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FEBRUARY 2020 ISSN 1030-2662 02 9 771030 266001 The VERY BEST DIY Projects! 9 $ 95* NZ $12 90 INC GST INC GST IS THE AIR YOU BREATHE MAKING YOU SICK? Build this Micromite-based Home/Building Air Pollution Monitor Brendan’s Wonderful Wombat Warning Watchamacallit! Remotely monitor or control just about ANYTHING with a 4G phone . . . and get a text on your phone to let you know that something is happening! THIS MONTH’S FEATURE: Underground mapping, leak detection and pipe inspection awesome projects by On sale 24 January 2020 to 23 February 2020 Our very own specialists are developing fun and challenging Arduino® - compatible projects for you to build every month, with special prices exclusive to Club Members. PROJECT OF THE MONTH: DIY Mini “Tesla” This is an updated version of our wall dodging robot, but now with a rechargable battery pack so it runs just like the electric cars on the road today! It is fully automated once it gets going, and includes a light sensor so it never gets lost in dark places such as under beds or wardrobes. A motor shield is used to save room on the robotic platform. CLUB OFFER BUNDLE DEAL 9995 $ SKILL LEVEL: Beginner SAVE 25% SEE PARTS LIST & STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/diy-dodging-robot KIT VALUED AT: $133.85 See other projects at www.jaycar.com.au/arduino Essential Tools For Your Project 25W 240V Soldering Iron Ideal for the hobbyist and handy person. MINI GLUE GUN Fast, easy and simple to use with trigger controlled glue feed. 30W Mains powered. Supplied with 2 x 7mm dia. glue sticks. TH1997 Pk6 Spare glue sticks TH1991 $3.95 Stainless steel barrel and orange cool grip impact resistant handle. Fully electrically safety approved. TS1465 JUST 1395 $ 200G DURATECH SOLDER 60% Tin / 40% Lead. Resin cored. 2 sizes available. 0.71mm NS3005 1.00mm NS3010 HOOK-UP WIRE PACK ONLY 1295 $ 2 metres of 8 different colours of 13 x 0.12mm hook- up wire. 16 metres in all. WH3025 ONLY 15 $ ONLY 95 EA 25% OFF EXCLUSIVE CLUB OFFER COMPUTER ADAPTORS* *Includes Serial, DVI, VGA & USB adaptors. See T&Cs for details. Shop the catalogue online! Free delivery on online orders over $70 Conditions apply 495 $ YOUR CLUB, YOUR PERKS KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON! Visit: www.jaycar.com.au/makerhub www.jaycar.com.au 1800 022 888 Contents Vol.33, No.2 February 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 12 Underground mapping, leak detection & pipe inspection How do authorities know what pipes and cables are buried down there, especially when they start excavating? And fixing leaks can be a nightmare if the maps you have are not quite accurate . . . – by Dr David Maddison 38 We review: chipKIT’s new “Lenny” Lenny is a new PIC32-based Arduino to come out of the Microchip stable . . . or is that the Atmel stable? It uses the Arduino R3 footprint and layout so you’re getting the best of both worlds – by Tim Blythman 75 El Cheapo modules: 8-channel USB Logic Analyser Finding or troubleshooting the services buried under your feet can be a real art – or is it a science? – Page 12 You may recall the $150+ “Saleae” Logic Analyser we reviewed a few years ago. Here’s a clone out of China which has even higher performance but is just $13 including postage . . . less than one tenth of the price! – by Jim Rowe Constructional Projects 26 Remote monitoring station messages or emails by 4G! AKA Brendan’s wonderful wombat warning whatchamacallit . . . you can monitor just about anything and receive a text message on your phone if it’s triggered, sprung, intruded, flat, overcharged, out of water – you decide! – by Tim Blythman 44 Indoor Air Quality Monitor based on Micromite BackPack Volatile organic air pollutants are said to create a whole raft of problems, including “sick building syndrome”. This monitor gives a direct readout in parts per billion. It’s built around the mighty Micromite V3 BackPack – by Geoff Graham 68 Low distortion, two-channel DDS audio signal generator This very low distortion, two-channel audio signal generator produces sinewaves, triangle waves, square waves, pulse trains and noise. It has adjustable output frequency, amplitude and phase, plus sweep and pulse modes – by Phil Prosser 84 Building the new “bookshelf” stereo speakers This month we complete construction of our new bookshelf speakers. They’re compact and economical to build and you don’t need specialist tools or even a lot of woodworking experience – by Phil Prosser Your Favourite Columns 61 Serviceman’s Log When in doubt, swap it out – by Dave Thompson 94 Circuit Notebook BUSHFIRE APPEAL: Original “Serviceman” (1) Two 100Mbit Ethernet connections over a single Cat6 cable Cartoon Art (2) Metered variable power supply uses inexpensive modules (3) “In situ” Ethernet cable tester (4) Signal Generator output booster using LM1877 98 Vintage Radio See P37 for details of this unique offer! Tecnico-Aristocrat 651 from 1946 – by Associate Professor Graham Parslow Everything Else 2 Editorial Viewpoint 4 Mailbag – Your Feedback 83 Product Showcase siliconchip.com.au 104 Ask SILICON CHIP 106 SILICON CHIP ONLINE SHOP 111 Market Centre 111 Advertising Index 112 Notes and Errata Monitor just about anything – wombat traps included – and get a message on your 4G phone when triggered – Page 26 chipKITs new “Lenny” is a PIC32based Arduino which uses a close relative of the IC in a Micromite – Page 38 How’s the air quality in your home or office? Does it suffer from “Sick Building Syndrome”? This nifty unit uses a Micromite BackPack to measure Volatile Organic Pollutants – Page 44 We’re re-purposing some existing project boards to create a high performance DDS Audio Signal Generator – Page 68 Just about anyone – even you! – can put these high performing bookshelf speakers together! – Page 84 www.facebook.com/siliconchipmagazine SILICON CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc Bao Smith, B.Sc Tim Blythman, B.E., B.Sc Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Art Director & Production Manager Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson, B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (12 issues): $105.00 per year, post paid, in Australia. For overseas rates, see our website or email silicon<at>siliconchip.com.au 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. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 * Recommended & maximum price only. Printing and Distribution: Editorial Viewpoint IoT is a security nightmare The more I hear about the “Internet of Things” (IoT), the more worried I become about how vulnerable these devices will be to hackers, viruses and worms. Microsoft is a multi-billion-dollar company which employs thousands of experienced programmers, yet we frequently find out about severe vulnerabilities in their software. Many of these allow attackers to take over computers remotely. While these are usually patched soon after they are discovered, there are still plenty of ‘zero-day exploits’ out there. It’s just a constant stream of bad news. And it isn’t just Microsoft. Apple, Linux, Google (Android) and many other vendors and devices have had serious flaws discovered in the last twelve months. If these people can’t make a secure system, how can we expect a smaller operation cranking out millions of internet-connected devices to do better? And how much worse is the situation going to be when, instead of having just a handful of PCs and mobile devices in your home or office, you might have hundreds of devices? To make things worse, many of these will probably have out-of-date software, with no easy way to keep them up to date. And if the vendor has gone out of business, or has stopped supporting that particular device, you’ll be totally out of luck. One particularly breathtaking vulnerability I just found out about (which was discovered in 2017) is called “BlueBorne”. The name indicates that it is an airborne Bluetooth attack. I’m mentioning it now because of the sheer incompetence required for such a vulnerability to exist left me gobsmacked. BlueBorne is thought to have (at least initially) affected more than 8.2 billion (!) devices, and all it requires for an attacker to take over your device is for them to be within Bluetooth range. While most newer systems have fixed this, I bet there are still plenty of affected devices floating around. So, how could a set of related vulnerabilities affect Android, iOS, Linux and Windows devices? After all, most of those systems (perhaps excepting Android and Linux) are written by totally different groups of people. Did they all make the same stupid mistakes? How can a simple communications protocol allow random people to execute code on your device? The root causes of the most serious BlueBorne problems come back to what is now starting to sound like a broken record: stack and buffer overflows. Any code which receives data from a remote location into local memory has to be very carefully written to ensure that the memory buffer is large enough to fit the received data. Otherwise, the excess data can spill over into unexpected memory locations. This can be exploited to remotely inject new code into the software, which can then be used to download and execute more malicious code. That can be prevented by fundamental safeguards like data bounds checking, but it must be used consistently. It is just basic good programming practice. But it seems that whoever was in charge of implementing Bluetooth drivers wasn’t disciplined enough to do this, with the result that gaping holes were created in the devices’ defences. Most recent CPUs and operating system an ‘NX bit’ which helps to reduce the chance such a flaw can be exploited, but it can’t totally prevent buffer overflow attacks. It’s better to avoid having them in the first place. I really hope people writing software for IoT devices can avoid this sort of basic mistake, but I am doubtful. This type of problem is going to be multiplied by the number of different devices deployed. So what can you do about it? Not much, unfortunately. Just try to buy devices from vendors you trust (until they break your trust…), and keep their software up-to-date, or avoid them altogether. Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia’s electronics magazine siliconchip.com.au MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”. Notes on Toyota hybrid system It was great to read the article in the December issue of Silicon Chip about Toyota’s Hybrids. I have owned two Camry Hybrids, and both of them are great cars to drive. Most of what is written about Hybrids centres on their fuel efficiency, and while this is one virtue, my favourite aspect of these cars is the smoothness of the electric traction. It is like driving one of those silky-smooth early model Royal Royce cars, with an engine that you could balance a coin on, or so I am told. I like to think about the so-called Power Split Device (PSD) this way: The internal combustion engine (ICE) is coupled to the stator of the motorgenerator (MG1), while the rotor is connected to the wheels. I know this is not how the system works (it uses a planetary gear train), but it is a handy mental image to have when thinking about how the power is split working as I drive along. The gearing is such that, at about the same ratio that you would get in fourth gear with a five- or six-speed gearbox, the stator and the rotor of my aide-memoire arrangement are locked and are rotating as one. Your article didn’t show the situation where the car is driven fast and MG1 acts as a motor, using sustained power from MG2, which is then running as a generator. This operates as a sort of ‘over-drive’ to move beyond that ‘fourth-gear’ ratio. The main purpose of the PSD is to avoid the losses associated with a series hybrid system (as used in diesel locomotives), in which power is lost in the conversion of mechanical power to electrical power and then back again. Parallel hybrid systems also avoid this loss, but almost all of the vehicular implementations of such systems have the electric motor/generator permanently connected to the internal 4 Silicon Chip combustion engine or transmission shaft. As a result, whenever the electric motor is rotating, so is the ICE, with the large frictional losses that implies. The PSD tries to get the best of these two worlds, by allowing the ratio of rotational speeds to vary between the ICE and motor/generator, and also by allowing the ICE to stop entirely (or freewheel) while the vehicle is still moving. Many other carmakers are now using this power split system, while both parallel and series systems are used in diesel-electric submarines. The electronics that feed motorgenerators MG1 and MG2 do so with the usual variable pulse width arrangement of an H-bridge circuit, but this design also varies the switching frequency. While the hybrid battery voltage varies from model to model, it is generally around 200V DC. That is stepped up to 600V DC to drive the H-bridge circuits, presumably to suit the properties of the motor-generators. Several aftermarket kits are available to convert these hybrids to plugin electric vehicles. Surprisingly few modifications are required. The conversions mainly involve the addition of extra batteries, but how they integrate into the existing system is interesting. It is easy to intercept the car’s data management system to determine the state-of-charge of the hybrid battery. That state-of-charge information is used to control the power of a DC-DC inverter feeding power from the extra battery to the hybrid battery. The only modifications needed besides a few bolt holes to secure the extra bit of kit, are a single electrical connection to the hybrid battery and a connection the vehicle data bus. The hybrid battery is then always fully charged, and there is no need to use the ICE for shorter trips. Ken Moxham, Urrbrae, SA. Australia’s electronics magazine Comment: our article did mention the possibility that MG2 can act as a generator to provide power for MG1 at higher speeds, in the box at the bottom of page 50. However, as noted in that box, while such a mode makes sense, official Toyota documentation does not describe it. Toyota hybrid system is complex Roderick Wall’s article on Toyota’s hybrid system in the December issue was well worth reading. I never realised the system was so complicated. Even so, the end result justifies the complexity since simple methods of improving efficiency were exhausted a long time ago. The engineers and designers at Toyota should be proud of what they have achieved. But there is always a dark cloud hanging over all complex mechanisms, and that is maintenance and servicing, and in particular, fault finding. My neighbour has once again given me a reason to despair at the march of progress. It has to do with the complexity of the cars that he services and repairs, and especially the computerbased diagnostic systems. We were discussing the ability of the current generation of technicians to fault-find and their reliance on the computer-based diagnostic system. He told me of a particular car which would report a fault at start-up. Turn the car off and turn it on again, and it would indicate a different fault. Repeat, and it indicated a totally different fault. Thankfully for the customer, my neighbour is intimately familiar with this model and so quickly discovered the fault. So he was able to repair it, despite the red herrings that the computer was throwing up. So I feel sorry for the technicians who have to work on misbehaving vehicles with the Toyota hybrid system. While it works, it will be great, siliconchip.com.au siliconchip.com.au Australia’s electronics magazine February 2020  5 but once it develops faults, it will be pushing the abilities of technicians to the limit. George Ramsay, Holland Park, Qld. Response: proper automotive faultfinding indeed appears to be becoming a lost art, with an over-reliance on OBD2 scanners. I have brought a car to the dealer on more than one occasion complaining of a fault, only to be told (I’m paraphrasing) “the computer isn’t showing any codes so we can’t fix it”. As if I would bother bringing the car to them unless there was something wrong with it! It’s especially frustrating when you can describe the fault clearly, and there are only one or two components that could possibly be causing the fault, but they refuse to replace or repair them because the problem is not staring them in the face. Still, the Toyota hybrid control computers likely have comprehensive diagnostics which would inform technicians of the location of a problem with minimal fuss. And this hybrid system has proven to be very reliable – it is used in many taxis, some of which have racked up one million plus kilometres! So we would not recommend anyone avoids this system just because of its complexity. Toyota Hybrid article enjoyed Roderick Wall’s article in the December 2019 issue (siliconchip.com. au/Article/12172) was a very informative read; I’ve often wondered about the internal workings of the Toyota Prius and other similarly powered vehicles. This is motor vehicle technology at its best. However, the article didn’t go into any great detail on the function of the rechargeable battery, specifically in terms of charge and discharge cycles. I have long wondered how batteries with their limited numbers of charge/ discharge cycles can last for so long in this application. Typically, it is said that Li-ion batteries can be expected to supply 1000 or so charge/discharge cycles before performance deteriorates to something around 80% (so it is said for mobile phones). NiMH batteries purportedly support even fewer charge/discharge cycles. Having said this, a friend of mine has owned a Toyota Prius for more than 10 years, and it’s still on the origi6 Silicon Chip nal NiMH battery. I would appreciate it if Silicon Chip can throw some light on this subject. Geoffrey Richardson, Denistone, NSW. Response: A future article on electric car/bike/etc batteries is a good idea. We’ve put it on Dr Maddison’s list of possible future articles. Our understanding is that longer life is usually achieved by avoiding fully charging and discharging the battery. That also gives some room for degradation without noticeably affecting the capacity/range. It certainly is impressive that the Toyota NiMH packs last so long. We suspect that they’ve adjusted the cell chemistry to favour life over capacity. Note that while Li-ion batteries are generally limited to around 1000 charge/discharge cycles, that’s based on full charge/discharge cycles. The cell life is considerably longer if that can be avoided, especially full discharges. Temperature inversion causing TV reception problems On the 28th of December 2019, from about 8:30pm to 10:00pm, we had an event where the higher frequency VHF TV channels in the Sydney area “disappeared” due to a phenomenon known as tropospheric ducting (see siliconchip.com.au/link/aaz1). It was apparently an extreme event, according to the following website: www. dxinfocentre.com We live about 10km south of the transmitters in a hollow (with no line of sight), so this affects us now and again around summertime, but never to this extent. I’d be interested to know if anyone else has had a similar experience. Denis McCheane, Allawah, NSW. Old double adaptors are not very safe Regarding your article in the December 2019 issue on “The Electrical House of Horrors”, it reminded me of the double adaptor shown in the accompanying photo. I purchased it in Sydney way back in 1962. Note how, on one outlet socket, the Active and Neutral pins are swapped. I think that was legal back then. The adapter is branded ELMOCo and rated for 250V, 10A. I don’t use it now; I just keep it as a souvenir. By the way, I used to work Australia’s electronics magazine for Pye at Marrickville, then later AWA at Ashfield. Those were good days, when electronics were locally manufactured. Graham Street, Auckland, New Zealand. “Suicide leads” considered harmful Your article on emergency backup power (January 2020; siliconchip.com. au/Article/12215) was timely given the potential loss of power this time of year from the extreme summer thunderstorms, system overload due to air conditioning loads and potential damage to electrical distribution networks from bushfires. However, I would like to add a warning to anyone who might be tempted to skip using extension leads to each appliance and liven up a whole power circuit from a generator or inverter by using a suicide lead (ie, a lead with male three-pin plugs at each end). This is a very dangerous practice, and it is more common than you would expect. I had this hammered home to me when I was very young when a university science student that I knew was electrocuted using such a lead. Peter Chalmers, Brisbane, Qld. Response: We have heard of such things, but it’s hard to believe that any of our readers would do something like that. Raspberry Pi volume control I am writing to congratulate Tom Skevington on his contribution (December 2019; Mailbag) to make the TDA1543A DAC chip work in the speech synthesiser project (July 2019; siliconchip.com.au/Article/11703). I ordered the PCB and TDA1543 from the Silicon Chip Online Shop, but unfortunately, I was provided with TDA1543A chips, so I ran into the same difficulties as Tom. His modification saved the day. siliconchip.com.au I would also like to describe how it is possible to provide a master volume control for the “hat”, which can be done in software. The Pi operating system images are all loaded with alsamixer, which controls the volume level of your selected audio output. To make alsamixer work with this project, edit or create a file named “/etc/asound.conf” using your favourite text editor and put the following in it: pcm.hifiberry { type softvol slave.pcm “plughw:0” control.name “Master” control.card 0 } pcm.!default { type plug slave.pcm “hifiberry” } This mod works as-is with either the TDA1543 or TDA1543A chips with no changes. To adjust the volume, type “alsamixer” on the command line, which brings up the graphical screen, and use the up/down arrows to change the volume and ESC to quit. This will also work over a serial connection, as long as you are using a suitably capable terminal emulator and have set the correct terminal type. When logged in using SSH, you can also use your mouse to control the master volume. Alternatively, the volume can be to any percentage via the command line like this: amixer set Master 50% Brian Roberts, Eaglemont, Vic. Comment: it appears that our suppliers are now sending either TDA1543 or TDA1543A chips, depending on what they can get. We’ll see if we can get some TDA1543 chips as that version was used in another project (the Bad Vibes Infrasound Snooper from July 2015). At least the A-suffix chips can be made to work with the relatively simple changes provided by Tom Skevington (which can be downloaded from siliconchip.com.au/Shop/6/5097). Making a parabolic reflector from a lampshade I was interested to read the letter siliconchip.com.au asking about parabolic sound reflectors from D. H. in the Ask Silicon Chip section of the December 2019 issue (page 108). I was after some sort of directional reflector for my video camera (it doesn’t have an external microphone input). I intend to use it mainly for recording operating stationary engines at old machinery meets, where all the engine sounds tend to blend into one. I started off using a rather large acrylic bowl, cut to fit over the front of the camera, with its front microphones roughly in the centre and somewhat near the focal point. I fashioned a bracket to screw it to the shoe fitting hole. It worked reasonably well, but was rather large and cumbersome and prone to pick up extraneous noises when it came into contact with objects. I also got plenty of odd looks and questions when using it. I then decided to try to design one which could be made using my 3D printer. I found making this design to be quite fun. While I was working on that, I happened to look up into a desk lamp and noticed that it was roughly the size and shape I needed. I happened to have an old lamp in the shed, so I went and checked it out. It seemed to be ideal for the task. Using the acrylic reflector as a rough template, I set about fashioning a new one out of the lampshade. It works quite well; I am now able to reasonably separate fairly noisy and quiet engines several meters apart. Fortunately, the camera has provision for microphone gain attenuation, which is needed. I don’t really know how close to the focal point the mics are, but they are facing the wrong way anyway, so I’m not terribly concerned. As well as being smaller and stronger than the original unit, it made the camera easier to use, gives better results, and a lot fewer odd looks. Keep up the good work with the magazine. Brian Playne, Toowoomba, Qld. Regulating via the mains transformer primary I follow your magazine every month and have done so since it first started. During this time, you have published many bench supplies and similar power supplies. Australia’s electronics magazine February 2020  7 A letter in the Mailbag section of the December issue titled “A handy trick for linear power supplies” (starting on page 6) from Roger Curtain describes a method for reducing dissipation in the output devices by regulating the mains transformer primary voltage. I did something similar years ago where I needed to supply 60V at 10A, and for a linear supply under short circuit conditions, that means it must handle a very high dissipation, requiring a huge heatsink. I produced a small circuit board which sampled the voltage across the regulator transistors and then fed a control voltage to a zero-crossing detector, which controlled a Triac feeding the primary of the mains transformer. The regulator was a fairly standard series linear regulator. This kept the series element dissipation level low, and provided good regulation at the same time. Bill Bool. New Plymouth, NZ. Solar Shed uses Victron solar charger I was so impressed when I read the article on Emergency backup power supplies in the January 2020 issue (siliconchip.com.au/Article/12215). I have had a two-year journey and have ended up with a power system which is similar in concept to what you have built. Like so many projects, it started as “I need a light in my new shed”, with a fairly simple (but typical) solution of two SLA batteries from eBay, a 40W solar panel and 28W internal light (both from Jaycar), a cheap PWM eBay charger (marked MPPT) and two lowcost external lights. Cut to today, and I now have two 200W panels, an excellent Victron charger, eight of the 12Ah SLA batteries (about $30 each) and a serious Jaycar inverter fed through a 200A circuit breaker. The Victron app is excellent, and shows that the panels can deliver their rated power. This system powers internal and external shed lights, charges all our power tools including a Ryobi 36V brushless mower, powers the water feature and provides 230V AC power for when the mains disappears (50W continuous in summer). Our fridge is not overly big, it draws an average of 50W, so this system can keep it going in a blackout. We can also charge phones etc, and boil the occasional camping kettle. I realise that the SLAs have a limited life, but $240 every 3-4 years is OK in my view, until Li-ion costs reduce more. The good thing is that the Victron charger has an algorithm for almost any known battery. And I can even add two more panels, pairing up the 12V panels to deliver 24V to the Victron unit, which can still charge a 12V battery bank. Rick Arden, Gowanbrae, Vic. More evidence that many UPSs don’t last long I find your article on Emergency backup power (January 2020; siliconchip.com.au/Article/12215) to be timely. I purchased a UPS from a reputable retailer in April 2017. Then in December 2019, I noted that the battery indicator percentage on the display had started dropping, even though mains power was available. I put my hand on the unit, and it was stinking hot, even though the ambient temperature was 23°C. Clearly, this needed further investigation. 8 Silicon Chip Australia’s electronics magazine So I disconnected it and removed the cover pronto. Well! The transformer was hot enough to cook eggs on, and the batteries were not touchable. I was amazed that neither had ruptured. If I had left it much longer, I am convinced that was on the cards. As you can imagine, I am not happy. I lodged a complaint with the retailer and am awaiting a response. This raises the spectre of a device that is not particularly safe, and one I now have little confidence in. The time and effort required to remove the batteries (a job that should be simple) suggest it was not designed to be repaired or even maintained. While this UPS has venting of sorts, there are no fans. It is a triumph in bad design as far as I am concerned. It is obvious that there is no protection against a battery dropping a cell. It reminds me of early alternators in cars, where the battery would fail, and the alternator would boil it dry, resulting in a fire. I’ve seen several. As a consequence, when a car battery fails, I don’t jump start it and drive it to get a new one. While there is a primary fuse in the UPS, the danger lies in this thing having no detectable thermal protection either on the batteries or the transformer. It would not take much to put a thermal resettable fuse on its transformer. Also inconceivable is the placement of the circuit board. A solid board on top of a hot transformer, restricting airflow and offering the heatsinks on top of it little air. Not very clever! Speaking of heat-related problems, I’ve also had some issues since our old fuse box was ‘upgraded’ with RCDs and circuit breakers. Unlike the old fuses, they are temperature sensitive. So after a 43°C day, when my water pump fires up it trips the circuit. It can’t be resolved until the temp drops well below 40°C. I’ve checked the pump, and it has no significant Earth leakage. The next-door neighbour did, however, recently have a grey water pump fail with significant Earth leakage, and had their insurance company not required that they upgrade their fusebox, the house may have been razed. When the electricians opened the box to replace it, it was black inside and hot. Marcus Chick, Wangaratta, Vic. siliconchip.com.au Impressive Christmas lights display Rather than sending you a problem with a kit, I thought I’d send you some information of a completed project based on a Silicon Chip design. This is one of the more impressive I’ve come across recently. I’ve been helping a customer who’s built a setup using your Christmas Lighting Controller (October-December 2010; siliconchip.com.au/Series/14) from an Altronics kit (Cat K5885 plus four Cat K5887 DC slave units). There were some minor issues along the way, such as modifying some of the boards to run off voltages outside the intended range to accommodate particular strings or displays. Also, the 10kW resistor used to count the number of attached units giving some problems (it had to be left off one unit for everything to work). All the problems were eventually sorted out, and the results are rather amazing. The whole system ran for December without problems. He was also collecting donations for the Alzheimer’s Research Foundation during the display. An FM transmitter is provided for those wanting to listen along to the light show. It’s probably the most professional looking setup I’ve seen. They’ve posted a video of the 10 Silicon Chip system in action: https://youtu.be/ mBgLltJ5br8 I always enjoy seeing the result of these more complex builds, so I’m sure your readers would also enjoy seeing how your designs are being used. We very recently discontinued the Cat K5885 kit due to sales slowing to almost nothing, so it would be nice if you could revamp the design, perhaps using the “NeoPixel” RGB LEDs you described in your January 2020 issue (siliconchip.com.au/Article/12228). If you do that, please consider adding an RF link using nRF24L01+ modules, with support for addressable LEDs alongside direct LED string driving. Tom Skevington, Kits Manager, Altronic Distributors Pty Ltd, Balcatta, WA. Tiny Xmas Tree is a hit I am just writing to say we had a bit of a breakthrough here at home. I bought two of your Tiny LED Christmas Tree kits a couple of weeks ago (November 2019; siliconchip.com.au/ Article/12086) and last night, my nineyear-old daughter and I built one each. It was my daughter’s first attempt at doing an electronic kit, and she was totally absorbed in the project and is busting to do another. She had one LED around the wrong way, which I made her diagnose and fix herself – all part of the experience. I am very glad she’s so enthusiastic, especially considering the kit was all surface mount components. I think you guys have hit the perfect size project for raw beginners in that the project goes together fast, low component count, many similar components and the kit containing the battery. She’s suggested making the same circuit on PCB shaped as Christmas tree decorations, reindeer, bells, baubles etc. It was also my first attempt at building with surface mount components, which I’ve been avoiding like the plague. I found the process quite easy, probably more enjoyable and quicker than through-hole. Thanks for the great project Anthony and Annabel Brazzale, Bumberrah, Vic. Response: the idea of putting the same circuit on differently shaped (and presumably, coloured) PCBs is a good one. We think we will do that in time for Christmas 2020! Australia’s electronics magazine Disagreement over purpose of antenna coil In reference to the Ferris 106 portable/home/car radio described in Vintage Radio, December 2019 (siliconchip.com.au/Article/12183), my attention was drawn to the description of the inductor L1 in the aerial input circuit. Most car radios include this coil, consisting of a few turns of wire, as an ignition filter. It is designed to introduce a high impedance for ignition interference. Refer to the fourth edition Radiotron Designer’s Handbook. Chapter 35, section 8 covers the design of car radios. L1 is described as “a choke, consisting of a few spaced turns of thick wire, resonant to about 40Mc/s. It is used to minimize incoming ignition interference without seriously affecting the desired signals.” The example aerial input circuit is, in fact, identical to that used in the 106. Given the few turns of L1, it would have virtually no effect as a loading or matching coil at MW frequencies. In any case, the design of the aerial coil itself is such that the primary winding resonates just below the broadcast band when fed from an aerial of correct capacitance. Typically, a car aerial has a capacitance of less than 100pF, and part of this is due to the coaxial transmission line. In this regard, if the transmission line is replaced with another type, or its length changed, it may not be possible to peak the RF input circuit of the radio. Similarly, if the set is peaked with the aerial partially retracted, RF alignment will be out when it is fully extended. Concerning the knobs, the set referred to on the Radio Museum site is fitted with old 1940s Bakelite knobs. The knobs shown at siliconchip.com. au/link/aay3 are those fitted to my set, and are likely to be the correct ones, being made of a later coloured thermoplastic. Also, further information on the 30W inverter used to power the 106 for in car use can be found here: siliconchip.com.au/link/aay4 John Hunter, Hazelbrook, NSW. Ian Batty responds: Thanks for the information about the knobs and inverter, but I must disagree with your statements regarding inductor L1. While I don’t have a Ferris 106 to check out, the antenna circuit of the Kriesler 41-21 is similar. It also has an “L1”, in this case, siliconchip.com.au wound onto a 3.9kW 1W resistor. I coil is effectively a self-contained par- and I thought that it might be interestmeasured it at around 100µH, which allel resonant (band-stop) circuit, but ing to show what the original knobs etc is way too high for self-resonance at now we’re back to trying to find some look like as they are not the same as 40MHz. But even if it were resonant rational reason for blocking out a fre- shown in the “Radio Museum” link. I at 40MHz, it wouldn’t have the effect quency some 30~80 times the design have sent a couple of photos of my set. described in the Radiotron Designer’s tuning range of the set, which makes The only repairs I had to make so far no sense. I’ve looked at similar coils were to replace the loudspeaker transHandbook. A car radio, with a tuning range of in other sets (the physical similarity former (years ago), then more recently, 535~1605kHz, would not respond to implying a similar amount of induct- I found capacitor C7 was shorted, so a 40MHz signal of ordinary strength. ance and thus a similar self-resonant I snipped its leads. I didn’t know its Such a signal would need to be many frequency), none of which had few value at the time (I realise now it’s a volts at the antenna terminal to make enough turns to be self-resonant at 50pF mica type). I don’t know what it past the antenna tuned circuit; these 40MHz. it’s supposed to do, as the radio works Given the low value of the shunt re- perfectly without it. are highly selective. One concern with this sort of inter- sistor, if it were resonant at 40MHz, the Christopher Ross, ference is that the RF amplifier/con- bandwidth would be broad enough to Tübingen, Germany verter could go into grid rectification drive a B double through, sideways. Assoc. Prof. Graham Parslow responds: with a signal of sufficient amplitude. I measured the 41-21’s L1 (100µH) Since I wrote the article, Radio MuBut immunity to grid rectification is a and found it self-resonant at around seum has changed the photo in their 3.8MHz, with some ±1MHz of band- entry for the Ferris 106. It’s not at all principal reason that weRAYMING use remote TECHNOLOGY width (-3dB). cutoff valves as RF amps PCB and convertclear why they have done this, since Manufacturing and PCB Assembly Services I therefore must conclude that the ers (yes, it’s useful for AGC, but you the new photo not only shows a set Fuyong Bao'an Shenzhen China Radiotron Designer’s Handbook is ei- in poor condition but it also has the can apply AGC to any valve). The fact is that there 0086-0755-27348087 is no simple ther in error in the description of the wrong knobs. I appreciate you trying Sales<at>raypcb.com electrical circuit at the antenna input purpose of this coil, or was describ- to assist in this matter. Your radio does (comprising resistors, inductors and/ ing a coil of very different inductance have the correct knobs. www.raypcb.com or capacitors) that can selectively im- than any I’ve found in the sets I’ve The 50pF capacitor C7 is also an prove the noise figure of a receiver. For examined. enigma to me. I have briefly looked at To summarise, I assert that no an- other portable RF amplifier circuits a simple single-conversion superhet, tenna input circuit can selectively im- from Philips and HMV, and they have whatever the signal-to-noise ratio is at the antenna terminal (including inter- prove the desired signal’s power rela- no equivalent tap on the transformer ference from ignition etc), that is what tive to that of an interfering signal. In secondary connecting to such a feedany linear, analog system, the noise back (or feedforward?) capacitor. It’s you get at the speaker. Consider also that this inductor is figure at the input terminal cannot be interesting that they went to the trouin series with the antenna, which in improved electronically. ble of tapping the IF transformer if it For example, Dolby Noise Reduction has little or virtually no effect on pera car, behaves like a capacitor. When you have a capacitance in series with applies frequency-selective correction, formance. an inductance, you get a low imped- and is thus is not strictly linear. I remember hearing something ance at the resonant frequency, not a vaguely about it making the response Vintage radio knobs & unnecessary high impedance. more even over the whole MW band, In other words, the result will act a capacitor or something like that. I was most interested in Graham bit like a bandpass filter. Hence, I agree I have now managed to locate a with Assoc. Prof. Parslow’s assertion Parslow’s article on the restoration of set of the correct knobs for my Ferris that it’s there to improve the match- the Ferris 106 portable in the Decem- 106, so I have taken a good photo of ing of a highly capacitive antenna to ber 2019 issue (siliconchip.com.au/ the set and submitted it to Radio MuArticle/12183). the antenna tuned circuit. seum, with a request to replace the I have one in very good condition, current picture. You can argue that a self-resonant SC RAYMING TECHNOLOGY Fuyong Bao'an ,Shenzhen, China Tel: 0086-0755-27348087 email: sales<at>raypcb.com web: www.raypcb.com PCB Manufacturing and PCB Assembly Services siliconchip.com.au Australia’s electronics magazine February 2020  11 by Dr David Maddison As you walk along any street, you probably have no idea of the many pipes, cables, conduits, tunnels and other structures that are right under your feet. For utilities, this makes excavation difficult; a digger blade going through a gas, water or electricity mains or a major internet cable is a disaster! Technology comes to the rescue with techniques to find and map what’s underground. T he ability to locate underground utility services is important for several reasons: • The location of old services might not be accurately recorded on maps, if marked at all. • Underground service density is increasing, and in some urban areas, it has become extreme. • While digging to add more services, there is a desire to avoid damaging existing services. • There needs to be minimal disruption (and restoration cost) during and after such digging. 12 Silicon Chip • The high and increasing population density of Australian (and other) cities requires more underground services. The roll-out of the Australian National Broadband Network (NBN) has created a large demand for utility location services, as new cables are being installed in virtually every street. Existing services need to be accurately located; in many cases, existing Telstra conduit is used, but these are not necessarily accurately mapped. Additional challenges are provided by the now-wide- Australia’s electronics magazine siliconchip.com.au Finding an underground utility the hard way! This gas pipeline was breached by a digger in Los Angeles, 2016. Image from   https://youtu.be/nBBANQU4PlM spread use of plastic pipes for water supply, replacing traditional metal pipes. “Plastic” gas pipes generally have an aluminium layer, so are more easily detectable. New technologies enable the location of underground services which were previously not easily locatable without digging. Underground utility location relies on the physical properties of the services being looked for. There must be some property of the utility that contrasts with the surrounding material. This might be due to something being carried in a pipe (gas or liquid); backfill material which is a different composition or consistency than the surrounding earth; or properties such as emission of electromagnetic radiation (eg, mains hum from power cables). If the utility being searched for doesn’t possess a suitable contrasting property, it can be enhanced. Methods to do this include energising an electrically conducting utility like a wire, cable or metal pipe with a suitable electromagnetic signal, or the insertion of a transmitter inside a pipe that transmits an electromagnetic, magnetic or acoustic signature. In the case of a broken or shorted electrical conductor, time-domain reflectometry (TDR) can be used to find the location of the fault In the case of fluid leaking from a pipe, visual evidence may be found at the surface, or acoustic methods can be used to find the leak. For a gas leak, the smell may give the Fig.1: finding a buried cable using electromagnetic induction in Germany around 1910. The search coil is wrapped around a roof truss. A very large coil was needed, as there was no convenient means of signal amplification at the time. location away; chemical sensors can also be used, along with acoustic detection methods. Technologies also exist for inspecting the interior of pipelines, some of which are described below. It is important to note that no single instrument can detect or examine all underground utilities. A variety of different tools are needed depending on the type of utility, its construction material and the particular local conditions. You may remember an article on “Horizontal Drilling for Oil” in the July 2016 issue, which had a section An augmented reality model can help plan an excavation in an urban environment with a complex layout of utilities. This could even guide an excavator operator in real-time. See the video titled “Augmented Reality Underground Utilities” at https://youtu.be/KS_5OHoHHuo siliconchip.com.au Australia’s electronics magazine February 2020  13 Fig.2: the principle of passive or active electromagnetic locating. A metallic pipe or cable is energised with a lowvoltage AC signal (by induction in this case), and an operator uses a detector to find the area of highest signal strength. External energising is not necessary if the cable already carries an AC signal. The signal can bleed onto other utilities when lots of cables or pipes or buried together, making detection of a specific pipe or cable difficult. on directional drilling for installing utility cabling and pipes. That is related to this topic, but we won’t go back over that ground here. Earliest underground mapping Electromagnetic induction (similar to what is used by modern metal detectors) was used from around 1910 to find buried cables. The first patent awarded for a metal detector went to Gerhard R. Fisher in 1937 for his “Metalloscope” (US Patent 2,066,561). One of the stated uses for it was to find buried pipes. The company he founded, Fisher Labs, is still operating today and makes utility-finding equipment among other things; see www.fisherlab.com/industrial/ What is to be detected The following underground objects may need to be detected or located: • power cables (AC or DC, high or low voltage) • telephone and other telecommunications cables including copper and optic fibre • sewer, drinking water, stormwater or gas pipes (metal or non-metal) 14 Silicon Chip Fig.3 (left): the Schonstedt RD5100H2O+ transmitter (grey box) and handheld receiver unit, for passive or active location of electrically conductive utilities. • irrigation pipes • traffic signal cables • voids, such as tunnels or underground tanks Unexpected objects which may be encountered during digging, besides the above, include: • underground storage tanks • septic systems • old building foundations • artefacts of archaeological interest • buried rubbish Overview of location methods There are a variety of methods that have been developed to find the above. At the most basic level, underground services can be located visually, such as by observation of surface penetrations like access covers. Recently-buried cables or objects may also be marked on plans which have been filed with the appropriate authority (councils, etc). Utilities which are not found via either of these methods can be located by either passive or active means. Passive methods of location include: • detecting energy leakage from a cable, such as 50Hz mains hum from a power cable or RF noise from an unrelated RF source such as a low-frequency transmitter Fig.4 (right): the RD5100H2O+ at work, with the transmitter connected to a utility and handheld receiver unit in the background. Presumably, the Earth wire is being traced as the transmitter is connected to the body of the metal pole. The transmitter can also be used in an inductive mode, with or without a clamp. Australia’s electronics magazine siliconchip.com.au Fig.5: active location, where the yellow transmitter box is connected directly to a pipe and a ground stake provides the current return path. Image from video “Schonstedt’s Principles of Pipe & Cable Locating” at: https://youtu.be/ ACOHwbov19g • noise from an active water or gas leak, or other noise generated by a fluid pipe such as the sound of fluid rushing through it • perturbation of the earth’s magnetic field by a buried ferrous object such as steel pipes, or the field of a magnet inserted into a non-ferrous or non-metallic pipe, or a magnet buried as a marker. Active methods of utility finding involve injecting energy into the utility line of interest, then detecting that energy with a separate receiver. Forms of energy injected might be RF energy for an electrical conductor, sound energy for plastic water or gas pipes, or sound from a miniature transmitter on an extendable rod (rod and sonde method). Other methods include looking at bulk soil properties such as resistivity to reveal the presence of underground structures, or to determine soil electrical properties. Sometimes dye or radioactive markers are injected into a gas or liquid line if only the outlet needs to be established, and not the route. Visual methods Visual location is the most basic method of finding underground utilities. A series of access covers can indicate the path of an underground cable or pipe. The danger in Fig.7: the Radiodetection RD-1500 GPR software can interpret a series of GPR vertical ‘slices’ to produce a map for a particular depth. The two red lines on the left image show the slice depth. siliconchip.com.au Fig.6: the result from a ground-penetrating radar showing several detected utilities. GPR scans require some interpretation. Figure courtesy of https:// undergrounddetective.com this approach is that it requires the assumption that cables or pipes run in straight lines between access covers, pits and junction boxes. Other things to look for are above-ground valves, marker posts and warning signs, kerb markings and damaged surfaces indicating that area has been dug up before. Sometimes partial excavation can also help to establish the likely path of the utility. Electromagnetic methods Electromagnetic methods are the most common methods used for finding underground utilities. Of these electromagnetic methods, passive and active detection and groundpenetrating radar (GPR) are the most frequently used. For passive or active detection, a metal utility cable or pipe is energised with an AC signal, and the radiated magnetic field from this is then detected with an appropriate receiver. Passive location can be used if the utility naturally radiates a signal. Fig.8: the MALÅ Object Mapper is a software package that can be used to plot GPR data on a Google Maps image. The black lines on the top image show the path of the GPR machine and the coloured crosses represent utilities found from the vertical slices shown at right. Australia’s electronics magazine February 2020  15 Fig.9: a typical Ground Penetrating Radar (GPR) machine in operation. It is pushed along the ground like a lawnmower, and data is recorded as a function of position. Fig.10: the AML Pro uses a 2.45GHz beam and is said to be able to find plastic pipes or any buried object that has an edge, including metal pipes. In this case, only the receiver is needed. Active methods Passive electromagnetic detection The passive method can be used when there is already an alternating current flowing through a cable. Sufficient current flow is required for the radiated signal to be detectable. Some cables also radiate signals due to coupling of long-wave or medium-wave radio stations. One problem with this method is that the signals are liable to change without notice. Another problem is that it can be challenging to differentiate between multiple cables, since the same signals might travel in all of them. Single-phase power cables radiate strongly at mains frequencies and related harmonics but three-phase cables radiate much less, as the phase fields tend to cancel out if the current flow is balanced. For finding three-phase cables, lower radio frequency signals present in the environment that naturally couple into cables can be detected by many types of locating receivers (via a “radio” setting). But in this case, performance varies based on how well the cables are grounded, the soil conductivity and the line length. The main advantages of passive detection are that it is fast, and only a receiver is required. But it can miss unexpected cables and pipes which may not be radiating anything. Fig.11: a French airborne magnetic survey from a drone, looking for unexploded ordnance (UXO). The rectangles represent unexploded shells (obus) and their orientation, horizontal or vertical and dimensions. Source: ECA Group. 