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APRIL 2024 ISSN 1030-2662 04 The VERY BEST DIY Projects! 9 771030 266001 $ 50* NZ $1390 12 INC GST INC GST Pico Gamer A RETRO GAME CONSOLE WITH NINE GAMES INCLUDED Amateur Radio and becoming a “ham” ROCK Model 4C+ SBC Review; Page 58 Skill Tester 9000 Project; Page 62 Free entry to the Altium Roadshow 2024 Thursday April 4th, 12:00 – 5:00PM AEDT Pullman Sydney Olympic Park, NSW 2127 <at> NEXUS ROOM see page 7 ESP32-CAM LCD BackPack Project; Page 72 Reference MEMS Mics Project; Page 79 S SP ILI EC CO IA N L CH O FF IP ER Make amazing projects with our ROCK 4 C Plus Single Board Computer Higher processing power compared to competitor SBC makes it perfect for demanding IoT, automation, and multimedia applications. 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Savings on Original RRP (ORRP). Contents Vol.37, No.04 April 2024 22 Becoming a Radio Amateur Being an amateur radio operator (also known as a “ham”) can be a rewarding hobby, and is perfect for those who are already interested in electronics. I recently earned my licence; here’s what you need to know. By Dr David Maddison, VK3DSM Amateur radio Becoming an Amateur Radio Operator 58 ROCK Model 4C+ SBC review The Radxa ROCK Model 4C+ is compatible with much of the Raspberry Pi ecosystem and is in the same form factor as the Raspberry Pi Model 4B, but it has some unique features that differentiate it from the Pi. By Tim Blythman Single board computer review 90 Fender Bassman Guitar Amp The Fender “Tweed” Bassman is one of the most famous guitar amplifiers. We take a look at the model 5F6-A from 1958, which is notable for the same circuit being used in the later Marshall JTM45. By Brandon Speedie Vintage electronics 36 Pico Gamer Page 22 Pico Gamer Page 36 Page 72 The Pico Gamer is a PicoMite-powered retro game console that includes nine games, with three of them inspired by Pac-Man, Space Invaders and Tetris (with more that can be added). It uses a rechargeable battery with a runtime of approximately eight hours and sports a 3.2in colour LCD screen. By Geoff Graham Video game console project ESP32-CAM LCD BackPack 49 Pico Digital Video Terminal, Pt2 This project adds the ability to communicate with and control a Micromite, PicoMite, WebMite or similar using a USB keyboard and HDMI display. See this article for how to build it and get it running. By Tim Blythman Computer interface project 62 Skill Tester 9000, Pt1 The Skill Tester 9000 is a reimagination of an old dexterity tester game, with added lights, timers, countdowns, sounds and competition! Construction is made easy as the PCB can be built in stages. By Phil Prosser Game project 72 ESP32-CAM LCD BackPack The ESP32-CAM is a WiFi camera module we previously reviewed and have now incorporated into a BackPack design. It includes a powerful processor, so you can use it as the basis for a remote monitoring project or similar. By Tim Blythman Microcontroller project 79 Reference MEMS Microphones Rather than electret microphones, here is how you can use microelectromechanical system (MEMS) microphones as a calibrated measurement mic with a good frequency response. By Phil Prosser Audio project 2 Editorial Viewpoint 5 Mailbag 16 Circuit Notebook 78 Product Showcase 82 Serviceman’s Log 96 Online Shop 98 Subscriptions 99 Ask Silicon Chip 103 Market Centre 104 Advertising Index 104 Notes & Errata 1. Humidicrib temperature controller 2. LoRa mesh networking SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Jim Rowe – B.A., B.Sc. Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $70 12 issues (1 year): $127.50 24 issues (2 years): $240 Online subscription (Worldwide) 6 issues (6 months): $52.50 12 issues (1 year): $100 24 issues (2 years): $190 For overseas rates, see our website or email silicon<at>siliconchip.com.au * recommended & maximum price only Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: Editorial Viewpoint Asking questions We get quite a few questions from readers and do our best to provide helpful responses. However, some questions are difficult to answer due to the way they are formed. There are ways to ask questions that are more likely to get you the answer you need, so here is some advice on how to do so effectively. • Keep in mind that these are just guidelines designed to make it more likely that you get the right answer to your question the first time. We’ll still try to answer enquiries regardless, but if you can help us by keeping these in mind, please do! • If asking a question about a specific project or article, quote the year and month of publication. It’s common that we have published several articles or projects on the same topic and with similar names. Specifying the year, month, and article name is the best way to identify a particular article unambiguously. • If you are having a problem, explain what the problem is. For example, if you say, “I built your widget in the January 2020 issue, but it doesn’t work”, that doesn’t leave us much to go on. Does it power up? Are any lights on? Is it doing anything at all? What is it doing, and how does that differ from your expectations? Have you tried any testing or troubleshooting steps in the article? • Try to keep questions short and to the point. We don’t need a lot of background information. Condensing the question into its essentials makes it easy for us to focus on what we need to answer. • If possible, send questions by email. Primarily, that’s because we can easily forward the email to the person who can best answer the question. That is not so easily done with phone calls (not everybody works in the same office) or letters. We may need to do some research, making it hard to give an immediate answer in the case of a phone call. • Try to avoid asking too many questions in one go. When we get several questions at once, different people may need to answer the various questions, complicating the process. It’s also easy to miss some questions (or their significance) when there are several. Ideally, ask the most important question(s) first, then follow up with more when you get a response to the first one. • Remember that you may not get an answer straight away, but you probably will get one within a few days. Sometimes, that’s because we need to do some research or have discussions before we can provide a definitive answer. In other cases, it’s because we’re busy (eg, trying to finalise a magazine). If we can answer your question quickly, generally, we will. Otherwise, we appreciate your patience. • If your question is about a project, have you checked if there are any notes or errata for it? You can download yearly PDFs of all our published notes and errata from our website at siliconchip.au/Articles/Errata (they’re arranged by the original article’s publication date, not the notes/errata). I hope this advice proves useful to our readers. Renesas acquiring Altium Japan’s Renesas Electronics Corporation, makers of many electronic products, including microcontrollers, announced the purchase of Altium this February for around $9 billion. Part of the rationale for the purchase was that they wanted to integrate ECAD software more tightly with their existing product portfolio, which makes a certain amount of sense. It is unclear how this will impact existing Altium users (if at all). Perhaps this will become evident following their Sydney ‘roadshow’ event at Olympic Park on April 4th (see the announcement in their ad on page 7). by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia's electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. Vintage style Pong machine is finished Thanks for publishing my letter and the photo of my daughter soldering chips into the Mini Arcade Pong board in the September 2023 issue (Mailbag, page 5). My daughter and I just finished building the cabinet and wanted to share some pictures (see the photo at lower right). It took quite a while for me to have the panels made due to needing some help from a friend. My daughter and her younger siblings have been having a blast playing, and it gets pretty competitive! Thanks again for everything; we’re super pleased; my daughter has gained quite a bit of knowledge and experience along the way. I can’t wait for her to take on another project. James VanDever, Hawthorne, California, USA. Improvements in Australian broadcast TV Sony released their first MPEG-4 capable TV to the Australian market in 2010, but it wasn’t until 2015 that Australian Standard AS 4933 was upgraded to include MPEG-4 compression. It enables the transmission of sharper high-definition pictures with better sound. Viewer Accessed Satellite Television (VAST) has been MPEG-4 capable from the start. Unfortunately, telecasters were not game to put their primary HD programs on their original blurry standard definition logical channel numbers of 2, 3, 5, 6, 7, 8 & 9. Instead, they added them using a pair of digits such as 20, 30, etc. In October 2023, Tasmania moved its HD main programs to channels 2, 3, 5, 6 & 8, retaining the blurry versions on double-digit channel numbers. All other programs moved from the old MPEG-2 to the new MPEG-4 compression, enabling more HD programs to be transmitted on their existing channels. This trial has been successful, and the upgrade is spreading through regional and remote Australia. Simulcasting of the old MPEG-2 programs will cease. I have yet to find out when this upgrade will occur in other cities; however, Network 10 has put their HD TEN program on channel 1. Streaming services have Ultra High Definition (UHD) programs available, which can be viewed on all new Smart TVs. They use High-Efficiency Video Coding (HEVC), which supersedes MPEG-4 and is efficient enough to fit a UHD program in place of two HD MPEG-4 programs. The streamed sound on Netflix and some others is the latest, most efficient sound compression algorithm, xHE-AAC. Current DVB-T modulated programs have 23Mbit/s of program data. DVB-T2 modulation increases this to siliconchip.com.au 36Mbit/s. The BBC commenced transmitting HD using DVB-T2 in 2010. They also started transmitting progressively scanned images, reducing the jagged edges in moving detail, such as in sports events. This will enable broadcasters to keep up with streamers by broadcasting UHD and HD programs. The price difference is insignificant since receivers with DVB-T2 tuners have been marketed for 14 years. It does however require an upgrade to DVB-T2 for every transmitter in Australia. VAST uses the latest DVB-S2 modulation for satellites in all receivers; it can carry five HD MPEG-4 programs per broadcaster, which can be enjoyed by 300,000 subscribers for free. Receivers will need to be upgraded to decode HEVC signals and xHE-AAC/MPEG 3D H sound. Our current HD TV has Dolby AC3 digital surround sound, which was released in 1991. To reduce the bit rate, xHE-AAC (released in 2016) can be combined with MPEG H 3D sound (2015), as used in all the newest digital TV system specifications, such as UHD. Australia's electronics magazine April 2024  5 The conversion of all of our TVs to MPEG-4 compression is occurring nine years after the Australian standard required it. We need to specify DVB-T2 modulation, HEVC video compression and xHE-AAC/MPEG H sound compression now so that in nine years (or hopefully fewer), we can switch to DVB-T2 from DVB-T as well as using HEVC for all programs. This changeover will be like the change from analog to digital TV, but with a switchover on a specified day in each licence area. Mandating the receivers ahead of time minimises receiver costs because of the economies of scale, and because we are using standardised technologies. By comparison, New Zealand has used DVB-T and MPEG-4 since their analog switchover was completed in 2013. Freeview Satellite uses DVB-S and standard definition MPEG-2 compression. Sky TV sends UHD in HEVC to customers using fibre optics or DVB-S2 satellite signals. There is also a terrestrial Sky Open channel that uses DVB-T2. Alan Hughes, Hamersley, WA. Fake ultrasonic pest repellers from eBay For years, I have very successfully used ultrasonic pest repellers to repel mice, ants, cockroaches, and spiders, with some limitations. I live in a remote bush home initially constructed over 100 years ago from bush timber and enlarged when I was a youngster over 60 years ago, again using much bush timber, with plenty of gaps and holes. With the mouse plague last year, these little fellows invaded our home, including my bed, where they happily made a nest. Until this period, I had a single ultrasonic repeller in the main living room, repelling mice from the open fire area where food was dropped etc. At this stage, I bought a few more repellers. They weren’t cheap at around $43 each. I converted them to run from 12V DC, as I live over 50km from the nearest grid supply. I also bought several plug-in mains units that were much cheaper. After determining what voltage the circuit ran from, I cut the plugs off and installed 780x voltage regulators so they ran on 12V. If mice were hungry and already feeding on things like spilled chook food in a shed, a small number would still come in after the repellers were installed. These mice appeared to be tracking behind barriers that protected them from the direct ultrasonic sound. Once these mice were eliminated with traps or bait, it was rare for new mice to emerge; the 6 Silicon Chip sound stopped them from exploring the area. Spilled wheat in one shed has now been untouched for over six months. There were a handful of exceptions, and when caught in traps, they did not appear to be young mice. I suspect they were old mice possibly going deaf. None of these repellers worked on rats, which are larger and appear to communicate on a lower frequency. As I no longer have ants, cockroaches, or spiders in the areas with repellers, I decided to get some more for areas not covered where I was forever ploughing through cobwebs. Since COVID, I have bought most of my supplies from eBay and have found most sellers to be reputable and reliable. Many different sellers stocked one particular plug-in repeller; I bought eight for only $18 delivered. They duly arrived, so I pulled one apart to make the changes to run from 12V. What a surprise I got! There was only a circuit board with three capacitors, eight resistors, one diode and one LED. There was no microchip or speaker to transmit at ultrasonic frequencies. Other components had been stencilled on the circuit but not attached. The LED is the only thing that works; it is connected to the mains supply through a diode and resistor. These units are fakes that are designed to look genuine from the outside. As the frequencies involved with repellers are above the human hearing range, most people would not be aware that this product is a fake. I have sent messages over the eBay network to many sellers and received replies like “Dear customer, We have sold a lot of this product on eBay and Amazon and haven’t had a problem yet.” I do not believe eBay or most sellers are to blame for some of this; the manufacturers should be held accountable. Please give this some coverage, as there are very good, honest ultrasonic repellers that really do work. L. Ralph Barraclough, Licola, Vic. Using solar power for hot water In the January 2024 issue, Brian Day commented about the change in pricing on the controlled load hot water charges. Some related discussion followed in the February and March issue Mailbag columns. My hot water storage is also connected as a controlled load, but my system is actually a solar-electric boost system. The cost to change to an ordinary system is too high to justify, and it would likely discharge my battery storage or reduce/stop its charging. An integrated managed system is needed to make the two storage systems work seamlessly together. Note that the controlled load switching times are not changed for daylight saving time and thus will incur peak charges if the element is still on in the overlap time in the morning when EDST is active. I think that has been solved by having peak only from 15:00 to 21:00 for domestic customers. In Victoria, the only thing that has happened to me to date is the loss of my energy concession for the controlled load. That is not a big deal as the water heater only uses mains power infrequently and in winter. I had the 3.6kW element replaced by a 2.4kW element at installation so I could use the same cabling of the old system, which was rated at 2.4kW with 2.5mm2 copper. I currently have a 3kW solar panel system with a Tesla Australia's electronics magazine siliconchip.com.au ALTIUM DESIGNER 24 The New Standard in Electronics Design PCB CoDesign Dramatically compress design cycles and accelerate the overall design process, which is required to help meet scheduling milestones, significantly reduce layout time, and achieve faster time to market. Real-time notifications and comparison tools ensure quick conflict resolution. Ansys CoDesign Streamline design changes between layout and simulation with the ability to seamlessly exchange data with Ansys, communicate and implement design changes based on simulation results, and access simulation reports without having to leave Altium Designer. New Constraint Manager Ensure adherence to design rules and constraints, reducing the chances of costly errors and revisions. The Constraint Manager optimises workflows, minimises risks, and lowers production costs in the fast-paced electronic design landscape. 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To register, visit: https://go.altium.com/04-04-roadshow-sydney.html Thursday, April 4th | Pullman Sydney Olympic Park, Nexus Room | 12:00PM – 5:00PM AEDT We are Australia’s only power semiconductor manufacturer based in Queensland. We offer ASIC designs for OEMs as well as off-theshelf devices for distributors. Here’s a small slice of the technologies that we offer at Quest Semiconductors: ● SiC High Voltage Wafers ● SiC Mosfets & Membranes ● SiC Homogeneous SBDs (Schottky barrier diode) ● Solar diodes ● Australian SiC Diode Fabrication and Technology ● IGBTs & TCIGBTs (trench clustered insulated gate bipolar transistor) ● Power Modules ● Sensors and JFETs ● ASICs PowerWall 2 battery, intending to increase the number of solar panels by 6 or 7 units with micro inverters. I have now disconnected gas, saving more than $30 per month. The gas stove has been replaced temporarily with a Westinghouse two-position induction portable cooktop. It only uses 2.4kW, so it plugs into a standard 10A power point. This unit will be replaced with a standard induction cooker, which can be power-limited to match the currently available circuit power, avoiding an upgrade to the meter box (in the short term, at least). Wolf-Dieter Kuenne, Bayswater, Vic. More on photovoltaic solar water heating Further to John Chappell’s letter regarding solar energy and hot water services in the February 2024 issue (Mailbag, page 6), I had a look at my own switchboard wiring. I found an incoming single-phase mains supply feeding a smart meter. This meter contains two individual meters, the first for the house, with the second ‘off-peak’ meter feeding only the hot water service, in our case, an electric heat pump controlled by its own thermostat. The solar inverter is connected via a circuit breaker directly to the house busbar, which feeds light, GPOs, aircon etc. Consider this: the solar energy generated flows to the household loads, and any excess is returned to the grid via the main meter, rebated at 13¢/kWh. For the solar energy to reach the hot water system (HWS), it now has to pass back through the off-peak meter, billed by the energy supplier at 20¢/kWh. So we pay 7¢/kWh for the privilege of using our own solar energy to run the HWS! The fix is to relocate the HWS feed from the off-peak supply to the main house busbar. Then, as Mr Chappell wrote, you need to add a time clock so that the HWS can only run when there is likely to be sun available, say 8am to 5pm. These digital time clocks are readily available with a 30A rating, DIN rail mount and battery backup for under $30. Even if there is no sun, your HWS will have daytime power during the timer hours, so you will never run out. To confirm that this modification will work for you, switch off the HWS in the afternoon and check that you can still have a hot shower in the morning. Naturally, the work needs to be done by a licensed electrician; my job was done in less than an hour. Since then, I have received two quarterly bills, each $100 less than before making the changes. Bruce Boardman, Highfields, Qld. Using Christmas ornaments as LED brooches Quest Semiconductors Pty Ltd Unit 1, 2-8 Focal Avenue, Coolum Beach, QLD 4573 email: sales<at>questsemi.com Tel: +61 (07) 3132 8687 8 Silicon Chip I built several of your Tiny Christmas Ornament designs (November 2020; siliconchip.au/Series/392) as brooches for Melinda. Mel is a hospital ward clerk, and for some time, I contemplated building a wearable LED-based arrangement with which she could spread Christmas cheer among her fellow hospital staff and the patients on her ward. When I spotted the Tiny LED Christmas Ornaments article, I immediately recognised a simple solution – just rig them as brooches. They sure have proved to be a hit in this guise. I built four brooches with the supplied programming. The candy cane, the stocking and the bauble are more popular than the tree. Some folk find the tree’s flash pattern a Australia's electronics magazine siliconchip.com.au siliconchip.com.au Australia's electronics magazine April 2024  9 Soldering Irons We stock a WIDE RANGE of gas and electric soldering irons at GREAT VALUE to suit your needs and budget. 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Jaycar reserves the right to change prices if and when required. little confusing because of the contrast between the dark green PCB and the bright LEDs and the close proximity of the LEDs. This surprised me because I had expected the tree to be the most popular. The solution may be in a tree change, such as a different flash sequence or a lighter-coloured PCB, but that will have to wait till next Christmas. Maybe I’ll try airbrushing some snow onto it. The method for converting them to brooch mode is shown in the accompanying photo. I’ve done little more than add a loop to pass a safety pin through. The loop is formed from a single copper strand cannibalised from a house wiring off-cut. The loop ends have been overlapped and soldered to prevent it from accidentally opening. If you study the photo of the bauble, you will see that the loop passes through a hole that the programming connection header would otherwise occupy. I’ve simply covered the header mounting pads with a piece of red stickybacked paper. I did the same thing with all four brooches, keeping my programming options open. Nobody notices this and, with the possible exception of the stocking, we reckon it improves the appearance. For example, it gives the tree the appearance of a trunk set in a red pot and many baubles are formed with a short plastic or metallic cylinder at the top. Another modification I made is the addition of three blue LEDs on each ornament. The additional colour also improves the effect. Fellow readers could earn a few brownie points by building these as brooches for mothers, wives, sisters, aunts, girlfriends, mistresses etc. I tested a couple by wearing one on visits to my local shops. The women behind the counter were greatly impressed! George Clauscen, East Oakleigh, Vic. Comment: the Tiny LED Christmas Tree PCB is available in white and red as well as the green that you used. Those other colours might be better for your application. One disadvantage of the Arduino Uno R4 Once again, it was a very good article by Jim Rowe about the latest Arduino Uno R4 Minima in the December 2023 issue. There is one issue regarding compatibility, though. The digital output pins on the R4 Minima are limited to just 8mA per output, compared to 20mA for the Uno R3 (200mA total). This needs to be taken into account when using the latest Uno R4 Minima instead of the old Uno R3. For example, when using the outputs to drive LEDs, the current limiting resistors should be selected to limit the maximum current to 8mA. That should be enough for high-brightness LEDs. Michel Adriaens, Christchurch, New Zealand Advice on backing up files Reading your editorial on backups in the February issue reminded me of an incident that affected me many years ago. I was using three 1TB portable hard drives for my backups. 12 Silicon Chip I added data to the drives periodically; some data was from a long time back and may not have existed elsewhere. When I went to add data to the drives, I found that one drive had failed completely and one was corrupted, leaving only one good copy of all the data. I bought a replacement portable hard drive for the dead one and was able to format the corrupted drive and then copy the data from the remaining good drive to the other two drives. It certainly pays to have more than one device with the backups. Since then, I have been using 2TB portable hard drives and recently purchased 4TB hard drives. My laptop has two hard drives. I have a 250GB SSD divided into C: and D: drives, plus a 2TB mechanical hard drive as the E: drive. I use the D: drive to store some data and periodically copy it to the E: drive. The E: drive data is periodically copied to two portable 2TB hard drives. The 4TB portable hard drives are on standby for when they will be needed. Bruce Pierson, Dundathu, Qld. Comment: that sounds like a good strategy. We have ‘rolling backups’, where we copy drive B to drive C, then drive A to drive B, then back up our files to drive A. That way, if something gets corrupted or deleted, there should still be a good copy somewhere, at least for a few backup cycles. In our case, the working data is on SSDs (with redundancy), but the backup drives are either external mechanical drives or data-centre-grade mechanical drives in a redundant array. What to call the Vintage column I favour calling the column “Vintage Electronics” as “Vintage Radio” is too narrow to cover all the devices you might want to feature. “Electronics” is the driver behind all sorts of industrial and consumer equipment, not just “Radio”. Vintage Electronics covers the broader topics of amplifiers, TVs, industrial controls, welders and so on, all the places where electronics took over. Now that I’ve said that, I wonder whether “Vintage Equipment” could be better still! Then projects like my mechanical vibrating point voltage regulator and magnetic core power supply are covered. Fred Lever, Toongabbie, NSW. Comment: thanks for the feedback. We think “electronics” covers electromechanical devices like vibrators and electromagnetic control devices too. This month, we’re calling it “Vintage Electronics” since the subject is a guitar amplifier rather than a radio. Common problems with Ideal Rectifiers I have some experience with various types of Ideal Rectifiers, similar to the one you presented in the December 2023 issue (siliconchip.au/Article/16043). All sorts of ‘smart diodes’ have turned up now. Some act as two-terminal devices; they work by switching the Mosfet on about 95-98% of the time. The rest of the time, the higher voltage across its internal diode (conducting in the forward direction when the channel is off) is enough to acquire the charge to enhance the Mosfet later. They are used in solar systems and alternators to minimise losses. Other types of ideal diodes (‘ideal diode current switches’ like the LM5050) do it by having an Earth or common reference, so they are really a three-terminal device, with a control circuit that needs to be powered, not a two-terminal device like a diode. In these cases, if Australia's electronics magazine siliconchip.com.au CNC PLASMA ROBOT KGS ONLY 16 With Simple Trace™ technology, 4,389 (P8990) $ No external software or cad skills are required * Shown with optional plasma torch IF YOU CAN DRAW IT, DOWNLOAD IT, TRACE IT OR IMAGINE IT, YOU CAN CUT IT ARCDROID - Corner Wizard - Centre Wizard ARCDROID - Laser Stylus - Simple Trace 66 (P8991) $ 77 (P8992) $ Portable powerful and easy to use. ArcDroid™ brings CNC plasma to your garage or workshop. ArcDroid™ combined with our custom operating system with Simple Trace™ can accurately reproduce your designs delivering fast, accurate and repeatable parts from your plasma cutter. Any table is a plasma table with ArcDroid™ Precision encoders and high resolution drives mean ArcDroid™ accurately reproduces your design with fast, accurate and repeatable parts from your plasma. With a cutting envelope of 660mm x 380mm you can cut like a Pro in your own workshop! ARCDROID X2 Large cut indexing system Simple Trace 658.90 (P8994) $ SIGN-UP TO WIN PRIZES & GiftcRECEIVE ard DISCOUNTS Point to point or free hand, trace your template and ArcDroid™ creates a cut file instantly. Simply use the ArcDroid™ arm to follow the contours of your template and high accuracy encoders map your every move. • Light and compact, goes anywhere, weighs less than 16kgs! • Fits in any shop and easily portable to job sites • Glove friendly touch screen interface, easy to use and intuitive user interface • Quick change holders to move from trace to cut mode • With simple trace, no external software or cad skills are required View and purchase these items online: www.machineryhouse.com.au/SIC2403 SYDNEY BRISBANE MELBOURNE (03) 9212 4422 (08) 9373 9999 1/2 Windsor Rd, Northmead 625 Boundary Rd, Coopers Plains 4 Abbotts Rd, Dandenong 11 Valentine St, Kewdale (02) 9890 9111 Specifications and prices are subject to change without notification. (07) 3715 2200 PERTH 02_SC_280324 NEW RELEASE the reference wire or ground wire disconnects, depowering the IC, they can fail to enhance, and the Mosfet will overheat and be destroyed. I think a circuit with a bridge simply uses a zero voltage reference created inside the IC from the two AC inputs. No harm is done if one wire to the bridge disconnects and all the current stops. That is, if the transformer feeding the bridge was indeed a single isolated winding, which it can be, but sometimes it is not. Many manufacturers chose the bridge rectifier module because they want four power rectifiers to create a split (positive and negative) DC supply with respect to a common, which is the centre tap of the driving transformer. It occurred to me that people replacing standard diode bridges with the Ideal Diode Mosfet Bridge might not realise what this could mean. I think (though the theory would need to be tested) that in this configuration, if just one of the AC wires from the transformer to the ideal diode bridge failed, the conducting Mosfets would fail to enhance and likely be destroyed. In many cases, the transformer connections plug into the PCB, and the connections can be intermittent or less than perfect. We are used to things blowing up when we short them out, rather than a connection coming loose and going high resistance, so it is counter-intuitive. I looked up the data sheet on the LT4320, and it did not really give enough information on the control circuits inside the IC or what would happen in the circuit configuration with a centre-tapped transformer for me to figure out if it is a realistic concern. It depends on how they acquired the enhancement voltages for the Mosfet gates inside that particular IC. It could be tested with a practical experiment with a centre-tapped transformer at some point. Dr Hugo Holden, Minyama, Qld. Comment: there would be Ideal Bridges that can work with a centre-tapped transformer where a loose connection could cause damage, as you suggest. For our design, as mentioned in the article, a single Ideal Bridge does not support a centre-tapped transformer. Two Ideal Bridge modules are required for that configuration, one to generate the positive rail and one for the negative. That means for a split supply, they operate similarly to where a single Bridge is generating a single output voltage. If one of the connections to a Bridge goes open-circuit, either the power supply is disconnected from it or the load is, so no damage should result. MEN stands for Multiple Earth Neutral In the “Ask Silicon Chip” section of the January 2024 issue, you refer to MEN as meaning “Mains Earth Neutral”. As mentioned in a previous issue, it’s actually “Multiple Earth Neutral”, as it refers to the practice of bonding Neutral and Earth together at several points to provide a low impedance path for RCDs. Could you publish an article describing the MEN system in full? Dave Horsfall, North Gosford, NSW. Comment: you are right about the name. We did publish an article on that topic in the very first issue of Silicon Chip (November 1987; siliconchip.au/Article/7867), but it is hard to find because it was titled “Your House Wiring Could Kill You”. We will publish an article about mains Earthing, including the MEN system, later this year. SC 14 Silicon Chip Australia's electronics magazine siliconchip.com.au Rack Equipment Ideal for IT Networking, Small Offices, Recording Studios, Sound & PA Equipment. GREAT VALUE and IN STOCK at your conveniently located stores nationwide. 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Jaycar reserves the right to change prices if and when required. FROM 139 $ 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. Temperature controller for humidicrib This PICAXE08M2-based circuit controls a heater for a wildlife humidicrib. However, it could be adapted for anything needing temperature control. Readers may want to adapt or refine my software, which should be easy to follow as just about every line is commented. The temperature is read from a DS18B20 sensor, compared with a value set in EEPROM and a relay is triggered to operate a heater. Storing the value in EEPROM enables the Circuit Ideas Wanted 16 Silicon Chip unit to resume if power is interrupted. Pulses from the fan are monitored and the unit triggers an alarm and shuts down if the fan stalls. Over-temperature and under-­ temperature alarms are included, with the over-temperature alarm shutting the system down and under-­ temperature alerting the user. The circuit uses standard PICAXE interface circuitry straight from the manuals, with a 20×2 character LCD screen driven by a serial LCD controller by the late Peter Anderson (https:// phanderson.com/), which is similar to the Serial LCD Driver (August 2005 issue; siliconchip.au/Article/3154). The control codes used for air circulation can be changed in the software to suit other serial LCDs. I used the READTEMP command, as it provides a hysteresis of ±0.5° and temperatures below 0°C are treated as 0°C. An improvement could be made using the READTEM12 command and possibly a PWM output driving a Mosfet. You might be wondering how I came 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, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia's electronics magazine siliconchip.com.au Fast and reliable temperature measurement. Digital Thermometers We stock a GREAT RANGE of thermometers, at GREAT VALUE, for domestic or commercial applications. 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Jaycar reserves the right to change prices if and when required. The top and bottom of the wildlife humidicrib. The underside of the crib has a singular 120mm fan. The controller circuitry is located inside a cavity in the crib, with the serial LCD and pushbutton mounted on the outside. 18 Silicon Chip Australia's electronics magazine to design a controller for a wildlife humidicrib. A wildlife group asked me to help fix it. The crib was a CIG Thermocot, an exceptionally wellmade, durable and somewhat heavy humidicrib originally intended for human babies but now with a second life looking after wildlife babies. Someone had clearly “had a go” at it; many pieces were loose, the PCB badly corroded, wires cut and the circulation fan was missing. There were also signs of modifications during its life as it now had an IEC input for 230V and the NATO-style military power socket was disconnected. The crib was designed to operate from 115/230V AC or 12/24V DC. I sourced a service document on the internet and determined that a replacement fan and tachometer were impossible to find. I had a working transformer, heaters and a Sonalert alarm, so it had potential. The wildlife carers had purchased a new commercial unit for over a thousand dollars, but were very disappointed with the noise it made. Clearly, the fan noise level is critical for animal care. Jaycar had a “silent” computer fan with a tachometer output, which looked ideal and had sufficient flow for the heaters. It was perfect; I just needed a controller. In addition to the serial stream to update the LCD, I needed a microcontroller with an alarm output, a heater control output, a temperature sensor input, a means of setting the temperature, an in-circuit programming port and a tachometer input for the fan. That was 7 I/Os but I managed to squeeze all those features into the 08M2. I learned to use EasyEDA, a web-based design system, to design the PCB. I eventually had a very professional looking PCB. It remained to fit the hardware in the crib and put it through its paces. I was pretty proud of the result. The unit is blissfully silent, easy to operate and incorporates all the required features, including a status display, fan speed monitoring and over/under-­ temperature alarms. Bonorong Wildlife Sanctuary near Hobart gratefully accepted the repaired humidicrib in time for the busy orphaned joey season. The software can be downloaded from: siliconchip.com.au/Shop/6/404 Rowan Wigmore, Hadspen, Tas. ($120) siliconchip.com.au ADD MOTION DETECTION TO YOUR PROJECT PIR MOTION DETECTION MODULE ADD OBSTACLE DETECTION OR AVOIDANCE DUAL ULTRASONIC SENSOR MODULE • Adjustable delay times XC4444 $6.95 • 2cm - 450cm 15° range XC4442 $8.95 Expand your projects with our extensive range of Arduino® compatible Modules, Shields & Accessories. OVER 100 TYPES TO CHOOSE FROM AT GREAT PRICES. 