Fullscreen HTML5Med Res (??MB)HTML4

JANUARY 2022 ISSN 1030-2662 01 The VERY BEST DIY Projects! 9 771030 266001 $ 50* NZ $1290 11 Batteries INC GST INC GST imagine life without them Metronomes with 8 or 10 LEDs protect up to six amplifier modules with our Multi-Channel Speaker Protector Build your own Trailer Battery Voltage Monitor A great easy to build project that will monitor the voltage of a 12V battery for your trailer’s ‘electric brakes’. The circuit’s not limited to trailer batteries - it can also be used on a caravan/house battery, trolling motor battery, or any type of battery that you don’t want to get so flat that it won’t take a charge anymore. SKILL LEVEL: INTERMEDIATE USB lead not included. CLUB OFFER BUNDLE DEAL For step-by-step instructions & materials scan the QR code. 2995 $ www.jaycar.com.au/trailervoltagemonitor See other projects at SAVE 20% www.jaycar.com.au/arduino 2 FOR 2 FOR 8 12 $ SAVE 20% BUY 2 AND SAVE Logic Level Converter Module Provides two bi-directional channels to safely marry 3.3V with 5.0V. Drops straight into solder-less breadboard. XC4486 $4.95EA 100 gift card BUY 2 AND SAVE DC Voltage Regulator Module Accepts voltage from 4.5- 35VDC, and outputs from 3-34VDC. 2.5A max output current. XC4514 $7.95EA Got a great project or kit idea? 15 $ SAVE 20% BUY 2 AND SAVE 2.4GHz Wireless Transceiver Module Allows communication on the license free ISM band. Supports on-air data rates of up to 2Mbps. XC4508 $9.95EA If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com Looking for your next build? Silicon Chip projects: jaycar.com.au/c/silicon-chip-kits Kit back catalogue: jaycar.com.au/kitbackcatalogue 1800 022 888 www.jaycar.com.au Awesome projects by On2 Sale 27 S December ilicon 2021 Chip to 23 January 2022 2 FOR $ SAVE 15% $ KIT VALUED AT $37.55 Australia's electronics magazine Shop online and enjoy 1 hour click & collect or free delivery on orders over $99* siliconchip.com.au Exclusions apply - see website for full T&Cs. * Contents Vol.35, No.1 January 2022 12 All About Batteries – Part 1 24 Life without batteries would be unthinkable. We’d be stuck with fixed phones, non-portable computers, and have to crank-start cars. This series covers everything you need to know about batteries. By Dr David Maddison Science 37 Dick Smith Autobiography Dick Smith – businessman, adventurer, publicity stunt creator, publisher, food brand, environmentalist and great promoter of Australia. His new autobiography is a great read for just about anyone. By Nicholas Vinen Book review 64 38 Solar Power with Batteries After collecting data on my solar panels over their lifetime I wanted to see whether adding batteries to my system would be worthwhile, what type I should use and how large it should be. By Dr Alan R. Wilson 96 72 LTDZ Spectrum Analyser Geekcreit’s low-cost LTDZ V5.0 spectrum analyser can perform analysis over the range of 35MHz to 4.4GHz. It’s controlled from a PC via USB, and includes a tracking generator, RF amplifier and more. By Jim Rowe Low-cost electronic modules 24 Two Classic LED Metronomes These two metronomes, one with eight LEDs and the other with 10 LEDs, simulate the classic pendulum design, with a pointer swinging left-and-right. They are great projects for beginners due to not requiring any programming. By Randy Keenan Musical project 46 Multi-Channel Speaker Protector This compact Speaker Protector works with up to six amplifier modules and can operate from the same supply (up to ±40V DC). It perfectly suits the Hummingbird Amplifier module described last month. By Phil Prosser Audio project 64 The PicoMite The PicoMite is a BASIC interpreter running on the Raspberry Pi Pico (MMBasic, in fact). It can be easily connected to a variety of displays, including OLED and e-Ink panels, with extensive support for other peripherals. By Geoff Graham & Peter Mather Raspberry Pi project 96 Remote Control Range Extender Converting your remote control from infrared to UHF will bring its working range up to 25m with this project! All you need to do is build these two boards, one goes near the receiving device and the other fits inside the remote. By John Clarke Remote control project 2 Editorial Viewpoint 4 Mailbag 11 Subscriptions 52 Product Showcase 61 Circuit Notebook 78 Vintage Radio 89 1. Conway’s Game of Life on Micromite 2. PCB joiner for the MIDI Keyboard 3. Compact reed relay module The Mysterious Mickey Oz by Ian Batty Serviceman’s Log 106 Online Shop 108 Ask Silicon Chip 111 Market Centre 112 Advertising Index 112 Notes & Errata SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke – B.E.(Elec.) Technical Staff Jim Rowe – B.A., B.Sc. Bao Smith – B.Sc. Tim Blythman – B.E., B.Sc. Nicolas Hannekum – Dip.Elec.Tech. Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Allan Linton-Smith Dave Thompson David Maddison – B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Dr Hugo Holden – B.H.B, MB.ChB., FRANZCO Ian Batty Phil Prosser – B.Sc., B.E.(Elec.) Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson – B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (Australia only) 6 issues (6 months): $65 12 issues (1 year): $120 24 issues (2 years): $230 Online subscription (Worldwide) 6 issues (6 months): $50 12 issues (1 year): $95 For overseas rates, see our website or email silicon<at>siliconchip.com.au Recommended & maximum price only. Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. ISSN 1030-2662 Printing and Distribution: Editorial Viewpoint Risk aversion stifles innovation Reading Dick Smith’s autobiography for the review (p37), I noticed several recurring themes. Two of them are “surround yourself with capable people” as a business strategy (good advice!) and the concept of “responsible risk-taking”. I have felt for a while that the latter is sorely missing from the Australian landscape, especially now; clearly, Dick feels the same way. He’s referring to the concept of being willing to take risks as long as you judge them to be reasonable, such as climbing a cliff or flying a helicopter through bad weather. For this to work, one has to be capable of assessing risk and taking personal responsibility for one’s own safety (what a quaint concept!). While I see over-the-top risk aversion all over our modern landscape, one area in which it is evident within Australia is in the fields of business, technology and innovation. Have you noticed how most multi-billion-dollar global juggernaut companies, especially those which are technology-based, are from the USA (or sometimes Europe)? Australia has plenty of fine minds, including scientists and engineers, so why can’t we create success stories like those? ‘Brain drain’ is part of the problem, with many Australians moving overseas to America (or other places) chasing better prospects (including me, briefly). A lot of it comes down to risk vs reward, including both ends of that equation. In terms of risk, American and European investors are more willing to bet their money by investing in up-and-coming technologies and concepts. Australians seem to view the stock market as a kind of bank account, especially now that we have enforced superannuation, and demand low risk (and get relatively low returns as a result). Many people turn up their noses at rich people, but it’s the drive to become one of them that has made so many people work hard to create the foundations of modern life. Dick Smith did this when he created Dick Smith Electronics (his ex-senior manager, the late Gary Johnston, did it again with Jaycar Electronics). Dick decided to ‘quit while he was ahead’, unlike many others in his position, but that’s beside the point; his desire for money and success drove him to create something valuable more than once. But younger generations (and this includes me) have mostly been raised in a cocoon, never being allowed to take many risks. I don’t think I’d have the guts to do what Dick or Gary did. I’m not sure I could have even created Silicon Chip from scratch like Leo Simpson and Greg Swain back in 1987, even though I seem to be able to keep the magazine going just fine. Unless we allow young people to use (and hone) their judgment responsibly and learn how to weigh up risks and rewards, I don’t see how we can compete on the global business and technology stage. And that can’t happen if we don’t allow people to use their judgment. Innovation and risk-taking are activities that often go hand-in-hand. How many realise that there is risk in the act of not taking any risks? You miss many opportunities when you’re laser-focused on the negatives and ignore the potential positives. We wouldn’t be where we are today if our ancestors were huddled in caves, scared to go out into the dangerous world. Some of them took journeys of thousands of kilometres in small canoes to settle far-off lands; they didn’t even know if, or when, they would see land again. Imagine having the fortitude to do that! And we’re pretty much all descended from those brave explorers. by Nicholas Vinen 24-26 Lilian Fowler Pl, Marrickville 2204 2 Silicon Chip Australia's electronics magazine siliconchip.com.au siliconchip.com.au Australia's electronics magazine January 2022  3 MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd had the right to edit, reproduce in electronic form, and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman’s Log”. What to do with historic electronic gear I have come across an old PMG test instrument in the family storeroom – the old Gracemere Station office. It is an AWA Type R667 Capacity Unbalance Measuring Set. A calibration note attached to the lid is dated 15/2/68, but the instrument might be older than that (see the images below). I have little idea what it was for; I presume for improving crosstalk in either open-wire lines or cables. I have not opened it, so I don’t know what is in it. It has a vernier dial reading Capacity in uuF/nF (I think – not very clear). It has a battery compartment – again, I have not opened it, but I suspect it has some active components – valves, I presume. It also has two mic earpiece headsets. I don’t have any idea how it came into the family. It is in Rockhampton but I live in Brisbane. It is secure where it is, but there may be a more appropriate place for it to live, such as a museum. Do you have any suggestions? Patrick Durack, Ashgrove, Qld. Comments: we aren’t sure what to do with this device but perhaps one of our readers has a suggestion. 4 Silicon Chip USB Cable Tester & SMD Test Tweezers What a challenge, especially with soldering the USB-C ports. I completed the USB Cable Tester (November & December 2021; siliconchip.com.au/ Series/374) without any soldering remediation or fault finding, and it will be useful on my hobby bench. My soldering skills and techniques were definitely tested and improved. This experience highlighted that traditional magnifiers now need to be supplemented with a digital scope for quality control, although my phone camera set to super macro assisted this time. The recent SMD Test Tweezers project (October 2021; siliconchip.com.au/ Article/15057) is also a great and useful project and was a fun build. Barry Hinz, Charleville, Qld. Farewell Geoff Nichols Those who followed ETI Magazine would have been familiar with Geoff as a staff member/Project designer. My good friend Geoff passed away on the 19th of October, aged 64, of pancreatic cancer. Craig Laybutt, North Ryde, NSW. Australia's electronics magazine Test Tweezers survived reverse polarity I am delighted to report that you can insert the battery the wrong way and it will still work after correcting that error! Horst Leykam, Dee Why, NSW. Comment: We believe that it’s possible for a new CR2032 cell to supply more current (100mA) than the maximum specified for the microcontroller’s clamp diodes (20mA). However, it may be that components in the OLED module are also shunting current. PICs are pretty robust and will generally withstand much higher currents than the maximum ratings if they are of limited duration. Beware of fake solar panel ratings I bought a solar panel from a toprated seller on eBay. The panel was rated at 200W, but after receiving it, I became suspicious that its rating was incorrect. I later realised that the panel was unusually cheap for 200W, a warning sign I should have paid more attention to. The panel measures 0.58m2 (820 x 710mm). This is smaller than is physically possible for a 200W panel. siliconchip.com.au Our capabilities CNC Machining UV Colour Printing Enclosure Customisation Cable Assembly *** Box Build *** System Assembly Ampec Technologies Pty Ltd Australia’s electronics magazine siliconchip.com.au Tel: (02) 8741 5000 Email: sales<at>ampec.com.au Web: www.ampec.com.au FEBRUARY 2021 37 Helping to put you in Control ESP32 Controller Arduino-compatible ESP32 controller with 2 relay outputs, 2 transistor outputs, 2 opto-isolated inputs, 2 0/4-20 mA analog I/ Os, 2 0-10 VDC analog I/Os and 4 GPIOs. Interfaces using USB, RS-485 serial, I2C, Wi-Fi or Bluetooth. DIN rail mountable. SKU: KTA-332 Price: $251.90 ea CS Series Closed-Loop Stepper Driver Closed-loop stepper motor driver with encoder feedback input and encoder A/B/Z outputs. Operating at 20-50VDC, max 7A output current. Suits 2 phase CS Series Closed Loop Stepper Motors. SKU: SMC-162 Price: $215.60 ea Low transformer output mystery solved Ethernet Closed Loop Stepper Driver CS3E-D507 is a new Ethercat closed-loop stepper motor driver with encoder feedback input, operating at 20-50 VDC. Suits 2 phase stepper motors up to 7.0 A. Has digital inputs and outputs for control such as limit switch and brake. SKU: SMC-171 Price: $439.95 ea CS Series Closed-Loop Stepper Motor 3.0 N·m, 2 Phase NEMA 24 closed loop stepper motor with 1,000 line encoder for feedback. Rated at 5.0 A phase current, Nema 17 to 34 sized motors available and 8.0 mm shaft diameter. SKU: MOT-162 Price: $202.29 ea Liquid Level Sensor Detector A budget priced level sensor for detecting high and low levels of water in plastic and glass vessels or tanks. SKU: HEI-140 Price: $19.20 ea LogBox Connect WiFi LogBox Wi-Fi is an IoT device with integrated data logger and Wi-Fi connectivity. It has three universal analog inputs one digital input and an alarm output. SKU: NOD-012 Price: $604.95 ea N322-RHT Temperature and RH Controller 230 VAC Panel mount temperature & relative humidity controller with sensor probe on 3 metres of cable. 2 independent relay outputs. 100 to 230 VAC powered. SKU: CET-109 Price: $290.35 ea For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. 6 Silicon Chip A general figure for solar irradiance at the surface in Australia is 1100W/m2. The quoted panel efficiency was 17%, which seems reasonable. We can therefore calculate 0.58m2 × 1100W/m2 × 17% = 108W. Allowing for empty space, this is probably a 100W panel being incorrectly sold as a 200W panel. I also made some electrical measurements. The short-circuit current is 5.84A in peak sunlight. According to the label on the panel, peak power is at 18V. This means that the panel can generate no more than 105W. The open-circuit voltage measured 21.7V. The sticker on the panel does not show the power rating or short-circuit current, which is most unusual. The situation was somewhat resolved by the seller refunding half the purchase cost after I presented these facts. The panel was worth keeping as it seemed to be of good quality for a no-name panel. But many purchasers of solar panels would not be aware they are getting much less than they paid for. I wonder how common such fraud is. Dr David Maddison, Toorak, Vic. I read the Vintage Radio article in the November 2021 issue of Silicon Chip by Graham Parslow with great interest (siliconchip.com.au/Article/15107). Graham writes in a relaxed yet informative style, easy to read and with plenty of detailed photos. I always enjoy his articles. Graham describes the restoration of a Stromberg-­ Carlson model 496 autodyne superhet receiver from 1936. The cabinet looks stunning and the knobs look the part too. It’s a real shame the electrodynamic speaker was unable to be repaired; a reality faced by restorers from time to time. Graham mentioned the problem experienced with the 6.3V heater voltage winding running at 4.9V. This could be explained by the 6V6 heater being connected to the 6.3V winding. For example, the 6C6 and 6F7 each draw 0.3A heater current and the two dial lamps draw 0.3A each, for a total specified loading of 1.2A for the 6.3V winding. Adding the 0.45A heater current required by the 6V6 modification takes the total load on the 6.3V winding to 1.65A, an increase of 37% above the power transformer’s 1.2A load specification. This could explain why the 6.3V winding voltage has dropped to 4.9V. Graham mentioned that this particular radio was manufactured before the 6V6 became available, so I presume it was manufactured with an AL3 output valve, per the circuit. Graham stated he received the radio with the 6V6 fitted. To improve the originality of the radio, the retrofitted 6V6 and socket could be removed and replaced with an AL3 and suitable socket. This would require the AL3 heater to be wired to the 4V winding, which would also remove the additional loading on the 6.3V winding. That should allow the 6.3V winding voltage to return closer to the specified 6.3V figure, overcoming the low heater voltage problem Graham reported, as well as increasing the originality of this very nicely restored radio. Graeme Dennes, Bunyip, Vic. Graham Parslow responds: I took some measurements of the 6.3V winding with Australia's electronics magazine siliconchip.com.au POWER SUPPLIES PTY LTD ELECTRONICS SPECIALISTS TO DEFENCE AVIATION MINING MEDICAL RAIL INDUSTRIAL Our Core Ser vices: Electronic DLM Workshop Repair NATA ISO17025 Calibration 37 Years Repair Specialisation Power Supply Repair to 50KVA Convenient Local Support SWITCHMODE POWER SUPPLIES Pty Ltd ABN 54 003 958 030 Unit 1 /37 Leighton Place Hornsby NSW 2077 (PO Box 606 Hornsby NSW 1630) Tel: 02 9476 0300 Email: service<at>switchmode.com.au Website: www.switchmode.com.au 8 Silicon Chip various loads after receiving the suggestion from Graeme Dennes. Graeme was correct in his analysis; the winding cannot cope with the load imposed on it with the 6V6 added. I did not consider this initially because most comparable 6.3V windings can handle multiple amps. In hindsight, looking at the gauge of the winding, it is thinner wire than usual (this was not immediately evident due to being sheathed in spaghetti tubing). I measured a 5.7V output when loaded with just the two 0.3A dial lamps; the low voltage is no longer a puzzle. What is padder feedback, really? In researching radio designs, I have often come across the term “padder feedback”. There are plenty of references that explain its purpose (to improve local oscillator activity and reliability), but I have not found any good explanations of its principle of operation. It looks like the classic Armstrong oscillator, which puts a feedback transformer between anode and grid. The classic circuit sees one end of each winding (anode and grid) return to RF ground: the anode winding to decoupled HT, the oscillator winding to circuit ground. The only common variant returns the secondary to ground via the padder. Since this puts the padder in series with the inductor, its effect is identical to grounding the secondary and connecting the padder between the secondary’s ‘hot’ end and the oscillator tuning gang section. This has the advantage of returning one end of the padder to ground, minimising ‘hand effect’ during alignment. But the padder feedback circuit sees the two cold ends joined (either directly or via a capacitor; C14 in the Astor Mickey Oz circuit, see page 80 of this issue for example) and returned to ground via padder capacitor C12. Whatever this forms, it is not a true Armstrong oscillator. Is it some kind of Hartley oscillator (two inductors, L5 & L6, with mutual coupling), a modified Colpitts (padder C12 and tuning capacitor C10 with a single inductor L5), or a pi-filter resonant circuit (padder C12, inductor L5 and capacitor C10), as used in permeability-tuned radios (essentially a Colpitts oscillator)? If it is a Colpitts oscillator, why bother with the transformer primary? I trust that someone is less confused than I am! Rather than clog the Editor’s inbox, readers who can explain its principle/s of operation might reply to me at the email below. Ian Batty, Rosebud, Vic. – ianbatty311<at>gmail.com Hydrogen as a storage medium for renewals As usual, the July, August, and now the September issues have been worth reading. I was intrigued to see that you published one of my earlier letters in the September edition. Unfortunately, I have not progressed very far with the Li-ion battery charging project or any other projects. It seems that there is almost a limit on how much a person can do. It has been almost 40 years since I began experimenting and creating electronic and mechanical devices plus PC and embedded programs. I have devised many hundreds of circuits, plenty of mechanical devices, and many hundreds of programs during that time. It seems that the effort has caught up with me. Australia's electronics magazine siliconchip.com.au Design Contest Win $500+ Dick Smith challenges you Win $500 by designing a noughts-and-crosses machine that can beat 14-year old me! Dick Smith has described in his new autobiography how one of the turning points in his life, at age 14, was successfully building a ‘noughts-and-crosses machine’ (also known as tic-tac-toe) that could play the game as well as anyone. Keep in mind that this was in 1958, when nobody had computers; it was a purely electromechanical device. Email Design to Enter Design your own noughts-andcrosses circuit and send your submission to compo<at>siliconchip. com.au including: a) Your name and address b) Phone number or email address (ideally both) c) A circuit or wiring diagram which clearly shows how the device works d) The display can be anything as long as it’s understandable e) Evidence that your device can always play a perfect game (it never loses) f) A video and/or supply images and text describing it g) Entries requiring software must include source code The deadline for submissions is the 31st of January 2022. ➠ ➠ Win $500 + Signed Copy of Dick Smith's Autobiography ➠ Four winners to be decided, one each for the following categories: ➊ The simplest noughts-andcrosses playing machine most ingenious noughts➋ The and-crosses playing machine youngest constructor to ➌ The build a working noughts-and- DICK SMITH crosses playing machine most clever noughts-and➍ The crosses playing machine not using any kind of integrated processor The entry we judge overall to be the best will also be featured in our Circuit Notebook column and receive an additional $200. ‘Part Bear Grylls, part Bill Gates, but Dick is a great innovator, philanth 100% Aussie larrikin. ropist and adventurer, who in my eyes can do no wrong.’ PAUL HOGAN Conditions of entry Dick Smith writes 1) You must be a resident of Australia or New Zealand 2) One entry per family (Silicon Chip staff and their families are not eligible) 3) Submissions will be confirmed within 7 days. If you do not receive a confirmation of your submission, contact us to verify that we have received it 4) Chance plays no part in determining the winner 5) The judges’ decision is final 6) The winners will be decided by the 3rd of February 2022 and will be notified immediately By 1958 I’d advanced from building crystal radio sets to designing and building what I called a noughts and crosses machine. It really was an early computer. I used second-hand parts from a telephone exchange to build it. It would play noughts and crosses against anyone and no one could beat it. This was a great boost to me, because while I was no good at rote learning and theory, I was fine at practical things. The fact that my mind was capable of working out how to build this complex machine gave me confidence as I left school. Now I just had to find a job. Because this was such a turning point in his life and he’s so enthusiastic about youngsters learning electronics, he’s putting up $2000 of his own money to award to people who can come up with a modern version of his noughts-and-crosses machine. Silicon Chip will judge the entries. Winners will be announced in the March 2022 issue of Silicon Chip magazine and will also be contacted directly for payment information. siliconchip.com.au Australia's electronics magazine January 2022  9 I used to wonder why authors of novels would need to take substantial rest after writing a novel. Now I know. Currently, I am finding it hard to do anything involving electronics and/or robotics. Instead, I have been catching up on home maintenance and seriously overdue home projects. Hopefully, in the near future, my electronics drive will return. On another topic, there is a problem with the storage of solar energy using batteries of any type, and that problem occurs when the batteries are fully charged. There is almost certainly more energy available but it cannot be stored. However, immediate conversion of solar energy into hydrogen avoids this problem. Storage tanks are far cheaper than electrochemical cells. They do not suffer significantly from cycling, nor do they suffer from over-discharge. More storage is simply changing to a bigger tank or adding more tanks. Currently, both electricity-to-hydrogen and hydrogen-­ to-electricity converters are available off the shelf. Storage tanks almost certainly would be available as well; if the high leakage of steel can be tolerated, steel tanks are readily available. The main reason for bringing this subject to your attention is that solar energy storage via hydrogen is at the stage where it is feasible for hobbyists to make their own systems. Of course, there are safety concerns, and I have no doubt that our governments’ health and safety departments will react in their usual “it’s dangerous” manner. But hydrogen is far safer than LPG with the ability of hydrogen to rapidly disperse upwards and not lay around the lower levels of a house. It is unnecessary to store hydrogen at very high pressures, and a physically large tank is not a problem like it is for vehicles. An external installation in a well-ventilated enclosure should be far safer than any current fuel storage schemes, except perhaps fuel oil, coal, coke and wood. George Ramsay, Holland Park, Qld. Comments: Most city dwellers, even those with a house, might disagree about your statement that the size of a hydrogen storage tank is not a concern. Also, safety concerns aside, the round-trip energy efficiency is not likely to be that great. Regarding motivation, try working for an electronics magazine where you have to come up with and complete four or so project articles per month. Somehow we’re not only still coming up with new ideas (admittedly, in many cases, improved versions of previous ideas), but we’re turning them into working prototypes and documenting them after all these years. Article on electric vehicle charging I recently sent you an email relating to the logistics of charging multiple electric vehicles (EVs) in a suburban front yard. I don’t know whether this topic piqued your interest, but here is a link to an ABC article that relates to EV charging and the future of service stations: www. abc.net.au/news/100627312 The broader issue becomes providing the appropriate domestic and public infrastructure to support an EV based transport sector. David George, Montmorency, Vic. SC 10 Silicon Chip Australia's electronics magazine siliconchip.com.au Subscribe to DECEMBER 2021 ISSN 1030-2662 12 The VERY BEST DIY Projects! SMD 9 771030 266001 $ 50* NZ $1290 11 INC GST INC GST Trainer and how to solder surfac e-mount parts The small but powerfu l Hummingbird Amplifier Australia’s top electronics magazine Silicon Chip is one of the best DIY electronics magazines in the world. Each month is filled with a variety of projects that you can build yourself, along with features on a wide range of topics from in-depth electronics articles to general tech overviews. Hands-on with the Raspberry Pi Pico The smallest Raspberry Pi yet! Published in Silicon Chip If you have an active subscription you receive 10% OFF orders from our Online Shop (siliconchip.com.au/Shop/)* Rest of World New Zealand Australia * does not include the cost of postage Length Print Combined Online 6 months $65 $75 $50 1 year $120 $140 $95 2 years $230 $265 $185 6 months $80 $90 1 year $145 $165 2 years $275 $310 6 months $100 $110 1 year $195 $215 2 years $380 $415 All prices are in Australian dollars (AUD). Combined subscriptions include both the printed magazine and online access. Try our Online Subscription – now with PDF downloads! Big Brother is Tracking You; November 2021 USB Cable Tester; November 2021 Hummingbird Amp; December 2021 Raspberry Pi Pico; December 2021 An online issue is perfect for those who don’t want too much clutter around the house and is the same price worldwide. Issues can be viewed online, or downloaded as a PDF. To start your subscription go to siliconchip.com.au/Shop/Subscribe A ll A bout Part 1: by Dr David Maddison batteries Batteries Imagine life without batteries. We’d have to crank-start our cars; we’d be stuck with fixed phones, non-portable computers, no interactive toys for kids... the list goes on. But you can’t take batteries for granted either. This series will cover just about Background Source: everything you need to know about batteries. https://unsplash.com/photos/F_EooJ3-uTs B atteries are one of our most important technologies. Today, nearly everyone carries a smartphone, and its rechargeable battery is expected to last all day (or sometimes two or three), even with several hours of active use. Many people also have an electronic watch, an electronic key for their car and possibly even electronic implants like a heart pacemaker. Little thought is given to such devices until the battery inevitably fails. Two other important uses for largescale batteries today are electric cars and storage for intermittent electricity production. In this article, we will look at the history of batteries, how they work, some interesting or common types and possible future developments. We will also look in detail at how some of the more common battery types from the past work. Two following articles will have more details on lead-acid batteries and other battery types, information 12 Silicon Chip on vehicle batteries, battery monitoring and miscellaneous extra facts about batteries. in this article. Still, we prefer “cell” when referring to one cell or “battery” for multiple. Terminology The perfect battery Any discussion of batteries has to distinguish between electrochemical cells and batteries. A cell is the basic unit of a battery and uses a chemical reaction to produce electrical energy. A battery is a collection of multiple cells connected together, usually in series, to produce a higher voltage than an individual cell – see Fig.1. Cells can also be paralleled to increase the maximum charge/discharge current and sometimes are connected in series/parallel to form a high-voltage, high-current pack. A typical example of a cell is a standard AA-size alkaline 1.5V cell, often erroneously referred to as a “battery”. The 9V batteries used to power smoke alarms are actual batteries, usually having six internal 1.5V cells in series. Given that it is common terminology, we might use the term battery for cell A perfect battery might have the following characteristics: • be made from inexpensive, non-exotic materials using simple manufacturing processes • be non-toxic when disposed of • be recyclable • be rechargeable a large number of times • provide a useful voltage, not too high or low • work consistently over a wide range of temperatures, including polar or desert regions as well as at room temperature • provide a long life • be fast to recharge • be tolerant of high discharge currents • can be fully discharged safely and repeatedly • have low weight Australia's electronics magazine siliconchip.com.au • be compact for its capacity • survive a large number of charge and discharge cycles • have low self-discharge in storage • will not leak • have a relatively stable voltage during discharge (ie, a small difference between fully charged and fully discharged voltages) • will not catch fire or explode even if misused or badly damaged Of course, there is no perfect battery. Like all engineering solutions, every battery type has advantages and disadvantages and will meet some of the above criteria, but never all (yet!). How does a battery work? A battery (more precisely a galvanic or voltaic cell) is a device that stores energy in chemical form and converts it to electricity via a chemical reaction. There are usually two interfaces to conductors (ie, anode and cathode), and a current flow is created due to the motion of electrons. This is known as an electrochemical or redox reaction. Two reactions are involved; one is called oxidation, the other is called reduction and there is an external electron flow. This is different from ordinary chemical reactions, in which electrons are also exchanged between atoms or ions but in a bulk volume, with no electrodes. In that case, there is no net flow of electrons or current. A discharging battery works spontaneously, ie, nothing is required to start the reaction. The chemical process is known as a spontaneous redox reaction. Not all electrochemical reactions are spontaneous, so not all can be used for a battery. When the battery is discharging, the positive terminal is called the cathode and the negative terminal the anode. The negative terminal is the source of electrons that flow through an attached electrical circuit to the positive terminal (see Fig.2). During oxidation, a chemical species loses one or more electrons, while in reduction, the chemical species gains one or more electrons. In a discharging galvanic cell, oxidation occurs at the anode. That is, electrons are lost, and this is the source of the electrons for the negative terminal. During discharge, reduction also occurs at the cathode. That is, electrons are gained, and the cathode is the positive terminal (www.ausetute. com.au/pbbattery.html). siliconchip.com.au Fig.1: a cell (above) is a single electrochemical cell, generating something like 1-4V via a chemical reaction between the anode and cathode. A battery (right) consists of two or more cells, usually connected in series (but sometimes in parallel or series/parallel), generating a multiple of the cell voltage. Fig.2 (below): the electrode designations, current flow and electron flow of a secondary cell during discharging and charging. Electrons are labelled as “e−”. Original source: Wikimedia user Electroche (CC BY-SA 4.0) An alternative way to state the above is that oxidation involves the loss of electrons and always occurs at the anode, while reduction involves the gain of electrons and always occurs at the cathode. The polarity of the anode and cathode (+ or −) is determined by which way electrons flow or current flows during charging and discharging. Main battery categories Batteries are classified as either primary or secondary types. A primary battery can be used once until it is exhausted and is not designed to be recharged. The chemical reactions are not generally easily reversible. AA or AAA ‘alkaline’ cells are a typical example. Note, though, that limited recharging might be possible, even if not generally Australia's electronics magazine recommended. We will discuss that later. A secondary battery is designed to be recharged multiple times; its chemical actions are reversible by applying a reverse current to recharge the battery. An automotive lead-acid battery is a typical example. Secondary batteries eventually wear out and have to be disposed of, recycled or remanufactured because the internal electrodes corrode or the structure of the cell deteriorates. Another less-common type of battery is the reserve battery. These are used in equipment that is stored for a long time and then has to be suddenly activated and used, such as certain types of military equipment like missiles. One way to activate such a battery is to add the electrolyte just before January 2022  13 Fig.3: the Baghdad Battery with a disputed interpretation assuming it was a battery. The ceramic pot is 14cm tall and has an asphalt plug at the top, a copper cylinder with an iron rod inside it immersed in ‘electrolyte’. Source: Wikimedia user Elmar Samizadə (CC BY-SA 4.0) Fig.4: an early “battery” of Leyden jars. Today we would call this a capacitor bank, not a battery. Benjamin Franklin pioneered this method and is believed to have owned this example. Source: American Philosophical Society use. Sometimes, car batteries are sold like this as well (dry). The Baghdad Battery An ancient artefact called the Baghdad Battery dates to somewhere between 150BCE to 650CE (Fig.3). Some interpreted it to be an ancient battery (more correctly a cell), but there is also evidence to suggest that it wasn’t. A copy of this artefact can be made into a workable cell. The TV show “Mythbusters” looked at this in Episode 29, first broadcast on the 23rd of March 2005. They were able to make a replica Baghdad Battery produce voltage, but only a fraction of a volt; they got more voltage by sticking metal fragments into fresh lemons. Fig.5: Jesse Ramsden’s frictional plate electrostatic machine of 1768. It was not a battery but it could produce an electrical charge. Leyden jars (as shown in Fig.4) were used as charge storage devices. Source: gutenberg. org/files/35092/35092-h/35092-h.htm 14 Silicon Chip It could have been something other than a battery. Still, it happens that the presence of an acidic solution such as vinegar enables a current to be generated due to the presence of dissimilar metals. This object disappeared during the looting of the Iraq Museum in April 2003 and has not been seen since. Origin of the term “battery” Benjamin Franklin first used the term battery, akin to an artillery battery, in 1749 to describe how he had linked up Leyden jars, an early form of capacitor, to store electricity from his static generator (see Fig.4). The first battery in Australia Sir Joseph Banks performed electrical experiments onboard the HMS Endeavour, the vessel Captain James Cook used to explore and claim Australia. Two electrical machines were carried. One was made by Jesse Ramsden (Fig.5), a famous instrument maker, and the other was a machine belonging to astronomer Charles Green and made by Francis Watkins. Banks and some other gentlemen amused themselves by giving each other shocks. Both machines appear to be frictional plate electrostatic generators. The charge from each was stored in an ‘electrostatic battery’ (basically a capacitor bank), in what were presumably Leyden jars (see Fig.6). However, they were not described by Banks by that name. Banks noted “the ill success of the Fig.6: a drawing of a Leyden jar being charged, in 1746. The jar was independently invented by German Ewald Georg von Kleist in 1745 and Dutchman Pieter van Musschenbroek of Leiden (Leyden) in 1745-46. Portrayed in the drawing is a similar experiment to the one performed by Banks, although the electrostatic generator uses a rotating glass sphere instead of the disc. The electrical charge produced is stored in the Leyden jar. Australia's electronics magazine siliconchip.com.au Electrical experiments”, possibly due to excessive humidity or moisture. For those interested, an account of Sir Joseph Banks’ electrical experiments onboard the Endeavour can be seen in “The Endeavour Journal of Joseph Banks” at https://setis.library. usyd.edu.au/ozlit/banks/banksvo1. pdf (Fig.7). See pages 81 to 93 of the PDF document (not the diary page numbers). Electrical experiments were performed on the 25th of October 1768 (two months after leaving Plymouth, England) and then again on the 19th of March and the 23rd of March 1770. Cook was still charting New Zealand on the March date and did not leave New Zealand for Australia until the 31st of March 1770, so the second battery experiment was performed in New Zealand waters. However, the equipment was brought to Australia, so it can be argued that it was the first battery in Australia. Cook landed in Botany Bay on the 29th of April 1770. Thanks to S. M. of the State Library of NSW for their assistance in finding some of the source documents on this topic. If you want to perform an experiment similar to what Banks would have, or see the type of spark that might have been generated (but using modern materials), see the video titled “William Gurstelle shows How to Build an Electrostatic Generator and a Leyden Jar” at https://youtu.be/ H5wr1Ishmx0 Fig.7: the cover of the 1747 book by Francis Watkins on his electrical experiments. He made one of the machines brought by Banks to Australia. You can read this book online at https://books.google.com.au/ books?id=AzRWAAAAcAAJ Fig.8: one of Volta’s original voltaic piles, on display at the Tempio Voltiano in Como, Italy; see siliconchip.com.au/link/abbp – Source: Wikimedia user GuidoB (CC BY-SA 3.0) The first true battery Alessandro Giuseppe Antonio Anastasio Volta invented the first electrochemical battery in 1799, publishing the results in 1800. This is a true battery in terms of our modern definition of it being an electrochemical device, not a capacitive charge storage device like a Leyden jar. Volta’s original battery or voltaic pile (shown in Figs.8 & 9) comprised a column of alternating copper and zinc discs separated by cloth or cardboard soaked in a brine (saltwater) electrolyte. Volta initially misunderstood how the battery worked. He thought the electricity was generated by the contact between dissimilar materials. Later, it became apparent that the corrosion of the zinc discs was related to the current produced by the battery. Thus, he realised that the battery siliconchip.com.au Fig.9: this shows how Volta’s voltaic pile was constructed. Original source: Wikimedia user Borbrav, SVG version by Luigi Chiesa (CC BY-SA 3.0) Fig.10: a cross-section diagram of the original Daniell cell. Original source: Armando-Martin, public domain worked by an electrochemical process. Even though the original batteries produced by Volta were flawed and only worked for about one hour, they enabled many new discoveries to be made. We will now discuss some of the more important types of primary batteries, both historical and in current use. We will look into some of these in more detail and other types of batteries in the following article next month. Batteries after Volta Primary batteries Early batteries, including Volta’s, were primary (non-rechargeable) batteries. Secondary (rechargeable) batteries were developed later. In 1836, John Frederic Daniell solved some of the problems with Volta’s battery with the Daniell cell. This was a copper pot containing copper Australia's electronics magazine January 2022  15 Fig.11 (left): the construction of a gravity cell. This particular variant is called the crowfoot cell due to the shape of the negative terminal. Original Source: Cyclopedia of Telegraphy and Telephony, 1919 Fig.12 (above): the cross-section of a zinc-carbon battery with ammonium chloride electrolyte. Original source: Wikimedia user Mcy jerry (CC BY 2.5) sulfate into which was immersed a porous earthenware vessel containing sulfuric acid and a zinc electrode (see Fig.10). Ions could pass through the earthenware vessel, but the solutions could not mix. It produced 1.1V and became the first practical cell. It was widely used in the new telegraph networks. There followed several improvements to the Daniell cell such as Bird’s cell (1837) by Golding Bird, the Porous pot cell (1838) by John Dancer and in the 1860s, the gravity cell by mysterious Frenchman Monsieur Callaud, whose first name is unknown. The gravity cell dispensed with the porous barriers used on Bird’s and Dancer’s cells, thus giving it a lower internal resistance and improved current delivery capability. In the gravity cell, the different electrolytes (zinc sulfate and copper sulfate) are not separated by a barrier but by gravity due to the different densities of the two electrolytes (see Fig.11). This gravity separation also renders the cell unsuitable for mobile applications. Also, a current must be continuously drawn from the cell; otherwise, the electrolytes will mix. The gravity cell became standard on the US and UK telegraph networks and was in use until the 1950s. Chromic acid cells were another type of primary cell developed; one was the Poggendorff cell. It used zinc and carbon plates, but the zinc would 16 Silicon Chip dissolve even when the cell was not in use, so a mechanism was needed to lift the zinc out of the electrolyte when the cell was not in use (see Fig.14). A further development of the Poggendorff cell was the Fuller cell (Fig.15). It used mercury to form an amalgam with zinc to prevent its dissolution. Later came the Grove cell (1839) comprising zinc, sulfuric acid, platinum and nitric acid and the Dun cell (1885) comprising iron, carbon and a mixture of hydrochloric and nitric acids. This mixture is known as aqua regia; it is a very powerful acid that can dissolve gold or platinum. The Leclanché cell was invented in 1866 by Georges Leclanché. It consisted of a zinc anode, manganese dioxide and carbon cathode and ammonium chloride as the electrolyte (Fig.16). It produced 1.4V. It was used in telegraphy, telephony, rail signalling and electric bells. One disadvantage was that the battery current would diminish during long telephone conversations due to increasing internal resistance. In 1886, a variant of the Leclanché cell was produced by Carl Gassner in which he mixed the liquid ammonium chloride electrolyte along with zinc chloride (to extend the shelf life of the electrolyte) with plaster of Paris to make a ‘dry cell’ producing 1.5V. In 1896, the National Carbon Company in the USA developed it further, replacing the plaster with rolled cardboard. The battery could be used in any orientation and was maintenance-­ free. The first battery they made was a telephone battery (see Fig.13), and in 1898, the company introduced what later became known as the D-cell or ‘flashlight (torch) battery’. These became known as zinc-carbon cells and were the first mass-produced battery for widespread use, leading to the development of the battery flashlight (torch). This type of cell is still common and available today. Fig.16: a Leclanché cell. This example is a Samson No.2 brand ammonium chloride, zinc and manganese dioxide/carbon battery, c.1906-1916. Such a battery is also featured in the 25th catalogue of Manhattan Electrical Supply Co. c.1910. The complete battery sold for US$1.60 and all parts were replaceable. Source: Harvard University, The Collection of Historical Scientific Instruments Australia's electronics magazine siliconchip.com.au Fig.13: Columbia Gray Label dry cell telephone batteries of the type first produced by the National Carbon Company. It isn’t known when these were made, but they bear the Eveready trademark, so they must have been made after 1917 when Union Carbide acquired Eveready. This type of battery was produced until at least the 1950s. Source: www.flickr.com/ photos/51764518<at>N02/36670011780 (Creative Commons) In parallel with these developments, in 1887, another dry battery based on the Leclanché cell was developed independently by Dane Wilhelm Hellesen. Sakizou Yai of Japan also developed a dry cell in 1887 (said to involve carbon and paraffin), which were used with great success in the Sino-­Japanese war of 1894-95, earning him the title “king of the dry battery”. He established a battery factory in 1910. Improvements were made to the zinc-carbon cell over the twentieth century, including about a fourfold capacity increase. Other improvements were a longer shelf life, better sealing and the use of less toxic components, such as the elimination of mercury. Standard zinc-carbon batteries use Fig.14: the Poggendorff cell, described as a “Student’s Plunge Cell”. Source: 25th catalogue of Manhattan Electrical Supply Co. c.1910, page 176 Fig.15: the Fuller cell, both regular and high-current versions. Source: 25th catalogue of Manhattan Electrical Supply Co. c.1910, page 173 an ammonium chloride electrolyte with possibly some zinc chloride. “Heavy-duty” cells use mostly zinc chloride as the electrolyte. A heavyduty battery has about twice the capacity of a standard battery. However, zinc-carbon cells have been mostly replaced these days by the alkaline variety, which have about eight times the capacity (see below). zinc reacts to produce two electrons and is consumed during discharge. The electrons flow through the external load to the cathode, where the manganese dioxide reacts with either ammonium chloride or zinc chloride (or both). The reaction for batteries with an ammonium chloride electrolyte is: Chemistry of zinc-carbon cells A zinc-carbon cell comprises a zinc ‘can’, which constitutes the negative terminal or anode of the cell and a carbon rod with manganese dioxide, which is the positive terminal of the battery or cathode – see Fig.12. The electrolyte is either ammonium chloride or zinc chloride (or a mixture). Regardless of the electrolyte, the Zn + 2MnO2 + 2NH4Cl ⇌ Mn2O3 + Zn(NH3)2Cl2 + H2O The reaction for batteries with a zinc chloride electrolyte is: Zn + 2MnO2 + ZnCl2 + 2H2O ⇌ 2MnO(OH) + 2Zn(OH)Cl This type of battery is widely available in the AAA, AA, C, D and PP3 (9V) size formats – see Fig.17. These batteries have a typical voltage when Fig.17: a selection of modern disposable consumer batteries. L to R, top to bottom they are: 4.5V (3LR12) battery (primarily used in Europe), D, C, AA, AAA, AAAA, A23, 9V, LR44 and CR2032. There are many proprietary designations for battery sizes; the ANSI and the IEC establish standard names. Source: Wikimedia user Lead holder (CC BY-SA 3.0) siliconchip.com.au Australia's electronics magazine January 2022  17 Collecting old batteries Believe it or not, some people collect old batteries. For some good examples, visit www.ericwrobbel. com/collections/batteries.htm new of 1.55V to 1.7V and are considered flat when they reach around 0.8V under load. Alkaline cells In alkaline cells, the acidic ammonium chloride or zinc chloride electrolyte of regular zinc-carbon batteries is replaced with zinc powder in an alkaline potassium