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JUNE 2021 ISSN 1030-2662 06 9 771030 266001 The VERY BEST DIY Projects! $995* NZ $1290 INC GST INC GST Right To Repair the ability to repair your own devices The History of USB Advanced GPS Computer RECREATING ARCADE PONG 4 siliconchip.com.au Australia’s electronics magazine 2 June 2021  1 Want to build your own Resistor & Capacitor Tester? If like us and you're always having to sort through your junk drawer workbench and have trouble with your resistor colour codes, here's a handy project for you. This tester will try to work out whether you are connected to a resistor or a capacitor and then show you the relevant value. If it’s a resistor, it’ll also suggest the nearest resistor from the Jaycar ½W range. No more sorting through your draws blindly! Breadboard not included, for presentation purposes only. For step-by-step instructions scan the QR code. CLUB OFFER BUNDLE DEAL 4995 $ www.jaycar.com.au/rct See other projects at www.jaycar.com.au/arduino SAVE 30% KIT VALUED AT $74.35 FROM 345 $ Jiffy Boxes Manufactured from ABS plastic. Sizes are compliant with industry standards externally and PCB fitting internally. Four sizes from 83x54x31 to 197x113x63mm available. HB6005-HB6025 100 $ gift card Mini Breadboard with 170 Tie Point JUST 4 $ 95 17 holes x 10 rows. Self-adhesive or can be permanently mounted. 46Lx35Wx9Hmm. PB8817 JUST 13 $ 55-pce Electrolytic Capacitor Pack If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com On Sale 24 May to Silicon Chip 23 June, 2021 300-pce 0.5W 1% Mini Size Metal Film Resistor Pack Contains 5 of each value from 10Ω to 1MΩ. RR0680 Looking for your next build? Silicon Chip projects: jaycar.com.au/c/silicon-chip-kits Kit back catalogue: jaycar.com.au/kitbackcatalogue 1800 022 888 www.jaycar.com.au Awesome projects by 2 $ Ideal for prototyping. Values range from 1μF to 470μF. RE6250 Got a great project or kit idea? JUST 1995 50 Australia’s electronics magazine Shop online and enjoy 1 hour click & collect or free delivery on orders over $99* siliconchip.com.au Exclusions apply - see website for full T&Cs. * Contents Vol.34, No.6 June 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 12 The Right to Repair (and Modify) We should all have the legal “right to repair” our own equipment, or have a third-party (non-manufacturer) do it for us, without voiding the warranty. There is a growing worldwide movement behind this – by Dr David Maddison 32 The History of USB Over 25 years ago, the Universal Serial Bus (USB) was developed to make it easier to connect external devices to computers. This article describes how USB standards have been enhanced and expanded over time – by Jim Rowe 48 The History of Videotape – Camcorders & Digital Video While it took a few iterations, digital video recording eventually overtook popular formats like VCR due to better portability, and thus eliminated the need for videotape – by Ian Batty, Andrew Switzer & Rod Humphris Our Advanced GPS Computer uses a Micromite BackPack V3 to provide real-time speed and location readouts. It even has a speaker to deliver sampled audio or synthesised speech – Page 24 70 First Look: Arduino IDE 2.0 The beta release of version 2.0 of the Arduino IDE introduces significant improvements to this free software – by Tim Blythman 84 Review: Weller T0053298599 Soldering Station Previously known as the WE1010, this temperature-adjustable soldering station from Weller won’t waste your time – by Tim Blythman Constructional Projects 24 Advanced GPS Computer – Part 1 Sporting a 3.5-inch touchscreen, our new Advanced GPS Computer has a customisable interface which can display speed, heading, altitude and more, including directing you to saved points of interest (POIs) – by Tim Blythman USB was designed to make connecting devices simple, but over time, a plethora of different types of connectors and protocols have developed. USB-C is the first USB connector that can be inserted in either orientation, and provides very fast transfer speeds – Page 32 38 Recreating Arcade Pong This project recreates the original video game Pong as closely as possible, using the same parts but on a smaller board. It also incorporates fixes for all six known bugs in the original design – by Hugo Holden 64 PIC Programming Helper 8-, 14- and 20-pin PIC series microcontrollers from Microchip can be easily programmed (and debugged) using this helper board – by Tim Blythman 72 Programmable Hybrid Lab Supply with WiFi – Part 2 The construction, setup and testing procedures for the Hybrid Lab Supply, including connecting it to a WiFi network – by Richard Palmer Your Favourite Columns Pong was a hugely popular game back in the day, so here’s a way to recreate it, accurate to the original, using nearly identical components – Page 38 61 Circuit Notebook (1) Building a better mousetrap (2) In and out of circuit LED tester 91 Serviceman’s Log Trying to fix unbranded, generic equipment is frustrating – by Dave Thompson 98 Vintage Radio 1940 RME Model 69 communications receiver – by Fred Lever Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback siliconchip.com.au 86 Product Showcase 97 Silicon Chip Online Shop 108 Ask Silicon Chip 111 Market Centre Australia’s magazine 112 Noteselectronics and Errata 112 Advertising Index The PIC Programming Helper comes in two versions, one just for 8-pin PICs and a larger one that covers 8, 14 and 20-pin PICs. It doesn’t just help you program micros, but also to breadboard and debug them – Page 64 June 2021  1 www.facebook.com/siliconchipmagazine SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc. Bao Smith, B.Sc. Tim Blythman, B.E., B.Sc. Nicolas Hannekum, Dip. Elec. Tech. Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Reader Services Rhonda Blythman, BSc, LLB, GDLP Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson, B.Bus., FAICD Staff (retired) Ross Tester Ann Morris Greg Swain, B. Sc. (Hons.) 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. Semiconductor shortages are becoming serious When the news of COVID-19 hit, it was evident that there would be widespread effects on industry from factory shutdowns, reduced capacity due to mitigation efforts, etc. It was almost a miracle that so many sectors seemed to be marching on throughout 2020 and early 2021, somewhat unaffected. There was plenty of talk about semiconductor shortages, but that mainly seemed to be related to desktop CPUs and graphics processors, many of which have been essentially unobtainable for the past year. But now we are noticing many ICs being out of stock and with very long lead times. The worst-hit appear to be microcontrollers, more-or-less across the board. Many PICs are out of stock at all major retailers, as are micros from NXP, ST Micro and many others. To get an idea of how bad it is getting, at the time of writing Digi-Key lists 91,292 different microcontrollers on their website, but only 21,176 or 23.2% are in stock. And many of those listed have single-digit quantity in stock. During better times, I would expect that figure to be closer to 50%. It isn’t just microcontrollers, either. We’re having trouble getting some of the other semis that we sell in our kits, such as regulators and Mosfets. For those parts which are out of stock, the wait for the next batch can be very long indeed. Some parts are showing expected delivery dates in 2022! I don’t know why the situation has degraded recently, but it has. There’s no easy way to tell how long it will continue, but I suspect it won’t be resolved anytime soon, or even this year. So don’t be surprised if you have difficulty sourcing specific components required for some of our designs (or perhaps your own). For devices like Mosfets, it is sometimes possible to find an equivalent device. But often, we are finding that most or all of the compatible devices are also out of stock. I wouldn’t be surprised to see a shortage of many consumer electronics lines in the next few months, due to the manufacturers finding it impossible to get all the parts they need. The right to repair Printing and Distribution: It should not come as a surprise that we are generally supportive of the efforts of many people to secure the legal ‘right to repair’. We see this as a way to push back against companies that deliberately (or perhaps through incompetence) make it difficult or overly expensive for people to repair their possessions when they go wrong. Given that automobiles are one of the most expensive (and often troublesome) purchases that an individual can make, it’s no surprise that some of the earliest (and strictest) right to repair legislation has involved that sector (back in 2012, in the USA). New laws, proposed to come into effect in Australia from the 1st of July next year (assuming they are legislated), will require car-makers to provide service and repair information to independent repairers. This is a step in the right direction, as manufacturer-authorised dealers can be costly. And despite this expense, in my experience, they can provide worse service than a good independent mechanic. More on this at: http://consumersfederation.org.au/morrison-government-levels-theplaying-field-for-independent-repairers/ 24-26 Lilian Fowler Pl, Marrickville 2204 Cover Image: https://unsplash.com/photos/C1r9pODhfQ4 Subscription rates (Australia only): 12 issues (1 year): $105, post paid 24 issues (2 years): $202, post paid For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. ISSN 1030-2662 2 Editorial Viewpoint Silicon Chip by Nicholas Vinen Australia’s electronics magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine June 2021  3 MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”. The origin of Presspahn If anyone ever wondered where Presspahn insulation comes from, it’s here in Yorkshire – God’s own county, of course! You can see the location of the factory at the following link. siliconchip.com.au/link/ab8e Alan Winstanley, PE Magazine Online Editor, Brighton, UK. Transistor Test Set identified The “TRANSISTOR TEST SET” shown in the photo on page 4 of the May 2021 issue is an Electronics Australia project from August 1968, presented by your own Jim Rowe. I built one of these at the time and still use it. It’s a very useful piece of equipment. As to the “ACE” on the meter face, I think this refers to a company called ACE Radio, a regular advertiser in EA at the time. They appear to have sold mostly surplus items, but also kits for some EA projects, the Transistor Test Set being one of them. It was available as either a fully built item, or as a DIY kit. Peter Caprin, Valley Heights, NSW. it did nothing for a few turns; then it started to rise, very slowly at first, then exponentially faster. After a good half an hour of adjustment, I could get it to hover around 6V and would hold there for about thirty seconds or so, then very slowly, it started rising again, getting faster and faster. To keep the voltage below 8V, I had to wind the trimpot anticlockwise two or three turns, which started the voltage decreasing, and it continued doing so until it was under 1V. I couldn’t get it to hold at 6V. That stumped me, so I decided to finish building the second module, and was surprised to find that it had the same unstable quiescent current. I figured the problem wasn’t the SC200 modules but something in the power supply, although it was testing fine. As I was clutching at straws, I started wondering if the leads from the power supply to the amp modules were picking up EMI as I had extended them with some leftover hook-up wire (about one metre long) to make adjustments easier. So I cut the extensions off and fitted the power supply wires properly, and that cured the problem. I adjusted the quiescent current and offset as per instructions. The amp is now working perfectly, and (to our ears) my wife, daughter and I all agree that music sounds clearer, more precise and the bass is much more potent than the old ETI modules, with no hum. I wouldn’t have believed the difference in sound quality could be so evident between the two. Tony Brazzle, Bumberrah, Vic. Comment: based on the symptoms you described, we would not have guessed that it would be the power supply wiring at fault. It sounded more like a case of mismatched transistors. We’re glad you managed to sort it out, and your listening tests confirm what our test equipment shows – that the SC200 modules are high-performance modules, only falling short of the very best amplifiers, like our Ultra-LD series. Expanding the Remote Monitoring Station A huge belated thank you for the article on the Arduino-based 4G Remote Monitoring Station from the SC200 audio amplifier problem solved While trying to set the quiescent current of the SC200 amplifier module I had just completed (January-March 2017; siliconchip.com.au/Series/308), I ran into a strange problem. Everything tested fine up to the point of fitting the 68W resistors in place of the fuses. Feeding a signal into the module produced a clean waveform on the scope at the output. The problem I had was some sort of funny runaway effect happening while adjusting the voltage across the 68W resistors to the 6V specified. With the trimpot turned fully anti-clockwise, the voltage was just under 1V, which was correct. As I wound it clockwise, 4 Silicon Chip Australia’s electronics magazine siliconchip.com.au February 2020 issue (siliconchip.com.au/Article/12335). I decided to take your design and expand on it. Attempting to learn a new language and learn the inner details of the SIM7000 module at the same time may not have been the easiest choice. Learning a new language meant I spent a lot of time undoing the good work of Silicon Chip, only to put it back later. I have a water pressure sensor to monitor for stock water for cattle. The electric pump is 10km away from home. A no-pressure situation will eventually lead to no water for thirsty cows, especially in the summer months. On power-up, it sends me a text message indicating the firmware revision and the pressure level. An SMS is generated should the pressure go outside a preset range at any time. I can also make a query by sending a “q” or “Q” to the remote Arduino. The water pump will stop if AC power is lost for more than a few seconds. Manual intervention is required to reset the pump. The Arduino/SIM7000 restarts when power is restored and sends a text message. This is my cue to go to the pump. Before installing the Arduino/SIM7000, this required a visit to the pump or checking if water came out of one of the float valves. The latter is never fun in the winter, as it requires one’s arm to be immersed in the water. I obtained the gravity water pressure sensor by DFRobot (SEN0257) from Core Electronics. It has a BSP thread. I cut off the supplied connector and fitted a three-way Deutsch DT connector to provide a degree of weatherproofing. I doubled up the supplied wires for the crimp contacts. The SIM7000E is no longer sold by Core Electronics but can be obtained directly from DFRobot (www.dfrobot. com/product-1732.html). As I do not require the GPS or air pressure sensor functions of the SIM7000 card, I removed the associated code. I also modified it as I did not require the power-saving shield. I then housed the system in a waterproof enclosure from Jaycar. I used the following links to confirm that the SIM7000E was compatible with my local tower: https://whirlpool. net.au/wiki/mobile_phone_frequencies www.stelladoradus.com/finding-my-frequency-onmy-iphone/ The CAT-M frequency bands supported by the SIM7000E are B3/B5/B8/B20/B28. The band number of my local tower was 3. I determined this using the notes at www.stelladoradus.com I then added several hard-coded commands to the code to ensure that the SIM7000E is configured as I intended, rather than taking a chance. I send the SIM7000E the following commands on power-up: To set the preferred mode to LTE only (2 = Automatic, 13 = GSM only, 38 = LTE only and 51 = GSM and LTE only): MODEM.println(“AT+CNMP=38”) To set the band to CAT-M (the other choice is NB-IOT): MODEM.println( “AT+CBANDCFG=CAT-M”) To select CAT-M only (1 = CAT-M, 2 = NB-Iot, 3 = CAT-M and NB-IoT): MODEM.println(“AT+CMNB=1”) Enables full phone functionality (there are six options; 1 is the default): MODEM.println(“AT+CFUN=1”) 6 Silicon Chip Information on these commands can be found in the SIM7X00 Series_SMS_Application Note_V1.00 and SIM7000 Series_AT Command Manual_V1.04 documents. To test the SIM7000 thoroughly, I began sending it photos to see if it would be robust enough to cope. This did not go well; I would be interested from other readers how they dealt with this sort of abuse dished out to the SIM7000E. I had to keep the SIM7000E powered up for over 24 hours and wait for the network to put things right before it functioned normally again. I am building my second monitor now. I will upgrade the firmware in the future to monitor pressure trends and the duty cycle of the mains-powered pump. Ed O’Brien, Heyfield, Vic. Comments on DIY Reflow Oven project I’m building the DIY Reflow Oven controller (April-May 2020; siliconchip.com.au/Series/343) and have looked back over the previous uses of the same control board (eg, the DDS from February 2020; siliconchip.com.au/ Article/12341). I am having a little trouble understanding the logic behind the two regulator designs. Why is a low-dropout regulator specified for REG2 that is quite expensive to buy with delivery charges, rather than the readily available LM317? After all, the LD1117V is rated at only 0.8A (instead of 1A) and has far more voltage “headroom” than the 5V regulator used for REG3. Could I use an LM317T instead? Also, the data sheet for the LD1117V shows a recommended 120W value for the top resistor with the 10μF capacitor, whereas 330W has been used instead – whilst this may improve ripple performance, would it not also degrade response times? I know this project utilised a design from another application. Still, I wonder if a Micromite BackPack might have been a better option – the touchscreen has higher resolution, and it would do away with the need for a separate board, rotary encoder, cabling etc. Also, using PWM on a leading-edge dimmer-type circuit would put less thermal shock and stress on the oven elements and might be a lot less expensive than the solid-state relay. As another observation, many people have difficulties with soldering smaller SMDs. Yet, this board uses 2012 (imperial 0805) rather than 3216 (imperial 1206) parts with 3226 (imperial 1210) pads, for example – that would be much easier to deal with. The board is obviously very heavily packed, with very little clearance between parts – this caused me some problems; for example, the 100nF X7R 2012 capacitors are less readily available (unless in large quantities), and I had to fit 3216 parts onto the rather small pads. Also, many of the connectors are too close together (although, with heavy trimming, I was able to fit a few boxed headers that I prefer to avoid later connection mistakes). The specified flag heatsink does not fit due to connector and capacitor clearance issues. I did manage to get the board together – without heatsink – but with the aid of Geoff Graham’s recommendation of a stereo microscope, and a spring-loaded stylus I made to hold the parts in place for soldering. I am waiting for another part before commencing the testing phase. Ian Thompson, Duncraig, WA. Australia’s electronics magazine siliconchip.com.au Comments: In some projects, that controller board is powered from 5V DC, so the LD1117V is needed for a regulated 3.3V rail. You are correct that in the DIY Reflow Oven, this board is powered from 9V DC, so you could use an LM317 instead. The advantage of the 120W resistor compared to the 330W resistor we’ve used is that it guarantees that the regulator’s minimum load requirement is met even if nothing is drawing current from the regulator’s output. However, other devices on the board constantly draw current from the regulator’s output, so the lower value is not needed. It won’t affect the response time. Yes, the Reflow Oven could have been controlled using a BackPack controller, but a third party contributor designed this project, and he decided to re-use his existing controller design. We didn’t think it was worth the effort to redevelop the project to use the Micromite BackPack (even though we would prefer that), given that it was presented to us as a fully working, completed design. We don’t consider 2012-size parts to be all that difficult to hand solder; they are not that much smaller than 3216 metric (being 1.2mm wide rather than 1.6mm wide), and the pads tend to be a bit more generously sized in relation to the parts. We usually avoid going any smaller than that, although the next size down (1608) is not much harder to manage. We agree that the controller board for this project is packed, although we were able to successfully build and test it without having to trim anything. That includes the heatsink, which we somehow managed to fit – perhaps ours is a fraction smaller than yours. Of course, different constructors will have different skill levels and visual acuity, and we realised these projects will be challenging for some. We publish a mix of projects that use a wide variety of differently-sized components. You should not have trouble getting 100nF X7R 2012/0805 capacitors. They are a very standard item used in the millions (if not billions). Element14 sells a variety of suitable capacitors starting at around 3¢ in quantities of 10+ (cat 1759166), while RS sells them for 9.7¢ each in quantities of 100+ (cat 135-9033). One hundred might seem like a large quantity to purchase, but considering how many 100nF bypass capacitors are in the average design, and the fact that 2012 capacitors will usually comfortably fit on 3216 pads, we think it’s worthwhile to stock up on them. Dodgy switches becoming common The Serviceman’s Log entry in March 2021 about G. C.’s problem with a membrane switch on a coin counter prompted me to write in. I recently came across several faulty switches, and am beginning to think that they are getting poorer and poorer. The first one was a switch on an electric chainsaw that used to weld up and not switch off. I stopped using the chainsaw for that reason. Later, I came across an old switch that has the quick on/off function - no matter how slowly you operate the switch, it changes over really fast, and it has big contacts. I managed to fit this to the chainsaw, and that was the end of that problem. siliconchip.com.au POWER SUPPLIES PTY LTD ELECTRONICS SPECIALISTS TO DEFENCE AVIATION MINING MEDICAL RAIL INDUSTRIAL Our Core Ser vices: Electronic DLM Workshop Repair NATA ISO17025 Calibration 37 Years Repair Specialisation Power Supply Repair to 50KVA Convenient Local Support SWITCHMODE POWER SUPPLIES Pty Ltd ABN 54 003 958 030 Unit 1 /37 Leighton Place Hornsby NSW 2077 (PO Box 606 Hornsby NSW 1630) Tel: 02 9476 0300 Email: service<at>switchmode.com.au Website: www.switchmode.com.au Australia’s electronics magazine June 2021  7 Helping to put you in Control Mini Temperature & Humidity Sensor 0-10V output The Pronem mini from Emko Elektronik are microprocessor based instruments that incorporate high accurate and stable sensors that convert ambient temperature and humidity to linear 0 to 10VDC. Dimensions are only 40x 79 x 16mm. SKU: EES-001V Price: $149.95 ea Modbus TCP Analog Output Module The analog output module MU110-501 has 8 analog outputs (0/4-20 mA, 0-1/10V). Support for Modbus TCP, MQTT, SNMP, SNTP. SKU: AKC-263 Price: $545.95 ea Proop 7 Control 7” HMI with 2 Ethernet Ports This is a budget priced Touchscreen with a resolution 800 x 480 pixels and 260K colors; Ethernet, WiFi, RS-232 and RS-485 communication and 8 digital inputs/outputs for control. SKU: EEI-012 Price: $619.95 ea Digital ON/OFF Temperature Controller DIN rail mount thermostat with included PTC sensor on 1.5m m lead. Configurable for a huge range of heating and cooling applications. 230 VAC powered. SKU: EEC-010 Price: $89.95 ea Isolated Load Cell 2mv/V 0-10V Transmitter with Display Converts a signal for a 2 mV/V load cell to a 0 to 10 V signal. Able to power 2 load cells in parallel. DIN-rail mount. SKU: ALT-415 Price: $249.95 ea LabJack T7 Data Acquisition Module LABJACK T7 Multifunction DAQ with Ethernet, wifi and USB. Features 14 analogue inputs, 2 analogue outputs and 23 digital I/O SKU: LAJ-045 Price: $739.30 ea Ultrasonic Wind Speed & Direction Sensor RK120-07-AAC Economical Ultrasonic Wind Speed & Direction Sensor with Modbus RTU RS485 output and 4 metre cable. 12~24VDC powered. SKU: RKS-028M Price: $499.95 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Low-cost buck/boost module warning Prices are subjected to change without notice. 8 Silicon Chip The second one was the remote control for my garage door. Since new, the button always required a few presses before the door opened. Then it stopped working altogether. I took it down to the workshop and split the case open to check the battery (two 3V button cells). They tested OK, so I removed the PCB. The first thing I tested was the continuity of the pushbutton switch. When pressed, it remained open circuit. I had some good quality push button switches, but they had a much higher profile, so I installed one of these and cut a hole in the case to accommodate it. The remote not only worked fine after that, but now only needs one press of the button to open the door. The final switch problem was with an auto-darkening welding helmet. I had been using it for some months when it became unreliable. I put a new 3V button cell in it, but that made no difference, and after getting a few more flashes while using it, I tossed it aside and went back to my old faithful. A medical problem put me on light duties for a while, and while wondering what to do with myself, I thought I would have a look at the faulty helmet. These helmets have a shade adjustment on the side with a grind position, which I wished was not there, because if you put the helmet down a certain way, it turns the knob onto grind, giving you a flash. When adjusting the shade on the auto-darkening filter (ADF), the screen used to flicker, which I put down to a noisy potentiometer. So I thought that was a good place to start. The ADF cartridge is made to be removed easily to facilitate the replacement of the front cover lens. The switch is removed by pulling off the knob and undoing the nut behind the knob. With it on the workbench, I prised up some plastic tabs and removed the cover to reveal an ordinary pot with a switch on the back. I was going to substitute another pot, but as it was easier to test the switch, I did that first. With the control in grind position, the switch was open, and I measured some volts across it. When I turned the pot to the darkening position, I got a reading of 1.2V. I had expected a lot lower than that, but the ADF worked fine. However, when I turned the control further, the voltage ranged all over the place, going as high as 1.6V, and the ADF did not work. As I needed little excuse to do away with the grind position, I simply soldered a piece of wire across the switch terminals. It was easy to put back together, reversing what I did to take it apart. I have used the helmet for some months now, and I have not had a single flash. Not only that, but the shade control gives a smooth change over the whole range with no flickering. Also, I have been able to adjust the other settings more precisely to suit me. I am very pleased with the result. It worries me just how many of these devices are scrapped just because of poor-quality switches. Ron Groves, Cooloola Cove, Qld. I am writing about the “Reliable solar lighting system” circuit published in the Circuit Notebook column of the January 2021 issue (siliconchip.com.au/Article/14711). Australia’s electronics magazine siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build *** System Assembly Ampec Technologies Pty Ltd Australia’s electronics magazine siliconchip.com.au Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au FEBRUARY 2021 37 The circuit shows a solar panel with a nominal 12V output feeding what is described as an “XL6009 based buck/ boost converter module” producing a 5V output. Converter modules using the XL6009 IC are readily available from numerous vendors online. On paper, these modules are very attractive, with wide input and output voltage ranges. While some XL6009 modules are single-mode only (buck or boost), some offer automatic changeover depending on the input supply, guaranteeing a fixed output voltage regardless of whether the input is above or below the preset output voltage. Such modules can be identified by the presence of two inductors, rather than the one used in the fixed-mode modules. There are pitfalls with the XL6009, however. Despite websites having descriptions to the contrary, according to the manufacturer’s data sheet, the minimum input voltage of the XL6009 is 5V. So it is not guaranteed to produce a regulated output voltage when the input drops below 5V. Usually this would be of little consequence, but there is a flaw with the XL6009 which, depending on how it’s used, could end up destroying the device it is powering. Within a certain range of input voltages under 5V, the output rises many times higher than the set output voltage. For example, on the multi-mode module I tested with its output set to 5V, the fault occurred with input voltages between approximately 3.0V and 3.2V. Output voltages ranging from 14V up to 51V were produced, and adding a load resistor showed that non-trivial currents could be supplied when the high output voltages were present. Obviously the XL6009 does not contain a low voltage cut-off circuit, which it needs given this behaviour. The fault could be triggered by a slowly rising input voltage (eg, when light is applied in the early morning to the solar panel mentioned above), or if something such as a flat battery prevents the input voltage from rising high enough to guarantee correct operation. It could be that the TP4056-based LiPo charger used in the “Reliable solar lighting system” is not adversely affected by short bursts of very high voltages on its input. Alternatively, perhaps the solar cell cannot supply sufficient current at voltages in the critical range to do damage. If this is the case, then the immunity of the described circuit to the XL6009 problem is due mainly to good luck. However, if anyone is tempted to use the XL6009 to power something more sensitive (such as a Raspberry Pi or Arduino board), this fault with the XL6009 could end up destroying the board. I was planning on using a dual-mode XL6009 module to power a Raspberry Pi board, but decided to thoroughly test the module first. It was while smoothly varying the input voltage that I noticed a sudden jump to over 50V on the output, which prompted a more careful investigation. As a result of this observation, I will never use anything based on the XL6009 – the IC is simply not reliable. While an external low voltage cut-off circuit could mitigate the problem, the XL6009 still has its potentially devastating problem, and I am not willing to chance it with anything of value. More recently, I discovered that others have encountered similar issues with XL6009 modules; see https:// owenduffy.net/blog/?p=12435 10 Silicon Chip Australia’s electronics magazine siliconchip.com.au I think it is worth warning your readers of this serious problem with the XL6009 and modules which use it. While such modules appear to be very useful in theory for various situations, in my opinion, they are best avoided. Jonathan Woithe, Valley View, SA. Strange capacitor value readings For the second time, I have had the curious situation where several capacitors do not measure as their stated value, but all return almost the same capacitance. Over a year ago, I measured the 200V 330μF main capacitors in two PC power supplies. All four returned a value close to 220μF. The supplies were the same brand, and the capacitors the same manufacturer. More recently, I checked three identical 440VAC 10μF power factor correction capacitors from mercury arc control units. They were made in 1981, and all three tested at about 6.5μF. If there is anything wrong with these, it is not showing. I charged them to 40V, and after an hour, they still measured over 20V, with most of the discharge due to the DVM. This makes me suspect that the manufacturers incorrectly marked the capacitors. I just cannot think of a reason why they would similarly decrease in value. I did verify that the capacitance meter was reading correctly. George Ramsay, Holland Park, Qld. Comment: we suspect that these are from ‘bad batches’ of capacitors that had some sort of variation in their manufacturing process or inputs, causing them to all have similar capacitance deficits. Or they could have been fraudulent; lower value capacitors altered with higher values to be sold at a premium (perhaps with a few ‘good ones’ on top to avoid suspicion). Digital Insulation Meter displays incorrect values I have just finished building Jim Rowe’s Digital Insulation Meter (June 2010; siliconchip.com.au/Article/186) as a “rainy day” project. I now have it up and running. I have pretty much followed the published circuit diagram; however, I built my own PCBs using a slightly different layout to accommodate a different LCD screen (the 1602A type) than the one used in the article. My meter appears to be working correctly, producing close to the correct test voltages and, pleasingly, displaying on the LCD close to the right leakage current and resistance measurements for known test resistor values of 10MW and 1MW. On the 500V setting, when the test button S2 is pressed, I obtain the following results on the LCD: Ix = 49μA, R = 10MW and Ix = 0.4mA, R = 1MW respectively. However, when test button S2 is released, the LCD then displays Ix = 16μA, R = 30MW and Ix = 1μA, R = 260MW for the 10MW and 1MW test resistor values, respectively. These values don’t appear to have much meaning, and I’m wondering if they’re correct as they create some confusion. Upon releasing S2, I expected the LCD to return to displaying something like the screen “Set Volts, Press button to Test:” that initially comes up on powering up the meter. I changed the code to behave this way by adding a couple of extra instructions in the program’s main loop to ensure that the current and resistance readings on the LCD are blank between measurements, ie, when switch S2 is released. siliconchip.com.au I’m not sure if this was what Jim originally intended, but it makes more sense to me, and it was a simple fix. An extract of the code follows, with the added instructions highlighted in red: CALL InitDig CALL SetVolts BTFSS PORTA,4 CALL Display3 BTFSS PORTA,4 GOTO $-1 I’m now very happy with the performance of my Digital Insulation Meter, so thanks to Silicon Chip for the great project (from some years ago, but it’s still very useful and was fun and educational to build and modify!). Stephen Denholm, Howrah, Tas. Comment: Jim did not experience the same problem as you with his prototype, and we think it might have to do with the characteristics of the button you have used or some other detail of your build. Regardless, your solution is a good one. The only disadvantage is that you need to make a note of the readings before releasing S2. The easiest way to cut your power bill How can Bruce Pierson of Dundathu, Qld doubt the claims of Voltex (Mailbag, May 2021, p10)? I also have a device that I guarantee will cut your power bill in half! It’s shown in the accompanying photo. This versatile device can also be used to cut you phone bill, water bill, gas bill etc in half. But seriously, it is a shame that nobody is held to account for perpetuating these obviously fraudulent claims/ sales. I imagine the people who fall for these products are the ones least able to afford them. Ron Walker, King Creek, NSW. Worshipping a greater power The accompanying photo (shown below) is of a local church that caught my eye. I guess you could call this “Heavenly Power”! SC John Chappell, Caloundra, Qld. Australia’s electronics magazine June 2021  11 The Right To Repair (and Modify) The “Right to Repair” broadly refers to consumers (and presumably, businesses) having the legal right to repair their own equipment, or get non-factory service agents to do so, if desired or necessary. P roponents argue that this ‘right’ comes from the fact that they are (apparently) the legal owners of the equipment in question. It is spurred on by the fact that many manufacturers won’t sell or otherwise provide spare parts, service documentation such as circuit diagrams, specialised tools and the software required to service equipment. Consider that a manufacturer could go out of business, or decide to stop servicing a particular product. This would leave owners with no means to repair or modify that equipment should it become necessary. And even if the manufacturer does offer service, it could be limited in scope, overpriced, slow, require long-distance transport of the equipment in question etc. So there are many reasons why owners of equipment could argue that they need the ability to repair it themselves, or have a third party do it for them. “Right to modify” in this context refers to enhancing a device’s 12 Silicon Chip performance or capabilities by modifying software settings alone. A device might have a certain capability, but it is disabled in software unless a payment is made for the additional features. Note that generally, this equipment is out of its warranty period; this is not about a manufacturer avoiding an obligation to repair equipment for whatever reason. Companies that are currently in the right to repair spotlight include: • Apple (and other phone and computer manufacturers), for not providing spare parts to non-authorised service agents. • Tractor manufacturer John Deere in the United States, for not providing the software to diagnose, repair or integrate new accessories into the tractor system to individual farmers or mechanics. Another example is companies By Dr David Maddison (including automotive manufacturers) using “tamper-proof” fasteners on their products, making them more challenging to repair. Fortunately, though, third party manufacturers now make appropriate driver bits so that this is less of a problem. Other ways manufacturers can restrict non-factory repairs include: • requiring proprietary software (possibly available to manufacturer representatives only) for service, such as requiring dealer tools to install a new starting battery in a vehicle. • “serialising” components, so that replacement parts can only work if their particular serial number is programmed into the device’s firmware. An identical replacement part with a non-matching serial will simply not work or will give an error message. This was a strategy introduced by Apple in their iPhones, even including batteries. See the videos titled “Apple’s NEXT move in the war on repair” at https:// Australia’s electronics magazine siliconchip.com.au youtu.be/GlvlgmjMi98 and “An important message from Louis Rossmann” at https://youtu.be/PPnz7DjM4CE Valid reasons to restrict service For fairness, we should present both sides of this story. Manufacturers might offer some or more of the following points: • They wish to maintain certain performance standards (and thus reputation) for their equipment, so they want control of the repair processes and software, including updates. It is arguably beyond the scope of third-party technicians to diagnose and repair the complicated software used in many products today (although some specialists are well-qualified). • Using “hacked” software or other unauthorised repair procedures might compromise the safety of a machine, or cause it to operate illegally (such as transmitting on an unlicensed frequency). • Botched repairs or modifications by third parties of devices under warranty could cause extra warranty service work down the track for the manufacturer (although in this case, they could refuse service if they realise what happened) • A manufacturer repair ensures a service record is maintained for equipment maintained by them (but it’s questionable how important this is). Reasons for self-repair Individuals might want to repair their own equipment, or have an independent repairer do it for them, especially if manufacturer repairs are expensive or take too long. If the item is within warranty, you would typically expect the manufacturer to repair it (although, in our experience, they don’t always do so successfully). There are many experienced exfactory technicians and other highlyexperienced individuals who can competently make repairs, as long as they have access to the required tools and software. A manufacturer might declare a part or device to be unrepairable. Louis Rossman and Jessa Jones have both repaired devices that Apple said were unrepairable. See the following videos: • “Apple REFUSED to fix our siliconchip.com.au Phillips Phillips II Phillips/Slot Combination (Combo) PoziDrive Phillips1a Phillips Square Supa Drive Slotted Square Slot Combination Torx external (6-lobe) Torx internal (6-lobe) Torx – internal Tamper-proof pin (6-lobe) Frearson Clutch Fluted Socket 4 flutes Fluted Socket 6 flutes Mortorq Tri-wing Hex Socket Allen Head internal Hexagon external Hexagon internal Tamper-proof Phillips Hex Head 5 Node Security 7 Node Security Slotted Tamper-proof (One Way) Spanner Drilled (Tamper Proof) Slotted 6-lobe Combo Spanner Slotted (Tamper Proof) Quadrex Square Socket (Robertson) Fig.1: a selection of screw head shapes; most are security types designed to prevent easy removal. iMac Pro” at https://youtu.be/ 9-NU7yOSElE • “Fixing the Unfixable iMac Pro with Louis Rossmann!” at https://youtu. be/EdwDvz47lNw • “An incredibly sad case: iPad 4 found on body of deceased hiker” at https://youtu.be/zMuap2fgGuY There is also a concern that an item becomes useless once a manufacturer stops supporting it. A device could be even made useless by a forced software upgrade or a built-in end-of-life counter. Those who advocate the right to repair are against such actions. For example, read the news article headlined “Apple fined for slowing down old iPhones” at www.bbc.com/news/ technology-51413724 Some examples of repairability concerns follow. 