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NOVEMBER 2023 ISSN 1030-2662 11 9 771030 266001 $1250* NZ $1390 INC GST INC GST K–Type Thermocouple THERMOSTAT MEASURES FROM -50° -50°C UP TO 1200° 1200°C! Modem Watchdog AUTOMATICALLY REBOOTS A FAILED MODEM Raspberry Pi Pico Audio Analyser Refresh your workbench with our GREAT RANGE of essentials at the BEST VALUE. Here's just a small selection of our best selling workbench essentials to suit hobbyists and professionals alike. ALL THE REGULAR OSCILLOSCOPE FUNCTIONS IN A SMALL FORM FACTOR 2 CHANNELS SuperPro Gas Soldering Tool Kit SOLDER ANYTHING, ANYWHERE! DURABLE CASE WITH EXTRA TIP STORAGE Ideal for soldering, plastic cutting, heat shrinking, etc. • Includes two double flat tips, hot air blow, hot knife & hot air deflector tips • Up to 580°C temperature range • Up to 120 minutes run time ONLY 189 $ TS1328 GREAT ES. FEATUR GREAT PRICE! 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Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. ONLY jaycar.com.au/workbench 1800 022 888 Contents Vol.36, No.11 November 2023 18 The History of Electronics, Pt2 Page 18 We round-up significant inventors and their inventions dating from 1848 onwards. Compared to last month, you’ll find many of the inventions are more closely related to devices used today such as television & computers. By Dr David Maddison Electronic inventors & inventions 46 16-bit precision 4-input ADC The ADS1115 provides up to four 16-bit ADC channels (analog-to-digital conversion) to nearly any microcontroller. It has a built-in I2C interface, making it trivial to connect to an Arduino or similar. By Jim Rowe Using electronic modules 62 Microchip’s new PICkit 5 We tested out the new PICkit 5 programmer from Microchip, to see what new features it has. We also took the time to evaluate the latest version of the free MPLAB X IDE software. By Tim Blythman Microntroller tools review 98 Recreating Sputnik-1, Part 1 The History of Electronics Raspberry Pi Pico Audio Analyser Page 36 Recreating Sputnik-1 The Soviet-designed Sputnik-1 satellite, launched in 1957, carried two D-200 1W radio transmitters. Dr Holden decided to create an authentic replica of the D-200 transmitter. By Dr Hugo Holden Vintage Radio 36 Pico Audio Analyser Our compact Audio Analyser uses a Raspberry Pi Pico to generate and analyse audio signals. It has oscilloscope and spectrum modes and can perform harmonic analysis to check signal quality. By Tim Blythman Test & measurement project 50 K-Type Thermostat Our Thermocouple Thermostat doubles as a thermometer and easily measures temperature from -50°C to 1200°C! It has an onboard relay for thermostat control of heating or cooling applications. By John Clarke Temperature control project 68 Modem / Router Watchdog This simple Watchdog will automatically restart your modem or router if it stops working. It's a useful device that saves you the hassle of getting up and restarting the modem yourself. By Nicholas Vinen Networking project 74 1kW+ Class-D Amplifier, Pt2 Continuing from last month, we cover how to assemble and test your new and powerful Class-D monoblock amplifier. The assembly process is straightforward due to the Amplifier using pre-built modules. By Allan Linton-Smith Audio project Page 98 2 Editorial Viewpoint 5 Mailbag 35 Product Showcase 82 Serviceman’s Log 90 Online Shop 94 Circuit Notebook 97 Subscriptions 1. Minimal WiFi water tank level gauge 2. Demonstrating magnetic levitation 3. Discrete microamp LED flasher 108 Ask Silicon Chip 111 Market Centre 112 Advertising Index 112 Notes & Errata 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. 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 – M.Ed. Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Louis Decrevel loueee.com 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): $70 12 issues (1 year): $127.50 24 issues (2 years): $240 Online subscription (Worldwide) 6 issues (6 months): $52.50 12 issues (1 year): $100 24 issues (2 years): $190 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 194, Matraville, NSW 2036. Phone: (02) 9939 3295. ISSN: 1030-2662 Printing and Distribution: 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Editorial Viewpoint Computer keyboards need an update Standardisation is generally a good thing. In primarily English-speaking countries, we mainly use keyboards that mimic the IBM 104-key (Model M) keyboard. There are variations, of course, but we all have access to similar symbols and so on. However, these keyboards are lacking when it comes to fields like mathematics, physics, engineering or other sciences. They make it really awkward to type many symbols used frequently in these disciplines. Even relatively common everyday symbols like degrees (°) are missing and must be entered in a complex multi-step process. For example, you can hold down the Windows key (if you have one), press “.” (full stop) and then navigate the pop-up window to find a glyph. Still, that takes a lot more time than just pressing a key on your keyboard. Given that there are plenty of keys on our keyboards that we (almost) never use, like scroll lock, pause/break, SYSREQ and so on, one should be changed to a SYM key. The 36 letter and number keys on the keyboard can then provide an extra 36 symbols (with legends under the letters or to the right of the numbers) to make typing the following symbols much easier: Mathematics: × (multiply), ÷ (divide), − (subtract [not hyphen]), ± (plus or minus), √ (square root), 3√ (cube root), ≈ (approximately equal to), ≠ (not equal to), ≤ (less than or equal to), ≥ (greater than or equal to) Fractions: 1/2 (one half ), 1/3 (one third), 1/4 (one quarter), 1/5 (one fifth), 1/8 (one eighth), 2/3 (two thirds), ¾ (three quarters), 1/10 (one tenth) Currencies etc: ¢ (cents), € (Euros), £ (pounds), ¥ (yen/yuan), ° (degrees), – (en dash), — (em dash) Greek letters: α (alpha), β (beta), γ (gamma), Δ (delta), θ (theta), λ (lambda), μ (mu/micro), π (pi), φ (phi), Ω (omega/ohms), ω (lower case omega) This could be difficult on keyboards used for other languages since they already use a technique like this for typing accents, different letters etc. Still, as US/UK/AU/NZ keyboards don’t currently need to produce a lot of extra symbols, why not provide such a function? The cost of doing so is almost nil. Australia Post wants to put prices up again! According to the ACCC at siliconchip.au/link/abpu, “Australia Post is proposing to increase its stamp prices by 25 per cent from January 2024”. They already increased stamp prices by nearly 10% in January 2023, so a 25% increase a year later seems excessive. The basic letter rate would go from $1.10 at the end of last year to $1.50 at the start of next year, a 36% hike! This proposed increase will also affect Print Post, meaning our cost of mailing magazines to subscribers (a significant proportion of our subscription cost) could go up by 25% as well. I have already written a submission to the ACCC. I wrote that while an increase in the letter rate is not totally unreasonable given the high inflation we’ve experienced this year, 25% is too much in one go, especially so soon after the last increase. I’ve suggested they make the increase smaller, perhaps half of what they are asking for. We’ll have to wait and see what happens. This goes to show what a vicious cycle inflation causes. AusPost wants to increase its rates, likely because its expenses are growing. That then causes everyone else’s expenses to go up, so we must keep raising our prices to keep up, causing even more inflation. It has to end somewhere unless we want to wind up like Zimbabwe or Argentina. There was an error in the Editorial Viewpoint column from the August 2023 issue: the new prices for the Australian print and combined subscriptions (six months) should be $70 and $80 respectively, as listed in the September 2023 editorial. Cover: https://unsplash.com/photos/red-and-black-artwork-ioJBsYQ-pPM Australia's electronics magazine by Nicholas Vinen siliconchip.com.au Build on your proficiency Quick tips, tools and articles for purchasing professionals mou.sr/purchasing-resources +852 3756-4700 australia<at>mouser.com 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”. Grid interconnects are DC‽ I loved the story on the Australian electrical grid in the August 2023 edition (siliconchip.au/Article/15900) and was stunned to learn there’s so much high-voltage DC in the system. Please tell me there will be a follow-up article that will go into more detail on how rectification, AC ‘restoration’ and synchronisation take place at that scale. Greig Sheridan, Hamilton, NSW. Comment: We published an article in the September 2008 issue on Basslink that you might like to read (siliconchip.au/ Article/1943). It explained how the AC-to-DC and DC-to-AC conversion worked. It is very common for long-distance links to be DC because there are significant advantages in both efficiency and cost at higher power levels. It also means that different AC sections of the grid don’t have to be synchronised. Notes on building the LC/ESR Meter I noticed in the LC & ESR Meter project article (August 2023; siliconchip.au/Article/15901) that you suggested the Altronics H0401 case for this instrument. Since I had purchased the two separate boards and a H0400 case (the larger one), I thought that would be a suitable option. The photos shown below are of the completed instrument, which works very well. I mounted the connectors and switch on an internal panel so that the case can be opened without disturbing the wiring. The ‘zero’ switch for ESR has been mounted at right angles to the board and is accessible at the back of the case. The Arduino Uno board I used has a second set of solder pads just inside the header strips, so I ran all the wires from them except two wires to the LC board. Once I decided this would work, I fitted header pins to the LC board but only in the positions used, which allowed the two boards to be stacked again as per the original version (June 2018). In hindsight, I should have put the Uno stack on the right-hand side of the case, as the I2C adaptor for the LCD screen is almost pressed against the relays when the case is closed. I also modified the print statements for line 3 of the display so it shows which range is in use. I noticed a schematic error: the wiring for switch pole S1a is shown reversed in relation to what the software requires, ie, +5V should go to the ESR side of the switch. The same error is repeated in Fig.3 on page 60. Ian Malcolm, Scoresby, Vic. Comment: thanks for reporting that error, which we have put into an erratum in the October 2023 issue. If wired as per the original diagram, the software can be easily changed to reverse the sense of the switch. The combined PCB was verified to work with the original software, so the switch on it is wired correctly, as expected by the published software. Transformers have a hard life A few years ago, I modelled the behaviour of the common ‘linear’ power supply circuit with a transformer, bridge rectifier and filter capacitor(s) to determine the currents involved. I write ‘linear’ because the circuit is not truly linear; it is called that to distinguish it from switchmode supplies. One alarming outcome was that the RMS transformer current was over twice the DC load current. More recently, the publication of your bench supply (30V/2A; siliconchip.au/Series/403) re-awakened my interest, so I decided to make some measurements with a real supply. I used an old 1980s piece of equipment fitted with A finished LC/ESR Meter fitted into a larger Altronics H0400 case. siliconchip.com.au Australia's electronics magazine November 2023  5 an AR 5502 transformer (two 22V 1.5A secondaries wired in parallel). The results were less extreme but were still somewhat concerning. The circuit used a 4700μF filter cap and produced 33.6V DC unloaded and 28.4V when loaded with a 33W resistor. The measured load current was 0.85A DC, and the transformer secondary current was 1.503A RMS. The ratio of secondary RMS current to DC load current is therefore 1.77. All measurements were taken with a single Keysight U1242C DMM. The DMM burden voltage for current measurements could be up to about 0.5V, which would have a noticeable but ultimately inconsequential effect in my view. I was able to download a data sheet for AR transformers (from 1966!), which describes the 5502 as having two 22V 1.25A secondaries, rated to supply 25V DC at 1.5A when connected in parallel. This implies 55VA to supply 37.5W, and the ratio of secondary RMS current to DC load current is about 1.67. Also notable is that the DC voltage is much lower than the 31V DC that might be expected at first sight. No information was furnished about the required rectifier and filter circuit. The peak voltage of a nominally 22V sinewave that we might expect the filter capacitor to charge to is over 31V, although the rectifier would take off a volt or two. I measured the secondary resistance and leakage inductance of the 5502 transformer at 100Hz with primary shorted and secondaries in parallel, and they came out to 2.5W and 1.7mH, respectively, so that would account for some of the voltage loss. So, a transformer with secondaries rated at 2.5A is underrated for a 2A DC supply. These results suggest that a secondary rating of about 3.5A is recommended to keep the transformer within specifications at the full current of the supply. This is not to say that the supply is in imminent danger of fire or explosion; transformers are pretty robust, in my experience. However, other components inside the case could be affected by the heat produced, and ultimately, if the supply is run at full current for extended periods, the transformer insulation is likely to degrade over time and could eventually fail. I appreciate that it is not always convenient to specify parts of bespoke design for projects such as this. Still, perhaps a warning about continuous operation at full current might be prudent. Phil Denniss, Darlington, NSW. Comments: You are right, and we are aware of this when we design circuits powered by transformers. It’s unavoidable that a transformer feeding a bridge rectifier and capacitor filter bank will draw high peak currents as most of the current is drawn near the mains sinewave’s peak. Also, the rectified DC voltage is higher than the RMS AC voltage. Thus, the VA drawn from the transformer will be substantially higher than might be expected from a basic analysis. Pretty much all power supplies we have published in Silicon Chip and that have been in EA, as well as similar commercial power supplies, suffer from this in that their transformers are technically required to produce more VA than their specification at full load. Typically, transformer ratings are conservative as the transformer designers/manufacturers know they will likely be used with a rectifier and capacitor filtering. The transformers will have a rough time but, in our experience, you 6 Silicon Chip Australia's electronics magazine siliconchip.com.au can draw the specified DC VA from the transformer without any problems. Partly, this is because the transformer output will begin to reduce as it is loaded beyond its ratings. Some transformers with less generous margins could run hot under these conditions, but in our experience, that is relatively unusual. Running a power supply at its maximum rating (where the transformer is effectively overloaded) will cause heat buildup and sometimes shut down from the output regulator. It is very rare to find a transformer that has failed, even with supplies that have been used for decades and used near their maximum ratings. It is usually a semiconductor or capacitor that goes faulty first. Feedback on magazine price changes Thank you for your efforts in keeping the online subscription price increase very reasonable. Considering the change in your electricity tariff, a $5 increase for a 12-month online subscription is justified. I have been a Silicon Chip reader from the very beginning. I visited Leo Simpson’s house when he and Greg Swain were assembling the second issue on Leo’s table tennis table under his home. Due to my previous military service, my body is not that of a young person anymore, and I don’t get the time in my workshop that I would like. I look forward to receiving my copy of Silicon Chip each month. The enjoyment I receive from my online subscription is well worth the 5% increase. Well done, guys and gals. Keep up the magazine’s high standards. Jeff Monegal, North Maclean, Qld. How vibrators were adjusted pre-CRO Further to R. H.’s query in Ask Silicon Chip, October 2023, concerning vibrator calibration in the pre-CRO era, adjustments were first made statically. Contacts were set to a specific gap using feeler gauges. The RCA 7604 vibrator from 1933 (which I described in the HRSA’s “Radio Waves” magazine, January 2020) also had a tension adjustment, set by hanging calibrated weights from the contacts. Adjustment instructions can be seen at www.cool386.com/files/rca_vib_adjust.jpg These static adjustments were then fine-tuned with a crude dynamic adjustment, which essentially was to set the contacts for minimum sparking. In the early days of vibrator power supplies (1931-1934), their operation was not yet fully understood, so determining suitable adjustment specifications to start with involved a degree of trial and error. Hence, the seemingly vague and non-scientific approach. A later improvement was to set the contact gap using a microscope with a calibrated graticule. By the mid-1930s, oscillographic displays were being used for the dynamic adjustments. Dwell meters have also been used, but they only suit separate drive type vibrators (such as the Oak). This method was described in the “Radio & Hobbies” Serviceman article for November 1947. However, by this time, tolerances in the parts were so small that little or no adjustment was required in the final assembly. Contact adjustment entails obtaining a specific duty cycle, typically 70-90%, depending on manufacturer and type. For Oak, it is 80% for the primary contacts. The secondary contacts for synchronous types are set to a few percent less since these contacts must open before and close after the primary contacts. The choice of duty cycle is a compromise between efficiency and mechanical considerations. Contacts must also be adjusted for an equal duty cycle. Otherwise, a DC component is created, reducing efficiency due to transformer core magnetisation and rapidly eroding one set of contacts. The components making up a vibrator power supply are all interdependent, and their specifications are critical. In simple terms, a particular transformer and timing (buffer) capacitance must be selected to suit a specific vibrator type, as well as each other. Any deviation could lead to transformer saturation and/or contact erosion due to the timing capacitance being too little or too great. The important point is that there is reason behind the adjustment settings. Unfortunately, the apparent simplicity of a vibrator power supply is a trap for the unwary. Merely getting a vibrator to function with random adjustments will likely lead to poor reliability. Up until around 1934, vibrator manufacturers provided repair and adjustment instructions for service technicians, along with replacement parts. However, one technician’s Dual-Channel Breadboard Power Supply Our Dual-Channel Breadboard PSU features two independent channels each delivering 0-14V <at> 0-1A. It runs from 7-15V DC or USB 5V DC, and plugs straight into the power rails of a breadboard, making it ideal for prototyping. Photo shows both the Breadboard PSU and optional Display Adaptor (with 20x4 LCD) assembled. Both articles in the December 2022 issue – siliconchip.au/Series/401 SC6571 ($40 + post): Breadboard PSU Complete Kit SC6572 ($50 + post): Breadboard PSU Display Adaptor Kit 8 Silicon Chip Australia's electronics magazine siliconchip.com.au A must have reference for your projects in the year ahead. 2024-25 Catalogue OUT NOW! Register for your complimentary printed copy at www.altronics.com.au/catalogue/ Your electronics supplier since 1976. Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or shop online 24/7 <at> altronics.com.au © Altronics 2023. E&OE. Build It Yourself Electronics Centre® ability to adjust a vibrator correctly might not be as good as another, so reliability, along with the manufacturers’ reputations, began to suffer. Furthermore, once the science of vibrator power supplies was better understood, it was realised that few service personnel would have the necessary skills or instruments to provide the precision adjustments required outside of the factory. For this reason, from the mid-1930s, most vibrator manufacturers sealed the mechanism inside the can, with the whole unit to be replaced if it failed. If someone “had a go” at repairing it, the obviously deformed can seal would absolve the manufacturer of any ensuing reliability problems. John Hunter, Hazelbrook, NSW. Trick for troubleshooting HDMI to VGA converters I recently bought a HDMI to VGA converter from OfficeWorks but it didn’t work correctly. The display flickered about once a second. I then tried a different brand from Jaycar and the same thing happened. After buying a few on eBay, I finally found one that worked. The one that works communicates with the VGA monitor to get its list of supported resolutions, while the faulty ones don’t. I discovered a simple way of finding out if the design of a HDMI to VGA converter was faulty. Just measure the voltage between VGA pins 9 and 10, which should be 5 volts. Converters should provide 5V to a display monitor to power up its 24LCS22A or similar EEPROM and then use the I2C protocol to read Extended Display Identification Data (EDID). Faulty ones don’t. I had assumed that a reputable brand $40 converter would work better than a no-brand $10 converter, but I was wrong. John Rajca, Mount Kuring-gai, NSW. Possible cause of mains switch arcing I am responding to the query on “causes of mains switch arcing” on page 106 of the October issue. As I test many different products for immunity at high levels of surge and fast transients, I often see the failure of bypass capacitors usually used across motors or in the AC filter circuit. The worst of the older type is the RIFA brand in a clear case, particularly if they are a few years old. Most will temporarily short out, then the offending capacitor’s internal wrap will burn through and usually, but not always, spill out or crack the case. If such a capacitor is fitted across the motor, its failure would pop the circuit breaker due to the high instantaneous current. If the capacitor was in the AC filter, it could have tripped due to Earth leakage for a three-pin plug product. If there is no capacitor anywhere, your editorial suggestion may have been the cause. Often, the use of a calibrated hammer around the motor housing will show up the intermittent motor. Still, after applying the hammer, I suggest that an ohmmeter check to Earth would be sensible before plugging it in and testing further. Braham Bloom, EmiSolutions, Russell Lea, NSW. We should have long-range digital radio broadcasts The Cambridge Consultants/CML module is the most significant consumer development in radio since the invention 10 Silicon Chip of the superheterodyne receiver in 1918. This device uses the inverse Fourier calculation in a chip invented by the ‘black hole’ hunting astronomers at the CSIRO in Australia in 1997 (see siliconchip.au/link/abpt). The use of Fourier Analysis enables the increase in data transmission speed to allow the insertion of gaps in the transmissions, which allows reflections to dissipate. That means crystal-clear high-frequency (shortwave) broadcasting over thousands of kilometres. The above technology is also used in DAB+, which has been broadcasting at high power in major Australian cities since 2009. DRM is much better for regional and remote areas because its lower-frequency transmissions cover much larger areas. There are currently three digital radio standards: Digital Radio Mondiale (DRM), HD Radio (HDR) and Digital Audio Broadcasting+ (DAB+). Analog TV was shut down in 2013, freeing up the 45-68MHz range, which is now unused except for the 6m amateur radio band. These frequencies are lower than the FM band (87.5-108MHz). Simulcasting is possible without coverage area restrictions from interference with other broadcasters. It is also possible to install a high-powered HF DRM transmitter in the centre of Australia and cover the whole continent. Radio New Zealand Pacific is now building a new HF DRM transmitter to be a companion to the existing DRM transmitter, which started transmitting in 2007. While Gospell is using the module mentioned earlier in pocket radios, I hope you will now extend its design for use in vehicle infotainment systems so that TPEG data can be used during emergencies for causing the navigation system to re-route vehicles around police roadblocks. Journaline includes slideshow images in all their receivers with larger touchscreens, so multiple emergencies can be indexed with separate maps, and instructions can be selected and displayed. This would be very useful with high-frequency broadcasting in Australia and the Pacific, for example, where cyclones and tsunamis travel across large areas. India already covers 1.4 billion people with DRM broadcasts. Now Pakistan, with 248 million people, has started rolling a high-power medium-frequency DRM transmitter that can also cover adjacent countries. China (1.4 billion) and Indonesia (279 million) have also adopted DRM, so over 3.3 billion people will be able to receive DRM broadcasts soon. The USA (340 million), Canada (39 million) and Mexico (130 million) can access HDR radio. The European Union (451 million) and the UK (68 million) have access to DAB+ radio. A low-cost DRM/DAB+ receiver could be built. With both technologies, no wasteful carrier signal is radiated, reducing transmission costs and pollution even compared to the digital transmissions used for wireless internet. In the 2021 census, Australia has 26 million people, including around 16 million covered by DAB+, leaving 9 million needing DRM for digital radio in rural and remote regions. The biggest advantage of broadcast radio in emergencies is that it will continue operating when the mobile phone network fails when needed most! The CML module can receive all broadcast bands used in Australia, including HF (shortwave), which the ABC Australia's electronics magazine siliconchip.com.au closed down in 2017 despite having crystal clear broadcasting over huge areas. A high-power DRM HF transmitter in the centre of Australia could give millions of people access to two broadcasts. They currently have no access to live radio while mobile. Those programs could continue at lower quality while emergency information is transmitted simultaneously. With the closure of regional newspapers, DRM can also transmit an electronic newspaper, including a touch index to stories that can include coloured images. This would be considerably cheaper than trying to cover the 80% of Australia’s land area not covered by streaming using the mobile phone network. Finally, I am pleased that high-definition TV channels will soon be the default selection for terrestrial TV, instead of the blurry standard-definition version. This will commence in Tasmania on Thursday, 5th of October. Alan Hughes, Hamersley, WA. More on LED light bulb interference with AM radio Readers who are shortwave radio listeners or amateur radio operators may be interested in a short video from Peter Parker, VK3YE, prominent Melbourne amateur radio operator and “ham” radio author. He just published a short video demonstrating problems with RFI (radio frequency interference), or as hams call it, QRM, from LED light bulbs. This is a significant contributor to electrical noise in the environment. See https://youtu. be/H8twPwskQNI Dr David Maddison, Toorak, Vic. An idea for dealing with junk email I have just read your editorial covering spam emails (“Junk email is getting out of control”, June 2023). A solution for those with a website could be as simple as blocking all emails by default unless they are solicited. Let’s say that I would like to email you. I would go to your web page and register my email with your site. You then send me an email that contains my email passkey. That passkey is unique to my email address and is registered with your site. Every email I send to your domain must contain the passkey in the subject heading. At your end, you set your spam filter to scan the subject heading, any email without a valid passkey is filtered out, and your server sends back a single email that advises of the process required to email Silicon Chip. No passkey, no email to your desk. Of course, you could program your server to accept some businesses that will not follow this rule; let’s call them exceptions. And, of course, if any user abuses their passkey, even selling it on or by becoming a spambot, you withdraw their access. You could even send an email advising of their breach and the process for reinstatement. Until a better solution is found, involving some real effort to catch those paying for the spambots, we will continue to be plagued by unsolicited advertising and scams. In the interim, best of luck with your spam filters and if you happen to adopt the process listed above, please send me your bank account details so that the Nigerian prince and I can reward you for your actions. Ian Ashford, Taminick, Vic. Comment: that is an interesting idea; it has been raised ...continued on page 14 siliconchip.com.au Australia's electronics magazine November 2023  11 Explore our GREAT RANGE of Filament 3D Printers Create amazing 3D prints with our great selection of 3D printers. The best brands at great prices, stocked with spare parts, great service and advice. CREALITY ENDER-3 NEO & V2 NEO FLASHFORGE ADVENTURER 3 NEO^: • 128x64 Mono screen TL4256 Common features: • Prints up to 220x220x250mm • Auto bed levelling • Prints up to 150x150x150mm • Built-in camera for remote monitoring • Carborundum glass bed • Easy to assemble V2 NEO: (Shown) • 4.3" Colour screen TL4752 • PC Spring steel bed • Quick & easy to assemble TL4750/52 GREAT VALUE! 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Nozzle Temp 260°C 260°C 240°C 300°C 260°C 300°C 265°C 240°C 300°C 275°C 275°C Main Interface 150mm/s 150mm/s Coated Flex Coated Flex Dial & button Dial & button Touchscreen Touchscreen Touchscreen Touchscreen Touchscreen Dial & button Touchscreen Screen 128x64 Mono 4.3" Colour 2.8" Colour 4.3" Colour 4.3" Colour 4.3" Colour 4.3" Colour 128x64 Mono 55" Colour Touchscreen Touchscreen 55" Colour Filament Sensor - • • • • • • • • • • Levelling System Auto Auto Assisted Auto Auto Auto Assisted Manual Assisted Auto Auto 55" Colour ^ Available online only. before, although this is the first time a Nigerian prince has suggested it. Still, we think that it’s infeasible in our situation. We run a business that needs to be contactable by our customers and the general public; we can’t expect all our customers to go out of their way to adhere to such a solution. This problem needs to be solved at a high level by governments and internet infrastructure providers. There needs to be a way to report spam to a central authority that permanently blocks all internet traffic from the originating addresses until they can prove they have stopped sending the junk. That would force virus-infected computers acting as botnets and open relays to be fixed. Renewables do not provide base load generation I have been a hobbyist in electronics since the days of building crystal sets and have enjoyed Silicon Chip magazine since its first publication (also previously Radio & Hobbies, EA etc). I would like to comment on your editorial on ‘renewables’ (April 2023). I have retired after sixty years in the commercial refrigeration service, installation and maintenance industry. Most switchboards I worked on required three-phase power, ie, 440V AC at 400-600A per phase 24/7. As far as I can see, my work area was a fraction of the power grid state-wide, much of which requires baseload power generation. I applaud the domestic solar panel scheme as worthwhile; however, it is not a practical means of providing base load power, nor are those expensive, disastrous wind farms. Should we have to look at alternatives to coal, the obvious choice is nuclear. Everyone, including me, would love to have solar-powered semi-trailers, trains etc, but it ain’t gonna happen. Could I ask you to explain the term ‘renewables’? As far as I can see, the energy is not ‘renewable’ but generated alternatively. Rex Mower, Empire Bay, NSW. Comment: “renewable” refers to the fact that power derived directly or almost directly from the sun (solar photovoltaic, wind, hydroelectric etc), as well as geothermal, can be expected to operate almost indefinitely. It should be five billion years or so before the sun becomes a red giant; until then, PV panels, wind generators etc should continue to operate. While much of the energy in coal, oil, natural gas and so on would have also been derived from the sun (eg, causing ancient trees to grow that eventually became buried and turned into coal), that is over a much longer timescale (hundreds of millions of years) so those resources will be used up much faster than they could ever be replenished. So, while it is a matter of timescales, we think “renewables” is a fair enough term. While hydro and geothermal energy can provide baseload generation, the amount of energy that can be generated that way is limited mainly by geology. Hence, as per the April editorial you referred to, energy storage is the problem that needs to be solved to allow renewables to provide large-scale baseload power. The debate about whether and SC how they can do that is ongoing. 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ENTRY LEVEL * QM1500 QM1517 QM1527 MID LEVEL QM1529 QM1321 QM1020 QM1446 Display (Count) 2000 2000 2000 2000 4000 Analogue Security Category Cat II 500V Cat III 600V Cat III 500V Cat III 600V Cat III 1000V Cat II 1000V • • Autorange True RMS PROFESSIONAL QM1323 QM1552 2000 4000 2000 4000 4000 2000 4000 6000 4000 Cat III 600V Cat III 600V Cat IV 600V Cat III 600V Cat IV 600V Cat III 600V Cat IV 600V Cat IV 600V Cat III 1000V • • • • • • QM1551 QM1549 • • • • • XC5078 QM1594 QM1578 • Voltage 1000VDC/ 750VAC 500V AC/DC 500V AC/DC 600V AC/DC 1000VDC/ 750VAC 1000V AC/DC 1000VDC/ 700VAC 600V AC/DC 1000VDC/ 750VAC 600V AC/DC 1000V AC/DC 600V AC/DC 600V AC/DC 1000V AC/DC Current 10A DC 10A DC 10A DC 10A AC/DC 10A AC/DC 10A DC 10A AC/DC 10A AC/DC 10A AC/DC 10A AC/DC 10A AC/DC 200mA AC/DC 10A AC/DC 10A AC/DC Resistance 2MΩ 2MΩ 2MΩ 20MΩ 40MΩ 20MΩ 20MΩ Capacitance 100mF Frequency 10MHz Temperature Duty Cycle 20MΩ 40MΩ 200MΩ 40MΩ 40MΩ 40MΩ 60MΩ 100μF 100µF 100mF 100µF 100µF 100µF 6000µF 10MHz 10MHz 10MHz 10MHz 10MHz 10MHz 10kHz 1000°C 760°C 1000°C 760°C 750°C 760°C • • • • • • • • • • • • • • • • • • • Continuity • • • • • • Relative Min/Max/Hold • Non Contact Voltage • • • $33.95 $39.95 $59.95 Max Hold • • • $64.95 $87.95 $87.95 IP Rated Price • Max Hold • • $28.95 *Lifetime warranty excluded on models: QM1500/QM1517/QM1527 $35.95 $65.95 1000VDC/ 750VAC 4000MΩ • • • IP67 $16.95 QM1493 $119 IP67 $109 $179 $219 $329 Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. The History of Electronics Inventors and their Inventions Physicist Isaac Newton wrote, “If I have seen further it is by standing on the shoulders of Giants”. The field of electronics is no different; we could not have the technology we have today without the contributions of thousands of brilliant people. This series of articles is about them. Part 2: by Dr David Maddison T he first article of this three-part series, published last month, listed significant electronics-­ related inventions of individual inventors born before 1848. This part will cover all the individual inventors (that we can fit) born from 1848 onward, while the third part next month will discuss significant inventions credited to companies and other organisations. Inventors by date of birth (1848 onward): Shelford Bidwell photocells 1848-1909 Experimented with selenium photocells in the 1870s, and in 1880, reported how he also duplicated the “photophone” experiment of Alexander Graham Bell (siliconchip.au/link/ abnc). In another experiment, he used a selenium cell to scan an image and transmit it to another device via wires, which burned the reproduced image onto paper. He reported the results of his “Tele-­ Photography” in 1881 (siliconchip.au/ link/abnd). He was the first to use a photocell to scan an image (Bain and Bakewell did not; see last month). He also invented a device that could scan an original document without 18 Silicon Chip redrawing it on special media, analogous to a modern fax machine. In 1908, he published “Telegraphic Photography and Electric Vision” (siliconchip.au/link/abne), on transmitting motion video (ie, TV) and the large amount of data involved. Chichester A. Bell tape recorder 1848-1924 Bell and Sumner Tainter (18541940) received US patent 341,214 in 1886 for a recording and playback device where sound was recorded on a wax-coated paper strip in a reel-toreel arrangement. It was the earliest tape recorder, but was considered inferior to Edison’s wax cylinder for recording and playback and was not commercially released. Sir John Ambrose Fleming 1849-1945 thermionic valve, trans-Atlantic transmission Invented the first thermionic valve, otherwise known as a “vacuum tube”, in 1904 (see Fig.29). Fleming called them oscillation valves “for the rectification of high-frequency electric oscillations as used in wireless telegraphy”. They were diodes, the simplest type of valve. Fleming’s valve is considered the beginning of electronics because it was the first active electronic component. As radio detectors, Fleming’s valves were not more sensitive than crystal detectors. However, they did not need Fig.29: Fleming’s first vacuum tube diodes from 1904. Source: https://w.wiki/7DAU Australia's electronics magazine siliconchip.com.au constant adjustment for use on ships due to the movement like crystals did. In 1899, Fleming, under contract from Marconi, designed the first highpower radio transmitter, much larger than the 200-400W transmitters used by Marconi. It was a spark-gap transmitter powered by a 25kW alternator and it performed the first trans-­ Atlantic transmission in 1901, over 3500km, which was credited to Marconi despite Fleming’s involvement. Charles Fritts 1850-1903 solid-state solar cells He made the world’s first solid-state solar cells in 1883 with selenium and a thin layer of gold. They had an efficiency of 1%, making them too expensive and inefficient for generating power, but they were used as light sensors for cameras and in other applications into the 1960s. Oliver Heaviside mathematical equations, E region etc 1850-1925 Reformulated and simplified Maxwell’s equations to make the Maxwell-­ Heaviside equations and put them in their modern form. He also invented the Heaviside step function to calculate the current drawn when an electrical circuit is switched on, and developed transmission line theory (or telegraphers’ equations). The latter increased the transmission rate of the trans-Atlantic telegraph cable ten times, to one character per minute. He discovered that telephone line transmissions could be improved by a series inductance in the cable. He and Arthur Edwin Kennelly (1861-1939) independently predicted the presence of the Heaviside layer, Kennelly-­ Heaviside layer or E region, part of the ionosphere that reflects medium-­ frequency waves. William Edward Sawyer electricity distribution 1850-1883 Sawyer worked on telegraphy and electric lighting. With Albon Man, he founded the Electro-Dynamic Light Company (1878-1882), later purchased by Westinghouse, to provide lighting and distribute electricity into cities. His lighting system contained a safety switch and a current regulator. His company had patents dated 1877 and 1878 for incandescent lights, predating Edison. Sawyer’s lights were not long-lasting, a problem he never solved. Karl Ferdinand Braun 1850-1918 cathode ray tube (CRT), oscilloscope etc He discovered the rectifying properties of a metal-semiconductor junction (schottky diode) in 1874, using mercury as the metal and copper sulfide or iron sulfide as the semiconductor. He also invented the cathode ray tube and the oscilloscope in 1897. He worked on wireless telegraphy and invented a crystal detector in 1898, among other contributions. In 1905, he devised the phased array antenna. Edward Weston 1850-1936 Weston Cell, Constantan & Manganin alloys Invented the Weston Cell in 1893, a highly-stable electrochemical cell used as a voltage reference. It was the international standard for EMF from 1911-1990. He invented the alloy Constantan in 1887, which has a low variation in resistivity with temperature, used in thermocouples, and Manganin in 1892, with almost no variation in resistivity with temperature, used in precision resistors. In 1888, he founded the Weston Electrical Instrument Corporation, which became famous for the wide variety of high-quality electric meters it manufactured. Sir Oliver Joseph Lodge moving-coil loudspeaker etc 1851-1940 Lodge identified electromagnetic radiation independent of Hertz. He also made an improved Hertzian wave detector based on metal filings in a tube he named a “coherer”, based on Branly’s earlier work (see last month). Under the influence of a radio signal, the conductivity between the two electrodes would change. The device had to be regularly tapped to restore its sensitivity. It was used until 1907, when Marconi’s crystal detector replaced it. He also invented the moving-­coil loudspeaker in 1898. In 1898, he invented and patented “syntonic tuning” to tune radio equipment to specific frequencies, causing a patent dispute with Marconi. He developed a form of electric spark ignition for internal combustion engines. Emile Berliner 1851-1929 microphone, Berliner Gramaphone Record Developed an improved type of telephone transmitter (microphone); his patent was acquired by the Bell Telephone Company. It was contested by Thomas Edison, who won the case. There were many expensive and complicated court cases in the USA in the 1870s and 1880s contesting the invention of the telephone; see https://w. wiki/7DYJ In 1887 and 1888, Berliner received US patents 372,786 & 382,790 for the “Berliner Gramophone Record”. They were flat discs, like the records we know today, although the Berliner records were only 18cm in diameter, played two minutes per side and rotated between 60RPM and 75RPM. They competed against wax cylinder recordings. There is a project to put about 18,000 Berliner recordings on Flickr: siliconchip.au/link/abpa Leonardo Torres y Quevedo 1852-1936 “Telekino” remote control, El Ajedrecista game Quevedo demonstrated a remote control he invented in 1903, called the “Telekino” (Fig.30). It was remarkably advanced for the time and was the second remote control invented after Tesla’s in 1898. 19 different commands could be sent, with the command Karl Ferdinand Braun was a founder of Telefunken. Source: www. cathodique.net/ FBraun.jpg Fig.30 (right): the Telekino receiver in the Torres Quevedo Museum in Madrid, Spain. Source: https://w. wiki/7DAV siliconchip.com.au Australia's electronics magazine November 2023  19 sequence recorded. He tested it with dirigibles in 1901. In 1905, he demonstrated the device with a three-wheeled vehicle, and in 1906, a boat with people onboard. The work was abandoned due to a lack of money. He also invented what was arguably the first computer game. It was called “El Ajedrecista” and could play certain chess moves (see Fig.31). Mechanical arms moved pieces while sensors detected the opponent’s moves. It still works today and can be seen at the Torres Quevedo Museum in Madrid. Temistocle Calzecchi-Onesti experiments leading to the coherer Fig.31: the remarkable El Ajedrecista chess-playing machine. Source: www. torresquevedo.org/LTQ10/images/ PrimerAjedrecista.jpg (CC BY-SA 3.0). 1853-1922 Conducted experiments from 1884 on the electrical conductivity of tubes of metal filings and how they were affected by various electrical influences. This led to Branly’s invention of the coherer (see Lodge’s entry on page 19). Heike Kamerlingh Onnes superconductivity 1853-1926 He discovered superconductivity in 1911 (the loss of all electrical resistance of some materials at certain low temperatures). It is used to generate powerful magnetic fields in machines like MRI scanners. High-temperature superconductors with less stringent cooling requirements are currently being developed. Jonas Wenström three-phase electrical system Fig.32: the operation of a Hall effect IC. Original source: www.ablic. com/en/semicon/products/sensor/ magnetism-sensor-ic/intro/ 1855-1893 Received a Swedish patent for a three-phase electrical system in 1890. He developed it independently of Mikhail Dolivo-Dobrovolsky (see his entry on page 22). Edwin Herbert Hall Hall effect 1855-1938 He discovered what is now known as the Hall effect in 1879, the basis of modern magnetic field detectors and Hall thrusters on spacecraft. It explains that a voltage is produced at right angles to a current flow in a conductor with a magnetic field perpendicular to the current flow – see Fig.32. Paul-Jacques Curie piezoelectricity Fig.33: Hertz’s 1887 spark-gap transmitter, with an induction coil, dipole antenna, capacitance (C) at the ends, a spark gap (S) and resonant loop antenna receiver with a spark micrometer (M) to measure signal strength. It operated at around 50MHz. Source: https://w. wiki/7DAW (CC-BY-SA-3.0). 