hydroxide gel. A current pickup spike forms the negative electrode (anode). The carbon electrode is replaced with manganese dioxide with carbon powder to make the positive electrode (cathode) – see Fig.18. A patent for the modern alkaline cell based on zinc-manganese dioxide was filed by Canadian Lewis Urry in 1957, awarded in 1960. Most of the energy of these cells is contained within the zinc electrode. The nominal voltage is 1.5V. They are direct substitutes for carbon-zinc batteries in common appliances and come in the standard sizes of AAA, AA, C, D etc. The reaction for alkaline zinc-­ manganese dioxide cells is as follows: Zn(s) + 2MnO2(s) ⇌ ZnO(s) + Mn2O3(s) Standard alkaline batteries are said to be rechargeable a few times, with reduced capacity and some risk of leakage. This practice is not recommended by manufacturers, although you can find chargers designed for this purpose, such as the ReZAP charger (https://rezap.com/) from an Australian company. It also supports various other battery chemistries. Some alkaline cells (known as RAM or rechargeable alkaline manganese) have been designed to have limited rechargeability, up to about 10 times. They are primarily suitable for lowdrain devices. These days, they might not be cost-effective due to the low cost of low-self-discharge NiMH cells, which are rechargeable hundreds of times. acid electrolyte. The original design was improved in 1881 by Camille Alphonse Faure, who replaced the cathode with a lead grid into which lead dioxide was pressed, allowing multiple plates to be stacked together. This basic design is still in use. The lead-acid battery is heavy and bulky but is relatively cheap and can produce a very high current for a short period, making it ideal as a car starting battery. It is one of the most recycled of all products, as virtually all parts are highly recyclable. We will discuss lead-acid batteries more, including describing different versions like gel cells and AGM batteries, in the article to follow next month. Secondary (rechargeable) batteries Nickel-cadmium cells Primary batteries have the obvious disadvantage that they must be replaced (or in early types of primary batteries, various components had to be replaced) once they are depleted. Replacing them with rechargeable batteries would, in the long term, reduce both cost and waste products. Lead-acid batteries The first rechargeable battery was invented in 1859 by Gaston Planté, based on lead-acid chemistry. This is still popular today, used in car starting batteries, backup power systems, emergency lighting, UPSs, off-grid systems, caravans, boats and more. These comprise a lead anode and lead dioxide cathode with a sulfuric The NiCd, nicad or nickel-cadmium cell was invented in 1899 by Waldemar Jungner in Sweden. It was a wet cell using an alkaline electrolyte of potassium hydroxide and was commercialised in 1910, being introduced in the USA in 1946. It was originally a competitor to lead-acid batteries. Later models were made as sealed dry cells and were available in the same form factors as zinc-carbon cells such as AA, C, D etc. The terminal voltage is 1.2V, which remains relatively constant during discharge. They are capable of high discharge rates. Nicad batteries are also robust and tolerant of deep discharge and can even be stored in a fully discharged state. They have a longer life than lead-acid in terms of lifetime charge and discharge cycles. Fig.18: a cross-sectional diagram of an alkaline cell, the most common type of primary cell used today. Original source: Wikimedia user electrical4u (CC BY 3.0) Fig.19: a nickel-hydrogen storage battery for space applications. This model (21HB-7) is from Russia. It weighs 5kg, has a capacity of 7Ah, a working pressure of up to 6.2MPa (900psi) and a service life of five years or 25000 cycles at an operating voltage between 21V and 325V. Source: https://ueip.org/ 18 Silicon Chip Australia's electronics magazine siliconchip.com.au A common myth surrounding nicad cells is that they suffer a “memory effect” where a battery will “remember” an incomplete discharge followed by a charge and suffer a voltage drop when the battery is again discharged to the point of the incomplete discharge. The authors of the original paper that claimed this retracted it. Nicads were once common in mobile phones, power tools and other portable devices but were supplanted by NiMH types (described below), which themselves have been superseded by lithium-ion cells. Their use has been decreased dramatically, partly due to the disposal problems of toxic cadmium and their higher cost compared to NiMH cells. Nickel-hydrogen batteries The nickel-hydrogen battery was first patented in 1971 and is a specialised battery primarily suitable for spacecraft such as the Hubble Space Telescope. They are now being considered for stationary storage applications. They can be regarded as a hybrid battery, with elements of both an electrochemical cell and a fuel cell. They operate at high pressures within a vessel, and use nickel as the positive electrode and a hydrogen fuel cell as the negative electrode – see Fig.19. They contain nickel, hydrogen in gaseous form at a pressure of up to 8.2MPa (1200psi) and potassium hydroxide as electrolyte. They have an energy density of about one-third that of a lithium battery; their main advantage is long service life. They also have a relatively high self-discharge rate, but this is not a great concern in space, where the battery is regularly recharged in orbit as the solar cells exit the earth shadow. As the battery discharges, the hydrogen pressure drops. A single cell has an open-circuit voltage of 1.55V. The NiH2 batteries on the Hubble Telescope were replaced after 18 years, although they were still working with only some loss of capacity. They were designed to last just five years. Nickel-metal-hydride cells Nickel-metal-hydride cells (NiMH) are now a common rechargeable type, replacing nicad cells in consumer items. They are available in standard sizes such as AAA, AA, C, D etc. They are similar to nicads, using a positive siliconchip.com.au Fig.20: the structure of a NiMH cell. The electrodes are rolled up in what is known as a “jelly roll” construction, common in many rechargeable cells such as 18650s. Source: Radio Shack nickel electrode, but instead of cadmium for the negative electrode, they use a hydrogen-absorbing metal (see Fig.20). They have two to three times the energy density of nicad, but still lower than lithium-ion, and are relatively non-toxic. Their nominal voltage is 1.2V, and they can typically replace alkaline cells. They were invented in 1967 but weren’t released onto the consumer market until 1989. The first commercial NiMH batteries had a significant self-discharge rate of 0.5-4% per day, but in 2005, Sanyo developed a low-self-discharge battery under the Eneloop brand that had a capacity of 70-85% after one year. The low self-discharge is due to thicker separators between the positive and negative electrodes, but this means less room for active materials and thus lower capacity. A low self-discharge AA cell might have a capacity of 2500mAh and a regular one, 2700mAh. Panasonic took over ownership of Sanyo in 2009, and FDK Corporation now produces NiMH batteries for Panasonic. Before lithium-ion batteries became commonplace in electric vehicles (EVs), NiMH cells tended to be used, such as in the General Motors EV1 and early Toyota Prius models. Nickel-iron (Edison) batteries The nickel-iron or NiFe battery has nickel(III) oxide-hydroxide positive plates and iron negative plates, an alkaline electrolyte of potassium hydroxide, and a nominal cell voltage of 1.2V – see Fig.21. They were invented by the Swede Waldemar Jungner in 1899, when he substituted the cadmium in nicad batteries for lower-­ cost iron. The best disposable batteries Disposable AAA, AAA, C, D and 9V batteries from the “big two” (Duracell and Energizer) are generally good but don’t ignore batteries and cells from other sources. We have had success with cells from Aldi or Varta cells from Bunnings, where 30 AA or AAA cells can be had for less than $10. Australia's electronics magazine January 2022  19 Safety warning for lithium button cells Always store and dispose of lithium button cells correctly, keeping them away from children and pets. If ingested by children or pets, gastric juices can corrode the battery case and cause the harmful contents to leak out and cause chemical burns. Current flowing between the terminals can also damage internal tissue. disadvantage, but which may be an advantage, as we will now discuss. Proponents of intermittent energy sources like wind and solar power are investigating nickel-iron batteries because they can store energy and produce hydrogen as a byproduct. They continue safely making it even when the batteries are fully charged (continued charging would harm most batteries). The hydrogen can be used later as a fuel – see Fig.22. Such batteries are called battolysers, a combination of a battery and an electrolysis cell. A battolyser is better than an electrolytic cell for making hydrogen because there is minimal cell degradation with the battolyser; in fact, the battery improves in capacity once it has been used to produce hydrogen when fully charged. He patented the invention but abandoned development because of lower charging efficiency and excessive hydrogen production. In the USA, Thomas Edison patented the NiFe battery in 1901. He saw it as the ideal battery for electric vehicles (the preferred type of car in the early 1900s) and superior to the lead-acid battery. As internal combustion engines became popular, Edison was disappointed that his battery was not chosen as the starter battery in such vehicles. At the time, his batteries could be charged faster and had a higher energy density than lead-acid batteries. However, they performed poorly in cold weather and were also more expensive. Despite not being adopted in motor vehicles, Edison batteries (as they were also known) were produced from 1903 to 1972 by the Edison Storage Battery Company. They had a wide range of applications such as in railroads, forklifts and backup power. These batteries are still available today, made by other companies, and can be suitable for offgrid power systems, among other uses. NiFe batteries have the advantages of cheap materials, long life, durability, high depth-of-discharge (80%), tolerance of overcharging/overdischarging and short circuit resistance. While somewhat more expensive than leadacid and lithium-ion batteries for the same total energy storage, they have a claimed lower cost over their lifetime, which can be 50 years or more. Modern NiFe batteries also have a wide temperature tolerance, working from -30°C to +60°C. Due to their high self-discharge rate (1% per day), it is best to use them in situations where they are frequently recharged. Disadvantages include: • not being maintenance-free; they have to be checked and topped up regularly but do not need to be ‘equalised’ like lead-acid batteries • lower energy density than leadacid batteries (although the high depth-of-discharge helps to make up for this) • lower charge and discharge rate due to higher internal resistance (about five times that of lead-acid) NiFe batteries produce a lot of hydrogen during charging, usually a Fig.21: the Edison nickel-iron battery. Source: Edison Storage Battery Company, 1917 Fig.22: the usage scheme for a nickel-iron battolyser. Source: Delft University of Technology 20 Silicon Chip Australia's electronics magazine Lithium and Li-ion batteries At the moment, lithium-ion batteries are in the news more than any other battery type. They are mostly standard in consumer devices, phones, watches, electric cars and many largescale energy storage systems. Lithium is attractive as an active material in batteries because of its low weight, high atomic mobility (ease of movement through the electrolyte) and its specific electrochemical properties. Lithium-based primary cells usually contain metallic lithium, while rechargeable batteries usually contain siliconchip.com.au Fig.23: older lithium/iodinepolyvinylpyridine (or Li-I2) batteries, as used in cardiac pacemakers. lithium in ion form instead; an important distinction. Lithium primary cells are sometimes referred to as “lithium metal” to distinguish them from lithium-ion rechargeable cells. Note though that rechargeable lithium metal batteries are being developed (described next month). Lithium-based batteries are relatively lightweight, have a high energy density, low self-discharge, and can be optimised for either high energy density (mAh capacity) or high power density (maximum current that they can handle). They usually produce no gas, so they can be fully sealed. However, of all batteries in use, they have probably been involved in the most safety incidents. Lithium-based batteries can be manufactured with a variety of chemistries and were first commercially produced in the 1970s as primary cells (non-­ rechargeable). Depending on the specific chemistry, their voltage can range from about 1.5V to 3.7V (or 4.2V fully charged). A lithium/iodine-­polyvinylpyridine primary battery was first patented in 1971-72 by James Moser and Alan Schneider and used in a cardiac pacemaker implanted in 1972. This dramatically improved the life of the device and reduced its size compared to the mercury-zinc batteries it replaced (see Fig.23). This type of lithium battery is still in use in pacemakers and other implanted medical devices today. They have a terminal voltage of 2.8V and a high internal resistance of around 10kW, so they can only be used for low-current/low-power applications (eg, 1mW), such as pacemakers. These batteries have outstanding reliability in their pacemaker application. Battery life is typically 5-15 years, depending on pacemaker activity. In the 1980s, there were major developments towards lithium-based secondary (rechargeable) batteries. In 1985, Akira Yoshino developed the siliconchip.com.au Fig.24: a Panasonic 18650 lithiumion battery taken out of its case. Note the “jelly roll” construction of the battery core (green). The 18650 form factor is very popular in various applications. Source: Wikimedia user RudolfSimon (CC BY-SA 3.0) Fig.25: a lithium-polymer (LiPo) battery as used in a mobile phone. Source: Wikimedia user Kristoferb (CC BY-SA 3.0) first prototype lithium-ion rechargeable battery based on earlier research in the 1970s and 1980s by John B. Goodenough, M. Stanley Whittingham, Rachid Yazami and Koichi Mizushima. In 1991, a commercial lithium-ion battery was then made by Sony and Asahi Kasei, with a team led by Yoshio Nishi. In 2019, John B. Goodenough, M. Stanley Whittingham and Akira Yoshino received a Nobel Prize for their work. In 1997, the first lithium polymer (LiPo) battery was produced by Sony and Asahi Kasei. These have a flexible wrapping that can be made in any desired size and shape rather than the rigid, typically cylindrical casing of lithium-ion batteries (see Figs.24 & 25). There are numerous lithium-based battery chemistries, along with a few common ones (see panel overleaf). Fig.26 shows the trade-off between power delivery and cell capacity. The greater the current delivery, the lower the capacity. The negative electrode of a lithium battery is usually carbon (eg, graphite), while the positive electrode is a metal oxide or “polyanion” such as the one first identified by John Goodenough, lithium iron phosphate. It is treated in various ways to make it more electrically conductive. The electrolyte is a lithium salt in an organic solvent. For a lithium-ion battery using a negative carbon (C) electrode and a positive lithium-cobalt-oxide (LiCoO2) electrode, the full chemical reaction is as follows (also see Fig.27). Left to right Fig.26: the trade-off between energy density and power density for lithium-ion cells (mostly 18650 size) based upon cathode surface area. Australia's electronics magazine January 2022  21 Substituting batteries in old radios and tape players Vintage transistor radios and cassette tape players often need four, six or eight relatively expensive C or D cells. Modern AA alkaline cells are usually capable of powering these devices as well or better than the C or D cells that were available in the 1960s or 1970s, when these devices were designed. All that’s needed is to buy a “sabot” adaptor, commonly available online. Right: this “sabot” adaptor allows a AA cell to be used in place of a C cell. Other adaptors exist that let you substitute two AA cells for a D cell. is discharging, right to left is charging. LiC6 + CoO2 ⇌ C6 + LiCoO2 Because lithium-ion cells can be easily damaged if overcharged or overdischarged (and in extreme cases can catch fire or explode), they are generally packaged with protective electronics in each cell or battery. This disconnects them from external circuitry if it detects a problem such as the voltage being outside the normal range, high temperature or excessive current flow (see Fig.28). Safety of lithium batteries Lithium batteries are generally considered safe. Some lithium-ion chemistries, such as LiFePO4 (lithium-­ironphosphate), are notably more robust than others and will withstand abuse without failing (unless the abuse is extreme) or catching fire. Regular lithium-­ion and LiPo types are more sensitive. There have been some notable incidents such as: September 2010: UPS Airlines Flight 6, a Boeing 747-400F, crashed after an onboard fire in a cargo pallet containing 81,000 lithium batteries and other material. It is not known what caused the auto-ignition. January 2013: there was a problem with Boeing 787 onboard lithium-ion batteries catching fire. Fortunately, no one was hurt, but investigations revealed a ‘thermal runaway’ event due to a shorted cell that was attributed to inadequate quality control at manufacture and inadequate scenario testing by Boeing engineers. The problem was solved with better quality control by the battery manufacturer and better thermal and electrical Fig.28: a battery management circuit, as used in many lithium cells such as 18650s, to prevent overcharging, overdischarging and provide short circuit protection. Source: Wikimedia user Oldobelix (public domain) insulation, along with other changes. The problem was solved by April 2013, and the aircraft returned to service. 2016: Samsung Galaxy Note 7 phones were prohibited from being taken on planes due to a manufacturing fault related to the battery, which could cause the device to catch fire or explode after thermal runaway. The product was recalled, and Samsung issued software updates that stopped the phone from being charged at all. August 2018: Australia’s CASA (Civil Aviation Safety Authority) has published a procedure to deal with lithium battery fires onboard aircraft – see siliconchip.com.au/link/abbl July 2021: General Motors announced a combination of hardware and software alterations to their Chevrolet Bolt and Bolt EUV cars to address fire risks. At the same time, Fig.27: a simplified view of the processes in a lithium-ion battery during charging and discharging. 22 Silicon Chip Australia's electronics magazine siliconchip.com.au Common primary (lithium metal) types: Figs.29 & 30: Contingency East (emergency services) in Copenhagen developed this device to contain electric vehicle fires. Source: the Danish Institute of Fire and Security Technology they withdrew their previous advice to park the car more than 15m away from other vehicles or structures after 12 spontaneous fires in their battery packs (made by LG). See siliconchip. com.au/link/abbm August 2021: there was a large lithium-­ion battery fire in Moorabool, near Geelong, Victoria, at the Victorian Big Battery (Tesla). It took more than three days to extinguish. You can read the report of the investigation by Energy Safe Victoria at siliconchip. com.au/link/abbn The investigation revealed that “The most likely root cause of the incident was a leak within the Megapack cooling system that caused a short circuit that led to a fire in an electronic component. This resulted in heating that led to a thermal runaway and fire in an adjacent battery compartment within one Megapack, which spread to an adjacent second Megapack...” “The supervisory control and data acquisition (SCADA) system for a Megapack took 24 hours to ‘map’ to the control system and provide full data functionality and oversight to operators.” siliconchip.com.au “The Megapack that caught fire had been in service for 13 hours before being switched into an off-line mode when it was no longer required as part of the commissioning process. This prevented the receipt of alarms at the control facility.” Container for EV fires Local emergency services in Copenhagen have developed a container to place over an electric vehicle in the event of a battery fire (see Figs.29-30). A damaged or burning electric car is lifted into or pushed into the container. It has nozzles to spray cooling water and a pump for recirculation. More on lithium-ion batteries For more details, see our article on lithium-ion cells (August 2017; siliconchip.com.au/Article/10763) & the article on LiFePO4 cells (June 2013; siliconchip.com.au/Article/3816). In the second article in this series, to be published next month, we’ll describe quite a few new and upcoming battery chemistries/technologies. We’ll also have considerably more detail on lead-acid batteries, which SC are still in widespread use. Australia's electronics magazine Li-MnO2, 3V The most common consumer primary lithium battery Li-(CF)x, 3V Used for memory backup and aerospace applications Li-FeS2, 1.4V-1.6V Can replace alkaline consumer batteries Li-SOCl2, 3.5V Works at low temperatures (down to -55°C), used by militaries, expensive, hazardous Li-SO2, 2.85V Wide temperature range (-55°C to 70°C), used by militaries, toxic, hazardous Li-I2, 2.8V Used for medical implants Li-Ag2CrO4, 2.6V-3.1V Used for medical implants Li-Ag2V4O11 / Li-SVO / Li-CSVO Medical use, emergency beacons Li-CuO, 1.5V Replacement for consumer alkaline batteries; no longer popular Li-Bi2Pb2O5, 1.5V Replacement for silver-oxide batteries Li/Al-MnO2, 3V Made by Maxell Common secondary (lithium-ion) types: LiCoO2 or LCO (lithium-cobaltoxide), 3.7V Good overall performance, used in mobile phones, tablets, laptops, remote-controlled vehicles etc but less safe than most other types NMC (nickel-manganese-cobaltoxide), 3.6V-3.7V Longer-lived and higher-capacity compared to LiCoO2; used in power tools and electric vehicles NCA (nickel-cobalt-aluminiumoxide), 3.6V-3.7V Used in electric vehicles (eg. the Panasonic batteries used by Tesla) and consumer devices LiFePO4 (lithium-ironphosphate), 3.0V-3.2V Robust but lower capacity density; applications in vehicles, power tools, backup power systems etc January 2022  23 Classic LED Metronomes These two Metronome designs simulate the classic mechanical, invertedpendulum metronome with its batonlike pointer swinging left-and-right, producing a click at each extreme. Both designs use only discrete components and simple logic chips, making them easy to understand and build. Plus they are both great projects for a beginner. By Randy Keenan I dislike typical “modern” electronic metronomes that only click and/or blink once per beat. I came up with these designs to better simulate the mechanical metronomes that I know and like. Both designs light a series of LEDs, accompanied by a speaker that produces beat sounds. The first design uses eight LEDs and fits in a standard plastic case, while the second, slightly more complicated design has 10 LEDs and uses a custommade timber case. So the latter is a good project for those readers who have some woodworking experience. In both cases, the LEDs are arranged in an arc and light up in sequence, forward and reverse, to mimic the swing of an inverted pendulum. A click at each end of the LED arc further simulates a mechanical metronome. A typical metronome tempo range is 40-208 beats/minute, a ratio of 5.2 to one; in these Metronomes, the range is extended to 36-216 beats/minute, a ratio of six to one. Either project is excellent for a beginner; there are no high-frequency signals, high voltages or tricky wiring involved. Nor is there any need to program a chip with software. However, some measurements and adjustments will be needed to calibrate the instruments after construction, given the expected component tolerances. Two designs The slightly simpler 8-LED Metronome uses 74HC-series logic ICs and can be battery-powered, while the 10-LED Metronome uses CD4000series logic ICs and is intended to be powered from a plugpack. The two circuits operate similarly: A pulse generator clocks an up/down counter IC at Fig.1: the 8-LED Metronome is based around three 74HC-series digital logic ICs. The 74HC132 generates pulses at a selectable frequency. These clock the 74HC191 counter, and its three-bit output drives the eight LEDs via the 74HC137 decoder chip. The remaining three gates in the 74HC132 quad NAND package are used to form a set-reset flip-flop to reverse the LED chaser’s direction each time it reaches one end, and to generate a pulse from the speaker. 24 Silicon Chip Australia's electronics magazine siliconchip.com.au although it is a different logic chip. Both versions enable the LEDs at each end of the arc to flash brighter. You could also use either of these circuits anywhere a LED ‘chaser’ is needed. LED options The LED metronome comes in two versions; one with eight LEDs and another with 10 LEDs (shown in this photo). The case to house it can be as simple as a small timber frame with a clear plastic panel at the front. the rate required for the desired tempo. Another IC decodes the counter value to light the LEDs sequentially. A set/reset flip-flop (SR-FF) switches the counter direction when either end LED is lit, giving forward and reverse LED sequences. The click is produced by ORing the signals to the end LEDs, followed by a differentiator to shorten the pulse and a one-transistor amplifier to drive a small loudspeaker. The block diagrams of the two Metronomes are shown in Figs.1 & 2. In the 8-LED design, the tempo pulse is generated by a Schmitt-trigger NAND gate (part of a 74HC132). This clocks fourbit up/down counter IC2 (7HC191). Only three of the four binary outputs are used to drive 3-to-8-line decoder IC3 (74HC137) that lights the LEDs in sequence (eight is the 137’s limit). The SR-FF is made from two more NAND gates in the 74HC132. In the 10-LED design, the pulse is generated by a CMOS version of the ubiquitous 555 timer. It clocks fourbit up/down counter IC3 (CD4029) which drives decoder IC4 (a CD4028) with 10 outputs. The SR-FF logic is again provided by two gates from IC1, There are many options for the LEDs in these Metronomes. The parts lists indicate the suggested LEDs, but other sizes, shapes and colours can be substituted. The two end LEDs could even be different from the middle LEDs. However, all LEDs should have high luminous intensity, ideally at least 4000mCd (sometimes called “superbright”). This is to reduce power consumption. For the 8-LED Metronome, that maximises battery life, while in the 10-LED design, it limits the load on the CD4028 driving IC to a safe level. Both Metronomes were made using 5mm oval LEDs: green for the 8-LED version, and red for the 10-LED version. I used oval LEDs because they glow in a line rather than a dot, providing a more interesting display. 3mm & 5mm round LEDs are also suitable. Tinted and diffused lenses look best. You can use different LEDs from those specified, but you might need to adjust some resistor values. The 8-LED version The LEDs should be of the same type and matched; if using different LEDs at the ends, use matched LEDs for those two and separately matched LEDs for the rest. The minimalist circuit is shown in Fig.3 and it works as follows. Schmitt-trigger quad NAND gate IC1d is configured as a pulse generator. Fig.2: the 10-LED Metronome uses a 555 timer IC instead of a logic-gate-based oscillator as the pulse generator. The remaining logic ICs are from the 4000-series; a 4029 acts as the up/down counter, while a 4028 is the 4-to-10 decoder that drives the LEDs. Two of the gates of the 4001 quad NOR IC form the set-reset flip-flop, and the other two gates form the click pulse. siliconchip.com.au Australia's electronics magazine January 2022  25 The pulse frequency, and thus the metronome tempo, is determined by potentiometer VR1, resistors R1 & R2 and capacitors C1-C3. For an explanation of the operation of a Schmitt-trigger pulse generator, see the adjacent panel. Its pulses clock IC2, an up/down binary counter. IC2’s outputs are fed to decoder IC3 to light the eight LEDs in sequence. The outputs of IC3 and the inputs of IC1a, IC1b and IC1c use negative (active-low) logic because IC1 is a NAND gate rather than a NOR gate (see the panel on SR-FFs). The alternative would have been to use the 74HC7002 Schmitt-trigger NOR gate with a 74HC237 decoder and positive logic, but the 74HC7002 is less common and more expensive than the 74HC132. When IC3 is counting up, it lights each LED in sequence, from LED0 to LED7. When LED7 lights, the low level at pin 7 of IC3 (Y7) is also applied to the SR-FF formed by IC1a and IC1b. This causes pin 6 of IC1b (Q) to go high, causing IC2 to reverse its direction and count down. Each LED is now lit in sequence in the opposite direction. When the first LED, LED0, is lit, the SR-FF is reset, IC2 reverses and counts up, and the cycle repeats. VR2 controls the overall LED brightness. The circuit is designed to make LED0 and LED7 brighter than the others. The relative brightnesses of the end-vs-middle LEDs is maintained as VR2 is adjusted by LED8 or a zener diode, ZD2. Whenever current is applied to LED1-LED6, LED8/ZD2 is in series with that LED, reducing the voltage across the current-limiting resistors and thus the LED current. VR2 could be changed from 500kW to 1MW to extend the brightness range down to very dim levels. If you want VR2 to turn the LEDs completely off at minimum, fit R3 (300kW), but note that this creates a large ‘dead zone’ in the lower range of VR2. LED8 may be the same type as LED0 through LED7, but for more brightness contrast between the end and middle LEDs, use a type with higher forward voltage such as blue or white, or use a zener diode of approximately 4.7V. If you want all LEDs to have equal brightness, fit a wire in place of LED8/ZD2. Click sounds When either end LED is lit, the low level at Y0/Y7 is also sent to IC1c, which behaves as a NOR gate when operated in negative logic mode (a low at either input causes a high output). Its output is fed to the Click Loudness control (VR3) and then to a simple transistor amplifier. However, the pulse from IC1c is too long and would cause a click at the end of the pulse as well as at its beginning, and the current would be high during the pulse on-period. To avoid this, the pulse passes through C4 and/or C5 to yield a short pulse at each end of the original pulse, a positive one at the beginning and a negative one at the end. Diode D1 shunts the negative pulse so that only the positive pulse is applied to the base of transistor Q1. Power supply This design is powered by a battery of four AAA cells. 74HC ICs are used rather than 74HCT or 74LS because the 74HC series allows a slightly higher supply voltage, up to 6V. Fresh standard alkaline AAA cells supply marginally more than 6V, so the voltage rail for the ICs is limited using a 47W resistor and a 6V zener diode (ZD1). Alkaline, dry cell, rechargeable NiMH or Li-ion AAA cells can be used. Fig.3: this 8-LED Metronome circuit shows more details than Fig.1. VR2 allows you to set the LED brightness while LED8 or ZD2 reduces the brightness of the middle six LEDs compared to the outer two. Extra capacitors C2-C3 and resistor R2 allow you to adjust the frequency range to match the beats-per-minute (bpm) range shown on the dial. Additional capacitor C5 is provided to change how the clicks sound. 26 Silicon Chip Australia's electronics magazine siliconchip.com.au Using a Schmitt-trigger gate as a pulse generator Gate IC1d of the 74HC132 Schmitttrigger input NAND chip generates the pulses that clock the counter (IC2). So what is a Schmitt-trigger gate, and why are we using one? An ‘ordinary’ non-Schmitt-trigger gate or inverter is effectively a highgain but mostly linear amplifier. As a result, the output transition from high-to-low or low-to-high takes place over a narrow input voltage range, as shown in Fig.a, a plot of the output voltage versus the input voltage. As a result, the negative-feedback RC circuit shown in Fig.b will typically reach equilibrium at some point (E), with the output ‘stuck’ at an intermediate voltage. If the input were to increase in voltage, as indicated by the arrow, the output would respond by decreasing and would restore the circuit to point E with a time constant determined by R and C. The reverse is true if the input voltage decreases. You can test this yourself on a breadboard if you have a spare 74HC00 NAND gate chip. Just remember to connect all the unused inputs to one supply rail or the other. A DVM will show that the voltage at pin 3 is stable. In contrast, the Schmitt-trigger version of the gate ensures oscillation due to its built-in hysteresis and associated positive feedback. This is illustrated in Fig.c, an equivalent plot to Fig.a but for a gate with Schmitt-trigger inputs. Once the input voltage increases above the upper-threshold input voltage (VT+, point U), the output immediately ‘snaps’ to a low level (point V). It remains there until the input decreases below the lower-threshold input voltage (VT−, point L) and the output ‘snaps’ high (point W). This can be demonstrated by breadboarding the circuit shown in Fig.d. Begin with the pot at extreme clockwise (pins 1 & 2 at +6V) and apply power. The LED should remain off. Slowly decrease the input voltage via the pot until the LED goes on; note the input voltage. Now increase the input voltage gradually until the LED goes off. There should be a couple of volts difference; this is the hysteresis spread (VT+ − VT−). You have made one clockwise trip siliconchip.com.au Fig.a & b: the transfer function of a standard NOR gate. The output is low when the input is high and vice versa, but if the input voltage is intermediate, the output voltage can be anywhere in between. Fig.c & d: a Schmitt-trigger inverter has hysteresis, so once its input voltage is high enough, the output snaps low and stays low until the input voltage drops significantly. Similarly, when the input voltage drops and the output goes high, it remains high until the input voltage increases significantly. Fig.e: the input & output waveforms for a Schmitt-trigger inverter used as an oscillator. around the hysteresis rectangle, as indicated by the arrows in Fig.c. Because of this, if you substitute a Schmitt-trigger 74HC132 for the 74HC00 in Fig.b, you will find that it oscillates, generating a square wave at the output. The input exhibits an Australia's electronics magazine exponential pseudo-triangle wave of amplitude equal to the hysteresis spread, as shown in Fig.e. One crucial point to consider is how the rate of oscillation will vary with supply voltage (especially in a battery-powered circuit). As it turns out, the deceased capacitor charging current is somewhat compensated by the decrease in hysteresis spread (as it is somewhat proportional to the IC’s supply voltage). Thus, the pulse rate only changes by a few percent from 6V to 5.5V (an 8% change in voltage). January 2022  27 The 4700μF and 470μF bulk bypass capacitors, in combination with the 47W series resistor, reduce the supply voltage pull-down by the click-pulse current through the speaker. As PCB-mounting potentiometers with built-in switches are rare, a separate power switch is used. A regulated 6V DC plugpack could be used instead of a battery. Make sure you verify it is regulated as otherwise, its output voltage would be too high for the circuit. The 10-LED version The circuit for this version is shown in Fig.4. It is similar to the 8-LED version but positive logic is used throughout. The pulses are generated by CMOS 555 timer IC2. It clocks IC3, a four-bit up/down counter. IC3’s outputs are decoded to 10 individual outputs by IC4, lighting the 10 LEDs in sequence. When an end LED (LED0 or LED9) is lit, the SR-FF formed by IC2a & IC2c is set or reset, thus switching IC3 into up or down mode, reversing the LED sequence. VR5 controls the LED brightnesses. Instead of the technique used for the 8-LED design to make the end LEDs brighter, this version uses a current mirror comprising Q1 and Q2 with trimpot VR4, control potentiometer VR5 and some fixed resistors. VR4 adjusts the brightness of the middle LEDs relative to the brightness of the two end LEDs. See the adjacent panel for an explanation of how this works. Click generation and circuit variations are the same as for the 8-LED design. The higher supply voltage of this version provides a louder click. Construction Fig.5 is the PCB layout diagram for the 8-LED version, while Fig.6 is for the 10-LED version. Most components mount on the boards. A few might need their values tweaked; that is why some parts do not have an associated value. Whichever version you are building, the construction process is initially similar. Start by fitting all the resistors with fixed values given, using a DMM to check the values before soldering them in place. Follow with the diode(s), ensuring their cathode stripes face as shown Fig.4: the 10-LED Metronome uses a more complicated LED brightness control scheme with PNP transistors Q1 & Q2 forming a current mirror, so the brightnesses of the middle eight and outer two LEDs track over a wide adjustment range. LED10 lights up the beats-per-minute adjustment dial. Besides these differences, and using a CMOS 555 timer as the pulse generator, the circuit is quite similar to the 8-LED version. 28 Silicon Chip Australia's electronics magazine siliconchip.com.au How a current mirror works A current mirror circuit is used to match two or possibly more currents under varying conditions. Fig.f shows a basic example; similar NPN bipolar transistors Q1 and Q2 have their bases tied together and set at a control voltage, Vb. Thus, their emitters will be at equal voltages, approximately 0.6V lower than Vb. If the emitter resistors, R1 and R2, are of equal resistance, they will conduct equal currents of approximately Ic = (Vb – 0.6V) ÷ R. Assuming a sufficiently high current gain (>≈100) for the transistors, and thus negligible base currents, the collector current of each BJT would be the same as its emitter current; in other words, the currents through LOAD 1 and LOAD 2 would be matched. If the base voltage (Vb) is varied, the emitter and collector currents will vary, but will remain matched between the two transistors. Likewise, if one or both loads vary in resistance – within limits – their currents will still be equal and given by the equation above. For the brightness control of the 10-LED Metronome, we want the current to the middle LEDs to be a fraction of the current to the end LEDs, and to be the same fraction over a wide range of currents. If we used the above scheme, the circuit would be something like Fig.g, with R being a fraction of VR + R, ie, unequal emitter resistors. However, there is a problem with this: since each group of LEDs is alternately turned off, that load resistance becomes extremely high. As a result, the transistor in the off leg of the circuit has no collector current, and the base current becomes large because the base-emitter junction is a forward-biased diode. This reduces the base voltage, and thus the collector current of the other transistor. For example, Fig.g shows one of the middle LEDs on, while the end LEDs are both off, resulting in high base current through their transistor (Q2). To avoid this, I devised a different scheme for the 10-LED Metronome, shown in Fig.h. This works because the two loads are, in practice, nearly constant and equal, each consisting of one LED at a time. The current-mirror circuit is turned on its head, using PNP transistors rather than NPN. Each group of LEDs is made part of an emitter circuit, in series with a resistor that will determine its current and relative brightness. When lit in sequence, each middle LED is in series with R1 + VR4, which is made larger than R2 in series with each end LED. The collector current of Q1 will be a fraction of that of Q2 (R2 ÷ [R1 + VR4]). This fraction — the ratio of currents — will be maintained over a range of Vb as controlled by VR5, and thus the brightnesses of the eight middle LEDs will be a fraction of the brightnesses of the two end LEDs over a wide range. This situation will break down if Vb is above 12V − Vled − 0.6V or about 10V. This is avoided by padding the ends of VR5 with fixed resistors. Trimpot VR4 allows the resistance ratio R2 ÷ [R1 + VR4] to be set as desired, thus setting the brightness difference. Fig.f: a basic current mirror circuit. Since Q1 & Q2 are similar transistors, and thanks to the negative feedback provided by the emitter resistors, varying their base voltages using the potentiometer results in closely matched currents through the two independent loads. Fig.g: different emitter resistor values can be used to make the load currents different, but they keep similar current ratios when the base voltage is varied. Fig.h: the circuit shown in Fig.g can suffer from excessive base current problems when the loads can be switched on and off independently. This circuit solves that by swapping the NPN transistors for PNP and keeping the currentsetting resistor connections at the transistor emitters. siliconchip.com.au Australia's electronics magazine January 2022  29 Fig.5: most of the 8-LED Metronome components mount on the PCB, as shown here. Assembly is straightforward but be careful to orientate the ICs, LEDs and diodes as shown. Also, don’t get the potentiometers mixed up as they all have different values (check the codes printed on their bodies). in the appropriate overlay diagram and that you don’t get the different types mixed up. Remember that for the 8-LED version, you either fit zener diode ZD2 or LED8, not both. If using LED8, push it down onto the board with the longer lead to the pad marked A and then solder it in place. The ICs are next. They can be soldered directly to the PCB or plugged in via sockets; it’s up to you. Either way, make sure the pin 1 notches/dots face as shown and don’t get the two different 16-pin ICs mixed up. Note that IC3 on the 8-LED board (74HC137) is oriented opposite to the other two ICs. Fit the capacitors next, starting with the smaller non-polarised types and then moving onto the electrolytic capacitors, which must be orientated with their longer positive leads placed towards the + symbols. The 1000μF capacitor on the 10-LED board is laid over as shown before soldering and trimming its leads. As with the resistors, leave off any that don’t have values indicated as those pads are for tuning later. There are no trimpots or discrete transistors on the 8-LED board. However, on the 10-LED board there are three trimpots: two 5kW (VR1 & VR3) and one 100kW (VR4); as well as two PNP transistors (Q1 & Q2) and one NPN transistor (Q3). Fit them now, being careful not to get the different 30 Silicon Chip types of transistors mixed up. If your Q3 transistor is taller than the others, bend its leads so that it is laid over on its side before soldering to ensure sufficient clearance for the front panel later. Note that the PCB has footprints to accommodate different types of transistors from those specified; assuming you are using the BC558 suggested in the parts list, they are placed as shown in Fig.6. Both boards use a 3-way terminal block for power, although you can solder wires to its pads instead. If fitting it, do that next, with the wires entering the front of the board and passing around to the rear via the notch on the edge of the board. Continue by selecting the LEDs you are going to use. You might wish to order extras so that you can pick out a matched set from the larger number. Fig.7: a drilling template for the front panel of the 8-LED version. Eleven holes need to be drilled: eight for the LEDs (size & shape to suit the LEDs you are using, marked “A”) and three 8mm holes for the potentiometer shafts, marked “B”. The dashed circles show the positions of mounting posts within the specified case; do not drill those. While we specify 3mm diameter holes for “A”, the size will depend on what type of LEDs you are using. Australia's electronics magazine siliconchip.com.au Fig.6: the 10-LED Metronome is slightly more complicated than the 8-LED version. Note the components laid on their sides and make sure to place the transistors in the positions shown, unless you are substituting those with a different pinout. Note that it’s common for their brightnesses to look similar when fairly bright, but at very low currents (say around 30μA), they can vary considerably when dim. Try to select the ones which match best for the middle LEDs. If you have a bench supply, one good way to compare the brightness is to connect several in series, along with a current-limiting resistor, then power the entire string from the bench supply and slowly wind its voltage up. That way, you can make a direct comparison over a range of brightnesses. The construction now diverges for the two versions. Finishing the 8-LED Metronome Measure the resistance across VR1’s track (from one end pin to the other) and divide the reading by five. This is the value you should aim for with R1 + R2. We’ve specified two 10kW resistors in the parts list because VR1 should be close to 100kW. If VR1 does not measure close to 100kW, vary the values of one or both of those 10kW resistors (eg, changing one to 9.1kW or 11kW) to get their total as close as possible to 20% of VR1’s value. The 8-LED version fits in a Serpac siliconchip.com.au 131-BK plastic enclosure, but other enclosures could be used instead. If using the 131-BK, use the side with the best appearance as the upper end. After selecting the LEDs, drill the LED and potentiometer holes in the front half of the enclosure. Fig.7 may be used as a drilling template. You can print the guide onto card stock, punch out the mounting holes to 5mm and temporarily glue the guide to the inside of the front half of the enclosure. If using the recommended oval LEDs, you will need to carefully elongate the holes after drilling. Note that the illuminated line from an oval LED is perpendicular to the larger dimension of the LED body. Decide which orientation you want and orientate the LEDs and holes accordingly. When drilling or adjusting the LED holes, check that the LEDs fit into the holes snugly but do not require excessive insertion force. Fit the three pots to the PCB without soldering them, and attach the PCB to the front of the enclosure. I removed the small protruding bits on the front of each pot. To allow space for the components on the PCB, you might need spacers on the screws. Check the shaft Australia's electronics magazine lengths and shorten them as needed for your knobs. The shaft-gripping sections of the knobs that I used were recessed by several mm. So for pots VR2 and VR3, I sanded down the backs of the knobs to about 12.5mm total height to enable the knobs to grip the shorter pot shafts adequately. If the knobs are not tight enough, the plastic shafts of the potentiometers can be deformed a bit by pinching them with pliers. Solder the three pots now, after re-checking they have the correct values. Now, paying attention to their orientations (see the A & K markings on the PCB), insert the LED leads into the board without soldering them. If using oval LEDs, they will need to be twisted slightly to conform to the arc. Again, attach the PCB to the front half of the enclosure and manoeuvre each LED into its proper hole in the front of the enclosure. It’s best to have them protruding slightly. Check the LEDs’ appearance and adjust as necessary, then solder the LEDs to the PCB while it is in place. The LEDs will probably not be seated on the PCB but spaced away from it by several millimetres. January 2022  31 Fig.8 is the tempo dial; this can be downloaded from the Silicon Chip website. It is a good idea to print it on photo paper for a good appearance. This assumes that VR1 is equivalent to the type specified in the parts list; it needs to rotate through a 280° arc. Align the dial to the tempo pot shaft and glue it to the front of the enclosure. Fit the knob to the tempo pot such that its rotation extends equally beyond the 36 and 216 tempo lines; this is because pots typically have a dead zone at each extreme where the resistance changes very little. NPN transistor Q1, the 4700μF capacitor, switch S1, the speaker, and the battery holder are not mounted on the PCB but attached to the rear half of the enclosure (see the photo below). The speaker holes may be in any pattern. I used a perforated metal sheet, selected a drill bit of the diameter of its holes, clamped the sheet to the inside of the rear half of the enclosure and used it as a drilling guide. Attach the slide switch to the panel using small screws and nuts. The battery holder and speaker are held in place with clips made from a large, heavy-duty paper clip. Q1 and the 4700μF capacitor are mounted close to the speaker and wired directly to the speaker terminals to minimise parasitic resistances; they are not switched by S1, likewise to reduce parasitic resistance. This can be important since the supply voltage is relatively low and speaker impedance is 8W. When the Metronome is switched off, there will be only a minuscule leakage current through these components. However, if the Metronome is unused for an extended period, it’s best to remove the cells. Solder the emitter lead of transistor Q1, the negative lead of the capacitor, and a wire to a solder lug before fitting them to the enclosure. Check the wiring of these components carefully: a mistake can cause excessive current and damage Q1 or cook the speaker coil and cone. Cut a timber base to suit the enclosure and attach the rear half to it using screws, giving the enclosure a slight backward tilt. Finally, attach the off-PCB parts to the 3-way terminal block as shown in the photos. If you don’t want to use a terminal block, you can solder the wires directly to the PCB pads. Adjustments The tempo and its range will likely need adjustment. Eight different 74HC132 ICs showed a spread of a few percent, with one about 7% above the average. The tempo may not correspond to the dial markings because of this, plus variations in the timing capacitors and the resistances of VR1 and R1/R2. Pots can vary by as much as 20%. For the LED Metronome, some of the components such as the speaker and battery holder are not mounted on the PCB, but are instead fitted onto the rear of the enclosure. This photo shows the 8-LED Metronome arrangement. 