November 2021 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Standardising on USB-C: a good idea
Feature: Big Brother is Tracking You! – Part 1 by Dr David Maddison
Project: USB Cable Tester – Part 1 by Tim Blythman
Feature: El Cheapo Modules: 6GHz Digital Attenuator by Jim Rowe
Review: R80 Synthesised Aviation Band Receiver Kit by Andrew Woodfield
Project: Pocket Weather Station by Aarav Garg
Project: Model Railway Carriage Lights by Les Kerr
Vintage Radio: Stromberg-Carlson model 496 radio by Associate Professor Graham Parslow
Project: Two- or Three-Way Stereo Active Crossover – Part 2 by Phil Prosser
Serviceman's Log: That ‘80s gear and the art of printer repair by Dave Thompson
PartShop
Ask Silicon Chip
Market Centre
Advertising Index
Outer Back Cover

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NOVEMBER 2021 ISSN 1030-2662 11 The VERY BEST DIY Projects! 9 771030 266001 U S Cable B Tester FREE 572 PAGE JAYCAR CATALOG included with this issue $1150* NZ $1290 INC GST How you are being tracked on the Internet Pocket Weather Station using an Arduino Nano R80 Aviation Band Receiver Kit for just $50 Carriage Lights for Model Railway sets INC GST Build your own Solar MPPT Charge Controller Ever wondered what goes into a solar charge controller and what makes MPPT (Maximum Power Point Tracking) better than PWM (Pulse Width Modulation)? Find out yourself, by making this project. Uses a simple Arduino to control and regulate the flow of power from the solar panel to to the battery. The project also includes an output relay to automatically turn off when the battery gets too low voltage. A great project for DIY amateurs and solar aficionados. CLUB OFFER BUNDLE DEAL 7995 $ SAVE 40% KIT VALUED AT $143.36 SKILL LEVEL: ADVANCED For step-by-step instructions & materials scan the QR code. www.jaycar.com.au/solar-mppt-charge-controller See other projects at www.jaycar.com.au/arduino JUST 40 ONLY 1 5 $ 85 $ 95 55 PIECES EA PIECES 40 PIECES 150mm Jumper Leads Voltage Regulator 7805 +5V 1A. TO-220 case. ZV1505 100 $ gift card Awesome projects by On Sale 24 October to 23 November, 2021 Plug to Plug Socket to Socket Plug to Socket WC6024 WC6026 WC6028 JUST 9 $ 95 Hobby Solar Module 3 cells per module. 1.5V rated. Idea for powering solar projects, hobbies, etc. ZM9012 Got a great project or kit idea? If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com ONLY 1350 $ Electrolytic Capacitor Pack Values range from 1μF - 470μF. Pk 55. RE6250 Looking for your next build? Silicon Chip projects: jaycar.com.au/c/silicon-chip-kits Kit back catalogue: jaycar.com.au/kitbackcatalogue 1800 022 888 www.jaycar.com.au Shop online and enjoy 1 hour click & collect or free delivery on orders over $99* Exclusions apply - see website for full T&Cs. * Contents Vol.34, No.11 November 2021 SILICON CHIP www.siliconchip.com.au Features & Reviews 16 Big Brother is Tracking You! – Part 1 Spying isn’t just the traditional method of watching someone with a camera. Governments, businesses & individuals could be spying on you via the internet, recording more information about you than you might expect. So what can you do about it? – by Dr David Maddison 37 El Cheapo Modules: 6GHz Digital Attenuator This article describes another self-contained digital attenuator with an OLED screen. Compared to the 3.8GHz attenuator from last month, this module attenuates a signal from 1MHz-6GHz by 0-31.75dB in 0.25dB steps, making it potentially more useful – by Jim Rowe 40 Review: R80 Synthesised Aviation Band Receiver Kit For just $50 you can own an easy-to-build radio receiver kit which is ideal for monitoring local airport traffic – by Andrew Woodfield Constructional Projects “If you aren’t paying for it, you’re the product”. Companies such as Facebook, Google and others collect huge swathes of information about their users. So why is it done, what do they collect and how can you prevent or reduce it? – Page 16 28 USB Cable Tester – Part 1 This USB Cable Tester helps you determine if you have faulty USB cables; an important step when troubleshooting equipment. It tests most common USB cables such as USB Type A, Type B, Micro-B, Mini-B and the newer USB-C connectors – by Tim Blythman 56 Pocket Weather Station Perfect as a beginner’s project, this mini Weather Station can be carried everywhere and uses just five low-cost pre-built modules. All that needs to be done is assemble it into a custom 3D-printed case and solder a few of the wires together – by Aarav Garg Cables with USB Type A, Type B, USB-C, Micro-B and Mini-B connectors can be tested with our new project. It detects and reports faults with the cable, or if the cable is power-only – Page 28 60 Model Railway Carriage Lights Designed for OO-gauge model railways, these carriage lights are batterypowered, can be controlled by an external magnet, and can fit inside the roof of the model train – by Les Kerr 78 Two- or Three-Way Stereo Active Crossover – Part 2 Following on from the article in last month’s issue, we cover PCB assembly and how to set up and use it, along with a small section on troubleshooting – by Phil Prosser Your Favourite Columns 53 Circuit Notebook (1) Modifying Micromite software to use a 3.5in display (2) Voice-operated and proximity lift controls Built into a 3D-printed case, and using an Arduino Nano, this Pocket Weather Station is the perfect project for beginners due to requiring only basic soldering skills – Page 56 64 Vintage Radio Stromberg-Carlson model 496 mantel radio from 1936 – by Associate Professor Graham Parslow 84 Serviceman’s Log That ‘80s gear – by Dave Thompson Everything Else 4 Editorial Viewpoint 6 Mailbag – Your Feedback 90 Silicon Chip Online Shop siliconchip.com.au 92 Ask Silicon Chip 95 Market Centre 96 Advertising Australia’s electronicsIndex magazine Measuring just 28 x 16mm and shown at actual size, this Carriage Lights driver can easily fit inside most model trains to provide some extra decor to your railway layouts. 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Technical Staff Jim Rowe, B.A., B.Sc. Bao Smith, B.Sc. Tim Blythman, B.E., B.Sc. Nicolas Hannekum, Dip. Elec. Tech. Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<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 Ian Batty Phil Prosser, B.Sc., B.E.(Elec.) Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson, B.Bus., FAICD Staff (retired) Ross Tester Ann Morris Greg Swain, B. Sc. (Hons.) 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): 12 issues (1 year): $120 24 issues (2 years): $230 new prices from October 31st 2021 For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. ISSN 1030-2662 Printing and Distribution: Editorial Viewpoint Standardising on USB-C: a great idea The EU is again looking at forcing manufacturers to standardise on a single charging connector, almost certainly USB-C this time. They have been discussing this since 2009; I’m not sure why it is taking so long to finalise. In the time they have been considering it, several ‘standard’ USB connectors have come and gone, with mini-B giving way to micro-B and now Type C. I don’t like the idea of governments forcing manufacturers to use particular technology for a host of reasons. For example, industry leaders are likely to have a much better idea of suitable technologies than those in government. Also, imagine the nightmare if different governments (eg, EU & USA) introduced conflicting requirements. But ignoring all that, standardising on USB-C for charging the vast majority of portable devices is a fantastic idea. Most phone and tablet manufacturers have already switched to USB-C. It is superior to the connector used on fruit-themed phones, giving higher transfer rates and much higher power delivery. Having a connector standard across all devices would mean that we all only need to buy one type of charger to power and charge virtually all our devices. Even low-cost gadgets are switching to USB-C for power and charging these days, and I think pretty soon, power-only Type-C connectors will cost little more than a micro-B connector. It’s also nice that the cables can be symmetrical, with Type-C plugs on each end. The only people that such standardisation would not benefit would be those who are dead-set on using proprietary connectors to lock consumers into using their products. Ahem. The USB-C connector is much easier to insert and remove. It also has higher power delivery capability with USB-PD, much higher data transfer rates and significantly less chance of damaging the connector if you yank the cable. It’s certainly a lot better overall than either micro-B USB or Lightning connectors. While the USB-C connector was introduced with USB 3.0, it also supports Thunderbolt and USB4. So it clearly is the way forward. Our USB Cable Tester (which I think is a brilliant project, starting on page 28) features two USB-C sockets to test cables with these connectors at one or both ends. I will definitely be building one of those as I have lots of USB cables, and I’m unsure which ones are good. The USB naming scheme is a disaster When USB 3.2 was introduced, they decided to eliminate the USB 3.0 and USB 3.1 naming schemes and retroactively rename all these standards as variations on USB 3.2. USB 3.0 becomes USB 3.2 Gen 1, USB 3.1 becomes USB 3.2 Gen 2x1 and the newly introduced standard is USB 3.2 Gen 2x2. How confusing! It would have made a great deal more sense if USB 3.0 was used for 5Gbps capable devices, USB 3.1 for 10Gbps capable devices and USB 3.2 for 20Gbps capable devices. Worse still, USB 3.2 devices capable of either 10Mbps or 20Mbps will carry the “SuperSpeed+” designation, even though 10Mbps is no faster than USB 3.1. Most consumers will not understand this scheme and will be bamboozled, thinking that a slower device supports the faster technology. Hopefully, the naming will become a lot simpler with the upcoming USB4, which will merge USB with Thunderbolt. Thankfully, USB4 also uses the Type-C connector. by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 4 Silicon Chip Australia’s electronics magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine November 2021 5 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 had 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”. Right to repair and digital TV I believe that major manufacturers (who wish to maintain their unsustainable global business models and greed thereof) have submitted misconceptions or inappropriate responses to the Productivity Commission on the issue of the right to repair and planned obsolescence. The global structures sustaining these problems need to be dealt with effectively. For a particular model of a consumer product or series thereof, I believe that spare parts including new firmware updates should be available for a minimum of five years after discontinuation; firmware and software tools should be available forever. Also, the right to repair should also extend to the right to repurpose; for example, displays in certain Apple iPad models and server power supplies are two good candidates for repurposing. In 2009, I noted a labelling scheme for digital TV equipment that did not require MPEG-4 capability (even on high-definition units, although it was included on receivers provided by the Household Assistance Scheme) before MPEG-4 became an Australian Standard in 2015. That was unacceptably slow. In some cases, it’s hard to tell from the manufacturer-provided documentation what type of digital tuner is included! It is also unacceptable for DVB-T2 not to be an Australian Standard when it was ratified about 10 years ago and DVB-T2 trials concluding in the Gold Coast in 2018; the same also goes for HEVC and the latest audio codecs. Support for DVB-T2 and HEVC along with the latest audio codecs should be a prerequisite for the Energy Rating label and MEPS compliance, which would mean certainty for manufacturers, broadcasters and consumers alike. It would help prevent Australia 6 Silicon Chip from being used as a dumping ground for products that will quickly become obsolete. Instead of reallocating 600MHz of spectrum, carriers could partially reallocate the 3G/4G spectrum for 5G services, considering that 5G uptake would reduce traffic on the 3G/4G spectrum. This is like how Optus and Vodafone partially reallocated the 900MHz 2G spectrum for 3G services 3-4 years after 3G services were introduced on the 2100MHz band in 2005. Bryce Cherry, via email. I take my hat off to Tim for writing such a clever program. Tim went to a great deal of detail to explain the software operation. While I understand the concept of scanning a TV screen to produce an image, I struggle to grasp how the program knows when the ball has struck the bat and the random way the ball bounces all over the screen—very clever stuff. Geoff Coppa, Toormina, NSW. The designer of the tinySA writes in I got an email last week from our Vishay rep advertising a stunning new range of thin-film Nichrome chip resistors under the name “P2TC”. They come with a 0.01% tolerance, ±2ppm/°C TCR, are available in SMD packages from 1005M/0402 imperial to 5025M/2010 imperial and with resistances from 100W to 3MW. Amazing! But as you would expect, they are not cheap, at over $10 each even in quantities of 100. Still, for specific precision applications, they are game-changers. See www.vishay.com/ docs/53080/p2tc.pdf Duraid Madina, Sydney, NSW. I’m the designer of the tinySA spectrum analyser you reviewed in the September 2021 issue of your magazine (siliconchip.com.au/Article/15032). I’d like to suggest that the author (Allan Linton-Smith) should update the firmware of the tinySA, as many small improvements have been implemented since its release. Erik Kaashoek, The Netherlands. Slightly less ‘nano’ TV Pong Thanks for presenting the Nano Pong game in the August issue. This piqued my interest as they were popular when I was a child. I balked at the SMD construction as I like to be able to easily modify or repair my projects if needed at a later date. I sourced the through-hole version of the PIC through element14 and lashed up a simple through-hole PCB (see photo). Australia’s electronics magazine Incredibly precise resistors introduced Voltage vs current drive for loudspeakers I read the article on negative feedback with interest and still can’t understand why audio power amplifiers continue to use voltage feedback. Voltage feedback is appropriate if you are directly driving an electrostatic speaker. When you are driving voice coil or ribbon speakers, they are current-driven devices. John Cornwall, Warnbro, WA. Response: we published a discussion on this topic on page 94 of the February 2016 issue. siliconchip.com.au siliconchip.com.au Australia’s electronics magazine November 2021 7 The point made there is that, while the voice coils are inductors, the cone suspension system and the action of the air inside the cabinet combine to provide a restoring force. This, along with back-EMF feedback from the voice coil, essentially mean that most speakers respond more-or-less linearly to the signal voltage within the range of frequencies they are designed to reproduce. I ran that answer past two contributors who are experts on loudspeakers, having designed several good ones (Allan Linton-Smith and Phillip Prosser), and both agreed that the answer we gave back then was essentially correct. The last 50-odd years of mainstream hifi development has been primarily based on the idea of the amplifier being a voltage source and the loudspeakers being driven from this voltage source. The resulting designs have been optimised to provide good linearity under those conditions. So the combination of the voice coil, suspension systems, crossovers and cabinet properties in modern speakers are designed to respond linearly to voltage signals within their design operating ranges. There has been some research into current drive of loudspeakers, but it has not become mainstream. Quite a few aspects of the design would have to change for current drive to work well, especially any passive crossovers in the system. The most significant difference between voltage drive and current drive will be around driver resonance. Most loudspeaker designs tend to avoid operation around resonance (for good reason). We think it would be necessary to re-engineer the whole system, including the amplifiers, crossovers, drivers and cabinets to switch from voltage drive to current drive, and it’s unclear whether that will provide any real benefits. Thorium reactors: better than sliced bread? China is in the process of firing up a compact thorium-based experimental reactor with a power of 2MW. Its dimensions are only 3 x 2.5 metres. Cooling is based on molten salt rather than water, so it does not need to be close to a water source. Thorium has many advantages over uranium as an energy source. Compared with uranium, waste is much less of a problem and byproducts cannot be weaponised. The shutdown can be instantaneous and meltdown is impossible. Thorium is cheap and abundant. Geosciences Australia has estimated that Australia has half a million tonnes of thorium, the largest resource in the world. Molten salt cooled reactors are not new. The first was built in the 1940s at Oak Ridge in the USA and ran for nearly 30 years. This would be a great topic for an article in Silicon Chip. James Goding, Princes Hill, Vic. Comment: it’s interesting that, for all their theoretical advantages, thoriumbased reactors have not (yet) gained traction since they were first proposed in the 1950s. What a portable radio looked liked in 1936 I came across this cover page (shown adjacent) in an old American magazine, Radio-Craft, for a portable radio back in 1936. It looks great with the battery belt and the aerial as part of the sunshade! If you had that today, do you think you could board a plane while wearing it? Graham Street, Auckland, NZ. 8 Silicon Chip Australia’s electronics magazine siliconchip.com.au Delivering more The widest selection of semiconductors and electronic components in stock and ready to ship au.mouser.com siliconchip.com.au Australia’s electronics magazine November 2021 9 australia<at>mouser.com Digital Preamplifier comments Helping to put you in Control Spectrally Flat Class C Pyranometer DeltaOHM PPYRA03AC – Spectrally Flat Class C Pyranometers according to ISO 9060:2018. Complete with levelling device and calibration report. SKU: OHM-001 Price: $1545.50 ea UC100 USB Motion Controller Directly replaces the traditional Parallel port with modern USB. Can control up to 6-axis with Mach3, Mach4 or UCCNC software. Up to 100kHz step frequency operation, Fast communication with data buffer for robust and stabile operation. SKU: CND-001 Price: $198.00 ea M18 Shielded Inductive Proximity Sensor NPN, NO+NC IPSI/L-18NOC5B Shielded (flush) M18, 4-wire NPN-style output with NO+NC contact type. It has a sensing distance of ~5 mm. Screw on connector. Choose 2m cable with straight or 90 degree 4 wire M12 connector. SKU: IBS-0280 Price: $30.25 ea Programmable Range Pressure Sensor Novus Automation’s NP620 Programmable Range pressure sensor with input range of 0 to 10 Bar. 2-wire 4 to 20 mA output, 0.25% accuracy and 1/2” BSPP process connection. SKU: NOS-206 Price: $259.60 ea 604 Differential Pressure Switch Huba 604 is used as a DP flow switch in ventilation ducts for the control of filters and fans, and in control systems for the control of dampers. Pressure range 0.2-3mbar option 1-10, 0.5-5, 10-50. SKU: NOS-2600 Price: $307.95 ea Thermostat Controller with NTC Sensor and Buzzer Panel mount thermostat with included NTC sensor on 2 m lead. Configurable for a huge range of heating and cooling applications. Fitted with Buzzer for alarm. 100 to 240 VAC powered. SKU: CET-0012 Price: $121.00 ea 2.0 N·m NEMA 23 Integrated Stepper Motor iST-2320 2.0 N·m NEMA 23 stepper motor with integrated driver. Standard pulse and direction (or CW/CCW) input. Advanced antiresonance DSP driver. SKU: SMC-126 Price: $241.95 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. 10 Silicon Chip There seems to be an error in the schematic of the Digital Preamp last month. It shows IC6 & 7 being supplied from the 12V line when the text states a few times that this device operates with a 5.5V supply. I notice that there seems to be no provision for a balance control. Presumably, one may be readily implemented by an offset between the channel gains. Of course, wellpositioned speakers in a good room should not require any offset between channels, but not all domestic listening situations have that luxury. The article says that the equalisation bypass relay is not required, because, at unity, the equaliser otherwise has a negligible effect on sound quality. And while that may be so, a bypass switch does have other uses. As a sound engineer, bypass switches on any processing stage permit you to do a quick A/B check to hear what it is doing to the sound. Without that, there is a tendency to keep adding a bit more of that effect, and then a bit more again, etc... Doing an A/B check with a bypass switch makes it clear what you’re doing to the sound, and will often make you reduce the amount of the effect that you add, usually to the benefit of the sound. Of course, that is much more important in production and mastering, where what you do affects what many other people hear. But in a domestic situation, the user is really the only one whose perception of the sound is affected. Noel Bachelor, Global Recordings Network (Aus). Comments: You are right about the circuit; the VDD pins of IC6 & IC7 are connected to the +5.5V rail, not the 12V rail. Yes, the hardware is capable of balance adjustments. We did not add that to the software because the interface is already quite busy and complicated. Similarly, the hardware can provide a bypass function by simply switching the digital pots between their midpoint settings and those determined by the user. The relay is not needed for this, just the appropriate software. Again, that function was left out mainly to avoid more UI clutter. Early days of electricity in Australia As one with fading eyes, I have not been much interested in recent projects involving surface-mounted components. However, the series of articles on how things work and the history behind the way of things today still makes Silicon Chip a good buy. The following memories may be of interest to your readers. In my pre-teen days, I sometimes helped my father install 32V DC wiring in farmhouses where the SEC (State Electricity Commission, Victoria) was not yet available. These were wired in TRS (Tough Rubber Sheath). This has become some of the most dangerous wiring in Australia because over time, the rubber decomposes, and if touched by human or rodent it just falls off the wire, potentially creating short circuits. Being 32V, fuses were much heavier in those systems to carry the greater currents required at lower voltages, so fire is a possibility. Before the Second World War, most installations used DCC (double cotton covered) wire, in steel conduit. In the long run, that was probably safer but much more difficult and thus costly to install or alter. Australia’s electronics magazine siliconchip.com.au What if the future isn’t something we dream, but something we create? At Analog Devices, we believe staying ahead of what’s possible means embracing new opportunities to make our company stronger. And now that Maxim Integrated is joining Analog Devices, our collective expertise in power management, advanced sensing, and connectivity will help make what if become what is. See What If: analog.com/Maxim Where what if becomes what is. siliconchip.com.au Australia’s electronics magazine November 2021 11 POWER SUPPLIES PTY LTD ELECTRONICS SPECIALISTS TO DEFENCE AVIATION MINING MEDICAL RAIL INDUSTRIAL Our Core Ser vices: Electronic DLM Workshop Repair NATA ISO17025 Calibration 37 Years Repair Specialisation Power Supply Repair to 50KVA Convenient Local Support SWITCHMODE POWER SUPPLIES Pty Ltd ABN 54 003 958 030 Unit 1 /37 Leighton Place Hornsby NSW 2077 (PO Box 606 Hornsby NSW 1630) Tel: 02 9476 0300 Email: service<at>switchmode.com.au Website: www.switchmode.com.au 12 Silicon Chip Although all the houses wired by my father passed inspection by the SEC when mains power became available, being less than the supposedly safe 50V, one did not have to be a licensed electrician to do the actual installation. It just had to pass inspection when converted. As well as 32V DC, 110V DC and 240V AC systems were used in private plants. I was never involved in 110V plants, but generally they followed the same procedure as 32V, except for operating at lethal voltages and thus presumably needing a licensed electrician. DC plants consisted of an engine, generator and the necessary number of 2V lead-acid cells, associated switchboard and wiring. If the battery was not allowed to get too flat, the generator could be switched to starter motor mode simply by stepping on a floor switch. The engine on a 32V system could be started by hand cranking if necessary, being usually a 3-4 horsepower Cooper petrol engine made in Australia. 110V motors were a bit harder to start because they were generally larger diesels, typically imported from England. The only way in those days to know the state of charge was by measuring the specific gravity of the electrolyte in the cells with a hydrometer. Sealed low-maintenance batteries had not been heard of, let alone deep discharge types. Completely flatten the battery, and you were looking for new cells very soon. In a 32V system, the generator could be used in compound or series mode depending on the position of a large knife switch on the switchboard. In series mode, the field coils were in series with the armature for maximum output. To do the ironing or run the washing machine, the engine had to be run with the generator in this mode. I think the battery was still in-circuit as a voltage regulator. In compound mode, the generator charged the battery, with a large rheostat provided to regulate the output by varying the current to the field coils. As the battery neared full charge, the current had to be manually adjusted like an automatic battery charger does today. Over-charging was nearly as destructive as over-discharging. Distilled water also had to be added to the cells on just about a weekly basis depending on the amount of system use. There was only one 110V DC system in my area that I know of, and it was soon converted to SEC power. However, there is an interesting story involving that plant. On one occasion, the engine would not start, so something had to be done urgently to prevent the battery from becoming over-discharged. The serviceman was called, and he decided that the diesel injectors needed cleaning. But woe, due to carbon build-up around the injectors, they could not be withdrawn from the engine head. The standard procedure in such a case was to loosen the holding nuts a couple of turns and then stand on the starter switch, allowing the engine compression to loosen the injector. But our hero had neglected to disconnect the injector from the fuel pipe, and this time the engine decided to fire. The injector, nuts and fuel pipe disappeared through the engine shed roof. Strangely enough, the story seems to stop at that point; I guess there was some degree of embarrassment. The only other farm plants I ever saw were 240V AC, essentially mains power with automatic start if a light was switched on. I could not work on the electric side Australia’s electronics magazine siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build *** System Assembly Ampec Technologies Pty Ltd Australia’s siliconchip.com.au Australia’selectronics electronicsmagazine magazine siliconchip.com.au Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au ovember2021 2021 13 FNEBRUARY 37 of these, but I did get called to the occasional problem involving their use. I have told the story before of farm children kicking their football into the open wires between the engine shed and the house. The engine would start and then shut down as soon as the voltage rose high enough to switch to load. It was a safety cutout operation, but for a long while, it looked like an engine fault. When the twisted wires were discovered and fixed, so was the engine. These plants were known as Startamatic, and a 12V battery was used to crank the engine and to put a voltage across the load so that when anything was switched on, it was detected, and a series of relays were activated to crank and start the engine, and when up to speed, switch on the 240V power. I was called to a larger installation one day to see to a problem with the shearing gear it also powered. When I found no power was available, the farm worker told me that the system was wired to only run when power was required at the owner’s house. To get the shearing gear to run, a light had to be switched on in the house, causing the engine to start. The employee also had a house as part of his package, with power supplied. But when the property owner went to bed, the employee and his family had to also because the engine stopped when the lights at the main house were turned off! In those days, fuel prices were much lower; I doubt that such systems could be viable today. But on a recent trip to the Northern Territory, I stopped at a service station and motel complex in the middle of nowhere, only to find that they had generators consisting of three V8 diesels with two operating at any time, and one being serviced or on standby. So, I suppose it is still viable to generate your own power if the need is great enough, and the grid is too far away. For two alternators to be used jointly, they have to be in synchronisation before the second is connected; otherwise, there is the potential for much damage. These days it is possible for automatic gear to make the connection at the right time. It’s best to do it at the zero-crossing point in the AC cycle when the voltage is effectively zero. When done manually, as it was in the early days of the SEC, alternators were known to connect with extreme bangs. Once synchronised, the alternators would remain so with each powering the load according to its capacity, unless automatic gear detected a problem and took one out of service. R. Graeme Burgin, Ararat, Vic. Advanced Imaging article appreciated A quick congratulations on another great issue. Your regular feature articles are just so good. And following the link in “Advanced Imaging” to the Antikythera video (September 2021; siliconchip.com.au/Article/15021) left me breathless. This subscriber is very happy to pay more for the magazine. The high quality and varied articles are worth every cent! The way it draws such premium advertisers says it all. David Humrich, Greenwood, WA. SC 14 Silicon Chip Australia’s electronics magazine siliconchip.com.au 1 MONTH Up to daily use on a single charge [2] 3 HEAT MODES Under plus BOOST Function 10 Model No: ESM-50WL 50Wh seconds Lithium Ion Powered CORDLESS SOLDERING IRON Superior runtime 10 second heat up Boost function Lasts up to 270 mins on low setting[1], 160 mins on high setting, or up to 1 month[2] of daily usage out of every charge. Get in and get out - rapid flameless heat to quickly get the job done. Increase tip heat for 25 secs at 27W when needed before returning to preset temp. Easy to use Modes panel Designed & engineered in Australia Suitable for use in any environment to heat up Complete Kit With Heat setting & Battery State of Charge LED indicators Featuring 14.4V 50Wh protected Lithium Ion battery pack for exceptional runtime. LED worklight No gas or flame means it’s safer for use in confined spaces, or in high wind, wet, or potentially flammable areas. On/Off Button (also activates ‘Sleep Mode’) Direct plug in to charge Ideal for: Car stereo installers 25% 50% 75% 100% Auto electricians Mechanical workshops Truck & taxi companies Interchangeable soldering tips [1] Temperature indicators Battery level indicators Carbon fibre texture Under 25°C ambient temperature. [2] Based on 40 solders per day for 20 working days with a solder dwell time of 20 seconds per solder. No gas, No ﬂames, No leaks. No worries. www.soldermaster.com.au siliconchip.com.au Australia’s electronics magazine Security companies Telco industry Marinas and more For distributor enquiries Ncontact ovember 2021 15 us at (02) 9519 1200 Big Brother is tracking you! Part One: By Dr David Maddison When people picture what spying looks like they might think of the more traditional methods, but governments, businesses and individuals – benign or nefarious, nearby or far away – can and do track just about everything you do online (and a lot more besides). H uman society has never been under as much surveillance as it is today. This is partly because the widespread use of computers means that every transaction, interaction and movement can be recorded. It’s also because many governments and businesses have an insatiable lust to surveil their subjects, often with very few protections to guarantee any sort of privacy. Many private organisations and criminals seek advantage from watching you as well. While this all sounds pretty sinister, please note that surveillance itself is not necessarily illegitimate. There are good reasons (or excuses) to watch certain people, for example, violent criminals. But the ease with which surveillance data is collected from people, both by government and corporations (especially ‘social media giants’), makes it likely or even inevitable that such information will be misused. Put it this way: it’s much easier to trawl the ocean with a giant net, pull it up and see what you’ve caught than it is to catch a particular fish with a rod and line. But what if the net catches more than is intended? Perhaps some tasty but endangered fish. Can we trust the fisherman to throw those ones back? Big problems can arise when the collected data is sold to third parties (usually for profit – how do telemarketers get your phone number?). Or when government(s) or corporations want to dictate what you see and hear. Do you accept the adage “if you have nothing to hide, you have nothing to fear”? Famous whistleblower (or, depending on whom you ask, criminal leaker) Edward Snowden said that “Arguing that you don’t care about the right to privacy because you have nothing to hide is no different than saying you don’t care about free speech because you have nothing to say.” As you read the following, note that all the information presented in this article is readily available from public sources. We won’t discuss old-fashioned surveillance methods like reporting on your neighbours, as is standard in dictatorships. We will restrict ourselves to providing a taste of some of the more interesting and current electronic methods. We say taste because there is so much digital surveillance going on that we can only scratch the surface (and not all of it is public knowledge). Facebook, Google, Twitter and LinkedIn are examples of ‘free’ services which collect user information. It’s a matter for the individual whether the information they give out is worth the benefit from the platforms they use. 16 Silicon Chip Australia’s electronics magazine siliconchip.com.au On related topics, see our past articles on the History of Cyber Espionage and Cyber Weapons in the October and November 2019 issues (siliconchip. com.au/Series/337). Tracking privacy concerns can be broadly divided into two categories: governmental & non-governmental. Given that the government makes the laws (and often can ignore them), clearly there is more scope for losing privacy to government actors. Part one of this article will concentrate on investigating non-government actors (typically large corporations) and will also discuss some options you have for enhancing your privacy. Next month, the follow-up article will detail how governments, including ours, can and do track their citizens. Free services Pretty much nothing is truly free – as the old saying goes, “there ain’t no such thing as a free lunch”. ‘Free’ services offered on the internet and via your phone usually compromise your privacy with extensive recording and analysis of almost everything you do. One of the objectives is to use your information for targeted advertising or other purposes. You may be receiving a ‘free’ service but giving away an extensive profile of yourself. There’s another, more modern saying which goes something like, “If you are not paying for it, you’re not the customer; you’re the product.” Until the universal adoption of mobile phones, the main ways people could be surveilled was by inspection of telephone and banking transaction records (eg, credit card purchases). But with smartphones, everyone has their own personal tracking device, and many details of one’s life is frequently recorded on it (or on other nearby devices). In addition, effective facial and car number plate recognition technologies mean that you can be recognised anywhere there is a camera or anywhere a picture is posted online. EXIF data It is often possible to tell where a photo is taken. Many photos posted online contain so-called EXIF data, which often includes GPS coordinates. Even if it doesn’t, it is possible to use Google Earth (or other) imagery to work out where a photograph was taken. Sometimes even if an image file lacks EXIF data, it might be possible to find another copy of the image online with the EXIF data intact by using a “reverse image search” (described later in this article). Now virtually the whole Earth has been mapped, including street views, in visual databases such as Google Earth. So there is enough data available that a skilled person can use Google Earth to determine the location a photo was taken using only visual clues. Other tracking methods Every smartphone has a GPS, but even if this is deactivated, mobile phones can still be tracked by signal triangulation or via nearby WiFi networks, regardless of whether you have connected to them. Some Apps track your location this way. Voice recognition is now good enough to work reliably, without training, in real-time. A stream of your voice converted into plain text can be easily searched by anyone who has access to it. Social media companies have been known to search speech-to-text logs for ‘forbidden’ topics they wish to censor, blocking posted videos and the like, regardless of the author’s qualifications. EXIF (exchangeable image file format) data is created when taking photos using a camera, phone or other system. It stores some identifiable information such as GPS co-ordinates, the date & time when the photo was taken along with camera information such as focal length, aperture etc. How people are surveilled or tracked We should first consider some ways that surveillance is possible before we discuss specific technical details. The following, at a minimum, allows you to be surveilled: • Using an internet connection (wired or wireless), or other network connection such as Bluetooth or a mesh network. • Using a wired or wireless phone. • Connections established via Internet of Things devices (“IoT”). • Making purchases with a credit card, debit card or mobile phone. • Being subject to facial, voice or car number plate recognition (see our April 2019 article at siliconchip. com.au/Article/11519). • Being listened to or observed by microphones or cameras on your smart TV, mobile phone or PC. siliconchip.com.au Some see this as a challenge; there is a YouTube channel by “GeoWizard” (www.youtube.com/c/GeoWizard) who, in his “Geo Detective” series, invites viewers to submit random photos of themselves. He then uses his Google Earth skills to work out where the photo was taken. See “Can I pinpoint the EXACT location of my fans using a single image?” at https://youtu.be/k-5J0kL7aRs If one had high-level access to the Google Earth database (or similar), this could possibly be done automatically, using scene-matching algorithms without human intervention. Australia’s electronics magazine November 2021 17 Fig.1: a WiFi and cellular network map of part of Melbourne from https://wigle.net/ You can check the website to see if your own home or business access point (AP) is shown. You can also participate in data collection for this database using an App on your Android smartphone or laptop. Tracking via wireless networks Every WiFi access point (AP), public and private, including any you have at home, has a unique ID. These are freely visible to anyone with a WiFi device (even if they don’t have the AP password), and maps showing their locations are freely available. An example of a freely available WiFi map is https://wigle.net/ (see Figs.1-3). This information is available by necessity, because a WiFi network has to identify itself to authorised users who can then log on using a password. Information for these WiFi maps is collected by private individuals who may do it as a hobby, such as with wigle.net It is also done by major corporations such as Google and Apple. A lot of information can be obtained apart from the unique ID called the SSID (service set identifier), which is a natural language name, and the BSSID (basic service set identifier), which is a 48-bit number following MAC (media access control) address conventions. A MAC address is permanently assigned at manufacture to addressable devices on a network and is printed on the device. The user can change the SSID but not the BSSID. Smartphones act as a 24/7 monitoring tool for Google and Apple, reporting the WiFi networks near you. Using triangulation, they can determine your Fig.2: a zoomed-in view of a foreign city showing SSIDs and BSSIDs. To see this level of detail, you need to establish an account, but that is free and takes only seconds. 