20 Silicon Chip 1855-1941 With his brother Pierre Curie (18591906), discovered piezoelectricity (used for guitar pickups etc) in 1880. They also studied pyroelectricity. Nikola Tesla 1856-1943 polyphase electrical system, Tesla coil etc Tesla was a prolific inventor and genius. He developed the polyphase electrical system (AC power with Australia's electronics magazine more than one phase) and associated induction motors, licensed by Westinghouse in 1888. From 1890, he tried to develop a wireless lighting system using Geissler tubes powered by a Tesla coil he invented in 1891. He was photographed at his Colorado Springs facility in 1899 with the “magnifying transmitter” Tesla coil (done using double-exposure; see the lead image). It produced 12MV 150kHz arcs up to 41m long with an input power of 300kW. In 1893, he consulted on the design of a Niagara Falls hydroelectric power station. In 1898, he developed the first wireless radio remote control for a boat, a concept he called teleautomatics. In 1906, he demonstrated a bladeless turbine for a power station, which spun at 16,000RPM and produced 150kW. The unit of magnetic flux intensity, the tesla (T), is named after him. Sir Joseph John Thomson acoustic waveguide 1856-1940 Contributed to atomic physics. In 1893, he proposed the acoustic waveguide, and in 1894, Oliver Lodge experimentally verified it. In 1897, Thomson suggested the existence of the electron. He also conducted experiments with cathode rays. Heinrich Rudolph Hertz spark gap transmitter, radio waves 1857-1894 Hertz proved the existence of radio waves, first predicted by Maxwell’s equations, from 1887 onward. He demonstrated properties such as polarisation, reflection and standing waves. In 1887, he also built the first spark gap transmitter (Fig.33). The unit of frequency, the hertz (Hz), is named after him. William Stanley Jr 1858-1916 AC transformer and complete AC system Built the first practical AC transformer in 1885 based on the prototype of Gibbs and Gaulard; see US patent 349,611. In 1886, he demonstrated a complete AC system with generators, transformers and high-voltage transmission lines in Great Barrington, Massachusetts, lighting offices and stores. Sir Jagadish Chandra Bose 1858-1937 millimetre waves, microwave components etc He produced millimetre (5mm wavelength) 60GHz electromagnetic waves in 1894 because they were a more convenient size to work with in his small laboratory – see Fig.34. In 1895, he demonstrated how siliconchip.com.au Fig.34: 60GHz microwave apparatus by Jagadish Bose. The galvanometer and battery are modern. The transmitter on the right generates microwaves from sparks between tiny metal balls. Above the galvanometer is a galena point-contact detector inside a horn antenna. Source: https://w.wiki/7DAY (CC-SA-3.0). millimetre waves could go through the human body and walls, achieving a range of 23m. Bose was not interested in patenting or commercialising his amazing work, although he was persuaded to patent a metal-­ semiconductor diode in 1901, awarded in 1904 (US patent 755,840). He developed a galena semiconductor crystal microwave detector and many other now-familiar microwave components, such as waveguides, horn antennas, dielectric lenses and polarisers. Much of his equipment can be seen at the Bose Institute Museum in Kolkata, India (www.jcbose.ac.in/ museum). Nobel laureate Sir Neville Mott said that Bose was 60 years ahead of his time and that he had anticipated p-type and n-type semiconductors. One of his concepts from a paper he wrote in 1897 was used in the 1.3mm multibeam receiver of the National Radio Astronomy Observatory (NRAO) 12m telescope in Tuscon, Arizona. Friedrich August Haselwander 1859-1932 electric arc lamp Invented an electric arc lamp in 1880, and in 1887 invented and put into service a synchronous threephase generator in Europe (Fig.35). It developed about 2.8kW at 960RPM and 32Hz. Aleksandr Popov lightning detector (radio receiver) 1859-1906 Popov built a wireless lightning detector in 1895 (see Fig.36), one of the first radio receivers, and in 1896 transmitted radio signals over 250m. Some of his work was based on the findings of Sir Oliver Joseph Lodge. In 1898, he performed ship-to-shore communication using wireless telegraphy over 10km, and in 1899, 48km. In ex-USSR countries, the 7th of May is celebrated as Radio Day, the day Popov first demonstrated his lightning detector. Herman Hollerith punch(ed) cards 1860-1929 Developed punched cards for data storage and analysis, used in the 1890 US Census. These evolved into IBM punched cards, used as late as the early 1980s. See our January 2023 article on Computer Memory for more on punched/punch cards (siliconchip.au/ Series/393). Ottó Titusz Bláthy 1860-1939 modern transformers, voltage regulator etc Sir Jagadish Bose demonstrating the horn antenna. Source: https://w. wiki/7DuL Fig.36: Alexander Stepanovich Popov’s 1895 “coherer receiver”, one of the first radio receivers, designed to detect lightning strikes. Key: A) antenna, B) bell, C) coherer (detector), E) electromagnet, G) ground, L) chokes for noise immunity, R) relay, V) battery. Source: https://w. wiki/7DAa siliconchip.com.au Fig.35: Haselwander’s three-phase generator with stationary ring armature and four-pole rotor, as displayed in 1891 at the International Electrotechnical Exhibition in Frankfurt. Source: https://w. wiki/7DAZ Australia's electronics magazine Bláthy, Károly Zipernowsky (18531942) and Miksa Déri (1854-1938) applied for a patent for the first modern transformers in 1885, which were much more efficient than the designs of Gaulard or Gibbs. The trio also designed the first power station with AC generators “to power a parallel-­ connected common electrical network”. Bláthy also invented the voltage regulator, AC watt-hour meter (1889), motor capacitor for single-phase AC motors and turbo generator for steam power plants. Paul Julius Gottlieb Nipkow Nipkow disc 1860-1940 Invented the Nipkow disc in 1883. It was a disc with a spiral pattern of holes to divide a picture into a linear series of points to enable opto-electronic November 2023  21 Paul Gottlieb Nipkow is considered to be one of the fathers of television. Source: https://w. wiki/7DuZ imaging of an object. There was little interest at the time. It became the basis of the first electro-­optical television systems in the 1920s-30s (see our articles on Display Technologies in the September & October 2022 issues - siliconchip.au/ Series/387). Peter Cooper Hewitt 1861-1921 mercury vapour lamp, mercury arc rectifier He invented the mercury vapour lamp in 1901, the predecessor of the fluorescent lamp. In 1902, he invented the mercury arc rectifier, the first commercially available non-mechanical rectifier. In 1916, he was involved in developing the Hewitt-Sperry Automatic Airplane, the predecessor of the cruise missile. Mikhail Dolivo-Dobrovolsky asynchronous three-phase motor 1862-1919 Invented an asynchronous threephase motor in 1888, which had low torque at low speeds. This problem was solved with a variation of that motor, the slip-ring motor, with high torque at low speeds in 1891. He also developed the delta-wye transformer for three-phase distribution systems in that year. television would be solved by electronic systems with CRTs at both ends. Walther Hermann Nernst Nernst (incandescent) lamp 1864-1941 Invented the Nernst lamp (Fig.37) in 1897 as an improvement to the incandescent lamp. The way it works is very interesting. An element heats a ceramic rod made of zirconium oxide and yttrium oxide. The rod’s resistance decreases as it heats up and the heating element is turned off. A current sustains the glowing ceramic rod due to ohmic heating. It can operate in the air, as the ceramic rod will not degrade like a metal filament. They are obsolete as a visible light source but are still used as an infrared light source in spectroscopy, as they emit infrared over a wide range of wavelengths. See the video titled “The Nernst Lamp” at https:// youtu.be/1vCQySb6ulA Charles Proteus Steinmetz Steinmetz’s equation 1865-1923 He contributed to AC hysteresis theory from 1890 and solved practical problems with heat build-up in AC motors. This resulted in him building a powerful motor for Otis Elevators to reach higher floors. His work led to Steinmetz’s equation for calculating losses in magnetic core materials, published in 1892 (see the PDF at siliconchip.au/link/abnf). 22 Silicon Chip 1866-1932 He first transmitted speech by radio in 1900 and made the first twoway radiotelegraphic communication across the Atlantic in 1906. He invented an electroacoustic transducer called the Fessenden oscillator in 1912, and in 1914, it detected icebergs 3km away. It was also used for underwater telephony and depth sounding. For more information on that, see our June 2019 article on Bathymetry (siliconchip.au/Article/11664). Marie Curie 1867-1934 mobile X-ray machine Invented the mobile X-ray machine in around 1915, powered by a dynamo. Henri Abraham 1868-1943 astable multivibrator He and Eugene Bloch (1878-1944) invented the astable multivibrator. The work was done during WW1 but published in 1919. He made the first measurements of the speed of electromagnetic propagation between 19111914 and developed the first French triode valve. Worked in telephone technology and radios. In 1890, he started work on a mathematical analysis of telephone links for American Bell Telephone Co. In 1900, he developed “selective four-circuit tuning” for radios to improve their selectivity and reduce noise. Lenard began investigations of cathode rays in 1888 and developed a modified Crookes tube with what was to become known as a “Lenard window”, a thin aluminium window that made it possible to study the radiation from outside the tube. Boris Lvovich Rosing early television 1869-1933 Fig.37: a Nernst lamp, an early form of incandescent light. Source: https://w.wiki/7DAb He started considering ideas of what we now know as television in 1897, but he called it the “electric telescope”. His approach for the receiver was purely electronic, using a CRT, unlike other ideas for television around that time that were mainly mechanical. By 1902, he made a device that could draw a basic figure on a CRT. Instead of a slow-reacting selenium cell detecting light for the camera, he used a fast-reacting photocell onto which the image was projected by a rotating mirror system. He obtained patents for his invention in 1907 and 1911. It was presented Australia's electronics magazine siliconchip.com.au 1863-1930 Alan Archibald Campbell-Swinton experimented with cathode ray tubes (CRTs) in 1903 for transmitting television images. Prompted by Shelford Bidwell, on the 18th of June, 1908, his letter in Nature entitled “Distant Electric Vision” (siliconchip.au/link/abpb) said the problems of mechanical radio, sonar etc 1869-1943 telephone links, selective four-circuit tuning 1862-1947 Lenard window (aluminium) for Crookes tube transmitting television images Reginald Aubrey Fessenden John Stone Stone Philipp Lenard Alan Campbell-Swinton He worked on AC circuit theory and analysis, which he greatly simplified from previous methods, announcing his findings in 1893. He also investigated AC transient theory and other transient phenomena, such as lightning bolts. Fig.38: Valdemar Poulsen’s magnetic wire recorder, invented in 1898. Source: https://w.wiki/7DAd (CC-BYSA-2.5). in Scientific American, 1st of April, 1911: siliconchip.au/link/abng Valdemar Poulsen magnetic audio recordings 1869-1942 Successfully implemented the first means to magnetically record audio in 1898 by magnetising wire along its length (Fig.38). There was no amplification, so the recording was faint but audible with headphones. The device was called the Telegraphone and had limited commercial success due to its low volume and complexity. With his assistant, Peder Oluf Pedersen, he developed other recording devices using tape and discs. In 1903, he also invented the Poulsen Arc Transmitter (Fig.39), widely used as a radio transmitter in the early 1920s before vacuum tubes were developed. Arthur Korn fax machines 1870-1945 Korn pioneered the modern fax machine, which he used to transmit photographs. He used light-sensitive selenium cells in his “phototelautograph” or “Bildetelegraph”. In 1906, he sent a photo of Crown Prince Wilhelm over 1800km via the telegraph network. In 1913, he transmitted a movie recording, although the specifics are unclear. We assume it was a frame-byframe transmission. In 1923, German police used Korn’s system to transmit photos and fingerprints. Paul Langevin ultrasound transducer Fig.39: a 1919 Poulsen arc transmitter from a US Navy radio station with a continuous power rating of 500kW (1MW short-term). Source: https://w.wiki/7DAe making tungsten ductile, allowing it to be drawn into filaments for light globes. The globes were sold by General Electric from 1911. Lee De Forest 1873-1961 three-element triode, recording audio Invented a three-element triode thermionic tube in 1906, the “grid Audion” (Fig.40), for use as an amplifier and an oscillator. This invention is regarded as the start of the Electronic Age. In 1919, he patented the DeForest Phonofilm system for optically recording audio waveforms onto movie films. Guglielmo Marconi 1874-1937 wireless transmission, spark gap transmitter etc Guglielmo Giovanni Maria Marconi built a device to receive radio waves produced by lightning in 1894. That year, he also demonstrated wireless transmission to ring a bell across a room. He developed a spark gap transmitter and coherer receiver. A coherer was a glass tube with metal filings that radio waves caused to become closer together and therefore more conductive. In 1895, he designed a system that could transmit over 3km. By 1896, he had transmitted over 6km, then 16km. In 1899, he transmitted across the English Channel. In 1907, he established a commercial trans-Atlantic telegraph service. making tungsten ductile Just Sándor Frigyes tungsten filament light globe 1874-1937 Also known as Alexander Friedrich Just, he and Franjo Hanaman (18781941) were the first to invent an incandescent light globe with a tungsten filament in 1904. They were brittle due to the way they were made, although they lasted longer and were very efficient compared to carbon filaments. They licensed their patent to the Tungsram company (which also licensed Bródy’s patent for using krypton gas in globes in 1934). In 1904, they applied for a Hungarian patent and, in 1905, applied for US Patent 1,018,502. The tungsten filament globe became practical with the invention of Coolidge’s fabrication method for tungsten filaments. Alexander M. Nicholson crystal oscillator unknown Invented the first crystal oscillator in 1917 using Rochelle salt, a piezoelectric material, and filed for US patent 2,212,845 in 1918. Walter Guyton Cady quartz crystal oscillator 1874-1974 He invented a quartz crystal oscillator in 1921 and realised that such devices could be used as frequency standards. He filed US patents in 1921 (1,472,583) and 1937 (2,170,318). Fig.40: an early grid Audion, invented in 1906, which many regard as indicating the start of the electronic age. Source: https://w.wiki/7DAf (GFDL-1.2). 1872-1946 Invented the first ultrasound device in 1917, the quartz sandwich transducer for submarine detection. William David Coolidge Marconi’s radios were important in rescuing survivors of the RMS Titanic (1912) and RMS Lusitania (1915). 1873-1975 Coolidge developed a method for siliconchip.com.au Australia's electronics magazine November 2023  23 Édouard Belin Bélinographe, image transmission 1876-1963 Invented the Bélinographe, which used a photocell to scan and transfer press photos (see Fig.41). It was developed in 1907 and first used commercially in 1913-1914 to transmit pictures over dedicated leased telephone lines. Later models could use ordinary telephone lines. In 1921, a version was used to transmit a photo by radio across the Atlantic. By 1926, RCA was using it to transmit Radiophotos. Miller Reese Hutchison 1876-1944 electronic hearing aid, tachometer, Klaxon He developed the first commercial electronic hearing aid in 1898 (going to market in 1899), with a carbon microphone he called the “Akoulallion”. In 1900, he developed a portable battery-­ powered device that he called the “Akouphone”, then the Acousticon 1 in 1902. For more details: siliconchip. au/link/abnl In 1908, Hutchison invented an electric tachometer for ships and the Klaxon in 1910. Robert Von Lieben triode with control grid 1878-1913 Lieben, with engineers Eugen Reisz and Siegmund Strauss, invented the gas-filled (low vacuum) triode with a control grid in 1910. It was the first thermionic valve designed for amplification rather than demodulation and was used as a telephone repeater. Ernst Alexanderson Alexanderson alternator 1878-1975 Ernst Frederick Werner Alexanderson invented the Alexanderson alternator in 1904. It produced radio waves more efficiently and with a narrower bandwidth than the spark-gap transmitters used until that time, and it could deliver them continuously at high power. Alexanderson alternators were used to transmit long-wave radio communications from shore stations from 1906 to the 1990s, although they were too big and heavy for most ships. The first commercial model would generate a frequency of 100kHz and had a power rating of 50kW. The last transmitter in regular use was Grimeton Radio Station in Sweden, which was used until 1996 and is occasionally used today (see page 17 of our March 2023 issue). Albert Einstein 1879-1955 theory of relativity, photoelectric effect Published his theory of relativity in 1905. Relativity must be considered in operating satellite navigation systems such as GPS and many other applications. He also explained the photoelectric effect in 1905, expanding on the work of Planck, which went on to be used in night-vision devices, among others. Alexander Behm echo sounding, Echolot 1880-1952 He invented echo sounding in 1912 to measure water depth and detect obstacles, obtaining a patent in 1913. In 1922, he produced the Echolot to measure water depth beneath a ship. Albert W. Hull dynatron vacuum tube, magnetron 1880-1966 Invented the dynatron vacuum tube in 1918 and the magnetron in 1920, which was used as an amplifier and low-frequency oscillator. The latter is still used in microwave ovens (albeit in a modified form; see the entry for Russell Harrison Varian on page 27). Louis Blattner 1881-1935 Blattnerphone Blattner, under license by Kurt Stille (1873-1957), produced a new audio recorder using steel tape instead of wire called the “Blattnerphone” in 1925. It was also based on the magnetic recorder of Valdemar Poulsen (see his entry on page 23). In 1933, the Marconi Company acquired the rights to the Blattnerphone and made an improved version called the Marconi-Stille recorder, which the BBC used from 1935 into the 1940s (Fig.42). Irving Langmuir vacuum pump improvements Improved the vacuum pump, which led to high-vacuum rectifiers and amplifier tubes. He, along with Lewi Tonks, also discovered that an inert gas improved the lifetime of incandescent globes. He also found that twisting a tungsten filament enhances efficiency. Fritz Plfeumer magnetic tape for sound recording Cpt Henry Joseph Round LEDs, vacuum tubes 24 Silicon Chip Australia's electronics magazine 1881-1966 He contributed to vacuum tube development and developed a triode around the same time as Lee de Forest. He discovered feedback in vacuum tubes independently of Alexander Meissner and Edwin Armstrong. He made the first report of what we now know to be a light emitting diode (LED), utilising ‘cat’s whisker’ detectors, the first type of semiconductor detector, made of silicon carbide and producing faint yellow light. field-effect transistor (FET) Fig.42: the Marconi-Stille tape recorder. Source: Birmingham Museums Trust – https://w.wiki/7Dup (CC-BY-SA-4.0). 1881-1945 He invented magnetic tape for sound recording in 1927 and received a patent for it in 1928. He used paper and iron oxide, with lacquer as an adhesive to bind the oxide to the paper. In 1932, he granted rights to this invention to AEG. They used it with the first practical tape recorder, the Magnetophon K1, demonstrated in 1935. Julius Edgar Lilienfeld Fig.41: the Bélinographe used a photocell to scan and transfer photos in 1907. Source: https://w.wiki/7DAk 1881-1957 1882-1963 Filed for US patent 1,745,175 in 1926, awarded in 1930, for the field-­ effect transistor (FET) but could never build a practical device because of the unavailability of high-purity semiconductor materials at the time. Max Dieckmann video camera tube “image dissector” 1882-1960 Dieckmann and his student Rudolf siliconchip.com.au Fig.43: an Armstrong or Meissner Oscillator. Original source: www.itwissen.info/en/Meissneroscillator-127183.html#gsc.tab=0 Hell (1901-2002) obtained a patent in 1927 (applied for 1925) for a video camera tube called the “image dissector”. However, Philo T. Farnsworth was the first to make it actually work (see his entry on page 28). Alexander Meissner 1883-1958 radio navigation systems, Meissner oscillator Invented the Telefeunken Kompass Sender in 1911, one of the earliest radio navigation systems, comprising a directional beacon used to navigate Zeppelin airships (see siliconchip.au/ link/abnm). In 1913, he discovered positive feedback as applied to vacuum tube amplifiers. He co-invented the oscillator in 1913 (independently with Edwin Armstrong, 1912) and received a patent in 1920. The Armstrong oscillator or Meissner oscillator (Fig.43) uses an inductor and capacitor to produce oscillation with a valve (or transistor in modern implementations) as the amplifier. Its frequency is determined by a resonant circuit, with oscillation maintained by a feedback process. Saul Dushman vacuum tube diodes 1883-1954 While at General Electric, he produced the first vacuum tube diodes in 1915, usable as rectifiers in power supplies. Edith Clarke Clarke (graphical) calculator 1883-1959 Filed US patent 1,552,113 for the Clarke Calculator (Fig.44) in 1921, awarded in 1925. It greatly simplified calculations for long transmission lines. It was a physically simple graphical calculator, which we assume was made out of cardboard or similar, but with some complex mathematics behind it. It also embodied a correct understanding of how inductance and siliconchip.com.au Fig.45: Burnie Lee Benbow’s “coiled-coil” tungsten lamp filament from his 1917 US patent. Fig.44: the Edith Clarke calculator from US patent 1,552,113. capacity are uniformly distributed in long transmission lines, contrary to assumptions made at the time. Burnie Lee Benbow 1885-1976 coiled-coil tungsten filaments Benbow invented “coiled-coil” tungsten filaments for incandescent lamps in 1917 (Fig.45), extending their life due to less tungsten evaporation. Although simple in principle, there were enormous practical difficulties to overcome in fabrication. Georges Rignoux transmitting still images physics. The schottky diode (with a metal/semiconductor junction) is named after him. Hidetsugu Yagi Yagi-Uda antenna 1886-1976 Published articles to the West on the Yagi-Uda antenna (Fig.46), which was invented by his assistant, Shintaro Uda (1896-1976) in 1926. It is a directional antenna of simple design, commonly used for TV antennas and also widely used by radio amateurs. ~1885-unknown Rignoux and A. Fournier of La Rochelle transmitted still images in Paris in 1909. They were updated every few seconds, using a sensor with an 8×8 matrix of photo-sensitive selenium cells. The resolution was enough to reproduce the English (or French) alphabet. Walter Han Schottky thermionic valve, schottky diodes etc 1886-1976 Invented the screen grid thermionic valve in 1915, co-invented the ribbon microphone and ribbon loudspeaker with Erwin Gerlach in 1924 and made many contributions to semiconductor Australia's electronics magazine Fig.46: the basic configuration of a 3-element Yagi-Uda antenna. November 2023  25 John Logie Baird television 1888-1946 He made the first television image in 1925 (see Fig.47). It was of a rotating head, made using a Nipkow disk with 30 vertical lines of resolution. In 1926, he produced the first commercial television. In 1927, he transmitted a television picture over 705km via a telephone line. In 1928, he transmitted a television image across the Atlantic and in 1929, the BBC transmitted the first television programs. In 1940, he started work on the first single-tube electronic colour television system, Telechrome, which was demonstrated in 1944. He also worked on Phonovision between 1926 and 1928 (more on that next month). Sir C. V. Raman Raman effect 1888-1970 Sir Chandrasekhara Venkata Raman and Sir Kariamanikkam Srinivasa Krishnan (1898-1961) discovered the Raman effect in 1928. It is a form of light scattering used for analysing substances. A Raman spectrometer was used on the Mars lander Perseverance. Vladimir Kosma Zworykin ~1888-1982 iconoscope (television camera tube) Filed for US patent 2,141,059 for the iconoscope in 1923 (awarded 1938). This was the first practical television camera tube and it was used for the 1936 Olympics. In Europe, it was replaced that year by the Super-­ Emitron and Superikonoskop. However, it remained in use in the United States until 1946, when it was replaced by the image orthicon tube. Edwin Howard Armstrong 1890-1954 positive feedback (“regeneration”), superhet He was interested in how vacuum tubes work; they were not understood when the triode or “Audion” was invented by Lee de Forest in 1906. As a student, Armstrong experimented with these tubes with Professor John Harold Morecroft. Armstrong made a breakthrough discovery in 1912 that positive feedback or “regeneration” with a triode could dramatically increase the amplification possible, allowing the use of a loudspeaker rather than headphones. He also discovered that an Audion with sufficient feedback could be used to generate a high-frequency signal for radio transmitters. A complicated 25-year legal battle ensued between him and de Forest about patent rights for these discoveries, but Armstrong retains credit. 26 Silicon Chip In 1918, he invented the supersonic heterodyne or superhet circuit, which enabled radio receivers to be more selective and sensitive. That invention was also subject to legal disputation with Lucien Lévy of France, with most claims awarded to Lévy. He developed wideband FM radio and first presented a paper on the subject in 1935, published in 1936. Imre Bródy krypton light globes 1891-1944 Filled light globes with krypton instead of argon in 1930, resulting in a much longer-lasting globe, becoming one of Hungary’s biggest exports. The gas was expensive, so in 1937, he devised a cheaper way to extract it from the air. Lucien Lévy 1892-1965 superheterodyne (superhet) circuit etc Developed a low-frequency amplifier to listen to enemy telephone communications and for other applications during WW1 (1914-1918). He invented the superheterodyne circuit, filing a patent in 1917, resulting in a patent dispute with Armstrong, resolved mostly in favour of Lévy. Robert Watson-Watt radar 1892-1973 He worked on detecting the direction of lightning strikes to warn pilots of storms from 1916. From 1935, he started working on and developing concepts to detect aircraft using radio reflections or radar. By the start of WW2, 19 radar stations had been established, ready for the Battle of Britain, and 50 were in place by the war’s end. Sir Edward Victor Appleton 1892-1965 proving the existence of the ionosphere Proved the existence of the ionosphere in 1924, a layer of the atmosphere that reflects radio waves, and won a Nobel Prize for the discovery in 1947. Homer W. Dudley 1896-1980 Vocoder (Voice Coder) – speech analysis He invented the Vocoder (Voice Coder) in 1936 at Bell Labs. It is a speech analysis and synthesis system to encode speech by analysing it and reducing it to a series of control signals. Those signals could be transmitted over a limited bandwidth connection, such as an undersea cable or radio link, then reconstructed to the original speech. Based on that work, in 1937, he and Robert Riesz invented the world’s first electronic speech synthesiser, the Voder (Voice Operation Demonstrator), receiving US patent 2,121,142. It had a human operator pressing keys to produce the sound and was challenging to operate. It was demonstrated at the New York World’s Fair in 1939. See the video titled “The Voder – Homer Dudley (Bell Labs) 1939” at https://youtu.be/5hyI_dM5cGo and the free eBook PDF at siliconchip.au/ link/abnn During WW2, he worked with Alan Turing (see his entry on page 29) on SIGSALY, a high-level cryptographic machine for voice transmissions that employed technology from Vocoder and Voder (Fig.49). Harold Stephen Black 1898-1983 negative feedback amplifiers, op amps Invented the negative feedback amplifier in 1927. It increased circuit stability, improved linearity (reducing distortion), increased the input impedance, decreased the output impedance, reduced noise, enhanced bandwidth and frequency response. Early practical applications were the reduction of overcrowding on long-­ distance telephone lines, improved Fig.47: shown at left is John Logie Baird with his Televisor, the first commercial television from 1926. The adjacent image is of Baird’s business partner, as seen on the Televisor. Source: https://rts.org.uk/article/remembering-logie-bairdninety-years Australia's electronics magazine siliconchip.com.au Fig.49: the SIGSALY highlevel voice encryption machine used in WW2. Source: https://w. wiki/7DAh Fig.50: the first point-contact transistor from 1947. Source: https://w. wiki/7DAi (CCBY-SA-3.0). fire control systems in WW2, forming the basis of operational amplifiers (op amps) and precision audio oscillators. See our article on the History of Op Amps (August 2021; siliconchip.au/ Article/14987). Russell Shoemaker Ohl solar cell 1898-1987 Ohl filed for US patent 2,402,662 in 1941 for what is regarded as the world’s first solar cell made with a silicon P/N junction. This design continued to be developed, reaching an efficiency of around 5% in the 1950s and 1960s. Russell Harrison Varian klystron (linear-beam vacuum tube) 1898-1959 He and his brother Sigurd Fergus Varian (1901-1961) invented the klystron in 1937 and published the results in 1939. It is a vacuum tube that generates microwave frequency signals. It was the first device to generate these frequencies at a reasonable power level. The Axis powers used it for jamming H2S radar during WW2 (many of the principles had already been published before the war). German radar used more conventional techniques to generate lower-frequency microwaves, while the Allies used the more powerful cavity magnetron (see the entry for Randall and Boot on page 28). Kenjiro Takayanagi all-electronic television receiver 1899-1990 He developed the world’s first all-­ electronic television receiver in 1926, with 40 lines of resolution. A Nipkow disc was used to scan the image at the source, but unlike other systems at the time, the receiver used a cathode ray tube to display the image. This was months before Philo Farnsworth demonstrated the first fully electronic TV system that did not require a Nipkow disc. In 1927, Takayanagi increased the resolution to 100 lines. Howard Aiken Harvard Mark 1 1900-1973 Aiken created the concept for the Harvard Mark 1, one of the earliest computers (see Fig.48). He went to IBM for funding the creation of the design, which was approved in 1939 and finished in 1944. Dennis Gabor holography 1900-1979 Invented holography in 1948, a process best known for the ability to reproduce 3D images but with many other Fig.48: the Harvard Mark 1, designed by Howard Aiken, is an electromechanical computer, more than 15m long. Source: Encyclopædia Britannica – www.britannica.com/technology/minicomputer#/media/1/44895/19205 siliconchip.com.au Australia's electronics magazine applications. He received the Nobel Prize for this work in 1971. Enrico Fermi & Paul Dirac Fermi-Dirac statistics Enrico Fermi (1901-1954) and Paul Adrien Maurice Dirac (1902-1984) independently created Fermi-Dirac statistics in 1926, which describe the behaviour of semiconductors. Stuart William Seeley Foster-Seeley FM discriminator 1901-1978 Seeley and Dudley E. Foster invented the Foster-Seeley FM discriminator in 1936 and published it in 1937. It would be called a demodulator today. It reduced the cost of FM radios to a comparable level to AM radios. It was widely used until the 1970s, when ICs allowed other modulator types to be used. Alfred Kastler 1902-1984 optical pumping Invented optical pumping in the early 1950s, a technique that led to the development of masers and lasers. The coherent light from lasers is crucial to semiconductor fabrication. Walter Houser Brattain magnetometers 1902-1987 He worked with a group developing magnetometers during WW2 to detect submarines and applied for US patent 2,605,072 with others, including Norman E. Klein, in 1944. In 1947, with John Bardeen and William Bradford Shockley Jr, he demonstrated the first working transistor (a point-contact design) – see Fig.50. Bardeen and Brattain were awarded a Nobel Prize for the point-contact device and Shockley for the junction transistor. Bell Labs credits 12 people as being involved with the invention of the transistor. Alan Dower Blumlein 1903-1942 weighting networks, stereophonic sound etc He measured the frequency response of human ears in 1924 to design November 2023  27 weighting networks to minimise noise and better utilise telecommunications bandwidth. In 1924, he also published work on high-frequency resistance measurements. In 1938, he submitted US patent application 2,218,902 for what was to be called an “Ultra-­ Linear” audio power amplifier. In 1931, he filed UK Patent 394,325 for what is now known as stereophonic sound, but it was only commercially exploited in the 1950s after the patent expired. “Matrix processing” was used to efficiently encode sound as a common signal between left and right and a differential signal to define the spatial distribution. After 1933, he worked on the development of television and patented several technologies, and mostly developed the 405-line Marconi-EMI TV system. During WW2, he was involved in developing the H2S radar system for the RAF to identify ground targets for night and all-weather bombing. He was killed during a flight testing the system, but it went on to be a success. Oleg Vladimirovich Losev light-emitting diode (LED) 1903-1942 Extensively studied the silicon carbide point-contact junction, discovered by H. J. Round, which emitted green light. He published the results between 1924 and 1941. He produced a device, but no one saw a use for the weak light, although Losev thought it would be useful for telecommunications. We now know this device to be a light-emitting diode (LED). John Vincent Atanasoff Atanasoff-Berry Computer (ABC) 1903-1995 He completed the Atanasoff-Berry Computer in 1942, which was under development since 1938. It is arguably the first digital computer, although it was not programmable, had no CPU and was not Turing complete (see Alan Turing’s entry opposite). Sir John Turton Randall cavity mangetron fully-electronic television system 1906-1971 Demonstrated a fully electronic TV 28 Silicon Chip Paul Eisler printer circuit board (PCB) 1907-1992 Eisler invented the modern printed circuit board (PCB) in 1936 while working in the UK. He had experience in the printing industry, which helped with the project. The ‘intellectual property’ of the invention was not well protected, as he did not read a contract he signed. There were contributions to ideas and technologies leading up to this, such as from Thomas Edison, who made electrical tracks of glue and charcoal on a substrate in 1904; Arthur Berry, who in 1913 etched metal away to make items such as heating elements; and Charles Ducas, who described plating of copper patterns onto an insulating substrate in 1925. Victor Ivanovich Shestakov switching circuit theory 1907-1987 Developed a way to implement Boolean algebra logic in electromechanical relay circuits in 1935 (switching circuit theory). This was essential for the operation of computers and other digital devices. Claude Shannon independently invented the same theory (see his entry opposite), as well as Akira Nakashima (1908-1970). Manfred von Ardenne 3NF vacuum tube 1907-1997 He obtained a patent for the 3NF vacuum tube in 1923, at age 15. It had three integrated triodes (akin to an integrated circuit) and was used in the low-cost Loewe-Ortsempfänger OE333 AM radio (Fig.52). He also produced the flying-spot scanner as a television camera in 1930 (although not a camera tube, as such) and demonstrated it at the Berlin Radio Show in 1931. John Bardeen point-contact transistor 1908-1991 Bardeen and Walter Houser Brattain demonstrated the first working point-contact transistor in 1947. Oskar Heil microwave vacuum tube 1908-1994 Published a paper in 1935, along with his wife Agnessa Arsenjeva, for a microwave vacuum tube, which subsequently led to the production of the first practical device. It predated the invention of the klystron, another type of microwave vacuum tube. He also invented the air motion transformer, used in certain high-end loudspeakers (there is a video on it at https://youtu.be/-wYxHYVO6sU). Konrad Zuse first Turing-complete computer 1910-1995 He invented the first programmable “Turing-complete” computer in Germany in 1941. William Shockley transistor 1910-1989 He led a research group at Bell Laboratories that included the co-­inventors of the transistor, John Bardeen and Walter Houser Brattain, who produced the first transistor in 1947. In 1956, he founded Shockley Semiconductor Laboratory in Mountain View, California, but unfortunately, he was regarded as a very poor manager. This led to the “traitorous eight” Fig.51 (left): the first digital voltmeter from 1952. 1905-1984 Randall and Henry Albert Howard Boot (1917-1983) invented the cavity magnetron in 1940. It was an extremely important vacuum tube device used to produce high-power microwaves for radar and other applications. The klystron, as used by the Germans then, could not produce high-power microwaves. The cavity magnetron went on to be used in microwave ovens. Philo Taylor Farnsworth system in 1927 (camera and receiver). He used a video camera tube he developed, which he called the image dissector, to capture the image. He demonstrated it to the press in 1928. Fig.52: the Loewe-Ortsemfänger OE333 AM radio used the 3NF vacuum tube made by Manfred von Ardenne. See our Vintage Radio column, in the July 2020 issue (siliconchip.au/ Article/ 14513). Australia's electronics magazine leaving and founding Fairchild Semiconductor in 1957. For more on this, see our article in the June 2022 issue on IC Fabrication (part 1; siliconchip. au/Series/382). John Robinson Pierce communications satellites 1910-2002 Published an article titled “Orbital Radio Relays” in the journal Jet Propulsion in April 1955. He was a pioneer of communications satellites and participated in the development of Telstar 1. Arthur C. Clarke acknowledged Pierce as one of two pioneers of such satellites, along with Harold Allen Rosen. Hedy Lamarr radio guidance system 1914-2000 In the early 1940s, along with George Antheil, she developed spread spectrum and frequency-hopping technology to create an unjammable (at the time) torpedo guidance system. Both techniques were used in later communications systems. Alan Turing cryptography, Turing machine etc 1912-1954 Turing is one of the founders of computer science and a significant figure in the development of cryptography. He created the concept of the Turing machine that can be used to compare the capabilities of different kinds of computers and the Turing test to determine if a machine can fool a human into thinking it’s another human. Claude Shannon 1916-2001 signal flow graphs, Minivac 601 computer Demonstrated circuits in 1936 to simplify the arrangement of relays in telephone network switches. He also invented signal flow graphs in 1942. In 1961, he designed the Minivac 601 electromechanical computer for educational purposes. There are plans to build a replica at siliconchip.au/ link/abno Sir Arthur Charles Clarke communications satellites 1917-2008 He wrote a Wireless World article in 1945 proposing what we would now call communications satellites (in particular, geostationary satellites). Harry Wesley Coover Jr super glue 1917-2011 Invented cyanoacrylate adhesives (‘super glue’) in 1942. A commercial product was not released until 1958, marketed by Kodak as Eastman 910. These adhesives bond almost instantly and have wide application in commercial electronic assembly. Andrew F. Kay digital voltmeter 1919-2014 He invented the digital voltmeter (Fig.51) in 1952. Otis Frank Boykin 1920-1982 precision wire-wound resistors, pacemakers Produced many inventions, including an improved form of precision wirewound resistor with low inductance and reactance. He also invented a precision control unit for cardiac pacemakers in 1964. Norman Joseph Woodland barcode 1921-2012 He applied for a patent for a barcode in 1949, to encode price and product description and other data (see US patent 2,612,994). It was a sound idea, but there was not yet a suitable computer to implement it. Rubin Braunstein 1922-2018 gallium and indium-based semiconductors He measured infrared emission from devices he made from the semiconductors gallium arsenide (GaAs), gallium antimonide (GaSb) and indium phosphide (InP) in 1955. This is the basis for LED lights and semiconductor lasers. David Paul Gregg optical disc 1923-2001 Invented the optical disc in 1962 (although it was discussed as early as 1958). He filed for US patent 3,381,086 in 1962, granted in 1968. Jack St. Clair Kilby first integrated circuit (IC) etc The German’s Enigma machine from WWII was cracked by Alan Turing and others. Source: https://w. wiki/7Dwg (CC-BY-SA-4.0). siliconchip.com.au 1923-2005 He is credited for the first integrated circuit (IC) in 1958, along with Robert N. Noyce. He also invented the handheld calculator and thermal printer. Seymour Cray CDC660 supercomputer 1925-1996 Designed the first silicon transistor Australia's electronics magazine Fig.53: a Cray-1 on display at the Science Museum in London. Source: https://w.wiki/7DBY (CC-BY-SA-2.0). supercomputer in 1964, the CDC660, considered the first successful supercomputer. Germanium transistors, in use until that time, were not fast enough. It was the fastest computer in the world at the time, about ten times faster than others. In 1972, Cray started his own company, Cray Research, and designed the famous Cray 1 (See Fig.53). It was released in 1976 and became one of the most successful supercomputers. Narinder Singh Kapany fibre optics 1926-2020 Kapany invented fibre optics (he coined the term). In 1953, along with Harold Horace Hopkins (1918-1994), he transmitted an image through a bundle of 10,000 optical fibres with better image quality than had previously been achieved. This led to the first practical gastroscope for medical investigations, developed by other researchers in 1956. Junichi Nishizawa 1926-2018 avalanche photodiode, solid-state maser etc Invented the avalanche photodiode in 1952, a solid-state maser in 1955 and, in 1963, proposed the idea of fibre-optic communications. He also patented graded-index optical fibres in 1964. Among his other inventions was the static induction thyristor in 1971. Robert Norton Noyce monolithic silicon IC 1927-1990 Noyce invented the monolithic silicon integrated circuit in 1959 and co-founded Fairchild Semiconductor in 1957 and Intel Corporation in 1968. November 2023  29 Credit is also given to Jack Kilby for the invention of the integrated circuit. Theodore Harold Maiman laser 1927-2007 Invented the first laser in 1960, a device to produce light with all emissions of the same wavelength and all in phase. Nick Holonyak Jr visible light laser diode 1928-2022 He invented the visible light laser diode in 1962. It lased at low temperatures and functioned as an LED at room temperature. Manfred Börner optical fibre communication system 1929-1996 Demonstrated the first working optical fibre communication system at Telefunken Research Labs in 1965. James Robert Biard infrared LED 1931-2022 Biard held numerous patents and also invented, along with Gary Pittman, an infrared LED in 1961 (receiving US patent 3,293,513). In 1962, Texas Instruments released the first commercial LED (SNX-100) for US$130 each, almost $2000 today! binary multiplier in 1964 for arithmetic operations in computers. Sir Charles Kuen Kao 1933-2018 reducing signal attenuation in optical fibres He and George Alfred Hockham (1938-2013) at British STC proposed that making optical fibres out of more pure materials could dramatically reduce signal attenuation in 1965. Today, losses in optical fibres are extremely low, making repeaters only necessary every 70-150km. George Harry Heilmeier liquid crystal displays (LCDs) 1936-2014 Discovered effects in liquid crystals in 1964, which led to the first liquid crystal displays (LCDs) using what he called dynamic scattering mode (DSM). Gary Keith Starkweather laser printer 1938-2019 He invented the laser printer in 1969. The first commercial laser printer on the market was the IBM 3800, released in 1976 to replace line printers, with the Xerox 9700 following in 1977 for high-quality printing. Another reason the 9700 is significant is that when Xerox refused to supply code for that printer (as they had done for a previous model) in 1980, Richard Stallman (see below) and others at the MIT AI Lab started the free software movement. Richard Stanley Williams memristor 1951~ Developed a practical version of the memristor (memory resistor ) at HP in 2008. The memristor was first postulated in 1971 by Leon Ong Chua (1936~). Richard Matthew Stallman GNU project, GCC, Emacs 1953~ He started the free software movement in 1980 and, in 1983, founded the GNU Project. He also founded the Free Software Foundation (FSF) in 1985. The tools developed by the GNU Project were instrumental for Linus Torvalds and others to make Linux a practical operating system. Linus Torvalds 1969~ Linux operating system The driving force behind the opensource Linux operating system. However, thousands of others have significantly contributed to its development, including Andrew Morton, Alan Cox, Greg Koah-Hartman and Ingo Molnar. Linux is licensed under the GNU GPL. Linux currently powers the majority SC of the world’s top web servers. Songbird Chris Wallace hardware binary multipler 1933-2004 Wallace invented the hardware An easy-to-build project SC6633 ($30 plus $12 postage*): Songbird Kit that is perfect as a gift. * flat rate postage Australia-wide Choose from one of four colours for the PCB (purple, green, yellow or red). The kit includes nearly all parts, plus the piezo buzzer, 3D-printed piezo mount and switched battery box (base/stand not included). See the May 2023 issue for details: siliconchip.au/Article/15785 30 Silicon Chip Australia's electronics magazine siliconchip.com.au November Tech Build It Yourself Electronics Centres® DEALS SAVE $54 225 $ Latest releases & discount deals across the range. Only until November 30th. FIRE THE WEATHER MAN! 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Computer Do you need an easy way to connect HDMI sources to a second TV in the house? It’s hard to believe, but these cable adapters have an in-built wireless HDMI sender capable of sending 1080p signals over distances up to 50m. Previously these sorts of senders would cost up to $600! Available in two types, standard HDMI or USB type C for sending your laptop, tablet or phone screen to your TV. Excellent latency performance also makes it perfect for sending your game console signal to a second room or your PC to your couch. All you need is USB power at each end - typically found on the back your TV, or via a USB wall charger. Cantilever Arm TV Bracket Silky smooth cantilever adjustment, stays just where you want it to. It even has 15° of tilt adjustment. Engineered for flat screens up to 90” using 800 x 400mm VESA. Max weight, 60kg. 39.95 $ NEW! TV / Monitor Wireless Transmission up to 50m. A 1117 119 D 0295 $ Mini USB External Sound Card Add Bluetooth® to your existing speakers! 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Includes control unit and intelligent sensors (2) that allow building of line tracking, obstacle avoiding and following robot designs. Includes 4 wheels for mobile projects. Blocks are compatible with other major brands. Fully programmable using Scratch. Includes storage box. This 300pc set contains the parts for 72 different project designs which can be built using Makerzoids 3D app tutorials. It includes an intelligent motor controller which can be programmed with Scratch, plus distance and light sensors. Includes 4 wheels for mobile projects. Blocks are compatible with other major brands. Includes storage box. Suitable for ages 6 and up. Compatible with big brand name building blocks. X 3062 NEW! NEW! 45 19.95 $ $ X 3061 NEW! 49 $ RC Drifting Motorcycle Ride like a MotoGP pro with this USB rechargeable bike, only requires 2xAA batteries for the controller (not included). Blasts around smooth surfaces for hours of fun. Ages 3+. Mini Rock Climbing/Dune Buggy RC driving fun for kids and big kids alike! 