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APRIL 2022 ISSN 1030-2662 04 9 771030 266001 $ 50* NZ $1290 11 500 INC GST POWER WATTS AMPLIFIER DELIVERS 500W RMS INTO A 4Ω LOAD The History of Transistors Part Two siliconchip.com.au Geiger Counters and Measuring Radioactivity Australia's electronics magazine April 2022  1 Rosehill Gardens , Sydney – 5-6 A pril INC GST Build your own Intruder Alert An update on our Intruder alert project - now much simpler and cheaper to make! The kit uses a Passive Infrared (PIR) sensor to detect movement and send an email notification to your phone via Wi-Fi controller with a bit of coding and help from IFTTT. The project is flexible once it's up and running. It can also be set up to interact with smart home devices i.e when movement is detected, it could email you or turn on lights, change the colour of smart bulbs, play music on a smart speaker etc. Easy to build. No special wiring required. SKILL LEVEL: BEGINNER TOOLS: SOLDERING IRON CLUB OFFER BUNDLE DEAL 2495 $ For step-by-step instructions & materials scan the QR code. SAVE 30% www.jaycar.com.au/intruder-alert See other projects at KIT VALUED AT $37.60 www.jaycar.com.au/arduino JUST 5 $ JUST 7 95 $ JUST 995 95 $ ADD A SENSOR ADD A DETECTOR RECORD A MESSAGE Add a light sensor to this project to measures light levels night/day. XC4446 Measure distances up to 4.5m. Use it to add proximity detection to your Intruder Alert project. XC4442 Run a pre-recorded message to alert the intruders. Records up to 10 seconds. XC4605 Photosensitive LDR Sensor Module 100 $ gift card Awesome projects by On Sale 24 March 2022 to 23 April 2022 Dual Ultrasonic Sensor Module Got a great project or kit idea? Record & Playback Module 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 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 Shop online and enjoy 1 hour click & collect or free delivery on orders over $99* Exclusions apply - see website for full T&Cs. * Contents Vol.35, No.4 April 2022 14 Geiger Counters and Radiation 14 Radioactivity is everywhere! But since you can’t see it, how do you tell how much, if any, is present? This article investigates ways to measure radioactivity electronically plus some of the basics of radioactivity. By Dr David Maddison Science 38 The History of Transistors, Pt2 Transistor technology progressed rapidly in the ~20 years between the first commercial transistor being produced and the development of manufacturing techniques that are still in use today. By Ian Batty Semiconductors 50 80 New 8-bit PICs from Microchip When updating our SMD Test Tweezers we found out the micro used in it wasn’t in stock, so we had to pivot to using the newer PIC16F15214. So what does it offer over the previous 8-bit micro we were using? By Tim Blythman Microcontrollers 82 Dick Smith Contest Results We received some great submissions for the Noughts & Crosses competition. This article summarises the entries of the five winners (with one special prize awarded) and four runners-up. By Nicholas Vinen Competition 27 500W Power Amplifier, Part 1 Big, clear sound with low noise and distortion are just some of the aspects of our gigantic Amplifier module. It can deliver 500W RMS into a 4W load, or 270W into 8W. Two of them can also be bridged together to deliver 1000W! By John Clarke Audio project 50 Railway Semaphore Signal This realistic-looking OO gauge semaphore is modelled on a real British semaphore. It has a ‘flag’ that is driven by a servo and a bicolour LED to indicate to a train whether to pass or stop. By Les Kerr Model railway project 72 Update: SMD Test Tweezers The Improved SMD Test Tweezers are an in-place upgrade. All you need to do is slot in the new PIC to enable a swathe of extra features. The display can also be rotated 180° to help those who are left-handed. By Tim Blythman Test equipment project 100 Capacitor Discharge Welder, Pt2 After following the steps in this article you will have built your own Capacitor Discharge Welder, which forms a neat package. It is customisable and we also provide some tips on using it. By Phil Prosser Tool project in Sydney on the 5-6th 65 Back of April at Rosehill Gardens, ElectroneX returns with a plethora of companies and workshops to visit. 2 Editorial Viewpoint 4 Mailbag 37 Subscriptions 89 Circuit Notebook 92 Serviceman’s Log 98 Online Shop 1. Very simple adjustable electronic load 2. Three games that test reaction times 3. NBN battery backup 110 Vintage Radio 116 Ask Silicon Chip Monopole D225 radio by Graham Parslow 119 Market Centre 120 Advertising Index 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. Advertising Enquiries (02) 9939 3295 adverts<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com Former Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $65 12 issues (1 year): $120 24 issues (2 years): $230 Online subscription (Worldwide) 6 issues (6 months): $50 12 issues (1 year): $95 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 Printing and Distribution: Editorial Viewpoint Writing clearly and concisely You might notice that the style and grammar in SilChip magazine do not follow any particular set of rules except our own. This sometimes irks people who don’t like certain words we use even though, in many cases, they are the standard spelling and usage for Australian/UK English. But we have good reasons for making the choices that we do. First and foremost, especially with the kind of technical writing in this magazine, clarity is vital and ambiguity is to be avoided. We should not blindly follow grammar rules if they make the result more difficult to read or understand, and that certainly can be the case. I prefer generally to stick to most grammar rules because there is a certain logic in them, and sometimes advantages to adhering to them. However, I am willing to bend those rules when the result is improved clarity or brevity. For example, there is a rule that supposedly you can’t start a sentence with a conjunction. But often, the only way to avoid that is either to have a sentence that is much too long, which would be hard for the reader to parse, or one that reads in a very stilted or awkward way. So we tend to avoid it, but if the best clarity is achieved by ignoring that rule, we will certainly do that. There are two main reasons we like to have brief and concise text. One is that if you can get the same concept across in fewer words, unless it’s compacted to the point of obtuseness, it makes for easier reading. The other is that we have limited space in the magazine. It isn’t unusual in a longer article to save an entire page primarily by removing words that aren’t needed. However, there is the risk of ‘losing the voice’ of the author in doing that. It is nice to have different articles convey the author’s characteristics as long as it is not detrimental to understanding. But there are also benefits to having consistency, as a lack of it can be pretty jarring. It’s a difficult balance to strike. One of the biggest problems I find in the text submitted to us is a tendency to have really long sentences and paragraphs, often with very little punctuation. It’s fatiguing to try to read such text. I have even had submissions of more than one page of text with no paragraph breaks! It’s really hard to know where to start when faced with a wall of letters like that. Comma placement is also quite important, to help break up sentences into manageable chunks. I prefer to place them where one would naturally pause when reading a sentence, but that can vary depending on the reader and their style. Some people say that commas should not be placed next to conjunctions. That works for shorter sentences, but sometimes that’s the best place to put one in a longer sentence. To summarise, I hope it’s clear that we do things the way we do to make reading the magazine as easy as possible, even when explaining complicated concepts. icon Electronex is finally back! After all the problems caused by COVID-19, it seems that Electronex will finally be happening again, in Sydney, on April 5th & 6th. This is an excellent opportunity to get out of the house/office and see the new electronic products on offer. We have a sampling of what will be on show starting on page 65. Also see the Electronex ad on page 5 for more details. by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia's electronics magazine siliconchip.com.au siliconchip.com.au Australia's electronics magazine April 2022  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 has the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. AGM batteries are tough I thought the attached story might be of interest following your recent articles on batteries. I knew those concerned and can confirm it is accurate. It happened circa 2000 when I was nearing the end of my career in the Army as the Senior Advisor for batteries and battery chargers. The battery in the story was a Chloride “Armsafe” 12V 100Ah absorbed glass mat (AGM) sealed lead-acid battery (SLAB) that had a damaged terminal post due to a poorly fitted terminal – it hadn’t been adequately tightened. We used it as a workshop battery for jump-starts and other temporary power requirements. We got a call for help from an operator whose truck would not start due to a flat battery. The workshop battery was loaded on the back of a ute, and a driver set off to assist the stranded operator. Unfortunately, the tailgate of the ute was not properly closed and, as the driver negotiated a roundabout, the battery slid out and fell onto the road. Being an AGM battery, no acid was lost (it’s held in the mats like a sponge holds water), so the driver picked up the battery and the side panel pieces, put them back into the car and continued to the stranded vehicle. On arrival, the vehicle crew laughed and then mocked the rescue driver, but he was undeterred. He connected the damaged battery via the jumper leads and started their truck. When he returned and told his story to the workshop people, being curious about the inner connections of a battery, they removed the top for a closer look. After this, for safety, they connected the battery to a load (four headlight globes in parallel) to remove the remaining charge before sending it to the recycling facility. The initial open-circuit terminal voltage was 12V. It 4 Silicon Chip took over 10 hours for the voltage to drop to 10.5V and an additional three days to reach 0V. Gordon Dennis, Mill Park, Vic. Magazine & parts giveaway I have some magazines and some electronic bits and pieces to give away. I wonder if you can mention this in your next issue. There are about 140 mags all up, from the 50s to the 70s. I have Electronics Australia, Radio TV and Hobbies, Radio Constructor, ETI, Practical Electronics and Practical Wireless, Popular Mechanics, Popular Science, Science and Mechanics and Mechanix Illustrated. They are free to anyone who wants to pick them up. It would be a shame to throw them out. Feel free to list my number, 0409 104 658. There are also some assorted electronic bits that I haven’t yet sorted, but it would be a mixture. Alex Danilov, Naremburn, NSW. Another magazine giveaway I was wondering if you have any use for some older magazines. I have Electronics Australia from approx 1980 to their demise, ETI from about the same period, Silicon Chip from about 1999 to current, also some Your Trading Edge and Wired. The magazines are in Perth but could be posted at the receiver’s expense if needed. Peter Golding, Ardross, WA. Will Tesla Coil cause interference? I may be wrong, but I suspect that the Tesla Coil presented in the February issue is most likely unlawful to use due to the interference this device produces. Richard Allende, via email. Response: a couple of other people wrote in with similar comments. Of course, we considered this before publishing it as we are aware that such devices can generate RF and the article warns explicitly about this. Without having such a unit to test, and appropriate equipment, we don’t have definitive measurements. Still, our assessment is that it’s unlikely to generate such powerful RF emissions that it will be a major problem. Consider that many other pieces of equipment generate broadband RF interference, including some power tools with large brushed motors, and they are not banned. We would not be surprised if some large power tools generated more severe RF interference than the relatively small Tesla Coil we presented. The Tesla Coil is not something that you would run full-time. Still, constructors would be wise to check with Australia's electronics magazine siliconchip.com.au Design, Develop, Manufacture with the latest Solutions! Powering New Technologies in Electronics and Hi-Tech Manufacturing Make new connections at Australia’s largest Electronics Expo. See, test and compare the latest technology, products and solutions to future proof your business SMCBA CONFERENCE The Electronics Design and Manufacturing Conference delivers the latest critical information for design and assembly. Industry experts will present the latest innovations and solutions at this year’s conference. Details at www.smcba.asn.au In Association with Supporting Publication Organised by SEE EXPO FEATURE THIS ISSUE neighbours to verify that its operation is not causing problems with the reception of TV, wireless internet, radio etc. The designer of that project, Flavio, adds: we made sure to warn about the possibility of RF interference in the article. As stated above, it is a device that would be operated only briefly. We also expect that anyone who would attempt building such a device would be aware of the need to mitigate interference, such as the possibility of operating it in a Faraday cage. A Tesla Coil of substantial magnitude operates at Questacon in Canberra. The unit described in the article is a low-power device in comparison. Yes, it could cause interference to nearby devices. However, any person undertaking such a project is expected to exercise due care. Consider that the main application of such a device is for education and learning. Servicing help wanted I have had a Kogan KALED24LH6000DVA TV & DVD Combo since April 2018 and, in general, it has performed flawlessly. However, I am using my TEAC HDR9650TS Twin Tuner HD DVR almost all of the time to record and watch TV programs, so the TV remote rarely gets any use. When I am recording two programs on different channels and want to watch a third program on another channel, I need to use the remote. When I try to select the TV as the source, the “OK” (“Enter”) button becomes “problematic” in that I can’t get it to activate and apply the selection. I was wondering if you could put me in contact with a serviceman in the Karabar/Queanbeyan (postcode 2620) area who may be prepared to take a look at it and see if it can be “rejuvenated” and restored to proper operation. Paul Myers, Karabar, NSW. How padder feedback works In reply to Ian Batty’s query on how padder feedback works in the January 2022 issue (page 8), the tuned grid oscillator was the most commonly-­used circuit in vintage superhets. Because the feedback is by negative mutual inductance, the amount of feedback doubles at the high end of the broadcast band (or worse than that for the shortwave band). Padder feedback is shunt capacitive, so it increases at the low end of the band. Using both, the feedback can be level across the band, leading to better mixer performance. With the padder feedback circuit, the padder feedback is in series with the mutual inductance: Feedback impedance = -iωM – i ÷ (ωCp) The other reason it was often used is that it appears in The Radiotron Designers Handbook. With the Astor Mickey Oz receiver featured in that same issue, the 6A7 mixer may have suffered from the problem of feedback from the anode back to the signal grid. This provides negative feedback at the low end of the broadcast band. The compact layout could have made the feedback problem worse. The positive feedback from the IF bypass to the cathode was probably introduced to cancel or neutralise this negative feedback. The virtually identical 6A8G was notorious for its lack of shielding. The metal 6A8 was much better, but was not made in Australia. 6 Silicon Chip Australia's electronics magazine siliconchip.com.au The EK2G was made by Philips Australia from 1937, being an octal version of the EK2. Later, Philips introduced the EK32 worldwide. Earlier, they had produced UX7 pin versions of the AK1 which had better performance than the 6A7 or 6A8G. The metallised external shielding was quite effective. The Philips valves also had suppressor grids, which meant they could be operated with equal anode and screen grid voltages. Rogers used the same idea of external shielding in Canada with their 6A7M, but for some reason, metallisation was not fashionable in the USA. Robert Bennett, Auckland NZ. Ian Batty replies: Thank you for the information on padder feedback. I finally have a good idea of how it works. Advice for powering the Driveway Gate Controller Thanks for publishing my Driveway Gate Remote Control design in the February 2022 issue (siliconchip.com. au/Article/15197). I want to make some comments to clarify the transformer mounting arrangement. Probably it was not all that clear since I did not have a photo of the inside of my control box. In my case, the power transformer, a mains to 24V toroidal type, is mounted in the box along with the PCB. I think many are like this. My hand-wired prototype PCB is mounted on one side of the box, as it is about half the length of the final PCB design. Because of the depth of the box and the fact that the PCB components are not very tall on the side with the ICs, I think it would be possible to mount the PCB on the lid with the transformer underneath. The transformer would have to be positioned so it’s under the IC area of the PCB. There would still be plenty of room for the radio board next to the transformer. Of course, mounting the transformer and PCB together would be even easier if one were to use an even larger box. Regardless of how you do it, though, you’d have to be very thorough in insulating and anchoring the mains wiring to the transformer. You wouldn’t want any possibility that it could come loose and contact the non-mains section of the PCB! Hugo Holden, Minyama, Qld. An unknown figure behind AC electricity? During my nightly random viewing of YouTube videos, I was surprised to discover that an ‘unknown’ person, Charles Proteus Steinmetz, had a very large part in commercialising electricity in the USA. Wikipedia says: “He fostered the development of alternating current that made possible the expansion of the electric power industry in the United States, formulating mathematical theories for engineers.” I think that you should educate your readers about this ‘giant’ from the start of the electrical age. October next year is the 100th anniversary of his death. Perhaps that would be a good opportunity to publish an article about him. Jon Hornstein, Bentleigh, Vic. Comments on PV solar battery backup I have been reading the justifications of battery storage for homes in both the January and March issues. They Silvertone Electronics sells a range of Signal Hound spectrum analysers from 4.4GHz up to 24GHz. There's even a 43GHz analyser coming soon! « This 4.4GHz spectrum analyser is yours from just $1677.50 This product and even more can be purchased from Silvertone's Online Store https://silvertoneelectronics.com/shop/ ► UAV & Communications Specialists 1/21 Nagle Street Wagga Wagga NSW 2650 Phone: (02) 6931 8252 https://silvertoneelectronics.com/ contact<at>silvertone.com.au Spike RF analysis software included for FREE with every Signal Hound analyser Silvertone is a reseller of these brands BitScope 8 Silicon Chip Australia's electronics magazine siliconchip.com.au Delivering more The widest selection of semiconductors and electronic components in stock and ready to ship™ au.mouser.com australia<at>mouser.com Helping to put you in Control LabJack T7 Data Acquisition Module A USB/Ethernet based multifunction data acquisition and control device. It features high data acquisition rates with a high resolution ADC of 4 ksamples/s at 18 bits to 50 ksamples/s at 16 bits. SKU: LAJ-045 Price: $902.00 ea + GST Temperature probe 5m Teflon Cable RTD probe with magnet fixing for surface temperature measurement. -50 to 200 ºC range and 5meter teflon cable. SKU: CMS-007T Price: $153.95 ea + GST J Thermocouple Temperature probe with magnet fixing This J type Thermocouple sensor has magnet fixing for surface temperature measurement. The 2 wire sensor has a silicone cable which is 3m long. Temperature range is -50 to 200 ºC. Class B. SKU: CMS-017J Price: $142.95 ea + GST 400W ACM Brushless AC Servo Motor Leadshine ACM604V60-T-2500 400W brushless AC servo motor with 2500 line encoder suitable to work with the ACS806 brush-less drive. SKU: MOT-450 Price: $347.60 ea + GST ACS806 Brushless Servo Motor Drive Brushless servo motor driver for 50 to 400 W, AC brushless motors with encoders. SKU: SMC-410 Price: $319.00 ea + GST Are Silicon Labs pulling an FTDI? LCD Temperature and Humidity Sensor The Pronem Midi from Emko Elektronik are microprocessor based instruments that incorporate high accurate and stable sensors that convert ambient temperature and humidity to linear 4 to 20 mA. Dimensions are only 60x 126 x 35mm. SKU: EES-020A Price: $241.95 ea + GST TxIsoloop-1 Single Loop Isolator Loop isolators provide signal protection by electrically isolating the 4-20mA input signal from the 4-20mA output. SKU: SIG-201 Price: $168.19 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. 10 Silicon Chip were only concerned with whether it was possible to recover the costs of the battery systems. It is well understood that the government likes to tell you to have battery storage but does everything in its power to make it unprofitable. For example, they reduced the feed-in rates in some cases to zero (no export allowed), so it will be a long time if ever that you will get some money back. Forming local micro-grids with batteries will be made harder by the introducing of a 50ms measuring criteria (AEMO) instead of the 100ms the industry wants. This has been called a “coal-keeper tax” by some. The Victorian authorities also want to charge an export energy tax which further erodes the benefits of having a solar system at home. The government’s claim of reducing the cost of electricity is also a big bend of the truth. My usage charges were very slightly reduced, but the supply charge increased dramatically, and the feed-in tariff was cut. The net result is not a reduction in cost to me at all. As far as the battery is concerned, one needs to ask what you want it for. I wanted grid backup when the supply failed, with a sufficient capacity to last at least a couple of days. The battery also doubled the daily kWh usage from our solar panels. Solar usage only averaged about 30% with just the solar panels, but it went to over 60% with a battery. The other benefit is that you are doing your bit for climate change, something our government resists at every turn. My system is 3kW of original German Q CELLS Pro panels with an SMA inverter which is AC-coupled to an Alpha 15kWh battery storage system. I am very happy with what I have done; I only wish I had done it sooner. Note, though, that not all solar battery backup systems behave as if they were a UPS due to a 90 second transfer time using standard electromechanical contactors, with delays for the transfer functions. You also cannot use a UPS on the backup circuit. Wolf-Dieter Kuenne, Bayswater, Vic. The Silicon Labs CP210x chips for USB-to-UART communication are used widely. But some chips in that series can test OK and yet refuse to work when Microsoft drivers are involved. Silicon Labs are based in Houston, Texas, in the USA. Some time ago, they found they were competing with other companies selling chips based on their design at lower prices. So they took another company, Cygnal (also based in Houston), to court. That well-publicised court case resulted in Cygnal losing, which resulted in Cygnal going bankrupt. I cannot find any real evidence of what happened to Cygnal’s stock of counterfeit/cloned chips. But they were just one source of these chips, and it seems that many others remained on the market, sold in countries where such legal action is either impossible or unlikely to succeed. This is presumably why Silicon Labs modified the Windows driver code to detect and ignore any other compatible chips to prevent them from working. If you recall, FTDI did something similar in late 2014, which resulted in such outrage that the Windows update that installed that version of the driver was withdrawn. Australia's electronics magazine siliconchip.com.au “Setting the standard for Quality & Value” Established 1930 ’ CHOICE! 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FREIGHT RATES! TO YOUR DOOR *Remote areas may require depot collection in your town DISCOUNT VOUCHERS VIEW AND PURCHASE THESE ITEMS ONLINE AT www.machineryhouse.com.au/SC0422 NSW (02) 9890 9111 QLD (07) 3715 2200 1/2 Windsor Rd, Northmead 625 Boundary Rd, Coopers Plains VIC (03) 9212 4422 4 Abbotts Rd, Dandenong WA (08) 9373 9999 11 Valentine Street Kewdale Specifications & Prices are subject to change without notification. All prices include GST and valid until 28-04-22 02_SC_280322 STEVE It is said in some reports that Silicon Labs asked Microsoft to destroy any chips deemed to be “pirated” by overwriting the write-once internal USB memory to render the chips unusable, but Microsoft refused to go that far. It’s very hard to verify that story, but it seems likely given what happened with FTDI. Instead, the Windows drivers identify the chips from what the USB data contains and simply ignores them if they appear to be clones. That has been the case for many years, but that is just starting to change. In 2015, I bought a Yaesu FT-991 Amateur Radio transceiver that would not work when I tried to use digital data communications that require CAT (Computer Aided Transceiver) over USB. This is used in applications like FT-8 data communications for propagation reports throughout the world, mainly in the HF amateur radio bands. It seems that many people can’t work out why the USB ports of transceivers will not work, when it likely has to do with the CP210x drivers. I even saw Yaesu transceivers on eBay being offered by frustrated radio hams for as low as $50 when they paid several thousand dollars for them, maybe just a year or so earlier. They couldn’t get them to work and just gave up. I contacted the Yaesu and was told that any problems with the CAT communications must be referred directly to Silicon Labs. Yaesu did offer to replace the motherboard in the transceiver, but only if I paid postage both ways. That postage nearly came to the cost of a new transceiver, and I had no guarantee that it would work when they returned it, so I declined the offer. In an attempt to determine what was going on, I bought some ESP32 modules that used CP210x series chips to communicate. I examined the USB interface using Linux using the “lsusb” command and saw the vendor listed as “Cygnal” rather than Silicon Labs! I ran the same test with my transceiver and once again saw “Cygnal” listed as the vendor! Next, I tried using Linux software called “Rigctl”, and it was able to work with my transceiver, so I knew the transceiver’s USB interface must be working. I could connect via USB and read and set the frequency etc using CAT commands. The chip was clearly working, so the problem had to be in the software, and I think it’s the Windows drivers that are causing these problems. This problem has even impacted companies like Lockheed Martin, who are apparently unaware of why some of these chips are unusable in some cases. I wonder how much perfectly operational hardware has been discarded simply because of the software deeming a small chip in it to be “pirated”. Who do you think is to blame? Rick Matthews, via email. Comment: we cannot find evidence that Silicon Labs ever sued Cygnal Integrated Products. But it is widely reported that Silicon Labs acquired Cygnal in 2003 for US$58 million. However, that doesn’t rule out the existence of clone/ 12 Silicon Chip counterfeit CP210x chips, nor does it prove that the drivers are not written to ignore them. Still, we wonder whether the CP prefix of those ICs indicates that Cygnal developed them initially, and Silicon Labs obtained the rights when they acquired them. In that case, it would not be at all unusual for these chips to use Cygnal’s Vendor ID. We found multiple reports on the internet of people with devices containing CP210x chips where they would work in Linux but not Windows. We wonder whether this results from a driver bug rather than purposeful disablement. Museum for historic electronic component donation In the Mailbag section of the February 2022 issue, Dr David Maddison wanted to donate Australian-made electronic components to a museum. The Tamworth Powerstation Museum (website at: https://tamworthpowerstationmuseum.com.au) might be interested in them. They have an extensive collection of electrical-related items. Due Hoylen, Taringa, Qld. Another museum suggestion There is a Telstra museum in Sydney at Bankstown, staffed by volunteers. It is at 12 Kitchener Parade. You can contact them on (02) 9790 7624 or 0417 247 417. Thank you for producing a great magazine with varied articles. Chris Robertson, via email. Help identifying special capacitors I wonder if any of your older readers might recognise the old tight tolerance capacitors shown in the photos. I obtained them in the early 1970s when analog frequency-­ division line telephony was coming to an end at Philips Hendon works. This line of equipment used vast numbers of tight-­ tolerance capacitors in the many bandpass filters; they had to remain stable over decades and temperature variations. When production ended, many leftover components were sold off through the disposals store and some came into my possession. I have chilled some of these capacitors for several hours in the freezer to about -20°C, measured them, then later, heated them to approximately +40°C and measured them again. The change in capacitance was extremely small. Measuring several dozen of the capacitors on an accurate instrument indicated that (at room temperature) they all read well within ±0.3% of each other. If they have drifted over the years, what are the odds that they all drifted by more or less the same amount? I suspect they probably use mica as a dielectric, as the oldest units look like 1950s vintage or earlier and are pretty large. I wonder if anyone recognises them or knows anything about them. SC Graham Lill, Lindisfarne, Tas. Australia's electronics magazine siliconchip.com.au DELIVERING YOU EXCELLENCE IN ENGINEERING BRANDS we represent » Accelerometers » Airswitches » Analog Meters » Control Levers » Control Stations » Custom Controllers » Data Loggers » Digital Displays » Digital Meters » Door Access Systems » Draw Wire Sensors » Emergency Stops » Encoders » Foot Pedals » Foot Switches » Grip Handles » Gyroscopes » Hand Controls » Inclinometers » Inertial Measurement Units » Inertial Navigation Systems » Interface Modules » Joystick Controllers » LED Indicators » Limit Switches » Linear Position Sensors » Liquid Level Sensors » Motor Controllers » Panel / PCB Switches » Pendant Controllers » Pressure Sensors » Rotary Position Sensors » Sensor Boxes » Slip Ring Collectors » Temperature Controllers » USB Controllers CONTACT US Unit 13, 538 Gardeners Road ALEXANDRIA NSW 2015 02 9330 1700 sales<at>controldevices.net www.controldevices.com.au siliconchip.com.au Australia's electronics magazine 5 - 6 APRIL 2022 Visit us at stand C11 April 2022  13 Geiger Counters and Measuring Radiation Radioactivity is all around us, both from natural and artificial sources. But it is usually invisible, so how do we tell if it is there? There are quite a few passive and electronic methods for detecting and classifying radiation. This article investigates radioactivity, radioactive sources and ways to measure radioactivity electronically, including Geiger counters. By Dr David Maddison N atural sources of radioactivity include soil and rocks (terrestrial radiation) and radiation from space (cosmic radiation). Artificial sources include atomic bombs, nuclear reactors, the concentration of natural radioactive materials by mining and the refinement or irradiation of non-radioactive materials such as in particle accelerators. Radioactivity may be referred to as “radiation” but as well as nuclear radiation, that term also covers non-­ ionising electromagnetic radiation like radio waves plus visible and infrared light. Image Source: https://unsplash.com/photos/sS5TcHkSxe8 expressed as a half-life. This is the time required for the radioactive atoms to decay to half the original number. Less common forms of radioactive decay include neutron emission, when a nucleus loses a neutron; electron capture, in which a nucleus captures an electron causing a proton to convert to a neutron; and cluster decay, in which a nucleus other than an alpha particle is emitted. Fig.1 & Table 1 show the penetrating 14 Silicon Chip Atoms and isotopes Atoms are a basic building block of matter that form chemical elements and compounds. They consist of a nucleus comprising positively charged protons and neutral neutrons, with a surrounding cloud of negatively Table 1: Characteristics of the three main types of radiation Alpha (α) (4He) Beta (β) Gamma (γ) Electromagnetic energy Nature A helium nucleus – two protons and two neutrons An electron (e−) or a positron (e+) Electric charge +2 -1 or +1 (positron) 0 Mass Relatively large Very small None Speed Slow Fast Speed of light Ionising effect Strong Weak Very weak Most dangerous Inside the body Outside the body Outside the body What is radioactivity? Put simply, radioactivity is the spontaneous emission of sub-atomic particles known as alpha and beta particles, or gamma rays, from the nuclei of unstable atoms. While individual radioactive decay events are random, when a great many atoms are involved, the decay process becomes predictable and can be power of the common types of radioactivity. Alpha and beta radiation are most easily stopped, while gamma radiation requires robust shielding. Australia's electronics magazine siliconchip.com.au α β γ Paper Aluminium I Period Fig.1: the penetrating ability of different common forms of radiation, as investigated by Rutherford. Alpha particles are stopped by paper (or human skin), a sheet of aluminium stops beta particles, while gamma rays are only stopped by a substantial thickness of dense matter such as lead. Source: Wikimedia user Lead Group Stannered (CC BY 2.5) II III 1 1 H 2 3 Li 4 Be 3 11 Na 12 Mg 4 19 K 20 Ca 21 Sc 22 Ti 23 V 24 Cr 25 Mn 26 Fe 27 Co 28 Ni 29 Cu 5 37 Rb 38 Sr 39 Y 40 Zr 41 Nb 42 Mo 43 Tc 44 Ru 45 Rh 46 Pd 47 Ag IV V VI VII VIII 2 He Half-lives 6 55 Cs 56 Ba 7 87 Fr 88 Ra stable over 4 million years between 800 and 34,000 years between 1 day and 130 years highly radioactive; between minutes and a day extremely radioactive; no more than a few minutes Fig.2: the traditional (Bohr) model of a carbon atom. 5 B 6 C 7 N 8 O 9 F 10 Ne 13 Al 14 Si 15 P 16 S 17 Cl 18 Ar 30 Zn 31 Ga 32 Ge 33 As 34 Se 35 Br 36 Kr 48 Cd 49 In 50 Sn 51 Sb 52 Te 53 I 54 Xe * 72 Hf 73 Ta 74 W 75 Re 76 Os 77 Ir 78 Pt 79 Au 80 Hg 81 Tl 82 Pb 83 Bi 84 Po 85 At 86 Rn ** 104 Rf 105 Db 106 Sg 107 Bh 108 Hs 109 Mt 110 Ds 111 Rg 112 Cn 113 Nh 114 Fl 115 Mc 116 Lv 117 Ts 118 Og stable 1014 yr 160 1012 yr 1010 yr 140 108 yr 106 yr 120 104 yr 100 yr 100 1 yr Z=N 80 100 s 60 1s 40 * Lanthanides 57 La 58 Ce 59 Pr 60 Nd 61 Pm 62 Sm 63 Eu 64 Gd 65 Tb 66 Dy ** Actinides 89 Ac 90 Th 91 Pa 92 U 93 Np 94 Pu 95 Am 96 Cm 97 Bk 98 Cf Fig.3 (left): a periodic table of the elements showing the properties of the most stable isotope of each element. Source: Wikimedia user Armtuk (CC BY-SA 2.5) charged electrons. The overall charge of an atom is neutral unless the atom is chemically combined or ionised, such as in extremely hot gas (plasma). Fig.2 is a representation of a carbon atom. Although this is not what an atom looks like according to current understanding, it illustrates the basic structure of a typical atom. The nuclei of most common atoms are stable and are not subject to radioactive decay over short periods. Still, some are unstable and decay over periods from tiny fractions of a second to billions of years. Most elements also have one or more isotopes. Isotopes are chemically (almost) identical, but they vary by the number of neutrons in the nucleus, hence the atomic mass. Isotopes can be separated by techniques exploiting their slight mass difference, such as in a mass spectrometer or centrifuges. There can be very slight differences in the chemical behaviour of different isotopes of the same element; these are more pronounced in isotopes of siliconchip.com.au 106 s 104 s 67 Ho 68 Er 69 Tm 70 Yb 71 Lu 20 99 Es 100 Fm 101 Md 102 No 103 Lr N 10−2 s 10−4 s 10−6 s Z 20 40 60 80 100 10−8 s no data Fig.4 (right): a ‘nuclide chart’ showing the half-lives of various isotopes by their colour. The horizontal axis indicates the element number (Fig.3), and the vertical axis is the number of neutrons in each isotope. Each element has many isotopes; darker colours represent more stable ones, with blue indicating less stable isotopes. lighter elements such as hydrogen; in this case, protium (1H), deuterium (2H or D) and tritium (3H). Deuterium (2H) atoms have roughly twice the mass of ordinary hydrogen (1H). So deuterium compounds behave quite differently than regular hydrogen compounds. Deuterium combined with oxygen makes heavy water or D2O. It has various scientific uses, including moderating nuclear reactions such as in ‘heavy water reactors’. Sometimes you will see isotopes written with a number after the element, eg, U235, U-235 or uranium-235 for 235U, but we will stick with the latter scientific notation in this article for clarity. The periodic table A periodic table is a common way to list and show the relationship between the chemical elements. The one shown in Fig.3 colour codes the chemical elements by their half-lives. The longer the half-life, the more stable the element or isotope is and the Australia's electronics magazine less radioactive. Notice that it’s mostly the higher numbered, less common elements that are less stable. A similar relationship is shown in the ‘nuclide chart’, Fig.4. Such charts in their full versions are highly detailed and contain thousands of entries and data. A popular one is the Karlsruhe Nuclide Chart. There are no stable elements or isotopes above element 82 (lead). The highest numbered natural element is 92, uranium. Elements above 92 do not exist in nature in any significant quantity because of their instability. The discovery of radioactivity It started with Henri Becquerel (1852-1908). In 1896, he used naturally phosphorescent compounds such as potassium uranyl sulfate to investigate X-rays (discovered by Wilhelm Roentgen the previous year). The uranium compound caused photographic plates to become exposed. When it was noticed that even non-phosphorescent uranium April 2022  15 Fig.6: an alpha particle being emitted from an atomic nucleus. Source: https://commons.wikimedia.org/wiki/ File:Alpha_Decay.svg Fig.5: the apparatus used by Becquerel to show the particles he discovered were influenced by a magnetic field. In this diagram, the magnetic field is perpendicular to the page. compounds did this, they realised that they must be emitting something similar to light but invisible. In fact, much earlier in 1861, Abel Niépce de Saint-Victor wrote that uranium salts produce “a radiation that is invisible to our eyes”. Becquerel’s father made similar written observations; however, Becquerel is credited with the discovery. Becquerel used an apparatus similar to that shown in Fig.5 to demonstrate that the particles had a charge, as they were deflected in different directions by a magnetic field. But other particles went straight ahead, like X-rays, meaning they were electrically neutral. Marie Curie (1867-1934) and her husband Pierre (1859-1906) started investigating the phenomenon reported by Becquerel. They coined the term radioactivity. Marie’s investigation was the subject of her PhD thesis. They used a quadrant electrometer, which measures electric charge, to measure radioactivity (see https://lamethodecurie.fr/ en/article23.html). They extracted uranium from its ore but then found that the leftover ore was more radioactive than the extracted uranium, and concluded there must be other radioactive elements present. They eventually discovered polonium and radium, but these were present in minute quantities, and many tonnes of ore had to be processed to get usable amounts. One tonne of pitchblende ore had to be processed to obtain 1g of radium, which was one million times more radioactive than uranium. Marie also co-discovered independently that previously-discovered thorium was radioactive. 16 Silicon Chip Ernest Rutherford (1871-1937) from New Zealand is regarded as the “father of nuclear physics”. In 1899, he coined the terms for two of the three common types of radiation: alpha and beta. Alpha and beta particles were influenced by a magnetic field, while gamma rays were not. He is credited with the discovery of alpha and beta particles. Then, in 1903, he investigated and named gamma rays, the third common type of radiation. However, these had been discovered by Frenchman Paul Villard in 1900 but not named at the time. Rutherford classified the three types of radiation according to their penetrating power. He also discovered the concept of radioactive “half-life”. Common types of radiation Alpha particles consist of two protons and two neutrons (a helium nucleus) and have a charge of +2 (see Fig.6). An alpha particle with an energy of 5MeV can travel a few centimetres in air. Beta particles are electrons with a charge of -1 or antimatter positrons with a charge of +1. A beta particle with an energy of 0.5MeV can travel about 1m in air. Gamma rays are high-intensity electromagnetic radiation. These are the shortest waves of the electromagnetic spectrum, with a frequency of 3 × 1019Hz. They are highly penetrating and can travel long distances in air. Thick, dense shielding such as lead or concrete are required to stop them. Gamma rays usually originate after alpha or beta emission leaves a nucleus in an excited state, which then emits a gamma ray when it relaxes to a lower Australia's electronics magazine Example images of Beta and Gamma decay can be respectively viewed at https://w.wiki/4ma6 and https://w. wiki/4ma7 energy state. Gamma rays also originate in nuclear explosions and fission and fusion processes, thunderstorms (a terrestrial gamma-ray flash), solar flares, cosmic rays and other processes. Intense neutron radiation can be generated during fission or fusion reactions or in particle accelerators, and due to a lack of charge, penetrate similarly to gamma rays. Measuring radioactivity Geiger counters are a common way to measure radioactivity, but there are other methods such as scintillation counters, proportional counters, ionisation chambers, semiconductor detectors, dosimeters (which can be worn) and particulate air monitors in nuclear facilities. Radiation may need to be monitored for reasons such as health and safety, use of medical isotopes for medical imaging (see August & September 2021; siliconchip.com.au/Series/369), scientific research, some types of smoke alarms, product sterilisation, evaluation of the density of materials, elimination of static electricity, tracing of groundwater flows and more. The Geiger counter The Geiger counter is probably the most well-known type of radiation measuring device. The detecting component is a Geiger–Müller tube. This is a tube filled with a low-pressure inert gas with a central anode and outer cathode, with about 400-900V applied between them – see Fig.7. As a radiation particle enters the window, which may be at the end or around the circumference, it causes the gas in its path to become ionised and siliconchip.com.au Fig.7: how a Geiger counter works. Source: Wikimedia user Svjo-2 (CC BY-SA 3.0) Fig.8: how an ionisation chamber works. Original Source: Wikimedia user Dougsim (CC BY-SA 3.0) conductive. This results in a cascading discharge known as a Townsend Avalanche, causing a large, easy-to-­ measure current pulse. This makes Geiger counter electronics cheap and simple to manufacture. The limitations are that they cannot measure a high radiation rate or determine the energy level or identity of the incident radiation. Ionisation chambers Ionisation chamber radiation measuring devices are widely used in nuclear industries. They have a good response over a wide range of radiation energies, and are the preferred method of detecting and measuring high-­energy gamma rays. These devices typically have two parallel plates with an electric field (typically 100-400V) between them and a chamber, usually at air pressure – see Fig.8. When a radiation particle enters the chamber, it disassociates gas molecules along its path into ion pairs that drift to the chamber’s anode or cathode. This creates an ionisation current, and the more pairs produced, the greater the current and thus radiation dose. The current is usually tiny, on the order of femtoamperes to picoamperes, so electrometer circuitry is needed to sense it. A domestic smoke detector of the type that uses a radiation source, as shown in Fig.9, is an example of an ionisation chamber. Most Cold War era devices for radiation surveys after a nuclear attack were based on an ionisation chamber rather than a Geiger-Müller tube. The latter tends to saturate at high radiation levels, giving a falsely low reading. An example is shown in Fig.10. siliconchip.com.au Fig.9: an ionisation-type smoke detector sensor, which uses an ionisation chamber and alpha-emitting 241Am (americium) to detect smoke. Fig.10: a US radiation survey meter of the Cold War era, the Victoreen Instrument Co. model CDV-715 (1961-1974). It is an ionisation chamber device and is most sensitive to high range gamma rays for radiation surveys after a nuclear attack. These are sold on eBay and elsewhere as collector’s items. Source: Wikimedia user Mrcomputerwiz (CC BY 3.0) Australia's electronics magazine April 2022  17 The boy who built a nuclear reactor In 1994, David Hahn (USA), aged 17, scavenged vast amounts of radioactive materials from sources such as smoke alarms, lantern mantles, radium-faced clocks and watches, uranium from Czechoslovakia and any other radioactive materials he could find. He also obtained the required lithium for his device from US$1000 worth of batteries. He researched and tried to build a breeder reactor with the hope of creating fissionable isotopes from thorium and uranium. It is widely reported that he made a reactor, but it was more correctly a neutron source that he managed to construct. At one point, he found that the radiation levels kept on rising and could even be detected from a long distance away from his bedroom. When he discovered that he could detect radiation from five houses down the street, he started to get worried and wanted to dismantle the device. When trying to load it into his car, his neighbours called the police because they thought he was stealing something. The boy warned police not to search the car as the material was Scintillation counters A scintillation counter uses a scintillation crystal that turns incident radiation into light photons, which can be detected with a photomultiplier, charge-coupled device (CCD) or photodiode – see Fig.11. Examples of scintillator materials are sodium iodide with thallium, zinc sulfide, lithium iodide or anthracene. Proportional counters A proportional counter combines features of both the Geiger-Müller tube and an ionisation chamber in a single device. It generates a pulse proportional to the radiation energy detected, and is typically used when accurate energy levels must be known. Semiconductor detectors Semiconductor detectors use a material such as doped silicon, germanium, cadmium telluride and cadmium zinc telluride to detect radiation. They work on the principle that Ionisation track High energy photon radioactive. The police thought he had an atomic bomb, so they called the bomb squad. Government authorities argued over whose job it was to clean up the site. A book was written about him by Ken Silverstein called “The Radioactive Boy Scout: The true story of a boy and his backyard nuclear reactor” (2004). There was also a 2003 movie made about him titled “The Nuclear Boy Scout” – see www.eagletv. co.uk/projects/the-nuclearboy-scout.html Also see the video “Radioactive Boy Scout – How Teen David Hahn Built a Nuclear Reactor” at https://youtu.be/ G0QMeTjcJDA radiation striking the semiconductor causes charge carriers to be spontaneously created, increasing the material’s conductivity briefly and causing spikes of extra current to flow above the baseline. Radiation hardening of electronics We have previously written about the need to provide radiation hardening for chips in military and space applications; see the article in the July 2019 issue titled Radiation Hardening (siliconchip.com.au/Article/11697). Electronics operating in high-­ radiation environments like space or a nuclear reactor need significant amounts of shielding and must be designed to tolerate radiation harmlessly, with larger and more robust semiconductor junctions etc. But there is also the problem of radiation emanating from within electronic devices, including solder and the material used to package the devices. Photomultiplier tube (PMT) Photocathode Focusing electrode Low energy photons Scintillator Primary electron Secondary electrons Connector pins Dynode Anode Fig.11: a scintillation counter using a photomultiplier tube. Source: Wikimedia user Qwerty123uiop (CC BY-SA 3.0) 18 Silicon Chip Australia's electronics magazine High component density devices like modern CPUs need to be made from silicon with no radioactive isotopes present; otherwise, radioactive decay can trigger unwanted state changes in the device. Onboard ECC (error checking and correction) is another vital tool for handling cosmic rays and other sources of spontaneous radiation. Radiation measurement units SI units are typically used for radiation measurements in Australia, New Zealand, Europe and most other countries. A few countries like the USA use non-SI units. Radioactivity is measured in terms of how many particles or photons (in the case of wave radiation such as gamma rays) are emitted per second. The SI unit is becquerel (Bq) while the US unit is the curie (Ci). For example, a Geiger counter giving two counts per second means the substance has a radioactivity of 2Bq (becquerel). The use of the curie unit is discouraged (even in the USA), but 1Ci is about 37GBq. Some Geiger counters give measure counts per second for a direct readout in Bq. A related measurement is particle flux, which is typically counts per square metre per second. The radiation exposure of humans is of particular importance. For this, there are three parameters to consider: • Absorbed Dose, which is the energy deposited by the radiation into the person • Equivalent Dose, which is the siliconchip.com.au Living near nuclear power station annually <0.01mSv Mammogram procedure 0.42mSv Fig.12: a radon detector as used to monitor radon levels in the basements of homes in radon-rich areas of the United States of America. Absorbed Dose with a weighting factor taking into account the relative harm of different types of radiation in a person • Effective Dose, which is the Equivalent Dose with a weighting factor taking into account the susceptibility of different tissues to radiation The Roentgen (R) is an obsolete unit of radiation exposure for X-rays and gamma rays in air. It has been replaced by rads (USA) and gray (Gy; SI). 