1. Security screws Many manufacturers use screws with special heads to prevent repair Fig.2: the pentalobe screw head. Apple first used this on the MacBook Pro to secure the battery in 2009 – then used from 2011 on the iPhone 4. Source: Wikimedia user Ruudjah2. Australia’s electronics magazine or modification of their products (see Figs.1 & 2). Drivers to fit so-called security or tamper-resistant types were not always readily available. When communication was much slower, these were somewhat effective in preventing access to devices. But with widespread access to the internet, it’s much easier to find suitable drivers. As soon as a new security screw is released, a manufacturer produces a driver for it. These are typically available at low cost from eBay, as well as electronics and hardware stores. An early example of a tamper-proof fastener was used on original Macintosh computers. It was impossible to remove the back without a special tool, which a third party eventually made. This was a combination of a long-handled Torx T15 driver, uncommon at the time, and a “spudger” used to pry the case apart without damaging it (as a flat-bladed screwdriver would). Another example is the pentalobe screws on an iPhone. These were used in an attempt to prevent non-Apple repairers working on the phones, but appropriate drivers were soon released onto the market by third parties. Sometimes when a security bit is used and the screw is recessed deeply in a narrow hole, a typical driver bit won’t be long enough, so the screw might be inaccessible. June 2021  13 Fig.3: an aftermarket water-resistant seal for a Samsung Galaxy S9 phone. Many official factory seals are not available to nonofficial repairers. Fig.4: the infamous “Error 53” when the Touch ID sensor was replaced on certain Apple devices. This resulting in Apple Inc. being fined by the Federal Court of Australia. Image credit: iFixit. Such was the case with a recent uninterruptible power supply (UPS) I tried to disassemble. 2. Water-resistant seals on phones After repair, many independent phone repairers cannot guarantee a phone’s water-resistance because manufacturers will generally not sell the water seals, gaskets, tapes or adhesives needed to render the phone resistant to water. However, there are some aftermarket products available (see Fig.3). If you need to get your water-resistant phone repaired, check with the repairer whether they will guarantee a factory level of water resistance after the repair. Note that most phones are not fully waterproof, but many now offer limited resistance to water penetration. 3. Apple Inc. and “Error 53” In 2018, Apple Inc. was fined $9 million by the Federal Court of Australia after the ACCC (Australian Competition and Consumer Commission) took them to court concerning “Error 53” (see Fig.4). This started to occur in 2016 when some iPhone or iPad users had the Touch ID sensor replaced by a thirdparty repairer instead of Apple. After the replacement, the phone worked correctly until the phone software was updated, at which point the phone was ‘bricked’, ie, unable to be used. Apple argued that this was a security Fig.5: one of the ‘end-of-life’ messages given by Epson printers. The pads referred to are not serviceable in some models, and not economically worthwhile for others. 14 Silicon Chip measure, as the pairing between fingerprint data stored on the sensor and similar data stored in a “secure enclave” would be broken, leading to the phone becoming disabled. Apple refused to help affected users because Apple did not repair the phone. The claim that this was related to security is contradicted by the fact that devices would only be bricked at the time of software update, which could be many months after the sensor was replaced. Anyone with malicious intent would have plenty of time to act, and in any case, the sensor replacement still required a user to know the passcode for the phone. See further comments in the video below. Fig.6: a solution from iFixit to the Epson ‘end-of-life’ problem. An overflow bottle is installed to capture surplus ink, because for the L200 printer, it is almost impossible to remove or replace the ink pads. Australia’s electronics magazine siliconchip.com.au Fig.7: the ECU encryption on the 2019 C7 Corvette ZR1 has been cracked by HP Tuners, for those for whom the stock 563kW/755 horsepower output is not enough… The ACCC argued that consumers had a right to have the phone repaired. They said, “the court declared that the mere fact that an iPhone or iPad had been repaired by someone other than Apple did not, and could not, result in the consumer guarantees ceasing to apply, or the consumer’s right to a remedy being extinguished”. Apple eventually apologised to customers and issued a software update to fix the affected phones. They also offered to reimburse customers who paid for an out-of-warranty replacement. See the news articles at siliconchip.com. au/link/ab79 and siliconchip.com.au/ link/ab7a for more details. Also see the video titled “Apple FINED MILLIONS for misleading customers on Error 53 in Australia” at https://youtu.be/cDYeby1Vanw That video is by Louis Rossmann, a prominent personality in the right to repair movement (https://en.wikipedia.org/ wiki/Louis _ Rossmann). He has a repair shop in New York City and a popular YouTube channel. Apple also remotely deployed a “feature” that slowed down ageing phones, ostensibly to put less load on old batteries (mentioned earlier). Many investigators disagreed with Apple’s reasoning. Incidentally, Apple will not unlock a device for a new owner of used devices. The onus is on the purchaser to ensure that the previous owner has unlocked the phone. So if buying a use Apple device, make sure that it is not locked. 4. Difficult-to-access car components I recently had to replace the side mirror on my car. I discovered that it was secured with security Torx screws, having the central pin. These screws are not accessible from the vehicle’s exterior (I had to remove a considerable amount of internal trim to get to them). It is difficult to imagine why the manufacturer would use these more expensive screws, unless they wanted you to go to a dealer to replace the mirror. Fortunately, I had the appropriate drivers in my collection. Fig.9: a farmer with a mostly functioning GPS receiver from a John Deere tractor. In this unit, the TCM (terrain compensating module) is no longer functioning, but the manufacturer will not repair or replace just that module; a whole new unit had to be purchased. From the video at https://youtu.be/EPYy_g8NzmI siliconchip.com.au Fig.8: the wiring loom layout for the GM Global B architecture, which features strong encryption. For a description of the OBD connector, see the video titled “Global B architecture Data Link Connector Description” at https://youtu.be/J1gOz2cFDm8 5. Tesla making it difficult for thirdparty repairers Rich Benoit has a YouTube channel called “Rich Rebuilds”. His experience started when he purchased a flood-damaged Tesla vehicle cheaply at auction and tried to repair it. He discovered that as an ‘unauthorised repairer’, Tesla would not sell him parts. This started his quest to find ways to repair Teslas, including using parts from wrecked vehicles. Eventually, he opened an independent repair shop called the Electrified Garage. See the video titled “Tesla Hacker: The Rogue Mechanic Taking On Tesla” at https://youtu.be/3Ytm_ GnTkl0 He has extensively documented Tesla repairs, and the (unnecessary) difficulties involved, on his YouTube channel. 6. Wheelchairs and other mobility equipment A wheelchair user testified in a government inquiry in the USA about how they can more quickly and cheaply Fig.10: a Russian Belarus 3522 tractor, available with US-made Caterpillar or Cummins engines, and relatively simple and accessible diagnostics. Australia’s electronics magazine June 2021  15 “Most consumers who are out of warranty elect to replace a lower-cost printer when they receive an end of life service message.” I have personal experience with this. My printer was working perfectly; then I started receiving these messages. One extension was allowed for a limited number of pages, then the printer ceased working. I could have taken it to Epson for repair, but it was not worthwhile. Replacing the affected ink pads was not possible. Solutions to this problem include software that resets the end-of-life page counter, plus replacement pads or modifications to the printer to enable pads to be replaced or installing an external ink collection bottle (see Fig.6). iFixit has published a guide on how to repair an Epson L200 printer with this problem at siliconchip.com.au/ link/ab7b Fig.11: a page from the freely available manual for a Russian Belarus model 3522.5 tractor, showing error codes from electronic modules. These are displayed on the vehicle dashboard and do not require a plug-in reader or special software. You can view Belarus manuals at siliconchip.com.au/link/ab7k repair their own wheelchair with parts from eBay compared to returning it to the manufacturer. See the video titled “Boston State House - Right to Repair hearing - FULL HQ VERSION” at https://youtu.be/ QHpXJzjin7k?t=435 7. Epson printer ‘end-of-life’ When the print heads of an inkjet printer need cleaning, ink is squirted onto cleaning pads. When these are full, Epson inkjet printers issue a warning that these need replacing (shown in Fig.5), which is not generally worthwhile as it is so involved. According to Epson (https://epson. com/Support/wa00819), “At some point, the product will reach a condition where either satisfactory print quality cannot be maintained, or components have reached the end of their 16 Silicon Chip usable life...” “If you want to continue using the printer, Epson recommends having the printer serviced at an Epson Authorized Customer Care Center. In most cases, when this message occurs, other printer components also may be near the end of usable life, and satisfactory print quality cannot be maintained.” 8. Vehicles with encrypted ECUs Cars have been released with encrypted engine control units, such as certain Bosch ECUs on the BMW M3 and M5 platforms, which were eventually cracked. According to an online report, the cracking of the M5’s ECUs (the vehicle has two) involved a process where they had to be removed and sent to a tuner, where they had to have a hole drilled into them (for reasons not stated). Hardware was used to read the encryption key, at considerable risk to the device and of voiding the warranty. More recently, the ECU of the predecessor of the current model of Corvette, the C7 ZR1 (Fig.7), was also cracked by HP Tuners in the USA (as stated at siliconchip.com.au/link/ab7c). The current model, the C8, makes it considerably more difficult. The GM E99 PCM (powertrain control module, often incorrectly referred to as the ECU) cannot be Fig.12: a Telstra 4GX USB + WiFI Plus E8372H, also known as a Huawei Mobile Broadband E8372 modem (with different firmware). This can be unlocked for a fee so it can be used overseas, or with another carrier in Australia. Australia’s electronics magazine siliconchip.com.au reprogrammed to provide increased power output or accommodate certain engine modifications tuners may wish to perform. The encryption uses “multi-factor authentication and a Diffie-Hellman 2048-bit key exchange using an SHA256 hash digest that is unique for each VIN and PCM” (VIN being the unique vehicle identification number). It is regarded as extremely difficult to crack, and has not been (yet). There is an alternative to cracking an encrypted ECU; it can be replaced with an unencrypted third-party ECU. This is somewhat more expensive, and might eliminate some of the ‘niceties’ of modern vehicles. But it would run the engine and might offer tuning features that the factory ECU does not, such as better monitoring. See our in-depth articles on ECUs and other automotive modules in the December 2020 & January 2021 issues (siliconchip.com.au/Series/353). 9. Vehicles with encrypted communications General Motors are in the process of introducing their Global B vehicle electronic architecture or “VIP” (“vehicle intelligent platform”), shown in Fig.8. It will be utilised by most GM vehicles by 2023, and is already on the Cadillac CT5, CT4 and C8 Chevrolet Corvette. Its communications systems manage 4.5 terabytes of data per hour, with intra-vehicle communications of 10Gbps. The system can also be updated ‘over the air’. One feature (or not, depending on your point of view) is that the system will be resistant to ‘hacking’, either from tuners or criminals who want to take control of your vehicle. Fig.13: this Belarus tractor wiring diagram shows its relative simplicity and demonstrates the availability of servicing-related data. GM President Mark Reuss is aware of the problems this will cause for tuners but said, “I don’t wanna cut anybody out from an aftermarket Fig.14: Apple’s T2 security chip. It prevents some third-party repairs. siliconchip.com.au Australia’s electronics magazine standpoint, but we have to pick and choose who are the good guys.” Perhaps at some point, tuners will be given access to the ECU, PCM or other parts of the vehicle electronics they need. 10. Tractors and other farm machinery In Australia, many farmers believe they are dealt with poorly by farm machinery manufacturers. This matter is currently under investigation by the ACCC, and there is a discussion paper entitled “Agricultural machinery: After-sales markets” at siliconchip. com.au/link/ab7d (PDF) Matters identified in the discussion paper include: • access to independent agricultural machinery repairs is limited. June 2021  17 Fig.15: a post from Hugh Jeffreys’ Twitter page on repair difficulties with the iPhone 12. • farmers may lack recourse in the event of a problem with their machinery. • agreements between manufacturers and dealers may limit access to repairs. • data ownership and management may raise privacy and competition issues. A report is due out soon. It will be available from the following site: siliconchip.com.au/link/ab7e In the USA, farm machinery manufacturer John Deere has been singled out over right-to-repair concerns. John Deere advocates the concept of “digital agriculture”, which is perfectly valid and by no means unique to them. For more information on this, see siliconchip.com.au/link/ab7f and our articles on “The Farm of the Future” in the June & July 2018 issues, at siliconchip.com.au/Series/324 As part of this, John Deere tractors and implements make measurements of ground conditions such as soil moisture, nitrogen levels, seed placement, fertiliser and pesticide usage, and many other parameters. This data is used to make future farming decisions. This requires highly-digitised farm equipment. John Deere’s reluctance to provide service data to non-authorised service centres reflects a possible concern that inappropriate adjustments to software settings might compromise such an all-encompassing system. Julian Sanchez, John Deere’s Director of Emerging Technology, said, “One tweak could cascade throughout an entire software system and lead to unintended consequences”. On the other hand, it is difficult to see how the replacement of most broken parts would upset such a software system (eg, see Fig.9). To service their John Deere products, some US farmers are turning to pirated Fig.17: the US Army’s Joint Light Tactical Vehicle (JLTV). Even it has right-to-repair problems. 18 Silicon Chip Fig.16: the F(x)tec Pro1 is an Android phone, but the bootloader is unlocked so that you can install other operating systems such as Lineage (Android-based) and Sailfish (Linuxbased). Android Apps can also run on Sailfish. John Deere software from Ukraine. They argue that it’s the only way to service their machinery economically and without downtime, or the hefty towing or cartage costs to take broken machinery to the nearest official service centre. See the video titled “Farmers Are Hacking Their Tractors Because of a Repair Ban” at https://youtu.be/EPYy_ g8NzmI If you search YouTube with the terms “john deere right to repair” (without the quotation marks), you can see much more on the topic. It has been reported that some farmers are reverting to older tractors, that are not under computerised control, over these concerns. This is despite the fact that older machinery may not be as productive as more modern equipment, lacking autonomous operation features. Belarus tractors (see Figs.10, 11 & 13) were initially designed with simplicity and serviceability in mind. After the Fig.18: sometimes, it pays to read the End User License Agreement. It earned Doug Heckman US$1000. Australia’s electronics magazine siliconchip.com.au Fig.19: upgrading some Tesla models from a 60kWh to 75kWh battery pack was as simple as paying the fee. The battery capacity was restricted only by software. fall of the USSR, they became more advanced and comfortable, but retained the ideals of serviceability and relative simplicity. These tractors offer an option to farmers frustrated by the inability to do most servicing on other tractor brands. They are exported to 100 countries including Australia, New Zealand, the UK, the USA and Canada. 11. Network-locked phones and modems Often, when an internet service provider (ISP) supplies modems/routers as part of their internet package, they are locked to that provider and cannot be used with others. This is wasteful given that most ISPs do not ask for the equipment back if a customer leaves (and it would usually be out-of-date by then anyway). Certain modems and phones can be unlocked for a fee; for example, one portable 4G device from Telstra (Fig.12) can be unlocked with the procedure explained at siliconchip.com. au/link/ab7g Similarly, a phone provided as part of a plan is usually locked to that provider. The phone can be sometimes unlocked once the contract has expired, for a fee. Some services claim to unlock a locked phone, but you would have to decide if these are a breach of your service agreement, and they might compromise the software or firmware on your phone. 12. Apple’s T2 chip Apple’s T2 security chip (shown in Fig.14), present in some Apple products such as MacBook Pros, encrypts data and provides other services. It ensures that only ‘genuine’ Apple operating systems are used to boot the computer, and checks fingerprint scans. It removes the job of encryption from the CPU, saving CPU cycles. It also performs Fig.21: the unofficial Ingenext performance improvement module, available for the Tesla Model 3 and Model Y dualmotor variants. siliconchip.com.au Fig.20: the difference in range between a Tesla Model 3 with the extra battery capacity installed locked and unlocked. audio and visual image processing. But it prevents some third-party repairs or modifications, by requiring software diagnostics to be run for some replacement components, which only authorised Apple dealers can complete. 13. Repair difficulties with the iPhone 12 Australian Hugh Jeffreys looks at repair problems for the iPhone 12 in the video titled “iPhone 12 Anti Repair Design - Teardown and Repair Assessment” at https://youtu.be/ FY7DtKMBxBw (see Fig.15). 14. Linux phones for better repairability The F(x)tec (www.fxtec.com) Pro1 (Fig.16) is an example of a phone with support for multiple operating systems and support from the open-source community. It was explicitly designed for repairability, with the intention of Fig.22: an in-vehicle notification from Tesla stating “Incompatible vehicle modification detected”. Australia’s electronics magazine June 2021  19 Fig.23 (above): an example of an iPad opening tool kit available from iFixit. It will apparently open all phones or tablets that use an adhesive to hold the case together, which is released by applying heat during the disassembly process. Fig.24 (right): a replacement screen for the Samsung Galaxy S10 available from iFixit. It comes with installation tools. having spare parts readily available. 15. Right to repair and the US military Of all institutions, you’d think military branches ought to be able to repair their own equipment. But even they have been affected by this problem. There is no reason other militaries, such as Australia’s, aren’t similarly affected. The New York Times has an article at siliconchip.com.au/link/ab7h about how the US military is put at risk by not being able to repair some of its equipment in-house, even though they are fully capable. The equipment has to be sent back to the manufacturer, often taking it out of service for months. The examples given relate to warranty repairs or contractual obligations in mission-critical equipment, with lives possibly at risk. Another right to repair issue with the US Army is the Joint Light Tactical Vehicle (JLTV), shown in Fig.17. According to a report, it was difficult or impossible to repair for the following reasons: “Units [could not] maintain the JLTV without support from the contractor field service representatives due to vehicle complexity; there were issues with ineffective training, poor manuals, and challenges with troubleshooting the vehicle; the maintainer training was not effective and required additional familiarization and hands-on time to increase the competency of military maintainers to troubleshoot the vehicle; and the health monitoring system [was] not accurate and [it] reduce[d] crew and maintainer confidence in the system.” 16. Restrictive software licences Software licences usually state that you have no right to modify the software, even though that is not easy without the source code. The details are in the almost-never-read End User License Agreement (EULA). Someone did actually read a EULA once and got a pleasant surprise. In 2005, a company called PC Pitstop included a clause in their EULA that promised a “consideration” to anyone that read the EULA that far. All they had to do was send an email to the address listed (see Fig.18). It was four months and 3000 downloads before Top five right to repair wins of 2020 In the video by iFixit titled “Top 5 Right to Repair Wins of 2020” at https://youtu.be/gJLLybOzKrk the following are cited: 1) A 2019 Apple iMac repair manual was found online – by accident, they ask? 2) France introduced the index of repairability. 3) During the COVID-19 crisis, manufacturers of medical equipment did not make repair information available, so there was a massive crowdsourcing campaign to create a medical repair database with 13,000 manuals – see www.ifixit.com/Device/ Medical_Device 4) The European Parliament voted in support of consumers’ right to repair. 5) In Massachusetts, USA, the automobile right to repair was extended. Manufacturers have until model year 2022 to install a standard open data platform, accessible to all. 20 Silicon Chip Fig.25: the components of a disassembled Fairphone 3. It is a highly modular design; individual modules can be repaired, and disassembly requires no special tools. This phone has a perfect repairability score. Source: iFixit (Creative Commons License). Australia’s electronics magazine siliconchip.com.au Doug Heckman spotted that clause and won US$1000. It is not certain whether EULAs legally restrict the purchaser’s rights. According to Wikipedia’s page on the subject, “The enforceability of an EULA depends on several factors, one of them being the court in which the case is heard. Some courts that have addressed the validity of the shrinkwrap license agreements have found some EULAs to be invalid, characterizing them as contracts of adhesion, unconscionable, and/or unacceptable...” It goes on to say that “Other courts have determined that the shrinkwrap license agreement is valid and enforceable...”. Australian consumers have more rights than most worldwide, so it seems likely that many clauses in the typical EULA are unenforceable. It’s hard to say for sure until a particular clause is litigated. Some companies have attempted to use their software copyrights to prevent its use by others to perform thirdparty repairs. 17. Medical equipment repairs US company Summit Imaging (www.mysummitimaging.com) repairs ultrasonic and mammography imaging equipment. They argue that “repair monopolies, created by equipment manufacturers, are driving health care costs up and patient care down”. See the video titled “Right to Repair with Biomedical Equipment Technology” at https:// youtu.be/giTU-UznidQ iFixit has established a medical equipment repair database, but there is also Frank’s Hospital Workshop in Tanzania (siliconchip.com.au/link/ab7i). It comprises a collection of documents and training materials to address the following problems found in Africa: “No spare parts for repairs and maintenance, no technical manuals, poorly or no trained biomedical technicians, no (financial) support by the responsible authorities, no technical support from the manufacturers, lack of awareness of the advantages of preventive maintenance.” 18. Identical equipment with different performance levels This is tangentially related to the right to repair, but worth mentioning. Consider two oscilloscopes available siliconchip.com.au Fig.26: the scene at a typical Repair Café. Source: Wikimedia user Ilvy Njiokiktjien. with 50MHz and 100MHz bandwidths. It is often the case that they use precisely the same hardware, even though they are priced differently. The difference is effected by a bit set differently in the firmware. While we don’t advocate this, some tinkerers have developed software hacks that convert a cheaper (say 50MHz) model into a more expensive (say 100MHz) model by merely changing this internal software switch. Along the same lines, Tesla’s superseded model S 60 and 60D vehicles, with a usable battery capacity of 60kWh, actually had 75kWh batteries software locked to 80% capacity. In the USA, owners paid US$3000 or even more to unlock that extra capacity. See Figs.19 & 20, and the video titled “Model S 60d to 75d upgrade: real time no edits” at https://youtu.be/ VW_w4bQGg4w Another procedure for Teslas is ‘uncorking’. This software-only upgrade applied to some older models such as the model S and model X with a 75kWh battery pack, providing faster acceleration. Newer versions of those models came from the factory with uncorking already applied. See the video titled “Tesla 75D Uncorking experience” at https://youtu. Australia’s electronics magazine be/p9ibsOldbsM Tesla software is inaccessible to non-authorised repairers, making modification or repair difficult, if not impossible. Despite that, unauthorised modifications have been developed and marketed. Tesla offers an official software upgrade for the Model 3 dual motor model that adds an extra 37kW/50hp for US$2000 in the USA. But Canadian company Ingenext (https://ingenext.ca/) offers a similar modification (Fig.21) for US$935, plus extra features are included as well. KEEP YOUR COPIES OF AS GOOD AS THE DAY THEY WERE PRINTED! ONLY 95 $ 1P6LUS p&p A superb-looking SILICON CHIP binder will keep your magazines in pristine condition: no torn pages or dog ears! * Holds up to 14 issues * Heavy duty vinyl * Easy wire inserts Available in Aust only ORDER NOW AT www.siliconchip.com.au/shop June 2021  21 a repairability score comparing, on a scale of 0 to 10, with 10 being the easiest, for various devices such as laptops, smartphones and tablets. See www.ifixit.com/Search?doctype =pages&query=repairability Of all phones listed, the Fairphone 2 of 2015 and Fairphone 3 of 2019 (shown in Fig.25) are the only ones to get a perfect 10. They are rated highly because frequently replaced components such as the battery and display can be swapped with just a screwdriver; standard Philips screws are used; and “individual modules can be opened, and many components can be individually replaced”. Fairphone’s website is at www. fairphone.com/en/ For documentation of a teardown of the Fairphone 3, see siliconchip.com.au/link/ab7j Fig.27: part of a spreadsheet to calculate the index of repairability for a TV. Rather than being a software modification, an extra module is added that presumably intercepts and modifies certain control signals on the car’s data bus. In response to this modification, Tesla has updated its software to detect it, notify the owner, and presumably Tesla headquarters. The notification reads: “Incompatible vehicle modification detected” (Fig.22) and “Potential risk of damage or shutdown”. At this time, no further action is taken, such as disabling the vehicle. See the video titled “Boost 50 - Add 50 HP to your Tesla model 3” at https:// youtu.be/-VHIyq03mK0 Many Tesla owners believe that once they own the vehicle, they should be able to do whatever they like with it. Naturally, such modifications might void the warranty. Organisations Here are some organisations involved in the right to repair movement. 22 Silicon Chip 1. iFixit iFixit (www.ifixit.com) is both a private company and a global community of people. In its own words, “iFixit is a wiki-based site that teaches people how to fix almost anything. Anyone can create a repair manual for a device, and anyone can also edit the existing set of manuals to improve them. Our site empowers individuals to share their technical knowledge with the rest of the world.” iFixit promotes a consumer’s right to repair and provides free repair guides, product teardowns, a forum to discuss repairs and offering for sale specialist tools (Fig.23) and spare parts (Fig.24) for repairs. During the COVID-19 pandemic, it has also accumulated a vast collection of repair manuals and guides for medical equipment to support health care providers, due to increased equipment usage and therefore, maintenance and repair requirements. iFixit repairability score iFixit has for some years provided Australia’s electronics magazine 2. The Repair Association The Repair Association (www. repair.org) is a US-based lobby group for independent repairers, and they fight for the right to repair. Their philosophy is, “We have the right to repair everything we own. You bought it, you should own it. Period. You should have the right to use it, modify it, and repair it wherever, whenever, and however you want. We fight for your right to fix.” 3. Repair Cafés Repair Cafés (www.repaircafe.org/ en/) are a worldwide movement consisting of meeting places where visitors bring objects to be repaired by skilled volunteers (see Fig.26). The focus is on repairing things rather than throwing them away. For some, this may be a way to get items repaired that are too difficult or expensive to repair via the usual channels. To find a repair café near you, including in Australia and NZ, visit the website link above. Laws We will now look at some relevant laws and inquiries. Index of repairability (France) The French Government has introduced an index of repairability (“Indice de réparabilité”). It applies to aspects of repairability such as documentation, ease of disassembly, availability of spare parts, price of spare siliconchip.com.au Dave Thompson’s opinion on the Right to Repair Fig.28: examples of the index of repairability scores, with differently-colour icons for different score ranges. parts and specific criteria for individual devices. These criteria include the presence of a usage counter, remote assistance and the availability of software or firmware updates. As a pilot program from 1st January 2021, it initially applies to the following five products: laptops, smartphones, front-load washing machines, televisions and mowers (see Fig.27). It will be later extended to other products. By 2024, there will also be a durability index that rates a product’s durability. Indices of repairability are published at www.indicereparabilite. fr (see Fig.28). You can translate the pages with Google Translate by right-clicking in Chrome (and possibly other browsers). The index is calculated based on five criteria: documentation; ease of disassembly and access, tools, fasteners; spare parts availability; spare parts price; and criteria specific to the product category. will also mostly apply to the UK, since they trade heavily with the EU. EU laws Apart from French laws such as the Index of Repairability, new EU laws already came into effect on 1st March 2021. These require the supply of spare parts to professional repairers for certain appliances such as dishwashers, fridges, TVs and computer displays for seven to ten years. There are also new requirements that devices can be disassembled with standard tools, and that devices come with repair manuals (welders and computer servers were already covered under previous rules). A prominent European right to repair lobby group with a website at https://repair.eu/ feels that the new laws don’t go far enough. These laws Australia currently has no right to repair laws; however, the Productivity Commission is holding an inquiry; see www.pc.gov.au/inquiries/current/ repair#issues A draft report is due in June 2021. In 2020, the ACCC released a discussion paper on farm machinery repairs at siliconchip.com.au/link/ab7e See also the section on tractors and other farm machinery above. siliconchip.com.au US laws The USA is where the right to repair movement started, and laws were first passed in Massachusetts in 2012 concerning repair issues for motor vehicles. These required manufacturers to provide the necessary information to independent repairers. Car manufacturers voluntarily agreed to observe the provisions of the Massachusetts law in all other states for the 2018 model year. The law was amended in 2020 to remove loopholes used by Tesla, among others. At least 17 states now have right-to-repair legislation of various kinds. Someone in the USA went to prison over the right to repair. See the video titled “Do You Have a Right To Repair Your Phone? The Fight Between Big Tech and Consumers” at https://youtu. be/urPMZwW52Z8 Australian laws and inquiries Other considerations It may well be that much right to repair legislation will become unnecessary. Market forces will provide easily repairable items if that is what consumers demand. Two such examples mentioned above are the Fairphone and Belarus tractors. SC Australia’s electronics magazine We asked our (non!)-resident serviceman, Dave Thompson, what he thought about this article and here is his response... “ Having just read Dr David Maddison’s excellent article on the right to repair, I agree 110% with all the points he makes. I have long railed against those dumb anti-tamper fasteners and deride any company’s attempts to prevent a device from being repaired by anyone with the wherewithal to want to do it, whether they succeed or not. I acknowledge any company’s right to protect their copyright and IP, including having watertight policies regarding voiding of warranties for their products. But I object to those who build in premature end-of-life, deliberate obsolescence or otherwise impede the right to repair, and I’ll continue to raise my voice against those practices. I come from a generation who rolled their sleeves up, broke out the tools and had a go, rather than being shoe-horned into the often expensive and drawn-out repair systems offered by many official servicing agents. Obviously, this carries some risks, though many service-people (with the skills to pull any given repair off) will weigh this against any downsides such as voiding warranties or junking the item in question. At least this is our choice. My point is that deliberately nobbling a device to prevent anybody but the typically slow and money-gouging repair agents to service it is very much against my principles. As such, I’ll continue to fight for the right to repair. ” June 2021  23 What’s your transport mode? Shanks’ Pony? Car? RV? Boat? Plane? Hot Air Balloon? With a 3.5in touchscreen, our new Advanced GPS Computer is a great tool for on the road, in the water or even up in the sky. It can be customised to exactly how you want it. You’ll wonder how you ever did without it! Advanced GPS Computer Part I – by Tim Blythman T he Touchscreen Boat Computer with GPS has been a phenomenally popular project. First released five years ago (April 2016; siliconchip. com.au/Article/9887), it became one of the first projects to show just how handy and versatile the first Micromite LCD BackPack could be. Over the years, we’ve had numerous requests for features to be added. It was clear that people weren’t just using it in their boats, but on the road, in the bush and even in the sky. The latest minor revisions came in November last year, with two contributors to Circuit Notebook each adding their own touches (see siliconchip.com.au/Article/14644). One example was tweaked to provide three simple screens for use on the road. One screen provides GPS ground speed and a compass display, while the others show the time, date and satellite data. The second example is also designed as a speedometer, and adds automatic backlight control. So we thought, why not combine all these features (and more) into a newer and even better unit? It could use the larger 3.5in touchscreen to make the display more visible, with software changes so that users could adjust the displays to their liking. 24 Silicon Chip While doing this, it also made sense to integrate the features of our GPS Finesaver with Automatic Volume Control from June 2019 (siliconchip.com.au/Article/11673). That project also needed an update, mainly to give it a larger display. So the Advanced GPS Computer supersedes both the GPS Boat Computer and the GPS Finesaver, combining the features of both and adding new capabilities and refinements. The new GPS Computer The GPS Computer is a culmination of all these features and advancements. Naturally, it incorporates the POI (Point Of Interest) feature from the Boat Computer. This allows GPS coordinates to be ‘bookmarked’. The GPS Computer can then display the heading and distance to the POI, allowing simple navigation, or perhaps helping you to find that favourite fishing spot again! It won’t give you turn-by-turn navigation, but it can at least point you in the right direction. The large speedometer display is also present, as are numerous other GPS and time-related data. These include latitude, longitude, altitude, compass heading and average speed. Australia’s electronics magazine siliconchip.com.au The automatic volume control feature from the GPS Finesaver works precisely like it did in that device. You can feed audio through the device, via a 3.5mm stereo jack socket, and it will automatically adjust the volume according to vehicle speed. The output is louder at higher speeds, to help overcome increased noise from the vehicle. Our GPS Finesaver article goes into more detail about why this is a handy feature to have. Our revised design adds many more new functions. An audio synthesiser can inject warning sounds, alerts and even spoken words to the audio path, which can be fed either to the 3.5mm output jack or a small onboard amplifier and speaker. An RTC (real-time clock) IC provides accurate timekeeping, even if the GPS receiver has not locked onto enough satellites. A rechargeable battery provides an integrated power supply. The battery state is displayed onscreen, and the unit allows low-power sleep operation, which keeps the GPS active as well as a complete power-off mode. But we think that the most important new feature is the high degree of customisation that is possible. Four user-customisable displays are available that can be changed to show various parameters in different units. The displayed screens are also fully customisable to show exactly the combination of information that you want. As the user interface is written in MMBasic, it can be further tweaked by advanced users as needed. Hardware Our photos show the main electronics for the GPS Computer consisting of three boards sandwiched together. This stack fits neatly into a plastic UB3 Jiffy box. The top two boards will be familiar to readers as the Micromite V3 BackPack and its accompanying 3.5in LCD touchscreen. If you aren’t familiar with that device, we recommend reading the article describing it in the August 2019 issue Features & Specifica tions • Based on Micromite LCD BackPack V3 with 3.5in LCD touchscreen • Custom display and inf ormation screens including current and average speed along with time • Powered by a rechargea ble batter y and/or DC sup ply • Adds automatic volum e control to vehicle entert ainment systems • Automatic backlight con trol • Programmed in MMBas ic • Points of interest (POIs) can be saved and navigated to • Internal speaker for wa rning announcements and tones (siliconchip.com.au/Article/11764). The Micromite V3 BackPack used here is close to its minimum configuration. JP1 is fitted so it will draw power from its USB socket, and it is set up for pulse-width modulation (PWM) backlight control. This is necessary to allow for automatic backlight adjustment. The only optional parts fitted to the V3 BackPack board are to enable the RTC feature, and include the DS3231 clock IC and its accompanying passives; two 4.7kΩ I2C pull-up resistors and a 100nF bypass capacitor. Also, a two-pin header is fitted to the BackPack’s CON9 to supply power to the battery input of the RTC IC. The other optional parts supported by the V3 BackPack should not be fitted as they might conflict with some pin assignments. In particular, the parts in the flash IC box must not be fitted, nor should the IR receiver. The latter won’t cause a conflict, but the receiver is unusable from within MMBasic when programmed with this project’s software. Add-on PCB The third board in the stack mentioned earlier is the custom add-board for this project. It just plugs into the Micromite BackPack, and the circuit for this board is shown in Fig.1. One of the frequently suggested improvements we had for the GPS Finesaver from June 2019 was that its display was too small. The Advanced GPS Computer offers a speed display which takes up most of the 3.5in LCD. And if you don’t want a speed display, you can customise it to include a selection of other information. siliconchip.com.au Australia’s electronics magazine June 2021  25 The Advanced GPS computer PCB fits to the rear of a stack consisting of a Micromite V3 BackPack and a 3.5in LCD. A tactile switch can be mounted to the rear at the pads labelled SW2 (S2) to allow operation from the rear of a UB3 Jiffy Box. Note that an integrated Li-ion battery and holder fit into a cutout within the rear PCB. Connection to the BackPack is via three headers. The 18-way and four-way headers provide connections for the Micromite’s I/O and power pins, as for most Micromite projects, while two-way header CON4 connects to the BackPack’s CON9 as noted above. About half of the components on the GPS Computer PCB are to implement the automatic volume control function, which is broadly the same as that implemented in the GPS Finesaver. We’ll start with that. Audio path Stereo audio comes in via 3.5mm jack CON1. We’ll follow one audio channel signal as they are identical. A 100kΩ resistor DC-biases the signal to ground to prevent it from floating when nothing is connected, after which it passes through a 1kΩ series resistor. This protects against high currents flowing into the device, and blocks RF signals that the external wiring might pick up. The signal is AC-coupled by a 1µF ceramic capacitor and biased (via a 22kΩ resistor) to a 2.5V mid-rail. This rail is generated by a pair of 10kΩ resistors across the 5V supply, bypassed by a 220µF capacitor to eliminate supply noise. IC1 is an MCP4251 5kΩ dual gang digital potentiometer with 257 steps. The ‘lower’ end of the track (pin 10 for the left channel or pin 5 for the right channel) is tied to the 2.5V rail, while the other ends are connected to the conditioned audio signals (pin 8 for the left channel, and pin 7 for the right). The 5kΩ resistance in series with the 1kΩ input resistance 26 Silicon Chip and the biasing components means that the signals at pins 7 & 8 are around 80% of the initial magnitude. The signals on the potentiometer ‘wipers’, pins 9 (left) and 6 (right), are attenuated depending on the internal potentiometer setting. This is controlled by an SPI serial bus on pins 1 (CS), 2 (SCK) and 3 (SDI) of IC1. The bus is driven from pins 10, 25 and 3 of the Micromite respectively, via the 18-way I/O header. Note that the MCP4251 is designed to accept different analog and digital voltage levels. So it will happily accept the 3.3V digital control signals from the Micromite alongside the 5V maximum audio signals and digital supply voltage. Dual-channel rail-to-rail op amp IC2 is set up to provide a gain of about three times, both to improve the output drive level and expand the volume range. Thus, the fullscale output corresponds to around 240% of the incoming signal; close to 1% per potentiometer step. A rail-to-rail op amp is needed here due to the narrow Fig.1 (opposite): the Micromite V3 BackPack PCB includes the USB data interface, a 32-bit microcontroller, the touchscreen interface and a DS3231 real-time clock IC. The remaining functions are on the GPS Computer PCB, the circuit of which is shown here. It primarily has a GPS module for speed, time and location data, a digital pot for volume control, op amps for signal conditioning, a power amplifier to drive the small speaker for warning sounds, plus a Li-ion battery charger that runs from 5V. Australia’s electronics magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine June 2021  27 supply range. We’ve specified an LMC6482, but other similar rail-to-rail devices like the MCP6272 should work fine. Both IC1 and IC2 have 100nF supply bypass capacitors. The volume-adjusted audio is fed into non-inverting input pins 3 and 5 (left and right) of IC2, with a 10kΩ/5.1kΩ divider connected between the output pins (1 for left and 7 for right) and inverting input pins (2 for left and 6 for right). These dividers set the gains to around three times. The output signals are AC-coupled and passed through 100Ω resistors to ensure stability and protect the op amp outputs, then biased to ground via 22kΩ resistors and made available at CON2, the 3.5mm output socket. Signal injection Another signal can be injected into the audio path from the Micromite’s pin 24, which is PWM-capable and thus can generate tones or PWMsynthesised analog signals. The signal from pin 24 is fed into VR1 to provide level control. VR1, the 470Ω series resistor and 10nF capacitor form a low-pass filter to remove any supersonic artefacts from PWM analog signal synthesis. At this point, there are two options for where this synthesised audio signal goes. With two jumpers on each of JP1/ JP2 (across positions 1 & 2, and positions 3 & 4), the 2.2kΩ resistors and 1µF capacitors AC-couple this signal into the left and right channels of the existing stereo path, just before they are fed into IC1. This has the advantage that the warning sounds will be heard through your vehicle speakers. The disadvantage is that these components introduce a small amount of cross-talk between the channels, reducing stereo separation slightly. In this mode, the jumpers on positions 3 & 4 feed the audio from the op amp outputs to a pair of mixer resistors and then into inverting input pin 4 of SSM2211 audio amplifier IC3. Its non-inverting pin, pin 3 is tied to pin 2, which outputs a mid-rail bias voltage and is bypassed by a 100nF capacitor. A second 100nF capacitor provides supply bypassing between, pins 6 and 7. IC3’s SHDN pin 1 is held low to enable the amplifier. The output signal from pin 5 is fed back to pin 4 via a 22kΩ resistor, giving close to unity gain, as the two 47kΩ input resistors are effectively in parallel. A speaker connected at CON3 is driven by the push-pull signal from pins 5 and 8 of IC3. The unity-gain setting means that (as much as possible) the full 5V headroom is available to both the op amp and amplifier. IC3 is capable of delivering around 1W into 8Ω or up to 1.5W into 4Ω. The alternative configuration is to have a single jumper on both JP1 and JP2, between positions 2 & 3. This keeps the 3.5mm audio path separate from the synthesised audio, and only the synthesised audio is fed to the speaker connected to CON3. Battery circuitry A small Li-ion cell is connected to the circuit at the BAT+ and BAT- terminals. A slot in the PCB provides space for a 14500-size cell (roughly the same as AA cells). The cell can be connected via a PCB-mounting cell holder, or by soldering the cell tabs directly to the PCB. It provides power to the real-time clock IC on the BackPack via D2 and CON4. The diode drops the voltage slightly from the 4.2V that a fully-charged Li-ion cell delivers, reducing the quiescent current slightly. The diode also prevents power from being fed back into the cell. The cell is charged from 5V USB power when available. IC4 is an MCP73831 battery charging IC (in a small SOT-23-5 SMD package). The 4.7µF supply bypass capacitor between pins 4 (VIN) and 2 (ground) is as specified in the data sheet, while the 10kΩ resistor between pin 5 (PROG) and ground sets the charge current to a nominal 100mA. The cell and another 4.7µF capacitor are connected between pin 3 (BATTERY) and ground. Pin 1 (STAT) is driven low during charging and high when charging is complete. This is displayed on bi-colour LED1, with one lead connected to the STAT pin and the other to the midpoint of a 1kΩ/1kΩ divider between 5V and ground. When STAT is low, the red LED illuminates with current flowing via the upper resistor, while the green LED illuminates when charging completes, STAT goes high and current flows through the lower resistor. With 5V power absent, the LED is off, and no current flows through the divider. Schottky diode D1 feeds the battery voltage into the rest of the circuit, and is forward-biased when the circuit is drawing current from the cell. The diode is needed to prevent the 5V supply from being back-fed directly Many readers have made their own tweaks to the various screens used by the older Micromite Boat Computer. This new GPS Computer allows custom screens to be laid out without having to delve into the MMBasic code. At left, we see the screen that allows various tiles to be placed, while at right, the screen is seen in use, containing exactly the information that is needed. 