18 Silicon Chip Australia’s electronics magazine location fairly accurately (probably to within 10m). You don’t even have to be connected to those networks; your phone always sees them. Your Google or Apple ID is associated with your current position with respect to WiFi networks and GPS location. This feature cannot be turned off (unless WiFi is turned off) because your phone is constantly broadcasting its BSSID. However, a de-Googled Android or Linux phone will not do this, as discussed later. Google and Apple are constantly tracking you. By default, Google records where you visit and the route you take. Apple is also tracking you 24 hours a day, and monitoring your WiFi devices have a BSSID which is both a unique and unchangeable identifier. Software such as Cain & Abel can also be used to demonstrate how insecure these networks can be. siliconchip.com.au Map Net ID SSID Name Est. Long Channel Bcn Int. QoS map 00:01:38:74:9E:58 mcdonalds map 00:01:38:81:AF:C7 McDonalds infra -20.72732735 139.49467468 6 0 0 49.99446106 36.23361206 4 0 map 00:01:9F:11:5D:69 Mcdonalds 2 2020-08-02T16:00:00.000Z 42.98684311 -84.54867554 6 0 map 00:01:E3:46:78:25 McDonalds 1 2014-06-20T20:00:00.000Z 2014-06-28T14:00:00.000Z 51.25014496 6.47709274 9 0 map 00:02:2D:27:D7:DE Mcdonalds 2 2002-06-15T02:00:00.000Z 2004-07-05T00:00:00.000Z 33.35100555 -111.82453156 1 0 map 00:02:2D:5F:EF:97 McDonalds 5 2001-01-01T00:00:00.000Z 2006-04-03T14:00:00.000Z 32.51906204 -84.95638275 1 0 map 00:02:2D:75:5B:D1 McDonalds 0 2001-01-01T00:00:00.000Z 2004-05-03T18:00:00.000Z 32.50689697 -84.97121429 0 0 map 00:02:2D:C4:3C:C0 Mcdonalds 0 infra 2005-08-14T16:00:00.000Z 2020-08-06T00:00:00.000Z 32.81165695 -116.91766357 11 0 map 00:02:6F:08:0D:53 7 McDonalds ???? 2004-05-25T04:00:00.000Z 2004-05-24T23:00:00.000Z 40.63832474 -116.9475174 0 0 map 1 00:02:6F:08:0D:54 McDonalds ???? 2004-05-25T04:00:00.000Z 2004-05-24T23:00:00.000Z 40.95933151 -117.74948883 0 0 1 map 00:02:6F:30:E9:55 McDonalds Prism I infra 2004-06-19T08:00:00.000Z 2005-09-24T18:00:00.000Z 39.17835617 -119.76688385 1 0 2 map 00:02:6F:33:B1:1F McDonalds WiFi Hopper infra 2006-10-04T05:00:00.000Z 2008-10-26T02:00:00.000Z 35.15372849 -106.58855438 3 0 4 map 00:02:6F:36:B4:0F McDonalds 2001-01-01T00:00:00.000Z 2007-11-27T11:00:00.000Z 34.07216644 -106.89331818 6 0 0 map 00:02:6F:38:5B:47 McDonalds 2001-01-01T00:00:00.000Z 2007-11-27T11:00:00.000Z 34.0725174 -106.89299774 7 0 0 map 00:02:6F:71:11:13 McDonalds infra 2010-11-23T21:00:00.000Z 2012-05-07T07:00:00.000Z 42.21239471 -71.18297577 10 0 7 map 00:02:6F:98:A2:2C McDonalds infra 2012-02-08T12:00:00.000Z 2012-04-01T09:00:00.000Z 4.68668699 -74.0754776 3 0 7 Mcdonalds 1 Type First Seen Most Recently 2001-01-01T00:00:00.000Z 2009-02-28T00:00:00.000Z 2013-01-02T16:00:00.000Z 2013-04-03T02:00:00.000Z infra 2001-12-17T16:00:00.000Z infra BBS McDonalds11915 Prism I Crypto Est. Lat Found by Me Free Pay Comment Fig.3: a search on wigle.net for an SSID that might correspond to the name of a famous fast-food restaurant chain. This shows some of the information that is freely transmitted by WiFi access points and also recorded, in this case, by https:// wigle.net/ users. Google and others collect similar information. activity patterns; that’s how it can predict where you’re going and your estimated time of arrival. The tracking can be disabled to a certain extent in both cases; search online forums if you are interested in doing so. If you have a Google account, your location history is viewable at https:// maps.google.com/locationhistory/b/0 Apart from Google and Apple, if you knew or could guess someone’s SSID, you could search one of these public databases to find where that AP is located and find their BSSID. However, keep in mind that if the device in question is mobile, the position would not necessarily be accurate unless it was updated very recently. The SSID is given a default name by Apple devices, using a user’s first name, such as “John’s iPhone”. When I searched “iPhone” on wigle.net, I got over one million hits. Someone who knew John had an iPhone and lived within a particular geographical area and could guess their SSID would have a fair chance of finding where they live. Even if John became wise and changed his SSID, the BSSID would remain with the device, and if it was already known before the SSID was changed, John could still be located. Suppose the device had been used regularly at any location away from home, such as at work, a pub or a family member’s home. In that case, John might still be locatable if his SSID or BSSID has been recorded at that location. siliconchip.com.au For this reason, it is advisable not to use Apple’s default SSID or an identifiable SSID on any wireless device. If you don’t want such information to be recorded, the only answer is to use a hardwired connection to your laptop or phone and turn off WiFi on all your devices, including the router and modem. It is actually possible to buy Ethernet adaptors for phones – see Fig.4. Yes, your phone would be plugged into a cable and attached directly to your router, but it’s not much different to connecting to a charger. Alternatively, you could only use 3G/4G/5G data and not WiFi. In 2010, Google admitted they were (apparently mistakenly) using Google Street Cars for WiFi sniffing as well as photography; see siliconchip.com.au/ link/ab9n If you want to keep using WiFi but don’t want Google to use the information gathered in the process, see the following website on how to opt out of providing that data: siliconchip.com. au/link/ab9o However, that doesn’t stop your SSID or BSSID from being broadcast to others. You can hide the SSID broadcast, but should you? See siliconchip. com.au/link/ab9p for a discussion on the subject. Fig.4: a safer way to connect your smartphone to the internet. Some such adaptors also have a power pass-through to keep your phone charged at the same time. This is a screengrab from the video titled “Connect Network Adapter to Smart phone” at https://youtu.be/I215rJy7y10 Australia’s electronics magazine November 2021 19 Relevant video links ● Skynet is Here – Ready for the Singularity? – https://youtu.be/DVzY5bk1EZA ● You’re WRONG about Linux phones – https://youtu.be/z29aJCTn-mY ● The Best Browser for Internet Privacy? – https://youtu.be/fZTXGUjHTJc ● The MOST private browser (2021) – https://youtu.be/G09oVgDurTI ● Tracking Our Locations – New Tech in 2021 – https://youtu.be/p0_nXC30snk ● Book review: www.politico.com/magazine/story/2018/06/03/cyrus-farivarbook-excerpt-stingray-218588/ Facebook The social media website Facebook is ‘free’ but makes its revenue from vacuuming up the data of everything its users post, such as photographs, status updates, friendships, the pages they follow, etc. This enables a detailed profile of each user to be created, which is then used for targeted advertising. Data is gathered, and your privacy is lessened through various means such as: • Facial recognition being used to determine who is in pictures you post, along with the time and location of those photos • Others can “follow” your posts without your knowledge • Pending (yet-to-be-approved) “friends” can see your posts • Facebook shares collected user data with third-party Apps • They track your location and if other users are nearby • They track places you “check in” to • They track links you click on • Almost anything you do on Facebook is collected and analysed The Guardian has an article on how Facebook violates users’ privacy at siliconchip.com.au/link/ab9x You can opt out of some features of Facebook to improve your privacy. The data collected can be reviewed by checking your “off-Facebook activity”, see www.facebook.com/ help/2207256696182627/ According to a 2016 report in the Washington Post (siliconchip.com. au/link/ab9y), 98 separate parameters are included in users’ profiles, with probably more by now. The complete list is too long to publish here, but it includes things like: • Education level • Field of study • Ethnic affinity • Income and net worth • Job type, employer or employee and sector • Users who are away from family or hometown • Users who are friends with someone who has an anniversary, is newly married or engaged, recently moved, or has an upcoming birthday • Mothers, divided by “type” (“soccer”, “trendy” etc) • Users who are likely to engage in politics and their leanings • Users who plan to buy a car (and what kind/brand of car, and how soon) • Style and brand of car or bike the user drives • Users who donate to charity • Users who invest • Users who carry a balance on their credit card • Preferences for TV shows • Consumption behaviour of users, eg, do they buy a lot of medicine, Starting just two years ago, Facebook now provides a way to check and manage what data is collected by third-party websites and applications when browsing Facebook – https://about.fb.com/news/2019/08/off-facebook-activity/ 20 Silicon Chip Australia’s electronics magazine siliconchip.com.au alcohol, beauty products, pet food etc • Types of restaurants user eats at • Kinds of stores user shops at • Users who are ‘receptive’ to offers from companies offering online insurance, higher education or mortgages, and prepaid debit cards/satellite TV • Users who are interested in sport • Users who travel frequently, for work or pleasure There’s a lot more information on how Facebook tracks users in the book “Anti-Social Media: How Facebook Disconnects Us and Undermines Democracy” by Siva Vaidhyanathan. Google Google, like Facebook, is another ‘free’ service. They are most famous for their search engine. They also offer a free email service (Gmail), cloud data hosting (Google Drive), the YouTube video platform and the Chrome web browser. Google also maintains massive map databases and Google Earth, with high-resolution imagery of the Earth from above, street-level photos and imagery of other planets. Google probably knows more about you than you do, and tracks your movements. However, that (and certain other monitoring features) can be disabled if you know how. Like Facebook, Google earns revenue from targeted advertising based on your profile, including advertising related to the things you search for and the contents of your Gmail account. By using their services, Google and others build a profile on you. This profile is used for purposes such as deciding what ads to serve you to but it can also affect what results you get from web searches. There are many articles about how to improve your privacy with Google. Search for “how to improve privacy on Google”. This is a humorous video related to ordering pizza and what Google might know about you, titled “Google Pizza Joke 2021” at https://youtu. be/Fr0Vl_ovbjw The name “cookies” might seem fairly innocuous, or even enticing, they play an important role in storing information about website visitors. Authentication cookies can be a useful way to retain login details for websites you commonly visit, while tracking cookies may be used to create a record of one’s browsing history. Apart from these there are a wide variety of terms used to describe the different uses of cookies – https://w.wiki/3hJb use that EXIF data for their own purposes, such as to suggest people you may know who happened to be in the same location as your photo at around the same time. Also, consider that there are websites that offer reverse image searches (including Google), which, combined with social media, can find photos that you feature in via facial recognition. This could reveal whom you know, where you have been, what you have done etc. Reverse video search Say you have a video and want to find its origin, or you might want to see if your video has been plagiarised. It is currently not possible to upload a video clip and find other instances of it as you can for still images. This is technically feasible, but the storage and computational requirements would be massive, so it is not really done yet. But it will happen sooner or later. Today, to do a reverse video search, it is necessary to do one or more screengrabs of individual frames from the video of interest and upload those still images to reverse image search engines. A free plug-in tool for Chrome and Firefox called inVID, primarily for journalists, automates the above process and makes a reverse video search easier. See siliconchip.com.au/link/aba2 and siliconchip.com.au/link/aba3 for more details. Cookies & tracking pixels Cookies are small files that are stored on your computer to remember various settings when you visit a website. This way, you don’t come to a previously visited website as if you are a new visitor. For example, it will remember whether you logged into the website recently and keep you logged in. Unfortunately, while these can be very useful, they can also be abused to keep track of what pages of which websites you visit, so that certain sites can show you ads for products they think you might be interested in. If you’ve ever searched for a product or service online, you will usually find you are presented with numerous ads for that good or service afterwards. This is called “remarketing” (see Fig.5). Google dominates the field with its Google Ads. The technique used by marketers (and spammers and phishers) is to implement a “web beacon” or “tracking pixel”. This involves an invisible image, often a single pixel, embedded in a web page. The initiation of the download by your computer involves sending identifying information such as your IP address, device type, OS, screen size, referring site, time of visitation, browser or email client and cookies that may have been previously sent. This allows the remote server to generate a unique session ID and target you for future advertising, plus Photos on social media Even though photos uploaded to social media sites typically have their EXIF data automatically stripped for publication, social media giants may siliconchip.com.au Fig.5: how ‘remarketing’ works. They keep track of items you view or search for online, then advertise them on other websites you visit. Australia’s electronics magazine November 2021 21 GDPR, tracking cookies and ‘opting in’ Up until 2016, websites were generally free to use cookies how they wanted to, including tracking users for serving targeted advertisements or other purposes. In 2016, the EU brought in its General Data Protection Regulation (GDPR; https://gdpr-info.eu/) laws. Because of the difficulty in knowing where website visitors are located, these laws have affected the way everyone interacts with websites. One of the biggest changes was requiring users to agree both that they are willing to accept tracking cookies, while also providing information on what other data is kept about user activity (eg, logging user IP addresses and search terms). The result of this is the widespread track your visits to other websites or App usage. All this is added to your ‘online profile’. Tracking pixels can also use cookies. Advertising networks that use tracking pixels include Facebook Ads, Google Ads, Snapchat, Pinterest, Quora, Twitter, Linkedin and Bing, among others. Other search engines There are many other search engines apart from Google, although Google is by far the largest with well over 90% of the market. The next most popular search engine is Microsoft’s Bing (USA). Yahoo (USA) holds third place, followed in no particular order by Baidu (China), Yandex (Russia), DuckDuckGo (USA), Ask (USA), Ecosia (Germany), Qwant (French) and AOL (USA). No search engine will be completely private or bias-free. DuckDuckGo has a good reputation for maintaining privacy and not having biased search results. It doesn’t track users, store search results or identify computers it’s being used from. Editor’s note: for improved privacy, consider a metasearch engine such as Searx (https://searx.me/). use of popups that appear when you first visit a website (or possibly every time), asking you whether you are willing to accept the cookies or not. Of course, they want you to accept them (why else would they be providing them?), so there is usually an “Accept All” button which dismisses that popup. However, under the GDPR law, they also need to provide you with an easy way to opt out of these cookies. So if you are concerned about being tracked, you should obviously do that. Unfortunately, it must be done for every website you visit - currently, there is no good way (apart from using a blocking tool) to apply that choice to every website you visit. There is some question whether However, it should be noted that email is an intrinsically insecure protocol. See the video titled “Is Protonmail Safe for Security and Privacy?” at https://youtu.be/8Ppl62Bl9RE You can also choose to host your own mail server in a non Fourteen Eyes nation (https://w.wiki/3jpk), or you can try encrypting all messages using PGP. Alternatives to Google Maps The collaborative OpenStreetMap is likely the largest alternative to Google Maps (found at www.openstreetmap.org). There is also software such as QGIS (www.qgis.org/en/site/) for many websites are truly compliant with the GDPR rules. For example, the rules state that it must be just as easy to opt out of the cookies as it is to opt in. They also say that users cannot be denied access to any services if they choose to opt out. Not all websites appear to adhere to those rules. Still, the fact that you have the option to opt out of many tracking cookies is arguably very good, despite the inconvenience caused by all those pop-ups (some of which are so large that they cover virtually the whole screen!). The GDPR also provides the guarantee that you can have your data deleted from the website’s servers if requested (called the “right to be forgotten”). people who want an alternative to Google Earth. Virtual assistant devices Amazon Alexa, Apple Siri, and Google Assistant are examples of virtual assistants that use artificial intelligence to provide natural-language interactivity to answer questions, manage emails and to-do lists, and control devices. By their very nature, they are always listening. Some devices perform voice recognition ‘in the cloud’ while others do it on the device. These and other virtual assistant devices have all raised privacy and security concerns. Free email Gmail offers a free email service but monitors the content of emails to generate targeted advertising. Some other free email providers do similar. ProtonMail (https://protonmail. com/) offers a secure, advert-free service but with some capacity limitations which can be extended for a fee. 22 Silicon Chip Amazon Alexa is a device used for home automation, and it has been noted to record conversations it hears while operating – www.nytimes.com/wirecutter/ blog/amazons-alexa-never-stops-listening-to-you/ Australia’s electronics magazine siliconchip.com.au Do tech giants listen to your conversations? It is often claimed that the tech giants listen to your conversations via your phone or webcam, pick out keywords and then deliver targeted advertising to you. We don’t know for sure that this is happening, although many people have tested it. Here are two random videos which suggest they do: “Is my phone listening to me? We tested it, here’s what happened” (https://youtu.be/CVazBWGgg64). “Facebook iPhone Listening into our Conversations for Advertising TEST” (https://youtu.be/U0SOxb_Lfps). There is an Australian video which could find no evidence, titled “Is Facebook listening in on your Conversations?” at https://youtu.be/ NX9dW5YYdMQ There is further discussion on the issue in the video titled “Is Facebook listening to your conversations?” at https://youtu.be/G1q5cQY4M34 If they do listen to what users are saying, it could be region-dependent, which might explain the differing results of these investigations. The Apple AirTag This is a tracking device to put on items such as key rings so they can be found if lost. They communicate via Bluetooth Low Energy (BLE), Ultra Wide Band radio (UWB) and near-field communication (NFC). All Apple devices participate in the tracking process. Fig.6: a vision of Bluetooth Mesh connectivity, from local sensors and up to ‘the cloud’. Source: Ericsson The Washington Post (note this is owned by Jeff Bezos of Amazon) claimed they could be misused to stalk people, at siliconchip.com.au/link/ ab9v But it’s not quite so clear cut: siliconchip.com.au/link/abb9 Tile is a similar product, also using BLE. The Samsung SmartTag uses either UWB or BLE, depending on the model. Mesh networks Most people are familiar with using Bluetooth to connect devices such as headphones, mice and wireless keyboards to computers or mobile phones. With Bluetooth Low Energy (BLE) version 5.0, ranges of 1000m or even more are possible outdoors (shorter in indoor or cluttered environments). Bluetooth Mesh is a mesh networking Content blockers, browsers and the like When using a browser in today’s internet, a content blocker or more can be essential to maintain security when browsing the web. These typically come as web browser addons and can be used to block adverts, trackers, malware sites and other scripts/content on webpages. This can be important as there have been cases of malware sneaking into Google Adverts. The most reliable blocker would be uBlock Origin (https://github.com/gorhill/ uBlock, the Origin name is important) and possibly in conjunction with uMatrix. For a network-wide supplement you can use a Raspberry Pi and install Pi-hole onto it (https://pi-hole.net/). This will let you block content even on your smart TV. For secure web browsers, you can look at un-Googled versions of Chromium (https://github.com/Eloston/ungoogled-chromium or https://iridiumbrowser. de/, the binaries can also be compiled yourself). There are many other alternatives if you’re willing to search for them, for example you can use a virtual private network (VPN) combined with TOR (https://www.torproject.org/). VPNs redirect your internet traffic through another location, making it harder for others to determine where that traffic is coming from. To reiterate a point, a ‘free’ VPN is likely not truly open about what they do with your data; Hola is an example of this: siliconchip.com.au/link/abb0 siliconchip.com.au Australia’s electronics magazine standard based on BLE. BLE was not commonly used until it was implemented on the Android and iOS platforms, where it is used (among other things) for COVID-19 contact tracing via Apps that use this feature. Bluetooth Mesh was introduced in July 2017 and the standard was finalised in December 2020. It can interconnect all manner of so-called “slave” devices such as sensors, lighting systems, actuators, security systems, environmental controls, phones, tablets, PCs, appliances and almost anything else IoT-related. Bluetooth Mesh devices can send and receive messages, but “gateway” devices also act as relay stations for messages from elsewhere on the mesh. Like any mesh network, Bluetooth Mesh networks do not need access to the internet to work. Data can travel long distances using only mesh nodes. That independence from the internet can be considered an advantage, depending on your point of view. The vision of Bluetooth Mesh is to have vast numbers of mesh devices rolled out throughout the world and controlling everything. An example is a “smart building” that would sense your arrival by some sort of wearable or implanted identity device (eg. NFC) and then adjust lights and heating and other controls to your liking and logs on your computer – see Fig.6. This automation is another way you could be surveilled. For example, every visit to the bathroom could be logged. A further extension is that millions of sensors everywhere could track every aspect of your life, wherever you are. And all without an internet connection. November 2021 23 ► ► Fig.7: a mobile automatic numberplate recognition (ANPR) system fitted to a NSW highway patrol vehicle. Source: www.flickr.com/ photos/34236324<at>N05/5017098510 Fig.8: the PortaPow is said to prevent ‘Juice Jacking’ by breaking the connections in the USB data lines. Amazon Sidewalk is another mesh network technology that connects and shares many low-bandwidth devices. Sidewalk is built into things like the Amazon Echo, Ring Security Cameras, outdoor lights, motion sensors, Tile trackers and other home automation devices. It is enabled by default in these devices, but can be turned off. It uses BLE for shorter ranges, 900MHz LoRaWAN (Long Range proprietary low-power wide-area network) for longer ranges and FSK (frequency-shift keying) for interacting with devices such as older garage door openers. The 900MHz frequency gives much better range than higher frequencies. With permission, other users such as neighbours can utilise up to 80kbps bandwidth on your Sidewalk device. We are not suggesting there are security defects in this. Nevertheless, some people have raised concerns about massive connectivity over a wide area, including the possibility that criminals could get access to the system. Apple HomeKit is a software framework from Apple to control smart appliances. It uses Bluetooth, BLE and WiFi for communications. Automatic car number plate recognition Today, automatic recognition of number plates is a fairly straightforward technology (see Fig.7), and many police vehicles are equipped with it. It is also likely that surveillance cameras 24 Silicon Chip around Australia (public or private) can also track motorists via their number plates; this is definitely true for the ‘point-to-point’ average speed cameras in various locations such as between Victoria and NSW. Most Australian shopping centres also now use number plate recognition for car park billing, to track how long you have spent in their parking lot. Possibly compromised commercial products In 2018, Chinese Hikvision and Dahua cameras were banned from critical infrastructure by the US Government because many security researchers have been concerned they have deliberately installed “backdoor” code to transmit video and network data for espionage purposes. Many such cameras have been installed around critical infrastructure in Australia. The Sydney Morning Herald published an article (siliconchip.com.au/ link/ab9z) stating that various Australian Government agencies, including the Department of Defence, have removed Hikvision cameras. However, it is not clear if they have been banned in Australia. A few months ago, I saw a Hikvision camera being installed in Victoria as part of a fixed speed and red light camera installation. I reported it to my local member of parliament, but he did nothing. See also articles from the ABC (siliconchip.com.au/link/aba0) and Australia’s electronics magazine GadgetGuy (siliconchip.com.au/link/ aba1). There are similar concerns with Huawei 5G mobile data systems, which were banned in Australia and the USA over espionage concerns. Juice Jacking Charging your phone by plugging it directly into a USB charging port at public places (eg, airports) has potential risks. Criminals have been known to compromise these data ports to install malware on your phone, or steal your personal information. This type of attack is known as “Juice Jacking”. It can be prevented by only charging your phone using a mains adaptor, or using a USB charging cable with the data lines disconnected (which you can buy or make yourself). Hikvision cameras were banned by the US government from being used in “critical infrastructure”. siliconchip.com.au making it harder to track them. John McAfee’s Privacy Phone Fig.9: movements of Sydneysiders using the Citymapper App from the 2nd of March 2020 to the 17th of July 2021. A device called a PortaPow (Fig.8) enables charging, but has no data lines connected, and there are others like it. Both Apple and Android have taken measures to minimise Juice Jacking. Citymapper (https://citymapper. com/) is an App you can voluntarily install to upload your movements to build a database of aggregate movement data in various cities worldwide. Even without the map, you can view the data (see Fig.9). mobile phone location data such as via GPS or tower triangulation, nearby WiFi or mesh networks, IP address ranges etc. Various apps use geofencing for purposes such as advertising. For example, there have been times when I have walked into a store and received a notification on my phone that a particular product was on sale (because I had that retailer’s App installed on my phone). Until that point, I was not aware that the retailer was tracking my movements. Geofencing Privacy phones A geofence is a designated geographic area in which some type of notification is sent or received if a subject leaves, enters or is present in an area (Fig.10). Location information comes via such means as GPS, RFID, OK, so it’s clear that all sorts of people want to track you. What can you do about it? One of the biggest offenders is the smartphone, so here are some phones that aim to offer greatly improved privacy to their users, Citymapper Fig.10: an example of how location data and a geofence can be used to send an advertising message. siliconchip.com.au In 2017, John McAfee of MGT Capital Investments (https://mgtci.com/), who recently died under mysterious circumstances, announced what he believed was the most “hackproof” phone ever created, called the McAfee Privacy Phone (see Fig.11). It was Android-based and designed in conjunction with the Nordic IT Sourcing Association https://nordicit. org/, with features such as physical switches to disconnect the battery, WiFi, Bluetooth and GPS antennas, camera and microphone. It was also said to be able to detect and not connect to IMSI-catcher devices (to be described next month), and had an anonymiser for web searches. The phone appears never to have been released. The Braxman Privacy Phone Rob Braxman is a Los Angeles based security consultant and privacy expert (The “Internet Privacy Guy”) and has a YouTube channel at www.youtube. com/c/BraxMe In the interest of privacy, he produces de-Googled phones. de-Googling (or deGoogling) is a worldwide privacy movement established due to privacy concerns about data collection by private companies. A de-Googled phone is based on the Android Open Source Project (AOSP) with no GAPPS (Google Apps) or Google Play Store, only software drivers for the individual phone. The phone is mostly like a standard Android phone, but without any meaningful communication with Google’s servers. Fig.11: the never-released McAfee Privacy Phone. Source: https://twitter.com/officialmcafee/status/856880269160325120 Australia’s electronics magazine November 2021 25 Google will not know who owns the phone or any form of identity to do with the phone. There will be no Google services such as constant location tracking via WiFi scanning, reports to Google of App usage, contact tracing, Google ID, device fingerprinting, or uploading any audio, photos, video, etc. Rob Braxman regards this as the only current solution to a privacy phone, apart from Linux phones, which are still under development. When turning on a de-Googled phone, there is no login to Google and no association with your email address, so your activities can’t be tracked and logged by Google and associated Apps. However, the phone carrier will still be able to identify the phone by its SIM card and IMEI number, as would law enforcement agencies. A phone can collect a lot of data such as location via WiFi scanning, GPS, movement via inertial movement sensors, facial recognition, cameras, microphones, fingerprints etc. But a de-Googled phone prevents the collection of any of this data in a central repository. Android versions that come with standard phones are tightly integrated with Google, so the original version in ROM has to be replaced (not a recommended procedure unless you are an expert). Not all phones can be de-Googled. There are many flavours of Android for de-Googled phones, the most popular being LineageOS (https://lineageos. org/; we don’t recommend you attempt de-Googling your phone, unless you know what you are doing). A list of other Android versions, or custom ROMs (or firmware) as they are also known, is at: https://w.wiki/3uRX Rob Braxman notes that privacy can never be achieved on an iPhone because of Apple’s tight control over the phone identity via Apple ID and Apps. Also consider the new ‘backdoor’ Apple has introduced to allow for client-side scanning of end-to-end encryption on iMessage (see the EFF at siliconchip.com.au/link/abaz). In the video by Rob Braxman titled “What it’s like to use a De-Googled phone in real life? (Q&A of concerns)” at https://youtu.be/mqSCmT5S-2w he addresses numerous concerns about de-Googled phones. The most 26 Silicon Chip interesting questions & answers (abbreviated) are: What Google Apps can be used on a de-Googled phone? No Google Drive, Google Photos, Gmail, YouTube, Google Play Store, or Chrome browser. You can still do a Google search via other browsers or use other search engines. Waze no longer works as it now uses Google Maps. NewPipe can be used as a YouTube client, K-9 Mail to access Gmail and other email providers, NextCloud for cloud services. Can I install my favourite Apps? About 90% of Apps will work on a de-Googled phone as long as two additional Apps are included: Aurora Store, a replacement Google Play Store client, and MicroG, an open-source implementation of proprietary Google Play Services Android libraries to spoof Google Maps and Google Notifications, as might be required by some Apps. Why do some Apps not work on a de-Googled phone? These Apps rely on Google infrastructure (apart from Maps and Notifications) or Google Pay (eg, the Uber App will not work without it). Can the phone be used with zero connection to Google? There will still be traffic with Google even if spoofed and anonymised, such as via Aurora and MicroG. If zero connectivity with Google is desired, you can use the F-Droid Store. What can I use for navigation and maps? Open-source and free OsmAnd can be used for maps and navigation. However, it doesn’t have the crowdsourced information of Waze, such as traffic hazards. What about battery life? Without Google services, the battery life can be doubled. What is Google services doing that uses so much battery life? No one knows precisely, as the code is proprietary. But one thing Google themselves stated was that each phone collects the MAC addresses, GPS locations and signal strengths of every WiFi router the phone receives signals from. This builds the Google Australia’s electronics magazine database for WiFi location tracking. And all that data is associated with your Google ID. Other activities might include using Bluetooth contact tracing. The code is there, whether it is used or not. App usage is also monitored. The constant telemetry back to Google services all uses energy and thus battery life. Contact tracing is part of Google (and Apple iOS) and will not work on de-Googled phones. Google contact tracing was introduced around May 2020. What other privacy measures are needed for a de-Googled phone? The key is “identity management” and to ensure Apps don’t give away too much of your data such as IP address, email address, location etc, which can all be used to make a unique “fingerprint”. Facebook and associated Apps are regarded as particularly bad in this regard, so it is recommended not to use these on a privacy-oriented phone. Deny Apps any unnecessary information such as location. One should also use a VPN on a phone or at home or the office. How do I transfer phone service to a de-Googled phone? Just move the SIM card to the new phone. How do I acquire a de-Googled phone? You can do it yourself with advanced skills if you are aware of the possibility of ‘bricking’ the phone. You need a phone capable of being de-Googled (see https://lineageos.org/), or purchase one. Make sure any phone you purchase is suitable for use in Australia or wherever you live. We haven’t tested them, but for those interested, various privacy products from Rob Braxman can be seen at siliconchip.com.au/link/aba5 The Freedom Phone The just-released Freedom Phone (https://freedomphone.com/) is from the USA (but made in China...). It is described as “a free speech and privacy first focused phone. With features like tracking blockers and an uncensorable app store”. It runs FreedomOS (https:// github.com/agravelot/FreedomOS), a de-Googled version of Android for OnePlus devices. siliconchip.com.au The e Foundation The e Foundation builds de-Googled Android operating systems for smartphones with an emphasis on privacy (https://e.foundation/). They say: “Your smartphone is harvesting your data all day long, capturing with great detail where you are, who you are, and what you’re doing 24/7. Time to escape from Mobile Surveillance!”