1Gy = 100rad. The units of Equivalent Dose are sievert, Sv (SI units) or rem (USA) for “roentgen equivalent man”. 1Sv = 100rem. The weighting factor for x-rays, gamma rays and electrons absorbed by human tissue is 1, while for alpha particles, it is 20. To establish the Equivalent Dose, multiply the Absorbed dose in grays by the weighting factor, giving a result in sieverts. The units of Effective Dose are sievert, with a weighting factor for different organs, with organs having the most rapidly dividing cells being the most sensitive with the highest weighting factor. For more details, see www.epa.gov/radiation/radiationterms-and-units Natural sources of radiation Natural radiation is usually nothing to worry about, with rare exceptions. As mentioned above, it is either of terrestrial or space origin. Natural radioactive materials are often referred to as Naturally Occurring Radioactive Material (NORM). Natural radioactivity is one of the causes of mutations in living organisms that siliconchip.com.au Chest X-ray procedure 0.1mSv Terrestrial Radioactivity annually 0.21mSv Radiation in the body annually 0.29mSv Cosmic radiation living at sea level (low elevation) annually 0.3mSv Cosmic radiation Head CT Radon in average Upper gastroWhole body CT living in Denver procedure 2mSv US home intenstinal X-ray procedure 10mSv (high elevation) annually 2.28mSv procedure 6mSv annually 0.8mSv Fig.13: radiation exposure for people living in the USA; the main differences in Australia is that we don’t live at high elevations, have virtually no nuclear reactors, and Australian homes do not usually have radon-accumulating basements. Note the figure for radiation from within the body, caused by naturally occurring radioactive elements. lead to genetic diversity. Examples of natural radiation that can be harmful include the accumulation of radon in certain buildings or mines, which must be monitored and controlled by appropriate ventilation measures (see Fig.12), and the possibility of exposure of flight crews to excessive cosmic radiation. Exposure of flight crews is not generally considered a serious problem, but it is monitored and restricted by following certain recommendations. These include limiting flights over the poles or high latitudes where there is more cosmic radiation and avoiding flying during solar flare events. The Equivalent Dose in a commercial airliner at high altitudes (around 40,000ft/12,192m) can be close to 60 times that at ground level; about 4.5μSv/h compared to 0.08μSv/h. Some recommendations for flight crew safety are at siliconchip.com. au/link/abcy Radiation in space is usually hazardous to both humans and electronics, and special measures must be taken to protect against its effects. Fig.13 shows some of the primary sources of radiation we are exposed to and how they compare in terms of Equivalent Dose. tends to accumulate. Basements need to be monitored and ventilated to prevent the accumulation of radon. Australian rates of radon exposure are low by world standards. According to a 1990 report by ARPANSA, the average concentration for indoor exposure was 1/4 the world average. In Australian homes, the average level was found to be about 10Bq/m3 compared to a worldwide indoor average of 40Bq/m3. Levels are higher along the Great Dividing Range than the coastal plain – see Fig.14. Cigarette radiation exposure Fertilisers contain naturally occurring radium. This decays into radon and sticks to the hairs called trichomes Radioactive basements According to the US EPA, 1 in 15 homes in the USA have more than the recommended amount of radon. It is believed to be responsible for 20,000 lung cancer deaths per year in that country. Since it is heavier than air, it Australia's electronics magazine Fig.14: an interactive radon map of south-east Australia from www. arpansa.gov.au/understandingradiation/radiation-sources/moreradiation-sources/radon-map April 2022  19 beneath tobacco leaves. The radon decays into lead-210 and polonium210, with polonium-210 being more hazardous. The radiation in tobacco depends to a certain extent on the soil in which the plant was grown and the origin of the fertiliser. Over time, these isotopes accumulate in smokers’ lungs, causing radiation damage on top of the damage from the smoke. A typical smoker is exposed to 40 times the annual radiation dose limit imposed on radiation workers (see www.bmj.com/rapid-­ response/2011/10/28/radioactivity-­ cigarettes). Cosmic radiation Cosmic radiation includes high-­ energy photons and atomic nuclei moving through space that originate in the sun, our galaxy or distant galaxies. When these particles hit the upper atmosphere, they induce showers of secondary particles including x-ray photons, muons, protons, antiprotons, alpha particles, pions, electrons, positrons, and neutrons. Cosmic rays are detected by dedicated cosmic-ray observatories (see Fig.15). You can see a video of a simulated cosmic-ray shower at https:// youtu.be/Wv0CtPskhus Artificial sources of radiation Non-natural sources of radiation include radiation associated with nuclear medicine, certain household products (eg, ionisation smoke detectors), food irradiation, industrial uses Fig.15: cosmic rays and gamma-ray air showers on Earth can be measured by various means. Original Source: Konrad Bernlöhr (CC BY-SA 3.0) of radiation (eg. radiography), scientific experiments (eg. those requiring a neutron source from a reactor for investigations into the structure of matter) and radioactive waste. A brief nuclear history of Oz Australia has a long nuclear history. We have vast deposits of radioactive minerals containing both uranium and thorium. We have had atomic explosions on our territory, and we have a medical isotope reactor at Lucas Heights, NSW. Australia has never committed to civilian nuclear power (sadly, in the author’s opinion). However, in the The Gilbert U238 Atomic Energy Laboratory This educational toy was sold in the USA in 1950-51 to teach children about radioactivity. The set contained a Geiger–Müller counter, electroscope to detect electric charge, a spinthariscope to observe individual nuclear disintegration events, a Wilson cloud chamber with an alpha source, four samples of different uranium ores, radioactive sources: betaalpha (210Pb), pure beta (possibly 106Ru – ruthenium) and gamma (65Zn – zinc), spheres to make a model alpha particle and various literature. Imagine trying to sell such an educational set today! The Gilbert U-238 Atomic Energy Laboratory from 1950-51. Source: Wikimedia user Tiia Monto (CC BY-SA 3.0) 20 Silicon Chip Australia's electronics magazine 1960s, two sites were identified for possible reactors, at Jervis Bay, NSW and French Island, Vic. Preliminary construction was undertaken at Jervis Bay. Also, we have now committed to purchasing nuclear submarines for the Navy. Australia’s first mine for radioactive minerals was at Radium Hill, SA, which operated from 1906-1961 and produced radium for medical purposes and uranium for glass and glazes. Here is an extraordinary quote from The Advertiser newspaper, 13th May 1913, about the radium mined there, long before nuclear energy was fully understood or appreciated (the full article is at https://trove.nla.gov.au/ newspaper/article/5404770): That one ounce of it is equal to one hundred thousand nominal horsepower, and that small quantity would be sufficient to drive or propel three of the largest battle ships afloat for a period of two thousand years; ...It will mean that foreign nations will be obliged to seek from us the power wherewith to heat and light their cities, and find means of defence and offence. In 1950-1971, uranium was mined in Rum Jungle, NT, and the ore was sent to the USA and UK to support nuclear weapons programs. Australia currently has several active uranium mines – see Figs.16 & 22. Thorium is not directly produced, but it is present in the mineral monazite, which is incidentally unearthed during the mining of mineral sands. siliconchip.com.au Fig.16: nuclear and radiation sites in Australia. This map was prepared by an anti-nuclear group; we do not necessarily support their views but the map is reasonably comprehensive. (CC BY-SA 3.0) April 2022  21 Australia's electronics magazine siliconchip.com.au Your body is radioactive Our bodies are naturally radioactive because we ingest natural radioactive materials found in the environment. The primary radioactive element in people is 40K (potassium), which emits beta particles 11% of the time and gamma rays 89% of the time. In a typical 70kg person, around 5000 atoms undergo radioactive decay each second, 550 of which emit gamma rays. Other radioactive isotopes in the body include alpha emitters 238U (uranium), 232Th (thorium) and their decay products and beta emitters 14C (carbon, hence carbon-14 dating) and 87Rb (rubidium). Other radioactive elements found in the body are 210Po (polonium) and 210Pb (lead). 40K is 0.0117% of all potassium, and the human body is about 0.2% potassium, so a 70kg person would have 16.38mg of radioactive potassium. One in 1,000,000,000,000 carbon atoms are radioactive, and a 70kg person is 23% carbon by weight, so 16.1ng of that carbon would be 14C. Despite all this, the dose rate is insignificant. It requires extremely sensitive and specialised instrumentation to measure. While gamma rays can be detected emanating from our bodies, alpha and beta emissions cannot be detected because the body absorbs them. However, gamma rays from decay products after alpha and beta emission can be detected. For more details, see http://hps.org/publicinformation/ate/faqs/ faqradbods.html The unwanted monazite is returned to the ground after the other minerals have been extracted. Nuclear tests in Australia Atmospheric nuclear weapon tests in Australia left radioactive soil contamination, which has since been cleaned up. Radioactive clouds also caused people to suffer medical conditions many years after ingesting radioactive materials. 12 British nuclear weapons were detonated between 1952 and 1957 (kt = yield in kilotonnes of TNT): • Montebello Islands: 1952 (25kt), 1956 (15kt & 60kt nominal, with the true yield claimed to be 98kt – see Fig.17) • Emu Field: 1953 (10kt & 8kt) • Maralinga: 1956 (12.9kt, 1.4kt, 2.9kt & 10.8kt), 1957 (0.93kt, 5.67kt & 26.6kt) That doesn’t include a series of minor tests involving conventional explosives and highly radioactive materials, including plutonium, polonium, beryllium and uranium, to improve bomb designs and test how radioactive materials dispersed. These tests were at Emu Field and various locations around Maralinga. Detecting nuclear explosions and materials Nuclear explosions can be detected by seismic, hydroacoustic and infrasound methods but of interest for this article are radiation measurements. One reason for detecting such explosions is to enforce international arms control treaties. Radiation is detected through ground-based or airborne atmospheric sampling, looking for 241Am (americium), 131I (iodine), 137Cs (caesium), 85Kr (krypton), 90Sr (strontium), 239Pu (plutonium), 3H (tritium), 133Xe and 135Xe (xenon); all signature isotopes of nuclear explosions. During the Cold War, the USA had a system of 12 satellites known as Vela, which had X-ray, neutron and gamma-­ ray detectors. These satellites were decommissioned around 1980. Their function has now been replaced with the Nuclear Detection System (NDS) as an auxiliary payload on US GPS satellites. The NDS sensors consist of a global burst detection (GBD) suite of instruments and a space environment dosimeter (BDD) – see Fig.18. The GBD consists of: • the BDY (bhangmeter), to detect an optical flash from the fireball of a nuclear detonation • the BDX, an X-ray sensor to discriminate between terrestrial and space explosions • the BDW, an electromagnetic receiver that detects the electromagnetic pulse (EMP) from a nuclear explosion (a signal is only reported if it is consistent with an optical flash from the BDY instrument) • the BDP (burst detector processor), which coordinates and controls measurements from the other instruments The BDD detects particulate radiation and gamma radiation. Australia helps monitor compliance with the Comprehensive Nuclear-­TestBan Treaty (CTBT) via several monitoring stations in Australian territories, shown in Fig.19. EMP Low-Band Antenna (BDW) L-Band Space Environment Dosimeter (BDD; under) Fig.17: the largest atomic explosion in Australia at the Montebello Islands on 19th June 1956. It had a nominal yield of 60kt but was claimed by journalist Joan Smith to actually have been 98kt. Public domain image 22 Silicon Chip S-Band X-ray Sensor (BDX) EMP HighBand Antenna (BDW) Optical Sensor (BDY) Fig.18: the Nuclear Detection System sensors on US GPS satellites. Visit siliconchip.com.au/link/abd0 for more detail on the sensors. Source: ilrs.gsfc. nasa.gov/missions/satellite_missions/past_missions/gp35_general.html Australia's electronics magazine siliconchip.com.au Concealed nuclear material in locations like shipping containers can be detected by techniques such as neutron-­ gamma emission tomography (NGET). For details on this, see our article on Advanced Imaging, September 2021, page 21 (siliconchip.com.au/ Article/15021). All materials have a particular ‘isotopic signature’ with slightly different ratios of different isotopes depending upon their origin. The isotopic signature of nuclear materials can typically be used to determine their origin. This general area is known as ‘nuclear forensics’. Low-background steel Certain applications for steel such as Geiger counters, radiation counters in medical imaging devices, scientific equipment and air/space sensors require steel produced before atmospheric atomic detonations. These started on 16th July 1945 and continued until China’s last known atmospheric nuclear test in 1980. This is because modern steel production uses atmospheric gases contaminated with radioactive particles from nuclear testing. The levels are exceptionally low, but the presence of any unwanted radioactive elements can affect extremely sensitive radiation measurements. Another source of unwanted radiation in steel is 60Co (cobalt), which is used in the refractory lining of steel furnaces as a wear indicator. Small amounts of cobalt are embedded at various depths in the lining of a furnace. As the furnace lining wears out and reaches the depth of the cobalt, it shows up in the steel product, which indicates the extent of wear. This causes unwanted radiation in the steel, although it is not a safety concern at the levels used. Low-background steel has been sourced from German World War 1 ships scuttled in Scapa Flow in the Orkney Islands of Scotland, old railway lines and vehicles, and World War 2 surplus ship armour from the Norfolk Navy Shipyard (USA). Atmospheric radioactivity peaked at 0.11mSv/year in 1963 when the Partial Nuclear Test Ban Treaty was passed and has now declined to just 0.005mSv/year above natural levels. Present levels of artificial radioactive products in the atmosphere are siliconchip.com.au Interesting links Experimental demonstration of the radiation inverse square law: www. csun.edu/scied/6-instrumentation/inverse_square_law/demonstration_ equipment.htm 2. A Geiger counter project for advanced constructors: www.instructables. com/New-and-Improved-Geiger-Counter-Now-With-WiFi/ 3. An excellent free book full of nuclear experiments you can do: www. imagesco.com/geiger/pdf/geiger-counter-experiments-book.pdf Some experiments require low-level “license-exempt” nuclear sources, which private citizens can freely purchase in the USA, but you would have to establish their legality in Australia. Some of the experiments do not require special nuclear sources. 4. Detection of cosmic rays of extraterrestrial origin using the technique of coincident detection: https://physicsopenlab.org/2016/01/02/cosmic-rayscoincidence/ 5. A 2017 Australian project with 16 detectors to demonstrate how cosmic rays arrive as showers: https://core-electronics.com.au/projects/cosmicarray 6. An Australian website for amateur cosmic-ray astronomy: https:// cosmicray.com.au/ (there is an earlier version of the site at https:// hardhack.org.au/book/export/html/2). 7. Cosmic-ray muon detector projects for amateurs: https://quarknet.fnal.gov/ toolkits/new/crdetectors.html 8. A video titled “The tunnel where people pay to inhale radioactive gas”: https://youtu.be/zZkusjDFlS0 9. A video titled “Radioactive camera lens”: https://youtu.be/FW2rM1kaRug 10. Software for a variety of compatible Geiger counters: ● https://sourceforge.net/projects/geigerlog/ ● www.mineralab.com/GeigerGraph/ ● https://medcom.com/product/geigergraph-software/ ● www.amazon.com/dp/B00WAK68U4 11. A real-time world radiation map by Geiger counter company GQ Electronics: www.gmcmap.com 12. Software examples for the RadiationD-v1.1(CAJOE) Geiger counter board available online: ● https://github.com/RuzgarErik/I2Cgeiger/ (will drive an I2C LCD) ● www.instructables.com/Arduino-DIY-Geiger-Counter/ ● https://github.com/SensorsIot/Geiger-Counter-RadiationD-v1.1-CAJOE1. Fig.19: Australian monitoring stations for the Comprehensive Nuclear-Test-Ban Treaty: RN04 (Melbourne); RN06 (Townsville); RN07 (Macquarie Island); RN08 (Cocos Islands); RN09 (Darwin); RN10 (Perth) and PS05 (Mawson). Source: DFAT Australia's electronics magazine April 2022  23 The fascinating RadiaCode-101 The RadiaCode-101 (siliconchip.com.au/link/abcr) is both a detector of ionising radiation and a gamma-ray spectrometer based on a scintillation radiation sensor. It is said to be able to detect “Gamma, high energy Beta, and continuous X-rays in the energy range 0.05...3.0MeV and in the power range 0.1-1000μSv/h” – see below. It can also overlay radiation measurements on Google Maps. It can identify various isotopes by their gamma-ray spectra. The RadiaCode-101 spectrometer. The RadiaCode-101 display as seen on a linked smartphone. sufficiently low that steel produced today is considered satisfactory for use in all but the most sensitive radiation measurement applications. Lead from before the atomic bomb era Lead is another metal used in sensitive radiation measurement instruments and is susceptible to radioactive contamination from the modern era. So there is a demand for lead from before 1945 (see Fig.20). Sources include 3t of lead recovered from the pipes of Boston’s wastewater system and now in storage at the US Government’s Los Alamos National Laboratory, where the atomic bomb was first developed. Another source was from a 300-year-old British shipwreck. Contamination of gold jewellery In the USA in the 1930s and 1940s, radioactive gold that was used as a ‘seed’ to hold radon for medical treatment was recycled into gold for jewellery. The radium decay products contained 210Pb (lead) which contaminated the gold. Fly ash radioactivity Fly ash is the non-combustible material left over after burning coal. It has various applications, such as being added to concrete, or if unused, it is buried in a landfill. Concerns have been raised that it is radioactive and constitutes a health hazard because there are trace amounts of uranium in coal, as with many other minerals. The concern has been shown to be Fig.20: very old “low activity lead” from a company that specialises in the sale of such material. It can be made into radiation shielding for sensitive instruments. Source: www.nuclearshields.com/low-activity-lead.html 24 Silicon Chip Fig.22: the location of uranium and thorium deposits in Australia. without foundation; see siliconchip. com.au/link/abcz Uranium extraction from fly ash has shown to be technically possible, although the economics are questionable; see siliconchip.com.au/link/abck A natural nuclear reactor Around 1.7 billion years ago in what is now Oklo, Gabon in Africa, a natural nuclear reactor formed that ran for several hundred thousand years, Fig.21: an ancient natural nuclear reactor in Oklo, Gabon. Source: Robert D. Loss (https://apod.nasa. (https://apod.nasa. gov/apod/ap100912.html)) gov/apod/ap100912.html Australia's electronics magazine siliconchip.com.au Bananas are radioactive Bananas are relatively high in potassium. Some figures we saw were for different sized bananas are 362mg (small), 422mg (medium), 487mg (large) and 544mg (extra large). Natural potassium contains around 0.012% of the radioactive isotope 40K. In the video titled “Potassium Metal From Bananas!” at https://youtu.be/ fmaZdEq-Xzs the experimenter chemically processes 6.5kg of bananas to extract 9g of potassium metal. At 16m 18s, he measures the radioactivity of the extracted potassium and establishes that it is about twice the background level of radiation. So, it is true that bananas are radioactive. However, a medium-sized banana with 450mg of potassium will expose you to 0.01mrem of radiation. A chest X-ray is about 10mrem, so 10,000 bananas would have to be consumed to produce the same radiation exposure as one chest X-ray. In any case, the human body contains about 120g of potassium, so the extra dose is negligible. Feel free to enjoy a banana! Note that as a home experimenter without extremely sensitive laboratory equipment, you are unlikely to be able to measure the extra radioactivity of a single banana above the background radiation. That’s why so many bananas had to be processed and the potassium purified to get even a doubling of the background count. producing about 100kW from a self-­ sustaining fission reactor. The discovery was made in 1972 – see Fig.21. Such a phenomenon could not occur today because there is insufficient fissile 235U in natural uranium ore today; only about 0.72%, which is not enough for a self-sustaining fission reaction. In a much younger Earth, uranium ore had about 3.1% 235U, comparable to what is used in civilian nuclear reactors (typically 3-5%). There is a lower percentage of 235U in ore today due to radioactive decay over the Earth’s history. Conclusion There is radiation all around us but it’s generally far below the level of concern. Various instruments exist that allow you to confirm that, with Geiger counters being one of the simplest and cheapest. Still, they are quite limited in terms of accuracy and sensitivity. If you really want to explore the radioactivity that might be around you then the RadiaCode-101 shown opposite is one of the best consumer-­ grade pieces of electronics that you could use. While somewhat expensive with an RRP of US$275 (about $400), its capabilities far exceed those of a basic Geiger counter that you could purchase for around $80 (such as the one shown overleaf). Continued on page 26 Radioactive isotopes used for industrial purposes Isotope Uses 241Am Backscatter gauges for smoke detectors, fill height detectors & ash content sensors 90Sr Thickness gauging up to 3mm 85Kr Thickness gauging of thinner materials like paper, plastics etc 137Cs 60Co 226Ra, 255Cf 192Ir, 169Yb, 60Co Density and fill height level switches Density and fill height level switches, monitoring of furnace wear Ash content sensors Industrial radiography Safety Note Use common sense when dealing with radioactive materials. Although plenty of videos and web pages show it, we do not recommend you disassemble smoke detectors to obtain the radioactive source unless you know what you are doing and follow appropriate safety precautions. Source: Non-Destructive Testing and Radiation in Industry by Colin Woodford and Paul Ashby – https://inis.iaea.org/collection/NCLCollectionStore/_ Public/33/034/33034305.pdf siliconchip.com.au Australia's electronics magazine April 2022  25 Measuring radiation and experiments for the enthusiast Geiger counters for measuring radiation can be bought relatively inexpensively. As a general rule, the more expensive the Geiger counter, the more sensitive it will be and the more types of radiation it will be sensitive to. Some Geiger counters are less sensitive or insensitive to alpha and beta radiation (which are more common in natural settings). Geiger counters cannot distinguish between alpha, beta and gamma rays. A different type of instrument is required for this; some can even identify specific isotopes, such as scintillation counters and proportional counters. A typical Geiger counter will click about 10 to 30 times per minute from natural background radiation, but this varies depending on geographic area, cosmic ray activity, and the detector’s sensitivity. Cheaper Geiger counters frequently come with SBM-20 type tubes (see siliconchip.com.au/link/abcl). These were initially developed in the Soviet Union. J305 tubes are also relatively common. The website at siliconchip.com.au/link/ abcm lists all common tube types. J305 tubes have a clear glass tube with a central conductor. The outer conductor is a coating of the transparent electrical conductor indium tin oxide. As Geiger counter tubes run at high voltages, be careful when experimenting with them, especially if using unenclosed circuit boards. One inexpensive Geiger counter we looked at is the RadiationD-v1.1(CAJOE), shown in Fig.23; it comes without a case. Other popular fully-enclosed Geiger counters of interest are made by GQ Electronics (siliconchip.com.au/link/abcn). Depending on airline rules, you might be able to bring a Geiger counter on a plane to see how altitude affects its measurements. You can also examine granite such as in benchtops or other stonework to see if it is radioactive, as it may contain uranium or thorium. This has been confirmed in some cases, but it is unlikely to be harmful; see the following videos for details: ● “Radioactive Granite” at https://youtu.be/jKIXKo5QgT8 ● “Special Report: Radioactive Kitchen Counters” at https:// youtu.be/8tgxXOqCwTI Other items which might be radioactive include: ● some Brazil nuts, due to their radium content (see the video “Are Brazil Nuts Radioactive?” at https://youtu.be/ Pt-SMAVN898) ● antique “uranium glass”, also known as “Vaseline glass” (see Fig.24) ● “static elimination” brushes (see Fig.25, siliconchip.com. au/link/abcp and siliconchip.com.au/link/abcq) ● uranium ore (www.amazon.com/dp/B000796XXM) ● luminous markings in old clocks and watches ● tritium vials as used on certain watches, gun sights and compasses ● lantern gas mantles that contain thorium ● salt substitutes with potassium instead of sodium ● some camera lenses from 1950-70s which use 232Th (thorium) to alter the index of refraction ● some Fiesta Ware brand dinnerware from the mid 20th century use uranium glazes, especially red; these are collectable and not harmful ● thorium concentrated from certain beach sands, often black sands (see siliconchip.com.au/link/abco) 26 Silicon Chip Fig.23: an inexpensive Geiger counter board labelled RadiationD-v1.1(CAJOE). It uses a J305 Geiger-Müller tube and is primarily sensitive to beta and gamma radiation. It also supports M4011, STS-5 and SBM-20 tubes. It can be interfaced to an Arduino or work in a standalone mode where it beeps for every radiation event detected. Fig.24: antique uranium glass vases fluoresce under UV light as well as being slightly radioactive. Source: Wikimedia user Realfintogive (CC BY-SA 3.0) Fig.25: static elimination brushes typically contain alpha-emitting polonium-210. They generate charged particles in the air, making the staticcharged item electrically neutral so it will no longer attract dust (until it becomes charged again). Source: Oak Ridge Associated Universities (ORAU) Museum of Radiation and Radioactivity Fig.26: you can buy ionisation chambers for smoke detectors online for $4-6 delivered to Australia. Although not considered harmful, we don’t recommend opening one of these. If you want to see the radioactive ‘pill’ inside, there are photos at www.instructables.com/ How-to-Obtain-and-ExtractAmericium/ ● ionisation chamber smoke detectors containing 241Am (americium), producing alpha particles – see Fig.26 ● ordinary glass if it has enough 40K (potassium) or 232Th (thorium) ● some fertilisers with potassium or phosphorous from SC certain sources Australia's electronics magazine siliconchip.com.au 500 POWER WATTS AMPLIFIER PART 1 BY JOHN CLARKE This large power amplifier produces big, clear sound with low noise and distortion. It delivers 500W RMS into a 4Ω load and 270W into an 8Ω load. It has been designed to be very robust and includes load line protection for the output transistors and speed-controlled fan cooling that remains off until needed. With two of these, you could deliver 1000W into a single 8Ω loudspeaker. Good luck finding one that will handle that much power! Features and Specifications Output power: >500W into 4Ω, >270W into 8Ω – see Fig.3 Frequency response: +0,-0.1dB over 20Hz-20kHz (-3dB <at> 97kHz) – see Fig.1 Signal-to-noise ratio: 112dB with respect to 500W into 4Ω or 250W into 8Ω Total harmonic distortion (4Ω): <0.005% <at> 1kHz for 1.5-350W – see Figs.2 & 3 Total harmonic distortion (8Ω): <0.025% <at> 1kHz for 2-270W – see Figs.2 & 3 Input impedance: 10kΩ || 4.7nF Input sensitivity: 1.015V RMS for 500W into 4Ω, 1.055V RMS for 270W into 8Ω Power supply: ±80V nominal from an 800VA 55-0-55V transformer Quiescent current/power: 94mA, 15W Protection: DC fuses, dual-slope thermal tracking, SOA current limiting, output clamping diodes Other features: output offset nulling, blown fuse indicators, onboard power indicator O ur 500W amplifier is big in several ways. It is physically big, requiring two heatsinks stacked end-to-end to keep the temperature under control. It requires a significant power supply using an 800VA transformer, and the amplifier and power supply fit into a three rack unit (3RU) rack case, again of rather large dimensions. It does deliver a prodigious amount of power. It is ideal for a public address system where high power can be necessary for sound reinforcement in a large venue. It is also well-suited to driving inefficient loudspeakers. As noted above, used in bridge mode, it could deliver just over 1000W per channel. Build two pairs for a sound system so massive, it would need to be plugged into two different mains power points! Two of these amplifiers could also be the basis of an amazing stereo system for use in a large listening room. You might think that a 500W per channel stereo system is just too much power. Whether that is true depends on what sort of music you like listening to and how efficient your loudspeakers are. If you like rock music with its somewhat limited dynamic range, then with this amplifier, you will be able to play it loud. That makes it ideal for music that just has to be loud to be enjoyed. But please don’t deafen yourself with the extreme sound levels possible with such a large amplifier. You might also need to provide ear protection for your neighbours! It isn’t just for rockers, either. Classical music requires lots of power as well. This is not because the performance is necessarily loud, but it allows the wide dynamic range in volume of concert hall performances to be replicated. You want high power without distortion to produce the high peak volume levels of the performance, like massive kettle drum hits or pipe organ stings, with low noise from the amplifier so that it does not drown out the whisper-­ quiet passages. Fig.1: the frequency response of this amplifier is exceptionally flat, varying by less than 1/20dB between 20Hz and 20kHz. The upper -3dB point is just short of 100kHz. While the lower -3dB point is not visible in this plot, it’s likely around 1Hz. An active subsonic pre-filter would be necessary to prevent over-extension if you’re using this amp to drive a subwoofer directly. 28 Silicon Chip Big power like this does not come easily. The amplifier uses 12 output transistors and they are all mounted on a 400mm-wide heatsink. The main circuit board is also significant at 402 x 124mm. The final installation within the 3U rack enclosure measures 559mm x 432mm x 133.5mm and weighs just over 12kg. This article will concentrate on describing the Amplifier Module circuit. Over the next two months, we’ll also give the full assembly details for this Module, plus describe a suitable power supply. Then we’ll show you how to build Module, power supply, speed-controlled fan cooling (which switches off at light loads), speaker protector and clip detector all into an aluminium 3RU rack-­ mountable chassis. Performance The main performance parameters are summarised in the specification panel and Figs.1-3. These indicate that just because a power amplifier delivers a lot of power, that does not mean that it cannot deliver high performance as well. For one, the frequency response is ruler-flat from 20Hz to 20kHz, a mere 0.1dB down in response at 20kHz. Power into 4W is a genuine 500W. At typical power levels, between 1.5W and 350W, the total harmonic distortion plus noise (THD+N) is below 0.007% at 1kHz. For an 8W load, maximum power is around 270W until the onset of clipping, with <0.004% THD+N at 1kHz at more typical power levels from 1W to 200W. Under ideal conditions, it’s close to what we’d call ‘CD quality’ at around 0.002% THD+N. As you can see from Fig.2, distortion rises somewhat with frequency; in fact, it’s considerably lower than quoted above at more typical audio frequency ranges for most instruments of around 100-500Hz. Above 1kHz, distortion rises modestly, although it’s still relatively low even Fig.2: THD+N plots for 8W, 4W and 3W loads (two different power levels are shown for 4W) with 20Hz22kHz bandwidth. You can see that the base distortion largely depends on the load impedance, and it rises steadily with frequency above about 100Hz. The 3W curve is mainly presented as a ‘worst-case scenario’ and shows that it can drive very low load impedances without too much difficulty. Australia's electronics magazine siliconchip.com.au Two of our previous projects: the Cooling Fan and Loudspeaker Protector (February 2022; siliconchip. com.au/Article/15195) and Amplifier Clipping Indicator (March 2022; siliconchip.com.au/ Article/15240) are both used in the 500W Amplifier. by 10kHz, above which the filters in our test equipment start attenuating the harmonics. The THD+N result of under 0.05% for 266W into 3W shows that the performance of this amplifier does not degrade significantly even under harsh conditions, driving lower load impedances than you’d expect to see with most high-power 4W loudspeakers. Perhaps the most important aspect of this high-power amplifier is the very good signal-to-noise ratio of 112dB. This means that you can get a very high output level, including loud transients, without an annoying background hiss the rest of the time. The full circuit diagram is shown in Fig.4. Aside from the large number of output transistors, the circuit is similar in configuration to many of our previous amplifiers, including the Ultra-LD Mk.2 to Mk.4 amplifiers (August & September 2008, July-September 2011 & July-September 2015). One major difference is the addition of safe operating area (SOA) protection for the output transistors. This helps prevent damage to them if the amplifier is short-­ circuited or presented with a load that exceeds their safe operating area (SOA). This is not just protection against a short circuit; it works over the entire operating range of the amplifier. We’ve heard it stated in the past that SOA protection degrades the performance of an amplifier, but we tested this one with it in-circuit and disconnected, and we couldn’t measure any differences. So you don’t need to be concerned about its impact on sound quality. The supply rails are ±80V or 160V in total. This high Fig.3: THD+N vs power at 1kHz. Distortion starts to rise above 350W for 4W loads but it delivers 500W without gross distortion (and even more on a short-term basis). The performance is pretty good in the middle power range, from a few watts to a couple of hundred watts; it will give ‘CD quality’ into 8W up to about 200W. Double the numbers on the horizontal axis and check the 4W curve for 8W bridged performance! The finished Amplifier module shown mounted in its 3RU case with heatsink and fans. Note the 120mm PWM fans attached to the heatsink, as anything larger wouldn't fit in the case with its lid on. Circuit details siliconchip.com.au Australia's electronics magazine April 2022  29 Fig.4: the main difference between this amplifier and our last few designs is the sheer number of output devices (six pairs) and the addition of SOA/load line protection circuitry. This protection circuitry is based on voltage references REF1 & REF2, transistors Q25 & Q26 and the associated resistor network, including the series of 3.3kW resistors connected to the emitter of each output transistor. voltage requires rugged transistors, particularly the output and driver transistors, which need a large SOA. We could have used the NJL3281D/ NJL3282D ThermalTrak transistors as used in the Ultra-LD amplifiers. However, we would have needed 12 of these transistors per side or 24 in total to ensure it was robust. The ThermalTrak transistors have two main advantages: good linearity and each device includes a separate diode for biasing. The diode within the transistor package allows the quiescent (idle) current to be controlled accurately with temperature variations. Unfortunately, the sheer number of these transistors required would make the amplifier impractically large and expensive, so they are unsuitable. Instead, we are using MJW21196/ 30 Silicon Chip MJW21195 transistors, with only six required per side, thanks to their generous SOA curves. The input signal is AC-coupled via a 47μF non-polarised electrolytic and high-frequency stopper components, ferrite bead FB1 and a 22W resistor to the base of transistor Q1. The 22W input resistor and 4.7nF capacitor constitute a low-pass filter with a -6dB/ octave roll-off above 1.5MHz. Q1 is part of the input differential pair of Q1 & Q2, which are Toshiba 2SA1312 PNP low-noise transistors. These are responsible for the very low residual noise of the amplifier. 2SA1312 transistors are becoming somewhat challenging to get, but we have secured a good supply for our readers as we couldn’t find any suitable alternatives. Australia's electronics magazine Editor’s note – this practice of manufacturers discontinuing components with no direct replacement is very frustrating, and it has bitten us several times. The bias resistor for Q1 and the series feedback resistor to the base of Q2 are set to a relatively low value of 10kW to minimise signal source impedance and thereby reduce thermal noise. The 10kW input resistance and the 47μF input capacitor provide a low-frequency roll-off at 0.34Hz. The amplifier gain is set by the ratio of the 10kW and 220W feedback resistors at the base of Q2. This gain is 46 times (33dB), while the 2200μF capacitor sets the low-frequency rolloff (-3dB point) in the feedback loop to 0.33Hz. The relatively high gain helps to keep the amplifier stable and makes siliconchip.com.au the input sensitivity reasonable at around 1V RMS for full-power output. Coupling capacitors The high-value electrolytic capacitor for the input coupling (47μF) and feedback (2200μF) networks eliminate any effects of capacitor distortion in the audio pass-band and also minimise the source impedance. To explain, if we use a smaller input capacitor at say 2.2μF, its impedance will be 1447W at 50Hz. This will only have a small effect on the audio frequency response but represents a substantial increase in the source impedance at low frequencies. By contrast, the 47μF input capacitor we used has an impedance of only 67.7W at 50Hz. This also means that the voltage across these capacitors is minimal siliconchip.com.au compared to the audio signals, so the inherent non-linearity of electrolytic capacitors does not matter. Diodes D1 & D2 are included across the 2200μF feedback capacitor as insurance against possible damage if the amplifier suffers a fault where the output is pulled to the -80V rail. In this circumstance, the capacitor would have a significant reverse voltage. We use two diodes instead of one to ensure that there is no audio distortion due to the non-linear effects of a single diode junction at the maximum feedback signal level of about 1V peak. This prevents diode conduction under normal operating conditions. Voltage amplification stage Most of the amplifier’s voltage gain is provided by Q9, fed via Australia's electronics magazine emitter-follower Q8 from the collector of Q1. Together, these transistors form the voltage amplification stage (VAS). Q8 buffers the collector of Q1 to minimise non-linearity. Q9 is operated without an emitter resistor to maximise gain and also maximise its output voltage swing. Maximum voltage swing is required from the voltage amplifier stage to obtain as much power as we can from the output stages. Current mirror The collector loads of Q1 & Q2 are NPN transistors Q3 & Q4 which operate as a current mirror. Q4 acts as a sharp cutoff diode, providing a voltage at the base of Q3 equal to the base-emitter voltage drop of Q4 (about 0.6V) plus the voltage drop April 2022  31 Parts List – 500W Amplifier Module (to build one) 1 double-sided, plated-through PCB coded 01107021, 402 x 124mm 2 200mm-wide heatsinks [Altronics H0536] 2 small PCB-mounting heatsinks [Jaycar HH8516] 12 TOP-3 silicone insulating washers 3 TO-220 silicone insulating washers 2 insulating bushes for the TO-220 transistors 4 M205 fuse clips (for F1 & F2) 2 fast-blow ceramic M205 fuses (5A for 8W load, 10A for 4W load) (F1, F2) 1 ferrite bead (FB1) [Jaycar LF1250, Altronics L5250A] 1 6-way PCB-mount screw terminal with barriers (CON2) [Altronics P2106] 1 2-way pluggable vertical terminal socket (CON3) [Altronics P2572, Jaycar HM3112] 1 2-way pluggable screw terminal (CON3) [Altronics P2512, Jaycar HM3122] 1 vertical PCB mount RCA (phono) socket (CON1) [Altronics P0131] 1 pot core bobbin for L1 [Altronics L5305, Jaycar LF1062] 1 2m length of 1.25mm enamelled copper wire (for winding L1) 1 60mm length of 0.7mm diameter tinned copper wire (wire links) 12 M3 x 20mm panhead machine screws 5 M3 x 15mm panhead machine screws 6 M3 x 6mm panhead machine screws 17 M3 hex nuts 12 M3 steel washers 6 M3 tapped 9mm spacers 2 transistor clamps [Altronics H7300, Jaycar HH8600] 1 15mm length of 25mm diameter heatshrink tubing (for L1) 1 60mm length of 1mm heatshrink tubing (for the wire links) 1 small tube of heatsink compound/thermal paste Semiconductors 6 MJW21196 250V 16A NPN transistors (Q13-Q18) [element14 1700966] ● 6 MJW21195 250V,16A PNP transistors (Q19-Q24) [RS 790-5410] ● 1 MJE15035G 350V 4A PNP transistor (Q11) [Mouser 863-MJE15035G] ● 1 MJE15034G 350V 4A NPN transistor (Q12) [Mouser 863-MJE15034G] ● 1 FZT558TA 400V 300mA PNP transistor (Q7) [RS 669-7388P] ● 1 FZT458TA 400V 300mA NPN transistor (Q9) [RS 669-7326] ● 2 2SA1312 120V 100mA low-noise PNP transistors (Q1,Q2) ● 3 BC546 65V 100mA NPN transistors (Q3, Q4, Q25) 1 BC639 80V 500mA NPN transistor (Q8) 3 BC556 65V 100mA PNP transistors (Q5, Q6, Q26) 1 BD139 80V 1.5A NPN transistor (Q10) 2 1N4148 75V 200mA signal diodes (D1, D2) 4 UF4003 200V 1A ultra-fast switching diodes● (D4-D7) 32 Silicon Chip 1 BAV21 250V 250mA low-capacitance switching diode● (D3) [RS 436-7846] 2 TL431 programmable voltage references, TO-92 (REF1, REF2) [element14 3009364] ● 1 5mm green LED (LED1) 2 5mm red LEDs (LED2, LED3) Capacitors 1 2200μF 16V or low-ESR 10V electrolytic 3 470μF 100V electrolytic [element14 3464457] 1 47μF non-polarised (NP/BP) electrolytic 1 47μF 50V electrolytic 1 47μF 16V electrolytic 1 1μF 100V MKT polyester 1 470nF 100V MKT polyester 2 100nF 100V MKT polyester 1 100nF 250V AC metallised polypropylene X2-class 2 10nF 100V MKT polyester 1 4.7nF MKT polyester 1 1nF 100V MKT polyester 1 75pF 200V COG [Mouser 80-C315C750JCG or 80-C325C750KAG5TA] ● Resistors (all 1/4W, 1% thin film unless specified) 1 1MW 2 35.7kW ● (or 2 82kW & 2 62kW) 1 33kW 2 33kW 1W 5% (carbon type OK) 1 22kW 2 18kW 5 10kW 1 10kW 1W 1% thin film [Yageo MFR1WSFTE52-10K] ● 2 8.2kW 2 4.7kW 14 3.3kW 3 2.2kW 2 470W 2 220W 2 205W ● (or 2 430W & 2 390W) 3 100W 1 100W 1W 5% (carbon type OK) 2 68W 2 68W 5W 5% wirewound (for testing purposes) 8 56W 1W 5% (carbon type OK) 2 47W 1 39W 1 22W 1 10W 12 0.47W 5W 5% wirewound 1 100W single-turn top-adjust trimpot (VR1) [Altronics R2591] 1 200W multi-turn top-adjust trimpot (VR2) [Altronics R2372A] ● these parts are also available in the Silicon Chip short form kit (Cat SC6019) while stocks last The parts list for the power supply, chassis, wiring etc will be presented in an upcoming issue. Australia's electronics magazine siliconchip.com.au The first part of our 500W Amplifier series focuses on describing how the amplifier module works; assembly and testing will be handled in later parts. across its 68W emitter resistor. If Q2 draws more than its share of emitter current from Q5, the voltage at the base of Q3 increases, so Q3’s collector current also rises. This forces Q1 to pull a bit more current and stop Q2 from taking more than its fair share. As Q3 mirrors the current of Q4, Q1 is provided with a collector load that has a higher impedance than would otherwise be the case. The result is increased gain and improved linearity from the differential input stage. Similarly, the collector load for Q9 is a constant current load comprising transistors Q6 & Q7. Interestingly, the base bias voltage for constant current source Q5 is also set by Q6. Q5 is the constant current tail for the input differential pair of Q1 and Q2, and it sets the current through these transistors. LED1 is connected to this circuit as a ‘free’ power-on indicator. The reason for the somewhat complicated bias network for Q5, Q6 and Q7 is to produce a major improvement in the power supply rejection ratio (PSRR) of the amplifier. Similarly, the PSRR is improved by the bypass filter network consisting of the 100W 1W resistor and 470μF 100V capacitor in the negative supply rail. siliconchip.com.au Why is PSRR so important? Because this amplifier runs in class-AB, it pulls large asymmetric currents from the positive and negative supply rails. The currents are asymmetric in the sense that it’s pulling from one or the other at any given time; the waveforms will be a similar shape for a sinewave, just time-shifted compared to each other. So, for example, when the positive half of the output stage (Q13 to Q18) conducts, the current waveform is effectively the positive half-wave of the signal waveform; ie, rectification occurs. Similarly, when the negative half of the output stage (Q19 to Q24) conducts, the current is the negative half-wave of the signal. So we have half-wave rectification ripple of the signal superimposed on the supply rails, as well as the 100Hz ripple from the power supply itself. And while the PSRR of an amplifier can be very high at low frequencies, it is always worse at high frequencies. If these ripple voltages can get into the earlier stages of the amplifier, they will cause distortion, so we need to minimise them there. Diode D3 is included to improve recovery performance when the amplifier is driven into hard clipping. It makes the recovery from negative Australia's electronics magazine voltage clipping as clean and fast as that from positive voltage clipping, improving signal symmetry and reducing ringing under these conditions. For this role, we are using a BAV21 diode with a low capacitance of 2pF at 1MHz so that it doesn’t affect sound quality. Feedback & compensation As mentioned, the feedback components at the base of Q2 set the closedloop gain of the amplifier. The bottom end of the feedback network is connected to ground via a 2200μF electrolytic capacitor. As this reduces DC gain to unity, the amplifier output offset voltage is dramatically lower than it would otherwise be (by a factor of 38 times). The 75pF compensation capacitor connected between the collector of Q9 and the base of Q8 prevents oscillation by limiting the slew rate. The 22kW resistor in Q8’s collector limits the current through Q9 under fault conditions. Should the amplifier output be shorted, it will try to pull the output either up or down as hard as possible, depending on the output offset voltage polarity. If it tries to pull it up, the output current is inherently limited by the 15mA current source driving Q9 from April 2022  33 Q7. However, if it tries to pull down, Q9 is capable of sinking much more current. The 22kW resistor limits Q9’s base current and therefore, its collector current and dissipation. The 1nF parallel capacitor is required to keep its AC collector impedance low, improving stability. Driver stage The output signal from the voltage amplifier stage Q9 is coupled to driver transistors Q11 and Q12 via 47W resistors. The 47W resistors act as stoppers to help prevent parasitic oscillation in the output stage. They are also needed to allow the load line protection circuitry to override the drive from the VAS. Q10 sets the DC voltage between Q7 & Q9, and this determines the quiescent current and power in the output stages. It provides a bias of about 2.3V or so between the bases of Q7 & Q9 so that they are always slightly conducting, even without an input signal. Q10 is a ‘Vbe multiplier’, multiplying the voltage between its base and emitter by the ratio of its collector-­ emitter and base-emitter resistances. While trimpot VR2 varies the resulting collector-emitter voltage, it is actually adjusted to set the quiescent current through the output transistors. It is important that the bias voltage produced by Q10 changes with the temperature of the output stage transistors. As the output transistors become hotter and their base-emitter voltages reduce, Q10’s collector-emitter voltage should also drop, so that the quiescent Fig.5: here are the load lines for 4W and 8W operation. The straight lines are for resistive loads, while the arched lines are for reactive 4W (2.83W + j × 2.83W) and 8W (5.65W + j × 5.65W) loads. The green and mauve lines are the power limit hyperbola at 25°C and 50°C, while the orange line is the one-second SOA curve for six MJW21195/6 power transistors. The dashed green and mauve lines are the dual-slope load line protection curves at 25°C and 50°C. current is the same or less as at lower temperatures, averting the danger of thermal runaway. Output stage The amplifier’s output stage is effectively a complementary symmetry emitter follower comprising six NPN transistors (Q13-18) and six PNP transistors (Q19-Q24). Each output power transistor has a 0.47W emitter resistor, and this moreor-less forces the output transistors to share the load current equally. The emitter resistors also help to stabilise the quiescent current to a small degree, and they slightly improve the frequency response of the output stage by providing current feedback. Output offset adjustment DC offset adjustment is provided by the 100W trimpot (VR1) between the emitters of the input pair, Q1 & Q2. VR1 adjusts the current balance between the input pair, and this causes the DC offset at the output to vary. The trimpot is set to make the DC offset as close to 0V as possible; it should be possible to keep this within ±5mV. This is generally a good figure to keep low, but it’s especially critical if using the amplifier to drive a step-up transformer for 100V line operation. That’s because the DC resistance of the transformer primary is much lower than that of a loudspeaker voice coil, so significant DC can otherwise flow through it. Load line protection It is crucial to prevent the output transistors from operating beyond their Safe Operating Area (SOA). A high-power amplifier like this is quite likely to see abuse, being driven beyond its limits at times. Fig.5 shows plots of collector current versus collector-emitter voltage (Vce) for the six-per-side paralleled MJW21196 and MJW21195 output transistors. Of the two types, the MJW21195 (PNP) has the lower SOA curve, with a lower current allowed beyond 150V than the complementary MJW21196, so that is the curve we’ve plotted (the solid green line). The SOA curve is based on a transistor junction temperature of 150°C and a case temperature of 25°C. That is not a very practical case temperature to maintain, especially when the transistors are dissipating significant power. 