28 Silicon Chip Australia’s electronics magazine siliconchip.com.au into the cell when powered externally. High-side P-channel Mosfet Q1 switches battery power to the majority of the circuit, but is usually held off by the 1kΩ resistor between its source and gate. The gate can be pulled low by switches S1 or S2, or N-channel Mosfet Q2. When the gate is pulled down, the battery supplies power to the circuit. Mosfet Q2 is similarly held off by the 10kΩ resistor on its gate, and can be turned on by Micromite pin 9 going high. S1 is simply a two-pin header to which any momentary switch can be wired, while S2 is a PCB footprint suiting a tactile switch; in effect, they (and Q2’s drain and source) are simply connected in parallel. Typical operation is as follows. When USB power is applied, the Micromite starts up and runs its program. One of the first things it does is pull pin 9 high, so that Q2 conducts and thus Q1 is switched on. This means that if USB power is removed, the Micromite will continue to run from the battery. If the Micromite wishes to shut down and stop running from the battery (either due to the battery being depleted or a user request), it pulls pin 9 low, shutting off Q1 and disconnecting its own supply. If the user wishes to start up the Micromite from battery power, they simply press S1 or S2 for a second, turning on Q1 and allowing the Micromite to start up. It then sets pin 9 high which latches Q1, allowing the switch to be released. Sensing A handful of other components are provided to sense some other parameters. LDR1 and a 1MΩ resistor form a divider with an output voltage related to the current ambient light intensity. This is filtered by a 100nF capacitor, to avoid sudden changes, and read by the ADC (analog-to-digital converter) peripheral on the Micromite’s pin 4. The software uses the resulting value to modulate the LCD backlight brightness. With a nominal LDR resistance between 100kΩ and 10MΩ, the measured voltage spans around 0.3V to 3V. It is mapped to brightness levels selected by the user. The backlight brightness is controlled by a PWM signal from the Micromite’s pin 26 and effected by components on the V3 BackPack board. siliconchip.com.au Parts list – Advanced GPS Computer 1 Micromite LCD BackPack V3 with DS3231 RTC (see below) 1 double-sided PCB coded 05102211, 123x58mm 1 UB3 Jiffy box 1 laser-cut acrylic panel to suit (Cat SC5856) 1 VK2828U7G5LF or similar GPS module (GPS1) [Cat SC3362] 1 PCB-mount AA cell holder (for BAT1) 1 14500 Li-ion cell with nipple (BAT1) 2 PCB-mount switched stereo 3.5mm sockets (CON1,CON2) [eg, Altronics P0094] 1 small, slim 4-8Ω 1W speaker [eg, Digi-Key 2104-SM230808-1] 1 100kΩ-10MΩ LDR (LDR1) [ORP12 or equivalent; eg, Jaycar RD3480] 1 tactile switch (S1/S2) [see text for overall height considerations and alternatives] 1 2-pin male header (CON4) 1 18-pin male header (CON5) 3 4-pin male headers (CON6,JP1,JP2) 4 jumper shunts (JP1,JP2) 4 M3 x 15mm panhead machine screws 4 M3 x 10mm panhead machine screws 4 M3 x 12mm tapped spacers 4 M3 x 10mm tapped or untapped spacers 4 M3 Nylon washers 1 10cm length of 1.5mm diameter heatshrink tubing 1 10cm length of light-duty hookup wire (for the speaker) Semiconductors 1 MCP4251-502E/P dual 5kW digital potentiometer, DIP-14 (IC1) 1 LMC6482AIN dual rail-to-rail op amp, DIP-8 (IC2) [MCP6272 is a substitute] 1 SSM2211SZ push-pull 1.5W amplifier, SOIC-8 (IC3) [Digi-Key, Mouser, RS] 1 MCP73831T-2ACI/OT Li-ion battery charger, SOT-23-5 (IC4) [Digi-Key, Mouser, RS] 1 3mm bi-colour (2-wire) red/green LED (LED1) 1 1N5819 1A schottky diode (D1) 1 1N4148 small signal diode (D2) 1 IRLML2244 P-channel Mosfet, SOT-23 (Q1) 1 2N7002 N-channel Mosfet, SOT-23 (Q2) Capacitors 1 220µF 16V electrolytic 2 4.7µF 16V multi-layer ceramic [eg, RCER71H475K3K1H03B from Digi-Key, Mouser or RS] 6 1µF 50V multi-layer ceramic [eg, Jaycar RC5499] 5 100nF 63V/100V MKT (Code 104 or 100n) 1 10nF 63V/100V MKT (Code 103 or 10n) Resistors (all 1/4W axial 1% metal film) 1 1MΩ (Code brown black green brown or brown black black yellow brown) 2 100kΩ (Code brown black yellow brown or brown black black orange brown) 2 47kΩ (Code yellow violet orange brown or yellow violet black red brown) 5 22kΩ (Code red red orange brown or red red black red brown) 6 10kΩ (Code brown black orange brown or brown black black red brown) 2 5.1kΩ (Code green brown red brown or green brown black brown brown) 2 2.2kΩ (Code red red red brown or red red black brown brown) 5 1kΩ (Code brown black red brown or brown black black brown brown) 1 470Ω (Code yellow violet brown brown or yellow violet black black brown) 2 100Ω (Code brown black brown brown or brown black black black brown) 1 1kΩ mini horizontal trimpot (Code 102) Additional parts for V3 BackPack PCB (In addition to the basic 3.5in BackPack V3 kit, Cat SC5082) 1 DS3231 real-time IC, SOIC-16 (IC4) [Cat SC5103] 1 2-pin female header socket (CON9) 1 18-pin female header socket (for Micromite I/O) 1 4-pin female header socket (for Micromite power) 1 100nF MKT capacitor 2 4.7kΩ 1% 1/4W axial resistors Australia’s electronics magazine June 2021  29 an accurate 3.3V supply voltage as the calculated pin voltage is based on an assumed 3.3V supply. On a 5V USB supply, the 3.3V regulator has no trouble maintaining this. When running from battery power, the Li-ion cell is not allowed to discharge below about 3.6V. Otherwise, the Micromite chip’s supply can drop below 3.3V (dropping about 0.2V due to D1 and another 0.2V in the regulator), which would affect ADC readings. This is also why LiFePO4 cells are not suitable for this design, as their normal operating voltage is below 3.6V. GPS receiver An LDR and LED fitted to the Advanced GPS Computer PCB protrude through the front of the enclosure. Their leads are protected by yellow heatshrink. This view also shows how the battery holder is recessed. The supply voltage is also monitored, by reading the voltage on the audio circuit’s mid-rail divider, via pin 5. The measured battery divider voltage is doubled in software to get its actual value. Two thresholds are used to determine the GPS Computer’s power state – the upper level discriminates between the 5V delivered by USB power, and the 4.3V of a fully-charged cell. A second threshold is used to determine a lower limit for the battery, to allow the Micromite to shut down before the battery is discharged excessively. Between these thresholds, a rough state-of-charge figure is calculated and is displayed when running from battery power. The Micromite’s pins 4 and 5 are also used for in-circuit programming, so the GPS Computer PCB must be disconnected if the chip needs to be reprogrammed. The optional flash IC that can be installed on the V3 BackPack uses pin 4 too; thus, it also would conflict with the GPS Computer’s operation. The 3.3V reference for the Micromite’s ADC depends strongly on having 30 Silicon Chip Of course, it wouldn’t be a GPS computer without being able to receive a GPS signal. Six-way header GPS1 allows a GPS module, such as the VK2828 type, to be attached. The header provides power and routes the GPS serial data back to the Micromite’s COM1 RX at pin 22. Power is supplied to the GPS module from the battery downstream of D1, allowing the 5V supply to preferentially feed the GPS module when available (via Q1). If this were not done, the GPS module would draw current from the battery even when USB power was available, and the charging circuit would not detect that charging is complete. The GPS module’s EN pin is connected to the nominal 5V rail, allowing the GPS module to go into lowpower mode when the GPS Computer switches off (either USB power is unavailable or Q1 is off). This allows the GPS module to retain satellite information when the GPS Computer is off, allowing faster satellite acquisition when needed. While the VK2828 datasheet indicates a 40µA power-down current, we measured around 2mA being consumed by the module. Removing the POWER LED on the GPS module saw this fall to the expected value. Software operation The photos of the GPS Computer that we’ve presented should give you a good idea of its capabilities; there isn’t much mystery as to how it achieves what it does. The Micromite receives GPS data from the GPS module and displays it on the LCD screen. Of course, there is quite a bit more going on than that suggests. We Australia’s electronics magazine wouldn’t be surprised if readers find some interesting ways to use the software we’ve written. CFUNCTIONs Micromite’s MMBasic is very powerful, but it isn’t especially fast. Fortunately, there is the option to incorporate so-called CSUBs and CFUNCTIONs into a program. These are effectively precompiled machine-code routines that can run without the MMBasic interpreter’s overhead, but can be invoked from the MMBasic code. We use the CSUBs and CFUNCTIONs for three broad roles. The first is controlling the 3.5in LCD panel. There is no native driver for the ILI9488 display controller on the 3.5in panel, and it would be far to slow to do this in MMBasic. We’ve used this code previously in the RCL Substitution Box from June and July 2020 (siliconchip. com.au/Series/345). The two other functions are diverse, but are combined into another CFUNCTION specifically for the GPS Computer. One handles audio synthesis, while the other processes data from the GPS receiver. Audio production While it is easy to create rough square-wave tones using a PWM output, they sound harsh. So we’ve written code that can play back PCM-coded audio samples. It’s limited to 8-bit data at 8kHz, as that is a reasonable compromise between the amount of space needed to store the samples and sound quality. The PIC32MX170’s TIMER1 is pressed into service as the 8kHz sampling timer. Since the IR receiver function on the Micromite also depends on TIMER1, these functions cannot be used at the same time; hence, our comment earlier that there is no point fitting the IR receiver. Pin 24 is set up to output the 8-bit PWM signal on a 156kHz carrier. With 256 levels, 156kHz is the highest PWM frequency available with a 40MHz processor clock. The RC filter noted earlier removes the 156kHz carrier, leaving just the audio frequency components. When stored in memory, each audio sample data set is preceded by a 32-bit number indicating its length. During playback, the timer interrupt steps through the data until it reaches the end, after which it shuts down the PWM signal. siliconchip.com.au A software flag can cause Prefix System the sample to loop, allow$GP GPS (USA) ing sounds to be compactly $GA Galileo (Europe) stored as just one cycle in $GL GLONASS (Russia) memory. For example, a $GB Beidou (China) 400Hz sine wave cycle can $GN Combined data from more than one GNSS be stored as 20 samples if Table 1: GNSS prefixes the sampling rate is 8kHz. With the PIC32’s flat 32-bit address sound is not great. But it’s recognisable space, these can be stored in flash and makes for a very intuitive interface. So the GPS Computer can deliver memory (program storage) or RAM (eg, variables). So the MMBasic code can either sampled audio or synthesised create samples at runtime, then play speech, although not at the same time, since they are output on the same pin. them back. There is also a facility to produce synthesised vocal effects using GPS CFUNCTION Our CFUNCTION also contains so-called Linear Predictive Coding compression. LPC is a very efficient routines to help process the NMEAcompression method for reproducing formatted data from the GPS module. the human voice. It’s what was used While MMBasic is quite capable of in many talking toys from the early performing this task, the CFUNCTION 1980s, such as the Texas Instruments speeds this up considerably, leaving more time for other tasks. Speak & Spell. The GPS data stream consists of a The compression is remarkable, needing fewer than 200 bytes per sec- series of ‘sentences’ which contain a ond. While Texas Instruments pro- variety of data. You can read more about duced custom ICs to convert this to their structure and content on p63 in speech, it’s now possible to do this in our April 2018 “Clayton’s GPS” project (siliconchip.com.au/Article/11039). software. Our code defines several parsers, The easiest method is to use the open-source Arduino “Talkie” library, each corresponding to a sentence type, which can be found at https://github. which is recognised from its prefix. Each parser then processes the data com/ArminJo/Talkie This allows an Arduino Uno (and into an MMBasic string array if it is other similar boards) to process LPC valid and correct, and sets a flag to let the main program know that new data data into audio. That page also has links describing how the LPC data is stored is available. We’ve also created some routines to and decoded. We’ve included this functionality in decode the curious latitude and longithe CFUNCTION to process LPC data to tude formats used in NMEA data. One generate synthesised speech. Like any routine extracts the number of degrees, data that has been heavily compressed another the number of minutes and a and output at a low sample rate, the third, the fractional number of seconds. There are a total of 23 different tiles that can be placed, including numerous parameters drawn from the GPS data and related to selected POIs (points of interest). A number of tiles appear as buttons, adding further functions to a screen, such as being able to quickly access a different screen. siliconchip.com.au With several different satellite navigation systems coming online to complement GPS, we’re also seeing variations in the data that receivers produce. Such systems include the Russian GLONASS and Chinese Beidou systems. (See our article in the November 2019 issue at siliconchip.com.au/Article/12083). For example, some receivers now generate sentence prefixes of “$GN” instead of “$GP”, even though the data is otherwise identical. This simply reflects that the receiver is using a different satellite system to calculate its position. The various strings generated by different types of receivers are shown in Table 1 above. But since it is only the third character of these sentences that changes, we simply ignore it instead of checking it, allowing the unit to process data from any receiver which outputs a similar format. Part II next month . . . In the next issue, we’ll describe construction of the Advanced GPS Computer PCB, modification of the Micromite V3 BackPack to add a realtime clock IC, loading of software and how to assemble the parts into a completed unit. Since we expect some people to be interested in making their own changes to the software, as they did with the previous GPS Computer, we’ll also delve deeper into how various parts of the software work. You might even be curious about using the various CFUNCTIONs in your own projects. SC One tile which we are sure will be popular is a simple, clear, large, easy-to-read speed readout. The units can be changed between many common road, nautical and aeronautical formats. There’s even enough room left over to add a handful of other tiles below this. Australia’s electronics magazine June 2021  31 The History of the Universal Serial Bus USB Explosion! About 26 years ago, a group of companies developed the Universal Serial Bus or USB to make it easier to connect external devices to PCs, replacing the plethora of connectors and interfaces that had been used previously. It also greatly increased communications speed compared to existing serial protocols. Since then, the performance and uses of USB have grown dramatically. By Jim Rowe W hen the first generation of PCs or personal computers appeared in the 1970s – machines like the MITS Altair, the Commodore PET, the Tandy TRS-80 and the Apple ][ – they were somewhat limited in their ability to connect to peripheral devices like printers, modems and external tape or disk drives. But when IBM released their first PC (the 5150) in 1981, things started to change. The IBM 5150 PC was available with up to two built-in floppy disk drives, 16KB of RAM and a colour graphics card (for which a colour monitor was available). Importantly, it also had slots at the rear for plug-in interface cards to provide a Centronics parallel printer port and one or two RS-232C serial ports. Before long, you could also connect the PC to a 10MB hard disk. Many new PCs then started to appear, most of them offering similar features. By about 1990, just about every available PC had around 64KB of RAM, a built-in 20MB hard disk, a colour graphics card or adaptor and both a Centronics printer port and a couple of RS-232C serial ports. Many could also take a plug-in Ethernet card, so that they could be connected to a LAN (local area network). A variety of more specialised interfaces started to appear as well; for example, one to connect to the GPIB bus to control test instruments from a computer. There was also “FireWire” (IEEE1394), a high-bandwidth serial bus designed to efficiently connect peripherals like high-speed disk drives. Soon, the back of many PCs had a multitude of different interface connectors, to connect many peripherals. USB is born The development of USB began in 1994, when a group of companies that were heavily involved in the PC industry (Compaq, DEC, IBM, Intel, Microsoft, NEC and Nortel) got together and decided to make it easier to connect external devices to PCs. This would involve replacing all of the different interface connectors with a group of simpler, identical multipurpose connectors which could each be configured by software to perform a variety of interfacing tasks. So was born the Universal Serial Bus, almost immediately identified by the acronym USB. The official USB 1.0 specification was introduced in January 1996, and it defined two data rates: 1.5Mb/s (187.5KB/s), called Low Speed or Low Bandwidth (designed for peripherals like keyboards, mice and joysticks) The original USB cable for connecting peripherals like printers, with a fullsize Type-A plug at the computer end (right), and a Type-B plug at the device end (left). This appears on USB devices which the USB Implementers Forum has checked and considers to perform acceptably. 32 Silicon Chip Australia’s electronics magazine siliconchip.com.au This USB icon, or a variation of it, generally appears on or nearly all USB-compatible plugs and sockets. A variation of the USB-IF certification logo which appears on devices that are compatible with USB 2.0+ at 480Mbps. The square Type-B plug is too big for slim devices like smartphones and tablets, so the smaller mini Type-A (left) and Type-B (right) plugs were designed. These are still used by some cheaper devices, especially those which use USB 5V for charging, but have mostly been superseded by the micro Type-B or Type-C sockets now. The USB type-B micro plug and socket solved several problems with the mini type-B socket; besides being considerably slimmer, it’s also designed so that the plug wears out well before the socket, avoiding premature socket wear and ultimately, the need for replacement. The USB connectors that started it all. The rectangular Type-A appears on host devices like computers, while the square Type-B is used for peripherals like printers. This makes it difficult to accidentally plug two host or device ports together, which at best would do nothing, and at worst, cause damage. and 12Mb/s (1.5MB/s), called Full Speed (to handle higher speed peripherals like printers, disk drives etc). Intel produced the first interface ICs designed to support USB in 1995, but few USB devices or PCs equipped with USB ports appeared on the market until August 1998, when the USB 1.1 specification was released. This was soon widely adopted, leading to what Microsoft dubbed the “legacy-free PC”. The USB connectors used for these initial implementations were the flat-rectangle Type A socket (or receptacle) for the ‘downstream’ ports on a PC, and the square-with-chamfers Type B socket for the ‘upstream’ port on a peripheral like a printer (see Fig.1). Both connectors had only four pins, two for data and two for providing 5V DC power to the peripheral. Most external devices were connected to a PC using a USB cable fitted with a Type A plug at the PC end and a Type B plug at the device end. The exterior of both types of plug were identified with a distinctive USB logo known as the “trident” (see above). This was the situation until April 2000, when a revised USB 2.0 specification was released. This added a third signalling rate of 480Mb/s (60MB/s), named High Speed or High Bandwidth, in addition to Low Speed and Full Speed. It also allowed for Mini-A and Mini-B connectors and cables, and before long, Micro-USB connectors and cables as well. Both the Mini-USB and Micro-USB connectors were provided with five pins, with the additional pin used for identifying the type of device, either peripheral or host, they were plugged into (‘device ID’). The USB 2.0 specification also allowed two peripheral devices to communicate directly, instead of only via a PC host – a feature called USB On-The-Go or USB-OTG. The specification was also expanded with support for dedicated battery chargers, as well as allowing increased current flow in a PC-to-peripheral USB cable compared with the original limit of 500mA (or 100mA for unconfigured devices). These days, when a device has a mix of USB 1.1 & USB 2.0 ports, the USB 1.1 ports tend to be colour coded with white plastic, while the USB 2.0 ports use black plastic. released in November 2008, when the overall management of USB was transferred from the USB 3.0 Promoter Group to the USB Implementers Forum (USB-IF). USB 3.0 added yet another transfer mode: SuperSpeed, providing for a nominal data rate of 5.0Gb/s (625MB/s) in addition to the three existing transfer rates. Communication in SuperSpeed mode is in full-duplex, whereas in the three earlier modes, it is in halfduplex. USB 3.0 also introduced the UASP protocol, which provides generally faster transfer speeds than the Bulk-Only-Transfer (BOT) protocol provided by USB 1.X and USB 2.0. The USB 3.0 specification added a range of backward-compatible plugs, sockets and cables. The SuperSpeed plugs and sockets have a total of nine pins (4 + 5) and are identified with a distinct logo and an internal insulation layer coloured in blue, in contrast with the black or white used for USB 1.1 and USB 2.0 connectors. Low-speed and high-speed devices remain operational in USB 3.0, but SuperSpeed devices can take advantage of the increase in available current to between 150mA and 900mA. We’ll siliconchip.com.au USB 3.0 arrives The USB 3.0 specification was Australia’s electronics magazine June 2021  33 You can clearly see the five new contacts and blue colour of this USB 3.0 socket. The USB-IF certification logo for devices compatible with USB 3.0 or later specifications at 5Gbps. Thunderbolt 1/2 uses the same connector as Mini DisplayPort and replaced FireWire on Apple computers. It merges PCI Express and DisplayPort signals and provides DC power. Source: https://w.wiki/o26 Thunderbolt 3 uses cables with the USB Type-C plug but provides more functions than just carrying data; it also offers more power than USB (eg, for charging laptops) and can carry video and even PCI Express lanes. USB 4.0 essentially merges Thunderbolt’s features into the USB lineup. Source: https://w.wiki/o27 34 Silicon Chip describe the various USB connectors and cables in detail a bit later. In July 2013, the USB 3.1 specification was released, providing two variations on the USB 3.0 SuperSpeed mode: USB 3.1 Gen1, much the same as the original USB 3.0 specification, and USB 3.1 Gen2, which introduces a new SuperSpeed+ transfer mode. SuperSpeed+ doubles the maximum data signalling rate to 10Gb/s (1.25GB/s), while reducing the line encoding overhead to just 3% by changing the encoding protocol to 128b/132b. Then in September 2017, the USB 3.2 specification was released. This introduced two more SuperSpeed+ transfer modes, designed to take advantage of the 24 pins (2 x 12) on the newly released USB-C connectors. Although the two rows of 12 pins had been provided initially to allow the Type C connectors to be inserted either way around, the USB 3.2 specification uses them to provide multilane operation (using additional wires in the cable) to allow data transfer rates of 10Gb/s or 20Gb/s (2.5GB/s). When computers have both USB 2.0/3.0 and USB 3.1/3.2 ports, typically the USB 3.1/3.2 ports will be colour-coded teal or yellow, with the USB 3.0 ports remaining blue and the older ports having black (USB 2.0) or white (USB 1.1) plastic. Thunderbolt 1, 2 & 3 Back in late 2008, Apple introduced a miniaturised version of the DisplayPort audio-visual digital interface, dubbed Mini DisplayPort or MiniDP. This replaced the DVI port on most of Apple’s models like the MacBook, MacBook Air, MacBook Pro, iMac, Mac Mini and Mac Pro. The MiniDP port also started to appear on notebooks from Asus, Microsoft, MSI, Lenovo, Toshiba, HP, Dell and other makers. Then in early 2011, Intel and Apple announced their Thunderbolt hardware interface, which combined the functions of PCI Express and MiniDP and superseded FireWire (IEEE1394). Thunderbolt cables combine copper and fibre-optic transmission, with the copper wires generally used to convey power while the optical fibres convey high-speed data. They use the 20-pin MiniDP connector. In June 2013, Intel announced Thunderbolt 2, which used the same connectors as Thunderbolt 1 but doubled Australia’s electronics magazine the data rate to 20Gb/s (2.5GB/s) by combining the two 10Gb/s channels. The first consumer products featuring Thunderbolt 2 were the Asus Z87-Deluxe/Quad motherboard and Apple’s Retina MacBook Pro, both released in the latter half of 2013. Then in 2015, Intel announced Thunderbolt 3, which doubled the maximum data rate again to 40Gb/s (5GB/s) while also halving power consumption. Using copper cables and the 24-pin USB-C connectors which had been introduced in 2014, Thunderbolt 3 can incorporate USB Power Delivery and transfer up to 100W of power along with the high-speed data. Devices with Thunderbolt 3 ports became available in November 2015, including notebooks from Acer, Asus, Clevo, HP, Dell, Dell Alienware, Lenovo, MSI, Razer and Sony running Microsoft Windows, as well as motherboards from Lintes Technology. Then in October 2016, Apple announced the updated MacBook Pro, featuring two or four Thunderbolt 3 ports depending on the model. USB-C The USB Type-C or USB-C specification was finalised by the USB-IF in August 2014, and is primarily associated with the miniature 24-pin (2 x 12-pin) USB-C connectors. Initially, these connectors were used with USB 3.1 interfaces so they could be inserted into the sockets either way around (they are also significantly more robust than Type-B mini or micro plugs). But when Thunderbolt 3 arrived in 2015, they were used for that as well. And when USB 3.2 arrived in late 2017, they also gained SuperSpeed+ capability. But note that a device fitted with a USB-C connector does not necessarily implement USB, USB Power Delivery or any of the defined Alternate Modes. An Alternate Mode dedicates some of the physical wires in a USB-C 3.1 cable being used for direct device-to-host transmission of other data protocols, such as DisplayPort. The four high-speed lanes, two sideband pins and (for docked, detachable device and permanent cable applications only) two USB 2.0 data pins and one configuration pin can be used for Alternate Mode transmission. The modes are configured using vendordefined messages (VDMs) through the configuration channel. siliconchip.com.au USB4 A further use for the USB-C connectors was defined in August 2019, when the USB-IF released the USB4 specification. USB4 is based on the Thunderbolt 3 protocol. It supports 40Gb/s (5GB/s) data throughput, is compatible with Thunderbolt 3 and backwards-compatible with USB 3.2 and USB 2.0. The architecture defines a method to share a single high-speed link with multiple end devices dynamically, designed to optimise the transfer of data by type and application. Thunderbolt 4 Thunderbolt 4 was announced in January 2020 at CES (the Consumer Electronics Show), and the final specification was released in July 2020. The main improvements are support for USB4 protocols and data rates, a minimum bandwidth requirement of 32Gb/s for PCIe link, support for dual 4K (or one 8K) displays, and Intel VT-d-based direct memory access (DMA) protection to prevent physical DMA attacks. The maximum bandwidth remains at 40Gb/s, the same as Thunderbolt 3 and four times faster than USB 3.2 Gen2x1. Still, the minimum that vendors are required to implement has been doubled from the 16Gb/s previously allowed in the Thunderbolt 3 specification. USB Power Delivery (USB PD) In July 2012, the USB Promoter Group finalised a USB Power Delivery specification (USB PD rev.1), to permit uniformly powering or charging laptops, tablets, USB-powered disk drives and similarly higher-powered consumer electronics. It is a logical extension of existing European and Chinese mobile telephone charging standards. The USB PD rev.1 extension specifies using certified “PD aware” USB cables with standard USB Type A and Type B connectors, to deliver increased power (more than 7.5W) to devices with greater power demands. Devices can request higher currents and voltages from compliant hosts – up to 2A at 5V (10W), and optionally up to 3A or 5A at either 12V (36W or 60W) or 20V (60W or 100W). In all cases, both host-to-device and device-to-host configurations are supported. The power configuration siliconchip.com.au protocol uses a 24MHz Binary FSK (frequency-shift keying) transmission channel on the Vbus line. Revision 2.0 of the USB PD specification (USB PD Rev.2.0) was released in August 2014 as part of the USB 3.1 specification. It covers the use of USB-C cables and connectors with four power/ ground pairs and a separate configuration channel, using DC-coupled low-frequency BMC (Biphase Mark Code or Differential Manchester) data encoding to reduce the possibility of RF interference. Since then, there have been further revisions of USB PD Rev.2.0. In March 2016, version 1.2 was released, creating new USB PD Power Rules which define four nominal voltage levels (5V, 9V, 12V and 20V) and output power levels ranging from 0.5W to 100W. Then in January 2017, the USB-IF released USB PD revision 3.0, which defines a programmable power supply (PPS) protocol that allows control of Vbus power in 20mV steps, to facilitate both constant current (CC) and constant voltage (CV) battery charging. This was followed up in January 2018 with the release of a “Certified USB Fast Charger” logo, for chargers that use the USB PD 3.0 programmable power supply protocol. USB connectors & cables There are now so many different USB connectors in use that it isn’t feasible to discuss them all in detail. But we have prepared some information to help you recognise the most common types of connectors and cables. As mentioned earlier, Fig.1 shows the ones you’re probably most familiar with: the Type-A socket and plug and the Type-B socket and plug. These are the original four-pin USB connectors, with the Type-A connectors intended to be used at the host/PC end, and the Type-B connectors at the peripheral/ external device end of the USB cable linking the two. The table below them shows the names usually given to the four pins, the nominated colour of the insulation for each wire, and the description of its function. Note that in a USB cable, the D- and D+ wires are a ‘twisted pair’, to reduce the risk of electromagnetic interference (EMI) – both in terms of reducing emissions and avoiding problems with EMI pickup. Australia’s electronics magazine The logo used on the fastest USB devices available today. USB Type-C plugs have more contacts, and they are arranged symmetrically so that the plug can be inserted either way around and it will still work. A closer view of the USB Type-C plug clearly showing all 24 contacts. This design appears on plugs and near sockets that support the fastest 40Gbps speed of USB4. A USB-IF certification logo for a device which supports USB-PD at up to 45W. This involves supplying both higher voltages and currents than the normal 5V/500mA at the request of the device. June 2021  35 These miniaturised versions of the original Type-B connector are much more suitable for smaller devices like mobile phones and tablets. They add a fifth Device ID pin and importantly, the micro Type-B plug is designed to wear out rather than the socket, so you just have to replace the cable if the plug wears out, instead of the socket or the whole device. The new plugs and sockets of USB 3.0/4.0 add five new contacts to carry higher bandwidth signals. They are designed so that USB 1.0-2.0 devices can still be plugged in and operate normally over the same four pins they have always used. USB 3.0/4.0 devices can plug into an earlier style Type-A socket, but the extra pins will not make contact, so communications occur at a slower speed. 