1:48 scale vehicle, with Requires 4xAA batteries (not included). Simple 4 way controls for the younger kids to try - ages 3+. Hover balls are back! We dare you to find more fun for under $20 this Xmas BARGAIN STOCKING STUFFER! Hugely popular when we first sold these in 2019, they scoot across hard floors for your very own family world cup! Requires 4xAA batteries. Ages 4+ Build It Yourself Electronics Centres® Sale Ends November 30th 2023 Find a local reseller at: altronics.com.au/storelocations/dealers/ X 3063 Learn to fly with the RC mini glider! Flying fun for indoors or out, this lightweight bi-plane is great for all ages 7 and up. The plane is USB rechargeable and features LED lights underneath. 2.4GHz remote requires 3xAA batteries (not included). 19.95 $ or 2 for $30 X 3090 Mail Orders: mailorder<at>altronics.com.au Victoria Western Australia » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 » Auburn: 15 Short St 02 8748 5388 » 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 08 9428 2188 08 9428 2166 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 New South Wales Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 » Prospect: 316 Main Nth Rd 08 8164 3466 South Australia © Altronics 2023. 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 0011 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. PRODUCT SHOWCASE Nordic Semiconductor expands nRF70 series with the nRF7001 The nRF7001 IC from Nordic Semiconductor offers a low-cost WiFi 6 solution for low power WiFi IoT products requiring 2.4GHz single-band connectivity only. It also complements the 2.4/5GHz capable nRF7002. The nRF7001 is useful for designs requiring single band capability for smart home, smart city, industrial automation and other low-power WiFi IoT applications. The nRF70 series WiFi 6 companion ICs provide low-power, robust, and secure WiFi connectivity as well as WiFi assisted locationing based on Service Set identifier (SSID) scanning. The nRF7001 companion IC can be used together with Nordic’s nRF52 and nRF53 series multi-protocol SoCs and the nRF9160 cellular IoT (LTE-M/ NB-IoT) SiP (system-in-package). It can also be used in conjunction with non-Nordic host devices. The nRF7001 companion IC supports Station (STA), software emulated Access Point (SoftAP), and WiFi Direct operation, and is compatible with the IEEE 802.11b, a, g, n (“WiFi 4”), and ax (“WiFi 6”) standards. It also offers ideal coexistence with Bluetooth Low Energy, Thread, and Zigbee. The nRF7001 supports Target Wake Time (TWT), a key WiFi 6 power saving feature. Interfacing with the nRF52840 or another host processor is done via SPI or Quad SPI (QSPI). The nRF7001 offers a single spatial stream, 20MHz channel bandwidth, 64QAM (MCS7), OFDMA, up to 86Mbps PHY throughput and BSS coloring. The nRF7001 IC, nRF7002 DK, and the nRF Connect SDK make it simple to add 2.4GHz WiFi capabilities to their products, allowing them to easily connect to nRF Cloud services and communicate with other devices over a WiFi network. The nRF7001 companion IC and the nRF7002 DK are available now from Nordic’s distribution partners. Nordic Semiconductor www.nordicsemi.com Creality 3D printer available from Altronics Microchip’s PIC18-Q71 The Creality CR-10 V2 Desktop 3D Printer is now available to purchase from Altronics. It features a large 300 × 300 × 400mm build area. The dual port hot end cooling fans allow filaments to cool down quickly. The filament breakage sensor can save your filaments when a strike occurs. The CR-10 V2 Desktop 3D Printer sports a triangular metal structure that ensures a solid, dimensionally stable work platform. The 350W MEAN WELL power supply is paired with a thermally efficient bed heater allowing for rapid heating up to 100°C. These new microcontrollers from Microchip are intended for high-­ bandwidth, mixed signal and sensor applications. They come in 28-, 40- and 48-pin devices and are equipped with: • Two integrated op amps • 12-bit differential ADC with computation and context switching • 8/10-bit DACs, high-speed analog comparator • Analog peripheral manager • 8-bit signalling routing port to interconnect digital peripherals • Three 16-bit dual PWMs outputs • Four direct memory access channels • Eight configurable logic cells (CLCs) and two UARTS To start your project, PIC18F56Q71 Curiosity Nano Evaluation Kits are available: www.microchip.com/en-us/ development-tool/EV01G21A It also has a print resume function in case a job is interrupted. From prototyping to making your own toys, a 3D printer adds incredible versatility to your workbench. It is currently available for $999 (including GST) from Altronics, Cat K8606. Altronics 174 Roe Street, Northbridge WA 6003 Phone: 1300 797 007 www.altronics.com.au/ Microchip Technology Australia Suite 32, 41 Rawson Street, Epping NSW 2121 Phone: (02) 9868 6733 www.microchip.com siliconchip.com.au Australia's electronics magazine November 2023  35 Project by Tim Blythman This handy little tool uses an inexpensive Raspberry Pi Pico microcontroller board and not much else to generate and analyse audio signals. It has oscilloscope and spectrum modes and can run a sweep to plot a frequency response or perform harmonic analysis to check signal quality. It fits in the palm of your hand, is portable and battery powered. PICO Audio Analyser T he Pico Audio Analyser is a compact handheld device that’s powered by an internal rechargeable battery. It can generate and analyse basic audio signals and is suitable for various tasks such as checking amplifiers, wiring, filters etc. It’s a handy tool for working in the field, and for troubleshooting and tinkering with audio circuits. You can even hook it up to a breadboard to test simple circuits like RC filters. This project was inspired by a Circuit Notebook submission, which used a dsPIC microcontroller with an LCD to create a spectrum analyser (August 2023; siliconchip.au/Article/15908). The concept is also similar to our Low Frequency Distortion Analyser (April 2015; siliconchip.au/Article/8441). We took those ideas and expanded them to include more features. One potentially interesting use is to monitor the distortion of the mains waveform, which theoretically is a sinewave, but often looks little like one! To do that, you’d connect the output of just about any AC plugpack to its input and put it in distortion analysis mode. Like the earlier designs mentioned Features & Specifications > Audio signal generator (up to 3V peak-to-peak/1.06V RMS) with selectable frequency > Sine, square, triangle, sawtooth and white noise waveforms > Audio signal input with switchable 3.6V and 34V peak-to-peak ranges (1.27/12V > > > > > > > > > > > 36 RMS) Oscilloscope and spectrum displays Harmonic analysis with THD measured down to 0.3% (1.2V RMS, 1.2kHz) Can measure and monitor mains distortion with a suitable plugpack Sweep analysis with frequency response display RCA sockets for input and output Runs from USB power or an internal rechargeable battery Uses 128×64 OLED display and pushbutton controls Compact and portable Controllable from a virtual USB serial port Typical current draw around 50mA Operates for around 12 hours with a fully charged 600mAh battery Silicon Chip Australia's electronics magazine above, the Pico Analyser uses a Fourier transform to examine the frequency components of a signal. That allows us to create a spectrum display and perform a sweep analysis. The April 2015 article explains in detail the use of Fourier transforms and how they are used to measure distortion. Design When planning this design, we had in mind that it should be inexpensive and compact. The circuitry fits in the smallest Jiffy box (UB5), measuring just 83 × 54mm. The front panel is also the back of the main PCB, recessed into the top of the box, meaning that the height is just 28mm and even less than it would be with the box’s included lid. The display is a 1.3-inch (33mm) diagonal OLED, about the smallest type of display capable of showing graphics. It can also display multiple lines of text. We used this sort of screen in the Advanced SMD Test Tweezers (February & March 2023; siliconchip. au/Series/396). No expensive ADC (analog-to-­ digital converter) or DAC (digital-to-­ analog converter) chips are used in this design. Instead, a Pico microcontroller board uses its onboard 12-bit ADC (see panel later) to sample the input and a filtered PWM (pulse width modulation) peripheral to drive the output. The Pico also has an onboard 3.3V switchmode regulator that can operate in PFM (pulse frequency modulation) siliconchip.com.au Fig.1: the Analyser is implemented mainly in software running on the Pico. By only making connections along one side of MOD1, we can mount the Pico on its edge, saving PCB space. and PWM modes. We use the PWM mode, as the PFM mode can introduce low-frequency artefacts under the light load levels that this circuit draws. A clean 3.3V rail is important for this application, as it is used to set the output level and as the reference for the ADC. While a switchmode regulator is not the best choice for high-­ quality audio, using the Pico’s onboard regulator also removes the need to provide separate circuitry and saves us further on hardware costs. Circuit details Fig.1 shows the circuit diagram of the Pico Analyser. MOD1 is the Raspberry Pi Pico microcontroller module. The input stage of the Pico Analyser receives a signal via the RCA socket at CON1. A 4.7kW resistor combined with a 1nF capacitor gives a low-pass filter with a -3dB point of around 34kHz. This reduces any high-frequency components that the ADC might alias. The 100kW resistor keeps this signal biased to ground whenever nothing siliconchip.com.au is connected. A 10μF capacitor AC-­ couples the signal so that the Pico’s analog input pin (AIN, pin 31) can be DC-biased to 1.65V (half of the 3.3V supply) by another 100kW resistor. The incoming network attenuates the audio slightly, to around 91% of its original level. That means that voltages up to 3.6V (peak-to-peak) can be measured before clipping occurs, corresponding to around 1.2V RMS. Switch S6 can connect a 510W resistor in parallel to the first 100kW resistor, changing the divider formed with the 4.7kW resistor. This allows levels up to 34V peak-to-peak (or 12V RMS) to be measured without clipping. This resistor does change the filter characteristics and may let in more higher-­ frequency components than the ×1 range. The output signal from the Pico (DOUT, pin 21) is a PWM signal at around 250kHz, so it first passes through two RC filter stages, each consisting of a 2.2kW resistor and 1nF capacitor. A 100kW resistor also biases Australia's electronics magazine this to the 1.65V rail so that a known level is present if the pin is not being driven. The two RC stages give a similar -3dB point to the input stage, attenuating the 250kHz PWM artefacts by 24dB in total, compared to the 12dB for a single stage. The result is not hifi, but good enough for our purposes. This signal is buffered by IC1b, then AC coupled and biased to ground by another 10μF/100kW pair before being made available at CON2. The filtering and biasing mean that around 3.1V peak-to-peak is available from a 3.3V rail, or about 1.1V RMS, although this is limited by the op amp’s drive near its rails and will depend on the output load. Buttons S1-S4 are connected to other available digital input pins. These are used to provide controls for the user interface. Internal pullup currents supplied by the Pico hold the corresponding pins high unless the switches are closed, pulling the attached pins to ground. November 2023  37 Power supply Important to the circuit’s operation is a schottky diode internal to MOD1, from its VBUS pin (40) to its VSYS pin (39). The Pico’s switchmode regulator is fed from VSYS and its output is available at the 3V3 pin. You’ll note that only one side of the Pico has connections. By mounting it on its edge against the PCB, we save much PCB space and it fits more easily in the box. The circuit can be powered from a USB supply via the Pico’s onboard USB connector, leaving around 4.7V available at the VSYS pin. Alternatively, power from a rechargeable lithium battery is provided via D1 when switch S5 is closed, giving around 3.4-3.9V at VSYS. The regulator on the Pico can handle between 1.8V and 5.5V, so these are all comfortably within its operating range. When USB power is available, the battery is charged by IC2. The two 10μF capacitors provide the input and output bypassing it requires, while a 10kW resistor between its pin 5 (PROG) and ground sets the charge current to 100mA. The STAT pin (pin 1) is low during charging and goes high when charging is complete, so the bi-colour LED will show the charging state: red during charging or green when charged; separate 1kW resistors limit the LED currents. MOD2 is a 1.3-inch (33mm) OLED display module. Its VCC pin is fed with whatever voltage is available at the Pico’s VSYS pin, and its onboard regulator provides 3.3V for its operation, as well as internal pullups for the I2C control lines, SDA and SCL. The I2C lines are taken back to the appropriate pins on the Pico so the Pico can update the display. IC1 is a low-voltage dual op amp, and it too is fed from the VSYS rail with a 10μF supply bypass capacitor. Since VSYS is slightly higher than 3.3V, this provides a bit more headroom than the 3V3 rail would allow. The 3V3 rail is divided by a pair of 10kW resistors and bypassed by the 10μF capacitor to give the 1.65V mid-rail reference. This is buffered by unity-­gain op amp IC1a. The Pico has four ADC channels, with one internally connected to VSYS via a divider, so two are left after we’ve fed in our audio signal. We’ve connected one of these to the 1.65V rail 38 Silicon Chip so the Pico can check that it is correct. The remaining ADC channel is connected to a divider comprising two 22kW resistors across the battery downstream of the switch. This allows it to read the battery voltage when S5 is closed, ensuring the battery is not drained when the unit is switched off. Software We used the Arduino IDE to create the software, mainly because so many libraries are available. We use OLED libraries from Adafruit that make generating the graphics needed for the spectrum, oscilloscope and frequency response modes easy. The audio generation software is a fairly straightforward PWM implementation, where the PWM duty cycle is updated between samples to provide a varying waveform. It is based on the software we wrote for the Pico BackPack, which has a stereo audio output (siliconchip.au/Article/15236). While we’re using 8-bit PWM, the data is calculated and stored as 16-bit samples, with the PWM data derived from the upper eight bits. Then the remainder due to the lower eight bits is dithered over several PWM cycles per sample period, slightly improving the effective resolution. A block of samples equivalent to about 200ms is generated to provide this data. For all but the lowest frequencies, this means that the frequency does not need to divide evenly into the sampling rate since the sample block contains multiple cycles. We use the second processor core to calculate and update the dithered samples. That is about all the second processor does, so not much can interrupt audio generation once it is running. A similar technique is applied to the analog input sampling. The 12-bit The right-hand end of the case has two holes for the RCA sockets and a notch for S6. ADC runs at 490kHz, very close to its maximum speed of 500kHz. The DMA peripheral captures a block of samples over about 1/10th of a second without interrupting either processor. This means we can detect frequencies down to around 10Hz. The performance of the ADC is a little disappointing; it turns out that the RP2040 chip on the Pico has some problems with the ADC peripheral (see the panel for details). Our software applies adjustments to the ADC readings to compensate for this somewhat. It helps, but the ADC still only has about nine effective bits. The oscilloscope mode uses the raw samples for its display, which provides adequate resolution for the 50-pixel vertical axis. The other modes apply downsampling before running a Fourier transform to extract the frequency elements of the sampled waveform. Much of the software is involved in drawing the various displays and user interfaces. Construction First, use the blank PCB to mark the box, then perform the cuts shown in Fig.2. One end of the box has a notch Fig.2: many of these cuts can be made without measuring. The notches for the switches at the top of the box can be marked using the PCB as a template, while the holes for the RCA sockets do not need to be precisely located, as the sockets are wired with flying leads. Australia's electronics magazine siliconchip.com.au Fig.3: the rear of the PCB also forms the device’s front panel, so all components are surface-mounting. It’s a bit cramped with the OLED and Pico adjacent. We recommend fitting the Pico first and ensuring it is aligned with the hole for its USB socket, then fit the OLED and check its operation before continuing. Note that the OLED is mounted face-down on the rear side. for S5 and the Pico’s USB socket, while the other has a notch for S6, plus two holes for the RCA sockets. The notches can be marked using the edge of the PCB, which might be easier than using a ruler to find the midpoint. Make a pair of vertical cuts on each side, not quite to the desired depth, with a sharp hobby knife or hacksaw. Score along the bottom of the notches with a sharp knife, then carefully flex the tab, which should break off along the scored line. Tidy the corners and edges to the correct depth with a small file or sharp knife if necessary. Mark out the slot for the USB socket and start by drilling two or three holes inside the lines. Then use a small file or sharp-pointed hobby knife to square up the edges of the slot. We can use this slot later to align the Pico correctly, or alternatively, we can make the Pico fit it more easily than we can adjust the hole! The RCA sockets mount in drilled holes that can be made with a twist or step drill. Their exact positions are not critical, as the sockets are connected by flying leads. The measurements shown match our prototype and work well. The front-facing side of the PCB. siliconchip.com.au Starting with a smaller 3mm pilot hole will make it easier to align the holes and adjust them if they are not aligned. We’ve specified 7mm holes to suit the RCA sockets we’ve used, but check if a different size is required for your parts. PCB assembly Many of the components are fairly large standard SMDs. There are a few parts that are mounted in a slightly unorthodox fashion. We recommend starting by fitting the SMDs; you will need a fine-tipped iron and solder, flux paste, tweezers and good illumination. Some solder-wicking braid will be handy, as will some solvent to clean up any excess flux. Use fume removal (such as a fume removal hood) to ensure you are not exposed to smoke from the flux. If that is not possible, work outside in fresh air. Refer to the Fig.3 overlay diagram for the component placements and orientations. You should also consult the photo showing the PCB fitted with surface-mounting parts. The components are pretty close together, and IC2 is the smallest part, so start with it. Put some flux paste on the pads and align the five pins with them; they will only fit one way. Tack one lead on the side with two pins and check that all the other pins are within their pads, adjusting as necessary. Solder the remaining pins and then go back to refresh the first pin. Check for bridges and use solder wick and fresh flux to draw excess solder away, if necessary. Use a similar technique for IC1. Its pins are more widely spaced, so soldering should be easier. Make sure pin 1 of IC1 (which might be marked with a bevel along one edge) is aligned to the dot on the PCB silkscreen. The capacitors are spread around the PCB. Be sure not to mix up the two values, although the 10μF parts will probably be thicker than the 1nF parts. The different resistor values all need to go in the correct locations too. For these passives, use the same basic soldering technique. Solder one lead, then check and adjust before soldering the other lead. The single diode is a bit larger, and you must ensure its polarity is correct, with its cathode stripe towards the “K” on the PCB. If this is reversed, you risk connecting the battery directly to the USB supply, which will probably cause something to burn out. Now is a good time to clean the PCB with a flux solvent. Doing so now avoids the possibility of solvents getting into the switch mechanisms. Isopropyl alcohol is a good all-round choice. Allow the PCB to dry thoroughly before continuing. Fit slide switches S5 and S6 next. They have small leads but are easy to align as they have locating pins in their November 2023  39 Use this photo as a guide to fitting the smaller components. This stage of assembly is a good point to clean off any excess flux in preparation for adding the final components like the switches, LED, Pico and OLED. undersides that lock into holes in the PCB. Tack one lead, confirm that they are flat and then solder the other leads. Next, fit the four reverse tactile switches, S1-S4. We found it helpful to splay the leads out from the bodies so that the switch stems protrude further through the PCB holes. This makes them easier to operate. After soldering one pin, it’s also a good idea to check that the switch stems are centred in their holes through the PCB. That will ensure the front panel looks good and eliminate the possibility of the stems jamming on the PCB. Once you’re happy with them, solder the other three pins on each switch. Be sure to use a generous amount of solder to ensure that they have good mechanical strength. The tricky bits The LED is mounted unusually. While bi-colour SMD LEDs are available, they often have independent leads for the two LEDs, making the pads small and tricky to solder, so we’re using a 3mm through-hole LED as a reversed surface-mounting device. The pad marked K corresponds to the cathode of the red LED inside such a device. If you’re unsure and don’t have the means to test it, just fit the LED one way; if it is incorrect, swap the leads. Carefully bend the leads by 180° and trim them so they are slightly longer than the LED lens. As you can see from our photo overleaf, the tip of the LED is pointed at the opening in the solder mask (facing towards the PCB). Solder the LED leads to the two pads. Fine-tipped tweezers will help to position the component until one lead is soldered. Solder the other lead, then refresh the first joint. The next part is the Pico module. Before proceeding, check that the PCB (with S5 and S6 mounted) sits flush and slots neatly into the box’s notches. The top of the PCB should sit level with the surrounding box. This is to ensure that the USB connector on the Pico can align correctly with the slot in the box. Adjust the notches in the box if necessary. Working with just one end pad on the Pico, tack it roughly into place at right angles to the main PCB. The Pico’s PCB should sit back slightly from the edge of the main PCB, with the USB connector protruding slightly. Note its relative orientation, with the VBUS pin closest to the edge of the PCB and GP16 at the other end. The USB socket should be above the corresponding marking on the silkscreen too. Tack one pad at the other end and carefully adjust the Pico to be at right angles to the main PCB. Test it in the box and see that it is aligned with the slot. Remember that the top of the PCB will sit flush with the top of the box. Once you are happy with the location of the Pico, solder the remaining pins. We found it easiest to feed in the solder from the bottom of the Pico (on the side facing the switches) and apply the iron to the other side, ie, the Pico’s top. Ensure there is a generous fillet on each of the 20 pins to hold the module securely. Now cut the LED lead offcuts (or other fine wire) into four pieces, each about 1cm long. It will help if they are all slightly different lengths to stagger their insertion into MOD2’s pads. Using the tweezers to hold each one, solder them to the centre of the pads for MOD2. They should sit vertically. The Analyser is fully wired up, with its lid open. Note how the LED, OLED and Pico modules have been mounted. Extending the wires from the battery holder allows the lid to be folded open as shown; a generous amount of neutral-cure silicone helps to secure and insulate the battery leads. 40 Silicon Chip Australia's electronics magazine siliconchip.com.au Remove the protective film from the front of the OLED and place it facedown over these wires and flat against the main PCB. You will see that the backwards markings on the PCB now correspond to the OLED pins. Finally, solder each wire to the OLED. Be gentle, as there is little more than surface tension holding the pin in place to the main PCB. You might need to adjust the wire with tweezers. Verify that the OLED is accurately aligned with the silkscreen markings. If it is not, the misalignment will be evident in use. Now is a good time to run some quick tests to ensure that the OLED and Pico are correctly soldered, but the Pico will need to be programmed if it is not already. Programming the Pico Hold the white BOOTSEL button while connecting the Pico to a computer via a USB cable. You might not need to hold the button if you have a new, unprogrammed Pico. Picos supplied in kits are generally not programmed as it’s easy for constructors to do. Then copy the 0410723A.UF2 file to the RPI-RP2 drive that should appear on your computer’s file system. If everything is working, you should see the OLED screen light up after a second. If not, go back and check the solder joints and component placement. Verify that the display contents are square within the PCB cutout. If they are not, you might be able to gently twist the OLED by a small amount. Completion With the OLED aligned, use the remnants of the lead offcuts to secure its two lower holes to the matching pads on the PCB. The connection should work much the same as for the four smaller pads on the top of the OLED module. Prepare the RCA sockets by disassembling them. Cut two pieces of white wire about 4cm long and two pieces of black wire about 4cm long. The colours are not critical, but using two contrasting colours will help identify them. Solder one end of each of the white pieces of wire to the centre connection of an RCA socket. Similarly, solder one end of each black wire to the washer, which becomes the ground connection. siliconchip.com.au Parts List – Pico Audio Analyser 1 double-sided PCB coded 04107231, 83 × 50mm, with black solder mask 1 UB5 Jiffy box (83 × 53 × 30mm) 2 chassis-mount RCA sockets (CON1, CON2) [Altronics P0161] 1 single AA cell holder with flying leads 1 14500 (AA-sized) Li-ion rechargeable cell with nipple 1 Raspberry Pi Pico micro board, programmed with 0410723A.UF2 (MOD1) 1 1.3-inch (33mm) OLED module (MOD2) [Silicon Chip SC5026] 4 reverse-mount SMD tactile switches (S1-S4) [Adafruit 5410] 2 SPDT SMD slide switches (S5-S6) 4 M3 washers, 1.5mm thick 2 20cm lengths of hookup wire (eg, white and black) 1 4cm length of fine bare wire (eg, lead offcuts from LED1) 1 small tube of neutral-cure silicone sealant 1 short RCA-RCA cable (for testing & calibration) Semiconductors 1 MCP6002 or MCP6L2 rail-to-rail dual op amp, SOIC-8 (IC1) 1 MCP73831-2ACI/OT Li-ion charge regulator, SOT-23-5 (IC2) 1 bi-colour red/green 3mm LED (LED1) 1 SS34 40V 3A schottky diode, DO-214 (D1) Capacitors (all M3216/1206 size, X7R ceramic) 6 10μF 16V+ 3 1nF 50V Resistors (all M3216/1206 size, 1% 1/8W) 4 100kW 2 2.2kW Pico Audio Analyser Kit 2 22kW 2 1kW 3 10kW 1 510W SC6772 ($50): includes the PCB and 3 4.7kW everything that mounts directly on it. The Pico is supplied blank and Assemble the sockets into the will need to be programmed using a holes in the enclosure by securing computer and USB cable. the washer with the nut. Adjust them such that the wires poke out the top We do not want these to come loose, of the box, then bend them over the as there is a good chance that their end of the box. bare ends would cause the battery to Next, place the PCB upside down be short-circuited. next to the enclosure and solder the While waiting for the silicone to wires, as shown in the photos opposite cure, you might like to also add some and overleaf. The two black wires go more to CON1 and CON2 on the PCB to to the GND pads on CON1 and CON2, secure the audio connections, as well while the white wires go to the corre- as any exposed metal on the outside of sponding pads marked IN and OUT. the battery holder itself (for example, Use a generous amount of solder to ensure a firm connection. Using neutral-cure silicone or similar gap-filling glue, secure the battery holder to the bottom back corner of the box, with the opening facing outwards. Solder the wires to the BAT+ and BAT- pads on the PCB, being sure to connect the red wire to BAT+ and the black wire to BAT-. If you do not have an RCA-RCA On our prototype, we slightly cable, a simple loopback cable extended one of the battery leads to like this can be made by soldering allow the PCB to fold fully open away a short wire between the centre from the box. That simplified testing pins of two RCA plugs. Such a and assembly. cable is necessary for testing and Like the RCA sockets, use a generous calibrating the Analyser. We also solder fillet to secure the battery leads. found it handy to have a pair Apply silicone around the BAT+ and of RCA plugs fitted with jumper BAT- pads to further secure the batwires to allow connecting to a breadboard for experimentation. tery leads and insulate any bare wire. Australia's electronics magazine November 2023  41 Another close-up of the finished Pico Audio Analyser. Note that the LED is mounted upside-down, as shown in the insert. the previous step. Press OK to proceed to the next screen. Screen 5 sets the INPUT LEVEL on the ×10 range, so leave the cable connected and change S6 to the ×10 range. You will see a prompt similar to the previous step; press DOWN when it appears. Screen 6 is used to save those parameters to flash memory; press DOWN to do so, and you should see a message reporting that this has occurred. If the settings have somehow become corrupted, you can use the UP button here to restore the defaults. Operation around the battery’s contacts with the holder). After the silicone has cured fully, fit the battery, making sure to check its polarity. Switch the unit on with S5 and confirm that the OLED illuminates after about a second. If it does not, remove the battery and check for any problems. Apply power to the USB socket and see that the LED lights up red initially and then goes green when the battery finishes charging. If the LED starts green, it might be reversed. It’s a good idea to remove the battery before making any changes to the circuit. Four washers sit between the PCB and the box’s pillars to keep the PCB flush with the top of the box, so thread these over the screws as you screw them into the box. Take care that you don’t pinch any of the wires. Calibration After some calibration steps, the Analyser will be ready to use. The Analyser will function without calibration, but its accuracy will not be as good. You’ll need a multimeter or oscilloscope that can accurately measure a 500mV AC RMS signal and an RCA plug to RCA plug cable to make a loopback connection between the input and output. We used a pair of RCA plugs with a short piece of wire connecting their centre terminals (the ground connection is made via the PCB in this case). 42 Silicon Chip Power up the Analyser using a USB cable to give the battery a chance to charge. The splash screen shows for a few seconds as the bias voltages stabilise. Press the MODE button until the SETTINGS screen appears (Screen 1), then press OK. Screen 2 shows the first calibration item, the INPUT OFFSET. Ensure nothing is connected to the input and wait until the value seen on the fourth line settles to a steady value and press the DOWN button, then OK. Screen 3 is the OUTPUT LEVEL calibration. The Analyser will deliver a nominal 500mV RMS sinewave, which should be measured at the CON2 output. Use the UP and DOWN buttons to adjust the calibration ratio until your meter reads 500mV, then press OK. Screen 4 sets the INPUT LEVEL for the ×1 range. Connect the CON2 output to the CON1 input and set switch S6 to the ×1 position. Since the Analyser knows it should be receiving a 500mV signal, it can calculate the calibration ratio easily. When you see the “DOWN to set” message, press the DOWN button to load the calculated ratio. This allows us to check that a valid signal is used for the calculations. If you don’t see this message and are sure that S6 is set correctly, there could be a minor problem with the PCB, such as a resistor being the wrong value. This step also depends on the 500mV reference being set correctly in Australia's electronics magazine The remaining screens show the operating modes. The MODE button cycles between the modes, while the UP, DOWN and OK buttons provide controls within each mode. Generally, a pair of angle brackets <> highlights the value being changed. When switching between ×1 and ×10, the input mode must also be manually changed on the SETTINGS page to match. Pressing DOWN selects the ×1 mode (and uses the ×1 calibration factor), while pressing UP selects the ×10 mode. The last line of this page shows the current scaling. The top right corner of the SETTINGS page shows the battery voltage when the power switch (S5) is turned on. Take care that the Analyser is not left switched on when not in use, as there is nothing to prevent the battery from being overdischarged. The first mode (seen in Screen 7) controls the WAVE OUTPUT. This will continue to run at its last setting unless another mode needs to take control of the output. This can occur when a SWEEP is run, or the SETTINGS needs to produce its calibration waveform. The OK button cycles between the various parameters, while the UP and DOWN buttons change them. The set frequency can vary between 10Hz and 10kHz; the frequency steps are smaller for lower frequencies. Since the Pico has a crystal oscillator, we have provided no frequency calibration adjustment. The frequency accuracy of the crystal is around 30ppm (0.003%), which is good enough. The output level can be set in steps of 50mV as either peak-topeak or RMS, and the corresponding equivalent values are displayed siliconchip.com.au depending on what is selected. The ratio between the peak-to-peak and RMS values changes depending on the waveform. Values up to about 2V peak-to-peak should give clean outputs before op amp drive limits come into play, depending on the output load. The chosen op amp is quite robust and can handle an output short circuit indefinitely. The next option cycles between sine, square, triangle, sawtooth and white noise waveforms, while the last option allows the signal to be turned off or on without changing any other settings. Internally, the Analyser generates a 0V amplitude waveform when the output is off. The SPECTRUM mode displays the spectrum of the input waveform (Screen 8). The UP and DOWN buttons change the horizontal scale, while the OK button switches the vertical scale between the PEAK and TOTAL (RMS) amplitude. As the Fourier Transform includes a windowing step, even a pure sinewave will typically be spread across multiple frequency bins. The Low Frequency Distortion Analyser article from April 2015 has more information about windowing (siliconchip. au/Article/8441). The calculated peak frequency is interpolated between the bins and may also be slightly off due to rounding errors. The SCOPE mode (Screen 9) simply shows the shape of the waveform as you would see on an oscilloscope. The UP and DOWN buttons change the horizontal (time) scaling, while the OK button toggles between dots and lines for the plot. You might find the line mode clearer when many cycles are displayed. The vertical scaling is automatic and based on the amplitude, shown as a peak-to-peak value on the left. The SCOPE attempts to trigger on a positive-­ going zero crossing and, if not, will simply display the last part of the sample it has taken. Screen 1: when the Analyser is first powered up, use the MODE button to cycle through to the SETTINGS page to perform the calibrations. Press OK to start the process. Screen 6: press OK again to see this screen and then DOWN to save the calibration values to flash memory. You will see a message confirming that it was done. Screen 2: to set the INPUT OFFSET, leave the input open and allow the displayed level to settle to a steady value. Then press the DOWN button to store this value, followed by OK. Screen 7: pressing OK on the WAVE OUTPUT screen cycles between the parameters, while UP and DOWN modifies them. The USB serial port can also control the output waveform. Screen 3: use an AC RMS meter or similar instrument to measure the output and adjust (using UP and DOWN) until the meter reads 500mV, then press OK. Screen 8: the SPECTRUM display uses UP and DOWN to change the horizontal scaling, while OK toggles the vertical scale between peak and total energy. Screen 4: connect the input to the output with an appropriate RCA cable for the next steps. Ensure the range switch S6 is set to 1x and press DOWN when prompted, then OK. Screen 9: the SCOPE display also uses UP and DOWN to change the horizontal scaling. The OK button changes between dot and line displays. Screen 5: follow the prompts and set the switch to 10x. You will see a message if S6 is set to the wrong position or a signal is not detected. Press DOWN to set the scaling factor, followed by OK. Screen 10: HARMONIC ANALYSIS provides information about the harmonic content of a waveform. Connecting the input to the output is a good way to check this feature. Harmonic analysis HARMONIC ANALYSIS (Screen 10) provides information about the detected fundamental frequency, an analysis of the harmonics and the measured THD (total harmonic distortion). The UP, DOWN and OK buttons do nothing in this mode. siliconchip.com.au Australia's electronics magazine November 2023  43 Flaws in the RP2040 ADC Our initial design for the Pico Analyser had some optimistic targets. As the RP2040 microcontroller claims to have a 12-bit ADC (analog-to-digital converter), we hoped to get something near the equivalent of 14 bits of resolution with oversampling. However, connecting the output of our Audio Precision System One (with a THD+N figure of around 0.0004%) to the Analyser only gave a reading of around 0.3%, closer to eight effective bits of resolution. Some digging into the RP2040 data sheet revealed an erratum relating to the ADC peripheral that stated the claimed ENOB (effective number of bits) was, in fact, closer to eight. The ADC is a successive approximation register (SAR) type, which uses tiny capacitors arranged with binary weighting within the chip to measure voltages. The total capacitance is around 1pF, meaning the smaller capacitors are on the order of femtofarads (fF or 10-15F)! 44 Silicon Chip Some people have determined, after thorough testing, that the value of some of these capacitors is off by around 0.8%, starting at the third most significant bit (MSB); see https://pico-adc.markomo.me/INL-DNL/ The folks at the Raspberry Pi Foundation have indicated that this is due to a discrepancy between their design simulations of these sampling capacitors and the actual silicon. To test the effect on our own hardware, we temporarily modified the program to count the number of times each different ADC value (4096 possibilities) appeared within a sample set. We then used the Analyser’s wave source to generate a triangle waveform. A triangle wave should spend an equal time at each level (within the waveform’s amplitude) since the slope (amplitude/time) is constant for each half cycle. Fig.4 shows the result of this analysis. Note the zero counts at each end, showing values outside the wave amplitude. There are also slight peaks near the tips of the waveform as the slope changes direction and the Fig.4 waveform is rounded off slightly. The four prominent peaks in an otherwise fairly flat plot show that the ADC ‘thinks’ the waveform is spending longer at these values than it should. The ‘troublesome’ ADC values are 511, 1535, 2559 and 3583, all pointing to problems with the third MSB. This means that the ADC can’t accurately measure voltage around these points. While the input changes by around 10 steps, the ADC output value doesn’t change. The reading is off at times by as many as five steps, and is not responding linearly. The INL (integral non-linearity) plot from the RP2040 data sheet (Fig.5) shows this in another way. This plot shows the deviation in the perforFig.5 mance of the actual ADC from that of an ideal ADC. In practice, the line should be quite flat. The final Analyser software includes a correction stage that attempts to compensate for the ADC non-linearity. This brings the measurable THD down to 0.3% from 0.4%. The applied correction is shown in Fig.6. This makes it act like the four ADC values noted above occupy a wider space in the span. That makes the overall plot more linear, but we still cannot get around the fact that these values occupy a wider range of voltages than the others. This plot is similar to the INL plot. We also tried to apply the INL plot as a correction, as well several Fig.6 others, including some that correct for the lesser errors in some of the other ADC bits. In practice, we chose this one as it gave the best improvement in distortion readings. The correction data is stored in an array named “ADCADJ” in the “util.h” file. To see the effects before adjustment is applied, you can comment out calls to the ADCfix() function. Currently, all RP2040 chips in circulation have this flaw. We may see future chip releases which correct the issue and render the adjustment obsolete. The lesson from all this is: always read the data sheet! Australia's electronics magazine siliconchip.com.au If you are measuring the Analyser’s output, you will see THD figures around 1% for a sinewave, with about 0.7% due to the output stage and 0.3% due to the input stage. These figures will vary depending on the frequency. The final mode is the frequency sweep and response. Screen 11 shows the setup, while Screen 12 shows the results. The lower and upper frequencies can be set in powers of 10 between 10Hz and 10kHz, and up to 30 steps can be applied. Each step takes about 1/3 of a second to process. There is also the option of running a single sweep pass or a continuously updating loop. The default of 10 steps over this range gives a typical display seen in Screen 12; this is with the output connected to the input. The horizontal frequency scale is logarithmic; the dashed grid lines correspond to the second and fifth divisions of their respective decades. The vertical scale is adjustable with the UP and DOWN buttons and the intermediate grid line corresponds to the -3dB point. As an exercise, we connected a simple low-pass RC filter circuit (using a 1kW resistor and a 1μF capacitor) between the input and output. As expected, the SWEEP showed a -3dB point around 160Hz, rolling off more at higher frequencies. While a direct connection from output to input should give a perfectly flat response, there are slight dips at 10Hz and 10kHz as the low-pass and high-pass filters start to take effect. The small peak around 20Hz is a side-effect of the windowing function. Pressing OK from the graph page will end the looping behaviour, or if <OK> is shown, return to the setup menu. Screen 11: SWEEP uses the UP, DOWN and OK buttons like the OUTPUT mode. There is the option of running a single sweep pass or performing a continuous loop. Screen 12: in this display, the UP and DOWN buttons change the vertical scaling; the unlabelled horizontal line being the -3dB point compared to the set level at the output. Most of the remaining commands emulate the controls of the WAVE OUTPUT mode. Since they will work while another mode is active, they can save you the time of cycling between modes to change settings and then trying to view the results. “a” or “A” followed by a number will set the output RMS amplitude in millivolts. For example, “a500” sets the output to 500mV RMS. Similarly, “p” or “P” will set the peak-to-peak amplitude in millivolts. The “f”/“F” option sets the frequency in Hertz, the “w”/”W” command sets the type of waveform, while “o”/“O” turns the wave output off or on. Note that setting parameters too high might result in corrupted waveforms. Another command, “d”/“D”, provides a ‘data dump’ of the next scan in the SCOPE, SPECTRUM, HARMONIC ANALYSIS or SWEEP modes. The data is formatted similarly to a CSV (comma-­separated variable) file, so you can paste the data directly into spreadsheet programs that support CSV data. For a SWEEP, the dump will occur after the next pass has completed; Screen 13 shows the same data as in Screen 12 as a spreadsheet. Finally, the “~” command resets the Pico. Holding the BOOTSEL button while issuing this command will enter bootloader mode for reprogramming the Pico. siliconchip.com.au The Pico Analyser is a simple and compact device that uses little in the way of hardware apart from the Pico itself. Its performance is modest, but we think its simplicity and cost make SC it a handy tool. Screen 13: the “d” command at the serial terminal triggers a dump of data in CSV format. We pasted the data shown here, from the SWEEP mode, into a spreadsheet program. Computer control Since we have a USB port on the Pico, we use it to provide alternative controls and data outputs. We recommend using a terminal program such as TeraTerm (on Windows) or minicom (on Linux), as the Arduino serial monitor is quite basic. Most commands are followed by the Enter key, but the commands that emulate the buttons on the Analyser act instantly. For a full list of commands, type “?” and press Enter. The keys listed at the bottom emulate the four onboard buttons. Conclusion Screen 14: this view of TeraTerm shows the commands provided by the virtual USB serial port. The list can be shown by using the “?” command. Australia's electronics magazine November 2023  45 Using Electronic Modules with Jim Rowe 16-bit precision 4-input ADC This month we’re looking at the tiny ADS1115 that can add up to four high-speed 16-bit analog-to-digital conversion (ADC) channels to almost any microcontroller. It has a built-in I2C serial interface, so it can be easily connected to popular microcontrollers like an Arduino Uno or Nano. L et’s say you want to make precise measurements of analog voltages or currents with one of the common microcontroller units (MCUs). The ADC in most MCUs provides a resolution of only ten bits over a range of either 3.3V or 5V, which corresponds to a precision of ±1.6mV (3.3V ÷ 1024 ÷ 2) or ±2.5mV (5V ÷ 1024 ÷ 2), where 1024 is equal to 210. That is acceptable for many applications, but not good enough if you want to make precision measurements, especially of small voltages. That’s where this module is worth considering because it allows you to add precision 16-bit ADC capability to any of the popular MCUs. As a result, you will be able to make much more precise measurements, even on quite small signals. It offers a precision improvement of 64 times compared to a 10-bit ADC or 16 times compared to a 12-bit ADC. It is not just useful for a single-ended full-scale range of 3.3V or 5V either, because the module gives you a choice of six different full-scale ranges: ±6.144V, ±4.096V, ±2.048V, ±1.024V, ±512mV or ±256mV. This means that the smallest step size on the highest range is 187.5µV, while on the lowest range, it’s 7.8125µV. Note though that the inputs must go no more than 0.3V beyond the supply rails and those measurement ranges can be between two inputs or from an input to ground. So you can’t actually measure voltages very far below ground or above the (typically 3.3V or 5V) supply range. A further feature of the module is that it has four analog inputs, which can be used to measure either four different voltages with respect to ground, or to provide two differential inputs. Another feature of the module which adds to its appeal is the ability to make measurements at eight different rates, from eight per second to 860 per second. It connects to the MCU via a standard two-wire I2C serial interface, with the ability to set the module’s I2C port to one of four addresses: 48h, 49h, 4Ah or 4Bh (h = hexadecimal). That means you can connect up to four modules to a single I2C port on an MCU, each set for a different I2C address. Even if you don’t need the improved precision, if you’ve run out of ADC channels on your micro, it might be worth considering this module for the extra analog inputs it provides. If you’re already using an I2C serial bus in your project, it won’t even take up any more pins on the micro to add as many as 16 more analog inputs. Otherwise, you can dedicate two digital pins – not a bad swap. In short, it’s a very flexible and impressive precision ADC module. All of these capabilities are due to the IC that forms the ‘heart’ of the module: an ADS1115 made by Texas Instruments. So let’s look at the innards of this impressive chip. Inside the ADS1115 Fig.1: a block diagram of the ADS1115 IC. This shows the ADS1115 can be configured as four single-ended channels or as two differential channels. 