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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”. Test Master origin revealed I was just browsing the March 2021 issue and I found an item that made me very excited. On page 18, in the article on Urban Electronic Archaeology (siliconchip.com.au/Article/14773), there was an ‘apparatus’ called a “Test Master”. I made this thing! I was a third-year apprentice/trainee tech with Telecom in 1984. This was one of the big projects we all had to complete as part of our apprenticeship. We had to cut and fold the mild steel base and lid, drill all the holes and populate the PCBs. The lid and base were anodised off-site. Every hole had to be precisely located, or we would have to start over. No one dared muck it up. The wiring had to be accurately laced as lacing cables would be, for many of us, our bread and butter when we qualified. It had to be perfect. I still have mine in my garage, slightly the worse for wear though, and I still occasionally use it. I cannot say for how many years this was part of apprentices’ training, but even when I was building it, I felt pride that I built it just about from scratch. At the time, there was some discussion about whether we should have made the PCBs from scratch (they were premade). Ahh, great memories! Tony O’Halloran Former tech, Telecom/Telstra, Healesville, Vic. More details on the Test Master In the March 2021 issue, you had a great article on hoarding by Dr David Maddison. One piece of equipment he found was a “Test Master”, and he was wondering about the origin of the device. Any Telstra technician who did their apprenticeship at the Tooronga training facility will immediately recognise it. It was built as a training ex4 Silicon Chip ercise by many apprentice electronic technicians. It taught metalwork, soldering, basic electronic theory, circuit reading and much more during the construction. Including, yes, cable lacing; considered an important and useful skill back in those days. I made my “Test Master” in the early-to-mid-80s, and it sat on my hobby desk, actually being used for many years. It’s currently packed away in a box after a move a couple of years ago, but was still occasionally used up until then. I hope this information is useful, though no doubt plenty of other ex Telstra techs will write in with similar stories. Peter Tremewen, Drouin, Vic. Very high-quality AM reception with DAB+ radio I am writing again with what will probably be the last update of my alternative AM/FM/DAB+ radio code, described in the Mailbag section of the October 2020 issue (January-March 2019; siliconchip.com.au/Series/330). I received a lot of feedback and suggestions from my friend Ingo Evers and have added a fair number of new features to the earlier version, and resolved many of its problems. It was helpful working on a project like this with a friend, because we have each found and fixed small problems with the way we constructed our radios. And by seeing the same unexpected behaviours on two independent radios, we have noticed and corrected some software problems. I’m motivated to share this update because we made a surprising discovery. A few weeks back, Ingo was lamenting that AM quality on this radio was not up to the standard of his other receivers despite great DAB and FM performance. I agreed that I felt my radio’s AM was the same. Australia’s electronics magazine But then I remembered from earlier in the lock-down when I was studying the radio chip’s programming guide, there was an AM setting for changing the audio bandwidth. I went back to the data, found that setting, and saw that the radio chip defaults to an AM audio bandwidth of 3.5kHz, which is barely equivalent to an analog telephone. You can easily change this setting in multiples of 100Hz. A quick experiment showed that the Silicon Chip DAB+ radio is more than capable of astonishing AM fidelity, and I was surprised in a good way. Now we can say even more than earlier that the radio is capable of providing a superb sound quality through a decent hifi setup, and we are even happier than we were with how the project has turned out. The latest version of my revised software lets you configure the AM audio bandwidth on a station-by-station basis, from the radio’s minimum of 1.5kHz (which sounds rather muffled) up to its maximum of 10kHz (which sounds almost the same as a welltuned FM station). You can change the audio bandwidth in near real-time, so the improvement is very noticeable as you wind it up. I had always assumed that the audio bandwidth of Australian AM broadcasts was just 4.5kHz (half of the 9kHz nominal channel spacing), and that this was the reason for the muffled sound we have all become accustomed to over the years. Clearly, that is not the case, and Australian AM broadcasts are transmitted with at least 10kHz of audio bandwidth. When I searched for information about how much audio bandwidth Australian AM broadcasters are permitted to utilise, I could not find the answer. It would be interesting if you can find out. I had also assumed you’d hear a siliconchip.com.au “Setting the standard for Quality & Value” ’ CHOICE! 