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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 CD Welder capacitor substitution & update I read your Errata regarding the CD Spot Welder (March & April 2023; siliconchip.au/Series/379) and the 39mF capacitors’ incorrect part code. I had already bought them, as indicated in the table in the original article. They are the same series as the 871-B41231A5399M000, with exactly the same specifications but a slight physical difference: they have three pins instead of two. The middle pin needs to be cut off for use on the CD Welder ESM board. As all the pins are 4.5mm long instead of 6mm, there is no need to trim them after soldering. The M002 version is 14.5 grams lighter, resulting in the welder being 435 grams lighter. Mouser currently has 664 of the M002 version, but the M000 versions are unavailable until February 2024. I suggest constructors get in quickly and pre-order them. The M002 versions are only $0.10 dearer, so $3 more for 30. I can’t see that there would be any performance difference between them. The physical differences will be of no concern with construction. My question is: what would the weight difference be attributed to, and would it make a performance difference? I wouldn’t think so. (P. V., Innisfail, Qld) ● Phil Prosser responds: I looked over the spec sheet and it makes no distinction between the three-pin and two-pin variants of those capacitors. I would have no hesitation in using them. Just make sure you have trimmed those leads in a way that will not allow them to scratch through the solder mask. The third pins are usually isolated, but for completeness and caution, trim them carefully. Not having had the chance to look one over, I expect that the weight difference comes down to the construction of the capacitor base. Using TFTP with Watering System Controller I built the August 2023 Watering System Controller (siliconchip.au/Article/15899) based on the WebMite (Raspberry Pi Pico W). I have been using CoolTerm 2.0.1 to communicate with it as there is no Mac version of Tera Term. I successfully copied the WebMite MMBasic Version 5.07.07 to the Pico, then connected to it and entered the SSID and password for my local WiFi router. The FILES and PRINT commands work OK, but when I attempt to use the TFTP command, I get “Error : Unknown Command”: WebMite MMBasic Version 5.07.07 Copyright 2011-2023 Geoff Graham Copyright 2016-2023 Peter Mather Connecting to WiFi... Connected 192.168.100.176 Starting server at 192.168.100.176 on port 80 > tftp Error : Unknown command > TFTP -i 192.168.100.176 PUT retic.bas Error : Unknown command How do I load the “retic.bas” file and associated files into the Pico? (B. R., Karrinyup, WA) ● tftp is an operating system command, not a PicoMite command. You run the tftp command on your local computer’s command prompt, not on the PicoMite. Using tftp with the WebMite is explained on page 25 of the WebMite manual, which you can download from our website at siliconchip.au/Shop/6/230 This web page, among others, says that the tftp command should work on macOS: siliconchip.au/link/abpr You could also try this tftp software on your Mac: siliconchip.au/link/abps 108 Silicon Chip Australia's electronics magazine I also have a follow-up to the CD Welder question published on page 109 of the October 2023 issue regarding whether it can weld copper strips. With shortened leads (50cm), I was able to make outstanding welds on heavy-duty nickel strips and excellent welds between 0.1mm-thick copper strips and batteries at only 17V. R. E.’s application called for 0.25mm copper, which is scarily thick. I think an ultrasonic welder is needed to achieve that. All he could find was a 0.3mm-thick ‘strip’. Even upping the voltage a tad over 25V and with short leads, this copper strip wouldn’t weld. So, as an update for potential users, this project will weld 0.1mm-thick strip with close to 100% headroom but will definitely not weld 0.3mm-thick copper to steel. Linkwitz mod affects frequency response? I am interested in building the through-hole version of the Calibrated Measurement Microphone described in the August 2023 issue (siliconchip. au/Article/15903) with the AliExpress WM61A ECM you offer. In the past, I have used the “Linkwitz modification” to ECMs as described in that article, as it gives extra headroom (although it’s pretty fiddly to do). My question is: does the ECM calibration file supplied with the capsule still apply if you do the Linkwitz mod? Did you check to see if it affects the overall response at all? (R. C., Collaroy, NSW) ● Phil Prosser responds: I tested the Linkwitz mod on a couple of sample electret microphones, and while it reduced the overall gain, it did not affect the overall frequency response significantly. Troubleshooting a fan speed controller I’m trying to troubleshoot a speed controller on a Braemar