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Jaycar reserves the right to change prices if and when required. jaycar.com.au 1800 022 888 Experimenting with LoRa mesh networking LoRa (‘Long Range’) digital wireless technology has been around for about 10 years. It uses data redundancy and spread spectrum to achieve long-range transmission with low power consumption. This typically only allows low data rates, so it is only useful for sensor data rather than voice or video. Zigbee is a similar technology often used for low data rate applications over short distances, such as home automation. The Zigbee network layer supports mesh communications. Mesh networks allow messages to be sent further than the distance between nodes, as messages take hops between multiple nodes to reach their destination and not necessarily via a central hub. LoRa nodes can also work as a mesh network with the right software. Meshtastic (https://meshtastic.org/) is an open-source software project designed to work on existing LoRa hardware. One such device is the Heltec ESP32 LoRa board, an ESP32 processor board that includes a LoRa radio and an OLED display. The Getting Started page of the website mentions other supported boards and how to set them up. The Meshtastic software collects data from I2C sensor modules such as barometric pressure, air quality, temperature and humidity sensors. The 20 Silicon Chip data is passed between the nodes over the LoRa mesh network and can be viewed on a mobile phone with the Meshtastic app. This circuit shows how to build your own module that’s compatible with the Heltec ESP32 LoRa board but at a lower cost. I built mine on perfboard with a BME280 barometric pressure sensor. You will need at least three nodes to demonstrate the mesh capabilities of Meshtastic. To install the software, you can use the web-based flasher at https://flasher.meshtastic.org/ This currently only works with the Chrome or Edge browsers. It also lists some other compatible boards that can be used with Meshtastic. This process can take a few minutes and requires a good internet connection. You might also need to hold the BOOT button on the board until the firmware upload is finished. If you wish to do this offline, I have included the firmware images and flashing software in a download package: siliconchip.com.au/Shop/6/402 Now that it has been programmed, power on the board and pair it with your phone using Bluetooth. The pairing code should be displayed on the OLED. The app is called “Meshtastic”, and This is the prototype node I have constructed from an ESP32 board, LoRa module, OLED display and BME280 pressure sensor, as shown in the circuit diagram. it is available for Android and iOS. Once paired, the app should connect to the board and show other nodes connected to the mesh network. Ensure that Detection Sensor is enabled in the Radio configuration → Detection Sensor menu. Currently, only I 2C sensors on addresses 0x76, 0x77, 0x78, 0x18, 0x40, 0x41, 0x5D, 0x5c, 0x70, 0x44 and 0x12 (plus 0x3c for the OLED) are allowed. More sensors are planned to be added later. You can also manually set pins to connect a GPS module (like the VK2828U8G5LF we sell) or output pins to drive an alarm device such as a buzzer or LED. Check that Radio configuration → External notification is enabled. Bera Somnath, Kolkata, India. ($100) siliconchip.com.au Discover New Technologies in Electronics and Hi-Tech Manufacturing See, test and compare the latest technology, products and turnkey solutions for your business SMCBA CONFERENCE The Electronics Design and Manufacturing Conference features seminars and workshops from international experts on the latest innovations and solutions for design and assembly. Details at www.smcba.asn.au In Association with Supporting Publication Organised by Becoming an Amateur Radio Operator with Dr David Maddison, VK3DSM Becoming a radio amateur, or “ham” as they are known, can be a rewarding hobby and is perfect for those who are already interested in electronics. D ue to my interest in electronics and communications, I have always wanted to become a radio amateur. I was first introduced to it in high school but never got around to it for various reasons. I finally decided to get my licence. This article describes that process and the sorts of equipment and activities associated with being a ham. This article is written from the point of view of a novice. There are many hams out there with decades of experience, but I wanted to document the process as someone who is entirely new to the hobby. This is a brief introduction to a hobby that is huge in scope. There are thousands, if not millions, of websites and links relating to amateur radio (Google lists 71,700,000 results for “amateur radio” without quotes). Here, we can only cover a tiny selection of possible topics. What is a radio ham? A radio ham is a licensed operator who uses approved portions of the radio spectrum for the following purposes, both recreationally and socially: 22 Silicon Chip • non-commercial radio transmission and reception • technical investigations and experiments with radio • self-education in the field of aspects of radio reception and transmission • communication with other radio hams For younger people, it can also open doors to a career in electronics and communications. It is certainly not to become a radio DJ or for entertaining others (someone asked me about that). A typical radio ham has equipment in a part of the house designated “the shack” (not necessarily a physical shack, but it can be!) including, at minimum, a transceiver, a standing wave ratio (SWR) meter for measuring antenna efficiency and an antenna tuner. Outside the house, there may be one or more antennas that can be connected to the transceiver. A ham may also be “mobile” and have similar equipment in a car or RV, or simply carry it to various locations in a backpack. Activities will be discussed later, but generally include making contact Australia's electronics magazine with other hams, either locally or across the world, using a variety of analog and digital modes. Apart from recreational use, for independent-minded people, there is the satisfaction of having a communication method that will work without other infrastructure. The recent Optus outage that left many Australians without communications is a reminder of the vulnerability of our communications infrastructure. What has changed over time? One of the biggest differences between the ‘old days’ of ham radio and the present is the extensive use of digital technology now, which has given the hobby a whole new lease of life and many new possibilities. One of the past attractions of becoming a radio amateur was free communication with friends and relatives around the world. Long-distance telephone calls were extremely expensive. That is no longer the case. Also, hams used to make most of their own equipment. Today, most equipment is commercially available. Even so, many prefer to make as much siliconchip.com.au Table 1 – radio frequency bands per the ITU (International Telecommunication Union) Frequency name Abbr. Freq. range Wavelength Some common uses Extremely low frequency ELF 3Hz-30Hz 100,000km10,000km Submarine communications Super low frequency SLF 30Hz300Hz 10,000km1,000km Submarine communications Ultra low frequency ULF 300Hz3kHz 1,000km100km Submarine communications, mine and cave communications Very low frequency VLF 3kHz-30kHz 100km-10km Submarine communications, radio navigation systems, time signals, geophysics Low frequency LF 30kHz300kHz 10km-1km Radio navigation, time signals, longwave AM commercial broadcasting in Europe and Asia, RFID, amateur radio (certain countries) Medium frequency MF 300kHz3MHz 1,000m-100m AM commercial broadcasting, amateur radio, avalanche beacons High frequency HF 3MHz30MHz 100m-10m Shortwave & amateur radio, 27MHz CB, long-range aviation & marine communications, radio fax, over-the-horizon radio Very high frequency VHF 30MHz300MHz 10m-1m Aircraft communications, amateur radio, emergency services, commercial FM broadcasts Ultra high frequency UHF 300MHz3GHz 1m-10cm TV broadcasts, microwave ovens, radars, mobile phones, GPS, wireless LAN, Bluetooth, ZigBee, satellites, Australian UHF CB Super high frequency SHF 3GHz30GHz 10cm-1cm Wireless LAN, radar, satellites, amateur radio Extremely high frequency EHF 30GHz300GHz 1cm-1mm Satellites, microwave links, remote sensing, amateur radio Tremendously high frequency THF 300GHz3THz 1mm-0.1mm Remote sensing, experimental uses siliconchip.com.au (continuous wave; for Morse code), beacon modes, narrow band, wide band, repeater inputs & outputs, amateur TV (slow scan TV), satellite etc. For further details and specific usage of the Australian amateur radio band plans, see the document from the WIA (Wireless Institute of Australia) at: siliconchip.au/link/absn Table 2: amateur bands and the radio spectrum 10m (28.0-29.7MHz) 2m (144-147MHz) 70cm (430-450MHz) 20m (14.00-14.35MHz) 6m (52-54MHz) 23cm (1240-1400MHz) 13cm (2400-2450MHz) 6cm (5650-5850MHz) As well as power limits, bandwidth limitations apply. EIRP is effective isotropic radiated power. Higher licence levels can also use bands for lower levels. 630m (472-479kHz), 5W EIRP 160m (1.800-1.875MHz) 30m (10.10-10.15MHz) 17m (18.068-18.168MHz) 12m (24.89-24.99MHz) 3cm (10.0-10.5GHz) 1.25cm (24.00-24.25GHz) 7.5mm (47.0-47.2GHz) 120W to 400W 15m (21.00-21.45MHz) ADVANCED 40m (7.0-7.3MHz) 2200m (135.7-137.8kHz), 1W EIRP 10W maximum 80m (3.5-3.7MHz) 30W to 100W Australia has three licence levels: Foundation, Standard and Advanced. You can sit for any of these for your first licence; Standard and Advanced require greater knowledge. You can migrate to a higher licence level by taking another exam. As the licence level increases, more bands and higher power output levels become available. The Foundation Licence is a popular starting point. There is no minimum age to obtain a licence in Australia. Additional types of licences include those to operate a repeater or beacon station for the benefit of other amateurs. A list of what bands you can operate is shown in Table 2, while Table 1 shows the frequencies, wavelengths and uses of the main ITU (International Telecommunication Union) radio bands (for all purposes). Amateur radio signals can operate in all the bands shown in that table from LF onward (even including the THF band). Note that the term “band” has FOUNDATION Licensing different meanings in different contexts. For example, the ITU bands describe frequency decades, while amateur bands, such as 10m, 20m, 40m etc are much narrower. Each amateur band is further divided into segments for voice or digital, various analog modes such as AM, FM, SSB (single-sideband), CW STANDARD as possible, but you can just buy it if you can’t or don’t want to make it. 3.7mm (76GHz-81GHz) 2.5mm (122.25-123.00GHz) 2mm (134-141GHz) 1.25mm (241-250GHz) April 2024  23 VK prefixes Fig.1: the 40m amateur band is accessible to Foundation Licence members. Original source: www.wia.org.au/members/bandplans/data/documents/ Australian%20Band%20Plans%20200901.pdf An example of band usage from that document is shown in Fig.1 for the 40m amateur allocation. For that band, amateurs have exclusive use of the first 100kHz (primary users) but have to share with other users on the upper 200kHz (secondary users). Listening in We will discuss options for transceivers shortly, but even if you are not a licensed ham, you can still listen in on the bands. There are a few ways to do that. You can listen using free online software-­ defined radios (SDRs) that can be found at websites like http:// kiwisdr.com/public/ and http:// websdr.org/ They are located all around Australia and the world. These are also useful for when you become a ham and want to check how your signal is getting out. A particularly good one is the Ironstone Range SDR in South Australia at http://sdr.ironstonerange. com:8075 You can buy an SDR receiver from Australian company WiNRADiO Communications (https://winradio.com). It connects to a PC to operate. One model that covers 9kHz to 49.995MHz is the WR-G31DDC “EXCALIBUR”; see https://winradio. com/home/g31ddc.htm and our review in the June 2012 issue (siliconchip.au/ Article/636). 24 Silicon Chip Inexpensive SDR ‘dongle’ receivers based on the RTL2832U chip are available that work with open-source software, but for lower frequencies, you may also need an upconverter, such as the SiDRADIO (October & November 2013; siliconchip.au/Series/130). Also see these websites: • www.rtl-sdr.com • www.nooelec.com/store/sdr.html • https://gqrx.dk/ • www.gnuradio.org Another way to receive ham and other bands is a shortwave receiver. One highly regarded example is the Tecsun S2000, which we reviewed in the August 2016 issue (siliconchip. au/Article/10047). It is still a current model; refer to siliconchip.au/link/ abte How many ‘hams’ are there? In Australia, at the time of writing, there are 15,499 radio hams (see www. wiaawards.com/charts/amateurs. php). Many other interesting Australian statistics can be found at www. wiaawards.com/charts/index.php As of March 2023, there were 6730 hams in New Zealand (as per the PDF at siliconchip.au/link/abso). There were about 780,000 in the USA as of 2021 (siliconchip.au/link/ absp). It is said that there were about 3 million hams worldwide back in 2000, but there has been a decline in numbers. At present, we estimate there are Australia's electronics magazine Australian hams are allocated a unique callsign with a prefix based on their state or territory of residence as follows: VK0   Australian Antarctic Territory, Heard Island, Macquarie Island VK1   ACT VK2   NSW VK3   Victoria VK4   Queensland VK5   South Australia VK6   Western Australia VK7   Tasmania VK8   Northern Territory VK9C   Cocos-Keeling Islands VK9L   Lord Howe Island VK9M   Mellish Reef VK9N   Norfolk Island VK9W   Willis Island VK9X   Christmas Island around 1.75 million currently active. Earning a Foundation Licence The Foundation Licence demonstrates that you have enough knowledge and skills to assemble a basic amateur station from commercial equipment and supplies, and operate it according to the correct procedures and without causing inappropriate interference to other radio spectrum users. You would typically attend a training course with a local amateur radio club (or by yourself). However, before that, you should purchase and study the WIA publication “The Foundation Licence Manual – Your Entry Into Amateur Radio, 4th Edition”, available from equipment suppliers and radio clubs. The exam is based on that book. It currently costs $35 plus $15 postage – see www.wia.org.au/licenses/ foundation/foundationmanual Another supplementary book from the WIA is Peter Parker’s “Australian Ham Radio Handbook”, available from his website (https://books.vk3ye.com). The hard copy costs $24.95. Finding a club To find your local club in Australia, visit www.wia.org.au/clubs/ and access the pull-down menu that says “Affiliated Radio Clubs” or search Google. siliconchip.com.au New Zealand clubs can be found at www.nzart.org.nz/contact/branches/ list and information about becoming a radio amateur in NZ is at www.nzart. org.nz/learn I contacted two nearby clubs in the Melbourne area, the Moorabbin & District Radio Club Inc. (https://mdrc. org.au) and the Eastern & Mountain District Radio Club (EMDRC; www. emdrc.com.au). I took my course and exam with the one that first offered it at a convenient time. It is OK to join two or more radio clubs; many do, as different clubs cater to various interests. You will find ham radio clubs to be very friendly, helpful and welcoming of new members. Some radio clubs offer free licence training when you first join the club. Some clubs also provide members with discounts at stores like Jaycar and Altronics. The exam There is a set course curriculum for all licence levels. For the Foundation Licence, the WIA website says, “… you will learn the how Amateur Radio relates to other users of the radio spectrum, licence conditions, technical basics of electricity and electronics, transmitters, receivers, feedlines and antennas, propagation, electromagnetic compatibility (EMC), and electromagnetic radiation (EMR).” Since 2004, knowing Morse Code has not been required, although many people still enjoy using it. Randomly generated Foundation Licence practice exams can be found on the WIA website at www.wia.org. au/licenses/foundation/onlineexams/ foundation.php You can repeat these practice exams as often as you want to. Once you have studied and perhaps taken a course with a radio club, you arrange with the club to sit the exam. The Foundation Licence has a written exam with 25 questions with a passing grade of 70% that you have half an hour to complete. There is also a practical component to the exam, involving some oral questions and a demonstration of practical knowledge in connecting up a basic amateur station and putting it on the air. The results are sent to the Australian Communications and Media Authority (www.acma.gov.au/amateur-radio), who issue you a licence if you get a passing grade. As for the cost, the radio club may still charge for coursework and ACMA charges for certain services, such as an exam fee and callsign assignment. However, there is no longer an annual fee for the licence, similar to the USA, Canada, New Zealand and the UK. Before taking the exam, you might also want to watch some YouTube videos by Ron Bertrand on the Foundation Licence course. Some are slightly outdated compared to the current syllabus, but the differences are not significant, see siliconchip.au/link/abtc We haven’t tried it, but it is possible to sit Australian or American amateur exams online via Volunteer Examiners of Australia (https://vea.org.au). Now that you have a licence The first thing to do is set up your station. At the minimum, it should have a transceiver, an antenna tuner, an SWR meter and an antenna. Many modern transceivers incorporate an SWR meter and an antenna tuner, so separate devices may be unnecessary. Ideally, you will also have an internet-­ connected smartphone or computer nearby to look up call signs or other information. You can then call other hams. There is a procedure to call other amateurs, which you will learn during your course. After checking that a frequency is not in use, you might broadcast: CQ CQ CQ this is VK1ABC VK1ABC VK1ABC, over The response might be: VK1ABC, this is VK2XYZ, over. See the WIA manual for further examples. Note that you can look up the call signs of other hams on the website www.qrz.com and maintain a page with information about yourself and your equipment. They also have discussion forums. When using voice mode to contact others, the conversation should be polite with no expletives. Topics can include technical aspects of your station, such as your rig or antenna, ham radio in general, or even topics not related to radio. You may relay personal messages, but encryption or secret codes are not permitted, and neither is station operation for commercial or entertainment purposes. Controversial or divisive topics are not in the spirit of amateur radio. Some people choose not to converse, as they are just interested in making contacts or using digital modes. Quite a few special ‘Q-codes’ are used to shorten common terms and situations (especially when using Morse code). Until you are familiar with them all, keeping the list on hand during radio conversations would be a good idea. Some examples are shown in Table 3. The NATO phonetic alphabet is used for spelling things out, as shown in Table 4. Long-distance transmission via the ionosphere The ionosphere is fundamental to Table 3 – common Q-codes Table 4 – the NATO phonetic alphabet using ICAO spelling Q-Code Meaning A: Alfa B: Bravo C: Charlie D: Delta E: Echo F: Foxtrot G: Golf H: Hotel I: India J: Juliett K: Kilo L: Lima M: Mike N: November O: Oscar QRZ who is calling me? P: Papa Q: Quebec R: Romeo S: Sierra T: Tango QSB fading signal U: Uniform V: Victor W: Whiskey X: Xray Y: Yankee QSL acknowledge receipt Z: Zulu 1: Wun 2: Too 3: Tree 4: Fow-er 5: Fife 6: Six 7: Sev-en 8: Ait 9: Nin-er QRM man-made interference QRN static crashes QRP low transmitting power QSO a conversation QSY change frequency QTH location siliconchip.com.au 0: Ze-ro Australia's electronics magazine April 2024  25 Table 5 – typical amateur radio transmission distances Fig.3: types of HF radio propagation, including line of sight (LOS), ground wave, skywave and NVIS (near vertical incidence skywave). Original Source: www.qsl.net/4x4xm/HF-Propagation.htm long-distance (DX) HF amateur radio operation. This layer in the atmosphere, from around 48km to 965km, contains layers of ionised gases (with the outer electrons removed by sunlight). That renders them electrically conductive and thus capable of reflecting HF radio waves. The layers in the ionosphere change from night to day, as shown in Fig.2. Fig.3 shows the several propagation modes of radio waves. LOS (line of sight) transmission is when stations are visible to each other. UHF CB (477MHz) or FM commercial broadcasting (88-108MHz) are common examples of such a propagation mode. Ground wave propagation occurs at frequencies below about 2MHz during daytime. Radio waves follow parallel to the Earth’s surface and are interrupted by mountains etc. AM Broadcast stations are an example of such propagation. Skywave propagation is where radio waves are reflected off the ionosphere. NVIS (near vertical incidence skywaves) is a special form of skywave propagation suitable for transmission over limited distances and from areas such as valleys. It is often used by military or emergency services. Skywave propagation is the main mode for radio waves from about 3MHz to 30MHz (commonly called shortwave). The ionosphere also refracts frequencies from ELF (3-30Hz) to LF (30-300kHz). MF waves (3003000kHz) propagate by ground waves by day or ground waves and ionospheric E and F layer refraction at night (which is why AM radio stations travel further at night). VHF signals (30-300MHz) occasionally propagate via ionospheric refraction, tropospheric ducting (through a layer of air of different refractive index caused by a temperature inversion which bends the signal back to Earth) or meteor scatter (off ionised meteor trails) but are usually line-ofsight, passing through the ionosphere and into space. The ionosphere is imperfect; parts of it can ‘come and go’, and the layers can move up and down somewhat, which is why radio signals can fade and return. One such layer is called “sporadic E” – see Fig.4. There is a critical frequency at which a signal is either refracted by the ionosphere and returns to Earth or passes through the ionosphere Australia's electronics magazine siliconchip.com.au Frequency Band Range 3.5-3.7MHz 80m Up to 150km during the day and 3000km at night. 7.0-7.3MHz 40m Up to 1000km during the day; worldwide during good conditions at night. 14.00-14.35MHz 20m Reliable worldwide contacts, day and night, during sunspot maxima or in the daytime during sunspot minima (requires a Standard or Advanced Licence). 21.00-21.45MHz 15m Worldwide, mostly during the daytime. 28.0-29.7MHz 10m Worldwide during high sunspot activity and up to 3000km in summer. This is the widest HF band and close to the familiar 11m/27MHz unlicensed CB band, with similar propagation characteristics. 52-54MHz 6m This VHF band has propagation characteristics between HF and VHF. During high sunspot activity, worldwide propagation is possible (requires a Standard or Advanced Licence). 144MHz 2m Local coverage (more via tropospheric ducting); worldwide via repeaters. 430-450MHz 70cm Local coverage (more via tropospheric ducting); worldwide via repeaters. Fig.2: the ionosphere’s radio-reflective layers and sub-layers change between night and day. Source: https://w.wiki/93Xz 26 Silicon Chip and goes into space. This frequency depends on the amount of ionisation in the atmosphere (electron density) and the radio wave’s incidence angle. With the right frequency and ionospheric conditions, even with the 10W or less permitted to a Foundation Licence operator, an amateur radio signal can propagate anywhere in the world. A beginner with a primitive hookup wire antenna around 10m long, raised a few meters or more off the ground (higher is better), and an antenna tuner, should have few problems getting 1000km contacts on the 40m/7MHz band. Far better antennas are easily possible and inexpensive; we will discuss them later. Of course, achieving long ranges is not the only criterion by which success in the hobby should be judged. Some operators are perfectly content with local contacts. Repeaters VHF and UHF signals, such as on the 2m and 70cm bands, propagate mainly via line of sight. A network of repeaters, maintained by volunteer hams, has been established to increase their range. They are primarily located on buildings, towers and mountains; they receive and re-transmit signals to dramatically increase the available range. Digital modes such as C4FM, D-Star (www.dstar.org.au), DMR (https:// vkdmr.com) and P25 are supported by various repeaters. Worldwide contacts are possible with some modes; some repeaters are connected via the internet. Repeaters have different ‘input’ and ‘output’ frequencies, as shown in Fig.5; this mode is called duplex, as opposed to station-to-station communication, which is called simplex (the same frequency for reception and transmission). Maps of Australian repeaters can be found at: www. onlinerepeatermap.com EchoLink (www.echolink.org) and IRLP (www.irlp.net) use software to connect individual amateur stations or repeaters over the internet. Typical transmission distances that can be achieved are shown in Table 5. Fig.4: the ionospheric layers during the day and night, including the sporadic E layer and electron density (ionisation level). Original source: www.sws.bom. gov.au/Educational/5/2/2 Sunspots Sunspots are temporary regions of lower temperature on the sun caused by intense magnetic fields. Sunspots come and go according to an 11-year siliconchip.com.au Fig.5: how a repeater works (top, duplex) compared to station-to-station transmission or “talk around”, in which the repeater is bypassed (bottom, simplex). Original source: https://w.wiki/93X$ Australia's electronics magazine April 2024  27 solar cycle (see Fig.6). The sun is more active when there are more sunspots, which causes more ionisation of the ionosphere, a favourable condition for long-distance radio propagation. We are currently approaching the peak of the present solar cycle, making it an excellent time to become a ham – see Fig.7! Building your own equipment Fig.6: historic sunspot activity showing the approximately 11-year cycle. Source: https://w.wiki/93Y2 (GNU FDL). Fig.7: the present Solar Cycle 25 measurements and predictions show favourable radio conditions for the next few years. Source: www.weather.gov/ news/102523-solar-cycle-25-update Fig.8 (above): Icom’s IC-705 portable transceiver. An optional backpack is available for transport. Fig.9 (left): the (tr)uSDX pocket transceiver. 28 Silicon Chip Australia's electronics magazine Because modern commercial SDRs (software-defined radios) are so good, it is tough to build a competitive transceiver, although some people do. Of course, it is still possible to make traditional analog transceivers, but these days, hams are more likely to focus on building antennas; there are lots of online instructions for doing so. If you want to build your own transceiver, Paul VK3HN has made several videos about ‘scratch-building’ various transceivers and other items. See his YouTube channel at siliconchip. au/link/abtf and also https://vk3hn. wordpress.com LimeSDR (siliconchip.au/link/absq) has applications in ham radio; for more on that, see siliconchip.au/link/absr Peter Parker VK3YE has also produced many books and videos about building your own equipment – see https://books.vk3ye.com Choosing a transceiver You could start with a second-hand rig from a hamfest, but there are risks with any second-hand goods. Inexpensive rigs are available that are made in China, some of which are frowned upon by some hams. Then there are the traditional quality brands commonly available in Australia, like Icom and Yaesu. Since I like travel and bushwalking, I wanted a portable rig. I also wanted a durable, high-quality rig that I could use at home as a base station, one that I could grow with that was supported with accessories and worked on HF, VHF, UHF etc. I also wanted a “waterfall display”, which shows which frequencies have activity. I chose the Icom IC-705 (Fig.8), as it had all the features I wanted; it is a veritable “shack in a box”. The IC-705 is highly regarded worldwide and does everything you need as a beginner ham, both for base station and mobile use. For example, it has full coverage for receiving and transmitting on all amateur bands in the siliconchip.com.au What happened to shortwave radio? Fig.10: the Quansheng UV-K5(8); you also need the programming cable. HF, VHF and UHF frequencies from 160m to 70cm (every band most amateurs are likely to use). The advantage of an all-mode, wide-coverage transceiver is that it theoretically avoids the necessity of buying more equipment later (but good luck with that!). Its power output is limited to 10W on external power or 5W on battery. 10W is the maximum power for a Foundation Licence; you could pair it with a compatible linear amplifier or buy a base station for more advanced licence classes. Do not use a linear amp with the optional AH-705 antenna tuner, as it won’t handle the power. The IC-705 costs a little under $2000 from Australian retailers, while the strongly recommended matching AH-705 antenna tuner is around $550. If you want only a base station, another possible model is the Icom IC-7300, for around $1600. It has a built-in antenna tuner and can deliver 100W, so it would be a better deal if you don’t need portability. The IC-705 is very similar to the IC-7300 but with fewer features. However, the IC-7300 does not have 2m and UHF coverage like the IC-705. Both rigs require a 13.8V power supply, which can be generic. The IC-705 requires 3A on external power, while the IC-7300 requires 21A at maximum output. Many radio amateurs got their start by listening to shortwave radio broadcasts at a young age. Many of these broadcasts came from national governments such as Australia (Radio Australia), the UK (BBC) and the USA (Voice of America). When the Cold War ended, the stations were either shut down (as in the case of Australia) or their services dramatically reduced. The abandoned frequencies were mostly taken over by the government of China, which now has hundreds of stations. China took over Australia’s radio slots for the Pacific Islands; however, Radio New Zealand Pacific maintains a presence (see www. rnz.co.nz/international). Australian radio amateur Dave Stuart VK3ASE took over two of Radio Australia’s frequencies, 2310kHz and 4835kHz. He broadcasts his own musical program from central Victoria at about 100W as a commercial licensee. The station is non-profit and is called Shortwave Australia. See the videos titled “Tuning in to Shortwave Australia” at https://youtu. be/qrfvcJHti0M (Peter Parker) and “Shortwave Aust Latest Developments” at https://youtu.be/V-0uag9qdhs Icom IC-7300, with HF and 6m but not 2m or UHF. Much smaller HF transceivers are possible for CW-only (Morse code) operation, so a much smaller transceiver is possible if you do not require voice capability. Handheld transceivers for the 2m and 70cm bands are common. The (tr)uSDX (Fig.9) is a five-band/ multimode QRP transceiver in a pocket format (90×60×30mm & 140g). It is an open-source kit, but there are many suppliers; make sure they are selling the authentic product as specified on https://dl2man.de/ The Quansheng UV-K5(8) (Fig.10) is an extremely cheap handheld transceiver that works on the 2m and 70cm bands at 5W. There is an enormous online ham community writing custom firmware for it; if you buy one, get a programming cable too. Some low-quality transceivers are available with unfiltered outputs that can interfere with other services. Be wary of fake equipment of all varieties, especially antennas. To name just two examples, an enormous number of fake “Nagoya” and “Diamond” brand antennas are available online. Don’t ruin your experience, and possibly your radio, with a fake; buy from reputable dealers. Note that transceivers imported from Japan or elsewhere might not conform with amateur bands in Australia and usually cannot be converted to do so, even if a similar model is sold here. So check first. Antennas Along with your transceiver, the antenna is a vitally important item. Antennas are usually cut to a specific length to resonate at a particular frequency or a range of frequencies, although there are also non-resonant designs. The basic antenna types are: • the dipole (Fig.11) or folded dipole antenna, half a wavelength long • the vertical antenna (Fig.12) with a ground plane • the Yagi (Fig.13), which is highly directional Other options The Elecraft KX3, Xiegu X600 and Lab599 TX-500 are other portable rigs worth considering. The Yaesu FT-710 AESS is a 100W base station radio with a built-in antenna tuner; it is worth considering for a beginner. It has a price and features similar to the Fig.11: a dipole antenna. Original source: www.arrl.org/single-banddipoles siliconchip.com.au Australia's electronics magazine April 2024  29 Fig.12 (left): a field-expedient vertical antenna supported by a squid pole. Source: www.vk5pas.com/squid-poles.html Fig.13 (below): David’s Yagi antenna (on the left; the TV antenna on the right is also a Yagi). • the end-fed antenna, one of the simplest and easiest to get started with • the magnetic loop antenna (Fig.14) There are vast numbers of variations on all of those designs. All antenna designs have advantages and disadvantages; there is no perfect antenna. For example, dipole antennas are large, especially for the lower HF frequencies. Magnetic loop antennas have a narrow resonance range (high Q) and must be retuned as you make slight adjustments to the frequency (some can do this automatically). It has been said that “the best antenna is the one you have at the moment”. Any antenna, no matter how primitive, is better than nothing; even a 10m or so length of random wire with an antenna tuner is better than nothing and can get you on the air. The higher off the ground it is, the better. An important consideration for an antenna is the take-off angle. Operation near salt water also significantly improves range. There is a German brand of thin wire for portable antennas called DX-Wire (www.dx-wire.de), which is lightweight and contains reinforcement. Quality antenna wire can be obtained from DXCommander (siliconchip.au/ link/abss). However, by all means, try regular wire for your antenna experiments. Some people swear by speaker wire, split in two to double your length! Antenna couplers/tuners can be purchased or made yourself. One DIY design by Peter Parker VK3YE is shown in the video “Yet another QRP L match antenna coupler” at https:// youtu.be/JwVuvu-C30c You can search YouTube for “VK3YE coupler” without quotes to find his other designs. It is possible to generate hundreds of volts on an antenna during transmission, so as a safety measure, they should not be touched during transmission and should be kept out of reach of people and animals. You can simply follow some basic rules to make your own basic dipole or long-wire antennas. However, experimenters can model more advanced designs with free software such as MMANA-GAL. A free basic Windows version for non-commercial use is at http://gal-ana.de/basicmm/en/ (see Fig.17 and the video “Our Obsession with Ham Radio Antennas” at https:// youtu.be/MSNvaDzCA1c). Fig.15: David’s radio shack (not the author). Fig.16: Stan “Stax” Schwartz (www.qrz.com/ db/KE5EE) lives in Molina, Florida and has an impressive antenna farm and shack, the latter shown here. If you have the money and the land, why not? 30 Silicon Chip Australia's electronics magazine siliconchip.com.au antenna made from power line cable and hardware, as it is designed to support such great spans. See the video titled “HAM RADIO MONSTER ANTENNA – ZL3SV” at https://youtu. be/7ah95zW9-WM and his website at https://angelsnz.net/zl3sv.htm A local ham, David, showed me his shack (Fig.15) and Yagi antenna (Fig.13). Standing wave ratio (SWR) Fig.14: a magnetic loop antenna. Source: https://w.wiki/93Y4 (GNU FDL). Another free antenna modelling program is 4nec2 (www.qsl.net/4nec2). For a Linux version of NEC2, see www. xnec2c.org EZNEC (https://eznec.com) is also free and has many tutorials, but there is no support or updates from the author, W7EL, as he has retired. There are also many online calculators and software for all aspects of radio ham activities. Generally, resonant antennas can be shortened to half or a quarter of a wavelength; fractions such as one-third or one-eighth are unsuitable for various reasons. An end-fed antenna should not be one-quarter wavelength long, as described online at siliconchip.au/ link/abst and siliconchip.au/link/absu Amateur Gary Watson, ZL3SV in New Zealand has a 640m-long The SWR measures the amount of power the antenna reflects back to the transceiver. Such power is not propagated, so the SWR should be kept as low as possible. It is minimised by correct antenna tuning and the correct use of baluns or ununs (more on them later). In general, aim for an SWR of less than 1.5:1, which indicates a 4% power loss. 2:1 represents an 11.1% power loss, while 3:1 is a 25% power loss. For much more detail on this, see the PDF at siliconchip.au/link/absv DIY end-fed antenna projects The end-fed antenna is just a length of wire that may or may not be resonant depending on the frequency and whether it is fed via a balun or antenna coupler/tuner. If resonant, it can be a half-wave antenna, a so-called EFHW (end-fed half-wave). The end-fed antenna is very versatile and cheap to make. One example is in the article by Peter Parker VK3YE at siliconchip.au/link/absw A good video about end-fed antennas titled “End Fed Antennas – Portable, Emergency, Stealth Installations” is at https://youtu.be/Fk2vahBnfbQ Another simple end-fed antenna project from EARC is described in the PDF at siliconchip.au/link/absx A “squid pole” is like a telescopic fishing pole and comes in lengths up to around 10m. It is suitable for elevating lengths of lightweight wire (like hookup wire) for use in portable operations or even for home use (as I am currently doing). The Haverford squid pole is an example; see siliconchip. au/link/absy Not all wire lengths are ideal for end-fed antennas. The best lengths are discussed at siliconchip.au/link/absz Antenna analysers A vector network analyser (VNA) was, until recently, an extremely expensive item of laboratory equipment to measure the amplitude and phase of a signal as it goes through a circuit. Such devices are now available to hobbyists at affordable prices. Of course, hobbyist-grade VNAs are not as good as expensive laboratory devices but they are still useful. They are great for various amateur radio applications, such as measuring antenna SWR, impedance, frequency response, cable losses, and filter measurements. The NanoVNA is an inexpensive VNA that uses open-source software and has a large support base. See our review from April 2020 (siliconchip. au/Article/13803). If purchasing one, make sure you get the appropriate adaptor leads for your application. Travel as a ham Fig.17: sample output from the MMANA-GAL antenna modelling software. siliconchip.com.au Australia's electronics magazine There are reciprocal arrangements with other countries to take your portable rig internationally; check with the authorities in the proposed country of travel. For overseas amateurs visiting Australia, check with the ACMA: www.acma.gov.au/ overseas-amateursvisiting-australia April 2024  31 The Mini 1300 is a similar antenna analyser, optimised for that purpose. Other devices for analysing antennas are RigExpert (https://rigexpert. com) and several from MFJ Enterprises (siliconchip.au/link/abt0). The SARK-100 is a public domain design available as various kits (https://sites. google.com/view/sark100), while the SARK-110 is a more advanced version (www.sark110.com). Antennas in difficult situations Most people are limited in how large an antenna they can use, so there are many ideas for compact antennas. Try searching for “stealth antennas” or “HOA antennas”. Some people build antennas in their roof spaces (not suitable with a metal roof or with aluminium sarking). Others use hollow, non-metallic flagpoles, although domestic flagpoles are not terribly common in Australia. There is a video titled “How to Build an All Band in an HOA Stealthy Backyard Broadband Antenna – Corey Ruth, KD3CR” at https://youtu.be/ lu3SDp7ZvXw The PDF at siliconchip.au/link/ abt1 describes a ‘broadband butterfly terminated dipole’ (BBTD) antenna, A short history of amateur radio Amateurs have been involved in radio since Hertzian waves were discovered and utilised for communications by Marconi in the 1890s, although no licence was required then. The first commercial devices for amateur radio use (transceiver and receiver) were sold in 1905 – see below. This is perhaps the first commercial ham radio set, in an advertisement from Scientific American, November 25th 1905, page 427. In 1908, US amateurs started the Columbia University Amateur Radio Club. The Wireless Institute of Australia was established in 1910. In 1912, the US Government passed the Radio Act, which restricted amateurs to wavelengths of 200m or less (1500kHz or more) to preserve the radio spectrum. Those frequencies were considered useless for commercial, military and maritime services, but amateurs discovered they could be used for long-distance communication via the ionosphere. Amateurs first communicated between the USA and Europe on 200m in 1921. After that, amateurs were shifted to shorter wavelengths, such as 150m/2MHz, as the commercial and other importance of the medium-wave bands was recognised. In 1924, three shortwave bands were allocated to amateurs: 3.75MHz/80m, 7MHz/40m and 14MHz/20m. In 1927, 28MHz/10m was added, which amateurs still use today. John Iringle was a 14-yearold ham radio operator from Chicago in 1922. He is in his shack with the equipment he made. Source: http://hdl.loc. gov/loc.pnp/ cph.3b39715 32 Silicon Chip Australia's electronics magazine invented by Bonnie Crystal KQ6XA. It is a type of ‘travelling wave’ antenna that is non-resonant and thus broadband in nature. Vertical antennas can be useful in restricted spaces. Peter Parker VK3YE discusses several designs on his YouTube channel (search for “VK3YE vertical” without quotes). These designs are typically used with a squid pole (mentioned earlier). Magnetic loop antennas are also helpful in space-restricted circumstances but are resonant over only a small range of frequencies and need constant retuning with frequency changes. See the video by Peter Parker titled “100 watt 7 MHz magnetic loop for units and apartments” at https:// youtu.be/Cv_RnLpZ9gw Lightning protection As a general rule, it’s a good idea to disconnect the antenna from your rig when it is not in use and, if possible, lower it to minimise the possibility of damage from nearby or direct lightning strikes. Lightning surge protectors are available to place in the antenna feed line to direct excessive charge buildup to ground, but are unlikely to do much in the event of a direct strike – see Fig.18. Remember that lightning strikes can travel many kilometres; there are limits to what you can do to avoid being hit. Do not operate a ham station during an electrical storm. For further information, see siliconchip. au/link/abt2 (PDF) and www.arrl.org/ lightning-protection Baluns and ununs ‘Balun’ is short for balanced/ unbalanced and describes a type of transformer used for RF impedance matching. The awkwardly-named ‘unun’ is a similar device with unbalanced windings at both ends. Some antenna designs require a balun or unun between the transceiver and the antenna, but not all do. In ham radio, a balun matches the impedance of a balanced antenna to an unbalanced feed line (like a coaxial cable). In contrast, ununs match an unbalanced antenna to an unbalanced feedline. The feedline connects to the transceiver, which has a 50W impedance. The objective is to minimise SWR and losses. Some antenna tuners