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FEBRUARY 2021 ISSN 1030-2662 02 The VERY BEST DIY Projects! 9 771030 266001 $995* NZ $1290 INC GST INC GST Radio Time Signals keeping tracking of time without GPS or the internet Making Android Apps using App Inventor How to Upgrade your Computer Battery Multi-Logger 6-100V <at> 10A (or even 100A!) Clean up your Workbench with this Micro Oscilloscope & USB-controlled Power Supply awesome projects by On sale 24 January 2021 to 23 February 2021 Our very own specialists have developed this fun and challenging Arduino® compatible project to keep you entertained this month with special prices exclusive to Club Members. BUILD YOUR OWN: Micro ROS Controller Cable not included. Do you build robots and need a neat and easy way to control them? Perhaps you’ve heard of the Robotic Operating System (ROS) but don’t know where to begin to create your own? Then have a look at our new project utilising our popular UNO with Wi-Fi board and LCD controller. This project gives you everything you need to set up a ROS environment on your PC and builds a small controller which you can use to control a simulator around on the page. Once you’ve built it, you can easily transport the controller to control any other ROS robot with a flick of a command. You can use your ROS controller on countless robotic projects: from 2 wheeled robotic platforms, to robotic arms, and anything in between, thanks to the capabilities of the Robotic Operating System. SKILL LEVEL: Beginner TOOLS: Side Cutters WHAT YOU NEED: 1 x Arduino® Compatible UNO Board with Wi-Fi 1 x Arduino® Compatible 2 x 16 LCD Controller Module 4495 $ XC4411 $39.95 XC4454 $19.95 SAVE 20% SEE STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/ros-controller See other projects at www.jaycar.com.au/arduino SCREW TERMINAL SHIELD FOR ARDUINO® UNO Simplify wiring for your Arduino® UNO board without soldering or using jumper wires. • Connections via screw terminal blocks • Large prototyping area • 72(W) x 67(D) x 24(H)mm XC3890 ONLY 15 $ 95 ACRYLIC BASE FOR ARDUINO® UNO AND BREADBOARD Allows mounting an UNO and breadboard to create an easy to use prototyping station. • Self-adhesive rubber feet • 120(L) x 83(W)mm PB8840 Note: Uno & Breadboard not included. ONLY 12 $ 95 KIT VALUED AT $59.90 CLEAR ACRYLIC ENCLOSURE FOR ARDUINO® UNO WITH GPIO ACCESS GREY VENTED ABS ENCLOSURES ONLY FROM Protect your Arduino® UNO board against damage, dust and scratches. • Pre-drilled to provide easy access to all ports XC4406 4 $ Got a great project or kit idea? If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com Shop the catalogue online! Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * CLUB OFFER BUNDLE DEAL 95 Protect your project from unwanted fingers or objects. • Satin textured finish • Moulded standoffs • Snap-fit assembly 40 x 40 x 20mm HB6114 $3.95 60 x 60 x 20mm HB6116 $5.45 80 x 80 x 20mm HB6118 $5.95 395 $ Looking for other projects to do? See our full range of Silicon Chip projects at jaycar.com.au/c/silicon-chip-kits or our kit back catalogue at jaycar.com.au/kitbackcatalogue www.jaycar.com.au 1800 022 888 Contents Vol.34, No.2 February 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 9 Radio Time Signals throughout the World Radio signals can provide a way to synchronise timekeeping devices without internet access or a GPS receiver – by Dr David Maddison 25 Follow-up: Quantum-dot Cellular Automata We cover a more efficient approach to the standard 3-input majority gate, and how to incorporate it into a full one-bit adder – by Dr Sankit Ramkrishna Kassa 74 Making Android Apps with App Inventor App Inventor is a browser-based tool which is used to make mobile applications. In this article we’ll show you how it can be used to make a time domain reflectometry calculator for your Android smartphone – by Roderick Wall Radio-controlled clocks and watches are an interesting way to maintain accurate time. They’re synchronised via a radio transmitter, connected to an atomic clock, over the LF and SW bands – Page 9 88 Upgrading your Computer to the latest CPU We’ll cover what to consider before making the leap and what pitfalls you might get caught on, and most importantly whether it’s worth it – by Nicholas Vinen 98 El Cheapo Modules: LCR-T4 Digital Multi-Tester The Geekcreit multi-tester will identify, check and anaylse bipolar transistors, JFETs, Mosfets, diodes, resistors, capacitors, inductors etc – by Jim Rowe Constructional Projects 28 Battery Multi Logger The Battery Multi Logger uses a dedicated Micromite BackPack, and can monitor a battery from 6-100V at up to 10A, or much more (100A+) with an external shunt – Page 28 Monitoring the condition of your batteries is essential for long-term use. This project helps you to monitor, log and even troubleshoot batteries from 6-100V at up to 10A, or 100A+ with external shunts – by Tim Blythman 38 Arduino-based Adjustable Power Supply This basic power supply has voltage/current monitoring and limiting, and only requires an Arduino Uno, matching shield and computer – by Tim Blythman 61 Electronic Wind Chimes Here’s an alternative way to play wind chimes using solenoids. You can even record and play back set tunes – by John Clarke 80 Making a Compact Virtual Electronics Workbench A Raspberry Pi can be used to create a remote, computer-controlled and electronically-isolated test bench. It incorporates a Bitscope Micro USB oscilloscope and an adjustable power supply – by Tim Blythman This 0-14V, 0-1A power supply based on an Arduino is a compact, portable supply which only needs a computer to operate – Page 38 Your Favourite Columns 46 Serviceman’s Log A feline-themed cautionary tale – by Dave Thompson 69 Circuit Notebook (1) LCD clock and thermometer (2) DIY laser rangefinder (3) Animal and pest repeller (4) Multi-frequency sinewave generator (5) WiFi snooping with a Raspberry Pi 102 Vintage Radio Philips 1952 BX205 B-01 AM/SW battery valve radio – by Charles Kosina Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback siliconchip.com.au 97 Silicon Chip Online Shop 107 Ask Silicon Chip 111 Market Centre 112 Notes and Errata Australia’s electronicsIndex magazine 112 Advertising Our bench space is at a premium, so we used a Raspberry Pi to create a low-cost development environment and testing system. It includes a two-channel oscilloscope and programmable power supply – Page 80 February 2021  1 www.facebook.com/siliconchipmagazine 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. Nicolas Hannekum, Dip. Elec. Tech. Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Art Director & Production Manager Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst 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 (12 issues): $105.00 per year, post paid, in Australia. 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 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 Printing and Distribution: Editorial Viewpoint New computer technology We haven’t published articles on personal computers in quite some time. The last one that I can find, in May 2012, is on optimising ADSL internet connections. There was also an article on the Linux operating system in July 2011 and a Macbook review in March 2010. Partly that’s because Silicon Chip isn’t a computer magazine, but of course, computers are made from silicon chips. The most advanced, powerful and flexible chips ever made are computer processors of various types. They contain billions of transistors and result from countless hours of engineering and testing, plus extremely impressive manufacturing techniques. One reason we’ve published so few computer articles of late is that computer technology has been somewhat stagnant over the last decade. There have been plenty of improvements in that time, but they’ve mostly been incremental. I think that’s starting to change now, so I plan to give computers some coverage, If you aren’t into computers, don’t worry, we’ll still have plenty of DIY and other articles. We’ll just be occasionally adding a computer-themed article into the mix. As evidence of the recent advances in computing technology, three major product series launches at the end of last year saw stocks of these new products almost immediately exhausted as production could not keep up with demand. Those were AMD’s Ryzen 5000 CPUs and Radeon 6000 series GPUs (graphics cards), and Nvidia’s RTX 3000 series GPUs. Apple also just released a line of Macs using their own ARM-based processors (the Apple Silicon M1) which have incredible levels of power efficiency and some other impressive features. The lack of availability was partly due to these new devices being so much more capable than the previously available equivalents, at similar prices (if you can find one). There were also supply problems due to COVID-19 (and many people being forced to stay at home also increased demand). It’s mind-boggling to realise that for a couple of thousand dollars, you can put together a computer that can perform over 30 trillion (3 × 1013) calculations per second! Solid-state data storage has also come a long way in the last year or two, with incredible speeds (more than four gigabytes per second for consumerlevel parts!), very high capacities and relatively low costs. So, we will likely have a handful of computer how-to articles this year. The first, in this issue, shows how to upgrade a PC to the latest AMD Ryzen 5000 series of CPUs (it is also mostly applicable to Intel CPU-based systems). We’ll also have some in-depth stories on the technology behind the incredible power of modern computers. The articles we have planned will describe some fascinating technology that I think many of our readers will not have heard of, or if they have, won’t know a lot about. To throw another almost unbelievable number out there, it is now possible to build a computer with over ten thousand computing units, each capable of executing instructions and performing calculations. We plan to do that and describe some of the challenges involved. By the way, Silicon Chip used to run quite a few computer columns in the early days, including one called “Computer Bits” from July 1989 to December 1998. We also had all sorts of other articles on topics like setting up a network, upgrading computer CPUs, computer reviews etc. Of course, PCs were not as mainstream back then and required a lot more DIY. So I don’t plan to go back to that sort of content. But the odd article on computer technology and some interesting computers you can build or modify yourself should be part of the mix of a magazine named after the very technology behind them. 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 may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”. Harbuch Electronics ownership change I just got the following email from Harbuch Electronics [edited for brevity and grammar – Editor]. It is great to know it will survive. We can ill afford any more losses in Australian electronics manufacturing. Hugo Holden, Minyama, Qld. Hi there, I’m sending you this email because you have dealt with Harbuch Electronics in the past and I wanted to update you on some recent changes. Unfortunately, the previous owner, Peter Terlich, fell seriously ill in May and couldn’t return to work. I was one of his larger customers through my other business Powerform Controls – Harbuch was making a current transformer for us that I had trouble sourcing elsewhere. After discussions with Peter’s family, I bought Harbuch Electronics. I love Australian manufacturing and have taken on Harbuch Electronics, aiming to continue to manufacture high-quality transformers locally. I’ve spent the last 25+ years working as an Electrical Engineer in various roles. Through Powerform Controls, we have a well-set-up manufacturing system that we will move Harbuch across to (Powerform also does all its manufacturing locally). We plan to continue making nearly all the transformers and things that Harbuch has made in the past: toroidal transformers up to 5kVA, E&I transformers, audio transformers, chokes, isolation transformers, powerboards and more. We’ve got all the manufacturing records going back 10 or so years – if you had a standard or custom design, we most likely have the manufacturing info for it. Garth and Vino, Peter Terlich’s staff, are also working with us. As a result of this, there is a new company, ABN, bank account and address. We have moved from Blacktown to the Powerform Controls factory in Artarmon. The old Hornsby phone number is our main phone number now, but the Blacktown landline also works. The preferred email address is sales<at>powerform.com. au – it is checked by Tim and myself, so things are less likely to get missed. I know Harbuch has let some customers down while Peter Terlich was sick – if that is the case, I hope you can give me a chance to restore the business relationship. If it has been a while since you dealt with us, I’d love to reestablish that relationship and make high-quality transformers for you. If you’d like to chat about anything, please give me a call. Peter McConaghy 02 9476 5854 4 Silicon Chip Smaller toaster oven for DIY solder reflow Santa was kind enough to buy me a Silicon Chip subscription, so I’m looking forward to more project building in 2021. At the moment, I am working on the DIY Reflow Oven (April & May 2020; siliconchip.com.au/Series/343). I got the controller working pretty well, so I went shopping for an oven. I purchased the baby sister of the Kmart oven that you mention in the article (www.kmart.com.au/product/9litre-oven/2487301). The capacity is much smaller (9L vs 28L), but it has a reasonable amount of power given the size (1050W vs 1500W) and is half the price ($29 vs $59). It has upper and lower heating elements, but they didn’t have room for the knob to select which elements are active. It is big enough for most circuit boards, and I can fit it more easily (space is at a bit of a premium at my place). My initial testing shows that it works fine using the PID parameters from the article. I think this is a better-suited oven for reflowing, mostly due to there being less empty space above the PCB. Thanks for all your hard work on these fantastic projects, and have a Happy New Year! Stephen Gordon, Thurgoona, NSW. Free circuit drawing and simulation software Around June 2019, Spectrum Soft called it quits and have released their Integrated Schematic Editor and Circuit Simulation software, Micro-Cap 12, for free. They have been in the business since the 1980s. Micro-Cap 12 used to retail for US$4,500 (about $6000). This is too good to miss. You can download it from www. spectrum-soft.com/download/download.shtm This is a great way to get one of the best schematic editors and simulation packages on the market. I found this info just by sheer luck on the But KIS Analog YouTube channel: siliconchip.com.au/link/ab62 They have several tutorials on Micro-Cap 12, with more in the pipeline. Greg Gifford, Laguna, NSW. Android app for calculating resistor values In the October 2020 Ask Silicon Chip column, R. M. of Melville WA asked for a BASIC program to calculate series/parallel resistor values. This prompted me to create Android apps for calculating series and parallel resistance using App Inventor (as described in the article I wrote, starting on page 74 of this Australia’s electronics magazine siliconchip.com.au issue). You can download these Apps from the Silicon Chip website under February 2021. The download package includes the Android .apk files and also the App Inventor .aia project files. These can be imported into App Inventor to make modifications by clicking on “My Projects”, then selecting “Import project (aia) from my computer”. Roderick Wall, Mount Eliza, Vic. BoM tide data outage On the morning of January 1st 2021, I got a message saying “Error – data not available” on my Raspberry Pi-based Tide Clock (July 2018; siliconchip.com.au/Article/11142). Our internet service is working OK. It started working again all by itself on the 3rd. I guess the Bureau of Meteorology shut the server down at midnight for the new year. It was down for at least one day. Roderick Wall, Mount Eliza, Vic. Helping to put you in Control PR200 programmable relay 230VAC A programmable logic relay with 8DI + 8DO + 4AI + 2AO (4-20 mA), LCD, 2x RS485 (Modbus RTU/ASCII) ports and 230VAC powered. Free easy to use Function-Block Software. SKU: AKC-002 Price: $399.95 ea + GST Simex SLI-8 8 Counter Modbus RTU module An 8 isolated digital input module with Modbus RS485 communications. Provides a non volatile 32 bit counter for each input. 24VDC powered. SKU: SID-003 Price: $239.95 ea + GST Getting into soldering SMDs I was always reluctant to try a Silicon Chip project that used SMDs, as I baulked at soldering those tiny components. However, when I saw the DAB+/FM/AM radio project, even though it bristled with SMDs, it was just what I was after, so I decided to give it a go. After buying the parts, I went to YouTube to see how to solder SMDs. I settled on the solder paste method. After buying some paste, I gave it a go. It was easy enough, but I had trouble keeping the components from moving while soldering, resulting in a wonky joint. After a while, I devised this system: 1. Put a dob of solder paste on the pads. 2. Locate the SMD. 3. Hold it down with the point of a scriber held vertically. 4. A few seconds with the soldering iron on the pins and the job’s done. With a hand on the top of the scriber, hand movement will not affect the component, and the soldering iron does not move the component. After I finally got the radio going, I noticed one channel was not working. I traced the trouble to a faulty SMD IC, which meant it had to be replaced. So I went back to YouTube to see how to remove an SMD IC. I settled on the desolder wire method. After buying some, I laid it along the IC’s pins and heated it with the soldering iron. The low melting point of the wire causes it to diffuse with the existing solder, and in no time, the IC lifted and floated to the side; a quick clean up with solder wick and it was ready for soldering the new IC. I learned a lot from this project, and am not reluctant to try others in the future. Trevor Vieritz, Burpengary, Qld. Comment: we are glad to hear that you got the radio working and are more comfortable working with SMDs, but you should be aware that there are problems with both methods described. We do not recommend using solder paste with a soldering iron. It is designed to be heated more slowly by hot air or infrared reflow, so the flux formulation is different. You siliconchip.com.au SPT-61 Transmitter PT100/500/1000 The SPT-61 signal converter is equipped with Pt 100 / Pt 500 / Pt 1000 type input, 4-20mA output. Loop powered. SKU: SIB-001 Price: $134.95 ea + GST BACnet MSTP Slave/Modbus Master - Converter The HD67671-MSTP-4-A1 BACnet Slave / Modbus Master Converter allows you to integrate a BACnet network with a Modbus net. It allows you to connect a BACnet Master (for example a Supervisory System...) with some Modbus slaves. SKU: ADW-001 Price: $586.80 ea + GST AirGate Modbus (Gateway RS-485/ Wireless) Wireless gateway for extending Modbus networks. USB and RS-485 interfaces. SKU: NOW-001 Price: $473.50 ea + GST 1-port isolated RS-422/485 Modbus Gateway Modbus TCP to Modbus ASCII/RTU converter gateway allows Modbus TCP masters to communicate with serial Modbus slave devices via isolated RS-422/485 interfaces with TB5 screw terminals. SKU: ATO-162 Price: $330.00 ea + GST Loop Powered 4-20mA Surface Temperature Sensor This is a simple 4-20mA output loop powered temperature sensor with measurement range from 0°C to +100°C designed for monitoring battery, heatsink and surface temperatures. SKU: KPS-015 Price: $83.00 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine February 2021  5 also risk flinging tiny solder balls all over the board, which is particularly bad for boards carrying high voltages as it could lead to arcing. The problem with desoldering wire is that once you have melted it into the solder on the board, it’s impossible to remove completely. It will change the formula of your solder, possibly leading to premature solder joint failures. Desoldering SMDs is very easy, quick and safe with a low-cost hot air wand. It can also be done with regular solder with some practice. BWD602 circuit diagram needed I love your magazine. I was wondering if any of your readers have a circuit diagram or manual for a BWD602 combination instrument. I am repairing one that I bought recently, and the diagram would be a great help. I am trying to build a collection of BWD instruments while some are still around, and am looking for more instruments if the price is right. Trevor Collins, Bellevue, WA. Comment: one of our readers, Bruce Williams, suggested it was a rebadged version of a Hung Chang OS650 oscilloscope from South Korea (siliconchip.com.au/link/ab63). It was also badged as Aron BS-601 or ProTek 6502. He included some PDFs of various manuals which can be downloaded for free from our website: siliconchip. com.au/Shop/6/5755 Trying to avoid price increases In your January editorial, you asked for feedback upon the content. I find the balance to be about right, and as a pensioner, I certainly would not like to see a larger publication with an attendant increase in price! Like you, I am surprised that it has been steady for so long. I do not read every article; for example, I’m not interested in the audio articles with cabinet making etc, but to each his/her own. The Vintage Radio section is quite interesting as is Circuit Notebook, along with the queries in Ask Silicon Chip (I have learned a great deal from the answers). One minor gripe is about the need for Windows to run some of the projects; many people refuse to run it due to its inherent bugginess and security problems. I understand that you have no control over the software that con6 Silicon Chip tributors use, but hopefully, some will see the light and make versions for better operating systems such as Linux, Mac, FreeBSD etc. All in all, the magazine balance is just about right. Dave Horsfall, North Gosford, NSW. Nicholas comments: As mentioned in a couple of editorials, I am putting off a cover price increase, but it will have to happen eventually. See the graph below showing the magazine cover price in 2020 dollars over time (calculated using the RBA’s inflation statistics). As you can see, the current cover price is the lowest it has been since 1996 in real terms (that was before the GST was introduced). Most of our projects which involve computer software these days will work on Windows, Mac or Linux. For example, the Arduino-based Adjustable Power Supply in this issue, the Flexible Digital Lighting Controller from October & November 2020 (except for the optional sequencing software reused from 2010) etc. Those all use software written in Processing which works in multiple different operating systems. Windows programs can often also be run on Mac systems (eg, via Bootcamp) or Linux (using WINE). Feedback on magazine content I’d like to comment about your Editorial Viewpoint in the December 2020 issue. I started electronics as a hobby when I was a teenager in the early 1990s, and at that time, I had a subscription to a French electronics magazine. I did not understand much of the schematics, so I bought some books to learn. It was only after I earned a master’s degree in microelectronics and digital communications that I really understood Australia’s electronics magazine the magic behind the transistors and other components. Many years later, in 2015, I came back to my hobby, and I was looking for a new magazine to subscribe to. Sadly, the magazine I previously subscribed to (Electronique Pratique) had ceased publication. Then I discovered Silicon Chip. Browsing the various issues, I could see many projects published in the magazine, some of the more complex ones over several issues. Some publications did not place much emphasis on projects, but rather technical articles instead. I also liked having the possibility to buy the PCBs and download the software. I thought that was a huge plus. Since I moved to Singapore and now live in a condo, I could not easily make my own PCBs anymore, but now it’s easy and relatively cheap to have them made. So I immediately took a subscription to Silicon Chip, and five years later, I have built many of your projects. I have to say I am delighted with the content of the magazine so far. I appreciate the balance between various types of projects and technical articles, Circuit Notebook, Ask Silicon Chip etc. What I really enjoy are those complex projects you publish over several issues, like the recent USB SuperCodec and its Attenuator board over five issues, or a few years back the great series of articles on the Mk4 UltraLD amplifier, the preamp, the power supply board and the speaker protection module. That was an amazing project that I built together with your 8-octave equaliser, LED VU meter and CLASSiC DAC! I had a great time building and testing all of them. You even published some pictures of my finished products (twice). Now there are also tons of smaller projects that are appealing for not only low-experienced readers and newbies, but also experienced ones. There’s something for everyone. I appreciate that you support your readers, not just by selling PCBs and supplying source code but also supplying hard-to-find parts, PCB layouts and answering readers’ questions. I work in the financial software world (trading platform), and support makes a huge difference between vendors, so does it for magazines, I believe. So I would not like to see you reduce siliconchip.com.au the number of projects from four. If you could increase the number of projects, that would be great! As I also enjoy the other sections of the magazine, I would like to see the number of pages increasing, like what you did a few times in the past with some issues. Consequently, I would be supportive if you increase the cover price with more content. As you said, the cover price has not increased in seven years. Not that this is a reason to do so now, but if you were to do so, I think most readers would understand. If you increase the price and add more pages, and thus more content, I believe most of the readers would understand that they have now more for their money. By increasing the number of pages, you might gain more readers, especially if that allows you to increase the variety of articles. For those who are very price-sensitive, there is always the option to subscribe online. That may not be the taste of all, but it’s an alternative. Olivier Aubertin, Singapore. VHF masthead amplifier works for DAB+ My boat is moored at Hastings on Western Port Bay, which is on the edge of DAB+ reception from Melbourne. Some times I can receive both multiplexes, sometimes the lower one, and often neither. I am using a 3-element Yagi, vertically polarised. Part of the problem is that it is looking out through a forest of aluminium masts, most with wire rigging. You recommended (in response to a query) that I use a VHF masthead amplifier to improve DAB+ reception. I did that, and it appears to be working well. Thanks for your advice. Geoff Champion, Hastings, Vic. Latest PICs & GPS disciplined oscillator I just read the article about the latest 8-pin PICs (November 2020; siliconchip.com.au/Article/14648). I have been testing out the PIC16F1455 lately – you’ve used it in several projects over the last few years, so I thought I’d see how it compared to the PIC16F628A I’d been using previously. I’m using it to build a much simpler GPS disciplined oscillator than the one you published in Circuit Notebook, siliconchip.com.au July 2020. It consists of little other than the 16F1455, a GPS receiver, an OSC5A2802 10MHz VCO and a thirdorder passive RC low-pass filter to convert PWM from the micro to a smooth control voltage for the oscillator. I think it’s about as simple as can be. The parts are quite cheap. Apart from the power supply, the total cost is less than $20, and who doesn’t have a 5V 1A power supply hanging about? The NEO-6 GPS receiver is a 3.3V part, so its TX data was marginal to drive the 5V PIC’s serial RX, a Schmitt trigger input. I got around that by creating a 9600 baud software UART using one of the input-only pins used for USB when USB is enabled. It operates as a TTL input, so it is quite happy receiving data at 3.3V. The 1PPS output of the GPS receiver is fed to the PIC’s internal comparator, with the other input being held at 1.9V by the internal DAC. The PIC is clocked from the 10MHz VCO, and it has an internal x4 PLL, giving a nominal base clock of 40MHz with a 10MHz instruction clock. Compared with the PIC16F628A I was using before, the 16F1455 has major benefits. The output PWM signal is now 40kHz, so it loops through the 24-bit dither system three times per second, and all artifacts disappear in the filter. Also, detection of the GPS 1PPS signal uses the gate function of TMR1, which clocks at 40MHz, so pulse timing can be determined to within 25ns. So there’s no need for the complex delay system of my previous circuit. The program evaluates data statistically, so the uncertainty decreases with more samples. The advanced 8-bit PIC architecture is much better than the PIC16F628A. Two indirect registers can access all memory (including program memory) instead of one that could access 256 bytes. Those registers can be used for moving data with auto-increment or auto-decrement. You can also load or store with an offset. There are added shift instructions, eg, logical shifts that don’t require the carry flag to be set/cleared before shifting; the older instructions rotated through the carry flag. There’s also an arithmetic right-shift that propagates the sign. There are added arithmetic operations that also affect the carry flag. Previously, a multi-byte add or subtract Australia’s electronics magazine February 2021  7 required four instructions for all bytes but the least significant byte; now it only takes two. The interrupt system is improved as much state data is saved when an interrupt occurs; previously, it was necessary to specifically save any register that the interrupt was going to use, and restore them on exit. Interrupts can be serviced without superfluous instructions – some of mine are now less than 10 instructions. There are new relative CALLW and BRW instructions that cater to page boundaries, and there are mechanisms to do just about anything. Program memory can be read and written (I now store constant text strings in program memory as two 7-bit characters per 14-bit memory location). The CALL stack can be manipulated, and the saved status from an interrupt can be manipulated. The only serious drawback is the banked memory model. Any operation involving a peripheral usually requires the user to change the bank register to access the peripheral, and not using the right bank results in unpredictable behaviour. You will remember the confusion about writing assembler code for MPASM, which is not included in the latest MPLAB X IDE downloads. I haven’t seen one positive comment regarding the replacement assembler, XC8; the almost universal consensus is to keep using MPASM as XC8 is only useful to write embedded assembler in C programs. I tried using XC8, but it was all too hard. I am using a threaded system so that the NMEA data from the GPS can be received and processed at the same time as the mainline is dealing with the 1PPS data. I couldn’t see how to make it work with XC8. Alan Cashin, Islington, NSW. A tale of two speed controllers First, I would like to say that I am very happy to see a PDF version of the magazine. Being a constant traveller, downloading the big file for the online issue via satellite on a slow shared connection was a problem. The main reason I wrote in is to say that just over two years ago, I built the first version of your Speed Controller for Universal Motors (February-March 2014; siliconchip.com.au/Series/195). Putting it together did not present any real problems, but it didn’t work 8 Silicon Chip straight away. I ran through the suggested troubleshooting, which was quite good. I checked the critical components with the power off and soon discovered the pots were open circuit. So I ordered new pots. Once I had replaced the cabling again, they checked out, but it still wasn’t working, So I powered it from my bench supply as the guide suggested. Everything seemed to be working as it was supposed to, so I disconnected the bench supply and made some checks when running from the mains. One of the first checks I made was to see that there was 15V getting to IC3 and REG1, but I only measured 7V. I had already checked BR2, the 1MW and 470W resistors and the 220nF capacitors. I thought that there might be a short or bad component, but nothing was running hot. I decided to try paralleling another 220nF X2 capacitor across one of the two feeding BR2. That gave me 9V across ZD1; an improvement, but still not enough. I tried replacing the two 220nF capacitors, but that didn’t help, So I swapped in 470nF X2 capacitors instead. Bingo, that did it! The speed controller was alive. It has been working well ever since. I was thinking about building another one so when I saw your new speed controller in the March 2018 issue (siliconchip.com.au/Article/10998), and realised that it would be much cheaper and simpler to build, I decided to go for it. Construction generally went OK, and it worked straight away, but I noticed that there wasn’t enough speed control. The main reason for building it was to convert a grinder into a polisher. I was a bit confused about how many turns were supposed to go through the current transformer. I had put in only one turn, and I had trouble with that. I changed it to two turns through the transformer core, and that fixed it. One of the uses I have for it is with my SDS hammer drill. It’s very good mechanically, but the contact protection override switch is terrible. Eventually, I will use the controller when contact detector and switch gives in totally, plus an earth-leakage circuit breaker (ELB) if working where I need the protection. Neil Brewster, Footscray, Vic. Comments: we aren’t sure why you Australia’s electronics magazine had to change the 220nF capacitors to 470nF in the first speed controller. 220nF should be adequate; perhaps your circuit is drawing more current than expected, eg, ZD1 may be leaky or trimpots VR1-VR3 may be lower values than the 10kW specified. For the second controller, the number of turns through the transformer is not critical (one or two turns is acceptable). The feedback adjustment trimpot can be used to compensate for the difference by reducing the feedback effect when two turns are used. Suggestion to redo rain gauge It might be a good idea to revisit your June 2000 Automatic Rain Gauge (siliconchip.com.au/Article/4325) and March 2000 Electronic Wind Vane (siliconchip.com.au/Article/4354), perhaps combined with your February 2018 Water Tank Level Meter (siliconchip.com.au/Article/10963). You could bring together the three projects to provide an online weather station with expanded capabilities. I think it makes excellent sense to use the project archive you already have and bring it forward in time by making it relevant to current circumstances. For example, by taking the rain gauge and weather vane projects and making them internet savvy with the online data logging functionality associated with www.thingspeak.com – you’re ticking many boxes from my perspective. Iain McGuffog, Indooroopilly Centre, Qld. Comment: we have looked at doing this sort of thing in the past, but we stopped when we realised that digital weather stations are now so cheap. We know that some people like to do it themselves, but the idea of spending several hundred dollars and many hours to build something that you can buy for $99 at Bunnings is not very appealing. Since it would take a lot of work to revisit such projects properly, we only want to do so if they will be popular with readers. Integrating the water tank level meter might make it more worthwhile, but keep in mind that the water level sensor itself is quite expensive (but worth it, in our opinion, as it is easy to install and works well). We will investigate this again to see whether it will be worthwhile, even though we already know that it doesn’t make much financial sense. SC siliconchip.com.au Radio time signals throughout the world Wouldn’t it be great if all your watches and clocks would adjust themselves automatically to the current time and also adjust themselves for daylight saving? There is a simple way to do this in many countries – and possibly even in Australia. It doesn’t require internet access or even a GPS receiver! M any people today use a phone, or a smartwatch linked to their phone, to tell the time. The time on most phones is very accurate, being derived from atomic clocks and associated time servers which is then broadcast over the mobile network. But some people still use a conventional watch or a clock to tell the time. Most digital watches are very accurate, only gaining or losing around 15-30 seconds per month, but they still have to be set manually. That is difficult to do precisely. Some clocks connect to WiFi networks and are synchronised to atomic clocks via time servers, and we have published several such designs in the past. Others synchronise to GNSS satellites such as GPS, which carry atomic clocks; again, we have published quite a few projects which do that. siliconchip.com.au But some watches and clocks synchronise their time with atomic clocks via radio signals, and that is the subject of this article. Timekeeping devices can receive radio signals through several methods. One is dedicated LF (low-frequency, 30-300kHz) signals from dedicated transmitters, which are operated in Europe, the United States, Japan and China. Another method is by dedicated signals transmitted on the shortwave band, with transmitters broadcasting on a variety of frequencies from 2.5MHz to 25MHz. These dedicated LF and SW time signals contain the time, date, leap second and other information encoded in digital form. Some stations such as DFC77 also by Dr David Maddison encode weather or other information. Many of these time signals can also be used as basic frequency standards. You can hear audio samples of a variety of LF and SW time signals at www.sigidwiki.com/wiki/ Category:Time Many normal AM (medium-wave) broadcast band stations also broadcast hourly “pips” at 1kHz, usually on the hour. These pips were first introduced by the BBC in 1924, and they were originally synchronised to Greenwich Mean Time (which varies slightly due to wobbles in the Earth) but since 1971 have been synchronised to International Atomic Time (which is more consistent). For those interested in those signals, there is additional information at www.miketodd.net/other/gts.htm No commercial receivers appear to take advantage of these pips, which Australia’s electronics magazine February 2021  9 Fig.1: demodulated audio of the BBC’s 1kHz Greenwich Time Signal “pips”, as heard on the hour since 1924. When there is a leap second, an extra pip is added. This was also used extensively in Australia but has now largely been replaced by the familiar six 500ms-long, 735Hz pips marking the start of the new hour. Image credit: Mtcv. are hour markers only and provide no further information. But they can be useful to visually determine that a clock is set accurately on the hour, if not necessarily to the correct time. In Australia, most AM stations (in particular) broadcast a series of six 735Hz pips in the five seconds before the hour, with the leading edge of the last pip marking the exact new hour. Most stations have radio silence during this period, although some use the otherwise “dead air” to play station ID or intro to news services over the top. Other methods of receiving time signals over the airwaves include: • digital television signals; both DVB (as used in Australia) and ATSC standards support time and date transmission to a receiver for program scheduling • commercial FM radio via the Radio Data System (RDS), which can be used to set attached clocks such as a car clock and time; timezone and date information is also sent • Digital Audio Broadcasting (DAB) which carries a timestamp in BCD (binary coded decimal) format • Digital Radio Mondiale (DRM), which can be decoded with a software-defined radio (SDR); see the S ILICON C HIP DRM article www. siliconchip.com.au/Article/10798 LF radio time signals Even today, with widespread internet access and low-cost GPS receivers, time signals over radio can be useful. LF (low frequency) radio time signals have very wide coverage (but not global, unfortunately) and the technology is relatively simple and cheap to implement. It is a lot simpler to have a wall clock, watch or other time-dependent device synchronise by LF radio signals compared to using a GNSS receiver or WiFi or phone connection. Also, the nature of LF radio propagation is that one transmitter with a relatively low power output can give excellent coverage, as the radio waves are propagated by either a ground wave or between the ground and the ionosphere (which acts as a waveguide) with a wavelength of kilometres. Edge diffraction helps the signals go around mountains and other obstacles, and building penetration is good. The wavelengths of LF time signals in use for consumer timekeeping are 1851-7500m. LF radio frequencies are used because their propagation characteristics are predictable and propagation delays are less than with shortwave, although shortwave time signals are also used. There are several different low-frequency time transmitters around the world. These are: • DCF77 in Mainflingen, Germany at Fig.2: locations and nominal (reliable) coverage areas for LF radio time signal transmitters. People report being able to receive JJY (Japan) at certain times in some parts of Australia and NZ. 10 Silicon Chip Australia’s electronics magazine siliconchip.com.au 77.5kHz (50kW with 30-35kW effective radiated power [ERP]) • MSF in Cumbria, UK at 60kHz (60kW with 17kW ERP) • JJY in Fukushima, Japan at 40kHz (50kW with 13kW ERP) and Kyushu Island at 60kHz (50kW with 23kW ERP) • WWVB in Colorado, USA at 60kHz (70kW) • BPC in Henan, China at 68.5kHz (90kW), although the signal is proprietary • RTZ in Irkutsk, Russia at 50kHz (10kW) • ALS162 (formerly TDF) in Allouis, France at 162kHz (800kW) These signals cover mostly Europe, the United States, Japan and China (see Fig.2). There is no official coverage for Australia or New Zealand, although it is possible to receive some of these signals in Australia under certain conditions, which we will describe later. While other services provide radio timekeeping on shortwave frequencies, most radio-controlled consumer clocks and watches use LF signals. The nearest radio time signals accessible in Australia under appropriate conditions are JJY Japan (LF), the proprietary BPC signal from China (LF) and also WWVH (SW) from Hawaii, USA. JJY is about 7773km from Sydney while WWVH is around 8200km and WWVB (LF) in Colorado is about 13,000km away. Note that many radio-controlled watches or clocks are called “atomic”. Seconds markers normally 50ms of 1000Hz but markers 55-58 are 5ms of 1000Hz and seconds marker 59 is omitted. Minute marker is 500ms of 1000Hz. During the 5th, 10th, 15th (etc) minute, seconds markers 50-58 are 5ms of 1000Hz Time code transmission (UTC) - valid at next minute. Binary ‘0’ duration is 100ms, Binary ‘1’ duration is 200ms. Parity check bits P1, P2 and P3: counting the binary ‘ones’ of each group plus the corresponding parity bit gives and even number. Normal seconds markers of 1000Hz, emphasised by 50ms of 900Hz. Tone immediately follows. Seconds marker 20 has a duration of 200ms. Designates the start of the time information. Fig.3: the now-extinct Australian Radio VNG time code format. VNG was considered unnecessary by the government and closed in 2002. This is not the correct terminology; it relates to the fact that the radio or GPS signals they receive are derived from atomic clocks. There is no atomic clock in the device itself. Apart from domestic watches and clocks, LF time signals, where available, are used by many industrial timekeeping devices. This includes radio stations, railways, energy supply companies, road control equipment such as traffic lights (which have to change to different schedules depending on the time of day), and just about anything that needs an accurate, reliable time within the range of a transmitter. Former Australian SW radio time signals Australia once also had its own shortwave (HF or SW, not LF) time signal station – radio VNG, Lyndhurst, Victoria. It was shut down in 1987 and relocated to Shanes Park, (Western Sydney) in NSW. This was again shut down in 2002. The closure inconvenienced many scientific users at the time. See Fig.3 and the video titled “A visit to VNG Lyndhurst 1986” at https://youtu. be/61C6IyWEqZE Apparently, the government thought that GPS timekeeping signals would take over. But in Europe, Japan and The Author has personally received a valid signal on his radio-controlled Citizen watch while camped on the side of Mt Bogong, Vic. Source: Casio. siliconchip.com.au Australia’s electronics magazine February 2021  11 Fig.4: legacy amplitude modulation WWVB time code format. Source: Wikimedia user Denelson83. the USA this is not the case, and there is still a huge and increasing demand for radio timekeeping services, especially on LF. Purely for interest’s sake, you may wish to look at plans published in Electronics Australia, July 1995 to use the 5MHz signal from VNG as a very accurate frequency reference. There is also a partial description of building a receiver and decoder for VNG time signals at www.electronicstutorials.com/receivers/vng-receiver. htm was used to synchronise power plants and phone networks. It is operated by the US National Institute of Standard and Technology (NIST). The location was chosen because of high soil conductivity, which provides good antenna performance. It broadcasts to an estimated 50 million radio-controlled watches, clocks and other devices in the USA. Original experiments with 60kHz transmission began in 1956, with station