48 44 40 38 36 54 60 72 88 104 120 160 216 50mm Fig.8: print this dial artwork for the 8-LED version on photo paper, cut it out and glue it to the front of the case. The exact diameter is not critical, but it should be close to 50mm. This is available to download from our website as a PDF. 32 Silicon Chip Australia's electronics magazine siliconchip.com.au If you are not happy and want to bring the tempos into agreement, a frequency meter is very helpful. The type built into many low-cost DMMs is adequate. Measure the pulse frequency at pin 11 of IC1 or pin 14 of IC2. With VR1 set at the lowest tempo (aligned with the marking showing 36 beats/minute), find a capacitor or paralleled capacitors for C1-C3 that give a pulse frequency of 4.2Hz (see Table 1). If you don’t have a selection of capacitors to try out (or want to save time), calculate the percentage error in the frequency (actual vs expected) and measure the capacitance across C1-C3. Multiply the capacitance reading by the percentage and divide by 100. This is how much capacitance you need to add (if it’s too fast) or subtract (if it’s too slow). To subtract capacitance, you’ll need to replace C1 and/or C2 with lower value capacitors, then re-check and possibly add a bit more capacitance by fitting C3 to get the frequency spot-on. Assuming you selected R1 & R2 as 1/5th the value of VR1, with VR1 aligned with 216 beats/min, you should get a frequency reading of 25.2Hz (see Table 1). If this is significantly off, you might want to adjust those resistor values, reducing the total to speed it up or increasing them to slow it down. Calculating the percentage frequency error relative to 25.2Hz tells you the percentage by which the total resistance must change. CON1 3 2 1 Similar to the 8-LED Metronome, the 10-LED metronome also has components mounted on the rear panel rather than on the PCB, as can be seen in the photo below, with the wires emanating from the top of this one. The final result should have all tempos from 36 to 216 (and thus pulse frequencies in Table 1) agreeing with the dial markings. Finally, check the click loudness and timbre. Check that VR3 varies the click loudness smoothly from zero to maximum. If it is too soft at maximum, a transistor with a higher hFE is needed. If the click does not vary smoothly, replace the 220W resistor with a higher value until the loudness variation is satisfactory. You can vary the timbre of the click by adding a capacitor at the position marked C5. Adding capacitance should give a more ‘mellow’ click. You can also try the speaker in both polarities as that can affect the sound. Troubleshooting If the LEDs don’t light up or behave Table 1 – Pulse frequency (Hz) versus tempo (beats/minute) Tempo (bpm) 36 38 40 44 48 54 60 66 72 80 88 104 120 160 216 8 LEDs (Hz) 4.20 4.43 4.67 5.13 5.60 6.30 7.00 7.70 8.40 9.33 10.3 12.1 14.0 18.7 25.2 siliconchip.com.au 10 LEDs (Hz) 5.40 5.70 6.00 6.60 7.20 8.10 9.00 9.90 10.8 12.0 13.2 15.6 18.0 24.0 32.4 CON1 pin 3 CON1 pin 1 CON1 pin 2 Australia's electronics magazine January 2022  33 strangely, check the orientation of all the parts. Check for solder bridges or poor joints and that IC pins are not bent. Check also that there is a pulse at pin 11 of IC1 and pin 14 of IC2. Finishing the 10-LED Metronome The mounting holes for VR2 can accept a 280° pot (matching the others) or a larger 300° pot. While the difference is subtle, the 300° pot allows the tempo numbers to be spread out slightly more. Before fitting VR2, measure its resistance, divide by 5.5 and check that this is close to 18kW. If not, you might need to replace the 18kW resistor with a different value that’s close to this. If your IC3 is a 4029, fit the solid red wire link shown in Fig.6. Otherwise, fit the wire link where there is a dashed red line. You can use a component lead off-cut for either. Insert LED10 through the PCB from the back (see the photo on page 33). Solder its leads on the back of the PCB to pads “K” and “A”. Rather than a dial applique as used in the 8-LED version, the 10-LED Metronome uses a transparent plastic disc printed black with clear tempo numbers (Fig.9). Choose the design appropriate for your VR2 potentiometer type. If the printed disc is not sufficiently rigid, a clear backing disc might be needed. Glue the disc to the back of a plastic bushing fitted by friction or glue onto the shaft of VR2. This bushing can be made from a cut-down knob. LED10 illuminates the tempo numbers of the disc to show through the plastic panel. LED10’s brightness is determined by the value of resistor R2, specified as 10kW; if you aren’t happy with the brightness, lower the value of R2 to make it brighter or increase it to make it dimmer. For the 10-LED version, the LEDs do not protrude through the front panel, but show through, so holes for the LEDs are not needed. The holes for the two lowest potentiometers (VR5/6) can be 8mm, but VR2 will require a larger hole to accomodate the bushing holding the tempo dial. You will need to cut a thin panel on which to mount the PCB with 15mm threaded standoffs. This panel will fit into the back of the timber frame. This panel also carries the speaker, power 34 Silicon Chip Parts List – 8-/10-LED Metronome 8-LED Metronome 1 double-sided PCB coded 23111211, 71 x 98mm 1 3-way terminal block (CON1) 1 Serpac 131-BK plastic instrument case, 111 x 82.5 x 38mm [Mouser 635-131-B, Digi-Key SR131B-ND] 1 timber base, 75 x 90 x 12.5mm (DIY) 4 AAA cells, preferably NiMH rechargeables (BAT1) 1 4xAAA battery holder (BAT1) [Keystone Electronics 2482; Mouser 534-2482, Digi-Key 36-2482-ND] 1 8W loudspeaker, 36mm diameter (SPK1) [DB Unlimited SM360608-1; Mouser 497-SM360608-1, Digi-Key 2104-SM260608-1-ND] 1 100kW linear 9mm/10mm vertical potentiometer (VR1) [Mouser 652-PTV09A4025UB104] 1 500kW linear 9mm/10mm vertical potentiometer (VR2) [Mouser 652-PTV09A4020UB504] 1 5kW linear 9mm/10mm vertical potentiometer (VR3) [Mouser 652-PTV09A4030UB502, Digi-Key PTV09A4030UB502-ND] 1 SPST or SPDT slide switch (S1) [Alpha SS60012F-0102-4V-NB; Mouser SS60012F-0102-4V-NB] 1 14-pin DIL IC socket (optional; for IC1) 2 16-pin DIL IC sockets (optional; for IC2 and IC3) 3 knobs to suit VR1-VR3 4 adhesive rubber feet 2 small machine screws and nuts (for mounting slide switch) 1 large, heavy-duty paper clip 8 No.4 x 6mm self-tapping screws 2 small, short (~10mm) panhead wood screws (for mounting case to base) 1 solder lug with ~3.25mm diameter hole various lengths and colours of light-duty hookup wire Semiconductors 1 74HC132 quad 2-input Schmitt-trigger NAND gate, DIP-14 (IC1) 1 74HC191 presettable 4-bit binary up/down counter, DIP-16 (IC2) 1 74HC137 or 74HC138 3-to-8 line decoder, DIP-16 (IC3) 1 30V 1A NPN transistor, TO-92 (Q1) [KSD471ACYTA, KSC2328AYTA or ZTX690B] 8 ‘superbright’ LEDs, round or oval (LED0-LED7) [Broadcom HLMP-HM74-34CDD (green, oval), Kingbright WP7083ZGD/G (green, 5mm), Jameco 2169846 (green, 3mm)] 1 6.0V 500mW zener diode (ZD1) [1N5233 or equivalent] 1 blue/white LED or 4.7V zener diode (LED8/ZD2) [1N5231] 1 150mA schottky diode; eg, BAT46/BAT48/BAT85 (D1) [Jaycar ZR1141, Altronics Z0044, Mouser 511-BAT46] Capacitors 1 4700μF 6.3V electrolytic [Mouser 667-EEU-FS0J472] 1 470μF 6.3V low-profile electrolytic [Mouser 232-63AX470MEFC8X75] 4 1μF 50V multi-layer ceramic 1 100nF 50V ceramic 1 220pF 50V ceramic Resistors (1% 1/4W, 1/8W or 1/16W small body metal film unless otherwise stated) 1 300kW (optional) 2 10kW While we recommend using 1% resistors, you can 1 2.2kW use 5% resistors if desired. It might need more 2 220W adjustments to get the tempo range correct. 1 47W 10-LED Metronome 1 double-sided PCB coded 23111212, 108 x 89mm 1 12V DC 100mA+ plugpack Australia's electronics magazine siliconchip.com.au Table 2: resistor colour codes 1 3-way terminal block (CON1) 1 chassis-mount barrel socket to suit plugpack (CON2) 1 8W loudspeaker, 50mm diameter (SPK1) [DB Unlimited SM500208-1; Mouser 497-SM500208-1] 2 5kW top-adjust mini trimpots (VR1, VR3) 1 100kW 280° linear 9mm/10mm vertical potentiometer (VR2) [Mouser 652-PTV09A4025UB104] OR 1 100kW 300° linear 9mm/10mm vertical potentiometer (VR2) [Mouser 652-PDB12-M4251-104BF] (see text) 1 100kW top-adjust mini trimpot (VR4) 1 20kW linear 9mm/10mm vertical potentiometer (VR5) [Mouser 652-PTV09A-4030UB203, Digi-Key PTV09A-4030U-B203-ND] 1 5kW linear 9mm/10mm vertical potentiometer (VR6) [Mouser 652-PTV09A4030UB502, Digi-Key PTV09A4030UB502-ND] 1 SPDT slide switch (S1) [Alpha SS60012F-0102-4V-NB; Mouser SS60012F-0102-4V-NB] 1 14-pin low-profile DIL IC socket (optional; for IC1) 1 8-pin low-profile DIL IC socket (optional; for IC2) 2 16-pin low-profile DIL IC sockets (optional; for IC3 and IC4) 1 timber base, 75 x 150 x 12mm (DIY) 1 timber frame, 110 x 130 x 40mm (DIY) 1 red-tinted transparent acrylic panel, 100 x 125 x 2.5-3mm (or to fit frame) 3 knobs to suit VR2, VR5 & VR6 1 clear, printable plastic and plastic backing for tempo dial, bushing or cutdown knob for mounting onto VR2 4 M3-tapped 15mm spacers (for mounting PCB to panel) 8 M3 x 6mm panhead machine screws (for mounting PCB to panel) 2 small machine screws and nuts (for mounting slide switch) 2 M3 x 10mm panhead machine screws, flat washers and nuts (for mounting speaker) 1 large, heavy-duty paper clip 6 small, short (~10mm) panhead wood screws various lengths and colours of light-duty hookup wire 1 55x55mm square of speaker cloth Semiconductors 1 CD4001BE quad 2-input NOR gate, DIP-14 (IC1) 1 TLC555IP or LMC555CN CMOS timer, DIP-8 (IC2) 1 CD4029BE, CD4510BE or CD4516BE 4-bit binary up/down counter, DIP-16 (IC3) 1 CD4028BE 4-to-10 binary decoder, DIP-16 (IC4) 2 BC558 30V 100mA PNP transistors, TO-92 (Q1, Q2) 1 30V 2A NPN transistor, TO-92 (Q3) [KSC2328AYTA or ZTX690B] 1 150mA schottky diode; eg, BAT46/BAT48/BAT85 (D1) [Jaycar ZR1141, Altronics Z0044, Mouser 511-BAT46] 10 ‘superbright’ LEDs, round or oval (LED0-LED9) [Cree C566D-RFE-CV0X0BB1 (red, oval) recommended] 1 5mm ‘superbright’ red LED (LED10) [Kingbright WP7113SRD/J4 recommended] Capacitors 1 4700μF 16V electrolytic, 13mm diameter [Mouser 232-16PK4700MEFC125X] 1 1000μF 16V electrolytic, 8mm diameter [Mouser 232-16ZLH1000MEFC8X2] 5 1μF 50V multi-layer ceramic 2 100nF 50V ceramic Resistors (1% 1/4W, 1/8W or 1/16W small body metal film unless otherwise stated) 1 22kW 1 18kW 2 10kW 1 4.7kW 1 3.3kW 2 390W ½W 4 220W 2 22W siliconchip.com.au Australia's electronics magazine jack, power switch, 4700µF electrolytic and two 22W resistors (see photo). Use the correct power socket to match your plugpack output. The speaker is held in place by screws and nuts, with washers that have been bent down on one side. You can use hot melt glue or silicone sealant to secure the large electrolytic capacitor. This panel, and thus the PCB, is secured to the frame by small wood screws that attach to four approximately 8 x 8 x 12mm pieces of timber glued to the inside corners of the frame. There’s nothing extraordinary about the case; I made mine in the same manner as a picture frame, with four 45° mitred timber pieces glued together. If you don’t like doing woodwork, you could probably find a plastic box with a clear lid that’s large enough to house the PCB and other components, and drill holes in the lid for the pots. Checkout and adjustment Before applying power, carefully check the wiring to the off-board components; a mistake here can cause excessive current and damage Q3 or cook the speaker coil or cone. Compare your wiring to that shown in our photos. Because of variations in components, the tempo will likely need to be brought into line. A frequency meter (even a very basic one as found in many DMMs) or scope is helpful for adjusting the tempos. January 2022  35 120 120 50mm Fig.9: there are two dials for the 10-LED Metronome to suit the larger 300° potentiometer (left), or the standard 280° potentiometer (right). Unlike the 8-LED version, these are printed on transparent film and connected to the rotating pot shaft. Thus LED10 behind can shine through and illuminate the selected tempo. Set-reset flip-flops (SR-FF) Both Metronome designs incorporate a set/reset flip-flop (SR-FF), a logic circuit with two states: set and reset. Applying a high level to the S input while keeping the R input low puts the flip-flop into the set state, and it remains there until reset. Similarly, applying a high level to the R input while keeping the S input low puts the SR-FF into the reset state, staying there until set again. By today’s naming standards, the SR-FF is a transparent latch and not a flip-flop as it has no clock input, but the traditional term “flip-flop” continues to be used. Another way of thinking of it is as a 1-bit memory store or a bistable circuit. An SR-FF is a simple type of sequential logic circuit, which means that its output depends on its ‘history’; it has a memory. Compare this to combinatorial logic in which the outputs depend only on the value of the inputs; there is no history or memory involved. An SR-FF can be made from two NOR gates, as shown in the adjacent diagram, or you can get dedicated flipflop ICs. In the 10-LED Metronome, we’re already using NOR gates for other purposes, so doing it this way avoids the need for an extra IC. It works as follows. Imagine that both the S and R inputs are low. The circuit can initially be in either state: set, with Q high and Q low, or reset, vice versa. Pulsing S high will cause Q to go low or to stay low, which will cause Q to go high, which is the set state. Further pulsing of S will have 36 Silicon Chip no effect since Q holds the upper NOR-gate input high, assuming that R remains low. Similarly, pulsing R will cause Q to go low and thus Q to go high, which is the reset state. Further pulsing of R will have no effect, assuming that S remains low. For the 8-LED Metronome, the SR-FF is constructed from two NAND gates rather than NOR gates. All this means is that the SR-FF uses negative logic; in negative logic, NAND gates become NOR gates, and the SR-FF is set and reset by negative (low) pulses, specifically, from LED7 (set) and LED0 (reset). The SR-FF Q output is sent to the 74HC191 counter to change its counting direction. The 10-LED Metronome has an SR-FF, constructed from two NOR gates in the CD4001. Positive logic is used, and the SR-FF operates as described above. Turn VR2 to the slowest tempo (36 beats/min) and measure the pulse frequency at pin 3 of IC2 or pin 15 of IC3. Adjust the control voltage (pin 5) of the timer, IC2, via trimpot VR1 to get a frequency of 5.4Hz (see Table 1). If adjusting trimpot VR1 cannot bring the frequency to 5.4Hz, you need to add another capacitor in parallel with C1 & C2 (at position C3) to slow it down, or reduce the value of C1 and/or C2 to speed it up. Once this frequency is correct, set the tempo to 216 beats/min and adjust trimpot VR3 to get 32.4Hz. If VR3 cannot bring the frequency to 32.4Hz, change the value of its 18kW series resistor, then repeat the adjustments for the slowest and fastest tempos. Finally, adjust trimpot VR4 to the desired difference in brightness between the two end LEDs and the middle LEDs. Click timbre and loudness can also be modified for the 10-LED version. Adjust the value of resistor R1 for a smooth variation in loudness, as described for the 8-LED version. To change the timbre of the click, experiment with the combined value of C4-6. A larger capacitance should produce a more mellow click. The speaker can also affect the tone, so try the speaker in both polarities if you aren’t satisfied with the initial result. Troubleshooting If the Metronome is not working, check the orientation of IC2 and associated parts. Also, check that the IC pins are all inserted correctly; they sometimes get bent and don’t go into the socket or PCB. Check if there is a pulse at pin 3 of IC2 and pin 15 of IC3. If the LED sequence is only in one direction, it is likely that the SR-FF is not working or not receiving the S and R pulses from IC4. Operation A set-reset flip-flop (SR-FF) made from two NOR gates. The Q and Q outputs always have opposite polarity; Q is brought high when the S input goes high, while Q goes low when the R input goes high. Both inputs must not be high at the same time. Australia's electronics magazine The operation of either version is straightforward. Turn the Metronome on and adjust the Click Loudness, LED Brightness and Tempo as desired. The supply current for the 8-LED Metronome is about 2-4mA, depending on the LED brightness, click loudness and tempo. AAA cells typically are rated at about 900mAh. Thus, assuming it is used for about half an hour a day, alkaline or rechargeable cells should power the 8-LED version for about a month. SC siliconchip.com.au Dick Smith’s Autobiography Review by Nicholas Vinen M y Adventurous Life T he saying “truth is stranger than fiction” is a cliché. But say you submitted Dick Smith’s autobiography to an overseas publisher who had never heard of him and claimed it is an adventure novel. I think they would reject it as being too unrealistic! A man who dropped out of high school at 16, became a successful businessman and flew helicopters and planes in record-breaking around-the-world flights? Then he set up a flourishing publishing company with an Australiawide network of shops, plus another business selling food, while giving away a significant chunk of his money to charitable causes? Preposterous! Come back with a more believable story. A life full of such exploits makes for exciting reading, and I found myself wanting to go back for more each time I had to put it down. It helps that the book is well-written and easy to read. It includes two maps of Mr Smith’s adventures and several dozen colour photographs which provide some important context for his words. One of the things that struck me about this book is that Dick Smith’s character really comes through. I can’t pretend to know the man all that well, but he has told me some of the stories in the book and reading the book gives much the same experience. Despite this, he credits three different writers and one editor at the end. It shows how much effort they all put in that the final result maintains so much of his personality. This book is not just for electronics nuts. The story of Dick Smith Electronics (DSE) takes up only a fairly small portion of the book. I would have liked more detail in that area, but I think I would be in the minority of readers. Saving more pages for the adventures is the right move for the book to have general appeal. And I think he has succeeded in that respect. It will be a great read for just about anyone who has heard of Dick Smith, and I reckon that’d be most Australians. I will be passing this copy on to my sister (definitely not an electronics nut, but loves nature) and my father (a doctor; I’m sure he will love the story-telling and historical aspects). I got into electronics by reading the Fun Way Into Electronics books (with Dick’s face emblazoned on the covers). So I was primarily curious about how DSE became so successful and why Dick sold the business to Woolworths, when he was clearly making a lot of money out of it. The book answered my questions, but I ended up enjoying many other aspects I hadn’t anticipated. I knew that he is really into flying and went on some famous adventures, but I didn’t realise the scope of his achievements until I’d finished reading the book. He had some close calls, and you can feel his pride in what he achieved coming through the pages (it doesn’t seem too boastful, although he drops plenty of names). siliconchip.com.au DICK SMITH ‘Part Bear Grylls, part Bill Gates, but 100% Aussie larrikin. Dick is a great innovator, philanthropist and adventurer, who in my eyes can do no wrong.’ PAUL HOGAN I understand now why he has dedicated so much of his autobiography to his adventures. This book is an excellent read for young or old; teenagers and young adults will not only find his adventures fascinating, but I think they will learn a great deal about what Australia was like in the past. It also has some fantastic lessons about how to be successful in life, have strong morals and live life to its fullest. Older readers will no doubt enjoy Dick’s recollections of Australia of the past. It feels like another world, reading about what life in Australia was like in the 50s, 60s, 70s and 80s. It was a pity that I could not write this review in time to make the December issue, as this book would be a great Christmas gift. If someone you know has a birthday coming up and you have no idea what to get them, this book would be a good choice due to its broad appeal and reasonable cost. A quick search finds many shops selling the hardcover version for well under $30. Dick Smith – My Adventurous Life (352 pages) is published by Allen & Unwin and is available from book stores, major retailers and as an ebook online. The hardcover RRP is $39.95, while the ebook has an RRP of $29.08. SC Australia's electronics magazine January 2022  37 Solar PV Update Are batteries worthwhile? By Dr Alan R. Wilson Image source: https://pixabay.com/photos/solar-system-roof-power-generation-2939551/ I have had a solar panel array installed for over 10 years now, and I have a pretty good set of data on how it has performed over those years. As I suspect the generous feed-in tariff will go away soon, I have been considering whether it would be worth adding a battery to the system and, if so, what type and how large. This article describes how my system has performed and the research I have undertaken. I wrote an article detailing my experience with an urban 5kW solar photovoltaic (PV) installation (May 2015; siliconchip.com.au/Article/8555). My array consists of 27 panels mounted on a north-facing roof with a 5.2kW inverter. With the system now around 10 years old, it is an excellent time to revisit the situation and consider adding batteries to the installation. To date, the system has performed flawlessly. A contributing factor might be the shade panel I constructed to shield the inverter from direct sun, mounted on a north-facing wall. One problem that I spotted late in 2019 was the growth of lichen on my solar panels. I caught it early enough because I could remove it using a long pole, a scraper and soapy water. Lichen can be a big problem, and there is a fair amount of ‘chatter’ on the internet about it. Here’s an example of lichen beginning to form on a solar panel. You can find more extreme examples online. 38 Silicon Chip It is critical to ensure algae does not grow on the panels because lichen is a symbiotic partnership of a fungus and an algae; any hint of green on PV panels and it is time to clean it off. The overall performance for the last 10 years is shown in Fig.1, including the daily (averaged) exported and imported energy. Clearly, more energy is exported than imported. There are two points, indicated by the black markers, where the crossover for these curves drops when circumstances changed, and the system started to export more energy. These correspond to when I installed an evacuated tube solar hot water system (1) and when one of my adult children left the house (2). Until a couple of years ago, I was not recording the amount of energy provided by the solar panels themselves. Doing so gives a greater insight into the pros and cons of Solar PVs, and this data can be used to determine whether batteries are a good option or not. Fig.2 shows the solar PV energy generated, the energy used by the household (both of these with a cosine curve fitted to them, see below), and the excess energy which is available for use by the grid, again presented as daily usage. The household uses about 11kWh a day in summer and 18kWh in winter. My house has neither electric heating nor cooling but does have an off-peak electric storage hot water system. Taking one year within this span, the system generates 6661kWh, with 5028kWh used, giving a net yearly excess of 1633kWh. Australia's electronics magazine siliconchip.com.au However, since much of the consumption is overnight, the actual yearly exported energy is 5105kWh with 3471kWh imported. This is currently a good position for me because I am the lucky recipient of the Victorian Government Premium Feed In Tariff which is significantly higher than my usage tariff. My electricity provider (and the taxpayer) pay me rather than me being faced with a yearly bill of $1609 (5028kWh at 32¢/kWh) if I did not have solar panels. This will change in the not-too-distant future, and the question is whether it is worthwhile to install batteries and a new inverter/charger. A bonus would be the capability of independent operation as insulation against power drop-outs, particularly in summer. However, how the house would be disconnected from the grid to allow this is an open question. Rather than diving directly into consideration of a solar PV + battery system, first I will assess the performance of my current PV system, followed by an analysis of commercially available batteries. Comparison with expected performance The Bureau of Meteorology provides a large amount of public data related to many aspects of the climate, including monthly measured kWh/m2 insolation values – see www. bom.gov.au/climate/data/index.shtml?bookmark=203 For December 2019 and June 2020, these values were 6.8kWh/m2 and 2.1kWh/m2 respectively (be careful to select the correct units when looking at the website). My PV array produced an average of 26kWh and 11kWh per day during these two months. With an area of approximately 28m2, this equates to conversion efficiencies of 14% and 19% for December and June respectively. The figure for December looks low, but it is a good demonstration of two effects: 1) the sun passes behind the solar panels, and 2) they run hotter and are less efficient in summer. My north-facing panels can only receive sunlight for at most 12 hours a day, but the sun is up from 5:55am to 8:42pm on December 22, nearly 15 hours (see www. timeanddate.com/sun/australia/melbourne). Considering Fig.3, sunlight before 6am and after 6pm contributes little to the energy received. More important is that the panels run hotter in summer. An increase in temperature from 20°C to 80°C can decrease performance by up to 30%, and 19 less 30% is about 13, as observed. The next parameter I considered was panel placement. Melbourne is 37.8° South, and my roof has a slope from the horizontal of about 32° North. This gives an incident angle to the sun of about 17.6° mid-summer and 29.2° mid-winter (the tropics are at 23.4°). The question is: should the panels be aimed more at the winter sun to gather more energy when it is needed? Fig.4 was obtained at midday a few days before the winter solstice in 2019 for a clear, cloudless sky and a more typical overcast day with around 80% cloud cover and the sun covered. The figure shows the percentage drop from the maximum power received by a small solar cell mounted under glass as a function of the angle with the northern horizon. Here, panels on a flat roof correspond to 0°. The clear day maximum power occurs at 58°. This is very close to aiming directly at the sun (37.8° + 23.4° = 61.2°), as expected. 20° either side of this point (38-78°) decreases siliconchip.com.au Fig.1: the energy I imported (blue) and exported (red) over the last 10 years. The two black triangles indicate the points when circumstances reduced the household’s energy usage. Fig.2: the energy generated by the 5kW PV array, the energy used by the household and the excess energy available for the grid over a 14-month period. The thin curves are fitted cosine functions used for my later modelling. Day d=0 is July 1. Fig.3: the relative strength of the incoming solar radiant power collected by flat PV panels as a function of time of day, at the start of summer (from www.eia.gov/ todayinenergy/detail.php?id=18871). Australia's electronics magazine January 2022  39 Fig.4: the percentage drop from the maximum solar energy detected by a small solar cell as a function of angle (0° corresponding to facing straight up) close to mid-winter for a clear day (blue triangles) and during an overcast day (grey triangles). Fig.5: the results from a simple model based on realworld experience for a 5kW PV array, showing the energy generated, day and night power usage, the energy stored (thin lines) and passing through (dotted lines) a 5kWh, 10kWh and 15kWh battery, and the energy exported and imported. the power by less than 2%. However, on an overcast day, peak power is at 38°. As the tilt angle increases, the solar cell sees less of the sky. The clouds scatter a large proportion of the incoming energy on an overcast day, so less of this is collected as the angle increases. 20° either side of 38° decreases the power by 10% in this case. The two sets of points suggest the optimum mounting angle is somewhere in the range 30-43°. This angle improves collection on overcast days but has a minimal effect when there is little cloud cover, being within the 38-78° range for a clear day. Fig.4 gives an idea of how this will affect the operation in summer. A panel angle of 30° maps to 76.8° in Fig.4 for a clear sky in summer, resulting in less than a 2% decrease in power. The figure implies it is best to keep the effective summer angle to less than 80°, suggesting that the ideal angle to mount panels facing North is 30-34° (80° - 46.8°). My panels are at 32°, so I do not need to do anything. Remember, this is for Melbourne. Further North, I expect the ideal angle to be lower, with 0° best at the equator. Thus Brisbane at 27.5° South would have an ideal panel angle of around 22-25°. The thin red line in Fig.2 is a good-looking cosine curve fit to the energy generated: 18.24kWh + 6.79kWh cos(π + 2π × [d + 15] ÷ 365) where d is days from July 1, and the peak occurs on December 16. We can use the same approach to give another fit to the energy used: 13.98kWh + 2.73kWh cos(2π × [d + 4] ÷ 365), with the peak occurring on June 27. Determining the total energy used is only half the solution; it must be split into day and night contributions to assess the flow to/from a battery. Unfortunately, my situation is complicated by the solar evacuated tube hot water system. In summer it uses no electricity, while in winter it uses off-peak electricity at night. It is preferable to divert the day-generated power into the hot water system before charging the batteries. To include this in the model requires an estimate of the energy used by the hot water system. My summer drop in consumption after the installation of the solar hot water system is 4.8kWh. But I decreased the water temperature by 10°C, which in a 250L tank corresponds to 0.7kWh, reducing this to 4.1kWh. Ignoring the slight offset between the energy generated and energy used, this leaves 12.6kWh (16.7kWh less 4.1kWh) used in winter compared to the 11.3kWh minimum use mid-summer. In Melbourne there are 9.5 hours of daylight mid-winter and 14.5 mid-summer. After removing the contribution by the hot water heating, the simplest thing to do is apportion the energy use according to the number of daylight hours. Yes, lights are on at night and not during the day, you might object. However, people sleep at night and use other electrical devices during the day. I am assuming these roughly balance. Table 1 shows the expected peak and trough (mid-winter and mid-summer) energy consumption figures after allowing for the number of daylight hours and shifting hot water heating to the daytime in winter. Because the model is a simple sinusoidal wave with a constant offset and known period and phase, the maximum and minimum are all that is required to determine the waveform. The estimates in Table 1 give: Are batteries worthwhile? When I lose my Premium Feed In Tariff, I am considering adding batteries to the system. With a battery, I could store energy during the day and use it at night, rather than exporting it during the day and importing it at night. But will that be worthwhile? The model I developed to analyse the financial aspect is based on real-world experience and can determine the optimal battery for a solar PV array. To do this, we need to determine how much energy is generated, how much is used when the sun is up, how much is drawn overnight from the battery and how much is imported and exported. A simplistic model for energy usage over the year is to assume it is due to the variation of daylight hours, and use a cosine function with a winter maximum and a summer minimum. 40 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.6: the modelled yearly operational income (negative is a cost) versus battery capacity for 1.5kW, 3kW, 5kW and 8kW PV arrays (red lines), and a 6kWh battery against PV size (blue line, same horizontal axis). It is clear that large batteries do not pay for themselves, but more PV panels do. The 0kWh point corresponds to PVs with no battery. Fig.7: a similar graph to Fig.6 but with air conditioner (A/C) and heating loads included for 5kW and 8kW PV arrays. As expected, due to the greater energy use, the yearly income decreases. The useful battery capacity also increases due to the larger throughput. Night use = 6.0kWh + 1.6kWh cos(2π × [d + 4] ÷ 365) Day use = 7.95kWh + 1.15kWh cos(2π × [d + 4] ÷ 365) Again, d is days from July 1. The power available to be stored in the battery is the PV energy less the day use, plus any not used the previous day, but only up to the battery’s capacity, the rest being exported to the power grid. The power used overnight is simply the night use figure. This is most easily calculated using the above expressions in a spreadsheet. We can also use the spreadsheet to determine the yearly kWh throughput for the battery, the amount of energy imported and exported and thus the annual cost of operating the system. This spreadsheet will be available to download from: https://alanrwilson.com/solar-batteries/ As a reality check of the model, the predicted total solar PV energy generated is 6658kWh, within 1% of the measured 6661kWh, and the total night + day consumption is 5092kWh, within 1.5% of the measured 5027kWh. Fig.5 is an example for a 5kW PV system using the models above. While it looks complicated, it encapsulates the results from the model and gives some immediate insight into the effect of battery capacity. The determined charge at the end of each day (Battery Charge) and Battery Throughput for 5, 10 and 15kWh batteries show that all the charge is used in winter due to the low PV energy available, irrespective of battery capacity. The energy Exported and Imported is only shown for the 10kWh battery; however, the graphs for all battery capacities are essentially the same, with a decrease in the total annual values of 147kWh exported and 127kWh imported moving from the 5kWh to the 15kWh battery. The amount of PV energy available is the governing factor, not the size of the battery. The only advantage of a bigger battery is for energy storage in case of blackouts. For my situation with a 5kW PV array, this suggests that the optimum battery size, including some latitude for estimation errors and a decrease in capacity, is about 7kWh. That’s assuming such a battery can deliver the power required. The ongoing operating costs can be calculated from the imported and exported energy figures. Fig.6 shows how the modelled yearly operational income (negative is a cost) varies with battery capacity for 1.5, 3, 5 and 8kW PV arrays. These are calculated with a feed-in tariff of 12¢ and a usage tariff of 32¢. Clearly, large batteries will not pay for themselves, but larger PV arrays do. Any battery larger than where the curves flatten out is not a good financial investment. It is also apparent that batteries are not helpful with a small PV installation: there is simply not enough energy to store. The variation in cost to operate a 6kWh battery with PV size is also shown (in blue) and more dramatically demonstrates the significant increase in income with a bigger PV array. Essentially, all the extra capacity of the larger PV array is generating more revenue in summer. This is for my situation and does not include heating or cooling, which is common in many houses. The spreadsheet can be modified to include both these cases, modelled as a half-sinewave with a start date and end date (zero to zero). Fig.7 is like Fig.6 but includes a hypothetical 3kW air conditioner, operating (cooling) for a peak of 0.6 hours during the day, 1.4 hours at night, from November 1 to April 1, using a total of 580kWh and 1590kWh of heating using a 3kW heat pump for one hour during the day and 2.9 hours at night, from April 1 to October 30. These figures are based on Law et al., “Energy consumption of 100 Australian residential air conditioners”, Ecolibrium November 2014. What has not been included is siliconchip.com.au Table 1 – estimates of energy used to split between day and night Winter peak (12.6kWh total) Summer trough (11.3kWh total) Day Night Day Night Portion of use 5.0kWh 7.6kWh 6.8kWh 4.5kWh Hot water +4.1kWh Total 9.1kWh 7.6kWh 6.8kWh 4.4kWh Energy used Australia's electronics magazine January 2022  41 the possible impact of limited power delivery by the battery, which would result in higher Imported energy costs. As expected, the operating costs increase, but it again is apparent that the size of the PV array is the most critical factor. With the extra energy throughput, the point at which any increased battery capacity has no effect is moved a little to the right. All of the operating costs above are well below the $1629 (my house) or $2324 (with heating and cooling) figures for PV or batteries at 32¢/kWh, and some even generate income. But what is missing is the up-front cost. Most systems on the market have a 10-year warranty. $25,000 spent on a system that fails after 10 years effectively costs $2500 a year just to cover the purchase price (ignoring opportunity costs associated with not having that $25,000). If the system does not generate a positive return, it will be more expensive than simply pulling power off the grid. The following sections consider a range of battery technologies, their pros and cons, how much they cost and whether they will pay for themselves. Battery choices Lithium-ion based batteries currently dominate the solar/ renewable energy market; however, one of their claims to fame (lightness) is not a consideration for static installations. Still, a quick survey of commercially available batteries offered for solar PV installations yielded 36 lithium-ion, one graphene super capacitor solution, one flow battery and one lead crystal battery. The faithful lead-acid battery is not considered in the race, primarily due to a low cycle lifetime. Nickel-iron batteries are another old and proven technology. They are robust and long-lived, but I will not consider them because they suffer from a number of disadvantages, including the evolution of hydrogen gas, low efficiency, low charge/discharge rates and a wide operating voltage needing special inverters. Irrespective of the type of battery, the parameters I consider important are: 1. It needs to have sufficient capacity for the requirement. This is rather obvious but beware, usable storage can be significantly less than nominal storage, and overdischarging a battery can significantly impact its useful life. The results in Figs.6 & 7 must also be kept in mind to not needlessly over-specify the battery capacity. A bank of A602 2V gel cells which is used to store energy from a 4kW solar array. Source: www.flickr.com/photos/ stephanridgway/14141342129 42 Silicon Chip 2. Many batteries suffer from a drop of capacity with use. Some warranties are for 10 years but at 60% of the original capacity. Other manufacturers using the same base technology make no upfront mention of reduced capacity. It is worth checking the fine print in the specifications; it might be that the initial battery capacity must be over-specified to ensure it is fulfilling the requirements at end-of-life. 3. The ability to deliver the power you need. High capacity does not necessarily mean the battery can deliver enough power. An 8kWh battery is not as useful if it can deliver at most 3kW and the household needs 6kW peak to run, say, an air conditioner (3kW) and cook dinner (3kW) at the same time. However, if peak powers are transient, it is worthwhile pulling power from the grid for a short time rather than installing a big, expensive battery. Off-grid use requires a big battery and/or a really smart energy management system that prioritises certain circuits and/or a lifestyle change. A small petrol or diesel-powered generator is not very expensive and could be a solution in these cases, if low available solar energy is a transient or rare event. 4. Warranted life: do not accept a battery with less than a 10-year warranty. This is really warranting the construction quality, the ‘nuts and bolts’, not the storage elements. 5. Warranted throughput: the lifetime warranty is usually expressed as a time or maximum kWh throughput with some capacity drop at the warranted kWh. Warranted throughput indicates the amount of energy the battery can store and deliver; it is directly linked with the gradual degradation of the chemistry/physics of the storage system. The yearly battery use needs to be determined to give the expected 10-year kWh input/output required from the battery. Ideally, the 10 years and the maximum kWh occur at much the same time. With ‘normal’ use, most modern batteries will have enough throughput to last 10 years. 6. Round-trip efficiency: this is an indication of the efficiency of energy storage and retrieval. Lithium batteries are generally in the 95-97% range. Some others are as low as 80%, which means more solar panels are required to compensate for the lost energy, but they may have other beneficial properties. 7. Off-grid capability: if you want it. Standalone batteries can be used anywhere, but some batteries come with integrated inverters and/or chargers, affecting how they can be used. 8. Compatibility: batteries and any associated parts of the system included with them must be compatible with the other elements of the system. One area to watch for is the different solar PV panels available. Some (which used to be the norm) are an array of solar cells connected in series string(s) to provide a high DC voltage. Others, which have some advantages, include micro-inverters that manage the power from each individual solar panel and generate the AC at the PV panel itself. These are all connected in parallel and provide a (nominal) 230V AC. Australia's electronics magazine siliconchip.com.au Table 2 – comparison of four battery types suitable for solar PV storage Lithium-ion, NMC (Nickel Manganese Cobalt) Lithium, LFP (Iron Phosphate, LiFePO4) Flow cell (FC) Super capacitor hybrid battery (SC) Robustness Fair Good Excellent Very Good End-of-life Capacity 60% 80% 100% 85% 27-32MWh 32-36MWh 36MWh 36-45MWh Round trip efficiency ~95% ~95% 80% >96% Available power per 10kWh 4-6kW 4-9kW 3kW (5kW peak) 13kW (33kW peak) Maintenance Requirement None None Needs period full discharge. None $8-10k $8-10k $13k $12k Energy density (lower weight). Cycle life. End life capacity. More Robust than NMC. Very robust. Full discharge. No drop in capacity. Very robust. Full discharge. No drop in capacity. (Projected long life) Large capacity drop over life. Medium capacity drop over life. Low efficiency. Low power. Mechanical pumps. Liquids. Maintenance. New technology. Warranted Life: throughput per 10kWh Cost per 10kWh Advantages Disadvantages Table 2 has details for two leading lithium-ion battery technologies and two other more novel technologies. Some of the figures presented have been factored up or down from quoted values to compare hypothetical 10kWh batteries. The cost is for a bare battery, and with the fluctuations in exchange rates and the rapid progress being made, these could very well be wrong by the time this article is published. The two common lithium battery technologies are very similar. Both technologies suffer from a gradual drop in storage capacity, with the LiFePO4 outperforming the NMC type. LiFePO4 also has higher lifetime energy storage, may deliver higher power, is a little more robust (especially if heavily discharged) and is considered safer. Both batteries may have prolonged life by reduced discharge, say to 50%, but then a larger capacity battery is needed to ensure sufficient energy is available for the requirement. They both offer good power delivery but could be challenged in an all-electric house over summer with air conditioning. They are reasonably mature technologies with a lower price than the other two. Flow cell (FC) technology is effectively like reversible electroplating. For instance, zinc-bromide systems plate out zinc in a reversible process. The FC battery is very robust, can be discharged entirely and holds its full capacity through life. Unfortunately, the round trip efficiency is only about 80% (10kWh is required for 8kWh to be later supplied), and FC has a more complex maintenance regime requiring a regular full discharge. Along with a low available power and higher cost than lithium-ion batteries, it is probably not suited for domestic energy storage. Super capacitor (SC) hybrid battery technology is much more interesting with a very high available power and high efficiency. It is like a hybrid between a super capacitor and siliconchip.com.au a lithium battery. Not shown in the table is the high charge rates that are possible. Like the FC battery, it is very robust, can be completely discharged and holds most of its capacity through life. Performance curves suggest 98% after 10 years; however, the warranty still only guarantees 85% capacity. It can also provide enough power for pretty much any domestic use. The only downside is that it is a relatively new technology. Still, I will keep my eye on it over the coming years (especially since the company involved is based in Melbourne). While more expensive than lithium-ion batteries, the projected life, as opposed to warranted life, is well beyond the 10-year warranty, which could make it cheaper in the long term. The other costs besides the batteries and solar panels are the inverter/chargers. Inverter/chargers usually include a battery management system and load management, making them more expensive than a grid-tied inverter. For comparison, I am allocating these a cost of $2000/kW. I decided to investigate 5kW and 8kW PV arrays and batteries with two primary requirements: 1. At end-of-life (ten years), they must be able to deliver 5kW. The minimum capacity to achieve this is 10kWh for NMC, 7.7kWh for LFP and 3.8kWh for SC, 3.8kWh. The NMC and LFP have a quoted spread of values, so I used the means. 2. The optimum capacities indicated in Fig.6 for my application, 4kWh for 5kW PV and 6kWh for 8kW PVs. Based on Fig.7, 7.5kWh must be available at the endof-life for either a 5kW or 8kW system for the inclusion of both air conditioning and heating. Combined with the first requirement and the capacity drops specified in Table 2, the relevant batteries for my theoretical situations are shown in Table 3. Australia's electronics magazine January 2022  43 Fig.8 shows the 10-year cost for the 5kW PV array, while Fig.9 is for the 8kW array. The cost with time is simply calculated as (up-front cost) + (operating cost) × years. The results are simple straight lines; however, a visual representation of the slopes and intersections gives a quicker comparative insight than numbers in tables. Both figures include the ongoing cost with No PV and the relevant PV arrays with no battery. The systems are priced at $1500/kW in the no-battery case due to the cheaper inverter required. It is clear from both figures that the most cost-effective course for the first 10 years is to not use batteries due to their high up-front cost. Both figures also clearly indicate that the payback rate is mainly independent of the battery capacity, with the average cost over time highly dependent on the up-front cost of the system and the size of the PV array. Both figures indicate that the PV arrays without a battery system pay for themselves after ~5-6 years. The batteryinclusive systems would eventually return more than the no-battery systems; however, this takes at least another 16 years in the best case, well outside warranty periods. While the 8kW PV array with no battery takes longer to pay for itself than the 5kW PV array, it pays back more, becoming superior to the 5kW PV array after about nine years. Given that the panels should last 20 years, it is better to install the higher capacity in the long run. In both cases, the payback is earlier with the higher consumption cooling and heating case simply because more energy is being used. If heating and cooling are included, the 5kW array can never generate income, whereas the 8kW array can. Throughput All of the above considers the 10 years life rather than throughput. The modelled 10-year throughput for the NMC, LFP and SC batteries are all much the same at 18MWh for the 5kW array and 28MWh for the 8kW array. These are likely to be on the low side since it does not consider times Fig.8: modelled total cost for a 5kW PV array in my situation (solid lines) and with cooling and heating included (dashed lines) with the NMC, LFP and SC battery capacity as indicated. The No PV and No Battery cases are included to show payback times. A negative slope indicates income. 