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JULY 2023 ISSN 1030-2662 07 The VERY BEST DIY Projects! 9 771030 266001 $ 50* NZ $1290 11 INC GST INC GST Build your own custom NFC Tag (page 34) Measure low frequencies with our Reciprocal Frequency Counter (page 52) ...plus much more inside How It’s done: Electric Vehicle Charging Starting on page 16 BEST COMPATIBILITY WITH SHIELDS, SENSORS & MODULES BEST SELLER BREADBOARD FRIENDLY FOR EASY PROTOTYPING ARDUINO® COMPATIBLE NANO ONLY ARDUINO® COMPATIBLE UNO XC4414 OUR MOST POPULAR DEVELOPMENT BOARD. 39 $ COMPACT DESIGN WITH SIMILAR FEATURES TO THE UNO 95 FROM 3495 $ XC4410/11 FOR MORE ADVANCED PROJECTS THAT REQUIRE MORE I/O & PWM PINS EMULATE A USB KEYBOARD, MOUSE, JOYSTICK, ETC. ARDUINO® COMPATIBLE LEONARDO BUILT-IN USB EMULATOR ONLY 3495 $ ARDUINO® COMPATIBLE MEGA • 54 DIGITAL PINS (15 PWM CAPABLE) • 16 ANALOGUE PINS & 4 SERIAL PORTS XC4430 FROM 5495 $ XC4420/21 Arduino® Compatible Development Boards NANO UNO LEONARDO MEGA Special Feature Compact Breadboard Friendly Best Shield Compatibility USB Emulator Extra Resources, Inputs & Outputs No. of Digital I/O 14 14 20 54 PWM Capable Pins 6 6 7 15 No. of Analog Inputs Serial Ports 6 1 6 12 (6 shared with Digital) 1 2 16 4 Processor / Speed ATmega328 / 16MHz ATmega328P / 16MHz ATmega32u4 / 16MHz ATmega2560 / 16MHz EEPROM / SRAM 512 bytes / 2kB 512 bytes / 2kB 1kB / 2.5kB 4kB / 8kB Program Memory^ 32kB 32kB 32kB 256kB ^Up to 4kB used by bootloader. Shop at Jaycar for: • Arduino® Compatible Development Boards • Great Value Starter Kits • Wide range of Shields, Modules, and Sensors • Great range of Breadboards and Prototyping Accessories Explore our great range of Arduino® compatible products, in stock on our website, or at over 110 stores or 130 resellers nationwide. jaycar.com.au/devboards 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Contents Vol.36, No.07 July 2023 16 Charging Electric Vehicles There are many ways to charge an electric vehicle (EV), and some charging stations only work on certain vehicles. With the amount of EVs increasing each year, it’s important to know about the various charging systems, connectors and charging rates. Read this article to find out. By Dr David Maddison Technology feature 31 VL6180X Rangefinding Module This module uses infrared (IR) light to accurately sense the proximity of objects from 0mm to over 100mm away. It additionally can measure ambient light levels using another one of its sensors. By Jim Rowe Using electronic modules 44 Electronics Magazines in Aus Jamieson (Jim) Rowe was an important figure at both Radio TV & Hobbies (RTV&H) and Electronics Australia (EA). Here is his journey through both magazines over 40-odd years. By Jim Rowe History feature 34 Dynamic NFC/RFID Tag Using a very basic PCB (or even none at all), you can create your own custom NFC tag which can then be programmed to contain text, a URL, business card details and other types of information. By Tim Blythman NFC/RFID project 52 Reciprocal Frequency Counter With an operating frequency from 10mHz to 10MHz, the Reciprocal Frequency Counter is designed to quickly measure low-frequency signals with accuracy. It is powered from three AA cells, providing approximately 24 hours of battery life. By Charles Kosina Test equipment project 62 Pi Pico Thermal Camera This DIY Thermal Camera is simple to build, requiring just three modules and some smaller components. You can use the Thermal Camera to identify overheating components in a circuit, or to find poor thermal seals in buildings, among other uses. By Kenneth Horton Raspberry Pi Pico project 68 Railway Carriage Uncoupler Build this mechanism to automatically uncouple carriages from a model locomotive or another carriage. It can be hidden under a section of the track and activated by a switch. The design is relatively simple and uses a servo-based mechanical system that you can make yourself. By Les Kerr Model railway project Page 34 Dynamic NFC Tag Page 58 Reciprocal Frequency Counter Page 62 Pi Pico-based Thermal Camera 2 Editorial Viewpoint 5 Mailbag 59 Circuit Notebook 77 Subscriptions 78 Vintage Radio 89 Online Shop 92 Serviceman’s Log 99 Ask Silicon Chip 1. Object recognition using an Arduino 2. Charging a battery with a load 3. Reducing Flexitimer power consumption Replacing Vibrators, Pt2 by Dr Hugo Holden 103 Market Centre 104 Advertising Index 104 Notes & Errata SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Jim Rowe – B.A., B.Sc. Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $65 12 issues (1 year): $120 24 issues (2 years): $230 Online subscription (Worldwide) 6 issues (6 months): $50 12 issues (1 year): $95 24 issues (2 years): $185 For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: Editorial Viewpoint We will continue to offer printed and online magazines The landscape of print media is changing, with many publications recently going ‘online only’. Given the popularity of the printed version of Silicon Chip magazine, we have no plans to follow that trend. Since our introduction of PDF downloads for the online edition in 2020, an increasing number of readers have moved to the digital edition. Still, a significant majority continue to value the tactile experience of a printed magazine. We intend to cater to both preferences, with no plans of discontinuing the print edition in the foreseeable future. We also offer a hybrid option, providing access to both the printed magazine and the online edition for a small extra cost. This popular choice allows you to enjoy the ease of browsing through a physical copy while benefiting from the advanced search capabilities of our online platform. On the topic of subscriptions, I can’t stress enough how vital they are for Silicon Chip. While I understand and appreciate the appeal of picking up a copy from your local newsagent, direct subscriptions form the core support for our magazine. I encourage our readers to consider subscribing if you don’t already. Not only is it cost-effective, with free home delivery, it also helps us reduce waste. Here’s why: for newsstand sales, we print more copies than we sell, and the leftovers are recycled. While an inevitable part of that distribution model, it is inefficient and not ideal for the environment. If more of our readers subscribed, we could print the exact number of magazines needed, reducing paper waste and saving on printing costs. It’s a win-win scenario! Subscribing offers yet another advantage – it lets you lock in the magazine’s pricing. It has been almost two years since our last price increase, and we’re due for a review later this year. If you take out a two-year print subscription now within Australia, you’ll pay $230 or $9.58 per issue for 24 issues, no matter what price changes occur during that period. In the face of rising paper costs, exacerbated by recent global challenges like COVID-19 and high inflation, our commitment to keeping the magazine affordable while producing great content has required careful management. Subscribers help us achieve the stability to keep it going long-term. I understand that subscribing might not suit everyone’s circumstances. Still, even if a small percentage of our non-subscriber readers were to take up direct subscriptions, it would significantly contribute to the longevity of Silicon Chip. If you’re contemplating a subscription, please visit our website at siliconchip.au/Shop/SubRates for options, siliconchip.au/Shop/Subscribe to sign up, or call our office to discuss it further. Your continued support ensures that Silicon Chip can continue to produce quality content. Finally, regarding the price review mentioned above, we will provide warning about any price changes, giving you time to take out or renew a subscription at the current price if you want. Expect an update in the September issue. Cover image: https://unsplash.com/photos/MBW3F1jEhh0 by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia's electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. Pegasus ‘flying car’ gains airworthiness certificate Time has flown since the Avalon Air Show, and the Pegasus “police” flying car has also taken flight! We are pleased to inform you that in mid-April of this year, Pegasus’ law enforcement flying car, which we exhibited at Avalon [covered in the May issue – Editor], received a certificate of airworthiness from CASA as an experimental aircraft. This milestone enables Pegasus to proceed with commercialising this model in Australia and globally. The Pegasus team has ambitions to eventually obtain US Federal Aviation Administration (FAA) airworthiness registration as well, an achievement that would be a world first for fully VTOL and roadable flying cars. FAA certification would position Pegasus flying cars for the growing global market, which Morgan Stanley expects to be worth nearly US$1 trillion by 2040. The engineering team is hard at work creating Pegasus’ four-seater Air Taxi prototype with a target completion of year-end 2023. Pegasus’ plans to commercialise the Air Taxi from 2024 onward coincide with CASA’s milestones on Remotely Piloted Aircraft Systems (RPAS) and Advanced Air Mobility (AAM) Strategic Regulatory Roadmap. That’s particularly the case regarding its near-term focus on establishing aircraft safety and operational standards that support the growth of air taxi networks as a new mode of transportation. As a local manufacturer of flying cars and an active member of Aviation Aerospace Australia (AAA), a leading industry association, Pegasus is keen to support CASA’s development of this critical regulatory framework. Having completed a fair amount of test flying and driving lately, Pegasus has also created some fresh new visual material, including both video and stills. These feature the law enforcement flying car in flight, driving, parking, and even filling up at a suburban petrol station! Some examples are available at the link: siliconchip.au/link/abm2 Debbie Thomas, Pegasus International Group Pty Ltd, Mount Waverley, Vic. Victory achieved over SMD Trainer kit I am writing for three reasons. The first is to congratulate you on producing a magazine that is always interesting. I was a reader of RTV&H when a teenager in the fifties, which started my interest in electronics. The second is to thank Tim Blythman for creating the SMD Trainer Board. I purchased a kit from Silicon Chip Shop and managed to install everything except LED5, having committed, I imagine, every error in the SMD mistakes book. With my shaky hands and ageing eyesight, I shied away siliconchip.com.au from projects with SMD devices because I did not think I could successfully solder them. I found that I needed some additional tools to deal with the M1005 and M0603 parts. I made some probes from sewing needles with the eye end fitted into plastic handles recovered from old interdental brushes (‘Picksters’), as even very fine tipped jewellers’ tweezers were too bulky and unwieldy. I also discovered that fixing the bandolier tape to my workspace with tiny beads of Blu-Tack allowed me to peel back the tape covering strip and expose a single chip at a time without firing the chips across the room. Also, using a tiny (chip-sized) bead of flux gel on the tip of a probe allowed me to pick up a chip from the bandolier tape, transport it to the PCB and then roughly place it onto blobs of flux gel on the pads, where surface tension was enough to detach the chip from the end of the probe. Then it was relatively easy to nudge the chip to its precise position with the aid of a USB microscope and a clean probe. I also soldered the M0603 chips by tinning the pads with a tiny amount of solder, removing the protective coating from the track immediately adjacent to the pads, pre-­tinning it, then applying heat from my soldering iron to the exposed tinned copper track. Once the chip was in place, I followed up by holding it with a probe and touching the end and pad together with the soldering iron tip. I realise that this technique is not practical for a realworld project. Even the 0.3mm soldering iron tip is like the smoking end of a baseball bat compared to these tiny parts. It seems that solder does not readily flow onto the end contacts of some SMD LEDs, but flows well onto resistors. Subsequently, the bandolier tape can be carefully removed from its Blu-Tack fixing, complete with any remaining chips. The third reason is to thank you for sending me more M0603 LEDs after I managed to lose a few. I was able to complete the SMD Trainer, even if LED4 is a red M1608 type instead of a white M1005, due to my destroying or losing most of those before realising I needed better tools. David Jane, Umina Beach, NSW. Welding with medical implants The June 2023 issue of Silicon Chip contained a Mailbag letter regarding welding with a medical implant (page 8). I have an Implantable Cardioverter Defibrillator (ICD) in my left chest and made a considered decision not to use an electric welder based on the information provided by the device handbook and my doctor. The manufacturer does not recommend the use of welding equipment and the handbook details 10 considerations Australia's electronics magazine July 2023  5 before welding. Importantly, it advises users to consult their doctor first. I am unaware of the composition of my ICD case, but it is clear on X-rays, with the internal electronics visible. I doubt that the case is a Faraday Cage, and regardless, there are three probes going to my heart. The surgeon who implanted the device is both a cardiologist and a cardiac electrophysiologist to whom I was specifically referred as he is an ‘electrical specialist’. He provided advice on electromagnetic radiation. Other devices considered in the ICD handbook are chainsaws with internal combustion engines and radio transmitters. I have become aware of other sources of possible danger to ICDs, namely mobile phones carried in the shirt top left pocket and keyless entry systems on cars that have transmitters in the centre console and doors. But, there are many more potentially hazardous systems that emit electromagnetic radiation. Peter Johnston, Merimbula, NSW. A small error in my letter last month I made a mistake in my letter on “Confusion over transistor neutralisation”, published in the June issue (Mailbag, p10). In the third paragraph, where I referred to “drainsource feedback in an untuned circuit”, I should have written “drain-gate feedback”. Thanks to Ross Stell for reading the letter and informing me about the error. Ian Batty, Rosebud, Vic. Pumped hydro is not practical In his book “Australia on the Brink: Avoiding Environmental Ruin”, Ian Lowe says that we will need fifty pumped hydro storage dams between Adelaide and Cairns if we are to reduce the intermittency of solar and wind. Can you imagine having fifty dams? That means fifty valleys flooded, with a dam up in the high levels, and another dam in the low levels to act as a reservoir so the water can be pumped back up again. I believe people will object to even one more dam, let alone fifty. Also, if you happen to live below the dam, there is the risk of it collapsing. The worst fatalities in the world came from hydro energy when a dam collapsed in China, killing tens of thousands of people. I am convinced that the only answer is nuclear power. You may be interested in the letter sent to the Prime Minister from a 16-year-old lad, Will Shackel. He is now starting a campaign under the heading “Nuclear for Australia”, encouraging us to make the sensible decision. Here are some links: • www.facebook.com/nuclearforaustralia • siliconchip.au/link/abm3 Dick Smith, Terrey Hills, NSW. Honesty in energy generation costs I have to agree with your excellent editorial in the April issue highlighting Dick Smith’s views on the viability of renewable energy systems. Except, it should not be based on the monetary cost analysis but rather on energy costs. Too long ago, in the mid-1990s, I wrote my final paper for a physics/technology-based social science major on this subject. The premise for the paper was the effect on the West Australian grid of renewable energy technology 6 Silicon Chip Australia's electronics magazine siliconchip.com.au and the consequences of subsidies. Coal-fired power generation was used as the base load, using production costs provided to me confidentially by Western Power. Incidentally, the cost per kWh compared realistically to the nominal design costs from the 500MW generator sets installed at Liddell Power station. These generators were made during my engineering training at a large electrical engineering company in the UK in the 1960s. It is hard for me to realise today that their 50-year design life has expired! All the factors mentioned in the editorial were considered in my paper, and many more, on an interactive variable spreadsheet for various renewable scenarios. The outcome of the cost analysis was terrible for renewables, the worst being solar farms. The best option in sunny WA is home solar with very large area collectors. Back then, grid-connected solar arrays had collector area limitations in WA. The peak load coincided with the peak solar output and reduced the need for gas turbines and their higher cost per kWh, something I believe has now happened in excess. The effect of subsidies and similar carbon-reducing schemes can only be described as economic sleight-of-hand masking the reality of energy physics. I did not consider batteries and pumped hydro; however, they are not power generators and perform a function intrinsic to a fossil- or nuclear-powered system, so they become an effective load, subtracting from the available dispatchable energy, apart from the massive initial energy investment. Today, I see the ramifications of those early findings playing out. Most grids worldwide with 15-20% renewables that support industrial loads show instability in terms of economics and supply reliability. I did not write a conclusion to my paper, only a secondary analysis. My results were so dismal for renewables, as were the faces of most fellow students when I gave the obligatory talk on my project; ‘green fever’ was high at that time with many young students. At the time, I did not know what to conclude, as during the writing of my project, I developed the beginnings of methods to describe the performance of different energy systems relative to each other. However, at that time, I was reluctant to stick my neck out, and I had limited time to finish my work; something I now regret. You cannot analyse the physical benefit of an energy system to society by monetary economic analysis. It has to be all in physical terms, as the energy economy drives all other economies, including all life on Earth. A proper analysis would require appropriate mathematical reasoning based on the fundamental energy principles in the biological systems underpinning our human energy supply, agriculture, and industry. To me, the AEMO and associated QANGOs (quasi-­ governmental organisations) are engaged in a hit-and-miss journey to a green energy reality. The rationale is manipulated and misdirected by powerful, deluded and naive political forces that are highly biased in terms of conventional economics, both external and internal. An exploitative commercial power industry adds to the high trauma. There is a simple bottom line to this energy quandary. We have been at the renewables game for around thirty years. If renewables had a superior performance envelope to the fossil/nuclear systems, steam and gas turbines would be 8 Silicon Chip only found in museums today. History shows that superior energy systems are rapidly adopted. Electric energy has a huge multiplier effect. Even a small drop in availability will have a significant impact on society. In normal economic terms, cost and gain are approximately inverse. The lower the gain of the system, the higher the cost of the dispatchable energy, as more of the generated energy has to be kept to keep the system running. The only solution I see is the coming of age of fusion energy systems. The gain factor for fusion energy systems is currently only just above one in laboratory conditions. It needs to be much greater for fusion to become a viable energy source, so society can still enjoy the energy freedom we have attained in only the last 150 years due to fossil/ fission nuclear generation systems. Kelvin Jones, Tasmania. Comment: the cost of generating electricity from the sun or wind has dramatically decreased since the mid-1990s. However, the problem of the mismatch between when power is available and when it is required due to the natural variability of such generation has yet to be fully solved. Batteries appear to be the only real answer, but it’s unclear if the required capacity can be achieved at a reasonable cost and with a sufficient lifespan. Substitute SD card socket for GPS Tracker I built the GPS Tracker (November 2013; siliconchip. au/Article/5449) many years ago, but recently, the regulator packed it in. As well as repairing it, I decided to build another one. I purchased what parts I could from Silicon Chip; the part I had trouble with was the SD card socket. Altronics no longer stocks that item, so I purchased element14 Cat 2847872. It is very similar, but the card detect (CD) and write protect (WP) pins differ. I managed to solder it to the PCB; it turned out that CD pin could be connected; WP would have needed a flying wire. Since it is not used, I just grounded the pin on the micro. Paul Cahill, Balgal Beach, Qld. Comment: the problem of what to do with designs that used the now discontinued Altronics P5720 SD card holder has been bothering us for a while now. We looked for alternatives but must have missed the one you found. Thank you for figuring it out! We have already been able to help one other reader with this information (see Ask Silicon Chip, p100). T12 soldering stations aren’t all the same I have a comment on the letter in the March 2023 issue about T12 soldering stations (starting on page 6). They are indeed very nice and a great budget alternative to something like a Hakko. However, people should know that “T12” is a generic designation, not a particular product; quality and safety vary widely among vendors. For example, those from the KSGER brand were rather dangerous in their earlier models due to lack of grounding and other problems; see siliconchip.au/link/abm1 That may make them sound like deathtraps, but they’re perfectly fine; you just have to be aware of their limitations. If you’re particularly worried, you can buy just the controller, sold as a “Mini Station”, and provide your own external 24V 4A power supply. Make sure you get them from the official “handskit” store (www.aliexpress.com/store/2070008) rather than one of the infinite clones and ripoffs. Australia's electronics magazine siliconchip.com.au Prototyping Accessories GREAT RANGE. GREAT VALUE. In-stock at your conveniently located stores nationwide. PB8815 QUICK AND EASY PROTOTYPING HP9572 MAKE YOUR BREADBOARD PROTOTYPE PERMANENT Solderless Breadboards PB8820 FROM 5 $ 6 models available. 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JUST 4495 $ HG9980 Shop at Jaycar for: • Soldering & Accessories • Components, Cables and Connectors • Magnifiers and Inspection Aids • Tools, Service Aids and Chemicals Explore our full range of prototyping accessories, in stock at over 110 stores, or 130 resellers or on our website. jaycar.com.au/prototyping 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Also, I had a look at the links for the Class-D amplifier module recommended in the April issue (p27, panel at upper right) because you mentioned that Nichicon data sheets don’t have a 1000μF 100V cap and Nichicon is the most widely-counterfeited capacitor brand in China. That rang alarm bells, but the capacitors in all three links aren’t Nichicon but Samyoung NHAs. Samyoung does list that capacitor in their data sheets: siliconchip.au/link/abm5 They are exactly the dimensions you give, so it’s a Samyoung, and given that they’re not the counterfeit-­ plagued Nichicons, they are probably the real thing. Peter Gutmann, Auckland, New Zealand. Phil Prosser responds: Thank you for the sleuthing! I suspect you detected our cautious approach in assessing modules before recommending them. Past experience has made us somewhat sceptical, especially when dealing with mains voltages and power ratings above 500W. It is comforting to find another point of confirmation on the likely provenance of the parts. Ultra long range reception of SLF signal I read with interest the March 2023 feature on Underwater Communication by Dr David Maddison (siliconchip. au/Article/15691). The 82Hz Kola Peninsular Transmit Facility signal was received at Moonah, Tasmania, in 2018, over a distance of more than 15,285km. Refer to siliconchip.au/link/abm4 Edgar, Moonah, Tas. A possible reason for Yamaha amp failure In his May 2023 Serviceman’s Log column, Dave Thompson talks about a big Yamaha amp that will not power on (siliconchip.au/Article/15790). He gave up on this particular repair. He has had a similar fault before in another model Yamaha, possibly a Yamaha RX-V459 (it is a tricky fault to fix). In the phase-shift energy-saving startup circuit, there is a 22nF/600V polycarbonate capacitor that goes partially open-circuit, dropping to about 8nF. A large proportion of these amps have a similar power supply; I’m not sure about this particular one, as he does not give a model number. If he needs a circuit diagram, I might be able to help. Rod Humphris, Ferntree Gully, Vic. Possible ‘gotcha’ with RF Signal Generator I built a second copy of my AD9834-based RF Signal Generator (June 2023; siliconchip.au/Article/15817) and modified the LPF on the AD9834 module. The response is much the same as the first one. While it is possible to increase the maximum output to +0.7dBm by changing the 1.2kW resistor in series with the 50kW potentiometer to 1kW, I don’t recommend it. It results in some distortion of the output waveform. However, I did notice a peculiar bug in the second unit. The frequency readout reduced in value by itself, about once a second. This only occurred when the output level was set to maximum. I eventually traced the problem to the INT0 pin on the processor (pin 4) picking up RF noise from the AD9834 unit. While that line has a capacitor to ground at the encoder, the track to pin 4 acts as an antenna to pick up the noise. I solved this by adding a 47nF M2012/0805 capacitor on the back of the PCB between pins 3 and 4 on the chip socket. 10 Silicon Chip Ideally, pin 4 at the chip should have the capacitor going to ground, but that would mean scraping off the solder resist on the ground plane. Pin 3 is not actually used for anything and is a low enough impedance to act as a virtual ground. This problem did not occur with the first unit I built. I am using ATmega168 chips as I have quite a few. The ATmega328 may have better noise immunity. It just goes to show that building multiple prototypes can be necessary to reveal hidden bugs! Charles Kosina, Mooroolbark, Vic. Slashed zero preferred I am writing regarding the series of letters about printing the number zero with a slash, starting in the January 2023 issue and continuing until April 2023 (page 14). That is more needed now than ever due to password errors, booking reference errors; anywhere ambiguity is possible. When printing passwords, it’s a must to distinguish between 0 and O. Some printing and character sets are appalling in this regard. So I say that all zeros should include a slash. Neil Brewster, Footscray, Vic. More support for slashed zeros This is regarding the Mailbag section of the April 2023 issue, on page 14, “In defence of the slashed Zero”. In the mid-1970s, when learning the Fortran computer language at uni, we had to provide coding sheets to keyboard operators who would then make us a punched card deck of cards for our coded program. We had to use the slashed 0, or the program just wouldn’t work when an O was used instead. Then, as an engineer and a programmer, typos (in variable names, library includes, labels etc) are still the most common error when testing completed code. Personally, I would welcome the slashed zero. Can you easily see the difference between 007 and OO7? Also, as a TAFE teacher, I would always draw a horizontal bar through the middle of the letter Z (Ƶ), similar to a European 7, as the Z was far too easily confused with the number 2. This got especially confusing when doing impedance calculations for multiple loops with Z1, Z2 and Z3 variables in the equations, as well as superscript 2s for squared terms. So I vote for a change in the keyboard to have the default of a slashed zero and crossed Z all the time. While on this subject, what about a DVORAK keyboard layout too? Barry Moore B.Elec.Eng (Hons), Minto, NSW. Communication between limestone caves and surface I was most interested in Dr David Maddison’s article on underground communications as I have been exploring caves for over 60 years with various caving clubs in Australia (April 2023; siliconchip.au/Article/15729). In the early 1960s, my club (now the VSA) ran a single-­ wire Earth return telephone through a 2km-long stream cave passage that was subject to flooding. The outside unit, built by a member, was transistorised and the exploration team kept in contact by connecting a headphone to various terminal points. I became interested in the possibility of locating where cave passages were compared to surface features. I had heard that low-frequency signals could penetrate the ground Australia's electronics magazine siliconchip.com.au Huge Range of 12/24V Switches Control power to your lighting and other devices in your car, 4WD, RV or boat. SAME GREAT RANGE AT SAME GREAT PRICE. TRANSLUCENT PROTECTIVE COVERS IP67 RATED FOR USE IN DUSTY OR WET CONDITIONS ONLY 3295 $ FROM 24 95 $ SP0798 Illuminated DPDT Dust & Waterproof Pushbuttons • 12V LED illumination • On/Off or momentary options available with red, green and blue illumination. 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Jaycar reserves the right to change prices if and when required. and, in about 1963, I built a transistor oscillator at around 2.5kHz and made two 50cm loop antennas that I made resonant. A transistor audio amplifier with a headphone was used as a receiver. With the audio oscillator connected to a loop placed horizontally on the cave passage floor and turned on at prearranged times for 20-minute intervals, the surface party could accurately locate the underground loop by holding their loop vertically and homing on the null (doughnut-­ shaped field) until it could be rotated 360° with the null in all directions. The accuracy was extremely good. Various clubs borrowed this unit over many years. The main problem was that, in most cases (depending on surface terrain), the surface party could find the location in a matter of minutes and then had to sit around. I decided to investigate adding voice communication to the system, which would speed up the surveying parties. That involved experimenting and frustration, like designing and building two SSB units on 12kHz and testing them in the Buchan caves, only to be drowned out by the Omega station tones. Still, voices could be heard in the gaps! I then conducted RF attenuation tests of limestone compared to air in about 1978, from 10kHz to 1MHz, and found the lowest attenuation was at about 40kHz for that limestone. I decided to settle on 40kHz AM as it was rugged for unskilled operators, and battery drain was not a worry. I built two experimental test units in about 1982 and found them to work well. After learning how to make PCBs, I made four identical units in 1998, which are still in use today. I incorporated some useful functions whereby the underground units can transmit a 400Hz tone for 20 seconds, then go into receive mode for two seconds, and then transmit the tone again until cancelled. When the surface party locates the underground unit, they press their tone-on button, and The transistor oscillator which was designed by the Victorian Speleological Association (VSA). 12 Silicon Chip when the underground unit receives, it turns off the transmitter and goes into receive mode. Voice communication between units is then available. The range of the units using the loops is 100m, in the deepest limestone at Buchan. A few years ago, a Canberra Speleological Society (CSS) member contacted me with the thought of using PICs to modernise the circuits, so I provided him with all the construction and circuit details. They are on their website under the heading “Projects”, “Cave Radio and RDF Unit” for anyone to view and improve upon. I am still investigating cave communication systems. Thanks for your articles; I enjoy them. Peter Robertson, Walkerville, Vic. Renewable energy costs and motor failures Your April 2023 editorial headline reads, “Renewable energy costs are seriously understated by the media”. That is wrong. The media do not have a clue; they are only repeating misleading information from self-appointed experts. I am not an expert, but with a few careful ‘ballpark’ calculations, I concluded quite some time ago that Australia has no hope of converting to totally renewable power within the foreseeable future without a drastic change in the rate of conversion to renewable power. The costs are enormous, and those who predict cheap power are flat-out wrong. How can adding a major extra component like energy storage reduce the cost of electricity? Energy storage of any type is expensive, and the cost must be passed onto the consumer. It is unfortunate, but Australians are facing a costly power future. The only thing we, as consumers, can do is reduce our power consumption wherever we can. That is, we reduce wastage and use energy-efficient appliances. I am sure that energy-saving projects would not go astray as well. In the Ask Silicon Chip section of the May 2023 edition, J. B. of Northgate, Qld asked for help concerning a spa pump motor. He did not say that he tested the windings for continuity, but if he does and the low-speed winding is an open circuit, a thermal fuse could have blown. In the shaded pole motor of a domestic pedestal fan, I found that the manufacturer had put a thermal fuse at the centre of the winding. There was no smell of burnt windings, so I assume the fuse failure temperature was below that to cause the insulation to burn. Manufacturers of larger motors may be inserting thermal fuses in their products. I will also add that small transformers of modern manufacture can be fitted with a thermal fuse in the centre of the windings. For example, Altronics advertise that their transformers are equipped with a 125°C thermal fuse. Once ‘blown’, these can be difficult, if not impossible, to fix or replace. Finally, I am trying to fix a problem with the motor in my van. It is not mechanical; it involves the computer, the sensors and the various actuating mechanisms. In other words, it is a technical problem that involves programming, electronics, and electromechanics. It is a pain. The marketing spin is that technology will improve our lives, and while everything works correctly, that is mostly true. But when a failure occurs, even the most competent people can be tested beyond their capabilities. Just ask Dave Thompson. George Ramsay, Holland Park, Qld. SC Australia's electronics magazine siliconchip.com.au CNC - WATERJET CUTTING The world’s first desktop waterjet. standup. desktop. Now cut anything with digital precision using high-pressure water TILES COPPER GLASS STEEL ALUMINIUM WAZER is the first desktop water jet that cuts any hard or soft material with digital precision. 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Nozzle Temp 260°C 260°C 240°C 300°C 260°C 300°C 265°C 240°C 300°C 275°C 275°C Main Interface 150mm/s 150mm/s Coated Flex Coated Flex Dial & button Dial & button Touchscreen Touchscreen Touchscreen Touchscreen Touchscreen Dial & button Touchscreen Screen 128x64 Mono 4.3" Colour 2.8" Colour 4.3" Colour 4.3" Colour 4.3" Colour 4.3" Colour 128x64 Mono 55" Colour 55" Colour Filament Sensor - • • • • • • • • • • Levelling System Auto Auto Assisted Auto Auto Auto Assisted Manual Assisted Auto Auto $349 $399 $599 $749 $799 $869 $1099 $1499 $2299 $2199 $2599 Price Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Touchscreen Touchscreen 55" Colour ^ Available online only. Electric Vehicle Charging As the number of electric vehicles (EVs) on the roads increases, charging them all becomes a challenge. There are many ways to charge an EV (AC or DC, fast or slow etc), and some charging stations can only charge certain vehicles. This article describes the various charging systems, connectors and varying charge rates, from a few kW up to 1MW! By Dr David Maddison hile there are obviously other difW ferences, the main practical difference between EVs and ICE vehicles is the method of recharging or refuelling. An EV can be charged at home, at work or via a dedicated charging station at a shopping centre, parking lot or other location. In contrast, an ICE or hybrid vehicle is refuelled at a service station or from a fuel can. The amount of time these procedures take can vary wildly. An EV can take hours (sometimes more than a day) for a full recharge, although a ‘top up’ at a fast charger can be much quicker, perhaps under half an hour. In contrast, refuelling an ICE vehicle usually takes a couple of minutes. The time to recharge, along with the distance between charging stations, can cause “range anxiety” for EV drivers. Still, petrol and diesel vehicles are not immune from that, especially when away from urban centres in a country as large as Australia! In places such as the USA, Europe and Japan, there is a sufficiently high population density that charging stations are relatively closely spaced, but that is not always the case in Australia. Also, long road trips of up to 1000km or more are rare in places like Europe and Japan. This article covers the practical and technical aspects of charging EVs, such as connector standards, power supply 16 Silicon Chip issues, charging times, the extent of recharging networks, limitations of charging at home and other relevant matters. Charging stations One of the most important aspects of EV ownership is locating charging stations, especially when planning a long trip. Many EV owners also install a home charger, although most can be charged from a regular power point (but that can be slow). The main components of an EV charging station are: • The power source (usually derived from the mains, but possibly solar panels, other batteries or a generator). • The charging cable. • The connector that plugs into the vehicle. As part of all this, there are various charging standards, data protocols and charging protocols, charger power ratings, voltages and currents. Some charging stations have their own cable and connector; others require you to provide a cable with a suitable connector, typically kept in the vehicle. There are also adaptors to convert from one type of connector to another. It would be grand if any EV could rock up to any charging station, plug in and get a charge, but unfortunately, there are too many competing Australia's electronics magazine standards for that always to happen. Now is as good a time as any to bring up that old chestnut from Andrew S. Tanenbaum: “The nice thing about standards is that you have so many to choose from”! EV charging stations in Australia and NZ There is now a reasonable network of EV charging stations in the more populated areas of Australia and NZ, documented at www.plugshare.com Fig.1: an EV charging station in Adelaide. Source: www.wikiwand. com/en/Plug-in_electric_vehicles_in_ Australia (CC BY-SA 2.0). siliconchip.com.au However, for longer-­distance trips, it is still necessary to ensure you have the range to get between charging stations on your proposed route, allowing for any side trips. Also, during peak periods such as school holidays, there can be 90 minutes of delays at some charging locations; for example, see this reporter’s video on what happened in Australia last holiday period at: https://twitter.com/PhilWilliamsABC/ status/1607951693039423490 Some remote charging stations run on diesel fuel or biodiesel (see Fig.2). An experimental 50kW charger was coupled with a diesel/biodiesel-­ powered generator by inventor Jon Edwards, who called it a “ChargePod”. It produces 3.392kWh/litre of diesel. Some trips in the Australian Outback are unsuitable for electric vehicles with present range limitations (such as the nearly 1900km Canning Stock route – https://w.wiki/6RUS). Battery configurations and charging Virtually every EV on the market today uses lithium-ion batteries (with lithium polymer or LiPo being one variant). They typically have large numbers of cells joined in mechanically and electrically complex ways with embedded cooling systems (between cells in the case of Tesla and some other models), along with sensors, fuses etc. We covered lithium-ion battery technology in detail in the August 2017 issue (siliconchip.au/Article/ 10763). To give an idea of the complexity, the Tesla Model Y has 4400 of 2170 size cells, meaning they are 21mm in diameter and 70mm long. There are 17,600 welded connections, four per cell. Tesla is starting to use 4680 cells in Texas-made models, which are 46mm in diameter and 80mm long. Those battery packs only need 830 cells and 1660 welded connections, giving a significant cost saving. The Tesla Model S battery pack (Fig.3) has 6912 18650-size cells arranged as 16 modules, each in the 6S72P configuration (72 paralleled strings of six series cells) and with individual cell voltages from 3.10V at 0% capacity to 4.15V at 100% capacity. Even though an EV may contain siliconchip.com.au What if your battery runs flat? Check your options with your EV supplier or roadside assistance organisation; for example, in NSW and the ACT, the NRMA offers roadside assistance vans to charge flat EVs. Two NRMA vans have been equipped with 4.8kWh lithium-ion battery packs that provide 1km of charge every two minutes (see siliconchip.au/link/abkc). Enough energy is provided to get to the nearest charging station; a ten-minute charge will get you about 5km. A company called RE:START (https://restartev.com/) has investment from the RACV (the Victorian motoring organisation) and produces a fast charging unit which they say will provide 50km of range in 15mins – see Fig.a. Another European solution is a trailer-mounted generator such as the EP Tender (https:// eptender.com/en/product/) shown in Fig.b. You can rent this trailer for longer trips to charge your battery as necessary, even while driving. The same company is developing a batteryFig.a: a roadside only trailer. assistance fastcharging unit produced Some people have also carried generators in by RE:START. Source: their EVs, but you need a large and powerful one https://restartev.com/ to charge at a reasonable rate. A YouTuber permanently installed a generator in his Tesla as an experiment, thus turning it into a hybrid – see Fig.c. The video is titled “Cordless Tesla (I Drive 1800 miles without charging)” and is at https://youtu.be/hHhf223jGIE If all else fails, you would have to either call a tow truck or a nearby friend with a portable generator. Fig.b: a solution to EV range anxiety. Source: https://eptender.com/en/ product/ Fig.c: a rear view of the ‘hybrid Tesla’ with a 10kW generator. Source: youtu. be/hHhf223jGIE Fig.2: a diesel/biodieselpowered EV charger in the Outback. Source: https:// thedriven.io/2018/12/14/ diesel-charge-evs-remotelocations-greener-thanyou-think/ Fig.3: a partially disassembled Tesla Model S battery pack with 6912 18650-size cells in 16 modules. It has a rated capacity of 85kWh at 400V DC. Source: https:// hackaday.com/2014/09/13/ tesla-model-s-batteryteardown/ Australia's electronics magazine July 2023  17 standards from Table 1 and adding those shown in Table 2. Fig.4: the charging scheme for a typical lithium-ion battery, like those used in most EVs. Charging Connector Types EV Charging connectors and protocols can be divided into AC charging (single-phase or three-phase) and DC charging, with preferences for different connector types by region shown in Fig.5. While we’re showing regional preferences, different connector types can still be found within the same region. The following types of connectors are in use or planned: AC ● Type 1 (Yazaki, SAE J1772, single-­ phase) ● Type 2 (Mennekes, SAE J3068, three-phase) ● Type 2 (GB/T, type 2 physical connector with different pinouts) ● Type 3 (Scame, uncommon) thousands of cells, each cell still has to be charged using the basic lithium-ion charging scheme shown in Fig.4. The primary charging scheme involves charging at a constant current until the maximum voltage is reached, then holding them at that voltage until the current drops below a certain level. If the initial state of charge is low, this scheme might also be preceded by a ‘conditioning charge’ at a much lower current, to allow the cell chemistry to stabilise before rapid charging begins. Regardless, the variation in charge voltage and current will be managed by the battery management system (BMS). Individual lithium cells might range in voltage from 3.10V to 4.15V in the case of the Model S, but due to the 6S configuration, each module charges to 24.9V. The modules are also arranged in series sets of 16, giving 398.4V (24.9V × 16), so the vehicle requires a 400V charger. There is no chance of connector incompatibility due to different connector standards if the EV owner uses their own cable, as long as the remote end is compatible with the charging station connector. However, at high-power DC charging stations, the cable is permanently attached to the charger because it is thick, heavy and often has coolant running through it. In Australia, the Type 2 connector (also used throughout Europe) is the most common to find. This can be used for AC or DC charging. We will come back to that a bit later. Charging stations and cables Table 1 – SAE J1772 voltage & power standards (limits) for North America Charging stations are either AC or DC. If the charging station supplies DC, it is applied directly to the battery pack, and the charge rate is limited only by what the pack can handle. However, if the station supplies AC, the vehicle uses an onboard AC-to-DC converter, which will typically be the limitation on the rate of charge. For example, many plug-in hybrids have an onboard converter that’s limited to 7.2kW (32A <at> 225V AC single-phase), while some EVs are limited to 11kW (16A <at> 432V AC three-phase); others can handle 22kW (32A three-phase). At lower-power AC charging stations, the EV owner can use their own cable, which is kept with the vehicle and plugged into the charging station outlet (or a cable might be provided). 