KK2XEI having a radiated power Fig.5: the antenna complex for WWVB at Fort Collins, Colorado, USA. of 1.4W. It proved that the 5km-wavelength signals could be propagated in the natural waveguide between the ground and the ionosphere, with 100 times more stability compared to shortwave transmissions. These signals could also travel great distances with a low transmitter power; the 1.4W signal could be received in Boston, 3137km away. A 4kW transmitter was then set up for more serious use, and it was increased incrementally to 50kW in 1999 and then again to 70kW in 2005. In 2012, an additional time code format called phase modulation was introduced, which improved decoding capability while maintaining backward compatibility with legacy devices. The extra power, along with the new modulation scheme, enabled many new and tiny devices to take advantage of the signal. It was anticipated that devices such as refrigerators, ovens, cars, traffic lights, irrigation systems etc would take advantage of the new encoding system. Legacy systems (with rare exceptions) are insensitive to the new phase modulation information transmitted, so continue to work. With phase modulation, a code independent of the legacy amplitude There is a trio of interesting, related projects at www.qsl.net/zl1bpu/ MICRO/VNGBOX/ One of these is a timecode generator for timestamping events using the VNG time code format, although the time signal is derived from GPS signals, since VNG no longer exists. We will now look at some of the radio time transmitters around the world. WWVB in the USA WWVB is the 60kHz LF station at Fort Collins, USA. It has been broadcasting since 5th July 1963, although it did not broadcast a time signal until two years later. At the time, the signal 12 Silicon Chip Fig.6: a diagram of the WWVB antenna arrangement, showing the capacitance hat structure (topload) of each antenna. Source: NIST. Australia’s electronics magazine siliconchip.com.au Fig.7: the time code format for WWVH (shortwave) from Hawaii, USA. This can be picked up in Australia under the right conditions. modulation scheme is transmitted via binary phase-shift keying of the carrier wave. A ‘one’ is transmitted by inverting the phase 180° or a ‘zero’ by a noninverted carrier phase. The rate of information transmission is one bit per second. For more details, see https:// tsapps.nist.gov/publication/get_pdf. cfm?pub_id=914904 WWVB has identical north and south antennas, each of which is a top-loaded monopole comprising four 122m-tall masts in a diamond shape, with a system of cables suspended between the masts. This is known as a capacitance hat or top hat (see Figs.5 & 6). The down-lead is the radiating element. Two antennas provide higher efficiency than a single antenna. The antennas are 857m apart. Since the wavelength at 60kHz is 5000m, and an antenna should be at least one-quarter wavelength long, theoretically the antenna should be 1250m tall. This is obviously impractical. This antenna is tuned, and the tuning is continuously adjusted under computer-control with a motorised variable inductor called a variometer. This allows it to cope with changing conditions. The use of longwave means that the siliconchip.com.au accuracy of the signal from WWVB is much better than shortwave stations WWV and WWVH (Fig.7), as there is much less multipath propagation. The WWV stations, along with radio amateurs, are also part of the US military’s Military Auxiliary Radio System (MARS). This provides emergency Fig.8: the JJY 60kHz tower at Hagene-yama, Japan with a transmission power of 50kW and an antenna efficiency 45%. The umbrella style mast is 200m high. Signals from this tower are what Australians are most likely to pick up on LF. Australia’s electronics magazine February 2021  13 Fig.9: the signal format of JJY, a variation of IRIG (see below). Source: Wikimedia user Cartoonman. radio backup systems in the event of a communications breakdown such as a major solar flare. There is a history of WWVB at www.ncbi.nlm.nih.gov/pmc/articles/ PMC4487279/ which includes a onetime plan to provide a global timekeeping service at 20kHz. nised to it, including many inexpensive domestic clocks. DFC77 also contains encrypted weather data plus civil defence data, if necessary (see Fig.11). It has been operating in its current format since 1973. standard and are designated A, B, C, D, E, G and H. Stations WWV, WWVH, and WWVB use IRIG H. JJY uses a variant of IRIG. BPC in China The first LF radio-controlled watch was the German Junghans 1990 MEGA 1 (see Fig.13). The first multiband radio-controlled watch was the Citizen model 7400, introduced in 1993. It could receive signals from the major radio time transmitters JJY, DCF77 and MSF but surprisingly, not WWVB (see Fig.14). You can view its PDF manual at http:// siliconchip.com.au/link/ab4w The first watch that synchronised its time via GPS was the Citizen Eco-Drive Satellite Wave Air in 2011; it could acquire a time signal from a GPS satellite in a minimum time of six seconds. JJY has two transmitters at different locations, one on 40kHz and the other on 60kHz (see Fig.8). JJY started as a shortwave broadcaster in 1940, but started transmitting experimental digital time signals on LF in 1966, followed by 40kHz transmissions in 1999 and 60kHz in 2001. The timecode is similar to WWVB, but each bit is inverted in comparison (see Fig.9). BPC is the Chinese 68.5kHz time signal broadcasting service. Its format is proprietary and little is know about it, although its data is known to be transmitted with amplitude modulation plus also spread spectrum. Due to its high power of 90kW, almost double that of JJY in Japan, it can be received in parts of Australia. Perhaps SILICON CHIP readers can see if they can capture it, at least to listen to, if not decode. MSF in the UK Time formats including IRIG MSF started in Rugby 1926, and in 1927, transmitted time signals at 15.8kHz in the form of 306 pulses in the five minutes before 10:00 and 18:00 GMT. In 1966, continuous 60kHz transmissions commenced. The facility was relocated to Anthorn in 2007. It has a transmitter power of 60kW with and ERP of 17kW. The modern MSF time format is shown in Fig.10. IRIG is the Telecommunication Working Group of the American Inter Range Instrumentation Group. Their time code is a standard method for transferring timing information via serial data with a modulated carrier wave over radio, coaxial cable or twisted pair. It can also be transmitted via unmodulated TTL signals over coaxial cable, or differential level shift over RS422 or RS232 (see Fig.12). The original standards were released in 1960 and have been continually updated. Different codes are defined within the JJY in Japan DCF77 in Germany DCF77 is the European 77.5kHz time signal station and it is enormously popular. Numerous devices such as parking meters and traffic lights are synchro- Fig.11: the DCF77 time signal format. It has provision for “meteotime” encrypted weather information and civil defence information. Source: http://arduino-projects4u. com/dcf77/ Fig.10: the MSF time signal format. 14 Silicon Chip Watches that use radio time signals Australia’s electronics magazine siliconchip.com.au Fig.12: the general structure of IRIG codes. Source: www.meinbergglobal.com/english/info/irig.htm The Satellite Wave F100, introduced in 2014, halved that time. The Casio Oceanus is a watch that combines both LF time signal reception and GPS time signal reception (Fig.15). LF works both inside and outside, but if no useful LF signal is present (such as in much of Australia), the Oceanus synchronises via GPS. The Citizen Satellite Wave and the Seiko Astron both synchronise their time via GPS satellites. Unlike watches and clocks that use LF signals, which don’t have universal receiver coverage, GPS signals are available all over the globe. However, they don’t tend to penetrate buildings as well as the LF signals. In practice, this is not really a problem because they will usually be carried outside regularly enough to remain in good synchronisation with GPS time. These watches capture not only the time but their position, so they can adjust to the correct time zone although they don’t indicate position data to the user (see Fig.16). Note that there is an additional category of watches distinct from these such as the Garmin Fenix series which are full-function satellite navigational devices. There is a video showing the inside of a fairly recent radio-controlled watch titled “Tearing Down a Radio Controlled Citizen Eco-Drive” at https:// youtu.be/-gZ8rmEB0ig Important note As there are no LF radio time signals specifically directed towards Australia or New Zealand, if you had one of these radio watches, it is unlikely that you would receive time synchronisation signals at a suitable strength. However, even though Australia and NZ are well out of the intended service range of JJY in Japan, there are numerous reports of JJY signal reception at certain times and in certain locations within Australia. We consider that JJY provides the best chance of receiving a time signal Fig.13 (left): while there were earlier consumer radio-synchronised clocks, this is the world’s first radio-synchronised watch, the Junghans Mega 1, released in 1990. The antenna was in the watchband. The original watch received only European DCF77 time signals. Source: Wikimedia user Pitlane02. Fig.14 (right): the Citizen 7400. Note the large antenna dominating the watch. The antenna is much smaller in more recent watches, and not visible. siliconchip.com.au Australia’s electronics magazine in Australia or New Zealand. While the JJY transmitter is approximately 7773km away from Sydney and 9051km from Auckland; its intended reliable range is only about 1000km. If you want to build some of the experimental circuits mentioned here, they will only work if 1) you can pick up a JJY signal with sufficient strength and 2) they are either designed to work with JJY signals or can be adapted if designed for another station, such as DCF77. Also, note that WWVH on shortwave from Hawaii can be received in Australia and NZ. It is about 8,200km from Sydney. The success of decoding such signals will depend greatly on reception conditions and equipment. Receiving and decoding time signals with software If you can receive an LF or SW radio time signal, you can decode it with your computer sound card and appropriate software. One such program is “Radio Clock” which you can download from www. coaa.co.uk/radioclock.htm (it says it works on Windows 7; we presume it will work on Windows 10 but have not tried it). Another is “Clock” which you can get from http://f6cte.free.fr/ horloge_e.htm This can decode time signals from multiple LF and MF radio clock transmitters, including the ones most likely to be received by Australians and New Zealanders: JJY (LF) and WWVB (SW). It can also decode GPS time from or via RFC868 Internet time server, along with various other methods. Radio clock kits, projects and ICs There are some LF clock kits, modules and ICs available, but since time February 2021  15 Fig.15: a Casio Oceanus OCW-G1000 watch, introduced in 2016. It receives both LF radio and GPS time signals. It follows on from the Casio GPW-1000, introduced in 2014, which was the world’s first watch that could receive both signals. signals are not explicitly directed toward Australia, we cannot guarantee they will work here (see Fig.17). These ideas are for experimenting only. YouTuber Andreas Spiess used a Raspberry Pi and other modules to capture and retransmit a radio time signal for remote control of a clock with no access to the radio signal. In Switzerland, he captures WWVB from the USA (8269km away) but not JJY 60kHz (9388km away). See the video titled “#287 Remote Controller for Clocks” at https://youtu. be/6SHGAEhnsYk A receiver kit (not stand alone) is Fig.16: a Seiko SBXB174 solarpowered, limited-edition GPS watch. available from siliconchip.com.au/ link/ab4x which can be interfaced to an Arduino. Links to code examples are given under “Interesting projects” on that page. Note that this is not suitable for beginners. Erik de Ruiter has developed a very impressive “DCF77 Analyzer / Clock” for the German DCF77 signal using Arduinos (see Fig.18). Full plans are available at siliconchip.com.au/link/ ab4y See the videos titled “DCF77 Analyzer / Clock v.2 demo” at https:// youtu.be/ZadSU_DT-Ks and “DCF77 Analyzer/Clock v2.0 - the inside explained” at https://youtu.be/sPb0La4Qb4 Note that it is unlikely you could receive a sufficiently strong signal Fig.17: this module comprises a ferrite antenna and a circuit board with a MAS6181B1 IC under the ‘blob’. Depending on the module version, it can receive DCF77 and MSF or JJY60 and JJY40 signals. in Australia, but this project demonstrates what can be done. It might be possible to adapt this for JJY reception in Australia. Another clock based on the above design can be seen at www.instructables.com/id/DCF77-Signal-AnalyzerClock/ and in the video titled “Arduino DCF77 Analyzer Clock” at https:// youtu.be/zsiVTP7clQg Simulating an LF signal for watch synchonisation If you are in an area where you can’t receive an LF signal to synchronise your watch reliably or at all, there are some clever apps and hardware that allow you to generate a suitable signal. One method is designed by an Australian and can be found at siliconchip. com.au/link/ab4z It uses a JavaScript program which generates audio signals at 20kHz with 200ms, 500ms and 800ms bursts. The audio signal is fed into an earpiece or wire loop, and an electromagnetic field is generated near the watch. The audio signals produced are Time synchronisation for mobile phones Fig.18: Erik de Ruiter’s home-built DCF77 Analyzer / Clock. 16 Silicon Chip Australia’s electronics magazine Most mobile phones derive their time from either NTP (via the internet) or NITZ (via the mobile phone network). Apple phones use Network Time Protocol time servers which get their time from GPS satellites, while Android phones typically get their time from Network Identity and Time Zone via the mobile networks. This is less accurate, although there are Android Apps to either display or set the time via NTP (warning: some require root access). siliconchip.com.au The Telstra “talking clock” Fig.19: the third harmonic of a square wave is the highest amplitude harmonic, and it is a sinewave at triple the fundamental frequency. So generating a 20kHz square wave pulse results in a 60kHz sinewave approximating the amplitudemodulated JJY time signal. Source: via https://wigglewave.wordpress. com/2014/08/16/pulse-waveforms-and-harmonics/ square waves, and as square waves have strong third harmonic content, the signal includes a significant 60kHz sinewave component (see Fig.19). This signal emulates the JJY time signal from Japan, with the 800ms bursts representing zeros while the 500ms bursts represent ones. The 200ms bursts are marker bits. There are also Android phone Apps such as JJYEmulator, WWVB Emulator and DCF77 Emulator, which are available in the Google Play store for use with Android devices. These work similarly to the JavaScript program, using an earpiece to generate an LF signal to synchronise the watch. Henner Zeller and Anatolii Sakhnik developed a Raspberry Pi based transmitter which emulates either DCF77, MSF, WWVB or JJY and sends a time signal to a watch if you cannot receive an actual radio signal (see Fig.20). See https://github.com/hzeller/txtempus and the video titled “Raspberry Pi DCF77 transmitter setting watch” at https://youtu.be/WzZnGimRj60 Johannes Weber shows how to use a Raspberry Pi with a DCF77 receiver as an NTP server (Internet time server) at http://siliconchip.com.au/link/ab50 It is unlikely you can receive that signal in Australia, but you may be able to adapt these ideas for JJY. Building or buying an antenna for LF reception There are several options for improved time signal reception, such as antennas, but we caution that reception in Australia is not reliable, and these systems should be regarded as experimental. Receiving LF signals requires great attention to minimising sources of electrical noise such as fluorescent lights and switchmode power supplies. Also note that any device you intend to synchronise must have an appropriate time offset capability from UTC for your timezone in Australia. There is an Australian company It used to be possible to dial a phone number and listen to the “talking clock” to get the exact time via recorded voice messages. Originally the phone number was B074 (which became 2074 when alpha prefixes were dropped) but later the universal “talking clock” number was changed to 1194. The automated service started with a mechanical recording from 1954 until 30th September 2019. Before that, a telephone operator read out the time. In September 1990, the mechanically recorded voice was changed to an electronic system. See the news article at siliconchip.com.au/link/ab57 You can listen to an online version at http://1194online.com/ The video titled “electronic talking clock” shows the latest version of the Telstra talking clock, now at the Telstra Museum in Hawthorn, Victoria: https:// youtu.be/BugAJm7-xUM The next video shows the changeover from the old mechanical equipment to the new electronic equipment, which happened in 1990. It is titled “Talking Clock Change Over Sept 1990, Hi Res” and is at https://youtu.be/XNcAJQOCMNo Other radio time transmitters in use around the world Apart from those mentioned, there are some other lesser-known, used or supported time signal transmitters as follows. They are currently active and may make good DX targets or experiment with decoding them. Not all operate full time. • BPM in Pucheng, China at 2.5MHz, 5.0MHz, 10MHz and 15MHz (10-20kW). • BSF in Chung-Li, Taiwan at 77.5kHz (460W ERP). • CHU in Ottawa, Canada at 3.330MHz (3kW), 7.85MHz (10kW) and 14.67MHz (3kW). See siliconchip.com.au/link/ab58 • EBC in San Fernando, Spain at 4.998MHz (1kW). See https://wikimili.com/en/ROA_Time • HLA in Taedok, Republic of Korea at 5MHz (2kW). • IAM in Rome, Italy at 5MHz (1kW). • LOL in Buenos Aires at 5MHz, 10MHz and 15MHz (2kW). • RAB-99 in Khabarovsk, Russia at 25kHz (300kW). • RBU in Moscow, Russia at 66.6kHz (10kW). • RJH-63 in Krasnodar, Russia at 25kHz (300kW). • RJH-69 in Molodechno, Belarus at 25kHz (300kW). • RJH-77 in Arkhangelsk, Russia at 25kHz (300kW). • RJH-86 in Bishkek, Kirgizstan at 25kHz (300kW). • RJH-90 in Nizhni, Novgorod at 25kHz (300kW). • RWM in Moscow, Russia at 4.996MHz (5kW), 9.996MHz (5kW) and 14.996MHz (8kW). • YVTO in Caracas, Venezuala at 5MHz (1kW). siliconchip.com.au Australia’s electronics magazine The Assman digital Talking Clock, now housed in the Victorian Telecommunications Museum February 2021  17 Fig.22: Citizen’s RCW/SU-3 signal enhancer. This is a screengrab from the referenced Russian video. Fig.20: a Raspberry Pi based transmitter for use when no radio signal is present, developed by Henner Zeller and Anatolii Sakhnik. called PK’s Loop Antennas (http:// amradioantennas.com/) which makes loop antenna products including a “Longwave Single Station Loop Antenna for Portables”. This is custom-made for specific frequencies such as 40kHz, 60kHz or 77.5kHz although it is not specifically marketed for its ability to receive time signals in Australia (see Fig.21). It is inductively coupled to a watch or clock. Given an interference-free environment, that antenna could assist in synchronising a radio-controlled watch or clock in Australia for JJY at 60kHz, which is the more reliable frequency for local reception. In Melbourne, JJY is best received from 8pm to midnight in winter. Clint Turner (KA7OEI) has described “a remote antenna for 60 kHz WWVB reception” at www.ka7oei. com/wwvb_antenna.html It is a remote antenna for use when Fig.21: an inductively-coupled 60kHz loop antenna from the Australian company PK’s Loop Antennas. This could be used to help a watch or clock receive the Japanese JJY time signal in Australia, in the right circumstances. suitable reception is not available for a radio-controlled timekeeping device inside a building. It is designed for WWVB reception but is described as also being able to receive JJY or MSF at 60kHz. It can also pick up JJY at 40kHz and DFC77 at 77.5kHz with appropriate adjustments to the resonant frequencies of the loops. YouTuber “Watch Geek” describes a remarkably simple method to enhance reception in watches without electronics. This person lives at the reception edge of DFC77, but the technique might work elsewhere. It involves attaching the watch to a large metal object such as a bicycle or metal pipe which acts as an antenna. In the comments, a user in Brisbane says it worked for them. See the video titled “DIY Amplifier for Atomic Radio Controlled watches that actually works & is VERY simple” at https:// youtu.be/wI4FwQMCN9w Citizen used to (and possibly still does) produce a passive antenna de- vice to amplify the DCF77 77.5kHz radio time signals for its watches (see Fig.22). It has been described as a tuned inductive coil around a ferrite core. The watch is placed near it for an enhanced signal. The model code is RCW/SU-3, and it works for all brands of radio-controlled watches. It was supplied free with some Citizen watches. We don’t know how well it would work for 60kHz signals. A Russian YouTube video on the device titled “Citizen Wave Receiver RCW/SU-3” can be viewed at https:// youtu.be/dQAesLWaCxY Note that you can use YouTube settings to automatically translate and generate English subtitles. Enhancing reception You may be able to enhance radio signal reception of a watch by placing it at the centre of a resonant loop antenna. The ends of the wire loop are connected with a capacitor to make a tank circuit; no connection to the watch is needed. It is the same principle of inductive coupling as used by some loop antennas for AM broadcastband radios. We found the following two ideas interesting, but we haven’t tried them ourselves. 1) At http://siliconchip.com.au/ link/ab51 Ivan describes the follow- Online software-defined radio (SDR) in Melbourne To try to receive and hear some time signals, you can visit http://sdr-amradio antennas.com:8071 (see right). This is an online SDR located in Croydon, Melbourne. A time code filter is also available for some modes. Naturally, you can receive a wide variety of other frequencies as well from about 12kHz to 30MHz. 18 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.24: the Nitsuki 7572B generates time and frequency reference signals from JJY in Japan on 40kHz and 60kHz. It provides 5MHz and 10MHz outputs with an accuracy of up to Up to 3 parts in 1012. It also has a built-in rubidium oscillator. 84mm (3.3 inches) wide, ie, 3mm x 28 turns. Fig.23: a 60kHz passive loop antenna designed by Australian Pete_JBK and described at siliconchip.com.au/link/ ab52 ing loop antenna: “… make a rectangular coil, about one foot by one foot, some 30 turns wound by a fairly thin magnet wire (#25 to #30). Bring it into resonance at 60kHz by a capacitor, some 8000-10000pF. Place the coil vertically, aiming to the transmitter, and place the clock to its center. You do not need any mods of the clock. The signal should be significantly stronger.” 2) Australian Pete_JBK posted plans for a loop antenna design to enhance watch reception – see it at siliconchip.com.au/link/ab52 In summary, this design uses two pieces of wood 52x120x20mm, joined to make an “X”, as a frame for wire (diameter not specified) that is 28 loops measuring 254x254mm with 3mm spacings (see Fig.23). The two ends are terminated with a capacitor of unspecified value. Using online calculators for square loop antennas at http://earmark. net/gesr/loop/joe_carr_calc.htm and https://earmark.net/gesr/loop/, we estimate that the capacitor for approximate 40kHz resonance would be 53nF, or for 60kHz, it would be 23nF. This is based upon the loop being 25.4 x 25.4cm (10 inches square) and Other uses for time signals Time signals have also been used for surveying and astronomical work in Australia for a long time. For example, JJY and WWVH are mentioned in a 1964 paper on correcting astronomical observations, which you can read at http://xnatmap.org/report_tdnm/ agb%20smcorn%20astro.pdf Time signals can also be used as a frequency standard (see Fig.24). Work described at siliconchip.com. au/link/ab53 involves simultaneous reception of GPS and LF radio signals to make propagation time measurements in the ionosphere. This allows ionospheric physics and the interaction of cosmic rays in the ionosphere to be studied. Accuracy of time signals The time and frequency standards for radio clock broadcasts are incredibly accurate, but keep in mind that there will be inaccuracies at the receiver. For example, a distance of 1000km from the transmitter will result in a 3ms delay due to the speed of light. Plus, in theory, a receiver will take one half of the signal period to synchronise, so, in the case of DCF77 at 77kHz, this would take 6.452µs. There are also inaccuracies introduced due to skywaves and groundwaves overlapping due to slightly dif- Fig.25: the Meinberg GEN170 timecode generator for testing DCF77-receiving equipment. ferent path lengths. But all these inaccuracies are of little consequence for most users. JJY has frequency stability of 1 part in 1011, WWVB has frequency stability on the carrier of 1 part in 1014, giving a time within 100ns of UTC and 20ns of US national time standards. DCF77 has a carrier frequency stability of 0.5 in 1012 over 24 hours, and no gain or loss of one second in 300,000 years. MSF has a carrier frequency stability of 2 parts in 1012. Specialised devices are or were available for testing receiver operation, such as the Meinberg GEN170 timecode generator (see Fig.25). Antennas used in watches Few details of the exact nature of the miniature antennas and receiving circuitry used in LF radio-controlled watches have been published. We think they are a type of highly-tuned magnetic core loop antenna (MCLA) with the core being ferrite or similar material (see Fig.26). These would then feed a differential amplifier which uses weak-signal techniques. The academic paper at siliconchip. com.au/link/ab54 has some information on simulating the performance of these types of antennas while another paper at siliconchip.com.au/link/ab55 has details on performance evaluation. One of the authors is from Casio. Fig.26: the evolution of Citizen radio controlled watch antennas. Source: Citizen. siliconchip.com.au Australia’s electronics magazine February 2021  19 Fig.27: some radio clock modules and ferrite antennas from commercial radio clocks. When these were removed, the digital clocks continued to function normally but without radio synchronisation. An amorphous metal or “metallic glass” core is discussed in the second paper as being superior to ferrite. To give an idea of the size of these antennas, one is mentioned in the second paper as being 16mm long with 1107 turns of 0.08mm diameter copper wire, with a core relative permeability of 8000 and an antenna factor of 30-40dB/m. Another antenna mentioned in the Videos on radio time signals Changing a Regular Clock to a Radio Controlled ‘Atomic’ Clock” – https://youtu.be/yll9ZzFnFqA You can find these movements online if you Google “radio clock movement” or “atomic clock movement”. You can also buy online (for less than AU$20) radio clock movements for all the common LF radio time signals, including WWVB, JJY, MSF, DCF77. An Australian, N. May (VK3NM) listens to JJY (LF) from Melb o u r n e : “ J J Y 6 0 k H z ” –    https://youtu.be/ZllHMZmDdKs A video of WWVH (SW) signals being received in Australia: “WWVH Time signal 10000Khz 18-11-2013” – https://youtu.be/pYnZF8VENmQ Fig.28: an inexpensive (US$19.94 on Amazon) consumer radio clock available in the USA. This clock synchronises only from WWVB in Fort Collins, Colorado. It is unlikely to receive a suitable signal in Australia. The symbol above the colon indicates that a radio signal is being received. first paper has a core 1.1mm x 16mm with 103 turns of 0.08mm diameter wire over 11mm of the core. The original radio controlled watch from 1990, the Junghans Mega 1, had a straight-wire antenna in the band. What’s inside a commercial radio clock? Arduino forum contributor ChrisTenone purchased some inexpensive consumer radio clocks in the USA and found the modules shown in Fig.27 inside. See siliconchip.com.au/link/ ab56 for more details. Figs.28-32 show current model radio clocks and two of historical interest. Radio time in Australia It’s a great shame that Australia doesn’t have such a service. It would probably save a lot of time(!) and money compared to manually setting the time on equipment, or doing it automatically by other methods. You may recall that Australia once had a tower which was used for the now-obsolete Omega Navigation Sys- A look at the radio clock module in a European clock: “Having fun with a 10 euro DCF77 clock - better than bare modules?” https://youtu.be/CnWuUlvN3bY Another look at the radio module in a European clock: “From the Lidl non-food Aisle: DCF77 Radio Controlled Clock” – https://youtu.be/OsVt3JCrGV 20 Silicon Chip Fig.30: a 1983 Heath GC-1000 clock. It used SW time synchronisation signals at 5MHz, 10MHz or 15MHz rather than LF. See the video titled “Heathkit GC-1000 most accurate clock demo” at https://youtu.be/WCP9dVtUJXI Australia’s electronics magazine Fig.29: the German Junghans Mega desktop clock from 1991. This particular one was tuned to the 60kHz MSF signal which was from Rugby, UK at the time. Other versions were for DCF77. It was one of the first, if not the first LF radio-controlled clock produced for home use. tem in Woodside, Victoria, that could have been repurposed for LF time signals. But that was demolished in 2015 after the government decided that they no longer had any use for it (see the article on Omega in SILICON CHIP, September 2014; siliconchip.com.au/ Article/8002). SC Fig.31: a rather blurry photo of a vintage Precision Standard Time Model 1020 WWV, which had various computer interface options for controlling equipment. This one is probably from the late 1980s. Source: Brooke Clarke, N6GCE. Fig.32: there’s quite a bit of circuitry on several sub-boards in the Heath GC-1000. It was available either prebuilt or as a kit (you might have heard of Heathkit). This is a screengrab of a comprehensive teardown/upgrade video you can view at https://youtu.be/ YpVSGYy4iH0 siliconchip.com.au Pre-Catalogue SALE! 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B 0091 Find a local reseller at: altronics.com.au/storelocations/dealers/ Follow-up By DR Sankit Ramkrishna Kassa, SNDT Women's University, Mumbai, India We introduced QCA technology in the August 2019 issue (siliconchip. com.au/Article/11774) as a possible future alternative to CMOS digital logic. It could possibly operate much faster than traditional logic and at a much smaller scale, but has not yet been made to work in commercial processes. This article investigates a more energy-efficient approach to QCA than the traditional 3-input majority gate structure. A s described in the previous article, Quantum-dot Cellular Automata (QCA) is an emerging nanotechnologybased approach for designing and implementing electronic circuits. The aim is to beat the well-developed Complementary Metal Oxide Semiconductor (CMOS) technology. QCA has the possibility of running at exceptionally fast speeds (in the terahertz range – 1000GHz plus!), at smaller sizes and with extremely low power consumption (in the picowatts). The two basic gates used in QCA logic are the inverter and the 3-input majority gate. Any digital circuit can be designed using these two gates. The majority voting function can be written in Boolean logic as M(A,B,C) = AB + BC + AC. This article describes a new style of 3-input majority gate (MG) struc- Fig.1: a comparison of the ‘standard’ QCA 3-input majority gate (a), the novel one described here (b), along with its truth table (c). siliconchip.com.au ture, which is analysed with the help of mathematical modelling. Fig.1(a) shows the standard 3-input majority gate, while Fig.1(b) shows the proposed new structure. Fig.1(c) is the truth table for both gates (they are logically equivalent). The main advantage of the new structure is that it gives the designer the flexibility to move all of the cells utilised by a certain amount. Fig.2: here’s how a two-input AND gate (a) or OR gate (b) can be formed from a single 3-input majority gate. Note that the fixed input (zero or one, shown in grey) can be any of the three. It’s up to the logic designer, and depends on the best routing for the other signals. Also note that the whole thing can be rotated or flipped to suit the design. Australia’s electronics magazine February 2021  25 Fig.3: the QCADesigner software simulation output for the AND and OR gates shown in Figs.2(a) & (b). By comparing the A, B & Y values, you can see that they provide the expected functions. This means that, when incorporated into a larger logic structure, it is possible to minimise the area used by the overall design. This also can lead to increased speed and lower power consumption. Two-input AND gates and two-input OR gates can be implemented easily using the proposed 3-input majority gate, as shown in Figs.2(a) & (b). General operating principles We won’t go back over all the operating principles of QCA in detail as they were explained in the August 2019 article. But as a refresher, each cell has four wells, and two electrons are trapped within. They can rest in two possible positions, with the electrons in diagonally opposite wells. The electric fields of the electrons in adjacent cells influence the resting position of any given cell. The electrons tend to rest in the lowest potential energy position. When cells are organised in rows, the positions of the electrons are identical in all cells (in one of the two possible states). This is because the electrons posses the same negative charge, and therefore weakly repel each other. So the system of QCA cells tends towards a stable position unless held in place by an external ‘power’ source. The potential energies for each cell are calculated via the formula for electrostatic potential energy of a point Table 1: full adder design comparison Proposed design QCA cells Area (µm2) Clock cycles 1 57 0.06 [1] 59 0.07 1 Reported design [2] 61 0.08 0.75 Reported design [3] 71 0.08 1.5 [4] 79 0.08 1.25 Reported design [5] 93 0.09 1 Reported design Reported design 26 Silicon Chip charge in the presence of another point charge. More detail on this topic can be found at: siliconchip.com.au/ Shop/6/5652 By taking advantage of the way that adjacent cells interact, we can design various functions, including the aforementioned 3-input majority function and the AND and OR gates. It is also possible to build 5-input majority gates, and even larger structures, which save space and time compared to using multiple 3-input majority gates. Full adder design Fig.4 shows a ‘full adder’ designed using this new gate style. A full adder takes two binary digits (zero or one) [1] Abedi D, Jaberipur G, Sangsefidi M (2015) Coplanar Full adder in Quantum-Dot Cellular Automata via Clock-Zone Based Crossover, IEEE Transactions on Nanotechnology 14: 497 - 504 [2] Angizi S, Alkaldy E, Bagherzadeh N, Navi K (2014) Novel Robust Single Layer Wire Crossing Approach for Exclusive OR Sum of Products Logic Design with Quantum-Dot Cellular Automata, Journal of Low Power Electronics 10: 259–271 [3] Hashemi S, Navi K (2015) A Novel Robust QCA Full-adder, in 5th International Biennial Conference on Ultrafine Grained and Nanostructured Materials, Procedia Materials Science 11: 376 – 380. [4] Hashemi S, Tehrani M, Navi K (2012) An efficient quantum-dot cellular automata full adder, Scientific Research and Essays 7: 177-189. [5] Zhang R, Walus K, Wang W, Jullien G (2005) Performance comparison of quantum-dot cellular automata adders Circuits and Systems, IEEE Int. Symp. Circuits Syst. 3: 2522-2526 Australia’s electronics magazine siliconchip.com.au Fig.4: a full one-bit adder (three bits input, two bits output) built using the novel 3-input majority gate along with a 5-input majority gate and some ‘free’ inverters (made by lining up the cells corner-to-corner). The inputs are cyan and the outputs are mauve, with the other colours indicating the quadrature clock domain on which each cell’s transitions are timed. Each path from input to output has four transitions (green, purple, yellow to red), as the adder takes one full clock cycle to operate. Fig.5: the equivalent logic diagram for Fig.4, along with its truth table. Fig.6: using QCADesigner to simulate the design shown in Fig.4 confirms that it operates as expected. Compare the Carry and S0 outputs here to the truth table in Fig.5. plus a ‘carry’ bit (also zero or one) and adds all three to produce a number between zero and three (two-bit binary values of 00 and 11 respectively). Fig.5 shows the logic functions used to implement this full adder while Fig.6 shows the result of simulating this adder using QCADesigner. Adders are widely used within digital ICs, so this is a very practical demonstration. Note the 3-input majority structure at the left of Fig.4, which is identical to that shown in Fig.1(b). Table 1 shows a comparison of this full adder design to previously reported designs. This shows that it is superior in terms of cell count and area occupied to all the previously reported designs, and as fast or faster than most of them. Note that almost all of these designs could be improved by modifying them to incorporate this new gate structure, reducing their occupied area and power consumption. SC siliconchip.com.au Australia’s electronics magazine February 2021  27 Off grid? On grid with battery backup? How do you monitor the state of your batteries? y r e r t e t Ba ti Logg l u M By TIM BLYTHMAN Knowing the condition of your batteries is essential for keeping them healthy long-term. A system that can monitor and log vital battery statistics is a great aid, and can help you to avoid having to shell out for expensive replacements. It can also be used for troubleshooting, such as when you don’t know which device is responsible for periodically discharging a battery. S olar and wind power is growing in use and getting cheaper, so there is a need to maintain batteries associated with such systems. You might also have a large battery in a shed, caravan, boat or another vehicle that you need to monitor. Backup batteries for mains power failures are another case where you might need a battery monitor or logger. Our new Battery Monitor Logger is versatile and capable, being able to handle a charger and two separate loads out-of-the-box. It is based on a Micromite LCD BackPack, so can be reprogrammed in MMBasic, Micromite’s variant of the BASIC language. But as we have written software with many useful features, you don’t need to do any programming. We last published a Battery Capacity Meter in June & July 2009 (www.siliconchip.com .au/Series/44). It featured a PIC microcontroller capable of monitoring a battery’s voltage and current via an external current meas28 Silicon Chip uring shunt. It could log data as well as calculate such things as battery capacity and estimated battery run time. New features The 2009 Battery Capacity Meter used a single shunt so it could only monitor the overall current moving into or out of the attached battery. Our new design supports up to three shunts, so it can monitor three separate current paths, helping you to split out the charging or discharging figures across multiple loads and/or generators. It even includes a fourth internal shunt for monitoring its own power usage. For example, you might have a solar panel array and a wind generator (or several) and want to keep track of the energy they generate separately. Or you might have several loads like a fridge, lights and a kettle and want to see which one is consuming the most energy. Australia’s electronics magazine siliconchip.com.au The old design was also limited to around 60V at its input (compared to 100V for this one) and could also store a minimal amount of data in the PIC. The PIC32 we have used in this design has much more storage space, so it can record more data for longer. The battery voltage and currents are sampled at 10-second intervals. That data is averaged every hour to give up to two days of hourly samples. The hourly samples are also averaged over each day to give about a fortnight of daily values. The flow of both charge and energy is logged, to provide capacity values in Ah (amp-hours) and Wh (watt-hours). You specify the full and empty voltages of your battery, plus the battery capacity, so that the unit can self-calibrate when the battery is either fully charged or discharged. A simple, linear voltage state-ofcharge value is also calculated, giving a rough indication of battery state when the more accurate information is not available. 10A, you can use the same arrangement except with external shunts. These will typically have a lower resistance and also can handle higher dissipation, both factors allowing greater currents to flow safely. For example, you can get 100A shunts quite easily, or even 500A shunts. Circuit design The circuit of the Battery Monitor Logger is shown in Fig.2. It has been designed as a complete Micromitecompatible board, rather than an add-on board for a Micromite LCD BackPack. This allows us to control its power usage better, reducing the current drawn from the battery. Operating concept Fig.1(a) shows the simplest way to use the Battery Monitor Logger. The battery connects to a two-way screw terminal (CON3) while the positive ends of up to three loads or charging sources connect to the contacts of three-way screw terminal CON3a. The negative ends of those loads/ charging sources connect directly to the battery negative (ground). This allows the Battery Monitor Logger to independently measure and display the current flowing to or from each load or charging source. It also produces a total current in/out figure and uses this to keep track of the battery’s state-of-charge in amp-hours (Ah). Multiplying this by the battery’s current voltage gives a nominal watthours (Wh) figure for the current state of charge. If you have more than three external devices to connect, they can share terminals on CON3a, as shown in Fig.1(b). For example, one terminal is shared by two loads (LOAD1 & LOAD2). The measurement on that channel will be the total load current for these two devices. Another terminal is shared by two charging sources (SOLAR & WIND), and likewise, their currents will be summed. The third terminal is shared by LOAD3 and a mains charger. In this case, the unit will measure the net current flow in/out – ie, it will see a flow into the battery if the charger current exceeds the current drawn by LOAD3, a flow out if the situation is reversed, and will measure zero if the two currents are equal (ie, the LOAD3 current is supplied by the charger). If you need to monitor currents over siliconchip.com.au Fig.1: three examples of how you could use the Battery Logger/Monitor. The simplest configuration, at top, uses its internal shunts to monitor the currents (up to 10A) into or out of three loads/charging sources. Or as shown in (B), you can connect more than three loads/charging sources, with some of them sharing shunts. For higher-current applications (up to hundreds of amps), external shunts can be used, as in (C). Australia’s electronics magazine February 2021  29 As with any battery-operated device, it’s important to consider power consumption during the design phase. The battery and load/charger terminals are at lower right, with the bottom half of the right-hand page showing the sensing circuitry. Other external connections (USB, serial, programming etc) are arranged along the left-hand side, with the BackPack circuitry occupying most of the left-hand page, plus the display at centre-right. The unit’s power supply is across the top of both pages. The Micromite V2 BackPack (May 2017; siliconchip .com. au/Article/10652) is the closest BackPack variant to our design. This comparison is only for the sake of explaining some of our design choices; it is not important if you are coming to this circuit without knowing about the earlier designs. We’ve opted to use the 2.8in (7cm diagonal) LCD touch- l SC Ó BATTERY multi-logger Fig.2: the circuit includes the equivalent of an entire Micromite V2 BackPack, a precision multi-channel ADC and a switchmode regulator capable of running the device from a DC supply between 6V and 100V. It monitors the battery voltage, the current to/from three external points and its own current consumption and logs all this (plus the current battery state-of-charge) to the internal flash memory of microcontroller IC1. 