. See a video review of the /e/ Phone titled “Android without Google: the /e/ Project blew me away!” at https:// youtu.be/C9fFiaGv2WA Linux phones There are several Linux distributions emphasising privacy available for smartphones, such as Ubuntu Touch, postmarketOS, Sailfish OS, Mobian and LuneOS. PureOS (https://pureos.net/) is a free Linux distribution emphasising privacy maintained by Purism, for the company’s Librem laptop and smartphone, but available free to all. Linux won’t work on all phones. We definitely don’t recommend you attempt to install it unless you have expertlevel skills. Can you track a mobile phone that is turned off? Maybe. Over the years, there have been claims that governments can listen in on the microphone of a phone that has been turned off, or track such a phone, or both. It is undoubtedly true that many electronic appliances, including some phones, are not truly ‘off’ when they are switched off; they are in a ‘standby’ state. TVs are a common example. Some circuitry is always active with modern TVs, awaiting inputs such as a switch-on signal from a remote control. According to the Washington Post in 2013, the US NSA (National Security Agency) since 2004 could use a technique called “The Find” to find a cell phone that was switched off. However, they gave no details on how that works. See siliconchip.com.au/link/aba6 In 2006, it was reported that the US FBI had a technique known as “roving bug” which allowed them to listen in on conversations heard by a mobile phone’s microphone, even though the phone was not engaged in a call, and which might have even been ‘turned off’ at the time. siliconchip.com.au Who is or was Big Brother? This image is an interpretation of what Big Brother might look like (credit: Free Art License, copyright Frederic Guimont). Big Brother was the fictional leader of the totalitarian state Oceania in George Orwell’s famous novel Nineteen Eighty Four. In Oceania, the ruling party was “Ingsoc”, and it exercised power over Oceania’s inhabitants “for its own sake”. Party members were under constant surveillance by “Telescreens”, but the majority of the population were Proles, deliberately uneducated manual labourers living in poverty, with short lives. But they were not likely to rebel as long as they were kept fed and entertained, so they were not surveilled. At the risk of being accused of Wrongthink, we would like to remind today’s leaders that George Orwell intended Nineteen Eighty Four to be a warning, not an instruction manual! In 2014, former CIA employee Edward Snowden (living in Russia since his leaks) said that the NSA could eavesdrop on cell phones when they are turned off. Regarding iPhones, he said, “They can absolutely turn them on with the power turned off to the device.” We are not privy to the techniques these security agencies use. It has been suggested that one possible method is to install malware in a target’s phone while it is switched on. The malware gives the appearance that a phone is turned off when the user turns it off, but it is actually on, and the microphone is recording and transmitting conversations. Location tracking could be done similarly. A further detail is that the above security exploits are achieved when the phone is placed in a low-power mode with only the baseband processor activated. The baseband processor in a phone has its own operating system and is responsible for the radio functions of the phone, which might be subject to exploitation. Quoting Wikipedia: Since the software which runs on baseband processors is usually proprietary, it is impossible to perform an independent code audit. By reverse engineering some of the baseband chips, researchers have found security vulnerabilities that could be used to access and modify data on the phone remotely. In March 2014, makers of the free Android derivative Replicant announced they have found a backdoor in the baseband software of Samsung Galaxy phones that allows remote access to the user data stored on the phone. Testing your internet security You can test aspects of your internet security by visiting www.grc.com/ shieldsup This company is highly reputable and has been around for a SC long time. PureOS is a Debian-based Linux distribution for Purism’s phone and laptop line focused on privacy and security. In the past Purism had done some interesting write-ups on Intel’s Management Engine, which some have described as a “backdoor” (EFF – siliconchip.com.au/link/abb1). Australia’s electronics magazine November 2021 27 Cable U S B Tester It’s frustrating when a USB device doesn’t work, and you don’t know if it’s a problem with the device itself or the cable. This is a huge problem if, like us, you have a drawer full of USB cables and don’t know which ones are good or provide power only. Bad cables can also cause intermittent problems. Now there is an easy way to test all manner of USB cables; this USB Cable Tester is so handy, we think you will find it indispensable! Part 1: by Tim Blythman T here is not much worse than an intermittent fault when it comes to checking and diagnosing faulty gear. It’s worse if it is due to a dodgy cable because you can never be completely confident that you have ruled out other problems. So it’s crucial to be able to test cables for this reason. These days, a lot of gear connects with USB cables and not just when it’s attached to a computer. Practically all mobile phones use USB for charging, and they’ve also found many niche uses due to their ubiquity, even for devices like shavers and toothbrushes. So we’ve designed a USB Cable Tester that can check practically all standard USB cables. If you’re like us, you probably have a mix of the latest cables (such as USB-C) and a good number of older types (such as miniand micro-USB). The USB Cable Tester will test any cable with either a USB-C or USB-A (2.0 or 3.2) plug on one end and any USB-C or USB-B plugs (such as 2.0, 3.2, micro or mini) on the other end. With some basic adaptors, you can also test common variants such as OTG (‘on-the-go’) cables and non-standard cables, such as those with USB-A plugs at both ends. 28 Silicon Chip This device is compact and automatic. Simply plug a cable into the appropriate sockets, and it immediately gives you an assessment. You will know straight away if the cable is suitable for your purpose. Testing The USB Cable Tester performs two primary tests. Initially, the various conductors in each cable are tested for continuity at low current. This test can pick up whether, for example, a given lead has the appropriate internal data connections for USB 2.0 or USB 3.2, or whether it can carry power only. It can also detect internal short circuits which can interfere with normal operation. The Tester can also perform a high-current test on the VBUS and GND leads to establish how much current the cable can handle without dropping excessive voltage. Checking the ability of the cable to carry current is arguably the most useful test, as it allows detection of the most subtle and intermittent faults. These are the faults where the device seems to operate normally but fails when a burst of current is needed. The Australia’s electronics magazine device resets due to its supply dropping out and might even immediately start working again. Devices like portable hard drives, which often require significant current, are especially prone to this problem. None of these tests characterise the high-speed data performance of the cable; much more specialised equipment is needed to do this. Still, these tests are performed very quickly and can be used to give a very fast ‘go/ no-go’ assessment on a cable. With the rise of the Right To Repair movement, we think that the USB Cable Tester will become indispensable in places like Repair Cafés. We shudder to think how much good gear has been discarded due to having a faulty USB cable. Background Before delving in, you might like to look at some recent articles we have published. The June 2021 article on The History of USB (siliconchip.com. au/Article/14883) describes the connectors and wiring that the USB Cable Tester needs to work with. That would be a good article to read if you’re interested in understanding and repairing USB cables. siliconchip.com.au The front panel gives access to the six USB sockets: two downstream facing ports (DFPs) at left and four upstream facing ports (UFPs) at right. To test a cable, you plug one end into either of the DFPs and the other end into one of the UFPs. It does the rest automatically. The July and August 2021 issues also included articles on How USB-C Power Delivery (USB-PD) Works (siliconchip.com.au/Article/14919), the operation of USB-PD Chargers (siliconchip.com.au/Article/14920), and USB-PD Triggers (siliconchip. com.au/Article/14996). USB power delivery is a relatively recent addition to the USB standards and is not something our unit tests; these power delivery features are usually built into devices rather than cables. Both this article and the USB Cable Tester use USB 3.2 to refer to any cables that you might know as USB 3.0 or USB 3.1, since the USB 3.2 standard replaced (and is backwards compatible with) both USB 3.0 and USB 3.1. This is a similar situation to the way that USB 2.0 encompassed and replaced USB 1.0 and USB 1.1; it's now common to refer to devices compatible with these as USB 2.0. Design Before delving too deeply into the circuit details, we’ll mention some of the design considerations that we made along the way. We designed the USB Cable Tester to be economical to siliconchip.com.au build, easy to use and robust enough for regular use. While it certainly would be possible to do this job without a microcontroller, that would entail a complicated design. Add in the fact that the nature of the test results are often more than a simple numeric result or basic binary go/no go, and a microcontroller is an inevitable part of the circuit. With that in mind, we’ve used a 40-pin PIC microcontroller. Any fewer pins would require a multiplexer or switch, adding complexity and cost. Rather than fall back on one of the old-fashioned 40-pin micros like the PIC16F877, we’ve decided to get with the times and use its modern descendant, the PIC16F18877. The microcontroller displays the test results on a 20x4 character LCD, allowing simple ‘human-readable’ assessments to be delivered. Thus the USB Cable Tester can be used by even those with no electronics experience. The low-power features of this new microcontroller mean that a power switch can be omitted. This may seem like a small saving, but it’s one fewer part to consider during design and construction and shaves a few dollars off Features & specifications for the USB Cable Tester 1. Test just about any USB cable 2. Current pulse tests at 100mA, 500mA and 1A 3. Downstream facing ports can accept USB-A (2.0/3.2) or USB-C (3.2) 4. Upstream facing ports can accept USB-B (2.0/3.2), USB-C (3.2), Micro-B (2.0/3.2) or Mini-B (2.0) 5. Reports faults with individual cable ends (eg, plug with bare wires or detect OTG cables) 6. Can differentiate between power-only, USB 2.0 & USB 3.2 cables 7. Will report short circuits, open circuits and other faults 8. Reports voltage drop and cable resistance at usable currents Australia’s electronics magazine November 2021 29 Fig.1: like the PCB, much of the schematic is taken up by the 26 resistors that isolate the microcontroller from the USB sockets. In the unlikely event of a ‘live’ USB cable being plugged in, they will afford some protection to the microcontroller and whatever is at the other end. 30 Silicon Chip Australia’s electronics magazine siliconchip.com.au the cost. The USB Cable Tester simply sleeps between uses, sipping a tiny 30μA from the battery. It runs from three AA cells which will last for many years with the USB Cable Tester sitting on the shelf. The 4.5V nominal supply voltage means that no regulator is needed; another part (and more money) saved. The device is housed in a compact 140mm x 110mm x 35mm instrument case, about the smallest that would fit everything. This means that it is sturdy and looks the part, too. Some parts we could not skimp on. The USB Cable Tester uses robust USB sockets, which cost a bit more but are paramount to the longevity of such a tool. We doubt that any other device will have USB leads plugged and unplugged so frequently. We have aimed to use through-hole parts to allow the parts to be easily obtained and the USB Cable Tester to be easily assembled. Still, it contains a handful of SMD parts for various reasons, primarily certain types of USB sockets. Many of these sockets are only available in that form. Circuit details Refer now to Fig.1, the complete circuit of the USB Cable Tester. CON3 and CON4 at upper left are the downstream facing ports (DFPs) – you can equate these to the ‘host’ ports from before USB-C. But since USB-C cables are end-to-end symmetrical, a new distinction needs to be made. CON3 is a USB-A 3.2 capable socket, while CON4 is a USB-C socket (which by nature supports USB 3.2). CON3 will also accept older USB-A 2.0 cables since it is designed to be backwards compatible. CON5-CON8 are the upstream facing ports (UFPs), analogous to the ‘device’ socket before USB 3.2. CON7 is USB-B 3.2 and, like CON3, can also accept a USB-B 2.0 plug; leads with these plugs are sometimes called printer leads due to printers being one of the few items large enough to fit such a port. CON6 is a USB-C socket and is accompanied by a USB micro-B socket, CON8. Like CON7, it can accept either a USB 2.0 or USB 3.2 plug. Finally, CON5 is a USB mini-B socket, which is only available in a USB 2.0 version. The various pins from CON3-CON8 are connected to one of 26 1kW resistors. To reduce the number of pins siliconchip.com.au Australia’s electronics magazine November 2021 31 that are needed, some pins are joined. For example, the GND pins of CON3 and CON4 are connected to the same resistor. That is because these pins perform similar functions in each connector and have no reason to be connected by a cable. They are functionally equivalent as far as the USB Cable Tester is concerned. This means that the USB Cable Tester does not know whether the cable is plugged into the USB-A or USB-C socket, but that isn’t necessary for checking cables. As we noted earlier, a 40-pin microcontroller does much of the work. IC1 is a PIC16F18877 8-bit enhanced midrange microcontroller. It’s one of the cheapest 40-pin microcontrollers available at the moment. There is a slightly more inexpensive version with less flash memory, but given the ongoing chip shortages, we’ve decided to standardise on the part with more flash. 26 of IC1’s pins are connected to those 26 1kW resistors, and these pins are used to probe the connectivity of the cable being tested. For the most part, IC1’s GPIO (general purpose input/output) pins are interchangeable. We use one feature that is not present on all the available pins, and that is the interrupt on change (IOC) feature. The ports that do have this feature have been wired into the downstream facing ports. Without using IOC, we would have to wake up the microcontroller periodically to test whether a cable is connected. This feature automatically wakes it up as soon as any connection is made between the downstream and upstream ports. This made laying out the PCB slightly more complicated but allows IC1 to use the deepest sleep mode available, thus saving the most power when the unit is idle. This circuitry is used to probe any pin combination between the upstream facing port and the downstream facing port. We’ll explain how that works in more detail in the software section below. Current affairs The cable current-carrying capability is tested by sending a brief burst of power through the VBUS (5V) and GND wires of the cable under test. 32 Silicon Chip The completed USB Cable Tester photographed from the front and rear. This shows that all connections are made from the front of the case. One tactile switch is raised so it can be more easily accessed through a hole in the lid. Since practically all the GPIO pins on IC1 can act as analog inputs for its internal ADC (analog-to-digital converter), we can probe the cable at several points to see how much voltage is dropped between them. Up to 1A is supplied by a circuit based around Q3, a P-channel Mosfet. Q3, L1, D3 and the 10μF capacitor form a fairly standard buck (stepdown) regulator arrangement. When Q3 is switched on by a signal Australia’s electronics magazine from the microcontroller via the 220W resistor, current flows from the battery positive through L1, charging the 10μF capacitor. When Q3 switches off, the inductor’s magnetic field collapses, causing current to continue flowing to the capacitor, through the path provided via D3 and into the 10μF capacitor. As in any other buck regulator, the duty cycle at Q3’s gate determines the voltage that the capacitor charges up siliconchip.com.au to but with the proviso that Q3 is a P-channel Mosfet and thus is on when its gate is pulled low. A 10kW resistor between Q3’s gate and source keeps it turned off when it is not being driven. The test voltage is applied to the cable by three of the contacts of RLY1 and RLY2. One set of contacts connects VBUS of the downstream facing port to the positive end of the storage capacitor. The second set of contacts connects the GND of the downstream facing port to the 220mW shunt resistor returned to circuit ground, used to measure the current. The third set of contacts connects VBUS and GND at the upstream facing port, which is necessary to complete the circuit. Note that current flows in the same direction as it would under regular use. It’s important to realise that none of the USB GND connections are connected directly to the circuit ground during this test. They are connected to either end of the 220mW shunt resistor but only when the relay contacts are closed. The 1kW resistor across the 10μF capacitor discharges it when the buck regulator is not running. This is mainly to reduce the current flowing when the relay contacts open, reducing relay contact wear. Both relays are controlled by N-channel Mosfet Q2, which sinks current from the battery through both relay coils when its gate is brought high by the microcontroller. A 10kW resistor keeps the Mosfet off when it is not being driven, and 1N4148 diode D1 absorbs the back-EMF from both coils. As we noted, power is derived from three AA cells, giving a nominal 4.5V. A separate battery holder is wired into CON1. This feeds the 1000μF bulk bypassing capacitor, Q3 and powers the buck regulator and relay coils. Schottky diode D2 feeds from the battery into microcontroller IC1’s supply, bypassed by 1000μF and 100nF capacitors. These also provide power to the LCD. The diode means that the microcontroller’s supply does not dip during the brief bursts of current draw during cable pulse testing. Display LCD1 is a 20x4 character LCD panel that has its supply fed directly from pin RD6 of IC1. The signal from RD6 is also connected to the gate of Q1, siliconchip.com.au Parts List – USB Cable Tester 1 double-sided PCB coded 04108211, 130mm x 102mm 1 green double-sided PCB coded 04108212, 134mm x 30mm (front panel) 1 laser-cut acrylic bezel to suit LCD [Cat SC5970] 1 140mm x 110mm x 35mm plastic instrument case [Jaycar HB5970, Altronics H0472] 1 3xAA battery holder with leads (CON1) 1 5-way pin header (CON2; optional, for ICSP) 1 USB-A 3.2 socket (CON3) [Würth Elektronik 63.2213.200] 2 USB-C sockets (CON4 & CON6) [Würth Elektronik 632723.20011] 1 Mini-USB socket (CON5) 1 USB-B 3.2 socket (CON7) [Würth Elektronik 69222103.200] 1 Micro-USB 3.2 socket (CON8) [Würth Elektronik 69262203.200] 1 2-way pin header (CON9; optional, for calibration ➊) 2 2-way pin headers and jumper shunts (JP1 & JP2; optional, for calibration ➊) 1 20x4 LCD module (LCD1) [eg, Jaycar QP5522] 1 16-pin header, 2.54mm pitch (for LCD) 2 1A telecom relays, 5V DC coil (RLY1, RLY2) [eg, EA2-5NU, Cat SC4158] 2 6mm tactile switches (S1 & S2; optional, for calibration ➊) 1 100uH 12x12mm SMD inductor (L1) [eg, Bourns SRR1280-101MCT] 4 M3 x 15mm machine screws 8 M3 hex nuts 8 No.4 x 6mm self tapping screws or M3 x 6mm machine screws 2 6-way stackable headers (for mounting LCD) Semiconductors 1 PIC16F18877-I/P ➋ microcontroller, flashed with 0410821A.HEX (IC1) 2 2N7000 N-channel Mosfets, TO-92 (Q1, Q2) 1 SUP53P06 or IPP80P03P4 P-channel logic-level Mosfet, TO-220 (Q3) 1 1N4148 signal diode (D1) 2 1N5819 1A schottky diodes (D2, D3) Capacitors 2 1000μF 6.3V electrolytic 1 10μF 16V electrolytic 1 100nF 63V MKT or 50V ceramic Resistors (all 1/4W axial 1% metal film except as noted) 1 10kW mini horizontal trimpot 4 10kW 28 1kW 1 220W 1 100W 1 220mW 1% 2W M6432/2512 SMD ➊ The USB Cable Tester will work fine without calibration, so these parts are optional. Still, see the text next month for information about how S1 can be used during regular operation. ➋ IC1 can also be a PIC16F18875 programmed with 0410821B.HEX. Either the I/P or E/P variants will work. A kit is available from the Silicon Chip Online Shop Because of the current semiconductor (& component) shortage, we we concerned that our readers might not be able to build this project. At the time of publication, several of the key components are difficult to source. So we made the decision to purchase all the parts in advance and make a kit available. This not only ensures you can build it, it also greatly simplifies getting the parts. The kit (code SC5966) will come with everything needed to build a complete unit as shown here, except for the case (available from Jaycar & Altronics) and the three AA cells (which are easy to get). The initial price is $110 + postage ($99 + postage for current subscribers) although that could go up if the initial batch sells out quickly. See the shop listing on page 90 or on our website at siliconchip.com.au/Shop/20/5966 Australia’s electronics magazine November 2021 33 microcontroller’s reset line (which is usually pulled up by a 10kW resistor) and circuit ground. Since the calibration menu is only displayed just after a reset, pushing S2 is a simple way to reset the microcontroller and enter calibration mode. S1 is connected between PGD and circuit ground. When it is pressed, it can trigger the IOC interrupt noted earlier and can thus be used to wake up the USB Cable Tester without plugging in a USB cable. Software This main screen is shown when the USB Cable Tester is idle and doesn’t have a cable plugged in. The battery voltage and a countdown timer (until the unit sleeps) are shown. which switches the LCD panel backlight cathode via a 100W resistor. A 10kW resistor also holds Q1 off when the micro is not driving the pin. Thus, when RD6 is low, LCD1 and its backlight are both off. When RD6 is taken high, LCD1’s internal controller is activated and its backlight is switched on. This means that the USB Cable Tester can completely shut off power to the LCD when IC1 is in sleep mode. Six more of IC1’s pins are connected to LCD1 to control it in four-bit mode. This makes the best use of the available pins without needing a separate I/O expander chip. CON2 is an optional in-circuit serial programming (ICSP) header for programming microcontroller IC1. The PGD and PGC pins are also used for USB cable sensing, so a USB cable must not be connected during programming. The PGD pin is also connected to CON9, a two-pin header, via a 1kW resistor. CON9’s other connection is circuit ground. This interface is used to connect to the transmit pin of a TTL-serial interface such as a USBserial adaptor which can be used to enter a dedicated software interface for calibration. No receive pin is provided. Instead, two-way communication is achieved by displaying data on the LCD screen 34 Silicon Chip during the calibration process. Test points TP1, TP2 and TP3 are provided for calibration. These connect to circuit ground, the positive microcontroller supply and the positive end of the 220mW shunt, respectively. JP1 and JP2 are also used only for calibration. When bridged, JP1 connects the upstream and downstream facing VBUS lines. Similarly, JP2 connects the upstream and downstream facing GND lines. When fitted, they leave only the relay contacts and shunt resistance in the current test circuit. Thus, the resistance of the relay contacts can be measured and entered into the calibration settings. This value is then subtracted from cable readings to give a true value. S2 is also intended to be used for calibration. It is connected to the The PIC16F18877 is a reasonably well-equipped microcontroller, and we’re using several of its internal peripherals to provide the features needed. The software loaded into the chip starts by initialising several of its internal peripherals. This includes setting most of the I/O pins as inputs with internal pull-ups, used to sense cable connectivity. It also sets up the UART (serial) receiver and PWM output for the buck converter, plus the seven I/O pins associated with the LCD. Timer (T0) is configured to fire an interrupt every 262ms (approximately four times per second). This is a reasonable rate for quick screen updates while still allowing the display to be legible. The timer is used to display a startup screen for around seven seconds. During this time, if an ESCAPE character is received on the UART, the calibration is started and a menu is displayed on the LCD. The calibration runs until either the microcontroller is reset or a Ctrl-C code is received on the UART. Otherwise, the UART is disabled after seven seconds, and the main ‘idle’ screen is displayed. A subroutine is called after 10 seconds of the idle screen to put the USB Cable Tester into low-power sleep mode. The Tester automatically runs tests as soon as a cable is plugged in. This known-good cable is identified as USB 2.0 compatible with no problems and a voltage drop of 116mV at 1A. Australia’s electronics magazine siliconchip.com.au GND GND VBUS DP DM TXP1 TXM1 RXP1 RXM1 TXP2 TXM2 RXP2 RXM2 1 VBUS DP 1 2 DM 2 3 TXP1 RXP1 3 4 5 TXP2 6 5 TXM2 RXM2 4 4 3 RXM1 RXP2 4 3 TXM1 5 6 6 5 6 Table 1: this data is stored in the microcontroller as arrays of 18 bytes, making up 144 bits (18 x 8). These correspond to the connection combinations that might be detected. It is compared with the data gathered during cable testing. This involves shutting down the peripherals mentioned earlier and setting low all the pins associated with the LCD. This reduces the quiescent current as it avoids leakage from any floating input pins. The upstream facing ports are pulled to a low level, and the downstream facing ports remain as inputs with pullups. Thus, any cable plugged in will pull one or more of the downstream facing port pins low. The IOC flags are set to allow a pin change to wake up the micro. Just before engaging sleep mode, the pins are checked one more time; if a cable is detected, sleep is bypassed. While unlikely to occur with so many pins, it is possible for a pin change to be missed, hence the reason for the double-check. When a pin change is detected (which could include a press on S1), the micro wakes up and initialises all the peripherals again before returning to the main idle screen. Whenever the micro is awake, it uses the timer to perform tests about four times per second. The results of the test dictate what is displayed. The idle screen is shown if no connection is detected; this also displays the battery voltage and a countdown timer until sleep occurs. The tests work simply. Each pin is typically set as an input with a pull-up. One at a time, in turn, each pin is pulled low and the states of the other pins are tested. The wires in the USB cable connecting pins in downstream and upstream sockets result in other pins being detected as being low. The tests are done in three phases. One phase simply checks for connections between the pins associated with the downstream facing port. A second phase checks the upstream facing port. For the most part, these should show no connections, except perhaps for the cable shield and USB-ID pin. USB-ID is grounded on USB OTG cables to indicate that the equipment connected to what would normally be a ‘device’ needs to behave as a ‘host’. Depending on how the cable is wired, there might also be a connection between the cable shield and ground. Any other connection within an A faulty cable is quickly identified; in this case, the GND wire is detected as open circuit (1-, Opens:GND) and naturally, it has no useful current-carrying capacity on its power lines. siliconchip.com.au Australia’s electronics magazine upstream or downstream port likely indicates a cable fault. So if one end of a cable is plugged in, any of these sorts of problems that are detected are displayed on the LCD screen. The third test phase is a complete ‘matrix’ analysis of every combination of downstream facing port pin and upstream facing port pin. This is turned into a cable-specific signature that is compared with a list of signatures corresponding to known cable types. Some cable types have multiple signatures. For example, the reversible nature of USB-C means that there are two equally valid signatures for a USB 3.2 cable. Table 1 shows what connections are expected for each cable type. An exact signature match means that the cable is a known type and displayed as such. An inexact match is shown as the nearest match and the differences are detected. For example, the LCD might indicate that a USB 2.0 cable is detected, but with the D+ line open; such a cable may be suitable for a power-only application but will be no good for data transfer. A simplified version of the decoding would work as follows. • Power-only cable: just the red points in Table 1 detected. • USB 2.0 cable: the red and mauve points are detected. • USB 3.2 cable (Gen 2x1): as for USB 2.0, plus any one of the four remaining groups of connections. • USB 3.2 cable (Gen 2x2): as for USB 2.0, plus either all the green points or all the orange points. November 2021 35 How we decided on which USB sockets to use We’ve spent a great deal of effort to make sure that the sockets we are using for the USB Cable Tester are durable and functional, as well as being hand-solderable. The latter is actually quite a tricky problem, especially for the USB-C parts. USB-C packs a lot of pins into a small connector. Since there are two rows of pins in the connector, breaking them out into two rows at the PCB makes sense. But having two rows of PCB pins will mean that the ‘bottom’ row cannot be surface-mounted, as there would be no way to access them from above. They’d be covered by the ‘top’ row of pins. Since one row of pins goes through holes on the board, soldering them will be slightly easier. But we think these are the finest pitch through-hole and SMD parts that we have used in any project. You’ll need to have the correct gear (including a magnifier and a syringe of flux paste). Therefore, soldering these parts is the trickiest part of constructing the USB Cable Tester despite our best efforts. Fortunately, the fullsize USB-A and USB-B parts are simple through-hole devices. We looked at utilising pre-built USB breakout boards, but they would have substantially increased the size of the final unit and cost quite a bit more too. The mini-USB socket, CON5, is a part we’ve used many times before. Since there is no USB 3.2 variant of this connector, a standard USB 2.0 part is adequate. The micro-USB part is small too, but not much different from the mini-USB socket. They both only have a single row of pins. The good news is that you can use the circuit itself to test that the sockets are soldered correctly. We’ll go into more detail during the construction, but briefly, we can use the existing hardware and logic to probe for any shorts in the socket soldering. A short in the socket soldering will appear to the USB Cable Tester like a fault in the cable, even if it only occurs at one end. Thus, we will advise an unusual order of construction, so that the USB Cable Tester’s microcontroller can run its tests during construction, well before it is complete. That way, you can take your time and check your work both visually and electrically to ensure that you end up with a functioning USB Cable Tester. A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A1 A2 A3 A4 A5 A6 A7 A8 A9 A10 A11 A12 GND RX2+ RX2− VBUS SBU1 D− D+ CC1 VBUS TX1− TX1+ GND GND TX1+ TX1− VBUS CC1 D+ D− SBU1 VBUS RX2− RX2+ GND GND TX2+ TX2− VBUS VCONN SBU2 VBUS RX1− RX1+ GND GND RX1+ RX1− VBUS SBU2 D− D+ CC2 VBUS TX2− TX2+ GND B1 B2 B3 B8 B9 B10 B11 B12 B12 B11 B10 B9 B8 B7 B6 B5 B4 B3 B2 B1 B4 B5 B6 B7 The two rows of closely spaced pins used in USB-C type plugs and sockets demand a tight pin pattern on the PCB. The part we have chosen will be the most challenging part of this project to solder, and we doubt there is anything easier to hand-solder available. Any additional connections detected beyond these constitute some form of short-circuit fault. When a cable is detected, the current pulse test is also performed once every five seconds. This is only done periodically to reduce battery drain and relay wear. The first test is done about half a second after detection, to allow time for the cable to be fully inserted. For this test, the micro sets all the pins associated with connectivity testing as inputs and closes the relays to complete the power circuit. The reference for the ADC is set to the 1.024V FVR (fixed voltage reference). Being a 10-bit ADC, each digital step then corresponds neatly to 1mV. The micro ramps up the PWM signal to Q3 while monitoring the voltages at various points along the VBUS and GND wires of the cables, including just 36 Silicon Chip above the current measuring shunt, which allows the test current to be determined. The ADC is sampled 16 times at four points over several PWM cycles to compensate for the relatively high amount of ripple in the applied voltage. At 100mA, 500mA and 1A, the voltages are stored. If the measured voltage rises above 1V (at any point in the cable) at any time, the test is cut short. The 1.024V reference used for these measurements puts an upper limit on what can be meaningfully measured. Another reason for cutting the test short is that it avoids a high load on the batteries. With a fixed 1A output, there is actually a greater load on the batteries when a high resistance cable is tested; this part of the circuit behaves much like a current source. In any case, a cable dropping Australia’s electronics magazine anywhere near 1V is not going to be of much use. The USB Cable Tester then displays the results from the highest test reading, including voltage drop and calculated cable resistance. When the cable is unplugged, the USB Cable Tester returns to the idle screen and counts down its timer to enter sleep mode unless another cable is plugged in for testing. Next month Next month we’ll describe the construction, calibration and use of the USB Cable Tester. We’ll also describe how the USB Cable Tester can check its own construction and assist with finding soldering faults in the SMD USB sockets we are using. See the panel for more information about the sockets and why such a feature will be handy. SC siliconchip.com.au Using Cheap Asian Electronic Modules By Jim Rowe Self-Contained 6GHz Digital Attenuator This new digitally-programmable module can attenuate signals from 1MHz to 6GHz by 0 to 31.75dB in 0.25dB steps. You control it using five small pushbutton switches, while a tiny OLED screen shows the current setting. I recently reviewed a new and small digitally-programmed UHF step attenuator module that could attenuate signals from 1MHz to 3.8GHz by 0-31dB in 1dB steps (October 2021; siliconchip.com.au/Article/15067). It has an inbuilt microcontroller, and the attenuation is set using four small pushbutton switches. The results were quite respectable overall, although there seemed to be a bit of contact bounce with the pushbutton switches and the RF output and power input connectors were too close together. As I finished writing that review, I became aware that a slightly larger digital attenuator had become available, with a broader frequency range and 0.25dB attenuation steps rather than 1dB. The OLED panel is mounted on the top of this PCB in the centre, along with the micro-USB power socket, the mini slider power switch and a tiny SMD power LED. Then along the PCB front are the five small pushbutton switches used to select the attenuation setting. Presumably, the rest of the controller circuitry is mounted on the underside of this PCB. The UHF attenuator chip is probably the Analog Devices HMC1119, a ‘big brother’ to the HMC472 used in the aforementioned 3.8GHz attenuator. According to the Analog Devices data sheet, the HMC1119 has a range of 100MHz to 6.0GHz and seven control bits, giving a setting range of 0 to 31.75dB in 0.25dB steps. It has a specified insertion loss of 1.3dB at 2.0GHz, drooping to around 1.5dB at 3.5GHz and a whisker below 2.0dB at 6GHz. Pretty impressive! As with the 3.8GHz attenuator, I couldn’t find a full circuit for the new module, so I could only work out a basic block diagram for it, shown in Fig.1. The RF1 input and RF2 output pins of the HMC1119 chip are coupled to the SMA input and output connectors via capacitors. Apart from various bypass capacitors, that makes up all of the actual attenuator section. Below is the control section, based on a microcontroller (possibly an New module The new module is likely available from several suppliers on the web, but I ordered the one shown in the photos from Banggood, catalog code 1648810. Currently, it’s priced at $51.80 plus $6.70 for shipping to Australia. Like the earlier 3.8GHz module, it’s almost certainly made in China. The new module measures 56 x 40 x 16mm overall, not counting the SMA connectors at each end for RF input and output. The digital attenuator section is on a small PCB fitted down inside a 56 x 40 x 10mm CNC machined aluminium block which forms the module’s ‘case’. The rest of the module’s circuitry is mounted on a second PCB measuring 56 x 40mm, which forms the top of the case. siliconchip.com.au Fig.1: a simplified version of what we expect the block diagram the 6GHz attenuator to look like, as there is no full circuit diagram