18 Silicon Chip Voltage and power standards Various EV charger power and voltage ratings have been defined. Table 1 summarises those for North America. The IEC (International Electrotechnical Commission) has produced standards for international implementation by adopting most of the SAE Method Current DC ● CHAdeMO (AA⋆) ● GB/T (BB⋆) ● ChaoJi (planned) ● CCS “Combo” Type 1 (EE⋆) ● CCS “Combo” Type 2 (FF⋆) ● Megawatt Charging System ⋆ AA, BB, EE & FF are designations under the IEC 62196 standard. AC & DC ● NACS (Tesla) Combined Charging System Combined Charging System (CCS) connectors are based on extensions to the Type 1 (North America & Japan) and Type 2 (Europe & Australia) Voltage Power Notes AC Level 1 16A 120V 1.92kW Standard domestic outlet AC Level 2 80A 208-240V 19.2kW 240V single-phase or 208V three-phase DC Level 1 80A 50-1000V 80kW DC Level 2 400A 50-1000V 400kW Table 2 – IEC additional charging standards (limits) Mode Type Current Voltage Power 250V 4kW 16A 480V 11kW 2 single-phase 32A 250V 7.4kW 32A 480V 22kW 3 single-phase 63A 250V 14.5kW 63A 480V 43.5kW 200A 400V 80kW 1 single-phase 16A three-phase three-phase three-phase 4 DC Australia's electronics magazine The three-phase power ratings are about 50% higher than the product of the voltage and current, since the current rating is per conductor and there are three conductors rather than two for singlephase. siliconchip.com.au Fig.5 (left): some common EV charge connector types. Not shown are Type 3, ChaoJi or Tesla. For more details, visit https://w.wiki/6RUd Fig.6 (below): the Type 1 connector pinout. L1 is AC Line 1, N is Neutral for Level 1 charging or AC Line 2 for level 2 charging, PE is protective earth, PP is the ‘plug present’ signal and CP is ‘control pilot’ for various control signals. Source: https://w.wiki/6RHE (CC BY-SA 4.0). L1 N PP CP PE Fig.7 (right): a Type 1 connector. Source: https://w. wiki/6RHF connectors. The extensions consist of two additional DC connector pins to allow high-power DC charging. In such a configuration, the AC pins of the original part of the Type 1 and Type 2 connectors are no longer used. The extended connector is called CCS Type 1 (CCS1), Type 2 (CCS2), Combo 1 or Combo 2. Power can be delivered at up to 350kW and 200920V. We will illustrate these connectors later. Type 1 and Combo 1 The Type 1 connector is also known as the SAE J1772, J plug or Yazaki (see Figs.6 & 7). It is also covered by the international standard IEC 62196 as the Type 1. It is common in Japan & North America, and is used in Australia on cars such as the Holden Volt, Nissan Leaf, Mitsubishi Outlander PHEV, BMW i3, BMW i8 and Porsche Taycan. The Combo 1 connector for highpower DC charging is a Type 1 with two DC charging pins added (see Fig.8); the AC pins are not used. Type 2 and Combo 2 Type 3 Also known as Mennekes or IEC 62196-2, Type 2 is a mandated standard in Europe and commonly used in Australia, mainly by Teslas and some European models. These are installed at Tesla charging stations, although only Teslas can connect at such stations. For AC charging, vehicles with this connector typically charge at 7.2kW for 230V/32A single-phase AC or 22kW for 400V three-phase AC. Two more DC charging pins are added for high-power DC charging, forming the Combo 2 or CCS2 F CP N DC+ Fig.8: a Combo 1 plug for high-power DC charging. Source: https://w. wiki/6RHG (CC BY-SA 4.0). siliconchip.com.au The Type 3 or Scame connector was used in France and Italy but has now been superseded by the European standard connector, Type 2. GB/T The Chinese GB/T 20234.2-2015 connector uses the same physical connector as Type 2 (AC) but with gender differences for the plugs and a different signalling protocol. GB/T (DC) The GB/T DC charging connector is mainly used in China (see Fig.11) M PP PE L3 connector (Figs.9 & 10), which can transfer power at 350kW. The AC pins are eliminated or not used. Where this connector is used in the USA, it is covered by the SAE J3068 standard. PP L1 L2 DC- L1 CP PE L2 DC- N L3 DC+ Figs.9 & 10: a Combo 2 connector (the leftmost cable in Fig.10); yellow AC pins are unused. Without the bottom two pins, it would be a Type 2 (the rightmost cable in Fig.10). F is the charging station outlet, while M is the car inlet. PP is the ‘proximity pilot’ signal, CP is the ‘control pilot’ signal, PE protective earth, N neutral and L1-L3 are the three phases. DC+ and DC- are only used for Combo 2 charging. Source: https://w.wiki/6RHJ & https://w.wiki/6RHK (CC BY-SA 4.0). Australia's electronics magazine July 2023  19 S+ CC2 S- CC1 DC+ A+ DCPE A- Fig.11: the GB/T DC connector. S+ & S- are CAN bus, CC1 & CC2 the charging confirmation signals, A+ & A- are auxiliary power, PE is protective earth and DC+ & DCcarry up to 1kV at 250A. Source: https://w.wiki/6RHM FG SS1 N/C DCP DC+ DCPP C-H C-L SS2 Fig.12: the CHAdeMO connector pinout. FG is ground, N/C is not connected, DCP charging enable, SS1 & SS2 are the charging start and stop signals, PP is the charge interlock to disable the drivetrain during charging, while C-L & C-H are CAN bus signals to communicate with the vehicle. Source: https://w.wiki/6RHL and is also designated as the BB configuration under IEC 61851-23, IEC 61851-24 and Chinese standard GB/T 20234.3. A power delivery of up to 250kW is possible, and CAN bus signalling is used. CHAdeMO CHAdeMO is a Japanese standard (see Figs.12 & 13). The name comes from “Charge de Move” (a French phrase), which its developers interpret as “charge for moving”. However, it originally comes as a pun on the phrase “o cha demo ikaga desuka” (おちゃでもいかがです か), which means “how about a cup of tea?”, referring to the time taken to charge a vehicle! CHAdeMO is popular in Japan but less widely used in the USA or Europe. The second generation CHAdeMO standard is capable of 400kW <at> 1kV/400A DC. In Australia, the CHAdeMO connector is used by the Nissan Leaf; as more EVs are bought to Australia, it might become more widely adopted. Tritium-brand charging stations support this connector. The connector supports bidirectional operation, such as using the EV as a power source (more on that later). A third generation, called ChaoJi, that can deliver 900kW is being co-­ developed with China; see https://w. wiki/6RHf ChaoJi Not to be confused with the Tesla Megacharger, the MCS (Fig.14) is a high-power charging connector under development for large EVs (eg, trucks, ferries and aircraft). It has a power rating of 3.75MW or 3000A at 1.25kV DC. 20 Silicon Chip Charging-related standards such as connectors, protocols and ‘vehicle to grid’ (V2G, described below) are covered by specifications in the following documents: ● China: GB/T 20234 ● International: IEC 61851, IEC 62196, IEC 63110 & ISO 15118 (V2G) ● North America: SAE J1772, SAE J3068, SAE J3105 (heavy vehicles) & SAE J3271 (megawatt charging) Some charging methods and protocols are proprietary and not covered by the above standards. fast DC chargers that form the Tesla Supercharger network and facilitate long-distance trips, usually at 120kW or 250kW. There are also lower-power Tesla ‘destination chargers’ at places like hotels and shopping centres, typically delivering 22kW. Tesla NACS Tesla has developed its own charging standard called the North American Charging Standard. It was initially proprietary, but Tesla has now published it for all to use, and Aptera Motors has adopted it. The connector is smaller than a J1172/CCS connector but uses the same pins. It has the same communications protocol as CCS, ISO 15118 and DIN 70121. In Australia, Tesla uses the Type 2 connector. A Tesla Model 3 has additional pins for higher power charging, with a CCS Type 2 connector, but it can also use a Type 2 connector only. ChaoJi, also known as CHAdeMO 3.0, is a proposed standard for an EV car connector developed between Japan and China for charging at powers up to 900kW DC with a maximum voltage of 1.5kV and a maximum current of 600A. It is designed to be backward-­ Adaptors compatible using an adaptor for Various adaptors (see Fig.15) are CHAdeMO and GB/T DC charging. A available to convert one charging conmegawatt charging connector called nector to another type, but data signals “Ultra-ChaoJi” is also under devel- must also be compatible. opment. Megawatt Charging System (MCS) Fig.13: a CHAdeMO plug. Source: https://w.wiki/6RHQ Charger & connector standards Tesla Supercharger Tesla Superchargers are high-power Australia's electronics magazine Charging levels Depending on the available power, there are different charging levels (not to be confused with connector type), as shown in Tables 1 and 2. The following names are commonly used in Australia. These charging level names do not conform with the IEC international recommended levels (which they call Modes), outlined in Table 2. siliconchip.com.au Fig.14: a prototype Megawatt Charging System connector v3.2. There are two DC pins, four data communications pins (white) and a protective earth pin (PE). Source: https://w.wiki/6RHN (CC BY-SA 4.0). Fig.15: a Type 1 to Type 2 adaptor sold by EVSE. Source: https://evse. com.au/product/type-1-to-type-2-evadapter-cable-32a-2 Level 1 uses a standard domestic single-phase 230V AC ‘GPO’ outlet. This is the most basic level of charging. The charging power is 2.3kW in Australia and NZ. At this rate, it takes one day plus eight and a half hours to fully charge a Tesla Model 3 from flat, with 14km of range added per hour. Single-phase 15A 3.45kW outlets can also be installed in premises in Australia & New Zealand, increasing that rate to 20km/hour and reducing the total charging time for that vehicle to around 22 hours. You will often see slightly higher powers quoted because the supply voltage is usually higher than the nominal voltage of 230V AC; those higher power ratings are generally based on an average of 240V. A proprietary single-­ phase Tesla charging station will deliver 7.2kW, adding 42km per hour of charging and fully charging the Model 3 in 10.5 hours. Level 2 charging is from a threephase (~400V) 16A outlet. Such outlets are not typical in homes in Australia or New Zealand but can be installed easily. The power delivery is 11kW, taking 5.5-7.5 hours to fully charge a Tesla Model 3 at a rate of 65km of range added per hour. Note that 400V 32A outlets are also possible and provide 22kW, doubling that charging rate and halving the total charging time. There is some argument over the exact definition of “Level 3”, but this refers to high-power DC charging, which is unlikely to be affordable and not always possible in domestic installations. The typical power delivery is 120kW, and it takes about half an hour to charge a Tesla Model 3 from flat to 80%. But note that repeated fast charging can prematurely age the battery. siliconchip.com.au Fig.16(a): An overall view of one of the chargers. There is a place to tap a payment card above the car symbol. Local council charging station I had a close look at my local council charging station, which is typical of what might be found around Australia – see Fig.16. Each side of the station has a Type 2 outlet (socket) into which you plug in your cable. The Tesla prime-mover Megacharger Terminology varies from country to country, but the ten-wheel unit that pulls an eight-plus-wheel trailer is called a prime-mover in Australia and New Zealand, or a tractor unit, among other names, in North America. Tesla Fig.16(b): Another charger with its own cables (Type 2 plug & socket); they can be unplugged from the charger socket to plug in your own. In the corner is a close-up of the Type 2 plug. The cost to charge an EV It depends on how much you pay for electricity and how efficient your charger is, but at around 30-40¢/kWh in Australia, assuming 10% losses, charging a typical 60kWh EV battery will cost around $20-26. Public fast chargers have a higher cost per kW (60¢/kWh for some 350kW chargers), so a full charge might cost up to $40. The ‘fuel economy’ of EVs is generally measured in kWh/100km. Some people overseas use “MPGe” or miles per gallon (equivalent). However, equating electricity to a volume of liquid fuel containing a similar amount of energy is flawed logic. At around 17kWh/100km (a figure measured in real-world testing), that $2040 charge will take you around 350km. By comparison, $20-40 will buy you 11-22 litres of petrol which, for a hybrid Camry, equates to a range of about 250-500km. The average fuel consumption of a purely petrol-powered vehicle was 10.8L/100km from the ABS 2020 figures. When charging an EV, you are not paying the 46¢ plus GST per litre “excise” applied to petrol and diesel. However, in Victoria, EVs are taxed at 2.6¢/km and hybrids at 2.1¢/km. The excise money is meant to pay for road building and maintenance, although it is actually a general revenue-raising tax. Australia's electronics magazine July 2023  21 is developing a prime-mover called the Tesla Semi (see Fig.17), not to be confused with the Tesla Cybertruck, a much smaller utility vehicle. The vehicle is said to have a 900kWh, 1000V battery, a range of 997km with no load, and a range of 480km or 800km with an unspecified load, depending on the model. It is to be charged with a 1MW DC charger called the Megacharger. This charger will also be used for the Cybertruck, which employs a 1000V battery system rather than the 400V system used in Tesla cars. Some industry experts are sceptical about the capabilities of the Tesla Semi and its cost-effectiveness. Ultimately, that will be decided by the marketplace. The Semi started deliveries in the USA in December 2022. A car charging cable such as the V3 would not be suitable for charging the Tesla Semi because it would take too long with battery capacities in the hundreds of kWh. Therefore, Tesla developed a V4 charging cable that can deliver 1MW. Like the V3 cable, it has active cooling, but instead of 12 power wires, it has two. Each wire is immersed in its own coolant return tube, with coolant supplied by two tubes along the body of the cable – see Fig.18. According to Tesla, a current density of 35A/mm2 can be achieved. Adding the coolant lines to prevent overheating means less copper is needed for a given current, saving expensive copper and reducing the weight of the cable. By comparison, the Tesla V3 supercharging cable (also shown in Fig.18) has a power conductor current density of about 14A/mm2, allowing up to 250kW to flow. The Tesla V2 cable Can the electrical grid handle mass EV charging? There are already problems in the upmarket suburb of Brighton in Melbourne, where EV-owning residents wanted to set up a charging schedule. See the articles at siliconchip.au/link/abjp (Herald Sun) and siliconchip.au/link/abjq (radio 2GB). We don’t know what future electricity policy will dictate. Still, in Australia, there is the big question of whether enough reliable, low-cost power will be available to charge all the anticipated EVs. Consider that total generation has been stagnant for the last few years. Secondly, what will happen if everyone goes home from work, plugs in the EV and draws an extra 2.3kW to 22kW (Level 1 and Level 2 charging) per vehicle per household, all at the same time? Our back-of-the-envelope calculations suggest that the total generation would likely have to at least double to provide enough power to charge all those vehicles, assuming the demand is evenly spread out. That’s based on electric passenger vehicles only; we haven’t considered delivery trucks, semi-trailers or other commercial vehicles, including those used in mining. The grid will also need significant investment to carry twice as much power, with many transformers needing to be upgraded, along with transmission lines. That makes local generation and storage, such as with PV solar panels and stationary batteries, seem attractive. Unfortunately, there are problems with that too. Each home would need a very large solar system to gather enough energy to charge an EV (depending on how much driving was being done). As it’s unlikely that the charging time would coincide with power availability, large batteries would be needed to store the energy when it is available, then charge the vehicle when it’s plugged in. is uncooled and has a current density of up to 4A/mm2. Electrical power losses in conductors scale with the square of the current, so losses can be reduced by reducing the current and increasing the voltage. To achieve four times the power rating of the V3 cable, the charging voltage has also been increased from 400V for the Tesla Models 3, Y, S and X to 1000V for the Cybertruck and the Semi. Increasing the voltage results in new problems, such as the requirement for more insulation and additional design elements to prevent electrical breakdown and arcing. The above is about the cable only; no details have yet been released on the type of connector used with the 1MW charging system. Wireless car charging The SAE J2954 standard relates to wireless charging or “wireless power transfer (WPT)” for EVs – see Fig.19. Power deliveries of 3.7kW, 7.7kW or 11kW are allowed for. There is also a provision for 500kW transfer for large vehicles under J2954/2. The principle of wireless charging is similar to inductive charging but uses ‘resonant inductive coupling’. Currently, the Genesis GV60 (a Hyundai 1 MW + DC CHARGING IMMERSION COOLING TECHNOLOGY CHARGING AMPACITY 40 HIGH VOLTAGE CONDUCTORS 2 AMPS / MM 35 V3 CHARGING CABLE 30 25 COOLANT TUBES 20 15 HV CONDUCTORS IMMERSED IN COOLANT RETURN TUBES 10 5 V2 Fig.17: a Tesla Semi EV. Source: Tesla. 22 Silicon Chip V3 V4 V4 CHARGING CABLE COOLANT TUBES Fig.18: a comparison of the Tesla V2, V3 and V4 charging cables with crosssections showing the power conductor parts of the V3 & V4 cables. Source: Tesla, screen grab from https://youtu.be/LtOqU2o81iI?t=1600 Australia's electronics magazine siliconchip.com.au luxury brand) is the only EV with wireless charging, and this option is only available in South Korea at the moment. For more details, see the video titled “How to make EVs - From EV Batteries to Wireless Charging Technology | Genesis GV60” at https://youtu.be/ npUNCgT68bE The Open Charge Alliance The Open Charge Alliance (OCA; www.openchargealliance.org) is an international consortium to promote the use of open standards via the adoption of the Open Charge Point Protocol (OCPP) and the Open Smart Charging Protocol (OSCP). These standards are for ‘cloud-based’ charger system (network) management. The OCA standards are for communications between the charge point or charge point network and the ‘back office’ and do not involve physical connector or charging protocol standards for an EV. The EV owner does not interact directly or knowingly with OCPP and OSCP, although they might operate ‘behind the scenes’. OSCP 2.0 (Fig.20) is for charging site owners and electricity utilities. It communicates predictions of locally available electrical production and generation capacity, fits production and generation resources to grid capacity and facilitates communication between the providers. In other words, it helps ensure that sufficient electricity will be available for the vehicles that need charging. OCPP 2.0.1 (Fig.21) is relevant to charging points, providing a consistent experience even when charging at locations owned and operated by different parties. It supports SOAP and JSON data formats, smart charging, load balancing, charging profiles, tracks the time spent charging and the current status while providing device management, transaction handling and security. Fig.19: a wireless charger for an EV, which can surprisingly deliver multiple kilowatts. Usually, a low barrier is placed so that the vehicle naturally comes to a stop over the charger. Source: https://w.wiki/6RHP (CC BY-SA 3.0). Fig.20: the Open Smart Charging Protocol (OSCP) communicates a 24-hour forecast of the available electricity (blue). Based on this, service providers generate charging profiles (red) for EVs to make the best use of the grid capacity. Source: www.openchargealliance.org/protocols/oscp-10/ Vehicle to Grid (V2G) Vehicle to Grid is a concept where an EV acts as an energy reservoir for the grid (https://w.wiki/6RHk). An EV has a convenient large battery, generally much larger than home energy storage batteries, such as: • Tesla Powerwall (13.5kWh; http:// siliconchip.au/link/abk3). • Enphase Energy (10.08kWh for IQ Battery 10; siliconchip.au/link/abjz) siliconchip.com.au Fig.21: the Open Charge Point Protocol (OCPP). EVSE is the Electric Vehicle Supply Equipment, ie, the charging station, while CSMS is the charging system management software. You don’t need to provide payment and charging details separately with every charging station you pull up to, as long as they support OCPP. Source: https://youtu.be/0exHWxV-uW8 Australia's electronics magazine July 2023  23 Fig.22: the Wallbox Quasar offers bidirectional power flow for V2G applications. Fig.23: a Ford F-150 Lightning connected to a home charging station. The vehicle might be charging or operating in either V2G or V2H modes. Source: www.ford. com/trucks/f150/f150-lightning/2022/features/intelligent-backup-power/ • LG Home Battery (16kWh for RESU16H Prime; siliconchip.au/link/ abk2) • sonnenBatterie Evo (10kWh; siliconchip.au/link/abk1) • Redflow ZBM3 (10kWh; http:// siliconchip.au/link/abk5) • DCS PV Series (15kWh; http://­ siliconchip.au/link/abk0) • Zenaji Aeon (1.93kWh, expandable; siliconchip.au/link/abk4) Note that some hybrid vehicles support V2G, but they have much smaller batteries than dedicated EVs, so they will not work as well in this role. The way it works is when an EV is plugged into a home charger, power can flow bidirectionally to either charge the EV battery from the grid or discharge it and export the energy into the home or back into the grid to meet local demand. As with grid-scale batteries, the objective is to charge the battery when power is cheap and use it in the home or export it when power is expensive. Still, you would want to avoid totally discharging it, especially when you might need to use it. Of cars available in Australia, V2G is supported by the Nissan Leaf (full EV, 39kWh), Mitsubishi Outlander PHEV (hybrid, 20kWh) and Mitsubishi Eclipse Cross (hybrid, 13.8kWh). V2G Jetcharge (siliconchip.au/link/ abk6) are doing work in this area in South Australia. The Wallbox Quasar (siliconchip. au/link/abk7), shown in Fig.22, is an example of a bidirectional charger What’s inside a DC fast charger? DC fast chargers are essentially switchmode power supplies converting AC from the mains grid to a variable DC voltage at high power for battery charging. Of course, they incorporate battery charging logic, communications with the vehicle, metering, communications with the owner and everything else required to do the job. All but the most basic fast chargers will incorporate multiple switch-mode units in parallel – see the adjacent photo. For a start, it’s very difficult to design a single device to deliver 100kW or more, while it’s relatively easy to design a supply capable of delivering, say, 10kW that can be paralleled for more power delivery. This also gives manufacturers the flexibility to design one charger board and then deploy it in a range of products, from the low end to the high end. suitable for V2G. It can charge or discharge at up to 7.4kW, operating between 150V and 500V and using a CHAdeMO connector plus internet connectivity. Other carmakers supporting V2G technology include: • Volkswagen Group are building V2G hardware into all their vehicles that use their Second Generation Modular Electric Toolkit (MEB), a standardised EV platform. Vehicles on this platform include various Audi, Seat-Cupra, Skoda and Volkswagen EVs using the Type 2 port. • Porsche (part of VW) has been testing the concept with the Taycan EV; it may be able to be implemented in future with a software update. • The Ford F-150 Lightning pickup truck in the USA supports V2G (see Fig.23), although V2G is currently only being tested: siliconchip.au/link/abk8 Tesla has not announced plans to support V2G, although presumably, they could implement it with a software upgrade in some models. Before using V2G, consider whether it will shorten the expected life of your EV battery and whether the cost of replacing it will be higher than the Fig.25: the Kerb Charge system, charging an EV in the street. Source: www.kerbcharge.com.au The power source for a Tesla V3 Supercharger being installed. Note the two rows of what appear to be metal boxes containing switchmode converters. Source: https:// teslamotorsclub.com/tmc/threads/supercharger-beaverton-or.283907/page-2 24 Silicon Chip Australia's electronics magazine siliconchip.com.au Hybrids vs EVs Fig.24: power outlets on the Ford F-150 Lightning pickup truck. Source: same as Fig.23 benefits of the V2G connection. Vehicle to Load (V2L) and Vehicle to Home (V2H) Vehicle to Load (V2L) refers to the ability to plug mains-powered appliances into your EV, such as power tools, floodlights or a kettle. This is useful for tradesmen working at building sites or recreational campers, for example. With Vehicle to Home (V2H), a vehicle can be plugged into your home via the right sort of charger interface, to power your home during a power outage. A variation of this is Vehicle to Building (V2B), where a vehicle powers an entire building, or V2X, where it powers ‘everything’, with bidirectional power flowing through a building to the grid. V2L is available on EVs such as the Hyundai IONIQ 5 (Fig.26) and KIA EV6. The Ford F-150 Lightning mentioned above also supports Vehicle to Load (V2L) and Vehicle to Home (V2H) during power outages. Battery charging efficiency According to tests by ADAC, a major German car association, electrical EVs are purely electric and only operate from a battery, while hybrids combine an internal combustion engine (ICE) with a battery. In both cases, regenerative braking is used to recover some kinetic energy into the battery during braking. Plug-in hybrids are hybrids where the battery can also be recharged from the mains. One advantage of a hybrid over a regular ICE vehicle is that the engine can mostly run at optimal efficiency, at a fixed RPM and throttle position, to charge the battery and/or drive the wheels. Not all models mentioned below are representative and are not necessarily current or available in Australia or New Zealand. We have included the range for all-electric EVs and plug-in hybrids on battery only. All-Electric: Audi e-tron (336-444km), BMW i4 (510-590km), Hyundai Ioniq electric (373km), Jaguar I-Pace (470km), Kia EV6 (484-528km), Lexus UX300e (305km), Mini Cooper SE (200km), Mercedes-Benz EQA (480km), Nissan Leaf (270-385km), Porsche Taycan (431-484km), Tesla Model 3 (491-614km), Tesla Model S (637-652km), Tesla Model X (580-547km), Volvo XC40 Recharge Pure Electric (380-418km). Parallel Hybrid: the ICE and electric motor are locked together and can drive the vehicle individually or together, eg, Honda Insight. They usually require the ICE to be running to move. Mild Parallel Hybrid: like a parallel hybrid but with only a small electric motor to keep various pumps and the aircon compressors running, and provide extra power for acceleration: Honda Civic Hybrid, Honda Insight 2nd generation, Honda CR-Z, Honda Accord Hybrid, Mercedes Benz S400 BlueHYBRID, BMW 7 Series hybrids, General Motors BAS Hybrids, Suzuki S-Cross, Suzuki Wagon R and Smart Fortwo. Series-Parallel Hybrid: two drive motors are used, ICE and electric. Depending on conditions, either motor can be used or both together, coupled in such a way that each can contribute any amount of the total power, eg, Toyota Hybrid Synergy Drive/Toyota Hybrid System II including: Toyota Prius, Ford Escape and Fusion Hybrid, Lexus RX400h, RX450h, GS450h, LS600h and CT200h. Series Hybrid: driven by an electric motor and can function as an EV when there is sufficient battery power, but an ICE drives a generator to charge the battery: BMW i3 with Range Extender, Fisker Karma, Nissan Note with ePower. Plug-in Hybrid: a serial or parallel hybrid with a larger battery that can act as a pure EV for shorter distances: MG HS Plus EV (52km), Ford Escape ST-Line PHEV (69km), Mitsubishi Outlander PHEV (69km), Mini Countryman All4 Hybrid (61km), Mercedes-Benz GLC 300e (46km), Range Rover Velar (69km), BMW X5 xDrive50e (94-110km), Porsche Panamera (51km). Note that the electric range of plug-in hybrids is limited; it’s 110km at most in those examples and usually much less. Long journeys will still invoke the ICE motor (still, many peoples’ commutes are within these ranges, possibly even the round-trip). Fig.26: an external V2L interface on a Hyundai IONIQ 5. There is also an interior outlet. There is a similar external adaptor for the Kia EV6 as well as an interior outlet. Source: www.hyundai.co.nz/v2l siliconchip.com.au Australia's electronics magazine July 2023  25 Considerations for a home EV charger If you want to buy an EV and charge it at home, here are some things to consider: 01 The standard plug-in charger that comes with your EV will take many hours, maybe days, to fully charge it. You need a dedicated hard-wired highpower charger to charge the car quickly. Still, the slow charger may be adequate if you only drive short distances or will leave it plugged in permanently between trips that do not fully exhaust the battery. 02 Many different chargers are available. Some are ‘smart’, with various features; some support solar panels; some are bidirectional and support V2G (see elsewhere). Choose one that suits your needs. 03 Consider whether you should buy a charger that supports standards from the Open Charge Alliance (www.openchargealliance.org). 04 Unless you are offered an excellent deal, consider whether you need a charger from your vehicle manufacturer that might only charge specific models. Would you be better off with a more generic model that will work on other vehicles in your household (perhaps later purchases) or others you may buy in future? Check that the charger will work with your proposed vehicle and does not affect the vehicle warranty (it shouldn’t). 05 Make sure you get the right cable length to go between the vehicle and the charger. You might usually charge it in a garage, but what if you sometimes want to charge it on the driveway? It might be worth getting a longer cable. 06 If you have multiple vehicles in your household, you might need multiple chargers to charge more than one car simultaneously. Will your household power supply support that? 07 If charging from solar panels, ensure you have enough capacity, especially for winter use. It is unlikely that you will be able to fully charge from solar panels unless you have a very large solar installation and can charge during most of the day. 08 Charging your car might cause you to drain your solar battery. Will the charger communicate with the battery and take power from the grid when necessary? Remember that there are substantial losses in charging from battery to battery. losses of between 10% and 30% occur when charging an EV from a wall socket at home, and losses of 5% to 10% occur when using a ‘wall box’ (dedicated hard-wired charger, presumably Level 2). In their tests, the Renault Zoe lost 30% at the wall socket, while the most efficient car was the Fiat 500e, which lost only 5%. Further losses occur due to some vehicles drawing power from the grid to heat or cool the battery at extreme temperatures. Battery heating and cooling is very important, since many early EVs that lacked active battery temperature management experience shorter battery lives with early reductions in range. Converting battery power back to motive power involves an additional 5% to 10% loss – see siliconchip.au/ link/abk9 Remember that those were only the losses from the wall to the battery and did not include grid losses or the inefficiencies of the power generation itself. More links & videos • A Daily Mail article highlighting the difficulty of finding a charging station that is not busy: siliconchip. au/link/abjs • “Towing with my Ford Lightning EV Pickup was a TOTAL DISASTER!” – youtu.be/3nS0Fdayj8Y • “Can a generator charge your Tesla?” – youtu.be/T92oxFrOA6M SC 09 Consider installing a three-phase power supply to your house if you don’t already have it. This will allow more charging power (and less charging time). My electrician said that adding three-phase power to a typical home would start at about $3,000 plus utility fees. It will be more expensive if power is supplied to the house via underground cables rather than overhead wires. 10 If you live in an apartment complex, find out whether you can get permission from your owner’s corporation to install charge points, likely at your expense. EVs have been banned at an underground parking garage in Germany due to fire risk, and this ban could conceivably extend to underground garages at apartment complexes, including in Australia. See siliconchip.au/link/abka Editor’s note: from October 2023 in NSW, new apartments must have the ability to charge electric cars; see siliconchip.au/link/abkb 11 What if you have to park your car on the street? Local councils have fined some people when they have run cables from their houses across footpaths to charge EVs. To alleviate this problem, some local councils are trialling schemes where a cable is run from a resident’s home, under the footpath and to a location near the gutter with a charging point, at your expense, of course – $6,000 plus other costs. You would have to hope no one took the adjacent parking space! See siliconchip.au/link/abjr 12 An Australian company that makes such charge points is Kerb Charge (www.kerbcharge.com.au) – see Figs.25 & 27. But also keep in mind that there are usually council regulations against blocking or placing obstacles on footpaths (eg, to ensure people in wheelchairs can get about), so you would need to verify you would not get in trouble before installing such a device. 26 Silicon Chip Australia's electronics magazine Fig.27: the inventor of the kerb charger, Rod Walker from Kerb Charge (www.kerbcharge.com.au). Source: www.portphillip.vic.gov.au/ media/1uwb0n2f/img_1574.jpg siliconchip.com.au UPGRADE & SAVE Build It Yourself Electronics Centres® ench upgrades Big savings on workbore... & much m 30 x 30 x 40cm build volume for larger prints Not just for desoldering r works great as a regula hot air gun! SAVE $431 719 $ SAVE $50 SAVE 25% 70 $ Q 1090 K 8606 T 1289 119 $ 9999 Count True RMS Multimeter Heat Gun & Hot Air Re-Work Desoldering Iron With in-built AC mains detection. Featuring a striking easy to read reverse backlit screen and a massive 9999 count readout. 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Features: • Two pairs of 6L6 beam power tetrodes • Two pairs of 12AX7 twin triodes • 2x10W RMS power output into 8 Ohm loads • Remote volume control K 5528 SAVE $250 499 $ HUGE ONLINE CLEARANCE SALE ON NOW <at> altronics.com.au Western Australia Build It Yourself Electronics Centres Sale Ends July 31st 2023 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au » Perth: 174 Roe St » Joondalup: 2/182 Winton Rd » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd Victoria 08 9428 2188 08 9428 2166 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St 02 8748 5388 Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd 08 8164 3466 Please Note: Resellers have to pay the cost of freight & insurance. Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. © Altronics 2023. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. *All smartphone devices pictured in this catalogue are for illustration purposes only. Not included with product. B 0007 Find a local reseller at: altronics.com.au/storelocations/dealers/ Using Electronic Modules with Jim Rowe Quason VL6180X - Laser rangefinder - Light level sensor This module should be of particular interest if you want to build robotic devices. It uses infrared (IR) light to accurately sense the proximity of objects from 0mm to well over 100mm. It’s based on a technology known as FlightSense, patented by ST Microelectronics. T he Quason VL6180X range-­ sensing module comes on a tiny 17.8 × 20.3mm PCB with a handful of SMD components on it. As you can see from the photos, it includes three SOT23-3 devices and one 12-lead SMD IC, itself only 4.8 × 2.8 × 1mm. The secret is all inside that innocent-­ looking 12-lead IC in the centre of the PCB. There’s a lot more in that tiny package than you might expect. It’s a complete optical ranging system with a tiny IR (infrared) laser, two optical sensors (one for IR, the other for ambient light sensing), plus a microcontroller unit (MCU) with internal memory. This IC is the heart of the VL6180X sensing module – the rest of the components are there just to support it. Inside the VL6180X The IR laser driver section is shown in the centre, with the range detection section just above the MCU. To make a ranging measurement, the MCU first sends a command pulse to the IR laser driver to send out a short IR light pulse at a wavelength of 850nm. Then, it measures the time until the ranging detection section reports that a reflected IR pulse has been received. The MCU can then calculate the current distance to the object that reflected the IR pulse, by taking into account the speed of light in air and the time taken for the out-and-back journey. The speed of light in air is close to 299,702,458m/s (metres per second), which equates to 299.702m per microsecond or 0.2997m per nanosecond. Fig.1: the block diagram for the VL6180X rangefinder IC. The internals appear quite simple, with a separate section for the light sensing, IR emitter and ranging. However, very precise timing is required to make calculations down to the millimetre resolution, so the actual circuitry is more complicated than you might think. It’s made by European semiconductor manufacturer ST Microelectronics and uses its patented FlightSense technology. Unlike optical sensors that attempt to detect distance by measuring the proportion of light sent to an object that is reflected back from it, ST’s technology accurately measures the time the light takes to travel to the nearest object and reflect back to its sensor, which ST calls the ‘time of flight’. In short, it’s a kind of light-based radar or ‘LIDAR’. Fig.1 shows what’s inside the VL6180X and should help in understanding how it works. Near the bottom is the MCU with its ROM (readonly memory) and RAM (random-­ access memory) below it, while above it is the ambient light sensing section. siliconchip.com.au So light takes close to 3.336ns to travel one metre or 0.3336ns to travel 100mm. If the out-and-back journey of the light takes, say, 0.6672ns, the total path length is 200mm, so the distance between the sensor and the object must be 100mm. The key to this method of determining distance is precise measurements of very short time delays. To measure over a range of 1-100mm with 1mm resolution, the chip must have a timer capable of measuring the difference between emission and reception from just 7ps (picoseconds) to 667ps with 7ps resolution or better. One picosecond is one trillionth (10−12) of a second! Such capability is thanks to modern semiconductor manufacturing Australia's electronics magazine July 2023  31 Here the module is shown at nearly three times actual size for clarity. techniques that can make tiny transistors with predictable properties. In addition to this ‘time of flight’ range measurement, the VL6180X can also measure the ambient light level using the sensor and ambient light sensing (ALS) section shown at the top of Fig.1. This appears to be a ‘bonus’ feature as it does not factor into the distance measurements It can measure light levels between 0.002 lux and 20,971 lux, with what is described as a ‘photopic’ response. That means it responds to light wavelengths in the visible range of 400700nm (with a peak at around 550nm) as seen by the human eye at ‘well-lit’ lighting levels. The MCU in the VL6180X can take these measurements either once or repetitively and can also interleave range and ALS measurements. It accepts commands and makes the measurement data available via the Fig.2: the top of the VL6180X IC features three tiny holes that are critical for its functionality. These apertures are required for sensing and emission, with the largest being only 0.58mm in diameter. There is also an even smaller ‘vent’ hole. It’s important to note that the light sensor has a very narrow ‘cone’ and measures objects up to 150-200mm away. 32 Silicon Chip I2C port (pins 5 and 6) at lower right in Fig.1. You are probably wondering how all these impressive things can be done by the very small and innocent-­looking chip visible in the centre of the module PCB. Although they are not easy to see with the naked eye, there are actually three apertures on the top of the device, located on its centre line as shown in Fig.2 (which shows the top of the VL6180X at six times its actual size). The largest aperture (0.58mm diameter) near the centre is for the ALS sensor, while the smaller 0.5mm diameter one near the far end is for the IR ranging laser emissions. The even smaller 0.3mm diameter aperture near the ALS at the pin 1 end is for the IR ranging return sensor. A fourth and very tiny ‘vent’ hole is at lower centre, midway between pins 3 and 4. The VL6180X is designed to operate from a supply of 2.8V ±0.2V, with an average operating current of 1.7mA in ranging mode or 300µA in ALS mode. The current it draws in standby mode is less than 1µA. And the I2C interface can operate at up to 400kHz, with a 7-bit address of 0x29 (41 decimal). The full module Fig.3 shows the complete circuit of the Quason module, with the all-­ important VL6180X device (IC1) visible at lower left. At top centre is REG1, an XC6206 LDO voltage regulator used to step down the 5V input supply (at pin 7 of CON1) to the 2.8V needed by IC1. The 2.8V from REG1 is also made Useful links • www.aliexpress.com • www.st.com/content/st_com/ en.html • www.arduinolibraries.info/ libraries/vl6180-x • github.com/adafruit/Adafruit_ VL6180X available at pin 6 of CON1, for possible use by external circuitry. Both the GPIO0 and GPIO1 pins of IC1 are pulled up to 2.8V via 47kW resistors. The GPIO1 pin is then taken directly to pin 4 of CON1, while the GPIO0 pin is connected to pin 3 of CON1 via diode D1. This allows IC1 to be held in standby mode by pulling pin 3 of CON1 to ground. That is why this pin of CON1 is labelled “SHDN” (for “shutdown”). Mosfets Q1 and Q2, connected between the SCL and SDA pins of IC1 and the corresponding pins 2 and 1 of CON1, provide logic-level conversion. This way, the 2.8V signal swings at pins 5 and 6 of IC1 are converted into 5V swings at pins 2 and 1 of CON1, and vice versa. This allows the module to be connected to external circuitry running from a 5V supply, like an Arduino or similar MCU. The way this kind of ‘passive’ level shifter works is quite clever. Q1 & Q2 are N-channel devices, so they switch on when their gate voltage (“G”) is significantly higher than the source voltage (“S”). At idle, the source is pulled to +2.8V via one 10kW resistor, while the drain is pulled to +5V via another. Fig.3: the circuit diagram for the Quason module which utilises the VL6180X IC. Q1 and Q2 are used for logic-level conversion. Australia's electronics magazine siliconchip.com.au With the gate and source both at +2.8V, the Mosfet is off, so no current flows. If IC1 pulls its end low, the gatesource voltage becomes +2.8V, so the Mosfet switches on and the corresponding pin on CON1 also goes low. Alternatively, if the pin on CON1 is externally pulled low (eg, by an MCU), the Mosfet is initially off. Still, its parasitic ‘body diode’ (visible in Fig.3) allows the corresponding pin on IC1 to be pulled down to about +0.7V. The gate-source voltage of that Mosfet is then 2.8V − 0.7V = 2.1V, high enough for the Mosfet to switch on, pulling the pin on IC1 down to 0V. So when one side goes low, the other does too, but if both sides are allowed to be pulled high by the pull-up resistors, they remain high at different voltage levels. Fig.4: the Quason module can be easily connected to an Arduino Uno (or similar), with just four leads. Connecting it to an Arduino As you can see from Fig.4, connecting the module to an Arduino Uno or compatible is very straightforward. The module’s VIN pin connects to the Arduino’s 5V pin, its GND pin connects to one of the Arduino’s GND pins, and its SCL and SDA pins connect to the same pins on the Arduino. You will also need an Arduino library to get the two communicating, plus a sketch to use the library to make measurements. A couple of these libraries are listed on the Arduino website at www.arduinolibraries. info/libraries/vl6180-x – in both cases, they provide links to the library ZIP files on GitHub. When you download and unzip either of these libraries, they generously provide example sketches to get you going. I downloaded one of these libraries, added it to my list of libraries in the Arduino IDE and then loaded one of its example sketches. It was only a few minutes before I could wave my hand up and down above the VL6180X and see its As you can see from this enlarged photo, the Quason VL6180X is miniature, measuring just 17.8 x 20.3mm. siliconchip.com.au Australia's electronics magazine distance varying in the ranging data on the Arduino IDE’s Serial Monitor. It was as simple as that! So it’s pleasingly easy to get the Quason VL6180X IR range sensing module going with an Arduino. This, plus its low cost, suggests that it would be very suitable for DIY robotics. You might even be able to use a couple of the modules to make a digital Theremin! Where to get it We obtained the module in the photos from the Quason Official Store, one of the vendors on AliExpress (see www.aliexpress.com/ item/1005001572022389.html), for $4 including shipping. But there are several other vendors on AliExpress offering it for similar prices, such as SuperModule Store, DIY-Victor Store and HARYE Store. It is also available from eBay supplier Cakemol8 for just over $10, including shipping. And Australian firm AHEM Engineering (https://shop. ahem.net.au) also seems to have it for $12.45 (including GST) plus postage cost. A very similar VL6180X-based module can be found on the website of Newcastle firm Core Electronics (https://core-electronics.com.au) for $23.15 + $6.00 for shipping. While it is considerably more expensive than the AliExpress and eBay sellers, you are likely to get it within a couple of days rather than a few weeks due to being shipped from Australia. SC July 2023  33 D Y NA MI Dynamic NFC Tag Features C − Compact tag (22 × 31mm) − Thin credit card/business card size tag (86 × 54mm) − Arduino sketch and jig allows custom tags to be easily created − Tags can also be written from apps Supported NDEF Tag Types − Text − URI/URL (http:, https:, tel:, mailto: and many more) − WiFi network handover − vCard − MIME file types N F C G Supported Chips A T − − − − − − ST25DV04K ST25DV04KC ST25DV16K ST25DV16KC ST25DV64K ST25DV64KC Project by Tim Blythman Near-field communication (NFC) devices have become widespread, especially for ‘contactless’ payments. The availability of dynamic NFC tags means you can now easily create your own custom NFC/RFID Tags. This article explains how to program NFC chips that can be used as smart business cards and more. Y ou likely have several NFC tags in your possession. Most bank cards and stored credit public transport cards use NFC technology. You might also hear them referred to as RFID or contactless cards. NFC protocols allow communication over distances up to around 5cm using antennas transmitting and receiving at 13.56MHz. The NFC Forum is responsible for standardising NFC technology. RFID is a broader term technology that includes NFC, also having systems that operate at 125kHz and around 900MHz. It’s now possible to implement your own ‘dynamic’ NFC tags using a handful of components. ‘Dynamic’ means that the tag’s contents can be easily reprogrammed. While you might be familiar with how easily NFC allows money to 34 Silicon Chip leave your bank account, NFC tags can also allow small amounts of data to be stored and transferred. With many mobile smartphones having NFC chips, we’ll look at some apps that can work with NFC tags, including reading and writing. Writing custom data to tags using a Raspberry Pi Pico microcontroller and the Arduino IDE is quite easy. Such tags can also be read back using the microcontroller too. These custom tags can contain, for example, a vCard file. That format encapsulates the sort of information typically found on a business card. A programmed tag thus behaves like a virtual business card and can be ‘taken’ by simply reading it with an appropriate NFC reader, such as a mobile phone. The phone can import those contact details into an address book. URIs (uniform resource identifiers) Australia's electronics magazine such as web addresses can also be written to a tag (a URI is a more general form of a URL, also known as a link). Customers can be directed to a website by tapping their mobile phone instead of manually entering a web address, similar to how QR codes are often used. NFC technology Jim Rowe covered an Arduino shield that uses NFC technology in an article from September 2018 (siliconchip. au/Article/11236). That article briefly explained the history and technology behind NFC. Despite being based on NFC technology, the shield from the 2018 article (which uses a PN532 NFC controller IC) will not work with these tags as they use different versions of the NFC standard. The PN532 can work with tags that comply with ISO14443A siliconchip.com.au (type 2, 3 or 4 tags), while the tags we are using comply with ISO15693 (type 5 tags). One of the great advantages of NFC is that the tag does not need its own power source. The reader creates an RF field at 13.56MHz that is picked up by the tag; it harvests energy from that to power its internal circuitry. Since the tag does not need a battery, it can be tiny. Tags the size of coins are commonplace, and smaller tags are possible. As shown in Fig.1, the coils in the reader and tag effectively form an aircored transformer, which limits the practical communications range. Data is transferred when either the reader or the tag modulates the RF field. The reader can do this easily, as it generates the field, while the tag can do this by changing its RF impedance. The reader senses this through changes in the load it sees as it drives the RF field. For this project, we’re using a specific type of chip that provides the dynamic tag feature. Unfortunately (?), this means that you won’t be able to hack into your bank card and trick it into thinking you have more money than you do! Terminology A reader is a device that generates an RF field and can use this to communicate. You might also hear the term emitter used, since this device emits the RF field. ‘Tags’ are simply devices that can communicate with an NFC reader. They are typically implemented by combining a tag-capable chip (which contains some non-volatile memory) with an appropriate antenna and perhaps a few passive components. The antenna is often little more than a printed foil loop, similar to a PCB trace antenna, but on a thinner This timetable pole at a bus stop in Queensland includes an NFC tag with an NDEF URI record. It directs users to a web page displaying live bus departure times for the bus stop. substrate. We tried a few variations on custom antennas that we’ll describe later. Some tags have an internal EEPROM, including the chips we are using, in which case the reader might be able to write to the tag and change its contents. Portable tags are commonly found in the form of a card or a keyfob that can be easily carried around. You might also see fixed tags, often in a more robust enclosure to prevent damage. The NDEF (NFC Data Exchange Format) specifies headers and other data that indicate what sort of data the tag carries; these are the sort of tags this project allows. NDEF tags are only a subset of NFC, and other types of NFC tags exist. The software we have written allows you to explore NDEF data at a low level. Briefly, there is a Capability Container (CC), which indicates that the tag contains NDEF data and the amount of available storage space. This, in turn, points to an NDEF message, which can contain one or more NDEF records. An NDEF record is roughly analogous to the contents of a single file, although the NDEF message doesn’t have a file system as such. While NDEF allows multiple Fig.1: with NFC, an unpowered device (the tag) is powered by the received RF field and can transmit data back to a reader or emitter by modulating that field. siliconchip.com.au Australia's electronics magazine messages and records on a tag, for simplicity, our software only writes one message containing one record at a time, although it can read multiple records. The ST25DV IC Dynamic tags are those tags that can be easily reprogrammed. In this project, we will use members of the ST25DV family from ST Microelectronics. These parts include the RF interface needed to implement NFC, an EEPROM and an I2C interface that allows their internal EEPROM to be modified and thus present changing data to an NFC reader. Many tags, including those from the ST25DV family, can also be written over the RF interface, provided that the ‘reader’ also has write capabilities, as many do. One of the apps we tried (from ST Microelectronics) can write to these chips. You don’t necessarily need to use the I2C interface to work with these chips, but it is an easy way to do so. In fact, many readers (especially those on mobile phones) can also emulate tags; this is the basis of how ‘pay by phone’ technology works. The phone emulates a virtual contactless credit card. The specific chips we are using are the ST25DV04K, and they have 512 bytes of EEPROM space (with maybe a dozen bytes taken up by the NDEF headers). Data such as that found in brief text files is an excellent candidate for being passed around, including the vCards mentioned earlier. Similar chips from the same family can hold up to 8kB, which will also work with all the software we will discuss, but we haven’t concentrated on them mainly because of how long it July 2023  35 takes to transfer that much data over an NFC link. Possible uses Some people will find it convenient to program tags once and then use them as smart business cards or to pass other information around. For example, you might provide a tag to allow guests to connect to your WiFi network when they visit. You could attach a tag to an object containing text information about that object. You might have heard of ‘smart posters’ being used in advertising. These are nothing more than printed posters accompanied by a tag that provides information beyond what is printed on the poster. One use we have seen ‘in the wild’ is a tag at a bus stop. The tag is enclosed in a sturdy plastic shell and attached to the post that holds up a printed timetable (see photo). This is a simple but practical application. This tag contains a URI NDEF message that points to a web page providing live bus departure times for that specific stop, supplementing the fixed information on the printed timetable. Screen 1 shows a scan of this tag by one of the apps we will discuss later. It also uses a chip from ST Microelectronics (but a different one). We have written an Arduino program that can add several types of records to these cards. As well as the Screen 1: an ST25 NFC Tap app scan of the bus stop tags shown in the photo. It has a much smaller capacity than the tags we are using, but still enough for a URI pointing to a web page. 36 Silicon Chip Fig.2: the circuit is very simple and, as you can see from our photos, it’s possible to create it on a small breakout board. Other variants of tag chip IC1 have other functions broken out on more pins, but they are in packages that are difficult to hand-solder, such as WLCSP (wafer-level chip scale package). vCards and URIs mentioned earlier, it can also create simple text file records and WiFi ‘handover’ records. Such a record simply contains sufficient information (SSID name, password and security type) to allow a device such as a mobile phone to connect to a WiFi network. Another NDEF record type is the so-called MIME (Multipurpose Internet Mail Extension) type. The MIME standard was developed for email file attachments and carries information about a file’s type. The vCard and WiFi handover record types are simply MIME records of a specific type (“text/vcard” and “application/vnd.wfa.wsc”, respectively). Thus, a MIME type record could be used to describe anything that could be considered a file, although it would have to fit in the available space on the tag. The receiving device would also need to know what to do with it; we found this was often not the case, even for common file types. Also, when we uploaded some ‘large’ files to the 8kB ST25DV64K chips, they took many seconds to be downloaded by a reader and often appeared not to be working due to this delay. On the other hand, vCards, WiFi handover records or URIs (in the form of web addresses or email addresses) are widely recognised and will be the most useful types for custom tags. With that out of the way, we’ll show you how to construct a Tag using these dynamic tag chips, then use our Arduino software to program them for a specific use. We’ll also show how to create Tags using various antennas, followed by using several apps to interact directly Australia's electronics magazine with the Tags over the RF interface, including reading and writing to them. PCB tags Fig.2 shows the schematic of our small PCB-based tags; IC1 is the chip that implements the dynamic tag function. It could be one of several chips from the ST25DV family, but we used the ST25DV04K variant for most of our testing, and that is what we specify in the parts list. We have developed two different PCBs that implement this same basic circuit (see Figs.3 & 4). CON1 provides a breakout for all the pins of IC1 except those that connect to the antenna. The two resistors are the pullups needed for the I2C SDA and SCL lines, while the 100nF capacitor provides supply bypassing when the chip is powered from CON1. Pins 2 and 3 (AC0 and AC1) connect to a PCB trace antenna. IC1 has an internal tuning capacitance of 28.5pF, meaning that an inductance of 4.7μH is needed for resonance at 13.56MHz. The larger PCB has five turns for the antenna, while the smaller PCB has fourteen turns, seven on each side. In practice, we found that the circuit wasn’t too fussy about the exact coil dimensions. Later, we’ll discuss some of the alternative coils that we tried. The remaining pins on IC1 are VEH and GPO. The GPO pin is an opendrain output that can be programmed to drive its output low under certain conditions, such as while an RF signal is being received, or a write is being performed to the internal EEPROM. The VEH pin (also when appropriately programmed) can deliver an unregulated voltage harvested from the external RF field, when available. In practice, we found this could be up to siliconchip.com.au ◀ Our prototype Tag is constructed on a SOIC-8 breakout board and uses a 4.7μH wirewound inductor as the antenna. The passive components are on the back of the PCB, and the circuit is practically identical to our final designs. Connecting an antenna to pins 2 and 3 of the IC is sufficient to create a functional Tag. The antenna can be as simple as a 4.7μH inductor or many turns of enamelled copper wire. The wire antenna shown here uses just over 1m of wire. Be sure to strip the enamel from the ends of the wire before attempting to solder it. about 4V at up to 10mA. Naturally, this will depend on the reader and other factors, such as the antenna efficiency. In one simple test, we hooked a light-emitting diode (LED) directly between the VEH and GND pins. After changing the appropriate registers to allow energy harvesting to operate, we got it to light up (when in a reader’s RF field). A simple tag (accessible by RF only) could consist of little more than the IC and an appropriate antenna. The passives are only needed if the I2C interface is required. Other tags Since the tag chips can be programmed by RF as well as I2C, it’s possible to create a tag with nothing more than a chip and an antenna. You also could set up a rig using an SOIC socket of the correct width to program the chips before soldering them to an antenna. We even used one of our smaller PCBs (populated with everything except the chip) as a programming rig with the trick of holding the chip in place using a clothes peg. That was sufficient to allow testing of the tag via its RF interface, too. The photos show a few of the prototypes we created to see whether it was possible to make a workable antenna without a PCB. As you can see, the answer is just about anything, within reason. The photo above shows our first prototype, based on a small SOIC-8 to DIP-8 IC adaptor PCB. The antenna is actually a 6mm SMD inductor that is designed for this application. This prototype was great for testing how things should work, including the I2C interface. siliconchip.com.au The group of photos at upper right shows some antenna-only designs, including the design that inspired our first PCB. It is simply fourteen loops of enamelled wire soldered to the AC0 and AC1 pins of a tag chip. The diameter of the coils is just over 2cm, using a little over a metre of wire. This set also shows a circuit with an axial leaded inductor with a nominal 4.7μH inductance, as well as the wirewound inductor seen in the previous photo. We also tried a tiny (M2012/0805) SMD inductor, shown in the upper right corner, but the reader did not pick it up. This correlation between size and sensitivity also extended to the larger tags, with the larger PCB design being the most sensitive. We judged this simply on the distance from which the tag could be detected by the reader, being nearly 5cm for the larger PCB design. Another reason the smaller SMD inductor didn’t work, besides its size, might be that it has a shielded construction. Larger shielded inductors ◀ are also available; avoid using them, as they will not work well as antennas. If you build a Tag without the I2C interface, you won’t be able to use the Arduino Programming Rig that we will describe later. You will only be able to program the Tags using apps installed on a mobile phone or a similar reader. PCB designs The two Tag PCBs are shown in Figs.3 & 4 and the photos overleaf. The smaller PCB is coded 06101231 and measures 22 × 31mm, while the larger PCB is coded 06101232 and measures 85.5 × 54mm. The usual SMD tools and supplies will be adequate for building the PCBbased tags. This includes solder, flux paste, tweezers, good lighting and a fine-tipped iron. Fume extraction is recommended when working with flux paste due to the amount of smoke it generates. For the smaller PCB (06101231), assembly is straightforward. Apply flux to the pads of the four SMD components and rest each in place. IC1 is Figs.3 & 4: assembling the smaller PCB is pretty straightforward. The larger PCB is a little trickier as the components are nestled into cutouts. Still, if you’ve done any SMD soldering, you should be able to use similar techniques to do that. Australia's electronics magazine July 2023  37 The larger card Tag PCB has cutouts so that the components are internal and don’t increase the overall thickness; the SOIC IC is nearly exactly the same thickness as the PCB! You’ll need careful use of flux and solder wick to fit the components. You can create a more polished look by gluing paper or cardboard (or sticking a sticker) to the front and back of the PCB. the only polarised part, so check that the chamfer along one edge (best seen from the end of the chip) aligns with the marking on the PCB. Tack one lead of each component and ensure the remaining leads are within their respective pads. Then solder the remaining leads and refresh the first leads. Check for solder bridges and use solder-wicking braid to remove them. The larger PCB (coded 06101232) is designed to have the components sit inside slots so that they are no thicker than the PCB itself. We used a silicone soldering mat to align the components vertically within the slots. Rather than resting on surface pads, the parts are soldered to exposed edges of the plated-­through holes. The photos above show the final result. Fig.5: the wiring from the Pico to the Tag is simple; you can solder a four-pin header to the Pico and plug the Tag onto that. You can also use a breadboard if you have soldered fulllength headers to your Pico. ◀ IC1 is very close to the same thickness as the PCB (1.6mm), while the passives are much thinner. This is an experimental technique, so it is best suited to constructors with some SMD soldering experience. Before soldering the components, check the pads for copper swarf or burrs, as some may be left from the milling process during PCB manufacture. We found it wasn’t necessary to remove any burrs unless they could cause a short circuit or interfere with component placement. The technique is similar to regular SMD work in that each component should be initially secured by one lead. Use tweezers to locate the part before tacking, after which the remaining leads can be soldered. You might need to build up a small fillet of solder to ensure a mechanically sound connection. Inspect the joints and use flux and solder-wicking braid as necessary to tweak the location and amount of solder. For IC1, first tack the leads along one edge. Then flip the PCB over and gently bend out the IC leads along the other edge to be closer to the PCB pads. Solder these leads to their corresponding pads. We found that the best results came from using a generous amount of solder and flux. We then applied solder braid to the PCB pads only to draw off excess solder, relying on surface tension to keep a suitable amount of solder connecting the lead. If you like, a pin header can be soldered to CON1 on either PCB, but if you only intend to program the tag The smaller Tag is a straightforward SMD design. The staggered holes on CON1 allow a header to be temporarily friction-fitted for programming. That avoids the need to fit the bulky headers permanently. 38 Silicon Chip Australia's electronics magazine siliconchip.com.au once, simply holding the header in place should be sufficient. We’ve offset the holes slightly to give a firm friction fit. If you wish to add some polish to your Tag PCBs, you could glue paper or cardboard (such as your own paper business card) to the front and back of the PCB. You could even get custom stickers of the right size made. The programming jig Our programming jig is simple and just requires a Raspberry Pi Pico (or Pico W) with four connections to CON1 on the Tag PCB. We used the Arduino IDE to write the program, as a good Arduino library is available to work with these chips. If you want to modify or work with our code and don’t have the Arduino IDE installed, download and install it from www.arduino.cc/en/software Still, you don’t need the Arduino IDE to try our sketch out. Simply hold down the white BOOTSEL button on the Raspberry Pi Pico while plugging it into a computer. Then copy the “0610123A.UF2” file (available from our website) to the drive that appears. It’s typically named “RPI-RP2”. If you want to program tags beyond what our sketch can do or tweak the sketch, you will need the SparkFun ST25DV64KC library in addition to the Arduino IDE. This will also work with other chips, including the -04K, -16K, -64K, -04KC and -16KC variants. We’ve included a copy of the version we used in the software download. It can also be found by searching for “st25dv” in the Arduino Library Manager. As well as the SparkFun library, this will show a library from ST Microelectronics, but that one appears to be designed to work with Arduino boards based on their (STM) microcontrollers and not the Pico. We’ve designed the interface to use four adjacent pins on the Pico. These correspond to the four I2C pins on CON1 of either PCB. Pin GP28 is driven high as an output to provide 3.3V. Next to it is a ground pin followed by pins GP27 and GP26 to provide I2C SDA and SCL, respectively. Fig.5 shows the connections needed. The simplest way to achieve this is to solder a four-way pin header to the Pico, allowing the Tag to be friction fitted. However, you could use a breadboard or even solder wires if you like. The RF and I2C interfaces can siliconchip.com.au TAG Programming Interface. ST25 found on I2C. ~ Reboot microcontroller. r Read NDEF entries (1,2,3,4 for specific entry or blank for all). a Decode NDEF entries (1,2,3,4 for specific entry or blank for all). c Decode CC and NDEF headers i Read UID data. e Erase EEPROM and write blank NDEF. w Write NDEF entries: wt Write text NDEF. ww Write WiFi NDEF. wu Write URI NDEF. wv Write vCard NDEF. wm Write text MIME type. wb Write binary (hex) MIME type. d Dump raw EEPROM. h Write raw hex (haaaadd) to EEPROM. o Open I2C session. s Dump system memory. l Set RF write lock bits (0=allowed 3=never). Screen 2: the main menu of our programming jig software has the options shown here. While there are quite a few commands, many are to explore the structure of the data on the Tags and are not needed to create your own Tags. i UID value: E0:02:24:67:09:12:1E:EA ST25DV04K-IE found. EEPROM is 512 bytes. c Capability Container: Short (4 byte) CC version 1.0, 512 bytes available for NDEF. TLV record at 0x0004: NDEF message 23 bytes starting at 0x0006: NDEF record found at 0x0006. MB ME CF SR IL TNF 1 1 0 1 0 NFC type URI type. 1 bytes of type, 19 bytes of payload, 0 bytes of ID. URI Prefix code: 4:https:// siliconchip.com.au ME flag ends message. TLV record at 0x001d: NDEF terminator. Scan complete. Screen 3: the “i” command checks what type of tag chip you have and its capacity, while the “c” command allows you to verify that the NDEF headers are present and correct. coexist, but communication cannot occur on both simultaneously. So you can leave the Tag connected to the programming jig while testing the Tag with a reader, as long as you don’t attempt to read or write at the same time. To control the programming jig from your computer, you will also need a serial terminal program, such as Tera­Term on Windows or minicom on Linux. The Arduino IDE’s serial monitor has limited functionality and will work for some commands, but not all. Verify that your serial terminal program uses CR or CR/LF as the line ending. The program checks for CR and ignores LF. Programming Tags After connecting to the Pico’s virtual Australia's electronics magazine serial port with the terminal program, you should see the main menu (Screen 2). Check that the message “ST25 found on I2C” is shown before proceeding. If you don’t see it, check your connections and use the “~” command to reboot the Pico if necessary, forcing it to test for communication again. Each command consists of one or two letters (followed by Enter), after which you may be prompted for additional parameters depending on the command. Screen 3 shows the output of the basic “i” and “c” commands, while Table 1 details the available commands. The “i” command provides information about the tag chip’s serial number, which can be used to deduce the part number. The part number includes July 2023  39 Table 1 – commands for the programming jig CMD Function Reprint menu ~ Reboot Pico Notes Simply press Enter on a blank line. Use to refresh after connecting a Tag. r Read NDEF messages Uses the SparkFun library to decode NDEF data. from EEPROM; use 1-4 for a specific record (eg, “r1”) a Decode NDEF Uses custom code to perform a more detailed messages from analysis than the “r” command. EEPROM. Use 1-4 for a specific record (eg, “a1”) c Decode capability container and NDEF messages Uses custom code and provides more detail of the structure of the NDEF data rather than contents. i Read UID data and check memory capacity The part number is printed if a known chip type is identified (including the supported chips). e Erase EEPROM (to zeroes) and write a blank capability container Use this on a new chip to format it and allow NDEF records to be written. You can also use this to remove any previous data when reusing a Tag. wt Write an NDEF text record to the Tag Prompts for text that can include line endings. Use Ctrl-D or Ctrl-Z to finish or Ctrl-C or Escape to cancel. ww Write a WiFi handover record to the Tag Prompts for SSID (name), password and security and encryption types. wu Write a URI NDEF record Prompts for URI type (eg, “http:”, “mailto:”) and URI to the Tag text. The URI type simply allows common types to be easily abbreviated and can be omitted by using URI type zero (blank). wv Write a vCard NDEF record to the Tag 40 Creates a version 2.0 vCard file and prompts for all mandatory fields for that format. Also prompts for custom fields. wm Write text MIME type to the Tag Uses the same scheme as “wt” but allows the MIME type to be specified. Most mobile phones will treat “text/plain” types the same as an NDEF text type record, if they have an app that supports that type. wb Write binary MIME type to the Tag Prompts for MIME type and accepts hex bytes (or single nibbles if separated by white space). Use Ctrl-D or Ctrl-Z to finish or Ctrl-C or Escape to cancel. d Dump ASCII and text contents of the Tag’s EEPROM This is handy for viewing the raw EEPROM contents if you want to see how the NDEF entries are encoded and decoded. h Write a single byte to EEPROM The format is “haaaadd” where aaaa is a 16-bit address and dd is 8-bit data in hexadecimal format. o Opens a security session using the default ‘00000000’ password This is needed to permit command “l” to work. s Dump system memory and dynamic registers You would only use this if you were interested in the advanced features of the chip. l Modify the RF lock bits “l0” clears the lock bits and allows RF writes to EEPROM. “l3” forbids RF writes to EEPROM, so the contents can only be modified via I2C. Silicon Chip Australia's electronics magazine the EEPROM size in kilobits; the ST25DV04K part shown has 4 kilobits (512 bytes) of EEPROM. The “c” command interprets any NDEF data that is present. What is shown in Screen 3 is typical for a tag with a single URI entry, in this case, a link to the Silicon Chip website. Screen 4 shows a raw dump of the EEPROM contents in both ASCII (at left) and hexadecimal (at right). The link text is visible, preceded by some header data. You don’t need to know the header formats, as the library can generate them. The minimal steps for creating a custom tag start with the “e” command to erase the tag contents if it is not blank. While the chips start out empty, the library depends on the appropriate capability container entry existing, which is also added by the “e” command. Follow that with one of the “w” commands to write an appropriate NDEF entry. The “wt” (text) and “wu” (URI) options prompt for a single entry to be written to the tag. The “ww” command asks for the WiFi name (SSID), password, authentication and encryption types. The two MIME commands, “wm” and “wb”, allow a MIME type to be specified, with the file contents following. The “wm” option can handle text input, including control codes like CR (carriage return) and TAB. Press Ctrl-D or Ctrl-Z (end-of-file) to complete these entries; Ctrl-C or Escape can be used to cancel. The “wb” command expects bytes to be entered as pairs of hexadecimal digits. Single hexadecimal digits can be entered if a space separates them. The same Ctrl-D or Ctrl-Z sequence completes the file. We often use the HxD hex editor on Windows to view files in hexadecimal format. This program also allows the hexadecimal data to be copied and pasted directly into the “wb” command. However, you should be careful only to paste small amounts of data at a time so that the terminal and Pico can keep up with processing the data. After entering the data, confirm the write and see that the data is written correctly. At this stage, the Tag should register if held near an NFC reader such as a smartphone. Most phones should process URIs, WiFi handover records and vCard files without needing extra apps. siliconchip.com.au If you have trouble, ensure your mobile phone has NFC (not all do!), and it is turned on in the settings. Most newer phones should allow you to search your settings; typing “nfc” should be sufficient to find the right one. If you wish to lock the Tag so that it cannot be edited by someone accessing it via its RF interface, use the “o” command to open a security session. There is a default password consisting of eight zero bytes, which is assumed to be unchanged. Finally, use the “l3” command to set the write permissions to ‘never allow RF to write’. This won’t change the I2C permissions, so you can continue to edit the Tag content without unlocking the Tag for RF writes. Unlocking for RF writes is done with the “l0” command. d Area 1 RF access lock bits are set Memory is 512 bytes. 0 1 2 3 0000 .<at><at>......U.silic E1 40 40 00 0010 onchip.com.au... 6F 6E 63 68 0020 ................ 00 00 00 00 . . . 0130 ................ 00 00 00 00 to 3;read always, write never allowed. 