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It has three universal analog inputs one digital input and an alarm output. SKU: NOD-012 Price: $549.95 ea N322-RHT Temperature and RH Controller 230 VAC Panel mount temperature & relative humidity controller with sensor probe on 3 metres of cable. 2 independent relay outputs. 100 to 230 VAC powered. SKU: CET-109 Price: $263.95 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Silicon Chip I never cease to be amazed at the geographical diversity of Silicon Chip correspondents and contributors. The March 2021 issue is a good example. The Circuit Notebook section contained contributions from Sofia, Bulgaria; Paraná, Argentina; Oran, Algeria; and Capetown, South Africa. There was also a letter in Mailbag from Singapore. A quick look at recent issues showed contributions from Dunedin and Hukerenui, New Zealand; Cambodia; Vindhyanagar, India; Tehran, Iran; and Hetauda, Nepal. Designs from Sofia and Tehran are prolific, and perhaps warrant a short biographical story on each of these clever circuit designers. To me, this indicates the worldwide appeal of Silicon Chip content. Peter Johnston, Merimbula, NSW. Average speed tracker needed Prices are subjected to change without notice. 6 9kHz squeal if the receiver’s AM audio was not severely band-limited. I guess that unlike traditional analog receivers, digital radios don’t have that problem. It would be great to explore that more. This (maybe) final version of the alternative software implements almost all of the features of the original Silicon Chip software, and several more. One of the many changes in this version is a new infrared remote control configuration file, to make it easier to use any remote control device without modifying the BASIC program. There are also now optional favourite buttons on the main screen; the in-built speaker is supported properly, there’s a mute function, it is much easier to customise the colour scheme and so on. As the code size grew, Ingo complained to me that it would no longer fit into his Micromite. I discovered that the Linux “CRUNCH” script that I’d been using actually generates smaller crunched code than the built-in MMEdit crunch function. The difference is rather significant; the MMEdit crunched code is maybe 15% larger than the Linux crunching script’s output. But MMEdit will happily load the Linux-crunched output onto the Micromite, so just load the pre-crunched version into MMEdit and download to the Micromite as you previously would have done with the uncrunched code. Cheers, and thanks again for publishing this design. I think I’ll screw down the lid of my radio now and move onto the next project! Stefan Keller-Tuberg, Fadden, ACT. Comment: we appreciate all the effort you’ve put into this. Legislation determines that an AM radio broadcast can be nominally flat to 7kHz, and while it can extend past 9kHz, it must be attenuated beyond 9kHz. Therefore, a receiver bandwidth greater than 9kHz may improve the resulting frequency response. The supplied software is freely available for download at siliconchip.com.au/Shop/6/4940 As usual, I’ll start by saying that Silicon Chip is a great magazine. I used to be a subscriber, but I like going into newsagents and browsing. Some Australian magazines have been lost lately (for example, Australian Model Australia’s electronics magazine siliconchip.com.au WHAT IF WE COULD STOP DISEASES BEFORE THEY COULDN’T BE STOPPED? The key to beating more illnesses is earlier detection, and ADI’s precision sensing technology is powering new, ultra-fast disease testing, bringing us one step closer to a healthier future for all. Analog Devices. Where what if becomes what is. See What If: analog.com/WhatIf Engineering Magazine), and I think one of the reasons was the low sales volume. Once it dropped out of the public eye, the closure was inevitable. I don’t want that to happen to Silicon Chip. You recently asked for feedback. Yes, I don’t read the whole magazine, but I read most articles. I don’t build many projects any longer, but I look forward to what is on offer as I like the idea of building things. I am in Bathurst, and recently our cash-strapped local government has changed the time/speed/distance cameras to monitor all traffic – it used to be just trucks – and at the same time has lowered the allowed error to +3%. There is one of those machines just east of Bathurst, in