44 Silicon Chip Table 3 – minimum battery capacities for two PV arrays with and without heating/cooling 5kW, no AC 5kW, with AC 8kW, no AC 8kW, with AC NMC 10kWh 12.5kWh 10kWh 12.5kWh LFP 7.7kWh 9.4kWh 7.7kWh 9.4kWh SC 4.7kWh 8.8kWh 7.0kWh 8.8kWh when the PVs become shaded during the day and will provide power from the battery. However, even allowing for a 33% increase to 24MWh and 37MWh, all of the batteries should be able to provide this, although 37MWh exceeds the NMC specification and is close to the LFP specification. If throughput is the critical ageing parameter then, provided the other mechanical and electrical systems do not fail, the lithium batteries for a 5kW PV array could have another five years or so of useful life left, and the SC around seven years. This increases the cost-effectiveness of the systems and making them all a sound financial proposition. For a 10kWh battery, the effect of a battery on imported and exported energy is shown in Fig.10. The squares are the results from my 5kW Solar PV with no battery. Doubling the size of the battery is not helpful, as shown before, and decreases the imported and exported energy by a miserly 10kWh. Power grid stability One of the complaints against solar PV is the wild fluctuations in available energy that can occur when the sun is, for instance, suddenly shaded by clouds. A smart energy management system could be implemented whereby stored battery energy is available to smooth out these fluctuations. This is the essence of the Virtual Power Plant concept, and there are some companies already doing this and making profits by feeding battery stored energy into the grid when the spot price is high. The Australian Capital Territory is Fig.9: model results similar to Fig.8 but for an 8kW PV array. Australia's electronics magazine siliconchip.com.au An example of a solar panel setup, the smaller panel along the wall is for a solar hot water pump. planning to implement this strategy in a distributed network of battery storage in the Territory. Going off-grid If the desire is to go off-grid then no energy can be imported. With everything electrical, the model for my situation indicates a 16kWh battery is required to cover the nightly use, with a 13kW PV array to fully charge it in mid-winter. Using the SC battery, this will cost around $45,000. That sounds like a lot, but it might not be too bad if you have to pay $20,000-30,000 to have power cables laid to a remote location and then have to pay for the connection costs and electricity. The combination of battery and PV array assumes there is always average sunshine and does not allow for cloudy days. The problem is the daily use is 28kWh; it rapidly becomes very expensive trying to install enough batteries to cover the occasional 2-3 day overcast period. A more cost-effective method is to use a small generator. Fig.10: imported and exported energy values from the model calculated with 3kW, 5kW and 8kW PV arrays and a 10kWh battery. The black and red squares are the real-world results from my 5kW system with no battery. A 3.8kW PV array is enough to generate all the power for the household over a year; the problem is moving the excess energy from summer to winter. siliconchip.com.au These are reasonably cheap (3.5kW for around $500) and can be run long enough to charge the battery when needed. But personally, I do not like this option in an urban setting. Conclusions Investing in Solar PV by itself is definitely worthwhile, with a suggested payback time of fewer than six years for the 5kW, north-facing installation considered here. From a purely financial point of view, batteries are still too expensive, except possibly for the newer SC batteries with their potentially longer life and their high power-to-capacity ratio allowing the use of a smaller, cheaper battery. But adding batteries does reduce the dependence on grid power and, with the right management systems, should help reduce power supply fluctuations from renewable energy. This is something which will need to be considered in the future. A network with a large number of (highly variable) solar PV-only generators that simply attempt to deliver as much power as possible to the grid will become unstable. The model shows that increasing the allowed household installation of solar PV to 8kW with a suitable battery backing it up can bring a house in Melbourne close to self-sufficiency. The situation will be even better closer to the equator. Keep in mind that some batteries have failed Australian tests, and some companies have failed too, and are not around to honour warranties. Doing business with mainstream companies and suppliers in this relatively new market is probably advisable. Choosing a great-sounding, cheap deal could very well leave you with expensive boxes that do not function. So what battery would I recommend? From a purely financial point of view, none at all. However, there might be other reasons for installing a battery. If you must have a battery and are on the conservative side, go for the LiFePO4 option from a reputable source, but be aware that the power requirement may be the governing factor. If you are more of a betting person, look very seriously at the ‘super capacitor’ option with its ability to deliver high power with a relatively low capacity. There is also the hope the SC technology will live up to its promise of a superior lifetime. And overall, keep the information in Figs.6 & 7 in mind; big batteries are definitely not worth it unless you are going off-grid. SC Australia's electronics magazine January 2022  45 Protects up to six amplifier modules (six single-ended or three bridged outputs) Very simple, small in size and low in cost Can operate from the same power supply as the amplifiers (up to ±40V DC) Disconnects the speaker(s) in 100ms for full rail DC fault <at> 30V Provides a 1-2 second turn-on delay, allowing amplifier outputs to settle Insensitive to low-frequency AC signals Uses DPDT relays with contacts rated to break 10A <at> 28V DC (repetitive) Multi-Channel Speaker Protector If you’re driving a lot of speakers, you will need a matching compact speaker protector to prevent driver destruction, should something go wrong! Our Speaker Protector, when combined with our Hummingbird Amplifier module (published last month), is excellent when driving stereo loudspeakers with an active crossover or for surround sound systems where you have many speakers to drive. A re your expensive speaker drivers protected if the worst happens, and an amplifier module failure results in them having direct current applied? This very simple and effective board matches our Hummingbird amplifier modules, protecting between one and six channels with a switch-on delay in a PCB measuring just 67 x 120mm for up to six channels, or 67 x 91mm for the four-channel version. Over a few years of building hifi and PA equipment, it would be fair to say that this author has not destroyed that many speaker drivers. But when I have, it has always been expensive, painful and inconvenient. The experience of watching a 60W amplifier deliver 40V DC to the voice coil of a very expensive driver that represented months of savings is burnt in my memory. This was a 250W driver but it was no match for 40V DC! In a matter of seconds, the voice coil turned into smoke, much faster than a human being could turn the power off—all for the sake of a $1 insulator. 46 Silicon Chip There have been two main destructors of my drivers: 1. Over-excursion of drivers, particularly in vented enclosures below resonance without appropriate subsonic filtering. This is a surefire way of killing a bass driver. That was addressed by the Active Crossover presented in the October & November 2021 issues (siliconchip.com.au/Series/371), which includes a subsonic filter. 2. By DC from the output of an amplifier, either due to a failure in the amplifier or finger trouble by the builder. (Have you ever left a fuse out or forgotten to connect a wire?) This project solves #2. You might ask: what about over-­ powering a speaker? Won’t it blow up that way too? In my experience, that takes a heroic effort if your crossover is set up correctly, so we leave the volume control to your discretion. By Phil Prosser Australia's electronics magazine The impetus Building an Active Crossover combined with six Hummingbird amplifier modules, I found myself running out of room. To fit this lot with power supplies into a 330mm-deep 2RU case, I had to move from beer mat sketches to CAD and ‘the computer said’ that I needed to make the speaker protector small. So I did. This device will protect your speaker from most amplifier failures. The modest investment will pay itself off the first time it activates, but we all hope this is one project that you never see ‘work’. There are many ways of approaching a speaker protector. This design aims to keep it simple and small by keeping the parts list to a minimum. Circuit details The circuit used is straightforward, as shown in Fig.1, with three duplicated stereo sections providing the six protection channels. The main part of the Protector siliconchip.com.au Fig.1: the Speaker Protector has three identical sub-circuits handling two channels each. Each input signal passes through a simple RC lowpass filter and is applied to three transistors. If a large DC voltage is detected, those transistors switch off the associated DPDT relay, disconnecting the speaker from the amplifier. A basic linear power supply provides around 24V to drive the relay coils and incorporates a switchon delay of around one second, to avoid thumps. circuit is elegant, but it might not be obvious how it works at first glance. Its first job is to detect the presence of DC at an amplifier output, connected to one of the AMP x OUT terminals at right. This is done by the 100kW input resistor and 47μF bipolar capacitor, which form an RC low-pass filter with a -3dB point (corner frequency) of 0.25Hz. The output of this filter feeds a DC detector that triggers at the Vbe voltage of a transistor, around 0.6V. So for regular operation, the amplifier must generate less than 0.6V at the output of this filter. Choosing 10Hz as a ‘safe’ low frequency limit and assuming an amplifier that can deliver 100W into 4W, we can calculate that only 135mV would appear on the output of the filter. So it won’t trigger during regular amplifier use. But say an amplifier goes faulty and delivers its rail voltage of 40V DC (of either polarity) to the output instead of an AC waveform. In that case, after 100ms (0.1s), the low-pass filter output will reach 0.84V, which will definitely trigger the DC detection circuit that follows. This filter operates identically for both positive and negative voltages. With 40V across 8W for 100ms, 20J of energy will be delivered to the voice coil (the impedance will drop over time, approaching its DC resistance value, but this is a good enough siliconchip.com.au Australia's electronics magazine January 2022  47 Parts List – Multi-Channel Speaker Protector 1 double-sided plated-through PCB coded 01101221, 67 x 121.5mm 3 (2) 30V DC 10A contact, 24V DC coil DPDT PCB-mount/cradle relays (RLY1-RLY3) [Altronics S4313, Jaycar SY4007] 8 (6) 2-way 5.08mm pitch mini terminal blocks (CON1-CON8) 1 44mm-tall, 16.5 x 10mm PCB-mount finned heatsink (HS1; for Q16) [Altronics H0645] 1 TO-126 or TO-220 silicone insulating washer and insulating bush [Altronics H7230, Jaycar HP1176] 1 M3 x 10mm panhead machine screw 1 M3 shakeproof washer 1 M3 hex nut 4 tapped spacers & 8 machine screws (to suit installation) Semiconductors 16 (11) BC547B/C 50V 100mA NPN transistors, TO-92 (Q1-Q3, Q5, Q6, Q8-Q10, Q12, Q13, Q15, Q17-Q19, Q21, Q22) 6 (4) BC557B/C 50V 100mA PNP transistors, TO-92 [BC558-9B/C will also work] (Q4, Q7, Q11, Q14, Q20, Q23) 1 BD139 80V 1.5A NPN transistor, TO-126 (Q16) 1 27V 1W zener diode (ZD1) [1N4750] 3 (2) 1N4004 400V 1A diodes (D1-D3) Capacitors 6 (4) 47μF bipolar/non-polarised electrolytic [Jaycar RY6820] 3 47μF 50V electrolytic [Altronics R4807 or Jaycar RE6344] Resistors (all 1/4W 1% metal film axial) 6 (4) 33k-100kW (see text; if unsure, use 100kW) 1 47kW 3 (2) 4.7kW (n) for the four-channel version (PCB code 01101222, 67 x 91mm), the quantities required are listed in red. approximation). This will make a solid thump and probably make you jump, but it won’t cause anything to catch on fire. Even better, if the fault exists from switch-on, the speaker will simply never be connected. The DC Detector comprises a total of three transistors. For the top-most section in Fig.1, these are Q2, Q3 and Q4. Positive DC detection is handled by Q2, which has its collector tied directly to the 4.7kW load resistor. A positive voltage from the filter of more than about 0.6V will switch this transistor on and consequently pull the base of Q1, an emitter follower, low and thus turn off the relay. Q3 and Q4 detect negative voltages. NPN transistor Q3 is connected in a common-base configuration; its base is tied to ground, and its emitter is the input. A negative input voltage will pull current from 0V via the base-emitter junction, causing its collector to sink current. Because the current it sinks at the collector goes to the emitter, this current must be kept low. Hence, this tiny current is buffered by Q4, a PNP device connected as an 48 Silicon Chip emitter-follower. The emitter of Q4 connects to the same resistor as the collector of Q1. So a negative DC voltage from the filter similarly pulls the base of Q1 low, switching the relay off. There is a balance in this circuit between setting a low cut-off frequency and the minimum DC voltage at which the circuit will switch the relay off. 47μF is a reasonable maximum for the filter capacitor, so any tweaking is best done by varying the value of the input resistor(s). We chose the 100kW value to guarantee no problems with false triggering for very high power, very low frequency applications. But if you are not protecting a subwoofer, any value greater than 33kW should be fine and, as a bonus, lower values will provide faster turn-off for fault conditions. The 100kW resistors also affect the lowest DC voltage that will cause the detector to trigger. A fault in the amplifier front-end could cause a few volts DC to be present at the output, and if applied to a driver for long enough, it could overheat and be damaged. So ideally, we want to detect that Australia's electronics magazine condition too, not just a fault where it immediately pegs to one of the supply rails. Assuming a minimum transistor hFE of 120, and that the relay will switch off with 20V across the 4.7kW resistor (leaving just a few volts across the relay coil), the transistor base current must be at least 20V ÷ 4.7kW ÷ 120 = 35μA (or thereabouts) to switch the relay off. This means the DC from the amplifier must be at least 3.5V (35μA x 100kW) to trip the relay off. But this is with a worst-case hFE value. We recommend using BC547B or BC547C transistors, which have higher guaranteed hFE figures and will switch the relay off with about 1.5V DC on the input. Lowering the input resistors would reduce that trip voltage further. The DC Speaker Protector disconnects the speaker any time that DC is detected. The relays used are robust and should be able to interrupt the fault current that can be expected from a Hummingbird amplifier module or similar. However, there is the possibility that upon disconnection, the voltage and current will be high enough to form an arc between the relay contacts. The normally closed contact of the relay is used to shunt this current to ground when the speaker is disconnected. So if an arc forms and current continues to flow, the amplifier’s DC fuse for that rail will blow, and the arc will extinguish. You likely have a failed output transistor already, so a blown fuse won’t exactly be high on your list of concerns. We have put three sets of this circuitry on one board, allowing six standard amplifier channels to be monitored and protected. The relay selected has a standard pinout and is available from many suppliers. Make sure that you get the correct version, though; we are specifying 24V DC coils, though you could use 12V provided you adjust the DC regulator, and the BD139 can handle its heat load (see below). The circuit uses the power ground pin as the ground reference. This connects to the Earth of the power amplifiers being protected. Since the inputs are already paired up, this Protector would work well for DC protection in a bridged amplifier. The power supply The power supply is a basic seriespass regulator generating about 25V siliconchip.com.au DC. The relays need 24V on their coils, and this suits amplifiers with various rail voltages. It can be adapted for supplies below ±25V or above ±40V (see below). The power supply provides a turn-on delay of about one second. This is because the 47kW resistor delays the charging of the 47μF capacitor at the base of Q18. This applies to all channels protected by the board. As you increase the supply voltage, the turn-on delay decreases slightly because the capacitor will charge faster. You could compensate for that by increasing the resistor value if needed. If you have an amplifier with rails below ±25V, you have the option of swapping the relays for 12V DC coil versions and make necessary adjustments in the regulator (we expect a 15V zener would work well for ZD4). Similarly, if you have higher rail voltages, this should be fine; just watch the sizing of the heatsink. The specified Altronics H0655 heatsink should be fine for any normal rail voltage. Construction Construction is straightforward. There are two PCBs available; a six-channel version (coded 01101221, 67 x 120mm) and a four-channel version (coded 01101222, 67 x 91mm). We have described the six-channel version here; the four-channel version is identical except that one relay and its associated components are omitted, so the PCB is smaller. Refer to the appropriate overlay diagram, Fig.2 or Fig.3, during assembly. Start with the resistors and diodes. Make sure you get the diodes in the right way around. Then mount the two-way terminals for power, each input/output pair and the Earth terminal to prevent arcing in the relays (CON8). Now is time to solder in the BC5XX transistors. Try to mount them at the same height so it looks neat. Next come the capacitors. The three 47μF polarised capacitors need to be rated at 50V DC, and all go in the same way, with the longer positive leads to the pads marked +. The six 47μF bipolar/non-polarised electrolytic capacitors do not need a high voltage rating as they will never see more than 0.6V – they mount to the PCB in any orientation. Now fit the BD139 to the heatsink siliconchip.com.au Figs.2 & 3: build the smaller board to protect up to four channels, or the slightly larger board for five or six channels. Assembly is straightforward; all components are through-hole types and can be fitted in order from shortest to tallest (the latter being the relays and heatsink for Q16). The finished Speaker Protector board will look something like this. Note the holes drilled into the board under the heatsink to allow convection to pull fresh air up from underneath. The CON8 (GROUND) terminal block is missing on this prototype version; you could leave it off, but it provides better protection for the speakers if you wire it up to the amplifier Earth. Australia's electronics magazine January 2022  49 The Multi-Channel Speaker Protector comes in a six-channel (pictured) and smaller four-channel version. The four-channel version would be suited to a two-way stereo speaker system with an active crossover or a bridged stereo amplifier. using an insulating washer, 10mm M3 machine screw, locking washer and nut. Solder the heatsink to the PCB, but remember it can be hard to get enough heat into it to solder those big pins. Finally, mount the relays. The PCB has 1.5mm holes which are the minimum that this family of relay recommends – the devices from Altronics and Jaycar leave a fair bit of room in the holes. Solder them in well. Testing Now that you have all the parts mounted, it is time to test it out. During the initial tests, leave the amplifier terminals (CON1-CON6) disconnected. First apply power and check for the 25V output of the regulator The end of the closest 4.7kW resistor right near Q11 is a convenient place to probe; you can use the anode of any of diodes D1-D3 as a ground reference. The reading should be between 24V and 26V for an input above 32V DC. If this is not present or correct, check that ZD4 has about 27V across it; if not, look to the 47kW resistor and transistors Q16 & Q18. Check that these two transistors are the right types and soldered in correctly. Also check for short circuits – is the BD139 getting hot? After a second or two, the relays ought to click in. If this does not happen, check the voltage on the bases of Q1, Q8 and Q15 (the driver transistors for the relays). Are these within a volt 50 Silicon Chip or two of the 25V rail? If not, check that they are the proper devices and soldered in correctly. Check the voltage at the output of the RC filters. The voltage at both ends of the 100kW resistors (or other value you might have changed them to) should be close to 0V. If not, check that the BC547 and BC557 parts are in the right places and orientated correctly. Assuming the relays do switch on, let’s check that they will trip off correctly. The easiest way to test it is to take a 9V battery and connect the negative end of the battery to the ground terminal on the DC protector. Then touch a wire from the positive pin of the battery to the “AMP” terminal of each installed channel of the DC protector. The associated relay should switch out almost instantly. Repeat this for all channels, checking that the relays switch quickly. Then repeat the test with the battery the other way around (ie, positive terminal to GND and negative to the AMP terminals). If a channel does not switch as expected, measure the voltage at both ends of the 100kW resistor. One should be ±9V, the other ±0.6V. If the ±9V end is not correct, there is a short or open circuit somewhere in that area. If the other end is not close to +0.6V, check the two NPN transistors on the DC detector (eg, Q9 and Q10), especially their orientations. Check the associated PNP transistor (eg, Q11) for a fault where you aren’t registering -0.6V. We don’t suggest you do this, but to verify that the Protector does indeed protect the driver, we connected a 4W subwoofer to the DC Speaker protector along with a 6A limited, -34V power supply to the “AMP” input of the Protector. There was a solid thump and click as the relay saved the sub from Scope 1: the blue trace is the voltage across a 4W loudspeaker driver (zero volts at top), while the yellow trace is -34V applied to the DC Speaker Protector from a bench supply. The speaker is disconnected in less than 80ms. The AC voltage generated by the cone movement due to back-EMF after the relay disconnected the driver will not occur in this final version as long as CON8 is connected to Earth, as that will brake the cone movement. Australia's electronics magazine siliconchip.com.au Silicon Chip Binders REAL VALUE AT $19.50 * PLU S P&P Remember to fit an insulating washer to the BD139 transistor (visible above) to prevent it from shorting out on the heatsink. Also note the use of shakeproof washers on all screws so they won’t loosen due to vibration or movement. inevitable destruction. We monitored this with an oscilloscope, and the result is shown in Scope 1. We noted a flash of arcing as the speaker was disconnected, which is no surprise when breaking the very high direct current flow. Please don’t try this at home, as a speaker protector does not make this sort of thing safe for your speaker. Application The DC Protector needs to be connected to the power amplifier ground/ Earth via the provided terminal (CON8) and supplied with 30-40V DC to the power connection (CON7). If your amplifier has a higher positive rail voltage than this, you can use a 5W wirewound resistor to drop the supply voltage to the Protector. The six-­ channel Protector draws about 100mA, so a 100W 5W resistor will drop 10V and dissipate about a watt. Connect the terminals marked AMP to the amplifier and the corresponding SPKR terminal to your speaker outputs. It’s OK to leave some channels unused; for example, if you have a 3or 5-channel amplifier. Once installed in your amplifier, let’s hope that you never hear those relays click unexpectedly. But if you do, you will be glad SC they are there! Are your copies of SILICON CHIP getting damaged or dog-eared just lying around in a cupboard or on a shelf? Can you quickly find a particular issue that you need to refer to? Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of S ILICON C HIP. They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. H 80mm internal width H SILICON CHIP logo printed in gold-coloured lettering on spine & cover Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Scope 2: this scope grab shows the response time of the Protector to a 20V DC fault. The input voltage step is at t=0 and the output starts to drop before t=60ms. It reaches 0V before t=80ms. The 80ms delay is due to the RC time constant of the filter reaching 0.6V. siliconchip.com.au Australia's electronics magazine Order online from www. siliconchip.com.au/Shop/4 or call (02) 9939 3295 and quote your credit card number. *See website for delivery prices. January 2022  51 PRODUCT SHOWCASE Global power supply repair Switchmode specialises in the repair of all power supply equipment, including those where technical information, support, spare parts and/or test fixtures are scarce or unavailable. Since 1984, Switchmode has serviced over 6000 models of equipment from more than 1400 different manufacturers. We have undertaken power supply repair for many standard power supplies as well as more unusual units. Switchmode’s engineers and technicians are supported by a technical database from which they can readily access computer records (held for more than twenty years) of every electronic component removed, tested and replaced in the power supplies repaired. For professional service, send your power supply repairs to Switchmode. Examples of power supply equipment that we regularly repair includes converters, amplifiers, rectifiers, UPSes, switch-mode power supplies, DC regulated power supplies and AC power supplies from medical lasers and radio broadcasting to ship’s anchors and radar systems. Switchmode is based in Hornsby, Sydney, serving all of Australia and beyond. Contact us to discuss how we can help you with your power supply repair requirements. Switchmode Power Supplies Ltd U1 37 Leighton Place, Hornsby NSW 2077 Phone: (02) 9476 0300 www.switchmode.com.au Espressif ESP32-S2 MINI WiFi modules from Mouser Mouser Electronics is now stocking the ESP32-S2 MINI modules from Espressif Systems. These generic 802.11 b/g/n WiFi microcontroller modules provide engineers with high-performance, single-core SoCs in both PCB and IPEX antenna configurations. They are an ideal choice for IoT, wearable electronics and smart home applications. The Espressif ESP32-S2 MINI modules offer secure and cost-effective communication, incorporating an Espressif ESP32-S2FH4 SoC with a 240MHz LX7 CPU. They have 4MB of external SPI flash and cryptographic accelerators to enhance security performance and protection. The ESP32-S2 MINI modules also include a low-power co-processor for monitoring SPI, I2S, UART, I2C, the camera interface, as well as the modules’ 43 GPIO pins. Both modules operate from -40 to +125°C, making them ideal for a wide range of industrial, consumer and lighting environments. Mouser also offers development tools for the ESP32-S2 MINI modules, including the Espressif ESP32S2-MINI-1 development kits and the DFRobot ESP32-S2-DevKitM-1 development board. To learn more about the ESP32-S2 MINI modules, visit www.mouser. com/new/espressif/espressif-esp32s2-mini/ Mouser Electronics Inc. 1000 North Main St, Mansfield, TX 76063 USA Phone: (852) 3756 4700 www.mouser.com Low input bias operational amplifiers from Microchip Microchip's new MCP6006/7/9 and MCP6476/7/9 series of operational amplifiers have low input bias currents and rail-to-rail input and output operation. This family is unity-gain stable and has a typical gain-bandwidth product of 1MHz or 3MHz. The benefits of these low-cost devices include: • Operation from a single supply as low as 1.8V • A low maximum offset voltage of only 1.6mV and low noise, enabling excellent measurement accuracy without breaking the budget 52 Silicon Chip • Both the MCP6006/7/9 and MCP6476/7/9 series of amplifiers consume as little as 90µW (1MHz GBW [gain bandwidth]) and 252µW (3MHz GBW) per channel, respectively • With a start-up time of only 6µs, these devices can be switched on and off, so they only draw power when they are needed • They are ideal for harsh, electrically noisy environments • Integrated EMI filters provide additional rejection of high-­frequency interference • They are specified over the Australia's electronics magazine extended temperature range from -40°C to +125°C. The MCP6006/6R/6U, MCP6007, MCP6009 are single, dual and quad 1MHz op amps - see siliconchip.com. au/link/abbc The MCP6476/6R/6U, MCP6477, MCP6479 are single, dual and quad 3MHz op amps - see siliconchip.com. au/link/abbd Microchip Technology 2355 West Chandler Blvd, Chandler Arizona 85224-6199 USA Phone: (480) 792 7200 www.microchip.com siliconchip.com.au Post as m t s i r Ch le a S Tech 27 IP67 True RMS Autoranging DMM 22 ale ry 20 On S anua J 3 2 21 er 20 mb Dece 4000 display count. 600VDC CAT IV rated. AC/DC currents up to 10A. Excellent meter suitable for most electrical works. QM1549 NOW 7995 $ EXCELLENT TEMPERATURE STABILITY SAVE $20 20MHz USB Oscilloscope 65W Anti-Static Soldering Station Ultra portable. USB interface plug & play. Automatic setup. Waveforms can be exported as Excel/Word files. Includes 2 probes. QC1929 NOW 249 $ 149 $ SAVE $80 SAVE $50 65W capacity heater. Adjustable temperature (200-480°C). ESD safe. Digital display. Mains powered. TS1440 See more on page 6 NOW 1249 $ NOW SAVE $150 SAVE $50 Swann 8 Channel 4K NVR Kit with 4 x 4K PIR Cameras Intelligent 15A Battery Charger 4K Easy to install and will keep your premises secure. 4K Spotlight cameras. Infrared LEDs. True Detect™ Heat and Motion sensor. QV9097 2TB HDD Ideal for cars, motorcycles, boats and caravans with battery capacities between 20-200Ah. 6V/12V/24V. MB3623 IP66 RATED USB TYPE-C WITH POWER DELIVERY NOW 7995 $ HANDS-FREE CALL SD & MICROSD NOW 2995 SAVE $10 FM Transmitter with Bluetooth® Stream music and take calls from your smartphone via Bluetooth® to your car's FM radio receiver. 12/24VDC. AR3142 Shop the catalogue online! 9-in-1 Multifunction Type-C USB Hub 4K Expand the number of ports and connect just about anything to your MacBook® or latest laptop. XC4975 Limited Stock. In-store Only. Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * 219 $ CD, BLUETOOTH® & FM RADIO USB 3.0 RJ45 1 X QUICK CHARGE™ 3.0 & 1 X TYPE-A USB PORTS NOW SAVE $50 SAVE $20 $ NOW 119 $ Turntable with CD Player Play and save your vinyl to a USB thumb drive or SD card. 33/45 Speed selection. USB/SD slot for recording & playback. GE4107 In-store only. www.jaycar.com.au 1800 022 888 Save on Sight & Sound EXTEND HDMI SIGNAL UP TO 50M RANGE PRICED TO CLEAR 89 $ Portable LED Projector SAVE $40 Accepts up to full 1080p inputs with HDMI, USB and SD card slots. Projection distance 0.8m-2m. AP4005 In-store only. 5.8GHz Wireless AV Sender & Receiver NOW 4995 $ SAVE $20 50m 1080p Mini HDMI Cat5e/6 Extender Plug straight into the HDMI sockets on the source and receiver. AC1726 NOW 89 $ SAVE $30 NOW 4995 $ Send your pay TV reception (or any other video source) to any part of your house. Up 60m range. AR1913 Spare receiver AR1916 NOW $49.95 SAVE $15 SAVE $20 USB 2.0 DVD Maker Transform VHS/camera videos into high-quality digital recordings! Easily edit and burn to DVD. Windows™ compatible. XC4867 Front NOW 34 $ 95 SAVE $15 CRYSTAL CLEAR SOUND Bluetooth® Rechargeable Headset with Mic Features voice command, last number re-dial, call rejection, and more. AA2080 NOW 89 $ • IPX5 WATER RESISTANT • TRUE WIRELESS STEREO (TWS) SAVE $60 Portable Boom Box Speaker Stream music from your Smartphone or Tablet via Bluetooth or connect directly through AUX input. CS2499 ® Network Gadgets Priced to Clear! NOW FROM 7995 $ IMPROVE YOUR WI-FI SAVE<at>$20 NOW 119 $ SAVE $30 2 X 25WRMS Compact Stereo Amplifier Volume, bass & treble controls. Microphone input. 18VAC 2.2A power supply included. AA0486 NOW 1995 $ SAVE $10 NOW FROM 149 $ Bluetooth® Dongle SAVE<at>$30 Connect a wide variety of popular Bluetooth® devices to your PC. XC4956 NOW FROM 4995 $ YN8394 Powerline Ethernet Extenders Extend your network using your home's existing electrical wiring up to 300m. Speeds up to 500Mbps. Standard YN8358 NOW $79.95 Primary with Wi-Fi YN8359 NOW $99 Smart Wi-Fi Routers Back UP TO 25WRMS OF POWER PER CHANNEL 10X FASTER THAN CONVENTIONAL FAST ETHERNET Ultra-fast data transfer to multiple devices simultaneously. AC2100 Dual Band YN8394 ORRP $169 NOW $149 AC3000 Tri-Band YN8396 ORRP $229 NOW $199 SAVE $20 USB Wi-Fi Adaptors Fast and stable access to Wi-Fi signal. Dual band. USB3.0 1300Mbps YN8336 NOW $49.95 USB3.0 1900Mbps YN8337 NOW $79.95 Save on Auto Tech IDEAL FOR 4WDS & LARGER VEHICLES 2.7" LCD 99 NOW 219 $ NOW $ 99 $ SAVE $40 SAVE $50 Wired Reversing Camera with 7" LCD LCD GPS Speedometer Automatic recording on impact. Wide 140° angle lens. Records to microSD card (sold separately). 12/24VDC. QV3848 16GB microSD card XC4989 $19.95 NOW 14 $ SAVE $10 1080p GPS Dash Camera Monitor the area to the rear of a large vehicle with a wider field-of-view. IR LEDs for night vision. Remote control included. 12/24VDC. QM3742 $ SAVE $5 Calculates and displays the speed of your car, boat or bike via GPS satellites. Rechargeable via USB, charger included. LA9025 NOW 4995 95 2" DISPLAY NOW NOW 169 $ SAVE $10 SAVE $30 In-Car Cup Holder Charger 10W Fast Wireless Qi Charger & Car Phone Holder Dual USB ports (3.1A total). Dual cigarette lighter sockets with individual switches. PS2118 Automatically close/open at touch of a button. HS9059 Super Bright Solid LED Light Bar 12V/24V 6,500 lumen. Combination spot and flood beam. Stainless steel mounting hardware supplied. SL4020 Suitable for off-road use only APPROXIMATELY HALF THE PRICE OF EQUIVALENT UNITS AVAILABLE ELSEWHERE IP68 RATED RUNS ON CARS OR TRUCKS NOW FROM 3495 $ SAVE<at>$40 QUICK CHARGE USB PORT Modified Sine Wave Inverters NOW 7995 $ Power small appliances such as laptops, stereos, phone chargers etc. 12VDC to 240VAC. Includes battery lead and alligator clips. 150W, 300W, 500W, 800W, & 1500W available. MI5300-MI5310 547mm SAVE $20 12V Jump Starter with Air Compressor Jump start a car, bike or 4WD. Huge 400A power. Cranks up to 3L diesel or 6L petrol engine. MB3736 NOW NOW FROM 169 $ 229 $ SAVE $50 SAVE $50 SUPPORTS LEAD ACID, AGM, CALCIUM, GEL OR LIFEPO4 BATTERIES Deep Cycle AGM* Batteries Designed to store large amounts of energy. Superior deep cycling performance for different recreational and industrial Dual Input DC/DC applications. 12VDC. Multi-Stage Battery Charger 75Ah SB1680 NOW $229 Designed to manage solar and alternator power inputs to charge an 100Ah SB1682 NOW $249 auxiliary (house) battery system. 20A max charging current. Six-stage 120Ah SB1683 NOW $349 *AGM = Absorbent Glass Mat battery charging. MB3940 Save on Soldering NOW 3495 $ OUTSTANDING, FAST AND ACCURATE 160 PIECES SAVE $10 Heatshrink Pack with Gas Blow Torch NOW FROM 4995 $ SAVE<at>$40 SAVE $80 DON'T FORGET THE GAS! Soldering Gas Refiller NA1020 $4.95 Gas Soldering Irons 95 Uses the proven Curie Point Technology to bring the tip up to operating temp using fast RF induction. 350°C to 398°C Temp range. Mains powered. TS1584 ALSO AVAILABLE: Spare Tips with Heating Element TS1586-TS1590 NOW FROM $19.95 SAVE 30% SAVE $10 Gas Blow Torch Adjustable flame. Temp range up to 1300°C. Piezo ignition with safety lock. TS1660 25% Off Specialised Meters NOW 29 NOW 44 95 $ SAVE $10 95 ACCURATE TO 1.5MM SAVE $15 Mini laser Distance Meter Measure water content in building materials and wooden fibre articles. Weighs only 83g. QP2310 NOW 4495 $ SAVE $15 Pocket Size Moisture Level Meter A MUST FOR SURFACE MOUNT HAND SOLDERING 50W Thermaltronics Soldering Station NOW 29 Compact power, convenient & reliable. Adjustable tip temperature. Technic TS1305 NOW $49.95 SAVE $20 SAVE $30 Pro Piezo TS1310 NOW $89 SAVE $40 Super Pro TS1320 NOW $99 $ 299 $ Includes 7 different colours & sizes, and a gas blow torch. Piezo ignition. Flame or flameless output. TH1620 $ NOW Digital Lightmeter Measure distance up to 20m with an accurancy of just 1.5mm! Metric or imperial measurements. QM1626 Measure light in 4 ranges from 0.01 to 50,000 lux. Auto zeroing. Separate photo detector. QM1587 Save on Arduino®-Compatible Products NOW 2495 $ SAVE $5 WATERPROOF Flexible RGB LED Strip Light NOW FROM 19 $ 95 SAVE 20% Development Boards with Wi-Fi ESP8266 Mini ESP32 UNO with Wi-Fi MEGA with Wi-Fi SAMD21 XC3802 NOW $19.95 XC3800 NOW $31.95 XC4411 NOW $31.95 XC4421 NOW $47.95 XC3812 NOW $54.95 More ways to pay: XC3920 NOW 1995 $ EA SAVE<at>50% Sewable/Wearable Development Boards CREATE DAZZLING EFFECTS ON CLOTHING/ COSTUMES Designed to be sewn onto fabric. Lilypad Plus XC3920 SAVE $15 ESP32 XC3810 HALF PRICE! NOW 6995 $ 120 addressable WS2812B RGB LEDs (60 LEDs/m) to create amazing lighting displays. 5V. 2m long. XC4390 SAVE $10 37 Piece Deluxe Module Package NOW 1295 $ SAVE $5 DAZZLING CIRCULAR PATTERNS Includes commonly used sensors and RGB LED Ring Module modules such as: joystick, magnetic, 24 x RGB LEDs with 256 brightness levels. temperature, IR, LED and more. 72mm diameter. XC4385 XC4288 Save on Workbench NOW 2495 $ SAVE $15 Vacuum Bench Vice Made from hard-wearing diecast aluminium. Ball joint clamp suction base. 75mm opening jaw. 160mm tall. TH1766 A handy bench voltmeter with analogue dial and banana plug connections. 3V & 15V scales. Zero offset adjustment. QP5040 BANANA SOCKET STYLE BINDING POST OUTPUT NOW 179 $ 29 Fixed 13.8V Switchmode Lab Power Supplies SAVE $40 High current general workshop power supplies for equipment, component testing, etc. Variable Laboratory Autotransfomer (Variac) 12A MP3079 NOW $59.95 SAVE $20 SAVE $30 20A MP3078 NOW $89 40A MP3089 NOW $159 SAVE $60 Heavy-duty steel housing case. 500VA (fused) rated power handling. 0~260VAC <at> 50Hz output voltage. MP3080 NOW 44 $ SAVE 25% Analogue Bench Voltmeter SAVE $10 0-150mm (0-6") measurement range, metric & imperial. 5-digit LCD. Case included. TD2082 NOW HALF PRICE 95 Digital Stainless Steel Caliper 5995 995 $ NOW $ NOW FROM $ NOW 59 95 $ SAVE $15 95 SAVE $20 DETECTS WOOD, METAL AND LIVE WIRE MEASURES IN CELCIUS & FAHRENHEIT SAVE $20 12:1 DISTANCE TO SPOT RATIO Hand-held Anemometer and Altimeter 3-in-1 Stud Detector with Laser Level Non-Contact Thermometer with Laser Pointer Provides wind speed, wind chill, temperature, barometric, and altitude readings. Includes tripod. QM1645 Works on vertical and horizontal surfaces. 1 x 9V battery included. QP2288 NOW 5995 $ Measure temperatures from -50°C up to 600°C in hard to reach places. Adjustable emissivity. QM7424 Save on Electromechanical 12V Hydrodynamic Fans Long-life hydro-dynamic bearing. 50,000hrs operational life at 40°C (even longer at 25°C). Flylead with 3 pin molex. 80, 90 & 120mm available. YX2570-YX2574 NOW FROM 1395 $ SAVE 30% SZ2031 • BALANCED BLADES • LOW NOISE NOW FROM 29 $ 95 SAVE 25% Illuminated Blue SZ1923 Rocker Switch Panels SZ1925 SZ1924 Rated at 20A for a 12V system (10A for 24V) up to a maximum 45A per panel. Easy installation. 2, 4 & 6 way available. SZ1923-SZ1925 HIGH QUALITY Looking for more product information? Visit your local store or our website jaycar.com.au NOW 3495 NOW FROM $ $ SAVE $5 SAVE 20% 2495 Fuse Blocks with Bus Bar Accepts up to 30A per output with handy fuse-blown indication. Negative bus bar. 6 Way SZ2031 NOW $24.95 12 Way SZ2032 NOW $34.95 SZ2032 EA Panel Mount Circuit Breakers High quality units with multi-wire gauge inputs/outputs. 60A, 120A & 200A available. SZ2081-SZ2085 We reward our industry professionals CCTV Kits Sale Selected range of Concord and Swann models available: • 4 channel & 8 channel • 4, 6, & 8 cameras WHILE STOCKS LAST! • 1080p & 4K DVR Kits Scan to view range Order online, collect in store Selected discontinued CCTV kits we can no longer afford to hold stock. See website or contact your local store to check stock. STOCK IS LIMITED. ACT NOW TO AVOID DISAPPOINTMENT. Sorry NO RAINCHECKS. NVR Kits QV5600 QV5000 NOW FROM NOW FROM 399 849 $ $ SAVE<at>$130 SAVE<at>$200 A DVR (Digital Video Recorder) uses coax cables to run video from the camera to the DVR. Each camera needs its own power source using a secondary cable between the power supply and cameras via a splitter. Limited stock. In-store only. An NVR (Network Video Recorder) records using IP cameras and Cat5/Cat6 Ethernet cables, which allows for an easy setup. Ideal for home/office or commercial environments. Limited stock. In-store only. All kit contents include: Digital video recorder (or Network video recorder), cameras, power and video cables, adaptor and splitter, USB mouse, HDMI cable and Network cable. MP5205 NOW FROM 129 SMART POWER BACKUP $ STAY CONNECTED DURING POWER FAILURE HIGH CAPACITY NOW FROM 2995 SAVE<at>$50 $ SAVE $5 Line Interactive UPS Alarm & NBN Back-up Batteries MP5224 High quality batteries for standby, emergency and back-up power applications. 7.2Ah SB2486 NOW $29.95 9.0Ah SB2487 NOW $39.95 Save on Wireless Security 1080p Smart Wi-Fi Cameras See and talk to visitors via your Smartphone, even when not home. Records to microSD card (sold separately). 170°C viewing angle. IR night vision. QC3886 32GB microSD card XC4992 $36.95 5995 NOW 24 $ 95 SAVE $10 Wireless Driveway & Entry PIR Alert Kit Alerts alarm when movement is detected. Up to 8m PIR detection range. Mounting hardware included. LA5178 SAVE $20 NOW FROM 99 INDOOR CAMERAS Bullet with Infrared LEDs QC3906 NOW $59.95 Pan Tilt QC3900 NOW $79.95 OUTDOOR CAMERAS IR Illumination QC3864 NOW $99 SAVE $30 Pan Tilt Zoom QC3859 NOW $119 SAVE $30 $ SAVE 20% QC3859 99 1080p Smart Wi-Fi Doorbell + Chime NOW FROM $ Used as standalone or as part of a system to keep an eye on your property. Built-in motion detection, app control and 2-way audio. NOW SAVE $50 SB2487 QC3900 Keep your surveillance systems, PC and other devices running longer during a power failure. 600VA/300W MP5224 NOW $139 SAVE $20 650VA/390W MP5205 NOW $129 SAVE $20 1500VA/900W MP5207 NOW $299 SAVE $50 $ SB2486 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 6: CCTV Kits Sale: Selected items only. In-store only promotion and not available to Resellers. No rainchecks. Page 7: Clearance: Selected items only as listed. In-store only promotion and not available to Resellers. SUPPLY CHAIN DISRUPTION. We apologise for factors out of control which may result in some items may not being available on the advertised on-sale date of the catalogue. Clearance Order online, collect in store Listed below are a number of discontinued (but still good) items that we can no longer afford to hold stock. Please ring your local store or search our website to check stock. At these prices we won't be able to transfer from store to store. STOCK IS LIMITED. ACT NOW TO AVOID DISAPPOINTMENT. Sorry NO RAINCHECKS. Test & Tools SAVE HALF PRICE QP5014 $17.95 $8.95 $9 2 Channel IR Extender Kit AR1812 $79.95 $44.95 $35 10W Hot Glue Gun TH2050 $12.95 $7.95 $5 2 Core Speakon Audio Cable 10m WA7102 $54.95 $39.95 $15 3.5 Digit Jumbo LED Panel Meter QP5585 $34.95 $19.95 $15 AC1757 $49.95 $24.95 $25 HALF PRICE QP5570 $27.95 $13.95 $14 23"-55" Slimline LCD TV Wall Bracket CW2864 $20 3000A True RMS AC High Current Clamp Meter QM1568 $49.95 $34.95 $15 ORRP $44.95 $24.95 50m 1080p HDMI Cat5e/Cat6 Extender with Infrared AC1783 $99.95 $69.95 $30 4P/6P/8P/10P Modular Crimp Tool TH1936 $54.95 $39.95 $15 Boom Box Amplifier with Bluetooth® QM3410 $49.95 $39.95 $10 6" Insulated Side Cutters TH1985 $24.95 $17.95 $7 Ceiling / Wall Speaker Bracket CW2841 $19.95 $12.95 6.5" Long Nose Pliers TH1986 $24.95 $17.95 $7 Composite AV to USB Video Recorder AC1790 $109 AC5010 AC5012 3.5 Digit LCD Panel Meter WAS Sight & Sound NOW 0 - 5A MU45 Panel Meter - Moving Coil Type Cat. No 600A True RMS AC Clamp Meter QM1630 $59.95 $44.95 $15 7" Bull Nose Pliers TH1984 $24.95 $17.95 $7 75mm 3" Sheet Metal Bending Pliers TH2336 Adjustable Compression Crimping Tool TH1800 $24.95 $17.95 Budget SMD Vacuum Pick-up Tool $29.95 $19.95 HALF PRICE Concord 4-Way 4K HDMI Switcher Concord 4x2 4K HDMI Matrix Switcher Splitter HOT PRICE WAS NOW SAVE $7 $79 $30 $129 $89 $40 $249 $199 $50 Digital Audio Converter & Repeater AC1592 $49.95 $29.95 $20 $7 Digital to Analog Audio Decoder AC1658 $99.95 $79.95 $20 $9 Economy UHF/VHF Masthead Amplifier LT3276 $49.95 $24.95 $25 $12 Gooseneck Microphone for DJ / Mixing Desks AM4012 $17 $99 $30 ORRP $39.95 $22.95 Grey Beanie with Bluetooth® Speakers ST3216 $29.95 $19.95 $10 HALF PRICE TH1816 $13.95 $6.95 $7 MHL™ to HDMI Lead with 11 Pin Samsung Adaptor TH1887 $14.95 $8.95 $6 PC Monitor Hanging Cubicle Bracket HALF PRICE TH1978 $17.95 $8.95 Heavy Duty Coax Crimping Tool TH1832 $34.95 $22.95 IP67 True RMS Autoranging Cat IV DMM with Wireless USB Interface QM1571 PLCC Extractor $10 2 Way DisplayPort Switcher Cat. No Precision 6 Long Nose Pliers $129 WQ7428 $19.95 $9.95 $10 HALF PRICE CW2834 $39.95 $19.95 $20 HALF PRICE TH1831 $39.95 $19.95 $20 Speaker Polarity Tester with Tone Generator AA0414 $34.95 $24.95 $10 Spiral Drive Drill/Driver TD2089 $25.95 $14.95 $11 TOSLINK & Coax Audio Cat5e/6 Extender with Infrared AC1733 $69.95 $49.95 $20 Thermocouple Thermometer - 2 Input QM1601 $79.95 $64.95 $15 USB Type-C Lapel Microphone HALF PRICE AM4015 $29.95 $14.95 $15 Ratchet Crimping Tool for F-Type Connectors Power Cat. No WAS NOW MB3816 $49.95 $29.95 10,000mAh Power Bank with USB and Qi Charger SAVE Security Cat. No WAS NOW SAVE $20 1080p Wi-Fi IP Camera with Security Alarm QC3870 $129 $89 $40 WQ7278 2 Outlet Power Garden Stake HALF PRICE MS4097 $19.95 $9.95 $10 20m CCD Camera Extension Cable 24-Hr Mechanical Mains Timer HALF PRICE MS6109 $19.95 $9.95 $10 4 Door RFID Access Controller HOT PRICE LA5359 $199 $149 $50 HOT PRICE QC8047 $229 $179 $50 QC3667 $16.95 $9.95 $7 $64.95 $44.95 $20 24VDC 2.5A 65W Switchmode Mains Adaptor with 7 Plugs MP3562 $49.95 $29.95 $20 720p Motion Wi-Fi Camera with Flood Lights 24VDC to 12VDC 6A Converter MP3064 $74.95 $59.95 $15 BNC to Cat5e/6 UTP AHD Video Balun Kit 40W 24V 1.67A Dimmable LED Power Supply MP3375 $79.95 $54.95 $25 Car Alarm Electronic Siren HALF PRICE LA8908 $19.95 $9.95 $10 60W 48V 1.25A Desktop Power Supply MP3256 $49.95 $29.95 $20 CCTV Camera External Mounting Bracket HALF PRICE QC3337 $14.95 $7.45 $7.50 75W 24V 3.15A Dimmable LED Power Supply MP3379 $99.95 $69.95 $30 Concord 5MP PIR Bullet IP Camera QC5620 $149 $109 $40 AC Power Meter with LCD QP2325 $29.95 $24.95 $5 Multifunction 5.5” GPS Head-Up Display LA9034 $99.95 $79.95 $20 Dual USB 4.8A Car Charger with LCD Voltage Display MP3692 $14.95 $5 Smart Lock Deadbolt Kit with Bluetooth® LA5095 $99.95 $79.95 $20 Dual USB Mains Power Adaptor MP3459 $26.95 $16.95 Swann 4MP IP Outdoor Camera QV9014 $149 $109 $40 Dual USB Wall Charger with LED Night Light MP3429 $14.95 HALF PRICE LA5206 $12.95 $6.45 $6.50 Fast Two Hour Ni-MH Battery Charger MB3549 $32.95 $22.95 $10 Wireless Panic Button Suit Wi-Fi Camera System HALF PRICE QC3872 $19.95 $9.95 $10 Lithium-Ion CR123A Battery Charger MB3581 $44.95 $29.95 $15 Wireless PIR Suit Wi-Fi Camera System QC3876 $29.95 $14.95 IT $9.95 $8.95 $10 $6 Cat. No WAS NOW SAVE HOT PRICE MP3471 $129 $89 $40 2 Bay USB 3.0 SATA HDD RAID Enclosure XC4688 $99 $79 $20 2GB Digital Voice Recorder XC0387 $79.95 $59.95 $20 3.5" USB2.0 External HDD Case XC4669 $29.95 $24.95 $5 3.5" USB3.0 SATA HDD Enclosure XC4667 $39.95 $29.95 $10 Miniature 1080p DV Camera with Wi-Fi QC8102 $69.95 $49.95 $20 Monitor Stand with USB Hub and Card Reader XC4312 $29.95 $24.95 $5 Mouse Pad with Wireless QI Charger XM5098 $29.95 $19.95 $10 144W 12-24VDC Laptop Power Supply OTG Type-C USB Card Reader Thunderbolt™3 Dock with 4K HDMI, USB 3.0 Port & Card Reader USB to Parallel Bi-Directional Cable HALF PRICE XC5621 $14.95 HOT PRICE $7.45 XC4938 $99.95 $59.95 HALF PRICE XC4847 $39.95 $19.95 Window & Door Entry Alarm - 2Pk Kits, Science & Learning Cat. No WAS NOW $15 SAVE 3MP USB Portable Digital Microscope QC3191 $59.95 $49.95 $10 5MP Camera for Raspberry Pi XC9020 $24.95 $14.95 $10 5MP Camera for Raspberry Pi with IR LED XC9021 $49.95 $34.95 $15 All Terrain Multifunction Tracked Robot KJ8918 $69.95 $49.95 $20 KJ9029 $19.95 Hydraulic Robot Arm Kit KJ8997 $59.95 $44.95 Long Range LoRa IP Gateway XC4394 MeetEdison Robot Kit KR9210 R/C Motorised Robot Arm Kit KJ8995 $40 Salt Water Fuel Cell Engine Car Kit KJ8960 $28.95 $19.95 $9 $20 Squishy Circuits Standard Kit KJ9350 $39.95 $29.95 $10 $7.50 Dual Motor Gearbox Kit HALF PRICE $99 $9.95 $69 $99.95 $79.95 $99 $89 $10 $15 $30 $20 $10 SAVE<at> 500 $ Desktop 3D Scanner 3X FILAMENT COLOUR MIXING TECHNOLOGY Watch real life objects become digitized before your eyes. Scans up to 250Hx180Dmm. Folds for easy storage. Supplied with MFStudio software with +Quickscan. TL4420 In-store only. 999 $ SAVE $500 CLEARANCE 699 109 $ DOBOT MOOZ-3Z Triple Filament 3D Printer SAVE<at>$150 19" Rack Mount Cabinets 6U to 12U in Swing or Fixed frame. Ideal for IT or phone system installations, PA systems, etc. Solid steel powder coated to provide high strength and rigidity. 6U Swing Frame 6U Flat Packed HB5180 NOW $164 SAVE $115 HB5170 NOW $109 SAVE $80 6U Assembled 12U Swing Frame HB5171 NOW $129 SAVE $90 HB5182 NOW $199 SAVE $150 12U Flat Packed HB5174 NOW $149 SAVE $100 Equipped with a three-color print head for colour mix print. Easy-to-use controller and mobile app. Featured with 3.5" LCD touch pad, Wi-Fi or USB connectivity, magnetic heat bed and more. Prints up to 100Hx100(Dia.)mm. TL4412 Limited stock. In-store only. SAVE 7" NOW 249 $ 50 $ 2.4GHZ EXPANDS UP TO 4 CAMERAS SAVE $50 4 Channel 720p Wireless DVR & Camera Kit Allows you to connect via Ethernet to your modem/router to view the camera while outside the home or office. Records to SD card (sold separately). Infrared camera for day/night recording. QC3764 Spare 720p Camera QC3765 NOW $119 SAVE $30 32GB microSD card XC4992 $36.95 Professional Sound Level Meter Wide dynamic range from 30dB to 130dB. Fast (125ms) or Slow (1s) response. USB connectivity. QM1598 SAVE $50 5MP USB Digital Microscope 10x to 300x magnification for extra detail. LED illumination. Adjustable focus dial. QC3199 NOW 249 $ SAVE $50 FAST WI-FI TO EVERY CORNER OF THE HOUSE NOW 199 $ NOW 149 $ CAPTURES GEOMETRY IN AS FAST AS 1 MINUTE! NOW FROM $ LCD NOW SAVE $50 AC1200 Wi-Fi Mesh Network & Satellite Kit Speeds up to 1200Mbps (5GHz 867Mbps + 2.4GHz 300Mbps). Expandable with additional satellite modules. YN8564 Extra Satellite Module YN8566 NOW $99 SAVE $30 LEARN, BE INSPIRED, PROJECTS, WORKSHOPS & MORE! 24/7. 