30 Silicon Chip Australia’s electronics magazine siliconchip.com.au screen in this design, rather than the 3.5in (9cm) version we’ve been using more recently (eg, in the V3 BackPack), as the smaller display uses slightly less power. The V3 BackPack also has many features which simply aren’t needed in this case, hence our choice of the V2 BackPack as the basis for this design. The main advantage it has compared to the original Micromite BackPack is the inbuilt USB-Serial interface. siliconchip.com.au Battery sensing The main battery sensing circuitry centres on IC5 (an AD7192) and REF1 (a MAX6071). IC5 is a four-channel 24-bit ADC (analog-to-digital converter) with an SPI serial interface. It is supplied from REG2’s 3.3V output, with its analog rail filtered by a 10µH inductor. Each of its 3.3V supply pins is bypassed by a 100nF capacitor. IC5 shares the SPI bus with the LCD touchscreen, with Australia’s electronics magazine February 2021  31 IC1’s pin 24 used for the If larger external CS function, to indicate shunts are used instead, when IC5 is being adyou just need to run low• Battery voltage: 6-100V dressed. current sensing wires • Current monitoring: up to three chargers or loads, IC5 needs a stable reffrom both their ends, monitored separately erence voltage to convert back to CON3/CON3A. • Current handling: limited only by the shunts used voltages into digital valThe shunt values can be ues, and this comes from set in the software to ac(10A with onboard shunts) REF1, a MAX6071 2.5V count for practically any • Current resolution: 0.1% (10mA with onboard shunts) reference. It is a very lowresistance value. • Operating current: <1mA while logging (with display off) noise and precise voltage A local analog ground • User interface: 2.8-inch colour touchscreen reference chip, and it is net separates the analog • Firmware: Programmed in BASIC supplied with 3.3V from voltages from digital SPI • Data logging: can be viewed on device graphically, REG2, with 100nF casignals. pacitors on its input and or downloaded as CSV files Supply current output. Its output sup• Measurements: current charge (Ah) and energy (Wh) plies IC5’s REFIN1+ (pin The current drawn by • State of charge: displayed based on voltage and charge 15), while IC5’s REFIN1the circuit itself is mod(pin 16) is tied to analog est but not insignificant, ground. and needs to be accountEach of the four analog inputs to IC5 is fed by a ed for to get accurate measurements. Since it is a fairly low 390kΩ/10kΩ divider, bypassed at the bottom by a 100µF current, we use a different technique to monitor it. Any capacitor. This means that the nominal full-scale reading current flowing into our circuit from the battery at CON3 is 100V with a resolution of around 6µV, and settling times flows out through a 100mΩ shunt resistor, generating a of around ten seconds. We use the ADC to perform a convoltage below ground proportional to the current. version cycle (of all channels) about once every ten secIC6 is a single-channel op amp in a five-pin SOT23-5 onds, a slow rate needed to obtain maximum resolution. SMD package. It is wired as an inverting amplifier with a One of the dividers is connected directly across the gain of 100 (100kΩ/1kΩ), presenting a voltage to IC1’s pin battery at CON3. The other three monitor the voltage at 4 where the micro’s internal ADC can read it. the load/charger end of the three shunts which connect The 100nF capacitor and 100kΩ resistor provide simibetween the BAT terminal of CON3 and the terminals of lar smoothing on this signal (a time constant of around ten CON3A. By measuring the difference between the voltages seconds) so that it too can be sampled at similar intervals fed to the ADC, we can determine the current flow into or to the other channels. out of each terminal. When the Battery Monitor Logger is operating, the LED The PCB provides pads for 15mΩ shunt resistors which backlight of the LCD panel consumes the most power, so allow a theoretical resolution under 10mA. These are 3W a high PWM frequency is used to ensure that this measparts, notionally allowing up to 14A to be sensed. In pracurement is accurate. tice, the terminals limit this to around 10A. Features & specifications Power supply There are two possible power sources in this circuit; USB socket CON5 can supply 5V, while the battery connection at CON3 handles up to 100V from the battery being monitored. There are several components on the board that have a 100V maximum rating, so this is a hard limit and should not be exceeded. A switchmode buck regulator chip, IC4 (LM5163) efficiently steps the battery voltage down to 5V. Its supply from the battery via CON3 is bypassed with These photos show an earlier prototype, which was missing the MISO series resistor and CON6 (which is not used by the current version of the software). Some of the resistor and capacitor values are slightly different too, but overall it looks quite similar to the final version. Take note of the values shown on the silkscreen PCB overlay diagram during construction. 32 Silicon Chip Australia’s electronics magazine siliconchip.com.au a 2.2µF capacitor and fed into pins 2 (VIN) and 1 (GND). A voltage above 1.5V on pin 3 (EN) enables the regulator, which is equivalent to a voltage of around 5.5V at CON3 due to the 1MΩ/390kΩ resistive divider. Apart from accepting up to 100V at its input, IC4 also has an extremely low idle current of just 10.5µA with no load, and not much more at light loads. Its efficiency varies with the input voltage and load current, but is typically in the 75-90% range. See the panel below for more details on this handy little chip. It switches its pin 8 output (SW) alternately between VIN and GND using a pair of internal N-channel Mosfets. The upper Mosfet has its gate voltage supplied from the 2.2nF capacitor on pin 7 (BOOST). The pulses are smoothed by the 120µH inductor and a 22µF capacitor to provide the output voltage. The voltage on feedback pin 5 (FB) is internally compared to a 1.2V reference, so the 30kΩ/10kΩ divider sets the output voltage to 4.8V. This is set to be slightly less than 5V so that if an alternative 5V supply is available, it takes over from the battery. Schottky diode D2 feeds the 4.8V into a pi filter formed of two further 10µF capacitors and a 10µH inductor. The 1nF capacitor across the 30kΩ resistor at the top of the FB divider helps with the stability of the circuit that drives the output pulses, by ensuring sufficient ripple at the FB pin for the circuit to operate correctly. See our panel for more detail on this. Microcontroller details This approximately 5V rail then feeds the Micromite sec- tion of the circuit. MCP1700-3.3 REG2 and its associated bypass capacitors provide the 3.3V supply for microcontroller IC1. This is a 32-bit, 50MHz micro (PIC32MX170F256B) and is surrounded by its own complement of bypass capacitors. IC1 is programmed with the MMBasic firmware and runs a BASIC program to implement the Battery Monitor Logger functions. While some Micromite BackPacks used the 28-pin DIP version of this IC, the Battery Monitor Logger uses the 28pin SMD (SOIC) part. It works identically but is smaller, so we can cram more onto the PCB, and most of the other ICs are only available as SMDs anyway. In this case, its pins are relatively far apart (on a 1.27mm/0.05in pitch) so it is not difficult to solder. To save power, the micro can switch 5V power on and off to the touchscreen via the 14-way LCD header. A high level on IC1’s pin 10 turns on N-channel Mosfet Q4, which is otherwise held off by a 10kΩ pull-down resistor. When Q4 is on, it pulls P-channel Mosfet Q3’s gate low, which allows 5V to flow from Q3’s source to drain and into the LCD panel’s supply pin. A similar arrangement, controlled by IC1’s pin 26 via Mosfets Q2 and Q1, switches power to the LCD panel’s LED backlight. Typically, a PWM signal is applied to pin 26, modulating the backlight brightness. Unlike the Micromite BackPack V2, which had PWM brightness control, we have omitted the option of manual backlight control as the backlight is easily the biggest user of power in the circuit. So it needs to be fully shut off during logging and monitoring. DS3231 MEMS variant The DS3231 real-time clock IC has been the go-to choice for keeping track of time for the last five years or so. Its appeal is no doubt enhanced by the fact that it is available in an easy-to-use module typically sold as an Arduino accessory. Such a module was the subject of our first El Cheapo Modules feature from October 2016 (siliconchip.com.au/Article/10296), which we used in several projects, typically in combination with a Micromite. The module includes I2C pullup resistors, an I2C EEPROM and a cell holder. The module simplifies connection as it includes all that is needed for the DS3231 chip to work, but sometimes it’s too big. We used the bare DS3231 IC (which comes in a wide 16-pin SOIC SMD package) in our Micromite BackPack V3 (August 2019; siliconchip.com.au/ Article/11764) and the Ol’ Timer II clock (July 2020; siliconchip. com.au/Article/14493). To support those projects, we kept a stock of those ICs. One day, we were surprised to receive a package of small 8-pin SOIC parts instead of the wide 16-pin SOICs that we were expecting. Had we been conned? No; we had received the DS3231M variant instead. Those familiar with the DS3231 will know that it only uses eight of its pins; the lower pins are marked NC (“not connected”). The reason for siliconchip.com.au the large package is not that it needs 16 pins, but because it includes a temperature-compensated crystal oscillator inside the plastic IC case, which would not fit inside an 8-pin package chip. But with the advance of MEMS technology (see our article in the November 2020 issue: siliconchip.com. au/Article/14635), the crystal oscillator inside the DS3231 has been superseded by a smaller MEMS device. So given their small size and decent performance, we decided to try them out in this project. We found the DS3231M to work the same as the DS3231. The nominal accuracy is slightly worse at ±5ppm compared to ±3.5ppm, but for situations where size is of concern, the smaller package is the overriding concern. The MEMS part doesn’t appear to suffer from crystal ageing either, which means that in the longer term, it could be more accurate unless this is compensated for in the earlier version of the chip. The backup battery current draw appears to be higher for the MEMS part in typical cases, but in most cases, the battery life will still be close to its shelf life. In this particular project, we’ve made allowances for either part in the PCB design, with a dual footprint that suits both the wide 16pin SOIC part and the narrower 8-pin SOIC part. We don’t know if the DS3231M will end up more popular than the original DS3231, but we’re ready for either eventuality. Australia’s electronics magazine February 2021  33 Screen1: The main screen provides all the critical statistics for your battery, as well as three simple menu options for accessing other features. The greyed values seen are capacity calculations which are not yet valid, as the Logger has not detected a complete charge and discharge cycle; they will light up brighter when that happens. Screen2: The Data screen provides a graphical view of the logged data. Different timespans can be shown, and the display will automatically scroll once a minute to show current data. The Weeks option provides around a fortnight of data. Data can also be dumped as CSV rows over the console serial port with the Export button. Serial communications Both IC1 and IC2 have their in-circuit serial programming (ICSP) pins broken out to the edge of the PCB at CON2 and CON1 respectively. This is a feature not seen on the other BackPacks, but we have included it here because the SMD ICs used here are more difficult to program out-of-circuit than through-hole (DIP) chips. A DS3231 real-time clock, IC3, provides accurate timekeeping over long periods. Its I2C serial bus pins 15 and 16 (SDA and SCL) connect to IC1 at pins 18 and 17, the I2C pins used by the Micromite firmware. Two 4.7kΩ resistors provide the pullups needed by the I2C protocol. The PCB is also fitted with a SOIC-8 footprint to allow the similar DS3231M (which uses a MEMS oscillator rather than a crystal) to be used instead. See the separate panel explaining the differences. IC1 sends display data and gets touch events back from the touchscreen using an SPI serial bus on its pins 3, 14 and 25 (MOSI, MISO and SCK). These connect to the LCD panel’s pin 6 and 12 (MOSI), pin 13 (MISO) and pins 7 and 10 (SCK). MISO stands for “master in, slave out” while MOSI stands for “master out, slave in”. The MISO line has a series 1kΩ resistor so that it can still operate when the LCD panel is switched off. These signals, plus a chip select signal from IC1’s pin 9, also connect to the SD card header at the other end of the LCD panel PCB via a four-pin header. We had planned to use the SD card to store data, but flash memory limitations in the micro mean that there isn’t enough space to include the (rather large) libraries needed to do this. IC2 is an 8-bit PIC16F1455 microcontroller programmed with the Microbridge firmware. This allows it to act as a USB-Serial bridge, and it can also program the PIC32 microcontroller. Pushbutton S1 is used to switch IC2 between USB-Serial and programming modes, with LED1 flashing to indicate that it is passing serial data, or lighting up solidly when in programming mode. Mini USB Type-B socket CON5 is used both for USB communications (D+/D-) as well as optionally supplying 5V power. Schottky diode D1 feeds USB 5V to the Micromite 5V rail. Jumper JP1 provides the means to bypass D1 if needed. REG1 is identical to REG2 and supplies 3.3V to IC2 independently. Serial TX and RX signals are bridged to and from the virtual USB-Serial port by IC2. These connect between its pins 5 and 6, via 1kΩ resistors, to Micromite console pins 11 and 12 on IC1. IC2’s pins 2, 3 and 7 can be used to program IC1 via its ICSP interface; they are connected to IC1’s pins 4, 5 and 1 respectively. The PGD signal travels via JP2, which allows IC1’s pin 4 to be used as an analog input when it is not being used for programming. 34 Silicon Chip Software operation Some of the following may seem obscure to those not familiar with MMBasic, but this information could come in handy if you want to change the code. MMBasic certainly makes driving the LCD (TFT) panel easy, as it performs startup initialisation and has built-in BASIC commands for drawing on and writing to the display. But it needs some help to work with our circuit arrangement, which starts with the LCD panel powered off, and therefore not ready to accept the initialisation commands that are automatically sent. So we need to add a routine (in the MM.STARTUP subroutine) to set pin 10 as an output and set it high, then rerun the LCD initialisation code. Every time we power up the display after shutting it down, we need to trigger that code. We also need to control the other lines that run to the LCD panel, as some of these idle high by default and would therefore waste power. MMBasic does not allow direct control of these, as the firmware reserves them to control the LCD panel, so we need to ‘POKE’ directly to IC1’s registers and then run a command to reinitialise the LCD controller. Similarly, shutting down the controller requires direct POKEs to shut down those pins. No software deinitialisation Australia’s electronics magazine siliconchip.com.au The LM5163 switchmode regulator IC Our initial design plans for the Battery Logger set the ambitious target of designing it to work at up to 80V, improving on the 60V limit of the old Battery Capacity Meter. That one used an LM2574HV integrated switchmode IC operating at a fixed frequency of 50kHz, requiring a sizeable toroidal inductor and electrolytic capacitor. Hoping that that state of the art had progressed in the last decade, we decided to look for newer parts. We found plenty of parts capable of working with a 100V supply, which is impressive. 1MHz switching frequencies are no longer uncommon. This much higher switching frequency means that a smaller inductor and capacitors are needed, helping us to keep our board compact. Many parts we found could only deliver 100mA. While this might have been sufficient with careful control of the LCD backlighting, we wanted more headroom. The LM5163 came in as the cheapest part capable of more than 100mA (500mA) in an easily-soldered SOIC-8 package, which is a good compromise between size and ease of handling. As is typical of modern buck regulator designs, it is a synchronous type, meaning it has two internal switches. The incoming voltage is switched to the inductor by a high-side internal Mosfet. When the Mosfet is off, a second low-side Mosfet is switched on to provide a path for the inductor current to circulate. This removes the need for an external diode to serve this role and increases its efficiency. The LM5163 is a COT (constant on-time) design; the time that the high-side Mosfet is switched on is set by an external resistor, after which it is switched off. The feedback pin monitors the output voltage, and when the output voltage has decayed, another on-cycle begins. So the duty cycle is modulated to maintain the desired output voltage, but the constant on-time means that the switching frequency varies, although it can be predicted. When we built our first prototype, everything worked as expected; we were truly impressed with how flexible and easy-to-use this tiny part was. But then, it started squealing! The tone would change with load (which we could easily modulate by adjusting the LCD backlight intensity) and input voltage. It was bad enough, especially around 12V, that we needed to do something about it. The cause was electrical noise, which was affecting when it would switch on. It might switch on early, which causes the output voltage to rise. This will cause the next switch-on to be delayed, as the controller will be waiting for the output voltage to drop below its threshold. The output pulses start to cluster into bursts, and it is these clusters that occur at audible frequencies, causing the high-pitched squealing we were hearing (‘subharmonic oscillation’) – see below. As we found with our Switchmode 78xx replacement (siliconchip. com.au/Article/14533), trying to get these sort of parts to operate optimally over a wide range of input voltages can be tricky. In that case, extra output capacitance helped. Fortunately, a section of the LM5163 data sheet (reproduced in Fig.4) describes methods to avoid this. The aim is to increase the ripple seen by the FB pin, so that the regulator has a clearly defined time to switch on, despite the presence of noise. We tried the Type 1 method, which involves adding series resistance to the output capacitor. The extra resistance means that the voltage seen at the FB pin is influenced less by the capacitor and more by the pulses from the inductor. But it also means that the output capacitor is less effective at filtering the output voltage, and we found it did little to reduce the squealing. So we tried part of the Type 2 method (omitting the series resistor from Type 1) and simply added the ‘feedforward’ capacitor in parallel with the top feedback divider resistor. This means that the FB pin sees the full amplitude of the output ripple voltage, as it is coupled directly by the capacitor rather than being simply divided by the resistor chain. This effectively quadruples the ripple seen by the FB pin with our 30kΩ/10kΩ divider, without degrading filtering. That eliminated the squealing, so we have kept it in our final design. Any switching device which depends on a feedback voltage from a divider to switch its output elements can benefit from having a feedforward capacitor. It depends on the frequency of operation, capacitor value and divider ratio, though. A word of caution: while this capacitor may appear to be a cure-all, it does have the side-effect of slowing down response to transients as it reduces the closed-loop gain for higher frequency components. Fig.4: Texas Instruments’ recommended solutions for subharmonic oscillation or ‘squegging’ in the LM5163. We tried Type 1, and it didn’t work, but Type 2 did. It only requires the addition of a low-value feedforward capacitor, Cff, across the upper half of the feedback divider. Type 3 is similar but adds another pole for improved transient response; that’s overkill in our application. Fig.3: usually, low ESR is considered desirable in a capacitor as it gives superior filtering, but when it filters out the ripple too effectively, it affects the regulator’s ability to produce pulses regularly. siliconchip.com.au Australia’s electronics magazine February 2021  35 Parts list – Battery Multi-Logger 1 double-sided PCB coded 11106201, measuring 86mm x 50mm 1 2.8in LCD touch panel with ILI9341 controller 1 UB3 Jiffy box (optional, depending on desired mounting) 1 laser-cut acrylic panel to suit LCD and UB3 box [SC3456, SC3337, SC5063 or sim.] 2 5-pin right-angle headers (CON1, CON2; both optional, for programming IC2 & IC1) 1 2-way 5/5.08mm-pitch screw terminal (CON3) 1 3-way 5/5.08mm-pitch screw terminal (CON3A) 2 2-pin headers (CON4 & JP1; both optional) 1 SMD mini-USB socket (CON5) 1 3-way pin header (CON6, serial port; optional) 1 3-pin header (JP2) 2 jumpers/shorting blocks (JP1,JP2) 1 SMD coin cell holder (BAT1) [BAT-HLD-001 – Digi-key, Mouser etc] 1 CR2032/CR2025 cell or similar (BAT1) 1 120µH 6mm x 6mm SMD inductor (L1) [eg, SRN6045TA-121M – Digi-Key, Mouser etc] 2 10µH 1206/3216-size SMD chip inductors (L2,L3) 1 SMD or through-hole 4-pin tactile pushbutton switch (S1) 1 14-pin header socket strip (for LCD) 1 4-way female socket strip (for LCD) 8 M3 x 6mm panhead machine screws 4 M3 x 12mm tapped spacers 4 M3 x 1mm untapped spacers (eg, stacks of 3mm ID washers) 3 heavy-duty current shunts [eg, Jaycar QP5415, Altronics Q0480 – optional, see text] hookup and heavy-duty wiring to suit shunts, batteries and load (see text) Semiconductors 1 PIC32MX170F256B-I/SO 32-bit microcontroller programmed with MMBasic or 11110620A.hex, SOIC-28 (IC1) 1 PIC16F1455-I/SL 8-bit microcontroller programmed with Microbridge firmware, SOIC-14 (IC2) 1 DS3231/DS3231M real-time clock IC, wide SOIC-16 or SOIC-8 (IC3) 1 LM5163DDAR synchronous buck regulator, SOIC-8 (IC4) 1 AD7192BRUZ 24-bit ADC, TSSOP-24 (IC5) 1 NCS325 CMOS op amp, SOT-23-5 (IC6) 1 MAX6071AAUT25+TT high-precision 2.5V reference, SOT23-6 (REF1) 2 MCP1700-3.3 low-dropout 3.3V regulators, SOT-23 (REG1,REG2) 2 IRLML2244TRPBF P-channel MOSFETs, SOT-23 (Q1,Q3) 2 2N7002 N-channel MOSFETs, SOT-23 (Q2,Q4) 1 3mm or SMD M3216/1206 LED (LED1) 2 SS14 (or equivalent) 40V 1A SMD schottky diodes, DO-214AC (D1,D2) Capacitors (all SMD M3216/1206 size) 4 100µF 6.3V X5R 1 22µF 16V X5R 7 10µF 50V X7R 1 2.2µF 100V X7R 10 100nF 50V X7R 1 2.2nF 50V C0G/NP0 1 1nF 50V C0G/NP0 Resistors (all 1% SMD M3216/1206 size 1/8W metal film except where noted) 1 1MΩ (code 105 or 1004) 5 390kΩ (code 394 or 3903) 2 100kΩ (code 104 or 1003) 2 30kΩ (code 303of 3002) 8 10kΩ (code 103 or 1002) 2 4.7kΩ (code 472 or 4701) 8 1kΩ (code 102 or 1001) 1 0.1Ω (code R100 or 0R10) 3 15mΩ 1% 3W (M6331/2512 size; not needed if external current shunts are used) 36 Silicon Chip Australia’s electronics magazine is needed as the LCD can simply be powered down from any state. Despite this complication, it’s relatively easy to sense touches on the LCD panel even if it is shut down. This is necessary, as the user needs some way to wake the unit up if it is in a low power state. Even when the LCD is powered off, the TIRQ pin (which is connected to IC1’s pin 15) is pulled to GND whenever the panel is touched. As the Micromite firmware provides a weak pullup on this pin, simply monitoring the state of this pin is sufficient to know if a touch has occurred. The main job of the MMBasic program is to read the battery voltage and the voltage across the three shunts to infer battery voltages and currents. It logs these to variables which are kept in RAM and they are regularly saved to internal flash memory. With the circuit running from the battery it is monitoring, it would take a major fault to shut it down and lose the contents in RAM, so only longerterm samples are saved to flash memory hourly. If the unit needs to be disconnected to work on the battery, at most one hour of data will be lost. When saving to flash, the data is averaged over a period before being archived. This means that less data needs to be stored, but a good amount of data can be kept for historical purposes. For example, you might like to compare how much power your solar panels are putting into your battery over a period of a few weeks. Data about current and power usage is also used to calculate parameters such as battery capacity and state of charge. The MMBasic program also provides a user interface to allow settings to be changed and values to be graphed and viewed. Plus there is the option to dump the data over a serial port so that it can be exported to a PC program for graphing and analysis. We’ll delve more into the software operation during the setup procedure next month. Next month In the second and final part of this feature, will have the complete PCB assembly details, microcontroller programming procedures, setup and operation instructions, calibration information along with the final construction procedure. SC siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build Ampec Technologies Pty Ltd Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au *** System Assembly 0-14V, 0-1A Output – controlled from your PC! Arduino-based Adjustable Power Supply By Tim Blythman We have published all sorts of fancy bench supplies over the years: linear, switchmode, hybrid, high-voltage, high-current, dual-tracking… But sometimes, all you need is a basic power supply with voltage and current monitoring and limiting; something that’s convenient and easy to set up and use. That’s exactly what this is – a very useful little power supply built on an Arduino shield! L ately, like many others, I have mostly been working from home. But unfortunately, my home workshop is not equipped to the same degree as the SILICON CHIP office/lab. I could bring my 45V 8A Linear Bench Supply prototype home (published in October-December 2019; see siliconchip.com.au/ Series/339). It would do pretty much everything I need, but my space is limited, and it would be a rare event to make use of its full capabilities. So I need something more compact but still useful. I decided to base it on something I already had at home, an Arduino Uno. It’s capable of delivering up to 14V at a maximum of 1A. That is modest, to be sure, but handy enough for most smaller projects. And multiple units can be combined if you need several different voltages (eg, 5V & 3.3V). 38 Silicon Chip     Arduino considerations Australia’s electronics magazine Using Arduino hardware means that it would be possible to add one of many plentiful shields and modules to add a custom display or controls for the Supply. But as I already have a computer on my desk, I decided to use the existing screen and keyboard to control it. I wrote a small computer program that controls the Power Supply, providing all of its useful functions without taking up valuable bench space. Thus, the Supply can sit tucked away out of sight, with nothing more than the two output leads snaking out to wherever they are needed. The control program takes up only a small amount of screen space. The combination of the microcontroller on the Uno and the control program allows many features to be added with no extra hardware. For example, the control program allows five preset combinations of voltage and current to be created siliconchip.com.au and instantly activated. This makes it harder to cause damage by inadvertently setting the wrong voltage or current limit. While the Power Supply does not have any form of temperature sensing, it can estimate the thermal effects of a connected load to warn the user of any problems with either the load or the Power Supply itself. Digital controls Features & specifications • • • • • • Output voltage and current: 0-14V, 0-1A Adjusted and monitored via a computer (desktop, laptop, notebook etc) All functions under software control Voltage resolution: around 20mV Current resolution: around 20mA Arduino-based design means it can be expanded upon Fig.1 shows the circuit of the Mini Digital PSU. It is effectively a ‘shield’ or daughterboard which plugs into the top of an Arduino Uno microcontroller board. The Uno board has an ATmega328 microcontroller, a USB-serial interface IC and some voltage regulation circuitry. IC1 is an MCP4251 dual digital potentiometer; it contains two 5kΩ potentiometers with 257 digitally-controlled steps. This chip is controlled over an SPI bus by the Uno, from its SC Ó pins 4, 13 and 11 to pins 1, 2 and 3 of IC1. The ‘tracks’ of the two ‘potentiometers’ are grounded at one end, with a fixed reference voltage at the other end. So the ‘wiper’ voltages vary linearly with the programmed position, up to that reference voltage. The voltage from pin 6 (‘wiper’ 1) is proportional to the desired output voltage, while the voltage from pin 9 (‘wiper’ 0) is proportional to the desired maximum current. ARDUINO-BASED MINI POWER SUPPLY siliconchip.com.au Australia’s electronics magazine Fig.1: the Power Supply uses an Arduino Uno to adjust the output voltage and current, which it does by sending commands to dual digital potentiometer IC1. This, in combination with rail-to-rail op amp IC2 and transistor Q2, forms a control loop to adjust the base drive to emitter-follower power transistor Q1 which regulates the output voltage. Current feedback is via a 15m shunt and amplifier op amp IC3, while the voltages and output current are monitored at the Arduino’s A0-A2 analog inputs. February 2021  39 Scope1: the response to an increase in load which triggers current limiting. The yellow trace is the voltage across the shunt resistor, so is proportional to the current, while the green trace is proportional to the output voltage. There is some current overshoot, mostly due to the output capacitance, after which the current limiting kicks in, reducing the output voltage to reach a steady-state within 1ms. Scope2: the response to a step-change in the set voltage from 5V to 3.3V (with no load). It takes just under 100ms due to the 10uF output capacitor being discharged by the voltage sense divider. Any significant load would speed this up dramatically. The wiper at pin 6 must be a fraction of the desired output voltage, as the digital pot IC has a maximum 5V supply voltage; hence, it can only generate voltages up to 5V. To have a steady output voltage, we need a stable reference voltage. In this case, we’re using the Uno’s 3.3V rail. It comes from a practically unused 3.3V regulator on the Uno, and this is fed to IC1 via jumper JP1. This is also connected to the Uno’s VREF pin, for its internal analog-to-digital converter (ADC) peripheral to refer its readings to. Thus the wiper of P1 (P1W, pin 6) produces a voltage in the range 0-3.3V, which is low-pass filtered by a 10kΩ/100nF RC circuit, then fed to non-inverting input pin 3 of op amp IC2. This is an LMC6482 rail-to-rail input/output CMOS dual op amp, which allows the output to go all the way down to 0V without a negative rail, and this also makes current sensing much easier (as described later). This op amp compares the wiper voltage to a divided version of the output voltage, produced by a 51kΩ/10kΩ divider, which feeds into its pin 2 inverting input. That gives a gain of 6.1 times. Thus around 20V at the output corresponds to the 3.3V full-scale output from digital potentiometer IC1. The output from pin 1 of IC2 drives the base of NPN transistor Q1, which is configured as an emitter-follower. Its collector draws from the Arduino’s VIN supply while its emitter feeds the supply output at CON1 via the contacts of relay RLY1 (more on this later). This transistor effectively boosts the current capability of the op amp output so that it can supply up to 1A (from the VIN supply). The base-emitter voltage drop of Q1 is cancelled out since Q1 is in the negative feedback loop – from pin 1 of IC2, through Q1, then through the 51kΩ/10kΩ output divider back to pin 2 of IC2. Hence, IC2 adjusts its output voltage higher to achieve the set voltage at the common contact of RLY1. While the circuit is set up to enable an output voltage of up to 20V, in practice, other circuit elements limit the practical output voltage to around 14V. The main limit is the 5V regulator on the Arduino board, which in the case of clone boards, is only rated to 15V (see our March 2020 Arduino feature on fixing Arduino for more details, at siliconchip. com.au/Article/12582). Voltage regulation Power transistor Q1 is an MJE3055. Usually, its emitter voltage (ie, the output) is around 0.7V below its base voltage (from output pin 1 of op amp IC2). If the emitter/output voltage rises (for example, due to the load drawing less current), then its base-emitter voltage decreases, which starts to switch it off, causing its emitter voltage to drop. Conversely, if the emitter/output voltage falls, the baseemitter voltage increases and Q1 turns on harder, halting the emitter voltage fall. This ‘local feedback’ provides a very fast response to load transients. While the emitter-follower circuit is fairly good at tracking its input at its output, the base-emitter voltage does vary somewhat depending on the load. To overcome this, the op amp will adjust Q1’s base voltage to maintain the voltage at the output voltage divider near that of the reference value on the digital potentiometer. The op amp reacts more slowly, though, due to its limited gain-bandwidth. Transistor Q1 is fitted with a small finned heatsink, as it works as a linear pass device, dissipating any excess voltage Scope3: a step increase in the set voltage (this time from 3.3V to 5V with a 12Ω load) is much faster due to the Australia’s 40 ilicon Chip lower S impedance of the output transistor, taking just a electronics magazine few milliseconds. siliconchip.com.au between the supply and output. This low-profile heatsink has been chosen so another board can be stacked on top if a custom control or display needs to be added. We have designed the shield so that it does not conflict with pins used for the LCD Adaptor described in May 2019 (siliconchip.com.au/ Article/11629), meaning we could turn this into an allin-one unit by adding an LCD touchscreen in the future. But the current version of the software does not support this. A 10µF output filter provides modest output bypassing, which also improves transient regulation. This value is a compromise since too little output capacitance would worsen its regulation, and too much capacitance would limit the Power Supply’s ability to quickly limit its output current under short-circuit conditions. Between Q1 and IC2, the feedback loop has a lot of gain, so care must be taken to ensure it does not oscillate. A 100nF capacitor from the reference voltage at pins 7 & 8 of IC1 preventing transients from being seen by the op amp, which would otherwise be duplicated at the output. Similarly, the desired voltage signal at pin 3 of IC2 is stabilised with another 100nF capacitor. There is also a 100nF feedforward capacitor across the 51kΩ upper feedback divider resistor, which reduces closedloop gain by a factor of six or so for fast transients. Also, a 1nF capacitor is connected between the output (pin 1) and inverting input (pin 2) of IC2, limiting the op amp output slew rate. Another way of thinking about this is that it provides increased negative feedback at high frequencies. This prevents it from oscillating. The low-pass filter formed by Q1’s 100Ω base resistor and the 10µF capacitor from its base to ground also helps to stabilise the feedback loop. Output relay The output switching relay is a reed relay. Its coil is driven from the Arduino’s D5 digital output. This is possible since the coil current of a reed relay is modest. Unfortunately, the digital potentiometers in IC1 start with their wipers at mid-point, so a voltage will be present at the output without RLY1 disconnecting it initially. RLY1 is only energised once the regulator output voltage has settled at the desired level. RLY1 also acts as a load disconnect switch, allowing the circuit to obtain the desired output voltage without the load being connected. It can then quickly connect the load to the already correct voltage, rather than having to ramp it up. Similarly, it can quickly disconnect the load in case of an over-current or short-circuit condition. Current limiting The current limiting employs a similar feedback loop to the voltage control. Here, we use the simplest current sensing possible. A 15mΩ shunt resistor in the return current path, from pin 2 of output terminal CON1 to ground, converts the load current into a voltage. siliconchip.com.au This is fed, via a 1kΩ/100nF RC low-pass filter, to the non-inverting input (pin 3) of IC3, a second op amp. Since this only needs to handle up to around 3.3V, we’re using a cheaper MCP6272 dual op amp IC (its other half is not used). IC3 amplifies the shunt voltage by a factor of 151 (150kΩ/1kΩ + 1). The amplified sense voltage is then fed to IC2’s pin 5 (its second noninverting input). So 2.2V voltage at pin 5 of IC2 corresponds roughly to a 1A output current. This voltage is compared against the wiper voltage from the other digital potentiometer in IC1. If the output current is above the setpoint, output pin 7 of IC2b goes high, forward-biasing the base-emitter junction of NPN transistor Q2. When Q2 is switched on, it pulls the voltage at pin 3 of IC2a down, reducing the output voltage. This should lead to a reduction in the current drawn by the load until it matches the current limit, at which point the drive to Q2 is moderated, so the output voltage should stabilise at a level where the output current is close to the set current limit. There are a few things to note here. Firstly, the apparent reversal of the inverting and non-inverting inputs on IC2b is because common-emitter amplifier Q2 inverts the polarity of the signal in the feedback loop. By swapping the inverting and non-inverting inputs, we effectively re-invert it and get the correct polarity. Also, like the voltage feedback loop, stability is improved by a 1nF capacitor between the output (pin 7) and inverting input (pin 6), plus there is a 100nF capacitor stabilising the current set voltage at pin 6. The voltage and current feedback signals also go to two of the analog-capable pins on the Uno board. Thus the Uno can sense (with its ADC peripheral) the voltage and current using pins A1 and A0 respectively. The VIN supply voltage is measured via a second 51kΩ/10kΩ divider at analog input A2. That allows the micro to calculate the voltage drop across Q1, and infer its thermal dissipation. On the PCB, there are test points for the four sense/reference voltages. These are labelled VFB, IFB (voltage and current feedback), VSET and ISET (voltage and current setpoints), plus one for GND. Arduino software The Arduino firmware produces SPI data to set the desired voltage and current limits, then closes the relay to enable the output when prompted by the user. The hardware on the shield then manages the output voltage, reducing it if the current limit is reached as described above. Once the voltage and current are set, the regulator operation is automatic; it does not depend on the software for control. The microcontroller measures the supply and output voltages, and load current, then sends this data to the program running on your computer for display. Calibrating the unit consists of determining the exact relationship between digital values (ADC readings and digital Australia’s electronics magazine February 2021  41 Fig.2: this deceptively simple Arduino shield turns an Uno into a regulated bench power supply. Apart from the pin headers, the only component on the underside (and the only SMD) is the 15mΩ shunt resistor. Power transistor Q1 has a small heatsink as it can dissipate several watts. The ICs, relay and transistors are polarised so must be orientated as shown, while the other components can go in either way around. Several test points are provided, but they are not needed for calibration. And to further assist in construction, here are the matching same-size photos of the shield, from both sides. potentiometer settings) and the resulting analog voltages. These coefficients can be calculated from measured component values. The Power Supply will be fairly accurate ‘out of the box’. But its accuracy can be improved by taking readings with a multimeter, determining the exact ratios and programming these into the code. A calibration routine in the PC program simplifies this process, automatically calculating the new ratios from measurements. Construction The main part of the assembly is building the shield. The parts all fit on a double-sided PCB coded 18106201, which measures 69mm x 54mm – see Fig.2. The first decision to make is whether you want to build it with plain headers or stackable headers. You will need stackable headers if you plan to plug any shields on top of this one. But we used regular pin headers on our prototype, as we don’t plan on doing that immediately. Assembly is then straightforward. To confirm everything is going in the right place and with the correct orientation, check Fig.2, the PCB silkscreen and the matching photos as you fit the parts. Start by fitting the 15mΩ surface-mounted resistor, which goes on the underside of the PCB. Some constructors like to use a wooden clothes peg to hold an SMD component in place while soldering it. Flip the board over and tack one lead in place with your iron. If the part is flat and square within the silkscreen markings, solder the other lead. Otherwise, remelt the first pad and adjust the resistor, using tweezers if necessary, until it is placed correctly. Then solder the second lead and flip the PCB back over. 42 Silicon Chip Fit the 11 through-hole resistors on the top of the PCB, as indicated by the silkscreen markings. Check their values with a multimeter, as some of the markings can look quite similar. Follow with the eight 100nF and two 1nF capacitors, which should be marked with their values (or codes representing them, like 104 and 102 respectively). None of those are polarised; nor are the 10µF capacitors which can be through-hole or SMD types. Mount them now. Next, install the smaller transistor, Q2. Crank the leads to fit the PCB pads, ensuring that when mounted, the body sits low in case you need to add a shield above this one. Ensure that it matches the outline on the PCB silkscreen. Follow with the TO-220 transistor, Q1. It is mounted on a finned heatsink. First, bend the leads backwards by 90º around 7mm from the transistor body, then thread the leads through the PCB pads. Check that the larger mounting hole is aligned and adjust the leads if necessary. Remove Q1 from the PCB and insert the M3 machine screw through the back of the PCB. Add the heatsink on top, then the transistor and thread on the nut. Before tightening, ensure that the heatsink and transistor are square within the footprint. Carefully tighten the nut (to avoid damaging the transistor leads), then solder its leads and trim them. Most of the remaining parts are in DIL packages. Avoid using IC sockets, as not only will they have a worse connection than direct soldering; they will also cause the components to sit much higher. RLY1 has eight pins but comes in a 14-pin size package. It sits above Q2; the notch in its case faces to the right. Gently bend the leads to line up with the pads and fit them. Solder two diagonally-opposite leads and check that the part is flat; adjust if it is not. Solder the remaining leads and then go back and refresh the solder on the first two leads. Australia’s electronics magazine siliconchip.com.au IC1 is a 14-pin part; its pin 1 notch should butt right up to the adjacent capacitor. IC2 is an LMC6482, as marked on the silkscreen. Do not mix it up with IC3, which is specified as an MCP6272, although you could use another LMC6482 instead. Use a similar technique as RLY1 to fit IC1, IC2 and IC3. Once that is done, check for any bridges or dry solder joints and repair as necessary by using a solder sucker or solder braid to remove excess solder. Apply the iron and fresh solder to finish the solder joint. Headers and jumper Attach the Arduino mounting headers, along the edges of the board, next. If you are using male headers, then fitting them is straightforward. Use the Uno as a jig and plug the pin headers into the Uno, then place the PCB on top. After checking that everything is flush and square, solder the pin headers from above and unplug the assembly from the Uno. If you want to use stackable headers, then it is a bit trickier, although the Uno can still be used as a jig. In this case, the headers thread through the PCB from above and into the Uno. Flip the assembly over so that the Power Supply PCB is at the bottom. Now you have access to the pins of the stackable headers from below. That should be sufficient to tack the endmost pin of each strip to keep the headers in place. Check that the headers are flat against the PCB and adjust if needed. Unplug it from the Uno to give better access to the remaining pins. Solder them, then refresh the end pins. In this case, you will probably also need to solder a twoby-three pin stackable header block to the R3 header location on the board, to pass those signals through to a board stacked above. JP1 consists of a male header and jumper shunt. Fit the shunt to the header, slot it into the PCB and solder its pins. The shunt will keep the pins in place even if the plastic shroud melts a little. Finally, it’s time to mount the output connector, CON1. We used a two-way screw header, although you might prefer something different depending on how you want to use the Power Supply. Solder CON1 in place and then fit the PCB to the Uno. Unless the Uno is new and unprogrammed, you should remove JP1, in case the existing sketch uses a different voltage reference which could conflict with the 3.3V supply and possibly damage it. Software There are two elements to the software of this project – the first is the firmware that runs on the Uno. The second is the computer application that interfaces with it. The Ar- Parts list – Arduino-based Power Supply 1 double-sided PCB coded 18106201, 69mm x 54mm 1 Arduino Uno or compatible board 1 12V-15V 1A plugpack with 2.1mm DC plug to suit the Uno, or a similar power source 1 2-way screw terminal (CON1) 1 6-way pin header (or stackable header, see text) 2 8-way pin headers (or stackable headers, see text) 1 10-way pin header (or stackable header, see text) 1 TO-220 finned heatsink (for Q1) [Jaycar HH8502] 1 2-way pin header and jumper/shorting block (JP1) 1 2x3-way stackable header (optional; needed if another shield to be attached above) 1 5V coil DIL reed relay (RLY1) [Altronics S4100, Jaycar SY4030] supplies built with the Jaycar relay should set the current limit no higher than 500mA to avoid damage to the relay, due to this relay only having a 500mA switch rating Semiconductors 1 MCP4251-5k 5kW dual digital potentiometer, DIP-16 (IC1) [SILICON CHIP ONLINE SHOP SC5052; Digikey, Mouser] 1 LMC6482 dual op amp, DIP-8 (IC2) [Jaycar ZL3482] 1 MCP6272 dual op amp, DIP-8 (IC3; LMC6482 can substitute) 1 MJE3055 10A NPN transistor, TO-220 (Q1) [Jaycar ZT2280] 1 BC547 100mA NPN transistor, TO-92 (Q2) [Jaycar ZT2152] Capacitors 