pressed. If the timer is counting down, it is displayed in small text (along with the low Vbus voltage) in the top left corner. The timer can be deactivated (as is the default), and we’ll discuss this in the configuration section. Sleep and battery The next screen allows the battery voltage to be checked by pressing the ∧ button. This actually measures the voltage supplied to the micro and adds an adjustment for the diode, REG1 and 10W resistor. So it will only be accurate when there is nothing powering CON5. This is on its own screen because it requires the boost regulator to be shut down and should not be done while the timer is running. It won’t cause any damage, but the readings will be inaccurate since the 4.096V reference will not be at specification. The reading should be treated like a typical Li-ion battery voltage; 4.2V is close to fully charged and 3.6V or lower is flat. Pressing the ∨ button on this screen will put the Monitor into low-power sleep mode. All timers and peripherals are shut down, as are REG1, MOD1, IC2 and IC3. If the timer from the main screen was running, it will be paused. The screen will show a SLEEPING message and then shut down. Pressing any of the buttons will wake it up. Any time the Monitor is not being used, it should be put into sleep mode to avoid flattening the battery. The time­out on the main screen has the same effect and will show the same SLEEPING message. siliconchip.com.au CC states The CC (configuration channel) lines are one of the new features that were introduced with USB-C. As we’ve noted in other articles, they have tripped up many engineers. So we thought that this screen (Screen 3) might help to shed some light on this feature. The Vbus voltage is also displayed at lower right. This screen depends on the connected devices complying with the standards, so if you see nonsensical readings, maybe there is a problem with whatever is connected to CON1 and CON2. It’s also possible that the 220W resistors in the Monitor are interfering with its operation, although they generally shouldn’t. The second line shows which of the two (CC1 and CC2) lines is used for CC signalling on the connected USB-C source; this corresponds to either the upper (A5) or lower (B5) connections on CON1 or CON2. This can help with troubleshooting cable orientation. A sink device must be connected to provide the pulldown on the CC lines before the source current can be read. If the text ∧ START is shown on the last line, the Monitor can provide that sink by pulling its internal 5.1kW resistors low. The ∧ button must be held down to apply the internal 5.1kW load and no other sink should be connected; this is the reason for the SOURCE ONLY warning. When a sink is provided, the second and third lines provide information about the source capabilities and status. You should see either → or ← pointing from source to sink, and some text describing the status. The direction is derived from the current through the 220W resistors. The status is derived from the voltage on the active CC line and the Vbus voltage. For example, a Vbus voltage over 5.5V is interpreted as a USB-PD voltage being negotiated; this is displayed with the text USB-PD. A LEGACY source is one that applies Vbus without a sink being connected. This implies a USB-A to USB-C cable or adaptor has been used on the source side. You might also see SOURCE LOW if the Monitor determines the source should be supplying 5V but is not. We have found that some devices don’t respond instantly to changes in the configuration channel. Some of the timeouts in the USB-C specification Australia's electronics magazine Screen 9: the low-current range works up to about 25mA, so a 220W resistor across 5V will provide an appropriate load for trimming on this page. Screen 10: the current offsets can be automatically trimmed by the page shown in Screen 4, but the value is shown here for completeness. Screen 11: you can also manually trim the current offsets by adjusting the parameter until the displayed current reads zero, as shown here. Screen 12: by default, the display timeout is disabled, but it can be switched on by adjusting the value upwards. The timeout only applies on the main screen if the Monitor is idle. Screen 13: the configuration is held in RAM, which will be lost if the battery runs flat. So we recommend you perform a SAVE after doing the initial calibration. allow over a second for some responses to occur, so this is to be expected. Offset trim Screen 4 shows a page used to trim the offset in the current-measuring channels. The offset changes with Vbus voltage, so it is best to have the expected voltage present when doing this. The default (zero) trim values are fairly accurate at 5V, since this is near the supply voltage of IC2 and IC3 involved in current measurement. When the ∨ button is pressed, the Monitor takes an average over 256 readings of the high and low current ranges. It then applies this as the offset to the raw ADC value, as shown at the bottom of the screen. As the text explains, the current September 2025  83 Left: this Adafruit 4396 USB-C socket breakout board is fitted with two 5.1kW resistors and a header. It will be handy during Monitor calibration and could also be useful if you need a 5V supply with a current readout. Right: a typical USB-PD trigger board has a USB-C socket, a USB-PD interface IC and an output connector. This example sets the requested PD voltage by solder jumpers; some can be controlled digitally, with an I2C serial interface or similar. should be zero for this to work correctly. If there is an idle or quiescent current that you wish to cancel out, this should be applied, and it can be trimmed out, too. An example of this is the load due to the Vbus sensing divider. Configuration Screens 5-13 are configuration screens. Most of these screens are fairly straightforward, and there are brief descriptions of each in the captions. The three TRIM screens adjust the multiplier used in calculating the Vbus voltage and high and low current ranges. The offset trim described above should be done before completing this step using the same Vbus voltage. You’ll need a multimeter or similar so that you can read a value to trim against. The parameter shown in the second line should be adjusted until the measured value (volts or amps) matches the displayed value. For the current ranges, you might see INVALID displayed if the Monitor thinks the analog voltage is near its limit or saturating; this is most likely on the low current range. The OFFSET pages are the same parameters as described in the Offset trim section, and there is little need to manually adjust these. They are simply provided for completeness. The Monitor will use the live settings at all times, although Screen 13 shows a page to save the settings to EEPROM. Since the Monitor has the battery permanently connected, there is little chance of the Monitor forgetting its settings in RAM. But if the battery were to run flat, it would do so. So we recommend you save the settings to EEPROM using the ∧ button once the Monitor is set up. If you ever have a problem with the settings being corrupted, the ∨ button will restore to active settings from the defaults in flash memory. You can then save these to EEPROM with the ∧ button to complete the RESTORE. Accessories During testing, we used various cables, adaptors and breakout boards to test and probe the operation of the Monitor. You’ll need a standard USB-C plug-plug cable to use the Monitor, just as you would need such a cable to operate the device you are testing. A small breakout board like Adafruit’s 4396 USB Type C Socket Features & Specifications ● Main screen reports current, voltage, power, energy (in J or Wh) & time ● Configuration channel (CC) status screen ● All 24 USB data lines pass through ● Self-contained with 400mAh rechargeable lithium battery ● Internal battery means no extra load on the USB circuit under test ● Compact case is only 80 × 40mm ● Automatic offset trimming ● Voltage measurements: up to 60V with 10mV resolution ● Current measurements: up to ±5A with 1mA resolution; 10μA resolution below ~25mA ● Power: up to 300W with 1mW resolution (limited by V and I) ● Energy: up to 999999J (1mJ resolution) or up to 999Wh (10μWh resolution) ● Battery consumption: <20mA, giving 20 hours of usage per charge ● Sleep mode: <10μA drawn from battery, less than typical self-discharge 84 Silicon Chip Australia's electronics magazine breakout (shown in the left-hand photo) could be handy for calibration. Any similar breakout board that exposes Vbus, GND and the CC lines of a USB-C socket should also work. We wired up the two CC lines to allow the breakout to behave as a sink; there is a 5.1kW resistor from pin A5 to ground and another 5.1kW resistor from B5 to ground. A three-way header socket with the middle pin removed has the right pitch to connect to ground and Vbus. The photos at upper left show this gadget from both sides. This can be used for calibration, as we mentioned earlier, or to turn the Monitor into a current and voltage display for a simple 5V power supply. If you need access to higher voltages, a USB-PD trigger board (as seen in the photo above) might be an alternative. Conclusion The USB-C Power Monitor is a necessarily more complex design than its predecessor from 2012. It allows monitoring of the higher currents and voltages that USB-C allows. It can also provide information about newer features specific to USB-C. After it is set up, operation is straightforward. Typically, you would connect your device to its host or power supply using a standard USB-C plug-plug cable. The Monitor is fitted inline with the device to be checked. USB-C’s reversible plug and socket mean that you have some flexibility in how it is connected. Once you have adjusted the trim offsets to your liking, you can monitor the current, voltage & power. Starting the timer will allow you to check total energy consumption over a period and thus also average power consumption. The CC Connection State page (Screen 3) allows you to check the behaviour of USB-C’s configuration channel. Make sure to put the unit into low-power sleep when you are finished so that the battery does not SC run flat. siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 194, MATRAVILLE, NSW 2036 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 09/25 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS $15 MICROS ATmega328P ATtiny45-20PU PIC10LF322-I/OT PIC12F617-I/P 110dB RF Attenuator (Jul22), Basic RF Signal Generator (Jun23) 2m VHF CW/FM Test Generator (Oct23) Range Extender IR-to-UHF (Jan22) Active Mains Soft Starter (Feb23), Model Railway Uncoupler (Jul23) Battery-Powered Model Railway Transmitter (Jan25) PIC12F675-I/P Train Chuff Sound Generator (Oct22) PIC12F675-I/SN Tiny LED Xmas Tree (Nov19) PIC16F1455-I/P Railway Points Controller Transmitter / Receiver (2 versions; Feb24) Battery-Powered Model Railway TH Receiver (Jan25) PIC16F1455-I/SL Battery Multi Logger (Feb21), USB-C Serial Adaptor (Jun24) Battery-Powered Model Railway SMD Receiver (Jan25) USB Programmable Frequency Divider (Feb25) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P K-Type Thermostat (Nov23), Secure Remote Switch (RX, Dec23) Mains Power-Up Sequencer (Feb24 | repurposed firmware Jul24) 8CH Learning IR Remote (Oct24), Heat Transfer Controller (Aug25) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Silicon Chirp Cricket (Apr23), Mic The Mouse (Aug25) PIC16F15214-I/P Filament Dryer (Oct24), Tool Safety Timer (May25) PIC16F15224-I/SL Multi-Channel Volume Control (OLED Module; Dec23) NFC IR Keyfob Transmitter (Feb25), Rotating Light (Apr25) PIC16F18146-I/SO Compact OLED Clock & Timer (Sep24), Flexidice (Nov24) Versatile Battery Checker (May25), RGB LED ‘Analog’ Clock (May25) USB-C Power Monitor (Aug25) PIC16LF15323-I/SL Remote Mains Switch (TX, Jul22), Secure Remote Switch (TX, Dec23) STM32G030K6T6 Variable Speed Drive Mk2 (Nov24) W27C020 Noughts & Crosses Computer (Jan23) ATSAML10E16A-AUT PIC16F1847-I/P PIC16F18877-I/PT High-Current Battery Balancer (Mar21) Digital Capacitance Meter (Jan25) Dual-Channel Breadboard PSU Display Adaptor (Dec22) Wideband Fuel Mixture Display (WFMD; Apr23) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23) ESR Test Tweezers (Jun24) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) Advanced GPS Computer (Jun21), Touchscreen Digital Preamp (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) STM32L031F6P6 SmartProbe (Jul25) $20 MICROS ATmega32U4 ATmega644PA-AU PIC32MK0128MCA048 Wii Nunchuk RGB Light Driver (Mar24) AM-FM DDS Signal Generator (May22) Power LCR Meter (Mar25) $25 MICROS PIC32MX170F256B-50I/SO + PIC16F1455-I/SL Micromite Explore-40 (SC5157, Oct24) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sep16) $30 MICROS PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC PICKIT BASIC POWER BREAKOUT KIT (SC7512) (SEP 25) USB-C POWER MONITOR KIT (SC7489) (AUG 25) MIC THE MOUSE KIT (SC7508) (AUG 25) RP2350B DEVELOPMENT BOARD (AUG 25) 433MHz RECEIVER KIT (SC7447) (JUN 25) VERSATILE BATTERY CHECKER KIT (SC7465) (MAY 25) RGB LED ‘ANALOG’ CLOCK KIT (SC7416) (MAY 25) USB POWER ADAPTOR COMPLETE KIT (SC7433) (MAY 25) Includes all parts except the jumper wire and glue (see p39, Sep25) Includes all non-optional parts except the case, cell & glue (see p39, Aug25) Includes all parts except a CR2032 cell (see p64, Aug25) Assembled Board: a pre-assembled PCB with all mandatory parts fitted, optional components are sold separately below (SC7514; see p49, Aug25) - 40-pin header (two are required, SC3189) - 8MiB APS6404L-3SQR-SN PSRAM SOIC-8 IC (SC7530) Includes the PCB and all onboard parts (see p66, Jun25) Includes everything in the parts list (including the case), except the optional components, batteries and glue (see p30, May25) $20.00 $60.00 $37.50 $20.00 $65.00 Includes everything in the parts list and a choice of one USB socket: USB-C power only; USB-C power+data; Type-B mini; or Type-B micro (see p80, May25) $10.00 (APR 25) Includes an assembled PCB, separate Raspberry Pi Pico 2 and front/rear panels $120.00 ROTATING LIGHT FOR MODELS KIT (APR 25) Complete kit which includes the PCB and all onboard components (see p60, Apr25): - SMD LEDs (SC7462) $20.00 - Through-hole LEDs (SC7463) $20.00 433MHz TRANSMITTER KIT (SC7430) Includes the PCB and all onboard parts (see p75, Apr25) (APR 25) PICO 2 AUDIO ANALYSER SHORT-FORM KIT (SC6772) (MAR 25) USB PROGRAMMABLE FREQUENCY DIVIDER (SC6959) (FEB 25) NFC PROGRAMMABLE IR KEYFOB (SC7421) (FEB 25) COMPACT HIFI HEADPHONE AMP (SC6885) (DEC 24) PICO COMPUTER (DEC 24) FLEXIDICE COMPLETE KIT (SC7361) (NOV 24) MICROMITE EXPLORE-40 KIT (SC6991) (OCT 24) DUAL-RAIL LOAD PROTECTOR (SC7366) (OCT 24) PicoMSA PARTS (SC7323) (SEP 24) The Pico Audio Analyser kit from Nov23, but with an unprogrammed Pico 2 Complete kit: includes all components (see p85, Feb25) Complete kit: includes all required items, except the cell (see p67, Feb25) $50.00 $60.00 $25.00 Complete kit: includes everything except the power supply (see p47, Dec24) $70.00 $30.00 CAPACITOR DISCHARGER KIT (SC7404) (DEC 24) $1.00ea Includes the PCB and all components that mount on it, the mounting hardware $5.00 (without heatsink) and banana sockets (see p36, Dec24) $30.00 Includes all the parts except the power supply. When buying the kit select either a BZ-121 GPS module or Pico W (unprogrammed) for the time source (see p66, May25) $65.00 PICO/2/COMPUTER (SC7468) siliconchip.com.au/Shop/ $20.00 For full functionality both the Pico Computer Board and Digital Video Terminal kits are required. Items shown unbolded are optional (see p71, Dec24) - Pico Computer Board kit (SC7374) $40.00 - Pico Digital Video Terminal kit (SC6917) $65.00 - PWM Audio Module kit (SC7376) $10.00 - ESP-PSRAM64H 64Mb SPI PSRAM chip (SC7377) $5.00 - DS3231 real-time clock SOIC-16 IC (SC5103) $7.50 - DS3231MZ real-time clock SOIC-8 IC (SC5779) $10.00 Includes all required parts except the coin cell (see p71, Nov24) Includes all required parts (see p83, Oct24) Hard-to-get parts: includes the PCB and all semiconductors except the optional/variable diodes (see p73, Oct24) Hard-to-get parts: includes the PCB, Raspberry Pi Pico (unprogrammed), plus all semiconductors, capacitors and resistors (see p63, Sep24) *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 $35.00 $35.00 $50.00 SERVICEMAN’S LOG Salvaging a soggy ceiling circuit Dave Thompson Why is it that when a pipe leaks, it’s always in the most inaccessible location, and the water always ends up where you don’t want it? It must be one of the variations of Sod’s Law. A weird thing happened a while back on the way to work. All of a sudden, I was sitting in Airlie Beach, which, as all you boffins know, is in Queensland, in the stunning country of Australia. I’d had surgery on my legs a few weeks before that, and the recovery time they mentioned was only valid when wearing very rose-tinted glasses. So I was sitting a lot, but told to walk. We did a lot of sitting, watching thousands of tourists a day head out on huge boats to the Whitsundays and, of course, the south end of the Great Barrier Reef. However, I also hobbled around the town to sample the local fare (which is very good) and the local wines, which are also excellent. Then we took a trip to a pontoon hotel floating on the reef itself. So it was idyllic, and the first holiday we went on that didn’t involve pandering or catering to our families in Europe and Western Australia. Our time, as Agent Smith says in The Matrix. This was all very well until the neighbour back home, who had kindly looked after our place and our pets, messaged to say he had found water pooled on the floor of our downstairs bathroom. He’d found a bucket and put it down; as we were going to be back in a few days anyway, there was no panic. It was all in hand, or at least in bucket. I got home to find that the water was dripping, slowly but surely, through the bathroom light fitting. This is a combination heater, extractor and LED light (the motor runs both ways depending on the four-way switch on the wall). Now, given that this is electrical – a mains-­powered unit – and water was pooling in it before dripping through the grille into the container, I was quite worried about switching it on! Items Covered This Month • A soggy ceiling circuit • Calibrating a Silicon Chip Differential Probe • Repairing an LG air conditioner 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 86 Silicon Chip Fortunately, we have an upstairs bathroom as well, so we could use that. Unfortunately, the water was coming from somewhere up there. While it was clean water, which gave a clue as to which pipes to look at, it was still coming from somewhere that it shouldn’t. So, the only thing for it was to get my old gammy legs into the roof space and see if I could locate the source of the leak, all without electrocuting myself or falling through the ceiling (which might not take a lot of weight if it was soaked!). A job for the young and limber Luckily, the guys who added the top storey to this house in the 90s included several access doors. These are almost hobbit-sized small cupboard doors; so not overly easy for an old man to clamber through, but located in the main areas upstairs to access the crawl space that surrounds the upstairs rooms. They do come in very handy for running network cables and the like. Of course, one must be very careful not to step on anything but a roof joist, or one would find themselves sitting on the downstairs floor, confused and covered in Gyprock fragments! ‘Luckily’, the extractor fan was exactly halfway between one access cover and another, so I would have to put on my gloves, knee pads and headband LED lamp, along with a 3M particulate mask, to navigate there. The space up there is dusty, to say the least. It is also inhabited by spiders and the odd mouse. Come spring, birds find their way in and roost, as well as make baby birds, so it’s a menagerie up there. Australia's electronics magazine siliconchip.com.au As I said, the top level was added a while back, and they did a real bodge job moving the hot water cylinder up there. There was nonstandard plumbing and wiring all over the shop. I redid the wiring when I renovated this place before moving in, under the supervision of a sparky who had damaged his leg and couldn’t move very well (perhaps it was just so he could sit and drink tea on our dollar!) We also installed a new Earth rod as we changed all the underfloor, rusted steel pipes for modern butylene, which meant new Earth connections for everything that needed them, as this plastic doesn’t really conduct electricity that well. Fortunately, they had put plastic piping in the roof space, but much of it was non-standard. Since we didn’t have to touch much up there back then, we concentrated on renovating the ground floor. This meant that those old pipes, which criss-cross the space, and were routed wherever they could fit them for the upstairs bathroom, are 30+ years old. I made my way through the dust and the spiderwebs until I got to where the extractor unit sat. Sure enough, it was full of pooled water. The drips were coming from a small hole in the housing, likely an unused screw hole, and slowly making their way down to the floor downstairs. There were several pipes in the vicinity, but none quite near the fan, so I lifted some insulation (gloves essential) and tracked a damp timber beam back until I found a fitting almost inside the wall of the upstairs bathroom. Reaching up the pipe, I found the fitting was wet, and my glove came away damp. It was dry above that, so this must be the source. The water was tracking down the pipe, dripping onto the joist and making its way to the lowest point, right into the extractor. The problem was that now I had to back out, go all the way downstairs and find the breaker for this unit, as it would likely have to come out to be dried and cleaned. That meant disabling the power, then getting up the ladder to take it out and clean it. Luckily, when I rewired this place, I made a map of all the breakers and circuits. Years of dust being drawn into it for the heating function and blown out of it in the extractor mode had left it looking almost flocked in a thick layer of dirt, which was now wet sludge in most places. The first thing I did was call a plumber, because plumbing work is above my pay grade and things could go seriously awry if I were let loose on it. He agreed to come that night, after his usual work, to have a look. Editor’s note: residents of New Zealand can legally do some of their own electrical work, including fixed mains wiring, with some provisos (eg, the work must be done to NZ standards). That includes disconnecting and reconnecting existing appliances. This is not permitted anywhere in Australia, where such jobs must be performed by a licensed electrician. And similar to NSW, you can only perform basic plumbing work by yourself in NZ. Anything more complex (eg, installing or replacing mains pipes) requires a licensed plumber. popped off with a knife blade, and I set them aside so I could refit them later, right at the end of the job. A few weak clips held the bottom ‘half’ of the unit on, and it came off easily. Half of that is a heater-style grille, and the other half is a large LED light; a flat, rectangular panel type. That had to be unplugged from the main body, but the plug is a standard barrel type, and it unplugged easily. I set that aside and looked inside the fan. I could see four ‘superscrew’ type fasteners had been used, two per side in each corner, to fix the main body of the extractor to the ceiling