require their use, as impedance matching may not siliconchip.com.au Fig.18: a lightning surge protector that can direct excessive charge buildup to the ground to minimise damage from a lightning strike. be possible with the antenna tuner alone. In other cases, such as the Icom AH-705 tuner I got with my radio, an external balun or unun is unnecessary; it appears capable of tuning and matching just about anything (within reason). A balun is stated to have a certain ratio, which relates to the ratio of turns of the windings. The impedance transforms according to the square of the winding ratio. So a 3:1 turns balun will give a 9:1 impedance ratio, allowing you to match a 450W antenna or feedline impedance to a 50W transceiver. There are a great many designs for these devices online; they are pretty easy to make, or you can buy them. They are basically a ferrite toroid with wires wound around it. One example of a DIY balun for an end-fed antenna is the “49:1 Impedance transformer for EFHW antenna” – siliconchip.au/ link/abt3 We also found an unun kit available at siliconchip.au/link/abt4 – see the video titled “TEST: Mini 49:1 UNUN (EFHW antenna)” at https://youtu.be/ OOe5EvYjiW0 Beacons The International Beacon Project (www.ncdxf.org/beacon) has a system of transmitters worldwide, including Australia and New Zealand, that send out signals for monitoring propagation conditions. The beacons transmit on 14.100MHz, 18.110MHz, 21.150MHz, 24.930MHz and 28.200MHz. Fig.19: the 324 Maidenhead fields of the world. Source: https://w.wiki/93Y6 • FreeDV (https://freedv.org), an open-source amateur digital voice mode. • FT8, supported by WSJT-X, is a popular mode for weak signal text message communications. • Echo is a mode supported by WSJT-X for moonbounce activities (see PDF at siliconchip.au/link/abt6). • PSK Reporter (https://pskreporter. info) shows reception reports for a large variety of digital modes. Map data can be seen at siliconchip.au/ link/abtg • Reverse Beacon Network (www. reversebeacon.net) maps reception reports and propagation paths from stations heard by listening stations. • VarAC (www.varac-hamradio. com) is a peer-to-peer chat program for hams developed by Irad Deutsch 4Z1AC. • WSJT-X (https://wsjt.sourceforge. io/wsjtx.html) is a software suite that can utilise many popular digital modes such as FST4, FST4W, FT4, FT8, JT4, JT9, JT65, Q65, MSK144, WSPR and Echo. • With WSPR (Weak Signal Prop- agation Reporter), a station sends out an extremely low-power digital signal that others hear and report via the internet. It enables the determination of current propagation paths. The mode is unsuitable for conversations. It is supported by WSJT-X. Some people run WSPR all the time; you can even buy a dedicated low-power transmitter to do so (www.zachtek. com/wspr-tx). You can find maps at siliconchip.au/link/abth For additional information on digital radio, see our articles on that subject in the April and May 2021 issues (siliconchip.au/Series/360). Maidenhead Locator System The Maidenhead Locator System, also known as the QTH locator, grid locator or grid square, among other names, is a system used by hams to indicate their approximate location for various applications (see Fig.19). The world is divided into 324 Maidenhead fields, which themselves are further divided into 100 squares. The locator for any address can be determined at siliconchip.au/link/abt7 Using ham radio in emergencies The large variety of digital modes that hams can use includes: • Digital mobile radio (DMR), a digital voice mode. • D-STAR digital voice mode for Icom, Kenwood & FlexRadio systems. After Cyclone Tracy hit Darwin in 1974, communications and power were lost. It was hams who first reestablished comms links to authorities. The story is detailed at https://armag.vk6uu.id.au/1984-dec-AR.html (pages 14-15). Also, from the WIA, “Amateur Radio notably handled emergency communications for the 1939 Black Friday bushfires, Cyclone Tracy in Darwin 1974, Ash Wednesday bushfires 1983, the Newcastle Earthquake 1989, and the Black Saturday disaster in February 2009. There have been numerous other rescues and searches.” The Wireless Institute Civil Emergency Network (WICEN; https://wicen.org. au) is an organisation of Australian hams that provides emergency communications in the event of a failure of public communications infrastructure. The Bendigo Amateur Radio and Electronics Club (www.barec.net.au) also practices emergency preparedness. A report on one of their exercises is at siliconchip.au/link/abtd siliconchip.com.au Australia's electronics magazine Digital modes April 2024  33 Field Fig.20: how a Maidenhead locator specifies a location. Source: https://w.wiki/93Y7 Square Subsquare Longitude Extended square Extended square Latitude Subsquare Field Square Fig.21: Hiro, VK3EHG demonstrates ‘working’ an amateur satellite. Entering the Silicon Chip office address gives a grid square ID of QF56pf. The coding of the Maidenhead locator is demonstrated in Fig.20. There are four pairs of numbers; the subsquare and extended square pairs are used for additional precision. handheld rig. Satellite QSOs were demonstrated at the recent Rosebud Radiofest near Melbourne by Hirotaka (Hiro) Horiuchi, VK3EHG (see Fig.21). It is also possible to use SSTV to contact hams on the International Space Station. Amateur radio activities Distance records A complete list of VHF and UHF distance records for Australia is available at siliconchip.au/link/abti A record was set in the 50-54MHz band at 28,397km, between VK6JQ and TL8MB. In the THF band at 324GHz, the longest distance obtained was The following is a small sample of possible activities apart from QSOs (conversations) and digital modes. Amateur satellite It is possible to contact other hams via satellite with as little as a between VK3KH and VK3XPD with a range of 25m (they probably could have just shouted!). Field days There are many field day contest activities. Typically, the objective is to make as many contacts as possible on given frequencies. One I visited at McLaughlins Lookout in the Wombat State Forest was run by EMDRC member Peter Forbes VK3QI, about 80 minutes’ drive from Melbourne. The contest was run for VHF and UHF frequencies 50MHz to 24GHz. Around 500 contacts were Fig.22 (left): a partial view of the (foggy) Field Day site showing some antennas, including two dishes and an equipment van. The top dish has a 24GHz amplifier and transverter behind it, while the lower dish contains preamps and an antenna for 1.2GHz – 10GHz. Fig.23 (below): the transverters and amplifiers for 1.2GHz to 10GHz. 34 Silicon Chip Australia's electronics magazine siliconchip.com.au made over the 24 hours of the contest – see Figs.22-24. Hamfests and radiofests You can find a schedule on the Hamfests Australasia Facebook page (siliconchip.au/link/abt8). Moonbounce This activity is for advanced amateurs. Signals are bounced off the moon and returned or used to establish contact with other amateurs. There is an ABC news story about an Australian moonbounce pioneer Ray Naughton, VK3ATN at siliconchip. au/link/abt9 Another Australian pioneer was Doug McArthur VK3UM – siliconchip. au/link/abta Outdoor activities IOTA, Islands On The Air (www. iota-world.org) “...promotes radio contacts with stations located on islands around the world...” POTA, Parks On The Air (https:// parksontheair.com/) is “...for international portable amateur radio operations that promote emergency awareness and communications from national/federal and state/provincial level parks.” SOTA, Summits On The Air (siliconchip.au/link/abtb) “...is an award scheme for radio amateurs and shortwave listeners that encourages portable operation in mountainous areas.” Amateur radio organisations and societies ● Wireless Institute of Australia (WIA; www.wia.org.au) ● New Zealand Association of Radio Transmitters (NZART; www.nzart.org.nz) ● American Radio Relay League (ARRL; www.arrl.org) ● International Amateur Radio Union (IARU; www.iaru.org) ● Australian Ladies Amateur Radio Association (ALARA; www.alara.org.au/index.html) ● The Radio Amateur Society of Australia (RASA; https:// vkradioamateurs.org) Radiosondes Some hams track, find, reprogram and repurpose radiosondes launched by the Australian Bureau of Meteorology (BoM) for weather measurements (see Fig.25). For example, they launch radiosondes twice daily from Tullamarine airport. They can be tracked via https:// sondehub.org and they eventually come down. If found, they can be reprogrammed and then used for ham balloon launches, radio orienteering (ARDF; https://ardf.org.au), or “foxhunting”, where one or more of these devices are hidden in the bush, and others have to find it. Note that these items are disposable, and the BoM does not want them back. WWFF “The WWFF program encourages amateur radio operators to operate portable equipment from designated parks and/or protected nature areas Fig.24: a ham radio operator using a transceiver inside the equipment van. siliconchip.com.au Australia's electronics magazine around the world...” (visit the www. wwffaustralia.com). Hamclock Hamclock (siliconchip.au/link/abtj) is a free app for the Raspberry Pi and other Unix-like systems that provide important information for hams. Specialised bands Specialised bands available to advanced amateurs, such as 2200m (ULF, 135.7-137.8kHz), 630m (VLF, 472-479kHz) and bands between 23cm (UHF, 1240-1300MHz) and 1.25mm (EHF, 241-250GHz). They usually require custom-made equipment, although the recent Icom IC-905 allmode microwave transceiver covers 144MHz (2m), 440MHz (70cm), 1200MHz (25cm), 2400MHz (13cm), 5600MHz (5cm) and 10GHz (3cm). That concludes our article, to find out more, we have placed useful links, YouTube channels and videos in a PDF SC (siliconchip.au/Shop/6/376). Fig.25: a disassembled Vaisala RS41 radiosonde, a type that can be reprogrammed. Source: https://0xfeed.tech/2022/05/ repurposing-vaisala-rs41radiosondes-for-amateur-radio-highaltitude-balloon-tracking/ April 2024  35 Project by Geoff Graham The Pico Gamer The Pico Gamer is a PicoMite powered ‘retro’ game console packed with nine games including three inspired by Pac-Man, Space Invaders and Tetris. With its inbuilt rechargeable battery and colour 3.2-inch (81mm) diagonal LCD screen, it will keep you entertained for many hours. T he Pico Gamer was inspired by the Game Boy series from Nintendo, introduced in 1989. They were small handheld battery-powered devices, initially with tiny monochrome screens and an eight-bit CPU. Over time, more feature-rich versions were introduced, and the series became a massive success, with over 100 million sold across all variants. The Pico Gamer is a marked upgrade on the original Game Boy, with a colour LCD screen, a dual-core 252MHz 32-bit processor, 2.5MB of internal game storage and a USB interface. It is easy to build, using just a handful of components, and fits nicely into a custom 3D-printed case. We based our design on the layout of the Game Boy Advance, with the control buttons on either side of the screen in a horizontal layout. Such a design is a natural fit for a handheld game console and has since been adopted by many other consoles. There are eight buttons on the console: four direction buttons (up, down, left & right) on the left, two control 36 Silicon Chip buttons (start and select) under the screen and two auxiliary buttons (A and B) on the right. An important feature is the built-in rechargeable lithium-ion battery; the original Game Boy used four AA cells. The Pico Gamer’s battery can last over eight hours, which is plenty for a long road trip, and can be recharged in under four hours using the built-in USB connector. It could even be recharged from a portable USB power pack in a pinch. The 3.2-inch LCD screen has a 66×50mm active area containing 320×240 pixels. It can display over 65,000 colours, which most games use to good effect. The screen is also touch-sensitive, although currently, no games use that feature. New games can be programmed in BASIC, so perhaps one of our readers will come up with one that does! The Pico Gamer has a mono audio amplifier and speaker for sound effects. Most games use them to create various beeps, squeaks and explosions. However, it is good enough to Australia's electronics magazine reproduce more complex sound effects and music, and some games do both. To see a gameplay video, visit: siliconchip.au/Videos/PicoGamer The processor The Pico Gamer is powered by the Waveshare RP2040-Plus. This is a pinfor-pin compatible clone of the Raspberry Pi Pico, with a few important upgrades. Firstly, it includes a lithium-ion battery charger, so that’s one less feature that needs to be designed into the circuit. It also uses a high-speed flash memory chip, so the RP2040 processor can be reliably overclocked to 252MHz, which is required for the more processor-intensive games. Finally, the RP2040-Plus has a 4MB flash memory chip rather than the 2MB of the standard Pico. This is important because we store the games in this flash memory, and the standard Pico has space for a limited number of games. However, the RP2040-Plus with 4MB can fit dozens of games, and you will be unlikely ever to fill that up. siliconchip.com.au Pico Gamer Kits (SC6911–3, from $85, two different cases available): see page 96 for more details Features & Specifications Games included in the Pico Gamer firmware » Dimensions: 198 × 90 × 22mm » Weight: 300g » Battery: internal 1100mAh LiPo battery » Runtime: approximately eight hours » External power/charging: 5V via USB at 260mA » Display: 66 × 50mm LCD, 320 × 240 pixels, 65,535 colours » Audio: 340mW from a 28mm diameter speaker » Internal storage: 14.5MB★ (sufficient for hundreds of games) » External storage: SD card up to 32GB, formatted as FAT16 or FAT32 » Sound test and demonstration » Button test » File Browser » A selection of pre-installed games (see the panel opposite) ★ or 2.5MB if 4MB RP2040-Plus is used, sufficient for 30+ games Using a standard Raspberry Pi Pico in the Pico Gamer would be possible. While it would work, you would have to keep it tethered via a USB cable for power. Also, you will need to install a custom version of the software because the software we supply is optimised for the 4MB (or 16MB) of flash on the Waveshare module. PETSCII Robots Lazer Cycle 3D Maze Pico Blocks Kingdom Snake Pico Man Pico Vaders Circle One In this complex strategy and exploration game, your goal is to enter the settlement and destroy the robots. The trick is finding the right tools and learning how to use them. Similar to the ever-popular Tetris game, your job is to rotate and position colourful blocks falling from the sky into a neat carpet, where they will vanish. If your pile gets too high, you will lose. You are on a fast Lazer Cycle, and so is your opponent. They will try to make you crash into a wall or track, and you try to do the same to them. It is a race to the death. You are the ruler of the Yellow River kingdom and must allocate resources between feeding the hungry people & defending against thieves. Don’t get it wrong, because the people might revolt. You are stuck in a 3D maze; your job is to explore and find a way out. You can call up a map to help, but it is not as easy as it looks. Guide your snake around the board, eating the good food and avoiding the bad. As you eat, your snake will get longer. You will need all your skills to avoid crashing into a wall! PicoMite software The software loaded onto the RP2040-Plus includes the PicoMite firmware we introduced in January 2022 (siliconchip.au/Article/15177). This is a powerful BASIC (MMBasic) interpreter for the Raspberry Pi Pico, with support for peripherals such as an LCD screen, SD card, sound etc. Because the BASIC language is built into the PicoMite, all games are written in BASIC. The latest versions of the PicoMite firmware provide an A: drive, which acts like an SD card that cannot be removed. This allows us to store programs, music files, images etc internally, without the need for external storage like an SD card. If you wish, you can plug an SD card (or microSD card in an SD card adaptor) into the socket on the LCD screen, and it will be available as “drive B:”. The menu system will allow you to siliconchip.com.au Inspired by the addictive Pac-Man game, you race around a maze, eating little dots while being chased by four ghosts. Eating a Power Ball gives you special powers, so you can pursue the ghosts instead! Based on the classic Space Invaders from the 1980s, you are faced with hordes of invaders who drop a steady stream of bombs while you dodge back and forth with your cannon, trying to shoot them down. switch to this drive and run games from it. However, this is not a requirement, and usually, the internal file system (drive A:) is sufficient to store all the games. The PicoMite also implements flash slots as alternative storage places for programs. There are three of them, and when a program is run from one of these, it does not need to be loaded Australia's electronics magazine This game’s objective is to eat the apples and grow while your opposition (the computer) will try to do the same. The one who grows to the maximum size wins. It is a simple but entertaining game that is perfect for young children. into the main program memory, so it executes quickly. The Pico Gamer’s menu program is stored in the first flash slot, so it is always ready to run. Acknowledgments The Pico Gamer is based on the work of many people from around the world. The concept of a Game Boy lookalike using the Raspberry Pi Pico April 2024  37 Fig.1: the Pico Gamer has three main components: the RP2040-Plus microcontroller module, 3.2-inch touchscreen and audio amplifier/speaker. The RP2040Plus module incorporates a battery charger, so we can just connect the LiPo battery directly to it. was pioneered by Tom Williams in the UK, and he designed the Game*Mite with some help from Australian Mick Gulovsen. He published his design on The Back Shed Forum (siliconchip.au/ link/absd) and it has been quite successful, with several hardware clones and many extra games added to its repertoire. The games themselves came from authors including Martin Herhaus (Germany), Harm (Netherlands), Tom Williams (UK) and Geoff Graham (Australia). Tom Williams also wrote most of the utility programs. You can contact these authors on The Back Shed Forum with suggestions and bug reports if you need to. We have kept the hardware features of the Pico Gamer compatible with the Game*Mite, so games and programs written for one will run on the other. If you wish, you can even load Tom’s full firmware package for his Game*Mite onto the Pico Gamer, and it will run equally well. Circuit details As you would expect, the circuit (Fig.1) is dominated by the 38 Silicon Chip RP2040-Plus module. The eight game buttons connect directly to the processor, pulling the associated input pin low when pressed. Programs running on the Pico Gamer configure these pins as inputs with internal pullup resistors, so external resistors are not required. The power switch in the off position disconnects the battery and disables the power supply in the RP2040Plus. The latter is done so that the Pico Gamer will shut down even if it is connected to a USB power supply. The battery charger in the RP2040Plus will terminate at 4.2V, the correct voltage for standard LiPo batteries, so it will not overcharge them. When the Pico Gamer runs on battery power, the protection circuit within the battery will automatically disconnect the load so you cannot damage the battery by accidentally leaving the console on. The LCD screen is connected to the processor via an SPI bus, which drives the display, touch controller and SD card socket. The LCD and the audio amplifier are both powered by the RP2040-Plus via its 3.3V output. This is used because the Pico’s onboard DC-to-DC converter ensures Australia's electronics magazine a constant output voltage regardless of the battery voltage, which can vary from 4.2V to about 2V. The sound output is generated as stereo pulse width modulated (PWM) signals from digital output pins GP20 and GP21. These signals are filtered and summed by the two 330W resistors and the 100nF capacitor. The resultant mono audio is fed to an SSM2211SZ audio amplifier, which drives the speaker in a bridged configuration. With a 3.3V power supply, the SSM2211SZ does not generate much power, but the volume is ample for a handheld device. Sourcing the parts We are offering kits that include all parts except the battery (which can’t be sent by airmail). There is the option of no case (if you want to print your own), a basic case that you can paint any colour and a more expensive black case that shouldn’t need to be painted. So that’s one way to get the parts to build the Pico Gamer. You can get a suitable 1100mAh 3.7V LiPo battery from your local Altronics store (Cat S4724) or a local seller on eBay. siliconchip.com.au The front of the PCB has the 3.2-inch LCD screen, buttons, switches, audio amp IC & passive components. The rear of the PCB holds the RP2040-Plus, battery, volume potentiometer & speaker. It is necessary to solder the RP2040-Plus flush with the PCB so that the USB connector aligns with the cutout in the case. If you want to gather the rest of the parts yourself, here are suggestions: The core of the Pico Gamer is the Waveshare RP2040-Plus, available from Waveshare (www.waveshare. com), Amazon and Australian distributors such as Little Bird Electronics (littlebirdelectronics.com.au) and Core Electronics (core-electronics. com.au). You only need the 4MB version; make sure you purchase it without header pins, as it must be soldered flush with the PCB. The battery charger socket on the RP2040-Plus is a two-pin Molex PicoBlade with a 1.25mm pitch. The matching plug with attached wires is commonly used in drones and can be purchased from drone suppliers (such as www.dronepartsgarage.com. au). Note that many battery connectors on offer are JST-style connectors, such as JST-SH or JST-XH, which are incompatible. Another way to get a matching connector is to buy a battery on eBay that comes fitted with a PicoBlade connector. You can then cut this off and use it as the charging cable, while the now unterminated battery leads can be soldered directly to the PCB. siliconchip.com.au The LCD is a 3.2-inch panel with a 320×240 pixel resolution using the ILI9341 controller. There are many on offer on eBay and AliExpress, but make sure the vendor’s photo matches Fig.4 (shown at the end of the article), as there are some incompatible designs that will not physically fit. You can purchase the display without the touch interface, which would work fine as no games currently use that feature. However, you will only save about a dollar, so you might as well get it regardless. The large, coloured tactile switches have 8mm diameter buttons and can be purchased from Altronics, Jaycar or RMS Components in Australia and New Zealand, as well as international suppliers. We found that the Altronics version had a better ‘clicky’ feel, but your preference might differ. The tactile switches for the start and select functions need a relatively long shaft of around 9mm, with a total height of 13mm (including the button base). These can be found on eBay and AliExpress. Alternatively, you can purchase a longer-shaft version from Altronics (Cat S1119) and trim it to a total height of 13mm. Australia's electronics magazine The volume potentiometer is a standard 16mm logarithmic type sold by Altronics (Cat R2233) and on eBay and AliExpress. The value is not critical; it can be in the range of 10kW to 50kW, but its depth must be less than 10mm to fit in the case, and it should have an 8mm-long knurled shaft as it is used without a knob in this design. The loudspeaker used in this design is the DB Unlimited SW280408-1 (Mouser Cat 497-SW280408-1, DigiKey Cat 2104-SW280408-1-ND). This was chosen as it’s small but has decent sound quality and is easy to mount using four small screws. Even if you don’t have a 3D printer, getting custom-designed 3D-printed case pieces is relatively easy. The two STL files defining the top and bottom halves of the case can be downloaded from the Silicon Chip website and sent off for fabrication. There are numerous online 3D printing services but we recommend JLCPCB. You only need to upload the files to their website and select their SLA process using LEDO 6060 resin (https://jlc3dp.com/3d-printingquote). They will then make and ship the case to you within a few days. The 6060 resin is strong, with no warping, and the surface is smooth in a slightly translucent off-white colour. However, note that this material can yellow slightly with age, so you might want to spray paint it. The 6060 resin readily accepts paint. An ideal paint for this purpose is Rust-Oleum Satin 2X Ultra Cover, available from Bunnings in many colours. Alternatively, you could use one of JLCPCB’s more expensive materials that are dyed or otherwise immune to yellowing, for example, “Black Resin” or “Imagine Black”. We offer one of those options in our kits for those who don’t want to mess around with paint and like the ‘stealthy’ appearance. Construction Only a few components are involved in the Pico Gamer, so construction can be completed in an hour or two. Four components (the RP2040-Plus, battery, volume potentiometer and speaker) mount on the rear of the PCB, with the rest on the front side. The PCB is marked FRONT and BACK to help with the orientation. The Pico Gamer PCB is coded 08104241 and measures 188 × 80mm. April 2024  39 Parts List – Pico Gamer 1 double-sided PCB coded 08104241, 188 × 80mm 1 custom 3D-printed case in two pieces (upper and lower), 199×90×26mm (see text) 1 Waveshare RP2040-Plus module with 4MB or 16MB flash memory, without header pins [Waveshare SKU 20290 (4MB) or 23503 (16MB)] 1 3.2in LCD touchscreen, 320×240 pixels, with ILI9341 controller and SD card socket 1 900-1100mAh 3.7V LiPo cell [Altronics S4724] 1 SSM2211SZ 1.5W audio amplifier, SOIC-8 (IC1) [DigiKey, Mouser, RS] 6 SPST momentary tactile switches with 8mm diameter buttons, 5×5mm pitch, in various colours (S1-S4, S7, S8) [Altronics S1094/5/6/8/9 or Jaycar SP0720/1/2/3/4] 2 SPST momentary tactile switches, 4×6mm pitch, 13mm height (S5, S6) 1 PCB-mount miniature DPDT slide switch (S9) [Altronics S2060, Jaycar SS0823] 1 DB Unlimited SW280408-1 8W loudspeaker [Mouser 497-SW280408-1, DigiKey 2104-SW280408-1-ND] 1 10kW logarithmic potentiometer with 8mm spline shaft [Altronics R2233] 5 100nF 50V X7R multi-layer (‘monolithic’) ceramic capacitors, 5mm pitch 1 4-pin header, 2.54mm pitch 1 2-pin Molex PicoBlade plug, 1.25mm pitch, with attached leads 4 M3 × 16mm panhead machine screws 4 M2 × 6mm panhead machine screws 1 can of spray paint (optional; see text for recommendations) 1 double-sided foam adhesive tape strip or pad [eg, from Bunnings] Resistors (all 1/4W 1% or 5% axial) 1 27kW 1 18kW 2 330W The PCB fits neatly into the 3D-printed case. When the two halves of the case are screwed together, it has the optimal dimensions for a handheld game console with a smoothly rounded shape that fits well in the hands. During construction, refer to the overlay diagrams, Figs.2 & 3, to see which parts go where. You can also check the photos. Start with the SSM2211SZ audio amplifier chip, which is in a small 8-pin surface mount package that is much easier to fit when no other components are in the way. This mounts on the front side of the PCB and should be soldered using the standard technique for SMD ICs. Apply a little flux paste to the PCB pads and place a small amount of solder on a corner pad. Position and hold down the IC, observing the dot marking pin 1, and tack solder one of the pins using the solder on the pad. Check and correct the IC’s alignment, then tack solder the pin in the opposite corner. With the IC secured, apply more flux paste and, with the bare minimum of solder on your iron, place its tip on the end of each pin, letting the solder flow around the pin and the solder pad. Finally, inspect your work with a strong magnifier (×10 or ×20) and correct any problems with more flux paste and solder-wicking braid. Next, you should install the RP2040Plus on the rear side of the PCB. This sits flush on the PCB, making it a surface-­mounted component. Ensure that it is aligned centrally on the solder pads and that the USB socket is at the top, protruding over the edge of the PCB. The battery charger plug and cable can be soldered now. Note that the colour of the wires (red/black) crimped to the connector might not match the polarity marked on the RP2040-Plus. Check this, and make sure that the lead from the + side of the connector goes to the pad marked + on the PCB regardless of the wire’s colour. Next, fit the resistors and capacitors. There are nine in total, and none are polarised, so installation should be easy. The parts list includes resistor colour codes, but you can also use a DMM set to measure ohms to verify their values. Installing the LCD screen 40 With its custom 3D-printed case, the Pico Gamer is a professional-looking game console. It comes with nine games, including some inspired by Pac-Man, Space Invaders and Tetris, that work well with its colourful 3.2-inch LCD screen. The inbuilt rechargeable battery lets you play for up to eight hours at a time. The next component to install should be the LCD panel. For height reasons, it is not socketed; instead, the pin headers go through the holes in the PCB and are soldered on the other side. These displays are notoriously Australia's electronics magazine siliconchip.com.au Silicon Chip sensitive to static discharge, so make sure that you ground yourself before unwrapping it and avoid handling it too much, especially its connecting pins. Most LCD panels are supplied with the main connector header pins installed, but you will need to add a four-pin header for the SD card interface in the locations marked SD-CS etc. Then insert the LCD panel into position on the front side of the PCB and push it down until it is flush with the PCB. Turn the PCB over and temporarily place it in the top section of the 3D-printed case, ensuring it sits correctly on the four mounting pillars. Next, push down on the LCD screen’s header pins until the LCD glass is flush with the case’s front bezel. You can then solder and trim the pins. The reason for this operation is to ensure that the LCD’s glass will sit flush with the front bezel while compensating for minor variations in the 3D printing of the case. Don’t force the LCD hard against the case, as that could interfere with the touch function; a flush contact is all that is required. Next, fit the volume potentiometer by inserting it through the back of the board, with its locating pin in the hole provided, then tighten the supplied nut over the washer to hold it in place. After that, bend the solder tabs towards the PCB and directly solder them to the pads provided. Now attach the speaker to the rear of the PCB, with the front of the speaker cone facing through the hole. The speaker is held in place by four M2 machine screws inserted from the front side of the PCB which self-tap into the speaker’s mounting holes; nuts and washers are not required. Once it is securely in place, solder its two wires to the nearby terminals. After that, mount the coloured button switches, the long shaft tactile Figs.2 & 3: there are components mounted on both sides of the board. As there are not too many, it shouldn’t take long to assemble. They are all pretty easy; IC1 is surface mounting, but its pins are wide enough to be soldered individually. siliconchip.com.au Australia's electronics magazine April 2024  41 switches and the power switch, all on the front of the PCB. You can use whatever coloured buttons you want; our kits will come with the same set shown in the photo below. If you order the kit with the dark grey/black case, the black button will be white instead for better contrast. The battery is soldered last. Secure it in its marked position on the rear of the PCB using double-sided adhesive foam tape. Kits will include a rectangular pad that might need to be cut down if it’s too large. The battery (cell) will typically come with a connector that needs to be cut off and the leads directly soldered to the PCB. Remember that the battery will be supplied partially charged, so do not accidentally short its leads when trimming them (cut them separately) and ensure that the power switch is in its off position before soldering the battery to the PCB. Also ensure that one lead doesn’t accidentally come in contact with the opposite lead or pad during soldering. Before installing the PCB in the case, if you have the off-white (6060 resin) case, both halves can be spray-painted in your choice of colour. This allows you to customise the case and protects the plastic from the environment so it won’t go yellow over time. The two halves of the case are held together by four 16mm-long M3 On the rear of the Pico Gamer is the USB Type-C connector for charging or connecting to a desktop computer for firmware updates and writing games. There is also a full-size SD card slot for extra game storage (microSD cards can be used with commonly available adaptors). machine screws inserted in the bottom half of the case that self-tap into the plastic of the top case. This works well, but it is not strong enough to survive repeated disassembly, so make sure that you test the completed PCB before you screw the case together. Loading the firmware Installing the firmware on the Pico Gamer is easy. All you need to do is press the left-hand button (marked Boot) on the RP2040-Plus and plug the USB interface into your desktop or laptop computer while holding down that button. The RP2040-Plus will connect to your computer and imitate a USB flash memory drive. Most computers will then open a file management window showing the contents of this drive (which you can ignore). The Pico Gamer firmware file can be downloaded from siliconchip.au/ Shop/6/370 It will have a filename similar to “PicoGamerV1-2.uf2”. There will be two versions, one for 4MB modules and one for 16MB, so select the appropriate one for your build. Drag and drop that file into the imitation USB drive created by the RP2040-Plus. When the copy has finished, your Pico Gamer will reboot and display the main menu. The firmware file you uploaded contains everything needed, including the BASIC interpreter with all the necessary options set, the menu program stored in flash slot 1 and the internal file system with all the games and their supporting files (images and music). There is nothing extra that you need to install or configure. Just start playing. In the future, you can update the firmware without opening the case by connecting the USB socket to a desktop or laptop computer and, using a terminal emulator, interrupt the running program by pressing CTRL-C, then enter the following command: UPDATE FIRMWARE This will have the same effect as disassembling the case and holding The original colour of the case is white as shown in this photo. The case in the lead photo was spray painted in the “Satin Claret Wine” colour. For the buttons, you can choose whatever colours take your fancy. This main menu is displayed immediately after powering on the Pico Gamer. The up/down buttons allow you to select a game and pressing SELECT will run it. If you choose a directory, the contents of that will be displayed instead. When an SD card is inserted, you will have the option of playing games from it too. 42 Silicon Chip Australia's electronics magazine siliconchip.com.au the Boot button on the RP2040-Plus. Using the Pico Gamer The first thing that you need to do is charge the battery. To do this, connect the USB socket on the rear of the console to a charger via a USB-C cable and switch the Pico Gamer on. The charging time from completely flat is about four hours. When the Pico Gamer is running on battery and the menu is displayed, an estimate of the battery’s charge (high, medium or low) will be displayed on the bottom line of the main menu. When you turn the Pico Gamer off, the battery is completely disconnected so that it will keep its charge for a long time if it is not used (a year or two). Because the battery is disconnected when the device is off, it will only charge when the device is switched on and plugged into power. Also on the rear of the case is the slot for a full-size SD card. Cards up to 32GB formatted in FAT16 or FAT32 can be used, and when a card is inserted, the main menu will show an option for selecting it (button B). When the SD card is selected, the menu system will show the directories and executable files on it in the same format as the internal file system. The A button allows you to swap back to the internal file system if needed. Whenever the Pico Gamer is powered up, it will run the menu program (in flash slot 1) and display the main menu. Using the menu is intuitive – you use the up/down buttons to select a game or program and press select (SEL) to run it. Subdirectories are also shown in the menu list, and if you choose one of them, it will show the contents of that directory. In most games and within the menu, the select (SEL) button on the front (under the LCD screen) is used to select an option or exit the current mode. The START button is generally used to start a game running or pause it if running, although that can differ between games. The functions of the other buttons are defined by the game. Typically, the four navigation buttons (on the left) are used to move in various directions, while the A and B buttons (on the right) fire guns, drop bombs or perform other similar functions. The easiest way to permanently install a new game is to copy it to an SD card and insert the card into the siliconchip.com.au The 3D-printed case While a few Silicon Chip projects have used a custom 3D-printed case before, this is the largest and most complicated one so far. The good news is that, besides being able to get the case in kits, companies also exist that can do the printing for you. And because they use large industrial machines and a wide range of materials, they can do a great job. In the past, we would make our own PCBs at home, including the cutThis ting, etching and drilling. case was Few people would do that made by these days because commercial JLCPCB using companies do such a good job fabriStereolithography cating PCBs at a very competitive price. (SLA) and the 3D printing is starting to go the same way. LEDO 6060 resin. A custom case has many advantages over buying a standard ABS plastic box. For a start, it has the optimal dimensions for the design, and it can have a smoothly rounded, ergonomic shape. It can also have the correct holes and cutouts precisely positioned, and they will be perfectly formed – not the jagged mess that can happen when they are cut by hand. Another benefit is the thin and professional bezel around the LCD panel. That has long bedevilled designs incorporating an LCD panel – achieving the perfect thin rectangular bezel by hand is tough. However, it can be done easily with a 3D-printed case. A typical medium-sized 3D-printed case will cost $20-50 to make, which is good value given that you get precisely what you want with all the holes and various features properly made for you. Design software If you wish to design your own case, you first need to decide on the 3D modelling software you will use. There are quite a few free packages to choose from. However, many are not quite as intuitive and accomplished as modern PCB design packages. Suitable packages range from Tinkercad, which runs in a browser and is aimed at beginner and educational users, through to more heavy-duty offerings such as Blender. Blender is free and open source; it is very capable and can do almost anything. It also has a very steep learning curve with many ‘gotchas’ and non-intuitive operations that can trip you up. We settled on Blender because we needed to create a very smooth bevel on the corners of the case, and we wanted to position features with a precision of a fraction of a millimetre. However, the steep learning curve caused us to pull out a lot of our hair in the process. If you plan to use Blender to design an instrument case, we recommend this tutorial video as it covers most of what you need to know: https://youtu. be/rN-HMVTB7nk Fabricating the case When you have finished the design, you can export it as an STL file and send it to your fabricator of choice. There are many, both within Australia and overseas. We used JLCPCB in China, who are better known for producing PCBs but now they are moving into 3D printing. They offer quite a few technologies and materials, including 3D printing in metal. We chose their stereolithography (SLA) technology for the prototype, using the LEDO 6060 resin. This is one of the more cost-effective processes, and it produced a perfect result with all the special features positioned with pinpoint accuracy. Australia's electronics magazine April 2024  43 Pico Gamer. Then plug the USB into a desktop or laptop and, using a terminal emulator, interrupt the running program on the Pico Gamer with CTRL-C (full instructions are in the PicoMite User Manual). This will return you to the command prompt, where you can copy the game to the Pico Gamer’s internal file system with the command: COPY “B:filename” TO “A:” To return to the menu, enter: FLASH RUN 1 You will see your new game included in the menu. Writing games One of the best features of the Pico Gamer is that you can write your own games for it. It is not hard to do and can be a great learning experience. Programs are written in the BASIC language, which is easy to learn by design. The version of BASIC running on the Pico Gamer (MMBasic) has many features for displaying graphics and text, playing various sounds (including music) etc. To learn about this, download the PicoMite User Manual from the bottom of https:// geoffg.net/picomite.html There is an active community on The Back Shed Forum for people who are writing games for the Game*Mite and the Pico Gamer and posting them on the forum (www.thebackshed.com/ forum/Microcontrollers). If you write a game, you should join the forum and post your efforts there for others to enjoy. The best way to write your games is to plug the Pico Gamer’s USB port into your desktop or laptop computer. You can then use a terminal emulator program such as Tera Term to gain access to the PicoMite’s console and use the editor built into MMBasic to enter the program. The PicoMite User Manual goes into more detail on how to use the editor; it is a very efficient process with the ability to quickly jump between running the program and editing it. Another method is to use MMEdit, a program that runs on your PC and allows you to edit the program on the PC, then transfer it over USB to the Pico Gamer and run it with a single keypress. MMEdit is written by Jim Hiley in Tasmania and you can download it from www.c-com.com. au/MMedit.htm Detecting button presses When you write a game for the Pico Gamer, you need to keep a couple of things in mind. The first is how to detect a button press. The eight buttons on the Pico Gamer are connected to I/O pins GP8 to GP15 (physical pins 11 to 20) and will pull the pin low (ie, logic zero) when pressed. The first thing that your program needs to do is configure these pins as digital inputs with internal pullup resistors. For example: For i = 11 To 20 On Error Skip SetPin i, Din, PullUp Next i The “On Error Skip” command is necessary because some pin numbers in the range are ground pins, and MMBasic will throw an error when we try to configure them (or you could change the code to avoid the SetPin command for i=13 and i=18). To detect which button has been pressed, you can define a series of constants representing the pin numbers like this: Const bDOWN = 11 Const bLEFT = 12 Const bUP = 14 Const bRIGHT = 15 Const bSELECT = 16 Const bSTART = 17 Const bB = 19 Const bA = 20 Then, in your program, it is easy to determine if a button is pressed (pulled to a low level). For example: If Pin(bDOWN) = 0 Then ‘down button pressed If Pin(bLEFT) = 0 Then ‘left button pressed Exiting to the main menu The second feature that all programs must implement is to return control to the main menu when the user has finished playing and wants to exit. To do this, you need to insert the following command in your program: Flash Run 1 Fig.4: this is the LCD you should purchase for the Pico Gamer. They are available on eBay and AliExpress, but check that the vendor’s photo matches this image, as some incompatible designs on offer will not physically fit. The front of our display reads “HR4 8637S G6/2” along the touchscreen. MMBasic will immediately transfer control back to the menu program in slot 1 when this command is encountered. The final step is to install your program on the Pico Gamer. To do this, you simply copy it as a file to the directory called /GameMite in drive A:, ie, the internal file. You can use the XModem command or copy the file to an SD card and use that to transfer the file to the Pico Gamer. When the main menu program runs, it will scan drive A:, discover the new program and include it in the menu. So there you go, a modern handheld game console that encourages you to write your own games. For software updates, keep an eye on: http://geoffg. net/picogamer.html SC Australia's electronics magazine siliconchip.com.au 44 Silicon Chip EPIC Electronic DEALS! Loads of new lines in store, plus great savings on best sellers! Only until April 30th. NEW! 69.95 $ Build It Yourself Electronics Centres® Easy to set up anywhere! A 3615 SAVE $30 159 $ Mini Wi-Fi LED Projector Great for movie nights with friends and family! This compact projector offers excellent LED picture quality with 800x480p resolution for screens up to 4m (170”) wide! Very simple to set up with adjustable focus & projection distance (1-5m). HDMI input or Wi-Fi screen mirroring for playback directly from your device. NEW! Mini USB Flexi Light T 2125 Add light anywhere you have a standard USB type A port available. Great for shedding light on your keyboard. 