46 Silicon Chip Australia's electronics magazine Fig.1 shows the basic block diagram of the ADS1115. The 16-bit delta-­ sigma ADC is in the centre, with the chip’s built-in voltage reference just above it and the internal clock oscillator just below. To the left of the ADC (on its input side) is a programmable-­gain differential amplifier (PGA), providing the chip’s six full-scale ranges. Left of the PGA is the input multiplexer (MUX), which selects which of siliconchip.com.au the four single-ended inputs (AIN0AIN3) are connected to the input of the PGA, or which two inputs are connected as a differential input. When one of the single-ended inputs is selected, the lower input of the PGA is connected internally to ground. In contrast, when two inputs are selected for differential measurements, each is connected to one of the PGA inputs. You can see the chip’s I2C interface to the right of the ADC. This provides two-way communication between the ADS1115 and the external MCU, with programming and control data inwards, and the measurement data stream outwards. This is done using the SCL and SDA pins; the ADDR pin sets the chip’s I2C address by linking it to one of the Vdd, GND, SCL or SDA pins, as will be explained shortly. Above the I2C interface is a comparator with its output connected to the chip’s ALERT/READY (or ALRT/ RDY) pin. The comparator can be programmed to perform one of two functions: either an alert ‘flag’ whenever the ADC output reaches the top or bottom threshold of its measurement range, or as an indication that a measurement has been made and the result is ready for ‘collection’ by the MCU. The final section of the ADS1115 is below the I2C interface. This comprises four 16-bit registers: 1. The Conversion register, which holds the last conversion data. 2. The Configuration register, which holds the programming bits for the chip’s input multiplexer, the gain/ range settings for the PGA, the sampling rate setting and whether the device is to operate in single-shot or continuous conversion mode – see Fig.2. 3. Lo-thresh, the lower threshold value for the Alert Comparator. 4. Hi-thresh, the upper threshold value for the Alert Comparator. Data in the Conversion, Lo-thresh and Hi-thresh registers is stored in signed two’s complement format: from 8000h (-32768) to 7FFFh (+32767). Because this ADC has differential inputs, it can produce negative results, meaning that a signed number is needed. This also means that there are effectively 15 bits of resolution when single-ended samples are taken. siliconchip.com.au Fig.2: how the configuration register is arranged. This 16-bit register handles the chip’s input multiplex (bits 12-14), the PGA (bits 9-11), whether the device is operated in single-shot or continuous conversion mode (bit 8) and the sampling rate (bits 5-7). Fig.3: the ADS1115-based module is extremely simple, as can also be seen in the lead photo. The values of the L1 & L2 inductors are unknown, they could be ferrite beads. Fig.4: it’s easy to connect the ADS1115-based module to an Arduino Uno or similar, as all you need to do is connect its I2C interface (SCL & SDA) and power rails to the Arduino. Australia's electronics magazine November 2023  47 As you can see, there’s quite a lot inside the ADS1115’s tiny (3.0 × 3.0mm) 10-pin VSSOP (very-thin shrink small-outline) package. It can be powered from supply voltages (Vdd) between 2.0V and 5.5V. However, the analog input voltages must be kept within the range of (GND − 0.3V) to (Vdd + 0.3V) to prevent the ESD diodes inside the input MUX from conducting, which would degrade the accuracy of the ADS1115 as well as possibly damaging it. When the ADS1115 is initially powered up, it is set to its reset/default mode: the input MUX selects AIN0 and AIN1 in differential mode, the PGA is set for a full-scale range of ±2.048V, the sampling rate set to 128 samples per second and the conversion mode set to one-shot mode. If any of those need to be changed, it can be done by sending the appropriate instructions from the MCU. The I2C address of the chip is not determined by anything in the Configuration register, but by the connection to the ADDR pin. The module circuit As you can see from the circuit in Fig.3, there’s very little in the module apart from the ADS1115 chip itself. There are three pull-up resistors connected between its SDA, SCL and ALRT/RDY pins and the Vdd line, a pull-down resistor between the ADDR line and GND, two small inductors (L1 and L2) of unknown value (they might even be ferrite beads), plus two 100nF capacitors which provide filtering for the module’s input power. The only other item is 10-pin SIL header CON1, which makes all the connections to the module. Connecting to an Arduino Fig.5: this wiring diagram shows how to connect the ADS1115 module to an Arduino Nano. Fig.6: by default the ADS1115 has an I2C address of 48h. If you plan to connect multiple ADS1115 modules to communicate with a microcontroller, then you will need to link the ADDR pin to one of the other pins as shown. 48 Silicon Chip As mentioned earlier, one of this module’s features is how its I2C interface makes it easy to connect to one of the popular MCUs. This is illustrated in Fig.4, which shows how easily it can be connected to an Arduino Uno. The module’s Vdd pin connects to the Arduino’s +5V pin, its GND pin to one of the Arduino’s GND pins, its SDA pin to the Arduino’s A4/SDA pin and its SCL pin to the Arduino’s A5/SCL pin. With R3 and later versions of the Uno, the last two pins can be connected to the SDA and SCL pins at upper left on the Arduino, just to the left of the AREF pin. These locations have the advantage of always being in the same position on Uno-compatible boards, regardless of which pins the micro actually uses for I2C. Connecting the module to an Arduino Nano is just as easy, as shown in Fig.5. As you can see, the module’s Vdd pin connects to the Nano’s +5V pin, the GND pin to one of the Nano’s GND Australia's electronics magazine pins, its SCL pin to the Nano’s A5 pin and its SDA pin to the Nano’s A4 pin. By default, the ADDR pin is connected to ground by a 10kW resistor, so the module will have the address 48h. To change it, link the module’s ADDR pin to one of the pins to its left, as shown in Fig.6. Linking this pin to the Vdd pin sets the I2C address to 49h; linking it to the SDA sets the address to 4Ah, while linking it to the SCL pin sets the address to 4Bh. It should be just as easy to connect the ADS1115 module to just about any other MCU, including one of the ‘Mite’ series (Maximite, Micromite, PicoMite etc). Whichever MCU you want to connect the module to, you will need software to configure it and interpret its output data stream. Let’s now consider how this can be done with an Arduino. This will involve finding a software library designed to communicate with the ADS1115, plus (hopefully) an example sketch to show how it’s done. Arduino software libraries Searching the web for Arduino libraries for the ADS1115, I came up with three choices: 1. A library called ADS1x1x, written by someone named hideakitai, with the documentation and the zipped-up library code at https://github.com/ hideakitai/ADS1x1x 2. A library called ADS1x15, written by Rob Tillaart, with the documentation and the zipped-up library code at https://github.com/RobTillaart/ ADS1X15 3. A library called ADS1115_WE, written by Wolfgang Ewald, with the documentation and the zipped-up library code at https://github.com/ Wollewald/ADS1115_WE All three come with at least one example sketch, while the third comes with no fewer than 10 examples illustrating different ways of using the ADS1115. After trying each of these libraries and their example sketches, I decided that the ADS1115_WE library and its examples were probably the easiest to use. I also found that Mr Ewald had a very informative piece on his blog site (linked at the end of this article) giving a lot of information regarding the ADS1115, how it works and how it is programmed. siliconchip.com.au I made a few minor changes to Mr Ewald’s single-shot example and tried using it to take measurements of different DC voltages. You can see the results in the Serial Monitor listing shown in Fig.7. I had connected the test voltage to AIN1, with the AIN0 and AIN2 inputs connected to ground and the AIN3 input left floating. The ADS1115 was programmed to set its measurement range to ±2048mV and to compare AIN1 to GND. When I set the sketch at 7:09:36am, the voltage fed to the AIN1 input was +100mV and remained so until 7:09:49am. Then I changed it to +200mV before changing it to +500mV at 7:05:58am. Then at 7:10:07am, I changed it to +50mV, passing briefly through +100mV. Finally, at 7:10:16am, I changed the voltage to +20mV. The AIN0 column remains fixed at readings of -0.00, as does the AIN2 column, reflecting the fact that both of these inputs were grounded. But because the AIN3 input was left floating, the readings in this column remained fixed at 0.27V. If you decide to try out my example sketch, remember to change the address in the code to match what you have configured your module for, as shown in Fig.6. Conclusion Overall, this module is easy to use, flexible, and far more accurate than most microcontrollers for measuring analog voltages. It doesn’t have as much precision as a good DMM, but it is nonetheless extremely handy. If you want to learn more about the ADS1115, you can view the datasheet at: www.ti.com/product/ADS1115 Also see the technical write-up on Wolles Elektronikkiste: siliconchip. au/link/abph Above: the ADS1115 module can run from a 2-5.5V supply, making it easy to use both 3.3V and 5V powered micros. The available sampling rates are: 8, 16, 32, 64, 128, 250, 475 and 860 samples per second (SPS). Fig.7 (right): we ran Wolfgang Ewald’s singleshot example code, with some minor changes, and used it to measure different DC voltages. Where you can get it The ADS1115 module I checked out is currently available from Altronics (stock number Z6221) for $20.75 (including GST). At the time of writing, it is also available from Paktronics for $30.07, eBay supplier duomin 87 for $16.01, Temu for $7.48 and AliExpress from $2.39 + P&P. There are some other modules using the ADS1115 that look a little different but are very similar in terms of circuitry. SC siliconchip.com.au Australia's electronics magazine November 2023  49 John Clarke’s K–Type Thermocouple THERMOSTAT With this Thermometer, you can easily measure temperature over a very wide range and control a device in response. It utilises a K-type thermocouple as its sensor and can drive a relay for thermostat control of either heating or cooling operation. T he K-type Thermocouple Thermometer/ Thermostat (known as the Thermometer or Thermostat from now on) can measure a very wide range of temperatures. It incorporates a relay that can control the power to a heating element or refrigerator compressor. While some digital multimeters can measure temperatures using a thermocouple, they almost universally cannot automatically control the temperature for heating or cooling. For heating, power can be switched on when the temperature is below a preset temperature and switched off when it reaches the preset. Alternatively, power is switched on for cooling when the temperature is above the preset and off when it goes below the threshold. Fig.1: a K-type thermocouple is often thought of as having a simple 41.276µV/°C sensitivity (the Seebeck coefficient), but it actually varies like this. We must account for this variation to get accurate readings, especially at lower temperatures. 50 Silicon Chip Australia's electronics magazine It has adjustable hysteresis to prevent rapid on/off switching of the relay near the threshold. This introduces a difference between the temperatures at which the relay will switch on and off. The hysteresis is adjustable from 0 to 60°C, although it usually would only be around 1-2°C. The temperature reading is shown on a two-line, 16-character LCD. While the unit can display a temperature from -270°C to +1800°C, the actual range depends on the probe used. Some K-type probes operate from -50°C to +250°C, some from -50°C to +900°C, some from -40°C to +1200°C, while others only operate above 0°C. Thermocouple probes can also be insulated or uninsulated. Insulated probes do not have an electrical connection to the thermocouple, so the probe can touch a material that is grounded or at some fixed voltage without producing erroneous readings. Uninsulated probes shouldn’t be used where there will be a potential difference between the thermometer ground and the probe. For our Thermometer, if that happens, it will show a fault (short to ground or short to supply). The Thermometer is housed in a small instrument case with controls on the front for power on/off, selecting the display view and adjusting settings. siliconchip.com.au Features » » » » » » » » » » » » » » Wide temperature measurement range (typically -50°C to +1200°C) Fine resolution of 0.25°C for all measurements and settings Accuracy of up to ±2°C from -200°C to +700°C; ±4°C up to +1350°C Compact unit powered from 12V DC Low current consumption – 75mA with full display brightness and relay on Linearised thermocouple readings Thermostat relay Adjustable thermostat switching temperature and hysteresis Heating or cooling thermostat operation Adjustable display backlighting brightness Thermometer reading averaging options Thermocouple connection fault indication Relay switches up to 30V at 10A External relay can be used for switching mains or higher currents (see text) Specifications » Measurement range: thermocouple dependent; up to -270°C to +1800°C » Ambient (cold junction) measurement range: -40°C to +125°C » Cold junction accuracy: ±2°C from -20°C to +85°C; » » » » » » » » » ±3°C from -40°C to +125°C Thermostat threshold: from below -270°C to above 1800°C Thermostat hysteresis: 0°C to 60°C Offset trim: -7°C to +7°C (compensating for offset & cold junction errors) Linearisation: corrected in 0.5°C steps with 0.25°C resolution from -161°C to 1311°C (cold junction at 0°C), -136°C to 1336°C (cold junction at 25°C) Reading averaging: over 1, 2, 4, 8, 16, 32, 64 or 128 readings Thermostat indication: animated up or down flowing bargraph during heating or cooling Display brightness control: 10 brightness steps plus off Automatic menu return to thermometer reading option Thermocouple error indication: open circuit, short to ground or short to supply Lead image: www.pexels.com/photo/frozen-river-near-mountainous-area-6685417 Background image: unsplash.com/photos/ynwGXMkpYcY At the rear of the case are the sockets for 12V DC power input and the K-type thermocouple. There is also a cable gland for wires to enter the box and connect to the Thermostat relay contacts via screw terminals. The common (C), normally open (NO) and normally closed (NC) contacts are available. K-type thermocouple principles A K-type thermocouple comprises a junction of two dissimilar wires. The K-type uses an alloy of chrome and nickel (called Chromel) for one wire and an alloy of aluminium, manganese, silicon and nickel (called Alumel) for the second. These two wires only make contact with each other at the temperature probe end. The other ends of the wires connect to a two-pin plug at the Thermometer. A thermocouple works because the junction of two dissimilar metals siliconchip.com.au produces a voltage that is dependent on temperature. A K-type thermocouple has a nominal sensitivity of 41.276µV/°C. However, using this one value has limitations; the sensitivity is not fixed but actually varies with temperature. For example, the K-Type thermocouple has a sensitivity of 35.54µV/°C at -100°C and 41.61µV/°C at +750°C. This variation will introduce temperature reading errors if a fixed value is assumed. The sensitivity of a K-type thermocouple over temperature is shown in Fig.1. The change in output per °C is called the Seebeck coefficient. It refers to the voltage change due to the temperature difference between the probe and the plug end of the thermocouple. A typical graph shows the Seebeck coefficient with the plug end of the thermocouple at 0°C. The coefficient is reasonably consistent over the 75°C to 1000°C range but Australia's electronics magazine drops off rapidly for temperatures in the negative region. If the 41.276µV/°C sensitivity figure were used in our Thermometer, the readings would only be truly accurate at 0°C, 500°C and 1000°C. It is not that convenient to maintain the plug end of the thermocouple at 0°C. Instead, the plug end is allowed to vary with the ambient temperature. The thermocouple driver measures its temperature and uses that reading to compensate readings at the probe end. This is called ‘cold junction compensation’ (the plug end is defined as the cold junction). Despite the name, this plug end isn’t necessarily colder than the probe; it could be hotter. In Fig.1, we added an extra curve for when the cold junction is at 25°C. That gives you an idea of the shift in the graph with varying cold junction temperatures. If the cold junction temperature is 25°C and the thermocouple probe end is measuring 0°C, the thermocouple is actually measuring -25°C. This is where the Seebeck coefficient rapidly reduces in value as the temperature measured by the thermocouple falls. That makes getting accurate readings in that part of the curve challenging. Our Thermometer uses a Maxim MAX31855 integrated circuit (IC). It provides a digital data output of the thermocouple reading, adjusted to account for the cold junction compensation. The IC itself measures the cold junction temperature. This gives a reading within ±2°C from -200°C to +700°C (not including errors due to the thermocouple itself). However, this accuracy figure does not include the variation in readings due to the Seebeck coefficient changes with temperature. It assumes a consistent 41.276µV/°C Seebeck coefficient over that temperature range. Temperature correction Fig.2 shows the temperature correction required. Again, the ambient cold junction temperature shifts the curve from 0°C. We show the 25°C cold junction curve as an example. The graph shows what value must be added to or subtracted from the reading to account for the Seebeck variation with temperature. For example, when the probe is measuring an actual 0°C with a cold junction temperature at 25°C, -1.55°C November 2023  51 Fig.2: this shows the error in temperature readings if they are made with the assumption of a fixed sensitivity. We can subtract these errors from the regular readings for more accurate results. needs to be added to the reading (ie, 1.55°C subtracted) to obtain a correct 0°C result. We have incorporated these linearisation corrections within the workings of the Thermometer software, covering the range from -161°C to +1311°C when the cold junction is at 0°C. Typically, the cold junction will be somewhat more than 0°C. When the cold junction is at 25°C, the range becomes -136°C to +1336°C. This linearisation is based on standard K-type thermocouple thermoelectric voltage versus temperature tables; see siliconchip.au/link/abmo Various methods can be used to make corrections. One is to describe the thermoelectric voltage versus temperature as mathematical polynomials and then calculate the required correction for the reading. That can involve many calculations. For a description of that and other techniques, see the Texas Instruments reference design document “TIDA00468 - Optimized Sensor Linearization for Thermocouple”; go to siliconchip.au/link/abmp and select the TIDA-00468 reference design. Another method is to have a table that lists corrections against Thermocouple output, which is our approach. Since the MAX31855 provides the Thermocouple output with the cold junction compensation included, the cold junction value needs to be 52 Silicon Chip removed from the value before the compensation table for the thermocouple is applied. After the correction is made by adding or subtracting the appropriate value, the cold junction value is added back to give the overall temperature reading. Linearisation is done in 0.5°C steps. After linearisation, temperature accuracy will be limited mainly by the errors and offsets of the MAX31855 IC and the thermocouple itself. Circuit details The circuit for the Thermometer is shown in Fig.3. It is based around the MAX31855KASA+T cold-junction compensated thermocouple-to-digital converter for K-type thermocouples (IC1) and a PIC16F1459 8-bit microcontroller (IC2). The microcontroller also drives a two-line by 16-character LCD to show the readings. The thermocouple socket (CON1) is designed specifically for the K-type thermocouple so that extra voltage is not produced due to dissimilar metal junctions. The voltage passes through ferrite beads (FB1 & FB2) with 100nF bypass capacitors shunting noise to ground. In conjunction with the capacitors, the ferrite beads act as high-­frequency suppression filtering for the thermocouple voltage entering IC1. Transient suppression devices TVS1 and TVS2 Australia's electronics magazine also clamp excessive input voltages to IC1. IC1 is powered from a 3.3V supply, while IC2 is powered from 5V. These are derived from the 12V supply input at CON2 with reverse polarity protection by diode D1. The result is that 11.4V is applied to the input of REG1 via a 100W resistor, and any over-­ voltage from the 12V input is limited to 12V by zener diode ZD1. These components provide some protection should a much higher voltage be applied to CON2. The 100W resistor also shares any heat dissipation with REG1 to spread heat more evenly inside the Thermometer enclosure. This helps to maintain a more consistent cold junction temperature. REG2 provides the 3.3V supply for IC1. IC1 draws a maximum of 1.5mA, so there is very little dissipation within REG2, around 2.6mW. That’s calculated as (5V – 3.3V) × 1.5mA. IC1’s dissipation is 5mW (3.3V × 1.5mA). Given its 170°C/W junction-to-­ ambient temperature coefficient, this amounts to a temperature rise of 0.84°C, so we can expect the cold junction measurement to be higher than the actual ambient temperature by this amount, plus whatever heat is provided by the 100W resistor, REG1, REG2 and IC2. The MAX31855 provides a digital version of the thermocouple reading, with cold junction compensation applied. The data is sent via a serial interface with pin 5 for the clock, pin 6 for the chip select and pin 7 for the serial data output. The serial data is monitored at the RA5 input of IC2 (pin 2), while IC2 controls the clock and chip select lines from its RC4 and RC5 outputs (pins 6 & 8). These use 1.1kW/2.2kW resistive dividers to reduce the 5V outputs from IC2 to 3.3V levels suitable for IC1. IC2 reads the temperature data provided by IC1 by clocking the data through one bit at a time. The available data includes the thermocouple temperature with cold junction compensation as a signed 14-bit binary value, the cold junction temperature as a signed 12-bit binary value and any thermocouple fault conditions. The fault conditions detected are an open circuit connection, a short to ground and a short to a positive voltage. Apart from reading the data from IC1, IC2 drives the LCD module and siliconchip.com.au backlighting, monitors the Menu, Up and Down switches (S1-S3) and drives the thermostat relay, RLY1. The LCD module is driven using a 4-bit parallel interface to its D4-D7 data inputs. These are connected to the RB4-RB7 digital outputs of IC2. The Enable (EN) and Register Select (RS) inputs of the LCD are driven from the RC2 and RC1 outputs of IC2, respectively. The data is sent as two sets of four bits to make up the full 8-bit data to produce characters on the LCD. The unused D0-D3 inputs of the LCD are connected to ground. The LCD could be driven with an 8-bit parallel interface if all D0-D7 inputs were connected to IC2. However, that would require more pins from IC2 than are available. LCD backlighting Backlighting for the LCD module is provided by driving LEDs behind the LCD screen. The LED anode connects to the BLA terminal at pin 16. We connect BLK (‘backlight kathode’) at pin 16 to the drain of Mosfet Q2 via a 68W current limiting resistor. The LEDs are on when Q2 is activated by a highlevel voltage at its gate from the RC5 output of IC2. When the gate is driven high, its drain voltage goes low. The RC5 output is switched on and off rapidly to dim the display. The duty cycle (on time to full period ratio) determines the brightness. When the duty cycle is 50%, the LEDs are driven at an average of half the maximum current. Higher duty cycles provide more brightness. The RC5 (pin 5) delivers a pulsewidth modulated (PWM) signal at 976Hz; that’s fast enough so that the on-and-off switching of the LEDs is not noticeable. Switches S1 to S3 are momentary Fig.3: the circuit is straightforward as the MAX31855 (IC1) measures the temperature and passes it digitally to microcontroller IC2, which then updates the LCD screen over a four-bit bus. The remainder of the circuit comprises the three control pushbuttons, the thermostat relay (RLY1) and a linear DC power supply. siliconchip.com.au Australia's electronics magazine November 2023  53 pushbuttons. They connect to the RC0, RA1 and RA0 inputs of IC2, which are pulled high to 5V using 10kW resistors. When a switch is pressed, the closure is detected as a low level at that pin (near 0V) and IC2’s software responds by selecting a menu or changing a menu value. Relay RLY1 is driven via transistor Q1, which is, in turn, driven from the RA4 digital output of IC2 (pin 3). When this output is high (5V), the transistor is switched on via base current through the 1kW resistor. The collector then goes low and the relay coil is powered, connecting the common (C) and normally open (NO) contacts. When RA4 goes low, Q1 switches off; the relay is not powered and the C and NC contacts are joined instead. Diode D2 quenches the high-voltage back-EMF the relay coil generates when it switches off, avoiding damage to Q1. Adjustments The Thermometer incorporates several display and adjustment settings that are stored in non-volatile memory. These values remain after the power is switched off. Settings are selected using the Menu button to cycle through each menu while the Up and Down buttons adjust settings. For temperature settings that can be changed, the Up button increases the value while the Down button decreases it in 0.25°C steps when pressed briefly. Holding a button changes values at a progressively faster rate over time. That allows large values to be reached in a reasonable time while allowing for smaller 0.25°C steps. Where the particular menu provides two choices, either The rear of the case with a K-type thermocouple attached. 54 Silicon Chip Fig.4: note how the two right-angle headers (CON4 and CON5) are mounted differently. The only components on the underside are the two TVS diodes, which are not polarised; their positions are shown on the PCB silkscreening. The two large ferrite beads have multiple turns of enamelled copper wire passing through them (see the instructions in the text). the Up or Down button can be used to select the other option. Details of each menu are in the separate panel named “Menu Summary”. Animations Thermostat operation during cooling or heating is indicated using an animated bar within a rectangle that progresses downward for cooling and upward for heating in the lower righthand corner of the display. The animation is shown for the Thermometer, Thermostat Set and Hysteresis menus. The rectangle indication is shown without the bar animation when the Thermostat is off. Construction The Thermometer is built using two double-sided plated-through PCBs, with the main 98 × 70mm PCB coded 04108231 while the 19 × 22mm front panel PCB is coded 04108232. These are housed in a Ritec ABS translucent black instrument case measuring 105 × 80 × 40mm. Relay RLY1 provides switched outputs at CON3. This can handle up to 10A at up to 30V. An external relay will be required if you need to switch mains voltages; we will provide details on wiring up an external relay later. Start building the main PCB by soldering IC1 in place. It is an SOIC 8-pin IC, one of the simplest surface-mount devices to solder. Start by orientating the IC correctly over the PCB pads (referring to Fig.4) and solder pin 1. Check the IC alignment with the remaining pads; remelt the solder and readjust the IC if the registration to the other pads needs to be corrected. Solder the remaining pins once The on/off switch is mounted to a cutout on the vertical pushbutton PCB (see Fig.5). siliconchip.com.au Fig.5: three tactile pushbuttons are the only components on this small front-panel PCB. It connects to the main PCB via rightangle header CON5. are going to use it. See the section on using this project for mains switching if that is what you require. Front panel PCB assembly This photo from the rear of the PCB shows the multiple windings for FB1 & FB2 and the LCD mounting arrangement. this is correct. You can remove any solder bridges that form with a dab of flux paste and the application of solder wick. The next components to install are the resistors, diodes and transient suppressors TVS1 and TVS2. Ensure D1, D2 and ZD1 are installed with the orientations shown on the overlay diagram and PCB screen-printing and don’t get them mixed up. TVS1 and TVS2 can be mounted either way around. Fit the socket for IC2, ensuring it is orientated correctly. Ferrite beads FB1 and FB2 are wound using five turns of 0.8mm diameter enamelled copper wire each. Strip the ends of insulation using a sharp knife or similar before mounting them on the PCB. The right-angle header strips, CON4 and CON5, can be installed now. These are 4-way and 16-way headers. If you have a longer strip, you can snap it into 4-way and 16-way strips. Note that CON4 and CON5 are installed differently. CON4 (for the LCD) is installed with the straight pin side into the PCB, while CON5 (for the front panel PCB) is installed with the right-angle pins into the PCB. This allows for the required positioning of the LCD module and switches at the front panel. Fit two PC stakes at the S4 power connection points, ready for wiring to the switch later. Now mount VR1, the capacitors, transistors Q1 and Q2, plus regulators siliconchip.com.au REG1 and REG2. The electrolytic capacitors must be orientated with the correct polarity; the longer leads are positive, while the stripe on the can indicates negative. Ensure that Q1, Q2 and REG2 are not mixed up, as they are different types that all come in similar TO-92 packages. The DC socket, CON2 and the K-type socket (CON1) can be fitted next. Finally, install the relay if you Assembly for the front switch PCB (see Fig.5) is straightforward and mainly involves installing the three switches: S1, S2 & S3. Switch S4 is installed later once it is attached to the front panel. The LCD module and front switch PCB can now be attached and soldered to the right-angle headers on the main PCB – see Fig.7. Panel cutouts Drill and cut the front and rear panels as shown in Fig.6. You can also download that diagram (siliconchip. com.au/Shop/11/294), print it out at actual size and use it as a template. The rectangular cutouts can be made using a series of small drill holes around the inside perimeter, removing the centre and carefully filing to shape. Fig.6: make the front and rear panel holes and cutouts as shown here. You can also download this diagram as a PDF from the Silicon Chip website, print it out at actual size, cut out the templates and stick them to the panels. Australia's electronics magazine November 2023  55 The completed PCB mounted in the case, ready for operation. Switch S4 is glued and attached by a soldered crimp lug to the small vertical PCB. Once the panels are complete, attach switch S4 to the front panel with one nut behind the panel and the other in front. Then place the front panel over the LCD and with S1-S3 switches protruding and install the assembly comprising the panel, switch PCB and main PCB into the enclosure. Secure the main PCB to the enclosure base with the screws supplied with the enclosure. Switch S4 can now be secured using epoxy resin to the switch PCB. Wait until the glue is cured before removing the assembly. As an alternative to gluing, the switch can be secured using a 6.3mm chassis-mount double-ended spade connector (Jaycar PT4916 or Altronics H2261) or a single-ended connector soldered to the front of the front panel PCB. The hole in the connector will need to be drilled out for the switch, and the spade connector lugs will need to be cut to size and bent. When installed correctly, the rectangular section of the switch body will be 2mm proud of the front panel PCB face. The wires from the switch’s top two terminals should now be connected to the switch contact PC stakes on the main PCB. Making panel labels Fig.7: this shows how the LCD and front panel PCB attach to the main PCB and how switch S4 is wired up. The LCD and front panel PCB are shown ‘folded’ down for clarity but they should actually be at right angles to the main PCB. Switches S1-S3 are located on the underside of the PCB. Fig.8 shows the front panel labels that can be downloaded, printed and affixed to the front and rear panels. The artwork can be printed onto an A4-sized Avery “Heavy Duty White Polyester – Inkjet” sticky label suitable for inkjet printers or a “Datapol” sticky label for laser printers. Cut out the holes and display opening with a sharp craft knife. Labels are available from: • www.blanklabels.com.au • www.averyproducts.com.au The first of those also has instructions and interesting information. For Avery labels: siliconchip.com.au/l/ ably For Datapol labels: siliconchip. com.au/l/aabx We have more information on making panel labels on our website: siliconchip.au/Help/FrontPanels The Thermometer can now be fully assembled without the lid and without IC2 installed. Apply power and check that there is about 5V between pins 1 and 20 of IC2’s socket. If so, disconnect power and insert IC2, ensuring the orientation is correct. VR1 will need to be adjusted so the Australia's electronics magazine siliconchip.com.au 56 Silicon Chip display does not just show blocks of ‘on’ pixels. Apply power, rotate VR1 anticlockwise to show the blocks and then rotate it clockwise until they just disappear. That gives the best display contrast. External relay and mains switching The internal relay for thermostat switching is recommended for up to 10A and 30V maximum. While the PCB tracks for the relay and CON3 are well separated from the rest of the circuitry, the enclosure is not strong enough to ensure that the mains wiring can be securely held in position. So, for mains switching, we recommend using an external relay securely mounted in an enclosure or within the appliance to be controlled. Using an external relay also enables higher-­ rated contacts better suited for switching a refrigerator compressor. Figs.9-11 show various ways to add an external relay. The three diagrams show how to connect the external relay when there is a 12V supply available, when there is no 12V available and for connections to the Thermostat using either a direct relay connection or via a mains plug and socket that is switched via the relay. If the external relay is mounted in a metal enclosure, this enclosure must be Earthed. The relay mounting screws must be made of Nylon for a plastic enclosure. If the mains plug and socket are required, and the enclosure is metal, there must be a mains Earth connection to the chassis. Otherwise, connect the mains input Earth directly to the mains Earth on the general purpose outlet (GPO). No chassis Earth is required for a plastic enclosure, but there must not be any unearthed exposed metal screws on the outside of the enclosure. Use Nylon screws to ensure safety. Suitable relays include the 12V DC SPST 30A 240V AC relays sold by Jaycar (SY4040) and Altronics (S4211). Solid-state relays rated for switching mains AC voltage could also be used. You will also need extra parts to finish it, such as cable ties, P-clamps, cable glands, screws, nuts, spade connectors, 10A mains wire etc. Setting it up The “Menu Summary” section (shown opposite) lists the available siliconchip.com.au Menu Summary The initial settings shown in brackets at the end of each menu description below are the defaults before being changed via the menus. Any changes to the values or settings will subsequently replace those. Thermometer This shows the temperature reading of the probe after cold-junction compensation. While it can display between -270°C and +1800°C, the probe may have a narrower operating range. This screen is shown on power-up. Offset Adjust (0.00°C) This applies a temperature offset adjustment to the Thermometer readings. It can compensate for any initial offsets in the thermocouple reading, cold-junction reading error and self-heating effects of the IC. The offset can be adjusted in 0.25°C steps above and below zero, from -7°C to +7°C. It does not affect the Thermostat setting value or cold-junction temperature reading. Thermostat Set (0.00°C) This is the temperature threshold for the Thermostat to switch off. It can be adjusted beyond the ranges of -270°C and +1800°C in 0.25°C steps. During operation, the thermostat relay will switch on or off only after three temperature readings are at or beyond the threshold. This prevents false readings from causing the relay to switch due to noise. Note that the thermostat switching will be delayed more with higher averaging values selected (see below). Hysteresis (4.00°C) Adding hysteresis prevents the Thermostat from switching rapidly when the temperature is near the threshold. For heating, once the Thermostat switches off, the temperature must drop by the hysteresis amount before the Thermostat switches on again to resume heating. For cooling, once the Thermostat switches off, the temperature needs to increase by the hysteresis amount before the Thermostat switches on again to begin cooling. It can be set between 0°C and 60°C in 0.25°C steps. Brightness (50%) The display backlight brightness can be set off to one of ten brightness steps, from low to full brightness. A bargraph shows the setting, while the brightness also changes as you modify the setting. Averaging (1) Higher averaging values slow the Thermometer reading update but allow a more constant temperature reading when the temperature probe is subject to mains hum and noise. The options are averaging over 1, 2, 4, 8, 16, 32, 64 or 128 measurements. When averaging is set to eight measurements and above, a backslash before the word “Thermometer” on the main menu shifts from one position to the other (upper or lower) to indicate when the temperature value is updated. If set to 128 samples, updating the new averaged value can take up to 10 seconds. This update is progressively faster for lower averaging values (around five seconds for 64, 2.5s for 32 etc). Thermostat (cooling) The Thermostat can be set up for either heating or cooling. For heating, the Thermostat is switched on when the temperature is below the preset temperature and switched off when it reaches the preset. Alternatively, for cooling, the Thermostat is switched on when the temperature is above the preset and off when it goes below the threshold. Auto Return (off) Enabling this causes it to return to the main Thermometer display if no buttons are pressed for four seconds. This saves having to cycle through all the menus to reach the main Thermometer menu. Linearisation (on) This determines whether the thermocouple readings are linearised (corrected) for the change in the Seebeck coefficient against temperature. You can select this to be on or off. When on, if the reading goes beyond the temperature range where linearisation is performed, the display will show “Linearisation Range Error”. Also, when set on, the non-­linearised reading can be shown on the main temperature display by pressing the down button. Cold Junction Shows the cold junction temperature as measured by the MAX31855 IC. It can range from -40°C to +125°C in 0.25°C steps. Typically, this shows ambient temperature, but it will include reading errors due to self-heating and measurement accuracy. Australia's electronics magazine November 2023  57 Parts List – K-Type Thermometer / Thermostat 1 double-sided, plated-through PCB coded 04108231, 98 × 70mm 1 double-sided, plated-through PCB coded 04108232, 19 × 22mm 1 Ritec 105 × 80 × 40mm ABS black translucent instrument case [Altronics H0192] 1 2×16 character alphanumeric LCD [Altronics Z7013] 1 K-type thermocouple probe [Jaycar QM1283 (-50°C to +250°C), QM1282 (-50°C to +900°C), element14 2947102 (0°C to +800°C)] 1 cable gland for 3-6mm diameter cable 3 SPST micro tactile PCB-mount switches with 6mm actuators (S1-S3) [Jaycar SP0603, Altronics S1124] 1 SPDT sub-miniature toggle switch (S4) [Jaycar ST0300] 1 12V DC 100mA+ plugpack with 2.1mm or 2.5mm ID barrel plug 1 12V SPDT 10A relay (RLY1) [Jaycar SY4050, Altronics S4197] 1 K-type thermocouple socket (CON1) [element14 3810628] 1 PCB-mount DC socket, 2.1mm or 2.5mm ID (to suit power supply; CON2) [Jaycar PS0520, Altronics P0621A] 1 3-way screw terminal, 5.08mm pitch (CON3) 1 16-way right-angle header, 2.54mm pitch (CON4) 1 4-way right-angle header, 2.54mm pitch (CON5) 1 20-pin DIL IC socket (for IC2) 2 large ferrite suppression beads (FB1, FB2) [Jaycar LF1256 (pack of 6), Altronics L4710A] 1 250mm length of 0.8mm diameter enamelled copper wire (for FB1 & FB2) 2 50mm lengths of light-duty hookup wire (for S4) 2 PC stakes 1 10kW single-turn trimpot (VR1) [Jaycar RT4600, Altronics R2597] 1 small amount of epoxy resin or 6.3mm chassis mount spade connector (for mounting S4) [Jaycar PT4916, Altronics H2261] Semiconductors 1 MAX31855KASA+T cold-junction compensated thermocouple-to-digital converter IC for K-type thermocouples (IC1) [element14 2515622] 1 PIC16F1459-I/P 8-bit microcontroller programmed with 0410823A.hex, DIP-20 (IC2) 1 7805 1A 5V regulator, TO-220 (REG1) 1 MCP1700-3302-E/TO or AMS1117-3.3 3.3V low-dropout linear regulator, TO-92 (REG2) [Silicon Chip SC2782, element14 1296588] 1 BC337 45V 500mA NPN transistor, TO-92 (Q1) 1 2N7000 60V 200mA N-channel Mosfet, TO-92 (Q2) 2 (P)4KE15CA or (P)4KE16CA 400W 12.8-13.6V standoff transient suppression diodes (TVS1, TVS2) [Jaycar ZR1162] 1 12V 1W zener diode (ZD1) [1N4742] 2 1N4004 400V 1A diodes (D1, D2) Capacitors 2 100μF 16V PC radial electrolytic 2 1μF 50V X5R or X7R radial ceramic 6 100nF 50V X5R or X7R radial ceramic Resistors (all ¼W, 1% unless noted) 4 10kW 1 1kW 2 2.2kW 1 100W 1W 2 1.1kW 1 68W ½W or 0.6W menus and their functions. These will need to be set according to your application. Typically, the averaging value will need to be more than one so that the temperature does not jump about, especially if you introduce hum and noise when touching the thermocouple probe. The thermostat settings require selecting heating or cooling plus adjusting the threshold temperature and the hysteresis. Hysteresis is to prevent the Thermostat from switching rapidly at the threshold, so set it high enough to prevent that from occurring. Calibration The Thermometer requires calibration to obtain the correct temperature reading due to offset values within the MAX31855 and the fact that the temperature within the enclosure is higher than ambient. The Offset menu allows adjustment to correct for these initial errors. This is best done by calibrating the Thermometer using a 0°C reference solution. This can be made using a jar of pure fresh water that has sufficient crushed ice stirred in so that the temperature reaches 0°C. You should be able to adjust the Thermometer reading using the Offset adjustment so that the display shows 0°C. You will need to check that linearisation is on (see how to check that under the Menu summary). It’s best to leave the Thermometer switched on for a while (eg, half an hour or more) before performing calibration to ensure it has thermally stabilised. If you wish to check the calibration at a higher temperature, a 100°C reference can be made by continuously boiling water at sea level. The boiling point of water drops with height above sea level by close to 0.325°C/100m. So water boils at 96.7°C at 1000m elevaSC tion and 93.5°C at 2000m. ► Fig.8: the front and rear panel label artwork. They can be printed onto adhesive-backed paper or photo paper as described under “Making panel labels”. 