34 Silicon Chip Australia's electronics magazine siliconchip.com.au The actual transistor case temperature depends on the dissipation, the thermal resistance of each transistor’s junction to its case (0.7°C/W) and the case-to-ambient thermal resistance, which is determined by the heatsink and fans. Having a large heatsink with fan-forced air greatly helps to keep transistor temperatures low. At elevated temperatures, it is essential to ensure the transistors are not operated beyond their maximum power rating, 200W at 25°C, reducing by 1.43W per °C. This power rating curve can further reduce the power they can handle beyond that imposed by the SOA secondary breakdown area. We plotted both the 25°C case temperature power curve (green curve) and the 50°C case temperature power curve (mauve curve). While a total of 1200W is available with the six 200W transistors at 25°C, only 985W is allowable with a 50°C case temperature. The curves assume that each of the six parallel transistors share the current equally, a fair assumption since each has a relatively high-value emitter resistor. If one of the power transistors tends to take more than its share of load current, the voltage drop across its emitter resistor will be proportionately higher. This will throttle the transistor back until its current comes back into line with the others. The blue and red curves show resistive 8W and 4W loads (straight lines) that assume the load is purely resistive. In practice, this is not true for loudspeakers as there is a considerable reactive impedance in a practical loudspeaker that causes its resistance to vary with frequency. The curved blue and red lines show the load impedance curves assuming that the resistive and reactive impedances are equal. The plots show the worst-case impedance that occurs over the operating frequency range. For example, for a 4W speaker, we plot the curve with a 2.83W resistance and 2.83W reactive impedance that’s 90° out of phase with it (“j” is like “i” in mathematics, the imaginary unit of value √-1, forming a complex impedance value). Calculation of the total impedance can be visualised as the two impedances forming two sides of a right-­ angle triangle with the hypotenuse length equalling the total, which in this case is either 4W or 8W. These plots are for a rather severe siliconchip.com.au A close-up of the front-end circuitry of the 500W Amplifier module. amplifier load. Typically, a loudspeaker will not exhibit such a load, but we want to ensure the amplifier will not be damaged by designing for worst-case loads. Note how the curved impedance plots encroach quite a bit closer to the SOA curve than the purely resistive loads. Note also that at elevated temperatures, the allowable dissipation curve comes close to the 4W reactive impedance plot, especially around the 60V to 100V Vce region. At case temperatures above 50°C, the allowable transistor dissipation could possibly be exceeded. The two protection lines on the graph prevent this. The dashed green line is for a transistor case temperature of 25°C, while the dashed mauve line is for a 50°C case temperature. The lines show the points on the graph where the output transistors are protected by reducing their base drive should the load reach the protection line. The protection lines shift closer to the 4W impedance curve with increasing temperature. Also, the protection lines have a dual slope with one straight line between the Y-axis and the small circle (dot), and the second line between that dot and the X-axis. Note that where the line meets the X-axis, it must be at least the total supply voltage (160V) to prevent spurious limiting near zero output current. As the temperature rises, the voltage at the zero current axis reduces. However, even the 50°C curve meets the axis above 160V, at 165V. If the amplifier gets significantly hotter, perhaps beyond 60°C, the output will probably get cut off, but maybe that is not a bad thing, as it’s a sign that the cooling system might have failed. While the difference between the Australia's electronics magazine two slopes in the protection curve is subtle, this is necessary to more closely follow the power rating curve and hence prevent the protection curve at 50°C and beyond from encroaching on the 4W impedance curve at a Vce of around 70V. SOA protection circuitry This dual-slope foldback protection scheme is based on the research paper titled “The Safe Operating Area (SOA) Protection of Linear Audio Power Amplifiers” by Michael Kiwanuka, B.Sc. (Hons) Electronic Engineering, which you can view at siliconchip. com.au/link/abc4 The supply voltage, output voltage and current through the output transistors are all monitored to provide loadline protection over the entire voltage and current ranges of the amplifier. Transistors Q25 & Q26 and diodes D6 & D7 provide the protection feature. Q25 (NPN) can shut off the MJW21196 transistors, while Q26 (PNP) acts on the MJW21195 transistors. The diodes are included to prevent Q25 & Q26 from shunting the drive signal when they are reverse-biased. This happens for every half-cycle of the signal to the driver transistors. The circuits around Q25 and Q26 are essentially identical. Normally, Q25 & Q26 are biased off and play no part in the amplifier’s operation. However, if the load encroaches upon the protection curve, Q25 and/or Q26 switch on to throttle back drive to the output transistors, limiting the output current and protecting the transistors. This also protects against short circuits. Transistor Q25 and Q26 are mounted on the amplifier’s heatsink so that the protection circuit curves shift with temperature as required. April 2022  35 The finished case is simple, with only a power button and clipping indicator LED on the front and audio input/output & power socket on the back. In more detail, the voltage across each 0.47W output stage emitter resistor is monitored via a set of 3.3kW resistors. These voltages are averaged (equivalent to being summed) at the base of Q25 or Q26. Resistive dividers formed from pairs of paralleled resistors provide output voltage and supply voltage monitoring by feeding extra current into these summing points. Effectively, what these dividers do is make it so that as the voltage across a set of output resistors reduces (either due to reduced supply voltage, or the output swinging closer to that rail), the protection circuitry becomes more insensitive and requires a higher output current to be triggered. Similarly, as the Vce increases, the trip current decreases, forming the ‘curves’ shown in Fig.5. The dual slope in the protection circuit is created by voltage reference REF1 for the positive half of the circuit and REF2 for the negative half. The bias current to operate these devices comes via 18kW series resistors. REF1 and REF2 are adjustable voltage references, with the 10kW and 3.3kW resistors setting the voltage across them to 10V. The protection circuit relies on the base-emitter voltage of Q25/Q26 36 Silicon Chip being around 0.6V at 25°C. This voltage drops to 0.55V at 50°C, so these transistors switch on with less applied voltage at higher temperatures. This shifts the protection line downwards with elevated temperature, following the downward movement of the output transistors’ power rating curve. Diodes D4 & D5 between the amplifier output and supply rails are also part of the protection circuitry. They absorb any large spikes generated by the loudspeaker’s inductance when the protection circuit cuts the drive to the output transistors. D4 & D5 are fast recovery diodes, included to ensure their operation at high frequencies and high power. These diodes are even more critical if driving a line transformer as its primary inductance is likely to be significantly higher than any loudspeaker load. Output RLC filter The remaining circuit feature is the output RLC (resistor, inductor and capacitor) filter, comprising a 2.2μH air-cored choke, eight paralleled 56W resistors (giving 7W) and a 100nF capacitor. This output filter effectively isolates the amplifier from any large capacitive reactance in the Australia's electronics magazine load, thereby ensuring unconditional stability. It also helps attenuate any RF signals picked up by the loudspeaker leads and stops them from being fed back to the early stages of the amplifier, where they could cause RF breakthrough. Fuse protection The output stage supply rails are fed via fuses F1 and F2 from the +80V and -80V main power supply rails. These provide ‘last-ditch’ protection to the amplifier, limiting the damage in the case of a severe fault. The recommended fuses are ceramic types. LED2 is a blown-fuse indicator for F1 and LED3 for F2. They light up if the fuse is blown as it isn’t always obvious, especially with ceramic types. Next month The following article next month will have the full module construction details, including the heatsink drilling and instructions for winding inductor L1. In the June issue, we’ll show you how to build a suitable power supply, mount it and the Amplifier module in the chassis, and wire it all up along with the fan controller, fans, Speaker Protector and Clipping Indicator. SC siliconchip.com.au Subscribe to JANUARY 2022 ISSN 1030-2662 01 The VERY BEST DIY Projects! Batteries 9 771030 266001 $ 50* NZ $1290 11 INC GST INC GST imagine life without them MetronoMes wi th Australia’s top electronics 8 or 10 LeDs protect to six amplifier modules up with our Multi-Channel Sp ea ke magazine r Protector Silicon Chip is one of the best DIY electronics magazines in the world. Each month is filled with a variety of projects that you can build yourself, along with features on a wide range of topics from in-depth electronics articles to general tech overviews. 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To start your subscription go to siliconchip.com.au/Shop/Subscribe siliconchip.com.au Australia's electronics magazine April 2022  37 The History of Transistors Last month, I described the invention of transistor technology and some of the early techniques used which were not well suited to mass production or high performance. This article continues where that one left off, covering the rapid progress in the 20 or so years between the first commercial transistor production and the development of manufacturing techniques that are still in use today. Part 2: by Ian Batty T he first article in this series described the ‘hand-made’ phase of transistor construction. Although some processes were automated, they were very much made one at a time. That’s still true of the first few techniques we’re about to look at. Alloying, for example, required each transistor’s indium dots and base slice to be individually assembled for loading into the alloying furnace. The breakthrough came with the application of photolithography. Combined with gaseous diffusion, 38 Silicon Chip this provided all stages of fabrication apart from terminal and lead attachment. This meant that manufacturers could automate the manufacturing process and apply batch processing to yield many devices from one feedstock wafer/slice, as we shall soon investigate. Alloyed-junction transistors Grown junction technology was demonstrably superior to point-contact but could not yield a base of sufficient thinness for operation much above Australia's electronics magazine 1MHz. The Regency TR-1’s designers were forced to use an intermediate frequency (IF) of only 262kHz to get reasonable gain. The alloyed-junction transistor was invented by John Saby at General Electric, with similar developments undertaken by Jacques Pankove at RCA. Inventorship had to be established in the US courts, as RCA had filed on Pankove’s work one day ahead of General Electric in June 1952. They were initially PNP types and commenced with a wafer of N-type siliconchip.com.au Fig.22: alloyed-junction transistors were made by adding indium pellets or ‘dots’ on the surface of the N-type (doped) silicon base, then heating the assembly in an oven until the P-type indium formed an alloy with sections of the base. germanium, typically doped with antimony (becoming the base). Some details of production are set out in Pankove’s patent at https://patents.google. com/patent/US3005132 The junction transistor was created by alloying emitter and collector dots onto the base slice at high temperatures. This design was reliable and economical to produce. The famous OC70/71 and OC44/45 series used in the late 1950s and early 1960s were all alloyed-junction types. Alloyed-junction transistors worked at moderately high frequencies – up to about 15MHz for the OC44. Point-­ contact transistors were still in limited use, as their highest operating frequencies extended to around 300MHz. Current flow in a PNP transistor originates at the emitter, crosses the emitter-base junction, diffuses through the base, then crosses the base-­collector junction. The slowest movement is within the base, so the first area for improvement was to make the base as thin as possible. The principal problem with this was in the alloying process. A typical transistor began with the N-type base slice having P-type indium ‘dots’ for the emitter and collector placed on it. The assembly was then heated to the melting point of indium, below germanium’s, forming a eutectic alloy that combined the indium into the germanium – see Fig.22. A practical transistor has a base thickness measured in micrometres; the base thickness is exaggerated in Fig.22 for clarity. You can see photos siliconchip.com.au of ‘delidded’ germanium alloyed-­ junction transistors in Figs.23 & 24, in which the alloyed indium dots are clearly visible. The molten indium penetrated the germanium base area from either side. The aim was to alloy the emitter and collector as closely together as possible without ‘shorting out’ the base region. An article extracted from the January 1961 edition of Mullard Outlook (siliconchip.com.au/link/abbi) describes just how laborious and handmade the OC71 and its fellows were. The Outlook describes how the collector sites were alloyed first, then the base slice removed from the furnace, turned over, the emitter sites placed and the entire assembly re-alloyed to complete the transistors. Raytheon solved the multi-pass problem by inserting the emitter dot into a recess in a small graphite ‘boat’, then placing the base slice, then the collector dot on top of the base to complete the ‘sandwich’. The entire assembly then went through the alloying furnace, creating the transistor in a single pass. In practice, base thicknesses of Fig.23: a delidded transistor from an IBM 1401 computer. Early versions of that computer used standard alloyedjunction germanium transistors, while later versions used faster, diffused ‘drift field’ transistors. Source: Marcin Wichary, USA (CC BY 2.0) much less than about 0.5 thou (0.0005in or about 0.013mm/13µm) proved difficult to produce reliably. Philips’ commonly-used OC44, with its cut-off frequency of around 15MHz, was bettered only by RCA’s 2N1308 at 30MHz, representing the state-of-theart for alloyed junction transistors. Many OC45s were simply OC44s that had not met the OC44 specifications and were marketed as perfectly good devices with a high-frequency cut-off of only 6MHz. You’ll see radios of the time with an OC44 converter and OC45s relegated to the IF. Once production was running smoothly, manufacturers concentrated on improving important parameters such as the power rating, maximum voltage, high-frequency response, temperature stability and noise. Many valves did not have frequency ratings, and some turned out to be suitable for use at much higher frequencies than intended, such as the 6BE6 pentagrid operating up to 108MHz in FM tuners. On the other hand, junction transistors universally have maximum frequency specifications. This is useful Fig.24: a small-signal alloyed-junction germanium transistor suitable for audio use. Note how the base and collector leads are insulated from the metal can while the emitter, hidden under the wafer slice, connects directly to the can for shielding. Image copyright: Jack Orman, www. muzique.com Australia's electronics magazine April 2022  39 for designers but also points to the intensive design and development efforts that now allow transistor operation up to and beyond 500GHz. Raytheon’s landmark 8TP portable radio was the second all-transistor radio behind the Regency TR-1. But unlike the TR-1, judged by Consumer Reports in April 1955 as a “toy that didn’t come at a toy-like price”, its performance was quite credible. The 8TP, like most Australian radios built in the 1950s, uses PNP types in the RF/IF section. This is a good indication of alloyed-junction construction as alloyed-junction types are most easily made using indium-alloying. It’s possible, but difficult, to create NPNs using alloying. Diffused construction Alloyed-junction transistors were incapable of working much above 30MHz, a limit easily surpassed by the less-reliable point-contact technology. With the physical base thickness restricted to a minimum of about 10μm using alloying techniques, designers turned to the question of current-­ carrier speed across the base. Four solutions were found. The first was to produce a graded doping concentration from emitter to collector, the ‘diffused junction’. The second was to alloy using the collector as the substrate; the base was diffused into the collector slice, and the emitter alloyed into the base ‘surface’. The third was to chemically etch a very thin base area for emitter and collector deposition. The fourth was to use diffusion to fabricate the base and emitter over the collector substrate. 1) Graded doping Charge carriers must diffuse across the base-collector junction, and a uniform doping concentration does not give the fastest transit time. If the doping concentration is modified across the thickness of the base, charge carriers experience less recombination and get a comparative ‘boost’ in their slow diffusion towards the collector. Light doping near the base-­collector junction also reduces the effective capacitance in that area, thus reducing collector-base feedback capacitance. RCA’s drift field process, proposed by Herbert Kroemer in 1953, was put into production by 1956. 40 Silicon Chip Fig.25: graded doping allowed for lighter doping in the collector area of the substrate, forming a ‘drift field’ transistor that accelerated electrons/holes more effectively, therefore improving high-frequency operation. Rather than doping the entire base slice at manufacture, just one side of the base was exposed to a doping gas in a furnace. This caused a high doping concentration on the exposed side, and progressively weaker doping as the doping gas diffused through the germanium base slice. The resulting doping gradient, shown in Fig.25, allowed higher-­ frequency operation. This method still relied on physically thin and fragile base slices, and offered no means of reducing the active base thickness. Drift transistors such as RCA’s 2N247 offered cut-off frequencies up to 60MHz. Even with strict control of the alloying process, 60MHz was probably the practical limit for such construction. While this technique went no further, it demonstrated that uniform doping of the base could be dispensed with, and hinted that the transistor might be fabricated on one side of the substrate. 2) Collector substrate Philips, meanwhile, had extended the concept of diffusion into the germanium slice. Rather than a two-sided approach fabricated on a base substrate, they began with a relatively thick and mechanically robust collector slice. The first approach was to create a thin doped layer to diffuse the base into the collector substrate using diffusion. An emitter ‘dot’ was placed onto the base surface and alloyed into the base layer, as Fig.26 shows. The initial design used a contacting ring to connect to the base diffusion, superseded by an alloyed base connection. The base dot was of the same Fig.26: gas diffusion allowed a very thin surface layer on the wafer to be doped to N-type while the bulk of the silicon remained P-type. The emitter was then alloyed on top. This thin base layer provided even higher frequency operation. Fig.27: a refinement of the scheme shown in Fig.26; here, a base dot is alloyed along with the emitter. The base dot is N-type material on top of the N-type diffused layer, so it doesn’t form a semiconductor junction; just a convenient electrical connection to the base layer. Australia's electronics magazine siliconchip.com.au Fig.28: another germanium audio transistor, apparently a diffusion type as no alloyed dots are visible, and the wafer slice is so small that it’s mounted on a stamped steel base to keep the bond wires short. Image copyright: Jack Orman, www.muzique.com polarity as the existing base (N-type in the OC169~171), the emitter dot of P-type. Alloying the base dot simply made electrical contact with the base layer, but the emitter dot would alloy into the base, forming the emitter-base junction, as shown in Fig.27. This principle is also known as the Post-Alloy Diffused Transistor (PADT), as the alloying follows base diffusion. In 1957, J. R. A. Beale reported experimental production with operating frequencies up to 200MHz. In full-scale production, devices such as the OC169~171 could operate at 100MHz. The AF118 RF/Video amplifier boasted a cut-off frequency of 175MHz. Production spreads still existed: Fig.29: by acid etching the base layer to make it as thin as possible before adding the emitter and collector, the effective base could be made thinner, thus speeding up current flow across it. This resulted in more fragile transistors. transistors were graded for performance at 100MHz, with the best-­ performing OC171s intended as RF amplifiers in the 88-108 MHz FM band. The OC170 and OC169 were recommended for converter and IF amplifier service, respectively, and came from the same production lines. Further development yielded some impressive results, with the AF186 posting a cut-off frequency of 820MHz. A UHF tuner design from 1967 gave a gain of 22dB with a noise figure of 10.5dB at 860MHz. This was already superior to competing valve designs, which principally used a valve local oscillator and solid-state diode mixer, but no RF amplifier. Microwave valves such as the discseal 6BA4 or the ceramic 7077 gave good RF amplifier performance, but were not considered practical in mass-produced consumer electronics. Even with this level of performance, the days of alloying were numbered. The AF186 came in two varieties, pre-amplifier and mixer-oscillator, implying that significant manufacturing variabilities still existed. Also, the entire alloying process was illsuited to high-yielding mass production demands. Some online sources describe the previous alloyed-junction construction as “diffused”. Early confusion over whether the indium-germanium consolidation was a diffusion or an alloying process was finally resolved by John Saby in 1953 (see siliconchip. com.au/link/abbj). A true diffused construction relies on diffusing a doping gas’ doping concentration into the depth of the base (or collector) at high temperatures when the base is manufactured. Against this, alloying relies on the eutectic process, where the alloy’s melting point is lower than that of either constituent, just as tin-lead solder melts before either tin or lead. But you can argue that an alloy also sees mutual diffusion of one part into the other. Saby recognised this, accepting ‘alloying’ over ‘alloy-diffusion’ for the alloyed-junction process to distinguish between the older dot on a slice process and the newer gaseous atmosphere processes being developed (see siliconchip.com.au/link/abbk). 3) Base-substrate etching Alloyed designs already used the thinnest practical base of uniform thickness, but only the section directly between emitter and collector needs to be as thin as possible. Why not use a suitably thick base substrate for mechanical strength, then thin out the area where the emitter and collector will be formed? Philco (https://en.wikipedia.org/ wiki/Philco) invented the surface barrier transistor (SBT) and used this technology to build the world’s first solid-­ state computer in 1957, the S-2000 Transac. Arthur Varela used precision etching to chemically erode the base slice, forming a ‘well’ on either side. Fig.29 shows how the etching created the thin base region, then transformed into a plating process, with the emitter and collector regions being plated onto the base surface. Devices such as the 2N240 could operate up to 30MHz. See also Fig.30. Fig.30: a page from US patent 2,885,571 shows how acid etching makes the base extremely thin, speeding up the transistor. siliconchip.com.au Australia's electronics magazine April 2022  41 Fig.31: the diffusion process for making diodes. Variations on this process could be used to add a third layer for making transistors. Impressive as the SBT was, it still relied on highly precise manufacturing that was not easily adapted to automated, high-volume mass production. Additionally, the very thin base was still mechanically weak, so the device was prone to damage from vibration or shock. The similar micro-alloy transistor (MAT) enjoyed a brief appearance, especially in England, where Technical Suppliers Limited and Clive Sinclair’s Sinclair Radionics offered these devices. Notably, the TSL catalog shows MATs with cut-off frequencies of 75MHz, but a competing alloy-­ diffused device with a cut-off of 400MHz. 4) Micro-alloy diffusion If diffused-base technologies such as the drift-field allowed operation up to 60MHz, why not apply diffusion to a very thin base? Would this improve the performance of the surface-barrier design? Philco engineers addressed this problem, applying etching techniques to a diffused base: the micro-­ alloy diffused transistor (MADT). As noted above, the entire base does not need to be extremely thin, only the section between emitter and collector. The 2N502A MADT could oscillate up to 500MHz. Micro-alloy diffusion works by using diffusion techniques to create a doping gradient through the base that promotes rapid charge motion from emitter to collector. ‘Wells’ are then etched into the base slice to form the thinnest possible base section between emitter and collector. Finally, the emitter and collector surfaces are ‘plated’ into the base wells, ready for lead attachment. All-diffusion techniques The previous fabrication methods (especially those using etching) could 42 Silicon Chip not make good use of high-volume, automated manufacturing techniques. Two solutions were found: mesa and planar processes, each allowing hundreds of transistors to be made on a single semiconductor wafer/slice in one go. That slice was then cut apart to yield individual transistor ‘chips’ ready for testing and packaging. Also, if devices other than transistors could be fabricated on a wafer and interconnected, it would be possible to create many individual, functional circuits on a wafer. Finished circuits could be tested in place, the good ones cut and packaged, and the rejects discarded. But that would come a bit later. The key to this revolution was photolithography (https://patents.google. com/patent/US2890395A), a refinement of the photographic techniques used to make printed circuit boards (PCBs). Paul Eisler’s 1943 patent application (GB639178) for the PCB became the basis for proximity fuse design in anti-aircraft shells. Post-war declassification was followed by Moe Abrahamson and Stanislaus Danko’s patent, granted in 1956 (https://patents.google.com/patent/ US2756485A) – see the last page. Mesa fabrication Working at Texas Instruments, Jack Kilby developed the monolithic (‘single stone’) mesa process. Mesa construction (named for flat-topped tablelands of south-western USA) began with a substrate slice of doped silicon, let’s say N-type. The substrate (commonly known as a wafer) was placed in a furnace and exposed to a P-type doping gas. This created a P-type layer over the entire surface of the substrate, forming a single diode junction (see Fig.31). At this point, the slice could be cut up into chips, each being one P-N diode. Photolithography The photolithographic process allows the creation of individual Fig.32: this is an example of how a circular slice of silicon (or germanium) crystal could be made into many separate diode dice using photolithography and acid etching. Australia's electronics magazine siliconchip.com.au Fig.33: the Mesa process was an early photolithographic transistor production method with important advantages. doped ‘islands’ on the slice rather than a continuous doped surface. Fig.32 shows an example mask applied to a germanium/silicon wafer. The key to the process is a photosensitive resist. This chemical responds to ultra-violet light by hardening and adhering to the surface it is applied to. Exposed resist will remain in place during processing, while unexposed resist (covered by opaque parts of the mask during UV exposure) is easily washed off to permit the doping atmosphere to diffuse into exposed areas of the wafer. Beginning with a wafer that has been processed to create a single large P-N junction, the slice is resist-coated, masked and exposed to ultraviolet light. The light not obscured by the mask passes through and hardens the resist layer. The unexposed resist is then washed off, leaving a protective pattern over the slice. This process is shown in Fig.33. The slice is then exposed to an etching acid so that the unprotected areas of the slice are dissolved, removing the P-type layer in the exposed areas. Precision control results in the desired P-type ‘islands’ over the surface of the N-type substrate. The etching creates side trenches, separating each ‘island’ from its neighbour, and giving the distinctive ‘Mesa’ profile. Finally, the resist layer is removed from the entire slice, and it is cut up to yield Mesa diodes. This process can be automated, with the slice never leaving the production line’s controlled atmosphere. This eliminates the possibility of surface contamination, giving much higher consistency and reliability. The example mask in Fig.32 would produce 160 diodes in one production run. In reality, 1969s standard siliconchip.com.au two-inch wafer/slice produced hundreds of diodes. Making mesa transistors The process for making transistors is similar, but naturally, it is a little more complicated. First, a fresh substrate is placed into a furnace and the entire surface is exposed to a doping gas, making a single P-N junction, as before. The next stage is to take the entire slice and coat it with resist, just as for the diodes. But this mask contains smaller holes – each one overlaying a part of the previously-doped P-type base material where the exposed area is to become the emitter of a transistor. UV exposure hardens the resist layer, and the unexposed portions are washed off. The slice is exposed to an N-type doping gas in the furnace, changing the exposed P-type silicon base areas to N-type doping, creating the small emitters. We now have an N-P-N structure. Finally, the edges of the useful area are etched to isolate each transistor from its neighbour (similar to Fig.33) and ensure that the N-type substrate is isolated from the collector around the edges – just like the diodes. The transistor has been made with two diffusion processes – first the base, then the emitter into the formed base area. Thus, this type of transistor is known as double-diffused. Mesa’s double-diffusion can be conducted in a single pass through the furnace. Beginning with an N-type substrate, aluminium vapour (a light, rapidly-diffusing acceptor impurity) can be made to diffuse and create the P-type base, a layer only 0.0001 inches or about 2.5µm thick. That’s a bit less than four wavelengths of visible red light. Simultaneously, and in the same atmosphere, a more slowly-diffusing antimony donor impurity penetrates less deeply, following the aluminium diffusion, overcoming and reversing the aluminium’s acceptor doping. This creates a shallower N-type emitter layer extending from the surface into the base region. Consider the astounding precision of control needed for this process and the fact that the substrate stock’s purity is measured in parts per billion. That’s why the Mesa process (and its successor, planar, described below) took so many thousands of laboratory hours, so many millions of dollars and so many years to reach perfection. Fig.34 shows a simplified example of a NPN transistor of Mesa construction. Notice the etched side ‘trenches’ that isolate the collector-base junction. Fig.34: this is how a transistor made using the Mesa process looked when finished. The name comes from its distinctive shape, like a desert mesa. Australia's electronics magazine April 2022  43 Input 1 Output 1 B+ Earth Output 2 Input 2 Mesa/double-diffused construction gives great improvements in yield: many individual devices can be fabricated on a single germanium or silicon slice, and the high-precision nature of photolithography allows for the creation of much smaller individual devices. Although the illustration does not show it, Mesa devices can also use epitaxial construction, described in the next section. A parallel development allowed robotically-controlled, microscopic probes to examine and test each finished device on the slice. Faulty or below-standard devices would be Fig.35: a photo of the first commercial integrated circuit, Fairchild’s µL902 flip-flop from 1961. It was made using a similar process to the epitaxial planar technique, with more complex lithographic masks to create the four transistors and their interconnections. Source: Fairchild recorded in computer memory and rejected once the slice was scribed and broken up to produce individual devices. Mesa technology drove costs down and yielded devices with greater reliability and performance figures. Texas Instruments advertised their germanium 2N623, with a maximum oscillating frequency of 200MHz, in July 1958. By March 1959, TI’s 2N1141 could operate to 750MHz. While this performance is about equal to the best alloy-diffused transistor, the process delivers higher yields and is therefore more economical. Although surpassed by its planar successor for high-frequency use, Mesa technology is still widely used for high-power transistors. At about this time, Jack Kilby pioneered integrated circuits by fabricating several devices onto one germanium “chip”, forming a simple digital circuit. Those devices still relied on fine interconnecting wires between the devices. He was awarded the Nobel Prize for Physics in 2000. Despite Kilby’s invention being regarded as ‘the first’ integrated circuit, Kilby does not have absolute priority (https://patents.google.com/patent/ US3138743A). Harwick Johnson filed a patent in 1953 for an analog phase-shift oscillator in a “unitary body” that we would recognise as an integrated circuit. Johnson’s device did not rely (as Kilby’s did) on manually-placed interconnecting wires to complete the device (https://patents.google.com/patent/ US2816228A). Six months later, Robert Noyce, one of the “Fairchild Eight”, perfected integrated circuit design by vapour-depositing metallic wiring interconnections over the chip surface, creating a device that could be Fig.36: the planar epitaxial diode manufacturing process, which can be considered the direct predecessor of many Fig.37: epitaxial planar transistor manufacturing starts with the output of the diode process and repeats essentially the 44 Silicon Chip Australia's electronics magazine siliconchip.com.au made entirely automatically. Noyce (in contrast to Kilby) used silicon, starting the IC revolution that has given us everything from supercomputers to smartphones with cameras (see Fig.35). Planar transistors The final phase of development coincided with the implementation of fully automated fabrication. As mentioned in part one, ideally, the base of a transistor should be as thin as possible for the highest frequency of operation. But the base still needs an electrical contact made to it, and such contacts have practical size limits. Mesa technology used edge-etching to define the edges of the junctions, potentially exposing the junctions to contamination. The collector should also ideally have excellent conductivity (for the least possible electrical resistance and best high-frequency performance), but this demands doping too heavy for practical devices, as it gives very high collector-base capacitances. A very thin collector with light doping would give the desired low resistance and low capacitance. But, as this would be too fragile for practical devices, some compromise was always forced on designers. Epitaxial planar Howard Christensen and Gordon Teal’s 1951 patent solved the thickness/resistivity problem by showing how to grow a very thin and lightly doped semiconductor layer over a more heavily-doped thicker substrate (https://patents.google.com/patent/ US2692839A). Jean Hoerni’s patent of March 20th 1962 demonstrated an advance on Mesa technology: epitaxial planar manufacture, using Christensen and Teal’s epitaxial process (https://patents.google. com/patent/US3025589A). The epitaxial (“arranged around”) layer has an identical crystalline structure to the substrate, but can have any degree of doping concentration and even the opposite doping type. This remains essentially the state-of-theart for semiconductor manufacture to the present day. Like the Mesa process, Hoerni’s technique uses double-diffusion: base into collector, emitter into base. Fig.36 shows the manufacturing of diodes with this technique. A lightly-­ doped N-type epitaxial layer is grown over the N-type substrate using gaseous diffusion – basically, a form of controlled condensation. The substrate is coated with photo-­ resist, then masked. Ultraviolet light shines through the mask, hardening the exposed resist layer. The unexposed resist is washed off, and the slice is exposed to a P-type doping gas to form a diode. After washing off the exposed resist, the anode and cathode connections are made, and the diode is complete. This gives the desired thin, lightly-­ doped layer needed for when the process continues to manufacture transistors (as shown in Fig.37). It has a low-capacitance junction in contact with a sturdy and highly conductive layer below. Beginning with the diode structure, the slice is resist-coated, masked and UV-exposed to leave part of the existing P-type diffusion unprotected. After washing off the undeveloped resist, the slice is exposed to N-type doping, which diffuses into the base. This gives the N-P-N structure for a transistor. Finally, the entire surface is oxidised to form a silicon dioxide protective surface. This oxidation phase makes epitaxial planar manufacturing modern transistor manufacturing processes. same steps to add the third (emitter) layer. siliconchip.com.au Australia's electronics magazine April 2022  45 Fig.39: a Fairchild ► epitaxial transistor die. The star shape conferred some performance advantages over a circle. Source: Fairchild Fig.38: a finished epitaxial planar transistor. The silicon dioxide (SiO2) layer on top insulates the transistor and provides a barrier against moisture and contaminants. This allows the transistor to be housed in a low-cost plastic package. unsuited to germanium devices: germanium oxide is soluble in water and fails to form a protective layer. A final masking-etching step produces small apertures in the SiO2 mask to allow metallisation for emitter and base contacts, as shown in Fig.38. Alternatively, it’s possible to diffuse directly through the SiO2 layer to make contact with the desired areas. The active device now has a thick substrate for strength with low resistance, a collector layer with the desired lighter degree of doping needed for transistor action and low collector capacitance, a diffused base layer and an emitter layer diffused into the base. This leaves a base layer of the desired thinness for the intended maximum operating frequency. The collector contact is made to the collector substrate. Individual transistors are robotically tested, the slice is broken up, ‘good’ chips are selected and encapsulated with connecting leads attached. The SiO2 passivation layer’s robustness makes encapsulation in cheap epoxy resin possible; germanium Mesa devices needed metallic casings to guarantee hermetic sealing. Fairchild released their 2N709 in March 1960, with a maximum operating frequency of 600MHz. The 2N709A pushed this to 900MHz. A final advantage of photolithography is the ability to create devices of any geometry. Simple circular cross-section devices do not give the best RF performance, especially at high power levels. Mesa and planar devices can use complex geometries unobtainable by previous processes. Fig.39 shows a microscope photograph of a star-shaped Motorola epitaxial 2N2222 transistor die. 46 Silicon Chip Note that all illustrations in this (and the previous) article significantly exaggerate the base thickness (and emitter, in some cases). In practice, base thickness is measured in micrometres. Several fine publications have attempted to give some impression of the true scale of fabrication, but the results are difficult to interpret because of their attempted fidelity. Fig.40 is an original alloy-diffused diagram from Mullard’s Reference Manual of Transistor Circuits (at approximate full size here), illustrating the problem of accurate visualisation. Silicon’s advantages over germanium Germanium’s relatively low melting point of 940°C made it the material of preference for point-contact and early junction transistors, but it has fallen into disuse for several reasons. Silicon NPN and PNP annular epitaxial transistors ... Designed for complementary high-speed switching applications and DC to 100 mc amplifier applications. First, the collector-base junction proved to have significant reverse (leakage) currents even with no forward base bias applied, meaning that the transistor could never be truly cut off. These leakage currents worsened at elevated temperatures. While this might be tolerable in diodes, leakage in transistors could lead to rapid increases in collector current. Such increased current causes increased heating, causing increased leakage, causing increased heating... this is thermal runaway. Think of a 1960s car radio in the middle of summer; cabin temperatures could easily exceed 50°C. In a power transistor, the device can rapidly increase its current from its desired bias value (of milliamps) to a current of many amps and be destroyed by overheating. Circuit designs must stabilise the transistor against such current variations. Also, Fig.40: this diagram from Mullard attempts to show the features of a transistor at actual size, making some of the details such as the base layer hard to see, as they are so thin compared to everything else. Source: Mullard Reference Manual of Transistor Circuits, 1960 Australia's electronics magazine siliconchip.com.au germanium junctions can only operate to about 70~90°C while silicon devices are commonly specified up to 200°C (although 175°C is more typical). One early car radio was notorious for its OC72 germanium output transistors overheating and being destroyed. Silicon junctions exhibit much lower leakage currents, giving better performance, especially at high power levels and high temperatures. Thermal runaway must still be considered, but it is far less of a problem with silicon. Also, silicon is much more plentiful. If you’ve ever rinsed sand out of your bathers, you’ve rid yourself of the raw material for thousands of transistors and many microprocessors! Germanium is a rare element. Back in the 1950s, germanium ore was so scarce that one transistor manufacturer was forced into recovering germanium from the flue ash of power stations. It’s still scarce, as expressed by its 2018 price of some $2600/kg, with pure silicon costing as little as $50/kg. Silicon’s advantages are somewhat counterbalanced by its much higher manufacturing temperatures (almost 1400°C) and the difficulties of adapting germanium manufacturing techniques. Impurity doping methods that worked well with germanium had to be modified. For this and other reasons, early silicon transistors performed poorly at high frequencies. Parallel advances in mass production techniques gave them an initial cost advantage, however. Once begun, silicon processing developed rapidly. Silicon did offer one major manufacturing advantage over germanium: the oxide of silicon (basically, glass) is highly insulating and resistant to liquid or gaseous contamination. Silicon devices could be ‘finished’ with a final layer of SiO2, creating localised hermetic sealing, greatly improving reliability and allowing encapsulation in cheap epoxy resins. Germanium dioxide lacks these properties. Early silicon transistors offered little performance improvement over germanium types. Still, manufacturers focused their efforts on improvement, finally offering devices superior in every parameter except for base bias voltage: about 0.6~0.7V for silicon compared to 0.15~0.25V for germanium. This single advantage was insufficient to outweigh germanium’s disadvantages. Gordon Teal somewhat mischiesiliconchip.com.au vously sprang TI’s first silicon transistors on an amazed IRE National