2 10µF 16V leaded X7R ceramic (or SMD M3216/1206-size) 8 100nF MKT (code 103, 100n or 0.1) 2 1nF MKT (code 101, 1n or .001) Resistors (all 1/4W 1% axial metal film except where noted) 1 150kW (brown green black orange brown or brown green yellow brown) 1 100kW (brown black black orange brown or brown black yellow brown) 2 51kW (green brown black red brown or green brown orange brown) 4 10kW (brown black black red brown or brown black orange brown) 2 1kW (brown black black brown brown or brown black red brown) 1 100W (brown black black black brown or brown black brown brown) 1 15mW 1% SMD, M6532/2512-size [SC ONLINE SHOP SC3943] duino firmware ‘sketch’ is available for download from the SILICON CHIP website. We’re assuming that you have some familiarity with the Arduino IDE (integrated development environment), although it isn’t too hard to figure out if you’re new to it. The IDE can be downloaded for free from siliconchip.com.au/ link/aatq We’re using version 1.8.5, but practically any version should be fine as the sketch is quite simple and doesn’t need any special libraries. With that installed, the next step is to load the Uno with the firmware. Connect the Uno to a USB port, select the Uno’s End-on views of the sandwiched boards – the power supply shield on top; the standard Arduino Uno (or compatible) below. siliconchip.com.au Australia’s electronics magazine February 2021  43 Screen1: our Processing application provides slider controls for voltage and current at the top, along with simple switches to switch the output on and off. Presets are displayed and selected below, along with power information. The incoming supply voltage can be monitored in the title bar. Screen2: the calibration procedure is simple. You adjust the controls until the multimeter reading matches the voltage and current readings shown at lower left, after which you simply copy the parameters to the configuration file. Screen3: the “config.txt” file contains calibration parameters and up to five named presets. You can also set the serial port and whether the application should automatically connect to it at startup. serial port from the Arduino IDE Tools menu, then ensure that the Uno board is selected as the target (Tools -> Board -> Arduino Uno). Press Upload, and once the sketch has uploaded, insert JP1 and open the Serial Monitor at 115,200 baud (CTRL + SHIFT + M in Windows). The sketch is fairly simple; it listens on the serial port for commands like “V100”, “I50” or “R1” to set the voltage, current or the relay state respectively. Since the communication to and from the Power Supply is simply over a serial line, we can also test the unit by typing commands into a serial terminal program such as the Serial Monitor. Such a simple scheme means that it can be manually controlled if necessary. But it also means the Power Supply can be very easily controlled by other software; they just have to send the correct commands and process the (simple) responses. Even if no 12V supply is available, the Uno itself will feed around 4V to the VIN pin (and thus the Power Supply) for testing. This is enough for us to do some simple, lowvoltage testing to check that the unit works as expected. host program converts the 0-1023 readings to real-world voltages and currents. To test the output with a multimeter connected to CON1, enter the command “R1”, followed by “V255” and “I255”. This should allow the output to get within about 0.7V of the VIN supply voltage (limited by the inherent diode drop of the emitter follower Q1). Try some lower values for V (eg, V25) to check that the output can be regulated to a lower level. That should give you about 2V, while V37 should give about 3V and V13 should give about 1V. To check higher output voltages, you will need to connect a 12-15V supply to the Arduino’s barrel socket (but watch that upper voltage limit!). For this testing, it would be a good idea to connect the Uno to your computer via a USB Port Protector, like our design from 2018 (siliconchip.com.au/Article/11065). That will mean that even if there is a fault in your Power Supply that results in 12V or more being fed back to the USB signal pins (which operate at 3.3V), it shouldn’t damage your computer. Testing Processing app With the Power Supply plugged in via USB and the Serial Monitor open, you should see a stream of lines showing values prefixed by J, U and S. The J and U values should be close to zero, but S will be around 200 (indicating around 4V at VIN). To test the relay, type “R1” or “R0” followed by Enter. You should be able to hear it gently clicking on (after R1) and off (after R0). You can send commands to the digital potentiometer by typing either V or I, followed by a number in the range of 0-256, then enter. These numbers are the raw digital potentiometer values, as all calibration is done on the host computer program. With the relay on and both the V and I values set to non-zero values, you should measure a voltage across the output terminals. The J, U and S values are raw ADC readings (0-1023) of the input and output voltage and current, taken several times per second by the Uno. The J, U and S letters chosen are to avoid confusion with the commands V and I. The We wrote the computer control app in the Processing language. The Processing IDE is available on Windows, Mac and Linux (including the Raspberry Pi). Using the IDE, you can run the program or compile it to a standalone executable file for your system. It’s based on Java, so you will probably need a Java runtime environment (JRE) installed to run the program. Processing can be downloaded for free from https://processing.org/download/ (we used version 3.5.3). There are no special libraries or add-ons needed. Open the Processing sketch (a file with a .pde extension) using the File menu and run it using the Ctrl-R key combination. A standalone executable can be created from File -> Export Application. Referring to Screen1, the actual and set voltages and currents are shown as bar graphs and in digital form at the top of the window. A similar display below shows the actual and set currents. Two large buttons are provided to turn the output on and off. Below this are five preset buttons 44 Silicon Chip Australia’s electronics magazine siliconchip.com.au and a button to access the calibrations page. Along the bottom are displays for output power (P) and transistor Q1 power (Q). These change colour as the power increases. At bottom right is an indicator for the serial port. The initial calibration of this software comes from our prototype, so it should be roughly correct within component tolerances. It’s easy to fine-tune it, though. Using it Press “+” and “-” on your keyboard to cycle through the available serial ports. When the Uno’s port is selected, press “s” to connect -- if the connection is successful, the serial port will turn green. If it does not connect, check that the port is not in use by another program (for example, the Arduino Serial Monitor). The “s” key has a toggle action, so it can also be used to disconnect from the Power Supply. Drag the arrows on the bar graphs with the mouse pointer to set the voltage and current. The green arrow is the setpoint, which corresponds to the leftmost digital display. The red arrow and rightmost numbers correspond to the actual voltage and current values. Click the “ON” button to energise the relay and enable the output. Note that the PSU reads the voltage before the relay, so it will show a value even if the relay is off. The “ON” button turns green when the relay is on. Use the “OFF” button to shut it off. Pressing any of the five preset buttons will load that preset into the voltage and current setpoints. In Screen1, preset three is loaded, so its button is highlighted. Calibration Pressing the ‘Calibration’ button will expand the window to show the calibration values (see Screen2). Our copy of Processing stalls for a few seconds when this happens; it is a known bug which will hopefully be fixed in a later version. To close the Calibration view, click in the lower part of the window. Calibration is achieved in two stages. The first is to calibrate the voltage, which requires a voltmeter to be connected across the Power Supply output (CON1). Turn on the output and set the current to any value above zero; this is to ensure that the current limiting doesn’t kick in, which would reduce the output voltage. Next, adjust the voltage slider until the multimeter reads as close to 6V as possible. A 12V-15V DC external supply is ideal for doing this, but even 9V DC would be sufficient. Note that the two pointers may not line up to 6V. This is expected, as we are still calibrating the unit. Now, write down the “VFACTOR” and “UFACTOR” values that are displayed in the bottom panel. To calibrate the current side, turn the output off and switch your multimeter into a mode and range capable of reading up to 400mA. You will probably need to change how the meters leads are plugged in too. Since your multimeter is effectively forming a short circuit, you can include a power resistor in series with the multimeter leads for extra protection, and to reduce dissipation in the output transistor. For example, a 10Ω 5W resistor would work well. Switch on the output and move the current pointer up until the multimeter reads 300mA, then note down the lower (“IFACTOR” and “JFACTOR”) calibration values and siliconchip.com.au turn the output off. Be quick about this, as the transistor can get quite hot during this stage. Configuration The calibration factors (along with other settings) are stored in a file called “config.txt”. This must be in the same folder/directory as the .pde file for the Processing sketch. Open it and add or modify the four calibration factors you wrote down. The result should look like that shown in Screen3. Note that the app does not care about upper or lower case in these settings. You’ll need to restart the program to load the new configuration. If you are running it from the Processing IDE (rather than an exported app), you should see that the calibrations are loaded in the log window at the bottom, like this: UFACTOR set VFACTOR set JFACTOR set IFACTOR set If these are not seen, then there may be an error, and the values have not been loaded. The configuration file also supports some other options. SFACTOR is used for calculating VIN; it is theoretically (within component tolerance) the same divider as that for UFACTOR, so you can use the UFACTOR value here too. It’s only used for display and dissipation calculations, so isn’t as critical as the other values. It is a simple scaling factor from the raw ADC result (01023) to voltage, so can also be adjusted by comparing with a multimeter reading. For example, if the displayed supply voltage is 1% too low, then increase SFACTOR by 1%. You can also set the default serial port and whether it should connect when you run the program with the PORTNAME and CONNECT parameters. The nominal supply voltage can also be provided with the VIN parameter. The PORTNAME should be set before the CONNECT line so that the correct port is opened. The naming scheme for ports will differ between operating systems. The five presets are set with PRESET1 to PRESET5, with the values being voltage (in volts), current (in amps) and name (cropped past seven characters). These parameters are separated by commas. Naturally, all configuration variables have reasonable defaults in case the configuration file is missing or empty. We’ve left a few potential lines in the file prefixed by an apostrophe; the program ignores these lines until you remove the apostrophes. Usage The Power Supply control app has been designed so that using it should be intuitive. We reckon that this way, it is much easier to use than a supply with physical controls like a few pots and a small display. It is by no means a high-accuracy piece of test gear but still very handy to have on your desk, especially since it doesn’t take up much space. We haven’t described how to fit it into any sort of enclosure, as you really can just use it as-is. If you do want to enclose it, a UB3 Jiffy Box is the simplest and cheapest option, and its generous size should allow some airflow for cooling. A pair of holes in each end will be sufficient to run all the necessary leads. SC Australia’s electronics magazine February 2021  45 SERVICEMAN'S LOG A feline-themed cautionary tale Dave Thompson Cats can be quite difficult to manage, especially if they each need specialised food. With modern tech you now have devices like a microchip pet feeder, which allow only certain cats access to a particular food/medicine bowl. However, there’s always a caveat with allencompassing one-trick problem solvers. Items Covered This Month • • • Do (not) feed the cat Tektronix TDS744A oscilloscope repair Restoring an electronic organ *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz It’s no secret we own a few cats (or should I say that we serve a few cats?). I have mentioned them before in this column. One of the problems with having multiple cats is that they are very much individual characters, with their own preferences for food and attention. So it is hard to implement a strategy for one cat without affecting the others. For example, one of our cats has allergies to something in the soil around our cat run. Every spring, these allergies flare up, but the other two cats aren’t affected at all. Having to dish out special food or medication to one cat and not the others can be a lesson in frustration, as they all graze on each others’ food. So when we saw an advertisement for “Microchip Pet Feeders”, we thought it might be the answer to our problems. Our cats are all microchipped within a few weeks of birth (as all pets should be). Having the ability to allow one cat to feed from a particular food/medicine bowl while the others have no access is very appealing. That is exactly what these devices claim in their advertising bumf; apparently, you can program access for up to 30 individual animals into each feeder using their unique microchip ID tag. In our situation, we only needed to register the one cat to it. To shop online or not We ordered one of these units online, and it duly arrived on the doorstep. I’m a modern guy; I like this ‘new’ way of buying products; not because I’m lazy, but these days one tries to avoid going out of the house (if one is even allowed!). Clearly, online shopping is boom46 Silicon Chip Australia’s electronics magazine ing at the moment. I have to wonder whether many people will go back to the ‘old ways’ even when restrictions are lifted. Who wants to deal with the hassle of driving to a shopping centre, finding a parking space and pushing your way through crowds to the shop, only to be disappointed that what you want isn’t even in stock? It’s quite convenient just to have stuff show up at your door a couple of days after clicking some buttons on the computer, and overall it doesn’t cost that much more since you are saving on petrol, stress and (perhaps more importantly) time. However, there are still problems with this approach. If you know what you want, or have used the products before, or they are the sort of items you can buy based on specifications (like a lot of electronic devices), it’s perfect because you know exactly what you are getting. But online shopping isn’t that suitable for buying the likes of clothes or shoes, for example. Unless you have gone to a bricksand-mortar store to try on the same product beforehand, and know it fits, buying these things over the Internet can be fraught with problems. What if it doesn’t fit? You are then in a position where you have to go through the hassle of contacting the vendor, returning the item, and possibly paying the return shipping costs. That can mean that your item ends up costing you more than if you had just gone down to the store and purchased it in the first place. At worst, you have no usable product and are out of pocket for all the related expenses. Defects and warranty returns can also be a can of worms. Some online sellers are great about returns, such as siliconchip.com.au most Amazon sellers and local computer stores. But I have experienced vendors who start ‘ducking and diving’ and trying to place the onus on the supplier or manufacturer, not wanting to accept the return themselves. High-street stores are bound by all manner of consumer laws to protect customers, but an online store might be located off-shore and so all that legal responsibility goes out the window. What happens then? Trying to outwit the cats Anyway, back to our new microchip feeder. We liked it so much we purchased another, and although we bought it from a different source, it is the same brand. The cats seem to love them, and weren’t as put off by the movement of the lid or the small amount of mechanical noise they make when opening and closing as we initially thought. However, cats are inherently very crafty and intelligent animals. The first feeder we purchased kept our alpha male out for a while, but he soon learned that in the few seconds it takes for the bowl door to close once the registered cat has left it, he can swoop in and hoover a large amount of any leftover food before the door slowly closes on him. Clever! The door-close-after-eating timing is variable, to a degree, via a three-position slide-switch (short, medium and long delay). But even on the shortest setting, there are a few seconds the contents of the bowl are vulnerable to pilfering. Our A1 male soon made good use of this potential design flaw by sitting very close nearby and swooping siliconchip.com.au when the registered cat leaves. I told you they were clever! Other than that, the device does what it says. There is a food bowl buried under a horizontally-closing bi-folded trap door. Once this door is closed, there is no way for the cat to actively lift the door to access the food or get to it in any way (and they try, believe me!). The door design is smart too; it cannot be opened by simply hooking a claw (or finger) under the split centre section and pulling upward, as the motor’s mechanical lever assembly and natural friction/resistance holds it firmly shut. It could probably be forced open with enough force, but cats aren’t strong enough (at least in the manner Australia’s electronics magazine required) to achieve that. It’s a good system; it works well and is quite robust. They have obviously put much thought into the design. There is a kind of plastic halo over the whole thing, and the cat must stick their head and neck through this to access the food (most microchips are inserted between the pets’ shoulderblades and are thus in the right place to trigger the device). That is probably the biggest aspect any pet would have to get used to. This halo obviously has the antenna for the microchip reader inside it. If the pet is not microchipped, a tag is supplied in the box, and this simple RFID disc can be attached to a pet’s collar and used instead of an embedded chip. As soon as the pet comes close to the February 2021  47 feeder, the sensor picks up the chip/ tag, identifies it and either allows or denies access. If the chip/tag ID is recognised, the door sequence starts. One LED flashes and the motor runs to open the door. Once the pet withdraws its head from the hoop, after the pre-set door-close time, the motor runs back the other way to close the hatch. While relatively simple, it’s a system that’s quite tricky to implement in a low-voltage (6V) battery-powered package. There is no provision for a mains supply, which in my opinion is a major design flaw. Batteries are expensive, wasteful and don’t typically last that long, and these units require pricey alkaline types for ‘optimal’ performance. An AC power option would have been a valuable addition. A turn for the worse However – there is always a however when a serviceman is involved – last week, the first feeder we purchased started misbehaving, with the door not operating correctly. According to the user manual, the indicator LED should flash red once every few seconds when the batteries get low, but that wasn’t happening, so I assumed it wasn’t a power problem. I changed the four C-sized cells for new alkaline ones to be sure, but the problems persisted. The door would not open fully, or then it would open fully but then not close properly. I removed the batteries and tested them with my multimeter, just to satisfy my nagging doubts. Of course, we all know this is not a complete indication of actual battery state anyway, but in lieu of a proper battery tester, a basic voltage test does tell me if they are getting past their best. All measured well over 1.5V, so I was reasonably confident the batteries were still OK. Things got worse over the next 24 hours, with the door often refusing to open at all. This feeder has several buttons that can be used to either program the pet ID, set times or open the door manually. Usually, a press of the manual door button would open the hatch straight away, but this became increasingly erratic. Something had to be done. And this is where the whole online shopping system can start to break down. I tried to find somebody to contact on the original purchase site for 48 Silicon Chip a warranty claim, and it turned out it is almost impossible to reach anyone there. The 0800 number (a free-calling toll number here in NZ) didn’t go anywhere, giving me only a pre-recorded message stating they ‘couldn’t take my call’, but at the same time providing no option for leaving a message. Great! There was also an e-mail form, complete with one of those annoying CAPTCHAs, but when I filled it in and clicked the Submit button, I got a page-not-found fault, along with the claim that the message could not be delivered. Excellent! This is increasingly the case with online sellers. They just don’t have any real customer service. Call me oldfashioned, but it makes much more sense to pay a little more and go to an actual store, where any potential problems can soon be ironed out without all this faffing about. Or maybe someone can open an online shop with slightly higher prices, where you can actually contact someone for help. I know it’s a crazy idea, but it just might work! But none of that helped me now. The only thing left to do was to open it up and have a look. And I also have another feeder to compare this one to, so what could possibly go wrong? Disclaimer: I am not a certified Microchip Pet Feeder serviceman, or even a non-certified feeder serviceman. Just so we’re clear. Four screws held the large moulded plastic back frame on. Once those were removed, the back split away cleanly, exposing the wrapped-wire chip sensor antenna, the underside of the door motor mechanism and a long, narrow, single-sided PCB absolutely stacked from one end to the other with surfacemounted components. I was surprised at the complexity of the circuitry and PCB, but then again, I guess there’s a lot going on in there. There was also a smaller ribbon-cable connected button-board PCB near the top rear of the unit, containing the manual door and programming buttons. Other than that, it was all fresh air inside. Fortunately, and against type, none of the component identification numbers had been obfuscated. I could see there was an ARM microprocessor mounted near the middle of the PCB and several other support chips for it surrounding that. At one end was the power supply section and at the other, Australia’s electronics magazine the motor driver, which included an array of what I assumed to be Mosfets or similar. The door motor appeared to be a simple 6V DC motor – nothing special. I unsoldered the two motor leads from the PCB (handily black and red) and used a benchtop power supply set to 6V to run it backwards and forwards. It operated perfectly and smoothly, so there was no mechanical reason it would be jamming or misbehaving. I wired it back in and used my power supply instead of batteries to power up the unit; the door opened to full travel and sat there trying to open further, with the motor ‘hunting’ slightly. Something was obviously not right. I was also not entirely sure how they were relating the position of the motor and door assembly to the driver circuit; how does it know when the door is fully open or closed? There are only two wires to the motor, so perhaps they are just sensing drive current in the line when the door won’t go any further and feed this information back to the micro to tell it to stop driving. I repositioned the door/motor manually back to closed, and powered on again. Once again, the door opened fully and tried to go further. It didn’t seem to matter where the motor was sitting; it just tried to open up and keep going. At this point, I realised there was little I could do. Without circuits, firmware or anything to work with, it was becoming a waste of my time. My cunning plan goes awry I know what you’re thinking: I have the other one! From a troubleshooting point of view, there is nothing like having another working unit to compare to a faulting one, so I went and brought the working one out to the workshop. Amazingly, though they looked very, very similar, they were actually completely different models. The PCB was very different; the case moulding was different, and even the door mechanism was different. So there was nothing I could use from the working one to relate to the non-working one. Awesome! All I could do at this point was button it all back up and go back to the seller’s website, and try to look for a way forward. After making many approaches with no luck, I ended up going directly to the feeder manufacturer, and they were siliconchip.com.au very happy to help me out. However, there are many hoops I now have to jump through, and I’ll likely end up having to ship this thing at my expense overseas. It isn’t a small package. This is not a great outcome, but better than nothing. In the meantime, we bought yet another feeder to replace this faulty model, and although we got it at a knock-down price (compared to the others), it does leave a bad taste when online vendors don’t play by the rules of civilised shopping. I’m fully prepared to write this one off, especially if it is going to cost too much to rectify. Cynically, I’m sure some of these online sellers take this into account, because at some point, it is just not worth the effort at the end of the day. It’d be a shame, as they are an excellent device and work very well. As an interesting aside, there is another aspect to this repair. The PCB inside the faulty feeder has a tiny screen-printed message visible on the top that reads: “My name is Ozymandias. King of Kings. Look upon my works oh ye mighty, and despair.” What a weird comment to add to your feeder’s PCB design! It is obviously meant to be read by somebody. At least it didn’t read “Help, I am being held inside an electronics manufacturing facility against my will!”. So should I despair? No, service work can be fascinating. Tektronix TDS744A oscilloscope repair A. L. S. of Turramurra, NSW, fixed his Tektronix TDS744A 500MHz 4-channel oscilloscope, but he had to totally disassemble it to get to the root of the fault, as he describes... I purchased this scope secondhand some years ago, and it worked perfectly until one day it refused to boot. It just flashed the LEDs on the front panel. Looking through the service manual, I could find no reference to this type of fault. This manual was obviously not designed for component-level repair because it had no circuit diagrams or even a block diagram! It had diagnostic procedures to isolate faults to a particular module, but it has to power up first, so that was no help. I immediately jumped to the conclusion that the power supply module was the culprit, so I started searching for a replacement or any information on it. siliconchip.com.au After trawling the net for some time, I discovered many other faults which are common to this model such as acquisition board failures, attenuator failures and poor SMD electrolytic capacitors, but nothing on power supply problems or any schematics. One guy on YouTube had the same flashing LEDs, but it was for an HP spectrum analyser, and it required a complex repair of the switchmode power supply. I also found some very good YouTube teardowns and repairs of this model, and some useful tips. They mentioned that there is an internal “protection” switch which can be accessed from the side panel through a hole. Sometimes, switching this can bring the scope to life. I switched it to protection mode, but nothing happened. So it was time to open it up and take a look. I thought there might be some visible evidence of burnt-out components, or perhaps it was just an internal fuse that had blown, or it just needed a reset. I always leave devices with highvoltage CRT power supplies alone for at least a couple of days to allow everything to discharge, especially when there is no available information on exactly where the high voltage is! After removing four screws at the back, the rear panel and outer case came apart with a light nudge from a rubber mallet. I removed two Tektronix “calibration is void if removed” stickers given that the warranty period had expired over a decade ago. This proved that the instrument had not been opened or messed about by the previous owner, at least since its last calibration. The internal layout was beautiful and well-designed for servicing. Each large PCB was easy to extract, starting with the one on top, which is the processor/display board with eight connectors. After these were removed, plus a small panel which has a Centronics connector and an RS-232 connector, the PCB slid out. Next, there is a large aluminium protector board with a high-voltage warning. I had to remove several screws to get that one out. I also had to gently lever it out of a slot, as it was very stiff. The power module was then exposed, so I removed it for a closer look. It was a pretty heavy board with a fairly standard switchmode architecture, capable of delivering all the low voltages for the scope. There were signs of overheating stress, but there were no immediately apparent shorts or problems, and all the electrolytics checked out fine incircuit. The inability to boot made it impossible to check the voltages given in the manual, so I had to look into other possibilities. I couldn’t find any power modules or identical ‘parts’ scopes for sale, except for a few scopes that probably had failed power supplies. But further research indicated that the TDS684A (1GHz, 5GS/s model) and the TDS784A (1GHz, 4GS/s model) have identical power modules and identical processor/display modules, so I took another look. I found one broken TDS684A for sale, which showed some activity on a very damaged and dull CRT screen. I therefore deduced it must have a functional power module, so I bought it for around $350. The bad screen wasn’t a huge worry because this model has a VGA output. My idea was to swap the modules to get my 500MHz scope working, and maybe even repair the 1GHz scope and get it working too! The non-working 1GHz scope arrived after a couple of weeks, and I hurriedly checked it out, but it was worse than the eBay seller’s photos led me to believe. The raster and graticule were folded over at the bottom of the screen. Was there something wrong with the power supply, or was the vertical amplifier or scan coil faulty? Would an external monitor even work? Also, the seller told me that he was pretty sure that it was showing all four traces, but there were no traces at all, Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column? If so, why not send those stories in to us? We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. Australia’s electronics magazine February 2021  49 so the acquisition board was probably kaput too! This appears to be a common problem with this model. It’s possible that the seller assembled the whole scope out of junk modules from previous repair jobs. I decided to try swapping the power module anyway – after all, it did boot up. So I tore down the spare scope and extracted the ‘good’ power supply board. Because I was getting good at disassembly, I had it swapped in no time. Then, after checking all the connectors five times and cautiously plugged the thing in, I stood back in anticipation of sparks and blue flashes and pressed the “on” button at arm’s length. The LEDs were flashing again, and no boot up at all! The fault must be on one of the other modules; perhaps the processor/display module. So I swapped that too. Again, nothing, just those darn flashing LEDs! I noticed that on top of the processor module was a single 7-segment red LED display, and it was flashing “8” in time with the LEDs on the front panel. I could find no mention of what this means anywhere. So, I thought I had better change the acquisition board, which required delving deeper because the screws into the BNC attenuators were behind the front control panel. The whole instrument had to be inverted because this module is on the bottom. The front plastic panel had to be removed and this was supposed to “snap off” (according to the manual), but 20 years of grease, dust and grime acted like an excellent glue, so I had to use two screwdrivers in tyre-lever fashion to ever-so-gently prise it off. Of course, it cracked, but luckily the crack was on the bottom, and it was almost invisible. Then I had to remove the BNC cover along with the front control panel to expose four screws which finally released the acquisition board. I smartly swapped this, hoping it would cure the boot problem at last. But no! I was still getting the LED light show. What next? Deep inside the bowels of the instrument, there are several PCBs which are stacked like a house of cards, inside a three-sided metal box. From this emanated myriad wires connecting the cathode ray tube (CRT) and the EHT tripler, along with the scan coil drivers and output transistors and some ICs. There was also a large processor IC, and I was horrified to see that the EHT cable had touched this, leaving black soot on it, but it was all part of the design to squeeze everything into a tiny space. The CRT and its associated scan coils, rear PCB and correction magnets were also squeezed into this box. This was all that was left, so the fault must be there somewhere, mustn’t it? I was beginning to doubt my ability to fix the two scopes, but I had already committed enough cash to motivate me to continue. The next step was to inspect this daunting mess, so I disconnected everything, taking care to note where all the wires went. I disconnected all the cables and connectors except for the EHT lead, which was blocked by the thick aluminium chassis. So the CRT had to come out, but first, more stuff had to be removed such as the softkeys, which were mounted on a thin metal bezel, and also the floppy disk drive. Then, very gently, I pulled out the CRT to the limit of the high voltage cable, about 4cm out of its housing. I was only just able to remove it from the tube by lifting the rubber insulator on the side of the tube and lightly squeezing the prongs with a medical clamp to release it. I made sure it was fully discharged by shorting these metal prongs to the chassis. Fortunately, the two-day safety discharge period I had allowed had done its job. I have some old-world experience with TV repair, so I was extra careful not to knock the skinny end of the tube because that is the weakest part. I also wore safety glasses because if these things are broken, they can implode and fling glass everywhere. I held it with all the delicacy of a newborn baby and stacked it face down in a cardboard box and set it aside away from harm. Now the whole instrument was stripped down to the bone (as shown at lower left), and all that was left was the box of components with the highly suspect board. Several electrolytics had to be bent out of the way to access the screws which needed to come out. Some of the electrolytics completely blocked the screwdriver access. I don’t know why they didn’t measure the electrolytics before they allocated the screw positions. Despite having removed the screws, the assembly just wouldn’t come out. It would not fit through the gap left The Tektronix oscilloscope was taken apart to determine the suspect components/boards. ► Some burnt and shorted tracks were found on the EHT module around the TIP30C driver transistor and associated electros. 50 Silicon Chip Australia’s electronics magazine siliconchip.com.au by the CRT, but by twisting it on its long axis and angling it in a certain position, it finally came out like one of those kids’ puzzle games. On the EHT module, I found some burnt and shorted tracks around the TIP30C driver transistor and its associated electrolytic capacitor (shown opposite at lower right). This was not visible from the top, and the cause was not immediately evident until I removed a capacitor and a transistor. This short had obviously caused an overload, shutting down the whole instrument. I repeated the extraction of the EHT assembly on the very cannibalised TDS684 1GHz scope, leaving it as a bare chassis. By this time, I had become very proficient with these techniques, and the extraction took just five minutes. I mounted up the suspect “spare” EHT module in my scope and inserted the original CRT to see what would happen. Well, it finally booted but as you might have guessed, that wasn’t the end of my problems! The raster and colour display were unexpectedly good, but I could not get a trace, and that meant that the substitute acquisition board was bad. Now I had to retrace my steps and put the original acquisition board back in, which proved pretty easy because I had so much practice. After I restored this board I got a trace, but the gremlins had multiplied, and error messages plastered themselves over the screen. Retracing my footsteps, I restored the original processor/display module and waited for the boot-up, which takes about a minute. I thought I was dreaming as everything worked perfectly; the self-test passed the display was steady, and it even came up with my last settings! The only downside was that the brightness was a little lower than it had been; that can be improved with the internal brightness adjustment, but I had just about had it, so that would have to wait for another time. If I can get the 1GHz acquisition board going, I can extend the scope’s bandwidth from 500MHz to 1GHz, so I will have a go at that later. For now, I just want to enjoy my once again working scope! Restoring an electronic organ K. V. of Kallangur, Qld, has put some time and effort into restoring electronsiliconchip.com.au ic organs, which are sought after these days, and quite valuable... Some years ago, my wife and I were given an old Hammond “Grandee” electronic organ. My wife can play quite well, but I can only fiddle with something electrical. The organ was on the way to the dump, beyond repair – but I was given first choice! I eventually got it all working thanks to a gentleman in Sydney, who obtained a service manual for me. This was a big help because one circuit board was missing. Apart from that, the cabinet had been home to a family of mice for some years, leaving quite a mess! My son helped me make up a new circuit board, and after a big cleanup, it all came to life. One of the first things I had to do was to add a speaker switchon delay to alleviate the loud thumps. Electronics Australia published a letter I wrote about these repairs back in 1997. Most of the problems we have had over the last 20 odd years have been because of poor contact in the many plug-in connections. It is good to be able to remove a circuit board to check by unplugging it, but generally, there is nothing wrong with it. Clean the contacts, a little wipe with Vaseline, plug it in and it goes! One problem that took 20 years to track down was that the hum level was higher than it should be. I had changed all the electrolytics in the power supply with very little improvement. The hum level on the two amplifiers was below Hammond’s specified level, so I left it at that. The connections to the organ from the power supply and amplifiers were by two 15-pin plugs. I never did like them. If they were wriggled, they made scratchy noises in the speakers. Pluggable terminal blocks looked to be the answer. These plugs carried a mixture of various DC voltages, signal voltages and mains voltages. The modifications involved a fair bit of work, but it was worth it. While I had the chassis out, I thought I might as well change the Leslie speaker plug to a pluggable terminal too. The Hammond drawing on the Leslie speaker shows six wires, two for the speaker and two each for the highspeed and low-speed motors. But this organ had five wires, not six! When this organ was built, someone decided to save a bit of wire (about 800mm), because all the returns were Australia’s electronics magazine February 2021  51 terminated off the one Earth bar on the chassis – but they added another 6-pin plug and socket at the Leslie speaker end. I decided to wire it up as per Hammond’s drawings and delete the extra 6-pin plug. It was superfluous. When the organ was put back together, everything worked OK. My wife played a few tunes and was quite happy with it. That annoying hum level had gone! I sketched out the connections of the Leslie speaker showing how they were and how they should be. The tremolo speaker return connected to the fast motor return, which is always running, then through two doubtful plug contacts to the common Earth bar. The tremolo speaker had every chance of picking up some 50Hz current, producing the hum. 52 Silicon Chip Sometimes the designers’ plans are not always carried out on the workshop floor, but the organ worked – so out it goes to be sold! All the soldering in the Hammond was excellent and I never had any trouble with dry soldered joints. That reminds me of another organ I had to repair, a Baldwin “Fanfare” built in 1977. It had been sitting idle for years, and it too had become the residence of mice. That meant another big cleanup, checking and replacing corroded contacts. When it was ready, I connected it to a variac and slowly increased the voltage in stages. At full voltage, most of the organ worked. About this time, a service manual arrived from W. D. Greenhill & Co in England, so I was able to check the power supply. I found that only one section Australia’s electronics magazine was within tolerance. I removed the power supply to the workbench, replaced the electrolytic capacitors and one open-circuit transistor. All voltages were set within the ±3% as specified. When it was replaced in the organ, the -12V supply was down to -7.5V, and clearly overloaded. A bit of circuit tracing revealed that the -15V and -12V supplies were crossed over in a plug. The organ worked much better after correcting this error. This is another case of an original fault that was ‘allowed through’ because most of the instrument worked! I did eventually get this organ all working after tracking down numerous faults, corroded connectors, poor solder joints and some faulty ICs, as well as fitting a delay relay to the speakers. SC siliconchip.com.au Home Projects for Summer Hardcore electronics by On Sale 27 December 2020 to 23 January, 2021 DUAL FILAMENT 3D PRINTER Allows you to combine colours and materials creating high-quality prints. Oversized bed screws for leveling the print bed. Dual cooling fans. SD memory card slot. • Prints up to: 300(L) × 300(W) × 400(H)mm TL4410 WAS $1299 MICRO:BIT SMART ROBOT KIT A fun to build robot that uses a micro:bit microcontroller board (sold separately XC4320 $34.95) that kids can code or control using their Smartphone via Bluetooth®. No NOW soldering required, plug and play. KR9262 WAS $99.95 See website for details. 1199 $ 69 $ 95 SAVE $100 SAVE $30 This official kit from Arduino includes all the essentials to get you started in the exciting world of Arduino®. Kit includes UNO board, breadboard and plenty of prototyping accessories. Perfect gift for a young electronics enthusiast or maker in the making. 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Single SL2250/54 WAS $19.95 EA NOW FROM NOW $14.95 EA SAVE $5 3 Pack SL2252/56 WAS $49.95 PK EA NOW $39.95 PK SAVE UP TO $10 SAVE $10 14 $ 95 SMART WI-FI PLUG Easily manage your household electronic devices using your Smartphone. Control via app or voice command. MS6106 RRP $19.95 EA 2 FOR 30 Smartphone not included. $ ALSO AVAILABLE: with 2 x USB MS6104 RRP $34.95 EA 2 FOR $50 SAVE $19.90 SAVE $9.90 Home Security JUST 8995 $ DOOR ENTRY ALERT Features a send & receive unit that transmits a beam. Buzzer sounds when the beam is broken. Effective range up to 6 metres. Mains power adaptor & mounting hardware included. LA5193 HIGH VOLUME WIRELESS DOOR BELL Loud volume with built-in strobe light. 7 selectable melodies. Medium & loud volume control. LA5002 JUST 5995 $ ONLY 1995 $ WINDOW & DOOR ENTRY ALARM • Security alarm or entry chime • Quick installation • Includes self-adhesive strips LA5209 In the Trade? THERMAL DETECT TECHNOLOGY 8 CHANNEL 4K NVR KIT WITH 4 X 5MP CAMERAS Versatile 5MP surveillance package for home, office, or commercial applications. 2TB HDD • Smart viewing and notification • Audio recording • Power-over-Ethernet • Expandable up to 8 cameras • Built-in infrared LEDs for night vision up to 30m QV5600 4K LINE INTERACTIVE UPS WITH LCD Great for connecting surveillance cameras up to 60m. Video & Power. Compatible with most DVR systems. 30m WQ7283 $19.95 (Shown) 60m WQ7287 $39.95 FROM 149 $ • Reed switch and magnet 4-Core WB1591 $24.95 • Normally CLOSED (NC) per pair 6-Core WB1596 $49.95 • Self adhesive or screw mount LA5072 5 25 999 FROM 1995 $ BALUN KIT SECURITY ALARM REED ALARM CABLES • 30m roll length SWITCH $ JUST $ CCTV EXTENSION CABLES • Easy to read LCD which displays battery and load values • 2 x RJ11 sockets for telephone and fax • USB socket 650VA 390W MP5205 $149 1500VA 900W MP5207 $349 ONLY 5MP FROM 24 $ 95 Simplify your CCTV installation by combining composite video, audio and power for transmission over one UTP CAT5 cable. QC3667 ALSO AVAILABLE: BNC/RCA/ Power to Cat5e/6 QC3669 $32.95 JUST 1695 $ QUAD ELEMENT PIR DETECTOR • Compact, reliable and effective • Built-in automatic temperature to help eliminate false triggers • Swivel bracket for quick position adjustment LA5046 $44.95 EA 3 FOR 99 $ SAVE OVER $35 55 think. possible. 