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Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. The Pico Digital Video Terminal allows you to use boot-to-BASIC computers like the Micromite or PicoMite with a USB keyboard and HDMI display. You can even embed a PicoMite or WebMite inside the compact enclosure to create a small, standalone system. Raspberry Pi Pico Digital Video Terminal Part 2: by Tim Blythman T he Pico Digital Video Terminal is intended to be an update to the ASCII Video Terminal from 10 years ago. These terminals allow a microcontroller board to be directly connected to a keyboard and display so that a separate computer is not required. The ASCII Video Terminal only works with a VGA monitor and PS/2 keyboard. These items are becoming rarer and more expensive, while USB keyboards and monitors with HDMI inputs are inexpensive and widely available. A PicoMite attached to the Pico Digital Video Terminal becomes a modern equivalent of older eight-bit computers like the Commodore 64 or early Apple computers that were ready to be programmed in BASIC immediately after they were powered on. Last month, we described the operation of the Pico Digital Video Terminal, including how it interfaces with these modern peripherals. Now we’ll cover assembling, configuring and using it. We’ll also explain how to put a Pico­ Mite or WebMite inside the Terminal. on jumper JP2 (not JP1, JP3 or JP4). You can still install the headers but leave them open. Link terminal LK1 should have jumpers between pins 1 & 2 and pins 3 & 4. Permanent wire links can replace those headers if you won’t use the Terminal board for any other purpose. JP3 and JP4 select different default display modes, although the mode can also be configured in software via the virtual USB-serial interface. LK1 can be changed to enable a PicoMite or WebMite to be installed inside the Terminal instead of using a separate device connected externally to CON2. We recommend building the Terminal with header pins and sockets for each Raspberry Pi Pico, allowing them to be detached. That will ease testing, troubleshooting and initial programming, although it does preclude using the slimmer H0190 enclosure since the headers are too tall. Digital Video Terminal features & specifications To act as a standard Video Terminal, there should only be a shorting block » 640×240 pixel monochrome (80×30 character) display option » 320×240 pixel colour (53×20 character) display option » HDMI socket with DVI-compatible digital video » USB-A socket for keyboard (works with wireless keyboards) » VT100 terminal compatibility » USB-C socket for 5V USB power » Three status LEDs » Fits in a compact enclosure (105 × 80 × 25mm) » Tested with the Micromite, PicoMite and WebMite » Turns a development board into a standalone computer » Works with other USB-serial capable boards, including: Raspberry Pi Pico/Pico W (including CircuitPython & MicroPython); Arduino Leonardo; CP2102 USBserial converters; and Micromite/Microbridge » Baseline DVI output over HDMI connector » USB host for keyboard » Flexible and modular design siliconchip.com.au Australia's electronics magazine Options April 2024  49 Fig.4: there are a few small SMD parts in the Terminal, but nothing too tricky. Even if you have a fixed application in mind, we recommend fitting the headers, jumpers and links to allow it to be reconfigured in the future. Different front panel PCB designs suit the H0190 and H0191 enclosure options. The rear panel might require a single hole to suit a micro-USB cable, but we have not designed a rear panel PCB; it is easy enough to make the hole in the supplied plastic panel if required. We will have cutting diagrams later for those who wish to cut their own front and back panels. connector. Otherwise, reapply the iron to the existing joints and gently push the socket in the desired direction. It’s best to get this right before too much solder is applied. Solder the remaining pins, applying extra flux and fresh solder as needed. If you get a solder bridge, use flux and braid to wick up the excess. If in doubt, add more flux paste! To thoroughly check the soldering on these fine pins, clean up the flux Construction residue using an appropriate solvent First, check that you have equip- to give you a better view of the solder ment for basic SMD work. You will joints. If you are unsure, it’s better to need solder, flux paste (ideally in a do this now, as the nearby resistors syringe), a fine-tipped or medium-­ might make it difficult to repair later. tipped soldering iron, tweezers and Soldering CON4 could also be a litsome solder-wicking braid. A magni- tle tricky as it does not have any alignfier and some sort of fume extraction ment pegs. Apply flux and position the are also recommended. USB-C socket in place. Tack one lead Refer to the PCB overlay, Fig.4, and check the position before proceedduring construction; you can refer to ing. You could even use the front panel the photos too. The Video Terminal PCB (over the HDMI socket against the is built on a double-sided PCB coded edge of the PCB) to check that CON4 07112231 that measures 98 × 69mm. is positioned correctly. Start by fitting the HDMI socket, Adjust it if necessary, then solder the CON1, as it has the tightest pitch pins. remaining pins. These are more widely We found that the socket’s through- spaced than on the HDMI socket, but hole pins had some movement within you can also use solder braid to clean their pads, even though they are the up any bridges if they occur. recommended size. Gently holding the The two SOT-23 transistors, Q1 and socket towards the edge of the PCB Q2, are the smallest components and should help to centre it. can be fitted next. They are near the Apply flux to the pins and the pads, then clean the iron’s tip and add a Table 1 – SMD resistor codes minimal amount of fresh solder. Tack Value Possible codes one or an adjacent pair of the smaller 10kW 103, 1002 pins in place and check that they are 5.1kW 512, 5101 aligned, using a magnifier if necessary. You might be able to see better around 1kW 102, 1001 the unsoldered pins. 270W 271, 270, 270R If the alignment looks good, solder the four larger pins to secure the 22W 22R, 220, 22R0 50 Silicon Chip Australia's electronics magazine right-hand edge of the PCB. Apply flux, tack one lead, check for alignment of all the pins and solder the remaining leads when you are happy with the positioning. The last of the surface-mounting parts are 23 resistors of five different values. Be sure not to mix up the values. The M2012 (imperial 0805) sized resistors are large enough to have their values marked, so you can check these as you go along, referring to Table 1. They aren’t polarised. In each case, apply flux to the pads, position the resistors with tweezers, then tack one lead. Adjust if necessary, then solder the other lead once the initial joint has cooled and solidified. You can go back and refresh the first lead, adding more flux if needed. With all the resistors in place, clean off any excess flux. Use the recommended solvent and allow the board to dry. You can use this time to perform another inspection before the subsequent components make fixing any problems harder. Through-hole components Fitting the remaining parts by height, shortest to tallest, will ease the process. Slot the three tactile switches into place and solder them to the PCB. Follow with USB sockets CON2 and CON3. The sockets should all line up neatly with the holes in the front panel PCB. Next, mount the header sockets for MOD1, MOD2 and MOD3. Use the header pins and Picos to ensure they are fitted squarely and will align when needed. Check that the headers are pushed flat against the PCB when soldering them. You can then use the sockets to hold the header pins in place while they are soldered to the Picos. Like the sockets, ensure that all the pins are fully pushed in. Unplug the Picos after soldering the pins; do this carefully so as not to bend their pins. If you wish to solder the Picos directly to the PCB, you can use 2mm screws fitted temporarily to the corner holes of the Picos to align them to the PCB. It’s also possible to solder the Picos to the PCB using header pins only. Next, solder the four two-way jumper headers JP1-JP4 and the single four-way header LK1. Fit a jumper to JP2 (but not JP1, JP3 or JP4). Also, fit jumpers between pin 1 and pin 2 of siliconchip.com.au LK1 and from pin 3 to pin 4 of LK1. These correspond to the positions marked “USB” on the PCB. The three LEDs are mounted with the horizontal lead section about 3.5mm above the PCB, so the lenses shine through the front panel holes. Bend the leads by 90° directly behind the lens, being sure to bend the correct way, accounting for the polarity markings on the PCB (the shorter lead is the cathode [K]). The LEDs will be set back slightly from the edge of the PCB but will still protrude out the front panel enough to be seen. If you want them to be more visible, start the bend a bit further from the rear of the lens. The easiest way to align them with the front panel is to temporarily assemble the main PCB and front panel PCB into the enclosure. Trim the LED leads to around 6mm long and place the lenses in the holes in the front panel. There should be enough exposed pad area to tack each LED in the correct location from above. Remove the PCB from the enclosure and refresh each solder joint on the LEDs. That completes the PCB assembly. Initial tests Some basic tests can be done before plugging in the Picos. Connect a USB power supply to CON4, and you should be able to measure 5V between the pins of JP2 (or pin 40 of MOD1, MOD2 or MOD3) and the grounded shell of any of the connectors. 5V power will also be available at CON2 and CON3, so you should be able to power up a USB device plugged into these sockets. The two 5.1kW resistors only come into play if you are using a USB-C to USB-C cable. If you find that 5V is not present when such a cable is used, try a USB-A to USB-C cable. If that works, it points to a problem with those resistors or the CC1 or CC2 (configuration channel) pins of CON4. If you can’t measure 5V, check the soldering around CON4 and CON1. At CON1, the 5V and GND pins are adjacent, so a short circuit there will prevent 5V from being supplied. Correct any problems before proceeding. Programming Next, the Picos need to be programmed. Each has a different siliconchip.com.au firmware image, so naturally, they should not be mixed up. The Picos have a bootloader that emulates a USB drive, so programming requires nothing more than a computer and a micro-B USB cable. You can just plug the Picos into your computer if they are blank. If they have already been programmed, hold the tactile switch (S1, S2 or S3) corresponding to the Pico (MOD1, MOD2 or MOD3). While holding that switch, press and hold the BOOTSEL button on the Pico, then release S1/ S2/S3 and finally, release the BOOTSEL button. When the bootloader runs, a drive called RPI-RP2 should appear on your computer. This is only a virtual drive; a firmware file in the uf2 format can be loaded by copying it to the drive. Once the firmware is loaded, the drive will disappear. Start with MOD1, which is loaded with the file named 0711223A.uf2. After copying this file to the RPI-RP2 drive, MOD1’s onboard LED should light. We added this feature to indicate that the firmware is running on all three Picos. You won’t get any other immediate indications, although MOD1 should now present as a virtual USB-serial device to your computer. A serial terminal program like TeraTerm or minicom might display some data, but that is the most you will see until MOD1 is plugged into the PCB. Plug MOD1 into the PCB and apply power to CON4. If the LED on MOD1 lights up, you can connect your HDMI display. That should cause LED1 to light up, indicating that a display sink has been detected on the HPD pin. The display should also show a black screen with a white flashing cursor in the top left corner. If so, everything is working as expected so far, and you should power off the unit. MOD2 and MOD3 MOD2 is programmed with the file 0711223B.uf2. Again, not much will happen apart from the onboard LED illuminating. There will be a virtual USB-serial port, but nothing will be transmitted yet. Similarly, MOD3 is programmed with 0711223C.uf2 and its onboard LED will light when programming finishes. It also has a virtual USB-­serial port, but it will not show anything immediately. Plug MOD2 and MOD3 into their respective slots on the PCB and apply power at CON4. Plugging a USB keyboard into CON3 should cause LED3 to illuminate within a second or so. LED3 will also flicker if any keys are pressed on the keyboard. The Terminal is a compact unit once assembled. It certainly wouldn’t look out of place tucked under a TV, next to the Blu-ray player. Attach the dongle for a wireless keyboard, and you can program in BASIC from the comfort of your recliner! Australia's electronics magazine April 2024  51 You can also plug a USB-serial device into CON2 to test it; similarly, LED2 should illuminate and flicker when keys are pressed on CON3’s keyboard. If you don’t have such a device on hand, running a USB cable from CON2 to MOD3’s micro-USB socket should have much the same effect, since MOD3 (and indeed MOD1 and MOD2) are programmed to be USB-­ serial devices. If LED2 lights up when a keyboard is attached to CON2, you might have MOD2 and MOD3 mixed up. The sockets will make it easy to swap them. You can also power the Terminal from MOD2’s onboard micro-USB socket, which should transparently transmit data from whatever device is connected to CON2. Final assembly If all is well, slot the front panel into place and secure the PCB to the enclosure using the included screws. A few configuration steps require access to the micro-USB sockets of all three modules, so they should be done before closing up the Terminal unless you provide access through the rear panel to do this. If you wish to cut your own front panel, refer to Fig.5. Fig.6 is the cutting diagram for the back panel. The latter shows three rectangular cutouts, although most people will only need the middle one (or none). If you want to be able to access the USB connector on MOD2 from the back of the enclosure, you just need to make the hole in the middle of Fig.6. Note the different vertical offsets that are used depending on your Pico mounting option. If you need access to MOD1 or MOD3, then their cutout locations are also shown in Fig.6. Configuration It is possible to use the Terminal itself (plus a monitor and keyboard) to configure MOD1 and MOD3 by running a cable from the micro-USB socket on MOD1 or MOD3 to CON2. As long as all three modules are in a working configuration, you can enter commands on a USB keyboard attached to CON3 and view the output on a display attached to CON1. Unsurprisingly, though, MOD2 quickly locks up if connected to itself in this fashion! The configuration options for each Pico are different and are explained below. All three Picos can be configured from their virtual USB-serial terminals, so if you are using a computer to Fig.5: we have produced a front panel PCB to suit the H0190 and H0191 enclosures but you can follow this diagram if you want to cut your own. The included panels are 22mm tall for the H0190 case and 27mm tall for the H0191 case. Fig.6: the horizontal spacings for the rear panel are the same as the front, although the size and height will vary depending on how you have mounted your Picos. Since the included panels are translucent, it is easy to visually confirm the measurements before cutting. 52 Silicon Chip Australia's electronics magazine do this, you will need a serial terminal program like TeraTerm on Windows or minicom on Linux. Connect each Pico in turn by a cable attached to its micro-USB socket. That makes it less likely to interact with the wrong Pico! Open your serial terminal program and select the serial port corresponding to the Pico you wish to configure. TeraTerm, for example, will only display the available devices, so having just one device plugged in at a time will make it clear which Pico is being configured. MOD1 (display) options There are four groups of settings, each corresponding to one of the four possible combinations of JP3 and JP4. This means that the Terminal’s display can be configured either by the jumper setting or through the Terminal. You could also connect an SPST switch to either or both of JP3 and JP4 and use that to switch between the different modes if you plan to switch modes often. For simplicity, only the active (according to JP3 and JP4) settings can be edited. Changing the JP3 or JP4 settings while the Terminal is powered on will cause MOD1 to reboot and load the new settings. This is necessary due to the way the digital video library uses the Pico’s memory. Also, certain settings can’t be changed once set, so the simplest method is to restart the processor. That means you should also reboot MOD1 after changing settings to ensure they are correctly loaded. Due to memory and processor constraints, the monochrome video mode has a higher resolution than the colour mode. One of the options selects between those two alternatives. There are also options to set the visible number of rows and columns. Due to the higher memory requirements, the number of visible rows and columns are reduced in colour mode. If too high a value is selected, the display is truncated. The colour mode can display up to 20 rows of 53 characters. Each character is twelve by six pixels to fit within a 320 by 240 pixel display. The monochrome mode can display 30 rows of 80 characters, with the characters being eight by eight pixels (stretched vertically) within a 640 by 240 pixel grid. The pre-loaded default settings may siliconchip.com.au well work for you. With these defaults, if JP3 is out, the text is white on black, while it is inverted (black on white) if JP3 is shorted. With JP4 out, the monochrome 80 by 24 character display is selected; that is what the various Micromites and PicoMites expect by default. With JP4 in, a colour 53 by 20 character display is selected. The colour mode depends on the correct colour-encoding Escape sequences to display colours different to the defaults. Screen 1 shows the initial status display you can get by pressing the ‘~’ key in a serial terminal window, followed by the menu of configuration options. Pressing ‘A’ selects colour mode, while ‘B’ enables black and white mode. Typing ‘C’ or ‘D’ followed by a number will change the number of columns and rows respectively. Entering ‘E’ or ‘F’ will allow a colour to be chosen for the foreground and background. A list of the eight colours is provided to choose from. These are the colours available in VT100 terminals. Using ‘G’ to enable debugging will display information about the VT100 data being decoded, including regular keystrokes and VT100 Escape sequences. After setting your parameters, use ‘Y’ to save and then ‘X’ to reboot and reload the settings. If you plan to use multiple jumper settings, change the jumpers and repeat for each setting. In other words, the jumpers allow you to have up to four custom configurations, replacing the four default configurations. Screen 1: the MOD1 status display and setup menu. This is a display from the Terminal, which is configuring itself by connecting MOD1’s micro-USB socket to CON2. The Terminal is already doing away with the need for a separate computer! Serial options (MOD2) Only one setting is available to change on MOD2: the downstream USB-serial connection baud rate. That is only important if you are connecting it to something that implements a hardware UART (universal asynchronous receiver transmitter). For example, the Microbridge on a Micromite BackPack communicates with the Micromite using a UART at 38,400 baud by default. Other boards, like the PicoMite, do not use such a signal, so this setting is effectively ignored. The baud rate is set by MOD2 whenever its host changes it; the value is stored immediately in flash memory, so the setting is retained even if the Terminal is powered off. To set the baud rate to work with a siliconchip.com.au Screen 2: the only setting for MOD2 is the downstream baud rate. This can be set by simply using a serial terminal program to set the current baud rate, which is then saved to flash memory for later use. Here is where that setting is found in TeraTerm. USB Keyboard to UART Press ~ to show Setup Menu ----------------------------------------------------------------------Setup Menu: A: Typematic delay (300 ms) B: Typematic repeat (200 ms) C: Terminal emulation mode (VT100) D: Line ending (CR only) E: Toggle debugging (currently OFF) F: Set baudrate (currently 115200) Y: Save to flash Z: Restore defaults Enter typematic delay in ms: 300 Typematic delay set to 300 ms. Screen 3: MOD3 has numerous setup options, but none need to be changed to use the Terminal with a Micromite or PicoMite. The debugging option will report USB keyboard packets as they are received. Australia's electronics magazine April 2024  53 Screen 4 (above): MOD3 will also report (over its USB-serial link) what data is sent to MOD2, including VT100 Escape sequences, as shown here. device like the Micromite, open a terminal program, select the desired baud rate, then close the terminal program. That’s all there is to it! Screen 2 shows this setting in the TeraTerm program; it is found under Setup → Serial Port. Keyboard options (MOD3) Pressing ‘~’ in the serial terminal window for MOD3 should show something like the top part of Screen 3. Each displayed setting can be changed by selecting an alphabetic option, possibly followed by a number, then Enter. For example, to change the Typematic rate to 300ms, press ‘A’, then ‘300’ followed by Enter. Then use ‘Y’ to save the changes to flash memory. Typematic is a feature that makes a key auto-repeat if it is held down. The delay is the time between the first two characters appearing. The Typematic repeat is the time between subsequent characters (second and third, third and fourth etc). These times are set in milliseconds. The Terminal supports three emulation modes, like the USB Keyboard Adaptor for Micros (February 2019; siliconchip.au/Article/11414). The default is the VT100 mode that will work with Micromites and the like. Plain ASCII mode will only send 7-bit ASCII codes and cannot handle any special keys like arrow keys or function keys. Extended ASCII mode adds extra codes to map special keys to 8-bit codes beyond those defined by 7-bit ASCII. The codes are the same as for the USB Keyboard Adaptor for Micros and are listed on page 71 of that article. 54 Silicon Chip ◀ Screen 5 (right): if your Terminal is configured correctly, its display output from CON1 should match that seen in a serial terminal program. We’ve used a(n) HDMI capture device to overlay the two displays to show that they match. You could use these modes for a custom microcontroller application if you don’t want the complexity of multibyte VT100 Escape sequences. The line ending (generated when Enter is pressed) can be set to CR only, LF only (like Linux) or CR and LF (like Windows). When switched on, the debugging option will print USB HID packets as they are received from the attached (CON3) keyboard. The Terminal will also show debugging data when keys on the keyboard (attached at CON3) are pressed; Screen 4 shows the outcome of typing ‘test’, followed by the Enter key, four different arrow keys and a function key. The baud rate setting here is for the data from the GP4 pin of MOD3. The default of 115,200 is what is expected by MOD2, so don’t change it unless you are connecting MOD3 to something other than the Terminal. The ‘Save to flash’ option stores the current settings to non-volatile memory so that the settings are loaded at power-up. ‘Restore defaults’ can be used if the settings are corrupted; that is triggered automatically if an error is detected in the saved flash data. For standard uses of the Terminal, you should not need to change any keyboard settings. Still, you may like to tweak the Typematic options to suit personal preferences [a shorter delay and faster repeat rate makes moving the cursor around the screen quicker – Editor]. Secure the lid and affix the feet to the underside of the enclosure. The Terminal is now ready to use. Australia's electronics magazine If any of the Picos have unexpected behaviour, try programming them with the “flash_nuke.uf2” file. It will completely erase the flash memory, including any saved settings that could be corrupted. Then reflash the appropriate uf2 firmware file for the module. Final testing A complete functional test requires a device connected to CON2. One with an interactive terminal will allow the main features to be exercised thoroughly. A Micromite, PicoMite or WebMite would be ideal for this. If you have a spare Pico or Pico W, loading it with the PicoMite or WebMite firmware is easy. The uf2 files for these can be found on Geoff Graham’s website at https://geoffg.net/ or the Silicon Chip website: siliconchip.au/Shop/6/20 siliconchip.au/Shop/6/230 Hold the BOOTSEL button while plugging the Pico into the computer, then copy the uf2 file to the RPI-RP2 drive that appears. You can then unplug the Pico from your computer and connect it to the Terminal. You can also use a Micromite but MOD2 must have its baud rate set to match the Micromite. The Micromite’s default baud rate is 38,400; however, it can be changed by the ‘OPTION BAUDRATE’ command. Hook everything up as needed to operate the Terminal. The HDMI display should be plugged into CON1 and a USB keyboard into CON3. The Micromite or PicoMite should be connected to CON2. siliconchip.com.au Screen 6: many different USB-serial devices will work with the terminal, including most of those based on PIC16F1455 and PIC16F1459 chips. Here is the Ol’ Timer II from 2020 being set up without a computer. You won’t need to connect power to CON4; instead, connect MOD2’s micro-USB socket to the computer and open a terminal for that virtual USB-serial port. Now type on the keyboard and check that the Terminal shows the same result as the HDMI display. For the various ‘Mites, using the EDIT command to view and modify a program should exercise the VT100 Escape sequences quite well. Screen 5 shows a WebMite connected to the Terminal. We have laid a TeraTerm window over a view of the HDMI capture device connected to CON1. Both show much the same display, so the Terminal is working and configured correctly. If all is well, you can disconnect MOD2’s micro-USB lead and use the Terminal as a standalone device. If things don’t work as expected, you might need to modify some settings. For the Micromite and PicoMite, there are several applicable OPTIONs that can be set. To use the colour-coded editor in the Micromite or PicoMite, you will need to enable the colour display mode and run the following command on the Micromite/PicoMite: match the settings used by MOD1. If the display is wrapping or scrolling oddly, try reducing the number of rows or columns by one. Some TVs will ‘overscan’ and render parts of the display outside the screen’s viewable area. If you can’t fix this from within the TV’s settings, change MOD1’s settings to reduce the number of rows or columns. You might also need to tweak the OPTION DISPLAY setting similarly. Other devices You’ve probably already hooked up a wireless keyboard and 65in TV so that you can program your Micromite from the comfort of your recliner. But when it comes to other devices that will work with the Terminal, we are specifically considering those that will plug into CON2 and behave as USB-serial devices. We mentioned earlier that Micromites and PicoMites are not the only devices that can work with the Terminal. It supports many USB-serial devices, particularly those that don’t require special drivers to operate. Since many microcontroller boards implement a virtual USB-serial port, we have found that many of them will work. These USB-serial ports are often configured in software, so we can’t guarantee that all implementations will be configured in a compatible way. We have tested boards like the Arduino Leonardo; MOD2 recognises these and will communicate with them. The Terminal also works well with the USB-serial library we use for projects based on PIC16F1455 and PIC16F1459 chips. That includes the Microbridge (as built into some Micromites), but we have tested projects such as the Ol’ Timer II from July 2020 (siliconchip. au/Article/14493). Screen 6 shows Ol’ Timer II’s configuration interface being accessed from the Terminal. We haven’t tested them all, but we expect that projects like the DC Motor Speed Controller (October and December 2018, siliconchip.au/Series/328) or the USB Digital and SPI Interface Module (November 2018, siliconchip. au/Article/11299) will also work with the Terminal. So, if you can’t (or don’t want to) hook up a fully-fledged computer to a device in your workshop to configure it, there is now an alternative. A small wireless USB keyboard and a OPTION COLOURCODE ON Since the 53 columns available in colour mode are less than the default 80 columns used by the Micromite and PicoMite, you can also use this command: OPTION DISPLAY rows,columns It will make the ‘Mite’s terminal siliconchip.com.au The middle Pico is the regular version, while the ones on both sides are the H suffix version that comes with headers fitted. Australia's electronics magazine April 2024  55 Compiling the code yourself We supply precompiled uf2 files, making programming easy. However, if you wish, you can compile the sketches yourself using the Arduino IDE. We used version 3.6.0 of the arduino-pico board profile, along with version 1.1.0 of the PicoDVI library and version 0.5.3 of the Pico PIO USB library. The libraries can be installed from the IDE, as can the board profile for the Pico. More information about the board profile can be found at https://github. com/earlephilhower/arduino-pico portable HDMI monitor combined with the Terminal would be handy for places where you don’t want to risk damage to a device like a laptop computer (or don’t have room). We have also found that modules based on the CP2102 USB-serial chip communicate with the Terminal. That opens up the possibility of easily communicating with devices with only a plain hardware UART since those modules provide 3.3V level UART outputs. We sell such modules in our Online Shop (siliconchip.au/ Shop/7/3543). Programming in Python with the Terminal Shown next to a 15in laptop for scale, the Terminal is connected to a 40in monitor and a WebMite. The text is clear, even with sunlight on the screen. If you were looking for something larger than a 3.5in LCD panel, the Terminal offers many possibilities. Screen 7: the included font has extended characters from code page 437, used on the original IBM PC. It contains symbols and characters that can be used to display boxes, mathematical equations and low-resolution graphics. The BASIC code at the bottom shows how the extended glyphs can be printed. 56 Silicon Chip Australia's electronics magazine We tested Picos programmed with the MicroPython and CircuitPython firmware. They were recognised by the Terminal when plugged into CON2. MicroPython and CircuitPython are variants of the Python programming language optimised to work with microcontrollers. They typically implement a REPL (read, evaluate, print, loop) interface similar to that on the Micromites, so they could be used interactively if you prefer Python over BASIC. These Python variants do not appear to have a built-in editing program, but some people are working on adding features like that. Nevertheless, the Terminal is a good way to interact with such a device if it is already running some code. Embedding a PicoMite or WebMite If you want to tinker with BASIC and don’t need much in the way of external access to I/O pins, you can embed a PicoMite or WebMite inside the Terminal’s enclosure. To do this, the ‘Mite replaces MOD2 and directly communicates with MOD1 and MOD3 over their respective serial links. In this case, CON2 and the corresponding 22W resistors are not needed. LED2 can be kept and driven from BASIC by setting the GP14 digital output high. Start by loading a Pico or Pico W with the PicoMite or WebMite firmware. You will need to use a computer or Terminal to configure the PicoMite from the USB-serial port, as the hardware serial port is not configured by default. Run the following OPTION command (on one line): siliconchip.com.au OPTION SERIAL CONSOLE COM1,GP0,GP1,BOTH Now slot the PicoMite in place of MOD2 and change the LK1 settings to only bridge pins 2 and 3. This matches the INT setting marked on the PCB silkscreen. Assuming you are using the default MOD1 configuration, leave JP3 and JP4 off. If you want to use colour mode, fit JP4 and set the following options: OPTION COLOURCODE ON OPTION DISPLAY 20, 52 Now you can power the Terminal via CON4 or a USB cable attached to the PicoMite that has replaced MOD2. You should see the BASIC prompt on your display (try pressing Ctrl-C) and be able to use the keyboard to enter BASIC commands. Graphics The VT100 emulation that the Terminal provides does not have native support for graphics. Still, the included fonts contain some elements that can display low-resolution bitmap graphics, line elements and symbols that can be used to draw things like line art and mathematical equations. The whole font is shown in Screen 7. This is the output of a BASIC program that prints the entire character set. The line at the end shows some BASIC code demonstrating how the character codes can be used to display characters beyond the standard ASCII set. Future enhancements This is a handy bit of hardware, and we have covered some of the many possible uses of the firmware we have written. Both the Pico-PIO-USB and PicoDVI libraries are under active development, and we expect to see enhancements to them in the future. It may be possible in the future to add support for different USB devices (connected via CON2 or CON3) or new display features. In particular, the Pico-PIO-USB library is adding support for devices that can be connected when it is operating in host mode. Devices like USB flash drives and mouses appear to be already usable from the library. So, if you want to build a custom device that interacts with other USB devices, these and other uses may eventually be possible. As the PicoDVI library is developed, more display modes may become available. Since HDMI can also carry a digital audio signal over the TMDS interface, future versions might add sound as a capability. Library updates might even allow minor improvements to the Terminal without affecting its fundamental operation. Stay tuned! Conclusion The Pico Digital Video Terminal is a comprehensive upgrade to the ASCII Video Terminal. It allows the use of a modern USB keyboard and HDMI display with devices like the Micromite and PicoMite, turning them into standalone computers reminiscent of those from the 1980s. Its USB interface also works with all manner of USB-serial devices; it provides a cheap and convenient substitute to a fully-fledged computer when all that is needed is a keyboard and display. It is modular, and we expect many readers will rework and reprogram the Terminal to perform different roles, possibly even emulating other comSC puters and terminal types. USB to PS/2 Keyboard Adaptors Make it easy to use a USB keyboard on most devices that support a PS/2 interface. Both kits include everything except the Jiffy box and 6-pin mini-DIN to mini-DIN cable(s) – see SC6869, $10. The mounting hardware and optional headers and sockets are supplied. The Pico is supplied blank and requires programming. This version is standalone and includes a mouse adaptor. Perfect for older PCs with PS/2 sockets. ps2x2pico Kit SC6864 : $32.50 + postage This version fits into our VGA PicoMite project (July 2022, siliconchip.au/Article/15382), replacing its PS/2 socket. Can also be used standalone. For the VGA PicoMite Kit SC6861 : $30.00 + postage For more details, see the January 2024 issue: siliconchip.au/Article/16090 siliconchip.com.au Australia's electronics magazine April 2024  57 ROCK Model 4C+ The last decade or so has seen the introduction of compact and affordable single-board computers, starting with the Raspberry Pi Model B and followed by numerous successors and similar products. The Radxa ROCK Model 4C+ is compatible with much of the Raspberry Pi ecosystem but adds several novel features. Single Board Computer Review by Tim Blythman T he Raspberry Pi Foundation has set the standard for single-board computers (SBCs) with many models that have appeared since the Model B in 2012. While initially intended as a computer cheap enough to be used by classrooms of students, they have found many other uses. We have reviewed a number of their models, starting with the original Model B in May 2013 (siliconchip.au/ Article/3781) and, most recently, the Model 4B in August 2019 (siliconchip. au/Article/11772). It has been around five years since the release of the Model 4B, and the Raspberry Pi Model 5 has just been released. It wasn’t easy to get one, but we are working on a review now. While waiting for the Pi 5, we decided to review this ROCK SBC as it will make an interesting comparison. You might have heard of the shamelessly named Banana Pi and Orange Pi boards. The ROCK 4C Plus from Radxa also claims compatibility with the Pi Model 4B but has some unique features that appear to set it apart from other SBCs. Altronics is selling the ROCK Model 4C+, so they sent us one to try. We have heard reports of people using single-­ board computers as desktop computers, so we included that as part of our tests. The manufacturer Radxa (https://radxa.com/about) was established in Shenzhen, China in 2012 as one of the earlier manufacturers of SBCs. Their product history includes several products that parallel those from the Raspberry Pi Foundation, including compact ‘Zero’ boards and ‘Compute’ modules. Compute modules are minimal single-board computers intended to be used in large numbers. Like many of Radxa’s single-board computers, the ROCK 4C+ uses a system on a chip (SoC) incorporating the processor, memory, peripherals, connectivity and graphics processing unit Photo 1: a small u.FL antenna (shown enlarged) is included with the ROCK 4C+ 58 Silicon Chip Australia's electronics magazine (GPU). This one is the RK3399 from the Chinese fabless semiconductor company RockChip. The RK3399 is also the main processor in several tablets and Chromebooks, as are many of RockChip’s other SoC products. Radxa’s website also mentions a commitment to opensource philosophies. Data sheets, circuit diagrams and 3D models can be found at https://wiki. radxa.com/Rock4/hardware and several software repositories are online at https://github.com/radxa The ROCK Model 4C+ The documentation for the ROCK 4C+ states that it is the same form factor as the Raspberry Pi Model 4B and is compatible with Raspberry Pi 4 accessories, so we will focus our comparisons on the Raspberry Pi 4B. Photos 2 and 3 show the front and back of the ROCK 4C+. The external connections look much the same as on the Pi 4B; the important connectors, such as USB, HDMI and Ethernet appear identically located, as do the mounting holes. Note the power button, eMMC module socket and an unpopulated SPI flash chip, none of which are present on the Pi 4B. A nice touch not seen on the various Pi models is the colour-coding of the GPIO header; the siliconchip.com.au plastic surrounding the pins is coded according to their functions. 