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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”. Harbuch Electronics ownership change I just got the following email from Harbuch Electronics [edited for brevity and grammar – Editor]. It is great to know it will survive. We can ill afford any more losses in Australian electronics manufacturing. Hugo Holden, Minyama, Qld. Hi there, I’m sending you this email because you have dealt with Harbuch Electronics in the past and I wanted to update you on some recent changes. Unfortunately, the previous owner, Peter Terlich, fell seriously ill in May and couldn’t return to work. I was one of his larger customers through my other business Powerform Controls – Harbuch was making a current transformer for us that I had trouble sourcing elsewhere. After discussions with Peter’s family, I bought Harbuch Electronics. I love Australian manufacturing and have taken on Harbuch Electronics, aiming to continue to manufacture high-quality transformers locally. I’ve spent the last 25+ years working as an Electrical Engineer in various roles. Through Powerform Controls, we have a well-set-up manufacturing system that we will move Harbuch across to (Powerform also does all its manufacturing locally). We plan to continue making nearly all the transformers and things that Harbuch has made in the past: toroidal transformers up to 5kVA, E&I transformers, audio transformers, chokes, isolation transformers, powerboards and more. We’ve got all the manufacturing records going back 10 or so years – if you had a standard or custom design, we most likely have the manufacturing info for it. Garth and Vino, Peter Terlich’s staff, are also working with us. As a result of this, there is a new company, ABN, bank account and address. We have moved from Blacktown to the Powerform Controls factory in Artarmon. The old Hornsby phone number is our main phone number now, but the Blacktown landline also works. The preferred email address is sales<at>powerform.com. au – it is checked by Tim and myself, so things are less likely to get missed. I know Harbuch has let some customers down while Peter Terlich was sick – if that is the case, I hope you can give me a chance to restore the business relationship. If it has been a while since you dealt with us, I’d love to reestablish that relationship and make high-quality transformers for you. If you’d like to chat about anything, please give me a call. Peter McConaghy 02 9476 5854 4 Silicon Chip Smaller toaster oven for DIY solder reflow Santa was kind enough to buy me a Silicon Chip subscription, so I’m looking forward to more project building in 2021. At the moment, I am working on the DIY Reflow Oven (April & May 2020; siliconchip.com.au/Series/343). I got the controller working pretty well, so I went shopping for an oven. I purchased the baby sister of the Kmart oven that you mention in the article (www.kmart.com.au/product/9litre-oven/2487301). The capacity is much smaller (9L vs 28L), but it has a reasonable amount of power given the size (1050W vs 1500W) and is half the price ($29 vs $59). It has upper and lower heating elements, but they didn’t have room for the knob to select which elements are active. It is big enough for most circuit boards, and I can fit it more easily (space is at a bit of a premium at my place). My initial testing shows that it works fine using the PID parameters from the article. I think this is a better-suited oven for reflowing, mostly due to there being less empty space above the PCB. Thanks for all your hard work on these fantastic projects, and have a Happy New Year! Stephen Gordon, Thurgoona, NSW. Free circuit drawing and simulation software Around June 2019, Spectrum Soft called it quits and have released their Integrated Schematic Editor and Circuit Simulation software, Micro-Cap 12, for free. They have been in the business since the 1980s. Micro-Cap 12 used to retail for US$4,500 (about $6000). This is too good to miss. You can download it from www. spectrum-soft.com/download/download.shtm This is a great way to get one of the best schematic editors and simulation packages on the market. I found this info just by sheer luck on the But KIS Analog YouTube channel: siliconchip.com.au/link/ab62 They have several tutorials on Micro-Cap 12, with more in the pipeline. Greg Gifford, Laguna, NSW. Android app for calculating resistor values In the October 2020 Ask Silicon Chip column, R. M. of Melville WA asked for a BASIC program to calculate series/parallel resistor values. This prompted me to create Android apps for calculating series and parallel resistance using App Inventor (as described in the article I wrote, starting on page 74 of this Australia’s electronics magazine siliconchip.com.au issue). You can download these Apps from the Silicon Chip website under February 2021. The download package includes the Android .apk files and also the App Inventor .aia project files. These can be imported into App Inventor to make modifications by clicking on “My Projects”, then selecting “Import project (aia) from my computer”. Roderick Wall, Mount Eliza, Vic. BoM tide data outage On the morning of January 1st 2021, I