Fullscreen HTML5Med Res (??MB)HTML4

APRIL 2020 ISSN 1030-2662 04 The VERY BEST DIY Projects! 9 771030 266001 9 95* NZ $12 90 $ INC GST INC GST GRID-SCALE ENERGY STORAGE TO BUILD: 7-band stereo or mono GRAPHIC EQUALISERS DIY Controller for SOLDER REFLOW OVENS Reference Signal DISTRIBUTION AMP FREE with this issue: 548 page JAYCAR 2020 CATALOG On sale 24 March 2020 to 23 April 2020 2020 ENGINEERING & SCIENTIFIC CATALOGUE OUT NOW! 495 $ EXCLUSIVE CLUB OFFER JUST BJ5000 FREE CATALOGUE WITH PURCHASES OF $30 OR MORE* *Applies to new & existing members for purchases made in-store or online. Valid 24 March - 23 April. See T&Cs for details. PROJECT OF THE MONTH: Intruder Alert CLUB OFFER BUNDLE DEAL 2495 $ An update on our Intruder alert project - now much simpler and cheaper to make! The main body of this kit uses a Passive Infrared (PIR) sensor to detect movement and send an email alert to yourself or the relevant authorities. SAVE 30% The project is flexible once it’s up and running. You could add a distance sensor to alert you when the family dog gets too close to the larder or a light sensor so you know exactly how late the teenagers got home! KIT VALUED AT: $37.60 Indeed, the sky’s the limit when you use this simple IFTTT IoT device to secure your premises. Easy to build. No special wiring required. SKILL LEVEL: Beginner TOOLS: Soldering Iron WHAT YOU WILL NEED: Wi-Fi Mini ESP8266 Main Board Arduino® Compatible PIR Motion Detector Module Prototyping Shield for Wi-Fi Mini 1.4mm SPST Micro Tactile Switch 5mm Round LED Red 5mm Round LED Green XC3802 $24.95 XC4444 $5.95 XC3850 $4.95 SP0601 $0.95 ZD0150 $0.40 ZD0170 $0.40 STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/intruder-alert See other projects at www.jaycar.com.au/arduino Upgrade Your Project ONLY 595 ONLY ONLY 795 $995 $ $ ARDUINO® COMPATIBLE PHOTOSENSITIVE LDR SENSOR MODULE ARDUINO® COMPATIBLE DUAL ULTRASONIC SENSOR MODULE Shop the catalogue online! Free delivery on online orders over $70 Add a light sensor to this project to measures light levels night/day. XC4446 Measure distances up to 4.5m. Use it to add proximity detection to your Intruder Alert project. XC4442 Conditions apply 1495 $ ARDUINO® COMPATIBLE RECORD AND PLAYBACK MODULE Run a pre-recorded message to alert the intruders. Records up to 10 seconds. XC4605 ONLY 2600MAH METALLIC POWER BANK - SILVER Add backup power to your Intruder Alert in case the power goes out. Only 96mm long. Strong aluminium case. MB3792 www.jaycar.com.au 1800 022 888 Contents Vol.33, No.4 April 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 12 Grid-scale energy storage Renewables are one thing – but how do you store the energy they produce for later use – when it’s needed? Dr David Maddison looks at ways they’re matching available energy and demand with some intriguing developments! 34 Review: 900MHz Touchscreen Vector Network Analyser Until not so long ago, you’d expect to spend $$$$$ – thousands of them – on a VNA. This one we bought on line for less than $AU60 – including postage! But is it any good? Is it value for money? Allan Linton-Smith certainly thinks so! 82 1st look: Tecsun Radio’s new HF SDR Amateur Transceiver It’s compact, it covers all HF bands with up to 20W output and it won’t break the bank! It even sports a 1.8in LCD panel with waterfall display. And with an SDR front end, its has performance you’ve only dreamed about! – by Ross Tester Constructional Projects 24 A DIY Reflow Oven Controller for modern soldering Soldering today’s components can be a challenge – but a Reflow Oven makes it a lot easier. Here we take a low-cost, standard (unmodified) toaster oven, add a micro-based controller . . . and voila! One Reflow Oven! – by Phil Prosser 38 Two new 7-band Audio Equalisers for hifi, PA and more! Tailor the sound of your listening experience to suit your preferences . . . or correct for room acoustics and deviations in loudspeaker response. We present both a stereo and a mono version to cover just about every application! – by John Clarke How DO you store bulk energy so that it is available when it is needed? – Page 12 Soldering SMDs? Want a reflow oven? Take a cheap toaster oven, build a cheap controller and you have one! – Page 24 A 900MHz VNA for less than sixty bucks? Surely it can’t be any good? Surely it is! – Page 34 64 Programmable Temperature Control with a Peltier, Part 2 Last month we introduced our new high-performance Peltier temperature controller. This month we show you how to achieve similar results, whether you need temperatures from near freezing up to 70° or so – by Tim Blythman 77 Frequency Reference Signal Distributor It’s one of those specialised pieces of test gear that you’ll only appreciate when you need it most! It allows you to feed a reference signal to up to six test instruments without attenuating or degrading the signal – by Charles Kosina Your Favourite Columns 84 Circuit Notebook (1) (2) (3) (4) Multi-code lock with 10 access codes Micromite-based chiming clock Self-resetting intruder alarm Two-wheel self-balancing robot 57 Serviceman’s Log It would be a waste of parts . . . by Dave Thompson 90 Vintage Radio Tecnico 1050 and 1140 – by Associate Professor Graham Parslow Everything Else 2 Editorial Viewpoint  99 4 Mailbag – Your Feedback 103 88 Product Showcase 104 siliconchip.com.au 96 Ask SILICON CHIP 104 SILICON CHIP ONLINE SHOP Market Centre Advertising Index Notes and Errata A stereo AND a mono audio equaliser. Whether you’re into hifi, recording, PA, band or any other use, we have you covered! – Page 38 One reference signal in, up to six out – without any attenuation or degradation – Page 77 Tecsun’s new SDR HF amateur transceiver is turning a lot of heads – especially at the price! – Page 82 On the cover: with a capacity of 100MW/129MWh, the world’s largest lithium-ion battery at Hornsdale, SA, along with its 99-tower wind farm. See the feature on Grid-Scale Energy Storage starting on page 12. www.facebook.com/siliconchipmagazine SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc Bao Smith, B.Sc Tim Blythman, B.E., B.Sc 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. Editorial Viewpoint “Second sourcing” should be applied to more than electronics You may have wondered why the same chip is available from different manufacturers – even relatively new parts which you would think they would want to keep exclusive. For example, the LM833 (OK, not that new a part…) was designed by National Semiconductor (as indicated by the LM prefix), but you can also buy LM833 chips made by ST Micro, On Semi and Texas Instruments (who now own NatSemi). Why is that? Well, mainly it comes down to the fact that many engineers (especially those designing products for military use) are unwilling to design using parts that are only available from a single source. No doubt they learned their lesson at some time in the past when a supplier went out of business, and could not get replacement parts for their multimillion-dollar new-fangled tank/fighter jet/whatever. Military contracts likely require second-sourcing, while commercial and industrial designers simply prefer having multiple sources to avoid future problems. I am reminded of this because of the supply chain disruptions due to the recent outbreak of the COVID-19 virus. We rely heavily on goods from southeast Asia and China in particular, including critical supplies like pharmaceuticals and other medical supplies (sutures, bandages etc). No doubt, most medical electronics are made overseas, too. You don’t have to be Nostradamus to see the danger in this sort of reliance. Sure, overseas suppliers can produce these items at such a low cost that local suppliers probably can’t compete. But for anything critical like medical supplies, food, fuel and so on, any rational government body or organisation must surely consider all the possible sources of disruption and have plans to deal with them. As much as I hate government subsidies, there is a case to be made to subsidise local industries which produce such vital products. This is to ensure that we have at least some sort of supply in times of war, disease, natural disaster, widespread strikes etc. Thus far (touch wood!) the impact of coronavirus in Australia has been relatively small and relatively well managed. But as we go to press, the mainstream media is full of reports of panic buying – some, like sanitisers, etc, related to misplaced fears of contracting the virus. However, there are all sorts of relatively mundane products running out on supermarket shelves – and there doesn’t appear to be a good reason for it. Even if the local supply is relatively small, it’s better than nothing and should be able to be ramped up, to deal with a loss of incoming goods from overseas during times of disaster. Perhaps now it will be realised how short-sighted it was to put so much reliance on overseas suppliers for critical items like drugs, and I hope plans are being put in place to ‘second-source’ (and third-source, and fourth-source…) them as quickly as possible. Initially, that might mean alternative drug suppliers from places like India or the UK (both of which have large pharmaceutical industries), but in the long-term, we should have the capability for domestic production. Now would also be a good time for the government to organise an inquiry into what other critical industries might be disrupted by an unpredictable event and what we can do, short-term and long-term, to minimise the impacts. Printing and Distribution: Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia’s Australia’selectronics electronicsmagazine magazine siliconchip.com.au siliconchip.com.au Australia’s electronics magazine April 2020  3 MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd 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”. Improved RF Signal Generator firmware I’ve had a lot of good feedback on my AM/FM/CW Scanning HF/VHF RF Signal Generator design (June/July 2019; siliconchip.com.au/Series/336). I have also received a few complaints about the operation of the on/off switch and glitches in the operation of the rotary encoder. I looked into why the power on/off switching circuit may not reliably turn off. Analysis has shown that variations in power supply bypassing capacitors fitted to AD9850 modules or the use of external power supplies (this can vary from just 1µF up to 100µF!) with moderate supply ripple may lead to this problem. A reader suggestion to increase the 1µF capacitor connected to the 270kW resistor on the input side to 10µF may improve this in some cases, but may not work reliably over a reasonable range of input supply voltages (eg, 10-15V). The optimum solution is 4 Silicon Chip to change the 1kW resistor from the collector of Q4 to pushbutton S3, to 8.2kW, while retaining the original 1µF capacitor. Silicon Chip published a note in the Notes & Errata section of the September 2019 issue which suggests that this resistor should be changed to 10kW; while 8.2kW is the ideal value, 10kW is close enough. In more detail, when the pushbutton is pressed to turn the power off, instead of Q5’s base voltage discharging into the 1µF capacitor via the 1kW resistor, this falling base voltage is overtaken by the residual voltage from the switched DC supply rail at Q4’s collector. Changing the resistor value increases the time available for Q5 to turn off. But if it’s made too high, Q5 cannot switch on at power-up. So 8.2kW is pretty much optimal with the timing capacitor of 1µF as used in the original circuit. As for the rotary encoder sometimes giving erratic tuning, it turns out that Australia’s electronics magazine there are two types of rotary encoders which are visually indistinguishable: ‘pulse’ and ‘level’ encoders. The ‘pulse’ type appears to be the most common type from overseas sources, and the cheapest. This type produces a pair of short quadrature pulses midclick, with both encoder outputs resting open circuit. The ‘level’ type of encoders change at each detent during rotation, and rest in one of encoder’s four quadrature output states. It is very hard to know when you are buying an encoder which type you will get. Once you have it, it’s easy to check. A pulse-type encoder will always have both switches open-circuit when at rest; they only close during rotation. A level-type will have one or both switches closed at rest in some rotational positions (but not all). The original software worked with the ‘pulse’ type but, as it turns out, not with the ‘level’ type encoders. I have now upgraded the software to V14, to siliconchip.com.au siliconchip.com.au Australia’s electronics magazine April 2020  5 handle both types. Adding a 100kΩ resistor from pin 28 (PC5) to ground selects the level-type encoder. Leaving it off (building the design as originally shown) suits a pulse-type encoder. The resistor, if fitted, can be mounted under the PCB, with one end soldered to pin 28 and the other to a convenient ground connection, such as at the Scan switch. Andrew Woodfield, Christchurch, NZ. Note: the revised software is available from our website, and is supplied on pre-programmed chips. Class-X vs Class-Y capacitors I just read the article “The Electrical House of Horrors” by Dr David Maddison in the December 2019 issue (siliconchip.com.au/Article/12169) and have found what I believe to be an erroneous statement. In the second main paragraph of the right-hand column on page 15, the author describes what would happen if a Class-Y capacitor connected between line and Earth went short circuit. Unless there is a fault in the Earth circuit, Earth and the Neutral are tied to the busbar at the property entry point. I believe that a short circuit will trip the fuse/thermal circuit breaker for that circuit. The effect would be similar to an Active wire of a refrigerator making contact with the metal case. The hardwired Earth wire should/will protect me from receiving a zap! Could the variation of capacitance between the value of the two elements in a Class-Y capacitor cause an RCD to trip? I believe the answer is yes. Why is the manufacturing process for Class-X and Class-Y capacitors dif different? It appears to me that only their position in the circuit and function is only slightly different. To me, the Class-X capacitor is simply half of a Class-Y capacitor. Ray Smith, Hoppers Crossing, Vic. Response: The description of Class-X and Class-Y capacitors in Dr Maddison’s article is correct. Here is an explanation of the difference between them: siliconchip.com.au/link/aaz2 A Class-Y capacitor may be manufactured similarly to a Class-X capacitor, but they are required to pass more strict tests. Current electrical safety regulations don’t allow ClassX capacitors to be used line-to-Earth. 6 SILICON CHIP Australia’s electronics magazine They can fail short-circuit and produce an electric shock should the Earth connection impedance be too high. As you say, this would not nor normally happen, but it is possible, so it is protected against. The photo you sent of an old ClassX capacitor showing connections between Active and Earth would not be legal to use in new equipment today. The Class-Y capacitors needed for this job are readily available from vendors like RS and element14. Remember that not all circuits are RCD protected. A circuit with a working RCD should trip if a line-to-Earth capacitor goes short circuit. It’s doubtful that a faulty capacitor would conduct enough current to trip a breaker, but it could still create a dangerous situation. Variation in Class-Y capacitor values should not cause an RCD to trip (at least with single-phase mains). However, if many devices with line-toEarth capacitors are connected to the same circuit, this may cause enough of a current imbalance to trip the RCD. Given that Class-Y capacitors used are generally in the range of 1-10nF, there would need to be many such capacitors on the circuit to reach the typical 30mA trip threshold. History of valve filaments I wrote the following in response to the October 2019 letter regarding running 1-series valves at 1V. Valves with oxide-coated cathodes are designed to run at a specific temperature, and if they run too hot or cold, the cathode will degrade over time. Confusingly, this was not a problem with the first valves, which had different cathode designs. In the US numbering system, the prefix represented the rounded-down value of the design heater voltage. Most 1-series valves were designed to run at the 1.4V ‘median’ voltage of a carbon-zinc cell, not 1V. Most 2-series valves were designed for 2.5VAC while most 6-series valves were designed for the 6.3V median voltage of a 6V leadacid car battery. 30-series valves suit a single 2V lead-acid cell and don’t use that system. The first high-vacuum triodes had directly-heated tungsten wire cathodes, which glowed brightly. When less gain was required, both HT and filament consumption could be reduced by lowering the heater voltage, siliconchip.com.au without harm to the valves. But these The power triode filament ran from its (“slip”). The slip is baked on, then valves were power-hungry, and when own low-voltage, centre-tapped wind- the filament bundle inserted into the radio took off in the early 1920s, manu- ing. The hum level was tolerable, par- cathode cylinder. This dramatically facturers looked for ways to reduce the ticularly with contemporary speakers. reduced the warm-up time, and that filament battery consumption. Next came “dull emitter” valves, is the system still used today. AC operation was the obvious an- still used today, where the filament The UY224 (“24”) appeared soon swer, but the AC superimposed on the is coated with a mixture of rare-earth after. It was an indirectly-heated tetfilaments acted like an audio signal, carbonates which turn to oxides dur- rode with a 2.5V filament, to match driving the valve like a grounded-grid ing the manufacturing process. The po- the then-new 2.5V directly-heated amplifier. Also, the thin filaments heat- tential of “glowing oxides” had been triodes (45) and pentodes (47). For ed and cooled at 50-60Hz, modulating known for about 20 years prior, but the first time, all the valves (except conductivity. So up until about 1925, sorting out the chemistry and manu- the rectifier) could run from the same all home receivers ran off batteries. facturing processes took some time. heater supply. For radio transmitters, these probThe lower operating temperature The 24 was short-lived as it was lems could be reduced by running meant much thicker cathodes were followed in the early 1930s by the thick wire filaments from a centre- practical, and in the US, this led to the groundbreaking 50-series: the 55 duotapped transformer winding. The anti- first triode specifically intended for AC diode triode, 56 oscillator triode, 57 phase voltages tended to cancel out, operation, the UX226, usually known remote cutoff pentode and 58 sharp and the thick filament had high ther- as the “26”. This had a directly-heated cutoff pentode. RAYMING TECHNOLOGY mal inertia. 1.5V, 1A filament. They were intended to be the This 1922 newspaper article It was and OK asPCB an RFAssembly amplifier, since heart of a radically new superheterPCB shows Manufacturing Services the circuitry used at KDKA Pittsthe Shenzhen 50/60Hz signal would be filtered odyne receiver design with either a Fuyong Bao'an China burgh, demonstrating this technique: out by the RF coils, and it was also 45 or 47 (2.5V) directly-heated out0086-0755-27348087 siliconchip.com.au/link/aaxv satisfactory for high-level audio. But put valve. This PDF shows examples: Sales<at>raypcb.com Then, in the early 1920s, lamp man- its hum level was still too high for siliconchip.com.au/link/aaxx ufacturers added a small amount of detector use. A radically new type of However, rapid improvements in www.raypcb.com thorium to tungsten, which made it valve was then introduced, the UX227 heater-cathode insulation technology easier to draw into a fine wire. When (27), which had an indirectly-heated saw the introduction of the 59 and 2A5 this was used for valve filaments, there cathode. This also wasn’t a new idea, indirectly-heated power pentodes, so was an unexpected increase in the but reliably manufacturing them was the need for 2.5V filament voltage disemission performance of the valves, a challenge. appeared. due to a minute layer of thorium conThe original 27 heater was a ceramic Meanwhile, car radios were prolifdensed on the surface of the tungsten. rod with two holes running the length erating, so 6.3V became the standard The resulting “thoriated tung- of it, through which a “hairpin” heat- heater voltage, and the “50” series besten” valves ran yellow-hot instead er was threaded. The cathode was an came the “70” series. For mantel raof white-hot, considerably reducing oxide-coated nickel cylinder that fit- dios, it was merely a matter of changpower consumption. The first attempts ted over the ceramic rod. It had a pain- ing the transformer secondary windat “all electric” radios were battery fully long warm-up time. Very few of ing voltage. set designs using thoriated-tungsten this type survive today. A less-appreciated reason for the valves, with an AC-filament triode This PDF shows a typical radio cir- change to 6V was that it allowed the ‘afterburner’. cuit with those valves: siliconchip. 300mA valve filaments to be run in The low-signal filaments (typically com.au/link/aaxw series across a US 110V AC line. A 3V <at> 60mA) were connected in series In 1928, the “slip coated” heater typical lineup was 6A7, 77, 75, 43 (a and run from ancestors of the type 80 was introduced, where the bare heater 25V version of the 42), plus a 25A6 directly-heated rectifier through drop- wire is compressed into a bundle, then indirectly heated rectifier. This adds per resistors and large filter inductors. dipped in a runny porcelain mixture up to about 75V and the other 30V or 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 8 Silicon Chip Australia’s electronics magazine siliconchip.com.au ai15831356619_Silicon Chip--mouser-widest-selection-205x275.pdf 1 2/3/2020 3:54 PM C M Y CM MY CY CMY K siliconchip.com.au Australia’s electronics magazine April 2020  9 ary or driving. It cost me $22 to drive down to Canberra and $23 on the way back. I use 91 octane unleaded; I will not use fuel with ethanol as it attracts moisture. Petrol stations have problems with water collecting in their E10 tanks in the ground. By the way, the electric steering is brilliant. The turning circle is very good to get in and out of tight places. Clever Mitsubishi. Toyota still has that clunky oversteer that has plagued them since my first Corolla SE in 1970. I have hired Toyotas when in Melbourne, Adelaide and Perth, including Camrys and Corollas. Both have the same handling problems. Jeff Rose, St Andrews, NSW. Australian ingenuity helped test the F/A-18 fighter jet As a significant example of Australian electronic ingenuity, you might like to have a look at is the “Digital Loop Controller” designed and developed at the Aeronautical (& Maritime) Research Laboratories, Fisherman’s Bend, Victoria. I was part of the team for over six years, retiring in 1999 (as shown in the article below). This was designed to perform real-time structural fatigue tests of the F/A-18 Hornet airframe, used by the RAAF. It employed an Inmos Transputer for fast throughput parallel processing to control test hardware, such as hydraulic actuators, linear airbag actuators etc. These simulated the structural loads encountered in the operational flight environment. Over 100 of these Loop Controllers were built for the test program. Overall, the program was a great success. Robert Sebire, Emerald, Vic. SC so could be absorbed by series resistors or special highresistance power cords (known as “curtain burners”!) Alternatively, another type 43 could be added for pushpull audio output, eliminating the need for a dropper resistor. This wasn’t just for economic reasons; large parts of the US were still on DC power at the time, and this was the only practical way to make a radio for DC mains! You can see an example here: siliconchip.com.au/link/aay0 In 1935, RCA introduced the octal valve base, followed in 1939 by the all-glass 7-pin types and slightly later, 9-pin types. The other major change was halving the heater current to 150mA and re-engineering the valve series to work directly from the 110V mains without a dropping resistor, so most small-signal valves became 12V instead of 6V, which also suited the later change to 12V car electrical systems. Keith Walters, Riverstone, NSW. More articles on hybrids wanted After reading your December 2019 article on Toyota hybrids, I was thinking, why not an article on the Mitsubishi Outlander PHEV (plug-in hybrid/electric vehicle)? It can drive on purely electric power, and does not need to engage the petrol engine unless the batteries are very low. Two electric motors run the show. One is in use 100% of the time; activating motor two gives you 4WD. Should you need more grunt, the petrol engine will cut in, or you can select it by a button to give more power or top up the batteries. Brilliant! The engine is there as a backup charger, whether station10 Silicon Chip Australia’s electronics magazine siliconchip.com.au ontrol evices Excellence in Engineering Products featured LED INDICATORS EMERGENCY STOPS ROCKER SWITCHES TOGGLE SWITCHES KEYPADS & SWITCH PANELS MINIATURE JOYSTICKS ANTI-VANDAL SWITCHES THUMBWHEELS MEC - HIGH PERFORMANCE TACT SWITCH ULTRA-WATERPROOF PUSHBUTTON PUSHBUTTONS AIR, PRESSURE & VACUUM SWITCHES Unit 17, 69 O’Riordan Street ALEXANDRIA NSW 2015 02 9330 1700 sales<at>controldevices.net siliconchip.com.au Australia’s electronics magazine April 2020  11 by Dr David Maddison H ere we describe several large-scale energy storage technologies and some which work at smaller scales. By “large scale”, we mean applications that are larger than a domestic battery system that might be installed as part of an off-grid solar electric installation. This means backup power systems large enough for a hospital, factory, data centre or other large institution, all the way up to grid-scale energy storage. Grid-scale storage might be used to back up intermittent solar and wind production, or for load balancing or frequency control on the electricity grid. For grid-scale storage, pumped hydro is by far the most popular and cost-effective method. But it is often limited by the availability of suitable sites (ie, by geography) and by opposition to building dams – a particular problem in Australia. We published an in-depth article on Pumped Storage Hydroelectricity in the January 2017 issue (siliconchip. com.au/Article/10497). We won’t go back over that again. The purpose of this article is to investigate and describe the alternatives. The most obvious means of storing electricity is batteries. But batteries for large-scale energy storage are both costly and have a limited lifespan. Hence, much effort has been 12 Silicon Chip There are many reasons why large amounts of energy may need to be stored. The most significant these days is to store excess energy from intermittent renewable generators and release it at times of low generation. Pumped hydro is the most common (and oldest) storage method, but there are numerous alternatives either in active use or proposed. put into looking for other options (or alternative battery chemistries which are better suited to this task). These other options are: 1) “mechanical batteries” or flywheels 2) compressed air storage, either in tanks, cavities in the ground or underwater 3) liquid air (cryogenic) energy storage or high-temperature storage 4) gravity potential energy storage, using masses raised to a higher level to store potential energy whether by towers, underwater structures or trains No energy storage method is ever 100% efficient. The so-called “round-trip energy efficiency” needs to be considered. This is the proportion of the energy used to charge the system that is recovered on discharge. For comparison, pumped hydro is typically regarded as having a 70-80% round-trip energy efficiency. Storing large amounts of energy, no matter how it’s done, is very expensive and requires significant space and volume. This is just one of the reasons why adding large amounts of variable generation such as solar or wind power to a grid, in a cost-competitive manner, is so difficult. Australia’s electronics magazine siliconchip.com.au Fig.1: this shows how Ecoult’s UltraBattery hybrid technology works. One must either live with their intermittency, or factor the cost of the required energy storage into the generation costs. Energy storage objectives The main objectives for large-scale energy storage are: 1) For intermittent renewable generators, to take up excess energy produced under favourable conditions and then release this when the intermittent producers are producing little power or are offline (eg, no wind or sun). 2) To improve grid stability such as frequency or voltage stabilisation when huge swings occur in demand or due to intermittent production. 3) To make money for storage owners via “arbitrage”. In other words, they buy and store electricity when it is cheap and sell it later when it is more expensive. 4) To enable the building of smaller and more economic power stations than would by themselves be incapable of supplying peak demand. Supposing peak demand was 1500MW in a particular market, a cheaper 1000MW power station could be built, and stored power could be used to supply the extra 500MW for the peak period (eg, two hours a day). Objective #4 is only economical if the cost of the storage is lower than the cost of generation capacity. This is one of the purposes of pumped storage in the original Snowy Fig.2: a large-scale UltraBattery installation. These are DEKA brand batteries, made by East Penn Manufacturing in the USA, the parent company of Ecoult. Mountains Scheme. Note that in this article, many storage systems are described as having a kWh/MWh/GWh capacity as well as a kW/MW/GW rating. The former describes the total energy that can be stored while the latter indicates how quickly that energy can be delivered. So for example, a 1GWh system with a rating of 100MW could be expected to deliver 100MW for 10 hours or 50MW for 20 hours. Electrochemical (battery) storage For applications such as backup power supplies in small or medium-sized data centres, telecommunications hubs and some other facilities, traditional lead-acid batteries are still frequently used. They are an old technology (invented in 1859) but are of relatively low cost, and when managed correctly, reliable and predictable. They are also highly recyclable. Despite the relatively low cost of lead-acid batteries, there are reasons to use other battery chemistries. For example, lithium-ion types have a higher capacity for a given volume, have a greater permissible repeated depth of discharge and can have a better lifespan. As a result, lithium-based batteries are now used for grid-scale storage. As an example of a (small, designed to serve 1600 Fig.3 (and opposite): Australia’s “Big Battery”: the Hornsdale Power Reserve battery in South Australia. The wind turbine in the background is part of the associated wind farm whose energy goes into the battery. siliconchip.com.au Australia’s electronics magazine April 2020  13 Fig.5: a cross-section representation of a liquid metal battery. Fig.4: six 10kWh Redflow ZCell zinc-bromine flow batteries on the Bates family farm in Queensland, 2.7km from the nearest power lines. The batteries are charged from 72 260W Tindo solar panels, with an 18.7kW peak power capacity, plus two Victron Quattro 48/10000 inverters to supply mains power to the home people) grid-scale lead-acid battery, the King Island Advanced Hybrid Power Station in Bass Strait, as of 2014, employed a 3MW-capable, 1.5MWh advanced lead-acid battery as part of its storage system. The specific manufacturer or details of the battery are not mentioned on the owner’s website, Hydro Tasmania. At the time of installation, it was the largest battery in Australia and could supply the needs of King Island (in Bass Strait) for 45 minutes. The advanced lead-acid battery replaced an earlier failed 800kWh vanadium redox “flow” battery (initially installed in 2003). For a live dashboard of power generation at King Island, see siliconchip.com.au/link/aayr Australian company Ecoult (www.ecoult.com) was formed in 2007 but has been US-owned since 2010. It produces the UltraBattery (Figs.1 & 2), which was invented by the CSIRO. This hybrid battery technology combines elements of a lead-acid battery and a supercapacitor. Fig.6: these 800Ah/ 160W Ambri cells come in 216 x 137 x 254mm sealed stainless steel containers and weigh 25kg each. 14 Silicon Chip Compared to traditional lead-acid batteries, it can charge and discharge continuously and rapidly in a partial state of charge due to its ultracapacitor element, making it ideal for smoothing the output of intermittent energy sources like solar and wind farms. Its lead-acid component provides bulk storage of energy for times when the generator is providing little or no power. For more information, see the video “UltraBattery The Movie” at https://vimeo.com/208600432 South Australia’s 129MWh “Big Battery”, otherwise known as the Hornsdale Power Reserve (Fig.3), was manufactured by Tesla and can deliver 100MW. It is said to be the world’s largest lithium-ion battery. In November 2019, it was announced that its capacity and power would be increased by 50%. This is taxpayer-funded, with $15 million from the SA Government, $50 million in cheap loans from the Clean Energy Finance Corporation and $8 million from the Australian Renewable Energy Agency. Other battery chemistries are also becoming available for large scale storage, including next-generation lithium batteries like LMP (solid-state lithium metal polymer batteries) by Blue Solutions (www.blue-solutions.com/en/) and other solid-state lithium batteries such as those under development by Australia’s CSIRO (siliconchip.com.au/link/aays) and Deakin University (siliconchip.com.au/link/aayt). Fig.7: the electrochemistry of the Ambri cell. Alloying and de-alloying occur during the discharging and recharging process, with no long-term degradation of components. Australia’s electronics magazine siliconchip.com.au Fig.8: the Ambri battery system. Cells are aggregated into modular 10-foot shipping containers with a capacity of 1000kWh/250kW and an operating voltage of 500-1500V. The containers come ready to install and the contents require no maintenance. Flow batteries Flow batteries are also used for large-scale electrical storage. In a flow battery, the electrolyte is stored in tanks rather than within each battery cell (as with regular batteries). This confers several benefits, such as improved safety and less degradation with charge and discharge cycles. Disadvantages include lower energy density and lower charge and discharge rates than regular batteries. Pumps are needed, which require maintenance. Some flow batteries used in Australia are: • Monash University, Clayton, Vic has a 180kW, 900kWh vanadium flow redox battery as part of a hybrid battery to store energy in their Microgrid system • The University of NSW has a 30kW, 130kWh CellCube (www.cellcube.com/) vanadium flow redox FB 30-130 system for research, and to store electricity from a 150kW photovoltaic system • Base64 in Adelaide (www.base64.com.au/) has a 450kWh Redflow Energy bromine flow battery to back up a 73kW (peak) solar system Redflow (https://redflow.com/) is an Australian company that produces 10kWh zinc-bromine flow batteries (Fig.4) They are “designed for high cycle-rate, long time-base stationary energy storage applications in the residential, commercial & industrial and telecommunications sectors, and are scalable from a single battery installation through Fig.9: Beacon Power’s (https:// beaconpower.com/) flywheel system. The rotor assembly (hub, shaft and motorgenerator) is integrated into the carbon fibre “rim”. The rotor, which spins at 16,000rpm, is supported on a magnetic lift system and is in a vacuum chamber. The units are buried to contain any fragments ejected due to rotor failure. to grid-scale deployments”. The Redflow ZBM2 battery is intended for commercial use, while the Zcell flow battery is intended for residential or office use. Ambri (https://ambri.com/) is a US company that has developed a unique liquid metal battery system, comprising a liquid calcium-alloy anode, a molten salt electrolyte and a cathode made from antimony particles (Figs.5-8). This battery system was explicitly designed using cheap “commodity” materials (no rare exotic materials, or those with supply uncertainty due to location). It was also designed to be intrinsically safe, with no risk of fire (even if the container is breached) and no requirement for external equipment such as pumps or cooling systems. The system does not degrade with cycling, unlike other battery systems, and is cheaper than current or projected lithium-ion battery prices due to cheaper materials and simpler manufacturing methods. The nominal open-circuit voltage of an Ambri cell is 0.95V and capacity is 800Ah, with a maximum continuous power of 160W. Voltage cycling is in the range of 0.5V Fig.10: Beacon Power’s 20MW/5MWh FES installation in Hazle Township, Pennsylvania, USA; the world’s largest flywheel installation. Its 200 flywheels are used for grid frequency regulation. The tops of the flywheels are in blue, with the rotating masses buried — each flywheel assembly weighs 5t. The shipping containers contain control equipment. siliconchip.com.au Australia’s electronics magazine April 2020  15 The two major forms of energy loss in FES are in the bearings and frictional losses of the surface of the rotor against the atmosphere; therefore, the bearings used are usually zero-friction magnetic types and the rotor operates in a vacuum. Uses for flywheels in large-scale energy storage include: • • Fig.11: a schematic view of the Hitzinger DRUPS. “CB” stands for circuit breaker. The kinetic module is the flywheel assembly. to 1.25V while DC efficiency is over 80%. The cells operate at 500°C. They are self-heating when started and so require no external heating to reach operating temperature or to stay there. In September 2019, NEC announced they would use Ambri technology for an energy storage system. NEC has committed to purchase a minimum of 200MWh of storage that will be used in grid applications to provide energy for four hours or more, with full depth of discharge cycling. See the video titled “The Liquid Metal Battery: Innovation in stationary electricity storage” at siliconchip.com. au/link/aazq backup for intermittent wind and solar systems grid stability services such as for frequency and load balancing • uninterruptible power supplies with zero switching time for large organisations like hospitals, data centres or Australia’s King Island Renewable Energy Integration Project • the electromagnetic aircraft launch system (EMALS) as used by the US Navy (see our article on Rail Guns and Electromagnetic Launchers in the December 2017 issue: siliconchip.com.au/Article/10897). STORNETIC (https://stornetic.com/) is a German company that makes flywheel energy storage systems (Fig.14). They have installed a system in Munich, Germany, comprising of 28 flywheels that spin at 45,000rpm with a capacity of 100kWh, used for grid stabilisation. See the video titled “STORNETIC - The Energy Storage Company” at siliconchip.com.au/link/aazr One type of flywheel-based uninterruptible power supply (UPS) system is a diesel UPS or D-UPS, also known as a rotary UPS or diesel rotary UPS (DRUPS). A DRUPS Flywheel energy storage Flywheel energy storage (FES) involves storing energy with a rapidly spinning rotor in the form of rotational energy, also known as angular kinetic energy. The flywheel is typically connected to a motor-generator; it is sped up by the motor and when energy is to be extracted, generator mode is engaged, which reduces the rotor RPM as energy is extracted (Figs.9, 10 & 13). Flywheel storage systems have long lives and have a round trip efficiency of up to 90%. Fig.12: a Hitzinger rotary UPS as used in the King Island Renewable Energy Integration Project. 16 Silicon Chip Fig.13: NASA’s 525Wh/1kW G2 flywheel. This was an experimental energy storage system demonstrated in 2004 for possible use in spacecraft. Its rotational speed was 41,000rpm and it weighed 114kg. Australia’s electronics magazine siliconchip.com.au Flywheel and gravitational energy storage equations The energy of a spinning flywheel can be calculated from these two equations: Ef = 0.5 × I × ω² I = k × m × r² Here, Ef = flywheel kinetic energy, I = moment of inertia, ω = angular velocity (measured in radians/second and proportional to RPM), k = inertial constant (a value from 0 to 1 depending on flywheel shape), m = flywheel mass and r = flywheel radius. If we combine the above equations and create a new constant K, we get Ef = K × ω² × m × r². For comparison, assuming the flywheels to be compared are the same shape, we can see that flywheel energy storage goes up with the square of the angular velocity (or RPM) and the radius of the flywheel. Thus, if either the radius or RPM doubles, the energy storage quadruples. The amount of potential energy in a mass hoisted above the earth, assuming perfect efficiency, is: PE = m x g x h Here, m is the mass in kg, g is the acceleration due to gravity in metres per second squared (around 9.8 at the Earth’s surface) and h is the height. The result, PE, is in Joules. To convert Joules to MWh, divide by 3.6 x 109. Fig.14: multiple STORNETIC flywheel energy storage systems. consists of a diesel engine, an electromagnetic clutch, an alternator, a kinetic energy module (flywheel) and a choke (see Figs. 11 & 12). In normal operation, a DRUPS conditions the incoming mains supply, producing power at the correct voltage and frequency. Incoming power drives a synchronous alternator as a motor, to which is attached a flywheel or “kinetic module” for energy storage. Fig.15: a proposal from Apex CAES (www.apexcaes.com/) for Bethel Energy Center in Texas. It will be capable of generating 324MW for 48h. It uses natural gas to heat expanding air during power production. The cost is US$21/ kWh versus $285/kWh for a lithium-ion battery and will last 30 years, or three times longer than a lithium battery. siliconchip.com.au Power is conditioned both by the alternator, which stabilises the frequency and blocks higher-frequency harmonics and transients, and the choke which further blocks highfrequency harmonics. The alternator, with a special stator configuration, also blocks the upper harmonics of lower frequencies (such as the 3rd, 5th, 7th harmonics etc). In the event of a power failure, the flywheel continues to rotate, driving the alternator to generate power and losing speed as it does so. If the power failure exceeds a certain number of seconds, an electromagnetic clutch is engaged and the diesel motor starts. This drives the alternator (and brings the attached flywheel back up to speed) to produce power until mains power is restored. For more information, see the video “Hitzinger Rotary Diesel UPS” at siliconchip.com.au/link/aazs Fig.16: a surface view of A-CAES at the old Angas Zinc Mine near Strathalbyn, about 60km south-east of Adelaide. The water reservoir is full when the system is charged and empty when the system is discharged. Image courtesy ARENA. Australia’s electronics magazine April 2020  17 Why energy storage is essential for renewables Conventional coal, gas, hydroelectric and nuclear power plants are usually much larger and have a much higher “capacity factor” than wind or solar plants. The capacity factor represents the amount of power generated long-term compared to its “nameplate” capacity. Wikipedia states that Australia has a total nameplate capacity of 5,679MW in 94 wind “farms”, with an average 60MW nameplate capacity (and a total of 2,506 windmills). As the typical capacity factor of a wind farm in Australia is 30-35%, these farms on average can be expected to generate 1,703-1,988MW, an average output per farm of 18-21MW. Because the output of such generators is so variable, to keep the grid stable and meet energy demand, they are best combined with energy storage systems. With sufficient storage, the output of a renewable energy source can be considered “dispatchable”, ie, available on demand. This is not usually necessary with traditional power plants as their capacity factors are close to 100% and downtime for maintenance is normally planned in advance. Compressed air energy storage Energy can be stored by compressing air, which can then spin a turbine to recover the energy. In a large-scale system, the compressed air is held in an appropriate containment such as an unused mined-out cavity of a salt mine (Fig.15). As anyone who has pumped up a bicycle tyre or released the contents of an aerosol can knows, compressing gas heats it while expanding gas cools down. For maximum efficiency of compressed air storage, the heat from compression needs to be preserved and put back into the air when the air is discharged to produce power, as the heat contains a lot of the original energy. In some compressed air installations, the air is heated not only with the heat recovered from the original compression but by burning natural gas as well. The two largest compressed air energy storage plants are in Huntorf, Germany and McIntosh, Alabama, USA. The Huntorf plant was built in 1978, and it uses two empty mined-out salt domes which are typically charged for eight hours per day. Its rated capacity is 870MWh, typically providing for three hours of discharging at 290MW. It has a 42% overall efficiency. Fig.18: a rendering of Highview Power’s 250MWh/50MW CRYOBattery plant, to be built in the north of England. 