16 Silicon Chip In the active method, an AC signal from a transmitter is induced into a utility service of interest that is to be traced. Unlike the passive method, specific lines can be positively identified and traced, which is very useful when there are many services in the same place. With some detection devices, the frequency of the injected signal can also be changed to suit conditions. Direct injection is the best and most reliable method. The transmitter is connected via a clip to a bare metal surface of the conductor under investigation. If that is not possible, a clamp around the pipe providing inductive coupling is the next best method. This is a similar arrangement to a current clamp meter, but operating in reverse. If that is not possible, an induction unit can be placed on the ground above the pipe to provide inductive coupling, but the amount of coupling in this case is small, and consequently, the received signal can be weak. This method can also be used for plastic pipes if the installer takes the small amount of trouble to install a tracer wire at the time of installation. It might also be possible to insert a metallic conductor inside an existing plastic pipe; see the section below on the “rod and sonde” method. Multi-frequency tracer units allow you to choose a frequency appropriate for the soil and other conditions. The Fig.12: a handheld magnetometer, the Schonstedt GA72Cd Magnetic Locator. This can be used to find UXO, and the military version is also used in de-mining operations in war zones. It looks for ferrous materials and does not respond to aluminium, brass or copper. Australia’s electronics magazine siliconchip.com.au DIY pipe, conduit and leak locating Fig.13: a concrete slab marked with the location of rebar and conduit, found with GPR. Image from www.ladsqld. com.au/services/concrete-scanning lower the frequency, the better it keeps to the line being located, and the less is radiated to nearby lines. However, there is also less chance of it passing through interruptions on the line such as joins and splices. It will also travel further. A higher frequency travels over joins better but does not travel as far along the utility. Generally, it is better to use a lower frequency if possible. As an example of frequencies available, the Schondstedt RD5100H2O+ detector has options for 4kHz, 8kHz, 9.8kHz, 33kHz, 65kHz, 83kHz, 131kHz and 200kHz. When it is using a sonde (see below), frequencies of 512Hz, 640Hz, 8KHz and 33kHz can be used. Ground-penetrating radar In ground-penetrating radar (GPR), the beam is directed downward into the soil to find buried objects. The frequencies used are in the range of 10MHz to 2.6GHz. Buried objects have a different electrical permittivity to the surrounding soil, so radar signals are reflected, refracted or scattered back to the surface. GPR uses include finding pipes (including plastic types), cables, underground voids and tanks, underground structures like old building foundations, buried pits, valves and tree roots. The performance of GPR is strongly dependent upon soil conductivity; higher conductivity soils attenuate the radar signal more. Lower-frequency signals penetrate soil further but offer a reduced resolution. GPR performance is consequently a compromise between resolution and soil penetration. You can make your own device to locate non-conductive pipes such as PVC. You push a wire up the pipe, which is attached to a signal generator. The signal is detected with an AM radio at approximately 760kHz. See the YouTube video titled “Homemade Electronic Plastic Pipe Locating Device(Circuit)” at https://youtu. be/NtI4ZPjsKqM It is claimed to work for pipes buried under concrete slabs as well, but it does not work on metallic pipes. Note that we haven’t tested this device. You can also use an acoustic method to detect a water leaks from a pressurised water pipe. This involves a length of PVC pipe as an acoustic waveguide, a foam cup and a stethoscope. See the video titled “DIY water leak detector” at: https://youtu. be/wfitM1KT8BM You can use a DIY method to trace a metal pipe or conduit, using a fixed frequency oscillator IC such as the MCO-1510A, and a transistor radio. This is shown in the video titled “DIY Wire/ Conduit Tracer” at: https://youtu.be/Ss6BWOsXiW8 GPR penetration through ice is excellent; ground can be detected several kilometres beneath the ice in Antarctica, compared to just a few centimetres of penetration in highly conducting soils. In Australia, GPR is said to be popular in WA due to favourable (dry, low conductivity) soil conditions but less popular in Victoria due to less favourable (moist, higher conductivity) soil conditions. The AML Pro series of underground utility locators (www.ssilocators.com/products/AML-PRO) use 2.45GHz beams to look for density differences in the subsurface. These are said to be able to locate plastic pipes or any other underground object with an edge. It is said not to suffer from the deficiencies of ground-penetrating radar and will work in clay, wet soil, snow or even standing water. For more on the AML Pro, see the video titled “change in densities” at https://youtu.be/U-Z0JgdIvMk Magnetometry Buried objects can be weakly magnetic, or cause perturbations in the earth’s magnetic field. These can be picked up by a sensitive magnetometer. Apart from archaeology and mineral surveys, magnetometry can be used to find buried Fig.14 (above): the MIRA Tomographer. Fig.15 (right): a 3D tomographic view of a concrete structure made with the MIRA Tomographer. siliconchip.com.au Australia’s electronics magazine February 2020  17 Sh W Lo Open conductor A large positive trace. Short circuit A negative trace. Cable splice/joint A small positive followed by small negative. T joint A negative trace followed by long positive. Wet splice/water Short positive/negative trace Fig.16: a Megger TDR2050 TDR in use. See the video titled “TDR2050 introduction, function and operation” at https:// youtu.be/SjAonwhZqVk ferrous objects such as utility pipes. This technique can also be used to find valve boxes, steel enclosures, manhole covers, marker magnets (see below), reinforced concrete septic tanks and well casings. A video on the use of magnetic location titled “Principles of Underground Magnetic Locating” can be seen at https://youtu.be/ sTFIUyL0-Ow Magnetometry can also be used to survey archeological sites and in mineral exploration. Plus it is commonly used to find unexploded ordnance such as on old bomb practice ranges or former war zones. Concrete scanning Services such as water and power are sometimes buried in concrete. It’s important to know where it is safe to penetrate a concrete structure, to avoid rebar and post-tension cables etc. Methods used to achieve this include x-rays and ground-penetrating radar. Ultrasonic tomography is an alternate means of examining the inside of a concrete structure for rebar, ducts and conduits. This uses ultrasound with a pulse-echo method. Water ingress Long irregular pulse Fig.17: example traces from a TDR. Signal strength is on the vertical axis and time along the horizontal axis. The distance to the discontinuity in the cable to be determined from the time delay. The velocity factor (relative to the speed of light) varies from 0.45-0.57 for an EPR power cable to 0.82-0.98 for coaxial cable. One instrument which does this is the MIRA Tomographer (http://germann.org/). Time-domain reflectometry A time-domain reflectometer (TDR) emits a signal on a conductor (eg, a power or telecom cable) and then ‘listens’ for reflections. These indicate the presence of a break or other discontinuity such as a short circuit or bad cable splice. It functions similarly to radar, but in one dimension, along the cable. TDR accuracy can be affected by twists and bends in the cable and also not knowing the precise speed of light in the particular cable under test. For best results, the cable should be tested from both ends, in which case the transmission speed is not critical. We published a DIY TDR design in our December 2014 issue (siliconchip.com.au/Article/8121). Acoustic methods Acoustic methods can be used to find non-metallic objects and are especially useful if an object like a sonde, metal- Fig.18: the SENSIT ULTRA-TRAC APL seismic acoustic pipe locator with inset above (Fig.19 above) the ULTRA-TRAC display. Fig.20: the Leaktronics PG-2 pulse wave generator connected to a domestic water pipe. 18 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.21: a pulse wave generator or ‘thumper’ attached to a water main. The device is self-powered by water pressure being released through the device (via the yellow hose), although in this case is electronically controlled for frequency and intensity. Image credit: SES Water Management. Fig.22 (right): a Sewerin “Knocker” which attaches to the outside of a plastic or other pipe with a chain and makes a knocking sound of adjustable frequency and intensity. This is conducted along the pipe and can be detected above ground. No water is released. cored rod or magnet cannot be inserted into a pipe. These methods include seismic, acoustic emission, active sonics, passive sonics and resonant sonics. Sonic methods can also be used to locate metal pipes. The seismic method is a relatively new technique, and ap- plicable to depths of 5-10 metres. A sound wave is injected into the ground, and a reflection from the buried utility is listened for. It is similar to SONAR. With the SENSIT ULTRA-TRAC APL device, a series of soundings are made in the form of “pings”, five in a row The SILICON CHIP Inductance - Reactance - Capacitance - Frequency HUGE 420x594m on h m READY RECKONER For ANYONE in ELECTRONICS: You’ll find this wall chart as handy as your multimeter – and just as ESSENTIAL! Whether you’re a raw beginner or a PhD rocket scientist . . . if you’re building, repairing, checking or designing electronics circuits, this is what you’ve been waiting for! Why try to remember formulas when this chart will give you the answers you seek in seconds . . . easily! Read the feature in Jan16 SILICON CHIP (you can view it online) to see just how much simpler it will make your life! All you do is follow the lines for the known values . . . and read the unknown value off the intersecting axis. It really is that easy – and quick (much quicker than reaching for your calculator! eavy pho to paper LAST CHANCE! Very few still available . . . If you want one, you’d best order online today! Printed on heavy (200gsm) photo paper Mailed flat (rolled in tube) or folded Limited quantity available foldedSorry, sold out! Mailed Folded: Mailed Rolled: ORDER NOW AT $10.00 $20.00 inc P&P & GST www.siliconchip.com.au/shop siliconchip.com.au inc P&P & GST Australia’s electronics electronics magazine magazine Australia’s FFebruary ebruary 2020  19 Fig.23 (left): a SubSurface Leak Detection (www. subsurfaceleak.com) LD-12 instrument in use. Such equipment is also used to trace utility pipes when a pulse wave generator device is connected. Fig.24 (below): the relatively inexpensive V18 water leak detector (http://etowos.com/). See the videos titled “Acoustic Water Pipe Leak Detector +905414883700” at https://youtu.be/QCaoX3Bfu2w and “V18 Water Leak Detector” at https://youtu.be/_wxJkkjt1hc with a minimum of three rows. Software then constructs an image from the reflections created by an impedance mismatch of the buried object with the surrounding soil. See the video titled “Locating with the ULTRA-TRAC® APL” at https://youtu.be/YNvi5-Dx46Y Three methods utilise acoustic emission: active, passive and resonant. Acoustic emission, as the name implies, involves using a transducer such as a microphone on the surface listening for noises generated by a pipe. The premise used is that the noise will be loudest when the transducer is above the pipe, so this is the presumed Fig.25: part of the Adelaide CBD street plan, showing acoustic emissions over several days and the location of a leak indicated by this data. 20 Silicon Chip location of the pipe. The emissions that can be heard are strongly dependent on surface type (eg, soil, concrete or bitumen), fill type and condition of fill, such as how compacted it is, plus the moisture level. Active sonics involves creating a sound on or within a pipe. A simple example is striking a metal pipe with a hammer at an exposed point and listening for the radiated noise at points along the ground, to trace its source. Also, if there are multiple pipes, a pipe of interest can be struck at one end and the pipe that makes the most noise elsewhere can be assumed to be the same pipe. Fig.26: a Hydro-Lok hydrogen leak detector (siliconchip. com.au/link/aaxf) in use. Hydrogen is an excellent tracer gas as it is cheap, there is a low natural concentration in air, it is relatively easy to detect, it is non-toxic (so it can be used in drinking water pipes) and it passes through tiny cracks. Australia’s electronics magazine siliconchip.com.au Fig.27: the Cues MPlus XL Push System for visual pipeline inspection (siliconchip.com.au/ link/aaxe). Helping to put you in Control UR35 Industrial Cellular Router Integrating embedded cellular modem and dual SIM function, the UR35 provides 3G/4G cellular network with 150 Mbps download and 50 Mbps uplink. It also has 5 ethernet ports and WiFi(optional). SKU: ULC-035 Price: $449.95 ea + GST AirGate Modbus Wireless gateway for extending Modbus networks. USB and RS-485 interfaces. SKU: NOW-001 Price: $449.00 ea + GST Hydreon RG-11 Optical Rain Sensor Senses rainfall with no moving parts. 6 different modes of operation. Works as a tipping bucket, skylight rain sensor, wiper control, drop detection or irrigation control sensor. SKU: HYS-001 Price: $99.95 ea + GST MA4 4-20mA Input 4 Digit Process Indicator Part of the MA4 series of DCBox indicators this budget priced 4 Digit Process Indicator(48 x 96 mm) with 4-20mA Input, Alarm relay output and 24 VDC Powered. SKU: DBI-030 Price: $149.95 ea + GST USB Data Acquisition Module A ‘thumper’ or pulse-wave generator is a device connected to a water pipe that causes a thumping sound when water is released through it. This sound is traced with above-ground listening equipment to trace the pipe. See the video titled “The Pulse Generator PG-2 by Leaktronics - For Locating Pipes and Plumbing Lines” at https://youtu. be/QqICLgDK8k4 Devices can also be attached directly to the outside of a pipe to knock the pipe, similarly to hitting it with a hammer. These methods are suitable for plastic pipes. It is also possible to listen for noises created by a pipe when deliberately releasing water from an outlet such as a tap or hydrant. The noise carries along the pipe, and it can be listened for to locate the pipe. The U3-HV has 12 flexible I/O (digital input, digital output, 12 bit 0 to 3.6 VDC analog input), 4 HV analog inputs (12 bit -10 to 20 VDC), 2 voltage outputs and USB interface. SKU: LAJ-022 Price: $192.00 ea + GST DigiRail VA Single Phase Voltage/Current Transducer A DIN-rail mount measurement transducer for single phase AC power. It can measure voltage, current, power and frequency up to 300 VAC and 5 AAC. It has 4 to 20 mA and 0 to 10 V retransmission outputs and RS-458 and USB for Modbus RTU communication. SKU: SIG-103 Price: $279.95 ea + GST 4-20mA Input 3 Digit Large Display Large 100mm three digit process indicator accepts 4 to 20mA signal with configurable engineering units. 10cm High digits. 24V DC Powered. SKU: DBI-020 Price: $449.00 ea + GST Fig.28: the Ryonic (www.ryonic.io/) Mini RMIS Crawler for inspection of 180-450mm diameter pipes. siliconchip.com.au For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine February 2020  21 Fig.30: the Radiodetection Flexitrace, a rod which can be used to insert sondes. It is stored as a coil, has an integral conductor and can itself be energised along with the sonde. Energising the sonde only allows a pipe blockage to be detected; energising the entire rod enables a pipe to be traced. Fig.29: a variety of sondes available from Radiodetection. The area of active and passive sonics also overlaps with the area of leak detection, whereby sounds generated by a leak are listened for. The equipment for hearing the sound is the same in both cases. Some devices therefore combine the functions of acoustic pipe location along with leak detection. Part of the Gen-Ear equipment package (https://drainbrain. com/en/home-page/) includes a device to inject compressed air into the pipe system to enhance the sound of the leak. We have also read about a method of setting up resonance in a pipe to aid in its location in the literature, but we could find no current commercial device using this principle. You can hear examples of various leak sounds, plus sounds from a hydraulic pulse wave generator at: https:// leaktronics.com/leak-sounds/ Also see the video titled “Gen-Ear LE Water Leak Locator - How-to Video” at https://youtu.be/JYMT7WNADcA Real-time acoustic leak detection The Adelaide CBD water network includes permanent, real-time acoustic emission monitoring to detect leaks. This comprises 305 acoustic accelerometers and associated communications, data logging and analysis equipment. There are also flow and pressure sensors installed. The purpose of this is to detect small leaks before they become much larger leaks. You can read more about this at: http://siliconchip.com.au/link/aaxc Underground leak detection using hydrogen Hydrogen can be used as a tracer gas when locating leaks in underground pipes using a gas sniffing device. Hydrogen is ordinarily flammable and explosive when mixed with oxygen, but a 5% hydrogen and 95% nitrogen mix is safe. It is used as a tracer gas because the molecule is so small it will pass through any crack. obtained can augment above-ground detection. A remote-controlled or robotic crawler can also be inserted into larger pipeline systems, to conduct a visual inspection to confirm the condition of the pipe and other information not determined by above-ground detection. Rod and sonde methods Many underground services are made of non-conductive materials such as plastic or clay, and have been installed without the foresight of a metal wire or detectable marker tape to enable them to be located. Ground-penetrating radar or acoustic methods could possibly detect such pipes if conditions are right, or they can be traced by a “rod and sonde” method. In the latter case, you need to know that they exist and have an access point to insert equipment. The sonde is an instrument that transmits a signal. It is attached to the end of a tracer rod, which is pushed along the pipe. The signal from the sonde is detected by receiving equipment above ground, which is the same as used for passive or active detection. In some instances, no sonde is used, but the rod has a metallic core which can be traced from above ground when inserted into non-metallic pipes. Examples of services that can be traced are plastic conduits containing optic fibre (if there is room for a rod or sonde), plastic or clay pipes as used for sewer or stormwater, concrete pipes, plastic water pipes (if depressurised to allow insertion of a rod and sonde) etc. As an example, sonde products from Radiodetection (www.radiodetection.com/en-au) operate at frequencies of 512Hz, 8kHz and 33kHz with sonde diameters from 6.4mm to 64mm, and stated detection depths are up to 15m. Push cameras and robotic inspection A push camera can be used for internal pipeline inspection. This is a camera attached to a long, flexible rod which is pushed along the pipeline of interest. The information Fig.31: the rod and sonde detection method. An electromagnetic signal from the sonde is picked up at the surface. 22 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.32: an electrical resistivity imaging plot from the ZondRes2D software (siliconchip.com.au/link/aaxg). Surface data (top two plots) is used to generate a cross-section of soil resistivity at the bottom, across a particular transect of the surface data. Electrical resistivity imaging Electrical resistivity imaging is not generally used to find utilities as it is a time-consuming method. It is used for Earthing design for major electrical infrastructure such as power lines and substations. A two-wire method is used to measure soil resistivity horizontally, while a four-wire method is used for vertical resistivity soundings. In the latter case, a constant current is applied across the outer electrodes and the potential difference measured across the inner ones. Frequency and time-domain electromagnetic methods Utility ‘potholing’ These methods are mainly used to examine major subsurface features. In frequency domain electromagnetics, the transmitter current is varied sinusoidally at a fixed frequency, and the magnitude and phase of the induced current are measured to provide a measurement of subsurface electrical conductivity. This can indicate subsurface features, include metallic objects such as pipes. In time-domain electromagnetics, pulsed current is sent into the ground, and a secondary magnetic field is established. The decay rate of that field is used to determine the subsurface electrical conductivity. It can map many types of subsurface features, including ferrous and non-ferrous metals. Potholing is a non-destructive excavation method to confirm the exact location of utility services in the vicinity of proposed construction works. Air and hydro vacuum excavators are used to create a loose spoil that can be vacuumed away, to expose utility services and other underground structures. After work, the holes created can be filled in with that spoil or other fill. Unlike a digging implement such as a shovel or backhoe, there is much less likelihood of damaging utilities with this method. This method is important because it confirms the exact location of utilities which have been found by other methods. This method can also be used to excavate utilities to effect repairs. Fig.33: a ground plot from the Geonics EM-31 frequency domain ground conductivity meter, showing various subsurface features. Source: Mundell & Associates, Inc. Fig.34: a Geonics EM31-MK2 ground conductivity meter, which operates at 10kHz. Source: GeoView Inc. Compare this with the build-it-yourself “Incredibly Sensitive Magnetometer” which we published in the December 2018 issue (siliconchip.com.au/Article/11331). siliconchip.com.au Australia’s electronics magazine February 2020  23 Fig.35: a Geonics EM-61 time domain metal detector. Note the GPS antenna. Source: GeoView Inc. Dial before you dig! Free information is available from public records in Australia on known locations of utility services. You can dial 1100 for the “Dial Before You Dig” service or visit the website at www.1100.com.au/ An equivalent free service is available in New Zealand by phoning 0800 B4UDIG (248344) or visiting www. beforeudig.co.nz/nz/home/ Location accuracy For surveyors and excavators, the location accuracy of utilities recorded on plans or maps are rated according to the following Quality Level (QL) scores, based on Australian Standard AS5488: • QL-A: sighted (eg, observed via pothole) • QL-B: traced typical accuracy of ±300mm horizon- Fig.36: a ‘potholed’ site showing tree roots and utility cables. Potholing can be done to either locate services with certainty, or to make repairs once a leak or break has been located. Image source: Core Engineering, Inc. • • tally and ±500mm vertically) QL-C: aligned from surface features (low accuracy) QL-D: any other method RFID pipe tagging An RFID tag can be affixed to a buried pipe to aid in later identification. One type from ELIOT Innovative Solutions (siliconchip.com.au/link/aaxd) can be detected at a depth of 1.5m. See the video titled “RYB ELIOT” at: https://youtu.be/MoUww2cIatY A tag does not have to be attached directly to a pipeline if it is deeper than 1.5m; a warning mesh with tags embedded in it can be buried above the pipeline at a detectable depth. Some tags are said to be detectable at depths to 7m, presumably in favourable soil conditions. Figures are hard to Fig.37: a time-domain electromagnetics plot from the Geonics EM-61. Various features are identified, including two USTs (underground storage tanks). Source: GeoView Inc. 24 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.41: warning mesh with embedded RFID tags from ELIOT Innovative Solutions. Fig.40: the detecting device for ELIOT RFID tags. possible. The marking colours are specified by Australian Standard AS5488. The digital urban model Fig.39: ELIOT Innovative solutions RFID tags on plastic (HDPE) gas pipe. come by, but we’ve seen a price quoted for tags at US$15 each and about 375 are needed per km. Much information can be loaded onto the tags. Marker tapes and magnets It is good practice (or compulsory in some instances) to bury a marker tape in the trench above a utility service, to ensure there is a visual warning for future excavators. Some such tapes are also electronically detectable. Magnets can be buried at the same time as a utility to aid in later finding. See the video titled “DEEP-1 Video - Underground Magnets for Utility Marking” at: https://youtu. be/N6GVP3LqD8Q Non-detectable marking tapes are covered by Australian and New Zealand Standards AS/NZS 2648.1 1995 and AS/ NZS 4275 Part 0 1995. Marker tapes for electrical services should comply with AS/NZS 3000 : 2007 clause 3.11.4.5, and should be located about halfway between the service and the surface. Once an underground utility service is located, it needs to be marked. This is commonly done with coloured spray paint on the ground, or flags pushed into the ground where Fig.42: these marker tapes have an embedded stainless steel wire to make detection easier. Nondetectable tapes are also available but only provide a visual warning as a digger comes close to an underground utility AND if the tape is spotted! siliconchip.com.au By combining data from a variety of sources, it is possible to create a “digital urban model”. This is a system where the location of utilities, buildings and all other structures are accurately recorded in a geographic coordinate system. This can also form part of an augmented reality model. This information can also be utilised by excavation equipment to automatically avoid buried objects during SC the digging process. Leak detection professionals don’t always get it right… I had a mains water leak under my home’s concrete slab. A professional leak detector was called in, who used listening equipment to find the leak. Unfortunately, after plumbers had dug through a tiled floor and 150mm of reinforced concrete, the leak was nowhere to be found. They eventually found it about two metres away, requiring further slab excavation work... A colleague reported exactly the same thing – in his case on a steep, reinforced concrete driveway. A significant mains leak was reported to the water board and they turned up with some very professional-looking equipment to find the source. When the first hole they jackhammered didn’t show water, they tried again again about three metres away – and even the second attempt was out by another metre or so, resulting in an even larger hole in the driveway (and, he reports, a very botched “repair”). Underground utility finding is based upon firm scientific principles, but different techniques apply to different conditions. Underground utility finding requires a good amount of skill, plus plenty of experience to interpret the results, especially when multiple utility services are located close to each other. Utility locating as a career If looking for a new career, this might be worth investigating. I have quite a bit of experience with utility locating firms, and one thing that I found quite consistent is that their fees are substantial! Australia’s electronics magazine February 2020  25 Remote Monitoring Station If you have an expensive car, boat, caravan, holiday house, farm . . . virtually anything at all . . . you need to know what’s going on when you are away. Is the battery going flat? Is your boat taking on water? Is your water pump running incessantly? You need to find out about these ASAP. All you need to do this is a couple of Arduino shields and a little software. You can even remotely trigger actions, such as switching off that misbehaving pump, before it drains all your water! W e have to admit: the raison d’être for this project originally had nothing to do with monitoring expensive cars or boats, remote holiday houses, farm water tanks or anything so esoteric. It was all to do with wombats. For the benefit of our overseas readers wombats, a somewhat threatened species, are cute, (usually) slow-moving furry animals that inhabit the Australian bush (and, incidentally, are unique in that their poo is cube-shaped!). But even that’s not the whole story. SILICON CHIP’s zany resident cartoonist, Brendan Akhurst, actually lives way out in the bush and is a member of his local wombat protection society. Part of their remit is to re-home wombats in areas where they are less likely to be attacked by other animals (eg, dogs). They do this by trapping them and relocating them. The problem is/was that wombats are very easily stressed and will die if they are trapped for too long. What Brendan wanted was a means of letting society members know, as soon as possible, that one of their traps 26 Silicon Chip 2G, 3G and 4G had been sprung. “Aha!” we said. “There is an idea we’ve been working on for a couple of months which will alert you, via your mobile phone, of virtually any incident.” “A sprung wombat trap included?” he asked. “We did say virtually any incident!” So Brendan’s Wonderful Wombat Warning Whatchamacallit is the result. . . Of course, what you use it for is entirely up to you! by Tim Blythman Australia’s electronics magazine The 2G (GSM) mobile network has already been essentially shut down, and some telcos are starting to threaten to shut down their 3G network. So to do this kind of job reliably for the next few years at least, you need a 4G device. When we found a locally-available Arduino 4G shield at a reasonable price, we jumped at the opportunity to design a Remote Monitoring Station around it. Since this Station is based on an Arduino board, it can be easily programmed to suit your specific requirements. It can monitor the state of switches, voltages, sensors – just about anything, provided there is an Arduino library to interface with it (and there usually is)! Similarly, you can send commands to the Arduino from your mobile phone or PC to do things like switch mains power on or off, using a simple add-on device, such as our OptoIsolated Mains Relay (October 2018; siliconchip.com.au/Article/11267). You might remember the GSM Remote Monitoring Station project from the March 2014 issue, which was also siliconchip.com.au The completed assembly is compact, needing only a few flying leads. Even the smallest 12V SLA battery dwarfs it. The Arduino board (in this case, a Duinotech Leonardo) is on the bottom, the SIM7000E board in the middle and our power control board is on top. The antennas for both the GPS module and the main antenna (at left of pic) should be mounted with a clear view of the sky for best reception. Arduino-based (siliconchip.com.au/ Article/6743). That is now well and truly obsolete. If you have already built that design, as the command set of the new 4G shield is very similar, you may be able to update it by simply replacing the shield and making some small code changes. One minor difference between that 2G shield and the 4G shield we are using here is that the power control signal is on a different Arduino pin. We haven’t tested this newer shield with the older Monitoring Station design, but it’s likely to work with some fiddling. The new shield has enough extra features to warrant a major update, and so this new 4G Remote Monitoring Station makes good use of many new features. As this is an Arduino-based project, you’ll need to be familiar with the Arduino IDE (integrated development environment) software. This is a free download from www. siliconchip.com.au/link/aatq 4G Shield This project revolves around a 4G Shield designed by DFRobot. It is siliconchip.com.au based on a SIMCom SIM7000E module, which provides the 4G capability. Its circuit diagram is shown in Fig.1. The SIM7000E module is fed power from the Arduino’s VIN pin via an MP2307 buck regulator. This produces a steady 3.3V with at least 4.75V at its input. We used an Aldi SIM card on the Telstra network to test our SIM7000 shield. This SIM cost $5 and did not need to add any extra credit, even after two months of testing. The shield also has sockets for external mobile and GNSS antennas. Australia’s electronics magazine While this eliminates the option of powering the shield from a 3.7V lithium-ion or LiPo cell, it will work with most Arduino applications powered from the VIN pin or DC barrel socket. Below the regulator is the power control section. The PWRKEY pin on the SIM7000E is pulled low to signal that it should power on or off. Pushbutton S1 connects this pin momentarily to ground, while NPN transistor Q1 allows Arduino pin D12 (driven high) to achieve the same effect. Communication between the host Arduino and the shield is with a serial TX/RX pair, via level-shifting transistors Q8 and Q9. Slide switch S2 routes the signals to either D0/D1 (which is usually a hardware serial port on Arduino boards) or D8/D7 on the Arduino. The SIM7000E’s USB port is broken out to a micro-USB connector. This does not supply power to the shield, but can be used by a PC to communicate with the SIM7000E module. We didn’t investigate this in detail, but it appears that many features of the February 2020  27 Here are the three boards used in this project. From left to right they are the SILICON CHIP power control shield, the DFRobot 4G shield and the Arduino Leonardo microcontroller unit. SIM7000E module module are useable via the USB conThe SIM7000E module is touted as nection. It may even be able to act as an NB-IoT/LTE/GPRS/GPS module. a USB 4G modem. LTE and GPRS are longstanding moThere are also sockets for a fullbile data transmission technologies, sized SIM card, 4G antenna and GNSS but NB-IoT is a newer standard. (Global Navigation Satellite System) NB-IoT is a low-power, narrowband antenna, which is used for GPS and variant of mobile phone technology, GLONASS. designed to be used by IoT (internet For more information on these and of things) devices. You can find out the many other GNSS systems that exmore about IoT from our November ist, see our article “A look at SatNav 2016 article on the topic (siliconchip. systems” in the November 2019 issue com.au/Article/10425). (siliconchip.com.au/Article/12075). We aren’t using the NB-IoT feature One common use for a remote moniin this project; at this stage, it appears toring station is vehicle tracking, and the technology is still being rolled out in this case, a GNSS receiver is pracin Australia, and an NB-IoT-specific tically mandatory. SIM card is required. We don’t need to add any extra hardThe SIM7000 module comes in sevware to implement tracking into our eral variants which support dif4G Remote Monitoring Station. ferent mobile frequency The two antennas are included when you purchase the shield. The mobile network antenna is a simple, self-adhesive PCB type. Some photos of the shield show a small whip-style antenna, but it appears this has been replaced by the PCB type. A ceramic patch antenna is supplied for GNSS use. Also on the shield is a BME280 temperature, pressure and humidity sensor. We covered modules built from similar sensors back in 2017 (siliconchip.com.au/Article/10909). This is a great addition as it adds even more sensor data to our 4G Remote Monitoring Station without needing extra hardware. The electrolytic We found that the temperature capacitor and 555 timer used on the read by the sensor was higher than ambient, probably due to the heat power control shield have been carefully chosen for low leakage and low quiescent generated by the surrounding circurrent, to extend battery life. Note the cuitry; think of how hot some mobile jumper wire connecting the Arduino’s D7 phones get! pin and the SLEEP terminal. 28 Silicon Chip Australia’s electronics magazine bands. We are using the SIM7000E (the model sold by Core Electronics), which is designed for the European market and supports bands 3, 8, 20 and 28. There is also a SIM7000C which is designed for the frequencies used in China. In our tests in suburban Sydney, we could not get reception with an Optus SIM card, but had success with a Telstra SIM card. This is despite the Optus network apparently using some of the above bands. Because not all frequencies are offered in all areas, your experience may be different. We suggest that you thoroughly research what frequencies are used where you plan to deploy the 4G Remote Monitoring Station, to make sure this shield supports them. This module does not support voice calls. Most monitoring stations typically use SMS (text messages) or data packets for communication. The SIM7000E module does support mobile data, and this is a great way to communicate lots of small snippets of monitoring data. Our design uses both the SMS and mobile data features of the shield. ThingSpeak data logging Our Water Tank Level Meter from February 2018 (siliconchip. com.au/Article/10963) is a remote device which periodically uploaded data to the ThingSpeak website, although it used a WiFi connection to an existing internet-connected network, limiting where it could be used. Such restrictions can be removed by using a 4G shield like this one. We’re also using ThingSpeak for this project. It has a simple API (application programming interface) siliconchip.com.au 2 VIN 100k 7 8 22 F 10nF 100nF BS IN REG1 MP2307 EN SW SS GND FB COMP 4 1 L1 10 H 10nF 3 VBAT 33k 100nF 22 F 5 6.8k 6 D0 C 4.7k B Q2 47k E S Q9 S2 52 GND D7 9 TVS10 D1 TVS9 10nF TVS3 MICRO USB RXD 7 CTS 8 RTS 4 RI 5 DCD 3 DTR PCM_SYNC 28 27 TVS1 TP2 TVS2 TP3 SIM CARD SOC KET 22 TVS7 23 GPIO0 /UART3_TXD USB_D– GPIO1 /UART3_RXD USB_D+ MDM_LOG_TX STATUS 38 I2C_SCL 37 I2C_SDA 16 1 C 4.7k Q1 B E NRESET PWRKEY BOOT S1 61 TVS60 62 63 10 14 13 11 47 H ANTENNA 2 33pF 50 49 UART +5V GND PINS 2 VBAT 12 67 GPIO2 68 GPIO3 48 GPIO4 25 ADC 51 NC 47 NC 44 NC 43 NC 42 NC 41 NC 40 NC 36 NC 35 NC 26 NC 22 NC 21 NC 20 NC 19 NC BOOT_CFG 66 100nF 3x 22pF TVS8 47k USB_VBUS 60 53 SIM7000E GNSS_ANT LTE-FDD & Dual-Band 54 GPRS/EDGE module GND SIM_VDD 33 SIM_RST 32 SIM_CLK 31 SIM_DATA 34 SIM_DET 22 TVS6 6 PCM_CLK 30 22 1 2 3 PCM_DOUT TXD 24 1 2 3 4 5 VDD_EXT PCM_DIN 10 Q8 TVS5 ANTENNA 1 RF_ANT NETLIGHT GND S 4 5 6 56 55 57 VBAT VBAT VBAT TP1 22 F 6.2V A K GND 15 +5V ZD1  ON TVS52 G D K A K D8 D 1.5k 10pF 1.5k 2x 4.7k G 33pF 100nF 100nF  NETL VDD_EXT 2x 4.7k 470 F A 10k 3.9nF +5V VBAT 4 3 17 18 29 39 45 46 58 59 64 65 TVS4 TXD 2 RXD 1 +5V I2C SCL SDA +5V 4 D1/TXD D0/RXD D3/PWM D2/PWM D4/PWM D5/PWM D7 D6/PWM D8 D10/SS D9/PWM D12/MISO D11/MOSI GND D13/SCK AREF SCL USB TYPE B MICRO SDA 3 SCL 2 SDA 1 1 2 3 4 5 6 ICSP ARDUINO UNO UNO,, DUINOTECH CLASSIC, FREETRONICS ELEVEN OR COMPATIBLE 2x10k A5/SCL A4/SDA A3 A2 A0 A1 VIN GND GND +5V +3.3V +5V RESET 2 Q11 3 D S 4 5 G +3.3V 3.9nF VIN SC 8 S G +5V 100k 100nF 100nF Q10 D DC VOLTS INPUT 2020 +3.3V 2x10k CSB SDI SCK SDO VDD 6 VDDIO IC2 BME280 GND 1 GND 7 100 RESET Fig.1: the SIM7000 shield circuit. It has several nice features, including an efficient buck regulator and a BME280 temperature/ pressure/humidity sensor. The slide switch (at upper left) allows the serial data to be rerouted; we are using pins D0 & D1. SIM7000 ARDUINO EXPANSION SHIELD siliconchip.com.au Australia’s electronics magazine February 2020  29 for uploading data, which is great for resource-constrained devices like Arduino microcontrollers. It also provides simple graphical visualisations of the recorded data. The data can also be downloaded as a CSV (comma-separated value) file. These files can be opened into a spreadsheet program to allow more advanced analysis to take place. Creating charts is also an option in many spreadsheet programs. Uploading data to the ThingSpeak website requires mobile data, so the SIM card used needs to support this. For the low cost, longer-expiry prepaid mobile phone plan that we tried, it was typically cheaper to send weeks of data to the ThingSpeak website than to send a single text message. Our 4G Remote Monitoring Station is ideally suited to providing continuous logging of data via 4G as well as sending text messages for raising alerts for unusual situations that need to be acted on promptly. Power control shield In addition to the pre-build 4G shield, our Remote Monitoring Station also uses a custom-designed shield to provide for battery power, solar charging of that battery and some power-saving techniques to give it a long runtime when using a small battery. Most Arduino boards have poor power efficiency; they have simply not been designed with this in mind. Even with the processor set to sleep mode, other components such as linear voltage regulators and LEDs have quiescent currents in the tens of milliamps. Our shield reduces the standby battery draw to microamps, which it does by completely disconnecting the Arduino board (and SIM7000 shield) from the battery using a Mosfet, and only powering those components up periodically. The shield provides a reasonably efficient way to charge the battery, and also monitors the supply and battery voltages via the Arduino’s analog inputs. Most of the unused pins are broken out to headers, allowing other sensors or peripherals to be connected. There’s even a small prototyping area on it, for extra components. Shield circuit The custom shield circuit is shown 30 Silicon Chip in Fig.2. Unregulated DC power is fed into CON1 (from a solar panel, plugpack etc), while the battery is connected via CON2. The battery needs to operate in the range of 7-15V, so a 12V lead-acid or SLA battery is suitable. We used a 1.3Ah SLA with our prototype. Power from CON1 feeds REG1, an LM317 adjustable regulator. The 220Ω fixed resistor and 10kΩ variable resistor VR1 allow you to set its output voltage. As REG1 maintains about 1.25V between its OUT and ADJ pins, around 5mA flows through the 220Ω fixed resistor. This current mostly also flows through VR1, so by adjusting its resistance, you change the voltage between ADJ and GND. Hence, you can set the voltage at VOUT, since this will be the voltage across VR1 plus the 1.25V. The output from the regulator is filtered by a 1µF capacitor and fed to the battery via 1A schottky diode D1. This prevents the battery discharging into the power source, eg, if it is a solar panel in darkness. The 1Ω resistor between the output of REG1 and anode of D1 reduces the output voltage as the current drawn from REG1 increases. Hypothetically, if the current through this resistor reached 1.25A (which would not be possible in practice), the voltage across this resistor would rise to 1.25V, cancelling out REG1’s reference voltage, so the output would drop to 0V. Thus, the output voltage drops approximately 1V for every 100mA of load current. So if a battery is heavily discharged and its terminal voltage is low, the regulator output current is moderated until its voltage rises to the normal range, at which point virtually no current will flow into the battery. In practice, the charging current is limited by dissipation to about 160mA for a 12V solar cell (with nominal 18V open-circuit voltage) feeding into a discharged 12V battery. While the range of VR1 allows a terminal voltage from 1.25V up to 56V to be set, it shouldn’t be set any higher than around 15V as this may damage the regulator on some Arduino boards, as well as IC1. If you don’t need to use a battery, power can instead be fed directly into Australia’s electronics magazine CON2. D1 will prevent back-feeding into the charge circuit. Arduino and SIM7000 shield power control Power control is provided by 7555 CMOS timer IC1 and P-channel Mosfet Q2. Q2 is simply used as a highside switch. Q2 can handle much more current than is required (hundreds of milliamps at most), so it does not need heatsinking. We have chosen the CMOS variant of the 555 for its low quiescent current of around 60µA, compared to about 10mA for the bipolar version. This is because it is active and drawing current from the battery at all times. IC1 is configured as a monostable timer. When power is first applied, the 470µF timing capacitor is discharged, and the threshold pin (pin 6) is below 2/3 of the supply voltage. The trigger pin (pin 2) is held high by the 10kΩ resistor. The transient conditions during power-up result in output pin 3 being high, and discharge pin 7 is in a high-impedance state. With output pin 3 high, Q2’s gate is high and so it is off, and the Arduino is not powered. The 470µF capacitor slowly charges up through the 1MΩ resistor. This capacitor needs to be a low-leakage type; otherwise, the leakage would prevent it from charging up fully. The time constant of this circuit is nominally 470 seconds (just under eight minutes). Due to the 555’s tripping point not being exactly 63% of the supply voltage, it actually takes around 10 minutes for the timer’s state to change. Once the trigger pin voltage reaches about 2/3 of the supply voltage, output pin 3 goes low, pulling down Q2’s gate, switching it on and connecting the battery to the Arduino board’s VIN pin. This powers on the Arduino board and attached 4G shield. IC1’s discharge pin, pin 7, goes low at the same time, discharging the 470µF capacitor quickly via the 470Ω resistor. Being a monostable circuit, it remains in this state until the Arduino decides that it needs to power down. To do this, it drives the base of NPN transistor Q1 positive, pulling the trigger pin (pin 2) of IC1 low. IC1’s flipflop toggles, output pin 3 goes high (switching off Q2 and the Arduino) and the discharge pin (pin 7) goes back to a high-impedance state, allowing siliconchip.com.au REG1 LM317T 1M VIN + – 1 F D1 1N5819 1 OUT IN 1 F ADJ CON1 100 220 1M VSENSE 2 VBAT VBAT K A 1M 470 6 VSENSE 1 470k 470k VR1 10k 1nF 7 10k 470 F 8 4 VBAT 3 IC 1 IC1 7 555 2 + – 100nF 5 CON2 1 1k JP1 BOOT SLEEP 1nF CON6 VSW D 1N5819 A K D1/TXD ANALOG 1 1 A3 2 BC547 B 2 4 E 6 C SUP53P06 ANALOG CON3 +5V 1 A2 2 A5/SCL A4/SDA CON4 +5V 3 3 5 A3 A2 A0 A1 VIN GND GND +5V +3.3V +5V RESET DC VOLTS INPUT Q2 SUP53P06 1 ICSP ARDUINO UNO UNO,, DUINOTECH CLASSIC, FREETRONICS ELEVEN OR COMPATIBLE S G Q1 BC547 E D0/RXD 2 D3/PWM 3 D2/PWM 4 D4/PWM 5 D5/PWM 6 D7 1 D6/PWM 2 D8 3 D10/SS 4 D9/PWM D12/MISO 5 D11/MOSI GND D13/SCK AREF SCL SDA B CON5 6 USB TYPE B MICRO C 1k G 3 D D S LM317T +5V OUT ADJ VSW VSW POWER 4 3 2 VSENSE 1 VSENSE 2 SC IN 1 CON7 2020 OUT Fig.2: the circuit of our control shield. Adjustable regulator REG1 sets the charge termination voltage and voltage/current characteristics for charging a battery connected via CON2, while IC1, Q1 and Q2 shut down the Arduino for a fixed time before powering it back up again, as a powersaving measure. The effect is that the Arduino is powered intermittently, for as long as necessary to do its monitoring tasks. SIM7000 POWER CONTROL SHIELD the timing capacitor to charge. When the Arduino is shut down, it can no longer keep Q1 switched on, so there is no chance of this state latching. Thus the cycle continues where it began. The Arduino has no way of turning itself on at a particular time; it just shuts down for the period of the monostable timer. It’s not exactly high precision, but it allows very low power consumption while ensuring that the Arduino is powered up periodically to do whatever it needs to do. Jumper JP1 allows the monostable circuit to be bypassed. If JP1 is shorted, IC1’s threshold pin is pulled above 2/3 of its supply, so Mosfet Q2 is forced on. As long as this jumper remains in place, the Arduino is unable to shut itself down. siliconchip.com.au This can be used to bypass the sleep mode during testing, or to force the 4G Remote Monitoring Station to operate when deployed. Sensing external voltages Two six-way headers, CON5 and CON6, are provided to make connections to the Arduino’s digital pins. A small prototyping area with nine pads is also provided. A pad connecting to SLEEP is placed nearby. This is intended to be connected with one of the digital pins via a short jumper wire, meaning the pin used for shutting down the Arduino is not fixed in hardware, but can be altered. For our prototype, we used D7. A small four-way header is also broken out for 5V, VIN and GND, since connected sensors or peripherals will Australia’s electronics magazine need access to power. Two analog pins are connected to resistive dividers to sense the battery voltage (A0) and incoming supply voltage (A1). The 1MΩ/470kΩ divider means that voltages up to 15.6V can be measured. These high values are chosen to minimise loading (to around 10µA), especially on the battery. The two 1nF capacitors provide a low source impedance for the analog inputs, as otherwise, these voltage readings would be inaccurate. Two more analog pins (A2 and A3) are broken out to separate three-way headers (CON3 & CON4), along with ground and 5V. These allow common three-wire analog sensor modules to be connected. Note that there is nothing about this shield which ties it specifically to the 4G Shield. Any application which reFebruary 2020  31 Fig.3: fit the components to the control shield PCB