1800 022 888 www.jaycar.com.au Over 100 stores & 130 resellers nationwide HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer confirmed at the time of print. Call your local store to check stock. Occasionally discontinued items advertised on a special / lower price in this flyer have limited to nil stock in certain stores, including Jaycar Authorised Resellers, and cannot be ordered or transferred. No rainchecks. Savings off Original RRP. Prices and special offers are valid from 27.12.2021 - 23.01.2022. 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. Conway’s Game of Life on the Micromite In 1970, mathematician John Horton Conway devised The Game of Life. It illustrates how complex patterns can be created by very simple rules. This has many parallels in the natural world. The Game is based on an infinite 2D grid of square cells. Thus, each cell has eight neighbours. Four simple rules are then applied: 1. If a live cell has one or no neighbours, it dies through loneliness or under-population. 2. If a live cell has two or three neighbours, it lives on to the next generation. 3. If a live cell has four or more neighbours, it dies through over-population or overcrowding. 4. If a dead cell has exactly three neighbours, it is born by reproduction. An initial pattern of live cells is entered into the grid, and the Game is started. The Game then steps through siliconchip.com.au each generation. Some patterns die out quickly, some become stable, and others multiply indefinitely. For more information, see https://w.wiki/3TKJ I have developed two versions of the Game of Life. The first runs on the Micromite LCD BackPack with the 2.8in ILI9341-based touchscreen and does not require any additional hardware. In addition to several pre-defined starting patterns, the user can create their own. The second is designed as a standalone PCB (using the circuit shown here) with a small 0.96in IPS display, and it can be used as an interactive display with the addition of two pushbuttons or an infrared (IR) remote control. Alternatively, it can operate in fully automatic mode, taking about 55 minutes to complete an entire cycle of all the preset starting patterns. This can be incorporated as wearable jewellery Australia's electronics magazine such as a brooch, or in other novelty applications. The software driver for the IPS display was written by Peter Mather and edited by Peter Carnegie – see www. thebackshed.com/forum/ViewTopic. php?TID=7137 While the original Game was designed for an infinite 2D grid of cells, in the Micromite version, the grid is limited to 32 x 24 cells for the BackPack version or 32 x 20 cells for the smaller IPS display. There is the option for cells to drop off the edge of the display, or wrap around from one side to the other. The best choice depends on how the initial pattern develops. For the circuit of the BackPack-based version, see one of the BackPack articles. The standalone version shown here uses the same PIC32MX170F256B-50I/SP microcontroller programmed with the Micromite software, plus a simple power supply and the 0.96in ST7735S-based 80 x 160 pixel January 2022  61 The circuit built on a home-etched PCB at upper left, with two close-up shots of the display in action. The software and PCB gerber files can be downloaded from siliconchip.com.au/Shop/6/6085 IPS display. The display is controlled using the SPI protocol via eight connections: • GND and Vcc supply 3.3V. • SCL (SCK in SPI mode) and SDA (SDI in SPI mode) are the two SPI protocol pins that connect to pin 25 (SPI Clock) and pin 3 (SPI out) on the PIC chip, respectively. • RES, DC and CS are control signals connected to pins 23, 22 and 21 on the PIC. • BLK is the backlight control pin. It is not used in this application. The power supply is a simple 3.3V linear regulator. An infrared (IR) receiver or two push buttons (or both) can optionally be connected to control the display. The IR receiver connects to pin 16 on the micro. If installed, you can access the menu of preset demonstration patterns. The optional pushbuttons connect to pins 9 and 10. They provide forward and backward scrolling through the menu of preset demonstration patterns. Alternatively, pin 9 or 10 (or both) can be permanently connected to ground by fitting a wire link in place of the switch. In this case, the display runs in automatic mode, scrolling through each of the pre-defined starting patterns in turn as soon as the power is applied. Pins 9 and 10 have weak internal pull-up currents and thus do 62 Silicon Chip not require external pull-up resistors. In operation Both versions start automatically when power is applied. With the BackPack version, you can select the various pre-defined starting patterns by using the up and down arrows on the touchscreen. Touching the screen whilst the Game is running returns to the menu. There is also the option of defining your own starting pattern by touching individual cells on the screen. Each touch toggles a cell on or off. In this case, a small red square at the bottom right-hand corner acts as an Enter and Start key. As mentioned above, the standalone version uses the IR receiver or pushbuttons to move through the starting patterns menu. Pressing the ‘next’ and ‘previous’ remote control buttons scroll through the menu of preset demonstration patterns. Pressing any other button on the remote selects the menu item. Pressing the ‘next’ or ‘previous’ button whilst the Game is running returns to the menu. You can set up your remote control codes without amending the program by pressing any key on your remote control while the initial screen is displayed. You will then be asked to press the key you want to assign to ‘next’ and then the one you want to assign to ‘previous’. These are then stored in non-volatile memory so that they will be preserved when the power is removed. Alternatively, set the constants IR_ device, IR_next and IR_previous in the Micromite program to match the codes produced by your remote control. With the pushbutton version, holding the pushbutton scrolls through the menu items and releasing the pushbutton selects the menu item. Pressing a button while the Game is running returns to the menu. Kenneth Horton, Woolston, UK. ($150) Circuit Ideas Wanted Got an interesting original circuit that you have cleverly devised? We will pay good money to feature it in Circuit Notebook. We can pay you by electronic funds transfer, cheque or direct to your PayPal account. Or you can use the funds to purchase anything from the SILICON CHIP Online Store, including PCBs and components, back issues, subscriptions or whatever. Email your circuit and descriptive text to editor<at>siliconchip.com.au Australia's electronics magazine siliconchip.com.au Alternative PCB joiner for Linear MIDI Keyboard Since designing the Linear MIDI Keyboard (August 2021; siliconchip. com.au/Article/14997), we realised there is another way to join the PCBs. The cut-down pin headers described in that article are inexact and tricky to fit, so we designed a small PCB to make it easier. We wrote that the pin headers should be fitted before the switches, but the Joiners are much easier to work with, allowing fully assembled Keyboard PCBs to be joined. Two of these Joiner PCBs are needed to join a pair of Keyboard PCBs; this means a total of 14 Joiner PCBs for a full 64-note Keyboard. The Joiner PCBs have a tight solder mask on one side to stop the solder spreading and bridging the pads, so this side should be against the Keyboard PCBs. The side with large solder pads goes on the outside. Place the Joiner PCB onto the Keyboard PCB. It should line up with the edges of the silkscreen printing on the Keyboard PCB. Like any surface mounted part, tack one pad to correctly locate the Joiner and adjust as needed. Unlike the pin header, you can apply the iron from directly above. Feed a generous amount of solder into each pad hole. Surface tension should pull the solder into the hole and onto the pad, as long as all surfaces are parallel and flush against each other. Gently flip the Keyboard PCBs over and repeat for the other side using a second Joiner. Now test for continuity between adjacent PCBs. The pads on CON1, CON3 and CON5 should bell out in sequence, while those on CON2 and CON4 will match and also should connect to different pads on CON6. If you are unsure, you can also check the troubleshooting tips at the end of the MIDI Keyboard article. Tim Blythman, Silicon Chip. Compact reed relay module Most of the relay modules available on the internet, although quite inexpensive, are very large due to uncertain voltage and current requirements. I needed something smaller, suitable for use on a breadboard. As many relays have very short pins, the only option was to design my own module. Reed relays are my best option, not only because of their small size, but also for their characteristics. Reed relays have hermetically-sealed contacts, protected against possible oxidation. They also provide more consistent switching at low signal levels, requiring less power to operate and with a better on-resistance. This is because reed relays use the magnetic field from the coil to pull sets of ferromagnetic reed switch contacts together, which are already in very close proximity. Thus they do not need a larger and more complicated armature arrangement. The relay module has four reed relays in 4-pin SIL packages along with SMD driver transistors, hidden on the underside, plus a set of telltale LED indicators. The driver base resistors and LED current-limiting resistors are also SMD parts, keeping siliconchip.com.au the module very compact. The two sets of relay contacts and the driving connections are each broken out to 4-pin headers, while power is supplied to the module via a 2-pin Australia's electronics magazine header. EAGLE and Gerber files for the PCB are available from siliconchip. com.au/Shop/6/6084 Gianni Pallotti, North Rocks, NSW. ($75) January 2022  63 The Pic Mite A BASIC compatible interpreter running on the Raspberry Pi Pico Words and MMBasic by Geoff Graham, Firmware by Peter Mather The PicoMite is a BASIC interpreter running on a Pi Pico which supports over a dozen display panels, including OLED and e-Ink panels. Connecting one is easy, as shown here. The PicoMite has extensive support for displaying graphs, images and graphical objects, plus more. T he Raspberry Pi Pico is a microcontroller module with plenty of memory, I/O and a USB connection. Even better, it is cheap as chips and readily available. The only problem is that you need to be an expert programmer to get it to do anything. That changes with the PicoMite, a version of our popular MMBasic interpreter running on the Raspberry Pi Pico. This lets you program it in the easy-to-learn BASIC language with full access to all of the Pico’s advanced features. And this costs nothing; the PicoMite firmware is entirely free for you to download and use. We have previously described the Raspberry Pi Pico (December 2021; siliconchip.com.au/Article/15125), covering the hardware and programming requirements for the Pico using the C or Micropython programming languages. However, programming in 64 Silicon Chip C is beyond most casual experimenters. Micropython is easier, but it is still a new language for most people and takes time to learn. MMBasic should be familiar to most regular readers of Silicon Chip. It is an implementation of the BASIC programming language, which is largely compatible with Microsoft BASIC. It has been used for over a decade (!) on our Maximite series of computers (since March 2011) and Micromite controllers (since May 2014). The BASIC language was initially designed to teach programming and therefore is easy to learn and use. You can get it to do something with just one line, and the programming environment is particularly easy. A single keypress will set your program running and, if it fails with an error, you will get a plain text error message. A second keypress lets you Australia's electronics magazine jump back into the editor with the cursor positioned on the line that caused the error. MMBasic also makes it easy to use the hardware features of the Raspberry Pi Pico. They are accessed using straightforward high-level commands that avoid the complexities of dealing with the RP2040 chip and its hundreds of programming registers (the data sheet for the RP2040 alone runs to over 600 pages). For example, this is all that you need to send the word “hello” out of a serial port: SETPIN GP13, GP16, COM1 OPEN “COM1:” AS #1 PRINT #1, “hello” The first line allocates the I/O pins as the serial port, the second initialises the port and the third sends the text. Easy. siliconchip.com.au MMBasic features A major feature of the PicoMite is that it uses a full implementation of the BASIC language, not some cut-down version. You have three data types (double precision floating point, 64-bit integers and strings), long variable names, arrays with multiple dimensions and user-defined subroutines and functions. The list opposite gives an idea of its other features. MMBasic is largely compatible with Microsoft BASIC, so many programs downloaded from the Internet will run with little change. MMBasic also includes a built-in full-screen editor which lets you edit large programs directly on the Pico­ Mite. The edit/run/edit cycle is very fast, with a single keypress to jump between editing and running the program, then another to go back to editing again. MMBasic supports the full Raspberry Pi Pico set of hardware features, many of which are mentioned in the features list. MMBasic also adds features not native to the Raspberry Pi Pico, including support for SD cards and over a dozen LCD panel types, including touch input and advanced graphics. These capabilities are all covered in detail in the PicoMite User Manual, downloadable from the Silicon Chip website at siliconchip.com.au/ Shop/6/6060, or the author’s website (http://geoffg.net/picomite.html). That’s an extensive document, so the remainder of this article will cover the highlights and most important aspects of the PicoMite. The firmware is structured to work on any module using the RP2040 processor with at least 2MB of flash memory. As described in our article on the Pico, the RP2040 processor is used on many boards, including the Arduino Nano RP2040 Connect, the Adafruit Feather RP2040 and other variants from companies like Sparkfun and Pimoroni. So you can load and use the Pico­ Mite firmware on these just as well. We have published several MMBasic programming tutorials, including a two-part series on Getting Started with MMBasic in February, March, May & June 2017 (siliconchip.com.au/ Series/311) and Advanced Programming with MMBasic in the November & December 2016 issues (siliconchip. com.au/Series/307). siliconchip.com.au Full-featured, Microsoft BASIC compatible interpreter running on the Raspberry Pi Pico. Will work on any RP2040-based module with at least 2MB of flash. Runs from 1.8-5.5V at 11-43mA, depending on the CPU clock speed. Variables can be floating-point numbers, 64-bit integers or strings with support for long variable names, arrays with multiple dimensions, extensive string handling and user-defined subroutines and functions. A focus on ease-of-use with a beginner-friendly programming language, informative error messages and a rapid development cycle. Full support for all 26 Raspberry Pi Pico input/output pins and features. All pins can be digital inputs or outputs, along with up to three analog inputs, two bidirectional serial ports to over 1Mbaud, two SPI master ports to over 30MHz, two I2C master ports, 16 pulse-width modulated (PWM) outputs and 1-Wire I/O pins. Up to ten programs can be saved on the module, each up to 80KB; chaining allows for programs up to 800KB. RAM for variables, arrays and buffers is configurable and can be up to 80KB. Any program can be set to automatically run on power-up or reset. Configurable clock speed (48 to 250MHz). Internal temperature sensing of the processor. Supports colour displays up to 3.5in (diagonal), allowing the BASIC program to display text and draw lines, circles, boxes, etc in 65,535 colours. Resistive touch controllers are also supported. SD cards up to 32GB formatted in FAT16 or FAT32 are fully supported. This includes opening files for reading, writing or random access and loading and saving programs. It can play audio files (WAV format) on PWM outputs. Built-in support for commonly used devices including infrared remote controls, ultrasonic distance sensors, temperature sensors, humidity sensors, text display modules, battery-backed clock, numeric keypads and more. Programming and control via USB with no special software required; any computer running a VT100 terminal emulator will work. Programs can be easily transferred from a computer (Windows, Mac or Linux) via SD card, by using the XModem protocol or by streaming the program over the USB console. The built-in full-screen editor includes advanced features such as colour-coded syntax, search and copy, cut and paste. Australia's electronics magazine January 2022  65 up; the PicoMite will disconnect and then reconnect as a USB flash drive on your computer, ready for the firmware upload. The console The Raspberry Pi Pico is a popular, low-cost microcontroller module with plenty of memory, speed and I/Os. With our PicoMite firmware, you can program it in the easy-to-learn BASIC language with full access to all of the Raspberry Pi Pico’s advanced features. Micromite compatibility For readers familiar with our Micromite series of microcontrollers, the PicoMite is fully compatible with just a few differences to accommodate the unique hardware aspects of the Raspberry Pi Pico. This compatibility is so complete that you can take a BASIC program such as that used on our Micromite Air Quality Monitor (February 2020; siliconchip.com.au/Article/12337) and run it on the Raspberry Pi Pico with few or no changes (see screen grab overleaf). The PicoMite essentially implements all the features of the Micromite Plus except for display panels with a parallel interface, the library function and attached keyboards. Features inherited from the Micromite Plus include embedded C code, support for serial LCD panels, embedded fonts, advanced graphical (GUI) controls and an SD card interface with full FAT32 filesystem support. The PicoMite has fewer I/O pins than the Micromite Plus but it runs faster (up to 250MHz) and can accommodate larger programs. Probably its best feature is that it is a complete module with a USB connector, power supply and breadboard-friendly interface pins—all for a ridiculously low price (as little as $6!). Loading the firmware The RP2040 processor has a small amount of fixed read-only memory reserved for loading the firmware (called the bootloader), making it easy to load and test new firmware without special software. The following process will work with any modern computer (Windows, macOS or Linux). 66 Silicon Chip First, download the PicoMite firmware from one of the sites linked above. This is a zipped archive and the firmware file inside it has an extension of “.uf2”. Hold down the white button marked BOOTSEL on the top of the Pico and plug its USB interface into your computer while still holding down the button. Your computer should make a sound indicating a new USB device has been discovered, and the Pico will appear as a USB flash drive on your computer. Finally, drag and drop the firmware file onto the ‘drive’ created by the Pico, and your computer will upload it to the Pico. When the copy is complete, the Pico will automatically restart running MMBasic and reconnect to your computer, this time as a virtual serial port over USB. The green LED on the top of the Pico board will start slowly flashing to indicate that the PicoMite firmware is now running. The only purpose of the drive created by the Pico is to load firmware; any other type of file copied to it will be ignored. The firmware file will vanish when the copy completes, so this drive cannot be used as a memory stick. The handy thing about this process is that you can use it to install whatever firmware you like – you can easily upgrade (or downgrade) the PicoMite firmware or install something completely different (like Micropython) then later revert to the PicoMite firmware if you so wish. To make it easier to upgrade the PicoMite firmware, you can issue the command UPDATE FIRMWARE at the MMBasic command prompt. This will be as if you had pressed the BOOTSEL button while powering Australia's electronics magazine When the Raspberry Pi Pico reconnects to your computer following the firmware installation, it will act as an asynchronous serial port over USB. This is the MMBasic console; using this, you can configure MMBasic, load/run/edit programs etc. This will be familiar to anyone who has worked with the Micromite and it works the same. The serial port uses the CDC protocol and the drivers for this are standard in Windows 10 and will load automatically. For Windows 7 or 8.1, you will need a tool like Zadig (https://zadig. akeo.ie/) to install a generic driver for a “usbser” device. For macOS and Linux, see the notes in the PicoMite User Manual (but generally, it will ‘just work’ with a recent version of either OS). To use the console, you need to install a terminal emulator which will send your keystrokes to the PicoMite and display anything sent back by it. The recommended emulator for Windows is Tera Term (http://tera-term. en.lo4d.com/) which is free to download and use. The terminal emulator will need to know the number of the virtual serial port generated when the PicoMite is connected to your computer. With Windows, you can find that using Device Manager. This port number is entered in Tera Term by going to Setup → Serial Port... The other settings, including the baud rate, can be left at their defaults. Note that setting the baud rate to 1200 is another way of forcing the Pico into its update firmware mode, so avoid using that rate. With everything set up, pressing the Enter key in your terminal emulator should cause the PicoMite to echo back the greater than symbol (>), which is the MMBasic command prompt. To verify that you are indeed connected to a miniature BASIC computer, you can try a few commands: PRINT MM.VER Displays the version number of the firmware. MEMORY Displays the amount of free memory. siliconchip.com.au PRINT PI Displays an approximation of pi (π). Test program The standard test that people use when experimenting with a new microcontroller is to get it to flash one LED on and off. For this, we can use the green LED on the top of the Pico’s PCB. When MMBasic is running, this will slowly flash on/off, but for our test program we will take control of it and cause it to flash much more rapidly. The easiest way to enter a short BASIC program to do that is with the PicoMite’s built-in editor. This works the same as most of the editors that you will have used in the past. For example, any text typed in will be inserted at the cursor’s location, the arrow keys will move the cursor around, the delete key will delete the character at the cursor and the backspace key will delete the character before the cursor. The MMBasic editor has many other functions (search, replace, copy, paste etc) and these are detailed in the PicoMite User Manual. Type in the command EDIT at the command prompt to start the editor, then type in the following program: SETPIN GP25, DOUT DO PIN(GP25) = 1 PAUSE 100 PIN(GP25) = 0 PAUSE 300 LOOP When you have finished, press the F2 key on your keyboard (or CTRL+W). This will save your program, exit the editor and start the program running. You should be rewarded with the LED on the Pico rapidly flashing. If something goes wrong, you will get an error message. In that case, rerun the editor with the EDIT command and it will place the cursor on the line that caused the error, ready for you to correct it. The program starts by defining the I/O pin driving the LED (GP25) as an output, which places it under our program’s control. Then the program enters a loop where the pin is set high (which illuminates the LED) followed by a short pause of 100ms, then low followed by a 300ms pause. This repeats continuously. siliconchip.com.au You can break out of this program by pressing CTRL+C, which will return you to the command prompt where you can (if you wish) restart the editor and modify the program—for example, altering the delays to change the flash rate. Saving the program On the PicoMite, the BASIC program is held in RAM. This is necessary for good performance; flash memory is on a separate chip to the RP2040 processor and is accessed via a relatively slow serial interface, while the RAM is inside the RP2040 and therefore quick to access. The PicoMite firmware also loads critical sections of the MMBasic interpreter into RAM. This way, even though most of the PicoMite firmware is held in flash memory, BASIC programs run just as fast on the Pico­Mite as on other microcontrollers with internal flash memory. RAM is volatile, and its contents are lost if the power is interrupted. So the PicoMite will automatically save a copy in a reserved area of flash memory and restore that on power-up – or when the processor is restarted. The result is that you are not aware of the volatile nature of RAM. You can save multiple programs in the PicoMite’s flash memory using the command “FLASH SAVE n”, where n is a number between 1 and 10 which indicates the saved program’s location in flash memory. This means that you can save up to 10 independent programs to flash. For example, to save your program in location 1, you would use this command: FLASH SAVE 1 And you can run it anytime using this command: FLASH RUN 1 If you want this program to start running automatically every time power is applied, issue the command: OPTION AUTORUN 1 Similar commands allow you to list the flash locations, erase locations, overwrite locations etc. If you have attached an SD card to the PicoMite (details below), you can also save, load and run programs from the SD card. Be aware that any programs saved to the flash memory can be corrupted when upgrading the firmware, so they should be backed up before upgrading. This is because programs saved to flash have had keywords converted to tokens, and the upgraded firmware may use different tokens. If you forget and find your saved programs corrupted, you can downgrade to the previous version, back up your programs and then upgrade again. PicoMite inputs & outputs The I/O pin layout of the Pico­Mite is shown in Fig.1. There are 26 usable I/O pins. All can act as digital inputs or outputs, while three can be used as analog inputs (to measure voltage). There are also seven ground pins, one 3.3V output for external circuitry Fig.1: the I/O pins on the Raspberry Pi Pico and their capabilities under MMBasic. The full details are in the PicoMite User Manual, but here are some notes. VBUS is the 5V supply from the USB port, VSYS is the 5V input to the SMPS, 3V3EN enables the 3.3V regulator (low = off), RUN is the active-low reset pin, ADC VREF is the reference for voltage measurement and AGND is analog ground. Australia's electronics magazine January 2022  67 and some other pins, which we will cover later. The pins can be referenced by their pin number on the Pico board (4, 5, 6 etc) or their logical reference (GP2, GP3 etc). These are shown in green in Fig.1. For example, within MMBasic, PIN(17) and PIN(GP13) refer to the same I/O pin. To define how a pin works, you use the command “SETPIN pin, function”. Here, ‘pin’ is the I/O pin reference (eg, GP13) and ‘function’ is how you wish the pin to act. Common functions are DIN (digital input), DOUT (digital output), AIN (analog input), FIN (measure frequency) and so on. The PicoMite User Manual describes these in detail. As an example, the following will configure GP7 to measure frequency: SETPIN GP7, FIN As the PicoMite firmware has been designed to run on other boards that also use the RP2040 processor, the four I/O pins that are hidden on the Raspberry Pi Pico (GP23, GP24, GP25 and GP29) are usable in MMBasic as they may be exposed on other modules. The pin allocations for functions such as SPI, I2C and serial are somewhat configurable. For example, the receive pin for the second serial port (COM2:) can be GP5, GP9 or GP21 and the transmit pin can be GP4, GP8 or GP20. These pins are marked in cyan in Fig.1, as COM2 RX and COM2 TX. These pin allocations work equally well but must be configured via the SETPIN command before opening the serial port. The Pico has two serial ports, two SPI ports, two I2C ports and 16 PWM-capable outputs. Within MMBasic, they are all accessed in the same way; first, allocate the I/O pins using Fig.1 as your guide, then open the channel or device, then use the function. Powering the PicoMite The Raspberry Pi Pico has a particularly flexible power system which gives the user several options for powering the module. The power supply is shown in Fig.2 and consists of the main USB input, where the 5V power from this source is fed via a schottky diode to a switch-mode power supply (SMPS) that is capable of both buck (step-down) and boost (step-up) operation. Its 3.3V output is used to power the rest of the board and is made available on an edge pin (3V3) for powering external circuitry. The SMPS has an input range from 1.8V to 5.5V, which lends a great deal of flexibility to the Pico. It means that it can be powered via USB or a USB charger, a single Li-ion cell or a couple of AA cells, to name a few options. In general, there are three ways to supply power. The first is simply a USB source such as a laptop plugged into the USB socket. An alternative power source might be required for embedded applications, and this can be supplied via a schottky diode to the pin marked VSYS (pin 39). The schottky diode means that either or both the USB and external power source can be present without interfering with each other. This is handy if you want to plug a laptop into the Pico’s USB socket to debug your code while the module is in-circuit. The third method is to short the 3VEN pin (pin 37) to ground and supply an external source of 3.3V to the module via the 3V3 pin (pin 36). Grounding 3VEN will shut down the SMPS regulator and disconnect its output so that the 3V3 pin can be used as a 3.3V power input. The switching regulator generates a lot of electrical noise, so using a linear regulator to supply 3.3V to the board will make it much easier to use the analog inputs and produce noise-free audio signals using PWM. The power consumption of the PicoMite is modest. At its default 125MHz CPU clock, it draws about 21mA. This does not include any power drawn from the I/O pins or the 3V3 pin. The RP2040 processor’s clock can be varied from 48MHz to 250MHz under control of MMBasic (using the “OPTION CPUSPEED” command), and the power drawn varies accordingly, from 11mA to 43mA. Three AA alkaline cells can power the PicoMite running at 48MHz for weeks of continuous operation. Note that the specified top clock speed for the Raspberry Pi Pico is 133MHz; anything above that is regarded as overclocking. We tested several modules and most worked at 250MHz, so that can be considered a viable option. Special device support The PicoMite inherits support for several special devices from the Micromite. This includes an infrared remote control decoder supporting Sony and NEC remote controls, allowing BASIC programs to act on signals from universal remotes. Other natively supported devices include temperature sensors, humidity sensors, ultrasonic distance sensors, numeric keypads, and two-line LCD modules. All of these are easy to use. For example, the DISTANCE() function will trigger an ultrasonic distance sensor, wait for the echo and return the distance to the target in centimetres for your BASIC program to act on. As another example, if you want to measure temperature, just attach a DS18B20 sensor and use the TEMPR function to get the temperature in °C with a resolution of 0.1°C. You do not need to load libraries or write many lines of code; these functions are built in, and they just work. SD card support The PicoMite has built-in support for SD cards up to 32GB, formatted as FAT16 or FAT32. This includes full read/write for both programs and data files, navigating through subdirectories and support for long filenames. The files created by the PicoMite can be read and written on computers running Windows, Linux or macOS. Fig.2: the Raspberry Pi Pico has a flexible power system. The input voltage from either the USB or VBUS inputs is connected through a schottky diode to the buck-boost switch mode power supply, which produces 3.3V. This accommodates input voltages from 1.8V to 5.5V, allowing the PicoMite to run from a wide range of power sources, including single Li-ion cells and 2-3 alkaline cells. 68 Silicon Chip Australia's electronics magazine siliconchip.com.au Fig.3: the PicoMite has full support for (micro)SD cards. This diagram shows one way of connecting an SD card to the PicoMite and matches the example configuration commands listed in the text. MMBasic can open files for reading, writing or random access and load or save programs with cards up to 32GB formatted with FAT16 or FAT32. Communication with SD cards is via the SPI protocol, also used by many LCD panels and touch controllers. These all use what is called the System SPI port on the PicoMite, and the I/O pins used by this port need to be specified before any of these devices can be used. This is done using the following command: OPTION SYSTEM SPI CLK, TX, RX Here, CLK, TX and RX are the pins to use for these functions (as determined from Fig.1). For example, the following will dedicate the second SPI channel (called SPI2) to the System SPI function and define the I/O pins to use: OPTION SYSTEM SPI GP10, GP11, GP12 This option will be saved in flash memory and will be automatically reapplied on power-up, so it only needs to be entered once. Additionally, other SPI devices such as display panels will also use this port, so it does not need to be redefined for them. When allocated to the System SPI function, that port will not be available to the BASIC program (ie, it will be dedicated to the firmware). One thing to watch out for is that this command and other similar OPTION commands will cause the PicoMite to restart and that will disconnect your USB console connection, so you will need to re-establish it after entering the OPTION command. With the System SPI port defined, you can tell MMBasic that an SD card is connected and what pin to use for the Chip Select signal (CS). For example, if you used GP22 for Chip Select, the command would be: OPTION SDCARD GP22 As before, this option will be saved and automatically reapplied on powerup. It will also cause the PicoMite to restart. Fig.3 shows how the SD card socket should be wired up. With that done and the SD card interface configured in MMBasic, you can pop a card into the socket and try the “FILES” command, which should list the files and directories on the card. PWM and audio output With 16 PWM outputs, the Pico­ Mite has so many that you could (for example) dedicate some to controlling indicator LEDs. Your program can then create some cool effects by ramping the brightness up and down rather than simply switching the LEDs off and on. An RGB LED driven by three Connecting an SD card is simple and MMBasic provides full access to the files and directories on the card. BASIC programs can open or create files for reading, writing or random access, navigate the directory structure and create or delete directories. The files created by MMBasic can be accessed by computers running Windows, Linux or macOS. This does not match Fig.3 exactly, but only because a different GND pin has been used. siliconchip.com.au Australia's electronics magazine January 2022  69 PWM outputs would let you create almost any colour. One important use for PWM outputs is to generate program-controlled voltages, which can control analog devices such as motor speed controllers. For this, you just need to add a simple low-pass filter (details in the user manual) on the output to remove the carrier frequency. Another use is to play stereo WAV audio files from an SD card via a lowpass filter. These sound effects can be almost anything: chimes, voice instructions, a warning siren or simply background music. Playing the audio does not interrupt the BASIC program as MMBasic will play it in the background, so your program can continue doing its job (eg, controlling some process) regardless of the duration of the audio output. The audio output can also generate precise sinewaves for a simple “beep” or, because the frequency is very accurate, test the response of loudspeakers and other audio components. Display panels The PicoMite includes support for many display panels using various controller chips. These are mostly LCDs, but it also supports OLED and e-Ink based panels, ranging from a tiny 84 x 48 pixels to a more substantial 480 x 320 pixels. All of these use either the SPI or I2C interfaces. Panels using a parallel interface (as on the Micromite Plus) are not supported as there are not enough I/O pins on the Raspberry Pi Pico to practically implement that type of interface. Two popular series of LCD screens are based on the ILI9341 and ILI9488 controllers. The ILI9341 version comes in various sizes from 2.2in to 2.8in diagonal with 320 x 240 pixels. The ILI9488-based panels are generally 3.5in diagonally and have 480 x 320 pixels. Both use the System SPI bus, which needs to be configured as described above. Both LCD panels are set up similarly: OPTION LCDPANEL CTRL, OR, DC, RST, CS Where CTRL is the name of the controller chip, OR is the orientation (portrait, landscape etc), DC is the pin to use for the data/control signal, RST is the pin used for the reset signal and CS is the chip select pin. For example, to set up a panel with the ILI9341 controller in landscape orientation, wired as in Fig.4, the command would be: OPTION LCDPANEL ILI9341, L, GP26, GP27, GP28 That’s assuming you already have System SPI on GP18, GP19 & GP20 to suit the wiring shown in Fig.4. With the display panel configured, you can test it by running the command GUI TEST LCDPANEL and you should be greeted with multiple overlapping circles popping up all over the LCD screen (as shown in the lead photo). To terminate the test, press any key. Two of the supported displays use an I2C interface. To connect these, the System I2C interface must be configured similarly to the System SPI interface. The command is: Fig.4: here’s one way to wire up a touchscreen to the PicoMite. If you connect an SD card at the same time, you need to use the same SPI RX, TX and CLK connections for both. While this shows an ILI9341-based 320x240 display, the connections required for the ILI9488-based 480x320 touchscreens are virtually identical. 70 Silicon Chip Australia's electronics magazine OPTION SYSTEM I2C SDA, SCL Currently, the only other device that uses the System I2C interface is the real-time clock. Many LCD panels incorporate a resistive touch interface. This controller also uses the SPI protocol and should be connected as per the System SPI interface (like in Fig.4). Configuring the touch interface is straightforward, but it needs to be done after configuring the display panel. The command is: OPTION TOUCH CS, IRQ CS is the Chip Select output pin and IRQ is the interrupt input pin. For the circuit shown in Fig.4, this would be: OPTION TOUCH GP22, GP21 After the PicoMite has restarted, you need to calibrate the touch system with the GUI CALIBRATE command. This will progressively draw a target on all four corners of the screen for you to touch and the firmware will use that to accurately identify the pixel coordinates of any touch. Graphics support Connecting an LCD screen is quite common in the microcontroller world. What sets MMBasic apart is its extensive support for displaying graphs, images and graphical objects on the screen. This, along with the touch input, means that a user of your program can control your gadget using a colourful LCD screen with intuitive on-screen objects such as switches, keypads, dials and lights. The basic drawing commands allow you to set any pixel to any colour, draw lines, circles and boxes and draw text anywhere on the screen in any colour. The PicoMite includes seven differently-sized fonts, and you can embed more fonts in the BASIC program to provide precisely the look you want. If an SD card is fitted, the program can load images from the card and display these on the LCD panel. You can use this to show a logo or load a textured graphical background. The PicoMite has also inherited the advanced GUI controls from the Maximite Plus. These include radio buttons, checkboxes, on-screen dials, numeric input fields and much more. All of these require just one command in the BASIC program to define their siliconchip.com.au One feature (of many) that sets the PicoMite apart is its extensive support for graphs, images and graphical objects. Along with the touch input, this means that users can control your gadget using a colourful LCD screen with intuitive on-screen objects such as switches, keypads, dials and lights. position and characteristics (colour, size etc). From then on, MMBasic will manage the control for you. That includes making a button look like it is depressed when touched, checking a check box, drawing a graph etc. All that the BASIC program needs to do is check the status of a control (ticked, depressed etc) and take the appropriate action. The most advanced GUI control is the Text Input Box. When touched by the user, MMBasic will pop up a full on-screen QWERTY keyboard for text input. This allows the user to enter any text required by the program. While a full keyboard sounds as if it would be impracticable on a small display panel, it is actually quite useable, even on the 2.8in LCD screens. More information The PicoMite is fully compatible with our Micromite series of microcontrollers, with just a few differences to accommodate the unique features of the Raspberry Pi Pico. This screenshot shows the PicoMite running our Micromite Air Quality Monitor from February 2020, originally designed for the Micromite LCD BackPack. The PicoMite is supported by the PicoMite User Manual, which can be downloaded from the S ilicon Chip website at siliconchip.com.au/ Shop/6/6060, or the author’s website (http://geoffg.net/picomite.html). This manual runs to over 160 pages and covers the details of using the Pico­ Mite and writing programs, including a tutorial on programming in the BASIC language. There is also an active user community on The Back Shed Forum (thebackshed.com/forum/ViewForum. php?FID=16), where many PicoMite users and experts in BASIC programming hang out. They are a friendly bunch and will be happy to help out if you are stuck on a complicated problem. The PicoMite firmware is completely free, and you can get the Raspberry Pi Pico for as little as $6, so the cost of playing with this powerful little fellow is tiny. Why not give it a go? You might just want to have fun making a LED flash, but it could evolve into your next burglar alarm or reticSC ulation controller. While it has fewer I/O pins, you can also turn other RP2040based boards like this Tiny2040 into a PicoMite with the same firmware. siliconchip.com.au When the user touches a text box on the screen, a keyboard like this pops up, allowing them to enter a name or other text string. Australia's electronics magazine January 2022  71 Using Cheap Asian Electronic Modules By Jim Rowe Geekcreit’s LTDZ V5.0 Spectrum Analyser This compact unit is low in cost but can perform spectral analysis from 35MHz to 4.4GHz. It also includes a tracking generator for frequencydomain analysis of filters, RF amplifiers and similar items. It needs to be controlled from a PC via a USB cable (which also provides its 5V DC power supply), using a very impressive free application. A bout a year ago, I bought an earlier version of the Geekcreit LTDZ spectrum analyser, which came as a ‘naked PCB’ module. The idea was to check it out and write a review for Silicon Chip, but I wasn’t too impressed when I tried it out. The software needed to control it was both difficult to find and rather flaky, and the unit itself had poor sensitivity combined with a relatively high noise floor. There wasn’t much I could say about it that was positive, so I decided to give it a pass. But earlier this year, I found that an improved version of the analyser had become available (the LTDZ V5.0), coming inside an extruded aluminium case and not costing all that much more than the original ‘naked’ version. I also discovered that although Geekcreit was still recommending the same control software that I had found so problematic, a much better program had appeared – one that you can download for free. It’s called VMA Simple Spectrum Analyser (VMA SSA), written by Vitor 72 Silicon Chip Martins Augusto, who lives in Portugal, and it can be downloaded from his site: siliconchip.com.au/link/ab87 So I went ahead and ordered an LTDZ V5.0 from the Banggood website (siliconchip.com.au/link/ab88), paying US$46 plus US$4.87 for shipping, which came to a total of $75. I also downloaded Mr Augusto’s VMA SSA software. As you can see from the photos, the LTDZ V5.0 is quite compact at 62 x 55 x 19mm, not counting the two SMA connectors extending from the input/ output end. It also weighs only 83 grams. It comes complete with a 950mm-long USB2.0 cable, with a Type-A plug at one end and a micro Type-B connector at the other end, to connect it to a PC. The LTDZ V5.0 is quite well made, although the panels at each end of the case in the unit I received had holes for the countersink-head mounting screws which were not countersunk. This made it look unfinished until I removed the panels and countersunk their holes to complete the job. Australia's electronics magazine This also gave me the opportunity to examine the PCB inside and take its photo. All of the components in the LTDZ V5.0 are mounted directly on this PCB. Like the Geekcreit VHF-UHF signal generator module I reviewed recently (December 2021; siliconchip.com.au/ Article/15139), the LTDZ V5.0 uses the Analog Devices ADF4351 digital PLL synthesiser chip. In fact, it uses two of them: one in the analyser section, and one in the tracking generator (TG) section. The ADF4351 is quite a complex device, but we had a pretty detailed description of how it works in the May 2018 issue, specifically my review of the Digitally Controlled Oscillator module (May 2018; siliconchip.com. au/Article/11073). So please read that article if you want to know more about how this chip works. You can also find the data sheet for it at: siliconchip.com. au/link/aajc By the way, the LTDZ draws about 100mA from the PC in standby mode, siliconchip.com.au Fig.1: block diagram of the LTDZ 5.0 module. The most important sections are the two ADF4351 synthesisers and the STM32 ARM microcontroller. rising to about 350mA when it’s scanning with the tracking generator also running. How the analyser works I have prepared a block diagram (Fig.1) that shows how the LTDZ 5.0 works. The ADF4351 chip at the bottom of this diagram forms the heart of the analyser section, while the one at upper right provides the tracking generator function. The STM32F103 MCU (microcontroller) handles the operation of both sections, directed by the software running in the PC. The two USB signal lines (D- & D+) from the LTDZ’s micro-USB connector at upper left pass through a CH340G USART chip before reaching the MCU. The micro has an 8MHz clock crystal, while the CH340G has a 12MHz crystal. Both ADF4351 synthesiser chips are supplied with their master reference clock from the 25MHz crystal oscillator at centre right. But they are controlled by the MCU via two separate SPI (serial program interface) ports. The analyser ADF4351 is controlled via the MCU’s SPI1 port (SPI_SCK, SPI_MOSI and SPI_NSS), while the tracking generator ADF4351 is controlled via the SPI2 port. The spectrum analyser section of the LTDZ involves the devices and signal paths shown at lower left in Fig.1. This spectrum analyser operates similarly to a ‘superheterodyne’ radio receiver, where incoming signals at a relatively high frequency are shifted down to a much lower fixed IF (intermediate frequency) before being detected. In this case, the ADF4351 at lower centre corresponds to the local oscillator (LO). Its output is fed to one input of the IAM-81008 double-balanced mixer while the Analyser’s input signal goes to the other input. So its output will be the heterodyne products of the two signals. The mixer’s output signal then goes through a low-pass filter to remove any ‘sum’ heterodyne components, leaving only the difference, which is the IF signal we want. This is then fed to an AD8307 logarithmic amplifier and detector, which generates a DC output voltage proportional to the IF signal level. This, in The internals of the Geekcreit LTDZ spectrum analyser. siliconchip.com.au Australia's electronics magazine January 2022  73 Screen 1: the VMA SSA software output when the LTDZ input is terminated with a 50W resistor over its frequency range of 35-4400MHz. Screen 2: the LTDZ input was now connected to an external VHF/UHF discone antenna with a plot over 200-208MHz. The average signal level was -49dBm over that range. turn, goes to an analog-to-digital input (ADC123) of the MCU. As a result of all this, the MCU can measure the input signal level corresponding to the current frequency of the ADF4351’ local oscillator’. As the MCU changes the LO frequency over the selected range, it can send measurements of the input signal level at each point back to the software running in the PC. The software can then take these measurements and present them as a graph, plotted against frequency. That’s how this type of spectrum analyser works. This is the same basic system used in many spectrum analysers (while some instead use very fast sampling and a digital Fourier transform). But in place of the simple low-pass filter