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MS6147 ALSO AVAILABLE: 1 Outlet + remote JUST MS6148 $19.95 39 $ 95 7 499 Designed for mobile or permanent power installations it will run sensitive electronic and power hungry devices such as a microwave, power tools or TV. 12VDC to 230VAC. Short circuit, overload, low/ over voltage, and over temperature protection. MI5740 ALSO AVAILABLE: 24V 2000W MI5742 $599 450 $ 95 EA WATERPROOF SOLAR POWER PV CONNECTORS IP67 rated for maximum environmental protection. 4mm Male PP5102 4mm Female PS5100 /m SOLAR PANEL POWER CABLES Dust, age and UV resistant, tinned copper conductors to minimise corrosion. • IP65 rated 50A 4.0mm2 Full range of other 50A WH3121 $4.50/m wiring hardware 70A WH3122 $6.50/m available in-store or online. Power to the Home 10A DOUBLE GPO WITH RCD* Designed to be a direct replacement to your standard GPO fittings. 2 x 10A GPO. Built-in RCD to prevent electric shock. LED indicators. 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Universal T10/211/BA9S. 2.5W 260 Lumen ZD0585 $9.95 3.0W 310 Lumen ZD0587 $12.95 4.5W 450 Lumen ZD0589 $14.95 FROM 7 $ 95 WATERPROOF DEUTSCH 2-WAY CONNECTOR SET Perfect for connecting up sensors/ lights in the bay due to their superior corrosion protection. • 13A rated. 2-Way PP2150 $7.95 4-Way PP2149 $9.95 6-Way PP2148 $11.95 More ways to pay: FROM A range of 150 lumens ultra-bright white LED replacement globes for car interior lights. Compatible with modern "CANBus" sytems. 120° wide beam. 12VDC. 3 sizes available. ZD0750-54 NOW 2795 $ EA SAVE $5 FROM 89 $ 95 PR H4 HI/LO LED POWERED HEADLAMP KIT Bright and efficient. Equipped with advanced Luxeon Z ES LEDs. • 3800 lumens 40W NOW • 12/24VDC SL3524 WAS $169 JUST 6995 $ AUTOMOTIVE MULTI-FUNCTION CIRCUIT TESTER WITH LCD Designed to test the electrical system of an automotive vehicle running on 12V or 24V. Tests voltage and polarity of a circuit. 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Provides acoustic isolation and insulation for roof, firewall, floor, quarter panels, doors and under bonnets. 330mm wide. WAS $32.95 EA Butyl AX3687 Butyl/Foam Combo AX3689 95 FROM NOW SOUND DEADENER 94 $ 12V REVERSING CAMERAS ONLY Perfect for the workshop as an an engine analyser as well as basic DMM. Full dwell angle measurement and tacho. Max/ data hold and bright backlit LCD. • 2000 Display count • RPM x 10 QM1446 4995 $ Micro USB Plug (Mini USB adaptor included) Get rid of unsightly power cables floating around car dash that powers GPS, Dash Cam or mobile device. • 2.5A continuous current • Cable length 1.3m MP3675 IN-CAR BATTERY MONITOR AND TEMPERATURE DISPLAY Plugs into an available power socket to display system voltage and interior cabin temperature. Easy to read LED display. QP2222 ONLY 1995 $ 57 D E N I A T ENTER keep the kids AMAZING SELF-FLYING DRONE! 9995 $4995 LASER GUN & DRONE SET REMOTE CONTROLLED 2-IN-1 TANK CONSTRUCTION KIT 4995 Build your own 'marble' roller coaster. The spiral "elevator" lifts the marbles to the top of the rail, and gravity takes care of the rest. 170 piece. Requires 1 x C battery (sold separately). Ages 15+. KJ9004 2 PK C Batteries SB2416 $4.50 TOBBIE THE ROBOT - HEXAPOD KIT A 6-legged robot that you can build. Walks and spins in any direction and will beep and flash its eyes. Ages 8+. KJ9031 Assembled into two different tanks. Drive around on caterpillar tracks and raise/lower the turret. Equipped with gunfire sounds. 759 pieces. Ages 6+. Requires 3 x AAA and 6 x AA batteries (sold separately). KR9242 4 PK AAA Batteries SB2413 $3.25 12 PK AA Batteries SB2333 $7.95 JUST 2995 $ VIDEO ONLINE JUST Runs on potatoes or with tomatoes, lemons, apples, even soft drink or beer! Safe and highly educational. Ages 10+. KJ8937 95 NOW 1995 SAVE $3 4995 $ ANYWHERE TABLE TENNIS • Collapsible net • Spring-clamp net support posts • Includes 2 x paddles & 2 x ball GH1162 WAS $22.95 NOW 95 POTATO CLOCK KIT Interchangeable 4WD tyres for speed and caterpillar tracks for rough terrain. Speeds up to 10km/h. 2.4GHz remote requires 2 x AA batteries (sold separately). Ages 8+. GT4247 2 PK AA Batteries SB2424 $1.95 JUST Simulates the movements of human hand/ fingers, using hydraulic power. It allows every finger joint to adjust at different angles for close-fist/or open-palm precisely. Ages 10+. KR9266 12 $ REMOTE CONTROLLED 2-IN-1 ROCK & DIRT CRAWLER $ HYDRAULIC CYBORG HAND KIT 49 $ JUST $ SPACE RAIL CONSTRUCTION KIT JUST JUST JUST $ Launch this amazing 'obstacle avoidance & self-flying drone and watch it fly, then pull out the gun, take aim - shoot! Hit the drone and it shudders, strike it 3 times and it falls safely to ground. Warning - The drone shoots back. Full colour lighting and multiple sound effects. Add up to 3 drones. Ages 8+. GT4082 See website or in-store for details. Additional Drone to Suit GT4082 GT4084 $24.95 Due early January. ...at home FROM 995 $ KJ89 70 SNAP-ON ELECTRONIC KITS All in bright coloured pieces. Parts simply snap together without any screws or soldering. Ages 6+. KJ8970-KJ8985 Full range available in store or online. 1495 $ SAVE $2 MAKE YOUR OWN: CLOCK KIT Easy to assemble. No batteries required. 31 pieces. Ages 6+. KJ8996 WAS $16.95 80W 240V Soldering Iron TS1485 $24.95 WEARABLE BADGES & ELECTRONIC DICE KITS These kits are a great way for your kids and grand kids to start soldering and pick up some electronics on the way. They will also learn about how various components work including LEDs, transistors, integrated circuits and more. Each kit requires a CR2032 battery (SB2522 $3.25 sold separately). $19.95 EA 6 DIFFERENT KITS AVAILABLE: 1. Skull Badge 2. Owl Badge 3. Rocket Badge 4. Pirate Badge 5. Robot Badge 6. Electronic Dice with Alternating Flashing LEDs with Touch Sensitive LEDs with Flashing LEDs with Flashing LED Eye with Touch Sensitive LEDs & Buzzer with Flashing LEDs 58 5 40 3 $ 6 SAVE $19.85 In the Car RETRO STYLE HANDHELD GAME CONSOLE WITH 256 GAMES Hours of entertainment to keep you and the kids entertained. Features a 2.8" colour screen, built in speaker and a 3.5mm to RCA and USB recharge cable. Available in Black or Red. Ages 15+. GT4280 Due early January. KM1090 KM1092 KM1094 KM1096 KM1098 KM1099 ANY 3 KITS FOR JUST CONNECT IT TO YOUR TV 29 $ click & collect ONLY 95 129 7" TFT LCD WIDESCREEN COLOUR MONITOR WITH IR REMOTE $ Wireless Headphones Suitable for in-car and home entertainment, use it to watch video AA2047 RRP $39.95 from any composite source such as a DVD player or game console. QM3752 Buy online & collect in store JUST 3995 $ bonus free gift WIRELESS INFRARED STEREO HEADPHONES Add these wireless headphones to the monitor on the left and enjoy automotive bliss! Soft cushioned pads. AA2047 ON SALE 27.12.2020 - 23.01.2021 CLEARANCE ORDER ONLINE, COLLECT IN STORE Listed below are a number of discontinued (but still good) items that we can no longer afford to hold stock. Please ring your local store or search our website to check stock. At these prices we won't be able to transfer from store to store. STOCK IS LIMITED. ACT NOW TO AVOID DISAPPOINTMENT. Sorry NO RAINCHECKS. AUDIO & VISUAL SECURITY Cat. No WAS NOW SAVE 150m 1080p HDMI Cat5e/6 Extender with Infrared HOT PRICE AC1746 $219 $169 $50 1080p AHD Dome Camera with IR HOT PRICE AM4201 $69.95 $39.95 $30 1080p Wi-Fi IP Camera with Pan/Tilt 2 Way DisplayPort Splitter AC1755 $49.95 $39.95 $10 12V AC/DC Door Strike release 2 Way DisplayPort Switcher AC1757 $49.95 $39.95 $10 15m CCD Camera Extension Cable 2 x 15 WRMS Portable Stereo Amplifier AA0504 $69.95 $49.95 $20 4 Door RFID Access Controller 2 x HDMI to VGA/Component & Analogue/Digital Audio Converter AC1721 $99 $20 720p AHD Dome Camera with IR 3.5mm Plug to Socket Cable with Microphone and Volume Control - 0.5m WA7120 $14.95 $9.95 $5 720p AHD Wireless Receiver & Camera Kit QC8663 $99 $89 $10 4 Way Digital Audio Switcher AC1723 $39.95 $34.95 $5 720p Outdoor Trail Camera QC8041 $149 $129 $20 6 Way Speaker Selector with Internal Protection AC1683 $129 $99 $30 Ceiling Mount Alarm with Remote Control 6.5" Rechargeable Cube Speaker with Bluetooth® Technology CS2489 $119 $89 $30 Concord 8 Ch. 4K DVR Package - 4x5MP Cameras HOT PRICE QV5100 $299 $249 HOT PRICE QV5602 $1,299 $1,099 2 Channel Mixer with Microphone Preamp $119 Cat. No WAS NOW HOT PRICE QC8687 $129 $89 HOT PRICE SAVE $40 QC3858 $89.95 $69.95 $20 LA5078 $49.95 $29.95 $20 WQ7277 $49.95 $39.95 $10 LA5359 $199 $149 QC8639 $99.95 $69.95 LA5215 $34.95 $24.95 $799 $699 $50 $30 $10 $100 $50 Concord 8 Ch. 4K NVR Package - 6x5MP Cameras Economy UHF/VHF Masthead Amplifier LT3276 $49.95 $34.95 $15 Motion Sensor Camera recorder with 38 IR LEDs QC8027 HDMI 4K Repeater AC1717 $34.95 $24.95 $10 Non-Contact Infrared Door Exit Switch LA5187 $74.95 $49.95 $25 Rechargeable Solar Sensor Light SL3239 $69.95 $54.95 $15 Concord 50m 4K HDMI Fibre Optic Cable Portable 5.8GHz Wireless 1080p HDMI AV Sender HOT PRICE WQ7496 HOT PRICE AR1901 $229 $179 $50 Cat. No WAS NOW SAVE POWER $89 $79 $200 $10 IT & COMMS 125A Dual Battery Isolator (VSR) MB3687 $49.95 $39.95 $10 0.5W 80 Ch UHF Transceivers 12V 8.5A Desktop Power Supply HOT PRICE MP3258 $99.95 $69.95 $30 3W UHF CB Radio Tradies Pack - Pair 5W UHF CB Radio Tradies Pack IP67 $5 Cat. No WAS NOW DC1027 $69 $59 $10 HOT PRICE DC1076 $329 $229 $100 HOT PRICE DC1069 $449 $349 $100 18W USB Type-C Mains Power Adaptor with Power Delivery MP3410 $24.95 $19.95 240VAC Aluminium 48 LED Light Strip with Switch ST3946 $59.95 $49.95 $10 Advanced 2 Watt 80 Channel UHF Transceiver with CTCSS DC1049 $69.95 $59.95 240VAC Aluminium 72 LED Light Strip with Switch ST3948 $69.95 $59.95 $10 Ethernet Over Power N300 Wi-Fi Access Point YN8357 $149 $129 SAVE $10 $20 $99 $30 Ethernet-Over-Power Kit YN8355 $99.95 $89.95 $10 2600mAh Metallic Power Bank Rose Gold MB3794 $14.95 $9.95 $5 VGA To Composite & S-Video Converter XC4907 $49.95 $39.95 $10 2600mAh Metallic Power Bank Silver MB3792 $14.95 $9.95 $5 Waterproof Floating 80 Channel 3W UHF CB Transceiver DC1074 $129 $99 $30 2600mAh Metallic Power Bank Space Grey MB3793 $14.95 $9.95 $5 ST3487 $4.95 2500 Lumen Rechargeable LED Torch 3 x Oslon Osram LED Torch HOT PRICE 1/2 PRICE! ST3499 $129 $9.95 $5 30W 5V 6A Encapsulated Mini Power Supply MP3301 $42.95 $29.95 $13 5VDC 1A USB Mains Adaptor with Micro-B Cable MP3544 $19.95 $14.95 $5 6300 Lumen 6.5 Inch Solid LED Driving Light SL3920 $149 $129 $20 EDUCATIONAL KITS & GADGETS AUTO & OUTDOORS 1080p Wi-Fi Dash Camera with GPS 3G GPS Vehicle Tracker HOT PRICE Cat. No WAS NOW SAVE QV3865 $189 $169 $20 LA9026 $199 $149 $50 Bluetooth® In-Car Earpiece with USB Charger AR3135 $19.95 $14.95 FM Transmitter with USB & SD Playback AR3136 $14.95 $9.95 $5 $5 Cat. No NOW SAVE Cat. No WAS NOW SAVE Circuit Scribe Maker Kit KJ9310 $89 $69 $20 Crookes Radiometer GG2108 $59.95 $39.95 $20 Draw Circuits Circuit Scribe Basic Kit KJ9340 $69.95 $59.95 $10 30 Piece Tool Kit with Case TD2166 $29.95 $19.95 $10 QM1568 $49.95 $39.95 $10 HARDCORE KJ9300 $149 $109 $40 3000A True RMS AC High Current Clamp Meter Makeblock mBot Blue Robot Kit KR9200 $199 $169 $30 300W Hot Air SMD Rework Station MakeBlock Neuron Inventor Kit KJ9190 $99 $79 $20 8 Piece 1000v VDE Set Draw Circuits Circuit Scribe Ultimate Kit HOT PRICE HOT PRICE TS1645 WAS $159 $129 TD2031 $59.95 $39.95 MeetEdison Robot Kit KR9210 $99.95 $79.95 $20 Benchtop 16-Bin Storage Organiser HB6341 $49.95 $34.95 Motion Drone GT4224 $34.95 $24.95 $10 2 Bay USB 3.0 SATA HDD RAID Enclosure XC4688 Portable 14L 12V Cooler / Warmer Puppy Go AI Smart Dog HOT PRICE $89 GH1373 $119 $89 $30 Arduino Compatible 16x16 LED Dot Matrix Module XC4607 $24.95 $19.95 KR9234 $169 $129 $40 Arduino Compatible 3W 200 Lumen LED Module XC4468 $10.95 $49.95 $39.95 Space Rail Construction Kit - Glow in the Dark KJ9001 Squishy Circuits Deluxe Kit KJ9352 Vinyl Record Carry Case GE4101 $39.95 $29.95 More ways to pay: $99 $129 $99 $6.95 $10 Arduino Compatible Ultraviolet Sensor Module XC4518 $29.95 $24.95 $30 Long Range LoRa IP Gateway XC4394 $10 USB Port Voltage Checker Kit KC5522 $33.95 $19.95 $99 $79 $30 $20 $15 $10 $5 $4 $5 $20 $14 59 HOT OFFERS: THREE FILAMENT 3D PRINTER SAVE $200 COLOUR MIXING TECHNOLOGY DESKTOP 3D SCANNER V2 WITH SOFTWARE Watch real life objects become digitized • CAPTURES before your eyes. Scans up to 250 x GEOMETRY IN 180mm. Sleek, foldable design for AS FAST AS workspace storage. Comes packed with 1 MINUTE! MFStudio software with +Quickscan. • SCAN OBJECTS • Scans up to 250(H) x 180(D)mm WITH AN TL4420 WAS $1499 ACCURACY See website for details. WITHIN +/- 0.1MM NOW RESOLUTION. MOOZ-3Z TRIPLE FILAMENT 3D PRINTER • Equipped with a three-color print head for colour mixing • Easy-to-use controller and mobile app • Featured with 3.5" LCD touch pad, Wi-Fi USB connectivity, magnetic heat bed and more • Supplied with a roll each of cyan, magenta and yellow filament to get you started. • Prints up to: 100(H) x 100(Dia.)mm TL4412 WAS $1499 1299 $ SAVE $200 Stream music from your Smartphone or Tablet via Bluetooth® in true stereo, or connect via 3.5mm Aux input. • IPX5 Water resistant • Bluetooth® Wireless Technology • True Wireless Stereo (TWS) • Google Assistant & Siri® Support CS2499 WAS $149 NOW 5 PORT USB CHARGING STATION WITH STORAGE COMPARTMENT • Charge up to 5 USB devices at the same! • Maximum power output of 2.4A per port. • Includes 6 dividers and a 12VDC, 4A power supply. WC7766 WAS $59.95 NOW 119 $ SAVE $30 2 FOR 70 SAVE $49.90 15,000MAH PORTABLE POWER BANK • 4 x LEDs show charge status • Dual USB Type-A ports & 1 x USB Type-C port • Up to 3A total power output MB3806 $59.95 EA. Modern touch sensitive monitor with clear vision to idenitfy visitors. Provides electronic door strike and gate control, as well as full talk-back to the outdoor unit. QC3884 WAS $399 • 2-way audio intercom • Various melodies • IP44 rated 329 $ 95 SAVE $70 SAVE $20 $ 7" LCD WIRELESS 2.4GHZ VIDEO DOORPHONE NOW 39 $ SAVE $200 LOTS OF FILAMENT COLOURS & STYLES AVAILABLE PRICE FROM $19.95 See website for details. PORTABLE BOOM BOX SPEAKER NOW 1299 $ WIRELESS TWS SPORT EARPHONES WITH BLUETOOTH® WI-FI IP CAMERAS WITH INFRARED LEDS R/C MOTORISED ROBOT ARM KIT Suitable for night time use. 720P QC3849 WAS $69.95 NOW $49.95 (Shown) 1080P QC3862 WAS $79.95 NOW $59.95 Ideal for anyone interested in robotic construction. 100g lift capacity. Supplied as a kit of parts with detailed instructions. Requires 4xD batteries (SB2321 $8.95 sold separately). Ages 12+. KJ8995 WAS $139 NOW NOW FROM NOW Fits comfortably and pairs very easily. Up to 3hrs play/talk time. • Bluetooth® 5.0 • True Wireless Stereo (TWS) • Built-in Microphone AA2147 WAS $69.95 5995 $ SAVE $10 4995 $ SAVE $20 99 $ SAVE $40 TERMS AND CONDITIONS: REWARDS / CLUB MEMBERS FREE GIFT, % SAVING DEALS, & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / membership at time of purchase. Refer to website for Rewards / membership T&Cs. IN-STORE ONLY refers to company owned stores and not available to Resellers. Page 1: 10% OFF Flashforge Filament applies to all colours and sizes. FREE GIFT: Buy Dash Cam (QV3849) and get 32GB microSD card (XC4992) FREE. 15% OFF TV Mounting Brackets apply to CW2805, CW2811, CW2819, CW2834, CW2840, CW2851-53-59, CW2864-66-67-68-69, CW2874-75-78, CW2880-82-83. Page 3: Buy 1 x QC3890 + 1 x QC3896 for $249. MULTIBUYS: 2 x MS6106 for $30. 2 x MS6104 for $50. 3 x LA5046 for $99. Page 4: Buy 1 x MP3741 + 1 x MP3746 for $219. Page 6: MULTIBUYS: Buy ANY 3 KITS for $40 applies to KM1090, KM1092, KM1094, KM1096, KM1098, KM1099, KM1097 & XC3758 or any combination. FREE GIFT: Buy In-car Monitor (QM3752) and get Headphones (AA2047) FREE. Page 8: MULTIBUYS: 2 x MB3806 for $70. SUPPLY CHAIN DISRUPTION. We apologise for factors out of control which may result in some items may not being available on the advertised on-sale date of the catalogue. For your nearest store & opening hours: H NY BA AL Y W Maddington Unit 1A/1808 Albany Hwy Kenwick, WA 6107 (08) 9493 4300 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer were confirmed at the time of print but delays sometimes occur. Please ring your local store to check stock details. Occasionally there are discontinued items advertised on a special / lower price in this promotional flyer that has limited to nil stock in certain stores, including Jaycar Authorised Resellers. These stores may not have stock of these items and can not order or transfer stock. Savings off Original RRP. Prices and special offers are valid from catalogue sale 27.12.2020 - 23.01.2021. By John Clarke ELECTRONIC Wind Chimes Aaaah . . . wind chimes! They’re so soothing . . . listening to the random notes as the wind creates its own melodies. But what do you do if there’s no wind? Aim a fan at it? We have a better idea: our Electronic Wind Chimes removes your reliance on the wind, and even gives you the possibility of playing tunes using the wind chime, enriching the experience! T his circuit drives a wind chime it. Read on to understand why this at their tuned frequency when struck. The clapper is moved by a sail, which using solenoids. It does so in a is so. is driven by the wind. Fig.1 shows the way that neither affects the tobasic arrangement. nality of the result, nor prevents the Wind chime basics Wind chimes play a series of notes The notes and sounds are very dechimes from being operated by the wind in the normal way. So you get that are generated by a clapper strik- pendent on chime tube length, thicking the sides of chime tubes. These ness and diameter and the hanging the best of both worlds. More good news is that electroni- tubes hang freely, so they can resonate point. The frequency is cally, it is fairly simhigher with smaller ple and uses readily- Features & Specifications wind chimes – these available parts. So you • Drives wind chimes with up to 12 elements (or multiple smaller chimes) tinkle away with a should not have diffi- • Suits a wide range of sizes from miniature chimes up to large ones light breeze, producculty building it, nor • Individual calibration of solenoid drive control parameters ing high-pitched notes is it likely to break the • Sequence recording and playback at a fast rate. Larger bank. • Sequences with long delays can be recorded in shorter periods wind chimes produce However, you will • Optional randomisation of the time between chime strikes lower-frequency tones need a degree of me- • Adjustable randomisation parameters at a slower rate. chanical skill to make • Optional automatic switch-off in darkness siliconchip.com.au Australia’s electronics magazine February 2021  61 where it produces an entirely different tone to the resonance sound of the chime tube. Often, the clapper is a circular piece of timber with a bevelled edge, so that a small area of its side strikes the tube. Timber clappers are much better than metal types. Once struck by the clapper, a chime tube will move away from its resting position due to kinetic energy transfer. The chime tube will resonate to produce sustained tones that differ from the initial strike sound. If you are after more detail on wind chimes, the science behind them and how to build them, a good site to visit is www.leehite.org/Chimes.htm This includes calculators to design a wind chime to produce the desired notes. Be aware that the notes perceived from a wind chime can be very different from the fundamental resonance of each chime tube. duced in this manner is rather poor. A very simple solenoid-driven wind chime arrangement is shown in Fig.2. The solenoid push ends can be arranged to strike the chimes in a straightline wind chime, which can be made from a disassembled wind chime. While this is easy to build, apart from poor sound, it also has the disadvantage that it can no longer be played by the wind. A more complex solenoid-driven wind chime, which retains the original configuration, is shown in Fig.3. Good sound quality is maintained by using the solenoids to pull the clapper that, in turn, strikes the tubes similarly to when driven by the wind. Additionally, the wind chime is not significantly prevented from its normal operation of playing sounds due to wind. So building this device involves some electronic assembly, mechani- Solenoid drive The biggest challenge in making solenoid-driven wind chime is in maintaining the original sound quality. While a wind chime could be played using solenoids that directly strike the chime tubes, the sound pro- Wind chime sound quality is also dependent upon the clapper. Its mass, density, shape and what it is made from very much determines what sound you get. Tonal differences can be demonstrated by tapping the chime tube with various implements such as a screwdriver blade, screwdriver handle and various pieces of timber. Compare the resulting sounds against the original clapper. When using a good-quality wind chime, the clapper will enhance the sound. A low-quality wind chime will have the sound spoiled by the clapper, 62 Silicon Chip Fig.1: in a standard wind chime, the wind blows the sail which moves the clapper, bringing it into contact with the chime tubes. Each time it strikes a tube, it makes a sound and then bounces off, possibly hitting other tubes. The result is a non-repetitive series of tones, varying with the strength and direction of the wind. Australia’s electronics magazine Fig.2: the easiest way to drive a wind chime with solenoids would be to rearrange the tubes in a row and then place a row of solenoids alongside. This is not a very good approach, though, as the solenoid plungers will make a different sound when striking the tubes compared to the (usually timber) clapper. Also, this modified chime would no longer work the same (or possibly at all) when driven by the wind. siliconchip.com.au cal fabrication and a little bit of woodworking. The electronic side involves the assembly of a circuit board, initial solenoid calibration and other adjustments. On the mechanical side, you need to arrange the solenoids and other bits and pieces to activate the clapper. The woodworking aspect involves making a frame to support these solenoid movements, which are arranged around the outside of the wind chime. Design features Our Electronic Wind Chime circuitry can drive up to 12 solenoids, so it can be used to play up to 12 different chimes. These chimes don’t have to be within the same wind chime. You could use the same circuitry to control two or more wind chimes, so long as there are no more than 12 chimes in total. You can also mix and match solenoids – for example, using smaller solenoids for small chimes and larger solenoids for larger chimes. Each solenoid can be independently set up for how it is driven. There are two adjustments. One controls the voltage applied to each solenoid. This can be varied from the full 12V down to near 0V via pulse width modulation. This feature is used to prevent the solenoid from being too aggressive. A lower voltage will slow down the solenoid action, so that the wind chime is not sent into disarray. The second adjustment is the duration the solenoid is driven. This needs to be sufficient to allow it to produce a strike against the chime and then pull away before the chime tube returns. The electronics includes the option to manually ‘play’ the wind chime by pressing small pushbutton switches. These are useful during calibration, to check whether each chime is being struck correctly. But these switches have another purpose – you can record a sequence by manually playing the solenoids using these buttons, then play it back later, to play a tune (for example). The sequence of solenoids and the period between each activation is recorded. There is also a facility to record long breaks between solenoid strikes without having to wait the full period. This feature increases the period that’s recorded by a factor of 10, so you can record a very long, slow sequence in a reasonable amount of time. During recording, a variety of different sequences can be included. This siliconchip.com.au Fig.3: while more work to achieve, this arrangement is far superior as it allows the chime to be driven by the wind or electronically, depending on the weather and your mood. It also retains the original tone. The solenoids now press on levers that pull the clapper via a string to strike the associated tube. A second set of strings prevents the chimes from swinging back and striking the clapper again, due to inertia, unless the associated solenoid is re-energised. Australia’s electronics magazine February 2021  63 l l Fig.4: the circuit for the Electronic Wind Chime comprises mainly microcontroller IC1 and transistors Q1-Q24, which are used to drive the solenoids. For each pair of transistors (Q1 & Q2, Q3 & Q4 etc), only one is fitted. The BC337s work up to 500mA while the Mosfets can handle up to 3A. The rest of the circuit allows you to set up the unit, record a sequence and optionally, have it switch off at night. l SC Ó ELECTRONIC WINDCHIME will decrease the perceived repetition as the played back sequence repeats in a loop. The recording time available is well over what you might require. This means that you are free to record without concern of running out of memory. The recording is permanently stored, unless overwritten with a new recording. There is also an option to randomise the pauses between solenoid strikes 64 Silicon Chip during playback. At the maximum randomness setting, the delays vary between one and five times longer than those recorded. The randomness changes to a new value at intervals of between 10 seconds and 21.25 minutes; this, in itself, varies randomly. This is all designed to remove any hint of a machine-driven wind chime, making it sound more natural. The maximum randomness values Australia’s electronics magazine can be changed to smaller values if desired. Optionally, the Electronic Wind Chime can be set to switch off during darkness. This is useful if you (or your neighbors!) prefer peaceful serenity at night. Circuit details The circuitry, shown in Fig.4, is based around microcontroller IC1. It stores the recorded sequences in its siliconchip.com.au Scope1: the 500Hz, 5V PWM drive to the base/gate of the output transistor is shown in the top trace (yellow) with a 50% duty cycle, and the resulting (inverted) 12V drive voltage to the solenoid is shown below in cyan. The duty cycle (ie, percentage of time that the solenoid receives current) is adjustable for each solenoid, to control how hard it is driven. flash memory, then plays them back by using its digital outputs to drive transistors or Mosfets that, in turn, drive the solenoids. The microcontroller also monitors a light-dependent resistor (LDR1), a control switch, jumper link and a trimpot and drives a status LED (LED1). Twelve of IC1’s twenty pins are used as digital outputs for driving the solenoids. There are two types of solenoid drivers you can use. One option is NPN transistors for driving low-current solenoids. This is a considerable cost saving compared to N-channel Mosfets, but Mosfet drivers must be used for solenoids that draw over 500mA. There is a small circuit change when using a transistor rather than a Mosfet: the resistor value (R1-R12). When a transistor is used, the resistor value is 2.2kΩ, which sets the transistor base current. For a Mosfet, the resistor value is 100Ω instead, and this drives the Mosfet gate. Diodes D1-D12 at the transistor collector or Mosfet drain are there to conduct the reverse voltage (backEMF) from the solenoid coil when it is switched off. This protects the bipolar transistor or Mosfet from damage. PWM drive The solenoids can be driven with a PWM signal. This is where the Mosfet or transistor is switched on and off at 500Hz with a particular duty cycle. The average voltage produced is the duty cycle multiplied by the supply voltage. So for a 12V supply and a 50% duty cycle, the average voltage applied to the solenoid is 6V. The frequency needs to be high siliconchip.com.au causes the associated solenoid to be driven with the full 12V for the duration that the switch is pressed. But when the solenoid is driven via the microcontroller, the drive is a PWM waveform with a preset on-period and duty cycle. More circuit details enough to prevent the solenoid from driving the plunger in and out at the PWM rate. But too high a frequency can also cause problems such as increased dissipation in the transistor/Mosfet or reduced response from the magnetic properties of the steel core. Our choice of 500Hz was suitable for a wide variety of solenoids that we tested. Oscilloscope waveform Scope1 shows the gate drive to the Mosfet at the top (yellow) with a 5V drive voltage. The drain voltage waveform (blue) is the lower trace with a 12V supply voltage. The solenoid has 12V across it when the drain voltage is 0V, and 0V across it when the drain is at 12V (the negative end of the solenoid connects to the drain). The duty cycle is around 50% at almost 500Hz. The solenoid driver pins on IC1 usually are set as inputs. The Mosfet or transistor is held off via the associated 10kΩ pull-down resistor. Having the pins as inputs allows switches S1-S12 to pull the input high when pressed. If the pin were set as a low output instead, the pull-up switch would ‘fight’ the microcontroller output, causing a high current through the output pin. The pin is changed to a high-level output when required to switch on the Mosfet or bipolar transistor. In this case, pressing the associated switch will not cause problems since the output is already high. For a low level, the pin is made an input again, so the Mosfet or bipolar transistor switches off (unless the associated switch is currently being pressed). Note that pressing switches S1-S12 Australia’s electronics magazine IC1’s pin 18 (digital input RA1) monitors the LDR so that the circuit can optionally switch off at night. During the daytime, the LDR resistance is low, so pin 18’s voltage is below the low threshold of the RA1 input. A 100kΩ resistor and trimpot VR2 form a voltage divider with the LDR across the 5V supply. This trimpot allows the detected light threshold to be varied. When the LDR is in darkness, the LDR resistance is high, and this pull-up resistance causes the RA1 voltage to be above its high threshold. IC1 detects this, and the software stops running. The RA3 digital input monitors control switch S13. This pin can be used as an external master clear signal (MCLR) or a general-purpose input. We are using it as an input, and it is usually pulled high, to 5V, by the 10kΩ resistor. This input goes low when the switch is pressed; it serves many functions, as described later. The status LED (LED1) is driven via the RC1 output via a 1kΩ resistor. It is used to indicate various modes when recording a sequence and calibrating the solenoid settings. Trimpot VR1 is connected across the 5V supply, and its 0-5V wiper voltage is monitored at IC1’s analog input AN4 (pin 16). VR1 sets the solenoid pulse width/duty cycle and drive duration in conjunction with jumper JP1. JP1 is monitored by IC1’s RA0 digital input (pin 19). This input is held high by the 10kΩ pull-up resistor unless there is a shorting link across JP1, which would pull it low. Power supply 12V power for the circuit is applied at CON7. This flows to the solenoids is via fuse F1. This supply is bypassed with two in parallel 1000µF low-ESR capacitors, which help to supply the peak solenoid current. Reverse polarity protection uses 3A diode D14. If the supply is connected backwards, this conducts to blow the fuse. February 2021  65 Fig.5: circuit board assembly is straightforward; simply install the components as shown here. Small rectangles are provided above the manual control switches so you can write the musical note produced by that switch, or a solenoid number. During construction, take care with the orientations of the diodes, ICs, transistors, terminal blocks and electrolytic capacitors. SILICON CHIP The voltage to the remainder of the circuit is applied via reverse polarity protection diode D13, and is switched by S14 before being applied to the input of the 5V regulator, REG1. Two 100µF capacitors, one at the regulator input and the other at the output improve the regulator’s stability and transient response. Microcontroller IC1 also has two 100nF supply bypass capacitors pins at pins 1 and 20. LED2 lights up when power is applied, with its current limited to around 2-3mA by its 1kΩ series resistor. Memory storage Twelve bytes of the flash memory are dedicated to storing the PWM duty cycle and on-period parameters for each solenoid (ie, one byte per solenoid). 1182 bytes of flash memory are used for storing the playback sequence. Two bytes of memory are used to record which solenoid(s) to activate, followed by a two-byte delay period. Each delay period can be up to 10.9 minutes in 10ms steps. If the delay period is over 10.9 minutes, then the next two bytes continue that delay. 66 Silicon Chip This means that the maximum sequence can be up to 107 hours (1182 ÷ 2 x 10.9 minutes). However, as extra bytes are consumed for each solenoid strike, the practical maximum is somewhat less than that. For a more realistic calculation, say that a recording consists of a series of eight strikes, spaced two seconds apart, with a 10-second delay before the next little tune. That consumes 32 bytes (8 x 4 bytes) for every 24 seconds of recording (7 x 2 seconds + 10 seconds). The 1182 byte memory can record up to 37 such sequences, for a total recording or playAustralia’s electronics magazine back time of 888 seconds or 14.8 minutes. Typically, you would leave a longer period between solenoid drive sequences, so the maximum recording (and hence playback) time will be longer. There is no need to completely fill the memory, as during playback, it only cycles through the number of bytes that were recorded in memory PCB assembly The Electronic Wind Chime circuit is built on a PCB coded 23011201 which measures 147 x 87.5mm – see Fig.5. This fits into a UB1 Jiffy box. Which siliconchip.com.au parts you install depends to some extent on the number of solenoids you will use and the solenoid sizes. See the accompanying panel on this topic. The parts list specifies the parts required to drive the maximum 12 solenoids. Asterisks indicate which parts you can buy fewer of if you plan to drive a smaller number of solenoids. This includes S1-S12, R1-R12, the 10kΩ pulldown resistors, Q1-Q24, D1-D12 and CON1-CON6. CON1 and CON6 are three-way terminal blocks, with two terminals for a pair of solenoids plus a common positive connection for each set of six. CON2-CON5 are two-way terminal blocks which do not have the common positive connection, only the negative connections for two solenoids. So if you have an odd number of solenoids, you will end up with an unused terminal in one of the connectors. You can have a mix of low- and highcurrent solenoid drivers. Say you might wish to control two wind chimes, with each having three large chimes and three smaller ones. You could fit Mosfets at the evennumbered positions (Q4, Q8, Q12 etc) and corresponding 100Ω gate resistors. You would then fit transistors at the odd-numbered Q position (Q1, Q5, Q9 etc) with 2.2kΩ base resistors, for the smaller chimes. Do not install both a Mosfet and bipolar transistor in the same position. This complicates construction a little, but you can save quite a bit of money as the bipolar transistors cost far less than the Mosfets. Start by fitting the resistors on the PCB where shown (remember to vary the R1-R12 as described above). The resistor colour codes are shown in the parts list, but it’s always best to check the values with a digital multimeter (DMM) set to measure resistance. Continuing on, install diodes D1 to D12 (or as many as required) and D13. Make sure that the cathode stripes face toward the top of the PCB as shown. Also fit D14 now, which faces the opposite direction compared to the others, and is the largest diode. Then mount switches S1-S12 (where used) and S13. These will only fit onto the PCB the right way, so if the switch does not seem to fit, try rotating it by 90°. We recommend that IC1 is installed using a socket. Make sure the end notch faces toward the left edge of the PCB. siliconchip.com.au Parts List – Electronic Wind Chimes 1 double-sided plated-through PCB coded 23011201, 147 x 87.5mm 1 UB1 Jiffy box, 158 x 95 x 53mm [Jaycar HB6011 (black), Altronics H0201 (black) or H0151 (grey)] 1 12V DC plugpack or similar supply, ideally with 2.5mm ID barrel plug (current rating dependent on solenoids used, up to 3A maximum) 12* 12V DC spring-return pull solenoids with lever slot [see text] 2* 3-way screw terminals with 5.08mm spacing (CON1,CON6) 4* 2-way screw terminals with 5.08mm spacing (CON2-CON5) 12* SPST momentary switches (S1-S12) [Altronics S1120, Jaycar SP0600] 1 SPST momentary switch (S13) [Altronics S1120, Jaycar SP0600] 1 SPDT toggle switch (S14) [Jaycar ST0335, Altronics S1310] 2 M205 PCB-mount fuse clips (F1) 1 3A M205 fast blow fuse (F1) 1 5A DC PCB-mount 2.5mm ID barrel socket (CON7)   [Jaycar PS0520, Altronics P0621A] 1 20-pin DIL IC socket (for IC1) 1 48kW to 140kW light-dependent resistor (LDR1)   [Jaycar RD3480, Altronics Z1619] 2 2-way pin headers with jumper shunts (JP1,JP2) 2 PC stakes (optional; GND & TP1) 2 or more cable glands for 3-6.5mm cable entry Semiconductors 1 PIC16F1459-I/P 8-bit microcontroller programmed with 2301120A.hex (IC1) 1 7805 1A 5V regulator (REG1) 1 3mm red LED (LED1) 1 3mm green LED (LED2) 12* 1N4004 1A diodes (D1-D12) 1 1N4004 1A diode (D13) 1 1N5404 3A diode (D14) Capacitors 2 1000µF 16V PC low-ESR electrolytic 2 100µF 16V electrolytic 4 100nF MKT polyester Resistors (all 1/4W 1% metal film 1 100kW (Code brown black black orange brown) 12* 10kW (S1-S12 pull-down resistors) (Code brown black black red brown) 2 10kW (Code brown black black red brown) 2 1kW (Code brown black black brown brown) 1 500kW miniature horizontal trim pot, Bourns 3386P style (VR2) (Code 504) 1 10kW miniature horizontal trim pot, Bourns 3386P style (VR1) (Code 103) Parts for high-current solenoid drivers (>500mA) 12* STP16NF06L, STP60NF06L or CSD18534KCS 60V, 16/60/73A logic-level N-channel Mosfets (Q2,Q4,Q6...Q24) [Jaycar ZT2277 or SILICON CHIP ONLINE SHOP Cat SC4177] 12* 100W 1/4W 1% metal film resistors (R1-R12) (Code brown black black black brown) Parts for low-current solenoid drivers (<500mA) 12* BC337 NPN 500mA transistors (Q1,Q3,Q5...Q23) 12* 2.2kW 1/4W 1% metal film resistors (R1-R12) (Code red red black brown brown) Miscellaneous Suitable exterior board or timber, aluminium sheet, wire loom, cable ties, wire, screws, paint, string etc * reduce these quantities for driving fewer than 12 solenoids and note that low- and high-current solenoid drivers can be mixed and matched (up to a total of 12) Australia’s electronics magazine February 2021  67 The trimpots can be installed next. VR1 is the 10kΩ trimpot that may be marked as 103 rather than 10k. VR2 is 500kΩ and may be marked as 504 rather than 500k. Now mount the fuse clips, making make sure these are installed with the correct orientation, ie, with the end stops toward the outside of the fuse. It is a good idea to insert the fuse before soldering the clips to ensure the fuse is aligned within the clips, and that the clips are orientated correctly. PC stakes can also be installed at GND and TP1. However, these can be left out, and multimeter probes pressed directly onto the pads for voltage measurements. Fit the two-way headers for JP1 and JP2 next, then the DC socket (CON7). Follow with the 3-way and 2-way screw terminals (as many as needed), with the wire entry holes towards the lower edge of the PCB. Now mount the capacitors, noting that the electrolytic capacitors must be orientated correctly, with the longer positive leads through the holes marked “+”. Transistors It is time to fit the transistors and/or Mosfets (along with regulator REG1), noting again that which ones and how many you install depends on what solenoids you are using, and how many. The power switch (S14) and the two LEDs can be mounted in one of two ways: either directly on the PCB or onto the lid of the box, with wires making the connections between the component and PCB. We opted to mount the switch and LEDs on the PCB – this way, they will not be seen or accessible once the lid of the box is in place, but that’s OK as they are mainly used during setup and recording. Without the power switch being accessible, the unit can still be switched on and off via the 12V plugpack. If you intend to use the LDR to switch the unit off at night, solder this in place now. It can be mounted so that the face of the LDR is toward the back edge of the PCB (by bending the leads), so it is exposed to the outside light via a hole in the side of the enclosure. If you don’t need the LDR feature, link it out or place a shorting block over jumper JP2. Housing The PCB is held in the plastic case by the integral clips holding the sides of the PCB. You will need to drill holes in the box for the DC socket and the solenoid wiring. We recommend that this wiring passes through several cable glands before being connected to CON1-CON6. The 9mm hole for the DC socket is 21mm above the outside base of the case and 26mm in from the outer edge. Cable glands can be placed 15mm down from the top edge of the enclosure, adjacent to the screw connectors CON1-CON6. Next month The electronics section is now virtually complete, but we still need to describe how to modify your wind chime to add the solenoids, plus the testing, setup and sequences recording procedures. All that will all be covered in a second article next month. This PCB has five high power Mosfets in positions Q2-Q10 with seven lowerpower transistors in Q11-Q23. The reason (and difference) is explained in the text. The PCB mounts in the case without screws – it simply clips into the slots on the side guides. As yet, the holes are not drilled into the lid for the on/off switch nor LED – these can be done using the front panel artwork as a template. We’ll look at this in more detail next month. 68 Silicon Chip Australia’s electronics magazine Choosing your solenoids The circuit has been designed to cater for many types of solenoids. We used D-frame spring-return pull types, although push-pull types can also be used. The sizes available range from miniature through to heavy-duty types that can draw up to 3A. What you need depends on the size of the wind chime you are using. There are several specifications you need to look for; for example, the circuit requires 12V solenoids. Another important specification is the movement length, or stroke. Other useful features are a means to attach to the solenoid plunger. Some will have holes in the plunger, but others will not have any means to attach anything to the solenoid plunger. For small wind chimes, a solenoid stroke of 4mm might be sufficient, but for larger chimes, something like 12mm is required. For use with mini wind chimes (tubes around 6.35mm in diameter) and using a direct solenoid plunger hit to an inline set of chimes as shown in Fig.2, a push-pull solenoid with a frame section that measures 21 x 11 x 10mm having a 4mm stroke would be suitable. Their overall length is 30mm, and they draw 120mA at 12V DC. The solenoids for the wind chime we used have a 30 x 16 x 14mm frame section and 10mm stroke. Their overall length is 55mm. The plunger includes a mounting slot and securing hole suitable for a lever attachment. At 12V DC, they draw 2A. The initial pull is 300g with an ultimate retention force of 3kg when fully closed. Both Jaycar and Altronics sell suitable solenoids, and many others are available via on-line marketplaces such as eBay. SC siliconchip.com.au CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions will be paid for at standard rates. All submissions should include full name, address & phone number. LCD clock and thermometer This circuit demonstrates my userfriendly alphanumeric LCD library (lcd.c) that can be employed for interfacing an ATmega micro to an LCD in 4-bit mode using just six pins. All the interface functions of the LCD library are used in this sample program, which includes a digital clock and a thermometer that can show degrees Celsius or Fahrenheit. The LCD interface functions include character printing, user-defined custom characters, writing text, showing integer numbers, floating-point numbers, scrolling text to the left or right and clearing the LCD. The user just needs to select the data direction register (DDRX) and therefore the I/O port used to communicate with the LCD. By default, it is defined as “DDRD” in the “lcd.h” file with pins PD0-3 mapping to pins D4-7 on the LCD, and pins PD4 & 5 on siliconchip.com.au that port going to the RS and EN lines of the LCD. The port used can be changed to DDRA, DDRB or DDRC. In fact, you can change which port and pin are used for each LCD function if necessary. The type of LCD you are using (16x1, 16x2, 16x4 or 20x4) is also defined in the “lcd.h file”. You can change the lines which read “#define lcd_lines 2” and “#define lcd_characters 16” to different values to suit 1-line, 4-line or 20-column displays. The cursor style can also be controlled by changing the number on the “#define LCD_cursor 0” line to 1 or 2 to show a solid cursor (1) or have it blink (2). The default value of zero means that no cursor is visible. The circuit is designed around an ATmega328P, a 16x2 alphanumeric liquid crystal display and an LM35 temperature sensor. When the cir- Australia’s electronics magazine cuit is powered up, the clock starts at midnight. There are two pushbutton switches used to set the time; S2 changes the hours and S3 increments the minutes value. Internal pull-up currents allow the micro to sense when these buttons are pressed, pulling the pins low. The LM35 temperature sensor is used for the thermometer function. It produces an output of 10mV/°C. In this circuit, the temperature range is 0-100°C, so the 0-1V output of IC2 is fed to analog input ADC0 of microcontroller IC1 (pin 23). It converts this voltage to a digital value and then scales it for display on the second line of the LCD. The units used are defined in the software file which can be downloaded from siliconchip.com.au/Shop/6/5754 Mahmood Alimohammadi, Tehran, Iran. ($75) February 2021  69 DIY laser rangefinder I bought a TFMini lidar module intending to build a radar-like device, but then I realised that at work we spend a lot of time measuring the length of ERW pipes with measuring tapes. ERW (electrically resistant weld) pipes are 300mm plus in diameter and up to 12m long. They are used in our power plant for ash slurry transportation. It’s difficult to measure ERW pipes accurately. So I decided to create a device to accurately measure the length of pipe sections (to within 1cm) using the TFMini TOF (time-of-flight) laser module. Two varieties are available: the TFMini-S (US$35) and TFMini Plus (US$45); both have a serial interface. But the TFMini Plus has a wider measurement range (10-1200cm compared to 30-1200cm), can take 1000 measurements per second instead of 100 and is rated to operate from -20°C to +60°C rather than 0-60°C. Just placing the TFMini at one end of the pipe and directing it towards the edge plate will give accurate length reading. To increase the precision, I average a few readings. 