36 Silicon Chip Fig.2 shows the Mini-USB and Micro-USB connectors, still used for connections to many compact devices like tablets and PDAs (personal digital assistants), smartphone and digital cameras. Although there were Mini Type-A plugs and sockets when USB 2.0 and Mini-USB were introduced in 2000, they were officially ‘deprecated’ in 2007 along with a Mini Type-AB socket. That is why you won’t come across many of them nowadays, and as a result, we haven’t shown them. The same applies to Micro Type-A plugs and sockets. It’s worth noting that although the functional part of Micro-USB plugs is similar in width to Mini-USB plugs, they are approximately half their thickness. Despite this, they are rated for at least 10,000 connect-disconnect cycles, which is significantly more than the Mini-USB plugs. Fig.3 shows the details of the USB 3.0 SuperSpeed connectors that were introduced in 2008. They are essentially a modified version of the original Type-A and Type-B connectors, with five pins added to cope with the SuperSpeed requirements, while keeping backwards compatibility with USB 1.X and USB 2.X. Perhaps the most obvious difference at first sight (especially with the Type-A connectors) is the blue colour of the plastic insulation inside the connectors, compared with the white or black insulation inside the earlier connectors. Inside the Type-A connectors, the additional five contacts are located a short distance away from the first four, parallel with them and spaced slightly further apart. On the other hand, in the Type-B connectors, the top of the functional part of the connector is extended upwards by about 3mm, with all of the additional five contacts mounted closely together in the narrower upper section. This allows the Type-B socket to accept older Type-B plugs, but of course, the SuperSpeed Type-B plug is not compatible with the older Type-B socket. As before, the table below the connector diagrams shows the name and significance of each of the nine contacts. Note that contacts 5, 6, 8 and 9 have a different name for the A connector and the B connector. Australia’s electronics magazine Fig.4 shows the details of the distinctive USB 3.0 SuperSpeed Micro-B connectors, in which the additional five contacts are alongside the original five contacts in their ‘chamfered rectangle’ and inline with them, but in a separate group. The table below shows the names and significance of all ten contacts. Finally, we come to the 24-pin USB-C connectors. Fig.5 shows the details of the USB-C socket and plug, at twice actual size for clarity. The contacts are in two rows of 12 and are labelled A1-A12 and B1-B12. These were originally just duplicates of each other, to allow the plug to be introduced to the socket either way around. But nowadays, to cope with the many expanded applications for USB-C, most of the contacts have different functions, shown in the table below the plug and socket. Contacts A1, B12, B1 and A12 are now all devoted to ‘power ground’, while A4, B9, B4 and A9 are all devoted to Vbus power, to provide the added power capability for USB PD. B5 is also dedicated to Vconn, to supply power for powered cables. The other thing to note about the USB-C connectors is that in addition to the original USB differential data pair (allocated to contacts A6 and A7), they also provide for four pairs of shielded differential pairs for SuperSpeed, SuperSpeed+, USB4, Thunderbolt 3 and Thunderbolt 4 high-bandwidth data transmission. These are allocated to contacts A2 and A3, B11 and B10, B2 and B3, A11 and A10. There is also a configuration line assigned to A5, and finally, two ‘sideband’ lines allocated to contacts A8 and B8. How it has grown... Clearly, USB has grown dramatically over the past 26 years, both in terms of performance and functions. It has changed from a system intended to simplify the connection of basic devices like keyboards and mouses, to a system with at least nine different types of connector – some with as many as 24 contacts – and nine different data transfer speeds, ranging from the original 1.5Mb/s right up to the 40Gb/s of SuperSpeed+ and Thunderbolt 3. The ability to provide power to devices via a USB cable has also grown significantly. From the modest 100mA siliconchip.com.au Rather than add extra contacts internally, as was done with the Type-A plugs and sockets for USB 3.0, the USB 3.0 full-size Type-B expands the plug shroud. But as the lower square section is identical to the earlier USB 1.0/1.1 & USB 2.0 Type-B plug, older cables can still be used in devices with sockets that accept this newer plug. Similarly, the USB 3.0 micro Type-B plug adds a whole new section to one side with the five extra contacts. Once again, sockets are compatible with older (4-contact) plugs, but not the other way around. RUN LONGER GO FURTHER – Upgrade your dead or dying batteries EBIKE? SEGWAY? MOBILity BUGGY? GOLF CART? ESCOOTER? The SuperSpeed micro connectors are wider, adding a separate section with the five added pins alongside the original socket. Therefore, these sockets are also backwardscompatible with older cables and hosts. The USB Type-C plug and socket is similar in size to the micro-B plug and socket, but is capable of much higher data speeds and greater power delivery. It’s also reversible and considerably more robust than the micro-B. or 500mA at 5V available via USB 1.X and USB 2.X, USB PD now allows devices to request one of four different voltage levels (5V, 9V, 12V or 20V), at current levels up to 5A. This opens up the ability to run much higher-powered peripherals, as well as allowing many more battery-powered devices like laptops, tablets and mobile phones to have their batteries fast charged via a USB cable. These days, you can run a single USB Type-C cable between a portable computer and a monitor, and not only will it charge the computer (from the monitor’s internal power supply), it will also carry high-resolution video signals and even connect a keyboard, mouse, printer, fast storage devices and more. We wonder whether the originators of USB would have even considered that possible back in 1994, when they set it all in motion! siliconchip.com.au Further reading • • • • • • • USB standard: https://w.wiki/Usb USB 3.0: https://w.wiki/ntm USB4: https://w.wiki/ntn USB Type-C: https://w.wiki/nto Thunderbolt: https://w.wiki/ntp USB PD: https://w.wiki/ntq USB Implementers Forum: www. usb.org/ SC Australia’s electronics magazine Premier Batteries can recell and/or custom manufacture Lithium Ion batteries for Segways, Ebikes, Electric Golf Carts, Scooters and Mobility Buggies –– often with increased capacity and range etc. Quality cells: Sanyo, Samsung or LG and batteries are Fully Guaranteed PREMIER BATTERIES High quality batteries for all professional applications SUPPLIERS OF QUALITY BATTERIES FOR OVER 30 YEARS email: info.premierbatteries.com.au Web: www.premierbatteries.com.au June 2021  37 MINI ARCADE PONG WITH SIX ‘CLASSIC’ BUGS FIXED 3 5 by Dr Hugo Holden Pong was one of the first commercially successful video games, and I reckon that Arcade Pong was the best version ever made. So I decided to make a fun home version of the game, copying the arcade version as closely as possible, but on a significantly smaller board. While I was at it, I thought I’d fix six bugs that were in the original design! A rcade Pong is the most sophisticated and brilliant version of Pong ever created. Mr Allan Alcorn created this masterpiece at Atari in 1972. It completely outclasses any coded or software-based Pong, and also outclasses any hardware-based Pong on a single LSI chip. Editor’s note: there was also the Magnavox Odyssey, a home video games console which was released a few months before Atari released the Pong arcade machine. The Odyssey featured a “table tennis” game. Original Arcade Pong boards are large and becoming rarer, so for history’s sake, I decided that I wouldn’t modify one. Instead, I would create my own, more compact version based on that design. I used discrete logic ICs placed in a neat grid, in the same arrangement as the original. This way, when an IC is referred to at a particular location in the Atari documentation, it matches up with my board. My design eliminates the six bugs present in the original, and it also provides some simple onboard diagnostics via two TIL311 hexadecimal displays. I have seen PCB designs from others aiming to recreate Arcade Pong, 38 Silicon Chip but they have the ICs in a completely different configuration, and they are generally larger than my design. The bugs in the original design did not detract at all from the brilliance and creativity of the original circuit from 1972. For a circuit of such complexity, needing to get to market quickly, some unresolved problems are to be expected. How a Pong machine works The original circuit (including bugs, which as described below, I fixed) is shown in Fig.1. It also includes an onboard rectifier and regulator, which I didn’t bother with in my version, since regulated DC power supplies are now readily available and inexpensive. The paddle architecture alone in Pong’s arcade version was more complicated than any home Pong version, with 42 possible states of ball motion. The ball motion “vector” (to think of ball motion in analog terms) is formed from combined horizontal and vertical motion components. On the vertical side, there are three up and three down ball motion components. There is also a state of zero vertical motion, leaving a horizontal motion component only in that condition. Australia’s electronics magazine There are three horizontal motion components too, determined by the HIT counter, which combine with the vertical motion components to produce an overall perceived motion vector for the ball that a player observes on the video screen. Although the ball motions are generated digitally, the player perceives the motion in a more analog manner, due to the persistence of the phosphor on the CRT screen and other factors. The three horizontal and three vertical motion components combine to produce a motion vector, and this occurs in four screen quadrants because the ball could be travelling up or down, or left or right. So this gives 36 states of motion or ball ‘velocity vectors’ (4 quadrants x 3 x 3 components). However, there are three additional states of motion that have zero vertical velocity. These are the horizontal states of motion on their own, determined by the HIT counter during gameplay. This adds another six states of possible ball motion during gameplay (3 x 2), giving 42 total unique ball velocity vectors. This is more than enough to convince the player that the game is functioning in a smooth and analog fashion. siliconchip.com.au The genius of the game was that the vertical components of ball motion were determined by where on the paddle the ball made contact. When this interaction occurs, data relating to the condition is clocked into the vertical velocity encoder circuitry, one of the many very clever sub-circuits. The further away from the paddle centre that the ball and paddle interact, the higher a vertical velocity is encoded. The upper half of the paddle is encoded for increasing vertical velocity upwards, while the lower half is encoded for increasing downward motion. The paddle centre is encoded for zero vertical velocity. Also, the horizontal motion speeds up in a volley when there are no misses by either player. After four consecutive hits, the horizontal component of ball velocity increases. By 12 hits with no misses, the horizontal velocity component speeds up yet again. These ball motion features, combined with the sound effects and score-keeping, make for a version of Pong that outclasses all other versions. One of the earliest prototypes made for the Pong circuit. Clever design Out of all the circuits I have seen after a lifetime of interest in electronics, Pong is up there in the top two most impressive. One reason for this is the combination of technical creativity and fun, making the best out of the current technology of the time, seldom seen together, all wrapped up in one design. To give you an idea of how cleverly the sub-circuits are implemented, a single standard binary-to-7-segment display encoder IC is multiplexing the video for both players’ on-screen score displays. Also, the size of the player paddles and score segments on the screen in the arcade game were a well-proportioned use of the video display area; much better than in some home Pong versions where the scores and paddles (bats) appeared larger. Clearly, some compromises were made when this arcane circuit of around 66 TTL ICs was miniaturized down into a single integrated circuit for home Pong versions. Bugs in original Pong The original Arcade Pong “Syzygy E” PCB contains six known bugs. My version, besides being considerably smaller, also addresses and fixes all six. siliconchip.com.au Another later revision prototype PCB being tested before the final design. 1960s and 70s plastic TTL ICs aren’t made of the same kind of plastic as modern chips; it is a much harder type of resin. I find them reliable; these new-old-stock parts were 35-45 years old, but worked perfectly the first time I powered it up. 60Hz displays on 50Hz mains power Like the original Arcade Pong, this design produces a more-or-less NTSC-compatible composite video signal, using the American frequencies of 59.97Hz for vertical sync and around 15,750Hz for horizontal sync. But many small monochrome PAL (50Hz/15,625Hz) monitors have sufficient horizontal and vertical hold adjustment range to lock onto this signal. Sometimes with vintage 50Hz CRT monitors, you need to reduce the value of the vertical oscillator timing capacitor a tad to get the vertical hold control into range. Australia’s electronics magazine June 2021  39 Fig.1: the original circuit diagram for the arcade version of Pong. 40 Silicon Chip Australia’s electronics magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine June 2021  41 Fig.2: this modification to the original Pong circuit fixes one of the bugs whereby the ball becomes ‘trapped’. This can occur if the paddle range pot is out of adjustment. 1. The Ghost in the Machine Bug This bug was not found for over 40 years. It came about due to a mistake in the original PCB design. Pin 10 and pin 1 of IC A6 (a 7450) had reversed labels on Atari’s original schematic, and the original PCB designer copied this. This meant that the least significant bit of paddle data, processed by the vertical velocity encoder, was switched between the two players. The result was that one player’s paddle could influence the other player’s interaction with the ball. Also, this reduced the number of possible ball motion states. It produced a “spooky” and unpredictable effect, in that sometimes the ball would bounce from an unexpected angle from the paddle, depending on where the other player’s paddle was positioned. This bug was fixed by connecting the tracks correctly to the 7450 IC at location A6, ie, swapping the connections to pins 1 & 10. This bug is not present in Arcade Pong Doubles, only the original Pong E Syzygy boards. 2. Ball Trapped in Blanking Bug This is a very complex and infrequently presenting bug. In effect, it represents a ‘logic race’ that the game cannot escape from if it gets into it. The result is that the ball can become ‘trapped’ inside the vertical blanking interval instead of inside the active raster scan time interval. It can occur if the paddle range potentiometer is out of adjustment (or the paddle range is increased; see below). In this case, the ball oscillates between the paddle edge and vertical blanking. The ball becomes ‘trapped’ in synchronicity with the vertical blanking interval and appears in a vertically elongated form (if the vertical blanking area is visible on the monitor screen), moving horizontally to and fro in the vertical blanking interval, unable to escape. This can usually be corrected by turning the game off and on again. It 42 Silicon Chip is a rare bug to appear, but the game ‘locks up’ when it does. Very rarely, the bug would appear at switch-on, disabling the game until it is reset. The cure is to deploy an unused 74107 flip-flop in IC A2, as shown in Fig.2. Flip-flop A2a is used to reverse the ball’s vertical velocity after the ball signal V.VID and vertical blanking V.BLNK become coincident. The addition of the second flip-flop, A2b, and rewiring A2a solves the problem, allowing enough time for the ball to always escape the vertical blanking interval without remaining trapped there. Also, flip-flop A2b with both J and K tied high toggles very reliably. More details on this can be found in the link at the end of the article. 3. Paddle Range Limitation The original paddle range was limited. This has the effect of allowing the ball to travel above a player’s paddle no matter how hard they rotate the control against its stop. This made some players angry as they knew they could have hit the ball if the control had allowed them. The designer pointed out that this ‘feature’ always meant the game would finish, as two experts could otherwise play it for a very long time. But even with good players, someone usually misses, especially when the ball’s horizontal velocity is at maximum after 12 consecutive hits (especially if the player has a beer or a hamburger in the other hand and they are chatting to friends). The modification made here allows full range of the paddles close to the vertical blanking intervals, so that the ball cannot get around (over or under) the paddle. It does not cause any problems, provided the ball trapped in blanking bug fix, described above, is present. If not, the extended paddle range can more likely push the ball into blanking, where it can get trapped. This change is made by replacing one Australia’s electronics magazine 1N4148 in the original design with three in series, as shown in Fig.3. Note: do not attempt to use any other variant of the 555 timer IC than the NE555N; preferably, use an early Signetics unit. Many other 555 types, whether CMOS versions, the NE555P or the LM555, have small differences that show up in the timing and generation of the paddle image, with the paddle appearing early or late or exhibiting non-linear control. 4. Screen Video Horizontal Image Displacement Bug The horizontal sync pulse is located with respect to horizontal blanking so that, with the horizontal hold setting of the monitor properly adjusted, the screen image is displaced to the left (especially the ‘net’ line). To improve this, the horizontal hold control on the monitor can be turned a little. This is because most monitors have a horizontal AFC circuit with a DC control to their local horizontal scan oscillator, so any offset in the sync timing with respect to the video (image) signal causes a horizontal phase shift or displacement of the video image on the scanning raster. However, when the horizontal hold control is centred, the monitor can sometimes lose horizontal picture lock when first turned on from cold, as the AFC circuit goes out of “capture range”. Therefore, the sync pulse is better repositioned within the blanking time to be closer to video industry standards (NTSC). There are several ways to do this with the spare gates and flip-flops available in the circuit. The method I used is simple, as it just uses one spare flip-flop – see Fig.4. The NEW H.SYNC signal replaces the HSYNC signal that feeds into pin 12 of the sync-pulse-mixing XOR gate at location A4. Although this arrangement doesn’t exactly give a standard sync pulse to blanking relationship, it is very close, and the picture centring is much better on the monitor. siliconchip.com.au ► The 16H signal is available from pin 4 of the IC at location E4, while 32H is from pin 9 of the IC at location F9. HBLNK is available at pins 4, 8 and 12 of the IC at location H5. This bug was fixed in Atari Pong Doubles, but that particular circuit fix required three extra gates, as well as the flip-flop, to achieve the same result. Also, I found that if a modification is made to place the sync pulse almost identically to industry standard (NTSC video), and the net line is centred almost perfectly, then the score images appear to be displaced a little to the right. So the better picture position is with the net displaced a tiny bit to the left and the score a little to the right, when the horizontal hold control on the monitor is set correctly. Some monitors (very few) have an internal horizontal phasing control, so the image horizontal picture centring can be adjusted after the horizontal hold control is correctly set. 5. The Weak Net Bug This bug occurs due to the propagation delays in the two 7493 counters in the horizontal sync generator. Cumulative delays in this ripple counter system can upset the timing in the generation of the net signal. When specimens of the 7493 counter IC had shorter propagation delays in each flip-flop, typically the 7493AN counter chips, a timing error developed in the drive to the flip-flop pulse synchroniser circuit (F3 and G3) that generated the net pulses. The result is weak-looking, thin or faint net on the screen image. The fix is to clock the flip-flop at pin 9 of the IC using the 1H signal rather than the clock signal. This way, the timing errors or differences in 7493 ICs do not affect the net pulse width. This modification is shown in Fig.5. The earlier 7493 counter ICs had about 18ns delay per internal flip-flop, siliconchip.com.au Fig.3 (left): this modification is used in conjunction with the ‘fix’ in Fig.2 to extended the paddle range so that it can be used close to the vertical blanking intervals. This means the ball can’t get around the paddle in edge cases. ► Fig.4 (right): a new horizontal sync pulse is made with a spare flip-flop to improve the horizontal hold control and fix screen displacement. Fig.5: propagation delays in the 7493 counter ICs (F8/9) cause a faint net on the screen image. This is fixed by clocking pin 9 (CLK) of flip-flop F3 using the 1H signal from one the horizontal sync generators. and there being eight flip-flops in two 7493s, this yielded a delay of about 144ns. Add about 16ns for the 74107 flip-flop, giving a total of 160ns between the 256H going high and the clock pulse going low. The clock pulse has an interval of about 140ns, so in this case, the 256H signal rises about 20ns after the clock pulse goes low. This results in a typical Australia’s electronics magazine net pulse length of about 120ns. However, the 7493AN counter IC is often faster than the earlier 7493N, with a delay of about 13ns per flipflop, giving a total delay of 120ns. So 256H rises about 20ns before the clock pulse goes low, upsetting the net pulse generator. This results in a net pulse of only about 20ns long, which looks very weak on the screen image. June 2021  43 Fig.6: gates at C1 and D1 are used to create a NEWBALL signal to help deal with screen tear due to the ball being visible during blanking periods. The final PCB, with a bit of glare from the camera flash. Since this was originally a 1970s design, it seemed fitting to populate the PCB with vintage TTL ICs. Clocking flip-flop F3 with the 1H signal, instead of CLOCK, results in a net pulse in the range of 140 ±20ns, with the variability caused by the difference in the 7493 counter IC specimens. It always gives a normal-looking net pulse on the screen, regardless of the properties of individual ICs. 6. The Ball Monitor Sync Disturbance Bug In the analog video signal, picture information should not appear inside the horizontal and vertical blanking periods. These intervals are the province of the sync pulses during the monitor’s beam fly-back time. In the original Pong design, the ball was not gated out of the blanking intervals, and appeared in this area when the ball ‘bounced’ off the screen edges. This makes the picture on the monitor jump vertically a little sometimes, or get a small horizontal picture tear as the ball bounces, depending on how vulnerable the particular monitor is to a sync disturbance. The designer had given thought to the vertical blanking interval, because the net pulse is gated out of vertical blanking. But the ball signal is not gated out of horizontal or vertical blanking. The BALL signal appears on output pin 4 of the IC at G1. Unused gates at locations C1 and D1 are deployed to create a NEWBALL signal, gating the ball signal out of both the horizontal and vertical blanking time (Fig.6). Making it more compact An Apple IIc monitor undergoing modifications so that it can be powered from the same 12V DC supply as the rest of the Pong game. 44 Silicon Chip Australia’s electronics magazine With no negative reflection on the genius of the original design implied here, the arcade PCB design was large and cumbersome at 395 x 220mm. Of course, there was plenty of space inside an arcade game cabinet, so it hardly mattered. This variant of Arcade Pong, with all the above bugs corrected, fits on a PCB measuring just 245 x 165mm, as shown overleaf – including the details of all the components. It has been possible to design a much smaller version than the original arcade PCB by altering the track design and running the IC power rails down the long IC axes, unlike the original design, which had them perpendicular to the long axis of the ICs. I designed this new PCB by hand, like the original arcade game PCB. I worked on this design for about two years on and off. siliconchip.com.au I added some ‘onboard diagnostics’ via two TIL311 hexadecimal displays. One display monitors the 4-bit data from the vertical velocity encoder output, while the other shows the 4-bit data from the hit counter. This is useful to see that everything is working normally, but most, perhaps not all faults, if present, are usually evident in gameplay. Another advantage of the new PCB is that it can be powered from any common garden-variety 5V switchmode power supply. This saves space by not having the power supply components on the PCB, as in the original Arcade version. It still uses the original 74-series DIL TTL ICs. LS-TTL ICs can also be used, reducing the power consumption to around 360mA <at> 5V rather than about 1.2A with standard TTL. However, there is something quite wonderful about the power-hungry 74-series TTL ICs. This is the sort of robust technology which comprised the computers in the Apollo spacecraft. They are very trustworthy chips. If you are keen to build your own copy of my Mini Arcade Pong, you can do so. You can get the PCBs from the Silicon Chip Online Shop, and all the other parts are easy enough to obtain. The possible exceptions are the TIL311/DIS1417 7-segment displays, but they are not necessary – they are mainly for ‘debugging’ purposes. You can get them from sellers on eBay if you feel you need them. Fig.7: the upper half of this circuit is an optional buffer transistor which is used to help drive a 75W input impedance for the monitor. The lower half is the audio amplification and volume control. sync tip to sit just at +50mV to +100mV or thereabouts. A reasonable starting value is 1kW. The original coupling capacitor should be linked out. The 33-75W resistor is chosen so that when the output is terminated with 75W, the overall amplitude (sync + video) is about 1V peak-to-peak across the termination resistor. Audio-wise, in my Mini Arcade Pong ‘cabinet’ (pictured), I just used the Champ amplifier (February 1994; siliconchip.com.au/Article/5303), which uses an LM386 IC, to drive the speaker. A small single or two-transistor amp would be fine, as long as there is a volume control. Some video monitors have sound and a speaker built-in, but not all. A simplified version of the basic arrangement I used for volume control and audio amplification is shown at the bottom of Fig.7. Another possible solution would be to use a video buffer IC like the MAX497. This contains four buffers; one could be used for the video, with the other three paralleled for the audio. These ICs work fine with Video buffering The video output is formed using just three resistors to mix the sync pulses and video. This was simply fed into the high-impedance video input of a domestic TV set, which would have had an impedance of a few kilohms. Most newer video monitors, CRTs or other types, have a 75W input impedance, although some have a switch select ‘High Z’ mode. So you might need to add a buffer transistor to this design to feed the signal into your display, to make sure that the video output can successfully drive a 75W cable that is terminated with 75W. This can be done simply with an emitter-follower, as shown in Fig.7. This circuit (or a similar one) could be built on a small daughterboard. The pull-up resistor value (X) needs to be adjusted to get the bottom of the siliconchip.com.au The finished product has a retro vibe, except perhaps for the LED-illuminated start button! Australia’s electronics magazine June 2021  45 Parts List – Mini Arcade Pong 1 double-sided Pong PCB coded 08105211, 245 x 165mm 1 5V DC 1.5A regulated supply 1 monochrome TV or monitor with composite video input 2 5kW 24mm linear panel-mount potentiometers (for paddles) 1 50kW 24mm logarithmic panel-mount potentiometer (volume control) 1 small amplifier module (eg, the Champ) 1 speaker to suit amplifier module 1 enclosure to fit all assemblies 2 large knobs, to suit 5kW pots, for paddles (larger is better for ease of use) 1 smaller knob, to suit 50kW volume control pot 1 SPDT momentary pushbutton switch 2 50kW mini horizontal trimpots 1 14.31818MHz crystal (X1) 1 red binding post 1 black binding post 14 PCB pins (optional) Various lengths & colours of medium-duty hookup wire Hardware to mount PCB, power supply & other components in the enclosure Semiconductors 2 TIL311 or DIS1417 hexadecimal 7-segment displays with inbuilt logic (optional – A1, B1) [eBay] 10 7400 or 74LS00 quad 2-input NAND gate ICs (B2, B7, C1, C3, E1, E6, G3, H1, H4, H5) 7 74107 or 74LS107 dual JK flip-flop ICs (A2, C8, D9, F3, F6, G6, H2) 4 74161, 74LS161 or 9316DC synchronous 4-bit counters (A3, B3, G7, H7) 1 7486 or 74LS86 quad 2-input XOR gate IC (A4) 5 7474 or 74LS74 dual positive-edge triggered flip-flop ICs (A5, B5, C2, E7, H3) 2 7450 or 74LS50 dual 2-input AND-OR-invert gate ICs (A6, B6) [Rockby] 2 7420 or 74LS20 dual 4-input NAND gate ICs (A7, H6) 7 7493 or 74LS93 dual 2-bit up-counter ICs (A8, B8, E8, E9, F1, F8, F9) 4 NE555N timer ICs (A9, B9, F4, G4) [eBay] 1 7483 or 74LS83 4-bit binary adder IC (B4) [Rockby, Futurlec] 6 7410 or 74LS10 triple 3-input NAND gate ICs (C4, D4, D5, D8, E2, G5) 1 7448 or 74LS48 BCD to 7-segment decoder IC (C5) [Futurlec] 2 74153 or 74LS153 dual 4-input multiplexer ICs (C6, D6) 2 7490 or 74LS90 modulus-10 decade counters (C7, D7) 3 7404 or 74LS04 hex inverter ICs (C9, D1, E4) 3 7402 or 74LS02 quad 2-input NOR gate ICs (D2, F5, G1) 2 7430 or 74LS30 8-input NAND gate ICs (D3, F7) 3 7427 or 74LS27 triple 3-input NOR gate ICs (E3, E5, G2) 1 7425 or 74LS25 dual 4-input NOR gate with strobe IC (F2) [Rockby, Futurlec] 2 2N3904 NPN small signal transistors (Q1, Q3) 1 2N3906 PNP small signal transistor (Q2) 1 6.8V 1.5kW unidirectional TVS (eg, 1N6267) 1 1N4004 400A 1A diode 9 1N4148 small signal diodes Capacitors 2 220μF 10V axial electrolytic 1 4.7μF 10V tantalum or multi-layer ceramic 1 4.7μF 10V axial electrolytic 1 1.0μF 10V tantalum or multi-layer ceramic 2 120nF 63V MKT 33 100nF 50V ceramic 1 100pF ceramic or greencap Resistors (all mini 1/4W 1% metal film) 1 330kW 3 1kW 46 1 220kW 2 470W Silicon Chip 2 56kW 3 330W 1 2.2kW 4 220W 2 1.5kW 3 100W 1 1.2kW Australia’s electronics magazine high-value input resistors in the range of 5kW, but most circuits show the inputs terminated with 75W. Their input impedance is actually very high. Building the cabinet Once I confirmed it worked, the next step was to mount the PCB in a housing and pair it up with a suitable monochrome monitor. A suitable monitor for this job is the small monitor used with the vintage Apple IIc computer. I got my hands on one of those old Apple IIc computer monitors and modified it to run from 12V DC rather than mains power. This way, the monitor can be powered from the same power supply as the rest of the Pong console. This is also convenient because the Apple IIc typically runs from 115V AC. The Apple IIc monitor also has a handy stand that elevates it to a good viewing level. Apple IIc monitors generally come with a green phosphor (P31) CRT; however, I changed this for a white phosphor CRT, since monitors used with Pong were generally modified TV sets with white (P4) phosphor CRTs. I then mounted the completed Pong PCB, power supply (compact switchmode PSU), speaker and Champ amplifier module in a high-quality Hammond painted aluminium enclosure for the final result. I also added an illuminated push-to-start button. Once all the components are mounted in the cabinet, it’s just a matter of wiring them up. The power supply outputs go to the binding posts (positive to red). Connect either the VID & GND terminals to your display input (possibly via a buffer circuit, as described above). GND & SND go to the amplifier input, with its output going to the speaker (and whatever power supply arrangement the amplifier requires). Wire the N/O, GND & N/C terminals to your momentary game start pushbutton switch (which was a coin detector in the arcade version). The remaining two pairs of three terminals are wired across the two controller paddles, with PLL to the wiper of the left-hand player’s pot and PLR to the right-hand player’s. Connect the +VE terminals to the clockwise track ends, and GND to the anti-clockwise ends. A full circuit analysis can be found at www.worldphaco.com/uploads/ LAWN_TENNIS.pdf Continued on page 85 siliconchip.com.au siliconchip.com.au Australia’s electronics magazine June 2021  47 The History of Videotape – part 4 Camcorders and Digital Video By Ian Batty, Andre Switzer & Rod Humphris As detailed in the previous three articles in this series, videotape recording culminated in the incredibly popular VCR format. But it was not really suitable for portable recording, being too bulky. Before digital video totally replaced tape, there were still some significant technological developments, mainly in the field of miniaturised tape formats for more practical handheld video recording. T he camcorder began with Sony’s record-only Betamovie. But what led Sony to design such an oddball machine? Impressive as Betamax and VHS were, their portable versions left much to be desired. Lugging a klutzy VCRplus-camera kit was far from ideal. Aside from colour recording and a longer running time, these weren’t much better than the old half-inch reel-toreel Portapak. The revolutionary ‘camcorder’ design put the camera and VCR together into one case. The unit would 48 Silicon Chip have to sit on the operator’s shoulder, which gave improved stability over previous wobbly hand-held cameras. So, leaving aside the inconvenience of post-processing, why not stick with a (smaller) 8mm movie camera with colour film? That is a question that users of Sony’s Betamovie must have asked themselves. Sony has a history of going out on a limb, and in this case, they appear to have prioritised compactness over practicality in their first camcorder. It was a unitised design, but it had no playback facility. To find out just Australia’s electronics magazine what you had (or had not!) recorded, you had to remove the tape from the Betamovie and play it in a ‘proper’ Beta machine. National Panasonic’s first outing, the full-size M3 VHS camcorder, did offer standard recording and playback. But it was way bigger than a shoebox, and so it was never going to be madly popular. The VHS-C cassette, at less than 30% the size of a standard cassette, and giving 20 minutes of recording time, helped to shrink the VHS camcorder. Reducing the size of the head siliconchip.com.au drum from 62mm to 41.3mm helped, but added complexity by demanding a 270° tape wrap and four video heads. Even with VHS-C’s smaller size, cute packaging and flip-out viewfinder/ playback screen, it wasn’t going to be too long before someone went back to the drawing board and came up with a new format that would redefine portable video. It would have to be something close to the size of the extinct Super 8mm film camera, with its unitised pointand-shoot convenience. The Ultimate (analog) VCR: Kodak/Sony’s Video8 The need for a new, compact format saw Sony and Kodak cooperate in the early 1980s. The project was announced by Kodak’s 1984 release of the Kodavision 2200 and 2400 models. At a base price of US$1600 (~$5700 today), sales were modest. 1985 saw Sony release their cheaper, simpler and smaller CCD-V8. Borrowing some of the cachet from Super 8 movie film, Video8 would become the last major analog video tape format, and would ultimately morph into a digital form. Video8 used a 95 x 62.5 x 15mm cassette containing 8mm-wide tape running at 2.051cm/sec for standard play. Using a smaller head drum (40mm) than either Beta or VHS, the headto-tape speed was down to 313cm/s. Like all other colour formats, Video8 used FM luminance and heterodyne colour (4.2~5.4 MHz and around 734 kHz respectively). The slow tape speed meant that linear audio recording would give very poor results so Video8 only used FM audio, similar to that of hifi Betamax and hifi VHS. Video8 was designed using Sony’s U-loading system, developed two generations back with U-matic. As the M-load vs. U-load comparison in Fig.56 shows, U-loading suffers from the loading ring having to completely encircle the head drum. Video8 camcorder designers (needing to miniaturise the tape mechanism as much as possible) adopted the M-loading system from VHS, keeping Video8’s original record/playback format and speeds. This allowed Sony to produce the much smaller CCD-FX270 Video8 and to realise the miniaturisation inherent in the Video8 format (Fig.57). siliconchip.com.au Fig.51: reel-to-reel “portapaks” were the first truly portable video recording system. Clearly, though, further reductions in size and weight would be required! Source: www.rewindmuseum.com Fig.52: the Akai VT-100S was an improvement but still pretty awkward to carry around. The hand-held black/white camera VC-100 is shown separately. Main image source: https://youtu.be/iaPAyVcXz_0 Sub image: www.catawiki.com/ l/15944111-akai-vt-100s-video-set Australia’s electronics magazine June 2021  49 Needing to maximise tape real estate, Video8’s designers dumped the control track used to position the video heads for exact tracking of the recorded signal stripes in replay. Instead, a servo signal embedded in the video tracks allowed the head-positioning servo in replay to correctly sync the video heads to the tape. The embedded Dynamic Track Following (DTF) servo had already been pioneered by Philips in their ill-fated Video 2000. The embedded servo design, rebranded as Automatic Track Following (ATF), was successful, but Video8 was unable to use the missing control track pulses as a highly-accurate tape counter. Video8 was forced to revert to uncalibrated mechanical counters. The slow head-to-tape speed forced higher flux-change densities onto the tape, so conventional oxide-particle formulations were replaced by metal/ metal particle coatings. These had been pioneered in audio cassettes, taking the Compact Cassette from its original ‘dictation quality’ (due to low-performing ferric oxide coatings) to true high-fidelity in the best models. Fig.53: a Sony Handycam from the late 90s. That’s much more like it! The end of the road: digital video Digital measuring instruments had been converting analog quantities to digital signals since the mid-1950s, and the principles of analog-to-digital and digital-to-analog conversion were well-understood by the 1970s. Most digital audio recordings from the 1980s were recorded on U-matic tape via a Sony PCM-1600 audio interface. Digital audio has a wide signal bandwidth, easily accommodated by the luminance channel of U-matic. Since the PCM-1600 was based on U-matic record/play parameters, Compact Disc’s well-known 44.1kHz sampling rate was chosen to be compatible with both NTSC and PAL video line scanning rates. Digital audio, recorded on U-matic tape, was the first system used for mastering audio Compact Discs in the early 1980s. So it was just a matter of time before VCR designers turned to digital signal processing for the video channel. Video8 had already used Pulse Code Modulated (PCM) audio in some models, but with a 32kHz sampling rate and only 12-bit sampling (a 60dB dynamic range), its audio performance was inferior to hifi Betamax/VHS. 50 Silicon Chip Fig.54: the National M3 was a full-size VHS Camcorder. You can see how big it is in comparison to the later Sony Video8 Camcorder next to it. Leaving aside the complexities, digital processing uses a codec (CoderDecoder) to store and retrieve signals. The Digital Video (DV) codec borrows an old idea: luminance and chrominance are processed separately. The luminance signal is processed with a 13.5MHz sampling rate, while the separated U (yellow-blue) and V (redcyan) chroma signals are sampled at the much lower rate of 3.375MHz. Australia’s electronics magazine That’s pretty much what analog VTRs/VCRs had done, allocating more bandwidth for the luminance signal and less for the extracted chroma. Economising on signal processing wasn’t enough though. Digitising the video into 8-bit data streams gave a bit rate greater than 100 megabits per second, so the digital images were compressed before recording, then decompressed in playback. siliconchip.com.au DV. Using an even smaller cassette, DV would finally produce a handycam smaller than a Super 8mm movie camera, but with a lot more features! Fig.55: this VHS-C Camcorder was much more practical than the full-size VHS units, but the 20-minute tape length was pretty limiting, and it wasn’t long before the superior Video8 system came along. Nearly forgotten: Laserdisc Yes, you can do all this on a video disc. Just use the high-density optical recording techniques developed for Compact Disc, but lay down analog audio and video signals. Developed by an MCA-Philips consortium, the format was first demonstrated in 1972 and publicly released in 1978. Double-sided discs were limited to a maximum of 64 minutes per side, and could not be recorded on. Laserdisc’s high quality (equal to 1-inch C-format videotape) could not overcome the convenience and home-recording features of Betamax and VHS. G RING ADIN LO Fig.56: a comparison of the size required for U-loading (blue) and M-loading (red) mechanisms. They do more-or-less the same job of wrapping the tape around the head drum, but with M-loading taking up barely half the space outside of the cassette. SUPPLY REEL The compression algorithm is lossy – it works by discarding picture detail that, in theory, won’t be missed. Picture an aeroplane flying across a uniform blue sky. We’ll need to portray the ‘plane accurately and in fine detail (high bit rate), but the sky can be broken up into blocks (low bit rate). As you can imagine, such complex processing demanded intensive and innovative design. siliconchip.com.au DC servos TAKEUP REEL Digital8’s moderate success was a matter of timing. Intended as a carryover medium for users already familiar with Video8, but not released until 1999, it actually followed Digital Video’s 1995 launch. Digital Video The last iteration, before hard disk drives and solid-state storage mostly obsoleted tape, was Digital Video or Australia’s electronics magazine Portable VTRs, lacking constantfrequency mains power, used several types of capstan motors such as the brushless servo motor. This used a three-phase synchronous motor with a permanent-magnet rotor. A threephase oscillator either drove the motor directly, or supplied a power amplifier to drive the capstan motor for constant tape speed. But this still left the VTR needing to regulate the head drum according to the control track. The simplest method was to use an ordinary DC motor for the head drum, regulated by a servo and driven by a motor drive amplifier (MDA). Ultimately, mains-powered VCRs would adopt these techniques, and would incorporate sophisticated direct-drive motors for the capstan and head drum. While more complex mechanically and electronically, these advanced motor designs did not need speedreducing belts or gears, were lighter and more reliable, could be controlled more accurately, and could easily be slowed or reversed for slow motion, reverse play and other useful modes. The incredible shrinking video camera Continuing miniaturisation and the adoption of digital processing saw Canon deliver the truly compact MV-800, which included two viewfinders: the conventional ‘peep’ sight, and a handy swing-out screen; both in colour! June 2021  51 A Video8 cassette (https://w.wiki/nGy), followed by a Hi8 cassette (https://w. wiki/nGz). Both formats are in similar packages and are analog. Fully digital tapes didn’t come along until Digital8. Fig.57: Video8 was the last hurrah for analog video recording before digital tape systems like DV made it essentially obsolete. Of course, it wasn’t long before DV was replaced with solid-state digital recording… But the cassette’s end was in sight. Somebody was going to take the extreme miniaturisation of the charge-coupled device (CCD) camera chip and marry it with digital processing and solid-state memory. And pack it all into a popular smartphone, such as the Sony Xperia (bottom right of Fig.58). Conclusion For some forty years between 1955 and 1995, analog (and then digital) videotape recording in its various incarnations embodied the most complex combination of electrical, electronic and mechanical designs of the day. References Fig.58: the incredible shrinking Camcorder. From top to bottom at left, VHS, Video8, a smaller Video8 unit, then at right, a solid-state Handycam and a modern mobile phone with superior video recording in terms of both quality and duration (the Handycam still has much better zoom capability). 52 Silicon Chip Australia’s electronics magazine • Video Cassette Recorders, Humphris, Rod, 1998, TAFE Course Notes • How to use a Portapak: siliconchip. com.au/link/ab5s • U-matic development by Sony: siliconchip.com.au/link/ab3i • Technology Connections’ Youtube channel: www.youtube.com/channel/ UCy0tKL1T7wFoYcxCe0xjN6Q • An extensive picture gallery of VTRs, Philips VCR, Beta and VHS: www.oldtechnology.net • The history of video tape recorders: www.labguysworld.com • Special thanks to Rewind Museum for Fig.51: www.rewindmuseum.com Lead images: • https://w.wiki/nGs • https://w.wiki/nGt • https://w.wiki/nGu SC siliconchip.com.au DIY e Hom s l a e D 24 Digital Microscopes 1 ale On S une, 202 23 J o t y Ma Excellent for educational purposes and suitable for many applications. 600x magnification. 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Prices and special offers are valid from 24.05.2021 - 23.06.2021. 