18 Silicon Chip Fig.17: a Hydrostor system. Compressed air is stored in caverns and kept pressurised with water. The salt caverns are 600m deep and have a 310,000m3 total volume. They are at 100atm of pressure when fully charged. The plant in McIntosh was built in 1991, with a capacity of 2860MWh and it can discharge 110MW for 26 hours. It also utilises mined-out salt domes for storage. It burns natural gas in a “recuperator” to heat the expanding air and has an overall efficiency of 54%. Hydrostor (www.hydrostor.ca/) is developing Australia’s first Advanced Compressed Air Energy Storage (A-CAES) facility. The project is taxpayer-funded to the extent of $6 million from the Australian Renewable Energy Agency (ARENA) and $3 million from the Government of South Australia Renewable Technology Fund. It will use a disused zinc mine near Adelaide for compressed air storage, and will deliver 5MW with a 10MWh storage capacity (see Figs.16 & 17). Air will be compressed and the heat captured using a proprietary thermal storage system. The compressed air Fig.19: a schematic representation of cryogenic energy storage. Australia’s electronics magazine siliconchip.com.au Fig.20: Highview Power’s 5MW Pilsworth Grid Scale Demonstrator Plant. It began operation in April 2018 and is backed by UK taxpayer funding. See the video “World’s first grid-scale Cryogenic Energy Storage System launch” at siliconchip.com.au/link/aazt will be stored in underground caverns in the mine, filled with water to maintain pressure. During the charging process, water will be forced out of the caverns and up to a surface reservoir. Upon discharge of the air to produce electricity, water will return to the caverns to replace the air. The discharged air will also be heated with stored heat from the compression process. See the video “How Hydrostor A-CAES Technology Works (2018)” at siliconchip.com.au/link/aazu There are two different proposals for keeping compressed airbags at the bottom of the ocean. These are detailed in the videos titled “Underwater Energy Bags” at siliconchip. com.au/link/aazv (by Prof. Seamus Gravey) and “Underwater Energy Storage in Toronto” at siliconchip.com.au/ link/aazw (by Hydrostor). There is also a concept from the German Fraunhofer Institute for Wind Energy and Energy Systems Engineering for concrete energy storage spheres at the bottom of the ocean. See the following websites for more information: siliconchip.com.au/link/aayu siliconchip.com.au/link/aayv siliconchip.com.au/link/aayw Cryogenic energy storage Cryogenic energy storage is a type of compressed air storage where the air is compressed and cooled to a liquid form. UK company Highview Power (siliconchip.com.au/ link/aazx) has developed the CRYOBattery which is scalable from 20MW/80MWh to more than 200MW/1.2GWh (see Figs.18-20). It is claimed to be the cheapest form of grid-scale energy DIY Rubber band energy storage YouTuber J.L. Ibarra Avila built a simple device to use energy stored in rubber bands to turn a generator, producing a small amount of electricity to light an array of LEDs. See the video “Energy stored in rubber bands to generate electricity” at https://youtu.be/LT_nB07r-4g siliconchip.com.au Fig.21: the failed Crescent Dunes Solar Energy Project in Nevada, USA. One problem with such facilities is that they kill birds and insects that fly into its concentrated solar beam. Australia was to have one just like it. storage (£110 [around AU $206] per MWh for a 10-hour, 200MW/2GWh system). It has an efficiency of 60% in a standalone configuration or 70% when combined with the utilisation of waste heat and cold. In October 2019, Highview Power announced a 50MW/250MWh CRYOBattery project in the north of England with a five hour discharge time. See the videos “Highview Power – True Long-Duration Energy Storage” at siliconchip.com.au/link/aazy and “Liquid Air Energy Storage Animation 2018” at siliconchip. com.au/link/aazz Thermal energy storage Thermal (heat) energy can be stored when energy is plentiful or cheap and released later when it is needed. Heat energy is commonly stored in molten salt, and this was the subject of two commercial grid-scale projects as follows. There was a large $650 million, 135MW solar thermal power plant planned for South Australia, announced by the SA Premier on August 14, 2017. But despite extremely generous government backing of various kinds (including a $110 million loan), its cancellation was announced on April 5, 2019. The reason given was that it was not able to attract sufficient investor funding, perhaps because it was unlikely to ever make a profit, even with Australia’s very high electricity prices. The plant was to use a system of mirrors to heat molten salt in a tower during times of high solar radiation, and use the heat of the molten salt to drive a steam turbine to generate electricity including during cloudy periods and at night. So the heat stored in the molten salt could supposedly be used to generate power 24 hours per day. Could you run your home on compressed air storage? To store 3kWh of energy, you would need a compressed air cylinder of 2.5m in diameter and 13.7m long, charged to 750kPa or 7.4atm. Consider that the average Australian household consumes at least 10kWh per day. For more details, see the PDF at siliconchip.com.au/link/aayz Australia’s electronics magazine April 2020  19 Fig.22: the “Energy Vault” stores energy by lifting concrete blocks to form a tower. When later lowered to the ground, they drive a motor-generator to produce electricity. The proposed developer ran the only other such plant in the world based on the same technology, in Tonopah, Nevada, USA (see Fig.21). It was also dependent on government subsidies, failed to produce sufficient power and was shut down in April 2019. There is a working solar power tower in Ivanpah, California but its production has been disappointing, and it lacks thermal storage; the water used as the heat transfer medium has to be heated up every morning with natural gas. One ongoing problem with solar tower systems like these is that they tend to incinerate insects and birds; for example, see the video titled “Insects and birds affected by Ivanpah solar tower” at siliconchip.com.au/link/ab00 is not suitable for all locations. Bear in mind that gravitational potential energy storage has a relatively small energy density. For example, to store the energy of a single AA battery, you need to lift 100kg 10m. Or to store the equivalent of one litre of petrol, you need to lift about 30 tonnes 100m. So to store enough energy to be worthwhile, the mass or volume lifted must be very high. Besides pumped hydro, a few methods have been proposed for large-scale storage: 1) hoisting concrete blocks onto a tower using a crane, then lowering the blocks on the crane to drive a motorgenerator attached to the cable. 2) a similar method by which heavy weights on cables Gravitational potential energy storage Gravitational potential energy storage involves moving mass from a lower level to a higher level and then releasing it to liberate its potential energy. The most common form of large scale gravitational potential energy storage by far, also known as a gravity battery, is pumped hydroelectric power. Pumped hydro uses water as the mass medium as it is relatively dense and easy to move around using pumps and pipes. However, as mentioned above, pumped hydro Fig.23: a rendering of the SINKFLOATSOLUTIONS Heavy Underwater Gravity Energy Storage system, showing weights suspended from barges. 20 Silicon Chip Fig.24: the MGH gravitational potential energy storage system. A floating platform at sea lowers masses 1000m+ to the seafloor to release energy. Australia’s electronics magazine siliconchip.com.au Fig.26: the Gravitricity gravity storage system, with winches powered by motor-generators lowering masses down a specially-built shaft (up to 150m) or disused mineshaft (up to 500m). The masses are at least 500t each. Fig.25: a system outlined on the YouTube channel “McMillion Watts” to harvest ocean wave energy. are lowered into the ocean to a depth of 4km, or down a shaft in the ground, then later hoisted back up. 3) driving a train filled with rocks uphill and generating electricity when it later descends. 4) a (far-fetched) scheme where weights are hoisted and then lowered from a floating structure in the stratosphere. A simple and familiar example of gravitational energy storage at a small scale is the pendulum clock or a cuckoo clock, where weights are raised to “charge” the mechanism and released to power it. Energy Vault (https://energyvault.com/) proposes a gravity storage system whereby concrete blocks are raised with a crane powered by a motor-generator to charge the system, and lowered to produce power (see Fig.22). The company claims it costs half as much as pumped hydro with a 90% round-trip efficiency, a 30-year plus life and no cycle degradation. The system is modular and scalable and provides 20, 35 or 80MWh storage capacity and 4-8MW of continuous power for 8-16 hours. Each brick lifted weighs 35 tonnes. The system is said to be simple and inexpensive to build. A YouTuber by the name of Thunderf00t has critically analysed this proposal and disagrees with its claims of efficacy. One stated concern is the stability of the weights in high winds; see the video titled “Energy Vault -BUSTED!” at siliconchip.com.au/link/ab01 A French company called SINKFLOATSOLUTIONS (http://sinkfloatsolutions.com/) proposes to lower large concrete masses into the depths of the oceans (up to 4km deep) from barges. The system is called HUGES or Heavy Underwater Gravity Energy Storage (Fig.23). See the video titled “Underwater Energy Storage - How It Works” at http://siliconchip.com.au/link/ab02 MGH Energy Storage (siliconchip.com.au/ link/ab03) is another French company that proposes a maritime gravitational potential energy storage system (Fig.24). Offshore floating structures would be used to harvest wave energy. This energy is then used to raise weights up shafts dug deep into the ground onshore (up to 3000m deep). See the video “MGH Energy Storage – multi weight operation” at siliconchip.com.au/link/ab04 Note that most, if not all, schemes to harvest wave energy built so far have failed. See the video “WAVE AMPLIFICATION, WAVE POWER HARNESSING, SOLID MASS GRAVITATIONAL ENERGY STORAGE” at siliconchip.com. au/link/ab05 (see Fig.25) Gravitricity (www.gravitricity.com/) proposes a system of energy storage whereby weights of 500-5000t are raised in a deep shaft dug into the earth, or possibly using an abandoned mine shaft; see Fig.26. The company claims the following advantages on their website: • 50-year design life with no cycle limit or degradation • response time from zero to full power in less than one second • efficiency of 80-90% Fig.27: the ARES pilot installation with a 6t vehicle on a 9% rail grade near Tehachapi, California. A full-scale system would be much larger than this. Fig.28: an artist’s rendition of the proposed 12.5MWh/ 50MW ARES train in Pahrump, Nevada. The track length would be 9km with an elevation difference of 610m, a grade of 7-8%, a footprint of 19ha and total train mass of 8700t. It will be used for “ancillary services” such as frequency regulation to aid grid stability. siliconchip.com.au Australia’s electronics magazine April 2020  21 Fig.29: the StratoSolar concept of large helium or hydrogen-filled platforms floating 20km up with solar panels for electricity generation and masses on cables for gravitational potential energy storage for night-time energy production. • • • can run slowly at low power or fast at high power easy to construct near networks levelised cost well below lithium batteries Gravitricity says that each gravity storage unit can be configured to produce 1-20MW for between 15 minutes and eight hours. As with all gravity storage methods, the amount of energy stored is relatively modest. A 3000t weight lowered 1250m into a shaft will store about 10MWh. ARES or Advanced Rail Energy Storage (siliconchip.com. au/link/ab06) is a gravity potential energy storage system that uses masses raised on a rail system for energy storage (Figs.27 & 28). ARES proposes three levels of capacity, 20-50MW for ancillary services; 50-200MW with 4-8 hour duration for “renewables” integration; and grid-scale systems of 2003000MW with 4-16 hour duration. During charging, masses are picked up by the train in a lower storage yard and dropped off at an upper storage yard. After the masses are dropped off, the empty train returns to the lower yard to pick up more. The discharge process is the reverse. The process is automated and requires no new technology. All that is required is two storage locations with an appropriate height differential and an appropriate grade, and a path between them. ARES has developed a cabledrive system called “Ridgeline” for where the grade is too steep for conventional rail traction, allowing the use of sites with as little as 240m elevation change with grades from 20-50%. Fig.30: the internals of the GravityLight. The weight bag is not shown. See the videos titled “ARES-Technology” at: siliconchip. com.au/link/aaz0 and “A New Kind of Renewable Energy Storage” at siliconchip.com.au/link/ab09 MAPS (MAglev Power Storage) is a proposed system similar to ARES but using magnetically levitated “maglev” trains instead of traditional rails and wheels like ARES. It is claimed to be 90% efficient with a storage cost of US$0.020.03 per kWh. Studies and presentations appear to have been published around 2010 but nothing since. StratoSolar Inc. (www.stratosolar.com/) proposes energy generation and storage in the stratosphere! This company has planned buoyant platforms filled with helium or hydrogen 20km up with solar production by day and gravity potential energy storage at night (Fig.29). Multiple 1kg weights are to be suspended beneath the Using compressed air for off-grid energy storage The video “AMISH air POWER ~ OFF GRID” at siliconchip. com.au/link/ab07 shows how an Amish community in the USA uses compressed air to power their ceiling fans, sewing machines and other equipment (Figs.32&33). The compressed air is produced either with a petrol-powered compressor or by a windmill. The air is stored in tanks. A variety of machinery can be powered using air-powered motors, such as those available from Gast Manufacturing, Inc. (siliconchip.com.au/link/aayx) or DEPRAG SCHULZ GMBH u. CO. (siliconchip.com.au/link/aayy). 22 Silicon Chip Australia’s electronics magazine Fig.31: a GravityLight with weight bag. A DIY gravity phone charger YouTuber Tom Stanton converted a hand-cranked USB charger to a gravitypowered one (Fig.34). It was an interesting exercise, but clearly, not a practical one (as you will see if you watch his video). It demonstrates the low power density of gravity energy storage. See “Gravity Powered Phone Charger” at siliconchip.com.au/link/ab08 siliconchip.com.au Fig.34: modified hand-cranked USB charger components inside a 3D-printed case, converting it into a gravitypowered charger. Frame grab from Tom Stanton’s video. Fig.33: an example of a compressed-air powered air vane motor from Deprag. Inset shows the vane arrangement and off-centre rotor. Rotational speeds of 100-25,000rpm can be achieved. platforms, which will rise or fall the 20km between the ground and the platform to generate energy via a motorgenerator. Each kilogram mass will store about 54Wh of energy so 500 tonnes of masses will store 25MWh. This project seems to be inactive and we think it’s highly impractical. See the video “StratoSolar Introduction” at: siliconchip.com.au/link/ab0a Two other concepts of gravitational potential energy storage involving the use of large pistons and water were discussed in the SILICON CHIP article on Pumped Hydroelectric Storage in January 2017 (see link above). Storing energy in hydrogen gas Water can be electrolysed to produce hydrogen in a “power to gas” operation, to store excess energy for later use in an electrochemical fuel cell or via combustion. This concept is under investigation, but there appear to be severe economic and efficiency constraints. Japan has already committed to using hydrogen as a trans- Fig.32: a compressed air system powering various equipment in an Amish community, as shown in the linked video. The Amish have religious objections to using electricity. siliconchip.com.au port fuel, and there is a taxpayer-subsidised pilot project in Victoria to convert brown coal to liquid hydrogen for export to Japan for this purpose. The process was developed in the mid-nineteenth century for “producer gas”, and is a coal gasification method. Coal is reacted with oxygen and water at high pressure and temperature to produce, at the end of the reaction process, carbon dioxide and hydrogen. The hydrogen is then separated, liquefied and transported, and the CO2 is disposed of. Some general constraints of the use of hydrogen as a fuel are discussed in the video titled “The Truth about Hydrogen” at siliconchip.com.au/link/ab0b SC A gravity-powered light GravityLight (siliconchip.com.au/link/ab0c) is a gravitypowered LED lighting system design to replace dangerous and expensive kerosene lights in Africa and other undeveloped areas (see Figs.30 & 31). The user attaches the device to a sufficiently strong overhead support and fills a bag with up to 10kg of heavy objects such as rocks. As the bag descends about one metre, it turns a generator, powering one LED light. One raising of the weight bag provides 20 minutes of light, and two satellite lights can also be attached. The light output of the GL02 model is a modest 80mW/15 lumens for the primary light and 15 lumens combined for the two satellite lights. That is sufficient to see inside a typical African dwelling at night and also for reading. You can purchase this light if you want one. Another device intended to provide basic light in undeveloped countries is the solar-powered LuminAID. See the videos “What is GravityLight?” at siliconchip.com.au/link/ab0d and “Gravity Light Review” at siliconchip.com.au/link/ab0e Australia’s electronics magazine April 2020  23 DIY Solder ReFLow Oven by Phil Prosser with PID Control Make short work of soldering boards full of surface-mounting components with this low-cost and easy-to-build DIY solder reflow oven. It’s quite cheap to build but it runs your PCB(s) through a temperature profile much like a professional reflow setup costing thousands of dollars! It can also be used to ‘bake’ components, cure glue or paint or any other task where you need to hold something at a stable, elevated temperature for some time. Features • Self-contained controller converts a toaster oven into a reflow oven • Temperature profile follows standard reflow soldering profiles closely • Closed-loop PID (proportional-integral-differential) temperature control using thermocouple and solid-state relay • Can hold oven temperature at any point in the range of 20-230°C (eg, for ‘baking’ components or curing paint/glue) 24 Silicon Chip siliconchip.com.au T here are several reasons that SMD components are becoming so common, to the point that it’s becoming very difficult to avoid them. It is due to the need to make products ever smaller, and the lower cost of mass manufacturing these parts and the boards that use them. As a result of these and other factors, most manufacturers do not release new components in anything but surface-mount packages. If you have young eyes, a microscope or good magnifying glass and some patience, this is not such a problem. So while we are conscious that surface mount devices (SMDs) present a challenge to some, we use them where we need to. But some of the smaller packages present a real challenge, especially those with thermal pads in the middle of the device, and leadless packages to name a very annoying few! These cannot be soldered with a regular iron. If you see yourself building projects with SMD parts and especially the pesky ones that do not lend themselves to hand SMD soldering techniques, then this project is for you. Alternatively, if you are looking for a simple way to control the temperature of an electrically heated oven, this is also a very handy device for that job. Working with SMDs We have, at times, used a hot-air blower on the device, to heat it and the board until a thermal pad under an IC reflows. This generally works, but it’s a bit of a hit-and-miss method, requires quite a bit of skill, and can regrettably lead to the demise of expensive chips! Not only that, but a hot-air blower invariably tries to blow the SMDs out of position! In commercial manufacture, these devices are generally ‘reflow soldered’ in one form of oven or another. This project presents a more controlled alternative to our brute force methods. It follows in the footsteps of others who have repurposed a toaster oven as an SMD reflow oven (eg, as described in our March 2008 article on “How to solder surface-mount devices”; siliconchip.com.au/Article/1767). What is reflow soldering? Reflow soldering is a process where solder paste is applied to the pads on a PCB, the SMD components are loaded onto this paste, and the entire PCB goes into a reflow oven. This subjects the board to a temperature profile that heat soaks the components, then briefly bumps the temperature up to melt and ‘reflow’ the solder paste. The entire process in a commercial environment is automated, with robots loading the components and the reflow oven having sophisticated thermal control and the ability to ramp the temperature up and down from the reflow point very quickly. While that’s nice, you don’t need all that complicated a rig to get a good result. This project repurposes a regular toaster oven to allow you to reflow one or several boards. We are using tin/lead solder, and recommend that you use this too, due to its lower temperature requirements. It may be possible to use such a rig with lead-free solder, but we haven’t tried it. This allows you to solder pretty well any SMD to a PCB, and to handle those pesky devices with heat spreaders and LCC packages. It works just as well for your usual resistors, capacitors and semiconductors. And the great thing siliconchip.com.au This project uses hardware which was previously used in the DSP Crossover (May-July 2019: siliconchip.com.au/Series/335 siliconchip.com.au/Series/335). ). However, the firmware loaded into the PIC32 microcontroller is, naturally, quite different. Pre-programmed chips, along with the PCBs required are available from the SILICON CHIP ONLINE SHOP (siliconchip.com.au/Shop siliconchip.com.au/Shop). ). Most of the other components should be easily obtainable from your favourite parts supplier, although there are a few specialised components whose sources are shown in the parts list. What is PID? There are many ways to control a temperature. The simplest is to switch the heater on if the target is below the setpoint, otherwise, switch it off. This is sometimes called “bang-bang” control; it is either flat out or off. This works, but is subject to errors and lots of overshoot, as it does not consider how far the sensed temperature is from the setpoint, nor how fast the temperature is approaching the setpoint. A proportional/integral/differential (PID) controller addresses these shortcomings. It has parameters for: • Proportional control, ie, linearly related to the difference between the two temperatures. • Differential control, ie, how fast the temperature is changing; this affects how hard we drive the temperature. This uses the rate-of-change of temperature to minimise overshoot. • Integral control, ie, looking at how much the sensed temperature missed the target. We integrate the error in temperature and feed this into the algorithm to ‘trim’ the error out long-term. This seems complex, but don’t worry. The supplied software handles all the details, and comes with a good initial set of parameters which give you a decent starting point. The main reason we’re using PID control is to minimise temperature overshoot. The toaster oven has a lot of thermal mass, as does the heating system, so it is slow to respond. Once the element has been on for a while, after you switch it off, the temperature keeps rising for quite some time. This makes a ‘bang-bang’ controller very prone to overshoot. The differential term in the PID controller helps us tame this. Despite this, it’s likely that your oven will still experience some overshoot. This can happen for several reasons; it may be that the PID parameters used are not ideal, but the fact is that the parameters can really only be tuned properly for a single temperature. Given that it’s crucial to avoid overshoot at higher temperatures, you’re more likely to experience it at lower temperature set points. The controller’s user interface lets you adjust the PID variables to tune the controller for various ovens. Inside our controller software, we have put modifications into the PID controller settings that reduce the drive and increase the damping for temperatures below 100°C, in an attempt to mitigate the aforementioned low-temperature overshoot problem. We also disable PID control for the last ‘reflow sprint’, to get this over with as quickly as possible. The result is that the errors are relatively small; certainly, a lot less than a ‘bang bang’ controller would produce. Australia’s electronics magazine April 2020  25 PID REFLOW OVEN CONTROLLER USER INTERFACE THERMOCOUPLE AMPLIFIER ROTARY ENCODER PUSH BUTTON OVEN CONTROLLER (PIC32MZ) CON10 CON8 128 x 64 PIXEL LCD K TYPE THERMOCOUPLE TTL CONTROL CON5 9V DC SOLID STATE RELAY (OPTO ISOLATED) 230V MAINS INPUT SWITCHED 230V TOASTER OVEN Fig.1: a block diagram showing the basic operation of the DIY reflow oven. The oven temperature is sensed by a thermocouple placed within, and this is fed back to the PIC-based controller board via a thermocouple amplifier. It then controls the temperature by switching the oven element on or off via a mains-rated solid-state relay (SSR). is that you can solder many components at once; a whole board (or even a few) is possible, depending on the design. We should point out here that some board designs may not be suitable for reflow soldering. It’s generally best to have a consistent amount of copper across the PCB to use this technique. A board with a large ground plane on one side and sparse tracks on the other will not heat evenly, and so you could end up with unmelted solder paste at one end, or in the worst case, a burnt PCB at the other! Having said that, a great many SMD-populated boards can be soldered in a reflow oven. So it’s a very useful tool. The simple method With a stopwatch, a K-type thermocouple and some practise, it is possible to work out an “on/off” timing sheet that you can use to reflow SMDs manually. But this is a bit hit and miss, and if you have a moment of inattention, things can come unstuck. This project takes the guesswork out of using an oven for reflow, and the controlling computer should not have any moments of inattention! What is it? I have designed a proportional-integral-differential (PID) controller which oversees the oven heating, with user-defined heat soak and reflow temperatures. I have determined the PID coefficients that work for my test oven, but they are ‘tunable’ for your oven (you may find that my values work fine). The basic configuration of the device is shown in the block diagram, Fig.1. The control block at left is built using a PIC32MZ-based microcontroller board that we have used in two projects already (more on that later). It senses the oven temperature using a K-type thermocouple and a prebuilt thermocouple amplifier module. A solid-state mains relay controls the oven heating elements, and it’s rounded off by an LCD so you can see what’s going on, and a basic power supply. In the development process, I pulled a couple of ovens 26 Silicon Chip SC 2020 apart intending to integrate the controller into the oven itself. This is definitely possible, and experienced constructors may take this approach. But for this project, we have chosen to present a standalone controller for a few reasons. Firstly, once you are inside the oven, you are presented with a lot of exposed live parts, and every oven will be different, so it’s difficult for us to describe how to do this safely. Secondly, there is generally no insulation between the oven wall and the equipment space behind the controls. Typical PVC wiring is rated to 70°C. While some types of wire can operate at higher temperatures, they still cannot withstand the temperatures at which the oven operates. So you would have to choose carefully where to mount the controller, and insulate it thoroughly against heat. Note that the oven manufacturers utilise fibreglass-insulated wiring and crimp/weld connections exclusively. This is a good choice for an oven but not conducive to DIY modification. So we decided to leave the oven completely unmodified. One of the nice features of this controller, besides the ability to follow a reflow-soldering profile, is the ability to accurately bring the oven up to a set temperature and hold it there. Now that I have this feature, I often use it for curing paints and glues at 60°C. If you recall your chemistry lessons, for every 10°C (or 10K) increase in temperature, chemical reactions typically double in speed. I’m impatient, so using the oven to fastcure paints and glues is hard to resist! Note that many SMDs also require you to bake them at a particular temperature for a particular time before soldering if their packages have been open for more than a few hours/days/weeks. This is usually printed on the packaging. So this oven is ideal for doing that too. Limitations There are one or two limitations that we have accepted in this project: • The choice of oven limits the temperature ramp rate. Australia’s electronics magazine siliconchip.com.au This is to whet your appetites ready for next month (when we’ll assemble the various components into the case). Note that this photo was taken BEFORE the Presspahn safety shield was installed. For your continued health, it must be included! We chose a 1500W oven, and it works well. We recommend that you use an oven with a similar power rating. • Convection ovens are a touch more expensive. We tried both and found convection ovens to be a better choice, but not by enough to recommend that you spend the extra cash. One limitation of a convection oven is that, unless you modify the oven, when we switch the element off, the convection fan also switches off. • We have not built a “door opener”. At the end of the reflow cycle, professional ovens cool the board reasonably quickly. In this project, you need to open the door of the oven a crack yourself. This results in a cool-down that is remarkably close to the recommended temperature profile. One advantage that we did note when using convection ovens (which are basically toaster ovens with fans) is that they have reduced overshoot at low temperature settings. That is not a big deal for SMT reflow but makes a surprising difference if you’re running the oven at lower temperatures, like 60°C, for drying paint or curing glue faster. However, to get this benefit, you need to modify the oven so that it has a separate mains supply for the fan, to allow it to run all the time and not just when the heating element is on. Because of the safety implications of doing that, we suggest that only experienced constructors with plenty of mains wiring experience take on this job. siliconchip.com.au The overshoot on a non-convection oven going from 20°C to 60°C is about 10°C, while for a convection oven with the fan wired to run constantly, it is closer to 3°C. Setting the PID parameters to avoid this with a non-convection oven would result in super-slow heating times. Safety This project has been developed to minimise the amount of mains wiring that you need to do. The only mains wiring we need to do is to connect the solid-state relay in the controller to a dual IEC mains socket. All other parts of this project operate from a 9V plugpack, so most of the assembly work is easy and safe. Choosing an oven We bought the toaster oven shown here from Kmart. You need an oven with manual control, a mechanical timer, dual elements (top and bottom), a minimum power of 1500W, with no LCD or other electronic controls. If you can get a convection oven that matches these requirements without spending much more money, then do so. Our oven cost $59. If you feel tempted to spend much more than $100, check yourself, as you might be buying something beyond what is needed. The thermocouple Thermocouples are the ‘go-to’ device for measuring high Australia’s electronics magazine April 2020  27 Fig.2: the circuit of the control board. 32-bit microcontroller IC11 derives its internal clock from 8MHz crystal X2 and has numerous supply bypass capacitors. It runs from a regulated 3.3V supply 28 Silicon Chip Australia’s electronics magazine siliconchip.com.au provided by adjustable low-dropout regulator REG2. EEPROM IC12 is used to store the settings (PID parameters, temperatures settings etc). The graphical LCD is connected via CON8, the front panel controls via CON11 and the thermocouple and SSR via CON10. siliconchip.com.au Australia’s electronics magazine April 2020  29 4.7k R1 4.7k R2 S2 SELECT S1 EXIT TO PORTE CON20 3.3V 1 5 PS0 PS1 ROTARY ENCODER 4 B COM 2 A 3 2 2 3 4 5 6 7 8 9 10 1 RE1 (PS0 & PS1 NOT PRESENT ON ALTRONICS ENCODER) 4.7k R3 4.7k R4 22nF 22nF FOR ENCODER TYPE 1 (Simple Grey Code per click): FIT R3 & R4 FOR ENCODER TYPE 2 (One complete cycle of Grey Code per click): FIT R1 & R4 FOR ENCODER TYPE 3 (Three changes in phase per click): FIT R2 & R3 SC 20 1 9 solder reflow oven FRONT PANEL CIRCUIT temperatures. Thermocouples rely on the thermo-electric effect of two dissimilar metals in contact. A K-type thermocouple has wires made of chromel (nickel/chromium) and alumel (nickel/aluminium/manganese and silicon). These are standard and very interchangeable. They work to well over 1000°C, plenty for this application. A thermocouple amplifier interface module is also needed. It converts the tiny voltages the thermocouple generates to a higher voltage that we can measure with the PIC. It also performs ‘cold junction’ compensation. Just as the thermocouple generates a voltage from the dissimilar metal junction at its tip, it also generates a voltage where the chromel and alumel wires join our controller. The thermocouple amplifier has a built-in compensation for this (which depends on its own temperature). This meant that if you need the ultimate precision, you will need to connect the thermocouple wires straight to the thermocouple amplifier, and not use plugs as shown in our project (Jaycar also has a thermocouple without the plugs, Cat QM1823). We bought our K-type thermocouple on ebay for just over one dollar – including postage! Fig.3: the components shown here mount on a front-panel board that allows you to control the unit. Rotary encoder RE1 and pushbutton S1 connect back to the control module via CON20. S2 is only required if you use a rotary encoder without an internal switch. The capacitors debounce the rotary encoder signals. But we think this compromise is OK, as the error from using the plugs and sockets is small. Incidentally, the thermocouple amplifier we used has a purple PCB. If you search ebay or AliExpress for “AD8495”, then you should be able to find one which looks like ours. Note though that some of these devices come with the wrong reference voltage; we’ll explain later how to fix that if it happens. We want a board that uses a 1.25V offset for 0°C. If yours is 2.5V instead, it will not work. The simple fix for this is short the AD8495 reference pin (pin 2) to ground (pin 3), effectively making the reference 0V. The SSR We used an Altronics S4416A solid state relay, rated at 40A. This is ideal, although a 20A mains-rated SSR would theoretically be sufficient. The other thing to check for is to make sure that your SSR (like the Altronics one) will work with a 3.0-3.6V control voltage. Our PIC will drive it with a nominal 3.3V DC to switch it on. The controller The controller is based the same 32-bit PIC microcontroller board, LCD screen and set of controls that we used previously in a couple of projects. The front panel components (as per the circuit of Fig.3) ready for assembly into the case as seen earlier. 30 Silicon Chip Australia’s electronics magazine siliconchip.com.au Namely, these are the DSP Active Crossover and 8-channel Parametric Equaliser (May-July 2019; siliconchip.com. au/Series/335) and Low Distortion DDS Signal Generator (February 2020; siliconchip.com.au/Article/12341). The controller module is a lot more powerful than needed, but takes advantage of the graphical user interface (GUI) that I already created for those projects, along with other storage and control code. So it saved a lot of development time, and you at least get a nice user interface. To this, I added a K-type thermocouple amplifier I bought from ebay for less than $10 including delivery, along with a 40A solid state relay (SSR). With these few additions, we have ourselves the makings of a pretty capable oven controller. The CPU board circuit is shown in Fig.2. We won’t describe this in great detail, partly because we already described it in the June 2019 issue (starting on page 77) but mostly because, despite appearances, it’s relatively simple. It consists mainly of microcontroller IC11, two crystal oscillator circuits, an EEPROM chip, a simple power supply and a bunch of connectors for routing signals. The main change is in the firmware, which has been modified to implement the temperature control loop and to provide a real-time display of the temperature profile achieved. The overall function of the resulting controller is simple. In operation mode, the microcontroller reads the temperature about 10 times a second, and averages this over half a second. Every half-second, the PID control parameters are updated and the controller decides whether to switch the oven on or off. See the accompanying panel for a description on how PID temperature control works. In setup mode, you can save the settings, alter the PID 330 CON5 K 10 F The first job is to assemble the PIC32 microcontroller module. Its PCB overlay diagram is shown in Fig.4. Use this as a guide to which parts go where on the 60.5 x 62.5mm PCB, which is coded 01106193. Start with IC11, the 64-pin SMD microcontroller (it sure would be handy to have a reflow oven at this stage, DSP SPI1 LK1 8MHz LK2 470 F 1 * BOTH CAPS UNDER PCB OR LAID OVER ON TOP SIDE CON6 20 19 47 47 2 1 47 +7VDC Fig.4: use this diagram as a guide when assembling the control board. It’s easiest to fit the SMDs first, starting with the ICs. Watch the orientation of the ICs, diodes, electrolytic capacitors and regulators. Some components are not required for this application, including CON6, CON7, CON9 and CON12. siliconchip.com.au Construction V2.0, 2019-03-27 User interface PIC32MZ DSP S1 GRAPHICAL LCD LED 2 D16 + GND REG2 A 1 CON8 D14 FB12 X2 ALPHA LCD 100nF 390 10 F 1.2k 20pF GND 470 20pF 330 10 F CON23 ICSP 1 470 SD04 100nF 560VR1 10k 100nF 10 F 1 CON10 IC11 PIC32MZ 2048 EFH064 10k 100 100nF RDO X1 100nF 32768Hz 100nF REG3 PORTB 20pF100nF 20pF20pF 20pF 100nF PORTE D15 10 F –I/SN IC12 CON12 100nF 100nF 1 CON11 1 parameters, set the temperatures for heat soak and reflow, or set the thermocouple temperature coefficient and offset. Fig.3 shows what’s on the front panel control board that connects to the CPU board via a ribbon cable. Rotary encoder RE1 (with integral switch) and switch S1 allow the user to step through menus, select options and alter values. Switch S2 is only needed if an encoder is used without an internal switch. The capacitors are for debouncing while the resistors, two of which are omitted, tell the CPU what type of encoder was used. CON7 25AA256 1k 100nF SPI2/I2S JP5 1k VEE CON9 1 The assembled control board, ready for installing in the case. As noted below, some connectors are not used in this project. S2 RE2 SILICON CHIP 22nF* 22nF* 4.7k 4.7k 4.7k 4.7k R4 R2 R1 R3 1 RE1 01106195 RevB CON20 (UNDER) DSP Crossover front panel board Fig.5: the front panel PCB. Note that only one of RE1 (Jaycar SR1230) or RE2 (Altronics S3350) is fitted and in the case where RE1 is used, pushbutton S2 is redundant and may be left off. Also, if RE1 is fitted, fit resistors R2 and R3; if RE2 is fitted, fit resistors R1 and R4. SILICON CON21 Fig.6: this small adaptor board CHIP converts the SIL header on the LCD (UNDER) 1 screen to a DIL header for connecting 1 CON22 to an IDC ribbon cable. The connectors are mounted on opposite sides; make sure the pin 1 connection at both ends is at the same end, as shown. Australia’s electronics magazine April 2020  31 Parts list – Reflow Oven Conversion 1 260 x 190 x 80mm plastic instrument case [Altronics H0482] 1 200 x 115mm sheet of 1.5mm-thick aluminium 1 205 x 185mm sheet of Presspahn or similar [Jaycar HG9985] 1 K-type thermocouple with banana plugs [Jaycar QM1284] 1 AD8495-based K-type thermocouple interface with purple PCB [eBay/AliExpress] 1 populated PIC32MZ CPU board - see below 1 populated front panel control board - see below 1 128 x 64 pixel graphical LCD with 20-pin connector 1 10A dual (male/female) chassis-mount IEC power connector [Altronics P8330A] 1 9V DC 2/3A regulated plugpack with 2.1mm inner diameter plug [Altronics M8923] 1 2.1mm inner diameter chassis-mount barrel socket [Altronics P0628] 1 red binding post/banana socket [Altronics P9252, Jaycar PT0453] 1 black binding post/banana socket [Altronics P9254, Jaycar PT0454] 1 double-sided PCB, coded 01106196, 51 x 13mm 1 40A 24-240VAC solid-state relay (SSR1) [Altronics S4416A] 1 SPST, SPDT or DPDT 12V DC, 1A toggle switch (main power switch) 1 IEC C14 male to 3-pin mains socket [Jaycar PS4100] 1 IEC mains power cable [Jaycar PS4106] 1 15x2 pin header 1 20-pin header 2 20-pin IDC line plugs 3 10-pin IDC line plugs 1 small tube of neutral-cure silicone sealant 1 small tube of heatsink (thermal) paste Cables & hardware 4 M3-tapped 15mm Nylon standoffs 8 M3-tapped 10mm Nylon standoffs 25 M3 x 15mm panhead machine screws 25 M3 x 6mm panhead machine screws 25 M3 star/lock washers 10 M3 hex nuts 8 5mm red eyelet crimp connectors [Altronics H2041A] 1 20cm length of three-core 10A mains flex 1 50cm length of red light-duty hookup wire 1 30cm length of black light-duty hookup wire 1 30cm length of green light-duty hookup wire 1 25cm length of 20-way ribbon cable 2 25cm lengths of 10-way ribbon cable 1 6cm length of 40-50mm diameter clear heatshrink tubing wouldn’t it!). Make very sure that it is orientated correctly before soldering its leads. You can purchase this micro pre-programmed with the software for this project (2910420A.HEX) from the SILICON CHIP ONLINE SHOP. Otherwise, the required HEX file is available for download from our website. So if needed, you can program the PIC using a PICKit 3 programmer once the board has been assembled (see Fig.10 for the slightly unusual wiring required). Tack down a couple of pins and make sure that all of its pins are correctly located over their