between the mixer and the log detector, high-end models have several selectable bandpass filters which offer a choice of resolution bandwidth (RBW) settings. Most higher-end units also have a wideband amplifier between the RF input connector and the mixer’s input, increasing the analyser’s input sensitivity. This is so that they can analyse lower level signals, like those from many antennas. The tracking generator is really just the second ADF4351 chip, which the MCU can program to provide an output signal of the same frequency that is currently being sensed by the analyser section, at a relatively constant level of approximately 0dBm (224mV). The tracking generator can be switched on or off using pushbutton switch S1, so it can be turned on only when needed. There are also four indicator LEDs shown in Fig.1. LED1 indicates when the tracking generator is enabled, LED3 when the LTDZ has power applied, LED4 when the analyser section is working, and LED2 when both ADF4351s are locked to the designated frequency. The VMA SSA application Screen 3: a Gratten GA1484B VHF-UHF signal generator was used to provide the LTDZ with an unmodulated 2.5GHz output at 0dBm. The software was then set to scan over 2.4-2.6GHz. 74 Silicon Chip Australia's electronics magazine As mentioned earlier, Mr Augusto’s VMA SSA software can be downloaded for free (siliconchip.com.au/ link/ab87). You can also download a 54-page PDF User Guide from the same page. However, after downloading and installing the app, you have to contact him by email to obtain an activation code before you can run it. This siliconchip.com.au activation code will only function for up to three months, after which you will have to request another code. Or, if you wish, you can make a small donation via PayPal of around US$10, after which you will be sent a ‘permanent’ activation code. After using VMA SSA for a short time, I was so impressed that I sent Mr Augusto a donation of $25 and received a permanent activation code. There is no doubt in my mind that it’s massively better and much easier to use than the NWT4.11.09 software that Geekcreit still recommends. Incidentally, the file you download from Mr Augusto’s site is zipped, but when you unzip it, you will get the main EXE file plus several auxiliary files. All you have to do is copy it to a suitable folder and then launch the executable. But don’t install it to “C:\ Program Files” or “C:\Program Files (X86)” because Windows 10 limits access to files in those folders, which can cause problems. The ‘front’ of the LTDZ module houses the SMA sockets for the RF input and output connections. There are two status LEDs which show the current operating mode. Trying it out All I had to do initially was plug the LTDZ into my computer using the supplied cable and launch the VMA SSA software. Next, I clicked on its Setup menu, to tell it the virtual COM port number which the LTDZ has been assigned (in my case, COM3) and the particular Analyser model. The VMA SSA application can work with five different units, with the LTDZ V5.0 listed as “SMA Simple Spectrum Analyser Version 2 – 35MHz-4.4GHz – ADF4351”. You then need to select the “Spectrum” option at the top left of the screen. This gives you the main screen for spectrum analysis, as shown in the screen grabs. Most of the screen is occupied by the centre plotting graticule, with a narrower graticule below it that can show a ‘waterfall’ display (although the two can be swapped, if you wish). On the right are most of the control setting controls, with a large START/ STOP button at the top. Click on any of the small Frequency setting boxes on the right opens a ‘keyboard’ dialog box that makes it easy to enter a new frequency. This also applies if you click on any of the other small boxes, for example, the “Samples” box, the “Wait (us)” box or the “Marker1” or “Marker2” boxes. siliconchip.com.au The ‘rear’ of the module houses a micro Type-B USB socket for connecting to a computer, plus two more status LEDs to indicate STM32 operation and power, and a pushbutton labelled “KEY” which controls the tracking generator. Screen 1 shows what was displayed when I fitted a 50W termination to the LTDZ input, set VMA SSA for the full span of 35-4400MHz and clicked the START button. This is the ‘noise floor’ of the LTDZ, which is almost constant at -76.9dBm over the whole frequency range. Screen 2 shows what was displayed when I connected the input of the LTDZ to an external VHF/UHF discone antenna, and set the VMA SSA software to scan from 200MHz to 208MHz (the frequency range used by Sydney’s DAB+ transponders). The full range of transponder signals is shown, with an average level of about -49dBm. Note Australia's electronics magazine those five sharp ‘notches’ though; more about this shortly. The next step was to power up my Gratten GA1484B VHF-UHF signal generator and set it to produce an unmodulated output of 2500MHz (2.5GHz) at 0dBm. I then connected its output to the LTDZ input via a 2m-long SMA-SMA cable, and set the VMA SSA software to scan from 2400MHz to 2600MHz (a span of 200MHz). This resulted in the display shown in Screen 3, where you can see the main signal spike at 2500.00MHz accompanied by a pair of smaller spikes (about -66dBm) about 25MHz on either side. There are also a couple January 2022  75 Screen 4: a ‘close-up’ of the output from Screen 3, this time with a range of 2495-2505MHz, which shows the singular peak from before was actually a pair. Screen 5: the bandpass curve over 800-1300MHz of a FlightAware ADSB filter. Note the flat response between 1000-1150MHz that falls away at both ends. Screen 6: the plot of a Mini-Circuits -30dB attenuator over the full 35-4400MHz range is fairly smooth until it starts dipping past 3.7GHz. 76 Silicon Chip Australia's electronics magazine of much smaller spikes of -73/-74dBm, about 75MHz on either side. I’m sure those extra spikes are not coming from my signal generator, because they don’t show up when I check it with my Signal Hound USB-SA44 spectrum analyser. They are probably the result of the LTDZ’s fixed and relatively wideband RBW. The other thing to note about this display is that the amplitude of the main signal in the centre is about -13dBm, quite a bit lower than the generator’s 0dBm output. This is considerably lower than you’d expect, even allowing for losses in the 2m long SMA-SMA cable (about 2.5-3.0dB). Notch artefact The next step was to leave the signal generator set to 2500MHz with 0dBm output and connected to the LTDZ input, but to change the VMA SSA app’s frequency settings to give a much smaller spectrum span of 10MHz (ie, 5MHz either side of 2.5GHz). This gave the display shown in Screen 4. The spike at 2500MHz has now expanded into a pair of ‘twin peaks’, with a fairly deep notch between them. The twin peaks reach an amplitude of about -2.5dBm, much closer to the correct value. But the notch in the centre reaches down to about -31dBm, which is a bit disconcerting. It turns out that this kind of notch is basically due to the fixed and relatively wide RBW of the LTDZ and similar low-cost analysers. As Vitor Augusto explains in his blog post dated 13th October 2017 (siliconchip.com.au/ link/ab8a), the fixed and wide RBW causes them to have a ‘blind spot’ in the centre of their ‘scanning slot’ as the Analyser moves the input signals past it. It’s this blind spot that causes a notch in the centre of signals with a narrow bandwidth. That’s why professional (and much higher-cost) spectrum analysers give you a choice of RBW settings, as low as 10kHz Mr Augusto has included a notch function into his VMA SSA app, which, when selected, can fill in this kind of notch by replacing it with a straight line between the twin peaks. But this is just a cosmetic workaround, as he admits; crunching the scanning data to truly remove the notching would be pretty complicated. siliconchip.com.au In another post dated 4th February this year (siliconchip.com.au/link/ ab89), Mr Augusto announced that a colleague of his named Domenico had put much work into improving the performance of LTDZ analysers. This is both in terms of improving the hardware (presumably concentrated around the low-pass filter) and revising the firmware in the STM32F108 MCU. In his February post, Mr Augusto provided a link to a beta version of Dominico’s revised firmware. However, he didn’t give any details of Dominico’s changes to the LTDZ’s hardware. More details on the current product Getting back to my review of the product as it stands today, I decided to try using the LTDZ’s tracking generator to perform a couple of spectrum scans of circuitry connected between the tracking generator output and the Spectrum Analyser input. The first item I scanned was a FlightAware ADSB bandpass filter. This was connected via a 150mm-long SMASMA cable. Then after pressing the “Key” button (S1) on the rear of the LTDZ’s case to turn on the tracking generator, it was simply a matter of setting VMA SSA to scan between 800MHz and 1300MHz, and clicking on the START button. The filter’s bandpass curve was then displayed, as shown in Screen 5. The filter has a flat response from 1000MHz to 1150MHz, with an insertion loss of about 4dB, falling away quite steeply at either end. Just the shot for receiving ADSB signals centred on 1090MHz! Finally, I ran a series of tests using SMA-SMA fixed attenuators, again connected between the TG output and the analyser’s RF input using a 150mm-long SMA-SMA cable. For these tests, the VMA SSA app was set for a full scan from 35MHz to 4400MHz, to show how the attenuators behaved over the entire range. I also checked the span with the 150mm long cable by itself, for reference. Screen 6 shows the result for a Mini-Circuits -30dB attenuator. As you can see, it’s reasonably smooth over the full range, apart from a small bump in the centre and a couple of dips at about 3700MHz and 4100MHz. Overall, it just curves slowly upward from -30dBm at 35MHz to -25dBm at 2400MHz, then slowly downward to -30dBm at about 3400MHz and further down to about -40dBm at 4400MHz. The result when checking the 150mm cable by itself was somewhat flatter, varying from about -5dBm at 35MHz to -3dBm at 470MHz and then curving down and up by less than 2dB right up to 4400MHz. But it also had dips at 3700MHz and 4100MHz, which might be due to reflections in the cable. My verdict The Geekcreit LTDZ V5.0 spectrum analyser is a low-cost unit that must be used in conjunction with a PC, and operates over a wide frequency range, from 35MHz to 4400MHz. It also boasts a tracking generator covering the same frequency range, with an output level of around 0dBm. Used together with Mr Augusto’s VMA SSA application, it’s capable of performing a surprising number of spectrum analysis jobs. But it does have a few shortcomings, of which the most irritating is probably those ‘notches’ which appear in the centre of narrow-band signal peaks. These are caused by the fixed and wide bandwidth of the low-pass filter between the IAM-81008 double-balanced mixer and the AD8307 log amplifier/detector. The LTDZ does have another shortcoming: its relatively low sensitivity. Its noise floor is about -76dBm, which corresponds to 35μV. That means it will be effectively ‘blind’ for signals below 50μV or so. Presumably, this low sensitivity is because there is no amplifier between the LTDZ’s RF input connector and the input of the IAM-81008 mixer. So it might be possible to improve the sensitivity by connecting a lownoise wideband amplifier ahead of its RF input. There are a few of these currently available, some even having the amplifier circuitry inside a shield – either on the PCB, or by fitting the complete amplifier inside a small metal case. I have ordered a couple of these amplifier modules to try them out with the LTDZ, and if the results are satisfactory, I will cover them in a future SC article. SMD Test Build it yourself Tweezers ● Resistance measurement: 10W to 1MW ● Capacitance measurements: 1nF to 10μF ● Diode measurements: polarity & forward voltage, up to about 3V ● Compact OLED display readout ● Runs from a single lithium coin cell, ~five years of standby life ● Can measure components in-circuit under some circumstances Complete Kit for $35 Includes everything pictured, except the lithium button cell and brass tips. October 2021 issue siliconchip.com.au/Article/15057 SC5934: $35 + postage siliconchip.com.au/Shop/20/5934 Vintage Radio The Mysterious Mickey OZ by Astor By Ian Batty This is an iconic, well-performing radio from the early 1930s; it was built into a Queensland Maple case, and is a ‘must have’ for any serious collector of Australian electronic technology. However, it’s a nightmare to work on. T his radio was previously described by Rodney Champness in the March 2004 issue (siliconchip.com. au/Article/3438), but as it’s an important early Australian set, I decided to revisit it in a more in-depth manner. That earlier article went into very little detail on how the circuit operates, and the radio was not actually restored nor tested. Some aspects of the circuit are unusual and interesting, as I shall describe later. The Astor Mickey began as a transformerless AC/DC set adapted from an American 110V design. All valve heaters were in series, with the US design modified for the Australian release as serial numbers 1 to 460. The 110V set’s heater dropping resistor was increased to 580W to permit operation on our nominal 230V mains and maintain the heater string voltage of around 69V. This resistor dissipated some 51W of the total 80-odd watts. This heating was managed by ventilation slots in the sides and bottom of the compact timber cabinet, and by inserting a sheet of asbestos inside the upper right (viewed from behind). The asbestos heat shield continued well in to the 7000 series. From around 1935, some early models that 78 Silicon Chip had been returned to the factory were re-released with a repaired chassis and new cases. The sets are distinguished by the curved ‘ogee’ depression in the case’s front edge, but low serial numbers. Also, some sets had an asbestos sheet fitted between the output valve and the mains transformer. Asbestos is a known carcinogen. The complete serial numbers of these sets are not known. At some point, the asbestos sheet was replaced by a thin sheet of timber. Readers are advised to examine their sets to determine whether the asbestos is in place. For advice on how to handle asbestos, see siliconchip.com.au/link/ab9k Notable aspects Donald Haines lodged his US2148266 pentagrid patent in 1933 (the design used in the 2A7/6A7/6A8 and descendants), and Astor released the AC/DC Mickey in that same year. So it’s a standout example of a very early superhet. Other notable aspects of this set are the use of back bias for the 6B7 and the use of regeneration in the converter, a most unusual circuit strategy used Article sources This article draws on Philip Leahy’s Circuits 1934-1940 Book 11, Astor/Breville Circuits and its Supplement, published by the Historical Radio Society of Australia (HRSA). Philip, assisted by Jim Easson, has collected comprehensive circuits and technical notes for very many radios made and sold in Australia, and the Astor/Breville book has proven invaluable in writing this article. Refer to Philip’s book for complete descriptions, circuit diagrams, circuit voltages and sensitivity/performance figures. Consider also getting Philip’s entire series – it contains many Australian radios not listed in the famous Australian Official Radio Service Manuals that were either not included, released before the AORSMs began publication in 1938, or manufactured after the AORSMs ceased publication in 1956. See the HRSA website (www.hrsa1.com) for Leahy’s ten-volume series’ contents, but note that book ten is still in preparation at the time of writing this. Australia's electronics magazine siliconchip.com.au It’s important to note that most models of the Astor Mickey OZ used asbestos in the timber cabinet, so the utmost care should be taken when handling this – siliconchip. com.au/link/ab9k The cabinet itself is small for its time at 305mm wide, 180mm high and 140mm deep. only by a very few designers, and one that had disappeared by the late 1930s. Returning to the power supply, serials 461 onward used a mains transformer with full-wave rectification. The change to AC-only operation resulted in the OZ circuit of 1933 (Leahy, p11; see adjcaent panel). This design underwent frequent change; consult Leahy for the most complete collection of circuits. He lists six variants. The basic circuit was also used for other Mickey sets (the Bakelite EC and the stunning Mickey Grand among them) and for other, later sets from Astor. The set I’m describing, serial number 7490 (OZ7490), appears in the Leahy Supplement on p11. The principal difference from the more common issues is the use of back-bias for the demodulator/AGC/audio valve, a duo-diode pentode 6B7. There were many changes to the OZ circuit, the cabinet and even the dial cloth and cabinet ventilation/geometry over the production run. Philip Leahy and Jim Easson have compiled the most complete list of these changes (see the adjacent panel). nightmare to work on is that it looks as though one team bolted the power transformer, IF cans and gang on to the top of the chassis, the next team turned it upside down and threw in a handful of parts before the final team just soldered everything to everything else. Using the military criteria of Reliability, Maintainability and Availability, I give it scores of 8, 0, 10, getting zero for maintainability only because you can’t give a negative score. All wiring is point-to-point without tagstrips; my set had several instances of connected components just having their pigtails twisted together in midair and soldered. You can pick repairs and modifications pretty easily. Resistors are mostly the old ‘cartridge-cap’ body-end-band coded or cylindrical ‘dogbone’ bodyend-dot coded types. All original non-electrolytic capacitors were from Aerovox or TCC. The picture overleaf of an original Mickey, supplied by Andrew Wakeman, shows four ‘dogbone’ resistors (three green and one red), and one cartridge-cap resistor (purple body). There is also a large paper capacitor (C27, sitting vertically) with a band of black friction tape insulating some of the back-bias circuit’s solder connections. The undisturbed friction tape is factory-original. Reality check The reason I described this set as a The overall layout of the chassis was very compact, with metal sheeting needed to help with airflow. This set was serial number 7490. siliconchip.com.au Australia's electronics magazine January 2022  79 A simple notch filter (rather than the bandpass filter used) would have given immunity to IF breakthrough without compromising the performance. Converter The top view of the chassis gives a better look at the ‘messy’ arrangement near the tuning gang which is for the antenna circuitry. Circuit description The circuit is shown in Fig.1. There is a filter circuit (L1/C1) between the antenna connection and the antenna coil primary (L2). Some references describe this as necessary to suppress interference/IF breakthough from marine/spark transmitters in the lower end of the HF band, and to suppress image responses in the 986~2111kHz range. By 1932, 500kHz had been declared as the International Distress Frequency, but would have presented little interference due to infrequent traffic. ‘Everyday’ maritime communications were relocated to frequencies of 425, 454, 468, 480 and 512kHz, so the potential for IF breakthrough (especially from the 454kHz allocation) would have been a reality. The filter certainly does have significant attenuation towards the bottom end as the sensitivity graph (Fig.4) and the IF injection voltages on the circuit diagram show. It would also (as the manufacturer’s description states) improve image suppression as the set is tuned past about 1000kHz. Unfortunately, it does this by cutting receiver sensitivity, by a factor exceeding two times at the top end. The 6A7 converter uses grid 1 for the oscillator grid and grid 2 as the oscillator anode in the conventional pentagrid circuit. It uses ‘padder’ feedback, where the primary winding couples via 1nF capacitor C14 to the secondary, in addition to the mutual inductance between primary and secondary. That RF connection goes to ground via padder C12, a fixed 300pF shunted by a variable 30~60pF. Padder feedback is used to improve oscillator activity (and thus conversion gain) in converters with known weak oscillator performance. Although the 6A7 is specified for anode voltages as low as 100V and should work reliably with the conventional circuit, OZ7490 showed considerable variation in oscillator output over the tuning band. The use of padder feedback suggests that the conventional transformercoupled “Armstrong oscillator” design was found inadequate with the set’s low HT. The tuning dial, with reduction drive, is uncalibrated. It is marked (confusingly) as “100” at the low end of the band to “0” at the high end – see Fig.2. Fig.1: a redrawn version of the Astor Mickey OZ (serial 7490) circuit with suggested test points. The original circuit is available but the labels are hard to make out. 80 Silicon Chip Australia's electronics magazine siliconchip.com.au An original Mickey showing four ‘dogbone’ resistors and one large paper capacitor. IF circuitry The IF transformers have tuned primaries and secondaries. Despite their somewhat ‘agricultural’ construction, OZ7490 returned a -3dB bandwidth of ±2kHz, and a -60dB bandwidth of ±35kHz, an acceptable selectivity even today. The first IF’s primary tuning capacitor (C9) is a bit of a head-scratcher, as its ‘cold’ end is returned not to the HT side of the primary (as is nearuniversal), but to the converter cathode. This gives a feedback path from The vacant space in my set and the chassis hole to the right would have been occupied by the internal/external speaker switch on earlier releases. No original electrolytic capacitors remain in my set. the converter’s anode to its cathode via the first IF primary tuning capacitor, C9. As there is no signal inversion between cathode and anode (the ‘grounded grid’ principle), C9 forms a capacitive voltage divider with cathode bypass capacitor (C8) to give positive feedback and a moderate boost in gain. This explains the ‘low’ value used for C8. OZ7490 used 10nF, while Leahy (Supplement, p11) shows 6nF. You would expect it to be the same as the IF amplifier’s C16 bypass value, 50nF. This is a reminder of just how clever some early designs were. In practice, the feedback circuit in OZ7490 gives a gain of some +4dB, about 1.5 times; the lower value of 6nF would give more boost. For a full description of this part of the circuit, including a warning about oscillation, see Leahy, p108. That reference describes the design’s use in the similar model AC. Loudspeaker driving The OZ model uses an electrodynamic speaker on a plug-in frame that mates to a chassis-mounted four-pin socket, held in by two side catches. This allows the entire speaker assembly to be removed easily. The initial release used a 1.9kW field coil, which was reduced to 1.35kW, then 1.2kW. The Type 43 output valve is specified for a 4kW load, implying that that the speaker transformer has a 4kW primary. As the field coil is used as the filter choke in a back-bias circuit in most versions, back-bias voltages change with field coil resistance. The power transformer’s HT secondary voltage must be suited to the field coil resistance, thus restorers need to know Fig.2: this is how the dial markings correspond to the actual tuned frequencies. Not only is the tuning dial unusual because it is marked 0-100 without any frequencies, but also because setting it to 0 tunes it to the highest frequency, and 100 the lowest. siliconchip.com.au Australia's electronics magazine January 2022  81 which field coil they have if they intend to replace the power transformer. Be aware that there were at least three different mains transformers over the life of the model. OZ7490’s speaker was marked as 1.35kW but it measured as 1.195kW. If the speaker is replaced with one having a different field coil resistance, that will alter the back-bias supply, so unless you also change the power transformer secondary voltage, the resistive divider may need modification to preserve the output valve’s bias supply of around -19.5V (measured as -18.5V at the grid using a 10MW input impedance voltmeter). Some sets also use back-bias for the 6B7 demodulator/AGC/first audio stage. Matching the divider to the field coil’s voltage drop is vital for correct operation. You might see sets with a 550W resistor in series with the field. This allowed the lower-resistance 1.35kW (later 1.2kW) speaker to be substituted for the original while demanding no modification to the back-bias circuit. The “Minnie” (ad shown in Fig.3) also used an electrodynamic speaker with transformer attached. Contained in a case approaching the size of a console radio, it gave much-improved bass response. Connecting via a fourpin socket on the back of the chassis, output was switched from the internal speaker to the Minnie via a side-mounted switch. The switch was no longer fitted by OZ9490, with the hole in the cabinet side remaining, and the socket hole in the chassis rear blanked by a Bakelite sheet. Power supply The AC/DC set used the 25Z5’s two diodes in parallel to form a half-wave rectifier. This would have given an HT of only about 140V, common in early US mains-powered sets. From 461 onwards, a conventional mains transformer with a centretapped secondary and the 25Z5 were used in a full-wave circuit. While it would have been possible to wind the mains transformer to give a more common (higher) HT voltage, Astor’s designers chose to keep the original RF/IF/Audio design, keeping the low HT. The basic Mickey design was used for other models for several years, so low HT voltages were a feature of Astor designs for some years following the OZ. The 25Z5, with two independent, indirectly-heated diodes, was also used as a voltage doubler in 110V AC sets, for an HT closer to the more common 200~250V. Readers may hesitate over the speaker field being in the negative Fig.3: an ad for the Astor Minnie Mouse “console-size” extension speaker. Despite a similar style to the OZ cabinet, it gave better bass response. 82 Silicon Chip Australia's electronics magazine supply lead. This arrangement works just as well as the more common positive-lead connection, with the same total voltage loss, and with two advantages. Firstly, the voltage drop across the field can be used to provide ‘free’ back bias; the voltage drop is there anyway, so why not use it rather than adding an extra resistor with more HT loss? Secondly, since the entire field is no longer at HT potential, failures due to electrolytic corrosion are much less likely. The two HT filter capacitors were originally contained in a single tinplate case, but these were absent from OZ7490. The capacitors were described as ‘dry’ electrolytics, distinguishing them from the liquid-filled vertical cylindrical types common at the time. The original filter caps were replaced by a Ducon ‘pigtail’ tubular type (more on that later). The paper types in the set were Chanex, Ducon and Aerovox brand while the mica types were TCC. Valve biasing Valve biasing varies from one model to another. The AC/DC set used back-biasing on the output valve but individual cathode biasing on the other three. Converter biasing, initially using fixed-cathode bias, was changed to preset variable from around serial number 7100 on, as found in OZ7490. The converter’s local oscillator anode is supplied from the main HT via a 10kW resistor in all circuits, but the converter screen supply comes from the R13-14-15 voltage divider strung between HT and ground. The original cathode bias on the 6B7 circuit deserves comment. From the initial issue to about serial 7100, it was supplied by a 7kW cathode resistor and bypassed using a 5μF capacitor, raising the cathode above ground and providing negative bias for the pentode section. But this also put a negative bias on the demodulator/AGC diode pair, so that the demodulator would not respond to weaker signals at all. To prevent this, the volume control, acting as the diode load, is returned to the 6B7 cathode. The demodulator works as usual, and the AGC operates with no delay bias. The only odd effect is to put the entire AGC line a volt or two above siliconchip.com.au ground. This means that the converter and IF amplifier grids are also above ground. This unusual biasing is compensated by the cathode voltages being a little higher than usual. The 6B7 uses very low screen and anode voltages (19V and 36V respectively), derived from the R13-R14-R15 HT divider. However, this ‘starved’ design gives a stage gain close to 50 times, adequate for the application. Against this, the Type 75 triode used in the later model EC can achieve a similar gain with a simpler circuit. From about serial 7100 onward (including OZ7490), the 6B7 cathode is connected to ground, with backbias for the pentode section. This corrected the problem of a positive AGC line, so the AGC circuit works just as you’d expect it: 0V for no signal and increasingly negative as the signal strength increases. No manufacturer drawing exists, but Leahy’s Supplement has the correct circuit. The later EC model also uses back-bias on its Type 75 duo-diode triode’s audio section. OZ7490’s output valve has around -19.5V applied from the back-bias divider, with its control grid returned to ground. Serial numbers from about 1300 to 5300 see the control grid returned to ground with an 810W cathode bias resistor and 5μF electrolytic bypass capacitor. A final note on terminology: original texts refer to semi-variable capacitors as ‘padders’, regardless of their function. Thus the semi-variable capacitor C9 (tuning the first IF primary) is described as a ‘padder’, as is C12, the LO tracking circuit. Modern terminology describes C7 (and C9, 11, 13, C16 and 18) as trimmers, reserving ‘padder’ for capacitors such as C12 alone. Repairs I bought this set at an HRSA auction some years ago and it was on display until just recently. On inspection, it showed some activity, mostly hum. Some capacitors had been replaced, along with the 6B7 load resistor (R11). Bias divider R16-R17-R18 had been modified to add a resistor in parallel with R18, and an extra bypass capacitor had been added across R18. The mains lead was figure-8 flex and was not secured against twisting or pulling. I replaced it with a clothcovered three-core lead that is held to siliconchip.com.au the chassis with a cord anchor. While the anchor is a modern device, it gives complete security and will not split or perish as rubber grommets can. The bias voltage on V4 (the output valve) was low, as was the HT voltage. The first HT filter capacitor (C23) was missing. Valve testing showed converter V1 to be weak, so I replaced it. All the others tested OK. This was a relief, as the Type 43 and 25Z5/25Z6 (with 25V heaters) are not so readily available as the 6V heater types. I attacked the bias divider first. The added electrolytic capacitor (across R18) had enough leakage to leave the 6B7 with virtually no bias. As the capacitor was disrupting the circuit and was not needed, I removed it. The leakage would have been acceptable in a cathode bias circuit but was a disaster in a high-resistance bias circuit passing only microamps. C27 was also leaky, so I replaced it with a fawn-coloured Philips type. I reworked the set with new resistor values to give the correct voltage for the output valve, setting the bias for the 6B7 audio driver on a trial-anderror basis for maximum gain, winding up with 13kW for resistor R18. But the HT was still low. I had assumed that since V4 draws the most HT current, its low bias would have caused excessive current drain, pulling down the HT. OZ7490 has an octal 25Z6 rectifier fitted as a replacement of the original 6-pin 25Z5. Sets later than OZ7490 still have the 6-pin 25Z5 in place, and all circuits show this valve rather than the 25Z6. This is a reminder of just how hard it can be to find a Mickey in original condition. Circuit modifications – and the absence of the correct schematic for this set – meant that the missing first HT filter had been overlooked. Putting in a replacement brought the HT up to around 130V, so the faulty bias circuit probably had less effect than I first thought. The audio stage now worked but there was a background hum at 50Hz. This was not a filtering problem; the unshielded lead from the 6B7’s demodulator circuit up to the volume control ran past the mains-supplied heater wiring. The fix was to strip off the braid from an old piece of shielded wire, sleeve it over the existing audio lead and solder it to ground, then slide a piece of old-fashioned waxed cambric ‘spaghetti’ over the braid. This addition blends with other insulation in the set. Tip: warming up cambric with a heat gun or hair dryer makes it much more flexible. Next, I checked the function of the RF/IF end. The IF channel lined up pretty well, and feeding in about 20μV to the converter grid gave good output. The IF seemed ‘happy’ at 466kHz, so I didn’t attempt to force it down to the specified 456kHz. This might upset the purists, but it’s only about 2% off and the set works just fine. I was concerned about possibly causing hard-to-fix damage if I tried to adjust it any further. That said, it was very deaf from the antenna terminal. As described earlier, the L1-C1 combination is aimed The side view of the Astor Mickey OZ clearly shows the filter circuitry for the antenna. Australia's electronics magazine January 2022  83 at attenuating signals below the broadcast band to prevent breakthrough. Disconnecting L1-C1 and injecting a signal to C3 gave a better result, but still not what I expected. Resistance checks confirmed that inductor L1 was continuous and that capacitor C1 was not shorted. Then I noticed twisted wires in the antenna circuit assembly, taped with black friction tape. I realised that this is C4, a ‘gimmick’ capacitor to improve top-end sensitivity. Undoing the tape, I discovered that the wire ends had been twisted together. This was clearly a factory error. After rectifying this, the sensitivity was better (see Fig.4) but still low. This turned out to be caused by the L1-C1 filter. Bypassing that, I got 50mW output for just 7μV input at 600kHz (this is without the L1/C1 filter – red line in Fig.4). That’s up there with the better sets. So if you have a Mickey with that L1-C1 filter circuit and want the best performance, disconnect it and connect your antenna to C3! Performance This set gives surprisingly good performance; the figures quoted below are with the L1-C1 bandpass filter in circuit and using a standard dummy antenna between the signal generator and radio. See the sensitivity chart (Fig.4) for the intrinsic performance without the filter. For 50mW output the sensitivity is 7μV at 600kHz and 28μV at 1400kHz. It’s noisy, though, with a signal plus noise to noise ratio of about 14dB in both cases. To get 20dB, the tested set needed around 145μV and 60μV respectively. The RF bandwidth is ±2kHz at –3dB and ±35kHz at –60dB. The AGC circuit gives an output change of 6dB for a 40dB input range. It would not overload even with 1V at the input! The maximum audio output is 0.5W at 10% THD. At 50mW, THD is 1.5%, and at 10mW it’s 2%. The response from antenna to speaker is 155Hz to 1.9kHz; from the volume control it’s 150Hz to over 3.2kHz. Marcus and Levy (p47) quote the input level for an equivalent all-octal set of 5~12μV. So this set’s best figure of 7μV without that bandpass filter is remarkably good. Leahy (p119) quotes figures for the very similar BC set that confirms my test results, and agree with Marcus and Levy’s figures. Conclusion & thanks Restored to original cosmetic condition, this is a set that will have visitors dwelling on it and admiring its design and finish. Restored to proper working condition, it’s a solid performer that ranks among the better sets of any era. And it’s a midget. We’re probably used to compact mantel sets from the 1950s and 1960s, but this was serious miniaturisation for 1933. Read radio magazines and journals of the day and you won’t see too many sets that rival the Mickey for compactness. These come up for sale from time to time, and I think the Mickey OZ is a ‘must have’ for any Australian collector. I’d like to thank Jim Easson and Philip Leahy of the HRSA for background information on the entire Mickey product line. You’ll find HRSA founder Ray Kelly’s history of the Mickey, including the controversy with Disney Studios over naming rights, in Philip’s book. Thanks also to Alby Thomas and Andrew Wakeman of the HRSA for their generous provision of the original filter capacitor block and underside photos, and to the HRSA’s Mickey Special Interest Group (MSIG) for their advice. Not an HRSA member? Visit www. hrsa1.com and find out how we can help you explore the wonderful (and weird) world of radio. And don’t forget our Mickey Special Interest Group. References Fig.4: sensitivity measurements were made across the broadcast three different ways: feeding the test signal directly into the antenna terminal (blue line), directly into L2, bypassing the input filter (red line, giving the best sensitivity figures) and with the factory error that caused C4 to be shorted out (green line). As you can see, this simple mistake had a significant impact on sensitivity. 84 Silicon Chip Australia's electronics magazine • Leahy, P. N., Circuits 1934-1940, Book 11, 2019, Historical Radio Society of Australia (www.hrsa1.com) • Leahy, P. N., Astor ‘Mickey’ OZ Supplementary Information to HRSA Circuit Book 11, (siliconchip.com.au/ link/abav) • Johnson, R., The Astor “Mickey Mouse” and its descendants, Electronics Australia, July 1996. • Marcus, W., & Levy, A, Elements of Radio Servicing (PDF: siliconchip. com.au/link/ab9l) SC siliconchip.com.au HAPPY NEW Build It Yourself Electronics Centres® GEAR Commercial grade cells with high discharge cap ability! SAVE $139 these deals... Tool up for 2022 with 749 $ t. Sale ends January 31s Throw away your old jumper leads! Top quality LiFePO4 Lithium battery with 100Ah capacity, PLUS a bonus battery box valued at $139. Powers your whole campsite, and is easily connected to a solar panel for recharging. One box for all your entertainment. SAVE $76 169 $ Make your TV even Smarter! Stream direct to your TV from streaming services, plus play games and connect to local media on your home network. Capable of streaming stunning 4K videos <at> 60fps! 4GB ram with 32GB on board storage. Requires 2A USB power supply. Includes FREE A 0981 trackpad/keyboard valued at $29.95. SAVE $45 130 $ Lithium-Ion Car Jump Starter Suits 12V battery vehicles. 20000mAh rated battery provides up to 1000A peak output when cranking. Two USB ports are provided for charging devices (like a giant battery bank!). It also has a super bright 1W LED torch in built. • 178L x 84W x 45Dmm. for the first 30 customers! Portable Battery Power Combo! Ultimate family charging station! M 8195A FREE SL4576B + T 5098 M 8882A* Charge 10 USB devices at once! • Great for families, classrooms & business. • Massive 19A charge output • QC3.0 on 2 ports • Includes adjustable dividers & power supply. *Devices & charging leads not included rs! Handy gadget for travelle D 2816 + A 0981 SAVE $29.95 139 $ FREE! SAVE $200 SAVE $30 A 0319* 59 $ Q 0203A SAVE 12% 40 $ T 1461 Ultimate Flexible Helping Hands Upgrade to the ultimate in soldering helper hands. Includes magnifier to assist with those fiddly jobs. Arm length ≈30cm. Recharge your phone ANYWHERE A do-it-all USB power delivery charger (18W), Qi wireless charger and portable battery bank (6700mAh) for phones and tablets for use wherever you travel. Includes Australian, US, UK and European adaptors, plus carry case. *Phone for illustration purposes. T 2865A Side Cutter T 2870A Long Nose Plier T 2860A Bull Nose Plier SAVE 10% 20ea $ 11 Pc Screwdriver Set T 2198B Quality set of flat blade and phillips screwdrivers for general repairs. Chrome vanadium. 100MHz 2 Ch. Digital Storage Oscilloscope Perfect for those in R&D or servicing. • 2 channels with real-time 1GSa/s sampling. • Colour 7” TFT screen • Displays waveform plus the measured wave voltage, peak to peak plus RMS, frequency, duty cycle etc. • Realtime measurement PC software. • USB datalogging • 2 year warranty. Mini Pocket Scales SAVE 24% 25 $ 1000V Rated Electrical Tools VDE 1000V rated electrical tools constructed from quality drop forged steel with insulated handles. SAVE 15% 30 $ Weigh anything up to 600gm with 0.01g precision. Includes case. T 2555 SAVE 30% 40 $ T 2261 699 $ Hands free, head worn magnifier. Thousands sold! Offers 1.5, 2.6 and 5.8x magnificatio with LED lamp. Requires 2xAAA batteries. Your one-stop electronics shop since 1976. | Order online at altronics.com.au Gear for the open road. Solar Panels for DIY remote & mobile power projects. Stay in touch on the open road with 4G internet access! Sourced from one of the worlds leading solar manufacturers. Aluminium frames, waterproof junctions, tempered glass panels. 25 year output warranty. 5 year workmanship warranty. CEL-Fi 4G Boosters For Vehicles TM The best solution on the market for addressing the universal challenge of poor cellular coverage on the road in Australia. Simply install Ce-Fi GO inside your vehicle and enjoy having great 3G or 4G mobile reception. No longer will you need to stop or drive to a particular spot to be able to make and receive phone calls. Available in truck/4WD, caravan and marine packages to suit your needs. Easy self install can be completed in just a couple of hours. D 4400 Truck/4WD • 3.5dBi Adhesive • 6-8dBi External 1070mm (5m cable) D 4405 Caravan • 3.5dBi Adhesive • 5-7dBi Wall Mount Internal • 10-11dBi Wideband External (10m cable) 1175 D 4415 Marine • 3.5dBi Adhesive • 5-7dBi Wall Mount • 7-10dBi Marine External (10m cable) 1357 $ $ 1515 $ SAVE 27% 89 .95 $ 50 $ Q 0594 Model Wattage RRP NOW N 0020F 20W $53.95 N 0040F 40W $89.95 N 0065G 65W $115 N 0080G 80W $129 N 0110F 100W $175 N 0160F 160W $225 N 0200F 200W $325 $45 $79 $99 $105 $149 $199 $285 GREAT SAVINGS! Carry 240V Power Anywhere! M 8199A This portable solar generator is fitted with 14Ah battery bank & 240V mains inverter. Allowing you cable free power for both AC and DC appliances anywhere! Plus 2.1mm DC power & USB charging. 40W solar panel 240V (N0040F) to suit power from $55. a lithium battery! SAVE $80 219 $ T 1539 SAVE 20% Ideal for DIY DC power wiring The Ultimate Battery Fuel Gauge. Accurately measures battery voltage, current, power, real capacity and remaining run time of your connected battery (suitable for any type of chemistry and voltages between 8V to 120V). Includes 50A shunt with 2m cable. 1% accuracy. Cut out dimensions: 53.5 x 37.5mm. 40 Weather resistant! $ N 2099A Easy DIY install! Great for 4WDs Ratchet Lug Crimper Quick and easy crimping for Anderson SB50 connectors and other uninsulated lugs between 20AWG & 8AWG. 30 $ Monitor your car battery from your phone! X 0225A The ultimate camping, fishing, anything light! Ensure your battery doesn’t go flat with this handy Bluetooth® battery monitor. Provides live feedback on your vehicle or auxiliary battery, plus handy long term stats. Provides 5 hours use from a high spec lithium battery - or use it as a USB battery bank to charge your phone. Folds flat for easy storage. 10W, 1000 lumens. L 2003 Includes 10m cable & mounting hardware 89 Premium Deep Cycle SLA Batteries $ Caravan/Boat Television Antenna Get crystal clear TV reception wherever you travel! Omnidirectional 360° design requires no adjustment when you park up. Easy DIY install. Anderson Style Panel Socket Easy connection for solar panels and auxiliary batteries. Mounting hole: 40x21mm. SAVE 38% M 8521A SAVE 16% 30 $ 6/12V Plug In Battery Charger & Maintainer P 7810 14.95 $ Offers hassle free maintenance charging for 6 & 12V lead acid batteries. Ideal for protecting seldom used vehicles from battery discharge. Croc clip or ring terminals. 600mA output. Ideal for every day discharge in equipment such as golf buggies, wheelchairs, forklifts etc. Easily user replaceable. Model Capacity RRP NOW SG4554 26Ah $129 SG4560 33Ah $159 SG4563 40Ah $199 SG4567 60Ah $259 SG4571 80Ah $342 SG4573 90Ah $359 SG4577 110Ah $435 $99 $129 $159 $209 $275 $319 $345 Order online at altronics.com.au | Sale pricing ends January 31st Commercial grade cells for high performance Top workbench savings! SAVE $370 SAVE $44 K 8604 145 $ Super hot 1350°C flame with high output nozzle. Handheld or self standing design for tasks such as heatshrinking, the gas! Don’t forget r can. model making, silver pe .35 $9 T 2451 soldering! Easy to refill. SAVE 22% 999 $ High Output Blow Torch M 8305 5A SAVE $40 Everything a maker space needs in one compact unit! 119 $ M 8303 3A T 2496 Compact 30V Lab Power Supply 62 $ Great for servicing, repair and design of electronics. Low noise switchmode design. Fine & coarse voltage and current controls. 3A or 5A max models. Size: 85Wx160Hx205Dmm. SAVE $22 88 $ Charges a laptop, a phone & tablet at the same time! SAVE $34 85 $ or 2 for $120 D 2323 T 2098 Bench Mount USB PD Charger A 96W USB type C power delivery charger, plus dual QC 3.0 USB charging in the one compact near flush mount unit. Requires 60mmØ hole. Includes power supply. 300W Adjustable Solder Pot Tin multiple stranded hookup wires or remove multi-pin connectors from boards quickly and easily. Takes up to 1350g of solder. Stable temperature control: 200480°C. Suitable for lead free and leaded work. 1kg leaded solder bar $64.95 (T 1140A). 300W. Creality® CP-01 3D Printer / CNC Router / Laser Engraver 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. SAVE 27% 29 $ T 2186A T 4015A SAVE 15% 29 $ 101 Pc Ratchet Driver Kit Never lose a tiny screw again! Features 95 security, philips, pozi and slotted bits made from tough S2 alloy. Includes ratchet handle with comfy rubber grip. See web for full contents list. A 35x26cm heat resistant silicon work mat, plus a 25x20cm magnetic mat to keep screws and materials organised while you work. INCLUDES: • Conical tip • Hot air blower • Hot knife/plastic finishing tip • USB cable • 1m solder • Tip sponge. SAVE $40 T 2694A 30W Lithium ‘Go Anywhere’ Soldering Iron 45 minute run time. 600°C max. Ideal for occasional soldering jobs or light duty repairs and field servicing. Recharge by USB power adaptor in your car or at home - or USB battery bank. Includes replaceable 18650 battery. Cut, Polish, Grind, Sand & Carve. TOP VALUE! T 2802 T 2748A 22 $ .95 27 $ .95 X 0433 16.95 $ 5” Premium Cutters Chewed out a screw? Get a crisp close up view! Tough chrome vanadium blades stay sharp for longer. Ideal for PCB assembly, cutting solid core wiring etc. No problem! This unique set of pliers features serrated jaws, plus serrated opening on the front for extracting screws up to 13mmØ. A handy accessory for any workbench, this 130mm 6x magnifier uses premium quality glass and LED lighting for a clear view. 165 $ Great for finishing and smoothing your 3D prints and plenty of other odd jobs and hobbies! Powerful 130W motor with variable speed between 8000 and 33000 RPM. Included is a 172pc SAVE 18% accessory kit of grinding wheels, drills, cutters, sanding discs & polishing pads. T 2120 69 $ Order online at altronics.com.au | Sale pricing ends January 31st Expand your AV system. Opus One® 140W Soundbar Wireless Subwoofer SAVE $40 Demo in store! 199 $ Our new premium finish soundbar offers rich, clear sound from it’s 6 high performance speaker drivers, plus a 8” subwoofer which can be placed anywhere in your lounge room thanks to wireless connectivity. Offers bluetooth audio streaming from your favourite devices, plus S/PDIF digital audio input for connection to your TV (cable included). C 5064 $90 299 SAVE $ Opus One® Bluetooth Bookshelf System Soundbar: 97 x 8 x 7.5cm, Subwoofer: 30 x 25 x 30cm C 5059 Similar spec to $600 systems with sound quality that’s just as good! Want top notch sound for your games, hi-fi listening or home theatre? These new active bookshelf speakers need no amplifier, just plug them in and connect via Bluetooth, digital S/PDIF or stereo RCA. Amazing sound for their price with a sleek oak grain finish - looks great with grilles on or off! Size: 146 x 164 x 240mm. SAVE $50 SAVE $40 189 119 A 4201 A 1116 SAVE $30 LED base light shows when your mic is on $ $ 109 $ D 0981 SAVE $19 50 $ Add Bluetooth® audio to your favourite speakers! Why buy new bluetooth speakers when you can add this module to existing speakers? Streams music direct from your phone! 2 x 25W RMS output. Bluetooth 4.1. Includes power supply. SAVE 33% 59 Bluetooth® 2x50W Amplifier Stream audio directly from your device to your speakers in the study or entertaining area. 3.5mm and RCA inputs. Class D design. Internal headphone amplifier. Includes power supply, banana speaker plugs & 3.5mm to RCA cable. 4 Channel USB Mixer With Equaliser & FX USB Gooseneck Mic A 2548 Want to get into recording podcasts, voice overs or making your own audio samples? This mini USB mixer connects directly to your PC or Mac and is powered directly from USB. Includes 3 band EQ and effects. Great for gaming, YouTube and livestreaming. Quality omnidirectional mic insert. Mic gain and mute control knob with LED lighting. Indoor Pan & Tilt Wi-Fi Camera A 0920 $ AE1101 Adds up to 200m range to your IR remote controls! Wireless Infra-Red Repeater Use your remote control up to 200m away (line of sight) from your equipment. Perfect for controlling your AV system from the patio or entertaining area. Includes plugpacks, IR emitter & receiver. SAVE $20 SAVE 24% Bluetooth® 3.5mm Jack 15 $ Instantly add wireless audio to any 3.5mm input - like your car, headphones or home amp. USB rechargeable battery provides 4 hrs listening. S 9846 1080p Wi-Fi Cube Camera • Internal battery - set it up anywhere! • Day/night with IR • USB rechargeable • Includes stand • Simple motion activated recording. Western Australia Build It Yourself Electronics Centres Sale Ends January 31st 2022 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au 69 $ » Perth: 174 Roe St » Joondalup: 2/182 Winton Rd » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd Makes a great baby or pet monitor, this camera features intelligent tracking of moving objects within the frame. 