available. Australia’s electronics magazine November 2021 37 The 6GHz digital attenuator from Banggood has an OLED screen and weighs about 57g. STM32F103C8T6, like the one used in the 3.8GHz attenuator). Operation The microcontroller (MCU) controls the attenuation settings of the HMC1119 via the seven programming lines, while the user determines the attenuation setting using the five small pushbutton switches S1-S5. To make this easy, the MCU displays the current attenuation setting on the OLED screen, controlled using a standard I2C serial interface. When power is first applied, the MCU sets the attenuation to 00.00dB. To change this, you first press S3 (the OK button) and then press S1 (<) or S5 (>) until the display is flashing the setting digit you want to change. Then you can press either S2 (+) or S4 (-) to change the value of this digit. To change other digits, use either S1 or S5 to move to them, then use S2 or S4 to change their value. Then if you press S3 again, this will be the new setting. It’s pretty straightforward, and although the tiny pushbuttons used for S1-S5 seem to be the same as those used on the 3.8GHz module, the additional two buttons seem to allow the setting to be changed more reliably. Perhaps the firmware in the MCU has also been improved to make it less susceptible to contact bounce. I have also shown a USB-serial interface chip in Fig.1. This chip may or may not be in the 6GHz module; I’ve shown it purely because it was present in the 3.8GHz module. It’s possible that, in this case, the data lines from the micro-USB connector go directly to two pins of the MCU, but they certainly are routed somewhere on the PCB. Either way, it would allow the attenuation setting to be programmed from an external PC, as well as from its own ‘keyboard’. So the micro-USB socket is not just to feed power to the module, but also for external control. As with the 3.8GHz attenuator, there’s virtually no information provided on doing this external control, but I found a very cryptic suggestion in the ‘Customer Q&As’ section of the Banggood info on the module: “Go to github.com/emptemp/att6000_control for Python code.” I’m not familiar with the Python programming language, so I sought help from other Silicon Chip staff. They advised me that all the ‘att6000’ Python code seemed to do was send 38 Silicon Chip serial text commands in the format “wv0XXYY<LF>”, where the XXYY characters indicate the desired attenuation setting XX.YY. In other words, sending the command “wv02375<LF>” should change the attenuator’s setting to -23.75dB. They also informed me that the command should be sent at 115,200 baud, not the 9600 baud that seemed to be used previously. I did try this out, and the results are described below. Performance I measured the performance of the new attenuator module using my Signal Hound USB-SA44B HF-UHF spectrum analyser and its matching USBTG44A tracking generator. Both were controlled by Signal Hound’s Spike software (V3.5.15) in its SNA (scalar network analysis) mode. Since the SA44B and TG44A combination will only work up to 4.4GHz, I could only check the module over this range. I first used this setup to check the module’s performance at an attenuation setting of 00.00dB to see its insertion loss. This is shown in Fig.2; the measured insertion loss is less than -2.5dB up to about 1.3GHz, then droops down to about -6.0dB at 2.5GHz, then improves to about -2.5dB at 3.0GHz. It then droops to about -4.5dB at 4.0GHz, before moving up again to reach -4.0dB at 4.4GHz, which looks promising for its insertion loss at frequencies up to 6GHz. After this, I did response tests at ‘major’ attenuation steps: -5dB, -10dB, -15dB, -20dB, -25dB and -30dB. These settings were chosen to give a good idea of the module’s overall performance. After examining the results I then checked the response at a number of ‘fine detail’ settings: -1dB, -1.5dB, -2dB, -3dB, -4dB, -7.5dB, -10.75dB, -14dB, -19dB, -28.25dB and -31.75dB. During each of these tests, I saved an image of Spike’s plot of the test results. Then, knowing that there wouldn’t be enough space to reproduce all 18 of the plots separately, I combined all of the plots into a single composite plot, to allow for easier evaluation – see Fig.3. The upper plots in Fig.3 (down to about -20dB) have a shape almost identical to that of the top 00.00dB plot, just separated from it by the chosen attenuation setting. Fig.2: using Signal Hound’s Spike software the 6GHz module could be checked at an attenuation setting of 0dB to measure its insertion loss. Note that the setup used for testing can only measure up to 4.4GHz, so not the full range of the attenuator. Australia’s electronics magazine siliconchip.com.au For frequencies above about 1.75GHz, the higher attenuation plots (-20dB and greater) develop an increasing number of bumps and dips. These are very apparent in, for example, the red -25dB plot, the purple -28.25dB plot, the red -30dB plot and the blue -31.75dB plot. All of these four plots show an increasing tendency to have a significant dip between 2.5GHz and 3.1GHz. I suspect that this may be due to small resonances inside the HMC1119 chip and/or its surrounding tracks on the attenuator section’s PCB. There might also be standing waves inside the attenuator box at specific frequencies. These plots tell us that the attenuator’s performance is quite respectable, at least for frequencies up to about 2.2GHz and for settings up to about -20dB. But the errors do increase for frequencies above 2.2GHz and with settings above -20dB. Of course, the attenuator would still have many practical uses at frequencies above 2.2GHz and with settings above -20dB, especially if you were to use Fig.3 to correct for likely errors. Armed with the information mentioned earlier on how to control the device over a serial connection, it didn’t take me long at all to test sending new attenuation settings from my Windows 10 PC, using the TeraTerm serial terminal application. All I had to do was plug the cable from the attenuator into a USB port, then go into Settings → Devices to find out to which Virtual COM port it had been assigned. Then I started up TeraTerm and set it up to communicate with that port at 115,200 baud, with the 8N1 data format and with only an LF (line feed) at the end of each line. I was then able to change the attenuator’s setting at any time simply by typing in a command like “wv01575” and pressing the Enter key. No problem! The attenuator’s OLED immediately showed the new setting (like “-15.75dB”) and also sent back an “OK” message, to confirm that the command had been received and acted upon. I should perhaps note that there does seem to be provision on the top of the attenuator (just to the left of the OLED) for connecting a separate serial interface, as you can see in the photos. But there’s no information on doing this. I guess that the command interface is the same, but I haven’t tried it, so I can’t say for sure. Conclusions Overall this new attenuator module seems reasonably good value for money when you consider its relatively wide frequency range and low price. I also like its ability to be programmed using the built-in MCU, control buttons and tiny OLED screen, or from a PC via the USB port (and presumably from a separate microcontroller, via the serial port header). My only real gripe is that when I tried to unplug the USB cable from the micro-USB socket after testing it, the socket lifted straight off the PCB. It seemed to have been poorly soldered, and as a result, I had to spend quite a bit of time soldering it back on (under a microscope). I’d have preferred a mini-USB socket, as these seem to be a bit more rugged and also attach more SC securely to the PCB. Fig.3: a graph showing the combined result from a variety of response tests on the attenuator at various settings. siliconchip.com.au Australia’s electronics magazine November 2021 39 Review by Andrew Woodfield R80 Synthesised Aviation Band Receiver Kit This moderately priced receiver kit (about $50) is easy to build, simple to use and ideal for monitoring local airport traffic. It uses digital frequency synthesis for excellent stability and ease of tuning, and has a digital frequency readout. C ommercial aviation uses HF, VHF or even satellite frequencies to serve their communication needs. The majority of voice calls use the 118136MHz VHF aviation band. This band extends to 137MHz in many countries, including Australia. Conversations between pilots and airport towers, air traffic controllers, ground services and local aero club aircraft traffic are all routinely heard on this band. It has long been a very popular band for those interested in monitoring local radio services. Amplitude modulation (AM) is used on this VHF band, rather than either frequency modulation (FM) or one of the new digital modes, which are usually encountered with commercial VHF and UHF mobile radio or amateur (‘ham’) radio services. While some perceive AM as outdated, it improves communications safety and has proven to be very reliable over many decades. Even today, AM is also surprisingly spectrally efficient. This R80 aviation band receiver is a recent entry targeting this band. Offered primarily as a DIY kit, it features a digital phase-locked loop (PLL) tuning system and digital display on a compact 120 x 85mm PCB. This kit offers several improvements over older aviation receiver kits, which typically used traditional analog tuning and lacked any form of frequency display. 40 Silicon Chip Kit delivery While it is available from various internet suppliers (including on eBay and Amazon), I bought mine from a seller on AliExpress. It was well-packed with all of the parts and PCBs in plastic bags. A couple of layers of bubble wrap had been wrapped around the kit before placing it inside a cardboard box. The parts supplied are of good quality, with the seven ICs shipped in pin-protecting foam. It is not antistatic foam, but that’s still a lot better than getting a bag full of loose ICs (and that is, sadly, all too common when you order from places like AliExpress these days). Most of the chips supplied are not static-sensitive, only the PIC microcontroller. Assembly instructions must be obtained by email from the kit supplier. These were in Chinese, but most details were fairly obvious. The schematic, also partly annotated in Chinese, was included in these instructions. A detailed English translation is available can be downloaded from siliconchip.com.au/Shop/6/5950 Three PCBs are supplied in the kit: the main receiver PCB, a smaller display PCB and a PLL PCB. SMD parts are pre-fitted on these PCBs, saving builders from any anxiety on that issue. One minor point: the 7-segment LED display driver SMD IC had its part Australia’s electronics magazine number sanded off. If it fails, finding a replacement could be a problem. Checking against the parts list in the instructions revealed that two parts were missing: a 100μF capacitor and a 10-way right-angle pin-strip connector for the display PCB. Three extra ceramic capacitors were supplied. To avoid delay, I purchased replacements from a local retail supplier and set the extra parts aside. How the receiver works Fig.1 shows a block diagram of the receiver. It’s a double-conversion superhet with a first intermediate frequency (IF) of 10.7MHz and second IF of 455kHz. The incoming signal passes first through a bandpass filter (BPF) and the NE5204 10dB gain RF amplifier, then into the first mixer, an NE602. The oscillator for this mixer uses the popular Si5351a digital PLL chip. Its 25MHz reference crystal delivers both excellent stability and tuning accuracy. One of the three square-wave outputs of this chip is filtered via a five-pole low-pass filter to give the desired sinewave signal for the mixer. A Motorola MC3361 FM mixer/ demodulator chip contains the second mixer. This converts the 10.7MHz first IF signal down to the second IF of 455kHz using a 10.245MHz crystal oscillator. The receiver’s selectivity is mainly provided by 15kHz bandwidth 455kHz ceramic IF filter. siliconchip.com.au Fig.1: the block diagram of this doubleconversion superhet AM receiver. It features a four-digit LED display coupled with a stable phase-locked loop and digital volume control. Since the MC3361’s FM IF chain cannot detect AM signals, the receiver’s IF amplifier chain and AM detection is handled by a TA7640. This also supports a ‘signal level’ red LED indicator. Its brightness depends on the strength of incoming signals. The detected receiver audio is then passed to both the LM386 audio amplifier and the receiver squelch circuit via a two-channel software-controlled FM62429 audio attenuator chip. The receiver audio output can be muted until the squelch circuit detects a signal. The MC3361 supports this squelch functionality. A PIC18F1320 microcontroller monitors the rotation of the tuning encoder, drives the four-digit 7-segment LED display, controls the audio levels and the PLL. The rotary encoder also includes a switch to select the 100kHz or 10kHz tuning step size. In addition, a small pushbutton on the front panel gives access to volume, squelch and PLL reference settings. solder-tack this onto the main PCB, and a tidy design solution for this sub-assembly. A further small display PCB requires adding a pair of capacitors and the LED display before being fitted to the main PCB, one of the final steps of the build process. Here’s where the missing right-angle pin strip was required, although component leads off-cuts can be used if necessary. An experienced constructor could build this receiver in around four hours. Those with less experience, or constructors wanting to enjoy the kitbuild process a little more, will probably take eight to ten hours. While not a difficult kit, the absence of detailed step-by-step instructions means it does require some attention. It’s not suitable as a first kit for beginners but, if help is obtained from an experienced constructor, it could be successfully completed by those with only a few builds under their belt. Just watch out for the four tiny semi-transparent display spacers! They are hard to spot if they fall out of the plastic bag onto the floor. I’m just saying... Performance Following construction, the receiver worked first time. That’s important for a kit of this relative complexity. The alignment was delightfully simple. I first adjusted the IF transformer for maximum noise output with no input signal. I then adjusted the two input bandpass filter inductors for Kit construction Assembly follows the usual approach: fit the lowest-profile components to the PCB first, then move on to the taller components. The component locations are all clearly marked (in English), and the boards are all logically laid out. Fit the wafer-sized PLL PCB subassembly once all of the smaller parts are mounted. It’s a quick job to siliconchip.com.au The R80 aviation band receiver kit looks complicated, but two PCB subassemblies and a welldesigned main PCB make it straightforward to build. Australia’s electronics magazine November 2021 41 with the pushbutton and display menu system. The PLL required no additional adjustment for accurate operation, although the reference frequency can be precisely adjusted via the front panel controls if desired. Squelch problem & resolution Fig.2: the front-end filter response at 3dB/division, showing the 118-136MHz band (red bar) is within the -6dB response. The receiver has an adjustable squelch. It’s set with the front panel pushbutton and LED display. The receiver’s squelch circuit aims to silence (‘mute’) the receiver noise when no signals are present, and weak signals too, if desired. Unfortunately, this part of the R80 circuit did not appear to work properly. If a signal unmuted the receiver, the squelch would then promptly mute the receiver again, an effect known as ‘talk-off’. This occurs when the squelch circuit initially (correctly) detects a reduction in receiver noise when a valid signal arrives, but then (incorrectly) detects the desired received audio as noise and promptly mutes the receiver! This occurred repeatedly until the signal disappeared. The result was a series of brief bursts of chopped-up speech whenever a signal was received. This effect was also clearly audible in one of the early online video reviews of this receiver kit. I modified the original squelch circuit into a more conventional AM noise detector. Combined with a signal level squelch for stronger signals, that solved the problem. Details of this modification are provided in the separate panel. Putting it in a case Fig.3: the front-end filter response at 10dB/division, showing the valuable attenuation of the 88-108MHz FM broadcast band (blue). maximum signal strength using a signal generator. Because the receiver is very sensitive and the receiver’s frequency display is accurate, it’s likely that this bandpass filter alignment could also be completed using local airport signals. The front-end filter’s tiny green Kuibiaochi MD505-series adjustable inductors are a little unusual. These use brass tuning slugs rather than the typical ferrite core. The coil’s inductance therefore decreases (!) as the slug enters the coil. Fig.2 shows that this simple peak tuning provided a good receiver input 42 Silicon Chip filter response over the desired 118– 136MHz band (shown in red) with low insertion loss, important with such a wide tuning range. Fig.3 demonstrates helpful rejection of the nearby FM broadcast band (shown in blue). Tuning to a specific frequency is easy – just rotate the single front panel control – and precise, thanks to the digital display. The received audio was clear and distortion-free. Weaker signals were naturally a little noisier, but that’s typical for a 15kHz bandwidth AM receiver. Volume adjustment was practically a ‘do it once’ function, easily achieved Australia’s electronics magazine The kit did not come with any sort of case, nor was there an option to purchase one with it. As shown, I housed it in a trimmeddown box I bought from Altronics a couple of years ago, which is unfortunately no longer stocked. The box originally measured 130 x 90 x 48mm (lwh); I trimmed it down to reduce the height to 38mm. No adjustments were required to the length, as the box fitted the receiver board like a glove. After some research, I discovered that similar cases (with apparently identical dimensions) can be purchased from vendors on AliExpress, by searching for “BDH20002” (unventilated) or “BDH20006” (ventilated). Like me, you would have to cut them siliconchip.com.au Squelch modification to fix the ‘talk-off’ problem This modification converts the original high-gain filter/limiter squelch circuit into a conventional noise squelch with an 8kHz active bandpass filter and half-wave noise detector, combined with a large AM signal squelch gate. It is not a difficult modification, and there are no tracks to cut. The circuit along with my changes is shown in Fig.5, while the extra parts needed are listed below. The steps are: 1. Remove CP4 (10μF) and replace it with a 4.7nF Mylar or MKT capacitor. 2. Remove D1 (1N4148) and replace it with a 6.8kW resistor. 3. Remove CP6 (10μF) and then re-fit it with a 4.7kW resistor in series, while maintaining the original polarity. 4. Add a 150kW resistor on the copper side of the PCB, between pin 4 of U5 (MC3361) and the common connection between C16 and D2. 5. Add the two transistors shown in Fig.4 on the copper side of the main PCB, adjacent to the display PCB connections. Squelch adjustment can now follow the method described in the assembly instructions, ie, select the “Set100kW 100k W tings” mode using the front panel pushbutton, then select Mode 3 (Squelch Adjustment). Without any signal present, rotate the tuning control to adjust the squelch setting until the (noise-only) receiver audio is muted. Then, return 10kW 10k W to the standard tuning mode. To check that the squelch operates correctly, tune the receiver until you can hear a suitable speech signal. The 4.7kW 4.7k W signal audio should be audible when a signal is received, and the audio should be quickly muted when that signal disappears or when no signal is present. Readjust the squelch setting to achieve this, if necessary. Parts required for Squelch modification 1 BC548 NPN small signal transistor 1 BC558 PNP small signal transistor 1 4.7nF MKT or greencap capacitor 1 150kW 1/4W 5% resistor 1 100kW 1/4W 5% resistor 1 10kW 1/4W 5% resistor Fig.4: this shows where the extra components need to 1 6.8kW 1/4W 5% resistor be fitted on the underside of the PCB to fix the squelch 2 4.7kW 1/4W 5% resistor problem. Other changes need to be made to some parts on 1 short length of 1.5mm diameter heatshrink tubing the top side of the board, as described in the panel. Fig.5: the original squelch circuit, as designed by the kit makers, with my changes shown in red. They make a huge difference in how well the squelch function works. The additions are an 8kHz bandpass noise filter, biased diode noise detector and a high-signal level mute using the two extra transistors. siliconchip.com.au Australia’s electronics magazine November 2021 43 Fig.6: the front and rear panel cut-outs required to house the receiver in a suitable case. Even though your case will likely have differently-sized end panels, as long as you keep the clearance requirements in mind, you can transfer these to panels of any shape and size. down, though, taking 5mm off the top and bottom halves, using a rotary cutting tool or similar. Also, the box from Altronics used clips to hold the covers together while these versions use pillars and screws. They would need to be removed to allow the PCB to fit flat. These could be replaced by internal side gussets and screws. Fig.6 show the panel cut-out dimensions. These might seem useless given that the box is no longer available, but that is not so. All the dimensions in those drawings are all referenced to a 44 Silicon Chip pair of vertical and horizontal datum lines, shown in blue, so they can be transferred to any surface. The clearances noted from PCB edges should allow the minimum box size to be determined/verified. Most builders should be able to locate a suitable enclosure, or design/print one themselves. What’s missing? Once I made the modification, the receiver worked very well. But there are a few features I’d like to have seen in the receiver. Australia’s electronics magazine One is full 118–137 MHz coverage. To balance this, the vast majority of VHF aviation communication falls within the current tuning range of the receiver. I would also like support for 8.33kHz bandwidth channels. These are gradually becoming more widely used, particular across Europe. The current receiver software supports 10kHz and 100kHz tuning step sizes only. These neither match legacy 25kHz channel assignments, nor the new 5kHz-based steps required for the mix of 25kHz and 8.33kHz channels in use. The R80 receiver’s current wide bandwidth allows both types to be received, although, on occasions, you may hear traffic from several adjacent channels simultaneously! It would only require a minor software change to provide 100kHz, 25kHz and 5kHz tuning steps rather than the current 100kHz and 10kHz tuning steps, along with the use of a narrower 6kHz wide 455kHz ceramic filter. This filter (around $5) would also reduce receiver noise slightly and further improve performance. I’d also like to have channel memories for a few frequently-used channels. This would reduce the tuning required to move between widely spaced channels. However, that would require a more significant software upgrade. The lack of these features does not limit the widespread use and enjoyment of the current receiver kit. In time, these features may well be developed by the user community, given the performance and functionality of the existing R80 receiver and the ease with which such upgrades can be made. Conclusions Despite the (now resolved) squelch fault, my overall impression of the kit and the receiver is very positive. The kit is well-priced at $50, enjoyable to assemble, easy to align and simple to use. It’s a sensitive little aviation band receiver, completely free of the instability frequently encountered with earlier analog aviation kit receivers. The very stable PLL allows rapid tuning to a precise frequency. That makes it ideal for a variety of monitoring applications, and it’s now in regular use at the writer’s home. In short, I recommend it. SC siliconchip.com.au 1 2 0 2 gue o l a t Ca Now! 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BONUS 1 x 600g Flashforge Filament with purchase of Entry Level 3D Printer (TL4432), select from TL4260-TL4267. BONUS 1 x Mozzy Zapper (YS5544) with purchase of Multi-function Power Centre (MB3749). Page 2: CLUB OFFERS: 20% OFF Electronics Magazine applies to BE5025 and BE5030. Multi-buys: Any 2 x Aerosol Service Aids applies to NA1002, NA1012, NA1008, NA1004 or any combination. Multi-buys: Any 2 x 1kg Flashforge Filament applies to TL4260, TL4261, TL4262, TL4263, TL4264, TL4265, TL4266, TL4267 or any combination. Page 3: Page 2: Buy a Power Supply (XC9122) to suit Raspberry Pi Board XC9100 on the same transaction for $14.95. Page 7: BONUS 1 x 16GB microSD card (XC4989) with purchase of 1080p Event Camera (QV3872). SUPPLY CHAIN DISRUPTION: We apologise for factors out of control which may result in some items may not being available on the advertised on-sale date of the catalogue. 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LT3251 IP67 RATED BONUS* 16GB microSD Card FROM 1695 $ 99 $ Valued at $19.95 Door Lock Actuators 720P HD Slave LR8813 $16.95 Master LR8815 $19.95 JUST 1995 $ 12V 4 x RGB LED Light Strips for Car Interior SL3948 NOW 49 $ 95 SAVE $10 2.4" LCD ODB-II Engine Code Reader Accurately identify car problems. Displays data from engine system, reads & remove fault codes, retrieves vehicle information & more. PP2147 JUST 69 $ 95 2.5" LCD 1080p HD DVR Event Camera Automatic recording on impact, wide 170° angle lens. G-sensor function. Records to microSD (sold separately). QV3872 * XC4989 16GB microSD card with purchase of QV3872 NOW 149 $ 4.3" LCD SAVE $50 Inspection Camera with 4.3" Display & Record Pocket-size endoscope with LED illumination to inspect hard to reach areas. Record vision or snapshots to microSD card (sold separately). 1m long camera lead. 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QC3191 ORRP $99.95 NEW LOW PRICE 5995 Swann 1080p Battery Powered Wi-Fi Cameras NEW LOW PRICE JUST 149 $ Outdoor Wireless Wi-Fi PTZ Camera Wire-free security camera with face recognition feature. 2-way audio. Wide 180° viewing angle. Single QC9100 $189 ORRP $219 Twin QC9102 $379 ORRP $439 Single With Solar Panel QC9101 $249 ORRP $299 1080p recording. Records to microSD card (sold separately). 2way audio. IP65 water and dust resistant. Motion detection, mobile push alerts and more. QC3859 ORRP $229 16GB microSD Card XC4989 $19.95 NEW LOW PRICE NEW LOW PRICE NEW LOW PRICE JUST JUST 199 99 $ Concord 4K HDMI Cat5e/6 Extender Send UHD 4K signals from a set top box, media player, or other video source to another room. Support High-Dynamic-Range (HDR) video. AC5020 ORRP $249 NEW LOW PRICE JUST 49 69 $ 95 2.4GHZ & 5GHZ FREQUENCIES NEW LOW PRICE JUST 6995 $ NEW LOW PRICE JUST 7995 $ Mazzy Xtreme Bots Kit Tribo 3-In-1 Keypad Coding Kit Build a doodler, shooter or sweeper robots. 182 pieces. 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NEW STORE: BATHURST, NSW 3 Pat O’Leary Drive, Bathurst 2795 Ph: 02 6323 2902 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer confirmed at the time of print. Call your local store to check stock. Occasionally discontinued items advertised on a special / lower price in this flyer have limited to nil stock in certain stores, including Jaycar Authorised Resellers, and cannot be ordered or transferred. No rainchecks. Savings off Original RRP. Prices and special offers are valid from 24.10.2021 - 23.11.2021. 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. Modifying Micromite software to use a 3.5in display Our readers often ask if it is possible to make software written for the Micromite BackPack V1 (February 2016; siliconchip.com.au/Article/9812) or V2 (May 2017; siliconchip.com.au/ Article/10652) which normally use a 2.8in touchscreen to instead work with the larger 3.5in display. At the very least, a different display driver is needed. The ILI9488 controller used on the 3.5in touchscreen does not have a native Micromite MMBasic driver, so we need to load an external CSUB library. This consumes around 6kB of library space, so it won’t fit if the original program comes close to filling the available flash memory space. Assuming the driver fits, rewriting the MMBasic code to function with the 3.5in display is possible, but it is tedious, time-consuming and requires thorough testing. That’s because these display controllers cannot perform scaling to fill the screen. Also, Micromite fonts are bitmap-based and cannot be resized easily, except in integer multiples. The 2.8in display has 320x240 pixels, while the 3.5in display has 480x320 pixels. Pixels would have to be mapped 2:3, which would appear chunky and grainy as this must be done on a per-pixel basis. Also, screen elements may be anchored to the different parts of the display, so they could become scattered confusingly around the screen. But there is another, easier solution. It tricks MMBasic into thinking that it is connected to a 320x240 display, so all display elements are where they should be. As far as the MMBasic program is concerned, it is connected to a 320x240 screen. The downside is that these 320x240 pixels are located in one corner of the larger screen, meaning that the entire 3.5in display area is not available. In fact, since the pixel pitch of the 3.5in display is smaller than the 2.8in display, the resulting active display area is actually smaller. Still, as long as you have 6kB of flash memory spare, it will give you a functional, working display. Most importantly, it will be the same as far as the software is concerned. All you need to do is load our Library file (available for download from siliconchip.com.au/Shop/6/5949) instead of the inbuilt LCD driver, usually done with the OPTION LCDPANEL command. The main part of the Library file is the ILI9488 driver that we have used previously. The MM.STARTUP subroutine runs when the Micromite starts up. This loads the driver, clears the display and then uses POKE commands to override the display driver resolution. After this, the display is indistinguishable (as far as MMBasic is concerned) from the ILI9341 display driver. By initialising and clearing the display before changing the resolution, the unused parts of the display are simply left blank. You could also add other commands here to set this area to a contrasting colour if needed. The POKE commands are as follows. You could modify the values to emulate other display sizes: ‘set width POKE WORD PEEK( WORD &H9D000094),320 ‘set height POKE WORD PEEK( WORD &H9D000098),240 The sequence of commands needed to configure the Micromite is as follows; these are also listed in the Library file. After loading Library.bas into the Micromite (eg, using MMEdit or TeraTerm), type: LIBRARY SAVE WATCHDOG 1 OPTION TOUCH 7, 15 GUI CALIBRATE GUI TEST LCDPANEL GUI TEST TOUCH While not elegant, this solution is fully functional and results in a pixelidentical image to what would be seen on a 2.8in screen. Here’s what a typical screen from the DDS Signal Generator (April 2017; siliconchip.com.au/ Article/10616) looks like. siliconchip.com.au Australia’s electronics magazine Following these steps, develop or load your MMBasic program. This solution will only work with the V1-V3 Micromite BackPacks (using the PIC32MX170 processor) and not the Micromite Plus. Tim Blythman, Silicon Chip. November 2021 53 Voice-operated and proximity lift controls One big problem with lifts is that you usually have to press a button to select which floor you want to go to. And with everyone pressing these buttons, there is the possibility of spreading disease. So I came up with these voice-operated controls for the service lift at my workplace. It takes a voice command from people inside the lift and converts them into electrical signals which operate solenoids to press the lift buttons. To call the lift, one or two proximity sensors are provided at each floor, for up & down. All you need to do is wave your hand near the sensor to call the lift. This project can handle other voice commands, such as opening and closing doors, controlling a fan or triggering an alarm. A laptop with an Intel Core i3 processor handles the voice recognition, passing commands to the Arduino via a USB connection. Within the lift, nine solenoid thimbles placed on the control switch touchpad operate the buttons. This is attached to the lift using a 160mm x 10mm wire frame on top of the lift command keypad. A technician from 54 Silicon Chip the turbine maintenance department made the small cage-like solenoid holding pads which push the switch pads. After receiving a command, the machine speaks out the intercepted command and then executes the command to actuate the right solenoid to press the button. This is handled by the Arduino triggering a transistor to drive the solenoid coil using one of its digital outputs. Commands are supported in English and Hindi, including “first floor”/“ek number”, “second floor”/“do number”, “third floor”/“teen number” and “fourth floor”/“char number”. If the command is not understood, it will ask for you to repeat it. Arduino digital outputs D5-D13 provide the following functions, in order: fan stop, fan start, alarm, door open, door close, first floor, second floor, third floor and fourth floor. The extended commands “pankha chalu”/“fan on”, “pankha band”/“fan on”, “darvaja kholo”/“door open”, “darvaja band”/“door closed”, “ghanti”/“alarm” are used for the other commands on digital outputs D5-D9. Australia’s electronics magazine The software running on the PC was developed using Python and Google Speech. Its source code (plus the Arduino program that it controls) is available at siliconchip.com.au/ Shop/6/5780 The solenoids are powered from a 5V 2A plugpack, while the Arduino is powered from the laptop’s USB 5V supply. As the solenoid driver transistors are on the low side, 12V or 24V solenoids could also be used with a matching power supply. Each solenoid has a diode, which is normally reverse-biased, connected across it to absorb the back-EMF spike when it switches off. The circuit below is much simpler, providing the interface to call the lift. The ATmega328 is programmed using the Arduino IDE and it periodically sends pulses to the two ultrasonic distance sensors and ‘listens’ for an echo. If it senses an object near one of the sensors (within about 22cm), it triggers the associated solenoid, in much the same manner as the in-lift circuit shown at right. Bera Somnath, Vindhyanagar, India. ($150) siliconchip.com.au Circuit Ideas Wanted siliconchip.com.au Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia’s electronics magazine November 2021 55 POCKET WEATHER STATION By Aarav Garg We’re often describing how you can buy and use very low-cost electronic modules. They’re great because they save you a lot of assembly time and soldering work, and they usually cost less than the parts you would need to build them! Here is an excellent beginners’ project that uses five such modules to make something useful – a mini weather station you can carry everywhere with you. I s it hot in here, or just me? That’s a question you don’t have to ask anymore with this Pocket Weather Station. It is a compact device, powered by an Arduino Nano board, that you can carry anywhere, right in your pocket. It displays the current temperature and humidity on its OLED screen. Sure, you may have the local weather report on your phone, but it’s amazing how much local temperatures can vary from those recorded elsewhere in your area. Plus, knowing the indoor temperature and humidity can be pretty helpful, as how hot or cold it ‘feels’ is strongly affected by humidity, not just temperature. Even with moderate temperatures, high humidity can make you sweat more than a more intense dry heat! One reason it’s so portable is beacuse of its integrated, rechargeable 160mAh LiPo battery. It is an excellent project for learning and is also really fun to make. It even comes in handy sometimes! 