as shown here. It shouldn’t take you too long to assemble. Just watch the orientation of diode D1, IC1, Q1 and the electrolytic capacitor. Also, ensure that the wire entry holes for CON1 and CON2 face outwards. You can use standard male headers (fitted to the underside of the board), or stackable headers, depending on how you plan to use the shield. quires battery charging, monitoring and low power consumption could use this shield. Building the shield Use Fig.3, the PCB overlay, as a guide during construction. The shield is built on a double-sided PCB coded 27111191 which measures 53.5 x 68.5mm. We built our shield with simple headers to plug into the 4G Shield below it. If you intend to add another shield above this one, you could use stackable headers instead, but that would make it difficult to access the pin headers on top of this board. Start construction by fitting the resistors. There are several different values, so check the resistance of each with a multimeter. Then solder one of the lead off-cuts between the pad marked “SLEEP” and the Arduino digital pin that you want to use for the shutdown function. We used D7, simply because it is close to the SLEEP terminal and it is not usually used for any specific purpose. Next, mount the three rectangular MKT capacitors, which are not polar- ised. The 100nF part may be marked with the code 104 or possibly 0.1µF, while the 1nF parts may be marked 102. Follow with the two 1µF ceramic capacitors, which are also not polarised. The final capacitor is the low-leakage electrolytic type. It is polarised, and we have left space on the PCB for it to be mounted on its side so that another shield can be fitted above. The negative lead (usually shorter and indicated by a stripe on the can) goes into the pad closer to Q2. If you want to use a larger capacitor for a longer delay, we have left a bit of extra room. You may wish to apply a small dab of hot glue or neutral-cure silicone sealant to help hold it in place in case the unit is subjected to vibration. Fit the semiconductors next. D1 is the only diode and goes near CON2, with its cathode stripe closest to CON2. Mount Q1 near the middle of the PCB, orientated a shown. Carefully bend its leads to suit the PCB footprint, push down firmly onto the PCB and solder it in place. Q2 and REG1 are both in TO-220 packages that are mounted flat against the PCB, to keep the overall height low. Don’t get them mixed up. Bend the leads back on each part, around 8mm from where the body meets the leads. Push the leads into the PCB pads and make sure the tab hole lines up with the PCB, then use an M3 machine screw and nut to secure the regulator before soldering its pins. Next, fit timer IC1. You may need to gently bend the leads inwards to fit the IC to the PCB. Check its orientation to make sure it matches the PCB overlay diagram, then solder two diagonally opposite pins and check that it is flat against the PCB. If not, remelt the solder and adjust, then solder the remaining pins. To solder the Arduino headers, plug them into another Arduino board (such as the Leonardo) to keep them straight. Place the shield over the pin headers and once you are happy that the headers are straight, solder each pin to the PCB. Plain headers are soldered on top while stackable headers are necessarily soldered underneath. Then remove the shield from the Arduino board. Now mount CON1 and CON2, the screw terminal connectors. They are identical, and care should be taken With stackable headers, the three shields (PCBs) simply connect together via their header pins and sockets, as shown here. 32 Silicon Chip Australia’s electronics magazine siliconchip.com.au that the wire entry holes face out from the PCB. You can now fit headers for JP1 and CON3-CON7 for breaking out the various Arduino pins. They aren’t needed for the most basic usage of the 4G Remote Monitoring Station, but they are handy for adding extra sensors if and when necessary. We used a four-way female header strip for CON7, to allow the VIN voltage to be monitored easily. To help test whether the shield is feeding power to the VIN pin, we rigged up a test LED by soldering a 1kΩ resistor to one lead. We then plugged this LED/resistor combo into the VIN/ GND pair on CON7, with the LED anode to VIN. Testing We can do a few basic tests to check that everything is working as expected. The shield must not be connected to any boards during these tests. Wind VR1 fully anti-clockwise before powering it up. The first step is to adjust VR1 for the correct battery charging voltage. This is done without a battery connected. To do this, connect a power supply to CON1 which supplies at least 3V more than the fully charged battery voltage. Adjust VR1 until the correct maximum charge voltage is reached at CON2. For an SLA or similar 12V nominal type battery, set it to around 14.4V. In practice, this voltage is only reached at zero current, so the actual charge voltage is a bit lower than this. If you are unable to set the voltage correctly, check the components relating to REG1. Otherwise, connect the battery and check that it is charged. You should see the battery voltage rising slowly. Next, check the voltage between VIN and GND, using the LED we mentioned earlier or a voltmeter. These pins are easily accessible on CON7. You will probably get a zero reading, meaning that Q2 is off. In this case, if you check the voltage across the electrolytic capacitor, you should find that it is slowly rising. This can be measured at pin 6 of IC1 referred to GND. Note that the load presented by your multimeter might affect this reading. Now bridge JP1, to force Q2 on, and re-check the VIN voltage. It should be close to the battery voltage and the siliconchip.com.au voltage at pin 6 of IC1 should be low. To simulate the Arduino activating the switch-off, momentarily connect the SLEEP pad to the 5V pin of CON2 using a 1kΩ resistor. VIN should drop to zero, and the electro should start charging. If it isn’t, that could indicate that your capacitor is leaky. If you’re fussy about the exact timing of the sleep period, you can measure the time and change the values of the timing components to tweak it. Keep in mind that the Arduino needs to operate for at least 30 seconds to update its state, so sleep periods shorter than two minutes are not that useful, as the Arduino will spend much too much time starting up. Once testing is complete, disconnect the power supply and batteries. Building the Remote Monitoring Station Having built the shield, now we can put it all together. We chose to use an Arduino Leonardo board for our prototype. It uses the ATmega32U4 micro rather than the Uno’s ATmega328. The “U” indicates that this IC supports USB. Their specs are otherwise quite similar, but the Leonardo has the advantage that the hardware serial port on D0/D1 is not shared with the USB host serial interface used for programming. We can therefore use this to communicate with the SIM7000. The Leonardo also has an extra 512 bytes of RAM; this can be handy for remote monitoring as we need to store and process data before sending it. If we had used an Arduino Uno, we would have been forced to choose between using the hardware serial port (D0/D1) to communicate with the SIM7000, which would interfere with programming and debugging, or using a software serial port which is slow and has a lot of overhead. So we set the switch on the SIM7000 shield to the D0/D1 position, and as mentioned above, we used D7 as the sleep control pin. To set up the 4G Shield, fit the two antennas and a working SIM card. As with many of these sorts of applications, a prepaid SIM is preferred in case the microcontroller ‘goes nuts’. With a prepaid limit in place, there is no chance of accidentally racking up huge data or call charges. Now plug the 4G Shield into the Leonardo and then plug the power Australia’s electronics magazine Parts list – 4G Remote Monitoring 1 Arduino Leonardo or compatible board 1 DFRobot SIM7000 shield [Digi-Key/Mouser (Cat DFR0505) or direct from www.dfrobot.com] 1 4G SIM card for SMS and data use 1 power control shield (see below) 1 12V rechargeable battery and suitable charging source (eg, a small 12V solar panel) Parts for power control shield 1 double-sided PCB coded 27111191, 53.5 x 68.5mm 2 2-way, 5mm-pitch PCB-mount terminal block (CON1, CON2) [Jaycar HM3172, Altronics P2032B] 1 set of Arduino headers (1 x 6-way, 2 x 8-way, 1 x 10-way – see text) 1 2-way male pin header with jumper shunt (JP1) 2 3-way male pin header (CON3,CON4) 2 6-way male pin header (CON5,CON6) 1 4-way female header (CON7) 2 M3 x 6mm machine screws & nuts (for mounting REG1 & Q2) Semiconductors 1 7555 CMOS timer IC, DIP-8 (IC1) 1 LM317 adjustable voltage regulator, TO-220 (REG1) 1 BC547 NPN transistor, TO-92 (Q1) 1 SUP53P06 P-channel Mosfet, TO-220 (Q2) 1 1N5819 schottky diode (D1) Capacitors 1 470µF 25V low-leakage electrolytic 2 1µF multi-layer ceramic [Jaycar RC5499] 1 100nF MKT 2 1nF MKT Resistors (all ¼ W 1% metal film) 3 1MW 2 470kW 1 10kW 2 1kW 1 470W 1 220W 1 100W 1 1W 1 10kW mini horizontal trimpot (VR1) control shield on top. Check for any fouling between the shields; if you have not trimmed all the leads closely, they may short together. Our sample software simply logs data from the onboard sensors. We’ve also marked some places in the code to add your own tests or actions. For example, you could monitor a voltage and send an SMS if it gets too low or high. Or similarly, you could send an SMS if a switch is opened or closed. February 2020  33 Fig.4: apply for a ThingSpeak account via the web page shown here. This is needed to use the software we’ve written, as ThingSpeak lets you upload data to “the cloud”. MATLAB users can use their existing account for ThingSpeak. You will need to set up a ThingSpeak account to make full use of our sample code. Setting up a ThingSpeak account ThingSpeak can be accessed for commercial use with a time-limited free period, but a free license is available for personal use and offers four ‘channels’ and up to three million updates per year. If we were to send an update every ten minutes, then we would only need around 50,000 updates per year. Go to https://thingspeak.com/users/ sign_up and enter the information as shown on Fig.4. You may be prompted to confirm that you wish to use a personal email address, and also to click on a link sent in an email to verify that email address. Once this is done, create a user ID and password, accept the Online Services Agreement and click continue as per Fig.5. You will be prompted to select how you will use ThingSpeak. To be able to use the free license, you should choose “Personal, non-commercial projects”. The next step is to create a channel. Each channel consists of up to eight fields, so in theory, you could have up to four 4G Remote Monitoring Stations, each writing to their own 34 Silicon Chip Fig.5: as with many online services, you need to create a username and password for ThingSpeak. This page indicates if your chosen username is free, and how strong it thinks your password is. independent channel. Click on “New Channel” and fill out the information as shown in Fig.6. You don’t need to use all eight fields, but we have set the Arduino software to use all eight as shown. You should use the same fields unless you plan to modify the software. Click Save, and you are shown the Channel data on the Channel management page, as seen in Fig.7. Note that we did not create fields for latitude and longitude. ThingSpeak has hidden fields for this information. It can’t be seen on the graphs, but is downloaded in the CSV data. Our Arduino code logs latitude and longitude to these hidden fields. API keys To allow our device (and only our device) to upload data to our channels, we need an API key. It must be programmed into the Arduino code for your 4G Remote Monitoring Station to work with your ThingSpeak channel. Copy the 16-character alphanumeric code under “Write API Key” to somewhere safe; we’ll add this to the Arduino code soon. You can test that your channel is working by copying the text after the word “GET” in the “Write a Channel Feed” box. Paste this into a web browser and hit Enter; you should see Australia’s electronics magazine a blank page with the number “1”. This indicates that this is the first update, and shows how the 4G Remote Monitoring Station uploads data to ThingSpeak. This only updates one field; if you are familiar with HTTP, you might want to experiment with this. Browse back to the “Private View” of the created channel, and you should see some activity in the first field; this is the data you sent from the web browser. You can leave this window open while testing, as it will update in near-realtime and you can see the results. Arduino libraries There are four libraries needed for the software we have written; two are included with most Arduino IDE distributions. We used version 1.8.5 of the Arduino IDE. The avr/sleep and Wire libraries are the two usually included. The first library provides functions for low-power modes, while the second provides an I2C interface for communicating with the BME280 sensor. The third library, which we created, is named “cwrite”. It lets us read and write from a character array as though it is a stream object, so we can use the print function’s ability to format floating-point numbers to form a URL. siliconchip.com.au Fig.6: we recommend that you (at least initially) create a ThingSpeak channel and set up its fields as shown here. These fields suit the data produced by the 4G Remote Monitoring Station software. They can be changed later if necessary. The resulting datum can then be sent to the 4G Shield in one go. This library can be seen as two extra tabs in the Arduino project. If you make a copy of the project (by using File -> Save As...), then this library is copied too. The final library is to make the actual temperature, humidity and pressure readings from the BME280 sensor. It is written by a company called SparkFun and can be installed via the Library Manager utility of the Arduino IDE. Search for “sparkfun BME280” under the Library Manager and click Install. We have included this library in our software bundle for this project, in case you can’t find it. Arduino software We set up the Arduino software to work with the eight fields that we have just created, plus three hidden fields of latitude, longitude and height above sea level. These three fields are from by the GNSS receiver on the SIM7000 module, plus the BME280’s atmospheric pressure sensor to determine altitude. The software is modularised in such a way that proficient Arduino users can modify it to behave differently, if needed. In any case, you will need to edit the siliconchip.com.au Fig.7: once the channel has been created, you can go to its overview, which defaults to a series of charts. You can add more with the “Add” buttons. By default, the channel data is private, but you can set it to be visible to others if you’d like to. software to suit your API key. Around line 28, change the text API_KEY_ HERE to the API key that you copied earlier. You should end up with a 16-character sequence surrounded by double quotes. Below this, on lines 29 and 30, are entries for phone numbers. Any incoming text messages have their number checked against the AUTH_NUMBER string. The sequence AUTH_ NUMBER_HERE should be replaced by the trailing digits of your phone number. We have done it this way to allow matching of both national and internationally formatted numbers. Thus for an Australian mobile number, the first digit should be the ‘4’, meaning the leading ‘0’ is dropped. The sketch simply matches whatever digits are present. So if this were changed to “693”, then any number ending in “693” would be accepted. If you don’t wish to use this feature, leave it as the default string, as this is highly unlikely to match an incoming number. The outbound number should be a fully-qualified international mobile number; eg, an Australian mobile phone number including country code would start with “+614” followed by eight digits. This is used for outgoing text message alerts. Australia’s electronics magazine Many of the other ‘defines’ are set to set things like the analog input voltage measurement ratios, and how much memory is available. There is no reason to change these unless you are modifying the hardware. The software performs basic initialisation of the hardware in the setup() routine. More initialisation happens in the loop() function, particularly for the 4G Shield. The code sends the shield some data to see if it is powered up and if not, toggles the power line. A set of fixed sequences are sent to put the 4G Shield in a known state. The shield is given ten seconds to get a GNSS fix. If this is successful, the unit’s speed is checked, and a message is sent if it is higher than 100km/h. This is a basic demonstration of how easily an action can be performed based on sensor state. The code then sends an update to ThingSpeak; this is wrapped up in a single function which validates the GNSS data and only sends that data if it is valid. The Arduino then checks for text messages from the authorised number. If one is found, a canned response is sent. You can modify the code to check the message content and perform different actions (and supply different February 2020  35 Fig.8: here is some sample debugging data from the serial port of the Remote Monitoring Station during normal operation. Your data may differ, if, for example, you have a different telco. responses) depending on it. If the GNSS data is not valid, then instead of powering off, the Arduino goes to sleep and leaves the 4G Shield running to allow it to get a fix. This does not reduce power as much as switching the Arduino off, but does give it a chance to get a position fix. If the GNSS data is valid, then the modem’s power pin is toggled (to perform a controlled shutdown), and D7 is driven high to power down everything else. Next time the Arduino powers back up, the sequence repeats, resulting in ThingSpeak updates about every 10 minutes. Each update uses around 2kB of data, which, according to our mobile plan, costs around $0.0001. During our testing, we sent around 6000 updates (over a month worth of updates) for a total cost of $1.08. Your plan might vary. Fig.9: as the 4G Remote Monitoring Station is only powered up infrequently, it may not respond to an SMS command immediately. The two-minute delay shown here occurred during testing, when we had the Interface Shield set to power down for about one minute at a time. The canned response can be changed by editing the Arduino code. Connect the battery to CON2 and the power source to CON1. Briefly short out JP1 and check that the whole assembly powers up. The upload to ThingSpeak should take less than a minute. If it does not, then you may need to do some debugging to find out what’s wrong. Re-connect the Leonardo board to the computer and open a serial terminal program to monitor the output. It should look like that shown in Fig.8. Look for a 200 HTTP code and “ThingSpeak Success” message. If you get this, then uploads to ThingSpeak are working correctly. You might find that the Arduino Serial Monitor does not behave well when the Leonardo powers down. We had success with a program called TeraTerm, as this automatically reconnects to the serial port if it discon- Finishing it off Connect the Arduino board to your computer and select the Leonardo board and its corresponding serial port from the Arduino IDE menus. Compile and upload the “4G_ Monitoring_Station.ino” sketch. Unplug the Leonardo and attach the two shields. 36 Silicon Chip Here’s the USB Port Protector from our May 2018 issue – we used one of these without components, except for the USB plug and socket, during testing. This allows data to be transferred, but not power. Australia’s electronics magazine nects and reconnects. Unfortunately, the USB lead will also power the Leonardo, so the power down functions may not work as expected while connected to a computer. A trick for testing To test our prototype, we needed a way to allow USB communication but without powering the Leonardo, as this interferes with the power control hardware. To achieve this, we used one of our USB Port Protector PCBs described in May 2018 (siliconchip.com.au/ Article/11065). If the Port Protector PCB is wired up with no components except the USB plug and USB socket (CON1 and CON2), then it connects GND, D+ and D-, but not 5V. Thus this ‘dongle’ can be used to connect a USB device to allow data but not power to be transferred. The Leonardo is then powered via its onboard 5V regulator fed from the VIN pin. Take care that the ground of your computer is not at a different potential to the ground of the 4G Remote Monitoring Station; for example, if you are powering it from a bench supply or similar, make sure the outputs are floating. You can use a battery-powered comsiliconchip.com.au puter for testing if you are not sure about this. Debugging While the code is quite complex, we did not run into many problems with it. But in case you do, we’ll run through some of the error messages the Arduino might display. If you don’t see the “GNSS on” or “Format set” messages, your Arduino is probably not communicating with the 4G Shield. According to the shield’s data sheet, it communicates at 115,200 baud, but our unit was set to 19,200 baud. You can change this setting at line 5 in the Arduino code. After the “GNSS on” message, you should see “Success” and a network name. If you see “Fail” here, the 4G Shield is not registering with the network. This generally happens when the 4G Shield has no reception. It could be due to the shield not supporting your telco’s frequency band, or you may be out of range of a cell tower. Check that the antennas are connected correctly. You will occasionally see “GNSS fix fail” as the 4G Remote Monitoring Station compromises getting a fix at all times for saving power. The code tries to retrieve the APN (access point name) from the 4G Shield and use it to connect to mobile data. If you see a message referring to APN, CSTT or bearer failing, then this is not being set up correctly. Check the APN name that your provider uses. The URL that the 4G Remote Monitoring Station uses should be displayed, followed by an HTTP result code. If it is not 200 (HTTP success), check https://au.mathworks.com/help/ thingspeak/error-codes.html to see what other error codes mean. If it still isn’t working, numerous extra debugging lines in the code have been commented out (by adding “//” to the start). You can enable the extra messages by removing these and compiling and uploading the code again. You can also try our “Leo_FTDI_ with_passthrough.ino” sketch. This configures the Leonardo to allow direct communications between the serial port and the 4G Shield. You can try different baud rates to see what works and send commands directly to the 4G Shield. Upload this to the Leonardo and short JP1 on the power control shield. You may need to press the 4G Shield’s BOOT button to power it up manually. Once you have confirmed the correct baud rate, upload “4G_Monitoring_ Station.ino”’ to the Leonardo again. Conclusion We’ve deliberately left this as an open-ended project; we expect that readers will customise the hardware and code to suit different applications. For outdoor use, we recommend housing everything in an IP-rated plastic enclosure, with both antennas mounted on the underside of the lid. Including some vent holes, facing down, can help to drain any condensation which may form, and allow the outside air to be sampled by the BME280 sensor. SC UNIQUE ORIGINAL CARTOON ARTWORK! 100% of proceeds go to the NSW RURAL FIRE SERVICE and “WOMBATISED” We mentioned earlier that this project came about because of Wombats - or more particularly, our zany cartoonist Brendan Akhurst(whose work features in our “Serviceman” column). We also mentioned that Brendan lives way out in the bush – what we didn’t know then is that his whole area was severely impacted by last month’s bushfires. Brendan told us about the incredible work of both “Wombatised”, the group helping to save Wombats in the wild, and the volunteer Rural Fire Service whose members not only saved his house but many of his neighbours (along with countless Wombats!). He wanted to organise some way to thank the RFS and “Wombatised”. Now we are often complimented about Brendan’s cartoons in SILICON CHIP and he suggested that we could sell the ORIGINAL ARTWORK of his Serviceman cartoons, with the whole of the proceeds being split between the RFS and Wombatised. So here’s the offer: if you’ve admired Brendan’s wacky cartoons in the past, you can now purchase that original art, autographed by him, for the bargain price of just $100 each – and you’ll know that 100% of that money will go to the two charities. Of course, if you want to pay more than $100, we’ll make sure that every cent is donated. And we’ll even pick up the postage charge. Simply look back through the magazine and choose the cartoon(s) you want to buy. If someone else has beaten you to the draw, (ok, crook pun!) we’ll let you know so you can choose another. siliconchip.com.au Australia’s electronics magazine Original cartoon artwork, signed by Brendan Akhurst himself Only $100 each (or more if you want to donate more!) Tell us the issue date and page no of the cartoon you want. If that cartoon is already sold, we’ll let you know. Order now online: via siliconchip.com.au/shop/3/5289, or call SILICON CHIP 9AM-4PM, Mon-Fri on (02) 9939 3295 VISA and MASTERCARD accepted February 2020  37 “Hands on” review by Tim Blythman Introducing the – a PIC-based Arduino Arduino started out using 8-bit Atmel AVR micros, but these days, there are Arduinos based on all sorts of chips. This one happens to use basically the same device that Geoff Graham used in his 28-pin Micromite series. As you would expect, it’s very capable, and it can take advantage of most of the vast range of Arduino software and hardware that’s available. T he battle between Microchip and Atmel has been going on for a long time now, with neither side giving any ground; that is, until Microchip ended the argument by purchasing Atmel! Despite that, to this day, we still see a clear line dividing the Atmel AVR-based Arduino boards and PIC-based boards such as the Micromite. Even though Microchip took over Atmel in 2016, the two families remain essentially distinct, although some features have flowed between the two and you can now use Microchip’s MPLABX IDE to program some Atmel microcontrollers. The chipKIT family blurs this line further, allowing a PIC32-based microcontroller to be programmed with the Arduino IDE. The Lenny is only one member of this family; there are numerous other chipKIT boards with PIC32 microcontrollers and varying features. They all sport a 32-bit PIC32 microcontroller, and with that comes all the advantages of a 32-bit microcontroller compared to the 8-bit AVRs. And like all PIC32 devices, they operate from a 3.3V supply, compared to the 5V that’s typical for AVRs (although AVRs can run from 3.3V too). To work with the Lenny, you’ll need a copy of the Arduino IDE (integrated development environment), which can be downloaded for free from: siliconchip.com.au/link/aatq chipKIT history The first chipKIT boards were introduced around nine years ago by a partnership between Microchip Technology 38 Silicon Chip and Digilent. The idea was to create a PIC32-based board that could use Arduino-compatible add-ons (such as shields and modules) and also provide a programming experience for those familiar with the Arduino IDE. The first boards were known as the chipKIT Uno32 and Max32, and were intended to be interchangeable with the Uno and Mega respectively. The Uno32 uses a PIC32MX320F128 while the Max32 sports a PIC32MX795F512, the same processor as the original Maximite (siliconchip. com.au/Series/30), also from around nine years ago. Several chipKIT boards have been developed, most using PIC32MX variants, although a few use the higher-specced PIC32MZ series. Hardware compatibility is achieved by using the standard Arduino header layout, although there is the proviso that any attached boards must support 3.3V logic levels and not just 5V. The PIC32 microcontrollers have a small edge here over some other 3.3V chips, in that many have some pins which are 5V tolerant, which simplifies interfacing to other 5V parts. Much of the magic is in the software; the compiler and libraries mean that (for the most part), the same Arduino sketch code can be used for an ATmega328-based Uno and a PIC32 based chipKIT board. The original IDE for working with chipKIT boards was called the MPIDE (multi-platform IDE) and was forked from the open-source Arduino IDE. Finally, with support for non-AVR boards being introduced into the Arduino IDE, Australia’s electronics magazine siliconchip.com.au Features: • • • • • • Arduino R3 footprint and layout 32-bit PIC microcontroller (PIC32MX270F256) Native USB interface 256kB flash memory (244kB usable) 64kB RAM 40MHz processor clock the chipKIT core for the Arduino was introduced. So now, chipKIT support can be added to the Arduino IDE using the Boards Manager, after which the chipKIT boards appear in the usual list. The chipKIT Lenny While many of the early chipKIT boards were produced by Digilent, the open-source nature of the hardware and software meant that variants inevitably followed. A company called Majenko Technologies designed the Lenny board; they specialise in open-source hardware designs. We could have reviewed any of the chipKIT variants, but we chose the Lenny because it’s one of the cheaper chipKIT boards available. It also appears to be well designed regarding Arduino compatibility. In particular, it follows the R3 layout. It has dedicated pins for I2C and SPI in the correct places, as well as secondary I2C and SPI connections where you would find them on the Uno. So it has the best chance of working with shields, even if they date back to the days when the Uno was the only option. It uses a PIC32MX270F256D micro. We used the DIP variant of this chip in our February 2019 USB Adaptor for Micros (siliconchip.com.au/Article/11414). Its immediate predecessor, the PIC32MX250F256B, was also used in the ASCII Video Terminal project from July 2014 (siliconchip. com.au/Article/7925). These chips have an onboard USB peripheral. In this case, it is used for direct communication with the host PC, similarly to the Arduino Leonardo. And it’s the Leonardo which is the inspiration for the Lenny design and name, in case you hadn’t guessed. The hardware Fig.1 shows the schematic of the Lenny. As it is opensiliconchip.com.au source hardware, all the design files (such as PCB files) are available online via siliconchip.com.au/link/aaxi The DC jack, CON1, supplies up to 12V to 5V LD1117S50T regulator REG1 via schottky diode D1. Alternatively, REG1 can be supplied directly from the VIN pin. The 5V rail powers 3.3V MCP1825S-3302 regulator REG2. The LD1117S50T regulator can handle up to 15V, but the Lenny manual notes an absolute maximum of 12V. Since 12V automotive systems can easily reach above 14V, this reduces the board’s apparent usefulness. IC2, an op amp configured as a comparator, controls Q1 to connect the 5V from the USB socket unless power is available from VIN. This part of the circuit is virtually identical to that used in the reference Uno R3 design. An 8MHz clock is provided by clock oscillator XO1 and fed into the OSC1 pin of the PIC32MX270F256D, IC1. The pins of IC1 are broken out to the various headers around the board, as well as to the micro-USB socket, CON3. There are two tactile push-buttons on the board. S1 is marked PROG and is used to activate the bootloader for uploading sketches, while S2 is used to reset the microcontroller. Near the USB socket is the ICSP header (CON9) with staggered pins to allow a header to be friction-fitted temporarily. The ICSP header is not needed during regular operation, but can be used to program the PIC32 microcontroller directly or to update the bootloader firmware. There are four LEDs onboard. Two indicate serial data activity (TX and RX), one is for power and one flashes during programming, and can be used for other tasks in your own code. The usual array of bypass capacitors surround the microcontroller. While the board is sparse, the simplicity lends itself to the possibility of being the basis of other PIC32based designs. Table 1 shows the capabilities of each pin that’s broken out to one of the usual Arduino headers. Software As mentioned above, to use the Lenny with the Arduino IDE, we need to install the chipKIT core. This contains several parts, but they are all installed as a single unit. It includes a series of board definitions, which ensure that the pins marked on the board are correctly associated with the physical pins on each specific microcontroller. It also includes a C++ compiler. Like the AVR Arduino core, it is based on the open-source gcc (GNU Compiler Collection). This turns the Arduino-flavoured C++ code into PIC32-specific machine code. There are also libraries which translate the common Arduino-specific functions into code which correctly interfaces with the peripherals on a PIC32 microcontroller. This includes such simple functions as digitalWrite() and analogRead(), as well as things like the SPI and I2C interfaces. There are also utilities to upload the sketch to the board; in the Lenny’s case, this is pic32prog, the same program that can be used to program some variants of the Micromite. We’re using version 1.8.5 of the Arduino IDE. To program the Lenny, you need an IDE new enough to include the Boards Manager, which was first included with version 1.6.7, but Australia’s electronics magazine February 2020  39 D1 CON1 A REG1 LD1117S50TR 3 2 VIN K VIN REG2 MCP1825S-3302 Vcc (+5V) VOUT 10 F 4 VOUT GND 10 F 1 OUT IN S 10k GND GND 2 4 1 F 4 +3.3V 5 G 1 IC2 3 PROG D2 IC2: MCP6001T A +3.3V 17 RESET 10 42 9 8 CON2 33 PROG 35 AVDD 5 1 3 15 34 4 RB8/SCL1 USB D–/RB11/PGEC2 +3.3V 100nF E 30 CLK MOSI2/RA9/TDI 13 32 A0 SCK2/RB15 RC3 RC5 MISO2/RA4/SOSCO RC7 CLKI/RA2 RC6 RA10/TMS RC4 RA7/TCK RB7 RA8/TDO RC9 RC8 20 A0 21 25 A2 27 A3 23 A4 24 A5 CON4 A A   K CHIPKIT LENNY K  LED1 K AREF 19 GND SCK1 14 MISO1 22 MOSI1 11 D10 D9 D8 38 31 D7 3 D6 41 D5 2 D4 37 D3 43 D2 5 D1 4 D0 AN1 /RA1 AN2 /RB0 AN6/RC0 AN8/RC2 AN4/RB2 VCAP AN5/RB3 VSS 6 VSS 29 VSS 39 7 10 F  LED2 K Fig.1: there isn’t much to the Lenny circuit. The main microcontroller handles the USB interface, so there is no need for an interface IC. The remainder of the circuit is mostly involved with power supply and voltage regulation. we haven’t tried it with a version that early; it may work. We’re using Windows 10, but the same process should work for macOS, Linux (x86 and x64) and even a Raspberry Pi. Board installation Firstly, open the Preferences window (File -> Preferences) and add the following URL to the Additional Boards Manager URL list: https://raw.githubusercontent.com/chipKIT32/chipKITcore/master/package_chipkit_index.json Silicon Chip SCL1 SDA1 1 A A LED0 CON5 CON6 AVSS 16 PWR LED 18 44 RB13/MOSI1 IC1 26 PIC32MX270PIC3 2 MX270RC1 F256D 36 4x 1k A1 40 RB14/SCK1 RB5 12 2 1 AREF OUT 3 GND CON9 SC AN0/RA0 RESET S2 100nF PROG/RB4/SOSCI RA3 8 MHz XO 1 6 2020 RB9 /SDA1 USB D+/RB10/PGED2 VDD RESET 3 5 MCLR RB1/MISO1 +3.3V VIN 40 VDD VUSB3V3 CON8 +5V GND 28 VDD VBUS +3.3V GND 100nF 6 2 4 +3.3V RESET LK1 FAST PROG L1 100nF +5V F1 500mA L2 S1 1M 4 10k 100nF K 2 1 2 3 X 4 2 1 F 10k Q1 D 1 Vdd (+3.3V) 3 +5V 10k CON3 1 Separate this from any existing entries with a comma. Now open the Boards Manager from Tools -> Board -> Boards Manager. It may take a few moments for the list to be populated, as each URL is checked. Unfortunately, you cannot remove URLs after the boards are installed, as this makes them unavailable from the IDE. We understand this behaviour may change in future versions of the Arduino IDE. The chipKIT option should appear, as shown in Screen1, so click the Install button. Installation may take a while as Australia’s electronics magazine siliconchip.com.au Pin Features D0.....................5V tolerant digital I/O, serial RX D1.....................5V tolerant digital I/O, serial TX D2.....................5V tolerant digital I/O, serial1 TX, interrupt D3.....................5V tolerant digital I/O, PWM, interrupt D4.....................5V tolerant digital I/O, serial1 RX, interrupt D5.....................5V tolerant digital I/O, PWM, interrupt D6.....................5V tolerant digital I/O, PWM, interrupt D7.....................3.3V digital I/O D8.....................5V tolerant digital I/O D9.....................PWM D10...................PWM D11...................SPI MOSI D12...................SPI MISO D13...................SPI SCK SDA...................5V tolerant digital I/O SCL...................5V tolerant digital I/O A0......................analog or 3.3V digital I/O A1......................analog or 3.3V digital I/O A2......................analog or 3.3V digital I/O A3......................analog or 3.3V digital I/O A4......................analog, 3.3V digital I/O or I2C SDA A5......................analog, 3.3V digital I/O or I2C SCL ICSP SCK..........3.3V digital I/O ICSP MOSI........5V tolerant I/O ICSP MISO........3.3V digital I/O Table 1 - Lenny pin capabilities there are the various board definitions and compilation and upload tools to be installed. The total size is around 1GB. Note that the Lenny board doesn’t appear in the list on this screen, but it is supported by version 2.1.0 of the chipKIT core, as shown in Screen2. Using it We found that there are a few quirks when using the Lenny compared to a typical AVR board like the Uno. These are apart from obvious differences such as the 3.3V I/O voltage. The first is the “PROG” button. The Lenny needs to be manually put into programming mode by pushing the PROG button, which isn’t necessary on the Uno. This is because the onboard USB interface is shared between the programming interface and user programs. If you don’t press this button before initiating a code upload, that upload will fail. The PROG button can be a little awkward to access if a shield is fitted to the top of the Lenny. We were just able to get a finger into the gap, but we imagine some people might struggle with this. Also, note that this means that the serial port number (COMx) changes between programming mode and run mode. This happens with the AVR-based Leonardo too, but the upload utility detects it, so it works seamlessly, and there is no need to change the serial port manually. The Lenny software does not do this, so to work with a program that uses the serial port (especially for debugging), the serial port has to be changed twice for each program upload. siliconchip.com.au The way we sidestepped this is to use another serial terminal program, specifically, TeraTerm. TeraTerm has the advantage that it can resume communication even if a serial port disconnects while the terminal is open, as is the case when the Lenny switches to programming mode. The TeraTerm window can simply stay open in the background. It operates a bit differently to the Arduino Serial Monitor, but it’s perfectly adequate for most purposes. Benchmarking We decided to run some benchmarks on the Lenny, to compare its performance to other Arduino boards – see Table 2. We used the same method as in our review of the new Arduino Nano boards in October 2019 (siliconchip. com.au/Article/12015). Since one of those boards, the Nano 33 IoT, also has a 32-bit chip (an Atmel SAMD21), this makes a good comparison for the Lenny. The benchmark tests show the Lenny to be by far the fastest overall. Note that the Lenny runs at 40MHz while the Nano 33 IoT runs at 48MHz. The Nano 33 IoT is ahead by a tiny margin when doing byte, integer and long multiplies, but otherwise, the Lenny comes out firmly on top. There are vague mentions of a 50MHz bootloader configuration for the Lenny, which we imagine would put it even further ahead. But the PIC on our Lenny is the 40MHz variant, so this upgrade is a bit dubious; it may work, but perhaps not reliably. Compatibility We don’t expect that the Lenny will be immediately compatible with all Arduino sketches, in particular, those which use direct port writes. When such techniques are used, those sketches will only work on the specific board they are written for, which is typically the Uno. To test this, we tried compiling a few different sketches written for different shields. The first one we tried was for the Jaycar XC4454 LCD Shield. This uses the common HD44780-type LCD controller and is supported by the ‘LiquidCrystal’ library, which is usually included with the Arduino IDE. Once we had the pins set correctly (the Jaycar shield uses a different pin configuration to the default), the sketch worked as expected. Since this shield uses one-way communication, it depends on the LCD controller accepting 3.3V logic levels, which it appears to do. The next test was one of our own shields, the 3.5in Touchscreen Arduino Adapter from May 2019 (siliconchip.com. au/Article/11629). We found that the display worked fine, even with the level converting resistors in place. The level-converting resistors are intended to allow 5V I/O signals to drive the 3.3V controller on the LCD, but in this case the 3.3V I/O is being divided down to 2.2V levels. So, it’s remarkable that it worked! The touch controller did not fare so well; we could not get it to work, even modifying the level-converting resistors to deliver 3.3V I/O signals (by removing the lower resistors from the dividers). We could not resolve this issue, but expect that there is some way to make it work. After all, the same display works perfectly well with the practically identical PIC32MX170F256 chip in the Micromite. We suspect that this has to do with the different ways that SPI interfaces are handled, particularly as the touch Australia’s electronics magazine February 2020  41 digitalRead digitalWrite pinMode byte * byte / byte + integer * integer / integer + long * long / long + float * float / float + itoa() ltoa() dtostrf() random() y|=(1<<x) bitSet() analogRead() analogWrite() Nano 5.032µs 4.532µs 4.470µs 0.632µs 5.412µs 0.443µs 1.386µs 14.277µs 0.883µs 6.102µs 38.662µs 1.763µs 7.932µs 80.162µs 10.107µs 12.957µs 125.987µs 78.637µs 91.412µs 0.569µs 0.569µs 111.987µs 7.167µs Nano    EveryNano33 IoT chipKIT Lenny 6.679µs 0.948µs 0.804µs 6.459µs 1.913µs 1.066µs 3.244µs 1.931µs 1.644µs 0.570µs 0.197µs 0.199µs 5.297µs 0.636µs 0.451µs 0.381µs 0.197µs 0.149µs 1.263µs 0.171µs 0.174µs 14.052µs 0.591µs 0.396µs 0.759µs 0.171µs 0.124µs 5.547µs 0.168µs 0.174µs 38.362µs 0.596µs 0.396µs 1.514µs 0.169µs 0.124µs 7.314µs 3.016µs 1.329µs 78.337µs 11.721µs 4.296µs 9.692µs 2.806µs 1.276µs 12.792µs 3.041µs 0.876µs 125.487µs 16.196µs 2.696µs 76.687µs  46.896µs 90.512µs 9.546µs 2.121µs 0.444µs   0.099µs 0.444µs 0.123µs 0.099µs 112.887µs 422.946µs 21.046µs 6.932µs 6.801µs 1.401µs Table 2 - chipKIT Lenny benchmark (lower controller IC on the 3.5in panels works at a much lower maximum bus speed than the LCD. We also tried our updated Seismograph shield from April 2019 (siliconchip.com.au/Article/11532). Amongst the other hardware, the main shield used has an SD card interface that uses the SPI peripheral and a real-time clock (RTC) module that uses the I2C peripheral. This project did not compile immediately, as we used a specific format of an I2C command that had not been implemented in the chipKIT core. This format (where a third argument is presented in the requestFrom() function call) is documented in the official Arduino reference. Further investigation shows that this issue has been identified but not fixed in the chipKIT core (see https://github.com/ chipKIT32/chipKIT-core/issues/240). The specific SD card file system library we used in this project was not able to read the SD card either. We also tried an example SD card sketch (CardInfo) from the Arduino IDE, and this was able to correctly identify the card and list its contents. So it appears there are some minor differences between the AVR and chipKIT libraries. six; pin D11 is the one that is missing this feature. Fortunately, the extra speed of the PIC32 microcontroller means that software-based PWM is available and can perform this task instead. The ‘SoftPWMServo’ library uses the core timer to generate PWM signals (and servo signals) on pins that do not have hardware PWM support. The library notes that it may be subject to approximately 50ns of jitter in the output. This equates to around 1% of the pulse width resolution, so is unlikely to be noticeable for most applications. Special features While browsing through the list of included examples, we noticed a folder called “USB_MSD”. Inside, there are two example sketches which program the Lenny board to behave as though it is a USB Mass Storage Device. At first, we could not get either of the examples to compile, but by adding two lines (and commenting a third out), we got the sketch “AnalogToFile” to compile and upload. These changes are shown in Screen3. is better) Once uploaded, the Lenny was visible to the attached computer as a USB Mass Storage Device. After formatting it, we were able to copy files to it. There was only 26kB of space available, as the contents are held in a 48kB RAM buffer. The “AnalogToFile” sketch also creates a file in this file system, which can be read by the USB host computer. Being able to program a board to emulate a USB stick that can modify its own contents is very interesting. Previously, to copy log files from an Arduino project, you needed an SD card or a clunky custom interface, such as copying data from a serial terminal. Now, using the Lenny, you can simply get the board to PWM support You might have also noticed from Ta- Screen1: once the chipKIT URL has been added to the preferences page, the ble 1 that the Lenny only has five hard- chipKIT core can be selected from the Boards Manager. Though the Lenny is ware PWM pins, compared to the Uno’s not in this list, its profile is installed. 42 Silicon Chip Australia’s electronics magazine siliconchip.com.au to set aside some time to work through the minor niggles which pop up. The chipKIT core files are common to all chipKIT boards; thus, it would be a similar process to get such shields working with any chipKIT board. But unfortunately, some libraries depend on AVR-specific features, so they cannot be made to work easily. The Lenny verdict Screen2: the full list of available chipKIT boards can be seen after the chipKIT core is installed. While they have diverse names, all are based around PIC32 microcontrollers. generate its log file to the internal RAM image and then it can be easily copied and pasted via a file browser program. We haven’t looked into this too deeply, but there is probably a way to attach to an SD card and just use the Lenny as a card reader that can also write to itself. While it is a limited and simple interface, we think there are many potential uses for it. We’re impressed with the speed of the Lenny board, as shown in the benchmarks. The 32-bit processor is much faster at mathematically-intensive programs than an 8-bit processor, and generally quicker than other 32-bit boards such as the Nano 33 IoT. The extra speed also means that software PWM on all pins is possible. While not as accurate as hardware PWM, it is certainly adequate for most purposes. The writers of the chipKIT core have worked hard to make it compatible with other Arduinos, but there are still some gaps present in important libraries. So it is not always a trivial process to port existing projects from 8-bit AVR-based boards to the Lenny. The ability of the Lenny to behave as a USB Mass Storage Device is really powerful, since it is such an intuitive way to move files around. Overall, the Lenny is a great board, but perhaps not capable of being a drop-in substitute for AVR-based boards. We expect that it will be best used in applications where its specific features would be a benefit over other boards, rather than as an upgrade in existing applications. In particular, we expect to see projects spring up around USB Mass Storage Device examples. SC Other USB features Some other USB-equipped boards like the Leonardo can emulate a keyboard or mouse. We used such a board (called a ‘Beetle’) in our project from August 2018 to interface an IR remote control to a computer by emulating a keyboard (siliconchip.com.au/Article/11195). We tried the keyboard and mouse examples that are available for the Lenny, and they performed as expected, although we could not get an infrared interface working, as the IR library uses AVR-specific interrupt code to receive the signal. Screen3: the “USB_MSD” examples show off what we think is one of the Lenny’s The overall impression here is that most interesting feature, being able to act as a USB Mass Storage Device. We needed most things will work, but you need to make some minor changes to the code to get it to compile, which are shown here. siliconchip.com.au Australia’s electronics magazine February 2020  43 Putting your Touchscreen Micromite BackPack to work... INDOOR 'POOR AIR QUALITY' MONITOR By Geoff Graham Do you sometimes get the impression that the air in your office or home is rather “stuffy”? That can be rather subjective – but there is an objective way to measure air quality. That is with a volatile organic compound (VOC) meter. The mighty Micromite BackPack and a cheap module make building one of these dead easy! Now you really can find out whether you are being impacted by “Sick Building Syndrome”. 