joists. The problem with this is that I was going to need three arms to get it down, and standing on a ladder makes it even trickier. I used a drill with a long-form Robinson bit in it to spin out the first three screws. I then held it up with my head and used the other hand to remove the last one. The assembly fell clear, dangling on the power cables. Before I went anywhere near them, I checked with my trusty mains detector pen to make sure I had switched off the right breaker. The light and fan no longer worked from the switch, but I don’t like to just assume there’s nothing still there that could kill me, especially as water poured everywhere when the unit dropped down. We all know that electricity and water are not good bedfellows! It all seemed good, so after taking a photo of it, I used my equally trusty electrician’s screwdriver to undo the terminal screws and free the wires. With the unit out, and now a large hole in the roof, I stuck a bath towel in the gap to stop any drafts and soak up any more water that might still be coming out. I set about trying to clean this thing up. The water had discoloured the plastic because it had run over treated timbers on its way down, leaving an almost tobacco-coloured brown stain on the plastic. I tried isopropyl alcohol and methylated spirits, but it looks pretty much permanent. It did clean some up, but not all. The unit’s chassis was mostly pressed or cast metal, so that was relatively easy to clean with damp rags and a bristle Meeting one of my fans Pulling the decorative bezel from the extractor unit body was relatively simple, after I had figured out that the screws were concealed under small plastic covers. The covers siliconchip.com.au Australia's electronics magazine September 2025  87 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. brush. Once as dry as I could get it, I left it – I’d blow out the fan with the air compressor tomorrow, and any other dust that might be left in the nooks and crannies. While I was there, I would also lubricate the motor bushes and check that everything else was in good shape. The fan motor does a lot of work, and sometimes it runs much of the day, in both directions. It’s actually quite a high-­quality unit; I was impressed with the build quality. Mind you, from memory, even eight years ago it wasn’t a cheap appliance, even though it came from one of the big hardware chain stores. It has been a very faithful unit, although we don’t use the built-in fan heater much, because that thing eats power like Homer Simpson at an all-youcan-eat seafood restaurant! A prompt tradie As promised, the plumber turned up on time (a miracle in itself!) and I pointed out the problem. While we could just see the pipe from the hole in the bathroom roof, there was no way to access it from there. I showed him where the access hatch was, and with the grace and flexibility mostly only young people have, he grabbed his headlight and ventured in. He made his way around behind the walls, and I went down and stood at the bottom bathroom gap as he explained that whoever had set this up originally had used a bad industry practice of putting two different plastic pipes together in an inline join. He said it was leaking from there. It was the clean water feed to the upstairs toilet and vanity. As is typical, the joint was buried behind some roof beams, and while he could see it from there, he couldn’t access it. So back he came, and while I went and turned off the water mains, and some outside taps on to drain as much as possible out of the pipes, he rummaged through the copious boxes of spare parts in his van and found a brass fitting specially designed for this type of job. 88 Silicon Chip Unfortunately, the toilet had to come out to get proper access. This meant undoing the screws and cutting the caulk away, but then it just slid out, and five minutes later, he redid the join (with a lot of water on the floor). Soon after, it was back in, and I would caulk it in a few days if no more water came out. So, it was a cheap and relatively easy fix, and he looked after us payment-wise (another miracle for a plumber!). Now, all I had to do was put the extractor unit back in, and once again, I’d need three hands to do it; two to hold the unit, and one to reconnect the wires to the terminal blocks. The obvious problem is that I’m not an octopus, so I had to just hold the unit in the gap with one hand, line up the mounting holes and use my driver to reinsert the superscrews in the same holes they came out of. Rewiring it all over again Of course, the wiring was just sitting up there disconnected. I would simply have to get all my gear on and venture back into the cave to re-terminate everything. First, I replaced the now-stained plastic bezel and used the four PK-style screws to fix it to the chassis. The screw covers popped back on without any hassles. It all looked pretty neat there, but now it was time to break out the hazmat gear and get back into the roof space. Fortunately, I had taken that photo before removing all the cables, as it was quite a complex setup, from the switch end to the unit itself. I took my phone up there with me and squeezed into the area. It wasn’t easy to get to, but possible, and with a bit of fettling, I managed to get the screwdriver in and attach the wiring to the terminals. After using some cable ties to anchor it all, I made my way back out and downstairs to reset the breaker. I went to the bathroom and tried the fan-only switch. The fan fired up and sounded good; the lubricant had done its job. I tried the light, and it lit up nicely. I noticed when I turned it off, though, that it seemed to linger and fade out over a second or two. Usually, it is instantly dark. So that was odd. I then tried the first heater setting, 1200W. I have to turn the extractor off first; otherwise, this switch reverses the fan motor, and just dumping it in reverse is no better for it than it would be for a car transmission. With the fan switch back on, sure enough, warm air blew into the bathroom. I switched on the second heater switch (2400W) and the breaker tripped instantly. That was new, too. I switched it all off, reset the breaker and tried again with the same result. Maybe I’d damaged something cleaning it, or the water had gotten into it somewhere. Either way, it didn’t bode well. I got all kitted up again and went back into the roof. I should install a walkway for all this traffic! I just wanted Australia's electronics magazine siliconchip.com.au to check I hadn’t been a dolt and wired something wrong – easy enough to do in cramped quarters with a mask and gloves on. It looked OK, but I redid it anyway. At least the pipe fitting was now dry, although it would take a few days for the damp up there to dry out. That was all I could do, so I once again made the knee-shattering journey back out. I really am getting too old for this, especially after my recent leg surgery. I went down and tried it again. Same result. So, during the coldest parts of winter, we could only use the low setting, by the looks of things. I was sure I’d rewired it the same as it had come out. Off came the bezel again, and everything looked OK there too. All I could do was consider buying another one. However, after a few days, I thought I’d try the second heat setting again, and this time, the breaker didn’t trip. Perhaps some water had encroached, and now it was dried out. I’ll take the win, but I’ll be keeping an eye on it! High-Bandwidth Differential Probe repair The High-Bandwidth Differential Probe published in the February 2025 issue (siliconchip.au/Article/17721) looked like a very useful addition to my toolkit, so I set about ordering the components, being very careful to procure the correct 0.1% tolerance parts. It made good sense to build three units to facilitate measurements on multi-phase applications. All up, I had to go to four different suppliers to get all the parts. After a few weeks, everything was in hand, and I proceeded with the construction as outlined in the article. A good friend was kind enough to solder REG5 (the SMPS chip) in his reflow oven, but it was still a challenging task. I used my hot air workstation for the remaining components. As per the instructions, I successfully tested the power siliconchip.com.au supply before proceeding to install the remaining SMD components. I arrived at the point where the instructions say to apply the conformal coating. While I was questioning if I should really coat the components without first testing the circuit, I decided to go with the instructions and apply the coating. Before doing so, I used a masking paste to cover the remaining through-hole parts so that they didn’t get lacquered. Many years ago, I purchased a can of Circuit Board Lacquer NA-1002, which had a sufficient quantity left in it. I applied three coats of this lacquer and let it set for 24 hours before installing the remaining components. Now for the fun part – calibration. Step 1 was easy; adjust VR2 to read <10mV. Step 2 (the CMRR adjustment) was asking to adjust for a reading under ±20μV. Using a bench meter with the required resolution, I was very surprised to see the voltage measurement fluctuating in the mV range, some magnitudes above my target. The power supply I was using to feed 64V DC into the measuring inputs was a lab-grade Rigol unit with excellent specs, and it checked out OK. My oscilloscope showed this ‘noise’ to be at 50Hz, and it was equally present on all three PCBs. To allow me to progress to the next step, I decided to use the graph display of the bench meter and to get the fluctuating voltage around the 0V line; the screenshot below shows the changing measurement as I adjusted VR1. I knew I had to come back and find the problem, but at least I could move onto the final calibration of offset voltage trim and frequency compensation, both of which worked as advertised. Now onto testing all three units in full operation. Using a variac connected to an isolation transformer, I was able to adjust the voltage being fed into the probes. That’s where I discovered the three probes provided different readings, and none of them were correct when compared to my R&S ScopeRider measurement! The difference between the probes was over 20V looking at a peak-to-peak measurement with an oscilloscope. I went through my components purchase details to double check that I had ordered 0.1% resistors and I couldn’t find any obvious errors. The difference I was seeing was just not possible with those components. I had to put this project aside for a few days, as it was driving me crazy. Nothing seemed to make sense. After a few days of thinking about this, I decided to tackle this Adjusting VR1 let me change the DC offset but a significant AC noise voltage was superimposed on the output signal. Australia's electronics magazine September 2025  89 project again and to take some more measurements to discover the source of the difference between the three probe boards. The challenge was the circuit board lacquer all over the critical resistors. I shouldn’t have lacquered the board until after circuit testing, and with the variac in place, I could keep the voltage low enough so the lack of coating wouldn’t cause any issues. Hindsight is a great thing! So I scratched off the coating around all components of the input circuit voltage divider. I did this on all three boards – it really tested my patience! However, the result of the hard work was well worth the effort. After recalibration, I compared the measurements with all three boards, and they were practically the same. So it appears that removing the coating fixed the problem. The only conclusion I can draw is that the conformal coating provided a high-resistance path in parallel to the 1MW resistors and therefore affected the voltage divider