pads before applying 32 Silicon Chip 1 50cm length of 10mm diameter clear heatshrink tubing 1 30cm length of 8mm diameter clear heatshrink tubing cable ties as required PIC32MZ CPU board parts 1 double-sided PCB coded 01106193, 60.5 x 62.5mm 1 2-way mini terminal block, 5.08mm spacing (CON5) 5 5x2 pin headers (CON7,CON9-CON11,CON23) 1 10x2 pin header (CON8) 2 3-pin headers (LK1,LK2) 1 2-pin header (JP5) 3 shorting blocks (LK1,LK2,JP5) 1 ferrite bead (FB12) 1 32768Hz watch crystal (X1) 1 miniature 8MHz crystal (X2) OR 1 standard 8MHz crystal with insulating washer (X2) 1 10kΩ vertical trimpot (VR1) 1 TO-220 flag heatsink (for REG2) [Altronics H0630] Semiconductors 1 PIC32MZ2048EFH064-250I/PT 32-bit microcontroller programmed with 2910420A.HEX, TQFP-64 (IC11) 1 25AA256-I/SN 32KB I2C EEPROM, SOIC-8 (IC12) 1 LD1117V adjustable 800mA LDO regulator, TO-220 (REG2) 1 LM317T adjustable 1A regulator, TO-220 (REG3) 1 blue SMD LED, SMA or SMB (LED2) 3 LL5819 SMD 1A 40V schottky diodes, MELF (MLB) (D14-D16) Capacitors 1 470µF 10V electrolytic 5 10µF 50V electrolytic 11 100nF SMD 2012/0805 50V X7R 4 20pF SMD 2012/0805 50V C0G/NP0 Resistors (all SMD 2012/0805 1%) 1 10kΩ 1 1.2kΩ 2 1kΩ 2 470Ω 1 390Ω 2 330Ω 1 100Ω 3 47Ω 1 560Ω Front panel control board parts 1 double-sided PCB coded 01106195, 107.5 x 32.5mm 1 5x2 pin header (CON20) 2 4.7kΩ 1/4W through-hole resistors 2 22nF through-hole ceramic capacitors 2 PCB-mount snap-action momentary pushbuttons (S1,S2)* [Jaycar SP0721, Altronics S1096] 1 3-pin rotary encoder (RE1/RE2) [eg, Altronics S3350 or Jaycar SR1230 with integrated pushbutton] 1 knob (to suit RE1/RE2) * only one required if using Jaycar SR1230 encoder flux paste and soldering the rest. Solder bridges are almost inevitable if hand-soldering, but these can be cleaned up with the application of more flux paste and some solder wick. Follow with the other SMDs, making sure that IC12 and the diodes are orientated correctly. You don’t need to fit CON6 for this project. Next, fit the through-hole components; don’t get REG2 and REG3 mixed up and note that REG2 now has a small flag heatsink fitted. When mounting X2, if there is any chance of the bottom of its metal package shorting to components below, fit an insulating washer underneath. CON12 Australia’s electronics magazine siliconchip.com.au Dimensioned diagrams for drilling this plate, the front and rear panels and drilling/cutting the Presspahn safety shield can all be downloaded from www.siliconchip.com.au can be left off. You can now move onto building the front panel control board. Its overlay diagram is shown in Fig.5. The PCB is coded 01106195 and measures 107.5 x 32.5mm. There isn’t a lot to assembling it; if you’re using the recommended Jaycar SR1230 rotary encoder, besides that part, you just need one pushbutton (S1), two capacitors, two resistors (R2 & R3) and header CON20. The capacitors and CON20 are mounted on the underside, with the caps laid over. Now is also a good time to solder the two headers to the small board coded 01106196 which measures 51 x 13mm, shown in Fig.6. The SIL header goes on one side and the DIL header on the other. Then solder its SIL header to the LCD module, with this board mounted on the back. Next, make up the two ribbon cables. One has 20 wires, and one has 10 wires. They are the same length; see Fig.7 for details. Cut each section of the ribbon cable to length, leaving around 5cm extra in each case for crimping to the connectors. You can strip these cables out of ribbon cables with more wires, by making a small cut between two wires and then separating the sections by pulling them apart. It’s best to use a dedicated IDC crimping tool for this job, such as Altronics T1540. You can use a vice, but you have to be careful to avoid crushing and breaking the plastic IDC connectors. Each connector has three parts: the bottom part, which has the metal blades that cut into the ribbon cable; the middle part, which clamps the cable down onto these; and a locking bar at the top that holds it all together once it has been crimped. Note how, as shown in Fig.7, the cable passes between the locking bar and upper part before folding over on the outside edge and then being crimped underneath. So with this in mind, slightly separate the three pieces without actually taking them apart, and feed the ribbon cable through as shown. Ensure there is enough “meat” for the metal blades to cut into, then place it into your crimping tool or vice without allowing the cable to fall out. Clamp the three pieces together, gently at first, then more firmly. The trick is to crimp it hard enough to ensure that the blades cut fully through the insulation and make good contact with the copper wires, without pressing so hard that you break the plastic. If using a vice, it’s best to wedge a piece of cardboard between each end of the connector and the vice, to provide some cushioning. Once you’ve crimped a connector at one end of the cable, do the one at the other end, making sure that when you’re finished, the locating spigots will both be facing in the same direction. In the second and final part of this project, which will appear in our May issue, we’ll cover the steps involved in putting the controller in a case and safely checking that all is operating correctly. We’ll also have a list of troubleshooting suggestions in the unlikely even that you cannot get your controller to . . . control! But in the meantime, you can gather all the components, PCBs and everything else you need. SC Don’t forget the oven! LOCATING SPIGOT UNDER 1 0 -WAY IDC SOCKET 1 0 -WAY IDC SOCKET 1x200mm 1 0-WAY IDC RIBBON CABLE CABLE EDGE STRIPE LOCATING SPIGOT UNDER 20-WAY IDC SOCKET 20-WAY IDC SOCKET 1x200mm 20-WAY IDC RIBBON CABLE siliconchip.com.au Fig.7: you need to make two ribbon cables: one to connect the front panel to the CPU board, and the other to connect the LCD. Note the orientation of the connector tabs, so that pin 1 is aligned with the red stripe at both ends. Make sure the IDC blades are pressed down hard enough to fully pierce the insulation and make good contact, but not so hard that you crack the plastic! CABLE EDGE STRIPE Australia’s electronics magazine April 2020  33 A 900MHz Touchscreen Vector Network Analyser for less than $60.00? It wasn’t long ago that a Vector Network Analyser (VNA) would cost as much as a car, or more. But now you can buy one for peanuts: this one was under $AU55 delivered! In case you don’t know, a VNA can be used to test and analyse antennas, transmission lines, filter networks and other RF-related passive networks. So it’s a very useful instrument to have if you are doing any RF work at all. T his little device was only released recently, but it already has countless fans, umpteen discussion groups and hours of YouTube videos showing how to use it – by people from novices to super experts. The NanoVNA is available from many sellers on ebay and AliExpress, so as long as you are willing to wait a little while for it to arrive from China, it isn’t hard to purchase your very own VNA. By the way, VNAs aren’t just useful for radio engineers. High-speed digital buses can have very high edge rates that translate into frequency components in the multi-GHz range. So a good VNA can be used to characterise such buses, assuming you know how to use it! As the name suggests, the NanoVNA is small, measuring just 85 x 54 x 16mm and weighing 73.5g. It’s powered by an internal 400mAh lithium-polymer battery that’s recharged from a 5V USB source, and has a colour touchscreen interface and two SMA connectors for interfacing to the outside world. The only other adornments are an on/off slide switch and left/right ‘joy- stick’ pushbutton for control. Ours came with three SMA terminators: open, closed and 50Ω, plus a USB Type-C cable for charging the internal battery and for connecting to a computer. The SMA terminators are required to calibrate it, and this there were quite a few holdouts still using type-B connectors until recently, and plenty of random devices still use the B types. Is this a harbinger that type-C connectors are becoming more standard now? Anyway, for some handy Joe Smith tips regarding the physical handling, calibration and connecting to USB software, see this video: https://youtu.be/ mKi6s3WvBAM What is a VNA? should be done regularly. Some sellers also include a short SMA cable, but ours didn’t come with one. As an aside, this is one of the first ‘el cheapo’ devices we’ve seen with a USB type-C micro socket on it. This has been the ‘new standard’ for smartphones for some time now, but Vector Network Analysers are one of the predominant lab/field instruments used for RF and microwave design purposes. They are ideally used to test the response of DUTs (devices under test) as a function of frequency. Fig.1 shows the basic arrangement of a VNA. It applies a swept frequency signal source to one end of the DUT, and measures the amplitude and phase of the signals at both ends of the DUT relative to a separate fixed reference signal source (the “local oscillator”). These measurements are often made by mixing the local oscillator and test signals to get a sum and difference Review By Allan Linton-Smith 34 Silicon Chip Australia’s electronics magazine siliconchip.com.au signal, then feeding this through a low-pass filter to isolate the difference signal. The resulting signal (which is much lower in frequency) then goes to an analog-to-digital converter. By using three such receivers, and digital signal processing, the VNA can measure the amplitude and phase of the original, transmitted and reflected signals and thus fully characterise the DUT. The DUT can be a passive or active device. Examples of passive devices that can be tested by a VNA are cables, filters, splitters, connectors, couplers and antennas. Active devices for testing this way can be RF amplifiers, RF filters and semiconductors. The NanoVNA is basically a sweep generator which can measure the reflected signal and calculate the amplitude, phase, standing wave ratio (SWR), impedance, capacitance and inductance all at the same time! The primary signal from the internal sweep generator output is fed to the DUT, and the reflected signal is compared to the transmitted signal. The power ratios (actually, their square roots) vs frequency are then processed. Much information can be obtained from the results, including: • losses (such as cable and antenna losses) • standing wave ratios • impedance (at very high frequencies) siliconchip.com.au A OR B SIGNALS FROM DIRECTIONAL DEVICES MIXER DIGITAL SIGNAL PROCESSOR LOW-PASS FILTER ANALOG TO DIGITAL CONVERTER LOCAL OSCILLATOR SC GENERIC VNA RECEIVER BLOCK DIAGRAM SIGNAL SOURCE 2020 DIRECTIONAL COUPLER DIRECTIONAL COUPLER TEST PORT 1 TEST 1 REFERENCE MIXER MIXER ADC IF AMP ADC IF AMP LOCAL OSCILLATOR IF AMP TEST 2 ADC TEST PORT 2 MIXER TRANSMISSION/REFLECTION VNA BLOCK DIAGRAM SC 2020 Fig.1: an overview of how a typical VNA works. The receiver block at top is repeated three times in the diagram below (dashed red outlines), to measure the test signal and the signals at either end of the DUT relative to a common reference signal (local oscillator). A digital signal processor (DSP) crunches the numbers from these three receivers to generate useful plots which describe the RF behaviour of the DUT. Australia’s electronics magazine April 2020  35 Fig.2: this plot shows out the signal generator built into the NanoVNA cannot deliver anywhere near as much amplitude over the 300-900MHz range as compared to the 54-300MHz range. So measurements made above 300MHz will likely contain a lot more noise than those at lower frequencies. • capacitance • inductance • phase information This is all highly useful to designers of RF circuits, antennas and HF or microwave devices. The low cost of this particular unit finally makes such tests easily accessible to amateurs and experimenters. VNAs can also be useful test instruments for tracking down faults and, as we discovered, it can also double as an accurate and convenient RF frequency generator. The NanoVNA manufacturer claims that it makes these measurements at up to 900MHz, although it really is only fully effective to 300MHz, as we shall demonstrate. One of the disadvantages of the VNA is that it makes all measurements in the frequency domain, unlike an oscilloscope, which measures in the time domain. So the information gleaned from the VNA must often be translated into the time domain to be useful. signal level is still high enough to give useful qualitative information up to 900MHz. This plot was obtained by feeding the NanoVNA’s output into a spectrum analyser which was set to “maximum hold”, thus memorising a succession of all the maximum points. The roughness of the graph from 300-897MHz is merely an artefact where the analyser sweep has not coincided with the generator sweep, because the analyser sweep is much slower (66ms). Due to the number of points and the sweep time, this measurement took several hours to make! You can use the NanoVNA as a reasonable accurate frequency generator. Fig.3 shows a spectrum analysis of the unit’s output when set to 250MHz; we measured a peak noise reading of -115dBm at an offset of 100kHz offset from 250MHz fundamental. This noise level is quite acceptable, being around 100dB below the signal level. To set it up for a fixed frequency output like this, you merely set identical start and stop frequencies, or select a single frequency from the menu. As shown in Fig.4, we detected signals up to around 1.2GHz, which are the harmonics of lower frequencies when the NanoVNA was set to sweep over its full range. -4.91dBm at 1.2GHz is 127mV into 50Ω. Some sellers are charging upwards of 5x the price for Nanos which have supposedly been extended to 1GHz, so look out! Conclusion While the NanoVNA has some limitations compared to a multi-thousanddollar instrument, it is nonetheless a Tests Fig.2 shows our measurement of the output signal level from the NanoVNA generator over the range of 54897MHz. The output is not linear and drops significantly, by about 9-11dB, above 300MHz. We believe that the 36 Silicon Chip Fig.3: a spectrum analysis of the test signal fixed at 250MHz. This indicates that the test signal is very clean, with noise levels around 100dB below the signal itself. So it could be quite useful just as an RF signal generator. Australia’s electronics magazine siliconchip.com.au very useful device. Anyone working with RF circuitry or antennas will likely find it well worthwhile, especially considering the price. It helps to be aware of its limitations to make full use of it; you will likely also have to do a fair bit of reading on the operation of VNAs to understand which modes to use and how to interpret the rather esoteric information and graphs displayed! Even if you only need a VNA occasionally, for little more than the price of a nice dinner, it’s hard to argue that the NanoVNA is not good value. You might as well get one ‘just in case’ you never need it... You may find the following links useful. * Beginners’ guide: siliconchip.com. au/link/ab0f * A video that would be useful to amateur enthusiasts: https://youtu. be/8kx9SWbEcXI * A complete guide to and mathematical explanations of VNA operation: siliconchip.com.au/link/ab0g (or purchase the complete book, “The VNA Applications Handbook”). SC Fig.4: this plot shows spurious signals in the 900-1200MHz range, generated during a sweep across its normal 54-900MHz test range. These are presumably from test signal harmonics. So the device may not be very useful above 900MHz, even if it could generate test signals that high. AUSTRALIA’S OWN M I CR O M I T E TOUCHSCREEN Since its introduction in February 2016, Geoff Graham’s mighty Micromite BackPack has proved to be one of the most versatile, most economical and easiest-to-use systems available – not only here in Australia but around the world! Now there’s the V3 BackPack – it can be plugged straight into a computer USB for easy programming or re-programming – YES, you can use the Micromite over and over again, for published projects, or for you to develop your own masterpiece! BACKPACK The Micromite’s BackPack colour touchscreen can be programmed for any of the following SILICON CHIP projects: Many of the HARD-TO-GET PARTS for these projects are available from the SILICON CHIP Online Shop (siliconchip. com.au/shop) Poor Air Quality Monitor (Feb20 – siliconchip.com.au/Article/12337) GPS-Synched Frequency Reference (Oct18 – siliconchip.com.au/Series/326) FREE Tariff Super Clock (Jul18 – siliconchip.com.au/Article11137) PROGRAMM Altimeter & Weather Station (Dec17 – siliconchip.com.au/Article/10898) ING Buy either tell us whichV2 or V3 BackPack, Radio IF Alignment (Sep17– siliconchip.com.au/Article/10799) for and we’ll project you want it Deluxe eFuse (Jul17 – siliconchip.com.au/Series/315) program it fo r you, FREE OF C DDS Signal Generator (Apr17 – siliconchip.com.au/Article/10616) HARGE! Voltage/Current Reference (Oct16 – siliconchip.com.au/Series/305) Energy Meter (Aug16 – siliconchip.com.au/Series/302) Super Clock (Jul16 – siliconchip.com.au/Article/9887) Micromite Boat Computer (Apr16 – siliconchip.com.au/Article/9977) V 3 BackPack: Ultrasonic Parking Assistant (Mar16 – siliconchip.com.au/Article/9848) * JUST $7500 See August 2019 (Article 11764) P&P: Flat $10 PER ORDER (within Australia) *P Price is for the Micromite BackPack only; not for the projects listed. siliconchip.com.au Australia’s electronics magazine April 2020  37 By John Clarke 7-Band Stereo Stereo These stereo or mono 7-Band Equalisers let you tailor the sound of your listening experience to suit your preferences. They can also be used to correct for room acoustics and deviations in loudspeaker response. The stereo version suits hifi systems, while the mono version is best for musical instruments or PA systems. Both feature extremely low noise and distortion, so they won’t degrade your signal. W e published a 5-Band Equaliser way back in December 1995 that was intended for musicians, which could be installed within an amplifier. That design was so popular that it is still sold as a kit by Altronics (Cat K5305) to this day – a quarter of a century later!! While we published an excellent 10-Band Stereo Graphic Equaliser much more recently, in the June & July 2017 issues (siliconchip.com.au/Series/313), that design is considerably more complex and more expensive to build. And the slide pots do not lend themselves to being fitted +20 7-Band Equaliser Frequency Response into an existing amplifier. Besides, for musical instrument use, you generally don’t need the stereo function. Hence, we decided to come up with a new design, similar to the one from December 1995 but modernised and upgraded. We’ve added two more bands, giving finer control over the sound, and while we were at it, we also designed a stereo version. We are still using similar rotary pots, making it easy to mount in an existing amplifier (provided there is space). As a bonus, they’re cheaper than slide pots. We’ve also made the power supply much more flexible, 26/01/20 13:01:58 .01 +10 +5 0 -5 -10 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.1: the blue curve shows the frequency response with all controls set to the centre position, with a flat response across Fig.1 the 20Hz to 20kHz band. The red and green curves show the response with all pots in the maximum boost setting (red) and with all pots in the maximum cut setting (green). Finally, the purple and orange curves show the response with alternate full cut and full boost between each band. 38 .002 .001 .0005 .0002 -15 -20 26/01/20 14:28:22 2V stereo (L) 22kHz bandwidth 2V stereo (R) 22kHz bandwidth 2V mono 22kHz bandwidth 2V mono 80kHz bandwidth 1V mono 80kHz bandwidth .005 Total Harmonic Distortion (%) Relative Amplitude (dBr) +15 7-Band Equaliser THD vs Frequency Silicon Chip .0001 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.2: the harmonic distortion performance is excellent with less than 0.0006% distortion at 2V from 20Hz to 20kHz Fig.2 measured with a 22kHz low pass filter. Even with an 80kHz filter, distortion does not rise above 0.001% for a 2V signal. Noise was measured at 108dB down with 2V as a reference level. The 0.0005% distortion means that the noise and distortion measured is -106dB down in level from 2V. Australia’s electronics magazine siliconchip.com.au Mono or Equaliser so it can run from 15-16V AC, 30V AC with a centre tap, 18-20V DC or a regulated source of ±15V DC. Plus we have considerably improved the performance, giving it extremely low noise and distortion figures. Having different versions of the PCB for mono and stereo makes it easier to construct the version you want, and keeps the mono version as small as possible, keeping in mind the limited space that may be available for it to fit into. Perhaps surprisingly, the mono version of this 7-band equaliser, at 143 x 63.5mm, is smaller than the original -0 7-Band Equaliser Channel Separation 26/01/20 14:59:13 -10 Relative Amplitude (dBr) -20 -30 left-to-right coupling right-to-left coupling -40 -50 -60 -70 -80 -90 -100 20 50 100 200 500 1k 2k Frequency (Hz) 5k 10k 20k Fig.3: channel separation between Fig.3left to right channel (blue) and right to left channels (red) show that separation is worse for the left to right coupling as frequency rises. These graphs are for the stereo version only. Separation figures obviously do not apply with the mono version. siliconchip.com.au 5-band version, which used a PCB that measured 167 x 65mm. We’re presenting both versions of the 7-band equaliser as bare PCBs. All the components mount onto these PCBs, including the input and output RCA sockets; you just need to organise a case and power supply. Typical applications The stereo version of our new Equaliser can be connected to an amplifier or receiver in several ways. First, it can be connected in the “Tape Monitor” loop that’s still provided on many amplifiers and receivers. Alternatively, the equaliser may be connected between the preamplifier and power amplifier. Some home theatre stereo receivers include preamp output and power amp input connectors for this purpose. If you’re using a separate preamp or input switcher, then the equaliser can be interposed between it and the power amplifier. Or, if you only have a single sound source that has a nominal line level output level (anywhere between 500mV and 2V RMS), the equaliser input can be connected to that source output and preamplifier/amplifier input. For sound reinforcement use, you can connect the equaliser between the sound mixer output and amplifier input. In that case, you may need to add balanced-to-unbalanced and/or unbalanced-to-balanced converters on each channel. We published suitable designs for this in the June 2008 issue; see siliconchip.com.au/l/aacv Performance The overall performance is summarised in the Features & specifications panel and Figs.1-3. Its signal-to-noise ratio for a 2V RMS input is excellent at 108dB, and the distortion curves show that there is virtually no harmonic distortion Australia’s electronics magazine April 2020  39 STEREO LEFT INPUT: CON1 STEREO RIGHT INPUT: CON3 MONO INPUT: CON1 L1 L2 470nF STEREO LEFT IC9a STEREO RIGHT IC8b MONO: IC5b 1k 5 (3) OPA1642 8 10k 7 (1) FERRITE BEAD 100k 6 (2) 100pF 4 STEREO: 9 x 100nF CERAMIC CAPS (ONE BETWEEN PINS 8 & 4 OF IC1 – IC9) MONO: 5 x 100nF CERAMIC CAPS (ONE BETWEEN PINS 8 & 4 OF IC1 – IC5) 100pF (NOTE: SIGNAL CIRCUITRY SHOWN ONLY FOR MONO VERSION [GREEN] AND LEFT CHANNEL [BLUE]; COMPONENTS FOR RIGHT CHANNEL SHOWN IN RED) BOOST L: VR1a R: VR1b M: VR1 50k CUT 1 F 270nF 470nF 1.8k V+ 22nF 5 (3) 6 (2) CUT 33nF 7 (1) 2 (6) 100nF 1 (7) 6 (2) STEREO LEFT IC1b STEREO RIGHT IC1a MONO IC1b Silicon Chip 2 (6) 91k BOOST L: VR4a R: VR4b M: VR4 50k CUT 33nF 1.8k V+ 7 (1) STEREO LEFT IC3b STEREO RIGHT IC3a MONO IC2b 1 (7) 6 (2) 8 LM833 7 (1) 4 V– V– 2.5kHz 1kHz 82k L: VR5a R: VR5b M: VR5 V+ 5 (3) 8 LM833 10 1.8k 1nF 4 410Hz STEREO LEFT IC4b STEREO RIGHT IC4a MONO IC3a 68k STEREO LEFT IC5b STEREO RIGHT IC5a MONO IC3b Fig.4: the circuit for the mono version, minus the power supply (shown overleaf). The stereo version essentially duplicates all the parts for the second channel, except for the shared power supply and the use of dualgang potentiometers in place of single-gang. Green labels apply to the mono version, blue to the left channel portion of the stereo version and red, to present; the THD+N figures are consistent with pure noise. Fig.1 has several coloured response curves which show what you can do with the controls. The blue curve shows the frequency with all controls set to the centre position, giving a ruler flat response over the audio band of 20Hz to 20kHz (it’s tough to get it precisely flat due to pot variances, hence the slight amount of ripple visible). The red and green curves show the response with all potentiometers in the maximum boost and cut settings, respectively. The mauve and orange curves show the response with the potentiometers alternately set for maximum boost and cut; these show the effective width of each band. Note that you would never use an equaliser in these extreme settings as the result would sound very strange. Instead, you usually use comparatively small boost or cut settings. For example, if your loudspeakers are a touch too bright in the 6kHz region, you might apply a couple of decibels of cut to the respective potentiometer. Or if you wanted to lift the bass response at around 60Hz, you could apply some amount of boost on the 63Hz band and get a much more subtle effect than would be possible with a conventional bass control. The Equaliser’s overall performance is far beyond CDquality audio. Fig.2 demonstrates that the harmonic distor40 12nF V– 160Hz 7-BAND GRAPHIC EQUALISER CUT 3 (5) 4 STEREO LEFT IC2b STEREO RIGHT IC2a MONO IC2a 50k 2.2nF 8 LM833 V– 110k BOOST 68nF 1.8k V+ 4 63Hz SC CUT 4.7nF 8 LM833 L: VR3a R: VR3b M: VR3 50k 5 (3) V– 2020 BOOST 100nF 1.8k V+ 3 (5) 4 130k L: VR2a R: VR2b M: VR2 50k 10nF 8 LM833 BOOST 100nF 100nF 100nF 100nF V+ V+ V+ V+ tion performance is limited by the residual noise “floor” of the crucial gain stage in the circuit; that of IC9b and IC8a for the stereo version and IC5a in the mono version. With a realistic bandwidth of 20Hz-22kHz, the THD+N level is below 0.0006% for all audible frequencies. Even with 80kHz measurement bandwidth, there is virtually no rise in distortion at higher frequencies. While the plot does seem to have a small rise up to 0.001% at 20kHz, other measurements we’ve taken under similar circumstances did not have such a rise, so we think it is probably a measurement artefact. Suffice to say that the harmonic distortion introduced by this circuit is so far below that from a typical CD, DVD, Blu-ray or computer source that it will not adversely affect the sound quality of signals from such sources. Finally, Fig.3 shows the channel separation for the stereo version of the equaliser. It exceeds 50dB at all frequencies and for both channels, and is at least 80dB for signals up to 1kHz. Circuit details Fig.4 shows the circuit of our 7-Band Equaliser. This is the complete circuit for the mono version, minus the power supply. The stereo version essentially duplicates all the parts for the second channel, except for the shared Australia’s electronics magazine siliconchip.com.au V+ STEREO LEFT IC9b STEREO RIGHT IC8a OPA1642 MONO IC5a 3 (5) STEREO LEFT OUTPUT: CON2 STEREO RIGHT OUTPUT: CON4 MONO OUTPUT: CON2 1 F 470 1 (7) 1 F 2 (6) 1M 10k 1nF 8 V– BOOST 50k CUT BOOST L: VR6a R: VR6b M: VR6 CUT 4.7nF V+ 5 (3) 6 (2) 8 LM833 V– V– 16kHz 6.2kHz 62k 7 (1) 4 4 STEREO LEFT IC6b STEREO RIGHT IC6a MONO IC4a 51k STEREO LEFT IC7b STEREO RIGHT IC7a MONO IC4b the right channel portion of the stereo version. Similarly, red pin numbers are for the right channel; the black pin number applies to the left channel and the mono version. Numbers in blue brackets are for the left channel, with the number for the mono version and right channel of the stereo version in black. power supply and the use of dual-gang potentiometers in place of single-gang. Labels in green apply to the mono version, in blue to the left channel portion of the stereo version and in red, to the right channel portion of the stereo version. When pin numbers are in red brackets, that is for the right channel and the black pin number applies to the left channel and the mono version. Numbers in blue brackets are for the left channel, with the number for the mono version and right channel of the stereo version in black. We have used dual low-noise/low-distortion LM833 op amps for the gyrators (described below). These have a noise level of 4.5nV÷√Hz and very low distortion. These op amps use bipolar input transistors, with a typical input bias current of 500nA (1µA maximum). While this is not a problem for the gyrator circuits, as they are AC-coupled to the rest of the circuit, it is too high for the main signal path. That’s because, if such a current were to flow through the adjustment potentiometers, they could produce a noticeable scratching noise when rotated. So for the main signal path op amps (IC5 for the mono version and IC8/IC9 for the stereo version), we are using OPA1642 op amps which have JFET input transistors. These have an ultra-low-distortion specification of 0.00005%, low noise at 5.1nV÷√Hz and a 2pA typical (20pA siliconchip.com.au Supply options: 15-16V AC, 15-0-15V AC, 12-24V DC, ±15V DC Channel separation (stereo version): >50dB, 20Hz-20kHz (880dB 20Hz-1kHz) 1.8k V+ 1 (7) Output impedance: 470Ω Other features: compact design, uses rotary pots for easy panel mounting 220pF 8 LM833 L: VR7a R: VR7b M: VR7 50k 1.8k 470pF 2 (6) Boost/cut: approximately ±12.5dB (bands overlap; see Fig.1) Input impedance: 100kΩ || 100pF 4 1 3 (5) Equaliser bands: seven (63Hz, 160Hz, 410Hz, 1kHz, 2.5kHz, 6.2kHz, 16kHz) Total harmonic distortion: <0.0006%, 20Hz-20kHz, 20Hz22kHz bandwidth (see Fig.2) 10 2.2nF Channels: one (mono) or two (stereo) Signal-to-noise ratio: 108dB (2V RMS), 102dB (1V RMS) 100pF 10nF Features & specifications maximum) input bias current. So their input bias current is typically 250,000 times less than the LM833s. The following description is for the mono version, but the operation of the two channels in the stereo version is identical. The incoming signal is applied to RCA socket CON1. It passes through an RF-suppressing ferrite bead (L1) and is then AC-coupled to non-inverting input pin 5 of buffer op amp IC5b. The 1kΩ/100pF RC low-pass filter feeding that pin is to filter out RF signals that pass through FB1. This signal is then fed, via another RF-suppression filter, to non-inverting input pin 3 of op amp IC5a. At first glance, this also appears to be operating as a buffer, albeit with a 10kΩ feedback resistor between its output pin 1 and inverting input (pin 2) rather than a direct connection. However, there are also seven 50kΩ linear potentiometers (VR1-VR7) connected across the two inputs of IC5a, and these change its operation. The wipers of these pots are connected to seven op amp stages arranged along the bottom of the circuit diagram. These are all very similar, and are equivalent to seriesresonant LC circuits built around the gyrators mentioned. There is one for each of the equaliser bands. An important aid in understanding how this circuit works is to consider what happens when the pot wipers are centred. Whatever the impedance seen by the wiper in this case, the effect is divided equally between the two 25kΩ half-tracks of the pots, and so equally affects the non-inverting and inverting inputs (pins 3 and 2) of IC5a. Therefore, in this case, that particular stage does not affect the circuit’s behaviour. It is only when the pot wipers are moved away from the centre positions that they start having any effect on the signal. While we said earlier that these seven circuits are equivalent to tuned LC resonant networks, you will note that there are no inductors present. That’s because the closetolerance, low-distortion inductors that would be required for good performance are very expensive and bulky, as well as being prone to hum pickup. Therefore, as with virtually all equalisers designed over the last 50 years or so, we use gyrators instead. The gyrator is an op amp based circuit that simulates an inductor Australia’s electronics magazine April 2020  41 IN 10k OUT 50k Fig.5: This is the circuit of an equaliser reduced to its basic essentials. It shows just one gyrator connected rather than the whole seven. 10k CUT BOOST C1 L1 GYRATOR R2 1.8k C2 Ic Iout Vin Vin Ic R1 Vout Vout Fig.6: each gyrator in the circuit is essentially a capacitor (C2) and op amp which work together as though they are an inductor. The accompanying waveforms show how the current at VOUT lags VIN in the same way as an inductor. and can be connected in series with a capacitor to provide a resonant circuit. Series-resonant circuit To understand how these circuits work, let’s consider a simplified version of the circuit with just one resonant circuit, as shown in Fig.5. As mentioned earlier, with the pot in its centre position, the impedance of the series network (C1+L1) affects both inputs of the right-hand op amp identically and so the frequency response is flat. When the pot wiper moves to the boost end, more of the feedback from the output pin to the inverting input is shunted to ground by the series tuned circuit at frequencies around its resonance. Since its impedance is high at all other frequencies, this means that the feedback is only reduced over the narrow band centred around the resonance of the series tuned network. As the feedback at these frequencies is reduced, the right-hand op amp will have to compensate by increasing its output signal swing at those frequen42 Silicon Chip Iout cies, to return the feedback voltage to the same level as usual. So frequencies in that band will be boosted while others will be unaffected. When the potentiometer is rotated towards the cut end, the tuned circuit instead shunts more of the input signals in its resonant band to ground. This results in a reduction of gain for the frequencies at or near the resonance of the series tuned network As you would expect, the amount of boost or cut is proportional to the potentiometer setting, so intermediate settings give an intermediate level of signal boost or cut. Gyrators Fig.6 shows the circuit of a gyrator made with an op amp. It effectively transforms a capacitor into an inductor. In an inductor, the current lags the voltage by 90° while in a capacitor, the voltage lags the current by 90°. Another way to explain this is that if you apply a large voltage step across a capacitor, a very high current flows Australia’s electronics magazine initially, tapering off as the capacitor charges up. By comparison, if you apply a large voltage step to an inductor, at first the current flow remains the same as it was before, but eventually the current flow increases as the magnetic field density increases. To understand how the gyrator behaves like an inductor, consider an AC signal source, VIN, connected to the input of Fig.6. This causes a current to flow through the capacitor and resistor R1. The voltage across R1 is thus proportional to the capacitor current. This voltage is fed to the op amp, which is connected as a voltage follower (or buffer). The voltage at the output of the op amp thus tracks the voltage across R1. This then causes a current to flow through resistor R2. This current, IOUT, adds to the input current IC, the sum of which is the current drawn from the source and this lags the input voltage. So as far as the signal source is concerned, the gyrator appears like an inductor. The formula to calculate the equivalent inductance is L = R1 x R2 x C2 with L in Henries, R1 and R2 in ohms and C2 in Farads. Consider the effect of a large voltage step at the input; for example, say the input rises suddenly by 1V. This is initially coupled through C2 directly to the op amp, and so its output also rises by 1V, keeping the voltage across R2 the same. Thus, the current flow from the input changes very little initially. The current flowing is just the current required to charge C2, and the value of C2 is typically chosen to minimise this. As C2 charges, the voltage across R1 drops and so does the op amp output voltage, causing the current flowing from the input, through R2, to increase. As described above, this behaviour is much the same as if an inductor were connected instead of the gyrator. To make the tuned LC circuit shown in Fig.5, all we need do is to connect a capacitor (C1) in series with the input to Fig.6. The result is a circuit with a dip in its impedance around a specific frequency. The values in our circuit set the bandwidth of each circuit to approximately 2.5 octaves. Back to the Equaliser So remember that we have one op siliconchip.com.au REG1 7815 POWER A STEREO CON5 MONO CON3 S1 FUSE T1 500mA AC1 15V K D1 0V CT E OUT IN 15V K A K K 470 F D4 A D2 AC2 A D3 A GND 25V 220nF 470 F 220nF 25V 10 F IN (a) POWER SUPPLY CONFIGURATION WITH A CENTRE-TAPPED TRANSFORMER K JP1 1 LED1  2 3.3k Vcc/2 3.9k 10 F GND N V+ A JP2 OUT V– REG2 7915 REG1 7815 POWER AC PLUGPACK S1 STEREO CON5 MONO CON3 AC1 ~ ~ OUT IN K D1 A A 0V 470 F D4 GND 25V 220nF 470 F 220nF V+ A 10 F LED1  K JP1 1 2 3.3k Vcc/2 K AC2 25V IN (b) POWER SUPPLY CONFIGURATION WITH AN AC PLUGPACK 3.9k 10 F GND JP2 OUT V– REG2 7915 REG1 7815 STEREO CON5 POWER MONO CON3 S1 A AC1 DC + SUPPLY IN – OUT IN D4 470 F 25V GND 10 F 220nF V+ A  K LED1 1 JP1 2 10k 3.3k K 0V 3.9k AC2 10k JP2 V– (c) POWER SUPPLY CONFIGURATION WITH A DC SUPPLY D1–D4: 1N4004 78 1 5 LED A K K A GND OUT STEREO: IC10a MONO: IC1a 7 91 5 GND IN 100nF siliconchip.com.au 3 LM833 2 4 100 F OUT Fig.7: the three power supply variants: shown at top is (a), for operation from a 30V centre-tapped mains transformer; (b) for operation from an 15V AC plugpack or non-centre tapped transformer and finally (c), as shown at the bottom, for operation via a DC supply of up to about 20V. The greyed out rectifier-diodes aren’t used and could be left off the PCB during construction. Errata: the 100µF capacitor in the Mono version of the PCB connects directly to chassis GND and not via JP2. amp buffer stage with seven pots connected inside its feedback loop. The wiper of each potentiometer is connected to one of a series-tuned circuit described above. Each is tuned to a frequency that is two and a half times that of the last (ie, about 11/3 octaves higher), to provide seven adjustable frequency bands. The output signal of the Equaliser appears at output pin 1 of op amp IC5a, and this is fed via a 470Ω resistor and a 2µF DC blocking capacitor (using two parallel 1µF capacitors) to the output at CON2. The 1MΩ resistor to ground sets the 8 1 IN GND IN 100 DC level for the output signal while the 1nF capacitor shunts any out-ofband high-frequency noise to ground. The 470Ω resistor determines the output impedance of the equaliser, while the 2µF output capacitor and 470nF input capacitor set the low frequency -3dB point of the entire circuit to about 4Hz. Power supply As already noted, there are three power supply options and these are depicted in Figs.7(a)-(c). You can use a centre-tapped 30V transformer, a 15-16VAC plugpack or Australia’s electronics magazine STEREO: IC10b MONO: No IC 5 7 6 SC 2020 a DC supply of up to 20V. There are two ground/earth connections shown on the circuit with different symbols for each. One is the ground for the power supply, signal inputs and signal outputs, shown with an Earth symbol (although it’s only actually connected to Earth if a mains transformer is used). The second is the ground reference signal for the op amp circuitry, and this ground symbol is identical to the one used in Fig.4; indeed, all the points shown connected to ground in Fig.4 connect to the ground in Figs.7(a)-(c). The two grounds are connected diApril 2020  43 1 F 7-BAND STEREO EQUALISER SILICON CHIP IC7 LM833 1 IC6 LM833 IC5 LM833 10 100nF 100nF 1 1.8k 4.7nF 51k 1.8k 62k 2.2nF 1 F 470 OPA1642 100pF 220pF 10nF 1.8k 68k 1M 10k 470pF 2.2nF 4.7nF 10 220pF 51k 1.8k 10nF 62k 1.8k 1nF 68k 1.8k 470pF 82k 12nF IC9 100 F 100nF IC10 LM833 1.8k 82k 1.8k IC3 LM833 33nF 1nF 100k 100nF 1 IC4 LM833 IC8 10k 91k 1.8k 68nF 100nF 1 4.7nF 100nF 100 1nF 2.2nF 1.8k 470nF 100k 100pF 1k 12nF 91k 1.8k 130k 1.8k 10 3.3k REG1 7815 1 F 100pF 1 F 10nF 22nF 1.8k 10 F 100nF 1 10k 100nF 1 OUT L CON2 100pF 470nF FB1 10k 1k 100nF 110k 220nF 100nF 1 IC2 LM833 10 F 1 IC1 LM833 220nF 1 33nF 2 4.7nF 100nF 100nF 1 IN L CON1 10k 470nF 100pF JP1 JP2 470nF 1.8k 270nF 10nF 110k 1 F 130k 10 REG2 7915 470 1 F 470 F 25 V 22nF 25V 100nF FB2 OPA1642 + 1 3.9k + CON5 470 F Jumper settings for AC supply 10k + IN R CON3 100pF 1nF 1M REV.B Jumper settings for DC supply OUT R CON4 D1 D2 4004 AC2 4004 AC 1 0V 4004 C 2020 01104202 4004 D4 D3 270nF 33nF 100nF 68nF VR2 50k lin VR3 50k lin VR4 50k lin LED1 A VR1 50k lin 33nF 2.2nF VR5 50k lin VR6 50k lin GND VR7 50k lin D3 100pF 4004 44 Silicon Chip Australia’s electronics magazine 1 F 10k 100nF FB1 470nF 7-BAND Mono EQUALISER SILICON CHIP 51k 4.7nF 1.8k 100k OPA1642 IC5 IC4 LM833 2.2nF 10k 10nF 62k 1.8k 100pF all signals to the op1 amps now must be biased at half supply so that there will 100pF 10a Fsymmetrical signal swing between be 10 1k the 100nF and 0V. 10 100nFpositive DC supply This is derived using 220pF two series 1 1nF rail470pF 10kΩ resistors across V+ and V-, with the centre connection bypassed to Vwith a 100µF capacitor, to reject supply ripple. Op amps lC10a (stereo version) and lC1a (mono version) buffer GND VR5 VR6 50krail.  lin supply  lin VR7 50k lin this50khalf The spare op amp (IC10b) is not used in the stereo version, but is connected as a buffer from IC10a’s output. This is to prevent the op amp inputs floating and causing oscillation. The mono version uses an existing spare op amp (IC1a) for the Vcc/2 buffer, so there is no unused op amp half. 1M 12nF IC3 LM833 68nF 82k 1.8k 91k 100nF 1.8k IC2 LM833 33nF 100nF 1.8k 470nF 10k 130k 1.8k 270nF LED1 1 F IC1 LM833 100 3.9k 25Vbetween 0V and AC1 rectly together when using an AC sup- 25V This connects + 10k ply, via JP1. In this case, the power sup- at CON5, and+diodes D1 and D4 form F 220nF ply ground is connected to the10k centre two half-wave rectifiers to 10 derive the 220nF JP1 1 JP2 tap of the transformer and100nF the ground 2 positive and negative 100nF rails. Diodes D2 1 pins of REG1 and REG2. The AC from and D3 are thus unused, may 1be 2.2nF 1 4.7nF and the transformer is converted to pulsat- 22nF omitted. 