44 44  S Silicon Chip Australia’s Australia’s electronics electronics magazine magazine siliconchip.com.au NOTE : Th specificall is monitor is y volatile for indoor airborn It does NO organic compounds e T me . ticulate asure airborne p Given the s, such as smoke. arhig smoke rec h levels of bushfire e shortly loontly, we hope to ka sensors in t alternative measure p tended to articulates . There are no switches: all controls are based on the Micromite BackPack touch screen, The CCS811 Air Sensor can be seen on the top right of the Jiffy Box. A reading of 53 parts per billion (as shown here) would indicate pretty clean air! T he amount of volatile organic compounds (VOCs) in the air is a fundamental measure of air quality. VOCs include thousands of chemicals that can be present in the air, many of which are recognised to have a significant impact on the health of people breathing them in. This monitor uses a CCS811 metal oxide (MOX) sensor made by ams AG, Austria, to measure the total VOC level in the air. This sensor comes in a tiny surface-mount package that is very difficult to solder. Fortunately, it can be purchased as part of an inexpensive (~$15) fullyassembled module which, when coupled with a Micromite LCD BackPack, makes a capable air quality monitor. The VOC reading varies with temperature and humidity, so the sensor module also includes temperature and humidity sensors, allowing it to compensate for variation in both. Once per second, the Micromite’s BASIC program reads these values and feeds them to the CCS811 sensor, which then uses them to adjust its VOC reading to maintain accuracy. The BASIC program then extracts the VOC reading and displays it as a number, expressed in parts-per-billion (ppb). It also draws a graph on the LCD screen, so that you can see the trends in the reading. Other functions of the BASIC program allow you to set the baseline for the VOC reading (ie, essentially set the zero reading) and even upgrade the firmware running in the CCS811 sensor. We’ve described a few different versions of the LCD BackPack in past issues of the magazine. You can use any of them for this project. See the panel is built on a semiconductor substrate using normal manufacturing processes. By varying factors such as the type of oxide, the grain size and the heating temperature, the manufacturer can adjust the sensitivity to suit various reducing gases. The CCS811 sensor used in our Air Quality Monitor is especially sensitive to alcohols, aldehydes, ketones, organic acids, amines, aliphatic and aromatic hydrocarbons. These are typically produced by humans and building materials. Humidity has a strong influence on the performance of metal oxide gas sensors. Reactions between the surface oxygen and water molecules cause a reduction in the resistance of the MOX layer, reducing its sensitivity. Temperature also has an effect. This is why the module used in our Air Quality Monitor includes a temperature/humidity sensor. The program running on the Micromite reads the temperature and humidity values once per second and transfers them to the CCS811 sensor. The internal algorithms of the CCS811 then use these to adjust the readings accordingly. The sensor needs an initial burn-in period of 48 hours to remove manufacturing contaminants from the surface. It also needs a 20-minute warm-up period whenever power is applied. The sensor can become contaminated, so it has a limited lifetime. According to the manufacturer of the CCS811, this is at least five years MOX Sensors MOX stands for Metal OXide which, in a sensor such as the CCS811, is a thin film of a metal oxide such as tin oxide (SnO2) in a porous granular state. In clean air, oxygen is adsorbed on the surface of the metal oxide and this attracts free electrons in the material to the surface which, in turn, has the effect of increasing the resistance of the MOX layer. In the presence of a reducing gas (eg, a volatile organic compound), the oxygen is pulled from the metal oxide surface to react with this gas. This frees the previously trapped electrons, causing a measurable decrease in resistance. To assist in this process, the MOX layer is raised in temperature by a built-in heater. In a modern sensor, the whole structure siliconchip.com.au Australia’s electronics magazine February 2020  45 The sensor module does not contain many components, and so is quite tiny (it’s shown here about twice life size). Search eBay or AliExpress for the two keywords CCS811 and HDC1080. Many of the available modules will match either of the keywords but not both, so make sure that the module you purchase matches this photograph and has both the CCS811 and HDC1080 sensor ICs. below which lists which issues these articles appeared in, with links to the online versions and the respective kits. We recommend that you build the V2 or V3 BackPack for this project, as those versions allow the screen brightness to be controlled by the BASIC program. But note that the software is written with the 2.8in 320x240 LCD screen in mind, so if you build V3 with a larger 3.5in 480x320 display, you will have to modify the software to suit. The program controlling the Air Quality Monitor is written in the easy-to-use BASIC programming language, so you are free to get in there and modify it to suit your preferences. But we don’t suggest that you undertake the job of modifying the software for the 3.5in screen unless you have some prior MMBasic programming experience. By the way, if you are designing on another project based on the Micromite LCD BackPack, you may wish to extract segments of the Air Quality Monitor program for your own needs. For example, the graph drawing algorithms could come in handy for many other tasks. any one of the thousands of organic (ie, carbon-containing) chemicals that are present in the air. These are mostly gases at room temperatures. The list includes both man-made and naturallyoccurring chemicals. The amount, or concentration, of VOCs present is expressed in a variety of units, but in the case of our sensor, it is reported in parts-per-billion (ppb). For example, if the concentration is 10ppb, for every billion molecules of air, there are ten volatile organic compound molecules. Sources of VOCs include plants, manufactured products (such as plastics) and animals (including humans). An important subset of VOCs are semivolatile organic compounds, which come from building materials, furnishings, cleaning compounds, air fresheners, pesticides and activities such as tobacco smoking and cooking with a gas stove. Some of the key indoor sources of semi-volatile organic compounds are pesticides, building or decorating materials containing flexible plastics such as vinyl wallpaper or vinyl flooring and materials containing flame retardants. One common VOC that has been recognised as having significant health impacts is formaldehyde, which is widely used in the manufacture of building materials and household products. It is also a by-product of combustion and other natural processes. The CCS811 sensor used in our Air Quality Monitor reports on total volatile organic compound concentrations. This term refers to the concentration of many different VOCs that LCD DISPLAY MODULE WITH TOUCH SCREEN DC POWER SOCKET RED BLACK CON3 GND RX TX 5V GND +5V VCC GND CCS811+ HDC1080 GAS SENSOR MODULE +3.3V 26 SCL 25 SDA 24 WAKE 22 INT 21 RST 18 ADDR MICROMITE LCD BACKPACK 17 16 14 10 Volatile organic compounds 9 5 The side box describes how a MOX sensor works; essentially, it measures organic carbon molecules that are in vapour form suspended in the air. Many are given off by humans, and the CCS811 is particularly sensitive to these. In scientific literature, the term VOC (volatile organic compound) refers to Fig.1: the Air Quality Monitor circuit consists of just two modules. These are the Micromite LCD BackPack and the sensor module, with the CCS811 and HDC1080 ICs onboard. The sensors communicate via I2C, so the sensor module connects to the SCL and SDA pins on the BackPack. 46 Australia’s electronics magazine Silicon Chip SC 20 1 9 MICROMITE AIR QUALITY MONITOR 4 3 RESET siliconchip.com.au are present simultaneously in the air, and the CCS811 is more sensitive to the subset of VOCs that are typically caused by human activity. Taken together, the total VOC reading indicates the quality of the air that we breathe. For example, a reading of zero indicates clean, fresh air. A reading of 4000ppb to 8000ppb (4-8ppm) would indicate a stuffy room, while a reading of over 16,000ppb (16ppm) would indicate a particularly bad environment. Note that the CCS811 does not claim to be highly accurate; in fact, the data sheet talks in terms of indicated levels of VOCs in the air. So, if you are thinking of suing your employer over a sick building environment, you would need to employ much more accurate equipment that could measure specific chemicals (and hire some pretty good lawyers!). Regardless, the CCS811 is quite sensitive. We tested it in a large room without much ventilation and with two people present, the VOC reading climbed to more than 3000ppb over a couple of hours. Opening a window just a crack caused the reading to drop back to near zero within half an hour. The Micromite-based Air Quality Monitor before it is put into its Jiffy box, ICSP CON4 47 F 1 http://geoffg.net/micromite.html 07102122 USB CON3 LCD Backlight 100 VR1 S1 10 F 5V TX RX GND CON1 (UNDER) + 100nF Mode 1 Fig.2: if you’re building the Air Quality Monitor around the original Micromite LCD BackPack, this overlay shows how to fit the components. The orientations of IC1 and REG1 are critical. You may have polarised or non-polarised highvalue capacitors. Also, a 10µF capacitor can be used in place of the 47µF capacitor if it’s a ceramic type. CON1 and CON2 are fitted to the underside of the board. siliconchip.com.au 10k 1k CON4 47 F + + A 100nF S1 RESET LED1 10 F + (UNDER) 10 F REG1 MCP1700-3302E IC1 PIC 32 MX170F256B-50I/SP 2.8-Inch Micromite LCD BackPack CON2 10 F REG1 MCP1700-3302E IC1 PIC 32 MX170F256B-50I/SP CON3 LCD 100nF 100nF 2N7002 Q1 Micromite LCD BackPack V2 PWM 07104171 Backlight DMP2215L Q2 1k 10k 100nF (UNDER) + 1 + (UNDER) JP1 CON1 Construction is quite simple and consists of just assembling the Micromite LCD BackPack (which should take less than an hour) then mounting 10k CON2 Construction IC2 PIC16F1455-I/P RESET 3 4 5 9 10 14 16 17 18 21 22 24 25 26 3V3 5V GND The circuit of the Air Quality Monitor basically consists of just two modules connected together, as shown in Fig.1. These are the Micromite LCD BackPack and the sensor module (with the CCS811 and HDC1080 chips). Both the CCS811 and HDC1080 communicate via I2C, so the sensor module’s SCL (clock) and SDA (data) 5V TX RX GND Circuit description There are many modules on offer that will match either of the keywords, so you need to make sure that your module includes both sensors, and preferably looks identical to the one shown here. This last part is important as there are many sensor modules circulating that claim to incorporate both sensors, but the images displayed by the vendor show that the module does not include the HDC1080 temperature and humidity sensor. This is critical to the correct operation of the device. RESET 3 4 5 9 10 14 16 17 18 21 22 24 25 26 3V3 5V GND pins are wired to the corresponding I2C pins on the Micromite LCD BackPack. The module runs from 3.3V, so its VCC pin goes to the 3.3V output on the BackPack, and the GND pin is the common ground. The other pins on the sensor module (WAKE, ADDR etc) are not used in our application so they can be left unconnected. The sensor module does not contain many components besides the CCS811 and HDC1080 ICs; just a few pull-up resistors and bypass capacitors. It is also surprisingly small, barely large enough to cover the tip of a finger. The module that we used can be found on eBay or AliExpress by searching for the keywords CCS811 and HDC1080 together. Manual Backlight VR1 100 Fig.3: use this overlay diagram instead if you’re building the V2 BackPack. The main difference is the addition of the Microbridge, IC2, which also must be orientated correctly. You may receive three 10µF ceramic capacitors (their orientations are not important) and one can be used in place of the 47µF. If you’re building a V3 BackPack, refer to the August 2019 issue or just follow the PCB silkscreen. Australia’s electronics magazine February 2020  47 If using the laser-cut lid from the SILICON CHIP ONLINE SHOP (see parts list opposite), there are only five extra holes required in the UB3 Jiffy box – one for the power socket, as seen at left, and the others for mounting the CCS811 sensor module. Two of these holes are drilled to form a “figure 8” hole which allows plenty of air circulation to strike the sensor module (see right). The project can be powered from a 5VDC regulated plugpack, from a computer’s USB socket or even from a 5V “powerbank” to allow fully portable operation. and connecting the sensor module. All three versions of the BackPack are available as more-or-less complete kits from the SILICON CHIP ONLINE SHOP: • Original BackPack kit Cat SC3321, $65 + postage: siliconchip.com.au/Shop/20/3321 • V2 BackPack kit Cat SC4237, $70 + postage: siliconchip.com.au/Shop/20/4237 • V3 BackPack kit Cat SC5082, $75 + postage: siliconchip.com.au/Shop/20/5082 (note: comes with 3.5in LCD screen) These kits do not include a box, power supply or cables. But they have everything you need to build the BackPack module. The BackPacks comprise about a dozen components, and in each case, the PCB is printed with the component placement and values. So it is simply a case of populating the board and attaching a suitable LCD panel. We have reproduced the BackPack M3 x 10mm BLACK MACHINE SCREW V1 and V2 PCB overlay diagrams here (Figs.2 & 3) in case you need them. Note that CON1 & CON2 go on the underside of the board. If in doubt when it comes to assembling the BackPack, refer to the relevant constructional article referred to earlier. All three versions of the BackPack fit neatly into a standard UB3 plastic box. All of the kits mentioned above come with a laser-cut lid for the UB3 jiffy box with a rectangular hole for the touchscreen, but you need to purchase the jiffy box itself separately. Fig.4 provides the box mounting details. The result is a neat looking assembly with the display and BackPack securely fastened. The laser-cut panel is thicker than the lid supplied with the UB3 box (3mm), and it lacks recesses, so the self-tapping screws supplied with the box may or may not be long enough. If they’re too short, replace them with four 10mm-long 4G self-tapping screws. If you don’t buy one of our kits, you can still get the custom lid from the SILICON CHIP ONLINE SHOP for $5 plus p&p. It’s available in matte/gloss black (Cat SC3456; www.siliconchip. com.au/Shop/19/3456) or clear (Cat SC3337; www.siliconchip.com.au/ Shop/19/3337). The black lid can be fitted either way around, so you can have either a matte or gloss finish on the outside. The kits have the same choice of lid colour. You can cut your own holes in the lid supplied with the UB3 box, but it is tricky to make a clean cut around the LCD screen. If you choose this route, make sure that no part of the box is pressing on the surface of the LCD as that will upset the touch sensitivity of the panel. Final assembly Use an M3 x 10mm machine screw on each corner with a 1mm thick plastic ACRYLIC LID WITH CUT-OUT FOR LCD (REPLACES ORIGINAL UB 3 BOX LID) SC 20 1 9 TOUCH -SCREEN LCD M3 x 12mm TAPPED SPACER M3 NYLON WASHER (1mm THICK) M3 x 6mm MACHINE SCREW 2.8-INCH LCD PCB NYLON M3 NUTS NYLON M3 SCREWS MICROMITE 2.8-INCH BACKPACK PCB SENSOR MODULE UB3 CASE Fig.4: this shows how the touchscreen, BackPack PCB and laser-cut lid go together before the lid is attached to the UB3 Jiffy box base using four self-tapping screws. The screws supplied with your Jiffy box may or may not be long enough to go through the thicker laser-cut lid; if not, you will need four No.4 x 10mm (or thereabouts) self-tappers. 48 Silicon Chip LASER-CUT LID LCD MODULE HEADER PINS HOLE CUT IN THE CASE TO ALLOW AIR TO REACH SENSORS Fig.5: the sensor module is mounted separately on the side of the box and wired to the BackPack via its eight-pin header and flying leads. Make sure the two sensor ICs sit adjacent to holes drilled in the side of the box, so they can sample the air outside. Note the nut between the sensor PCB and inside surface of the case, so those sensors are not too close to the holes. Australia’s electronics magazine siliconchip.com.au M3 washer and an M3 x 12mm tapped spacer to attach the LCD panel to the acrylic lid. This ensures that the surface of the LCD will be flush with the acrylic lid. Then, the BackPack can be plugged into the LCD and fastened by M3 x 6mm machine screws to each spacer, as shown in Fig.4. The module with the CCS811 and HDC1080 sensors typically comes with an eight-pin header that is not soldered to the board. So you need to fit this, but make sure that the header pins point out from the back (noncomponent) side of the board. After you have cut two holes in the box (for the two sensors), this arrangement will allow you to mount the component side of the sensor board close to the wall of the box. The sensors will be next to the holes and therefore sampling the freely circulating air outside the box. The sensor module should be held in place using two Nylon M3 machine screws, with a nut between the sensor PCB and the inside wall of the case, as shown in Fig.5. This will space the components on the sensor module slightly away from the case wall, but still keep them close enough that they are exposed to the outside air. We are currently experimenting with several other air quality sensors (ie, CO2 and particulate sensors). If they work out, we will update the BASIC program to incorporate them in conjunction with the VOC sensor. So the VOC sensor module should be mounted to one side of the case, leaving space for the other modules if later required. The best method for connecting the sensor module to the BackPack is to use “DuPont” jumper leads. These are lengths of wire with single pin female header sockets on each end. They are designed to slip onto header pins like those of the sensor module and LCD BackPack. Parts list – Air Quality Monitor 1 Micromite LCD BackPack module with a 2.8in LCD touchscreen (eg, built from a SILICON CHIP kit – see text) 1 CCS811 air quality sensor module with onboard HDC1080 temperature and humidity sensors (see text and photos) 1 UB3 Jiffy box 1 laser-cut lid for UB3 Jiffy box (included with kits or available from SILICON CHIP ONLINE SHOP – see text) 1 5V DC 500mA+ regulated plugpack OR 1 USB cable with a female 2.1mm DC power connector on one end [Altronics Cat P6701] AND 1 USB (5V) power supply 1 chassis-mount DC barrel power socket, to suit the power cable (2.1mm or 2.5mm inner diameter) 4 120mm-long DuPont female-female jumper leads 2 120mm-long DuPont female-bare wire leads 4 No.4 x 10mm self-tapping screws 4 M3 x 10mm tapped spacers 4 M3 x 10mm panhead machine screws 4 M3 x 6mm panhead machine screws 2 M3 x 6mm Nylon panhead machine screws 4 M3 Nylon hex nuts 4 1mm-thick Nylon washers, 3-4mm inner diameter You can get these from Altronics (Cat P1017) or Jaycar (WC6026), or search eBay for “dupont jumper”. Using these not only makes assembly easy, but you can also replace the sensor module for testing or if the CCS811 chip becomes contaminated. Loading the software The program running on the Micromite consists of three parts: the MMBasic interpreter, the BASIC program for the Air Quality Monitor and the configuration settings for the LCD panel. The easiest method of loading all three at once is to program the PIC32 chip with the file “AirQuality.hex” which can be downloaded from the SILICON CHIP website. This is easy if you are using either a V2 or V3 LCD BackPack, as both of these include the capability to program the PIC32 chip (ie, Micromite) with new firmware. If you are using a V1 BackPack, then you will need a PIC32 programmer such as the PICkit 3 or PICkit 4. If you do not have such a gadget, you can purchase a fullyprogrammed microcontroller from the SILICON CHIP ONLINE SHOP. This firmware file contains everything that you need, including the MMBasic interpreter, the LCD configuration and the BASIC program for the Air Quality Monitor. So as soon as you load it, you’re ready to go. But be aware that the touch calibration in the combined firmware and BASIC program file was done using a standard LCD panel. So your unit might require display recalibration if it is significantly different from the one that we used. Unfortunately, we’ve seen panels with the touch sensor rotated 180° from others, and they are not easy to tell apart! Luckily, recalibration can be easily performed by connecting the BackPack to a desktop or laptop computer via USB, opening the serial port in a terminal emulator, halting the program 5V 4 Tx 3 2 Rx 1 USB CONNECTOR TYPE A MALE GND DC PLUG DC INPUT SOCKET (ON END OF BOX) 4-PIN FEMALE HEADER CONNECTOR (OR DUPONT POWER CABLE) MICROMITE CON 1 POWER AND CONSOLE CONNECTOR Fig.6: here is our suggested method for powering the Air Quality Monitor from a USB port or charger. You can make up the USB-to-DC-plug cable, or you can buy one from Altronics (Cat P6701) or Jaycar (PP1985). Alternatively, use a 5V DC regulated plugpack which will most likely already have a concentric plug with the right polarity (+ to centre). siliconchip.com.au Australia’s electronics magazine February 2020  49 Screen1: the main display shown at power-up, with the current VOC reading at the top and a graph of VOC over time at the bottom. The graph’s vertical scale can be configured from 500 to 64,000ppb while the horizontal scale can be adjusted to cover 15 minutes to 32 hours. Screen2: touching the main screen takes you to this setup screen. Here you can adjust the graph parameters, set the VOC baseline (the zero point for the CCS811 sensor), upgrade the CCS811’s firmware and set the screen brightness. The raw data from the CCS811 and HDC1080 sensors is also shown at the top of this screen. Screen3: this screen allows you to set the baseline (zero point) for the CCS811 sensor. Initially, this should be done once a week, but after a couple of months, the baseline will only need to be set once a month. with CTRL-C and re-running the calibration routine. For further information on this procedure see the Micromite User Manual (which can also be downloaded from the SILICON CHIP website). Alternatively, if you have a BackPack that’s already programmed with the Micromite firmware, you can set up the LCD screen (if that hasn’t already been done), then load the Air Quality Monitor BASIC code into it. This file is named “AirQuality.bas” and is part of the same download package for this project, from the SILICON CHIP website. the inner barrel conductor connects to the positive supply wire. If you are using a USB charger as the power supply, you can make up a power cable by cutting off one end of a standard USB cable while retaining the Type A socket on the other end, as shown in Fig 6. Then solder the free end to a suitable DC power plug. Most sockets have either a 2.1mm or 2.5mm inner pin, so make sure your plug matches it; 2.5mm plugs will go into 2.1mm sockets but won’t make good contact! The red wire in the USB cable (+5V) should go to the centre pin of the plug and the black to the sleeve. The other two wires (the signal wires) can be cut short as they are not used. Alternatively, suitable ready-made cables are available, such as a Jaycar PP1985 or Altronics Cat P6701 (USB Type A Male to 2.1mm DC Plug). Using the device Power supply The completed Air Quality Monitor requires a 5V power supply with a minimum capacity of 500mA. You can use a 5V plugpack or a USB charger. If you are using a plugpack, make sure that it is regulated and that its unloaded output does not rise above 5.5V, as that could cause damage. We built the prototype with a DC power socket (the barrel or ‘concentric’ type) for the incoming power mounted on the side of the UB3 box. The two flying leads from this socket were fitted with female header sockets and slipped over the BackPack’s header pins. The centre pin of the socket should go to the 5V pin on CON1 while the sleeve should connect to the pin marked GND (ground). That matches up with the most common plugpack wiring scheme, where 50 Silicon Chip Testing Before connecting the sensor board to the Micromite LCD BackPack, you should confirm that the BackPack itself is working correctly. The testing procedure for this is described in the Micromite User Manual and the relevant SILICON CHIP articles linked above. It’s then simply a matter of connecting the sensor board and powering up the whole gadget. If it does not work straight away, carefully check and re-check each connection. Then measure the voltage across the pins marked VCC and GND on the module; you should get a reading very close to 3.3V. Australia’s electronics magazine Using our Air Quality Sensor is quite straightforward. You plug it into a source of 5V DC power, and after a warm-up period, it displays the air quality as a number and draws a graph showing how it changes over time. The VOC reading is displayed in parts-per-billion, in large digits at the top of the screen, with the time-based graph below (see Screen1). The vertical axis of the graph can be configured in steps from a very sensitive 500ppb full scale to 64,000ppb, while the horizontal time scale can be set to cover from 15 minutes to 32 hours. When you build the Air Quality Sensor and turn it on for the first time, there is a burn-in period of 48 hours that you need to observe. This is necessary as the CCS811 sensor’s readings will drift considerably as surface contaminants from the manufacturing process are burnt off from the sensitive metal oxide layer. So, when you first turn it on, leave it powered up and running for at least two days before taking any readings. You might be tempted to interpret its readings during this period, but it will be futile until the burn-in period has run its course. Another requirement of the CCS811 is that it needs a 20-minute warm-up period every time power is applied. This is different from the initial burnin period and applies whenever the Air Quality Monitor is turned on. During this period, the BASIC program displays a countdown. You can siliconchip.com.au Screen4: you can update the firmware inside the CCS811 sensor to the latest version (V2.0.1) using this screen. Touching the “Update” button will initiate the upgrade, which takes less than 30 seconds. You do not need a firmware file or anything else for this operation as everything is contained within the BASIC program running on the Micromite. Screen5: this screen allows you to set the display brightness and also the auto-dimming feature, which has the benefit of reducing the unit’s power consumption. If your LCD BackPack only supports manual display brightness adjustment (ie, using a trimpot) then these settings will do nothing. skip it if you wish, but like the original 48-hour burn-in, it is much better to let the sensor stabilise. Otherwise, the readings could be nonsense. practice, it was high by a few degrees. This is likely due to its proximity to the CCS811 sensor, which has an onboard heater. Despite this, it is accurate enough for its primary purpose, which is to allow the CCS811 to compensate for variations in temperature and humidity. Setup screen To access the setup screen from the main screen, touch anywhere on the LCD panel. This will take you to a display where you can see the raw readings from the sensor and configure things like the graph’s parameters (see Screen2). Raw data from the sensor module is shown at the top of this screen. The VOC reading is the same as that on the main screen, but there is also a CO2 reading. This is an estimate of the amount of CO2 in parts-per-million (ppm) that would be present in the air if the measured VOCs were created by human respiration. The CCS811 sensor calculates the CO2 reading, but it does not necessarily relate to the actual level of CO2, because the VOC reading used for this estimate could be partly or wholly due to other processes (eg, paint drying). Regardless, the CCS811 sensor produces this reading so we display it on this screen for you. The temperature (°C) and humidity (%RH) readings come from the HDC1080 temperature/humidity sensor that is included on the sensor module. They are used by the CCS811 to give an accurate VOC reading, as mentioned earlier. The temperature reading made by the HDC1080 is supposedly accurate to within ±0.2°C, but we found that in siliconchip.com.au Graph parameters There are two buttons below the raw readings on the setup screen that allow you to change the parameters for the graph on the main screen. The “Vert Scale” button shows the current vertical scale for the graph in parts-per-billion (ppb). Repeated- ly touching this button will step you through a sequence of full-scale values from 500ppb to 64,000ppb. This setting is automatically saved by the BASIC program and will be reloaded when the Air Quality Monitor is next powered up. Similarly, the “Time Scale” button selects the horizontal time scale for the graph. Repeatedly touching this button will step you through various time scales from 15 minutes (full scale) to 32 hours. This setting is also saved for the next power-up. There are also buttons on the setup screen to set the baseline (zero) reading, update the firmware in the CCS811 and set the screen brightness. Finally, to exit the setup screen, touch the “Exit” button to return to the main screen. Setting the baseline The CSS811 documentation refers to “Manual Baseline Correction”, which in effect means determining the zero point for the VOC reading. The MOX (Metal Oxide) sensor used in the CCS811 (see the earlier panel for a description) can be contaminated over time, causing the zero point to drift. The manufacturer recommends that the baseline should be set once a week for the first couple of months of use, and from then on, the baseline will only need to be set once a month. To set the baseline, place the device outside in clean air and touch the Micromite LCD BackPack versions There are three generations of the Micromite LCD BackPack, and all will work in the Air Quality Monitor using the same software. The main difference in this application is that Version 1 only has manual brightness control, so the Air Quality Monitor firmware can not control its brightness. The others (V2 & V3) have optional software control of the LCD backlighting, so if the appropriate components are installed, you can adjust its brightness via the settings screen. This also enables the auto-dimming feature. The V2 & V3 BackPacks also have an onboard USB/serial and PIC32 programming interface called the Microbridge. See: • Version 1: February 2016 (www.siliconchip.com.au/Article/9812) V1 kit Cat SC3321, $65 + postage (www.siliconchip.com.au/Shop/20/3321) • Version 2: May 2017 (www.siliconchip.com.au/Article/10652) V2 kit Cat SC4237, $70 + postage (www.siliconchip.com.au/Shop/20/4237) • Version 3: August 2019 (www.siliconchip.com.au/Article/11764) V3 kit Cat SC5082, $75 + postage (www.siliconchip.com.au/Shop/20/5082)                [comes with 3.5in LCD screen] We also published the Micromite Plus LCD BackPack in the November 2016 issue (siliconchip.com.au/Article/10415). However, we have not tried to run the Air Quality Monitor BASIC program on this version of the BackPack. It may work as-is or might require some changes. There are no apparent advantages to using the Plus BackPack for this project. Australia’s electronics magazine February 2020  51 “Baseline” button on the setup screen (see Screen3). The BASIC program will step through this process which involves waiting for the sensor to stabilise from the power-on condition (20 minutes), then allowing the sensor to determine the baseline over a 10-minute period. This baseline is saved in non-volatile memory by the BASIC program and copied to the CCS811 every time the power is turned on. This is necessary because, without this bit of information, the CCS811 will essentially be forced to ‘guess’ the baseline. At the conclusion of this process, the Air Quality Monitor will return to the main screen showing the reading and graph. Updating the CCS811 firmware The CCS811 sensor is quite a complicated device, and it includes a microcontroller, which is used to measure the resistance of the MOX sensor, control the heater and many other functions. At the time of writing, the latest version of the firmware for the CCS811 is V2.0.1. However, many modules manufactured in China are still using sensors running V1.1.0 firmware or even earlier versions. The V2.0.1 firmware incorporates an improved algorithm for the VOC calculation, and the range of readings has been extended to 64,000ppb VOC (the old firmware limited the sensor to a maximum of 1187ppb VOC). This firmware can be updated by the BASIC program running on the Micromite. This is done by touching the “Firmware” button on the setup screen. You will then be taken to a screen which displays the current version of the firmware running on the CCS811 and an offer to update it (see Screen4). Touching the “Update” button will initiate the upgrade process, which takes less than 30 seconds. Note that you do not need a firmware file or anything else for this operation; everything is contained within the BASIC program running on the Micromite. After this process, the Air Quality Monitor restarts with the new firmware running in the CCS811. Setting the screen brightness As mentioned above, recent versions 52 Silicon Chip of the Micromite LCD BackPack (V2 onwards) include the ability to control the brightness of the screen from within the BASIC program. You can control this by selecting the “Brightness” button on the setup screen. If your LCD BackPack only supports manual adjustment of the brightness (ie, a trimpot), this setting will do nothing. On the brightness screen (shown in Screen5), repeatedly pressing the “Brightness” button will step you through a range of brightness levels from 10% to 100% in 10% steps. If you enable the “Auto Dimming” checkbox, you can set a time period and a second brightness level which applies after that long with no activity. This is useful if you are using the Air Quality Monitor in a bedroom at night, or if you are running it from a battery. The auto-dimming function operates when the main screen (with graph) is displayed and if it has dimmed, touching anywhere on the screen will restore full brightness. A second touch will then take you to the setup screen. Updating the BASIC program One of the great features of the Micromite is that it is easy for you to get in there and modify or update the BASIC program that provides this instrument with its unique functions. This program is stored on the chip in clear text, so you can do things like change colours, menu choices and other features as you wish. If you are using V2 or V3 of the Micromite LCD BackPack, this is as easy as plugging your desktop PC or laptop into the USB socket and running a terminal emulator on your computer. Typing CTRL-C into the terminal editor will interrupt the running program and display the command prompt at which point you edit the program using the EDIT command. This is covered in detail in the Micromite User Manual (downloadable from the SILICON CHIP website), so we will not go into detail here. If you have an earlier version of the Micromite LCD BackPack, you will need a separate USB-to-serial converter (they are cheap). All the details on this are in the Micromite User Manual. Battery operation You might want to power the Air Quality Monitor from a battery, so it’s truly portable. This would allow you Australia’s electronics magazine to make a quick survey of a large office space or house. The best option for this is to use a USB “power bank” as sold for recharging mobile phones while on the go. These have everything that you need in a portable power source including a charging circuit, protection circuits and a regulated 5V output. Even better, because they are a common item in mobile phone shops, they are quite cheap. They cost much less than the parts that you would need to build a similar device yourself! The most significant power drain in the Air Quality Monitor is the LCD screen backlighting. That alone can consume up to 250mA at full brightness. This is one of the reasons for the auto-dimming feature described earlier; with that enabled, you can reduce the brightness of the display to (say) 10% after a short period of inactivity. This reduces the current drawn by the backlight to about 25mA, essentially halving the unit’s power consumption. For the record, the Micromite itself draws about 26mA and the CCS811 and HDC1080 sensors combined about the same. So, with the displayed dimmed to 10%, the total drain on the battery should be about 80mA, or about 2Ah/ day. So a 5000mAh power bank should last for around two days of continuous operation. However, consider that the actual energy delivered is lower than rated, due to the difference between the average battery voltage of 3.7V and the output voltage of 5V, and the voltage conversion is less than 100% efficient. Don’t forget that many cheap power banks grossly overstate their capacity! For truly portable use, you would ideally incorporate the power bank into the case. That would require you to use a larger box and to add an on/ off switch. Some of the smaller cylindrical power banks could fit into the UB3 box and still provide sufficient capacity for many hours of use. The details of these modifications are something that we will leave as an exercise for the reader. Firmware updates For firmware updates for the Micromite and the BASIC program for the Air Quality Monitor, check the author’s website at http://geoffg.net SC siliconchip.com.au Hardcore electronics by The Latest Computer Tech, Test & Tools On sale 24 January 2020 to 23 February, 2020 Tech Talk: UNIVERSAL TYPE-C LAPTOP CHARGER Automatic voltage selection. Additional USB 2.0 charging port. Mains powered. 60W. MP3340 ONLY 5995 $ ONLY 9995 $ SUITS MACBOOK® & GOOGLE CHROMEBOOK® new MICRO:BIT SMART ROBOT KIT A fun to build robot that uses a micro:bit microcontroller Take advantage of high performance USB Type-C connectors to convert to an existing VGA & HDMI signal. Delivers up to 1080p resolution. VGA XC4961 $29.95 HDMI XC4965 $49.95 DIGITAL LIGHTMETER USB TYPE-C TO 3.5MM AUDIO SOCKET LEAD Quick and easy headphone connection for your USB Type-C enabled device such as Smartphone, tablet, laptop or PC. Built-in Realtek DAC (digital-to-analogueconverter). WC7930 NOW 4995 $ SAVE $10 2-IN-1 LASER MEASURING TAPE Measure up to 30m using the laser or up to 5m with the retractable tape. Metric and imperial. USB rechargeable. QM1627 WAS $59.95 NOW 54 $ 95 SAVE $5 Packed with features found on more expensive units such as True RMS, non contact voltage etc. Ultra-high current 1000A AC and DC current measurement. QM1634 WAS $129 2995 $ Add storage space to your Smartphone or Tablet. Supports microSD cards up to 256GB. TYPE-C XC5621 $14.95 MICRO USB XC5623 $14.95 LIGHTNING™ XC5627 $24.95 119 $ SAVE $10 Shop the catalogue online! SUPPORTS NEW GENERATION MACBOOK® & PCS ONLY 2995 $ USB 3.0 TYPE-C 4-PORT HUB This 4 port hub expands your computer's connectivity and makes the most of the lightning fast speed. All 4 ports support USB 3.0 Super Speed. Compatible with USB 2.0. XC4306 Product may vary from image shown. ONLY 1995 $ 4-PORT USB 2.0 HUB OTG USB CARD READERS FROM Compact design to reduce desk clutter. Powered by the USB port and includes a 360mm lead. XC4302 See website for details. 1495 $995 $ ONLY ALL-IN-1 USB 2.0 CARD READER Reads most memory cards in use today. Plug & play. USB cable included. XC4926 ONLY 1995 $ ONLY 2995 $ Free delivery on online orders over $70 Conditions apply - see page 8 for full T&Cs. Allows a computer to use any RS-232C serial device via the USB port. Suitable for POS systems, ISDN adaptors etc. Over 1Mbps data transfer rate. 1.5m long. XC4834 ONLY 6995 $ AC1200 DUAL BAND WI-FI USB TO DB9M RS232 CONVERTER NOW CAT III 6000 COUNT USB Type C features a new, smaller connector shape that’s reversible so it’s easier to plug in. USB-C cables can carry significantly more power, so they can be used to charge larger devices like laptops. They also offer up to double the transfer speed of USB 3.0 at 10 Gbps. While connectors are not backwards compatible, the standards are, so adapters can be used with older devices. FROM See website for details. 1000A TRUE RMS AC/DC CLAMPMETER USB Type-C is the emerging standard for charging and transferring data. Right now, it’s included in devices like the newest laptops, phones, and tablets and—given time—it’ll spread to pretty much everything that currently uses the older, larger USB connector. TYPE-C CONVERTERS board (sold separately XC4320 $34.95) that kids can code or control using their Smartphone via Bluetooth®. No soldering required, plug and play. KR9262 A handy meter for lab work, architectural, engineering and construction applications. Measures light in 4 ranges from 0.01 to 50,000 lux. • 3.5 Digit LCD display • Separate photo detector QM1587 WAS $59.95 Why You Need USB Type-C RANGE EXTENDER Quickly eliminate dead-spots or provide an access point on your existing wired network. It plugs straight into an available mains power point. YN8372 Whilst Stocks Last. www.jaycar.com.au 1800 022 888 Tech Talk: Secure Your Wi-Fi Network WEP, WPA & WPA2 Wireless Security Protocols, which is the best? SUPPORTS WEP, WPA & WPA2 PROTOCOLS WEP, WPA and WPA2 are names for different encryption protocols used to secure your wireless connection. Encryption scrambles the network connection so that no one can “listen in” to your network. For example, WEP stands for Wired Equivalent Privacy, and WPA stands for Wireless Protected Access. WPA2 is the second version of the WPA standard. new SUPPORTS WEP, WPA PROTOCOLS JUST 49 $ SUPPORTS WEP, WPA PROTOCOLS 95 EA. $ SAVE $20 AC1200 SMART WI-FI ROUTER Featuring the latest wireless standards for solid streaming, fast gaming, and interruptfree networking. Two wired ports and USB port for centralised storage and network sharing of data. YN8392 WAS $99.95 N300 WIRELESS BROADBAND ROUTER Provides 300Mbps wireless connectivity, as well as four wired ethernet ports. Dual antennas help boost signal strength and reduce dead spots. NBN compatible. YN8390 AC2100 WI-FI ROUTER Incredibly fast Wi-Fi speeds up to 2100Mbps for strong, steady signal throughout your home so you can enjoy exceptionally smooth, responsive gaming and uninterrupted streaming. 6 antennas to help boost signal strength and reduce dead-spots. YN8394 N300 WIRELESS ADSL2+ MODEM ROUTER Allow multiple computers to share an integrated high speed ADSL2+ connection. Features four built-in 10/100 Ethernet LAN ports, wireless access point, firewall protection, and QoS for smooth, secure transfer of photos, files, music. YN8347 AC1200 VDSL/ADSL MODEM ROUTER SUPPORTS WEP, WPA & WPA2 PROTOCOLS JUST 169 $ NOW 7995 Using some encryption is always better than using none, but WEP is the least secure and most widely used of these standards, with 128-bit encryption. WPA offered a significant security improvement over WEP with 256-bit encryption and message integrity checks between access point and client. WPA2 is the most secure of the three. If your wireless devices and router support WPA2, it is recommended to use this protocol. One of the most significant changes between WPA and WPA2 is the mandatory use of AES algorithms and the introduction of CCMP (Counter Cipher Mode with Block Chaining Message Authentication Code Protocol), this significantly reduces the risk of attacks against devices within the network. EA. • SUPPORTS WEP, WPA & WPA2 PROTOCOLS • 5 X GIGABIT PORTS • CONNECT MULTIPLE DEVICES Unlock the full potential of your internet connection. Combined dual band Wi-Fi speeds of up to 1.2Gbps, eliminating lag and buffering from your online experience. YN8440 AV1000 GIGABIT POWERLINE KIT Extend your ethernet over already installed AC1300 DUAL BAND WIRELESS NETWORK ADAPTOR JUST $ EXTEND UP TO 300M MAINS RANGE 139 $ Fast and stable access to any Wi-Fi signal. Ideal for hardware that's not Wi-Fi equipped or for upgrading powerlines to any room. an old adaptor. YN8336 High-speeds of up WAS $69.95 to 1200Mbps for HD NOW streaming and more. YN8442 USB 3.0 LOW LOSS 5M SMA ETHERNET CONVERTER EXTENSION LEAD Connect an Ethernet cable to an existing USB port. Perfect for Apple® MacBook® and Ultrabooks®. YN8418 JUST 3995 $ 54 click & collect Enables you to reposition your Wi-Fi modem/router's antenna up to 5m away to improve the signal range. WC7824 JUST 3495 $ Buy online & collect in store 4995 USB 2.0 WIRELESS NETWORK ADAPTORS Secure, sleek and convenient upgrade for home or office. N150 NANO YN8309 $19.95 N300 MINI YN8307 $24.95 FROM 1995 $ SAVE $20 2.4GHZ WIRELESS NETWORKING ANTENNAS These antennas are specifically designed for 2.4GHz applications and 802.11 wireless networking. Supplied with detachable magnetic base. 5dBi 195mm AR3273 $19.95 (shown) 11dBi 380mm AR3277 $39.95 FROM 1995 $ JUST 1695 $ CAT5 UTP SPLITTER Save time, money & space! Usually used in pairs, this UTP splitter enables two different devices to share the same CAT5 cable. YT6090 Note: Cannot be used to run two computers from one network and not suitable for gigabit networks. ON SALE 24.01.2020 - 23.02.2020 YOUR DESTINATION FOR: Data Communications Terminate your own cable SOLID NETWORK CABLES MODULAR CRIMP TOOL WITH NETWORK & POE TESTER Used for long runs in permanent installations. ACA approved. CAT5E 100M ROLL WB2022 $1.45/M 30M POLYWRAP WB2023 WAS $39.95 NOW $29.95 SAVE $10 CAT6 Combination crimper tool and a cable tester in one unit. Tests both UTP and STP cable. Single and multi-wired cable crimping. Detachable cable tester. TH1939 JUST 6995 $ 100M ROLL WB2030 $1.75/M FROM 1 $ 45 /m Packet of 10 RJ45 plugs for stranded and solid CAT6 cable. PP1447 A packet of boots to suit RJ45 8/8 plugs. PK10 PM1441 $4.95 PK50 PM1442 $15.95 FROM 4 $ 95 CAT-5 PUNCH-DOWN TOOL & STRIPPER Strip wire up to 5-6mm, and doubles as a punch-down tool for 110/88-type terminals with blade. TH1738 ONLY 8 $ 95 ONLY 1395 $ 2-IN-1 NETWORK CABLE TESTER & DIGITAL MULTIMETER 7495 $ YN8048 $69.95 More ways to pay: 4995 $ MP3338 USB Leads & Adaptors ACTIVE USB 2.0 EXTENSION LEADS All units feature built-in extenders to run your USB devices over longer distances with minimal signal errors. 5M XC4839 $24.95 10M XC4120 $39.95 20M XC4124 $49.95 $ USB RJ45 EXTENSION ADAPTOR Connect any USB device to your computer from up to 50m away via a standard Cat 5 network cable (sold separately). PC and MAC compatible. Transmitter and Receiver included. XC4884 NOW FROM 139 $ SAVE UP TO $70 JUST 69 $ 95 ONLY 2995 $ D9 MALE TO D9 FEMALE EXTENSION CABLE NEED A PC LEAD? We stock a huge range of computer leads. Listed below are the most popular ones. All pins wired straight through. 1.8m long. WC7534 JUST See website or instore for full range. 9 $ 95 DVI-D TO DVI-D VIDEO CABLE Male to male. 24pin. 2m long. WC7590 VGA MONITOR CONNECTING CABLE FROM 49 $ 95 D15HD Male to D15HD Male. 1.8m long. WC7582 FROM 2495 SAVE UP TO $10 24-PORT PATCH PANELS CAT6 FROM 2995 19" RACK MOUNT ENCLOSURES Online Available via Click & Collect 5995 $ $ Rack Mount Cabinets 24 port patch panel with a hard metal exterior. Numbered ports and a labelling area for each port. CAT5E YN8046 $49.95 Store Only. FROM NOW FROM SAVE $10 Power up to six components in your rack setup. 6 X 240V outlets and fits any standard 19" rack. 10A output. 1.6m long. MS4094 In-car power supplies for charging laptop computers. Includes multiple plugs to suit different laptops. 90W MP3338 $49.95 150W MP3472 $74.95 Suitable for high speed USB 3.0 applications. USB A plug to socket. XC4128 has option for external 5V power. 5M XC4126 WAS $34.95 NOW $29.95 SAVE $5 10M XC4128 WAS $69.95 NOW $59.95 SAVE $10 NOW 6-WAY PDU WITH SURGE & OVERLOAD PROTECTION BRING YOUR OLD UNIT IN & WE'LL HELP YOU FIND THE RIGHT ONE POWERED USB 3.0 EXTENSION LEADS Check cable integrity or measure AC & DC voltages up to 600V, current, ressistance. CAT III, 2000 count. XC5078 WAS $84.95 Ideal for IT or phone system installations, studios & PA systems, sound reinforcement etc. Solid steel powder coated to provide high strength and rigidity. 6U to 12U in Swing or Fixed frame enclosures available. 6U FLAT PACKED HB5170 WAS $179 NOW $139 SAVE $40 6U ASSEMBLED HB5171 WAS $199 NOW $149 SAVE $50 6U SWING FRAME HB5180 WAS $269 NOW $199 SAVE $70 laptop charger without having to buy expensive branded replacements. Compatible with most brands. Slim, manual & automatic models available from 65W to 144W. MP3321 - MP3476 IN-CAR LAPTOP POWER SUPPLIES RJ45 MODULAR PLUGS RJ45 BOOTS LAPTOP POWER SUPPLIES Replace your lost or broken JUST 11 $ 95 ONLY 2995 $ 55 YOUR DESTINATION FOR: Maker Projects PROJECT: MOTHERLOAD DATALOGGER The data-logger project to end all data-logger projects! Imagine you find that power has been cut from your freezer. Knowing exactly when the power was cut could save a lot of spoilage, and this is the datalogger to do it with! Not just a temperature sensor, it could also be set up for humidity, smoke detection, PIR movement, light detection, or with any other Arduino compatible sensor. This is the single most universal data logging device we have ever sold! Includes instructions on how to send email alerts, detects movement with the PIR motion sensor, or when the temperature of your computer gets too hot. Cloud capability allows you to use the Google Cloud Platform to upload data to google sheets. SKILL LEVEL: Intermediate SEE STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/motherload-datalogger UNO with Wi-Fi Board Arduino Compatible Data Logging Shield 28 Pin Header Terminal Strip 150mm Socket to Socket Jumper Leads 40pk Economy Breadboard Jumper Kit PLUS your choice of Sensor Modules XC4411 XC4536 HM3211 WC6026 WH3032 CLUB OFFER BUNDLE DEAL $39.95 $19.95 85¢ $5.95 $4.50 5495 $ • CLOUD CAPABLE • EMAIL ALERTS • LARGE NUMBER OF INPUTS SAVE 20% CLUB EXCLUSIVE OFFER 20% OFF SENSOR MODULES* KIT VALUED AT $71.20 *See T&Cs for details NOW JUST 9 $ 95 1495 $ SAVE 20% MEGA PROTOTYPE SHIELD WITH BREADBOARD This shield gives you plenty of room to prototype your latest MEGA project. The stackable shield provides access to all of the MEGAs pins and plenty of solder pads to prototype on. XC4416 WAS $12.95 PROTOTYPING SHIELD This stackable shield makes semi-permanent prototyping simple. Includes reset button. XC4482 WAS $15.95 MICRO:BIT PROTOTYPE BOARD NOW JUST 1295 $ SAVE 15% Supplied with 400hole breadboard, designed to break out all IO pins on your micro:bit for you to create additional circuits and hardware. XC4332 WAS $23.95 56 9 $ ONLY 1995 $ SAVE 15% click & collect ALSO AVAILABLE: Sleeve bearing & magnetic fans Suitable for computers, office machinery, amplifiers, air conditioning etc. All fans are ball-bearing and are built to last with long service life of up to 100,000 hours at 25°C. 12V 60mm YX2505 $17.95 12V 80mm YX2512 $17.95 FROM 12V 120mm YX2518 $28.95 240V 80mm YX2508 $36.95 240V 120mm YX2517 $36.95 17 $ The 555 Timer IC is probably the most used IC in the world. This book describes the functions and operation of the 555, then explains 21 projects to build using the IC. 76 pages. BM2466 Pack of 40 in various colours for prototyping. Ideal for Arduino® and DIY projects. Each flexible lead have pins to suit breadboards or PCB headers. Plug to Plug WC6024 Socket to Socket WC6026 Plug to Socket WC6028 Build your very own customised Arduino® compatible projects. Comes with Uno bootloader and 16MHz crystal oscillator. ZZ8727 WAS $12.95 HIGH QUALITY AXIAL VENTILATION FANS 7 $ Buy online & collect in store Foam filter prevents dust particles entering the fan. Made from plastic rated to UL 94V- 0. 60mm YX2550 $6.95 80mm YX2552 $6.95 120mm YX2554 $7.95 FROM 695 JUST 24 ONLY PLASTIC FAN GUARDS $ 95 $ EA. 150MM JUMPER LEADS ATMEGA328P MCU IC Ideal for electronic prototyping and Arduino® projects. Labelled rows and columns. Adhesive back for mounting. PB8815 BOOK - 555 TIMER & ITS APPLICATIONS NOW JUST 95 SAVE 20% BREADBOARD WITH 830 TIE POINTS JUST 595 $ NOW JUST 95 PROGRAMMING ARDUINO®: GETTING STARTED WITH SKETCHES Introduces you to the Arduino® programming language (called C). Describes the basic configurations of Arduino® modules. Finishing with a discussion on C++ and more sophisticated applications. 