Conference in Dayton, Ohio in 1954. TI’s silicon devices rapidly supplanted germanium types. This advance contributed to the total collapse of Philco’s and Raytheon’s transistor divisions, as they could not rapidly shift from germanium feedstock and processes to silicon. Growing from a humble electrical company founded in 1892, Philco became a supplier of batteries for first-generation electric vehicles in 1906 and was the creator of the first all-transistor portable television and the world’s first all-transistor computer. Despite landmark aerospace and computing contracts, Ford bought out Philco in 1961 and ceased to exist as an independent corporation. By the 1960s, silicon had become the dominant material for semiconductor fabrication. A final ‘wrinkle’ in the story is that, for alloyed germanium, the PNP structure is optimal, but for silicon planar, it’s NPN! Now we know why all those germanium Philips transistors in our junk boxes need a negative battery supply, and why their silicon cousins need the opposite. Simply, it’s all about doping. Why not tetrode construction? All modern transistors, aside from dual-gate FETs, are triodes (ie, they have three terminals). Compare this to valves where triodes gave way to tetrode and then to pentodes in amplifying circuits. Junction transistors are built from three distinct layers – emitter, base, collector – and the device current originating from the emitter must pass through the base layer to arrive at the collector. This current path is equivalent to that of a thermionic triode, where the cathode current must pass through the grid to reach the anode. Field-effect transistors have no ‘intermediate’ electrode between the source and drain. Source current passes directly along the channel, but is influenced by the electrical bias field from the gate. Part of the reason behind the popularity of tetrode and pentode valves has to do with two principal limitations of thermionic triode operation. First, the proximity of the anode to the grid created significant capacitance that limited triode performance at high frequencies. This problem was eventually solved by the addition of the screen grid, creating the tetrode. A valve tetrode’s electron stream simply passes through the screen’s thin wire helix. Such screening construction proved impractical with junction transistors, so the problem of collector-base capacitance could not be eliminated. Designers had to work to reduce the existing collector-base capacitance to the lowest possible value instead. Tetrode transistors were made, but they still possessed only two junctions, as shown in Fig.41. The extra connection went to the opposite side of the usual base contact. Applying a repelling bias to the B2 connection forced charges away from that side, narrowing the flow of charge carriers. In effect, the active junction’s area could be controlled electrically. Fig.41: dual-base or ‘tetrode’ transistors were created early on to overcome some limitations of the transistor technology of the time. But since then, other ways have been found to improve the transistor’s performance. So except for a few dual-gate Mosfets or Mosfets with separate substrate connections, pretty much all modern transistors have three terminals. Australia's electronics magazine April 2022  47 This improved high-frequency performance; the amount of internal resistance in the electrically-smaller base slice was reduced, as was the base-­ collector capacitance. Tetrode transistors enjoyed a brief period of implementation but were overtaken by improvements in ‘triode’ designs, and are now obsolete. The second reason for using the screen grid in valve amplifiers was to achieve much higher voltage gain than triodes could provide. That was a discovery made after the primary aim of reduced anode-grid capacitance had been achieved. Thermionic triode voltage gains are limited by the fact that the anode voltage affects anode current; lower anode voltages mean lower anode currents. The ratio of grid control of anode current to anode control of anode current is the valve’s amplification factor, its mu (µ). Valve voltage amplifier triodes have µ values from around 3 to 100, with the ‘negative feedback’ effect of anode voltage forbidding any higher practical gain. Even early tetrodes gave µ values of several hundred or more, and the 6AU6 pentode can give a µ as high as 5000. The screen grids of tetrode and pentode designs eliminate the ‘feedback’ effect of anode voltage; anode current remains virtually unchanged with changing anode voltages. This can be expressed in either of two ways: the valve appears in-circuit as a very high resistance, acting as a constant current device, and the characteristic curves are virtually flat above some 20% of normal operating voltage. Transistors, both junction and field-effect, all exhibit ‘pentode’, constant-current characteristics as amplifiers. Changes in collector (or drain) voltage have little effect on current. Transistor output resistances or impedances range typically from tens to thousands of kilohms. Such characteristics mean that, even if a screen layer could be added, it would deliver little extra in the way of gain. Mullard detail a (triode) OC70 circuit with a voltage gain of 330; about the same as available from the 6AU6 pentode valve (Mullard Reference Manual of Transistor Circuits, 1960). from output back to input). Field-effect transistors (FETs) JFETs (junction FETs) and Mosfets (metal oxide semiconductor FETs) are important types of transistors and will be covered in some detail in the following article next month. Why are they called “transistors”? Many references state that the name “transistor” is a combination of ‘transFeedback in transistors fer/transconductance’ and resistor. As triodes, junction transistors However, a May 28th, 1946 survey exhibit considerable collector-base conducted by Bell Labs offered “a discapacitance, and this has the same cussion of some proposed names”. The circuit effect as for valves – reduc- list encompassed the awkward (“surtion of input impedance and poten- face state triode”) and the whimsical tial oscillation. (“iotatron”). The first-generation alloyed-­ The successful candidate, “transisjunction transistors suffered particu- tor” was “an abbreviated combination larly from collector-base capacitance. of the words ‘transconductance’ (or OC44/45 specifications show feedback ‘transfer’) and ‘varistor’” – see www. capacitances of some 10pF. Given that beatriceco.com/bti/porticus/bell/pdf/ valve triodes proved unworkable with transistorname.pdf these kinds of capacitances, how were Some other sources differ on just transistor triodes used? how the name was arrived at, but this Transistor base-emitter junctions at least seems credible. are forward-biased. This means that transistors present a very low input Summary impedance. At audio frequencies, the Solid-state devices had been demonOC44 has an input impedance of some strated before the start of the 20th cen2.5kW. This low impedance reduces tury and were well-known by 1920. the effect of collector-base feedback, Julius Lilienfeld patented the two and such feedback has little effect at types of amplifying devices that we audio frequencies. now recognise as transistors in the In RF/IF amplifiers, collector-base mid-1930s. His patents were not comfeedback can be so severe as to reduce mercialised, though the Bell Laboratogain or provoke oscillation. The ries team referenced them, and Lilienunwanted in-circuit feedback is com- feld’s patents did forestall some lines plex due to combined capacitive and of enquiry at Bell Labs. resistive effects. The most thorough Building on the development of designs add external components to microwave diode detectors during provide unilateralisation – a fancy World War II, a Bell Laboratories team, name for “single-direction” (signal including John Bardeen and Walter flow is only from input to output, not Brattain and led by William Shockley, published details of the point-­ contact transistor. The device showed the practicalities of solid-state design, but it was difficult to manufacture, fragile and unusable in some circuit configurations. Slightly in advance of Bardeen and Brattain, Welker and Mataré (working in France) released the Transistron, which was successfully taken up by French telecommunications companies. Fig.42: a Mosfet is similar to a JFET, but instead of using a reverse-biased PN Shockley had not been named on junction to isolate the gate from the channel, it uses an extremely thin layer of the landmark Bell Labs’ patent. His semiconductor oxide. The gate's electric field typically enhances electron/hole inventive spirit drove him to develop flow in the channel when applied; it is pinched off otherwise. These are thus and patent the junction transistor – the known as ‘enhancement mode’ devices. More on Mosfets next month. 48 Silicon Chip Australia's electronics magazine siliconchip.com.au device we now universally recognised as the transistor. But Shockley’s patent was a theoretical paper, showing the principles but not the manufacturing details. The first grown-junction transistor created a single crystal device that exhibited much more stable, predictable and reliable characteristics than point-contact designs. However, it suffered from poor high-frequency operation due to its thick base layer. The alloyed junction design, using much more controllable doping by diffusion at near melting-point temperatures, offered much thinner base layers and could operate to 30MHz. This was improved on by the drift-field design, which employed graded doping across the base and pushed frequency limits to 60MHz. The alloy-diffused design abandoned the two-sided construction of all types so far, building the transistor over the collector substrate. The base was diffused into the collector, followed by emitter alloying into the base layer. The Mesa design further developed the all-diffusion process. The final design – epitaxial planar V – uses a thin, lightly-doped epitaxial layer over a heavily-doped substrate giving low resistance; together, these form the collector. The base and emitter are diffused into the collector substrate. Photolithographic masking allows transistors to be fabricated to tiny sizes, with outstanding reliability and reproducibility. The first transistors were fabricated in germanium. Germanium’s temperature sensitivity, leakage, scarcity and its oxide surface’s solubility led to its replacement by silicon as a feedstock. Although alloyed silicon processing was initially more difficult to engineer, its advantages over germanium have seen germanium phased out. References/links • The most comprehensive and best single collection of references available (created by Mark P. D. Burgess): siliconchip.com.au/link/abcj • A replica and description of the first transistor: siliconchip.com.au/ link/abce • A fine general history of transistors: siliconchip.com.au/link/abcf • A detailed description and analysis by van Zeghbroeck: siliconchip.com. au/link/abcg • On diffused transistors generally: https://w.wiki/4fiz • Early History of Transistors in Germany, Herzog, R., 2001: siliconchip. com.au/link/abch • Transistor Production Techniques Next month at RCA, Fahnestock, J. D. ElectronThis article has described the tran- ics, October 1953: siliconchip.com. sistor mass-production techniques au/link/abci that are still in use today. The follow- • RCA Transistor Manual 1964, Radio ing article will explain in more detail Corporation of America how a transistor works, including • Crystal Fire, Riordan, M., and Hodbipolar transistors as well as field-­ deson, L., W. W. Norton and Company, effect transistors (FETs). It will also ISBN 13:978-0-393-31851-7 give some pertinent performance • History of Semiconductor Engicharacteristics, including a descrip- neering, Lojek, B. Springer-Verlag tion of the limitations of transistor Berlin Heidelberg, ISBN-13 978-3SC performance. 540-34257-1 intage Radio Collection March 1988 – December 2019 Updated with over 30 years of content Includes every Vintage Radio article published in Silicon Chip from March 1988 to December 2019. In total it contains 404 (not an error) articles to read, or nearly 150 more articles than before. Supplied as quality PDFs on a 32GB custom USB All articles are supplied at 300DPI, providing a more detailed image over even the print magazine. Physical and digital versions available Buying the USB gives you access to the downloadable copies at no extra charge. Or if you prefer, you can just buy the download version of the Collection. Own the old collection on DVD? If you already purchased the previous Collection on DVD, you can buy this updated version for the discounted price of $30 on USB (plus postage), or $20 for the download version. $50 PDF Download SC4721 siliconchip.com.au/Shop/3/4721 $70 USB + Download SC6139 siliconchip.com.au/Shop/3/6139 Postage is $10 within Australia for the USB. See our website for overseas & express post rates. siliconchip.com.au Australia's electronics magazine April 2022  49 Semaphore Signal For OO Gauge Model Railways This realistic-looking OO Gauge Semaphore has been modelled on a real British semaphore. It has a red/white ‘flag’ that tilts down by 45° and lights a green LED to signal an oncoming train to continue, or is horizontal with a red light, indicating it should stop. It’s made from parts that are relatively easy to obtain, although it requires some machine tools and experience to build. S emaphore signalling was one of the first signalling systems used by railways. Semaphore signals were first patented in England in the early 1840s. They were so successful that they were adopted throughout the railway world. With the advent of coloured lights, they were slowly replaced, but a few remain in use. Adding them to a model railway makes it look very realistic. British signals come in two forms: lower and upper quadrant. Lower quadrant signals pivot the arm downwards for the off indication (trains can pass), while upper quadrant signals pivot the arm upwards for off. I decided to make a lower quadrant signal as most of the old signal photos I found showed this form. Current British practice mandates that semaphore signals, both upper and lower quadrant types, are inclined at 45° from horizontal to indicate ‘off’. 50 Silicon Chip The British semaphore signal arm consists of two parts: a timber or metal arm (or ‘blade’) that pivots at different angles and a ‘spectacle’ holding coloured lenses that move in front of a lamp so the signal is visible at night. To save having to make coloured lenses, the lamp is replaced with a 3mm red/green bicolour LED in the model. When the arm is horizontal, the red colour is switched on, and when it is down, the green colour is on. A miniature servo motor moves the signal arm up and down (see Fig.1). The servo collar is connected to the connecting rod (#10), which in turn is connected to the lever (#3). When the servo moves through 45°, the connecting lever does the same. As the connecting lever is joined to the signal blade by the pin (#4), the signal BY LES KERR Australia's electronics magazine blade follows the movement of the servo collar. In real life, the height of the signal blade above ground was determined by how far away it could be seen from an approaching train. If you only have a small layout, you can easily lower its height to make it look to scale. This is done simply by reducing the length of the connecting rod (#10) and the mounting pole (#11). We will present details of both the mechanical and electronic assembly. Just about any hobbyist should be able to assemble the control board as it is a simple single-sided design using all through-hole parts. However, note that making the parts for the mechanical assembly will require some machining experience and some advanced tools. Specifically, you will need a lathe; just about any small one will do, as long as it’s built to reasonable siliconchip.com.au Fig.1: this shows in detail what the Semaphore Signal looks like when it’s assembled and where all the pieces go. It’s essential to refer to this diagram during each construction step to make sure the parts go together correctly. tolerances. Most of the machining involves either brass or aluminium, both of which are relatively soft. You will also need a precise drill press and a good selection of drill bits. While you can probably get away without it, to produce an exact copy of the Semaphore presented here, you will also need a basic mill with an end mill tool, and the knowledge and ability to use it. A video showing the Semaphore in operation: siliconchip.com.au/Videos/ Model+Railway+Semaphore+Signal Circuit description The straightforward controlling circuit is shown in Fig.2. The speed at which a servo motor rotates is a function of the servo itself. In the case of the semaphore signal, we need it to rotate much slower than its maximum speed to make it look realistic. This is achieved by feeding a series of pulses to the servo’s control terminal, with a time delay between each pulse. When the up/down switch (S1) is siliconchip.com.au moved to the up position, digital input RB0 of microcontroller IC1 (pin 6) goes high, causing the microcontroller to produce a series of such pulses at its digital output RB1 (pin 7). The result is that the servo motor moves slowly clockwise by 45°. At the same time, digital output RB2 (pin 8) is brought high and output RB5 (pin 11) low, causing the red LED to light. The 100nF capacitor from pin 6 of IC1 to +5V stops any contact bounce produced by the switch. If the switch is returned to the down position, RB0 is pulled low by the 10kW resistor, resulting in another series of pulses from output RB1 that return the servo motor to its original position. At the same time, output RB2 goes low and output RB5 high, resulting in the LED changing colour back to green. Servo motors are not as accurate as stepper motors when moving through a specific angle, being out by as much as 10%. Similarly, any variation in the position of the signal blade hole, the LED plate or the connecting lever and Australia's electronics magazine The finished Semaphore will look like this, with wires connected to the PCB. April 2022  51 Fig.2: the control circuit, which runs from a 5V supply, is quite simple. Microcontroller IC1 monitors switch S1 and, depending on its position, sends pulses to the servo to control its angle while lighting either the red or green elements of LED1. Trimpots VR1 & VR2 fine-tune the angles of the flag in the horizontal and down positions, respectively. the servo collar can produce errors. To solve this, two 1kW trimpots are provided. The first varies the position of the signal blade in the horizontal position, and the second in the 45° down position. The trim potentiometers vary the voltage on analog inputs RA0 and RB7 of IC1 (pins 17 & 13, respectively). These feed into IC1’s internal analog-to-digital converter (ADC) which converts the voltages into numbers. The microprocessor uses these values to determine the pulse widths to produce in the two static positions. Mechanical assembly Many of the mechanical Semaphore parts need to be made, and the details of these are shown in Fig.3 (#1-9) and Fig.4 (#10-14). They are made as follows. #1 Cap and cap pin I turned the cap from a piece of 6mm aluminium rod by mounting the rod in the three-jaw chuck of a lathe, facing the end (ie, squaring it off) and turning down the diameter to 5.2mm for 5mm. I then cut the 127.6° taper. I reversed the job in the chuck and parted it off to 3mm, then used a centre drill followed by a 2mm drill to a depth of 2mm, taking care not to break through to the taper. I made the cap pin from an 8mm length of 2mm rod, glued in the hole I drilled in the cap using Loctite GO2 (available from Bunnings). The shape of this item isn’t critical, as it varied between different signal 52 Silicon Chip manufacturers. Paint the cap assembly red. #2 LED plate I made this from a piece of 1/32-inch (0.8mm) thick brass sheet. The distance between the holes is the critical dimension. Drill the holes, then cut the plate to size. Finally, clean up the edges. #3 Connecting lever This was made from a piece of 1/16-inch (1.6mm) thick, 1/4-inch (6.35mm) wide brass. Again, the distance between the holes is critical. Drill the holes first, then cut and file the lever to size. Paint the connecting lever blue-black. #4 Pin Cut a piece of 1/16-inch (1.6mm) diameter steel rod to a length of 11mm. Clean up any burrs on the ends. #5 Pillar (4 required) Similarly, I made these from 0.8mm diameter (1/32-inch) brass rod cut to 12mm in length. Again, clean up any burrs on the ends. #6 Railing This was also made from 0.8mm (1/32-inch) diameter brass rod. I turned a short length of scrap round to 11.2mm diameter and used that as a mandrel to form the curve. A small amount of heat applied by a gas torch makes bending easier. #7 Platform base This is made from a piece of 1/32inch (0.8mm) brass sheet. Drill all the holes, then cut the plate to size. Next, using a fine saw and file, cut out the square section so that it is a tight fit around the 1/8 inch square mounting Australia's electronics magazine pole (see #11 below). Finally, clean up the edges. #8 Ladder support This is made from a length of 0.8mm (1/32-inch) diameter brass rod. Use a piece of 1/8-inch (3.2mm) square brass as a mandrel to form the shape. Again, a small amount of heat applied by a gas torch makes bending much easier. #9 Support Place a piece of 12mm diameter aluminium rod in the three-jaw chuck of a lathe and face the end. Turn it down to 20mm to make it a slide fit in a 3/8-inch (9.5mm) diameter hole. Use a centre drill followed by a 4.3mm (11/64-inch) drill to bore it out to a depth of 20mm. Next, reduce the end to 5.25mm diameter for 8mm and part it off to length. Finally, drill and tap the hole in the side for the 2.5mm grub screw. Paint the support blue-black and when dry, then fit the 2.5mm grub screw. #10 Connecting rod I made this from 0.8mm (1/32-inch) diameter brass rod. Bend one end of the rod through 90° but only bend the other through about 20°. This is because the rod has to pass through the 2.6mm hole in the 5.5mm-thick base. We will bend it to 90° later in the assembly process. Paint the connecting rod blue-black. #11 Mounting pole The mounting pole is made from a length of 1/8-inch (3.2mm) square hollow brass tube. Drill the 1/16-inch (1.6mm) diameter hole at 92mm from the pole end. You can make the slot by drilling two 1mm holes 1mm apart siliconchip.com.au Fig.3: this shows the smaller parts (#1-#9) that need to be made. Some can be made on a lathe, while others require a saw, files and drilling. #6 and #8 are made by bending thin cylindrical bar stock on rectangular formers. Note that all dimensions are in millimetres. Fig.4: the remaining parts to make, including the larger items (#10-#12) plus a detailed view of the partially assembled Semaphore at right. siliconchip.com.au Australia's electronics magazine April 2022  53 and using a file to remove the remaining metal. Make sure that the insides of the slot and the insides of each end are free of swarf and are smooth, as when we insert the LED wires, we don’t want to cut their insulation. #12 Base My layout is made on a 2-inch (51mm) thick sheet of polyurethane foam. I buried the signal in the foam so that it was flush with the top of the base. This left a 0.5mm step down all around the Semaphore that I later filled with ornamental grass, so that the base was more in keeping with the scale. Depending on your layout, you might decide to leave out this step down. The base is made from 6mm aluminium plate. Cut it to size, then drill and tap the required holes. I made the step using an end mill in a milling machine. Paint the base blue-black and when dry, fit the 2.5mm grub screw. #13 Servo bracket This is made from 1/16-inch (1.6mm) thick aluminium sheet. Drill the two 3mm holes 29mm apart, then cut it to size. Clean up the edges with a file. #14 Servo collar Place a length of 12mm diameter aluminium bar in the lathe three-jaw chuck, face the end and turn it down to a diameter of 9.8 mm for 10mm. Bore it out to a depth of at least 5mm using a centre drill followed by a 4.8mm diameter drill. Part off a 3mm section, transfer this to the drilling machine and drill the 2mm hole for the grub screw. Thread the hole with a 2.5mm tap and fit the grub screw. Finally, drill the 0.8mm diameter hole exactly 4mm from the centre. Parts List – Semaphore Signal 1 single-sided PCB coded 09103221, 51 x 37mm (controller) 1 double-sided red PCB coded 09103222, 31 x 20.5mm (blade) 1 PIC16F88-I/P microcontroller programmed with 0910322A.hex (IC1) 1 5V DC power supply 1 DF9GMS 9g micro servo [Core electronics SER0006] 1 18-pin DIL socket (optional; for IC1) 2 1kW mini top-adjust trimpots (VR1, VR2) 1 3mm red/green LED, three-lead type (LED1) [element14 Cat 2148798] 1 miniature SPDT toggle switch (S1) [Jaycar ST0300] 2 M3 x 16mm panhead machine screws (for mounting servo) 10 1mm PCB pins 1 10mm length of 1mm diameter heatshrink tubing various lengths & colours of light-duty hookup wire 1 tube of Loctite GO2 adhesive 1 tube of Tarzan’s Grip or similar adhesive Capacitors 1 100μF 16V electrolytic 2 10μF 16V electrolytic 2 100nF 50V multi-layer ceramic Resistors (all 0.25W 1% metal film) 1 10kW 1 5.6kW 1 4.7kW 1 2.2kW 1 820W 2 680W Mechanical parts 1 300mm+ lengths of 0.8mm (1/32-inch) diameter brass rod 1 20mm+ length of 1.6mm (1/16-inch) diameter steel rod 1 20mm+ length of 2mm diameter aluminium rod 1 20mm+ length of 6mm diameter aluminium rod 1 40mm+ length of 12mm diameter aluminium rod 1 103mm length of 3.2mm (1/8-inch) square hollow brass tube [KS Metal] 1 20mm+ length of 1.6mm (1/16-inch) thick, 6.53mm (1/4-inch) wide brass bar 1 20 x 20mm rectangle of 0.8mm (1/32-inch) thick brass sheet 1 46 x 55mm rectangle of 6mm-thick aluminium sheet 1 35 x 7.5mm rectangle of 1/16-inch (1.6mm) thick aluminium sheet 1 OO-scale ladder [D.J.’s Models] 3 2.5mm grub screws 54 Silicon Chip Australia's electronics magazine Mechanical assembly With the parts now made, refer back to Fig.1 to see how they all go together. The LED plate (#2), platform (#7) and ladder support (#8) are all soldered to the mounting post. Clean, tin and flux the mating surfaces between the LED plate and the mounting post. Insert a temporary pin in the 1/16-inch (1.6mm) hole and use it to align the two pieces. Using a small blowtorch, heat the assembly until you see solder coming out of the joint. File off any excess solder. Now clean, tin and flux the mating surfaces between the platform and the mounting post. To align the plate squarely, use a small timber cube as a support and clamp it to the mounting post. Using a small blowtorch, heat the assembly until you see solder coming out of the joint. The next step is to solder the four 12mm pillars into the platform. Do this one at a time using a soldering iron. To keep them vertical in this operation, drill a 0.8mm hole vertically into a piece of scrap timber into which you insert the pin. The railing can then be soldered into place, making sure it is parallel to the platform. File off any excess solder. Next, clean, tin and flux the mating surfaces between the ladder support and the mounting post. To keep it level, make a small timber cube for it to rest on and clamp that to the mounting post. Using a small blowtorch, heat the assembly until you see solder coming out of the joint. File off any excess solder. The whole assembly can then be painted white. Signal blade The signal blade can be purchased as a PCB, coded 09103222 and measuring 31 x 20.5mm – see Fig.5. Using a small pair of side cutters, carefully remove the blade from the PCB. You can also snap it at the weak points deliberately created by holes drilled into the supports. Clean up the blade edges with a file. The PCB should already be coloured red/white, and you can easily paint the spectacle area (see Fig.6) by masking it and applying spray paint, painting it with a brush, or even using a black permanent marker. However, if you aren’t happy with the PCB colour, or you made the flag some other way, you can download the artwork (Fig.6) from the Silicon siliconchip.com.au Chip website, print it on a colour printer and cut out the front and back shapes. Use two-part five-minute epoxy to glue the front shape onto the face of the blade. Once dry, carefully clear the paper from the holes. Glue the rear label on and again remove the paper from the holes. should rotate 45° anti-clockwise while the LED should change to green. Add the short again and switch off the power. Leave the servo in this position as it will make the final assembly process easier. Now is a good time to give the bottom of the PCB a coat of clear varnish to protect it from corrosion. Control module Final assembly The heart of the semaphore signal is built on a single-sided PCB coded 09103221, which measures 51 x 37mm. Fig.7 is the PCB component overlay diagram. Start its assembly by fitting the PCB pins, then the IC socket. The reason for the IC socket is that there is no provision for in-circuit programming, although if you have purchased a pre-programmed micro, you could just solder it to the board. Alternatively, if you have a blank micro, download the firmware from the Silicon Chip website and program it using an external programmer now, before fitting it. Take care to orientate the socket/ IC correctly. Next, add the vertically-­ mounted resistors; you can replace the 0W resistor with a wire link. Follow with the capacitors; check that the electrolytic types are the correct way around, with the longer leads to the + symbols. Next, add the 1kW trimmer potentiometers and temporarily connect the servo motor and LED1 (as per Fig.8). Finally, connect the positive of the 5V power pack to +5V and the negative to 0V. Check that all the connections are correct and that there are no dry joints or solder bridges. At this stage, don’t plug in IC1 yet if you have used a socket. Refer back to Fig.1 during final assembly to see how the Semaphore goes together. 1. Push the red/green LED into the LED plate. Before trimming the leads as short as possible, note which is the shortest as this connects to the red LED. The centre lead is the common, and the other goes to the green LED. 2. The connecting wires must be very fine to fit through the mounting pole. I found suitable wires in an old computer mouse connecting cable. I selected red, yellow and black and made them about 300mm long. Using a fine-tipped soldering iron, connect the red wire to the red LED terminal, the yellow wire to the green LED terminal and the black wire to the common (middle) terminal. 3. Cut a 5mm length of 1mm diameter heatshrink tubing and slide it over the wires. Insert the wires one at a time into the post until they protrude from the end. Be very careful not to strip the insulation off in this process. Straighten up the wires and shrink the tubing down over the exposed portion of the wires using a heat gun. 4. Insert #4 (the 1/16in [1.6mm] diameter steel pin) into the signal blade and lock it into place using Loctite GO2. When dry, slide the assembly into the mounting pole (#11). 5. Push the support (#9) into the base (#12) with the grub screw in the support on the right-hand side when looking at the front of the signal. Tighten the grub screw in the base. 6. Push the three wires at the bottom of the post through the hole in the support, then push the post into the support and lock it temporarily in place using the grub screw in the support. 7. Take the connecting rod (#10) and push the end with the 20° bend up through the base and platform to the signal blade height. Use pliers to increase the 20° bend to 90°. 8. Insert the end of the connecting rod into the 0.8mm (1/32in) hole in the connecting lever (#3) and push Testing Switch on the power supply and connect the negative lead of a voltmeter to pin 5 of the IC socket and the positive lead to pin 14. The meter should read +5V. If it reads -5V then the IC socket or IC is the wrong way around. Switch off the power and insert the IC (if you used a socket), checking that it is correctly orientated. Switch the power on, and the LED should glow green. Short S1’s two terminals together and the LED should now glow red, while the servo motor should rotate 45° clockwise (looking at the shaft). Remove the short, and the servo siliconchip.com.au Australia's electronics magazine Fig.5: the semaphore flag is too small for most PCB manufacturers to make by itself, but they will make this larger PCB which can be snapped or cut apart (at the holes represented by black filled circles) to give you something very close to the correct flag shape. After cutting or snapping it out, all you have to do is file the top and bottom edges flat. Fig.6: this artwork can be printed, cut out and glued to the flag if it isn’t already coloured or you aren’t happy with the colour or surface finish. Fig.7: it shouldn’t take long to assemble the PCB as it only has a handful of parts on it. Make sure the chip is programmed first if you’re going to solder it directly to the board and watch the orientations of the electrolytic capacitors (the longer leads are positive). April 2022  55 the pin attached to the signal blade into the 1.6mm (1/16-inch) hole in its other end. With the signal blade horizontal, adjust the position of the connecting lever so that it is parallel to the axis of the signal blade. Lock the connecting lever temporarily in place with a blob of Tarzan’s Grip or similar glue. 9. Attach the servo bracket (#13) to the base using the two 16mm M3 screws. Align the servo motor as shown in Fig.1, and attach the servo collar to the shaft with the grub screw hole at the bottom. 10. Loosen the grub screw holding the mounting post in place. Slide the servo motor assembly under the retaining bracket. By adjusting the height of the post, you should be able to align the connecting rod with the 0.8mm (1/32in) hole in the servo collar. Push the end of the connecting rod into the collar. 11. Move the servo until the connecting rod is vertical, then lock it in place by tightening the screws. Adjust the height of the column until the connecting lever at the top of the signal is horizontal. Tighten the grub screw holding the mounting post in place and the grub screw in the servo collar. 12. Check that the signal blade is parallel to the front of the mounting base. If it is not, loosen the grub screw in the base and rotate the post until it is. Tighten the grub screw. Wiring Wire up the signal as shown in the wiring diagram, Fig.8. Check this before applying power, as reversing the supply polarity will destroy IC1. Then, with the switch closed, apply power. The LED should glow red, and the signal blade should be horizontal. Open the switch; the LED should light green and the signal blade should move down about 45°. Operate the signal several times to make sure it changes over smoothly and that nothing is binding. Check the tightness of the three grub screws and the servo screws. The two potentiometers on the PCB allow you to fine-tune the position of the two holes over the LED in the signal blade. The potentiometer closer to the LED connections on the PCB (VR1) adjusts the position of the signal blade in the horizontal position and the other (VR2) in the down (45°) position. Once you are happy with the blade position, use a drop 56 Silicon Chip Fig.8: once you’ve assembled the Semaphore and the control PCB, here is how to wire them up. Be very careful to get this right, especially the 5V power and servo wiring, or you could damage IC1 or the servo when you apply power. of Loctite GO2 to glue the connecting lever in place. Fitting the cap and ladder Attach the red cap and pin assembly into the top of the mounting pole using Loctite GO2. Take one of the supplied ladder lengths and paint it blue-black. When dry, lay the ladder up against the platform support and check that the top rung is level with the platform. Cut it to size and use Loctite GO2 to glue the ladder to the platform and support. I deliberately didn’t glue the ladder to the base, as that would stop the post assembly from being adjusted later. Using it The Semaphore could be combined with a level crossing, such as my design (July 2021; siliconchip.com. au/Article/14921), or you could use it on its own, such as before a switch or a station. The simplest method is manual control. Position a toggle switch at a convenient location in the layout. With the Semaphore in the stop (horizontal) position, manually stop the train in front of it. Then, switch the Semaphore off at an appropriate time, and the train can move away. There are also methods to automate it. For example, if used near a level crossing, you could arrange for the Semaphore to usually be in the stop Australia's electronics magazine (horizontal) position and then automatically switch to the down position when the level crossing boom gates are fully down. It could change back to the stop position as soon as the boom gates start to lift. All you need to organise this is to have a microswitch or reed switch arranged so that it is open when the boom gates are fully down and closed the rest of the time. If you can’t easily do that, the other option is to use a delay circuit that’s triggered by the same signal that activates the level crossing. Set the delay so that it closes a set of relay contacts or activates an open-collector/drain transistor after the boom gates have had a chance to fully lower. Use those contacts or that transistor to trigger the Semaphore into its off position, and arrange it so that the contacts open or transistor switches off as soon as the Level Crossing trigger switches off. You could also consider positioning a reed switch under the tracks and placing a magnet in the train. This way, when the train pulls to a stop in front of the Semaphore, it triggers a delay circuit that disables the Semaphore signal after a couple of seconds. It would need to hold it off until the train has passed, possibly sensed by a second reed switch. I’ll leave the details of that arrangement as an exercise for the reader. SC siliconchip.com.au Gear Up & Build On Sale 24 March - 23 April 2022 8995 $ JUST 499 $ SAVE $10 IP67 True RMS Autoranging DMM Anycubic Resin 3D Printer 4000 display count. 600VDC CATIV rated. 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WATER RESISTANT FROM NOW FROM 169 99 $ $ 95 4K 2.4" LCD SAVE<at>$50 1080p Smart Wi-Fi Cameras QC3900 Used as standalone or as part of a system to keep an eye on your property. Built-in motion detection. 2-way audio. Indoor Pan Tilt QC3900 $99.95 Outdoor IR Illumination QC3864 $129 120° ANGLE VIEW Outdoor Trial Cameras Monitor local wildlife or use as an outdoor security camera. 10sec-3min motion detection recording onto microSD card up to 32GB (XC4992 $22.95 sold separately). Time lapse recording. 2.4” LCD. Requires 8 x AA batteries (SB2333 $7.95 sold separately). 1080p QC8043 NOW $169 SAVE $30 4K QC8051 NOW $249 SAVE $50 GREAT VALUE SECURITY SOLUTIONS NOW 14 95 $ SAVE $5 Reed Switch - Twin Pack Self-contained audible alarm for use on doors and windows. Quick installation. LA5209 JUST 8995 $ UP TO 6M EFFECTIVE RANGE NOW FROM 12 $ Doorway Beam Commercial grade, entry warning system designed for use in shops, restaurants etc. Mounting hardware included. LA5193 ALSO AVAILABLE: Additional Buzzer to suit LA5188 NOW $34.95 SAVE $10 More ways to pay: 95 SAVE 10% Dummy Cameras LA5332 Simple and effective visual deterrent. LA5325-LA5342 NOW 14 95 $ SAVE $5 12V Siren/Strobe Combined 120dB siren and strobe for alarm systems. LA5306 Portable Power FROM 3995 $ QUICK CHARGE USB PORT Modified Sine Wave Inverters Get 240VAC mains power from your 12VDC source (i.e batteries). Will power electronic devices such as laptops, battery chargers, etc. Includes battery connections and a 5V USB outlet. 150W up to 1500W models available. MI5300-MI5310 79 $ • POWERFUL • FAST RECHARGE • LONG LIFE • PORTABLE ONLY 399 $ 12.8V Lithium Deep Cycle Batteries 12V 200W Solar Blanket Drop in replacement for most lead acid batteries. Featuring up to 10 times the battery cycle life with only half the weight of its lead-acid equivalent. 7Ah up to 200Ah models available. SB2210-SB2217 Foldable with charge controller, battery clamps, carry bag and lead included. ZM9124 JUST 199 PT4444 $ $ FROM 1695 High Current 50A Connector Leads 30cm long adaptors or 5m extension. 5 types available. PT4440-PT4448 JUST 14 95 PT4446 $ 1YR WARRANTY ANL In-line Fuse Holder High current nickel plated solid brass fuse holder. Mounts securely, removable lid for easy maintenance. SZ2078 MUCH LIGHTER & TAKE UP LESS SPACE THAN TRADITIONAL FOLD-UP PANELS 355mm 180mm FROM 2 X 50A HIGH CURRENT CONNECTORS 12V/24V DC Control Box ILLUMINATED SWITCHES This control box has a heap of connections all in one place. 6 switches, 3 cigarette sockets, 2 high current 50A sockets, dual USB a power meter and fuse panel. Mounting Hardware included.HB8520 TURN A 12V BATTERY INTO A POWER STATION AUTO & COMMS INCLUDES 2 RADIOS, BATTERY PACKS, CHARGERS & MORE BONUS* 16GB microSD Card Valued at $12.95 REVERSED IMAGE REFLECTS CORRECTLY ONTO WINDSCREEN NOW 4995 $ 2.5" LCD SAVE $10 Head Up Display Speedometer Keep your eyes on the road and read important driving info such as speed, RPM & battery voltage from an auto-brightness adjusted head-up display reflected off the windscreen when connected via OBD II. LA9036 JUST 6995 $ 1080p HD DVR Event Camera Automatic recording on impact in full HD, wide 170° angle lens. G-sensor function. Records to microSD (sold separately). QV3872 *XC5015 16GB microSD card with purchase of QV3872 Looking for more product information? Visit your local store or our website jaycar.com.au FROM 145 $ IP67 GME UHF Radio RATED -Compact Twin Packs and lightweight. Easily rechargeable via USB. Mains adaptor & leads included. 1W TX667TP DC9047 $145 2W TX677TP DC9049 $209 5W TX6160TP DC9053 $579 We reward our industry professionals Build & Code BEST SELLER NOW 8995 $ SAVE $10 JUST 5995 $ UNO BOARD INCLUDED BBC micro:bit V2 Starter Kit Arduino® Compatible Learning Kit Includes micro:bit V2 board, resistors, servo and all the necessary prototyping accessories to get you started in the world of electronics and coding. XC4326 Includes UNO board, breadboard, plenty of prototying hardware, modules, components and instruction booklet to get you started. XC3900 NOW NOW 69 $ 995 95 $ SAVE $10 SAVE 20% 37 Piece Deluxe Module Package Mega Prototype Shield with Breadboard Includes commonly used sensors and modules for Duinotech and Arduino®: joystick, magnetic, temperature, IR, LED and more. Packaged in a clear plastic organiser. XC4288 Gas Soldering Iron / Torch Kit Provides access to all of the MEGA pins and plenty of solder pads to prototype on. Stackable. XC4416 JUST 595 $ Everything you need to solder, silver solder, braze, heatshrink, strip paint etc. Extra soldering, torch and cutting tips included. TS1112 Also available: Soldering Iron only TS1111 NOW $24.95 SAVE $5 DON'T FORGET THE GAS! Soldering Gas Refiller NA1020 $4.95 MICRO:BIT BOARD INCLUDED EA FROM 550 $ NOW 2995 $ SAVE $10 Vero Type PC Boards 150mm Jumper Leads Plug to Plug WC6024 Socket to Socket WC6026 Plug to Socket WC6028 Alphanumeric grid, pre-drilled 0.9mm, 2.5mm spacing. 95mm wide. 75mm, 152mm, 305mm lengths available. HP9540-HP9544 NOW 6995 400+ PIECES $ SAVE $30 Smart Robot Kit Fun to build robot that uses a micro:bit board (sold separately) that you can code or control using Smartphone via Bluetooth®. KR9262 JUST 69 $ 95 Remote Controlled Robot Construction Kit Drives forwards, backwards, left, right or spin 360°. Turning head, Swinging arms. KR9238 NOW 4995 $ SAVE $20 ALL TERRAIN Tracked Robot Use the 6 terrestrial tracks/crawlers to create a working gripper, rover or forklift. KJ8918 NOW 89 $ IN-STORE ONLY SAVE $40 SuperBot Robot Kit Build 18 cool multi-functional models. Coding is done by graphical programming language. e.g Scratch. Compatible with major building block brands Ages 8+. KJ9354 iPad not included. Not sure what to build next? Here's some inspiration: jaycar.com.au/projects 400+ PIECES Double Up & Save 2 FOR 2 FOR 10 2 FOR 12 $ 15 $ SAVE 15% 18 $ SAVE 20% BUY 2 AND SAVE 2 FOR $ SAVE 20% BUY 2 AND SAVE SAVE 20% BUY 2 AND SAVE PIR Motion DC Voltage 2.4GHz Wireless Detector Module Regulator Module Transceiver Add motion detection to your project. Accepts voltage from 4.5- 35VDC, Module 0.3-18s adjustable delay. 5-20VDC. and outputs from 3-34VDC. XC4444 $5.95 EA JUST 24 95 $ Allows communication on the license free ISM band. Supports on-air data rates up to 2Mbps. XC4508 $9.95 EA 2.5A max output current. XC4514 $7.95 EA Assorted LED Paxk Contains 3mm and 5mm LEDs of mixed colours. ZD1694 JUST 1995 $ JST Connectors Kit Includes the popular JST XHP 2.54mm and PH 2.0mm housings & headers. Used for prototyping, repairs, and hobby applications. PT4457 FROM 12 95 $ BUY 2 AND SAVE 9G Micro Servo Motor Connect directly to an Arduino board. 3.5V-6V. Torque 1.6kg.cm <at> 4.8V. Arduino compatible. YM2758 $11.95 EA Prototype Resistor Packs 0.25W 5% Carbon film. 300 Pieces RR1680 $12.95 850 Pieces RR1697 $22.95 1700 Pieces RR2000 $39.95 JUST 1695 $ Quartz Clock Movement Self starting one second stepping motor. Supplied with three sets of hands. XC0100 MAKE OR REPAIR A CLOCK JUST 1995 $ 6-in-1 Solar Educational Kit Six different projects to build. Power from the sun or household 50W halogen light. Ages 10+. KJ8926 NOW 1995 $ SAVE $9 Salt Water Fuel Cell Engine Car Kit Demonstrate the concept of a salt powered automotive engine. 120mm long. KJ8960 ARDUINO® COMPATIBLE This icon indicates that the product will work in your Arduino® based project. JUST 2995 $ Mini Space Rail Construction Kit 170 PIECES Build your own marble rollercoaster. The spiral “elevator” lifts the marbles and gravity takes care of the rest. KJ9004 2pk C Batteries SB2416 $4.50 RASPBERRY PI COMPATIBLE This icon indicates that the product will work in your Raspberry Pi project. Workbench Heroes BEST SELLER BEST SELLER JUST 5995 $ Digital Multimeter with Temperature Measures voltage, resistance, capacitance, temperature and more. CATIII 600V 10A. 4000 count display. QM1323 BEST SELLER JUST 14 $ CURES UNDER UV JUST 5995 $ 48W Soldering Station Lightweight. Anti-slip grip. Temp range from 150°C to 450°C. Mains powered. TS1620 Precision 127mm Angled Side Cutters Bondic Liquid Plastic Welding Kit Bond, build, fix & fill virtually anything in seconds. Solvent-free. Stays liquid until cured with the included UV LED Light. NA1530 JUST EA 200g Duratech Solder 2995 LED Headband Magnifier Fits over prescription or safety glasses. Adjustable head strap. 1.5x, 3x, 8.5x or 10x magnification. Requires 2 x AAA batteries. QM3511 2 x AAA Batteries SB2426 $1.95 15g, 200g, 500g & 1kg available. FROM $3.45 NS3008 Easily cut leads, ideal for fine PCB work. Soft padded handles. Carbon steel. TH1897 JUST $ 60% Tin / 40% Lead. Resin cored. 0.71mm &1.0mm size available. NS3005-NS3010 95 44 95 $ 2995 $ JUST 25M EACH ROLL JUST 24 95 $ 160 PIECES 17 $ JUST 3995 $ JUST 95 Solder Flux Paste Non-flammable, non-corrosive. 56g tub. NS3070 Heatshrink Pack Contains 160 lengths of different sizes in a handy storage case. WH5524 Light Duty Hook-up Wire Pack Quality 13 x 0.12mm tinned hook-up wire on plastic spools. 8 rolls of different colour included. WH3009 SAVE ON WORKBENCH EQUIPMENT NOW 69 $ 95 55 PIECES BIT SET SAVE $20 Rechargeable Lithium-Ion Screwdriver Used for assembling or repairing phones, watches, laptops, etc. 150 RPM no load speed. USB rechargeable. TD2510 NOW 149 $ SAVE $50 20MHz USB Oscilloscope Ultra portable. USB interface plug & play. Automatic setup. Waveforms can be exported as Excel/Word files. Includes 2 probes. QC1929 NOW 199 $ SAVE $50 Solder/Desolder Rework Station 60W Soldering iron and 300W rework blower. Dual digital display. Adjustable temperature up to 480°C. Quick heat-up. TS1648 TERMS AND CONDITIONS: REWARDS / CLUB MEMBERS FREE GIFT, % SAVING DEALS, & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / membership at time of purchase. Refer to website for Rewards / membership T&Cs. INSTORE ONLY refers to company owned stores and not available to Resellers. Page 1: CLUB OFFER: BONUS 200-points for every purchase of Anycubic Resin 3D Printer (TL4422). BONUS 1 x Butane Gas (NA1020) for every purchase of Gas Blow Torch (TS1660). CLUB OFFER: FREE Pocket Screwdriver (TD2541) for purchases of $30 or more on Test & Measurement, Tools & Soldering, Service Aids, Kits, Science & Learning, Passive & Active Components, Electromechanical & Enclosures. Page 7: CLUB OFFER Multibuys: Any 2 for $44 applies to TL4260-TL4267. Any 2 for $70 applies to TL4454, TL4460, TL4462, TL4464, TL4477, TL4425-TL4429. Any 2 for $105 applies to TL4433-TL4439, TL4440-TL4442. Any 2 for $125 applies to TL4443-TL4449. Any 2 for $30 applies to NM2836 & NM2838. Any 2 for $18 applies to NA1002, NA1012, NA1008 & NA1004. 2 x NM2810 for $25. CLUB OFFER: BONUS 50-points for every purchase of Filament Storage Box (TL4430). CLUB OFFER: BONUS 20-points for every purchase of Parts Cabinets (HB6323 & HB6330). SUPPLY CHAIN DISRUPTION. We apologise for factors out of control which may result in some items may not being available on the advertised on-sale date of the catalogue. Double Up & Save THIS MONTH'S CLUB OFFER: FREE* POCKET SCREWDRIVER In-store only. Whilst stocks last. *With over $30 of in-store purchases of selected hardcore products. Limit 1 per customer. Full T&C's www.jaycar.com.au/40th-anniversary CLUB OFFER ANY 2 FROM 105 $ SAVE 10% 59 95 EA 3995 $ Anycubic 500ml Resin Wide range of resin available in 5 colours. Black TL4425 Grey TL4426 Clear TL4427 Blue TL4428 Green TL4429 30 EA $ 50 points CLUB OFFER 95 EA 70 $ SAVE 20% Aerosol Service Aids Gaffer Tape - 25m Waterproof. Very adhesive and strong. 