4 5 6 7 8 9 A B C D E F 03 17 D1 01 13 55 04 73 69 6C 69 63 69 70 2E 63 6F 6D 2E 61 75 FE FF FF 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Screen 4: a raw dump of the tag chip’s EEPROM can be handy for exploring the layout of the NDEF card structure. You can make out the URI content as raw text. ◀ Screen 5: the tabs on the ST25 NFC Tap app allow you to view and edit the tags and their NDEF contents. This app might be all you need to program tags. Apps We’ll look at a couple of Android apps to read and write to these Tags. At the time of writing, it appears that there are iOS versions of these apps, which we expect to be fairly similar, although we haven’t tried them. The first is ST Microelectronics’ “ST25 NFC Tap” app, which is clearly targeted to work with this range of chips. You should, of course, ensure that your mobile phone supports NFC and that it is turned on. This app allows you to do many of the things that the Arduino Programming Rig can do, although we found it occasionally crashed if the card was moved while reading or writing. Screen 1 shows a typical overview. The NDEF and CC FILE tabs allow the NDEF data to be viewed and edited, while the MEMORY tab allows the EEPROM to be directly viewed (similar to using the “d” command in the Programming Rig). Screen 5 shows the NDEF tab. You can use the button at bottom right (cut off in the screen grab shown) to create a new NDEF record, while one of the buttons at top right allows NDEF records to be cloned. If you haven’t built the Arduino programming rig, cloning is probably the easiest way to create multiple identical Tags. This app can add multiple NDEF records to a single Tag; Screen 6 shows some of the record types that can be added. SMS and email records are specific types of URI records. An SMS record has the format “sms:(phone number)?body=(message siliconchip.com.au Screen 6: the ST25 NFC Tap app can create various NDEF record types, as shown here. There is also a tab that allows the EEPROM to be directly edited. ◀ Australia's electronics magazine July 2023  41 Parts List – Dynamic NFC Tag 1 22 × 31mm double-sided PCB coded 06101231 OR 1 86 × 54mm double-sided PCB coded 06101232 1 ST25DV04K dynamic NFC tag chip, SOIC-8 (IC1) ● 2 4.7kW ⅛W M3216/1206 SMD resistor 1 100nF 50V X7R M3216/1206 ceramic ‘chip’ capacitor Programming jig parts 1 Raspberry Pi Pico (or Pico W) microcontroller board programmed with 0610123A.UF2 1 4-way male pin header, 2.54mm pitch ● there are other options, listed in the introduction of the article Dynamic NFC Tag Kit: we will be selling kits containing one of the two types of PCB, the tag IC and three passive components. SC6747 ($5) is for the kit which includes the smaller PCB SC6748 ($7.50) is for the kit which includes the larger PCB. Screen 7: the NXP TagInfo app can read tags and also decode NDEF messages and records. There is also an NXP TagWriter app that we have not tried. It could possibly be used to customise Tags too. text)”, with the bracketed items replaced by the phone number and message text (without brackets), respectively. You could also use the Arduino Programming Rig to create such a record as a URI type. An email record has a similar format, using the “mailto:” URI type (type 6) followed by an email address. It can optionally have a “?subject=...” field as well as body text (“&body=...”). Most mobile phones that we tested were able to handle all those records. We’re familiar with the NXP TagInfo app, as this can also read ISO14443A cards, such as those that can be read by PN532-based modules. Screen 7 shows a scan of a Tag containing a URI NDEF record using the TagInfo app. Since it can read and interpret NDEF messages, this can be used to validate that Tags have been written correctly by either the Arduino Programming Rig or the ST25 app. Conclusion NFC tags are common these days, and we think many readers will relish the opportunity to create their own smart business cards and custom Tags. We are investigating other ways to use these Tags. One idea is to use them to configure projects wirelessly without needing screens, displays or buttons to be built into the project. That could save quite a bit of time and money. In such a project, the Tag circuit described here becomes part of the project, with IC1 accessed over an I2C bus. The project can read (or write) its configuration to a text NDEF record on the Tag, which a suitably equipped smartphone or tablet can then view or edit. There are undoubtedly other excellent applications for these Dynamic Tags, and we look forward to thinking of new ways to use them in future SC projects. We soldered a four-way header to the GP26, GP27, AGND and GP28 pins of the Pico. The holes in the Tag PCBs are staggered slightly to make good enough contact for programming without soldering. Check that the orientation and pin connections are correct, so you don’t destroy the chip or the Pico. 42 Silicon Chip Australia's electronics magazine siliconchip.com.au Stay connected with our 4G Antennas & adaptors Compatible with 2.4GHz & 4/5G networks for cross-compatibility 1 5dBi Antenna • Magnetic mount • Suitable for LTE, AMPS, GSM, PCS, UMTS and Wi-Fi • 2m lead with FME connector • 337mm long AR3340 ONLY $59.95 4 5m SMA Extension Lead 5 SMA to Induction 3G Plug 6 SMA to Modem Leads • Low loss • 50Ω coax • Flexible lead WC7824 ONLY $54.95 7dBi Antenna • Magnetic mount • 3m lead with FME connector • 435mm long AR3344 ONLY $79.95 2 • Adhesive backing AR3330 ONLY $27.95 7dBi Spring Mount Antenna • ½ wavelength design • 5m lead with FME connector • 740mm long AR3342 ONLY $159 3 3dBi Glass Mount Antenna • ¼ wavelength design • 3m lead with FME connector AR3338 ONLY $49.95 Range of leads that plug into the antenna socket on your USB modem. AR3332-AR3336 ONLY $27.95 EA SMA to Huawei E160/618 Plug AR3332 1 2 SMA to Sierra TS9 Plug AR3334 Telstra 4G USB Modem AR3336 We stock a great selection of Networking Antennas, Leads, Plugs, Sockets and Adaptors to improve the range and reliability of your wireless network. Explore our wide range of wireless networking products, in stock on our website, or at over 110 stores or 130 resellers nationwide. jaycar.com.au/4gwireless 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Electronics in Australia Jim Rowe’s time at RTV&H and Electronics Australia In August & September 2022, Silicon Chip founder Leo Simpson covered the magazine’s history and touched on some of its predecessors: Radio, TV & Hobbies and Electronics Australia. Jamieson (Jim) Rowe was an important figure at both magazines, working on and off for them over 40-odd years before joining the Silicon Chip team. Here is his part of the story. ◀ Editor John Moyle on the front cover of the May 1948 issue of Radio & Hobbies, using a micrometer to check the thickness of a quartz crystal he was grinding. The July 1987 issue of Electronics Australia, when Jim Rowe returned to head the magazine, after Leo Simpson had departed – soon to found Silicon Chip. ◀ F irst, I will give a bit of early magazine history. The first 12-page issue of Wireless Weekly was published in Sydney on the 4th of August, 1922. It was published by W. J. Maclardy, one of the founders of Sydney radio station 2SB (later renamed 2BL), at the suggestion of Florence Violet McKenzie. Florence was Australia’s first female electrical engineer and first female radio amateur, who owned a wireless shop at that time in the Royal Arcade (where Sydney’s Hilton Hotel 44 Silicon Chip currently stands). Ms McKenzie wrote many articles for Wireless Weekly and later was awarded an OBE for her work in founding the Women’s Emergency Signalling Corps (WESC). We reviewed her biography, “Radio Girl” in the February 2022 issue (siliconchip.au/Article/15203). By the start of commercial radio broadcasting in 1923, the magazine flourished, with issues often over 64 pages. Later in 1923, the magazine was sold to Wireless Newspapers Ltd and Australia's electronics magazine continued to grow until April 1939, when it was changed into a monthly release and renamed Radio and Hobbies (R&H). Initially, the Editor of the magazine was A. G. (‘Braith) Hull, while the Technical Editor was John Moyle, who had joined Wireless Weekly in 1932 as a technical writer and record reviewer. Within 12 months, A. G. Hull had left to join rival magazine Australasian Radio World as its Editor, while John Moyle took over as Editor of R&H. siliconchip.com.au ◀ Neville Williams, who joined Radio & Hobbies as Technical Editor in 1941. He became the Editor of Radio, TV & Hobbies in 1960 and then Editor-in-Chief of Electronics Australia in March 1971. Jim Rowe pictured at his typewriter in late 1963, when he was Technical Editor of Radio, TV & Hobbies. He remained in this position when the magazine became Electronics Australia in 1965. ◀ Then, in 1941, Neville Williams joined R&H as Technical Editor. Later in 1941, John Moyle joined the RAAF to become an instructor in the then-highly-secret radar technology. He remained in the RAAF until 1946, rising to the rank of Squadron Leader and working mainly in Melbourne, where he was made responsible for the production of all radar manuals. He visited the R&H office in Sydney occasionally, where Neville Williams had taken over as Acting Editor for the duration. When John Moyle returned to R&H in 1946, he became Editor once again, and Neville Williams returned to the position of Technical Editor. They worked together very well, and the magazine flourished. They developed and published many designs for radio sets, stereo hifi amplifiers and monochrome TV receivers, the latter initially using war-surplus cathode ray tubes and other ‘bits and pieces’. Later, they published four full-scale TV receiver projects but stopped when the prices of commercial TV receivers dropped to the point where home-built sets became unattractive. In February 1955, the magazine’s name was changed from Radio and Hobbies to Radio, Television & Hobbies to better indicate its relevance to the rapidly expanding field of television. In 1956, John Moyle went on an around-the-world fact-finding tour, visiting many places in the UK, Europe and the USA and meeting many leaders of electronics research and manufacturing firms. He had been an amateur radio enthusiast for many years and served as president of the NSW Division of the Wireless Institute of Australia (WIA) before holding Federal office. Then, in 1959, he attended the siliconchip.com.au International Telecommunications Union (ITU) conference in Geneva, Switzerland, representing Australian radio amateurs. Originally he had planned to revisit the UK and the USA after the ITU conference, but he became quite ill in Geneva and was advised by a doctor to return home without delay for urgent treatment. He passed away in hospital on the 10th of March, 1960. He was only 52 but had achieved a great deal during that short life. This was how his passing was noted by the Institution of Radio Engineers (Australia) in their Proceedings for April 1960: He was one of the best technical journalists this country has known; his lucid thinking and enquiring mind led him along paths which few of us have travelled. His journalistic talents are forever engraved upon the technical pedestal of Australian literature. slog, but AWA was very good at giving its trainees a solid practical grounding in just about every aspect of radio and TV manufacturing. I spent a couple of months in the press shop, a couple of months in ‘mills and drills’, another couple of months in the plating shop, a month in the section where they made rotary switches, a month in the section where loudspeakers were assembled and tested, another month in the section where they made tuning gang capacitors, and a month in the section in Belmore where they ground and tested quartz crystals. It was comprehensive training, but by the end of 1958, I became restless at AWA. I was still doing tedious ‘process’ work, like assembling complex wiring looms for broadcasting transmitters or testing small Army transceivers. Some personal prehistory I (Jim Rowe) was born in 1939 (the same year that R&H began!) and grew up in South Belmore - then regarded as an outer western working-class suburb of Sydney. As a teenager, I became interested in electronics while working on Saturdays for Stan Blackmore, who ran a radio and TV sales and repair shop near Belmore station. When I left high school with my leaving certificate in March 1957, I was lucky enough to be accepted as an engineering trainee by AWA (Amalgamated Wireless Australia), then the largest radio, TV and electronics manufacturing plant in the southern hemisphere. In early 1957, I began work as a trainee at AWA’s main manufacturing facility in Ashfield and studying parttime at Sydney Technical College in Ultimo, working towards a diploma in radio engineering. It was a bit of a Australia's electronics magazine The AWA building in York Street, Sydney was their head office until the 1990s. It was also the tallest building in Australia until 1958, the same year Jim Rowe left AWA. Source: https://w.wiki/6cuL July 2023  45 At about that time, some of the engineering schools at Sydney Technical College cut their ties with the College and moved out to Kensington. They became part of the newly formed University of Technology, soon to be renamed the University of NSW. The School of Electrical Engineering was one of the schools that had moved, and although most of my lectures were still held in their Ultimo building, they had moved some of their research and teaching labs to a building on the Kensington campus. A fellow student (John Barker) who had gained a job as a lab assistant in one of the Ultimo labs told me that they were looking for lab assistants for some of the Kensington labs. The pay was not only better than that for AWA engineering trainees, but that job also gave me plenty of time to do homework and course projects. So I took a deep breath and applied for one of those positions. I was lucky enough to get a lab assistant position in the Servomechanisms and Control Labs at Kensington. It worked well, giving me time to do my course homework and teaching me quite a bit about servomechanisms. a letter arrived from Mr Williams offering me the job and inviting me to front up at the magazine in early March 1960. So began my first period of employment with the magazine, which was to last for almost 20 years. Unfortunately, when I joined the RTV&H staff, its Editor, John Moyle, was already in hospital and died the following month. So sad to say, I never even met him. Before long, Mr Williams became Editor of RTV&H. While I was working at the Kensington campus, the Uni of Technology became the Uni of NSW. At the same time, we students in the Radio Diploma course were offered the opportunity to transfer into a B. Sc. (Technology) degree course. It was with that degree that I finally graduated in early 1963 while continuing to work at RTV&H. By the way, after that, I enrolled in a part-time ‘Arts’ degree course at Sydney University. I eventually graduated with a somewhat lacklustre B. A. Introducing RTV&H About halfway through 1959, I learned that my friend John Barker had left the Ultimo labs for a job with the magazine, Radio, TV and Hobbies. John told me he was really enjoying the work at RTV&H, as it was almost “being paid to do what he would be happy to do for nothing”. Not long after that, he rang me at work and told me that another staff vacancy was becoming available at RTV&H. He suggested that I apply for the job, as he felt sure that I would enjoy the job as much as he did. I summoned the courage to apply and, in due course, fronted up at the magazine office on the 12th floor of the Sydney Morning Herald building in Jones Street, Ultimo for my interview with the acting Editor at the time, Mr W. N. Williams. I found the interview rather daunting because Mr Williams was highly respected throughout the Australian electronics industry, having worked with the famous Fritz Langford-Smith on the early editions of the world-­ renowned “Radiotron Designers Handbook”, the ‘bible’ of valve technology. “Fundamentals of Solid State” was one of the many educational series that Jim Still, just after Christmas in 1959, Rowe wrote. 46 Silicon Chip Australia's electronics magazine siliconchip.com.au degree in early 1967 [that possibly came in handy when Jim came to work for us drawing diagrams – Editor]. Still, I seemed to have ‘found my niche’ working for RTV&H, and not long after graduating in electronics, Mr Williams promoted me to the Technical Editor position. I remained in that position when the magazine was revamped and renamed to Electronics Australia (EA) in mid-1965. My early days with EA It was very satisfying and enjoyable working at RTV&H and then EA during the 1960s. Neville Williams was a very experienced, calm and intelligent Editor and leader of the team, and most of the other staff members were very techsavvy and collaborative. We produced a great many electronics projects, news features and technical articles. Sadly, my friend John Barker left the magazine at the end of 1960 to pursue greater things. I hope he achieved them; I am still very grateful that he helped me join the magazine. Early in the 1960s, Neville Williams had written a series of introductory articles for RTV&H called “Basic Radio Course”. It was so well received that some of the other staff members and I revised and updated the articles, and they were republished in the magazine between August 1963 and November 1965. The demand for back issues containing the articles was so great that we were encouraged to combine them into a single magazine-format ‘one-shot’ book called “Basic Electronics Course: An Introduction to Electronics”, published in 1966. This was also so successful that it had to be reprinted many times and sold over 55,000 copies. Then, from June 1966 to May 1967, I wrote a series of 12 articles on digital electronics called “Logic and counting circuits”, which was again so well received that they were published in 1967 as another one-shot book called “An Introduction to Digital Electronics”. In 1970, it was revised and expanded as a second edition. As with “Basic Electronics Course”, it ended up being reprinted several times, eventually selling over 50,000 copies. I recall that Leo Simpson (later to become the founder of Silicon Chip) joined the editorial staff of EA in June 1967. Starting in about 1968, I wrote a series of articles in EA titled “Fundamentals of Solid State”, introducing the basic concepts of semiconductor devices like diodes, bipolar transistors, FETs, SCRs and other thyristors – how they operate and how they are used. In 1970, the articles were published as another one-shot, which ended up being reprinted several times, selling around 50,000 copies. I could not have written the above series without help from Neville Williams and other staff members like technical draftsman Bob Flynn. In March 1971, Neville Williams was promoted to Editor in Chief of EA, and I was promoted to the position of Editor – much to the chagrin of one or two other staff members. Designing the EDUC-8 computer The early 1970s was a time of rapid developments in electronics and information technology, with major breakthroughs in integrated circuits and computers coming every other week or so. So-called ‘minicomputers’ (about the size of a refrigerator) had just appeared. As a result, the Fairfax/ Sydney Morning Herald organisation installed a couple of gleaming new Digital Equipment PDP-8 minicomputers to begin trialling them for computer typesetting. The company’s new IT manager, John Cockram, invited a few people from various departments to learn about computers and programming by attending informal lectures. We could also gain some practical experience with the minicomputers during our lunch hours. I was one of the lucky few invited to do so, and it gave me an invaluable introduction to computers, how they worked and how to program them. This led me to set myself a personal challenge: to design a small computer from scratch, based on what I had learned about their operation as a user and beginning programmer. Very few books were available at that time dealing with the nitty-gritty of internal computer operation, but somehow, I managed to meet the challenge. ◀ In the early 1970s, Jim Rowe was lucky enough to get some hands-on experience programming and using one of the first Digital Equipment PDP-8 minicomputers in Australia, like this one. It inspired him to design the EDUC-8 DIY microcomputer, published as a project in Electronics Australia (there is still interest in the design to this day). The EDUC-8 micromputer has a maximum clock rate of 500kHz, five primary registers and a top power draw of ~60W. You can still purchase the handbook for this project from our website at siliconchip.com.au/Shop/3/1816 siliconchip.com.au Australia's electronics magazine July 2023  47 A ‘humorous’ (?) sketch of a not-toohappy Jim Rowe, drawn in 1973 by Garry Lightfoot. I used readily available medium-­ scale ICs and designed a set of PCBs – drawing them the old-­ fashioned way, with pens and Indian ink. With a go-ahead from Neville Williams, I described my little “EDUC-8” DIY computer in a series of 12 articles published in EA between August 1974 and August 1975. It became the first DIY computer project to be described in Australia and only the second in the world. A bloke in the USA had described a computer based on one of the new Intel 8008 microprocessor chips in the July 1974 issue of Radio Electronics. Still, the EDUC-8 project turned out to be surprisingly popular. We turned the articles describing it into a oneshot called “EDUC-8: AN EDUCATIONAL MICROCOMPUTER”, published in 1975 and selling about 2,500 copies [still available as a scanned PDF download; siliconchip.com.au/ Shop/3/1816 – Editor]. About 400 people built one of the original EDUC-8s, and improved versions also appeared. Incidentally, all these magazine articles, projects and one-shot books were produced using old-fashioned technology. The articles were typed one paragraph at a time on A5-sized ‘copy slips’ using clunky manual typewriters, the circuit board patterns were created using stick-on tapes and circles, and all circuit diagrams were done by Bob Flynn on paper using pens and other drawing tools. This was before the advent of personal computers, after all. Late in 1976, all of the magazines in the Sydney Morning Herald (SMH) magazine subsidiary Sungravure were moved from the SMH building in Jones Street to a much smaller building a few blocks away on Regent Street. The EA editorial office was moved to the ground floor of the Regent Street building, with magazines like Woman’s Day and Dolly moving to the upper floors. The Regent Street building was much closer to Central Station, which was a plus for a few of us! By 1977, we had published quite a few articles in EA about the rapidly expanding field of microprocessors. These had again been quite popular, so we put them all together as a oneshot book called “Getting into Microprocessors”. I edited the book, and staff member Greg Swain produced it [the other founder of Silicon Chip – Editor]. It was again pretty successful, selling around 10,000 copies. Moving on By the middle of 1979, I had worked on the editorial staff of EA for nearly 20 years and had been its Editor for nearly nine of those years. But I was only 40 and was beginning to feel that Dick Smith and Jim Rowe with one of the System-80 ‘business computers’, around 1980. Jim wrote the user manuals for the System-80 and also some programs for it. 48 Silicon Chip Australia's electronics magazine I would be stuck in that position for the rest of my working life. Earlier that year, I had become friendly with entrepreneur Dick Smith, whose rapidly growing retail electronics firm had become the magazine’s largest advertiser. Dick was just about to move his firm’s headquarters and warehouse to a brand new facility in North Ryde, and in July 1979, he sent me a letter inviting me to join his firm as Technical Manager/Director (a fancy name for ‘in-house technical boffin’). He made me a very generous offer of around twice the salary I was getting at EA, so I was very happy to accept. I resigned from EA and joined Dick Smith Electronics in November 1979. Although it involved a 55-minute drive to North Ryde each weekday, and the same time to drive home, I enjoyed working at DSE. Dick had assembled a dynamic team of employees, including General Manager Ike Bain, Marketing Manager Gary Johnston, Service Manager Gary Cratt (founder and director of Av-Comm) and many other good people. Dick Smith himself was a ‘human dynamo’ – working very hard and encouraging everyone else to do so. He was also very generous in sharing his enthusiasm and enjoyment with us all. Part of my job at DSE was getting samples of products from overseas that were good potential products to sell in Australia, then testing them to see if they really were suitable. In the case of minicomputer products like the Exidy Sorcerer, System 80 and VZ-200, once they were ordered, I usually set about preparing readable user and servicing manuals. I also wrote several user manuals for PC applications software: a word processor, a stock control system, a simple invoicing system and others. In 1982, I was involved in writing and publishing the book “Dick Smith’s Fun Way into Computers”, in collaboration with external writer Sue Robinson. Over 30,000 of these were sold. I also designed what became the first 300-baud direct coupled data modem to be approved by Telecom for private sale (up until then, only acoustically-­ coupled modems had been approved). Over 3000 of these low-cost ‘Dataphone’ modems were sold. It was hard work for the first three years, but very satisfying and rewarding. However, things started to change siliconchip.com.au when Dick Smith sold a 50% share of the business to retailing giant Woolworths. At first, the changes were not dramatic because Dick had to stay at the helm for a year, to ensure that the profits continued to rise. When that did happen, Woolworths bought the remaining half of the business and Dick departed. His deputy Ike Bain took the reins, but Ike didn’t have the same energy or talents as Dick. At almost the same time, Marketing Manager Gary Johnston resigned and left, to put into practice all of the knowledge and skills he had learned from Dick. He bought the almost defunct electronics retailer John Carr and Sons and soon resurrected it as Jaycar Electronics. And with Gary at the helm, it quickly grew into the very successful and profitable electronics chain it is today. When Gary passed away in March 2021, the Jaycar Group operated over 180 stores throughout Australia and New Zealand and also had quite a few ‘agencies’ selling their products. After Gary and Dick left DSE, I was foolish enough to take on Gary’s position as Marketing Manager. I soon found that I couldn’t cope with the pressure it involved. At that time, DSE had its own in-house marketing and advertising production departments. There was not only a staff of 23 people to manage (including Ross Tester, who later moved to Silicon Chip), but advertising to plan and produce each week. There was also a huge annual catalogue to plan and produce. It soon became clear to me that I had none of the talents of Dick Smith or Gary Johnston, as I ‘wilted’ under the strain and decided that I needed to depart. Above: the Dataphone is a direct connection telephone modem. It was sold by Dick Smith Electronics in the mid 1980s for $169 each. Right: Dick Smith Electronics also sold imported minicomputers such as the VZ-200 produced by VTech Laser. Jim Rowe would normally go about testing the products and producing user & servicing manuals. Moving to Federal Publishing In late 1984, quite by chance, I met Leigh Emery, who was at the time General Manager of a company called Federal Publishing. It was owned by siliconchip.com.au The February 1985 editorial of ETI was written by Jim Rowe, as the previous Managing Editor, Collyn Rivers, had recently departed. Australia's electronics magazine July 2023  49 a trio of companies: Eastern Suburbs Newspapers (owned by the Hannan family), Consolidated Press (owned by the Packer family) and Fairfax/SMH. Among various other magazines, Federal had acquired EA’s chief competitor, Electronics Today International (ETI), its sister magazine Your Computer and Sonics, a magazine for the pop music and recording industry. When Leigh realised that I was out of my depth at DSE, he asked me to think about joining Federal as managing editor of those three technical magazines. The Managing Editor of ETI, Collyn Rivers, had departed, and they were already having problems with the new Editor of ETI, Roger Harrison. Rather foolishly (with the benefit of hindsight), I decided to take up his offer and began working at Federal/ ESN in April 1984, at their facility in Rosebery. I soon realised that things would not be easy: I would not be working for the very reasonable Leigh Emery, because shortly before I arrived, he was fired following a disagreement with Michael Hannan, the Managing Director. Instead, I would be answering to a pair of accountants. It was all pretty much downhill from there, although things did look up when Geoff Baggett joined Federal as the new General Manager. While I was there, though, two quite significant things happened. One was that both Fairfax and Consolidated Press sold their shares in Federal to the Hannans, so Federal became a wholly-owned subsidiary of Eastern Suburbs Newspapers. The other thing was that Fairfax sold Electronics Australia to Federal Publishing. I think this was because Neville Williams had retired, and Fairfax management had difficulty dealing with the Editor who had taken my place at the magazine: Leo Simpson. I was given the responsibility of moving my old magazine and its staff to the Federal Publishing campus in Joynton Avenue, Rosebery, and then managing it and the other three technical magazines. I found it easy to get on with Leo and the other EA staff members, with whom I was already familiar, but it wasn’t so easy dealing with the problems concerning the other three magazines. In fact, the situation soon became just as fraught as the one I 50 Silicon Chip had left at DSE. By October 1985, I was fired/asked to resign from Federal Publishing, which was a relief because the situation had become so difficult. And on to MicroBee After spending about a month unemployed at home, licking my wounds and doing some much-postponed jobs around the house, I was invited to join the home-grown Australian personal computer company MicroBee Systems, by its Chairman and Managing Director, Owen Hill. The company had just been floated on the stock exchange, and Owen wanted me to join as Publishing Manager to look after the writing, printing and publication of their hardware and software manuals. He even flew me up to their bustling West Gosford factory to show me around and convince me that the offer was genuine. Since I was currently without a job and we had a large mortgage and a family to feed, I took the job at MicroBee. But things began to deteriorate not long after I started work at the MicroBee office and warehouse complex in North Ryde (just down the road from DSE). The Marketing Manager departed after a disagreement with Owen Hill, and as a result, I became Communications Manager – responsible for marketing and advertising as well as publishing manuals. Soon after that, the company began having serious problems, especially in developing the new computer models necessary to ensure its future success. This seemed to be at least partly due to Owen Hill frequently revising the specifications for the new models, forcing the design people to ‘go back to the drawing board’ over and over again. In the meantime, the marketing people and I were having a harder and harder battle to achieve sales of the somewhat dated computer models the factory was still producing. Gradually, staff numbers had to be reduced to lower overheads, and the company’s link with its advertising agency had to be terminated. So I had to write, lay out and book the company’s ads myself. The North Ryde warehouse and office also had to be closed, and the remaining staff and myself were moved to the rear of MicroBee’s store in Waitara. But things continued to get worse, and before long, the board brought in a ‘company doctor’ (Mr Ron Bunt) to try and save the company from oblivion. When I had my interview with Mr Bunt, he told me that the company was probably “doomed” and suggested that I look elsewhere. So I took his advice and did so. Luckily, a colleague from the early days at EA, Dick Levine (who had been Editor of the short-lived EA offshoot Modern World), was by then Editor of the electronics trade publication Electronics News. It was part of the IPC Business Press stable. When I told Dick I needed to jump from the sinking MicroBee ship, he offered me a job as a technical journalist for his magazine. It didn’t pay nearly as much as my jobs at DSE, Federal Publishing, or even MicroBee, but it would allow us to eat and pay the mortgage – just! It was quite pleasant working with Dick Levine and his crew on Electronics News, and I was able to ‘lick my wounds’ once again and more or less recover my self-confidence after the MicroBee ordeal. However, that didn’t last very long because there had apparently been a series of confrontations at Federal Publishing between MD Michael Hannan, The MicroBee ‘Computer-in-a-book’ system was one of the products developed by MicroBee in the 1980s. Source: https://w.wiki/6cue Australia's electronics magazine siliconchip.com.au his bullying General Manager Bernie McGeorge and Leo Simpson – who had been promoted to my old position after my departure. Leo had then departed with some acrimony to plan the startup of Silicon Chip, and many of the remaining staff of EA were planning to join him when it began publication. As a result, I was approached first by the General Manager of FPC, Geoff Baggett, then by his very amiable personal assistant Cassie Bailey, both of whom tried to talk me into returning to Federal to save EA from extinction. Leo had told them, as he departed, that I was probably the one person who could do this, although he didn’t think they would be able to convince me to return after my previous very unhappy time there. Leo was right – I didn’t want to return, and told them so, despite the financial strain we were experiencing trying to live on my modest earnings at Electronics News. However, after a week or two, I received a phone call from MD Michael Hannan himself, asking if he might call into our home in Arncliffe that night, to try to talk me into returning. I warned him that I was unlikely to be convinced, but he was free to try if he wished. He did visit at about 7pm, and we had a ‘full and frank’ discussion for about three hours. I found out later that he had not been home for his evening meal. The result was that we finally agreed I would go back and try my best to keep EA going. Returning to Federal Publishing Around the middle of June 1987, I returned to ESN/Federal Publishing, then located at Bourke Road, Alexandria, next to the large ESN printing works. I then began rebuilding EA – finding new staff and working with them for long hours to keep EA coming out every month and hopefully to increase its reader appeal as well. We must have been reasonably successful because we managed to keep EA profitable for the next 12 years or so, despite several major challenges. One of these was a disastrous fire in mid-1988 that destroyed half of the Federal Publishing building and caused a lot of water and smoke damage to the EA offices and lab. We had to keep working while they rebuilt everything. siliconchip.com.au But the main and ongoing challenge was the very strong competition from Silicon Chip, which Leo Simpson had started publishing in November 1987 with most of the former EA staff. By the middle of 1999, the situation had become more difficult. Advertising revenue was falling along with drooping readership, despite our best efforts. As I had just turned 60, Federal management decided I should ‘retire’ from full-time work on the magazine and be replaced by one of the younger staff members. So Graham Cattley inherited the role of Editor, but I kept writing and working for EA as a ‘Contributing Editor’. This situation continued for the next year or so, with muggins still doing almost as much work as before but doing it from home. However, with me ‘out of the loop’, the magazine was redesigned to supposedly make it more appealing to a broader and less technical readership. Unfortunately, this revamp didn’t work, and the magazine closed down in early 2001, after a run of around 62 years as a monthly publication. So I was out of a job once more, along with Graham Cattley, Technical Editor Rob Evans and others. Luckily for me, I was able to keep earning a modest living by working for Gary Johnston’s firm, Jaycar Electronics – mainly writing ‘how-to’ technical booklets. Before long, Leo Simpson asked me to draw circuit schematics and other diagrams for Silicon Chip. As time passed, I was also able to design electronic projects, write them up and have them published in Silicon Chip. I have continued drawing diagrams, Jim Rowe pictured at his desk at Federal Publishing in late 1989, when Electronics Australia had moved into a new building after the disastrous fire in 1988. You can see the employee car park under construction through the window. but my article contributions for the magazine have transitioned mainly to reviews and technology feature articles. This ‘working from home’ arrangement has worked well for around 21 years and will hopefully let me keep earning a living for the next year or two. Thanks to the internet, there’s no need to commute to the Silicon Chip office at Brookvale, as everything can be moved back and forth via emails and FTP. So there’s much less stress than before, and as a bonus, I get to have morning coffee, lunch and afternoon tea almost every day with my dear life partner Laraine. What more could SC you ask? The “Low Cost 1GHz Frequency Counter” project was published in the April 1993 issue of Electronics Australia. It was developed by Jim Rowe and was meant as the ‘big brother’ to EA’s 50MHz Frequency Counter. Australia's electronics magazine July 2023  51 Project by Charles Kosina This design measures low-frequency signals accurately and quickly. A traditional frequency counter must sample over a long period to get an accurate result. This one instead measures the average period and calculates the inverse, so it only needs to monitor a few pulses to get a precise reading. It’s useful up to about 10MHz. Reciprocal Frequency Counter bought a frequency counter Iaccuracy over 30 years ago, but its is very poor by today’s stan- the frequency is 10,000,000 ÷ 199,900 = 50.025Hz. That’s a great improvement in resdards, being out by as much as 50Hz olution, but highly dependent on the at 10MHz. I replaced its not-very-­ accuracy of the hardware in measuraccurate clock module with a 10MHz ing precisely one cycle. Also, as the TCXO, and I can now rely on it to be signal frequency increases, the resowithin 1Hz at 10MHz. By adjusting lution and accuracy decrease. the TCXO frequency to match that One good thing about this scheme of my GPS-disciplined 10MHz fre- is that the exact measurement time is quency standard, I can be assured of not critical, as the frequency calculasuch accuracy. tion is ratiometric. This means that we But what happens when I want to should get reasonably accurate results measure low frequencies? For exam- as long as we have a clock source with ple, a 50Hz signal. With a gate time of an accurate frequency and synchronise one second, it will most likely show a the measurement period to the rising reading of 50, even if it is not exactly edges of the input signal pulse train. that. It might flip to 49 or 51, but the What do we need to measure with resolution is only 1Hz. such precision? Mains frequency was To improve that, we could have a the first thing I tried. I connected the gate time of 10 seconds and a reso- output of a 6V AC mains transformer lution of 0.1Hz. For a 10mHz resolu- to an RC network to reduce the volttion, a 100-second gate time would be age and filter out noise. required, which is quite ridiculous. The frequency did vary slightly A better way to measure low fre- from reading to reading, and the largquencies is to measure the period. est variation was about 30mHz. This is With the same example of 50Hz, using within the required Australian Energy a 10MHz clock, it would accumulate Market Operator (AEMO) specification 200,000 pulses in one 20ms period. If of 49.85-50.15Hz. The frequency varithe number of pulses measured were ation is caused by constantly changing actually 199,900, that would mean that load conditions on the network. Also, musical instruments need to be tuned to very precise frequencies. In the equal-tempered scale, C4 (middle C) should be 261.63Hz. Concert pitch A4 must be 440.00Hz. All other notes require the same precision, to two decimal places, and a trained ear can pick the slightest differences in pitch. Such frequencies could be measured accurately and quickly using a microphone amplifier and this device. Functional description ► Operating frequency range: 10mHz-10MHz (maximum ~13.5MHz) ► Input sensitivity: 100mV peak-to-peak (~35mV RMS for a sinewave) ► Accuracy: typical error <0.001Hz up to 9.999MHz after calibration ► Sampling time: 0.1s, 1s or 5s ► Reference oscillator: temperature-compensated crystal oscillator (TCXO) ► Power: three AA cells for about 24 hours of battery life Refer to the timing diagram, Fig.1, which is not to scale. The input signal is fed into the clock input of a D-type flip flop (74HC74). While the D input (GATE TIME) remains low, the Q output remains low, and the counters are inhibited. We start the counting period by applying a logic one (high level) to the D input. On the next rising edge of the input signal, the Q output (COUNTEN) will go high after the short propagation delay. Two NAND gates are turned on as a result. The reference clock (REF COUNT) is then applied to 32-bit counter IC5, and the input signal, INPUT COUNT, is applied to the other 32-bit counter, IC8. After one second, the D input of the 74HC74 is taken low. The Q output remains high until the next positive edge of the input signal, when it will go low. This stops the accumulation of counts in both the 32-bit counters. Importantly, we have an exact input count as the period is synchronised with the rising edges of the input signal. Australia's electronics magazine siliconchip.com.au Features and Specifications 52 Silicon Chip Fig.1: when counting starts and stops is synchronised to the input signal. GATE TIME indicates roughly when counting should occur. However, the synchronised COUNTEN signal actually starts and stops counting (of INPUT COUNT and REF COUNT). The two count values are then divided to get a ratio and thus determine the actual input signal period. The reference counter is not synchronised the same way, so the count could be out by one. With a 10MHz reference oscillator, this results in an error of one part in 107. But, with a 30MHz reference, it reduces to 0.33 parts in 107, which is insignificant. We now have three parameters. The reference clock is a TCXO and so it is very accurate. IC5 will contain a number accumulated over the (approximate) one-second period, and this is the Reference Count, which will be near the Reference Oscillator frequency. The other counter, IC8, has the Input Count. The frequency is then calculated from the equation: f = Input Count × Ref Oscillator ÷ Reference Count prevent overload. The output of the second op amp (IC7b) is squared up by a 74HC14 schmitt trigger inverter (IC3a). Its output feeds into the clock input of 74HC74 flip-flop IC2a that produces the COUNTEN flag at its Q1 output, as well as a 74HC10 NAND gate (IC1c) producing the COUNT signal. I am using two 74HC10 three-input NAND gates with two of their inputs tied together instead of the two-input 74HC00 purely because of what I had in stock. I only need two of these gates, so using a 74HC00 with four gates wouldn’t be more helpful. The COUNT signal goes to both clock inputs of a 74LV8154 32-bit counter, IC8. A second such counter, IC5, is driven by the TCXO output, also gated by the COUNTEN signal, thanks to NAND gate IC1a, as described earlier. The microcontroller can clear both counters using the CCLR signal before initiating a count. That same signal also resets flip-flop IC2a, de-asserting the COUNTEN signal. Once counting is finished, the microcontroller can read the values from both 32-bit counters using an 8-bit data bus (CNTR07), selecting one byte from one 32-bit counter at a time (for a total of eight). Which byte is read out depends on the states of the SIG COUNT and 30MHZ_COUNT lines, which select one counter, and the SEL0/SEL1 bits, which select which byte of that counter is on the 8-bit bus, controlled by both halves of the 74HC139 dual 2-to-4 line decoder, IC4. The processor used is an Arduino Nano microcontroller module with an onboard ATmega328 microcontroller. These are available from multiple sources and are cheaper than buying the separate individual components, plus it removes some of the hard work in assembly. The display is the same 0.96-inch monochrome graphical OLED I have used in several previous designs. The Nano updates its display over a Circuit description Fig.2 shows the full circuit of the Counter. The input signal from CON2, a BNC or SMA connector, is amplified by the Analog Devices ADA4891-2 dual op amp, IC7. With the values shown, the gain is about 32, but that could be increased by changing a couple of resistors. A minimum input signal of 50-100mV peak to peak is needed. I chose that op amp as it has a high input impedance, a gain bandwidth (GBW) of 220MHz and a respectable slew rate of 170V/µs. It is also readily available from multiple suppliers at a modest price. The gain is applied in two stages of about five times each, to keep the overall bandwidth high. Inverse parallel diodes D2 & D3 limit the input level to the first op amp & siliconchip.com.au The Counter is batterypowered, making it convenient to use. Australia's electronics magazine July 2023  53 54 Silicon Chip Australia's electronics magazine siliconchip.com.au two-wire I2C serial interface with two 4.7kW pull-up resistors as required by the I2C standard. Switch S2 provides three sample time options: 0.1s, 1s or 5s. One second is adequate for most measurements. The five-second option may give marginally better resolution and accuracy. The 0.1 second gives a fast approximate reading. The microcontroller reads the position of centre-off switch S2 using its analog-to-digital converter to measure the voltage at pin 11 (ADC7). The switch either presents 0V, half-supply (2.5V) or close to full supply (5V). The power supply for basically all the chips in the design is a regulated 5V from boost regulator REG6. It produces this 5V from the 3-4.5V generated by three series AA cells, and its input is switched on/off by switch S1. CON3 and three more of the inverters in IC3 provide a serial debug interface. Unless you plan to modify the code, it isn't that useful, so CON3 and D4 can usually be left off the board. Software calculations The formula above certainly is simple, with just one multiplication and one division, but the numbers involved are large. We need to multiply before dividing so that we don’t lose accuracy, meaning we need to calculate an intermediate value that can be as high as 3,000,000,000,000 (three trillion; with a 10MHz input and 30MHz oscillator). That is way beyond 32-bit integer arithmetic. I use the BASCOM compiler, which can perform double-­ precision floating-point calculations using 64 bits. That’s enough to store numbers that large without any accuracy loss. For an 8-bit processor running at 16MHz, the above calculation takes 0.4ms, which is quite impressive for such an inexpensive chip. The oscillator Fig.2: the entire Frequency Counter circuit. Signal conditioning is at upper left; the counters are left of centre, the power supply is at lower left and the microcontroller and display are on the right. The micro decides when to start and stop counting and when to reset the counters. It is responsible for reading the counter values, computing the frequency and displaying it on the OLED screen. siliconchip.com.au Australia's electronics magazine TCXOs are readily available from AliExpress for about $16. I tried four different frequencies: 10MHz, 25MHz, 30MHz and 40MHz. The only change needed in the BASCOM source code was the substitution of one number. The higher frequencies give the advantage of slightly better resolution and accuracy. 