got a message saying “Error – data not available” on my Raspberry Pi-based Tide Clock (July 2018; siliconchip.com.au/Article/11142). Our internet service is working OK. It started working again all by itself on the 3rd. I guess the Bureau of Meteorology shut the server down at midnight for the new year. It was down for at least one day. Roderick Wall, Mount Eliza, Vic. Helping to put you in Control PR200 programmable relay 230VAC A programmable logic relay with 8DI + 8DO + 4AI + 2AO (4-20 mA), LCD, 2x RS485 (Modbus RTU/ASCII) ports and 230VAC powered. Free easy to use Function-Block Software. SKU: AKC-002 Price: $399.95 ea + GST Simex SLI-8 8 Counter Modbus RTU module An 8 isolated digital input module with Modbus RS485 communications. Provides a non volatile 32 bit counter for each input. 24VDC powered. SKU: SID-003 Price: $239.95 ea + GST Getting into soldering SMDs I was always reluctant to try a Silicon Chip project that used SMDs, as I baulked at soldering those tiny components. However, when I saw the DAB+/FM/AM radio project, even though it bristled with SMDs, it was just what I was after, so I decided to give it a go. After buying the parts, I went to YouTube to see how to solder SMDs. I settled on the solder paste method. After buying some paste, I gave it a go. It was easy enough, but I had trouble keeping the components from moving while soldering, resulting in a wonky joint. After a while, I devised this system: 1. Put a dob of solder paste on the pads. 2. Locate the SMD. 3. Hold it down with the point of a scriber held vertically. 4. A few seconds with the soldering iron on the pins and the job’s done. With a hand on the top of the scriber, hand movement will not affect the component, and the soldering iron does not move the component. After I finally got the radio going, I noticed one channel was not working. I traced the trouble to a faulty SMD IC, which meant it had to be replaced. So I went back to YouTube to see how to remove an SMD IC. I settled on the desolder wire method. After buying some, I laid it along the IC’s pins and heated it with the soldering iron. The low melting point of the wire causes it to diffuse with the existing solder, and in no time, the IC lifted and floated to the side; a quick clean up with solder wick and it was ready for soldering the new IC. I learned a lot from this project, and am not reluctant to try others in the future. Trevor Vieritz, Burpengary, Qld. Comment: we are glad to hear that you got the radio working and are more comfortable working with SMDs, but you should be aware that there are problems with both methods described. We do not recommend using solder paste with a soldering iron. It is designed to be heated more slowly by hot air or infrared reflow, so the flux formulation is different. You siliconchip.com.au SPT-61 Transmitter PT100/500/1000 The SPT-61 signal converter is equipped with Pt 100 / Pt 500 / Pt 1000 type input, 4-20mA output. Loop powered. SKU: SIB-001 Price: $134.95 ea + GST BACnet MSTP Slave/Modbus Master - Converter The HD67671-MSTP-4-A1 BACnet Slave / Modbus Master Converter allows you to integrate a BACnet network with a Modbus net. It allows you to connect a BACnet Master (for example a Supervisory System...) with some Modbus slaves. SKU: ADW-001 Price: $586.80 ea + GST AirGate Modbus (Gateway RS-485/ Wireless) Wireless gateway for extending Modbus networks. USB and RS-485 interfaces. SKU: NOW-001 Price: $473.50 ea + GST 1-port isolated RS-422/485 Modbus Gateway Modbus TCP to Modbus ASCII/RTU converter gateway allows Modbus TCP masters to communicate with serial Modbus slave devices via isolated RS-422/485 interfaces with TB5 screw terminals. SKU: ATO-162 Price: $330.00 ea + GST Loop Powered 4-20mA Surface Temperature Sensor This is a simple 4-20mA output loop powered temperature sensor with measurement range from 0°C to +100°C designed for monitoring battery, heatsink and surface temperatures. SKU: KPS-015 Price: $83.00 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine February 2021  5 also risk flinging tiny solder balls all over the board, which is particularly bad for boards carrying high voltages as it could lead to arcing. The problem with desoldering wire is that once you have melted it into the solder on the board, it’s impossible to remove completely. It will change the formula of your solder, possibly leading to premature solder joint failures. Desoldering SMDs is very easy, quick and safe with a low-cost hot air wand. It can also be done with regular solder with some practice. BWD602 circuit diagram needed I love your magazine. I was wondering if any of your readers have a circuit diagram or manual for a BWD602 combination instrument. I am repairing one that I bought recently, and the diagram would be a great help. I am trying to build a collection of BWD instruments while some are still around, and am looking for more instruments if the price is right. Trevor Collins, Bellevue, WA. Comment: one of our readers, Bruce Williams, suggested it was a rebadged version of a Hung Chang OS650 oscilloscope from South Korea (siliconchip.com.au/link/ab63). It was also badged as Aron BS-601 or ProTek 6502. He