162 pages. BM7133 new FROM 4-way or 10-way screw terminal block for temporary or prototyping applications. No soldering required. Mini B, micro B & Type-C plug available. PA0950 - PA0956 PA0950 995 $ ON SALE 24.01.2020 - 23.02.2020 USB 2.0 TO SCREW TERMINAL HEADERS YOUR DESTINATION FOR: Networking & Data Management ESP-13 WI-FI SHIELD RS-232 TO TTL UART CONVERTER MODULE Uses the powerful ESP8266 IC and has an 80MHz processor. An excellent way to get into the Internet of Things. Integrated TCP/IP stack. Simple AT command interface with Arduino main board. XC4614 ONLY 39 $ 95 Connect a legacy device (or computer) to your existing Arduino® board. Providing a full RS-232 port, this shield allows you to directly communicate with a huge variety of serial peripherals. XC3724 WAS $9.95 NOW 795 $ SAVE $2 NOW 32 $ SAVE $10 USB HOST EXPANSION BOARD ETHERNET EXPANSION MODULE A network shield that will allow you to set your Arduino® up as web server, control your project over your network or even allow your Arduino® to connect to the world wide web. XC4412 WAS $39.95 Data Storage Brings the ubiquitous USB Host connectivity to your Arduino® project. Supports Google Android® ADK allowing connections to Smartphones and Tablets. XC4456 WAS $39.95 MICROSD CARD SHIELD FOR WI-FI MINI 3295 95 SAVE $3 Arduino® project over Wi-Fi and allow it to access the Internet. Contains a tiny Linux computer with Wi-Fi, ethernet & USB. XC4388 WAS $69.95 SAVE $7 DATA LOGGING SHIELD NOW 6 95 SAVE $3 NOW 6 $ YUN WI-FI SHIELD Allows you to easily program and operate your NOW $ $ Add gigabytes of storage to your Wi-Fi Mini Main Board with this tiny shield and a microSD card. Allows you to use cheap microSD cards with the easy-touse Arduino® SD library. XC3852 WAS $9.95 5995 $ 95 SAVE $7 NOW SD CARD INTERFACE MODULE Features 5V and 3.3V power inputs and resistors to allow safe on either IO voltage. Works with inbuilt libraries. XC4386 WAS $9.95 Save your data to an SD card (not included), and use the inbuilt battery backed clock module to timestamp your readings. Uses a 3.3V converter to avoid damaging your SD card. XC4536 WAS $19.95 NOW 1495 $ SAVE $5 Make your own e-wearable clothing LIGHT DUTY SILICONE HOOK UP WIRES Extremely flexible and capable to withstand temperatures from -60°C up to 150°C. Supplied on a handy 8m roll and available with red or black insulation. WH3034 - WH3036 new JUST 995 $ EA. STAINLESS STEEL CONDUCTIVE THREAD 3495 $ DUINOTECH LILYPAD PLUS Add a microcontroller to your Sparkle Stitch Kit for dazzling effects and control your e-wearable project or costume. 10 Mini RBG LEDs. Accelerometer. Microphone and more! XC3920 POWER PAD COIN CELL HOLDER A highly flexible thread made conductive by the inclusion of stainless steel strands. 2m long. WW4100 ONLY 695 $ RGB LED RAFT PAD Designed to be sewn onto a costume or fabric based project to provide amazing lighting effects. Selectable red, green and blue colour. KM1040 ONLY Designed to be sewn onto a costume or fabric based project to provide power to a circuit. Suits CR2025 or CR2032 batteries (not included). KM1060 CR2025 Battery SB2942 $4.95 CR2032 Battery SB2944 $4.95 ONLY 795 $ new In the Trade? ONLY 6 $ 95 99 $ new SPARKLE STITCH KIT Learn simple sewing and electronics and make spectacular light-up wearable technology. Kit includes everything you need to get startedfelt cloth, needles, thimble, thread, glue gun, multimeter, electronic components, 62 page guide & more. KM1080 LED RAFT PADS Designed to be sewn onto a costume or fabric based project to provide amazing lighting effects. LEDs on a micro circuit. Available in yellow, green, red & white colour. KM1032 - KM1038 VALUED AT OVER $125 JUST See website for details new FROM 4 $ 95 POWER PAD SLIDE SWITCH Designed to be sewn onto a costume or fabric based project to turn power on or off to a circuit. KM1058 new ONLY 7 $ 45 57 YOUR DESTINATION FOR THE BEST REWARDS & PERKS love jaycar? you're going to love our rewards! SHOP In store & online EARN POINTS For dollars spent GET REWARDS eCoupons for future shops in store 1 point = $1 200 points = $10 eCoupon + PERKS offers, event invitations, account profile and more... exclusive offers: CLUB OFFER 79 $ SAVE OVER $40 XC4687 CLUB OFFER 15% OFF 49 $ HDD DOCKING STATIONS Suits 2.5" or 3.5" HDD. Single or dual docks. XC4672, XC4687-89 See T&Cs for details. CLUB OFFER SAVE 95 SAVE 20% 2-PORT USB KVM SWITCH Connects 2 Computers to 1 monitor. YN8402 RRP $69.95 Designed for hardcore gamers who enjoy many hours of gameplay. Includes: Keyboard & mouse, mouse pad & headphones. See T&Cs for details. Valued at $119.85 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE DOUBLE GPO WITH 2 X USB CHARGE PORTS SELF-POWERED RED LED VOLTMETER SEALED ABS ENCLOSURE 20% 30% 1 Channel 3.5W. AA0223 RRP $24.95 CLUB $19.95 Charge and power USB devices PS4065 RRP $29.95 CLUB $19.95 UNIVERSAL AMPLIFER MODULE GAMER'S BUNDLE CLUB OFFER 30% Super simple to install. QP5581 RRP $14.95 CLUB $9.95 20% 240 x 160 x 90mm. IP65 rated. HB6134 RRP $37.95 CLUB $29.95 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE SILICON TUFF TAPE UNDER DASH DOUBLE CIGARETTE LIGHTER SOCKET MOTOR START CAPACITORS 28 COMPARTMENT STORAGE CASE 20% 50% 25mm x 3m. Red, black & clear colours. NA2830-NA2834 RRP $14.95 EA. CLUB $7.45 EA. CLUB OFFER SAVE 20% Heavy duty, steel frame.PS2009 RRP $12.95 CLUB $9.95 ZP9102 RRP $24.95 CLUB $19.95 Removeable partitions. HB6313 RRP $14.95 CLUB $12.95 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE SPRAY-ON CONTACT ADHESIVE HEAVY DUTY PANEL MOUNT CIRCUIT BREAKERS Bonds to almost any surface. 400g. NA1504 RRP $16.95 CLUB $10.95 15% SZ2081-SZ2083 RRP $39.95 CLUB $32.95 25% OFF EXCLUSIVE CLUB OFFER COMPUTER ADAPTORS* *Includes Serial, DVI, VGA & USB adaptors. See T&Cs for details. 58 click & collect 10% RU6600 - RU6608 RRP $16.95 EA. CLUB $12.95 EA. 35% THERMOELECTRIC (PELTIER) MODULE 20% Buy online & collect in store 20% 7 CORE TRAILER WIRING LOOM - 10M WH3090 WAS $44.95 CLUB $34.95 YOUR CLUB, YOUR PERKS KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON! Visit: www.jaycar.com.au/makerhub ON SALE 24.01.2020 - 23.02.2020 YOUR DESTINATION FOR: Workbench Essentials $ The best, most consistent and most tested PLA filament engineered and manufactured by FlashForge. Various colours available in 600g or 1kg rolls. TL4260-TL4276 FROM 2495 $ NOW 39 1.75MM PLA FILAMENT 95 SAVE $10 3D PRINTING TOOLKIT Includes commonly required tools that you need to service your printer or to unclog a blocked print head. TD2132 WAS $49.95 TRUE RMS Tech Talk: True RMS A True RMS (Root Mean Square) multimeter more accurately measures non-sinusoidal AC waveforms compared to a standard average responding multimeter, including square waves, half waves, sawtooth, triangle, trapezoid, etc. IP67 TRUE RMS AUTORANGING CAT IV DMM • Cat IV 600V • 4000 display count • IP67 waterproof, data hold, relative measurement QM1549 JUST 89 $ 95 TRUE RMS INDUCTANCE/ CAPACITANCE DMM Powerful frequency measurement with high accuracy, as well as capacitance up to 100mF! • Cat III 1000V / Cat IV 600V • 2000 display count QM1552 JUST 5995 $ IP67 TRUE RMS AUTORANGING DMM WITH WIRELESS USB INTERFACE ADVENTURER 3 3D PRINTER Control print jobs via the cloud using flashcloud and/or polar cloud. Compact structure with no angular design. Ready to use and no levelling printing. Removable, heatable and bendable plate. • Low noise operation • Automatic filament feeding • Print up to 150(L) x150(W) x150(H)mm TL4256 ONLY 899 $ CAT III TRUE RMS AUTORANGING DMM WITH TEMPERATURE • Cat III 600V • 4000 display count • Continuity, diode check, fold-out stand QM1551 ONLY 6495 $ TRUE RMS DMM WITH BLUETOOTH® CONNECTIVITY • Cat IV 600V • 6000 display count • Wireless USB, IP67 waterproof, non-contact voltage, datalogger QM1571 WAS $129 • Cat III 1000V / Cat IV 600V • 6000 display count • IP67 waterproof, Bluetooth® connectivity, duty cycle, datalogger QM1578 WAS $189 NOW NOW 99 149 $ $ SAVE $30 SAVE $40 Don't forget your essentials SAFETY GLASSES WITH LED LIGHTS VERNIER CALIPERS • Individually switched LED modules • Adjustable arm lengths TH3000 • 5-digit LCD • 0-150mm (0-6") measurement range • Metric & imperial measurement Budget TD2081 $13.95 (Shown) Precision Stainless Steel TD2082 $39.95 JUST FROM 9 $ 95 BENCHTOP WORK MAT Durable A3 size cutting mat for protecting work benchtop. • 3mm thick PVC • 450x300mm HM8100 JUST 12 $ 95 More ways to pay: 13 $ 95 LARGE RARE EARTH MAGNETS • Exceptionally strong • Made from NdFeB (Neodymium Iron Boron) • Nickel case • Sold as a pair LM1652 JUST 29 $ 95 CLUB OFFER BONUS $100 GIFT CARD WITH PURCHASE STAINLESS STEEL WIRE STRIPPER, CUTTER, PLIERS Strips wire up to 2.6mm and cut steel wires up to 3.0mm. TH1841 ONLY 1595 $ RATCHET CRIMPING TOOL FOR NONINSULATED LUGS Comfortable grip & ratchet mechanism relieves strain on hands. TH1847 JUST 3495 $ QUICK CHANGE RATCHET CRIMP TOOL Heavy duty ergonomic crimper allows you to quickly and easily change dies, no screw driver required. Features ratchet mechanism for maximum power or quick release. TH2000 JUST 3995 $ MAGNIFYING LAMP • Powerful 125mm diameter 3 dioptre lens • High / low light setting • Fully adjustable arm with clamp mount • Large diameter magnifier • Interchangeable lens option QM3554 WAS $119 NOW 99 $ SAVE $20 JUST 9995 $ 48W HOBBYIST SOLDERING STATION Ideal station for the advanced hobby user. Adjustable temperature (150450°C). Ceramic element and lightweight pencil. Mains powered. TS1564 59 What’s new BUILT-IN MEMORY RECALL VERY LOW POWER DIGITAL TACHOMETER PROFESSIONAL SOUND LEVEL METER Designed for all kinds of environmental sound measurement projects. Wide dynamic range from 30dB to 130dB. Fast (125ms) or Slow (1s) response. USB connectivity. QM1598 1.54" MONOCHROME E-INK DISPLAY MODULE Uses E-ink technology to display black, white, and red text and graphics on the 200 x 200 pixel screen. Very low power design. Wide viewing angle. XC3747 ONLY 6995 $ INCLUDES CALIBRATOR JUST JUST 299 $ Provides fast and accurate RPM and surface speed measurements. Measures from 2 to 99,999 RPM. 5-digit backlit LCD. Integrated laser pointer. Carry case included. QM1449 JUST 4995 $ 14 $ 4 INPUTS 95 AUDIO MODULE 4K HDMI MATRIX SWITCHER/SPLITTER Simultaneously routes up to four HDMI sources to two HDMI displays for up to 4K resolution on all ports. Support for 3D signals, High Dynamic Range (HDR), audio up to 7.1 surround, and smart EDID management. Includes IR remote control and mains power adaptor. AC5012 LARGE CAPACITY 100AH LITHIUM DEEP CYCLE BATTERY NEW LOW PRICE 799 $ Drop in replacement for most lead acid batteries. Provide continuous current up to 50A, with peaks of up to 100A. Perfect for house batteries, backup batteries, • FAST CHARGING etc. 12.8V. SB2215 • EXCELLENT LIFE SPAN WHY LITHIUM? • LIGHTER THAN See video online: LEAD ACID jcar.link/lithium ONLY 249 $ Play MP3, WAV, or WMA files from an onboard microSD card (sold separately) with your next electronics project. 5W power. XC3748 ONLY 995 $ AUDIO AMPLIFIER MODULE WITH SPEAKER An easy way to add audio effects or music to your next project. Features 23mm diameter speaker, 2W amplifier, and a trimpot for volume control. XC3744 ONLY 1995 $ 8 X 16 MATRIX LED DISPLAY MODULE Create amazing patterns or messages with this LED matrix module on your next electronics project. Features 128 bright blue LEDs arranged in an 8 x 16 grid, brightness control, and communicates to your microcontroller via I2C. XC3746 ONLY 1995 $ HAND GESTURE SENSOR MODULE Control your project with touchless hand gestures. Detect hand movements in six different directions then sends data to your microcontroller via I2C communications. XC3742 ALSO AVAILABLE: HEARTBEAT SENSOR MODULE XC3740 $9.95 TERMS AND CONDITIONS: REWARDS / NERD PERKS CARD HOLDERS FREE GIFT, % SAVING DEALS, DOUBLE POINTS & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / membership at time of purchase. Refer to website for Rewards / membership T&Cs. IN-STORE ONLY refers to company owned stores and not available to Resellers. Page 4: Club Offer: 20% OFF Sensor Modules applies to XC4494, XC4520, XC4470, XC4603, XC4540, XC3700, XC4604, XC4442, XC4446 & XC4610. Page 6: Club Offer: 15% OFF HDD Docking Stations applies to XC4687, XC4689, XC4672 & XC4688. Club Offer: Gamer’s Bundle includes 1 x AA2126, 1 x XM5096 & 1 x XC5132 for $79. Club Offer: 25% OFF Computer Adaptors applies to Jaycar product category 701B: Connectivity - Computer Adaptors. Page 7: Club Offer: BONUS $100 Gift Card applies with purchase of TL4256. HOXTON PARK RD HOXTON PARK RD McDONALD’S N DE TOTAL TOOLS LYN PARA SUPERCHEAP REPCO KENNARD’S SELF STORAGE OUR WARWICK FARM IS MOVING TO HOXTON PARK T8, Hoxton Park Central, 2 Lyn Pde Prestons, NSW 2170 PH: (02) 9821 3100 For your nearest store & opening hours: 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 were confirmed at the time of print but delays sometimes occur. Please ring your local store to check stock details. Occasionally there are discontinued items advertised on a special / lower price in this promotional flyer that has limited to nil stock in certain stores, including Jaycar Authorised Resellers. These stores may not have stock of these items and can not order or transfer stock. Savings off Original RRP. Prices and special offers are valid from catalogue sale 24.01.2020 - 23.02.2020. SERVICEMAN'S LOG When in doubt, swap it out I’ve had a few cases recently where components tested OK with the usual procedures, but they were still far enough out of spec that they fell over when put back into use. This can be a very frustrating aspect of troubleshooting; dud components can throw up all sorts of red herrings, without having any really obvious signs that they’re toast. Servicemen are much like detectives, in that we are always looking for evidence to explain why something doesn’t work or isn’t performing as expected. The majority of the time, we are familiar enough with the job we are doing (whether from experience or just dumb luck), so we don’t need to overwork our ‘little grey cells’. But there are times we need to think outside the box to fix a problem. Most of the electronics repair jobs that come through my workshop are too mundane to mention. The most common ailment in many of these devices is dodgy soldering. Regardless of whether it is the result of mass-production quality control or the solder breaking down over years of use, if any one of those joints fails, things stop working. This means that a simple clean-up and re-solder may be all that is required to resolve a seemingly complex problem. Anybody with a little soldering experience should not be afraid to give this a try. Coming a close second would have to be faulty capacitors; leaking and bulging electrolytics, and those which have gone high-ESR due to the electrolyte drying up, have felled many a gadget over the years. Computer motherboards are notorious for this, but any device which operates at an elevated temperature is at particular risk. Plastic film caps can also go bad, especially those on the mains input side. But back in the golden age of electronics, there was a whole other class of electronic component failures. Often, fixing a device would require resiliconchip.com.au placing parts that had ‘worn out’. In the days of valves, this meant pulling the tubes, plugging them into a tester (which any workshop worth its salt had on hand), and if the machine told us the valve was ‘weak’ or ‘gassy’, we’d simply replace it with a new one. Over-reliance on such machines put one at risk of being labelled a “valve jockey”! Valve replacement became such a regular task that many corner shops or local hardware stores would have a tester in one corner, along with a display stacked with commonly-used tubes. Anyone could go to the store with their suspect valves, plug them into the tester and this would then display the results on a traffic-light style go/no-go meter. Usually, there was also a well-thumbed substitute manual for those who owned radios and TVs using oddball valve types, to help them choose something more common that might work. Australia’s electronics magazine Dave Thompson Items Covered This Month • • • The art of troubleshooting Chromagen water heater repair Multiple capacitor replacements *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz In cases where the tubes weren’t the problem, it became a job for the serviceman. More than likely, some capacitors, inductors or resistors would need replacing, typically failing due to the high voltages and operating temperatures valve gear could reach. The point-to-point wiring commonly used at the time meant it was a relatively straight-forward job to test and, if necessary, replace old components. February 2020  61 it did click in, it would soon let go again. At one point, it chattered, engaging and quickly disengaging, so I quickly powered it down. Something was obviously wrong in there somewhere (that’s a really technical statement, I know). Working on this type of amp is a real pleasure. They are designed to come apart easily, and everything inside is laid out so it can be worked on. Everything is clearly identified with part numbers, track outlines and board designations all screen-printed on the PCBs. Wire-wrapped connections When we transitioned to transistor circuits, PCB construction became commonplace, making troubleshooting more challenging. Circuit boards enabled complex circuits to be crammed into smaller areas, and often these were not laid out logically as tube gear often was, requiring more attention to detail and an increasing reliance on documentation. A behemoth arrives on my workbench I recently had a large, 70s-era Pioneer transistor amplifier through the workshop. Like many decent amps of the time, this beast weighed a ton. Most of this weight came from the massive power transformer, although the heavy steel chassis and polished walnut case also contributed significantly. Crucially, it also came with a comprehensive service manual and dinnertable-sized fold-out circuit diagram, all of which makes working on these older devices so much easier. The amp’s main symptom was an increasing trend for the anti-thump/ speaker connection relay not to kick in, meaning zero sound output. If the relay did engage, it would then drop out at various times. Usually, this points to either the relay itself getting tired, or perhaps a related ca62 Silicon Chip pacitor failing. So those components were the obvious place to begin troubleshooting. I first confirmed the fault before proceeding; while I did not doubt that after 40 years, the amp’s owner knew every little thing about it, there is nothing as informative to a trouble-shooter as witnessing the actual fault in action. So when possible, this is what I prefer to do. I plugged the amp in and toggled the seriously solid power switch to on. I found the relay wouldn’t kick in at all most of the time. The odd time Australia’s electronics magazine This amplifier also used the now mostly forgotten technique of solderless wire-wrapping. Individual, colour-coded single-core wires are laid out and then the ends are twisted a dozen times or so around numbered PCB pins, usually mounted on the edges of the boards, connecting the different sub-systems together. This makes it relatively easy to logically track inputs and outputs and also helps to relate everything to the circuit diagram. Admittedly, there are downsides to this method of construction; over time, vibration can wreak havoc with this type of connection, though this is not too much of an issue with a big heavy amplifier (unless it is sitting on a subwoofer!). It also becomes a pain if we want to remove or replace one of these wrapped wires, because once it is un-twisted from its post, it is almost impossible to reattach it in the same manner without a proper wire-wrapping tool. Another potential problem is that over time, dissimilar metal or galvanic corrosion between the wire and post can cause even the most tightlywrapped wire to go high-resistance, or fail altogether. In their defence, the designers probably didn’t anticipate their amps would still be in regular use 40 years later! Fortunately, the PCB pins are tinned and thus readily soldered, so reconnecting the wires is easy. You just need to trim off the old wrapped part of the wire, strip about a centimetre of insulation and tin the core before twisting it around the post a few times and then sweating it all together. Wrapping it the old way would retain the vintage vibe of the amp, but siliconchip.com.au two things prevented me from doing this. One, I don’t have the wrapping tools needed. And two, I’d need about 25mm of wire to wrap it back onto the post, and while most of these wires had some extra length, there wasn’t enough spare for me to chop them down and still have it run nicely in the existing looms. While the owner didn’t care about that aspect of the repair, I did make it a point to ask him, as some people can be very finicky about such details. Tracing the fault I started by working backwards from the speaker connectors. The next component in line was the anti-thump relay. Getting it out was as easy as desoldering the relevant wires from the terminals at the bottom, and removing a single mounting screw. The relay cover and relay then lifted out through the upper section of the amp. Basic tests on the coil and contacts using a multimeter and my benchtop power supply proved the relay was still very much alive and working correctly. This was fortunate; according to my research, it was hard to get a direct replacement. I’d have needed to substitute it with a relatively expensive type, with modifications to the relay’s cover, terminals and the chassis to make it fit and work. The next step was to check the relay driver board. This, according to the circuit diagram, should have 24V present on a couple of the output pins. While I measured a voltage on those pins, it was low and variable. I disconnected the relay coil wires and measured again, with the same result. There were about half a dozen electrolytic capacitors on this board; several of the larger caps had distorted plastic jackets, a sure sign of excessive heat and/or possible damage. So the board would have to come out, but there were 25 wire-wrapped connections divided between the input and output sides of the board. I therefore took several detailed photographs before removing it. I didn’t want to have to rely on the circuit diagram to track every connection in and out of that board if I didn’t have to! The various satellite boards in the amplifier are held in using white plastic ‘AT’ style standoffs, similar to those used back in the day to attach motherboards to a computer case. These have an expanding clip at the siliconchip.com.au end that pop into place once the board is seated down. The PCBs have a 3mm hole in each corner that fit onto the clips. These simple fasteners work so well in anchoring the PCBs, that they can be a pain if you want to release the board. Many people use a pair of sidecutters or long-nose pliers to pinch the expanded splines together, one by one, so they can ease the board up off the clips. I use an ancient pair of Xcelite transverse end-cutter pliers that I poached from dad about 45 years ago. While once probably sharp on the cutting edges, they certainly aren’t now. As they fit perfectly over the clips, it’s really easy to pinch the splines without fear of mangling them, or worse still, accidentally chopping one off flush with the board. Finding more faulty components With the driver board out, I removed and measured the suspect caps to work out which ones might be failing. I use one of those little Peak LCR40 meters to test capacitors, resistors and inductors. I won it years ago in some competition or other, and it was such a useful device that I went out and bought another one, just in case. That one has never been out of the box, except for me to take the battery out for storage. I suppose I should pass it on to someone who could get some use out of it. Perhaps SILICON CHIP can dream up some reason for a giveaway… Anyway, to test a component, I clip the leads on, hit a button and read the results. While they claim this machine can be used in-circuit, I’ve found it not as accurate as if the component is tested off the board. In this case, half the capacitors were well out of tolerance, with some obviously very leaky. I replaced them all. While the board was out, I also tested the dozen or so transistors. For these, I used my Peak Atlas semiconductor analyser. This is another extremely useful tool. Whether the component has a part number on it or not, this tool will tell me what it is, the pinouts and whether it is any good. Obviously, it is better to have a type number so I can refer to a data sheet for specs, but in a pinch, when I haven’t been able to identify some ancient TO92 or TO-18 package device due to age Australia’s electronics magazine FEBRUARY 2020 63 or deliberate part-number obfuscation, it has saved me many times. I removed each transistor and tested them. I found two that gave “component not detected” on the Atlas, which is always a bad sign. Fortunately, the numbers were clearly visible, though I also had the circuit diagram which clearly stated which part went where. I replaced these older NPN types with a suitable (tested) substitute from my parts bins. Once that was done, I re-mounted the board onto the standoffs, being careful not to push it down below the clips in case I needed to lift it out again. I stripped, tinned, wrapped and soldered the connection wires back into place. Something smells a bit off When I powered it up to test it, the relay didn’t click in at all, and I noted the faint-but-familiar smell of some- 64 Silicon Chip thing heating up. Old electronics getting hot have a distinct scent, and I am very attuned to it. After powering the amp down, I broke out my laser thermometer and aimed it around the relay driver board; nothing remarkable there. I then shone it over the main power supply board, which sits adjacent to the relay driver board. I got some high thermal readings from the heavier-duty components near the output of the PSU board. This PCB contained everything necessary to provide the wide range of voltages the amp needs. Its output voltages range from ±3.5V to just over 50V. One of the four TO-220 heatsink-mounted output transistors and some of its associated components were heating up under load, so it was clear that this board would also have to come out. More photos and wire-unwrapping followed before I could remove the power supply PCB. While that was disconnected, I measured the outputs of the power transformer, just in case something was wrong with it. All AC outputs measured within a volt of what the circuit diagram specified, so the problem had to be somewhere in this power supply board… Once again, I worked through the caps and smaller transistors associated with the suspect part of the supply. While some of the voltage outputs were achieved using simple resistive voltage-divider networks, the rest was set out in clearly defined sections of the board, making troubleshooting a bit easier. As I found several more dead capacitors, I replaced all of them on the board. A few of the TO-92 driver transistors were also suspect (and I broke one getting it out for testing), so I swapped them all out too. I removed the output transistors and tested them; one was significantly different in my test results than the other three but still ‘passed’ according to my tester. I substituted a similar spec device from my parts bins anyway. One of the more timeconsuming parts of this process is tracking down all the different datasheets for these old 2Sx series (Japanese coding scheme) Australia’s electronics magazine components and finding equivalents. Fortunately, I have Google and a good supply of older transistors so I can replace any dodgy components with similar types. I used new electrolytic capacitors, but all the replacement transistors were new, old stock (NOS) devices around the same age as the originals. There wasn’t that much else on this power board; no complicated, mysterious, impossible-to-test proprietary ICs or other unknown parts, just meat-andpotatoes analog components. Working on this type of hardware is such a pleasure compared to the stuff manufacturers churn out for today’s throwaway culture. All my effort pays off I reconnected all the wiring and sat the power supply board in-place, again without clipping it home. This time when I flicked the power switch, nothing happened, until a satisfying clunk from the relay pulling in signalled that the anti-thump was working. On powering down, the relay dropped instantly. I cycled it about a hundred times over the next few hours; the relay pulled in without fail every time. A scan using my thermometer over the boards revealed nothing was getting warmer than ambient temperature. I was very happy with the result. But this story serves a cautionary tale that just because any given tester says a component is good doesn’t mean it will work properly. My motto is: when in doubt, swap it out! Editor’s note: on a similar theme, I had multiple people test the battery in my wife’s car and tell me it was OK, but we continued having problems with certain 12V-powered accessories in the vehicle. Running out of ideas, I decided to replace the battery on a hunch. Out of the car, I charged it fully and left it to sit overnight. The voltage dropped to 12.68V, when it should have stayed above 12.9V. I suspect that those battery testers only check how much current can be drawn, which will detect some faults but not others. Now that I have a good battery in there, I realise that it was faulty right from the day she bought the car new. We just weren’t familiar enough with it at the time to notice the signs. For example, we can now sit in the car with the radio going for more than two minutes without it shutting down! siliconchip.com.au AUSTRALIA’S OWN MICROMITE AUSTRALIA’S OWN N E E R C S H C U O T MICROMITE BACKPACK TOUCHSCREEN F PROG REE Since its introduction in February 2016, RAMMIN Buy eit tell us wher V1 or V2 Ba G for and which project yo ckPack, u e’ll p g ram want it FREE O FroR PROGFRCAHEAERitGfoE r you, MMIN! Buy eit Geoff Graham’s mighty Micromite BackPack has proved to be one of the Smost ince versatile, its introduction in Februaryand 2016, most economical tell us her V1# or V2 Ba G hich p ckPack for and w Geoff Graham’s mighty Micromite easiest-to-use visual display and touchscreen control systems available – not only here in Australia but around the world! we’ll p roject you wan , FREE O rogram it for yot it BackPack to be of the mostBackPack: versatile,the most economical and easiest-to-use visual display andPLUS, published u, F There are has threeproved versions of one the Micromite original V1, published February 2016; the Micromite in November C # Supers eded but HARGE! still avail to orderbe able touchscreen control systems not only here in 2017. Australia around the world! There nowV2 four versions 2016, and now there’s the V2 available BackPack –published in May The but main difference between the are V1 and versions is the V2 can plugged #); the Micromite PLUS, published in November 2016, of the Micromite BackPack: V1, published February 2016 (now superseded straight into a computer USBthe fororiginal easy programming or re-programming “in situ”, while the V1 requires a separate programmer – YES, if you the BackPack published in May 2017 over and now there’s the V3 July If you your wish,own themasterpiece! Micromite (which is wishV2the Micromite can be programmed and over again, for BackPack published published projects, orinfor you2019. to develop programmed can be in programmed andsoover againeasy – fortopublished for you to develop your own masterpiece! The MicromiteinisBASIC) programmed a version ofover BASIC it’s quite learn andprojects, write yourorown! BACKPACK Micromite BackPack V3 – Jul 19 V2! – May Micromite BackPack Plus BackPack Micromite V1 – Feb–16Nov 16 Micromite Micromite BackPack Plus BackPack – Nov17 16 Micromite BackPack V2! – May 17 The V3 BackPack is the most We have taken the best The Micromite LCD BackPack features of the Micromite combines a full colour touchLCD and the Explore 64 sensitive LCD panel with a lowand put them together onto cost 32-bit microcontroller running single board. Use itIt to supercharge your aa BASIC interpreter. packs an incredible BackPack oran just as a convenient and amount of project power at amazingly cheap price cost-effective controller module. and will leave you thinking up project after KIT INCLUDES: project where you could put it to good use. PCB, 2.8-inch touchscreen and lid Programmed PIC32MX470F512H-120/PT KIT INCLUDES: 3.3V LDO regulator plus Mosfets for PWM control backlight PCB MCP120-270 supply supervisor 2.8-inch touchscreen with 320x240 pixels 20MHz low-profile crystal Microcontroller (programmed with your choice) and IC socket green SMD LED 3.3V low-dropout regulator micro USB & microSD sockets All capacitors (ceramic types supplied) Right-angle tactile switch 10kΩ resistor and 100Ω trimpot SMD capacitors and resistors Pin headers (male and female) pin headers and shorting block Tapped spacers and machine screws mounting hardware UB3 lid (laser-cut 3mm acrylic) MicromiteBackPack BackPackV1PLUS Kit SC3321) (Cat SC4024) – $70.00 Micromite Kit (Cat – $65.00 The V2 version of the We have taken the best Micromite LCD BackPack features of the Micromite incorporates the MicroLCD Backpack and athe bridge, which adds USB Explore 64 them interface andand theput ability to together onto a single to it's program/reprogram theboard. 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KIT INCLUDES: KIT INCLUDES: PCB, 2.8-inch touchscreen and lid PCB (green) PIC32MX470F512H-120/PT (programmed with your choice) 2.8-inch touchscreen with 320x240 pixels 3.3V LDO regulator plus Mosfets for PWM control backlight Programmed microcontrollers and IC sockets MCP120-270 supply supervisor Mosfets for PWM-controlled backlight dimming 20MHz low-profile crystal 3.3V low-dropout regulator green SMD LED All capacitors (ceramic types supplied) micro USB & microSD sockets 2 1kΩ & 2 10kΩ resistors SMD tactile switch Pin headers (male and female) SMD capacitors and resistors UB3 lid (laser-cut 3mm acrylic) pin headers and shorting block Tapped spacers, machine screws and Nylon washers mounting hardware Micromite BackPack PLUS V2 KitKit (Cat(Cat SC4237) – $70.00 Micromite BackPack SC4024) – $70.00 The latest version of the yet! convenient and powerful Micromite LCD BackPack It has all the features of the V1 incorporates the Microand V2 BackPacks and supports bridge , which USB both 2.8in andadds 3.5ina touchscreen displays plus interface the ability to extra memory, a realfive new and optional features: program/reprogram the PIC32temperature, chip while it's time clock, infrared receiver, onboard. And the BackPack V2 also adds humidity and pressure sensors and more! software control over the LCD backlight. KIT INCLUDES: PCBINCLUDES: (green) KIT 3.5-inch colour touchscreen with 480x320 pixels PCB (green) Programmed microcontrollers and IC sockets 2.8-inch touchscreen with 320x240 pixels 3.3V low-dropout regulator and IC sockets Programmed microcontrollers All capacitors (through-hole backlight ceramic dimming Mosfets for PWM-controlled types supplied) 3.3V low-dropout regulator 2 1kΩ & 2 10kΩ resistors All (ceramic supplied) Pincapacitors headers (male and types female) 2Mosfets 1kΩ & 2for10k Ω resistors backlight dimming PWM-controlled Pin headers (male and female) Tapped spacers, machine screws and Nylon washers UB3 acrylic)black 3mm acrylic) UB3 lid lid (laser-cut (laser-cut3mm matte/gloss Tapped spacers, machine screws and Nylon washers Micromite BackPack BackPack PLUS V3 KitV2(CatKitSC5082) – $75.00 Micromite (Cat SC4327) – $70.00 For more information search for all BackPack articles siliconchip.com.au Individual PCBs and microcontrollers areMicromite also available separately foratall Micromite BackPacks Specialised components for MICROMITE BACKPACK projects published in SILICON CHIP Parking Assistant Black/clear/blue UB5 lid & ultrasonic sensor: siliconchip.com.au/Shop/7/3338 Boat Computer VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 $7.50 $25.00 Super Clock VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 DS3231 real-time clock (RTC) with mounting hardware: siliconchip.com.au/Shop/7/3491 DS3231+ rechargeable LIR2032 cell: siliconchip.com.au/Shop/7/3519 Energy Meter DS3231 real-time clock (RTC) with mounting hardware: siliconchip.com.au/Shop/7/3491 DS3231 + rechargeable LIR2032 cell siliconchip.com.au/Shop/7/3519 ACS718 20A isolated current monitor IC: siliconchip.com.au/Shop/7/4022 Main PCB [04116061 RevI]: siliconchip.com.au/Shop/8/4043 Matte black UB1 lid: siliconchip.com.au/Shop/19/3538 $25.00 $5.00 $7.50 $5.00 $7.50 $10.00 $15.00 $10.00 Voltage/Current Reference Short form kit: All parts including PCB, but not including the BackPack module, case, power supply, PCB pins and wire siliconchip.com.au/Shop/20/3987 Matte black or blue UB1 lid: SC4084/SC4193 Main PCB [04110161] as separate item: siliconchip.com.au/Shop/8/3988 $99.00 $10.00 $12.50 DDS Signal Generator AD9833 DDS module: siliconchip.com.au/Shop/7/4205 $25.00 Deluxe eFuse IPP80P03P4L04 P-channel Mosfet (2 rqd): siliconchip.com.au/Shop/7/4318 LT1490ACN8 op amp (2 rqd): siliconchip.com.au/Shop/7/4319 BUK7909-75AIE N-channel SenseFET (2 rqd): siliconchip.com.au/Shop/7/4317 Main PCB [18106171] siliconchip.com.au/Shop/8/4370 Matte black UB1 lid: siliconchip.com.au/Shop/19/4316 $4.00 $7.50 $7.50 $12.50 $7.50 Radio IF Alignment AD9833 DDS: siliconchip.com.au/Shop/7/4205 $25.00 Altimeter/Weather Station DHT22/AM2302 temp. & humidity sensor: siliconchip.com.au/Shop/7/4150 $7.50 1A/500mA Li-ion/LiPo charger board: siliconchip.com.au/Shop/7/4308 $15.00 GY-68 pressure/altitude/temperature sensor: siliconchip.com.au/Shop/7/4343 $5.00 5V 0.8W 160mA solar panel: siliconchip.com.au/Shop/7/4339 $4.00 Tariff Super Clock VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 DS3231 real-time clock (RTC) with mounting hardware: siliconchip.com.au/Shop/7/3491 $25.00 $5.00 GPS-synched Frequency Reference Short form kit: All SMD parts and PCB. Not including BackPack module, case, power supply, GPS module, connectors and a few through-hole parts: siliconchip.com.au/Shop/20/4762 $80.00 VK2828U7G5LF GPS module with antenna and cable: siliconchip.com.au/Shop/7/3362 $25.00 Main PCB [04107181] as a separate item: siliconchip.com.au/Shop/8/4728 $7.50 FOR MORE DETAILS ON ANY OF THESE BACKPACK PROJECTS OR COMPONENTS, LOG ONTO SILICONCHIP.COM.AU/SHOP AND SEARCH FOR THE ITEM OF INTEREST siliconchip.com.au Australia’s electronics magazine February 2020  65 Previously, I thought that this behaviour was simply due to an over-cautious low battery cutout setting. Chromagen water heater repair R. W., of Mount Eliza, Vic noticed a problem with his Chromagen gas/solar water heater. As in past cases of similar faults, the repair was simple once the faulty part had been tracked down. Here is what happened... How do you know if a solar hot water system is working correctly? I was checking it by seeing if the pump was working and testing the temperature of the return pipe with my hand, to see if it was hotter than the supply pipe to the roof. Because the return pipe was hotter, it appeared that it was working correctly. But I was wrong, One night, I was by the hot water tank and noticed that the pump was still running even though there was no sun. The supply and return pipes were at the same temperature. This meant that it was pumping the hot water from the tank and dissipating heat energy into the air. No wonder the gas bill was high! I set out to determine the reason for this. There is a temperature sensor that is mounted on the solar panels on the roof, and a second temperature sensor at the bottom of the hot water tank. A Kanitti Solar Controller mounted on the tank controls the mains-powered water pump. When the solar panel sensor temperature is at least 4°C above the tank temperature, it switches on the water pump. The pump is switched off when the solar panel sensor temperature is less than 1°C above the tank temperature. The temperature sensors are connected to the controller via RCA plugs and sockets. I disconnected the sensors and used a multimeter to measure their resistances. The solar panel sensor read 392W while the tank sensor read just under 10kW. I e-mailed Kanitti requesting a service manual or a circuit for the solar controller, so I could determine whether these readings were correct. Even though it was midnight, within 10 minutes, I got a reply indicating that I should not try to service the controller as it could be dangerous. They also told me that the problem is more likely to be the temperature sensors and indicated that the sensors are 10kW NTC thermistors. 66 Silicon Chip This indicated that the solar panel sensor resistance reading was wrong, because 392W for a 10kW NTC thermistor corresponds to a temperature of about 120°C! The problem could be either in the sensor itself or in the extension cable. I got up onto the roof and disconnected the sensor, then measured the resistance across the cable wires, which was very high. So it must be a faulty sensor. I ordered a new sensor from Chromagen for $64 plus $20 postage and received it the next day. I then searched the Chromagen website and found a manual that included (on pages 36 and 37) a test procedure for the controller and temperature sensors. Before replacing the sensor, I turned off the main water tap and mains power to the controller. I carefully got up on the roof to swap in the new sensor. The connection to the extension cable is under the roof tiles, so I had to slide up a roof tile to gain access. I then disconnected the old sensor and connected the new one. I tied the connectors together to stop them from coming apart, then slid the roof tile back into place. The installation procedure also shows how to purge any air that might get into the system. But I used a simpler procedure; I partly screwed in the temperature sensor and turned on the mains water tap. The water pressure allowed the air to escape. When water started to escape too, I completely screwed in the sensor to finish the job. Back at the solar controller, I used my multimeter to re-check the sensor resistance. I measured 13.46kW, which equates to 14°C. The tank sensor measured 11.53kW, which corresponds to 17°C. So these readings now seemed sensible. So I plugged them back in and switched on mains power to the controller. As the temperature difference was less than the 4°C required to activate the pump, I had to wait for the solar panel temperature to rise before the water pump would turn on. Which it did, indicating that it was working correctly. When reading the manual on how to purge any air that gets into the system, I noticed a section that indicates that the water flow rate should be 0.75L/ min for a single solar panel and 1.75L/ min for two-panel systems. On checking the flow rate, I found that it was well over 3L/min. Australia’s electronics magazine The water pump has a switch to select between three different speeds. It was set at the highest speed. Setting the switch to the lowest speed caused the flow meter to indicate a flow rate of 3L/min. I then rotated a screw above the flow meter to make the final adjustment, setting the flow rate to 1.75L/ min as we have two solar panels. From now on, I will check that the water pump is not working at night when there is no sun. Only Harry Hindsight knows how long the system was not working correctly. He should have told me earlier! Multiple capacitor replacements R. E., of Townsville, Qld appears to be cursed because pretty much every motor in his house has failed lately, and in some cases, more than once! Luckily, he is now pretty adept at fixing them… Some time ago, our clothes drier started acting up. My wife complained that it sometimes rotated and sometimes did not. After a lifetime of repairing electromechanical devices for the government, none of which I could throw away, I am reluctant to throw out an appliance without attempting a repair first. So I carried the drier outside to the patio area where I had more room to work. This is as close to using laundry equipment as I am allowed, since the time I tried to wash a red T-shirt with some white socks and ended up with pink socks. Getting access to the inside of the drier required removing the rear panel, which provides support for the drier drum and some rigidity for the entire structure, as it has no framework. So as soon as the rear was removed, the drum basically fell out, being held in only by the drive belt around the motor pulley. There is very little inside a drier, apart from the motor, pulley, belt and drum, and the front-mounted control board. I removed the drum and drive belt from the motor, then powered up the drier and selected “dry”. The motor did not turn at all. No surprise there. A large white motor capacitor was quite visible, and as it had a real possibility of affecting the motor operation, I bought a replacement from a local electrical supplier for $15, installed it and tried the unit again. The motor siliconchip.com.au now ran without fail. I then re-fitted the drum, pulley and rear panel, and re-installed the drier in the laundry for my wife to further test it in use. It operated successfully for several years until my wife rushed into the lounge room one day to tell me that the laundry was filling with black smoke coming from the drier. I knew that it couldn’t be from burning lint, as my wife religiously cleans the lint filter before each use. Flicking off the laundry circuit breaker, I figured that this time the drier was surely finished, and took it outside to air out and cool down, as well as air out the laundry itself. The next day I took it apart again. Amazingly, everything looked fine inside, with no fire damage or even soot visible. But it was evident that the motor capacitor had ruptured and split, and was obviously the source of the thick black smoke. Replacing it yet again returned the drier to service, and it has been running for another couple of years since with no problem. So, when our pool pump motor became intermittent a year or so later, my suspicion naturally fell on any capacitor attached to the motor, if there was one. Removing the terminal cover showed just such a motor capacitor. Replacing it with an identical unit restored the pool pump to normal action; an expensive pump replacement avoided. The replacement capacitor cost less than $20, whereas a new pump would have been anywhere from $350-600 depending on the quality and power, so I was pleased with the result. A few years later when it failed again, I found that the replacement capacitor had failed similarly to that of the clothes drier, catching fire and even melting the plastic electrical connection cover, making it very clear where the problem lay. But like the drier, a new capacitor once again returned it to operation. More recently I had a problem with my electric garage door opener, which became intermittent, sometimes opening, sometimes not. When it wouldn’t open, it instead emitted a buzzing noise. Fortunately, it is possible to open the door mechanically by pulling a latch on the mechanism that disconnects the door itself from the chain driven shuttle, but it is hardly an ideal long-term solution. Not feeling particularly optimistic, siliconchip.com.au I removed the cover over the drive mechanism mounted to the ceiling of the garage, to see if there was an obvious problem. One of the first things that I saw was the large white motor capacitor. Due to my previous experiences, I decided to look no further and immediately started looking for a replacement. It was impossible for me to purchase an exact match, as no 12.5µF capacitor was available at our local electrical supplier, but I found one 12µF capacitor in their spares collection, which I had no doubt would be suitable. For some reason, it is considerably smaller than the original, with a correspondingly smaller slot for the metal mounting screw frame to slide into. So it does not fit as well as the original, and it now sits off to one side of the mounting hole. But that isn’t a real problem. The garage door opener’s operation returned to normal as soon as I fitted the new capacitor, with no hesitation by the motor. It now seems to run quieter as well, possibly due to re-tightened cover screws etc. I have since found a wide selection of motor capacitors at, of all places, a local plumbing supplier, but will leave the current capacitor in place while it continues to function. Capacitors in our current ceiling fans have also caused me some problems, noticeably slowing their operation. I found the motor capacitor in the cap under the fan where a light could be attached. It was a small, flat black 1.5µF unit. I found a replacement part at our local spares store, Solex, and have now replaced all the capacitors in the ceiling fans, as many of them were showing signs of slowing down. This is something I never recall needing to do in the past with cheaper ceiling fans. Repairing so many household items by simply replacing the motor capacitor makes me wonder what people do if they are not capable of doing such work. Do they call in repairmen who offer an economical repair on-site, or do they end up having to buy expensive new appliances? After all, if you saw thick black smoke pouring out of a clothes drier, would you expect it to be so easy to repair? SC Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column? If so, why not send those stories in to us? We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. Australia’s electronics magazine February 2020  67 Low Distortion DDS Signal Generator This two-channel audio signal generator produces very low distortion sinewaves as well as triangle waves, square waves, pulse trains and noise. It has adjustable output frequency, amplitude and phase, plus sweep and pulse modes. Control is via a rotary encoder knob and graphical LCD screen with an intuitive graphical user interface (GUI). It’s ideal for testing amplifiers, loudspeakers and all sorts of audio equipment, as well as for general purpose use. by Phil Prosser O n my work bench, I find the most useful test equipment – after my multimeter – are a signal generator and an oscilloscope. When testing analog circuitry, I find it very important to be able to ‘stimulate’ a circuit and then look to see how it responds. In the past, I used simple oscillators for this job, usually Wien Bridge types due to their high performance at low cost. But when testing speakers, it is very useful (in fact, almost essential) to be able to sweep the generated tone frequency. This allows multiple drivers and crossovers to be tested. And when testing amplifiers and speakers, it is very handy to be able to generate short bursts of a tone with a silent gap. A simple oscillator can’t easily do either of those things. Burst tones serve a couple of purposes. Firstly, when testing a power amplifier driving a low impedance, it can be quite stressful on heatsinks, dummy loads and power supplies using a continuous waveform. If you can generate, say, two cycles at 1kHz followed by a second of silence, you can see what the amplifier does at and near clipping and at high currents without really stressing things. Also, when building loudspeakers, it is really useful to be able to generate tone bursts at and around the crossover point. This lets you set up a microphone to measure the time delay for the tone burst through a bass driver and a tweeter. 