40MHz is the maximum that can be used with the 74LV8154 counters, but it appears to be pushing the limit, as the accuracy seemed to July 2023  55 Table 1 – readings from high-precision source without calibration Division ratio Input signal Table 2 – high-frequency measurements Measurement Error 610.352Hz 1mHz 1MHz 999,999.990Hz ÷8192 1,220.703125Hz 1220.703Hz <1mHz 2MHz 1,999,999.870Hz 130mHz ÷4096 2,441.40625Hz 2441.406Hz <1mHz 5MHz 4,999,999.670Hz 330mHz ÷1024 9,765.625Hz ÷16384 610.3515625Hz Input frequency Measurement Error 10mHz 9765.625Hz <1mHz 8MHz 7,999,999.530Hz 470mHz ÷512 19,531.25Hz 19,531.249Hz 1mHz 10MHz 9,999,999.330Hz 670mHz ÷256 39,062.5Hz 39,062.500Hz <1mHz ÷128 78,125.0Hz 78,124.998Hz 2mHz ÷64 156,250.0Hz 156,249.995Hz 2mHz ÷32 312,500.0Hz 312,499.990Hz 10mHz ÷16 625,000.0Hz 624,999.980Hz 20mHz drop off. So 30MHz is the best option. It would be nice to have the frequency readout in one row of large digits. But in keeping with the style of my previous designs, I have used the same small OLED to show four lines of eight characters per line. That is not enough to display the frequency on one line, so it is split into two lines. The top line shows “FREQ” while the second line display up to 9,999,999 (Hz). The third line shows the remainder in mHz, from 0 to 999, while the final line displays the battery voltage. Accuracy The primary factor that affects accuracy is how close the TCXO is to its stated frequency. The second factor is the precision of the mathematical calculations, but with the use of 64-bit floating point arithmetic, any errors are minimal. SC6742 kit ($60 + postage) This kit includes everything in the parts list except the case, TCXO and AA cells. I used my 10MHz GPS-disciplined oscillator as an input to a 14-bit counter (74HC4060) and fed ten different divided frequencies into the Reciprocal Frequency Counter. Table 1 shows the results with the 30MHz TCXO straight out of the box with no adjustment. I then tuned the 25MHz TCXO to within less than 1Hz, and the errors were 1mHz or less for all of the frequencies shown in Table 1. The TCXOs I bought from Ali­ Express suppliers have been very close to the stated frequency, but it is possible to adjust them by peeling the label off the TCXO, which gives access to a trim capacitor. However, this is not for the faint-hearted, as it is an extremely fine adjustment, and unless you have the equipment and patience, I don’t recommend it. You need a dual-trace oscilloscope with one channel connected and locked to a GPS-disciplined 10MHz oscillator and the other to the TCXO output. The latter will drift left or right, and the trimmer should be adjusted for minimum drift. If it takes five seconds to drift one cycle, that’s an error of 0.2Hz (1Hz ÷ 5). Frequency limits The maximum frequency of this counter is partially limited by the op amp used in the input amplifier. The ADA4891 has a gain bandwidth (GBW) of 220MHz and a slew rate of 170V/µs (it was also chosen for its high input impedance and GBW). This limits the maximum usable frequency to about 15MHz; however, readings above 10MHz tend to become rather erratic. I used my calibrated AD9851 signal generator to check frequencies above 1MHz; the results are shown in Table 2. Fig.3: most parts are SMDs that mount on the top side of the board, but there are a handful of through-hole parts plus a few components on the back, notably the TCXO and Arduino Nano module. L1 can be either a through-hole type on the front or a 4 × 4mm SMD inductor on the back. Watch the polarity of all the ICs, the regulator and the diodes. 56 Silicon Chip Australia's electronics magazine siliconchip.com.au The higher error rates above 1MHz seem to be due to the TCXO being slightly off its nominal 30MHz frequency. The lower end of the frequency limit is determined by the input components (10μF/1MW) which gives a -3dB point of 16mHz. Therefore, the practical lower limit is about 10mHz. Measuring a 0.1Hz signal would take around 10-20 seconds, but that is the nature of low-frequency signals. Construction The assembled PCB is designed to fit into the Altronics H0324 plastic enclosure with a clear lid, so we don't need to cut a hole for the display. Before mounting any components on the PCB, use it as a template to drill holes into the clear lid. The PCB just fits in the front detent. Attach it with sticky tape and drill the four corner mounting holes with a 3mm drill. Use a 1.5-2.0mm drill for the two switch centre holes. Remove the PCB, drill out the switch holes to 6mm and countersink the mounting holes for M3 countersunk head screws (in this case, 6mm long). The triple AA battery holder should be attached to holes in the bottom of the enclosure using self-tapping countersunk head screws of around 3mm in diameter (4G in the old scheme). Next, move on to building up the PCB, which is coded CSE230101C and measures 76 × 63.5mm. During construction, refer to the PCB overlay diagram, Fig.3. Most of the components on it are surface-mount devices (SMDs). The two 32-bit counters, IC5 and IC8, come in relatively fine-pitch 20-pin TSSOP packages, so solder them first. The first and most important job is to identify pin 1 and ensure it is positioned correctly; you don’t want to finish soldering an IC to realise it’s around the wrong way! There should be a dot, or similar marking, in the pin 1 corner but you might need a magnifier to see it. Working one at a time, carefully position the chip on the pads and solder opposite corners without worrying about shorting pins. You need to ensure the pins are accurately aligned over the pads on both sides, though, so tack one corner first and only solder the other once the alignment looks good under a magnifier. Next, spread flux down both sides siliconchip.com.au Parts List – Reciprocal Frequency Counter 1 125 × 85 × 55mm IP65 sealed ABS enclosure [Altronics H0324] 1 3 × AA battery holder (BAT1) 3 AA cells 1 double-sided PCB coded CSE230101C, 76 × 63.5mm 1 double-sided PCB coded CSE230102, 1mm thick with black solder mask, 76.5 × 63.5mm (front panel) 1 Arduino Nano module (MOD1) 2 15-pin headers (for MOD1) 2 15-pin low-profile female header strips (to plug MOD1 into) 1 0.96-inch 128×64 pixel I2C OLED screen module (MOD2) [SC6176] 1 10μH axial RF inductor OR 4 × 4mm SMD inductor (L1) [eg, NRS4018T100MDGJ] 1 SPDT miniature solder-lug on/on (latching) toggle switch (S1) 1 SPDT miniature solder-lug on/off/on (latching centre-off) toggle switch (S2) 1 2-pin polarised header and matching plug (CON1) 1 SMA edge connector socket (CON2) 1 3-pin polarised header (CON3 for debugging; optional) 1 4-pin female header (for MOD2) 4 M3 × 6mm panhead machine screws 4 M3 × 6mm countersunk head machine screws 4 M3-tapped 12mm spacers 4 M3 flat washers 2 8mm-long untapped spacers (minimum 2mm inner diameter) 2 M2 × 16mm machine screws and nuts 2 3mm/4G x 6mm countersunk head self-tapping screws (for battery holder) Semiconductors 1 74HC10 triple 3-input NAND gate, SOIC-14 (IC1) 1 74HC74 dual D-type flip-flop, SOIC-14 (IC2) 1 74HC14 hex schmitt trigger inverter, SOIC-14 (IC3) 1 74HC139 dual 2-to-4 line decoder, SOIC-16 (IC4) 2 SN74LV8154PW 32-bit counters, TSSOP-20 (IC5, IC8) 1 ADA4891-2ARZ dual high-bandwidth op amp, SOIC-8 (IC7) 1 MCP1661T-E/OT or MP1542DK-LF boost regulator, SOT-23-5 (REG6) 1 4-pin through-hole 30MHz TCXO, 20×13mm (OSC1) [eg, www.aliexpress.com/item/32789207591.html] 1 MBR0540 40V 500mA schottky diode, SOD-123 (D1) 3 MMDL770T1G 75V 200mA signal diodes, SOD-323 (D2-D4) Capacitors (all SMD M2012/0805 size) 7 10μF 16V X7R 7 100nF 50V X7R Resistors (all SMD M2012/0805 size, 1%) 4 1MW 1 390kW 2 220kW 1 150kW 2 22kW 3 12kW 4 4.7kW 1 1kW and slowly drag the soldering iron tip along the pins. You might finish up with a blob of solder on the last couple of pins, so use a bit of extra flux paste and some solder braid (wick) to remove it. Use a loupe or similar to check that all the pins have been soldered properly and that there are no shorts between them. If there are, break out the flux and wick again. It helps to clean off the flux residue using an appropriate solvent and then do a final inspection before moving on because the residue can hide mistakes. With those nicely soldered, use a similar technique to solder the remaining SMD ICs, which have larger lead Australia's electronics magazine pitches, so they should be easier. Don’t get IC1, IC2 & IC3 mixed up; they all come in 14-pin SOIC/SOP packages. Regulator REG6 has three pins on one side and two on the other, so its correct orientation should be obvious. Start by tacking one of the two pins on one side as they have better separation. Use a similar technique as for the ICs, noting that a single pass with solder wick should clear any bridges from the three-pin side. Move onto the four diodes, noting that the different types come in different style packages, all rectangular prisms but with D2-D4 being smaller (there are various compatible types). In July 2023  57 each case, ensure the cathode stripe is facing towards the nearest “K” marking on the PCB (cathode is “Kathode” in German). After that, solder the SMD passives (capacitors & resistors) similarly. The resistors will be marked with codes indicating their values, while the capacitors will likely be unmarked, so don’t mix them up once they are out of their packages. Still, the 10µF caps will probably be thicker than the 100nF types. Moving onto inductor L1, there are two options. A moulded 10µH axial inductor may be used on the front side of the board, but a better choice is a 4 × 4mm SMD inductor on the other side of the board. The SMD option gives slightly higher boost converter efficiency and thus marginally longer battery life. With most of the SMDs in place, mount the through-hole parts. The OLED plugs into a 4-pin socket strip and is attached by two M2 × 15mm screws and untapped spacers. Carefully slide off the plastic spreader on the pins of the OLED header to reduce its height, then cut 3mm off the pins using side cutters. The OLEDs come in two slightly different sizes, and some are slightly shorter. If necessary, attach it using the holes on either side of the connector rather than the bottom pair. The Arduino Nano mounts on the back of the board and plugs into socket strips. Don’t solder it in directly, as you then can’t get at the OLED screw holes! It’s important to use low-profile pin sockets; otherwise, there is not enough room for the battery underneath. Fit the other components on the reverse side next, ie, the connectors, TCXO and additional 100nF capacitor. The input connector is an edgemounted SMA type. Ensure the TCXO is mounted with the correct orientation, having its pointy corner (indicating pin 1) towards the top of the board. The 3-pin header is only needed if you want to use the debugging interface. While the switches have solder lugs, they are mounted on the PCB like through-hole components. Ensure they are perpendicular to the board surface and fully pushed down before soldering them. S2, the centre-off type, goes on the right side (from the front). After cleaning the board, inspect it for missing or badly-formed joins and shorts between pins. You can then move on to programming the microcontroller. Microcontroller programming While we are using an Arduino Nano module with an onboard ATmega328 chip, we are not programming it with the Arduino IDE. The software is written in BASCOM and compiled into a HEX file. You can load that HEX file with an AVR ISP programmer, if you have one, via the 6-pin header on the Nano, but there is another method that doesn’t require the programmer. If you use the six-pin header for programming, there is a conflict with the I/O pins on the board, so it is necessary to unplug the Nano and connect it via the USB cable for power before flashing the chip. No fuses need to be changed; the defaults are fine, so it's ready once you’ve uploaded the HEX file. Alternatively, plug the Nano into your computer using a USB cable. The Nano is mounted via sockets, so the screw holes under it can be accessed, although in this case they are not used. A yellow sticker covers the TCXO calibration hole. 58 Silicon Chip Australia's electronics magazine Then install and load a program like AVRDUDESS for Windows. You can use the AVRDUDE command-line program in Linux or macOS. Set the programmer to Arduino, select the Nano’s USB serial port, the baud rate to 115,200 or 57,600 (depending on your Nano) and click “Detect”. If it doesn’t find the chip, adjust the settings and try again. Once it does, go to the Flash window, open the HEX file for this project (available for download from the Silicon Chip website) and click the program button. Final assembly Plug the Nano back into the PCB, and it can then be attached to the front panel (coded CSE230102) using 12mm spacers and M3 screws. Add a washer between the spacer and the front panel to increase the distance slightly. The front panel is another PCB, 1mm thick, with a black solder mask and white printing. It is held in place by the two switch nuts. Using a PCB here saves the trouble of printing out a label and making the cutouts. Power is from three AA cells; this is stepped up to a nominal 5V by REG6, although, with the resistor values shown, it is more like 4.4V. That’s intentional, as it reduces the current drain slightly. As mentioned earlier, attach the battery holder to the case using screws, as the battery can be pretty heavy, and we don’t want it coming loose. Wire the battery up to the plug that matches CON2, being very careful that the battery’s negative output goes to the ground pin closest to the corner of the PCB. There is no reverse polarity protection on the board, so if you get this wrong, you could smoke it! Once you’re sure that’s right, plug it in, switch on S1 and check that the display comes up as expected. The circuit will continue operating even when the cells have discharged to about 0.8V each. With fresh alkaline cells, it draws 75mA. With each cell at 1.2V (3.6V total), the current drain is 100mA, increasing as the battery voltage decreases further. Rechargeable cells (eg, Eneloop) could also be used. If you’d prefer to use an external power supply, use a 5V phone charger and leave out REG6, D1, L1 and the 150kW and 390kW resistors, plus short out D1 and L1. That will apply the 5V from CON1 directly to the circuit. 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. Object recognition with Arduino and ESP32 CAM The website edgeimpulse.com lets you train an AI module to recognise images quite easily. One of its best aspects is the way you can deploy the results to many different operating systems, including devices like Arduino, ESP32 CAM, ESP-Eye, Python and Raspberry Pi, as well as most computers. It can create an output as a C++ library that can be used almost everywhere! For example, let’s say you need to separate fruit & vegetables like lemons, onions and tomatoes. You can use a Raspberry Pi or ESP32 CAM and a few relays or solenoids to segregate these items into different locations. When the computer detects a tomato, it redirects it to the appropriate basket etc. First, you need to create a login for edgeimpulse.com – to do that, you just need an email address. Once logged in, you need to create a classification project. We then have to collect photographs of these items (lemons, onions, tomatoes etc) in groups, from several angles, and the website will build the project based on those. If you don’t already have such images but have some of the items, you can take the photos directly using a smartphone. After logging onto the website, in the top middle siliconchip.com.au of the screen, there should be a link that reads “Collect new data”. Click that, and a QR code will appear (along with other options). Scan the QR code with your smartphone and you will get three options: collecting images, collecting audio and collecting motion. In this case, we want to collect images. Press that, follow the prompts, then you are ready to start gathering data. After you have collected a good number of pictures of all three fruit & vegetables, say around 200, you need to divide them with an 80:20 ratio for training & testing (the smartphone app will automatically do that by default). You need to add bounding boxes to the object in question in all the images. To avoid this repetitive task, go to the “labelling queue” link at the top of the page and select “Classify using YOLOv5” from the drop-down in the upper right-hand corner. Unselect any unwanted objects in the list on the left, then click “Save labels” on the right. It will load the next image. Continue until all have been processed. Now click the “Create impulse” link on the left and add the “Image” and “Object Detection” blocks, then click “Save Impulse”. Next, go to the “Image” link and click “Save image”, then “Generate features”. Once that Australia's electronics magazine has finished (it can take a while), click the “Object detection” link on the left, then the green “Start training” button. Training can also take a while. At the end of the training, check that the “F1 score” is at least 0.85 (85%). To improve the score, you might have to change the model or remove some outlier images, which can reduce the overall score. Now to test the model using the 20% of the images we set aside. Click on “Model testing” on the left, then click “Classify all”. Check the resulting F1 scores. Note that 100% accuracy is not considered good for the model; it should be between 81% and 90%. Model deployment The model can now be deployed on various hardware, including Arduino, ESP eye, C++, Raspberry Pi and many more. For the Raspberry Pi, edgeimpulse has the linux-sdk-python software that lets you easily run/tweak the installation. Download the edgeimpulse model file and run the python file, like the following command. It is very simple! # python classify.py model.eim In my case, I wanted to run it on the ESP32 CAM. For that, I clicked the July 2023  59 The objects in the photos need to be labelled with bounding boxes to help train the model. Here two tomatoes and an onion have been identified by YOLOv5. Deployment link on the left, selected the “Arduino library” model and pressed the “Build” button at the bottom. The Arduino sketch and the necessary library will be downloaded on your local computer. In Arduino IDE, install this zip file as a new library (Sketch → Include library → Add .zip library). Once installed, go to File → Library and find the latest library. The model is set for the ESP-EYE camera board. However, the cheapest ESP32 camera available is the “ESP32 AI Thinker cam” or, for a little more, the “ESP32 TTGO T plus camera” board. My sketch (available for download from siliconchip.com.au/ Shop/6/200) suits both those boards and camera models. You just have to uncomment the right model, and the sketch is all set for installation. Due to the size of the code, the uploading process takes a substantial amount of time (sometimes 7-8 minutes). Therefore, have patience while uploading the sketch. Light is required during the identification process so the camera can capture a reasonable image of the subject. The ESP AI Thinker cam has a superbright LED that my code switches on for extra light. You can see how well it works in the accompanying photo. As well as the fruit & vegetable example, I have included another one that distinguishes between pens and pencils. As provided, the fruit & vegetable example is set up for the TTGO T plus camera board, while the pen/pencil example is set up for the ESP32 CAM. The diagram circuit shows the simple configuration I used, with a small OLED screen to show the classification results, a battery and 3.3V regulator for the power supply and a relay or solenoid that can be switched via a driver transistor depending on the object classification. The ESP32 CAM sketch will bring either the GPIO12 or GPIO13 output high depending on whether it detects a pen or a pencil, with the relay/solenoid activating only when GPIO13 goes high. While the TTGO T-Camera Plus ESP32-DOWDQ6 module is quite a bit more expensive than the ESP32 CAM, it has a better camera and more RAM. Bera Somnath, North Karanpura, India. ($120) Left: the module being used to recognise a lemon with 52% confidence. Below: edge impulse can convert trained models into code to suit a wide range of platforms. Here you can see some of the options including Arduino and Linux. 60 Silicon Chip Charging a battery with a load We had an enquiry about using the Multi-Stage Buck-Boost Battery Charger (October 2022; siliconchip.au/ Article/15510) while the battery had a significant load. The Charger would be powered by a car and would charge a battery running a 12V refrigerator. The problem is that the charger only sees the net current flow, ie, that current being absorbed by the battery being charged plus any current required to supply load(s) on the battery. For most batteries, charging is terminated when the current falls below a particular level; the load current could be high enough to prevent that from happening entirely, or at least delay it, possibly causing overcharging. A large enough load might also cause the Battery Charger to trigger a low battery voltage error, stopping charging entirely. That’s not to say it’s impossible to charge a battery under load. But there are too many parameters at play to even suggest what might work. You would have to have excellent knowledge of both the charger and the load profile to work out safe settings that will work under all conditions. The solution we are proposing here only works if the charging source (in this case, the car alternator), battery and load all operate at the same nominal voltage. Because of the versatility of the Battery Charger, that may not be the case; for example, it can handle a 12V supply charging a 24V battery or vice versa. Our solution is to use a relay to switch the load to run directly from the alternator while charging occurs. The circuit diagram summarises the connections. When the accessories are switched siliconchip.com.au off, the relay is in the normally closed position, and the fridge runs from the house battery. When the car is started, the relay is energised, and the refrigerator is fed directly from the starter battery (which is being charged by the alternator as the engine is running). There might be a very brief dropout while the relay switches over, but most fridges should handle that without any problems. Otherwise, add more supply bypass capacitance for the load to cover the dropout. Note the use of a separate circuit from the battery; this allows the fridge to be separately and appropriately fused. This arrangement is also more efficient in that the Charger is bypassed, so losses within the Charger are avoided. It will also reduce the duty on the Charger, as it would otherwise have to supply both the battery charging current and fridge load current. This scenario is not limited to a fridge but should work fine with any load that can handle the supply voltage of both the starter and house batteries. Note that if you are using the standalone Buck-Boost LED Driver as a pure float charger, as described in the BuckBoost Battery Charging article (October 2022; siliconchip.au/Article/15509), you do not need to add this relay. That is because the voltage applied to the battery is not elevated, so there is negligible risk of damage. However, charging will be much slower without it when the load is drawing current. Therefore, we still recommend using the relay circuit; it reduces the load on the Buck-Boost Driver, if nothing else. Tim Blythman, Silicon Chip. Australia's electronics magazine Reducing Flexitimer power consumption The May 2023 issue included my contribution regarding a simple modification of the Flexitimer to allow a mostly on output with a short offtime sequence (“An even more flexible Flexitimer”; siliconchip.au/ Article/15786). I sometimes feel the Flexitimer has become my life’s work as, in the great tradition of one thing leading to another, I noticed that the plastic box housing the timer was getting quite warm, with the heat coming from the relay. Around half a watt is dissipated by the relay coil, and in a confined space, that results in a noticeable temperature rise. Adding a resistor in series with the coil is a tried and tested option to reduce coil power. Since there is a 0W link between the relay coil and ground, the circuit board layout lends itself to another easy modification. After some trial and error, I settled on 560W, reducing the coil power from 500mW to 57mW. That results in a significantly cooler plastic box. To ensure the relay latches reliably with the reduced current flow, solder a 470μF electrolytic capacitor across this resistor with the negative side to ground. Some Flexitimer boards have DPDT relays (the original design used an SPDT relay). If yours has this second spare set of contacts, connect the NC and COM terminals of the unused pole across the added resistor/and capacitor. That will ensure the capacitor is fully discharged each time the relay switches off. Unless the timer is switching the relay rapidly, that isn’t required. Chris Sweet, Carlingford, NSW ($60). A thermal infrared camera measures hot or cold spots compared to the surrounding area. This is extremely useful in diagnosing hot spots in electronic circuits, which may indicate a failing component or the need for a heatsink. They can be pricey, but not this one, a DIY version that’s easy to build. Pi Pico-based Thermal Camera IR thermal cameras have many uses beyond those listed above, such as checking for overheating mechanical bearings or identifying areas of heat loss in a building. Panasonic produces the AMG8833 Infrared Array Sensor (“Grid-EYE”) that detects IR emissions on a 64-pixel 8 × 8 array. It uses the I2C serial protocol, so it can easily interface with a Raspberry Pi Pico running the Pico­ Mite operating system. Objects emit infrared energy in proportion to their temperature; the higher the temperature, the more IR energy is emitted and the higher its frequency. For really hot objects, the frequency extends into the visible wavelengths, which is why hot objects are seen to glow. By measuring this energy, we can get a pretty good idea of the temperature. There are some pitfalls, which we will mention later. With the Grid-EYE sensor, each pixel has a viewing angle of approximately 7.5°, so the overall sensor has a viewing angle of 60° (7.5° × 8). Each pixel has a tolerance of ±2.5°C when operated within specification. We can minimise this error by calibrating the sensor, as described below. Also, there can be random operating ‘noise’ of up to ±2.5°C per pixel. To reduce this, the sensor is used in moving-­average mode, which averages two readings when the sensor is set up for a 10Hz frame rate or 20 readings when for a 1Hz frame rate. If the raw output of the Array Sensor is displayed directly on an LCD screen, it appears very ‘blocky’. Still, it can easily be upscaled using a 62 Silicon Chip technique called bilinear interpolation to give the appearance of many more data points. The PicoMite Thermal Camera can upscale by factors of two, four or nine. These factors were chosen as they make the best use of the screen width. Below the thermal image display is a text read-out showing the maximum, minimum and average temperatures and the current operating mode. As mentioned above, the Array Sensor can sample at 10 FPS (frames per second) or 1 FPS. The former is most suited to fast-changing subjects, while the latter better smooths out random noise in the sensor, giving a more stable and accurate output. Bilinear interpolation This involves drawing an imaginary straight line between two data points, then generating new data points in between that lie on that line. It’s a simple technique that produces a much smoother-looking result than the more basic ‘nearest neighbour’ technique that gives a blocky image. More complicated interpolation schemes like trilinear, bicubic, Lanczos or anisotropic interpolation involve considerably more processing (arithmetic) than bilinear. In this case, their advantages are minor; bilinear gets us most of the improvement compared to no filtering with very little processing. Object emissivity The ‘fly in the ointment’ for a thermal camera is that objects vary in emissivity. An ideal IR emitter is called a Australia's electronics magazine by Kenneth Horton ‘black body’ with 100% electromagnetic emission/absorption. Shiny objects like mirrors have an emissivity closer to 0%. If you point an IR thermometer or camera at them, you will measure the temperature of an object that the mirror is reflecting, not the mirror itself. Luckily for us, many electronic components are dark colours and will have an emissivity of 90%+, so a thermal camera will measure their temperature accurately. Human skin has an emissivity of 97-99.9%, so IR thermometers also work well for measuring our temperature. This isn’t a fatal flaw but be aware that the temperature measurements of metallic objects using this IR camera could be inaccurate. It isn’t just well-polished metal surfaces either; even rough, oxidised aluminium only has an emissivity of about 20%, with polished metal surfaces usually below 5%. A known work-around to measuring the temperature of shiny surfaces (eg stainless steel pipes) is to apply some matte painters tape, which has a better emissivity. For more information, see: https://w.wiki/6R6E Circuit details As shown in Fig.1, the hardware for the project is relatively straightforward, consisting of just three modules: the Infrared Array Sensor, a Raspberry Pi Pico running the PicoMite operating system (MMBasic) and a 1.8-inch SPI TFT LCD screen with a resolution siliconchip.com.au Fig.1: the Thermal Camera circuit is straightforward, with the IR sensor array (MOD1) communicating with the Raspberry Pi Pico over an I2C bus (SDA/SCL) and the LCD screen being driven over an SPI bus (CS, SCK & MOSI). The only other components are the pushbutton for changing modes (S1) and a 39W resistor to set the LCD backlight current. of 128 × 160 pixels and an ST7735 controller. The sensor array is connected to the Pico via an I2C interface, while communications with the LCD screen are over an SPI interface. The only passive components are a pushbutton to change modes and a 39W resistor to set the current at which the display backlight operates. The following Pico GPIO pins are used: • GP08: LCD data/control (D/C) • GP09: LCD chip select (CS) • GP10: LCD SPI clock (SCK) • GP11: LCD SPI data (MOSI) • GP15: LCD reset (RST) • GP18: pushbutton sensing • GP20: AMG8833 I2C data (SDA) • GP21: AMG8833 I2C clock (SCL) The double-sided PCB is a carrier for the three modules, the pushbutton and the resistor. The display runs from a 5V DC supply from the Pico. On the Pico board, this is stepped down by a regulator to 3.3V. That 3.3V runs the RP2040 microcontroller on the Pico and is also available off-board, where it is used to power the AMG8833 IR sensor array. The Array Sensor is available from the usual auction sites pre-mounted on a breakout board, and you can find the display on the same sites. There are some suggested links in the parts list. The prototype was powered via the USB port on the Pi Pico, but there are also pads on the PCB for an external 5V power supply. This way, the Thermal Camera can be powered by a battery. The pushbutton is connected so that siliconchip.com.au it pulls the GP18 pin to GND when it is pressed. The Pico has an internal pull-up current enabled on that pin, so its voltage is high when the button is not pressed and goes low when it’s pressed, allowing the digital input to sense the change. Software operation The basic flow of the program is as follows: 1. Initialise the PicoMite, LCD screen and IR sensor array 2. Restore the calibration data and last pushbutton settings 3. Load the colour spectrum from the table 4. Enter the main loop Read 64 pixels from the sensor and adjust with the calibration data b. Calculate the maximum, minimum and average temperatures c. Convert the absolute temperatures to points on the colour spectrum d. Interpolate the intermediate colour values for each row using bilinear interpolation e. Interpolate the intermediate colour values for each column using bilinear interpolation f. Update the display g. Check the pushbutton state h. Delay if necessary Repeat items a-h above indefinitely a. The rear of the enclosure (86 × 33.4 × 57.3mm) has a cutout for the AMG8833 IR sensor; you can also see a small cutout for the Pi Pico’s USB connector on the lip. July 2023  63 by Silicon Chip), they will be plated, and nothing else needs to be done. If you etch the board yourself, those nine vias need to be drilled and short wire links soldered between the top and bottom layers in each location. The LCD screen and switch mount on the underside of the PCB, while the Pi Pico and IR sensor are on the top. For convenience, the three modules can be mounted via socket strips rather than soldering them directly to the PCB. You can cut them from longer strips if you don’t have 6-pin and 8-pin sockets. The resistor can be mounted on either side of the board. The switch is a two-pin or three-pin SIL-type vertical pushbutton that solders directly to the PCB. Alternatively, there is a provision in the 3D-printed enclosure to mount other types of pushbutton below the LCD screen and The Raspberry Pi is mounted on pin headers in sockets to make it easy to replace. wire them up to the pads on the board using short connecting wires. LCD screen limitations good imagination), and the span from Once plugged into its socket, the IR Although the LCD screen is, in the- yellow through green to cyan seems sensor is secured to the board by two 20mm-long M2.5 machine screws and ory, a standard item, displays from particularly compressed! Also, the different suppliers have different char- display is extremely sensitive to the nuts with 3D-printed spacers (Fig.4) acteristics. One display tested had the viewing angle and must be viewed between the PCB and sensor. One of red and blue colours reversed, whilst head-on to get the full spectrum of the spacers for the IR sensor has a cutthe latest batch had random pixels at colours. Otherwise, adjacent colours out to fit around an SMD component next to the module's mounting hole. the bottom and right-hand side of the blend into each other. With the IR sensor array and LCD display. As a result, three constants are attached to the PCB, now is also a good defined to allow the program to be tai- Construction The Thermal Camera is built on a time to plug the Raspberry Pi Pico into lored to the attached display: double-sided PCB coded 04105231 its sockets. ' Set to false for RGB displays that measures 60 × 52.5mm. The comYou can print the custom-made and true for BGR displays ponents are mounted as shown in enclosure in two parts (body and lid), Const BGR_display = False Figs.2 & 3. shown in Fig.5. The STL 3D printer ' Some ST7735 displays have a There are nine vias on this board. files (available to download from pixel alignment problem! Try = 2 If you are using a commercially-­ siliconchip.com.au/Shop/6/202) are Const HRES_offset = 0 produced board (such as the one sold optimised for 0.2mm layer height, ' Some ST7735 displays have a pixel alignment problem! Try = 1 Const VRES_offset = 0 Despite the display supposedly having 65,536 colours, they can’t actually show that many. Firstly, RGB(247,251,247) is one step down from white but looks significantly dimmer. The difference between this and the next step down, RGB(239,247,239), is less noticeable, as is each subsequent step. For dimmer values, the less effect each step has. RGB(127,127,127) is very dim, and RGB(63,63,63) is almost black! Another, more technical way of saying this is that the display has a very high gamma value. As a result, it is difficult to get more than about 38 distinct colours across the spectrum (even with a 64 Silicon Chip Figs.2 & 3: components are mounted on both sides of the board. On one side are the Raspberry Pi Pico and IR sensor, both plugged in via header strips. The LCD screen, pushbutton and resistor are mounted on the other side, although the resistor can go on either side. Australia's electronics magazine siliconchip.com.au 0.4mm wall thickness and 100% fill. Note that the first layer of the screw holes is filled as it gives a more pleasing appearance to the front and back of the case – just drill them out after printing. The holes in the lid are countersunk under the top layer and are best cleared with an 8-10mm drill by hand. The PCB assembly is held in the case by four 25mm-long M3 machine screws and nuts, with 3D-printed spacers between the display and the PCB at the opposite end to the connector. It is necessary to insert the display into the case first, insert the machine screws from the front of the case, place the spacers over the screw shafts and then plug the PCB onto the display. Finally, secure it with the nuts. Loading the software It is assumed that readers are familiar with loading PicoMite software, which was described in the article on the PicoMite in the January 2022 issue (siliconchip.au/Article/15177). Briefly: 1. Download the PicoMite operating system from http://geoffg.net/picomite. html and unzip the file. 2. To load the operating system onto the PI Pico, plug the USB cable into a PC while holding down the white button. 3. The Pi Pico will appear as a USB drive. Copy/drag the file PicoMitexx. xx.xx.uf2 onto that drive. 4. Connect to the PicoMite’s USB serial port using your preferred serial terminal emulator (eg, TeraTerm or PuTTY). 5. Once connected, enter each of these commands in turn, but note that many of them reset the Pi Pico, so the USB connection is lost and will need to be restored before entering the next: The pushbutton is visible on the back of the PCB at upper left. A few different compatible types can be obtained. camera.bas” file into the PicoMite, again using your preferred serial terminal emulator or MMEdit. Use the “Autosave” or “XMODEM receive” commands, depending upon your preference. 