56 Silicon Chip Sound interesting? Then let’s dive right in! First steps The first thing to do when beginning with any project is gathering the required components. The required components are listed in the Parts List. They are mostly available from online marketplaces like eBay, AliExpress and Amazon. While they are inexpensive, chances are they will come from overseas, so allow a few weeks (or even months) for delivery. By the way, the DHT11 is a smaller, less accurate version of the DHT22 temperature/humidity sensor that we have used in the past and described in the February 2017 issue (siliconchip. com.au/Article/10529). Its small size is useful in a pocket device. As it incorporates both temperature and humidity readings, we only need the one sensor. The other parts are the Arduino board to query it, the display Australia’s electronics magazine to show the readings and the charger to keep the battery topped up. You need a few basic tools to build the Pocket Weather Station: a soldering iron, hot glue gun (or even better, a tube of neutral-cure silicone sealant and a caulking gun) and, if you’re going to make the optional case, a 3D printer. Preparation Now we need to plan the position of all the components inside the enclosure. I wanted to keep the device as thin as possible, so it is actually convenient to carry in a pocket. Thus I spread all the components out and did not go with a layered structure. That would decrease the width and height, but increase the thickness. Fig.1 shows how I stacked the components inside my Pocket Weather Station. I used an Arduino Nano board because of its size, which is perfect for this project. You could also come up with your own method of stacking the components in ways that reduce the siliconchip.com.au ► ► Fig.1: this is how I laid out the components so that they would fit inside a custom-made case. Fig.2: this diagram serves as both the wiring diagram and a form of circuit diagram; it shows all the connections necessary to turn the separate modules into a Weather Station. You don’t need to use the same colour coding as we did, but we strongly advise that you stick to the red/black colours for the power wires, and make sure that black only goes to ground or negative pads, and red to positive pads. Take note that different DHT11 modules may have different pin-outs. size of the device even further! After you have planned your preferred arrangement, refer to Fig.2, the wiring diagram. This shows how all the modules need to be connected. It’s relatively simple, as there are few modules and none of them need to be modified. Wiring it up Before you build the Pocket Weather Station, you might like to watch my YouTube video showing how I assembled it, at https://youtu.be/ ZhOhBuKC80M There are two types of connections to be made: power (red/black wires) and signal (green/orange/yellow wires). The charger board connects to the battery as well as all the other modules, to power them. The only other connections required are for the I2C serial bus between the Arduino Nano and the display and one signal wire from the DHT11 to the Nano, so it can get readings. Start by connecting the battery to the battery charging module. We aren’t connecting any wires to the switch yet, because that has to be done once everything is installed in the case. You can connect the power supply wiring of the Arduino, OLED and DHT11 modules to each other, and the ground back to siliconchip.com.au the charger module; leave the wires for the switch loose for now. Try to keep the wire lengths just long enough to prevent a mess of wires later on. For all the power supply connections, make sure you get the polarity correct, with black wires to the GND pins only and red wires to the positive pins. If you connect them the wrong way around, chances are that some of the modules will be damaged. Also, try to solder everything accurately to prevent any kind of short circuit. It might be a tedious process, but believe me, later on it will feel worth the effort. After you have finished soldering all the components (excluding the switch), it should look something like Fig.3. I am sure we can’t carry it around like this, so clearly we need an enclosure for our Pocket Weather Station to give it that professional look. And the best option that we have here is 3D printing. I don’t have a 3D printer, so I used an online 3D printing service based locally in India (www.iamrapid.com). I uploaded my .stl files to get an instant quote and ordered the parts right away. The enclosure I designed the enclosure in Tinkercad, which is a fantastic CAD software package. It supports all skill levels, so even if you are a beginner, you can still use it. You can download my 3D files (.stl format) from the Silicon Chip website. Australia’s electronics magazine Fig.3: once you have finished wiring nearly all the components together, it should look like this. November 2021 57 The 3D-printed case for the Pocket Weather Station. There are a few 3D printing services around Australia which can process the supplied STL file for you. The enclosure they delivered to me has a great build quality. Chances are you will find a similar local service. Do a web search for “3D printing service” or go to your nearest Jaycar Maker Hub, which offers a 3D printing service (see our June 2020 issue for details; siliconchip.com.au/ Article/14472). You might also find a nearby maker space (see https://wiki. hackerspaces.org/australia). Fortunately, all the cutouts that I had made in the design were in the exact spots I needed them, so I didn’t have to get a second prototype made. Putting it all together Now, we need to place the whole circuit inside the enclosure that we designed earlier and 3D printed. It is vital that all the parts go in their respective cutouts to give the device the much-needed professional look. It is also important that all the components are firmly fixed in their place and do not move inside the enclosure, to ensure proper and smooth functioning of the device. I used hot melt glue to fix the parts inside the enclosure. However, while this is convenient, it can fail if exposed to enough heat (eg, if it’s left exposed in direct sunlight inside a car). For this reason, you could instead use the slightly more permanent neutral cure silicone sealant. It takes longer to cure, but it’s not going to fall apart if it gets hot. As you fix the components in the case, make sure the two USB sockets line up with their access holes around the edges, as you will need to connect to both of them later. Now it is time to add the slide switch in its dedicated slot. We did not connect the switch previously because the switch needs to be inserted into the enclosure from the outside. After putting the switch into its slot, use two small screws to fix it in place. Then connect the two wires to it, one from the Vcc pad of the Arduino board At left is the (nearly) completed project, it just needs the wires soldered to the switch at lower right. Hot melt glue was used to make sure the components were secure. Note that this glue can fail if exposed to enough heat. 58 Silicon Chip Australia’s electronics magazine siliconchip.com.au and one wire from the positive output of the battery charging module. If it has three terminals, make sure to connect those wires to two adjacent terminals. This way, the circuit will be completed with the switch slid to that end. Now we need to complete the enclosure. I used screws to fix the lid in place. I had already made screw holes in the design, so that was easy. Just make sure that the cover is securely in place so it looks professional and is convenient to carry. I have put my logo on the lid design to give it a more aesthetic and customised look. After closing it up, all that’s left is to program the Arduino. Programming We need to upload some code to our Pocket Weather Station. Without code in the Arduino, our device is just a plastic box with no functionality. First, download my Arduino sketch from the Silicon Chip website. It is a zipped directory containing a file with a .ino file extension. Unzip the package, install the latest Arduino IDE (integrated development environment) and open the .ino file. If you wish to, you can get your hands dirty and write the code yourself. But if you’re a beginner (and even if you aren’t), it’s best to start with my version since we know it works. You can always modify it once you get it working. See the panel if you are interested in how the software works; that information could come in handy if you plan to make changes to it. Once you have the code open in the Arduino IDE, plug the Arduino Nano into your computer’s USB port (don’t plug into the USB charger port as it does not pass data to the Arduino). Then press CTRL+U (or select Sketch → Upload) to compile the code and load it into the Arduino. Check the output at the bottom of the window for error messages. Compilation takes a few seconds, and if it finds a problem with your code, it will tell you there. Otherwise, you should get an “Upload successful” message, and your Pocket Weather Station will be fully operational. Don’t forget to charge the cell (via the other USB port) so it is ready for use. The cell charge lasts quite a long time, so you will barely need to charge it. Now, you can proudly carry the device wherever you go and flaunt siliconchip.com.au Parts List – Pocket Weather Station 1 Arduino Nano or equivalent board 1 USB cable, to suit the Nano 1 DHT11 temperature sensor module 1 0.96in OLED screen with I2C interface and SSD1306 controller 1 TP4056 li-ion battery charging module (Silicon Chip Cat SC4305) 1 small 1S LiPo cell (eg, 160mAh) 1 slide switch 1 set of 3D printed case pieces (optional) 6 small self-tapping screws (two for mounting the switch, four for the lid) various lengths of light-duty hookup wire How the software works The software for this project is relatively simple. Don’t be daunted by the length of the code; half of it is simply the bitmap graphics for the splash screen! The first few lines include all the libraries we will need: the graphics libraries, humidity/temperature sensor interface library, fonts etc. It then creates the object to communicate with the DHT temperature sensor using pin D4 and another object to drive the screen with a resolution of 128x64 pixels. Following this is the logo bitmap, then below that the main body of the code, which comprises three functions: setup() (for initialisation), loop() (the part which runs continuously after setup) and testdrawbitmap(), which draws the logo on the screen. The setup() function starts the serial port and DHT temperature sensor communications, then initialises the display, draws the logo and pauses for one second. Once the setup() routine has finished (ie, after that one-second delay with the logo on the screen), the loop() function is repeatedly called as long as the unit has power. Each time the loop() function runs, it starts by acquiring temperature and humidity readings from the DHT11 sensor, then prints that data to the serial console. It follows by clearing the screen, then printing the same information on that screen, including what the temperature ‘feels like’ based on the combination of temperature and humidity. It then pauses for two seconds before the process repeats. As this code is all relatively straightforward, you should be able to modify it (eg, to change the way the readings are displayed on the screen) should you wish to do so. your creation (or maybe actually use it as a weather station). Troubleshooting If you are here, that probably means that you have built the project, and it didn’t work. Don’t worry, you will get it working and you will learn a lot from troubleshooting it: 1. The OLED screen is blank You might have damaged your OLED display due to an incorrect connection, but more likely, you haven’t connected the signal wires properly, so re-check them. There might also be an error in your code (for example, if you have forgotten to initialise the display). Try using my code first as we know it works, then modify it from there once you it working. Australia’s electronics magazine 2. All readings are “NA” This will happen if it can’t communicate with the temperature sensor. You might have a problem with the connection between the temperature sensor to the Arduino board. Just re-check the connections. If they are correct, you might have a problem with the sensor itself; try replacing it. 3. It works when the USB cable is plugged in, but not from the battery If this happens, there is a problem with your battery or perhaps the connections between the battery and the rest of the circuit. Links This project on the Instructables website: siliconchip.com.au/link/ab9r This project on the HackSpace website: siliconchip.com.au/link/ab9s SC November 2021 59 Model Railway Carriage Lights BY LES KERR It’s nice to have carriage lights on a model train, to add to the realism. These model train carriage lights (designed for OO-gauge) are batterypowered and can be switched on and off with an external magnet. I t might seem trivial to add lights to a model railway carriage, but there are a few considerations that make it a bit more difficult than that. One important factor is that the battery must be small, so the circuit must avoid discharging it when the lights are off. Also, you need a way of switching the lights on or off easily. This little circuit powers five white LEDs and only draws a couple of microamps when off, and just 8mA when on. The low off-current puts a negligible load on the battery. The low 8mA operating current means that you can use two AAA batteries (cells, really) in series giving 3V this will power the circuit for about 100 hours. If you lack the space for that setup, you can use a single 3.7V Li-ion 800mAh battery such as the Jaycar SB2300. The carriage size determines which batteries can be used. The circuit stops working when the battery falls below 2V. Until recently, lights in model railway carriages were powered from the track. This is because small incandescent lamps required a relatively large current, so they couldn’t be battery powered. To obtain the power, the carriage needed to have metal wheels 60 Silicon Chip with some form of voltage pickup attached to them, and they had to be insulated from each other. Today, most carriage wheels are made of plastic, so they need substantial modification to pick up power from the track. Also, it isn’t that easy to make a reliable pick up. Now that efficient white LEDs are available, it is practical to power them from a small battery inside the carriage. The problem then becomes how to switch the lights on and off. My simple solution is to mount a normally-open reed switch inside the carriage, either under the roof or on the floor. When a magnet is placed near the reed switch, its contacts close, signalling the circuit to toggle the lights on or off. You can see a video of the prototype’s operation at siliconchip.com. au/Videos/Carriage+Lights With this arrangement, you can add a magnet on the tracks just outside a tunnel so that when the train approaches, it switches the lights on. Another magnet placed near the tunnel exit switches off the lights when the train leaves the tunnel. If you want to use the train at night, you can mount the reed switch under the roof so that Australia’s electronics magazine you can manually switch the lights on and off by waving a magnet across it. Circuit description Fig.1 shows the full circuit diagram. The LT1932 IC2 constant-current DC-to-DC LED driver provides a fixed current that drives the series LED lights from the battery. It is about 70% efficient and will work down to a battery voltage of 2V. It has a shutdown input that, when taken low, switches off the LEDs and reduces its current draw to less than 1μA. I have specified high-intensity white LEDs which give adequate light when driven with 1mA. The 70% efficiency figure given above is for a 10mA LED current. To reduce this to the 1mA required without unduly affecting the efficiency, the shutdown pin is fed with a 10% duty cycle (1-to-9 markspace ratio) PWM waveform. The driver oscillates at 1.2MHz and uses inductor L1, schottky diode D1 and a 1μF ceramic capacitor to step up the battery voltage to the 15V or so needed by the LED string. To protect IC2 in case the LEDs are accidentally disconnected, 24V zener diode ZD1 clamps the maximum output voltage. The peak current through the LEDs is siliconchip.com.au Fig.1: the Carriage Lights circuit is based on a 6-pin LT1932 (IC2) constant-current switchmode (boost) LED driver and an 8-bit, 8-pin microcontroller (IC1). The role of IC1 is twofold: it monitors the contact closure of reed switch S1 to switch the lights on and off, and when the lights are on, it drives the SHDN pin of IC2 with a 10% duty cycle square wave, reducing the LED current consumption without impacting the efficiency of the driver circuit. set to about 10mA by the 2.2kW resistor from IC2’s Rset pin to ground. An inexpensive PIC12F617 8-bit microcontroller is used to generate the PWM waveform to drive the pin 5 SHDN input of IC2. When reed switch S1 closes, it takes the GP2 digital input (pin 5) of IC1 high. The 10kW pulldown resistor and 100nF capacitor help to debounce the switch contacts. This signals the microcontroller to come out of sleep mode and provide the switching waveform to IC2, turning on the lights. If S1 is operated again, IC1 goes back into sleep mode, and its GP0 output at pin 7 goes low, switching off the lights. In sleep mode, IC1 draws about 1μA from the battery. If you add to this the <1μA of IC2 in shutdown mode, you get a total current drain of less than 2μA, which is a negligible load on the battery. Construction There are components on both sides of the PCB, so there are two overlay diagrams, Figs.2 & 3. The Carriage Lights controller is built on a 28 x 16mm PCB coded 09109211. It has been deliberately kept small to fit inside a typical OO-gauge carriage. Since I etched mine myself, it is a single-sided design, although you can get the double-sided version from Silicon Chip, which avoids the need to fit a wire link. To enable this PCB to be kept small, most of the components are SMDs. This is a good project if you’re siliconchip.com.au interested in improving your SMD soldering skills since it has a few different types and sizes of components, but nothing especially difficult. Perhaps unsurprisingly, the surface mount components go on the copper side of the board, while the throughhole components are inserted from the opposite side. The SOIC-package PIC12F617 micro will need to be programmed at some point. The easiest way is to purchase a pre-programmed PIC, although it is possible to program it in-circuit; see the panel below if you plan to do it that way. Use a flux pen or syringe of flux paste to coat IC1’s leads and its associated pads. Hold IC1 in place (eg, using tweezers) with the correct orientation and use your soldering iron to tack solder one lead into place, then check that it is positioned correctly (it’s also a good idea to re-check its orientation). If so, solder the remaining leads. Clean off the flux residue and inspect the leads under magnification to ensure that all the solder joints have formed correctly. If you are not sure about any of them, add more flux and apply heat (and possibly more solder) to reflow the joint. If you have bridged any pins, use more flux and some solder wick to remove the excess solder. Here is an example of how you can ► mount the project into a carriage. Note the clear plastic insulation under the battery and PCB. Australia’s electronics magazine November 2021 61 Parts List – Carriage Lights Figs.2 & 3: the top and bottom side PCB overlay diagrams (shown enlarged). To save space and allow the board to use single-sided copper, all the SMDs are on one side and the through-hole parts on the other. The orange wire link does not need to be installed if a double-sided PCB is used (eg, from our Online Shop). Watch the orientations of the ICs, diodes and electrolytic capacitor during assembly. Now that you’ve done that successfully, move on to IC2, which is slightly trickier as its pins are smaller and closer together. As its body is also quite small, you might have trouble seeing the pin 1 indicator. You will need to make sure you’ve found that (eg, using a magnifier) as it must be placed with the correct orientation. Use the same basic procedure to solder it as IC1, but keep in mind that it’s very difficult to avoid bridging the pins with solder. If you have flux paste, once the part has been tacked down, you can drag-solder the three pins on the opposite side and then the three pins on the other side. Still, it’s also acceptable to just solder them individually without worrying too much about creating bridges. After all, it’s pretty easy to remove any bridges that have formed with solder wick, as long as you add a bit of flux to make the process go smoothly, and avoid heating the wick any more than necessary to prevent damage to the PCB. Once again, clean the flux residue away from IC2 and scrutinise its solder joints, then go back and fix any that do not appear to have formed correctly, or are still bridged. Now use a similar procedure to fit all the remaining SMDs, except for the 6.8μH inductor. The only remaining SMD where polarity is important is schottky diode D1; its cathode stripe should be visible on the top of 62 Silicon Chip 1 single-sided or double-sided PCB coded 09109211, 28 x 16mm 1 6.8μH 200mA inductor, SMD 2.0x1.6mm up to 2.5x2.0mm, 200mA+ <0.5W DCR [RS Cat 879-0742 or Taiyo Yuden LB2016T6R8M] 1 miniature single-pole normally-open (SP-NO) reed switch (S1) [RS Cat 3622518 or Jaycar SM1002] 1 magnet suitable for use with a reed switch [RS Cat 118-7108] 1 3V battery pack [eg, 2 x AAA pack or 1 x 3.7V 800mAh Li-ion, Jaycar SB2300] various lengths and colours of light-duty hookup wire Semiconductors 1 PIC12F617-I/SN or PIC12F617T-I/SN 8-bit microcontroller programmed with 0910921A.HEX (IC1) 1 LT1932ES6#TRMPBF LED driver, SOT-23-6 (IC2) [RS Cat 7618504] 1 1N4749 24V 1W zener diode, through-hole (ZD1) [Jaycar ZR1424] 1 SS14 40V 1A schottky diode, DO-214AC (D1) [RS Cat 6387915] 5 high-intensity 3mm or 5mm white LEDs (LED1-LED5) Capacitors 1 100μF 6.3V radial electrolytic capacitor [RS Cat 390176] 1 1μF 50V multi-layer ceramic through-hole capacitor [Jaycar RC5499] 2 100nF 50V X7R SMD ceramic capacitor, M2012/0805 size [RS Cat 135-9033] Resistors (all SMD 1% 1/8W M2012/0805 size) 2 10kW 1 2.2kW the body, and this must be located as shown in Fig.2. As the inductor has only solder pads on the underside at either end, it’s harder to solder it in place compared to the rest of the components. To enable you to do this, I made the PCB lands for the inductor larger than the component body, so there is room to get your soldering iron tip in to heat the lands. Coat both the lands and inductor pads with flux and lightly tin the pads with solder. Place the inductor on the PCB and apply heat from your soldering iron to the land on one side until you see the solder melt. Do the same for the other side. Depending on how much solder you applied to the pads initially, you might want to feed a bit of extra solder into the sides while heating them. Now make a final check of the SMD components to verify there are no solder bridges or shorts, and if there are, fix them up with a bit of flux paste and the solder wick. Turn the board over and solder in the wire link (if you are using a single-sided board), zener diode, 1μF ceramic capacitor and the 100μF electrolytic, making sure the diode and electrolytic capacitor are the right way around. These components are all shown in the underside overlay diagram, Fig.3. Wiring it up While Fig.3 shows the basic external wiring connections, there are more Programming IC1 in-circuit To program the micro in-circuit, you will need to solder wires to the +3V and GND battery pads (see Fig.3), as well as the PCB pads provided to connect to the PCLK pad (pin 6 of IC1), PDAT pad (pin 7 of IC1; the pad is also used for the wire link) and the MCLR pad (pin 4 of IC1). As IC1 is mounted over the PCLK pad, solder this wire first and use as little solder as possible. Cut the part of the wire that projects from the solder joint as short as possible so that when you solder IC1, it isn’t lifted above its pads. With those wires in place and IC1 soldered to the board correctly, connect the soldered wires to your programmer. For the PICkit series, the triangle indicates pin 1, and the connections are MCLR to pin 1, +3V to pin 2, GND to pin 3, PDAT to pin 4 and PCLK to pin 5. With those connections made, load up the programming software, open the HEX file, “carriage lights (0910921A).HEX” and upload it to the chip. If you are using a pre-programmed PIC12F617, it isn’t necessary to solder these extra wires to the board. Australia’s electronics magazine siliconchip.com.au Here are both sides of the finished project shown greatly enlarged for clarity. While you can definitely etch the single-sided board yourself given the right supplies, we will be selling a doublesided version for convenience. 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 details shown in the wiring diagram, Fig.4. So that you can work out the length of the board connecting wires, you need to decide how and where the components fit into the carriage. In my case, I glued the 5mm white LEDs and the reed switch to the underside of the carriage roof and taped the battery and PCB to the floor of the carriage. If you have a smaller carriage, you might prefer to use 3mm LEDs. Another solution for the LED mounting is to solder them to a thin strip of Veroboard which can be attached to the underside of the roof. If the floor of your carriage is black like mine, you can improve the radiated light by covering it with aluminium foil to reflect the light back up. If you do this, insulate the PCB with tape so that none of the tracks short out on the foil. Once you have decided on the layout, cut the wires to length and solder them to the PCB. Testing Connect up the reed switch and LEDs, and before connecting the battery, have a last look at the board for any faults or dry joints. Make sure that you connect the battery the right way around, as the circuit will be destroyed if you don’t. If you now place the magnet parallel to the reed switch a few millimetres away, the LEDs should light. Remove the magnet, then put it back where you had it, and the LEDs should SC extinguish. Tiny LED Stocking 41 x 83mm PCB SC5688 – $3.00 Tiny LED Reindeer 91 x 98mm PCB SC5689 – $3.00 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 Fig.4: there are just three items to wire to the board; the power supply (in this case, a 3V battery pack using two AAA cells), the reed switch and the string of white LEDs. You can use just about any type of white LED as long as the voltage required to power the string is in the range of about 5-20V. Various LED mounting arrangements are possible, too – whatever suits your carriage(s). siliconchip.com.au Australia’s electronics magazine We also sell a kit containing all required components for just $14 per board ➟ SC5579 November 2021 63 Vintage Radio Stromberg-Carlson Stromberg-Carlson 1936 1936 model model 496 496 mantel By Associate Professor Graham Parslow mantel radio radio T his radio was a one-family treasure until it came to me for restoration from Peter Lockhart (retired from careers in electronics and IT). Peter wrote: “My first recollection of this Stromberg Carlson 496 was that it belonged to my great aunt, Beatrice Krentzin, who lived in Perth most of her life. She grew up in the goldfields of WA at the turn of the 19th century. It was used as a mantelpiece set. Though not very loud, it had a ‘lovely tone’.” “For a long time, it was the family radio (ie, the only one). I recall it was not particularly sensitive to radio stations, particularly as the ABC 50kW 6WF transmitter was only 6km away. The fact that it could not play ‘pop music’ loudly added to its general appeal. It was a trusty deliverer of the news and sports and world events over a long period.” “The radio passed to my mother in the 1970s and was fully functional at that time. It then became something of a favourite ornament. I have carted this radio around for more than 30 years with good intentions to restore it. Unfortunately, the opposite occurred, and suboptimal storage only added to the woes of the poor old 496.” The circuit After many years at the masthead of Vintage Radio, finally, here is an article on the feature radio! It’s an early superhet with Art Deco styling. You can see the dramatic change between its pre- and post-restoration appearance. 64 Silicon Chip Australia’s electronics magazine Fig.1 is the radio’s circuit diagram. Later superhet radios used dedicated converter valves with functionally distinct oscillator and mixer sections. Instead, the model 496 uses a 6C6 6-pin pentode as an autodyne oscillator with the signal introduced at the top-cap grid, at the frequency selected by the aerial coil and tuning capacitor. The coupled oscillator coils are drawn below the 6C6 valve. Local oscillator (LO) action is accomplished using anode-cathode feedback. The mixing function is created by the LO-modulated electron stream from the cathode interacting with the input signal at the control siliconchip.com.au The 7-inch (178mm) electrodynamic speaker was missing its cone. A ferrite-magnet 4W speaker was instead placed inside the area where the cone would normally be as shown in the adjacent photo. grid. This sort of autodyne configuration only became common again when transistor radios appeared. The first intermediate frequency (IF) transformer feeds the signal into the top-cap grid of a 6F7 pentode-triode. The 6F7 pentode performs IF amplification and feeds into the second IF transformer. The signal is detected in a slightly unconventional manner, by connecting the 6F7 triode grid and anode together to make a diode. The audio signal is then conventionally passed to the AL3 output valve. The gain of the 6F7 pentode is controlled by the 4kW volume control potentiometer that acts as a variable grid bias resistor. I measured the grid bias in this radio as varying between 0V (maximum volume) to -40V, even though volume was negligible at -20V. The aerial coil is also shorted out at minimum volume. The AL3 valve used in the output stage was released in March 1935 and had an 8-pin European side-contact base, with a recommended filament supply of 4V and a grid bias of -6V. Many restored radios of this type have the AL3 replaced with more readilyavailable octal types. A 6V6 valve installed in this radio is definitely a retrofitted modification because the label at the cabinet base is stamped 10 July 1936, and Ken-Rad did not release the 6V6 until late 1936. Substituting a 6V6 for an AL3 requires only installing an octal socket and a higher-value grid bias resistor. However, with a 6V6 in place of the AL3, the sensitivity will be only about half that with the original valve. The seven-inch (178mm) speaker is an electrodynamic type and forms part of the high tension filter circuit, its coil acting as the 1kW choke. The circuit is so minimalist that I had expected an easy electrical restoration, but this was not to be. Cabinet restoration I restored the case by taking the flat surfaces back to bare timber and finishing with polyurethane. Next, I repainted the parts and replaced the clear dial cover with a polycarbonate sheet. I also installed new speaker cloth. Finally, I selected appropriate knobs from my collection, because none came with the radio. Electrical restoration There was an obvious starting point for this radio. The seven-inch speaker cone was completely missing, presumably due to a moth or mouse attack. The family had tried to repair the cone, but I was told that they never managed to restore its tone. I decided not to replace the cone, but rather insert a modern ferrite-magnet speaker into the cone space. One of the 4W speakers in my parts bin was perfect for the job. I painted the exterior of the new speaker matte black and, at first glance, it appears to be the cone of the original speaker (it’s amazing how we see what we expect to see). Fig.1: the circuit diagram for the Stromberg-Carlson model 496 (the model 493 shares the same design). siliconchip.com.au Australia’s electronics magazine November 2021 65 ➠ Shown at left is the underside of the chassis after restoration. A subsection is shown above of the green multi-section wire-wound resistor which was replaced with a tag board. capacitors were originally installed – the only two in this radio. One of the replacement electrolytics added below the chassis was modern; I replaced the other, which was 1940s vintage. Visual inspection suggested that it was now time to see if power would bring the radio to life. Testing It was not difficult to hook this speaker into the secondary of the speaker transformer. However, because the new speaker was a few millimetres proud of the old speaker rim, a reworking of the original baffle with an additional three-ply spacer was required. It was an excellent mental and physical exercise to finalise this solution. The pictures show the result. I abraded the rust on the speaker transformer and speaker frame away and repainted them to optimise the appearance from the rear (the sides of the speaker cannot be seen in the 66 Silicon Chip assembled radio). The next task was to clean up the rust and debris that degraded the appearance of the chassis. The two dial-lamp holders looked forlorn, but they cleaned up well and remained serviceable. Unfortunately, the set had a short length of modern figure-8 flex coming out from the rear. I replaced that with a cloth-bound threecore mains lead, allowing the chassis to be Earthed. Two circular holes in the chassis at the front of the power transformer show where canned electrolytic Australia’s electronics magazine The first power-up was to check the transformer, with only the dial lamps as a load (no valves). This made an excellent start, with a stable, low power consumption and two shining lamps. I then plugged in the valves and gave it another go. After warming up, the radio was using a stable 41W and making no sound. The high-tension (HT) rail was slightly lower than expected at 235V after the choke. Optimistically, I tried a substitute 6V6 output tetrode, to no avail. All the DC voltages at the octal base of the 6V6 checked as OK, so the speaker transformer primary was intact and conducting high tension from the screen to the anode. Applying an audio signal to the 6V6 siliconchip.com.au grid produced clear sound, affirming that the speaker transplant was successful. There were only three original Chanex-brand paper capacitors left in the radio, so I replaced all of them. None of them proved to be leaky, so there was no change in function. The circuit diagram indicated an IF of 465kHz, so I used a signal generator to check whether a 465kHz signal injected into the grids of the 6C6 or 6F7 would produce any output. Nothing. Checking the voltages at the bases of the 6C6 and 6F7 showed no screen voltage. This usually indicates a leaky bypass capacitor, but new capacitors had already been put in place. Checking the large green multisection wire-wound resistor showed that the only functional section was the 140W grid bias resistor. The other clamps were not making contact with the wire beneath them. This explained why there was no screen voltage, because this is derived from a 15kW segment that was open-circuit. To restore the function of the resistor series, I decided to populate a tagboard with discrete resistors. The tagboard I selected was unused and dated from about the time of this radio, so installing it was not an outrageous affront to its character. A previous modification had been to add a 150W resistor in series with the 140W resistor in the output valve grid bias circuit, so that the AL3 could be replaced with a 6V6. The result was that bias at the 6V6 was -15V. I instead used a 100W + 150W pair, resulting in a -14V bias. The radio remained dead with its newly installed resistors. The only improvement was that an IF signal injected into the 6F7 grid now produced audio output, indicating functional IF amplification and detection. The 6C6 oscillator had a screen voltage but no anode voltage, and this was traced to an open circuit in the tuned coil of the Armstong oscillator circuit. I removed the coil and tested it; both coil sections in the oscillator were open circuit. My first attempted fix was to wire in a replacement from my salvage shelf. This was a failure, so it was back to repairing the original coils. This was not trivial because whole segments of the Litz wires connecting the base lugs to the coils were missing. Some siliconchip.com.au On the rear of the chassis you can see the cloth-bound mains lead which was a replacement for a figure-8 flex as a way to Earth the chassis. An additional power transformer was mounted on the top of the chassis (at far left) to provide higher filament voltage. This was mounted where two old electrolytic capacitors used to be. monumental trauma had been inflicted on the coils and hidden below a thick layer of green wax. I used a heat gun over a ceramic tile to melt most of the wax away. Some micro-surgery then allowed me to re-establish the coil connections. Mega relief! At last, the radio sprung into life, albeit rather feebly. Nevertheless, it was tuning with reasonable selectivity and behaving as a superhet should. The HT rail measured 282V, Australia’s electronics magazine and the screens for the 6C6 and 6F7 were at +110V. Testing with a signal generator led to the unexpected result that the intermediate frequency (IF) was 436kHz, not 465kHz as published. Why so feeble? Stuart Irwin had told me before I started this restoration that a model 496 he restored was a surprisingly good performer for its type and age, with a sensitivity of 125μV <at> 600kHz (I also need to thank Stuart November 2021 67 Price Changes For Silicon Chip Magazine This photo clearly shows the new speaker inside the old speaker’s frame. From October 31st 2021, the price of Silicon Chip Subscriptions will change as follows: Online (Worldwide) Current Price New Price 6 Months $45 $50 12 Months $85 $95 24 Months $164 $185 Print Only (AUS) Current Price New Price 6 Months $57 $65 12 Months $105 $120 24 Months $202 $230 Print + Online (AUS) Current Price New Price 6 Months $69 $75 12 Months $125 $140 24 Months $240 $265 Print Only (NZ) Current Price New Price 6 Months $61 $80 12 Months $109 $145 24 Months $215 $275 Print + Online (NZ) Current Price New Price 6 Months $73 $90 12 Months $129 $165 24 Months $253 $310 Print Only (RoW) Current Price New Price 6 Months $90 $100 12 Months $160 $195 24 Months $300 $380 Print + Online (RoW) Current Price New Price 6 Months $100 $110 12 Months $180 $215 24 Months $330 $415 All prices are in Australian Dollars The cover price of the October issue onwards is now $11.50 in Australia. The New Zealand cover price remains the same at $12.90. SILICON CHIP 68 Silicon Chip for providing the circuit diagram for this radio). The AC filament voltage measured as only 4.9V, an apparent reason for the poor performance. Valves usually specify a maximum of ±10% filament voltage tolerance. Cathodes subjected to chronic low filament voltage change their chemistry to poison the oxide layer, resulting in lower emission. The reason for the low filament voltage is a real puzzle. The solder joints at the transformer showed no interference by anyone after the factory (at least before I made some modifications). A possible cause of this low voltage is shorted turns, but the transformer without load only drew 4W and did not overheat. It’s truly strange. The 4V secondary on the power transformer was left unconnected after the AL3 was removed. So a confusion with windings did not cause the low filament voltage. The web has many references on cathode poisoning, but I failed to find a detailed source. The usually informative Radiotron Designer’s Handbook makes only passing reference to the problem. Full of hope to get better performance, I used an external filament transformer as the heater source that provided 6.9V on load (a bit up from the nominal 6.3V). The improvement in output was dramatic, although not as good as could be expected with new valves unaffected by cathode poisoning. A surprise was that reverting to the onboard 4.9V AC supply produced a dead radio that thankfully came back to life with 6.9V applied. Any chemical change in the cathodes that might explain this could not be found online. To provide the required higher filament voltage, I mounted an additional transformer on top of the chassis over the two holes formerly occupied by electrolytic capacitors. After a longer-than-usual period at the bench, it was highly satisfying to marry the chassis back to its resplenSC dent cabinet. Why doesn’t this set use a converter valve? Many sets produced earlier than the model 496 used dedicated converter valves. It is unusual that they reverted to the autodyne converter. The 2A7 and 6A7 were readily available from about the middle of 1933, the 6A8 from 1935 and the popular European AK1 from 1934. Using a 6C6 instead of a 6A7 also means forgoing automatic gain control (AGC), as an autodyne converter can’t be gain-controlled easily. It might have been a cost-saving exercise by Stromberg Carlson to use a 6C6. It isn’t easy to find out for sure, but they might have had to pay higher royalties for using a proper converter valve, as well as the difference in the cost of the valve itself. As an aside, royalties on the number of electron streams in the valves used in the set might be why reflexing was so popular in Australia. A reflexed valve was counted as only one electron stream in terms of royalty payments, even though it was being used twice. Australia’s electronics magazine siliconchip.com.au Build It Yourself Electronics Centres® s n o i t u l o S y d n Ha E L A S % 0 5 O T P U E SAV r up a big ar to powe Great value ge ts. ctronic projec le e f o r e m m Su r 30th. embe Sale ends Nov Power your camping fridge without risk of draining your battery! SAVE $30 N 1130F 209 $ 130W Remote Power Folding Solar Panel Going bush? Have power wherever you go on your next 4WD/camping adventure. Includes 130W panel, solar regulator, battery connection cables and canvas carry case. 3 stage solar charger. Adjustable stand for best sun placement. 