a 100km/h area for about 26km. The road is virtually straight with no blind spots, some overtaking lanes, and generally very safe. Not a ‘blackspot’, so seemingly, this is just a cash-raising exercise. My idea is to have an Arduino or Raspberry Pi take GPS data and convert that to an average speed. A large button could start the process, and a second press could clear the data, ready to begin again. I am not advocating speeding or unsafe driving, but it is quite easy to stray slightly over the limit, and the penalties are severe. A loss of license would be catastrophic to my ability to work – yes, at 69, I am still working and plan to for a few years yet. Ed Pinder, Bathurst, NSW. Comment: You’ll be pleased to know that we are working on an updated version of the GPS Car/Boat Computer (originally from April 2016), and have added this to our list of features. It should appear in the magazine later this year. Thanks for the idea! Compact compass for Car/Boat Computer I have used the Micromite LCD BackPack for many purposes over the years. Recently, we bought an old Cray boat with a Sumlog, which was not reliable. I have replaced it with Greg Hoyes’ version of the BackPack-based Boat Computer, which works well. This version has the best compass; it works like a gyro repeater and is easy for navigation. I have upgraded the code to give a speed readout in knots to one decimal place, and it is very reliable. 8 Silicon Chip I am currently working on upgrading it to use the BackPack V3. The bigger display looks more in scale with other instruments, and is easier to read. But I came unstuck with the compass card, as the code is customised to the 2.8in screen. I am having some difficulty modifying this code to work with the 3.5in screen, as it is not documented and uses lots of constants. Ross Munn, Paynesville, Vic. Comment: we agree that this compass card style is useful, so we have added support for it to our new GPS Car/Boat computer, which also uses the 3.5in screen and will be described within the next few months. Advantages of DIY electronics The request to comment in your Editorial Viewpoint, January 2021, is much appreciated. I am a long-time reader of your magazine, and for over 60 years I have built my own electrical equipment and continue to use many past projects from Silicon Chip and other magazines that no longer exist. I live off-grid in a remote location, and have built my own power supplies, mainly from salvaged materials at a fraction of the cost of the commercial alternatives. I have a bias towards building my own gear which I can repair myself, as I have to drive around two hours to where I can purchase replacements for anything that fails. I believe that some of my projects work much better than the commercial alternatives. For example, I get almost twice the usable power from my solar panels, so don't need anywhere near as many. When I went to tech school in the early sixties, there was a hoard of us kids who made our own crystal sets etc, and tried to repair valve radios. We just went through every copy of Radio, TV & Hobbies. L. Ralph Barraclough, Licola, Vic. Details about VNG radio shutdown Thank you for replying to my query about projects requiring the insecure and buggy Windows OS; I did not know about Bootcamp for Mac, so I might try it (but I see that Windows 10 is still required). I have tried WINE with some success on simpler programs, but things like SPICE need libraries (DLLs) that are only provided with Windows. Australia’s electronics magazine The article on time sources was most interesting, especially VNG, as hearing its "beeps" is what introduced me to shortwave listening, thence Amateur radio. Did you know that when the Western Sydney site was going to be shut down by the short-sighted government, the then NSW Division of the Wireless Institute of Australia considered running it from its Dural site VK2WI? Unfortunately (or perhaps, fortunately), the idea was discarded, as the power bill would have been prohibitive (not to mention wiping out the callbacks!). As for the "talking clock", there used to be a human one, consisting of a woman sitting in front of two clocks with a telephone by her side. I have long since lost the link to the photograph. Dave Horsfall VK2KFU, North Gosford, NSW. Information on Philips BX205 radio Charles Kosina's article on the Philips BX205 B-01 radio in the February 2021 issue (siliconchip.com.au/ Article/14756) was both interesting and excellent. It started with some head-scratching regarding the unmarked dial. I can possibly enlighten him. It was originally intended for use in the tropics, which meant Indonesia or Malaysia in the 1940s and 1950s. Apparently, new radio stations popped up, disappeared or changed frequency at random intervals. Regulation