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OCTOBER 2020 ISSN 1030-2662 10 The VERY BEST DIY Projects! 9 771030 266001 $995* NZ $1290 INC GST INC GST GPS In Space how it can e used for space travel D1 Mini BackPack Improved ADS-B Flight Detection THE CAE SOUNDCAM – NOW YOU CAN SEE SOUND awesome projects by On sale 24 September 2020 to 23 October 2020 Our very own specialists have developed this fun and challenging project to keep you entertained this month with special prices exclusive to Club Members. BUILD YOUR OWN: LOW BATTERY ALARM KIT Use this adjustable low voltage alarm kit for your next outdoor adventure and make sure you’ll never run a flat battery by turning it off before it’s completely flat. Uses a 2.5V reference with the 358 Dual op-amp to compare the battery voltage and to oscillate a small buzzer on the board if it gets too low. Has two outputs (both solid-on and pulse ) for you to wire up your own LEDs, buzzers, or relays in any way you want. Perfect for 12 - 24V boating applications! Please note: A 12V bezel is included for illustration purposes only and not part of kit. SKILL LEVEL: Intermediate TOOLS REQUIRED: Soldering Iron WHAT YOU NEED: 1 x Small Breadboard Layout Prototyping Board 1 x Mini PC Mount Buzzer 9-14V 1 x LM336-2.5 2.5V Voltage Reference TO-92 case 1 x 10k Ohm 25 Turn Trimpot 1 x LM358 Low Power Dual Op-Amp Linear IC 2 x 2 Way PCB Mount Screw Terminals 1 x 1N4148/1N914 Signal Diode Pk5 1 x 10k Ohm 0.5W Metal Film Resistors Pk8 1 x 47μF 25VDC Electrolytic RB Capacitor HP9570 AB3459 ZV1624 RT4650 ZL3358 HM3172 ZR1100 RR0596 RE6110 $4.95 $4.95 $3.95 $2.95 $2.25 $1.35 EA. $0.95 $0.85 $0.35 CLUB OFFER BUNDLE DEAL 1495 $ SAVE 35% SEE STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/low-battery-alarm See other projects at www.jaycar.com.au/arduino SOLDERLESS BREADBOARD WITH POWER AND I/O BREAKOUT BOARD • 830 tie-point breadboard with removable power supply module • Power from USB or 12V plugpack. • 64 mixed jumper wires of different lengths and colours PB8819 ONLY JUMPER LEAD MIXED PACK 100 PIECES • 30 Plug-Plug • 40 Plug-Socket • 30 Socket-Socket • All 150mm long WC6027 ONLY 2195 1495 $ $ KIT VALUED AT $23.90 ARDUINO® COMPATIBLE BREADBOARD POWER MODULE • Adds a compact power supply to your breadboard • Plugs straight into most breadboards • Power from a USB socket or DC socket. XC4606 ONLY Got a great project or kit idea? If we produce or publish your electronics, Arduino or Pi project, we’ll give you a complimentary $100 gift card. Upload your idea at projects.jaycar.com Shop the catalogue online! Free delivery on online orders over $99* Exclusions apply - see website for full T&Cs. * 995 $ BREADBOARD LAYOUT PROTOTYPING BOARDS Transfer your breadboard design without having to rework it. Includes five holes on each side per row and power rails running the length of the board. SMALL 25 rows/400 holes HP9570 $4.95 LARGE 59 rows/862 holes HP9572 $9.95 HP9572 HP9570 FROM 495 $ Looking for other projects to do? See our full range of Silicon Chip projects at jaycar.com.au/c/silicon-chip-kits or our kit back catalogue at jaycar.com.au/kitbackcatalogue www.jaycar.com.au 1800 022 888 Contents Vol.33, No.10 October 2020 SILICON CHIP www.siliconchip.com.au Features & Reviews 10 Satellite Navigation in Space Satnav signals, like GPS, can also be used in space to help determine the receiver’s position. This could be used to help with future space travel, like a manned landing on the Moon – by Dr David Maddison 32 Improved ADS-B Reception on a Computer Automatic Dependent Surveillance-Broadcast (ADS-B) is a system which helps track flights. In this article, we review a purpose-built USB dongle for ADS-B reception as well as ways to improve reception – by Jim Rowe 68 Review: The CAE SoundCam Now you can see sound! The Cae SoundCam uses a video camera and phased microphone array to provide visual and spectral analysis of sounds, so it’s not just for show – by Allan Linton-Smith It’s hard to believe that the same satellite signals that help you navigate while walking or driving could also be used to help with space travel – Page 10 100 The Matrox ALT-256 Graphics Card The Matrox ALT-256 is likely the world’s first computer graphics card. It was released in 1978 for S-100 bus computers and produces a monochrome display at 256 x 