48mm wide x 25m roll. Black. NM2810 HB6389 BONUS 20 points CLUB OFFER Drawer Parts Cabinets Designed for storing small components. 30 Drawers HB6323 $39.95 33 Drawers HB6330 $36.95 Not a member yet? Sign up in-store or visit: jaycar.com.au/member-access JUST 1150 18 $ $ *Filament not included 95 PETG & ABS+ TYPES ALSO AVAILABLE NOT STOCKED IN ALL STORES, BUT CAN EASILY GET ONE FOR YOU CLUB OFFER ANY 2 FOR PROTECTS YOUR TEST EQUIPMENT Keeps your filament dry by using heat. 80°C max heat temp. Sealed protection, dust-free. TL4430 FROM 36 JUST 95 eBox Filament Storage Dry Box BUILT IN HEATER $ JUST 16 $ 99 BONUS High quality. Produce smoother prints and better adhesion. 2 types. Various colours available. PLA+ TL4454-TL4464 SILK TL4477 CLUB OFFER ANY 2 FOR SAVE 25% Seals and protects electrical connections. Black and red colours available. NM2836-NM2838 EA eSun 3D Printer Filament 1.75mm 1kg 25 28g Liquid Electrical Tape JUST 3995 $ SAVE 20% 19 The best, most consistent and most tested PLA filament engineered and manufactured by FlashForge. Various colours available. TL4260-TL4267 $ CLUB OFFER 2 FOR $ 95 44 SAVE 10% CLUB OFFER ANY 2 FOR $ SAVE 10% EA Flashforge 3D Printer Filament 1.75mm 600g EA WASHABLE TYPE ALSO AVAILABLE NOT STOCKED IN ALL STORES, BUT CAN EASILY GET ONE FOR YOU! JUST SAVE 10% 70 JUST $ TL4454 Standard Higher resolution & precision. Optimised for both colour and mono printers. 3 types. Various colours available. PLA TL4433-TL4439 RRP $59.95 EA OR ANY 2 FOR $105 PLA Pro TL4440-TL4442 RRP $59.95 EA OR ANY 2 FOR $105 Standard TL4443-TL4449 RRP $69.95 EA OR ANY 2 FOR $125 CLUB OFFER ANY 2 FOR TL4477 eSun 3D Printer Resin 1kg CLUB OFFER ANY 2 FOR $ FROM $ JUST 24 95 $ Circuit Board Lacquer Contact Cleaner Circuit Board Cleaner Electronic Cleaning Solvent EA NA1002 NA1012 NA1008 NA1004 STORAGE SOLUTIONS HB6381 NOW FROM 2195 $ SAVE 10% ABS Instrument Cases with Purge Valves Robust cases with stainless steel pins, waterproof seals and very solid catches. Small to x-large, sizes from 173Wx125Dx50Hmm to 530Wx355Dx225Hmm. HB6381-HB6389 FROM 345 $ Jiffy Boxes ABS plastic. Industry standards sizes from 83x54x31mm to 197x113x63mm available. HB6011-HB6015 Join now, it's FREE & start earning points! $1=1 point. 200 points = $10 eCoupon What's 4 X GIGABIT LAN PORT USB3.0 PORT 1 X GIGABIT WAN PORT 2 x USB PORTS 3-STAGE CHARGING FROM 109 $ 12/24V 30A Solar Charge Controllers 149 $ Features three stage charging, constant current, constant voltage and float charging. Backlit LCD screen with voltage displays. PWM* for Lead acid batteries MP3766 $109 MPPT† for Lithium & lead acid batteries MP3768 $249 *Pulse Width Modulation † Maximum Power Point Tracking LIGHTWEIGHT QI WIRELESS CONSTRUCTION CHARGE YOUR SMARTPHONE HEADPHONE HOLDER AX1800 Dual Band Smart Wi-Fi 6 Router Incredibly fast and steady Wi-Fi performance. Simultaneous dual AX bands of 573Mbps<at>2.4GHz and 1201Mbps<at>5GHz. YN8398 EASILY ADDS EXTRA SCREENS ONLY 4995 ONLY 29 $ JUST $ 95 Headphone Stand with Qi Wireless Charger Sleek stylish headphone stand, with built-in wireless charger perfect for phones and other accessories. Supports 5W/7.5W/10W Qi charging. MB3641 Accessories not included JUST 6995 Rechargeable Bluetooth® 5.0 Headset with Charging Cradle Feature noise cancelling technology for crystal clear conversations. Can connect to two Bluetooth® devices at the same time. AA2180 $ Type-C to Dual HDMI 2.0 Adaptor Allows you to connect up to, two 4K monitors running independently to any computer with USB-C output. Plug & play. WQ7429 30m m INFO ONLINE 2.5” SATA3 SSD Fast and reliable replacement for slow-performing HDDs. Reads/write up to 540/490MB/s. 256GB XC5686 $69.95 512GB XC5688 $119 FROM 119 $ FROM 6995 $ M.2-2280 NVMe/PCIe SSD Super fast & reliable. Reads/ write up to 2500/1950MB/s. Designed for PC enthusiasts, gamers, etc. 256GB XC5930 $69.95 512GB XC5932 $109 mm 6995 $ SCAN HERE FOR MORE INFO FOR COMPLETE MEDIA STORAGE 10 0 FROM SSD Hard Drives with USB Type-C Ultra slim, ultra portable storage. Super-fast transfer speeds up to 440MB/s via USB Type-C. 500GB XC5920 $119 1TB XC5922 $199 Got a great project or kit idea? If we produce or publish your electronics, arduino or pi project, we'll give you a complementary $100 gift card. projects.jaycar.com 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer confirmed at the time of print. Call your local store to check stock. Occasionally discontinued items advertised on a special / lower price in this flyer have limited to nil stock in certain stores, including Jaycar Authorised Resellers, and cannot be ordered or transferred. No rainchecks. Savings off Original RRP. Prices and special offers are valid from 24.03.2021 - 23.04.2021. ElectroneX 2022 Rosehill Gardens, Sydney – 5-6 April E lectronex charges back to life on 5-6 April at Rosehill Gardens in Sydney. The Electronics Design and Assembly Expo and Conference will feature over 90 companies and exhibitors. Electronex is a must-visit event for designers, engineers, managers, and other decision-makers involved in designing or manufacturing products with electronics. It will include a wide range of electronic components, surface mount and inspection equipment, test and measurement products and related products and services, including contract manufacturing. Many companies will launch and demonstrate new products and technology at the event. A series of free seminars with overviews of some of the latest technology and insights into future developments will also be held on the show floor; sessions and times are available on the show website. Visitors can register for free at www.electronex.com.au and your badge will be emailed. The hours are 10am – 6pm on Tuesday 5 April, and 9am – 4pm on Wednesday 6 April. Free parking is available off James Ruse Drive. SMCBA Conference The Surface Mount & Circuit Board Association (SMCBA) is conducting Australia’s only conference dedicated to electronics design and manufacture concurrently with the expo (see the full program or book for sessions at www.smcba. asn.au). Topics include: “Designing the Signal Return Path” half-day workshop (Susy Webb, senior PCB designer at Design Science PCB) PCB signal routing is critical, but the return portion is often the last thing considered or even forgotten. This presentation on the importance of that return path will include the physics, where the energy flows, interference caused when it is not controlled and the planes and stackup needed. “HDI Routing Solutions” half-day workshop (Susy Webb) With tighter pitches and higher pin counts, maximum board routing on as few layers as possible is essential. HDI can help achieve this. The topic includes possible stackup siliconchip.com.au types, ways to get signals and power between layers and patterns/grids like via in pad, offset or swing vias to maximise fanout and routing opportunities. Routing return, power distribution and layer paired routing are considered. “Low Temperature Soldering – A new challenge in electronics assembly” (Keith Sweatman, Senior Technical Advisor at Nihon Superior Ltd, Japan) There are benefits to lead-free solder alloys that can be used at process temperatures even lower than for tin-lead solder. But there are also complications and challenges. This presentation will review the emerging low-­temperature soldering technology. “Printed Circuit Board Inspection & Field Failures – Causes and Cures” (Bob Willis) Covering test methods and tricks of the trade to understand how PCBs and PCB assemblies can fail and how to eliminate many of the common causes. “Supply Chain Challenges and Strategies” (Matt Wild, General Manager at Future Electronics Australia & New Zealand) A discussion about the latest supply trends and cost changes, focusing on practices to mitigate the impact and what is being done to ensure future supply. For further information, contact: Electronex – Noel Gray Australasian Exhibitions and Events Pty Ltd Phone: 0407 943 817 www.electronex.com.au ngray<at>auexhibitions.com.au SMCBA Conference – Anthony Tremellen Surface Mount & Circuit Board Association Phone: 0450 395 454 www.smcba.asn.au anthony<at>smcba.asn.au Australia's electronics magazine April 2022  65 ElectroneX Exhibitors Stand B20 ADM Instrument Engineering is a family run business established in 1986. They are Australia’s largest stockist of MEAN WELL power supplies, Eurotherm process control and data management solutions, industrial transducers and sensors, encoders, and test & measurement instrumentation, including EMF radiation meters and monitoring equipment. Alfatron Pty Ltd Stand B7 is Australia’s only truly sovereign full-turnkey electronics contract manufacturer. They offer fast turnaround prototyping, full production run printed circuit board fabrication, assembly, testing and final product assembly. They are DISP accredited, ISO 9001 and IPC 610 Class 3 certified. ElectroneX Exhibitor List Stand A2 Altronic Distributors have expanded their Powerhouse range of deep-cycle leadacid AGM batteries designed for use in buggies, wheelchairs, forklifts and remote power applications. The new range is available in sizes from 26Ah up to 110Ah capacity and is available locally through Altronics distribution centres around Australia. They have also added to their battery range with a new lithium-­ iron-phosphate (LiFePO4) range designed to provide significant benefits over the traditional lead-acid battery. LiFePO4 batteries are half the weight of lead-acid batteries, have a low self-discharge when not in use, a longer run time and a non-toxic chemistry that doesn’t use environmentally damaging rare earth metals. Their expanded Raspberry Pi range includes the new Raspberry Pi 400 all-in-one computer and the Pico microcontroller board, plus a suite of accessories. The new Raspberry Pi 400 is not only a complete personal computer with a keyboard in a single case; it can also be used for open source development and STEM coding. B20 B7 A2 C20 A2 A7 D25 B8 B26 A20 C11 B20 A2 A2 A19 A2 D31 D6 66 ADM Instrument Engineering Alfatron Altronic Distributors Ampec Technologies Amphenol* AppVision Australia Bosch Electronics Chemtools CNS Precision Assembly congatec Australia Control Devices Australia Curiosity Technology* Deutsch* Dinkle Dyne Industries Electro Harmonix* element14 Elexon Electronics Silicon Chip D21 B1 C32 B20 B21 B20 B16 C32 B16 B12 A12 C31 D35 D2 D24 D1 D10 C24 AppVision Australia Pty Ltd is offering the ADLINK MCM216/218 Ethernet DAQs, based Stand A7 on ARM Cortex-A9 processors with built-in 16- or 8-channel, 16-bit voltage or current input. They can function as a standalone edge device without a host PC supporting edge computing. They include a built-in web console and RESTful API for periodic machine condition polling. They can also supply the Ceyear 4024L handheld spectrum analyser, the first 9kHz~67GHz handheld analyser in the industry. It is a high-performance device with many functions and easy operation. Features include excellent displayed average noise level, low phase noise and a high sweep speed. Bosch Australia Manufacturing Solutions Stand D25 is a leading provider of testing solutions for Australian manufacturers. They draw on the experience, knowledge and resources of talent across the globe for manufacturing solutions in Australia. This means that their customers receive innovative manufacturing and logistics solutions while delivering world-class results. They provide: • bespoke integrated testing solutions • portable testing systems • product test systems • robot-based automation • vision & sensing systems • AGV/AMR solutions • communication interfaces • data analysis • data acquisition congatec Australia are offering the conga-HPC/ cTLU COM-HPC Client Size A module, as well as the congaTC570 COM Express Compact Stand A20 with new scalable 11th-gen Intel Core processors for extreme temperatures ranging from -40°C to +85°C. Then there’s the conga-TCV2, a brand-new Express Compact Computer-­on-Module based on AMD Ryzen Embedded V2000 processors. The module sets a new performance per watt benchmark with double the performance compared to the AMD Ryzen Embedded V1000, finding its sweetest spot in 15W TDP designs. Embedded Logic Solutions Emona Instruments ETS-Lindgren* ESI Technology Ltd* Europlacer Eurotherm* ExtraEye FAI* Faraday FS Bondtech* Fuseco GLW* Glyn High-Tech Distribution GPC Electronics Harbuch Electronics Hawker Richardson Helios Power Solutions Henchman Electronics Hetech Australia's electronics magazine D16 A1 C5 A1 B21 B21 A30 A9 A27 A12 A12 B16 C26 D28 D21 C29 D26 B20 HW Technologies Innovative Mechatronics Group Industry Update Injectronics Interflux* JBC* Juki* Keysight Technologies Kobot Systems Kolb Cleaning Technology* Komax Kabatec* Kulicke & Soffa* Leach (SZ) Co Ltd Lintek LPKF Laser & Electronics* Marque Magnetics Ltd Mastercut Technologies MEAN WELL* siliconchip.com.au Control Devices Australia will be showcasing FND-­series rocker switches which are Stand C11 designed for easy forward and reverse control with an excellent tactile feel. This rocker switch is extremely well-sealed, making it suitable for demanding environments, especially on an all-in-one joystick control. Backlighting is available in five colours. The new RT handle for XD series joysticks is designed for the APEM XD series joystick and for vehicle applications requiring right-hand operation. The RT handle features both front and rear-facing configuration plates that allow the user to easily reach all forward-facing functions with just their thumb. This ergonomic control grip offers a wide selection of pushbuttons and hall-effect thumbwheel combinations to be incorporated into the one handle. The handle provides up to four axes of proportional control and 10 momentary switching functions, with IP67 above panel sealing. They are ideal for off-highway vehicles and industrial machinery. The new APEM WP series pushbutton with new high-performance momentary switch is for interfaces that must be easily identifiable. The pushbutton increases the visibility of your critical functions with its extra-large activation surface. It comes with a large-format personalised laser marking and an anodised 25mm diameter bearing area which can be tinted in blue, black, green or red. The WP series is IP67 and IP69K rated, suitable for harsh applications including outdoor and military. The series meets the waterproof and reliability needs within the market. Also available is the WPG series security cover for specific metal security guard requirements to prevent unwanted activation, especially in outdoor applications. Three switch guard types and eight colours are available. element14 is now selling the Raspberry Pi-designed RP2040 chip. Stand D31 The Raspberry Pi RP2040 microcontroller offers high performance for integer workloads, a large on-chip memory, and a wide range of I/O options, making it a flexible solution for a wide range of microcontroller applications. Professional design engineers who are already comfortable C8 A2 B20 B6 C2 B16 C27 B21 A2 D30 A17 B16 A2 A6 A2 A21 A2 D31 Microchip Technology Micron* Midori* Nano Di (APAC) NPA Pty Ltd ONBoard Solutions On-Track Technology Oritech Oupiin* Permark Industries Phoenix Contact Pillarhouse Soldering* Powertran* Precision Electronic Technologies Pros kit* QualiEco Circuits Radytronic* Raspberry Pi* siliconchip.com.au A8 B32 D24 A1 A2 D29 A16 A28 A2 A11 D32 D18 B16 C16 C32 A12 B29 A2 working with Raspberry Pi will easily adopt the Raspberry Pi Pico and appreciate its ease of use and affordability. element14 are also now a distributor of Jabil Cutting Tools, including the long-lasting high precision DK20004JS End Mill for mold steel. It is ideal for finishing and fine machining Mold Steel HRC 50±2 material used in industrial manufacturing operations. The cutter has a flute diameter 2mm +0,-0.01mm with a radius tolerance of ±0.01mm, a shank diameter of 4mm and a length of 45mm. The DK01001ZO CBN ball endmill is another solution for high quality surface machining and high precision for mold steel HRC 50-68. The tool has a flute diameter of 1mm with a tolerance of +0,0.01mm and a radius of 0.5mm ±0.003mm. Its shank diameter is 4mm and length is 50mm. Elexon Electronics specialises in designing, developing, and manufacturing electronics for niche markets. Elexon’s talented engineers and designers are always empowered to think Stand D6 outside the box. They like to solve problems in original and inventive ways, and pride themselves on developing products that exceed customers’ expectations. Their competencies include: • PCB and product assembly • Intelligent Factory 4.0 SMD assembly line including jet solder paste printing, two intelligent pick & place MY300 machines, vacuum vapour phase reflow and automated material handling • final unit assembly and testing • X-ray inspection • fast turnaround prototyping • mobile digital signage systems Embedded Logic Solutions will be demonstrating the Neoden K1830 pick & place machine. It has been refined from the Neoden7 design for Stand D21 maximum efficiency, ease of use, and increased compatibility. It boasts a placement speed of up to 16,000 components per hour (CPH), made achievable using an eight-nozzle gantry head. The Neoden K1830 transports PCBs in a self-adjusting automatic rail system (standard) and can hold up to sixty-six 8mm pneumatic or electric tape feeders (Yamaha). Redback Test Services Reid Print Technologies Re-Surface Technologies Rigol Technologies* Ritec* RMS Components Rohde & Schwarz (Australia) Rolec OKW - ANZ Salecom* SC Manufacturing Solutions Semikron Silicon Chip SJ Innotech* Skyzer Solar - EMC* Suba Engineering Successful Endeavours Sunon* Australia's electronics magazine A29 Surface Mount & Circuit Board Assoc. A12 Tagarno* B35 Tarapath C34 TecHome* C31 Telit Wireless Solutions* B20 Thermo Fisher* B20 UniMeasure* D8 Unitronics B30 UV Pacific D17 VGL - Allied Connectors A15 Vicom Australia B24 Wago A5 Whats New in Electronics C12 Wurth Electronics D24 Yamaha* May be subject to change * Co-Exhibitor Company/Brand Represented by Exhibitor April 2022  67 Usually, machines of this production calibre face component size restrictions; not the Neoden K1830. It can handle 0201, 0402, LED, BGA, 0.4mm pitch QFP, SMT connectors with compatibility for cut tape, loose, tube, or tray feeders. The Neoden K1830 is the ideal machine for low-volume assembly due to its feature set and economical price. Stand B1 Emona Instruments will launch the new Rigol D S 7 0 0 0 0 s e r i e s h i g h -­ performance DSOs at Electronex 2022. The DS70000 StationMax Series is available in 3GHz or 5GHz bandwidths and combines the new UltraVision III oscilloscope technology and UltraReal spectrum analysis technology into Rigol’s most powerful test and measurement instrument. The UltraVision III platform combines updated oscilloscope and spectrum analysis technology with its custom front-end Phoenix ASIC chipset. The StationMax provides four channels, 20GSa/sec (10GSa/sec on all channels), 1 million waveforms/sec capture rate, 2Gpts maximum storage depth and high-resolution measurements up to 16 bits. The DS70000 interface is designed around a unique 15.6inch multi-touch tilting display. Powerful analysis capabilities include real-time spectrum analysis, multi-domain analysis, eye diagram and jitter analysis, high-speed bus compliance, and serial bus decoding. Complementing this instrument is a new family of high-speed precision probe solutions. Active differential probes are available in 3.5GHz and 7GHz models, delivering excellent measurements to the probe tip. They will also have Rigol DS8000-R Series 4-channel digital oscilloscopes. These compact 1U half-rack-width instruments are available in 350MHz/1GHz/2GHz versions with a maximum sampling rate of 10GSa/s. The DS8000-R series has been designed around Rigol’s proprietary Phoenix ASIC chip and UltraVision II technical platform. It integrates six independent instruments into one unit, including a digital oscilloscope, a spectrum analyser, a 25MHz arbitrary waveform generator, a digital voltmeter, a high-precision frequency counter and totaliser, and a serial protocol analyser. Stand B12 Fuseco imports and distributes specialist electrical products to the Australian & NZ markets. Their brands are carefully selected to ensure that they are well respected for quality, reliability and safety. Their product range includes: test equipment; programmable power supplies and loads; EMC chambers; LV and MV fuses; protection relays and CTs; RFI filters and more. Stand C31 GLYN High Tech is a specialty electronics distributor serving the Australia/NZ region. They partner with reputable brands to cover the main pillars of IoT: sensors, processing, power and wireless technologies. 10% OFF IN APRIL WITH CODE ACAPR10 SCAPR10 FREE SHIPPING AUSTRALIA WIDE 68 Silicon Chip Australia's electronics magazine siliconchip.com.au Stand D35 GPC Electronics is a contract electronics manufacturer based in Sydney, with factories in Sydney (Penrith), Christchurch (New Zealand) and Shenzhen (China). GPC Electronics’ engineering team supports NPI, assembly, test, development, final product assembly and qualification. In a competitive market, customers expect a fast turnaround, high yields and attractive pricing. GPC Electronics provides scalable solutions for high-value niche products right through to those with stable high volumes. They partner with many top-level OEMs in industries that include communications, aerospace, defence, automotive, transport, industrial, agriculture and medical. Hawker Richardson will be showcasing the new Yamaha YRM20 Mounter at Electronex. The very latest in SMT innovation from Yamaha, it delivers world-class performance with a new platform. With rotary or conventional spindle heads and the ability to accommodate everything from 0201s and components up to 30mm height, the new YRM20 is the most flexible system on the market. Utilising a new multi-­purpose rotary (RM) head with 18 nozzles, the YRM20 can place Stand D24 components to a height of 12mm. This new mounter has an incredible speed of 115,000CPH (under optimal conditions). It also has an impressive mounting accuracy of ±25µm (Cpk ≥ 1.0), making it ideal for high accuracy and high-speed production. Hetech Pty Ltd has built elaborate and extensive jigs for clients in defence, mining and many more. Test jigs Stand C24 ensure that every build during production and manufacturing of your product is 100% working and operating as expected before delivery. These benefits are achieved by testing various aspects of the product, such as potential errors in the PCB, board components and software. Hetech can build any type of test jig to suit to suit your application, such as ‘bed-of-nails’ testing jigs, functional testing jigs and software/computer-operated jigs. Stand A9 Keysight Technologies will show off their new FieldFox high-performance handheld microwave analyser. It speeds up the installation of 5G, radar and satellite communication systems. The FieldFox, an integrated handheld analyser with a task-driven user interface, incorporates spectrum and signal analysis plus signal generation. It can accurately measure signal interference, antenna and cable performance, electromagnetic field (EMF) exposure levels and path loss in communication systems. It ensures that 5G services in frequency range 2 (FR2) can reach their full potential. They have also launched a portfolio of Smart Bench Essentials (SBE) lab products that deliver the power of four instruments: a Experience the INTEK difference: A quality PCB Manufacturer! LINTEK is one of the most innovative PCB companies in the world. Using a patented, high vacuum deposition process, LINTEK can manufacture a large variety of printed circuit boards, ranging from 1.8-metre long antennas, to sub-miniature transmitters, using a variety of different substrates. And the best part of all? They’re right here in – no waiting, no translation issues, no freight delays . . . no worries! CALL INTEK NOW to discuss your special PCB requirements. There’s no obligation; no risk – and you could $ave a fortune! INTEK 20 Bayldon Rd, Queanbeyan NSW 2620 PTY LTD www.lintek.com.au Tel (02) 6299 1988 siliconchip.com.au Australia's electronics magazine April 2022  69 triple-output power supply, an arbitrary function generator, a digital multimeter and an oscilloscope, all through one combined graphical interface with integrated data management and analysis capabilities. Keysight’s SBE series is a combination of hardware and software that accelerates an educators’ teaching experience and students’ learning experience, as well as improves an electronic design and manufacturing engineers’ ability to analyse and troubleshoot products. For a limited time, receive a free Keysight U1733C handheld LCR meter with a qualifying purchase of a Keysight power supply. NPA Pty Ltd has been Australasia’s leading supplier of cable and wiring accessories, Nylon fasteners Stand C2 and electronic hardware for over 30 years. NPA has recently acquired the exclusive distributorship for Delaunay high-performance cable glands and accessories targeting the marine, mining, rail and defence industries. NPA will be exhibiting its wide range of products, including: cable glands and accessories, solar clips and accessories, liquid-tight flexible conduit, tubing and fittings, strain-relief bushings, venting solutions, heatshrink and sleeving products, and much more. ONBoard Solutions Stand B16 supplies automation equipment for manufacturing industries across Australia and New Zealand. Exclusive show special offer: purchase a Quick 861DW Hot Air Soldering Rework Station for $399, excluding GST. The regular price is $595 excluding GST. This multi-purpose unit has a brushless whirlpool motor plus wide-range, stepless adjustable airflow. It has a temperature range of 100-500°C and a maximum airflow of 120L/minute. Their Promosolv 70ES cleaning & flux removal solvent is a specialty solvent to clean the residues from solder pastes and solder fluxes. It is clear, colourless and only has a slight odour. It is designed to replace existing solvents to be used with ultrasonic cleaning. It has outstanding flux removal and drying characteristics when used in vapour phase with azeotropic mixtures. Humiseal UV20GEL high-performance staking & vibration protection UV gel is a fast-curing, non-sag thixotropic paste that cures to give a flexible urethane acrylate, bonding well to engineered plastics and metal-based substrates. In addition to the UV cure, this material has a secondary moisture cure mechanism to ensure cure in areas shadowed from UV light. Stand C27 On-track Technology Is a leading local (and flexible) contract manufacturer with a new manufacturing facility in the Sydney metropolitan area (Milperra). They have been helping many local businesses to re-establish manufacturing in Australia. They have experienced increasing demands for local manufacturing of electronic PCB assemblies. Businesses that previously manufactured their electronic assemblies offshore are now looking to 70 Silicon Chip bring their offshore electronics manufacturing back into Australia. They are currently providing clients with a reliable 2-3 week turnaround time on PCB assembly. Oritech Stand B21 has upgraded JBC CD compact soldering stations. The smaller and more intuitive Compact Stations (version F) improve on an already versatile station. They feature: • 3 to 7 keys which allow quick and easy configuration of the station • connectivity with JBC fume extractors via an RJ12 connector • a new cable collector, designed for a perfect adaptation to movement while soldering • a cartridge holder to store up to four cartridges The Omni 3 from Ash Vision is an advanced digital microscope system with the new AshCam+ 30x zoom lens camera. It has many new features for smart inspection and measurement. The Omni 3 offers superb image quality in full-HD video at 60fps. With AshTruColour, advanced camera settings, improved depth of focus and no video latency, it is three times faster than previous Ash systems. The FLIR ETS320 is a non-contact thermal measurement system that pairs a high-sensitivity infrared camera with an integrated stand, for hands-free measurement of printed circuit boards and other small electronics. This sensitive camera detects minute temperature shifts (<0.06°C) and quantifies heat generation up to 250°C. Reid Print Technologies Stand B32 is Australia’s most advanced printed electronic manufacturer. Recently, their manufacturing team has focused on the development and commercialisation of flexible printed circuits. Wearable technology is a printed circuitry that transforms any material into a smart fabric, enabling many performance capabilities. FPC UHF & RFID antennas are manufactured on PET substrates. Features include low electrical resistance, excellent flexibility and easy application to any surface using 3M transfer adhesives. Reid Print Technologies VHF and UHF capabilities which currently range up to 4GHz. Applications include medical, defence, farming, industrial and automotive. A flexible positive temperature coefficient (PTC) heater is a modern solution to many industry problems. Flexible heaters are fully customisable and made to order. PTC flexible heaters provide a great way to enhance new and innovative products with a range of temperature resistances, shapes, sizes, and configurations. They are suited to a range of industries and applications. Stand A11 SC Manufacturing Solutions Brings over 30 years of experience and can provide you with the right products and services to keep your production going. Specialising in new machinery, spare parts, service repairs and used equipment, we are sure to have what you need. Whether it is a part for a feeder, motor, servo drive, camera, laser or cards, we can source it all. Australia's electronics magazine siliconchip.com.au Stand B29 Successful Endeavours develops smart electronics products that are intended to be manufactured in Australia. These products perform advanced monitoring, communications or control functions or have unique features, size, power consumption, performance, battery life or cost effectiveness. Custom IoT devices and the supporting technical web services are a speciality. They are the current holders of the Environmental Solution Award for Australia and Manufacturer of the Year for their region of Melbourne. UV Pacific will have the ecoDUOMIX450, the latest development by ViscoTec of their “preeflow” range of adhesive dispensing tools. Using the well-­established positive displacement technology of the ecoPEN, theecoDUOMIX combines a two-­component dispensing head with dynamic mixing. The use of dynamic mixing overcomes problems associated with cases where the two materials have widely different viscosities. The range of applications include silicones, epoxies, polyurethanes and acrylates. Stand B30 Stand B24 WAGO Pty Ltd has a new Gelbox for splicing connectors for reliable moisture protection. It is ready for immediate use in a wide range of low- and extra-low voltage applications. The WAGO Gelbox is a compact box pre-filled with silicone-free gel. The Gelbox is available in six sizes and provides IPX8 levels of moisture protection for WAGO’s 221 Series COMPACT Splicing Connectors. The connectors are completely sealed against water and can be permanently immersed in water. WAGO Gelbox’s distinctive feature is that it protects the electrical installation exactly where it matters – at the connection points – without permanently encapsulating the junction boxes. Unlike silicone-­ based gel, the WAGO Gelbox’s silicone-free gel supports a virtually unlimited number of applications. The new 221 Series Inline Splicing Connector with lever for all conductor types from 0.2mm² to 4mm² combines all the trusted advantages of the 221 Series Splicing Connectors into a slim design. Offering unsurpassed simplicity, speed and reliability, the 221 Series provides universal conductor connections – with lever technology that eliminates tools – while offering a visibly secure conductor contact. The new MCS MAXI 16 family of connectors are the world’s first lever-actuated connectors for power electronics. They permit direct, in-hand wiring of conductors up to 25mm2 (4AWG). Two versions of the new pluggable connectors are available (wireto-wire and wire-to-board), and each version offers variants ranging from 2-6 poles. All models are designed for a nominal conductor size of 16mm2 with ratings up to 1000V and 75A (IEC). Stand C12 Würth Electronics Australia is a manufacturer of electronic and electromechanical components that spearheads pioneering electronic solutions. WürthElektronik eiSos is one of the largest European manufacturers of passive components and is active in 50 countries. They have production sites in Europe, Asia and North America that supply a growing number of customers worldwide. Their product range includes EMC components, inductors, transformers, RF components, varistors, capacitors, resistors, quartz crystals, oscillators, power modules, Wireless Power Transfer, LEDs, sensors, connectors, power supply elements, switches, pushbuttons, connection technology, fuse holders and solutions for wireless data transmission. SC www.okw.com.au VISIT US AT ELECTRONEX 2022 / STAND A28 TO EACH HIS OWN HOUSING ROLEC OKW Australia New Zealand Pty Ltd Unit 6/29 Coombes Drive, Penrith NSW 2750 Phone: +61 2 4722 3388 E-Mail: sales<at>rolec-okw.com.au siliconchip.com.au Australia's electronics magazine April 2022  71 Our SMD Test Tweezers project from the October 2021 issue has been extremely popular. This did not come as a surprise given that they are handy, compact, easy to use, easy to build and the kit cost is reasonable. We decided to see what features we could add simply by upgrading the microcontroller at its heart. Improved Test SMD Tweezers T he SMD Tweezers are a simple but clever design. A PIC12F1572 eightpin microcontroller powered from a button cell is used to probe resistors, diodes and capacitors and then display its findings on a tiny OLED screen. The PIC12F1572 does a respectable job, but the Tweezers software takes up all but 42 bits of the available flash memory, leaving no room for expansion. We used the PIC12F1572 for the original SMD Test Tweezers as it was the cheapest available at the time, apart from its close relative with less memory, the PIC12F1571. Until recently, the PIC12F675 and later PIC12F617 were our 8-pin micros of choice, but Microchip keeps bringing out new parts with better performance and more features at lower prices, so we try to keep up. The PIC12F1572 is more capable than the older PIC12F675, as we explained in our feature at the time (November 2020; siliconchip.com. au/Article/14648). We also used the PIC12F1572 for our Christmas Ornaments in the same issue (siliconchip. com.au/Article/14636). However, when we looked into upgrading the Test Tweezers with some software improvements, we realised that the PIC12F1572 did not have enough free memory to add new features or improve existing ones. For that, we would have to move to the latest PIC generation. So when a new family of PICs became available, we began to investigate what we could add by using them. For more background on what these parts offer and what we learned in programming them, see the accompanying feature article on the new PICs that starts on page 80. A new PIC The original SMD Tweezers don’t use any exotic peripherals within the micro; the analog-to-digital converter (ADC) and watchdog timer that the software requires are found in most PIC microcontrollers. The low power sleep mode is quite standard too, and is essential for standby operation when powered from a cell. This allows the Tweezers to be left idle but ready to work at a second’s notice. The I2C interface to the OLED display is emulated in software by toggling GPIO (general purpose input/ output) pins, a technique often known as “bitbanging”. This all means that just about any 8-pin microcontroller with more program memory could be used for the SMD Tweezers. In mid-to-late-2021, after developing the original Tweezers, we became aware of the PIC16F152xx series of microcontrollers. The range spans parts from eight to 40 pins. While the range has features that are modest by current standards, they are still more capable than older parts like the PIC12F675. The PIC16F15213 and PIC16F15214 are the 8-pin parts in the range, and they are cheaper than the PIC12F1572, although the current part shortages mean that availability is poor. Importantly, the PIC16F15214 is available in the SOIC package and has twice the flash memory of the PIC12F1572. As we mentioned in our feature from November 2020, Microchip does a pretty good job of maintaining pin compatibility between parts, and the PIC16F152xx series is no exception. The upshot is that the PIC16F15214 is both cheaper and fully capable of replacing the PIC12F1572 as the controller for the SMD Tweezers, while also having the larger program space needed for us to add new features. Tweezers 2.0 We have implemented three major updates to the Tweezers. Firstly, we expanded the capacitance measurement range in both directions (it can measure both larger and smaller capacitances than before). Secondly, we added a calibration and setup procedure. Finally, we improved usability for left-handed people (or those who want to hold something like a soldering iron in their right hand) by allowing the screen display to be rotated by 180°. These improvements have all been made in software, so apart from changing the PIC12F1572 to the By Tim Blythman 72 Silicon Chip Australia's electronics magazine siliconchip.com.au Features & Specifications ∎ Uses identical hardware to the original Tweezers (October 2021; siliconchip.com.au/Article/15057) apart from the PIC microcontroller ∎ Identifies component type (resistor, capacitor, diode or LED) and measures critical values ∎ Resistors: value from 10W to 1MW ∎ Diodes: forward voltage up to about 3V ∎ Capacitors: value from (approximately) 10pF to 150μF ∎ Cell voltage with nothing connected ∎ Low power sleep when idle avoids the need for an on/off switch ∎ Instant wake-up by touching probe tips together ∎ Option to select left-handed or right-handed display ∎ Calibration of internal and contact resistance PIC16F15214, the hardware is identical and the general operation is much the same. Circuit details Fig.1 shows the circuit, which is the same as last time, besides IC1. All the readings are displayed on a tiny OLED module connected to CON2. IC1 drives its RA5 (pin 2, IOTOP) and RA4 (pin 3, IOBOT) pins high and low and measures the voltage present on pin 5 with its ADC peripheral. For example, it can determine the resistance of a resistor connected between the CON+ and CON− points using the voltage divider equation. Diodes will present their forward and reverse voltages between CON+ and CON− when the micro applies a voltage. The micro determines the diode’s orientation, showing its polarity and forward voltage. Capacitors are first charged by bringing IOTOP high and IOBOT low and then characterised by measuring the rate of discharge when IOTOP is brought low. The Tweezers can even measure their own supply voltage by reading the voltage of its internal 1.024V reference relative to that supply voltage. These features are already present in the original Tweezers, so we suggest you refer to the original Tweezers article (October 2021) for more detail on how these original features work and how the values are calculated. In theory, this expands the range by a factor of 256, but in practice, using this entire range is not possible. The upper limit is around 150μF now, equivalent to about 12 bits or a factor of 16 higher. The first reason for this is that higher values would overflow the 32-bit mathematical calculations that are required. The second is that the time needed to charge and discharge a larger capacitor becomes unreasonably long, in the order of several seconds between readings. The only way to overcome this would be to change the series test resistor, which would affect the other readings too. The relatively high value of the series test resistor also means that capacitance readings can be distorted by leakage current. Since leakage is typically higher in higher-value parts, especially in electrolytic capacitors, the accuracy and usefulness of these higher ranges are less than what seems theoretically possible. So higher value capacitors can be measured and will return a reading, possibly after a brief delay, but the accuracy will not be as good as for lower values. Low capacitance measurements Values lower than 1nF are measured in an entirely different fashion. This method is so sensitive that it can measure the capacitance of the touch of a hand, in the order of picofarads. It’s called shared capacitance sensing, and we used it to detect finger touches in the ATtiny816 Breakout Board of January 2019 (siliconchip. com.au/Article/11372). It works by comparing the relative magnitude of two capacitors by initially charging one and discharging the other, as shown in Fig.2. When they Improvements The upper limit of the capacitance range was limited by the use of an 8-bit counter to time the discharge. With more flash memory and RAM available, we can instead use a 16-bit counter. siliconchip.com.au Fig.1: the circuit for the updated Tweezers is practically the same as the old version, except IC1 is now a PIC16F15214. It can perform all its tests by applying different voltages to the IOTOP and IOBOT pins and testing the voltage on the IOTEST pin. Australia's electronics magazine April 2022  73 A few constructors had difficulty finding the brass strips we recommended for the original Tweezers. Standard header pins are a substitute and are easily aligned for soldering while in their plastic shrouds. There are even gold-plated versions available. We used a low-profile header socket (Altronics P5398) so that we could remove the OLED module during prototyping, to allow access to the programming pins. This also required us to cut down the header pins on the underside of the OLED and remove the plastic spacer block. The alternative is to simply solder the OLED directly to the main PCB. are connected, the charge present is shared between the two in proportion to their capacitances. The ratio of the initial and final voltages relates directly to the ratio of the capacitances. The theory and mathematics are explained further in the ATtiny816 Breakout Board article. In the case of our new Tweezers, a capacitor connected to CON+ and CON− is charged up via the 10kW resistor. The second capacitor is actually the tiny internal capacitor that is used to sample and hold the voltages read by the microcontroller’s ADC. This capacitor is nominally 5pF, and it is discharged by sampling an ADC channel connected to ground. Fortunately, the ADC peripheral has a selection to make an internal ground connection, so this does not require an extra pin. The external capacitor is disconnected from its resistor, and the two capacitors are connected by taking an ADC reading from the external capacitor. An equation similar to the voltage divider equation is used on the ADC result to calculate the value of the external capacitor. The way the capacitors share the charge is analogous to how resistors share voltage in a divider chain. The software also makes minor adjustments to account for some of the stray capacitance that is present and significant at these magnitudes. We made some tests on real capacitors in the picofarad range to fine-tune these readings. The lower limit is fairly arbitrary and is chosen to avoid the Tweezers detecting stray capacitance as a component to be measured, which could cause them not to power down correctly. At these scales, even the way the Tweezers are held can change the reading substantially. As the ADC reading nears its upper limit for larger capacitances, the resolution is poor around 1nF, and steps grow to be as far as 100pF apart. So the Fig.2: Cx is the device under test (DUT) connected to the Tweezer probes, while C1 is the ADC sample-and-hold capacitor inside the microcontroller. The capacitors are connected by sampling Cx with the ADC. If the value of Cx equals C1, the resulting voltage is half the initial voltage. It’s analogous to a resistive voltage divider, and the formulas are much the same, with the capacitor charge replacing the voltage across the resistors. 74 Silicon Chip Australia's electronics magazine readings using this method are always shown as pF, and other methods are used for measurements in nF or μF. We’ll detail the calibration and setup process after construction is complete. Construction The assembly procedure is identical to the October 2021 design, but we’ll go over it again for those who haven’t seen that article. The SMD Test Tweezers are built using three PCBs, with the main one coded 04106211 and measuring 28 x 26mm. Refer to the PCB overlay diagrams, Figs.3 & 4, during construction. The main PCB is not hard to build, even if the parts are all surface-mounting types. Gather your SMD tools and supplies. We recommend a fine-tipped soldering iron, a magnifier, some flux paste, solder wicking braid and tweezers, at a minimum. The small PCB needs something to hold it in place. If you don’t have an appropriate vice tool, you can use an adhesive putty like Blu-Tack instead. If possible, set up some fume extraction to deal with the extra smoke that comes from working with flux, or work near an open window or outside. A tip cleaning sponge is handy too. Apply flux to the top PCB pads for IC1 and the three passive components, then rest IC1 in place using tweezers, ensuring the pin 1 dot or bevel is towards the curved end of the board. Align the part within the pads, clean the iron’s tip, apply fresh solder and tack one lead in place. Adjust the IC if necessary to ensure it is flat against the PCB and aligned to the pads. Then solder the remaining siliconchip.com.au Fig.3: construction of the Tweezers is the same as last time (October 2021) except that IC1 is a different, pin-compatible microcontroller with more memory. There aren’t many components to fit but make sure that IC1 is orientated correctly. pins, cleaning your iron’s tip and adding solder as necessary. Use the braid to remove any solder bridges by adding more flux, then pressing the braid against the excess solder with the iron. Carefully drag both iron and braid away when the solder has been absorbed. The remaining three components are not polarised, so their orientations are unimportant. The capacitor sits near CON−, while the two identical resistors flank IC1 at its other end and side. Use a similar technique to IC1. Tack one lead, adjust the part, then tack the other lead. You can also go back and refresh any leads if the joint doesn’t look right. It should be smooth and glossy; you can add more flux at any stage to help improve solderability. Then solder the single component to the back of the PCB. Centre the cell holder to align the two external pins to their pads. If your iron is adjustable, turn it up while soldering this larger part. You should also ensure that the wider opening on the cell holder faces the rounded edge of the PCB to allow access for the cell to be fitted and removed. As before, apply flux, tack one lead in place and adjust the position. Then solder the other lead. For these much larger pads, it can help to apply extra solder directly to the pad to create a robust fillet, which you can see in our photos. With the surface mounted parts fitted, you can clean up the PCB using the flux cleaner designated by the flux’s data sheet. Methylated spirits or isopropyl alcohol are good all-round alternatives for cleaning many fluxes siliconchip.com.au too, while general-purpose flux cleaners are also available (and generally work better than plain alcohol). Just ensure that any flammable solvent has fully evaporated before moving on to the next steps. need a fairly new programmer and a new version of Microchip’s MPLAB X IPE (integrated programming environment). It can be downloaded as part of the MPLAB X IDE from siliconchip. com.au/link/abd2 We’ve tested with versions v5.40 Programming IC1 and later. You may also need to downUnless you’ve bought a pre-­ load a DFP (device family pack); this programmed PIC, IC1 will need to be can be downloaded from within the programmed with the firmware for this IDE, and the IPE then detects that the project. You can jump over this step DFP is installed. You should look for if your microcontroller has been pro- the PIC16F152xx family. grammed already. You will also need a recent proAs we noted in the panel, the grammer such as a Snap or PICkit 4 PIC16F15214 is a much newer part as the older PICkit 3 is not supported than the PIC12F1572, so you will for these parts. Parts List – Improved SMD Test Tweezers 1 double-sided PCB coded 04106211, 28 x 26mm (main PCB) 2 double-sided PCBs coded 04106212, 100 x 8mm (Tweezer arms) 1 PIC16F15214-I/SN or PIC16F15214-E/SN 8-bit microcontroller programmed with 0410621B.HEX, SOIC-8 (IC1) ● 1 0.49-inch 64x32 OLED module (Silicon Chip Online Shop Cat SC5602) 1 surface-mount coin cell holder (BAT1) [Digi-key BAT-HLD-001-ND, Mouser 712-BAT-HLD-001 or similar] 1 CR2032 or CR2025 lithium coin cell 1 5-pin right-angle male pin header (CON1; optional, for programming IC1 in-circuit) 1 100nF SMD 50V X7R ceramic capacitor, 3216/M1206 size [Altronics R9935] 2 10kW 1% SMD resistors, 3216/M1206 size [Altronics R8188] 2 15 x 2mm short pieces of thin (eg, 1mm) brass sheet for tips (optional) OR 2 gold-plated header pins for tips (see text) ● 1 40mm length of 30mm diameter clear heatshrink tubing (optional) 2 100mm lengths of 10mm diameter heatshrink tubing (optional) 1 4-way low-profile female header strip (optional, for CON2; can be cut from Altronics P5398) ● ● these parts have been changed compared to the original Tweezers A complete kit (SC5934) is available at siliconchip.com.au/Shop/20/5934 Australia's electronics magazine April 2022  75 Fig.4: the PCB for the Tweezer Arm section. Connect the programmer to the PCB at CON1, aligning the arrows that mark pin 1. You could solder on a header, but we find that holding a short header strip in place and pressing it firmly against the pads to make contact is usually sufficient. Select the PIC16F15214 part and open the 0410621B.HEX file. You may need to change the settings to allow the programmer to apply power. Then click “Program” and check that the part programs and verifies correctly. Tweezer arms The two arm PCBs should be attached next, as the OLED module covers much of the main PCB, limiting access. Our first version of the Tweezers used small pieces of brass strip to give the arms finer tips than just the bare PCBs would provide. If you can’t find a brass strip, then we suggest an alternative that will provide your Tweezers with gold-plated tips! Many header pins are gold-plated and are a good size for working with small components. These can be used instead of the brass strip, but unlike the brass strip, we found it easier to solder these to the arms after attaching the arms to the main PCB. The other advantage of using the header pins is that they are a good fit for breadboards and jumper wires, making it very easy to connect the Tweezers to other components for hands-free readings. The updated kits will include gold-plated headers for this purpose. We recommend fitting the arms roughly in line with the edges of the PCB but slightly tilted inwards with It helps to apply extra solder directly to the pad of the Tweezer arms to make a robust fillet. 