664x631x75mm (folded). A stylish glossy white table lamp with adjustable dimming, colour temperature & wireless charging. Great for the desk or bedside table. Powered by any USB wall charger 2A minimum (M 8863 $19). SAVE 24% A great bedside or study lamp *Device shown for illustration purposes. Table Lamp With Wireless Charger 30 GIFT IDEA! 279 $ X 7063 With outdoor sensors & smartphone app! Fitted with secure lid clips & colourful LED voltmeter Get live, local weather at home. Fire the weather man! This fantastic home weather station displays all your local weather data - great for boaties & gardeners. Bright & clear base station provides readings for indoor/outdoor temperature, humidity, air pressure, rainfall, wind speed and direction. Plus handy weather trends. You can even connect it to your home wi-fi to monitor readings & data with your smartphone. 100m sensor range. $ X 4221 SAVE $30 109 $ T 5098 Powerhouse® Portable Power Battery Box Fits a standard 90-120Ah automotive battery for powering appliances at your camp site - a totally self contained power unit! Fitted with 2.4A USB charger, dual Anderson sockets, volt meter, car acc. socket & battery terminals, plus 2x50A fuses for added safety. SAVE 10% 29.95 $ 20 SAVE $20 $ 79 $ X 0705 T 2188 1000V Precision Screwdriver Set Smaller sizes than most 1000V driver sets. 3 flat blade (2.0, 2.5 & 3mm) & 3 phillips (#000, #00, #0). Great for uni students! SAVE 18% 69 $ Cut, Polish, Grind, Sand & Carve. Great for finishing and smoothing your 3D prints! Perfect for odd jobs and hobbies. Powerful 130W motor with variable speed between 8000 and 33000 RPM. Included is a 172pc accessory kit of grinding wheels, drills, cutters, sanding discs & polishing pads. T 2120 Take high quality audio notes with ease! Record CD quality audio with excellent audio pick up for taking audio notes during lectures & recording interviews. 8GB on board memory with Micro SD slot. USB rechargeable. 5 Piece Plier & Cutter Set T 2758A A must have for any electronics enthusiast. Includes: • Side cutters. • Flat long needle nose pliers. • Flat bent needle nose pliers. • Long nose pliers/cutters. • Bull nose pliers SAVE 29% 19.95 $ 19 $ T 1489 13 Piece Precision Knife Set T 1489 Includes aluminium handle with 13 blades to suit different cutting jobs. Includes plastic carry case. 20 Piece Screwdriver Set T 2185 Ferrule top driver handle & 19 pozi, hex, torx and blade tips is a carry case. Your one-stop electronics shop since 1976. | Order online <at> altronics.com.au Upgrade your test bench. 100MHz 2 Ch. Digital Storage Oscilloscope SAVE $200 Perfect for those in R&D or servicing. • 2 channels with real-time 1GSa/s sampling. • Colour 7” TFT screen • Displays waveform plus the measured wave voltage, peak to peak plus RMS, frequency, duty cycle etc. • Realtime measurement PC software. • USB datalogging • 2 year warranty. 699 $ SAVE $100 Turn a laptop into a 25MHz scope! Q 0207 229 $ The Velleman PCSU200 is a do-it-all solution to save space on your workbench and make use of your PC or laptop. It connects via USB and provides function generator, 25Mhz oscilloscope, transient recorder, bode plotter and spectrum analysing functions. Includes Windows software & USB cable. Q 0203A FOR THE PRO USER WATER PROOF! SAVE $26 189 $ Q 2112 Peak® LCR & Impedance Analyser Identifies inductors, capacitors and resistors. Can also display parameters as a complex impedance, admittance or magnitude and impedance phase. 2 year warranty. Made in the UK. VALUE! SAVE 20% 18 $ SAVE $26 SAVE $50 33 .95 99 119 $ $ $ Q 1088 19 Range Digital Multimeter Amazing value for a meter under $20! Features 19 ranges, hFE transistor and diode test functions. Backlit screen for working in dark spaces. Perfect meter for the cash strapped student! Q 1121B Auto Ranging True RMS Meter With non-contact AC voltage detection in-built! An affordable auto ranging meter with True RMS accuracy for AC voltages. Plus temperature measurement! (probe included). Q 1134A Q 1068 Water & Dustproof True RMS Multimeter Top of the range - great features and price! Ideal for marine & mining techs. • True RMS measurement • 40MHz freq. counter with bar graph • Max/min recording • Capacitance to 40mF. • Temperature with thermocouple. Do-It-All Multimeter With in-built AC mains detection. This is one of the best DMMs we have evaluated when it comes to build quality and features. Its perfect for the serious enthusiast or tradesperson • LCD bargraph • 3.75 digit display • Mode assistance indicators. • Includes case, temp probe & insulated test leads. NEW! Q 3004 12.95 Provides quick and easy way to test alternator/charging system function in 12V vehicles. Provides instantly whether your alternator output is the problem or your battery is in poor condition. Checks status of data and power over ethernet connection. Includes lead for testing socket points. $ $ 12V Alternator Tester Simple PoE Port Tester 39.95 16.95 $13.95 $ SAVE 26% 22 $ D 3002 Q 3001A Sheath Piercing Q 3000A Standard Handy Automotive Voltage Probes A handy tool for troubleshooting wiring faults in vehicles and wiring looms. 6-24VDC range. Standard probe or sheath piercing versions. HDMI Cable Tester Detect faulty HDMI wiring and bad cables in an instant with this handy tester. Easy to read status LEDs and remote unit for testing long runs. X 6015 OBD II Bluetooth Scanner Connects your car via Bluetooth to your smartphone to provide a wealth of diagnostic information. Monitor performance in real time! It works with a number of OBDII compatible apps. SAVE 23% 70 $ Q 2030A SAVE $40 229 $ Q 2115 Peak® DCA Pro Analyser A detailed component analyser for connection to your PC. Ideal accessory for designers & technicians. 2 year warranty. Made in the UK. Battery Health Analyser SAVE $60 139 $ Q 2120 Detects and analyses voltage, cold cranking amperes, resistance and cell condition in 12V lead acid cells. Easy connection and operation. Ideal for vehicle servicing or checking 12V SLA cells in backup systems. Handy Zipper Carry Cases Great for test equipment, $ .75 made from tough woven canvas material. Q 1054A Q 1054A: 183x83x35mm. Q 1057A: 260x110x45mm. 6 Order online <at> altronics.com.au | Sale pricing ends November 30th. 8 $ .95 Q 1057A Solder it! Fix it! Screw it! Iroda® 125W Gas Tool Kit SAVE 20% Includes hard to find bit types for latest phones & laptops 40 $ T 2164A Pro 72pc Repair / Servicing Tool Set 62 Don’t forget the gas! T 2451 $9.35 159 SAVE 34% 30 $ X 0435 T 2631 SAVE 30% 55 With customisable foam inner and eggshell foam lid to keep equipment secure & safe. Ext. size: 495x365x128mm. $ Lockable Tool Field Case With tool pocket & perforated foam inner to keep equipment secure. Ext. size: 445x330x128mm. 2 for $ SAVE 15% 30 29 $ SAVE 24% T 4015A T 5036A Double Sided Parts Case T 5018A A handy Inspect-A-Gadget magnifier powered by a USB port Provides a crisp, clear view of your workbench. 430mm long. 1.5m USB lead. Clips to any desk or bench in an instant! $ Lockable Equipment Case $ USB Clip On 5x Magnifier Lamp SAVE $36 A premium finish aluminium driver handle with silent ball bearing ferrule top. Contains a huge variety of driver 4x28mm driver bits, double ended opening tools, spudger, curved tip tweezers and flexible drive extension. It makes servicing high tech devices easy! SAVE 25% 1000’s sold! Top choice for enthusiasts & trade Totally wireless operation - No need to run extension leads! Easy to light, one-click piezo ignition. Blow torch & soldering iron in one. 2 year warranty. Includes hot air tip, heat deflector, additional gas cartridge, solder, sponge and hard carry case. 15 compartments on one side, plus 10 removable containers on the other side. T 5021 26.95 *Solder not included. Every workshop needs good drill bits. $ SAVE 22% T 2306 Never lose a tiny screw again! A 35x26cm heat resistant silicon work mat, plus a 25x20cm magnetic mat to keep screws and parts organised while you work. Self standing lantern or hand torch Great for heavy duty soldering & braizing. 13 $ X 0431 SAVE 22% Premium Grade HSS-R Drill Bit Set 19pcs between 1-10mm for plastic, wood & metal. Metal storage case. Bench essential! 19.95 $ 19 $ Pop-Up Mini Magnifier A pocket sized 3x magnifier with LED illumination. Great for hobbies & repairs. Requires 3xAAA batteries. T 1302A Dual Solder Reel Holder X 0209B Rechargeable 2 In 1 Lantern Torch Powerful 300 lumen, 3W LED torch with aluminium body, adjustable beam & USB recharging. Includes battery. Heavy weight base with solder guides. All metal construction. T 2367 SAVE $50 SAVE 20% 45 $ Multi-Angle Bench Vice Made from diecast alloy. Clamps to your work bench and provides total 360° freedom when working. Jaws open to 55 mm. Includes soft jaws for holding delicate connectors. 169 $ TOP VALUE! T 2651 X 0433 16 $ .95 T 2748A 22 $ .95 Get a crisp close up view! 5” Premium Cutters A handy accessory for any workbench, this 130mm 6x magnifier uses premium quality glass and LED lighting for a clear view. Tough chrome vanadium blades stay sharp for longer. Ideal for PCB assembly, cutting solid core wiring etc. T 2802 27.95 $ Chewed out a screw? No problem! This unique set of pliers features two serrated jaws, plus serrated circular opening on the front face for extracting screws up to 13mmØ. A Gas Gun to DO it all! 185 Watts of heating power for both blow torch and soldering work. Powered by refillable butane cartridges (2 included) this Iroda® hand held or self standing gun provides 500°C soldering temperatures and a whopping 1300°C blow torch. Kit includes tips, spare filter, solder sucker, flux paste, cutters and solder. Order online <at> altronics.com.au | Sale pricing ends November 30th. Power up your Summer! 3 Way Breaker & Switch Panel USB C Power Delivery LITHIUM READY to Includes MPPT circuitry get the most juice out of your solar panels! Features 3 x 20A 12V DC rated switches with red illuminated with individual 15A DC breakers. Dimensions: 114W x 96H x 60Dmm. 59.95 $ 4 USB charging ports 80W mains output NEW! S 2750 Dual LED Torch SAVE $146 199 $ SAVE $60 209 $ N 2088 SAVE 22% P 0699 29.95 $ 6-30V DC. -10 to 100°C. Temp sensor with 2m cable. 6-30V DC range. Aux & Primary battery displays. 29mm mounting hole. SAVE $54 119 $215 $ M 8534A 6/12V 4.5A This dual input design connects to a solar panel and your cars alternator (12 or 24V) to provide 3 stage charging for secondary batteries such as those used in campers, caravans and trades service vans/trailers. It is compatible with the latest smart alternators and start/stop systems found in modern vehicles. Suitable for Lead Acid, AGM and Lithium Fe PO4 batteries. Dual Battery Monitor Voltmeter & Thermometer SAVE $26 P 0692 Solar MPPT & 25A DC Battery Charger 23 $ NEW: M 8536A 12V 10A Multi-Stage Vehicle Battery Chargers Now suits LiFePo4, lead acid & calcium type batteries! DC Power Distribution Posts High current DC power distribution posts with reinforced nylon base (bolt head is encapsulated). 48V DC max. Each model utilises a microprocessor to ensure your battery is maintained in tip-top condition whenever you need it. Helps to extend battery service life. Suitable for permanent connection. Great for caravans & seldom used vehicles. Weatherproof casing. Reading Light M 8197 Carry 240V Power Anywhere! This air travel friendly portable power generator is fitted with 6Ah battery bank, 80W 240V mains inverter, 18W power delivery USB C charger & QC3.0 USB charger. Offers you cable free power for both AC and DC appliances! Recharge by USB or included power adaptor. Model Type ONLY P 2172 Single M8 Red P 2173 Single M8 Black P 2175 Dual M8 Red P 2176 Dual M8 Black $10.95 $10.95 $12.95 $12.95 $10.95 $10.95 $14.95 $14.95 $13.75 $13.75 P 2182 Single M10 Red P 2183 Single M10 Black P 2177 Dual M10 Red P 2179 Dual M10 Black P 2180 Bridging M8 Red P 2181 Bridging M8 Black Easy DIY install! Great for 4WDs SAVE 20% 40 $ N 2099A Monitor your car battery from your phone! Ensure your battery doesn’t go flat with this handy Bluetooth® battery monitor. Provides live feedback on your vehicle or auxiliary battery, plus handy long term stats. SAVE 12% Top deal! 70 $ HOT SELLER! SAVE 50% SAVE 32% M 8881 44 $ Charge 8 USB devices at once. Got a family full of devices to keep charged? This handy charger outputs up to 12A or charging current to keep all your tablets and phones juiced up! Includes power cord. Remote Control Power Saver Cut standby power usage by switching appliances off at the wall. 30m RF range line of sight to power point not requred! Requires 2xAAA batteries. 10A (2400W). Extra outlets, A 0347 $13.95. A 0346 34 $ .95 M 8868 SAVE 28% 70 $ D 0511B Need an extra laptop charger? Jumbo QC3.0/USB C Power Bank This 45W USB-C power delivery (PD) charger offers recharging for MacBooks, Nintendo Switch and other type C equipped devices. Also provides two type A USB outputs. Offering both the latest QuickCharge 3.0 charging and 18W USB-C PD output, this enormous 20,000mAh power bank will keep your devices charged away from mains power. 136x70x25mm Keep your laptop charged up in the car M 8627B Simply plugs into a car accessory socket. Up to 90W power output for most laptops. Includes 9 laptop adaptors - see web for product compatibility list. Say goodbye to messy charging cables! SAVE 24% 15 $ SAVE $20 D 0515* 39 $ Wireless Charging Battery Bank Charge two phones at once with wireless charging. Suits iPhone and most Android. For fast charging you’ll also need a QC3.0 USB wall charger, such as M 8863 $20. Includes USB cable. USB & wireless charging in the one device. Stay charged up anywhere you go. 10,000mAh capacity. Includes charging cable. *Devices for illustration purposes. Order online <at> altronics.com.au | Sale pricing ends November 30th. SAVE 50% 24.95 $ D 2327* Build & have fun this Xmas. SAVE 25% Tobbie II Hexapod Robot Kit SAVE 22% 45 45 $ $ K 1095 Tobbie is back and he’s had an upgrade! Powered by the popular BBC micro:bit board, this version has unlimited scope for self programming. Front screen displays text & symbols. Great for teaching kids coding. Requires 4xAAA batteries & micro:bit board. Ages 8+ K 1152 Build it 3 ways! Cute Scurrying Hedgehog Kit 3 In 1 All-Terrain Robot Kit Great fun for the kids to build and play with! This single kit can be built (and re-built) three ways! Lifting capacity ≈100g. Wired remote control. Requires 4 x AA batteries. Ages 10+ K 1150 This cute hedgehog toy kit bristles his spines when he hears a loud noise (such as a hand clap). He will even curl up and roll away if you scare him! Assembles in <2 hours, no special tools required. Requires 4 x AAA batteries. Ages 8+ SAVE $9.95 50 Requires Z 6439A micro:bit ($27.95). $ SAVE 28% 28 Build it 4 ways! Learn coding! Have fun! $ SAVE 22% Build it 14 ways! 59 $ SAVE 15% 33 SAVE 25% K 1126 $ 22 $ K 1135 K 1113 K 1107 Full Motion Robotic Arm & Claw Kit 14 Solar Kits In One! 4 in 1 Robotics Kit Air Powered Buggy Kit Assemble 4 robot designs which teach kids about geared movement in a fun way! Requires 1xAA battery. No soldering required. Ages 7+ Requires no batteries, electric motor or any conventional fuel to make it drive. Use the air pump to fill the bottle - let it go & watch it fly! Travels up to 50m. Ages 8+ A great introduction to basic robotics. Five motors allow base rotation, shoulder, elbow & wrist motion, plus claw for picking up objects (up to 100g). Includes wired controller (add USB PC control for $35 - K 1108A). Ages 9+ A fun and educational kit designed to assemble 14 different ways to inspire your kids to learn about solar power. No soldering required. Requires no batteries. Ages 8+ SAVE $10 39.95 $ TOP SELLER! K 1154 Build one robot up to 5 ways! SAVE $10 39 $ .95 K 1148 The Original Tobbie Robot Kit A six legged robot kit designed to avoid objects or follow you around the room. Easy to build. Requires 4 x AAA batteries. Ages 8+ 5 In 1 Smart ‘Coding’ Robot Kit Features a central coding ring which tells the robot directions and when to perform actions. Can be built and re-built 5 ways. Teaches kids about coding with no computers required! Requires 1xAAA battery. Ages 8+ K 1149 VALUE! Build it 12 ways! VALUE! 49.95 39 $ K 1141 .95 $ Hydraulic Cyborg Hand Kit 12 In 1 Solar & Hydraulic Kit A huge parts kit which can be built and rebuilt into 12 different solar powered designs. Hours of fun for kids aged 8 or over (or younger with adult help). Build your own full size hydraulic powered robotic hand. Fits over your own hand like a glove and simulates joint movements to pick up objects. No batteries. Left & right handed. K 1119 SAVE $10 39 $ SAVE $10 SAVE 18% 18 $ .50 49 $ SAVE 20% K 1138 K 1139 K 1097 19.95 $ Solar Powered Wild Boar Kit Solar Powered Rover Kit A basic solar DIY toy, it is ideal for a do-ityourself school holiday project with the bonus of being educational! Ages 6+ Build this fun 6 wheel all terrain vehicle modelled on famous NASA designs. No soldering or batteries required! Ages 8+ Build yourself an Aussie icon! Robot Frilled Neck Lizard Kit. Build it up and have it follow you like a pet. Or sneak up and surprise it, making it spread its frill. 37cm long. Requires 4xAAA. Ages 8+ Tribo 3 in 1 Coding Robot An easy to build and program robot which uses keypad entry commands to program movements and actions. No PC required! Uses 4xAAA batteries. Ages 8+. Order online <at> altronics.com.au | Sale pricing ends November 30th. Maker parts a plenty! SAVE $26 99 $ Z 6315 SAVE $51 Great for DIY test gear! 119 66 $ $ H 5039 3RU 19” Rack Cases With Sub Chassis Allows vertical or horizontal sub chassis mounting for PCBs along the full height and length of the case. Aluminium front & rear panels. Tough powdercoated chassis. 430W x 330Dmm Value packed! SAVE 30% SAVE $28 37 In 1 Sensor Kit 99 A huge array of sensors for building into your next project design. See website for complete listing. Z 6311 $ H 5038 2RU 165pc Sensor Parts Pack Includes a huge selection of sensor boards, LEDs, pots, jumper wires, a breadboard, LCD screen and much more! A handy storage case keeps it neat when you’re finished building. Includes links to projects and example code. SAVE UP TO 40% SAVE 38% SAVE 34% SAVE 30% 6 $ ea Colourful Arcade Gaming Switches S 0910 Red S 0911 Green S 0912 Blue S 0913 Yellow S 0914 White Jumbo arcade machine momentary switches with 12V illumination and customisable button plate. 25mmØ hole. S 1147 14 $ S 1148 Heavy Duty Arcade Joystick USB Interface For Joystick & Buttons 15 SAVE $60 90 SAVE $51 85 $ 69 $ Z 6516 7” 1024x600 Great for retro gaming projects or for direction control in serious projects. Adjustable plate allows 2, 4 or 8 way control. 95x59mm mounting plate. A handy interface board for a joystick and up to 12 arcade buttons. Includes pre-terminated cables. SAVE $59 $ $ Z 6514 7” 800x600 Z 6513 5” 800x480 Large Touchscreens For Raspberry Pi® • Great for integrated projects, game consoles, information stands, mini PCs etc • Works with raspbian & ubuntu • HDMI connection. SAVE 15% JUMBO value pack! NEW! 19.95 14.95 $ W 2431 Stranded. W 2430 Solid Core. $ Jumper Header Kit Hobby Wire Packs 6 colour hobby pack for project building. 10m of each colour. NEW! K 9642 A huge assortment of single row header connectors. Includes male & female pin headers, plus 2.54mm housings. K 9643 Plug & Header Connection Kit Straight boxed 2.54mm PCB connectors and plugs in 2, 3, 4 and 5 way. Plus crimp pins to suit plug housings. 150pcs total. 22 $ P 1018A 350pc SAVE 23% Z 6432 SAVE 30% 12 $ SAVE 29% 20 $ 42 P 1014A 140pc $ Z 6333 Add GPS location to a Arduino/Pi project, aircraft or drone. 3.3/5V logic level. Includes 6x20mm ceramic antenna. Also available as an Arduino shield with active 28dB antenna (Z 6332 $69.95). LoRa Arduino Data Shield Allows long range communication with an Arduino without the need for a GSM 4G network - even over distances of up to several kilometres! 3.3/5V input. DIY Jumbo LED Signs 171pcs of 75mm & 45mm lengths in a range of colours & sizes (3.2 to 12.7mm). 2:1 shrink ratio. SAVE 25% Great for remote IoT projects! U-Blox Neo-6M GPS Module & Antenna 19.95 $ Prototyping Wire Packs Handy packs of pre cut and trimmed solid core wire for breadboarding your next design! Z 6517 32 x 32 Was $59, NOW $30 Z 6518 63 x 32 Was $89, NOW $60 19 $ Heatshrink Mega Pack W 0884A Breadboard for big designs! Huge breadboard with aluminium base for those designs that are beyond the scope of your average breadboard! Easy power connection via binding posts. P 1012A 1660 Hole Link multiple panels together! Order online <at> altronics.com.au | Sale pricing ends November 30th. Must have for the electronics designer SAVE 28% 35 $ Build & Experiment. SAVE $19 70 Control more with 2 shields! SAVE $26 $ 89 $ Z 6454 Z 6314 SAVE $30 Requires Z 6439A micro:bit board. Add one for $27.95 STEM bot is an easy to program 2 wheel obstacle avoidance and line tracking robot. Coding your program is easy using the standard BBC Micro:bit software. Simple construction with easy to folow instructions. Can also be controlled via Bluetooth. Runs from 18650 rechargeable lithium cells (S 4736 $18.50). Ages 8+ SAVE 35% 14 A handy dual motor base for building your own mini robot design. Supplied with both wheels and rotating bug like legs. Developed in house by Altronics, this MegaBox has space for two shields, plus five 2A 5V relay outputs and eight opto isolated outputs. All UNO/ Mega pins are broken out to header sockets for easy connection to other breakouts. A small 160 hole prototyping area is included for connecting to other sensors. *Arduino board & shields not included. Includes an Arduino UNO compatible board, proto-shield, alphanumeric LCD, dot matrix LED module, 7 segment displays, two breadboards, stepper motor, servo, IR remote, connection leads, battery box and a variety of components, buttons and sensors. $ Robot Vehicle/Bug Base MK2 Arduino MegaBox Kit by Altronics. DIY Tinkerers Kit For Arduino SAVE 28% K 1102 SAVE 50% 33 $ Vehicle Base Builder Kits With individual motors for each wheel with acrylic base for mounting control and sensor boards. Ideal base for your own Arduino robo-car design. Includes battery holder. SAVE 35% Tried the new Pico Pi? Z 6467 25 $ K 1090 2WD Arduino UNO+Ethernet Board Connect your Arduino design to the internet-ofthings with this handy W5500 ethernet board with atmega328p on board. Fully UNO compatible with USB download & micro SD slot. VALUE! 22 Z 6426 19.95 $ CAN-BUS Arduino Shield Z 6510A 2.8” Touch Arduino Shield A 240x320px touchscreen shield for Arduino utilising the ILI9341 chipset. 3.3/5V input. 18 $ K 9815 ATDev Shield for ATTiny Kit A powerful and versatile programming and breakout shield for ATtiny. Combine with a UNO for instant programmer and debugging. The latest Raspberry Pi microcontroller board. Get yours for just $8.95 Arduino Keypad Plate Arduino Control Plate SAVE 38% SAVE 20% Must have for Arduino builders! 34 $ K 1092 4WD $ 109 $ K 9670A Build & code your own robot. Allows you to interface Arduino’s with CAN-BUS control systems found in automotive electronics. Use an Arduino to build your own vehicle monitors. Perfect for Arduino based automation projects, this handy wallplate has a atmega328p chip SAVE 50% and is suitable for .95 use with standard $ shields. K 9655 39 Perfect for Arduino based access control designs, this handy wallplate has a atmega328p chip and is suitable for use with standard shields. K 9650 SAVE 50% 24.95 $ SAVE $46 159 $ SAVE 25% K 2200 29 $ SAVE $91 10 in 1 Electronics Lab Kit 200 in 1 Electronics Lab Kit A great way to pique a budding engineers interest with 10 exciting projects including a morse code generator, burglar alarm and a radio. Requires 9V battery. A huge array of fun projects to build for your little ‘engineer of tomorrow’. Easy to read and follow instructions - teaches the fundamentals of electronics in a safe and fun way. Requires 6 x AA batteries. 229 $ K 2209 300 in 1 Electronics Lab Kit K 2222 The ‘Rolls-Royce’ model with all the bells and whistles. Teaches you about electronics from A to Z. You will learn about electronic parts, how to read schematics, and wiring diagrams. All this, while building up to 300 different projects. Requires 6 x AA batteries. Order online <at> altronics.com.au | Sale pricing ends November 30th. Make your home smarter. Wi-Fi RGB Strip Lighting Kit X 3227* Answer the door when you’re not home! 75 .95 $ This kit includes 5m of RGB strip lighting, power supply, controller unit and IR remote control allowing you to create colourful lighting effects around your home. Controller features a music sensor input allowing the lighting to trigger to music being played in the room. Great for home entertaining. Works with Alexa and Google Assistant. 60 LEDs per metre. 139 $ Wi-Fi Video Doorbell with Tuya smartphone app control and 2 way audio. This stylish doorbell connects to your wi-fi and notifies your mobile phone when a person arrives at your doorstep. Great for telling the postie where to put packages. • Security camera mode • Motion detect notification • Includes power supply and indoor doorbell ringer unit. Music sensor can trigger lights to the beat! SAVE 13% 2 For S 9455A 37 $ HOT PRICE! P 8149 Automate your Xmas lights! Switch any connected appliance on or off remotely from anywhere in the world. Set schedules, monitor and control via your using the Tuya Android/iOS app. Maximum 10A 2400W. Works with Google Home and Alexa What is Tuya® Smart Home? Tuya is a common application for thousands of products from the worlds leading Smart Home suppliers. It provides a single point of control for home security, lighting and appliance power allowing you to control everything you need from a the one smartphone app. The Tuya IoT platform powers over 250,000 home automation products across the globe! Tuya® Compatible Cameras. NEW! All Tuya cameras provide 1080p HD vision with audio and can be located anywhere you require camera coverage in your home. Camera measures just 10mm across S 9845A 89.95 Wi-Fi HD Camera Clock Wi-Fi Camera Module • Internal battery - set it up anywhere! • Day/night with IR • USB rechargeable • 100 mins motion activated recording time. • Ultra compact module can be built into custom enclosures • Completely wireless - set it up anywhere! • USB rechargeable • 100 mins motion activated recording time. Cable Free Wi-Fi Surveillance This handy 1080p camera can be installed just about anywhere indoors or out and has an in-built battery so you don’t need to run any cables! Offers 4-6 months of motion detect recording. When it’s flat, just take it off the wall & recharge via USB. Suits sheltered outdoor use. Also includes ball joint bracket. 199 $ S 9850 S 9844 Mini Wi-Fi Cube Camera S 9843B • Real alarm clock function • Two-way audio (mic & speaker) • Motion detect recording • USB or battery powered (S 4736 x 2 $18.50ea) *Note: We encourage this item be used responsibly for legitimate CCTV use. Outdoor Pan & Tilt Wi-Fi Camera Provides extra coverage to your outdoor spaces with motorised pan (355°) and tilt (100°). Auto-tracks moving objects within the frame. Constructed from UV stabilised plastic with weatherproof rating to IP66. 2-way audio with mic and speaker. 30m IR night time coverage. Requires 5V 2A USB power supply. S 9020 139 $ Sale Ends November 30th 2021 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au » 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 Outdoor Solar Powered Camera • IP66 rated for outdoor use • Two-way audio (mic & speaker) • Motion detect recording • 2MP 1080p HD sensor • Day/night operation with IR • Battery powered (included) with solar recharging - mounts anywhere! Indoor Pan & Tilt Wi-Fi Camera Makes a great baby or pet monitor, this camera features intelligent tracking of moving objects within the frame. 2-way audio with mic and speaker. 5m IR night time coverage. Requires 5V 1A USB power supply. Western Australia Build It Yourself Electronics Centres $ $ $ S 9846 199 169 89.95 $ HOT PRICE! 79.95 $ S 9017A Victoria 08 9428 2188 08 9428 2166 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St 02 8748 5388 Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd 08 8164 3466 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. © Altronics 2021. 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 0091 Find a local reseller at: altronics.com.au/storelocations/dealers/ Design Contest Win $500+ Dick Smith challenges you Win $500 by designing a noughts-and-crosses machine that can beat 14-year old me! Dick Smith has described in his new autobiography how one of the turning points in his life, at age 14, was succesfully building a ‘noughts-and-crosses machine’ (also known as tic-tac-toe) that could play the game as well as anyone. Keep in mind that this was in 1958, when nobody had computers; it was a purely electromechanical device. Email Design to Enter Design your own noughts-andcrosses circuit and send your submission to compo<at>siliconchip. com.au including: a) Your name and address b) Phone number or email address (ideally both) c) A circuit or wiring diagram which clearly shows how the device works d) The display can be anything as long as it’s understandable e) Evidence that your device can always play a perfect game (it never loses) f) A video and/or supply images and text describing it g) Entries requiring software must include source code The deadline for submissions is the 31st of January 2022. ➠ ➠ Win $500 + Signed Copy of Dick Smith's Autobiography ➠ Four winners to be decided, one each for the following categories: ➊ The simplest noughts-andcrosses playing machine most ingenious noughts➋ The and-crosses playing machine youngest constructor to ➌ The build a working noughts-and- DICK SMITH crosses playing machine most clever noughts-and➍ The crosses playing machine not using any kind of integrated processor The entry we judge overall to be the best will also be featured in our Circuit Notebook column and receive an additional $200. ‘Businessman, adventurer, philanthropist…Di ck Smith is a true Australian legend.’ JOE CITIZEN Conditions of entry Dick Smith writes 1) You must be a resident of Australia or New Zealand 2) One entry per family (Silicon Chip staff and their families are not eligible) 3) Submissions will be confirmed within 7 days. If you do not receive a confirmation of your submission, contact us to verify that we have received it 4) Chance plays no part in determining the winner 5) The judges’ decision is final 6) The winners will be decided by the 3rd of February 2022 and will be notified immediately By 1958 I’d advanced from building crystal radio sets to designing and building what I called a noughts and crosses machine. It really was an early computer. I used second-hand parts from a telephone exchange to build it. It would play noughts and crosses against anyone and no one could beat it. This was a great boost to me, because while I was no good at rote learning and theory, I was fine at practical things. The fact that my mind was capable of working out how to build this complex machine gave me confidence as I left school. Now I just had to find a job. Because this was such a turning point in his life and he’s so enthusiastic about youngsters learning electronics, he’s putting up $2000 of his own money to award to people who can come up with a modern version of his noughts-and-crosses machine. Silicon Chip will judge the entries. Winners will be announced in the March 2022 issue of Silicon Chip magazine and will also be contacted directly for payment information. siliconchip.com.au Australia’s electronics magazine November 2021 77 PART 2: BY PHIL PROSSER Low-cost Two- or Three-Way Active Crossover This Active Crossover, described last month, is very flexible. It can be configured as a two-way or three-way crossover, runs from AC or DC supplies, has adjustable levels for all the outputs and has an optional subsonic filter. It’s ideal for building two-way or three-way speakers with each driver powered by a separate amplifier, or it can be used as a signal conditioner for the Tapped Horn Subwoofer described in the September issue. I n the introductory article last month, we explained why you might need an active crossover, how they are used and how this design works. We also showed some performance graphs, indicating that it is suitable for use in a hifi system, plus listed the parts you need to buy in order to build it. Picking up where we left off then, we’ll go over the PCB assembly process, followed by information on how to set up and use it. There is also a troubleshooting section at the end of the article, in case you run into difficulties. There are a few different ways to build the Active Crossover; we’ll explain which parts can be left off in some cases, and how to set up the jumpers for your particular application. coded 01109211 that measures 176 x 117.5mm. The assembly process is pretty straightforward. First, work out where it will be mounted and powered. If you can slip it into its own metal box with an internal power supply, that is ideal. Determine how you will power it and thus the parts you need. Refer also to the panel below on power supply options. Second, select your crossover frequencies. Check the panel describing how to do this from last month. That will affect some of the resistor and MKT capacitor values needed. If you are not sure about the crossover frequencies you require, you could fit PC pins to those component pads and solder the resistors and capacitors to these, to make it easier to change them later. If you only need a two-way crossover, none of the components in the high-frequency section are required (outlined with a red dashed line). Top tip for soldering the resistors and capacitors Fig.15 is the PCB overlay diagram, which should help you during construction. The Active Crossover is built on a double-sided PCB If you envisage yourself significantly ‘tweaking’ the crossover frequencies, we suggest that you select a resistor/capacitor (R and C) combination that is about right for your application and then mount the capacitors on the board. These are more expensive than resistors and do not need to change. Then fit PC pins for all the resistor pads marked “R” and solder your resistors onto these, on the top side of the board. This will allow you to easily shunt them or change them later. Remember that you can use E24-series or parallel resistor combinations to get the exact frequency that you want. 78 Australia’s electronics magazine Construction Silicon Chip siliconchip.com.au The components marked in red should be changed in value to match the chosen crossover frequency – see Table 1 in last month’s issue. Fig.15: use this PCB overlay diagram to help you build the Active Crossover. Note how the design is split into boxes, with the subsonic filter at the top, high-frequency filter section at the bottom, low/mid filter in the middle and power supply/ de-thumping on the left. If you don’t need the subsonic filter, you can omit all the components in the blue outlined area, and if you are building a two-way Active Filter, you can leave off the components in the red outlined area. Single supply applications don’t require the parts in the green outlined area. Similarly, if you don’t need the subsonic filter, you can leave out the components in the blue dashed area. Once you have figured out the component values needed and gathered them all, start by fitting all the resistors. Don’t forget to change R1 to 3.6kW if you will be using a single DC supply rail. In that case, you can also leave off REG2 and its associated components. With the resistors in place, fit the ferrite beads after inserting resistor lead off-cuts through them. Ensure they’re tight on the PCB before soldering them in place (a dob of neutral-cure silicone will help stop them from rattling). After that, fit all the diodes, ensuring they are orientated as shown. Don’t get the three different types mixed up. Now you can install the op amps, either by soldering them directly to siliconchip.com.au the board (the most reliable method) or by soldering sockets, making it much easier to change them later. Regardless of which approach you use, be careful to make sure that they are all orientated correctly. Follow with all the MKT and ceramic capacitors, then the relays. The stripes on the relays must face as shown in Fig.15; note that if you’re building a two-way crossover, you can leave off RLY3. Next, fit the headers. You can place the polarised headers either way around, although our recommended orientations are as shown in Fig.15. After that, solder the single terminal block in place with its wire entry holes towards the nearest edge of the PCB. Now it’s time to solder in all the electrolytic capacitors, starting with Australia’s electronics magazine the smallest ones and working your way up. There are two non-polarised (bipolar) devices at the input, on either side of CON1, but all the rest are polarised. So the longer leads should go to the holes marked + on the overlay diagram. With those in place, fit the three potentiometers, or two (excluding VR1, “high”) if building a two-way crossover. Then attach the regulators to the heatsinks using the insulation kits and solder the heatsink pins to the PCB, followed by the regulator pins. Don’t get the two devices mixed up. Jumper setup Fit shorting blocks (‘jumpers’) to the headers for JP1-JP6 and LK1 now. There are instructions printed on the PCB, but in case they aren’t clear: November 2021 79 The single-rail powered version of this project is suitable for use at 24-30V DC 1. For single-rail DC operation, place the blocks between pins 2 & 3 of JP1 & JP2. For dual-rail (split rail) or AC operation, place them between pins 1 & 2. 