ratios. Due to the variation in thickness and uneven application, the resistance provided by the coating was different between the boards, hence producing different readings on each board. I have now ordered a different conformal coating spray, one where the data sheet states “Surface Insulation Resistance 1 × 1015W”, I couldn’t find any “Surface Insulation Resistance” rating for the NA-1002 spray (now consigned to the recycling bin). The CMRR calibration problem remained unresolved, but without the conformal coating, it became easier to take measurements. The measurements still indicated a fluctuating voltage of ±2mV where I need to adjust to within ±20μV. I disconnected the 64V DC supply from the measuring inputs, but the fluctuation remained. Even after I switched off the probe using S1, the fluctuation was there. This was a clear indication that I was measuring an external interference signal which was being induced in the components on board. Since the measuring point for CMRR calibration is across the ~20kW part of the divider, I took a 22kW resistor and connected it to the input of the bench meter. You guessed it, I still saw ±2mV, obviously from the workbench environment where I was performing my calibration! To convince myself that my assumption was correct, I removed power from everything except the bench meter and the fluctuation was reduced to <2μV with the 22kW resistor. Upon restarting everything, the measurement returned to ±2mV. I am an Amateur Radio operator and my workbench is my radio shack, so there are lots of mains cables and many devices located in very close proximity to my workbench top. In fact, when the measuring leads with the resistor accidentally dropped onto the floor, the ±2mV fluctuation disappeared, so it’s just the top of my workbench, which is exposed to a 50Hz field. It looks like the solution is to perform the CMRR calibration under the workbench instead of on top of it! Erwin B., Wodonga, Vic. LG aircon repair My wife informed me that the kitchen air conditioner would not work. This is a small window-mounting unit I installed around 2000; it has never been touched except for cleaning the air inlet screen. It’s the type that has a very simple control system with no electronics; a ‘vintage aircon’, if you like! It has a temperature knob and a power switch with a couple of modes of operation, fan or cool. With those, you get two speeds of running and that’s it, simple. No remote control or fancy computer stuff. I switched it on to test it. It made a humming noise only; neither the fan nor the compressor operated. Should I bin it and buy a new one at about $600, or try to work out what’s wrong and fix it? That’s a no-brainer! I always try to fix things even if they’re past their ‘use-by date’. I found a postage-stamp sized circuit diagram on the frame under the front plastic cover. That confirmed there are not many electrical parts to go wrong! I then pulled the main cover off the unit, which took some time because a lot of the screws were rusted solid; some had to be cut out. Once inside, I traced out the wiring by colours and took The 1.5μF + 25μF 400V AC dual capacitor unit shown at left was open-circuit; the LG aircon is shown on the right. 90 Silicon Chip Australia's electronics magazine siliconchip.com.au photos to be sure. The wiring looked the same as the circuit, and since both motors would not run, this indicated maybe a common component had failed. I measured the resistance of the motor windings and insulation-tested them, just to make sure nothing was shorted or grounded. The compressor motor (COMP) had about 6W in each winding and the fan motor (MOTOR) measured hundreds of ohms. Both motor windings were infinity to chassis. The capacitor (C) was a dual 1.5μF + 25μF 400V AC unit. The capacitors inside the can were simply open-­circuit; I couldn’t get a capacitance reading anywhere. Most likely, the internal fuse link in the common leg had failed. I wanted to run the unit to test the motors before buying a new capacitor. In my junk box, I found an oil-filled 2μF capacitor and a similar 30μF capacitor, both with 250V AC ratings. I patched them temporarily into the circuit in place of the original dual unit and, when powered up, the fan and compressor promptly started! After a few minutes of pulling 2.3A (the nameplate rating is 2.8A), the back air got hot and the front air cool. That looked promising, so I left it for half an hour. Nothing blew up or overheated and the temperature differential between the evaporator and the condenser (front and back) was about 23°C. The open-circuit capacitor sections are in series with the startup winding of each motor. Without any power to the phase-shift windings, neither motor would spin and they just sit stalled and humming. I checked eBay for 1.5μF + 25μF motor start capacitors and there were plenty available. I ordered one from a local air conditioner supplier at $30, including postage. The new capacitor arrived in a couple of days, so I fitted it and repeated the test run. The operation was normal. This unit is probably past its service life, as the base frame is rotting away with pinholes, but the gas circuit is still charged and electrically it’s OK. Fixing it was the easy part. The hard part was cleaning out the rust from the bottom water tray and evicting the spiders and webs! I just cleaned it up as best as possible. I am very careful about not moving any of the gas pipe work. On an old unit like this, the pipes will be brittle and have no ‘give’ in them; moving them, you risk cracking a pipe or joint. If that happens, the unit loses its gas and is scrap. It would have been nice to drop the bottom base tray off, de-rust it and seal up any leaks. Still, that would mean moving pipes, so I just cleaned the loose stuff out and flooded the area with rust killer/undercoat to slow the rot down. I took a fair bit of time cleaning the fins on the heat exchangers with mould detergent and removing any build-up on the air duct surfaces and fan blades. All that was left was to refit the cover and strong-arm the unit back into the frame. As we all know, there is a phenomenon where any cabinet unit grows slightly in all outside dimensions after servicing on a bench! That caused required a bit of wriggling, and the cabinet needed a few healthy thumps to slide it back into the frame. A quick run showed normal performance, so the repair was a success. This fix illustrates that it is always worthwhile looking at a faulty appliance for an obvious failed component that can be easily replaced and the whole unit made serviceable again. SC Fred Lever, Toongabbie, NSW. siliconchip.com.au Australia's electronics magazine September 2025  91 Vintage Radio The Pye PHA 520 “Colombo Plan” Radio circa 1960s The Pye PHA 520 radio was developed to help improve education and cohesion in Southeast Asia, along with strengthening ‘soft power’ in the region. By Alby Thomas Circuit Description by Ian Batty F ollowing World War 2, there was a fear among Commonwealth countries that the scourge of communism would filter from China down through the Asia Pacific region. A meeting of major Commonwealth nations (including Australia) was held in Colombo (Ceylon, now Sri Lanka) in 1951, with the view of improving standards of administration and commerce in the developing Asian countries. At times, the assistance was misguided, with tractors sent to areas of labour excess and tiny farm holdings. While not a Commonwealth country, the USA funded educational programs, scholarships and medium-­ powered broadcast transmitters. The Colombo Plan still exists today, with 28 member countries, including Chile and Japan. As part of the Australian effort to improve education and cohesion in Southeast Asia, a network of radio broadcast transmitters was set up in Asian Commonwealth countries. Radio receivers were supplied, with contracts to manufacture these radios were granted by the Department of Supply in 1963 to Pye Australia. The HRSA’s Kevin Poulter advises that these receivers were made by Pye Communications, well-known for its A close-up view of the instruction sheet which is attached to the top of the case and the Pye PHA 520 dial which is... 92 Silicon Chip Australia's electronics magazine siliconchip.com.au The telescopic antenna for the set is attached along the rear edge of the plywood cabinet. This antenna and a separate Earth stake are connected to connectors also visible on the rear. taxi radios, not Pye Domestic, which would have typically manufactured radio receivers. AWA supplied medium-powered (5kW) HF transmitters as well as a transistorised receiver similar to the PHA 520 for use overseas. I have seen one of these with no ARTS&P label (Australian Radio Technical Services and Patents), no Australian stations shown on the dial and similar coverage to the Pye sets. It was similar in appearance to Radiola’s model 893P. Before that, in the early-to-mid 1950s, AWA provided valve radio sets for the Colombo Plan. They were the model 1548MA, a five-valve set operating from 110-240VAC, and the model 546PZ, a five-valve dry-cell battery set. Around 1000 of each model were produced. Pye was awarded contracts amounting to just over £A245,000 (about $8,000,000 today) for transistorised radio receivers and associated equipment. The sets are pretty large at 280mm (11 inches) high, 395mm (15½ inches) wide and 190mm (7½ inches) deep, with a large 15 × 23cm (6 × 9-inch) speaker. They weigh just under 7kg each without batteries. The cabinet is plywood with a grey/ green vinyl fabric covering. There is no internal loop or ferrite aerial, but the sets were supplied with an Earth stake and a long aerial wire that connected to terminals at the rear of the set. Power was from six D cells fixed in place in their carrier by a metal bar. There is no provision for an external power source. The sets tune from 525kHz in the AM broadcast band to 30MHz (shortwave) in four continuous bands. The set lid operates a switch that controls the power. The set I have (serial number 4244) was found at a dealer in Geelong under some boxes of other radio gear. I thought it was so ugly that I just had to have it! A two-metre-long telescopic whip aerial had been screwed to the side of the set as an afterthought. Another of these radios (serial number 0882) is owned by the HRSA’s Ray Gillett, purchased at a Ballarat flea market, while a third set (serial number unknown) was presented to a Pye manager, then passing through different hands until it reached the AVRS’s Warwick Woods. Other sets would have been brought back from Asia to Australia by migrating families and will be out there somewhere. As purchased, my set was dead. I had no circuit or other documentation, so I traced out the circuit, revealing a reasonably standard superhet with an RF stage, germanium transistors and a transformer-coupled output stage. ...using knobs sourced by Alby Thomas (rather than the ones shown in the lead photo). siliconchip.com.au Australia's electronics magazine September 2025  93 Unusual was the use of back-to-back 25μF electrolytic capacitors to get a non-polarised high capacitance. I had heard of this principle but had not seen it in practice. Editor’s Note: this approach is almost always cheaper and more compact than using a bipolar electrolytic capacitor Testing showed that all electrolytics (11 total) were either short-­circuit or open-circuit. Replacing them all did not bring it back to life until I replaced the OC171 RF amplifier transistor. The set’s construction is robust and neat. It performs very well, with good reception on all bands, although there are not many usable shortwave transmissions to tune into. Circuit details by Ian Batty Pye’s diagram follows the drawing conventions of the day. Transistors are prefixed with “TS”, while germanium diodes are