5V pins are red, 3.3V pins are yellow and ground pins are black. The generally usable GPIO pins are green, with two special function pins being blue. It’s no substitute for a full pin map, but it could help to avoid accidental damage. Table 1 shows the main features compared to the Pi 4B. When we reviewed the Pi 4B, the 8GB RAM option was not yet available. So, in the hardware stakes, the ROCK 4C+ is similar to the Pi 4B we reviewed. The big difference is the processor; most other features are identical. Keen readers will note that the Pi 4B was specified at 1.5GHz at launch, similar to the two primary cores of the ROCK 4C+; the 1.8GHz upgrade comes courtesy of a hardware update. Differences Some interesting features are noted in the Product Brief, which can be downloaded via the User Manual link on the Altronics ROCK 4C+ product page at siliconchip.au/link/absi Page seven notes that most of the GPIO (general purpose input output) pins are rated to 3.0V nominal logic levels, with a 3.14V maximum. However, one GPIO pin is specified to work with nominal 3.3V levels (up to 3.498V). In practice, we found that the I/O pins deliver a voltage close enough to 3.3V, so perhaps there has been an undocumented update to the hardware to match the more common 3.3V levels. Our board is marked version 1.41. One GPIO feature of the ROCK 4C+ that the Pi 4B lacks is an ADC (analog-­ to-digital converter); we can’t recall any other single-board computers that have an integrated ADC. This pin appears to be only connected to the ADC, so it cannot be used as a digital input or output. The ROCK 4C+ also supports an optional eMMC module (and Radxa offers such modules and adaptors for working with them), which it can also boot from. eMMC stands for embedded multimedia card and usually provides better performance and endurance than a microSD card. eMMC is an often-requested feature for the Raspberry Pi range, so clearly, Radxa is listening to its potential customers. The ROCK 4C+ can also boot from SPI flash, and the pins to do this siliconchip.com.au Photo 2: there are few surprises on the back of the ROCK Pi 4C+ except the optional eMMC module socket. Radxa sells eMMC modules and adaptors for those wanting storage beyond the standard microSD card. Photo 3: the main connectors of the ROCK Pi 4C+ are in much the same locations as those on the Pi 4B. The provision of a footprint for an (optional) SPI flash memory chip is sure to be handy for certain users. Table 1 – comparison between the ROCK 4C+ and Raspberry Pi 4B ROCK 4C Plus Raspberry Pi 4B RockChip RK3399T (6 cores) Dual 1.5GHz ARM-Cortex A72 + Quad 1.0GHz ARMCortex A53 1MB + 512KB L2 caches BCM2711 (4 cores) Quad 1.8GHz ARM-Cortex A72 1MB L2 cache Processor (CPU) 600MHz Mali T860MP4, four shaders, 256KB L2 cache 500MHz VideoCore 6, 1MB L2 cache shared with CPU cores GPU two micro-HDMI, up to 4K + 2K (60Hz with one or both) two micro-HDMI, up to 4K + 4K (60Hz with one or 30Hz for both) Display output HD stereo, up to 24bit/96kHz Stereo, PWM-based Audio output 4GB 1GB, 2GB, 4GB or 8GB RAM 5V/3A, USB-C or pin header 5V/3A, USB-C or pin header Power requirements 2× USB2, 2× USB3 2× USB2, 2× USB3 USB 1× Gigabit 1× Gigabit Ethernet 802.11 b/g/n/ac (WiFi 5) Bluetooth 5.0 u.FL antenna 802.11 b/g/n/ac (WiFi 5) Bluetooth 5.0 PCB antenna Wireless 40-pin header: 1× PWM 2× SPI channels 2× I2C channels 1× ADC (analog) channel 40-pin header: 4× PWM 2× SPI channels 2× I2C channels I/O Australia's electronics magazine April 2024  59 Screen 1: the Debian 11 image is the only official image with a usable graphical desktop environment. The desktop is quite familiar, even to those who may not have used Linux before. are available on the GPIO header or as an unpopulated footprint on the PCB. The ROCK 4C+ includes an RTC (real-time clock) chip; its function is part of the PMIC (power management IC), although it does require an external battery to provide backup power. The presence of an RTC is helpful, although marginally so, as NTP (network time protocol) is readily available through the internet. The MIPI (mobile industry processor interface) camera and display connectors are different from those on the Raspberry Pi boards, so we couldn’t try them out using the official Raspberry Pi displays and cameras. Adaptor cables exist that should allow the official Raspberry Pi devices to be used with the ROCK 4C+. Hands-on testing Screen 2: the Discover app allows other apps to be installed. We installed the LibreOffice Writer word processor and the Arduino IDE with ease. We even wrote part of this article on the ROCK. With the ROCK 4C+ being very similar, feature-wise and in general size and layout, to the Pi 4B, we need to look at software and support to see the differences. Like the Raspberry Pi computers, various Linux operating system (OS) images based on Debian and Ubuntu are available for installation, as well as an Android image. We started with the Debian distribution as this would theoretically be the most similar to the Raspberry Pi OS (formerly ‘Raspbian’). Installing the OS is much the same as for other single-board computers and requires a disk image file to be written to a microSD card. The zipped files for the ROCK 4C+ can be downloaded from https://wiki.radxa.com/ Rockpi4/downloads That page also has files for other ROCK boards, so be sure to choose the correct tab before downloading! We used a 3A USB Type-C mains power supply designed for use with a Raspberry Pi 4B, and it worked fine. You will also need one or two micro-HDMI to full-size HDMI adaptors (type-D male to type-A female) or cables, plus a USB keyboard and mouse. Debian Screen 3: the Ubuntu distribution only offers a command line interface (CLI) on the ROCK 4C Plus. Still, it was pretty easy to connect to a WiFi network and update the operating system. 60 Silicon Chip Australia's electronics magazine Screen 1 shows the Debian desktop after booting up, installing updates and basic configuration, such as connecting to WiFi. The Firefox web browser is pre-installed and shows the Radxa ROCK 4 operating system downloads page. siliconchip.com.au We were also able to install the free LibreOffice Writer word processor and actually wrote some of this article on the ROCK 4C+ using this software. Apps are easily installed through the Discover app, as shown in Screen 2. We found the Writer word processor app was quite functional, but the ROCK 4C+ struggled if a few web browser windows were open at the same time. All the included software was functional and intuitive enough to find, install, and use, but it tended to be a bit sluggish. We had no trouble using Bluetooth to send files to another computer. Those with meagre requirements might find the ROCK 4C+ a useful substitute for their Windows PC or as a second machine. The range of included and available software is quite good, but the processor is not fast by modern PC standards. We found many familiar programs ready to install, including the Arduino IDE. For all the time we were running Debian, the main processor chip was quite hot to the touch; it is clearly being worked very hard. We didn’t try any heatsink or fan options, but they may be worth considering for prolonged use in this role. Ubuntu The Ubuntu distribution available for download is actually a commandline-only server edition; its boot screen is shown in Screen 3. It is intended for users who prefer a command line interface, although there is a good introductory guide at https://wiki.radxa.com/ Rockpi4/Ubuntu The distribution is set up for headless operation (without a keyboard or display) and has an SSH server enabled by default. This could be a good way to get started with command line Linux, as the guide has information about using Bluetooth, WiFi and the GPIO header from the command line. It would be suitable for use as a web server, file server or similar roles. If you manage to corrupt the installation, it is easy enough to reflash the operating system image to the microSD card to recover it. Android We tried the Android 11 image available on the downloads page. It is currently the oldest supported version of Android, with version 14 being current. The Android system was siliconchip.com.au Screen 4: the Android operating system image had a few glitches that we could not easily resolve. As a result, we could not thoroughly test it, but most of the things that we tried worked as expected. functional (with a mouse instead of a touch screen), although it is apparent that the diminishing support affects usability. Screen 4 shows the home screen; the white banner at the top could not be dismissed and continued to sound an alert. That could only be muted by turning down the notification volume. Some of the installed apps needed to be updated to work, but we couldn’t do so due to the Google Play Protect error. So, the Android image will mainly be useful if you have a specific app you wish to run and can install without using the Play Store, for example, by side-loading the APK. After testing this, we came across a forum post explaining a multi-step process that can get rid of this error message and allow Google Play Services to run on the ROCK 4C+ but we have not tried it. You can find the instructions at siliconchip.au/link/absj Other options The downloads page lists around ten other third-party operating system distributions, including options for media centre use and game emulation. So it appears the ROCK 4C+ has broad community support for many operating systems. Forum The communities that have developed around ecosystems like the Raspberry Pi computers and the Arduino IDE have been instrumental in their usability and thus broad acceptance. The Radxa forum (https://forum. radxa.com/) is handy for engaging Australia's electronics magazine with other ROCK board users and finding answers to common problems. While trying out the ROCK 4C+, if we could not find where to change a particular setting, an internet search usually led us back to the forum and the answer to our question. Summary The ROCK 4C+ is an interesting alternative to the Raspberry Pi Model 4B. It has certain features, such as the optional eMMC module, that could give the edge to users with specific use cases. The analog (ADC) input on the GPIO header is another feature that could be very handy under some circumstances. The Debian distribution offers a decent desktop computer experience, even for those who have not tried Linux before. It will undoubtedly be familiar to anyone who has worked with Raspbian or Raspberry Pi OS. We don’t think it’s ready to replace a desktop computer completely, but it could be handy for light duties or as a second machine. Other distributions could turn the ROCK 4C+ into a games machine or media centre. At the time of writing, the ROCK 4C+ retails for about the same as a Raspberry Pi Model 4B. Altronics is selling the ROCK 4C+ (Cat ZR6302G) for $133. Order one before the end of April and get a free USB QC3.0/PD power supply/charger (normally $29.95). Jaycar is also selling the ROCK 4C+ (XC9300) and has a special price for Silicon Chip readers – see the inner front cover advert for details. SC April 2024  61 Skill Tester 9000 Part 1 – by Phil Prosser This old-school dexterity tester has added lights, timers, countdowns, sounds, noises and competition between players! Plus, it has plenty of construction fun, and you can modify it to your heart’s content. Background image: https://unsplash.com/photos/gaming-room-with-arcade-machines-m3hn2Kn5Bns T his project reinvents that simple and fun game of skill where you need to navigate a loop of wire along a convoluted path without sounding a buzzer. That old game had no clear ‘win or lose’ scenario, nor did it add competitive factors such as time limits or measuring your speed against your friends. The buzzer version is easy to design, but how about we add more sounds than just the buzzer, making it more exciting to play? Enter the Skill Tester 9000! This project is all about fun mixed with a bit of learning. Younger builders can just solder parts to the PCB to get a working game, while more mature constructors can look into how the logic works and change the sounds by varying resistor and capacitor values. When considering how to design this game, the obvious answer in 2024 is to grab a microcontroller and write everything in software, including the game logic and sounds. That would result in a board with just a handful of parts and a loudspeaker, which would be small and cheap. The problem is 62 Silicon Chip that it is not that much fun, and constructors cannot easily tweak any aspect of the project. There’s also relatively little to learn from such a design unless you’re willing to delve into the source code. Responding to feedback for ‘less micro stuck on a board’ projects and seeking to give builders a test bed on which they experiment with some old-fashioned discrete logic, we decided to stick to commonly available 4000-series logic chips and discrete through-hole components. While there are a lot of parts to solder, it is easy to build overall and delivers that therapy of soldering a bunch of parts to a board. We also think the result is pretty cool in an old-school way. Given this implementation, there is little in this project that you cannot tweak. Maybe it is just me, but I find that fun. As can be seen from the photos, the Skill Tester 9000 has a complicated wire ‘maze’ that you need to run a hoop along without touching. We have just added a bunch of technology to make it more fun and competitive. When Australia's electronics magazine building it, you need to decide how dastardly you make the wire maze, which affects the difficulty factor. It’s powered by a 9V battery that gives decent runtime and avoids the need for plugpacks and the like. It is, of course, possible to use a 9V DC mains supply, and all the parts on the board can operate over a wide voltage range, so there is no need for regulation if you take that route. Given that this project is entirely made from parts that have been available for around 50 years, the following question came to mind: why hasn’t it been done already? I think the answer lies in the cost of materials, especially the PCB. This project would be impractical without a double-sided PCB and moderately thin traces. As recently as 10 years ago, the PCB cost would have been prohibitive. Designing the game Watching youngsters play modern games, a few themes became apparent. • The games are competitive. • They often incorporate difficulty levels. siliconchip.com.au Fig.1: this simplified version of the game logic shows how it broadly works. The game starts after the circuit is reset and is won if the Win Pad is touched before either Lose condition is met (out of Time or out of Health from touching the wire). Sounds are produced for each time tick, if the wire is touched (and Health is lost), if the game is won and if the game is lost. • Characters ‘take hits’ and lose health; if this runs out, they lose. • The games have a sense of urgency, often in the form of time limits. • Sound plays a big role; we want to hear things like time passing, an alarm if the wire is touched, a distinctive tune for winning and a depressing tune for running out of time or losing all your health. We decided to use 4000-series CMOS logic to implement these functions, which is both cheap and widely available. We can do that as follows. Health is a commodity that starts full and is reduced each time the player touches the wire. A logic block must detect if the wire is being touched and determine the duration. We do this using a 4017 decade counter that we can ‘clock’ at a slow, medium or fast rate to implement three difficulty levels. That determines how long you can touch the wire before you run out of health and lose. To win, the player must navigate the course within a set Time. This is implemented in a logic block comprising a clock source, a 4026 digital counter and a 7-segment decoder. The clock speed for this counter can also be varied to determine how quickly you need to traverse the game to win. siliconchip.com.au Winning is pretty important. We have added a pad at the end of the course that the player must touch. This stops the timer and health counter, and if you have health and time left, it will play a victory song. The majority of the circuit components are to track health and time, determine the winning and losing conditions, and play the various sounds. Sounds are triggered if health is reduced as time passes and if the player wins or loses. While these parts all interact, they can be analysed as standalone blocks. Melodic sounds are better than a simple buzzer. We have taken a couple of approaches here, illustrating a few concepts we have seen over the years. The ‘touch’ sound uses a couple of logic-­based oscillators to make a twotone siren noise. This is implemented using Schmitt-trigger NAND gates and a few discrete parts. We have tweaked this to make it a nasty, alarming sound. The Tick sound for time passing is derived from the overall game timer and uses a similar siren circuit, but adds a very simple circuit to ‘shape’ the sound into a fast attack and slow decay. We have tweaked this to make the tick less of an alarm but still add urgency to the game. For the Win sound, we have used a Australia's electronics magazine circuit that allows us to play 10 notes, each at an independent frequency. This amounts to a clock circuit that defines each note length and a 4017 decade counter that changes the resistance in a 555 astable oscillator circuit. After each clock pulse, the resistor in series with the respective 4017 output sets the frequency of the 555, allowing us to program a 10-note tune by choosing those resistor values. The Lose tune is precisely the same circuit as Win, but we have set the resistors to make a sad tune rather than a happy one. Those of you with more musical sense than us may disagree with the tunes we have set – all you need to do to make your own is fiddle with these resistor values! Adding a diode would allow you to change the tune length if you want to; we will leave that to you. The resulting game logic is shown in the simplified block diagram, Fig.1. It performs the following tasks. • When the game is reset, the Time counter starts running, and the Health counter is reset to full. It is ready to play. • A ticking sound is made each time the Time counter is reduced. • During the game, touching the wire decreases your health and makes a noise. April 2024  63 Fig.2: this half of the circuit diagram includes all the game logic. Three identical debouncing sections are provided for each input (all at upper left), while the State Machine Registers section in the middle keeps track of the game state. The remaining sections implement the health counter, the time clock and some debugging LEDs. • If you reach the wire’s end and touch the Win pad before the time or health run out, the system goes into the Win state. It plays a happy song, and the Win LED latches on. • If the time or health hit zero before you touch the Win pad, the system 64 Silicon Chip goes into the Lose state. It plays a sad song, and the Lose LED latches on. The Win state can no longer be triggered until a new game is started. • In the Win or Lose state, the Time counter stops so you can see how fast you did it and the Health counter stops Australia's electronics magazine so you can see how much health you had left. • Pressing Reset starts another game. The Reset button is best as a pad at the start of the wire rather than a separate button. That way, you’re ready siliconchip.com.au can see each part of the circuit operate without the whole thing having to be complete and operational in one hit. That’s especially good for those with shorter attention spans. We have used a range of coloured LEDs on the health bar, starting with green and then going to yellow, orange and red as the Health bar runs down. After all, sound and colour communicate good and bad well, creating excitement, which matters in a game like this. Circuit details to go as soon as you start the game. Implementation This is intended to be a fun project that allows people to build and play with one another, show off some oldschool logic, and let people see how it works. Thus, the entire game is built on one PCB that houses the battery and speaker. It can be screwed to the board siliconchip.com.au that holds the Skill Tester 9000 wire. All solder pads have been made as large as practical and with good spacing so that younger people can build it successfully. There are quite a few bits, but you will note that, for example, all bar one of the diodes are the 1N4148 type that’s dead easy to solder. We have incorporated a lot of extra LEDs that show the system states so we Australia's electronics magazine The game is controlled by three key latches: Win, Time Lose and Health Lose. If implemented in software, it could be done as a classic state machine. The states have been simplified to a reset state and the three win/lose states to keep the parts count manageable. We use three D-type flip-flops to store the state of the game. After Reset has been asserted, the Win, Time Lose and Health Lose latches are all cleared to 0, and the game runs. The game continues until one of these latches is set; then, the game stops. While a flip-flop is technically not identical to a latch, they are similar, so we can consider them equivalent here. IC4a, IC4b and IC7a are the flipflops that store those states. These are 4013 D-Type flip-flops, part of the 4000 series of logic that came out in 1968, still widely available and used today. A flip-flop stores a single bit of data, where the Q and Q outputs represent the value stored. (Q is the inverse of Q; 1 instead of 0 or 0 instead of 1). The bar over the name means it is active low, or the inverse of the plain signal name. The device has data (D), set (S) and reset (R) inputs. The logic value present at the D input is stored in the flip-flop when the clock (CLK) signal transitions from low to high and then appears on the Q output. This only happens on the rising edge for most flip-flops, which is very important in digital design. The fact that data is only latched on the clock rising edge allows digital designers to work out all the delays in their system to ensure that the D input level is stable before the clock edge, or else things would go haywire. The set and reset pins on these ICs allow these latches to be set to one or cleared to zero asynchronously (ignoring the April 2024  65 clock input). That means these flipflops can also act like latches. Thankfully, our clock rates are 1-20Hz, about a billion times slower than your PC and a million times slower than the 4000 series logic can handle. However, the principle of latching and storing our few bits of data still applies. Our control logic is shown in the “state machine registers” section of the first part of the circuit diagram, Fig.2. Yes, this game is truly asynchronous! When the Reset line is high, all the latches are reset (the counters are also reset, but we’ll get to that later). When Reset goes low again, all three flip-flops have Q=0, and diodes D9, D7 and D12 ‘OR’ these signals together, producing a 0 on the Win Lose Latch line, starting the game. That line remains low until one of the flip-flop Q outputs goes high, at which point Win Lose Latch goes high. That means the game ends, and the counters stop, whether the player won or lost. The associated 4017 or 4026 counter IC will overflow if either time or health runs out. When this occurs, they have a carry-out (Co) pin that goes from low to high. That is connected to the clock input of our D-type flip-flop, which you will recall will clock the data on the D input to the Q output on the rising edge of the clock. So, if you run out of health or time, the Health Lose or Time Lose signal will go high. Our D-type flip-flops have a convenient Q inverted output, which is high when the game starts, and we can use AND gates to enable the Win input signal using IC5a and IC5b. When one of the Time Lose or Health Lose outputs goes high, the respective Q output goes low. That disables the input to the Win flip-flop, so you can no longer win the game until it is reset. If the player touches the Win pad at the end of the course, that generates a high Win signal that is ANDed with Time Lose and then Health Lose. The resulting signal drives the clock input of the Win flip-flop, causing its Q output (Win Latch) to go high. Once one of the latches is triggered, the only way for the system to become active again is for Reset to be touched, which resets the system to its initial state. Now that we know how the game control works, let’s look at how the timers and sound generation work. Each section is quite self-contained and generally is either triggered by a state or enabled by an event such as a clock tick. Sound generators The completed PCB of the Skill Tester 9000. We recommend you assemble the PCB in sections as shown on the silkscreen. The sound-generating part of the circuit is shown in Fig.3 (see overleaf). Together with Fig.2, these two diagrams show the complete circuit of the game. That’s except for the wand, wire, reset (start) and win pads, which connect to the terminals of CON2, CON3 & CON4; as shown in Fig.4. The touch sound generator is a classic CMOS logic sound circuit using two oscillators. The pin 1 input of NAND gate IC15a is tied to the positive rail (logic high), so the gate acts as an inverter, with pin 2 being the input (we could get the same effect by tying the two input pins together). The output goes back to the input through a resistor, and the input has a capacitor to ground, creating an RC (resistor/capacitor) oscillator. We use a NAND gate here because we have a Schmitt trigger input NAND gate IC, with positive-going and negative-­going input voltage thresholds about 1V apart. The voltage difference or ‘hysteresis’ is needed for it to oscillate when we apply feedback. To put it another way, let’s say the voltage at the input is increasing from 0V, and at 5V, the output switches low. The input voltage then starts to decrease, but it has to drop to 4V before the output will go high again. The resistor and capacitor values and hysteresis voltage combine to determine the oscillation frequency. So, with the 470kW resistor and 1μF capacitor, IC15a oscillates at about 1Hz. Its output produces a square wave that switches between 0V and Vdd (about 9V), which feeds pin 6 of IC15b. IC15b is also configured as an oscillator, and the time it takes to charge or discharge the 10nF capacitor to its threshold voltage depends on whether the output of IC15a is high or low. In this way, IC15a causes IC15b to oscillate at alternating frequencies (like a siren). The output of IC15b is gated by AND gate IC5d, controlled by the outputs of the three state latches and the touch Australia's electronics magazine siliconchip.com.au 66 Silicon Chip buffer. When the player touches the loop on the wire, the Touch line goes high, allowing the signal from oscillator IC15b to pass through to pin 11 of IC5d and the Touch Sound Out line. However, we only want touching the wire to produce a sound if the game has yet to be won or lost. Thus, if the game is in the Win state or one of the Lose states, the Touch line cannot pull pin 13 of IC5d high via the resistor because the Win or Lose latch is holding pin 13 of IC5d low via the associated diode. The resistor and diodes create a crude but effective four-input AND gate (Touch AND Win Latch AND Time Lose AND Health Lose). Parts List – Skill Tester 9000 How do we make a tune using 4000-series logic? Some may say that “tune” is generous. Others might think this is pretty cool. I find it amazing that parts like the 4000-series logic chips and 555 timers are half a century old and still in use. 1 double-sided PCB coded 08101241, 174 × 177mm 1 0.5in (12.7mm) common-cathode 7-segment LED display (DS1) [Altronics Z0190 (red) or Jaycar ZD1855 (red)] 1 PCB-mounting vertical SPDT regular (on-on) toggle switch (S1) [Altronics S1315] 2 PCB-mounting vertical SPDT centre-off (on-off-on) toggle switches (S2, S3) [Altronics S1332] 1 PCB-mounting 9V battery holder (CON1) [Altronics S5048, Jaycar PH9235] 1 9V battery (alkaline recommended) 1 57mm 8W loudspeaker [Altronics C0610, Jaycar AS3000] 3 2-way mini terminal blocks, 3.5mm pitch (CON2-CON4) [Altronics P2028] 1 2-way mini terminal block, 5/5.08mm pitch (CON6) 4 16-pin DIL IC sockets (optional) 6 14-pin DIL IC sockets (optional) 5 8-pin DIL IC sockets (optional) Hardware, wire etc 1 500 × 200mm × 12mm (approximately) timber baseplate 4 M3 × 16-25mm panhead machine screws (depending on baseplate thickness) 4 M3 × 6mm panhead machine screws 8 M3 shakeproof washers 8 M3 × 20mm tapped spacers 4 5mm or 3/16in × 30mm gutter bolts 8 5mm or 3/16in hex nuts 8 5mm or 3/16in flat washers 1 1m length of 2mm diameter steel wire (eg, from a coathanger) 4 1m lengths of heavy-duty hookup wire (eg, red, black, blue & yellow) 1 1m length of super-flexible silicone-insulated cable (for the wand) 1 1m length of 1mm diameter tinned copper wire 4 50mm lengths of 4mm diameter heatshrink tubing 4 ring or fork crimp lugs (to connect wires to the board) [Altronics H2051B, H2058B] 4 stick-on rubber feet [Altronics H0940] 1 small tube of superglue Semiconductors 1 4026B CMOS decade counter/divider, DIP-16 (IC1) 4 555 timers, DIP-8 (IC2, IC6, IC9, IC14) 3 4017B decade counter/divider, DIP-16 (IC3, IC8, IC13) 3 4013B dual D-type flip-flops, DIP-14 (IC4, IC7, IC12) 1 4081B quad 2-input AND gate, DIP-14 (IC5) 1 LM386N 1.25W mono audio power amplifier, DIP-8 (IC11) 2 4093B quad 2-input Schmitt-trigger NAND gates, DIP-14 (IC15, IC17) 4 green 5mm LEDs (LED1-LED4) 2 yellow 5mm LEDs (LED5, LED6) 2 amber/orange 5mm LEDs (LED7, LED8) 9 red 5mm LEDs (LED9-LED17) 55 1N4148 or 1N914 diodes (D1-D50, D52-D56) 1 1N5819 40V 1A schottky diode (D51) Capacitors 1 470μF 16V radial electrolytic 1 220μF 16V radial electrolytic 1 22μF 50V radial electrolytic 6 10μF 50V radial electrolytic 2 1μF 50V radial electrolytic 1 1μF 63V MKT 2 470nF 63V MKT 2 330nF 63V MKT 23 100nF 50V multi-layer ceramic 1 47nF 63V MKT 1 33nF 63V MKT 1 10nF 63V MKT 1 4.7nF 63V MKT Resistors (all 1/4W 1% unless noted) 2 680kW 5 220kW 6 56kW 1 22kW 30 1kW 2 470kW 3 120kW 2 27kW 3 18kW 1 10W 5 270kW 3 100kW 4 24kW 16 10kW siliconchip.com.au Australia's electronics magazine The ticking sound The Skill Tester 9000 makes a ticking noise every time the timer value decreases, from the initial value of zero until it reaches the terminal count of nine, and the game is lost. The circuit to generate the ticking noise is similar to that for Touch. While the Touch noise is supposed to be ‘angry’, we want the tick to create a sense of urgency and doom, but with just a little hope of finishing! The siren oscillator circuit, based around IC15c and IC15d, is the same but set for higher frequencies. We have added an amplitude modulator based on the components between output pin 10 of IC5c and the Tick Out line, which softens the sound somewhat. In a sense, this is a poor person’s voltage-controlled attenuator, so very much in the spirit of this project! It works as follows. Each time the Trigger line goes high, the two capacitors form a capacitive voltage divider, bringing the cathode of D47 to about half the supply rail voltage. This voltage decays as the capacitor discharges via the 10kW resistor to GND, or both 10kW resistors if pin 11 of IC15d is low. The result is a fast rise time with a slow, exponential falloff. In this way, the ‘tick’ pulses on the Time CLK line amplitude modulate the ~20Hz waveform from the IC15c/d oscillator. Winning and losing songs April 2024  67 68 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.3: the remainder of the circuit is dedicated to producing the various sounds. The Win song generator (top left) and Lose song generator (below) are similar but use different resistor values to produce different tunes. The touch siren and time tick sections are shown below those, and the output of the four sound generators are mixed using diodes, feeding power amplifier IC11 to drive the speaker. siliconchip.com.au Australia's electronics magazine April 2024  69 Fig.4: this diagram (reproduced from the article next month) shows how the Touch, Reset and Win terminals (CON2-CON4) connect to the wand, game wire and start and finish pads. Note that the ground wire going to the wand can connect to the lower screw of any of the three terminals. Fundamentally, the tunes are generated by a 555 timer set up in an astable oscillator configuration. That’s a fancy way of saying “free running”. The frequency of operation is defined as f = 1 ÷ (C × [Ra + 2 × Rb]). In our circuit, Ra = 1kW, C = 100nF and Rb is the resistance in series with the diodes from the 4017B (IC8 after winning or IC13 after losing). As the 4017B IC counts from 0 to 9, only one of its Q output pins is high at a time. The high output becomes the charging source for the 100nF capacitor in the 555 timer circuit, and the series diodes stop the other resistors from loading this down. This means we can set 10 different frequencies that the 555 oscillates at in sequence to make notes in our tune. The clocks for the 4017 that set the note pace/duration come from the sequence clock, another simple Schmitt-trigger oscillator based on IC17d. The 4017 ICs will count from 0 to 9 and then back to 0, repeating forever if we don’t stop them. To stop the tune after the 10th note, we use an extra flip-flop per 4017 IC, triggered by the 4017’s carry output. When triggered, the flip-flop latches the reset input of the 4017 and the RESET input of the corresponding 555 oscillator (they are different). After being reset, the Q output of the flip-flop (IC7b or IC12a) is high and the Q output is low. This holds both the 70 Silicon Chip 4017 and 555 in reset, so they are initialised but doing nothing. When the Win Latch or one of the Lose latches goes high, that clocks the WinSong or LoseSong flip-flop, taking the 4017 and 555 out of reset, and they start playing the 10 notes. The 4017’s carry output (CO) goes low after five notes and goes high again after 10. By combining these carry-out signals through two diodes, which are pulled high by 10kW resistors, we can use the carry-out lines from both 4017 counters to trigger End Of Tune as it is that final rising edge that the D-type flip-flop uses. This End Of Tune signal resets the WinSong and LoseSong flip-flops, putting both the 4017 and 555 ICs back into reset, thus stopping the tune. If you analyse the circuit, you will see two 10kW resistors that do nothing in regular operation, at the reset and RESET inputs of the 4017 and 555, respectively. We have included these so we can test the circuit before all parts have been mounted on the board; the final controller chips are added at the last stage. The timer To limit the game time, we are using a 4026 decade counter that can drive a 7-segment LED display. To minimise the parts count, we simply use unbuffered series resistors for the LEDs, which achieves good brightness but will cause reduced output Australia's electronics magazine voltage from the 4026 due to loading the CMOS outputs. The 4026 IC needs a clock, which we generate using a 555. This allows us to switch in different timing capacitors to make slow, medium and fast difficulty levels. The clock rate is about 1.5Hz on the quickest setting, giving a total of six seconds. On the slowest settings, each count is a little under 4 seconds, for a total of around 30 seconds. If you wish to change these speeds, you can change the values of the 10μF & 22μF capacitors. The Timer clock is cleared by the system reset line, ensuring that at the start of each game, the timer starts at 0. The Clock Enable input is driven by our combined Win Lose Latch signal that goes high if any of the Win, Time Lose or Health Lose latches goes high. This way, if the game ends for any reason, this timer stops. The only output from this circuit is the carry-out signal from the 4026, which in our circuit is labelled Out Of Time. This drives the clock input to the Time Lose latch; the rising edge of this ends the game. Health The ‘health’ status in games is usually a bargraph that goes from green to red. We use the now-familiar 4017 decade counter IC for this (IC3). In this case, we have connected LEDs to its output rather than clocking it to make a tune. That allows us to get creative with the LED colours. The 4017 is not intended to drive LEDs, but it does OK, provided you don’t want the 4017 outputs to drive other CMOS logic reliably, as the voltages will droop. The health counter is implemented like a hit counter. The longer you touch the wire, the more hits you take. We have implemented this by using the Touch input to enable a 555 timer. With that input low, the 555 (IC2) is in reset and produces no output pulses. While the Touch line is high, the 555 oscillator runs free. The output of the 555 drives the clock input to the 4017 counter. After either 10 touches or a time period long enough for 10 counts of the 555, the hit counter reaches zero health and Carry Out goes high. The remainder of the logic around this is identical to the Time counter. In this case, we have set the clock rate for the 555 to a much faster pace. siliconchip.com.au With the same 10kW and 100kW resistors for Rb and Ra, the slow count rate is set by a 1μF capacitor in parallel with a 33nF capacitor, resulting in 6.6Hz, allowing about 1.5 seconds of touch. The fast count runs at about 150Hz, so pretty much any touch ends the game. You can change these capacitor values. If you want to use electrolytics in these locations, you can; we have marked the “+” end of each on the silkscreen. The selection of LED colours warranted some discussion with my helper. The advice is that it definitely starts with green and ends with red. In between are as many colours as you can get a hold of. We have recommended using red, amber, yellow and green in the parts list. You can tweak the series resistor values if some are too bright or dim. Audio output The audio output section has a mixer/combiner implemented using more 1N4148 diodes. The output is pulled to ground with a 10kW resistor, then capacitively coupled to the LM386 amplifier. Its gain has been set to produce a generous sound level. Note that this diode mixer only works because we are combining digital signals. This circuit takes lo-fi to new levels! If you want to reduce the volume, we suggest adding a series resistor for the loudspeaker. 