2. For two-way operation, fit the blocks between pins 1 & 2 of JP3 & JP4. For three-way operation, place them across pins 2 & 3 instead. 3. If you want to use the recommended subsonic filter, bridge pins 2 & 3 of JP5 & JP6. Otherwise, bridge pins 1 & 2. 4. If you want the ‘low’ (woofer/subwoofer) outputs to be in mono, insert a shorting block on LK1. Otherwise, leave it open. Making the connections We have used pluggable, polarised pin headers for all inputs and outputs. This allows you to make cables that suit your installation. Being able to unplug the board keeps things neat and makes testing/fixing it much easier. You have the option of soldering cables directly to the header pads if you never expect to service the device, but you will achieve a much more professional result if you invest the time in making plugs. Setup and testing Having set your jumpers as per above, connect your power supply to CON3. For a centre-tapped transformer 80 Silicon Chip (18-24V AC), the tap goes to the middle pin and the ends of the windings to the other two (it doesn’t matter which way around). For a transformer with a single secondary (9-12V AC), connect one end to the middle pin and the other end to either of the outer pins. For single-rail DC (around 24-30V DC), connect ground to the centre pin and the positive output to either outer pin. For dual-rail DC (±12-15V), connect 0V to the centre pin and the two supply rails to the outer pins, either way around. If you’re socketing the op amps, you could leave them out during testing. Now apply power and check the output voltage of REG1. You can use the central screw of terminal block CON3 as the ground reference and probe the test point labelled “+9Volts” near REG1. The reading should be +17-19V for single-supply operation or +8-10V otherwise. For a dual-rail or AC supply, check the output of REG2; there is a “-9Volts” test point near REG2 that you can use. Expect a reading between -8V and -10V. If you are using a single-rail DC supply, check that the half-supply voltage is correct by dividing your REG1 output reading in half, then probing the left-hand end of the two 1kW resistors to the left of the leftmost potentiometer. You should get Australia’s electronics magazine a reading very close to the predicted value. If using a power supply with current metering (or connect an ammeter in series with your supply), check for a current draw of around 150mA with the op amps installed or less than 50mA without them. If it’s significantly higher than this (say >250mA and >100mA respectively), then you have a problem, possibly a short circuit somewhere. The final test is to check that each output produces the correct range of frequencies and that you can adjust the level with the appropriate potentiometer. While you can do this with the aid of a swept sinewave generator and oscilloscope, it’s easy enough to check without either of those instruments. Simply connect a wide-range signal source to the device’s inputs (such as rock or pop music) and connect each pair of outputs to an audio amplifier in turn (make sure it’s turned down initially!). Check that you get mostly bass from the low outputs, mid-range signals (eg, human voice) from the mid outputs and treble (cymbals etc) from the high outputs. Also check that the sound is clean and that the potentiometers correctly adjust the output levels. The only aspect you can’t really test using your ears is the operation of the subsonic filter, as it is intended to remove signals that you can’t hear. For that, you will need a sinewave siliconchip.com.au generator set to a low frequency (eg, 10Hz) and a scope to verify that the signal is heavily attenuated. It should be 6dB down at 20Hz and much more than that (less than 1/10th its original amplitude) at 10Hz. If any of the above checks fail, switch off the power and see the troubleshooting section below. Final setup & usage The setup of an active crossover comes down to setting the appropriate attenuation values for each channel. If you are building a complicated speaker system, you will need to make many measurements and tweaks to get the crossover frequencies and levels right. That is beyond the scope of this article. You will notice that we haven’t gone into many details of how to house or wire up the Active Crossover. You could build it as a standalone unit, integrated into a preamplifier, integrated into a power amplifier or as part of a complete preamp/crossover/ amp system. For standalone use, we have specified some shielded cable and chassismounting RCA sockets in the parts list. Mount these RCA sockets on the box with one pair as the inputs and two or three pairs of outputs, then wire them up to polarised header plugs using the shielded cable. The ground shields go to the middle two pins, with the left/right signals to the outer two (it doesn’t matter which as long as you are consistent). That would just leave the power supply wiring, which could go to a chassis-mounted barrel socket for operation from a DC or AC plugpack. Alternatively, you will need a case large enough to fit a mains transformer. However, do not take that approach unless you are experienced in building mains-powered equipment and know how to do it safely. That includes Earthing the metal case and transformer frame. If integrating it with a preamp, the input connection can go directly to the preamp’s output rather than to sockets (or you could fit sockets and bridge them externally for maximum flexibility). Similarly, if building the amplifiers into the same chassis (most likely with a mains power supply), the output headers can be wired directly to the amplifier module inputs, or via sets of pre-out/pre-in sockets. siliconchip.com.au While the Active Crossover does not need to be built into its own separate case, you can do so as shown above. The example provided uses an Altronics H0480F, which is 200mm wide, 155m deep and 65mm tall. A 12V AC plugpack (Altronics M9267A) was used to supply power, but a 0.5A version will work fine. Table 2 – resistor colour codes Australia’s electronics magazine November 2021 81 Power supply changes between single & dual-rail modes For single-rail DC operation, we want the positive rail to be about 18V (17.9V actual). The virtual ground splitter then generates a +9V signal ground, allowing the op amps to operate from virtual ±9V supply rails. For this, the LM317 (REG1) reference resistor, R1, needs to be 3.6kW, as shown on the circuit and overlay diagram. In this case, there is no need to fit the negative rail components (LM337 and associated parts). For dual-rail operation (including any AC supply), we want the LM317 voltage to be about 9V (8.7V actual). For this, LM317 (REG1) reference resistor, R1, needs to be 1.6kW instead of 3.6kW. The LM337 produces -9V (-8.9V actual) by default. Regardless, this unit draws less than 150mA (our prototypes drew 120mA), so any 24V DC or ±15V supply capable of delivering 150-200mA should be fine. Keep the supply voltage below 35V DC; if necessary, use a 5W resistor to drop excess voltage. A 100W 5W resistor will drop about 12V. Note that while you could power the Active Crossover from the preamp power supply in an integrated system, this does introduce a risk of Earth loops and hum injection. Using an independent power supply avoids the potential for such problems. If you experience hum, the first thing to try is powering the Active Crossover from an independent source. Using it with the Tapped Horn Subwoofer While this is a flexible design suiting many applications, its design was in part kicked off by my Tapped Horn Subwoofer design published in the September 2021 issue (siliconchip. com.au/Article/15028). That subwoofer needs a bandpass filter as it has a very uneven frequency response above about 80Hz, and can easily be damaged by subsonic signals. This Active Crossover is ideal for driving it; the two-way configuration is fine, although the three-way configuration will also work. Leave the lowpass filter for the LF output at 80Hz and make sure to enable the subsonic filter. You can then feed your regular hifi system from the MF outputs. The LF output level control will let you set the subwoofer level to be appropriate for your room. Troubleshooting A comparison shot showing what parts are omitted in the single-rail version (shown above) compared to the dual-rail version below. 82 Silicon Chip Australia’s electronics magazine If you can’t get it to work, first check that you have set all the jumpers correctly. Next, examine the board carefully. Look for dry or incompletely formed solder joints, short circuits (eg, solder blobs connecting pads that should not be connected), reversed components, swapped components and so on. Check that all the resistor and capacitor values match those shown in Fig.15. Fix up any problems you find, then start the tests over again. If it still doesn’t work, verify that the power supply input voltage(s) are correct and that the onboard power supply is working. For single-rail versions, check that the virtual ground is about half the overall voltage rail, as described above, plus or minus 200mV. Also check that the overall voltage between pins 4 and 8 of each op amp is double this, ie, 17.8V±200mV. For dual-rail versions, check that the positive and negative rail voltage amplitudes are within ±200mV. siliconchip.com.au You should hear a click from the relays about five seconds after you apply power. It is not loud but should be discernible. If not, that suggests a problem with this part of the circuit, a supply rail imbalance or a shortcircuit on the virtual Earth, causing it to fail to release. If the relays do not click in, check the voltages around Q1 and Q2 in the power detection circuit. After a few seconds, the base-emitter voltages of Q1 and Q2 should be less than 400mV (ours settled to about -30mV). If you are reading 0.6V or so, check the resistor values in this part of the circuit. Check that Q4 is off after a few seconds. You can check this by verifying that its base-emitter voltage falls close to zero. Check that the base-emitter voltage of Q5 is about 0.6V after things settle. This will switch this Darlington pair on, and thus the relays. Verify that you have the correct relays installed and they are the right way around. If the supply rails are too low, the voltage regulators will stop functioning. The de-thump circuit will then detect the ripple on the supply rails and disconnect the output. With the power supplies working and “turn off muting” working, apply an input signal and trace it through the circuit. Are there output signals from the state variable filters that go to the potentiometers? Are the potentiometers appropriately set? Remember that 24dB/octave filters are pretty steep, so if you apply a 1kHz signal with the filter values in the article, you will see nothing on the low outputs and only a small signal at the high outputs. Final thoughts The maximum allowable input voltage to the active crossover is 35V DC, at which point you will find the heatsinks become quite warm. Check this in your installation, and if they are warmer than you like, insert a 5W resistor in series with the power source to drop the voltage. Start with 100W and work from there. With a current draw of 120mA, that will drop 12V and dissipate 1.5W. With this all up and running, now it is time to connect your speakers. We recommend that you connect the tweeters through high-value bipolar electrolytic capacitors to protect them from any DC or low-frequency siliconchip.com.au Building it into its own case While we expect many constructors to build the Active Crossover into another piece of equipment, it can certainly be housed in its own case, as shown in the lead photo. Putting it into a case is quite simple. For our application, we chose to power it using a 12V AC plugpack containing a small mains transformer with a single 12V AC secondary. In this configuration, the onboard rectifier diodes act as a half-wave voltage doubler, producing the +12V and -12V DC (approximately) rails to power the onboard +9V and -9V linear regulators. In this case, each filter capacitor is ‘recharged’ at 50Hz rather than 100Hz, as would be the case with a transformer having dual 12V secondaries or a centre-tapped 24V secondary. This is convenient, and analysis shows that it works just fine and doesn’t affect performance. This configuration worked perfectly, with no noise at switch on or off. Even with the Horn-loaded Subwoofer with an efficiency close to 110dB <at> 1W/1m, there was no hum or noise evident (that was the application for this particular unit; see the article in the September 2021 issue for details on how to build it). The extra parts used to build the Active Crossover into a case are listed below. Note that some of these parts are suggested in the main parts list, but this is more comprehensive. First, mount the PCB in the bottom of the case using the tapped spacers and machine screws, the connectors to the rear panel and the switch to the front panel. Then it’s just a matter of soldering all the wires to those connectors and switches and connecting the other ends to the appropriate points on the board. Part list – for building into a separate case 1 ABS plastic instrument case, 200 x 155 x 65mm [Altronics H0480F, Jaycar HB5912] 1 12V AC 500mA plugpack [Altronics M9265A, Jaycar MP3058] 1 panel-mount barrel socket, 2.1mm inner pin diameter [Altronics P0628, Jaycar PS0522] 4 M3 tapped, 20mm-long spacers [Altronics H1250, Jaycar HP0907 25mm] 8 M3 x 6mm panhead machine screws [Altronics H3110A, Jaycar HP0400] 4 gold-plated red panel-mount RCA sockets [Altronics P0152, Jaycar PS0259] 4 gold-plated white panel-mount RCA sockets [Altronics P0151, Jaycar PS0261] 1 small knob to suit 18T spline shaft [Altronics H6510, Jaycar HK7734] 1 panel-mount power switch [eg, Altronics S1040, Jaycar ST0581] 1 1m length of red light-duty hookup wire [Altronics W2250, Jaycar WH3010] 1 1m length of black light-duty hookup wire [Altronics W2251, Jaycar WH3011] 1 2m length of shielded figure-8 audio cable [Altronics W2995, Jaycar WB1506] 1 100mm length of 5mm diameter heatshrink tubing [Altronics W0913A, Jaycar WH5533] 1 100mm length of 1.5mm diameter heatshrink tubing [Altronics W0910A, Jaycar WH5530] transients your amplifier may put out. A 100μF 50V non-polarised capacitor such as Altronics Cat R6590A will work well. This device has a ripple current rating of 900mA, more than enough for a tweeter. At 2kHz, this will have an impedance of 0.8W and introduce a loss of about 0.8dB. If you want to reduce that, you can double up the capacitor. Usually, your volume control would remain in your preamp, which drives Australia’s electronics magazine the input to the active crossover. Ideally, you will use test instruments to set the Crossover levels. If you don’t have much in the way of fancy test equipment, an FM receiver set between stations gives pretty good white noise. Use this to set the three level controls to get apparently equal volumes from the speaker drivers. That is a pretty good starting point from which to fine-tune the levels. SC November 2021 83 SERVICEMAN'S LOG That ‘80s gear and the art of printer repair Dave Thompson Regular readers of this column will know that I’m not one for throwing stuff away. They will also know that I’m a fan of stuff made a couple of decades ago. So when a client brought in his circa 30-year-old dot matrix printer, despite not normally repairing these things, I thought let’s give it a shot. Especially since it was described as ‘only’ having a broken wire. D on’t get me wrong; I’m not one of those hoarders who has to stand up to sleep because there is no more room in the house. However, my workshop is, shall we say, quite ‘busy’ with bits and bobs I’ve collected over the years. For example, a long-time client recently moved ‘up north’ [to Yorkshire? – Editor] and brought me a couple of presents before he left: a classic Avo meter and a Megger, both with original leather storage cases, user manuals and even leads. I couldn’t say no to those beauties, but they take up shelf space that I don’t really have. Still, I’m not the only one in this position. I fondly recall visits to my uncle’s electronics workshop in Melbourne when I could spend hours poking around, looking at all the gadgets and devices I’d not seen before. It was my idea of heaven. Recently, another long-time client brought in some familiar devices for me to repair – again. He has several Swedish-made electronic gadgets, built in the early 80s, using that nowclunky analog technology. I have had these in the workshop several times over the years for things like broken RS-232 socket wires or buttons that no longer work properly. Fortunately, the owner has a couple of extra similar devices that stopped working years before I was involved with them, and he now uses these for spares, especially as the buttons wear out frequently. The gadgets look surprisingly similar to my dad’s early HP calculator back in the 70s (Google tells me it was the HP-65 model). It boasted a swipe card with a magnetic strip that could ‘program’ the calculator’s functions, something I was quite taken with at the 84 Silicon Chip time. The red, bubble-lens LED display also looks similar and was very much of its time as well. When opened up, the Swedish gadgets contained three PCBs packed with EPROMS and other common chips of the time, plus room for a rechargeable 3V battery. I’m still not sure what my client does with these devices, but as he is retiring soon, he just wants to keep things going until that happens. I know he goes to various establishments, plugs these gadgets into machines (pokies maybe?) and downloads information onto them. He then takes the gadgets home and connects them via old serial-type cables to a green-screen computer I have also been keeping limping along. He can then print out the data he needs on a couple of old printers. What they do isn’t really important anyway; I just need to be able to keep them going. As with many handheld devices, he only uses a few of the keypad buttons to perform common tasks, so those wear out pretty quickly. If the plastic button’s top is popped off, a retained tension spring comes with it, and the contacts beneath are revealed. By today’s standards, I think they are a bit basic, but they do the job. Underneath the cap is a U-shaped copper spring contact about 15mm square overall but made from very thin metal, which looks quite flimsy. The top-left corner of this spring contact is connected through the plastic base of the switch to the button PCB underneath. When the button is pushed, the bottom right corner Australia’s electronics magazine of this piece deflects and touches the other contact, which is also moulded into the plastic base of the button. The obvious problem is that this main metal piece just wears out with use and eventually work hardens and breaks off, meaning the button stops working. Sometimes, I can just use a finetipped soldering iron to re-join the primary spring contact to the broken piece in the base, but this is a temporary fix only; the usual procedure is to replace the button itself. As I mentioned, he has several spare devices, and I have already used many of the buttons from these units. While the buttons are coloured and numbered, I just use the original plastic top from the broken one and put it onto the ‘new’ replacement base to restore functionality. Unlike a lot of stuff from that era, I got the distinct impression these weren’t designed to be worked on by anyone but the manufacturer. There is siliconchip.com.au Items Covered This Month • That ‘80s gear • Replacing the plugpacks in a • • dual-handset phone system A blown and charred mobile phone charger Repairing a 15-year-old Epson scanner *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz no information about them anywhere; no circuits, schematics or other data except for the user manuals the client got with them when he bought them in the early ‘80s. To get an entire button out, for example, the whole device must be disassembled. Many through-wires must be disconnected/unsoldered with much gnashing of teeth and wringing of hands until the bottom of the button PCB is revealed. There is no other option, though, so we just soldier on. One good repair deserves another Recently, the same client called and asked me about having a look at his printer, which apparently had a “broken wire” and had stopped working. This sounded reasonably straightforward; I’m not bad at repairing broken wires, but printers in general are not my thing. I usually refer clients with printer issues to a specialist printer place. However, I said I’d have a look, and when he arrived with it, the job took on a different angle. This printer is 35 years old, one of two he uses every day to do whatever he does with them (my assumption is printing data!). Anyone who remembers these printers will know the type I’m talking about. They work very much like a typewriter, but instead of individual keys striking paper through an ink ribbon to make their mark, these printers have a matrix of pins within a print head which moves back and forth along the line and forms the characters instead. The major disadvantage is the sound they make; the name impact printer probably says it all. I recall going to offices and they’d have a special room set up just for these printers because they were so loud! One such office didn’t have a ‘printer room’, and the poor workers there had to suffer constant high-level noise; I could barely sit in the office chair for five minutes, let alone spend the day there with that racket going on! Still, these types of printers had their place and are still used by people who need duplicate (or even triplicate) copies, all done simultaneously. Of course, modern inkjets or laser printers can easily do multiple copies. However, some businesses still prefer that old tractor-feed printing that does it all at once (for POS systems where the customer gets one copy, for example). Anyway, the client brought the printer in and as a testament to the build quality of these older machines, it was the first time he’d ever had to take it in for a service. It showed; covered in dust and dirt, it really did need cleaning up. The biggest problem was this “broken wire” the client talked about. It wasn’t a broken electrical wire, but the main drive cable that connected the printer’s moving head assembly to the stepper motor, which of course, means nothing worked because the head no longer moved back and forth. This connecting cable is much like a bicycle’s brake cable; multi-stranded and designed to carry quite a substantial load. It is fixed to the movable print head of the machine, which is mounted on a couple of heavy-duty chromed rods, and the cable wraps around several pulleys and the stepper motor’s main drive shaft, allowing the print head to traverse the printer at some speed. You certainly wouldn’t want to get your fingers stuck in there when it’s going, which is why there is a removable plastic cover over the whole assembly. The cable was lying in the bottom of the printer, and it had obviously come unstuck somewhere. I’ve repaired a few cables like this before in different devices, so I said I’d take a look to see what I could do. ALSO AVAILABLE 10% OFF YOUR NEXT NOVEMBER ORDER WITH DISCOUNT CODE SCNOV10 FREE SHIPPING AUSTRALIA WIDE siliconchip.com.au THE TOOLS TO BUILD THE FUTURE w w w. p h i p p s e l e c t r o n i c s . co m Australia’s electronics magazine November 2021 85 Most repair people would just tell him it has had its day and to buy a new one, but there were a few problems with doing that. One, while still available, due to COVID19, there is not one to be purchased in New Zealand at the moment. Two, even if one was available, the cost is prohibitive now for a similar machine. Repair seemed like the only feasible option. Threading the cable back onto the various spools and pulleys wasn’t too onerous, except for the fact it has formed itself into very strong coils as it has been sitting in the same position for the last 35 years. At least this gave me a clue as to how it wound back on and where it could actually go, because it isn’t apparent just by looking at it from under the top cover. True to form, I couldn’t find a service manual for this printer anywhere on the web. I had only a vague idea of where everything should go back into place, so there was a bit of toing and froing as I tried different methods to get the cable back on track. Eventually, I got it into place – or where I thought it should be – and manually moved the print head back and forth. The cable was firmly connected to that, and I assumed that I didn’t want to move it because that might throw everything else out of whack. I theorised that if it had come off with the head in that fixed-cable position, it should go back on there as well. That was the theory anyway. With the cable in place, I manually moved the head along the shafts, and almost instantly, the cable pinged off the far-right hand pulley. I was back to square one. With a bit of fettling, I got the cable back into place and tried it again. Once again, everything just popped off; it was becoming evident that something else was wrong. The problem seemed to be with that far pulley, a plastic moulded disc running on what appeared to be a metal hub in the centre. It bore a lot of the cable load and, as soon as anything moved, the cable simply peeled off it. I took out the circlip holding it on and removed it for a better look. Straight away, I could see the problem; over the years, the cable had ground away at the channel it sits in, and it had simply worn through the plastic. Looking at it from the side, the bottom of the pulley channel was fine, but the top edge had disappeared completely, so there was nothing for the cable to run in anymore. It needed replacing, so I got on the phone and called a few printer places I know of to ask if perhaps they had an old dead unit sitting under the bench I could burgle parts from. No joy; as I suspected, most examples of this printer were skip fodder years ago. And new parts are not an option either, so it was back to looking at what I could do with this one. Jury-rigging it The pulley itself might be able to be repaired, and if I had a 3D printer, I might have been able to make a new one. But I didn’t, so I couldn’t. Still, I had an idea. The bottom edge was not worn through, so obviously, all the stress was on the top section, which had worn out. I thought I might be able to simply turn the pulley upsidedown and use it that way. Unfortunately, the cable wouldn’t stay on this way either, just falling off the bottom as soon as I moved the print head, so that wasn’t going to fly. But then I thought 86 Silicon Chip about using something to build up the missing bottom part of the pulley. I looked through my parts bins and found a large washer, which I know variously as a ‘penny’ washer or a ‘fender’ washer. Basically, it’s an oversized metal washer with a relatively small hole in the centre. I figured that if I bored out the hole to the size of the shaft the pulley ran on, I could glue this washer to the bottom of the pulley and essentially replace the worn-out edge. As it would be on the bottom now (because I would flip the pulley over), it wouldn’t be subject to the upward forces of the cable, and the now unworn plastic edge of the pulley would do the job its other half did for the last 35 years. Drilling the hole out on the washer was no problem, and I used a 24-hour epoxy resin and a press to glue the washer to the bottom of the pulley. I made sure to scuff the plastic to give the glue something to adhere to and centred everything up using an 8mm drill bit shank which I could remove easily later. It wasn’t brilliant, but I reckoned it should work. I reassembled everything once the glue had time to set, and other than a bit of cleaning of the glue around the cable run of the pulley, it looked pretty good. One problem was that now the pulley was around 50% thicker in cross-section, and I could no longer use the original circlip to hold this pulley to the shaft. I ended up drilling and tapping a small hole down the centre of the shaft, which turned out to be hardened steel, and mounted a small bolt and washer to hold the pulley in place. Threading the drive cable back into place was by now relatively straightforward, as I’d done it so many times, and the washer-bottomed pulley seemed to rotate and move just as well as it had before, with no binding or noise. The proof of any repair is whether it works or not, and so I plugged the printer in and hit the power button. The head shot back into its usual resting place, and all the right lights showed on the front panel. I didn’t have a parallel port with which to test it, so I asked the client if he could bring what he needed to try it out. He duly arrived with a handheld gadget and a bunch of cables and interfaces, which he plugged in, and soon we were rewarded with the dulcet tones of an impact printer doing its thing. The client has since reported that all is well and it is going better than it has in years. A job well done! Changing the plugpacks in a dual-handset phone system P. R., of Canterbury, New Zealand took pity on a Gigaset C300A dual-handset DECT phone system at a local church fair. It came with UK plugpacks, so it would not be usable for the average buyer, but it looked clean and tidy, and still in its original box, so he bought it... Once I got it home, I removed the two AAA cells from each handset, and they all showed signs of leakage, but the damage to the phones looked minimal. A new pair of cells brought life to one handset, but not the other. The next step was to sort out the plugpacks. I found two transformer-style plugpacks in my junk boxes, large enough to house the fairly small plugpack innards from the UK versions, held together by screws, not ultrasonic welding. Australia’s electronics magazine siliconchip.com.au It did not take long to cut open the plugpacks and reassemble them into the Australia/NZ style housings. I then cleaned up the battery housing of the working phone, set up the smaller charger and plugged the phone in. When I came back later, the battery was fully charged. It worked as a regular cordless phone, including an answerphone (I deleted four old messages). So that just left the non-working phone. There were no screws, so this would be one of those Humpty Dumpty jobs, crack the egg and try to end up with an intact, unblemished egg at the end. After watching a fuzzy video on the web, I could see that it was possible, and I knew which end was best to start from (the battery end). Lacking the usual tools for this, I finally managed to crack the case by apply gentle pressure using my bench vice on the battery end until I could fit a small steel ruler in the gap. I could then work my way up each side of the case with a small flat-bladed screwdriver until the whole thing gave up and opened. I could see some verdigris around the two battery terminals and other areas, but not so bad that it was not worth trying to save. A quick clean with warm water and a toothbrush, and it looked pretty good, but it was still not working. There is one LED between the two terminals that looked like the worst affected area. I removed the negative terminal, which was surfacemounted on two rectangular pads. Again, everything looked good, but an ohmmeter showed no continuity in the track joining the two pads together, nor in the zig-zag track through a low-ohm resistor to the ground plane of the phone. I could not see any breaks, but it turned out that both tracks were open at the point where they attached to the rectangular pads. This brought me right back to my early days servicing in the early 1970s. Back then, I discovered that some PCB designers had no concept of pad-to-track transition or sensible track widths. This was particularly apparent in an old pocket transistor radio that always suffered broken tracks when the user changed the batteries and accidentally applied pressure to vertical resistors. The designer of this phone would probably try to empty a football stadium through a standard house door. In the end, I had to repair seven tracks with fine wire, two on the negative terminal, three on the positive terminal and two on the LED. Only two tracks had an almost sensible width, and one of those was open-circuit. All these tracks could have been at least five times wider in the space available, and fillets are always good practice on pads that could be subject to stress (like battery terminals!). While this was a corrosion problem, not a stress fault, it could have saved all the re-work. Once reassembled, this phone joined the other and charged its old battery just fine – looking only a little battered along one edge from the case opening. Was it all worth it? Probably not, but for only $4 plus my time made this a reasonable upgrade from my old phone. A blown mobile phone charger B. P., of Dundathu, Qld got a rude surprise when one of his children handed him a blackened lump to diagnose and fix. It’s a good thing it didn’t burn the house down... My son handed me a phone charger and told me that siliconchip.com.au Australia’s electronics magazine November 2021 87 Even just a glance at the phone charger shows substantial burn marks which could be likely attributed to a blown diode and failed electrolytic capacitor. he was charging his phone after he went to bed last night, when the charger blew up with a loud bang, bright flash and smell of burning. I opened up the charger by undoing the two screws at the back. The inside of the top cover was blackened and I could see that the likely cause of the near-disaster was the failed 2.2μF 400V electrolytic capacitor that had a bulging top. Further investigation showed that one of the diodes had a piece blown out of its lead, and when I checked resistor R1, it was open-circuit. I have not previously seen one of these chargers blow up like this; they usually just fail silently and just don’t work anymore. It was only worth a few dollars, but I thought it would be interesting to see if it could be returned to service. I started by looking through my collection of reclaimed capacitors for a replacement 2.2μF 400V electrolytic capacitor, but the only 400V capacitors of the correct physical size I had were only 1μF. Then I thought to check another failed phone charger that I hadn’t been able to repair because of its more complex circuitry, and luckily, it had a good 2.2μF 400V electrolytic capacitor I could salvage. I did have a 1W 1W resistor in my collection, along with four 1N4004 diodes. I didn’t bother testing the remaining three diodes that hadn’t blown up, as I decided to just replace all four to be safe. With the replacement components fitted, I set the top back on the charger in case it decided to blow up again when plugged in. I plugged it into a power board, and nothing happened other than the indicator LED lighting up; a good sign. I plugged in a USB voltage tester and it showed that I had just over 5V, so the charger was now working again. This was somewhat surprising, as I had half expected it to blow up again when it was plugged in. I reassembled it, and it can now be returned to service. I wonder how many house fires are started by unattended chargers like this one failing spectacularly. Epson scanner repair A. L. S., of Turramurra, NSW went down a rabbit hole trying to fix his trusty old scanner. It probably wasn’t 88 Silicon Chip Australia’s electronics magazine siliconchip.com.au worth the time he spent given how cheap they are to buy these days, but it’s a pity to throw it away just because a couple of low-cost, easily replaced components have gone bad... My 15-year-old scanner started stopping halfway through a scan. Repeating the scan occasionally produced a complete image, but over time it got worse, eventually refusing to scan documents at all. I checked YouTube to see if anyone else had a similar problem. There was one person who had a sticking Epson scanner and described the repair in excellent detail. He described it as being “a reasonably easy repair” (https://youtu.be/RsmRNWoYkQI). His scanner was a different model to mine; the workings looked similar, but the repair involved disassembling all the mechanical components and cleaning the running rails which guide the scanning assembly. He also used replacement parts cannibalised from another scanner. I checked out available parts online for this scanner in the hope that I could find a dead one “for parts only” or some spare belts and pulleys, but all I could find was a used controller board for $90 including postage, which seemed way too steep. I thought it would be a waste of time and money anyway because I assumed my problem was mechanical, as it stopped scanning at the same location each time. If it was a mechanical failure then all I likely needed to do was free up the movement, so I split the case to get to the mechanical gear. It didn’t quite go according to plan because only two screws were holding it together, and as I prised the case open, I heard the horrible sound of plastic retainers snapping. There were several of these around the perimeter, and they all completely broke off. The plastic retainers required some sort of magic trick to separate, and I am still unsure what that was! I have repaired hundreds of similar devices and never came across a case like this. Fortunately, the absence of the plastic bits made no real difference, and the two halves of the case snapped back together again after I had finished cleaning the rail for the scanning assembly. The assembly moved very smoothly after I cleaned it. The belt and pulleys were all OK, and I was convinced that siliconchip.com.au Two faulty 10μF 6.3V SMD electolytics were removed from the controller board of the scanner and replaced with through-hole electrolytics rated at 25V. the scanner would now come back to life. After I plugged it in again and set it off for a scan – nothing had improved; it still scanned only half a document. I was really puzzled! If the mechanicals were operated smoothly, what else could be going wrong? I put it all down to a faulty motor or motor controller, but the curiosity was slowly killing me, so I eventually dragged it out, dusted it off and fired the thing up again. This time it scanned half a document immediately, but when I tried again, it stubbornly refused to obey any command. My thoughts turned to the plugpack; it might have a low output voltage or be overheating or somehow limiting the current delivered to the scanner. I checked it out by loading it with a 68W 10W resistor, but it maintained its rated voltage, so I had gone up another blind alley. It then struck me that I had not even inspected this controller board when cleaning it. That’s because it was entirely covered by a ‘full metal jacket’ that was screwed in place and also hidden by