ducted gas system. Going through the troublesiliconchip.com.au shooting process, I have become very interested in how the room fan speed control circuitry works. The motor seems to run OK at the higher supply voltage of 150V AC, but at start-up speed 1, giving 97V AC, the motor doesn’t turn. From googling photos, I think the large heatsink on the control board is a Triac that chops the AC waveform to lower the voltage to the motor to slow it down. There is what looks like an opto-coupler between the low-­voltage DC and high-voltage AC part of the PCB. I want to learn more about how these Triac-switched speed controllers work. I bought and downloaded your April 2012 back issue with the Induction Motor Speed Controller as my motor would be similar. It seems to be a fancy solution where both the voltage and frequency are reduced to change speed. My motor has a run capacitor wired in series and has a start and run winding. Do you have a back issue with a Triac motor controller project? (E. M., Hawthorn, Vic) ● We published a Triac-based motor speed controller, the Refined FullWave Motor Speed Controller (April 2021; siliconchip.au/Article/14814). Check the motor start capacitors. They often go low in capacitance, preventing the motor from starting, especially at lower applied voltages. Is AN618 IC compatible with AN6180? I have a garden light that is a later batch than those from our original set that use the YX8018 IC, and I suspect the ANA6180 IC may be faulty. However, I can only find ANA618 listed on eBay, and the ANA6180 does not seem to be listed anywhere. Is there any difference between the ANA618 and the ANA6180, or is it just a different manufacturer? (B. P., Dundathu, Qld) ● Like you, we suspect that the O or 0 suffix just indicates a different manufacturer of the ANA618, as we can’t find any sensible information on a chip coded ANA6180 either. Check if the PCB connections match those expected for an ANA618 and, if so, try replacing it with an ANA618. Given that you can get them for around $1 each, including delivery, it’d be worth a try. siliconchip.com.au Compilation error with Arduino Seismograph I built the April 2018 3-axis Seismograph (siliconchip.au/Article/11030) when you published it. Unfortunately, my Uno died, so I purchased a replacement. Now, when I try to upload your code, I get the following error: error: ‘FilterOnePole’ does not name a type Any ideas? (I. M., Drouin, Vic) ● That is a library problem but not due to a missing library. We tried compiling the sketch with Arduino IDE version 2.1.1 and AVR boards version 1.8.5. Before installing the Filters library, we got a different error: fatal error: Filters.h: No such file or directory After installing the Filters library from the software download (copy the Filters folder from the zip file to ../Documents/Arduino/libraries/) and restarting the IDE, the sketch compiled successfully. We suspect that you have a different library named Filters or a different version of the library installed. The suggested fix is to remove the existing Filters library and replace it with the library from the download package. The reader later confirmed that using the recommended library fixed his problem. That time of year is nearly here... CHRISTMAS Spice up your festive season with eight LED decorations! Tiny LED Xmas Tree 54 x 41mm PCB SC5181 – $2.50 Tiny LED Cap 55 x 57mm PCB SC5687 – $3.00 Tiny LED Stocking 41 x 83mm PCB SC5688 – $3.00 Tiny LED Reindeer 91 x 98mm PCB SC5689 – $3.00 Transformer for SC200 Amplifier power supply I want to build a stereo version of the SC200 Amplifier (January-March 2017; siliconchip.au/Series/308). I have purchased two SC200 Amplifier Module PCBs and two sets of hardto-get parts from your Online Shop, along with one 135W Stereo Amplifier Power Supply kit and the Loudspeaker Protector kit. I intend to build the Touchscreen Digital Preamp (September & October 2021; siliconchip.au/Series/370) to complete the amplifier. Unfortunately, I cannot locate a suitable toroidal transformer with 40 + 40V AC outputs and 15 + 15V AC auxiliary windings. Is there a suitable replacement? What is the best configuration to supply the required power for the stereo amplifier? I probably do not need the full 135W into 8W, but I would not like to otherwise compromise the amplifier’s capabilities. (J. E., Beachmere, Qld) Australia's electronics magazine Tiny LED Bauble 52.5 x 45.5mm SC5690 – $3.00 Tiny LED Sleigh 80 x 92mm PCB SC5691 – $3.00 Tiny LED Star 57 x 54mm PCB SC5692 – $3.00 Tiny LED Cane 84 x 60mm PCB SC5693 – $3.00 We also sell a kit containing all required components for just $15 per board ➟ SC5579 November 2023  109 ● Unfortunately, Altronics stopped selling the 40-0-40 + 15-0-15 transformer we used a few years ago. We suggest you use a 300VA 40-0-40 transformer (eg, RS 117-6065) plus a small 15-0-15 transformer (eg, Altronics M4915C). The RS