prefixed with “MR” (“metal rectifier”). Band change switch SWA’s labelling was only partly legible on the best available manufacturer’s diagram, so I have renumbered its sections from 1 to 12. Pye’s original diagram is very dense (especially the tuner section), observing the need for compactness on the page. I have expanded the diagram for legibility and ease of description in Fig.1. This has displaced some components from Pye’s original locations. For compatibility, I have retained Pye’s component numbering. Legibility problems may have led to numbering at odds with Pye’s. I welcome any feedback on this, especially a clearer example of the original circuit! I have retained Pye’s coil numbering in the tuner coil set. I have put Band 4 (broadcast) coils at the top of my diagram for convenience. This is the opposite of Pye’s placements, but I have preserved their numbering. This has placed the coils in apparent reverse order from top to bottom. For example, broadcast aerial coil L4 appears at the top of my diagram. Because of this, the 3~30pF trimmers are also designated in reverse vertical order. The four bands In common with other shortwave radios, band numbering starts with the highest band: Band 1 (red): 14.8~30MHz Band 2 (green): 4.8~15MHz 94 Silicon Chip Band 3 (yellow): 1.6~5MHz Band 4 (blue): 525~1600kHz The tuning gang is cut for straightline frequency, so Band 2 to 4 scales show equally divided calibrations. Band spreading on Band 1 (a 1:2 ratio) causes the calibration to deviate, so Band 1’s scale is not equally divided. The tuner circuit The tuner section, in common with multi-band equipment, is complex at first glance. It’s also complex at second glance. The aerial circuit and local oscillator circuits, especially, switch different component configurations for each band in addition to the expected changes in coil sets. SWA/1 conveys the incoming RF signal to the selected aerial transformer, L1 (14~30MHz) to A4 (Broadcast). A series capacitor (C2, 220pF) is connected for all bands except Band 1. This series capacitor compensates for an aerial that is shorter than the ideal quarter-wavelength for the broadcast band. Bands 2, 3 and 4 give the usual 1:3 ratio for frequency coverage. Band 1’s coverage, in contrast, is only about 1:2. This demands a reduction in the tuning gang’s capacitance swing. Capacitor C7 (180pF) pads Band 1’s aerial circuit, reducing its span to 1:2. Band 1’s RF transformer is also padded by 180pF capacitor C20. SWA/2 connects the signal from the appropriate aerial transformer to the base of RF amplifier transistor TS1. This connection also conveys bias from the automatic gain control (AGC) line, via the selected transformer, to TS1’s base. SWA/3 connects the appropriate transformer to the tuning gang’s aerial section, C9. All inductors in the coil set are closely packed, creating the possibility of interaction between selected and unselected coils. SWA/4 shorts out the other three unselected aerial transformers to prevent interaction. The tappings on RF transformers L5 to L8 are driven from TS1’s collector, as selected by SWA/7. The tappings match the medium-to-high collector impedance of TS1 to the higher impedance of the selected RF transformer, ensuring maximum selectivity. Although TS1 operates as a common-­ emitter amplifier, it is not neutralised for two reasons. Firstly, RF amplifiers have low gains compared to fixed-­ frequency IF (intermediate frequency) Australia's electronics magazine amplifiers, so collector-base feedback is less likely to load the input circuit or cause oscillation. Secondly, Philips’ OC169/170/171 series of transistors use alloy-diffused construction, coming between the preceding alloyed-junction OC44/45 and follow-on ‘all-diffused’ Mesa transistors such as the AF139. The alloy-­diffused collector-base feedback capacitance of some 1.5pF apparently has no serious effect on this circuit, with its maximum frequency of only 30MHz. The RF amplifier gang connects to its selected coil via SWA/5, with unselected transformers being shorted out (as for the aerial circuit). The RF section uses SWA/6 for this. The converter Converter transistor TS2 receives both the incoming RF signal and the local oscillator (LO) signal on its base. The RF signal from the secondary of the selected RF transformer (L5~L8) comes via SWA/8. LO injection is more complicated. Each LO transformer is permanently connected, either via a tap (L11/L12) or a secondary winding (L9/L10) to the ‘bottom’ end of its companion RF transformer secondary. In concert with SWA/7’s selection of the active RF transformers primary, the selected RF transformer secondary’s combined RF and LO signals (selected by SWA/8) are conveyed, via 100nF coupling capacitor C21, to the base of converter TS2. TS2 works with fixed combination bias (R2/R3/R8/C23). The IF channel begins with a bandpass filter comprising IF transformers T1 and T2, with associated tuning capacitors (C34/C39), resistors R13/ R14 and coupling capacitor C37. While any IF amplifier, by virtue of its design frequency, is a bandpass filter, the term is usually reserved for circuits with several coupled resonant circuits and no amplifiers between them. T1 receives the converter’s four output signals: the input signal and LO signal, as well as the LO+ input and LO– input products. As this receiver uses ‘high-side’ LO injection, the IF strip selects LO– input, ie, the 455kHz signal. The local oscillator Local oscillator transistor TS3 (an OC171) operates in grounded-base mode. This configuration allows the siliconchip.com.au Fig.1: the Pye PHA 520 circuit is dominated by the tuning and band-changing circuitry (the top section). Band change switch SWA is a 12-gang wafer switch with most gangs having four poles, all shown in the Band 4 position. Most gangs are one-of-four selectors (eg, SWA/3) or three-of-four selectors (SWA/4). SWA/1 is like a one-of-four selector except it also shorts out C2 for Band 1. This side of the chassis is where the tuning gang and coil pack mount. Note the tightly packed inductors on the coil pack at right, and the use of a PCB for the components. transistor to exhibit constant oscillation to over 30MHz. TS3 operates with fixed combination bias (R4/R5/ R8). TS3’s base is bypassed to ground by 100nF capacitor C23; TS3 has a typical input impedance under 100W. TS3’s collector selects one of the L9-L12 LO transformers via SWA/12. The LO gang section, C38, connects to the tuned winding of the selected LO transformer via switch section SWA/10. As with other tuning connections, unused LO transformers are shorted out to prevent unwanted interaction, in this case by SWA/11. Each tuning range needs its LO frequency span reduced to guarantee tracking between the LO and aerial/ RF amplifier circuits. Broadcast band 4 uses C35. At 470pF, this is close to the value commonly used in broadcast-­ only superhets. As they need a wider frequency span (less restriction), Bands 3 and 2 use 1.5nF (C34) and 4.7nF (C33) capacitors, respectively. In theory, Band 1 can operate without padding – the required 455kHz offset is minimal compared to Band 1’s 14~30MHz tuning range and would cause only minor tracking errors. However, remembering that this band has a limited 1:2 frequency coverage, band spreading is applied by 180pF capacitor C32, the same value used to spread Band 1 in the aerial and RF amplifier circuits. The feedback for TS3 is taken from the low-impedance secondaries of LO transformers L9~L12. It’s common for oscillators to suffer frequency variations with variations in supply voltage. It’s mainly a problem with battery-operated equipment as the batteries run down. The PHA 520 ensures dial calibration by providing a stabilised LO supply using 4.7V zener diode ZD1 as a shunt regulator, supplied from the main battery voltage. Capacitors C11 (Band 1, 180pF) to C14 (Band 4, 8.2 nF) control the proportion of feedback needed for each band. SWA/9 selects these, in series with LO transformer feedback windings. IF section The rear view of the cabinet provides a good view of the major sections of the radio such as the Rola speaker and Panasonic battery pack at lower left. The converter’s signal is sent to the single winding of the first IF transformer, T1. This transformer has a single tuned winding, as it’s only needed to develop the 455kHz signal. T1 connects to T2 via 27pF capacitor C37, coupling the two tuned circuits. While 27pF seems like a low value, both T1 and T2, at resonance, will have impedances close to their loading resistors R11 (68kW) and R13 (68kW). C37’s reactance is only about 12kW but, considering it as part of each tuned circuit, it will convey the 455kHz signal from T1 to T2 with little practical loss. This part of the circuit acts as another bandpass filter. T2 accepts the 455kHz signal at its high-impedance Australia's electronics magazine siliconchip.com.au 96 Silicon Chip The other side of the radio chassis houses the components. tuned primary and conveys the IF signal to its low-impedance secondary. This feeds the base of first IF amplifier transistor TS4, an OC169. Like the transistors in the tuner, this is an alloy-diffused type. As it has low feedback capacitance, neutralisation/ unilateralisation is not needed, unlike transistors from the previous generation of alloyed-junction types. TS4 is gain-controlled by the DC voltage developed by demodulator diode MR1. In common with reverse gain-controlled stages, TS4 operates at a low collector current (around 0.3mA), allowing easy reduction of its stage gain on strong signals. TS4 feeds the tuned primary of T3, shunted by 18kW resistor R18. T3’s secondary feeds the base of second IF amplifier TS5, another OC169. This operates with fixed bias at a collector current of around 5mA, giving full gain with no AGC control. TS4 feeds the untapped, tuned primary of T4, whose secondary feeds demodulator diode MR1, a germanium OA90. MR1 demodulates the 455kHz IF signal, which is filtered principally by 22nF capacitor C52, with additional filtering by 100W resistor R25 and 22nF C54. MR1 also feeds the AGC line via 1.5kW resistor R24. The low-pass filter formed by R24 and back-to-back 25μF capacitors C47/C48 removes the audio signal. Electrolytic capacitors are ineffective at high frequencies, so a ceramic capacitor (22nF, C52) is added in parallel to C47/C48 to ensure complete filtering of the IF siliconchip.com.au signal and prevent feedback in the high-gain IF strip. The back-to-back connection of C47 and C48 allows for the AGC line (a negative voltage in most designs) going positive with very strong signals. A second filter section (1.5kW resistor R21 and 25μF capacitors C43/C44) supplies the AGC voltage to the first IF amplifier, TS3, and to RF amplifier transistor TS1, in the tuner section. Unusually, the PHA 520 does not have an AGC extension diode, as is common in high-quality domestic radios and near-universal in shortwave and communications sets. Both IF amplifiers use ‘single point’ Earthing. For example, TS4’s collector circuit bypass (C49, 100nF) and base circuit bypass (C40, 100nF) both return to TS4’s emitter rather than to ground, as in most designs. This gives more effective bypassing, with the advantage that no emitter bypass is needed. The demodulated audio is coupled via 25μF capacitor C56 to the base of audio driver transistor TS6. This drives transformer T5, which supplies push-pull audio to the output transistor pair, TS7/TS8. 