76 Silicon Chip around 15mm separation at the tip ends. Like the SMD parts, roughly tack the arms in place and adjust them to your liking. We prefer fitting the arms with the writing and main contact trace running down the inside. This helps shield and isolate the trace from outside contact or stray capacitance. Test the action and pressure of the Tweezers when the arms are positioned, then when you are happy, apply a generous amount of solder on both sides of the main PCB to secure them firmly in place. To fit the tips, find a strip of about six pin headers (to maintain the 15mm separation) and while the pins are still in the plastic holder, solder the tips of the arms to the short ends of the headers. Using the holder will keep the pins parallel and even. Again, apply a generous amount of solder when you are happy with the tips, then carefully and evenly pull the arms and their tips out of the plastic holder. We find that some pointynosed pliers are handy to help in this situation. OLED screen The final step is to fit the OLED display module. You can solder the module directly to the main PCB. But since we had to do a lot more testing for this new version, we used a low profile header socket to allow the OLED to be removed. This is necessary because the programming pins are also used to interface with the OLED screen. We used the PIC Programming Helper from June 2021 (siliconchip. com.au/Article/14889) to help with our testing. But we also needed to do some testing and tweaking on the final design, so having a removable display was handy for these later stages. We used a low-profile (5mm high) header socket to keep the unit compact, and it’s what you can see in our photos. But we recommend using the direct mounting method unless you are considering designing your own firmware. So we’ll describe that. If the OLED module’s header is not attached, solder it now, at right angles to the module’s PCB. Then mount the module onto the PCB. You might find that the back of the OLED module touches IC1. In this case, use BluTack or a cardboard shim to keep the two apart until the module is securely soldered. That should leave the long pins protruding at the back of the PCB. You can trim them carefully with a sharp pair of sidecutters. Testing Fit a CR2025 or CR2032 3V coin cell into the cell holder, noting the polarity on the cell holder. After about a second, the OLED should show R HAND as per Screen 1. If not, check your soldering and that 3V is present on either the OLED module’s header pins or pins 2 and 3 of CON1. If 3V is not present, the cell may be flat or there is a short circuit. Remember to check the reverse of the PCB, as the cell holder, arms and OLED header are all very close together. Before you proceed to use the SMD Test Tweezers, you might like to go through the calibration procedure as detailed in the panel overleaf. Operation With the calibration and setup The tips might look a bit wonky, but when the arms are squeezed to bring them together they become parallel at about the distance you would typically use them (wide enough to hold a typical SMD component). Australia's electronics magazine siliconchip.com.au complete, normal operation will start. You should see a display indicating the battery voltage preceded by the letter B. After five seconds, the Tweezers will enter sleep mode and can be woken by touching the tips together. At this point, the new Tweezers work much the same as the older version, apart from the expanded capacitance range. If you close the tips to measure the short circuit resistance, you should see a value jumping around between 0W and 1W if everything is working correctly. We measured the current consumption on our prototype as much the same as the original Tweezers. The new Tweezers use around 4mA when working and 5μA when sleeping. So the cell life will depend mainly on how much they are used, tending towards the shelf life of the cell. Finishing touches Like we did with the original Tweezers, you might also consider adding some heatshrink to the Tweezers to add some protection and to keep the battery from being removed. The 10mm heatshrink can be put over the arms, leaving just the tips exposed. It should be pushed up firmly against the main PCB before being shrunk with a heat gun. The wider heatshrink fits over the main PCB and should overhang the end enough to prevent the cell from being removed. Of course, you will have to remove and replace the heatshrink to replace the cell. Screen 1: the first display when the Tweezers are powered on is the HAND setting, orientated in correspondence to the setting. Leaving the tips open selects right-handed operation. Also, be careful to not shrink the large heatshrink too tightly around the OLED, as its glass screen can be fragile. Aim heat along the edges to avoid heating the OLED and battery, and only shrink enough to secure everything in place. Kit availability & upgrading As the hardware is the same as before, we will update our SMD Test Tweezers kit to include the new micro programmed with the latest software. The kit still includes the heatshrink tubing mentioned above, along with everything else you need to build the tweezers. We’ve also added two goldplated pin headers for the tips. While we think the kit cost is low enough that it’s worthwhile simply building new Tweezers, if you really want to upgrade a pair you’ve already built, you can order the programmed micro from us and swap it over. We suggest you only do this if you are confident in removing SMDs and cleaning up the board to accept a new chip. This is most easily done with a hot air station, although it can be done with a regular soldering iron if you know how. Future improvements The SMD Tweezers are somewhat limited by only having one resistor to apply voltages to components, which is in turn limited by the 8-pin PIC. The 10kW resistor limits the applied current to about 300μA, meaning that the diode forward voltages reported are much lower than expected, and LEDs do not light very brightly. We are considering a more complicated SMD Tweezers design using a chip with, say, 14 pins. That might let us add new test modes and improve the existing ones. The extra pins mean we could have multiple current-­limiting resistors and thus a choice of test current. As well as expanding the range, additional test resistors will also improve the overall accuracy. Caution Like any project that uses coin cells, the Tweezers should be kept well away from children who may ingest them. The Tweezers also have quite pointy tips, another reason to keep them out of reach of curious fingers. Improved SMD Test Tweezers Complete Kit for $35 Includes everything pictured (now comes with tips!), except the lithium button cell. ● ● ● ● ● ● Resistance measurement: 10W to 1MW Capacitance measurements: ~10pF to 150μF Diode measurements: polarity & forward voltage, up to about 3V Compact OLED display readout with variable orientation Runs from a single lithium coin cell, ~five years of standby life Can measure components in-circuit under some circumstances siliconchip.com.au SC5934: $35 + postage siliconchip.com.au/Shop/20/5934 Australia's electronics magazine April 2022  77 Setup and calibration The accuracy of modern surface-­ mounted resistors is excellent and, as built, the SMD Tweezers will distinguish resistors well enough for most constructors. Still, the extra program space available on the PIC16F15214 gives us room to add some routines to add some settings and calibration constants. With all of us at Silicon Chip being right-handed, we now realise an overlooked aspect that probably makes the original Tweezers very difficult to use for the left-handed. So the first new setting is the option to flip the display so that it is legible when the Tweezers are held in a left hand. There is also the option to set the value of the nominally 10kW series resistor between pins 2 and 5 of IC1. Rather than trying to measure its value, we recommend testing an external part of a known value and adjusting the calibration until the Tweezers measure it correctly. The series value is simply adjusted in proportion to the desired change in calculated resistance. For example, if your displayed test resistor is 1% low, increase the series resistor value by 1%. This won’t adjust for things like trace and contact resistance, so there is a separate calibration step for those. Still, the preset value we have loaded into the Tweezers firmware will be quite accurate, as long as your Tweezers build is similar to ours. You may have noticed that the Tweezers do not have any buttons. So the various settings are configured using the only input device available: the probe tips! We can step through the setup and calibration by opening and closing the tips of the Tweezers at various points. It’s a slow but effective process, made easier by having a screen to show what is happening. Look at the flowchart shown in Fig.5 as we explain the process. The setup procedure only runs when the microcontroller is powered up, so it can be triggered by removing and reinserting the cell. The right-hand or left-hand operation setting is selected at the instant power is applied. If the tips are open, right-handed operation is selected; otherwise, left-handed operation is set. A message is also shown to RELEASE (Screen 2) the tips, and the microcontroller waits for this to happen so that later calibration steps are not triggered inadvertently. If you find it fiddly to insert the cell while holding the tips closed, join the tips with a female-female jumper wire while inserting the cell. The handedness setting is kept in RAM, saving on wear to flash memory. Since it is set every time power is applied, there is no need for non-volatile storage. As the remaining calibration steps can be a bit fiddly, there is the option to skip them. You enter calibration by holding the tips together when prompted (Screen 3) or leaving them open to skip. If the tips are left open for about the first 10 seconds after powerup, the settings are the same as the original Tweezers. The next step is to adjust the value of the nominally 10kW series test resistor. The OLED displays CAL R+ and a countdown timer (Screen 4). Any time the tips are closed during this phase, the displayed value will increase, and the timer will reset. This is followed by the CAL R- phase (Screen 5), which works much the same but allows the value to decrease. If any changes are made, the cycle repeats the CAL R+ and CAL R- steps until no more changes are made. The OLED then prompts to save the value; again, touching the tips together before the displayed timeout is confirmation that the value is to be saved Screen 2: at various times during setup, you may be prompted to RELEASE the Tweezers by opening the tips to ensure that multiple settings are not inadvertently made. Screen 3: the first prompt is to complete the calibration process and is accompanied by a nominal five-second timer. If the tips are left open during this time, calibration is skipped. Screen 4: when the tips are closed on this screen, it will increase the saved value of the series test resistor in 1W steps. See Fig.5 for a flowchart explaining the process. Screen 7: this screen shows while the value is saved to confirm that your selection has been acknowledged. Screen 8: you are prompted to close the tips to calibrate their contact resistance. If you don’t, the saved value is not changed. Screen 9: the contact resistance is measured around 20 times to get an average. The value shown here is higher than the default value of 16W. 78 Silicon Chip Australia's electronics magazine siliconchip.com.au ► and, if this is done, a brief message is shown indicating this. These are seen in Screen 6 and Screen 7. Finally, whether any changes are made or saved, the value of the series test resistor is freshly loaded from flash memory and displayed for user confirmation. The next step to set the contact resistance is simpler, as this is measured rather than entered. Note that the timers shown on these screens are not high-precision. The internal timings vary depending on what is displayed (especially changing numbers, which take time to render). We’ve tried to make the countdown timers appear reasonably consistent as seconds, but they are not highly accurate. The prompt seen in Screen 8 is the start of the contact resistance calibration. When the tips are held together, Screen 9 is seen. This shows the measured contact resistance, averaged over several readings. The default value is 16W, as measured on our prototype. If the tips are accidentally opened, the process aborts, and you will need to restart the calibration process to repeat it. Otherwise, the averaged value is shown along with a prompt to save it, as seen in Screen 10. Close the tips to Fig.5: a flowchart representing the setup and calibration process that occurs when power is first applied to the Tweezers. It looks complicated, but it is simple to go through once you understand the concepts, and the Tweezers prompt you with what to do at each step. confirm or leave them open to allow the counter to time out. Screen 11 shows the actual value loaded from SC flash memory. Screen 5: similarly, this screen allows the series test resistor value to be decreased. If any change occurs, these two steps are repeated until no change is detected. Screen 6: this prompts you to confirm that you wish to save the entered value to non-volatile flash memory. Close the tips to do so. Screen 10: if you don’t get this message, the Tweezers have detected that the tips may have been opened, so the measured value is inaccurate. Screen 11: finally, the actual value saved in flash memory is reloaded so that you can confirm that the saved value is correct. siliconchip.com.au Australia's electronics magazine April 2022  79 Working with the latest 8-bit PICs from Microchip seem to be releasing a new series of PICs virtually every year. We’re trying to keep up with them by using the latest devices in our designs, mainly because each new series offers better value than the last. Here is what we’ve found in switching to the latest series. W hile the current parts shortage makes things difficult, we always relish the opportunity to work with new parts and learn about their new features. In updating the SMD Test Tweezers (article starts on page 72), we’ve been using the PIC16F15214 and we’re also anticipating some fresh new parts being released later this year. The crisis strikes back With the electronics parts shortage showing no signs of easing, we found that the PIC12F1572 that we have used in a number of our designs were no longer available in the -I/SN variant, which is the SOIC package version [SN] specified for the industrial temperature range [I]. The -E/SN part (E = extended temperature range) variants are a drop-in substitute, although they are slightly more expensive. We got some of those while they were available. But soon, we couldn’t get either. We then noticed that there are also PIC12LF1572 variants, where the “LF” infix signifies a part designed for operation at lower voltages (not all PICs have LF variants). As we were powering many of these devices from 3V lithium coin cells, these parts were also suitable, so we grabbed some before they (quickly) became unavailable. The LF variants are suitable for use with our SMD Tweezers and Tiny LED Christmas Ornaments designs (November 2020; siliconchip.com.au/ Article/14636), both running from the previously mentioned coin cells. In fact, the LF parts have slightly lower current demands than the F parts, so they are a better choice in designs that don’t go over 3.6V, and are well suited to battery operation. Even so, we found ourselves 80 Silicon Chip struggling to get parts that we needed to supply kits for projects using the PIC12F1572 microcontrollers and their variants. As well as the Ornaments and SMD Tweezers, the Nano TV Pong (August 2021; siliconchip.com.au/ Article/14988) and Digital FX Unit (April & May 2021; siliconchip.com. au/Series/361) also use this or similar chips. As our stocks dwindled, we discovered that the newer PIC16F15213 was available, so we adapted the Xmas Ornament firmware to work on these chips and started supplying them with kits. The PIC16F15213 is much the same as the PIC16F15214 we’re using in the Improved SMD Test Tweezers, but with half the RAM and half the flash program memory. Even then, the simple program for the Ornaments only uses a small fraction of the PIC16F15213’s resources. The control firmware for the Nano TV Pong was written mostly in assembly language to allow it to be fast enough to generate a composite video signal in real time. Assembly language is more part-­ specific than the C language we normally use, so it is not so easily transferred to a different microcontroller. But by using the 16F15213s for the Xmas Ornaments, we were able to keep enough 12F1572s on hand. Having been exposed to a new 8-pin PIC series, whether we wanted to or not, we decided to see what we could do with it, and the Improved SMD Test Tweezers was the logical outcome. Return of the IDE The PIC16F152xx family is quite By Tim Blythman Australia's electronics magazine new, with the data sheet dated 2020. So you will need a fairly new version of the MPLAB X IDE to work with these parts and you will also need to install the correct DFP (device family pack), as well as a compiler. We’ve successfully used MPLAB X versions 5.40 and 5.50 with these parts. Note that these versions only support 64-bit processors on your computer, so you might have trouble working with these parts if you have an older computer. We’re using XC8 compiler v2.20 for the updated version of the Tweezers. The older v2.00 appears greyed out when the PIC16F15214 part is selected, while the newer v2.32 appears to be compatible. The device support list also indicates that the PICkit 3 can’t handle these parts either. We have been using an MPLAB Snap programmer and it appears that the PICkit 4 will also work. On that note, we should point out that programming these parts is blindingly fast; fast enough that you aren’t really sure the programmer has done anything! The PIC16F152xx family is described as an enhanced mid-range 8-bit microcontroller. The ‘enhanced’ designation mostly describes the processor core and instruction set, which have been designed to work with features of the C programming language. The enhanced core has been around a while, with parts like the PIC16F1455 (used in the Microbridge project from the May 2017 issue – siliconchip.com. au/Article/10648) having this feature. Still, the PIC16F152xx family appears to have a slightly newer generation of the enhanced core which lacks the OPTION register and thus also the OPTION opcode. Remarkably, the TRIS opcode (which was long ago siliconchip.com.au Silicon Chip Binders REAL VALUE A T $19.50* PLUS P&P Like most microcontrollers from Microchip, the PIC16F15214 comes in multiple different packages with only some of them shown above. marked as deprecated) is still around. The peripheral pin select (PPS) function allows certain digital peripherals to be mapped to different digital pins. It appears that for all PIC16F152xx parts with twenty or fewer pins, just about any digital peripheral (including PWM, timers, counters and serial communication) can be mapped to any digital pin. There are a few other novel features that we found while perusing the data sheet. The flash memory can now be partitioned with the MAP (memory access partition) settings. This allows certain parts of the flash memory to be allocated to various purposes. For example, regions can be marked as boot block, application block and storage area. If a storage area is marked, code cannot be run from that area, which is sensible if the area is used to store data which should not be executed as code. These devices lack an internal EEPROM, so the storage area is typically used to provide an equivalent place for non-volatile, infrequently changed data to be stored. Unlike EEPROM, it can only be erased a page at a time. The boot block and application block can both be separately write protected. A typical implementation for upgradeable firmware would provide for a write protected boot block and a writeable application block. Code in the boot block could be written to receive and modify firmware in the application block to upgrade the firmware. These restrictions only apply to code running on the actual chip and naturally, an external programmer is always able to make changes or erase the device. An internal high-frequency oscillator can provide a main system clock from 1MHz up to 32MHz (in powers of siliconchip.com.au two) and this can be changed dynamically during program operation by setting the OSCFRQ register. There is also a low-frequency oscillator which runs at a nominal 31.25kHz; this is used for the watchdog timer and can even be used as the main system clock, allowing the high-frequency oscillator to be completely shut down to save power. The PIC16F152xx family is an interesting group of parts. Despite only having the most basic of peripherals, they do have some useful processor features, and they are generally excellent value for money. Still, as we noted, you may need to upgrade your software and programmer to work with them. A new hope While reading the data sheet for the PIC16F15214, we came across a page describing a future PIC microcontroller family, the PIC16F171xx. Among other features, these will boast a 12-bit ADC (analog-to-digital converter) peripheral. That alone would add a noticeable boost in accuracy for our SMD Test Tweezers design. This family of devices should appear in mid-to-late 2022 (with the usual caveats about availability under the current circumstances). We will definitely try to get our hands on some, and will likely start using them in projSC ects in late 2022 or early 2023. The PIC16F17146-E/P is one of the upcoming 8-bit PICs from Microchip. It boasts a 12-bit differential ADC. Australia's electronics magazine Are your copies of SILICON CHIP getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of S ILICON C HIP. They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. H 80mm internal width H SILICON CHIP logo printed in gold-coloured lettering on spine & cover Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Order online from www. siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *See website for delivery prices. April 2022  81 Winners and runners-up to Dick Smith’s Noughts & Crosses Competition We were pleased to receive nine entries in this competition, with four different winners selected for the $500 prizes (plus signed copies of Dick Smith’s autobiography). Most of the runners-up did a great job too. Here are all the details. We’ll start with the four winners, then mention the other five entries. Most submissions span multiple pages, and we don’t have space to reproduce all of that information here, but we’ll try to include the basic details of each submission. Winner #1 – Dr Hugo Holden (most ingenious entry) We received this submission first, and frequent readers will recognise Dr Holden as a regular contributor to the magazine. We had to award him the prize for two reasons. Firstly, his design is relatively simple yet based entirely on discrete logic and an EPROM chip spread across two neat PCBs. Secondly, he used a very clever method to allow the computer to play the game. He 82 Silicon Chip fabricated discs with Xs and Os on them, and the game is played by placing those discs in the grid of 3 x 3 depressions on the device’s front. The discs contain magnets with opposite polarities for Xs and Os, and Hall effect sensors determine which discs are placed where. When the computer wants to make a move, it lights up the LEDs in one of the recesses, and the human player places the computer’s disc there. They then make their own move, and the process repeats until someone wins or it’s a draw. If the computer wins, it makes a beep to alert the player. We think that’s a very innovative and intuitive ‘user interface’. Not only does it look and feel like a board game, but it’s also very easy to play, and it looks very professional too. It’s so good that we plan to run it as a project article later this year. Winner #2 – Max Morris (youngest entrant) Max is 12 years old, and his entry uses an array of pushbutton switches and a separate array of LEDs as the user interface, controlled by an Arduino Australia's electronics magazine Uno. He supplied the code as a ‘sketch’ that uses much the same approach as a human player, assessing the situation and deciding whether it needs to block the opponent’s move or try to form a line. He sent photos of the finished version, reproduced here, plus his original breadboard prototype. We think it’s a great effort given his age, and he definitely deserves the prize for the youngest entrant to submit a design that meets all the criteria. You can see a video of Max’s machine in operation at siliconchip. com.au/Video/6335 Winner #3 – Mark Wrigley (best entry without a micro) While we felt that Dr Holden’s entry was very clever, and it does not use a microprocessor, Mark’s design is also very commendable. As for the photo, well, let’s just say it’s a good thing that neatness wasn’t one of the criteria! Mark used bicolour LEDs and an array of pushbuttons for the user interface, and similarly to Dr Holden, he used a flash chip to store the data needed for the machine to make its siliconchip.com.au moves. And again, like Dr Holden’s machine, that chip drives some discrete logic that maintains the game state, decides when to make a move and so on. Mark was also fairly economical with his use of ICs as, besides the flash chip, it mainly comprises some latches and decoders. So overall, a simple concept and an elegance to the circuitry hidden behind that “rat’s nest” assured him a place on the podium. His use of a chopping board, similar to the way people used to build radios on breadboards, was also quite endearing. Winner #4 – Martin Irvine (simplest entry) Steve Schultz’s incredible 3D-printed electromechanical Noughts & Crosses machine has to be the most ambitious submission we were given. It earned him a special extra prize. Martin was the last person to enter the competition – at the last minute, in fact – but he took a different approach from most other entrants that we felt earned him the final prize. He used the fewest discrete parts to build his machine, with a total of just 30 components, including the nine LEDs and nine buttons that are almost unavoidable. It would be hard to use any fewer! Essentially, what he did was take a 16-pin microcontroller and connect one pushbutton and one bicolour LED to each of nine digital input/output pins. The LEDs are furnished with current-limiting resistors. The micro can turn on one LED to be either green or red by driving the associated I/O pin high or low, or it can switch that pin to be a digital input to sense when the corresponding button is pressed. The only other parts on the board are a coin cell for power and a bypass capacitor. He also designed and assembled quite a neat PCB for his submission, shown below. You can see Martin’s entry in action in the YouTube video at https://youtu. be/LjqZjLTh7x0 We like the simplicity of Martin’s design so much that we plan to run it as a small project in an upcoming issue. Special prize winner: Steve Schultz ► Dick decided to award a ‘special’ unannounced $250 prize to Steve as he was the only person so enthusiastic about this challenge that he tried to build an electromechanical noughtsand-crosses machine, similar to the one Dick made all those years ago. In many ways, what Steve attempted to do was considerably more difficult than what Dick did because he fabricated many of the parts for the machine himself. He did this by 3D-printing most of the mechanical parts. It uses solenoids to drive plastic selectors, a bit like the old uniselectors that Dick used. It appears that Steve built a fully working electromechanical Noughts & Crosses playing machine, so he might have been a winner. But he admitted that he hadn’t had time to thoroughly test it, to verify that it would always play the correct strategy. Still, he did such a good job that Dick decided to award him a prize anyway. You can see a demonstration video of Steve’s machine at siliconchip.com. au/Video/6334 ► siliconchip.com.au Martin Irvine went to the trouble of populating this neat little credit-card style PCB. It has just 30 onboard parts in total and runs from a coin cell. Talk about a “rat’s nest!” But what Mark Wrigley’s design lacked in aesthetics, it made up for in the cleverness of the circuit. Australia's electronics magazine April 2022  83 ► If there was a prize for the least amount of assembly, Keith Anderson would have won it with this minimalistic build. David Such’s design is the definition of overkill, ► using a 32-bit micro plus an FPGA to play the game. But there’s no doubt that it is an effective solution! Runner-up #1: Keith Anderson Runner-up #3: Dr George Galanis Final entrant: Angus McPherson Keith’s entry was the other submission we were considering for winning the prize for the simplest entry. If you only count the parts you have to buy and put together, there are just two: an Arduino Uno and an Adafruit TFT colour touchscreen. That’s the fewest parts of any entry. Of course, both those parts have a lot of discrete components on them, and there are no doubt many, many transistors spread across both devices. So ultimately, we couldn’t conclude that this was the simplest design. Still, it’s a solid effort, and we will publish the details (including the Sketch code which, let’s face it, is basically everything) in an upcoming Circuit Notebook entry. Dr George Galanis submitted a treatise covering the logic required to play Noughts & Crosses in great detail. He also sent CAD files of the 12 (!) boards he designed that carry said logic. Apparently, it forms a monster of a game-playing machine when put together. The circuitry is spread across eight schematic sheets! He obviously put a tremendous amount of work into the design, so while we didn’t feel his entry fell into any of the winning categories, we awarded him a smaller runner-up prize. You have to admire the dedication involved in creating such a design, even though it would be impractical to build it (see below). Angus also attempted to design a Noughts & Crosses playing machine using mainly discrete logic, with quite a few transistors added into the mix. Unfortunately, he ran out of time to finish it, so he was not considered for one of the prizes. Still, we appreciate that he sent in his partially completed work. Conclusion We were very pleased with the number and diversity of the entries. Each entrant took a different approach to solving the problem, and in most cases, they succeeded. We hope that they enjoyed making the designs as much SC as we did seeing them. Runner-up #2: David Such If there were a prize for the most unnecessarily overpowered entry, David Such would surely have won with his entry that includes an FPGA (field-programmable gate array) IC! He built it on an Arduino MKR Vidor 4000 board which includes both a SAMD21 32-bit microcontroller and the aforementioned FPGA, and he used both to play the game. The user interface is quite clever, consisting of an 8x8 bicolour rectangular LED matrix to display the current state of play and a pushbutton/ joystick shield for control. We were sufficiently impressed with David’s design that we plan to feature it in the Circuit Notebook section of an upcoming issue. 84 Silicon Chip An Altium-produced 3D rendering of Dr George Galanis’ monster entry. He was nothing if not thorough. You have to appreciate the dedication involved in putting this much work into the competition. Australia's electronics magazine siliconchip.com.au Prices end April 30th. 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Sale Ends April 30th 2022 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au A 1012A SAVE 20% 27 $ ebay.com.au/str/altronicsaustralia Western Australia Build It Yourself Electronics Centres 59 $ D 0985 Dog ate your remote? This handy replacement features IR learning plus preprogrammed codes for 100’s of popular equipment brands. » 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 Find a local reseller at: altronics.com.au/storelocations/dealers/ 88 Silicon Chip siliconchip.com.au © Altronics 2022. 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 Australia's electronics magazine 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. 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. Very simple adjustable electronic load There are many occasions when finding the correct load resistor is difficult, especially when the load will dissipate more than 10W. It is also helpful to have a variable load to gradually increase the current such as when testing a switchmode regulator, to see how it behaves across its full load range, or if you are trying to find the trip point of a fuse, PTC thermistor or circuit breaker. This elementary circuit is based on an N-channel Mosfet with a controllable gate voltage. Almost any N-channel Mosfet will work as it is not necessary to have ultra-low drainto-source resistance Rds(on). Arguably, a linear Mosfet like the BUZ11 will work best if very gradual and stable adjustments are desired. The circuit as presented uses an IRF1405, a very rugged switching Mosfet, and it works well. One critical component is the multi-turn potentiometer, which needs a high enough resistance to not exceed its power rating at the maximum expected voltage. This circuit uses a 10kW pot, but 5kW or even lower may be a better choice as long as it has a sufficient power rating. A good heatsink for the Mosfet is essential, especially if you intend to load the unit for more than a minute or so. I used a Jaycar fan type heatsink (Cat HH8570) which fits neatly across the back of a small sloping-front instrument case holding the ammeter and potentiometer. The Mosfet should be mounted directly to the heatsink with some thermal paste (not insulated) to improve heat transfer. Note that the heatsink will be at drain potential (ie, the load voltage). I included a ‘kill switch’ to close down the gate if there is any sign of Circuit Ideas Wanted siliconchip.com.au thermal runaway. In practice, this unit is very stable as an increasing temperature tends to lower the load current. The low-value resistor connected in series with the Mosfet’s source terminal is critical for stability. For a maximum current of 5A, a 5W wirewound resistor works well there. Still, for higher amperages, a higher wattage will be necessary (or use three 0.33W 5W resistors in parallel with plenty of air around them). The fuse needs to be rated no higher than the meter range, which can be as high as you wish, subject to adequate heatsinking and being careful to stop increasing the load when approaching full-scale. My need for this unit arose from having some apparently faulty plugpacks and other power supplies that I needed to test. Unless you are very sure the device under test (DUT) can handle an overload, you should gradually increase the current while watching the voltage supplied by the DUT. I received considerable help from John Clarke in designing and building this circuit. It is simple but effective. Jon Kirkwood, Castlecrag, NSW. ($80) The heatsink (above) and finished electronic load (below). Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia's electronics magazine April 2022  89 Three reaction time games This circuit provides three games to measure the fastest reaction time of the players. Which game is played is chosen by the GAME SELECT switch (S2), and instructions are shown on the LCD screen. Game one gives one player four chances to get the best reaction time. Game two is designed for two players, each having two chances. Game three can be played by two, three or four players, each with only one chance. By default, the device is set to game one for one player. To play the game, apply power and wait for the “Press Start Button” message on the LCD screen. The game begins by pressing the START/RESET button (S7), causing LED1 to start blinking randomly 1 to 3 times. Then it stays lit, and the sounder beeps to signal to the player to press the PLAYER 1 button (S3). At this point, an increasing counter appears on the lefthand side of the first line of the LCD. It counts up in milliseconds from 1 to 8000. At the appropriate time (when LED1 stays lit or the beep is heard), the player must press PLAYER 1 (S3) as fast as they can to stop the counter. This causes a second counter to appear on the left side of the second line, and it starts counting up. Right away, the player must press PLAYER 2 (S4) to stop this counter 90 Silicon Chip and start a third counter on the third line, then press PLAYER 3 (S5) to stop this counter and start another on the fourth line. Finally, the player presses PLAYER 4 (S6) to stop that counter. The four counters now show the registered reaction times, with the sum of the reaction times of the four steps on the right-hand side of the bottom line. The lower the value, the shorter or faster the reaction time of the player’s finger. Game two is selected by a long press of pushbutton S2. The first player uses the S3 and S4 buttons, while the second player to S5 and S6 buttons. Again, the game begins by pressing the S7 button, causing LED1 to flash randomly one to three times and then stay lit while the sounder generates a beep. At this moment, two counters appear on the left and right sides of the top line. Right away, players one and two must press S3 and S5 respectively to stop these counters and cause two more to appear on the second line, and these start counting up. Then they must press S4 and S6 to stop counters these counters. The reaction times of both players are now registered, and their sums are shown on the third line of the LCD. The player with the lower value of the sum (faster reaction time) is the winner. The winner is also displayed on Australia's electronics magazine the fourth line (for instance, “Winner: Player 2”). Game three is selected by another long press of S2. To select the number of players (2-4), press and hold S4, S5 or S6 for a two, three or four-player game respectively, then press S7 and release both. For instance, to select a two-player game, press and hold S4 first and then S7 and finally release both buttons. In a four-player game, there are four counters on the left side of the four lines of the LCD, which all start siliconchip.com.au NBN backup battery at 0. The game begins by pressing S7, causing LED1 to flash randomly one to three times and then remain on while the sounder generates a beep. Once LED1 is on, or the beep is generated, all four counters start counting up in milliseconds from 1 to 8000. Now each player should press their own pushbutton switches as fast as possible to stop their relevant counters. The fastest player to press their button wins. Then the player with the quickest finger or the minimum reaction time (the minimum counter value) is announced as the winner on the LCD screen (eg, “Winner: Player 4”). It’s possible to have multiple winners if the buttons are pressed simultaneously. In all three games, if a button is pressed too early (in the start status while LED1 is blinking), it will continue flashing, and the sounder will beep until the button is released. Then after another random flashing cycle, LED1 will stay on while a beep is made to signal to the players to press the play buttons to resume the game. If one or more buttons are not pressed within eight seconds (8000 milliseconds), the counters stop at 8001. The display will then clear to show “Timeout Error” on the first line and “Press start button to play again” on the third and fourth lines. To reset and restart the game, press S7. The software for this circuit can be downloaded from: siliconchip.com. au/Shop/6/6339 Mahmood Alimohammadi, Tehran, Iran. ($80) siliconchip.com.au Having recently had the NBN installed, I found that now I had two devices (the NBN modem and the wireless router) both powered by plugpacks and both dependent on mains power to keep working. We get the occasional blackout in my area, and without these devices, I have no internet connection on my tablets and other battery-powered devices. Reading past articles in Silicon Chip inspired me to design a simple backup power supply. The circuit operates as follows. The mains power supply is connected via CON1. I used one of the NBN plugpacks (12V DC). IC1 is a precision adjustable shunt regulator, but is being used here as an open-collector comparator with a precision voltage reference connected to one of its inputs. With voltage across CON1, transistor Q1 is switched on and it pulls the reference input of IC1 low. This prevents IC1’s output transistor from conducting, so Q2 is off, and the only path to output connector CON3 is from CON1 via schottky diode D1. LED1 is also lit as it is powered from the DC supply, indicating normal operation. When the plugpack voltage disappears, as long as the battery voltage is above 9.25V, IC1’s reference input is allowed to rise above 2.5V. So IC1 sinks current from its anode terminal, switching transistor Q2 on, supplying the output from the backup battery. Australia's electronics magazine Since I used a lithium-ion battery as the backup battery, I needed to be able to disconnect the output if the backup battery voltage fell below 9V. You would probably change the 27kW resistor to 33kW for a lead-acid battery, raising the cut-out threshold to 10.75V. The green LED indicates that plugpack power is available, and the red LED indicates when the output is supplied from the battery. If both LEDs are off, there is no output voltage. This circuit does not include any way for the battery to be charged, because where I live, power outages are infrequent and I am happy to recharge or swap the battery manually every few months. If you need to keep the battery charged, you can permanently connect a mains trickle charger (for lead-acid types) or lithium-ion maintenance charger to the battery. D1 should be a schottky diode of sufficient rating for the load current. Transistor Q2 can be any PNP transistor rated for the output current; something in a TO-126 or TO-220 package will do, and it does not have to be heatsinked. I built my version on stripboard and housed it in a small plastic box. Of course, this can be adapted for many other uses where a simple backup supply is required. Robert Budniak, Denistone, NSW. ($80) April 2022  91 SERVICEMAN’S LOG Gaining a superpower, at least temporarily Dave Thompson I’ve always wanted to be able to see in the dark, but sadly, that is not among my superpowers (mainly, I’m just good at repairing stuff). But when the opportunity presented itself to try a ‘toy’ that could give me that power, if only briefly, I jumped at the chance. Every now and then, a job comes into the workshop that I find very interesting. Much of my work is boring computer stuff that any current 12-year-old can do, and is barely worth mentioning. But there is a wealth of projects out there built by keen hobbyists that sometimes don’t go to plan, and sometimes they need help getting them going. Any newly-built electronic device, powered up for the first time, might not work. At least not correctly. In the worst case, the magic smoke escapes in a catastrophic failure. I’ve had plenty of all of these scenarios in my time, but I have learned not to be so reckless when powering up newly built devices! I remember all too clearly that eagerness to solder everything in, wire it all up and just throw the switch (while throwing caution to the wind) without first checking thoroughly whether I have made mistakes. In that moment of excitement, the thought doesn’t even occur! Errors are not always lethal in hobby electronics, but caution is still more prudent than impatience. A blast from the past A while ago, a local guy brought in a device that I 92 Silicon Chip recognised immediately because I’d wanted to make one since I first saw plans and kits advertised in those small ads typical of late ‘70s to early ‘80s American electronics magazines. It was a ‘see in the dark’ “scope”, and back then, I thought it was merely a joke, like those X-Ray glasses you could buy for a buck. We all know they were a con – disappointingly, you couldn’t see the bones in your hand or see-through clothes like the ads promised. That was until, in the mid-1980s, I sent away for a book titled “Build Your Own Space-Age Projects” by a chap named Robert Ianini. Buying anything from overseas was a real mission in those days, before the internet existed or was widely accessible. I had to write to the company in America and enclose a money order, sourced from the post office, for an equivalent number of US dollars. Hopefully, after about six months, I’d receive the book. It did eventually arrive, and that ‘see in the dark’ project was one of the devices featured (along with such projects as anti-gravity machines and various home-built high-powered lasers and electron “ray” guns). It was then that I realised it was a legitimate electronics project that could be built by the home hobbyist. I’ve always been fascinated with night-vision stuff, and here was something I could potentially build myself. Although it was adequate for basic experimentation back in the ‘80s, it was nowhere near as good as commercial equivalents available at the time. Night-vision hardware – or, more correctly, the image intensifier tube inside the device – is typically classified in ‘generations’. This starts at Generation 0 and goes up to 3rd generation for modern starlight-amplified devices – at least for civilian use. These days, it is almost impossible to import any of today’s Gen3 night-vision devices from the USA or the UK without an export license from those countries, which of course isn’t easy (or cheap) to acquire. This DIY device would likely be somewhere between Generation zero and one, in that it requires an external illumination source to see anything at all. In other words, it doesn’t amplify available ambient light as the later generation devices do. The biggest problem for me back then, and what eventually stopped me from building one, was the requirement for a very specific type of vacuum tube called an “image tube” or “image converter tube”. This tube has a mirrored 28mm ‘lens’ at the front and a small, green, phosphor-coated Australia's electronics magazine siliconchip.com.au cathode-ray-tube style ‘viewer’ at the rear, about 15mm in diameter. These tubes were not available anywhere in New Zealand at the time (or even Australia as it turned out; I looked for one on a couple of my early visits there). So this project was dead in the water from the beginning. Even the supplier in the USA – the guy who wrote the book (still) runs a company there providing kits and plans – couldn’t supply the tube, so it had to be sourced separately. Oh well, just another dead idea among many others! And this is the way it remained until a few years ago. I was browsing an overseas auction site for valves for guitar amplifiers when, suggested to me at the bottom of the listings, was one of these image tubes, a Capehart Farnsworth 6302 Image Converter tube. I remembered, from all those years ago, that it was a direct substitute for the original IR16 type tube specified in the plans. This one was ‘new old stock’ (NOS), still in the box for only US$80, including shipping. As this triggered my memories, I thought I might just revisit this project after 30 years. So I snapped it up and hoped it didn’t get broken in transit. It arrived safely, and I put it with my other tubes in a drawer. There it sat, unused. I never did get around to building a ‘see in the dark device’ because, well, just because. to check it, but even with fresh batteries, the output (invisible to the naked eye) was pretty weak. I had an idea to fix Enter the customer this, but I would talk to the client