was not a strict affair. All radios destined for the tropics were fitted with a 'standard' dial layout, having a zigzagged centre line, sometimes embellished with frequency or wavelength indications. Other manufacturers, mostly Dutch, also copied this layout. Bakelite versions were known as "Radio Roti" and were mostly transformerless. Yes, exciting times! Ben Heij, Caloundra, Qld. Building a DC-DC battery charger Being a semi-retired electronics engineer, I have tried to build my own DC-DC charger to fully charge the camper batteries via the vehicle Anderson socket. As you may be aware, the commercial DC-DC chargers are prohibitively expensive for us ‘grey nomads’ on a limited income. siliconchip.com.au WHAT’s new Our dedication to provide you with Excellence in Engineering APEM offers the broadest range of quality HMI products in the industry. They have the largest profile of Switches, Joysticks, LED indicators and Keypads to cater to several markets. 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WP SERIES PUSH BUTTONS FNR SERIES ROCKER SWITCH Q25 & Q30 SERIES LED INDICATORS MECA SWITCH PANEL OTHER products SWITCHES E-STOPS LED INDICATORS LINEAR SENSORS ROTARY SENSORS TILT SENSORS Anti-vandal Switches Rocker Switches INDUSTRIAL JOYSTICKS FINGERTIP JOYSTICKS DIGITAL PANEL METERS ANALOGUE METERS PCB SWITCHES TACTILE SWITCHES Emergency Stop Switches Toggle Switches FOOT SWITCHES HAND CONTROLS ENCODERS ACCELEROMETERS INCLINOMETERS INTERFACE MODULES Push button Switches Miniature Joysticks Air Switches Switch Panels USB Desktop Joysticks Hand Controls ContaCt us today for a quote. www.controldevices.com.au TOGGLE SWITCHES ROCKER SWITCHES AIR SWITCHES PRESSURE SWITCHES VACUUM SWITCHES SWITCH PANELS CONTROL DEVICES Unit 17, 69 O’Riordan Street ALEXANDRIA NSW 2015 sales<at>controldevices.net 02 9330 1700 I built mine using a Geekcreit 400W DC-DC boost converter module I bought from Banggood for $15 (siliconchip. com.au/link/ab77). I found that if I set the output to 14.5V, it would charge the half-discharged camper battery bank (two 100Ah AGM deep cycle batteries) with the voltage at the Anderson plug on the 4WD showing 12.5V. But it runs fairly hot at 15A, so it would require a cooling fan if mounted in an enclosure. I was reasonably happy with the performance of this cheap solution. Still, I noticed that without the vehicle running, the voltage would drop below the minimum required for the module at this load, and the output voltage would drop. Even when the vehicle was restarted, the output voltage would not recover until the Anderson connection was broken and reinserted. Most commercial DC-DC chargers have an MPPT solar input as well, so if that could be incorporated, I’m sure it would be a very popular project. I know MPPT can be complicated, so perhaps just an input from a solar charge controller would suffice. An LCD status screen would also be a nice addition. The option of selecting either lead-acid or lithium-ion type storage batteries of different chemistries would also be great. Onboard Bluetooth or WiFi could be used to monitor the charger remotely using a suitable app on a smartphone. I hope your technical team will give some serious thought to a project such as this. With the explosion of caravan and camper sales due to COVID-19, and the popularity of off-road self-sufficient camping, there is a real need for a reasonably priced DC-DC charger to keep these expensive batteries in peak condition. Bruce Hinton, Cleveland, Qld. High voltage and current tracking supply wanted Here’s a challenge for you. How about taking the 45V 8A Linear PSU (October-December 2019; siliconchip. com.au/Series/339) and turning it into a bi-polar or tracking supply? One obvious use of a bench supply would be to test a power amplifier. ±45V DC at 4A or so should cover a lot of the power amplifier applications out there. I’d imagine that a bi-polar supply is well within your capabil10 Silicon Chip Australia’s electronics magazine ities. The trick would be a sensible modification to the original project. If that could be done, then serious kudos to you. Iain McGuffog, Indooroopilly Centre, Qld. Easier way to transfer files to and from Raspberry Pi I am writing about your article “A Virtual Electronics Workbench” from the February 2021 issue (siliconchip. com.au/Series/357). After installing RealVNC on a laptop and enabling VNC server on the Raspberry Pi, Tim Blythman then describes how to install and use WinSCP to transfer files between the RPi and laptop. But there’s an easier way; VNC viewer and VNC server can both perform file transfers. To transfer files from the laptop to the RPi, move your mouse to the top middle of the VNC viewer window on the laptop, and a drop-down menu will automatically appear. Click the centre