10nF ing DC by the bridge rectifier formed by The rest of the circuit works identiD1-D4 and filtered by two 470µF 25V cally to the case in Fig.7(a); the only capacitors, one for the positive supply difference is that there will be twice and one for the negative. as much ripple on the filtered but unA VR2 50k 50k lin the VR1 50kregulated lin  lin 50k lin VR4 inputs The DC across these capacitors (with DC railsVR3 that form significant ripple) is then fed to regula- to REG1 & REG2. tors REG1 and REG2 which provide the For a DC supply, as shown in Fig.7(b), +15V and -15V regulated supply rails the positive voltage is applied to the to run the op amps. AC1 terminal of CON5 and the negaThe power LED, LED1, is powered tive voltage to the 0V terminal. Diode from the +15V rail and its current is D4 provides reverse polarity protection; set to around 4mA by a 3.3kΩ resistor. diodes D1-D3 may be omitted. A 3.9kΩ resistor between 0V and For input voltages below 18V, REG1 the -15V supply rail provides a simi- should be omitted and its input and lar current flow in the negative supply output terminals shorted, so that the rail, so that the supply rails collapse at external supply runs the circuit dithe same rate when power is switched rectly via D4. off. This prevents the op amps from osWhen using a DC supply, no negative cillating as the supply capacitors dis- rail is available so REG2 can be left off. charge, and also prevents the output A shunt is placed on header JP2 to convoltage from shifting markedly from nect the V- supply rail to the negative 0V during power down. side of the external DC supply. JP1 is You can use a 15-16VAC plugpack, then positioned to connect the op amp as shown in Fig.7(b), instead of the grounds to a Vcc/2 half supply rail. centre-tapped transformer in Fig.7(a). This half supply rail is required as 1 F 470 F 470 470 F REG2 7915 68k REG1 7815 1nF 33nF 1.8k D4 4004 D2 4004 D1 100 F CON3 REV.B 4004 01104201 3.3k Fig.8: the overlay diagram (and matching photo opposite) for the stereo version of the equaliser. Take care to orientate the ICs, diodes, electrolytic capacitors and the regulators correctly. Before you solder the grounding wire to all pots (also see photo at right) you will probably have to scrape or file some of the passivation off the pot CON2 bodies, otherwise soldering may IN OUT CON1 be very difficult. This wireCconnects to the PCB at the “GND” pad at the right side. 2020 AC1 0V AC2 Construction The stereo version of the equaliser is built using a double-sided PCB coded 01104202, measuring 157 x 86mm. Its component overlay diagram is shown in Fig.8. The mono version is built on a different double-sided PCB coded 01104201, measuring 143 x 63.5mm. If building this version, refer to the mono overlay diagram, Fig.9. Note that if you are building the stesiliconchip.com.au reo version and you are not using a DC supply, op amp IC10 does not need to be installed. That’s because it’s only used to buffer the Vcc/2 supply rail required for the DC power configuration. Begin construction by fitting the surface-mount ICs. These are IC8 and IC9 for the stereo version and IC5 for the mono version. (This type of op amp is not available in a through-hole package). In each case, make sure you have orientated the IC correctly; a white line is printed on the top of the package between pins 1 and 8. Position the IC over the PCB pads and solder one corner pin. Check its alignment and re-melt the solder if you need to adjust its position. When the IC is aligned correctly, solder the remaining seven pins. Make sure that there no solder dags bridging any of the adjacent pins. However, keep in mind that the following pins are joined on the PCB, so bridges between them do not matter: (stereo version) pins 1 & 2 of IC9 and pins 6 & 7 of IC8; (mono version) pins 6 & 7 of IC5. Continue by installing the resistors. You should check their values using a multimeter set to read ohms to be safe. siliconchip.com.au Then fit the two ferrite beads by feeding a resistor lead offcut through each bead before soldering them in place. Diodes D1-D4 can be mounted now; make sure they are orientated correctly. As shown in Figs.7(b) & (c), if you are powering the unit from a plugpack or DC supply, you may omit some of these diodes, although it doesn’t hurt to fit them all. Continue by installing the remaining ICs. These are in dual-in-line packages, so you can use IC sockets if you prefer. This makes it easier to swap them later, or replace a failed op amp; however, the sockets themselves can be a source of problems due to corrosion in the metal which contacts the IC pins. Regardless of whether you are soldering sockets or ICs to the board, make sure they are all orientated correctly. Now fit the ceramic and MKT polyester capacitors, which are not polarised, followed by the electrolytic capacitors, which are. Their longer leads must go into the holes marked with the “+” symbols on the PCB; the striped side of each can indicates the negative lead. LED1 also needs to be mounted with the correct orientation. Its longer lead is the anode, and this goes to the pad Australia’s electronics magazine marked “A” on the PCB. Fit it with the top of the lens 12mm above the PCB. The leads can be bent over so the LED is horizontal later, when installing the Equaliser into its case. When mounting the RCA sockets, the white ones are for the left channel and the red ones are for the right channel. The 3-way screw terminal (CON5 for the stereo version or CON3 for the mono version) can then be installed with its wire entry holes towards the edge of the PCB. Fit regulators REG1 and REG2 next. These are mounted horizontally, with the tabs secured using screws and nuts. If you are using a DC supply for the equaliser, then REG2 and associated components do not need to be installed (this includes the 470µF and 220nF capacitors at REG2’s input and the 10µF capacitor at the output). If you are unsure of which component to leave off, fit them all. This means the board will work if you decide to use an AC power source later. For the DC supply version, use a 7815 for REG1 if the supply is between 18V and 24V (25V absolute maximum). If the supply is 15-18V, use a 7812 regulator. For 12-15V, dispense April 2020  45 LED1 A VR1 50kW lin VR3 50kW lin VR4 50kW lin VR5 50kW lin 1kW 100nF 10W 220pF 51kW 4.7nF 1.8kW IC4 LM833 2.2nF VR6 50kW lin VR7 50kW lin SILICON CHIP 100pF 7-BAND Mono EQUALISER FB1 100kW IC5 470nF 10W 1 10nF 1.8kW 62kW 68kW 12nF IC3 LM833 470pF OPA1642 1 10kW 1mF 1m F 100p F 470W 1MW 1nF 1 33nF 1.8kW 2.2nF 68nF 100nF IC2 LM833 33nF VR2 50kW lin 10kW 100nF 100nF 4.7nF 100nF 1.8kW 470nF 10nF 10kW 130kW 1.8kW 270nF IC1 LM833 1m F 100W 4004 100nF 1 22nF 10mF 10mF 220nF 220nF JP2 1 Jumper settings for DC supply D4 4004 + 82kW 100nF JP1 1 25V 1.8kW 2 1nF REG2 7915 470mF 91kW 10kW REG1 7815 + IN CON1 100pF 1.8kW 10kW OUT CON2 D3 D2 4004 D1 4004 470mF 25V 3.9kW Jumper settings for AC supply 100mF AC1 0V AC2 CON3 REV.B 3.3kW C 2020 01104201 G ND Fig.9: the overlay diagram (again with matching photo opposite) for the mono version of the equaliser. The mono version would best suit musical instruments or a public address amplifier. It’s a little simpler than the stereo version and the PCB is smaller. The most obvious difference (but not the only one!) is the use of single-gang pots instead of dual-gang. Note our comments on the stereo overlay (Fig.8) regarding soldering the grounding wire to the pot bodies. with REG1 and instead fit a wire link between the IN and OUT terminals (the two outer pads). In this case, the incoming DC supply will need to be reasonably free of noise and ripple for good performance We don’t recommend using a supply lower than 12V as the op amp signal swing becomes limited. Once you’ve figured out which regulators to install, start by bending their leads to fit into the holes in the PCB, with the tab holes lined up with the PCB mounting holes. Attach the regulator bodies with screws and do them up tight before soldering and trimming the leads. Mount jumper header JP1 & JP2 next. For an AC supply, insert the jumper link on JP1 in position 1 and leave JP2 open. For a DC supply, insert the jumper link on JP1 in position 2 and also fit a jumper link on JP2. All that’s left now are the potentiometers. The pot bodies should be grounded using tinned copper wire that is soldered to each pot body and then to the GND terminal point (see photos). To do this, you will need to scrape off some of the passivation coating on the top of each pot body before soldering them to the board. Selecting the knobs You must use knobs 16mm in diameter or less, and this includes any flange/skirt at the base (ie, measure the maximum diameter). 46 Silicon Chip Note that some potentiometers have a D-shaped shaft while others are fluted, so you will need to make sure that you purchase knobs which match your shafts. Also, keep in mind that knobs for 6mm (metric) shafts will not fit pots with 1/4” (6.35mm) shafts. Whether you use a knob with a skirt depends on how you will be mounting the potentiometers. Knobs with skirts are designed to cover the potentiometer nut, if this is exposed on the mounting panel. If the pot is mounted on a recessed panel, it is not necessary to use knobs with skirts. Suitable knobs for the 1/4” D-shaft potentiometers from Jaycar or Altronics are Jaycar Cat HK7760 and Altronics Cat H6040. Both have skirts. More expensive (and more classy) aluminium knobs without a skirt are also available: Jaycar Cat HK7020 (silver) and HK7009 (black), plus Altronics Cat H6331 (silver) and H6211 (black). Altronics also has the black Cat H6106 and coloured cap series, Cat H6001-H6007. All of the above are grub screw types. These allow the knob to be secured with the pointer opposite the flat portion of the D-shaped shaft. Knobs with an internal D-shaped hole should not be used unless the pointer can be reorientated. Fixed pointer knobs generally point in the direction of the flat portion of the D-shaped shaft, which is the opposite of what we require. Australia’s electronics magazine Initial testing You can now power up the Equaliser board to test for voltage at the op amps. Refer to Figs.7(a)-(c) for how to wire up the power supply. If using a mains transformer, make sure everything is fitted in a properly Earthed metal box with tidy and suitably insulated mains wiring. Do not attempt this if you don’t have experience building mains-based projects. If fitting the Equaliser into an existing chassis and using the pre-installed transformer, that transformer must be capable of supplying the extra current drawn by the equaliser circuit. This is 70mA maximum for the stereo version and 45mA for the mono version. That’s low enough that it’s unlikely it will cause any problems. Power up the circuit and check that LED1 lights, then measure the DC voltage between pins 4 and 8 of the op amps. This should be close to 30V (29.5V-30.5V) if you are using the AC supply. For the DC supply version, check that this voltage is close to 15V (14.7515.25V) if you’ve fitted a 7815 or 12V (11.75-12.25V) if you’ve fitted a 7812. If REG1 is linked out, you can expect about 0.7V less than the incoming supply voltage. The voltage between pin pairs 4 & 1 and 4 & 7 of each op amp should show half the supply voltage. In other words, this voltage should be 7.5V or thereabouts if you measured 15V besiliconchip.com.au tween pins 4 & 8. All that’s left then is to centre the pots, connect a signal source to the in- put and an amplifier to the output and check that the sound from the amplifier is clean and undistorted. Experi- ment by rotating the various knobs and check that you can vary the frequency response as expected. SC Parts list – 7-band Graphic Equaliser (Parts common to both versions) 7 knobs to suit pots (16mm maximum diameter) – see text 1 3-way PCB mount screw terminal, 5.08mm pin spacing (CON3 [mono]/CON5 [stereo]) 1 3-way header, 2.54mm spacing (JP1) 1 2-way header, 2.54mm spacing (JP2) 2 jumper shunts/shorting blocks (JP1,JP2) 2 M3 x 6mm panhead machine screws and nuts 1 PC stake 1 150mm length of tinned copper wire 1 power supply (see text) Semiconductors 4 LM833P dual low-noise op amps, DIP-8 (IC1-IC4)* 1 OPA1642AID JFET-input op amps, SOIC-8 (IC5/IC8)* [Digi-Key, Mouser, RS Components] 1 7815 +15V 1A linear regulator (REG1) 1 7915 -15V 1A linear regulator (REG2) 4 1N4004 400V 1A diodes (D1-D4) 1 5mm or 3mm LED (LED1) Capacitors 2 470µF 25V PC electrolytic 1 100µF 16V PC electrolytic 2 10µF 16V PC electrolytic 3 1µF MKT polyester* 2 470nF MKT polyester* 1 270nF MKT polyester* 2 220nF MKT polyester 7 100nF MKT polyester* 1 68nF MKT polyester* 2 33nF MKT polyester* siliconchip.com.au Note: quantities shown are for the mono version. All components marked with an asterisk (*) should have quantities doubled for the stereo version 1 22nF MKT polyester* 1 12nF MKT polyester* 2 10nF MKT polyester* 2 4.7nF MKT polyester* 2 2.2nF MKT polyester* 2 1nF MKT polyester* 1 470pF ceramic* 1 220pF ceramic* 3 100pF ceramic* Resistors (all 1/4W, 1% metal film) 2 10Ω* 1 100Ω 1 470Ω* 1 1kΩ* 7 1.8kΩ* 1 3.3kΩ 1 3.9kΩ 4 10kΩ 1 51kΩ* 1 62kΩ* 1 68kΩ* 1 82kΩ* 1 91kΩ* 1 100kΩ* 1 110kΩ* 1 130kΩ* 1 1MΩ* Extra parts for the stereo version 1 double-sided PCB coded 01104202, 157 x 86mm 7 50kΩ dual-gang linear 16mm potentiometers (VR1-VR7) 2 vertical PCB-mount white RCA sockets [Altronics P0131] (CON1,CON2) 2 vertical PCB-mount red RCA sockets [Altronics P0132] (CON3,CON4) 2 5mm-long ferrite beads (FB1,FB2) 2 10kΩ 1/4W 1% metal film resistors Extra parts for the mono version 1 double-sided PCB coded 01104201, 143 x 63.5mm 7 50k single-gang linear 16mm potentiometers (VR1-VR7) 1 vertical PCB-mount white RCA socket [Altronics P0131] (CON1) 1 vertical PCB-mount red RCA socket [Altronics P0132] (CON2) 1 5mm-long ferrite bead (FB1) Australia’s electronics magazine April 2020  47 new catalogue Hardcore electronics by out now On sale 24 March 2020 to 23 April, 2020 Image for illustative purposes only. new RETRO ARCADE GAME CONSOLE FOR RASPBERRY PI JUST 495 $ BJ5000 EXCLUSIVE CLUB OFFER FREE CATALOGUE* with purchases of $30 or more. *Applies to new & existing members for purchases made in-store or online. Valid 24 March - 23 April. Let the games begin with this exciting retro arcade console. Simply install your own Raspberry Pi 3/3B+ into the console, insert a Retropie installed micro SD card, copy over some ROMS, connect it to your TV, computer or projector with a HDMI or VGA cable and you are ready to battle! • Each player has joystick and 6 buttons XC9062 new 1080P INDOOR SMART WI-FI CAMERA Detect and record movement indoors. The smartphone app and two way audio allow you to communicate with your visitors from anywhere in the world. • 110° wide angle view • Secure storage via Cloud backup • Built-in siren • True Detect™ Technology QC9114 In-store only or via Click & Collect. ONLY 119 4K MINI DISPLAYPORT TO HDMI ADAPTOR Allows you to view your DisplayPort equipped device on any HDMI monitor. Supports output resolutions up to 4K <at> 60Hz for high quality viewing. • 155mm long WQ7420 new Due Early April. JUST 249 $ Shop the catalogue online! DOZENS OF FILAMENT COLOURS & TYPES FROM $19.95 With purchase of TL4410. 48W HOBBYIST SOLDERING STATION Ideal station for the advanced hobby user. Adjustable temperature (150-450°C). Ceramic element and lightweight pencil. Mains powered. TS1564 new 30:1 DISTANCE TO SPOT RATIO • DUAL COLOUR PRINTING • 4.3" COLOUR TOUCH SCREEN • SILICON PRINTING PLATFORM • LARGE POWER SUPPLY FILAMENT 119 2995 Sold Separately $50 $ $ Measure temperatures in hard to reach places. • -50° to 1650°C • Dual laser 500ms detection time • USB interface • Carry case included QM7430 1299 $ RASPBERRY PI 3B+ (XC9001 $89.95) BONUS JUST ONLY PROFESSIONAL NON-CONTACT THERMOMETER DUAL FILAMENT 3D PRINTER CR-X Allows you to combine colors and materials ONLY 2 PLAYER ARCADE CONSOLE SEE MORE DIY GAMING CONSOLES ON PAGE 3 creating high-quality prints. 300 × 300 × 400mm print area. Oversized bed screws for leveling the print bed. Dual cooling fans. SD memory card slot. TL4410 $ 169 $ ALSO AVAILABLE: SD CARD PRE-LOADED WITH RETROPIE XC9031 $24.95 Just in! JUST ARDUINO® STARTER KIT Includes all the essentials to get you started in the exciting world of Arduino® including an UNO board, jumper leads, resistors and more. XC3902 See website for details. JUST 3995 $ BONUS 60/40 SOLDER 200G* VALUED AT $16.95 * Choice of either 0.71mm (NS3005) or 1.00mm (NS3010) Solder with purchase of TS1564 Free delivery on online orders over $70 Conditions apply - see page 8 for full T&Cs. Hold PCBs up to 200 × 140mm. Adjustable angle. TH1980 WAS $19.95 JUST 1495 $ DESKTOP PCB HOLDER SAVE 25% PCB not included. MORE HOT OFFERS ON PAGE 8 www.jaycar.com.au 1800 022 888 YOUR DESTINATION FOR PROJECTS & DIY. Think. Possible. PROJECT: GPS Tracker Make your own GPS tracker with this cool project. Using our GPS module (XC3710) and a Leonardo board, it will store time and co-ordinates in a compact form that you can view using free open source software on your computer. The compact nature of the data ensures that a 16GB SD card will literally store years of vehicle movement! It can be used to track a fleet, or just monitor/ track kids whereabouts when they borrow the car etc. CLUB OFFER BUNDLE DEAL SKILL LEVEL: Intermediate (with programming) TOOLS: Soldering Iron WHAT YOU WILL NEED: Arduino®️ Compatible GPS Receiver Module Arduino®️ Compatible Leonardo r3 Development Board Arduino®️ Compatible Data Logging Shield 16GB Class 10 microSDHC Card 2600mAh Power Bank 3PDT Mini Toggle Switch 150 Ω 0.5W Metal Film Resistors Pk8 5mm LED 8mcd Diffused Red 5mm LED 80mcd Diffused Orange 5mm LED 80mcd Diffused Green MICRO:BIT SMART ROBOT $ KIT A fun to build robot See other projects at www.jaycar.com.au/arduino See website for details BUNDLE & SAVE FROM BREADBOARD WITH 400 TIE POINTS Prototyping breadboard with 400 tie points. PB8820 RRP $7.95 50 SEE PARTS & STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/gps-tracker NOTE: UNO board not included. 375 14 $ 95 SAVE 25% VALUED AT $20.90 click & collect 99 $ $ JIFFY BOXES WITH FLANGED LIDS Identical to the UB3 and UB5 jiffy boxes, but have mounting flanges on either side for bulkhead/surface mounting. UB5 BLACK HB6016 $3.75 UB3 GREY HB6024 $5.25 UB3 BLACK HB6014 $5.25 BUNDLE DEAL VALUED AT OVER $125 electronics and make spectacular light-up wearable technology. Kit includes everything you need to get started - felt cloth, needles, thimble, thread, glue gun, JUST multimeter, electronic components, 62 page guide & more. KM1080 that uses a micro:bit microcontroller board (sold separately XC4320 $34.95) that kids can control using their Smartphone via Bluetooth®. Includes base, modules, wheels, jumper wires and mounting hardware. KR9262 • Self-adhesive rubber feet • Measures 120 x 83mm PB8840 RRP $12.95 KIT VALUED AT $139.75 SPARKLE STITCH KIT Learn simple sewing and 9995 ACRYLIC BASE FOR UNO & BREADBOARD SAVE 35% XC3710 $44.95 XC4430 $29.95 XC4536 $19.95 XC4989 $19.95 MB3793 $14.95 ST0505 $7.95 RR0552 $0.85 ZD0150 $0.40 ZD0169 $0.40 ZD0170 $0.40 ONLY + 8995 $ ONLY 9 $ 95 WIRE GLUE Hundreds of hobby, trade and electronics uses. Lead-free. 9ml. NM2831 Buy online & collect in store JUST 595 $ 150MM JUMPER LEADS 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 ONLY 595 $ ATTINY85 IC 8 PIN DIP8 RISC-based microcontroller in an 8 pin DIP IC. Operates between 2.7-5.5V. ZZ8721 EA. JUST 99 $ PROGRAMMING & CUSTOMISING THE PIC MICROCONTROLLER Comes with more than 600 illustrations and provides comprehensive, easy-tounderstand coverage of the PIC microcontroller's hardware and software schemes. 1264 pages. BT1347 ON SALE 24.03.2020 - 23.04.2020 YOUR DESTINATION FOR ARDUINO, PI & IMAGINATION. RASPBERRY PI 3B+ (XC9001 $89.95) Think. Possible. ARDUINO®️ COMPATIBLE This icon indicates that the product will work in your Arduino® based project. Sold Separately RASPBERRY PI COMPATIBLE This icon indicates that the product will work in your Raspberry Pi project. LILYPAD PLUS DEVELOPMENT BOARD An all-in-one Arduino-compatible board to add dazzling effects to your next project or costume. 10 Mini RBG LEDs. • Programmable buttons • Accelerometer • And lots of other sensors • 50mm dia. XC3920 OLED DISPLAY MODULES 3495 $ 240 x 320 LCD TOUCH SCREEN Large, colourful touch display shield which piggybacks straight onto your UNO or MEGA. Fast parallel interface. microSD card slot. • Resistive touch interface XC4630 XC 3 72 8 Give your next project a dazzling display. Two options available. 1.3" Monochrome XC3728 $24.95 1.5" Colour XC3726 $69.95 ONLY FROM ONLY 24 $ 29 95 $ 95 Let the Games Begin 10" SCREEN RETRO ARCADE GAME CONSOLE FOR RASPBERRY PI Simply install your own Raspberry Pi 3/3B+ into the console, insert a RetroPie installed micro SD card, copy over some ROMS and you are ready to play. • Includes a joystick and 6 buttons • Built-in speaker ONLY • 345(H) x 290(L) x 280(W)mm XC9064 ALSO AVAILABLE: RETROPIE ON 16GB SD CARD XC9031 $24.95 249 $ new ONLY DIY GAME CONSOLE BUILD-A-GAME LEARNING KIT An Arduino-based 8-bit handheld game console that you can code or upload your favourite games. Driven by an Arduino® Leonardo and features a 1.3” OLED screen and volume control. USB powered or from 2 x AA batteries (not included). XC3752 5995 $ new FINGERPRINT SENSOR MODULE Add fingerprint access control to your next Arduino® or Raspberry Pi project. Runs off 3.3V and TTL serial to send data back and forth between mainboard and fingerprint sensor. • Measures just 44 x 22mm See website for more information. AUTO LEARNING XC4636 ONLY 49 $ 95 16 KEY TOUCH KEYPAD MODULE • Compact 16 key touch interface for your Arduino® compatible project. • Onboard power indicator • Two wire serial data interface • Works on 2.4-5.5V XC4602 RFID READ & WRITE MODULE Allows you to both read and write MiFare- Type RFID cards. Includes one credit-card style tag and one key-fob style tag. • 3.3VDC operating voltage XC4506 ONLY ONLY RETRO NES STYLE CONTROLLER RETRO NES CASE 9 $ 3995 95 $ SNES layout. Features A/B/X/Y buttons, start, select, and direction controls. Easily configurable, USB powered. XC4404 ONLY 17 $ 95 9 $ 95 SMOKE DETECTOR MODULE Detects butane, propane, methane, alcohol, hydrogen, and smoke. XC4470 ONLY 895 $ In the Trade? ONLY 1995 $ Mount your Raspberry Pi 3B+ securely to the back of your monitor or TV. • 100 x 100mm VESA mounting holes • Perspex • Includes mounting screws XC9003 PIR MOTION DETECTOR MODULE Detects motion, a must for any security application project. Adjustable delay times changeable via two potentiometers. XC4444 ONLY 595 $ RETROPIE OS ON SD CARD FOR RASPBERRY PI Preloaded with RetroPie, and autoinstalls when used for first time. • 16GB microSD card • Supplied with an SD card adaptor XC9031 Note: Best compatible for Raspberry 3B/3B+ GAMING CONSOLE TOOL KIT - 26PCE ONLY 2395 $ POWER SUPPLY FOR RASPBERRY PI new new JUST $ 2495 VESA MOUNT CASE TO SUIT RASPBERRY PI ONLY Perfect for building a Raspberry Pi 3/3B+ based emulator. • HDMI, 3.5mm, and micro USB (power) access • USB Ports: 4 (Standard, Type –A) XC4403 5.1V 2.5A. Use with Raspberry Pi 3/3B+, charge power banks, etc. 1.5m lead with micro USB connector. MP3536 JUST 2495 $ Everything you need to get into your console and accessories. • Nintendo & X-Box security bits • X-Box opening tool • Stainless tweezers and more TD2109 See website for full contents. 51 YOUR DESTINATION FOR SECURITY. Think. Possible. Control with your phone via app 1080P WI-FI CAMERA WITH SECURITY ALARM Security & Monitoring at your Fingertips Use your Smartphone, Amazon Alexa, or Google Home device to control the lights, or your mains power points. Easy DIY installation, no electrician needed. CONTROL POWER, MONITOR ENERGY USAGE Smartphone not included. Control includes automatic schedules, countdown & timers. 240V 10A rated. STANDARD PLUG MS6106 $24.95 MS6104 WITH ENERGY MONITORING & 2 x USB PORT MS6104 $34.95 FROM 2495 $ Control includes colour, brightness, setting schedules, turning them on and off, even tracking energy used. Single: $19.95ea Bayonet SL2250 Edison SL2254 3 Pack: $49.95 Edison SL2256 VALUED AT $198.85 Includes QC3870 + QC3876 + QC3874 + QC3872 • 12m detection range • 1 year battery life QC3876 RRP $29.95 REED SENSOR • Protects against intrusion QC3874 RRP $19.95 View live footage on a Smartphone. PANIC BUTTON • Trigger security system in duress QC3872 RRP $19.95 FROM 1995 $ 1080P WI-FI IP CAMERA WITH PAN/TILT SAVE $4985 PIR SENSOR LED BULBS WITH COLOUR CHANGE new 149 $ Use as a stand-alone camera to record audio and video or expand it with sensors (sold separately) to turn it into a security system. QC3870 RRP $129 ADJUST LIGHT OUTPUT, MONITOR ENERGY USAGE SMART MAINS PLUGS SECURITY BUNDLE DEAL Smartphone not included. QC3872 QC3874 Ideal stand-alone surveillance or as a system. Free iOS™ and Android app to remotely access the camera, pan, tilt, review footage, etc. using your Smartphone, iPad or Android tablet. • Full HD recording • 2-Way audio • Records to micro SD card (16GB XC4989 $19.95 sold separately) QC3858 QC3876 ONLY 129 $ Essentials to Complete your Alarm System EASY DIY ALARM SYSTEM BUNDLE Build your own home alarm system using this awesome bundle. You can customise it by adding other components too (sold eparately). BUNDLE INCLUDES: Quad Element PIR Detector LA5046 RRP $44.95 Alarm Relay Module 2 x 15A LA5558 RRP $27.95 Mains Adaptor 12VDC 1.5A MP3486 RRP $24.95 Indoor Alarm Piezo LA5256 RRP $10.95 Reed Switch - Double Throw LA5070 RRP $6.25 12V 7.2AH SLA BATTERY Avoid being left unsecure or without internet & comms in case of power outage. Check and replace at regular intervals. 12V 7.2Ah. SB2486 ALSO AVAILABLE: 12.8V 7.5AH LITHIUM DEEP ONLY CYCLE BATTERY SB2210 $79 ALARM & NBN BACKUP BATTERY 3495 $ STAINLESS STEEL WIRE STRIPPER, CUTTER, PLIERS BUNDLE DEAL 78 $ 95 Strips wire up to 2.6mm and cut steel wires up to 3.0mm. TH1841 SAVE 30% GIGABIT POE INJECTOR Adds inline power to a single network cable up to 100m so you don't need mains power at the device. Supports up to gigabit for ultra-fast connectivity. YN8040 ONLY 6495 52 POE NETWORK SWITCHES Power Over Ethernet (PoE) devices are becoming more common place, such as IP cameras, routers, telephones, etc and require a small amount of power to operate. 5 PORT 10/100Mbps YN8074 $119 10 PORT GIGABIT YN8049 $239 119 $ click & collect YN8074 Designed for security alarm systems but also highly useful for electronics or robotics projects. ACMA approved. WB1598 ONLY 1 $ 95 /M MODULAR CRIMP TOOL WITH NETWORK/ POE TESTER 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 ONLY FROM $ ONLY 1995 $ VALUED AT $115.05 6 CORE ALARM CABLE 74 $ Buy online & collect in store 95 ON SALE 24.03.2020 - 23.04.2020 FROM 345 $ CAT5E LEADS Suitable for most Ethernet & LAN applications. RJ45 to RJ45. 0.5m to 30m. YN8200-YN8234 YOUR DESTINATION FOR NETWORKING. Think. Possible. Speed Meter: Fast Faster Fastest HIGH PERFORMANCE WIRELESS MODEM ROUTERS Our range of high performance modem routers offer the best cost-effective networking solution for home or office setups. Provides superb reliability N300 WIRELESS and customisable security BROADBAND ROUTER features found on more Sharing your internet connection and network expensive units. Choose is made easy. Help boost signal strength and from our N300 to high reduce dead spots. NBN compatible. speed AC2100 for a • Speed up to 300Mbps (2.4GHz) powerful yet affordable • 2 x 5dBi Omni-directional antennas wireless networking • 4 x Ethernet ports solution. • 802.11n/g/b ONLY YN8390 49 $ Switch, Split & Extend 4K HDMI SPLITTERS Split a single HDMI signal to multiple HDMI outputs. Supports 4K UHD, 3D video, DolbyAC3, DSD audio and more. 2 PORT, 2 OUTPUTS AC1710 $52.95 4 PORT, 4 OUTPUTS AC1712 $84.95 AC1710 95 AC1200 VDSL/ADSL MODEM ROUTER Unlock the full potential of your internet connection. Dual band, eliminating lag and buffering from your online experience. • Speed up to 1.2Gbps (2.4GHz/5GHz) • 3 fixed external antenna • 4 x Ethernet ports • 802.11a/n/ac YN8440 169 299 $ Easily create and expand your wired network. 5 PORT 10/100/1000Mbps YN8384 $34.95 8 PORT 10/100/1000Mbps YN8386 $54.95 34 95 More ways to pay: 0 Super flexible coax lead that makes it easier to run through entertainment cabinets and along skirting boards, etc. • Quality RG6 quad shielded coax cable GOLD-PLATED TV PLUG TO TV PLUG 3M CONNECTORS WV7460 $14.95 TV PLUG TO TV PLUG 10M WV7462 $24.95 TV PLUG TO F-PLUG 3M FROM WV7464 $14.95 TV PLUG TO F-PLUG 10M WV7466 $24.95 ONLY COMPACT ETHERNET SWITCHES 02 FLEXIBLE TV COAX LEADS High quality, ideal for long runs. Uses both fibre optic and copper cores to transmit Ultra HD 4K signals. Supports up to 6Gbps per channel(18Gbps). • 50m long WQ7496 HIGH QUALITY USES FIBRE OPTIC 7995 5 AC 0 AC501 4K HDMI FIBRE OPTIC CABLE $ $ ONLY 249 129 FROM 169 $ $ $ Ideal for long runs. Designed to compensate for any loss over the length of the run. Suitable for Full HD, 4K, 3D, and UHD signals. 10M WQ7437 $79.95 15M WQ7438 $99.95 20M WQ7435 $119 30M WQ7439 $139 1495 MAGNETIC MOUNT 4G ANTENNAS N300 WI-FI RANGE EXTENDER ONLY ONLY ONLY Tests UTP/STP/Coaxial/Modular network cables by manually or automatically detecting missing or disordered wiring, and open or short circuits. • Includes PoE (Power-over-Ethernet) finder to indicate power loss XC5084 39 95 new $ NETWORK CABLE TESTER WITH POE FINDER $ ONLY Send UHD 4K signals from a set top box, media player, or other video source to another room up to 50m away over an ethernet Cat6 cable. • High-Dynamic-Range (HDR) video support AC5020 Switch up to 4 different HDMI signals from multiple sources to a single output. 4 INPUTS, 1 OUTPUT AC5010 $129 4 INPUTS, 2 OUTPUTS MATRIX AC5012 $249 FROM 4K HDMI AMPLIFIED LEADS Incredibly fast speed. Strong, steady signal throughout your home so you can enjoy exceptionally smooth, responsive gaming and uninterrupted streaming. • Speeds up to 2100Mbps (2.4Ghz/5Ghz) • 6 x Omni-directional smart antennas • 5 x Gigabit Ethernet ports • 802.11a/b/g/n/ac YN8394 4K HDMI CAT5E/6 EXTENDER - 50M 4K HDMI SWITCHERS 5295 $ ONLY $ FROM FROM AC2100 WI-FI ROUTER Help boost 4G data signals for a reliable flow of data. Simply attach to the roof of your vehicle using the strong magnetic base. • Includes lead with FME connector. 5DBI AR3340 7DBI AR3344 49 $ 95 EA. Quickly eliminate dead-spots or provide an access point on your existing wired network. Plug straight into an available mains power point. • Supports up to 300Mbps YN8370 ALSO AVAILABLE: AC1200 DUAL BAND WI-FI RANGE EXTENDER YN8374 $99.95 4995 $ 53 YOUR DESTINATION FOR THE BEST REWARDS & PERKS love jaycar? you're going to love our rewards! GET REWARDS eCoupons for future shops in store 1 point = $1 200 points = $10 eCoupon Detects wireless transmitters and eavesdropping devices. QC3506 RRP $99.95 Includes 720P outdoor camera (QC8041 $149), 12V Battery (SB2485 $29.95), Adaptor (PP1996 $9.95) & Battery Charger (MB3619 RRP $21.95). CLUB OFFER 179 $ CLUB OFFER 20 OFF 79 % $ 95 *Applies to LA5325,LA5332, LA5336-38, LA5340-42. + PP1996 KIT VALUED AT $210.85 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE PIEZO BUZZER RJ12 6P/4C EXTENSION CABLE LEAD-FREE SOLDER 500G 3.5 DIGIT JUMBO LED PANEL METER 35% 15% 6-14VDC. Weatherproof. AB3466 RRP $19.95 CLUB $12.95 15% 25% US plug to US plug. 10m. YT6041 RRP $11.95 CLUB $9.95 99.3% tin, 0.7% copper lead-free. NS3090 OR NS3096 RRP $54.95EA. CLUB $44.95EA. CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE TINNED COPPER WIRE BUTYL BASED SOUND DEADENING MATERIAL MICROPHONE/AMP FOR CCTV CAMERAS CIRCUIT BREAKERS 35% 30% Tin plated. 100g roll. WW4030 RRP $29.95 CLUB $19.95 CLUB OFFER SAVE 25% BANANA PIGGYBACK TEST LEADS High quality, ultra-flexible. 500VDC 12A. WT5326 RRP $29.95 CLUB $21.95 20% Measure voltages 200mV to 500VDC. QP5585 RRP $34.95 CLUB $24.95 25% High current. 12-14VDC. 70A or 100A option. SF2265 OR SF2266 RRP $34.95EA. CLUB $24.95EA. CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE DC PWM CONTROLLER XVGA MONITOR CONNECTING CABLES IR ADJUSTABLE PROXIMITY SENSOR 10% 12VDC 8A. Suitable for marine environments. MP3209 RRP $34.95 CLUB $29.95 25% D15HD Male to D15HD Male. 5m. WC7588 RRP $39.95 CLUB $29.95 10% OFF DOORPHONES & INTERCOMS* *See T&Cs for details. click & collect 21MM DIGIT HEIGHT High sensitivity microphone (-65dB). 12V. QC3434 RRP $24.95 CLUB $19.95 Self-adhesive. 330mm wide. AX3687 RRP $32.95 CLUB $19.95 EXCLUSIVE CLUB OFFER 54 MB3619 SAVE OVER $30 SAVE $20 DUMMY CAMERAS* account profile and more... RECHARGEABLE OUTDOOR MONITORING CAMERA DETECTOR CLUB OFFER + PERKS offers, event invitations, QC8041 EARN POINTS For dollars spent SB2485 SHOP In store & online Buy online & collect in store 25% 3-80cm detect range. ZD1906 RRP $16.95 CLUB $11.95 YOUR CLUB, YOUR PERKS KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON! Visit www.jaycar.com.au/makerhub ON SALE 24.03.2020 - 23.04.2020 YOUR DESTINATION FOR WORKBENCH ESSENTIALS Think. Possible. FINDER ADVENTURER 3 Fully assembled and easy to use. Features slide-in build plate, assisted levelling, filament-run-out detection and more. Single non-toxic PLA filament option keeps your creations simple and fun. • Prints up to 140(L) × 140(W) × 140(H)mm • 3.5" touchscreen panel • Wi-Fi and USB connect • Low noise operation TL4220 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. • Automatic filament feeding • Low noise operation • Print up to: 150(L) x150(W) x150(H)mm TL4256 3D PRINTER 3D PRINTER/CNC/ LASER ETCHER 3D PRINTER 3D PRINTER The best fabrication tool for entry level users. 3D print, engrave and laser cut with a single machine. Easy swap & interchangeable modules. Includes easy to use software. • 3.5" Touchscreen • Heated Build Plate • Prints up to 125(L) x 125(W) x 125(H)mm TL4400 See website for details. BONUS ONLY 1349 $50 $ FILAMENT With purchase of TL4256. JUST 899 $ JUST 599 $ DON'T FORGET YOUR FILAMENT BONUS $100 FILAMENT With purchase of TL4400. Check in-store or online for full range FROM $19.95 3D PRINTERS. THINK JAYCAR. We stock a wide range of 3D printers and accessories for every budget, including reputable big brands. Pop in-store to discuss what printer would suit your needs with our knowledgeable staff. ESD SAFE SOLDER/ DESOLDER REWORK STATION For professional and hobbyist QUICK HEAT UP use. • 60W Soldering pencil and 300W rework blower • Innovative heater and sensor • Adjustable temperature • Dual digital display TS1648 JUST 249 $ FREE* LEATHER TOOLBELT (HB6373) With any purchase of the below tools: * 8 PIECE 1000V VDE SET Includes two Phillips, two slotted, long nose pliers, side cutters, mains tester, and PVC electrical tape. VDE approved to 1000V. • Insulated right to the tip TD2031 ONLY ONLY 34 $ 95 PCB HOLDER WITH MAGNIFIER • Perfect for PCB assembly & soldering • 2X magnifying lens • Requires 3 x AAA batteries (SB2413 $3.25 sold separately) TH1987 ONLY 2495 $ More ways to pay: 5995 $ FREE LED HEADBAND MAGNIFIER MODULAR STORAGE CABINET ONLY 1995 $ Features 12 slide-out drawers to keep your components organised. Modular slide locking system allows stacking vertically and horizontally. • 295(W) x 200(H) x 160(D)mm HB6332 ONLY 17 $ 95 MINI BENCH VICE Made from strong, lightweight aluminium. Will clamp to surfaces up to 1" thick and hold material up to 2" thick. 50mm opening jaw. TH1764 ONLY LIQUID PLASTIC WELDING KIT With purchase of TS1648 (QM3511 valued at $29.95) 22 PIECE LONG BIT SCREWDRIVER SET WITH CASE • Includes popular slotted, Phillips, Star and TRI bits • Storage case included TD2114 Limit 1 per customer 5995 $ Bond, build, fix and fill virtually anything in seconds. A solvent free formula stays liquid until cured with the included UV LED Light. NA1530 2-IN-1 LASER MEASURING TAPE new JUST 4495 $ IP67 TRUE RMS AUTORANGING CAT IV DMM 150MM PRECISION SIDE CUTTERS • Made from carbon steel • Designed for sharp cutting in precision wiring • Insulated soft-touch handle TH1891 JUST 44 $ Measure up to 30m using the laser or up to 5m with the retractable tape. Metric and imperial. USB rechargeable. • Auto power-off • Non-slip grip QM1627 95 WATERPROOF • 600V, 4000 count • AC/DC voltages up to 1000V • AC/DC currents up to 10A • Data hold, relative measurement QM1549 ONLY 9995 $ 55 HOT OFFERS SAVE UP TO $100 QUICK CHANGE RATCHET CRIMP TOOL A MUST FOR SURFACE MOUNT HAND SOLDERING • Heavy duty ergonomic • Interchangeable dies, no screwdriver needed • Ratchet mechanism designed for maximum power or quick release TH2000 ONLY 3995 $ • PC CONNECTION VIA USB • SD CARD SUPPORT NOW 299 $ 100MHZ DUAL CHANNEL OSCILLOSCOPE SAVE $80 WORKSHOP/TOOL KIT MUST HAVE 30% OFF 11 X DIES TO SUIT! With purchase of TH2000 See website for details. 50W ESD SAFE SOLDERING STATION An outstanding, fast, accurate soldering station from Thermaltronics uses the proven Curie Point technology to bring the tip up to operating temp using fast RF induction. It works with leaded and unleaded solder. Mains powered, 350°C to 398°C Temp range. 0.5mm chisel tip included. TS1584 WAS $379 ALSO AVAILABLE: Spare Tips With Heating Element FROM $29.95 100M HDMI 1080P EXTENDER WITH INFRARED EXTENDER Extend your HDMI signal using CAT5e/6 cable up to 100m*. Use your remote in either location with the built-in infrared transmitter. *Depending on cable used & resolution. AC1734 ORRP $179 NOW 159 $ SAVE $20 LED STROBE LIGHT WITH MAGNETIC BASE High powered amber LED vehicle warning light for alerting other drivers or pedestrians. • Multiple strobe and flash patterns • 12-24VDC operation • Magnetic mounting or optional fixed mount ST3278 WAS $129 SUITABLE FOR CARS & TRUCKS NOW 99 $ Lightweight and compact unit for greater control and data storage options. 7" colour LCD. Built-in waveform generator for various testing applications. Two channel. High accuracy. QC1936 WAS $899 NOW JUST 799 $ SAVE $100 5W UHF CB RADIO TRADIES PACK Has everything you need to stay in touch when on the go! Includes: • 2 x 5W Waterproof UHF transceivers • 2 x Mini speakers/microphones • 2 x 12V Cigarette lighter charger • 2 x VOX Headset • 1 x Dual charging cradle with mains supply • Plastic carry case DC1069 WAS $449 NOW 349 $ SAVE $100 SAVE $30 NOW 39 $ 95 SOLAR LIGHT KIT WITH REMOTE CONTROL LI-ION / NI-MH BATTERY CHARGER EA SAVE 20% 2 WAY DISPLAYPORTS SPLITTER Send identical signals to two monitors simultaneously. AC1755 WAS $49.95 SWITCHER Select between two signal sources to send to a single monitor. AC1757 WAS $49.95 Designed to charge a 3.7V rechargeable Li-ion battery or 1.2V AA, AAA Ni-MH/Ni-Cd battery. • USB powered NOW • LCD screen MB3702 WAS $19.95 9 $ 95 HALF PRICE! Long life, lightweight Li-ion battery pack. Includes 3 x individual 3W lights and 1 x 3W solar panel. Doubles as a power bank with 5V 1A USB port to keep your phone changed. MB3693 WAS $79.95 NOW 4995 $ SAVE $30 TERMS AND CONDITIONS: REWARDS / CLUB MEMBERS FREE GIFT, % SAVING DEALS, & MEMBERS OFFERS requires ACTIVE Jaycar Rewards / membership at time of purchase. Refer to website for Rewards / membership T&Cs. IN-STORE ONLY refers to company owned stores and not available to Resellers. Page 1: BONUS 60/40 SOLDER 200G applies to 1 x NS3005 or NS3010 with purchase of Soldering Station (TS1564). BONUS $50 Worth of Filament with purchase of TL4410 includes all colours Standard, Exotic & Flashforge range. Page 2: Club Offer: GPS Tracker bundle includes 1 x each of XC3710, XC4430, XC4536, XC4989, MB3793, ST0505, RR0552, ZD0150, ZD0169, ZD0170 for $89.95. Bundle & Save: 1 x PB8820 + 1 x PB8840 for $14.95. Page 4: IP Camera Bundle includes 1 x QC3870, 1 x QC3876, 1 x QC3874 and 1 x QC3872 for $149. Easy DIY Alarm System Bundle includes 1 x LA5558, 1 x LA5046, 1 x LA5070, 1 x LA5256 and 1 x MP3486 for $78.95. Page 6: Club Offer: 20% OFF Dummy Cameras applies to LA5325, LA5332, LA5336-38 and LA5340-42. Rechargeable Outdoor Monitoring Bundle includes 1 x QC8041, 1 x SB2485, 1 x PP1996 and 1 x MB3619 for $179. 