2-way audio with mic and speaker. 5m IR night time coverage. Requires 5V 1A USB power supply. SAVE $10 S 9017A 69 $ Victoria 08 9428 2188 08 9428 2166 08 9428 2167 08 9428 2168 08 9428 2169 08 9428 2170 » Springvale: 891 Princes Hwy » Airport West: 5 Dromana Ave 03 9549 2188 03 9549 2121 New South Wales » Auburn: 15 Short St 02 8748 5388 Queensland » Virginia: 1870 Sandgate Rd 07 3441 2810 South Australia » Prospect: 316 Main Nth Rd 08 8164 3466 Please Note: Resellers have to pay the cost of freight & insurance. Therefore the range of stocked products & prices charged by individual resellers may vary from our catalogue. © Altronics 2021. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. *All smartphone devices pictured in this catalogue are for illustration purposes only. Not included with product. B 0091 Find a local reseller at: altronics.com.au/storelocations/dealers/ SERVICEMAN’S LOG Designing for unrepairability Dave Thompson A lot of equipment these days is designed to be compact and easy to assemble, but little attention is given to repairability. That’s why so many devices are essentially disposable. There’s no information like circuit diagrams or repair manuals available, so once something goes wrong, in the bin it goes. It’s sad. I ’ve mentioned before that I get a lot of random devices into the workshop for repair. Once people hear I can do this sort of thing, they all seem to pour out of the woodwork with all manner of strange and wonderful things for me to fix. One of the problems I have with this is that many of these devices are no longer supported, built to fail and designed not to be repaired, or simply not worth the considerable time it would take to fix them. The other day, a guy brought in a hand-held Garmin Rino 650 GPS siliconchip.com.au transceiver. This is a very handy unit because not only is it a fully-featured satnav system, it is also a two-way radio, so hunters who have other compatible transceivers can talk to each other over quite long distances in the bush. These devices have a touchscreen menu system and a PTT (push-to-talk) button on the side of the rubberised case, so they work much like the typical ‘walkie-talkie’ type devices we all know and love. The problem with this one was that there was no sound output, so while it can still be used as a standard navigation system, there were no audio Australia's electronics magazine prompts and obviously no radio transceiver function. These devices are designed to be rugged. They use heavy rubberised plastics and lots of rubber bungs and stoppers to provide basic weatherproofing. Pulling them apart isn’t too onerous, with the usual long Torx-type screws (which require the exact driver bit or they aren’t going anywhere) and the increasingly typical hidden screws buried beneath barely-removable case flashings. If one isn’t thorough, trying to pry apart a case that still has screws holding it together can end up a real mess, especially if one isn’t having a good January 2022  89 day and the red mist comes down in frustration! With all the screws removed, the two halves of the case separate relatively easily, but then the space is so tight that you have to hold your tongue one way while the planets align before the board assembly can be eased out. There is literally only one way it can come out, and finding just where that sweet spot is can be maddening. Once I got the board out, it was pretty obvious I was not going to be able to do much with that part of it unless the problem was caused by something simple like a blown or faulty speaker. The speaker was one of those super-thin permanent-­magnet types, about 25mm in diameter and plastic-welded into the front of the case. There was no physical wiring connecting the speaker; the board simply pressed against it, and a couple of tiny gold spring contacts on the PCB rested against the speaker’s terminals. I guess with everything crammed in so tightly, this system does work well, but I’d imagine any moisture that gets inside might interrupt this type of connection, so I resolved to take that into account as well. I decided to check the speaker first. My trusty multimeter could handle this with a quick touch to the speaker terminals with the meter set to x1 on the ohms scale. A click from the speaker told me it was working, which, to be honest, made my heart sink a little because I was hoping it would be one of those silly fixes that resolves everything with a minimum of fuss and expense. But no. There was obviously something further up the audio chain that was stopping this from making noise. As is usual in these situations, I hit Google to see if I could locate any circuit diagrams or schematics that may help. I found nothing but a wealth of misinformation. However, one theme kept cropping up: that on this model, it is easy to mute the output by accident whilst perusing the menu system, so many people had resolved the no-sound issue by simply un-muting the audio. I reassembled the GPS to the point that I could fire it up and go through the menu options on the touchscreen. The sound was not muted, which was disappointing, but there was also an option to set the handset to vibrate. I had seen the tiny vibrator motor mounted on the circuit board, so I knew it had that feature available. 90 Silicon Chip I set that to on, so at least there was some haptic feedback when something happened, though that wasn’t going to help get the two-way radio working... Breaking it down the second time wasn’t as finicky a job as the first time, so that was something. But trying to track anything back from the speaker side was a nonstarter. The multi-layer PCB was stacked with the smallest SMD components I’ve seen for a while, and though some did have numbers printed on them, I could find nothing about what they were. Even if I could find a replacement, removing them would require specialised tools that I don’t have, and if I tried to do it, I’d likely have just damaged the board further. So, this was one that I couldn’t help with. Garmin no longer runs a swap-out refurbishment program for this model, so they were no help. While I did check the usual auction sites for spares and replacement units, I could only find models being sold for spare parts, and they could very well have the same problem as this one – the vendors couldn’t tell me what had gone wrong with them. At almost half the price of a new unit, buying dead handsets in the hope that something might work was just not feasible (or sensible). The owner was philosophical about it; at least we’d had a look and determined it wasn’t worth pursuing. He’d still use it as a GPS but would have to do without the radio/audio side of it. Next! Another client brought in an old ’70s clock radio. It had been in the family for years, and though it worked, one of the red seven-segment LED displays had faded enough that it was difficult to read the time. This is a classic example of whether to repair or not, and why each case should be taken on its own merits. The clock radio had been bought for the current client back in the day by his dad, and so it had a lot of sentimental value. He had used it in his workshop for many years and wanted to see it going properly. I advised him that I could likely fix it, but he might be looking at way more than a replacement clock radio from some big-box store might cost. He was OK with that because the sentimental value was greater than that for him. I told him I’d see what I could do. Working on these older devices is so much nicer than a lot of today’s stuff: plain screws, simple engineering holding it all together and basic analog components with designations printed on them. Almost anything inside it could be repaired, or even fabricated to fit if that’s what it takes. This clock just had a single dim display from the four onboard, and I guessed that it had simply faded with age, as many LEDs of all types of this era do. The big question was what type of display it is and the pin configuration, because I literally have a parts drawer full of reclaimed and NOS (new old stock) red seven-segment LED displays, and I felt confident one would fit in this old-timer. I’ve said before; I’m not exactly a hoarder – at least not to the extent I have to sleep standing up in the laundry because all the rooms are stacked floor to ceiling – but my workshop is quite ‘busy’, with parts drawers and shelves groaning under the weight of stuff I’ve accumulated over the last 40 years or so. That’s not including all the other things I inherited from dad’s very similarly-­appointed workshop. Australia's electronics magazine siliconchip.com.au The new display was a little brighter, but not too bad. I guess I could have installed a resistor in the ground line in an effort to dull it, but I thought that once the plastic front was in place, it would look OK. I was right; once reassembled, the red plastic cover the LEDs shone through, which was a bit faded and scratched itself, tempered any bright spots on the new display, and it looked just as good as the others. The customer was pleased, and I’m trimming down my component stocks the right way, one at a time. On the slow boat from China The rationale is that if I come across a new-old-stock seven-segment display, I’m not about to throw it out just because I’m running out of room, so it gets squeezed into the drawer with the others. While there isn’t a huge call for components like this anymore, I could almost guarantee that if I did have a colossal clean-out and biffed a lot of this stuff away, the very next day, a job would come in that requires something I have just binned. This clock-radio job has proven that it would have been folly for me to throw these displays away because, as luck would have it, I had several that could do the job. My main concern was that if I fitted it successfully, this ‘new’ one would be much brighter than the remaining original displays. As I didn’t have four the same, I couldn’t replace them all. Still, I’d cross that bridge when I got there. It was a bit tricky to manipulate the various PCBs into a position that I could de-solder the dud display. The separate boards were all linked together using that multi-stranded, hard plastic insulated joining cable. It’s great stuff for a strong interconnecting joint, but over time it gets brittle and breaks easily. If I did break a link, I could always replace it, but it’s better not to bend these old parts around too much. The smell of the old solder brought back memories of watching dad in his workshop when I was a little kid; it’s strange how some odours stay with you. It’s likely seriously unhealthy, with all the fumes that come off when heated, but it smells of home to me. Getting the old dim display out was easy; I just wiggled it free after removing all the solder. The PCBs are pretty hardy from those days, but like all electronics, excess heat can do a lot of damage. So I just took care not to overcook it. I lined the new one up with the others and soldered it in – it was really that simple. I flexed the boards back into their original positions and sat it all carefully on the bench before plugging it in and lighting it up. siliconchip.com.au You might recall a story a while back about an electric bike that I couldn’t finish repairing as I was waiting on parts from China (June 2021 issue; siliconchip.com. au/Article/14895). More specifically, I was waiting for a new speed controller, because the old one had gone up in a puff of smoke. The problem was that I didn’t know if it was just the controller that had failed, or whether the motor assembly built into the back wheel had shorted and burned things out, or both. The controller was far cheaper to replace than the wheel/motor assembly, so that’s the bit I bought first. I’d sourced one easily enough, as they appear to be at least partially standard devices, but it took forever to get here. When it did arrive, I installed it – thankfully, most of the connections are also relatively standardised – though I’d taken lots of photos before I pulled the old one out as a precaution. I charged the battery, which had been sitting for a while and was discharged, and when all was ready, turned the key and wound in a bit of throttle. In a flash, the new controller was toast. As I’d already previously checked the external wiring to the motor for obvious shorts between themselves and to ground, I thought nothing was apparently wrong with it. Still, without a compatible controller, I couldn’t check it properly. Therefore, the controller was intended to be a sacrificial lamb and did its job by telling us that there was no point in carrying on and sinking even more money into it. It was a shame, really, as it was a cute little thing and not cheap to buy in the first place. Last call And finally, I had a guy bring in a PCB from a heat pump compressor. These are pretty large, and he said no one in town is repairing them anymore after a well-known repairer shut up shop due to the pandemic. Items Covered This Month • • • • The art of unrepair Macbook Air repairs Repairing a double-clicking computer mouse Replacing damaged varistors in two Panasonic microwaves Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz Australia's electronics magazine January 2022  91 I know next to nothing about these things, but how hard can it be? Circuit diagrams for common models are widely available for service guys, and the bloke (an installer/engineer) said he could get a circuit if I needed one. The fault was that the compressor motor no longer ran, and he suspected the motor driver section of the PCB had failed. To start with, I asked him if he’d tested the motor itself. He hadn’t but claimed not many fail, so it was most likely the board. He left it with me, and I got out the magnifying glass to see if I could find something obvious. I could see no burned areas and there was no acrid ‘dead component’ smell, so I doubted this was the problem. There were two onboard fuses, though, so I checked them. One was blown. I replaced it with one of the same specifications and called the installer chap to say there was nothing obvious here. He went back to the house and pulled the motor, bringing it straight around. It was shorted every which way I could measure it according to my meter, so that was likely the problem. Whether it had smoked the PCB itself was anyone’s guess. But again, it is way cheaper to replace a motor than a PCB in these units, so he took both away and installed a new motor, wired in the old PCB and voila! The thing fired up and is still running well today. It just goes to show that sometimes the simplest things can go wrong, but our tendency to over-complicate things can point us off in the wrong direction. He cursed himself for not checking those onboard fuses instead of wasting time taking the board out, but he made his assumptions on his own experiences. If he’d tested the motor, he’d have found the fault straight away, so I can be sure that’s what he’ll do next time. Either way, it was a super-easy fix for me, and everyone was happy. Macbook Air repairs B. P., of Dundathu, Qld previously wrote in to describe several MacBooks that he brought back into service. Well, he’s up to it again, this time rescuing some MacBook Airs from the rubbish tip... Some time back, a friend gave me several MacBook notebooks. I was able to repair three using parts from those 92 Silicon Chip and others that I already had. There was also a MacBook Air, but I’d been unable to test it because I only had Magsafe 1 chargers and the MacBook Air uses a Magsafe 2 charger. More recently, I was given another MacBook Air notebook, but I still didn’t have a Magsafe 2 charger. Now I had two of these MacBook Air notebooks and no way to test them. I’d previously looked into the price of a charger, but as they were around $40 or more, I didn’t want to spend that sort of money without knowing if these notebooks even worked. I decided to look on eBay for a replacement Magsafe 2 cable, and I found one for $11.95, so I ordered it. When it arrived, I dug out a 14.5V charger with a Magsafe 1 cable, and I cracked the charger apart using circlip pliers. One side of the shell came off fairly easily, but the inside of the charger proved challenging to get out of the other half of the shell. After I managed to remove it, I desoldered a wire and removed the copper wrap. I was then able to desolder the old cable and solder in the new one. Then I refitted the copper wrap and re-soldered the wire, and put the charger back together. The case clipped back together nicely, without needing to glue it. I grabbed one of the notebooks and connected the charger to it. I waited a minute and then pressed the power button. I heard the familiar Mac boom, so that was a good sign. The MacBook loaded up with the previous user’s account without needing a password, but something wasn’t right. There was no dock. Then I discovered that the keyboard and trackpad didn’t work, and I wondered if they had been disabled, so I decided to boot from a USB installer and check. I had an earlier version of Catalina on a USB, so I’d use that for now and update it later. I pressed the Option key and got the option of booting from the HDD or the USB drive. The trackpad now worked, so I chose the USB installer. I returned later, but now the keyboard and trackpad no longer worked; they were obviously faulty and only worked intermittently. I put this MacBook aside and grabbed the other one to check it. Once again, it started up, but I got a folder with a question mark in it, indicating that the eSATA SSD had either been wiped or removed, so I booted from the USB installer. There was still no HDD present, so I guessed it had been removed. I took the back off, but I found that the SSD was actually present. I removed it and replaced it and tried again, but it still didn’t show up. I suspected it might be faulty, so I took the back off the first MacBook Air, removed the SSD and installed it in the second MacBook. But it still didn’t show up; I knew it was good, which meant there was a fault with the motherboard. I decided that the best option was to swap the good motherboard from the first MacBook Air into the second MacBook Air. But this second MacBook had been dropped and there was a significant dent in the front righthand side of the base and the lid, as well as the base being bent where the left USB port is, and the lid would not close properly. The other shell was in much better shape, but I didn’t want to swap over the keyboard, which is a massive job. From what I’ve seen on YouTube videos with MacBook repairs, the keyboards are held in with a million tiny screws, so I would have to repair the damaged case. I managed to tap the front corner of the top case back into shape and straighten the bent area at the USB port, but I didn’t want to try to fix the lid, as I could risk breaking the screen. Instead, I would swap over the good lid. I started by dismantling the first MacBook with the working motherboard. I removed the battery, then the motherboard. I put the battery, motherboard and back of the shell aside to Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column? If so, why not send those stories in to us? We pay for all contributions published but please note that your material must be original. Send your contribution by email to: editor<at>siliconchip.com.au Please be sure to include your full name and address details. Australia's electronics magazine siliconchip.com.au Left: the left-most charger is a Magsafe 1, while the one on the right is Magsafe 2. The Magsafe 2 charger uses the same pins, but has a slightly longer connector, fit to the repaired case. The reason for using this back is that it has the correct serial number of the motherboard on it. I’d use this battery, as it was already fully charged, and I knew it was good. I disassembled the second MacBook similarly, then swapped in the good lid and fitted the good parts. Now the lid closed properly after the shell repair. I also put fresh thermal compound on the heatsink and cleaned the fan at the same time. For the moment, I just sat the back on, in case I had to do anything else inside, and I turned it over and connected the charger. The MacBook started up, and this time, all was well with the keyboard and trackpad and I finished the installation. I decided to check for updates and was offered the latest version of macOS as an upgrade. The download finally finished, so I copied the installer to an external hard drive, and I also copied it to a folder on the desktop before running it. After some time, it was installed and I was greeted with a terrible wallpaper, which I quickly changed to the Big Sur photo after I logged on. Further testing indicated that this MacBook Air notebook was working correctly, so the $11.95 investment for a replacement Magsafe 2 cable was a good move. I screwed the back on permanently, gave it a quick clean and it was complete. This was a successful exercise in taking two unusable notebooks and making one good one. I don’t yet know if the leftover parts will be of any use, but I have kept them in case I get another broken MacBook Air in the future. When I’d had the other MacBook Air apart, I could see some corrosion around the connection for the trackpad, so that explained why it didn’t work reliably. It looks like someone had spilled liquid on the trackpad, which had seeped through and got into the connector. I haven’t looked into it any further to see whether that damage is fixable. It might be. Apparently, the small chip in the trackpad cable also controls the keyboard, explaining why both had stopped working. Working on Mac computers and MacBook notebooks is vastly different to working on PCs and Windows laptops. Mac computers and Macbooks need a lot more different tools, and they are a lot more compact. siliconchip.com.au Below: the Macbook Air opened up, so that the motherboard could be swapped. Australia's electronics magazine January 2022  93 Repairing a computer mouse that double-clicks D. S., of Maryborough, Qld made a similar repair to our own serviceman, who described fixing a computer mouse in the May 2021 issue... Dave’s mouse repair story made me chuckle. A couple of weeks ago, I was in a similar situation. A young fella had a problem with his mouse; apparently, it was double-clicking on the right mouse button whenever it was pressed. This, I was told, was “not a good thing when facing off with opponents in various online games”. I asked if he had played with any of the settings in the PC or the mouse’s installed software. He said he hadn’t, and without the PC, I had to take his word for it. I did ask if it was worth repairing, given that the repair might cost more than a new mouse. I was told in no uncertain terms that this was his “gaming mouse”, and he simply could not replace it, as it had cost over $100 new. I plugged it into my PC and ran it through its paces. It certainly had many buttons, and they all worked as expected, except the right button. It did indeed double-click with every single press. The screws holding it all together were hidden under more of those Teflon coated cushions, which I managed to save. Internally, the mouse looked like it was a nesting home for a cat or other small pet. The internal optics for the scroll wheel were buried under a soft blanket of pet hair, which extended across most of the mainboard. After I removed all that, I could test the microswitch on the board, and sure enough, it was faulty. After removing the small daughterboard, the mainboard came out, and I removed the offending microswitch. It was a fairly common part, even though it did have the Logitech logo on the side, so I quickly found a replacement. It all worked fine once reassembled, and the young gentleman was very happy. I did mention the pet hair inside the mouse (shouldn’t that be the other way around, mouse hair inside the cat!), and he smiled and said the family cat often slept on his desk, so that answered that question. I have also repaired his monitor twice, once for a bad tactile on/off switch and again when the mainboard stopped working. Both were easy fixes, although I had to buy 250 tactile switches in a nice neat little case; I will soon be ordering more, as I replace more and more of these switches. Like Dave Thompson, my eyes are not so good nowadays, so soldering the 2.1 x 2.8mm switches required the use of a desktop magnifier. I also have a repair story involving Coca Cola and a JVC 65cm LED TV. I won’t bore you with the details; suffice to say, it no longer worked. The photo below shows what I found after checking the power supply board and the T Con board. Coke always makes a mess of electronics. When these accidents happen, turn it off and get it to a service person ASAP. Don’t ignore it just because the TV (or whatever it is) still works. That’s what this teenage customer did, and check out the resulting damage. After I explained the fault and the time it may take to repair, I got the feeling that this young fellow would be mowing the lawn to pay Dad back for the cost of the repair. It took a couple of hours to clean it up and get it working again. Rest assured that the offending teenager learned a lesson and got Dad out of mowing for a while... Damaged varistors in two microwave ovens R. S., of Fig Tree Pocket, Qld has been busy fixing many appliances, including two microwaves. Despite being different models (both by Panasonic), they failed for the same reason... Both microwave ovens had intact mains fuses, but the protective varistor across the mains on both microwave ovens’ control/display boards were damaged. I think this could be due to mains surges. This varistor is a VDR10D511 10mm diameter, 511V varistor. There are also protective capacitors on the mains supply input board. The NN-SF574 oven (quite new) uses an inverter for the control board supply with a Panasonic flyback control IC and a high-frequency transformer. The varistor across the mains is fed by a fine track marked PF1, which acts as a fuse. This saved the board; replacing the track with some fine wire and fitting a new varistor got the oven going again. A new control board is about $110, and a new oven about $225. The NN-ST671 oven is an older design, with The doubleclicking mouse’s PCB, shown at left, had faulty microswitches. At right is a section of the power supply board of a 65in monitor. Some corrosion can be seen on the connectors from a soft drink spillage. 94 Silicon Chip Australia's electronics magazine siliconchip.com.au a small 50Hz transformer on the control board. Again, the mains varistor is fed by a fine track, which I had to replace along with the varistor. In this case, the varistor was sleeved with a high-temperature fabric. Perhaps varistors have caught fire or exploded in the past. I also repaired a Dome 24 wine cooler, Item No 900096. Taking the back cover off showed it was a Peltier Effect cooler with a large heatsink. There were two fans on the outside to remove the outside heat, plus one on the inside to distribute the cold air. The constant current switching power supply for the Peltier device had a blown fuse on the mains side. The supply uses a TL494 switching regulator driving two 13005 400V transistors connected in a totem-pole arrangement, probably to increase the voltage rating. Both 13005 transistors measured short circuit, as did the STPS2045 dual schottky output rectifier (2 x 10A 45V). After replacing these, I put a light bulb across the blown fuse and connected the mains. The bulb stayed on, so there was still a problem. I was surprised to find that two of the 1N4007 rectifiers in the full-wave bridge were also shorted on the mains input side. I am used to the large, sturdy rectifier bridges used in microwave oven inverters which never fail; the switching IGBT goes first. Replacing the 1N4007s and the fuse got the cooler working again, with about 1.5V across the Peltier Effect device. I did not measure the current. The big test will be when summer comes, to see if the wine stays cool. I also fixed a Kambrook K1780 steam iron. The series capacitor in its power supply was a 560nF 250V DC rated type that was down to about 430nF, so there was not enough voltage to operate the 24V relay that connects the mains to the iron heating element. So the iron would not heat. I notice that the capacitor manufacturers derate the voltage rating for AC, to about 60% of the DC voltage rating. For example, a 400V DC capacitor has an AC rating of about 240V. On that basis, the original 250V DC rated capacitor was not adequate for the task. It seemed to have been chosen for its small size, to fit in the space, rather than for a suitSC able voltage rating. The damaged VDR10D511 511V varistors taken from the Panasonic microwave ovens. siliconchip.com.au Australia's electronics magazine January 2022  95 REMOTE CONTROL RANGE EXTENDER Most remote controls use pulses of infrared light to control equipment. This usually only works reliably up to a few metres and is easily blocked by furniture, people, plants... just about anything. Convert an IR remote to use UHF instead, and it will work at much longer ranges. It will even work when something is between the remote and the device, regardless of where the remote is pointed! M ost of the time, infrared remote controls work very well. But there are times where they are woefully inadequate. This could be because there is an obstruction between the remote control and appliance to be controlled. Or the receiver on the device may be awkwardly placed, making it difficult to direct the infrared beam to it. Sometimes you might even want to use the remote control in a different room from the appliance to be controlled. Or you might need to position the appliance so that the receiver is not facing where you will usually be located, such as a projector, where it will typically be behind you. Sometimes you can reflect the IR signals using the projector screen, but that doesn’t always work reliably. Regardless of why the IR signal doesn’t work well, this device is a great solution. It allows you to convert the infrared remote to transmit using UHF radio signals rather than infrared light. Another small box positioned in front of the infrared receiver on the appliance picks up these radio signals and transmits IR directly into the device’s receiver. Note that if you have more than one appliance to be controlled, you could convert all their remotes to transmit on UHF and use a single UHF-to-IR converter to relay the signals to all those devices. That’s provided the appliances are in the same vicinity, so that the light from a single transmitter can reach all their receivers. Concept Fig.1 shows the general arrangement for the Range Extender. Fig.1(a) shows how the IR-to-UHF Converter works, while Fig.1(b) shows the UHF-to-IR Converter. Fig.1(a): the Remote Control Range Extender has two parts. The first is the IR-to-UHF Converter which runs from the remote’s battery and converts its IR LED drive signal to a UHF transmission. The second is the UHF-to-IR Converter which picks up those UHF signals and drives an infrared LED with appropriate modulation to control the appliance(s). 96 Silicon Chip Australia's electronics magazine siliconchip.com.au IR-to-UHF Converter ❚Transmission range: 25m through one Hardiplank and Gyprock wall ❚Signal delay: 56μs ❚UHF transmitter power-down period: 600ms after the last signal ❚Standby current: 80nA typical at 3V supply (90nA measured) ❚Operating current: 8mA average during transmission UHF-to-IR Converter ❚Valid transmission detection: requires 3ms minimum quieting period ❚Acknowledge LED lighting: 654ms time-out after a valid signal ❚Modulation frequency: 32.4kHz to 41.4kHz in 32 steps ❚Modulation duty cycle: 33.3% ❚Current consumption: close to 50mA during signal reception ❚IR transmission range: typically 2m to appliance receiver By John Clarke The IR-to-UHF Converter monitors the signal that would normally be fed to the IR LED. When a button on the remote control is pressed, it produces a ~36kHz modulated signal to drive that LED. IC1 instead demodulates that signal, and its output (waveform B) is shown in scope grabs Scope 1 & Scope 2 (which can be seen overleaf, with the other scope grabs). ‘Demodulation’ converts the series of brief 36kHz pulses to a signal that’s high when the pulses are present and low otherwise. When IC1 detects it is receiving a signal, it powers the UHF transmitter (IC2) and sends the demodulated signal to the UHF transmitter’s input. The result is that the UHF transmitter produces a 433.92MHz modulated signal to the transmitting antenna. This is waveform C. So overall, the original 36kHz modulated signal is converted to a 433.92MHz modulated signal for wireless transmission. The corresponding UHF-to-IR Converter has a UHF receiver (RX1) that provides the demodulated waveform, shown as waveform D. This matches the B waveform – see Scope 3. Processor IC1 on the second board then uses a new 36kHz carrier to produce a modulated waveform, waveform E, that matches the original waveform A, as shown in Scopes 4 & 5. This modulated signal then drives an infrared LED that sends the signal onto the appliance(s) via their onboard IR receivers. Note that 36kHz is a typical modulation frequency used in infrared remote controls. You can adjust the modulation frequency of the final infrared output to match that of the original remote control, since the remote control could use another frequency between about 32kHz and 41kHz. Overall, the original handheld remote signal is duplicated at the output of the UHF-to-IR Converter. The appliance receiving the signal is none the wiser that any processing has occurred. Previously Note that we published a similar project named “Add a UHF link to a universal remote control” (July 2013; siliconchip.com.au/Article/3846). While that project is still valid, this one has a much smaller transmitter circuit that can be fitted into small infrared remote controls, unlike the one from 2013. This became apparent when we tried to install our earlier design inside a small remote control for an LCD projector. There just wasn’t any room for it. Subsequently, the entire IR-to-UHF circuit has been redesigned using surface mount components. Fig.1(b): the waveforms at right, both here and in Fig.1(a) opposite, show how the original IR LED drive signal is demodulated, then remodulated to 433.92MHz, then demodulated, then finally remodulated to around 36kHz to drive the IR LED. siliconchip.com.au Australia's electronics magazine January 2022  97 A real soldering challenge! One of the main goals of this design was for the UHF transmitter to be tiny enough to fit inside just about any remote control case. That rules out using a pre-built UHF transmitter module, and due to the relatively high frequencies involved, the components need to be small. Very small. This project uses by far the smallest components we’ve ever specified in a design. The 68nH inductor comes in a metric 0603 SMD package (imperial 0201) Instead of using a large pre-built UHF transmitter module, we use a very small UHF transmitter IC with a few discrete components. Remote’s battery life One question that arises is what happens to the battery life of the modified remote. Will the battery be flattened in a short time when the UHF transmitter circuitry is added? We have made sure that there will be a negligible effect on battery life by having the circuitry in a sleep mode when you are not using the remote. A typical infrared remote control draws about 1-2μA from the battery continuously and around 10-20mA during infrared transmission. The UHF transmitter’s added power draw has almost no effect on these figures. With the IR-to-UHF Converter installed, we measured the standby current increasing by a mere 90nA – that’s 0.6 x 0.3mm! Unless you have excellent vision, it will just look like a dot to you (if you can see it at all). And the metric 1206 SMD inductors (imperial 0402) aren’t all that much bigger at 1.2 x 0.6mm. Soldering these devices is a challenge, to put it mildly. If you decide to go ahead, we suggest you purchase at least 10 of each (hey, they’re cheap!). That way, if you mangle or lose them, you can grab another one and try again. (0.09μA)! The current drain when a button is pressed is essentially unaltered and possibly even a little less than before, as the remote’s IR LED is not used and replaced by UHF transmission, which is on average 8mA when active. By the way, we measured the 90nA figure by connecting a 100kW resistor in series with the device’s supply and shorting it out until it went into sleep mode. We then measured 9mV across this resistor, which equates to 90nA (9mV ÷ 100kW). Receiver The companion UHF-to-IR Converter is housed in a small plastic case. One end of the case has a red acknowledge LED and an IR LED to re-transmit the received UHF signal as an IR signal. There is also a 3.5mm jack socket to allow the connection of an external IR LED via a cable. Even the larger (by comparison) devices on this board are a little tricky to solder because it’s so packed with components – again, to keep it small and also so it can transmit 434MHz signals efficiently. Besides being a useful little device to build, if you have reasonable SMD soldering skills and want to push yourself to achieve the next level of skill, assembling the transmitter module described here would be a great way to do that. This device either runs from a 9-12V DC plugpack or USB 5V. The circuit draws a maximum of 50mA when transmitting, so any 9-12V DC plugpack or USB power source should be suitable. Circuit details Fig.2 shows the circuit of the IR-toUHF Converter that’s designed to be built into the remote control. It comprises a PIC10LF322 microcontroller (IC1), a MICRF113 UHF transmitter (IC2) and associated components. IC1 monitors the infrared LED drive signal originally used to drive the infrared LED. The handheld remote output will drive either low or high to power the LED. An open-collector driver transistor or Mosfet within the remote control IC is normally used. This output requires a pull-up resistance to turn it into a digital signal for sensing, which Fig.2: the IR-to-UHF Converter section circuit deliberately uses few components to make the PCB as small as possible. It’s powered by the typically 3V supply of the remote control (from two 1.5V cells). IC1 demodulates the drive signal that would normally go to an infrared LED. When it detects a button press, it powers up UHF transmitter IC2 and feeds it the demodulated signal that is then radiated by the antenna at 434MHz. 98 Silicon Chip Australia's electronics magazine siliconchip.com.au Scope 1: the top yellow trace is the infrared LED drive signal from the remote control, applied to pin 1 of IC1. This is a series of 36kHz pulses. The lower blue trace shows the output of IC1 at pin 4 that drives the ASK input (pin 6) of the MICRF113 434MHz transmitter (IC2). This signal is high whenever there is a 36kHz signal at the input and low otherwise. is supplied by a Mosfet we enable inside IC1. A 1kW pull-down resistor is shown on the circuit, but this is only required if the remote control has an open-collector (or open-drain) output that drives high to power the LED. We will describe how to check for this later. IC1 converts the LED drive modulation (typically 36kHz) into a demodulated output at pin 4. That pin goes high when a modulated signal is present and low when the modulation is absent. IC2 is a UHF transmitter that sends digital data using two different carrier wave amplitudes. This is known as Amplitude Shift Keying (or ASK). For our purposes, there is no UHF transmission when the digital signal is low (near 0V) and a 433.92MHz carrier transmission when the digital signal is high (near 3V). IC1’s demodulated signal at pin 4 is suitable for driving IC2 at its ASK input (pin 6). Note that the pin 3 output of IC1 drives the supply input for IC2, at its pin 3. This way, IC2 can be shut down when not needed, drawing no power at idle. The transmission frequency is set using a crystal oscillator that is multiplied by 32 within IC2 to produce the UHF carrier. So the 13.56MHz crystal gives a carrier at 433.92MHz. This matches the carrier frequency used in most UHF ASK transmitter/receiver modules that are available for lowpower UHF data transmission. The MICRF113 and its associated components are tiny, fitting in a much tighter space than most pre-built UHF transmitter modules that are available. The supply current for IC2’s RF output stage is via two series-connected 220nH inductors, also acting as a 440nH driver load. The following 12pF series capacitor and 68nH inductor plus the 5pF capacitor to ground act as a filter that removes second and third harmonics from the UHF signal before it passes to the antenna. We mainly use two 220nH inductors instead of one 470nH inductor because we found suitable 220nH inductors easier to source. Any inductor used in the circuit must have a self-resonance (SR) frequency above 433.92MHz; otherwise, it will not function as an inductor at that frequency. Scope 2: this is the same capture as Scope 1 except with a faster timebase, so the 36kHz modulation is visible. Note the delay of about 56μs between IC1 receiving the 36kHz pulses and producing the demodulated pulses at its output. This does not distort the signal because it is symmetrical. Scope 3: the top yellow trace shows the IR drive signal from the handheld remote as in Scope 1, but the lower trace is the output from the UHF receiver in the UHF-to-IR Converter, ie, after it has passed over the wireless link. Scope 4: the top yellow trace is the infrared LED drive signal from the original infrared remote, while the lower blue trace is the IR LED drive signal in the UHF-to-IR Converter. The two waveforms are essentially the same except for the slight delay in the second trace, and the different voltage levels due to the UHF-to-IR circuit powered from 5V instead of 3V. The signal inversion is of no consequence. Scope5: a zoomed-in version of Scope 4 showing the modulation on both signals. The rise time of the original waveform at the top is slow due to the low pull-up current from pin 1 of the PIC10LF322. The lower blue trace is the IR LED drive from the UHF-to-IR Converter. The frequency has been set to about 36kHz to match the handheld remote. The top trace is inverted compared to the lower trace, as the original LED in the handheld remote was on when the output was low, whereas the IR LED in the UHF-to-IR Converter LED drive is active-high. Power for IC2 IC2’s power rail at pin 3 is bypassed with a 1μF ceramic capacitor, while a siliconchip.com.au Australia's electronics magazine January 2022  99 100nF capacitor bypasses the output stage supply. These two capacitors are essentially in parallel but are at different locations on the PCB so that the supply for each part is bypassed directly at its supply connection. We include schottky diode D2 between the ASK signal and the IC2 supply to boost the supply whenever the IC is transmitting. The pin 3 output drops in voltage when supplying current; current flowing from pin 4 of IC1 via diode D2 assists in maintaining a stable supply voltage for IC2. While IC2 can operate down to 1.8V, it’s best to keep its supply voltage as close as possible to the 3V from the remote battery for the best efficiency. IC1’s supply is bypassed by another 100nF ceramic capacitor. Diode D1 is included in case the cells in the remote are inserted the wrong way around, causing a reverse polarity to be applied. In this case, D1 will conduct and reduce the reverse voltage applied to IC1, preventing it from being damaged (at least in the short term). UHF-to-IR Converter The UHF signal needs to be detected and converted back to a stream of infrared pulses to control the appliance being operated. The UHF-to-IR Converter circuit is shown in Fig.3, and comprises UHF receiver RX1, a PIC12F617 microcontroller (IC1) and an infrared LED (LED1). The circuit is powered via either DC socket CON1 or micro-B USB socket CON2. The UHF receiver is powered continuously, ready to receive a transmission from the IR-to-UHF Converter in the handheld remote. With no signal present, the data output from the UHF receiver is just random noise with an amplitude of 5V. In this state, the receiver operates at maximum gain due to its automatic gain control (AGC). When a UHF signal is received, the AGC reduces the receiver’s sensitivity so that the detected signal is essentially noise-free. This is fed to the GP5 input (pin 2) of PIC micro IC1. To determine if a signal is valid, IC1 checks for periods where the data line from the UHF receiver is at 0V for at least 3ms. This indicates that the AGC has reduced the sensitivity of the receiver and that a transmission is occurring. The data output from the UHF receiver matches that data applied to the UHF transmitter. This data signal, in part, becomes the Acknowledge waveform that drives LED2 via digital output GP0. The 1kW resistor limits the LED current to around 3mA. IC1 drives the IR LED (LED1) from its GP1 and GP2 outputs in parallel to provide sufficient current. The 220W resistor limits this current to around 18mA. The infrared LED drive signal needs to include the same or similar modulation as that used by the original remote. So when the data output from the UHF receiver goes high, the GP1 and GP2 outputs are driven with pulse-width modulated signals. The duty cycle is 33.3%, so they are high 1/3 of the time and low 2/3 of the time. The GP4 input of IC1 monitors the voltage set by trimpot VR1, connected across the 5V supply rail. Its wiper voltage is converted to a digital value within IC1, allowing the IR carrier frequency to be adjusted to match the original transmitter. The adjustment range is from 32.4kHz to 41.4kHz in 32 steps. Setting VR1 to its mid-position gives 37kHz. Usually, somewhere near the middle setting is satisfactory, but some devices might require a different carrier frequency to operate reliably. A second output is provided via 3.5mm jack socket CON3 for an external IR LED (if necessary). This LED can be mounted near the IR receiver of the appliance(s) being operated. Power from a 9-12V DC plugpack is fed in via diode D1, providing reverse polarity protection. A 78L05 3-terminal regulator then provides a 5V supply for RX1 and IC1. Power via the USB connector is applied to the 5V supply rail via a 4.7W resistor. Fig.3: the UHF-to-IR Converter PCB uses a pre-built UHF receiver module (RX1) to pick up the signals from the transmitter, then microcontroller IC1 adds modulation at a frequency adjustable by VR1, and drives onboard infrared LED1 plus an external LED when plugged in via CON3. It can run directly from a 5V USB source via CON2 or 9-12V DC from barrel socket CON1, regulated to 5V by linear regulator REG1. 