256 pixels (or a colour display with three cards) – by Hugo Holden Constructional Projects 22 D1 Mini LCD BackPack with WiFi This easy-to-build project combines a 3.5-inch touchscreen with an ESP8266based module to provide wireless internet access. It’s programmed using the Arduino IDE and can be used for a variety of tasks – by Tim Blythman The D1 mini BackPack combines the power of the Arduino with a touchscreen and WiFi. For example, we are using it to provide real-time weather updates – Page 22 36 Flexible Digital Lighting Controller Exactly a decade after our last one, we’re here to present a much improved Digital Lighting Controller that’s even more useful. While you can use it for Christmas lights, it’s definitely not limited to them – by Tim Blythman 72 USB SuperCodec – part three In the final part of the series we detail all the testing and construction procedures, and how to use it. There’s also a guide on connecting the SuperCodec to a computer and what software to use with it – by Phil Prosser 90 High Power Ultrasonic Cleaner – part two You’ve seen how the Ultrasonic Cleaner works last month, so now it’s time to build it, and the good news is that it’s self-calibrating – by John Clarke Your Favourite Columns Our new Flexible Digital Lighting Controller is a trailing-edge dimmer that can control up to 64 channels at 250W per channel. It’s also easily controlled via a two-wire serial interface – Page 36 48 Circuit Notebook (1) Automatic solar panel checker (2) Touch-switch using a 4011B IC (3) Induction headphones for hearing aids (4) NTP clock that works anywhere 61 Serviceman’s Log Decisions, decisions, decisions... – by Dave Thompson 85 Vintage Radio AWA model 501 console radio – by Associate Professor Graham Parslow Everything Else 2 4 51 98 Editorial Viewpoint Mailbag – Your Feedback Silicon Chip Online Shop Product Showcase 107 111 111 112 Ask SILICON CHIP Market Centre Notes and Errata Advertising Index The CAE SoundCam uses 64 MEMS microphones to help identify sound sources which it can then display visually. It’s useful for troubleshooting mechanical faults, finding sound leaks etc – Page 68 www.facebook.com/siliconchipmagazine SILICON SILIC CHIP www.siliconchip.com.au Publisher/Editor Nicholas Vinen Technical Editor John Clarke, B.E.(Elec.) Technical Staff Jim Rowe, B.A., B.Sc Bao Smith, B.Sc Tim Blythman, B.E., B.Sc Technical Contributor Duraid Madina, B.Sc, M.Sc, PhD Art Director & Production Manager Ross Tester Reader Services Ann Morris Advertising Enquiries Glyn Smith Phone (02) 9939 3295 Mobile 0431 792 293 glyn<at>siliconchip.com.au Regular Contributors Dave Thompson David Maddison B.App.Sc. (Hons 1), PhD, Grad.Dip.Entr.Innov. Geoff Graham Associate Professor Graham Parslow Ian Batty Cartoonist Brendan Akhurst Founding Editor (retired) Leo Simpson, B.Bus., FAICD Silicon Chip is published 12 times a year by Silicon Chip Publications Pty Ltd. ACN 626 922 870. ABN 20 880 526 923. All material is copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Subscription rates (12 issues): $105.00 per year, post paid, in Australia. For overseas rates, see our website or email silicon<at>siliconchip.com.au Editorial office: Unit 1 (up ramp), 234 Harbord Rd, Brookvale, NSW 2100. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 9939 3295. E-mail: silicon<at>siliconchip.com.au ISSN 1030-2662 * Recommended & maximum price only. Printing and Distribution: Editorial Viewpoint The balance between historical and forward-looking articles We have published quite a few ‘historical’ features this year, and we will continue to do so, as I have had many fascinating articles on such subjects submitted. That includes the three-part series on the Tektronics type-130 LC meter in the June, July and August issues (siliconchip.com.au/Series/346); the article on the history of Aussie GPOs last month (siliconchip.com.au/ Article/14573); articles on very early computer graphics cards in this (page 100) and the next issue; a battery power supply for vintage radios; a fourpart series on the history of videotape recording; and more. I’m mentioning this because I don’t want to turn off our younger readers, or those more heavily into the latest technology. Of course, we will have plenty of articles on new technology, including the one on satellite navigation in space