transformer’s 115V AC primaries can be wired in series to get a 230V AC primary. That would then be wired in parallel with the smaller transformer’s primary, with the latter having a 500mA fuse added in series with its primary. The main fuse that protects the whole lot (eg, in a chassis IEC mains input connector with fuse) should be rated at 3.15A, slow blow (eg, Altronics S5657). If you don’t need full power and would be happy with somewhere in the region of 100W per channel, you could use a 35-0-35 300VA transformer, which might be a little easier to obtain. Still, the 40-0-40 transformer isn’t too expensive or difficult to get, so we suggest you stick with that. Relay for Currawong Amp not available Thank you for supplying the PCB and some parts so I can build the Currawong Stereo Valve Amplifier (November 2014 to January 2015 issues; siliconchip.au/Series/277). I am having trouble sourcing the Altronics S4141B relays specified. Altronics have told me that these are now obsolete. Can you advise of any replacements? (J. Z., Tranmere, SA) 110 Silicon Chip ● S4141B was a 5V DC coil version of the S4140B (12V DC). In the Currawong, these relays are used to disconnect the loudspeakers when a pair of headphones are plugged in, and they are powered from its 12V rail via an 82W 1W resistor with an open jumper, LK3, across it. While the purpose of that jumper was to allow the S4141B relays to work with a 6V DC rail rather than 12V DC, it turns out that it’s also perfect for allowing S4140B relays to be substituted for the discontinued S4141B types. All you need to do is place a jumper shunt on LK3 (you can omit the 82W resistor if you want). The relay coils will then have the full 12V DC applied. The only other change you need to make is to increase the 330W series resistor for LED2 to 1kW to keep the LED current the same as before. Changing the frequency of a 555 timer circuit I recently developed a pest problem, and some research revealed an article by Colin Dawson in Electronics Australia magazine, November 1985, titled “Zap ‘em with the Pest off”. The circuit is shown below. Although I have had a fair bit of success experimenting with normal 555 astables, this is the first time I have come across this type of 555 design, and it is proving to be a bit more of a challenge. I am trying to calculate the component values between IC2 (4017) and IC3 (555) to change the frequencies. Australia's electronics magazine This design is unique in that Colin has installed a diode across pins 7 and 6, effectively bypassing the 22kW resistor when charging the 820pF capacitor. I have read through the project article, but I can’t understand how he calculated his values, and further research hasn’t provided any useful information either. I have considered using separate 555s connected to each of the 4017 outputs, providing the frequencies I want, but why use six when one will provide the same result? Can you provide the formulas used to calculate the frequency, time high, time low and duty cycle or any other helpful information? (Ken, New Zealand, via email) ● Introducing the diode means that the 820pF timing capacitor for IC3 is charged via the 10kW resistor from the high 4017 output rather than via the 22kW resistor. So initially, the capacitor charges via the 10kW resistor and is discharged via the 22kW resistor connecting to pin 7. There is a slight complication due to the diode voltage drop compared to the overall supply, but they don’t significantly change the charge rate due to the relatively low voltage. So the charge and discharge times can be calculated separately and added to give a total period. The frequency is the inverse of that. The charge period is 0.693 times the 820pF (8.2 × 10-10F) capacitor value multiplied by the charge resistor value (10kW). The discharge period is 0.693 × 820pF × 22kW. continued on page 112 siliconchip.com.au I have successfully built the 40V Hybrid Switchmode/Linear Bench Power Supply (April-June 2014 issues; siliconchip.au/Series/241), a really excellent and compact, fully adjustable supply to modernise my workbench. As I was testing it, before enclosing it in the case, I noticed the heat dissipation of the two linear regulators was quite high for an input of 19.5V. This design accepts up to 24V at the input, meaning the dissipation could be higher than in my instance. Based on my finger test, these internal 7805 and LM2940 regulators appear to run above 50°C, and the case has no ventilation. I was pondering the lack of ventilation and whether I should drill holes in the case but concluded that would detract from its looks. I then recalled Advertising Index Altronics........... 9, 31-34, 73, 81, 89 Dave Thompson........................ 111 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Hare & Forbes............................. 15 Jaycar................. IFC, 12-13, 16-17, .................................... 