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. Building a better mousetrap Here in rural SE Queensland, there has recently been a proliferation of mice. Apart from spreading nasty diseases like leptospirosis, they can also do a lot of damage. We had one in the house, and every night it would go through the pantry, ripping open packets and destroying the contents. So I purchased a cage trap from the local hardware store. This has a mechanical trigger, operating via a rod to release a hinged door. This door is spring-loaded with a bar which falls as it closes, preventing the door from being pushed back open. This looked like a good concept, but unfortunately, that was not the case. Most times, the bait would be taken, but the trap would not trigger. Who said mice were dumb? I concluded that a more sensitive trigger would be the solution, and decided to design a light-beam trigger for the trap. This subsequently proved successful. I removed all the existing trigger parts siliconchip.com.au and made an aluminium plate which clips onto the cage and can be easily removed to facilitate mouse removal. This plate was fitted with a solenoid release mechanism, a microswitch (to turn off the power once triggered), and also provides support for the electronics and the IR LED and receiver. A primary criterion was to minimise current consumption so that it could be powered by dry cells (eight AA cells giving around 12V). My final design draws only 1mA, so it should run for at least a year. I selected an IR receiver as used in all manner of remote-controlled devices. They cost less than $1 and are easily sourced from local suppliers or eBay. They have an amplifier with AGC, and a bandpass filter at 38kHz plus a data detector and output driver. The 38kHz BPF provides immunity from outside optical interference. They run from 5V. I initially tried sending a 38kHz square wave via an IR LED, but the receiver detects for only about 200ms then stops. I concluded that the IR LED needs to be modulated to simulate data so that the IR receiver will operate continuously; the data sheet is not clear about this. I subsequently pulsed the 38kHz IR LED at 15Hz, and this gave a continuous 15Hz square wave at the receiver output. IC1a-IC1d are schmitt trigger NAND gates. The 470nF capacitor is alternately charged and discharged as output pin 10 of IC1c toggles, producing a 15Hz square wave. This is fed to pin 1 of 38kHz oscillator IC1a, switching it on and off. The pin 3 output of IC1a feeds the 180pF/10kW RC high-pass filter, and on each falling edge, a short pulse toggles IC1c, reducing the output duty cycle to 1.7µs. This greatly reduces the current drawn by the IR LED, which is driven by 2N7000 N-channel Mosfet Q1. I found that the optical path had a range of a few metres, far more than required for my application, so in the 61 interest of minimising current drain I adjusted the dropping resistor for the IR LED to 3.3kW, giving a range of about 300mm. Too much LED current can also saturate the area with the optical signals, causing reflections to prevent the beam from breaking when it should. The receiver output is a steady 15Hz signal, and to detect that the beam is broken, this is fed to IC2a, a monostable wired as a missing-pulse detector. The R & C values set it to about 160ms, so the light beam has to be broken for at least that long to trigger the trap. This prevents false triggering. I used a solenoid purchased from eBay, rated at 28V AC, but found it works fine on 12V DC. The 5600µF capacitor delivers a hefty pulse and the solenoid closes very rapidly (I wouldn’t want to put my finger into it!). The output of IC2a feeds a pulse to another 2N7000 (Q2) via a 4.7µF capacitor, and Q2 switches on P-channel Mosfet Q3 which drives the solenoid. Q3 is seriously oversized for the job, but I had it in my junk box. The diode across the solenoid protects against any back-EMF. The reason for the RC network on the output of IC2a is to deliver a single drive pulse. Without this RC network, if the power were left on with the light beam broken, the solenoid would be permanently activated, flattening the battery. The red LED in series with the 5V regulator input shows that the power is on, and it flickers with the 15Hz modulation. I wired it in series as the regulator only draws about 1mA, and that gives a noticeable glow without adding to the overall current consumption. The IR detector I used was mounted on a small PCB, with a 10kW pull-up resistor. Checking the data sheet revealed that the device already has an internal pull-up, so I removed that external resistor to save current. I then placed this PCB in a small box to prevent the entry of unwanted external light. If you have an oscilloscope, you can monitor the optical receiver’s signal output to set the correct amount of transmitter LED current. Editor’s note: due to variation in schmitt trigger thresholds, it’s worth checking that the signal at pin 3 of IC1a is close to 38kHz, and if not, adjust the value of the 6.8kW resistor. Bruce Boardman VK4MQ, Highfields, Qld. ($125) 62 Silicon Chip Australia’s electronics magazine siliconchip.com.au In & out of circuit LED tester The idea for this circuit came to me when I was having difficulty locating faulty LEDs in a string, as used in an LED light bulb or infrared illuminator. Assuming that you’re prepared to spend the time, repairs can be made or good sections isolated to repair other units. Probing with a multimeter works, but you have to reverse the probes quite often. So I built this simple circuit around a 4093 quad schmitt trigger input NAND gate IC (one of my favourite chips for quick and dirty solutions). IC1d is configured as a simple oscillator. I have tied input pin 13 to ground via a 4.7MW resistor, so the siliconchip.com.au oscillator will not function until this pin goes high, accomplished with a simple touchpad made from a piece of Veroboard. Until this is activated, power consumption is virtually nil. When it does oscillate, it drives two gates in series out-of-phase (IC1c & IC1b), so their outputs continually swap polarities. These outputs are connected by the device under test (DUT) via a 22W resistor and LED2/LED3. These LEDs are connected in parallel with opposite polarity. LED2 and LED3 can only light when the DUT passes current. In the case of a functional device, the LED that turns on must have the same polarity Australia’s electronics magazine as the DUT. If both turn on, you have a short; if neither do, then there is an open circuit. A low resistance across the DUT could cause both LEDs to flash, but that is uncommon. The DUT can be connected by a simple socket or a pair of probes, used to check devices in-circuit. The accompanying breadboard diagram shows how you could build this circuit on a breadboard, or an IC style protoboard. Graham P. Jackman, Melbourne, Vic. ($80) June 2021  63 8-pin 14-pin 20-pin PIC PROGRAMMING HELPER It’s incredible what you can achieve with an 8-pin microcontroller. However, programming and debugging these chips can be a challenge due to the need to use the programming and reset pins for other purposes. This little board makes working with these (and some larger) PICs much easier! W e include 8-pin PIC microcontrollers in many of our projects because they are very handy for doing certain jobs, and cheap to boot. Apart from a handful of 6-pin parts, which are only available in SMD packages, they are some of the smallest microcontrollers around. For example, we used a PIC12F1572 8-pin micro in our LED Christmas Ornaments project (November 2020; siliconchip.com.au/Article/14636). In that case, despite only having eight pins with two dedicated to power, it was able to control twelve LEDs and light them up in patterns. We have also used parts like the PIC12F617 in projects such as the Car Radio Dimmer Adapter (August 2019; siliconchip.com.au/Article/11773), the MiniHeart heartbeat simulator (January 2021; siliconchip.com.au/ Article/14706) and the Refined Fullwave Universal Motor Speed Controller (April 2021; siliconchip.com.au/ Article/14814). If you only need five or six I/O pins, then devices like these are handy and compact, while still being computationally very capable. John Clarke even used one to replace a hard-to-get rotary switch with a potentiometer in the Digital Effects Pedal from April 2021 (siliconchip.com.au/Series/361) But consider that once you subtract the power pins, you’re left with at most six I/Os, and you usually need three of 64 Silicon Chip these (MCLR, PG[E]D and PG[E]C) for programming and debugging. Unless your application only needs three I/ Os, you will inevitably end up sharing some of these pins’ functions. These shared connections can cause significant hassles. This became apparent as we worked on an upcoming project that pushes a PIC12F1572 to its limits, using five I/O pins and running the processor at its highest operating frequency. Some background Microchip PIC microcontrollers have long used a five-wire programming interface. The voltages and protocol have varied over the years, but these five wires have always performed broadly the same roles. The PICkit 2 and PICkit 3 programmers both sport six-way headers; the later PICkit 4 and Snap programmers have eight-way headers. This is because these programmers now support Microchip parts that do not belong to the PIC family, such as AVR and SAM devices which came into Microchip’s stable with their 2016 purchase of Atmel. While the exact pin mapping of these five wires varies between PIC families and pin counts, the small number of pins on the 8-pin parts means that there are not many permutations. By Tim Blythman Australia’s electronics magazine The purpose of the Helper device we have developed is to switch the function of some pins on your micro between programming/debugging and application-specific I/Os during development. This will make your life much easier. While we can’t promise that this Helper will work with all 8-pin PICs, it should work with most. The main exception we’re aware of is PIC10F parts (some of which come in 8-pin packages, but only six are connected). Table.1 shows the five connections used for PIC programming, their order on the programming header and what pins they connect to on an 8-pin PIC. Note that the ground pin is located in the centre of the group, reducing the chance of damage if the header is reversed. One way to re-use pins 4, 6 & 7 on an 8-pin PIC is to mount it in a socket on the board, then when you need to program it, unplug it and insert it into a programming socket. After programming, it can be re-inserted into the original socket on the board. But this can quickly become tedious as the chip is repeatedly moved between the programming socket and the test circuit. It also means you can’t perform in-circuit debugging (ICD). The alternative is so-called ICSP (in-circuit serial programming), which allows the chip to stay in place and be programmed ‘in circuit’. But siliconchip.com.au Fig.1: most of the circuitry is for switching the pin connections for PIC chip IC1 between the ICSP header (CON3) and the TGT PCB pads, which plug into a development board. S2 is used to energise the relays. The board can be split between CON1 and CON2 to allow some distance between the circuits if necessary. this might not be possible when pins 4, 6 or 7 need to be used for the project at hand, depending on how they are used. Pins 6 & 7 are usually fully featured; in the case of the PIC12F1572, they can be used as analog inputs to the ADC (analog-to-digital converter), comparator or as PWM outputs. In most cases, MCLR can also be used as an input, if desired. In our recent design using the PIC12F1572, we used pins 6 & 7 as analog inputs to sense the rotation of potentiometers, so both are connected to a low-impedance analog voltage source. This prevents successful in-circuit programming. Also note that some programming modes apply up to 13V to the MCLR pin (pin 4). If this is being used as an input, anything else connected to it must handle this during in-circuit programming. A solution to this is that some PIC parts are available with a so-called debug header variant. This is a specialised part with extra pins to separate the programming and debug functions from the other pin functions. A board fitted with jumpers often allows the header to emulate different parts. But these parts are much more expensive than their off-the-shelf counterparts, as might be expected for something that sees very limited production. And they are not available to suit all PIC parts. An example is the AC244053, which can emulate the PIC16F1454, PIC16F1455 or PIC16F1459. This specialised chip is a 28-pin SOIC (SMD) device, necessary to provide all 20 pins of the PIC16F1459 plus the separate debugging/programming pins. You can purchase it from the Digi-Key website for around $75: www.digikey.com.au/products/en? keywords=AC244053 Our solution Header pin Pin on PIC Label 1 4 MCLR Master clear and reset. It can also be used to apply Vpp (above 5V) to enable programming mode on the attached chip. 2 1 Vcc Power, which could be provided by the programmer or the connected circuit. 3 8 GND Circuit ground 4 7 PGD Programming data signal; driven by the programmer during writes and driven by the chip during reads. 5 6 PGC Programming clock signal, usually driven by the programmer. For a slightly cheaper and more generic solution, we’ve designed a tool that works with most 8-pin PIC microcontrollers. We use a set of relays to switch between the programmer and the target PCB, ensuring only one is connected at a time. This removes conflicts, ensuring that the pins are dedicated to only one role at a time. So you can easily switch between programming the chip and testing its functions. Note, though, that it might or might not allow you to use in-circuit debugging; it depends on whether your code will still work with the debugging pins disconnected from their other roles. While debugging a semi-functional circuit is annoying, we have done so in the past and successfully fixed difficult bugs in our code. You might need to temporarily modify the code to ignore the state of the dual-use pins; that’s still better than not being able to use in-circuit debugging at all! Fig.1 shows the circuit diagram of the Helper. In a similar vein to the debug header, the Helper has a set of Australia’s electronics magazine June 2021  65 Table.1: PICkit programming header & 8-pin PIC pin mapping siliconchip.com.au Role pins that slot into a DIL socket on the target PCB, where the programmed chip will go when development is complete. This header is marked TGT PCB, and its pins run to the headers marked CON1 and CON2. We’ll explain what these are for shortly. Pins 1, 4, 6 and 7 of the TGT PCB header are wired to the normally-closed contacts of 5V DPDT miniature telecom relays RLY1 and RLY2. The common contacts of RLY1 and RLY2 are wired back to IC1, which is where a real 8-pin PIC will be installed during development. Pins 2, 3, 5 and 8 of the TGT PCB header are also connected to the corresponding pins of IC1. This socket and header combination is our ‘emulated’ chip. When RLY1 and RLY2 are not energised, the target circuit will behave as though it has a PIC chip directly plugged in. The normally-open contacts of RLY1 and RLY2 are wired back to ICSP header CON3 (along with the ground connection, pin 8, from IC1). When the relays are energised, IC1 is connected to the ICSP header, allowing it to be programmed. Mini-USB socket CON4 and screw terminal CON5 allow 5V to be provided, via S2, to the coils of RLY1 and RLY2 so that the switchover can be effected by holding down pushbutton S2. D1 is the back-EMF suppression diode for the relay coils. So far, we have described the critical parts of the Helper that provide trouble-free programming. But since we’ve gone to the trouble of designing a PCB, we thought we’d add a few more features. CON1 and CON2 are wired straight through, and the PCB can be scored between these connectors, allowing it to be broken apart and the two parts wired together (eg, using a ribbon cable). The need to have the two parts physically distant is handy, but we found a degree of mechanical separation was also very useful. The TGT PCB header is a fair but not firm fit into a standard IC socket, so having the flexible wire connection allows some movement of the main PCB without affecting the seating of the emulated IC. You could also use the pads of CON1 or CON2 to wire directly to your development system’s PCB if it isn’t an 8-pin DIP part. For example, enamelled copper wire could be soldered directly to the pads of a SOIC (or smaller) IC footprint. Both CON1 and CON2 have their pins arranged to match the standard numbering used on 8-pin chips for simplicity. If bridged, JP1 and JP2 connect the relay power circuit (CON4 and CON5) to the target circuit. We joined these to allow the relay to be powered by our These photos show the construction we used for our first project using the Helper. Both CON4 and CON5 are unused, as we can provide power from our modified Snap programmer. 66 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.2: many larger (14-pin and 20-pin) PICs have the same configuration on their top 8 pins as an 8-pin PIC. By expanding the number of lines, we can make a board that will work with those chips too. Just make sure to check your PIC’s pinout before connecting it up; if it is one of the recent ‘enhanced’ 14-pin or 20-pin chips, chances are it will work. programmer, so we don’t need to supply power via CON4 or CON5. Note that this requires JP4 (see below) to be closed too. JP3 is connected across S2’s contacts, so it provides a slightly more permanent way of setting the relays to the programming position. You could also use this to connect an external toggle switch if you prefer something with a non-momentary action. JP4-JP7 can bridge the relay contacts of the Vcc, MCLR, PGC or PGD lines, respectively. We jumpered out Vcc in our rig to prevent the IC from losing power as the relay contacts change over. Still, you might prefer to leave it open to allow any other circuitry to fully reset after a programming sequence. S1 simply connects the MCLR pin to GND, resetting the microcontroller under normal conditions. It shouldn’t be pressed while S2 is active (and the programmer is driving the MCLR line), but it’s often handy to reset the microcontroller while testing. We’ve also provided a position (marked C1) for a bypass capacitor for IC1. Since the target circuit will usually have provision for this, it is not normally necessary. We didn’t populate it in our prototype. siliconchip.com.au Depending on the load incurred by your circuit, this capacitor could be used to maintain power to IC1 while the relay contacts change over. The capacitance needed for this to work depends heavily on the circuit current draw and switching time. The specified relays are rated to switch in about 4ms, so for example, if your circuit (including the microcontroller) typically draws 20mA, you would need 47μF to keep the supply voltage from dropping below 4V during that 4ms period, or 22μF to prevent it from falling below 3V. You can scale the capacitor value proportionally for heavier or lighter loads. Handling larger chips Despite having more I/Os, larger chips such as those with 14 or 20 pins can still suffer from the same problems as 8-pin chips. We tend to use all the pins for something, regardless of how many there are, which means that we often have to be careful what we connect to the programming pins. The good news is that many 14-pin and 20-pin PICs use the same pinout as the 8-pin types, just with more pins added below. So all we have to do to make the Helper usable with these devices is to expand the PCB slightly, Australia’s electronics magazine adding extra pins on both the socket for IC1 and the target chip header, as shown in Fig.2. CON1 and CON2 change to DIL headers to accommodate the extra pins, allowing a ribbon cable with standard IDC inline sockets to join the two boards if split apart. Note that 18-pin parts like the PIC16F88 that we’ve used for many years (but no longer recommend for new designs) has a different pinout from the newer ‘enhanced’ range of PICs, so it and similar chips will not work with this project. Most chips with more than 20 pins use a different pinout too, and many are also wider, so we didn’t think the compromises necessary to make this board support them were worthwhile. Construction The 8-pin PIC Programming Helper is built on a double-sided PCB coded 24106211 which measures 37 x 72mm, with a narrowed section at one end. Refer to the PCB overlay diagram, Fig.3, during construction. The 14/20-pin version (which also supports 8-pin PICs) uses a PCB coded 24106212 which is 37 x 105.5mm (Fig.4). The assembly procedure for the two boards is essentially the same. June 2021  67 Fig.3: construction of this 8-pin version of the Helper is straightforward, but we recommend fitting a socket for IC1 so that you can change it out for different parts in the future. Also note that the pins fitted to the TGT pads should be installed underneath for the correct orientation when plugged in. Fig.4: building this version that suits 8, 14 & 20-pin PICs is almost the same as the 8-pin only version. It just uses larger sockets for IC1 and the TGT connections, and larger headers for CON1 and CON2 (if fitted). 68 Silicon Chip If you intend to separate the PCB between CON1 and CON2, do this now so that no components are damaged. Carefully score both sides of the PCB to break the copper connections. This will reduce the chance of tearing them off the PCB. Then, while firmly holding the larger half of the PCB in a vice or pliers, flex the smaller (CON1) half of the PCB with pliers along the line. Once the PCB separates, you can tidy up the rough edges with a file. Take care to do this in a ventilated area (such as outside) to minimise inhalation of the resulting glass fibre dust. The first part to fit is the mini-USB socket (CON4), as it’s the only surfacemounted part. Some flux paste is handy, but since only the two outer power pins need to be connected, you could get away without it. Apply flux to all the pads and slot the connector into the holes in the PCB. Solder the smaller pads to the PCB. We’ve extended the two mandatory (power) pads to make this easier. If you created any solder bridges, remove them using solder wicking braid and a bit more flux paste. Then solder the four larger pads to the PCB to mechanically secure the part. Some time and heat may help here due to the larger metal mass. Clean up any excess flux at this point. Fit diode D1 next, noting the location of the cathode band. Then install the relays. They will have a stripe on their body to indicate the pin 1 end, or perhaps have a pin 1 dot like an IC. This end goes nearest the diode, as shown in Figs.3 & 4. Solder two leads to secure the relays roughly in place and adjust them to be flat against the PCB one lead at a time. Finally, solder the remaining pins. We recommend using a socket for IC1 so that the PIC chip can be changed when necessary. Our photos show the socket fitted with a PIC12F1572 for our current project in progress. Use the technique described above to ensure that the socket is flat. The seven jumpers (JP1-JP7) are simply two-pin headers. These can be easier to handle if fitted with the jumper shunt first, as it provides plastic surfaces that won’t transfer heat as quickly. Solder these in the positions marked. CON5 is intended to take a two-way screw terminal, but you could solder wires directly to the pads instead. Australia’s electronics magazine CON3 should ideally be a rightangled header to suit your programmer; our photos show the Helper connected to a low-cost Snap programmer, but the PICkit series is also suitable. You can temporarily fit the header to your programmer to ensure it is correctly aligned while soldering. Next, fit buttons S1 and S2, pressing down firmly to snap them into place before soldering. For the TGT PCB pad, we simply soldered header pins to the underside of the PCB. We aligned them by slotting them into an 8-pin DIL IC socket during soldering. If you are using machined-pin IC sockets, you should solder machined pins to the Helper, or else they will not plug in properly. Test fit them before soldering to ensure that they will be held securely in the socket. The advantage of using standard square header pins is that your prototype board (that the TGT PCB will plug into) could be fitted with socket strips during the testing phase, making plugging and unplugging this board very easy. They will also fit standard dual-wipe sockets, although they are a tight fit. Regardless, as you can see from our photos, these pins are fitted to the underside of the PCB to maintain the correct pinout. If you have broken the PCB between CON1 and CON2, use a ribbon cable to bridge the gap. For the 8-pin version, simply wire pin 1 to pin 1 through to pin 8 to pin 8. You could also fit header pins to both ends and use jumper wires to join them. For the 14-pin/20-pin version, you’re better off fitting 2x10-pin headers to the boards at both ends, then using a length of 20-way ribbon cable fitted with IDC line sockets at either end. Make sure when you plug it in that the pin 1 stripe is at the pin 1 end of both headers. Testing Apply 5V power via CON4 or CON5 and press S2; you should hear the relays clicking. If not, then the relays or diode D1 might be reversed. You should get a similar result by shorting JP3. Another simple test is to use any circuit that has a socketed 8-pin PIC (or 14-pin or 20-pin if you built the larger version). Remove the PIC from the socket and place it in IC1’s socket, then fit the TGT PCB pins into the vacated siliconchip.com.au Usage See the separate panel at right for information about how we modified our Snap programmer to provide 3.3V or 5V power to the target circuit. With this modification, we’re able to use the much cheaper Snap in a wider variety of roles. Since this modification provides adequate USB power when set to 5V, it can easily power the relays, and we don’t need to supply any other power to the Helper; JP1 and JP2 just need to be shorted. Other programmers (such as the PICkit 2, PICkit 3 or PICkit 4) can be used with this arrangement, although these programmers might only be able to source a limited amount of current. Our experience is that they can supply a fair bit beyond what a PIC needs, but if it is not sufficient, power the relays on the Helper via CON4 after removing shunts from JP1 and JP2. In our setup, we’ve also fitted JP4 to provide 5V to the programming target. Our project is intended to be powered externally, but this means we don’t have to make a separate power connection to our breadboard prototype. Plug your development PIC into the onboard socket, then connect the TGT PCB header to your custom PCB’s IC socket to complete the ‘emulation’. At this stage, the breadboard project is in normal operating mode and can be powered up. To reprogram IC1, press and hold S2 (or toggle a switch attached to JP3), then start the programming process. Once it is complete, release S2 (or re-toggle the switch across JP3). If necessary, press S1 momentarily to reset your target PIC, and it will be back in the normal operating mode. Summary While we had a specific use case in mind when designing this project, it is generally useful while working with most 8, 14 or 20-pin PIC microcontrollers. The various jumpers provide the means to set up different combinations of connections, including powering it from various sources. We hope it will become a handy tool in your development and prototyping toolkit, as it has for us. SC siliconchip.com.au Modifying the Snap programmer to provide power The Snap programmer is great value, packing many of the same features as the PICkit 4 for around a third of the price. But two features it lacks are the ability to provide power to a target chip, and providing the higher Vpp voltage needed to use high-voltage programming mode. Luckily, the second aspect is becoming less important. Practically all newer PICs support low-voltage programming for most cases. Where the MCLR pin is not needed as an input, it’s likely that high-voltage programming is not required, except for a few older PICs. If we can use the Snap to provide power to its ICSP header, then it can come very close to supplanting the PICkit 4. In a stroke of luck (or was it by design?), there are a pair of test pads on the Snap which provide both 5V and 3.3V power. These are located adjacent to U5, a 3.3V MCP1727 linear regulator capable of delivering up to 1.5A. Our update is to solder a 3-pin socket header to these pins. They are spaced around 6mm apart, so this can be done reasonably elegantly with a 0.1in (2.54mm) pitch header simply using the outside pins. The photo below should make this fairly clear. Start with a 3-way female socket and trim the middle pin close to the plastic shroud. Solder one pin to the pad marked 5V0 and the second pin to the pad marked 3V3. To connect power to the ICSP header, we used half a jumper wire soldered to pin 2 of the ICSP header. You can plug this into the left-hand socket for 5V, the right-hand socket for 3.3V (which is necessary for most PIC32 parts) or the centre socket to provide no power. Just make sure that the shortened middle pin isn’t contacting anything on the board. With this simple addition, we are now using the Snap for practically all our development work. Note that it doesn’t have the current limiting that a PICkit 4 would provide. ► socket. If all the pins are connected correctly, then the circuit should work as designed. The added header has been tilted to prevent it from being too bulky, and to allow the flying lead to enter at a comfortable angle. Parts List - PIC Programming Helper 1 double-sided PCB coded 24106211 measuring 37 x 72mm, for 8-pin PICs only, OR 1 double-sided PCB coded 24106212 measuring 37 x 105.5mm, for 8, 14 or 20-pin PICs 2 compact 5V DIL telecom relays (10-pin DIP, eg, TQ2-5V or EA2-5NU) [Silicon Chip Online Shop Cat SC4159 or SC4158] 7 2-way male pin headers and jumper shunts (JP1-JP7) 2 4-way male pin headers OR 2 10-way male pin headers (to connect to TGT PCB; see text) 1 5-way male right-angle pin header (CON3, ICSP) 1 8-pin, 14-pin or 20-pin DIL socket (for IC1) 1 2-way mini screw terminal block (CON4) 1 mini Type-B USB socket (CON5) 1 1N4004 1A diode (D1) 2 tactile switches (S1, S2) Optional parts to split 8-pin version 1 10cm length of 8-way ribbon cable Optional parts to split 8/14/20-pin version 1 10cm length of 20-way ribbon cable 2 20-pin IDC line sockets 2 10x2 pin headers Australia’s electronics magazine June 2021  69 The New Arduino IDE 2.0 Review by Tim Blythman The Arduino boards and software are incredibly popular, mainly because of the free, powerful and easy-to-use integrated development environment (IDE) for developing code. Now there has been a significant revision of the IDE with the beta release of version 2.0. Here is what you can expect from it. I t was just in March last year that we took an in-depth look at the Arduino ecosystem (siliconchip.com.au/ Article/12575). That article included details on the history of the Arduino software; primarily, the IDE. Tracing its history back almost 20 years to the Wiring IDE (http://wiring. org.co/), it has been nearly 10 years since the official version 1.0 release of the Arduino IDE. It is open-source, which means that it is easy to write libraries, add support for new boards and even make clones of existing boards. Some people have noted that the Arduino IDE lacks some features that experienced programmers have come to expect from other development environments. These include features such as debugging, auto-completion and source code management. command-line-based Arduino-cli (command-line interface) and the Arduino Pro IDE. We understand that a lot of what has gone into the new IDE has been informed by those programs. First look Opening up the IDE after installation opens a window as shown in Screen 1. The overall appearance is similar to older versions, but with a few extra buttons down the left-hand side and a new drop-down list near the top. These extra buttons are to access the Boards Manager, Library Manager and the debugging and search functions. These are features we expect to use a lot, so it’s handy to have them just one click away. The new drop-down selects a board and port combination. This makes it easier to work with different projects, as the board and port can be changed easily and together, meaning less chance of getting these mixed up or changing one and not the other. At this stage, the debugging function only works with some SAMD and Mbed boards and requires a separate debugging probe. So we weren’t able to test that feature out. The debugging console and controls are visible in Screen 2. We also found a comprehensive list of keyboard shortcuts; they are accessed from the File → Advanced → Keyboard Shortcuts menu item. The Output window is hidden by default, so pressing the Verify or Upload buttons doesn’t immediately Arduino IDE 2.0 The Arduino IDE 2.0 was released in February, and not long after that, we downloaded it and tried it out. If you don’t wish to switch over fully, it can run alongside the current version 1.8.13 (and older versions). We downloaded the .zip installer version from siliconchip.com.au/link/ab85 Note that Arduino IDE 2.0 is still in the beta stage of development. This means that it is essentially complete, but still has some minor bugs and glitches. The blog announcement (found at siliconchip.com.au/link/ab84) indicates that the new version will include some of the requested features that we mentioned above. In the March 2020 article, we noted that some Arduino software variants had popped up, such as the 70 Silicon Chip Screen 1: simply hovering your mouse over a keyword will bring up a tooltip, pressing F12 will open the file where the keyword is declared. Australia’s electronics magazine siliconchip.com.au Screen 2: the debug controls are shown at left, while the list of keyboard shortcuts is shown in the main editor window. appear to do anything, which is disconcerting. Once the Output window appears (when verification completes), this is less of a problem. The Boards Manager and Library Manager now appear as panels in the Editor window (see Screen 3), rather than modal windows, meaning that they don’t block working on sketches. The Serial Monitor appears as a panel rather than a separate window too. The context-sensitive help feature is also visible in Screen 1. In this case, it is showing the value of an enumerated symbol. This makes it much simpler to follow and troubleshoot code inside sketches. It’s even possible to right-click on an item in the code to jump to the library file which defines it. Line numbering is turned on by default, and small arrows allow functions to be collapsed, making it easier to view and navigate a sketch. Screen 3: the Library Manager is now an integral panel and can be toggled from the block button at left. Screen 4: auto-completion is activated by the Ctrl-Space key combination; the results are often very extensive. siliconchip.com.au Quirks One slight problem we ran into was that opening a new window takes a few seconds in the IDE 2.0, while it is practically instantaneous with older versions. But this is not something that needs to be done often. We also noticed that the IDE did not prompt us to save a changed file when closing the window, but rather it appears to save the changes without prompting. The auto-complete feature (see Screen 4) is very comprehensive (for boards that support it), giving a great number of options, but we had to use Ctrl-Space to trigger it, even though this is not noted in the getting started guide. Interestingly, the IDE 2.0 does not come with any board profiles installed. This suggests that the Arduino developers no longer favour the older AVR boards (their profiles came with older versions of the IDE). Despite this, we Australia’s electronics magazine don’t think we’ll see them disappear any time soon. In any case, they are easy to install from the Boards Manager. Otherwise, the newer version has all the same features and menu items in much the same places, meaning that it’s straightforward to transition between the two. Summary While we haven’t had a chance to test-drive the Arduino IDE 2.0’s full range of features, we’re happy that it does everything that the older versions do and more. We’re looking forward to testing out the debug feature once we have the hardware required. We haven’t come across any glitches in the beta version that have been show-stoppers, but we expect that updated versions will quickly follow that iron out some of the minor quirks we noted above. We’re planning to continue using the Arduino IDE 2.0 to find out what else it has to offer. More information on using the new and improved features of the IDE 2.0 can be found at siliconchip.com.au/ SC link/ab86 June 2021  71 Programmable Hybrid Lab Power Supply with Part II – by Richard Palmer Our new Lab Power Supply delivers 0-27V at up to 5A <at> 16V, and can be controlled remotely via WiFi. You can even set up multiple units to track automatically and connect them in series or parallel. After describing the configuration and circuitry last month, this follow-up article shows how to build the two PCBs and wire up everything neatly into a modestly-sized plastic instrument case. A s previously explained, this supply uses a three-stage hybrid arrangement, with two switch-mode supplies followed by a final linear stage. This gives excellent efficiency and keeps the whole thing compact and light, while still delivering very good performance. It has quite a few useful features, such as soft-starting and a fast settling time with minimal overshoot. With these features, plus its programmability, it can produce controlled pulses of power or voltage steps for testing how devices handle transients. The AC-DC switch-mode supply is a prebuilt module, but the other two modules in the device must be assembled before the whole thing can be fitted into its case and wired up. So let’s get onto building those two boards. Construction The first step is to assemble the boards. Fig.6 is the PCB overlay diagram for the Regulator board, while Fig.7 is the diagram for the Control board. All the parts on the Regulator board mount on one side, 72 Silicon Chip and most are surface-mount types. The Control board has components on both sides, but just a few SMDs, and they are all on the same side. It’s best to solder the SMDs first, then move on to the through-hole components. If you have a solder reflow oven, (or make your own! See Control board features & specs • Dual core ESP-32 240MHz, 32-bit processor • Onboard 2.8in or 3.5in colour LCD touchscreen display • 520kB RAM, 4MB flash memory • Full-size and micro SD card sockets • Touch interface plus detachable switches, LED and rotary encoder • 20-pin expansion header with I2C x 2, SPI, DAC x 2, ADC x 2, serial communications and GPIOs • Maximum of 17 GPIO/PWM pins can be used • WiFi (802.11 b/g/n) with 150Mbps throughput • Bluetooth & BLE support • USB-serial port • Web server and web client functions • Over-the-air (OTA) or USB reprogramming Australia’s electronics magazine siliconchip.com.au Fig.6: all components mount on the top side of the Regulator board in these locations. It’s generally easiest to fit all the SMDs before moving onto the through-hole parts, and leave the devices along the top that attach to the heatsink until after testing the basic functions. Note that SMD diode D3 has two anode terminals and three cathode terminals, two of the latter being on the sides. Errata: REG4 was incorrectly listed in the parts list last month as a VXO7803, when it should be the 5V version labelled VXO7805. If you purchased it, the “7803” suffix part will still work. Also, IC4 should be an MCP4725A0T-E/CH. Q3 & Q4’s base and emitter pins are swapped, and therefore should be soldered upside down relative to the overlay. how in our feature April/May 2020 issues – siliconchip. com.au/series/343) you can solder all the SMDs at once by manually adding solder paste to all the SMDs pads, then carefully placing the parts on top, and finally running both boards through a reflow cycle. Once they have cooled down, inspect all the ICs carefully to ensure there are no bridges between pins or unsoldered pins. Unsoldered pins can be fixed by adding a little flux paste, then a little solder. Bridged pins can be fixed by adding a little flux paste, then applying solder wick and removing it as soon as the excess solder is drawn away. The parts used can certainly be hand-soldered, and the only ones which are a little tricky are IC1, IC2 & IC6 on the Regulator board. The rest should all be straightforward, but be careful with the polarised parts. They are the ICs and diodes, including the LED. Verify that all the pin 1 markers are in the correct positions before soldering the parts. With the SMDs all loaded, move on to the through-hole parts. It’s best to start with the two box headers; make sure they are orientated as shown. On the control board, we recommend that you fit the Construction options Both side panels of the Control board are detachable, providing layout flexibility. The 2.8in LCD can be upgraded to a 3.5in type as long as there is room (you would need a larger case than the one specified). If doing that, make sure you program the chip with the alternative binary file, as the 3.5in LCD has a different controller to the 2.8in type. siliconchip.com.au pushbuttons next, then the LED, with the top of its lens about 2-3mm below the top of the switch caps, and the flat side orientated as shown. Solder the two 19-pin female headers for the ESP-32 module next. They can be cut from one 40-pin header strip, but make sure you cut beyond the 19th pin location in both cases, to avoid damaging it. The DC socket and micro SD card socket are not needed for this project, although you might want to install the DC socket to assist with testing. That leaves REG1 on this side of the board, which is only needed if you already fitted the DC socket. Its metal tab faces towards CON2. After fitting the rotary encoder on the other side of the board, that just leaves the LCD. None of the solder links need to be bridged, and the solder stakes shown at the two test points (EXT_PWR and EXT_GND) are also optional. Aligning the height of the display with the switches is essential for a neat panel layout. Refer to the bottom of Fig.7 to see what the final arrangement should look like. Set the top of the display 2-3 mm lower than the tops of the switch buttons for a good result. This should mean that the touchscreen will be 0-1mm proud of the panel face, and the buttons should protrude A more compact 75W switching supply could be used (eg, MeanWell LRS-75-24), which would reduce the overall heat generation, although it would also limit the maximum output current. While you can build two separate Supplies and gang them together as a tracking supply, it would also be possible to connect two Supply boards to a single Control board to make an all-in-one tracking supply which could also be configured to provide twice Australia’s electronics magazine the current (with the outputs in parallel) or twice the voltage (outputs in series). That would require an added isolator so that the two Supply boards could float relative to each other, as well as two separate AC-DC supplies. This two-channel design will require a larger case, such as Jaycar Cat HB5556. It will also require revised software. We hope to present the required changes for that possibility in a future article. June 2021  73 Fig.7: the Control board is sparsely populated, with all the SMDs on the front side along with the touchscreen, rotary encoder, switches and LED. The only required components on the back side are the ESP-32 module (which plugs in via header sockets) and box header CON2. CON3, CON4 and the wires shown going to their corresponding headers are only required if the board is cut along the slots when using a different front panel arrangement. by about 1.5mm. The length of pins provided on displays differs, so you might have to remove any existing pins and add longer ones if they are too short. The dashed lines shown in Fig.7 indicate where wires would be connected if you cut the board apart along the slots, but we don’t recommend that you do that unless you have specific plans to mount the control panel in a different case than the one specified. Finishing the Regulator board On the Regulator board, mount the fan header next, followed by the vertical axial resistors and electrolytic capacitors, observing the latter’s polarity markings. Follow with REG3 & REG4, ensuring that you don’t get the two different 74 Silicon Chip types mixed up as they have different pinouts. You can then mount the relay and toroidal inductor. The PC stakes shown for VIN, GND and VOUT are optional. There are advantages in soldering wires to stakes (it can be easier to make a good joint and there is less chance of strain-related failures), but it is certainly possible to solder wires directly to the board. That just leaves the components which mount on the heatsink: REG1, REG2, Q1, Q2 and the NTC thermistor. Don’t forget to insulate the device tabs and mounting screws from the heatsink using washers and bushes. Commissioning the Control board The bare ESP32 module and a USB cable are all that are Australia’s electronics magazine siliconchip.com.au The prototype used a support panel to mount to the front panel to avoid additional mounting holes. When building it as described in the article, standoffs will need to be used to mount the Controller board directly to the fascia. required for the first stage. Mounting the module on the Control board will come later. We’re assuming that you’re already somewhat familiar with the Arduino development environment. If you don’t already have the Arduino IDE (integrated development environment) install, you can download it from www.arduino. cc/en/software You will need to add ESP32 board support to the IDE if you haven’t already. To do this, go to File → Preferences and add “https://dl.espressif.com/dl/package_esp32_index. json” to the Additional Boards Manager URLs. Next, open the Boards Manager (Tools → Board → Board Manager), search for ESP32 and click “Install”. This will set up the development environment and add an extensive list of example programs to the list. Set the Board to “ESP32 Dev Module” via the menu (see Screen1). The rest of the settings may be left as the defaults. Plug in the ESP32 module and select the new communication port that appears from the menu. To check that it is working correctly, open the Communication → ASCII Table example and upload it (CTRL+U in Windows). Open the Serial Monitor, set the baud rate to 9600, and the screen should fill with the ASCII output from the test sketch. Loading software over-the-air To demonstrate other possible applications for the Control board, we’ve created a version of the WiFi weather app used as a demonstrator program for the D1 Mini BackPack (October 2020; siliconchip.com.au/Article/14599). This also happens to be a good way to test the Control board independently. We have made a ZIP file available for download from the SILICON CHIP website which includes two display options: a 2.8in or 3.5in touchscreen (you can also download it from siliconchip.com.au/link/ab72). The 2.8in version ends in -28. BIN while the other version ends in -35.BIN. Load it using the OTA update process described below. The Weather app has a built-in OTA function to simplify loading of the power-supply controller code. Over-the-air programming of the ESP32 is a two-stage process. First, we load a simple sketch with the over-the-air (OTA) updater via USB. Load up the ArduinoOTA example (File → Examples → ArduinoOTA → OTAWebUpdater). Fill in your WiFi credentials (SSID and password) at the top of the program (see Fig.8). Open the Serial Monitor and change the baud rate to 115,200. Save the Arduino sketch, as we’ll be using it again. Compile and upload the sketch, and note the IP address displayed in the Serial Monitor. Now you can disconnect the ESP-32 module and plug it into the Control board, making sure that it is aligned as in the photo below. Plugging it in the wrong way around could be catastrophic! Do not connect the Control board and Regulator board together just yet, but do make sure that the TFT touchscreen is mounted on the Control board. Power this combination up, using a USB cable or (if you fitted CON1 and REG1) a DC supply of 9-12V. The To provide a better layout for the front panel, the Controller board was split into three parts and linked with rainbow cable. The mounting arrangements shown here use a piece of clear perspex, which is not required to complete the project. siliconchip.com.au Australia’s electronics magazine June 2021  75 Screen2: if your module has been assembled and programmed correctly, once it has connected to your WiFi network, it should give local weather data as shown here. The assigned IP address is at the bottom right. Screen1: once you have selected the correct Board in the Arduino IDE Tools menu, the settings should look like this. Fig.8: to upload code to the ESP-32 via WiFi (OTA update), you need to add your network credentials towards the top of the program, as shown here. The hostname can be left as-is or changed to suit your requirements. Fig.9: when presented with the ESP-32 login page, use the default credentials of “admin” & “admin”. There’s no need to change these as they are only used once. Fig.10: once logged into the OTA page, you can select a file and then upload it into the ESP-32’s flash memory remotely using the “Choose file” and “Update” buttons respectively. 76 Silicon Chip USB cable doesn’t have to be plugged into your computer, although it could be. Open a web browser on your computer and type in the ESP32’s IP address. You should be presented with a login screen (Fig.9) The username and password are both “admin”. There’s no point in changing these to something more secure, as we’ll only be using this sketch once. After logging in, select the software file you’ve downloaded with the “Choose file” button (Fig.10), then “Update”. The web page will track the upload progress; then, after a short delay, the ESP32 will reboot, running the weather app (see Screen2). Once you have verified that the Control board is working correctly, you can load the power supply program. It is part of the same ZIP package that contained the weather app. There is only a single binary for the power supply program as this project is designed around a 2.8in display (ergo, use file -28.BIN). Once you’ve loaded that program using the same OTA update procedure (or uploaded directly via USB), disconnect the DC supply (if present) and connect the USB cable to your computer (for both power & communications). Open the Arduino serial monitor at 115,200 baud, and you should see some start-up commands, ending with the “SCPI Command?” prompt. If you type “*IDN?” into the command field and click Send, the software should respond with something like “SiliconChip,PSU01,PS01-01,1.0,NONE”. We will discuss setting up WiFi and other configuration options for the power supply a bit later. Screen rotation & calibration Some TFT screens come with the origin of the touchscreen rotated 180° from that of the display. If your touchscreen appears to not be working, that could be why. Try tapping the screen near the SET legend at upper right. If this takes you to the calibration screen, simply tap the ROT button in the centre of the screen (see Screen4 at upper right). The number below it should change from 3 to 1. Wait for the yellow [E] indicator to go out (after around 60 seconds), and the new value will be stored permanently in the ESP32’s EEPROM. Australia’s electronics magazine siliconchip.com.au Screen3: a mockup of the main screen that appears at switch-on. The present voltage, current and power are shown at left, with the input voltage and heatsink temperature above. The voltage and current setting are at right, with the buttons to enable/disable current limiting and tracking below. The device’s status is shown in the top right-hand corner of the screen. Screen4: the calibration screen shows the unit’s voltage and current readings at upper left, with the adjustable calibration offsets to their right. The save and cancel buttons are at lower right, with the screen rotation button in the middle and the touch calibration menu button at lower left. (All menus are accessed by pressing the buttons which appear along the bottom when appropriate). To align the touchscreen accurately with the display, tap the TCH button at the calibration screen’s bottom-left corner. Follow the prompts, touching each of the two + symbols six times. As above, it will permanently store the values after 60 seconds. The PSU software download also contains PDF manuals for the two boards, with information beyond that contained in these two articles. immediately. At this point, the green box should disappear, leaving the main menu displayed. A small green “W” near the top right corner indicates that WiFi is operating. The On button should light the LED, and the Off button should turn it off again. Touching any of the menu buttons along the right-hand side of the display should highlight the setting value next to it, or change the mode of a function. As described last month, when a setting is selected on the touchscreen, the encoder should change the selected digit’s value, and the SW_L and SW_R buttons should shift the highlighted digit left or right on the screen. Setting up the WiFi network Now that the Control board has been programmed, when you power it up, the control menu (Screen3) should appear with a green box overlaid. The program will try to connect to a local WiFi LAN, and time out after 10 seconds, as we have not yet provided it with credentials. Then another 10-second delay should occur, while it seeks for an existing ESPINST network. Finally, it should become the Access Point for the ESPINST network almost Screen5: the WiFi settings screen allows you to set the device’s hostname, network SSID and password, and also shows the unit’s current IP address and hostname. The “AC” setting stands for auto connect. siliconchip.com.au Further testing Now it’s time to power off the Control board and connect it to the Regulator board using a 20-wire ribbon cable about 10cm long, with IDC plugs at either end. If you haven’t made this cable up yet, do so now, making Screen6: the tracking screen lets you assign the Supply to a tracking group (GRP) and then set whether it tracks the voltage, current or both of other units in the group. Australia’s electronics magazine June 2021  77 sure that the pin 1 indicator on each IDC plug (usually a triangle moulded into the plastic at one end) points to the same wire in the cable. Grey ribbon cable typically has one red wire to indicate pin 1. If you’re using rainbow cable, use the black wire (black = 0 in the resistor colour code scheme). Ensure that the IDC headers are crimped firmly enough for all the blades to pierce the ribbon cable insulation fully. You can usually tell that this is the case because the two (or three) pieces of each IDC plug will be completely flush and parallel. Partially crimped IDC plugs will usually have a gap at one or both ends, visible upon close inspection. This is the most common cause of ribbon cable failures. Connect the two boards together. It should be impossible to misconnect them due to the keyed headers. Still, just to be sure, it is a good idea to verify that the GND, 5V and 3.3V rails are correctly connected at either end using an ohmmeter or continuity tester. Also check that none of these rails are shorted to each other. Now plug the USB cable back to the ESP32. As there is currently no other source of power, this is quite safe. A USB port can also provide sufficient current to test the PSU’s basic functions, other than the fan. Now check that the 5V and 3.3V rail voltages are correct on the Regulator board. The cathode (striped end) of diode D7 is a convenient point to measure the 5V supply, while the thermistor connector pin closest to the power transistors should register 3.3V. On the Arduino serial monitor screen, the power-on selftest (POST) should report that three I2C devices have been detected. If any do not show up, a solder bridge on one of the ICs is the most likely culprit. The LED on the power supply board should follow the one on the control board as the output on/off switches are operated. Failure here is most likely due to the LED being soldered in backwards, or a solder bridge on IC6. On the control panel screen, the output current should be showing 0A a few seconds after turn-on, once the autozero function has completed. The input and output voltages should read less than a volt, as there are some current paths from the 3.3V and 5V supplies to these rails. The temperature reading will be out of range until the thermistor is soldered in. Set the output voltage to 2.0V, as this will be needed for calibration. Next, disconnect the control panel from the power supply board and connect a 7-12V DC supply between the Vin terminal and GND on the Regulator PCB. Check the output voltages on the +5V and -5V regulators. The nominally +5V rail should read approximately 4.5V, as the reverse bias protection diode (D1) is in series with this supply. Low-current testing of the supply itself can safely proceed without the heat sink. Using the same 7-12V DC supply to Vin as before, and with the Control board disconnected, test the output voltage of REG1, which appears across ZD1. It should read somewhere between 3.6V and Vin, with a value approximately 3.6V higher than the voltage at the output of REG2 (the middle pin). Turn off the power, reconnect the Control board and switch back on. The relay should now switch on and off with the LED when the control panel switches are operated. Set the output voltage to 2V, switch the output on, and check the voltages at Vout (2V) and Vpre (about 5.6V). Adjust the output voltage and check that Vpre is tracking at around Vout + 3.6V. Next, attach a 47Ω (or slightly higher value) 1W resistor across the output. Set the voltage to 5V and make sure the output current reads approximately 100mA. Before turning off the control panel, set the output voltage to 2V and wait for that value to be saved to flash memory, after approximately 60 seconds, when the [E] indicator at the top right corner of the screen has gone out. Then unplug the USB cable. This sets us up for initial testing when we’ve assembled the entire supply. Panel preparation Drill and cut holes in the plastic instrument case’s front panel as shown in Fig.11. The holes should line up with the parts on the Control board (refer also to the bottom of Fig.7 for the mounting details). Hole “B” at left is for the output on LED, while the 12 holes marked “A” correspond with the mounting screws for the display and Control board to the rear of the front panel. The three “C” holes at lower-right are for the panel-mounted output and Earth binding posts. Fig.12 shows the cutting and drilling required for the rear panel, which is relatively straightforward. When finished, Remote control via SCPI The Standard Commands for Programmable Instruments (SCPI) protocol used in this project was developed in the early 1990s to provide a standard syntax and command structure for programmable instruments from power supplies to oscilloscopes and beyond. It was designed as a master-slave protocol, with the controlling computer always being master. While it was initially implemented on the GPIB bus (IEEE 488), other communication channels such as serial (including USB serial) and TCP are now commonly employed. SCPI commands consist of casesensitive keywords separated by colons. Commands ending in a question mark are 78 Silicon Chip queries, and the instrument returns a value, or set of values, to any query. Each keyword may have parameters associated with it, ergo: “:SET:VOLTage 350 mV” or “:MEASure:VOLTage?” Parameters may be integers, floating-point numbers or strings, depending on the command. Numeric commands may be followed by a unit, such as V, mV, A or mA. Full SCPI understands all the multipliers from yotta (1024) to yocto (10-24). This instrument only accepts ‘bare’ units or milli-units, avoiding the problems associated with setting megaamps when you intended milliamps! Each command, such as “MEASure” can Australia’s electronics magazine be issued using the full form or an abbreviation, which is always the part in upper case, and almost always four characters long. Thus “:MEAS:VOLT?” is equivalent to “:MEASure:VOLTage?” The IVI Foundation, which is the successor to the non-profit SCPI Consortium, has a website with exhaustive documentation on SCPI and more recently developed, and more flexible instrument communication protocols such as VISA and VXI at www.ivifoundation.org/specifications/ default.aspx The SCPI commands used for this programmable supply are fully detailed in the manual included with the downloads for this project. siliconchip.com.au Fig.11: the front panel drilling and cutting template scaled by 75%. The rectangular hole for the touchscreen can be made by copying this diagram, attaching it to the panel temporarily and then drilling a series of small (2-3mm) holes just inside the outline. Use a cutting tool like a rotary tool or, in a pinch, a pair of sidecutters to join all the holes together until the panel falls out, then file the edges smooth and until the touchscreen fits. Fig.12: the rear panel drilling and cutting is relatively simple, as you just need holes to mount the IEC mains input connector and cooling fan. While we’ve shown slots for the fan exhaust, it would be much easier just to drill a series of 5mm diameter holes in the area shown. Don’t make them larger than that so that small fingers can’t be inserted. Fig.13: the heatsink drilling details, plus the plan for the DIY version made from sheet aluminium at right. All holes are drilled to 2.5mm for tapping to 3mm on the commercial heat sink; drill to 3.5mm for folded version. Do not drill the mounting holes in the heatsink base until the components are attached to the heatsink. The holes can then be positioned by drilling through the bottom of the case. The DIY heatsink uses two pieces of 1.6mm aluminium sheet, 145 x 95mm and 145 x 85mm. The bottom edge of the heatsink is 3mm below the bottom of the PCB. siliconchip.com.au 79  S ilicon Chip Australia’s Australia’s electronics electronics magazine magazine siliconchip.com.au June 2021  79 5,5 44,5 31,0 21,0 11,0 16,0 20,0 9 26,0 2,5 12,5 9,0 4,0 2,0 20 9 14 9 27,0 181,0 4,5 4,5 8,5 8,5 18,0 16,0 189,0 16,0 64,5 26,0 2,5 16,0 9,0 12,5 4,0 248,0 24,0 25,0 27,0 48,0 48,0 27,0 26,0 24,0 Fig.14: this shows how to prepare the bottom of the case. The mounting holes are marked green and should be drilled through (3.5mm) and countersunk from the bottom. File the top of these posts down to the height of the lower posts. Only two of the green holes need to be drilled, depending on whether the commercial or DIY heatsink is used. The orange lugs also need to be filed down, but not drilled. The PCB mounts directly onto the two blue lugs with 9mm x 4G round head self-tappers, as does the MeanWell AC-DC converter. A second mounting hole is required for the MeanWell supply. It is 51mm forward of the blue mounting hole and 73.5mm inwards. Fig.15: the front panel artwork for the instrument is reproduced here at 75% of life size – in other words, you will need to enlarge it by 133% before photocopying. Alternatively, it can be downloaded at full size from our website so you can print a high-quality version to attach to the instrument. 80 Silicon Chip Australia’s electronics magazine siliconchip.com.au The completed prototype regulator module attached to the heatsink, which was reused from another project (hence the extra holes). Note the insulating washers under the device tabs and plastic bushes under the mounting screws. If using mica washers, add thermal paste on both sides. Check for full insulation between each tab and exposed metal on the heatsink before powering it up. mount the fan and IEC mains socket on the inside (with the mains socket inserted from the outside). The same-size front panel label artwork can be downloaded from the SILICON CHIP website, printed, laminated and glued to the front of the panel. (Note that Fig.15 is undersize – if photocopying, enlarge to 133%). Cut out the holes with a sharp hobby knife, and then the Control board can be attached and the knobs fitted. Making/attaching the heatsink All the basic functions have now been validated, so you can mount the heatsink. Fig.13 shows where to drill holes on the specific commercial heatsink, plus details on how to make your own. The bottom edge of both heatsink types protrudes 3mm below the bottom of the PCB as shown. The end of the heatsink closest to the back panel also protrudes 3mm past the end of the PCB, to allow the mounting hole to be set in from the end. Once you’ve finished that, mount the fan and power supply connector on the back panel of the case, and wire up the AC side of the AC-DC converter. The AC cables need only be about 7cm long, as the converter will be mounted quite close to the power socket. The Earth wire will need to extend to the front panel terminals. Insulate the ends of the mains cables at the power socket with heatshrink tubing. Several mounting lugs on the bottom of the instrument enclosure need to be trimmed, and three mounting holes drilled – see Fig.14. Depending on the heatsink option chosen, either the middle (CINCON) or front (DIY) lugs are drilled through. This is because the CINCON heatsink is slightly too short to reach the front mounting lug. siliconchip.com.au Drill a 3.5mm hole at the red dot, to secure the AC-DC converter. It is directly in line with one of the existing (unmodified) pillars, but 31mm closer towards the centreline of the case. Mount the AC-DC converter in the case with a 4G x 9mm round head, self-tapper through the hole next to the terminals, and a countersunk 3mm machine screw cut to length, with a spacer, through the hole that was drilled. Fold up a plastic cover for the AC terminals and power socket, and secure it under the converter’s edge. I made mine from a red polypropylene cutting mat. Now connect the AC-DC converter to Vin and ground and solder in the Earth and negative terminal wires for the front panel binding posts. Wind 4-5 turns of hookup wire around the toroidal core for the output filter inductor, then solder one end to the Vout terminal on the PCB, and mount the PCB/heatsink in the case. Connect all three wires to the front panel. I used crimp eyelet lugs to enable easy removal from the binding posts; however, you can also solder wires directly to them. The toroidal choke tucks into the corner of the case between the heatsink and the front panel. Finishing it up At this point, the Lab Supply assembly is substantially complete, and we move on to further testing. If you didn’t remember to set the output voltage on the control panel to 2V before switching it off, disconnect the mains, reconnect the USB cable and follow the instructions above. Disconnect the USB cable. Set the AC-DC converter’s output voltage to its lowest setting using its trimpot (fully anticlockwise) and then switch on the power. Vin should read within a few volts of 20V (the Australia’s electronics magazine June 2021  81 Table 1: CON2 pin mapping Expansion possibilities 20-pin header CON2, along with the two optional headers associated with the rotary encoder and pushbutton switches, offers a broad range of inputs and outputs for expansion, or when the Control board is used for other purposes. A total of 17 ESP32 pins are connected to these headers, besides the SPI bus, which is shared with the SD card and touchscreen (see Table 1). Several general-purpose I/O (GPIO) pins and the I2C bus are used in this Power Supply project; however, the SPI bus, serial port, USB port, DAC and ADC channels are unused and so are available. The I2C bus supports all modes up to 5MHz with 7-bit or 10-bit addressing. It is best to stick with 400kHz/7-bit operation, though, as many older I2C chips do not support the more advanced modes. I2C pull-up resistors are provided onboard. A second I2C bus is available as one of the configuration options for pins 13 and 14 of CON2, as alternates to GPIO0 and the second DAC channel. The SPI bus has been extended to the 20-pin expansion connector; one GPIO pin will need to be allocated as a chip select (CS) line for each additional SPI device used. As the SPI signals traverse the ribbon cable, it’s best to stick to 10MHz bus frequencies or lower. SD card file storage is supported. As with the ESP8266-based Mini D1 LCD backpack, an onboard micro SD card socket has been provided in addition to the full-size one on the LCD module. Either may be used, but not together, as a single chip select line is shared between them. Optionally, the card detect (CD) switch in the socket can be jumpered to GPIO3. It is grounded when a card is inserted, and will require a pull-up current to be configured in software for that pin. The two-channel ADC is capable of 12-bit resolution, and the maximum sample rate is around 27kHz under software control. Pads are provided between these pins and GND to reduce input noise when GPIO pins 34 or 35 are used as ADC inputs. The specified 100nF capacitors provide substantial filtering at even moderate frequencies, as the input draws just 50nA. Two 8-bit DAC channels are provided, with a practical throughput of around 200k samples per second. A logic-level serial interface is available, able to transmit and receive at up to 5Mbps. USB-serial is also supported. As noted in the text, unisolated USB power or communications are not recommended for the Power Supply project. Other than the I2C and SPI signals, the remainder of the pins are multi-function. Any GPIO pin can be configured as an interrupt input or PWM output. Most of the specialised pins (ADC, DAC and serial) can also be used for digital I/O, bringing the total number of GPIO-capable pins to 8, or 17 if the rotary encoder and pushbutton switches are not required. If there are insufficient GPIO pins for a specific project, an I2C I/O expander such as the MCP23008 can be added. CON2 pin # ESP-32 function ESP-32 pin PSU function 1 GND GND 2 GND GND 3 SPI:MISO GPIO19 – 4 SPI:SCK GPIO18 – 5 I2C1:SDA/GPIO GPIO21 I2C control for IC1,IC2,IC4 6 SPI:MOSI GPIO23 – 7 I2C1:SCL/GPIO GPIO0 I2C control for IC1,IC2,IC4 8 I2C2:SDA/GPIO GPIO22 – 9 COM2:TX/GPIO GPIO17 Sense DRDY signal from IC1 10 COM2:RX GPIO16 – 11 GPIO GPIO2 – 12 GPIO GPIO4 Sense SW_ON press 13 DAC1/GPIO GPIO25 – GPIO26 Control fan on/ off 14 DAC2/I2C2:SCL/ GPIO 15 ADC1-7/GPIO GPIO35 – 16 GPIO GPIO12 Sense SW_OFF press 17 ADC1-6/GPIO GPIO35 – 18 +5V +5V 19 +5V +5V 20 +3.3V +3.3V BLE modes, they have not been used in the power supply project. Also, a second serial port is available on the 20-pin expansion connector. It too is unused in the Power Supply project. USB-serial communication is available, via a micro USB socket on the ESP-32 module, providing a ready means of programming the device and debugging code using one of the available integrated development platforms, such as Arduino. The USB port also provides one of the SCPI control interfaces for this power supply project. It is highly recommended that a USB isolator is used with the Power Supply project to avoid ground loops that might destroy the ESP-32 or your computer’s USB port. These isolators are available in eBay or AliExpress for around $15 that work in either full-speed (11Mbps) or high-speed (480Mbps) modes. I have successfully used the variety illustrated in the photo below. Communication The ESP32 offers a broad range of WiFi options; it can connect to an existing 2.4GHz WiFi LAN or create a local network in ‘soft-AP’ mode. Both modes are enabled for the Power Supply project. First, the controller attempts to connect to an existing LAN, with credentials entered on the COMMS submenu. If that fails, it attempts to join an existing network with an SSID of ESPINST. If that fails, it creates the ESPINST network for other instruments to join. While the Control board supports both traditional Bluetooth and 82 Silicon Chip Australia’s electronics magazine siliconchip.com.au Your completed Hybrid Lab Power Supply should look not too dissimilar to this photo of the prototype. converter’s minimum setting). Note the voltages at Vout and Vpre (approximately 3.6v higher). If all is in order, it is safe to turn the trimpot to its highest setting, which will raise Vin to around 30V. Basic testing is now complete, and you can start using the instrument to provide power for projects on your bench. Calibration Calibrating the supply is optional, as current and voltage measurements will be accurate within a few percent, depending mainly on the resistors’ tolerances. To calibrate the voltage measurements, set the output voltage to 25V (or any other setting a few volts below the maximum value) and select the CAL menu on the screen (lower left of Screen3). With no load connected, turn the supply’s output on and measure the voltage with your multimeter. Using the numeric value controls, enter the difference between the multimeter reading and the value displayed on the screen at left. If the multimeter reading is higher, input a positive value. In the example shown in Screen4, the Power Supply is reading 25.00V but the reference multimeter is reading 25.12V, so 0.12V is set as the offset at upper right. Touch the SAVE button to save the result. This will also exit the Calibration menu. Wait for the [E] indicator to extinguish before turning the instrument off, so that the siliconchip.com.au new calibration value is permanently stored in flash memory (EEPROM). Repeat the same calibration process for current, with the output on, using a load resistor that draws 1A or more at any output voltage. A 1Ω 1W or higher power resistor will work fine. There is no need for zero current calibration, as this value recalibrates automatically after a short period whenever the output is off. If you want to use a WiFi network connection to the instrument, enter the COMMS sub-menu (Screen5). Fill in your WiFi credentials and tap the auto-connect (AC) button, if it is not already green. This will initiate the WiFi connection protocol. A green rectangle will appear showing connection progress. Once complete, “W” indicator at the top of the screen should be green and the IP address displayed at the bottom of the COMMS screen. Conclusion The Lab Supply, as presented here, is a very useful instrument indeed. Still, it could be expanded to have even more features due to the power of the ESP-32 WiFi & microcontroller module. Also keep in mind that the BackPack-style Control board is powerful and versatile in itself, and could be used to power various other designs. SC Australia’s electronics magazine June 2021  83 Review by Tim Blythman Weller T0053298599 Soldering Station Any serious electronics enthusiast needs a proper temperature-controlled soldering iron; ideally, one with interchangeable tips, to suit working with different sizes and types of components. We were given the chance to try out the Weller T0053298599 Soldering Station (previously known as the WE1010). W e probably all started with a simple iron that plugs directly into a wall socket. But once you get good at soldering, you’re much better off with a station that offers temperature control and less resistance to movement, with a supple cable connecting to the pencil. We do a lot of soldering at Silicon Chip; probably more than most people. But likely not as much as anyone working in a production environment. The Weller T0053298599 is pitched at ‘prosumer’, trade and professional users, so it is designed to be used for long periods on a regular basis. Therefore, it should have no trouble handling our sort of usage. base from sliding around. The underside vents are complemented by another set at the rear, providing simple convective cooling. The pencil The supplied WEP70 pencil has a 7-pin plug to suit the power unit and an approximately 120cm-long lead. The lead is coated in heat-resistant silicone and feels light and unobtrusive. The included tip is a 1.6mm ETA ‘screwdriver’ tip (like a cut-off chisel tip), with other ET types being compatible with the iron. The pencil is slim too, and has a textured foam grip. There are various types of tips optional to this tool that you can purchase, including conical, chisel, bevel and knife tips in various sizes. We reckon that it’s helpful to purchase a few different tips when you get a station like this, as they are useful in different situations. Sometimes you need a long, narrow tip to reach a part on a packed board. Other times you need a big tip to solder heavy leads or large components. Tips with flat edges Power station The power unit, labelled WE1, is what we know as a soldering station base. It has an IEC mains receptacle at the rear and a 7-pin socket at the front, accompanied by an LCD screen. There are three control buttons on the right side of the screen, and a mains on/off rocker switch on the left. The station is marketed as a 70W device. It is weighty and contains a transformer, just visible through the vents. Four rubber feet prevent the 84 Silicon Chip The Weller soldering station includes a 1.6mm ‘screwdriver’ tip. Australia’s electronics magazine siliconchip.com.au The T0053298599 is well-suited for heavy-duty usage. It is solid and includes a settings lock feature to prevent tampering in production environments. can be beneficial when working with solder wick. So having a good variety of tips available at reasonable prices (around $8 each) is definitely a plus in our books. Safety rest Included with the station is a PH70 safety rest, which is also equipped with rubber feet. Like the power unit, the safety rest feels weighty and is not likely to slide around. The rest has a generous space for the included sponge and several holes to store spare tips. Controls The three buttons form a simple and intuitive interface. The menu button cycles between standby time, offset, units and lock, with the up and down buttons changing the selected value. The lock feature is intended for a production environment, to prevent operators from adjusting the settings, although you might also find it useful to avoid accidental changes. The manual is quite thick, but mostly from including almost 30 languages. There are detailed pictograms, so even if there weren’t any words, the unit would be easy to use. Hands-on testing The manual states that the iron can heat from 50°C to 350°C in 28 seconds. We timed it at 50 seconds from ambient (around 20°C) to 380°C; perhaps this varies depending on the type of tip fitted. The nominal operating range is 100°C to 450°C with a stability of ±6°C. That’s a reasonably wide range, and if you need to work with a range of low-melt solders, for example, in constructing white-metal models, then the Weller T0053298599 should have the range and accuracy to do so. We had no trouble using the iron with a typical 99.3% tin/0.7% copper lead-free solder, which has a much higher melting point than standard tin/lead solder. Even working along rows of closely spaced pins, the iron was able to keep up the heat. Having said that, our work typically doesn’t involve really heavy-duty soldering. But based on our experience, we think that it would handle larger jobs reasonably well, as long as you used a suitable tip. We found that the default standby timeout of two-minutes was a little short, but it can be increased to 99 minutes, which we think should be sufficient for most cases. Conclusion We would certainly have no complaints about using this station for our everyday soldering tasks. It is sturdy, adjustable and responsive, and would be well suited to duties much more intensive than we could throw at it. The Weller T0053298599 kit is available at Bunnings Warehouse for $249, including GST. This unit was provided for review by Weller Tools. Visit www.bunnings.com.au/ weller-70w-240v-soldering-station_ p0248144 to purchase the station and/ or spare parts, including tips. Here’s a short link to the above: siliconchip. SC com.au/link/ab8n Suite 201, Level 2, 184 Bourke Road Alexandria NSW 2015 www.weller-tools.com.au/ Arcade Pong: the ANT terminal (continued from page 46) You might be wondering about the purpose of the "ANT" terminal on the PCB. It's close to the VID terminal, so you might think it's meant to drive a TV set's antenna input. But that is not its purpose. In the arcade machine, the ANT terminal was connected to a wire about a meter long, leading nowhere in the arcade cabinet. It connects to the base of the transistor that resets the game, which is floating, except for the tiny leakage of a diode. So the base voltage can float to be just on the verge of causing the transistor to conduct. siliconchip.com.au Back in the 1970s, it was surprising how resourceful teenagers were at trying to get free credits on arcade games. One trick was to deliver an electrostatic charge, or burst of RF, into the machine to clock up credits, as though multiple coins had been put in the coin mechanism. It was possible to prevent this with extensive RF filtering on all the logic circuits and wires leading to coin mechanism, switches etc. In Pong, however, one coin gave one game play credit. Atari decided to simply detect any electrostatic or RF burst, using Australia’s electronics magazine that antenna wire, and reset the game, making it impossible to get a free credit. That is one reason why the original transistors used (2N3643 and 2N3644) in the game's reset circuit were RF types. I left the "ANT" connection on my design so that my PCB could be used to replace/ repair a genuine arcade game console. It is surprising how few people can fix the original boards and run around in circles until they have replaced nearly every IC. The originals were not socketed, and many original arcade machine PCBs have been destroyed by botched repair jobs. SC June 2021  85 PRODUCT SHOWCASE Achieving water authority compliance with automated wastewater treatment Wastewater usually contains various contaminants (ie, acids, alkalis, copper, lead, arsenic, antimony, ammonium, solvents etc). Fortunately, automated wastewater treatment systems can help semiconductor manufacturers remain in compliance with EPA and local standards, while significantly reducing the cost of treatment, labour and disposal. These automated systems can eliminate the need to monitor equipment in-person. It can separate suspended solids, heavy metals, emulsified oil and encapsulate the contaminants, producing an easily de-waterable sludge in minutes. The water is typically separated using a de-watering table or bag filters before it is discharged into sewer systems or further filtered for re-use as process water. Other options for de-watering include using a filter press or rotary drum vacuum. When dried, the resulting solids will pass the TCLP leaching test and are considered non-hazardous and can be disposed of in a landfill. The treatment systems are available in batch, semi-automatic, or fully automatic form and can be designed to be part of a closed loop system for water reuse or to provide legally dischargeable effluent suitable for disposal in a municipal sewer system. A new, fully customised system is not always required. In many cases, it can be faster and more cost effective to add to, or modify, a facility’s current wastewater treatment when feasible. Sabo Industrial 2 Little Britain Road Newburgh, NY 12550 USA Tel: (845) 562 5751 mail: info<at>saboindustrial.com Web: https://saboindustrial.com Maxim’s MAX78000 & Aizip bring ultra-low-power human figure detection to IoT Create the Future Design Contest Maxim’s MAX78000 neural-network microcontroller can detect people in an image using Aizip’s Visual Wake Words (VWW) model, consuming just 0.7mJ per inference, with greater than 85% accuracy. That is 100 times less power consumption than conventional software solutions, making it the most efficient IoT person-detection solution available, providing up to 13 million inferences from a single AA/LR6 battery. That means significantly longer operation for battery-powered IoT systems that require human-presence detection, such as building energy Mouser Electronics announced its sponsorship of the 19th Create the Future Design Contest, a global challenge to engineers and innovators around the world to design the next great thing. The contest is open for submissions until July 1, 2021. The grand prize winner receives worldwide recognition and a cash prize of US$25,000 for an innovative product that benefits society and the economy. Previous grand prize-winning entries include a small, self-contained device for organ and limb transport and an economical rapid screening device to prevent food-borne illness. The contest was created in 2002 by the publishers of Tech Briefs magazine. For more information, go to https:// www.mouser.com/createthefuture/ management and smart security cameras. Extreme model compression enables accurate smart vision with a memory-constrained, low-cost AIaccelerated microcontroller and budget-friendly image sensors. For details about VWW visit www. aizip.ai – you can view a demonstration at http://bit.ly/DetectVideo The MAX78000 microcontroller and MAX78000EVKIT# evaluation kit are available now from Maxim’s website (siliconchip.com.au/link/ ab8o) for US$8.50 and US$168.00 respectively. Maxim Integrated 160 Rio Robles, San Jose CA 95134 USA www.maximintegrated.com/ 86 Silicon Chip Australia’s electronics magazine Mouser – https://mouser.com/ siliconchip.com.au Tax Time Build It Yourself Electronics Centres® DEALS! out the range. EOFY savings through June 30th. Sale prices valid until 199 $ The MaonoCaster Lite provides everything you need to get started in podcasting, live streaming, YouTube & Twitch. 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Clean & revive tiny parts This USB rechargeable screwdriver features a fully adjustable torque drive for fast and accurate driving of precision screws found in modern high tech devices. Two way direction control. Standard 4mm driver bits (40 included). 