about it later. Imagine my great surprise when a customer brought one I also put a fresh 9V battery into the handle of the ‘scope’ of these exact units in to see if I could fix it! He’d been and pressed the button, but there was no life from the tube given it by an uncle or some-such who had built it way at all. That didn’t bode well. The problem could be caused back when and he knew very little about it, except that it by the tube or any part of the power supply or oscillator used to work, but it didn’t anymore. boards. It looked almost identical to the project from all those The circuit is pretty straightforward; the power input years ago, so I was keen to get stuck in and see what was takes 6-12V DC (9V rechargeable battery preferred). A reawhat. sonably standard single-transistor, free-running LC oscilThe customer – as is typical – didn’t want to spend a lator drives the primary of a custom transformer. fortune on it, so I said I’d assess it and see what I could do. The secondary connects to a 12-stage full-wave voltage I started with the illuminator. This was a crudely-­ multiplier (in this case, a classic Cockroft-Walton arrangeconverted torch, with the reflector chopped up to accom- ment of diodes and capacitors) which supplies high-­voltage modate a small array of infrared LEDs. I used my camcorder DC ranging from 12-20kV (typically 15kV depending on the battery state) to drive the tube. There is also a tap from early on in the voltage multiplier that provides about 1/6th of the overall potential to connect to the tube’s focus ring, allowing builders to adjust focus within the tube. This is typically done once the rest of the circuit is operating. Various taps can be taken from different junctions on the multiplier and tried until the sharpest image displays on the viewing end. Items Covered This Month • • • • • Gaining a brief superpower Fixing a ducted gas heater Tektronix 556 oscilloscope repair The revolving door of PVR repairs Fixing an aircon with a faulty switch Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Cartoonist – Louis Decrevel Website: loueee.com siliconchip.com.au Australia's electronics magazine April 2022  93 By itself, the tube image is inverted from one end to the other, so a sliding lens arrangement is used at the input end to correct this, allowing manual optical focus and also making things a bit larger. An eyepiece mounted at the back end of the PVC tube body is added mainly to protect the rear of the tube; it is basically a plain, unmagnified ‘lens’. Acquiring the right lens and eyepiece was another giant hurdle in the project back then, but obviously, the guy who made this one had purchased the short-form kit and sourced an image tube from somewhere else. Judging by the condition and colour of the PVC pipe used to build the device, it was likely quite old. Pulling it apart was easy enough – at least he hadn’t glued it all together. Pulling out the power supply from the handle and the tube-driver board from the main body of the viewer was also straightforward. The build quality was average, with some relatively sloppy perfboard point-to-point soldering employed. When boosting a voltage to this level, it is imperative that nice round solder joints are used on the multiplier, or at least normal joints insulated with enamel paint or corona dope, because arcs can form at the solder junctions if they are sharp and exposed. It all looked a bit rough and ready, but it obviously had worked at some point, so all I had to do was figure out why it wasn’t going now. Battery power was certainly getting to the board but stopped at the transistor, a classic TO-220 style MJE3055. From memory, this should have a heatsink, but it had none. I had several similar transistors in my parts bins, so I pulled this one and replaced it with a known-good one. This time, when I fired it up very carefully on the bench, I could hear the familiar faint HV crackle from the multiplier, which could indicate that something might be breaking down somewhere. The tube remained dark. It was good to know that at least the oscillator was working. The proprietary transformer used was also likely not open-circuit, but working around these Cockcroft-Walton circuits always makes me very nervous. I’ve experimented with them before many times, in the likes of air ionisers and various electrostatic experiments. It’s a case of once bitten, a hundred times shy! This one ‘only’ puts out in the region of 200µA at the nominal 15kV, but that’s enough to make someone jump and yell! flying leads, so a standard valve tester wouldn’t be of any help. I could find nothing about testing them online, so it was just a matter of swapping it out and hoping for the best. I temporarily put my tube alongside the unit. The IR16 has pre-connected wiring while the 6032 doesn’t, and that meant soldering directly to the metal body and rings around the tube itself. That also made me nervous, and the other thing was that the book plans (which I’d since dug out of storage) didn’t show which wires went where with this particular tube. There was nothing to do but try it, so I guessed where they were supposed to go by the physical layout of the tube itself. I mean, there are only three connections: one at the front, one as a ‘ground’ on the main metal body of the tube and one for the focus, which I assumed was the middle ring. What could possibly go wrong? As it turned out, nothing. I wired it how I thought, was über-careful soldering to the tube’s metal parts and used one of my trusty bench power supplies to power it all up. I started with severe current limiting, just in case, but gradually increased it until things started happening. It all looked OK, and the tube started glowing at the rear end. I could vaguely see an image, but it was very faint in bright light. I’d need to mount it and adjust the lenses and the focus voltage to really test it properly, not to mention using it with a decent IR source. I called the client and told him what the costs would be, and as he was OK with it, I persevered with the rest of the job. First, I resoldered all the multiplier’s connections and any others that looked dodgy, then mounted a heatsink on the transistor. I didn’t have a lot of room, but a small Jaycar heatsink I had (HH8514) fitted in the case and should suffice. As I might need to have the tube in and out to set the focus voltage, I temporarily mounted it in the PVC body and held it in place with sponge wedges. With the workshop lights out, and the illuminator on, I could make out some outlines, but the focus was off. So out it all came, and I used another tap to test it. There is a provision in the plans for adding a resistive voltage divider network to further fine-tune it, but as it turned out, the image was pretty sharp with the next tap along, so I left it at that for now. The converted torch illuminator was very crudely made, Taking the tube I don’t have the gear to measure that kind of voltage, but it appeared to be working, so that left the tube itself. This one was the IR16 version of the tube, which was different in connections and size to my 6032 type, but if necessary, I could make it work – as long as my tube was functional. I wouldn’t know unless I tried it, so I set about removing the IR16 from the body tube. It was held in with three long screws, 120° apart, threaded into the PVC body. These pressed lightly on the tube and centred it. They had been coated in what looked like RTV or some other silicone sealant to stick it all together. Space was tight, but with patience, perseverance and a sharp hobby knife, I managed to get it all out without breaking anything. From the outside, there’s no way to tell if the tube is working or not. It has no pins like typical tubes, just three 94 Silicon Chip Australia's electronics magazine siliconchip.com.au and while it would work, I had a better solution. When dad was alive, he experimented a lot with then-quite-new LED torches, and he had several that were rechargeable and about the size of a three-cell Maglite torch. I inherited several working models and a few he had used for parts. The torches use an array of bright white LEDs mounted in a specially-moulded reflector and were very bright; all I’d have to do is swap the white LEDs for infrared versions, and I’d have a very powerful, self-­contained IR illuminator. I’d already factored in the cost of this to the client, and while I was happy to give him the torch, I did need to buy 25 IR LEDs for the job. I disassembled the torch and, using my trusty Goot desoldering pump(s) and lashings of solder wick, managed to extract the old LEDs without damaging the PCB they were all mounted on. It was then simply a matter of installing the IR LEDs and putting it all back together. Turning it on resulted in absolutely nothing because it is invisible. But my camcorder showed a powerful beam. That night, I fired up the whole thing and scanned our backyard. The output from the tube was patchy in darker areas, but everything was visible. I was pretty impressed and spent quite a while playing with it. Satisfied that it was operational, I used RTV to bog in the tube and buttoned it all up properly. So, after all these years, I finally got to play with one and didn’t mind losing my tube to a working model. Sometimes I love this job. Fixing a ducted gas heater which had a faulty ignition M. H., of Albury, NSW had a whole range of electronic appliances fail in a short time. Is he cursed? Probably not, considering that he managed to fix them all with just a few dollars’ worth of parts and some hard work... My pool chlorinator cell wore out. My attempts to repair it worked for a short time, but the plates were corroded away after seven years of hard work. A new one was the only option, and $650 later, it was back in service. At the same time, some small ants had entered the chlorinator supply box and destroyed the SMPS driver IC. After an eBay purchase and a few weeks delay, the supply was back in service. Then tree leaves got past the filters, entered the impeller and jammed the motor, and the pool started going green again. The motor is designed to be easily split to remove the obstruction, and the motor ran again without relying on the thermal cutout device to protect itself. If I had called the pool company to fix all these problems, I would have probably spent $1000 more than I did, given all the service call fees and the fact that they would likely replace all the parts rather than fix them. I realise that they have a lot of overheads, and quoting for a new part is the best option for them. In part, that’s because it moves the warranty for the repair restoration to the manufacture for 12 months (or more) and moves liability away from the serviceman. Next? Now my ducted gas heater would not start. With an ear pressed to the outer case of the in-ceiling heater, I could hear the combustion chamber fan start and run. After a short delay, the fan stopped and the unit smelled of gas with no ignition. The cycle repeated endlessly. siliconchip.com.au Australia's electronics magazine April 2022  95 I removed the power for five minutes and tried again. Success, the combustion chamber fan ran, the gas relay operated and ignition. But the ignition lacked the aggressive volley of sparks sound that it usually had. The Honeywell ignition box was sad; most likely, it uses capacitor discharge via an SCR. The unit was easy to remove, easy to open, but impossible to repair. The manufacturer had covered the EHT section with epoxy resin. A lot of heat, wiggling and cutting eventually got the single-sided PCB out of the case to reveal a dry joint on the discharge capacitor (1μF 250V polyester). The remainder of the circuit design looked (to me) straightforward and expected, with a thin, cheap singlesided PCB manufactured by solder reflow. The capacitor measured close to 1μF, but I replaced it anyway with a 1μF 2kV polyester capacitor pinched out of a plasma TV. The unit produced the clearly audible volley of aggressive sparks while the flame established itself. Success! A professional serviceman (in my opinion) would not be inclined to diagnose the fault. After a quick assessment of the age of the unit, they would give the expected “I will get a quote for a new one” and “that model is not made anymore”. The replacement ignition system would come in about $500 plus the hourly service rate and call out fee. Again, I was greeted with a small pop and two blown 30W resistors. This had me quite confused, as all components for that rail tested good, and no other faults were obvious. These 30W resistors are no slouches, being 5W wirewound types, making me think there must be a catastrophic short somewhere. I then realised that testing the transistors out-of-circuit was a mistake; when installed back onto the heatsink, there was a short from collector to ground. On one of the little boots that insulate the transistor screw from the heatsink and allow a connection to the collector, there was a burned carbonised track from a previous arc. This was impossible to see as the boot is black. All that separated the 225V rail and ground was 1mm of burned plastic. Upon replacing this and the two 30W resistors again, the scope powered up as it should. I left it for half an hour before trimming the -150V, 100V and 225V rails. I’ll need to recalibrate the timebase as I fiddled with the voltage rails, but that can wait for another day. I can only assume that a build-up of dust and condensation from recent cold days caused the insulator to arc over. Evidence of greasy, dusty grime was present. So before reassembling the scope, I gave it a thorough cleaning throughout in the hope that this never happens again. Fixing a fried Tektronix 556 oscilloscope The revolving door of PVR repairs D. V., of Hervey Bay, Qld got a shock when one of his prized possessions had a minor explosion when he powered it on. The cause appears to be age-related, but perhaps not in the way you might think... I have a collection of old Tektronix oscilloscopes; the latest acquisition was a mint-condition 556. Even though I had switched it on several times before, on this occasion, I was greeted with a loud bang followed by what could only be described as the sound an egg makes when frying on the barbie. Reaching to switch it off felt like an eternity, but in reality, only a few seconds passed. However, the damage had been done. On inspecting the underside, I found two 30W resistors had burned out. These are part of the +225V circuit, and the fact they were damaged at all surprised me, as the 225V rail is individually fused and the fuse was intact. This led me to believe the fault was within the power supply unit (PSU). Scopes like my 556, while discontinued mid-1970s, are marvels of engineering. It is a true dual-beam scope and boasts tunnel diode triggering, dual plugins, individual timebases and 50MHz bandwidth. It is a monster weighing 40kg, with 34 valves and sinks 840W when in operation. No wonder it was the last of the 500 series scopes to be made! The regulator circuits in the 556 are semiconductor-based whereas the previous 500-series scopes used valves. Transistors T03 and T02 in the PSU are mounted on a heatsink directly behind the fan assembly because Tektronix had difficulty keeping these components cool. T03, the main pass transistor for the 225V rail, had gone short-circuit. It was a 2N4348, so I substituted a 2N5672 from the junk box. I removed all the other transistors from the defective rail and they tested OK. I replaced the two 30W resistors and wondered if this will be the magic bullet, but I had doubts. So with the 225V rail fuse removed for posterity, I proceeded to switch the unit on for just a second to see what would happen. 96 Silicon Chip B. P., of Dundathu, Qld has had to fix the same devices multiple times due to similar faults. It seems that they were made with poor quality components... We use two Beyonwiz DP-P2 Personal Video Recorders (PVRs) to record and play back TV programs. I originally bought both of these units on eBay as “not working, for parts”, both with an ERROR 0000 fault. In both cases, the cause of the faults were bad electrolytic capacitors in the power supply. I fixed both these units when I got them a few years ago by replacing the bad capacitors, and both worked well for some time, although I had the same fault return in one unit when another capacitor failed. Recently, my son told me that the PVR in the camper Australia's electronics magazine siliconchip.com.au was playing up. Sometimes it would work correctly; other times, it would show the ERROR 0000 and yet other times, it would be on when it should be off. Usually when it’s off, it shows the time on the front panel, and everything else is on standby. But sometimes, it would be off with the hard drive still running. Removing the lid, I could see a bad 3300μF 10V capacitor. I looked through my salvaged capacitors, found a suitable replacement and fitted it. While looking over the circuit board, I spotted a small capacitor that looked suspicious. It was a 330μF 25V capacitor, so I removed it. Then I noticed another one of these capacitors that looked suspicious, and this kept happening until, in the end, I had removed at least six of the same value electrolytic capacitors. I later tested these with my ESR meter, and all read well above what they should have. I found replacement capacitors in my salvaged capacitors collection, installed them, and then put the power supply board back in the PVR. After buttoning it up again, it was working well. Not even a week later, I turned on the other PVR in the lounge room, and it showed ERROR 0000. This PVR had been working well since its original repair, apart from Channel 7 being corrupted during the day, although it was usually mostly OK at night. There was also occasional corruption on SBS. None of the other channels had this problem. After removing the lid, I could see a really badly bulged 3300μF 10V electrolytic capacitor. Not only had the top bulged, but the seal on the bottom had been pushed out, and the capacitor was sitting at a significant angle. This was obviously the cause of the ERROR 0000 fault. I removed the defective capacitor and I found a replacement Nichicon capacitor in my salvaged capacitors. I scanned the PCB, but I could not see any other problems. All the rest of the capacitors, including the small ones I’d replaced in the other PVR, were fine. A quick test again showed the unit to be working. Since the repair, the corruption on Channel 7 seems to have disappeared. It’s really handy being able to make these repairs; otherwise, taking the unit(s) to get repaired could easily run into hundreds of dollars, and purchasing replacements would be similarly expensive. Aircon repair reveals a faulty switch R. W., of Hadspen, Tas offered to fix his friend’s air conditioner (which was said to be unrepairable) and traced the fault came back to poor installation practices... Many years ago, I was asked by a friend whether I knew anything about air conditioners. He had 5kW and 2.4kW units from a reputable manufacturer installed in an innercity apartment in Brisbane, and the 2.4kW unit stopped working after a year or so. An air-conditioning tech looked at the unit and told him it needed replacement, as the boards and refrigerant were no longer available. A quick check on the internet revealed that was not the case; while there would be benefits in replacing the unit with an inverter system, the cost seemed unwarranted on such a relatively new unit. I thought it was worth a look. During the installation, the electrician had routed the single-­circuit power cable through the downstairs ceiling and had cut several holes in the plasterboard, which were siliconchip.com.au Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? It doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to cars and similar. We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. later covered by four blank switch-plates and a snap-in ventilator. The smaller unit had a square section of adhesive conduit emanating from a bedroom power point, then passing through the external wall to the outside isolator switch. My friend was not happy with the blank plates, and had a plasterer make good the ceiling. He put up with the conduit as it was largely hidden by a bedside table. This suboptimal installation should have given me a clue. The 2.4kW unit responded to the remote commands, and when the internal fan started the louvres were able to be adjusted. About three minutes after powering it on, I could hear a relay click, but no cold nor warm air emanated. The problem seemed to be in the outdoor unit. This air conditioner had all of the control electronics on a board in the indoor unit with two switched Active wires going to the outdoor unit, one for the compressor and outdoor fan and one for the reverse-cycle solenoid – all fairly simple. I monitored the outdoor unit, and after the compressor timer had run, the outdoor fan ‘kicked’ but that was all. It was time to look at the circuit board. After removing some connectors and prising some clips off, the board was easy to remove. I looked for the usual suspects like dry joints, bulging capacitors and burnt components but found none. I decided to connect the infrared sensor and bench test it with mains applied, taking the usual safety precautions. The board behaved faultlessly. The relay clicked in, and power was available to the outdoor unit terminals. I connected a fan heater to these terminals in case the relay contacts had failed, but it sustained a 10A load. It had to be something in the outdoor unit. I was thinking possibly a failed compressor or motor run capacitor, but this did not explain why the outdoor fan would not run. I reinstalled the board and put it through its paces again while up on the ladder. This time, I noticed something that I should have realised earlier. The relay clicked in then dropped out, and the indoor fan lost speed when it clicked in. I connected a voltmeter to the input mains and noticed it drop to less than 100V AC when the relay energised. This drop was not apparent at the power point. I flipped the power circuit breaker and went to recheck the outdoor unit. It was then that I noticed a rust stain down the wall behind the isolating switch. I took the switch cover off, and rusty water poured out. The switch was not sealed against the wall; water had entered, rusted the mounting screws and caused a high impedance path within the switch. My friend engaged a better electrician to replace the switch, and the unit is still running some ten years later. SC Australia's electronics magazine April 2022  97 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 139, COLLAROY, NSW 2097 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 04/22 YES! 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PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS $15 MICROS 24LC32A-I/SN ATmega328P ATmega328P-AUR ATtiny85V-10PU ATtiny816 PIC10F202-E/OT PIC10LF322-I/OT PIC12F1572-I/SN PIC12F617-I/P Digital FX Unit (Apr21) RF Signal Generator (Jun19), Si473x FM/AM/SW Digital Radio (Jul21) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) Range Extender IR-to-UHF (Jan22) LED Christmas Ornaments (Nov20; versions), Nano TV Pong (Aug21) Car Radio Dimmer (Aug19), MiniHeart Heartbeat Simulator (Jan21) Refined Full-Wave Universal Motor Speed Controller (Apr21) Model Railway Level Crossing (two required – $15/pair) (Jul21) Range Extender UHF-to-IR (Jan22) PIC12F617-I/SN Model Railway Carriage Lights (Nov21) PIC12F675-I/P Motor Speed Controller (Mar18), Heater Controller (Apr18) Useless Box IC3 (Dec18) PIC12F675-I/SN Tiny LED Xmas Tree (Nov19) PIC16F1455-I/P Microbridge (May17), USB Flexitimer (June18) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) PIC16F1455-I/SL Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) PIC16F1459-I/P Ultrasonic Cleaner (Sep20), Electronic Wind Chime (Feb21) 20A DC Motor Speed Controller (Jul21) Fan Controller & Loudspeaker Protector (Feb22) PIC16F15214-I/SN Improved SMD Test Tweezers (Apr22) PIC16F1705-I/P Flexible Digital Lighting Controller Slave (Oct20) Digital Lighting Controller Translator (Dec21) ATSAML10E16A-AUT PIC16F1459-I/SO PIC16F18877-I/P PIC16F88-I/P High-Current Battery Balancer (Mar21) Four-Channel DC Fan & Pump Controller (Dec18) USB Cable Tester (Nov21) UHF Repeater (May19), Six Input Audio Selector (Sep19) Battery Charge Controller (Dec19), Railway Semaphore (Apr22) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) Advanced GPS Computer (Jun21) Touchscreen Digital Preamp [2.8in/3.5in version] (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) PIC32MX795F512H-80I/PT Touchscreen Audio Recorder (Jun14) $20 MICROS dsPIC33FJ64MC802-E/SP dsPIC33FJ128GP306-I/PT dsPIC33FJ128GP802-I/SP PIC32MX470F512H-I/PT PIC32MX470F512H-120/PT PIC32MX470F512L-120/PT 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb13) Ultra-LD Preamp (Nov11), LED Musicolour (Oct12) Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Micromite Explore 100 (Sep16) $30 MICROS PIC32MX695F512L-80I/PF Colour MaxiMite (Sep12) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC 500W AMPLIFIER HARD-TO-GET PARTS (SC6019) (APR 22) All the parts marked with a red dot in the parts list (see p32), including the 12 output transistors, driver transistors, VAS transistors, input pair (2SA1312), BAV21 & UF4003 diodes, TL431 ICs, 75pF capacitor, E96 series resistors and 10kW 1W resistor $200.00 IMPROVED SMD TEST TWEEZERS KIT (CAT SC5934) (APR 22) Complete kit with PCBs, all onboard parts, new microcontroller and gold-plated header pins to use for the tips. Does not include a lithium coin cell $35.00 RASPBERRY PI PICO BACKPACK KIT (CAT SC6075) (MAR 22) CAPACITOR DISCHARGE WELDER (MAR 22) INTELLIGENT DUAL HYBRID POWER SUPPLY (FEB 22) IR-TO-UHF MODULE FOR RANGE EXTENDER (CAT SC5993) (JAN 22) SMD TRAINER KIT (CAT SC5260) (DEC 21) HUMMINGBIRD AMPLIFIER (CAT SC6021) (DEC 21) USB CABLE TESTER KIT (CAT SC5966) (NOV 21) Complete kit, includes all parts except the optional DS3231 IC $80.00 Parts for the Power Supply – includes the power supply PCB, IC1-3, D1, the 1W shunt and sole SMD capacitor (Cat SC6224) $25.00 Parts for the ESM – includes one ESM PCB, IC8, Q3 & Q4 (IRFB7434G), D9 plus the SMD capacitors and resistors (Cat SC6225) → 8-14 sets typically needed $20.00ea Hard-to-get parts for the regulator module – all the ICs & regulators ◉ needed to build one module, plus the schottky diode, 10μH inductor, 4700μF 50V capacitors, 1W shunts and SMD capacitors – does not include PCB (Cat SC6096) $125.00 ◉ does not include the LM2575T as it comes with the CPU module parts Hard-to-get parts for the CPU module – most of the required parts, including programmed PIC32MZ, EEPROM, LM2575T, LM317 & LD1117V regulators etc. You just need the PCB, headers, a ferrite bead, trimpot and electrolytic capacitors (Cat SC6121) $60.00 PCB and all SMDs (including the programmed micro) for the IR-to-UHF module Complete kit includes the PCB and all on-board components, except for a TQFP-64 footprint device $20.00 Hard-to-get parts includes: two 0.22W 5W resistors; plus one each of an MJE15034G, MJE15035G, KSC3503DS & 220pF 250V C0G ceramic capacitor Short form kit with everything except case and AA cells $25.00 $15.00 $110.00 siliconchip.com.au/Shop/ MODEL RAILWAY CARRIAGE LIGHTS KIT (CAT SC6027) (NOV 21) NANO TV PONG SHORT FORM KIT (CAT SC5885) (AUG 21) MODEL RAILWAY LEVEL CROSSING (JUL 21) MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) (AUG 19) Includes PCB, IC1 (programmed), IC2, D1, L1, SMD capacitors and resistors. Does not include reed switch, magnet, LEDs or through-hole parts PCB and all onboard parts only (does not include controllers) - Pair of programmed PIC12F617-I/Ps - ISD1820P-based audio recording and playback module $25.00 $17.50 $15.00 $5.00 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) $35.00 - 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) $4.00 - 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 - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) $1.50 VARIOUS MODULES & PARTS - DS3231 real-time clock SOIC-8 IC (Pico BackPack, Mar22) - DS3231MZ real-time clock SOIC-16 IC (Pico BackPack, Mar22) - 4-pin PWM fan header (Fan Controller, Feb22) - 64x32 pixel white 0.49in OLED (SMD Test Tweezers, Oct21) - pair of AD8403ARZ10 (Touchscreen Digital Preamp, Sep21) - Si4732 radio IC (Si473x FM/AM/SW Radio, Jul21) - EA2-5NU relay (PIC Programming Helper, Jun21) - VK2828U7G5LF GPS module (Advanced GPS Computer, Jun21) - MCP4251-502E/P (Advanced GPS Computer, Jun21) - pair of Signetics NE555Ns (Arcade Pong, Jun21) - 2.8-inch touchscreen LCD module (Lab Supply, May21) - Spin FV-1 digital effects IC (Digital FX Unit, Apr21) - 15mW 3W SMD resistor (Battery Multi Logger / Arduino PSU, Feb21) $4.00 $7.50 $1.00 $10.00 $35.00 $15.00 $3.00 $25.00 $3.00 $12.50 $25.00 $40.00 $2.50 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # P&P prices are within Australia. Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT UHF DATA REPEATER AMPLIFIER BRIDGE ADAPTOR 3.5-INCH LCD ADAPTOR FOR ARDUINO DSP CROSSOVER (ALL PCBs – TWO DACs) ↳ ADC PCB ↳ DAC PCB ↳ CPU PCB ↳ PSU PCB ↳ CONTROL PCB ↳ LCD ADAPTOR STEERING WHEEL CONTROL IR ADAPTOR GPS SPEEDO/CLOCK/VOLUME CONTROL ↳ CASE PIECES (MATTE BLACK) RF SIGNAL GENERATOR RASPBERRY PI SPEECH SYNTHESIS/AUDIO BATTERY ISOLATOR CONTROL PCB ↳ MOSFET PCB (2oz) MICROMITE LCD BACKPACK V3 CAR RADIO DIMMER ADAPTOR PSEUDO-RANDOM NUMBER GENERATOR 4DoF SIMULATION SEAT CONTROLLER PCB ↳ HIGH-CURRENT H-BRIDGE MOTOR DRIVER MICROMITE EXPLORE-28 (4-LAYERS) SIX INPUT AUDIO SELECTOR MAIN PCB ↳ PUSHBUTTON PCB ULTRABRITE LED DRIVER HIGH RESOLUTION AUDIO MILLIVOLTMETER PRECISION AUDIO SIGNAL AMPLIFIER SUPER-9 FM RADIO PCB SET ↳ CASE PIECES & DIAL TINY LED XMAS TREE (GREEN/RED/WHITE) HIGH POWER LINEAR BENCH SUPPLY ↳ HEATSINK SPACER (BLACK) DIGITAL PANEL METER / USB DISPLAY ↳ ACRYLIC BEZEL (BLACK) UNIVERSAL BATTERY CHARGE CONTROLLER BOOKSHELF SPEAKER PASSIVE CROSSOVER ↳ SUBWOOFER ACTIVE CROSSOVER ARDUINO DCC BASE STATION NUTUBE VALVE PREAMPLIFIER TUNEABLE HF PREAMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) NUTUBE GUITAR DISTORTION / OVERDRIVE PEDAL THERMAL REGULATOR INTERFACE SHIELD ↳ PELTIER DRIVER SHIELD DIY REFLOW OVEN CONTROLLER (SET OF 3 PCBS) 7-BAND MONO EQUALISER ↳ STEREO EQUALISER REFERENCE SIGNAL DISTRIBUTOR H-FIELD TRANSANALYSER CAR ALTIMETER RCL BOX RESISTOR BOARD ↳ CAPACITOR / INDUCTOR BOARD ROADIES’ TEST GENERATOR SMD VERSION ↳ THROUGH-HOLE VERSION COLOUR MAXIMITE 2 PCB (BLUE) ↳ FRONT & REAR PANELS (BLACK) OL’ TIMER II PCB (RED, BLUE OR BLACK) ↳ ACRYLIC CASE PIECES / SPACER (BLACK) IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION USB SUPERCODEC ↳ BALANCED ATTENUATOR SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE DATE MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 JUN19 JUN19 JUN19 JUN19 JUL19 JUL19 JUL19 AUG19 AUG19 AUG19 SEP19 SEP19 SEP19 SEP19 SEP19 SEP19 OCT19 OCT19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 DEC19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 APR20 APR20 APR20 APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 NOV20 AUG20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 PCB CODE Price 15004191 $10.00 01105191 $5.00 24111181 $5.00 SC5023 $40.00 01106191 $7.50 01106192 $7.50 01106193 $5.00 01106194 $7.50 01106195 $5.00 01106196 $2.50 05105191 $5.00 01104191 $7.50 SC4987 $10.00 04106191 $15.00 01106191 $5.00 05106191 $7.50 05106192 $10.00 07106191 $7.50 05107191 $5.00 16106191 $5.00 11109191 $7.50 11109192 $2.50 07108191 $5.00 01110191 $7.50 01110192 $5.00 16109191 $2.50 04108191 $10.00 04107191 $5.00 06109181-5 $25.00 SC5166 $25.00 16111191 $2.50 18111181 $10.00 SC5168 $5.00 18111182 $2.50 SC5167 $2.50 14107191 $10.00 01101201 $10.00 01101202 $7.50 09207181 $5.00 01112191 $10.00 06110191 $2.50 27111191 $5.00 01106192-6 $20.00 01102201 $7.50 21109181 $5.00 21109182 $5.00 01106193/5/6 $12.50 01104201 $7.50 01104202 $7.50 CSE200103 $7.50 06102201 $10.00 05105201 $5.00 04104201 $7.50 04104202 $7.50 01005201 $2.50 01005202 $5.00 07107201 $10.00 SC5500 $10.00 19104201 $5.00 SC5448 $7.50 15005201 $5.00 15005202 $5.00 01106201 $12.50 01106202 $7.50 18105201 $2.50 04106201 $5.00 04105201 $7.50 04105202 $5.00 08110201 $5.00 01110201 $2.50 01110202 $1.50 24106121 $5.00 16110202 $20.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE BK1198 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG Si473x FM/AM/SW DIGITAL RADIO 20A DC MOTOR SPEED CONTROLLER MODEL RAILWAY LEVEL CROSSING COLOUR MAXIMITE 2 GEN2 (4 LAYERS) BATTERY MANAGER SWITCH MODULE ↳ I/O EXPANDER NANO TV PONG LINEAR MIDI KEYBOARD (8 KEYS) + 2 JOINERS ↳ JOINER ONLY (1pc) TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS HUMMINGBIRD AMPLIFIER DIGITAL LIGHTING CONTROLLER TRANSLATOR SMD TRAINER 8-LED METRONOME 10-LED METRONOME REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL FAN CONTROLLER & LOUDSPEAKER PROTECTOR SOLID STATE TESLA COIL (SET OF 2 PCBs) REMOTE GATE CONTROLLER DUAL HYBRID POWER SUPPLY SET (2 REGULATORS) ↳ REGULATOR ↳ FRONT PANEL ↳ CPU ↳ LCD ADAPTOR ↳ ACRYLIC LCD BEZEL RASPBERRY PI PICO BACKPACK AMPLIFIER CLIPPING DETECTOR CAPACITOR DISCHARGE WELDER POWER SUPPLY ↳ CONTROL PCB ↳ ENERGY STORAGE MODULE (ESM) PCB DATE OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 JUN21 JUN21 JUN21 JUN21 JUL21 JUL21 JUL21 AUG21 AUG21 AUG21 AUG21 AUG21 AUG21 SEP21 SEP21 OCT21 OCT21 NOV21 NOV21 NOV21 DEC21 DEC21 DEC21 JAN22 JAN22 JAN22 JAN22 JAN22 JAN22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 FEB22 MAR22 MAR22 MAR22 MAR22 MAR22 PCB CODE 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 18104211 18104212 10103211 05102211 24106211 24106212 08105211 CSE210301C 11006211 09108211 07108211 11104211 11104212 08105212 23101213 23101214 01103191 01103192 01109211 12110121 04108211 04108212 09109211 01111211 16110206 29106211 23111211 23111212 15109211 15109212 01101221 01101222 01102221 26112211/2 11009121 SC6204 18107211 18107212 01106193 01106196 SC6309 07101221 01112211 29103221 29103222 29103223 Price $20.00 $3.00 $12.50 $12.50 $5.00 $2.50 $7.50 $2.50 $5.00 $10.00 $5.00 $2.50 $5.00 $10.00 $5.00 $12.50 $2.50 $7.50 $7.50 $7.50 $5.00 $10.00 $10.00 $7.50 $7.50 $7.50 $5.00 $7.50 $35.00 $7.50 $7.50 $5.00 $15.00 $5.00 $2.50 $2.50 $5.00 $1.00 $12.50 $2.50 $15.00 $30.00 $7.50 $5.00 $2.50 $5.00 $5.00 $5.00 $5.00 $7.50 $2.50 $2.50 $7.50 $5.00 $5.00 $7.50 $20.00 $25.00 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $2.50 $5.00 $5.00 $5.00 SMD TEST TWEEZERS (3 PCB SET) 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) OCT21 APR22 APR22 APR22 04106211/2 01107021 09103221 09103222 $10.00 $25.00 $2.50 $2.50 NEW PCBs We also sell an A2 Reactance Wallchart, RTV&H DVD, Vintage Radio DVD plus various books at siliconchip.com.au/Shop/3 Capacitor Discharge Welder This Capacitor Discharge Welder has been carefully designed to deliver just the right amount of weld energy each time. When completed, it makes a neat package that’s easy to build and safe to use, so long as you follow our advice. Having described how it works, let’s get into making it. Part 2: By Phil Prosser Safety warning Capacitor Discharge Welding works by generating extremely high current pulses, and consequently, strong magnetic fields. Do not build or use this project if you have a pacemaker or similar sensitive device. This device can generate sparks and heat. Users must wear appropriate personal protective equipment such as AS/NZS 1337.1, DIN 169 Shade 3 welding glasses. These provide mechanical and IR/UV protection. 100 Silicon Chip Australia's electronics magazine siliconchip.com.au T he Capacitor Discharge Welder comprises three main electronic modules: the Power Supply, which is responsible for charging the capacitors; the Controller Module, which determines when voltage is applied across the welding tips; and an Energy Storage Module bank, typically made from around 10 modules joined to a common pair of bus bars, that hold the storage capacitors and Mosfets. Because of this modular approach, not only can you scale the system to meet your needs, but the PCB cost is kept down, and assembly is relatively straightforward. You build and test the modules, assemble them into the case, make the welding tips and cables, and finally wire it all up. Construction The first step in building the CD Welder is to assemble one Power Supply Module, one Controller Module and several Energy Storage Modules (ESMs). Each is built on a different PCB, but all the PCBs are the same size at 150 x 42.5mm. We’ll start with the Power Supply Module. Its PCB is coded 29103221 and Fig.6 is its overlay diagram, which shows where the parts mount on the board. Start by soldering the sole SMD ceramic capacitor (100nF) near the MC34167 regulator IC. Next, mount the INA282 current sense amplifier, which comes in an SMD package (SOIC). Watch its orientation; make sure its pin 1 is facing as shown before soldering its pins and then check for bridges. Follow with all the resistors and diodes (except for diode D1) with the diode cathode stripes facing as shown, leaving the taller shunt resistor until last. There are three different diode The CD Welder fully assembled and ready to be used in anger (or calmly, it’s up to you). types used: 1N4148, 1N4004 and zener, so don’t get them mixed up. Pay attention to the two different resistor value options shown in Fig.6. If you are using a DC power supply that can deliver at least 5A, you can use the values shown for 5A charging. Otherwise, stick with 2A charging. Now install the sole transistor facing as shown, then all the capacitors. Many of the latter are not polarised, but for those which are polarised (the electrolytics), these all have the longer positive leads going to pads on the right-hand side. Note that while you could use 100nF MKT capacitors, multi-layer ceramics will also work. Next come the connectors. There are two screw terminals, a polarised header for the Charge LED and a 2x5 pin header to connect to the other modules. Make sure the screw terminal wire entries face the outside of the board as shown. Mount the 6TQ045-M3 diode (D1) close to the board by pushing it down fully before soldering and trimming its leads. Also install the fuse clips (with the tabs towards the outside) and fuse, the LM358 op amp and 10kW linear voltage control potentiometer. Now fit the LM7815 regulator and attach a small flag heatsink using a machine screw, shakeproof washer Fig.6: the Power Supply board is built mainly using through-hole components. The only SMDs are IC2 and one 100nF capacitor near IC1, so fit those first. Watch the orientations of IC2, IC3, the diodes, electrolytic capacitors, REG1 and the terminal blocks. siliconchip.com.au Australia's electronics magazine April 2022  101 and nut as it gets warm during operation. Mount the 220µH toroidal inductor on the board, then finally the MC34167 switch-mode regulator. This also requires a small heatsink such as Altronics H0625 with an insulating bush and silicone pad. Hold this all together using an M3 machine screw, star washer and nut in the usual manner. Control board The Controller PCB is coded 29103222 – refer to Fig.7. Start by installing all the resistors and diodes, checking that the diodes are the right way around, then follow with the four NE555 timer chips, with their pin 1 notches/dots to the left. Next, fit all the ceramic MKT and electrolytic capacitors. Note the use of two different types of 1µF capacitor as well as different types for the 220nF capacitors. The electrolytics have longer leads for their positive connections, and these go to the side marked + on the overlay. Now mount the small transistor, facing as shown, followed by the 100kW linear potentiometer and the 2-way and 10-way headers. If you want to make the controller switchable for two pulses, make a cable with a switch at one end and a header plug on the other so that it can plug into CON8. Alternatively, you could install a jumper on CON8 and fix this setting, as we did. Energy Storage Modules The ESM boards are coded 29103223, and the components are mounted as shown in Figs.8 & 9. Presumably by now you will have figured out how many you need to build and obtained the appropriate capacitors. Generally, there are three caps per board, but some of the recommended configurations use two. In this case, fit the two closest to the headers. Start by fitting the surface-mount resistors and capacitors on the underside of the PCB. Make sure the 100nF capacitors are mounted either side of the Mosfet driver (IC8). Then solder that driver IC, being careful not to short any leads (you can clean up any bridges using flux paste and solder wick). Next, mount the RFN20NS flyback diode (D9) to the PCB. It’s easier if you spread a thin layer of flux paste on all its pads first. You will want to get a good lot of heat into the PCB; start by tacking down the two anode leads, then solder the main body of the diode. This will not dissipate much power, but you want a good solder joint here. Then fit the two Mosfets, keeping their leads short. Their metal tabs face away from the capacitors, and their source and drain pins connect to copper fills. These junctions will see very high current pulses, so be sure to get these properly hot when soldering to form nice-looking fillets. Now mount the 2x5 control header, the terminal block and finally, the capacitors. Make sure their positive sides go in the direction indicated, and the negative side stripes face away from this. Reversed capacitors will likely lead to an Earth-­shattering kaboom! Repeat the ESM assembly until you have enough of these modules, and are ready to test them and then proceed to final assembly. Testing Start by testing the modules individually, beginning with the Power Supply Module. To start with, solder the leads of one LED to a length of light-duty twin-lead cable (eg, two wires stripped from ribbon cable) and solder/crimp the other end into a pluggable header, and connect this to CON3, the charge LED header. Make sure the anode (longer LED lead) goes to pin 1. Connect the Power Supply board to a DC voltage source of at least 25V – up to 35V is acceptable. Make sure you have set the current limit (2A or 5A) to match your supply. Set your DVM to a DC volts range and put a 5W 82W resistor across CON2, “Power Output”. Apply power and check the following: • The output of the LM7815 is 15V ±0.25V. Its output is accessible on pin 2 of CON4, the control header. If not, check that it is the right way around and there are no shorts. • Check that pin 1 of CON2, the “Power Out” connector, is between 2V and 25V. Also check that this can be controlled using potentiometer VR1. If this is not working, check the following: • Check that you have the INA282 (IC2) in the right way around. • Verify that the 82W test resistor is connected correctly (eg, measure the resistance across the terminals of CON2). • Check that the MC34167 is oscillating; there will be a 72kHz signal at pin 2. • Check that D1 is in the right way around. • Check that the feedback pin 1 of the MC34167 has about 5.05V on it. If not, verify that the LM358 op amp is operating properly. Check the voltages at its power and ground pins (pins 8 & 1, respectively), and verify that the voltage at input pin 5 is an appropriate fraction of the output voltage, and that pin 7 is an amplified version of this. Check that diodes D4 and D5 are in the right way around. • Assuming that’s working, put an ammeter on its 10A range across the terminals of CON2 and check that the current is close to the expected 2A or 5A. If not, look for problems near the INA282 (IC2). Fig.7: the Control board uses all through-hole parts and assembly is straightforward. Again, be careful to orientate the diodes, electrolytic capacitors and ICs as shown. 102 Silicon Chip Australia's electronics magazine siliconchip.com.au The bus bar layout for 10 modules, five on either side of the bus bars. The holes at the end of the bus bars are drilled and tapped for M4 to secure the welding leads; all the other holes are M3 tapped. We have allowed enough length for the bus bars to protrude through holes in the case, as we do not want any joints in these. Testing the Controller To test the controller, ideally, you will need an oscilloscope. Make a 10-way IDC lead to connect the Power Supply module to the Controller module, ensuring that pin 1 connects to pin 1. Apply power and check the following: • Each NE555 chip has 15V at its pin 8. • The base of transistor Q1 is pulled up to within 0.6V of the 15V rail, turning it off. • The TRIGGER output of IC6 (pin 3) is close to 0V The next part is easiest if you assemble the foot pedal trigger by extending the existing lead with the two-metre length of microphone cable. You can simply snip off the screen wires as they are not required; just use the two internal conductors, then add liberal layers of heatshrink to protect the junction. Now temporarily soldering a length of light-duty twin lead to the other end (eg, stripped from spare ribbon cable) and solder/crimp this to a polarised header plug which connects to CON5. Connect your oscilloscope to the output pins (pin 3) of IC4, IC5 & IC7. If you only have a single-channel or two-channel oscilloscope, start with IC4 and/or IC5 and then test the rest later. Press the footswitch and check that IC4 generates a pulse of about 0.1ms and IC5 generates a pulse of about 5ms. Then check that IC7 generates a pulse length that is controllable using potentiometer VR2, from about 0.2ms to over 20ms. Next, check that the trigger output on pin 9 of the 2x5 header (or pin 3 of IC7) contains one or two pulses as set by the switch/jumper on CON8. If there are problems, check the power supply to the NE555 ICs; there should be 15V between pins 8 and 1 of each chip. Verify that the trigger input (pin 2) is being pulled low on IC4, and that the inputs to subsequent NE555s have a short negative-going pulse (this is capacitively coupled, so look closely with the scope). Check also that the diodes are in the right way around, that Q2 is indeed a PNP device and that the INHIBIT line is not pulled low by the Power Supply. Make sure that you are happy with the operation of the power supply and controller modules before assembling the CD Welder. Testing the ESMs To check out each Energy Storage Module, connect one at a time to the Controller and Charger modules. Use medium-duty hookup wire (0.7mm diameter copper/21AWG) such as Altronics Cat W2261/W2260 or Jaycar Figs.8 & 9: the ESM has parts on both sides, although the underside components are limited to a few SMDs near the Mosfets; mainly, the driver IC and associated passives. Fit all those first, then flip the board over and solder the remaining components to the top side. Be very careful with the electrolytic capacitor and Mosfet orientations, as putting them in backwards would be disastrous. siliconchip.com.au Australia's electronics magazine April 2022  103 Cat WH3045/WH3046 to connect the Power Out connector on the Power Supply board (CON2) to the Power In connector (CON10) on the Energy Store Module. You’ll also need a control ribbon cable with three 10-way IDC line sockets to connect the Power Supply, Controller board and ESM together. Connect an 82W 5W test resistor across the ESM output using 16mm M3 machine screws, nuts and washers. Apply power and check that the capacitors charge and that you can adjust the voltage using VR1. The “Output -VE” connection (right near the edge of the PCB) will be pulled 104 Silicon Chip up to the same voltage by that 82W resistor. Use an oscilloscope to watch the voltage on that pin and press the trigger. There is a convenient ground on the power header; we also added a ground via on the board between the capacitors. After triggering, you should be able to see the output pulled to ground in two pulses (with dual pulse mode on). If this does not work, use the scope to check for the trigger pulses on the control cable, check the +15V rail and check that the TC1427 is sending pulses to the Mosfet gates. Check all cabling and the orientation of the components. Australia's electronics magazine Now swap that 82W resistor for a 0.27W 5W resistor. Repeat the test, and check that everything works. At 25V, this will pass close to 100A. You will see the Charge LED come on, especially with long pulse lengths and high voltages. You will also feel the 0.27W resistor get hot after several shots. This is normal. You may blow this resistor, so if things look odd, check it is still 0.27W. At this point, Dr Evil is smiling. Bus bars Once you’ve tested the modules, it’s time to put them all together. We have laid these boards out such siliconchip.com.au that they can mount back-to-back on two 260mm-long bus bars. Fig.11 shows where to drill holes to allow M3 screws to hold pairs of modules into common tapped holes. Mount the modules to the bus bar using 6mm-long M3 panhead machine screws and star washers. As you assemble the modules to the bus bars, put 10mm M3 spacers, 6mm screws and star washers between the holes at the far end of the PCBs from the bus bars, securing pairs of boards to one another, stabilising the assembly. Now tighten the screws well; these will be carrying a lot of current. You may find another way to lay the modules out. While it might be possible to run machine screws right through holes drilled in the bus bars with nuts on the other side, we feel that using threaded holes into the aluminium is important to keep the resistance down. So we strongly advise you to take the time to tap all these holes (aluminium is soft, and you can use a through-tap, so it isn’t that hard). Cabling We have endeavoured to keep cabling as simple as possible. Fig.10 shows the complete layout. We extended the ribbon and power cable from the Energy Store Modules to the Charge and Control modules to suit our application. Try not to make these more than a few hundred millimetres long, though. Fig.12 shows the layout we came up with to fit the modules inside the case and how most of the wiring is routed. Note that it is necessary to cut the Inhibit line in the ribbon cable so that it only connects the Controller and Power Supply modules. This is to prevent it from acting as an antenna and picking up pulses during welding. You will need to make up a cable for the enable switch similar to the one you made before for the charge LED. This will plug into CON6 at one Fig.10 (left): this shows the required cabling for the complete system, which is relatively simple. You can have more or fewer ESMs, but six is the minimum. All cables connect to headers or terminal blocks, except the optional voltmeter we added, which tacks onto a solder pad that joins to the +15V supply rail. Fig.11 (below): to make the bus bars, cut 10mm square aluminium bar to two 260mm lengths and drill and M3 tap holes in the locations shown. Use kerosene or light machine oil to lubricate the tap and if it sticks, withdraw it and clear out the swarf before continuing. You don’t want to break the tap off in the bar. siliconchip.com.au Australia's electronics magazine April 2022  105 Fig.12: this diagram shows how we mounted the modules in the recommended case and wired them up (62.5% scale). end and go to the terminals of a toggle switch at the other end. Now would also be a good time to disconnect the twin lead from the microphone cable in the footswitch assembly you made earlier, and instead solder these to the microphone plug (footswitch end) and socket specified in the parts list last month. In our application, we started with 300mm lengths of twin lead and trimmed them as required. The power connection from the chassis DC socket to the Power Supply board needs to be made using 5A-rated cable; the type of wire used earlier to connect the Power Supply to the ESMs should be suitable. While the ribbon cable connects the output of the Power Supply to each ESM, it is only rated at 1A per wire. Two wires are used for power, plus two for ground, limiting charging over the ribbon cable to 2A. So if you want to charge at 5A, the IDC headers will ‘need help’. This is the purpose of CON10 on each ESM. You will need to wire all those headers back to CON2 on the Power Supply using 5A-rated cable. We used Altronics Cat W2109 for this job. Don’t use thicker wire if you can avoid it, as you need to fit two pairs into each terminal block to daisy-chain them. For this, we cut nine 60mm lengths plus one long length, stripped and tinned these together and used a bit of heatshrink to make it look tidy. This is a little fiddly, but it is the best approach we could come up with that was not big or too expensive. By paralleling the ribbon cable, this heavy-duty wire will take the majority of current during charging. Make sure you connect each terminal with the same polarity; otherwise, it will short out the Power Supply! To make the ribbon cable that connects all the modules, assuming you have 10 ESMs, you need 12 10-way IDC line sockets and about 610mm of Fig.13: we used 610mm of ribbon cable to connect our 12 modules as shown here. Adjust the total length and connector positions if you aren’t using 10 ESMs or want to arrange them in a different layout. 