70 Silicon Chip Both the TFMini-S and TFMini Plus have a viewing angle of 3.4°. Therefore, for long pipes, the aim is crucial to get a correct reading. To aid in this, I have incorporated a visible laser pointer with a push-on button (S2). It’s lined up with the TFMini module so you can see to where it measures. The TFMini works on reflection of invisible laser light from the surface of the object. In case the object does not reflect back or completely absorb or diffuse the incoming laser light, the reading will be erroneous. Such surfaces include water or slanted and highly reflective glass windows. For all other kinds of objects, the light gets reflected, and the measurement is correct. It’s accurate even with moving objects. Besides the TFMini module and laser pointer, my circuit uses an ESP32 microcontroller module, a 128x64 pixel OLED screen, two regulators, two capacitors and a battery. The OLED screen is an I2C device so it’s wired to the ESP32’s D21 and D22 I/O pins (just about any pins on the ESP32 can be used for I2C). As mentioned earlier, the TFMini uses serial, so it’s wired to the second UART on the ESP32. Australia’s electronics magazine A 3.3V low-dropout linear regulator (REG1) provides 3.3V to run the ESP32 and OLED display. The TFMini and the laser diode are supplied with 5V generated from a small boost module that runs off a single Li-ion or LiPo cell, with S1 provided for power switching. For use at my workplace, the device has to be portable so that my team can use it out in the field. That is why I ended up using a single LiPo cell and a boost module. It can also run from two 1.5V cells in series. The only real trick to assembling the unit is making sure that the TFMini and laser pointer are aimed at the same spot. To do this, set up a small object just under 12m away from your testing location, aim the TFMini at it until you get a sensible reading, adjust the laser pointer so that the dot is centred on that object and then fix the laser pointer in place. The ESP32 is programmed using the Arduino IDE. You can download the sketch and all the required libraries from siliconchip.com.au/Shop/6/5753 The libraries used are tfmini.h, Adafruit_GFX.h and Adafruit_SSD1306.h. Bera Somnath, Vindhyanagar, India. ($80) siliconchip.com.au Animal and pest repeller A family cat always clawing my prized speaker, a dog constantly marking an area and a possum chewing off my seedlings were problems that I needed to solve. I designed this circuit to deter their actions. A common fear for the animals is the sound of a spray can, so I designed this circuit to simulate the repetitive quick squirt of a can along with flashing red LED ‘eyes’. The PIR sensor module, PIR1 (Jaycar Cat XC4444) detects movement and sends out a high pulse with a duration based on the delay setting of the PIR detector. When this pulse is received, it switches on power to the rest of the circuit as it forward-biases the baseemitter junction of NPN transistor Q1. This, in turn, pulls current from the base of PNP transistor Q2, supplying 9V via its collector. If night-time only use is required, an LDR such as Jaycar Cat RD3485 or Altronics Cat Z1621 can be wired across the 1MW base-emitter resistor of Q1, as shown. This will prevent triggering during daytime by shunting Q1’s base drive current due to siliconchip.com.au its lower resistance when exposed to light. When the PIR is triggered, power is supplied to a multivibrator based around PNP transistors Q3 & Q6 and NPN transistors Q4 & Q5. This alternatively drives the LEDs via Q6’s collector, and the white noise circuitry via Q3’s collector. When current flows from Q3’s collector, white noise is generated by a reverse-biased small signal silicon transistor junction (Q7). This is then amplified by NPN transistor Q8, operating as a common-emitter amplifier, followed by audio amplifier IC1, which drives a miniature 8W speaker. I built the circuit into UB3 jiffy box with LEDs as the ‘eyes’, the PIR as the ‘nose’ and the speaker as the ‘mouth’. For best results, set the PIR sensor to single trigger mode and adjust its trimpots to almost minimum sensitivity and delay. A piezo speaker can be used instead of a standard speaker, but it will produce less volume. It will also reduce the overall current drawn from the 9V battery. Australia’s electronics magazine The majority of small-signal transistors will stop breaking down to produce white noise at 7.7V. Highfrequency types like the BF494 will operate down to 6.8V, so if the battery voltage drops below 8V, white noise won’t be generated. One solution is to place a 3V lithium cell in series with the 100kW resistor to Q7’s emitter, boosting the voltage. There is negligible current drawn from this cell. However, I found this wasn’t required with a good 9V battery. Overall battery drain is less than 100µA at idle, then up to 50mA when triggered if the amplifier is set to maximum volume via potentiometer VR1. The power switch is an SPDT centre-off type. The lower on position powers the PIR module only, to enable stabilisation which can take a minute. Then the switch is thrown over to the upper on position, which fully powers the circuit. As the PIR module has a wide view angle, it may be necessary to mask some areas off to achieve the required viewing angle. Warwick Talbot, Toowoomba, Qld. ($90) February 2021  71 Stable multi-frequency sinewave generator Although modern DDS signal generators can produce signals with a stable frequency and amplitude, they can usually only generate 1-2 waveforms at a time. This simple circuit generates four sinewaves at different frequencies but with fixed phase relationships and six square waves at lower frequencies, also phase-locked. The outputs are stable due to the use of a crystal oscillator circuit as the timebase. It’s based on a 74HC4060 14-stage asynchronous binary counter IC and two dual rail-to-rail input/output (RRIO) op amps, all running from a 5V DC power supply. The 74HC4060 72 Silicon Chip (IC1) also has an internal oscillator, so it only needs one crystal, two load capacitors and a couple of resistors to form an all-in-one oscillator/divider, producing ten square waves with related frequencies. One of the crystal’s load capacitors is a trimmer capacitor (VC1) so that you can set the oscillator frequency to exactly 32,768Hz, provided that you have an accurate frequency counter to measure the frequency of one of the outputs while adjusting it. Otherwise, you can replace VC1 with a 22pF fixed capacitor; the result should still be pretty close (less than 0.01% error). Australia’s electronics magazine While IC1 is a 14-stage binary counter, only 10 stages have their outputs fed to IC pins. Output Q3 has a division ratio of 16 times (23+1), so has a frequency of 2048Hz (32,768Hz ÷ 16) or just over 2kHz. Output Q4 is at half that frequency, ie, 1024Hz or just over 1kHz. And so on, until output Q13 which has a division ratio of 16,384 times (213+1), so has a frequency of 2Hz (32,768Hz ÷ 16,384). These output signals are all square waves, so they have a large number of odd harmonics. To get a sinewave, we need to filter out these harmonics. The 256Hz, 512Hz, 1024Hz and 2048Hz outputs are filtered identically. In each case, a 1kW potentiometer allows the output level to be adjusted. Then the siliconchip.com.au signal from the wiper goes through a multi-stage RC low-pass filter. The setting of the potentiometer will vary the source impedance seen by the filter and thus slightly alter the corner frequency. Still, since the square wave harmonics start at three times the fundamental frequency, this won’t materially affect its ability to filter them out. The fourth-order filters roll off at 24dB per decade, so the third harmonic will be attenuated by well over 30dB. The filters each have four passive stages, each with the same corner frequency but ten times the impedance of the last, so as to not overly load the previous stage. The output of each set of filters is AC-coupled to an op amp two-times gain stage, DC biased to the 2.5V half-supply rail generated using a pair of 10kW resistors and filtered by 100µF and 100nF capacitors. These stages not only apply gain to make up for signal lost in the filters, but also convert the high-impedance output of the filters into a low imped- WiFi Snooping with a Raspberry Pi Smartphones send out WiFi “probe requests” to see what access points are close by. These requests contain the MAC address of the WiFi module in the smartphone, which is a unique identifier for that phone. The first three bytes of the MAC address contain the OUI (Organisational Unique Identifier), sometimes called the Vendor ID. The IEEE assigns OUIs to vendors. The last three bytes are the unique device serial number assigned by the vendor. A monitoring device can silently capture probe requests, collecting information such as the date and time, MAC address and the signal strength, which indicates how close the phone is. Several devices can be strategically placed to triangulate the signal levels and pinpoint the location of the phone. Shopping centres, train stations, airports etc are already using systems like this. You can use a Raspberry Pi as a silent monitoring device by running a Python program called “probemon”. Probemon captures all the data mentioned above. Also, the probe request sometimes contains the Access Point details that the phone was last connected to. When that happens, it is also captured by probemon. To use this software, you will need a USB WiFi adaptor that supports “monitor” mode (the internal WiFi on the Pi does not). I bought a RaLink RT5370 via eBay for less than $10. First, install Raspbian Buster on the Pi. Then plug in the USB WiFi adaptor and check it with the following command: lsusb Note the WLAN number of the USB WiFi (probably wlan1). Unplug and replug the USB adaptor, and check again siliconchip.com.au to be sure. Then install aircrack-ng: sudo apt-get install aircrack-ng Run airmon-ng (a part of aircrackng) to kill processes that will conflict with Monitor Mode: sudo airmon-ng check kill Put the WiFi adaptor into monitoring mode: sudo airmon-ng start wlan1 Check that you now have a virtual adaptor (wlan1mon): ifconfig Install netaddr, scapy and probemon: mkdir python cd python git clone https://github.com/ drkjam/netaddr cd netaddr sudo python setup.py install cd ~/python git clone https://github.com/ secdev/scapy.git cd scapy sudo python setup.py install cd ~/python git clone https://github.com/ nikharris0/probemon.git cd probemon Now test probemon: sudo python probemon.py –i wlan1mon –f –s –r –l It will take a few minutes before you see any results. You will likely get some errors that need fixing by editing the file “/home/pi/python/probemon/ probemon.py”. If you encounter the error type object ‘datetime.datetime’ has no attribute ‘datetime’, change line 36 of that file from: Australia’s electronics magazine ance signal, suitable for driving other equipment. These signals are again AC-coupled to remove the 2.5V DC bias and then fed to the output terminal pairs via 10W isolating resistors. The remaining six square wave signals are simply fed to a separate set of outputs via 47W isolating resistors. The whole thing is powered from a 5V USB supply, with LED1 lighting to indicate the presence of power. Petre Petrov, Sofia, Bulgaria. ($80) log_time = datetime.datetime. now().isoformat() to: log_time = datetime.now(). isoformat() The RSSI value doesn’t work, so change line 56 from: rssi_val = -(256-ord( packet.notdecoded[-4:-3])) to: rssi_val = packet.dBm_AntSignal Now the list of approved MAC Address Vendors has to be updated: curl http://standards-oui.ieee. org/oui.txt --output /home/ pi/python/netaddr/netaddr/ eui/oui.txt cd ~/python/netaddr/netaddr/eui python ieee.py cd /home/pi/python/netaddr sudo python setup.py install Rerun the capture program, and it should be fully working: cd ~/python/probemon $ sudo python probemon.py –i wlan1mon –f –s –r –l Captured data is stored in probemon.log. iPhones use MAC address randomisation, so the only time the correct MAC address is sent in a packet is when it is connected to a WiFi Access Point. Other times, it is recorded in the log file as “UNKNOWN”. When previously connected SSIDs are captured, you can search www. wigle.net which has a vast number of Access Points in its worldwide database. You can also enter your home address into www.wigle.net and see what Access Points are near you. Sid Lonsdale Cairns, Qld. ($80) February 2021  73 Making Android Apps with App Inventor The Android logo is Copyright Google Inc. App Inventor is a free, cloud-based tool that lets you make your own Android apps. It’s maintained by MIT and is run through most standard web browsers. Roderick Wall shows you how it can be used to make a simple TDR (time domain reflectometry) calculator for your phone, which can help with testing electrical cables for faults. By Roderick Wall T he Massachusetts Institute of Technology (MIT) in the USA has released a free “App Inventor”. This allows you to use blocks to design applications that run on Android phones and tablets. I used it to create a TDR (time domain reflectometry) calculator, which calculates the distance to a fault in a transmission line, as in the TDR Dongle project from December 2014 (siliconchip.com.au/Article/8121). You can download my Silicon Chip TDR Android calculator app from siliconchip.com.au/Shop/6/5733 – see the end of this article for hints on how to install it on a phone or tablet. Building an App I used the following steps to design and create the TDR application. You can use a similar procedure to make your own custom Android application. App Inventor is a cloud-based tool, which means you can build applications right in your web browser. The website offers all the support you need to learn and how to develop basic applications. Start by opening the following link in your browser: https://appinventor.mit.edu/explore/ get-started MIT also has an App Inventor Community forum where you can ask ques- tions about your project. See https:// appinventor.mit.edu/explore/library While designing your project, if you run into a problem, try doing a Google search like “App Inventor How to X” (where X is replaced with your query) for quick answers to your questions. There is lots of information on how to use App Inventor on the internet. Fig.1 shows the first window of the MIT App Inventor. To start a new project, click “My Projects” and select “Start new project”. Note that you can download a source code file for the project (with a .aia file extension) that can be shared with your friends. It is a good idea to use this method to View your projects Start new project Provides a .aia file of your current project which can be shared Fig.1: starting a new project in App Inventor is quite simple and the interface isn’t as complex as most programming IDEs. 74 Silicon Chip Australia’s electronics magazine siliconchip.com.au Adds another screen Change screens in the Designer window Components Select the device the application will run on Generate Blocks code Design and move components onto the phone screen Fig.2: the App Inventor main window is where most of the work happens. It is important to familiarise yourself with the Palette panel at the far left. save your project often, in case something goes wrong. Be careful with the delete button. If you delete a control in the Designer window, it will also delete the code blocks that were attached to it in the Blocks window. There is no way to undo or redo in App Inventor. After you provide details of the device your application is optimised for, look at the two buttons at the top right of the window (see Fig.2). The “Designer” button goes to the screen where you can move and drag components onto the phone screen. The “Blocks” button goes to a screen where you can generate the code blocks for the project. Fig.3 shows the components that are used to design the TDR Calculator application. This was done by dragging components from the left side of the Designer window onto the phone screen. You can add a component later by dragging it into a space between two components which are already on the screen. There is a list of the components and their properties on the right side of the Designer window. You can edit the properties of each component as required for your project, including customising their names. As I have selected Screen1 here, the properties for components on Screen1 are displayed. For the TextBox components for RefTime, VelocityFactor, Result1 and Result2, I have set the “NumbersOnly” property so that only numbers can be entered in those fields. Tips and tricks: • Enter the screen title into the Screen Property Title box, not in the About Screen box. Button Label Invisible labels that are used in the Blocks code Set Set Notifier Set Invisible spacer TextBox App icon Load files from PC Fig.3: in the Designer window, elements are dragged & dropped from the User Interface (UI) box at left onto the screen/ viewer. Placed objects are then listed under the Components/Media panel at right. siliconchip.com.au Australia’s electronics magazine February 2021  75 Select Media Drag onto screen Sound1 is selected Fig.4: selecting the Media sub-panel at left lets you add your own sound/video files etc to your application. • The two non-visible Notifier components are used to notify that the entered Reflection time and/or Velocity Factor data was not valid. • Three invisible labels (Result1, Result2 and LabelFLAG_T_F) are used by the Blocks code to store calculation results and status. Do not select the property “Visible” setting for these three components. However, they can be made visible while troubleshooting your code to see what the results are. Sounds After selecting “Media” components (see Fig.4), drag the two non-visible sound components onto the screen. Select the Sound1 component, and in the property window, select the BlopMark.mp3 sound file after uploading it from your computer. Do the same for the Sound2 component, but this time select SoundStart.mp3. Making the block code Fig.5 shows some of the code blocks used to build the app, not yet put together. You drag the generic blocks on the lefthand side of the window into the main part of the window to add them. Fig.6 shows the blocks once they have been put together to form the code needed to drive Screen1 in the TDR App. When the Calculate button is pressed, first the LabelFLAG_T_F status flag is set to “F” (false). Both the Reflection Time and Velocity Factor inputs are checked to ensure that they have been entered and are within the valid ranges. If there is an error, the “LabelFLAG_T_F” is set to “T” (true) and a notification is sent to the user. It then checks to see if LabelFLAG_T_F is “F”, indicating that there was no error. It then divides Reflection Time (RefTime) by 1,000,000,000 (one billion) to convert nanoseconds 2 Control Empty space 3 Logic 1 2 3 All these smaller blocks are combined together to form the larger block below (not all are labelled). The dashed lines indicate what block fits where. 4 4 VelocityFactor 1 BtnCalculate This is then updated with some math blocks. Fig.5: in the Blocks window, built-in procedures like logic, math, variables etc are selected from the left-most menu and dragged onto the Viewer. These pieces can then be combined into more complex nodes performing multiple functions. Blocks are combined based on their shapes and what open space they have. 76 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.6: part of the Blocks screen for the TDR (time domain reflectometer) calculator. Most of the program is made from conditionals, and some basic programming knowledge can help to understand it, but it is not required. Main program Check if the velocity factor is equal to 0, less than 1 or greater than 100, if so display and set an error (“Invalid Data”) otherwise continue the program. Error flag (initially set to false) Check if the reflection time is equal to 0, less than 1 or greater than 10 digits long, if so display and set an error otherwise continue the program. Play Sound1 (1) Convert reflection time from nanoseconds to seconds (2) Convert velocity factor from percentage to decimal value. This is then multiplied by the reflection time and the speed of light which gives us the distance to the reflection point and back (3) Divide the result by two to get the distance to the reflection point (in metres) (4) If there’s an error clear the final result into seconds. The Velocity Factor is divided by 100 to convert it from a percentage to a decimal, eg, 75% becomes 0.75. To calculate the distance to the reflection point and back, the Velocity Factor is multiplied by the Reflection Time and the speed of light (C). Result2 is divided by two to obtain the distance to the reflection point in the transmission line where the fault has been located (see Fig.6). You can also add and view comments in the code. Right-click on the background and select “Show All Comments” to see them. To add a comment, click on the question mark (?) and then on the block, and write a comment for it (see Fig.7). Right click on the Viewer background to open this menu Click the “?” to add comments Show and hide all comments Fig.7: comments can be added to sections of a program by clicking the question mark (?) symbol on blocks. Generally, comments are useful if you need to come back to the program months later or for describing complex functions. siliconchip.com.au Australia’s electronics magazine February 2021  77 Button Image Invisible labels acting as spacers Objects can be made visible or invisible Fig.8: Labels can be set to invisible and then used to help separate other interface elements. Fig.8 shows the second screen (Screen2) in this application. To add a screen, click the “Add Screen” button at the top left of the window (see Fig.2). Click “OK” to accept the “Screen2” name, or give the screen a name and click OK. Add the required components for Screen2 as shown, and edit their properties as required. Next, select “Connectivity” components and move (drag) the ActivityStarter components onto the phone screen (Fig.9). These will be shown as non-visible components. ActivityStarter components are used in Screen2 Blocks code to go to the Silicon Chip website. Fig.10 shows the Blocks code for Screen2 and what it does. Note that there is a build problem with the website address being swapped, but works correctly when set up as shown. When the application has been tested in App Inventor and is complete, the project .apk file can be built and downloaded onto your computer or Android phone. As shown in Fig.11, click “Build” and select “App (store .apk to my computer)” to download onto your computer. Or select “App (provide QR code for .apk)” to get the download address to paste into the phone browser. Instead of using the QR code to download the application onto an Android phone, you can copy the download address that is under the QR code into your phone browser and download it. Before you can install the app, go to phone settings and then under Security, set the phone to allow the applications to be installed from Unknown Sources. Then use a File Manager to open the .apk file to install the application. Once the application has been installed, do not forget to go back and disable installation from Unknown Sources. Uploading your app to the Google Play Store After having finished developing Fig.9: the ActivityStarters are used, in this case, to go to a website. ActivityStarter Located in the Connectivity dropdown menu 78 Silicon Chip Australia’s electronics magazine siliconchip.com.au your application, you need a way for other people to use it. The best way to do this is to publish your application on Google Play Store. This is quite an extensive task, involving many steps. But once you submit your application to Play Store, it will be easy for other people to install it. The following web page describes the steps to upload your application to the Play Store: https://techzillo. com/publish-android-app-googleplay-store/ As listed on that page, the main steps are: 1. Sign up for Play Publisher 2. Add information about your app 3. Upload your app’s APK file 4. Set a content rating for your app 5. Add pricing and distribution information 6. Publish your app Each of these steps has up to a dozen sub-steps. But the overall, the procedure is straightforward. Google Play Publisher is used to publish the application onto Play Store. You can sign up for this at https://play.google.com/ apps/publish/signup/ It costs around US $25. Search in the App Inventor community Forum for “Play Store” and “bundle” for more information, as you will not be using Android Studio to create your application. You can find dozens of tutorials on other features of MIT App Inventor at https://appinventor.mit.edu/explore/ SC ai2/tutorials Fig.10: this is the code for ActivityStarter shown in Fig.9; it simply goes to the listed website when one of the buttons are pressed. You also have a back button to return to the original screen. Generate a QR code to download the APK from, or you can go directly to the provided hyperlink Or you can generate the APK directly. Fig.11: once you’ve built the app then you can generate the APK file which is used to install it. siliconchip.com.au Australia’s electronics magazine February 2021  79 A Virtual ElectronicsWorkbench By Tim Blythman It’s great to work in a well-provisioned electronics lab with lots of bench space and plenty of test instruments and tools. But we don’t all have that luxury! So we decided to come up with a way to cram all the most essential electronics tools into a small space, such as a typical desk, sharing space with a computer and possibly other gear. We even managed to keep the cost low! W e noted in our Mini Digital PSU project starting on page 38 that its design was partly driven by the need to create a compact solution that would fit on a small workbench. Not only is the hardware for that design small, but because it can be controlled from a PC via a USB interface, it can be tucked out of sight altogether, taking up practically zero space on your bench. We realised that, in addition to a power supply, another vital piece of test gear which usually takes up a lot of bench space is an oscilloscope. USB oscilloscopes have been around for a while now, so we decided to look into adding one to our setup. BitScope Micro A ’scope is very handy to have when it is needed, but you might go weeks 80 Silicon Chip or even months without touching it. And we wanted to keep the cost low. After doing a bit of research, the BitScope Micro appeared to be a good option. It has two analog channels with 20MHz bandwidth as well as six digital logic channels – enough for common jobs like sniffing serial, I2C and/ or SPI traffic. It interfaces with programs that can run on Windows, macOS and Linux, including on the Raspberry Pi. There isn’t just one suitable piece of software, but several. A DSO program allows the BitScope Micro to be used as either a digital or mixed-signal oscilloscope, and it can also generate analog waveforms. There is also a Logic program which can perform protocol analysis, including SPI, I2C, CAN and UART and a generator program can be used to generate arbitrary waveforms. Australia’s electronics magazine The Micro is only one of an extensive range of BitScope test gear; their products all work with the same software. In any case, because the BitScope Micro is one of the cheapest USB oscilloscopes, and it can run from a Raspberry Pi, we decided to get one to test. And then we had an idea . . . The Virtual Workbench While testing the Mini Digital PSU, it occurred to us that sometimes it would be necessary to isolate the power supply output from the control PC. The grounds may need to be at different potentials; a direct connection cannot work as the ground of the Mini Digital PSU is is plugged into the ground of the USB host it is connected to, which is typically Earthed. You could use a laptop or notebook computer running from its internal siliconchip.com.au battery, but this exposes a second problem. Often, you are connecting to gear that might be faulty, or that could generate voltages that would damage your laptop. And you also need to touch that computer, so you want to be sure it isn’t being fed any hazardous voltages! Our Virtual Workbench takes care of both of these problems. How it works You’ve probably gathered by now that we’re going to connect the Mini Digital PSU and BitScope Micro to a Raspberry Pi. The Pi is undoubtedly less expensive than a laptop, but that doesn’t give us any isolation. To provide that, we’re going to interact with the Raspberry Pi remotely, via another computer, using the VNC protocol over WiFi. This is what is sometimes referred to as ‘headless’ operation. With only the compact Pi needed, the entire rig is no longer tied to your computer by wires. It could be deployed beyond the reach of typical leads, or even tucked into a sealed cabinet. As many of BitScope’s products are designed with the idea of remote data logging in mind, with devices having many more channels than the Micro, it is well suited to this type of usage. A USB power supply or even a USB Features • Computer-controlled, isolated electronic test and measurement gear • Includes a 14V, 1A current-limited adjustable power supply, oscilloscope with two analog and six digital channels, and arbitrary waveform generator • Remote access capability • Easy screenshots for recording observations and measurements • Capable of data logging battery pack supplies power to the Raspberry Pi and the attached devices (power supply & scope). Communications over WiFi ensures that the equipment under test is safely isolated from your computer. A good-quality USB power supply will ensure that the supply to the Pi is floating with respect to Earth, while providing all the power that the Pi and the attached hardware need. So in summary, our configuration has the BitScope Micro and Mini Digital PSU plugged into the USB ports on a Raspberry Pi. Rather than connecting the Pi to a monitor and controlling it with a keyboard and mouse, the Raspberry Pi runs a program called VNC Server. This allows other computers to connect via WiFi (or LAN) and operate the Pi as if you are sitting in front of it with a monitor, keyboard and mouse attached. This arrangement is not difficult to set up if you follow our steps. We also have a few useful tips for using such a configuration. The Raspberry Pi Raspberry Pi single-board computers are quite amazing for their price. They’re powerful but almost disposable! That’s why they make an excellent choice for interacting with equipment that might be prone to let the smoke out of any test gear that they’re connected to. We used a Raspberry Pi 3B+ for our testing, although just about any variant with WiFi will work. The Pi Zero variants are cheaper, but you might also need to fork out for an adaptor or hub Hidden inside the black case above left is our Raspberry Pi, which forms the heart of this project. At lower right is the Bitscope Micro, protected from accidental shorts by its clear heatshrink sleeve. At top right is our brand new Mini Digital Power Supply – so new it also appears in this issue (see page 38). siliconchip.com.au Australia’s electronics magazine February 2021  81 Screen1 (left): if you haven’t used Raspbian (or Raspberry Pi OS as newer versions are named), you should find that it is not too different in operation to Windows. But note that instead of a “Start” menu, it has the Raspberry icon in the top left corner. Screen2 (below): the only change we’ve made from the Raspberry Pi’s Configuration System defaults is to give it a unique hostname. You can also experiment with the resolution so that the VNC viewer window is a useful size. to connect USB devices. If you’re only using the ’scope feature, then a simple USB OTG adapter might be enough. Naturally, you will need the WiFi version to go wireless. If you already have a Pi set up, then you can skip the operating system installation and look at what settings are needed to allow VNC to work. The Raspberry Pi needs to have an operating system installed on a microSD card, which you can load onto a blank card yourself, or you can buy ‘pre-flashed’ cards. Look for a ‘NOOBS’ (New Out Of Box Software, see parts list) SD card, or follow instructions for creating such a card on the Raspberry Pi website (www.raspberrypi. org/documentation/installation/ installing-images/README.md). Connect up the keyboard, mouse and monitor to perform the initial setup. Then connect a suitable power Screen3: during setup, we recommend enabling the VNC and SSH interfaces. VNC is needed to allow connections from the remote VNC viewer, while SSH can be used to access a terminal remotely and also interface to SCP programs for easy file transfers. 82 Silicon Chip supply. Allow the Pi to boot up to the desktop screen, as shown in Screen1. The keyboard, mouse and monitor only need to be connected during the initial setup. After this, remote access makes the extra gear unnecessary. Setting it up You might be prompted to enter locale information (eg, your country of residence) after booting it up. Next, connect to a WiFi network using the icon at top right. You can use an Ethernet connection if you prefer, although you won’t get the same degree of isolation. Then at top left, open Pi icon –> Preferences –> Raspberry Pi Configuration (Screen2). To use VNC, under Interfaces, you will need to set VNC to Enable (Screen3). SSH is also a handy interface to enable. Another useful item to set (under System) is to change the hostname; we set ours to ‘bitscope’. This will give your Pi a distinct name which allows it to be easily found instead of using its IP address. See our screenshots to check your settings; we didn’t need to change anything else, but your setup might be different if it isn’t a fresh install. In case the hostname method doesn’t work, it’s a good idea to note Screen4: installing the Processing IDE requires the use of the terminal, but can be completed with a single command. The script downloads the necessary files and installs them. Once complete, the Processing menu item should become available. Australia’s electronics magazine siliconchip.com.au The Bitscope Micro USB Oscilloscope and Analyser COMPENSATED ATTENUATORS HIGH SPEED A/D CONVERTERS CHA LED RANGE CONTROL & WAVEFORM SAMPLING LED GENERATOR POWER LED USB • CHB LEDLED POWER SIGNAL I/O • • • • • • • CHB LED DATA LED INPUT BUFFERS COMPARATORS AND SWITCHES CPU & DSP USB COMMS • • • • 20MHz bandwidth 40MSps logic capture 2 analog scope channels 2 analog comparator channels 6 logic/protocol analyser channels 8 & 12 bit native analog sample resolution Decodes serial, SPI, I2C, CAN and more Windows, Linux, Mac OS & Raspberry Pi Built-in analog waveform & clock generators User programmable, C/C++, Python, VM API Tiny, lightweight (14g) and water resistant Standard oscilloscope probe adaptors available The Australian-designed and produced Bitscope Micro USB Oscilloscope and Analyser is around 120mm long (seen here about life size), so doesn’t take up much space at all. Our unit came with a full complement of short, colour-coded test leads, with a grabber at one end and a header to suit the I/O breakout at the other. As seen above, the pins are marked on the back of the PCB, with the green and yellow CHA and CHB designations matching the trace colours in the DSO application. It is available direct from Bitscope (www.bitscope.com) or from numerous resellers. the IP address; it can usually be found by hovering your mouse pointer over the WiFi (or LAN) icon. We also set the display resolution (using the Set Resolution button under System) to something quite low so that the Pi’s window is not full of empty space. The DSO app runs at around 700x500 pixels, while the Mini Digital PSU is only 480x320 when calibration is not running. We’ll finish setting up the Pi while we’re at it, but the remainder can also be done via the VNC interface later, if you like. The Pi has its own web browser, so you can directly download software via WiFi onto the Pi if you have an Internet connection. You can download the BitScope apps f r o m h t t p : / / m y. b i t s c o p e . c o m / download/?p=download&f=APDA Start with the DSO app. Download the .deb file to your Raspberry Pi and run it. If prompted, the default username and password for the Pi are “pi” and “raspberry”. This should create a menu item for BitScope DSO under the Program- ming sub-menu; you can add a shortcut to the desktop by right-clicking the item and selecting “Add to desktop”. The other BitScope apps are installed similarly. There are many features to the BitScope DSO app; to try them, plug in the Micro and start the app. Press the SETUP button and select a USB port. Our unit appeared as /dev/ttyUSB0 and did not need any drivers to be installed. Then press the POWER button to access the DSO screen. We’ll have a closer look at some of the BitScope apps, including DSO, a bit later. Installing Processing Screen5: since Processing is available on numerous platforms, our Mini Digital PSU software can even run on the Raspberry Pi. There is room on the virtual screen to set up the DSO and PSU apps next to each other for a complete Virtual Workbench. siliconchip.com.au Australia’s electronics magazine To use the Mini Digital PSU, you will need the Processing application. There are a few ways to achieve this, as listed on the Processing page at https:// pi.processing.org/download/ One option is a downloadable image file which can be written to an SD card (although this appears to be a few years old and thus might not support the Raspberry Pi 4 variants). But we suggest that you use the simple terminal command to download and install it, if it is not already. Open a Terminal window by pressing Ctrl-Alt-T (or via the Pi’s menu, under Accessories) and enter the command: curl https://processing.org/ download/install-arm.sh | sudo sh February 2021  83 Screen6: with a suitable hostname for our Raspberry Pi, we can access it from the VNC Viewer app by simply typing that name in the address bar. This is far easier than using the IP address, especially if you are using DHCP rather than static IP addresses. (The vertical bar symbol can usually be found on the backslash key). This will download and install Processing – see Screen4. Like BitScope DSO, a menu item will appear under the Programming submenu. To use the Mini Digital PSU, you will also need our sketch file. You could use the browser to download this directly on the Raspberry Pi, or copy it to a USB stick. But we’ll show you another method after we set up our PC to access the Pi remotely. Once you have Processing and the sketch file installed, fire up the sketch and check that you get a display like that shown in Screen5. You can now shut down your Pi, disconnect the keyboard, mouse and monitor and then power it back up, so that it can be accessed remotely. ating systems (but they don’t all use the same protocols). You could even use an old Android phone to connect to the Pi, making for a compact, portable display as RealVNC also has an Android port. Download and install the VNC viewer and run the program. Type the Pi’s hostname or IP address in the address bar (Screen6) and press Enter. You will be prompted for a username and pass- word; the defaults for these are “pi” and “raspberry”. At this point, you should have a view and control over the Pi’s desktop and can run the apps as needed, almost as though they are running on the local machine. We also need a program to allow us to get files on and off the Pi easily. One important use for this is to download screenshots, which are saved as .png files to the /home/pi folder when you press the Print Screen key. As we enabled SSH earlier, we can connect to the Pi using a terminal emulator such as TeraTerm. But SSH also provides a way to move files using an SCP (secure copy protocol) program. SCP uses an SSH session to transfer files over a network link. We use WinSCP (https://winscp.net/ eng/index.php) on Windows computers, but a cross-platform alternative is FileZilla (https://filezilla-project.org/). Use the same hostname/IP address, username and password combination as for VNC. The default SSH port number 22 should work, unless that has been changed on your Pi – see Screen7. Once logged in, a pair of windows for local and remote filesystems is shown. Files can be copied and pasted using the usual shortcuts. The version we use even allows files to be copied and pasted directly into other windows, such as native file explorers. PC programs You need a VNC viewer on your PC. The pre-installed Raspberry Pi VNC server (which we activated earlier with the VNC option) is designed to work with the RealVNC viewer, which can be downloaded for free from www. realvnc.com/en/connect/download/ viewer/ But you are not limited to a PC, or RealVNC’s software. Many different VNC clients are available which run on various oper84 Silicon Chip Screen7: using WinSCP for remote file access requires logging into the remote computer using its credentials; in this case, the Raspberry Pi. We found that we were also able to use the hostname to make this connection. Australia’s electronics magazine siliconchip.com.au Screen8: setting up the BitScope Micro is not much more involved than plugging the unit in and selecting its serial port. The settings shown here are typical for most Linux distributions, including those on the Raspberry Pi. We didn’t even need to install drivers. BitScope apps Once you have connected to the BitScope (Screen8), the DSO app presents a screen that looks as you might expect for a ‘scope (Screen9), with most of the window taken up by the waveform display. Horizontal (time) controls are at lower left, followed by the vertical (voltage) controls to the right. Unlike a desktop unit, many of the displays have alternative, hidden functions which can be accessed by either clicking on the button or by right-clicking for a menu. Usually, the left mouse button will toggle between the most recent selections made from the right-click menu. The mixed-signal options can be viewed by clicking on the buttons to the right of the main display, while the small display at upper left controlling both the trigger and waveform generator. These have unusual but intuitive slider controls. The hidden slider controls can be used by pressing down on you mouse button over the control and then moving up/down or left/right. The control’s value will change and is fixed by releasing the mouse button. We also looked at the Logic app (Screen10), as we figured this would siliconchip.com.au be another one we would be likely to use. Like the DSO app, there are numerous options, including automatic decoding of I2C, SPI, CAN and UART. The sampling duration and frequency can be set, as well as the pretrigger period (as a percentage of the duration). It appears that the buffer holds around 6000 samples, which is quite small, but sufficient for many applications. A good selection of trigger options makes it easy to capture the important parts of the data and thus conserve the limited sample space. Once we worked out where all the settings were located, we found it easy to trigger and view the decoded data, as this occurs automatically. You might be thinking that the BitScope Micro would make an excellent data logger with the right software. Fortunately, the BitScope Chart application provides data logging and virtual chart features. The Chart app can derive values such as frequency, duty cycle and RMS values and log to the SD card in CSV format, allowing the data to be easily exported (using SCP for file transfer) and analysed in a spreadsheet program. We can’t possibly cover all of its features, but there are links to tutorial videos and other educational articles at www.bitscope.com/product/ Screen9: the BitScope DSO app is fairly intuitive and works much like a benchtop ‘scope, although there are more options, including some hidden in rightclick menus. The function generator at upper left is included in the DSO app, so you can easily feed test signals to your circuitry. Australia’s electronics magazine February 2021  85 Parts list – Virtual Workbench 1 Raspberry Pi (eg, 3B+ or 4B) [Jaycar XC9001, Altronics Z6302G] 1 SD card with Rapsbian operating system installed [eg Jaycar XC9030, Altronics D0313A; see text] 1 power supply to suit the Raspberry Pi 1 BitScope Micro USB Oscilloscope (or similar model) 1 Mini Digital PSU (see construction article starting on page 38) 1 keyboard, mouse & monitor set (for setup only) Screen10: the Logic app provides logic analyser functions and can automatically decode SPI, I2C, CAN and UART, with several extra options available for each protocol. BS05/ Since the BitScope Micro (and its larger brethren) all use a simple serial protocol, it would be very easy to write a custom application to add more features. The folks at BitScope are already onto this and have written the BitLib software library to allow custom applications to be created using C/C++, Python and Pascal. For more information, see www.bitscope.com/software/library/ BitScope server Some BitScope hardware natively supports an Ethernet