another PCB carrying the switches and the power indicator LED. Instead of opening it all up again and taking the time and effort to pull the circuit board out, I took a shortcut and zoomed in on the photo of the replacement control board on eBay. As I zoomed in on the tiny fuzzy photo, I had a light bulb moment – this thing had two 10μF 6.3V SMD electrolytics, the same type which caused me grief on a previous repair and that are famous for going bad! One of the symptoms was that the Australia’s electronics magazine scanner started to work when it was cold, but it would not work after being switched on for any length of time. I think that this might be because the electrolytic capacitors had degraded and become temperature-sensitive. So I extracted the circuit board and removed those two SMD electrolytic capacitors. This is easy if you know how to do it correctly. The best method is to gently rock the SMD electro from side to side with needle-nose pliers. This fatigues the pigtails, but you have to be patient and “gentle” is the operative word. After removing them, I checked them with a capacitance meter and they measured a measly 0.73μF and 2.3μF! I did not replace these with SMD capacitors but instead used conventional electros because modern through-hole types are small enough and are easy to solder, as you can see in the photo. These replacements also had a higher rating of 25V and were easily soldered to the SMD pads and insulated with some plastic tubing, mounted horizontally to allow space for the metal jacket to clear. I also replaced two other suspect conventional electrolytics with new, higher-rated ones and bingo! The scanner worked perfectly. I suspect it was only scanning half the page because it was getting to a point where greater demand was placed on the power supply, and with such poor bypassing, the voltage dropped too much and reset the controller electronics. This symptom was a live red herring designed by an ingenious gremlin. SC November 2021 89 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 139, COLLAROY, NSW 2097 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 11/21 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS 24LC32A-I/SN ATmega328P ATmega328P-AUR ATtiny85V-10PU ATtiny816 PIC10F202-E/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F617-I/SN PIC12F675-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-E/P PIC16F88-I/P $15 MICROS Digital FX Unit (Apr21) RF Signal Generator (Jun19), Si473x FM/AM/SW Digital Radio (Jul21) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) LED Christmas Ornaments (Nov20; specify variant) Nano TV Pong (Aug21), SMD Test Tweezers (Oct21) Car Radio Dimmer (Aug19), MiniHeart Heartbeat Simulator (Jan21) Refined Full-Wave Universal Motor Speed Controller (Apr21) Model Railway Level Crossing (two required – $15/pair) (Jul21) Model Railway Carriage Lights (Nov21) Motor Speed Controller (Mar18), Heater Controller (Apr18) Useless Box IC3 (Dec18) Tiny LED Xmas Tree (Nov19) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20), Electronic Wind Chime (Feb21) 20A DC Motor Speed Controller (Jul21) Flexible Digital Lighting Controller Slave (Oct20) Automotive Sensor Modifier (Dec16) Remote-controlled Preamp with Tone Control (Mar19) UHF Repeater (May19), Six Input Audio Selector (Sep19) Universal Battery Charge Controller (Dec19) ATSAML10E16A-AUT High-Current Battery Balancer (Mar21) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC16F18877-I/P USB Cable Tester (Nov21) 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) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) Advanced GPS Computer (Jun21) Touchscreen Digital Preamp [2.8in/3.5in version] (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) PIC32MX795F512H-80I/PT Maximite (Mar11), miniMaximite (Nov11), Colour Maximite (Sep12), Touchscreen Audio Recorder (Jun14) $20 MICROS dsPIC33FJ64MC802-E/SP dsPIC33FJ128GP306-I/PT dsPIC33FJ128GP802-I/SP PIC32MX470F512H-I/PT PIC32MX470F512H-120/PT PIC32MX470F512L-120/PT 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb13) Ultra-LD Preamp (Nov11), LED Musicolour (Oct12) Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Micromite Explore 100 (Sep16) PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sep12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) $30 MICROS KITS, SPECIALISED COMPONENTS ETC USB CABLE TESTER KIT (CAT SC5966) $110.00 (NOV 21) Includes PCB, IC1 (programmed), IC2, D1, L1, SMD capacitors and resistors. Does not include reed switch, magnet, LEDs or through-hole parts SMD TEST TWEEZERS KIT (CAT SC5934) $35.00 (AUG 21) $17.50 PCB and all onboard parts only (does not include controllers) MODEL RAILWAY LEVEL CROSSING (JUL 21) $15.00 $5.00 - Pair of programmed PIC12F617-I/Ps - ISD1820P-based audio recording and playback module AM/FM/SW RADIO (JAN 21) $2.50 $3.00 $7.50 - PCB-mount right-angle SMA socket (SC4918) - Pulse-type rotary encoder with integral pushbutton (SC5601) - 16x2 LCD module (does not use I2C module) (SC4198) LED CHRISTMAS ORNAMENTS (CAT SC5579) (NOV 20) Complete kit including micro but no coin cell (specify PCB shape & colour) RGB STACKABLE LED CHRISTMAS STAR (CAT SC5525) $14.00 (NOV 20) $38.50 Complete kit including PCB, micro, diffused RGB LEDs and other parts MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) $25.00 (OCT 21) PCBs, micro, other onboard parts and heatshrink (no cell or brass tips) NANO TV PONG SHORT FORM KIT (CAT SC5885) VARIOUS MODULES & PARTS (NOV 21) Short form kit with everything except case and AA cells MODEL RAILWAY CARRIAGE LIGHTS KIT (CAT SC6027) siliconchip.com.au/Shop/ (AUG 19) Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $35.00 - DHT22 temp/humidity sensor (Cat SC4150) $7.50 - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor $5.00 - BME280 temperature/pressure/humidity sensor (Cat SC4608) $10.00 - DS3231 real-time clock SOIC-16 IC (Cat SC5103) $4.00 - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) $5.00 - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) $1.50 - 10µF 16V X7R through-hole capacitor (Cat SC5106) $2.00 - 64x32 pixel white 0.49in OLED (SMD Test Tweezers, Oct21) $10.00 - pair of AD8403ARZ10 (Touchscreen Digital Preamp, Sep21) $35.00 - Si4732 radio IC (Si473x FM/AM/SW Radio, Jul21) $15.00 - EA2-5NU relay (PIC Programming Helper, Jun21) $3.00 - VK2828U7G5LF GPS module (Advanced GPS Computer, Jun21) $25.00 - MCP4251-502E/P (Advanced GPS Computer, Jun21) $3.00 - pair of Signetics NE555Ns (Arcade Pong, Jun21) $12.50 - 2.8-inch touchscreen LCD module (Lab Supply, May21) $25.00 - Spin FV-1 digital effects IC (Digital FX Unit, Apr21) $40.00 - 15mW 3W SMD resistor (Battery Multi Logger / Arduino PSU, Feb21) $2.50 - DS3231(M) real-time clock SMD IC (Battery Multi Logger, Feb21) $3.00 - Pair of CSD18534 transistors (Electronic Wind Chimes, Feb21) $6.00 - IPP80P03P4L04 (Dual Battery Lifesaver / Vintage Radio Supply, Dec20) $5.00 - 16x2 LCD module (Digital RF Power Meter, Aug20) $7.50 - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) $15.00 - MAX038 function generator IC (H-Field Transanalyser, May20) $25.00 - MC1496P double-balanced mixer IC (H-Field Transanalyser, May20) $2.50 - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) $12.50 - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) $5.00 - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 - SMD 1206 LEDs, packets of 10 unless stated otherwise (Xmas Ornaments, Nov20): yellow – $0.70 ¦ amber – $0.70 ¦ blue – $0.70 ¦ cyan – $1.00 ¦ pink (1 only) – $0.20 - ISD1820-based voice recorder / playback module (Junk Mail, Aug19) $4.00 - 23LCV1024-I/P SRAM & MCP73831T (UHF Repeater, May19) $11.50 - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) $1.50 - 1nF 1% MKP (5mm) or ceramic capacitor (LC Meter, Jun18) $2.50 - ESP-01 WiFi Module (El Cheapo Modules, Apr18) $5.00 - WiFi Antennas with U.FL/IPX connectors (Water Tank Level Meter with WiFi, Feb18): 5dBi – $12.50 ¦ 2dBi (omnidirectional) – $10.00 - NRF24L01+PA+NA transceiver, SNA connector & antenna (El Cheapo, Jan18) $5.00 - ERA-2SM+ MMIC & ADCH-80A+ choke (6GHz+ Frequency Counter, Oct17) $15.00 - VS1053 Geeetech Arduino MP3 shield (Arduino Music Player, Jul17) $20.00 - MAX7219 red LED controller boards (El Cheapo Modules, Jun17): 8x8 SMD/DIP matrix display – $5.00 ¦ 8-digit 7-segment display – $7.50 - microSD card adaptor (El Cheapo Modules, Jan17) $2.50 - DS3231 real-time clock module with mounting hardware $7.50 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # P&P prices are within Australia. Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT LED CHRISTMAS TREE DIGITAL INTERFACE MODULE TINNITUS/INSOMNIA KILLER (JAYCAR VERSION) ↳ ALTRONICS VERSION HIGH-SENSITIVITY MAGNETOMETER USELESS BOX FOUR-CHANNEL DC FAN & PUMP CONTROLLER ATtiny816 DEVELOPMENT/BREAKOUT PCB ISOLATED SERIAL LINK DAB+/FM/AM RADIO ↳ CASE PIECES (CLEAR) REMOTE CONTROL DIMMER MAIN PCB ↳ MOUNTING PLATE ↳ EXTENSION PCB MOTION SENSING SWITCH (SMD) PCB USB MOUSE AND KEYBOARD ADAPTOR PCB LOW-NOISE STEREO PREAMP MAIN PCB ↳ INPUT SELECTOR PCB ↳ PUSHBUTTON PCB DIODE CURVE PLOTTER ↳ UB3 LID (MATTE BLACK) FLIP-DOT (SET OF ALL FOUR PCBs) ↳ COIL PCB ↳ PIXEL PCB (16 PIXELS) ↳ FRAME PCB (8 FRAMES) ↳ DRIVER PCB iCESTICK VGA ADAPTOR UHF DATA REPEATER AMPLIFIER BRIDGE ADAPTOR 3.5-INCH LCD ADAPTOR FOR ARDUINO DSP CROSSOVER (ALL PCBs – TWO DACs) ↳ ADC PCB ↳ DAC PCB ↳ CPU PCB ↳ PSU PCB ↳ CONTROL PCB ↳ LCD ADAPTOR STEERING WHEEL CONTROL IR ADAPTOR GPS SPEEDO/CLOCK/VOLUME CONTROL ↳ CASE PIECES (MATTE BLACK) RF SIGNAL GENERATOR RASPBERRY PI SPEECH SYNTHESIS/AUDIO BATTERY ISOLATOR CONTROL PCB ↳ MOSFET PCB (2oz) MICROMITE LCD BACKPACK V3 CAR RADIO DIMMER ADAPTOR PSEUDO-RANDOM NUMBER GENERATOR 4DoF SIMULATION SEAT CONTROLLER PCB ↳ HIGH-CURRENT H-BRIDGE MOTOR DRIVER MICROMITE EXPLORE-28 (4-LAYERS) SIX INPUT AUDIO SELECTOR MAIN PCB ↳ PUSHBUTTON PCB ULTRABRITE LED DRIVER HIGH RESOLUTION AUDIO MILLIVOLTMETER PRECISION AUDIO SIGNAL AMPLIFIER SUPER-9 FM RADIO PCB SET ↳ CASE PIECES & DIAL TINY LED XMAS TREE (GREEN/RED/WHITE) HIGH POWER LINEAR BENCH SUPPLY ↳ HEATSINK SPACER (BLACK) DIGITAL PANEL METER / USB DISPLAY ↳ ACRYLIC BEZEL (BLACK) UNIVERSAL BATTERY CHARGE CONTROLLER BOOKSHELF SPEAKER PASSIVE CROSSOVER ↳ SUBWOOFER ACTIVE CROSSOVER ARDUINO DCC BASE STATION NUTUBE VALVE PREAMPLIFIER TUNEABLE HF PREAMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) NUTUBE GUITAR DISTORTION / OVERDRIVE PEDAL THERMAL REGULATOR INTERFACE SHIELD ↳ PELTIER DRIVER SHIELD DATE NOV18 NOV18 NOV18 NOV18 DEC18 DEC18 DEC18 JAN19 JAN19 JAN19 JAN19 FEB19 FEB19 FEB19 FEB19 FEB19 MAR19 MAR19 MAR19 MAR19 MAR19 APR19 APR19 APR19 APR19 APR19 APR19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 JUN19 JUN19 JUN19 JUN19 JUL19 JUL19 JUL19 AUG19 AUG19 AUG19 SEP19 SEP19 SEP19 SEP19 SEP19 SEP19 OCT19 OCT19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 DEC19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 PCB CODE 16107181 16107182 01110181 01110182 04101011 08111181 05108181 24110181 24107181 06112181 SC4849 10111191 10111192 10111193 05102191 24311181 01111119 01111112 01111113 04112181 SC4927 SC4950 19111181 19111182 19111183 19111184 02103191 15004191 01105191 24111181 SC5023 01106191 01106192 01106193 01106194 01106195 01106196 05105191 01104191 SC4987 04106191 01106191 05106191 05106192 07106191 05107191 16106191 11109191 11109192 07108191 01110191 01110192 16109191 04108191 04107191 06109181-5 SC5166 16111191 18111181 SC5168 18111182 SC5167 14107191 01101201 01101202 09207181 01112191 06110191 27111191 01106192-6 01102201 21109181 21109182 Price $5.00 $2.50 $5.00 $5.00 $12.50 $7.50 $5.00 $5.00 $5.00 $15.00 $.00 $10.00 $10.00 $10.00 $2.50 $5.00 $25.00 $15.00 $5.00 $7.50 $5.00 $17.50 $5.00 $5.00 $5.00 $5.00 $2.50 $10.00 $5.00 $5.00 $40.00 $7.50 $7.50 $5.00 $7.50 $5.00 $2.50 $5.00 $7.50 $10.00 $15.00 $5.00 $7.50 $10.00 $7.50 $5.00 $5.00 $7.50 $2.50 $5.00 $7.50 $5.00 $2.50 $10.00 $5.00 $25.00 $25.00 $2.50 $10.00 $5.00 $2.50 $2.50 $10.00 $10.00 $7.50 $5.00 $10.00 $2.50 $5.00 $20.00 $7.50 $5.00 $5.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT DIY REFLOW OVEN CONTROLLER (SET OF 3 PCBS) 7-BAND MONO EQUALISER ↳ STEREO EQUALISER REFERENCE SIGNAL DISTRIBUTOR H-FIELD TRANSANALYSER CAR ALTIMETER RCL BOX RESISTOR BOARD ↳ CAPACITOR / INDUCTOR BOARD ROADIES’ TEST GENERATOR SMD VERSION ↳ THROUGH-HOLE VERSION COLOUR MAXIMITE 2 PCB (BLUE) ↳ FRONT & REAR PANELS (BLACK) OL’ TIMER II PCB (RED, BLUE OR BLACK) ↳ ACRYLIC CASE PIECES / SPACER (BLACK) IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION USB SUPERCODEC ↳ BALANCED ATTENUATOR SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE BK1198 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG Si473x FM/AM/SW DIGITAL RADIO 20A DC MOTOR SPEED CONTROLLER MODEL RAILWAY LEVEL CROSSING COLOUR MAXIMITE 2 GEN2 (4 LAYERS) BATTERY MANAGER SWITCH MODULE ↳ I/O EXPANDER NANO TV PONG LINEAR MIDI KEYBOARD (8 KEYS) TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM SMD TEST TWEEZERS (3 PCB SET) DATE APR20 APR20 APR20 APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 NOV20 AUG20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 JUN21 JUN21 JUN21 JUN21 JUL21 JUL21 JUL21 AUG21 AUG21 AUG21 AUG21 AUG21 SEP21 SEP21 OCT21 OCT21 OCT21 PCB CODE 01106193/5/6 01104201 01104202 CSE200103 06102201 05105201 04104201 04104202 01005201 01005202 07107201 SC5500 19104201 SC5448 15005201 15005202 01106201 01106202 18105201 04106201 04105201 04105202 08110201 01110201 01110202 24106121 16110202 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 18104211 18104212 10103211 05102211 24106211 24106212 08105211 CSE210301C 11006211 09108211 07108211 11104211 11104212 08105212 23101213 01103191 01103192 01109211 12110121 04106211/2 Price $12.50 $7.50 $7.50 $7.50 $10.00 $5.00 $7.50 $7.50 $2.50 $5.00 $10.00 $10.00 $5.00 $7.50 $5.00 $5.00 $12.50 $7.50 $2.50 $5.00 $7.50 $5.00 $5.00 $2.50 $1.50 $5.00 $20.00 $20.00 $3.00 $12.50 $12.50 $5.00 $2.50 $7.50 $2.50 $5.00 $10.00 $5.00 $2.50 $5.00 $10.00 $5.00 $12.50 $2.50 $7.50 $7.50 $7.50 $5.00 $10.00 $10.00 $7.50 $7.50 $7.50 $5.00 $7.50 $35.00 $7.50 $7.50 $5.00 $15.00 $5.00 $2.50 $2.50 $5.00 $12.50 $2.50 $15.00 $30.00 $10.00 NOV21 NOV21 NOV21 04108211 04108212 09109211 $7.50 $5.00 $2.50 NEW PCBs USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS We also sell an A2 Reactance Wallchart, RTV&H DVD, Vintage Radio DVD plus various books at siliconchip.com.au/Shop/3 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 Tapped Horn Subwoofer orientation I have built the Tapped Horn Subwoofer (September 2021; siliconchip. com.au/Article/15028) but I cannot figure out which part is supposed to be the top. In the article, the author has possibly swapped the top and bottom designation in the part about the fitting of the final panels. I tried to look carefully at the author’s photos in the construction article, but there is no photo of the finished speaker looking at the front panel, with the exit port visible. It probably does not matter, but my question is: should the exit port be at the top or close to the floor? Regardless, it is an excellent article/idea/construction project. (P. M., Loftus, NSW) • Phil Prosser responds: I put the “mouth” of the horn at the bottom. Ideally, it should face into the corner of the room. My reasoning is that the base is screwed on but not glued, allowing access to the driver, so it will not have screw holes neatly filled and invisible. Also, I think that having the port right at floor level in the corner will more effectively couple it into the room. Though given the frequencies involved, this is almost certainly of negligible impact. As I noted in the text, a tapped horn is not horn loaded in the way the name suggests and is more like a resonant system with many parallels to a transmission line. To this end, the relationship of the exit from a tapped horn to the walls/floor is less critical than with a conventional horn. I did model the tapped horn in ‘quarter space’ (into a corner) and ‘half space’ (against a wall) with a preference for the corner, as that is a good place to hide this thing in a typical house. This placement does not substantially impact the roll-off rate like with a regular horn, where you can create an effective extension of the horn using reflections from the walls. Beyond this, I do not have an opinion on up or down. I hope people try 92 Silicon Chip these things out and get into using the “Hornresp” software; have a play and share your experience. Battery Balancer with a stack of LiFePO4 cells Regarding your High Current Battery Balancer projects (March & April 2021; siliconchip.com.au/Series/358), does it redirect charge to cells that are discharging more quickly than others in the stack, or is it only active when charging? Eg, see siliconchip.com.au/ link/abbb I’m tired of replacing SLAs in my UPS. I want to replace them with an 8S1P LiFePO4 battery – and this project looks like it has all the right features, but there is the issue of the behaviour of the built-in charger. What can I do about this? I’m also keen to apply a Balancer to a 15 cell stack of LiFePO4 cells, notionally rated at 150Ah charged by a 40A charger. Is it possible to daisy-chain four balancers to achieve this, or is the limit of two a hard limit? As always, a great magazine! (M. S., Doncaster East, Vic) • The Balancer is always active as long as the cells are between the low and high voltage settings. So, provided the battery is not over-discharged (or under extreme load), the Balancer will transfer charge from cells with higher voltages to those with lower voltages (as long as the difference is larger than the threshold setting). The Balancer is entirely independent of the charger: its only job is to keep the cells in balance. It aims to be invisible to the charger. So in that regard, you cannot change the battery chemistry to a type not supported by (or suitable for use with) the charger. There are numerous LiFePO4 rechargeable batteries that are designed as drop-in replacements for lead-acid types, so those are probably your best bet. You could theoretically charge a Li-ion/LiPo pack safely with a multistage lead-acid charger. It would need Australia’s electronics magazine enough cells that its fully charged voltage is higher than the termination voltage of that charger, with cells that can handle the peak charging current. However, you would almost certainly be leaving a significant percentage of the battery capacity unused if you did so. For example, if the charger delivered a maximum of 10A and terminated at 14.4V, you could use four Li-ion/LiPo cells in series as long as they can handle the 10A charge rate. But that battery would normally have a fully charged voltage of around 16.8V, so you would only be charging them to about 50% of their full capacity. LiFePO4 is better suited to the role as 14.4V = 4 × 3.6V. Currently, the Balancer is only designed to operate by itself or in pairs. It would be possible to construct a separate device to allow more than two units to be used together, but we have not done that yet. We will consider doing so. One thing that might be possible, but we have not tried, is to arrange two Balancers in pairs, balancing eight cells per pair, then connect the bottom eight of your 15 cells to one Balancer and the top eight to the other. There would be one cell common to both Balancers, and therefore (in theory at least), all 15 cells would ultimately become balanced. However, it might not work efficiently, and the common cell might wear out faster than the others as all balancing current between the top and bottom halves would flow through it. Battery Multi Logger questions & suggestions This project (February & March 2021; siliconchip.com.au/Series/355) is welcome and looks like an extremely useful addition to any type of off-grid service battery installation. I’m mainly thinking of batteries for UPSs, remote sites or caravans. I have some questions regarding the operation. How many High Current Battery siliconchip.com.au Balancer modules are supported by the Battery Multi Logger? I suspect that only one is supported as there is no discussion of this capability. Suppose only one High Current Battery Balancer is supported. In that case, one might think of using “nested” Balancers: four Balancers, each balancing a stack of four cells and a fifth Balancer monitoring the four stacks connected to the Battery Multi Logger. Is this a possible solution? Is the Battery Multi-Logger data logging retained as originally described, ie, hours/days/weeks? I’m a little disappointed that the cell voltage history seems to be limited to “around 100 data points” to give “around 15 minutes of balancing data”. I think there is a way to increase the “history” to a much larger number as cell balancing for large capacity LFP batteries/cells can take a long time. A 32Mb SPI flash memory chip is under $10. (M. S., via email) • You’re right in that the Manager can only communicate with one Balancer directly. The design is quite squeezed for space and I/O ports, so it would not be an easy task to add more serial ports to it. The nested solution would likely work but requires quite a bit of extra hardware. The data retained by the Manager is less than the Logger due to the need to set aside space for storing the Manager settings for the Balancer and Soft Switch in the Micromite’s limited “VAR SAVE” space. Using an external flash chip makes sense, but that would require a fair bit of the program to be reworked. Since it is already quite close to reaching the flash memory limit, adding this extra capability wouldn’t be easy, even with storage offloaded to the external chip. We’ve run into similar problems with many 28-pin Micromite-based projects; it doesn’t take much code to occupy all the flash space (and RAM too). So expanding its storage capabilities will probably involve entirely new hardware. Perhaps a better option would be to regularly send the data to another device over the serial port (especially as functions already exist to do this). There is a function that is called each day to update the stored data; it could be done then. The receiver could be another micro that simply receives and logs data to siliconchip.com.au an SD card or flash chip. However, this will probably affect the low-power performance of the Logger/Manager. Reducing soldering iron power I am using an old-fashioned soldering iron to push brass inserts into 3D-printed plastic. As the full bore temperature is a bit on the hot side, I need a means of reducing the temperature. The actual temperature is not very critical. I am looking at some sort of PWM Mosfet arrangement with a knob to twiddle the temp. Do you have anything in your catalog which would do this? (G. C., Mount Dandenong, Vic) • Presumably, this soldering iron is mains-powered, in which case a phase controller would be suitable. The Refined Full-Wave Motor Speed Controller (April 2021; siliconchip.com. au/Article/14814) would be suitable, although perhaps more complicated than necessary. The feedback control is not required. Depending on the wattage, a standard light dimmer would also work if installed in a suitable enclosure with mains input and GPO (mains socket) for the soldering iron. Our Heat Controller design is also suitable (July 1998; siliconchip.com. au/Article/4687), and the PCB for that project is still available from our Online Shop. Original Colour Maximite limitations I cannot find any reference on TheBackShed forum to the Maximite computers. I need to produce a completely random dice roll using MMBasic for something I am working on using the original Colour Maximite. The other program I want to do is for resistor colour codes, but it does not have the right colours. Is there any way around that besides using the Colour Maximite 2? (R. M., Melville, WA) • There is some discussion of the Maxmite computers on TheBackShed forum, but it doesn’t seem to be organised into any specific location. You have to search the forum. For random numbers, see the RANDOMIZE and RND functions in the MMBasic Language Manual Ver 4.5 published for the original Colour Maximite. Australia’s electronics magazine The Colour Maximite only supports eight colours as the hardware only has three digital lines physically driving the VGA connector. Since there are ten resistor colour codes and the Colour Maximite only supports eight colours, there is no way it can produce them. You definitely need something like the Colour Maximite 2. Using BMP280 sensor with the Micromite Many of your projects have incorporated the BMP180 pressure sensor (eg, the Micromite LCD BackPack V3 from August 2019; siliconchip.com. au/Article/11764). The BMP280 has superseded it, but I don’t think the code for the BMP180 is still valid for this newer device. Would you consider doing an El Cheapo project on using this device with a Micromite? (J. H., Nathan, Qld) • We mentioned the BMP280 in the December 2017 El Cheapo Modules article on page 82 (siliconchip.com. au/Article/10909); however, we did not provide any example code for it in that article. The main difference is that it offers higher resolution readings. You can find Micromite software for interfacing with a BME280 at www. thebackshed.com/forum/ViewTopic. php?TID=8362 The only difference between the BMP280 and the more expensive BME280 is that the latter incorporates a humidity sensor. If you remove all the code from that example that has to do with the humidity measurements, it will work with a BMP280 instead. Improving GPS Disciplined Oscillator I just completed building your Programmable GPS Synched Frequency Reference (October & November 2018; siliconchip.com.au/Series/326) and it works very well. However, there is 0.8V of ripple on the output at about 116MHz, which appears to be from the 3.3V supply. The ripple on the 3.3V supply is about 0.1V near the DAC chips and about 0.8V near IC4, but I can’t tell where it’s coming from. Also, the PLL chip (IC2) gets very warm. The Micromite by itself does not have this ripple, and I can’t see any large oscillations on the unused outputs on IC4. I tried adding a ground plane to November 2021 93 the underside of the board and that improved things slightly. It appears the signal I am seeing is from approximately 100MHz ringing on the Schmitt trigger outputs (IC4 & IC5). I have seen this mentioned elsewhere on the internet and in TI’s application notes. I confirmed this by removing IC5. I note you have included damping resistors on the outputs. Any suggestions to reduce this ringing? I added a wire from pin 7 of IC5 to the ground side of the bypass capacitor but it made little difference. I also piggybacked a 10nF and 10μF capacitor onto the 100nF capacitor, but that too made little difference. I ran a 3.3V and a ground wire directly from the header connector to the connections near IC5 on the board’s underside, which reduced the ringing a bit. I also added the extra ground links per your previous suggestions and my ground plane on top of that. That made the unit much more stable but still with some ringing. I am also finding that at 80MHz+, the signal from the PLL is barely enough to trigger IC5. I tried 22pF and 4.7pF capacitors across the 510W resistor, but they made the PLL unstable. I then paralleled a 560W resistor with the 510W resistor and that seemed to fix the problem, but I am not sure if that is a good idea. The only remaining problem now is that the outputs of IC5 are sensitive to what is happening at its other inputs/outputs. Changing the settings for CON4 affects the signal from CON3. However, the output from CON3 (IC4) is now very stable. I have the unit in a box now, and with the extra ground links, ground plane and 560W parallel resistors, it is working well. There is still a bit of ringing on the outputs but not too bad. The GPS receiver (VK2828U7G5LF) fits perfectly into a 2xAA battery box with room for a magnet for mounting it on the top of something steel. I also put a piece of clear perspex wrapped in reflective tape on the bottom, poking through a hole in the case in an attempt to make a light pipe to see the flashing green LED. To my surprise, it worked pretty well! Finally, there is something strange happening during GPS disciplining. The c-value often jumps to 0 or 16,777,215 on an update and is rarely in between. Any ideas what could be 94 Silicon Chip causing this? (M. H., Mordialloc, Vic) • You appear to have seen the previous suggestions we published from readers to attach extra ground wires in parallel with the PCB traces to decrease the impedance for the ground return currents. Another reader suggested adding more bypass capacitance around the PCB. Extra wire links could also be added to the 3.3V rail. The 510W resistors simply limit the current out of the PLL pins; there is certainly some scope to reduce their value. At those frequencies, the input pin capacitance is probably the next most significant load; we estimate around 400W at 100MHz. So your parallel 560W resistors should be fine. With IC5 appearing to be the culprit, you could also look at adding extra supply bypassing to it. I would also have a close look at its pins. We can’t see any errors in the photos you sent, but we have been caught more than once by a pin that appeared to be soldered correctly but wasn’t. It’s good to hear that the extra grounding helped. It sounds like the disciplining code is overreacting. Try reducing the Gain Value as discussed on p85 of the second article and see if that stops the overshooting. We wonder if the micro is not detecting or counting the frequency correctly, which would also cause erratic behaviour. How does the 40MHz signal look, from pin 19 of IC2 through LK1 to the Micromite TX pin? Choosing a solar panel to charge a battery Thank you for your wonderful magazine. I’ve enjoyed assembling projects going back to Radio Television & Hobbies and have put together some 30-40 kits. I’m not good at theory but can follow construction guides to successfully complete most projects. Recently I built the 12/24V 3-Stage MPPT Solar Charge Controller Rev.1 (March 2012; siliconchip.com.au/ Series/29) but have not yet bought a matching solar panel. I have two Mobility Scooters and two Mobility Wheelchairs in my household; each is powered by two 12V gel batteries connected in series for 24V. All batteries are identical Sonnenschein GF1244Y rated at 44Ah (C5) or 50Ah (C20). The batteries in the two wheelchairs have just been replaced with new, identical batteries. Australia’s electronics magazine I intend to keep charged the old batteries as two separate 24V systems because they still have a useful life for other purposes. The solar panel I am considering is as follows: Maximum Power (Pmax): 250W Voltage at Maximum Power Point (Vmp): 37.8V Current at Maximum Power Point (Imp): 6.6A Open Circuit Voltage (Voc): 44.8V Short Circuit Current (Isc): 6.9A Type: Q-Cells Grade A Monocrystalline Maximum System Voltage: 1000V DC Operating Module Temperature: -45°C to +90°C These are, in some aspects, a little above those recommended in the original article from February 2011 (pages 40 & 41). Is this panel a satisfactory match, or should I look for another? (K. U., Sunbury, Vic) • The solar panel you have chosen is well-suited to the lead-acid gel-cell batteries you are using. Wideband Oxygen Sensor revisions I bought a Jaycar KC5485 Wideband Oxygen Sensor Controller kit. I want to use a Bosch 4.9 O2 sensor with the Bosch CJ125 control chip. Can I integrate that into your kit? Is there any upgrade? (T. M., via email) • The KC5485 kit is based on our original Wideband Oxygen Controller design from the September and October 2009 issues. That was superseded by an improved design (June-August 2012; siliconchip.com.au/Series/23). Both used the Bosch 4.2 wideband sensor with a microcontroller to control the sensor. They do not support the Bosch 4.9 sensor, which would require a new design. Both units provide a narrow band output to simulate a narrowband sensor for the engine so that you can replace the old one entirely. That way, the wideband sensor can be installed near the engine and accurate Lamdba readings taken with the engine controlled via the narrowband simulator output. As we are using a microcontroller in both cases, we are not using the Bosch CJ125 controller chip. It is not possible to integrate the CJ125 on either of the Wideband Controller boards we published. continued on page 96 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE FOR SALE KIT ASSEMBLY & REPAIR LEDsales VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com LEDs and accessories for the DIY enthusiast PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. SILICON CHIP ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. Some of the books may have already been sold, but most are still available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote, quote the number directly below the photo when referring to a book: silicon<at>siliconchip.com.au LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au TRONIXLABS PTY LTD would like to thank all of our customers for their support and feedback. For any enquiries or customer technical support, please email support<at>tronixlabs.com PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au DAVE THOMPSON (the Serviceman from S ilicon C hip ) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia’s electronics magazine November 2021 95 Advertising Index Altronics.................................69-76 Ampec Technologies.................. 13 ADI Maxim Integrated................. 11 Dave Thompson.......................... 95 Dick Smith Contest..................... 77 Digi-Key Electronics...................... 5 Emona Instruments.................. IBC Hare & Forbes............................ 2-3 Jaycar.............................. IFC,45-52 Keith Rippon Kit Assembly......... 95 LD Electronics............................. 95 LEDsales..................................... 95 Microchip Technology......... 7, OBC Mouser Electronics....................... 9 Ocean Controls........................... 10 Phipps Electronics...................... 85 PMD Way..................................... 95 SC Christmas Decorations......... 63 Silicon Chip Shop.................90-91 Silicon Chip Subscriptions........ 68 Solder Master............................. 15 Switchmode Power Supplies..... 12 The Loudspeaker Kit.com.......... 87 Tronixlabs.................................... 95 Vintage Radio Repairs................ 95 Wagner Electronics..................... 14 Next issue release The December 2021 issue is due on sale in newsagents by Thursday, November 25th. Expect postal delivery of subscription copies in Australia between November 23rd and December 13th. 96 Silicon Chip Controlling motor speed with an Arduino I want to build your June 2011 Motor Speed Controller (siliconchip.com.au/ Article/1035) using the Jaycar KC5502 kit. Can the external potentiometer be replaced by connecting to an Arduino for speed control? I have been purchasing motor controller boards from the website: www. dimensionengineering.com (Sabertooth 2x12 R/C boards). This alternative would be of great interest to my group of friends that also build Star Wars robots. I am scratch-building robots having left aircraft engineering after 36 years. One of my builds was in DIYODE magazine issue 3. (F. H., Engadine, NSW) • You can use an Arduino to control the June 2011 Motor Speed Controller via a pulse width modulated (PWM) output. The PWM signal is filtered to give a varying voltage to feed the Speed Controller. Disconnect the trimpot or potentiometer connected to the +IN1 input (pin 1) of IC1 and instead, connect the PWM output of the Arduino via a 10kW resistor. The supply ground of the Arduino must connect to the Motor Controller ground. PWM frequency should be set for at least 500Hz so that the 10kW resistor and existing 1μF capacitor at the +IN1 input provide a smooth DC voltage. The motor speed can then adjusted by varying the duty cycle of the PWM signal from the Arduino. A 50% duty will result in 2.5V DC at the Motor Controller input and will set the motor at full speed. A 0% duty cycle will turn the motor off. If you want the motor to run at maximum speed when the duty is set at 100%, change the 10kW resistor to 22kW and connect another 22kW resistor from the +IN1 input to ground. This will effectively halve the applied voltage. Details on using PWM with Arduino is covered in the tutorial at siliconchip. com.au/link/abb7 Transformer for 20W Class-A Amplifier Where can I obtain the 160VA 16-016V shielded toroidal power transformer for the 20W Class-A Amplifier Module project (May-September 2007; siliconchip.com.au/Series/58)? Australia’s electronics magazine In Leo’s April 2011 article titled “Fixing transformer buzz in the Class A amplifier”, he suggests using an 18-0-18V transformer when the mains is reduced to 230V AC (it’s around 239V AC here in Melbourne suburbia) and adding chokes which reduce the DC output voltage of the power supply by more than a volt. As ordinary 16-0-16V toroidal transformers are not off-the-shelf items (it’s either 15-0-15V or 18-0-18V), should I be looking to get an 18-0-18V transformer? In the 1998 15W Class-A amplifier version, its designers had lots of trouble with hum, even when using the transformer inside a steel box inside the amplifier chassis. Would an ordinary unshielded 160VA toroidal transformer be OK if placed about 400mm below the Class A amplifier PCB, as in the separate power supply version of 1998? (I. H., Essendon, Vic) • We checked all four articles and couldn’t find any mention of a source for the transformer. These were supplied with the contemporary kits but they have long since sold out. It was probably made by either Harbuch or Tortech. Regardless, either of them should be able to wind one for you. Email sales<at>harbuch.com.au or see siliconchip.com.au/link/abba Don’t forget to specify the electrostatic shielding. You should be able to use the 18-018V transformer. If the voltage ends up being too high, wind on extra turns in the opposing direction to the original winding for each 18V winding to reduce the voltage. But the chokes will probably drop the voltages enough. Placing the transformer in a separate box will reduce the hum significantly. 400mm spacing from the amplifier should be sufficient. If hum is still heard, try rotating the toroid to get the lowest hum or move the toroid further away. Finally, note that the 20W Class-A amplifier is essentially made obsolete by the Ultra-LD Mk.3 (July-September 2011; siliconchip.com.au/Series/286) and Mk.4 amplifiers (August-October 2015; siliconchip.com.au/Series/289), which have similar distortion (lower in the case of the Mk.4), significantly more power and higher efficiency. Importantly, they also do not suffer from the same hum problems that plague Class-A amplifiers. SC siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! 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