58 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.9: note the wire links on the main board in place of RLY1 so that 12V is fed to the relay output terminal to control the external relay coil. Fig.10: the extra wiring to control a mains appliance using the Thermostat. It needs to be in its own suitable enclosure with properly insulated wiring. This assumes you have an external source of 12V DC; otherwise use Fig.9. Fig.11: if using an external mains relay, you can wire it to an IEC mains input socket and GPO output mounted on the box that contains the mains relay, like this. Use the correct wire colours, and don’t leave off the cable ties. siliconchip.com.au Australia's electronics magazine K-Type Thermostat Kit SC6809 ($75 + postage): includes most components except the case, LCD, thermocouple proble, cable gland and switches S4 & S5. November 2023  59 Multi-function Weather Stations GREAT RANGE. GREAT VALUE. In-stock at your conveniently located stores nationwide. FROM 8995 $ • Indoor & outdoor temperature • Temperature alert alarm • 12 Hour weather forecast XC0366 $89.95 A GREAT PRICE FOR A 7 MODELS PRINTER / ENGRAVER / GREAT VALUE! LASER ETCHER ALL OF THE WEATHER DATA AT THE BUDDING METEOROLOGIST'S FINGERTIPS 7" Colour Touchscreen with 5-Way Long Range Transmitter • Indoor & outdoor temp • Wind speed with direction • Dew point & heat index • Rain gauge with rate • 12 Hour weather forecast XC0432 $239 • Indoor & outdoor temperature • Wind speed with direction and chill • Dew point & heat index • Rain gauge with rate • 12 Hour weather forecast XC0434 $369 Our stylish weather stations are feature rich with useful atmospheric measurements such as temperature, humidity, barometic pressure, moon phase, rainfall plus data logging, alarms, time, calendar and more. T GRE A GIEFATS! ID From simple forecast displays to detailed modelling we have a model to suit any budget. Shop Jaycar for environmental meters: • Desktop Thermometers • Light, Wind and Sound Meters • Digital Multimeters & Data Loggers AUTOMATICALLY UPLOADS WEATHER DATA TO ONLINE WEATHER SERVICES 5.4" Colour Screen & Wi-Fi 5.4" Colour Screen & Wi-Fi • Indoor & outdoor temperature • Wind speed with direction and chill • Dew point & heat index • Rain gauge with rate • Upload data via Wi-Fi to Weather Underground & Weathercloud • Indoor & outdoor temperature • Wind speed with direction and chill • Dew point & heat index • Rain gauge with rate • Supports ProWeatherLive, Weather Underground, Weathercloud & more with separate Temp/Humidity Sensor XC0440 Model Comparison with 4 Day Forecasting JUST 349 $ 449 $ XC0450 ENTRY LEVEL MID JUST PROFESSIONAL XC0366 XC0412 XC0400 XC0432 XC0434 XC0440 XC0450 Indoor Thermometer √ √ √ √ √ √ √ Outdoor Thermometer √ √ √ √ √ √ √ Min/Max Records √ √ √ √ √ √ √ Hygrometer √ √ Touchscreen √ √ √ √ √ √ √ Wind Speed √ √ √ √ √ Wind Direction √ √ √ √ √ Wind Chill √ √ √ √ √ Dew Point √ √ √ √ √ Rain Gauge √ √ √ √ √ Rain Rate √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ √ Barometric Pressure √ √ √ √ Time/Date Display √ √ √ √ √ √ √ √ √ Transmitter Power 2 x AAA 2 x AA 2 x AA 3 x AA 3 x AA 7 x AA 3 x AA √ √ √ √ Transmission Range 30m 30m 100m 150m 150m 150m 150m $89.95 $129 $159 $239 $369 $349 $449 Moon Phase High/Low Alarms Colour Screen Price √ √ Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. Explore our full range of weather stations, in stock at over 115 stores, or 130 resellers or on our website. jaycar.com.au/weather-stations 1800 022 888 Microchip PICkit 5 and MPLAB X v6.10/.15 We frequently work with Microchip microcontrollers, so we were keen to try the new PICkit 5. Microchip Technology kindly sent us a sample. This was also our introduction to the latest version of their free MPLAB X software, which has several new features. Review by Tim Blythman S ince we primarily use Microchip’s PIC microcontrollers for our projects, we’re keen to stay up-to-date with the latest hardware and tools for programming and debugging them. The PICkit range is intended as a low-cost tool for evaluation and development. It stretches back to the original PICkit 1 from 2003. They offer other devices, such as the ICD 5, which are more capable and provide more features, such as device emulation. In 2016, Microchip Technology purchased Atmel Corporation, best known for their 8-bit AVR microcontrollers and 32-bit ARM chips. In 2018, they released the PICkit 4, which introduced support for the chips previously made by Atmel. Earlier PICkits had a six-pin programming header; the PICkit 4 introduced an 8-pin header to handle a broader range of chips and programming protocols. The PICkit 5 is a direct update to the PICkit 4 and keeps the same 8-pin socket. MPLAB X IDE is the software we use most to develop firmware for PIC microcontrollers. With an appropriate compiler installed, it allows you to write programs in C or assembly language. Version 6.10 is the first version to support the PICkit 5 (until recently, we were using v6.00). Version 6.15 was released while we were writing this article. Later, we’ll discuss the MPLAB X IDE, focusing on new features introduced over the last few years. “IDE” stands for integrated development environment and describes software with the necessary tools for writing, testing and deploying software. The MPLAB X IDE includes (among many other features) a text editor, compiler integration, a debugger and a programmer interface. When we reviewed the PICkit 4 in the September 2018 issue (siliconchip.au/ Article/11237), we found it substantially faster than its To program recent Microchip microcontrollers, you’ll need a PICkit 4, Snap or PICkit 5. They all contain a SAM E70 processor, but only the PICkit 5 has Bluetooth and the ability to connect to the MPLAB PTG app. The yellow wire on the Snap is a modification we described on page 69 of the June 2021 issue. 62 Silicon Chip Australia's electronics magazine predecessor, especially for in-circuit debugging. That article also explains what in-circuit debugging involves. For more background on MPLAB X, see our introductory guide in the January 2021 issue (siliconchip.au/ Article/14707). That article also covered setting up and using MPLAB X, specifically version 5.40. In case you aren’t familiar, we’ve provided a Glossary at the end of the article, explaining some of the terms that are in this article. The PICkit 5 The PICkit 5 comes in a black plastic enclosure of about 85 × 43 × 13mm. Most of the front is covered by a brushed aluminium panel with the Microchip and MPLAB PICkit 5 logos. Protruding about 5mm is an eightpin header socket at one end and a USB-C socket at the other. The back has a microSD card slot. Included in the box with the PICkit 5 is a USB-A to USB-C cable, about a metre long, plus a sheet of PICkit 5 stickers. A small hole near the USB socket provides access to an emergency recovery button. On an adjacent corner is a hole for a lanyard to be attached. The PICkit 5 is almost identical in appearance to the PICkit 4. Apart from the front panel label, the only external difference is the change in the USB socket to USB-C. This is a welcome but not unexpected upgrade. So much equipment seems to wear out or break at the USB connector; the more robust USB-C socket will hopefully avoid that and also provides commonality with most modern smartphones and tablets. The other big difference is that the PICkit 5 incorporates a Bluetooth 5.0 module. The intent is for the PICkit 5 to siliconchip.com.au Fig.1: although it might look like a simple device, you can see that there are quite a few parts needed for the PICkit 5 to do all that it does. communicate with a smartphone running the MPLAB PTG (Programmer-­ to-go) app. The Programmer-to-go feature has been available since the PICkit 3 and allows a firmware image to be programmed into a device without needing a full computer. The user guide indicates that the PICkit 5 supports PIC and AVR microcontrollers, dsPIC digital signal controllers and SAM and CEC (Arm Cortex) microcontrollers and microprocessors. A full device support list (including other Microchip programmers) can be found at siliconchip.au/ link/abpl Checking that list, we see that the PICkit 5 supports much the same range of parts as the PICkit 4. The PICkit 5 supports interfaces such as Microchip’s own ICSP, JTAG (Joint Test Action Group), SWD (Serial Wire Debug) and various AVR protocols like UPDI, PDI, ISP and TPI. It can also provide a virtual USB serial port (known as the “data stream interface” in the user guide). Hardware Ever curious, we opened up the case for the PICkit 5 to see what is ‘under the bonnet’. It sports a 300MHz SAM siliconchip.com.au E70 processor along with numerous peripheral components to generate the variety of programming voltages that are needed and interface with various targets. You can see the internals in the photos overleaf. Our review of the PICkit 4 also included photos of the PCB, and it’s clear that the resemblance doesn’t end with the enclosure. Indeed, the PICkit 5’s internals look very similar. Most components are in the same place in both programmers, except where they needed to be moved to accommodate the USB-C socket and Bluetooth module. Fig.1 shows the block diagram of the PICkit 5. The Snap programmer (reviewed in the March 2019 issue; siliconchip. au/Article/11628) also bears a SAM E70 processor but lacks the capability of high-voltage programming (high-­ voltage here means above 5V and up to 14V) and it can’t supply power to the target processor. Even with the upgrade to a USB-C socket, the PICkit 5 is only capable of USB 2.0 speeds. Still, 480Mbit/s is quick enough for most of its tasks. Since many modern PIC microcontrollers require at least a PICkit 4 or Snap for programming, we expect many readers will already know about Australia's electronics magazine these devices, so we’ll focus on the updated features. As expected, programming and debugging with a PICkit 5 is the same fast and simple experience that PICkit 4 users will be familiar with. App and Bluetooth Being able to program a microcontroller without it being connected to a computer is a handy thing, especially since it gives complete galvanic isolation. The Programmer-to-go (PTG) feature was available with the PICkit 3 and PICkit 4, but the new app makes it easier to use. The app is available for Android and iOS and is called “MPLAB PTG”; a search for this on your respective app store should find it. We used the Android version in our testing. Screens 1-3 show what the app looks like. A PTG image must be loaded onto the PICkit 5 before the app can be used. You will also need a microSD card to hold the image. We’ll discuss this process later when we get into the MPLAB X IDE. Screen 1 shows the results after scanning for devices; the app has detected the PICkit 5. Tapping on the device serial number takes you November 2023  63 to Screen 2. The BROWSE SD button shows a picker (the individual PTG images are actually folders on the microSD card filled with numerous files). Toggling the app’s PTG mode switch causes the PICkit 5’s light to flash green. This indicates that PTG mode is active; the same pattern is seen if PTG mode is activated from a computer. With a PTG image selected, the PROGRAM button takes you to Screen 3, which, in this case, has logged a successful programming effort. The diagnostic message shown when programming fails could be more descriptive; it simply says it failed. Programming from the IDE or IPE will give a much more detailed message, such as whether an incorrect voltage was present, a different chip was detected or even the specific location at which program memory could not be programmed or verified. The PICkit 5 can take power from the target circuit (through the eightway header), and we had no trouble programming a chip in this scenario. The ability to easily select and program different images in the field will be convenient, as will not needing to worry about connecting a separate power supply. We also tried hooking the PICkit 5 up to an Android mobile phone via a USB-C to USB-C cable. In this case, the phone supplied power to the PICkit 5 (and thus the target chip). We even tested serial communications using the ‘Serial USB Terminal’ app on Android and were able to send (typed into the Android phone) and receive data using the PICkit 5’s serial data pins. So, with a suitable mobile device and perhaps other apps, the PICkit 5 becomes a much more useful tool for working in the field. We see great potential for the MPLAB PTG app and Bluetooth connectivity and for many different features to be added in the future. If you don’t have the app, it’s still possible to initiate PTG programming. Like the PICkit 4, it’s done by pressing the logo on the front of the programmer, activating the internal switch, as long as the PICkit has previously been set to PTG mode. MPLAB is Microchip’s development ecosystem that includes an IDE, IPE (integrated programming environment), compilers and a wide range of programming and debugging devices. Several other code tools exist, including MPLAB Harmony and MPLAB Code Configurator. The MPLAB X IDE replaces the older Windows-only MPLAB IDE, which dates back over 20 years. The significant change was that the MPLAB X IDE became available for Mac and Linux operating systems. It’s proprietary software that’s free to download and use, although some compiler optimisation options are only available with a paid license (“PRO”) upgrade. We try to design our projects to require only the free compiler options so that anyone can modify the code, although sometimes that isn’t possible. Note that free evaluation trials are available for the PRO license versions. Also, if you want to try the IDE software without installing it on your computer, there is a cloud-based version at siliconchip.au/link/abpm Apart from the IDE, there have been updates to the compilers (which have their own version numbers) and the device family packs (DFPs). These elements mean that the overall development environment is quite modular. Different versions of the IDE, compilers and DFPs can be installed alongside each other. Screen 1: the PTG app is intuitive to use. After scanning for devices, the specific PICkit 5 can be identified by its serial number and selected. Screen 2: the microSD card can be browsed to select a PTG image. Pressing the PROGRAM button changes to Screen 3. Screen 3: the programming screen provides some simple pass/fail statistics, much like the MPLAB IPE, as well as a status log. 64 Silicon Chip MPLAB ecosystem Australia's electronics magazine siliconchip.com.au MPLAB X IDE will prompt you if there is a version mismatch (eg, the selected DFP is not installed); resolving the problem is as simple as clicking on the link in the prompt to download the correct version. You can check and update DFPs from the Tools → Packs menu item. For example, support for the newer 8-bit PIC parts is available by installing the PIC16F1xxxx pack (see our article in the October 2022 issue; siliconchip. au/Article/15505). If you need older versions of the software (for example, to maintain an old project), there is an archive, see: siliconchip.au/link/abpn Compilers Three different compiler families work with the MPLAB X IDE. XC8 targets 8-bit devices, including PIC10, PIC12, PIC16 and PIC18 parts. With the takeover of Atmel, this also includes many 8-bit AVR devices. XC16 works with 16-bit microcontrollers with PIC24 and dsPIC prefixes. XC32 is a 32-bit compiler for the wide variety of 32-bit processors from the Microchip and Atmel stables. This includes PIC32 (MIPS and ARM) and SAM parts. All compilers include other tools, such as assemblers. Late 2021 saw the release of version 6.00 of the MPLAB X IDE, followed not long after by version 4.00 of the XC32 compiler. This marked the time at which all three compilers were truly C99 compliant and began to share a standard C Library. MPLAB X IDE v6.xx The 6.xx version projects are not backwards compatible with older versions, although there is a tool to convert back to the older version. Our full Windows install of version 6.10 of the MPLAB X IDE, including support for all processor families, comes to around 11GB. The latest versions of the compilers add around 2-3GB each. Version 6.15 is much the same. The XC8 Compiler Options now allow optimisation level 2 to be selected without requiring a PRO license. Previously, only up to optimisation level 1 could be used with the free license. That is excellent news! The PICkit 5 circuit board looks quite similar to the PICkit 4. The main differences are the USB-C socket and the Bluetooth module, just visible under the notch in the main PCB. Note the tactile switch under the light guide, which is activated by pushing on the front of the PICkit 5. Compiler Advisor One new tool since version 6.00 is the Compiler Advisor. According to siliconchip.com.au Fig.2: the PRO Comparison option starts a Compiler Advisor analysis. Note how the Debugging build option is now the default. Australia's electronics magazine November 2023  65 Fig.3: even if you don’t have a PRO license, the Compiler Advisor will allow you to see how it would perform against the free compilation options. This can even be a handy tool for free licence users, as occasionally, the obvious optimisation setting is not necessarily better. Fig.4: the PTG options available on the Setting page of the MPLAB IPE are similar to the PTG app, although there is the option to change the image name from the IPE. The IPE is the best way to manage multiple PTG images. 66 Silicon Chip Australia's electronics magazine the documentation, this can be used with XC8 from version 2.30, XC16 from version 1.26 and XC32 from version 3.01. The Compiler Advisor window can be opened from the Tools → Analysis → Compiler Advisor menu, and it can be run from the Build or Clean and Build dropdown buttons (Fig.2). This option is labelled as (Clean and) Build with PRO Comparison. The project is compiled with several different optimisation settings, and the results (specifically program memory and data memory usage) are shown as a chart, as in Fig.3. The Compiler Advisor takes a bit of time to run, as it effectively runs a build for each available optimisation option (four in our example). You can easily switch to using one of the suggested optimisation configurations by clicking the link on the chart. You don’t need a PRO license to use the Compiler Advisor, although you will get more compilation options displayed if you do. As you can see (at least for this project), the PRO option offers substantial reductions in program memory usage. The release notes for version 6.15 of the IDE mention improved tool stability and using recent releases of the compilers to reduce build (compilation) times. We compared XC8 versions 2.40 and 2.41 and did notice quicker compilation with the newer version. The compilers are now throwing up more warnings, particularly in relation to C language standards. That’s a good thing, as it could pick up code errors that are not obvious. Another subtle difference we noted since versions 6.05 is that the “Build” (and “Clean and Build”) button now defaults (in versions 6.10 and 6.15) to doing a “Build for Debugging”, which you can see when you hover your mouse pointer over it. This can be a problem if you intend to build for production (deployment to a device), as debug builds can misbehave if no debugging tool is connected. Fig.2 shows how this appears in the IDE, with the “Clean and Build for Debugging” as the default at the top. So to do a Clean and Build for production now requires using the dropdown menu to select that specific item. You can also use the F11 and Shift+F11 key combinations. siliconchip.com.au Programmer-to-go Setting up the PICkit 5 to use the Programmer-to-go feature means sending a PTG image to the programmer. From the IDE, a dropdown option on the Program Device button will do that. Alternatively, the IPE has a section on the Settings tab to manage the PTG images. Fig.4 shows that section of the Settings tab and the Browse PTG window that can be opened. The IPE is the best option if you want to view and organise the PTG images and give them specific names. The PTG images are more than just the HEX files; they are folders incorporating all the settings used by the PICkit 5, such as whether the target or the PICkit circuit supplies power (and, if so, what voltage) and the programming speed. PICkit 4 obsolescence With the introduction of the PICkit 5, it appears that the PICkit 4 is being phased out, with Microchip Direct (www.microchipdirect.com) now listing it as “not recommended for new designs”. The PICkit 5 is listed at US$94.99, while the PICkit 4 is not much cheaper at US$88.54. Conclusion The PICkit 5 does everything the PICkit 4 can and more. Bluetooth, the PTG app and the USB-Serial port are all features that we plan to use. We see great potential for wireless communication in a programming and debugging tool. If your PICkit 4 is working well and you don’t need these new features, you probably don’t need to get a PICkit 5 right away. But for those looking at buying a programmer, the PICkit 5 is not much more expensive than the PICkit 4 and looks like it will have support into the future. Look for part number PG164150. As mentioned, you need at least MPLAB X 6.10 to use the PICkit 5. Even if you don’t have a PICkit 5, we don’t see any reason not to upgrade to the latest MPLAB X, although you will have to watch out that the Build buttons have changed their default behaviour. The PICkit 5 is available (at the time of writing) from the following suppliers: Microchip Direct: PG164150 DigiKey: 150-PG164150-ND Mouser: 579-PG164150 SC siliconchip.com.au PICkit 5 – Glossary of Terms Assembler Converts assembly language code (a human-readable low-level language) into binary object code. Compiler Converts code in a high-level language (such as C) into assembly language or object code. The process might be called compiling or building. Debugger A hardware or software tool that can be used to monitor what a program is doing and determine the cause of incorrect operation. Firmware Software that is programmed into persistent storage on an embedded device, typically a microcontroller, usually in the form of binary or hexadecimal code. IDE Integrated Development Environment; software that includes all necessary tools for writing software, compiling it into object code and programming the object code into a target microcontroller. Some also feature a debugger. Interactive debugging The process of interacting with a running microcontroller to see what it is doing and to assist in finding bugs/errors. This can include pausing operation through the use of breakpoints, inspecting variables and registers and stepping slowly through program instructions. The debugger may require specific object code produced by the compiler to work. Microcontroller A chip typically containing a microprocessor, integrated peripherals, memory and sometimes storage. These features allow such a device to operate as a standalone computing device that can directly interface with attached hardware. Basically, a one-chip computer. Object code Code in a machine-readable format that can easily be converted into a memory image for programming into a target device, ready to run. A typical image format is the Intel Hex (.HEX) file format that MPLAB X IDE can generate. Production build Object code that can be used for deployment to a finished product, as distinct from a debugging build, which contains extra information only needed by the debugger. Production code is usually smaller and faster than debug code. Programmer A hardware tool that can be used to transfer a firmware image to a microcontroller. Some programmers (including the PICkit range) are also capable of debugging. Target A microcontroller (and perhaps the circuit it is part of) that will be programmed or debugged. The LED status bar (located just above the logo) adds a slash of colour to the PICkit 5; its intensity can be adjusted. Blue indicates the device is idle, while flashing green means it is in PTG mode. Australia's electronics magazine November 2023  67 Keeping the Internet Up By Nicholas Vinen This simple device for the home or office will automatically restart your modem or router if it stops working. It can’t stop your internet connection from dropping out, but it will save you the hassle of pulling the power to see if it’s the router at fault (which is often the case, unfortunately). I t is a sad fact that many of the routers used for NBN connections these days are not terribly reliable. They might work OK for a few days or weeks, then will suddenly quit for no apparent reason. Power cycling them will usually restore your internet connection, which can be annoying if you are not home, but other family members are. Or if it’s in a remote unoccupied office that you have lost your connection to. Ask me how I know! This device is based on the WebMite, with Geoff Graham’s MMBasic software running on a low-cost Raspberry Pi Pico W with built-in WiFi (August 2023 issue; siliconchip.au/ Article/15897). The MMBasic code periodically tries to make a connection to a remote server that you can expect to be operating most of the time (eg, Google, Apple, Microsoft etc). It will try several of those, and if it can’t connect to any, it will briefly interrupt the DC or AC power to your Modem Watchdog Kit SC6827 ($35 + postage): contains all the required (non-optional) items listed (12V relay). You just need a small enclosure to house it. 68 Silicon Chip router to restart it. It will then wait a little while and resume operation; hopefully, after that, it will be able to connect and continue monitoring the connection until it stops working again. It’s built on a small circuit board using only a dozen or so components. To keep it safe and simple, it is connected between the router’s power supply and the router, and it is powered from that same power supply. It will work with modems/routers powered with 9-24V DC or 6-15V AC and it only draws about 50mA extra from that supply. Circuit details The Watchdog circuit is shown in Fig.1. As most of the hard work is done by software running on the WebMite (Pico W), there isn’t much to it. AC or DC from the router’s supply comes in via CON1 or CON2 and is fed to header CON3 via the normally-­ closed contacts of relay RLY1. So most of the time, power is fed straight through to the router. RLY1 is activated for a few seconds when the router needs to be rebooted, briefly cutting its power. When RLY1 is released, the router starts back up and reconnects. Australia's electronics magazine RLY1 is controlled by the Pico W (MOD1) via NPN transistor Q1. When the Pico W’s GP22 digital output is floating or low, Q1 is off and so is RLY1. When the Pico brings that pin high, Q1’s base-emitter junction is forward-biased, and it sinks current from the negative end of the coil, energising it. The 470W resistor limits the base current to the required level; (3.3V – 0.7V) ÷ 470W = 5.5mA, so when multiplied by the transistor’s gain, it can sink around 100mA, more than enough for most typical 12V relays. Diode D2 prevents the coil’s negative end from flying above 12.7V when it switches off, which could damage transistor Q1. The positive end of the relay coil connects to the main DC supply rail via resistor R2. This can be a 0W link when that rail is close to 12V DC, or a 1W resistor with a value chosen to drop the voltage seen by the coil to 12V if the supply rail is higher. A 5V coil relay can be used with a suitable series resistor for a lower supply rail; more on choosing its value later. We also included a 4.7kW/1kW divider across the supply rail that feeds the Pico’s GP28 pin, which can be used for voltage measurements. We siliconchip.com.au USB supply feeding back into REG1. The Pico has an onboard 3.3V regulator, so we don’t need to provide it with exactly 5V. Software Fig.1: the main part of the Watchdog is the Pico W module (MOD1), relay RLY1 and NPN transistor Q1. They conspire to reboot the modem or router powered via CON3 when it stops working. Power for both the modem/router and the circuit comes in via CON1 or CON2. It is rectified, filtered and regulated to power MOD1. did this in case it was helpful for the Pico to monitor the plugpack’s output, which would allow something like a ‘brownout protection’ feature to be added. We’ve tested this function but haven’t enabled it by default, as it doesn’t seem that useful. Power output header CON3 can be wired to a suitable plug cut off a defunct plugpack or cable, or made from a new plug soldered to a length of twin lead. The CON1 input is an onboard 2.1mm or 2.5mm inner diameter barrel socket that many plugpacks will plug into, while header CON2 can instead be wired to an offboard socket if that’s easier, or your power supply’s plug does not fit CON1. Power supply To derive power for the Pico W, first, we apply the input from CON1 or CON2 to bridge rectifier BR1, which has a 220µF filter capacitor across its outputs. This will convert AC to DC, or if the input is already DC, it will ensure that a positive voltage is applied across that capacitor regardless of how the supply output plug is wired. For a 6-15V AC input, we can expect around 7-20V DC (6-15V AC × 1.414 – 0.7V × 2) across the 220µF filter siliconchip.com.au capacitor. We’ll get around 1.4V less than the incoming supply voltage for a DC supply, ie, 7.6-22.6V DC for the stated input range of 9-24V DC. 5V linear regulator REG1 is powered from the voltage across the 220µF capacitor with a 10W series dropper resistor and 100nF input bypass/output filter capacitors. The 7805 has a specified maximum input voltage of 35V, so it will easily handle the maximum expected voltage at its input. Its dropout voltage is around 2V at 1A, so it will be in regulation down to 7V. The WebMite is in sleep mode a lot of the time; when it is operating, it draws around 50mA on average. With a 24V DC input, we can expect REG1 to dissipate 880mW ([22.6V – 5V] × 50mA). That’s within the capabilities of a TO-220 package without a heatsink, although the PCB is designed to allow you to attach a small heatsink if you need to. In most cases, the input voltage will be lower, no more than 15V, so most users will not need to add a heatsink. The Pico W is powered from the output of REG1 via diode D1, which allows you to connect the Pico W to the USB port of a computer without the possibility of the computer’s 5V Australia's electronics magazine The software is written in MM-­ Basic, using Geoff Graham’s WebMite firmware to simplify the code. That is especially useful if you want to modify or customise it, as there is lots of documentation available for the WebMite, and it’s easy to alter its code over a USB or WiFi connection. The program is simple. It updates its onboard clock every two minutes using the internet NTP protocol. If your router is not working, that will fail. In that case, it then tries to connect to major web servers (google.com and microsoft.com), although it doesn’t request any data; it is just checking to see if it can connect. If all three attempts fail, it brings the GP22 pin high for five seconds to cut power to the router, then waits five minutes and reboots, to reinstate the WIFI connection, before it starts monitoring the internet connection again. The watchdog timer is also enabled so that, should something go wrong and the Pico W freezes for too long (at least six minutes), it will automatically reboot. Programming the Pico W You can do this before building the unit. It can be programmed before or after; it doesn’t make much difference, but it’s a little bit easier dealing with the Pico W before it has been soldered to our board. Use a micro Type-B USB cable to connect it to your computer and a virtual flash drive should be detected. You can either load MMBasic onto it, making it a WebMite, then install the BASIC code and set it up yourself, or load our “RouterWatchdogV1.uf2” The Modem Watchdog shown at actual size with the PicoW unplugged. November 2023  69 Replace ssid and password with your WiFi network credentials. After typing that command and pressing Enter, the Pico W will reboot and attempt to connect to your WiFi network. You can verify this has worked by reconnecting to the USB serial port, pressing CTRL+C again and typing: PRINT MM.INFO(IP ADDRESS) This should give you an address like 192.168.1.100, indicating that it is connected to your network, which means the device is now working. You can unplug it and proceed with construction. Component selection The assembled board, ready to be mounted in a small plastic case. file, which already has the BASIC code loaded and most of the settings configured. You can download that file from our website at siliconchip.com.au/ Shop/6/260 See the panel on loading the BASIC code and setting the options if you’d prefer to do that yourself. There are a few settings we can’t provide, like the WiFi network credentials, so once the firmware is loaded, you’ll need to open a serial connection to the WebMite to finish the setup. You can use a free program like PuTTY or Tera Term to connect to the WebMite’s virtual serial port at 115,200 baud. Press CTRL+C, and after a while, you should see the “>” prompt (be patient, as it won’t respond to key presses in sleep). Enter the following command: OPTION WIFI “ssid”, “password” 100nF CON2 REG1 VERIFY POLARITY CONSISTENCY COIL 100nF ~ – + ~ COIL 40 30 + ~ – + ~ MOD1 1 38 37 39 36 2 35 3 5 4 34 31 33 7 8 32 6 9 11 28 29 10 12 26 27 13 25 14 16 23 24 15 18 17 21 22 40 38 Silicon Chip Q1 CON3 ALTERNATIVES CON1 D2 Fig.2: the missing parts are for optional features. See the “Component selection” section of the article to calculate the value for R2 and select an appropriate relay. 70 19 20 1 2 37 39 36 R2 The Watchdog PCB layout is shown in Fig.2. Some components may depend on your router’s power supply voltage or are for features that aren’t required for the basic function, so those components are shown translucent, with their values in parentheses. Start by mounting the axial components, such as resistors and diodes; the diodes must be orientated with the cathode stripes facing as shown. Fit the bridge rectifier next, ensuring its + symbol is in the location shown, then the transistor with its flat face towards the top of the board. Now fit the two smaller capacitors, followed by the DC socket; try to make the latter parallel/perpendicular to the PCB edge before soldering it. Then you can install the two polarised headers, the electrolytic capacitor D1 10W B R1 RLY1 3 5 CON1 4 33 220mF 35 470W 34 31 + 32 28 30 Q1 29 CON2 26 CON3 27 23 25 24 21 22 (1kW) Construction MICRO USB–B PORT RASPBERRY PI Pico W SWDIO (4.7kW) 7 8 GN D 6 9 10 13 12 11 14 15 16 18 17 19 20 RP2040 MCU WIFI SWCLK MODULE The only components you may need to change are the relay (RLY1) and its coil’s series resistor (R2). Start by using a DVM to check the output voltage of the plugpack powering your modem or router. Determine whether it is AC or DC and its magnitude. If it’s 12-15V DC or 9-12V AC, you should be able to build the unit as per Figs.1 & 2 and the parts list, with R2 replaced with a wire link. If it’s above 12V DC but below 24V DC, or above 10V AC, use a 1W resistor for R2. For a DC supply with a voltage of Vin, its ideal value is (Vin − 13.4V) ÷ 0.044A. That’s based on the 44mA coil current for the JW1FSN-DC12V relay specified. For example, if the supply is 18V DC, you would use 104.5W ([18V − 13.4V] ÷ 0.044A), which we can round to 100W. For an AC supply above 12V (Vacin), multiply the voltage reading by 1.414, then plug the result into the formula above. For example, for 12V AC, 12V AC × 1.414 = 17V DC, which gives us a value of 81.8W, close to the preferred value of 82W. If your supply is close to 24V DC, you could go back to using a wire link for R2 and substitute a 24V DC coil relay for RLY2. For supplies below 12V DC or 9V AC, use a 5V DC coil relay for RLY1 with a series resistor. The formula for that resistor value is (Vin − 6.4V) ÷ 0.106A; if it’s an AC supply, again multiply the voltage by 1.414 first. For example, for a 9V DC supply, use a 5V relay with a series resistor value of 24.5W ([9V − 6.4V] ÷ 0.106A), which we can round to 22W or 24W. Similarly, for 6V AC, use 19.7W ([6V × 1.414 − 6.4V] ÷ 0.106A), so select either 18W or 22W. Fig.3: the only wiring strictly required is for the output cable that goes to the modem/router, as shown here. An external power input connector can be wired into CON2 if the onboard connector doesn’t suit your modem/router’s power supply. The polarity only matters because it must be consistent between the input socket and output plug if using a DC supply. Australia's electronics magazine siliconchip.com.au and the regulator. The electro has its longer (positive) lead towards the top of the board and the stripe on the can, indicating the negative side, towards the bottom. The regulator shouldn’t need a heatsink but its tab is near the edge of the board, so you can fit one if you want to. There are a few different ways to mount the Pico W. You can mount it horizontally or vertically; either way, you have three ways to solder it: solder the two boards directly to each other, use a header to join them, or use a header and socket, allowing you to easily unplug the Pico W. In our prototype, we mounted it horizontally into a socket so we could unplug the Pico W during development if necessary. However, it’s much easier to solder it directly using a header (straight or right angle), depending on what will fit in your box best. Therefore, the kit will include headers but no socket. Before soldering it, check if it will block access to two of the PCB mounting holes. If so, you’ll have to attach spacers to them first, and you might want to use Nylon screws to ensure they can’t short against the Pico W. We’ll leave the choice to constructors, but regardless of your method, check that you’re connecting it the right way around. Only half the pins of the Pico are soldered to the board, with pin 21 on the connector end of our board and pin 40 at the regulator end. If in doubt, check Fig.2. If mounting it horizontally, it will hang off the edge of our board. Finally, fit the relay. It will only go in one way. Ensure it is pushed down fully before soldering its pins. Then attach tapped spacers to the corners of the board using machine screws. Wiring For the power supply cable to the router, you will need a length of twin lead with a suitable socket on the end, as shown in Fig.3. We will supply a USB-to-barrel-socket cable in the kit, with the reasonably common 2.1mm inner diameter plug type. It will suit many routers but probably not all. The idea is to cut off the USB plug and crimp and/or solder it to a polarised header plug, then plug that into the output header, CON3. If the supplied cable is no good, you’ll need to find or make one with the correct plug for your router. siliconchip.com.au Parts List – Modem/Router Watchdog 1 double-sided PCB coded 10111231, 51 × 42mm 1 Raspberry Pi Pico W microcontroller module (MOD1) 1 12V DC coil 5A+ SPDT relay (RLY1) ● [Jaycar SY4050, Altronics S4197 or JW1FSN-DC12V] 1 PCB-mounting barrel socket, 2.1mm or 2.5mm inner diameter (CON1) 2 2-way vertical polarised headers with matching plugs (CON2, CON3) 1 20-way straight or right-angle header (for mounting the Pico W) 1 20-way female header socket (optional; to socket the Pico W) 1 barrel plug and cable from a disused plugpack or USB to barrel plug cable 8 M3 × 6mm panhead machine screws 4 10mm long M3-tapped spacers Semiconductors 1 7805 5V 1A linear regulator, TO-220 (REG1) 1 BC547 100mA 45V NPN transistor (Q1) 1 W02M/W04M/2W02/2W04 bridge rectifier (BR1) 2 1N4004 400V 1A diodes (D1, D2) Capacitors 1 220μF 50V electrolytic 2 100nF 50V ceramic or MKT Resistors (all 5% unless noted) 1 470W ¼W 1 10W 1W 1 1W 5% resistor (value depends on supply voltage and relay used; see text) ● a 5V or 24V relay might be required if the router power supply is unusually low or high MMBasic Code Listing WATCHDOG 65000 PRINT “Watchdog initialising” SETPIN GP22, DOUT PIN(GP22) = 0 SETPIN GP28, AIN ON ERROR IGNORE CPU SLEEP 60 DO WATCHDOG 65000 CPU SLEEP 60 WATCHDOG 200000 PRINT “Checking NTP” WEB NTP -10 IF MM.ERRNO THEN PRINT “Checking Google” WEB OPEN TCP CLIENT “google.com”, 80 IF MM.ERRNO THEN PRINT “Checking Microsoft” WEB OPEN TCP CLIENT “microsoft.com”, 80 IF MM.ERRNO THEN PRINT “Rebooting router” PIN(22) = 1 WATCHDOG 10000 CPU SLEEP 5 PIN(22) = 0 WATCHDOG 200000 CPU SLEEP 180 CPU RESTART ELSE PRINT “OK” WEB CLOSE TCP CLIENT ENDIF ELSE PRINT “OK” WEB CLOSE TCP CLIENT ENDIF ELSE PRINT “OK” ENDIF WATCHDOG 65000 CPU SLEEP 60 Australia's electronics magazine LOOP November 2023  71 Silicon Chip Binders REAL VALUE AT $21.50* PLUS P&P 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 goldcoloured lettering on spine & cover Silicon Chip Publications PO Box 194 Matraville NSW 2036 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. 72 Silicon Chip It doesn’t matter which way you wire it to header CON3, except that it needs to be consistent with the input connection to CON1 or CON2. To check this, ensure the output is not connected to anything and plug the power supply into CON1 or CON2. Use a DMM to check for continuity between the outer barrel of the power supply’s plug and the outer barrel of the plug that will go to the router. If not, swap the connections at CON3, then check again. We don’t want to reverse the polarity of the power applied to the router (although that won’t matter if it’s low-voltage AC). It’s a good idea to double-check this by plugging the power supply into a mains GPO and using a digital voltmeter to check the polarity of the Watchdog’s output plug. Make a note of whether the inside of the socket is positive or negative relative to the outside, then unplug the supply from the unit and verify that its output polarity is the same as what you measured coming out of the Watchdog. You can also check the sticker on the back of your router to verify it’s expecting the same polarity. Housing it The board is unfortunately too large to easily fit into the smallest Jiffy box (UB5), although it will fit comfortably into the next larger one (UB3). You could put it in just about any enclosure, or even use it as a bare board, as long as you’re careful that it can’t short against anything! If the onboard barrel socket doesn’t suit your router power supply, you will probably have to put it in an enclosure so you can wire up an appropriate chassis-­mounting socket via CON2. Testing Connect the output power plug to your router, along with all the other cables the router needs to operate. Power the whole thing up and check that the router lights come on and your internet connection is working after a few minutes. Leave it for 15 minutes to verify that the Watchdog relay does not trigger, causing your router to reboot. If it does, it probably can’t connect to your WiFi network, so connect the Pico W back to your computer and correct the WiFi credentials. Assuming it’s working, disconnect the internet cable from your router (from the NBN box or whatever is upstream). Wait a few minutes; you should hear the Watchdog relay click, and the router will reboot. Plug the internet cable back in, as it is all working as expected. If that doesn’t happen, you might not have loaded the firmware correctly. If you can’t figure out what has gone wrong, you might need to load the Pico W firmware again from scratch. That involves holding the white button down on the Pico W while plugging it into your computer via a USB cable so that the virtual flash drive SC appears again. Loading the firmware manually Start by loading the WebMite firmware onto the Pico W. You can refer to the August 2023 article on the WebMite (siliconchip.au/Article/15897). However, the procedure is basically the same as mentioned in the article; you just load the WebMite .uf2 file rather than the one specific to this project. It is also available to download from our website (siliconchip.au/Shop/6/230). The next step is to connect to the WebMite using the USB virtual serial port (as described in the article text), then load the BASIC code and set up the options. The BASIC file is called “ModemWatchdog.bas” and is part of the download package linked in the article text. Open the BASIC file in a text editor like Windows Notepad. Connect to the WebMite using Tera Term or PuTTY, run the “AUTOSAVE” command, and then in Notepad, press CTRL+A (to select the whole program) and CTRL+C (to copy it). If using PuTTY, right-click in the windows to paste the program, then press CTRL+Z. If using Tera Term, go to that window, press CTRL+V (or ALT+V) to paste the program, then press CTRL+Z. You should be back at the MMBasic prompt with the code loaded. You can check it has been loaded by running the LIST command. Now set up the options as below. Note that you’ll probably need to reconnect to the WebMite between some of them: OPTION WIFI “ssid”, “password” OPTION TELNET CONSOLE ON OPTION AUTORUN ON Australia's electronics magazine siliconchip.com.au 259 $ K 8673 200 in 1 179 $ K 8672 100 in 1 Introducing the Makerzoid® Robot Master Sets The Robot Master sets support the building of up to 200 different robotic projects - plus encourage kids imagination to go wild by letting them build whatever inventions they want! Each set contains hundreds of blocks, plus multifunction sensors, programmable motor and host controller. Kids will learn conepts such as transmissions, gearing, mechanical movement and Scratch programming along the way. Great for both home or classroom use. STEM building block sets for kids aged 6 and up. Builds skills gradually through levelled lessons. Uses Scratch programming as used in Australian schools. 47 robotic building courses across 3 skill levels. Compatible with big brand name blocks. Parent friendly storage case for all parts. Your electronics supplier since 1976. Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or shop online 24/7 <at> altronics.com.au Build It Yourself Electronics Centre® © Altronics 2023. E&OE. Prices stated herein are only valid until 30/11/23 or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. 1kW+ Class-D Part 2 by Allan Linton-Smith Image source: https://unsplash.com/photos/SP9HcRASMPE Mono Amplifier This seriously powerful mono amplifier module uses the International Rectifier IRS2092S Class-D controller and four IRFB4227 Mosfets. This amplifier module is available from DigiKey ready-built and can deliver over 1000W RMS! Having described how it works and is configured last month, we will now cover assembly and testing. W hen building such a powerful amplifier, the power supply is the biggest stumbling block. The only practical way to power this amplifier at a reasonable cost is by using multiple off-the-shelf switchmode power supplies. In this case, six 25V 20A DC supplies are wired in series, giving a total of 150V or ±75V when using a centre tap. Consider that you would need at least six 500VA transformers to provide the ±75V DC at 18A. Not only would that be extremely costly and heavy (over $1000 and 25kg), but the initial surge from switching it on would blow a fuse or circuit breaker unless some sort of soft starting was implemented. For comparison, the six switchmode supplies cost us $347, including delivery, and they weigh around 4kg in total. Our setup provides ±72V at a maximum of 20A DC. Each switchmode unit is an independent supply and is adjustable to 25V, which would give the recommended ±75V, although we didn’t find that necessary; we got plenty of power with the ±72V supply. The only supply adjustment we made was to match the positive and negative supplies within 0.1V to maximise the PSRR (power supply rejection ratio). Our performance tests were not conducted with any additional capacitance, although we will describe how you can add some if you want to. According to IR, it will lower the noise level, but the large capacitors required are a bit expensive. Photo 1 shows the all-important Class-D amplifier module with the basic connections made. Audio comes in via a double-sided RCA socket and is fed to a front panel volume control (a basic logarithmic response potentiometer) using an RCA plug lead. It then goes to the amplifier module via another similar lead. An internal volume control on the amplifier module PCB can set a maximum level, to frustrate ambitious volume twiddlers. Mains Wiring Caution This device uses connections to 230V mains power, so attention must be given to insulation and earthing. Only those who are experienced with mains-powered devices should attempt this project. Ensure you follow all our instructions regarding the mains wiring. High DC voltages (150V) will also be present during and after operation, and high voltages of up to 60V AC can be present at the speaker outputs. Avoid physical contact with exposed metal surfaces when operating the device and immediately afterwards. Switch off power and allow the supply rails to discharge before placing or removing measurement probes. 