10% OFF Doorphones and Intercoms applies to AI5500, AM4310, QC3880, QC3884 & QV9090. Page 7: BONUS $50 or $100 Worth of Filament with purchase of TL4256 or TL4400 includes all colours - Standard, Exotic & Flashforge range. FREE LED Headband Magnifier (QM3511) applies with every purchase of Solder/ Desolder Station (TS1648). Page 8: 30% OFF Dies applies to TH2001, TH2002-TH2011 valid with purchase of Heavy Duty Crimp Tool (TH2000). For your nearest store & opening hours: 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide MONA VALE 48 Darley Street. Mona Vale, NSW 2103 PH: (02) 9979 1711 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 24.03.2020 - 23.04.2020. SERVICEMAN'S LOG It would be a waste of parts Dave Thompson One of the bigger challenges we face as electronic servicemen is finding replacement parts. It’s bad enough that many parts are no longer being made, but it seems that many manufacturers go out of their way to make it difficult for repairers. Some manufacturers use a combination of methods to frustrate us: obfuscating critical component values, using single-use or anti-tamper fasteners, withholding data sheets or circuit diagrams, or by using proprietary parts and either not making them available, or restricting access to them via ‘official’ repair agencies. Gone are the days when comprehensive back-end parts supply networks supported products for years after they were sold. Note that some companies do not use this model. BMW, for example, still stock or supply parts for every car they’ve ever made. Having said that, if you’re cynical, you might think that this is part of their business model. Who else do you know that makes cars with rod bearings that are maintenance items! And don’t get me started on the plastic water pump impellers or selfdestructing VANOS pumps... But at least you can fix your BMW when it breaks. That’s something. There are other ‘good guys’ out there, include the likes of Kenwood and a handful of well-known home appliance manufacturers. Admittedly, even for these manufacturers’ products, getting hold of some of the rarer parts for older models can be expensive or difficult (or both); but at least they are available. It’s a shame more companies don’t do the same; instead of us repairing their products, they prefer we simply dump them and buy a new one, which has never made sense to me. Wasteful business practices If I buy a product that fails and cannot be repaired, I am far less likely to buy another one made by the same company. My knee-jerk reaction is to take my business (and money) elsewhere. So it may help them make a quick buck now, but it’s going to cost them in the long run. That’s not to say the next manufacturer’s product won’t be exactly the same, but at least I’ll feel empowered about not throwing good money after bad. I’d also be more inclined to do my due diligence next time, and buy instead from a manufacturer who offers ‘real’ after-sales service and support. But perhaps more importantly, the amount of waste this generates is horrendous. Over the years, my microcompany has recycled (where possible) or dumped tonnes of plastics and metals, some of which is probably quite toxic to the environment. Multiply that by millions, and the result is mountains of e-waste. I’ve said it before; throwing away an entire device (for example a printer), for the sake of an unobtainable 10cent part, is disgraceful; something must change. Items Covered This Month • • • • A lack of replacement parts leads to much waste An old TV repair A series of Diesel Peugeots HP4350dtn printer repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz siliconchip.com.au Australia’s electronics magazine April 2020  57 Usually, it is those of us at the front lines who have to break the news to incredulous owners that their appliance is now junk because we can’t get some component for it. In many cases, even if we can get a circuit diagram, or are clever enough to change the design to allow newer parts to be used, the repair costs often exceed (or at least, come close to) the cost of a replacement unit. When it comes down to it, the less-expensive choice usually wins. I don’t think I’m being too dramatic if I say things have to change. Most manufacturers of old (say, one generation ago) would be appalled at the built-in obsolescence and the sheer waste of materials that modern companies create. My suggested remedy is simple: if a company makes and sells a product without a reasonable life expectancy, or fails to provide spare parts or information to support it, they should then be liable for that device when it fails. This would mean the company has to take the products back at endof-life and be made to dispose of the waste responsibly. Obviously, this would take some doing, but at least if they sell junk that lasts a year, they then have to deal with the fall-out from it. I know what you are thinking; these people could simply sell their toxic mountains of rubbish to a developing country for ‘processing’ and wash their hands of the whole thing, and of course, this is already happening. But a well-run system would make them prove that the items had been disposed of properly. Perhaps then, manufacturers would put more of a focus on long product lifespans and sustainability, and less emphasis on making quick profits. This would no doubt result in more expensive hardware, but I, for one, would be happy paying more for this. Anyway, if you pay 50% more for a product which lasts twice as long, you’ve come out ahead. almost every unit. The company must have known of the problem for years, especially as existing supplies of what spare PCBs there were available dwindled. Instead of admitting to the problem and producing more spares, to keep these not-insubstantial instruments going at very minimal cost, they chose instead to try to coerce owners into buying a brand new unit. I think that’s an immoral and unethical way to treat your customers, and wasteful to boot. The rub is that many of these pianos aren’t creaky old junk. They are well-loved pieces of furniture and most are still 100% working except for the failing flexible PCBs. It didn’t take me long to identify the problem; even a cursory Google search revealed many dozens of irate owners in the same position. There was talk of class-action lawsuits, but a rag-tag bunch of end-users have no real chance against some multibillion-dollar conglomerate with deep pockets. Even when such lawsuits are successful, the damaged parties usually get a pittance. The only real winners are the lawyers. The result is a group of people who will likely never buy another piano made by that company. So does this make for good business practice? The company seems to do all right, regardless. So I guess they got away with it. also threw up some parts challenges. The amp used a couple of output (power) modules I hadn’t seen before. Amplifier modules were all the rage back in the 70s and 80s. Possibly the best-known of these was the Sanken range. They made a family of hybrid thick-film stereo and monaural units. They look like a huge, flattened integrated circuit, with either a pressedmetal or moulded-plastic body and with legs protruding (usually) only from the bottom edge (making them effectively SIL or DIL packages). I used plenty of them in my homebrewed amps back then, and while the specs might be a little iffy compared to today’s offerings (or even discrete transistor-based circuits of the time), they still hold up pretty well. The SI-10X0 mono versions especially suited my needs, coming in 10W, 20W, 30W and 50W flavours. I got the most mileage from the SI-1050G, the 50W version. This was especially good for guitar, bass and general sound reinforcement applications. They were great bang-for-buck, being very robust, relatively inexpensive, able to run from a single or split power supply and requiring just a handful of external components to create a halfway decent power amplifier. This meant that the output stage could be kept pretty much the same from amp to amp, with only the Case study two Recently, I had an almostvintage stereo amplifier through the workshop, and this Case study one The reason for the above rant is a few jobs I’ve had through the workshop of late. One was an electric piano, which would have been landfill fodder if I hadn’t been able to manufacture a replacement for the dead flexible PCBs. From all accounts, these failed in 58 Silicon Chip Australia’s electronics magazine siliconchip.com.au preamp sections needing tweaking to suit the amp’s intended purpose. This also made them ideal for a generalpurpose workshop amp. Sanken made large quantities of these devices over a fairly long period, so there are still many floating around today. Most varieties are available at very reasonable prices from the usual surplus and second-hand outlets. Some are even NOS (new, old stock) parts. I have bought dozens over the years when they’ve come up on local auction sites; I even scored a couple of 30W modules from a home-built hifi amp I was given at an estate sale. So when I encounter modules in an older amplifier, they are often Sankens of one sort or another, meaning that my stock of the more common modules frequently comes in handy. If I don’t have the right one on hand, I can usually source it from the likes of eBay or direct from China. However, with this recent amp, the modules were not made by Sanken but rather, RCA. Worse, they had no model numbers visible. Faded and missing part numbers are another test for servicemen working on older gear. As a youngster, I was sometimes given boxes of old components from defunct workshops. Many had no markings, or the numbers had faded or rubbed off from rummaging. Often, with the part held at an angle to the light, a quick huff on the component would show an outline of the markings (the moisture in one’s breath adhering differently to the various textures on the part’s surface). Sometimes, a dab of moisture from the soldering sponge similarly revealed enough information to allow one to make an educated guess. These days, we have good-quality USB microscopes which can also help. While these older methods still work, for simple components like transistors, I often just use a component tester. As long as the unidentified component is still working, I can connect a suitable tester and it will (hopefully!) tell me all I need to know. However, these testers aren’t much chop on most integrated circuits, including old audio modules like this one. If someone really wants to prevent their components being identified, they are usually successful. (It isn’t uncommon to see component siliconchip.com.au labels ground off the top of packages!) In this case, I resorted to asking my old friend Google. Using the image search, I soon came up with a pretty good guess as to its identity. The mystery components appeared to be RCA TA8651As, sometimes marked HC2500. This is a ‘vintage’ 100W audio amplifier module, similar to the Sanken types. Fortunately, there are several used and NOS versions of these sold by vendors on overseas auction sites, though a good number of these will not ship to us down here in the dominions. After a few emailed enquiries, I managed to find someone who would ship them, complete with a data sheet, at a reasonable cost. So this particular amplifier was repaired and the owner happy. But that isn’t always how these stories turn out. In more than a few cases, I’ve hit a dead-end as the required parts are just not around anymore, meaning that the device either has to be modified and rebuilt with different parts, or consigned to the scrap heap. For example, I was asked to repair an older Pioneer stereo system that also used modular output devices, also unmarked and unknown to me. This was back in the pre-internet and pre-search-engine days (practically pre-history!), so I could not conduct an image search and had limited access to circuit diagrams. Back then, manufacturers seemed to give out circuit diagrams freely, although in this case, the owner couldn’t put his hands on the one that came with this unit. So, in the end, I could not identify them. The customer wanted to retain the unit, as he’d spent a lot on setting up his system and the amplifier matched the rest of his components. I ended up replacing the output sections completely with Sankenbased versions, complete with purpose-made PCBs. I suppose it sounded close enough to the original – the customer was happy with it – but of course, the modification likely killed any value it might have had as vintage hardware. Repairing a poorly-designed guitar amp More recently I had a 100W solid-state guitar amplifier in for repairs. This wasn’t an old amp, but it wasn’t exactly new-fangled either. Australia’s electronics magazine It is just a typical, run-of-the-mill combo with one 12-inch speaker and the amp itself sitting inside a folded metal chassis-mounted at the top of the wooden case. But it has a design quirk that makes it difficult to live with long-term. The amp’s output transistors are mounted to a compact heatsink assembly, tacked onto the rear of the chassis. While the heatsink looks quite beefy, it is barely adequate for the job, especially if the player is thrashing the amp at higher volumes. Design constraints meant there was no room for more heatsinking, so the manufacturer added a couple of cooling fans instead. This may seem like a good idea, but the problem is that smaller fans (in this case, 76 x 76mm) have to run at very high speeds to move enough air, and this means noise, especially once the fans get a bit older. These fans look similar to CPU cooling fans of the same era, and those fans used to wear out and get noisy reasonably quickly too. These days, CPU cooling fans (in desktops at least) tend to be bigger, with a more efficient blade design, and they run slower. While most are around 100mm, it isn’t uncommon to see 120mm fans cooling some of the higher-spec processors. Small fans may be able to move just as much air, but the noise they produce can be very distracting to some people. Larger, slower fans still produce noise, but generally not as much and at less annoying frequencies, even while they move the same amount of (or more) air. The fans in this guitar amp are thermostatically controlled, so they speed up as the output stages get warm, but that doesn’t take long even at normal practice levels. When the fans kick in, you have to crank up the amp volume to hear over them, which makes the amp work harder and the fans run faster, creating a vicious cycle. Recording in even a rudimentary studio would be out of the question with this amp, at least if you wanted to mic up the built-in speaker. It is possible to avoid using a microphone altogether by running a line-out from the amp’s preamp out socket, or by using a direct injection/ DI box and piping the signal straight into the mixing console. But many guitarists prefer to capture the combined sound of their amp and speaker, April 2020  59 which inevitably means sticking a mic in front of it. Since the customer wanted to record this way, we need to find a viable solution. My first thought was to replace the fans, but of course, there are no identical replacements to be had. Because the fans in all these amps wear out, genuine replacements have long since dried up. Using CPU fans instead is the only feasible route, but it means a bit of sheet-metal working and tinbashing, which the customer wasn’t overly keen on. After much gnashing of teeth and wringing of hands, we agreed that this was the best solution. I promised him that it would look as factory as possible, and with that pledge set to work. I decided to use larger fans to quieten them down a bit; specifically, 120mm models. So I’d have to trim the existing holes out to almost the edge of the metal case. The old fans sat over two circular holes; I reasoned that re-shaping these holes to a square would allow more airflow through, so I marked the lines out and then cut out the extra material using a Dremel rotary tool fitted with a small cutting disc. I finished off the edges with files and sandpaper, then marked and bored new mounting holes. I used eight standard M5 x 10mm PC fanmounting screws to hold the fans to the chassis. The old fans were connected with inline connectors, which I didn’t have, so I cut them off and soldered the new fan leads to the PCB, finishing things off with cable ties and heatshrink tubing. I broke out my workshop Telecaster and played the amp until the fans fired up. The noise difference was remarkable. The customer was very satisfied and as far as I know, still uses the amp today. That sure beats chucking it in the bin! a bright young spark (with much to learn) by one of my instructors, as he used to work for that company. When I joined, I was the junior of the western suburbs group. This group had some of the company’s best and most experienced servicemen, so I thought myself lucky to be in such exalted company. In those days, we used two-way radios to send servicemen to the next job – this was an open channel so everyone could hear what was said. If you got a radio call to phone the field service manager, it usually meant you were about to get a rocket over something. I was surprised upon receiving such a call, as I thought I had been a good boy that week. I was even more surprised when I was asked to go and have a look at a TV set that was usually handled by our group’s most senior technician. Obviously, our field service manager did not want to bruise any egos by letting everyone know he was sending ‘the kid’ to have a look at it. This lady was complaining that the set had a bright dot in the middle of the screen, and she could not see her favourite show properly. Most TV sets in those days were under a service contract; this one had been subject to many callbacks in recent times. Each time, no fault was found. I did not get off to a great start with the lady when she opened the door and exclaimed: “now they are sending children to fix my set!” But all was forgiven as she made great tea and scones. It was company policy that every call-out was recorded on a card in the back of the set. The card had a description of the work done on the set, including the components used and the signature of the attending technician. I was astounded by the number of calls recorded on this set, not only by our group’s senior serviceman, but by other very experienced technicians and the field service manager himself; all “no fault found”. The set had even been sent to the workshop twice and returned with “no fault found”. The trouble appeared to have started after the picture tube (CRT) had been changed. It was not unusual that old picture tubes would produce a dot in the middle of the screen when the set Old TV repair V. R. S., of Kelvin Grove, Qld is perhaps the only technician we know who solved a longstanding problem in a TV set without having to replace any components or make any adjustments. He didn’t even need any tools! Read on to see how he did it... In the late 1960s, I was in my twenties, and I worked for a large TV service company in Brisbane as a field technician. I was recruited from college as 60 Silicon Chip Australia’s electronics magazine siliconchip.com.au was switched off, or if the spot swallower circuit was faulty. The components in the swallower circuit had already been changed. I checked these against the circuit, and they were all the correct values. If the EHT (extra high tension) 15kV regulation were the problem, the picture would grow in size as the brightness was increased. There was no sign of this, so this left the new CRT as the culprit. I turned the set on and off several times but could not fault it. The set had been on for some time, so I asked the lady to leave it turned off for an hour, and I would return and try the set from cold. It took me more than an hour to return, and by that time she had given up and turned the set back on to see the midday news. I then had to reassign the job for first up the following morning as I was not available that afternoon. I pleaded with the lady to leave the set off until I arrived. The next morning, you guessed it, the set was on when I arrived – frustration was building. Again, I asked her to turn the set off and leave it off until after midday. She promised she would, but I had to be back before her favourite show began at 3pm. On arrival at about 2:45pm, I walked over to the set and turned it on, and all appeared to be functioning normally. Turning to the lady, I said: “I am sorry, I can’t find anything wrong with your set”. Her reply was: “are you bloody blind, can’t you see the white dot in the middle of the screen?” Oh! I then did an about-face, walked over to the window and drew the blinds, thereby removing the reflection of the window from the screen. The sun only shone on that side of the house in the afternoon. It appears that I was partly correct. The problem arose when the tube was changed, and the lady asked the technician to help her move the set to the opposite side of the room. It was previously under the window, where it would not reflect the incoming light. Checking the job card, I realized no-one had been there in the late afternoon. I took great delight in filling in the card with “problem found”, but deliberately not saying what the problem had been. This way, my compatriots would have to ask and I would smugly answer: “the kid one, all the others nil”! siliconchip.com.au A series of diesel Peugeot electrical repairs The TV series “Roadkill” describes a “plague car” as a car that runs fine but nobody wants it, because it’s not in fashion, it’s ugly, or it has some minor problem that is annoying but difficult to fix. You can pick them up cheap, but you’ll be lucky to sell them for more than scrap value. W. S., of Numurkah, Vic has quite a bit of experience purchasing them and fixing them up, as he now recounts... With over 450,000km on the clock, my Peugeot 405 (which I run on home-made biodiesel) was getting a bit clapped out. So when I spotted a diesel Peugeot 406 for $750, I jumped on it. It was filthy and had a few dings and rattles, but its main problem was that the speedo was not working. This prevented the owner from renewing its registration. The owner had been told that to repair it, the gearbox would have to come out. Hence the low price. After a good clean, the car started to look like something. I repaired a tie rod and a couple of other things, then turned my attention to the speedo. I found the speed sensor buried in the engine bay. It had to be removed from under the vehicle, which was not easy. It’s a two-wire reluctor. I put it on my scope and spun it, and got a nice-looking sinewave. I then put the sensor back in (again not easy), and re-checked the output, this time with the wheels jacked and the car running in gear. Again, I got a sinewave output. So at least the gearbox didn’t have to come out. This model has an analog-to-digital converter for the speedo signal behind the glove box, which I suspected was not working. But when I checked its output, I got a reasonable-looking signal. So I thought maybe the speedo itself was broken. I removed it and set up my power supply and fed it a pulse train, and it came to life. This had me quite puzzled and I spent a couple more weekends checking the wiring and re-checking everything. I ended up replacing all the caps in the converter, but the sensor, converter and speedo still would not work together. I decided to replace the speed sensor, but found that this type of sensor is not available new. It was only used for a couple of years and was replaced Australia’s electronics magazine April 2020  61 with a three-wire Hall-effect sensor. These are only around $20 each, so I got one. I had to climb under the car again, to remove the old sensor and modify the wiring to suit the new one. I found the transmission gear didn’t fit the new sensor quite right, so I 3D-printed a small adaptor. I removed the converter and re-wired everything, crossed my fingers and took it for a drive. To my surprise, everything worked as it should, and a quick check on my GPS confirmed that the speedo was accurate. I’ve now driven it another 70,000-odd km and so far so good. 406 number two A few months later, I suggested a Peugeot to a friend wanting to replace his Hilux. He wasn’t interested, but I convinced him to take mine for a drive. He came away suitably impressed, and when I told him it does 1200kms to a tank and cost me $750, that was it, he had to have one. So I found another 406 on Gumtree with an immobiliser problem for $600. I pointed out to my friend that HDI tuning in the UK will delete the immobiliser from your ECU for around $400. It turns out that the owner had taken the car to several places, but no-one knew how to fix it. The dash was still in pieces from the last autoelectrician who looked at it. That being the case, he managed to get the car for $450 and spent the afternoon putting it back together. He was about to order the remapped ECU when on a whim, he decided to put a battery in and see what would happen. The car started straight up; he drove it for about two years on biodiesel before the immobiliser fault came back. So, he ordered a new ECU with a remap and the immobiliser turned off. All that he had to do when it arrived was disconnect the battery, remove the old ECU (which is under the bonnet), plug in the new one, connect the battery and not only would it start again, he’d gained an extra 45 horsepower. The 306 I saw a diesel Peugeot 306 listed for sale on Gumtree with 160,000km. The listing said it wouldn’t start. I didn’t really want another car, but I phoned my buddy because his son (who had just gotten his learner’s permit) was looking for a car. This one had a similar story; it had been to many workshops, including the Peugeot service centre, but nobody could fix it. The car was purchased for $300 and towed home on a trailer. A new battery was fitted, and the car started straight up. The car was well looked after and drove like a new vehicle, so a roadworthy certificate was arranged. All it needed was a new tyre. But after a week or so, it stopped and refused to start. At first, I thought it was the immobiliser problem again, but the 306 is quite different from the 406. It doesn’t have a display to tell you there is a fault. I plugged in an OBDII reader which wasn’t much help, as Peugeot uses their own software called PP2000. I had access to another running 306, so I swapped the ECU, body system interface module and the immobiliser chip in the key to see if the fault would move to the other car. It did not, so I knew that these parts were not part of the problem. 62 Silicon Chip It was then I noticed that I could not hear the in-tank fuel pump coming on when the ignition was switched on. After removing the rear seat, I checked the pump by running 12V directly to it. The pump ran, and the engine started. Then I checked the wiring loom and found that there was 12V present at the pump end, but it dropped to 3V with the pump connected. After a bit of research on internet forums, I found that the fuel pump relay was a common problem; it is buried in the engine bay. I eventually managed to get the sealed relay out and then used a hacksaw to remove the cover. Once the cover was off, it was easy to see the problem: the contacts were entirely burnt off. I ordered a new relay and fitted it, but the car still would not start. There was still no voltage getting to the pump. I re-checked the wiring, plugs and terminals. It was time to buy a service manual and the PP2000 OBDII software. The software arrived, and I was disappointed to get the message “P0087 code low fuel pressure”. With the pump not running, this was just stating the bleeding obvious. So I took a look at the wiring diagram. The fuel pump relay gets 12V from the fusebox, and its ground is connected to the ECU via the inertia switch, which cuts the fuel supply if the car is in an accident. It turns out that with all my wresting to get the relay out, I must have bumped it as it was open circuit. Pushing the top reset button on this switch allowed the engine to start. I took the car for a drive, and the engine just didn’t sound right, so I plugged the OBDII reader back in and re-checked the codes with the PP2000 software. It came up with “3rd piston deactivator”, which is on the highpressure pump which is driven by the cambelt. The plug to the deactivator looked fine, but the wiring to the plug looked like someone had played with it, the insulation tape was starting to fall off. After removing the tape, I could see that the wiring had been cut and modified and the deactivator had 12V feed to it all the time. I put the wiring back to standard and the codes cleared from the ECU. The car has run reliably on biodiesel until a couple of weeks ago, when the harmonic balancer came apart. Fortunately, that was an easy fix. 406 number three I got another phone call from my friend to say that his Holden Cruze had an automatic transmission fault and wouldn’t go. Long story short, while it was still under warranty, the dealer had in the fine print that they would only pay for $1500 in repairs and the trans repair would cost around $6000. I didn’t want to go near it, but I saw another 406 on Gumtree. Again, it had a few ‘issues’; it was going into limp mode, and the climate control wouldn’t work. It was bought for $600 and towed home. I connected up my reader to its OBDII port and got what must have been 20 error codes. I reset them all, and we took the car for a drive. It still didn’t seem right, so we re-checked the codes, this time just getting one code for the MAF (mass air flow) sensor. A quick check found that the sensor had been disconnected and the plug taped up. This probably was done because if the MAF sensor is faulty, it turns Australia’s electronics magazine siliconchip.com.au the engine check light on and for some reason, disconnecting the sensor turns the light off. The sensor was removed and cleaned with contact cleaner and refitted. That fixed it; the codes were gone, and the engine ran properly again. Turning to the climate control, I found that one fuse had blown. Predictably, after replacing it, it blew again. I read up on the Peugeot forums and found the speed controller for the blower motor was a common problem. This is located under the glove compartment. Access is difficult, but I managed to remove it, and I sensed that burnt PCB smell. The plug was also melted. A new controller and plug with wiring was ordered and fitted to the car, and the fuse replaced. But the fan would only run flat out and wasn’t blowing any air out of the vents. After much investigation, swearing and frustration, I determined that the blower motor was running backwards, which was very odd. I ended up going back to Peugeot 406 number two and comparing its voltages. It turns out that the new speed controller and plug had the 12V and ground colours reversed. Brand new, out of the box, the red wire was ground and black was 12V! I fixed that and fired off a stern e-mail to the supplier; finally, the climate control worked how it should. The car went in for a roadworthy certificate; all it needed was a tail light and new wiper blades. So it turned out to be another great deal! If you are thinking of buying a plague car, be aware that Peugeots are not that common in Australia, so many garages are not familiar with them. They don’t want to put in the effort or time to fault-find problems with them. The good news is they are very common in the UK, so advice and parts are available on UK forums and via ebay.co.uk Helping to put you in Control IP65 Loop Powered 4 Digit Process Indicator The Simex SWE-N55L is a 4 Digit Process Indicator which accepts 4-20mA input signals and is loop powered. It comes with 1 Relay for alarm or control. SKU: SII-110 Price: $189.95 ea + GST IP65 Current/Voltage Input 4 Digit Process Indicator The Simex SRP-N118 is a 4 Digit Process Indicator which accepts 4-20mA, 0-5V or 0-10V DC input signals. It comes with 2 Relays for alarms or control and RS485 communications. DC 19~50V powered. SKU: SII-102 Price: $289.95 ea + GST Temperature Sensor for Temperature Instruments PT100 temperature sensor with handle. Operating range -40 to 150C. SKU: HES-150 Price: $29.95 ea + GST SZP-73 4-20mA Panel Mount Calibrator Current test set allows for generating user-defined current (in the 4-20 mA range). SKU: SII-401 Price: $239.95 ea + GST HP4350dtn printer repair D. M., of Toorak, Vic knew that it would be difficult and expensive to fix a faulty PCB in his printer. But he came up with a much easier and cheaper fix that worked just as well... I have had a Hewlett-Packard LaserJet 4350dtn printer for a while now. It’s a heavy-duty, business-grade 1200dpi laser printer and as such, comes with an embedded Ethernet port as well as USB. Recently, its Ethernet port failed, so I could not use it over my home network, only via direct USB connection. This is apparently a known problem with these printers; the problem develops in their main control board, known as a “formatter” board. Instead of replacing the formatter board, which otherwise worked apart from the Ethernet section, I found it was much easier and cheaper to plug an HP620N JetDirect print server card into one of the printer’s EIO (Enhanced Input/Output) accessory card slots. I purchased this from overseas via eBay for less than $20 delivered. Once I installed the card, I plugged in the Ethernet cable and the printer immediately worked over the network; no additional configuration was needed. The card took over the failed Ethernet function of the formatter board. So an oldish but extremely robust and economical printer was saved from the scrapheap for a small outlay. SC siliconchip.com.au DA284 Pressure Compensation Valve Prevents pressure differentials in encIosures with a high degree of protection are a result of internal and external temperature changes. SKU: SPE-200 Price: $13.95 ea + GST Conductive liquid level sensor Simex DRS-303 is a liquid level sensor for conductive liquids. Ideal for use in sumps, water tanks and detect water leaks. SKU: SIS-001 Price: $109.95 ea + GST N322-RHT-24V Temperature & RH Controller 24 V Panel mount temperature & relative humidity controller with sensor probe on 3 meters of cable. 2 independent relay outputs. 12 to 30 VAC or DC powered. SKU: CET-108 Price: $235.00 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine April 2020  63 Last month we told you what it does and how it works. Now we put it all together and start hatching chickens! Part II – by Tim Blythman and Nicholas Vinen In our March issue, we introduced this versatile Arduino-controlled heating/cooling device. It uses Peltiers to heat or chill water in one or more loops, and it’s pretty easy (if a bit involved) to build. It can be used for many tasks, including (but certainly not limited to!) brewing, making cheese and cooking . . . and even hatching chooks! This article has all the instructions describing how to build the two Arduino shields, program the Arduino, build the water loops and tweak it to suit your needs. J It will only use as much energy as We’re sure that readers will think of ust to prove that this project has many possible uses, here’s another needed to maintain that temperature, other uses that we haven’t. But enough of that; it’s time to deone we thought of since last month: and on a sweltering day (which can    it could be used for an egg incuba- kill the embryos), it can actually pro- scribe how to put it all together, and get it up and running. tor, to keep bird or reptile eggs warmed vide a little cooling! to a constant temperature so Construction that they will hatch. We’re going to start by buildThat is often done with a ing the two shields, as this is a heat lamp, but that’s wasteful prerequisite to getting the whole and doesn’t take into account thing up and running. However, varying ambient conditions. if you wish, you can do some baChicken eggs are ideally sic testing of the ‘water circuit’ kept at 37.5°C until they hatch, without the control circuitry. and most other birds and repYou can rig up the fans, tiles are reasonably similar. pumps and Peltier devices to By looping some water tubrun directly from a 12V source ing under the eggs (ideally to check that everything is workmade from a thermal conducing before proceeding. tor like copper) and placing a The I2C character LCD allows sensor amongst them, you can a number of parameters to be displayed. Peltier Driver shield set up the Thermal Regulator Temperatures from all six sensors are available, as The Peltier Driver shield uses to maintain this ideal tem- well as fan speeds, temperature setpoint, mode and Peltier device drive level. a mix of surface-mount and perature. 64 Silicon Chip Australia’s electronics magazine siliconchip.com.au siliconchip.com.au CON1 25A CON2 12V INPUT 10 F L1 15 H 10 F 10 F SILICON CHIP © 2020 F1 10 F GND REG1 10 11 12 # 9 # # 8 Q1 Q2 Q4 Q3 IRLB8314 IRLB8314 IRLB8314 IRLB8314 # = PWM 6 4 3 # RX TX 2 1 IC1 HIP4082 # 0 D1 D2 1.8k 10k 10k 100nF 100nF 4148 4148 100nF # 5 7 VIN GND 5V 3V3 RST 13 A5 A4 A3 A2 A1 A0 through-hole parts; its overlay diagram is shown in Fig.7. None of the surface-mounted parts are too difficult to solder; the smallest parts are the 3216/1206-size capacitors, which as their name tells you, are relatively large at 3.2 x 1.6mm. Tweezers, solder flux and solder braid (wick) will be handy – if not mandatory – for working with these parts. Start with those capacitors. They connect to some large copper areas, so may require a fair bit of heat to solder correctly. Apply a small amount of flux to their pads, then solder one lead of the capacitors in place. If it is square and flat, solder the other lead, otherwise use tweezers and a soldering iron to adjust the first lead before continuing. The other surface-mounting part is the inductor. As well as connecting to some large copper tracks, it also has a fair amount of thermal mass itself; (if you can) it’s time to turn up the iron even higher! Just as for the capacitors, apply flux (be generous this time), then solder one lead to the PCB. Once the component is in the correct location, solder the other lead. Now is a good time to clean up the excess solder flux using a dedicated flux cleaner or isopropyl alcohol. Fit the fuse holder parts next, with a fuse temporarily fitted. This ensures that they are spaced and orientated correctly. The fuse can stay in place once they are mounted. The iron temperature can be reduced for the remaining parts. Continue by fitting diodes D1 & D2 with the cathode stripes orientated as shown, then mount the three resistors. If you aren’t sure which is the 1.8kΩ type, measure it with a DMM. Next fit IC1, ensuring its pin 1 dot/notch goes to the left. We recommend you solder this directly to the board, rather than using a socket. Now bend the leads of Mosfets Q1Q4 to fit the pad pattern and attach each one to the board using a machine screw and nut before soldering and trimming the leads. Make sure to do the screw up tight before soldering, as tightening it after soldering could damage the solder joints. Follow with the through-hole capacitors, which are all the same type and not polarised. But make sure to push them fully down before soldering, as there will be another board stacked above this one. Fig.7: this diagram and photo show where to fit the parts on the Peltier Driver shield. There are five SMDs (four capacitors and one inductor), but they’re all quite large. Flux paste will help you solder these; you will need a hot iron to solder the inductor. REG1 is not needed if 12V is being supplied to CON2. In this case, you can install a link across the lower two pads instead. Similarly, push REG1 down as far as you can before soldering it. As mentioned last month, depending on how you will be applying power, you may want to leave REG1 off or link it out (with a wire between its left-most and right-most pads). But in most cases, it is safe to fit it anyway. (The photo at top right shows our board as fitted with a link in place of REG1). The 5x2 header can be soldered now. You can use two 5-way SIL headers side-by-side. Next, fit CON1 and CON2. Since CON1 sits above the USB socket on the Uno and CON2 above the DC socket, make sure to trim their leads as short as possible after soldering. These are large-leaded parts sitting on copper pours, so might require the iron temperature to be increased slightly. That just leaves the four stackable headers. We recommend sandwiching the shield between the Uno (underneath) and another shield (above), if you have one. This will help to align the pins. Tack the end pins of each row in place and ensure that all four of them are flat against the PCB at each end. This can be fiddly as moving one can tend to move the others. Remove the Uno from below and solder the remaining pins before going back and refreshing the end pins of each row. Jumpers Insert the three jumpers/shortAustralia’s electronics magazine ing blocks, as shown in Fig.7. You shouldn’t need to change these unless you are radically changing the software for your own purposes. This sets LK1 to use Arduino pin D10, LK2 to use D9, LK3 closed and LK4 open. Building the Interface shield Refer to Fig.8. Start with the resistors. As mentioned earlier, it’s best to check each batch with a DMM to verify their value before fitting them. This is especially important as the 100Ω, 1kΩ and 10kΩ types have similar colour bands. Follow with the three diodes, which are all the same type, but ensure they are orientated as shown in Fig.8. Install the tactile pushbutton (S2) next. Push it down until it clicks and sits flat against the PCB. There are only two capacitors, both 100nF MKT or ceramic types, one at each end of the board near each IC. Solder these next. Then mount IC1; again, we don’t recommend that you use a socket. Ensure that it is fitted with its pin 1 towards CON11. Solder two leads and check that the device is flat; if not, re-heat one of the solder joints and adjust it. Then solder the remaining leads. Next, install transistors Q1-Q3 and temperature sensor IC2, all of which are in TO-92 packages. Q3 is a different type from Q1 & Q2, so don’t get them mixed up. Match the transistor bodies with the silkscreen outlines. You may need to crank their leads out to fit the PCB pads. April 2020  65 k PB1 D2 D1 4004 CON10 4004 CON11 P2 Q3 + Q2 AREF GND 13 11 12 1k 1k 1k 1k 1k 1k 100 10k # 10 + IC1 74HC4053 100nF 4.7k 4.7k 4.7k 1k 1k 5V GND VIN 12V 5V IC2 TS5 1 # 9 # 8 #=PWM 7 6 # 5 # 4 # 3 2 1 Q1 TX RESET 3V3 A5 A4 A3 A2 A1 A0 100 + TS2 1 Fan 3 + S1 F1 JP1 Fan 1 Fan 2 TS4 + 4004 TS3 + LED1 1k D3 IRX1 TS1 + LED3 I2 C GND SDA SCL VCC LED2 Power 100nF P1 RST CON12 + S2 0 RX – Fig.8: building the Interface shield is straightforward. We recommend that you orientate the polarised headers as shown here, but only the fan headers are critical. S1, F1 and JP1 can be omitted if 12V will be supplied from the Peltier Driver shield rather than via CON12. You can use stackable headers along the edges, as shown here, or regular headers fitted on the underside. Then fit terminal blocks CON10CON12 and all the polarised headers. Only the orientation of the fan headers is critical; make sure there are rotated as shown in Fig.8 and also ensure that the terminal blocks are mounted with their wire entry holes towards the nearest board edge. Use a similar technique to the IC when soldering these headers; solder one pin to secure the part, then check it is flat and square before soldering the remaining pins. Note that we’ve shown the I2C display header rotated relative to the fan headers; this makes it harder to mix them up as you will damage the display if you accidentally plug it into a fan header and apply power. The twoway headers should all be mounted facing the same way, so that it’s easier to rearrange how the temperature sensors are plugged in later. The three LEDs can be fitted next. The red LED is closest to the edge of the board, green in the middle with the blue LED nearest the switch S1. The cathodes of all three LEDs go towards that switch. Depending on how you are planning on using the finished project, you may wish to attach these via flying leads or even fit pin headers in their place and panel-mount the LEDs. A similar comment applies to IRD1; this can also be fitted off-board, although if you’re doing that, you’d best keep the leads short if it is to work reli66 Silicon Chip ably. Mount this now; if installing it on the board, make sure its hemispherical lens faces in the direction shown on the PCB silkscreen. You can bend it to face upwards, although you’ll have to be careful to avoid interfering with the nearby two-pin header. The piezo buzzer PB1 sits near the centre of the PCB. Check its polarity before fitting it. If you are planning to power the finished assembly via the Peltier Driver shield, you can leave off switch S1, fuse F1 and jumper JP1. But it doesn’t hurt to fit them anyway. If fitting them, try to ensure they are all sitting flat against the PCB. The switch and fuse holder are quite chunky and may require more heat than smaller components. Completing the Interface shield simply requires fitting the Arduino headers. Standard male headers will be sufficient for most cases, although we fitted stackable headers to our prototype ‘just in case’, as seen in the photographs. Like the headers for the Peltier Driver shield, you should use other Arduino boards as jigs to ensure the pins are flush and straight. Assembling the stack The shields are designed so that the Peltier Driver shield fits between the Arduino Uno at the bottom and the Interface shield on top. The Interface shield must be on top so you can acAustralia’s electronics magazine cess its various vertical headers. The simplest way to supply power is to feed it in through the Peltier Driver shield. It will feed modest amounts of 12V power to the boards above and below. But note that if you are supplying more than 15V to the Peltier Driver shield, REG1 (which is quite small) cannot provide much current to run any pumps or fans connected to the Peltier Interface shield. In this case, it is better to omit REG1 and supply 12V directly to CON12 on the Interface shield. The power supplied to CON12 on the Interface shield will also power IC1 on the Peltier Driver shield, but this will not draw much. When assembling the stack, you may find some places where leads or pins touch components on the board below. Trim these if possible; otherwise, insulate with electrical tape. The USB socket of the Uno should have tape placed on its top to protect it from the power connections on the Peltier Driver shield. If necessary, temporarily disassemble the stack if you need to attach power cables to the Peltier Driver shield. Preparing the LCD screen You can purchase the LCD from the SILICON CHIP ONLINE SHOP or buy the parts separately from Jaycar. Either way, you will have to attach the I2C adaptor to the LCD. Line up respective pin 1s on the I2C adaptor module and the LCD board and tack one pin in place. Confirm that the two PCBs are parallel but not touching before soldering the remaining pins. You will also need to make up a lead to go between the I2C header on the LCD and the I2C header on the Interface shield. We used female-female jumper wires to test our prototype, but these were quite short. The best option for a permanent setup is to make up a cable with a fourway polarised locking plug at each end. See Fig.8 for the required connections, and check the labels on the LCD I2C adaptor board. As the pins are in a different order (GND, SDA, SCL, VCC on our board and GND, VCC, SDA, SCL on the LCD), some of the wires will have to cross over. The connection at the Interface shield is keyed while the header supplied with the LCD adaptor is not. You siliconchip.com.au The Interface shield sits on top of the stack as cables need to be plugged into its vertical headers. So the height of the components on this board is not critical. Note that the fuse holder is empty as 12V is supplied via VIN. So we could have omitted S1, F1 and LK1. might like to replace the header on the LCD with a keyed type so a reversed connection cannot be made. Starting to put it all together At this stage, you need to decide on the exact configuration required for your application(s), if you have not already. Most likely, you will want to build something that looks like one of Figs.3-6 in last month’s article. The water paths are critical. Ideally, these should be as short as possible, although if you wish to save on elbows, the tubing can be run in gentle arcs instead of at right-angles. Remember that you have the option of placing the water connections at the same or opposite ends of the water blocks. We did not test which method would give better results; we suspect the difference will be quite small. Another point to consider when designing your system is that air from the radiator or heatsink should not blow onto other parts of the assembly, as this will reduce its overall effectiveness. In our case, we also ensured that the two radiators (one existing on the laser cutter and one on our new boost circuit) blew air in different directions. This can be achieved by placing them next to each other, so that they pull fresh air from the same direction and exhaust in parallel. Note also our comments last month about insulation. For running a wasiliconchip.com.au ter bath near ambient temperature for cheesemaking or brewing, the demand will not be too high on the Peltier devices, but sous-vide cooking around 60°C or higher will require decent insulation to be able to reach the more extreme temperature targets. If you struggle to reach your temperature target, improved insulation may help. Peltier device mounting Our kit came with some hardware for mounting the water blocks to ei- ther side of the Peltier devices. It included several strap pieces which are clamped by M4 machine screws. Small springs ensure that a uniform and not excessive amount of clamping force is applied. These straps are intended to clamp two water blocks, one each side of a row of Peltier devices. If you are using one water block and a heatsink, see below. Start by assembling the water blocks and Peltier devices. This can be fiddly as several things need to come together at the same time and they will all have a coating of thermal compound. Clean the water blocks and Peltier devices with isopropyl alcohol or similar to remove any contamination and residues. Allow it to dry. Lay a row of straps on your workbench, with machine screws and washers fitted through the holes; the heads should face down. Rest one water block on top and apply a minimal amount of thermal compound to one side of each Peltier device, spreading it out. The optimum amount of thermal compound is as thin as possible, but covering the entire area of the contacting surfaces. Ensuring that the Peltier devices are orientated the same way, press them down onto the water block, sandwiching the thermal compound. If you have (for example) all the red leads to the left and all the black leads to the right, they should be orientated correctly. We