100W 1W would be a good place to start. To keep assembly simple, we have put a cutout on the PCB that will accept a 57mm speaker, which can be glued in place with super glue, Araldite or whatever comes to hand. Input debouncing Earlier on, we skipped over some of the details of how we detect touches on different parts of the wire in favour of explaining the game logic. The Win, Touch and Reset inputs have identical debounce circuits. When a switch closes, it is never perfect, and the connection ‘bounces’ for a few milliseconds. Many digital circuits are so fast that such bouncing can interfere with their operation. In each case, our input starts with a 1kW series resistor and normally reverse-biased diodes to ground and Vdd. This protects the circuit from static, which we expect will be present with enthusiastic hands and feet on the carpet. The inputs have a 56kW pull-up resistor and a 470nF capacitor to GND, which gives a time constant of 26ms. The arrangement of two 56kW resistors makes it roughly the same for rise and fall. This signal feeds a Schmitt-trigger input buffer, adding further immunity to bounce through its ~1V input hysteresis. The output of the Schmitt triggers goes to the game control logic and debugging LEDs, which let you see that these inputs are working. Next month Next month’s second and final article in this series will give all the construction details, including the PCB overlay diagram and how to make the wire and attach everything to the baseplate. Importantly, PCB construction is broken up into stages, and you can test new functions at the end of each stage. We’ll also have some hints on troubleshooting and how to play the game, SC including tournament rules. Silicon Chip as 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. ¯ 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). The USB also comes with its own case EACH BLOCK OF ISSUES COSTS $100 OR PAY $500 FOR ALL SIX (+POSTAGE) NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 JANUARY 2000 – DECEMBER 2004 JANUARY 2005 – DECEMBER 2009 JANUARY 2010 – DECEMBER 2014 JANUARY 2015 – DECEMBER 2019 WWW.SILICONCHIP.COM.AU/SHOP/DIGITAL_PDFS Ordering the USB also provides you with download access for the relevant PDFs, once your order has been processed siliconchip.com.au Australia's electronics magazine April 2024  71 Project by Tim Blythman ESP32-CAM LCD BackPack After we reviewed the Altronics Z6387 ESP32 WiFi camera module, we thought it would be great with an LCD BackPack. The ESP32-CAM LCD BackPack PCB connects the ESP32 WiFi camera module to a 3.5in LCD touch panel and makes it easy to reprogram the ESP32 module. W e were impressed by the ESP32 WiFi camera module when we reviewed it in the February 2024 issue (siliconchip.au/Article/16129). It is a compact module with a WiFi-­ provisioned ESP32 microcontroller and an OV2640 camera chip. It is also called the ESP32-CAM (the name is printed on its board). The module is easy to use. While the easiest way to retrieve camera images was to use a separate microcontroller (such as a Pico W BackPack) with WiFi, the onboard ESP32 is a capable 32-bit microcontroller. So it makes sense to use it in a standalone fashion and remove the need for a second microcontroller. This straightforward LCD BackPack for the ESP32-CAM module lets you do that. The ESP32 microcontroller can display camera images on the 3.5in LCD touch panel, while other circuit features simplify programming and communication. We’ve also written some sample Arduino code that will provide a basic demo of the BackPack and form a starting point for writing your own ESP32CAM LCD BackPack code. To demonstrate the standalone nature of the BackPack, the demo code does not use the WiFi features of the ESP32 processor (but you can if you want to). ESP32-CAM recap The ESP32-CAM contains an ESP32 sub-module, which in turn contains the ESP32 processor plus some passive components and a flash memory chip, the latter storing the program that runs on the processor. There is also a 72 Silicon Chip PCB antenna for WiFi and Bluetooth. The ESP32-CAM module adds a camera chip that uses 1.2V and 2.8V supply rails, provided by a pair of onboard regulators. A serial PSRAM (pseudo-static random access memory) chip provides working memory for image processing. There is a microSD card slot, a pair of eight-way headers for external connections, one LED to perform the role of a camera flash, plus the necessary smattering of passive components. We included a circuit for the module in the review article. The ESP32 sub-module has a socket for an external WiFi antenna, which can be used (instead of the PCB antenna) by changing the position of a single jumper resistor. ESP32-CAM LCD BackPack Kit SC6886 ($42.50 + postage): comes with the PCB and all nonoptional onboard components except the ESP32-CAM module. It does include the touchscreen. These lines are not connected to anything unless a microSD card is fitted in the socket, so the solution is simply not to insert one. While disabling the microSD card slot is a hindrance, the ample flash memory of the ESP32-CAM module still allows data to be saved in non-­ volatile storage. There are Arduino libraries, such as LittleFS, that can treat the flash memory as a file system to read and write files. Fig.1 shows the resulting circuit of the ESP32-CAM LCD BackPack. As you can see, it mainly provides connections between the headers for the ESP32-CAM and the LCD touch panel via CON3. The six signals we freed up are the minimum necessary to update the LCD screen and sense touches on the panel. Three lines are used for SPI communication: SCK (IO14), MOSI (IO2) and MISO (IO4). The LCD and touch panel controllers each have a CS (chip select) line, for which we use IO12 and IO15, respectively. The LCD controller also has a D/C (data/command) line, which we connect to IO13 on the ESP32 microcontroller. The LCD controller’s RESET line is tied to the ESP32’s E32_RST line, so the LCD is reset whenever the processor is reset. In any case, a software reset command can be sent to the LCD controller over the SPI bus. The LCD panel’s LED control line is tied high, meaning there is no control of the LED backlight; it is fully illuminated as long as the BackPack is powered. The biggest compromise we have made is that one of the lines to the Australia's electronics magazine siliconchip.com.au ESP32-CAM LCD BackPack We noted in our review that practically all the ESP32’s I/O pins are used up by features on the module. The camera chip alone requires 15 lines. To free up enough pins to control an LCD touch panel, we need to lose some functionality on the ESP32-CAM. We have chosen to disable the microSD card slot, as there is no other way to free up six easily-accessible pins. Fortunately, its control lines are broken out to the module’s headers, so we do not need to modify the module to access them. Fig.1: the ESP32CAM LCD BackPack is a little more than a breakout board that allows the ESP32-CAM module to be connected to a 3.5in LCD touch panel. A header for a CP2102 USB-serial module and a pair of tactile pushbuttons allow communication and programming of the ESP32 processor on the module. LCD touch panel (IO4) is also used to control the flash LED. However, it was already shared with the microSD card socket, so that brings no new challenges. We are using this line for MISO (master in/slave out), which is only used by the touch panel interface chip. Since there is a pulldown resistor on this pin, and it is only driven high when the touch panel sends binary ‘1’ data bits, the flash remains off except for brief moments when the touch panel controller is communicating. It’s low again so quickly that the resulting LED illumination is barely visible. We have added extra rows of pads on the PCB to allow the available pins to be broken out. There likely isn’t much that can be done with these, short of sourcing 3.3V or 5V power for external circuitry. Still, there is plenty of free space on the board, and no extra cost to add those pads. We have also added a CP2102 siliconchip.com.au USB-serial module, attached to CON1. It can be used to supply 5V power to the ESP32-CAM’s onboard 3.3V regulator from a USB power source. We could have taken 3.3V from the CP2102 module. However, its regulator is integrated into the CP2102 chip and would probably not be able to supply the current needed by the ESP32 processor and camera chip. Naturally, the CP2102 module also connects to the ESP32-CAM’s serial communication lines, providing a USB serial terminal to interact with the BackPack. Since there is spare space, we’ve also added a mini-USB socket footprint, CON2, which can be used to provide power to the BackPack if the CP2102 module is not fitted. Finally, two tactile pushbuttons, S1 and S2, are connected to the RESET and IO0 pins, respectively, pulling them to ground when pressed. These can be used to reset the processor or to Australia's electronics magazine put it into bootloader mode for uploading new firmware. So, even if you don’t need to connect an LCD panel to the ESP32-CAM, the BackPack can make programming and communicating with the module easier. It is much tidier than using a breadboard, which is what we used when prototyping the software for this design. If you wish to experiment, you could carefully follow the Fig.1 circuit diagram and wire it up on a breadboard. Still, the ESP32-CAM LCD BackPack is easy to build and inexpensive, so we recommend doing that instead. Construction The ESP32-CAM BackPack is built on a double-sided PCB coded 07102241 that measures 99 × 55mm. During construction, refer to its overlay diagrams, Figs.2 & 3 that show which parts go where. The only somewhat tricky part of April 2024  73 the assembly process is ensuring that all the components are fitted to the correct sides of the PCB, but the overlay diagrams and photos will help with that. They are all through-hole parts except for the optional mini-USB socket, CON2. CON2 should only be fitted if you aren’t using a CP2102 module. Be aware that you will need another way to program the ESP32-CAM module in that case. If you are fitting CON2, do so first. Apply flux to the pads and solder the larger mechanical leads to the PCB after checking that the locating pins have aligned the socket correctly. Then, clean your iron and carefully solder the smaller pads. Clean off any flux residue once you have finished soldering CON2 using an appropriate solvent (most pure alcohols will work). Allow the PCB to fully dry before continuing. Two eight-way female header strips are used to mount the ESP32-CAM module. Temporarily fit them to the ESP32-CAM and slot those into the pads on the PCB, making sure it is on the side marked for the module. Solder the headers in place, ensuring everything is neat and square, then detach the ESP32-CAM module so it doesn’t get damaged during subsequent steps. Slot the two switches into place on the other side of the PCB and solder them to it, then fit the tapped spacers to the outermost set of holes on the main PCB, on the same side as the switches. They should align with the holes for the 3.5in LCD panel. The innermost holes will align with a 2.8in LCD panel, although our software will not work with the ILI9341 controller on those displays. Numerous libraries are designed for these controllers, so if you want to utilise a 2.8in panel, you could develop your own software to work with it. Most constructors should stick with the higher-resolution 3.5in panel as it doesn’t cost much more. Plug the 14-way header socket into the header on the 3.5in LCD panel and align the LCD panel to the main PCB with the tapped spacers. This will allow you to solder the header socket squarely to the PCB. Note that you cannot have the four-way header (for the SD card socket on the LCD panel) fitted to the LCD panel, as it would foul the tactile switches. Also, remember that the CP2102 module needs to fit under the LCD panel. This module is usually supplied with right-angled headers, but you must use straight headers to mount it flat against the PCB. Sandwich the straight header between the PCB and the CP2102 module and ensure the CP2102 module is pushed down against the header. Tack one lead to the PCB and module, then confirm that everything is square and fits under the LCD panel before soldering the remaining pins. You can then trim the excess pin header length to keep the headers clear of the LCD panel. Another option is to use a matching set of male and female headers to allow the CP2102 module to be detached, although you may need to be creative to ensure that this fits under the LCD panel. If you haven’t already done so, fit the camera to the FFC (flexible flat cable) socket on the ESP32-CAM module. A pivoting black bar rotates upwards, allowing the cable to be slotted in. The black bar is pushed down to secure the camera. Then, use the attached tape to affix the camera chip to the microSD card holder on the module and plug the ESP32-CAM module into the headers. Fit the LCD panel and secure it with the screws. If you apply power now to the CP2102 module, you should see the LCD backlight illuminate, but not much else will happen until the ESP32-CAM is programmed to work with the LCD panel. Programming it Figs.2 & 3: the PCB is not difficult to assemble, although there are components on both sides. The eight-way male and female headers are fitted to the side marked ESP32 CAMERA MODULE. The remaining parts go on the other side, which faces the back of the LCD, allowing the camera to face outwards. We are using the Arduino IDE to program the ESP32 chip on the ESP32-CAM. To add support for ESP32 boards, go to the Board Manager section under the File → Preferences menu item and add “https:// dl.espressif.com/dl/package_esp32_ index.json” to the list of Board Manager URLs. Next, open the Board Manager itself and add the ESP32 board profile (search for “esp32”). You should add Australia's electronics magazine siliconchip.com.au 74 Silicon Chip Screen 1: the demo sketch updates the LCD panel as quickly as possible, showing the image at native resolution. At 96×96 pixels, it refreshes at 25fps, making it appear smooth. The camera orientation means horizontal and vertical flip must be on so the displayed image is the right way up. the version provided by Espressif Systems; there is also a version provided by Arduino, but it does not support the ESP32-CAM. We used version 2.0.14, but later versions should work equally well. Choose the “AI Thinker ESP32-CAM” board from the dropdown menu and set the serial monitor baud rate to 115,200. That is the default rate used by the ESP32, so it is handy for viewing boot and diagnostic data. Open the serial monitor to the serial port of the CP2102 module. Now open the “ESP32CAM_BACKPACK_DEMO” sketch and put the ESP32-CAM LCD BackPack into programming mode by pressing and holding S1 (RESET). While holding S1, press and hold S2 (IO0), then release S1, followed by S2. S2 must be held down when S1 is released to set the correct boot state. Pressing S1 first ensures that IO0 is not being driven by the ESP32 microcontroller when S2 is pressed. If IO0 is pulled low by S2 while being driven high, that could damage the chip (although it’s unlikely). You should see a ‘waiting for download’ message in the serial terminal, meaning that the ESP32 is in programming mode. If you see something different, try again. Upload the sketch, and the LCD should initialise and display an image. If that doesn’t happen within a second or two, briefly press the S1 (RESET) button to reset the microcontroller. If you still don’t see anything on the LCD, check the serial monitor for any error messages. That will include information about whether the camera was correctly detected and which model was found. There will be a constant stream of data as the sketch describes the images it is processing, so you may have to turn off auto-scrolling in the serial monitor. If the camera is not detected, power off the ESP32-CAM LCD BackPack and check the connection to the FFC connector on the ESP32-CAM module. Screen 2: the TEST button at upper right turns on the camera chip’s colour bar test. If you are not making out a clear image, the colour bar test should help identify whether the ESP32 is receiving correct image data. The colour bars’ appearance will change at different resolutions. Screen 3: at higher image capture resolutions, the demo sketch crops out the centre 240×240 pixels, which is like performing a digital zoom on the central part of the image. Here, we have tweaked the brightness and contrast settings to improve the image quality. Screen 4: the EFFECT setting activates image processing on the camera, providing special effects without extra load on the ESP32 processor. The EFFECT 2 setting is monochrome (compare this to Screen 3). The default effects set also offers reverse video and several colour tints. Demo sketch functions Screens 1 to 4 show some views of the LCD panel as it runs the demo sketch. The camera was pointed at a laptop screen showing the Silicon Chip website. The camera image is refreshed as quickly as possible and displayed inside the white rectangle. siliconchip.com.au Australia's electronics magazine April 2024  75 Parts List – ESP32-CAM BackPack 1 double-sided PCB coded 07102241, 99 × 55mm 1 UB3 Jiffy box (optional) 1 laser-cut Jiffy box replacement lid (optional) [SC5083 or SC5856] 1 ESP32-CAM module (MOD1) [Altronics Z6387] 1 3.5in LCD touchscreen (MOD2) [Silicon Chip SC5062] 1 CP2102 USB-serial module (MOD3) [SC3543] 1 6-way 2.54mm-pitch pin header (CON1; for CP2102 module) 1 SMD mini-USB socket (CON2; optional, instead of CON1) 1 14-way 2.54mm-pitch header socket (CON3; for LCD touchscreen) 2 8-way 2.54mm-pitch header sockets (CON4 & CON5) 2 8-way 2.54mm-pitch headers (CON6 & CON7; optional) 2 right-angled tactile switches (S1, S2) 4 12mm-long M3 tapped spacers 8 M3 × 5mm panhead machine screws 4 M3 × 8mm panhead machine screws (optional, to mount to acrylic lid panel) 4 1mm-thick, 6mm outer diameter M3 Nylon washers (optional, to mount to acrylic lid panel) The calculated frame rate is shown below the image. We found that the ESP32-CAM could achieve about 25fps (frames per second) when running at 96×96 pixels. Most of the processing time involves transferring data to the LCD controller. Several touch panel buttons are provided on the right. They are only scanned once per display update, so you may need to press longer when higher resolutions are set. The flash LED will flicker when the touch panel is scanned. The buttons provide access to a useful subset of the settings available on the camera chip. Later, in the Software section, we’ll note how you can find the full range of settings that can be changed from within an Arduino sketch. From the top, the TEST setting enables a colour bars test pattern, as seen in Screen 2. This can be used to test whether any problems are due to the camera chip itself, or if they are due to communications or processing faults elsewhere. The SIZE parameter cycles through several preset resolutions up to 640×480 pixels. Although the camera chip supports images up to 1600×1200 pixels, processing images that size would take too long and wouldn’t fit on the LCD screen without substantial cropping. Smaller images are displayed with a grey border, while images larger than the LCD resolution of 480×320 pixels are cropped, giving the effect of a digital zoom. 76 Silicon Chip The H-FLIP and V-FLIP settings mirror the image horizontally or vertically. We found that they both had to be turned on for the Altronics module to align the camera image with the image displayed on the LCD panel. The QUALITY setting changes the JPEG compression level used by the camera chip. Perhaps confusingly, lower numbers correspond to better image quality. This value can vary from four to 63, although we didn’t see much difference between the settings. The BRIGHTNESS and CONTRAST settings work as expected, although they can only vary from -2 to +2. Finally, the EFFECT setting provides some special effects performed on the camera chip, so they do not require any extra processing from the ESP32. The available effects include reverse video, black-and-white and several colour tints that can be applied. EFFECT 0 means that no special effect is applied. Software details Much of the demo sketch is involved in providing the user controls, allowing the settings to be tweaked. There is not much code needed if you simply wish to display an image from the camera on the LCD panel; the following is a guide to the minimum required to do so. The Arduino setup() function should call displaySetup() to initialise the LCD panel and camInit() to configure the camera chip. These functions can be found in the sketch folder, inside the files “LCD.h” and “camera_pins.h”, respectively. If you need to change the resolution, use the set_framesize() function. Like many other camera settings, this and similar functions are found in the “sensor.h” file, which is part of the ESP32 board profile. If you can’t find it on your computer, you can view it at https://github.com/espressif/ esp32-camera/blob/master/driver/ include/sensor.h To acquire an image, call the esp_ camera_fb_get() function. The frame buffer contains JPG data and can be converted to RGB bitmap data with the frame2bmp() function. Finally, the drawBitMap() function can be used to draw the bitmap to the LCD panel. This function definition can be found at the bottom of the main sketch. It takes care of cropping and Here is the BackPack board without the touchscreen panel, so you can see the positions of the USB-serial adaptor and right-angle tactile pushbuttons. The ESP32-CAM module mounts on the opposite side (it’s shown separately on the right). Australia's electronics magazine siliconchip.com.au ensuring that the RGB data triples are output in the correct order. You need to release the JPG buffer with esp_camera_fb_return(), and the bitmap buffer with free() once you have finished processing the data and before starting the next acquisition, or the program will quickly terminate due to memory exhaustion. The “ESP32CAM_BACKPACK_ DEMO_minimum” sketch from the software downloads is nearly the minimum needed, apart from some diagnostic error messages. It simply displays a camera image in the centre of the LCD. We have also written a sketch named “ESP32CAM_BACKPACK_FILE_ CAMERA”. This sketch programs the ESP32-CAM LCD BackPack to behave like a very basic digital camera, capturing and displaying images to and from the internal flash-based LittleFS file system. It has a small viewfinder preview that constantly updates and buttons to allow digital zooming up to four times. You can also scroll through the saved images and format the file system to delete all saved images. Enclosure option The stack of three PCBs, including ESP32-CAM module, BackPack PCB and LCD panel, stands roughly 40mm deep when assembled. It will thus fit neatly into a 44mm deep UB3 Jiffy box, such as Altronics’ H0203. The camera lens will sit a few millimetres inside the base of the box, so you will need to drill a hole to allow the camera lens to ‘peek out’. Alternatively, longer spacers, like the stackable headers used for Arduino boards, could be used to position the camera lens just outside the base of the box through a hole. You can use our SC5083 or SC5856 laser-cut acrylic lid panels to mount the assembly. These are available from the Silicon Chip Online Shop. You might also need longer self-­tapping screws that can thread through the extra depth of the acrylic. We have noted these optional parts in the Parts List. Note that the lens is not centred on the BackPack PCB due to the asymmetry of the ESP32-CAM module. The LCD panel and thus the acrylic panels are not symmetrical either. Conclusion A camera is a very useful sensor to be able to connect to a microcontroller, allowing images of the world to be captured and displayed. While the ESP32 is known for its WiFi capabilities, it is also a capable 32-bit processor wellsuited to image processing. The ESP32-CAM module is useful on its own, providing many of the features of a basic WiFi camera. The ESP32-CAM LCD BackPack adds to this by processing and displaying camera images on an LCD touch panel. We think it will be of interest to those looking to perform low-level image capture and processing. While adding the LCD panel to the ESP32CAM means that the onboard microSD card slot is not usable, alternatives such as the LittleFS flash file system SC exist. Ideal Bridge Rectifiers Choose from six Ideal Diode Bridge Rectifier kits to build: siliconchip. com.au/Shop/?article=16043 28mm spade (SC6850, $30) Compatible with KBPC3504 10A continuous (20A peak), 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: MSOP-12 (SMD) Mosfets: TK6R9P08QM,RQ (DPAK) 21mm square pin (SC6851, $30) Compatible with PB1004 10A continuous (20A peak), 72V Connectors: solder pins on a 14mm grid (can be bent to a 13mm grid) IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ 5mm pitch SIL (SC6852, $30) Compatible with KBL604 10A continuous (20A peak), 72V Connectors: solder pins at 5mm pitch IC1 package: MSOP-12 Mosfets: TK6R9P08QM,RQ mini SOT-23 (SC6853, $25) Width of W02/W04 2A continuous, 40V Connectors: solder pins 5mm apart at either end IC1 package: MSOP-12 Mosfets: SI2318DS-GE3 (SOT-23) D2PAK standalone (SC6854, $35) 20A continuous, 72V Connectors: 5mm screw terminals at each end IC1 package: MSOP-12 Mosfets: IPB057N06NATMA1 (D2PAK) TO-220 standalone (SC6855, $45) 40A continuous, 72V Connectors: 6.3mm spade lugs, 18mm tall IC1 package: DIP-8 Mosfets: TK5R3E08QM,S1X (TO-220) This is how the ESP32-Cam module mounts to the headers marked CON4 & CON5. The pin descriptions are marked on the other side of the PCB, as that is where we expect most readers will attach any accessories. siliconchip.com.au Australia's electronics magazine See our article in the December 2023 issue for more details: siliconchip.au/Article/16043 April 2024  77 PRODUCT SHOWCASE Altium Roadshow comes to Sydney this year Elevate your design expertise and engage with your peers, “fellow PCB Designers and Engineers”, at a no-cost event that is tailored just for you. Join us at the Altium Roadshow 2024 in Sydney, where the Altium team will delve into innovative strategies to unleash the full potential of our latest features of AD24 and more. Secure your exclusive seat today! The agenda for the Roadshow follows: Altium 4225 Executive Square, Suite 700 La Jolla, CA 92037 USA www.altium.com email.info.au<at>altium.com 12:00 PM: Registration & Refreshments 12:30 PM: Opening - Welcome & Introduction 12:35 PM: Company Update & What’s New 1:00 PM: Keynote speaker 1:40 PM: Altium Designer 24 Overview 2:30 PM: Tea Break 3:00 PM: Customer Story 3:40 PM: Ansys & Altium Collaboration 4:20 PM: Closing Note: The program is subject to change and will be continuously updated leading up to the conference. Visit https://go.altium.com/04-04roadshow-sydney.html for the most up-to-date information. Enjoy networking with the speakers and Altium experts. Altium Application Engineers will be available for one-on-one discussions, addressing technical questions, and engaging in conversations to gain insights into your priorities. This event is tailored for electronic engineers or PCB design team managers. Register early as seats are limited. Light refreshments provided. For any inquiries, email: email.info. au<at>altium.com ElectroneX Sydney 2024 headed for a sellout! Electronex – The Electronics Design and Assembly Expo returns to Rosehill Gardens Event Centre from 19-20 June 2024. Following a record event in Melbourne in 2023, which featured more than 80 exhibitors and was attended by over 1900 trade visitors, the Sydney event is close to being sold out. Electronex is Australia’s only major exhibition for companies using electronics in design, assembly, manufacture and service. The SMCBA Electronics Design and Manufacture Conference will also be held, featuring technical workshops from international and local experts. Electronex will feature a wide of range of electronic components, surface mount and inspection equipment, test and measurement and other ancillary products and services from local and international suppliers. 78 Silicon Chip Trade visitors can also talk to contract manufacturers that can design and produce turnkey solutions to meet their specific requirements. IPC Soldering Competition Following the success of the inaugural soldering competition in Melbourne, in an exciting new development, this year’s competition will be a round of the IPC World Championship with the winner invited to the finals in Munich in November! This is a first-of-its-kind joint promotion by IPC and SMCBA and further details will be announced in the lead up to the event. SMCBA Conference Since 1988, the Surface Mount & Circuit Board Association (SMCBA) has conducted Australia’s only conference dedicated to electronics design and manufacture in conjunction with Electronex. This year’s conference will feature a stellar line up of local and international experts. David Bergman, VP of IPC International, will give the keynote address “Digitalization of Electronics Manufacturing – Towards Smart Factory enabling Industry 4.0”. Other presenters include: • Mike Creeden, Founder of San Diego PCB Designs, who will present “Three Mutually Required and Australia's electronics magazine Competing Perspectives for Printed Circuit Engineering Success: Solvability, Performance and Manufacturability”. • David Hillman, Hillman Electronic Assembly Solutions LLC, will present “IMCs: Basic Metallurgy and Impact on Product”. • Rick Hartley of RHartley Enterprises will deliver “System Mechanical Design to Control EMI”. • Chris Turner, PCBA Test Engineering SME, will discuss “Creating an optimal PCBA design and manufacturing process” and “Examples of Design For Test (DfT)”. Visitors to the expo can register for free at www.electronex.com.au and for details on the soldering competition and conference visit www.smcba. asn.au Australasian Exhibitions and Events Pty Ltd Suite 11, Pier 35-263 Lorimer St Port Melbourne VIC 3207 Tel: (03) 9676 2133 mail: ngray<at>auexhibitions.com.au Web: www.auexhibitions.com.au siliconchip.com.au Using a MEMS Microphone as a Reference Microphone by Phil Prosser MEMS (micro-electromechanical system) microphones have advantages over electret mics, such as operating at ultrasonic frequencies. They also have good frequency response characteristics, so you can use them as reference microphones, as described in this article. W e received some Knowles SPU0410LR5H MEMS microphone elements from a kind reader named Richard Stone. They were sent to determine their suitability for use as calibrated microphones. That was prompted by our Calibrated Measurement Mic project (August 2023 issue; siliconchip.au/ Article/15903) that used inexpensive electret capsule microphones (ECMs). It used compensation and calibration to provide a flat frequency response, allowing those microphones to be used as measurement devices, eg, to plot the frequency response of a loudspeaker. The MEMS microphones we received are tiny (3.76 × 2.95mm) and connect to a PCB via under-chip pads. They also require a hole in the PCB that’s used as the aperture for the microphone, so they must be soldered to a PCB designed explicitly for them. Soldering them would be tricky for most of our readers. They are surprisingly inexpensive at only around $1 each (less in quantity). Happily, it turns out that you can buy these microphones already assembled to a board from TeensyBat: siliconchip.au/link/abt5 That is just one example; there are quite a few suppliers of similar ‘carrier boards’. The ones we tested came mounted on 7mm circular PCBs. The Knowles MEMS microphone needs a 1.5-3.6V DC power supply and provides an AC output. As a result, they can be connected to our Calibrated Microphone board but some minor modifications are required. These involve adding a 3.3kW series resistor and 3.3V zener across the microphone power supply to obtain a suitable voltage, as shown in the revised circuit diagram, Fig.1. To do this on the SMD version of the PCB, you have to cut the track between capacitor C6 (10μF) and resistor R4 (100kW), which is small but not too fiddly. This is shown in Fig.2, along with the added 3.3kW resistor and microphone wiring. If using an SMD resistor, it can be soldered across the pads spanning the cut location, although adding a miniature through-hole resistor, as shown, is easier. The equivalent changes for the through-hole version of the PCB are shown in Fig.3. In both cases, the rear of the 7mm round microphone PCB mentioned above is illustrated for the wiring. However, you might prefer to route the wires from the other Fig.1: the changes required to the original Calibrated Microphone preamp circuit are minimal. R8, R14 and the four compensation components are not fitted, a 3.3kW resistor replaces the track between pin 1 of CON2 and the 10μF capacitor, and a 3.3V zener across pins 1 and 3 of CON2 limits the microphone’s supply voltage to a safe level. siliconchip.com.au Australia's electronics magazine April 2024  79 Fig.2: this shows how to assemble the SMD version of the PCB and wire it up to the MEMS microphone. The through-hole 3.3kW resistor shown could be replaced with an SMD resistor across the cut section of track (soldered on top of the leads of the other components). Your microphone board might differ from the one shown here, so be careful to wire it up correctly. Fig.3: as with the SMD version, several components are left off the through-hole version of the PCB, one track is cut and a resistor and zener diode are added. Note how the striped end of the extra zener diode goes to the positive (supply) terminal of CON2. side to keep the area with the sensing hole clear. The pads labelled “G” are ground, “O” is the output and “+” is the positive supply. Note that while both of our boards have mounting locations for frequency compensation parts (two resistors and two capacitors), we leave them off for this microphone as it does not require compensation. The MEMS microphone connected this way works a treat. The resulting ‘calibration curve’ is shown in Fig.4. The cyan curve is the frequency response of this microphone, while the Dayton EMM-6 reference mic we used for the original project is in red. The calibration data we have for the Dayton unit only runs from 20-20000Hz, so I cut the measurements off there. Note that the speaker used for this test was rolling off in its response at low frequencies, so the measurements are noisy down low. The measured response is entirely consistent with published data. The MEMS microphone’s output level is much higher than the Dayton microphone, and per the data sheet, the SPL (sound pressure level) limit is not that high, so you will be limited in making near-field measurements or dealing with high SPLs. In terms of calibration, if you only want to measure up to 10kHz, you can probably ignore the calibration file or Fig.4: the raw frequency response of the Knowles MEMS microphone (blue) compared to the reference Dayton EMM-6 (red). The Knowles response is very close to what’s stated in their data sheet. The thinner, dashed red curve is the Dayton curve shifted up to make it easier to compare to the Knowles curve. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au Scope 1 (left): the MEMS microphone picks up 22kHz sound waves just fine. According to the data sheet, it will work up to at least 80kHz. The sensitivity drops off above about 25kHz, but it will definitely still pick up signals above that. Photo 1: this MEMS microphone has a footprint under 4 × 3mm and picks up sound via the small ‘acoustic port’ hole in the base. You can see how the pad arrangement makes it tricky to solder; the only practical method is reflow (IR or hot air). make one by taking data from the published curves. In my opinion, the critical frequency response areas are in your crossover zones, typically in the 100-5000Hz region, making these microphones an interesting option if you are OK fiddling with tiny ICs. Richard was interested in using them to measure the output of ultrasonic parking sensors. The only ultrasonic source I knew I had was an old-school remote from the 1960s, in which the ‘buttons’ make springloaded hammers tap brass rods. The resulting ultrasonic signals were picked up by the TV set. It was an unusual arrangement! I used this circuit to measure the output of that remote control, with the result shown in Scope 1. The two buttons generate high frequencies at relatively high levels; the one shown in Scope 1 is at 22kHz. That is above the range of human hearing, although it might freak out your dog or cat! The bursts are short, so if you could hear them, it would be as a click. So, as far as I can see, these are a real option for ultrasonic measurements. They are also pretty good for use as a basic calibrated microphone over the SC audible frequency range. Parts List – MEMS Reference Microphone SMD version Through-hole version 1 double-sided PCB coded 01108231, 64 × 13mm 1 Knowles SPU0410LR5H MEMS microphone on carrier PCB Semiconductors 2 BC860 45V 100mA PNP transistors, SOT-23 (Q1, Q2) 1 BC849C 30V 100mA NPN transistor, SOT-23 (Q3) 3 6.8V ¼W zener diodes, SOT-23 (ZD1-ZD3) [BZX84C6V8] 1 3.3V 0.6-1W axial zener diode (ZD4) [1N4728] Capacitors (M2012/0805 50V X7R, unless otherwise noted) 1 100μF 50V radial electrolytic (max 8mm diameter) 1 100μF 10V low-ESR radial electrolytic 1 10μF 16V X5R 3 1μF 50V non-polarised SMD electrolytics, 4mm diameter [Altronics R9600] 2 2.2nF 5% NP0/C0G 2 1nF 5% NP0/C0G 2 470pF 5% NP0/C0G Resistors (all SMD M2012/0805 size 1%, unless noted) 2 150kW 1 100kW 1 39kW 1 5.6kW 1 2.2kW 1 1kW 1 330W 2 47W 1 3.3kW (through-hole or SMD, 1/4W 1%) 1 double-sided PCB coded 01108232, 99 × 13mm 1 Knowles SPU0410LR5H MEMS microphone on carrier PCB Semiconductors 2 BC560 45V 100mA PNP transistors, TO-92 (Q1, Q2) 1 BC549C 30V 100mA NPN transistor, TO-92 (Q3) 3 6.8V 400mW or 1W axial zener diodes (ZD1-ZD3) [1N754] 1 3.3V 0.6-1W axial zener diode (ZD4) [1N4728] Capacitors 1 100μF 50V radial electrolytic (maximum 8mm diameter) 1 100μF 10V low-ESR radial electrolytic 1 10μF 35V radial electrolytic 3 1μF 63V/100V MKT 2 2.2nF 63V/100V MKT 2 1nF 63V/100V MKT 2 470pF 50V C0G/NP0 ceramic Resistors (all axial 1/4W 1%) 2 150kW 1 100kW 1 39kW 1 5.6kW 1 3.3kW 1 2.2kW 1 1kW 1 330W 2 47W This is an updated version of the parts list from the August 2023 issue. In short, the changes were the addition of the SPU0410LR5H MEMS microphone, 3.3V zener diode, 3.3kW resistor; and the removal of one each of the 10kW and 2.2kW resistors. The case parts are not included; see the August 2023 issue for those. siliconchip.com.au Australia's electronics magazine April 2024  81 SERVICEMAN’S LOG Power tool batteries, part two Dave Thompson If you read my November 2023 column, you will recall that I have recently had some run-ins with troublesome power tool batteries. I might have opened a can of worms by relating what I went through with my yellow power tools to my friends! You may recall me going through the motions of jump-starting some dead cells in my less-than-two-yearold battery pack and having some success in getting it working again. By working, I mean it was at least working enough for me to keep using the garden tools in their intended roles. Sadly, while it appeared the resurrection was at least partially successful, the rosy after-glow didn’t last, and soon the pack was back to its old trick of not lasting for more than a few minutes in the tool, and worse, nor was it being ‘seen’ by the charger. There was only one possible recourse: to take it back to the big-box vendor I’d purchased it from and thrash it out with them. Surprisingly, I met with almost no resistance (pun intended!), and they openly acknowledged it was a known problem. Even though the pack was literally one day out of the two-year warranty (pure coincidence – I had no idea, and thought it was a lot younger than that!), they said they’d put it back through the repair system with the caveat that it was entirely up to the yellow tools manufacturer as to whether they would honour the warranty. They also warned that obtaining a resolution could take up to four weeks, whichever way it went. However, being the good retailer they are, they gave me a loaner battery from their pool of spares in the meantime. This involved digging through a rather large box of batteries designed for various tools from many different manufacturers until we found an 18V version of the 54V battery I’d be leaving there. 