included some PDFs of various manuals which can be downloaded for free from our website: siliconchip. com.au/Shop/6/5755 Trying to avoid price increases In your January editorial, you asked for feedback upon the content. I find the balance to be about right, and as a pensioner, I certainly would not like to see a larger publication with an attendant increase in price! Like you, I am surprised that it has been steady for so long. I do not read every article; for example, I’m not interested in the audio articles with cabinet making etc, but to each his/her own. The Vintage Radio section is quite interesting as is Circuit Notebook, along with the queries in Ask Silicon Chip (I have learned a great deal from the answers). One minor gripe is about the need for Windows to run some of the projects; many people refuse to run it due to its inherent bugginess and security problems. I understand that you have no control over the software that con6 Silicon Chip tributors use, but hopefully, some will see the light and make versions for better operating systems such as Linux, Mac, FreeBSD etc. All in all, the magazine balance is just about right. Dave Horsfall, North Gosford, NSW. Nicholas comments: As mentioned in a couple of editorials, I am putting off a cover price increase, but it will have to happen eventually. See the graph below showing the magazine cover price in 2020 dollars over time (calculated using the RBA’s inflation statistics). As you can see, the current cover price is the lowest it has been since 1996 in real terms (that was before the GST was introduced). Most of our projects which involve computer software these days will work on Windows, Mac or Linux. For example, the Arduino-based Adjustable Power Supply in this issue, the Flexible Digital Lighting Controller from October & November 2020 (except for the optional sequencing software reused from 2010) etc. Those all use software written in Processing which works in multiple different operating systems. Windows programs can often also be run on Mac systems (eg, via Bootcamp) or Linux (using WINE). Feedback on magazine content I’d like to comment about your Editorial Viewpoint in the December 2020 issue. I started electronics as a hobby when I was a teenager in the early 1990s, and at that time, I had a subscription to a French electronics magazine. I did not understand much of the schematics, so I bought some books to learn. It was only after I earned a master’s degree in microelectronics and digital communications that I really understood Australia’s electronics magazine the magic behind the transistors and other components. Many years later, in 2015, I came back to my hobby, and I was looking for a new magazine to subscribe to. Sadly, the magazine I previously subscribed to (Electronique Pratique) had ceased publication. Then I discovered Silicon Chip. Browsing the various issues, I could see many projects published in the magazine, some of the more complex ones over several issues. Some publications did not place much emphasis on projects, but rather technical articles instead. I also liked having the possibility to buy the PCBs and download the software. I thought that was a huge plus. Since I moved to Singapore and now live in a condo, I could not easily make my own PCBs anymore, but now it’s easy and relatively cheap to have them made. So I immediately took a subscription to Silicon Chip, and five years later, I have built many of your projects. I have to say I am delighted with the content of the magazine so far. I appreciate the balance between various types of projects and technical articles, Circuit Notebook, Ask Silicon Chip etc. What I really enjoy are those complex projects you publish over several issues, like the recent USB SuperCodec and its Attenuator board over five issues, or a few years back the great series of articles on the Mk4 UltraLD amplifier, the preamp, the power supply board and the speaker protection module. That was an amazing project that I built together with your 8-octave equaliser, LED VU meter and CLASSiC DAC! I had a great time building and testing all of them. You even published some pictures of my finished products (twice). Now there are also tons of smaller projects that are appealing for not only low-experienced readers and newbies, but also experienced ones. There’s something for everyone. I appreciate that you support your readers, not just by selling PCBs and supplying source code but also supplying hard-to-find parts, PCB layouts and answering readers’ questions. I work in the financial software world (trading platform), and support makes a huge difference between vendors, so does it for magazines, I believe. So I would not like to see you reduce siliconchip.com.au the number of projects from four. If you could increase the number of projects, that would be great! As I also enjoy the other sections of the magazine, I would like to see the number of pages increasing, like what you did a few times in the past with some issues. Consequently, I would be supportive if you increase the cover price with more content. As you said, the cover price has not increased in seven years. Not that this is a reason