used a pair of Molex connectors (in this case, Jaycar Cat PP0744) to share the current drawn from the ATX power supply. These connectors are rated at around 10A each, so two are needed for our application. Australia’s electronics magazine April 2020  67 The minimal hydraulic circuit (corresponding to Fig.5 from part one) uses a finned heatsink supplemented by fans to remove heat from the Peltier devices and water block. It’s the same arrangement as used on many amplifier and power supply circuits. Spread thermal compound onto the top of the Peltier devices, then rest the second water block on top of this, making sure that the barbed ends are orientated as you require. Place the remaining strap pieces in place, followed by the springs, washers and then nuts. Tighten the nuts until the springs start to pull up. Ensure that the Peltier devices are square and evenly spaced; at the very least, they should not protrude from the water blocks. The nuts can then be tightened down, ensuring that the springs are not compressed to the point that the coils are touching. Using a heatsink instead To test whether we could get away without a radiator, we used a heatsink much wider than the Peltier devices (40mm). Therefore, we could not use straps on both sides to pull the whole assembly together. If you have a heatsink that’s 40mm wide, that may be possible, but you’d probably have to cut down a larger heatsink to get one the right size. We recommend you use a larger heatsink anyway, as this will allow 68 Silicon Chip larger fans to be used, giving more effective heat transfer to the air. Assuming your heatsink is significantly more than 40mm wide, you will need to drill and tap holes on the face of the heatsink to mount the Peltier devices. Lay out the Peltier devices and water block on the heatsink to determine where the holes need to be and mark them, lined up with the gaps between the fins if possible (this will allow the holes to be tapped through). If you do not have a tap, and you can line the holes up with the spaces between the fins, instead of tapping you could drill right through and use long screws held in by nuts fed in between the heatsink fins. We know from experience that this works but doing it is very fiddly. If tapping, drill holes to the diameter specified for that tap. The holes required are usually slightly smaller than the tap size. Many taps are supplied with appropriately sized drill bits. Having drilled the holes, carefully tap them. Take your time with this and reverse the tap if it jams; this is usually enough to clear the swarf. You need Australia’s electronics magazine to use a lubricant to help as well; we have used WD-40 or 3-in-1 oil with success, although kerosene is also said to be ideal for aluminium. Clean any residue off the heatsink and sand down any high spots around the tapped holes. Since the brackets have a good amount of clearance from the Peltier devices, it is not critical that the site is perfectly flat. Clean the water blocks and Peltier devices with isopropyl alcohol or similar to remove any residues and allow to dry. Apply a very thin layer of thermal compound to both sides of each Peltier device and place it on the heatsink in the correct location. It’s not a problem to adjust them, but it can be messy if the thermal compound gets everywhere. Ensure that the Peltier devices are all facing the same way. As well as the coloured leads, many have identifying marks on one side only. Rest the water block on top and then rest the straps on it. For each hole, first place the washer, then spring and thread the machine screw into the heatsink. siliconchip.com.au Once all have been started, check that everything is where it should be and tighten the screws so that the springs pull up, but the coils are not touching. For our tests, we mounted the fans with cable ties around the entire assembly. Your heatsink may be designed to have machine screws threaded directly between the fins, in which case this will work quite well. Another option is to drill small holes through the fins near their tips. You can then thread cable ties through these holes and the fan mounting holes. In any case, ensure that the airflow from the fan in blowing towards the heatsink. Pumps The input (suction) side of the submersible pumps we’ve specified must be fully under the surface of the water, as they are not self-priming. Using the submersible type means that a hole does not have to be cut in the side of the water vessel, avoiding the possibility of leaks. For our laser cutter, we placed the pump near the top of the vessel; the intent here is that if there is a leak in the Peltier cooling circuit, only a small portion of the laser cooling water will be lost. The pump could run dry, but that is better than having the laser fail. We managed this by cutting a hole in the lid, which is a firm friction fit for the hose. If the hose is loose, a couple of cable ties can be used to limit vertical movement. We found that if we placed the pump too close to the surface, a vortex would form, allowing air to be sucked in. The solution is to lower the intake, which will make a vortex less likely to form. Since our pump was resting on the laser’s pump in this vessel, we could not lower the pump, so we attached a small piece of hose and an elbow facing downwards to lower the suction point. Another option is to simply increase the water level, if there is room to do so. You might find that after starting the pumps that the level drops due to water being moved to the piping and you may need to add water anyway. As the water passes through devices such as the water block and radiator, it should enter at the bottom and leave from the top. This is to ensure that any water bubsiliconchip.com.au This close-up of the Peltier Drive Shield gives a better view of the jumper shunt and also shows how all parts sit low to clear the shield fitted above. bles can rise up and out. Any voids where air has collected internally will not be contributing to heat transfer, so these should be minimised. The water path should return to the initial vessel to complete the circuit. We cut a second hole in the lid to fix the return pipe in place. It can also be locked in place with the judicious use of cable ties (or silicone sealant). Situate the return slightly above the water level. This will allow the return flow to be seen while minimising the amount of air entrained. Air is not a good conductor of heat and air in the water lines should be avoided. If possible, situate the return as far as possible (on the vessel) from the pump. This allows the water to mix freely and take on a uniform temperature. With the water circuit complete, the pump can be tested by connecting it to a 12V supply. The return should be a steady, continuous stream, indicating that a good amount of flow is occurring. Check for leaks and that there is no air trapped in the pipes. Top up the water if necessary. If there is no flow, check the pump polarity and flow direction. The pumps we used are quiet but audible. With the pumps running, you could also try powering the fans and Peltier devices to see what kind of performance the system can achieve. Keep Australia’s electronics magazine in mind that without any controls, the water can still get quite hot. Once this is satisfactory, mount everything in place so that it does not move around. We found a spare shelf panel on which to mount everything. Thermistors The 10kΩ thermistors we are using came potted into a small ring lug for mounting. They also had a reasonable length of cable attached, so all we needed to do was terminate each thermistor with a polarised plug to suit the Interface shield. The thermistors are not polarised, so it doesn’t matter which wire goes to which pin. But if you are looking to place a sensor in your brew liquid (as in our diagram), we don’t suggest that you use these. Instead, you would use one which is clad in food-grade stainless steel. These are available, but cost a bit more. You can mix and match thermistor types, as long as they all have the same nominal value and similar curves (check the specified Beta value). We weren’t sure whether the beads we got were waterproof, so we shrank a good length of heatshrink tubing on those which were to be immersed in water, extending past the thermistor. We then firmly clamped the free April 2020  69 This view shows our complete system which will be installed in our laser cutter. The plastic tray was in case of leaks. end in pliers, sealing it, although injecting silicone into the open end before clamping it would make a more reliable seal. Another option is to assemble these from scratch, using leaded thermistors, wire and socket headers. Our software has been written to work with either 10kΩ or 100kΩ thermistors; just be sure to check the code before compiling to make sure that it’s expecting the values that you’ve used. We prefer 10kΩ types as these are less likely to be affected by EMI or other stray fields. in the circulating water must be thoroughly waterproofed. It should also be mounted to prevent it from falling in above the sealed part, if it is not fully sealed. If it does not need to be removed, a pair of small holes in the side of the container (above the waterline!) could be used to thread a cable tie around the thermistor lead. Attaching the thermistors to the water blocks (and thus near the Peltier devices) was quite straightforward. We simply loosened one of the mounting straps and slipped the flat end of the thermistor under the strap before tightening. Power supply To power our Thermal Regulator, we used a spare ATX power supply, as designed for use in a personal computer. This is an attractive option if you have a surplus unit available. But if you have to purchase one, they are also relatively inexpensive, and can be quite efficient. An alternative is one of the many open-frame power supplies that exist. Altronics M8692 is such a device. Mounting the thermistors The small ring lug on the thermistors we used made mounting them straightforward. Although we did not end up using the heatsink option, a simple tapped hole and machine screw would be adequate to fasten the thermistors to the heatsink. For the radiators, an existing mounting screw was co-opted to thread through the thermistor’s mounting hole and thus fasten it. As noted above, the thermistor used 70 Silicon Chip ATX power supplies require the green wire to be pulled to 0V (any black wire) to turn on. We made a simple jumper with a 2-pin header and some heatshrink; the power supply now activates when it receives 230V. Australia’s electronics magazine siliconchip.com.au You will need to do some mains wiring to use this unit; the mains wires are exposed but protected behind a barrier strip. It is intended that this sort of supply is installed inside an enclosure and we think this is wise, whatever your power supply, as it will help to keep the water and electronics separate. If the enclosure is metal, be sure to Earth it properly. The 12V wiring needed for this sort of supply is straightforward and requires nothing more than a 30A twin cable (ideally red/black) to be terminated at each end. ATX power supplies need a bit more work on the 12V side but only require an IEC type lead to be plugged in to supply the mains. There are usually multiple 12V (yellow) and GND (black) wires; you will need to use several of each to ensure that you can draw sufficient current. ATX power supplies also have a power signal that needs to be pulled low to command the power supply to start. This wire is usually coloured green; we simply used a jumper to short it to an adjacent ground wire. See the photos which show how we wired up our supply. If you are sure you do not need the power supply for use on a computer in the future, then several yellow wires (12V positive) and black wires (ground) can be bundled together and spliced into a single pair of high-current conductors. Whatever your source of power, connect it to the 12V input terminals on the Peltier Driver shield. The positive terminal is the one closest to the fuse. Wiring it up You may need to take the Arduino stack apart to wire the Peltier devices to the Peltier Driver shield. The orientation with which the Peltier devices are connected will determine the voltage polarity required for heating or cooling, but it is easy to change the software if it is reversed, so don’t worry about it too much. Just make sure they are all connected with the same polarity. We used a small piece of terminal strip to break out the connections; it also allows us to run the short leads on the Peltier devices further from the Driver shield. Fit the Uno below and the Peltier Interface shield above. Plug in the siliconchip.com.au Sensor TS1 TS2 TS3 TS4 TS5 Location Temperature to be regulated On Peltier water block, TS1 loop On Peltier water block, opposite loop from TS1 & TS2 On radiator/heatsink, same loop as TS3 Spare (currently unused) Table 1 – thermistor connections fans, I2C LCD and thermistors. See Table 1 for which thermistor should be plugged into which header. If necessary, the sensor mapping can also be changed in software. The pump(s) connect to the two screw terminals near IC2. Check the polarity is correct as the pumps will not work correctly if they are spinning backwards. If you have a separate 12V supply for the Peltier Interface shield, connect that now. Only a fairly small fuse is needed (say, 3A) unless you have some very large fans and pumps. Control software The software we have written is somewhat basic but provides most or all of the necessary functions for a variety of jobs. It measures the temperature of all six sensors, but only uses the data from three to make decisions. The remaining temperatures are displayed but not used by the control software. You will need to install the Arduino Integrated Development Environment (IDE) to program the Uno board, and this also contains everything you need to customise the software, if you choose to do so. We used IDE version 1.8.5, and suggest that you do the same to avoid any problems which may occur due to changes between versions. As with many advanced Arduino projects, some external libraries are needed. They might seem complicated, but using them is easier than having to write our own interface functions. These are all included in the download package, along with the Arduino ‘sketch’ (program code) itself. The I2CLCD library is one we have adapted from another open-source library. We have added the ability to auto-detect the I2C address of the LCD. The easiest way to add this library is to copy the “I2CLCD” folder from the .ZIP archive to your libraries folder (in Windows, this is inside your Documents folder, within a subdirectory called “Arduino”). Australia’s electronics magazine The connections we made on our prototype are shown here although only the first three are critical for the software to be able to control the Peltier devices. You might as well copy the remaining three supplied libraries too, as the versions we have included are known to work. These three libraries can also be installed by finding them by name in the Library Manager. To do this, search for “OneWire”, “DallasTemperature” and “Irremote” and install each in turn. If you already have folders with one of these names, you may already have the library installed, so you probably don’t want to overwrite it unless you find our sketch doesn’t work. If you install libraries by copying the files, you may need to close and re-open the Arduino IDE for it to detect them. Preparing the sketch We won’t go into too much detail of the sketch operation here, as you can easily examine the source code. It works by scanning the thermistors once per second, along with the fan’s tachometer signals. At the same time, any received infrared commands are processed. It selects a mode (heating, cooling or off) depending on the above, and then updates the fan, pump and Peltier control signals. The sketch is well-documented with inline comments, so these are a good place to start if you want to dissect and change the code. The sketch is called “Peltier_Controller_V10”, although this may change if we update it further. For the programming stage, you might like to remove the Uno from the board stack and connect it (by itself) to the computer’s USB port. This will avoid any problems that might occur with the fact that the IR receiver signal is shared with one of the pins used for programming. If your Peltier ‘rig’ is not near your computer, this can also make your life easier. Open the sketch file, select Uno from the Tools→Board menu and ensure that the correct serial port is selected. Upload the sketch (CTRL+U), and assuming that’s successful, detach the April 2020  71 In most modes, the temperature and fans speeds are displayed. This shows Heating mode, which drives the Peltier devices at +100%; Cooling mode uses -100% USB cable and replace the Uno in the board stack. The display should spring to life, showing an array of temperatures. Nothing else should happen yet. By default, the sketch accepts commands from a Jaycar XC3718 remote control, or an Altronics A1012 universal remote set to use TV code 089. Other remote controls programmed with a Philips TV protocol may work. Basic operation There are four basic modes: full heating, full cooling, proportional control with a fixed target temperature, or proportional control following a temperature profile that’s defined in the sketch. For the first two modes, the Peltiers are driven at full pelt (hah) with one polarity or the other. In each mode, the LCD shows a variety of status information, as seen in the accompanying photos. In the last two modes, the unit tries to maintain the main thermistor temperature (T1) at the desired value by heating or cooling to varying degrees, as needed. The following buttons on the remote control can be used to control it: • CH+ and CH- (on either type of remote) enable full heating and full cooling respectively. A second press of either of the same button turns the Thermal Regulator off. • To program a setpoint for the third (fixed temperature) mode, enter three digits on the numeric keypad; the entered number is divided by ten to give the target temperature. For example, entering 1, 2, 3 will set the target to 12.3°C. This can only be done while the unit is idle, as it might otherwise cause it to change between heating and cooling rapidly. 72 Silicon Chip • Pressing the power button (on the Altronics remote) or play (on the Jaycar remote) will start or stop operation in setpoint mode. The setpoint can be tweaked in this mode by using the volume up and down buttons. This can be done while it’s operating as small changes are OK in this case. • The temperature profile mode is activated by pressing the EQ button on the Jaycar remote or “-/--” on the Altronics remote. Instead of showing the fan speeds, the LCD indicates the time, step number and next timed target. The unit steps through the array of temperature/time points set in the sketch, interpolating the temperature between each point. This could be used to implement the timer-based sous-vide cooker that we mentioned earlier, or a brewing or cheesemaking profile determined by the exact product you are trying to make. You can usually get an idea of the profile you will need from a recipe, but some experimentation and tweaking may be required to obtain the best result. Troubleshooting You can check whether your Peltier devices are wired with the expected polarity by putting the unit in full cooling mode and then checking that the main sensor temperature (T1) goes down rather than up. If it goes up, then comment out this line in the code by adding “//” to the beginning: In Profile mode, the setpoint is varied according to a timed series of temperature points with ramps in between. Instead of fan speed, the time, step number and ramp target are displayed at right. // setBipolar(-(pDrive*PWM_ TOP)/100); //scaled output, ie, setBipolar(-(pDrive*PWM_ TOP)/100); //scaled output, If your LCD does not light up or displays nothing, check that the red LED is flashing rapidly. If so, the software did not detect the I2C module, so it could not initialise and control the display. Our sketch includes code to automatically detect the I2C address of the display, so it should work if the LCD is connected correctly. Check your wiring and reset the Arduino by pressing the RST button on the Peltier Interface shield. If this does not fix the problem, there may be a problem with your LCD module. Now what? In Set mode, the Peltier Controller modulates the PWM to drive the T1 temperature (top left) towards the setpoint (bottom left). In this case, moderate cooling of 30% is needed. We’ve presented a good number of options and uses this circuit can be put to, but we don’t have the space to go into detail on all the possibilities. There are many ways that you could modify the code to suit your application. For example, you could add a DS3231-based real-time clock module to your Arduino by connecting it to the I2C pins (we sell these for a few dollars in the SILICON CHIP ONLINE SHOP). That would allow you to set up the code to automatically start and stop the unit at preset times. Or you might want to modify the code so that you can have multiple temperature profiles set up to suit different processes, with a way to select between them (eg, pressing different buttons on the remote control). There are so many ways that this project can be used; we would love to hear from our readers about the applications they come up with for the SC Thermal Regulator! Australia’s electronics magazine siliconchip.com.au setBipolar((pDrive*PWM_ TOP)/100); //scaled output ie, // setBipolar((pDrive*PWM_ TOP)/100); //scaled output and remove the “//” from the start of this one: Build It Yourself Electronics Centres® 1190 $ K 8604 Everything a maker space needs in one compact unit! Easter break e th r e v o g in Get build savings... t a e r g e s e th with T 2128 $ This USB rechargeable screwdriver features a fully adjustable torque drive for fast and accurate driving of precision screws such as those found in modern high tech devices. Two way direction control. Standard 4mm driver bits (14 included). 3 hours use per charge. See web for full contents list. Dynalink® F2 Pro $ Gaming Headset Creality® CP-01 3D Printer / CNC Router / Laser Engraver 59.95 Listen while you walk, run or lift! C 9042 Multi-platform ready! Suits PC, Playstation, Xbox and Switch with included TRRS adaptor. Offers excellent comfort for long gaming sessions with RGB lighting effects (when USB is plugged in). 2m cable. 54 $ .95 Flexible Wireless Sports Headphones Great sound and even better battery life! These over ear style headphones offer up to 16 hours listening time in a super comfortable & compact design. Bluetooth 5.0 for great range and audio quality. NEW! The ultimate do-it-all maker machine for the workbench. Create amazing prototypes and one off designs with this all in one mini home factory. Includes three interchangeable machine heads for cutting, etching and printing each with excellent accuracy. Easily assembled from flat-pack in just a few minutes. Router & engraver suitable for plastics, wood, PCBs, laminates etc. 25% OFF all PLA printer filament! C 9044 Phone Holder with Qi Wireless Charging K 8391 K 8392 K 8393 K 8394 K 8395 Orange Green Yellow Purple Blue WAS $44.95 34.95 $ D 2207 USB-C Type Car Charger SAVE 28% 25 $ M 8632 K 8396 K 8397 K 8398 K 8399 99 $ 15A Skt. 29.95 $ Red Black Grey White NEW! A must have for trades in the field or at home in the workshop - protects users from appliance faults just like your home RCD switch. It’s also a great safety item for use with 240V inverters with RV’s and campers. In-built USB sockets for charging your devices, plus 1.8m cord. Easy to reset with surge protected outlets. P 8172 10A & SAVE 25% Assorted colour 1kg rolls of 1.75mm PLA. Ultracharge® RCD Protected Powerblocks Simply place your phone in the holder to keep it topped up whilst you’re driving! Convenient windscreen or air vent mounting. Great for Uber drivers or road reps. Includes USB A-C cable. 18W power delivery charger with QuickCharge 3.0 for faster device charging. NEW! 129 Repair faster with a lithium powered screwdriver. NEW! .95 $ 79 A 0319 USB Travel Charger & Wireless Power Bank 109 $139 $ P 8174 5 x 10A Skt. P 8176 3 x 10A, 2x 15A Skt. See last page for store locations or visit altronics.com.au A do-it-all USB power delivery charger (18W), Qi wireless charger and portable battery bank (6700mAh) for phones and tablets. Includes Australian, US, UK and European adaptors, plus carry case. *Phone for illustration purposes. Sale pricing ends April 30th 2020. Build the ultimate maker workspace. Print bigger with the Creality® CR-10 V2 The CR-10 offers reliable large volume printing up to 30Wx30Dx40Hcm! The dual port fan cooled hot end offers reliable and precise print quality whilst the triangular design provides excellent stability. Heated print bed reduces warping, ensuring great prints every time! Cut, Polish, Grind, Sand & Carve. This workbench essential is just the shot for electronics projects, crafts, hobbies and odd jobs around the house! Powerful 130W motor with variable speed between 8000 and 33000 RPM. Included is a 172pc accessory kit of grinding wheels, drills, SAVE $14 cutters, sanding discs, polishing pads and more! T 2120 30 x 30 x 40cm build volume for larger prints S 1kg roll of Includes BONU your choice in t en am fil A PL at $39.95 ed lu Va ur of colo K 8606 950 $ Great for finishing 3D prints! 60 $ NEW! 39.95 $ T 2161 62pc Precision Servicing Driver Kit A quality servicing kit for high tech devices - including special bits for iPhone disassembly. Includes a huge variety of 4mm driver bits, opening tools, spudger, tweezers & extension. All in a neat self opening case. Swing Arm Benchtop Fume Extractor SAVE 14% SAVE 15% 85 $ Whisk away irritating solder fumes instantly as you work. T 1297 The replaceable active carbon filter absorbs fumes for a cleaner work environment. Includes 100mm ducting adaptor. Easily screw clamps to your work bench. SAVE 22% T 2162 27 $ ‘Getting Started’ Electronics Kit Great for enthusiasts and students. Includes pliers, cutters, 30W iron, solder sucker & carry case. All you need to get soldering! 30 $ T 2555 Hands free, close up viewing while you work. Offers 1.5, 2.6 and 5.8x magnification with LED lamp. Requires 2xAAA batteries. T 1499 NEW! This really sucks! 9 $ .95 Screen Removal Suction Cup Pliers 18 T 2480 A toolbox essential! Strip Wires Faster! Easy squeeze spring loaded quick action wire strippers for 0.5 to 2.0mm2 conductor wire. T 2444A 34 .95 $ SAVE 22% SAVE 22% T 1527 169 $ NEW! For removing outer glass from phones tablets & laptops. Cups rotate for larger screens. $ SAVE $66 Durable all metal chassis T 1349 35 $ Pick up tiny parts with ease. All heat & no flame! A battery powered (1xAAA) continuous suction pump for picking up tiny SMD parts & screws. Easy single button operation. ESD safe. Iroda® Pocket thermo-gun. Great for removing adhesives & heatshrinking. 650°C max. Refillable. Add T 2451 butane gas for $8.50. Whisk away those soldering fumes! #1 choice for schools! This 60W soldering station has a powerful in-built fume exhaust fan which sucks away the smoke when soldering. The active filter helps to reduce airborne pollutants. SAVE 29% 19 $ NEW! NEW! Precision Screwdriver Set 27 $ T 2185 Ideal for general electronics servicing! Features a ferrule top driver handle & 19 pozi, hex, torx and blade tips. Includes premium carry case. 11 Pc Screwdriver Set .95 T 2198B Quality set of flat blade and phillips screwdrivers for general repairs. Chrome vanadium. 29 $ .95 NEW! 9 $ .95 T 4015A T 2376 Never lose a tiny screw again! ESD Safe Tweezer Set A 35x26cm heat resistant silicon work mat to keep screws and materials organised while you work. Also includes a separate 25x20cm magnetic mat for keeping tiny metal parts from rolling away. Durable nylon carbon fibre tweezer set which are anti-static, antimagnetic, acid and alkali resistant. See last page for store locations or visit altronics.com.au Sale pricing ends April 30th 2020. Expand your AV system & save. Magnetic ‘edge to edge’ grilles. C 0876 Instant, powerful PA sound! 379 $ /pr NEW! An all in one portable PA sound system with amplifier that sets up in just seconds - no expertise required. Just plug into 240V power, switch it on and connect a mic. USB playback makes it easy to play your favourite tunes. Great for clubs, sports events, fetes, carnivals & bingo nights - any crowd up to 500 people! Opus One® 2x30W Bluetooth® Wireless Ceiling Speakers 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. C 0991 8” 100W SAVE $66 199 $ A great small venue audio mixer! Featuring USB/SD card playback with easy to use controls. All channels feature balanced XLR, unbalanced 6.35mm, insert inputs, high/mid/low adjustment, pan & gain level. SAVE $100 150 $199 $ $ The best range and reliability from any HDMI sender we’ve ever evaluated! 1080p <at> 60Hz over distances up to 100m line of sight. In-built IR repeater for control of equipment. Supports multicast to up to 3 extra receivers (A 3603 $199ea). A 2651 6 Ch Mixer With USB Audio Player C 0993 10” 180W SAVE $85 359 Send HDMI signals wirelessly! LIMITED STOCKS AT THIS AMAZING PRICE! 49.95 49.95 $ $ NEW! A 3602 A 1111 C 9034 SAVE $56 OFFER! FREQUENT FLYER dphones hea 4 903 C of r pai a y Bu ptor for $89. & A 1111 bluetooth ada0 SAVE $10.9 Supports up to 4 screens from one sender! NEW MODEL! A 4199 Multi-zone Audio Made Easy! 4x30W Zone Amp 329 $ Ideal for small businesses or simple multi-zone home audio systems. Switch between up to 4 different audio sources - connect up to 8 speakers. Toslink digital audio input for TV audio. Great for background music use. Also fitted with 6.35mm microphone connection. Very easy to pair. USB recharge. Great Bluetooth Sound For Less! Get wireless in-flight entertainment The perfect every day commuter earphones with top notch wireless sound, compact folding design and up to 18 hours of listening between recharges. Very comfortable! Transmits audio from any single or dual jack airplane audio socket to your Bluetooth wireless headphones. It can even pair with a second set of headphones - great for couples. Battery provides 4-5 hours listening. SAVE $46 169 $ A 4201 SAVE $50 SAVE $100 299 This digital DAB+ radio tuner with Bluetooth® audio streaming provides instant access to local digital FM stations & the music on your phone! 20 station presets. S/PDIF & RCA outputs. Includes remote. SAVE $80 Superb high power USA designed amplifiers! A 2698A Bluetooth 2x50W Amp ® Stream audio directly from your device to yourspeakers in the study or entertaining area. 3.5mm and RCA inputs. Class D design. Includes power supply, banana speaker plugs & 3.5mm to RCA cable. SAVE $80 545 $445 A 4157 2x250W The perfect compact 7” TV/monitor for your car, 4WD or caravan! Features in-built HD tuner to receive all digital channels. AV input provided, plus USB PVR recording. MP3 & video USB/SD playback. 12V/ 240V operation (includes plugpack). 79 $ SAVE 10% A 4155 2x150W The latest release from Biema® with several key enhancements in cooling, efficiency and circuit protection. High power non-bridgeable design is perfect for DJs, bands, function venues using foreground sound reinforcement. 3 pin XLR and 6.35mm inputs. Speakon and binding post outputs. 2 year warranty. S 8861B Monitor With HD TV Tuner SAVE $40 $ Biema® Power Amplifiers. Stunning performance! 149 $ Get Digital Radio: More channels, more choice! $ Send TV audio to your headphones! 49 $ A 1103B Transmits or receives audio via Bluetooth 4.1. Can be powered via USB on your TV (cable included). Includes 3.5mm & RCA cables. aptX low latency - no lip sync issues! See last page for store locations or visit altronics.com.au A 0930 Infra-Red Extender Kit Got your AV equipment in a cabinet or rack? This handy bi-directional IR extender kit will relay control signals between two locations. Powered by USB port on your TV/amp. Includes emitter & target. Sale pricing ends April 30th 2020. Great value security deals. 499 NEW! $ REDUCED FROM $899 115 $ S 9900H 4 Domes SAVE $400 IS PRICE! 20 SYSTEMS ONLY AT TH Why settle for just HD? This system features 2K detail and clarity. Affordable 4 Megapixel CCTV Surveillance System. Simple to install with instructions supplied. Cameras can be remote viewed on iOS/Android. Each pack includes: • HD digital video recorder • Pro grade 4MP resolution weatherproof cameras • 20m connection leads • Power supply • HARD DRIVES TO SUIT: 1TB $110 (D 5514), 2TB $155 (D 5516). S 9018 NEW! TP-Link® Wi-Fi Indoor Camera 89.95 S 9017 $ Crystal clear wide angle 1080p vision with instant alerts of movement, plus two way audio. Excellent night vision performance and easy remote viewing via the Kasa home app (Android/iOS). TP-Link Wi-Fi Pan/Tilt Indoor Camera ® Get the full picture with 360° horizontal and 118° vertical motorised viewing. Kasa app allows easy swipe pan/tilt movements. Provides 1080p full HD video with object tracking mode and night vision. Test & Tool Clearance... 30 $ X 0225 The ultimate camping, fishing, anything light! Provides 5 hours use from a high performance lithium battery. Folds flat for easy storage and recharges from any USB mains (M 8861) or car charger (M 8628). 10W, 1000 lumens. 40pc Ratchet Driver Kit Infra-Red Non Contact Thermometer 30 only at this price! Take temperature readings safely from a distance, even when equipment is running. -50°C to 500°C Q 1287 range. Adjustable SAVE $30 alarms & emmisivity, plus K-type probe $ input. 85 Fix high tech devices SAVE 20% T 2173 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. Tough DMM. Built like a tank! Space Saver Multimeter This new multimeter is built tough with water and dust resistance, plus a impact resistant case for the rough and tumble of every day use in the field. Auto ranging design offers a feature list as long as your arm with a clear large digit backlit display. Includes carry case & leads. Precision 28 Range DMM Not much bigger than your average mobile phone (16mm thickness), this auto ranging meter saves space in your tool box. Simple rotary dial operation with volts, current, amps and resistance. ULTRA SLIM CASE SAVE $44 Excellent for the service technician or enthusiast. Massive 20A rating AC/DC to 1000V. Includes on-screen prompts to ensure correct connection to test leads. Temp probe included. LAST CHANCE! SAVE $50 129 $ 45 $ Q 1069 Q 1064 60 $ 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 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 T 2168 Whenever AC is detected at a power point, sheathed or bare ended cable, the tester will light up red. A must have safety device for techs! SAVE 24% 15 $ Q 1067 Q 3002 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 A great selection of 1/4” drive bits and metric sockets (up to 13mm) and a quality ratchet driver with comfy rubberised grip. Includes storage case. BEST SELLER! Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au 40 $ Detect Live AC Wiring Safely SAVE 24% Sale Ends 30th April 2020 Build It Yourself Electronics Centres 23 $ SAVE $23 » 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 SAVE $19 By Charles Kosina If you have multiple test instruments and one very accurate frequency reference, you need a way to feed that reference signal to each test instrument without attenuating or degrading the signal. That’s precisely what this device does. It has one input and six outputs, and while it’s designed with a 10MHz reference in mind, it can handle other frequencies too. Frequency Reference Signal Distributor T his design was prompted by a ham radio friend who has a GPS-disciplined 10MHz frequency reference and needs to feed its output to several different pieces of equipment. This means that not only are they operating with maximum accuracy (those with internal references aren’t always spot-on), but they are also in lockstep. siliconchip.com.au A typical 10MHz reference signal generator has only the one output, and this cannot easily be fed to more than one device. You can’t just use a Y-cable since it will then have a 25Ω (or lower) load rather than a 50Ω load, which would certainly reduce the signal level and might also overload the generator and cause other problems. You really want a +10dBm (0.7V RMS) reference signal when terminatAustralia’s electronics magazine ed 50Ω at the reference input of each instrument. I decided on a design that will provide six such outputs. In principle, it is elementary. It comprises just six high-bandwidth op-amps feeding the outputs through broadband HF transformers, giving six fully isolated and buffered outputs. Circuit design Fig.1 shows the circuit design. April 2020  77 pot connects to a +3.5V half supply DC bias source via a 39Ω resistor. The bottom of the resistor is bypassed to ground, so the input impedance is 139Ω (100Ω+39Ω). This is a little higher than the 50Ω or The incoming reference signal is fed via BNC connector CON1 and pin header CON2 onto the board. It is then AC-coupled to VR1, a 100Ω trimpot which is used to adjust the output level. The bottom end of the D1 1N4004 CON3 CON10 +12V A REG1 7805 IN K +7V OUT GND 0V 75Ω that most generators are designed to drive, but the VSWR on the short run of coax from the generator will not be significant, so this should not cause any problems. If anything, this means that the Distributor gets a signal with a 470 1.2k 10 F +3.5V 10 F 180 1.2k 2.7k A  100nF IC1–IC6: MAX4450 3 POWER LED1 4 K 5 IC1 1 +7V 100nF OUTPUT 1 (BNC) 51 T1 CON4 2 180 560 +7V 100nF INPUT (BNC) TP CON1 CON2 100nF 100nF 3 VR1 100 4 5 IC2 1 OUTPUT 2 (BNC) 100nF 51 T2 CON5 2 180 39 +3.5V 560 100nF 100nF 100nF 3 ALTERNATIVE TO USING POTENTIOMETER 68 4 5 IC3 560 A 3 K 4 1 2 3 K A T3 +7V GND IN GND 5 IC4 1 OUTPUT 4 (BNC) 100nF 51 T4 OUT 180 560 2020 CON7 +7V 100nF 100nF SC  CON6 2 7805 LED 4 51 100nF 100nF 5 100nF 100nF +3.5V MAX4450 1 OUTPUT 3 (BNC) 2 180 39 1N4004 +7V 100nF SIGNAL DISTRIBUTOR 3 4 5 IC5 1 OUTPUT 5 (BNC) 100nF 51 T5 CON8 2 180 560 +7V 100nF Fig.1: the circuit of the Signal Distributor is relatively simple. The incoming signal is AC-coupled to trimpot VR1 for level adjustment, then fed to six four-times op amp gain stages based on IC1-IC6. These each drive 1:1 RF transformers via 51Ω Ω resistors, which in turn drive the fully isolated outputs. REG1 provides a 7V supply for the op amps. A half-supply rail to bias the signal fed to the op amps is present at the junction of two 1.2kΩ Ω resistors in series across the 7V supply. 