68 Silicon Chip This is essential if you want to ‘timealign’ drivers in a speaker cabinet. For some time, I used the free Audacity software on my PC to do these jobs. But that set-up was a bit clunky, so I set about designing a more convenient hardware device that could do all this for me. The device that I came up with, presented in this article, uses the same hardware as my DSP Active Crossover/ Parametric Equaliser project that was published in the May, June and July 2019 issues (see: siliconchip.com.au/ Series/335). If you’ve already built that, it’s simply a matter of reprogramming the microcontroller to perform these waveform direct digital synthesis (DDS) functions. If building it from scratch, you can build it as described in those earlier articles, although you only need one of the stereo digital-to-analog converter (DAC) boards (not two) and you don’t need the analog-to-digital converter (ADC) board at all. ±9V Lout +5V +3.3V MCLK DAC BOARD OUTPUTS SCLK LRCK +5V DSP CPU BOARD MCLK POWER SUPPLY & SIGNAL ROUTING BOARD DATA2 Rout SCLK LRCK DATA1 DATA2 DATA3 GPI/O 9V AC 128x64 MONOCHROME GRAPHICAL LCD 9V AC GPI/O FRONT PANEL CONTROLS 9V AC PLUGPACK OR 9-0-9V MAINS TRANSFORMER SC 2020 Fig.1: the powerful 32-bit PIC processor on the DSP CPU board generates a stereo digital audio signal which is routed to the DAC board (at upper right) through the central power supply/signal routing module (upper centre). The DAC board (upper right) converts the audio data into two analog output signals. It’s all controlled via an LCD screen, one knob and two buttons. Australia’s electronics magazine siliconchip.com.au The May 2019 article gave an overview of the hardware and then described how all the separate boards worked, except for the CPU control board and the front panel controls. Those were covered in June 2019, along with the PCB assembly details. The July 2019 article gave programming and final assembly instructions, along with usage instructions that are not directly relevant to this project, as the software is different. However, if you have seen that, the user interface of this new software will be familiar to you. Those were long and detailed articles so we won’t reproduce all that information here. We’ll just give a quick overview of how the hardware works and then jump into describing the new software. The hardware There are four PCBs involved in this project, and the basic arrangement is shown in Fig.1: first is the CPU board which hosts the powerful PIC32MZ2048 32-bit processor, a couple of regulators and a crystal to provide an accurate clock source. This connects to a power supply and signal routing board which derives the DC supplies required to power the various other boards from a 9V AC plugpack or transformer. Digital audio signals from the CPU are routed through this central board to a stereo DAC board which provides the two analog outputs via onboard RCA connectors. The fourth board is a front panel control board with a rotary encoder (which may have an integral pushbutton) and one or two separate buttons. The CPU board drives the graphical LCD module directly. Fig.1 only differs from Fig.3 on page 28 of the May 2019 issue, which shows the DSP Active Crossover/Parametric Equaliser configuration, in that we’ve removed the unnecessary ADC input board and the second stereo DAC out- put board. Otherwise construction is identical. Principle of operation In case you aren’t already familiar with how a DDS works, we’ll give a quick description and describe why they are so much more useful than basic oscillators. We had a detailed description of DDS operation on pages 23 & 24 of the April 2017 issue, in an article on modules based around the AD9833 DDS chip. If you have that issue, you may wish to (re-)read that article now. Direct digital synthesis is a process for mathematically generating a waveform. The system comprises a clock source, a ‘phase accumulator’ and a lookup table that determines what analog output is generated at any given time. Fig.2 shows this configuration. The clock source runs at a high frequency compared to the output waveform frequency; the clock frequency is often hundreds of times more than the Reproduced from the DSP Signal Processor project in our May, June and July 2019 issues, here are the four main PC            boards used in this DDS Signal Generator. Top left is the main CPU board, bottom              left the power supply board, top right is the digital to analog (DAC) board              while bottom right is the front panel board. Not shown                here is the graphical LCD module nor                   the AC transformer. siliconchip.com.au Australia’s electronics magazine February 2020  69 PHASE ACCUMULATOR Fig.2: the basic configuration of a direct digital synthesiser. The phase increment value (chosen for a specific output frequency) is added to the phase accumulator on each pulse from the clock source. The accumulator is then used to index a waveform lookup table, and the values looked up feed the DAC to producing a varying analog waveform at the output. Its shape is determined by the values in the lookup table. FREQUENCY (PHASE INCREMENT) REGISTER BINARY ADDER + FREQUENCY PROGRAMMING waveform frequency. On each clock cycle, the DDS system adds the phase increment to the phase accumulator. The lookup table can hold any waveform, though conventionally it would be a sinewave or something similar. As the content of the phase accumulator increases in value, the system ‘steps through’ the table, feeding subsequent values in this table through to the output, reconstructing the waveform stored within. The rate at which it steps through the table (determined by the phase increment) determines the frequency of this reconstructed waveform, ie, how many times it runs through the table each second. For example, if the clock frequency is 48kHz and you want an output frequency of 4800Hz, then you would need to produce one full sinewave every 10 clock cycles. Thus the phase increment needs to be 1/10th of the maximum phase value (equivalent to 36°). WAVEFORM LOOKUP SAMPLE TABLE (ROM) ACCUMULATOR REGISTER DAC ANALOG OUTPUT SC MASTER CLOCK INPUT 20 1 9 If instead, you want to produce a 1Hz output with the same clock frequency, the phase increment needs to be 1/48,000th of the size of the phase accumulator (0.0075°). You can see then that for good low-frequency performance, a high-resolution phase accumulator is desirable. The PIC Microcontroller has a natural word size of 32 bits. That’s suitable for moderate clock frequencies (up to a few MHz). Also, to make the software simple, you want to use numbers in the DDS that the processor can divide easily. Using 32 bits makes things easy, since dividing by powers-of-two is very easy and fast (it can be done with simple shift/bit masking operations). So we have a phase accumulator that is used to look up the waveform. For high precision, we need the sinewave to be very accurate. The limited memory in the PIC makes this a little tricky, as the largest practical sinewave table is around 4096 entries long. That’s quite good, but not good enough for extremely low distortion. The configuration of a basic DDS using a 4096-entry (12-bit) table is shown in Fig.3. This works reasonably well but, as shown, there are rounding errors in the values produced which makes it not quite a pure sinewave. To solve this, we use the top 12 bits of the 32-bit accumulator to look up values from the 4096 entry (212) table, with the remaining (bottom) 20 bits determining where the current point in the waveform falls between samples in the table. This value can then be used to linearly interpolate between the two nearest (adjacent) entries in the table, to emulate having a much larger table. The error in the resultant sinewave is vanishingly small. So the DDS configuration is now as shown in Fig.4. It’s just a little more complicated than the one shown in Fig.3 and the extra calculations are well within the capabilities of a PIC32. The result is now 32-BIT ACCUMULATOR REGISTER 32-BIT ACCUMULATOR REGISTER 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 TOP 12 BITS TOP 12 BITS 12-BIT LOOKUP HAS ERRORS WAVEFORM LOOKUP SAMPLE TABLE (ROM) DAC CURRENT & NEXT POINT SC 20 1 9 INTERPOLATE BETWEEN POINTS, CALCULATE CORRECTION DELTA CORRECTIONS ANALOG OUTPUT SC  BOTTOM 20 BITS WAVEFORM LOOKUP TABLE (12-BIT)  ERRORS IN 1–2 LSB DAC 20 1 9 Fig.3: here’s how the contents of a 32-bit accumulator are used to index values in a 4096-entry (12-bit) lookup table. The bottom 20 bits are ignored (although they are still needed to achieve the correct output frequency) while the top 12 bits are used directly as the table index value. This results in an output waveform with an accurate frequency but varying amplitude errors, leading to increased (but not necessarily excessive) waveform distortion. 70 Silicon Chip Fig.4: by adding a little extra complexity to the table lookup scheme, we can dramatically reduce the waveform distortion. The table lookup now retrieves the current and next values, and the bottom 20 bits of the accumulator are no longer ignored. Instead, they are multiplied with the difference between the two values from the table, to produce an error correction term which means that the values fed to the DAC are linearly interpolated between the table values. This reduces the instantaneous output amplitude errors to a tiny fraction of full-scale, and they essentially become negligible. Australia’s electronics magazine siliconchip.com.au very close to a perfect sinewave at just about any frequency. The DDS needs to do all these sums and interpolations 48,000 times a second. But this is what computer chips are really good at. The net result is that the data fed into the DAC is correct to within 1-2 least significant bits. Without interpolation, spurs in the output are between -70dBc and -80dBc, which makes sense as the errors are about 1/4096 of the full amplitude (20 x log10 (4096) = 72dB). Fig.5 shows the frequency spectrum of the output without interpolation, and Fig.6 shows the same output with interpolation. The DDS running without interpolation gives a creditable performance; those spurs (they are not harmonics) at -75dBc are around 0.02% of the waveform amplitude. For the version with interpolation, the largest signal by far is the hum being picked up by the test set at -100dBc or about 0.001% of the amplitude, with the distortion products being 1/10th of this or around 0.0001%! So with interpolation, we can get a result close to the limits of the DAC’s performance. Along with getting the correct amplitude values to the DAC, we need to send them at the right time. Jitter in the clock which determines when data is sent to the DAC can also distort the resulting waveform. So we set up the PIC32MZ and the SPI port going to the DAC so that the notional DAC clock is an integral fraction of the PIC32MZ system clock of 252MHz. By choosing the DAC clock this way, there is no jitter or error on the timing of the DAC signals. This is critical in all the clocks, phases and precisions being controlled. It does result in a rather unusual DAC clock rate of 49,218 samples per second, but that This table shows how the Signal Generator’s sinewave performance varies with the output frequency and amplitude. You can see that the harmonics are very low, only increasing to a significant level when the output amplitude is below -20dBV. Amplitude Amplitude (on DDS) (Measured) Harmonics 110Hz 0dBV 0dBV -105dBc (0.00056%) 110Hz -3dBV -3dBV -116dBc (0.00016%) 1kHz 0dBV 0dBV -104dBc (0.00063%) 1kHz -6dBV -6dBV -113dBc (0.00022%) 1kHz -10dBV -10dBV -109dBc (0.00035%) 1kHz -20dBV -20dBV -103dBc (0.00071%) 1kHz -30dBV -30dBV Approx -90dBc (0.003%) 1kHz -50dBV -50dBV Approx -70dBc (0.03%) 1kHz -80dBV -80dBV Approx -40dBc (1%) 2kHz -3dBV -3dBV -116dBc (0.00016%) 5kHz -3dBV -3.1dBV -116dBc (0.00016%) Table 1 - measured performance with various sinewaves doesn’t really matter, except to slightly complicate our phase increment calculations. The PIC32MZ can generate a very accurate 48,000kHz clock, but this uses a ‘trim’ on the DAC clock, which introduces jitter. We don’t want that! Construction & programming As mentioned earlier, the construction steps were detailed in the June & July 2019 articles on the DSP Active Crossover. My only suggested change, other than leaving out the redundant second DAC board and the ADC board, is that you may wish to mount the DAC board with its two output RCA sockets coming through the front panel, rather than the rear. That makes it more practical to use as a test instrument. The software for this project, both as a compiled HEX file and an MPLAB X IDE C project, can be downloaded from the SILICON CHIP website. You can then upload that HEX file to the PIC32MZ chip using the procedure described on pages 87-88 of the July 2019 issue. You can use that same procedure to reflash a DSP Active Crossover so that Screen 1: this screen lets you set the output frequency of the currently selected channel. siliconchip.com.au Frequency it can perform the DDS role outlined here. There is absolutely nothing stopping you from flashing it back to the Active Crossover / Parametric Equaliser firmware when you have finished with that. Remember that these chips eventually do wear out if you keep reflashing them, but given the PIC32MZ’s specification of a minimum of 10,000 erase cycles, you’re unlikely to wear it out this way. User interface When the unit is first powered on, you can cycle through the following four main screens using the rotary encoder: • Load settings • Save settings • Channel 1 options • Channel 2 options Once you’ve selected one of the channels, by pressing the Select button or pushing the rotary encoder, it jumps to the output frequency setting screen (see Screen 1). Turning the dial does the obvious thing, ie, increments and decrements Screen 2: here, you can change the size of the frequency steps in the previous screen. Australia’s electronics magazine February 2020  71 Fig.5: to prove the advantages of the linear interpolation scheme, here is a spectrum analysis (FFT) of the output of the unit using just the basic 12-bit lookup scheme shown in Fig.3 (ie, no linear interpolation). You can see that there are a large number of spurious signals at various frequencies present in the waveform, although most of them are not harmonics of the output sinewave. This leads to a distortion level of around 0.02% (the level shown in the screengrab is not accurate). Fig.6: this is a spectrum analysis of exactly the same signal as in Fig.5, but this time, with linear interpolation. You can see that there is a lot less noise in the signal, and the actual harmonics are now visible, along with some mains interference at 50Hz, 100Hz and related frequencies. the frequency. The Exit button returns to the channel selection screen, and the Enter button advances to the next menu page. As you change frequency, if you turn the dial continuously for about a second or so, the step size increases by a factor of 10, allowing you to use both fine and larger frequency steps from the one screen. This is one of a few data entry screens that are ‘sticky’; if you leave the controls untouched for a long while, the interface will remain on this screen, rather than reverting to the initial screen. The reasoning here is that if you are fine-tuning a speaker or a filter, you may need to make the occasional frequency adjustment and it would be annoying to have to go through the menus again each time. If you press the select button/knob on the frequency setting screen, it takes you to a step adjustment screen (Screen 2), which lets you increase the base step size from 0.1Hz to 1Hz, 10Hz or 100Hz. This may be useful if you are making lots of rapid changes to the output frequency and don’t need to be extremely precise. The behaviour of the Exit button on this screen is different; exiting from this screen takes you back to the previous frequency setting screen, rather than the initial screen. Pressing Enter on this screen takes you to the output level adjustment screen (Screen 3). The output level is set in dB Volts (dBV). 0dBV = 1V RMS, -20dBV = 0.1V RMS, -40dBV = 0.01V RMS etc. The resolution is 0.1dB, which is quite a small step. As you rotate the control, if you rotate for more than a second or so, the increment size increases (as with the frequency adjustment), allowing you to make larger changes in output level reasonably quickly. The output range goes from +5dB Volts (1.78V RMS) to -123dB Volts (0.7mV RMS), but note that -123dB Volts is essentially the noise floor of the DAC. The Exit button takes you back to the main screen, while pressing Enter takes you to the waveform selection menu (Screen 4). On this page, rotating the encoder cycles through the various waveform types, including Sine, Triangle, Square, Pulse and Noise. If you select Pulse, a secondary menu pops up, allowing you to set the duty cycle in 1% increments. Having chosen a new waveform, press Select to reprogram the waveform lookup table and change the output signal. This also takes you to the next screen, which is the sweep Screen 3: the next screen lets you set the output level from -123dBV (0.7mV RMS) to +5dBV (1.78V RMS) in steps of 0.1dBV. Screen 4: as you rotate the knob on the waveform selection screen, you can select Sine, Triangle, Square or Pulse. For Pulse, you can set the duty cycle from 1% to 99%. 72 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.7: an example output waveform from the unit in sweep mode (blue trace). It is sweeping from a high frequency down to a low frequency. Fig.8: a sample pulse train output, with five pulses on (at 1kHz), followed by five pulses off. This sequence then repeats endlessly. selection menu (Screen 5). As usual, pressing Exit will take you back to the channel selection menu. Sweeping and pulses Sweep options include None, Linear and Log (logarithmic). Logarithmic sweeps (actually exponential) are very useful for wideband tests and audio testing. Your ear is much better ‘tuned’ to a logarithmic sweep than linear, giving the sense of a constant rate of pitch increase or decrease. The frequency at which the sweep starts is the frequency set on the main frequency menu. Having chosen the sweep type, you can then adjust the sweep end frequency. This may be above or below this start frequency. This allows sweeps upward and downward without complicating the interface. A sweep is implemented by the DDS frequency being changed in 4096 steps throughout the sweep. Without getting into too much detail, the sweep involved repeatedly changing the phase increment value. This has the benefit of the output phase from the DDS always being continuous (ie, no phase ‘jumps’). A sample of the sinewave output in sweep mode is shown in Fig.7. Having adjusted the end frequency and pressed Select, you can then adjust the sweep time from 0.1 seconds to 60 seconds in 0.1-second steps using the knob. Press Select Screen 5: you can disable sweeping, or have a linear or log (exponential) sweep. If enabled, you set the end frequency and sweep time in the next couple of screens (the start frequency is the channel’s set frequency). It can sweep up or down. siliconchip.com.au Screen 6: the unit can be set to produce a continuous waveform or a pulse train. With a pulse train, you can have 1-1000 pulses followed by 1-1000 gaps. Each pulse or gap is the set waveform period (the reciprocal of the frequency), eg, 1ms for 1kHz, 10ms for 100Hz etc. Australia’s electronics magazine February 2020  73 Many years ago, long before the days of smartphones and computers, even before the days of television, it was considered a “rite of passage” for dads to sit down with the their sons (or daughters) and help them as they built their own radio receiver. FM? Not on your life - no such thing! DAB+? Hadn’t been invented yet! No, it was all good, old reliable AM Radio. Imagine the thrill of listening in to radio stations hundreds, perhaps thousands of miles away . . . maybe even overseas! The beauty of it all was that they were building something that actually worked, something they’d be proud to show their friends, to their school teachers, to their grandparents! Enjoy those days once again as they build the SILICON CHIP Super-7 AM Radio See the articles in November & December 2017 SILICON CHIP (www.siliconchip.com.au /series/321) SUPERB SCHOOL PROJEC T! PCB & Case available from the SILICON CHIP Online Shop • • • • • • • Conclusion All the PCBs to build this project are already available from the SILICON CHIP ONLINE SHOP. As we mentioned earlier, they were also used in the DSP Active Crossover/ Parametric Equaliser project. They are coded 0110619201106196. We can also supply a PIC32MZ microcontroller pre-programmed with the software for either project. Many of the parts are SMDs, some of them fine-pitched, so this is not an ideal project for beginners. But you will get a test instrument with excellent performance, that can carry out many important audio tests, especially for hifi gear. You could even combine this Signal Generator with a high-quality ADC connected to a computer, feeding into spectrum analysis software, as an audio analyser capable of measuring distortion in devices like amplifiers, preamplifiers and filters, down to very low levels. It can also be used in conjunction with our High-Resolution Audio Millivoltmeter project, published in the October 2019 issue (siliconchip.com.au/Article/12018), for making signal-to-noise ratio measurements. That would be a great way to make and save frequency response plots, with the Signal Generator in sweep mode and the Millivoltmeter connected to a USB port, for logging the results, which could then be fed to a plotting program. Covers the entire AM radio broadcast band. Has on-board speaker ... or use with headphones. SAFE! – power from on-board battery or plug-pack. Everything is built on a single, glossy black PCB. All components readily available at normal parts suppliers. Full instructions in the articles including alignment. Superb see-through case available to really finish it off! IT LOOKS SO GOOD THEIR FRIENDS WON’T BELIEVE THEY BUILT IT! 74 again to move onto the next screen, or Exit to go back to the main selection screen. The next screen configures pulse train mode (Screen 6). The pulse train can be set to off or on. If you turn pulses on, you need to set the number of pulses on and off for the train. Both can have values of 1-1000 pulses. So with a 1kHz tone, you could have a single 1kHz cycle followed by one second of silence. As noted earlier, this is very handy for high power amplifier testing (especially stability testing into very nasty or low impedances), and for testing loudspeaker driver phase centres. Fig.8 shows an example of the output using the pulse mode, with a 1kHz waveform set for five pulses on and five pulses off. Pressing Select after the last pulse mode screen takes you to the phase shift screen (Screen 7), which allows you to change the relative phase between the two output channels. This only really makes sense where both channels are set to identical frequencies. This is particularly handy when you want to use one channel to trigger an oscilloscope. The phase shift lets you move the waveform of the second channel on the oscilloscope screen. Silicon Chip Screen 7: finally, if you wish you can set a phase offset between the two channels, although this only makes sense SC if they are set to the same frequency. Australia’s electronics magazine siliconchip.com.au Using Cheap Asian Electronic Modules by Jim Rowe USB Logic Analysers This 8-channel USB logic analyser, is essentially a clone of the original version of the well-known and respected Saleae Logic unit. It’s completely compatible with the Saleae design, but you can get this one for as little as A$12.40 – less than one-tenth the cost! I n the September 2009 issue, we published a review of the then-new Saleae USB Logic Analyser, written by Geoff Graham (siliconchip.com.au/Article/1558). Although Geoff pointed out a few limitations (like only having eight channels), on the whole, he found it an excellent little performer. He wrote that it was probably suitable for 95% of the analysis work done by hobbyists, technicians and designers. In 2009, you could buy the original Logic direct from Saleae (www. saleae.com/) in the USA for US $149 plus delivery, which ended up being about AU $250. This was still only a fraction of the previous cost of getting a ‘professional’ logic analyser, which made it an attractive purchase – particularly since Saleae allowed you to download the matching control and analysis software for free. Prompted by Geoff’s review, I bought one myself. Then when Saleae brought out a 16-channel version, I bought one of those too. And I’ve been very happy with them both, especially as Saleae has kept their software up-to-date. But recently, USB logic analysers like the original Saleae Logic began to appear on the world market, at a much lower cost. They all seem to be made in China, and many of them are virtual ‘clones’ of the original Saleae Logic. They’re all 8-channel units with a maximum sampling rate of 24 Megasamples per second (MS/s), and in most cases, they work exactly the same as the Saleae Logic when hooked up to your PC. Even Saleae’s software can’t tell the difference. What was that old saying about “imitation being the sincerest form of flattery”? However, their “Terms of Service” says that you may not use their software with unauthorised clones of their products (www. saleae.com/terms-of-service/). But there is a alternative, which we’ll get to a bit later. At the time of writing, there are quite a few of these Saleae Logic clones available on various online sites, at prices varying between $12 and $36 depending on the supplier and their location. Sources include Banggood in China, Sparkfun Inside the logic analyser (shown enlarged for clarity), we found a board with a 56-pin Cypress Semiconductor USB-capable micro, a 24C02 EEPROM, octal bus transceiver chip, regulator, crystal, transistor, two LEDs and a handful of passive components. The bus transceiver operates as a level shifter and also protects the micro inputs. siliconchip.com.au Australia’s electronics magazine February 2020  75 For comparison, here is the original Saleae Logic unit which I purchased a few years ago, along with the supplied (functional!) USB cable and high-quality test clips. in the USA, Sparkfun’s supplier Core Electronics in Australia and quite a few others you can find on eBay and AliExpress (www.ebay.com.au/ itm/193121890194). I should point out that Saleae no longer makes the original 8-channel 24MS/s logic analyser. Instead, they offer the Logic 8, which samples at up to 100MS/s (priced at $639) and the Logic Pro 8, which offers 500MS/s sampling ($1119). They also sell the Logic Pro 16, offering 500MS/s sampling of 16 channels. So Saleae has moved up-market, leaving the lower end to the clones. Cheapest & most popular Unsurprisingly, the most popular of these clone logic analysers is the cheapest one. It’s available from Banggood for approximately $12 (Banggood 1177821; siliconchip.com.au/link/ aax7). This includes a USB type-A to mini type-B cable (the analysers are powered via the USB cable) and a set of 10 ribbon cable test leads, with female pin sockets at each end. 76 Silicon Chip The clone from Sparkfun for US $19.95 appears to be identical (www. sparkfun.com/products/15033), apart from a more attractive label on the top, as is the one which Core Electronics sells for just over $35 plus delivery (siliconchip.com.au/link/aax8). This device is housed in a plastic box measuring 55 x 27 x 14mm, which appears slightly smaller than the original Saleae Logic unit. That came in a nicely finished machined metal box measuring 41 x 41 x 8.5mm. Apart from this, the main physical difference is that the ‘el cheapo’ unit has a 10-pin DIL connector for the test leads, whereas the original Saleae Logic had a 9-pin SIL connector. Another difference is that, while the original Logic (and the later Saleae models) came with a set of nine highquality E-Z-Hook Micro test clips, the clone units just come with female-tofemale ribbon cable leads. If you want test clips, you have to buy them separately – more about this a little later. Finally, whereas the original Saleae Logic (and later versions) came with a Australia’s electronics magazine sturdy little storage case for itself, its USB cable, test leads and clips, the clones come without a case. Electrically, the clones seem to be virtually identical to the original Saleae Logic. When you connect them up to a USB port of a PC, they are recognised as a Saleae unit. And if you fire up Saleae’s software, it behaves in precisely the same way as it does with a genuine Logic (but you’re not really allowed to do that...) Alternative software If – like me – you’re not willing to violate Saleae’s terms of use and use their software with one of these clone units, there is an alternative. The open-source software website http://sigrok.org has a software package for download called PulseView. This comes in three versions, to suit Windows, Linux, macOS etc. For PulseView to be installed on a Windows machine (XP or later), the WinUSB driver must already be installed. If this isn’t already installed, you can install this using software siliconchip.com.au Screen 1: the free PulseView software working with one of the ‘el cheapo’ clone logic analysers to decode SPI serial data. It’s easy to use and can decode a great many different digital protocols. Screen 2: the official Saleae logic software operating with one of their logic analysers to decode the same bus as shown in Screen 1, although there’s slightly different data this time. While there are some visual differences, the two pieces of software work similarly. siliconchip.com.au Australia’s electronics magazine February 2020  77 called Zadig (http://zadig.akeo.ie/), which we have used in the past for driver installation (eg, in the Banggood SDR kit, reviewed in November 2017; siliconchip.com.au/Article/10879). I downloaded and installed PulseView, and found using it to be quite similar to the Saleae software in operation. You can also download a 24-page PDF user manual from the sigrok website, to help you figure out how to use it (https://sigrok.org/doc/pulseview/ unstable/manual.html). PulseView worked equally well with both the Saleae Logic and the clone, and offers an even larger range of protocol analyser options (54 in all), including all the popular ones like I2C, SPI, UART, CAN, I2S, 1-wire, S/PDIF, HDMI CEC, JTAG, MIDI, PS/2 Keyboard/Mouse, USB LS/FS, RGB LED (WS281x) and PWM. Most importantly, there is no limitation on using PulseView with the clone logic analysers! That, and the fact that it has more features, makes PulseView the way to go. You can see a typical display from the PulseView software in Screen 1, which again shows the SPI signals on one of my Arduino-based Audio Millivoltmeter prototypes (October 2019; siliconchip.com.au/Article/12018). As this software works with both the original Logic and the clones (as shown in Screen 2), I was able to make a direct comparison when analysing both I2C and SPI signals on one of the prototypes of my Audio Millivoltmeter. I’m glad to report that the results were identical. Sparkfun have a short tutorial on using their USB logic analyser with PulseView at siliconchip.com.au/ link/aaxa USB cables and test clips An end-on view of the clone logic analyser showing its 10-pin DIL box header and the supplied USB cable which was missing a pin. available for only a few dollars (and you’re likely to have a few already, as they’re pretty common). As mentioned earlier, these ultralow-cost USB logic analysers don’t come with any test clips – just a set of female-to-female ribbon cable leads. So unless you’re only going to be testing signals already routed to pin headers, you will need a set of test clips as well. The E-Z-Hook XKM-S micro test clips originally supplied by Saleae are available separately, but at a fairly steep price. For example, you can buy a set of 10 from Digi-key (461-1012ND), but they’ll set you back about $40 plus shipping. This doesn’t seem all that attractive, since it’s around three times the price of the USB logic analyser itself! I found some likely-looking sets of 10 ribbon cable leads with micro hook test clips on eBay for just over $6, so I ordered a couple of them. But when they arrived, I found that the micro hook test clips were not nearly as well The genuine E-Z-Hook test clips, shown at right, are much easier to use and more reliable than the cheap test hooks I initially purchased, at left. I eventually found a much better-looking set of low-cost test clips at Banggood (see text). I ordered two of these low-cost analysers to check them out for this review, and when they arrived, I tried connecting them to a PC using the supplied USB cables. But neither of them were identified by Windows when plugged in. It was only when I tried using another, known-good USB cable that they sprang into life. When I looked inside the type-B mini plugs on the end of the supplied cables, they were both missing the pin 4 contact! Presumably, that’s why the analysers wouldn’t work with those cables. That was a bit disappointing, but luckily this type of cable is readily 78 Silicon Chip made as the genuine E-Z-Hook clips. The female connector on the end of the lead would not attach securely to the pin at the back of the clip, and the hook tips didn’t seem to have the right shape to mesh properly and attach securely to an IC pin. So it was “back to the drawing board” – or more accurately, back to the web. On the Banggood website, I found sets of “logic analyser test leads with hook clips” that looked more promising. These have the lead wires soldered to the rear of the hook metalwork inside the plastic housing, removing the problem of connecting the clips reliably to the leads (Banggood 956251; siliconchip.com.au/link/aaxb). These sets of leads were priced at just over $7 for 12, or over $11 for 20. So if you don’t want to invest in a set of genuine E-Z-Hook clips, these would probably be your best alternative. You can also try Jaycar Cat HM3037 for SC $1.75 each. Australia’s electronics magazine siliconchip.com.au Top Tech Build It Yourself Electronics Centres® Deals Opus One® 2x30W Bluetooth® Wireless Ceiling Speakers Leap into Altronics for these great deals. Only until February 29th. Built to stream the best content from your favourite music streaming service, app or podcast player. Bluetooth 5.0 technology offers superb audio performance and range. Each speaker pair has an in-built high performance 2x30W RMS amplifier. The ideal way to add permanent wireless sound to any room in the house. A modern, low profile finish is provided by frameless magnetic fit grilles. Includes power supply. Sold in pairs. NEW! Magnetic ‘edge to edge’ grille. 379/pr $ C 0876 Control more with 2 shields! Z 6457 Peace of mind for the family SAVE $21 99 MK2 Arduino MegaBox Kit by Altronics. Developed in house by Altronics, this new revised MegaBox is an upgrade of our original K 9670 - adding 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. Bargain 40W Soldering Station NEW! $ SAVE $119 59.95 $ Arduino Handheld Game Kit Great fun for anyone into their retro games. It provides all the hardware to build your own handheld console, then you can upload games from the many open source online communities or have a go at coding your own. Requires 2xAAA batteries. S 9395 Indoor Monitor + S 9396 Outdoor Camera 7” Touchscreen Video Door Intercom The safe & easy way to monitor the front door. Records photos of visitors when you’re not home. Easy to wire up yourself with 4 core cabling (ie: W 2341). 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SAVE 28% 50 $ SAVE 27% T 2164 26 $ Phone Repair Kit Everything you need to disassemble most phones and tablets - driver bits, plastic & metal spudgers, suction cup and more! SAVE 29% T 2185 19 $ Precision Screwdriver Set Ideal for general electronics servicing! Features a ferrule top driver handle & 19 pozi, hex, torx and blade tips. Includes premium carry case. Great for fixing high tech devices SAVE 20% T 2173 23 $ 30pc Precision Driver Kit An aluminium driver with rotating ferrule top for easy servicing of precision high tech devices. Includes 70mm extension and 28 x 4mm hex bits. See last page for store locations or visit altronics.com.au T 2175A 1000V Rated Insulated Tool Kit Ideal for technicians working on mains powered equipment. Includes cutters, pliers, wire strippers, 5 screwdrivers plus a neon test driver and 2 rolls of insulation tape - all in a handy carry case. Tool Kit Savers K 9670A Sale pricing ends February 29th 2020. Makers & designers rejoice! Stock arrives mid-February! Pre-orders welcome. CP-01 3 in 1 - Desktop 3D Printer, CNC Router & Laser Etcher. 3D printers now at COMING SOON! CR-10 V2 K8606 Large volume 3D Printing CP-01 K8604 3D Print / CNC / Laser Etch Ender 5 Pro K8602 Workhorse 3D Printer Ender 3 K8600 Desktop 3D Printer Easy to use prototyping for your workspace. See the range at www.altronics.com.au/creality/ Creality is a trademark of Creality Inc. For more information visit www.creality.com. © All rights reserved. Tools to make cable runs easy... 95 $ Take snapshots & record video SAVE $20 *Phone for illustration purposes. SAVE UP TO 15%! S 8747B Active Optical HDMI Cables Cutting edge Active Optical Cable (AOC) HDMI technology supporting 4K resolutions at longer lengths than copper cable. Plus, it’s thinner, lighter & more flexible! Lifetime warranty. Handy Wi-Fi Endoscope Camera Great for diagnosing problems in hard to reach places, this handy camera has a 3.6m lead with 2MP camera, viewable on your phone or tablet screen. Connects up to 4 devices at once. LED camera light provides a clear view. Includes hook, magnet & mirror attachments. Why use HDMI AOC? These cables totally eliminate the need for long distance baluns, UTP conversion and boosters for HDMI signals - get full 4K <at> 60Hz over the full distance! Model Length Normally NOW P 7427 10m $209 P 7428 12m $229 P 7429 15m $239 P 7430 20m $249 P 7432 30m $259 P 7434 50m $299 $185 $189 $199 $225 $235 $269 SAVE $24 $ Track, Trace & Verify LAN Cabling Q 1340A Got a rats nest of LAN cables? This handy tone based cable tracer allows detection and verification of STP cabling over distances up to 3km. A must have for the data and comms technician. Suits standard and PoE lines and provides cable mapping functionality. Includes battery. 95 $ T 1568A TOP OF THE RANGE! 259 NEW! Deluxe Ratchet Modular Crimp Tool 49.95 $ T 1520A SAVE 22% D 3009 20 $ PoE Network Tester Crimps 4, 6 and 8 way RJ connectors. Inbuilt stripper and cutter. All metal construction - built tough for every day use. Test live ethernet cabling for data and power. Works with any 802.3af/ at ports/cabling. Ideal for data/ comms installers. Simple Wire Stripping Quickly strip almost any type of cabling with ease. Adjustable depth with in-built cutters. Cat6 U/UTP Data Cable PC1389 SAVE $1 SAVE $10 Fully approved data cable for home or business use. 100m pull box. Blue. SAVE $20 SAVE $30 99 $ per box W 7130 SAVE $20 55 $ T 4704 SAVE $50 79 199 $ Easy back to back connection for use with pre-terminated leads. No fiddly punchdown terminals! Includes cable support bar on rear. $ D 5137A 24 Port 79 $ Coupler Cat6a Patch Panels D 5139 48 Port Through Wire Cat6 Plugs Unique through wire design for quick, easy termination. 100pc jar. Cable for illustration purposes. Requires no tools to terminate. Great for quick cabling fix ups. 29 NEW! Glow In The Dark Cable Snake Size Hard wearing 4m plastic coil makes running cable through a roof or wall cavity a breeze. Model ONLY White 26-24AWG Pk6 W 0800 Red 22-18AWG Pk6 W 0804 Blue 16-14AWG Pk6 W 0808 Yellow 12-10AWG Pk6 W 0812 $4.25 $4.50 $4.75 $4.95 TOP DEAL FOR INSTALLERS! SAVE 22% 13 $ 18 W 0884A 35 $ All heat & no flame! Iroda® Pocket thermo-gun. Great for removing adhesives & heatshrinking. 650°C max. Refillable. Add butane gas for $8.50. T 3022 12.5mm SAVE 20% 15 $ T 3024 20mm Bargain Punchdown Tool Heatshrink Mega Pack Hook & Loop Tape Suits Krone and 110 style data terminal blocks. 171pcs of 75mm & 45mm lengths in a range of colours & sizes (3.2-12.7mm). 2:1 shrink ratio. Back to back ‘velcro style’ tape (ie sticks to itself). 10m rolls. See last page for store locations or visit altronics.com.au 60 $ SAVE 24% 7 16 $ T 2480 $ ea $ SAVE 24% SAVE 22% SAVE 28% SAVE 19% T 1603 Tool Free Cat6 Plug $ T 4636 By popular demand! Heat up and join cables together without the need for manual soldering. Melts at 450°C. Packs of 6. Lightweight & easy to move around. Suits reels up to 400Ø x 430Wmm. Max reel weight 25kg. 2 $ .95 SAVE 15% Solder Splice Joiners Portable Cable Reel Stand P 1390 D 5118A Dual Cat6A J-Boxes Great for office cabling! Easily surface mounted. Punchdown termination. Q 2022 ‘Roadies’ Cable Tester Tests 13 types of leads for continuity. A real time saver! Tests: 6.35mm, DIN (3/5/7/8 pin), RCA, XLR (3/5 pin), Speakon (4P/8P), RJ45, USB & banana. Requires 9V battery (S 4970B $3.95). Sale pricing ends February 29th 2020. Great deals on power accessories... SAVE $14 135 $ D 0881 650VA Range of Anderson adapters also available! SAVE $35 285 $ D 0882A 1200VA Protects your work bench appliances! SAVE $40 335 $ PowerShield Defender D 0883 1600VA Backup UPS & Power Protectors ® Includes regulator, 5m battery cable & carry bag. Anderson Style Extension Cables Handy extension cables for products with Anderson connectors already fitted. 50A Rated. Provides power backup when mains fails, plus added protection for surges and spikes on power, phone & data lines. Includes monitoring software. 2 year warranty. For backup times check the website for the UPS run time calcuator. Model Length ONLY M 8639 1m M 8646 3m M 8647 5m $29.95 $64.95 $84.95 N 1130F SAVE $30 39 .95 $ A 0276 Charge 10 batteries at once! Recharges 10xAA/AAA or 2x9V batteries. Includes mains power supply & car adapter. Suits NiMH only. 119 SAVE 35% $ 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). SAVE 25% 30 $ A 0309B SAVE 15% 15 $ SAVE 26% 24 $ M 8520A Stay powered up on your travels! • Charges 4 USB devices at once • Australian, US, UK and European outlets • 5V 4.1A output • 100-240V AC • Travel case. S 9266 Power Over Ethernet Splitter Allows you to power non PoE equipped devices from a 802.3af Power Over Ethernet RJ45 cable. Eliminates the need for a power supply at the end of the cable run. 12V, 15.4W max. M 8627B 69.95 $ TOP VALUE! 55 $ SAVE $30 239 $ 130W Remote Power Folding Solar Panel Easy to use SLA battery charger With trickle charging function to ensure long battery life. Multi-stage charge control ensures long life from your batteries. 6/12V 1.3-8Ah. SAVE $60 N 2018 Trade price for everyone! This month only. Premium UPS Grade SLA Batteries Perfect replacements for alarm, UPS and NBN backup boxes. Dual 12V Car Battery Isolator Kit Provides everything you need to wire up a secondary battery in your vehicle - vital for powering appliances at campsites, inverters etc, and isolating the primary battery so you have enough juice to start your car! Instructions included. Type Normally NOW 1.3Ah $19.50 $15.50 $23.95 $22.95 $34 $44 $55 $89 $135 S 5080D 3.3Ah $29.95 Keep your laptop charged up in the car S 5084D 4.5Ah $28.50 S 5090D 7.2Ah $39.95 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. S 5094D 9Ah $49.95 S 5098D 12Ah $65 S 5100D 20Ah $110 S 5104D 26Ah $159 Sale Ends 29th February 2020 Build It Yourself Electronics Centres Western Australia » Perth: 174 Roe St » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au Victoria 08 9428 2188 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave SAVE 24% 12 3x Car Accessory Adaptor $ Plus dual USB charger for keeping your devices powered up on the road. M 8606 Find a local reseller at: altronics.com.au/resellers 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. Queensland 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St High current solar chargers were once sold for over $200 these new quality units are less than $100 and feature USB charging and a full LCD readout with essential battery information. Suits 12/24V systems. » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd 08 8164 3466 02 8748 5388 © Altronics 2020. 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. B 0091 S 2682 Model S 5075D Price Breakthrough! 20A Solar Charger PRODUCT SHOWCASE New dsPIC33CH512MP Dual-Core, High Memory, Dual CAN-FD DSC The new dsPIC33CH512MP508 dual-core Digital Signal Controllers (DSC) from Microchip build on the previously released Microchip dsPIC33CH128MP508. The dual-core DSCs enable designers to isolate time-critical and safety-critical functions from system functions and communication routines. This family is optimised for highperformance embedded, digital power, motor control and safety critical applications running sophisticated algorithms. Applications include wireless power, server power supplies, drones and automotive sensors. What’s new in dsPIC33CH512MP508? • • • • • Extends flash size from 128 to 512KB in the dual core dsPIC33CH device family 512KB flash on Master core for AUTOSAR, complex application, communication stacks; 72KB PRAM (Program RAM) on Slave core for complex control algorithms Dual cores and advanced peripherals make systems robust and functionally safe Dual CAN-FD for robust communication Unprecedented peripheral integration in 6x6 package for BoM cost saving Electronex Expo returns to Sydney in 2020 • Features for Functional Safety: ECC Memory, MBIST, DMT, Dual WWDT and more • ICSP Write Inhibit (OTP) for secure boot loading together with CryptoAuthentication devices to target secure applications • Automotive AEC Q100 Grade 1 qualified, -40°C to +125°C Development tools include: dsPIC33CH Curiosity Development Board (DM300028-2) dsPIC33CH512MP508 Motor Control Plug-In Module (PIM) (MA330046) dsPIC33CH512MP508 General Purpose Plug-In Module (PIM) (MA330045) Contact: Microchip Technology Inc Unit 32, 41 Rawson St Epping NSW 2121 Tel: (02) 9868 6733 Website: www.microchip.com JST’s “Wet Process” Semiconductor Cleaning Equipment Automated wet-process cleaning equipment is suitable for chips, wafers, semiconductors and other electronic devices including lasers. The more complex the equipment, the greater the need for advanced, adaptable cleaning options. JST’s 300 CLV Cleaner and Stripping Tool offers a dry-to-dry process. Once product is placed in the dry tank, it can process through either single or multiple chemical processes, rinse and dry according to a pre-programmed recipe without operator intervention or mechanical moving parts to maintain. Contact: Contact: Australian Exhibitions & Events JST Manufacturing Inc. PO Box 5269, Sth Melbourne Vic 3205 Tel: (03) 9676 2133 Website: auexhibitions.com.au 219 E. 50th St., Boise, ID 83714, USA Tel: (0011 1) 800-872-0391 Website: www.jstmfg.com siliconchip.com.au Following the success of last year’s Electronex in Melbourne, the event returns to Sydney this year. It will be held at Rosehill Gardens from 9 – 10 September 2020. The move to the MCEC in Melbourne was an outstanding success with more than a 12% increase in attendance and a record number of exhibitors participating in the 2019 event. In a further endorsement for the growth of the electronics sector and the success of the event, 53% of visitors had not attended Electronex previously and over 90% were engineers, managers or involved in production or purchasing. Electronex was first held in 2010 and has grown to become the preeminent trade event for companies that utilise electronics in manufacturing, assembly or servicing. The SMCBA Surface Mount Conference is also held concurrently with the Expo. Free seminars are also held on the expo floor and cover a range of hot industry topics to complement the conference workshops. The Sydney Expo is now open for bookings and around 60% of the space had already been booked by late December last year. Australia’s electronics magazine February 2020  83 Easy-to-build Active Hifi Bookshelf Speakers with Optional Subwoofers Part 2 – by Phil Prosser Last month we introduced this fantastic new active speaker system, which looks and sounds great but doesn’t cost a lot to build. Nor do you need extreme skills or specialised tools. We described the cabinet design, driver choice and performance last month. In this second article, we have the complete main speaker assembly details. W e decided to make these speakers out of plywood because, with a little care, they can be made to look really nice. But it’s still a relatively cheap and stiff material, and quite easy to work with. As explained last month, we’re using two types of Altronics drivers (or three if you build the optional subwoofers), all of which are quite reasonably priced while giving excellent results. All that’s required to achieve high fidelity performance are two carefully designed crossovers, the construction of which is described below. We’ll also describe how to put together the two ‘plate’ amplifiers which make these active speakers (they could also be used for other speaker designs). These are based on pre-built Class-D amplifier modules, so the assembly is quite straightforward. Building the passive crossovers You will need to assemble two passive crossovers for each system, ie, 84 Silicon Chip one per bookshelf speaker enclosure. The passive crossover is built on a PCB coded 01101201, which measures 137 x 100mm. Use the PCB overlay diagram, Fig.12, and matching photo as a guide when fitting the components. There are only three capacitors, none of which are polarised and three 5W resistors. All should be marked with their values, so simply fit them where shown. While not critical, it’s a good idea to fit the resistor bodies a few millimetres above the top of the PCB, to allow cooling air to circulate. Then mount the three identical twoway terminal blocks, with their wire entry holes facing the nearest edge of the PCB. That just leaves the three large air-cored inductors, which are simply “made” from whole reels of enamelled copper wire. To make these inductors, remove the stickers that are on each end. You will see 1-2cm lengths of wire in the middle of the reels. Prise these out and then scrape the enamel off with a sharp Australia’s electronics magazine blade. You need to be quite firm in doing this, and you will see the bright copper exposed. Extend this wire by soldering a few centimetres of tinned copper wire to the exposed end. All the reels we purchased had 1-2cm of wire inside the reel, which is insufficient to reach the PCB when the reel is laid flat. Next, drill a small hole through the side of the plastic bobbin, to allow you to pull the other end of the copper wire through, and secure it with hot melt glue or sealant. Make sure to pull the wire tight on the reel, so nothing can shake and move around. Scrape the end of this wire clean of enamel, too. We chose to liberally paint the wire on the reel with lacquer. This sets hard and holds everything tight, so it can’t hum or vibrate. That is an optional step, though. While we used hot melt glue to hold the inductors to the PCB after soldering their leads, we realised after doing this that it wasn’t such a great idea. Hot melt glue is quite effective for assembly siliconchip.com.au Fig.12: building the passive crossovers is not a huge job since there are only three inductors, three capacitors, three resistors and three terminal blocks. The inductors (which are full reels of copper wire!) are bulky and heavy, so make the sure they are properly anchored using cable ties (as shown here) or acrylic/ silicone sealant. An early prototype PCB is shown below, a little less than life size. There are some component differences between the photo and the overlay at right. Follow the overlay! Two are required – one for each enclosure. Also note our comments regarding hot melt glue – while it holds the inductors nicely, it can soften and even let go if the coils get hot. Hence the provision for using cable ties, as shown at right. like this, but can get a little messy if you are not cautious. And it can let go if the board gets too hot during use. If you use it, watch out that you don’t get it on your fingers; it gives terrible (and excruciating!) burns. Gluing the coils down using neutral-cure silicone sealant is probably a better option but even better, use cable ties. So the final board has holes to allow you to strap those inductors down using suitable large cable ties, as shown in Fig.12. the middle to get the bottom, sides and tops for a pair of speakers with minimum cost and fuss. This allows 6mm for the cut. If your pieces end up slightly wider than 297mm, that’s unlikely to be a major problem, as long as they’re all the same size. The material we used was 15mm fiveply from Bunnings. This is available from most hardware stores. We chose Building the monitor enclosures Fig.13 (overleaf) shows how to cut two 600 x 1200mm sheets of 15mm ply into the pieces you will need to build two bookshelf (monitor) speakers. The piece labelled “Subwoofer 2 front” is only needed if you are going to be building the subwoofers; otherwise, you can leave it as part of the off-cuts. The cutout drawings are also shown. By choosing the speaker depth to be 297mm, you can slice the one sheet right down siliconchip.com.au this based on price and availability. If you are after a really slick finish, you will benefit from choosing a higher grade timber, hence our suggestion in the parts list to use marine ply. If you plan to paint the boxes, then MDF would be better as the panels are extremely smooth. Some people may wish to use stiffer or denser material for the boxes. This is a personal choice and if it is your thing, go for it. In all the above cases, if you choose to use material that is not 15mm thick, you will need to go over the cut sheets and adjust the dimensions for a similar internal volume. Plus or minus a fraction of a litre is fine. This is not a difficult chore, but remember, it’s better to measure (or calculate) twice and cut once, than measure once and cut twice! You may wish to wait until the boxes are assembled to cut the holes for the drivers, amplifiers, terminals etc. However, it might be easiest to mark their positions now. Note our comments re the use of hot melt glue: a cable tie through the core of the coil (as shown in the diagram above) is much more secure (especially when the coil gets warm!). Australia’s electronics magazine A few assembly tips: ! Align the left side, top February 2020  85 • • (OFFCUT) (OFFCUT) SPEAKER 1 BOTTOM SPEAKER 2 BOTTOM • We used 15 x 15mm timber off-cuts for bracing. This is large enough to let you screw things together without taking away too much from the internal volume. If your bracing is slightly different to this, don’t worry about the effect on the volume. Once you have cut the pieces, assemble them as follows: The sides Start by attaching the braces to the inside of the side panels. Make sure to leave gaps at the front and back of each side panel, slightly wider than 48 • • Check that the longer wood screws that you have are the right length to go through the bracing material and into the speaker panels without going all the way through. We found that 28mm screws were just right for our material. Note also that for any screws going into the speaker from outside, you will want to drill pilot holes and countersink those holes, so the screws will end up flush. • You need to glue and screw. We used standard PVA glue. As you build, have some acrylic filler to hand, filling any gaps as you go. 210 • and right side on the panel such that the grain runs continuously up and over the speaker box. This is a little touch, but a nice one Mark the panels on the inside using a pencil or marker. This will let you keep track of things Choose sheets that allow you to cut with little waste You should be able to get your local Bunnings to cut this for you. There are only a few cuts for the whole speaker Keep the off-cuts; they make good bracing. 