connection; you might have seen this option appear while setting up some of the apps. This means that with a VPN or DNS software, it’s possible to connect to a BitScope device over the internet. BitScope keeps a Model 325 available online that you can try out, although, at the time of writing, it was not working. You can find out about this at www.bitscope.com/ software/?p=demo or access it by connecting to sydney.bitscope.com via the DSO application. The Model 325 has a native Ethernet connection, but the Micro does not. However, it can still be made accessible over Ethernet through the BitScope Server app. We tested this on our Raspberry Pi too. Like the other programs, the Server can be installed by downloading and running the .deb package. It won’t appear on the Pi’s menu as it is not a GUI application. Instead, it is started via the terminal. The version we tried appears to be an early beta version, so the options to run as a daemon (background ser86 Silicon Chip vice) have not yet been implemented. Still, we were able to start the Server by opening a terminal and running the “bitscope-server” command. Leave the terminal open to allow the Server program to continue to run in the background. Going back to the DSO app on our PC (where we are running the VNC client), we used the setup page to point it to an Ethernet device at “UDP:bitscope” (Screen11), as per the hostname set earlier; an IP address should work too. This option has the advantage of running the applications natively on what would typically be a faster PC than a Raspberry Pi. There’s also the option of being able to access the BitScope device from multiple machines, although we found the results were (unsurprisingly) unpredictable when we tried to do this from two PCs at the same time. Conclusion It’s incredible what is now possible with small computers like the Raspberry Pi, and we are already making good use of our Virtual Workbench. Since we often require ’scope grabs for printing in the magazine, having a USB oscilloscope makes that a bit easier. One of the nice things about the BitScope range is that even if the hardware doesn’t have a feature that you want, it is often possible to do it with other apps or through the scripting and library features. Being able to operate a scope and power supply over WiFi has benefits beyond our cramped home workshops. It is handy in any case where isolation is essential, or the device under test is far away from your bench. We’re sure that we’ll make use of this Workbench even when we have much more expensive pieces of equipment at hand! SC Screen11: the BitScope Server program runs in the background and makes the USB-connected BitScope Micro available over Ethernet (or WiFi). Since we have set up our Pi with the “bitscope” hostname, it can be easily found on our network. Australia’s electronics magazine siliconchip.com.au THIS . . . OR THIS: Every article in every issue of SILICON CHIP Can now be yours forever in Nov 1987 Dec 2019 digital (PDF) format! n High-res printable PDFs* * Some early articles may be scans n Fully searchable files - with index n Viewable on 99.9% of personal computers & tablets Software capable of reading PDFs required (freely available) Digital edition PDFs are supplied as five-year+ blocks, covering at least 60 issues. They’re copied onto quality metal USB flash drives (at least 32GB). Just order which block(s) you want! n n November 1987 - December 1994 January 2005 - December 2009 n n January 1995 - December 1999 January 2010 - December 2014 n n January 2000 - December 2004 January 2015 - December 2019 Each five-year block is priced at just $100, and yes, current subscribers receive the normal 10% discount. If you order the entire collection, the 6th block is FREE (ie, pay for five, the sixth is a bonus!). All PDFs are high resolution (some early editions excepted) and the USB Flash Drives are high quality metal USB3.0, so if you save the files to your PC hard disk, the USB Flash Drives can be used over and over! SUBSCRIPTIONS TO SILICON CHIP REMAIN THE SAME! Of course, so you won’t miss out on a current issue you can still subscribe to SILICON CHIP . . . and you’ll $ave money over the newsstand price. Your SILICON CHIP will be delivered every month right to your mail box . . . no waiting! n Subscribe to the printed edition n Subscribe to the digital edition n Subscribe to the combo printed/digital edition Want to know more? Full details at siliconchip.com.au/shop/digital_pdfs siliconchip.com.au Australia’s electronics magazine February 2021  87 Want to (almost!) DOUBLE your computer’s performance? by Nicholas Vinen Upgrading to a CPU The latest desktop processors from AMD, dubbed Zen 3 but also known as the Ryzen 5000 series, offer a 20% improvement in performance compared to their predecessors, making them the fastest desktop CPUs available at the moment. They are also quite affordable, and upgrading is relatively easy if you have a Ryzen processor on a newer motherboard. I was prompted to upgrade my office PC (and write this article) by the very impressive performance numbers and reasonable prices that were revealed at AMD’s Zen 3 launch last November. At the time of writing this article, this line of CPUs (currently four strong) have taken the performance crown from Intel and are quite reasonably priced, with a choice of 6, 8, 12 or 16 cores. For most people, the 5600X CPU with six cores for $469 is more than 88 Silicon Chip adequate, and will be a significant upgrade from previous generation chips. If you have an AMD motherboard and upgrade your cooler and memory at the same time as upgrading the CPU, you can get a 30-50% increase in performance for around $600. You might even get a bigger boost if you are using an earlier processor, and if you are willing to spend a bit more (up to say $1000), the gains can be huge. I bought my previous CPU only a year ago, in January 2020, for $315 (a Australia’s electronics magazine Ryzen 3600). It had six cores, with a base clock of 3.6GHz and a boost clock of up to 4.2GHz. It was already a massive upgrade over my previous (quite old) computer. I decided to upgrade to a 5800X with eight cores, a base clock of 3.7GHz and a boost clock of 4.6GHz, and I am delighted that I did since the difference is very noticeable! Even better, with the large air cooler I added, I am achieving clock speeds above AMD’s specification, with a siliconchip.com.au base clock of 3.77GHz, a boost clock of 4.84GHz and sustained boost to 4.7GHz on all eight cores under load. Or to put it in layman’s terms, what a little ripper! Upgrade requirements To upgrade to one of the new Zen 3 CPUs (Ryzen 5600X, 5800X, 5900X or 5950X), you need an AMD chipset motherboard with a three-digit code starting with a 4 or 5. That means a 450B, 470X, 550B or 570X based board. Assuming you have one of those, you need to perform a BIOS update to support the new CPUs. Then it’s just a matter of swapping over the chips, and away you go. As I mentioned earlier, unless you have a high-end air cooling or water cooling solution, it’s probably also a good time to upgrade that. With dynamic thermal throttling, the cooler you can keep the CPU, the faster it will perform under load. And also you can get silent operation at idle or moderate loads with a decently efficient cooler. Air vs water cooling The ‘stock’ heatsink/fan combination that came with my original Ryzen 3600 CPU did its job, but I immediately regretted not spending a bit more money on a custom cooler to make the computer quieter and run a bit faster under heavy load (going into thermal throttling later). Decent third-party air coolers range from about $50 up to $150 or so. Water cooling solutions start at the upper end of that range. The main advantage of water cooling a CPU is the potential for slightly better and somewhat quieter cooling under heavy load, and a much larger thermal mass which means that they cope well with ‘bursty’ loads. But they cost more, and while these days leaks are rare, they can happen. And air coolers are quieter at idle and light loads. So most people will probably stick with air cooling. We’ll cover air vs water cooling more in a future article. For my system, I bought a Deepcool Assassin III dual tower, dual-fan cooler for around $134 from Amazon as it was considerably cheaper than the other well-regarded large air coolers like the Noctua NH-D14, NH-U14S or NH-DH15. Since then, I have seen the Assassin III on sale for $20 off (about $114), which I think is an excellent deal. One thing that you should do, which I didn’t, is to compare the height specification of the cooler to the amount of space available in your case (ie, from the top of the CPU to the inside panel of the case) to make sure it will fit. This almost caused a disaster, which was narrowly averted, as you shall see. Choosing faster RAM Assuming that you have a compatible motherboard and can get your hands on a Ryzen 5000-series CPU, order a suitable cooler and then have a think about upgrading your RAM. Zen 3 CPUs can take advantage of very fast RAM, and 4000MHz DDR4 is ideal. I had 3200MHz RAM and decided to upgrade to 3600MHz, as I found that to be the best value (faster RAM than that is very expensive). You could also consider increasing your RAM capacity while you’re at it. But don’t forget to consider the column address strobe (CAS) latency, generally specified as a number following the letters “CL”. For example, you might see 2 x 8GB (16GB) 3600MHz DDR4 DIMMs for $135 and 2 x 16GB (32GB) 3600MHz DDR4 DIMMs for $239. The 2 x 16GB seems like a better option than two lots of 2 x 8GB (assuming your board has four DIMM slots) as it is $31 cheaper. But if you look closer, the first option is CL17 and the second option is CL18. That means that the 16GB DIMMs take one clock cycle longer to respond to column address changes compared to the 8GB DIMMs. How much does that matter? I am not sure. I suspect the CL17 DIMMs will give a couple of percent better performance in some tasks. I don’t think that is necessarily worth spending the extra $31 and also halving the maximum RAM you can install in your system, but it is something to keep in mind. I have seen other cases where doubling the memory per stick takes you from CL17 to CL19, or from CL16 to CL18, which is going to have a more significant impact, and often the price difference is negligible. Ultimately, you will have to do some shopping around and decide what combination of MHz rating, CL rating, Obviously (!) not to scale, here are the components which form the heart of my computer upgrade: at lower left is the ZEN 3 CPU; behind that a pair of 8GB 3600MHz DIMM sticks, while at right is the Deepcool Assassin 3 dual tower, dual-fan cooler. The first two items give dramatic improvement in performance; the latter ensures it all keeps its cool. siliconchip.com.au Australia’s electronics magazine February 2021  89 Screen1 (BEFORE!): I ran the PassMark CPU benchmark before upgrading the system. Unfortunately, as this was the first time I used the software, I forgot to click on the button to show the CPU Mark results in detail, so you can only see the final score of 18,199. capacity, number of sticks and price suits you the best. Don’t install fewer than two DIMMs, though, as you want to have dual channel operation for good performance! Doing the upgrade OK, so you have your new CPU, cooler and maybe some new RAM. While swapping them over is a bit of work, it isn’t too hard. I haven’t upgraded a CPU in probably more than a decade, and I managed to do it successfully. The steps are: 1) Upgrade your BIOS. You must do this first! Otherwise, if you swap the CPU, the system will not boot. (Some motherboards give you a way to upgrade your BIOS even if you can’t boot, but not all). First, find your motherboard model. In Windows 10, you just need to run Screen3: with the usual Windows background tasks, CPU usage is not zero, but the CPU is running at just under 1V at its ‘base clock’ of just under 3.8GHz on all cores. The CPU fan is set to silent mode, so the temperature is just under 40°C (it could be even lower if I didn’t mind a bit of fan noise). 90 Silicon Chip “System Information”, and it will be listed in the window that pops up. If you’re stuck, open up your case and find the label on the motherboard itself. Go to the manufacturer’s website and find that model. Under “Support” or “Downloads”, locate the latest BIOS and download it. It should have a date of November 2020 or newer. There are a few ways to do the actual upgrade, and they vary slightly by manufacturer. In some cases, you can download a software utility to do it from within Windows, or you can Screen4: during a relatively heavy multi-core workload, all eight cores are sitting happily at just under 4.7GHz. That’s almost 100MHz higher than AMD promises for the maximum boost clock for this processor! It can sustain this long-term with the CPU sitting at a hot, but not particularly worrying, 70°C with the fan set on silent mode. It would drop to around 60°C if I was willing to put up with some noise. Screen5: with a single-thread task active (eg, CorelDraw), one core will boost even higher, to 4.84GHz, ramping up Vcore to just under 1.4V and giving excellent performance. The temperature isn’t too bad considering, and would be lower if I was willing to put up with a little bit of fan noise. Australia’s electronics magazine siliconchip.com.au Screen2 (AFTER!): well, that’s certainly an improvement! The increase in the final score of over 50% to 30,013 is due to a few factors including the two extra cores and the higher clock speeds, but a lot of it is due to the approximately 20% increase in instructions per clock (IPC) moving from Zen 2 to Zen 3, faster inter-core communications and more memory bandwidth. make a DOS bootable USB drive and do it that way. But the easiest way is probably to save it to a USB flash drive (in the root directory), reboot into your BIOS configuration screen (usually entered by pressing F11 or delete during the Screen6: the CPU power reading spiked to just over 140W during an SSEintensive multi-core workload (note the slightly lower core boost frequencies with the temperature reading hovering just below the 90°C threshold). The chip has a rated thermal design power (TDP) of 105W, and will work with 105W worth of cooling. It just won’t run as fast as it does with the bigger cooler which gives it more thermal headroom. siliconchip.com.au power-on self-test [POST] process) and then select “BIOS upgrade” or a similar option. It will prompt you to locate the BIOS file you downloaded on the flash drive, then it will ask if you are sure you want to proceed. Most modern motherboards have dual BIOS, so even if the upgrade fails, you can still boot and recover it, so go ahead and upgrade. It will take a few minutes, then reboot. Assuming it is successful, we recommend that if you do have a dual BIOS, you go through the process again but select the option to overwrite both the primary and backup BIOS images. Otherwise, when you install the new CPU, if your primary BIOS fails you will not be able to boot the backup BIOS as it will be too old. 2) Power down your computer, unplug it and remove both side panels. You will need access both to the area around the CPU on top of the motherboard, and also the bracket which attaches under the CPU to hold the cooler on (unless you are reusing your existing cooler). Modern cases have a cut-out in the motherboard tray to give you access to the area under the CPU. Lay the case on its side, on a flat bench, with the CPU cooler facing up. 3) Remove the heatsink/fan combination (or if you have a water cooling solution, the water cooler block). In my case, I had the AMD Wraith Stealth which came with the Ryzen 3600 CPU. This is quite easy to remove – use a long-shaft Phillips screwdriver to loosen the four screws around the fan shroud. Once you have loosened them Screen7: somewhat confusingly, the Gigabyte tool for controlling fan speed is called “System Information Viewer”. I created this custom fan profile based off their “silent” profile which increases the idle RPM a bit (it’s still silent) while ramping up the fan more slowly at elevated temperatures. This results in virtually no noise except when the CPU is working very hard for extended periods. Australia’s electronics magazine February 2021  91 Step1: don’t forget to update your BIOS before powering down your computer and removing your old CPU. Generally, you download the new BIOS image onto a USB flash drive, reboot into the BIOS interface and flash it that way, but some manufacturers support other methods. It takes a few minutes to complete. enough, you should hear the plastic support bracket under the CPU fall onto the bench. Rotate the heatsink a few times clockwise and anti-clockwise, by say 10-20°. This helps to reduce the chance that when you pull the heatsink up, it will yank the CPU out of its socket. Then gently pull up until the heatsink comes free, and set it down upside-down, as the underside will likely be sticky with the remnants of a thermal pad or some thermal paste. 4) Gently clean the gunk off the top of the old CPU using some isopropyl alcohol and a lint-free cloth. My new cooler (the Assassin III – take that, heat!) did come with a pack containing an alcohol-soaked cloth for this purpose, but I already had the spray bottle ready. I would avoid using methylated spirits, as it could leave some residue behind. I also don’t recommend using acetone in case it dissolves something it shouldn’t. You might have to make a few passes before you get the CPU nice and clean. While you’re at it, you might as well clean up the bottom of the old heatsink, to make it less messy when you store it later. If you are upgrading your RAM, now is a good time to remove the old sticks, to give yourself more room to work. Press down on the little plastic tabs on either side, and they should pop up. You can then lift the modules out Step5(a): raise the lever and then lift the CPU out of its socket. It should come out easily. I also removed my RAM to give myself a bit more room, as I was going to upgrade it anyway. 92 Silicon Chip Step2: the mounting bracket for the stock AMD cooler. This usually needs to be removed (from the other side) to fit a third-party cooler. If you don’t have a cut-out like this in your case (and most modern cases do have one), you will have to remove the motherboard from the case to swap the bracket over. and place them somewhere safe (eg, in an anti-static bag) for future reuse. (I gave mine to a co-worker to upgrade his computer.) 5) Remove the old CPU by lifting the ZIF socket lever until it is vertical, then gently lifting the CPU out of its socket by the edges. As you do so, take note of the location of the small metal triangle in one corner. It should line up with a plastic triangle moulded into the corner of the socket. Place it upside-down on a flat surface for now, somewhere where nothing can be placed on top of it, and it can’t fall or slide. 6) Assuming you are upgrading the cooler, stand the case on its feet and put the old plastic bracket aside. Open your Step5(b): having removed the old heatsink, mounting bracket and RAM, I cleaned them up and put them away for future use. The RAM has already found a home in someone else’s office PC... Australia’s electronics magazine siliconchip.com.au Step3: to remove the stock heatsink and its mounting bracket, I just had to undo four screws. Make sure that you wiggle (rotate) the heatsink a few times after removing the screws and before pulling it off, to try to break the suction between the heatsink and CPU due to the thermal pad or paste in between. Said pad left a bit of a mess on both the CPU and the heatsink once I got them apart. new cooler and extract all the pieces plus the instructions. You will typically get the heatsink itself, one or two fans, some clips or other mounting hardware for the fans, various brackets and screws to attach it to the motherboard and some thermal paste. At this stage, the main job is to attach the new mounting bracket to the motherboard. In this case (and I believe this is typical), it consisted of a new plastic bracket for the underside of the motherboard, some screws that go through that bracket and the motherboard and some nuts that hold it on. Two plates then attach on top of those screws, with threaded holes for the heatsink itself to screw into. Even if you go slowly, take your time and are careful to follow the instructions, this step should only take about five minutes or so. 7) Open the new CPU packaging and gently lift it out by its edges. Take care not to bend any of the pins. Find the small metal triangle in the corner and line it up with the plastic triangle on the ZIF socket; this should give your new CPU the same orientation as the old one. Hover it over the socket, then gently drop it down on top. The pins should go into the holes, and the base of the package will rest on top of the ZIF socket. Give it a slight wiggle to make sure it has dropped down fully, then hold it down and push the ZIF socket lever all Step6: the new bracket in place on the back of the motherboard (supplied with the Assassin III heatsink). Note the alternative screw holes for older CPU sockets; if you use the wrong ones, it won’t fit through the motherboard. siliconchip.com.au Step4: I cleaned up the old CPU and heatsink using some isopropyl alcohol and a lint-free cloth. This also gets rid of any gunk left behind around the edges of the CPU socket. You want to get rid of it before removing the CPU so that it can’t fall into the holes where the pins go and foul it up. the way down so that it locks into place. At this stage, make sure it is sitting nice and flat on the socket, as you could damage it once you clamp the heatsink on top if it is wonky. You can now put your old CPU into the packaging from the new CPU to protect it until it finds a new home. 8) Apply thermal paste on top of the metal CPU IHS (integrated heat spreader). If your cooler didn’t come with some, you will have to buy a tube. Make sure to get the good stuff (eg, Arctic MX-4, available for around $10 per 4g on Amazon) as poor thermal paste will make your expensive cooler work inefficiently. There are lots of different suggestions for the best way to apply it: put Step7(a): the new CPU will drop straight into the socket if you get the orientation right. If you can’t find the metal triangle on the top corner of the CPU, check the underside; one corner of the CPU and socket will have missing pins. Australia’s electronics magazine February 2021  93 Step7(b): make sure the CPU is sitting utterly flat before lowering the lever to lock it in. With the CPU in, I popped in the new RAM modules. Press them down firmly on both sides! a blob in the centre, put five smaller blobs spaced out, draw it in an X-shape etc. I like to smear it around and then smooth it out into a thin layer using a flat piece of plastic. There’s even a credit-card shaped piece of plastic in the Assassin III box for this purpose. That way, at least I know the CPU will have full coverage. Remember that when you screw the heatsink down on top of the IHS, it will even out the distribution, and the excess will squirt out the sides. So don’t go overboard; you only need enough to just cover the IHS. 9) If upgrading your RAM, now is a good time to install the new modules, as access will be very limited with the heatsink installed. A notch in the bottom of the module lines up with a plastic separator in the socket, so it can only go in one way around. Don’t try to force the modules in the wrong way! Once you are sure they are lined up correctly, press down firmly at either end. The two plastic tabs should ‘click in’ to hold the module in place. Press at both ends again to make sure it is properly seated. We got some clicks out of modules we thought were already pushed in correctly! You can also push the plastic tabs inwards, as that sometimes pulls the module in, but it shouldn’t be necessary. If installing two modules into four slots, put one in the slot furthest from the CPU, and leave a gap, then put the other in the second-closest slot to the CPU. This ensures that each module is on a separate channel for dual channel operation, and also keeps them away from the heat of the CPU. 10) If your motherboard’s CPU fan Step11(a): attaching the heatsink is quite easy, as you just have to alternately do up the two screws a little at a time until the springs are fully compressed, and you encounter increasing resistance. 94 Silicon Chip Step8(a): applying thermal paste is a bit of a black art. I like to smear it all over the IHS, while others prefer just to place some blobs or lines and let the pressure from the heatsink redistribute it. header is close to the CPU (like mine), now is a good time to plug in the fan(s). My cooler came with two fans and a Y-splitter cable, allowing me just to plug in the Y-cable initially, then add the fans later. If you have a single fan, plug it in and put it somewhere out of the way. It might be impossible with the heatsink in place. 11) Carefully lower the heatsink (sans fans) down on top of the IHS, lining up its mounting screws with the threaded holes on the brackets you installed earlier. Rotate one screw clockwise until you feel it being pulled into the threaded hole, then do the same for the other. Alternately tighten each screw a couple of turns until you meet significant resistance on both. If you already had a water cooler, you can reinstall it now, using a similar procedure. Step11(b): once you have fully screwed down the heatsink (the screws are clearly visible between the two heatsink towers), it should have only a little play in it. That’s important given its weight, when the PC is upright. Australia’s electronics magazine siliconchip.com.au Step8(b): this “credit card” spreader came with the Deepcool heatsink. While you don’t really need to spread the paste out evenly (it will be redistributed when the heatsink is clamped down), I like to do it anyway. 12) Attach the fans. If there is more than one, make sure they are blowing in the same direction! The plastic surround of the fan normally has arrows to show the direction of rotation and airflow. You usually want the airflow from the front to the back of the case. In my situation, there is an exhaust fan right near the CPU, so I directed the airflow into that. Also, rotate the fans so that the wiring will be neat (you can choose which of the four sides the wires exit). Follow the instructions that came with your cooler for attaching the fans. The type of clips I got are common. These slot into two of the fan mounting holes each, and you then stretch them over the heatsinks, which have a channel cut for the clips to grab onto. If you can’t reach down to slip a clip into place, use pliers to grab the ‘handle’ in the clip and pull it until the clip clicks into place. 13) Wire up the fans. For me, this consisted of plugging the two fans into the free ends of the Y-cable, then tying all the wiring up into a neat bundle to avoid it interfering with the airflow (and looking messy). If you have a single fan and already plugged it in, you just need to bundle up the excess wiring. 14) Plug it in and boot it up! You might end up in your BIOS screen automatically as this is the first time you’re booting with a new CPU (and possibly RAM). You probably want to go into the BIOS anyway, to enable XMP, which will give you the best memory performance. This is also a good opportunity to select the “silent” profile for your CPU Step12: the last step before booting the system up is attaching the fans to the heatsink and plugging them in. With all the tricky bits out of the way, the pressure is off, and you can enjoy this last step. siliconchip.com.au Step8(c): I probably put a bit too much on, but I think that’s better than not enough (as long as you don’t put a ridiculous amount on!). The excess will be pushed out the sides when you clamp the heatsink down. fan, which will keep the fan speed low unless the CPU cores are getting especially hot. If you’ve gone for an ‘overkill’ cooling solution like I did, it will keep the CPU cool under light loads with the fan running very slowly, and probably an inaudible noise level. If your system doesn’t boot, the most likely cause is improperly seated RAM. Power the system down and push each module in firmly. If that doesn’t fix it, you might have to remove the heatsink and check the CPU mounting, although if you followed our instructions, that is unlikely to be the problem. (You did remember to update the BIOS, didn’t you?) 15) Enjoy the blistering performance! Screen1 shows the result of a CPU benchmark run with my old processor (Ryzen 3600) and RAM Step13: after clipping both fans onto the heatsink, I plugged them both into the Y-splitter power cable that I had already plugged into the motherboard. They’re both blowing towards the case’s rear exhaust fan. Australia’s electronics magazine February 2021  95 The end result: the finished system, which performs very well indeed. The new cooler dominates the inside of the case – it’s a good thing the window (right pic) is slightly raised (3200MHz), while Screen2 shows the result of the same benchmark with the Ryzen 5800X and 3600MHz RAM (XMP enabled). Wow, what a performance boost! It is very noticeable in just about every task, . . . otherwise, I would not be able to close the case. The plastic “spoilers” on top of the heatsink just touch the inside of the acrylic window! but especially CPU-heavy software like CorelDraw and Altium Designer. Here is the embarrassing bit. You can see from our photos that the only reason I was able to get the side panel back on my case is that there is a bulge just above the CPU. The Assassin III cooler actually projects out the side of the case, and just fits inside this bubble. Whew! Next time, I will check more carefully that it will fit before purchasing… SC AUSTRALIA’S OWN MICROMITE TOUCHSCREEN Since its introduction in February 2016, Geoff Graham’s mighty Micromite BackPack has proved to be one of the most versatile, most economical and easiest-to-use systems available – not only here in Australia but around the world! Now there’s the V3 BackPack – it can be plugged straight into a computer USB for easy programming or re-programming – YES, you can use the Micromite over and over again, for published projects, or for you to develop your own masterpiece! The Micromite’s BackPack colour touchscreen can be programmed for any of the following SILICON CHIP projects: BACKPACK Many of the HARD-TO-GET PARTS for these projects are available from the SILICON CHIP Online Shop (siliconchip. com.au/shop) Poor Air Quality Monitor (Feb20 – siliconchip.com.au/Article/12337) FREE GPS-Synched Frequency Reference (Oct18 – siliconchip.com.au/Series/326) PROGRAMM Tariff Super Clock (Jul18 – siliconchip.com.au/Article11137) ING Buy either Altimeter & Weather Station (Dec17 – siliconchip.com.au/Article/10898) tell us whichV2 or V3 BackPack, pr for and we’ll oject you want it Radio IF Alignment (Sep17– siliconchip.com.au/Article/10799) program it fo r you, Deluxe eFuse (Jul17 – siliconchip.com.au/Series/315) FREE OF C HARGE! DDS Signal Generator (Apr17 – siliconchip.com.au/Article/10616) Voltage/Current Reference (Oct16 – siliconchip.com.au/Series/305) Energy Meter (Aug16 – siliconchip.com.au/Series/302) Micromite V3 BackPack: * Super Clock (Jul16 – siliconchip.com.au/Article/9887) JUST $7500 Boat Computer (Apr16 – siliconchip.com.au/Article/9977) See August 2019 (Article 11764) Ultrasonic Parking Assistant (Mar16 – siliconchip.com.au/Article/9848) P&P: Flat $10 PER ORDER (within Australia) *P Price is for the Micromite BackPack only; not for the projects listed. www.siliconchip.com.au/shop 96 Silicon Chip Australia’s electronics magazine siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS H-FIELD TRANSANALYSER ROADIES’ TEST GENERATOR SMD VERSION ↳ THROUGH-HOLE VERSION COLOUR MAXIMITE 2 PCB (BLUE) ↳ FRONT & REAR PANELS (BLACK) OL’ TIMER II PCB (RED, BLUE OR BLACK) ↳ ACRYLIC CASE PIECES / SPACER (BLACK) IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION USB SUPERCODEC SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK MAY20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 AUG20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 06102201 01005201 01005202 07107201 SC5500 19104201 SC5448 15005201 15005202 01106201 18105201 04106201 04105201 04105202 08110201 01110201 01110202 24106121 Subscribers get a 10% discount on all orders for parts $10.00 $2.50 $5.00 $10.00 $10.00 $5.00 $7.50 $5.00 $5.00 $12.50 $2.50 $5.00 $7.50 $5.00 $5.00 $2.50 $1.50 $5.00 FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) SUPERCODEC BALANCED ATTENUATOR DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 16110202 16110203 SEE P31 16109201 16109202 01106202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 $20.00 $20.00 $3.00ea $12.50 $12.50 $7.50 $5.00 $2.50 $7.50 $2.50 $5.00 $10.00 $5.00 $2.50 BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD FEB21 FEB21 FEB21 11106201 23011201 18106201 $5.00 $10.00 $5.00 NEW PCBs PRE-PROGRAMMED MICROS As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS ATmega328P-PU ATmega328P-AUR ATtiny85V-10PU PIC10F202-E/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-I/P $15 MICROS RF Signal Generator (Jun19) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) LED Christmas Ornaments (Nov20; specify variant) Door Alarm (Aug18), Steam Whistle (Sept18), White Noise (Sept18) Trailing Edge Dimmer (Feb19), Steering Wheel to IR Adaptor (Jun19) Car Radio Dimmer Adaptor (Aug19), MiniHeart (Jan21) Tiny LED Xmas Tree (Nov19) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20), Electronic Wind Chime (Feb21) Flexible Digital Lighting Controller Slave (Oct20) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS 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 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS & SPECIALISED COMPONENTS MINIHEART HEARTBEAT SIMULATOR (CAT SC5732) (JAN 21) AM/FM/SW RADIO (JAN 21) LED CHRISTMAS ORNAMENTS (CAT SC5579) (NOV 20) RGB STACKABLE LED CHRISTMAS STAR (CAT SC5525) (NOV 20) D1 MINI LCD WIFI BACKPACK KIT (OCT 20) SHIRT POCKET AUDIO OSCILLATOR (SEP 20) COLOUR MAXIMITE 2 in stock now (JUL 20) All SMD parts, including IC2 – does not include PCB - PCB-mount right-angle SMA socket (SC4918) - Pulse-type rotary encoder with integral pushbutton (SC5601) - 16x2 LCD module (does not use I2C module) (SC4198) Complete kit including micro but no coin cell (specify PCB shape & colour) Complete kit including PCB, micro, diffused RGB LEDs and other parts Complete kit including 3.5-inch touchscreen, PCB and ESP8266-based module Kit: including 3D-printed case, and everything else except the battery and wiring - 64x32 pixel white OLED (0.49-inch/12.5mm diagonal) - Pulse-type rotary encoder with integral pushbutton Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (Cat SC5478) Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (Cat SC5508) $5.00 $2.50 $3.00 $7.50 $14.00 $38.50 $70.00 $40.00 $10.00 $3.00 $80.00 $140.00 MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) (AUG 19) Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $30.00 - DHT22 temp/humidity sensor (Cat SC4150) $7.50 - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor $5.00 - BME280 temperature/pressure/humidity sensor (Cat SC4608) $10.00 - DS3231 real-time clock SOIC-16 IC (Cat SC5103) $3.00 - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) $5.00 - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) $1.50 - 10µF 16V X7R through-hole capacitor (Cat SC5106) $2.00 VARIOUS MODULES & PARTS - 15mW 3W SMD resistor (Battery Multi Logger / Arduino Power Supply, Feb21) - DS3231 or DS3231M real-time clock SMD IC (Battery Multi Logger, Feb21) - MCP4251-502E/P (Arduino Power Supply, Feb21) - Pair of CSD18534 (Electronic Wind Chimes, Feb21) - IPP80P03P4L04 (Dual Battery Lifesaver / Vintage Radio Supply, Dec20) - 16x2 I2C LCD (Digital RF Power Meter, Aug20) - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) - MAX038 function generator IC (H-Field Transanalyser, May20) - MC1496P double-balanced mixer (H-Field Transanalyser, May20) - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 $2.50 $3.00 $3.00 $6.00 $5.00 $7.50 $15.00 $25.00 $2.50 $10.00 $5.00 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. To Place Your Order: INTERNET (24/7) siliconchip.com.au/Shop PAYPAL (24/7) eMAIL (24/7) Use your PayPal account silicon<at>siliconchip.com.au Australia’s electronics magazine silicon<at>siliconchip.com.au MAIL (24/7) PHONE – (9-5:00, Mon-Fri) Your order to PO Box 139 Collaroy NSW 2097 Call (02) 9939 3295 with with order & credit card details You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. 02/21 Using Cheap Asian Electronic Modules By Jim Rowe The Geekcreit LCR-T4 Mini Digital Multi-Tester It’s hard to believe, but you can get a compact digital tester which will identify, check and analyse bipolar transistors, JFETs, Mosfets, diodes, LEDs and thyristors, resistors, capacitors and inductors for less than most joints charge for lunch these days! The Geekcreit LCR-T4 does all of the above and will cost you about $12.50, or more if you want it in a case rather than just a bare board. W hen I first saw the Geekcreit LCR-T4 advertised on the Banggood website, I thought it was too good to be true. It was described as a “128x64 LCD Graphical Transistor Tester Resistance Capacitance ESR SCR Meter”, priced at only $8.74 plus $3.94 for airmail to Australia – a total of just $12.68! I was curious and so ordered a couple straight away. When they finally arrived (about five weeks later), unfortunately, I found that one of the two LCR-T4s was damaged in transit. There was a chunk of glass broken off the top right of its LCD panel, and the bottom half of the screen wasn’t working. Luckily, the other unit worked fine, so I was able to proceed with the review. I then discovered that it is also available with an assemble-it-yourself clear plastic shell, for $21.18 plus $3.93 air parcel shipping – a total of $25.11. I ordered one of those as well, based on my positive impression of the ‘naked’ version, but it hasn’t arrived yet. Components and construction The multi-tester is built on a sin98 Silicon Chip gle PCB measuring 73 x 60mm. The only components on the front are the 128x64-pixel LCD panel with green LED backlighting, a 14-pin ZIF socket used to connect to the device being tested, and a pushbutton switch to initiate testing. The rest of the tester’s components are on the rear of the PCB, including an ATmega328 MCU (microcontroller unit), an 8MHz crystal, a 78L05 regulator, a TL431AN 2.5V voltage reference, three small SOT-23 bipolar transistors, two 1N4148 diodes and a handful of passive components. The tester uses a 14-pin ZIF socket because it provides a range of options when it comes to components with different pin configurations and spacing. Although there are only three inputs (logically labelled 1, 2 and 3), the two rows of seven pin positions on the ZIF socket are connected in this order: 1-23-1-1-1-1 (left to right). This gives you quite a bit of flexibility for connecting different devices. There’s also a small ‘D-PAK’ type array of plated copper pads for receiving SMD components, just to the right of the ZIF socket. Presumably, SMD deAustralia’s electronics magazine vices to be tested have to be pressed against the PCB to make decent contact during testing. The complete tester is powered by a standard 9V battery via a battery clip lead. It’s straightforward to use What, no power switch? Well, the pushbutton switch on the front of the PCB does everything. If it hasn’t been pressed, the tester is in ‘sleep’ mode with its current drain from the battery less than 20nA. When you do press the button, the tester springs to life. The LCD backlight immediately turns on, and the screen displays the message “Testing ...”, together with an indication of the battery voltage, like “[Vbat = 9.15V]”. Then the tester starts checking to see if anything is connected to the inputs. If it doesn’t find anything, it displays a large question mark, plus the message “No, unknown or damaged part”. But if it does find an NPN or PNP bipolar transistor, a JFET, a Mosfet, a diode, an SCR, a Triac, a resistor, a capacitor or an inductor connected to the siliconchip.com.au inputs, it works out the component’s configuration and shows it, together with some basic measurement data. And the test results are displayed for about 10-30 seconds after you press the button, before the tester turns itself off again automatically. The tester’s current drain during the actual testing is less than 25mA, so if you power it from a 9V alkaline battery, it should last for quite a while. No user guide Unsurprisingly, the LCR-T4 came without any user guide, or even any link to a source of such a guide. However, when I did a bit of Googling, I came across this link to a very detailed and informative ‘white paper’ as a PDF at siliconchip.com.au/link/ab49 It’s quite big (127 pages), and not that easy to read since it appears to be translated from German. It was originally written by Karl-Heinz Kubbeler (kh_kuebbeler<at>web.de), and in it, I was able to find some information on both the origin of the LCR-T4, how it works and how to use it. The original design, called the “AVR Transistortester” was first published by Markus Frejek in 2011, in the German publication “Embedded Projects Journal”. After that, Mr Frejek refined the design and added various enhancements. It wasn’t long before quite a few ‘clones’ of his tester began to emerge from China. At first, these variations-on-thetheme sported 16x2 LCD character displays and used an ATmega8 MCU. But soon, other versions started to appear with 128x64 pixel graphic LCDs and an ATmega328, ATmega1280 or even ATmega2560 MCU (with much more program memory). And so the Frejek transistor tester snowball kept on growing... Nearly all of the components are located on the underside of the LCR-T4 multicomponent tester module. wave generator with an output up to 2MHz and adjustable duty cycle and/ or a frequency meter with a range up to 1MHz. But they all seem to have the same basic features offered by the Geekcreit LCR-T4, with prices moving upwards according to the addition of those extra features. How it works As you’ve probably guessed by now, the LCR-T4 and the other clones of Mr Frejek’s tester work in much the same way. Given the relatively small number of external components, clearly, most of the hard work is done by the firmware running on the microcontroller. Many variants Nowadays there seem to be a lot of different variations on the original Frejek design, and you’ll find them on offer by many different vendors online. As well as the Geekcreit LCRT4, there is the Fish8840, the WEI_M8, the DROK, the FD_it TC-T7-H (also known as the DANIU LCR-TC1), the LTDZ_M328_7735 and the GM328A. Some of these come in a plastic case, others with an assemble-it-yourself case or just as a naked PCB module like the LCR-T4. Others have extra features like a built-in PWM square siliconchip.com.au Here’s the LCR-T4 testing an NPN transistor (an AY1103 made by Fairchild Australia). Australia’s electronics magazine February 2021  99 The TL431AN voltage reference allows the MCU’s analog-to-digital converter (ADC) to measure device voltages accurately. At the same time, the three small bipolar transistors enable the MCU to wake itself up and turn on the LCD backlighting as soon as the ‘GO’ button is pressed, then turn off the power and go back to sleep after the testing has finished. I think you’ll agree that it’s quite nifty. Hats off to Mr Frejek for his innovative thinking! Measurement features Now let’s look at the measurement data displayed for the different devices the LCR-T4 can test. 1) For silicon, germanium or schottky diodes, it displays the an100 Silicon Chip ode and cathode connections (ie, the orientation), the forward voltage drop (Uf), and the junction capacitance (in pF) when the diode is reverse-biased. LEDs can be tested as well, with the tester displaying them as a diode with a higher-than-usual forward voltage. 2) For NPN and PNP bipolar transistors, it shows the pin connections for the base, emitter and collector (B, E and C), the current gain, hFE (also known as Beta) and a voltage reading “Uf”, which appears to be the baseemitter voltage during low-current conduction. When I checked several silicon BJTs, the Uf readings were always over 600mV, while for germanium BJTs, the Uf readings were generally below 200mV. 3) It’s claimed to be able to test Australia’s electronics magazine Darlington transistors, giving the same parameters as for regular BJTs. But when I tried testing a few Darlingtons, it didn’t seem to recognise that they were Darlingtons and gave relatively low hFE readings. So I would not recommend testing Darlingtons with this device. 4) For JFETs and depletion mode Mosfets, it displays the pin connections for the gate, source and drain, plus the orientation of a protective diode if it finds one present. It also shows the gate-source threshold voltage (usually written Vgs, but labelled “Vt” here) and the gate-source capacitance, Cgs. 5) For the far more common enhancement-mode Mosfets, it again shows the G-D-S pin connections plus the orientation of a protective diode if siliconchip.com.au it finds one. It also indicates the gatesource threshold voltage (“Vt”) and the gate-source capacitance, Cgs. 6) With SCRs and Triacs, it basically just identifies them and shows their pin connections. 7) For resistors, it measures and displays the resistance. The rated measurement range is from 0.1W to 50MW, and when I checked a fair number of reference resistors, it gave readings better than ±2% for values between 50W and 2MW. Below 50W, the error gradually rose to +7% at 10W, while above 2MW, it gradually increased to -4.4% at 50MW. That isn’t wonderful, but not bad for a low-cost tester making two-terminal measurements. 8) For capacitors, it measures and displays the capacitance. The rated measurement range is from 25pF to 100,000µF, although for capacitors with very high values, the measurement time can extend beyond one minute. For capacitance values 1µF and above, the tester also displays the capacitor’s ESR (equivalent series resistance). I checked quite a few reference capacitors with values between 25pF and 10µF, and obtained readings accurate to within ±2% over this range. Not bad for a low-cost tester. 