78 Silicon Chip 100nF 3 4 5 IC6 1 OUTPUT 6 (BNC) 100nF 51 T6 CON9 2 180 560 100nF Australia’s electronics magazine siliconchip.com.au slightly higher amplitude, so less gain is required to achieve +10dBm. The +3.5V half supply rail is simply derived from the regulated 7V supply rail via a 1.2kΩ/1.2kΩ resistive divider. The 100nF bypass capacitor to ground attenuates any supply noise which makes its way through the regulator and this divider, so it doesn’t affect the signal. The signal is then fed to the six op amp non-inverting inputs (pins 3 of IC1-IC6), which are all connected in parallel. For the op amps, I decided to use MAX4450s which each have a gain bandwidth of 210MHz. So for a 10MHz signal, the open-loop gain is about 21 times. They are configured as non-inverting amplifiers and the 560Ω/180Ω feedback resistors give a gain of about four times. The bottom end of each feedback divider connects to ground via a 100nF capacitor. The feedback network cannot be connected directly to ground due to the +3.5V DC signal bias, and also cannot connect to the +3.5V reference since it is unbuffered and thus has a high source impedance (600Ω). Each op amp has a 100nF supply bypass capacitor for stability. Their outputs are capacitively coupled to six Coilcraft 1:1 broadband transformers, T1-T6. A 51Ω series resistor sets the source impedance for the transformer drive close to the required 50Ω. The six BNC output connectors are isolated from ground; they are grounded by the instrument being fed, eliminating the possibility of any Earth loops. The transformers have a 50Ω output impedance, suiting virtually all device reference inputs. IC1-IC6 have a supply voltage range of 4.5-11V; I am using 7V as this gives enough headroom for the required output voltage swing. This is supplied by REG1, a 5V fixed regulator which has its output voltage raised to 7V by a 470Ω/180Ω voltage divider between its output and GND pins and circuit ground. The 7V rail also supplies around 2mA to power indicator LED1 via a 2.7kΩ currentlimiting resistor. REG1’s output is filtered by a 10µF capacitor, and its input is similarly bypassed. It is supplied with around 12V DC via header CON3 and reverse polarity protection diode D1. CON3 can be wired to a chassis-mounted DC barrel socket. siliconchip.com.au Fig.2: the scope grab of the signal from one of the unit’s outputs shows an amplitude of 2.18V peak-to-peak, which is just over +10dBm. And as you can see, the frequency is reading exactly 10.00MHz. Fig.3: the scope was also used to produce this spectrum analysis of the output waveforms, which demonstrates that harmonic distortion is low, with the first three harmonics all well below -40dB. Note that the circuit shows that you can replace trimpot VR1 with a 68Ω SMD resistor if you don’t need to be able to set the gain exactly. We won’t go into any more details about this option (and that part is not in the parts list), so if you want to build it that way, check out our board photos as that is how the prototype was built. x 1.6mm/imperial 1206) sizes which are quite easy to solder. The MAX4450 op amps are tiny chips as they only come in SOT-23-5 packages, so they require special care in assembly, but those with SMD assembly experience should be able to manage them with no real difficulties. PCB design The signal from the GPS-disciplined oscillator is a clean sinewave of 2.9V peak-to-peak (about 1V RMS or +13dBm). Its second harmonic is at -40dB, the third harmonic at -50dB and it has no significant higher harmonics. The outputs from the Distributor into 50Ω loads are similar, with the A good ground plane is essential for stability. Most components are surface-mount types, allowing most of the underside of the board to be a solid ground plane. The resistors and capacitors are metric 2012 (2.0 x 1.2mm/imperial 0805) and 3216 (3.2 Australia’s electronics magazine Performance April 2020  79 REG 1 7805 1 IC2 51 IC3 51 1 IC4 51 GND 1.2k 100nF 560 560 100nF 100nF 100nF 1 180 180 560 100nF 100nF 180 180 560 100nF 1 IC5 51 100nF 51 10 MHz DISTRIBUTOR 100nF IC1 39 CSE200103 100nF 1 100nF 1 IC6 51 T1 T2 T3 T4 T5 T6 CON4 OUTPUT 1 CON5 OUTPUT 2 CON6 OUTPUT 3 CON7 OUTPUT 4 CON8 OUTPUT 5 CON9 OUTPUT 6 2.7k 100nF 560 100nF 100nF 100nF 560 10 F 100nF 100nF 180 470 1 VR1 100nF 100 100nF 2 10 F 180 100nF TP 1.2k CON2 10MHz IN + – 180 CON3 + – 12V IN 4004 D1 A K LED1 Fig.4: use this PCB overlay diagram and the photo below as a guide during assembly. Most of the components are SMDs, with the op amps being in small 5-pin SOT-23 packages and the RF transformers in larger six-pin plastic packages. The only components which could be fitted with the wrong orientation are diode D1 and LED1. dered, check that there are no bridges. If there are, apply some flux paste and use solder wick to soak up the excess solder. That should leave just enough solder to form good joints which are not bridged. Next, solder all the SMD resistors and capacitors, referring to Fig.4 to see which goes where. Their orientation is not important; simply tack down one side, check that the part is flat on the PCB and not too crooked, then once you are sure the first joint has solidified, solder the other side. Make sure in each case that the solder adheres to both the part and the PCB pad. The last set of surface-mounting parts are transformers T1-T6. These are not entirely symmetrical, as they have a centre-tap on one side only, but we don’t connect to that tap. So it doesn’t matter which way you fit them, although we suggest you match the orientation shown in our photos to guarantee you get the stated performance. Use the same technique as with the smaller SMDs, tacking one pin and then checking the remaining pin locations are square over their pads before soldering them. Through-hole parts harmonics down by more than 40dB. Fig.2 shows the shape of the output waveform on my scope, while Fig.3 is a spectrum analysis of this waveform. The vertical scale is 10dB/div, which makes the second harmonic -44dB, the third harmonic -46.5dB and the fourth -46dB. Construction The Signal Distributor is built on a PCB coded CSE200103 which measures 125.5 x 60mm. Refer to Fig.4, the PCB overlay diagram, which indicates 80 Silicon Chip which parts go where. Start with IC1-IC6. These are the only ones with small pins close together. As they have two pins on one side and three on the other, their orientations should be obvious. Tack them down by one of the two pins which are more widely spaced, then check the part is sitting flat on the board and that all the pins are over their pads before soldering the other four. If necessary, re-melt the first joint and nudge the part. Once all the pins have been solAustralia’s electronics magazine Solder diode D1 in the usual manner, ensuring it is orientated as shown in Fig.4. Then bend the leads of REG1 down so that they fit through their pads with the tab hole lining up with the PCB mounting hole. Attach it using an M3 screw and nut, and do it up tight before soldering and trimming the leads. Follow with headers CON2 and CON3, orientated as shown, then trimpot VR1. Orientate VR1 with its adjustment screw on the side facing away from CON2. Then mount the six BNC sockets. They are quite bulky, so make sure they are sitting completely flat on the PCB before soldering the two signal pins and the two larger mounting posts in place. In terms of board assembly, that just leaves LED1. We’ll solder it in vertically now, but it can be bent over later to protrude through a front panel hole next to the BNC connectors. Its anode (longer) goes to the pad closest to the 2.7kΩ SMD resistor. The flat side of siliconchip.com.au the lens indicates the cathode, opposite the anode. Solder it with the base of its lens 10mm above the top of the PCB and trim the leads. Case preparation Fit the four tapped spacers to the corner mounting holes using short machine screws and place the board in the case. Slide it so that the BNC sockets are touching the side, and measure the distance from the top of the metal surrounds to the top of the box. If you measured from the top of the bump on the RCA socket, add 5.5mm to this measurement, otherwise, add 5mm. Then measure that far down from the top of the case on the outside, directly opposite one of the connectors, and mark the case there. For example, if you measured 23mm on the inside, from the top of the bump, mark the outside 28.5mm from the top. Then punch that location using a hammer and nail, and drill a pilot hole there (or use a centre punch, if you have one). You should find that this hole corresponds with the centre of the BNC socket. The connectors are mounted 3/4in (19mm) apart, so drill five more pilot holes at the same level each spaced 19mm apart, corresponding to the locations of the other BNC sockets. Then drill a 3mm hole 14mm to the right of the right-most socket for the LED. Enlarge the other six holes to 12.7mm (0.5in) diameter, then check that the BNC socket surrounds all fit. Once they do, remove the nuts and washers from the BNC sockets, along with one of the tapped spacers from the PCB. Push the BNC sockets fully through their mounting holes, then mark the location of that one hole in the base of the case. Refit that tapped spacer, remove another one and repeat until you have marked all four holes. Then drill them out to 3mm. Decide where you want to mount the input socket and DC power socket, then punch and drill those locations large enough to fit the connectors. Clean up the case and deburr all the holes. You can now mount the PCB in the case using four machine screws through the base and into the tapped spacers, and refit the BNC socket washers and nuts. Stick the rubber feet onto the bottom of the case, in the corners. siliconchip.com.au Parts list – Signal Distributor 1 double-sided PCB coded CSE200103, 125.5 x 60mm 1 diecast aluminium enclosure with room for the PCB and chassis connectors [eg, Jaycat Cat HB5046, 171 x 121 x 55mm 6 Coilcraft PWB-1-BLC 425MHz transformers, SMD-6 package (T1-T6) [element14] 1 chassis-mount BNC socket (CON1) 2 2-pin polarised headers and matching plugs (CON2,CON3) 6 PCB-mount BNC sockets (CON4-9) 1 chassis-mount DC barrel connector (CON10) 1 12V DC 150mA+ plugpack or other power supply 9 M3 x 6mm panhead machine screws 1 M3 hex nut 4 9mm tapped spacers 1 500mm length of single-core shielded cable 4 stick-on rubber feet Semiconductors 6 MAX4450EXK+T 210MHz op amps, SC-70-5 (IC1-IC6) 1 7805 5V 1A linear regulator, TO-220 (REG1) 1 3mm LED (LED1) Capacitors 2 10µF 16V X5R ceramic, SMD 3216/1206 size 20 100nF 16V X7R ceramic, SMD 2012/0805 size Resistors (all 1% SMD 3216/1206 size) 1 2.7kΩ 2 1.2kΩ 6 560Ω 1 470Ω 7 180Ω 6 51Ω 1 100Ω multi-turn vertical trimpot (VR1) [eg, Jaycar Cat RT4640] Measure the distance from the two chassis-mount connectors to their corresponding headers on the board, then cut a generous length of shielded cable to suit both. Strip back the outer sheath at each end of both cables, then separate out the shield wires and twist them together. Attach the polarised header plug pins to the inner conductor and shield at one end of each (we recommend you crimp and solder), then push them into the plastic plug housings, referring to Fig.4 to see which side the shield braid goes to (marked “–” in both cases). Solder one cable to the chassismounting BNC socket, so that the shield braid goes to the outer tab and the inner wire goes to the middle pin. Similarly, for the DC socket, solder the shield braid to the tab connecting to the outer barrel of the connector when it’s plugged in, and the inner wire to the tab connecting to the tip. Don’t be trapped by the fact that many sockets have a third switched negative tab. It’s initially connected to the outside of the barrel but is disconnected when a plug is inserted. Check for continuity between the tab and the outside of the barrel when the plug is inserted. Plug the polarised headers into the correct sockets and bend LED1’s leads Australia’s electronics magazine 1 39Ω so that the lens pokes through the hole in the front panel without shorting its leads together. Testing You can now apply power via the DC socket and check that LED1 lights up. If it doesn’t, check that you’ve wired up the DC socket to the board correctly, so that there is continuity from the centre pin of the DC socket to the anode of D1 (opposite the striped end). Also check that D1 and LED1 have been fitted with the correct polarity. If it still doesn’t work, your power supply may be a tip-negative type. In that case, you will have to swap the pins going into the plug for CON3. Now feed a signal into the input and use a scope or frequency counter to check that the correct frequency signal appears at each output. Assuming you have a scope or some other means of measuring the output amplitude, adjust VR1 for +10dBm which is around 0.7V RMS or 2V peak-to-peak. You could adjust for a different level if needed. Don’t forget to apply a 50Ω load when making these adjustments. Given that each buffer provides four times gain, it should be possible to get a +10dBm output with an input signal as low as +4dBm (350mV RMS or 1V peak-to-peak). SC April 2020  81 One for the radio amateurs: a first look by ROSS TESTER The G90: A High Spec, SDR QRP HF 12V Amateur Transceiver Best known for their range of quality radio receivers, Tecsun Radios Australia have recently expanded their product line-up with a compact HF Amateur Radio Transceiver from China. With an extensive list of features and a commendably low price, it's enough to make amateur operators take notice! F rom the age of 16 right through to my early-50s I held an amateur radio licence (first the old "Z" call and later a “K” call). But I found I was going on air less and less, to the point where I considered licence renewal an expense I couldn't justify. But if this new transceiver had been around at the time, I might have reconsidered that! Then again, it was not possible for this to be around back then – SDR (software defined radio) was yet to be invented and devices using SDR were therefore non-existent. We're looking at the Xiegu G90, which Tecsun Radios Australia have recently added to their range. They have “dipped their toe in the water”, so to speak, by gradually expanding into other communications equipment. While they are well aware that amateur radio is a strictly limited market, director Garry Cratt believes it is large enough to justify this expansion – particularly if they can offer quality product at a very realistic price. The G90, made in China, fits both of these criteria very nicely. Tecsun Radios Australia carried out extensive research into both the manufacturer and the transceiver itself after being offered distribution rights for Australia. With glowing (independent) reports from amateurs in countries where the G90 is already available, they decided to take up the offer. Incidentally, we should note that we have not used this transceiver on air (for the reason above!) but have relied on 82 Silicon Chip reports from licenced amateurs in our local amateur radio club for their reports. And they were quite enthusiastic! About SDR Software-defined radio (SDR) takes avantage of the capabilities of today's microprocessors to give features and performance that were only dreamed about in decades past. Many of the functions which SDR takes on were originally implemented in hardware – often complicated, intricate hardware – which of course came at a cost. With (usually) embedded processors undertaking all, or most, of the digital signal processing within the radio, the cost of high performance receivers, transmitters and transceivers has fallen dramatically. The SDR software performs all of the demodulation, filtering (both radio frequency and audio frequency) and signal enhancement (eg, equalisation). In the case of the Xiegu G90, the 24-bit data size and 48kHz sampling results in excellent performance and is highly configurable. The G90 The first thing you notice about this transceiver is its size – just 120w x 45h x 210d (mm). But in this small package is a full-featured transceiver covering the entire band from 0.5 to 30MHz (receive), with all HF amateur bands Australia’s electronics magazine siliconchip.com.au programmed in for transmit (10m to 160m inclusive) in AM, SSB and CW modes, with FM available as an option. What's more, it also includes an inbuilt antenna tuner so if you're away from home, you can use a random length of antenna wire (hoisted up a tree, or over a hotel balcony, for example) and the G90 will match into that with an SWR of 1.2:1 or better (many users report a solid 1:1). You'll also notice the front panel with its 1.8-inch colour screen, which has a ±24kHz bandwidth fast-scan spectrum display with waterfall. And there's also the oversize microphone, with 25 push-buttons for control, along with the standard PTT. What you won't notice, until you start reading the documentation and/or using it, is that it offers a transmit power of up to 20W (1W steps) in SSB/CW/FM modes and 5W in AM. Receive sensitivity is excellent at 0.25µV <at> 12dB SINAD. There are two independent VFOs with each capable of different frequencies and different modes. In SPL (split) mode, you can also have split transceiving operation (eg, VFO A for receive, VFO B for transmit). Operating frequencies can be direct-entered via the microphone keypad or “dialled up” using the front panel knob. In the latter case you can also select steps (using the same knob): 100Hz, 1kHz and 10kHz. The transceiver operates from (nominal) 12V DC (actual 10.5-16.5V) but you'll need a fairly beefy supply – at 20W out, it will draw about 8A (did someone mention mobile/ car battery?). Receive, as you would expect, is much lower at about 500-750mA. You probably also won't have noticed that the radio and its display unit can be separated, making for a versatile mounting arrangement. Conclusion Consistent with our earlier statement that we weren't able to fire the G90 up in anger, we can only go on the many favourable comments we've seen online (Google Xiegu G90) – there isn't one post which gives it a less than 4 out of 5 Features: • • • • • • • • • • • • • • • • • • • • • High-performance front end narrowband ESC preselector Covers the frequency range of 0.5~30MHz (receive) Covers all Australian HF amateur bands Three working modes; SSB/CW/AM; FM optional Built-in wide-range automatic antenna tuner 1.8-inch high brightness colour TFT LCD screen ±24k bandwidth spectrum display, waterfall display Software defined narrowband filter (CW mode: 50Hz) Detachable display unit RF power output: 1-20W (in 1W increments) Sensitivity: typically 0.25µV <at> 12db SINAD Adjacent channel suppression: 60dB Rx dynamic range: 90dB Spurious suppression: better than 50dB Sideband suppression: better than 55dB Audio output power: 0.5W into 4Ω Operating temperature range: 0-55°C Operating voltage: 10.5-16.5V DC (12V nominal) Current consumption: Rx 750mA, Tx 8A max Size: 120 x 45 x 210mm Weight: 1.85kg and, indeed, most give it 5 out of 5. And the members of the local radio club who have used it on air had nothing but praise. One comment we heard was that, despite the huge range of controls on this transceiver, the learning curve was virtually non-existent. “You take it out of the box, plug in an antenna and power supply and you're ready to go.” It also earned top marks for ease of use, for receive quality and for transmit quality reported back from club member's contacts. Yes, it is QRP (low power, for those who don't know radiospeak!). But there's an old adage in amateur radio: you can work the world with five watts . . . It becomes more of a challenge for avid amateur operators! Warranty and service The G90 Transceiver is guaranteed for 12 months from date of purchase. Warranty and any out-of-warranty service work will be undertaken by Tecsun Radios Australia in their fullyequipped service centre in Sydney, although they do reserve the right to send units back to the manufacturer for more specialised work, if required. Naturally, any units which have had hardware or firmware modifications are not covered by warranty. Price Aha! We knew you'd be asking that . . . The Xiegu G90, Tecsun Radios Australia (cat no Q5000), has a recommended retail price of $740.00, including GST and freight within Australia. Overseas customers should email Tecsun Radios Australia for a quotation for freight to their location. The G90 sports a very nice 1.8-inch TFT display which not only gives you both VFO frequencies, modes, receive "S" and even the antenna SWR via the inbuilt antenna matcher, it also has a fast-scan spectrum analyser with waterfall display. siliconchip.com.au More info? Log onto www.tecsunradios.com.au/store/product/ xiegu-g90-transceiver/ for more detailed specifications and user reports. There's also a range of accessories available but everything to get you going is supplied in the box! SC Australia’s electronics magazine April 2020  83 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. Multi-code lock with 10 access codes This circuit implements a keypad lock. It can be opened by using up to 10 different access codes, plus a master code. Each user can set and change their own code. It has an automatic relocking feature, causing the solenoid to return to the de-energised state after some time. The lock is also equipped with two other automated re-locking features, so you don't accidentally leave the door unlocked. For additional security, if three wrong master, ID or access codes are entered in succession, all codes are disabled for a short period (about one minute). This makes it a very slow process to try to guess one of the codes. The circuit energizes a door strike solenoid only when the correct 10-dig- 84 Silicon Chip it master code or 4-digit access code (one of ten) is entered via a numeric keypad. LED1 is used to acknowledge key presses; LED2 blinks when the door is unlocked. A 16x2 LCD module is used as a status display. The heart of this lock is Atmel ATmega8A AVR microcontroller IC1. The digit keys on the keypad are used for code input. Hash (#) is pressed after the master, ID or the access code is entered. The asterisk (*) key clears the entered code. The micro scans the keypad constantly and will unlock the door when the right sequence is entered. The 10 expected access codes are stored in the micro’s EEPROM and can be changed by authorised users whenever needed. Australia’s electronics magazine There are ten independent 4-digit ID codes for ten users. The default ID code for user 1 is 1001, 1002 for user 2, up to 1010 for user 10 (these can be modified in the software). To enter or change an access code, apply power and wait for the “Enter Code” message. Upon power-up, the unit only accepts the master code. Enter the 10-digit master code, which defaults to 1234567890, and press #. The keystrokes appear in the middle of the second line of the display as asterisks [***********]. If the code is entered in the correct sequence, it will momentarily show “Access Granted”, and the solenoid is energised. LED2 blinks to confirm the unlocked status. A progress bar appears on the left side of the second line, slowly progress- siliconchip.com.au ing to the right over five seconds. Then the solenoid returns to the locked position, and the display shows: “Enter ID Code” on the first line. A counter also appears on the left side of the second line counting down from 30 to 0 over 15 seconds. This is the time limit to enter one of the 10 ID codes. Again, the keystrokes appear in the middle of the second line as asterisks [*****]. For instance, the user enters the ID code: 1001 for user 1 and presses #. The display will clear to show “Access Granted” momentarily and then “Enter New Code”. Again, the counter appears on the left side of the second line counting down from 30 to 0 over 15 seconds. You then enter a new four-digit access code and press *. The LCD will momentarily display “New Code Saved”. This is the access code for user 1, which is stored in the EEPROM. Then the display returns to “Enter Code”. To verify, input the new access code and press # to unlock the door. The same procedure is followed for the other nine users. It is also possible to use the code lock without entering the 10-digit master code by inserting jumper JP1. If an incorrect 10-digit master code or a 4-digit ID code or access code is entered and # is pressed, the display shows “Access Denied” momentarily. A progress bar appears on the second line of the LCD progressing from left to right in three seconds. Then the LCD clears to display “Enter Code”, and the user can try again. If three wrong access codes, ID codes or master codes are entered in succession, then all codes are disabled for about one minute (this time can be modified in the software). The circuit is powered from a 12V DC supply with diode D1 for reverse polarity protection and REG1 to derive a regulated 5V rail for the LCD and micro. N-channel Mosfet Q1 drives the door strike solenoid, which runs directly from the 12V supply and has a parallel diode, D2, to absorb back-EMF spikes when it switches off. To change any of the initial ID codes or the 10-digit master code, you will need to modify the software. This can be downloaded from the Silicon Chip website. It can be compiled into a HEX file and uploaded using the free AVR Studio software. Mahmood Alimohammadi, Tehran, Iran. ($70.00) siliconchip.com.au Micromite-based Chiming Clock This chiming clock is based on Geoff Graham's Touchscreen Super Clock (July 2016; siliconchip.com.au/ Article/10004) which uses the hardware of his Micromite LCD BackPack (February 2016; siliconchip.com.au/ Article/9812) along with a DS3231 real-time clock module or GPS module. You can also build it using the V2 BackPack with USB (May 2017; siliconchip.com.au/Article/10652). I have added a DFPlayer Mini MP3 player module, which was described in the December 2018 issue (siliconchip.com.au/Series/306). That article showed how to hook the module up to a Micromite. So I have combined the Super Clock circuit with that one to produce the circuit shown here. The GPS module is optional, but it saves you having to set the time and also ensures long-term accuracy. The result is a Super Clock which Australia’s electronics magazine plays an MP3 file of clock chimes on the hour, every hour. The modified software and chime audio files are available as a download package from siliconchip.com.au ("Chiming Clock.zip"). This package contains a full MMBasic file, which includes comments, and a “Crunched” file which has all the unnecessary bits removed, as the full file is too big for the Micromite memory. You can upload the full file if you're using MMedit, as long as you set the "Crunch on upload" option. I used a 7.5cm, 8W speaker connected between pins 6 & 8 of the DFPlayer module. I had trouble with the sound level control of the DFPlayer module, so I found it easier to set it to maximum and fitted a 120W resistor in series with the speaker, to reduce the output level by 12dB. Ray Saegenschnitter, Huntly, Vic. ($75) April 2020  85 Two-wheel self-balancing robot A two-wheeled robot, the most common example of which is the Segway scooter, is essentially a type of inverted pendulum. Fast reactions are needed to keep it upright and stable, just like trying to balance a vertical stick on your hand. This design for a simple two-wheel robot uses an MPU-6050 inertial measurement unit which includes a 3-axis accelerometer and 3-axis gyroscope (Altronics Cat Z6324; as part of a GY521 module). This provides the feedback required to decide when to drive the wheels, to keep the robot upright. The wheels are independently driven with separate motors, allowing the robot to not only balance but move forwards or backwards, and turn left or right. Theoretically, only data from the gyros (mounted in the middle of the two wheels) is needed to control the robot. However, the gyros readings drift over time, so they must be periodically re- 86 Silicon Chip calibrated. This is done with the help of the three-axis accelerometer. The greater the angle from vertical, the greater the speed with which the motors are driven. As the angle of shift reduces to zero, the speed reduces. Thus, the top of the cart moves like a pendulum and maintains balance. This feedback control is achieved with a PID (proportional/integral/differential) loop. The battery should be slung underneath to prevent the centre of gravity from being too high, although the prototype was run from an external power supply via a long figure-8 cable. The motors are low-cost 12V, 300 RPM geared & brushed DC motors, fitted with 100mm wheels. Initially, the performance was great, but as the gears wear, they develop backlash, which makes balancing more difficult. The use of brushless DC motors would solve this, but their control is significantly more complex; you would need Australia’s electronics magazine a separate controller for each motor. The motors are driven by a 2A-rated L298 dual H-bridge IC. I tried the 1A-rated L293, and although it could handle the current, it got very hot. Diodes D1-D8 are essential to absorb back-EMF from the motor coils, which would otherwise destroy the L298 in short order. You can purchase a prebuilt module with the L298, eight diodes and 5V regulator for around $2 from the following link: w w w. a l i e x p r e s s . c o m / i t e m / 32994608743.html The controller is an Arduino. For the software, I used Jeff Rowberg’s libraries for the MPU-6050 IMU. The MPU6050 module needs to be aligned with its pin header row running along the front/back axis of the robot. The software has three PID coefficients which can be changed: kp, kd and ki. The default values are OK, but you may find that changing them improves the stability of your robot. The Arduino sketch (two_wheel. ino) is available for download from siliconchip.com.au siliconchip.com.au/Shop/6, along with a second sketch which calibrates the gyros (mpu_calibration.ino). Use the Arduino Library Manager to install the MPU-6050 library before compiling and uploading either sketch. It’s also available from GitHub: github. com/jrowberg/i2cdevlib/tree/master/ Arduino/MPU6050 Run the calibration sketch first and follow the prompts in the Arduino Serial Monitor with a 115,200 baud rate. It will produce a set of coefficients that you then add to the main sketch around line 55, replacing the line which reads: int MPUOffsets[6] = { … }; You can see a video of my robot in action at: siliconchip.com.au/Videos/Twowheel+balancing+robot Bera Somnath, Vindhyanagar, India. ($80) Self-resetting intruder alarm This device is designed to detect intruders. When a beam of light focused on the light-dependent resistor (LDR) is interrupted, this alarm produces loud noise for about ten seconds and then automatically resets. You may find this device useful in circumstances where the intruder need not be a thief; it may be a family member or an ‘expected’ person. This circuit is based on a 555 timer IC, used as a multivibrator, and a transistor-based audio oscillator. When the light beam is being focused on the LDR, its resistance remains low and hence trigger pin 2 of IC1 is held high, so the output at pin 3 remains low. When the beam is interrupted, the LDR resistance increases and a momentary negative pulse is applied to the trigger pin. Output pin 3 then goes high for approximately 10 seconds, as determined by the 100µF timing capacitor and 100kW charging resistor. With output pin 3 high, the ~3kHz audio oscillator based around transistors Q1 and Q2 is powered. This applies an AC waveform to the piezo transducer, producing a shrill noise and also lighting LED1, which flashes at a high frequency, so it appears to be solidly lit. The oscillator frequensiliconchip.com.au cy is set by the combination of 22nF capacitor and 10kW resistor. It works as follows. When pin 3 of IC1 goes high, the 22nF capacitor charges through the 270kW and 10kW resistor. Eventually, the voltage at the base of NPN transistor Q1 exceeds about 0.6V and so Q1 switches on, in turn switching on PNP transistor Q2, which pulls the anode of LED1 up (also connected to the piezo buzzer). This positive swing is coupled to the base of Q1 by the 22nF capacitor, so Q1 and Q2 remain on for a time, but eventually, this capacitor discharges Australia’s electronics magazine through Q1’s base-emitter junction. Eventually, Q1 and Q2 switch off and the anode of LED1 drops close to 0V. This also pulls the base voltage of Q1 down, and it takes some time for the capacitor to recharge and bring the base back up to 0.6V. It is the combination of this recharge time and the time that sufficient base current is supplied to Q1 to keep it switched on that sets the frequency to around 3kHz. The duty cycle is about 20%, as determined by the ratio of those two time constants. Raj. K. Gorkhali, Hetadu, Nepal. ($65) April 2020  87 PRODUCT SHOWCASE MachineryHouse don’t want you to buy new drill bits! Even though MachineryHouse do sell an extensive range of twist drill bits, they’d much rather you sharpen those blunt or broken drills that you’ve thrown (in disgust!) into the “dead drill” box – with their user-friendly, hand-operated HAFCO EDBD-13 Drill Sharpener. It restores blunt drill bits back to their original condition. This quality grinder can sharpen both metric & imperial drill bits, with a drill capacity of 3 – 13mm or 1/8” – 1/2” respectively. It is also capable of split point sharpening and grinds two flute drills of unlimited length. It features a single adjustable drill chuck-holding system, 118° fixed drill point angle as well as a built-in drill bit setting guide to ensure correct relief cutting angle sharpening. The diamond impregnated wheel is driven by an 80W, 230V motor rotating at 4200rpm, that provides a superior grind finish and hones the drill bit to a sharp cutting edge. To learn more about this great product or to order your very own drill sharpener please visit one of the MachineryHouse showrooms in Brisbane, Sydney, Melbourne or Perth, or go online to www.machineryhouse.com.au/d070 Contact: MachineryHouse Brisbane – Sydney – Melbourne – Perth (07) 3715 2200 (02) 9890 9111 (03) 9212 4422 (08) 9373 9999 Web: www.machineryhouse.com.au Check your hearing yourself with this smart online test. It’s important to catch hearing issues early. But many people are put off by the stigma, expense and inconvenience of visiting an audiologist. Blamey Saunders Hears has a DIY alternative to the traditional in-clinic hearing test. You can take their free, clinically validated Speech Perception Test (SPT) online, from the privacy of home. It’s no standard hearing test. Tests you take in a clinic measure how well you hear computergenerated tones and beeps. The SPT gives you information that’s more relevant to your daily listening experience. It measures how well you hear the different sounds that make up spoken words. And it takes less than 10 minutes. You receive an instant, easyto-understand interpretation of your results. And, your free report shows if Blamey Saunders technology is a match for your needs. Check your hearing yourself at: blameysaunders.com.au/test Contact: BlameySaunders 364 Albert St, East Melbourne Vic 3002 Tel: 1300 443 279 Web: www.blameysaunders.com.au New downloadable eBooks from Mouser cover electric vehicles, artificial intelligence Mouser has released two new eBooks, one covering electric vehicles and one looking at artificial intelligence (AI). “Electrification of the Vehicle” explores new components, technologies and strategies for the design and development of electric vehicles. To read, visit www.mouser.com/news/bourns-ev-ebook/mobile/index.html “Imagine the Possibilities”, written in collaboration with NXP Semiconductors, examines the myriad potential applications of artificial intelligence (AI) and identifying specific products for AI and machine learning (ML) solutions. To read this one, see www.mouser.com/news/nxp-ai-ebook-2019/ mobile/index.html 88 Silicon Chip Australia’s electronics magazine siliconchip.com.au MMCUAV’s drones used in the battle against the coronavirus outbreak The beginning of 2020 is special to most Chinese. When a sudden coronavirus outbreak occurred in Wuhan, China, all cities joined the effort to fight it. Shenzhen MicroMultiCopter (MMC) quickly launched their UAV prevention solution. They supplied a service team of over 200 people, rushing to the front line with over 100 drones deployed in many cities such as Shanghai, Guangzhou, Zhaoqing and other areas to participate in the battle, by which the risk of spreading among frontline staff has been greatly reduced. Drones are capable of 360° patrols to observe the ground condition through 40x zoom cameras. Crowds and those who don’t wear masks in public places are found and dispersed by the commanders through onboard megaphones. Daily broadcasting by drones is carrying out in different communities. From large areas such as stations and supermarkets down to small courtyards, where there is a need, MMC drones are used to spray disinfectant in public places. Compared to the traditional way, using drones can avoid direct contact especially in those places requiring regular disinfection. A drone with a thermal camera fitted can automatically sense each person through high accuracy infrared imaging. This has been widely used in crowded areas to assist in onsite management and evacuation if required. Since 1st February, MMC teams have been working with traffic police to monitor traffic flow. With larger coverage than fixed cameras, MMC drones greatly helped commanders figure out solutions quickly. As a company with complete supply chain of industrial UAV, MMC provides not only complete solutions but also UAV key parts and OEM/ODM coContact: operation. MMCUAV MMC is commitMMC Tech Park, No.1 Yihe Road, ted to boosting auShilong Community, Shiyan Street, tomation level so Bao’an District, Shenzhen City, people can work in Guangdong Province, PR China, 518108 greater safety, with Tel: +86 75526916770 lower cost and by Website: www.mmcuav.com higher efficiency. siliconchip.com.au New A365 cloud-based viewer Altium’s new A365 cloud-based viewer redefines the way that printed circuit board designs are shared between designers, part suppliers, and manufacturers. The A365 Viewer allows users to search for, select, crossprobe and inspect components and nets while moving seamlessly between schematic, PCB and 3D views of their board. Using the A365 Viewer requires no CAD tools or experience. The A365 Viewer is designed to work with multiple eCAD formats, currently supporting Autodesk️ Eagle and Altium Designer. Other popular PCB design software formats will be supported in the near future. Adding the Altium 365 Viewer has significantly enhanced the user experience when navigating the product documentation in the Altium website. Now Arduino users can freely browse schematics, PCB layout and even 3D models of the Arduino boards and modules online, without the need to download or install anything additional. The capability of being CAD-agnostic will shortly allow Arduino to add the Contact: online design viewer Altium to every product page, Level 6, Tower B, The Zenith, including the ones 821 Pacific Hwy, Chatswood NSW 2067 designed in Autodesk Tel: 1800 312 665 Website: www.altium.com Eagle. Self-driving cars are coming closer . . . and faster! With automotive self-driving systems evolving from 60km/h to 100km/h and beyond, LiDAR sensors are playing an increasing role in the fusion of vehicle sensors for their ability to provide accurate distance measurement of objects. With more than twice the bandwidth and the ability to accommodate 33 percent more channels within the same LiDAR module size compared to the closest competitor, the new Maxim MAX40660/MAX40661 transimpedance amplifiers (TIAs) provide optical receiver designers with higher-resolution images that enable faster autonomous driving systems. The system size of the MAX40026 high-speed comparator plus the MAX40660/1 TIAs is 5mm2 smaller than the closest competitive solution. These ICs meet the stringent safety requirements of the automotive industry with AEC-Q100 qualification, enhanced electrostatic discharge (ESD) performance and failure modes, effects and diagnostic analysis (FMEDA) to support ISO 26262 certification at the system level. An evaluation kit is available from Maxim and their authorised distribu- Contact: tors. Maxim Integrated F o r m o r e i n - 160 Rio Robles San Jose, CA 95134 USA f o r m a t i o n , v i s i t Tel: 0011 1 408-601-1000 http://bit.ly/Maxim_ Website: www.maximintegrated.com LiDAR _solutions Australia’s electronics magazine April 2020  89 Vintage Radio By Associate Professor Graham Parslow Tecnico 1950 Model 1050 At 9.6kg, this is a heavyweight table radio and it has suitably imposing styling. One could even accuse it of belonging to the early Brutalist period. Fortunately, the splendid walnutcharacter Bakelite case with decorative slots rescues it from being overly austere. In the Australian context, the iconic styling of this model is unique. However, Tecnico was in partnership with Bendix USA at the time, and the features of contemporary American Bendix radios influenced this radio. The perforated metal speaker grille copies Bendix radios and is painted in dappled shades, like military camouflage. Continuing with this theme, the case has the look of a World War Two concrete ‘pillbox’. (Military structures of the WW2 were a major inspiration on Brutalism). Other post-war manufacturers also offered radios with military-themed styling, particularly in portables. The mellow tone of the baffled Rola 6-9H speaker is in harmony with the impressive image of this radio. In keeping with the new demand for colourful radios at the time, the case was also available in shades of cream, green and blue with various degrees of mottling. The model shown here has four front panel knobs for power on/off (full DPDT switching), volume, tone and tuning. 90 Silicon Chip A smaller case on the styled-alike Model 1140 had only two knobs, offering control of volume and tuning (see the book Radio Days by Peter Sheridan & Ritchie Singer, p243, https://trove. nla.gov.au/version/46138998). The only resemblance between the models is in the case. The smaller Model 1140 has four valves, all different from the Model 1050, and the chassis is at 90° to the base. You might like to compare this set to the 1946 Tecnico Aristocrat (Model 651) I described recently, in the February 2020 issue (siliconchip.com. au/Article/12350). You will find that the power supply and output stage are virtually identical, however, the front-end valve lineup is different and some of the circuit details are varied between the two sets. Circuit details The circuit for this set is shown in Fig.1. The Model 1050 circuit is an evolution of previous Tecnico designs, but modernised with miniature valves for the RF section. Australia’s electronics magazine The HT rectifier and pentode output remain as octal-based valves. The circuit diagram also appears in the Australian Official Radio Service Manual (AORSM) volume 9 for 1950. There is no shortwave tuning, so the aerial feeds into a single aerial coil with a tuned secondary. This then feeds into the grid of the 7-pin 6BE6 converter valve. The 6BE6 was released in 1946 by RCA and was subsequently used over many years, manufactured under licence by various companies. The 6BE6 in this radio is a Philips Miniwatt. The remaining valves were sourced from AWV, a subsidiary of AWA (in turn affiliated with RCA). A Hartley oscillator is used, shown below the 6BE6, with a single tuned coil feeding the oscillator signal into the 6BE6’s oscillator grid. A tap on the oscillator coil connected to the cathode sustains oscillation. The 455kHz heterodyne signal passes to the first IF transformer. siliconchip.com.au negative feedback of the higher audio frequencies (passed by C27, 0.05µF) via 500kW potentiometer R17, as a tone control. The more of these highfrequency signals are fed back, the greater the top-cut. This works well, as judged by my ears. The HT of 280V from the 5Y3 dual rectifier cathode is filtered by C26 (8µF) and C31 (16µF). The total power consumption of this radio was 54W. With a rated maximum of 120mA, the 5Y3 is well suited to the set’s 75mA HT requirement. The 5Y3 is an octal repackaging of the widely-used 4-pin type 80 from the 1930s. Construction The rear of the Tecnico 1050 chassis showcases the miniature valves, power transformer, tuning gang, 9-inch speaker etc. The 6BA6 IF amplifier is a 7-pin miniature remote-cutoff pentode, used as an RF amplifier in standard broadcast and FM receivers. It was also released in 1946. The low value of gridto-plate capacitance minimises regenerative effects, while high transconductance provides good signal-tonoise ratios. Gain for this stage is up to 200 times with optimum grid bias. The output of the second IF transformer (L7) is detected by one of the diodes housed in the 6AV6 valve. The demodulated signal is then passed by R6 (50kW) and the PU shorting link to a 500kW volume-control potentiometer (R7). Audio then feeds to the grid of the 6AV6 triode for preamplification. The PU shorting link can be removed to allow audio from an external source to be fed directly into the set’s audio path, allowing it to be used as an amplifier/speaker, without the radio front-end. The second 6AV6 diode receives signal from the RF section via C21 (25pF). The negative voltage at this diode is proportional to signal strength, and this provides negative feedback to the grids of the first two valves via R8 (2MW). This automatic gain control (AGC) voltage is modified by the small reverse potential (relative to Earth) generated across R9 (15W). This provides a default grid bias for the 6BE6 and 6BA6 valves and delays the onset of AGC-reduced amplification until a siliconchip.com.au signal of moderate strength is tuned. For the output stage, Tecnico used a configuration inherited from other Tecnico designs (eg, the 1946 Model 651 described previously), with a 6V6 operating in Class-A. This design uses The rear of the chassis has five spring-clamp terminals: Aerial, Earth, Earth, PU input and Radio output (for linking to PU input). The radio was not originally Earthed via the mains supply. The output transformer is mounted on the elliptical Rola model 69H speaker. The speaker is secured to the front panel, thereby providing some baffling. Rola also provided the power choke that is mounted below the chassis. The choke is stamped “OCT 1950”, so this radio can be firmly dated. This side view shows the 5Y3GT rectifier valve with the 6V6G output amplifier adjacent. The speaker is mounted on a flat sheet of Masonite, and the curved decorative grille is in front of that. The control spindles are custom-made with extended length, to reach forward from the conventional rectangular steel chassis. The set also had two small lamps to provide a backlight for the dial; these aren’t shown on the circuit. Australia’s electronics magazine April 2020  91 Fig.1: the Tecnico Model 1050 circuit diagram. The printing for this diagram was a lot clearer than the 651, so it has been reproduced without alteration. Much of the circuit is similar, but note the jumper labelled PU below the 6AV6. This allowed external audio to be fed into the radio when removed. Restoration 92 Silicon Chip Australia’s electronics magazine The case was in excellent condition and was given a rub-over with Armor All protectant to enhance the gloss. The electrical restoration proved more demanding. Tecnico manufactured the radio with a figure-8 two core flex held against the inside of the chassis by a simple knot. This was standard practice at the time. A length of new black cotton-covered three-core flex was installed as the mains lead, clamped to the chassis. This cord is a modern reproduction to retain a period look, but has the contemporary colour codes for each wire. At initial switch-on, the power draw rapidly rose to 110W, so I promptly switched it off. The rapid increase to such a high power is possible because the 5Y3 is directly heated (the heater and the cathode are the same filament). Indirectly heated rectifiers, like a 6V4, take more time to warm up to conduct high currents. The high power use suggested the failure of an electrolytic capacitor connected between the supply rails, ie, a filter capacitor. C26 had been previously replaced with a Ducon type common in the 1960s. This was cold to the touch, but C31 (made by United Capacitors) was slightly warm. The reason this was warm but not hot is that with a low DC resistance, due to failure of the dielectric layer, most of the power is dissipated in the 5Y3 valve and choke L8. Either the valve or the choke can fail in this circumstance. Happily, they survived. I replaced both C26 and C31 with new 22µF 400V electrolytics. The power consumption then dropped to a much more normal 59W. The 6V6 grid measured 5mV, indicating no leakage through C22 (0.05µF). The 6V6 plate was at 222V, and the screen measured 240V. The 250W cathode resistor (R19) generated a grid bias of -10.6V. That all seemed right, but the radio sounded sick. There was intermittent distortion and the volume alternated between high and low of its own accord. Sometimes there was crackle. Both the volume and tone controls did little much of the time. I was immediately suspicious of the volume control potentiometer’s wiper contact resistance. So I removed the pot (made by Tecnico) and overhauled it. This resulted in faultless performance of the potentiometer on the bench. siliconchip.com.au To double-check whether it was the pot that was at fault, I soldered a new 500kW unit in, but the symptoms were unaltered. So I reinstalled the original pot, because it has a long shaft tailored to reach the front panel. The paper capacitors were my next suspects. Progressively replacing them produced no audible change, although the power use did fall from 59W to 54W. This left the mica capacitors as the next in the line of usual suspects. Eureka! The first mica to be replaced was C19 (100pF), manufactured by Simplex. The result was dramatic, with everything now performing as it should. That faulty mica was stamped 100pF but measured 220pF with a series resistance of 100kW. With 100V across it, it showed intermittent failure, passing up to 3mA. C19 bypasses any unwanted RF in the audio output of the 6AV6 plate to Earth. Because it was so leaky, it had been shorting the audio and the plate HT as well, thereby generating all of the symptoms. As others have noticed, mica capacitors are now increasingly failing, after up to 90 years of fault-free service. If a vintage radio has crackle then, as I need to remind myself, a mica capacitor should be the first suspect. Mica is a silicate mineral that can accommodate small numbers of various metal atoms in a matrix of silicon and oxygen atoms. 