100 Silicon Chip Australia's electronics magazine siliconchip.com.au This resistor prevents excess current flow between the REG1 output and the 5V from the USB should both be connected. Construction The IR-to-UHF Converter PCB is coded 15109212 and measures 15mm x 12mm. It has components mounted on both sides. Refer to the PCB overlay diagrams, Figs.4(a) & (b), to see which parts go where. If IC1 hasn’t been programmed, do that before fitting it. You can purchase pre-programmed PIC10LF322 microcontrollers from our Online Shop if you don’t have the equipment to do it yourself. Begin assembly by fitting the surface mount parts on the top side of the PCB. These can be soldered using a finetipped soldering iron. Good close-up vision is necessary; you might need a magnifying lens or glasses to see well enough. Some fine-point tweezers can help as well, to hold the components in place. It will be easier to install the two 220nH inductors first. Solder one pad first and check alignment. Reheat the soldered pad and move the device if the inductor needs moving before soldering the second pad. Then mount the two ICs. IC1 and IC2 are positioned so that the small pin 1 location dot aligns with that on the PCB. When the IC is held with pin 1 at lower left, the writing on the IC top face will be the right way up. IC1 will be marked LF followed by two traceability code numbers. IC2 will Before mounting the IR-to-UHF Converter inside the remote, you will need to check whether a pulldown resistor is needed. have “F_113” etched on the top face. Orientate the ICs on the PCB with the pin 1 dot at upper left. For each IC, solder one pad first and then check their alignment. Readjust the component positioning by reheating the solder joint if necessary before soldering the remaining pins. Any shorts between pins can be cleared using solder wick to draw up the excess solder (adding flux paste first will help this process). Now diode D2 can be soldered in before fitting crystal X1. Make sure D2 is orientated as shown in Fig.4(a). You can then install the remaining top-mounted components. Note that many of the capacitors and inductors in surface mount packages are unmarked, so you will need to rely on the packaging to show what they are and their value. Mount one component at a time to avoid mixing them up. We are using capacitors and a resistor in slightly smaller M2012/0805 packages compared to the M3216/1206 packages we use elsewhere. This makes it easier to avoid accidentally making solder bridges to adjacent components when fitting them. It is also possible to lose components, so be careful and, if possible, get spares (SMD resistors and capacitors are generally very cheap and sold in sets). We recommend that you mount the These two photos show the top and bottom of the IR-to-UHF PCB at approximately triple actual size. Fig.4 (right): the IR-to-UHF converter PCB is packed so it can fit inside just about any remote control case. Don’t worry too much about bridging the pins of IC1 & IC2 when soldering them as that can be fixed quite easily using solder wick and flux paste, but do be careful to orientate those ICs correctly and don’t mix them up. The 68nH inductor is minuscule, so be careful not to lose it. After soldering it, check for a low resistance reading between the antenna terminal and left end of the 12pF capacitor. siliconchip.com.au Australia's electronics magazine January 2022  101 Parts List – Remote Control Range Extender IR-to-UHF Converter 1 double-sided PCB coded 15109212, 15mm x 12mm 1 13.56MHz surface-mount crystal (X1) [RS Components 171-0468] 2 220nH 500MHz inductors, M1005/0402 SMD (L1) [RS 741-3797] 1 68nH 1.2GHz inductor, M0602/0201 SMD (L2) [element14 3386563] 1 170mm length of light-duty hook-up wire (for the antenna) 1 200mm-length of red hook-up wire Kit (SC5993) 1 200mm-length of green hook-up wire A kit is available for the IR-to1 200mm-length of blue hook-up wire UHF Converter, see page 106. Semiconductors 1 PIC10LF322-I/OT 8-bit microcontroller programmed with 1510921M.HEX, SOT-23-6 (IC1) [Silicon Chip Online Shop] 1 MICFR113YM6 ASK UHF transmitter chip, SOT-23-6 (IC2) [RS 177-3314P] 1 1A SMD diode, DO-214AC (D1) [SM4004 or GS1G; Altronics Y0174, Jaycar ZR1003] 1 BAT54S ➊ small signal schottky diode, SOT-23 (D2) [Altronics Y0075] ➊ BAT54, BAT54S, BAT54C, BAT54FILMY and BAT54SFIMLY are all suitable Capacitors (all SMD M2012/0805 size ceramic) 1 1μF 16V X7R (preferred) or Y5V [Altronics R8650] 2 100nF 50V X7R (preferred) or Y5V [Altronics R8638] 2 18pF 50V C0G/NP0 [Altronics R8533] 1 12pF 50V C0G/NP0 [Altronics R8527] 1 4.7pF or 5pF 50V C0G/NP0 [Altronics R8512] Resistors 1 1kW SMD M2012/0805 ⅛W (might not be required; see text) [Altronics R1220] 1 10kW to 470kW ¼W axial leaded resistor (for testing) UHF-to-IR Converter 1 double-sided PCB coded 15109211, 79 x 47mm 1 UB5 Jiffy box, 83 x 54 x 31mm 1 lid label, 78 x 49mm 1 433.92MHz receiver module (RX1) [Jaycar ZW3102, Altronics Z6905A] 1 PCB-mount barrel socket to suit plugpack (CON1) 1 micro-USB SMD Type-B USB socket (CON2) [Jaycar PS0922, Altronics P1309] 1 3.5mm PCB-mount switched jack socket (CON3) [Jaycar PS0133, Altronics P0092] 1 8-pin DIL IC socket (for IC1) 1 170mm-length of light-duty hookup wire 1 10kW miniature horizontal trimpot (VR1) Semiconductors 1 PIC12F617-I/P 8-bit microcontroller, DIP-8, programmed with 1510921A.hex (IC1) [Silicon Chip Online Shop] 1 78L05 5V 100mA linear regulator, TO-92 (REG1) 1 3mm infrared LED (LED1) 1 3mm red LED (LED2) 1 1N4004 400V 1A diode (D1) Capacitors 2 100μF 16V PC electrolytic 1 100nF 63V MKT polyester Resistors (all ¼W 1% thin film axial) 2 1kW 2 220W 1 4.7W Optional parts for extended IR transmitter lead 1 3.5mm mono jack plug 1 1m length of single-core screened cable 1 3mm infrared LED 1 100mm length of 3mm diameter heatshrink tubing 102 Silicon Chip Australia's electronics magazine 68nH inductor after fitting the 12pF and 5pF capacitors; otherwise, this inductor may become accidentally desoldered. Now turn your attention to the underside of the PCB. There are two 18pF capacitors, one 1kW resistor and diode D1. Taking care to position the diode correctly, with the cathode stripe, as shown in Fig.4(b). Note that the resistor might not be required, so leave it off for the moment. If you want to be sure that the components have been soldered correctly, you can trace the connections to the other sections of the PCB to where there should be continuity. For example, pin 3 of IC1 should provide a low resistance reading to pin 3 of IC2. Additionally, check that there are no short circuits between component pins on the PCB that shouldn’t be connected. Pull-up or pull-down As mentioned, the handheld remote control might drive its output high or low to turn the IR LED on. The way the LED is driven determines whether you need to install the 1kW pull-down resistor. The internal pull-up within IC1 is automatically activated if the pull-down resistor is not fitted. To determine this, first you will need to open the remote control case. Some remote cases are secured using screws that are easy to spot, but they also could be hidden under the cells. Open the battery compartment and remove the cells to check for screws. Once these are out, open the case by gently working around the sides with a thin implement to separate the two halves. Once inside, locate the positive and negative battery terminals. To check whether the resistor is needed, it is just a matter of making some measurements with a multimeter. Firstly, check the resistance between the battery’s positive terminal and the anode (+) of the LED. If it is low (less than 30W), you can expect that the pulldown resistor is not needed. That is because the cathode of the LED would be pulled down to power the LED. If the resistance between the cathode (-) of the LED and the negative battery terminals is low (less than 30W), that means the LED drive is active-high, so the 1kW pull-down resistor is needed. After the pull-down resistor is soldered in place (if needed), the siliconchip.com.au The IR LED in the remote is replaced with our IR-to-UHF PCB. This PCB can then be covered with heatshrink and placed in the remote's housing. ► ► The UHF-toIR PCB can be mounted inside a UB5 case and placed near the receiving device. You will need to drill holes in the UB5 case for the sockets and LEDs as shown in Fig.6. assembled board can be mounted in the remote’s case. The IR LED should be removed. Wire up the supply connections: + to the +3V on the remote, GND to the 0V terminal and IN to the LED drive pin on the remote’s IC (eg, to the pad where the LED was soldered). You might need to trace out the PCB to figure out which one to connect. Place the PCB in a suitable spare space within the remote, solder the antenna wire, and route this around the case in a position where it will not be caught when it is reassembled. Note that while we specify a 170mm length of antenna wire, the transmission range does not suffer significantly if it is shortened. We found that a 53mm length of antenna wire only reduced the range by 5m compared to the 170mm length. Finally, clip the case together and reinstall the securing screws if they were present. UHF-to-IR Converter assembly The companion UHF-to-IR Converter is built on a double-sided PCB coded 151009211 that measures 79 x 47mm. This clips neatly into an 83 x 54 x 31mm UB5 plastic utility box. A 78 x 49mm lid panel label can be attached to this. If IC1 for this PCB hasn’t been programmed yet, do it now before continuing. As with the SMD chip, we can supply a pre-programmed PIC12F617I/P if you don’t have the equipment to do this yourself. Fig.5 shows the parts layout for this board. Start with the micro USB socket, which is surface-mounted. Align the solder pads with the leads on the connector and solder one of the mounting tabs to the PCB. Re-check the alignment of the small signal pins before soldering the signal pins and then the remaining tabs. The solder on the mounting tab can be remelted, and the connector realigned if it is not correct. Check the signal pins for solder bridges; if you find any, clear them using solder wick. Make sure the pins are still soldered to the PCB. Now fit the resistors. The resistor colour codes can be used as a guide to their values but checking the resistances with a multimeter is also a good idea. Next, mount diode D1, ensuring it is correctly orientated. The capacitors can go in next; only the two 100μF electrolytics are polarised. As well as ensuring their longer leads go to the pads marked with + symbols, they must be bent over to clear the lid when the PCB is mounted in its case. REG1 can then be mounted, followed by the DC socket (CON1), the 3.5mm jack socket (CON2) and trimpot Fig.5: the assembly of this board is straightforward as the components are much larger than on the other board. Watch the orientations of the UHF receiver, IC1 and diode D1. siliconchip.com.au Australia's electronics magazine January 2022  103 The front panel label for the Remote Control Range Extender can be downloaded as a 1-1 scale PDF from siliconchip.com.au VR1 (set it mid-way now). Next, fit the UHF receiver (RX1), making sure it goes in the right way around. Installing the LEDs LED1 must be mounted at full lead length (25mm) so that it can be later bent over and its lens pushed through a hole in the side of the box (above the 3.5mm socket). LED2 is mounted with the top of its lens 20mm above the PCB surface. Make sure the LEDs are orientated correctly, with their anode (longer) leads going to the pads marked “A”. Now solder in an 8-pin DIL socket for IC1, but do not plug the PIC micro in at this stage. That step comes later after the power supply has been tested. Complete the PCB assembly by fitting the 170mm-long antenna wire made from insulated hookup wire. Final assembly The PCB simply clips into the integral ribs of the UB5 case. Before doing this, you need to drill holes in the case ends for the USB socket, the DC socket, the 3.5mm socket and the two LEDs. The drilling diagrams are shown in Fig.6. The DC socket hole can be drilled first. This is positioned 6.5mm down from the top lip of the base at the lefthand end. Start this hole using a small pilot drill, then carefully enlarge it to 6.5mm using a tapered reamer. The 3.5mm socket hole is centred along the horizontal axis at the other end of the case, 10.5mm down from the lip. Again, use a pilot drill to start it, then enlarge it to 6.5mm. The hole for LED1 can then be drilled 3.5mm down from the lip, directly above the socket hole. Drill this hole to 3mm, then drill a similar hole for LED2 about 12mm to the right. The rectangular USB cut-out can be first drilled and then filed to shape with needle files. Now clip the PCB into the slots in the side ribs of the box (push the 3.5mm jack socket into its hole first). Once it’s in place, bend the two LEDs over and push them through their respective holes in the adjacent end. Secure the assembly by fitting the nut to the jack socket. The lid label can be downloaded (in PDF format) from siliconchip.com. au (go to “Shop” and then “Panel artwork”) and printed out onto a suitable label (see information on making labels at siliconchip.com.au/ Help/FrontPanels) and affixed to the lid. The four corner holes for the case screws can be cut out using a sharp hobby knife. Making an extension cable Depending on how your gear is arranged, you may want to make up a cable with a 3.5mm jack plug at one end and an external IR LED at the other. Fig.7 shows the details. You will need to use a suitable length of single-core shielded cable, while the LED leads should be insulated from each other using heatshrink tubing. Use a length of larger diameter An extension cable can be made and attached to the UHF-to-IR Converter via the 3.5mm jack socket (CON3); Fig.7 has the details for how to design this cable. 104 Silicon Chip Australia's electronics magazine siliconchip.com.au heatshrink tubing to cover the end of the cable, including both LED leads and part of the lens, as shown below. ► Testing First, check that IC1 has not been installed. Apply power and check there is 5V between pins 1 & 8 of the IC socket. If not, verify the supply polarity and ensure that D1 and REG1 are correctly orientated. If you measure 5V, switch off and install IC1 with its notched end towards the adjacent 100nF capacitor. Now reapply power and check that the red acknowledge LED flashes when the remote control buttons are pressed. Next, test the appliance. The UHFto-IR Converter needs to have its IR LED pointing towards the appliance at a range of about 1m. If it doesn’t work, adjust VR1 as you operate the remote control until the appliance responds. Usually, setting VR1 mid-way (corresponding to a carrier frequency of around 37kHz) will be suitable. Once it’s operating correctly, try using the remote to control the appliance from another room. You should get a free-air range of 20-25m, but the range will be less than this inside a house, depending on any obstacles (walls, etc) between the remote and the UHF-to-IR Converter. Fig.6: here are where the holes need to be drilled or cut in the UB5 Jiffy box. The hole for the jack socket in the right-hand end of the box can be left out if you aren’t using the IR extension lead, and similarly, you only need to make one hole in the lefthand end, depending on whether you will be using the USB or barrel socket to supply power. Fig.7: if you need to mount the IR LED away from the receiver unit (eg, mounting it directly in front of the appliance’s receiver), you can make up an extension cable as shown here. It plugs directly into the socket on the receiver. ► SC U Cable Tester S B Test just about any USB cable! USB-A (2.0/3.2) USB-B (2.0/3.2) USB-C Mini-B Micro-B (2.0/3.2) Reports faults with individual cable ends, short circuits, open circuits, voltage drops and cable resistance etc November & December 2021 issues siliconchip.com.au/Series/374 DIY kit for $110 SC5966 – siliconchip.com.au/Shop/20/5966 Everything included except the case and batteries. Postage is $10 within Australia, see our website for overseas & express post rates siliconchip.com.au Australia's electronics magazine January 2022  105 SILICON CHIP .com.au/shop ONLINESHOP HOW TO ORDER INTERNET (24/7) PAYPAL (24/7) eMAIL (24/7) MAIL (24/7) PHONE – (9-5:00 AET, Mon-Fri) siliconchip.com.au/Shop silicon<at>siliconchip.com.au silicon<at>siliconchip.com.au PO Box 139, COLLAROY, NSW 2097 (02) 9939 3295, +612 for international You can also pay by cheque/money order (Orders by mail only) or bank transfer. Make cheques payable to Silicon Chip. 01/22 YES! You can also order or renew your Silicon Chip subscription via any of these methods as well! The best benefit, apart from the magazine? Subscribers get a 10% discount on all orders for parts. PRE-PROGRAMMED MICROS For a complete list, go to siliconchip.com.au/Shop/9 $10 MICROS 24LC32A-I/SN ATmega328P ATmega328P-AUR ATtiny85V-10PU ATtiny816 PIC10F202-E/OT PIC10LF322-I/OT PIC12F1572-I/SN PIC12F617-I/P PIC12F617-I/SN PIC12F675-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-I/P $15 MICROS Digital FX Unit (Apr21) RF Signal Generator (Jun19), Si473x FM/AM/SW Digital Radio (Jul21) RGB Stackable LED Christmas Star (Nov20) Shirt Pocket Audio Oscillator (Sep20) ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) Range Extender IR-to-UHF (Jan22) LED Christmas Ornaments (Nov20; specify variant) Nano TV Pong (Aug21), SMD Test Tweezers (Oct21) Refined Full-Wave Universal Motor Speed Controller (Apr21) Model Railway Level Crossing (two required – $15/pair) (Jul21) Range Extender UHF-to-IR (Jan22) Model Railway Carriage Lights (Nov21) Motor Speed Controller (Mar18), Heater Controller (Apr18) Useless Box IC3 (Dec18) Tiny LED Xmas Tree (Nov19) Digital Interface Module (Nov18), GPS Finesaver (Jun19) Digital Lighting Controller LED Slave (Dec20) Ol’ Timer II (Jul20), Battery Multi Logger (Feb21) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20), Electronic Wind Chime (Feb21) 20A DC Motor Speed Controller (Jul21) Flexible Digital Lighting Controller Slave (Oct20) Digital Lighting Controller Translator (Dec21) UHF Repeater (May19), Six Input Audio Selector (Sep19) Universal Battery Charge Controller (Dec19) ATSAML10E16A-AUT High-Current Battery Balancer (Mar21) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC16F18877-I/P USB Cable Tester (Nov21) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sep19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) RCL Box (Jun20), Digital Lighting Controller Micromite Master (Nov20) Advanced GPS Computer (Jun21) Touchscreen Digital Preamp [2.8in/3.5in version] (Sep21) PIC32MX170F256B-I/SO Battery Multi Logger (Feb21), Battery Manager BackPack (Aug21) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) PIC32MX795F512H-80I/PT Maximite (Mar11), miniMaximite (Nov11), Colour Maximite (Sep12), Touchscreen Audio Recorder (Jun14) $20 MICROS dsPIC33FJ64MC802-E/SP dsPIC33FJ128GP306-I/PT dsPIC33FJ128GP802-I/SP PIC32MX470F512H-I/PT PIC32MX470F512H-120/PT PIC32MX470F512L-120/PT 1.5kW Induction Motor Speed Controller (Aug13) CLASSiC DAC (Feb13) Ultra-LD Preamp (Nov11), LED Musicolour (Oct12) Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) Micromite Explore 100 (Sep16) $30 MICROS PIC32MX695F512L-80I/PF Colour MaxiMite (Sep12) PIC32MZ2048EFH064-I/PT DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS, SPECIALISED COMPONENTS ETC IR-TO-UHF MODULE FOR RANGE EXTENDER (CAT SC5993) (JAN 22) SMD TRAINER KIT (CAT SC5260) (DEC 21) HUMMINGBIRD AMPLIFIER (CAT SC6021) (DEC 21) PCB and all SMDs (including the programmed micro) for the IR-to-UHF module Complete kit includes the PCB and all on-board components, except for a TQFP-64 footprint device $20.00 Hard-to-get parts includes: two 0.22W 5W resistors; plus one each of an MJE15034G, MJE15035G, KSC3503DS & 220pF 250V C0G ceramic capacitor USB CABLE TESTER KIT (CAT SC5966) (NOV 21) MODEL RAILWAY CARRIAGE LIGHTS KIT (CAT SC6027) (NOV 21) SMD TEST TWEEZERS KIT (CAT SC5934) (OCT 21) NANO TV PONG SHORT FORM KIT (CAT SC5885) (AUG 21) MODEL RAILWAY LEVEL CROSSING (JUL 21) MINI ISOLATED SERIAL LINK COMPLETE KIT (CAT SC5750) (MAR 21) AM/FM/SW RADIO (JAN 21) MICROMITE LCD BACKPACK V3 KIT (CAT SC5082) (AUG 19) Short form kit with everything except case and AA cells Includes PCB, IC1 (programmed), IC2, D1, L1, SMD capacitors and resistors. Does not include reed switch, magnet, LEDs or through-hole parts PCBs, micro, other onboard parts and heatshrink (no cell or brass tips) PCB and all onboard parts only (does not include controllers) - Pair of programmed PIC12F617-I/Ps - ISD1820P-based audio recording and playback module All parts required to build the project including the PCB - PCB-mount right-angle SMA socket (SC4918) - Pulse-type rotary encoder with integral pushbutton (SC5601) - 16x2 LCD module (does not use I2C module) (SC4198) $25.00 $15.00 $110.00 $25.00 $35.00 $17.50 $15.00 $5.00 $10.00 $2.50 $3.00 $7.50 Includes PCB, programmed micros, 3.5in touchscreen LCD, UB3 lid, mounting hardware, Mosfets for PWM backlight control and all other mandatory on-board parts $75.00 Separate/Optional Components: - 3.5-inch TFT LCD touchscreen (Cat SC5062) $35.00 siliconchip.com.au/Shop/ - DHT22 temp/humidity sensor (Cat SC4150) - BMP180 (Cat SC4343) OR BMP280 (Cat SC4595) temp/pressure sensor - BME280 temperature/pressure/humidity sensor (Cat SC4608) - DS3231 real-time clock SOIC-16 IC (Cat SC5103) - 23LC1024 1MB RAM (SOIC-8) (Cat SC5104) - AT25SF041 512KB flash (SOIC-8) (Cat SC5105) - 10µF 16V X7R through-hole capacitor (Cat SC5106) $7.50 $5.00 $10.00 $4.00 $5.00 $1.50 $2.00 VARIOUS MODULES & PARTS - 64x32 pixel white 0.49in OLED (SMD Test Tweezers, Oct21) $10.00 - pair of AD8403ARZ10 (Touchscreen Digital Preamp, Sep21) $35.00 - Si4732 radio IC (Si473x FM/AM/SW Radio, Jul21) $15.00 - EA2-5NU relay (PIC Programming Helper, Jun21) $3.00 - VK2828U7G5LF GPS module (Advanced GPS Computer, Jun21) $25.00 - MCP4251-502E/P (Advanced GPS Computer, Jun21) $3.00 - pair of Signetics NE555Ns (Arcade Pong, Jun21) $12.50 - 2.8-inch touchscreen LCD module (Lab Supply, May21) $25.00 - Spin FV-1 digital effects IC (Digital FX Unit, Apr21) $40.00 - 15mW 3W SMD resistor (Battery Multi Logger / Arduino PSU, Feb21) $2.50 - DS3231(M) real-time clock SMD IC (Battery Multi Logger, Feb21) $3.00 - Pair of CSD18534 transistors (Electronic Wind Chimes, Feb21) $6.00 - IPP80P03P4L04 (Dual Battery Lifesaver / Vintage Radio Supply, Dec20) $5.00 - 16x2 LCD module (Digital RF Power Meter, Aug20) $7.50 - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) $15.00 - MAX038 function generator IC (H-Field Transanalyser, May20) $25.00 - MC1496P double-balanced mixer IC (H-Field Transanalyser, May20) $2.50 - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) $12.50 - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) $5.00 - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 - SMD 1206 LEDs, packets of 10 unless stated otherwise (Xmas Ornaments, Nov20): yellow – $0.70 ¦ amber – $0.70 ¦ blue – $0.70 ¦ cyan – $1.00 ¦ pink (1 only) – $0.20 - ISD1820-based voice recorder / playback module (Junk Mail, Aug19) $4.00 - 23LCV1024-I/P SRAM & MCP73831T (UHF Repeater, May19) $11.50 - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) $1.50 - 1nF 1% MKP (5mm) or ceramic capacitor (LC Meter, Jun18) $2.50 - ESP-01 WiFi Module (El Cheapo Modules, Apr18) $5.00 - DS3231 real-time clock module with mounting hardware $7.50 *Prices valid for month of magazine issue only. All prices in Australian dollars and include GST where applicable. # P&P prices are within Australia. Overseas? Place an order on our website for a quote. PRINTED CIRCUIT BOARDS & CASE PIECES PRINTED CIRCUIT BOARD TO SUIT PROJECT DAB+/FM/AM RADIO ↳ CASE PIECES (CLEAR) REMOTE CONTROL DIMMER MAIN PCB ↳ MOUNTING PLATE ↳ EXTENSION PCB USB MOUSE AND KEYBOARD ADAPTOR PCB LOW-NOISE STEREO PREAMP MAIN PCB ↳ INPUT SELECTOR PCB ↳ PUSHBUTTON PCB DIODE CURVE PLOTTER ↳ UB3 LID (MATTE BLACK) FLIP-DOT (SET OF ALL FOUR PCBs) ↳ COIL PCB ↳ PIXEL PCB (16 PIXELS) ↳ FRAME PCB (8 FRAMES) ↳ DRIVER PCB iCESTICK VGA ADAPTOR UHF DATA REPEATER AMPLIFIER BRIDGE ADAPTOR 3.5-INCH LCD ADAPTOR FOR ARDUINO DSP CROSSOVER (ALL PCBs – TWO DACs) ↳ ADC PCB ↳ DAC PCB ↳ CPU PCB ↳ PSU PCB ↳ CONTROL PCB ↳ LCD ADAPTOR STEERING WHEEL CONTROL IR ADAPTOR GPS SPEEDO/CLOCK/VOLUME CONTROL ↳ CASE PIECES (MATTE BLACK) RF SIGNAL GENERATOR RASPBERRY PI SPEECH SYNTHESIS/AUDIO BATTERY ISOLATOR CONTROL PCB ↳ MOSFET PCB (2oz) MICROMITE LCD BACKPACK V3 CAR RADIO DIMMER ADAPTOR PSEUDO-RANDOM NUMBER GENERATOR 4DoF SIMULATION SEAT CONTROLLER PCB ↳ HIGH-CURRENT H-BRIDGE MOTOR DRIVER MICROMITE EXPLORE-28 (4-LAYERS) SIX INPUT AUDIO SELECTOR MAIN PCB ↳ PUSHBUTTON PCB ULTRABRITE LED DRIVER HIGH RESOLUTION AUDIO MILLIVOLTMETER PRECISION AUDIO SIGNAL AMPLIFIER SUPER-9 FM RADIO PCB SET ↳ CASE PIECES & DIAL TINY LED XMAS TREE (GREEN/RED/WHITE) HIGH POWER LINEAR BENCH SUPPLY ↳ HEATSINK SPACER (BLACK) DIGITAL PANEL METER / USB DISPLAY ↳ ACRYLIC BEZEL (BLACK) UNIVERSAL BATTERY CHARGE CONTROLLER BOOKSHELF SPEAKER PASSIVE CROSSOVER ↳ SUBWOOFER ACTIVE CROSSOVER ARDUINO DCC BASE STATION NUTUBE VALVE PREAMPLIFIER TUNEABLE HF PREAMPLIFIER 4G REMOTE MONITORING STATION LOW-DISTORTION DDS (SET OF 5 BOARDS) NUTUBE GUITAR DISTORTION / OVERDRIVE PEDAL THERMAL REGULATOR INTERFACE SHIELD ↳ PELTIER DRIVER SHIELD DIY REFLOW OVEN CONTROLLER (SET OF 3 PCBS) 7-BAND MONO EQUALISER ↳ STEREO EQUALISER REFERENCE SIGNAL DISTRIBUTOR H-FIELD TRANSANALYSER CAR ALTIMETER RCL BOX RESISTOR BOARD ↳ CAPACITOR / INDUCTOR BOARD ROADIES’ TEST GENERATOR SMD VERSION ↳ THROUGH-HOLE VERSION DATE JAN19 JAN19 FEB19 FEB19 FEB19 FEB19 MAR19 MAR19 MAR19 MAR19 MAR19 APR19 APR19 APR19 APR19 APR19 APR19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 MAY19 JUN19 JUN19 JUN19 JUN19 JUL19 JUL19 JUL19 AUG19 AUG19 AUG19 SEP19 SEP19 SEP19 SEP19 SEP19 SEP19 OCT19 OCT19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 NOV19 DEC19 JAN20 JAN20 JAN20 JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 APR20 APR20 APR20 APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 PCB CODE Price 06112181 $15.00 SC4849 $.00 10111191 $10.00 10111192 $10.00 10111193 $10.00 24311181 $5.00 01111119 $25.00 01111112 $15.00 01111113 $5.00 04112181 $7.50 SC4927 $5.00 SC4950 $17.50 19111181 $5.00 19111182 $5.00 19111183 $5.00 19111184 $5.00 02103191 $2.50 15004191 $10.00 01105191 $5.00 24111181 $5.00 SC5023 $40.00 01106191 $7.50 01106192 $7.50 01106193 $5.00 01106194 $7.50 01106195 $5.00 01106196 $2.50 05105191 $5.00 01104191 $7.50 SC4987 $10.00 04106191 $15.00 01106191 $5.00 05106191 $7.50 05106192 $10.00 07106191 $7.50 05107191 $5.00 16106191 $5.00 11109191 $7.50 11109192 $2.50 07108191 $5.00 01110191 $7.50 01110192 $5.00 16109191 $2.50 04108191 $10.00 04107191 $5.00 06109181-5 $25.00 SC5166 $25.00 16111191 $2.50 18111181 $10.00 SC5168 $5.00 18111182 $2.50 SC5167 $2.50 14107191 $10.00 01101201 $10.00 01101202 $7.50 09207181 $5.00 01112191 $10.00 06110191 $2.50 27111191 $5.00 01106192-6 $20.00 01102201 $7.50 21109181 $5.00 21109182 $5.00 01106193/5/6 $12.50 01104201 $7.50 01104202 $7.50 CSE200103 $7.50 06102201 $10.00 05105201 $5.00 04104201 $7.50 04104202 $7.50 01005201 $2.50 01005202 $5.00 For a complete list, go to siliconchip.com.au/Shop/8 PRINTED CIRCUIT BOARD TO SUIT PROJECT COLOUR MAXIMITE 2 PCB (BLUE) ↳ FRONT & REAR PANELS (BLACK) OL’ TIMER II PCB (RED, BLUE OR BLACK) ↳ ACRYLIC CASE PIECES / SPACER (BLACK) IR REMOTE CONTROL ASSISTANT PCB (JAYCAR) ↳ ALTRONICS VERSION USB SUPERCODEC ↳ BALANCED ATTENUATOR SWITCHMODE 78XX REPLACEMENT WIDEBAND DIGITAL RF POWER METER ULTRASONIC CLEANER MAIN PCB ↳ FRONT PANEL NIGHT KEEPER LIGHTHOUSE SHIRT POCKET AUDIO OSCILLATOR ↳ 8-PIN ATtiny PROGRAMMING ADAPTOR D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) LED XMAS ORNAMENTS 30 LED STACKABLE STAR ↳ RGB VERSION (BLACK) DIGITAL LIGHTING MICROMITE MASTER ↳ CP2102 ADAPTOR BATTERY VINTAGE RADIO POWER SUPPLY DUAL BATTERY LIFESAVER DIGITAL LIGHTING CONTROLLER LED SLAVE BK1198 AM/FM/SW RADIO MINIHEART HEARTBEAT SIMULATOR I’M BUSY GO AWAY (DOOR WARNING) BATTERY MULTI LOGGER ELECTRONIC WIND CHIMES ARDUINO 0-14V POWER SUPPLY SHIELD HIGH-CURRENT BATTERY BALANCER (4-LAYERS) MINI ISOLATED SERIAL LINK REFINED FULL-WAVE MOTOR SPEED CONTROLLER DIGITAL FX UNIT PCB (POTENTIOMETER-BASED) ↳ SWITCH-BASED ARDUINO MIDI SHIELD ↳ 8X8 TACTILE PUSHBUTTON SWITCH MATRIX HYBRID LAB POWER SUPPLY CONTROL PCB ↳ REGULATOR PCB VARIAC MAINS VOLTAGE REGULATION ADVANCED GPS COMPUTER PIC PROGRAMMING HELPER 8-PIN PCB ↳ 8/14/20-PIN PCB ARCADE MINI PONG Si473x FM/AM/SW DIGITAL RADIO 20A DC MOTOR SPEED CONTROLLER MODEL RAILWAY LEVEL CROSSING COLOUR MAXIMITE 2 GEN2 (4 LAYERS) BATTERY MANAGER SWITCH MODULE ↳ I/O EXPANDER NANO TV PONG LINEAR MIDI KEYBOARD (8 KEYS) + 2 JOINERS ↳ JOINER ONLY (1pc) TOUCHSCREEN DIGITAL PREAMP ↳ RIBBON CABLE / IR ADAPTOR 2-/3-WAY ACTIVE CROSSOVER TELE-COM INTERCOM SMD TEST TWEEZERS (3 PCB SET) USB CABLE TESTER MAIN PCB ↳ FRONT PANEL (GREEN) MODEL RAILWAY CARRIAGE LIGHTS HUMMINGBIRD AMPLIFIER DIGITAL LIGHTING CONTROLLER TRANSLATOR SMD TRAINER DATE JUL20 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 NOV20 AUG20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 OCT20 OCT20 OCT20 NOV20 NOV20 NOV20 NOV20 NOV20 DEC20 DEC20 DEC20 JAN21 JAN21 JAN21 FEB21 FEB21 FEB21 MAR21 MAR21 APR21 APR21 APR21 APR21 APR21 MAY21 MAY21 MAY21 JUN21 JUN21 JUN21 JUN21 JUL21 JUL21 JUL21 AUG21 AUG21 AUG21 AUG21 AUG21 AUG21 SEP21 SEP21 OCT21 OCT21 OCT21 NOV21 NOV21 NOV21 DEC21 DEC21 DEC21 PCB CODE 07107201 SC5500 19104201 SC5448 15005201 15005202 01106201 01106202 18105201 04106201 04105201 04105202 08110201 01110201 01110202 24106121 16110202 16110203 16111191-9 16109201 16109202 16110201 16110204 11111201 11111202 16110205 CSE200902A 01109201 16112201 11106201 23011201 18106201 14102211 24102211 10102211 01102211 01102212 23101211 23101212 18104211 18104212 10103211 05102211 24106211 24106212 08105211 CSE210301C 11006211 09108211 07108211 11104211 11104212 08105212 23101213 23101214 01103191 01103192 01109211 12110121 04106211/2 04108211 04108212 09109211 01111211 16110206 29106211 Price $10.00 $10.00 $5.00 $7.50 $5.00 $5.00 $12.50 $7.50 $2.50 $5.00 $7.50 $5.00 $5.00 $2.50 $1.50 $5.00 $20.00 $20.00 $3.00 $12.50 $12.50 $5.00 $2.50 $7.50 $2.50 $5.00 $10.00 $5.00 $2.50 $5.00 $10.00 $5.00 $12.50 $2.50 $7.50 $7.50 $7.50 $5.00 $10.00 $10.00 $7.50 $7.50 $7.50 $5.00 $7.50 $35.00 $7.50 $7.50 $5.00 $15.00 $5.00 $2.50 $2.50 $5.00 $1.00 $12.50 $2.50 $15.00 $30.00 $10.00 $7.50 $5.00 $2.50 $5.00 $5.00 $5.00 8-LED METRONOME 10-LED METRONOME REMOTE CONTROL RANGE EXTENDER UHF-TO-IR ↳ IR-TO-UHF 6-CHANNEL LOUDSPEAKER PROTECTOR ↳ 4-CHANNEL JAN22 JAN22 JAN22 JAN22 JAN22 JAN22 23111211 23111212 15109211 15109212 01101221 01101222 $5.00 $7.50 $2.50 $2.50 $7.50 $5.00 NEW PCBs We also sell an A2 Reactance Wallchart, RTV&H DVD, Vintage Radio DVD plus various books at siliconchip.com.au/Shop/3 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 Capacitor value in USB Cable Tester kit I received the USB Cable Tester kit that I ordered and I noticed that a 100μF 16V electrolytic capacitor had been supplied, but no 10μF 16V capacitor per the parts list. Also, I have received a component marked 4P03L04, which I have confirmed is suitable for Q3. This is my first (and perhaps only) go at soldering SMDs, so it would help if you could point me to a previous issue of SC that has some tips. (R. L. C., Shelly Beach, NSW) ● While the 10μF specified in the article is the minimum required, we tested a 100μF capacitor in the prototype and found that it worked fine. So we supplied 100μF capacitors in the kit as we already had them in stock. There is quite a bit of information on SMD soldering in the December issue (which you would not have seen yet based on the date of your email). That includes the second USB Cable Tester (constructional) article and also a separate feature article in that issue (siliconchip.com.au/Article/15138). Electrolytic capacitors work well for coupling I am considering building the 2/3Way Stereo Active Crossover (October & November 2021; siliconchip. com.au/Series/371) for a PA system. I noticed that you are using low-ESR electrolytic capacitors for signal coupling between sections of the design. I thought that these caps were designed for switch-mode power supplies, not for use as coupling. As I will be using a split supply, should I be using bipolar caps instead? (P. S., Mount Pleasant, SA) ● Regular electrolytic capacitors, including low-ESR types, work well for coupling audio as long as their values are high enough. They’ve been used for decades in mixing consoles, amplifiers and just about all types of audio equipment. Arguably, low-ESR capacitors should do a better job than 108 Silicon Chip standard electros since they are closer to ideal capacitors. We don’t believe bipolar/non-­ polarised capacitors are needed for this design when used with a split supply. Polarised capacitors can be used without problems when the bias across them is close to 0V or even slightly negative (within a few hundred milli­ volts of zero). SMD Test Tweezers questions I recently received your SMD Test Tweezers kit (siliconchip.com. au/Shop/20/5934); thank you. As described, it didn’t come with a cell or brass tips. What type of cell is needed? What is the voltage required? Also, what type of tip is used in the image? What is the part called and where can I get it? (M. G., Endeavour Hills, Vic) ● The battery is listed as a CR2032 or CR2025 lithium button cell on p68 of the article in the October 2021 issue. These are nominally 3V. The tip is a small piece cut from a length of brass strip; these can usually be found in hobby stores (eg, the type that sells model railway gear) and will probably be sold in a 30cm length from which you will need to cut smaller pieces. The exact dimensions are not critical. An online search for “brass strip” or “brass bar” should give you a start. Note that round brass rod is also available, but we don’t recommend it as the rounded surface will not grip the components as well as a flat strip. R80 kit is different from the one reviewed Following your review about the R80 aviation radio (November 2021; siliconchip.com.au/Article/15101), I downloaded the circuit etc from your website and bought a kit from AliExpress. But the kit received is version 7, and now I have a kit without a circuit diagram which makes it very difficult! Australia's electronics magazine Do you know where to find a circuit diagram for this newer version? (M. T., Dodges Ferry, Tas) ● Andrew Woodfield responds: I was as surprised as anyone to find the recently released R80 V6 receiver kit has undergone such an early, rapid and substantial change into the new version 7. Some internet suppliers still appear to offer the kit reviewed in the November issue, but some now offer (or may deliver) the revised kit. One reason for the changes may be the inherent V6 squelch design fault. Other reasons may include difficulties with component availability and sharply increased costs for parts like the MC3361 and TA7640 chips. The new V7 design, which uses a pair of widely used TA2003 AM/ FM receiver chips, almost certainly resolves the availability and cost problems. I have not tested the performance of the V7 squelch circuit, so I cannot comment on its effectiveness on AM, but from what I understand, it does work better than the V6 squelch. To help readers with V7 kits, I have prepared a new English version of the kit instructions and it is available for download from siliconchip.com.au/ Shop/6/5950 Thanks to Silicon Chip reader Nigel Dudley for his help with obtaining the original Chinese V7 instructions. Is Ultrasonic Cleaner software correct? I built the High Power Ultrasonic Cleaner from the September & October 2021 issues (siliconchip.com. au/Series/350) and found it behaved incorrectly. I have gone through the included source code and I believe I have found the problem. I want to confirm my findings with the author. The software runs a self-calibration routine on startup and saves the result into non-volatile RAM. On the second run, it retrieves this stored value so it can proceed without having to rerun the calibration. Unfortunately, the author appears to have made an error siliconchip.com.au and it stores the data in the wrong register. This causes erratic behaviour on second and subsequent runs. The power data register declared in address H0702 is actually saved to address H0700, which was declared as the OSCTUNE value. I am having trouble getting the unit to operate on its maximum power setting. Using a scope and DVM, I ran the diagnostic program (holding both buttons on startup) and determined that my transducer (while mounted to my reservoir filled with 4L of water) resonates at 37.5kHz while producing a reading of 4.3V on TP1. Now when I run the unit (recompiled with the above address problem corrected), the unit steps down to about the 50–75% mark and a corresponding 3.3V before locking in. Any attempt to step it higher results in the unit stepping down again. (B. V. D., via email) ● The code to write the power to flash memory is correct. The power value is not written to H0700. The OSCTUNE, PR1 and Power values are written as a block write with the OSCTUNE value written first at H0700. The write address is then incremented (“incf PMADRL,f”) to H0701 and the PR2 value is written, then the address is incremented again to H0702 and the power value written. Regarding your difficulty achieving maximum power, when in diagnostic mode, find the frequency range where you can get a reading of 4.6V, try setting it to the next lower frequency and perform calibration. If that is not effective, try setting the frequency range when in diagnostic mode to the highest frequency within the range that gives the peak reading. Alternatively, the transducer resonance point may not be being found correctly. Try running the diagnostics and sweeping the frequencies to find the maximum current by measuring the voltage at TP1. If this voltage goes over the maximum allowable reading of 4.8V, reduce the number of secondary turns on the transformer. It is critical that current overload isn’t reached at resonance. Replacement op amps for the Digital FX Pedal I decided to build the Digital FX (Effects) Pedal published in the April & May 2021 issues (siliconchip.com.au/ Series/361) but I am having difficulty sourcing the OPA1662AID op amp IC. Can I substitute an NJM4585 or another op amp? (R. D. Z., Matara, Sri Lanka) ● We don’t suggest you substitute the NJM4585 for OPA1662AID. The minimum supply rail specification for the NJM4585 is ±4V (ie, a total of 8V), whereas the OPA1662AID specifies ±1.5V (a total of 3V). This IC runs from 9-12V DC in the Digital FX Pedal, so with the NJM4585, its swing will be severely limited, probably to the point that the unit doesn’t work. There certainly are other op amps that are suitable for this design but you would need to choose one with a similar supply specification to the OPA1662AID as well as low noise and distortion. The OPA1662AID is certainly available; at the time of writing this, element14, RS, Digi-Key and Mouser all have that part in stock. Arduino Profile changes broke some code I wonder if you could help with a problem I am experiencing with the Arduino code for the Clayton’s GPS Time Signal Generator (April 2018; siliconchip.com.au/Article/11039). Radio, Television & Hobbies: the COMPLETE archive on DVD YES! A MORE THAN RY U T N E C R QUARTE ICS N O R T C OF ELE HISTORY! This remarkable collection of PDFs covers every issue of R & H, as it was known from the beginning (April 1939 – price sixpence!) right through to the final edition of R, TV & H in March 1965, before it disappeared forever with the change of name to EA. For the first time ever, complete and in one handy DVD, every article and every issue is covered. If you’re an old timer (or even young timer!) into vintage radio, it doesn’t get much more vintage than this. If you’re a student of history, this archive gives an extraordinary insight into the amazing breakthroughs made in radio and electronics technology following the war years. And speaking of the war years, R & H had some of the best propaganda imaginable! Even if you’re just an electronics dabbler, there’s something here to interest you. • Every issue individually archived, by month and year • Complete with index for each year • A must-have for everyone interested in electronics Exclusive to: SILICON CHIP siliconchip.com.au ONLY 62 $ 00 +$10.00 P&P Order now from www.siliconchip.com.au/Shop/3 or call (02) 9939 3295 and quote your credit card number. Australia's electronics magazine January 2022  109 When I try to compile it, I get an error message at this line in the code: http.begin(ipapi); //URL The message is: call to ‘HTTPClient::begin’ declared with attribute error: obsolete API, use ::begin(WiFiClient, url) When the project first came out in April 2018, the source code compiled perfectly. Do you know why it’s throwing an error now? (J. H., Nathan, Qld) ● There has been a major version change of the ESP8266 Board Profile for the Arduino IDE, starting with V3.0.0 in May this year. The release notes at https://github.com/esp8266/ Arduino/releases show that quite a few breaking changes have been introduced since then. We tested our Clayton’s GPS sketch with V2.7.4 of the ESP8266 Board Profile, the most recent version before V3.0.0, and it compiles and works as expected. So one possible solution is to use this older version. You can install it using the Select Version drop-down menu in the Boards Manager. We have updated the sketch to work with the most current (V3.0.2) version. The new version of the sketch is available from siliconchip.com.au/ Shop/6/4593 Only two lines needed to be changed, and these are marked by comments in the source code. Getting Theremin volume plate working I bought a kit of the Theremin MkIII (January 2018; siliconchip.com.au/ Article/10931) to build for my sisterin-law for her birthday. I have a rough understanding of electronics and have become quite good at soldering from some previous projects (plus, my father is an electronics technician, so I’ve picked up some tips). Unfortunately, after building the kit, the volume plate does not seem to be working. Moving my hand closer or further away from the plate does not change the volume, no matter how the volume thumbwheel is set. Sometimes there is a slight pitch change when my hand is closest to the plate (which could be because my hand gets close to the antenna) and the sound cuts out completely when my hand touches the plate. I’ve checked that all the components 110 Silicon Chip are soldered correctly, in the correct orientation, etc and everything seems fine. The board and instructions make it very clear which component goes where and in which orientation when they are polarised. The test point voltage readings are as follows: TP 9V: 9.01V TP 9V’: 8.77V TP 9V’1’: 8.07V TP 9V’2’: 8.16V TP 9V’4’: 8.52V TP1: 1.24V TP2: 0.62V TP3: 1.17V TP4: 0.56V TP5: 0.79V TP6: 0.2V TP7: 1.08V TP8: 0.63V TP9: 2.01-8.48V ● TP10: 5.14V TP11: 5.78V TP12: 5.53V ● The highest voltage is when the VC2 thumbwheel is turned anti-­ clockwise (to the left when facing the component side). I’m not sure if this is normal, but when turning it clockwise, it will drop to the lowest voltage, climb to the highest voltage again, and then drop back to the lowest and sit at that setting for the last bit of turning. The ‘zero beat’ seems to be in the middle of the thumbwheel tuning. If there is anything you can suggest that I can check, it would be greatly appreciated. (C. S., Craigieburn, Vic) ● Your voltage readings look OK. Your problem is most likely related to VC2. Try adjusting the trimmers within variable capacitors VC1 and VC2 so that the plates can mesh fully. The setting of VC2 will be correct at one position only, and it is pretty sensitive, so adjust it carefully and slowly. VC2 is not meant to operate over the full VC2 range. Adding balanced input to Ultra-LD Mk.3 Amp I would like to add balanced input connectors to some Ultra-LD Mk.3 amplifier modules (July & August 2011; siliconchip.com.au/Series/286). I have a number of these in use, and it would be helpful for me to be able to connect them to other equipment using this method; I wouldn’t need adaptors to change between RCAs and XLRs. Referring to the circuit diagram, can I simply replace the unbalanced RCA connector with an XLR by connecting pin 2 of the XLR (+ve pin) to the 47μF input decoupling capacitor and pin 3 of the XLR (-ve, inverted signal) to the junction of the 1MW and 10W Australia's electronics magazine resistors, ie, the bottom of the feedback divider? Pin 1 (shield or Earth) of the XLR would connect directly to the amplifier chassis. Is this a valid option? Your advice would be appreciated. I have already replaced the 10W resistor with a 47W, as suggested in your performance tweaks article. (J. M., Auckland, NZ) ● Yes, the method you describe should work well, except when using long cable runs, when hum pickup may become evident. For a true balanced input, use our project from June 2008: the Balanced/Unbalanced Converter for Audio Signals (siliconchip. com.au/Article/1857). This appears to still be available as a kit from Altronics (Cat K5522), although the stock level is low. Alternatively, use a transformer-­ based balanced isolator such as the Jensen DM2-2XX or PB-2XX or similar isolators, and connect the balanced output as you describe. That way, there will be a genuine balanced connection to the isolator and an unbalanced connection to the amplifier. Locate the isolator close to the amplifier input. Studio 350 amplifier troubleshooting I recently put together a Studio 350 amplifier (January & February 2004; siliconchip.com.au/Series/97). I really like the double-sided PCBs. I installed it into an existing case with an inbuilt power supply; it only has a 40-0-40V transformer, but I stacked the two 15V windings onto the 40V windings to get ±61V DC on a good day. The power supply filter is two 8000μF caps per side, but I did add the 470nF caps and 15kW resistors as per the article. Setup was a breeze. I hooked up my dummy 4W load and got a really nice sinewave out, delivering 270W due to the reduced rails. It ran like that for about half an hour just fine. Now comes the rub. I switched the signal generator from 1kHz to 1.2kHz and promptly destroyed all the output devices, total short circuit E-CB. Q8 and Q9 both survived and are functional. Now confession time, I had failed to connect the mains Earth to the centre-­ tap Earth of the power supply. The whole amp was floating with no reference to Earth at all. I know, not good continued on page 112 siliconchip.com.au MARKET CENTRE Advertise your product or services here in Silicon Chip FOR SALE FOR SALE KIT ASSEMBLY & REPAIR LEDsales VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com LEDs and accessories for the DIY enthusiast PMD WAY offers (almost) everything for the electronics enthusiast – with full warranty, technical support and free delivery worldwide. Visit pmdway.com to get started. LEDs, BRAND NAME AND GENERIC LEDs. Heatsinks, LED drivers, power supplies, LED ribbon, kits, components, hardware – www.ledsales.com.au Lazer Security For Quality That Counts... QUALITY LED PRODUCTS + MORE Massive parts clearance sale, limited stock. Go to lazer.com.au ASSORTED BOOKS FOR $5 EACH Electronics and other related subjects – condition varies. Some books may have already been sold. Bulk discount available. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote, quote photo numbers when referring to a book: silicon<at>siliconchip.com.au TRONIXLABS PTY LTD would like to thank all of our customers for their support and feedback. For any enquiries or customer technical support, please email support<at>tronixlabs.com PCB PRODUCTION PCB MANUFACTURE: single to multilayer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au DAVE THOMPSON (the Serviceman from Silicon Chip) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, address & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. WARNING! Silicon Chip magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of Silicon Chip magazine. Devices or circuits described in Silicon Chip may be covered by patents. Silicon Chip disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Silicon Chip also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. siliconchip.com.au Australia's electronics magazine January 2022  111 Advertising Index Altronics.................................85-88 Ampec Technologies.................... 5 Dave Thompson........................ 111 Dick Smith Contest....................... 9 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Jaycar.............................. IFC,53-60 Keith Rippon Kit Assembly....... 111 Lazer Security........................... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology.................. 7 Mouser Electronics..................OBC Ocean Controls............................. 6 PMD Way................................... 111 SC SMD Test Tweezers.............. 77 SC USB Cable Tester................ 105 Silicon Chip Binders.................. 51 Silicon Chip Subscriptions........ 11 Silicon Chip Shop............ 106-107 Silicon Chip RTV&H DVD......... 109 Switchmode Power Supplies....... 8 The Loudspeaker Kit.com.......... 95 Tronixlabs.................................. 111 Vintage Radio Repairs.............. 111 Wagner Electronics..................... 10 and a complete oversight on my part. My question is, could this have been the cause for all the output devices to self-destruct? I have since connected the Earth wire from the mains socket to the power supply. I think that, as the amp worked well during my initial testing, it probably doesn’t have any incorrectly placed components or dry solder joints. I was very meticulous in the soldering and placing of components. Do you know what might have gone wrong? (P. S., Mount Pleasant, SA) ● It is possible that not having the mains Earth to the amplifier could have caused the destruction, but it seems a bit unlikely. Have you checked what happens to the output from the signal generator when switching frequency? Does the output initially clip on one half of the cycle that could cause the amplifier to have a DC offset for a short period, which could cause an overload that destroys the transistors? There is AC coupling on the amplifier input, but it may not be enough to save the amplifier if that happens. You could check what happens with no load on the amplifier, as that shouldn’t cause the amplifier to blow even if there is a significant DC pulse. Modern car radio antennas aren’t good I have a 2018 Volkswagen with a short 20cm roof-mounted aerial and the radio is full of hash when driving near railways and power lines. Is there a better replacement aerial or accessory to improve reception? Would ferrite rings over the aerial make a difference? (M. P., Croydon, Vic) ● The problem is probably due to Notes & Errata SMD Trainer, December 2021: The parts list and kit for the SMD Trainer Board only lists two 100nF capacitors when three are shown on the schematic and PCB. The kit has been updated, but those who have already received kits should note that the circuit will most likely work correctly without the 100nF capacitor below IC2. Hummingbird Amplifier Module, December 2021: in Fig.7 on p23, the “E” & “B” labels for Q12 have been swapped. In the body text of p23, MLJ15032/33 should read MJE15032/33. Pocket Weather Station, November 2021: in Fig.2 the DAT connection from the DHT11 should connect to pin D4 of the Arduino Nano, not D5. The February 2022 issue is due on sale in newsagents by Thursday, January 27th. Expect postal delivery of subscription copies in Australia between January 26th and February 11th. 112 Silicon Chip Australia's electronics magazine low-amplitude radio signals making their way to the radio’s antenna input. This could be due to bad connections, especially if you live near the sea. Make sure that all connections from the antenna to the radio are clean and undamaged. This would require removing the radio to check the antenna connection at the rear and also removing the antenna. Any ferrite ring over the antenna would likely reduce the antenna radio reception and detune the antenna. Alternatively, there may be a noise source in the car itself. The ignition can be the source of radio-frequency (RF) noise with petrol engines, although that is less of a problem these days with plug-on-coil systems that eliminate the spark plug leads. The alternator could also cause noise if the brushes are worn. Have those aspects checked out if the problem persists. Unfortunately, most modern vehicles simply don’t have very good radio reception because consumers don’t want ugly, long aerials sticking out of their cars. Many cars either have a small ‘shark-fin’ antenna like yours or use the rear demister element as an antenna. Neither is all that great of an antenna. If you don’t care about the appearance, you could consider having a flexible whip-style antenna mounted adjacent to the bonnet or on the door frame. Find a good installer who will route the antenna wire neatly and take measures to prevent rusting, or you could mount it yourself if you’re confident. Identifying a Silicon Chip PCB I came across a circuit board recently. I believe that it is a Silicon Chip design and would be grateful if you could tell me what it is used for. The board has the label “SC 11410971 LIGHTS” on it. (G. H., Camden, NSW) ● You can look up PCB numbers on our website at siliconchip.com.au/ Articles/ContentsSearch Simply type the PCB code into the “Kits / PCBs” field and click the “Search” button. Searching for that PCB number gives the following result: October 1997: The Flickering Flame For Stage Work (siliconchip.com.au/ Article/4790) by Ross Tester, kits: Jaycar KC5234, PCBs: SC 11410971, 1 shop item SC 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