82 Silicon Chip This was fine by me; the tool I needed to use (a weed whacker) would run on 18V anyway. I was mildly concerned when the woman dealing with this process informed me that this box of loaner batteries was never charged, with the store relying on people bringing them back after borrowing with some level of charge in them. I very briefly considered going into why that might not be a good idea and that leaving them to discharge in the box for what could be considerable lengths of time between charges might hurt them, but I wisely considered against doing so. It was simply not my place. All I cared about was that the loaner battery they gave me worked, and as a press of the onboard test button showed one bar of residual charge, I thought it would be fine after a decent time on my charger. And it was. Being the smaller type of battery for this range of tools meant it likely didn’t suffer from the design flaw that left the three cells buried furthest into the three chains of cells in the 54V version vulnerable to failure. I got the work done (that was my priority), and a mere three working days later, I received a text message saying that the battery I’d dropped off had been replaced under warranty and was ready for me to pick up. Could I please charge and bring back the loaner battery? I duly did that the following day. It was a good result, then, and a lesson for me to try to remember to keep my new 54V battery topped up to minimise the chance of a repeat performance. It is also good to know this new battery also has a two-year warranty, so if it happens again... Professional tool batteries fail too Since all that occurred, I related this tale of battery challenges to a few friends in the building trade as I was interested in their experiences with their cordless tools. Especially given that they usually use ‘professional’ level tools that are typically much more expensive compared to the lowly DIY versions the rest of us buy. I found their comments fascinating, and it seems that suddenly, I’m a local expert in battery tools, ready to be consulted! Of course, I’m no such thing, but this is very flattering. What I got from talking to these guys is that certain tools within the building and construction industries are well known for having inherent faults – and not just batteries. Most avoid them if they possibly can. Of course, manufacturers want people to ‘plug in’ to their Australia's electronics magazine siliconchip.com.au Items Covered This Month • Power tool batteries: electric boogaloo • Sometimes all a tractor needs is a good whack • Repairing a Dell power cable adaptor 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 range of tools, but it can be a considerable investment in plant and machinery only to discover that all might not be right in the state of Denmark. Nothing is worse than that feeling of remorse we get after spending thousands of dollars on a tool ‘system’ to find that the gear we’ve just purchased might not actually live up to the marketing hype. For example, many ‘sparkies’ here use a particular brand of drill/driver because it has a movable, asymmetric chuck assembly that allows holes to be drilled very close to a wall, off-centre from the centreline of the drill. That is a very cool feature. However, the batteries in these things are notoriously unreliable, and many of these guys now have their drivers lying useless in their toolboxes because the batteries are dead. The packs are no longer widely available, and those that are can sometimes cost half the price of a whole new tool, which comes with two new batteries! That is just another example of companies making consumable products with built-in finite lifespans (commonly known as ‘planned obsolescence’). Many of these guys either don’t know about repacking the battery pack with better cells, or if they do, they just can’t be bothered waiting and, in a fit of remorse, simply go and buy a new and likely different brand of tool. Of course, they probably believe that the new tool will come with a better generation of batteries and chargers, but we all know that is not necessarily the case. And the cycle continues. My neighbour kindly came over the other day to trim some of the wayward branches of the bushes growing on his property that overhang my fence. I sometimes get my manual loppers out (no batteries!) and knock back some of the bigger ones that get in the way of my bins. Still, he has one of those dayglo-green tool systems, including a rather tasty extendable and powerful hedge trimmer. Since some of these bushes are more than three metres tall, it’s a helpful tool to have. I’d love one of them in my yellow brand system, but I checked, and the cost is prohibitive for the amount of time I would use it. I asked my neighbour about his batteries, and being an 18V system, he commented that they seem to be OK. He has had the batteries since new for several years and keeps them refreshed religiously. They hold their charge, and as I hear his range of tools doing a lot of work over the fence; perhaps that is what keeps them healthy. I don’t use mine a lot; maybe once a month in the garden. Either way, it’s interesting... Repairing another failed battery pack I now have several packs and chargers in the workshop. The packs all come apart easily enough; while a siliconchip.com.au Australia's electronics magazine April 2024  83 the chips, a data sheet may have sample circuits that can be very similar. Thankfully, spares seem to be available from various sources. It also seems that a BMS from one pack can sometimes be used in a different brand of battery pack as well, but I have not fallen down that rabbit hole... yet. So it isn’t just about dead cells, although that’s where most problems seem to start with these packs. The electronics are robust since they have to be, but if a cell dies through not being charged properly, the whole pack is ruined. Simply replacing the cell(s) may not fix ongoing problems; the same cell could just fail again. Perhaps the manufacturers assume or hope that by then, the tradies will just buy another updated version of the tool instead. Welding in new cells couple had those Torx-type security screws buried down in the plastic moulding, the long bit for my driver easily reached them. They must be done up by a robot or someone with a mechanical driver because many were screwed in very tightly. There was no evidence of Loctite, Nylock or other type of adhesive on the screws, so I guess they were just done up very well. All the pack clamshells split apart to reveal the train of cells and a PCB of varying quality inside. I could see straight away that a few cells had vented – no prizes for guessing which ones could be dead! This is a pervasive problem with these 18360-type cells. They are the most-used cell in battery packs for tools because they are widely available and, if pushed, can deliver a very respectable 20A of point-load current when the tool is under stress. The problem is that the quality of these cells varies widely between manufacturers, and just because a cell has 2500mAh printed on it doesn’t necessarily mean it can deliver that promise. I have purchased many of these ‘replacement’ cells over the years from various vendors; honestly, some are just not worth the money. The problem is, as an end-user, how do we know? I guess all we can do is swallow the much higher prices of local vendors in the hope that the cells are of better quality than what we can buy from cheap Asian sites. There’s also the advantage that we can return them in case of premature failure. There isn’t much solace in that, though, when our customers come back complaining that the quality of the repair I carried out doesn’t live up to expectations! The other concern is that most battery packs now include a Battery Management System (BMS). It is usually in the form of a circuit board stuffed with surface-mounted components. It is there to regulate charging by apportioning the right current to the banks of cells themselves and to protect the cells in case of a short circuit, or if someone stalls the tool in use and the cell temperatures skyrocket. This PCB can also fail, causing the pack to no longer work or be seen by the charger, and this can be a trap when troubleshooting battery problems. As is typical, no circuits exist for these boards, although if you can identify 84 Silicon Chip For those of us who want to keep our existing tools going, though, repacking is the only viable option. Of course, there are plenty of local companies who do that kind of work, but it is well within the scope of the DIYer, as long as we can get good replacement cells. It also helps to have a spot welder because soldering to these cells is often problematic. I’m not saying it can’t be done; I imagine we’ve all done it or at least tried it at some point, but we have to be very careful of imparting too much heat for obvious reasons. I’ve also come across cells that must use a different type of metal on the caps, because no amount of sanding or application of flux will allow solder to stick; it annoyingly just beads and falls off. The splat welder method is achievable because they sell these relatively cheaply over on the likes of AliExpress, eBay and Banggood. They typically run from a high-­current model plane or car battery and do the job quite well. Editor’s Note: for a more capable version, see our Capacitor Discharge Welder project from March & April 2022 at siliconchip.au/Series/379 Mine has seen some use, and I much prefer this method to soldering because it is fast, easy and more permanent. The nickel strips can be purchased very cheaply too, in a roll, with different thicknesses available. It’s just a matter of cutting them to size, touching the welder to the strip once it is in place and ‘zap!’, it’s done. Another customer’s battery won’t charge I also had a case recently where a customer’s battery charger stopped working. That’s also a showstopper for many because a new charger can be expensive, especially if it is part of one of these ‘systems’ that use one battery for every tool in the range, which seems to be all the rage now. In this case, the battery checked out OK, with all the cells carrying a reasonable charge and being within 10% of each other in voltage, but the charger didn’t show any lights at all. The owner said he put the battery on to charge as normal, but nothing happened. The usual lights and fans didn’t come on, so he put it to one side and assumed that the battery had tanked. The charger comes apart as easily as the packs after removing the usual security screws. Since everyone has these bits now as part of kits we can buy from the local big-box store, what is even the point of using them? The fact is, these days, they present no real problem to even the most inexperienced DIYer. Australia's electronics magazine siliconchip.com.au As expected, the PCB inside is stacked with the usual mix of surface-mounted and through-hole components. As you’d also expect, there is very little information about these things online from the manufacturer. However, many people have delved into the inner workings and have posted their findings on the likes of YouTube. This is gold for those looking to repair the most common problems. Of course, some of the information isn’t relevant at all, but some is, and that’s what I was looking for. Apparently, with this charger, a couple of resistors can fail and replacing them can restore functionality. I checked and discovered one had been blown off the board. It was a surface-mounting device, but I replaced it with a standard 1/4W axial resistor, as suggested in the video. I also replaced the other prone-to-fail resistor and followed other recommendations to check the input power diodes, which look to be old-school 1N4007s or similar but, in typical fashion, have had their designations removed. They were all OK, as was every other component I could ring out with my multimeter. I reassembled it, installed the battery and was welcomed by the lights and a fan kicking in. It was a simple enough fix, but you’d think the people who make these things would have tested them thoroughly and known this could happen (basic engineering should have also revealed whether the resistors were undersized for the job). The issue is that by the time they sell these tools in stores, they’ve already made a million of them, and there’s likely a new model already being manufactured. There would be no recalls of such products unless there were a threat to health and safety. Still, all in all, there is a reasonable resolution for most of these jobs. The repacked or replaced batteries keep the tools going, while the dead charger is now charging. The customers are all happy, so job done! The tractor that dropped in its tracks R. M., of Scotsdale, WA found that even elementary electronics can have gremlins lurking. Sometimes, you must attack every possible failure point before you can evict the gremlin! On a farm, even a small one like ours, the most useful tool is the tractor. The compact three-cylinder diesel fourwheel-drive with power take-off, three-point linkage, dualrange continuously-variable hydraulic transmission and 4-in-1 front-end bucket is a modern marvel. Think of it as a 30 horsepower (22kW) Swiss army knife! We have a Korean-made “KIOTI” CK3010H tractor (pronounced “Coyote”). It’s a clever marketing strategy since Kioti sounds better to Western ears than “Daedong”. It even has a small bushy-tailed canine howling at the moon as its logo. I have had it for nine years and it has never failed me. That is until... I had driven it down to the lowest and most remote paddock (isn’t that always the way?) and turned the engine off. I did the required work, loaded the bucket, got back in the seat, pressed down the clutch pedal and turned the starter key. There was plenty of vigorous cranking but no starting. With a diesel engine, there is no ignition system to worry about and no electronic fuel injectors either. Just a mechanical high-pressure pump that squirts fuel into the cylinders as required. siliconchip.com.au Diesels are very fussy about the cleanliness of that fuel and I had been a bit slack with maintenance. I had bought a new filter kit, changed the engine oil and filter, but I hadn’t gotten around to the fuel filter. So I trudged back to the shed, got the new filter and appropriate tools and replaced the rather mucky filter in the field. The engine started without any delay! As you’ve probably guessed, that wasn’t the fix because the story doesn’t end there. It wouldn’t start again a couple of days later. Could the injectors be clogged? They can’t all block simultaneously. So it had to be the engine stop/ start solenoid. For petrol engines with spark plugs, stopping is not a problem. You can stop sparking, and the fuel cannot ignite; it’s also possible to close the throttle butterfly to cut off the air intake to the cylinders. Diesels don’t have throttles; their power output is controlled by fuel metering. With a diesel, because the fuel is ignited by cylinder compression, the only way to stop it, short of stalling it, is to cut off the fuel or, failing that, block off the air intake by jamming something into it. On the old machines, there was a lever on the injector pump and a bit of fencing wire that came up to a knob on the dashboard. Modern key-starting diesels use a hefty solenoid to perform this function. I knew where that solenoid was, so, assuming it might just be stuck, I gave it a sharp rap with a large wrench (I didn’t have a hammer handy). Editor’s note – any tool is a hammer when you need it to be. The tractor started first go. Problem solved? Oh no, it wasn’t! The misbehaviour continued intermittently. But a smart tap with whatever weapon was available did the trick. But that isn’t a proper fix, so I went a-Googling. I found a replacement part from an Australian source that wasn’t outrageously expensive and ordered one. It turned up two weeks later, and I swapped it out; an easy job with a three-pin waterproof plug making the connection. Ah, that fixed it! Australia's electronics magazine April 2024  85 Two weeks later, at another remote location, “whirrwhirr-whirr-whirrrrr”, but no start. And this time, a rap with a spanner didn’t help. I trudged home uphill and went back to Mr Google. And for $20, I got a full 400-page PDF workshop manual instantly delivered to my computer. This showed that the solenoid had two windings: a strong pull-in winding and a light-duty hold winding. The engine management computer feeds voltage to the hold winding and then puts a one-second pulse to the pull-in winding. With a hefty dose of amps, the solenoid plunger thumps in, the holding winding keeps it in, and the fuel flows until the ignition key is switched off. Now that I had a spare solenoid, I was ready to find out if the fault was the solenoid or (shudder) the injector pump. All I had to do was wait until it failed, swiftly switch the connector over to the spare external solenoid and watch the plunger pin. Sure enough, I confirmed that the plunger was not pulling in. So it was an electrical fault! That was a relief of sorts; it is much easier to deal with electrics than the very complex and fine tolerances of a fuel injector! The pull-in solenoid was fed from a relay that was, in turn, fed from a 25A fuse. That could be the problem. A bit of corrosion and a heavy current demand can result in a big voltage drop. I needed to find the fuse box. By rights, it should be on the firewall. The thing about compact tractors is that they are compact; everything is crowded together, especially under the bonnet. Also, the wide arms that raise and lower the bucket pass close by either side of the bonnet. Raising the bucket to its height limit and fitting the safety bars gave a bit more access, but lifting the bonnet didn’t help that much. A generously proportioned air cleaner obscured my view of the firewall. After much struggling with hidden clips and twisting hoses, I had a partial view of the firewall. And there was a fuse box that appeared not to be completely closed. Was water getting in and causing a bit of corrosion? Working primarily by feel and bright torchlight, I managed to open the box and extract a fuse: 15A. Okay, not the right one. More wiggling and swearing, and I had a 25A fuse in hand. It looked fine. No sign of corrosion. I gave it a squirt of contact cleaner anyway and put it back. I did to all of them, just in case. 86 Silicon Chip That didn’t help, but the problem intermittency got a bit longer until the rains came. Now this malignant fault had a new trick! The probability of failure was directly proportional to the distance to shelter and the volume of wetness. And then I had a breakthrough! When I turned the start key, just before the starter motor spun up, there was a faint click. I had assumed this was the starter solenoid, but what if it was the fuel stop/start solenoid? By locking the clutch pedal down, jacking up and securing the bucket out of the way again, and contorting myself, I could get one hand on the solenoid and also reach the starter key. And that was it! That click was the fuel solenoid, and sometimes it didn’t click. When it didn’t click, the tractor wouldn’t start! Going back to the wiring diagram, I found another diagram that showed more detail. The relay was fed from a 25A fused circuit, but the power it switched came directly from the battery with a 60A master fuse. The relay was situated on the firewall (of course it was). Still, at least this time, it was reasonably accessible. I managed to unbolt it and bring it out into daylight, dragging the wiring harness behind. I also found a damper diode effectively across the solenoid but packed away in its own little box taped into the harness. It checked out okay. The relay was a standard four-pin 70A type. Using the same hold, feel and activate technique, I determined it was working, but the solenoid wasn’t always complying. Obviously, the relay contacts were burnt out. A new relay from our friendly auto parts shop and, finally, no more no starting problems! The engine compartment of the tractor is packed with parts, making the fusebox and relay hard to get to. Australia's electronics magazine siliconchip.com.au Keep your electronics operating with our wide range of replacement Power Supplies Don't pay 2-3 times as much for similar brand name models when you don't have to. Bring in your device and we'll help you find the right power supply for your needs. 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Explore our full range of replacement power supplies, in stock at over 115 stores and 134 resellers or on our website. jaycar.com.au Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. 1800 022 888 So the 25A fuse I had struggled to access was just the relay activator, and the heavy current that operated the solenoid came directly from the battery via the relay. Now, there is a loud, healthy clack from the solenoid when the ignition key is turned. But here’s the catch. I performed bush surgery on the relay, and the internals looked okay – clean contacts and good snappy action when fed with 12V. So, is the gremlin still lurking, waiting to trap me? Three months and a lot of rain later and, fingers crossed, it hasn’t failed once. But is it still lurking? Time will tell. I now wait to hear the loud clack of the solenoid turning on the fuel before engaging the starter. Why was the fault originally ‘fixed’ by a tap on the solenoid when the actual problem was in a relay half a metre away? I put it down to pure Sod’s Law! That, and the downright evil malice of your typical intermittent fault. Repairing a Dell power cable adaptor G. C., of Cameron Park, NSW found that Dell laptops use various proprietary charging cables, causing all manner of problems... I recently retrieved a Dell laptop from my daughter that she borrowed a year ago. Annoyingly, it didn’t come back with an AC power adaptor. Naturally, the battery was completely flat, and the laptop wouldn’t turn on for even a second. Adding to my frustration, this laptop used the newer 4.5mm socket, while all of my Dell AC power adaptors had the older and larger 7.4mm connector. I wasn’t sure what to do. I didn’t want to spend a lot of money on a new Dell power adaptor when the laptop might have ‘expired and gone to meet its maker’. Feeling stuck, I decided it was time to do some Google searching. After, as usual, wasting some time on a few dead ends, I discovered that while Dell 7.4mm and 4.5mm connectors were virtually impossible to find, adaptor cables from 7.4mm to 4.5mm were readily available at very reasonable prices. I ordered several from an Australian supplier, which arrived within a week. However, when I connected everything and turned on the laptop, I received an error message that stated, “Alert! The AC power adaptor wattage and type cannot be determined. The battery may not charge. The system will adjust the performance to match the power available.” Annoyingly, the Dell laptop still wouldn’t boot up, most likely due to the completely flat battery that wasn’t charging at all. I verified this by going into the Dell BIOS (press F12) and checking the battery info, which showed it as charged to 0%. It wasn’t charging, and the power adaptor type was listed as “unknown”. Many laptop brands use just two wires in their power cables, but some, notably Dell and HP, use three: ground, power, plus a third ‘sense’ wire via a triaxial connector. Despite the adaptor cables being well made, they hadn’t bothered to include the important third sense wire! 88 Silicon Chip The centre sense pin is used to determine the adaptor’s power rating, allowing it to adjust the charging current to prevent overloading or overheating the AC power adaptor and avoid tripping its 19.5V DC power safety circuitry. Based on my past experience with Dell laptops, I knew this error could be caused by either a non-genuine power adaptor (which wasn’t the case) or a good power adaptor with a damaged sense connection. I knew the AC power adaptor was fine as it worked on another Dell laptop with the larger 7.4mm socket. It appeared that my brand new 7.4mm to 4.5mm adaptor cable was defective. This seemed strange since, externally, at least, the adaptor cable appeared well-made. However, a quick check with an ohmmeter revealed a different story; the sense wire wasn’t connected between the adaptor cable’s male and female ends. The identical issue was present in all three adaptor cables I had purchased. Even more strangely, on the plug end, I measured a resistance of 200kW between positive (19.5V) and the centre sense pin. Since these adaptor cables were less useful than a brick for their intended purpose of charging a laptop, I decided to take a closer look inside (the Serviceman’s Curse). I cut off the soft plastic from the plug and socket using sharp side cutters. It was tedious, but it worked. My initial assessment was accurate, as both the plug and socket were indeed well made. Interestingly, both had the correct three connections. However, in what has to be one of the most nonsensical designs I had ever seen, the wiring loom only had two wires, not the necessary three. The reason for the 200kW resistance on the plug became apparent: some engineer, in a futile attempt to trick the Dell sensor logic, had added a 200kW resistor between + and the sense pin. Needless to say, it did nothing useful, as the Dell BIOS error message confirmed. With the problem laid out before me, the solution was obvious: create a new loom using three wires. As a quick feasibility test, I desoldered the useless two-conductor cable and the kludgy 200kW resistor. I then quickly soldered three insulated wires between the 7.4mm socket and 4.5mm plug. Very carefully, I plugged in my temporary kludge adaptor (with its exposed 19V power) between the Dell power adaptor and Dell laptop and turned it on. Fortunately, everything worked perfectly, even with my dodgy exposed wires. Nothing had come into contact with anything untoward to produce that annoying smoke that electronic devices seem prone to emit. Of course, I needed a permanent and more durable solution. So, I decided to do it properly with 3D-printed replacement covers. I fired up OpenSCAD and designed covers for both the male and female connectors. After careful measurements with digital callipers and a few iterations to fine-tune everything, my 3D-printed replacement covers fit perfectly. After that, it was smooth sailing. I desoldered the three temporary wires, and since I didn’t have any suitable three-core cable on hand, I used a short length of Hakko soldering iron cable, even though it had five wires. After soldering this new cable between the 7.4mm and 4.5mm connectors, I fitted the covers and sealed each end with neutral-cure black silicone. Voilà, I had a professional-­ looking Dell 7.4mm to 4.5mm adaptor cable. Even better, this adaptor cable actually worked. SC Australia's electronics magazine siliconchip.com.au Huge Range of 12/24V Switches Control power to your lighting and other devices in your car, 4WD, RV or boat. SAME GREAT RANGE AT SAME GREAT PRICE. 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Jaycar reserves the right to change prices if and when required. By Brandon Speedie Fender “Tweed” Bassman 5F6-A guitar amplifier from 1958 The Bassman is one of the most legendary guitar amplifiers in history, despite originally being designed for bassists. This model from the late 50’s is notable as the circuit was directly copied by Jim Marshall in the JTM45, the first ever Marshall amplifier. T he early 1950s was a revolutionary time in the live music industry. The preceding 20 years had seen a slow shift away from big bands to smaller groups, enabled by electric amplification. The instrument of choice was the hollow-body electric guitar, which could replace an entire orchestral section. Hollow-body guitars weren’t without their problems. With performances getting louder, guitarists were increasingly having tone and feedback difficulties. Leo Fender read the situation beautifully, and in 1950, introduced the Fender Telecaster (originally named the Fender Broadcaster). Its solid body solved the problems hollow body players were facing, and its small size and light weight made it an instant hit with guitarists of the era. It was the first commercially successful solid-body guitar and is still one of the most popular to this day. The Telecaster kickstarted Fender’s 90 Silicon Chip luthier (stringed instrument manufacturing) business. The following year, he introduced the Precision Bass as a replacement for the upright double bass. Again, it was hugely popular. Its much smaller size, electric amplification and fretted fingerboard were groundbreaking. It is another Fender design that has stood the test of time. The next year, Fender introduced the Bassman, a 15-inch (~380mm) speaker cabinet with a built-in amplifier. Originally targeting Precision Bass players, the Bassman soon found favour with other instruments, including guitarists. The Bassman received various upgrades over the following years, including switching from a single 15-inch driver to four 10-inch (~250mm) drivers in 1954. In 1957, they added a middle EQ control to the famous Fender “tone stack”. The models with 10-inch speakers are considered by many to be the best guitar amplifiers ever made. The 5F6-A is the last update Fender made to the 1950s Tweed Bassman. Circuit analysis Valve amplifier chassis can retain very high voltages even when unplugged. Care should be taken when working on these devices. The Bassman circuit is shown in Fig.1. The input circuitry is centred around a 12AY7 dual triode configured as two independent common-cathode voltage amplifiers. The instrument is connected via TRS plugs to one of four inputs, split across two channels (“normal” and “bright”). The #1 inputs apply the input signal to the grid of the respective triode through a 68kW grid stopper resistor, with a 1MW grid leak resistor. The #2 inputs are for higher input signals and thus apply a pad through the action of the 68kW voltage dividers. Both channels share an 820W cathode Australia's electronics magazine siliconchip.com.au degeneration resistor, bypassed by a 250μF capacitor for increased AC gain. With plate loads of 100kW, this first stage provides a voltage gain of 32.2 times for the #1 inputs and 16.1 times for the #2 inputs. The outputs of these two amplifiers are AC-coupled by 20nF capacitors into variable voltage dividers formed by the 1MW potentiometers. The output signals from the two pot wipers are mixed before being fed to the following stage. The bright channel includes a 100pF treble bleed resistor in parallel with the volume control. This has no effect at full volume, but as the volume is reduced, there is more treble bypassing the volume pot, making the audio ‘brighter’. This capacitor is the only difference between the normal and bright channels. The second stage uses another dual triode, the venerable 12AX7. The first half is a voltage amplifier very similar to the input stage, except using 270kW grid stopper resistors (which also perform the channel mixing) and no capacitor bypassing the 820W cathode degeneration resistor. This stage’s voltage gain is 20.7. Its output is fed into the second half of the 12AX7, this time configured as a cathode follower with a 100kW resistor from the cathode to ground. The Fender Tone Stack The output of the cathode follower feeds perhaps the most copied circuit in audio electronics, the BMT (bass, mid, treble) Fender Tone Stack. The treble control is, somewhat unusually, a high pass filter made from the RC combination of the 250pF treble bleed resistor and the 250kW pot, giving a cutoff frequency of around 2.5kHz. The pot effectively works as a blend control; it has treble frequencies at the top of its range and bass/mid frequencies at the bottom. This blending also introduces some distortion, as the treble frequencies are not phase-aligned with the bass/mid. The resulting harmonics and intermodulation are colloquially called “Fender shimmer”, a desirable effect. The bass control is made from the 1MW audio (logarithmic) taper pot connected as a rheostat, in combination with a 20nF capacitor. This forms a high-pass filter with a variable cutoff frequency between 8Hz and 318Hz. siliconchip.com.au Fig.1: the Bassman circuit is fairly elegant, using just three twin triodes, two power pentodes and one rectifier valve. The first two twin triodes provide preamplification and are followed by a passive tone control network. The signal from that network is applied to the grids of the third dual triode, which provides more gain and acts as a phase splitter, driving the pentodes in a pushpull configuration. The four speaker drivers are wired in parallel. “PRES” stands for presence, a Fender specialty that boosts upper-mid and treble. Australia's electronics magazine April 2024  91 which shunts high frequencies to ground via the 100nF capacitor. The feedback loop therefore has a variable frequency response, which provides a treble boost when the control is up. Output stage Photo 1: the rear of the cabinet, showing the open-backed design and four 10inch (~250mm) Jensen speakers. Remarkably, this example still has the genuine tweed. In comparison, earlier models of the Bassman amplifier used just one 15-inch speaker and were rated at 26W. This image and the lead photos are reproduced with permission from truevintageguitar.com The mid control is effectively a swept band-stop filter, a low-pass and a high-pass filter connected in series. The low-pass filter has a cutoff frequency of 142Hz, formed by the 56kW tone slope resistor and the 20nF mid capacitor. The high-pass filter is thus formed by the mid capacitor and the 25kW potentiometer. With the mid control fully up, the cutoff frequency is 318Hz. With the control fully down, all mid frequencies are blocked. All three controls strongly interact with each other, as shown in Fig.2. Note the notch in the mid frequencies with all controls at the middle of their range, as shown by the red curve. This is to compensate for the response of electromagnetic pickups, which typically over-emphasise mid frequencies. Phase splitter The output of the tone stack feeds into another 12AX7 common-cathode amplifier, configured as a long-tailed pair. This stage provides voltage gain to recover signal attenuated through the tone stack and also produces phase-inverted signals for driving the push-pull output stage. The signal is AC coupled through a 20nF capacitor and fed to the grid of 92 Silicon Chip the inverting amplifier. With an 82kW plate load and shared 15kW tail, the voltage gain is around -21.9 for the inverted output. The gain is slightly higher for the in-phase output at 22.6 times, given the 100kW plate load. The other side of the long-tailed pair receives negative feedback from the secondary side of the output transformer. This signal is fed to the grid via a 27kW feedback resistor and 100nF AC-coupling capacitor. What is that 5kW pot doing? That is the so-called “presence” control, The two outputs from the phase splitter are derived from each side of the long tail pair and thus are roughly phase-inverted replicas of each other. These signals are AC-coupled through 100nF capacitors to the grids of the output stage tubes, with 220kW bias resistors to -48V DC. The screens are pulled up through 470W, an increase on the 100W used on earlier versions. Original versions of the 5F6-A used 5881 output valves, but most examples these days will have the more common 6L6 beam tetrodes. These tubes are arranged with grounded cathodes and plates directly connected to the output transformer, which drives its four paralleled speakers at 2W. The maximum output power is around 45W RMS. Power supply Power is derived from the 8087 mains transformer, which includes a centre-tapped 325-0-325V secondary, plus separate 5V and 6.3V filament heater supplies. The 325V secondary is full-wave rectified by a GZ34 and locally filtered by some bulk capacitance and a choke. This produces the nominal 430V HT supply, as well as the lower 385V and 325V supplies for the preamplification stages via series dropper resistors. Distributed capacitance at each preamp stage provides further filtering. The -48V DC supply for biasing the output stage comes from a selenium Fig.2: the Tone Stack frequency response with all controls individually swept. The red curve is with all knobs at 12 o’clock. There is no impedance buffering, resulting in strong interaction between the controls. rectifier operating on a separate transformer tap. This part runs hot and is a common source of failure. Typically, it will be replaced by a modern silicon rectifier diode such as the 1N4007 (1000V 1A). Perhaps the most interesting part of the power supply is its poor transient response and relatively high output impedance. When driven hard, the HT supply will sag by as much as 60V. This strongly interacts with the output stage, increasing distortion. While many circuit designers might consider this unacceptably poor performance, musicians love it! It is for this reason that valve (vacuum tube) amps have a reputation for sounding good when turned up loud. The valve amplifier sound doesn’t just come from this poor regulation, though. The soft overloading properties of the output valves naturally play a part; they don’t just go hard into clipping at higher volume levels but tend to compress the sound first. The speaker transformer is also an important part of the valve sound as it can introduce a lot of (desirable) distortion as the core starts to saturate. Another contributor to the ‘valve sound’ is the non-linearity of the preamplification and tone control stages, as there is no feedback around any of the triodes. So their non-linear transfer function and inherent quirks will ‘colour’ the sound. Another trick guitarists often use is to play their guitar Silicon Chip kcaBBack Issues $10.00 + post January 1995 to October 2021 $11.50 + post November 2021 to September 2023 $12.50 + post October 2023 onwards All back issues after February 2015 are in stock, while most from January 1995 to December 2014 are available. For a full list of all available issues, visit: siliconchip.com. au/Shop/2 PDF versions are available for all issues at siliconchip.com.au/Shop/12 We also sell photocopies of individual articles for those who don’t have a computer near the speakers, in the magnetic field, which induces feedback into the pickup. An interesting feature of the power supply is the “ground switch” that connects one of the incoming AC lines to Earth via a 50nF capacitor. It is set for minimum noise. One reason for this is that Active (Live) and Neutral can sometimes be swapped, so this switch can allow you to ‘find’ the Neutral and locally Earth it for higher AC frequencies. There’s also a standby switch that disconnects the HT but leaves the valve heaters powered. This way, the amp can warm up without producing any sound and is ready at a moment’s notice. Chassis layout The chassis layout is quite neat, as shown in Fig.3 and the photos. While not indicated on the circuit or chassis layout diagrams, you can see from the photo that the 12AY7 and 12AX7s in the input stages are fitted with shield cans to reduce hum and buzz pickup. Most of the resistors and capacitors are mounted on one long dual tag strip and wired to the valves, pots etc using point-to-point wiring – see Photo 3. There are a few resistors and capacitors soldered directly to valve socket, pot or switch tags. 1959 Bassman reissue The original Bassman has proven so collectable that in 1990 Fender began reselling the 5F6-A as a 1959 reissue. The circuit is largely original, except some changes to use less expensive or more readily available parts. The changes are: • The GZ34 rectifier valve was replaced with a plug-in solid-state dual common cathode rectifier. As a result, the HT rail voltages increased from 432/430/385/325V to 491/490/477/383V. This would have Fig.3: the chassis layout for the 5F6-A guitar amplifier. You can find a more legible version of this diagram from https:// robrobinette.com/5F6A_Modifications.htm siliconchip.com.au Australia's electronics magazine April 2024  93 Photo 2: the Bassman chassis. This amplifier is entirely original except for NOS replacement valves and a new power lead. Reproduced with permission from truevintageguitar.com increased the maximum output power by a few watts. • The 20nF capacitors were changed to 22nF and 250μF to 220μF. • The two 1MW volume control pots at the input were changed from logarithmic to linear types • The 56kW resistor in the tone control network changed to 100kW and the upper 20nF capacitor was increased to 100nF. • The 10kW biasing resistor for the final 12AX7 stage changed to 6.8kW. The 5kW bias adjustment potentiometer with the 100nF capacitor from its wiper to Earth was replaced with a 25kW potentiometer in series with the 100nF capacitor, both shunted by a 4.7kW resistor. • In the power supply, the 8μF capacitor filtering the +325V HT rail was changed to two 22μF capacitors in parallel, while the filter capacitor for the +385V rail was changed from 20μF to 22μF. • The 20μF filter capacitor for the +430V rail changed to two 47μF 350V capacitors in series, with 220kW resistors across each. The two 20μF filter capacitors for the +432V rail became two 100μF 350V capacitors in series, also with 220kW resistors across each. The JTM45 Across the Atlantic, Jim Marshall was selling the 5F6-A in his small music shop. In the early 1960s, the store was frequented by Pete Townshend of The Who. Pete bemoaned the expense of Fender’s equipment and encouraged Jim to make amplifiers locally in preference to the imported American product. The result was the Marshall JTM45. Electrically, it was almost identical to Fender’s 5F6-A Bassman. The only notable changes were the use of a 12AX7 in the first stage (rather than Fender’s 12AY7) and some minor tweaks to component values. The overall effect was an amplifier with similar performance to the Bassman but with higher gain and brighter voicing. This amplifier therefore tended to go into overdrive sooner, a characteristic Townsend had requested. Marshall amplifiers have since become known for this high gain, high distortion “British crunch”. Legacy Photo 3: the featured amplifier still has the original Astron filter capacitors and was manufactured using point-to-point wiring. 