8.2kW resistor R31 and 1nF capacitor C57 across T5 apply top cut (a reduction in treble). The output stage is biased into Class-B mode by bias supply divider R32 (3.9kW) and bias diode MR2 (AV2). This diode is effectively a This shows the other side of the coil pack. Australia's electronics magazine September 2025  97 Table 1 – Pye PHA 520 sensitivity vs frequency for 50mW output Table 2 – freq vs image rejection Frequency Input signal level S+N:N Signal level for 20dB S+N:N Frequency Image rejection 600kHz 7μV 10dB 25μV 1400kHz (band 4) 70dB 1400kHz 1μV 3dB 10μV 4.4MHz (band 3) 35dB 2MHz 2.5μV 3dB 20μV 14MHz (band 2) 31dB 4.4MHz 0.6μV 2dB 20μV 6MHz 4.8μV 3dB 15μV 14MHz 2μV 3dB 12μV 15.5MHz 7.5μV 10dB 9.6μV 28MHz 7μV 12dB 15μV circuit bandwidths increase, meaning less attenuation of the image signal. Table 2 shows the image rejection performance. IF bandwidth at -3dB is 5kHz, while at -60dB, it’s 25kHz. This relatively low figure would have made tuning easier for untrained operators, and it’s explained by the unusually high (nanofarad) values of IF tuning capacitors C34/39/42/50. Such capacitors are more commonly in the 200~300pF range. The AGC is effective. A signal increase of 78dB is needed for a 6dB rise in audio output. The set went into overload with an input signal of around 200mV. The audio response from the volume control to the speaker is 110Hz to 9kHz, while from the antenna to the speaker, it is 50Hz to 2.7kHz. Total harmonic distortion (THD) was only 2% for a 50mW output, and the same at 10mW, a sign that crossover distortion is well controlled. The maximum audio output at clipping is around 350mW. So, would I buy one? I would, if only to repeat Alby’s exercise of rescuing it from obscurity. If you come across one, I reckon you should, too! transistor with its base tied to its collector. This creates a low-voltage supply that delivers the correct bias for TS7/TS8. The AV1 has thermal characteristics identical to the base-­emitter junctions of the output transistors, giving accurate bias regulation with changes in ambient temperature. Feedback from the output terminals is applied to the emitter of audio driver TS6 via C59/R33/R30. The audio output can be directed to the internal speaker or muted, but it is always available at the 600W output connector. This allows the PHA 520 to be run at high volume as part The AVRS The Australian Vintage Radio Society is a not-for-profit organisation dedicated to preserving our radio and related electronic history. Members come from all walks of life and enjoy the company of persons with similar interests. Meetings are held on the first Saturday afternoon of the month; visitors and prospective members are most welcome. Most meetings include a talk by a presenter with experience in radio restoration or history, plus a display of radios and related equipment of the era. Advantages of AVRS membership include: ● Access to the Valve and Component Bank, where members can obtain valves and hard-to-get parts at reasonable prices. ● Access to the Circuit Diagram Service to assist members with their electrical restorations. ● Technical assistance. ● Restoration workshops. ● A bi-monthly newsletter. We meet at St Faith’s Anglican Church Hall at 4-8 Charles St, Glen Iris 3146, Victoria (Glen Iris is near Burwood). 98 Silicon Chip of a receiving or communications system without the nuisance of adding to noise in busy workplaces. The set was designed for simplicity of operation, with only three frontpanel controls: volume, band switching and tuning. It’s switched on by simply opening the cover, which actuates the lid switch, SWB. The set’s condition The set arrived in working condition, with all the electrolytic capacitors replaced. It had also been cleaned, so I didn’t have to do much; I just set about testing it. Unlike two other examples I am aware of, this set had black pointer knobs on the band change and volume controls, with a white ‘television’ knurled knob for tuning. The other examples used the white knobs for all controls. How good is it? It’s as good as commercial communications receivers of the day, lacking only such refinements as a signal meter and the beat frequency oscillator needed for Morse and single-sideband (SSB) reception. Given its purpose – receiving shortwave radio broadcasts rather than being part of a communication network – it’s perfect for its intended use. Operators were expected to have little previous radio experience. The straight-line dial makes tuning easy, especially towards the top end of the tuning range. Table 1 lists sensitivity figures for 50mW output (S+N:N is the signalplus-noise to noise ratio). As the RF amplifier adds an extra tuned circuit at the signal frequency, image response is improved over a converter-only front end. This improvement declines at higher frequencies, as the antenna and RF tuned Australia's electronics magazine Special handling It’s a robust set, made to operate anywhere, any time, by anyone. Just remember that it needs an external antenna to work. Conclusion Thank you to Ray Gillett of the HRSA for lending me his example, to HRSA member Alby Thomas for his research into the Colombo Plan, and to Kevin Poulter for his recollections of Pye manufacturing. I’d also like to thank Warwick Woods of the Australian Vintage Radio Society (AVRS) for the circuit diagram, parts list, parts layout diagrams and other assistance. For more information on these societies, check out the websites for the HRSA (https://hrsa.org.au) and AVRS (www.avrs.org.au). Also see the panel SC on the latter. siliconchip.com.au PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) LOUDSPEAKER TESTING JIG BASIC RF SIGNAL GENERATOR (AD9834) ↳ FRONT PANEL V6295 VIBRATOR REPLACEMENT PCB SET DYNAMIC RFID / NFC TAG (SMALL, PURPLE) ↳ NFC TAG (LARGE, BLACK) RECIPROCAL FREQUENCY COUNTER MAIN PCB ↳ FRONT PANEL (BLACK) PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT ARDUINO ESR METER (STANDALONE VERSION) ↳ COMBINED VERSION WITH LC METER WATERING SYSTEM CONTROLLER CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER 2M VHF CW/FM TEST GENERATOR TQFP-32 PROGRAMMING ADAPTOR ↳ TQFP-44 ↳ TQFP-48 ↳ TQFP-64 K-TYPE THERMOMETER / THERMOSTAT (SET; RED) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION MULTI-CHANNEL VOLUME CONTROL: VOLUME PCB ↳ CONTROL PCB ↳ OLED PCB SECURE REMOTE SWITCH RECEIVER ↳ TRANSMITTER (MODULE VERSION) ↳ TRANSMITTER (DISCRETE VERSION COIN CELL EMULATOR (BLACK) IDEAL BRIDGE RECTIFIER, 28mm SQUARE SPADE ↳ 21mm SQUARE PIN ↳ 5mm PITCH SIL ↳ MINI SOT-23 ↳ STANDALONE D2PAK SMD ↳ STANDALONE TO-220 (70μm COPPER) RASPBERRY PI CLOCK RADIO MAIN PCB ↳ DISPLAY PCB KEYBOARD ADAPTOR (VGA PICOMITE) ↳ PS2X2PICO VERSION 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) ARDUINO FOR ARDUINIANS (PACK OF SIX PCBS) ↳ PROJECT 27 PCB WII NUNCHUK RGB LIGHT DRIVER (BLACK) SKILL TESTER 9000 DATE JAN23 JAN23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 JAN24 JAN24 JAN24 JAN24 FEB24 FEB24 FEB24 FEB24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 APR24 PCB CODE 08111221 08111222 SC6658 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 04106181 04106182 15110231 01108231 01108232 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 01110231 01110232 09101241 09101242 16102241 16102242 07112231 07112232 07112233 SC6903 SC6904 16103241 08101241 Price $12.50 $12.50 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 $12.50 $5.00 $5.00 $5.00 $1.50 $4.00 $5.00 $5.00 $5.00 $2.50 $2.50 $5.00 $7.50 $12.50 $2.50 $2.50 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $3.00 $5.00 $2.50 $2.50 $5.00 $2.00 $2.00 $2.00 $1.00 $3.00 $5.00 $12.50 $7.50 $2.50 $2.50 $7.50 $7.50 $5.00 $2.50 $5.00 $2.50 $5.00 $2.50 $2.50 $20.00 $7.50 $20.00 $15.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT PICO GAMER ESP32-CAM BACKPACK WIFI DDS FUNCTION GENERATOR 10MHz to 1MHz / 1Hz FREQUENCY DIVIDER (BLUE) FAN SPEED CONTROLLER MK2 ESR TEST TWEEZERS (SET OF FOUR, WHITE) DC SUPPLY PROTECTOR (ADJUSTABLE SMD) ↳ ADJUSTABLE THROUGH-HOLE ↳ FIXED THROUGH-HOLE USB-C SERIAL ADAPTOR (BLACK) AUTOMATIC LQ METER MAIN AUTOMATIC LQ METER FRONT PANEL (BLACK) 180-230V DC MOTOR SPEED CONTROLLER STYLOCLONE (CASE VERSION) ↳ STANDALONE VERSION DUAL MINI LED DICE (THROUGH-HOLE LEDs) ↳ SMD LEDs GUITAR PICKGUARD (FENDER JAZZ BASS) ↳ J&D T-STYLE BASS ↳ MUSIC MAN STINGRAY BASS ↳ FENDER TELECASTER COMPACT OLED CLOCK & TIMER USB MIXED-SIGNAL LOGIC ANALYSER (PicoMSA) DISCRETE IDEAL BRIDGE RECTIFIER (TH) ↳ SMD VERSION MICROMITE EXPLORE-40 (BLUE) PICO BACKPACK AUDIO BREAKOUT (with conns.) 8-CHANNEL LEARNING IR REMOTE (BLUE) 3D PRINTER FILAMENT DRYER DUAL-RAIL LOAD PROTECTOR VARIABLE SPEED DRIVE Mk2 (BLACK) FLEXIDICE (RED, PAIR OF PCBs) SURF SOUND SIMULATOR (BLUE) COMPACT HIFI HEADPHONE AMP (BLUE) CAPACITOR DISCHARGER PICO COMPUTER ↳ FRONT PANEL (BLACK) ↳ PWM AUDIO MODULE DIGITAL CAPACITANCE METER BATTERY MODEL RAILWAY TRANSMITTER ↳ THROUGH-HOLE (TH) RECEIVER ↳ SMD RECEIVER ↳ CHARGER 5MHZ 40A CURRENT PROBE (BLACK) USB PROGRAMMABLE FREQUENCY DIVIDER HIGH-BANDWIDTH DIFFERENTIAL PROBE NFC IR KEYFOB TRANSMITTER POWER LCR METER WAVEFORM GENERATOR PICO 2 AUDIO ANALYSER (BLACK) PICO/2/COMPUTER ↳ FRONT & REAR PANELS (BLACK) ROTATING LIGHT (BLACK) 433MHZ TRANSMITTER VERSATILE BATTERY CHECKER ↳ FRONT PANEL (BLACK, 0.8mm) TOOL SAFETY TIMER RGB LED ANALOG CLOCK (BLACK) USB POWER ADAPTOR (BLACK, 1mm) HWS SOLAR DIVERTER PCB & INSULATING PANELS SSB SHORTWAVE RECEIVER PCB SET ↳ FRONT PANEL (BLACK) 433MHz RECEIVER SMARTPROBE ↳ SWD PROGRAMMING ADAPTOR MIC THE MOUSE (PCB SET, WHITE) DATE APR24 APR24 MAY24 MAY24 MAY24 JUN24 JUN24 JUN24 JUN24 JUN24 JUL24 JUL24 JUL24 AUG24 AUG24 AUG24 AUG24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 SEP24 OCT24 OCT24 OCT24 OCT24 OCT24 NOV24 NOV24 NOV24 DEC24 DEC24 DEC24 DEC24 DEC24 JAN25 JAN25 JAN25 JAN25 JAN25 JAN25 FEB25 FEB25 FEB25 MAR25 MAR25 MAR25 APR25 APR25 APR25 APR25 MAY25 MAY25 MAY25 MAY25 MAY25 JUN25 JUN25 JUN25 JUN25 JUL25 JUL25 AUG25 PCB CODE Price 08104241 $10.00 07102241 $5.00 04104241 $10.00 04112231 $2.50 10104241 $5.00 SC6963 $10.00 08106241 $2.50 08106242 $2.50 08106243 $2.50 24106241 $2.50 CSE240203A $5.00 CSE240204A $5.00 11104241 $15.00 23106241 $10.00 23106242 $12.50 08103241 $2.50 08103242 $2.50 23109241 $10.00 23109242 $10.00 23109243 $10.00 23109244 $5.00 19101231 $5.00 04109241 $7.50 18108241 $5.00 18108242 $2.50 07106241 $2.50 07101222 $2.50 15108241 $7.50 28110241 $7.50 18109241 $5.00 11111241 $15.00 08107241/2 $5.00 01111241 $10.00 01103241 $7.50 9047-01 $5.00 07112234 $5.00 07112235 $2.50 07112238 $2.50 04111241 $5.00 09110241 $2.50 09110242 $2.50 09110243 $2.50 09110244 $2.50 9049-01 $5.00 04108241 $5.00 9015-D $5.00 15109231 $2.50 04103251 $10.00 04104251 $5.00 04107231 $5.00 07104251 $5.00 07104252/3 $10.00 09101251 $2.50 15103251 $2.50 11104251 $5.00 11104252 $7.50 10104251 $5.00 19101251 $15.00 18101251 $2.50 18110241 $20.00 CSE250202-3 $15.00 CSE250204 $7.50 15103252 $2.50 P9054-04 $5.00 P9045-A $2.50 SC7528 $7.50 DUCTED HEAT TRANSFER CONTROLLER ↳ TEMPERATURE SENSOR ADAPTOR ↳ CONTROL PANEL USB-C POWER MONITOR (PCB SET, INCLUDES FFC) HOME AUTOMATION SATELLITE PICKIT BASIC POWER BREAKOUT AUG25 AUG25 AUG25 AUG25 SEP25 SEP25 17101251 17101252 17101253 SC7527 15104251 18106251 NEW PCBs $10.00 $2.50 $2.50 $7.50 $3.50 $2.00 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 SMD resistor power ratings When ordering SMD resistors, is there a presumed wattage rating? Yageo offers as low as 1/8W, and some suppliers quote tolerance only, with no power rating. I’m ordering parts for the SSB Shortwave Receiver (June-July 2025; siliconchip.au/Article/18308); what rating should I be ordering? Is it worth stating this in the parts lists? (T. R., North Manly, NSW) ● Typical power ratings for SMD resistors are 1/16W for M1005/0402, 1/10W for M1608/0603, 1/8W for M2012/0805 and 1/4W for M3216/1206. Higher-rated resistors are available (eg, 1/2W, 2/3W for M3216/1206) but generally, we will explicitly provide a power rating for anything above the ‘standard’ baseline power rating for a given resistor size. So, if we have not specified a power rating, it is safe to use resistors with the power ratings given in the paragraph above, or higher. The SSB Shortwave Receiver uses M2012/0805 