74 Silicon Chip Australia's electronics magazine The speaker output from the amp module connects to chassis-mounted binding posts via short lengths of heavy wire. You could customise it with a completely enclosed (Speakon type) speaker output socket. The latter would be a good idea since, at full power, the output can exceed 58V RMS, which is a shock hazard. The optional VU Meter mounts above the volume control; the needle enters the red zone when the output is over 1000W into 2W, 500W into 4W or 250W into 8W (see Photo 2). Housing it These parts are all housed in a metal case. We decided to use an aluminium toolbox as it was large enough, sturdy, not too expensive and convenient to carry around. We purchased ours from eBay (192790170418). The metal toolbox we used was made by “Sunrise”. It is 575 × 245 × 220mm, big enough for everything to fit snugly. It is sturdy, portable and has a latched lid for easy access, although it can be padlocked for safety. It is relatively easy to cut and drill. A handy plastic tool tray comes with the toolbox, although it is not used for this project. You might come up with a different idea; as long as it’s made of metal and large enough, it should do the job. Once you’ve obtained the case, power supplies, amplifier module and other bits and pieces, it’s time to siliconchip.com.au Photo 1: the IRAUDAMP9 ‘evaluation board’ with the Class-D amplifier IC (under the large heatsink) and support circuitry. The only required connections are the signal input at upper left, the speaker output at upper right and the ±72-75V DC supply rail inputs below that. If using the VU Meter, you’ll likely also terminate its signal wires to the two-way speaker terminal. Photo 2: while the VU Meter is a handy way to see how much of the amplifier’s power is being used, it needs to be calibrated for the particular load impedance to be accurate. start assembling it. Roughly, the steps will be: 1. Join the six switchmode supplies together into two sets of three and wire them together (see Photo 3). 2. Prepare the case by making the required holes and installing the chassis-­mounting components. 3. Add the chassis wiring. 4. Mount the switchmode supplies in the case & wire them to the chassis. 5. Mount the amplifier module on top of the switchmode supplies and connect it up. into the threaded holes of each switchmode unit with M4 machine screws and flat washers. It is critical that the twelve M4 screws that fix the top straps to the switchmode power supplies are no longer than 10mm; otherwise, they will touch the internals and may damage the supplies. Different supplies can vary (even if they look similar), so we recommend checking the “free-depth” in the data sheet for the supplies you purchased to verify that the 10mm screws are short enough to avoid damage. Leave at least 13mm between the switchmode units so that you can insert M10 bolts to attach them to the floor of the case, as shown in Figs.12 & 13 and our photos (including Photo Initial assembly You can see the final result we are aiming for at the end of the article in Photo 9, which shows everything mounted inside the case and wired up. For mounting the six switchmode power supplies, cut four top straps from 25 × 3mm thick aluminium flat bar and four bottom straps from 20 × 10 × 2mm aluminium rectangular bar and drill 4mm holes, as shown in Fig.11. Note that the negative (left) supply bank mains selectors are up, whereas the LEDs face up for the positive supply bank. The reason for this is to give better cooling and airflow. Flat straps can be used at the top, but rectangular tubes should be used on the bottom to keep the banks 10mm above the floor. That improves the airflow too. The top and bottom straps screw Fig.11: the four straps holding the power supply banks together are made from 170mm lengths of aluminium bar and rectangular tube. The bottom straps are thicker to allow enough air to circulate under the supplies. Holes for mounting the amplifier module to the top straps are not shown, as they are marked once the supplies are in the case. siliconchip.com.au Australia's electronics magazine November 2023  75 Photo 3: here’s how to wire up the six supplies in series and make the mains wiring. Note that we have not used crimp connectors at this early stage. They are not strictly necessary but, if crimped correctly, they give more secure anchoring with less chance of accidental shorts. Don’t skimp on the cable ties once the wire is finished, especially on the bundles of mains wires. 9). We used two bolts, but four would be better! Case preparation Remove the plastic tool tray from the Sunrise toolbox and remove the front decal (attached with some sort of sticky, rubber-like adhesive) to make room for the VU Meter and the front volume control. Next, make the holes for the M10 retaining bolts in the bottom of the box. Mark their locations after you have inserted the power banks because there is quite a bit of fiddling required so that the amplifier module will fit neatly on top of the straps, with its mounting holes located over the straps. The easiest way to check that is to attach four tapped spacers to the amplifier module mounting holes using short M3 machine screws and place it on top of the straps. Verify that the module is not wobbly and that the spacers are centrally located on the straps. Once you are happy with the setup, mark the bottom of the box with a bit of paint on the bolts. Drill 10mm holes and check out how the retaining bolts will work. We used a nibbling device to sink the bolt heads neatly into a small square at the bottom so they wouldn’t turn during tightening. With the holes made, remove the power supply banks and start marking out the other holes and cutouts in the case, shown in Fig.14. Some of these holes are optional; for example, you don’t need to make the VU Meter cutout at the front unless you’re going to install the VU Meter. You could also omit the volume control if you will have an external control (although we recommend you fit it anyway as it will probably come in handy at some point). You could also only drill one pair of holes for binding posts if your load impedance will always be below 8W. For the vent, ensure the rectangular cutout isn’t too large and leave the four corner mounting holes until last. You can mark the positions using the actual vent as a template to ensure they’re accurately placed. When mounting the vent, use M4 machine screws and nuts with washers under each nut. Be accurate when making the hole for the switched, fused IEC socket because it has to snap into place – see Photo 4. To do this, scribe the hole and use a small drill to make a hole in each Fig.12: a side view showing how the power supplies, amplifier module and optional capacitor bank are installed in the case. Both Figs.12 & 13 are shown at 25% of actual size. Fig.13: an overhead view showing how the power supply components are arranged in our toolbox case. While we used one M10 bolt to hold each supply bank in place, we recommend you use two for each. 76 Silicon Chip Australia's electronics magazine siliconchip.com.au Photo 4: the amplifier’s rear panel, with the input connector at the top, the 2-4W output terminals below that and the 8W output terminals just above the switched and fused mains input socket. The vent we used was discontinued, so we’ve specified a slightly smaller one. Also note that the RCA input socket has been moved down as we had trouble with the lid hitting it on the prototype. corner (3mm is good), then drill a larger hole to allow a hacksaw blade in your jigsaw to pass through and carefully run the blade up to each corner. File it until the IEC socket snaps into place. The hole for the VU Meter is 85 × 44mm. You can also cut it with a jigsaw; drill a hole in the centre slightly bigger than the blade, then cut up to each corner. You can also use a nibbler tool (Jaycar TH1768). The round hole for the front volume control will be either 7mm or 8mm in diameter, depending on the potentiometer you are using. Make a hole for the fan and fan guard on the right-hand side of the box. You could use a different sized fan to ours (eg, you could go for 80mm or 150mm) but 120mm fans are widely available and often very quiet for the amount of air they move. Cut the required hole for your fan by drilling a small hole, then drill a larger hole to enable you to use a jigsaw fitted with a hacksaw. A nibbler tool can also be used. Make sure everything fits and deburr all the holes; you can use a large drill bit to deburr the round holes and a file, sandpaper or emery paper to smooth the others. Clean out the box carefully after doing that by vacuuming and then wiping it down with a damp cloth, as you don’t want any metal filings floating about inside the amp. Mount the RCA socket, binding posts, IEC mains socket, vent, fan and fan grille and ensure they are all secure before proceeding. Verify that the binding posts and RCA socket are insulated from the toolbox chassis. If you find that the lid hits the RCA socket when opened, attach a rubber foot above the RCA socket to limit how far the lid can open. Photo 5: the inside of the case rear. The audio input is a double chassis-mount RCA socket, while output connectors are binding posts. The lower output for 8W loads has an extra 75µH choke to prevent a spike in the upper end of the frequency response that could damage tweeters. Wiring Cut the RCA-RCA cable such that you have a sufficient length to go from the input socket at the back to the potentiometer at the front, then solder its outer braid to the potentiometer’s anti-clockwise lug and the inner conductor to the clockwise lug. The remaining cable section will go from the pot to the amplifier module, with its braid also soldered to the anti-clockwise lug and the inner conductor to the wiper. While you still have good access, assuming you’re fitting two sets of binding posts (as we did), partially unwind the 100µH inductor until it has 25 turns left to make it siliconchip.com.au Fig.14: the positions for the required and optional holes in the specified case. The cutout for the VU Meter and the second set of binding posts are two that you could omit. If your case is different, you could use a similar arrangement. Regardless, it’s best to check that everything will fit after marking the hole positions before cutting and drilling. We have shown the fan cutout as 120mm, but you might need a smaller or larger cutout depending on your fan. Australia's electronics magazine November 2023  77 approximately 75µH, then crimp eyelet lugs to its leads and connect it between the two red binding posts. Secure the inductor to the side of the case using some neutral-cure silicone sealant, as shown in Photo 5. For all the crimping in this project, use a good-quality crimping set and mains-rated wire for the mains connections. Leave wires long enough to allow you to make connections before mounting everything in the case. Cut a length of heavy-duty figure-8 speaker wire or two similar heavyduty wires to go from the binding posts to where the output connector will be located on the amplifier module. Crimp eyelets onto the ends and connect them to the 2-4W binding posts, as shown on the wiring diagram. Make up a second short length of heavy-duty wire with eyelets on each end and connect it between the two black binding posts. Now is also a good time to crimp a spade lug to one end of a length of 10A mains-rated green/yellow striped wire and an eyelet to the other. Push the spade lug onto the IEC connector Earth terminal and ensure it is secure. Drill a nearby hole in the base of the case and use an M4 machine screw and two nuts to connect the eyelet to the exposed metal of the case. The Earth screw must not be used to attach anything else to the case, although it’s OK to connect other Earths (such as for the switchmode supplies) to the same screw. Use a shakeproof washer between the case and eyelet to ensure a good electrical and mechanical connection. Tighten the top nut onto the other to make it a lock nut. Power supply wiring The power supply wiring is shown in Fig.15. Start by wiring up the switchmode power units in series. While you can screw bare wire into the screw terminals, it’s far better to crimp a fork lug onto the ends of the wires. For example, that prevents any stray wires from causing short circuits. Use a proper crimping tool so they are secure. Note that each unit has three terminals for each of the positive and negative outputs, which are common. So you can use any +24V positive or any 0V negative connector when wiring it up. The translucent window clips into place for protection when you’ve finished. Ensure the mains wires are long enough to reach the IEC input socket, while the DC wires will need to extend to the screw terminal on the amplifier module. Use cable ties to tie the mains wires together and insulate them as shown. The Earth wire will go to the chassis Earth lug (place its eyelet lug on top of the other), while the Active and Fig.15: note that the specified switchmode supplies have three pairs of DC output terminals. If using a 24V fan, connect it to the outputs of one of the switchmode supplies rather than the buck converter. You can omit the buck converter entirely if using a 24V fan and no VU Meter. A LED and 39kW 1W resistor can be connected across the ±75V supply to indicate voltage. All mains wire is rated at 10A; power supply & speaker wire must be minimum 15A rated. 78 Silicon Chip Australia's electronics magazine siliconchip.com.au Photo 6: make sure your Jiffy box covers the IEC socket and wiring like ours. The Jiffy box can be secured by using small right-angle brackets, screws and nuts. One of the optional 10,000µF capacitors is visible in this photo; it was added after all the performance measurements shown in the first article. Neutral wires will go to the switched IEC socket. After checking that they will be long enough to reach, you can crimp insulated spade connectors onto the Active and Neutral wires (see Photo 8) and an eyelet lug onto the Earth wire. You will also need two short Active and Neutral wires with insulated spade connectors at each end to connect the IEC connector’s switch and mains input terminals, as shown in the wiring diagram. When finished, plug them in and check they are secure. The buck converter Note that this converter is not required if you use a 24V fan and no VU Meter. In that case, the fan connects directly to one of the spare sets of DC output terminals of the nearest switchmode power supply. If using it, connect the input wires of the 24V to 12V buck converter to the outputs of one of the switchmode power supplies (the one closest to the fan is probably the best) using crimped fork connectors. Solder the 12V DC output wires to the fan wires (assuming you’re using a 12V fan) and insulate the joints with heatshrink tubing. At the same time, if you are using the VU Meter, solder its two outer supply terminals to the same 12V DC output wires (the polarity doesn’t matter as the backlight is a tungsten lamp). Final assembly The wiring in the case should now be sufficiently complete that you are ready to drop the switchmode supply assemblies into the case and fix them in place using the M10 bolts. While doing that, connect the mains wires for the switchmode supplies to the IEC mains socket terminals, as shown on the wiring diagram. Place the left (negative) bank of three supplies into the toolbox. It will be a tight squeeze, but it should fit if you angle the bank with the wired side slanting into the front and then push the back down until it sits on the bottom. Mount the buck converter on top of the right bank using foam-cored double-­sided tape. Now cut 60mm off the end of a UB5 Jiffy box so you can place it over the mains connections, like in Photo 6. Later, once you’ve tested the amplifier and found it to be working, you will need to secure it in place using right-angle brackets, screws and nuts connected to the base. This is important; not only are there exposed mains conductors on the back of the IEC socket, but it’s also quite close to the input & output terminals. If one of those wires came loose and touched the IEC socket, it would be a severe hazard, so don’t skip this step. If using the optional chassis-­ mounting capacitors, you can install them now, in the middle of the case between the switchmode supplies. Wire them up to the DC bus being very careful to get the polarity correct. The positive terminal of one goes to the +75V rail, the negative of the other to the -75V rail and the two remaining terminals to the 0V rail. Getting this wiring wrong would be a disaster! It’s a good idea to test the power supply before installing the amplifier module. Double-check everything to ensure there are no errors and that none of the unterminated wires are in a position to short against anything (or each other). Also, if the switchmode supplies have a mains voltage range selector switch, ensure they are all set to the correct setting (220-240V for Australia & New Zealand). With the Jiffy box covering the mains terminals and the power supply Photo 7: the lefthand bank of (negative) supplies; you can see the orange trimmers that adjust the supply output voltage. The thick rail at the top goes into the bottom of the case (the supplies are flipped when installed) to allow cooling air to circulate under the supplies. This photo was taken before all the cable ties were added. Each cable should be tied in place and the mains should be separate from the other wiring siliconchip.com.au Australia's electronics magazine Photo 8: a close-up of the mains connections to the IEC input socket before the protective Jiffy box has been placed over them. November 2023  79 plastic shields clipped in place, connect mains power and turn it on. Use a DMM to check for 72-75V between the 0V wire and the other two DC supply wires. Verify that the polarity is correct for each too. You can now adjust the rails to within 0.1V using the adjusters on one or two switchmode units to ensure the lowest possible noise and distortion, but it is not critical. When finished, switch it off and let the capacitors discharge (connect wirewound resistors across the supply rails if necessary) until the outputs are below a couple of volts. Do not proceed to work on it until they are fully discharged. Amplifier module mounting It is time to mount the amplifier module on the upper supply rails. There are two basic approaches to mounting the module. The easiest is to attach the tapped spacers to the amplifier module, place them on top of the rails, and glue them to the rails using a generous amount of neutral-cure silicone sealant on each. That should give a secure anchoring (the module isn’t super heavy). The superior approach, which takes a bit more work, is to place the module on the rails and mark the four positions where the screw holes are located. Then you remove the rails from the switchmode supplies one at a time, drill 3mm holes and countersink them on the underside. Use short countersunk head M3 machine screws to attach the spacers to the rails, then reattach them to the supplies. You can then screw the spacers on top and use short panhead machine screws to attach the module once all four spacers are in place. With the amp module secured, you can complete the wiring. Plug the RCA input socket into the socket on the board and connect the +75V, 0V and -75V supply rail wires to its DC supply inputs, being very careful to connect them to the correct terminals. Connect the output wires to the binding posts you prepared earlier, as shown in Fig.15. That just leaves the VU Meter signal wiring, if you are using it. If so, connect its two inner terminals to the amplifier module’s output terminals as shown in the wiring diagram, with the required series resistor and diode connected inline with those wires, covered with heatshrink tubing (including the solder joints). The diode anode goes to the terminal on the meter labelled −. The 120kW resistor sets the VU redline at 1700W into 2W but you could use a lower-value resistor if your target output power is less, such as 33kW or 47kW. Heatsinking Given the forced airflow we’re providing with the fan, the heatsink on the amplifier module should be adequate. However, if you’re going to drive it flat out all the time, you might want to add more metal and area to the heatsink. The amplifier will cut out if the heatsink reaches 100°C. If doing this, make sure the heatsink you choose to add on will fit in the box with the lid closed. In this case, we recommend that you bolt it to the existing heatsink using a bracket, as shown in Fig.16, and use thermal compound between each heatsink and the bracket. Photo 9: the switchmode banks fit nicely into the aluminium toolbox and the kilowatt amplifier occupies a small area on top mounted on plastic insulators. The small module on the right provides 12V from the 24-25V output of any of the switchmode supplies, to power a 12V DC fan and the VU Meter backlight. 80 Silicon Chip Australia's electronics magazine Testing Now double-check all the wiring, especially the power connections to the amplifier. Once you’ve verified that everything is connected correctly, set the S1 & S2 switches on the PCB to their central positions (“on” and “self”) and also set the PCB-mounted volume control to the halfway position. Set the external volume control to the lowest position. Make sure the RCA cable is connected to the “CH1” RCA socket on the PCB. Begin the startup procedure: 1. Check that you have a 10A 250V rated fast-blow fuse in the IEC mains input socket fuse holder. If not, fit one now. 2. Connect a speaker to the output terminals. If you have two sets, make sure you use the right pair. 3. Connect a line-level signal source to the RCA input. Re-check that the volume control is at minimum. 4. After verifying that you are nowhere near any mains conductors, apply power. 5. The red LED (Protection) should turn on almost immediately and turn off after about three seconds. 6. The green LED (Normal) should then light up and stay on. 7. Slowly wind the volume control up and check that you get undistorted audio from the speaker. 8. If there is a problem, switch the amplifier off immediately, remove the plug from the mains and allow 15 minutes for the capacitors to discharge before investigating. If all is well, secure the Jiffy box with M3 screws and nuts. You’re ready to SC bring the house down! Fig.16: most users will find the heatsink supplied with the module adequate, but if you will be pushing the amplifier very hard, consider attaching a larger heatsink (or even just a strip of aluminium) to it. siliconchip.com.au SAVE $20 Dual 4K <at> 60Hz HDMI outputs. Get yours for 129 $ Pi HAT and camera friendly. ZR6302G On-board BLE, AC Wi-Fi & wired ethernet 4GB on board memory Pi friendly GPIO connections Welcome to the ROCK! The new Pi alternative. The ROCK 4C+ offers a reliable and high spec alternative to Raspberry Pi. With all the same GPIO connections, form factor and compatability with Pi 4 accessories such as HATs, cameras and cases. You can get started quickly with a range of operating system choices including Android, Debian and Ubuntu linux. Get making! Handy deals to build & design. Jakemy® 106 Piece Precision Driver Set T 2183 SAVE 22% 27 $ An affordable do-itall servicing set with 92 4mm chrome vanadium bits, flexible extension bar, tweezers & magnetiser ring. 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Shop in-store at one of our 11 locations around Australia: WA » PERTH » JOONDALUP » CANNINGTON » MIDLAND » MYAREE » BALCATTA VIC » SPRINGVALE » AIRPORT WEST QLD » VIRGINIA NSW » AUBURN SA » PROSPECT Or shop online 24/7 <at> altronics.com.au Build It Yourself Electronics Centre® © Altronics 2023. E&OE. Prices stated herein are only valid until 30/11/23 or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. SERVICEMAN’S LOG Charge of the light yardwork Dave Thompson Spring has sprung, the blossoms are out, days are getting longer and it isn’t as bone-crushingly cold as it was. It’s a time when the lawn starts growing like it’s on steroids and the garden is begging for a recharge of soil and nutrients. But the soil wasn’t the only thing that needed a recharge. Spring is also the time to break out the mechanised garden tools and lubricate chains, sharpen trimmers, recharge batteries, check oil levels and change plugs. There’s more than enough to do! Over the lockdown period, I built a garden shed to house all that stuff. I was sick of tripping over the mowers, chainsaws, spades and rakes stored in my main workshop, which I couldn’t use without removing all that stuff first. The shed was one of those build-it-yourself flat-pack kits you can buy at many of the big-box hardware stores. It came with about a million bolts and widgets, plus a booklet on how to assemble it, which is only helpful if you need to start a fire. None of the numbers on the bags of parts seemed to tally with the legends on the expanded diagrams of how to put each section together. It would say something like, “Take 15x A3 round-head bolts and 15x D5 square lug nuts, and using 15 x washer M6, assemble the door.” I should be so lucky! Nothing made sense at all. There are no prizes for guessing where this shed (and its user manual) was produced. I would usually have a very capable builder friend come and take a look at the whole thing and get him to suggest any improvements that could be applied during construction, but due to the lockdown, we couldn’t. Instead, I consulted with him using WhatsApp video calling. I ended up soldiering on with it myself, adding extra timber bracing, stronger door jambs and a few other ideas he pointed out. I also ditched the bolts and decided to use rivets instead. I had more than enough of all sizes and shapes that I had gathered over the years (I inherited about a gazillion from Dad’s estate). I also have a very handy pneumatic rivet gun, which saved the hand-crushing pain of doing it with a pop riveter. It also meant I could install the rivets from one side of the wall without needing to have someone holding a nut and spanner on the other side of the panel. That was going to make life much easier. The plan was also to use proper, heavy-duty Tek screws to hold the frames of the walls to the timber floor, which I’d already put in place before the lockdown. The kit came with inadequate (in our opinion) screws. I suppose the basic shed would be sound enough without adding the extras; after all, they sell them and people build them, but I felt better knowing it would remain standing in some of the gale-force winds we experience here at this time of year. I’ve already had one partial car-port-­under-construction wind up in the neighbour’s backyard. If it happens once, it could be considered an accident, but twice would make it seem deliberate! Note to prospective shed builders: having someone else to hold and steady the assembled walls whilst bolting and riveting them together is a real help. I managed it by balancing them on ladders and temporarily erecting scaffolds made from scrap timber. I also made sure to do it on days when the wind wasn’t blowing! So, now I have a shed to store all my tools, and they are handy to the garden as well. The weed wacker was knackered The other day, I went to get my weed whacker, a rather beefy, well-known brand yellow electric model and discovered that the 54V 9Ah battery was dead flat. I wasn’t too surprised; after all, it hadn’t been used for almost five months, although I had fully charged the battery before storing it. Pressing the button on the side, which usually shows the battery status via a three-stage LED display, resulted in three dark LEDs. Zero, zip, zilch, nada; nothing. So I took the battery to my workshop, where my array of chargers reside (there is no power in the shed) and plugged it into the matching yellow fast charger. The red charge light flashed briefly and went out. Usually, it would flash once a second, the internal cooling fan 82 Silicon Chip Australia's electronics magazine siliconchip.com.au Items Covered This Month • • • • • Not all instructions are created equal The malfunctioning security camera Solving TV program transmission problems Once upon a time in the Navy Repairing a weight scale 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 would fire up, and it would eventually turn solid red once the battery reached full charge. Hmm. I made sure the mains plug for the charger was seated correctly and that the four-way socket it was plugged into was switched on and had power to it, but I still got nothing. I removed the battery from the charger and replaced it again. No light at all. Uh-oh, this turned dark quickly! Anyone who knows anything about lithium-ion batteries will be aware of the ramifications of allowing them to fully discharge and fall below their minimum state of charge (SoC). That often results in one or more dead cells and, by extension, a dead battery pack. The minimum SoC is typically about 20% of a Li-ion battery’s capacity. If internal leakage drains it even further, such as when it’s being stored and not being charged, the cell will likely fail. The general rule is to only use the battery between 50% and 100% of its capacity, with cycling down to under 20% not recommended (as was the case with keeping NiCad batteries alive). For more information on this, see our series on batteries in the January-March 2022 issues (siliconchip.au/Series/375), especially p15 of February 2022 and p50 of March 2022. Still, let’s not get bogged down in the details. These 54V tools and batteries are not cheap, so just biffing it in the bin was out of the question, especially when I have the Serviceman’s Curse and ‘might’ be able to do something about it. And on closer inspection, the pack was only screwed together, unlike some which are glued, never to be opened (without some serious cutting, anyway). Bonus! Assaulting the battery So the obvious solution was to tear into this pack and see what we were dealing with. But I’ve been bitten before with battery packs. There could very well be a low cell (or more) inside, but I also knew there would be some electronics, like a BMS (battery management system) and perhaps also a thermistor, thermal cutout or a line fuse. The capacity of these batteries is approaching levels that shouldn’t be trifled with. There are now 60V and even 120V versions of this pack. They’re for a different family of tools, but are potentially dangerous to work with. My battery pack fits a wide range of 18V and 54V tools. It has a mechanical toggle switch that changes the output depending on what tool it is plugged into, and that switch is activated when you slide the pack into place. It’s a clever system. If I plugged this battery pack into an 18V drill, for siliconchip.com.au example, the cells are wired in series/parallel via that switching arrangement. If plugged into a 54V tool, they are all wired in series. It’s basic but clever. Of course, an 18V pack will do nothing in the 54V tools, but the 54V batteries are backwards-­compatible. So, it was time to open it up and see what was happening. In their wisdom, the company had screwed it shut with what looked like T9-sized Torx security screws. These are the ones with that annoying ‘nipple’ in the centre, so only a hollow-point tip would work. These screws really annoy me. Even many entry-level DIYers likely have a tip like this in their tool collection, so who is this security fastener folly meant to stop? Children playing with Torx drivers? I learned a little later via YouTube of a technique that involves using a pin punch or even a hardened concrete nail to ‘ping’ that little nipple out of the head of the screw (if you can clear gain access to the screw head, that is). Still, since I had the right tip, I decided just to use that. The heavy plastic side covers come off relatively easily once those screws are removed, revealing that the inside of the battery is built like a concrete bunker. The pack is quite heavy (1.4kg) and the construction is robust. There is virtually no free room inside, with the cells tightly packed. They all appear to be mounted into some kind of honeycomb-­style framework. The fifteen 18650 cells are connected in three groups of five, with the charging and output being controlled by a printed circuit board (PCB) that also varies the voltage output depending on the mechanical switch position. The cells are connected with spot-welded metal links, and I was very careful not to drop screws or bridge any of the links with a screwdriver. Significant flexible ribbon cables connect various points on the cell links on either side of the pack back up to the circuit board and charging socket. I could see I would have to do some research because it didn’t look easily repairable. If, for example, I had a dead cell (or several dead cells), I’d have to desolder the flexible connectors and break those splat-welded links. That’s likely easy enough to do, but putting it all back together again would be tricky given that I don’t have a spot welder that would handle links that size, and soldering directly to these batteries is usually fraught with problems. It might be possible to source new cells with solder tags already welded onto them, but I’m getting ahead of myself. A fatal flaw revealed I did what anyone would do and hit the interwebs. There’s a wealth of information on the ‘net, which presents a problem: sorting the gold from the dirt. Using very specific search words is the answer, and I found a lot of information on this particular battery pack, which proved incredibly helpful and saved me a lot of time and effort. As I’ve learned so many times before, just rolling my sleeves up and piling into something can often lead to disaster, or at worst, failure, and a waste of time and money. I found evidence of a known problem with these battery packs: the middle cell in each group of five is likely to fail because of how the packs are wired and how the charger works and supplies charge to them. The result is that those cells are charged less consistently than the others in the chain. Australia's electronics magazine November 2023  83 That could have caused my problem. If it had, I thought that buying another battery pack would be the best option. However, given that mine was less than 18 months old, I thought it was a short time for a battery to fail from such a fault, as it would have likely seen only about 10 hours of actual use. While browsing the web, I also began seeing a lot of YouTube videos offering a ‘hack’ on how to resurrect these batteries, but only if the symptoms were the same as mine. That is, no LED indicators light on the battery when the test button is pushed, and when put in the charger, it won’t charge, with the red charging light flashing briefly before going dark. These videos are legion and of course of varying quality, both visually and with the information they communicate. The majority of people making those videos don’t know why this fault happens or why the ‘fix’ works. They only state that the hack ‘jump starts’ the battery into charging again. This is an old trick with NiCads and other types of batteries, and while it has varying degrees of success with those types, it is not a recommended practice for lithium-ion batteries. Typically, even if the Li-ion battery does get some ‘kick’ out of it, the capacity and charging capability are usually way down on what they should be. So, at best, if anything, this hack is a stop-gap measure that might or might not give me a little more time to use the battery in my tools before I’d be buying a new one anyway. Most of these demonstrations on the internet have a couple of flaws. The first is that many of these guys use an identical battery to ‘jump’ the dead one. That leads to the question: if you have another battery, why don’t you just use that one in your tools? If you don’t have another battery, you have to use either a car or a bike battery to do the ‘jump’. Still, not many of us have a spare one of these sitting around, and besides, I wouldn’t be too keen on wiring this pack up to my Suzuki Vitara battery without at least removing it from the car. What a faff all that would be. Fortunately, I have several good bench power supplies 84 Silicon Chip I’ve built from excellent designs in this magazine (and others), so I decided to use one of those to jump this pack. One of the bench supplies is a bit more ‘disposable’ than the others, and indeed, I have rebuilt it several times over the last 20 years! The ‘method’ used by most of these ‘job site’ type guys making the videos is to simply connect the positive and negative terminals of the donor battery to the same terminals on the dead one. Usually, there is a spark and a splat when connected, and they only leave it for a few seconds before pulling the wires free. They then place the dead battery into the charger, and voila! The charge light comes on, the angels sing, and they have resurrected the dead pack. What they don’t say or cover in any of these videos is how long the charge takes or how long it remains useful compared to a new battery. That’s what I’d be more interested in, which is why I kept looking past the cheap ‘hack’ for more information. I finally found some in a video put together by one of the more switched-on YouTubers, Matthias Wandel, who actually bothered to dig into the reasons behind the failure of this type of pack. He broke one pack down and explained how it worked, likely why the same three cells fail and much more good information. Might as well jump Regardless, I still had a dead pack, so I made up some leads with some heavy-gauge wire and cranked the bench supply flat out to 20V and as many amps as it could deliver (theoretically, five). I connected it, got the sparks and held it for five seconds. I removed all the leads and put the battery in the charger. Well, cue the angels because the charger kicked in. I left it to complete its cycle and, the next morning, plugged it into my chainsaw and weed whacker. It certainly powered them OK! As to how long it lasts, it would be hard for me to say as I have no control battery to try, but I’ll use this one until it dies, then buy another one. For now, it works, so ‘hack’ confirmed and now to the garden! Editor’s note: it is common for the BMS to disconnect the cells from the outside world if the battery voltage falls too low. This will often make the charger fail to sense the battery (and hence refuse to charge it). A proper BMS will still allow some current to flow into the battery so that you can recover it externally, although some possibly don’t. The recommended practice for a Li-ion/LiPo battery that has fallen to a low voltage is to charge it very slowly, over a few hours or a day at perhaps 100mA, until its voltage returns to something more normal. It should ideally be charged on a non-flammable surface like concrete. You can then attempt to charge it normally, but keep an eye on it and switch off charging if it starts to swell or get hot. That approach has a good chance of restoring most of the battery’s capacity, even if it fell to quite a low voltage, but it is certainly not guaranteed. A malfunctioning IP security camera G. C., of The Gap, Qld probably spent too long on fixing a malfunctioning security camera. Still, the perseverance paid off and the camera eventually returned to service... We have several security cameras at our home, enabling us to look at the images anywhere in the world if we have Australia's electronics magazine siliconchip.com.au an internet connection. A few years ago, one of the neighbour’s vehicles was stolen from his driveway in broad daylight. We were able to provide the police with useful information from the recorded video of the incident. In 2021, on an extended caravan trip to Far North Queensland, my wife monitored the cameras regularly to check on our house. Our newspaper was still being delivered even though it had been cancelled, and she was able to request the provider to take corrective action. An unexpected parcel was delivered to our front doorstep, so we asked a helpful neighbour to collect it. One night on this trip, my wife noticed that one of the cameras facing the driveway was showing a very dark image. Over the ensuing weeks, we noticed it occurred about two nights every three. So there was an intermittent fault with that camera. These Swann cameras have a ring of red LEDs around the lens to illuminate the surroundings at night. I suspected a fault with them. I presumed that the wavelengths of these LEDs extended into the infrared region and wondered what type they were. In my spare time, I emailed a couple of my learned friends to see if they had any security camera experience. One replied that the problem might be caused by a faulty infrared (IR) cut filter. I had not heard of these filters before, so I had to do some internet sleuthing. I discovered that camera sensors detect near-infrared light that is invisible to the human eye. In daylight, a security camera uses an infrared cut filter to filter out unwanted IR light to represent colours accurately. When the camera is operating in night mode, the IR-cut filter is switched out to allow the camera’s light sensitivity to reach very low lux levels. I thought these infrared filters would use some material that became opaque to IR with an electric field applied, but research revealed that these filters were much more primitive. They were usually moved in and out between the lens and the photosensor device mechanically, using a solenoid. When we finally arrived home, I established that the red LEDs on the camera in question illuminated at night, so the IR cut filter appeared faulty. Interestingly, the IR cut filter was always switched in correctly during daylight without exception. It only failed to switch out some nights. Dismantling the camera, I found two wires going to a layer between the lens and the photo sensor. After removing three tiny screws, I could remove the lens and reveal the IR cut filter. I could see that the solenoid was driven directly by an SMD. The IR cut filter consisted of a moving ferrite magnet with an attached arm that toggled the IR filter in front of or away from the sensor. The magnet moved one way or the other depending on the polarity of the pulse applied to the solenoid coil. I found many shards of ferrite material sticking to the magnet, and the cause soon became apparent. There was a fissure in the ferrite, causing it to shed material, I suspect due to a manufacturing defect. I gently removed the shards with a small stiff artist’s brush and a jeweller’s screwdriver. I wondered if the floating bits of ferrite were intermittently stopping the magnet from pivoting the full 45°. Still, I had a niggling doubt that there may be something else wrong, given that it always switched the filter in during daylight. siliconchip.com.au After reinstalling the camera, it was disappointing to find that the IR cut filter did not ever switch out at night now. I don’t know what I had done, but the camera did not like it! It was probably beyond repair; although various IR cut filters were available online, none were like the one used in this camera. A few days later, I had a thought. I removed a fully operational camera and dismantled it. As expected, the ferrite magnet was in pristine condition. With a magnetic compass, I carefully identified the north and south poles of the magnet. Then, with an unmagnetised small screwdriver, I got some idea of the magnet’s strength – very subjective, but better than nothing. I again removed the IR cut filter from the faulty camera. This time, I endeavoured to clean out any debris between the magnet and the coil former with part of a razor blade. With a strong ferrite magnet recovered from a loudspeaker, I attempted to strengthen the magnetisation of the filter’s magnet, taking care not to reverse its polarisation. I suspected that the loss of magnetic material had reduced its field strength, resulting in marginal performance. After reassembling and re-mounting both cameras, it was pleasing to see both cameras working properly. Unfortunately, after six weeks, the camera failed again. This time, after much internet searching, I found a Chinese supplier of IR cut filters of similar dimensions. The new IR cut filters were not physically identical to the original, but after shaving off bits of plastic, I made one fit. The new filter was thicker than the original, so it was necessary to re-focus the lens. The camera manufacturer had been over-zealous with the glue used to stick the lens to its mount. I had to carefully scrape it off before the lens would budge. When the camera was reinstalled, I found, much to my chagrin, that the IR cut filter did not work. On one of the seller’s descriptions, I found that the filter should operate at voltages from 3.5V to 5.0V, and I verified that it worked after Australia's electronics magazine November 2023  85 completely disassembling the filter. However, it refused to operate when I reinstalled the cover over the mechanism and the lens mount. Pulling it apart again, I found that a plastic ridge around the optical opening was impinging on the operation of the moving arm. I gingerly pared away some material with a small wood carver’s tool and, when I reassembled the filter, it appeared to work satisfactorily on my workbench. However, when reinstalled, objects on the right side of the image were tinged in pink with the lights on, while at night, the image was black. I purchased an RJ45 coupler so that I could connect a long Cat5 cable to the cable going back to the security cameras’ recorder, which was hidden in an inaccessible place. With the camera plugged into the extension cable, I could conveniently work on it at a table. I removed the outer shroud, the lens mount and the plastic cover over the filter’s mechanism. By simulating day and night-time conditions, I could directly watch the operation of the filter. If only I had done this earlier, I would have saved myself much angst! Immediately, the problem was obvious. The filter plane was toggling perfectly, but it was entirely out of phase, ie, it was switching the filter in when it was dark and vice versa. It was a simple matter of cutting the wires to the filter and transposing them. Finally, after such a protracted period, the camera was working perfectly. Solving problems in TV program transmission G. G., of Macleod, Vic relates a servicing story from nearly 50 years ago. He likely remembers it because the cause was so unusual... From 1963, television stations in Melbourne and Sydney often shared program material via the three pairs of ‘tubes’ in the interstate coaxial cable. They would book time on the limited resource and, when it was their turn, the coax was connected with patch leads onto the ‘tail’ from the city out to their studios. The analog baseband signal in the tail required repeaters every few miles; in Melbourne, the longest tail was to ATV0 at Nunawading. When a program came from elsewhere, the receiving 86 Silicon Chip studio would synchronise with the source studio via the incoming program feed. This incoming signal became the master for the whole studio and its activities. In the early 1970s, ATV0 was having problems with their synchronisation late in the afternoon. They were taking children’s programming from Sydney and (apart from inserting local ads) were passing it straight to their Mount Dandenong transmitter (via a private microwave radio link). The synchronisation ‘hits’ were causing interference to the viewers’ pictures. That didn’t matter too much for the junior viewing audience. Still, other programs were being made in the Nunawading studios at the same time, and these synchronisation ‘hits’ were upsetting the studio recorders and ruining those recordings. The Sydney to Melbourne coax was checked out and found to be OK. The city to Nunawading link was found to be introducing spikes into the program material, but only between 5:30pm and 6:00pm. There were several repeaters on the tail, and the program was monitored on these sections progressively out from the city and was clean until the section into Toorak. Fortunately, there was a spare coax tube in that link, which we could monitor during the troublesome period. With no equipment connected except for our monitoring storage CRO, this raw tube suddenly showed significant but random spikes. The cable followed a tram line, which was a suspect as the return path for the 600V DC traction currents was their rail. If there were any broken rails or joints, it was typical for the telephone cables’ heavy lead sheath to become a convenient Earth return path for that fault current. But why only between 5:30pm and 6:00pm? An investigation began into what else was carried in the cable that could be a source of the interference. A bunch of coaxial tubes always had spaces between them, and those spaces were filled with copper wires called interstitial pairs. These pairs were considered premium as they were larger (less lossy) than regular pairs and shielded by the heavy lead sheath. They were usually first assigned as audio program lines for TV and radio stations connecting studios and transmitters or outside broadcasting locations. However, somehow many of these pairs in a section of the cable had been assigned to the basic alarm circuits for the shops in the Toorak shopping strip. These simply provided a DC loop back to the alarm company. Any break in the current would be treated as an alarm. When the shopkeepers shut up for the day soon after the standard 5:30pm closing time, they activated their alarms, which turned on their monitoring current. This instant step in current induced a voltage spike into the adjacent coaxial tubes. These alarm circuits were quickly transferred out of the coax, and the problem disappeared. Seven is greater than five G. D., of Glen Iris, Vic was a Navy repairman for many years. This incident must have stuck in his memory for him to remember it so clearly decades later... A young sailor with HMAS Torrens emblazoned around his cap walked into the Radio Workshop at Williamstown Naval Dockyard with a box under his arm. He plonked it down on the workbench and said it was a... (I have forgotten Australia's electronics magazine siliconchip.com.au what it was, but I couldn’t tell you even if I remembered. It came from the crypto room, so it was very hush-hush). He proceeded to tell us that the box was US – not American, unserviceable – which was the official Royal Australian Navy’s term for a bit of kit that doesn’t work. The sailor said his captain was desperate for us to fix the box because they were going to sea in a few days. As he disappeared down the stairs, he yelled that he would be back tomorrow morning to pick up the repaired box. It appeared that the sailor didn’t understand that asking Willie Dockies to fix something in less than 24 hours was wishful thinking. But my boss Bruce took the request seriously and handed the box over to his top technician – a man with many years of experience. The technician unscrewed the top cover and couldn’t believe what it was. Intrigued, we wandered over to see what he was moaning about. He pointed at dozens of black plastic rectangles with little legs that looked like caterpillars, which were soldered onto a green board. Having just finished a stint at RMIT (Royal Melbourne Institute of Technology), I recognised the caterpillars as integrated circuits. Old Max, a radio tradesman with years of sea trial experience, was outraged that our latest naval equipment didn’t have glowing glass bottles with 300V running to the anodes. Bruce sighed. Then he looked at me and reminded all that I had made a radio control encoder with integrated circuits, so I was nominated to have a crack at fixing the secret box. Not having a circuit diagram, I noted that the integrated circuit numbers started with the prefix 54. There were 5400s, 5404s and 5408s. It dawned on me that the 54 prefix was the military specification for TTL or ‘transistor-­ transistor logic’ digital integrated circuits. 