this month, MEMS devices next month, making PCBs with a laser engraver, a couple of articles on new PIC and AVR chips and more. My intention is to strike a balance between old and new. Even if you weren’t around (or were very young) in the days when video was stored on tape, or before the IBM PC set the standard for desktop computers, I think you will appreciate the ingenuity of the people who developed that early technology. They used some fascinating techniques to get around the technological limitations of the day. So even if you aren’t into this ‘old dude’ stuff, hopefully you get something out of those articles. Likewise, if you’re really into historical articles, I hope that you appreciate that Silicon Chip cannot be stuck in the past; we have to keep with the times, including the use of modern parts and techniques in our projects. We haven’t covered modern digital design techniques in great detail (for example, we’ve only covered FPGAs briefly), mostly because these techniques and parts are not very hobbyist-friendly, and they will be over many peoples’ heads. But FPGAs and digital ASICs underpin most modern technology, so we will definitely cover these topics in more detail in upcoming issues. I have had to reject a few articles lately, not because they were poorly written or uninteresting, but because I didn’t want to publish so many historical articles and retrospectives in a short period. The people who write these articles are clearly very passionate about them, but I’m not sure how many of our readers share their enthusiasm. I know that many do, but not all. So please appreciate the balancing act involved in planning the magazine, in trying to create a good mix of various kinds of articles and projects, from discrete or analog designs through to microprocessor and softwareheavy devices. To some extent, the content of the magazine reflects the interests of our staff and contributors. But I do try to avoid our articles becoming too monotonous or repetitive as a result. The aim is to have something which interests everyone in every issue, and ideally, most of our readers enjoy most or all of the content. 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 October 2020  3 MAILBAG your feedback Letters and emails should contain complete name, address and daytime phone number. Letters to the Editor are submitted on the condition that Silicon Chip Publications Pty Ltd may edit and has the right to reproduce in electronic form and communicate these letters. This also applies to submissions to “Ask Silicon Chip”, “Circuit Notebook” and “Serviceman”. New firmware for DAB+/FM/AM radio digital output would not work in DAB+ mode, but did work in the AM and FM modes, despite your article deYou published my letter on fixing some problems I scribing this as being the case (but without any satisfacdiscovered in the DAB+/FM/AM Radio I built (Januarytory explanation). March 2019, siliconchip.com.au/Series/330), in the SepI tried to fix this by making sure that the code conformed tember issue, page 10. The changes I described as having with the state machines published in Silicon Labs applifixed the cracks from the speakers on power-up and band TECHNOLOGY cation note AN-649, but I struggled to do this with the changing were not quite RAYMING complete. original code. So I ended up rewriting the BASIC softA crack remained, which is caused by the Si4689 proPCB Manufacturing and PCB Assembly Services ware for the radio. ducing a voltage impulseFuyong during certain mode changes or Bao'an Shenzhen China I was able to get the digital output working properly after specific SPI commands. Pins 18 and 19 of the Si4689 0086-0755-27348087 in DAB+ mode this way, and having started down that are its left and right audio outputs. They pass via a ferrite track, ended up developing an alternative feature set on bead to a 100µF capacitorSales<at>raypcb.com and 10kW resistor to ground bethe original hardware platform. I’ve also tried to eliminate fore entering the 4052 mux. www.raypcb.com other noise problems similar to those that I had written The time constant of the 100µF capacitor and 10kW reto you about earlier. sistor is about 1 second. Changing the 100µF capacitor to There were, for example, other noise problems even with a 2.2µF capacitor reduces this time constant by a factor the digital output functions of the original code which I of 50. However, changing the capacitor value alone does have tried to address in the attached code. not entirely avoid the clicks. A minor software change I have tried to extensively comment this code so that was also required to engage the 4052’s mute setting duranybody else that’s interested can understand how it ing band changes. works. The extended comment at the beginning of the The “SetRadioFrequencyHW” subroutine modificaprogram describes more fully how to use it and what is tions are as follows: different. 