8. If you’d prefer to skip most of the above sequence, you can download the “Thermal camera (RGB).uf2” or “Thermal camera (BGR).uf2” file from the Silicon Chip website and upload it in the third step above. That’s equivalent to running all the configuration commands and loading the BASIC code. The only difference between the two files is the expected LCD screen configuration, so if the displayed colours are wrong, load the other file. Operation The pushbutton has the following functions: • Short press (less than 1.5 seconds): cycles the display scaling factor through 1, 2, 4 and 9 • Long press (more than 1.5 seconds): toggles between 1 FPS and 10 FPS Fig.4: 3D-printed spacers are used rather than off-the-shelf types since we can make them exactly the right dimensions, and you can print them at the same time as the case. Note the cut-out in one to clear an SMD component near the mounting hole on the IR sensor module. OPTION RESET OPTION CPUSPEED 252000 OPTION SYSTEM SPI GP10,GP11,GP12 OPTION LCDPANEL ST7735,RP,GP8,GP15,GP9 OPTION SYSTEM I2C GP20,GP21 6. The following two commands are optional; the first shows you what you have configured, while the second lets you verify that the LCD screen is working: OPTION LIST GUI TEST LCDPANEL 7. Finally, load the “Thermal siliconchip.com.au Fig.5: the 3D printed enclosure base and lid. The holes do not go all the way through because it gives a neater result to drill the thin panels after printing the case than print the case with the holes. Australia's electronics magazine July 2023  65 Parts List – Raspberry Pi Thermal Camera 1 double-sided PCB coded 04105231, 60 × 52.5mm 1 Raspberry Pi Pico 1 3D-printed enclosure (body & lid) 4 3D-printed spacers 1 AMG8833 Grid-EYE IR sensor array breakout board module with pin order VIN, GND, SCL, SDA, INT & ADO [AliExpress www.aliexpress.com/item/33012193094.html] 1 1.8-inch 128×160 pixel SPI LCD TFT screen with ST7735 controller [Tempero Systems TS-S006; eBay; AliExpress www.aliexpress.com/ item/1005003797803015.html {1.8 inch option}] 1 SPDT momentary PCB-mounting subminiature pushbutton switch (S1) [Altronics S1493 or APEM TP32P0] 1 39W 5% ¼W axial resistor 2 20-pin headers, 2.54mm pitch 2 20-pin header sockets, 2.54mm pitch 1 8-pin header socket, 2.54mm pitch 1 6-pin header socket, 2.54mm pitch 2 M2.5 × 20mm panhead machine screws and hex nuts 4 M3 × 25mm panhead machine screws and hex nuts 4 No.2 × 6mm countersunk head self-tapping screws • Very long press (more than 10 seconds): enters calibration mode Note that the frame rates are sensor refresh times, not screen refresh times. At 10 frames per second, the screen update time is longer than 1/10th of a second for scale factors 4 and 9. At scale factor 4, the display will be updated approximately every 220 ms and, at scale factor 9, every 700ms. This is because the bilinear calculations take some time to complete for higher scaling factors. In calibration mode, the sensor is set to 1 FPS, and 10 readings are taken over a 10-second period. These are then averaged, and the correction factors for each pixel are stored in non-volatile memory. Good results are obtained by holding the sensor perfectly still 2-3cm from a white sheet of paper. If the button is pressed during calibration, calibration is abandoned, and the correction factors are cleared. We recommend letting the sensor stabilise for at least one minute with power on before performing calibration. Software tweaks In the software, the constant “Fahrenheit” can be set to “true” to display temperatures in Fahrenheit rather than centigrade/Celsius. The constant “Minimum_span” sets the minimum temperature span for the display when there is little temperature variation across the It’s critical you purchase a module with the same output pin layout as the one shown above. whole display. This prevents wildly varying colours for minimal temperature changes. Lower values make the display more sensitive when there is an almost uniform temperature gradient. Speeding up the refresh rate The latest version of the Pico­ Mite firmware (“PicoMiteV5.07.06. uf2”) allows the CPU speed to be increased from the old maximum speed of 252000 to 378000 with the command: Option CPUspeed 378000 This means that, with a scale factor of 4, the display will be updated approximately every 165ms rather than 220ms and, at scale factor 9, every 520ms rather than 700ms. However, note that this is ‘overclocking’ the RP2040 processor and it’s possible that it won’t work on every board or under all conditions. Still, most Pico boards should be capable of running SC at this speed. Dual-Channel Breadboard Power Supply Our Dual-Channel Breadboard PSU features two independent channels each delivering 0-14V <at> 0-1A. It runs from 7-15V DC or USB 5V DC, and plugs straight into the power rails of a breadboard, making it ideal for prototyping. Photo shows both the Breadboard PSU and optional Display Adaptor (with 20x4 LCD) assembled. Both articles in the December 2022 issue – siliconchip.au/Series/401 SC6571 ($40 + post): Breadboard PSU Complete Kit SC6572 ($50 + post): Breadboard PSU Display Adaptor Kit 66 Silicon Chip Australia's electronics magazine siliconchip.com.au Make building or servicing easier with our Magnifiers & Inspection Aids 4.3" OLED GREAT FOR TECHNICIANS OR ADVANCED HOBBYISTS 600X ZOOM ONLY 119 $ POWERFUL 127MM DIA. 3-DIOPTRE LENS Digital Microscope • LED illumination • Rechargeable QC3193 FULLY ADJUSTABLE Clamp Mount Desktop Magnifier with LEDs • 1.75x, 2.25x & 3x magnification • 60 LEDs with high/low brightness • Mains powered FULLY ADJUSTABLE ARM ONLY 139 $ QM3554 ONLY 34 95 $ RECORD & SNAPSHOT FEATURE FOR A BETTER VIEW LED Headband Magnifier • 1.5x, 3x, 8.5x 10x magnification • Can be worn over eye glasses LARGE 4.3" COLOUR LCD QM3511 720P WITH ILLUMINATION LED ILLUMINATION ONLY 13 $ 95 Handheld Magnifier • 3x magnification • Lightweight, just 200g Inspection Camera • 3x magnification • 3 x probe attachments included • Add an SD card to record vision or snapshots QC8718 QM3535 ONLY 239 $ Shop at Jaycar for: • Eye Magnifier • Handheld Magnifier • Headband Magnifier • Desktop Magnifiers • Inspection Cameras • Digital Microscope Explore our wide range of magnifiers & inspection aids, in stock on our website, or at over 110 stores or 130 resellers nationwide. jaycar.com.au/magnify 1800 022 888 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. CARRIAGE UNCOUPLER for model railways By Les Kerr This mechanism automatically uncouples carriages from a locomotive or other carriages, adding realism to a model railway layout. It’s hidden under a section of track and activated by a switch after the locomotive is driven into position. It’s actuated by a servo motor with simple control electronics and a relatively straightforward mechanical system that you can make. L ocomotives and carriages can be coupled by simply pushing them together, but uncoupling them requires more work. This device uses a special section of track to automatically uncouple carriages, allowing you to reconfigure your model trains in a realistic manner. You can see it in operation in the video at siliconchip.au/link/abl8 Initially, I thought I could use a solenoid to raise a platform above the rails, thus lifting the coupling hooks on both the carriage and locomotive, allowing them to be pulled apart. I found a miniature solenoid that moved through 5mm when activated. On checking with a carriage, I found that I only needed the solenoid to move through 2.7mm to uncouple it. However, even with a 50% duty cycle, the 1.1A solenoid required 600mA continuously from the power supply, which seemed like a lot to lift a little platform. The other problem is the speed at which the solenoid operates. 68 Silicon Chip It would be travelling very fast when it hit the platform-lifting pin, raising the platform too rapidly and making a lot of noise when it hit its maximum height. This made me decide instead to use a miniature servo motor. Such a motor would only draw a few hundred milliamps at most, and a basic 8-pin microcontroller could easily control its speed and travel distance. Initially, I thought I could couple the servo arm that came with the servo to lift the platform raising pin, but I found that the servo would only have to move through a few degrees to achieve the required 2.7mm lift. A 1ms control pulse change will make a servo move through 90°, so we would have to change the pulse length by just tens of microseconds to get a change of just a few degrees. To control the speed of the motor, we feed it with increments of about 1/20th of the total pulse width until the required duration is reached. Unfortunately, these increments would only Australia's electronics magazine be one or maybe a few microseconds, which is difficult to achieve reliably. The solution was to use a cam attached to the servo shaft, which provides the 2.7mm lift when the servo rotates through 90°. The minimum and maximum lift values are set using two potentiometers. Figs.1(a) & (b) show the final arrangement of the metalwork in both the Platform up and down positions. A piece of single-length Hornby OO scale rail is attached to two L-shaped brackets by two 10BA screws. With the Platform down, the cam is rotated fully anti-clockwise to its minimum lift position. As the pins are firmly fixed to the Platform by Loctite, the springs and gravity pull the Platform down until it touches the sleepers, so the Platform is roughly level with the rails. Having three pins means that the Platform always remains parallel to the rail. The cam is attached to the servo motor shaft by the 8BA screw. siliconchip.com.au Fig.1: three views of the completed Uncoupler mechanism; (a) from the side in the down position, (b) in the up position, (c) from underneath. The Platform slides on three Pins, two held in Collars supported by Springs, and one in a Bush that the Cam acts on. When the servo motor rotates clockwise, the cam follows, putting pressure on the centre pin with the result that the Platform lifts and the springs compress, as shown in the Platform up drawing. Servo control The control circuit is shown in Fig.2. To rotate the servo motor through 90°, it is fed with continuous siliconchip.com.au 2ms-wide pulses at about 50Hz in the down position and 1ms pulses in the up position. These come from the GP0 digital output (pin 7) of microcontroller IC1. The exact pulse widths and thus, up and down positions, are set using trimpots VR1 & VR2. They are connected across the 5V supply with padder resistors to generate 2-3V (VR1) and 2.7-3.7V (VR2) at their wipers. That Australia's electronics magazine voltage is measured ratiometrically (so the exact voltage of the 5V supply doesn’t matter) using IC1’s internal 10-bit analog-­to-digital converter via the AN1 (pin 6) and AN3 (pin 3) inputs, respectively. The 10-bit ADC produces values from 0 to 1023 (210 − 1) for voltages of 0-5V. The software multiplies the value measured at AN1 by two for a delay in microseconds, so the range is July 2023  69 Fig.2: the control circuit is straightforward, with microcontroller IC1 generating 50Hz pulses to control the servo motor. The up/down switch, S1, selects which of trimpots VR1 & VR2 determine the pulse width and hence target servo rotation. The positions are usually set to vary by about 90°. 0-2.046ms with 1.023ms at the midpoint. Similarly, the reading from pin 3 of IC1 is multiplied by 3 for a range of 0-3.069ms for VR2, with the midpoint giving about 1.535ms and about 2ms at its 2/3rds position. The 10μF capacitors from these two pins to ground stop any supply noise or ripple from affecting the ADC readings. When up/down switch S1 is in the down position, digital input GP2 (pin 5) of IC1 is low, so VR2 is used to determine the servo motor pulse lengths, resulting in it turning anti-clockwise. With S1 up, it changes to shorter pulses based on VR1, causing the motor to rotate clockwise. The 100nF capacitor from pin 5 to +5V protects the input from stray RF, while the 5.6kW pull-down resistor ensures GP2 is always high or low. The Fig.3: like the circuit, the PCB is pretty simple. The three + pads are for 5V power in/out, S1 is the switch common, SIG is the servo motor’s control signal, and the two 0V pads are grounds. The only polarised components that can be inserted incorrectly are IC1 and the three electrolytic capacitors. 70 Silicon Chip 100μF and 100nF capacitors across the supply stabilise the supply voltage for IC1. PCB assembly Assembly of the control PCB, shown in Fig.3, is straightforward. The PCB is coded 09105231 and measures 34 × 48mm, and the assembled PCB is shown in Photo 1. Pin headers are used to connect the wires to the board. Start by fitting the header pins, the 8-pin IC socket and the capacitors. The IC socket makes it easier to remove the microprocessor and re-program it later if necessary. Take care to orientate the socket and the electrolytic capacitors correctly. Now add the resistors, which are mounted vertically. Don’t fit the PIC12F617 microprocessor yet. If you have purchased this from the Silicon Chip Online Shop, it will already have the firmware loaded. If you wish to do this yourself, the files can be downloaded from the Silicon Chip website, but you will need a suitable programmer and socket adaptor. Wiring it up Using hookup wire, connect the up/ down switch, power pack and servo as shown in Fig.4. Check that the +5V lead of the power pack connects to the PCB positive terminal and the 0V lead goes to the 0V point on the PCB. The red wire from the servo should connect to the +5V terminal of the PCB and the brown wire to the 0V terminal on the PCB. Finally, the orange wire from the servo should connect to the servo output on the PCB (“SIG”). Testing the electronics Photo 1: the PCB is a single-sided design. This photo shows it fully assembled and wired up via singlepin headers. Before powering it up, check that the 100μF and 10μF capacitors are orientated correctly and inspect the rear of the PCB for dry joints or solder bridges between pads or tracks. Rectify if necessary. Next, power up the 5V supply and connect the positive lead of a digital voltmeter to pin 1 of the IC socket and the negative lead to pin 8. If you get a reading of +5V, you can proceed. If you read -5V, either the IC socket or the 5V supply is reversed. Remove power and plug in the PIC12F617 microprocessor as shown in Fig.3, with its pin 1 end over the socket notch. Set trimpots VR1 and VR2 to their mid positions. If you have Australia's electronics magazine siliconchip.com.au Fig.5: the Cam is a metal ellipse with one side cut flat and a couple of holes drilled. It’s made from a cylindrical piece of aluminium cut to 3mm thick and then ground into this shape. Fig.4: the wiring is straightforward, as shown here. Consider how long you need the wires to be, especially from the control board to the servo. Most servos come with relatively short wires, so they will probably need to be extended. an oscilloscope, connect it between the servo connection and ground, and set the vertical deflection to 10V and the timebase to 500μs. Switch the up/down switch to up (closed) and apply power. The servo motor should rotate clockwise to its maximum position, and the oscilloscope should display a positive-going 5V pulse of about 1ms width. Rotate VR1, and you should see the servo motor move and the 1ms pulse width change. Rotate VR1 back and both the servo motor and pulse widths should return to their original positions. Leave VR1 in its mid position. Now change the up/down switch to the down position, and the servo should rotate about 90° anti-­clockwise, with the pulse width increasing to about 2ms. This time, adjust VR2 and the pulse width and servo motor should change position. Leave VR2 in its mid position. In one of my previous projects that used the same servo motor, one user complained that the motor continually rotated. On investigation, we found that you can purchase a servo that is the same size but designed for 360° rotation. You need to use the 180° type in this project. Making the mechanical parts The next job is to make the Cam, shown in Fig.5. Chuck a piece of 25.4mm (one inch) aluminium round bar stock with about 5mm protruding from the chuck. Face the end and bore siliconchip.com.au Photo 2: print, cut out and glue the Cam shape guide onto the metal disc as a guide for grinding it to the required oval shape. Parts List – Model Railway Carriage Uncoupler 1 5V DC 1A plugpack 1 180° 9G servo motor [DF9GMS; Core Electronics SER0006] 1 Hornby R600 or R601 rail section 1 single-sided PCB coded 09105231, 48 × 34mm 2 2kW top-adjust mini trimpots (VR1, VR2) 1 PIC12F617-I/P 8-bit microcontroller programmed with 0910523A.HEX, DIP-8 (IC1) 1 8-pin DIL IC socket (for IC1) 1 SPDT toggle switch (S1) [Jaycar ST0335] 1 7-pin snappable header, 2.54mm pitch or 7 PC stakes Capacitors 1 100μF 16V radial electrolytic 2 10μF 16V radial electrolytic 2 100nF 50V ceramic Resistors (all 1/4W 1% axial) 1 10kW 2 5.6kW 2 3.9kW 1 2.7kW Hardware 1 aluminium plate, 60 × 10 × 2.5mm 1 205mm length of 40 × 25 × 1.6mm aluminium unequal angle [Bunnings 1138199] 1 20mm length of 25mm or 1in diameter aluminium round bar stock 1 70mm length of 3/32in [2.4mm] brass round bar stock [K&S Metals] 1 30mm length of 20mm diameter aluminium round bar stock 1 40mm length of 10mm diameter aluminium round bar stock 1 can of Rust-oleum Ultra Matte black spray paint Fasteners 2 10BA x 1/4in or 3/8in hex head machine screws [EJ Winter] 3 8BA x 3/8in, 12mm or 1/2in hex head machine screws [EJ Winter] 2 M3 × 6mm panhead machine screws 2 M2.5 × 8mm panhead machine screws 4 M2.5 hex nuts Wire 1 4m length of 0.315mm diam. nichrome resistance wire [Jaycar WW4040] various lengths and colours of light-duty hookup wire Australia's electronics magazine July 2023  71 Photo 3: after grinding, the Cam has had a flat cut in its side, a hole drilled in the middle and a tapped hole in the centre of the flat side. Fig.6: a 7mm hole needs to be made in the middle of the rail for the mechanism to project through, and the existing mounting holes need to be enlarged, as shown here. a 4mm deep hole using a centre drill followed by a 4.9mm drill. Reduce the outside diameter to 25.2mm and part off a 3mm section. You can download a 1:1 drawing of the Cam outline as a PDF from the Silicon Chip website. Print this at actual size and cut around the circumference using scissors. Glue this to the 3mm section using a suitable glue (such as Tarzan’s Grip), so it is symmetrically placed, as shown in Photo 2. Transfer the 3mm section to the linisher and carefully grind out the shape of the Cam on one side. Next, use a hacksaw to remove the lower section and clean up the edge with a file or an end mill in the milling machine. Then transfer the job to the milling machine and drill and tap the hole for an 8BA screw. The tapping drill size for 8BA is 1.8mm. Use emery cloth to clean up the remaining edges and the 4.9mm hole. The result is shown in Photo 3. Hornby rail modification The required modifications are shown in Fig.6 and Photo 4. You can use either the Hornby R600 single rail or the Hornby R601 double rail; the difference is the spacing of the 1.4mm holes. For the R600, it is 90.4mm, and for the R601, it is 76.8mm. Enlarge the two existing 1.4mm holes to 2mm in diameter. To allow clearance for the 7mm diameter end of the Bush, parts of the two middle sleepers have to be removed. Use a small half-round file to do this. Two Springs The two Springs to make are shown in Fig.7 and are visible in Photo 5. Use a piece of 8mm diameter rod as a former and close-wind two turns of 28 B&S (0.33mm diameter) nichrome wire at one end, followed by three turns spaced 3.2mm apart in the middle and finally, two turns at the end. Trim off the excess wire. Mounting Bracket The Mounting Bracket, shown in Fig.8 and Photo 6, is made from a 25 × 40 × 1.6mm aluminium L-shaped extrusion. Cut the extrusion to 100mm long and clean up the ends with a file, or do the whole operation in the milling machine fitted with a slot drill. Use a hacksaw to remove the rectangular sections at the ends of the 40mm side of the extrusion. Photo 4: the Hornby rail after modification. As well as making the central hole, the two preexisting attachment holes have been enlarged. 72 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.7: the Springs are wound from nichrome wire on a 8mm diameter cylindrical former. Photo 5 (right): the assembled Uncoupler with the Platform in the upper position. The Cam is rotated so that its long axis is pressing on the central Pin. Use a 1/8-inch or 3mm end mill in the chuck of a milling machine to clean up the cuts to size. For smooth operation of the Platform, the location of the 3/32in holes in the Platform should match the corresponding 2.5mm and 5mm diameter holes in the Mounting Bracket (fitted with the Bush) exactly. If they don’t line up, the Platform will jam in operation. If you haven’t any means of precision drilling, I suggest you clamp the Platform and the Bracket together, then drill the 3/32in holes through both (instructions for making the Platform are below). The end holes in the Bracket can then be enlarged to 2.5mm and the centre hole to 5mm in diameter. On the same centre line, drill and tap the 10BA holes. The drill tapping size for 10BA is 1.4mm. If you are using the single R600 rail, you need the holes marked F1, or if using the R601 double rail, you need the holes marked F2. Turn the Bracket over onto the 40mm side and use a centre drill followed by a 2.5mm drill to make the two holes in the centre of the slots. If you have a milling machine, use a 2.5mm slot drill to elongate the holes. If you don’t have one, use needle files to perform the same operation. Use a hacksaw and chain drilling to make the 23 × 24mm rectangular notch. If you don’t have a milling machine, smooth the sides with a series of files. I did this using a milling machine fitted with a 2.5mm slot drill. Next, using a 2.5mm drill and an M3 tap, make the holes for the cover bracket connecting screws. Bush This should be made after the Mounting Bracket as it must be a tight fit in it. The details are in Fig.9; you can see it inserted in the Bracket in Photo 6. Chuck a piece of 10mm diameter aluminium round bar stock with 12mm protruding from the chuck. Face the end and, using a centre drill, then a 2.4mm drill, bore a 12mm-deep hole. Reduce the outside diameter to 7mm Fig.8: the Mounting Bracket is cut from a length of aluminium angle stock. siliconchip.com.au Australia's electronics magazine for a depth of 11mm. Further reduce the outside diameter to just over 5mm for 7.5mm, then reduce it further by small amounts until it is a slide fit in the 5mm hole in the Bracket. Part it off to a length of 10mm. Finally, insert the Bush into the Bracket and lock it in place using Loctite 620. Be sure to clean out any excess Loctite from the centre of the Bush and any remaining on the Bracket. Leave the piece for 24 hours to let the Loctite set, then mask the holes in the Bush with tape and give the Bracket several light coats of Rust-oleum Ultra Matte black spray paint. Two Collars The Collar details are in Fig.10 and they are visible in Photo 5. Chuck a piece of 10mm diameter aluminium round bar stock with 6mm protruding. Face the end and, using a centre drill followed by a 2.4mm drill, bore a hole 4mm deep. Part off a 3mm section. Using the mill, drill the 1.8mm hole for the 8BA screw and tap Photo 6: the Mounting Bracket is on the right, with the Platform attached to it via the three Pins, while the Cover Plate is on the left. The Cover Plate mounts on the back of the Mounting Bracket. The Bush is the part around the central sliding pin. July 2023  73 Fig.9: the Bush fits in a hole in the Mounting Bracket and guides the central Pin that the Cam acts on. Fig.10: The collars keep the spring in place when they are under tension. for 8BA. Finally, clean up the 2.4mm diameter hole. aluminium extrusion and is shown in Photo 6. It hides the servo motor that sits next to the Platform. Cut the extrusion to 100mm long and clean up the ends with a file, or do the whole operation in a milling machine fitted with a slot drill. Use a hacksaw to remove the rectangular sections at the ends of the 40mm side of the extrusion, and reduce the width from 40mm to 15mm. With a 1/8in or 3mm end mill in the chuck of a milling machine, clean up the cuts to size, then drill the two 3.5mm diameter mounting holes. Photo 6 also shows two small holes on the 20mm side of the Cover Plate. My layout is made from polystyrene foam, so I insert small pins through these holes to lock the assembly down. If you want to do something like that, drill the holes in similar locations. Finally, apply several light coats of Rust-oleum Ultra Matte black spray paint. Three Pins The details are shown in Fig.11 and the three Pins are visible in Photo 6. Chuck a piece of 3/32in (2.38mm) diameter brass rod with 20mm protruding. Face the end and use fine emery cloth to clean up any burrs from the end, and polish the circumference for 20mm. Part off an 18.6mm length. For the two outer Pins, leave the burrs on the parted-off end, as these will prevent the Pin from going all the way through the mounting hole in the Platform when assembled. However, while the centre Pin is in the lathe, use a file and emery cloth to round the end that will make contact with the Cam. Two Spacers As shown in Fig.12, mount an M2.5 nut in the lathe chuck and use a drill to enlarge the hole to 2.5mm in diameter. Platform The details are shown in Fig.13 and the Platform is visible in Photo 6. It is made from a piece of 2.5mm-thick aluminium plate. Cut the plate to size using a hacksaw and file the sides smooth, or mill the plate out using a milling machine fitted with a slot drill. Cut the end chamfers with a file or use a milling machine. Precision-drill the three 3/32in (2.38mm) diameter holes, if you didn’t already do it when making the Mounting Bracket. Cover Plate The Cover Plate (Fig.14) is made from a 25 × 40 × 1.6mm L-shaped This shows the size and shape of the specified servo motor. 74 Silicon Chip Marker Post So that you know where to stop the train, a small Marker Post is mounted beside the rail opposite the centre of the Uncoupler Platform. In operation, you drive the train up to the Marker where you want to split it. When the Platform raises, the coupling hooks of the carriages next to the Marker are lifted, and when the train moves forward, the two carriages are split apart. The Marker Post consists of three parts: top, support & post (see Fig.15). For the top, chuck a piece of 10mm diameter aluminium rod with about 10mm protruding. Face the end and reduce the outside diameter to 8mm for a depth of 6mm. Cut the 0.4mm recess using a 1/4in, 6mm or 6.5mm slot drill. Part off a 3.5mm length, mount the other side in the chuck and cut the other recess using the same slot drill. Next, mount the piece in the milling machine vice and drill the 2.1mm hole for the post. For the support, chuck a piece of 20mm diameter aluminium rod with about 8mm protruding. Face the end Australia's electronics magazine Fig.11: the Pins slide up and down in the Bush and Collars, with the central Pin being acted on directly by the Cam that’s rotated by the stepper motor. and reduce the outside diameter to 4mm for 3.5mm, then to a diameter of 12mm for 3mm. Using a centre drill, followed by a 2.1mm drill, bore out the end hole for 6mm and part off a length of 3.5mm. For the post, cut a piece of 1/16in (1.58mm) square hollow brass to a length of 61mm and clean up the ends. Using Loctite 620, assemble the parts as shown in the drawing. Leave it for 24 hours, then apply two light coats of Rust-oleum Ultra Matte black spray paint. Mechanical assembly Refer back to Figs.1(a)-(c) as a guide during the final assembly. Photos 5 & 6 should also help. To start, join the Cover Plate to the Mounting Bracket using two M3 × 6mm panhead machine screws, forming a ‘T’ shape. Next, attach the modified Hornby rail to the Mounting Bracket using two ½in or 13mm long 10BA screws. Slide the centre Pin into the Platform with the round end going in first. If the Pin is too tight, slightly reduce its diameter by returning it to the lathe and polishing its outside with emery cloth. Use Loctite 620 to lock the pin in place. Be sure to clean off any Loctite, as the last thing we want is to lock the Platform into the Bracket. Do the same for the outer Pins, only this time, they must be fitted with the parted-off end last. Again, make sure to remove any excess Loctite. Leave the assembly for 24 hours to allow the Loctite to set fully, cover the Pins with masking tape, and apply several light coats of matte black spray paint. When the paint is dry, remove the masking tape and clean off any remaining glue from the Pins. If all is well, the Platform should slide into the Mounting Bracket under its own weight when the Bracket is horizontal. The Collars and Springs can now be fitted. The Collars are held in place by two 8BA screws. Before fitting the screws, if they are 1/2in long (12.7mm), reduce their length by 2mm, to around 10mm. siliconchip.com.au Fig.12: these Spacers are made from M2.5 hex nuts and are used for mounting the servo motor in the correct position. An alternative way to stop the Collars from coming off is to use a soldering iron to apply a small amount of solder onto the ends of the outer Pins. If you need them to come off later, remove the solder with your soldering iron and solder wick. Use two M2.5 × 8mm panhead screws and the Spacers to mount the servo motor loosely, as shown in Fig 1. Set trim potentiometers VR1 and VR2 to their mid positions. With the switch in the down position (switch open), apply 5V to the PCB. The servo motor should now be in its fully anti-clockwise position. Attach the Cam as shown in Fig.1(a), with the Platform in its lowest position, then tighten its retaining screw. The Platform and centre Pin should be fully down. Slide the servo motor until the middle Pin just touches the Cam and tighten the 2.5mm screws holding the servo motor. Change the switch to the up position, and the servo motor and Cam should rotate clockwise, lifting the Pin and Platform assembly. Set the height of the top of the Platform above the rail to 2.7mm by adjusting VR1. Change the switch to the down position, and the Platform should move down until it is flush with the rail sleepers. Its height can be trimmed with VR2. Fig.13: the Platform sits inside the rails (above the sleepers) and is moved up and down by the servo motor and Cam acting on the central Pin. Fig.14: the Cover Plate mounts opposite the Cam, so there is a continuous rectangle of painted metal under the rails, except where the Pins pass through to lift the Platform, hiding the mechanism. Fig.15: the Marker Post is placed next to the rail in line with the centre of the Platform, so you know where to stop the locomotive before activating the Uncoupler. After gluing it together, I suggest you paint it matte black like mine. Layout assembly I decided that the best place to fit the Uncoupler was one rail length before the end of a siding. This way, I could back a train into it and uncouple one or two carriages, then the rest of the train could leave the siding. Later, the train could return, recouple the carriages and remove them from the siding. My train layout is made from 50mm-thick polyurethane sheets that sit on a 15mm-thick timber board. I cut out some foam to enable the Uncoupler to fit flat with the surface, as shown in Photo 7. I then drilled a 7mm diameter hole in the upper right-hand corner to let the servo motor wires go through the timber. You can make a similar cut-out if your rails are mounted on timber. siliconchip.com.au Photo 7: this shows the hole I cut into the polyurethane foam on my layout to make room for the Uncoupler to sit below its surface. Note how the servo wires pass through a hole in the timber base. Australia's electronics magazine July 2023  75 An alternative circuit without a microcontroller Some builders are put off projects because they use microcontrollers that require programming. Usually, the design with a micro uses fewer components and hence is cheaper to build, but in this case, it is marginal. This alternative circuit (Fig.16) uses two inexpensive CMOS 4047 monostable/astable ICs. IC1 is wired as an astable that produces a symmetrical square wave output from its pin 10. The frequency is set by the 120kW resistor and the 39nF capacitor by the formula f = 1 ÷ (4.4 × R × C), which gives approximately 49Hz, close enough to the required 50Hz. IC2 is wired as a monostable that is triggered on every positive-going edge fed to its input pin 8. In this case, it is triggered every 20ms. The output is a positive-going pulse with a period set by the 33nF capacitor and the resistance between pin 2 and pin 3, according to the formula t = 2.48 × R × C. As explained in the main article, we need this to be about 2ms at the low position and close to 1ms at the upper position. These timings are adjusted by 10kW potentiometer VR2 and 5kW potentiometer VR1, respectively. The up/down switch selects which is active. If you do the sums, you will see that the 10kW potentiometer with 18kW series resistor enables the period to be changed from approximately 1.5ms to 2.3ms, and the 5kW potentiometer with 10kW series resistor gives a range of approximately 0.8ms to 1.2ms. Fig.16: if you don’t want to use a microcontroller, you could build this circuit using logic chips instead. It does much the same job, although I haven’t designed a PCB to host it. I mounted the electronics together with the up/down switch, then used light-gauge three-core cable (similar to the wires attached to the servo motor) to connect the PCB to the motor and the 5V power supply. I then covered the wire junctions at the servo end with heatshrink tubing. Photo 8 shows the Uncoupler installed. Using it Photo 8: the Uncoupler sitting under a rail section on my layout. Note how the Cover Plate hides the servo motor beneath and the way the Marker Post is positioned in line with the centre of the Platform. Back the train down over the Uncoupler, line up the carriage junction you wish to uncouple with the Marker Post and stop the train. Throw the Uncoupler switch into the up position and drive the train forward. The carriages should now be uncoupled, and you can return the Uncoupler switch to the down position. To reconnect the carriages, back the train slowly into the stationary carriage, and it will automatically hook up. SC Australia's electronics magazine siliconchip.com.au 76 Silicon Chip Subscribe to JUNE 2023 ISSN 1030-2662 06 The VERY BEST DIY Projects ! 26 | Basic RF Signal Genera Generate a test signal from 9 771030 266001 $ 50* NZ $1290 11 INC GST INC GST tor 10Hz to 25MHz 38 | The History of ETI Magaz ine What happened over ETI magazine ’s 19-year life 44 | Loudspeaker Testing Jig 60 | WiFi Time Source for GPS Clocks A convenient way to test and tweak loudspeakers Modify your GPS clock to use NTP time over WiFi 70 | The Y2K38 Bug The Year 2000 Problem wasn’t the last ...plus much more inside S T ARLINK Australia’s top electronics magazine How SpaceX iS providing globa l Silicon Chip is one of the best DIY electronics magazines in the world. Each month is filled with a variety of projects that you can build yourself, along with features on a wide range of topics from in-depth electronics articles to general tech overviews. wireleSS internet Published in Silicon Chip If you have an active subscription you receive 10% OFF orders from our Online Shop (siliconchip.com.au/Shop/)* Rest of World New Zealand Australia * does not include the cost of postage Length Print Combined Online 6 months $65 $75 $50 1 year $120 $140 $95 2 years $230 $265 $185 6 months $80 $90 1 year $145 $165 2 years $275 $310 6 months $100 $110 1 year $195 $215 2 years $380 $415 All prices are in Australian dollars (AUD). Combined subscriptions include both the printed magazine and online access. Try our Online Subscription – now with PDF downloads! Starlink, Swarm and Starshield; June 2023 Basic RF Signal Generator; June 2023 Loudspeaker Test Jig; June 2023 The Songbird; May 2023 An online issue is perfect for those who don’t want too much clutter around the house and is the same price worldwide. Issues can be viewed online, or downloaded as a PDF. To start your subscription go to siliconchip.com.au/Shop/Subscribe oscillator-driven mosfet vibrator replacement In this article, I present two more fully tested vibrator replacement designs, plus three additional circuits that readers may wish to experiment with. The first of the two designs is based on a pair of standard Mosfets and is the most efficient vibrator replacement I’ve made. It isn’t too complicated to build, either. Part 2: by Dr Hugo Holden L ast month, I presented a Mosfet-­ based vibrator replacement for older communications receivers and some vintage radios. While it works very well, it has a couple of drawbacks. One is the relatively large and obsolete TO-3 package Mosfets. The other is that it’s only about as efficient as the mechanical vibrator it replaces. This somewhat more complicated design also uses Mosfets, this time readily-available, low-cost types specified in TO-220 packages, so it’s a bit more compact. It also adds four small-signal Mosfets to form an oscillator to drive those power Mosfets. That makes it quite a bit more efficient and able to deliver a higher HT; I measured 72.7% efficiency at 289V DC output compared to 67% at 276V DC output for the self-oscillating Mosfet version and 66.6% efficiency at 267V DC output for the original mechanical vibrator. Most parts are available from local suppliers like Jaycar, Altronics, RS or element14. The brass plate and wire are available from Mr Toys in Australia, while the UX7 base is a standard American Amphenol part that can usually be found on eBay. Its circuit is shown in Fig.1. A multivibrator is formed by two BS270 Mosfets, Q3 & Q4. This zero-bias configuration gives more reliable starting from low voltages than biasing these Mosfets to an on condition, which would be analogous to the usual bipolar transistor multivibrator circuit. Due to the high impedance at the Mosfet gates, high-value gate resistors and low-value timing capacitors can be used (270kW & 10nF). This results in accurate timing and avoids the use of poor-tolerance electrolytic capacitors, as would typically be required for a low-frequency BJT-based multivibrator. Diodes D1 and D2 clamp the gate drive signals to -0.7V. The multivibrator runs close to 110Hz, similar to a V6295 vibrator that nominally operates at 100Hz. If anything stops the multivibrator, or it doesn’t start due to a very slowly rising supply voltage, the drain potentials of Q3 and Q4 would be high. That would be a problem if they drove the output Mosfets directly because both Mosfets would be on continuously, shorting out the transformer primaries. Therefore, an inverting buffer stage is included, made from identical Mosfets Q2 and Q5. These also help to isolate the multivibrator from the output stage. The 12V DC supply to the multivibrator is also heavily filtered with a 150W resistor and 15μF capacitor. These ensure that the significant voltage transients from pin 4 do not cause premature triggering of the multivibrator when it is in a vulnerable condition, about to change state. I used four BS270s rather than a CMOS IC here as they have much higher voltage ratings (60V) and are much more immune to damage from spikes and transients. They do not require as much protection on the power supply feed as a CMOS IC. This circuit will start from voltages as low as 6V. Mosfet switching times Fig.1: this vibrator replacement uses an oscillator built around signal Mosfets Q3 & Q4. They drive the gates of power Mosfets Q1 & Q6 via inverter stages Q2 and Q5, which prevent overheating in case the oscillator stops or can’t start. This is the most efficient of my vibrator replacement designs. 78 Silicon Chip Australia's electronics magazine It is standard practice in switchmode power supply design to drive the gates of the output Mosfets from a low impedance source, typically siliconchip.com.au Photo 1: the main physical structure of the Mosfet-based, oscillatordriven vibrator replacement is made from a 7-pin base, and a rectangle of 0.8mm-thick brass with a 15mm tapped metal spacer soldered to it. from 10W to 100W, for fast switching. The power Mosfet gates often have a significant capacitance of around 500-5000pF, depending on the Mosfet type. Suppose the gate series resistance is too high. In that case, it can slow the switching time down and decrease the efficiency (increasing the Mosfet heating) because it spends more time in an intermediate conduction state rather than on or off. The switching frequency is often in the range of 20-100kHz in switch-mode PSUs, so there are many switching events per unit of time, and these losses add up. In addition, switch-mode power supply transformers are generally wound with a low leakage inductance, often with bifilar wound primary windings. However, the ZC1 power transformer is not like this; it has a relatively high leakage inductance between the halves of the primary windings. It also operates at a much lower switching frequency than a modern SMPS. Therefore, the design rules for this application are different. Very rapid switching of the output Mosfets is disadvantageous because the transformer’s primary winding leakage inductance (and leakage reactance) is so high that this produces very high voltage transients on the contralateral Second diode down in hole Photo 2: the two series pairs of BY448 diodes are soldered directly to the base pins. siliconchip.com.au or fellow Mosfet’s drain at the moment one Mosfet switches on. These spikes are on the order of 70-100V with a resonant frequency of about 50kHz. This is ameliorated a little by the 1.5kW gate drive resistor network, which forms a mild LPF (low-pass filter) with the gate capacitances of the IRF540Ns. Also, the added 470nF ‘tuning capacitor’ lowers the resonant frequency of the leakage inductance-­ capacitance network to about 20kHz, and reduces the voltage transients on the Mosfet drains to an acceptable level when switching occurs. Fig.2: assembly on the doublesided PCB is straightforward, as shown here. The TO-220 package Mosfets are first attached to the brass plate, then the PCB mounts on the brass plate with the Mosfet leads bent up to meet their pads on the PCB. The three nuts in a triangle pattern are for spacers that attach the PCB to the brass plate and provide ground connections. Construction Start by populating the PCB sans the power Mosfets, Q1 and Q6. The PCB is coded 18106231 and measures 33 × 45.5.5mm, with the components mounting on it as shown in Fig.2. Fit all the resistors, using a DMM to check their values, then mount the diodes orientated as shown. Follow with the capacitors; only the tantalum type is polarised and should have a + marked on its body. Crank the leads of the four identical TO-92 package Mosfets out using small pliers, then solder them in place, as shown in Fig.2. A vibrator replacement requires a chassis or skeleton to support it, and preferably a metal heatsink for the output devices. The simplest way to do this is to start with a standard Amphenol UX7 plug and fit it with a structure composed of a brass spacer, brass plate and a ground wire from pin 7 of the UX7 socket. The basic parts are shown in Photo 1, and the ground wire details are in Fig.4. To ensure the 3mm diameter hole in the plug is drilled on-centre, a temporary 3mm spacer can be placed in Australia's electronics magazine Figs.3 & 4: details of the brass plate. Note how the tapped spacer is notched to slide onto the brass plate’s end so it can be soldered in place. The way to bend the 2mm-thick brass wire is shown adjacent to the brass plate, with the ground wire soldered to the plate (also see the photos). July 2023  79 Photo 3: the brass sheet has now been attached to the base via the spacer and the 2mm-thick ground wire has been soldered to it. Fibre washers around the ground wire help support the insulator. Photo 4: next, the Mosfets are mounted to the brass sheet with insulators in between, and the leads are bent up, ready for the PCB. Three wires from the base have also been bent and insulated to meet their PCB pads. Photo 5: with the PCB assembled and installed, the unit is now ready for operation. Note that some slight component placement differences exist between this prototype and the final PCB. the ¼in recess to guide the drill. The hole is then countersunk from the pin side of the plug. Next, solder the four BY448 rectifiers into the plug assembly, as shown in Photo 2. The brass plate can have its holes drilled before or after fitting to the spacer, but it might be easier to do it first because the plate sits flat. The required hole positions are shown in Fig.3. Cut a 2-2.5mm deep slot in the 15mm-long M3 nickel-plated hex brass spacer to accommodate the brass plate. To do this, I used a junior saw and a fine flat file. Make the plate a push-fit into the spacer, then solder them together by holding the assembly with grips over the flame of a gas stove or with a suitably powerful soldering iron. The spacer’s end needs to be rounded off a little to fit into the deep hole in the UX7 plug. You can temporarily fit the brass plate and spacer to the plug to align it correctly, with a brass wire positioned to pass from pin 7 (Earth) of the plug to the brass plate, as shown in Photo 3. Once it’s aligned, solder the brass wire to the plate. The thick (2mm diameter) brass wire ensures that the plate cannot rotate easily even if its fixing screw becomes loose. I put masking tape on the plate where the power Mosfets and PCB spacers will go to allow a good connection, then sprayed it with lacquer to prevent future oxidation. Once the lacquer is dry, you can assemble the hardware ready to receive the PCB, as shown in Photo 4. Make a 25mm washer from insulating material like Presspahn or similar to cover the rectifier connections. The other wires can be made from 0.7mm diameter tinned copper, covered in silicone rubber or PVC insulation, or small diameter heatshrink tubing. Add the ‘tuning’ capacitor, C1, between the drain connections of the IRF540N power Mosfets. Photo 5 shows the PCB fitted over the Mosfet leads and the output wires soldered to it. This prototype board differs slightly in layout from the final version shown in Fig.2 but has the same circuit. Photo 6 shows how the Fig.5: due to the design of the transformer the vibrator drives creates a leakage inductance (XL) in series with the currently undriven primary, which resonates with Ct, generating voltage spikes at the transitions. Resistance R of the transformer windings slightly dampens the ringing. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au Photo 6 (left): three short spacers between the brass plate and PCB hold them together and make the ground connections. The tuning capacitor connects across the insulated Mosfet mounting screws that connect to the Mosfet drains. Photo 7 (right): another view of the completed vibrator replacement unit. tuning capacitor mounts between the Mosfet tabs and how one of the output wires, plus the 12V supply wire, pass through holes in the brass plate. The PCB mounts onto the brass plate using three 5mm-long M2-tapped metal spacers. These also make the GND connections between the PCB tracks and the brass plate. Photo 7 shows the finished assembly, while Photo 8 depicts it being tested in the ZC1 communications receiver via an extension socket. It is a good performer, and there is no significant RFI, unlike the original mechanical vibrator: A metal can is not required as there are no contacts to protect, but if you want to hide the electronics, you could use just about any metal tube with an inner diameter of at least 34mm. It’s safe for the can to rest on the brass plate as it’s at ground potential. the transformer windings or tuning capacitor(s). Fig.5 shows the centre-tapped primary of a transformer driven from only one side, as it would be half the time in a push-pull scenario. In this case, the two halves of the primary are labelled primary (P) and secondary (S); even though they are both part of the primary in actual use, one acts as a secondary in this particular example. XL is the transformer’s leakage reactance, an inductance acting in series with the windings, which Photo 8: the vibrator replacement undergoing testing in a ZC1 Mk2 communications receiver. It’s plugged in via an extension that allows the connections to be probed during operation. Leakage reactance It is worth looking at the leakage reactance problem and why the vibrator transformer primaries have a tendency for voltage overshoot. If these overshoots (oscillations) are too large, they can exceed the drain-source voltage of the Mosfet (or collector-­ emitter rating if a bipolar transistor is being used) and are a potential source for insulation breakdown of siliconchip.com.au arises because not all of the magnetic field links both windings P & S. The leakage reactance appears in series with the primary, or the secondary winding when the other winding is shorted out or has a fixed voltage applied to it. The tuning capacitor, Ct, is the inter-winding capacitance plus any externally added capacitance. The resistance (R) is mainly that of the ohmic losses of the windings. Initially, no current flows. When switch S1 (which could be a transistor) closes, 12V DC is applied to the primary winding P, effectively shorting it out from the AC perspective (until the core saturates). The leakage reactance XL appears in series with the secondary winding S and induces a voltage that attempts to raise V2 to 24V, as one side of secondary winding S is connected to +12V. To achieve this, Ct must be charged; it forms a resonant circuit with the leakage reactance XL, with some damping by R. Therefore, oscillations (spikes or ringing) occur on terminal V2. The frequency of this resonance is primarily determined by the leakage inductance XL and the tuning capacitance Ct. Resistance R also plays a part in the frequency, as the damping is pretty heavy, but there can often be four or five cycles of oscillation or ringing before they dampen out. This is why increasing the tuning capacitance lowers both the frequency and the amplitude of these oscillations or ringing. To look at it another way, the Q of this resonant circuit comprising R, XL Australia's electronics magazine July 2023  81 Fig.6: a similar arrangement to Fig.5 but showing both halves of the push-pull configuration, which results in a burst of oscillation each time one of the Mosfets switches on. and Ct is lowered with a larger tuning capacitor because the resonant frequency is shifted down, and the inductive reactance of XL is lower at that lower resonant frequency. In the case of the push-pull rather than the single-ended example above, the same situation occurs, as shown in Fig.6; the resistance is omitted for clarity. When Mosfet Q1 switches on (red drive waveform high), voltage V1 goes rapidly to zero in a few microseconds or less. XL1 vanishes when Q1 is conducting as a fixed voltage +V is applied to winding P1, and all the leakage reactance then appears as XL2 in Q2’s drain circuit. Q2 is also off at this time. Ct is in resonance with XL2, so the leading edge of the voltage V2 has ringing and overshoot. The situation is reversed when Q2 conducts, making XL2 vanish and placing all the leakage reactance XL1 into Q1’s drain circuit. The peak amplitude is around twice the supply voltage, which holds true until the magnetic core of the power transformer starts to saturate. For the ZC1 radio transformer, this takes about 8ms, so a 100Hz drive waveform does not take it near core saturation. However, in a future issue I will present a different vibrator replacement using bipolar transistors that relies on core saturation to sustain oscillation. Scope 1 shows a ZC1 Mk2 radio’s primary winding voltages with the vibrator replacement unit presented here. The oscillations are visible on the drain connections (transformer primary) immediately after one Mosfet comes out of conduction and the fellow Mosfet goes into conduction. They switch quickly, over less than a few microseconds, even with the 1.5kW gate resistors. Scope 2 gives a closer look at the oscillations. With the 470nF tuning capacitor, the ringing frequency is about 20kHz: Without the added tuning capacitor, as shown in Scope 3, the ringing frequency is about 50kHz, and the peaks are much higher. Other smaller oscillations are superimposed due to the transformer’s high-voltage secondary windings, their leakage reactance and associated capacitance. The initial peak is very high at around 70V, and on its negative half-cycle, causes the Mosfet’s internal drain-source diode to conduct, clamping the negative half-cycle. Scope 4 shows the timing of this transient, which occurs just after the Mosfet switches on and its fellow turns off. Therefore, that 470nF tuning capacitor is important with this Mosfet version, or any version using silicon transistors driven by an independent oscillator (like commercial transistorised units). With the mechanical vibrator, this first peak is lower at around 30-40V. That’s because, with the reduced duty cycle, the transformer’s primary voltage falls from 24V to about 16V before the next switchover as the energy transfer to the circuit comprising Ct and XL is a little lower. Another potential method to solve the leakage reactance/voltage spike issue is to snub off the high-voltage transients with a TVS (transient voltage suppressor) to around 30V. However, there is a little more chance of RFI with this method versus tuning the Scope 1: the drain voltages of the Mosfets during operation. Scope 2: a close-up of the drain voltage of the Mosfets with a They switch pretty fast and the oscillation and ringing due 470nF tuning capacitor at transition, showing the oscillation to the transformer’s leakage reactance is well damped. and ringing at about 20kHz. 82 Silicon Chip Australia's electronics magazine siliconchip.com.au resonant frequency downwards with the added tuning capacitor. A bidirectional 30-40V TVS between the output Mosfet drains would work. The makers of commercial vibrator replacements with electronic driver circuits do not seem to consider the leakage inductance of the primary of the vibrator transformers. The tuning capacitors they specify do not suit an electronic driver with an independent oscillator; more capacitance is needed, or the voltage transients threaten the output devices and the transformer insulation. A safe design One thing that bothered me about the commercial designs, which have gates and logic or other ICs as oscillators, is what would happen if that clock stopped or did not start. This can occur if the power supply ramps up too slowly and is common with circuits that use logic gates. It leaves one transistor switched on and the other off, applying full voltage to one half of the primary and that will blow the fuse, if there is one, or overheat the device or the transformer. With this design, the output devices remain off if the multivibrator stops and/or doesn’t start, thanks to the two extra BS270 signal Mosfets. Darlington-based alternative Another vibrator replacement I came up with is based on Darlington transistors, and this one is simple enough that it doesn’t need a PCB, although the metalwork is a bit more complex. Fig.7: a simple self-oscillating, Darlington-based vibrator replacement. There are more efficient arrangements than this but it is simple and reliable. Darlingtons have a low input threshold voltage of around 1.4V, so the circuit will start (oscillate) from low power supply voltages. The circuit described here operates with a supply voltage as low as 3V. Darlington power transistors also have the advantages of internal base resistors and collector-­ emitter diodes, saving on parts. Frequency limiting and stable self-switching can be obtained with 47nF Miller integrator capacitors between the collector and base of each Darlington transistor. Without this negative feedback, the oscillator circuit is highly unstable and oscillates at a high frequency corresponding to the power transformer’s primary leakage reactance and associated capacitances in resonance. If this persists, the transistors can overheat and be destroyed. 20V/cm 10V/cm Scope 3: the overshoot is much faster and reaches higher voltages without the tuning capacitor. This could cause insulation breakdown or damage to the Mosfets. siliconchip.com.au Using Darlington transistors as switches results in a base drive power about 10-20 times lower than BJTs (bipolar junction transistors). The positive feedback capacitors to sustain oscillation from the collector of one transistor to the base of the fellow transistor can be a modest value of 4.7μF, meaning non-electrolytic types can be used. Electrolytic capacitors are best avoided where the values are responsible for setting time constants, due to their lax tolerances. The circuit, shown in Fig.7, is based on MJ3001 or MJ11016 NPN Darlington transistors, oscillating at close to 62Hz. Scope 5 shows the resulting transformer drive waveform (at one end of the primary). The collector-emitter Scope 4: the two Mosfet drain voltages at a short timebase (without tuning capacitor) shows a large spike at the switched-off Mosfet’s drain, after the other Mosfet turns on. Australia's electronics magazine July 2023  83 Scope 5: the Darlington collector waveforms are clean square waves with rounded edges due to the Miller capacitor slowing switch-on/switch-off. There’s little sign of ringing. saturation voltage drop of the Darlingtons in this application with a peak collector current of 2A is about 0.9V. Therefore, this Darlington unit results in an output power about 6% lower than the Mosfet version. However, the output voltage and efficiency are very similar to the original electromechanical V6295. The advantage is that the Darlington unit is relatively simple for the home constructor to manufacture. Scope 6 shows a close-up of the collector waveform for the Darlington unit. This shows only a small resonance during the switching event, with no significant collector voltage overshoot, due to the 47nF Miller capacitors and the switching frequency of just 60Hz. A 470nF tuning capacitor is not required here. Construction Prepare four brass plates, two of each type shown in Fig.8. When working with 0.8mm-thick brass plate, it is best to mark and drill 1mm pilot holes Scope 6: the Darlington collector voltage during switch-off with a short timebase. A tiny bit of oscillation is visible here, but nothing to worry about. first, then drill the holes out one size step at a time to get to the final size. 0.8mm (0.032in) thick brass plate is made by K&S Engineering and is stocked in Australia by companies selling models, such as Mr Toys. The results are shown in Photo 9. The machined brass base and top are shown in Photo 10. I had them turned by a local machine shop, then added the 7mm-deep threaded holes myself. The reason for the groove in the base is that my ZC1 Mk2 communications receiver has clips around the base of the vibrator to retain it, and they fit into this groove (see Photo 11). If your application is different, you may need to change the details of the groove, or eliminate it and simplify the machining if your device lacks such clips. When tapping into blind holes, use a tapered tap first and lubricate with WD40 (or the recommended lubricant for your metal) during the process. Then wash all the swarf out of the hole with a jet of contact cleaner from the applicator tube. After that, you can tap to the base of the holes with a bottom tap to ensure the thread runs to each hole’s base. Then wash out the swarf again with contact cleaner. It is critical to be patient and careful when marking, centring and drilling the holes, which are all 9mm from the edges of the square section, as per Fig.9. The Amphenol 7-pin plug base is prepared with the BY448 rectifiers, just like the Mosfet version described earlier. Only three wires (the two collector wires and ground) are required as the +12V connection (pin 4) is not used – see Photo 13. Glue this plug arrangement into the brass base. This is best done as a twostep procedure; use a small amount of 24-hour epoxy to attach it and align it on the correct axis when the unit is plugged in. Once cured, add more epoxy to the well created by the edges of the plug and the inside of the brass housing. There’s no risk of it draining out before it sets because the first bond has sealed it – see Photos 12 & 13. Photo 9: these four brass plates form the four larger sides of the housing. Two have holes drilled for the TO-3 mounting screws & leads. Photo 10 (right): I drilled and tapped 7mm-deep holes with 4-40 UNC threads in the lid and base to attach the sheets shown in Photo 9. A local machine shop made these pieces as I don’t have the required tools. 84 Silicon Chip Australia's electronics magazine siliconchip.com.au Photo 11: the groove in the base is designed to engage these retention tabs in the ZC1 Mk2 transceiver. Photo 14 is of the Augat TO-3 transistor sockets I used, usually available on eBay, plus an insulated standoff (it is a bit like a single-point tag strip). Both create convenient tie points for components, obviate the need for insulators, nuts/washers & lugs for the collector terminals, and the transistors are easily removed for testing or replacement. You also don’t have to solder to the transistor leads. These single insulated mounting posts are becoming rare. Surplus Sales of Nebraska still stock a range of mounting posts like this. Another option is a phenolic tag strip with a single lug. If TO-3 sockets are not used, and the transistors are instead mounted with the usual insulator set, reduce the 5.5mm holes in the brass plates to 4mm in diameter. Photo 15 shows the device partially assembled, with the capacitors and diodes mounted to the socket and post. Both sides are identical. Each transistor base has two capacitors and one diode connected to it. No resistors are connected to the bases because the base resistor is internal to the Darlington transistor. I scribed marks for the holes on the inside surfaces of the brass plates so they would not be visible from the outside of the assembled unit. Note that I sprayed the brass plates with DS117 clear automotive lacquer to prevent oxidation. Mount the transistors with the usual mica insulating washer, with thermal paste on both sides. Clear silicone siliconchip.com.au Fig.8: drilling details for the four brass plates (two of each) that make up the sides of the rectangular Darlington-based vibrator replacement. Fig.9: details of the machined base and top of the rectangular case. The groove in the round base is for the retaining clips in the radio to engage; not all radios with vibrators will have this feature. Second Bond First Bond Photo 12: start assembling the base by gluing the plug into the machined brass piece, sealing all around the perimeter with 24-hour epoxy. Australia's electronics magazine Photo 13: once the first lot of epoxy has set, you can add more around the perimeter at the top edge of the plug to make it really solid. July 2023  85 grease is less messy than the white compound, and the extra is easily wiped away. In this instance, each transistor’s dissipation is only 1-1.5W, so they only run warm; still, it is better to have some thermal coupling to the brass plate. Screw the transistors down with 12mm or ½in 6-32 UNC screws that fit the threads in the Augat sockets. Each screw has a split-spring lock washer under its head. Photo 16 shows the transistors installed, while Photo 17 shows the internals assembled. The 560W resistors pass from one side to the other, connecting the mounting post connection to the collector terminal lug on the opposite transistor. The screws used to attach the brass panels to the top and base are stainless steel 4-40 UNC, ¼in long with a Binder style head, similar but slightly different to a pan head. These are available from PSME (Precision Scale Model Engineering in the USA). Performance The Darlington version is almost a dead-ringer in performance to the electromechanical unit, but of course, with no reliability or wear problems. The output voltage is a little lower than the other electronic units due to the collector-emitter voltage drops of about 0.9V for the Darlingtons. The similarly low output voltage of the mechanical unit is due to the reduced duty cycle compared to the electronic units. So the two devices have about the same performance parameters for different reasons. Logic IC based vibrators Fig.10: a vibrator replacement circuit based on a pair of Mosfets & SN7400 quad NAND gate IC. Note the zener diode to protect the IC from voltage spikes, and the use of logic-level Mosfets, as their gates are only driven to 5V. AUGAT TO-3 SOCKET STANDOFF POST Photo 14: I mounted the TO-3 transistors via sockets to make construction and servicing easier. The insulated standoff post mounted near the socket also makes the wiring easier. Photo 15: the two identical halves of the circuit are fully assembled and ready to be merged. 86 Silicon Chip Australia's electronics magazine In reference to the Mosfet vibrator replacement described above, I mentioned in passing devices that use logic ICs for the oscillator. Figs.10-12 are circuits of unusual variants you will not see elsewhere. Fig.10 shows a 6V-powered unit I designed using a TTL logic gate. I built some of these using a beam lead style 7474, mil-spec 5474, or the 5400 NAND gate in ceramic packages, like those used in the Apollo 11 computers. These are incredibly robust parts, able to survive re-entry into the atmosphere in a satellite and still function! They are the most robust ICs ever created. The circuit of Fig.11 is an oddball arrangement that enables one flip-flop to be used as an oscillator and the other as a 2:1 frequency divider (both in the same IC) to give a spectacularly perfect square wave. If the wave duty cycle is not exactly 50%, the current consumption increases, and the efficiency drops as the transformer core develops a net flux. One of the problems I had with commercial electronic vibrator substitutes was that they used somewhat fragile CMOS ICs with an imperfect duty cycle. On top of that, the designers didn’t understand that in the case of replacing the secondary contacts of the synchronous vibrator, you need an extremely high PIV rated diode. And they ignored the requirement for additional tuning capacitance as well. Fig.12 is a 12V-powered design that uses a 7400 (or 5400) logic IC. The zener diode protects the IC from voltage transients on the +12V rail. If a reversed polarity is applied, the siliconchip.com.au Fig.11: another vibrator replacement circuit, this time based on two NPN Darlingtons and a dual flip-flop IC. The first flip-flop is the oscillator, while the second halves the frequency for perfect waveform symmetry. Fig.12: a similar circuit to Fig.10, only using Darlingtons instead of logic-level Mosfets, and with values changed to suit a 12V battery supply. All of these circuits (Figs.10-12) also need the diodes shown at right. Photo 16 (left): an outside view of the two halves showing how the TO-3 transistors are retained. Photo 17 (right): once the two halves are attached to the base, the wiring can be finalised by adding the two resistors that go from one side to the other, plus the two collector (blue) and two ground connections (black sheathed wire). siliconchip.com.au Australia's electronics magazine July 2023  87 Parts List – Vibrator Replacements Mosfet version 1 double-sided PCB coded 18106231, 33 × 45.5mm 1 Amphenol 7-pin base [www.ebay.com.au/itm/115461595962] 1 brass plate, 65 × 34 × 0.8mm (0.032in) 1 50mm length of 2mm diameter brass wire 1 200mm length of 0.7mm diameter tinned copper wire 1 200mm length of 1.5mm diameter heatshrink or spaghetti tubing 2 TO-220 transistor insulating kits (washers + bushes) 2 M3 × 6mm panhead machine screws and nuts 3 M2 × 12mm panhead machine screws and nuts 1 25mm disc of insulating material (phenolic, FR-4, Presspahn etc) 3 metal spacers (4mm diameter, 5mm tall) with matching screws and nuts 2 3mm solder lugs hardware etc (available from K & S Engineering USA) Photo 18: the rectangular prism brass case of the Darlington vibrator replacement forms the structure and provides heatsinking for the TO-3 metal can encapsulated transistors. Semiconductors 2 IRF540N 100V 33A N-channel Mosfets, TO-220 (Q1, Q6) 4 BS270 60V 400mA N-channel Mosfets, TO-92 (Q2-Q5) 2 1N4148 75V 200mA diodes, DO-35 (D1, D2) 4 BY448 1.5kV 2A axial diodes (D3-D6) Capacitors 1 15μF 35V tantalum 1 470nF 250V polyester or polypropylene axial 2 10nF 100V MKT polyester or greencap Resistors (all ¼W or ⅛W 1% axial) 2 270kW 2 10kW 4 1.5kW 1 150W 2 100W Photo 19: with the lid and four sides held together and to the base by screws, the vibrator replacement is ready for testing and use! Darlington version 1 Amphenol 7-pin base [www.ebay.com.au/itm/115461595962] 2 Augat or similar TO-3 sockets [www.ebay.com.au/itm/144066503423] 2 TO-3 mica insulating washers 4 brass plates, 68 × 42 × 0.8mm (0.032in) each (see Fig.8) 1 machined brass base, 40 × 40 × 14mm (see Fig.9) 1 machined brass lid, 40 × 40 × 7mm (see Fig.9) 1 200mm length of 0.7mm diameter tinned copper wire 1 200mm length of 1.5mm diameter heatshrink or spaghetti tubing 1 6mm or ¼in long stainless steel 4-40 UNC screws, panhead or Binder-style [PSME] 4 12mm or ½in long 6-32 UNC panhead machine screws 2 6-32 UNC split spring washers 2 insulated standoff posts with matching panhead machine screws Semiconductors & passives 2 MJ11016G 120V 30A NPN Darlington transistors, TO-3 (Q1, Q2) [RS Cat 463-000] OR 2 MJ3001 80V 10A NPN Darlington transistors, TO-3 (Q1, Q2) [www.ebay.com.au/itm/303226250083] 2 1N4004 400V 1A diodes (D1, D2) 4 BY448 1.5kV 2A axial diodes (D3-D6) 2 47nF 400V axial plastic film capacitors 2 4.7μF 63V axial plastic film capacitors 2 560W 1W axial resistors 88 Silicon Chip Australia's electronics magazine zener conducts in the forward direction, protecting the IC. In that case, the collector-­emitter diodes intrinsic to the Darlington transistors conduct, blowing the fuse (hopefully, there is one). I’m not presenting construction details for any of these because I believe the three discrete designs I’ve published so far (with one more to come) are more robust and generally better. Coming up I have built one more vibrator replacement design that is quite a bit more difficult than any of the versions described so far. It is based on two bipolar transistors, a custom transformer, and a few passive components. It is a design that could have appeared in the early days of transistors, when they were expensive, as it uses them sparingly. Despite this, it works just as well as the Darlington-­ based version described in this article, with similar efficiency and delivering a similar output voltage. You can expect to see that article within the next few months. SC siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 194, MATRAVILLE, NSW 2036 (02) 9939 3295, +612 for international YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. 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All prices in Australian dollars and include GST where applicable. # Overseas? Place an order on our website for a quote. See page 98 for a list of available PCBs $30.00 07/23 Don't pay 2-3 times as much for similar brand name models when you don't have to. IDEAL STARTER STATION IDEAL HOBBYIST ENTRY LEVEL STATION ONLY 4495 $ TS1610 LIGHTWEIGHT, EXCEPTIONALLY DELICATE • 10 WATT • ROTARY TEMPERATURE CONTROL DIAL TS1620 GREAT FOR ENTHUSIAST'S WEEKEND PROJECTS ONLY 139 $ TS1564 ONLY 7995 $ LIGHTWEIGHT IRON WITH ADJUSTABLE TEMPERATURE • 48 WATT • SLIMLINE DESIGN GREAT FOR EVERYDAY ELECTRONICS ENTHUSIASTS ONLY 209 $ TS1640 OUR MOST POPULAR STATION FOR HOBBYISTS • 48 WATT • ANALOGUE TEMP ADJUSTMENT Explore our great range of soldering stations, in stock on our website, or at over 110 stores or 130 resellers nationwide. 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ENTRY LEVEL MID LEVEL PROFESSIONAL TS1610 TS1620 TS1564 TS1640 TS1648 Key Feature Compact Design Slimline Ceramic Element Digital Display Soldering & Hot Air Power (Watts) 10W 48W 48W 60W 300W Temp. Range 100-450°C 150-450°C 150-450°C 160-480°C 50-480°C Soldering 100-500°C Hot Air Display Digital Digital ESD Safe • • $209 $349 Price $44.95 $79.95 $139 *Temperature rating is set by the soldering iron tip. ESD means Electro Static Discharge Shop Jaycar for your soldering essentials: • Soldering stations • Electric handheld irons • Gas powered irons • Classic 60/40, lead-free, silver & paste solder options • Multiple desolder braid and tools • Wide range of stands, cleaners and PCB holders Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. SERVICEMAN’S LOG Can’t stop servicing, even on holiday! Dave Thompson Five years have passed since I have had a proper holiday (not just the odd day off), where I get to laze around and do nothing, or at least whatever I want. All without the phone ringing, email notifications going off, or people turning up at the workshop, expecting me to fix something while they wait. Sometimes, it’s hard to stay above it all, a feeling I’m sure most of you are familiar with! Many people will likely synchronise whatever holidays they get each year with kids’ school holidays or their own time off work. As a sole trader with no school holidays to worry about, I often don’t get to have the usual days off. There is always something to do, whether it is researching or making components from scratch for weird jobs, or trying to track down spares for my work tools. Then there’s all the usual household maintenance. I suppose I could pay someone to do that, but it seems a bit silly to shell out for someone to come around and mow lawns, or clear gutters while I am still relatively capable of doing it. So, a holiday then, a real one, which involves travelling to Europe to visit family. We were due to go a few years ago, but sadly, world events got in the way. That made it difficult and expensive to go anywhere, so we knuckled down like everyone else and just got through it as best we could. Finally, things have returned (somewhat) to normal, so we took the opportunity to take some time off. My wife is lucky in that she permanently works from home, and part of the deal was that she would do a few days of remote work each week while we were overseas. That actually took a surprising amount of legal jiggery-­ pokery due to the sensitive commercial nature of her work and the fact she’d be bringing a work laptop with her. Some people cannot work remotely from certain countries; fortunately, Croatia is OK, being now part of the EU. The morning of our departure, a neighbour was to drop us off at the airport. We were lucky we didn’t have to be at the airport at some ungodly hour, so we had some time to relax. This spare time was important, as when the neighbour came to pick us up and I loaded our bags into the boot of his car, I caught one of the straps holding his folding rear parcel shelf and popped the plastic bung/holder from its anchor point. No matter; I should be able to simply pop it back in. Except I couldn’t because it had broken off, and the flexible expanding base part that would usually keep the mount in its hole was half missing. Great! Feeling sheepish about breaking his car, I realised that the bungs were very similar on our own car, so I fumbled through our luggage to find a key, politely avoiding his objections that he’d fix it, and pulled one from our boot. It was almost the same in looks and the same size, so I popped both from our car and replaced both in his car. Problem solved; I’d get new ones when we got back. So, job done! Just plane broken At the airport, we boarded our flight only to be told the entertainment/media screen on my seat was not working. The flight to Singapore was quite full, and the ‘fix’ the purser offered was that if I wanted to watch a movie, I could go to an empty seat way down the back in cattle class. That is obviously less than ideal, and I was not that pleased. We faced an almost-12-hour flight, and without a book, I’d only have my wife and my phone for company unless I sat at the back of the plane. The engineers had apparently been trying to fix it during the turnaround but ran out of time. The start of this trip was not looking promising! While everyone else was boarding, I looked over the screen in this Airbus A350. It was pretty big compared to what I was used to. The trim around it hadn’t been pushed closed properly, so like any good inquisitive serviceman, and against my wife’s protests, I gently unclipped it all the way and removed it. I know I shouldn’t have, but in my defence, they had left it like that, and I couldn’t help myself to take a look. 92 Silicon Chip Australia's electronics magazine siliconchip.com.au Items Covered This Month • • • • A servicing free holiday (not!) Bringing a mobile phone battery back to life Repairing a Zodiac pool cleaner Pfaff sewing machine repair Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com There was not much to see underneath anyway, but I did notice one corner of the screen’s frame hadn’t seated back in properly and was protruding by about 1-2mm. This could be why the trim hadn’t fitted flush like the rest of it. Now, stressing screens like this isn’t a good idea, even accidentally, but it appeared OK, with no obvious cracks. I’ve seen enough cracked internally after being flexed even less than this, though, so I didn’t hold out much hope. Regardless, I gently pushed on it right over the metal-framed edge and increased my pressure until I felt it click back into place (or break, I wasn’t sure which)! The boarding hullabaloo around me ensured that what I was doing wasn’t apparent to anyone other than my by-now horrified wife. Still, suddenly I got a message on the screen simply saying ‘rebooting’, and a progress bar told me it was almost done! I replaced the trim surround, and after the screen went blank for what seemed an agonisingly long time, up came the KrisWorld entertainment menu. I was pleased I wouldn’t have to change seats, and I hoped that the thing would hold out for the whole flight. Like so many of my repairs on stuff I know nothing about, it was just dumb serviceman’s luck and a complete fluke that it was now working. That reminds me, I should send my invoice to the airline... Fortunately, the rest of the flight went without me having to repair anything. We had a decent layover in Singapore, but not enough to leave the transit area. We found a lounge, paid our entry fees and parked up, partaking of the comfortable seating, endless buffet and bottomless drinks menu. The problem with bottomless drinks is the frequent need for restrooms. I made my way to the closest one, but it was closed for cleaning. That wasn’t a problem; in Terminal 3 at Changi, plenty of others are a short walk away. As I went to find one of those, I noticed through the open door a cleaner appearing to struggle with a floor-cleaning machine. did feel slogged out. I took the strain out of the connection and moved the cable into several positions while hitting the switch. The machine fired up with it in one position, but it stopped again after letting the cable go. The strain reliever where the lead entered the plug and the cable itself didn’t look stressed, so I assumed it was the plug. Physically moving the plug with the power switch on resulted in the motor kicking and stopping. So, the plug and/or socket, then. I looped the cable through one of the handles on the machine’s body and tied a knot in it, taking any stress off the connection but holding it in a position where power made it through. The machine fired up and stayed running, even with moving it around. There was no obvious burning or arcing at the socket. Not ideal, obviously, but she was relieved that at least she could finish this job, open the loos and then have the service guys look at it properly. I even got to use the toilet, so a reward in kind! Amazingly, nothing needed fixing for the rest of the two-day journey. I guess there were some things, but by that point, I was so sick of airports and lounges that the place could fall down for all I cared; I just wanted to get to our destination. I’ll wager I’m not the only traveller who greatly rues that we haven’t yet perfected a Star Trek-style transporter! Wife needs WiFi Reaching our final destination threw up some other challenges. It seems that once they knew we were coming, they started making a list of what I might be able to help them out with! While it’s nice to be wanted... Of course, the first thing we’d want to do is get connected to the internet. We couldn’t, at least not in the part of this partitioned house we would be staying in. The solid concrete and reinforced steel walls of these typical Croatian homes seem impervious to WiFi signals! That meant going to the other part of the house if we wanted any WiFi connectivity. Servicing around the world This thing looked like a mashup of an industrial vacuum cleaner and a floor cleaner/polisher. She was switching it on and off, and it seemed to be trying to start but failing. Exasperated, she gave up. Again, the Serviceman’s Curse stepped in, and I walked in and asked if I could help. She was very grateful and gladly accepted. I noticed as she operated the switch on the side of the machine, it rotated slightly with the pressure, pulling on the power cable. I suspected there could be a break in the power lead, or the machine’s socket and plug might be contacting intermittently. I checked that the plug was hard into the socket, but it siliconchip.com.au Australia's electronics magazine July 2023  93 It would do for a day or so, but something needed to be done as a long-term solution. Regular readers may recall me talking of this same scenario five years ago; work has been done on this house, and my previous repeater setup had been dismantled. Due to the new construction, that option was no longer available. Running cables by drilling holes in walls is a big no-no! We browsed the local computer store and purchased a decent long-range router; I wish hardware were this cheap in New Zealand! I may even take it home with me this time. Our only option was to run a cable from the existing router in the other part of the house up along the corners of rooms and tops of walls and down along the skirting boards. I would be taking full advantage of some gaps underneath doors, which were opened ironically due to a good earthquake here a few years back. The new router would be positioned on the dusty top of a cupboard just through the wall from where we’ll be spending the most time. This arrangement gave wider WiFi coverage and allowed us to get some reasonable speeds, although it maxed out at 30Mbps down and 5Mbps up. That’s a long way down from the 980Mbps down and 600Mbps up we usually get back home! Even then, my wife could not reliably use Microsoft Teams for her work, which was a major roadblock. We worked around that by buying a local data-only SIM for my dual-SIM Samsung Galaxy S22 and setting it up as a mobile hotspot. That gave us some excellent speeds, as this town’s mobile coverage is pretty good. She no longer has any problems doing her work, and I can surf the web and email, so that’s another couple of fires put out! They knew we were coming Many people here own what they call a beach house. This family is no different. In reality, these are more like apartments and the coastline is covered in them. Some have just one apartment for the family, while others have several that are rented out during the season to some of the millions of tourists who flock here every summer. 94 Silicon Chip Our visit, just pre-season, coincided with my mother-in-law going to her beach house to prepare her two apartments for guests. As you would surmise, these places sit empty for eight months of the year and, being by the seaside, nature can be harsh. Though pretty tightly locked and sealed against the elements with the amazing shutter and window systems they use here, most places need frequent maintenance. A repaint every few years is essential, and any metalwork such as railings and fittings (of which there is a lot) must also be sanded and painted. I did a lot of that last time and wasn’t overly keen to do more, but apparently, there was a problem with the TV in one apartment and the mains power in another. I could probably handle the TV – the mains power, well, we’ll see. The culture here is very much DIY or helped by your mates, with calling in a professional an absolute last resort. All the family members who could do this sort of stuff have moved on, so if I’m around, I’m tapped on the shoulder. The part of the coast the house is located is about 30km from where we are, over a very narrow road over the hills (although it’s infinitely better now than before). Once there (still nerve-wracking after all these years), I got into sorting the TV. It’s a wall-mounted flat screen, about 50 inches (1.27m) diagonally, and made by some local brand, likely stuffed with Blaupunkt or Phillips hardware. I’m guessing they are similar to the cheaper no-name brands the appliance stores sell back home; those usually have a well-deserved bad reputation for quality control. I’ve worked on a few back home, and I was hoping this wasn’t anything too serious this time. Due to the relatively low cost (for us tourists), it is often easier just to buy another one, but that seems to be against the ethos of many older people here! The TV powered on, but its reception was terrible. All the TVs in the block (three in different rooms) shared a common antenna, on the roof, of course. Cabling came down from the antenna and was embedded in the walls when the place was expanded upwards of 10 years ago. The antenna Australia's electronics magazine siliconchip.com.au points are screwed to the wall, and each TV connects via a coaxial cable and standard Belling-Lee plug. The TV reception in the top apartment wasn’t too flash either, so it was most likely the antenna. Great; I’m not good with heights, and the ladder system to reach the roof is rickety at best. Still, with the ladies watching, I couldn’t very well leave it at that, so up I went. I was fine once I was up there, except the typical red terracotta tiles were already so hot, so I couldn’t stay in one place for long. Luckily, it is relatively flat, as is typical in many temperate climates (average temperature here: 19.7°C). As you’d expect, the antenna was a feast of corrosion. I cleaned it up as best I could with sandpaper, stripped and reattached the cable at the terminal box, and reports from below claimed all TVs worked perfectly. The mains issue would have to wait. I was baking and needed a swim. This is our holiday, after all! Bringing a battery back to life J. W., of Bairnsdale, Vic was prompted to write in after reading the contribution by D. M. of Toorak, Vic in the Serviceman’s Log of December 2022, about reviving a lithium battery that had been over-discharged... I had a similar problem when I wanted to use a mobile phone that had been sitting idle for a while. There was no power and the phone would not charge. Since the battery was removable, I took it out and measured no voltage between the terminals. I’m a bit of a miser and didn’t want to spend the money on a new battery if the old one could be salvaged, so I had to be careful how I proceeded. My repair attempt would be no good if I destroyed the battery trying to open it. Some slow and careful probing, along with persistent levering, allowed me to separate the plastic divider on the negative side of the battery from the battery. I managed to do that without breaking the connection between the battery and the protection circuit, which was housed inside the divider. Further probing with a multimeter on the exposed cell terminals revealed that it was down to less than a volt, which was obviously far too low. With little hope in my heart, I nevertheless connected a regulated power supply to the cell terminals, set for 4.2V and, keeping the current limit low for safety, applied 500mA and then monitored the battery closely for signs of distress while it charged. Around two hours later and with no signs of distress, the cell was showing around 3.2V, so it was probably time to use the proper charger to finish the job. I closed the battery and inserted it into the phone. Although it was a little snug due to my ‘surgery’, it did fit. I connected the charger, and the battery took a full charge. It’s a wonder that the battery recovered, but I’m happy with the result. I won’t be entirely trusting that battery since spending some time at such a low charge level may have damaged it internally. Still, it seems that under-­voltage may be less of a concern for lithium batteries than over-voltage is. I saved approximately $50, which I otherwise would have needed to pay for a new battery. Pool cleaner motor repair R. S., of Fig Tree Pocket, Qld has been busy fixing (among other things) a pool cleaner... The Zodiac VX55 pool cleaner motor block has three motors: two geared ones for the wheels, plus a large one to pump water through the cleaner. There is also a circuit board that powers the motors. The wheel motors are each driven by four Mosfets, two N-channel and two P-channel so that they can be driven forwards and backwards. There is one N-channel Mosfet to drive the pump motor. A three-way cable feeds the motor block with 30V, Earth, plus a bidirectional data line from the external controller. The data line is serial, with commands sent from the controller and any error messages returned to the controller. If the controller cannot communicate with the motor block, it displays Error 10. The Mosfets can go short-circuit, and this will give a ‘motor shorted’ error. These can be replaced, but water leakage into the motor block can cause board corrosion. Clean the board if you can, or try to get a replacement on eBay. Also check the motors by powering them with an external supply. When you put the motor block back together, use a water seal compound; otherwise, the o-ring will leak. Sewing machine repairs B. M., of Powranna, Tas is usually a little reticent about diving into the unknown, especially mains-powered devices. Still, living in the country, he sometimes must tackle things he otherwise probably wouldn’t... Among the fixes I have undertaken since Christmas are two of my wife’s extensive collection of sewing machines The Zodiac cleaner body (left) and the main PCB that controls the motors (right). siliconchip.com.au Australia's electronics magazine July 2023  95 (she has many but still complains about my collection of toys etc!). The first was a computerised Pfaff, Model 1473CD, from the mid-to-late 1980s. She bought this second-­hand many years ago, so we know little about its history. It carries a label to the effect that it was made in West Germany. The Berlin Wall came down in 1988, and the two Germanies reunited in 1990, so it was pretty easy to date this one. It had seemingly died, the display remaining unlit and the motor refusing to start. I immediately suspected electrolytic capacitors, as the machine hadn’t been used for a few years. I persuaded her to leave it powered up for a few hours in case the electrolytics needed to reform. Sure enough, the next morning, there were signs of life on the display, and she could select a few of the 168 stitch patterns from the controls. It also started to run, although very slowly, and it wouldn’t stitch in reverse. Still, she was encouraged by the progress as it had been one of her favourites way back. So, there followed a further period of leaving it powered up to see if further capacitor reforming was possible. It was; many more stitches could be selected, and it looked like a very simple fix. The trouble was, the next time she tried it, all seemed OK until she stopped to have lunch, leaving the machine powered up. During lunch, we heard it start up and slowly start stitching away, all by itself! That struck me as a risky failure mode, but there it was, happily sewing some imaginary fabric with no operator within cooee. Time for some web research by yours truly. As suspected, I found a lot of reported instances over the years involving this behaviour with this model and several others in the Pfaff range. Most had been met by advice that the control board required replacing; of course, it is no longer available. Then I found one post that agreed with my suspected diagnosis, even identifying 22μF electrolytics as the likely culprits and suggesting that the faulty machine be taken to an electronics repair shop, rather than a Pfaff agent, for their replacement. That persuaded me to take the machine apart. We did find a repair manual for it online, but there was no circuit diagram included, just a note that the board should be replaced entirely. The only thing to do was to take a look. Getting at the board was as simple as undoing a few screws and removing a plastic base. A few more screws released the board from the metal machine frame, then came the unplugging of myriad cables. Talk about nostalgia. On turning the board over, I was greeted by a linear power supply, including the transformer, three 8-bit micros and numerous other chips, all clearly bearing their maker’s brand and type numbers, plus the typical range of discrete components. Best of all, it was all through-hole! There were five radial 22μF electrolytics to bypass the supply lines to the digital chips, a 4700μF 16V axial type to filter the supply for the digital chips and a 2200μF 63V axial in what I assume was the supply for the motor control circuitry. I could see no evident distortion on any of the caps. Still, as I had a few hundred 22μF caps on hand from several cartons of components I had bought from the family of a former TV serviceman back around 2005, I replaced them all (my wife also complains about my hoard of parts despite my insistence that they will all come in handy one day!). 