500 I pulled out my blue National Semiconductor TTL Data Book, and there it was – a 7400 quad NAND gate was functionally equivalent to a 5400 chip. Armed with our Tektronix 465 storage oscilloscope, I powered on the box and started looking at the 0V/5V signals going in and out of the gates. Then it happened – a 5404 hex inverter was changing state on the inverter input but not the corresponding output. It had to be blown. Off I went to the store to see Old Jock. It reminded me that when I worked in the mines in the Pilbara, our German foreman Klaus told us that the best storemen were from Scotland because they treated the store’s contents as their private property and didn’t give supplies out without a fight. Our storemen didn’t have to fight me because, when I asked for a 5404 integrated circuit, he looked at me as if I had predicted that Collingwood would win the premiership! He consulted his DSN books and pronounced there was no such thing as a 5404 (there were no computerised stores systems back in the day). I politely asked if he could order two 5404 chips and when they might arrive. That really made him laugh – he mumbled that he would have to send a signal to naval headquarters in Canberra, and it would take at least six months! I wasn’t happy with that news. Then an evil thought crossed my mind. On the way home after work, I made a detour to the new Dick Smith store in Melbourne. I parked on the footpath directly in front of the store (which is legal in the great state of Victoria, of course), walked in and purchased two 7404 chips. The next morning, I gingerly soldered a 7404 chip in place of the dud 5404 and powered the secret box up. It POWER WATTS AMPLIFIER Produce big, clear sound with low noise and distortion with our massive 500W Amplifier. It's robust, includes load line protection and if you use two of them together, you can deliver 1000W into a single 8Ω loudspeaker! PARTS FOR BUILDING: 500W Amplifier PCB Set of hard-to-get parts SC6367 SC6019 $25 + postage $180 + postage SC6019 is a set of the critical parts needed to build one 500W Amplifier module (PCB sold separately; SC6367); see the parts list on the website for what’s included. Most other parts can be purchased from Jaycar or Altronics. Read the articles in the April – May 2022 issues of Silicon Chip: siliconchip.com.au/Series/380 siliconchip.com.au Australia's electronics magazine November 2023  87 he was stunned by the Captain’s knowledge of digital ICs. “You went to RMIT, didn’t you, Gerard?” He had me – I confessed that I told the sailor about the study. Mr Caton shook his head and smiled, and we all went back to work. Fixing a clever weight scale circuit came up, blinking lights – the lot! But since a non-­militarygrade component was used to repair the box, we had to wait until a suitable replacement came before it could officially be used. Shortly after, I had returned with a naval officer in tow, wearing a white uniform with a lot of gold on his cap – he was the commander of HMAS Torrens and asked to speak to Mr Caton, the Radio Workshop Manager. Eventually, the Captain and Mr Caton walked out of the office and came into the workshop. Mr Caton announced that the captain was sending a naval signal to the Radio Workshop approving a temporary repair to their box using non-military-specification components. Mr Caton was impressed with the knowledge of digital integrated circuits the captain possessed. The captain said that he understood that studies at RMIT had revealed that commercial-grade 74-series digital integrated circuits were more reliable than their 54 military specification series equivalents. Evidently, the extra stress testing of the 54 series during manufacture can cause premature failure. So we agreed to the temporary fix using the 7404 chip. Afterwards, Mr Caton approached me and told me that Like many, M. H., of Albury, NSW prefers to fix faulty appliances rather than discard them. It’s worth giving it a try when the fault appears to be a simple one... Like many weight scales, you start ours by lightly stomping on it and waiting for it to complete an automatic zero calibration. You can then stand on it to get the bad news for the day. Over time, that stomping action increased to a jumping action and then to a lift and drop action. The wife had enough of this noisy forceful operation and bought a replacement set of scales. The faulty scales were then forced to the second bathroom to collect hair and baby powder, doomed to be discarded. My thinking moved to how its internal processor would be started with a stomping action. Maybe the sudden change in the load cell output produced the reset action, and a sad capacitor was to blame. However, that would consume the battery when the device was idle. So I had no choice but to open it up and see what was going on inside. Four small screws exposed the LCD screen and a small PCB. The four load cell wires went to the microcontroller and, as expected, it was a blob of black epoxy on the PCB. I was about to declare it beyond repair when I noticed a disc piezo element wired to the PCB and questioned why a set of scales would have a buzzer. Then it dawned on me – it wasn’t a buzzer! The buzzer disc operates as a microphone to ‘hear’ the stomping and wake the microcontroller up. Also, the solder joint that held the disc’s outer edge to the PCB had broken away. That explained the final lift-and-drop requirement. Using a piezo buzzer disc as a microphone is a wonderful idea. It is suspended by the outer edge into free space to amplify the stomping action, generating the impulse voltage required to start the processor. The disc generates its voltage from the kinetic thump and does not impose any battery drain when idle. I added a dob of solder to suspend the disc off the side of the PCB, and it was back in action. I will remember this idea to wake microcontroller projects where a tap to the SC side of the box lights up the screen. Photos of the piezo disc connected to the weight scale PCB. 88 Silicon Chip Australia's electronics magazine siliconchip.com.au 49.95 $ Battery Sensor Strip Lights 19 .95 $ X 3229 At only $20 you can afford to put these handy battery powered sensor lights in every cupboard or wardrobe! Lights up when you open the door. Includes 1m adhesive backed strip.30 second on time. No wiring required - just 4xAAA batteries. 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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 Digital FX Unit (Apr21) Si473x FM/AM/SW Digital Radio (Jul21), 110dB RF Attenuator (Jul22) Basic RF Signal Generator (Jun23) ATmega328P-AUR RGB Stackable LED Christmas Star (Nov20) ATtiny45-20PU 2m VHF CW/FM Test Generator (Oct23) ATtiny85V-10PU Shirt Pocket Audio Oscillator (Sep20) PIC10LF322-I/OT Range Extender IR-to-UHF (Jan22) PIC12F1572-I/SN LED Christmas Ornaments (Nov20; versions), Nano TV Pong (Aug21) PIC12F617-I/P Range Extender UHF-to-IR (Jan22), Active Mains Soft Starter (Feb23) Model Railway Uncoupler (Jul23) PIC12F617-I/SN Model Railway Carriage Lights (Nov21) PIC12F675-I/P Train Chuff Sound Generator (Oct22) PIC16F1455-I/P Digital Lighting Controller Slave (Dec20), Auto Train Controller (Oct22) GPS Disciplined Oscillator (May23) PIC16LF1455-I/P New GPS-Synchronised Analog Clock (Sep22) PIC16F1459-I/P Cooling Fan Controller (Feb22), Remote Mains Switch Receiver (Jul22) K-Type Thermometer/Thermostat (Nov23) PIC16F1459-I/SO Multimeter Calibrator (Jul22), Buck/Boost Charger Adaptor (Oct22) PIC16F15214-I/SN Tiny LED Icicle (Nov22), Digital Volume Control Pot (SMD; Mar23) Silicon Chirp Cricket (Apr23) PIC16F15214-I/P Digital Volume Control Pot (through-hole; Mar23) PIC16F1705-I/P Flexible Digital Lighting Controller (Oct20) Digital Lighting Controller Translator (Dec21) PIC16F18146-I/SO Digital Boost Regulator (Dec22) PIC16LF15323-I/SL Remote Mains Switch Transmitter (Jul22) W27C020 Noughts & Crosses Computer (Jan23) ATSAML10E16A-AUT PIC16F18877-I/P PIC16F18877-I/PT High-Current Battery Balancer (Mar21) USB Cable Tester (Nov21) Dual-Channel Breadboard PSU Display Adaptor (Dec22) Wideband Fuel Mixture Display (WFMD; Apr23) PIC16F88-I/P Battery Charge Controller (Jun22), Railway Semaphore (Apr22) PIC24FJ256GA702-I/SS Ohmmeter (Aug22), Advanced SMD Test Tweezers (Feb23) 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 (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS ATmega644PA-AU AM-FM DDS Signal Generator (May22) dsPIC33FJ64MC802-E/SP dsPIC33FJ128GP306-I/PT PIC32MX470F512H-I/PT PIC32MX470F512H-120/PT PIC32MX470F512L-120/PT 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb13) Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Micromite Explore 100 (Sep16) $25 MICROS $30 MICROS PIC32MX695F512H-80I/PT Touchscreen Audio Recorder (Jun14) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20), Dual Hybrid Supply (Feb22) KITS, SPECIALISED COMPONENTS ETC VARIOUS MODULES & PARTS - 5V 3-pin boost regulator module (2m CW/FM Test Generator, Oct23; SC6780) - 5V 3-pin buck regulator module (2m CW/FM Test Generator, Oct23; SC6781) - 20x4 blue backlit LCD with I2C interface (ESR Meter, Aug23; SC4203) - red & black PCB-mount banana sockets (ESR Meter, Aug23; SC4983) - two 1nF ±1% capacitors (ESR Meter, Aug23; SC4273) - 0.96in SSD1306-based yellow/blue OLED (RF Signal Gen, Jun23; SC6421) - CH340G-based USB/serial module (GPSDO, May23; SC6736) - NEO-7M GPS module with SMA connector (GPSDO, May23; SC6737) - GPS antenna with 3m cable and SMA connector (GPSDO, May23; SC6738) - DD4012SA 12V to 7.5V buck-converter module (GPSDO, May23; SC6339) K-TYPE THERMOMETER / THERMOSTAT (CAT SC6809) $3.00 $4.00 $15.00 $6.00/set $2.50 $10.00 $15.00 $20.00 $10.00 $5.00 (NOV 23) Short-form kit: includes most of the parts needed except the case, LCD, thermocouple probe, cable gland and switches S4 & S5. A 10A relay is included to suit the 12V supply (see page 58, Nov23) $75.00 PICO AUDIO ANALYSER (CAT SC6772) (NOV 23) Short-form kit: includes the PCB and everything that mounts on it including the Pi Pico (unprogrammed) and OLED screen. The case, battery, chassis connectors and wires are not included (see page 41, Nov23) $50.00 MODEM / ROUTER WATCHDOG (CAT SC6827) (NOV 23) PIC PROGRAMMING ADAPTOR KIT (CAT SC6774) (SEP 23) CALIBRATED MEASUREMENT MICROPHONE (AUG 23) Short-form kit: includes all non-optional parts, plus a 12V relay and unprogrammed Pi Pico. Does not include a case (see page 71, Nov23) $35.00 Includes all parts, except the optional USB supply (see page 71, Sept23) $55.00 SMD version kit: includes the PCB and all onboard components except the XLR socket. You also need one ECM set (see below) (Cat SC6755) $22.50 Through-hole version kit: includes the PCB and all onboard components except the XLR socket. You also need one ECM set (see below) (Cat SC6756) $25.00 Calibrated ECM set: includes the mic capsule and compensation components; see pages 71 & 73, August 2023 issue, for the ECM options (Cat SC6760-5) $12.50 DYNAMIC RFID/NFC TAG (JUL 23) Smaller (purple PCB) kit: includes PCB, tag IC and passive parts (Cat SC6747) Larger (black PCB) kit: includes PCB, tag IC and passive parts (Cat SC6748) $5.00 $7.50 siliconchip.com.au/Shop/ RECIPROCAL FREQUENCY COUNTER KIT (CAT SC6633) (JUL 23) BASIC RF SIGNAL GENERATOR (JUN 23) SONGBIRD KIT (CAT SC6633) (MAY 23) DUAL RF AMPLIFIER KIT (CAT SC6592) (MAY 23) SILICON CHIRP CRICKET (CAT SC6620) (APR 23) TEST BENCH SWISS ARMY KNIFE (APR 23) WIDEBAND FUEL MIXTURE DISPLAY (CAT SC6721) (APR 23) DIGITAL VOLUME CONTROL POTENTIOMETER (MAR 23) Includes all parts, except the case, TCXO and AA cells (see page 57, July 2023) $60.00 Kit: includes everything but the case, battery and optional pot (Cat SC6656) Includes all parts required, except the base/stand (see page 86, May 2023) Includes the PCB and all onboard parts (see page 34, May 2023) Complete kit: includes all parts required, except the coin cell & ICSP header $100.00 $30.00 $25.00 $25.00 Short-form kit: includes PCB, all onboard SMDs, boost module, SIP reed relay & UB1 lid. Does not include ESP32 module, case, 10A relay or connectors (Cat SC6589) $50.00 - ESP32 DevKitC module with WiFi and Bluetooth (Cat SC4447) $10.00 - 3mm black laser-cut UB1 Jiffy box lid (Cat SC6337) $10.00 Short-form kit: includes the PCB and all onboard parts. Does not include the case, O2 sensor, wiring, connectors etc (see page 47, April 2023) $120.00 SMD version kit: includes all relevant parts except the universal remote control and activity LED (Cat SC6623) Through-hole version kit: includes all relevant parts (with SMD PGA2311) except the universal remote control and activity LED (Cat SC6624) ACTIVE MAINS SOFT STARTER (FEB 23) Q METER SHORT-FORM KIT (CAT SC6585) (JAN 23) $60.00 $70.00 Hard-to-get parts: includes the PCB, transformer, relay, thermistor, programmed micro and all other semiconductors (Cat SC6575; see page 41, Feb23) $100.00 Includes the PCB, all required onboard parts (excluding optional debug interface) and the front panel. Just add a signal source, case, power supply and wiring $100.00 LC METER MK3 Short Form Kit: includes the PCB and all non-optional onboard parts, except the case, front panel label and power supply (Cat SC6544) *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # Overseas? Place an order on our website for a quote. (NOV 22) $65.00 PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) 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 SMD TEST TWEEZERS (3 PCB SET) 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 500W AMPLIFIER MODEL RAILWAY SEMAPHORE CONTROL PCB ↳ SIGNAL FLAG (RED) AM-FM DDS SIGNAL GENERATOR SLOT MACHINE HIGH-POWER BUCK-BOOST LED DRIVER ARDUINO PROGRAMMABLE LOAD SPECTRAL SOUND MIDI SYNTHESISER REV. UNIVERSAL BATTERY CHARGE CONTROLLER VGA PICOMITE DATE NOV20 NOV20 NOV20 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 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 APR22 APR22 APR22 MAY22 MAY22 JUN22 JUN22 JUN22 JUN22 JUL22 PCB CODE 16111191-9 16109201 16109202 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 04106211/2 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 01107021 09103221 09103222 CSE211002 08105221 16103221 04105221 01106221 04107192 07107221 Price $3.00 $12.50 $12.50 $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 $10.00 $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 $25.00 $2.50 $2.50 $7.50 $5.00 $5.00 $5.00 $7.50 $7.50 $5.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT SECURE REMOTE MAINS SWITCH RECEIVER ↳ TRANSMITTER (1.0MM THICKNESS) MULTIMETER CALIBRATOR 110dB RF ATTENUATOR WIDE-RANGE OHMMETER WiFi PROGRAMMABLE DC LOAD MAIN PCB ↳ DAUGHTER BOARD ↳ CONTROL BOARD MINI LED DRIVER NEW GPS-SYNCHRONISED ANALOG CLOCK BUCK/BOOST CHARGER ADAPTOR AUTO TRAIN CONTROLLER ↳ TRAIN CHUFF SOUND GENERATOR PIC16F18xxx BREAKOUT BOARD (DIP-VERSION) ↳ SOIC-VERSION AVR64DD32 BREAKOUT BOARD LC METER MK3 ↳ ADAPTOR BOARD DC TRANSIENT SUPPLY FILTER TINY LED ICICLE (WHITE) DUAL-CHANNEL BREADBOARD PSU ↳ DISPLAY BOARD DIGITAL BOOST REGULATOR ACTIVE MONITOR SPEAKERS POWER SUPPLY PICO W BACKPACK Q METER MAIN PCB ↳ FRONT PANEL (BLACK) NOUGHTS & CROSSES COMPUTER GAME BOARD ↳ COMPUTE BOARD ACTIVE MAINS SOFT STARTER ADVANCED SMD TEST TWEEZERS SET DIGITAL VOLUME CONTROL POT (SMD VERSION) ↳ THROUGH-HOLE VERSION MODEL RAILWAY TURNTABLE CONTROL PCB ↳ CONTACT PCB (GOLD-PLATED) WIDEBAND FUEL MIXTURE DISPLAY (BLUE) TEST BENCH SWISS ARMY KNIFE (BLUE) SILICON CHIRP CRICKET GPS DISCIPLINED OSCILLATOR SONGBIRD (RED, GREEN, PURPLE or YELLOW) DUAL RF AMPLIFIER (GREEN or BLUE) LOUDSPEAKER TESTING JIG BASIC RF SIGNAL GENERATOR (AD9834) ↳ FRONT PANEL V6295 VIBRATOR REPLACEMENT PCB SET DYNAMIC RFID / NFC TAG (SMALL, PURPLE) ↳ NFC TAG (LARGE, BLACK) RECIPROCAL FREQUENCY COUNTER MAIN PCB ↳ FRONT PANEL (BLACK) PI PICO-BASED THERMAL CAMERA MODEL RAILWAY UNCOUPLER MOSFET VIBRATOR REPLACEMENT CALIBRATED MEASUREMENT MICROPHONE (SMD) ↳ THROUGH-HOLE VERSION ARDUINO ESR METER (STANDALONE VERSION) ↳ COMBINED VERSION WITH LC METER WATERING SYSTEM CONTROLLER SALAD BOWL SPEAKER CROSSOVER PIC PROGRAMMING ADAPTOR REVISED 30V 2A BENCH SUPPLY MAIN PCB ↳ FRONT PANEL CONTROL PCB ↳ VOLTAGE INVERTER / DOUBLER 2M VHF CW/FM TEST GENERATOR TQFP-32 PROGRAMMING ADAPTOR ↳ TQFP-44 ↳ TQFP-48 ↳ TQFP-64 DATE JUL22 JUL22 JUL22 JUL22 AUG22 SEP22 SEP22 SEP22 SEP22 SEP22 OCT22 OCT22 OCT22 OCT22 OCT22 OCT22 NOV22 NOV22 NOV22 NOV22 DEC22 DEC22 DEC22 DEC22 JAN23 JAN23 JAN23 JAN23 JAN23 FEB23 FEB23 MAR23 MAR23 MAR23 MAR23 APR23 APR23 APR23 MAY23 MAY23 MAY23 JUN23 JUN23 JUN23 JUN23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 JUL23 AUG23 AUG23 AUG23 AUG23 AUG23 SEP23 SEP23 SEP23 OCT22 SEP23 OCT23 OCT23 OCT23 OCT23 OCT23 PCB CODE 10109211 10109212 04107221 CSE211003 04109221 04108221 04108222 18104212 16106221 19109221 14108221 09109221 09109222 24110222 24110225 24110223 CSE220503C CSE200603 08108221 16111192 04112221 04112222 24110224 01112221 07101221 CSE220701 CSE220704 08111221 08111222 10110221 04106221/2 01101231 01101232 09103231 09103232 05104231 04110221 08101231 04103231 08103231 CSE220602A 04106231 CSE221001 CSE220902B 18105231/2 06101231 06101232 CSE230101C CSE230102 04105231 09105231 18106231 01108231 01108232 04106181 04106182 15110231 01109231 24105231 04105223 04105222 04107222 06107231 24108231 24108232 24108233 24108234 Price $7.50 $2.50 $5.00 $5.00 $7.50 $7.50 $5.00 $10.00 $2.50 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $2.50 $7.50 $2.50 $5.00 $2.50 $5.00 $5.00 $5.00 $10.00 $5.00 $5.00 $5.00 $12.50 $12.50 $10.00 $10.00 $2.50 $5.00 $5.00 $10.00 $10.00 $10.00 $5.00 $5.00 $4.00 $2.50 $12.50 $5.00 $5.00 $5.00 $1.50 $4.00 $5.00 $5.00 $5.00 $2.50 $2.50 $2.50 $2.50 $5.00 $7.50 $12.50 $10.00 $5.00 $10.00 $2.50 $2.50 $5.00 $5.00 $5.00 $5.00 $5.00 K-TYPE THERMOMETER / THERMOSTAT (SET; RED) PICO AUDIO ANALYSER (BLACK) MODEM / ROUTER WATCHDOG (BLUE) DISCRETE MICROAMP LED FLASHER MAGNETIC LEVITATION DEMONSTRATION NOV23 NOV23 NOV23 NOV23 NOV23 04108231/2 04107231 10111231 SC6868 SC6866 $10.00 $5.00 $2.50 $2.50 $5.00 NEW PCBs We also sell the Silicon Chip PDFs on USB, RTV&H USB, Vintage Radio USB and more at siliconchip.com.au/Shop/3 Don't pay 2-3 times as much for similar brand name models when you don't have to. IDEAL STARTER STATION IDEAL HOBBYIST ENTRY LEVEL STATION ONLY 4995 $ TS1610 LIGHTWEIGHT, EXCEPTIONALLY DELICATE • 10 WATT • ROTARY TEMPERATURE CONTROL DIAL TS1620 GREAT FOR ENTHUSIAST'S WEEKEND PROJECTS ONLY 149 $ TS1564 ONLY 8795 $ LIGHTWEIGHT IRON WITH ADJUSTABLE TEMPERATURE • 48 WATT • SLIMLINE DESIGN GREAT FOR EVERYDAY ELECTRONICS ENTHUSIASTS ONLY 229 $ TS1640 OUR MOST POPULAR STATION FOR HOBBYISTS • 48 WATT • ANALOGUE TEMP ADJUSTMENT Explore our great range of soldering stations, in stock on our website, or at over 115 stores or 130 resellers nationwide. RELIABLE OPERATION WITH EXCELLENT TEMPERATURE STABILITY • 60 WATT • DIGITAL TEMP ADJUSTMENT • ESD SAFE • INCLUDES FULL SET OF SPARES INCLUDING REPLACEABLE PENCIL jaycar.com.au/solderstation 1800 022 888 Soldering Stations Soldering made easy with our BEST RANGE of soldering stations at the BEST VALUE, to suit hobbyists and professionals alike. SOLDER OR DESOLDER SURFACE MOUNT COMPONENTS COMPLETE SOLDER/DESOLDER STATION • 60 WATT IRON • 300W HOT AIR PUMP • RAPID TEMP RECOVERY • DUAL DIGITAL DISPLAY • ADJUSTABLE TEMPERATURE • ESD SAFE ONLY 379 $ TS1648 Use this colour coded selection guide to pick the soldering stationthat best suits your needs. GREEN labelled products suit hobbyists and those on a budget. BLUE suit makers who use a soldering station regularly and need ESD protection. For advanced hobbyists or technicians, choose from the ORANGE professional range. ENTRY LEVEL MID LEVEL PROFESSIONAL TS1610 TS1620 TS1564 TS1640 TS1648 Key Feature Compact Design Slimline Ceramic Element Digital Display Soldering & Hot Air Power (Watts) 10W 48W 48W 60W 300W Temp. Range 100-450°C 150-450°C 150-450°C 160-480°C 50-480°C Soldering 100-500°C Hot Air Display Digital Digital ESD Safe • • $229 $379 Price $49.95 $87.95 $149 *Temperature rating is set by the soldering iron tip. ESD means Electro Static Discharge Shop Jaycar for your soldering essentials: • Soldering stations • Electric handheld irons • Gas powered irons • Classic 60/40, lead-free, silver & paste solder options • Multiple desolder braid and tools • Wide range of stands, cleaners and PCB holders Prices correct at time of publication but are subject to change. Jaycar reserves the right to change prices if and when required. 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. A minimal WiFi water tank level gauge This circuit is inspired by the WiFi Water Tank Level Meter (February 2018; siliconchip.au/Article/10963) and the PIC-based Water Tank Level Meter (November 2007; siliconchip. au/Series/46). It uses the cheapest ultrasonic distance sensor module, the HC-SR04, which consumes little power and doesn’t need a preamplifier like other kinds of distance sensors. It also uses an inexpensive PIC microcontroller (a tiny 6-pin PIC10F322). For the WiFi connectivity, a small ESP-03 module does the job. It can be used as a wired solution, giving measurements every two seconds, displayed by a terminal application. The wireless solution provides a measurement once per minute, displayed on a UDP monitor. The PIC produces a 10μs high-level pulse from its RA2 digital output to the trigger input of the HC-SR04, which starts the ranging procedure. The latter responds with a pulse from its echo pin after a delay that’s proportional to the roundtrip distance. With a typical speed of sound of 344m/s at 20°C and 94 Silicon Chip sea level, we get a gauge resolution of 17.2cm. An optional temperature sensor (MCP9700A) may be connected to analog input AN0 (pin 1), to correct the speed of sound as it varies with temperature. The formula used is C = 331.3m/s + 0.606Tm/s, where T is in degrees Celsius, giving a negligible error of less than 0.2% for a 1°C difference. The PIC produces serial data from its RA1 digital output by ‘bit banging’ (8N1, 57,600 baud) every two seconds that includes the ambient temperature, battery voltage and distance to the top of the water. If a wired solution is preferred, one can simply use a TTL/USB cable between this prototype and a PC (with a terminal application like PuTTY). If a wireless solution is preferred, one can use the ESP-03 instead. It is powered periodically for brief periods (to preserve the battery), then put into deep sleep mode. I chose the ESP-03 over the popular ESP-01 as it is smaller and allows a direct link between its RST and WAKE pins, Australia's electronics magazine which is necessary when using the deepSleep function. It uses a dynamic IP and issues UDP broadcasts on port 6010. The periodic statistics can be displayed with a PC application (like Netcat) or an Android application (like UDP Monitor). With a 4000mAh LiPo cell, the prototype ran for 29 days, with the battery discharging from 4.2V to 3.5V. Below 3.5V, the HC-SR04 module gives false readings, but the ESP03 still works, as its 3.3V voltage regulator 3.3V is a low-dropout (LDO) type (MCP1702-33). For the distance sensor, I recommend using the waterproof JSN-SR04T model. It is directly compatible with the HC-SR04, with more options, and will operate down to 3.3V, although it is more expensive. Both the PIC software (HEX file and assembly language source code) and Arduino sketch for the ESP-03 module can be downloaded from the Silicon Chip website at siliconchip.au/ Shop/6/268 Mohammed Salim Benabadji, Oran, Algeria. ($90) siliconchip.com.au Magnetic levitation demonstration One of my friends asked me about magnetic levitation. On reading about it, I came across the Thompson Ring, which is made to levitate by a mainsdriven autotransformer. My design is similar, except it uses a simple circuit driven by a 9V DC 1A plugpack. You can see it working in the video at: siliconchip.au/link/abll The incoming 9V supply is reduced to 5V by the LP2950-5 regulator to power a PIC12F617 microcontroller. When switch S1 is closed, digital input GP2 of IC1 goes high, which triggers the software to produce two square waves from its GP0 and GP1 outputs. They are 180° out of phase with each other. The voltage at analog input GP4 determines the frequency of these square waves. The out-of-phase waveforms are applied to the DRV8871 H-bridge IC, resulting in an 18V peak-to-peak square wave across the coil. As the frequency reduces, more current flows into the coil due to its reactance (inductance), resulting in the continuous aluminium ring rising above the coil by an adjustable distance. To use it, set the potentiometer for the lowest frequency (maximum coil current) with the switch open. When the switch is closed, the ring flies into the air and then oscillates up and down in a damped motion until it becomes stationary at a fixed distance up from the coil. The frequency can then be increased, and the ring will slowly move down until it rests on the coil. Reducing the frequency after that will cause the ring to move up from the coil. If VR1 is a ‘logarithmic’ potentiometer, the height of the ring above the coil is roughly proportional to the rotation angle. The reason that the ring stabilises at a particular position is that the downward force due to gravity is constant but the upward force depends on the strength of the magnetic field emanating from the coil and the distance between the coil and the ring. Thus, for a given field strength, there is a distance at which the upward force from the magnetic field equals gravity, so the ring ‘levitates’. While aluminium is not a magnetic material, the magnetic field from the coil induces a varying current flow in the conductive aluminium, creating an opposing magnetic field. This is similar to how an induction motor induces magnetism in the metal rotor using coils in the stator, which opposes the field from those coils, causing the rotor to rotate. The breakout board for the DRV8871 H-bridge is available from a couple of Australian suppliers for about $15 and also can be purchased directly from Adafruit. The rest of the components are off the shelf. The PCB and programmed micro are available from: siliconchip. au/Shop/8/6866 & siliconchip.au/ Shop/9/6867 You can also download the firmware for the PIC from siliconchip.au/ Shop/6/282 The rod should be made of soft cast iron to enhance the magnetic field. Mild steel should work, but the lift would be less. I have also tested rings made of copper, brass, iron and stainless steel, plus an aluminium ring with a gap cut between the perimeter and the centre and a heavy aluminium ring. The copper ring goes nearly as far as the aluminium one, the brass one rises slightly, while the iron, stainless steel and split rings do not at all. The heavier aluminium ring rises nearly as high as the lighter one. Les Kerr, Ashby, NSW. ($150) POWER+ +9V REG1 LP2950-5 GND 1000F +5V OUT IN 100F 100nF 20F 100nF IRON ROD 100nF ADAFRUIT DRV8871 BREAKOUT MODULE 10k +5V START S1 FROM 9V 1A DC POWER SUPPLY 5 VR1 10k SET FREQUENCY 3 LP2950 GND IN 2 1k OUT 0V 4 1 100nF Vdd 5 GP2 GP4 IC1 PIC12F617 17 –I/P –I/P GP0 GP1 7 6 2 3 4 GP5 VM IC2 DRV8871 IN1 ILIM OUT1 GND 8 30k* POWER– 8 OUT2 IN2 Vss 10k ALUMINIUM RING GP3/MCLR 1 6 COIL PGND 7 SC 2023 * GIVES 2.13A MAXIMUM CURRENT siliconchip.com.au Australia's electronics magazine November 2023  95 Discrete microamp LED flasher This LED flasher has an average current of less than one microamp and flashes the LED roughly once every two seconds. The low current means it can be used as an ultra-low-power indicator in places where an indicator is not normally possible, such as a power-on indicator in devices powered by lithium watch batteries. A CR1620 cell has a usable capacity of about 70mAh, which will power this flasher for eight years. The component values in the circuit are for use with a 3V or 3.3V supply. Higher supply voltages can be used, but the average current will increase, and the flash rate will also increase. To use a higher supply voltage while keeping the supply current low, increase the value of all four 2.2MW resistors; for example, 3.9MW will work well for a 4.5V supply. The circuit is basically a relaxation oscillator. It charges a capacitor, then discharges the capacitor through the LED. There are three main sections in the circuit: • A trigger circuit, which detects when the capacitor reaches full charge. • A monostable, which generates a fixed-length pulse. • A power stage to drive the LED. The trigger circuit starts the monostable and the monostable’s output drives the power stage. The 1μF capacitor is charged over time, then powers the LED for each flash. It is charged mostly through 2.2MW resistor R1 and partially through Q2’s emitter and base resis- tors (and its emitter-base junction). PNP transistors Q1 and Q2, and the resistors around them, are the trigger circuit, which monitors the voltage across R1. As the 1μF capacitor charges, the voltage across R1 drops. When it’s below approximately 0.6V, the two transistors act as a Schmitt trigger, turning the gradually changing voltage across R1 into an abrupt signal at the collector of Q1 to start the monostable. NPN transistor Q4 and PNP transistor Q5, along with the resistors around them and the 100nF capacitor, form the monostable circuit. The 100nF capacitor charges through R6 at the same time as the other capacitor. Q4 and Q5 are wired as a discrete thyristor (SCR); once it gets the trigger signal, Q4 starts to switch on, which makes Q5 start to switch on, and they hold each other on. The monostable is powered by the 100nF capacitor, so while it is on, this capacitor discharges, ultimately Above: a 3D render of the Flasher PCB. Left: a plot of the current through LED1 (green) and R1 (blue) for the Flasher. 96 Silicon Chip Australia's electronics magazine dropping to a voltage too low to keep the transistors on, at which time the monostable turns off. NPN transistor Q3 is the power stage. While the monostable is on, the voltage across Q4’s emitter resistor is high enough to drive hundreds of microamps into the base of Q3, which goes into saturation and permits current to flow through the LED. The current through the LED discharges the 1μF capacitor, creating a flash that lasts a fraction of a millisecond. The LED choice is critical in this circuit. As the amount of power available to drive the LED is tiny, an ordinary LED will produce a barely-­visible flash. You need a wide-angle super bright LED; if the angle is too narrow, the flash won’t be visible when your eye is not on-axis with the LED. One suitable LED is Jaycar’s ZD0040 2mm red LED, rated at 600mcd with a 60° viewing angle. Although the circuit shows BC846 (NPN) and BC856 (PNP) surface-mount SOT-23 transistors, it works equally well with BC547 (NPN) and BC557 (PNP) transistors with leads. After building this circuit, clean off all solder flux residue, as flux can absorb moisture from the air and become conductive. Even a fraction of a microamp leaking through flux can prevent the circuit from working! I have designed a small SMD PCB for this circuit, shown in the 3D rendering (siliconchip. au/Shop/6/284). The accompanying LTspice simulation shows the LED current in green and the supply current in blue. We will also be selling a PCB at siliconchip.au/Shop/8/6868 Russell Gurrin, Highgate Hill, Qld. ($100) siliconchip.com.au Subscribe to OCTOBER 2023 ISSN 1030-2662 10 The VERY BEST DIY Projects ! 9 771030 266001 $12 50* NZ $13 90 INC GST INC GST 1kW+ Class-D Amplifi fieer make it yourself using pre-bu ilt modules Photographing Electronics how to take quality photogra phs 2m Test Signal Generator CW and FM in the VHF band Programming SMD Micros with our reconfifiggurable adap tors The History of Australia’s top electronics magazine Electronics 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 D-200 RADIO TRANSMITTER 7KH6RYLHW6SXWQLNVDWHOOLWHODXQFKLQVWDUWHG WKHoVSDFHUDFHp,WFDUULHGWZR:UDGLRWUDQVPLWWHUV %HFDXVHRILWVKLVWRULFDOLPSRUWDQFH,GHFLGHGWR FUHDWHDQDXWKHQWLFUHSOLFDRIWKHWUDQVPLWWHU DVVHPEO\GHVFULEHGLQWKLVVHULHVRIDUWLFOHV A Vintage Radio Story, Part 1 By Dr Hugo Holden S putnik-1 was an awe-inspiring accomplishment in the field of space exploration in 1957 and a credit to the Soviet engineers who designed it. The Sputnik-1 satellite confirmed that not only could an object be deployed from a rocket into space in a basically stable orbit, but that it could also carry a functioning radio transmitter. The transmitted signal could be easily received by many shortwave radios on the Earth, as long as they were within view of the satellite. Since the paths of radio waves and light are generally reversible, it also indicated that satellites could be used as radio relay stations in space. The idea that a satellite could be placed in a geostationary orbit was postulated by Arthur C. Clarke in 1948. Yet few people took him seriously at that time because he was a science fiction writer. Sputnik-1, as well as inspiring the world, triggered the formation of NASA. The impact of Sputnik-1 on 98 Silicon Chip space science and popular culture was very significant, even making it onto stamps (see Photos 3 & 4). I first saw images of Sputnik-1 in the early 1960s as a boy. It stirred my imagination in electronics, general science and space travel. I didn’t imagine back then that one day in the future, I would have a go at reconstructing Sputnik-1’s radio transmitter and “Manipulator”. The D-200 radio transmitter The satellite was as simple as possible, carrying two independent radio transmitter modules inside one D-200 transmitter unit, transmitting at 20.005MHz and 40.002MHz. One module is seen in Photos 5 & 6; the other is on the reverse side of the unit. Batteries and a cooling fan assembly surrounded the D-200. Essentially, the battery assembly formed a large octagonal structure inside the spacecraft and the transmitter was in the hole in the middle (see Photo 2). The inside of the 0.58m diameter polished spherical body was Australia's electronics magazine pressurised to 1.3 atmospheres (1.3 bar/1300hPa) and filled with dry nitrogen. The carrier wave was derived from a separate crystal-controlled oscillator in each module. The antennas were close to ¼ wavelength dipoles, folded into a V shape with the Satellite body in between, although they were physically shorter than exact ¼ wavelengths of the operating frequencies. The angled arrangement of the antennas on the satellite body helped it fit into the nose cone of the launch rocket. The effectively bent dipole also had a more uniform signal distribution than a straight dipole antenna’s typical ‘figure-8’ pattern. The transmitter output power was 1W per module. However, the two transmitter modules were alternately switched on and off by an oscillating relay system called the Manipulator (манипулятор). These unusual relays are the two cylindrical objects seen near the top of the D-200 unit in the photos. There was no RF carrier modulation, just simple interrupted carrier wave (CW) transmission. Due to the two transmitters being alternately switched on and off by the Manipulator, no more than 1W of radio-frequency power was transmitted at any time. There were three 2P19B miniature pentode valves in each transmitter module; one for the oscillator and two in push-pull for the RF power output stage. Radio wave propagation The designers used two transmission frequencies and two transmitter siliconchip.com.au Photo 1: Sputnik-1, the first artificial satellite, fully assembled. Photo 2: what was inside Sputnik-1. You can clearly see the octagonal battery pack, which had the D-200 transmitter module in the middle. modules for redundancy but also to ensure that under the worst expected conditions in the ionosphere, on a winter afternoon at that time of year, one of the signals would make it through the F layers. The F1 and F2 layers are regions in the ionosphere bombarded by UV light from the sun, where the pressure is low and free electrons and ions can move for a long time before recombining to become neutral atoms. These ionised layers react with electromagnetic waves and can absorb some of their energy, reflect them or let them pass through, depending on the angle of incidence and the frequency. The layer ionisation depends on the season, time of day and the year. The 11-year sunspot cycle affects them too, because it affects UV levels. The designers’ calculations were based on the satellite being above the horizon, 700km above the Earth’s surface and 3000km away. The designers concluded that it would require 1W for the signal to pass through the F1 & F2 layers from the satellite to the observer (radio receiver). They did mention in the design document that with a super-sensitive professional receiver, 10mW might be adequate. But the average member of the public would not have such equipment. The designers were clearly intent that average citizens, especially in the USA, should be able to tune into the satellite’s transmissions. The selection of 20.005MHz by the designers was a stroke of genius because it was 5kHz away from America’s time-frequency channel WWV on 20.000MHz. This would naturally beat siliconchip.com.au with Sputnik-1’s carrier wave transmission, creating a 5kHz audio beep that could be heard on a garden-variety shortwave radio without a BFO (beat frequency oscillator) if it was tuned to the 20MHz region. Many American citizens could grab a shortwave radio and tune close to WWV to hear Sputnik-1, if the satellite was in ‘radio view’. Battery power Sputnik-1 carried three specially-­ made silver-zinc batteries inside the octagonal housing. One battery Photos 3 & 4: North Korean and Soviet stamps featuring Sputnik. It was a big deal at the time! Photos 5 & 6: the D-200 transmitter unit that flew on Sputnik-1, shown from two different angles. You can see the two large relay cans on which the Manipulator is based at the top. The transmitter circuitry is in the section below. Australia's electronics magazine November 2023  99 powered the ventilation fan, while the other two formed the low-voltage battery for the 2P19B valve filaments. It also had a high-voltage battery to power the plates, screens and suppressor grids of the 2P19B valves. A 21V tap on the high-voltage battery powered the Manipulator circuit. The batteries were designed to power the craft for at least 14 days. However, after its launch on October 4th, 1957, Sputnik-1 transmitted continuously for three weeks; the transmissions stopped on October 26th. The satellite did not fall to Earth until January 4th, 1958. Sputnik-1 had a fairly elliptical orbit; the satellite’s apogee was 947km with a perigee of 228km. What ended Sputnik’s transmissions? The 7.5V filament battery for the valves was rated at 140Ah, while the total filament consumption was about 180-200mA for the two transmitter modules combined. The filament battery should have lasted about 700 hours or 29 days at that rate, but the current drops with voltage, so it could probably have lasted more than 30 days. However, the calculation to full discharge might not be helpful because the oscillators in the units would have stopped at about ⅔ of full discharge, after around 20 days. As the valve filament temperature drops, so does its transconductance and at some point, that would stop the oscillators. The tapped HT battery supplying the Manipulator with +21V had a negligible current draw, less than 1mA at 21V. On testing the single transmitter with its output loaded to give 1W of RF power, the average 130V supply current, operating at its usual 50% duty cycle (under Manipulator control), was in the region of 24mA. The total average screen current for the three valves was in the order of 7mA. That makes the transmitters’ on-power consumption from the HT battery 3.75W (7mA × 90V + 24mA × 130V). In the transmitter’s off condition, the 130V current (due to the oscillator anode) measured 7mA and the 90V current (for the screen grid of the oscillator) measured 3mA. The power then was 1.18W (3mA × 90V + 7mA × 130V). What about the Doppler Effect? Could the Doppler Effect have affected the historical audio recordings when the satellite was low on the horizon and moving away from or toward the observer? If the transmission frequency is ft, the observed frequency, fo, at the receiver is ft x c ÷ (c + v) for the transmitter moving away from the receiver and ft x c ÷ (c – v) when the transmitter is moving toward the receiver. The speed v of Sputnik-1 was approximately 8000m/s and c (the speed of light) is close to 3 × 108m/s. Ignoring curvature of the path, when the satellite is travelling away from the receiver, the observed carrier wave will appear to drop in frequency by 0.0027%, or when travelling toward the receiver, increase by 0.0027%. Applying that to the 20.005MHz carrier frequency, it would appear as 20.0046667MHz or 20.00553347MHz. The beep’s tone is generated at the receiver as a beat note of two frequencies, so it could therefore change in pitch from around 5.53kHz as the satellite breached the horizon to 5kHz (overhead) to 4.66kHz with the satellite going down on the far horizon, due to the Doppler effect. It would probably be less of a shift in practice due to the curved path. The beep rate (not beep pitch) of 2.5Hz would not change as the satellite went from horizon to horizon, as it would only shift over a range of 2.500066675Hz to 2.49993335Hz. The listener would never notice that. Period changes due to battery discharge were much more significant over time. Some of the historical audio recordings of Sputnik-1’s signal have more of a spooky ‘phasing in and out’ effect typical of multi-path shortwave radio reception. It was thought that the Doppler effects and the two different transmission frequencies might also help provide more information on the ionosphere. In some of the historical recordings of Sputnik-1, people are turning the BFO knobs on their radios during the recording, altering the beep pitch. That confused people about the transmitted signal’s nature and misrepresented what happened. To make matters worse, on tape loops, the pulses appeared on some to change spacing abruptly, but that is due to poorly spliced loops. 