9) With inductors, it measures and displays both the inductance and resistance. The rated measurement range is from 0.01mH (10µH) to 20H. I checked 14 different reference inductor values from 27µH up to 1.09H, and obtained readings that were within ±6% for values of 1mH and above, but rising to ±30% for lower values. The series resistance readings given were all quite sensible. The bottom line After testing the LCR-T4 mini multitester fairly thoroughly, I think it’s a ‘little blooming wonder’ and excellent value for money. I have a few small gripes, though. One is the lack of any user guide, forcing you to search the web and digest Mr Kubbeler’s big ‘white paper’. Then there’s that lack of clarification for the exact significance of the Uf reading for bipolar transistors. And thirdly, in its naked form, the tester is really quite fragile – which explains why one of the two units I ordered was damaged in transit. So I’m looking forward to receiving the siliconchip.com.au The LCR-T4 can measure capacitors from 25pF to 0.1F with an accuracy of about 2%, and inductors from 10µH to 20H with a worst case accuracy of 30%. matching assemble-it-yourself plastic case that I ordered recently. One last comment: if you compare the LCR-T4 with my Semtest Discrete Semiconductor Test Set design (February, March and May 2012; siliconchip.com.au/Series/26), you will see that there are huge differAustralia’s electronics magazine ences between the two in complexity and cost. The Semtest offers more tests, but Mr Frejek’s design is clearly very elegant. So all in all, the LCR-T4 may not be a complete replacement for the SemTest, but it will undoubtedly make a very handy companion tester. SC February 2021  101 Vintage Radio Philips Philips BX205 BX205 B-01 B-01 superhet superhet radio radio This 1950s valve radio is switchable between AM broadcast band and shortwave reception. Strangely, it uses battery valves but does not have a battery compartment, and it also has no internal antenna. Nor does it have any stations marked on the dial. It’s a bit of a head-scratcher! I bought this radio a couple of years ago on eBay. It didn’t work, and as I couldn’t immediately figure out why, I got bored with it. So it sat in a corner (metaphorically speaking) for quite a while. With the previous lockdown in Melbourne, “one of these days” finally arrived, so I decided to resurrect it. Its tuning covers two bands: the usual medium-wave band from 530kHz to 1600kHz, plus a shortwave band from about 5MHz to 16MHz. It uses four battery valves with 1.5V filaments, but there is no battery compartment. It came with a cord attached, but no plug on the end. Presumably, the idea was that you wired it up to 102 Silicon Chip a pair of batteries hidden away in a nearby cabinet. As it has no internal loop or ferrite rod antenna, it requires an external antenna. It doesn’t seem to be a model made specifically for Australia as the dial does not show radio station names, just a rough indication of frequency and wavelength. When I got it, the radio was in reasonable condition, with only minor scratches on the Bakelite case. To remove the chassis required removal of the rear heavy cardboard cover, two screws that held the chassis in place, and the knobs. The loudspeaker looked rather moth-eaten with a couple of holes, but seemed workable. Australia’s electronics magazine By Charles Kosina The speaker transformer is in an unusual large cylinder at top right, visible in the top view of the chassis. The bottom view shows the messy wiring which is typical of radios of that era. It makes modifications somewhat tricky. The circuit diagram (Fig.1) shows that it is a fairly standard design. The copy I managed to download did not have very readable lettering, but with the aid of Photoshop, I cleaned it up. I also added the component values and pin numbers for the valves. That made circuit tracing much easier. One of the banana sockets on the back of the set is for a ground connection and the other two are the antenna inputs. The top one connects directly to the input coil (S1 or S3) via the band selection switch. The second connection is via 100kW resistor R14 and is marked for LOCAL stations. I think that the station would have to be awfully close to get through that much attenuation. The input transformer secondaries (S2 or S4) are applied to grid 3 of B1, the DK92/1C2 pentagrid valve, again via the band selection switch. The local oscillator uses grids 1 and 2. The tuning capacitor is a two gang unit, C4 and C5. Band changing The switching between the two bands is rather complex, and interpreting the diagram is no mean feat! On the antenna coil side, it is essentially a 4-pole, 2-position switch. Two poles are used for switching the antenna between the mediumwave, S3 coil and the short wave S1 coil. The other two poles switch grid 3 of B1 between the tuned secondary coils, S2 and S4. The local oscillator gets a bit more complicated. The medium-wave tuning range is 985kHz to 2050kHz, ie, 450 kHz above the tuned input frequency. The padding capacitor C14 (476pF) is siliconchip.com.au Fig.1: I added the component values to this original circuit for the BX205 B-01. Note the switched (++) and unswitched (+) supply connections and the somewhat complicated band-switching arrangement. A single wafer switch is used to select between two sets of antenna coils and oscillator coils. effectively in series with tuning capacitor C5 for reasonable tracking with the signal input frequency. There are three coils on the shortwave oscillator, with two of them connected by 120pF capacitor C11. This appears to be an alternative way of tracking the oscillator with the input signal. Switching between the two bands is again by a four-pole, two-position switch in the same assembly as the others. The difference frequency of 450kHz passes through a double-tuned IF transformer (S11-S14) and is then amplified by variable mu pentode B2, a DF91 or 1T4. This is followed by another double-tuned IF transformer (S15/S16) feeding the diode in B3, a DAF91/1S5. As well as the envelope detection for recovering the audio, the filtered negative DC component is used to provide AGC to the two previous valves via 1.5MW resistor R4. The audio is then amplified by the pentode section of B3, and feeds into the grid of “power amplifier” B4, a DL94 or 3V4. A transformer (S17/ S18) couples this to the loudspeaker. The gain of these battery valves is not that high, so it can’t be wasted by having any negative feedback in the audio stages. Not shown on the circuit diagram is a connection to two screw terminals siliconchip.com.au on the side of the case. These connect to either end of the volume control R6, and are provided for external audio input. The audio signal from the radio is applied to R6 via 56kW resistor R15, so the external source should easily be able to ‘short out’ the audio from the radio (which presumably would be tuned off-station). Power supply Note that the power supplies do not have a common earth. The 90V negative goes via 560W resistor R13 to chassis Earth, resulting in a grid bias voltage of about -1.8V for the DL94. The 90V supply is connected directly to the anode circuits of B2 and anode and screen grid of B3, not via the switch. I’m not sure of the reason for this, but perhaps it keeps some capacitors charged up, preventing a thump from the speaker on turning the power on. Restoration Coupling capacitors are likely to be leaky after all this time, so I replaced C22 and C24 with modern high-voltage types, and also increased their values to 220nF. I fitted a suitable plug on the power cord and connected it to a mains supply that can deliver 90V and 1.5V. There was no sound at all from the speaker, so out came the chassis. The first thing I did was to test the continuity of the filaments in all the valve. Sadly, the DAF91 had an open filament. I decided to work backwards; connecting a signal genera- A close-up of the Philip BX205’s dial. Australia’s electronics magazine February 2021  103 tor to the grid of the DL94 provided a clean tone in the loudspeaker. At least this proved that the output valve and speaker transformer worked. The next problem was the defunct DAF91. Searching various websites, I found that this type is available, but at prices ranging from $26 to over $80, more than I paid for the entire radio! Valve substitution Fig.2: this is the circuit that I ‘juryrigged’ up to replace the open-circuit DAF91 diode pentode valve. It uses a JFET to perform a similar role to the pentode, plus a schottky diode for demodulation. I fitted this to the underside of the chassis and left the defunct valve plugged in for the sake of appearance. Fig.3: another cobbled together fix, this time for an open-circuit antenna coupling transformer. It’s made up of four separate chokes and relies on coupling through proximity; while it may seem crude, it works just fine. I did not want to hold up getting the radio working, so I decided on a workaround. My approach will no doubt offend the purists! How many of you are old enough to have heard of Fetrons? Teledyne Semiconductors made plug-in solid-state replacements for a number of different valve types. Editor’s note: In next month’s issue of Silicon Chip we’ll have a detailed article on Fetrons. They consist of two N-channel JFETs connected such that they have similar characteristics to a pentode valve. They are no longer available, and never were for this valve. But I thought I could whip up something similar. I decided on a simplified approach of using just one JFET and used the only type that I have in stock, a J310 (2N5484) to replace the pentode section. The arrangement that I came up with is shown in Fig.2. The 1MW resistor (R10) in the radio circuit is far too high for a drain load of the FET, so I reduced this to 33kW. This resulted in a drain voltage of 13V, well within the maximum rating of 25V. If we compare the performance of the JFET configured thus with the valve, they are surprisingly similar. The DAF91 has a transconductance of around 720µ℧ (or microsiemens, if you prefer). The load resistance is the parallel of R10, R12 and Ra (the plate resistance) which comes to 250kW. Hence, its voltage gain is 180 times (0.72µ℧ × 250kW). Doing the same calculation with the JFET, the current through it is about 1.9mA. This gives a Yfs of about 8500µ℧ and Yos of around 20µ℧, or 50kW. The effective load resistance is the 33kW in parallel with the 50kW, ie, about 20kW, resulting in a gain of about 170; not far short of the pentode. I left the defunct DAF91 valve plugged in as it does nothing; it’s just for show now. The JFET circuit plus the schottky 1N5711 diode replace its functions. Now I had the audio stages working, but injecting a signal into the antenna terminals still produced nothing. Putting a scope on the oscillator coils showed that the local oscillator was not working on either band (medium or shortwave). Faulty transformer Rather than trying to analyse what was at fault, I decided to replace all the capacitors in the oscillator section, and sure enough, the oscillator fired up The DAF91 diode pentode valve (B3) was open-circuit and therefore replaced with a circuit based around a J310 JFET shown in Fig.2. This is shown at the base of B3 which is circled in white below. 104 Silicon Chip Australia’s electronics magazine siliconchip.com.au The BX205 B-01 could be considered a portable version of the previous BX205U /00/ 35 & BX205U (a 5-valve mains powered superhet). The circuits between the BX205 and U-series are somewhat similar with some changes to account for one less valve and the use of an A & B battery instead mains. on both bands. However, I still could not receive anything from the antenna input on MW. Injecting a signal directly into grid 3 of the DK92 worked. This led me to suspect the input coil, and sure enough, the S4 winding was open-circuit. Taking apart the input transformer required much care, as the aluminium case is just pressed into place, and I had to prise it apart. The damage was then apparent. The HF input coils appeared intact, but the MW winding had loose, thin wires hanging off it. These are extremely thin wires, and after some attempts at repairing it, I decided it was just not possible. The thin wires would not accept solder at all. This presented something of a dilemma, so I came up with an alternative, shown in Fig.3. I used my collection of inductors to cobble up a suitable substitute that would fit in the case. The input from the antenna is ap- The chassis of the BX205 B-01 was rusted and the speaker grille had started to disintegrate. The non-working DAF91 valve (B3) was left in place as it has no impact on the rest of the radio. C1/2 S17 S10 S8 S11-14 B1: DK92 S2 S18 B2: DF91 B3: DAF91 B4: DL94 C4/C5 S4 siliconchip.com.au Australia’s electronics magazine February 2021  105 105 On the left is the short wave input transformer S1/S2, which is intact. The faulty S3/S4 was replaced by fixed inductors L1-L4. plied across a 10µH coil (L1). This is placed alongside a 100µH coil (L2). The side-be-side arrangement results in good coupling between the coils. I then added a 220µH coil in series with L2. The resulting total of 320µH was a bit too high for the tuning range of C4, so I added a 1000µH inductor, L4, in parallel which resulted in an effective value of 242µH. This may not be the exact value needed, but it was close enough so as not to adversely affect the tracking and performance. Alignment The standard alignment procedure is to set the receiver near the top of the frequency range, say 1500kHz, and adjust trimmer C7 for maximum output. Then the receiver is set to the low end, say 600kHz, and the inductor is trimmed. Obviously, I could only make the top-end adjustment, and as it turned out, the sensitivity at the low end was comparable, which meant that my inductance value must have been close enough. Fig.4: the set’s frequency response is down by 3dB at 60Hz and 3.3kHz. heavily polluted by hash from all the electronics inside. More accurate measurements with a signal generator showed that it requires about 10µV for something useable, but more like 100µV for a decent sound. This did not vary much over the range of either the MW or SW bands. It could probably be slightly improved with tuning the various coils, but quite frankly, I dared not touch them as by now they could be awfully brittle. I did a frequency response graph from the antenna to the speaker, shown in Fig.4. While the response at 50Hz is only down by 3.9dB, the waveform is extremely distorted, and the sound from the small speaker is minimal. The primary inductance of the speaker transformer is obviously not high enough for this frequency. The high-frequency -3dB point is about 3.3kHz, and by the time we get to 5kHz, the response is well down. This is primarily determined by the intermediate frequency bandwidth of the set. Without negative feedback, there is noticeable even harmonic distortion in the Class-A audio output stage. This is evident in Fig.5, which is a scope grab of the output just before clipping sets in. Unlike odd harmonic distortion, even harmonic distortion is not particularly objectionable, so the sound with a strong station is acceptable. The maximum power output is about 250mW, quite adequate for this sort of radio. SC Performance I decided it was time to install a proper outdoor antenna. I ran about 10m of wire between a 5m-tall mast at my back fence and a short mast on the metal roof. I connected the shield of the coaxial cable lead-in to the roof. The results were amazing; all the Melbourne stations came through cleanly with little noise between stations, and on shortwave, there were many stations with strong signals in the evening. By comparison, using a piece of wire indoors gave a signal 106 Silicon Chip Fig.5: as the set lacks any feedback around the output stage, there is plenty of second-order harmonic distortion in the output waveform. At least it is more pleasant-sounding than odd-order distortion! Australia’s electronics magazine siliconchip.com.au ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Epoxy for High Power Ultrasonic Cleaner I want to build your High Power Ultrasonic Cleaner (September & October 2020; siliconchip.com.au/Series/350), but I have found multiple J-B Weld epoxy products and am not sure which one to use. (M. T., Auckland, NZ) • We recommend using the original J-B Weld epoxy. It is sold by Jaycar (Cat NA1518). Charging USB host and OTG devices Is it possible to power a host USB device and USB accessory at the same time? I have found a lot of confusing and contradictory information concerning this question. There seems to be a standard, but I am unsure how the system is actually implemented. (T. F., via email) • Perhaps not all devices implement the standard correctly, but it does support charging both the host and accessory using a “USB Accessory Charger Adapter”. There is no technical reason why it should not work. See Wikipedia for more details: https://w.wiki/t76 https://w.wiki/t77 Updating Colour Maximite 2 firmware I have been enjoying MMBasic and the Colour Maximite 2 (July-August 2020; siliconchip.com.au/Series/348) for some time now. We are up to CMM2 V5.06.00, and things are looking good. The problem I have is with loading new firmware into the Colour Maximite 2 using the USB-A to USB-A cable in the keyboard port. I used this method twice successfully with the STM32Cube Programmer software in Windows 7, but now it will not detect the Maximite any more. I had to take the case apart and slide the BOOT switch to SYSTEM and try again, and now everything is back to normal – the software detected the siliconchip.com.au Maximite, and I could upload the latest firmware. Is there some way to fix this? I prefer to avoid pulling the case apart and switching the boot config switch whenever I need to load new firmware, even though I don’t have to do that every day. (R. S., Epping, Vic) • Geoff Graham responds: There is no known problem related to loading firmware upgrades on the Colour Maximite 2. It sounds as if there is some confusion with the UPDATE FIRMWARE command. This is equivalent to setting the BOOT CONFIG switch to “SYSTEM”, but this will only work when using the alternative method of loading the firmware via serial transfer over USB. It will not work when using the USB-A to USB-A cable in the keyboard port because you cannot use the keyboard to enter the command in the first place. When using this method, you must open the case and set the BOOT CONFIG switch to “SYSTEM”. Flashing LEDs on Ultrasonic Anti-Fouling We purchased, built and installed your Ultrasonic Anti-Fouling units (May & June 2017; siliconchip.com. au/Series/312) two years ago. Recently, the power LED suddenly stopped flashing. After two years of fabulous service, and a lovely clean bottom, we were taken aback. We found the 3A fuse had blown and replaced it. The green power LED came on, but did not stay on. No fuse blew, no fault light showed. We then replaced REG1 (LP2950ACZ) and carefully monitored the slow start-up. The green power light came on for approximately five seconds, went off, and the fault LED started a slow flash. We replaced both 2200µF capacitors, but no joy. Again, the green power LED lit up, but this time, the power light went off quickly, and a few seconds later, the fault LED started flashing. Australia’s electronics magazine Many thanks for this brilliant kit, and any help you can offer to get it back working. (W. B., Vancouver, Canada) • You could have a faulty driver Mosfet (Q1-Q4) or the transformer windings might have failed (unlikely but possible). Check the Mosfets for short circuits between the drain and source pins (if there is one, you will get a low ohms reading regardless of the lead polarity). If they check out OK, the problem may be that the soft starting feature has found fault with the low-ESR bypass capacitors, where there is current leakage. You could add in a resistor across the drain and source of Q5 to counteract the leakage so the circuit will start up. This can be done on the underside of the PCB. A 330W 1W resistor should counteract any leakage. Increasing boost supply output power I want to build a switching DC/DC converter to drive an audio power output valve from a low-voltage DC supply. I was thinking about modifying the supply from your Valve Stereo Preamplifier For HiFi Systems (January 2016; siliconchip.com.au/ Series/295) to do the job. I need about 1-2W continuously at about 250V, and maybe 3-5W peak. What changes do I need to make to your circuit to achieve this? I checked the data sheet for the MC34063 switching regulator IC, but it doesn’t give any details about using it to drive an external Mosfet as you have done in your circuit. The data sheet gives formulas involving the Vsat value of an external bipolar transistor. Do I use the Vgs(th) value of the Mosfet instead? (J. H., Glasgow, Scotland) • First, let’s cover your question about the Mosfet. When you’re substituting a Mosfet for a bipolar transistor, replace Vce(sat) with Rds(on) multiplied by the expected drain current (Id). Presuming that Vce(sat) was calculated using the peak current value, use that same current figure as Id. You February 2021  107 will need to know the Mosfet’s operating Vgs to determine the correct value for Rds(on). As for boosting the output power of our circuit, we calculate that the total current drawn by the 12AX7 in our design is 4mA, so at 250V, that’s 1W. And as described in that article, the converter is running flat out to achieve that. Increasing that to 2-3W is not going to be a simple job, but it’s probably possible. Start by reducing the value of the resistor between pins 6 and 8 of REG2 and loading up the output to see what it can deliver. We suggest the first test should be with a 0.1W resistor. If you can’t increase the output power to your desired level, the next step is to substitute a larger inductor for L1. Try a 100µH 3-5A toroidal inductor. You might get better results with a different inductance value. You can probably lower the resistor value further with a larger inductor. You will find it easier to achieve the desired output power with a higher input voltage, up to the maximum that the MC34063 and input capacitors can handle. That limit is 24V with the circuit as presented, or up to 40V if you increase the capacitor ratings. NiMH cell recharges suspiciously fast Recently, I decided to test several AA-size NiMH used cells that had been out of use for several years. It was no surprise that many were totally flat, but several showed an open circuit voltage of 0.6-0.8V. I have a mains charger with a 25V AC input that can charge two or four AA cells. The charger has a red & green LED indicator that flashes slowly when the cells are placed in the charger, then a steady red for about 20 seconds, then a steady green indication which suggests that the cells are fully charged. I find it hard to believe that halfflat AA cells can be fully charged in 20 seconds, although I measured their open-circuit voltage at 1.33V! Given that I know very little about the charging characteristics of NiMH cells, could you refer me to an article that would answer my query? What is a safe rate of charge for AA sized cells? Have you published an article or a construction kit with instructions to build a reliable charger with enough capacity to charge up to 108 Silicon Chip D-size NiMH cells? (R. W., Loxton, SA) • NiMH cells are typically charged at a ten-hour rate. So a 1000mAh cell would be charged over 10 hours at 100mA. Fast chargers require an endof-charge detection method, typically either using the drop in voltage of a cell (dV/dt) once charged, or via a rise in temperature (dT/dt) at the end. The cell(s) that charged in 20 seconds would have little charge capacity and are probably high-impedance and therefore no good. The voltage would drop as soon as a load is placed on it. A good cell would not rise to 1.3V so quickly. We have published many suitable chargers over the years, including the following: ■ SuperCharger for NiCd & NiMH batteries, November & December 2002 (siliconchip.com.au/Series/111) ■ A Fast Charger For NiMH & Nicad Batteries, September 2007 (siliconchip.com.au/Article/2337) ■ Float charger for NiMH cells, June 2010 (siliconchip.com.au/Article/180) ■ Burp Charger For NiMH & Nicad Batteries, March 2014 (siliconchip. com.au/Article/6730) ■ Intelligent Charger for Nicad & NiMH Batteries, July 2015 (siliconchip. com.au/Article/8677) Repairing speakers with substitute tweeters I have a pair of Sansui SP 1000 speakers, rated at 50W/8W. Each has two 20W 16W tweeters connected in parallel, and all four are open-circuit. Trying to source replacement/substitute tweeters is difficult, so would it be OK to use two 20W 8W tweeters in series? These speakers are 49 years old and have some sentimental value. (R. S., Humpty Doo, NT) • It is difficult to answer that question without knowing more about the original tweeters and the replacements, specifically, their respective sensitivity ratings in dB/W at 1m. You need those figures, plus the impedance numbers, to figure out how to correctly match the new tweeters to the existing speakers. For example, say that you connect the two new 8W tweeters in series, then connect a high-power 16W resistor in parallel with the pair. That will give you the same 8W impedance as presented by the original pair, but with 6dB less signal going to the tweeters Australia’s electronics magazine (the rest of the power will be dissipated by the resistor). If the new tweeters are 6dB more sensitive than the old ones (which is possible), that would be a good arrangement, giving you a similar balance of high and low frequencies as before. Otherwise, the result could sound too bright or too dull. Your suggested configuration will probably change the way the crossover works as the tweeters will have twice the original source impedance. Without knowing the details of the crossover design, it’s hard to say what effect that will have. Regardless of what you end up doing, you might need to make further changes (eg, adding padding resistors) to match the tweeter volume to the other drivers in the system. Higher power valve amplifier wanted I am currently building my second Currawong valve amplifier (November 2014-January 2015; siliconchip. com.au/Series/277). In past issues, you mentioned that you might develop a higher-powered version. Have you found ways to increase its power beyond 10W/channel? (C. J., Samson, WA) • The limiting factor in the output power of the Currawong is the pair of 15W output transformers. The 6L6s certainly should be capable of considerably more than they are delivering in this design, although they would likely need a higher anode voltage. When we looked at this in the past, we found that higher wattage output transformers were prohibitively expensive. The Currawong is costly enough to build in its current form already, so we didn’t think it was worthwhile to do the engineering work to design a higher-power version as it would probably cost over $1000 to build. A keen constructor might be able to figure out how to fit upgraded output transformers, change the power supply to deliver higher voltages to the 6L6s (but not the 12AX7s!) and obtain perhaps 20-30W per channel. But we just don’t think it’s worthwhile when solid-state amplifiers with much higher outputs power ratings, lower distortion, lower noise and with flatter frequency responses can be built for significantly less money. siliconchip.com.au Building a mains-based PortaPAL-D with effects I would like to build your PortaPAL-D portable PA system (December 2013-February 2014; siliconchip. com.au/Series/177), but I want it to be powered from the mains, not a battery. I also want to add the Digital Effects Processor (October 2014; siliconchip. com.au/Article/8033). My question is concerning the power supply. If I install the transformerbased dual rail power supply for the power amplifier, how can I get the +12V single rail supply for the Microphone input PCB and the Digital Effects Processor? I don’t think I can just step down one side of the dual rails, as the transformer ground will be shorted to the signal. What do you suggest? (V. S., via email) • That should be possible. The PortaPAL-D is based on the CLASSiC-D amplifier which originally used a mains power supply (that we published in December 2012) which produced ±57V and optionally ±15V rails from an extra set of transformer secondary windings, or a second lower-voltage transformer. Those extra components were not shown in the article, as the CLASSiCD did not need them, but the PCB has provision for them. The 7815 on that board could be changed to a 7812 to produce a +12V rail. A separate +12V supply from something like a plugpack or open-frame switchmode supply could certainly be used, as long as the two supply grounds are joined. Model train controllers damaged by short circuit I have purchased a few PWM train controllers off “fleabay”, but for some reason that no-one can tell me, I have lost the ability to control the speed. They give full power all the time. Do these controllers “blow up” if a train derails and causes a short circuit? Have you designed, or can you point me in the right direction for a topnotch PWM DC controller? I would like to use PWM on my two model train layouts, taking full advantage of the slow running speed that the usual transformer won’t allow. Scale speed is what I am after. I would also like a forward/off/reverse switch and speed control potentiometer. siliconchip.com.au Others who have tried to help me suggested adding a self-resetting thermal cut-out (whatever that is). I wouldn’t have a clue where to put one, and I cannot seem to find a 1A version anyway. (R. L. B., Pine Mountain, Qld) • It is possible that a short circuit could have damaged the PWM controllers you bought. You could try connecting a PTC between the controller and one of the tracks. It would need to be rated for a trip current slightly higher than the controller’s rated current. But we aren’t sure that this would prevent those controllers from being damaged. We published the Li’l Pulser PWM train controller in July 2013 (siliconchip.com.au/Series/178) and a revision in January 2014. It has short circuit protection and forward and reverse as well as speed control. We think it will do exactly what you want, and will not be damaged easily. Ignition system failure in an older car I built your High-Energy Ignition System for Cars (November & December 2012; siliconchip.com.au/ Series/18) from a Jaycar kit (KC5513) and installed it in a classic club car. It appeared to be working fine. However, after about ten hours of driving, the system failed. I found that REG1 (LM2940CT-5) had overheated and its ground return track had fused and burnt the PCB. Also, the label affixed to IC1 had melted away in its centre. Do I need to make changes to the circuit for better reliability? (B. C., Dungog, NSW) • The High Energy Electronic Ignition Module is generally very reliable. We think the return current for the coil ran through the PCB tracks rather than the connection to the case, due to a poor ground connection. Having fixed that, it also wouldn’t hurt to incorporate the extra protection components that we used in our Improved Jacob’s Ladder project from February 2013 (siliconchip.com.au/ Article/2369). It includes extra protection for the regulator, especially where the coil connection lead is adjacent to the power supply leads. Triggering a PIC from a high voltage source I am having a most aggravating time Australia’s electronics magazine with your High-Energy Ignition System (November & December 2012; siliconchip.com.au/Series/18). I have blown up three PIC microcontroller chips, and cannot understand why. I am hoping you can help. I have a dated two-stroke engine driving a vital piece of agricultural equipment, and the CDI ignition system has failed with no spark. I am unable to source a replacement part. I have been trying to manufacture a replacement ignition system using your High Energy Electronic Ignition System project. There is a signal on the HT lead, around +90V going rapidly to about -90V when unloaded, as the magnets on the flywheel pass the poles of the CDI unit. I hoped to use this as a timed trigger signal. I have attempted to condition this signal with increasing severity, but on each attempt, the PIC microcontroller input still fails. I currently have a 5V zener to clamp the voltage at the PIC pin, with a series resistor, plus capacitors before and after the resistors and another 27V zener with a series resistor closer to the signal source. Can you offer any advice or suggestions as to why my attempts to clamp this signal to 5V have failed? I still have one unused PIC chip. (D. L., St Andrews, Vic) • The unloaded CDI coil might be producing brief transient high peak voltage that destroys the PIC input despite your zener clamps. Zeners don’t always have a sharp ‘knee’, and the voltage across them can be significantly higher than expected if enough current is applied. Perhaps a better way to protect the PIC would be to use a transformer to step down the voltage, such as a strobe trigger transformer (eg, Jaycar MM2520) with the secondary connected to the CDI coil, and the primary to the PIC input (via the protection zeners and shunt capacitors). That might give you sufficient signal to drive the PIC input. Note that the CDI coil should be loaded with some resistance to reduce voltage transients. Alternatively, use a 6N138 optocoupler (a 4N28 might be fast enough) to provide voltage isolation. You would still need to have sufficient voltage protection for the LED in the optocoupler using zeners, a limiting resistor and a shunt capacitor like in your circuit. February 2021  109 CDI wanted for a two-cylinder engine I’m looking for a type of capacitordischarge ignition system (CDI) to install on a small two-cylinder engine that could still retain the original points. I’m just looking to take the high power draw off the points. Would your replacement CDI Module for Small Petrol Motors from May 2008 (siliconchip.com.au/ Article/1820) work for this? Do you have preassembled units or parts kits? I could not find any of this when I was directed away from your legacy website. (M. W., via email) • The May 2008 CDI Module is designed for motors with a trigger coil and a high-voltage generator coil. If you have points, then that CDI unit is not suitable. We don’t sell fullybuilt versions, but we can supply the PCB – see siliconchip.com.au/ Shop/?article=1820 For points-based ignition systems, our High-energy Ignition System (November & December 2012; siliconchip. com.au/Series/18) is suitable, provided there is a 12V supply available. Soft Starter for halogen lamp I have been having trouble with a bedside lamp fitted with a 28W halogen candle globe. We have a pretty constant 250V here, and this lamp has frequently been blowing globes at switchon. I remember reading quite a while ago about a soft starter for lamps, so I searched and found the Soft Starter listed in April 2012 (siliconchip.com. au/Article/705). The article I was thinking of was much earlier, but I went ahead and built this project anyway, and it seems to be working OK. However, there is no visible difference when first turned on and when the relay cuts in. It is just as bright as without the soft starter. I looked back at the article and realised that it was designed for highcurrent applications, and using it for a lamp may not be the best choice. The lamp has a steady current of 125mA and a cold resistance of 250W. The 10W thermistor with a current capacity of 15A may not have enough resistance to limit the current at switch-on. I thought maybe I should replace the thermistor with one of about 80W or 110 Silicon Chip so. This may provide more of an initial voltage drop to protect the lamp. (B. D., via email) • You certainly could do that. Try the MF72-400D9. It is cheap and rated for mains use. Its maximum steady-state current is 200mA so should be sufficient, and its cold resistance of 400W will reduce the initial current by about two-thirds, giving a much more gradual filament warm-up. Soft Starter modifications In reference to the Soft Starter from April 2012 (siliconchip.com.au/ Article/705), could I use a more readily available 12V DC coil relay instead of a 24V type? Obviously, the X2 capacitor and zener would need to be adjusted, and some resistors to keep the delay constant. In terms of decreasing the temperature and/or longevity of the thermistor, to use it with SMPS, LED lighting and computer equipment with a maximum continuous current of around 1A, could several thermistors be put in series (or parallel)? (B. A., Dee Why, NSW) • We did not use a 12V relay because it doubles the power drawn from the mains and requires a considerably larger capacitor. You would have to increase the X2 capacitor to at least 330nF. If it does not work reliably, try 470nF. As you said, you would also need to change ZD1 to 12V. You would also, as stated, need to roughly halve the value of the resistor which charges the delay capacitor for a similar delay to the original design. You can put several thermistors in series or parallel, but note that the softstart effect will be stronger if they are in series and weaker if they are in parallel. If the equipment is only drawing around 1A, then a series connection is the best option. A series/parallel combination of four thermistors could also be used and would give the same soft starting capability but with much less heat per thermistor. That’s assuming you could fit them all in the box. Using the Soft Starter with a bore pump I am looking at the Mains Soft Starter for Power Tools project from July 2012 (siliconchip.com.au/Article/601), and Australia’s electronics magazine I am wondering whether it is suitable for powering a single-phase (capacitor start) bore water pump of about 1.5kW nameplate rating. There is a noticeable torque/kick that physically moves the pump every time the low-pressure switch needs to activate – which is many times per day. I think it would be beneficial for the general longevity of the motor and pump components if a soft start controller could be implemented. Whether this circuit is exclusively for universal serial wound motors only hasn’t been conveyed in the original article, and would guide my attempt to implement this as a workable solution. (C. T., Sunnybank, Qld) • It’s possible that the Soft Starter would help in your case, but we do not think so. You have three things working against you trying to use a simple soft-starting circuit with an induction motor: 1) You’re reducing the voltage/current but not the supply frequency, so the motor torque will be very low during the soft-start phase; it probably won’t be enough to get it spinning, which means that it will still hard-start once the relay switches on. 2) The pump is presumably always primed, so it’s starting under load and therefore will need to draw a significant current to spin. The Soft Starter was intended more for use with motors which start up off-load or have a very brief initial current draw like most power tools, or devices with switchmode power supplies. 3) During the initial phase, if the motor doesn’t spin, it’s going to draw a lot of current and get rather hot (although the limited soft-start time means that it’s unlikely to be damaged). The Soft Starter is not exclusively for universal motors, but it is far from ideal for induction motors. It might work with some small induction motors, such as the shaded-pole motors often used to drive fans. Our 2012 1.5kW Induction Motor Speed Controller (siliconchip.com.au/ Series/25) would do what you want as it has a soft start feature, but it is much more complicated and expensive and only just rated for your application. Substitute low-noise PNP input transistors I am gathering parts to build a stereo continued on page 112 siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP PCB PRODUCTION KIT ASSEMBLY & REPAIR PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com FOR SALE GREAT VALUE PARTS and more are found in the Tronixlabs eBay store via tronixlabs.com.au – for enquiries or support please email support<at> tronixlabs.com LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote, quote photo numbers when referring to a book: silicon<at>siliconchip.com.au DAVE THOMPSON (the Serviceman from S ILICON C HIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com Silicon Chip Binders REAL VALUE AT $19.50 * PLUS P & P Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of SILICON CHIP. They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. Silicon Chip Publications Order online from www. siliconchip.com.au/Shop/4 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, ad­ dress & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. 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 February 2021  111 Notes & Errata Busy Loo Indicator, January 2021: at the bottom of the left-hand column on p79, where the text says the inputs of IC1b are normally high, it should read IC1d instead. Mini Digital AC Panel Meters, January 2021: if the current transformer secondary is not terminated with a low impedance, it will generate a very high (and potentially dangerous) voltage if any significant AC current is flowing in the primary. So make sure to connect the secondary leads of the CT to the panel meter before any current is allowed to flow through the primary. Radiating test antenna for AM Radios, Circuit Notebook, January 2021: the ferrite rod is 200mm long, not 400mm as stated in the text. Vintage Battery Radio Li-ion Power Supply, December 2020: on page 28, the text refers to a 220µF capacitor being charged via a 220W resistor. The capacitor value is actually 10µF. Colour Maximite 2, July & August 2020: the SD card socket specified for this project (Hirose DM1AA-SF-PEJ(21)) is being discontinued by the manufacturer. Instead, use the DM1AA-SF-PEJ(82) which costs the same and fits the existing footprint on the PCB. The March 2021 issue is due on sale in newsagents by Thursday, February 25th. Expect postal delivery of subscription copies in Australia between February 23rd and March 12th. Advertising Index Altronics...............................21-24 Ampec Technologies................. 37 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology............ OBC Ocean Controls........................... 5 Silicon Chip Binders............... 111 pair of Ultra-LD Mk.3 amplifier modules (March-May 2012; siliconchip. com.au/Series/27). The transistors specified for Q1 and Q2, 2SA970 lownoise PNP bipolar transistors (BJTs), seem to be no longer available. I am considering using KSA992s as a substitute. Do you think this will compromise the performance of the amplifiers? (I. S., Mitcham, Vic) • The KSA992 looks OK. It’s hard to be sure because the way they specify the noise voltage in the data sheet is not very useful. We don’t think you will notice the difference (if any). We can see some online sellers offering 2SA970s, but we think many of them are counterfeit parts. Some people have said that the clone parts work well, while others say they are not low-noise types; it probably depends on the luck of the draw. Your suggestion of using KSA992s is safer since you can get them from a reputable supplier. Old remote preamp not recommended I was browsing old issues of Silicon Chip and found a project by John Clarke called the Stereo Preamplifier with IR Remote Control (September & November 1993; siliconchip.com.au/ Series/168). Since then, many newer designs have been published like the Ultra-LD Stereo Preamplifier & Input Selector 112 Silicon Chip that I am happily using together with the Ultra-LD Mk4 amp. What caught my attention was the absence of a volume pot and the LED display. I was wondering if that design is still valid and if I could build it? I’d need to find a few replacement components that’d be obsolete by now. I checked that I could source the microcontroller online; however, I have no way to program it. Do you have any advice on this? (O. A., Singapore) • That Preamplifier would be extremely difficult to build at this late date, as many critical parts would be very difficult to obtain. The microcontroller would be difficult to program as we don’t have the facilities for that processor anymore. We do not recommend that you start building this project. Note that we are working on a new digital preamp design with remote volume, bass and treble controls; however, it is not yet finished, and we don’t know when it might be published at this stage. Problem with 3-channel Rolling Code Remote I built this project, described in your August & September 2009 issues (siliconchip.com.au/Series/39) from a Jaycar kit, Cat KC5483. All functions are operational, but the range is only about 3m. I have checked the antennas on both Australia’s electronics magazine SC Micromite BackPack............ 96 Silicon Chip PDFs on USB....... 87 Silicon Chip Shop.................... 97 The Loudspeaker Kit.com........... 7 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 51 the transmitter and receiver but cannot find a fault in the construction. Do you have any suggestions? (G. P., via email) • The most likely cause is the soldering to the coiled wire antenna. The wire is enamel-coated, and unless this is scraped off well before soldering, it may not form a good connection, reducing the effectiveness of the antenna. You probably have already checked these connections. However, a multimeter measurement of resistance from the antenna input on the receiver module (or output for the transmitter module) to the free end of the antenna will verify if this is a low-ohms connection, as expected, or high-resistance/ open-circuit. Another thing to check is that there is the full 5V DC supply to the transmitter and receiver modules and that the transmitter supply stays at 5V when transmitting. SC siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! 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