106 Silicon Chip Australia's electronics magazine siliconchip.com.au The finished Capacitor Discharge Welder, with the welding cables attached. 10-way ribbon cable, depending on your layout. Fit the IDC connectors as shown in Fig.13. We crimped the IDC connectors using a vice, although specific tools are also available to do this. If using a vice, add timber blocks or sheets on either side of the connectors to avoid marring them and make it less likely to break them when squeezed. As mentioned earlier, we recommend cutting the inhibit line (wire 7) between the Power Supply Module and the Energy Store modules. Simply slit the ribbon cable on either side of wire 7 over a 10mm section and snip a 5mm section from it using side cutters. This reduces the chance of EMI being picked up. Cables The footswitch is our solution to keeping your hands free to weld, but you could place a button on one of the leads as an alternative if you wish. The recommended footswitch comes with a short lead, hence our earlier instructions to extend it with about two metres of microphone cable. Now that you’ve added the plug and socket, this cable should be complete. For the all-important welding cables, we crimped Altronics H1757B non-insulated eyelet lugs at the Welder end (Jaycar PT4936 is equivalent). We were lucky and our crimping tool worked on these, but we know from experience that you can also solder them (with a powerful iron) or crimp them in a vice. We put 10mm heatshrink over the terminal to ensure nothing shorts to it. We made the welding handles and tips as shown in Fig.14. These comprise a 100mm length of 10mm square aluminium bar with a 4mm hole drilled in the end to accept the welding cable. Two additional M4 threaded holes allow 6mm-long M4 screws to fix the welding cable. After making them, we applied Fig.14: a cross-section of the welding probes we made from 10mm square aluminium bar. The welding tips are 3mm copper rods ground to a sharp point. A close-up of one of the tips is shown adjacent to this diagram. siliconchip.com.au Australia's electronics magazine April 2022  107 many choices out there, and the wiring is pretty straightforward. Welding! To illustrate the energy involved, and potential danger, this shows the result of placing the probes across the tab between two AA cells. The capacitors were charged to 15V, so this is about 127J of energy. A look inside a can used for testing, which shows the damage caused by excessive voltage. The higher energy welds have made holes right through. 13mm heatshrink tubing over the handles to make them easier to hold and act as strain relief for the cables. At the welding tips, we have again drilled 3mm holes in the end of the handles and drilled and tapped an M3 threaded hole to hold the tip. We tried various copper welding tips and feel that 3mm rod filed to a point are pretty good. We used small pieces of 20mm heatshrink to ensure the positive and negative welding cables remain close to one another along the bulk of their length. We do this to minimise the inductance in the welding cable loop. If there is a lot of inductance, then there will be much energy stored in this that the Mosfets have to switch, and the flyback diodes need to redirect. store to the case and put firm foam under the lid to hold it all together when the lid is attached. We folded and mounted a sheet of Presspahn between the output bus bars (visible in the lead photo) to ensure that accidental shorts cannot easily occur. Note that there is no danger here unless the “trigger” footswitch is pressed, but we do not want any chance of accidentally firing into a dead short. The cutting & folding details for this are shown in Fig.15. We cut two square holes in the front of the case to allow the bus bars to poke through, shown in Fig.16, along with the other front-panel cutouts. All controls were placed in locations that felt convenient, and we used four holes to fix the Presspahn sheet to the front panel. We found a cheap voltmeter on eBay and decided to add this – these are available on your favourite auction site for a few dollars if you go looking. We will leave the selection and integration of this to you, as there are Case assembly There are many ways of packaging this up. By avoiding mains wiring, we don’t need to be so worried about Earthing and suchlike. We used an Altronics H0364A case, which is just large enough to fit all the modules. This allows us to mount the ESM ‘bundle’ on its bus bars in the base with the Power Supply and Controller modules just behind the front panel, secured to the side of the case. The photo of the case with the lid off shows this arrangement pretty clearly. We found that the potentiometer shafts were only just long enough – you might find a better way of mounting these. As our application is stationary in the lab, we used long tie wraps (thick cable ties) to secure the energy 108 Silicon Chip You will need to experiment to find the settings that work best for you. We used flat AA and D cells to test the system out, and found that with 0.12mm nickel strip, setting the pulse width to maximum and voltage to about 12-14V gave extremely solid welds. We started with a low voltage and increased the voltage until the welds just stuck, which was about 8V. From that point, we increased the voltage to get a solid weld (in our case, at around 12V), then added a bit. To test your welds, take pliers and try to pull the tab off. It should be exceptionally well attached and require you to tear the weld ‘beads’ off. You will find the copper weld tips wear and get dirty if you experience arcing. Clean them up with sandpaper or a sharp knife for consistent results. Once you have worked your settings out, this CD Welder should provide solid service and consistent weld energy. Some tips • We found 12-15V to be the sweet spot for welding. While we did install 25V capacitors, if you are welding only light gauge battery tabs, you will probably find that you need to charge them no higher than 16V. Then again, you gain a lot of headroom for the slight cost increase of using 25V capacitors. • To check the effect of weld energy, we welded tabs to the top of a soup can, using this as a battery surrogate. From the outside, the 15V welds are reasonably light ‘dimples’, while with the 25V welds, some of the tab material has clearly been blown away. This was accompanied by sparks and a flash. The photo of the inside of the can shows that all the welds are visible, Fig.15: cut, drill and fold the Presspahn as shown here to make the bus bar insulator. This ensures that the Welder cannot be accidentally fired with a short circuit across the bus bars. Holes A are 3mm in diameter. All dimensions are in millimetres. Australia's electronics magazine siliconchip.com.au but with significantly more damage on the 25V welds. • Never short the output bus bars directly (say with a screwdriver); this will lead to dangerous arcing and probably break something expensive. • Always wear safety glasses. • Do not use welding leads with copper wider than 3.3mm in diameter (8 Gauge) or shorter than 1m, as this forms part of the design. • Always keep the leads parallel and never curl them into a coil. Coiling them will increase inductance in the system and give the flyback diodes a hard time. • Note that some plug packs have their negative output connected to mains Earth. Be careful of these packs as the output leads are at your weld voltage. Finally, for those interested, we have a couple of spreadsheets available for download from siliconchip. com.au/Shop/6/6306 that include many of the calculations used to verSC ify this design. Fig.16: the front panel cutting diagram for the layout used in our prototype. This box suits our application in the lab, but you might be able to come up with a better arrangement. siliconchip.com.au Australia's electronics magazine April 2022  109 Vintage Radio Monopole D225 tombstone radio from 1934 By Assoc. Prof. Graham Parslow Made in France in 1934, this ‘French Cathedral’ style radio was also sold separately as the model D25, which consisted solely of the chassis. The model D225 is a superhet design featuring five valves, with a total weight of nearly 16kg. Its original price was 1850 French francs. G. Bouveau et Cie Constructeurs started business in 1925 in Paris. Its name was changed in 1928 to Societé des Établissements Monopole and in 1934, it moved to the Montreuil-sousBois area of Paris. It manufactured a range of radios through the 1930s, ceasing after the German occupation in 1940. The radio featured here was one of their prestige models and nicely brings together form and function in the prevailing tombstone style. Radios of this era typically came with internal speakers, rather than requiring separate speakers as in the previous ‘coffin box’ era. This radio came to me for electrical restoration via Darren McBride, a French polishing professional with 110 Silicon Chip Hecdar Heritage in Melbourne. He restored the case magnificently but the electrical, fabric and mechanical restoration were my challenges. I have restored many timber cabinets using polyurethane, but French polishing is far more labour intensive and is justified by the unique quality of the outcome. As Darren McBride relates on his website, this traditional technique results in a high-gloss surface with deep colour and a striking three-dimensional vibrancy. The process of French polishing consists of applying many thin coats of shellac dissolved in alcohol, using a rubbing pad lubricated with oil (or even a microfibre cloth without oil). It is a lengthy and repetitive process, requiring a specific combination of Australia's electronics magazine various rubbing motions, waiting, and repeating, building up layers of polish. One advertisment poster (shown at the end of the article) states “Vague de Puissance et Harmonie etc” which translates roughly as “A wave of Strength and Harmony [will be delivered by your Monopole Radio], made by hand in France with the latest technology.” Monopole claims to have used the latest technology for 1934, which is a reasonable claim. The D225 is a superhet with fundamentals that would continue to the end of the valve radio era in the 1960s. It was not so much the basic superhet design that would evolve after this, but the efficiency and performance of the valves would increase. siliconchip.com.au The valve sockets for the D225 were designed to match the number of pins needed by a valve, rather than using a standard socket. The octal base was only released onto the market in April 1935 and did not immediately gain traction. The photo of the top of the chassis shows four different valve bases of 4 to 8 pins. It also shows the mains transformer without the top cover and reveals the unusual pattern of winding and lamination. Circuit details The model designation D225 describes the cabinet; the chassis mated to it is the model D25. The Monopole circuit diagram is among the clearest to be found from the early 1930s, with only one significant use of French notation – “H.P.” for haute parleur (high speaker), the primary of the output transformer. All of the valves have indirect heaters driven by 4V except the mains rectifier, which has a directly heated 4V cathode. In the radio featured here, the superhet mixer valve was an AK2 (equivalent to AK1 indicated on the circuit, but with an alternative base). The IF amplifier was an AF2, while the detector-audio preamplifier was a type TE44 (equivalent to the E444). The output valve was missing. The full-wave rectifier was type AZ1. The high tension filter choke is the field coil of an electrodynamic speaker. siliconchip.com.au The restored tombstone radio, along with some shots of the chassis during restoration. Note that the photo below has the dial already repaired. Australia's electronics magazine April 2022  111 The RF section has a tuned aerial coil primary as well as the usual tuned secondary. The radio has good selectivity for tuning, helped by the double-­tuned aerial coil. More significantly, the double tuning (preselection) improves image rejection generated by the intermediate frequency (IF) of 120kHz. Images (a second tuning spot) would exist at 120kHz × 2 = 240kHz above the transmission frequency. I did not find images generated by this radio. The third gang of the tuning capacitor is linked to the local oscillator, configured as an Armstrong tuned grid oscillator. They possibly chose an intermediate frequency of 120kHz because valves of the time were more effective amplifiers at lower frequencies. The normal MW range is calibrated on the dial as 200-550 metres. Shortwave is tuned by shorting sections of the coils used for MW. The radio is not highly sensitive, and strong local stations are noticeably louder than medium-strength stations. This is despite automatic gain control (AGC) mediated by the 1MW resistor feeding back from the audio detector to the AF2 valve. That 1MW resistor also feeds back to the mixer valve via a 250W resistor and the secondary of the aerial coil. The circuit diagram shows that the voltage to be expected at the first filter electrolytic is 328V DC, with 248V DC after the choke. These values proved useful in restoring the radio. Electrical restoration The top of the chassis was grubby and stained with a resinous film that is thought to be from material in the mains transformer that sublimates (turns from a solid to a gas) to cover surrounding components. Otherwise, its condition was fair. The temptation to immediately clean the components is one I try to resist because the radio probably worked in this state before. Sometimes cleaning introduces new problems, so I leave it for later unless the presentation is severe. The bad news at the top of the chassis was that the E463 audio output pentode was missing. The Historical Radio Society of Australia (HRSA) valve bank listed the E463 valve, but had no stock. This is not surprising for an old European type. I later came up with a work-around for this problem. The elegant AZ1 double diode mains rectifier was wrapped with bandage material at the base, but this no longer held the glass envelope to the base, and any knock may have separated them. I ran a line of thin-CA glue around the base. This glue sets relatively quickly and strongly (CA is cyanoacrylate, a form of superglue). Unfortunately, some leaked into the base where it continued to leak down the pins and glued the valve to the socket. The recovery from this mistake was tedious, but eventually successful. A lucky circumstance is that these veteran valve sockets have elongated claws rather than sockets, and I could prise the claws apart. Below the chassis was a mostly pleasant surprise. Someone had replaced all capacitors and many resistors with 1960s-vintage components. The circuit diagram for the D225 Monopole radio. 112 Silicon Chip Australia's electronics magazine siliconchip.com.au The electrodynamic speaker was a replacement Australian 8-inch (200mm) Rola of 1930s vintage, with the cone in perfect condition. The niggling thought when encountering such a comprehensive component replacement is to resolve whether it was motivated by the need to fix a difficult fault, and if so, whether it was successful. The HT filter electrolytics were contemporary black sheathed types (other replacement capacitors were from the 1960s). It appears that more than one person had worked on restoring this radio. For a radio of this vintage (with uncertain integrity) I decided to ramp up the AC input using a variac to avoid self-­destruction. I monitored the HT voltage at the first filter electrolytic, knowing that the circuit diagram indicated 328V. There was no surge of power consumption, but the HT reached 350V at 205V AC from the variac. On reflection, this made sense because the E463 output valve was missing, and this load would generally reduce the HT due to an increased drop from the internal resistance of the AZ1 diodes. Was the radio working? Linking a signal tracer to the volume control input gave instant gratification that audio signal was coming out of the RF section. This was a qualified joy because the signal crackled and intermittently dropped out. Tapping anywhere on the chassis upset the signal. After many hours, I located one dry joint and another joint that was merely a wire resting on a solder lug. Fixing these improved matters considerably, although, even at the end, there was still an intermittent crackle and sensitivity to tapping the radio. I concluded that one or all of these old valves was susceptible to microphonic instability. Unfortunately, no swap-in valves were available. To allow safe operation without the variac, I inserted a 400W 20W resistor in series with the primary of the mains transformer. The result was a drop of 40V across the resistor and an HT voltage after warm-up of 310V DC. At one point, the radio stopped working, and the HT rose to 395V. I traced this to a 5kW 2W resistor loading the screen grids of the AK2 mixer and AF2 IF amplifier. It had gone open-­circuit, so I replaced it without difficulty. siliconchip.com.au As the power supply was weak, and the output valve missing, I replaced that valve with an LA4160-based amplifier module at the top of this photo (taken from an old Sanyo cassette radio). Unexpectedly, the HT fell to 110V DC after this replacement, but this could be reversed by removing the AF2 valve. The screen voltages of the AK2 and AF2 valves were originally derived from an 8.5kW series resistor from the second filter electrolytic. A previous restorer had increased this series resistor to 15kW, a change that lowered the current drawn by the AK2 and AF2 valves. Even with this limited screen current, the power supply was not coping. Australia's electronics magazine Increasing this limiting resistor to 27kW brought the HT back, and the radio worked well. The severe limitation of the old AZ1 diodes to supply current was reinforced when I rigged up a 6V6 output tetrode to replace the missing E463 valve. I provided the heater current for the 6V6 from an external 6.3V source because the radio didn’t have any suitable windings. Initially, this replacement produced absolutely nothing, leading to the April 2022  113 discovery that the output transformer (labelled HP on the circuit diagram) had an open-circuit primary. This could explain why the E463 valve was missing. When the anode has no HT because the output transformer is open-circuit, a high current flows through the screen grid, which can destroy the valve. With a good output transformer, the 6V6 again produced nothing, this time because the HT had fallen to 88V. It was evident that the AZ1 dual diode valve had such low emission that it was not up to providing more than a few milliamps. Any output valve was going to over-tax the power supply. Looking through my collection of 1980s cassette radios (that my wife wonders why I keep), I selected a Sanyo model M2553F to sacrifice for the greater good. This model has a discrete amplifier section, separate from the radio module, that runs at 7.5V DC rectified from a small mains transformer. The Sanyo LA4160 amplifier IC on the module is good for 1.2W audio output. This is comparable to the 1.5W output from an E463 valve. Bench testing proved that this was a workable solution and that the old electrodynamic Rola speaker was in good condition. I mounted both the small power supply transformer and the amplifier module under the chassis so that the radio continued to look original. The other option would have been to replace the AZ1 with a solid-state rectifier, but the resulting inrush current can cause problems, so it isn’t as simple an option as it first appears. Restoring the dial A French advertising poster showcasing the D225 radio. The advert is stated to be from “Damour-Editions”, and measures 120cm high and 80cm wide. The earlier chassis photo had the transformer cover removed so that its windings and laminations could be seen. This is what it looks like with the ventilated cover in place. 114 Silicon Chip Australia's electronics magazine The celluloid dial was discoloured and cracked. It was so brittle that an attempt to glue the pieces together fragmented it even further. The chemistry of this is interesting. Celluloid dials are fabricated from nitrocellulose with an added plasticiser like camphor that makes the product supple. With age, the camphor evaporates, leaving a brittle sheet. UV light also catalyses denitrification of the cellulose with the release of nitrogen oxides that give the celluloid a brown colour (note how the area exposed to light is darker). The only solution was to completely redraw the dial at a larger scale and reduce it to size. I used PowerPoint to create the text and lines on a yellow siliconchip.com.au background, then printed it on 60gsm paper with adequate transparency to allow the dial light to shine through. I mated this to a rectangle of clear polycarbonate for support. The original dial lamp was open-­ circuit, so I replaced it with a 3.5V torch globe. Finishing touches The original speaker grille cloth was in tatters. Fortunately, I had material in my fabric drawer that closely matched the original, with a brown and gold pattern (unlike the plain fabric shown in the Monopole poster). I carefully installed the chassis into the cabinet to avoid damaging the French-polished finish. I then added a ventilated rear panel along with a warning of the high voltage hazard inside – the top caps on two of the valves are the anodes, not low-voltage control grids. I also included a note telling the user that an aerial must be installed (which you can see in the adjacent photo). I needed to give the radio a final check before all 15.7kg of this hefty unit could be returned to Darren. After warming it up, I was listening to only crackle, dreading the need to start again. My first check was to see that the wave change switch was still set to MW. It was not, so a click later, happiness prevailed. The radio produced excellent sound, with the speaker now baffled SC in its resplendent cabinet. This shows the rear panel and label I fabricated. Also present are (from left-toright) the power cord, mains voltage selection switch, speaker socket (hidden), a ‘pickup’ audio input socket, Earth connection and antenna connection. This speaker was not original, it was instead an Australian-made 8-inch Rola speaker of the same vintage. The celluloid dial originally came cracked and yellowed, due to the way celluloid degrades as it ages. It was much easier to make a new dial than fix it. siliconchip.com.au Australia's electronics magazine April 2022  115 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 Different CMOS timer IC versions Is the TLC555CP CMOS timer IC usable in your Amplifier Clipping Indicator (March 2022; siliconchip. com.au/Article/15240) instead of the 7555? I already have some of those. I was so taken with this project that I just purchased eight PCBs; thanks for a great project! (J. E., Millfield, NSW) ● Yes, the TLC555CP is directly compatible with the 7555. While there are many variations between CMOS 555 timers, such as minimum supply voltage, supply current and other parameters, in many designs, they are interchangeable. The main thing to watch out for is when the circuit is battery powered. In that case, check that the minimum supply voltage is not lower than the originally specified type if the battery voltage could fall that low. Sourcing the LCD for the Dual Hybrid PSU I am presently collecting parts for the Dual Hybrid Power Supply (February & March 2022; siliconchip.com. au/Series/377) and found that the LCD is perhaps not so easy to get. Do you know if Jaycar Cat XC4617 will work? It is the same type of display, but I’m not sure about the controller. Core Electronics have discontinued the one you specified. (R. W., Peakhurst, NSW) ● The LCD used in this project is a 128x64 LCD with the KS0108 controller. It appears the Jaycar XC4617 module uses an incompatible ST7920 controller, they look very similar and are both quite common. For a good source of low-cost displays, search eBay for “128x64 LCD KS0108”. We have used many displays from a range of vendors, some verging on ‘too cheap to be true’ and yet, they have all worked fine. While we have not bought these displays from Digi-Key, if you type “KS0108” into the search on their site, 116 Silicon Chip you will be offered a wide range of displays using this controller. Many of these are identical to those offered on eBay etc. We don’t currently sell this type of display as the cost to us is close to a colour touchscreen, making them seem like a bad deal. However, since Phil Prosser has used these screens in several projects and we’ve received a few questions about where to get them, we might start selling them just to provide an easy option for constructors. Checking the Remote Control Range Extender I bought three Silicon Chip kits for the Remote Control Range Extender (January 2022; siliconchip.com.au/ Article/15182) IR-to-UHF module, Cat SC5993. You warned that the construction of the tiny PCBs would be a visual and dexterous challenge. It was such fun. Thank you. However, there appears to be an error in RevB of the UHF-to-IR PCB. The micro-USB socket fails to supply power since pin 5 is unconnected. Pin 4 (USB designation “ID”) is connected to “SHIELD” and “GND”. Fig.3 on page 100 of the January 2022 issue matches the table on page 36 of the June 2021 issue. After correcting the above error for use with a functioning USB power cable by shorting pins 4 & 5 of the USB socket (checked with your fabulous USB Cable Tester), I was disappointed that there was still no ACK LED activity. Here are my checks of the IR to UHF module. Upon pressing a button on the remote control, it draws about 15-20mA. There is a short-lived supply voltage at Vcc pin 3 of IC2. Using a JYE Tech mini-scope (single channel), I am pretty sure there is a correct signal present at IC2’s pin 6 (ASK) and pin 1 (PAOUT). Thus I think that there is UHF transmission occurring. The antenna is 170mm long. On the UHF-to-IR unit, there is a signal at the GP5 input (pin 2) of the Australia's electronics magazine PIC12F617, so I think that the 433MHz UHF receiver module is working. There appears to be no output at pins 5, 6 or 7. Do you have any suggestions? My conclusion is that something is not right with all three PIC12F617 chips. I have no way of testing microcontroller chips or verifying their contents. (R. M., Ivanhoe, Vic) ● Thank you for pointing out the Micro USB connector ground pin error. We are publishing an erratum to cover that and will eventually have RevC PCBs that fix that error. As far as getting the project to work, one oscilloscope probe to the pin 4 output of the PIC10LF322 on the IR-toUHF converter board and a second probe to pin 2 of the PIC12F617 on the UHF-to-IR receiver should show almost identical signals. If not, check that the pin 4 output of the PIC10LF322 is the same as the pin 1 input except for the stripped out IR modulation. You should be able to duplicate the Scope waveforms in the article. A direct connection between the pin 4 output of IC1 of the PIC10LF322 and the pin 2 input of the PIC12F617, with the UHF receiver data line disconnected from this pin, will bypass the UHF transmission and reception. This way, you can verify that everything except the UHF link is working. Note that the grounds of the two boards must also be connected for this to work. Strange transistor incompatibility Congratulations on publishing the Hummingbird Amplifier, a most useful little amplifier (December 2021; siliconchip.com.au/Article/15126). Having just built several of these modules, I found that the BC556 transistors I bought have the collector and emitter leads reversed from what is shown on your circuit diagram and from what I understand is standard practice. It would seem that these are siliconchip.com.au Philips devices, and the Philips data sheet shows them reversed as well. It might be worth warning others about this. Another observation was that during testing, I found that if I drove the unloaded output beyond about 22V RMS, the output would latch to close to the positive rail (about 32V). Is this normal behaviour? When loaded, the output just goes into clipping above 22V RMS as expected. Finally, a technical question - why is the dominant pole (Miller) capacitor around the BC546/KSC3503 VAS 220pF instead of the more usual 100pF? (M. F., Brassall, Qld) ● Regarding the BC556 devices... wow. That could cause a few headaches! Constructors should be cautious about this as reversed leads are not the sort of thing you would look for in debugging. We recommend that readers check the hfe of their devices using a simple multimeter checker, which will both verify that the pinout is as expected and allow a rough gain check. We aren’t sure where you found a Philips data sheet for a BC556 showing a non-standard pinout. The one that we found (siliconchip.com.au/ link/abd9) shows the expected C-B-E pinout left-to-right looking at the face of the package with the leads down. We would argue that any PNP transistor that does not have this pinout cannot be a BC556. Manufacturers might make PNP transistors with different pinouts with “556” in their part codes. Still, we would not consider them equivalent devices, and we doubt that their part code contains “BC556” without some extra letters or numbers in the middle. Regarding your other queries, Phil Prosser responds: I have never seen the output latch positive. This is not behaviour I would expect of an amplifier designed using Douglas Self’s ‘blameless’ principles. I have seen odd behaviour when the ground is not connected correctly. Check that your input ground is wired back to the main Earth. Errors here can cause weird behaviour like you describe. The dominant pole capacitor in my early prototypes was 100pF. During testing using the wide selection of transistors, some combinations exhibited minor oscillation around negative clipping at high currents. The siliconchip.com.au increased capacitor value resolved this for all the combinations of devices we tried. The published design must behave well, so 220pF is what we recommended. However, you could likely reduce this. The main test we recommend if doing this is to drive a 4W resistive load with a sinewave at 1kHz, and look around the negative rail clipping. If there are bursts of oscillation on the sinewave near the clipping region, increase this capacitor value until they disappear. The impact of this 220pF capacitor value on performance is only just measurable over 5-20kHz as a minor increase in distortion. This is due to the reduced open-loop feedback at high frequencies. R80 aviation band receiver sensitivity I built the R80 aviation band receiver kit (November 2021; siliconchip.com. au/Article/15101), version 7.1. Unfortunately, its measured sensitivity in the aviation band is around 1mV – a long way from the hoped-for sensitivity of 1-2µV. What sensitivity did Andrew Woodfield obtain with his kit? (G. G., Bateman, WA) ● Andrew Woodfield responds: My receiver’s sensitivity is close to 0.5µV (10dB S/N), measured with a 30% modulated AM carrier on 119MHz. I suspect your low sensitivity is due to a faulty NE602 IC. From comments received from several other builders, some kits arrived with what appeared to be recycled/recovered NE602 chips, which showed some signs of wear and tear. These subsequently proved to be faulty. Replacing them brought the receiver back to life. Advice on coding PICs and using MPLAB I am an aspiring PIC assembly language programmer. I recently downloaded MPLAB X IDE but have not been able to program a PIC16F1847. The code I write builds, and I can program my target, but the PIC does not run at all. My investigations to date have not helped me unravel the mystery of my lack of results. What software do you use to edit and program the devices you use in your Silicon Chip project work? My programming experience for some years Australia's electronics magazine is in using AVR devices using the AVR Studio software. (G. S., Rangiora, NZ) ● We also use MPLAB X for software development on PIC microcontrollers. You haven’t described your hardware configuration (eg, circuit diagram and chip connections) or MPLAB X and compiler versions, so we can only give suggestions. We haven’t used the PIC16F1847, but it appears to be broadly similar to many of the other ‘enhanced’ parts that we have used, such as the PIC16F1455. Having also worked with AVR parts, the one factor we would pick out between AVR and PIC is the configuration ‘fuses’ (called Fuses for AVR parts or Configuration Bits for PICs). There is no doubt that the wrong fuse settings can result in the micro not running, either as expected or at all. At a guess, we suggest that your oscillator settings might not be correct. While an AVR part will usually have its fuses programmed separately to the program memory (and may not even need the fuses to be ever changed), a PIC part will almost always require both to be programmed together. Also, the AVR parts we have seen usually have an internal clock mode enabled when new (as needed for ISP programming), while the default PIC state is to expect an external clock, as these parts do not need a working clock to be programmed. Assuming you are using MPLAB X version 5.xx, you can access the fuses from the Window → Target Memory View → Configuration Bits menu selection. Choose a value for FOSC (Oscillator Selection) to suit (eg INTOSC if you don’t have an external clock source) and set WDTE (watchdog timer) to OFF. These two settings are the most likely to cause non-operation; the remaining settings should be fine to leave as-is. Click on Generate Source Code to Output. This will open a text window with a series of “#pragma config” lines, which you should then add to your source code. We use C; for the assembly language with pic-as, strip the “#pragma” from the front of each line and then add them to your .asm file. The compiler/assembler will see them and create the necessary bytes in the HEX file; thus, they will be written along with the program memory on the next programming cycle. Of course, it could be something else, but based on the information April 2022  117 provided, this is where we would look first. We assume you are initially trying to program some simple code, such as flashing LEDs; avoid starting with anything too complicated until you have verified that your code is running. But the easiest way to modify the font is to use a tool such as the Font­ Tweak program, which can be downloaded from the same page as Jim Hiley’s MMEdit program at www.ccom.com.au/MMedit.htm This page is also linked from Geoff Graham’s Micromite page at https:// Changing Digital geoffg.net/micromite.html Preamp splash screen Copy the end section, including the A few weeks ago, I ordered the DefineFont header and trailer, into a PCB for the Touchscreen Digital Pre- separate .bas file and open, edit and amp with Tone Control (September save the file with FontTweak. Then use & October 2021; siliconchip.com. the updated .bas file to replace the font au/Series/370) along with the pre-­ definition in the “Digital Preamp.bas” programmed Micromite LCD Back- and upload that file to the Micromite. pack V3 kit. While waiting for it to arrive, I’ve been poring over the arti- Vintage Radio Power cle and looking at how it functions and trying to figure out how the code Supply not shutting off works. I finally completed Power Supply I’ve done a little bit of programming for Battery-Powered Vintage Radios before, but not for the PIC. I have been (December 2020; siliconchip.com.au/ reading about MMBasic and have Article/14670), and I’m pleased to say been reading Geoff Graham’s website, that it works, producing a B+ supply which is quite good. You Aussies! of 99V DC unloaded and a 1.47V A I’ve been working quite a while on supply. an amplifier project that will be a gift However, I have discovered that the for my cousin and best friend. I actu- battery connected to CON1 (two Li-ion ally built a preamp from scratch that cells in series) becomes discharged works pretty well, but when I saw this overnight with the unit switched off preamp with both a touchscreen and (S1 off). remote, I decided to change course. The current drawn from this battery While I love you guys, I would like with S1 off starts at around 275mA, to customise the display and replace gradually reducing over several minthe Silicon Chip logo with something utes to about 240mA. If the 3.7V batelse. Is there a quick way to replace this tery is disconnected from CON2, the with either a different text in a differ- drain on the CON1 battery stops. ent font, or better yet, to put a simple If S1 is on, the drain on CON1 graphic in its place? (J. R. Norco, Cal- remains the same and the LED lights ifornia, USA) up to indicate that the unit is oper● Yes, doing that is fairly straight- ating. forward. The logo is implemented From the outset, I have not had any as a font with a single character that success in the VR3 and VR4 settings is printed to the display at line 241 to set the minimum voltages to pre(in the current version of the “Digi- vent damage to the Li-ion cells. From tal Preamp.bas” file in the download the beginning, the setting of VR3 has package on our website). The line of had no effect on the LED; it was lit as code is: soon as voltage was applied to CON1 and CON2. TEXTS 0,0,” “,LT,10,1,C. With two LiFePO4 cells in series LOGO,C.B ‘this is the SC logo connected to CON1 (8V measured), The C.LOGO constant defines the the gates of Q5 & Q6 measure 7.2V, and colour used to draw the logo. You there is no current flowing with S1 off. could simply delete or replace this When I connected the second batline, or modify the font as described tery to CON2 (4.1V), the LED turns on, below. even with S1 still off. I measure 5.45V The logo is contained in the font #10 at the gates Q5 & Q6. Do you know why definition at the very end of the “Digi- this is happening? (R. W., Loxton, SA) tal Preamp.bas” file. This is a 120x47 ● The measurement of 5.45V at the pixel font with only one character at gates of Q5 & Q6 with an 8V batcode point 32. If you’re game, you can tery connected and S1 off makes us modify the hexadecimal data directly. think that LED1 is going into reverse 118 Silicon Chip Australia's electronics magazine breakdown, pulling down the gates of the Mosfets and causing current to flow. But that can’t explain why LED1 switches on regardless of the settings of VR3 and VR4. That suggests a separate fault. Start by checking that LED1 is correctly orientated. A problem with transistors Q7 and/ or Q8, such as a high leakage when off, would explain both faults, so check them carefully. It might be easiest just to replace them with parts from a different source to see if that fixes it. With both batteries connected and S1 on, verify that IC1’s supply voltage is close to 3.3V and that you can adjust the voltages at TP1 and TP2 over 0-3.3V using VR3 and VR4. Then check that the voltage at pin 3 of IC1 is close to 1/3 of the CON1 battery voltage, and the voltage at pin 5 of IC1 is close to 2/ of the CON2 battery voltage. 3 Verify that with the voltage at pin 2 of IC1a higher than at pin 3, the base of transistor Q7 is close to 0V. Do the same with pins 6 and 5 of IC1 and the base of Q8. Ultimately, disconnecting Q7 or LED1 should ensure that the whole thing is switched off with S1 off. Depending on which component removal fixed it, that should give you an idea of where the fault lies. If LED1 is breaking down, adding a 1N4148 diode in series should fix it (LEDs are not guaranteed to break down much above 5V, but they usually will withstand substantially higher than that). Simulating steamboat engine sounds I want to build a sound generator to simulate a steam engine for a model tugboat. I found two articles, one in the September 2012 issue and one in September 2018. I would like to know if either would be suitable, if kits are available and how much they cost. What voltage power supply I will need, and what size and impedance of loudspeaker? Is there anything else I should know about? (G. C., via email) ● The September 2018 project produces steam or diesel horn sounds, not engine sounds. The Digital Sound Effects Generator (September 2012; siliconchip.com. au/Article/537) is an audio playback device so it can produce any sound you want, as long as you can get (or make) a suitable WAV file. We don’t sell a kit continued on page 120 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE FOR SALE KIT ASSEMBLY & REPAIR LEDsales DAVE THOMPSON (the Serviceman from Silicon Chip) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz 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 multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com Where do you get those HARD-TO-GET PARTS? Where possible, the SILICON CHIP On-Line Shop stocks hard-to-get project parts, along with PCBs, programmed micros, panels and all the other bits and pieces to enable you to complete your SILICON CHIP project. SILICON CHIP On-Line SHOP www.siliconchip.com.au/shop 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 April 2022  119 Advertising Index AEE Electronex.............................. 5 Altronics.................................85-88 Control Devices........................... 13 Dave Thompson........................ 119 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Hare & Forbes MachineryHouse......................... 11 Jaycar.............................. IFC,57-64 Keith Rippon Kit Assembly....... 119 LD Electronics........................... 119 LEDsales................................... 119 Lintek PCBs................................. 69 Microchip Technology......... OBC, 7 Mouser Electronics....................... 9 Ocean Controls........................... 10 Phipps Electronics...................... 68 PMD Way................................... 119 ROLEC OKW................................ 71 SC Vintage Radio Collection...... 49 SC SMD Test Tweezers.............. 77 Silicon Chip Binders.................. 81 Silicon Chip Subscriptions........ 37 Silicon Chip Shop.................98-99 Silvertone...................................... 8 The Loudspeaker Kit.com............ 6 Tronixlabs.................................. 119 Wagner Electronics..................... 95 for that project, but we have the PCB and programmed micro at: siliconchip. com.au/Shop/?article=537 You might be interested in the Super Digital Sound Effects Module (August & September 2018; siliconchip.com. au/Series/325). We sell a complete kit for that project, Cat SC4658, for $40 (siliconchip.com.au/Shop/20/4658). It runs from a 2-18V DC supply and drives an 8W speaker. The speaker size is not relevant (except in terms of fitting it in your boat), but you should look for a speaker with a high efficiency figure and good low-frequency extension to maximise the volume and realism of the sound. We also published a relevant project in October 1991, the SteamSound Simulator Mk.II (siliconchip.com.au/ Article/5853), which produces steam train engine simulation. But there is no PCB available, just the PDF pattern. Note that you can find all projects and kits (including any kits produced by Jaycar & Altronics) using the search page at siliconchip.com.au/Articles/ ContentsSearch For example, try typing “steam” or “sound effects” into the Name box and click the Search button. Remote control codes for older projects I built the Remote Volume Control for Stereo Amplifiers from June 2002 (siliconchip.com.au/Article/4062) from an Altronics kit (K5026). I also bought the latest version of the programmable remote control, the Dynalink A1012A. Unfortunately, I have not been able to get this combination to work. I checked the supply voltage and the voltage on the programmable chip socket before inserting the chip, and it all checked out OK. I have double-­ checked the components on the board to ensure the assembly was correct and checked the resistor values before soldering them. The BC338s are in the correct positions. The remote control is a newer version of the A1012 but the programming is straightforward. I have tried manual input of control codes as well as automatic searching for control codes without success. The A1012A unit requires a four-digit input code, and I tried about half of the numbers listed in the Philips TV section. Can you suggest how I can troubleshoot this project? (R. B., via email) ● Unfortunately, the A1012A is not directly compatible with the A1012. Our June 2002 project was published before either of those devices were sold, so the article doesn’t mention them. The codes used in the June 2002 design may be the same as our Remote Controlled Stereo Preamp from March & April 2019 (we tend to reuse the same codes). In that case, for the A1012A, one of the following TV codes should work: 0088, 0149 or 0169. If it still doesn’t work, you could have a problem with the infrared receiver or microcontroller. You will need to check to see if there are pulses at the microcontroller’s IR input pin when you aim the remote at the receiver and press a button. The rest of the time, it should idle high (near the receiver’s supply voltage). It would also be a good idea to try installing LK1 and/or LK2. Those change the codes the unit is expecting, and one set of codes might align with what the remote control is producing. SC Notes & Errata Dual Hybrid Power Supply, February 2022: in Fig.7 on p29, the pinout diagram for the LM1084 is incorrectly labelled LM1048. Also, on page 31, a little more than halfway down the text, it refers to the pre-regulator as REG4 when it is actually REG5. The Mysterious Mickey Oz, Vintage Radio, January 2022: the best sensitivity (without the problematic IF filter) was 7μV for 50mW output at 600kHz. However, the text states 70μV. 7μV is the correct value. Remote Control Range Extender, January 2022: the ground for the Micro USB B connector is connected to the 4th pin instead of the 5th pin on the RevB PCB. To fix this, a solder or wire bridge connection needs to be made between the 4th and the 5th pins of CON2. The RevC PCB will have this corrected. Solid-State Tesla Coil, February 2022: in the circuit diagram, Fig.1, F1 and PTC1 were shown wired in series in the opposite order to how they are wired on the PCB. This does not have any effect on the circuit’s behaviour. The May 2022 issue is due on sale in newsagents by Thursday 28th of April. 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