100 Silicon Chip Australia's electronics magazine With two transmitters alternately switched on & off, the total power would therefore be 4.93W (1.18W + 3.75W). I assumed for simplicity that this power came entirely from the 130V battery terminal, meaning the current drawn from the HT battery for Sputnik-1 would be close to 38mA. The HT battery was rated at 30Ah. Therefore, it should have taken about 789 hours or about 33 days to completely discharge or perhaps a day less, accounting for the tiny current consumption by the Manipulator. That is not dissimilar to the calculated life to complete discharge of the filament battery, at around 30 days. The probable running time for the circuitry, before the voltages were too low, is about ⅔ of that, accounting for the 21-day practical life. Since the filament power was 1.5W (7.5V × 0.1A × 2), one could say that Sputnik-1 used 6.5W to produce its 1W RF output. Sputnik-1’s operational duration of three weeks well exceeded its design life of 14 days, which is very impressive. It took a 50kg battery pack to do it. The Manipulator Since the release of Sputnik’s D-200 transmitter design document over a decade ago, electronics historians have mainly focused on the transmitters and largely ignored the Manipulator circuit. I’ve only read brief remarks on it, such as “relays switched the transmitters on and off”. It appears that nobody has investigated the Manipulator or exactly reproduced it and documented its features before. That’s partly because there was a paucity of information in the design document on the theory and function of the Manipulator. The Manipulator alternately switched off the screen supply voltages to the transmitter module’s two 2P19B output valves, thereby killing the transmitter output when the screen voltage abruptly fell to zero. Its circuit comprised two commonly available (at the time) Soviet-made twin-coil super sensitive magnetically latching change-over relays, the PnC4 model PC4. Sputnik-1 did not transmit information on satellite conditions, such as telemetry information. However, it had three simple switches (called “error switches” in this document) that could change the Manipulator’s siliconchip.com.au duty cycle and frequency if certain extremes of pressure & temperatures in the spacecraft were exceeded. A separate internal thermal switch operated the ventilation fan system, switching it on if the temperature exceeded 30°C and off if it dropped below 23°C. In Sputnik-1’s flight, none of the error switches deployed, so the signal from the two transmitters remained with close to a 50% duty cycle for each. However, the switching frequency dropped as the battery powering the Manipulator discharged over time. Relays as oscillators Magnetically latching relays had to be used for efficiency in this satellite application. The principle of using a relay as an oscillator, with a capacitor in the relay coil circuit and some resistors, appears simple enough; you will find many relay oscillator circuits on the internet. It is not so simple to produce a perfect 50% duty cycle from them. The reason is that the charge and discharge cycles of the capacitor are not always equal due to varying source resistances. This can be matched by diverting the discharge via an additional contact to a load. However, matching these exactly on each half-cycle is still a challenge. There are also electromechanical properties of the particular relay and the delay to magnetically latch and unlatch to consider. If you apply a voltage to the coil of a relay, you will notice a delay before anything happens. Part of this delay is the current rise time due to the inductance of the relay coil, while the magnetic field is being established. Another aspect is the time it takes to accelerate the mass of the armature (the moving mechanical arm) and for it to arrive at its new mechanical position. Typically, in a relay, the armature carries the relay contacts. Depending on the relay design and physical size, this combined electromechanical delay process could take from 1ms to 300ms or more. This raises the interesting question: how did the designers of the Sputnik1 Manipulator get the relay oscillator to produce a near-perfect square wave pattern? siliconchip.com.au Photo 7: an exploded view of a Sputnik-1 replica. Source: https://w.wiki/6tVc Part of the answer is that they used a symmetrical electrical circuit incorporating latching relays in a master/ slave configuration. Latching relays contain a permanent magnet that holds the armature (and its contact) in position once latched. This also makes them very energy efficient. Only pulses of current are required to change the state of the relay, or a drive waveform with a higher leading edge that can decay later. The wasteful direct holding current needed to hold a conventional relay (with an armature return spring) in one state is not required. The usual way to reset the latching relay is by either applying an opposite polarity pulse to the same coil that set its position, or applying a separate pulse to another coil on the relay bobbin with an opposite phase to the first. In addition, for a balanced square wave oscillator using magnetically-­ latching change-over relays, a perfect magnetic balance is needed in that both ‘halves’ of the relay must have a near-identical coil current sensitivity to initiate a state change. This balance is heavily affected by the mechanical adjustment of the relay’s magnetic pole pieces. The Manipulator’s designers used a system where each half of the full operating cycle relates to charging an 8μF capacitor. This matches electrically to the symmetrical (mirror) circuit. It then only requires that coil pole Australia's electronics magazine pieces on each side of the relay are in an exact position so that the magnetic forces balance. They could alter the oscillation duty cycle away from a balanced 50:50 condition by modifying the resistor values on each side of the charging circuit feeding the master relay coil. This allowed them to transmit the possible “error” or fault conditions. The Manipulator system using two twin-coil magnetic latching relays is astonishingly energy efficient. They quoted a power consumption of under 20mW in the design document. The relays in a master/slave configuration are somewhat analogous to a master/slave flip-flop. The DC resistance of the coils in the slave relay, close to 6kW, provides the charging resistance for the timing capacitors for the master, which saves on parts too. When the timing capacitors are sufficiently charged, the voltage across their terminals becomes high enough, in conjunction with a series resistor with the master relay coils, to cause the master relay to change state. In the design document, they argued against having a valve-based Manipulator because it would consume more power. They also argued against a gas-discharge valve relaxation oscillator because the lamp required is more sensitive to acceleration and vibrations. The system had to survive accelerations of up to 20g. November 2023  101 The final design had six possible patterns or duty cycles and frequencies for switching the two transmitters. However, as noted, none occurred during the 21-day flight to the point of flat batteries. Oscillator period The design document (siliconchip. au/Shop/6/224) refers to a Manipulator period of 0.4 seconds. However, it was unclear if that was the whole period of a Manipulator cycle or the period that one of the transmitters was turned on. If the latter were the case, though, Sputnik-1’s received signal, heard as beeps at the receiver, would have only been 75 per minute. Examination of the amateur radio audio recordings on the internet, early in the flight of Sputnik-1, indicated the beep rate to be around 144-150 per minute. This confirms that 0.4 seconds was for an entire Manipulator timing cycle and that each transmitter had an on-time close to 0.2 seconds early in the fight, with fresh batteries. The Manipulator’s oscillation frequency slows as the power supply voltage is lowered. The oscillator runs at half speed once the voltage drops from 21V to about 13V. Most of the recordings indicating that each transmitter was on alternately for 0.2 seconds were in the early phase of the flight of Sputnik-1, and the slower recordings, where it appeared to be closer to 0.3 seconds, were in the later stages as the battery voltage was dropping. The oscillator stops when the applied voltage is below 9-10V with the PnC5 relays. The design document mentions that the factory guarantees four million relay operations. In the nominal mode, the number of operations for 14 days should add up to about three million. There are 1,209,600 seconds in 14 days; three million divided by that number gives 2.48Hz, close to the 2.5Hz corresponding to an entire oscillator cycle. In summary, there is overwhelming evidence that the Sputnik-1, at least in the few days after launch, with fresh batteries, transmitted alternating bursts of unmodulated carrier waves at 20.005MHz and 40.002MHz that were very close to 0.2 seconds long each. However, some internet sources quote 0.3 seconds, likely corresponding to later in the flight. When the transmissions were received on a radio with a BFO, they became “beeps”. The pitch was typically determined by the BFO knob position on the amateur radio, while the ‘beep rate’ was close to 2.5Hz or 150 beeps per minute. Error switches The error switch configuration is shown in Fig.1. Normally-closed switch E1 would open below 0°C while normally-open switch E2 would close above 50°C. Normally-open switch E3 would close if the pressure inside the craft dropped below 250mmHg (1/3 bar, 333hPa). That would indicate Sputnik-1 had sprung a leak, possibly perforated by a small meteor. I had to deduce how these switches were connected to the Manipulator to agree with the duty cycle patterns in the design document. Those patterns were recorded on what appeared to be 35mm rolling film with a time marker signal on it. Using recordings on the internet of Sputnik’s transmitter taken a few days into its flight with fresh batteries, I determined that the time marker signal is 100Hz. Fig.2, taken from the design document, shows how the error condition switches affect the Manipulator timing. When side A is active, the 40MHz transmitter is on; when side B is active, the 20MHz transmitter is on. To have created these film recordings, the designers would have used a dual trace CRT, with the output of the central relay contact on the slave relay deflecting the beam vertically. Unlike an oscilloscope, there would have been no horizontal beam deflection. They likely used a positive and negative voltage supply connected to the two slave relay contacts. The film would have been rolling past the CRT’s face to expose it. The added calibration signal ensured that the film speed was not a factor in the measurement. It is more easily seen in close-up Fig.3. Most likely, the calibration pulses were derived from a full-wave rectified line power source since the line power frequency in Russia is 50Hz. Alternatively, they may have been created by a divided crystal source. Fig.1: the ‘Manipulator’ oscillator circuit based on two relays, a ‘master’ and a ‘slave’. It oscillates at close to 2.5Hz with a duty cycle very close to 50% unless one of the fault switches (E1-E3) changes state from its default. 102 Silicon Chip Australia's electronics magazine siliconchip.com.au Notice the short ‘dead time’ pulses, centred vertically, when neither slave relay contact is closed. When none of the error condition switches were active (as they turned out not to be in the actual flight), the duty cycle of the Manipulator was close to a square wave, alternately switching on each of the transmitters at close to 0.2 seconds on time and 0.2 seconds off time for each transmitter. PnC5 latching relays Photo 8 shows some PnC5 relays, which have the same form factor as the PnC4. Photo 9 is of one of the relays out of its canister, showing the structure, perhaps visible more plainly in the drawing, Fig.4. Each coil has two windings. It is possible to apply pulses of the same polarity to the different windings to set/reset the relay. Alternatively, you can apply pulses with opposite polarities to the same winding to achieve a similar effect. I could not acquire an exact PnC4 relay as used in Sputnik-1; however, the PnC5 relays I did manage to buy are almost identical. I discovered that the main difference is that the two pole pieces, P1 and P2, are adjusted slightly differently. I think there would also have been a difference in how the armature was suspended. The PnC4 would probably have used a friction-­ free pivot. When the pole pieces P1 and P2 are open enough, the PnC5 does not latch, and the armature returns to a neutral position. The armature is suspended on a thin metal strip and acts like a taut band suspension. However, closing up the pole pieces just a little on their adjustments allows the armature to latch in either position. Then, the PnC5 relay behaves like the PnC4 and becomes a latching relay. After I made this initial discovery and adjustment, it became clear that the overall sensitivity of the relay also depended on the combined average position of the pole pieces. If one considers using a capacitor as a timing element, ignoring the 75kW resistor in the capacitor charging process (as it is large compared to the resistance of the slave relay coils at about 6kW each), we can test some assumptions. In most RC timing circuits, a capacitor is seldom charged beyond one to two time constants to reach some siliconchip.com.au NORMAL Frequency = 2.5Hz; 100Hz reference pulse Side A 0.2s 75kΩ ERROR 1 t < 0°C; approximately 2Hz Side A 0.31s 91kΩ Side B 0.2s 75kΩ Side B 0.2s 75kΩ ERROR 2 t > 50°C; approximately 8Hz ERROR 3 P < 250mmHg; approximately 8Hz Side A 0.09s 75kΩ Side A 0.025s 14.5kΩ Side B 0.025s 14.5kΩ Side B 0.09s 75kΩ ERROR 1 & 3 t < 0°C, P < 250mmHg; approximately 6.5Hz ERROR 2 & 3 t < 50°C, P < 250mmHg; approximately 15Hz Side A 0.033s 14.5kΩ Side A 0.125s 91kΩ Side B 0.025s 14.5kΩ Side B 0.033s 14.5kΩ Fig.2: the various possible Manipulator oscillator waveforms, recorded by the original designers on 35mm film. Fig.3: a close-up of one of the Manipulator waveforms; note how the dead time is visible as dots where neither relay contact is closed. Photo 8 (above): four Soviet PnC5 dual-coil SPDT latching relays. There are 16 pins on the base as some other relays from the same series have multiple sets of coil windings. Photo 9 (right): the PnC5 relay mechanism out of its can. Australia's electronics magazine November 2023  103 Fig.4: the general configuration of the Soviet PnC4/PnC5 dual-coil latching relays used in the Manipulator. Their large coils make them very sensitive. threshold to initiate a state change. The reason is that the voltage profile across its terminals starts to flatten out after that and timing errors become more significant. One RC time constant charges the capacitor to 63% of the supply voltage, two time constants to about 86.5%, three to 95%, four to 98% and by five time constants, the capacitor is 99% charged; its terminal voltage changes little after at that point. I found that, once properly adjusted into a latching version with correct magnetic balance, the PnC5 relays worked in the Sputnik circuit but required a 36kW resistor, rather than 75kW, to achieve the correct 2.5Hz frequency with 8μF capacitors. This indicates that I achieved a relay sensitivity a little lower than I could have with the correct PnC4 relays. The sensitivity increases opening the pole pieces, but if one goes too far, the relay won’t latch reliably and it reverts to a non-latching condition. This is the effect of the taut band suspension in the PnC5 design; a small amount of extra energy is required to overcome that. Given the master-slave arrangement, for test & measurements only, I deleted the slave relay and replaced its coils with two 6.2kW resistors. That had little, if any, effect on the behaviour of the master (oscillator) relay. I was interested in the coil current required for the relays to change state. I made a voltage recording with a fully isolated scope across the 8.2μF capacitor in the initial test setup – see Fig.5. I later changed to using the original Soviet pairs of 4μF 160V PIO (paper in oil) types for the transmitter replica. Considering coil 1 (pins 1 & 2 of RLY1), the master relay, capacitor C1 charges when the relay contact feeding C1 is closed. Eventually, the master relay deploys when the threshold is reached and the relay changes state, magnetically latching to the opposite condition and initiating the charging process of C2 via contact 2. Fig.5 shows that this occurs when the voltage (marked in white) across the capacitor’s terminals has climbed from 9.5V to 18.5V. Therefore, 9V is required to cause the PnC5 Master relay to change state, in conjunction with the 36kW resistor and the 6kW coil resistance. That corresponds to a coil current of 214μA (9V ÷ 42kW). It’s close to but not quite as sensitive as the original PnC4 relay, which would have toggled at a mere 111μA. The capacitor discharges at a slower rate because, in the interval when contact C1 is open, the capacitor is discharging into the relay coil via the 36kW resistor. The yellow markings in Fig.5 show that the inverted exponential charging 21V (SUPPLY VOLTAGE) 18.5V 9.5V 0V 0.1 second/cm 0 RC 2RC 3RC 4RC Fig.5: a scope grab showing how the voltage (marked in white) across the relay coil varies during oscillation. The yellow annotations show roughly how the RC time constants correspond to the waveform. 104 Silicon Chip Australia's electronics magazine Fig.6: as the magnetic fields of both coils interact, we can sum them like this to see how the magnetic field strength varies over time. siliconchip.com.au curve seen is close to that of a four time constant RC curve. The charge time approximately matches an 8μF capacitor charging via 6.2kW (the slave relay coil) from a 21V source. Superficially, this does not seem ideal for setting a timing threshold, where one or two time constants would have a steeper approach. This is just considering the magnetic effects of the current in one of the master relay coils, but what about the other coil? As the applied voltage and therefore the current via one coil is climbing, the voltage on the other coil is falling, and the currents have opposing magnetic effects due to the polarity relationship of the two coils. If we chop up the scope recordings and invert the wave on coil side B, then add it to the wave from coil side A, we get a better idea of how the master relay approaches a state change. The approach to the threshold is much steeper, more like a two time constant inverted exponential curve, as seen in Fig.6. I have never seen any other large latching relay types that can change state with coil currents in the order of 100-200μA. Even the most sensitive relays I have seen before require at least 500-1000μA coil current, most much more. After finally finding the PnC4 data sheet for the part number PC4.520.350 used in Sputnik-1, it confirmed that the relay coils are 6.5kW ±1.3kW and that the relay operates in the range of 87-174μA, consistent with the Photo 10 (left): I made this relay test/adjustment jig using two bases that match the PnC5 relay pins. Photo 11 (right): the underside of the relay test/ adjustment jig showing the components and wiring that form the oscillator with the two relays. conclusions that I had made about it, switching at around 111μA. I suspect that the makers of these relays supplied specially tested and adjusted versions of the PnC4 relay to the Soviet Space Agency. I found out for myself that the pole-piece adjustments for the master relay are critical, especially for a perfectly symmetrical switching waveform. Once they are adjusted, though, the relay behaviour seems very predictable. Custom adjustment circuit To assist in setting up the PnC5 relays and adjusting their pole pieces, I built a custom circuit to monitor the duty cycle, shown in Fig.7. It also required a test jig with sockets to hold the relays – see Photos 10 & 11. Part of the setup involved using dummy 6.2kW resistors to take the place of the slave coils. The voltage developed across those is used to activate a comparator, with a 1V slice level, giving a stable 5V peak-to-peak output. A custom circuit using an op amp, shown in Fig.8, helped me make the required adjustments. The actual unit is shown in Photo 12. The output of the OP295 op amp swings rail-to-rail. The signal is heavily time integrated. The exact duty cycle was affected a little by the Fig.7: this shows how the major components are wired to the relay bases, for both the test jig and the actual Manipulator recreation. siliconchip.com.au Australia's electronics magazine November 2023  105 Fig.8: this test circuit aids in balancing the relays so that they give a 50% duty cycle in the Manipulator. operating frequency, so I made the relay pole piece adjustment at the operating frequency, close to 2.5Hz. One might expect that with an exact 50% duty cycle, the output from the integrator should be 2.5V with this circuit. However, when in perfect balance, the actual value achieved is around 2.66V because of the small gap in the timing where no contacts are closed (about 4ms on each side of the pulse) and the circuit being triggered by a low across the 6kW resistor, with the stage of inversion by the first op amp. A quick calculation suggested the measured (time-integrated) voltage would be 2.6V (2.5V × 208ms ÷ 200ms). The exact value of around 2.66V is of no concern, though, provided the voltages match precisely when the select switch is changed between the A & B sides. In other words, both halves of the relay must have identical magnetic properties and timing. When the relay is not in perfect ‘magnetic balance’, one voltage is lower than 2.66V, and the other is higher. This circuit could be doubled up, and the time-integrated voltage across each of the 6kW resistors could be fed into another comparator. However, it would need a window over which a range of voltages would be an acceptable difference. In practice, it was better to watch the meter and toggle the select switch to check that each half of the relay matched up. The sound of the Manipulator running With the complete Manipulator system running, the sound the relays make is very similar to a ticking watch or clock. It is easy to imagine Sputnik-1 flying around the Earth in 1957 at 8km/s with the relays inside it clicking like a clock. There is something quite magical about this, rather than it being deathly silent in there. You can hear the sound at the following links: • siliconchip.au/link/abmm • siliconchip.au/Shop/6/224 I doubt if anyone else would have recreated this circuit since Sputnik-1 launched. The design documents only appeared in the last decade, and it requires the now very difficult-to-get vintage Russian PnC4 or PnC5 magnetic latching relays, in good order and proper adjustment, to work correctly. Unfortunately, because these relays contained valuable precious metals, COMPARATOR SLICE LEVEL = 1V 0V 2V/cm Photo 12: this simple circuit, built on protoboard, helps determine when the oscillator duty cycle is at 50%. 106 Silicon Chip Australia's electronics magazine siliconchip.com.au most of them in Russia and Ukraine have been recycled because the plants doing it have offered good money for them. Power consumption As noted earlier, the design document stated that the Manipulator power consumption was less than 20mW. I measured a mere 14mW with the PnC5 relays and expect it would have been a little lower with the PnC4s. When I saw the 20mW figure and the 75kW resistors in series with the relay coils, I could hardly believe it and thought it might have been a misprint. I had to wait for the PnC5 relays to arrive from Ukraine to verify that the circuit really did work at such an astonishingly low power. If the slave relay contacts are connected to positive and negative voltage sources, the waveform shown in Photo 13 can be made, similar to the recordings of the original Manipulator on 35mm film. Note the small steps where, for a moment, neither contact is closed. You can see a video of the analog scope trace at https://youtu.be/k15GSKK_ UY0 The reaction to Sputnik-1 After Sputnik-1 was launched, the Americans were interested in seeing what telemetry might have been encoded into the transmissions. There was none, just alternate bursts of carrier wave at the two transmission frequencies at the 2.5Hz rate set by the Manipulator. Since none of the error conditions occurred, the Manipulator’s duty cycle remained at 50% during the whole flight. That could have disappointed the CIA or made them anxious, in case they had missed something secret embedded in the transmissions. Part of the genius of Sputnik-1 was its simplicity, and there is no doubt that the CIA, at the time, tried to overthink it. Next month At this stage, I had a working replica of the Manipulator, so the next job was to recreate the transmitter module. I would also need to build a copy of the metal housing that carried the transmitter circuitry and develop a suitable power supply. All of that will be described in the second and final instalment next SC month. ◀ Fig.9: the output waveform of the first op amp in Fig.8 during calibration. Photo 13: by connecting a bipolar supply to the outer relay contacts and the middle contact to the scope input, you get this sort of waveform. The steps in the middle of the ‘square wave’ indicate the dead time when no contacts are closed. siliconchip.com.au Australia's electronics magazine November 2023  107 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au CD Welder capacitor substitution & update I read your Errata regarding the CD Spot Welder (March & April 2023; siliconchip.au/Series/379) and the 39mF capacitors’ incorrect part code. I had already bought them, as indicated in the table in the original article. They are the same series as the 871-B41231A5399M000, with exactly the same specifications but a slight physical difference: they have three pins instead of two. The middle pin needs to be cut off for use on the CD Welder ESM board. As all the pins are 4.5mm long instead of 6mm, there is no need to trim them after soldering. The M002 version is 14.5 grams lighter, resulting in the welder being 435 grams lighter. Mouser currently has 664 of the M002 version, but the M000 versions are unavailable until February 2024. I suggest constructors get in quickly and pre-order them. The M002 versions are only $0.10 dearer, so $3 more for 30. I can’t see that there would be any performance difference between them. The physical differences will be of no concern with construction. My question is: what would the weight difference be attributed to, and would it make a performance difference? I wouldn’t think so. (P. V., Innisfail, Qld) ● Phil Prosser responds: I looked over the spec sheet and it makes no distinction between the three-pin and two-pin variants of those capacitors. I would have no hesitation in using them. Just make sure you have trimmed those leads in a way that will not allow them to scratch through the solder mask. The third pins are usually isolated, but for completeness and caution, trim them carefully. Not having had the chance to look one over, I expect that the weight difference comes down to the construction of the capacitor base. Using TFTP with Watering System Controller I built the August 2023 Watering System Controller (siliconchip.au/Article/15899) based on the WebMite (Raspberry Pi Pico W). I have been using CoolTerm 2.0.1 to communicate with it as there is no Mac version of Tera Term. I successfully copied the WebMite MMBasic Version 5.07.07 to the Pico, then connected to it and entered the SSID and password for my local WiFi router. The FILES and PRINT commands work OK, but when I attempt to use the TFTP command, I get “Error : Unknown Command”: WebMite MMBasic Version 5.07.07 Copyright 2011-2023 Geoff Graham Copyright 2016-2023 Peter Mather Connecting to WiFi... Connected 192.168.100.176 Starting server at 192.168.100.176 on port 80 > tftp Error : Unknown command > TFTP -i 192.168.100.176 PUT retic.bas Error : Unknown command How do I load the “retic.bas” file and associated files into the Pico? (B. R., Karrinyup, WA) ● tftp is an operating system command, not a PicoMite command. You run the tftp command on your local computer’s command prompt, not on the PicoMite. Using tftp with the WebMite is explained on page 25 of the WebMite manual, which you can download from our website at siliconchip.au/Shop/6/230 This web page, among others, says that the tftp command should work on macOS: siliconchip.au/link/abpr You could also try this tftp software on your Mac: siliconchip.au/link/abps 108 Silicon Chip Australia's electronics magazine I also have a follow-up to the CD Welder question published on page 109 of the October 2023 issue regarding whether it can weld copper strips. With shortened leads (50cm), I was able to make outstanding welds on heavy-duty nickel strips and excellent welds between 0.1mm-thick copper strips and batteries at only 17V. R. E.’s application called for 0.25mm copper, which is scarily thick. I think an ultrasonic welder is needed to achieve that. All he could find was a 0.3mm-thick ‘strip’. Even upping the voltage a tad over 25V and with short leads, this copper strip wouldn’t weld. So, as an update for potential users, this project will weld 0.1mm-thick strip with close to 100% headroom but will definitely not weld 0.3mm-thick copper to steel. Linkwitz mod affects frequency response? I am interested in building the through-hole version of the Calibrated Measurement Microphone described in the August 2023 issue (siliconchip. au/Article/15903) with the AliExpress WM61A ECM you offer. In the past, I have used the “Linkwitz modification” to ECMs as described in that article, as it gives extra headroom (although it’s pretty fiddly to do). My question is: does the ECM calibration file supplied with the capsule still apply if you do the Linkwitz mod? Did you check to see if it affects the overall response at all? (R. C., Collaroy, NSW) ● Phil Prosser responds: I tested the Linkwitz mod on a couple of sample electret microphones, and while it reduced the overall gain, it did not affect the overall frequency response significantly. Troubleshooting a fan speed controller I’m trying to troubleshoot a speed controller on a Braemar ducted gas system. Going through the troublesiliconchip.com.au shooting process, I have become very interested in how the room fan speed control circuitry works. The motor seems to run OK at the higher supply voltage of 150V AC, but at start-up speed 1, giving 97V AC, the motor doesn’t turn. From googling photos, I think the large heatsink on the control board is a Triac that chops the AC waveform to lower the voltage to the motor to slow it down. There is what looks like an opto-coupler between the low-­voltage DC and high-voltage AC part of the PCB. I want to learn more about how these Triac-switched speed controllers work. I bought and downloaded your April 2012 back issue with the Induction Motor Speed Controller as my motor would be similar. It seems to be a fancy solution where both the voltage and frequency are reduced to change speed. My motor has a run capacitor wired in series and has a start and run winding. Do you have a back issue with a Triac motor controller project? (E. M., Hawthorn, Vic) ● We published a Triac-based motor speed controller, the Refined FullWave Motor Speed Controller (April 2021; siliconchip.au/Article/14814). Check the motor start capacitors. They often go low in capacitance, preventing the motor from starting, especially at lower applied voltages. Is AN618 IC compatible with AN6180? I have a garden light that is a later batch than those from our original set that use the YX8018 IC, and I suspect the ANA6180 IC may be faulty. However, I can only find ANA618 listed on eBay, and the ANA6180 does not seem to be listed anywhere. Is there any difference between the ANA618 and the ANA6180, or is it just a different manufacturer? (B. P., Dundathu, Qld) ● Like you, we suspect that the O or 0 suffix just indicates a different manufacturer of the ANA618, as we can’t find any sensible information on a chip coded ANA6180 either. Check if the PCB connections match those expected for an ANA618 and, if so, try replacing it with an ANA618. Given that you can get them for around $1 each, including delivery, it’d be worth a try. siliconchip.com.au Compilation error with Arduino Seismograph I built the April 2018 3-axis Seismograph (siliconchip.au/Article/11030) when you published it. Unfortunately, my Uno died, so I purchased a replacement. Now, when I try to upload your code, I get the following error: error: ‘FilterOnePole’ does not name a type Any ideas? (I. M., Drouin, Vic) ● That is a library problem but not due to a missing library. We tried compiling the sketch with Arduino IDE version 2.1.1 and AVR boards version 1.8.5. Before installing the Filters library, we got a different error: fatal error: Filters.h: No such file or directory After installing the Filters library from the software download (copy the Filters folder from the zip file to ../Documents/Arduino/libraries/) and restarting the IDE, the sketch compiled successfully. We suspect that you have a different library named Filters or a different version of the library installed. The suggested fix is to remove the existing Filters library and replace it with the library from the download package. The reader later confirmed that using the recommended library fixed his problem. That time of year is nearly here... CHRISTMAS Spice up your festive season with eight LED decorations! Tiny LED Xmas Tree 54 x 41mm PCB SC5181 – $2.50 Tiny LED Cap 55 x 57mm PCB SC5687 – $3.00 Tiny LED Stocking 41 x 83mm PCB SC5688 – $3.00 Tiny LED Reindeer 91 x 98mm PCB SC5689 – $3.00 Transformer for SC200 Amplifier power supply I want to build a stereo version of the SC200 Amplifier (January-March 2017; siliconchip.au/Series/308). I have purchased two SC200 Amplifier Module PCBs and two sets of hardto-get parts from your Online Shop, along with one 135W Stereo Amplifier Power Supply kit and the Loudspeaker Protector kit. I intend to build the Touchscreen Digital Preamp (September & October 2021; siliconchip.au/Series/370) to complete the amplifier. Unfortunately, I cannot locate a suitable toroidal transformer with 40 + 40V AC outputs and 15 + 15V AC auxiliary windings. Is there a suitable replacement? What is the best configuration to supply the required power for the stereo amplifier? I probably do not need the full 135W into 8W, but I would not like to otherwise compromise the amplifier’s capabilities. (J. E., Beachmere, Qld) Australia's electronics magazine Tiny LED Bauble 52.5 x 45.5mm SC5690 – $3.00 Tiny LED Sleigh 80 x 92mm PCB SC5691 – $3.00 Tiny LED Star 57 x 54mm PCB SC5692 – $3.00 Tiny LED Cane 84 x 60mm PCB SC5693 – $3.00 We also sell a kit containing all required components for just $15 per board ➟ SC5579 November 2023  109 ● Unfortunately, Altronics stopped selling the 40-0-40 + 15-0-15 transformer we used a few years ago. We suggest you use a 300VA 40-0-40 transformer (eg, RS 117-6065) plus a small 15-0-15 transformer (eg, Altronics M4915C). The RS transformer’s 115V AC primaries can be wired in series to get a 230V AC primary. That would then be wired in parallel with the smaller transformer’s primary, with the latter having a 500mA fuse added in series with its primary. The main fuse that protects the whole lot (eg, in a chassis IEC mains input connector with fuse) should be rated at 3.15A, slow blow (eg, Altronics S5657). If you don’t need full power and would be happy with somewhere in the region of 100W per channel, you could use a 35-0-35 300VA transformer, which might be a little easier to obtain. Still, the 40-0-40 transformer isn’t too expensive or difficult to get, so we suggest you stick with that. Relay for Currawong Amp not available Thank you for supplying the PCB and some parts so I can build the Currawong Stereo Valve Amplifier (November 2014 to January 2015 issues; siliconchip.au/Series/277). I am having trouble sourcing the Altronics S4141B relays specified. Altronics have told me that these are now obsolete. Can you advise of any replacements? (J. Z., Tranmere, SA) 110 Silicon Chip ● S4141B was a 5V DC coil version of the S4140B (12V DC). In the Currawong, these relays are used to disconnect the loudspeakers when a pair of headphones are plugged in, and they are powered from its 12V rail via an 82W 1W resistor with an open jumper, LK3, across it. While the purpose of that jumper was to allow the S4141B relays to work with a 6V DC rail rather than 12V DC, it turns out that it’s also perfect for allowing S4140B relays to be substituted for the discontinued S4141B types. All you need to do is place a jumper shunt on LK3 (you can omit the 82W resistor if you want). The relay coils will then have the full 12V DC applied. The only other change you need to make is to increase the 330W series resistor for LED2 to 1kW to keep the LED current the same as before. Changing the frequency of a 555 timer circuit I recently developed a pest problem, and some research revealed an article by Colin Dawson in Electronics Australia magazine, November 1985, titled “Zap ‘em with the Pest off”. The circuit is shown below. Although I have had a fair bit of success experimenting with normal 555 astables, this is the first time I have come across this type of 555 design, and it is proving to be a bit more of a challenge. I am trying to calculate the component values between IC2 (4017) and IC3 (555) to change the frequencies. Australia's electronics magazine This design is unique in that Colin has installed a diode across pins 7 and 6, effectively bypassing the 22kW resistor when charging the 820pF capacitor. I have read through the project article, but I can’t understand how he calculated his values, and further research hasn’t provided any useful information either. I have considered using separate 555s connected to each of the 4017 outputs, providing the frequencies I want, but why use six when one will provide the same result? Can you provide the formulas used to calculate the frequency, time high, time low and duty cycle or any other helpful information? (Ken, New Zealand, via email) ● Introducing the diode means that the 820pF timing capacitor for IC3 is charged via the 10kW resistor from the high 4017 output rather than via the 22kW resistor. So initially, the capacitor charges via the 10kW resistor and is discharged via the 22kW resistor connecting to pin 7. There is a slight complication due to the diode voltage drop compared to the overall supply, but they don’t significantly change the charge rate due to the relatively low voltage. So the charge and discharge times can be calculated separately and added to give a total period. The frequency is the inverse of that. The charge period is 0.693 times the 820pF (8.2 × 10-10F) capacitor value multiplied by the charge resistor value (10kW). The discharge period is 0.693 × 820pF × 22kW. continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE KIT ASSEMBLY & REPAIR 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, New Zealand, but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com 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 OATLEY ELECTRONICS OCTOBER & NOVEMBER SPECIALS 10 x 12V/0.5m pure white LED bars, NOV.1: $30, (used in LT117PW) £ warm white LED lamp package of four 12V/5W LED lamps, NOV.2: $17 (used in IT1117) £ 4-channel UHF remote control pack, with 2 transmitters and a power adaptor, NOV.3: $40 (K180XPK) £ 4 x 6J6 twin triodes, NOV.4: $25 £ 4 x JAN6418 pentodes, NOV.5: $25 £ 6 x IAD4 pentodes, NOV.6: $25 £ 4 x XL6009 boost step-up regulator module, NOV.7: $15 £ 4 x 150W/12V speed controller, NOV.8: $40 (as in SPC150) £ 4 x 12V/3.5A power supplies, NOV.9 £ 4 4 x 12V/5m LED strips NOV.10: $15 (used in SB-5M-12V-NW) Order as many lots from this list for free postage. Please allow up to 2 weeks for delivery. Orders by email only: branko<at>oatleyelectronics.com For enquiries: 0428600036 £ 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 start at $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 (02) 9939 3295. FOR SALE LEDsales LEDs and accessories for the DIY enthusiast LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au V I S I T T H E T R O N I X L A B S par ts clearance store for real savings on parts at clearance prices, with flat rate express delivery Australia-wide – go to https://tronixlabs.com Lazer Security For Quality That Counts... After 38 Years, I am looking to move and semi-retire. Lazer Security needs a young and dedicated person to evolve and grow. We are currently based in Wolli Creek, NSW and we sell new components, unused (recycled) components and kits with an emphasis on LED lighting. If you are interested in purchasing the business from me, please contact tony<at>phoslighting.net 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 November 2023  111 I have successfully built the 40V Hybrid Switchmode/Linear Bench Power Supply (April-June 2014 issues; siliconchip.au/Series/241), a really excellent and compact, fully adjustable supply to modernise my workbench. As I was testing it, before enclosing it in the case, I noticed the heat dissipation of the two linear regulators was quite high for an input of 19.5V. This design accepts up to 24V at the input, meaning the dissipation could be higher than in my instance. Based on my finger test, these internal 7805 and LM2940 regulators appear to run above 50°C, and the case has no ventilation. I was pondering the lack of ventilation and whether I should drill holes in the case but concluded that would detract from its looks. I then recalled Advertising Index Altronics........... 9, 31-34, 73, 81, 89 Dave Thompson........................ 111 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Hare & Forbes............................. 15 Jaycar................. IFC, 12-13, 16-17, .................................... 60-61, 92-93 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology......... OBC, 7 Mouser Electronics....................... 4 Oatley Electronics..................... 111 SC Christmas Ornaments........ 109 SC Breadboard PSU...................... 8 Silicon Chip 500W Amplifier..... 87 Silicon Chip Binders.................. 72 Silicon Chip PDFs on USB......... 14 Silicon Chip Shop.................90-91 Silicon Chip Songbird................ 30 Silicon Chip Subscriptions........ 97 The Loudspeaker Kit.com............ 6 Tronixlabs.................................. 111 Wagner Electronics..................... 11 112 Silicon Chip another Silicon Chip project and wondered if the quiescent heat dissipation could be improved in this project by replacing the 7805 regulator with your 78xx Replacement project from August 2020 (siliconchip.au/Article/14533). It looks possible to replace the LM2940 12V regulator as well, using the same approach. Do you have any advice on whether this would introduce any problems or if it would require modifications beyond the 78xx Replacement substitution? (B. R., Eaglemont, Vic) ● Both linear regulators are provided with fairly generous heatsinks and contact with PCB copper, so they should run well within their specifications, even if they get a bit warm. 50-60°C might seem hot, but their maximum junction temperature ratings are 150°C. Still, we understand the desire to reduce power consumption and keep the case cooler. Using thermal paste between the regulator and heatsink, and heatsink and PCB, could reduce the junction temperature, as could using slightly larger heatsinks. However, the same total power would still be dissipated within the case. Your idea of using a switch-mode regulator is a good one. All that the 12V regulator (REG1) powers is a 7555 timer (IC2) driving charge pumps to generate some auxiliary rails (-5V and VBOOST) and 7805 regulator REG2, which delivers the +5V rail. None of those sections should be bothered by the extra noise expected from a step-down/buck regulator, such as the one we published in August 2020. By all means, try the substitution; just verify that the supply doesn’t have any odd behaviour after you swap the regulator over. If it does (which seems unlikely), you might need to add an Errata & Sale Date for the Next Issue Switchmode substitute for warm regulators RC or LC low-pass filter between the output of that regulator module and the rest of the circuitry. You could probably also replace REG2 (7805) with a 5V buck module but we’d be a little more cautious with that one. It drives the panel meters, which should not be a problem, but it also provides a reference voltage for the voltage and current adjusting pots and trimpots. The safest thing to do would be to leave REG2 as a 7805 but disconnect the 5V rails going to the two panel meters and run them from the output of a separate 5V buck converter. We don’t think that would cause any problems and would substantially improve efficiency. Identifying a kit sold by a third party I need your help to find the firmware for a PIC16F84 chip. I purchased a Big Clock kit from Quasar Electronics in England many years ago. The kit was a Big Clock model AS3073. My old but very exact clock suffered damage to the PIC16F84 microcontroller and does not work anymore. I know it will be difficult to find this old program, but I would greatly appreciate it if you could help me. (R. C., via email) ● We can’t find any mention of “Quasar” or “AS3073” in any of our magazines. Perhaps they took one of our designs and turned it into a kit without our knowledge. We have published many clock designs, but the one that seems most likely to be a match is the Big-Digit 12/24-Hour Clock (March 2001 issue; siliconchip.au/Article/4235). The software for that project is here (PCBs are also still available): siliconchip.au/ Shop/6/2171 SC Watering System Controller, August 2023: the original V1.2 version software had two serious faults. It was not driving the correct I/O pins as shown in the circuit diagram, and a calculation error could cause it to water on the wrong day. V1.3 fixes those and adds a new SMTP relay service for sending emails (SMTP2GO), as some users have had difficulty opening a free account with SendGrid. Several minor changes were also made to improve the web pages generated by the firmware. The new firmware is available for free download from our website. If upgrading an existing installation, you can just overwrite the four files in the WebMite’s internal file system, then type RUN “RETIC.BAS” and press Enter. The “settings.dat” file will automatically be upgraded. Next Issue: the December 2023 issue is due on sale in newsagents by Monday, November 27th. 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