94 Silicon Chip Australia's electronics magazine Fender and Marshall are giants of the industry. A large proportion of contemporary music has been performed using equipment from these manufacturers. Even today, any live performance with guitars will likely feature Fender and Marshall gear. Remarkably, their genesis is in these three inventions by Leo Fender in the early 1950s: the Telecaster, Precision Bass, and Bassman amplifier. SC siliconchip.com.au ONLY 329 $ QM1493 Specialty meters combined with multimeter functions. HIGH VOLTAGE INSULATION TESTING "MEGGER" • MULTIMETER FUNCTIONS • DIGITAL DISPLAY • ANALOGUE BARGRAPH • DATAHOLD ONLY 119 $ TAKE EASY ENVIRONMENTAL MEASUREMENTS • MULTIMETER FUNCTIONS • SOUND LEVEL • LIGHT LEVEL • INDOOR TEMP • HUMIDITY TEST WIRING INSULATION ONLY 179 $ QM1594 TEST ALMOST ANYTHING! 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Jaycar reserves the right to change prices if and when required. 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. 04/24 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS $15 MICROS 24LC32A-I/SN ATmega328P Digital FX Unit (Apr21) Si473x FM/AM/SW Digital Radio (Jul21), 110dB RF Attenuator (Jul22) Basic RF Signal Generator (Jun23) ATmega328P-AUR RGB Stackable LED Christmas Star (Nov20) ATtiny45-20PU 2m VHF CW/FM Test Generator (Oct23) ATtiny85V-10PU Shirt Pocket Audio Oscillator (Sep20) PIC10LF322-I/OT Range Extender IR-to-UHF (Jan22) PIC12F1572-I/SN LED Christmas Ornaments (Nov20; versions), Nano TV Pong (Aug21) PIC12F617-I/P Active Mains Soft Starter (Feb23), Model Railway Uncoupler (Jul23) PIC12F617-I/SN Model Railway Carriage Lights (Nov21) PIC12F675-I/P Train Chuff Sound Generator (Oct22) PIC16F1455-I/P Auto Train Controller (Oct22), GPS Disciplined Oscillator (May23) Railway Points Controller Transmitter / Receiver (2 versions; Feb24) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P Cooling Fan Controller (Feb22), Remote Mains Switch (RX, Jul22) K-Type Thermostat (Nov23), Secure Remote Switch (RX, Dec23) Mains Power-Up Sequencer (Feb24) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Tiny LED Icicle (Nov22), Digital Volume Control Pot (SMD; Mar23) Silicon Chirp Cricket (Apr23) PIC16F15214-I/P Digital Volume Control Pot (through-hole; Mar23) PIC16F15224-I/SL Multi-Channel Volume Control (OLED Module; Dec23) PIC16F1705-I/P Digital Lighting Controller Translator (Dec21) PIC16F18146-I/SO Volume Control (Control Module, Dec23), Coin Cell Emulator (Dec23) PIC16LF15323-I/SL Remote Mains Switch (TX, Jul22), Secure Remote Switch (TX, Dec23) W27C020 Noughts & Crosses Computer (Jan23) ATSAML10E16A-AUT PIC16F18877-I/P PIC16F18877-I/PT High-Current Battery Balancer (Mar21) USB Cable Tester (Nov21) Dual-Channel Breadboard PSU Display Adaptor (Dec22) Wideband Fuel Mixture Display (WFMD; Apr23) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) Advanced GPS Computer (Jun21), Touchscreen Digital Preamp (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS ATmega32U4 ATmega644PA-AU Wii Nunchuk RGB Light Driver (Mar24) AM-FM DDS Signal Generator (May22) $25 MICROS dsPIC33FJ64MC802-E/SP 1.5kW Induction Motor Speed Controller (Aug13) PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sep16) $30 MICROS PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC PICO GAMER KITS (APR 24) ESP-32CAM BACKPACK KIT (SC6886) (APR 24) PICO DIGITAL VIDEO TERMINAL (SC6917) (MAR 24) MAINS POWER-UP SEQUENCER (FEB 24) - SC6911: everything except the case & battery; RP2040+ is pre-programmed - SC6912: the SC6911 kit, plus the LEDO 6060 resin case - SC6913: the SC6911 kit, plus a dark grey/black resin case - 3.2in LCD touchscreen: also available separately (SC6910) Includes everything to build the BackPack, except the ESP32-CAM module - 3.5in LCD touchscreen: also available separately (SC5062) $85.00 $125.00 $140.00 $30.00 $42.50 $35.00 Short-form kit: includes everything except the case; choice of front panel PCB for Altronics H0190 or H0191. Picos are not programmed (see page 46, Mar24) $65.00 Hard-to-get parts: includes the PCB, programmed micro, all other semiconductors and the Fresnel lens bezels (SC6871) $95.00 Current detection add-on: includes the AC-1010 current transformer, (P)4KE15CA TVS and MCP6272-E/P op amp (SC6902) $20.00 MICROPHONE PREAMPLIFIER KIT (SC6784) (FEB 24) Includes the standard PCB (01110231) plus all onboard parts, as well as the switches and mounting hardware. All that’s needed is a case, XLR connectors, bezel LED and wiring (see page 35, Feb24) USB TO PS/2 KEYBOARD & MOUSE ADAPTOR - VGA PicoMite Version Kit: see page 52, January 2024 (SC6861) - ps2x2pico Version Kit: see page 52, January 2024 (SC6864) - 6-pin mini-DIN to mini-DIN cable, ~1m long. Two cables are required if adapting both the keyboard and mouse (SC6869) (JAN 24) $30.00 $32.50 $10.00 COIN CELL EMULATOR (SC6823) (DEC 23) MULTI-CHANNEL VOLUME CONTROL (DEC 23) - Kit: Contains all parts and the optional 5-pin header (see page 77, Dec23) - 1.3in blue OLED (SC5026) - Control Module kit: see page 68, December 2023 (SC6793) - Volume Module kit: see page 69, December 2023 (SC6794) - OLED Module kit: see page 69, December 2023 (SC6795) - 0.96in SSD1306 cyan OLED (SC6176) $70.00 $30.00 $15.00 $50.00 $55.00 $25.00 $10.00 siliconchip.com.au/Shop/ SECURE REMOTE SWITCH (DEC 23) IDEAL DIODE BRIDGE RECTIFIER (DEC 23) MODEM / ROUTER WATCHDOG (SC6827) (NOV 23) PICO AUDIO ANALYSER SHORT-FORM KIT (SC6772) (NOV 23) K-TYPE THERMOMETER / THERMOSTAT (SC6809) (NOV 23) PIC PROGRAMMING ADAPTOR KIT (SC6774) (SEP 23) CALIBRATED MEASUREMENT MICROPHONE (AUG 23) - Receiver short-form kit: see page 43, December 2023 (SC6835) - Discrete transmitter complete kit: see page 43, December 2023 (SC6836) - Module transmitter short-form kit: see page 43, December 2023 (SC6837) - 28mm square spade: see page 35, December 2023 (SC6850) - 21mm square pin: see page 35, December 2023 (SC6851) - 5mm pitch SIL: see page 35, December 2023 (SC6852) - Mini SOT-23: see page 35, December 2023 (SC6853) - D2PAK SMD: see page 35, December 2023 (SC6854) - TO-220 through-hole: see page 35, December 2023 (SC6855) $35.00 $20.00 $15.00 $30.00 $30.00 $30.00 $25.00 $35.00 $45.00 Short-form kit: includes all non-optional parts, plus a 12V relay and unprogrammed Pi Pico. Does not include a case (see page 71, Nov23) $35.00 Includes most parts, unprogrammed Pi Pico and OLED screen. The case, battery, chassis connectors and wires are not included (see page 41, Nov23) $50.00 Short-form kit: includes most parts except the case, LCD, thermocouple probe, cable gland and switches S4 & S5. A 10A relay is included (see page 58, Nov23) $75.00 Includes all parts, except the optional USB supply (see page 71, Sept23) SMD version kit: includes the PCB and all onboard components except the XLR socket. You also need one ECM set (see below) (SC6755) Through-hole version kit: same as the SMD kit (SC6756) Calibrated ECM set: includes the mic capsule and compensation components; see pages 71 & 73, August 2023 issue, for the ECM options (SC6760-5) DYNAMIC RFID/NFC TAG (JUL 23) Smaller (purple PCB) kit: includes PCB, tag IC and passive parts (SC6747) Larger (black PCB) kit: includes PCB, tag IC and passive parts (SC6748) *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. $55.00 $22.50 $25.00 $12.50 $5.00 $7.50 PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS HUMMINGBIRD AMPLIFIER DIGITAL LIGHTING CONTROLLER TRANSLATOR SMD TRAINER 8-LED METRONOME 10-LED METRONOME REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL FAN CONTROLLER & LOUDSPEAKER PROTECTOR SOLID STATE TESLA COIL (SET OF 2 PCBs) REMOTE GATE CONTROLLER DUAL HYBRID POWER SUPPLY SET (2 REGULATORS) ↳ REGULATOR ↳ FRONT PANEL ↳ CPU ↳ LCD ADAPTOR ↳ ACRYLIC LCD BEZEL RASPBERRY PI PICO BACKPACK AMPLIFIER CLIPPING DETECTOR CAPACITOR DISCHARGE WELDER POWER SUPPLY ↳ CONTROL PCB ↳ ENERGY STORAGE MODULE (ESM) PCB 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) AM-FM DDS SIGNAL GENERATOR SLOT MACHINE HIGH-POWER BUCK-BOOST LED DRIVER ARDUINO PROGRAMMABLE LOAD SPECTRAL SOUND MIDI SYNTHESISER REV. UNIVERSAL BATTERY CHARGE CONTROLLER VGA PICOMITE SECURE REMOTE MAINS SWITCH RECEIVER ↳ TRANSMITTER (1.0MM THICKNESS) MULTIMETER CALIBRATOR 110dB RF ATTENUATOR WIDE-RANGE OHMMETER WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD MINI LED DRIVER NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION DATE SEP21 SEP21 OCT21 OCT21 NOV21 NOV21 NOV21 DEC21 DEC21 DEC21 JAN22 JAN22 JAN22 JAN22 JAN22 JAN22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 MAR22 MAR22 MAR22 MAR22 MAR22 APR22 APR22 APR22 MAY22 MAY22 JUN22 JUN22 JUN22 JUN22 JUL22 JUL22 JUL22 JUL22 JUL22 AUG22 SEP22 SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 PCB CODE 01103191 01103192 01109211 12110121 04108211 04108212 09109211 01111211 16110206 29106211 23111211 23111212 15109211 15109212 01101221 01101222 01102221 26112211/2 11009121 SC6204 18107211 18107212 01106193 01106196 SC6309 07101221 01112211 29103221 29103222 29103223 01107021 09103221 09103222 CSE211002 08105221 16103221 04105221 01106221 04107192 07107221 10109211 10109212 04107221 CSE211003 04109221 04108221 04108222 18104212 16106221 19109221 14108221 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 04106221/2 01101231 01101232 Price $12.50 $2.50 $15.00 $30.00 $7.50 $5.00 $2.50 $5.00 $5.00 $5.00 $5.00 $7.50 $2.50 $2.50 $7.50 $5.00 $5.00 $7.50 $20.00 $25.00 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $2.50 $5.00 $5.00 $5.00 $25.00 $2.50 $2.50 $7.50 $5.00 $5.00 $5.00 $7.50 $7.50 $5.00 $7.50 $2.50 $5.00 $5.00 $7.50 $7.50 $5.00 $10.00 $2.50 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT 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 SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER 2M VHF CW/FM TEST GENERATOR TQFP-32 PROGRAMMING ADAPTOR ↳ TQFP-44 ↳ TQFP-48 ↳ TQFP-64 K-TYPE THERMOMETER / THERMOSTAT (SET; RED) PICO AUDIO ANALYSER (BLACK) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION MULTI-CHANNEL VOLUME CONTROL: VOLUME PCB ↳ CONTROL PCB ↳ OLED PCB SECURE REMOTE SWITCH RECEIVER ↳ TRANSMITTER (MODULE VERSION) ↳ TRANSMITTER (DISCRETE VERSION COIN CELL EMULATOR (BLACK) IDEAL BRIDGE RECTIFIER, 28mm SQUARE SPADE ↳ 21mm SQUARE PIN ↳ 5mm PITCH SIL ↳ MINI SOT-23 ↳ STANDALONE D2PAK SMD ↳ STANDALONE TO-220 (70μm COPPER) RASPBERRY PI CLOCK RADIO MAIN PCB ↳ DISPLAY PCB KEYBOARD ADAPTOR (VGA PICOMITE) ↳ PS2X2PICO VERSION MAINS POWER-UP SEQUENCER MICROPHONE PREAMPLIFIER ↳ EMBEDDED VERSION RAILWAY POINTS CONTROLLER TRANSMITTER ↳ RECEIVER LASER COMMUNICATOR TRANSMITTER ↳ RECEIVER PICO DIGITAL VIDEO TERMINAL ↳ FRONT PANEL FOR ALTRONICS H0190 (BLACK) ↳ FRONT PANEL FOR ALTRONICS H0191 (BLACK) WII NUNCHUK RGB LIGHT DRIVER (BLACK) ARDUINO FOR ARDUINIANS (PACK OF SIX PCBS) ↳ PROJECT 27 PCB DATE MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 NOV23 NOV23 NOV23 NOV23 NOV23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 DEC23 JAN24 JAN24 JAN24 JAN24 FEB24 FEB24 FEB24 FEB24 FEB24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 MAR24 PCB CODE 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 04106181 04106182 15110231 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 04108231/2 04107231 10111231 SC6868 SC6866 01111221 01111222 01111223 10109231 10109232 10109233 18101231 18101241 18101242 18101243 18101244 18101245 18101246 19101241 19101242 07111231 07111232 10108231 01110231 01110232 09101241 09101242 16102241 16102242 07112231 07112232 07112233 16103241 SC6903 SC6904 Price $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 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 $10.00 $5.00 $2.50 $2.50 $5.00 $5.00 $5.00 $3.00 $5.00 $2.50 $2.50 $5.00 $2.00 $2.00 $2.00 $1.00 $3.00 $5.00 $12.50 $7.50 $2.50 $2.50 $12.50 $7.50 $7.50 $5.00 $2.50 $5.00 $2.50 $5.00 $2.50 $2.50 $20.00 $20.00 $7.50 CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION SKILL TESTER 9000 PICO GAMER ESP32-CAM BACKPACK AUG23 AUG23 APR24 APR24 APR24 01108231 01108232 08101241 08104241 07102241 $2.50 $2.50 $15.00 $10.00 $5.00 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 Subscribe to MARCH 2024 ISSN 1030-2662 03 The VERY BEST DIY Projects ! 9 771030 266001 $12 50* NZ $13 90 INC GST INC GST Laser Communicator Transmit sound over a laser b Pico Digital Video Termi eam nal HDMI compatible display an d USB keyboard adaptor for microcontroller p rojects ‘Wii Nunchuck’ RGB Light Control up to four independe Driver nt RGB strips Arduino for Arduinians 70 Arduino projects to build in this book ...and much more! Australia’s top electronics magazine DATA STORAGE SYSTEMS how data is stored today and in Silicon Chip is one of the best DIY electronics magazines in the world. Each month is filled with a variety of projects that you can build yourself, along with features on a wide range of topics from in-depth electronics articles to general tech overviews. the future Published in Silicon Chip If you have an active subscription you receive 10% OFF orders from our Online Shop (siliconchip.com.au/Shop/)* Rest of World New Zealand Australia * does not include the cost of postage Length Print Combined Online 6 months $70 $80 $52.50 1 year $127.50 $147.50 $100 2 years $240 $275 $190 6 months $82.50 $92.50 1 year $150 $170 2 years $285 $320 6 months $100 $110 1 year $195 $215 All prices are in Australian dollars (AUD). Combined subscriptions include both the printed magazine and online access. 2 years $380 $415 Prices are valid for month of issue. Try our Online Subscription – now with PDF downloads! Computer Storage Systems; February & March 2024 Raspberry Pi Pico Digital Video Terminal; March & April 2024 Mains Power-up Sequencer; Feb 2024 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 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 Other uses for Mains Power-Up Sequencer The Mains Power-Up Sequencer articles in the February & March 2024 issues (siliconchip.au/Series/412) immediately caught my attention. Although it does solve a common problem I had, I hoped it was about sequencing to control the power output of a generator or inverter to run several loads in sequence during a power outage. Say a business has several fridges/ freezers to run from a small emergency power source. It would be very useful to be able to sequence the output to several loads for varying periods, like 15 or 20 minutes, making it unnecessary to manually switch loads to avoid overloading a generator or inverter. The device described could possibly be modified to supply power to each outlet separately, limiting the total load on a power supply. What would need to be done to allow that? (F. F., via email) ● The existing hardware would be capable of doing that job; it is just the software that would need to be changed to provide this function. We are planning to publish a short article with modified software for this application. Radio board for the RPi Clock Radio Regarding the Raspberry Pi Clock Radio project (January & February 2024; siliconchip.au/Series/410), the author mentions on page 78 of the February issue that he mounted a small radio board in the enclosure. Where did he get that board from? (J. A., Townsville, Qld) ● Stefan responds: I used a DigiKey FM radio kit, part number 1927-1016ND. The DigiKey website page for that kit has a link to a data sheet that includes two circuit diagrams. One is for the radio receiver (on page 7 of the data sheet), while the other is for the audio amplifier (on page 8). siliconchip.com.au I took the (mono) audio output from the left-hand side of resistor R5 on the kit board (a 0W resistor) and connected that to both the L and R radio inputs of the Clock Radio. I did not populate R5 or any components shown in the page 8 amplifier circuit section. I took power for the kit radio from the clock’s 5V switched power output. Wanted: power supply protection circuit The Raspberry Pi Clock Radio project starts on page 28 of the January 2024 issue. However, I am primarily interested in the power supply and protection circuit on page 32, at lower left. Has Silicon Chip ever published a project similar to this zener/SCR/ Mosfet circuit as a kit? I like the idea of building my own personal power supply protection box as an interface between my projects and the power supply, as a safety precaution against connecting the wrong switch-mode power supply. If you have not, do you know of anything similar? I would be very interested in building such a device. (J. T., Teneriffe, Qld) ● We haven’t published such a circuit as a separate PCB. It is not an ideal circuit for general use, as the diode will short out the input supply if the power supply polarity is reversed. If the supply can provide over 1A, the diode could fail. There is a circuit notebook from April 2012 (“Using Mosfets For Reverse Polarity Protection”; siliconchip.au/Article/713) on providing reverse polarity protection. You could add the SCR and Mosfet circuitry from the Clock Radio to provide over-voltage protection to that circuit. Since we think this is a good idea, we are working on designing a PCB based on that approach. For reverse polarity protection, you could also consider the Ideal Diode Bridge project from the December 2023 issue (siliconchip.au/Article/16043), especially the small (SOT-23) Mosfet Australia's electronics magazine version. It will make a DC-powered device polarity agnostic. It won’t do anything about over-voltage, though. Questions about TV antenna reception I live outside the ACT, and TV reception comes from Canberra’s Black Mountain Tower transmitter. I am not in a terrific reception area, and to make matters worse, I live just over the brow of a hill. These factors notwithstanding, reception is usually OK – affected principally by weather. A few weeks/months ago, SBS simply dropped right out. The other channels were unaffected, and everything is pretty much back to normal now! ACMA tells us that TV frequencies range from 177.5MHz to 226.5MHz (SBS is at 184.5MHz), all signals are vertically polarised, and all are transmitted at identical power (50kW). So I have no idea why I experienced this dropout, and neither did the good folk from SBS! If you have any thoughts, I am all ears. Between old age and bad weather, my external (commercial) TV antenna is falling apart. I am considering adapting your antenna design from the February 2018 issue as a replacement. Given the vertical polarisation, I will need to mount the antenna to match, but will it be OK to mount it adjacent to the vertical steel pole on my roof? Or should I contrive some form of stand-off, and if so, how far should the antenna be mounted from the pole? Thanks – I love the magazine. (G. B., Wamboin, NSW) ● Regarding the SBS signal dropout, perhaps the signal strength from your existing antenna is marginal; reception can be lost with slight drops in signal level. Mounting the Yagi for vertical polarisation will mean that the metal mast will affect the antenna pickup pattern. The primary solutions are to use a non-metallic (eg, fibreglass) mast or to separate the antenna from the mast by a horizontal bracket by a half April 2024  99 wavelength or more (>813mm) and mount it to the centre of the antenna boom. The coaxial cable needs to drop from the rear of the antenna. Recreating the original Pong game I am looking for a PCB that recreates the real Atari 1972 Arcade pong (I mean the exact gameplay and graphics). Does one of the two (Nano TV Pong & Mini Arcade Pong) that you sell fit with my wish? (I. B., via email) ● As stated in the Mini Arcade Pong article (June 2021; siliconchip.au/ Article/14884), it is a direct copy of the original arcade version of Pong. The only changes are that it uses a smaller PCB and fixes some ‘bugs’ in the original design. That’s all explained in the article. You should ideally read that article to see if it’s what you want before ordering the PCB. Sourcing Universal Speed Controller parts I intend to build your Refined FullWave Motor Speed Controller from the April 2021 issue (siliconchip.au/ Article/14814). Unfortunately, I don’t have a copy of that magazine, but I intend to purchase a back copy. However, it occurred to me that I will also need to buy (at least) a PCB and a programmed micro. I have become aware that there are two versions of the micro available. I may buy both, if available. With a bit of luck, these items can be included with the cost of the postage of the back issue of the magazine. Are there any other special parts for this unit that Silicon Chip can also supply? (P. W., Pukekohe, New Zealand) ● We can supply the hard-to-get parts as well as the PCB and programmed PIC (either version) at the same time as the back issue. The postage cost will be slightly higher since a magazine can be sent as a letter. We find that letters sent overseas often go astray, so we are not willing to send more expensive items as untracked letters. Note that the programmed PIC can be ordered separately or as part of the hard-to-get parts set. See siliconchip. au/Shop/?article=14814 for a complete list of parts for that project. This link can be found by searching for the article on siliconchip.com.au/Articles/ 100 Silicon Chip ContentsSearch, then following the resulting shop items link. Our set of hard-to-get parts (SC6503) includes the PCB, AX-1000 current transformer, programmed microcontroller (either version) and all the other semiconductors. The rest of the parts are available from Jaycar/Altronics. Adding a crystal to the Analog TV Modulator I built the Analog TV A/V Modulator for Vintage TV sets from the March 2018 issue (siliconchip.au/ Article/11007). It has had a lot of use since that time. The author of the article, Ian Robertson, mentioned that he considered using a crystal for the 64.25MHz vision carrier for Channel 2. However, no further information was provided. I would like to retrofit a crystal into my modulator, but I’m unsure how best to do that regarding both the circuit changes and physical mounting. I hope you or Ian can advise how best to make this change to the modulator. Even better, perhaps there’s a chance for a redesigned board that accommodates the crystal option for those wishing to use a crystal. (G. D., Bunyip, Vic) ● Ian Robertson responds: I did look at using a crystal for the modulator, but at the time, it would have been a special order and the quotes I got put me off the idea. In the meantime, in my day job, I’ve been talking to a supplier of programmable oscillator modules in Hong Kong. They may be able to supply a field-programmable oscillator that would be ideal for this task. If so, I’ll modify the design to incorporate it. I plan to build a few more on different channels for my vintage TV room! The MC1374 does not lend itself to a direct PLL solution. Assuming you can get the crystal, it’s pretty easy to add it to the existing board; you don’t even need to remove the coil. The crystal, Ra and C2 can be mounted under the board. The circuit from the Motorola Application Note AN-0829 can be seen below. I used this circuit in a version of this modulator we used to make many years ago for a set-top box, using CH0 on 46.25MHz, so I know it works. We This circuit from Motorola Application Note AN-0829 shows how to connect a crystal to the MC1374. Australia's electronics magazine siliconchip.com.au made hundreds of them. We found Rb unnecessary (at least for the crystal we were using), so you may be able to avoid cutting a track on the board. Reason for MPPT Solar Charger design changes Can you explain why the Solar MPPT Charger & Light Controller published in February 2016 (siliconchip. au/Series/296; which I see is a combination of the projects published in May 2010 and February 2011) has the output caps changed from three 4700μF electrolytics to just two 100nF X2 capacitors? Is it because of the new addition of the LiFePO4 battery? If I want to build several chargers for a 12/24V 200Ah LiFePO4 battery (let’s say a maximum of eight chargers hooked up to 150-180W solar panels), which version do you recommend? (C. G., Bucharest, Romania) ● The output capacitors are different between the designs since the 4700μF capacitors used in the original design to smooth the output of the switch-mode regulator were determined to be unnecessarily high in value. The paralleled 100nF capacitors were found to be just as effective, likely due to the battery acting like a high-value capacitor for lower frequencies (as any large battery will tend to do). If you’re considering building the MPPT Solar Charger, we recommend using the later February 2016 design. Producing an AM IF signal with DDS I recently bought the AD9833 DDS module and the appropriately programmed PIC for the DDS IF Alignment (September 2017; siliconchip. au/Article/10799). The unit seems to work when asked to deliver a sinewave, but when switched to “AM” mode, the output looks strange to me. Rather than modulating the signal’s amplitude, it seems to be switching the signal on and off at the audio rate. I have set the carrier frequency to 455kHz. Could you please give an opinion of what might be going wrong? (P. G., Hillbank, SA) ● We asked Geoff Graham to check this, and he responded that the amplitude-modulated output of the Micromite BackPack DDS project was initially intended to be a sinewave, but that turned out to be beyond the performance capabilities of the Micromite. So he changed it to a square wave. The original Micromite DDS article (April 2017; siliconchip.au/Article/10616) explained it thus: “The sinewave screen has a check box for turning on or off amplitude modulation at 1kHz. This simply modulates the output with a 1kHz square wave and is useful for signal tracing.” If you want to produce a 455kHz wave modulated by a 1kHz sinewave, we have published some circuits that can do that. For example, the AM/ FM/CW Scanning HF/VHF RF Signal Generator (June-July 2019 issues; siliconchip.au/Series/336) offers proper sinewave amplitude modulation. It has the advantage of using a prebuilt DDS module, avoiding the need to solder any SMDs. That one has a fixed 1kHz AM frequency. The later AM-FM DDS Signal Generator (May 2022; siliconchip.au/ Article/15306) has a variable AM frequency of 50Hz to 10kHz and some GPS-Synchronised Analog Clock with long battery life ➡ Convert an ordinary wall clock into a highlyaccurate time keeping device (within seconds). ➡ Nearly eight years of battery life with a pair of C cells! ➡ Automatically adjusts for daylight saving time. ➡ Track time with a VK2828U7G5LF GPS or D1 Mini WiFi module (select one as an option with the kit; D1 Mini requires programming). ➡ Learn how to build it from the article in the September 2022 issue of Silicon Chip (siliconchip. au/Article/15466). Check out the article in the November 2022 issue for how to use the D1 Mini WiFi module with the Driver (siliconchip.au/Article/15550). Complete kit available from $55 + postage (batteries & clock not included) siliconchip.com.au/Shop/20/6472 – Catalog SC6472 siliconchip.com.au Australia's electronics magazine April 2024  101 other benefits, but it does require soldering a few SMDs. Using Jaycar tweeters for Barking Dog Blaster I want to build the Barking Dog Blaster (September 2012; siliconchip. au/Article/529), the successor to the Woofer Stopper. However, the Motorola/CTS KSN1005A tweeters are no longer available. Jaycar is selling a generic version under the original part number specified in the original article, CT1930. It is unclear to me which product will be a close match for the KSN1005A, especially as the use case is a little unusual. I’d appreciate suggestions on what currently available tweeter will do the job well. (A. C., Auckland, New Zealand) ● The Jaycar CT1930 can be used in place of the KSN1005. They should fit right into the specified enclosure without any modifications. Designing and making printed circuit boards I’m 13 and I enjoy reading your magazine. I would like to make my own PCB but I don’t have a laser printer and I don’t want to go through a PCB-­ making company. Is there another way of making one? I also want to learn how to design PCBs. Can you explain how to do that? (Danni, via email). ● There are a few different ways of making PCBs. While we know you said you didn’t want to, ordering them from a manufacturer is usually the cheapest option for smaller boards, gives the best results and doesn’t involve messing around with any chemicals. You could try one of the manufacturers that advertise in the magazine, like www.pcbway.com or www. ldelectronics.com.au You could check your local Jaycar store to see if they have any PCB Etching Kits left (HG9990). Only a few stores have those left in stock, though. Other sodium persulphate or ferric chloride based etching systems are available. Whichever one you use, make sure you read and follow the safety instructions. As for the software, there are many options and it depends on what you want. CircuitMaker is free and has lots of features, see: www.altium.com/circuitmaker 102 Silicon Chip AWA Radiola audio distortion on strong stations I am currently restoring an AWA Radiola radio, but I am having significant problems with intermodulation distortion in the reflexed IF/AF stage. The radio doesn’t have enough gain to receive my favourite AM radio station without connecting an external aerial to it, and when I do that, the strong local signals distort. This distortion is centred around the reflexed stage, and I have checked & replaced all components around it. However, when I modify the stage to work purely as an IF amplifier, the audio at the detector is perfect, which seems to verify my belief that the distortion is intermodulation distortion. There isn’t enough audio at the detector to drive the 6F6 output valve. Now for the bit that will horrify the purists: I plan to add an extra audio stage, and the neatest way I have come up with is to fit a preamp under the chassis based on an LND150 depletion-mode Mosfet. I have found a suitable circuit on the internet. The only thing I don’t know how to do is compare the gain of this preamp to a single triode preamp of the type normally used in a valve radio. Can you guide me, please? (P. W., Pukekohe, New Zealand) ● Ian Batty responds: reflex sets are prone to overloading and to the ‘minimum volume effect’ (where you can turn it all the way to zero but still get some playthrough). I can’t comment on the intermodulation distortion, but you may have simple overloading/clipping/amplitude distortion. Do you know what the DC voltages for the stage should be? If they are incorrect, I would not expect the circuit to work as designed. Your set may have AGC applied to the reflex stage, or it may not, so you will need a circuit diagram to at least work that out. If the reflex stage has no AGC, the converter (and RF amp, if there is one) will be controlled. If it’s a really old set, there may be no AGC at all. If you tell me the model of the radio, I can probably get a circuit diagram and provide further advice. AWA sets were pretty well designed, so while your Mosfet preamp may well work, it’s better to fix a leaky sump than pop a drip tray underneath where you park. Associate Professor Graham Parslow adds: I am most definitely not a purist when it comes to what is hidden under a chassis, but I am when it comes to sound quality. So my advice is to keep trying all possibilities until it works. Excessive gain in a stage is easily fixed by a resistor or two. If the audio is fine after the detector, there has to be a way to get good output. At worst, you can replace the whole amplifier section with a solid-state module. Many vendors on AliExpress will sell you such a unit for under $4. Other possibilities include KiCad (www.kicad.org) and the free (limited) version of DipTrace (https:// diptrace.com). There are others, but three options should be enough for you to look into initially. Fixing a tachometer that’s reading too high I am trying to use a two-cylinder motorbike tachometer in a 1968 car with a V8 engine. Once the engine has warmed up, the reading on the tacho is 2000 RPM when it should be reading more like 500 RPM. I can only assume the increased number of cylinders is throwing out the reading. Are you aware of a device that can compensate for the number of cylinders and correct the reading? (N. B., via email) ● Presumably, the tachometer simply connects to the ignition coil at Australia's electronics magazine the points or a similar trigger point. Since the V8 will have four cylinder firings per rotation rather than one, the tachometer will need to ignore three out of every four pulses to give a correct reading. There are digital divider circuits that can do that, but first, the signal would need to be made suitable for a divider circuit. To do that, we suggest you use the input ignition processing section from the LED Tachometer (October 2006; siliconchip.au/Series/82). Duplicate everything from the tacho input up to pin 6 of IC3. The resulting signal can be applied to the clock input of a CD4040 IC to divide it by four. The Q2 output at pin 7 will be the divided output. Tie the reset pin to 0V. The 4040 should be powered from a 12V (7812) regulator. Information on the 4040 can be found at www.ti.com/product/CD4040B 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 PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au FOR SALE LEDs and accessories for the DIY enthusiast LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware. For a full list of the parts we sell, 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 SILICON CHIP For Quality That Counts... QUALITY COMPONENTS AT GREAT PRICES. Check out the latest deals this month. SMD parts and more. Go to www.lazer.com.au Silicon Chip Binders H Each binder holds up to 12 issues Price: $21.50 plus $12.00 p&p each (SC0578). Postage price quoted is only for Australia ASSORTED BOOKS FOR $5 EACH Electronics and other related subjects – condition varies. Most of the remaining books are data sheets. Some of the books may already have been sold. See the photos (updated once again 31/01/2024): siliconchip.au/link/ absm Email for a quote (bulk discount available), state the number directly below the photo when referring to a book: silicon<at>siliconchip.com.au ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone (02) 9939 3295. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia's electronics magazine April 2024  103 Advertising Index Altium............................................ 7 Altronics.................................45-48 Dave Thompson........................ 103 DigiKey Electronics....................... 3 Electronex................................... 21 Emona Instruments.................. IBC Hare & Forbes............................. 13 Jaycar..................IFC, 10-11, 15, 17 ................................... 19, 87, 89, 95 Keith Rippon Kit Assembly....... 103 Lazer Security........................... 103 LD Electronics........................... 103 LEDsales................................... 103 Microchip Technology.............OBC Mouser Electronics....................... 4 PCBWay......................................... 9 PMD Way................................... 103 Quest Semiconductors................. 8 SC GPS Analog Clock............... 101 SC Ideal Bridge Rectifiers........... 77 SC Keyboard Adaptor................. 57 SC PDFs on USB......................... 71 Silicon Chip Back Issues........... 93 Silicon Chip Binders................ 103 Silicon Chip Shop.................96-97 Silicon Chip Subscriptions........ 98 The Loudspeaker Kit.com.......... 83 Wagner Electronics..................... 14 Notes and Errata Microphone Preamplifier, February 2024: in Fig.8, the 150Ω resistor next to CON10 should be 330Ω and the two 3.9kΩ resistors above L2 should both be 3.0kΩ as described in the text on p33. Arduino DCC Controller, January 2020: transistor Q1 on the RevF DCC Power Shield PCB (09207181) has the connections to its collector and emitter reversed. To fix this, rotate the transistor 180° relative to the PCB silkscreen markings, swapping the collector and emitter. It might work with the original (incorrect) orientation, but it is not guaranteed. Next Issue: the May 2024 issue is due on sale in newsagents by Monday, April 29th. Expect postal delivery of subscription copies in Australia between April 26th and May 15th. 104 Silicon Chip LED Battery Voltage Indicator kit wanted Do you sell the KA1778 LED Battery Voltage Indicator kit? It was advertised as being sold by Jaycar in Electronics Australia magazine, September 1995 (pages 76-77). (S. W., Yungaburra, Qld) ● We have not made any kits for Jaycar. When they sell kits based on our designs, they make the kits themselves. Therefore, we do not have any Jaycar kits to sell, only our own kits. According to their website, that kit has been discontinued and is unavailable (www.jaycar.com.au/p/KA1778). You might be interested in our 10-LED Bargraph project from the February 2018 issue, which could be used for similar purposes (siliconchip. au/Article/10970). We don’t have a kit, but we can supply the PCB(s), as listed on our website at siliconchip. au/Shop/?article=10970 Tracing underground power lines I just bought a long property, and the power box is near the gate, while the shed is at the opposite end of the block. I don’t have dial-before-you-dig info and wish to avoid an accident. Have you published any articles on locating power lines underground? (S. B., Booval, Qld) ● We published a Magnetic Field Strength Meter that could be used to find the vicinity of powered mains wires in the October 1991 issue (see siliconchip.au/Article/5849). The LCD screen and driver chip (ICL7106) are not strictly necessary as a multimeter set for measuring DC volts could be used to monitor voltage after the full wave rectifier in the circuit. Essentially, you would need to walk around the area and use it to monitor the magnetic field strength, looking for a maximum reading. You would then be over the underground power lines. The best sensitivity would be when considerable power is drawn through the wiring. Detectors are commercially available but can be expensive. Building a low-power inverter I want to build a low-power AC inverter for electric toothbrushes and razors that do not have 12V charging capabilities. The 15W 240V Inverter in Australia's electronics magazine the June 1992 issue caught my eye, so I bought the magazine (siliconchip.au/ Article/5549). However, I need help as the main Mosfets (MTP3055E) are no longer made, and the article explicitly says not to substitute. Is there a modern equivalent? The dual transformers are pretty expensive at the moment ($15.75 each), so I thought element14 Cat 1214612 (16VA, 230V to 2 × 9V) might be a suitable replacement. I know it won’t fit the circuit board, but I will be designing a new (double-sided) one as you do not sell the old one anymore, and I want it to fit an existing case anyway. Before I start building it, do you have a newer version? Is there a pure sinewave version? Obviously, square wave drive is not suitable for many devices. Would switch-mode power supplies (shaver) and Braun Oral-B toothbrushes cope with the square wave output? (D. M., Hawthorn West, Vic) ● That design is somewhat outdated, although it would work for your purpose. The MTP3055E Mosfets can easily be replaced by many others. They were rated at 12A and 60V, and many better Mosfets are now available. The article said not to use alternatives because it utilised the avalanche rating of the Mosfet to clamp transients from the transformer windings when switched, and avalanche-rated Mosfets were rare then. The common IRF540(N) would be a suitable substitute. Yes, the element14 transformer would be appropriate. Although a square-wave inverter, the transformer will round off the squareness somewhat. A sinewave inverter would be better overall than a square wave type, but how much it matters depends on the charger’s design. Typically, a square wave inverter produces a 230V AC waveform with a 230V peak. A modified square wave inverter is better as it produces 230V AC with a 325V peak on the waveform, more like a sinewave inverter but with squarer edges. If you are after a small sinewave inverter, see our May 2016 project: the 230/115V AC, 50/60Hz Precision Turntable Driver (siliconchip.au/ Article/9930). The parts to build that should all still be available, although the transformer is now pretty expensive at over $60! 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