to do so now, but if you were to do so, I think most readers would understand. If you increase the price and add more pages, and thus more content, I believe most of the readers would understand that they have now more for their money. By increasing the number of pages, you might gain more readers, especially if that allows you to increase the variety of articles. For those who are very price-sensitive, there is always the option to subscribe online. That may not be the taste of all, but it’s an alternative. Olivier Aubertin, Singapore. VHF masthead amplifier works for DAB+ My boat is moored at Hastings on Western Port Bay, which is on the edge of DAB+ reception from Melbourne. Some times I can receive both multiplexes, sometimes the lower one, and often neither. I am using a 3-element Yagi, vertically polarised. Part of the problem is that it is looking out through a forest of aluminium masts, most with wire rigging. You recommended (in response to a query) that I use a VHF masthead amplifier to improve DAB+ reception. I did that, and it appears to be working well. Thanks for your advice. Geoff Champion, Hastings, Vic. Latest PICs & GPS disciplined oscillator I just read the article about the latest 8-pin PICs (November 2020; siliconchip.com.au/Article/14648). I have been testing out the PIC16F1455 lately – you’ve used it in several projects over the last few years, so I thought I’d see how it compared to the PIC16F628A I’d been using previously. I’m using it to build a much simpler GPS disciplined oscillator than the one you published in Circuit Notebook, siliconchip.com.au July 2020. It consists of little other than the 16F1455, a GPS receiver, an OSC5A2802 10MHz VCO and a thirdorder passive RC low-pass filter to convert PWM from the micro to a smooth control voltage for the oscillator. I think it’s about as simple as can be. The parts are quite cheap. Apart from the power supply, the total cost is less than $20, and who doesn’t have a 5V 1A power supply hanging about? The NEO-6 GPS receiver is a 3.3V part, so its TX data was marginal to drive the 5V PIC’s serial RX, a Schmitt trigger input. I got around that by creating a 9600 baud software UART using one of the input-only pins used for USB when USB is enabled. It operates as a TTL input, so it is quite happy receiving data at 3.3V. The 1PPS output of the GPS receiver is fed to the PIC’s internal comparator, with the other input being held at 1.9V by the internal DAC. The PIC is clocked from the 10MHz VCO, and it has an internal x4 PLL, giving a nominal base clock of 40MHz with a 10MHz instruction clock. Compared with the PIC16F628A I was using before, the 16F1455 has major benefits. The output PWM signal is now 40kHz, so it loops through the 24-bit dither system three times per second, and all artifacts disappear in the filter. Also, detection of the GPS 1PPS signal uses the gate function of TMR1, which clocks at 40MHz, so pulse timing can be determined to within 25ns. So there’s no need for the complex delay system of my previous circuit. The program evaluates data statistically, so the uncertainty decreases with more samples. The advanced 8-bit PIC architecture is much better than the PIC16F628A. Two indirect registers can access all memory (including program memory) instead of one that could access 256 bytes. Those registers can be used for moving data with auto-increment or auto-decrement. You can also load or store with an offset. There are added shift instructions, eg, logical shifts that don’t require the carry flag to be set/cleared before shifting; the older instructions rotated through the carry flag. There’s also an arithmetic right-shift that propagates the sign. There are added arithmetic operations that also affect the carry flag. Previously, a multi-byte add or subtract Australia’s electronics magazine February 2021  7 required four instructions for all bytes but the least significant byte; now it only takes two. The interrupt system is improved as much state data is saved when an interrupt occurs; previously, it was necessary to specifically save any register that the interrupt was going to use, and restore them on exit. Interrupts can be serviced without superfluous instructions – some of mine are now less than 10 instructions. There are new relative CALLW and BRW instructions that cater to page boundaries, and there are mechanisms to do just about anything. Program memory can be read and written (I now store constant text strings in program memory as two 7-bit characters per 14-bit memory location). The CALL stack can be manipulated, and the saved status from an interrupt can be manipulated. The only serious drawback is the banked memory model. Any operation involving a peripheral usually requires the user to change the bank register to access the peripheral, and not using the right bank results in unpredictable behaviour. You will remember the confusion about writing assembler code for MPASM, which is not included in the latest MPLAB X IDE downloads. I haven’t seen one positive comment regarding the replacement assembler, XC8; the almost universal consensus is to keep using MPASM as XC8 is only useful to write embedded