96 Silicon Chip The originals were rated at 6.3V, whereas my stock was all 16V, but I thought that should be OK. To my surprise, I didn’t have anything approaching 4700μF in axial form and nothing at all in higher voltage axials for the 2200μF. I wanted a few other bits but couldn’t see them in stock at element14, so I looked at Digi-Key, despite some bad experiences buying from overseas in the past. I noticed they match the free shipping on orders over $60 from element14 etc. They had all the parts I required in stock, so I ordered from them on Tuesday morning. I was stunned to receive the package on Friday morning, having come from the USA via UPS and then the final delivery into my PO Box by AusPost! With the bits on hand, replacing the two remaining capacitors went smoothly. There was also some corrosion on the board from a pair of AA cells that obviously supplied the memory backup (no flash etc in those days). Cleaning that away just left discolouration on the tracks where it had eaten through the solder resist. After reassembling the machine, I took the precaution of warning my wife that, again, the electrolytics might take some time to reform, especially the 22μFs from my stock that I knew had to be probably 30 years old. Sure enough, on powering up, only the work light came on, so we left it powered up. About an hour and a half later, I walked past the machine on the way to the kitchen and saw that the display was now alive with a series of numbers that meant nothing to me, so I called the cook. She immediately recognised them as stitch codes, so she sat down to explore some more and finally, fed in some fabric and stepped on the foot pedal. The machine immediately sprung into action and produced the selected stitch pattern. I think she then tried all 168 available and declared herself very happy! She later went onto one of her international sewing groups to tell of my miraculous fix and got swamped by queries from others with similar dead Pfaffs. I was just happy that the fix had proven so simple and cheap, even if I’m still not sure if the caps were the problem, or whether it was the corrosion. Anyway, it was a machine saved from being junked, and I enjoyed the brief period of hero status, knowing it couldn’t last long. Incidentally, I also came across reported instances of other brands of sewing machines from that era having similar symptoms and similar solutions. The second fix concerned a Husqvarna Huskylock 910 overlocker machine from 1997. I knew the age of this one The Pfaff sewing machine control board. Australia's electronics magazine siliconchip.com.au as we bought it new at the local agricultural fair not long after buying our property here. Of course, it had also been declared as her favourite overlocker and required fixing, despite the presence of at least three other overlockers, including another recently acquired model 910. Editor’s note: an overlocker is a special sewing machine used for cleaning up edges or forming tidy seams between pieces of fabric. The favourite had died mid-stitch last year when the motor slowed dramatically and then stopped entirely. I immediately thought it was probably the brushes, a very dirty commutator, or maybe the bearings. The motor is, of course, buried deep inside the machine, so major disassembly was required. I’m always worried when tackling plastic cases, as they seem to quickly embrittle, and bits are likely to break off, usually right where the fasteners go. In this case, though, it came apart fairly easily, so the motor was soon out. The brushes looked fine, so I disassembled the motor. The commutator had a bit of crud on it, but not enough to prevent the brushes from doing their thing. I polished it anyway, then took a close at the windings. They looked OK, with no sign of overheating etc. So, out with the multimeter. The windings were fine, so it was on to checking the brush holders and their wiring. Only then did I notice a small component in series with one brush holder. It measured open-circuit. I took it out to find it was a 150°C thermal fuse that hadn’t appeared in any of the videos I had seen on YouTube. It was rated at 2A/250V. A check of Jaycar’s catalog showed their nearest thermal fuse at 158°C and 10A. The catalog gave the physical dimensions; it was larger but looked like it could fit, so I was off on the 60km roundtrip to buy some. It was indeed a bit of a battle to fit the fatter fuse in so that it didn’t interfere with the armature, but I was confident it would do the job, and the extra current rating wouldn’t hurt. I couldn’t see any risk in it blowing 8°C degrees higher than the original. There was no trace of heat damage elsewhere in the motor, so I think it just failed rather than doing its job when the motor overheated. So it was another successful fix at the grand cost of $3.95 plus time and fuel costs. The second win was that I only had two surplus bits left over after re-assembly the first time, none after the second! Yet again, I had a happy wife, but I should have known better. She has since lined up other sewing machines for me to look at, including a four-thread embroidery device. I’ve had to search for a special needle-height setting gauge to get it back to being four-thread from its present unhappy three-thread status. Then there is another Husqvarna machine where I will probably have to salvage a 3.5in floppy drive from an old PC to get fully operational again. It is currently with the serviceman who aligned it in late December, but the floppy was not working on its return. It had been before his service. Luckily, I still have one out in storage. Then there is a clutch of much older, purely mechanical machines; I hope the problems only turn out to be motor related. To think that I knew virtually nothing about sewing machines just a few weeks ago, other than we had a lot of them! SC siliconchip.com.au Australia's electronics magazine July 2023  97 PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION USB SUPERCODEC ↳ BALANCED ATTENUATOR SWITCHMODE 78XX REPLACEMENT ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE BK1198 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG Si473x FM/AM/SW DIGITAL RADIO 20A DC MOTOR SPEED CONTROLLER MODEL RAILWAY LEVEL CROSSING COLOUR MAXIMITE 2 GEN2 (4 LAYERS) BATTERY MANAGER SWITCH MODULE ↳ I/O EXPANDER NANO TV PONG LINEAR MIDI KEYBOARD (8 KEYS) + 2 JOINERS ↳ JOINER ONLY (1pc) TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM SMD TEST TWEEZERS (3 PCB SET) USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS HUMMINGBIRD AMPLIFIER DIGITAL LIGHTING CONTROLLER TRANSLATOR SMD TRAINER 8-LED METRONOME 10-LED METRONOME REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL FAN CONTROLLER & LOUDSPEAKER PROTECTOR SOLID STATE TESLA COIL (SET OF 2 PCBs) REMOTE GATE CONTROLLER DUAL HYBRID POWER SUPPLY SET (2 REGULATORS) ↳ REGULATOR ↳ FRONT PANEL DATE JUL20 JUL20 AUG20 NOV20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 JUN21 JUN21 JUN21 JUN21 JUL21 JUL21 JUL21 AUG21 AUG21 AUG21 AUG21 AUG21 AUG21 SEP21 SEP21 OCT21 OCT21 OCT21 NOV21 NOV21 NOV21 DEC21 DEC21 DEC21 JAN22 JAN22 JAN22 JAN22 JAN22 JAN22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 PCB CODE 15005201 15005202 01106201 01106202 18105201 04105201 04105202 08110201 01110201 01110202 24106121 16110202 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 18104211 18104212 10103211 05102211 24106211 24106212 08105211 CSE210301C 11006211 09108211 07108211 11104211 11104212 08105212 23101213 23101214 01103191 01103192 01109211 12110121 04106211/2 04108211 04108212 09109211 01111211 16110206 29106211 23111211 23111212 15109211 15109212 01101221 01101222 01102221 26112211/2 11009121 SC6204 18107211 18107212 Price $5.00 $5.00 $12.50 $7.50 $2.50 $7.50 $5.00 $5.00 $2.50 $1.50 $5.00 $20.00 $20.00 $3.00 $12.50 $12.50 $5.00 $2.50 $7.50 $2.50 $5.00 $10.00 $5.00 $2.50 $5.00 $10.00 $5.00 $12.50 $2.50 $7.50 $7.50 $7.50 $5.00 $10.00 $10.00 $7.50 $7.50 $7.50 $5.00 $7.50 $35.00 $7.50 $7.50 $5.00 $15.00 $5.00 $2.50 $2.50 $5.00 $1.00 $12.50 $2.50 $15.00 $30.00 $10.00 $7.50 $5.00 $2.50 $5.00 $5.00 $5.00 $5.00 $7.50 $2.50 $2.50 $7.50 $5.00 $5.00 $7.50 $20.00 $25.00 $7.50 $2.50 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT ↳ CPU ↳ LCD ADAPTOR ↳ ACRYLIC LCD BEZEL RASPBERRY PI PICO BACKPACK AMPLIFIER CLIPPING DETECTOR CAPACITOR DISCHARGE WELDER POWER SUPPLY ↳ CONTROL PCB ↳ ENERGY STORAGE MODULE (ESM) PCB 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) AM-FM DDS SIGNAL GENERATOR SLOT MACHINE HIGH-POWER BUCK-BOOST LED DRIVER ARDUINO PROGRAMMABLE LOAD SPECTRAL SOUND MIDI SYNTHESISER REV. UNIVERSAL BATTERY CHARGE CONTROLLER VGA PICOMITE SECURE REMOTE MAINS SWITCH RECEIVER ↳ TRANSMITTER (1.0MM THICKNESS) MULTIMETER CALIBRATOR 110dB RF ATTENUATOR WIDE-RANGE OHMMETER WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD MINI LED DRIVER NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) LOUDSPEAKER TESTING JIG BASIC RF SIGNAL GENERATOR (AD9834) ↳ FRONT PANEL V6295 VIBRATOR REPLACEMENT PCB SET DATE FEB22 FEB22 FEB22 MAR22 MAR22 MAR22 MAR22 MAR22 APR22 APR22 APR22 MAY22 MAY22 JUN22 JUN22 JUN22 JUN22 JUL22 JUL22 JUL22 JUL22 JUL22 AUG22 SEP22 SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 PCB CODE 01106193 01106196 SC6309 07101221 01112211 29103221 29103222 29103223 01107021 09103221 09103222 CSE211002 08105221 16103221 04105221 01106221 04107192 07107221 10109211 10109212 04107221 CSE211003 04109221 04108221 04108222 18104212 16106221 19109221 14108221 04105221 04105222 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 04106221/2 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 Price $5.00 $2.50 $5.00 $5.00 $2.50 $5.00 $5.00 $5.00 $25.00 $2.50 $2.50 $7.50 $5.00 $5.00 $5.00 $7.50 $7.50 $5.00 $7.50 $2.50 $5.00 $5.00 $7.50 $7.50 $5.00 $10.00 $2.50 $5.00 $5.00 $7.50 $2.50 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 $12.50 $5.00 $5.00 $5.00 DYNAMIC RFID / NFC TAG (SMALL, PURPLE) ↳ NFC TAG (LARGE, BLACK) RECIPROCAL FREQUENCY COUNTER MAIN PCB ↳ FRONT PANEL (BLACK) PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 $1.50 $4.00 $5.00 $5.00 $5.00 $2.50 $2.50 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au GPS-Synched Clock hands stop moving I recently finished building my GPS-Synchronised Analog Clock kit (September 2022 issue; siliconchip. au/Article/15466). I’ve tried it with a couple of US-made clock movements. When I connected the PCB to the first movement, the onboard LED flashed as described, and the clock started on the half-hour. Unfortunately, after about three hours, the clock stopped, with the second hand moving back and forth slightly. The result was the same after only a few seconds on subsequent attempts to get it working. I then tried modifying a second movement in case the problem was with the first one. The result was the same – the LED flashed correctly, but the clock stopped after a few seconds, with the second hand moving back and forth slightly. Same again with new batteries. I’ve sent screenshots from my oscilloscope after the onboard LED has turned off, and the second hand should be moving but isn’t. The clock output looks as it should be. Do you have any suggestions? (D. H., Sorrento, WA) ● Geoff Graham responds: this is most perplexing. Your oscilloscope captures show that the firmware is doing its job perfectly and your test with two movements should eliminate a faulty movement. That does not leave much that could be wrong. Your oscilloscope capture does show that the pulse level is rather low at 1.2V peak-to-peak. With a new battery, it should be about 1.6V (or whatever the battery voltage is). So, one thing to check is the MCP6041 op amp and its associated resistors (are they the right value, are the solder joints good etc). Another useful test would be to disconnect the movement. Does the output level then equal the battery voltage? If so, that indicates an excessive load from the movement. If that is not the problem, another siliconchip.com.au possibility is problems with the movements themselves. There is a faint chance that the clock motor in your movements requires a different signal. If you can restore one of the movements to its original unmodified condition, you could then check that its output is as expected. There is also the possibility that with two identical movements, you might have accidentally created the same fault in both (eg, binding gears) when modifying them. I’m sorry that I cannot offer anything more positive. If it helps, hundreds of these clocks are now running perfectly, so the issue must be specific to your setup. The question is: what is it? Motor Speed Controller kit wanted I am interested in purchasing a kit for the Refined Full-Wave Motor Speed Controller (April 2021; siliconchip.au/ Article/14814) but Jaycar no longer stocks any kits for motor speed controllers. Altronics has some DC motor speed controller kits plus the Induction Motor Speed Controller, but none for brushed mains-powered motors. Where can I get a kit from? How do I purchase this article for you? (D. K., Wynnum, Qld) ● We can supply a set of the most critical parts for that project, available from siliconchip.au/Shop/20/6503 You can get a copy of the magazine or online access at the same time from siliconchip.au/Shop/2/5795 (print) or siliconchip.au/Shop/12/5797 (online). As far as a speed controller for brushed mains-powered motors, the April 2021 design is the one to build. Ultrasonic Cleaner has low operating frequency I built your High Power Ultrasonic Cleaner (September & October 2020; siliconchip.au/Series/350) from the Altronics Kit (Cat K6022) and am using a 1/3 Gastronorm stainless steel tray. I was initially using 4L of water and Australia's electronics magazine the default output transformer windings but only got about 1.3V at TP1. I tried increasing the output turns to 63 and decreasing the water volume to 3L, and I can now get up to 3V at TP1 at 38.62kHz. However, after running the troubleshooting (power off for 10s, holding the start and stop buttons down, turning on and releasing both buttons) and setting the frequency with the timer pot and pressing stop, once I start again, the frequency is around 13kHz. This is also the case with the calibration routine (hold stop, press start and release both). I noticed that the calibration routine happens so fast that I can not detect it on the oscilloscope; perhaps it is not running. Other than that, everything seems to be working as per the description: power LEDs, On/Run LED, over-­ current LED flashing (at resonance when standing waves start in the tank) etc. Any assistance or thoughts on what else I can try would be greatly appreciated. (G. G., Knoxfield, Vic) ● We think the transducer resonance point is not being found correctly. The voltage at TP1 is not enough for resonance. Try running the diagnostics and sweeping the frequencies to find the maximum current by measuring the voltage at TP1. If this voltage does not reach about 4.5V, increase the number of secondary windings. Otherwise, it might go past the resonance point during the calibration sweep. If the voltage then goes over 4.8V, reduce the number of secondary turns on the transformer. The turns need to be so that this current overload threshold isn’t reached at resonance. Once the voltage at TP1 reaches between 4.5V and 4.8V, the values should store correctly. Fixing a failed USB charger I recently went on a tour and took a dual USB charger to keep my phone and laptop charged. Unfortunately, it July 2023  99 Replacement for Altronics SD card socket I have just built the GPS Tracker (November 2013; siliconchip.au/Article/5449) but cannot find the SD card holder anywhere. It is specified as Altronics P5720 but that has been discontinued. I had no idea there were so many variations of the same part! I have looked through element14, Amazon, Banggood, Mouser etc, as best I can. Any help would be appreciated. (P. R., Linden, NSW) ● We also spent some time looking for an alternative but didn’t come up with any good options. However, another reader recently told us that element14 Cat 2847872 is pretty similar to the discontinued Altronics part (see Mailbag, page 8). He said he was able to get the GPS Tracker to work using that part. The main difference is in the location of the WP pin. A thin wire would need to be added to connect that pin to the PCB pad. We believe the WP pin is not used for the GPS Tracker, so you can instead connect the WP pin on the micro (pin 7) directly to the adjacent GND pin (pin 8). failed, and I had to buy a replacement. On arriving home, I took the faulty charger apart and found that all the parts which could be tested were OK. My suspicion fell onto an IC labelled TD6512. It seems to act like the chopper transistor in a switch-mode power supply. The problem is that I cannot find a data sheet for this device, let alone a supplier. If you or a reader can throw some light on this device or perhaps suggest an equivalent that is readily available, I might be able to repair my charger instead of throwing it away. I would be extremely grateful for any information you can provide. (J. H., Nathan, Qld) ● We can’t find much information on the function of that chip either, although we think you are right about its role. We did find a couple of suppliers of replacement chips, and they are not too expensive: 10 chips: www.aliexpress.com/ item/1005005106477998.html five chips: www.aliexpress.com/ item/1005005457789422.html You might just have to buy some of those, swap it and hope that fixes it. How to discharge valve amplifier capacitors I have wanted a valve guitar amp for ages and finally bought a kit for the famous Fender ‘57 Tweed with the iconic 5E3 Circuit. The originals of these amps are selling for many thousands of dollars and kits aren’t cheap either. I am very wary of valve-based equipment and the lethal voltages they use and can store, so I am very carefully following the kit instructions. My first question is what voltage to use on the transformer for Australia. 100 Silicon Chip I was considering using the 240V tap, but valve-based equipment might be more sensitive to varying mains voltages. Some little birdie in the back of my mind nags me that we actually use a 230V AC standard now. The transformer gives options of 110V, 220V, 230V and 240V. My second question is on how to make a “snuffer stick”. The instructions sensibly advise using this device to get rid of lethal voltages stored after power down in the capacitors. I could have purchased one when I bought the kit but declined, stupidly thinking that Jaycar might have one, but they don’t seem to. My thoughts were a couple of hefty alligator clips and a big resistor. There is little information about them on the amp kit site other than that I can buy one. What value should the resistor be? Will 1W be enough, or will it need 5W? As far as I can tell, I will be discharging 500-600V or more from a 22,500μF capacitor bank. I don’t want to sweep a pile of ash from where the amp used to sit, nor do I want anyone else sweeping away a pile of ash from where I used to be. (A. P., Wodonga, Vic) ● The Australian mains voltage for a single phase is 230V AC with a tolerance range of +10% to -6%. That means an expected range of 216V AC to 253V AC. So it would be safer to select the 240V tap on the transformer for your amplifier. A ‘snuffer stick’ could be made using two series 220kW 1W resistors housed in an insulated probe. However, a safer solution is to have permanent discharge resistors across the supply capacitors. That way, they will automatically discharge over time when the power is switched off. You could use two 220kW 1W Australia's electronics magazine resistors connected in series with each other and a high-brightness LED (anode to positive) across one of the capacitors. Since the supply capacitors are paralleled via relatively lowvalue resistors (4.7kW and 22kW), only a single set of discharge resistors is required. The LED will light until the capacitor bank voltages have dropped to safe levels. Burnt Philips 148 resistor value needed This long-time reader and subscriber would like to ask a favour. Inspired by Graham Parslow’s Vintage Radio article in the March 2018 issue on restoring a Philips 148C valve portable radio (siliconchip.au/ Article/11008), I decided to tackle my dead 148B. I found R15, a 2W resistor, burnt and open-circuit in the HT line. The first band is red, the others are blackened, and his circuit diagram does not give component values. My internet search has not helped, and the HRSA has yet to reply to my request for information. Could you forward this email to Prof. Parslow in the hope that he may have a value for R15? (T. B., Kogarah, NSW) ● Prof. Parslow responds: sorry that you have not had a response to your enquiry yet. That may be a consequence of my currently being in Bath, UK. R15 is 2kW 1W in the component list. I have a love-hate relationship with Philips tinnie portables; when they are working, they are excellent. High voltages from Valve Power Supply After recently constructing the Mains Power Supply for Battery Valve Radio Sets (August 2017; siliconchip. au/Article/10751) and following your testing instructions in the article, the T1 secondary measures 37.4V AC and the B outputs are measuring 157V & 111.5V instead of 135V & 90V with respect to B- under no load. My mains voltage is 250V AC. The A & C outputs are within spec, but the LED constantly flashes. All components have been checked for correct value & orientation, and no faulty solder joints are apparent. If you could advise me further, it would be appreciated. As a long-time subscriber to Silicon Chip, EA & ETI since 1973, I would siliconchip.com.au like to thank all involved. I immensely enjoyed Leo Simpson’s recent story about the magazine’s history (August & September 2022; siliconchip.au/ Series/385). (G. S., Darlington Point, NSW) ● Ian Robertson responds: the design value of the “90V” rail is actually around 100V with a 10mA load. That is because the power supply uses a readily-available transformer. In any case, a fresh 90V carbon-zinc B battery actually delivers around 100V. Under no load and with 37.4V RMS (from an unloaded 36V winding), if you multiply 37.4 by √2 to get the peak value, then double it, you get 105.72V. So you are not far off from that. The discrepancy could be due to your meter’s response to an RMS reading of a not-quite-sinusoidal mains waveform. It is not unusual these days with all manner of power converters feeding the grid. The “135V” output uses a tripler, so it will be proportionately higher. Rest assured that the slightly higher B voltage will not damage the radio. It was standard practice in battery/AC radios to run the B+ a little higher to improve the performance of the radio. As long as the A voltage is accurate, you will be OK. A high A voltage will shorten the life of the valves. As for the LED flashing, the only explanation I can think of for that is that you have accidentally used a flashing LED in place of a normal one! There is nothing in that circuit that could possibly flash the LED... Do not power Jacob’s Ladder from the mains I encountered something strange the other day when using the Jacob’s Ladder I built recently (February 2013 issue; siliconchip.au/Article/2369). The battery I was using was starting to go flat, so I hooked up the lab power supply to charge the battery directly to the battery while the coil was still running. I thought the power supply would provide enough additional kick with the battery to keep the Jacob’s Ladder running. It worked at first, but after a few seconds, I noticed the voltage on the power supply was fluctuating and had dropped to 11V, then the whole thing went dead. At first, I thought the PIC had died, but after probing with the DSO, there was still a good waveform on pin 9. That can only mean that I have blown the IGBT somehow. It seems very strange because the unit was only drawing a couple of amps, and the IGBT is rated way beyond anything I was throwing at it. I ordered a replacement IGBT, but what might have happened? I want to avoid blowing it up again, so I will only be running it on battery power, but have I come across another reason why Leo suggested running it off battery power only? (M. A., Kenthurst, NSW) ● Yes, the article warns against powering the Jacob’s Ladder from any mains supply because our experience is that it usually damages the supply and/or the device itself due to high voltage spikes being coupled back into the power supply. Usually, an IGBT fails as a short between the emitter and collector, which typically causes the gate to have a low resistance to the emitter. A resistance check can easily verify if that has happened. Since the gate drive waveform is good, the gate would appear to be undamaged. Silicon Chip as PDFs on USB ¯ A treasure trove of Silicon Chip magazines on a 32GB custom-made USB. ¯ Each USB is filled with a set of issues as PDFs – fully searchable and with a separate index – you just need a PDF viewer. ¯ 10% off your order (not including postage cost) if you are currently subscribed to the magazine. ¯ Receive an extra discount If you already own digital copies of the magazine (in the block you are ordering). The USB also comes with its own case EACH BLOCK OF ISSUES COSTS $100 OR PAY $500 FOR ALL SIX (+POSTAGE) NOVEMBER 1987 – DECEMBER 1994 JANUARY 1995 – DECEMBER 1999 JANUARY 2000 – DECEMBER 2004 JANUARY 2005 – DECEMBER 2009 JANUARY 2010 – DECEMBER 2014 JANUARY 2015 – DECEMBER 2019 WWW.SILICONCHIP.COM.AU/SHOP/DIGITAL_PDFS Ordering the USB also provides you with download access for the relevant PDFs, once your order has been processed siliconchip.com.au Australia's electronics magazine July 2023  101 As an alternative to IGBT damage, the insulating washer between the case and IGBT could have been punctured. Then the fuse connected between the coil primary and battery could have blown. Supply to the remainder of the circuit is not via this fuse. However, we think the most likely situation is that the coil was driven with too high a voltage, the insulation broke down and it has been damaged. That could result in an open-circuit primary winding. The primary resistance is typically under 4W, so you should measure it with a multimeter. If the primary winding is OK, you should see the collector waveform of Q1 pulling the coil low during the dwell period and the voltage rising above 300V when the dwell is released (make sure to use an oscilloscope and probes rated above 300V to check). Arc-over inside the coil can happen if the gap between electrodes on the Jacob’s ladder is too wide. If the primary is open-circuit, perhaps the dwell setting needs to be reduced. Mosfet is switching on by itself I have built a power supply that powers on two external hard disks when a computer is switched on. When the computer starts up, the device supplies 12V DC to the first hard disk, then a few seconds later (after the startup current settles), the second hard disk is powered. The power is switched with Mosfet transistors controlled by a PICAXE PIC microcontroller (powered by 5V DC). As soon as the first drive is powered on, the second Mosfet immediately switches on without any voltage at its gate (0V). Very strange! It should turn on a few seconds later, when the PIC applies 5V to its gate. The PIC outputs are connected to the Mosfet gates via 330W resistors to limit the PIC pin currents. The gate is also tied to ground with a 10kW resistor. The circuit behaves correctly if the loads (hard disks) are not connected. I have LEDs with series resistors across outputs to show the on/off state of each. I don’t understand how the Mosfet can turn on without gate voltage. (F. C., Maroubra, NSW) ● There are a few possible causes: If a Mosfet has a rapidly increasing drain voltage, drain-gate capacitance can cause the gate voltage to be pulled up, momentarily switching the Mosfet on. A low gate drive impedance or added gate-source capacitance can help to prevent this. It could also be that parasitic inductance or capacitance on the PCB is coupling a signal into the Mosfet’s gate circuit from elsewhere, especially when high current flows (eg, the startup current for the first hard disk). If the second Mosfet is switching on and staying on, even with 0V at its gate, that suggests it is faulty or there is a bad connection somewhere. Unless it’s a depletion-mode Mosfet (which seems unlikely), if the gate-source voltage is 0V, it should definitely be off and not conduct any current. Note that if the load is connected to the source instead of the drain, it will be powered via the parasitic sourcedrain diode. However, in that case, it would be on all the time. We also wonder if high currents through your circuit could be inducing voltages in or near the PIC, causing it to malfunction. If you disconnect the PIC from the Mosfet and tie its gate directly to its source, it should never switch on. If it doesn’t, that tells you that either the PIC is driving its gate high when it shouldn’t, or it cannot keep the gate low even though it is trying to. If it still switches on, the Mosfet is faulty or misconnected. Controlling treadmill motor speed I have a motor salvaged from an old treadmill that I would like to adapt to a new use. Has Silicon Chip ever published a design for a mains-­powered speed controller suitable for controlling a DC motor of the type used in some exercise treadmills? My online research suggests that many treadmills use DC motors rated at around 200V. Looking at my Silicon Chip magazine collection, I found several articles on constructing speed controllers for DC motors, but none were close to my requirement. The treadmill motor I have is marked as follows: • DC Motor – 180V, 4A • 1HP, 4000RPM, CW rotation Unfortunately, I do not have the original motor controller. (P. B., Macarthur, ACT) ● We have not published a suitable controller for treadmill motors. However, modifying our low-voltage DC Motor Controller (January & February 2017; siliconchip.au/Series/309) for higher voltage operation would be possible by using Mosfets with a higher voltage rating. The STP12NK30Z (300V 9A) should be suitable. Clamp diode D1 (IDP30E65D1) used in the project is already rated at 650V, so it would not need to change. Those Mosfets are available from Mouser at siliconchip. au/link/abl4 continued on page 104 Raspberry Pi Pico W BackPack The new Raspberry Pi Pico W provides WiFi functionality, adding to the long list of features. This easy-to-build device includes a 3.5-inch touchscreen LCD and is programmable in BASIC, C or MicroPython, making it a good general-purpose controller. This kit comes with everything needed to build a Pico W BackPack module, including components for the optional microSD card, IR receiver and stereo audio output. $85 + Postage ∎ Complete Kit (SC6625) siliconchip.com.au/Shop/20/6625 The circuit and assembly instructions were published in the January 2023 issue: siliconchip.au/Article/15616 102 Silicon Chip Australia's electronics magazine siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip KIT ASSEMBLY & REPAIR FOR SALE FOR SALE DAVE THOMPSON (the Serviceman from Silicon Chip) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, New Zealand, but service available Australia/NZ wide. Email dave<at>davethompson.co.nz LEDsales Lazer Security KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com LEDs and accessories for the DIY enthusiast LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au VISIT THE NEW TRONIXLABS parts clearance store for real savings on new parts at clearance prices, with flat rate express delivery Australia-wide – go to https://tronixlabs.com For Quality That Counts... QUALITY COMPONENTS + MORE The parts clearance sale continues, but stock is limited, this month check out the freebies – go to lazer.com.au ASSORTED BOOKS FOR $5 EACH Electronics and other related subjects – condition varies. Some of the books may have been sold. See photos (recently updated): siliconchip.au/link/abl3 Email for a quote (bulk discount available), state the number directly below the photo when referring to a book: silicon<at>siliconchip.com.au Issues Getting Dog-Eared? PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au Protect your Silicon Chip copies using our Australian-made Binders. Order online from www.siliconchip.com.au/Shop/4 See website for overseas prices or call (02) 9939 3295. REAL VALUE A T $21.50* PLUS P&P ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone (02) 9939 3295 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 July 2023  103 You would need to power the main controller section from 12V and the motor driver section separately from a suitable 180V supply. You could use a 500VA+ mains transformer with a 120V AC secondary (or 60V + 60V in series), then rectify and filter the output. Check that the transformer can handle the motor startup current, which likely will be well over 4A. If building this project, please read the relevant notes & errata in the 2017 PDF at siliconchip.au/Articles/Errata Displays for 2.5GHz Frequency Counter I am having trouble sourcing the four-digit, 7-segment LED displays used in the 2.5GHz 12-Digit Frequency Counter (December 2012 & January 2013; siliconchip.au/Series/21). They are specified in the parts list as coming from Futurlec, but they have no stock of the blue type. They can offer me a red type but the forward voltage is only 2.4V maximum at 20mA. The blue variety is rated at 3.2V <at> 20mA but can handle 4V maximum. Advertising Index Altronics.................................27-30 Dave Thompson........................ 103 DigiKey Electronics....................... 3 Emona Instruments.................. IBC Hare & Forbes............................. 13 Jaycar................... IFC, 9, 11, 14-15, ....................................43, 67, 90-91 Keith Rippon Kit Assembly....... 103 I have some similar red displays from AliExpress rated at 2V maximum <at> 20mA. Should I use the AliExpress parts, go with the alternative Futurlec displays, or wait for the blue ones to come back into stock? It could be a long wait. Changing the resistors to suit the alternative displays might be a solution, but what should their values be? I have built the main board but the display is holding me up from testing it. (E. B., Meadow Springs, WA) ● Readers asking where to find parts that have been discontinued or are out of stock is becoming something of a theme. While Futurlec doesn’t have stock of the displays we used, they are still available from other vendors. For example, AliExpress items: • 1005005352398426 • 1005001606190533 • 1005003246695690 You could use displays with a different colour if they are easier to get. Since, as you wrote, the red displays will have a lower voltage drop at the recommended segment current level of 20mA, we suggest replacing the eight 47W series segment resistors in the counter display board with 150W resistors to be on the safe side. The resistors concerned are at the upper left on the display PCB, looking from the front. PIR Mains Timer wiring question I have built your February 2008 PIR-Triggered Mains Switch project (siliconchip.au/Article/1751) from a Jaycar kit (KC5455). I am using Jaycar’s XC4444 PIR module. Unfortunately, I’m a bit stuck on this last step when connecting the PIR to the 3-way terminal block. The instructions state that I need to put a link between the ground on the PIR and the contact of the normally-­closed relay; could you please elaborate on this? Any help would be greatly appreciated. (E. C. H., via email) ● Before we get to wiring up the PIR module, we’d better check that it’s compatible with the PIR sensor shown in the article. That one had two normally-­closed (NC) switch outputs, ALARM and TAMPER. They were connected in series with one end to circuit GND so that they would usually hold the input low, but a resistor would pull it high if either switch opened. We downloaded the manual for Jaycar’s XC4444 PIR module from their website, and it appears to have a much simpler arrangement with just three terminals: Vcc, OUT and GND. The OUT pin idles low but goes high when the sensor detects movement (presumably to Vcc). Therefore, this appears compatible since it is also low when untriggered and goes high when triggered. The specifications for that module on the Jaycar website say it will operate from 5-20V, and our circuit is powered from 12V, so it should work. The connections for the 3-way terminal block are as follows: • Top terminal (+12V): goes to Vcc on the PIR detector • Middle terminal (IN): goes to OUT on the PIR detector • Bottom terminal (GND): goes to GND on the PIR detector Make sure you don’t get the +12V and GND connections mixed up. SC LEDsales................................... 103 LD Electronics........................... 103 Microchip Technology......... OBC, 7 Mouser Electronics....................... 4 SC Pico W BackPack................ 102 Silicon Chip Breadboard PSU... 66 Silicon Chip PDFs on USB....... 101 Silicon Chip Shop................ 89, 98 Silicon Chip Subscriptions........ 77 The Loudspeaker Kit.com.......... 97 Tronixlabs.................................. 103 Wagner Electronics....................... 6 104 Silicon Chip Mgazine Errata and Sale Date for the Next Issue Lazer Security........................... 103 Loudspeaker Testing Jig, June 2023: the 1kW resistor connecting to LK1 that filters the phantom power for the microphone should be 100W, not 1kW. It might work with 1kW, but it will depend on the microphone. Also, because pin 2 of XLR socket CON10 (“HOT”) connects to the INsignal and pin 3 (“COLD”) connects to IN+, the microphone phase will be inverted. To fix this, swap the wires to pins 2 & 3 of header CON11 on the PCB. Finally, the labels of transistors Q1 & Q2 in the circuit diagram (Fig.3) have been swapped, but they are correct on the PCB overlay and PCB. Vintage Radio, Astor APN, May 2023: there were some errors in the published circuit diagram for the set, mainly regarding the connection of capacitors #35, #36, #38 and resistors #6 & #10. The circuit diagram has been corrected in the online version of the magazine and has been made visible in the free preview of that issue on our website. Next Issue: the August 2023 issue is due on sale in newsagents by Thursday, July 27th. Expect postal delivery of subscription copies in Australia between July 26th and August 11th. Australia's electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! 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