718 (OFFCUT) 4 SPEAKER 2 RIGHT HAND SIDE SPEAKER 1 RIGHT HAND SIDE 360 ALL DIMENSIONS IN MILLIMETRES (OFFCUT) 88.5 A SPEAKER 2 REAR 95 4 HOLES A: 47.0mm DIAMETER SPEAKER 2 FRONT A 180 4 50 SUBWOOFER 2 FRONT 88.5 42 A 777 20 INPUT CUTOUT 42 4 40 68.5 (OFFCUT) SPEAKER 2 TOP SPEAKER 1 TOP 210 357 118.0 DIAM. 118.0 DIAM. 297 170 41 50 42 297 CUTOUT SPEAKER 1 FRONT AMPLIFIER A 136 180 357 SPEAKER 2 LEFT HAND SIDE SPEAKER 1 LEFT HAND SIDE 360 95 SPEAKER 1 REAR 177 177 177 4 6 4 Fig.13: here’s how to cut two 600 x 1200mm sheets of 15mm ply into the pieces you’ll need to build two monitor speakers, plus one piece for the optional subwoofers. The dimensions have been chosen to minimise waste; depending on the width of your saw, you may be able to simply cut the left-hand sheet in half down the middle. The holes for the driver, port and terminals are best made once the boxes have been assembled. 86 Silicon Chip Australia’s electronics magazine siliconchip.com.au Cut bracing as shown and use glue and 3-4 screws to attach these braces to the side panels. (Subwoofer panel shown here.) the front panel is thick. This is best achieved by holding a piece of off-cut material next to the bracing while you attach it. At the top and bottom edges, screw the bracing very slightly inside from the top and bottom edges, so that when the top and bottom panels are screwed on, the bracing pulls the top/bottom panel in tight to the side panel. This will minimise gaps on the side. Bottom panels Drill and screw the bottom panel to the sides, with screws going in through the bottom from the outside. If you plan to mount the speakers such that the bottom panel is visible, you will probably want to screw the bottom panel from the inside instead. If you are fixing from the inside of the box, drill holes in the bracing for the screws to pass through. Make sure to angle these holes so your screwdriver (drill) fits properly and the screwdriver bit engages the screw properly. If you pre-drill these perfectly vertically, it will be very difficult to screw the top/ bottom on. Top panels Get the top accurately aligned with the sides, and fix the screw at the rear of the box. Then check the alignment of the panels. If there has been movement during assembly, now is the time to fix it! Do not be scared to drill a new hole in the bracing, allowing a new screw to be used, then remove the first screw and use the second hole to try again. Nobody will ever see a second fixing hole on the inside of the box, but they will see a crooked panel. Once the rear of the top panel is properly aligned and tight, fix the front and middle of the panel. there to hold things secure until the glue sets. Before you do the screws up, get a T-square and check the box is square. Murphy’s law says that it will be crooked. There are several ways to pull the box square before you screw it together. One option is to use ratchet straps, but I will describe a cunning alternative. Put large screws in the gap between the side panels and front panel. Screw Front panels Before you fix the front panel, you really need to have a plan for how you will be finishing the boxes. I stained the boxes, so I was able to simply mount the front panel. This can be screwed and glued at this stage. Again, do this from the inside of the box. Acrylic filler is an excellent glue once it hardens. I used this to glue the front on. Remember that the glue will form the primary bond, and the screws are Various stages in the construction process. The photo at left shows the internal sealing as the box is built to ensure it is airtight. It’s also important to maintain panel alignment and “squareness” (as shown in the middle photo); the photo at right shows screws being used to ensure the gap remains constant all around. siliconchip.com.au Australia’s electronics magazine February 2020  87 Using a clamp while the glue sets will ensure that your square corners remain just that – square. these in far enough to get even gaps on each side and top/bottom. Provided your front panel is square – which we feel is a reasonable assumption – the overall box will necessarily be square now. Once it is nice and square, fit the final screws and allow the glue to dry for a few hours. Rear panels I suggest painting the inside of the mounting lip with black paint. Do not screw this on until everything is done. If you think you might want to take it off again, put foam sealer strip on the inside lip. This will give you a good chance of getting back inside the box. We got ahead of ourselves and glued the rear panel on too early. Working through a tiny woofer hole is tedious! tion of materials. The port The port is made from a 10.5cm length of 40mm PVC pipe. This has an internal diameter of about 38mm. Its length is moderately important, so get this within ±3mm. While you can still get inside the box, use your finger to put a fillet of acrylic filler around the inside of the port once it is inserted through the front panel. If you cut the hole for the port a touch too large, use the filler to secure it, and allow the filler to set. Finishing the boxes Use an off-cut to make a brace that goes horizontally across the speaker. Place this in about the middle of the side panels, and use acrylic filler to glue it in place. Fear not, once the acrylic sets the brace will be more than strong enough to dampen resonance in these panels. You will note that we routed that end grain of the plywood at 45°. This makes a feature of the fact that there is an end-grain there. The first time I did this was during an experiment to see if it affected edge diffraction on the front panel. I was much less convinced about the effect on diffraction compared to the aesthetic impact of the routing. This was done using a low-cost router and 45° bit with edge bearing. I did the route in two cuts, the first about half the final depth. Cutting the holes Staining/varnishing Once the carcasses of the boxes are done, it is time to cut the holes. Refer to the photo opposite. On the rear panel, you will have a large hole on one speaker for the plate amplifier, and a small one for the speaker terminals. Cut all holes before finishing the speakers. The cutout dimensions and locations are presented on the cut sheet drawings (Fig.13). Finishing the speakers is really a matter of taste and your selec- To stain and varnish the enclosures, sand, sand and sand some more. Always sand along the grain. If you go across the grain, the sandpaper will tear the fibres in the wood, and varnishing/staining will highlight this is a way that I am sure you will hate. As strange as it sounds, this means that orbital sanders are really of limited use. 120 grit sandpaper is your friend. Use it liberally and discard it as soon as it gets clogged. After that, two coats Adding a brace 88 Silicon Chip Australia’s electronics magazine of varnish are generally sufficient. Ideally, you should sand the box with 240 grit (or 400 grit) sandpaper after the first coat of varnish, then clean the dust off. Sand enough that you have a beautiful, smooth finish. The next coat then goes on smoothly, giving you a mirror-like finish. Now wire the woofer and tweeter with hookup wire of at least 1mm copper diameter. You don’t need to go crazy here; just don’t use tiny wire. When mounting the woofer and tweeter, put a run of foam tape around the edge of the mounting hole to form a nice seal between the driver and front panel. Don’t use acrylic or silicone filler. I have seen this done and it makes the speakers impossible to repair! Screw these on using 15mm wood screws. I find it much easier to drill pilot holes using a 1.5-2mm drill. This makes alignment a cinch, and reduces the chance of things slipping as you start screwing the drivers in. To mount the crossover in each box, first cut a pair of red/black heavy duty wires (or a figure-8 cable) long enough so that it will reach from the crossover input terminals inside the enclosure, out through the hole at the rear, with around 10cm of spare length outside the box. Strip the wires at both ends, and at- The finished enclosure, sanded and ready to be lacquered or painted. siliconchip.com.au Building the monitor ‘plate’ amplifier Cutting the holes with a jigsaw might not result in the most aesthetic of jobs but the edges are covered by the speaker surrounds, so it’s not vital they are works of art! tach each pair to the passive crossover input terminals. It’s also easiest to attach the wires which go to the woofer and tweeter at this point, making sure they’re long enough to exit the front of the box so that you can attach them to the driver terminals before installation. Now, stick foam to the underside of the crossover PCBs and screw them to the bottom panel of the enclosures, using 10-12mm screws. Wire up the woofer and tweeter as marked on the PCB. The inside of the speaker needs to have a layer of poly wadding stapled to it as shown. Staple this in place. If you don’t have a staple gun, just use 40mm nails and drive them in 10mm, then bend them over to hold the wadding in place. Wadding is available in craft shops such as Lincraft. Get the thick stuff and be reasonably liberal with it. Now screw in the drivers, being careful not to slip and put the screwdriver through the cone. Philips head screws help keep things under control, but the main point is: don’t slip! siliconchip.com.au Start by doing the metalwork. Cut and drill the 1.5mm aluminium sheet, as shown in Fig.14. You can download this diagram as a PDF from the SILICON CHIP website, print it out, cut it to size and stick it to the sheet. Or you can stick pieces of masking tape on the aluminium, make the measurements shown and mark the hole locations on the tape before drilling them. Centre-punch the holes before drilling. If you don’t have a centre punch, use a large nail and a hammer. The centre punching will assist in getting the holes exactly where you want them. Then drill pilot holes of 1-2mm. These will guide the final drill holes. When finished, deburr all the holes with a countersinking tool or an oversized drill bit. The mounting holes need to be drilled large enough to accept the screws you will use to fix the amplifier to the speakers. We suggest that 4mm is a good start. The four holes to mount the amplifier module (marked A) may need to be enlarged to 3.5 or 4mm to accept 3mm machine screws. The fifth hole marked “A” is for the locking pin on the volume potentiometer. If you don’t have a 10mm drill, drill holes “D” to the largest size you have and then use a tapered reamer or file to enlarge the holes. Or even better, purchase a stepped drill bit, which makes drilling larger holes in aluminium a breeze. Remember that this plate mounts on the outside of the speaker box, so be careful to finish it well, and preferably paint the aluminium to protect it. While you’re at it, now is also a good time to cut and drill the small aluminium plate which will be attached to the rear of the second (pas- The woodwork side – including a clear coat of woodstain – is now complete. All that remains is to build the amplifiers and crossovers, fit the speaker drivers and . . . relax! The two Altronics speakers selected for this project: at left is the C-3019 tweeter while at right (obviously not to scale!) is the C-3038 midrange. Australia’s electronics magazine February 2020  89 The foam glued to the back of the crossover PCBs prevents them rattling when they are secured to the enclosures. sive) monitor speaker. The details are shown in Fig.15. If you’re going to paint the metal plates (black is a good choice), now is the time to do it. This is not absolutely necessary if you’re planning on attaching a fullpanel label, an option which is described below, although it may still be a good idea, to prevent corrosion. To check this, remove the two screws that hold the heatsink to the PCB. These are on the back. Take the heatsink off and if it has heatsink paste on it, wipe it clean with a tissue. If not, thank goodness we checked! Now put on some fresh heatsink paste, then add a 3mm shake-proof washer to each of the mounting screws if they were not fitted. Our boards came without these, and we are pretty sure that after a few years inside a speaker box, the heatsink would come loose otherwise. When you replace the screws, do not over-tighten them. These put pressure on the amplifier IC is by pulling the heatsink down onto it and flexing the PCB a little. This works, as is evidenced by the During the survey of amplifiers we undertook (we bought many samples before settling on this unit), we noticed that the heatsink mounting was a bit of a weak point. In fact, some of the heatsinks were mounted with no thermal paste at all, and some were quite loose! B 10 B Preparing the TDA7398 amplifier module B 160 Before mounting the amplifier, check the mounting of the heatsink to the amplifier IC. A A 31 C 33 C 67.5 44 8 A 10 69 B 10 30 135 30 20 D C A B D C A 67.5 HOLES HOLES HOLES HOLES 35 A: B: C: D: 3.0 mm DIAMETER 4.0 mm DIAMETER 8.0 mm DIAMETER 10.0 mm DIAMETER 45 ALL DIMENSIONS IN MILLIMETRES B B 10 Fig.14: the monitor amplifier, terminals and volume control mount on this 1.5mm-thick aluminium plate. Once you’ve cut it to size, mark out and centrepunch the hole positions and drill pilot holes, then enlarge them to the sizes shown and deburr. 20 40 10 10 20 A A B B This shows how the acoustic wadding is installed in the speaker enclosures. These are actually the subwoofer boxes, which we will look at next month, but the principle is the same. 90 Silicon Chip 80 HOLES A: 4.0 mm DIAMETER HOLES B: 8.0 mm DIAMETER CL Australia’s electronics magazine Fig.15: this small plate, also made from 1.5mmthick aluminium, holds the pair of CL binding posts used to connect the passive monitor (or subwoofer) speaker back to the active one, which contains a stereo amplifier. ALL DIMENSIONS IN MILLIMETRES siliconchip.com.au A close-up of the TDA7498 80W/Channel Class-D stereo amplifier which we purchased on ebay for less than $20 – including postage! You couldn’t hope to build one for anything like the price. Add a 24V DC power supply and it’s ready to rock’n’roll (or classics, or swing, or orchestral . . .)! SIMPLY THE BEST Frequency Counter you will ever build! Based on the famous Micromite Plus d in Explore 100 e h s li As pub CHIP N SILICvO/Dec 2017 Oct/No way many computer CPU heatsinks are mounted, but this is a small chip, so we have to be careful with it. So once the first screw ‘grabs’, do it up an extra turn. Then do the same with the other. Repeat this until you feel the heatsink pressing against the amplifier IC. Add half a turn or so until you feel it is nice and firm and you sense the PCB taking up the strain. Let the PCB flex a bit; this is forming a spring that will hold the heatsink tight to the amplifier. After everything is together, it’s a good idea to add some red paint or nail polish over the screw heads to lock them tight and prevent them from unravelling due to vibration. Fitting the parts to the plate Now the amplifier is ready to be mounted to the base plate. But first, you should think about how you are going to label the rear plate. In our case, we dug through the bottom draw in the kitchen and found a labelling machine. This did a fine job of making labels for the back panel of the amplifier. These labels come in really handy in a few months when you have forgotten which plug does what! If you’re going to stick on labels, you can do that later. But as another option, we’ve prepared label artwork which can be downloaded as a PDF from the SILICON CHIP website and printed onto overhead transparency film (mirrored, so the ink goes on the inside) or a sticky label, fixed to the outside of the rear panel, if you prefer that approach. If you’re going to attach a full-panel label, you will need to do that before you fit the other components. Once you’ve stuck it on, cut out the holes for the various components with a sharp knife, and you are ready to continue construction. Now fit the amplifier, input terminals, output terminal for the second speaker and power connector to the plate. Use plenty of heat transfer compound on both the rear of the heatsink and the amplifier IC . . . siliconchip.com.au 10mHz to >6GHz Range! 800x480 pixel, 24-bit Colour LCD Touch Screen! 6VDC (or 5V USB) Power Frequency or Period Mode Just 140 x 55mm See the full series of articles at siliconchip.com.au/Series/319 The component mounting positions and wiring information is shown in Fig.16 and the photo below it. Start by attaching the input, output and power terminals, and the volume pot, then wire them up as shown. Make sure that the speaker terminal wire entries will be facing up once the plate amplifier is mounted. If you don’t check this, you might kick yourself later! Tighten the DC socket nut carefully, as the thread is aluminium. Make this tight, but be careful not to overdo it. When mounting the volume control pot, do its nut up tight. . . . and some form of locking compound (nail polish works well) to ensure the screws do not loosen over time. Australia’s electronics magazine February 2020  91 Fig.16: once the amplifier plate is ready, attach and wire up the components as shown here. The RCA input grounds and amplifier module input ground are all wired to the anti-clockwise end of the dual-gang potentiometer. The RCA input socket centre pins go to the separate clockwise end track terminals of the pot, while the amplifier inputs come from the corresponding pot wipers. = POT TOP TERMINALS TO PASSIVE CROSSOVER = POT BOTTOM TERMINALS VOLUME + + + + POWER IN 24V DC + JOIN EARTH TERMINALS RIGHT INPUT OUTPUT TO OTHER BOX LEFT INPUT – POWER AMPLIFIER MODULE If you drilled through the panel for the locking pin, seal the hole using a dab of neutral cure silicone on the inside. If you don’t have any, use some of the acrylic filler you used when building the boxes. The input RCA connectors specified are through-panel units with integral insulation bushings. When appropriately mounted, the bushing sits inside the 8mm hole, insulating the RCA socket from the panel. The amplifier module is mounted on the inside of the rear panel on 10-25mm long threaded standoffs with machine screws and shakeproof washers. Use shielded wire for the input and volume wires and reasonably heavyduty hookup or figure-8 wire for the power and output wiring. The amplifier inputs are via a 3-way, 3.96mm pitch polarised header. You will need to strip one end of the stereo shielded wire back and crimp and/or solder the two inner conductors and the outer shield into the pins for this plug, as shown in Fig.16. You can use two separate, singlecore shielded wires, or a single twincore shielded wire. The latter makes construction a bit easier. 92 Silicon Chip Note that the pins for this plug have two crimp sections, one to contact the bare copper wire and one to hold the plastic insulation. Make sure both are crimped securely. You should ideally use a tool designed specifically to do this, but in a pinch (no pun intended), you can use a pair of needlenosed pliers. We find it best to add a little bit of solder to the end of the copper wires once each pin has been crimped, to hold it all secure. Once all three pins are ready, push them into the socket, making sure the ground pin is in the middle. If the pins won’t click into place, you may not have crimped the wire insulation hard enough. When soldering the wires to the speaker terminals and DC socket, you will find it a lot easier if you add a bit Here is the final amplifier plate, ready to install in one of the enclosures (it is a stereo amp so only one is required). Cables connect from the output terminals to the other enclosure. This photo compares with the diagram above (Fig.16). Australia’s electronics magazine siliconchip.com.au The opposite (external) view of the amplifier plate seen on P91. This is screwed into the cutout on the appropriate enclosure (see below). While the volume control can be adjusted at will, it’s probably not going to be real convenient. We would imagine this control being “set and forget” to an acceptable level and the volume adjusted from the source. of flux to the terminals first. Once finished, use heatshrink tubing to make sure nothing can short together later. The vast majority of ‘brick’ type power supplies use a 2.5mm ID barrel plug, with negative on the outside and positive on the inner — Fig.16 shows the wiring for this case. Check your supply; in the unlikely case it is a ‘tip-negative’ type, swap the locations of the wires for the DC socket. You should have a complete monitor amplifier, ready to install in your desktop monitor, or any other speaker that you want to make “active”. Finishing the speaker assembly There isn’t much left to do here. If you’ve attached wires to the input terminals of the passive crossovers as recommended earlier, you just need to connect these to the free terminal block on the amplifier board in the active speaker, or attach them to the tabs on the inside of the binding posts in the passive speaker. Now would be a good time to wind the volume all the way down, plug in the power supply, connect a signal source and check that it all works. Assuming it does, screw the rear panels onto both enclosures, and you are ready to rock and roll! It’s a good idea to apply the same foam tape around the edges as you did with the drivers so that it forms a good seal. By the way, while we feel that the bass/mid/treble balance of these speakers is spot-on, should you feel that they are a bit ‘dull’, it is possible to slightly change the passive crossovers to increase the treble by about 2dB. To do this, remove the 12Ω resistors and change the 5.6Ω resistors to 4.7Ω. However, this may also lead to increased distortion as the tweeters will then be much less damped. We suggest you give the speakers a good listen first and make sure that you really want to make this change before going ahead. However, you can easily change it back if you try this change and are not happy with the result. SC Front and rear of the finished speakers. The rear shot is of the speaker which contains the inbuilt audio amplifier. NEXT MONTH: We’ll finish off this project with the description of the optional subwoofers. Of course, being optional, you can use the speakers as described so far. It’s up to you . . . but the subwoofers really bring out their best! siliconchip.com.au Australia’s electronics magazine February 2020  93 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. Two 100Mbit Ethernet connections over a single Cat6 cable Our new home has an Ethernet cable connection from the router to the office, which I used to connect a computer in the office back to the router. But I couldn't get the printer in the office to connect to the remote router via WiFi as the signal would not reliably penetrate the walls. Rather than installing a switch or router in the office, I decided that I wanted to run two Ethernet connections from the office back to the router. The computer and printer are both 100BASE-T 100Mbit/s Ethernet devices, meaning that they only use two of the four twisted pairs in a Cat6 cable. The house wiring uses gigabit-capable 1000Mbit/s four-pair cable, as is common these days. I therefore made two cable splitters, one for each end. This allows the computer and printer to run independently over the Ethernet cable wired into the house. Note that gigabit Ethernet requires all four pairs, so using this technique with gigabit devices will force them to revert to 100Mbit mode. I know that commercial splitters are available (eg, see Jaycar Cat YT6090 and RS 443-9165) but I already had RJ45 connectors, Cat5 cable and a crimping tool so I figured I'd make my own. Plus my splitters incorporate a cable, whereas the commercial splitters needs two extra regular Cat5 cables at each end. The wiring required is shown in the diagram. Connecting only four wires to the 8-pin RJ45 connector can be a bit of fun. Pins 1, 2 and 3 are easy but pin 6 can be a bit tricky. First, straighten the wires so that pins 1, 2 and 3 are parallel and close to each other, with a gap between pin 3 and 6. Slide the wires for pins 1, 2 and 3 so they just go into the wire guide slots, then wriggle the wire for pin 6 so it goes into pin 6 wire guide slot. Push all wires into the connecter and crimp it. I used long nose pliers to expand the connector hoods/boots to allow two thin Cat5 cables to fit. Wet the cables so that the hoods can slide over the two wires, as it is a tight fit. Be careful or you will split the hoods. Roderick Wall, Mount Eliza, Vic. ($65) 1 White / Orange 2 Orange 3 White / Green 6 Green 1 White / Brown 2 Brown 3 White / Blue 6 Blue 1 White / Orange 2 Orange 3 White / Green 4 Blue 5 White / Blue 6 Green 7 White / Brown 8 Brown Metered variable power supply using inexpensive modules Many switchmode voltage regulator modules are available from various retailers and on eBay. Many switchmode voltage regulator modules available online use the National Semiconductor (now Texas Instruments) LM2596S “Simple Switcher” IC. These modules are produced by several manufacturers, mostly in China, with manufacturer markings including “QSKJ”, “HW-411” and “RD086DY001”. All are similar, with only some minor component value variations and changes in auxiliary components. Usually, these modules have an output determined by the setting of a (typically 10kW) trimpot. If the trimpot is replaced by an external potentiome94 Silicon Chip ter, the module can form the basis of a quick and easy variable power supply. I used the “QSKJ” type module. These can then be desoldered individually. You could heat the solder joints until the trimpot can be pulled off the board, but it’s tricky heating all three joints at once. However, the easiest way to remove it is to cut it into pieces with side-cutters to the point where only the 3 pins remain on the PCB. Insulated wires can then be soldered to the PCB and taken to the new potentiometer. Replacing the 10kW trimpot with a 5kW pot reduces the upper limit of the output voltage range to about 15V. The lowest output voltage possible from these modules is the Australia’s electronics magazine LM2596S reference voltage of 1.23V. The actual output voltage is calculated as Vout = Vref × (1 + R2 ÷ R1), where Vref = 1.23V, R2 is the potentiometer resistance and R1 is the fixed feedback resistor (430W on my module). The LM2596 is capable of output currents up to 3A, but these modules have no heatsink, so it is not a good idea to operate them at maximum current continuously. I used a dual digital volt/amp panel meter to monitor the supply output voltage and current. I obtained one which can read up to 33V and 999mA. It does not have any manufacturer’s identification or model number markings. siliconchip.com.au Many variants of such meters are available, with different connector types and wiring colour codes. The connection details shown should suit most similar meters, but check the instructions for yours to make sure. Typically, such digital panel meters can be powered from the source they are measuring, but they require a minimum of about 4V. If the regulator output is required to be taken below 4V, another supply for the panel meter must be provided. I simply used a second unmodified switchmode regulator module set to provide an appropriate voltage (12V). They’re cheap enough. Circuit Ideas Wanted siliconchip.com.au I added a single-channel relay module to connect and disconnect the load, which is also powered from the 12V fixed supply. This allows the output voltage to be varied and read by the panel meter without the load connected. The relay module I used lets you set the control input to active-high or active-low via an onboard jumper. I set it to active-high working then used a panel-mounted push-on/pushoff switch with internal LED to control it. The switch and LED are connected in series from the 12V supply to the control input. No additional series re- sistor is required as one exists on the relay PCB. The LM2596 needs an input supply about 3V higher than its maximum output, but no higher than 40V. Given the 15V maximum output determined by my use of a 5kW potentiometer, I used a recycled 19V 4A laptop charger as the power source. You can use a DC input socket to suit the plug on your power supply. Bob Martindale, Mill Park, Vic. ($80) Editor’s note: we have a suitable LM2596-based module in our Online Shop (siliconchip.com.au/ Shop/7/4916). 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 February 2020  95 In-situ Ethernet cable tester I recently needed to install an Ethernet cable between buildings with the cable going through holes no larger than the cable diameter, so the RJ45 connectors had to be crimped on each end after installation. This also meant that I could not use my patch cable tester because both ends of the cable must be plugged into the tester. Low-cost in-situ Ethernet cable testers are readily available, but where is the fun in buying a tool when you can easily build your own? This circuit tests Ethernet cables of virtually any length using a small remote unit and a larger main unit. They connect at either end of the RJ45 cable. RJ45 stands for Registered Jack 45, which corresponds to an 8-position 8-contact or 8P8C plug/socket. The main unit contains an Arduino Pro Mini with 8 LED indicators to show the test results. The remote unit simply has an RJ45 socket and four diodes. To power the unit up, pushbutton S1 is held down. Initially, all eight LEDs are lit briefly (as a lamp test), followed by the eight digital outputs being sequentially pulsed high, one per second. Each output is connected to a status LED and an RJ45 socket pin via a diode, to prevent one Arduino pin shorting out another via the cable. As the receiver diodes are connected between cable pairs, a good cable 96 Silicon Chip will light two adjacent LEDs when an odd-numbered output is high, and only one corresponding LED when an even-numbered pin is high. Thus the correct LED sequence is: 1+2, 2, 3+4, 4, 5+6, 6, 7+8, 8 and this sequence then repeats. You can see a video of it in operation, with a good cable, at: siliconchip.com.au/link/aaxj Cable wiring errors, shorts or open circuits will show as an incorrect step in the sequence. The fault can be deduced by noting which LEDs are lit (or not) during the incorrect step in the sequence. The whole thing runs off a 9V battery to make it compact and portable. This connects to the VIN pin of the Arduino via S1. An option is shown for a remote unit to suit crossover cables, but this is unlikely to be needed now as most Ethernet cables are wired straightthrough due to the widespread use of auto MDI-X configuration. In other words, most modern Ethernet transceivers will detect when they are connected to another similar transceiver and automatically swap their receive & transmit pins to allow communication, regardless of the cable being a wired in a straight-through or crossover configuration. The Arduino sketch, consisting of three .ino files, is available for download from the Silicon Chip website. Australia’s electronics magazine To program the Pro Mini, you need to have the Arduino IDE software installed on your computer, and you also need a USB-to-serial interface. The marginally more expensive Arduino Nano is easier to program as it has an onboard USB interface. You could substitute a 9-position rotary switch for the Arduino, with one position used for power-off. Diodes D1-D8 could also be eliminated. However, counter-intuitively, it would cost more than the Arduino Pro Mini. However, it might make fault diagnosis simpler as the switching sequence can be paused on one conductor. Phillip Webb, Hope Valley, SA. ($75) Editor’s note: diodes D1-D8 could also be eliminated if the software is modified to set the outputs which are not being actively driven high as inputs, rather than active-low outputs. siliconchip.com.au Signal generator output booster using an LM1877 Like the Precision Audio Signal Amplifier project (October 2019; siliconchip.com.au/Article/12025), this circuit is designed to boost the output from an audio signal generator. This booster has two channels and can supply significantly more current. However, it doesn’t have as much precision or bandwidth, nor can it deliver the same amplitude. As it is a two-channel unit, it’s suitable for connecting to the headphone output of a computer, tablet or smartphone to turn it into a more capable signal generator (with appropriate software). It’s based on a single LM1877 chip, which is a 2W/channel audio amplifier in a 14-pin DIL package. It can drive loads from 8W and up, running from a 9-26V supply. When powered with a 24V DC regulated supply, it has an output signal swing of 18V peak-topeak, which equates to 6.36V RMS. The amplifier channels are configured with a gain of 10, which results in a full-scale input sensitivity of 636mV RMS (just under the 775mV RMS which is typical for a ‘line level’ signal), and a bandwidth of around 65kHz. The two signals are applied to CON1 siliconchip.com.au and CON2. Potentiometers VR1 and VR2 provide independent gain controls for each channel, and set the device’s input impedance to 1kW. The signals then go to SPDT switches S1 & S2, which allow the unit to be configured in a few different ways. With S1 in the up position and S2 in the down position, the signals are fed to amplifiers IC2a & IC2b, which each provide 10 times voltage gain. Their output signals are AC-coupled to output connectors CON3 and CON4 via 1000µF electrolytic capacitors, to remove the DC bias inherent in a single-supply amplifier. Alternatively, if both switches are in the lower position, the signal from input 2 is fed to output 2, while output 1 receives an inverted version of that same signal. Inversion is accomplished by op amp IC1. The two 300kW resistors connected to its inverting input set the gain to -1 while the non-inverting input is connected to a half-supply rail that’s internally generated by IC2 and stabilised by a 100µF capacitor. The 150kW series resistor is used so that the impedances seen by both inputs of IC1 are equal. The half supply rail from pin 1 of IC2 is also used to DC Australia’s electronics magazine bias the signals fed into IC2a and IC2b. The third configuration is with both S1 and S2 up, in which case the signal from input 1 is fed to both outputs. The gain for both IC2a and IC2b is set to 10 by the ratio of the 18kW and 2kW feedback resistors. This is the minimum gain required for stability. Each amplifier also needs a Zobel network for stability, consisting of a series resistor and capacitor from each output to ground. The 100µF capacitors at the bottom of the feedback dividers are necessary due to the half-supply DC bias at the inputs. Diodes D1-D4 protect IC2a and IC2b from back-EMF spikes from inductive loads and also from accidental output shorts or externally applied voltages. Diode D5 provides reverse supply polarity protection, as it will conduct and blow fuse F1 if a negative supply voltage is applied. LED1 provides poweron indication. If designing a PCB for this project, it’s a good idea to connect large copper pours to the pins of IC2 (especially the six ground pins) for heatsinking. You can also glue or clamp a small finned heatsink on top of the IC package. Petre Petrov, Sofia, Bulgaria ($75). February 2020  97 Vintage Radio By Associate Professor Graham Parslow Tecnico-Aristocrat 1946 Model 651 A stunning radio set from the “Streamlining” era that followed the Second World War. This style took its inspiration from the geometry of Art Deco but added rounded edges reminiscent of the streamlined jet aircraft which had just been developed. However, as so many resources had gone into winning the war, rather than developing consumer electronics, the performance is not quite as modern as the styling. This Tecnico Aristocrat table radio looks great and sounds good. At 8.5kg it is a substantial radio, and the walnut finish of the Bakelite is particularly attractive. Although Tecnico is a minor Australian brand, the company produced some iconic radios between the 1930s and 1960s, notably the Fortress and the Pacemaker in the 1950s. Tecnico Electronics Pty Ltd was founded in Sydney as the Electrical Speciality Manufacturing Company. Radios were marketed under either the Aristocrat or the Calstan brand. The name Tecnico was adopted during the second world war, and the company made various military aircraft parts under license for the US Bendix Corporation. In 1951, Bendix and Tecnico formed a jointly-owned company, Bendix-Tecnico Ltd. During 1946-1951, radios were branded Tecnico Aristocrat, as on the model 651 featured here. 98 Silicon Chip After 1951, the brand simply became Tecnico, as seen on the iconic Fortress and Pacemaker radios (to be described in upcoming issues). An advertisement on page 39 of Women’s Weekly, October 1946 (opposite), shows vacuum cleaners and Radios built to “aircraft quality”. The text of the advertisement proclaims that Tecnico Aristocrat radios are a brand new post-war range of receivers. Certainly, the brand was new, but the electronics within are largely of pre-war standard. A pamphlet aimed at radio retailers heralded a new style, new features and new performance. The model 651 is described as suitable for all but the most difficult reception areas (a sensitivity of 3µV is claimed). The same case was also used for the model 661 that included an RF stage and the model 657, a battery-powered farm radio. Australia’s electronics magazine All these models boasted an 8-inch speaker, which gave exceptional tonal quality. They also offered delayed automatic gain control (AGC). Sensitivity and selectivity were claimed to be greatly superior to equivalent pre-war models. Even so, Tecnico only claimed a signal-to-noise ratio (SNR) of 10:1. In addition to the walnut finish, cases could be purchased in ivory or eau-de-Nil (greenish blue; “water of the Nile”). The new style claim is valid in the Australian context. However, if you compare these to the 1939 StewartWarner Senior Varsity model from the USA, it becomes clear that the style was substantially ‘borrowed’. Valve lineup The set uses a 6J8 triode-heptode for the converter, a 6U7 high-gain pentode for the first IF gain stage, a 6B6 dual-diode/triode for the second IF siliconchip.com.au A Tecnico advert from page 39 of Women’s Weekly, October 5, 1946 – https://trove.nla.gov.au/aww/read/209220 siliconchip.com.au Australia’s electronics magazine February 2020  99 gain stage, detector and AGC, a 6V6 beam-power tetrode for the Class-A output stage and a 5Y3 dual rectifier in the power supply. The RCA description of the 6U7 is a “triple grid super control amplifier”. This refers to a pentode that responds smoothly to AGC applied to the grid, unlike a sharp cut-off valve. The 6J8 was released in 1938, as an improved version of the 6A8 from 1936. The 6U7 pentode was released in 1936. So as you can see, this is essentially a pre-war design. Accordingly, the claim of significantly superior performance to pre-war models is hard to justify. The 6V6 is an oldie, but a goodie, giving up to 3.5W of audio power in Class-A mode. The beam tetrode design was so good that it was re-encapsulated as the 6AQ5 7-pin miniature valve for 1950s radios. 