assembler in C programs. I tried using XC8, but it was all too hard. I am using a threaded system so that the NMEA data from the GPS can be received and processed at the same time as the mainline is dealing with the 1PPS data. I couldn’t see how to make it work with XC8. Alan Cashin, Islington, NSW. A tale of two speed controllers First, I would like to say that I am very happy to see a PDF version of the magazine. Being a constant traveller, downloading the big file for the online issue via satellite on a slow shared connection was a problem. The main reason I wrote in is to say that just over two years ago, I built the first version of your Speed Controller for Universal Motors (February-March 2014; siliconchip.com.au/Series/195). Putting it together did not present any real problems, but it didn’t work 8 Silicon Chip straight away. I ran through the suggested troubleshooting, which was quite good. I checked the critical components with the power off and soon discovered the pots were open circuit. So I ordered new pots. Once I had replaced the cabling again, they checked out, but it still wasn’t working, So I powered it from my bench supply as the guide suggested. Everything seemed to be working as it was supposed to, so I disconnected the bench supply and made some checks when running from the mains. One of the first checks I made was to see that there was 15V getting to IC3 and REG1, but I only measured 7V. I had already checked BR2, the 1MW and 470W resistors and the 220nF capacitors. I thought that there might be a short or bad component, but nothing was running hot. I decided to try paralleling another 220nF X2 capacitor across one of the two feeding BR2. That gave me 9V across ZD1; an improvement, but still not enough. I tried replacing the two 220nF capacitors, but that didn’t help, So I swapped in 470nF X2 capacitors instead. Bingo, that did it! The speed controller was alive. It has been working well ever since. I was thinking about building another one so when I saw your new speed controller in the March 2018 issue (siliconchip.com.au/Article/10998), and realised that it would be much cheaper and simpler to build, I decided to go for it. Construction generally went OK, and it worked straight away, but I noticed that there wasn’t enough speed control. The main reason for building it was to convert a grinder into a polisher. I was a bit confused about how many turns were supposed to go through the current transformer. I had put in only one turn, and I had trouble with that. I changed it to two turns through the transformer core, and that fixed it. One of the uses I have for it is with my SDS hammer drill. It’s very good mechanically, but the contact protection override switch is terrible. Eventually, I will use the controller when contact detector and switch gives in totally, plus an earth-leakage circuit breaker (ELB) if working where I need the protection. Neil Brewster, Footscray, Vic. Comments: we aren’t sure why you Australia’s electronics magazine had to change the 220nF capacitors to 470nF in the first speed controller. 220nF should be adequate; perhaps your circuit is drawing more current than expected, eg, ZD1 may be leaky or trimpots VR1-VR3 may be lower values than the 10kW specified. For the second controller, the number of turns through the transformer is not critical (one or two turns is acceptable). The feedback adjustment trimpot can be used to compensate for the difference by reducing the feedback effect when two turns are used. Suggestion to redo rain gauge It might be a good idea to revisit your June 2000 Automatic Rain Gauge (siliconchip.com.au/Article/4325) and March 2000 Electronic Wind Vane (siliconchip.com.au/Article/4354), perhaps combined with your February 2018 Water Tank Level Meter (siliconchip.com.au/Article/10963). You could bring together the three projects to provide an online weather station with expanded capabilities. I think it makes excellent sense to use the project archive you already have and bring it forward in time by making it relevant to current circumstances. For example, by taking the rain gauge and weather vane projects and making them internet savvy with the online data logging functionality associated with www.thingspeak.com – you’re ticking many boxes from my perspective. Iain McGuffog, Indooroopilly Centre, Qld. Comment: we have looked at doing this sort of thing in the past, but we stopped when we realised that digital weather stations are now so cheap. We know that some people like to do it themselves, but the idea of spending several hundred dollars and many hours to build something that you can buy for $99 at Bunnings is not very appealing. Since it would take a lot of work to revisit such projects properly, we only want to do so if they will be popular with readers. Integrating the water tank level meter might make it more worthwhile, but keep in mind that the water level sensor itself is quite expensive (but worth it, in our opinion, as it is easy to install and works well). We will investigate this again to see whether it will be worthwhile, even though we already know that it doesn’t make much financial sense. SC siliconchip.com.au