3 hours use per charge. See web for full contents list. T 2247A Uses water, detergent and ultrasonic waves to remove gunk from small parts, spectacles, jewellery, even DVDs! No solvents required. Stainless steel 18x8x6cm tank. 44 Precision measuring with ease! 150mm length, suitable for measuring internal, external and depth dimensions. 0.01mm, 0.0005” and 1/128th” display. Compact 30V Lab Power Supplies SAVE 20% 45 $ $ M 8303 3A M 8305 5A Made from diecast alloy. Clamps to your work bench and provides total 360° freedom when working. Jaws open to 55 mm. Includes soft jaws for holding delicate connectors. X 4205 5 Dioptre 60 $ 65 $ Protect your valuable appliances 750VA UPS Power Protection Board SAVE $45 130 $ 160 $40 OFF! 33 Toolbox space saver! Charge 10 USB devices at once! • Great for families, classrooms & business. • Massive 19A charge output • QC3.0 on 2 ports • Includes adjustable dividers & power supply. *Devices & charging leads not included Don’t miss a message while you charge! SAVE 24% 15 $ A 0290 $ M 8882A* D 0873 This quality PowerShield UPS unit will prevent appliance damage caused by power fluctuations, PLUS keep power on during a blackout! Also protects phone lines. SAVE 15% T 1528A Multi-Angle Bench Vice X 4204 3+12 Dioptre $ 119 149 $ SAVE $15 Why pay $300 for a MaggyLamp? The inspect-a-gadget illuminated desk magnifier is an absolute bargain at $69, we believe ours is every bit as useful. An incredible visual aid for detailed inspection and work on fine items with full clarity through the quality glass lens. Tackle complex miniature tasks with confidence! SAVE $15 Great for servicing, repair and design of electronics. Low noise switchmode design. Fine & coarse voltage and current controls. Size: 85Wx160Hx205Dmm. T 2367 LED Magnifier for micro tasks Ultimate family charging station! SAVE 24% $ Accurate Digital Vernier Calipers Say to goodbyein! eye stra USB NiMH & NiCad Charger Charges 4 x AAA/AA batteries via USB. Great for use at home or in the car. 39.95 $ D 2324 Handy upright 15W wireless charging stand allows you to read incoming notifications at a glance without having to stop charging. Requires QC3.0 USB wall charger (such as our M8863, $20) 15W fast charging! Wire Stripper & Kwik Crimper Combines a ratchet wire stripper, cutting blade & kwik crimper (red, blue and yellow sheaths). Suits 10-24 AWG cable. 19.95 $ T 2351 19 $ .95 6pc Soldering Helper Tool Kit A 6 piece set of tools for reworking solder joints, cleaning pad surfaces and removing debris. 44.95 $ T 3063 T 3132 10ml Tube 15.95 $ 2 for Bare Conductive Paint T 1489 T 1489 Precision Knife Set Includes aluminium handle with 13 blades to suit different cutting jobs. Includes plastic carry case. Draw real circuits on almost any surface! Great for repairing tracks or experimenting with DIY circuits on different materials. Also available in 50ml jar (T 3133). 20 $ Electronic Cleaning Spray T 3066A A do-it-all cleaning spray for electronic parts and boards. A workbench must have! 175g. The ultimate magic ‘fix-it’ spray Famous DeoxIT® Spray The gold standard in electronic servicing sprays. Deoxidises, cleans, preserves contacts & joins. 142g. USB C Power Delivery SAVE 16% 4 USB charging ports Reading Light 80W mains output 45 $ N 0020F 20W Dual LED Torch 55 $ N 0040F 40W SAVE $50 90 $ 219 $ N 0065G 65W GREAT FOR: • Motorbikes • Caravans • Boats • Jet Skis & more! SAVE $10 108 $ SAVE $10 49 69 $ Sourced from one of the worlds leading solar manufacturers. Aluminium frames, waterproof junctions, tempered glass panels. 25 year output warranty. 5 year workmanship warranty. These compact solar panels are designed for keeping your vehicle batteries topped up when parked. Easy croc clip or car accessory plug connection. Can even be permanently installed outdoors. 10W: 377L x 212W x 17D mm. 15W: 40L x 343W x 17Dmm. 99 $ M 8534A 6/12V 4.5A Power it up. 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These tough surface mount brackets offer a way to mount solar panels without penetrating the roof of the caravan or boat. They can be attached using a silastic or similar adhesive. Ensure your battery doesn’t go flat with this handy Bluetooth® battery monitor. Provides live feedback on your vehicle or auxiliary battery, plus handy long term stats. 45.95 $ N 2008 10A NEW! 54.95 $ N 2009 20A PWM Waterproof Solar Chargers Compact sealed design. Easy to connect to 12V battery systems. IP68 rated. 10A for <120W panels, 20A for <240W panels. Size: 82Wx45Dx21Hmm SAVE 22% 34 35 .95 $ USB C Power Delivery Charger P 0696 A combination QC 3.0 and 18W USB C power delivery charger for the car, 4WD or caravan. 29mm mounting hole. $ Easy Read DC Energy Meter Q 0589 Simultaneous display of voltage, current, power and energy (Wh) readings. Ideal for DC battery monitoring and small solar systems. Requires 85x45mm cutout. 20A max. 139 $ NEW! 8 $ .95 T 5098 P 7810 NEW! Trailer Plugs & Sockets New range of flat and round connectors for hooking up your trailer. 14 P 8092 7 Pin Flat Plug P 8093 7 Pin Flat Skt P 8094 7 Pin Round Skt P 8095 7 Pin Round Plug P 7824 XT60 DC Plugs Male & female included. 60A rated. SAVE 28% 4 $ ea Anderson Style $ Connector Panel A handy connection point for 4WD & camper installation. 60Wx40Hx42Dmm. EC5 Style DC Power Plugs 60A rated 5mm battery plugs. P 7823 SAVE 26% 5 $ ea .95 NEW! 12V DC+USB Power Panel 36 $ .95 Can be easily surface mounted to custom panels to provide power to your devices & portable appliances. 15A DC breaker. P 0697 50x130x70mm. Deans Style Plugs Offset 2 pin DC power plugs. 60A rated. P 7828 SAVE 33% 3 $ ea High Current Twin Flex Figure 8 Cable Rated up to 20A this handy 12AWG cable is ideal for automotive power cabling. Top mount connections, breaker & voltmeter. Powerhouse® Portable Power Battery Box Fits a standard 90-120Ah automotive battery for powering appliances at your camp site - a totally self contained power unit! Fitted with 2.4A USB charger, dual Anderson sockets, volt meter, car acc. socket & battery terminals. 40 $ per 10m W 4154 SAVE 25% 30A 10 Metre Handy Hook Up Reels Popular 30A high current. Tinned for reduced corrosion. W 2426 Red W 2427 Black SAVE 23% 25.95 $ Raspberry Pi Pico is here! NEW! The new Pi Pico is a tiny, fast and versatile board using RP2040 - a brand new microcontroller! Programmable in C and MicroPython this handy board can be used to integrate into any project of your own making! 8 per 1.3m 16.95 $ NEW! NEW! 14 $ 1.3m length of addressable RGB 5050 LED strip - this means you can program the colour of every individual LED using an Arduino/Raspberry Pi. 60 LEDs per m. WS2812B chip on board. 10mm width, adhesive backed. 5V, 3.6A/m (max). PiicoDev Expansion Board .95 14.95 $ K 9642 Z 6419 Jumper Header Kit 3mm and 5mm LEDs in green, red, blue, yellow and white. 300pcs. Single row header connectors. Includes male & female pin headers, plus 2.54mm housings. SAVE 15% Includes an Arduino UNO compatible board, proto-shield, LCD, LED module, 7 segment displays, breadboards, stepper motor, servo, IR remote, battery box and a variety of parts and sensors. Z 0003 LED Assortment Pack . s t r a p r e k a m p To 7 $ .95 DIY Tinkerers Kit For Arduino SAVE 30% SAVE 25% 12 $ 26 $ 14 $ P 1018A 350pc P 1014A 140pc Loads of parts to tinker & learn Arduino coding. SAVE $36 79 $ Create Amazing LED Light Effects! $ .95 $ A much requested item by our builders and makers, this handy clock kit comes with 3 different styles of hands to suit your DIY clock design. Requires 1xAA battery. 23 5050 size LEDs for superior light output! Design your own wall clock! X 1010A: Suits 2-6mm panel. X 1014A: Suits 16-21mm panel. 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Z 6510A 2.8” Touch Arduino Shield A 240x320px touchscreen shield for Arduino utilising the ILI9341 chipset. 3.3/5V input. Hobby Wire Packs 6 colour hobby pack for project building. 10m of each colour. Sale Ends June 30th 2021 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au Z 6426 19.95 $ CAN-BUS Arduino Shield Allows you to interface Arduino’s with CAN-BUS control systems found in automotive electronics. Use an Arduino to build your own vehicle monitors. 20% OFF Prototyping PCBs Allows you to keep the same PCB layout as your breadboard design. Solder masked for easy soldering. H 0701 94x64mm $6.40ea H 0703 164x64mm $9ea Western Australia Build It Yourself Electronics Centres 19.95 $ » 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 2021. 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 0092 Find a local reseller at: altronics.com.au/storelocations/dealers/ SERVICEMAN'S LOG Trying to fix unbranded, generic equipment Dave Thompson The first step in sourcing spare parts for a faulty piece of equipment is to take the manufacturer and model details and do some searching to find out if the manufacturer or a third party has spare parts available. But what do you do when there is no apparent manufacturer or model number? Go on a wild goose chase, it seems... Items Covered This Month Sometimes a job comes through the replacement tyre took many months to workshop that is a bit out of left-field. I’ll take a look at anything; if nothing else, it’s all experience. Recently, I received a call about an electric scooter that had failed. This was one of these ‘friend of a client’ type deals, and I, for one, appreciate such referrals. In business, getting work this way sure beats paying for expensive advertising. This ‘scooter’ was a cheap import. While this doesn’t necessarily indicate that it will be a tricky job, I’ve been down this path too many times before to assume it will be an easy repair. According to the customer, in the 18 months they’ve owned it, the thing has spent more time off the road than on it. The tyres were the first problem, with the rear tyre blowing early on. It was apparently paperthin and not fit for our rough roads. A siliconchip.com.au source, and had to come from Europe. Not an auspicious start! Then it simply stopped working. The owner brought the scooter into my workshop, and after the usual discussions about terms and conditions and possible outcomes, I dug into it. This isn’t one of those thin-line electric scooters you see hipsters riding all over town on. This model is about the size of those mini-bikes Honda used to make back in the 70s, before the powers-that-be decided they were too dangerous for the average citizen. Australia’s electronics magazine • Fixing generic equipment is • • • • frustrating Arlec battery charger repair Fixing a 50in Panasonic TV backlight Failing capacitor in clothes iron Mazda 3 aircon repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz June 2021  91 It has fat little 10-inch wheels, proper mudguards, apehanger handlebars and a comfortable padded seat. It’s more like a small electric motorbike than a scooter. The various controls also mimic a motorbike; a twist throttle and front brake handle on the right, with back brakes on the left grip. It has a headlight of sorts, a taillight, and a sturdy kickstand. It is driven by a brushless electric motor integrated into the rear wheel hub. A standard key lock switches it on and off, and a small electronic display on the bars indicate the juice remaining and some other telemetry I haven’t been able to determine yet. I know the display can show other items because if I angle it to the light, I can see several other ‘icons’. My guess is that this is a generic display and is used on many other devices. This one is just wired to show the rider whatever information this manufacturer wants us to know. It’s all actually quite solid and well-made, but while it’s a step up from those rental scooters, it isn’t really a motorbike either. Still, it suited the owner’s requirements of buzzing a relatively short distance to work and back each day in relative comfort. Or would if it was working, anyway. I would love to have a ride on it, being an avid motorbike rider myself (though not for a few years now), but unfortunately, it wouldn’t move under its own steam. While it powered on and the battery bar-graph style indicator on the handlebars showed plenty of herbs, twisting the grip did nothing. All the other electrics worked, which was a good sign. Also, the guy (a skilled retired avionics engineer) who referred this client to me had ‘run his Fluke’ over it, looking for things that could potentially go wrong, but he had not found anything obvious. He did re-terminate some of the connections to the controller in case there was something dodgy there, but the problem remained. He figured it must be either a controller or motor fault, at which point he recommended that the owner bring it all to me. it isn’t all potted together with impenetrable goo, and the numbers are still left on all the components, I likely won’t find a circuit diagram for it anywhere. Reverse engineering the controller to draw one up would take hours of headaches and all with no guarantee anything would work anyway. What fun the serviceman’s life can be! I then went with basic specs. I know the battery is a 48V Li-ion job, and it is easily removed after unplugging the single heavy-duty ‘E’ connector. The battery at least has all the specs printed on a label. Nothing else is identified, though. The wiring to and from the various bits and bobs looks to be colour-coded, though whether this code matches anything else remained to be seen. The controller box also appears quite well-made, from the outside at least. It is a sizeable chunk of hollow, extruded and patterned aluminium, with what appears to be integral heatsinking along one side. It has shaped aluminium caps screwed on at each end, using what appear to be ordinary PK screws. All the cables pass through sealed holes in one end of the controller, and the whole caboodle is stuffed into a protected gap in the chassis, along with the battery, below the seat and foot-well area. A key-operated moulded plastic panel covers it all up, and there are basic weather seals along all exposed joints. The controller must be at least partially working, because if we insert the key and turn it on, we get the battery-level indicators on the dash, and the lights and other stuff works. If the motor had simply burned out, we would get the same symptoms – lights but no action. It is also possible that the motor-driver section of the controller has failed, but the rest of it is still working. A frustrating search After confirming the symptoms described above, the next step was to try to identify this vehicle. It has no brand name printed on it, nor does it have any part or serial numbers anywhere. Par for the course. A Google image search picked up a few similar bikes, available from the likes of eBay, AliExpress and Banggood, but nothing exactly like this one that could give me some clues as to its identity. The company it was purchased from 18 months ago were of little help either, having no spares available. My guess is that this is a generic bike, with various companies using the chassis, controllers and other bits and pieces to make ‘their’ version of it. They then sell them all off and move on to the next project. This has pros and cons for me; if the controls and hardware are generic, I should be able to find similar (if not necessarily identical) parts from any of these suppliers who sell such hardware. I’d have to drill a little deeper into the individual components and try to identify them. I know what you’re thinking; fat chance! Even if I can open the hefty extruded-aluminium controller box, and 92 Silicon Chip Australia’s electronics magazine siliconchip.com.au Opening up the controller So opening the controller up was my next step. Removing the controller is a bit of an act, because there are terminals and wiring going everywhere. There are four quite heavy-duty main drive cables coming from the controller, and these terminate onto posts moulded into a large hard-plastic block that keeps them all physically and electrically separated, but close together in the same area. These connections need to be undone with a socket driver. The other wiring is generally a lighter gauge and utilises removable connectors (some installed by my friend, some that look factory), making removing the controller relatively straightforward. The problem with the motor being potentially unserviceable is that I can’t easily test it. It is a brushless type, so it needs a suitable controller to make it work. Just connecting it directly up to the battery isn’t going to make it go, and in fact, would likely damage it. Except for the different type of motor, this whole job reminded me of a treadmill I repaired a while back. That too powered on and showed lights, but had no motor drive. The treadmill used a 12-130V DC motor, and I tested this by hooking up a car battery to the motor’s red and black wires. While it moved slowly at 12V, it at least worked, which told me it was probably OK and the controller had likely failed. That unit was ‘simply’ a DC speed controller; altering the power level to the motor increased and decreased its speed. These (for me, at least) are a bit easier to troubleshoot. In that instance, I replaced all the IGBT output devices (which were blown), but I also sourced a new controller board, just in case my repair failed. That repair worked, so at least I now have a spare controller in case it goes again. There were more differences between that job and this one, though. That board had part and model numbers clearly printed on it, making it a doddle to find a replacement. Perhaps I’d be lucky here too? With the controller sitting on the bench, I could more easily remove the end caps and see if I could extract the PCB from the interior. One long side of the board is taken up with an array of what appear to be Mosfets, or perhaps IGBTs. These all bolt directly to a piece of bar aluminium, and then this is bolted to one side of the controller case with a smear of heatsink compound and four bolts. These four bolts also had to be removed before I could slide the board free. Once all the fasteners were out, the board came out without any problems. The first thing I noticed was how light-weight the componentry looked. That treadmill controller I worked on was a hefty beast with a large external heatsink, and it was mounted away from everything with lots of room for cooling air. This little brushless driver, which admittedly only has to cope with 48V, must be quite efficient given the small size of everything. Or, perhaps it is built down to a price, underrated and too weenie for the size of the battery involved, which might also explain why it isn’t working. No obvious problems A closer inspection revealed no burning, discolouration, overheated rails or any other obvious damage to the board. There was also none of that acrid ‘electrical’ smell siliconchip.com.au Australia’s electronics magazine June 2021  93 we’re all so familiar with that usually indicates something is wrong. I didn’t fancy pulling the very closely-packed output transistors to test each one, so I made do with trying to find part or model numbers I could cross-reference. Nothing. And while some components (quite a few SMDs and the like) did have visible numbers, a lot didn’t either. If I could find a data sheet for the numbered ICs, there might be a reference circuit I could check out. Either way, I was stuck; I needed a known-good controller to test the motor, or a known-good motor to test the controller. Back to Google image searching. After trying various search terms, I began to see some familiar results. I found plenty of controller boards, but none looked exactly like this one. There were also many different types, with seven, nine and sometimes 12 output devices for the various sizes and voltages of scooters, bikes and batteries. I had a lot better luck looking for the entire controller itself. While it also has no identifying labels, it did look very similar to many of the image search results. I narrowed things down until I had pages of almost identical controllers in the results. The cabling on each was one of the few visible differences between them, with the controllers shown mainly having one of three different configurations. The controller I had looked to be a widespread type, which was a welcome discovery. Another difference was the physical size; controllers for 72V systems are far larger than their 48V counterparts, so again, I could drill further down into what I was looking for. The surprising thing is that I was expecting that even if I found one, the controller would be stupidly expensive. That treadmill controller was almost (but not quite) prohibitively expensive, though I deemed it worth it at the time to get one. The controller I found for the scooter is from AliExpress and costs just US$25, plus a couple of bucks shipping. I was gobsmacked. How can these devices be made for such little money? The fancy piece of aluminium extrusion it is all contained in must be worth more than that by itself. There were a few sub-types listed, so I ordered the version intended for a 48V electric vehicle with a brushless motor. It looked to have identical connections and overall physical size to the one I already had. Hopefully, what arrives will be what was in the product pictures; more than once, I’ve purchased items from the product description and received something very different. If all goes well, it will at least help me determine whether the controller or the motor is causing problems, and the negligible cost can be wrapped up into the assessment phase of the job without significant financial outlay. It is undoubtedly cheaper than sourcing and buying a new motor/hub assembly – which we might yet need to do – but for now, it will tell us all we need to know without throwing good money after bad. At the time of writing, I’m still waiting for the controller to arrive. Given current world events, it’s no surprise shipping is slow. I’ll let you know what happens. A happier ending In the meantime, I got a call from an out-of-town rep for a company that provides exercise equipment for gyms and retirement homes. He had a dead machine in one of their spaces down here and an open day the following day. He wanted me to make an assessment or repair (if possible) of the controller board, which he would remove and bring over, along with the external power supply. I agreed, and offered assistance if he needed it. He didn’t; the controller came out easily, and a fault was immediately apparent; a 47μF 35V SMD electrolytic capacitor had exploded. He brought the board to the workshop, and we agreed that I would swap out the cap. If it blew again straight away, he’d return the board to the manufacturer for a replacement and forgo the open day. I soldered in a new cap, and we held our breath while we powered up the board, watching as the status lights lit up one by one. His grin said it all. He went back, reinstalled the board, fired up the machine, and the open day was a success. Sometimes we just get lucky! Arlec battery charger repair B. C., of Dungog, NSW took some time to refurbish an old Arlec battery charger that had seen some rough use, but it is now back into tip-top condition... I got an Arlec PS439 30 Deluxe Battery Charger from the local recyclers which wasn’t working. Also, the top cover was in pretty rough condition; it looked like it may have spent its former life at a local motor garage. My friend said he would clean it up and respray 94 Silicon Chip Australia’s electronics magazine siliconchip.com.au the top after I got it working. Removing this cover revealed an accumulation of debris and also some corrosion on the power transformer, heatsinks and the control PCB. Careful use of a toothbrush, paintbrush and solvent cleaned up most of the mess. Scraping, followed by an application of rust converter cleaned up the power transformer laminations. Fortunately, the front panel with the ammeter, timer and switches had been protected by the overhang of the top cover, and only required light cleaning. I was then able to greatly improve its external appearance using Nu Finish car polish on the case paintwork. I then sent a technical request email to Arlec in Melbourne and received back two circuit diagrams, a control PCB layout drawing and a “current-control switch connections” drawing. Interestingly, the drawings were all done in 1983. Talk about the thorough technical support for Australian made products! This battery charger was a wellmanufactured product and was meant to be foolproof to use. The charger would only work if the battery had some residual charge left in it and the connection polarity was correct. There are now plenty of modern chargers that use a similar system. Looking at the circuit diagram, I discovered that there are two main high-current secondary windings on the power transformer. A rocker switch selects the voltage to feed through a rectifier block to charge either a 6V or 12V lead-acid battery. A large rotary switch is then used to switch through a series of voltage taps to give current siliconchip.com.au control of the output, as displayed on the ammeter. A timer gives the user a preset charging time, to avoid battery overcharging, particularly on the higher current settings. There is also an extra transformer winding which gives a regulated 12V rail to run the control PCB electronics. After some basic voltage checks, I traced the fault to a lack of 12V at the output of the series regulator. This was because the TIP31C transistor (mounted on a small heatsink) was faulty. I also found that the BZX79C13 13V 0.5W zener diode controlling the voltage at the TIP31C base had gone short-circuit. Replacing these two parts brought the Arlec charger back to life. I then connected it to a partially charged car battery and set the timer to complete the charging cycle. As promised, my friend resprayed the top cover to match the orange enamel finish of the chassis. This charger now sits proudly on a trolley in his garage. Fixing the backlight in a 50in TV P. M. of Christchurch, NZ, had a badly-timed failure in a 50-inch LCD TV. Luckily, he has quite a bit of TV repair experience, so was able to tackle the job... As New Zealand was under “lockdown”, all businesses except essential services were closed, and everyone was told to stay at home. This meant that the home TV had become an essential entertainment and information device. Two days in, and suddenly our Panasonic 50in LCD in the lounge had Australia’s electronics magazine no picture. I have been trained to service TVs, but that was many decades ago when TVs had CRTs. But it looked like I had little choice under the circumstances, and attempted a repair. I soon had the beast off the wall and face-down on the kitchen table. I removed the back, hoping to find some sick-looking electrolytic capacitors which I could easily replace. I was surprised to see how few electros there were. None of them looked sick, and all tested OK with my ESR meter. I was surprised at how sparse the interior was, with a power supply board in the middle, a small video board on the right, a backlight driver board on the left and a display driver board at the bottom. The power supply rails all looked good, but I was not so sure about the backlight driver outputs. I managed to find a manual online, but the driver board was mainly SMD, and I didn’t have high hopes about being able to fix anything. In the meantime, I put a 32in Panasonic from another room on the wall in the lounge. After a day or so of squinting at it, I decided to have another look at the 50in set. Inside it, I noticed a label saying the display was made by LG. I Googled ‘repair 50” LG TV’ and found several hits on replacing the backlight LEDs. It seems this is a common problem with some models, made worse if the user chooses a high brightness setting. Gaining access to the backlight LEDs involves removing the LCD panel from the housing. In the Youtube video (https://youtu.be/CHmHb-Dxx3Y), the repairman used two suction cups June 2021  95 attached to the front of the panel to lift it out. Not having those suction cups meant I probably couldn’t continue, but then I remembered that we have a handle in our shower which is held on with suction cups (as shown in the photo at lower left). This handle was not ideal because the cups are quite close together, unlike the separate ones used in the video. I attached it carefully to the screen after removing the bezel, a bunch of screws and two flat ribbon cables. When I started lifting it, the panel got a bit bendy at the ends, but I managed to set it down safely. There are three sheets of Mylar that act as a diffuser to remove, and beneath those are six rows of 10 LEDs (as shown in the photo on page 95). The LEDs are on strips of circuit board which plug into a connecting circuit board at the right-hand end. They are wired in series, so with the aid of my bench power supply set to 30V at 20mA, I was able to power each strip separately, to find that two strips did not work. Upon closer inspection, I noticed a discoloured LED on one strip but I had to find the faulty one on the other strip with the aid of a meter. Not having suitable replacements on hand, I decided to simply short out the two faulty LEDs, and because they are wired as two strings of thirty, it would probably still work fine. I carefully reassembled everything and held my breath while I switched it on. It worked just fine, and the only time you could tell two LEDs are missing is on a pure white screen. Even then, it is not that obvious. The YouTube video had a link to a store which sells a full set of replacement strips for US$60, so I will order a set when I can. The heatless clothes iron R. S. of Fig Tree Pocket, Qld, had a problem which has been repeated many times over the last few years in these columns. You may get a sense of deja vu while reading it... Our Braun clothes iron stopped heating. It was more than two years old, so already out of warranty. If you take the grey rubber pad out of the end of the iron, you can undo two T20 ‘security’ screws. This allows the end to come off, and there is a black plastic box with a small circuit board inside. It contains an unmarked surface-mount 96 Silicon Chip 8-pin IC with its supply regulated by a 5V zener. The low-voltage supply from the mains is via a 220nF 220V AC rated X2 capacitor and a resistor. The capacitor tested OK using the capacitance range on a Fluke 77 IV multimeter, but I replaced it with another 220nF X2 capacitor, and the iron now works. It seems that the capacitance is lower at high voltages. I note that the replacement capacitor was many times the size of the original. This is another example of highvoltage series capacitor failure. I notice that the inverters in microwave ovens use a high-wattage resistor to drop the voltage for the control circuit. This is more reliable, but with a higher power loss. Mazda 3 aircon repair D. W., of Georges Hall thought his daughter’s car might have had a serious malfunction buried deep within, but luckily, it turned out to be a much simpler (and cheaper) fault than originally envisaged… My daughter told me that the air conditioner in her 2008 Mazda 3 was playing up. It didn’t work straight away; the car had to be running for about 15 minutes before it would produce cold air. Up close to the front of the car, I could hear a strange noise from under the bonnet somewhere. It sounded like it could have been a compressor belt or clutch problem. Maybe one or the other was slipping a bit, but then it eventually grabbed. That might explain the delayed turn-on. Maybe the belt had stretched or worse, the compressor could be on its way out. A faulty compressor would probably be a costly fix. That night, I found myself on YouTube searching for Mazda 3 aircon compressor faults and fixes. Sure enough, there were a couple of detailed and somewhat educational video clips depicting Mazda 3 compressor and clutch faults and fixes. A couple of days later, my daughter brought her car over, and I had a bit more time to look at the problem. Thanks to the YouTube video clip, I knew where to look for the compressor. The noise I had heard previously wasn’t evident on this occasion. Turning the aircon on and off and watching the compressor belt and clutch didn’t reveal anything unusual to my eye. Australia’s electronics magazine I noticed a slight coating of frost on one of the compressor pipes, so I thought that the compressor must be doing its job. I was now getting that feeling that I’d missed something. While sitting in the car operating the controls and mulling over things, it suddenly dawned on me that there was no airflow from the outlets in the car. Regardless of all else, there should be airflow. The fan control knob appeared to be working OK as the dash LCD was indicating the different fan speeds. So it was not a compressor belt or clutch problem; it was a fan blower problem. Not for the first time, my brain had led me up the garden path. So I headed back to YouTube for more advice. YouTube has a lot of video clips on Mazda 3 fan blowers. Unfortunately, everything is located up behind the glove box, and it’s hard to get to the fan assembly. I realised that since the blower fan does come on after a delay, the fan itself must be OK. So I had to think of what else might be causing this problem. I checked the 40A blower fuse (marked heater) and it was OK. Next, I pulled out the small quick-connect blower relay (also marked heater) close to the fan blower fuse and tested it on the bench with a 12V power supply and multimeter. And that was it! I could hear the relay clicking in and out, but the contacts were simply not closing. It was easy enough to lever off the relay’s dust cover and inspect the SPST contacts. I set about cleaning the contacts with wet and dry and contact cleaner but surprisingly, to no avail. While testing the relay, I could feel the relay getting warm while energised, and after about 15 minutes just sitting on the bench, the contacts eventually closed, as if by magic. I think heat and fatigue over the years had affected the spring steel relay contact arm. As a temporary fix, I bent the arm a fraction of a millimetre to close the gap a bit. After replacing the dust cover and returning the relay to the car, the problem had obviously been licked. I’ll source a new relay in due course, and I’m still a little worried about that noise I heard initially, but hopefully it was just the blower fan operating erratically with its control relay making dodgy contact. Time will tell. SC siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL 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 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 04105201 04105202 01110201 01110202 24106121 16110202 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 Subscribers get a 10% discount on all orders for parts $7.50 $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 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 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 18104211 18104212 10103211 $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 JUN21 JUN21 JUN21 JUN21 05102211 24106211 24106212 08105211 $7.50 $5.00 $7.50 $35.00 NEW PCBs ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG PRE-PROGRAMMED MICROS & ICs As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS 24LC32A-I/SN ATmega328P-PU ATmega328P-AUR ATtiny85V-10PU PIC10F202-E/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-I/P $15 MICROS EEPROM for Digital FX Unit (Apr21) RF Signal Generator (Jun19) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) LED Christmas Ornaments (Nov20; specify variant) Car Radio Dimmer Adaptor (Aug19), MiniHeart (Jan21) Refined Full-Wave Universal Motor Speed Controller (Apr21) Tiny LED Xmas Tree (Nov19) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20), Electronic Wind Chime (Feb21) Flexible Digital Lighting Controller Slave (Oct20) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) ATSAML10E16A-AUT High-Current Battery Balancer (Mar21) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) Advanced GPS Computer (Jun21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS & SPECIALISED COMPONENTS VARIOUS MODULES & PARTS MINIHEART HEARTBEAT SIMULATOR (CAT SC5732) - EA2-5NU relay (PIC Programming Helper) - 2.8-inch touchscreen LCD module (Hybrid Lab Power Supply, May21) - Spin FV-1 IC (Digital FX Unit, Apr21) - 15mW 3W SMD resistor (Battery Multi Logger / Arduino Power Supply, Feb21) - DS3231 or DS3231M real-time clock SMD IC (Battery Multi Logger, Feb21) - MCP4251-502E/P (Arduino Power Supply, Feb21) - Pair of CSD18534 (Electronic Wind Chimes, Feb21) - IPP80P03P4L04 (Dual Battery Lifesaver / Vintage Radio Supply, Dec20) - 16x2 I2C LCD (Digital RF Power Meter, Aug20) - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) - MAX038 function generator IC (H-Field Transanalyser, May20) - MC1496P double-balanced mixer (H-Field Transanalyser, May20) - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 ADVANCED GPS COMPUTER $3.00 $22.50 $40.00 $2.50 $3.00 $3.00 $6.00 $5.00 $7.50 $15.00 $25.00 $2.50 $10.00 (JUN 21) $75.00 $25.00 $3.00 - Micromite LCD BackPack V3 kit (SC5082) - VK2828U7G5LF GPS module (SC5135) - MCP4251-502E/P IC (SC5052) ARCADE PONG (CAT SC5834) (JUN 21) $12.50 Pair of Signetics-branded NE555Ns, for critical A9/B9 paddle ICs MINI ISOLATED SERIAL LINK COMPLETE KIT (CAT SC5750) (MAR 21) $10.00 All parts required to build the project including the PCB (JAN 21) All SMD parts, including IC2 – does not include PCB $5.00 AM/FM/SW RADIO (JAN 21) $2.50 $3.00 $7.50 - PCB-mount right-angle SMA socket (SC4918) - Pulse-type rotary encoder with integral pushbutton (SC5601) - 16x2 LCD module (does not use I2C module) (SC4198) COLOUR MAXIMITE 2 in stock now (JUL 20) Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (Cat SC5478) Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (Cat SC5508) $80.00 $140.00 MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) (AUG 19) Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $30.00 - DHT22 temp/humidity sensor (Cat SC4150) $7.50 - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor $5.00 - BME280 temperature/pressure/humidity sensor (Cat SC4608) $10.00 - DS3231 real-time clock SOIC-16 IC (Cat SC5103) $3.00 - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) $5.00 - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) $1.50 - 10µF 16V X7R through-hole capacitor (Cat SC5106) $2.00 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. To Place Your Order: INTERNET (24/7) siliconchip.com.au/Shop PAYPAL (24/7) eMAIL (24/7) Use your PayPal account silicon<at>siliconchip.com.au Australia’s electronics magazine silicon<at>siliconchip.com.au MAIL (24/7) PHONE – (9-5:00, Mon-Fri) Your order to PO Box 139 Collaroy NSW 2097 Call (02) 9939 3295 with with order & credit card details You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. 06/21 Vintage Radio 1940 1940 RME RME model model 69 69 communications communications receiver By Fred Lever receiver This communications receiver was designed in the mid-1930s. It appears to have been updated by the manufacturer to keep up with competing products. It’s a hefty bit of kit, packed with parts, with many functions and some interesting quirks. One of these is a complete lack of labels for the front panel controls! A matching tuned ‘pre-selector’ unit was eventually acquired; it too required repair and restoration. I was asked if I would like “an old radio” as the owner, a senior gent, wanted it to go to a good home. I am up for just about anything, so I said yes without even laying eyes on it. When I finally got my hands on the set, I could not get it home fast enough! It was heavy (15kg), in a steel box with a lift-up lid. The front panel had two big dials and a bunch of knobs, but there were no markings to indicate which knob did what. The only text was on a rear nameplate, advising that this was a Model 69, serial A98 made by Radio Manufacturing Engineers in Peoria, Illinois, USA. RME radio Thus I was introduced to RME and a type of receiver I have never had any interest in before, a wideband commercial radio receiver with a pedigree and high performance, at least for 1940. I searched the web and found many references to the model and a history of the company, including model numbers and employees. At a later stage, I was delighted to receive the matching DB-20 preselector unit. I believe these two items were rack-mounted in a complete ‘ham’ setup, and are the only surviving pieces of what would have been a comprehensive transmit/receive installation. The pre-selector also came with a treasure trove of books, notes and personal papers belonging to the owner. These items I have simply stored and not investigated at this time. The ‘restored’ RME69 receiver; sadly, the front dials are still cracked. 