100 Silicon Chip This circuit for the Tecnico Model 651 was scanned from the AORSM, volume 5, then re-labelled using the included parts list. Some of the larger filter capacitors seem to vary between sets, from 8, 16 to 24µF. This may have been due to the scarcity of larger value capacitors or problems with mains hum. The radio had separate tuning and oscillator coils for two band operation (broadcast and shortwave), switched via a DPDT switch on the front panel. This was done so that the IF was kept at 455kHz when either band was selected. Circuit description The circuit drawn by Tecnico appears in volume 5 of the Australian Official Radio Service Manual (AORSM). The printing quality from this source is poor, and the labels on many components are illegible. The Historical Radio Society of Australia came to my rescue when a fellow member referred me to an alternative circuit at: www.kevinchant.com/ tecnico1.html Editor’s note: we’ve included a relabelled scan of the AORSM circuit, as the one in the website above has quite a few differences. This re-drawing of the circuit was apparently motivated by frustration with the unreadable Tecnico circuit, and the anonymous contributor has my gratitude for the effort. The redrawing also records voltages and resistances that the contributor measured on the bench. The external wire antenna is connected to one of two coils via a switch, one each for the broadcast band and shortwave. The same switch also changes the local oscillator coil, to keep the IF at 455kHz regardless of the band being tuned. The tuned output from the secondary of the selected aerial coil feeds into the 6J8 converter valve via a top-cap connection (C2 on the circuit diagram). The RF signal is heterodyned with the output of the local oscillator, shown below the 6J8 on the circuit. The primary winding of the oscilla- Australia's Australia’s electronics magazine siliconchip.com.au The underside of the 651 chassis is where most of the connections are made. The 8-inch loudspeaker, is a giant when compared to the speakers commonly used in other radios of the time. As always with radios this old, it’s good practice to check and replace any of the paper capacitors and carbon resistors that have drifted too far from the specified value. tor coil is tuned by the second gang of the variable capacitor, and its output is fed to the grid of the converter triode section. The secondary of the local oscillator coil connects to the anode of the triode, to provide feedback for sustained oscillation. A basic description of how this Armstrong oscillator configuration works can be found at: siliconchip.com.au/ link/aav8 After IF amplification, the output of the second IF transformer is demodulated by the diode connected to pin 5 of the 6B6 valve. Volume control is provided by a voltage divider formed by the 500kW potentiometer (R6) in series with a 100kW fixed resistor (R5). The pot’s wiper feeds demodulated audio to the 6B6’s grid via a 20nF capacitor (C21). A 50nF capacitor (C26) couples the amplified audio from the 6B6 anode to the grid of the 6V6 beam-power tetrode. Automatic gain control (AGC) is derived from the second diode of the 6B6, at pin 4. The output from the second IF transformer is coupled to pin 4 by a 50pF capacitor (C22), to generate a negative AGC voltage proportional to the signal strength. Approximately -1.37V DC bias is generated for the grids of the 6J8 and 6U7 by a 30W resistor (R18) between the centre-tap of the HT transformer siliconchip.com.au and the set’s ground. This bias is fed into the AGC line via a 2MW resistor (R10). It provides the initial grid bias and ‘delays’ the onset of AGC until a sufficiently strong signal warrants reducing amplification in the first stages. Weak signals receive maximum amplification. This is described in Tecnico literature as “compensated inverse feedback”. The operation of the 6V6 output amplifier is modified by a tone control network which consists of a 500kW potentiometer in series with 3nF and 50nF capacitors (C30 & C31), connected between the driven end of the speaker transformer primary (and the 6V6 anode) and ground. This feeds back to the 6V6’s grid via an RC highpass filter and a 400kW resistor (R14). This has the effect of progressively cutting high frequencies as the tone pot is rotated. Set construction The large speaker nestles into a rebate punched into the front of the chassis and the HT choke, mounted below the chassis, can be seen through the space. Tecnico was a significant manufacturer of capacitors, for their own use and other manufacturers. The first HT filter capacitor (C34) on this radio is branded Tecnico and marked as 8µF at 525V. Australia’s electronics magazine Rola supplied the output transformer (5kW/3.5W) and the 8-in permanent magnet speaker, model 8L. Another hint at the 1930s heritage of this radio is the official Tecnico drawing of the speaker showing an electrodynamic type with a field coil. Tecnico re-labelled the field coil as a choke. Rola also supplied the HT choke that is stamped as type 14/60 (14 Henries inductance, capable of passing 60 mA). The other two metal-can electrolytics are 8µF each (one is listed as 16µF on the circuit) and surprisingly, supplied by Ducon-Aerovox. The three 8µF capacitors in this radio are likely on-the-shelf leftovers, before new postwar stock became available. Even though these provide minimal ripple filtering, this radio has low mains hum at the speaker, helped by the filter choke. I was tempted to replace the 8µF units with higher capacitance electrolytics, but it was not necessary, so the originals were left as-is. In the early 30s, 8µF capacitors were state-of-the-art. Higher values became available later as the theory and materials science improved. It is interesting to note that electrolytic capacitors were a serendipitous evolution of early electrolytic AC rectifiers. The “chocolate-dip” capacitors used in the set were made by Tecnico, and February 2020  101 Left: the chassis shown from the front without the speaker, valves or knobs attached. Below: the unrestored chassis shown in the case. The Bakelite case used for the 651 was also shared with the Model 657 and 661. few have distinct values printed on them. The more-common MSP types (made by AWA), by contrast, have clearly visible values moulded in the cases. Restoration The photo below shows the original condition of the back of the radio. The radio is made as a stand-alone unit with the speaker attached to the chassis. Only the knobs need to be removed to separate the radio from the case. Most of the restoration effort was cleaning and polishing. Only one significant component had failed. In general, the layout is excellent for servicing with few components obstructing others. The soldering is commendably neat. I found that the band switch contacts on the rotary switch were affected by corrosion and needed a spray of CRC contact cleaner to restore their function. I had a metre-long piece of wire handy when first working on the radio and installed that as the aerial. It worked so well on local stations that it remained as the aerial. The radio worked at switch-on, but used 56W of power (slightly high) and sounded distorted. I measured +15.4V at the grid of the 6V6, indicating overconduction, which suggested that the 50nF audio coupling capacitor was leaking HT from the 6B6 anode. Replacing this capacitor brought instant happiness with excellent sound and reduced the total power consump102 Silicon Chip tion to a more normal 47W. The three-core power cable covered with patterned cotton is not true to 1946, and the person who installed this replacement used a knot inside the chassis to secure the cord (subsequently altered in this restoration to a much safer and legally acceptable chassis clamp). Another clue that the cord is not original is a peculiar rule at the time that a three-wire line could only be installed if a DPDT switch isolated both Neutral and Active lines. This radio does not have a mains switch, so it would originally have been fitted with twin-core flex. The speaker grille fabric was stained, so I removed and washed it. It was reinstalled using craft glue. The dial is calibrated by screenprinted glass installed behind the pointer. The front screen was made of celluloid and had aged to brown. A Australia’s electronics magazine clear plastic replacement allowed the dial to show its true colours. The speaker cone was faded and water-stained. Some flat black acrylic paint restored the appearance without any audible changes. So with relatively little effort, I was able to bring this set back to its original glory. What happened to Tecnico? While continuing an association with Bendix USA, Pye Ltd of Cambridge, England bought half of Tecnico’s shares in 1955. The brand “PyeTecnico” was used until 1959, after which their products were branded Pye and were made from designs used internationally by Pye. The Pye company became over-committed to TV products in the 1960s and collapsed, leading to the closure of Pye-Tecnico as a radio manufacturer in 1967. SC WHAT DO YOU WANT? PRINT? OR DIGITAL? EITHER . . . OR BOTH The choice is YOURS! Regardless of what you might hear, most people still prefer a magazine which they can hold in their hands. That’s why SILICON CHIP still prints thousands of copies each month – and will continue to do so. But there are times when you want to read SILICON CHIP online . . . and that’s why www.siliconchip.com.au is maintained at the same time. WANT TO SUBSCRIBE TO THE PRINT EDITION? (as you’ve always done!) No worries! WANT TO SUBSCRIBE TO THE DIGITAL (ONLINE) EDITION? No worries! WANT TO SUBSCRIBE TO BOTH THE PRINT AND THE DIGITAL EDITION? No worries! SILICON CHIP, Australia’s most read, most respected and most valued electronics reference magazine, makes it so easy for you. And even better, we offer short-term subscriptions (as short as six months) so you can effectively “try before you commit”. Here’s the deal: If you’re in Australia, you can subscribe to the print edition (only) of SILICON CHIP for $105 for a full 12 months (12 issues) – that’s almost $15 less than the over-the-counter price AND we pick up the postage. If you’re overseas, you can subscribe to the print edition – email us for the rates for your particular country. If you’re anywhere in the world, you can subscribe to the online edition of SILICON CHIP for $AU85. And, of course, from anywhere in the world, you can subscribe to both print and online editions – in Australia, the price is just $125 (only $20 more than the print edition price). Overseas – again email us for the rates in your country. While your subscription is current, you can download software, PCB patterns, panel artwork etc FREE OF CHARGE! Want more information? Log onto our website and click on “subscriptions” www.siliconchip.com.au 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 How does anti-islanding work? Regarding the letter in December issue titled “Confusion over PV Inverter anti-islanding” (page 8), when a blackout occurs, would there not also be potential interactions with other PV inverters also connected to the same branch of the grid? How do the inverters “know” that the main supply from the grid has disconnected when there are other generators (ie, other PV systems) also connected? (P. H., Warwick, Qld) • This is a complex topic – more so than most people realise. Multiple techniques can be used to detect islanding. You can read about them in this Wikipedia entry, under “Islanding detection methods”: https:// en.wikipedia.org/wiki/Islanding These techniques mostly have the same principles at their root, namely, that the effective grid impedance seen by the inverter rises significantly when the large generators which provide the bulk of the power are disconnected. There is also the fact that large generating stations are locked to a very consistent frequency (ie, close to 50Hz), and no matter what the inverter’s output does, it cannot shift that frequency. However, within an ‘island’, each inverter is driving a much larger proportion of the remaining ‘grid’, and so can slightly shift the frequency. It’s interesting to note that the Wikipedia page claims that there is no real need for inverters to have ‘anti-islanding’ provisions. According to whoever wrote the page, research shows that islands cannot stably exist for very long, and this does not present workers with any hazards that they are not already exposed to. LiFePO4 batteries are a safe option John Clarke’s Clever Battery Charger Controller in the December 2019 issue (siliconchip.com.au/Article/12159) 104 Silicon Chip started me thinking about a suitable battery charger circuit for a 12V 7Ah Lithium-iron-phosphate battery, as sold by Jaycar (Cat SB2210). I tried asking the counter staff and got a general “don’t worry” sort of reply. I have one friend who lost half of his house when a lithium battery on charge blew up. I am becoming a little anxious about this. Is there a suitable product that can be built or bought which can be used to charge the battery overnight, to something like a full charge? You review lots of those little modules from China; is there one of them which would be suitable? With a 7Ah battery, I would only need a charge current of 1A or so. (R. J., via email) • You seem to be getting lithium-ion (Li-ion) and lithium-polymer (LiPo) batteries mixed up with lithium-ironphosphate (LiFePO4). Li-ion and LiPo batteries can catch fire if they are faulty or abused, while LiFePO4 is much more tolerant of abuse and is generally considered safe. We aren’t aware of any fires started by LiFePO4 cells, as used in Jaycar’s SB2210 and other similar batteries. Li-ion and LiPo batteries require different charging methods from LiFePO4 (and from lead-acid). The LiFePO4 charging method is more similar to that of lead-acid, which is why many such batteries are indicated by the vendor or manufacturer as able to be charged using a lead-acid battery charger. If you have a ‘dumb’ charger, you should definitely use our Charge Controller though. We would not hesitate to use any of the smart chargers sold and recommended by Jaycar to charge their range of LiFePO4 batteries. Increasing Linear Supply voltage/current Thank you for the circuit boards for the 45V 8A Linear Power Supply (October-December 2019; siliconchip. com.au/Series/339). I wish to upgrade the power supply to handle 50V 16A. Australia’s electronics magazine We have made a suitable long core transformer capable of producing 57V DC with good regulation at 0-16A. I have also ordered some suitable capacitors. I want to use eight or 10 FJA4313 transistors attached to the same heatsink. Four would be mounted on the main board, and four or six would be mounted on the heatsink, and connected by appropriate resistors to the main circuit. I set up a test rig to see if my heatsink was big enough. I used a 17A 60V switch-mode power supply to supply the DC. I mounted four of the FJA4313 transistors on the heatsink, along with an LM317HV. I made up a breadboard circuit with a TIP32C PNP transistor (which I had) instead of the BD140 and set up the voltage in the traditional manner for the LM317, with a fixed resistor and a 10kW potentiometer. My load was a 300W 1W resistor. I gradually increased my current to 16A and the input voltage to 55V DC. For cooling, I used a 50W 24V server fan which kept the temperature below 45°C. I want to put the transformer, rectifier and capacitors in a separate box, down on the floor out of the way, and feed the smoothed DC to the linear power supply. If I connect the two with 3m of 4AWG wire (21mm2), I can keep the voltage drop down to 0.1V. Can you foresee any problems with doing this? Can the TIP32C transistor drive eight FJA4313 transistors? Will they share the load OK? I will change the shunt. Are there any other components that need to be changed? (G. M., Sockburn, NZ) • We are concerned about the stability of the power supply given the nature of your proposed changes. That was what took the longest time to get right. In particular, a long cable run between the capacitors and transistors is likely to cause problems, in spite of the low resistance. We suggest adding some significant capacitance across the regulator end of those wires to address this. siliconchip.com.au As you are making major changes to the output circuit, it’s hard for us to speculate on what will and won’t work. You may need to change some of the other components there too. We don’t think load sharing will be a problem, but stability might. Having said that, your proposed changes are probably workable, provided you test it thoroughly and are prepared to tweak the circuit if necessary. You will need to check the output over a range of voltage and load conditions with an oscilloscope to verify there is no oscillation under any conditions. Also test the sudden addition and removal of loads to ensure that this does not trigger oscillation, or result in significant voltage overshoot or undershoot. LCD interferes with SPI RAM communications I wonder if you can assist me with a problem I’m having with the 23LC1024 RAM in the Micromite LCD BackPack V3 (August 2019; siliconchip.com.au/ Article/11764). Using the BackPack without the LCD connected, the RAM chip works fine with your sample RAM testing program. It faithfully reads from RAM the numbers written to it. But when I connect the LCD, the numbers read do not match the numbers written. I modified the test program to include the lines PIN(6) = 1 and PIN(7) = 1 to ensure the SPI lines were not being affected by the LCD. I also modified the test program to simply output the numbers 0 to 10 to the RAM and then read them back. The results below show the errors in the resulting reads. WRITE: 0 1 2 3 4 5 6 7 8 9 10 READ : 0 0 3 3 6 6 7 7 12 12 15 I feel that somehow the LCD is still affecting the SPI lines. Can you suggest anything else that I might try? (J. H., Nathan, Qld) • We ran the same tests you did, and agree that it appears that some screens do cause occasional interference with the MISO data line back to the Micro- mite, even with their touch controller’s CS pin held high (which, of course, they shouldn’t do). We were able to fix the issue by cutting the trace between pin 14 on IC1 and the LCD header and soldering a 220W resistor in its place. We also tried a 1kW resistor, but this value was too high to allow the touch controller to communicate correctly. After adding that resistor, the tests all ran successfully with or without the LCD screen plugged in. Using RF Signal Generator at 70MHz I have read with interest your articles on the AM/FM/CW Scanning HF/ VHF RF Signal Generator (June & July 2019; siliconchip.com.au/Series/336). I have selected some 70MHz crystal filters for a receiver project that have a pass bandwidth of ±10kHz (-3dB). Is it possible to sweep from 69.890MHz to 70.110MHz using this generator? If so, what is the step size? I assume Why do bookshelf speakers use passive crossovers? I’m attracted to the easy-to-build Bookshelf Speaker System project (January-March 2020; siliconchip. com.au/Series/341), but I’m mystified that the design relies on a mixture of active and passive crossovers rather than a wholly active crossover solution. My sketchy knowledge of active crossover systems tells me that an important disadvantage of them is the need for an amplifier for each driver, a significant cost until recently. By specifying plate amplifiers costing less than $8/driver, this disadvantage is greatly diminished. The cost of inductors alone for the pair of passive crossovers in the project is around $74. Am I missing something? (I. B., Moreland, Vic.) • You are probably right that it would have cost less to build active crossovers for the monitor speakers, given the low cost of the amplifier modules. But that would have complicated the build somewhat with the extra wiring and circuitry, and we would have either had to jam four amplifiers into one small speaker box, or run power to both. Phil Prosser adds: As the 5-inch siliconchip.com.au drivers are the limiting factor in the monitor design, active crossovers are not warranted for the monitors. The principal limitation in their performance is cone excursion below about 100Hz. If used as a monitor without the subwoofers, there is nothing that can be done to resolve this limitation. With a 30W per channel power amplifier, and with typical modern music, neither the bass nor treble frequencies are clipping before the bass driver struggles. The monitors, as standalone speakers, are pretty well giving you everything they can with the passive crossover. Adding the subwoofers changes things a bit. The function of the active crossover in the subwoofer is to stop bass getting to the 5in drivers in the monitor speakers. It also relieves the monitor amplifiers from amplifying the low-frequency signal content. This means that the monitor cone excursion is significantly reduced, and the power required for the monitor speakers is significantly reduced too. Consequently, the use of a 30W power amp and a passive crossover Australia’s electronics magazine on the monitors is quite generous. Even at silly volumes, there is no clipping in the monitor frequency ranges. The bass amplifiers can then drive the subs to full power with no midrange or treble to worry about. A subtle thing here is that if the bass driver/amp is clipping, the midrange and treble are not clipped too as they are on that separate amp. This allows you to drive the sub quite hard and not clip the majority of program material. I guess this is a long way of saying: yes, we could have used a threeway active crossover, but it would have gone against our idea to keep the project relatively simple. Also, we think the idea of using reels of enamelled copper wire as air-cored inductors is clever and worthy of publication. You are welcome to change the design and build your own set of speakers with 3-way active crossovers. It certainly can be done; we just don’t think it’s necessary. It can be made to work, and you may have some fun implementing it. That’s the great thing about DIY projects – you can customise them. February 2020  105 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. 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PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS ATtiny816 PIC12F202-E/OT PIC12F617-I/P PIC12F675-E/P PIC12F675-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1459-I/P PIC16F1507-I/P PIC16F88-E/P PIC16F88-I/P PIC16LF88-I/P $15 MICROS ATtiny816 Development/Breakout Board (Jan19) ATmega328P RF Signal Generator (Jun19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sept19) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) Temperature Switch Mk2 (June18), Recurring Event Reminder (Jul18) PIC16F877A-I/P 6-Digit GPS Clock (May09), 16-bit Digital Pot (Jul10), Semtest (Feb12) Door Alarm (Aug18), Steam Whistle (Sept18), White Noise (Sept18) PIC18F2550-I/SP Battery Capacity Meter (Jun09), Intelligent 12V Fan Controller (Jul10) Trailing Edge Dimmer (Feb19), Steering Wheel to IR Adaptor (Jun19) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) Car Radio Dimmer Adaptor (Aug19) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) Courtesy LED Light Delay (Oct14), Fan Speed Controller (Jan18) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) Driveway Monitor Receiver (July15), Hotel Safe Alarm (Jun16) GPS Boat Computer (Apr16), Micromite Super Clock (Jul16) 50A Battery Charger Controller (Nov16), Kelvin the Cricket (Oct17) Touchscreen Voltage / Current Ref. (Oct16), Deluxe eFuse (Aug17) Motor Speed Controller (Mar18), Heater Controller (Apr18) Micromite DDS for IF Alignment (Sept17), Tariff Clock (Jul18) Useless Box IC3 (Dec18) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) Tiny LED Xmas Tree (Nov19) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) Microbridge and BackPack V2 / V3 (May17 / Aug19) PIC32MX795F512H-80I/PT Maximite (Mar11), miniMaximite (Nov11), Colour Maximite USB Flexitimer (June18), Digital Interface Module (Nov18) (Sept12), Touchscreen Audio Recorder (Jun14) GPS Speedo/Clock/Volume Control (Jun19) $20 MICROS Five-Way LCD Panel Meter / USB Display (Nov19) dsPIC33FJ128GP306-I/PT CLASSiC DAC (Feb13) Wideband Oxygen Sensor (Jun-Jul12) Auto Headlight Controller (Oct13), Motor Speed Controller (Feb14) dsPIC33FJ128GP802-I/SP Digital Audio Delay (Dec11), Quizzical (Oct11) Ultra-LD Preamp (Nov11), LED Musicolour (Oct12) Automotive Sensor Modifier (Dec16) Stereo Audio Delay/DSP (Nov13), Stereo Echo/Reverb (Feb 14) Cyclic Pump Timer (Sep16), 60V DC Motor Speed Controller (Jan17) PIC32MX470F512H-I/PT Digital Effects Unit (Oct14) Pool Lap Counter (Mar17), Rapidbrake (Jul17) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Deluxe Frequency Switch (May18), Useless Box IC1 (Dec18) Remote-controlled Preamp with Tone Control (Mar19) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) UHF Repeater (May19), Six Input Audio Selector (Sept19) $30 MICROS Universal Battery Charge Controller (Dec19) PIC32MX695F512L-80I/PF Colour MaxiMite (Sept12) Garbage Reminder (Jan13), Bellbird (Dec13) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) GPS-synchronised Analog Clock Driver (Feb17) SPECIALISED COMPONENTS, HARD-TO-GET BITS, ETC VARIOUS MODULES & PARTS - WS2812 8x8 RGB LED matrix module (El Cheapo Modules, Jan20) $15.00 - 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 (Tiny LED Xmas Tree, Nov19): 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 - LM4865MX amplifier & LF50CV regulator (Tinnitus/Insomnia Killer, Nov18) $10.00 - 2.8-inch touchscreen LCD module with SD card socket (Tide Clock, Jul18) $22.50 - ESP-01 WiFi Module (El Cheapo Modules, Apr18) $5.00 - MC1496P double-balanced mixer (AM Radio Transmitter, Mar18) $2.50 - 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 - WeMos D1 Arduino-compatible boards with WiFi (Sep17, Feb18): ThingSpeak data logger – $10.00 | D1 R2 with external antenna socket – $15.00 - ERA-2SM+ MMIC & ADCH-80A+ choke (6GHz+ Frequency Counter, Oct17) $15.00 - VS1053 Geeetech Arduino MP3 shield (Arduino Music Player, Jul17) $20.00 - 1nF 1% MKP (5mm) or ceramic capacitor (LC Meter, Jun18) $2.50 - MAX7219 red LED controller boards (El Cheapo Modules, Jun17): 8x8 SMD/DIP matrix display – $5.00 ¦ 8-digit 7-segment display – $7.50 - AD9833 DDS modules (Apr17): gain control (DDS Signal Generator) – $25.00 ¦ no gain control – $15.00 - CP2102 USB-UART bridge $5.00 - microSD card adaptor (El Cheapo Modules, Jan17) $2.50 - DS3231 real-time clock module with mounting hardware (El Cheapo, Oct16) $5.00 DCC BASE STATION HARD-TO-GET PARTS (CAT SC5260) (JAN 20) SUPER-9 FM RADIO (NOV 19) Two BTN8962TA motor driver ICs & one 6N137 opto-isolator CA3089E IC, DIP-16 (SC5164) MC1310P IC, DIP-14 (SC4683) 110mm telescopic antenna (SC5163) Neosid M99-073-96 K3 assembly pack (two required) (SC5205) $30.00 siliconchip.com.au/Shop/ TINY LED XMAS TREE COMPLETE KIT (SC5180) (NOV 19) MICROMITE EXPLORE-28 (CAT SC5121) (SEPT 19) MICROMITE LCD BACKPACK V3 (CAT SC5082) (AUG 19) GPS SPEEDO/CLOCK/VOLUME CONTROL (JUN 19) TOUCH & IR REMOTE CONTROL DIMMER (FEB 19) MOTION SENSING SWITCH (SMD VERSION) (FEB 19) SUPER DIGITAL SOUND EFFECTS KIT (CAT SC4658) (AUG 18) Includes PCB, micro, CR2032 holder (no cell), 12 red, green and white LEDs plus four extra 100W resistors and all other parts. Green, red or white PCBs are available. $14.00 Complete kit – includes PCB plus programmed micros and all onboard parts Programmed micros – PIC32MX170F256B-50I/SO + PIC16F1455-I/SL $30.00 $20.00 KIT – includes PCB, programmed micros, 3.5in touchscreen LCD, laser-cut UB3 lid, mounting hardware, SMD Mosfets for PWM backlight control and all other mandatory onboard parts $75.00 Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $30.00 - 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) $3.00 - 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 1.3-inch 128x64 SSD1306-based blue OLED display module (Cat SC5026) MCP4251-502E/P dual-digital potentiometer (Cat SC5052) Q1/Q2 Mosfets (SIHB15N60E) and two 4.7MW 3.5kV resistors (Cat SC4861) IRD1 (TSOP4136) and fresnel lens (IML0688) (Cat SC4862) Kit (includes PCB and all parts; no extension cable) (Cat SC4851) SW-18010P vibration sensor (S1) (Cat SC4852) PCB and all onboard parts, but no SD card, cell or battery holder $3.00 $5.00 USB PORT PROTECTOR COMPLETE KIT (CAT SC4574) $7.50 All parts including the PCB and a length of clear heatshrink tubing $6.00 ec. *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. $15.00 $3.00 $20.00 $10.00 $10.00 $1.00 $40.00 (MAY 18) $15.00 # P&P prices are within Australia. Overseas? Place an order on our website for a quote. 02/20 PRINTED CIRCUIT BOARDS & CASE PIECES For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT DATE PCB CODE Price PRINTED CIRCUIT BOARD TO SUIT PROJECT DATE PCB CODE Price UNIVERSAL TEMPERATURE ALARM BROWNOUT PROTECTOR MK2 8-DIGIT FREQUENCY METER APPLIANCE ENERGY METER MICROMITE PLUS EXPLORE 64 CYCLIC PUMP/MAINS TIMER PCB SET MICROMITE PLUS EXPLORE 100 AUTOMOTIVE FAULT DETECTOR MOSQUITO LURE MICROPOWER LED FLASHER MINI MICROPOWER LED FLASHER 50A BATTERY CHARGER CONTROLLER PASSIVE LINE TO PHONO INPUT CONVERTER MICROMITE PLUS LCD BACKPACK AUTOMOTIVE SENSOR MODIFIER TOUCHSCREEN VOLTAGE/CURRENT REFERENCE VI REFERENCE CASE PIECES (BLACK / BLUE) SC200 AMPLIFIER MODULE 60V 40A DC MOTOR SPEED CON. MAIN PCB ↳ MOSFET PCB GPS SYNCHRONISED ANALOG CLOCK ULTRA LOW VOLTAGE LED FLASHER POOL LAP COUNTER STATIONMASTER TRAIN CONTROLLER PCB SET EFUSE SPRING REVERB 6GHz+ 1000:1 PRESCALER MICROBRIDGE MICROMITE LCD BACKPACK V2 10-OCTAVE STEREO GRAPHIC EQUALISER ↳ FRONT PANEL ↳ CASE PIECES RAPIDBRAKE DELUXE EFUSE ↳ UB1 LID VALVE RADIO MAINS SUPPLY (INC. PANELS) 3-WAY ADJUSTABLE ACTIVE CROSSOVER ↳ FRONT/REAR PANELS ↳ CASE PIECES (BLACK) 6GHz+ TOUCHSCREEN FREQUENCY COUNTER ↳ CASE PIECES (CLEAR) KELVIN THE CRICKET SUPER-7 SUPERHET AM RADIO PCB ↳ CASE PIECES & DIAL THEREMIN PROPORTIONAL FAN SPEED CONTROLLER WATER TANK LEVEL METER (INC. HEADERS) 10-LED BARAGRAPH ↳ SIGNAL PROCESSING FULL-WAVE MOTOR SPEED CONTROLLER VINTAGE TV A/V MODULATOR AM RADIO TRANSMITTER HEATER CONTROLLER DELUXE FREQUENCY SWITCH USB PORT PROTECTOR 2 x 12V BATTERY BALANCER USB FLEXITIMER WIDE-RANGE LC METER (INC. HEADERS) ↳ WITHOUT HEADERS ↳ CASE PIECES (CLEAR) TEMPERATURE SWITCH MK2 LiFePO4 UPS CONTROL SHIELD RASPBERRY PI TOUCHSCREEN ADAPTOR RECURRING EVENT REMINDER BRAINWAVE MONITOR (EEG) SUPER DIGITAL SOUND EFFECTS DOOR ALARM STEAM WHISTLE / DIESEL HORN DCC PROGRAMMER (INC. HEADERS) ↳ WITHOUT HEADERS OPTO-ISOLATED RELAY (INC. EXT. BOARDS) GPS-SYNCHED FREQUENCY REFERENCE LED CHRISTMAS TREE JUL16 JUL16 AUG16 AUG16 AUG16 SEP16 SEP16 SEP16 OCT16 OCT16 OCT16 NOV16 NOV16 NOV16 DEC16 DEC16 DEC16 JAN17 JAN17 JAN17 FEB17 FEB17 MAR17 MAR17 APR17 APR17 MAY17 MAY17 MAY17 JUN17 JUN17 JUN17 JUL17 AUG17 AUG17 AUG17 SEP17 SEP17 SEP17 OCT17 OCT17 OCT17 DEC17 DEC17 JAN18 JAN18 FEB18 FEB18 FEB18 MAR18 MAR18 MAR18 APR18 MAY18 MAY18 MAY18 JUN18 JUN18 JUN18 JUN18 JUN18 JUN18 JUL18 JUL18 AUG18 AUG18 AUG18 SEP18 OCT18 OCT18 OCT18 NOV18 NOV18 03105161 10107161 04105161 04116061 07108161 10108161/2 07109161 05109161 25110161 16109161 16109162 11111161 01111161 07110161 05111161 04110161 SC4084/193 01108161 11112161 11112162 04202171 16110161 19102171 09103171/2 04102171 01104171 04112162 24104171 07104171 01105171 01105172 SC4281 05105171 18106171 SC4316 18108171-4 01108171 01108172/3 SC4403 04110171 SC4444 08109171 06111171 SC4464 23112171 05111171 21110171 04101181 04101182 10102181 02104181 06101181 10104181 05104181 07105181 14106181 19106181 SC4618 04106181 SC4609 05105181 11106181 24108181 19107181 25107181 01107181 03107181 09106181 SC4716 09107181 10107181/2 04107181 16107181 $5.00 $10.00 $10.00 $15.00 $5.00 $10.00 $20.00 $10.00 $5.00 $5.00 $2.50 $10.00 $5.00 $7.50 $10.00 $12.50 $10.00 $10.00 $10.00 $12.50 $10.00 $2.50 $15.00 $15.00 $7.50 $12.50 $7.50 $2.50 $7.50 $12.50 $15.00 $15.00 $10.00 $15.00 $5.00 $25.00 $20.00 $20.00 $10.00 $10.00 $15.00 $10.00 $25.00 $25.00 $12.50 $2.50 $7.50 $7.50 $5.00 $10.00 $7.50 $7.50 $10.00 $7.50 $2.50 $2.50 $7.50 $7.50 $7.50 $7.50 $7.50 $5.00 $5.00 $5.00 $10.00 $2.50 $5.00 $5.00 $7.50 $5.00 $7.50 $7.50 $5.00 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 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 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 $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 BIG-DIGIT 12/24-HOUR CLOCK PROCESSOR PCB ↳ DISPLAY PCB STUDIO 350 POWER AMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) MAR01 MAR01 JAN04 FEB20 FEB20 04103011 04103012 01102041 27111191 01106192-6 $15.00 $15.00 $10.00 $5.00 $20.00 NEW PCBs We also sell an A2 Reactance Wallchart, RTV&H DVD, Vintage Radio DVD plus various books at siliconchip.com.au/Shop/3 that the step size can be set to 1kHz or 100Hz. I also assume that the alternative 125MHz high-pass filter would need to be fitted. (M. J. Y., Chirnside Park, Vic) • Andrew Woodfield (ZL2PD) responds: This frequency range is in the interval where aliasing is significant. However, using the design as published with the 70MHz filter, the measurement is feasible. The aliasing product (at around 55MHz with 70MHz output selected on the display) is about 25dB below the wanted product when using the upper tuning range, and that is likely to prove satisfactory for your crystal filter measurement. There is no need to fit the 125MHz filter option. Despite this frequency range (69-70MHz) being notionally out of range, the signal generator will permit you to tune in 10Hz or 100Hz steps across it to provide the desired test signal. You may also wish to check that there is no spurious crystal filter response around 55MHz that may lead to measurement error. I would not suggest using the generator’s SCAN function for this measurement. The scanning step size is calculated from the frequency difference, so it may not allow you to make adequately accurate measurements, especially on filter passband edges. The 10Hz and 100Hz generator tuning steps in normal operation should provide a useful result. For better accuracy, and given the potential error in the 125MHz oscillator on these AD9850 modules, you may need to also check for that potential error by checking the generator’s output using a frequency counter. USB to PS/2 keyboard adaptor I built your USB Mouse & Keyboard Interface for Micros (February 2019; siliconchip.com.au/Article/11414) and I am using it to interface a mouse to my Maximite microcomputer, and it works very well; thank you. I posted a demonstration program for the Colour Maximite on The Back Shed forum. You can see it here: www. thebackshed.com/forum/ViewTopic. php?TID=11245 Because both the Maximites and the Explore 100 have a PS/2 keyboard socket, I was wondering if a version could be created that can act as a USB 108 Silicon Chip keyboard to PS/2 interface. (B. McK, Wynn Vale, SA) • That’s a good idea. It could probably be done just with some software changes. We’ll investigate the feasibility. Adding a real-time clock to the DAB+ radio I want to build your DAB+/FM/ AM Radio (January-March 2019; siliconchip.com.au/Series/330), but I also want to make a few modifications. This primarily involves adding a DS3232 RTC module so that I can turn it into a clock/radio. An in-depth study of the circuit diagram of the radio (pages 30 & 31 in the January 2019 issue), in conjunction with the Explore 100 circuit diagram (pages 80 & 81 in the September 2016 issue; siliconchip.com.au/ Article/10141) reveals a slight problem for me. This is that the RTC GETTIME, RTC SETTIME, RTC GETREG and RTC SETREG commands used to communicate with the DS3231 all must use I2C port 1. This port on the Explore 100 uses pins 66 & 67 of IC1, which go to pins 34 and 32 on the main I/O header, CON8. Unfortunately, these pins are used for the up and down volume control signals (IC4UP/IC4DN) to the PAM8407 audio amplifier, IC4. I dare say that this chip would get utterly confused were it to be fed I2C data! By the way, this not only precludes the use of the RTC socket on the Explore 100, but also the I2C ability of the two mikroBUS sockets. I propose to lift the tracks from pins 32 & 34 of CON3 and bridge them to pins 2 & 4, which at present are unused and connected to pins 96 & 97 on the Explore 100 PIC. This would require a software change for CONST IC4UP to = 96 and CONST IC4DN to = 97. That would re-establish volume control to the audio amplifier and allow the Explore 100 I2C bus 1 to be used. The use of a DS3232 would, of course, require the addition of clock control code to the radio software, along with some extra GUI controls to allow the clock to be set and displayed. Are the four Explore 100 RTC Commands capable of addressing all the registers/memory in a DS3232 (0x00 to 0xFF hex)? Also, is there any way to shut down the PAM8407 if I connect amplifiers to Australia’s electronics magazine the line out outputs? Or should I write a software patch to manually manipulate the shutdown pin (pin 3) on the PAM8407? (J. C., Creewah, NSW) • The PAM8407 volume up/down signals just require a digital output for control, so any free Explore 100 pin can be used. We can’t see any problem with your suggested changes. The Micromite manual doesn’t explicitly state the range of registers for RTC SETREG and RTC SETREG, but it doesn’t mention any restrictions either, so presumably, these functions can access all available registers. The radio code is designed to shut down the PAM8407 when a headphone jack is inserted into CON5 via its pin 3, but this is an option in the software configuration that can be disabled if you want the headphone and speaker outputs active simultaneously. You can change the code to drive the SD pin however you like, shutting down the speaker outputs whenever desired. Cost of building the Useless Box I’m in the UK and have just seen your Useless Box project (December 2018; siliconchip.com.au/Article/11340). Please advise what’s required, including the cost, to purchase a full kit of parts to make a working version. (P. N., Shropshire, UK) • We only sell the PCB and programmed microcontrollers for this project. You need to source the remaining parts yourself, from your local electronics retailer(s). Our parts can be purchased at the following link: siliconchip.com.au/ Shop/?article=11340 The PCB and two micros cost $27.50 plus postage. The total price for the project will vary significantly depending on where you order them from, and there is some custom fabrication required for this project. If we had to guess the total cost of parts required, it would probably be around $100. Touchscreen Altimeter questions I purchased the basic kit for the Touchscreen Altimeter from your Online Shop shortly after it appeared in the December 2017 issue (siliconchip. com.au/Article/10898). For several reasons, I never opened the package siliconchip.com.au to assemble it, but now I have time to do so. I have some questions about the parts supplied. I got three 10µF 16V 1206 X5R capacitors. On the board are marked locations for one 47µF and two 10µF capacitors. The screen print shows a + sign to the left of the circles printed on board. The actual devices, however, have no markings whatsoever on them. I must assume that the orientation of these three items is not relevant. VR1, the 100W trimpot for manual backlight is not included, so I must assume it is not required. The SMD Mini USB connector supplied is not required unless it is wanted for programming. I assume the two PIC chips are pre-programmed. I have no programming skills; can this socket be left off the board? In the Altimeter article, Fig.3 on page 28 shows the AM2302 temperature module mounted on a sub-board, but it was not supplied with the rest of the parts. I assume there are no setting-up procedures to follow to get the Micromite BackPack operational. If there are, where can I find the instructions? Your help would be much appreciated. (H. M., Bowral, NSW) • You are right that the orientation of the three ceramic capacitors is not important. Ceramic capacitors are never polarised. The third capacitor does not need to be 47µF, as the performance of a 10µF ceramic is more than good enough to satisfy the regulator’s requirements. You are right that VR1 is not required, as the kit comes with the parts needed for software-controlled brightness adjustment. All the chips in our kits are supplied pre-programmed. You certainly can leave the USB socket off if you will not be using it. Instructions for the V2 BackPack are in the May 2017 issue (siliconchip. com.au/Article/10652); however, you should not need that article to build the Altimeter. Just fit the supplied parts where marked on the PCB, complete the assembly as per the Altimeter article and it should work. Regarding the sub-board that the AM2302/DHT22 module was mounted on, that is covered by the Notes & Errata for the Touchscreen Altimeter project, along with other important information about this project. You (or anyone) can view these notes at the following link: siliconchip.com.au/ siliconchip.com.au Articles/Errata Specifically: The circuit diagram on page 25 showed a bare DHT22/AM2302 sensor with correctly wired pins, however, pin 4 was shown on the left side of the device and pin 1 on the right, the opposite of how they are numbered on the physical module. Also, the module shown in Fig.3 and the accompanying photo is mounted on a small breakout board with two extra components which were not shown on Fig.1 and not mentioned in the text or parts list. The sensor we supply does not come with the breakout board. The circuit diagram in the online edition has been corrected to show the two extra components. If the sensor you purchased does not come on a breakout board, simply solder a 100nF capacitor between pins 1 and 4 of the DHT22/AM2302 and a 1kW resistor between pins 1 and 2. Note that the 1kW resistor could just as easily be fitted between the +5V and pin 21 (DATA) connections on the BackPack module. Improving the Soft Starter for Power Tools Recently I needed a soft starter, and was lucky enough to pick up one of the last remaining kits (July 2012; siliconchip.com.au/Article/7182) from Jaycar. After construction, the unit was completely dead, but I was able to locate that problem to a faulty fuse holder. Testing the unit, I found that with a 100W test lamp, the relay never pulled in. However, after adding a second 100W globe, the system seemed to behave normally. Using it on my 2000W table saw, however, I find that there is still a considerable kick when the saw starts up. I am hoping to soften the start even further. Ideally, I would like it to run up to speed over about 3-5 seconds. Is adding more thermistors the solution, or is there another alternative? My existing thermistors are on the low side of their spec, reading a total of 16.5W. (M. M., via email) • Our article says the minimum load is close to 100W, so your single test lamp was probably just below the threshold. Tools with large motors can have such a low impedance that they still kick, even with the two thermistors in series. It is possible to increase the Australia’s electronics magazine effect by adding more thermistors, or high-power resistors, but you will almost certainly need to use a larger box, and you will have to wire them in series with the existing thermistors. 3-5 seconds is a long time to spin up using a simple device like this. For that sort of extended spin-up, you are better off using a motor controller with a soft-starting feature, or manually ramp the speed up over several seconds. Our Full Wave 230V Universal Motor Speed Controller (March 2018; siliconchip.com.au/Article/10998) would be a good choice. Try its softstarting feature and see if you are happy with it. If not, start the motor with the speed knob set partway and then ramp it the rest of the way manually. If you do want to try enhancing the effect of your existing soft starter with additional resistance, make sure to insulate all the exposed wiring well (eg, with two layers of heatshrink tubing). The advantage of using resistors rather than thermistors is that their effect will not ‘fade’ with multiple restarts; however, they will likely be larger and can be damaged if the values and power ratings are not carefully chosen. The safest thing to do is to add more of the same type of thermistor in series, in a larger box, with fan-forced cooling. Increasing the number of thermistors to around 4-6 should hopefully significantly improve the soft starting effect. Cleaning mould and dirt from solar panels Hello, I am a subscriber to your magazine, and I have a few solar panels on my garage roof. They have a thick coat of black sooty mould, as do cars parked outside. A nearby paperbark tree in the street has a thick coat of this black stuff. I have washed the panels up to six times with soapy water without success. How do I clean the panels? (L. B., Burwood, Vic) • We suggest that you first try a power washer/pressure washer like those sold by Gerni, Karcher, Bosch, Ryobi etc. You can get these under $100 (although the $150-200 units are generally a bit better, coming with more accessories etc). They’re useful for a variety of other jobs, like washing cars and walkways. We suggest that you look for one that comes with (or to which you can add) a right-angle nozzle and possibly also an extension arm. These make cleaning February 2020  109 raised, horizontal (or near-horizontal) surfaces much easier. Be careful to keep the spray perpendicular to the panels and avoid spraying connectors or areas which could suffer from water ingress. Connectors which can handle rain or water immersion won’t necessarily cope with the high pressures spray that these devices generate. If you don’t want to spend that much, try a bathroom mould killer spray, as used to clean showers etc. This should not do any damage to the panels as they generally have an outer glass layer which will not be affected. We also expect the metal frames etc should be OK as they would need to be corrosion-resistant to be used outdoors. But we suggest that you test the spray on a small area first, to make sure it doesn’t affect any of the metals used, and wash it off with plenty of water around 5-10 minutes after application. This should reduce the chance of bleach-accelerated metal corrosion. Of course make sure to follow any water restrictions that may be applicable for your area. Upgrading Micromite with new firmware I have now purchased and built several Micromite kits of varying models, with the objective of building solar system monitors. I now need to upgrade the firmware to the latest 5.x version, where I can utilise the LCD functions as well as some of the other most useful additions. I can easily download the required versions of the firmware (.hex files and documentation), but trying to find the Bootloader.exe file has become an impossibility. It was supposed to come with the download but is nowhere to be seen. I’ve seen a panel where it is called Silicon Chip Bootloader v1.0. So I searched on the Silicon Chip website without any luck either. Am I missing something? (T. T., Para Hills West, SA) • We think you might have the Micromite and Maximite confused. The Bootloader.exe file is used to upload new firmware to a Maximite computer (latest version 4.5C), and it is part of the Maximite firmware download at: siliconchip.com.au/Shop/6/930 (or find it on Geoff Graham’s website, http://geoffg.net). This bootloader is not used to up110 Silicon Chip date the firmware on a Micromite (latest version 5.05.02). You instead use the onboard Microbridge (if it’s in V2 or V3 BackPack form), or lacking that, an external Microbridge (May 2017; siliconchip.com.au/Article/10648) or a PICkit 3/4 or equivalent PIC32 programmer. We have not heard of a Maximite which can drive an LCD panel (except for perhaps a basic alphanumeric type). That seems to be a feature exclusive to the Micromites. The Maximite utilises a VGA monitor instead. Source code missing floating-point library I am trying to compile the assembly language source which I downloaded for your Digital Insulation Meter (June 2010; siliconchip.com.au/Article/186) using MPASMX but I am getting the following error messages (abbreviated to remove similar messages): Error[113] ..\..\0410610A.ASM 859 : Symbol not previously defined (FLO24) Error[113] ..\..\0410610A.ASM 864 : Symbol not previously defined (FPA24) Error[113] ..\..\0410610A.ASM 875 : Symbol not previously defined (FPD24) Error[113] ..\..\0410610A.ASM 889 : Symbol not previously defined (FPS24) Error[113] ..\..\0410610A.ASM 962 : Symbol not previously defined (float_ascii) Error[113] ..\..\0410610A.ASM 972 : Symbol not previously defined (FPM24) Error[105] ..\..\0410610A. ASM 1120 : Cannot open file (Include File “FPRF24.TXT” not found) Are you able to help me so that I can get it to compile? (Sanjeev, Delhi, India) • We forgot to include the floatingpoint library (the FPRF24.TXT file mentioned in the last error message) in the download zip for that project. We have now fixed that. This library has been used in several of our PICbased projects that need to perform mathematical operations on fractional numbers. Place that TXT file in the same directory as the ASM file and the errors about missing symbols should go away too. By the way, this custom-made library is similar to the file FP24.A16 which is included in the FP.zip download from ME labs at: https://melabs. Australia’s electronics magazine com/resources/fp.htm The main difference is that our version also includes the float_ascii function, originally from Microchip, but it has been modified to operate with the 24-bit (three-byte) floating-point values that we’re using, rather than the 32-bit (four-byte) values it was initially designed for. Paralleling regulators not recommended Electronics Australia published a compact low-voltage regulator project in August 1997 (97va8), which used the LM317 adjustable regulator, and kits of it were available for many years. That regulator was very popular with hobbyists, and I used a number of them in radio-controlled boats. Although the kits are now generally not available, they have been very reliable. I recently attached a light string made up in 1V pea lamps, each nominally 100mA drain at 1V, and connected 10 sets of three series-connected lamps to a 3V output from one of these units. A 1A load is well within the capability of the regulator, but after about 10 seconds of quite bright lights, they dim substantially. And even with a heatsink, the regulator runs quite hot. Clearly, I need more current capacity for the same output voltage. But there’s no similar small regulator kit available that can deliver substantially more current. Can a second LM317 unit be connected in parallel with the regulator on this board, to increase the current output capacity, approximately doubling the nominal 1.5A? (D. K., via e-mail) • While it is theoretically possible to parallel LM317s, each regulator will need its own independent set of voltage adjustment resistors to allow for the fact that the reference voltages could differ. Each regulator could have a reference voltage of 1.2-1.3V, so if they shared the same set of resistors, their output voltages could be significantly different, and so one would do all of the work. You would also need to join the two regulator outputs using low-value resistors (eg, 0.1W 5W) to allow for the small remaining difference in output voltage after trimming, so that they will properly share the load current. These will slightly reduce the voltsiliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP KIT ASSEMBLY & REPAIR FOR SALE 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 RCA RIBBON MICROPHONE, 44-BX, ex ABC Good condition. $1500 o.n.o. 2x matching transformers. 2W / 200kW. Jorgan 0.32 no.251 Negotiable. Phone: 0408 335 241 AWST please! 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 PCB PRODUCTION PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au Advertising Index Altronics...............................79-82 Ampec Technologies............. OBC Dave Thompson...................... 111 Digi-Key Electronics.................... 3 LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects like audio, video, programming etc. Many of them are in poor condition. Some of the books may not be for sale, but the vast majority are available. Bulk discount available; post or pickup. All books can be viewed at: siliconchip.com.au/link/aawx Silicon Chip silicon<at>siliconchip.com.au Emona Instruments................. IBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEACH PCB Assembly............... 5 LEDsales................................. 111 Microchip Technology.................. 9 Ocean Controls......................... 21 RayMing PCB & Assembly........ 11 SC Micromite BackPack............ 65 MISCELLANEOUS LOOKING FOR: Set of Dick Smith Electronics catalogues from 1975-1982. Must be in pristine condition. Will pay $200 for the set (inc. postage), only one set needed. Contact Melanie (on behalf of inquirer on 02 8832 3100) Silicon Chip Shop...........106-107 Silicon Chip Subscriptions..... 103 The Loudspeaker Kit.com........... 7 Vintage Radio Repairs............ 111 Wagner Electronics................... 63 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. age regulation of the resulting device. Another, more conventional (and probably more sensible) method is to use a parallel transistor to boost the output current of a regulator. siliconchip.com.au For example, we did this in our High Power Linear Bench Supply project (October-December 2019; siliconchip. com.au/Series/339). You can even add multiple parallel transistors, as we did Australia’s electronics magazine in that case, which helps to distribute the heat and current even further. For more information, see the following website: www.bristolwatch. com/ccs/LM317boost.htm SC February 2020  111 Coming up in Silicon Chip An Arduino Retrospective It’s been almost ten years since the Arduino Uno was introduced, and in that time, a lot has changed. Many new Arduino boards have been released, and the Integrated Development Environment software has been upgraded to support dozens of different boards, including many different processor types. This article describes how the Arduino platform has evolved over the years, into the highly-capable ecosystem that it encompasses today. A Valve-based Guitar Distortion/Overdrive Pedal The Nutube twin triode that we used to build a stereo preamp in the January issue is a very flexible device. This time we’ve used it to build a distortion and overdrive pedal with many different adjustments, so you can get exactly the sound that you want. And thanks to the soft overload behaviour of the valves used, it gives a much better sound than most similar solidstate pedals. Digital Cartography Dr David Maddison described how satellite navigation works in the November 2019 issue, but knowing your latitude and longitude isn’t very useful unless you also have maps to show you where you are. In this article, he describes how those crucial digital maps are created, stored and displayed. Grid-scale Energy Storage Pumped hydro is the traditional method of storing energy on a large scale. But building new dams is becoming very difficult, so a number of other methods have been proposed. Some of these are already in use, although generally at smaller scales than large hydroelectric schemes, and that is the focus of this article. The energy stored is used to smooth out the electricity supply for remote locations, to store excess energy from renewable sources or as a source of back-up power for critical facilities like hospitals and data centres. Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The March 2020 issue is due on sale in newsagents by Thursday, February 27th. Expect postal delivery of subscription copies in Australia between February 26th and March 13th. Notes & Errata Digital Lighting Controller, October-December 2010: when operating the unit with four slaves, it may be necessary to leave the 10kW “chain length sense” resistor off one of the four slave boards for correct operation. You can check this by plugging in three slaves, then four; if it works with three but not four, remove that resistor from the fourth slave. DSP Active Crossover/Parametric Equaliser, May-July 2019: in the June issue, the parts list indicates that the 128 x 64 pixel LCD has a 16-pin connector. It actually has a 20-pin connector, and so instead of the 13x2 pin and 16-pin headers, you need 10x2 pin and 20-pin headers. The caption for Fig.14 also incorrectly describes it as having 16 pins, rather than 20. Super-9 Stereo FM Radio, November & December 2019: the BB156 varicap used in this design has been discontinued and may become difficult to obtain. The 1SV304TPH3F varicap, still in production, is a suitable replacement. Also the Jaycar catalog code given for potentiometers VR1 & VR6 in the parts list on page 36 of the November issue is wrong. They should be Cat RP7510, not RP7610. Finally, in the alignment procedure described on page 67 of the December issue, where it says to adjust transformer T2, it should instead read inductor L6. 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. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes FREE OPTIONS Bundle! New Product! 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