resistors; 1/8W or higher should be fine. If a supplier doesn’t state a power rating for such a resistor, it is pretty safe to assume they will be rated at 1/8W. NiMH cells can replace most NiCads I assume there are others with the same problem as me: NiCad batteries are becoming harder to get. This means that many devices that used these as power sources (early cordless drills, dust-busters, respirator motors etc) can no longer be repaired. I have all the above devices, but the one I would like to repair and, if possible, improve is a chemical respirator helmet that uses NiCad cells to power it when you cannot be tethered to a 12V power source, like a lighter socket or merit socket on a vehicle. The cost of replacement parts for the unit is beyond ridiculous; for example NZ$1280 for the blower unit. Within the blower unit sit eight NiCad sub-C cells, which I assume 100 Silicon Chip trickle charge while the blower is attached to the vehicle power socket. An easy solution for me is to remove the failed NiCad and permanently power the system via an external 12V battery worn on a belt. But having everything sit within the blower unit is convenient, neater and less likely to catch on something. I thought there could be a project in this, to enable an alternate battery type, like NiMH or Li-ion, to be substituted in place of NiCad, with a PCB to control charging and trick the existing NiCad charge controller into thinking that it is charging NiCad. (W. F., Atherton, Qld) ● In general, you can simply substitute NiMH cells for NiCad types. The charging (and other circuitry) can remain the same. Early NiMH cells couldn’t deliver as much current as NiCads, but modern NiMH cells are pretty good and so are usually an acceptable direct substitute. Using lithium-ion cells would require a different charger, and these cells may not be suitable as a replacement for NiMH or NiCad cells in equipment for various reasons. That includes their very different cell voltages, ~3.7V for Li-ion compared to ~1.2V for NiMH/NiCad. Li-ion cells are also a lot more sensitive to overcharging and over-discharging. 3D Printer Filament Dryer case query I have built the timber enclosure recommended for the 3D Printer Filament Dryer (October & November 2024; siliconchip.au/Series/428) as per the drilling and recommended dimensions documents, but I am not sure of the placement of the two ventilation covers. Are there recommended locations for their placement? Are the locations of these items important for the optimal operation of the dryer? (C. M., Hallidays Point, NSW) ● Phil Prosser responds: I decided to put these low down at either end of the enclosure I built. My thinking process was to position the inlet and Australia's electronics magazine outlet at opposite ends of the enclosure, both low, ensuring that neither would interfere with anything like the heating plate. I am not claiming these are objectively the ideal spots, but it seemed to work well enough. I run the dryer fairly continuously while there is filament in it, resetting it as needed. With a good foam seal on the lid, I feel it does a good job. Help designing a DDS sweep generator I am trying to design a function generator with a Raspberry Pi Pico 2W & PCM5102A DAC, programmed in MicroPython. I want to generate a sinewave on channel 1 with a phaseshifted version on channel 2. The target frequency is about 15kHz; a 10kHz to 20kHz sweep would be desirable. Generating lookup tables using MicroPython is easy. I am thinking of using two phase-shifted tables, one for each channel. I am struggling with the code, particularly writing from two tables to the DAC. Silicon Chip had a project by Richard Palmer called the WiFi DDS Function Generator (May & June 2024; siliconchip.au/Series/416). That does everything I would need plus more. I was wondering whether Mr Palmer might have a simplified design that I could use. (M. L., Glenroy, Vic) ● Richard Palmer responds: Lookup tables writing directly to the DAC may not be the best way to go, particularly if a sweep is required. The usual way of generating different frequencies is to use the DDS method, which uses a relatively short lookup table and interpolates (usually linearly) between entries for the exact value required. The key synthesis code for the WiFi DDS Function Generator is in the file DDS.h. CPU1 is just calculating and adding the next sample to the I2S buffer whenever space is available (line 303). Calculating a signal with a different phase merely requires adding a fixed value to the phase accumulator for each sample calculated. siliconchip.com.au There is a discussion of how this works in the project article. There are also very good explanations on the web, such as siliconchip.au/link/ac7t Unfortunately, I don’t have a simplified design; however, the C++ source code for the project is available for download from https://github.com/ palmerr23/DDS_Function_Gen Editor’s note: there’s no need for two separate tables just for a phase shift – you just need two indices into one table that change at the same rate but start at different locations. Also, linear interpolation is easy and quick to handle in software (requiring just one multiplication operation, one subtraction and a bit shift per sample). Using linear interpolation means you can also vary the frequency smoothly with a single, reasonably sized table. Capacitor substitution for Electronic Load I am trying to gather the parts for the WiFi Programmable DC Load (September & October 2022; siliconchip.au/ Series/388) but am stuck on the 1μF 200V polyester capacitor. Can I use an X2 polypropylene capacitor, such as Altronics’ R3137A? (B. L., Maidstone, Vic) ● An X2 capacitor (whether polyester or polypropylene) would work fine in that role, but would probably be too large to fit the board. The Altronics website says the lead pitch of that part is 27.5mm, while the PCB is designed for about half that. We suggest you use Altronics R3037B or Jaycar RM7170 (1μF 100V MKT) if you don’t plan to exceed 100V, or Altronics R2748B (1μF 250V greencap) if you do. All of these have a polyester dielectric. You may have to splay the leads of the smaller parts out to fit the pads. Bench Supply outputs normally float I built the first version of the 30V/2A Bench Supply (October & November 2022; siliconchip.au/Series/389). It seems to work well, other than I have a voltage between the negative output and Earth. It is similar to the voltage between the positive and negative posts. It is also present when the load switch is off. Should the negative and Earth be bonded? siliconchip.com.au Question on Triac variants I’m gathering parts to put the Hot Water System Solar Diverter (June & July 2025; siliconchip. au/Series/440) together, but I have been having trouble obtaining the specified BTA41800BQ Triac. DigiKey showed several hundred in stock, but when I tried to check out, it was shown as on back order until September. I had to ask that my entire order be delayed or pay something like $57 postage for that one part! They sent the order promptly anyway, without the Triac, so I thought I’d see if I could find it elsewhere. RS Components has the BTA41-800B, made by STMicroelectronics. Is the missing Q of any significance? I went back to DigiKey and followed the datasheet link for the BTA41-800BQ to the WeEn Semiconductor site. I did not get any hits when I searched for the BTA41-800BQ, only for the BTA41-800B. However, WeEn’s BTA41-800B datasheet specifies the Orderable Part Number as BTA41-800BQ. RS Components also has the BTA41-800BRG, which is just a variation of the delivery packaging (they come in a tube, rather than bulk). The STM datasheet says that BTA means isolated tab, whereas BTB is a nonisolated tab version, and the B in 800B specifies the sensitivity as 50mA. So I think it is safe to order the BTA41-800B. (A. P., Norwood, Tas) ● The BTA41-800B is suitable; the Q suffix is not important in this application. It appears to only be used by one manufacturer (WeEn, originally a joint venture between NXP and JAC Capital) and indicates that the Triac can be triggered in any of the four quadrants (4Q). The accompanying plot shows the trigger gate current normalised to 25°C for the four quadrants, one through four. Triacs can be triggered in all four quadrants, although quadrants two and four may require a larger gate current to trigger, depending on the Triac. For the BTA41 Triac, the gate current required to trigger it in each quadrant is similar over the 0-75°C range. It’s a DC voltage that varies with the voltage adjustment pot. When the leads on my multimeter are negative on the negative post and positive on the Earth post, I have a positive reading on the meter. (J. S., Lidster, NSW) ● Bench supply outputs are normally floating with respect to Earth to give you maximum flexibility. That means that if you measure the voltage between the negative terminal and Earth, it could be just about any reading within a couple of hundred volts of Earth, although it will tend to be a lot lower than that. This means that you can do things like connect two bench supplies in series to get a split supply, with the junction of them connected to Earth. One supply has its positive terminal Earthed and the other its negative terminal. You couldn’t do that if the negative terminals were permanently Earthed; you would be shorting out the Australia's electronics magazine outputs of one of the supplies. Also, sometimes you are using the bench supply to power a device that is separately Earthed, and it may not be via the negative terminal, or if it is, having the supply also Earthed could generate an Earth loop that would induce a low (but possibly problematic) AC voltage into the equipment’s negative supply. Even a relatively high resistance between the negative terminal and the Earth terminal will normally bring both outputs down close to the Earth voltage. You could test this using a 1kW resistor from the negative terminal to Earth. If the device you’re powering is definitely not Earthed, you certainly can connect a wire between the negative output and the Earth terminal provided on the front panel of the supply to ensure that the device’s 0V rail is close to Earth potential. September 2025  101 How to identify SMD component labels? It has been a great day today as I received my copy of Silicon Chip and also two kits I ordered late last week. Great work by Australia Post. One kit I ordered is the Rotating Light for Models, where I have a slight problem positively identifying the voltage regulator and the schottky diode from the markings on the tiny SOT-23 packages. Although the diode is a two-terminal device, it is in the same type of three-pin package as the regulator. A web search for the JLD7 code printed on the package of what I assume is the regulator didn’t give me any useful results. The other part appears to be labelled 12D. As I can not reliably identify the parts with multimeter measurements, it would help to know which codes to expect. (S. S., Gloucester, NSW) ● The best place to find the component labelling is in the data sheets. It can be a bit confusing since some parts have multiple revisions; for example, in this case, you need to look at the MCP1703A data sheet, not MCP1703, as the markings are different even though they are compatible devices (with the A suffix indicating a newer version of essentially the same part). The MCP1703A datasheet confirms that the 5V output version in the SOT23 package should start with JL. So JLD7 is definitely the regulator (D7 is a date or production code). We wonder if you are reading the diode upsidedown since its marking should be D2E and, by a process of elimination, that must be it. It is unfortunately difficult for us to publish the expected device codes because they are not standard and can vary over time. For