98 Silicon Chip Australia’s electronics magazine I downloaded a comprehensive operating manual from a website called “Boat Anchor”. This helped me to recognise what I had and figure out what was original. The handbook describes serial number A98 as a late production unit with a “Lamb Silencer” in the front end. The octal valve types and the history of the company mean that it was manufactured around 1940. The original production radios had 6-pin valves and no Silencer. My first move was to survey every part of the set and take photos. While parts of it were undisturbed, other parts had been replaced or looked like they had been modified. After some investigation, I elected not to try to refurbish the set but just make it safe to turn on and work in some fashion on the AM 500-1800kHz band only. I achieved that by replacing obviously faulty parts and removing some strange modifications. I then carried out what I confess to being a cosmetic ‘tart up’ on the set and the matching pre-selector, by cleaning them and misting with a light coat of gloss black, over the faded wrinkle finish. The insides and chassis were cleaned, masked off and a light coat of silver misted over the rust and patina. The accompanying photos show the dusty old thing as I received it, then in its cleaned-up state, as well as a view of the underside of the chassis post-cleaning. Not having any markings on the panel controls intrigued me. It seems that RME never marked their model 69 siliconchip.com.au front panels. The legend goes that the builders reckoned that if you could not figure out what knob did what, you did not deserve to own the set! I am not sure about that; I suspect more likely they did not possess the equipment to etch or engrave plates, and preferred not to spend the money to buy it. Circuit details The inside of the receiver, as originally received, was full of dust and showed some surface rust. XTAL 6K7 6L7 6H6 SW5 T5 T1 (Lamb Silencer) 6J7 6B7 IF amp 42 audio output T4 T3 6C6 1st det 6D6 RF amp C23/34/35 6D6 oscillator T2 L17/18 Cs L11/12 L5/6 CH1 The set’s circuit diagram is shown in Fig.1. It has a pretty conventional superhet arrangement for the time, with a 6D6 RF stage, a 6C6 mixer, two 6D6 IF stages, then a 6D7 as a combined detector, AGC and audio preamplifier and a type 42 based output stage. One 6D6 forms a separate oscillator while another acts as a BFO. A type 80 serves as the HT rectifier. All of that should add up to a high-performing design. One great feature of the set design is the careful sub-assembly of the tuning coils and wave change switch. The wiring of the coils is effected with heavy solid core leads in a very rigid assembly, and with the rigid cast chassis gives a stable platform for the front end. The tuning gangs operate with low-geared reductions and large, heavy knobs. This construction ensures stability and repeatability. I am not sure how far this set has been modified from the original design. The old lower-gain 6-pin valves in the RF and mixer stage had at some point been replaced with EF36 octal valves. These are sharp cut-off types that would not be so amenable to AGC control. The set also sported the aforementioned optional “Lamb noise filter” assembly with 6K7 and 6L7 octals in place of the 6D6. These seem to be factory modifications, perhaps in an attempt to keep up with other manufacturers’ new designs at the time. The two EF36 sharp cut-off audio valves did not sit very well with me, and the shield paint was flaking off, so I replaced them with 6K7 octals. These perform more similarly to the originally fitted types. Fixing the RME up T1 siliconchip.com.au 80 rectifier 6D6 amp SW1 Australia’s electronics magazine My first job was to remove all the existing mains wiring as it was not safe, due to rotting rubber and cracked insulation. I wired in a three-core cord with a chassis gland. After testing the insulation and Earth conductivity of the mains side of the circuit, I powered it up with low-voltage AC and June 2021  99 ramped up the voltage while monitoring the power consumption, HT and heater voltages. The power draw settled at 70W with 250V DC HT. Nothing smoked or caused concern, so the next job was get the audio section to work. The output transformer is a monster, with only 4kW and 600W output taps. I connected a 4kW:4W transformer to this so that I could use a 4W speaker for testing. I connected my audio signal generator to the cap of the 6B7 and wound the level up until I could see clipping on the output wave. At that point, the output was a couple of watts. I measured the stage voltages and noted that the type 42 cathode bias resistor had 20V across it, indicating a 50mA tube current. That seemed a bit high to me, so I checked the control grid and measured +12V. I found the wax coupling capacitor to be leaky (it measured 12MW). After replacing it with a new one, the grid voltage was then less than 0.1V, and the tube current dropped to about 34mA. That had the effect of taking some load off the type 80 rectifier, so the main HT rose to 260V. Poor performance Fig.1: the circuit diagram for the RME-69 receiver. Values for resistors and capacitors have been added. Note that there were some errors in the original service manual, such as C18 missing (estimated at 100nF) and C15 is listed as 0.00025µµFd rather than 0.00025µFd (250pF). 100 Silicon Chip Australia’s electronics magazine At this stage, I hooked up an aerial to the set, worked out which switch position selected the AM broadcast band (no panel markings!), and tuned in very faintly station 2RPH that in my locality (Toongabbie, Sydney) is usually overwhelming. So the set was working in some way, but producing less output than even a crystal set! I then re-read the handbook to work out what control did what, and with a bit of fiddling, could receive a few more stations at very low volume and at odd places on the dial. Even with low-gain tubes such as the 6K7 in the tuner, with one RF and two IF stages, the set should be highly sensitive, and stations should pull in from everywhere with a short aerial. I checked the AGC feedback loop, and the best voltage from the 6B7 diode was about -5V, with a couple of volts of 465kHz injected on the preceding IF valve plate. I measured the resistance from the AGC line to ground and found it to be low at 2MW, so I replaced all the time constant capacitors. Out of the circuit, they each measured about 10-20MW, so replacing them did lift the AGC voltage a bit. siliconchip.com.au The original mains wiring in the receiver was unusable and unsafe, as shown. It was replaced with threecore cord with a chassis gland. The IF section I then did another check of the plate, screen and cathode voltages of each IF stage. Measuring the gain from each grid to plate made it plain that the IF strip was low on gain. I injected a 465kHz sinewave and checked the peaking of each trimmer in the IF cans. All six were off frequency a bit, but importantly, each had a definite peak point with a drop-off one-quarter of a turn each way. That indicated to me that all the coils were active and resonating, and most likely, the low gain was a system problem and not due to the coils. What I found a bit odd was that the IF strip had oodles of gain when fed with the 465kHz signal, but the set was a lame duck when I let the oscillator control the frequencies. Then the penny dropped. The broadcast band oscillator frequency was way off, outside of the peak of the passband of the IF coils. This was why the stations were appearing at weird places on the dial. A screw loose! I manually forced the oscillator valve to run at the correct frequency by padding the tuning circuit with capacitance, and the set came alive with lots of background noise and stations all over the dial, in the correct order. That led me to conclude that something was badly adjusted or faulty with the oscillator tuning. I needed to check the padder and trim components and after much searching, realised that they were fitted inside the broadcast coil can. It was a heck of a job to get the can off, but once exposed, I found the adjusting screws on the calibration trimmers had simply unwound from vibration. You can see this clearly in the photo below. Simply recalibrating the settings made the receiver work in a lively manner with gain, not loss, from the IF stages. Therefore, those two loose screws crippled the receiver on the AM band! From the corrosion on the parts, I think they had been that way for a long while. Possibly, the receiver was not used on the broadcast band in its ham duty, so this fault was never found. Now that the receiver was working better, I turned my attention to some of the other aspects of this set. My experience in radio to this point has been Above: the underside of the RME chassis before any restoration work was done. Right: the calibration trimmers inside the broadcast coil had their screws unwind over time due to vibration. siliconchip.com.au Australia’s electronics magazine June 2021  101 The circuit is balanced like a seesaw, and if not set correctly or the wrong currents flow, the meter can easily go in reverse. The null control sets the meter to zero with no signal. The presence of a signal causes the valves to draw more current, so the meter reading goes up. The set had some prominent non-original parts fitted with strange values. I replaced them with the original values, and the S meter then worked sensibly. The crystal filter The carrier level indicator dial (“S” meter) needed to be checked for correct operation. with AM broadcast band receivers, so all the extra functions and knobs in a commercial set like this were mysterious to me. That “S” meter The meter circuit bugged me as it is not clear how it operates, and the zero adjustment (null) control did not do anything sensible. I was not sure if the meter was working, so I decided to pull it out and hook up to a bench test circuit that mimicked the set circuit. I found that the meter had an internal impedance of 32W and needed about 1.5mA for full-scale deflection (FSD). That seemed about right. The meter is actually in a bridge circuit with ~1kW upper arms and 100kW lower arms. The upper arms connect to the HT, with one of them being adjustable via the 500W zero-set pot. One lower arm is a fixed 100kW resistor passing about 2.5mA, while the other is formed by the current draw of the AGC-controlled valves of about 3-15mA, being equivalent to a resistor of about 20-100kW. Without the filter, tuning on the broadcast band is inherently very sharp, and the set will separate Sydney stations 2CH (1170kHz) and 2RPH (1224kHz) with ease. The set rides up and down the different signal strengths with AGC control (meter readings S9 to S3), and despite the vast S-difference, the audio output is level, and there is no adjacent channel chatter. The crystal (a BLILEY type CF1 465kHz, serial no. G20326) is supposed to resonate and provide a narrower pass filter at the intermediate frequency, to sharpen the selectivity for sorting out really close stations. There are panel controls to vary the insertion effect. The problem was that with the crystal switched in, there was no real resonant point around the nominal frequency of 465kHz, and the IF response was worsened. I stripped the crystal, thoroughly Fig.2: an IF pass response without the Bliley crystal filter The old carrier meter zero adjustment is shown above with its replacement circuit at right (200W potentiometer R10). 102 Silicon Chip Fig.3: the same IF pass with the crystal filter switched in. Australia’s electronics magazine siliconchip.com.au Fig.4: the “Lamb Silencer” section of the circuit, also called the LS-1 noise suppressor. cleaned and refitted it. This produced a result where the crystal does ‘something’ to the response of the IF strip, but I did not believe that it was working correctly. The IF pass response with filter out is about 10kHz (Fig.2) while with the filter switched in, the response is about 5kHz (Fig.3). What I expected to see was a mirror-image of the left side on the right, with maybe 1kHz width, not a ringing decay stretching the response out. The filter circuit is certainly not a narrow crystal resonance, but surely, this is not the best it can do. I think the crystal may be too old to work properly, but not having a replacement, I left it at that. Silencer of the Lamb So far, I had ignored the Lamb Silencer section. I had disconnected the The Bliley 465kHz crystal filter is shown enlarged for clarity, with an actual size of 30 x 40mm. Serial number: G20326. siliconchip.com.au IF feed to the control valve for all my testing so far, but now that the set was running, I decided to see what it did. The circuit diagram of this Lamb Silencer is shown in Fig.4. Upon reading a bit about this type of circuit, I determined that it is a type of ‘impulse blanker’. The Lamb patents are a treat to read; my eyes glazed over by the end of the second page. Ignoring all the scientific gobbledygook, it seems to me that the filter samples the IF 465kHz carrier, detects bursts of interference such as from vehicle ignition systems or lightning and gates an IF pass valve off during the interference burst. In this version, the IF signal is sampled from IFT2 to the grid of the 6L7. This 6L7 amplifies the IF signal in the usual way using control grid G1, but one of the other pentagrid inputs of the 6L7 is used as a back-fed DC gating control. The sampled IF signal is fed to a 6J7 wired as an amplifier, and the output of the 6J7 is fed to a resonant IF transformer. This is where the clever bit comes in. The output of this transformer, with the 465kHz removed, is rectified by a 6H6 diode to give a negative gating voltage. Some smart time constants ensure that the gating voltage is a derivative of the interference, and persists long enough to gate the 6L7 off during the interference burst. This gating is timed so that a ‘hole’ is ‘poked’ in the main IF signal right where the ‘pop’ was; therefore, you do not hear it. Upon testing it, I found that this filter was simply not doing anything. Fig.5: with the Lamb Silencer switched out, spark interference is visible in the output. Fig.6: with the Silencer switched in and threshold set, the interference spikes go away. Australia’s electronics magazine June 2021  103 The DB-20 preselector had a very worn filter choke hanging off the lower left of the chassis. This choke, the power supply transformer and the type 80 rectifier valve were removed and replaced with a π filter. With some signal tracing and testing, I found leaky capacitors; resonant IF transformer T1 needed peaking at 465kHz; and worst of all, the 6H6 was dead. Once that lot was fixed, the threshold control now suddenly cut the IF response at too high a setting, so the circuit was clearly active. I then rigged up an “interference tester” involving a magneto air spark gap next to the set, to simulate automotive ignition interference, and was delighted to see Mr Lamb’s patent theory vindicated. See the sweeps without (Fig.5) and with (Fig.6) the filter. Pre-selector The pre-selector looks like a baby version of the main set, with similarly styled metalwork. It also has a flip-top lid and many large parts shoved into a small space. Its circuit is shown in Fig.7. The range switch and coils looked just like those in the main receiver, but the circuit is a tuned radio frequency (TRF) receiver with manually adjustable gain. The first thing I noted inside was a huge filter choke held down by gravity! I eased the chassis out of the case and found that the choke was connected with BB points through a bit of figure-8 wire. It seems that the original had failed, and anything handy had been pressed into service. I again replaced all the mains wiring and removed the substantial floating choke. Next, I pulled the filter block can off, thinking of either re-stuffing it or just replacing the new units underneath. The power supply transformer and choke were big enough to run a small village! All it has to do is run two valve filaments at 0.6A, supply about 20mA of HT plus the type 80 filament current. I decided to ditch the choke altogether, wire in some silicon diodes in place of the type 80 valve and mount some appropriate filters and dropping resistors on some tag strip. In place of the choke, I put a 3.3kW 5W resistor and a pair of 150µF 400V capacitors in a π filter arrangement. I left a dud type 80 bottle plugged in the rectifier socket to fill the space. Left: the original underside of the DB20 pre-selector. The DB-20 provides continuous coverage from 550kHz to 32MHz in six bands, and has a gain of ~20-25dB which is the basis for its name. The DB-20 was also used by the US Navy under the name CME-50063. Below: a replacement switch for gain control “A” on the front panel. 104 Silicon Chip Australia’s electronics magazine siliconchip.com.au I ramped up the mains input voltage to form the electros, and once I reached typical mains voltages, the set drew 25W. The total HT draw is 30mA, and this arrangement gave me 270V DC at the HT feed point to the valves. A quick check with RF signal applied showed the TRF circuit amplifies the signal from the aerial and provides “pre-tuning”, to upgrade the overall specifications of the receiver to match the performance of later competing units. The overall gain is in the order of 16 times at maximum setting, but the unit was unstable, self-oscillating at the tuned frequency. This turned out to be a valve shielding problem, as one of the valves was a glass EF39 fitted in place of a 6K7. The red metallic shielding paint had flaked off. Swapping back in a 6K7 with a metal shield fixed that. I gave the cabinet and front panel a mist of black paint, burnished the knobs, cleaned the glass and put it all back together. When stacked onto the main receiver, I could hook the two together via the receiver antenna wires, and found they worked as a Fig.7: the circuit diagram for the DB-20 pre-selector. It’s a pretty simple 3-valve companion unit for the RME-69. This circuit has alternative versions around with most using two electrolytics to filter the power supply, while this one has three. There is no parts list to confirm it, but the capacitor C6 should likely be around 10-12µF 450V as noted here. siliconchip.com.au Australia’s electronics magazine June 2021  105 A Jaycar Cat. MM2007 transformer was rewound to act as the matching transformer for the speaker unit. pair, giving four tuning controls to play with! Making a suitable speaker One thing the set up did not have was its own speaker box. I sorted through my junk speakers, looking for a sensitive unit around eight inches (~20cm), and came across a Goodman Hi-Fi mid-range driver from the 1960s that had a very light movement. The frame was rusted, and the rubber surround had perished with splits and cracks, but the inner suspension was sound and a test showed that it played music. I painted a couple of layers of my favourite water-based latex over the cracked outer ring of the speaker, left that to dry and turned my attention to sourcing a matching transformer. I had an old Jaycar MM2007 240:30V AC transformer from a junked power supply. That gave me a primary winding capable of handling hundreds of volts, and a secondary that I could rewind to suit the speaker and radio. Having rewound it, I restacked the lamination with an air gap. I masked the speaker up and found a “copper” gold rattle can, so I gave the speaker and the assembled transformer a dose of that. That covered the rust and dirty bits nicely. I made a small open-backed cabinet from scraps of five-ply and bolted the speaker and transformer into it. I had some automotive rocker cover “crackle” paint, so I applied three coats of that over the ply, and that dried to a matte wrinkle finish not far off the RME radio wrinkle finish. A light coat of gloss black on top put some shine on it. Finally, I had a ‘matching’ speaker for the set. and close-enough capacitance values. Editor’s note: these capacitors can have age-related failures which damage other components, so ideally they should be replaced anyway. The wax dripping seems to be related to the type of wax used. It has a very low melting point, so in Australian summer temperatures, the wax simply runs, forming stalactites. The large carbon resistors seem very stable and generally were within 10% of the colour value. The present state As my first look at a commercial communications receiver from the 1940s (although in a sense, this is really a 30s design), I learned a lot about communications valve circuits. I also had the pleasure of preserving a serious piece of gear that was made over 80 years ago. This article is a shortened version of a series of vintage radio website posts in six parts, replete with much more tedious information and blowby-blow accounts of troubleshooting and testing. These posts can be seen at the following links: siliconchip.com.au/link/ab5a siliconchip.com.au/link/ab5b siliconchip.com.au/link/ab5c siliconchip.com.au/link/ab5d siliconchip.com.au/link/ab5e SC siliconchip.com.au/link/ab5f I removed the headphone socket and moved the BFO on/off function to that hole using a period switch. That put that function adjacent to the BFO pitch control. A new power on/off switch is now in the hole below that. Previously, the mains switch had been part of the audio “top cut” control that is located within the BFO shield box. Crazy stuff! The complete primary mains circuit is now short, well-insulated, Earthed and fused. It’s much safer than it was when I got it. The whole set-up is now operational, and most parts of it work. I decided not to replace any more parts and not pursue repair any further. Many of the capacitors left were dripping with wax, but had no measurable leakage Conclusion Since the speaker was an optional extra, one was made in lieu, with a black cabinet to match. 106 Silicon Chip Australia’s electronics magazine siliconchip.com.au The ‘restored’ underside of the chassis can be seen above, with the topside shown below. This receiver was manufactured by RME at 306 First Avenue, Peoria, Illinois USA as stated on the label on the rear of the set. Around 1953, RME merged with Electro-Voice who are still around today. siliconchip.com.au Australia’s electronics magazine June 2021  107 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 Using Battery Balancer with supercaps Can I use the High-current Four Battery/Cell Balancer (March & April 2021; siliconchip.com.au/Series/358) to balance a “battery” of capacitors? I have a bank of six supercaps (2,7V each) connected in series, which I am using instead of a lead-acid storage battery. So I wonder if the Battery Balancer can be used to keep these supercaps in balance. (C. B., Bonville, NSW) • It should work with capacitors, given that their fully charged voltages are not that far from something like LiFePO4 cells. However, keep in mind that capacitors can discharge to a much lower voltage than batteries; once the total voltage is low, the device will cease operation. If you’re only concerned about it balancing when the capacitor bank is mostly full, it should work. Incorrect resistor colour code given In the article on the Arduino-based Power Supply from February 2021 (siliconchip.com.au/Article/14741), for the 51kW resistors in the parts list, it lists colour bands of “green brown black orange brown”, which is 510kW. In the PCB photos, it looks like you have used 510kW and not 51kW. Which one is correct? (R. S., Epping, Vic) • There is a typo in the parts list; it should read “green brown black red brown”. It correctly gives “green brown orange brown” as the four-band code, matching the 51kW value shown in the circuit and parts list. The photos show a four-band 5% resistor with an orange multiplier band, which gives 51kW. 510kW would be too high a value in that divider. Recommended software for 3D printing I would appreciate an article on software for drawing objects to print with a 3D printer. Lots of software seems to 108 Silicon Chip be available, but as I inspect the products I find, I find lots of haystacks, but no needles. AutoCAD is an obvious candidate, but at the ‘open heart surgery’ end of the spectrum. I found a product from the AutoDesk stable targeting schools, but it seemed to be more for play than work. I could do lots of fun things, but when I tried to define the gadget I wanted to build, it seemed offended and to be telling me I should migrate to AutoCAD. A friend recommended DraftSight. He seems to love it, but when I grizzle about the difficulties I’m having, he describes the commands that flummox me in an enthusiastic tone. I recently found its user manual, which is helping, even though I’m only up to page 70 of 180+ pages. Do you have any better suggestions? (K. A., Kingston, Tas) • We generally use OpenSCAD (https://openscad.org/), which has great precision for engineering-type designs. We have also used FreeCAD (www.freecadweb.org/) with some success, although not specifically for 3D printing. It does some things in non-obvious ways but seems quite capable. Blender (www.blender.org/) is another very popular software package; among its other capabilities, it can create 3D models from orthographic (plan/elevation view) drawings. USB SuperCodec oscillator frequency Thanks for publishing what looks like a great piece of audio test gear in the USB SuperCodec (August-October 2020; siliconchip.com.au/Series/349). I have a question regarding the oscillator frequency that clocks the ASRCs (asynchronous sample rate converters). Why have you used a 25MHz oscillator when 24.576MHz (192kHz × 2 7 ) is available? The 24.576MHz crystal would allow the ASRC to do its interpolation much more ideally mathematically when Australia’s electronics magazine upsampling from a standard 48/96kHz sampling rate. Also, when recording, you would want to set the sample rate to say 96 or 192kHz, which evenly divides 24.576MHz but not 25MHz. Am I missing something? Also, how is the hardware sampling rate set when recording? Finally, years ago, when I was doing high-speed digital design, I learned that controlling transmission line effects on the PCB can be important. So I expected to see 22-47W series resistors in the clock lines between the chips, or some other method to minimise reflections by controlling line impedances. How did you get away without them? (I. B., Armidale, NSW) • Phil Prosser responds: You are correct that 24.576MHz is a standard crystal frequency for audio applications because it is a power-of-two integer multiple of several common sampling rates, including 48, 96 & 192kHz. But the ASRCs work a bit differently than your standard ADC or DAC. The ASRC chips require the clock frequency to be at least 130 times the master input/output clock rates. 25MHz achieves this nicely, as 192kHz × 130 = 24.96MHz. On the surface, it might seem that selecting a closer sampling rate to the actual audio clock would be better. But when you look at how the ASRC IC operates, all calculations are made with 32-bit resolution. The ‘digital domain’ THD + noise level is between -148dB and -173dB, depending on the ratio of converted sampling rates. So the impact of the digital calculations on the overall THD + N figure of the device is vanishingly small. Our test results of the analog performance are representative of the native performance of the ADC and DAC ICs themselves, which are shown in the article to be outstanding. The sampling rate for the ADC (ie, recording) is always 195.3125ks/s, irrespective of the sampling rate the PC operates at. That is why there are siliconchip.com.au two ASRC chips on the board, and not just the one for output. One converts the lower input sampling rate from the MiniDSP up to 195ks/s for the DAC, and the other converts 195ks/s from the ADC down to a lower sampling rate to feed to the MiniDSP. The driver software on your computer configures the MiniDSP’s clock rate. This will never be more than 192ks/s, so the ASRC is always downsampling the data from the ADC to feed it to the computer. As stated above, that does not reduce the quality in any measurable way. The use of the ASRCs allows us to drive both the ADC and DAC with a single clean, jitter-free clock source. The ASRC interfaces between this ‘clock domain’ to the lowerfrequency MiniDSP MCHStreamser ‘clock domain’, avoiding potential jitter problems from the XMOS processor used for the USB Interface on the MiniDSP card. As for the high-speed signals, the rise and fall times are what gets you in high-speed digital design. This can be mitigated with good layout techniques, including controlled impedance in the routing. There is termination on the MCLK line, which I included as a ‘belts-and-braces’ measure. I have designed quite a few circuits involving digital audio interfaces, and found them quite tolerant of ‘average’ routing practice. I did check the MCLK signals for bad behaviour. With the kit I have, I could only measure a very nice looking waveform. That said, a better test kit (say a 300MHz scope, now I have an excuse to buy one!) might have shown more. If you look at the top and bottom layers around the digital signals routed from the clock IC and the ASRC to the ADC and DAC, you will see that the bottom layer is an almost complete ground plane, with only one break that I could not avoid. I spent hours trying to get rid of that interruption! I believe this has helped keep the digital signals clean by minimising the size of current loops. Trouble calibrating Ultrasonic Cleaner I am having trouble with the HighPower Ultrasonic Cleaner (September & October 2020; siliconchip.com. au/Series/350). I tested the transducer siliconchip.com.au from the earlier version (August 2010; siliconchip.com.au/Article/244) and the one I bought recently from your Online Shop. Both transducers work fine on the older unit. Using the re-calibration method described in the October 2020 issue with 3L of water, the resonance climbs to 56kHz. If I reduce the water volume to 1.2L, the resonance after re-calibration is 19kHz. I have tried winding a different number of turns on the transformer secondary in steps of upwards of 10 each time, and I have tried it with as many as 75 turns. The results are similar. Using the diagnosis mode, with 57 turns and 1.2L of water, I get 2.09V (maximum) at TP1 at 38.73kHz, with 240V peak-to-peak at the transducer. With 75 turns and 1.2L of water, I get 2.09V (maximum) at TP1 at 38.73kHz, with 300V peak-to-peak at the transducer. I was able to achieve 4.3V at TP1 with about 500mL of water at 38kHz with 75 turns in diagnosis mode. As soon as I shut down and return to re-calibrate with different water levels, I end up with a resonance frequency that is either way too low or way too high. The supply voltage is correct. Any thoughts and help would be appreciated. (P. J., Adelaide, SA) • It seems that the current measurement is not working correctly, as the higher voltage applied to the transducer (300Vp-p) compared to 240Vp-p at the same frequency and the same amount of water does not change the current reading. Check the current reading section of the circuit, including IC2 and its associated parts. Check the 100nF capacitor at pin 5 of IC2. Also, check the windings on the transformer. The voltage output with 57 turns should be closer to 100V RMS. It is possible that the coupling to the water basin is damping resonance, depending on what is used to attach the transducer and what the basin is made from. Altering RGB Xmas Star bypass capacitors I have built the RGB version of the November 2020 RGB Christmas Star (siliconchip.com.au/Article/14638) and have mounted all components except for the 100μF electrolytic capacitors. Australia’s electronics magazine In place of the five 100μF electrolytic capacitors, is it acceptable to use 47μF tantalum capacitors? (K. J., Campbelltown, NSW) • That should be fine. Arguably, 47μF tantalum capacitors are superior to 100μF electrolytics. That project went a bit overboard on bypassing; probably only one capacitor per board is really necessary, or perhaps two. So reducing the capacitor values by half should not cause any problems, especially since your tantalum capacitors will likely have reasonably low ESR values. Shunt resistor values to use for audio pots Back in 2019, I built the Silicon Chip Ultra Low Noise Remote Controlled Stereo Preamplifier (March & April 2019; siliconchip.com.au/Series/333), but I had problems with the VR1b section of the motorised pot. The pot track’s ground end wasn’t connected properly to the solder tag, causing an open/high resistance circuit, which resulted in the right channel having a higher volume. I managed to use a pair of blunt cutters to squeeze the rivet together, restoring continuity. The preamp works fine; my only quibble is that the bass/treble pots are too close together, only allowing the use of tiny plastic knobs. Last year, I was given a 1RU rackmount case to put the preamp in, and decided to desolder all the preamp pots to space them apart further by using shielded cables, allowing the use of 32mm knobs. When the preamp was fired up in the 1RU case, the left channel had low audio volume intermittently, and the right channel had high volume intermittently. The VR1b ground end solder lug was going open circuit again, and the VR1a connection was also going open-circuit intermittently. I pulled the pot off the gearbox to allow better access to V1b’s track crimp. This restored the balance, but unfortunately, I think I left out/broke a part in the plastic clutch. The motor runs forward/back OK, but the pot shaft only occasionally moves now. Last week, the audio level problems recurred (Rotorua’s H2S levels don’t help either). VR1a’s ground end track rivet isn’t responding to recrimping. A new pot is the only solution. Altronics have the Cat R1998 motorised pot on June 2021  109 backorder, with no indication of when it will be available again. The March 2019 article stated that a dual 20kW log pot could be used instead, with a 4.7kW resistor shunting the wiper. But I can’t find any supplier that has a dual 20kW log pot. I can get 10kW or 50kW standard pots that I could use while waiting for a new motorised pot. What shunt resistor values should I use with those? (D. M. C., Rotorua, NZ) • You can use 10kW log pots without adding the 4.7kW ohm resistors (or any other value), although if you do want to add resistors to those, use 10kW. For the 50kW pots, use the 4.7kW resistors specified. These resistor values are not critical. They are there to lower the impedance when higher-valued potentiometers (compared to the 5kW specified values) are used. The resistors will alter the law of the log pot, so the values are a compromise between reducing noise, where low values are better, and obtaining a reasonable volume control resistance law, where higher values are better. Choosing a coil for Multi-Spark CDI Thanks for your answer to my questions on a CDI system for Kawasaki jet skis in the January 2021 issue (p110). Digging deeper into the articles and designs, I concluded the multi-spark was not suitable for twin-cylinder engines that use a wasted spark, firing both plugs every time. I can’t find any kits available for the High-Energy Multi-Spark CDI (December 2014 & January 2015; siliconchip. com.au/Series/279), so now I have ordered the PCB from you and am getting the parts from Jaycar today. I still have one design conundrum: how do I choose an appropriate coil that it will drive comfortably? Most coils don’t come with specifications, and automotive stores (Repco, Autobarn, Supercheap Auto etc) can’t give me specifications on the coils they sell either. For a 650 twin-cylinder two-stroke jet ski with CDI, the original coil specifications give a primary resistance of 92mW ±15% and a secondary resistance of 4.1kW ±15%. This is the lowest primary impedance that I can find. From the article, the primary is getting 350V from the CDI, not 12V, and 110 Silicon Chip there is no mention in the article about a suitable impedance. How can I tell if I am about to blow up the coil? I plan to replace the CDI and coil as a matching package. (L. C., Donvale, Vic) • The ignition coil specifications are not critical; the CDI unit should work with the coil you plan to use. Because it is a capacitor discharge type that applies a pulse to the coil, rather than charging the coil conventionally and releasing the charge to fire the coil, most coils will work. There is no coil saturation current to be concerned about. Problems compiling NTP time source code I am having problems programming the Internet Based Time Source (The Clayton’s “GPS” time signal generator, April 2018; siliconchip.com.au/ Article/11039). The ESP8266 code fails to compile with the following error code: Arduino: 1.8.13 (Windows 7), Board: “WeMos D1 R1, 80 MHz, Flash, Legacy (new can return nullptr), All SSL ciphers (most compatible), 4MB (FS:2MB OTA:~1019KB), v2 Lower Memory, Disabled, None, Only Sketch, 57600” ... Using library ESP8266WiFi at version 1.0 in folder: C:\ Users\Home\AppData\Local\ Arduino15\packages\esp8266\ hardware\esp8266\2.7.4\ libraries\ESP8266WiFi Using library ESP8266HTTPClient at version 1.2 in folder: C:\ Users\Home\AppData\Local\ Arduino15\packages\esp8266\ hardware\esp8266\2.7.4\ libraries\ESP8266HTTPClient exit status -1073741502 Error compiling for board WeMos D1 R1. (J. R., United Kingdom) • We tried installing the same versions of the software (Arduino IDE 1.8.13 and ESP8266 board files 2.7.4) on Windows 10, but can’t recreate your error. Since the error occurs at the ESP8266HTTPClient library, we suspect that you have a problem with the files installed for that library, or one of the other libraries that it depends on. We have read reports of similar problems when other (unrelated, but Australia’s electronics magazine incompatible) WiFi libraries are present, causing the compiler to become confused. More detailed (!) error messages can be set under the Preferences page (File → Preferences); tick “Show verbose output during compilation”. That could point to another library causing issues with the ESP8266HTTPClient library. Transformer choice for SC200 amp Your articles on the SC200 Audio Amplifier module (January & February 2017; siliconchip.com.au/Series/308) mention using a 30-0-30 160VA transformer for the lower-power version. Do you mean one transformer for each module in a stereo setup, or one transformer shared between both modules? (T. B., Bumberrah, Vic) • Unless you need to deliver full power continuously (unlikely with any sort of program material), one transformer shared between two modules should be fine. A 160VA toroidal type would be a reasonable choice for a lower-power version of the SC200. A 300VA transformer would probably be overkill, but it would allow both modules to deliver full power on a sustained basis. Converting mechanical speedo to electronic I have a rear-engined car. The speedo is a mechanical drive via a long flexible shaft that is prone to failure. I am also conscious of the load on the plastic gears in the car gearbox speedo drive. The speedometer instrument is part of a set on the dashboard, also containing the odometer and trip odometer. I wanted to adapt a small gear motor to drive the speedometer and control its speed with a PWM kit to overcome the mechanical unreliability. A quick test shows that 400RPM gives about 100km/h on the speedometer. What do you suggest as an electronic connection between the gearbox output and the motor on the mechanical speedometer? (G. T., Londonderry, NSW) • A standard speedometer sensor from a vehicle with electronic speedometer connections could be adapted to fit into the gearbox cable attachment. continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE FOR SALE KIT ASSEMBLY & REPAIR LEDsales VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com LEDs and accessories for the DIY enthusiast PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. SILICON CHIP ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. Some of the books may have already been sold, but most are still available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote, quote the number directly below the photo when referring to a book: silicon<at>siliconchip.com.au LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au TRONIXLABS PTY LTD would like to thank all of our customers for their support and feedback. For any enquiries or customer technical support, please email support<at>tronixlabs.com PCB PRODUCTION PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au DAVE THOMPSON (the Serviceman from S ilicon C hip ) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com 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 Glyn (02) 9939 3295 or 0431 792 293. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia’s electronics magazine June 2021  111 That signal could then be applied to the motor drive circuit. The motor drive circuit would need to convert the speedometer sensor signal to a voltage drive for the motor driving the mechanical speedometer. The required circuitry would depend on the components used. A simple voltage-controlled PWM driver might not be effective, as it will only provide open-loop control. Some form of motor speed feedback is required to ensure the motor rotates at the correct speed despite the varying battery voltage and temperature. You might be able to convert the speed sensor signal to a voltage using a simple RC filter that is then used to control a PWM motor controller such as our DC Motor Speed Controller Mk.2 (June 2011; siliconchip.com.au/ Article/1035). Alternatively, a vehicle instrument specialist can supply many of the parts you need. See www.attspeedautoinstruments. com 2-layer PCBs supplied for older designs I am currently building the Electrolytic Capacitor Reformer (August & September 2010; siliconchip.com. au/Series/10). I have received the PCB from you and am very impressed with the quality. The instructions say to solder in 11 wire links. However, the supplied board is double-sided with plated through-holes, and I assume it has printed wire links on the component side. Can I skip fitting the wire links? (K. C., Strathfield, NSW) • When we supply boards that were single-sided designs these days, we tend to place the links in the top layer as it costs very little to do so. That includes the board you have. You can check one or two of the links using a continuity meter, pressing the probes into the vias/throughholes at either end of where the link is supposed to be. That will verify the presence of those top-layer tracks. Rarely would we get boards made based on old designs without adding links to the top layer. Higher supply voltage for SC480 amp Can I use a 60V centre-tapped transformer to power SC480 Audio Amplifier modules (January & February 2003; siliconchip.com.au/Series/109) instead of a 56V centre-tapped transformer? (J. A., via email) • No SOA curves were published for the SC480, so it’s hard to evaluate the effect of changing the supply voltages. Given that you’re only talking about a couple of extra volts per rail, if you plan to drive 8W or 6W speakers, it should be OK. Still, we suggest changing the BC557s to BC556s for a bit of extra safety margin. It would help to know the VA rating of the transformer, and it would also be helpful to measure the actual voltage, as it can vary quite a bit from the nominal voltage. The DC supply rails are given as ±40V, so if you build the supply and get unloaded readings of around ±42V or ±43V, that would not be particularly worrisome. ±45V or higher might cause problems, though. SC Advertising Index Altronics...............................87-90 Ampec Technologies................... 9 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Hare & Forbes....................... OBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.................. 5 Ocean Controls........................... 8 PMD Way................................ 111 Premier Batteries...................... 37 SC Vintage Radio Collection..... 63 Silicon Chip Shop.................... 97 Switchmode Power Supplies....... 7 The Loudspeaker Kit.com......... 93 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 10 Notes & Errata Programmable Hybrid Lab Supply with WiFi, May 2021: in the parts list on page 36, the item at the top of the right-hand column should have read VXO7805-500 (5V) rather than VXO7803-500 (3V). The circuit should still work even with the 3V part fitted. Also, the MCP4725 DAC specified comes in several versions; MCP4725A0T-E/CH is the required part. Arduino-based Power Supply, February 2021: the 51kW resistor’s five-band colour code is incorrect. It should read “green brown black red brown”. DIY Reflow Oven Controller, April & May 2020: in the May 2020 issue on page 90, Fig.11 shows the 20-wire ribbon cable between the control board and LCD screen connected incorrectly. It is shown correctly in the photo at the top of p89, with the red stripe going to pin 1 on both boards. Deluxe Touchscreen eFuse, July 2017: The HEX file we have been providing has not had the AUTORUN flag set, meaning eFuses built with a preprogrammed chip or using the HEX file from the Silicon Chip website will not work without being run manually from MMBasic. We’ve updated the HEX and MMBasic files to fix this and also to fix a bug that may cause the Micromite to crash and reset if the screen timeout was set to certain values. The July 2021 issue is due on sale in newsagents by Monday, June 28th. 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