37 chemically distinct forms are recognised. The crystalline structure of mica takes the form of layers that can be split with nearly perfect cleavage into thin sheets. Silver can be plated onto opposite faces of a thin wafer of mica and joined to pig-tail leads either by soldering or simple physical contact to make a mica capacitor. Mica is possibly most familiar as the support sheet used to retain the heating wire in old electric toasters. Mica has generally high resistance to electrical breakdown under high voltage, dependant on thickness. Failure of mica capacitors over time can be due to (1) defects in the mica (mica has many grades from poor to high quality), (2) growth of silver whiskers from the electrodes, (3) failure of the pig-tail to silver joint and (4) ingress of moisture or reactive gasses into the encapsulated capacitor. The mesh behind the rear grille bars restricts heat transfer, so the gap below the handle at the top is the major ventilation port. All of these become more likely with increasing age. For a rigorous treatment of the causes of failure, see the paper titled “Some mechanisms of failure of capacitors with mica dielectrics” at: siliconchip.com.au/link/aav9 I feel that the 12 capacitors replaced in this restoration represented good value, restoring full function and guaranteeing future reliability. The result was an iconic radio that delivers a pleasant listening experience. But wait, there’s more! Shown below is the underside of the 1050’s chassis after all the paper and some of the mica capacitors were replaced. siliconchip.com.au Australia’s electronics magazine April 2020  93 Tecnico Tecnico 1951 1951 “Baby “Baby Fortress” Fortress” Model Model 1140 1140 By Associate Professor Graham Parslow Here is a short bonus article on a Tecnico Model 1140. The only similarity between this radio and the Model 1050 is in the case design. The restored radio does not have a truly “authentic” look as the case should be white, and the knobs and grille are not originals. A lthough this radio used a similar overall case design as the model 1050, it was significantly scaled down. It is a modest 270mm wide and weighs 4.9kg. By comparison, its 'big broth- er' model 1050 is 400mm wide and weighs 9.6kg. Electrically and mechanically, it is an entirely different radio. This one was created as a budget radio for the The 6CK6 output pentode is located below the power transformer. The loop coil antenna can be seen to the right of the 5-inch Rola model 5C speaker. From the mid-1950s, ferrite rods replaced woven coil antennas. 94 Silicon Chip Australia’s electronics magazine kitchen, rather than an imposing table radio for the lounge. The model numbers used by Tecnico combined the year of release (1 = 1941) with the number of valves, plus a gratuitous zero at the end. Hence the model 1050 is a five-valve radio released in 1950, and the model 1140 is a four-valve radio released in 1951. The example shown here was acquired lacking the front grille and knobs, so it needed some restoration work. In this case the replacement knobs were taken from an HMV stereogram. The genuine grille and knobs are the same as for the model 1050. The radio has an unconventional vertical chassis, more commonly seen in TV sets. In good reception areas, an external aerial was not needed because the primary tuning coil is also an antenna, as is common in portable models from this era. The chassis rear view shows the valves in this particular radio. In production, there were opportunistic valve substitutions, and some are shown on the official circuit diagram. At variance with the official circuit shown in Fig.1, the output pentode in this radio is a 6CK6 (designated as EL83 in Europe) that is rarely seen in Australian radios. The 6CK6 can be pushed to 9W audio output, so it is siliconchip.com.au Point-to-point wiring was used, ► with the smaller components mounted on tagstrips, as was common in 1950s radios. The switch at the back is a top-cut tone control (S1) which switches capacitors connected to the primary of the output transformer. (This photo was taken before all paper capacitors were replaced.) mismatched with this application. It is a nine-pin valve, described as a video power pentode capable of plate voltages up to 300V (the plate was measured at 220V in this radio). Eight of the nine pins are functional, allowing individual connection to all grids as well as an internal shield. The radio shown here needed a replacement 6AR7 due to an open filament in the original valve. All paper capacitors were replaced. For its compact size and given the limitations of the Rola 5-inch speaker, it performs well. SC 6X4 6CK6 ECH33 6AR7 Fig.1 (below): details on the 1140 can be found at https://vintage-radio.com.au/home.asp?f=3&th=587 including how to do the alignment. We’ve reproduced the circuit shown in that link as it’s the best quality scan available. It’s important to note that the valve line-up differs a bit from the actual radio shown, with a 6CK6 used instead of the N78 (and other substitutes). siliconchip.com.au Australia’s electronics magazine April 2020  95 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 Upgrading Micromite 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 function 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) • You seem to 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 update the firmware on a Micromite (latest version 5.05.02). You instead use the onboard Microbridge (if it’s a V2/3 BackPack), or lacking that, an external Microbridge (May 2017; siliconchip. com.au/Article/10648), 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. Designing moving magnet actuators I just finished reading the very interesting Serviceman’s Log column in your September 2019 issue (siliconchip.com.au/Article/11919). It’s about Dave Thompson repairing a speaker coil set. 96 Silicon Chip I am currently gathering information to replace the (noisy/energy wasteful) air drives for handheld and machine mounted “planishing hammers” drives for automotive panel shaping and repair machines. So I found parts of Dave’s article fascinating. These types of actuators are being used more and more in everyday equipment. I want to use moving-magnet voice coil actuators instead of moving coil types, because of the possibility of the coils being shaken to pieces from the repeated sudden stop forces involved. I have found some articles on building industrial-type moving coil actuators from Google searches, but there is very little information about moving magnet actuators. Could you maybe do an article about these moving magnet type actuators, or point me in the direction of finding out more information to enable me to build my own? Commercial actuators are very expensive to purchase for experimental use. I want to build a handheld unit in an alloy case about 75mm round, with variable stroke (0-4 mm) and frequency (0-700Hz) at about 550g force (5.4N). The fixed unit would be quite a bit larger, with variable stroke (0-25 mm) and frequency (0-700Hz) and about 4.5kg force (44N). Thank you. I enjoy the magazine. (H. H., Hampton, Qld) • Moving magnet voice coil actuators are a bit outside our area of knowledge. We realise that they differ from a standard solenoid, but perhaps a solenoid could be adapted, using some of the mechanical parts. Here are a couple of links that may be helpful. The thesis is quite comprehensive: siliconchip.com.au/link/ab0p siliconchip.com.au/link/ab0q Wide-range LC Meter giving odd readings I am having some problems with the Wide-Range LC meter (June 2018; siliconchip.com.au/Article/11099). I have assembled everything and finally got a read-out on the LCD. But the readings I’m getting are wildly inconsistent. I am testing 100nF 50V DC ceramic caps, and the readings I am getting range from 38.342pF to 632pF. I’m fairly confident that everything is soldered correctly, and I got all the parts listed Inductor core types On page 109 of the August 2019 issue, you suggested (in response to a question in Ask Silicon Chip) that powdered-iron core inductors would be better to use for the Class-D speaker filter in Dan Amos’ Digital Clock Radio project than ferrite types. But I am having trouble finding any reference to powdered iron-cored inductors in large toroidal formats. There are plenty of ferrite-cored SMD inductors to choose from. Can you suggest a part number for what you had in mind? (S. S., Barrington, NSW) • Most of the pre-wound toroidal inductors supplied by Jaycar and Altronics are compressed powAustralia’s electronics magazine dered iron types. The cores usually look green or yellow due to a coating that’s applied to them. They also sell the bare toroids so you can wind your own inductors on this type of core. Note that we have seen retailers incorrectly list powdered-iron inductors as having ferrite cores. Unless the core looks dark grey/black, it’s unlikely to be ferrite. Ferrite cores are normally much larger than powdered-iron cores for the same inductor value and current rating. In exchange for this, they usually offer lower losses, especially at higher frequencies (due to reduced eddy current losses). siliconchip.com.au Wiring Harness Solutions B- B- B+ B+ Ampec Technologies Pty Ltd siliconchip.com.au Tel: 02 8741 5000 Email: sales<at>ampec.com.au April 2020  97 Australia’s electronics magazine in the right ranges. Is there anything common that you guys have seen other readers encounter commonly with this project? (P. B., Invercargill, NZ) • We have had two or three people where the relays they have gotten are a different type to what we used. In some of these cases, we suspect that a variant of the reed relay with a slightly different pinout ended up mixed in with the correct relays at the parts retailer. So we suggest that you thoroughly check the relays for correct operation. You should hear them clicking as the unit cycles through its modes. The other component most likely to give trouble is the comparator. Perhaps you could try swapping this out. Try to avoid cheap LM311 comparators from sites like eBay as we’ve had reports from some people that they may not work as well as the genuine ones. If you have a scope, you can check that the test waveforms look correct. If that doesn’t lead anywhere, please send photos of your PCB and the LCD while a measurement is occurring, so we can check if you’ve missed anything. The serial port for the Arduino also produces some debugging information which may help diagnose your problem. Water Tank Level Meter questions I built your solar-powered Water Tank Level Meter with WiFi (February 2018; siliconchip.com.au/ Article/10963) and have some questions about it. Is this device directly powered by the solar panels, with a battery backup, or is it directly powered by the battery and then recharged from the solar panels? Once the battery is flat, my device will not operate. How long would you expect the solar panels to recharge the battery – hours, days or weeks? What is your experience? Also, is it possible to extend the reporting period from 10 minutes to say every 1 or 2 hours? Would this increase the battery life? (A. C., Largs Bay, SA) • The unit is always powered from the battery, but when the battery is being charged from the solar panel(s), power is effectively diverted from the panel(s). As long as the current from the panel(s) exceeds the board’s current consumption, the battery will still charge when the unit is active. That your unit won’t operate with a flat battery suggests that your panel 98 Silicon Chip cannot deliver enough current to both charge the battery and power the unit at the same time. But consider that it will typically take a little time for the terminal voltage of a flat battery to rise to the point where the circuit will operate. The unit can operate with a flat battery as long as there is sufficient energy from the panel(s). It’s best to choose a battery/panel combination which will rarely result in a flat battery, to ensure a good life. The single panel used on our prototype worked well enough during testing, but was ultimately not large enough since the location where we ended up mounting it did not get full sun for many hours per day. In this case, it is better to use two or more panels in parallel, combined with schottky diodes (or one larger panel), as they will recharge the battery more quickly. These panels are not expensive, but you will need a large enclosure to fit them all. Yes, you could increase the reporting period to one or two hours. One of two functions are used to set this period, either ESP.deepSleep() or delay(). The maximum time for deepSleep is just over an hour (siliconchip.com.au/ link/ab0r) while the maximum time for delay() appears to be around 49 days (siliconchip.com.au/link/ab0s). It would increase battery life a bit, especially if you’re using the deep sleep option. The difference may not be huge because it generally only takes the unit a few seconds to send an update. So with a ten minute, interval, it may be active around 2% of the time. With a two hour interval, you reduce that to well under 1%, but the power spent in sleep will become the limiting factor. If you want maximum battery life, I suggest you take advantage of the deep sleep option. WiFi burglar alarm wanted I wonder if you ever thought of doing an alarm project. You could use an ESP32 (which has built-in WiFi) in conjunction with RCWL-0516 microwave-based motion sensor board described by Jim Rowe in the February 2018 issue (siliconchip.com.au/ Article/10966). I bought a few of the detector boards after seeing Jim’s article, and they seem Australia’s electronics magazine to be very sensitive and work well. Used with an ESP32 or WiFi-enabled Arduino etc, it would make a neat alarm project. The reason I suggest this is that it might be very suitable for unattended premises, like a small factory, holiday home or even one’s own home when away. Keep up the great work at Silicon Chip, I’m a subscriber and look forward to it each month. (G. P., Narre Warren, Vic) • Jaycar have published a WiFi burglar alarm design. See: www.jaycar. com.au/intruder-alert Motor Speed Controller queries I’m an electronics enthusiast, and I’m trying to build your High-Power Motor Speed Controller from the January/February 2017 issue of Silicon Chip magazine (siliconchip.com.au/ Series/309). But I can’t find a source for the IRS21850S high-side Mosfet driver. Can I replace this with the FAN73711 from Fairchild, which looks similar? Also, the controller is supposed to work from a 12V battery. But the LM2940CT-12 regulator has a minimum input voltage of 13.6V. How do I get the 12V needed for the Mosfet driver? (A. D., via email) • The FAN73711 looks like a direct copy of the IRS21850S and so it should be a suitable substitute. But note that we still have a decent stock of the original IRS21850S parts for sale in our Online Shop (siliconchip.com.au/ Shop/7/2139). The LM2940CT-12 regulator has a dropout voltage of 0.5V. Including the series input diode drop due to D1 (0.7V), the input supply will need to be above around 13.2V to achieve a regulated 12V rail. However, IC2 (IRS2185) will work down to 8V, and the IPP023N10N5 Mosfets fully conduct with a 6V gate voltage. So the input 12V supply would need to drop down to below about 9.2V before shutting down. Regulator REG1 is included primarily to allow the circuit to operate from voltages well above 12V. For example, with a 48V battery, the battery voltage variation and properties of zener diode ZD4 could allow the input to REG1 to rise above the 20V maximum for IC2 and the Mosfets. REG1 therefore protects those components from damage siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS 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 TINY LED XMAS TREE (GREEN/RED/WHITE) SUPER-9 FM RADIO PCB SET ↳ CASE PIECES & DIAL HIGH POWER LINEAR BENCH SUPPLY ↳ HEATSINK SPACER (BLACK) JUL19 JUL19 AUG19 AUG19 AUG19 SEP19 SEP19 SEP19 SEP19 SEP19 SEP19 OCT19 OCT19 NOV19 NOV19 NOV19 NOV19 NOV19 05106191 05106192 07106191 05107191 16106191 11109191 11109192 07108191 01110191 01110192 16109191 04108191 04107191 16111191 06109181-5 SC5166 18111181 SC5168 Subscribers get a 10% discount on all orders for parts $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 $2.50 $25.00 $25.00 $10.00 $5.00 DIGITAL PANEL METER / USB DISPLAY ↳ ACRYLIC BEZEL (BLACK) UNIVERSAL BATTERY CHARGE CONTROLLER BOOKSHELF SPEAKER PASSIVE CROSSOVER ↳ SUBWOOFER ACTIVE CROSSOVER ARDUINO DCC BASE STATION NUTUBE VALVE PREAMPLIFIER TUNEABLE HF PREAMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) NUTUBE GUITAR DISTORTION / OVERDRIVE PEDAL THERMAL REGULATOR INTERFACE SHIELD ↳ PELTIER DRIVER SHIELD NOV19 NOV19 DEC19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 18111182 SC5167 14107191 01101201 01101202 09207181 01112191 06110191 27111191 01106192-6 01102201 21109181 21109182 $2.50 $2.50 $10.00 $10.00 $7.50 $5.00 $10.00 $2.50 $5.00 $20.00 $7.50 $5.00 $5.00 DIY REFLOW OVEN CONTROLLER (SET OF 3 PCBS) 7-BAND MONO EQUALISER ↳ STEREO EQUALISER REFERENCE SIGNAL DISTRIBUTOR APR20 APR20 APR20 APR20 01106193/5/6 01104201 01104202 CSE200103 $12.50 $7.50 $7.50 $7.50 NEW PCBs PRE-PROGRAMMED MICROS As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS ATtiny816 PIC12F202-E/OT PIC12F617-I/P PIC12F675-E/P PIC12F675-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1459-I/P PIC16F88-I/P PIC16LF88-I/P $15 MICROS ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sept19) Trailing Edge Dimmer (Feb19), Steering Wheel to IR Adaptor (Jun19) Car Radio Dimmer Adaptor (Aug19) Courtesy LED Light Delay (Oct14), Fan Speed Controller (Jan18) Motor Speed Controller (Mar18), Heater Controller (Apr18) Useless Box IC3 (Dec18) Tiny LED Xmas Tree (Nov19) Microbridge and BackPack V2 / V3 (May17 / Aug19) USB Flexitimer (June18), Digital Interface Module (Nov18) GPS Speedo/Clock/Volume Control (Jun19) Five-Way LCD Panel Meter / USB Display (Nov19) Deluxe Frequency Switch (May18), Useless Box IC1 (Dec18) Remote-controlled Preamp with Tone Control (Mar19) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) GPS-synchronised Analog Clock Driver (Feb17) ATmega328P RF Signal Generator (Jun19) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) GPS Boat Computer (Apr16), Micromite Super Clock (Jul16) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) SPECIALISED COMPONENTS VARIOUS MODULES & PARTS - AD8495 thermocoupler interface (DIY Reflow Oven Controller, Apr20) - WS2812 8x8 RGB LED matrix module (El Cheapo Modules, Jan20) - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) - 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) - 23LCV1024-I/P SRAM & MCP73831T (UHF Repeater, May19) - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) - LM4865MX amplifier & LF50CV regulator (Tinnitus/Insomnia Killer, Nov18) - 2.8-inch touchscreen LCD module with SD card socket (Tide Clock, Jul18) - ESP-01 WiFi Module (El Cheapo Modules, Apr18) - MC1496P double-balanced mixer (AM Radio Transmitter, Mar18) - 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) - 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) - VS1053 Geeetech Arduino MP3 shield (Arduino Music Player, Jul17) - 1nF 1% MKP (5mm) or ceramic capacitor (LC Meter, Jun18) - 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 $10.00 $15.00 $5.00 $4.00 $11.50 $1.50 $10.00 $22.50 $5.00 $2.50 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 $3.00 $5.00 $7.50 $6.00 ec. TINY LED XMAS TREE COMPLETE KIT (SC5180) (NOV 19) 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 MICROMITE EXPLORE-28 (CAT SC5121) Complete kit – includes PCB plus programmed micros and all other onboard parts Programmed micro bundle – PIC32MX170F256B-50I/SO + PIC16F1455-I/SL (SEPT 19) $30.00 $20.00 $5.00 MICROMITE LCD BACKPACK V3 (CAT SC5082) $15.00 $20.00 $2.50 GPS SPEEDO/CLOCK/VOLUME CONTROL (JUN 19) SUPER DIGITAL SOUND EFFECTS KIT (CAT SC4658) (AUG 18) (AUG 19) 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 on-board parts $75.00 1.3-inch 128x64 SSD1306-based blue OLED display module (Cat SC5026) MCP4251-502E/P dual-digital potentiometer (Cat SC5052) PCB and all onboard parts, but no SD card, cell or battery holder $15.00 $3.00 $40.00 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. PAYPAL (24/7) INTERNET (24/7) MAIL (24/7) PHONE – (9-5:00, Mon-Fri) eMAIL (24/7) To Use your PayPal account siliconchip.com.au/Shop Your order to PO Box 139 Call (02) 9939 3295 with silicon<at>siliconchip.com.au Place siliconchip.com.au Australia’s electronics magazine April silicon<at>siliconchip.com.au Collaroy NSW 2097 with order 2020  99 & credit card details Your You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. Order: 04/20 and allows them to operate normally over a wide range of supply voltages. Boat anti-fouling transducer placement I recently built your dual transducer Marine Ultrasonic Anti-Fouling unit (May & June 2017; siliconchip. com.au/Series/312) from a Jaycar kit (Cat KC5536). I am seeking guidance regarding where on the hull to place the transducers. The boat is a 28-foot Bertram. My first thought is to place the transducers aft and forward near the keel line. However, such positions are difficult to access. More accessible locations are outboard amidships in the engine bays. This would have the transducers about two meters apart (one meter each side of the keel line) and slightly aft of the centre of the waterline. Please advise if this configuration would give suitable transducer separation and effective anti-fouling. Please also advise if the transducer cable lengths are critical. My application would suit shortened cables if technically sound. (D. P., Wolumla, NSW) • Ideally, the transducers should be placed at either end of the boat. However, locating them amidship two metres apart would probably provide reasonable ultrasonic coverage. If this proves not to be as effective as it should be, one transducer could be moved forward and the other aft. The cable lengths between the AntiFouling unit and transducers are not critical. MPPT Solar Charger capacitor selection I have a question about your MPPT Solar Charger & Lighting Controller design (February & March 2016; siliconchip.com.au/Series/296). I would like to know why the 2200µF electrolytic capacitors are changed to 470µF for use with 24V solar cells and a 24V battery. Is that for tuning due to the switching frequency required, or due to the physical size of the components? Would 2200µF 50V capacitors work? Also, do you have the source code in C for this project? I want to build this device because most of my security cameras were blown up by a cheap solar regulator that allowed the battery voltage to rise above 30V. I have four 24V 215W solar cells and six 100Ah 12V batteries, with a heap of things hanging off them (7A load at night). Because I have a continuous load, normal smart chargers tend to keep the batteries under charge the whole time, risking damage to the batteries. So I have to use an Arduino to control the charger. (D. V., Salisbury Park, SA) • The 470µF 63V capacitors used in the 24V version were selected to fit in the same space as the 2200µF 25V capacitors used in the 12V version, while maintaining sufficient ripple current handling for reliable operation. You could use four 2200µF 50V MPTT solar charger has reduced charging current I built the Switchmode Solar Battery Charger described in Circuit Notebook, October 2018 (siliconchip. com.au/Article/11274) to use with a 20W solar panel. I left out the sunset switch as I do not need it. I designed a PCB, made it using the laser toner method and assembled the board without any problems. It seems to work OK but adjusting VR1 was a bit tricky. Initially, the wiper should be adjusted so that it provides a high resistance to the circuit. Otherwise, nothing happens when you connect it up, and you can’t be sure of a wiring problem or not. An audible buzzing can be heard when the Mosfet is switching, and this can be used to confirm the unit is working and as an aid in adjusting the cut off voltage. The voltage at the panel is about 17.2V, as described in the article. In testing the unit, I was somewhat disappointed, as I was expecting better performance than a directly connected panel. However, this seemed not to be the case. In full sunlight, my panel was putting out about 20V (maximum is 22V), and the current into the battery was 100 Silicon Chip about 1A. A direct connection to the panel produced 1.3A into the battery, which was unexpected. I am not sure why this is – possibly losses in the electronics. The toroidal inductor gets quite warm. Perhaps the “Simple solar charge regulator for campers” (Circuit Notebook, August 2015; siliconchip. com.au/Article/8806) or a relay could work better. (B. D., Mount Hunter, NSW) • It is true that under some conditions, an MPPT charger can result in slower charging than a direct connection due to inefficiency. But, in theory at least, they work better under a wide range of conditions. That the inductor gets so hot suggests it is a significant source of inefficiency. You could try replacing it with a part with a higher current rating or maybe with a ferrite core. It would be interesting to modify an MPPT charger to have a bypass relay, which could be energised during those times where a direct connection might be more efficient. But it’s not obvious how to determine when to energise it. The designer, Colin O’Donnell Australia’s electronics magazine adds: you are right about the way that VR1 needs to be adjusted. The audible buzzing is strange; it is probably coming from loose wiring on the toroid. I think detecting and adjusting the cutoff voltage using a DMM is probably a more effective approach. I did recommend a larger toroid for better efficiency, noting the smaller toroid got a little warm. I do not know what capacity battery you are charging, but a large automotive/marine battery would accept a direct connection and happily trickle charge at 1.3A all day. However, in my case, I’m using 20Ah golf-cart batteries. In this case, direct connection charging is a trap – the solar panel would charge the battery up to 20V+! Charging a low impedance, discharged battery at 1.3A can occur in full sunlight with this circuit. It seems to be the practical (and theoretical) upper limit for a 20W panel. The charging rate tapers off significantly as the battery voltage rises to 14.1V, or whatever cutoff voltage you have chosen. You will also notice that the panel input voltage rises to 18V+ as a result of surplus power. siliconchip.com.au capacitors as long as they also meet those requirements. If in doubt, compare their ripple ratings to those of the capacitors we specified and make sure that the total ripple current of all capacitors is at least as large as when using the capacitors we’ve nominated. The chip in this project is programmed in assembly language, so we have no C source code to supply. The ASM source code file is part of the ZIP download package for this project. Questions about Senator loudspeakers I just tried to buy the Celestion drivers specified for your Senator 10-inch two-way speakers (September-October 2015; siliconchip.com.au/Series/291), but they are no longer produced. Are you bringing out another speaker project, or can you recommend some other drivers that will be as good for that project? I have built two SC200 amplifier modules (January-March 2017; siliconchip.com.au/Series/308) and would love to plug them into a fantastic pair of speakers. Also, did you publish the additional information for the supply or manufacture of the discontinued Jaycar LF1330 crossover inductors used in this project, as stated on page 80 of the October 2015 issue? I look forward to your reply. (C. H., Gawler East, SA) • While some outlets may have sold out, the Celestion drivers are still available. For example, a quick search showed multiple sellers offering them on eBay. We published a revised version of those speakers in the May and June 2016 issues (siliconchip.com.au/ Series/300) which used the Altronics C3026 bass driver, but it still used the Celestion tweeter. The update on the inductors was also in the June 2016 issue (Budget Senator Loudspeakers part two). We used 325 turns of 1mm diameter enamelled copper wire on a custom former made from acrylic pieces. Those pieces are available for purchase on our website at: http:// siliconchip.com.au/Shop/7/3470 You might consider purchasing them at the same time as the crossover PCB. Editor’s note: we got a follow-up email a couple of days after sending our response. The reader indicated that he managed to purchase all the required siliconchip.com.au Celestion drivers and horns from Belfield Music, Bass Hill, NSW. LED query for HiFi Valve Stereo Preamp I bought copies of your January & February 2016 issues to build the Hifi Valve Stereo Preamplifier (siliconchip. com.au/Series/295) and tinker about with it. I’ve modelled the circuitry around indicator LED2, including the 220kW resistor and zener diodes ZD2 and ZD3 using TINA 7 Design Suite. The only way I can get LED2 to illuminate is to change the dropper resistor from 220kW to 33kW. When I change the value on the modelling software, LED2 illuminates, leaving me to assume that the 220kW value may be a print error. Without breadboarding this section (which I intend to do), I can’t be entirely sure, but it being a simple circuit I doubt the software would be at fault. I checked for errata on this article, but didn’t find any. (J. H., Scotland, UK) • LED2 on our prototype lit with the component values specified. You can see that we used a 220kW resistor by reading the coloured bands on the photo in the article heading. This sets the LED current to 1mA, which is plenty to illuminate it, as long as it is a reasonably efficient type. In the worst case, a high-brightness LED could be used to ensure that it’s bright enough at 1mA. A 33kW resistor in that position would dissipate nearly 2W and would probably cause the HT rail to sag. It would need to be a 3W-rated resistor. We do not suggest that you build this project (or even a part of it) on a breadboard, as breadboard is not rated to handle the nearly 300V DC that is present during operation! Power supply for UltraLD Mk.3 with Majestics I am currently building an UltraLD Mk.3 stereo amplifier (March-May 2012; siliconchip.com.au/Series/27) and a set of Majestic speakers (June & September 2014; siliconchip.com.au/ Series/275). I think it will be a good combination. I have a pair of toroidal transformers suitable for the amplifier. I was considering using dual power supplies, one for each channel, but that would require quite a lot of extra work. Do you think it would be worth the effort? Australia’s electronics magazine Harmon Kardon did it in the 70s. (A. J., Martin, WA) • Yes, that is a good combination; we approve. You certainly can build a stereo amplifier using Ultra-LD Mk.2, Mk.3 or Mk.4 modules and two separate power supplies. However, unless you plan on putting on a rock concert, it is not worthwhile for driving the Majestic loudspeakers. Those speakers are so sensitive that they are virtually deafening at just a few watts. You aren’t going to run into power limitations with an Ultra-LD series amplifier using a single power supply at any sort of reasonable volume level. Even with just 50W/channel, which an amplifier can easily sustain with a shared supply, you are likely to damage your hearing (and probably your neighbours’)! CLASSiC-D amp needs dead time adjustment Congratulations on producing such a great magazine, which I’ve been following since Electronics Australia was still on newsstands. I just built a CLASSiCD Class-D amplifier module (November & December 2012; siliconchip.com.au/ Series/17) and ran into some problems; I hope you can help me with them. Q2 failed in operation resulting in a permanently shorted drain-source junction. The failure was preceded by a loud clunk in the speaker, which was fortunately saved when the protection relay dropped out. I discovered a solder blob between the 10W and 7.5kW resistors connected to Q3, effectively shorting the base-emitter junction. The IRS2092’s protection circuitry didn’t save Q2 from destruction. With the solder blob removed and Q2 replaced, Q1 blew up, now shorted between its drain and source. I can’t really figure out why, but after replacing Q1, the unit has been robust, and I haven’t managed to blow up any further Mosfets, despite a lot of testing and troubleshooting. While trying to figure out why this all happened, I noticed that the heat sink on the board experiencing these failures becomes significantly hotter than the other. I replaced all components involved with the 15V ‘floating’ supply “just in case”, but the problem remains. Scope traces on Lo and Ho suggest the dead time is greater between Looff and Ho-on, compared with Ho-off April 2020  101 and Lo-on. It also appears that it takes longer for Q1 to switch off than Q2. The floating supply for Q1’s gate drive perhaps confuses the issue. Because it floats above Vs (ie, the output rail), it shows up on Ho as a large swing commencing above B+ and going down to B- (a peak-to-peak swing of around 124V, compared with the 15V swing of Lo). There’s a noticeable ‘knee’ in Ho’s falling slope, which adds to the time for Ho to reach its lowest value of around -50V. This knee is well above 0V, suggesting that at this point, Q1 is still on. A diode across Q1’s 22W gate resistor removes the knee and Q1’s switch-off time decreases, helping to ensure that Q1 is well and truly off before Q2 is on (as shown in the two supplied scope grabs). Despite the above changes, the heatsink was still getting very hot. After hours of checking, rechecking, removing many components and testing, I’m at a complete loss to understand why. I changed the dead time resistors to increase the dead time to option 3, resulting in the heatsink running significantly cooler. The amp has been working fine for quite some time now. Could the fact that the replacement Mosfets are from different manufacturers have something to do with this? In case that matters, I’ve now ordered replacement Mosfets (Infineon) from Digi-Key and will replace both of them. Hopefully, for the benefit of less distortion, I’ll be able to go back to dead time option two with two new Mosfets installed. On another topic, I want to add volume control to my CLASSiC-D amp, but the input impedance of 4.7kW is a bit low to directly wire in a potentiometer without overloading it. So I’m thinking that buffering may be required. Can you suggest the best way to do this? Your magazine has provided for a very rewarding hobby over many years. It’s a credit to everyone there to be able to keep coming up with so many great, high-quality projects and interesting articles month after month. Well done! (S. D., Wantirna South, Vic) • A solder blob short from Q3’s base to emitter could certainly have caused the initial destruction of Q2. With Q2 shorted, Q1 would have also been shorted to the supply rail and so would have been damaged before Q2 was replaced. The protection of the Mosfets against over-current is really only effective if IC1 is supplied its correct power voltages. It is interesting that you needed to increase dead time to have the heatsink run cool. A compromise has to be made between having the shortest dead time and having a satisfactory heatsink temperature. Differences in the output Mosfets switching characteristics due to manufacturing tolerances could account for the temperature differences between the two separate amplifiers. It only takes one Mosfet with differing characteristics to make both Mosfets run hotter. We do think that the amplifier would run cooler using Mosfets from the same reputable manufacturer. This increases the chances that the deadtime required for each Mosfet will be similar. Depending on what is driving the amplifier, you could place a 4.7kW dual logarithmic volume control pot Trace on Ho and Lo – no diode on Q1’s gate resistor. 102 Silicon Chip at the front without buffering. If you want to use a preamplifier, we suggest that you use the Ultra Low-noise Remote Controlled Stereo Preamp from March & April 2019 (siliconchip.com. au/Series/333). This can be mated with our Input Selector from September 2019 (siliconchip.com.au/Article/11917) to provide input switching. PIC programmer verification failures I have built the dsPIC and PIC programmer from May 2008 (siliconchip. com.au/Article/1824). When I program PICs with it, it comes back with heaps of verification errors. However, when I take the PIC and put it in a circuit, it usually works. If I add an extra delay of 1000µs before reading data in WinPIC, sometimes it can get through without errors. However, it then takes a very long time to program the chip. Can you tell me what is happening and any suggestions to fix this problem? (D. D., Lorne, Vic) • The ZIF socket contacts could be dirty and making poor contact. Try cleaning them with contact cleaner. Does taking a chip out of the socket and putting it back in help sometimes? The other potential cause of your problem would be the way that the PGD line is set up for a bidirectional data flow. The output of IC2f only pulls PGD low via 1N4004 diode D3; it relies on a 2.2kW resistor to pull it up, so any significant capacitance on that pin would result in very slow low-tohigh transitions and the sort of problems that you are experiencing. As 1N4004 diodes are not intended Trace on Ho and Lo – diode across Q1’s gate resistor. Australia’s electronics magazine siliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP KIT ASSEMBLY & REPAIR FOR SALE MISCELLANEOUS 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 BUSINESS FOR SALE Well known Australian electronics company for under $50,000. GENUINE BUYERS ONLY Phone: 0410600330 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) 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 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 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 KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, ad­ dress & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. to be used as ‘signal’ diodes, we suggest that you change D3 to a 1N4148 or 1N5819 (both of which should switch much faster). That design really should have incorporated a buffer from the anode of D3 to pin 8 of CON2, so that RS-232 cable capacitance doesn’t slow down these transitions. Clipping indicator wanted I was wondering if Silicon Chip siliconchip.com.au has ever produced a clipping indicator project that could be added to most power audio amplifiers. (M. J., via email) • We published a Clipping Indicator circuit in the Circuit Notebook section of our November 2003 issue (siliconchip.com.au/Article/4810). However, that circuit only monitored for clipping during positive excursions. More recently, our Ultra-LD Mk.4 amplifier design from August 2015 Australia’s electronics magazine incorporated a bidirectional clipping detector. That part of the circuit was presented separately (in Fig.2 on page 36) and could be added to any power amplifier. That circuit is a little more complex but has the advantage that a single LED indicates clipping at either extreme. It’s designed to suit an amplifier with a Darlington output stage, but can easily be changed to suit other designs by choosing different voltage zener diodes for ZD1 and ZD2. SC April 2020  103 Coming up in Silicon Chip Anodising aluminium Advertising Index Altronics...............................73-76 Professionally-made aluminium pieces are often anodised for protection against damage and corrosion, or to change their colour. Sometimes you don’t have that option, though, especially when you are making aluminium panels at home. But the anodising process is not that complicated and you can do it at home with just a few basic tools and chemicals. We’ll explain how. Stealth Technology Stealth technology doesn’t just apply to aircraft; ships, vehicles and even people can be rendered harder to detect using the various technologies described in this article. Dr David Maddison describes the latest developments in radar stealth as well as techniques for reducing infrared emissions, generated noise, and even attempts to make vehicles and people invisible to the naked eye! The H-field Transanalyser Dr Hugo Holden developed this all-in-one instrument for aligning, testing and troubleshooting AM transistor radios. It can also be used with valve sets; the modulated test signal can be coupled into a ferrite rod antenna without making any direct electrical connections to the circuit, thus avoiding detuning it or otherwise affecting its operation. Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The May 2020 issue is due on sale in newsagents by Thursday, April 30th. Expect postal delivery of subscription copies in Australia between April 28th and May 8th. Notes & Errata AM/FM/CW Scanning HF/VHF RF Signal Generator, June & July 2019: the de­ signer discovered that some rotary encoders look identical but work differently, re­ sulting in erratic operation. The V14 firmware addresses this; by default, it works with pulse-type encoders. You can identify these by testing continuity across the two internal switches; if they are both always open when the encoder is at rest, it is a pulse-type. With the level type, one or both switches may be closed at rest, depending on the encoder’s rotation. If you have a level-type encoder and the V14 software, solder a 100kW resistor from pin 28 of the Atmel chip to ground, on the underside of the PCB. That will change the software mode to work with level-type encoders. Ampec Technologies................. 97 Control Devices......................... 11 Dave Thompson...................... 103 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Jaycar............................ IFC,49-56 Keith Rippon Kit Assembly...... 103 LD Electronics......................... 103 LEACH PCB Assembly............... 5 LEDsales................................. 103 METCASE Enclosures................ 4 Microchip Technology........ OBC, 7 Mouser Electronics...................... 9 Ocean Controls......................... 63 RayMing PCB & Assembly.......... 8 SC Micromite BackPack............ 37 Silicon Chip PDFs.................... 48 Silicon Chip Shop.................... 99 The Loudspeaker Kit.com......... 61 Triple Point Calibrations............. 10 Vintage Radio Repairs............ 103 Wagner Electronics..................... 6 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. 104 Silicon Chip Australia’s electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! Ex GST RIGOL DS-1000E Series RIGOL DS-1000Z/E - FREE OPTIONS RIGOL MSO-5000 Series 450MHz & 100MHz, 2 Ch 41GS/s Real Time Sampling 4USB Device, USB Host & PictBridge 450MHz to 100MHz, 4 Ch; 200MHz, 2CH 41GS/s Real Time Sampling 424Mpts Standard Memory Depth 470MHz to 350MHz, 2 Ch & 4Ch 48GS/s Real Time Sampling 4Up to 200Mpts Memory Depth FROM $ 429 FROM $ ex GST 649 FROM $ ex GST 1,569 ex GST Multimeters Function/Arbitrary Function Generators New Product! RIGOL DG-800 Series RIGOL DG-1000Z Series RIGOL DM-3058E 410MHz to 35MHz 41 & 2 Output Channels 416Bit, 125MS/s, 2M Memory Depth 425MHz, 30MHz & 60MHz 42 Output Channels 4160 In-Built Waveforms 45 1/2 Digit 49 Functions 4USB & RS232 FROM $ 479 FROM $ ex GST Power Supplies 725 ONLY $ ex GST Spectrum Analysers 789 ex GST Real-Time Analysers New Product! RIGOL DP-832 RIGOL DSA Series RIGOL RSA Series 4Triple Output 30V/3A & 5V/3A 4Large 3.5 inch TFT Display 4USB Device, USB Host, LAN & RS232 4500MHz to 7.5GHz 4RBW settable down to 10 Hz 4Optional Tracking Generator 41.5GHz to 6.5GHz 4Modes: Real Time, Swept, VSA & EMI 4Optional Tracking Generator ONLY $ 749 FROM $ ex GST 1,321 FROM $ ex GST 3,210 ex GST Buy on-line at www.emona.com.au/rigol Sydney Tel 02 9519 3933 Fax 02 9550 1378 Melbourne Tel 03 9889 0427 Fax 03 9889 0715 email testinst<at>emona.com.au Brisbane Tel 07 3392 7170 Fax 07 3848 9046 Adelaide Tel 08 8363 5733 Fax 08 83635799 Perth Tel 08 9361 4200 Fax 08 9361 4300 web www.emona.com.au EMONA