icon, which has a left and right arrow. This is for file transfers. In the pop-up box, click “Send files ...”, navigate to the file you want to transfer to the RPi and double click it. It will appear on the RPi desktop. Transferring files from RPi to the laptop is similar. Move your mouse to the RPi taskbar and right-click the VNC server icon. Select “File Transfer ...” from the pop-up box. Click “Send files ...”, navigate to the file you want to transfer to the laptop and double-click it. It will appear on the laptop’s desktop. Peter Ihnat, Wollongong, NSW. Comment: thanks for this very helpful information. Various comments on the March issue It was interesting to see the article on Fetron valve substitutes by Dr Hugo Holden in the March 2021 issue. Late last year, I mentioned the Fetrons to my ex-Telecom mate. To my surprise, he told me that Telecom used them and that he had experience with them. Also, Fetrons were not the only FET-based valve substitute. Earlier this year, I found an advertisement in a magazine for another brand of FETbased valve substitutes, but I cannot remember the magazine or issue. Perhaps another reader will mention it. I was also happy to see the Battery siliconchip.com.au HIGH-PERFORMANCE SOLDERING IRONS A family of wattages: • Fast heat up time • Reliable performance • Comfortable ergonomics 25 40 80 Find your favorite. • 3 LED lights illuminate your work • The world’s No.1 brand in soldering 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 12 Silicon Chip Balancer project. For anyone who wants a battery system of some power, this is the solution for balancing the batteries. It is even more desirable for batteries that are charged from a limited power source. Unfortunately, I suspect that the SMD parts and their availability will probably deter some people from it. It is probably overkill for the small systems that I use. Also, the processor is not a PIC chip, and that goes against the project. It is not that I dislike the SAM processors. It is just that I prefer to use projects which are PIC-based. If things go wrong, I already have the means to reprogram it etc. I do not want to invest in tools that I might only use a few times. I read Dr Maddison’s article “Hoarding: Urban Electronic Archaeology” with some interest, since his friend and I are obviously clones. With a deep interest in most things technical, and the space to store things that might be useful, it is not hard to gather a large number of items that are personally desirable, even if others think that they are rubbish. I am faced with the same problem that Dr Maddison’s friend would have faced in his later years: what I should do with my collection? The beneficiaries of my will don’t want these items, but at the same time, I do not wish to dispose of them because they provide me with parts for my projects etc. I have asked those who have suggested getting rid of most of it to please tell me what I will need in the future. Then, I can dispose of the other things. Of course, prediction is impossible, and the replacement cost of what I have works against getting rid of anything. I have been experimenting with Li-ion cells. I have a large quantity of used but good 18650 cells. To get batteries with the desired voltage and sufficient current capability, I need to connect the cells in parallel and then connect the parallel assemblies in series. I am trying to find the limit for the number of cells in parallel, if there is one. I know that four cells can be joined, but is that the limit? I have seen websites warn about connecting cells of different capacities in parallel, but that makes no sense. I can understand that cells of different types should not be combined but not ones of varying capacity. Cells with different internal resistances will charge and discharge differently. Still, I would expect that cells with different capacities would maintain the same voltage, and hence the same level of charge. However, there might be other factors involved which are unknown to me. George Ramsay, Holland Park, Qld. Comments: now that Microchip owns Atmel, pretty much all their chips (including the SAM series used in the Battery Balancer) can be programmed using their software and the latest PICkit (as mentioned in the article last month). So the use of that microcontroller should not be a negative point for the Battery Balancer project. We agree that if it’s OK to connect two cells of the same type in parallel, there should be no practical limit to the number that can be combined as such, as long as their chemistries are identical. It would be a good idea to use cells of the same age/lifecycle point to prevent one or more from failing prematurely and taking out the whole pack. SC Australia’s electronics magazine siliconchip.com.au