example, different manufacturers will put different codes on the same device, like a BC847. The codes can also vary depending on whether it’s a BC847A, BC847B or BC847C, which may not matter for a particular circuit. So there might be half a dozen or more valid codes for a given part, and that’s before you even get to the sections of the code that vary between batches. Unfortunately, it is also possible to come across two different parts that use the same code, as they are usually limited by space to just three or so letters or digits. Thankfully, the chance of 102 Silicon Chip parts with identical codes being used in the same circuit is low. Help with the Ultrasonic Cleaner Thanks for all the great projects you have published over the years. I have built the High Power Ultrasonic Cleaner (September & October 2020; siliconchip.au/Series/350) and am now testing it, but I would like some assistance troubleshooting it. I built the PCBs in a diecast box together with a 10A DC rated switchmode supply. The transducer is glued to the side of a four litre metal bath from Nisbets using JB Weld epoxy, as recommended. The whole system appears to work, but the frequency is four times what it should be! I measured 167.6kHz at TP2. At first, I thought it was just a trigger problem at the counter, but then I confirmed the same frequency at the transducer using a high-voltage probe and oscilloscope. I suspected some ripple on the power supply could have caused IC1 clock to run fast, but testing using a 10Ah 12V battery gave identical results. I also measured the ripple, but there’s about 10mV AC (maximum) and 5V DC at IC1’s pin 1. I changed the 4700μF 16V capacitor in case it was not low enough in ESR, but that didn’t help. While changing the capacitor, I double-checked the soldering etc; all seemed OK. What sets the internal frequency in IC1? Could it be running too fast somehow? The software in IC1 seems to function OK; I can see the small frequency changes approximately every 10 seconds that you mention in the article. I can also ramp up the power as normal. But then it drops back to minimum (not surprising if it is trying to drive the transducer at such a high frequency). The voltage at TP1 seems to respond as normal. The unit will not stay at the highest power setting, so I cannot measure at that current, but with the second LED on, the voltage is 1.39V, and with the middle LED on, it is 2.85V. I have tried to recalibrate and also tried various fluid levels, all with no change. Thanks in advance. (G. J., Panania, NSW) ● It seems the transducer resonance is not found correctly; the software automatically tends to try higher frequencies. Here are some things to try. Australia's electronics magazine Initiate diagnostics by switching the power off, waiting 10 seconds, then pressing and holding the Start and Stop switches together while switching on the power. Diagnostics mode is indicated by all five level LEDs lighting up. In this mode, the frequency to the ultrasonic transducer can be manually adjusted using the timer potentiometer (VR1). The frequency is 40kHz when the timer pot is set midway, and it can be varied from 37.6kHz to 42.4kHz by rotating VR1. Further frequency changes can be made by setting the pot either fully anti-clockwise or fully clockwise and pressing the Start switch. When holding the pot fully anti-clockwise and pressing the Start switch, the frequency will drop by about 540Hz, so the overall adjustment range is 540Hz lower, ie, 37.06-41.86kHz rather than 37.6-42.4kHz. You can reduce this further in 540Hz steps to a minimum of 34.88kHz with the pot fully anti-clockwise, by pressing the Start switch repeatedly with VR1 at its fully anti-clockwise position. Similarly, the frequency range can be increased in 540Hz steps by holding the pot fully clockwise and pressing the Start switch. The maximum frequency can be increased up to 45.45kHz. You can monitor the drive frequency by connecting a frequency counter or meter at TP2 and the current draw with a voltmeter at TP1. You don’t strictly need to know the frequency; the most critical measurement is the current readings at TP1. Adjust VR1 to find the resonance point, where the current is at a maximum. For the transducer to be able to deliver full power, the measurement at TP1 needs to be 4.2V just below or above resonance. 4.2V equates to 300mV across the 0.1W resistor, so 3A. With a 12V supply, this represents a 36W power delivery. If there is a current overload and the voltage at TP1 goes above 4.8V, the transducer drive will be cut off. This is to limit the power applied to the transducer to a safe level. An overload is indicated by the outside and centre LEDs on the level display lighting. The drive is restored momentarily every two seconds to check the current. Adjust the potentiometer to restore continuous drive. continued on page 104 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 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. Lazer.Security PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au WE HAVE QUALITY LEDs on sale, Driver sub-assemblies, new kits and all sorts of electronic components, both through hole and SMD at very competitive prices. check out the latest deals at www.lazer.com.au Dual Mini LED Dice August 2024 SMD LED Complete Kit SC6961: $17.50 TH LED Complete Kit SC6849: $17.50 siliconchip.au/Article/16418 Includes either 3mm through-hole or 1206sized SMD LEDs. Choice of either white or black PCB. CR2032 coin cell not included. FOR FREE: To give away, one decommissioned and partly disassembled YUKI KP-480 pick and place machine. Contact: Graham – 0458 071 074 Location: Hobart, Tasmania ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone (02) 9939 3295. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia's electronics magazine September 2025  103 If at resonance there is an insufficient voltage at TP1, you will need more secondary turns on the transformer (or take water out of the bath). The correct number of turns or amount of water is when the voltage at TP1 is close to 4.5V at resonance. This allows some leeway in frequency control to achieve 4.2V at TP1, for 36W into the transducer when slightly off-­ resonance. If the TP1 voltage when approaching resonance is too high (above 4.5V), Advertising Index Altronics....................... 7, 29-32, 41 Dave Thompson........................ 103 Emona Instruments.................. IBC Hare & Forbes............................... 9 Jaycar............................. IFC, 11-14 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology.............OBC Mouser Electronics....................... 3 OurPCB Australia.......................... 6 PCBWay......................................... 5 PMD Way................................... 103 SC Dual Mini LED Dice.............. 103 SC Versatile Battery Checker..... 67 Silicon Chip PDFs on USB......... 47 Silicon Chip Shop.......... 61, 85, 99 Silicon Chip Subscriptions........ 15 The Loudspeaker Kit.com.......... 60 Wagner Electronics..................... 91 Errata and on-sale date Boeing 737 MAX & MCAS, August 2025: the MCAS system controlled the motors driving the trim tabs on the elevators, not the ailerons. Thin-Film Pressure Sensor, August 2025: in Fig.3 on p35, the S pin should go to A0 and the + pin to 5V. Next Issue: the October 2025 issue is due on sale in newsagents by Monday, September 29th. Expect postal delivery of subscription copies in Australia between September 26th and October 15th. 104 Silicon Chip reduce the number of secondary turns or use more water in the bath. When you find the frequency range in diagnostic mode and get the maximum peak at 4.6V, try to set it to the next lower frequency and perform the calibration. If that is not effective, try again with the next higher frequency from the peak value. If that’s unsuccessful, you will probably need to change the number of turns on the transformer secondary as described above. Once you get a reading of 4.5-4.7V with TP1 at resonance, the Cleaner should run correctly. Low-noise motor speed control wanted I am trying to find a project or kit for making a dual-thyristor speed controller that has very low noise and EMI, rather than a basic, noisy Triac-based speed controller. (P. F., New Zealand) ● We published a full-wave mains motor speed controller in the February & March 2014 issues (siliconchip. au/Series/195) that utilised a Mosfet instead of a Triac. Speed control is via pulse-width adjustment rather than phase control. The circuit essentially controls the motor with pulse-width modulated (PWM) DC that follows the envelope of a full-wave rectified mains voltage. In the past, for Triac-based dimmers controllers, we used a 100μH choke (in series with output) and a 10nF capacitor (from output to neutral) as an EMI filter. For controlling brush motors, any filtering of the Triac switching is totally masked by the EMI from the motor, so we don’t tend to use a filter in motor controllers. Connecting Frequency Relay to a fuel injector I have a Jaycar AA0377 Frequency Relay Module for Cars that I connected to my car’s injector signal wire and it worked perfectly. I then tried it on a Ford Falcon inline-six Barra engine’s injector signal wire, and that injector failed to work, resulting in the car misfiring while running. Removing the signal wire from the injector returned the engine running to normal. After some research, I found that the Falcon injectors are of the high-­ impedance type. I suspect that the loading of the Frequency Relay input circuit is stopping the ECU’s injector Australia's electronics magazine signal from getting to the injector or loading it down. Do you agree? If so, is there a way to match or reduce the Frequency Relay signal loading on the car’s injector circuit? I cannot use the ignition coil signal on this engine, as it produces three coil ignition pulses at idle. There is a tachometer signal, but it is a CAN bus signal that is not compatible with the Frequency Relay. Can you suggest a solution? I am trying to switch on a water pump above 4000 RPM. (M. S., Keilor Downs, Vic) ● Yes, the Frequency Relay input would be loading the injector signal. You could include an NPN transistor buffer, where the base of the transistor connects to the injector signal via a 10kW resistor. Another resistor (4.7kW) connects from the collector to the 0V supply. Then the emitter connects to ground (0V) and the collector connects to 12V via a 1kW resistor. The collector signal can then go to the Frequency Relay signal input. A BC337 would be suitable. EA Induction Loop projects are obsolete My question is regarding the Induction Loop TV Headphones published in Electronics Australia, October 1995, starting on page 68. I am looking for something cheap to build or purchase that will allow me to quickly check the status of a loop. Is this project for picking up sound from hearing aid loops, more commonly known as T-Loops? The circuit diagram shows inductor L1 is 800 turns on a 9 × 70mm ferrite rod. Where can I get this, or find a substitute for it? (B. A., Dee Why, NSW) ● The EA Induction Loop TV Headphones wasn’t designed to the standards of a T-coil hearing aid loop. Its output will be a low level if used with a hearing aid loop. It was meant for use with a small loop from a TV set’s audio signal, and is also very directional due to the long ferrite rod. The Jaycar LF1010 is a suitable replacement, and can be cut down to size if necessary. We published several projects that are compatible with T-Loops, including a Hearing Loop Receiver (September 2010; siliconchip.au/Series/11) and a Hearing Loop Level Meter (November & December 2010 issues; siliconchip.au/Series/15). You would be far better off building one of those to pick up signals from a T-Loop. 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