60-61, 92-93 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology......... OBC, 7 Mouser Electronics....................... 4 Oatley Electronics..................... 111 SC Christmas Ornaments........ 109 SC Breadboard PSU...................... 8 Silicon Chip 500W Amplifier..... 87 Silicon Chip Binders.................. 72 Silicon Chip PDFs on USB......... 14 Silicon Chip Shop.................90-91 Silicon Chip Songbird................ 30 Silicon Chip Subscriptions........ 97 The Loudspeaker Kit.com............ 6 Tronixlabs.................................. 111 Wagner Electronics..................... 11 112 Silicon Chip another Silicon Chip project and wondered if the quiescent heat dissipation could be improved in this project by replacing the 7805 regulator with your 78xx Replacement project from August 2020 (siliconchip.au/Article/14533). It looks possible to replace the LM2940 12V regulator as well, using the same approach. Do you have any advice on whether this would introduce any problems or if it would require modifications beyond the 78xx Replacement substitution? (B. R., Eaglemont, Vic) ● Both linear regulators are provided with fairly generous heatsinks and contact with PCB copper, so they should run well within their specifications, even if they get a bit warm. 50-60°C might seem hot, but their maximum junction temperature ratings are 150°C. Still, we understand the desire to reduce power consumption and keep the case cooler. Using thermal paste between the regulator and heatsink, and heatsink and PCB, could reduce the junction temperature, as could using slightly larger heatsinks. However, the same total power would still be dissipated within the case. Your idea of using a switch-mode regulator is a good one. All that the 12V regulator (REG1) powers is a 7555 timer (IC2) driving charge pumps to generate some auxiliary rails (-5V and VBOOST) and 7805 regulator REG2, which delivers the +5V rail. None of those sections should be bothered by the extra noise expected from a step-down/buck regulator, such as the one we published in August 2020. By all means, try the substitution; just verify that the supply doesn’t have any odd behaviour after you swap the regulator over. If it does (which seems unlikely), you might need to add an Errata & Sale Date for the Next Issue Switchmode substitute for warm regulators RC or LC low-pass filter between the output of that regulator module and the rest of the circuitry. You could probably also replace REG2 (7805) with a 5V buck module but we’d be a little more cautious with that one. It drives the panel meters, which should not be a problem, but it also provides a reference voltage for the voltage and current adjusting pots and trimpots. The safest thing to do would be to leave REG2 as a 7805 but disconnect the 5V rails going to the two panel meters and run them from the output of a separate 5V buck converter. We don’t think that would cause any problems and would substantially improve efficiency. Identifying a kit sold by a third party I need your help to find the firmware for a PIC16F84 chip. I purchased a Big Clock kit from Quasar Electronics in England many years ago. The kit was a Big Clock model AS3073. My old but very exact clock suffered damage to the PIC16F84 microcontroller and does not work anymore. I know it will be difficult to find this old program, but I would greatly appreciate it if you could help me. (R. C., via email) ● We can’t find any mention of “Quasar” or “AS3073” in any of our magazines. Perhaps they took one of our designs and turned it into a kit without our knowledge. We have published many clock designs, but the one that seems most likely to be a match is the Big-Digit 12/24-Hour Clock (March 2001 issue; siliconchip.au/Article/4235). The software for that project is here (PCBs are also still available): siliconchip.au/ Shop/6/2171 SC Watering System Controller, August 2023: the original V1.2 version software had two serious faults. It was not driving the correct I/O pins as shown in the circuit diagram, and a calculation error could cause it to water on the wrong day. V1.3 fixes those and adds a new SMTP relay service for sending emails (SMTP2GO), as some users have had difficulty opening a free account with SendGrid. Several minor changes were also made to improve the web pages generated by the firmware. The new firmware is available for free download from our website. If upgrading an existing installation, you can just overwrite the four files in the WebMite’s internal file system, then type RUN “RETIC.BAS” and press Enter. The “settings.dat” file will automatically be upgraded. Next Issue: the December 2023 issue is due on sale in newsagents by Monday, November 27th. Expect postal delivery of subscription copies in Australia between November 24th and December 12th. Australia's electronics magazine siliconchip.com.au