1) Add a “SetIC6(IC6MUTE)” statement immediately beI should point out that my program assumes that an low the variable declaration (at the entry to the subroutine). SD card is plugged into either the Micromite SD slot, or 2) Add the following statements immediately above the the LCD screen’s slot, and also assumes that the Microclosing “End Sub” mite options for the chosen SD slot have been configured. PAUSE 1500 While testing my FM RDS code, I saw that RDS servicIF stereoSwapSet=0 THEN SetIC6(IC6NORMAL) es transmit date/time information every minute and have ELSE added a decoder to display the date/time and set the MiSetIC6(IC6REVERSE) cromite clock accordingly. ENDIF The new software is available for download from siliconchip.com.au/Shop/6/4940 Of course, there may However, I didn’t stop there. It bothered me that the RAYMING TECHNOLOGY Fuyong Bao'an ,Shenzhen, China Tel: 0086-0755-27348087 email: sales<at>raypcb.com web: www.raypcb.com PCB Manufacturing and PCB Assembly Services 4 Silicon Chip Australia’s electronics magazine siliconchip.com.au still be bugs, but overall this version seems to work well on my radio. I would like to thank the original authors one more time for a great project. I have enjoyed working on this project, and I am delighted with how it has turned out. My original intent was to build a decent radio with a digital output that I could use along with my Silicon Chip “Crystal DAC” and Ultra-LD amplifier, and I feel like I achieved everything I set out to do. I would love to see a MkII radio project that takes on some of the learnings of the first project! The original radio was presented as a kind of portable radio, but I think that deep down, it would make an awesome hifi component, as I tried to build with mine. Stefan Keller-Tuberg, Fadden, ACT. Response: We’re very impressed with the amount of effort that you put into this! Thank you for doing so much hard work. The procedure to enable the digital output is theoretically the same in each mode, so we’re baffled why our code didn’t work in DAB+ mode. We think it must be a timing problem, solved by your use of the state machine. Note that while changing the 100µF audio coupling capacitors to 2.2µF should not affect the bass frequency response much, it probably will increase low-frequency distortion as the -3dB point increases to 7Hz. However, it’s probably a worthwhile change to eliminate the cracks. As you point out, the root cause is the transients from the radio chip audio outputs, which we were unfortunately not able to eliminate. That was one of the reasons for adding the multiplexer; it allowed us to mute the audio outputs during band changes, but apparently, that was not enough to get rid of the cracking sounds. Perhaps this is due to the magnitude of the transients. Helping to put you in Control N1540 Process Indicator + RT 240 VAC Five digit universal process indicator accepts thermocouples, Pt100, 4 to 20 mA, 50 mV and 10 V signals. 4-20mA programmable analog transmission . 240 VAC Powered. Mini USB interface. SKU: IPI-152 Price: $189.95 ea + GST S0 pulse counter with MODBUS RTU interface Designed for counting pulses from water, gas and electricity meters. It has 4 isolated 32-bit counters held in non volatile memory. SKU: TCS-080 Price: $179.95 ea + GST RW-TH Indoor air quality sensor Modbus and WiFi Unipi RW-TH indoor air quality sensors are designed for measuring Temperature, Humidity, VOC, Bar. Pressure and Ambient Light. Feature WiFi and RS485 Modbus RTU connectivity. SKU: UPS-001 Price: $259.95 ea + GST Dual Axis Inclinometer ±45º Degrees - Voltage Output MCA420T-45-V1 dual axis inclinometer senses tilt angles from -45º to +45º and gives a 0 to 5 V analog voltage out. SKU: SRS-071 Price: $175.00 ea + GST Learn electronics at your local library I noticed the following press release from Northern Beaches Council regarding being able to borrow kits for kids to learn electronics at Warringah Mall Library. I thought that your readers would be interested in it: siliconchip.com.au/link/ab4n (via email) Loop Powered Temperature Sensor DIN Rail Mount Premises Earthing goes bad over time Split core hall effect current transducer I would like to comment on a question answered for S. B. of Bundamba, Qld in Ask Silicon Chip, p112, August 2020. S. B. asked about the hazards of old mains wiring and the answer referred, among other things, to Leo Simpson’s columns in November 1995 and August 2008 regarding old fabric and rubber insulated mains. Our house was built in 1961 and later extended. It was wired throughout in three phases with Thermo-Plastic Sheathed copper conductor or TPS as it was known. I was, at that time, a leading hand electrical fitter with an electrician’s licence and did about half of the wiring myself, so I am aware of all the wiring in the house. It is still in good condition. However, last year, Ausgrid replaced all three meters, not because they weren’t still operating but as a general precaution because they were among several thousand in the district which were of similar age. A few months later, we lost one phase due to a failure in the 58-yearold main switch. siliconchip.com.au 4 to 20 mA output loop powered temperature sensor with measurement range from -10°C to +125°C, designed for monitoring RTU and PLC cabinet temperatures. DIN Rail Mount. SKU: KTD-267 Price: $54.95 ea + GST Split core hall effect current transducer presents a 0 to 5V DC signal representing the DC current flowing through a primary conductor. 0 to 50 A primary DC current range, 12VDC Powered, 25mm Window. SKU: WES-070 Price: $109.00 ea + GST Current Transformer 60:5 A FOX21 DIN-rail or foot mount current transformer with a 60 to 5 A ratio. With built in sliding sealable terminal covers. SKU: NTS-003 Price: $34.95 ea + GST For Wholesale prices Contact Ocean Controls Ph: (03) 9708 2390 oceancontrols.com.au Prices are subjected to change without notice. Australia’s electronics magazine October 2020  5 I am now long retired, no longer licensed and somewhat restricted in movement, so I called a licensed electrician. He pointed out that, as nearly everything on the board was a similar age, replacing just the main switch could be followed by other equipment failures. It might therefore be wise to replace the whole board. I agreed, considered his quotation was reasonable and accepted it. He made up a new switchboard, with a nice row of circuit breakers, brought it back a couple of days later and installed it. When he connected the board, he could not find a good Earth! It seems that not only had the equipment deteriorated over the years, so had the Earth connection. He had to drive a new Earth rod about 1.5m into the ground. If I remember correctly, Leo also advised checking old Earth connections. If you have an old installation, it’s important to check its Earths, too. Incidentally, on a matter of safety, both the technician working for Ausgrid’s contractor and the electrician who rebuilt my switchboard were working alone on live equipment. That, as a safety measure, would not have been allowed in my day. I always had to make sure that a ‘sparkie’ had a mate. It’s a different world now. Ron Le Marsney, Loftus, NSW. Two heads are better than one My 40-year-old tape deck sat in a cupboard for most of its life. A small problem had developed when it was about ten years old, and I just hadn’t gotten around to fixing it. It was a Pioneer T6600 stereo autoreverse reel-to-reel – quite a prize to have way back then. Not the top of the range, but still quite a respectable recorder that I purchased second hand. The thought of those frozen, gooey belts and drive rollers, worn out switches and myriad possible faulty capacitors bothered me as I didn’t want to get started and find that it was beyond my capability. Recently, I watched a video on YouTube about successfully repairing similar decks, so I purchased a new set of drive belts from the USA and decided to have a go. Anxiously awaiting the delivery of the belts, I dismantled and cleaned all the drive components, removed all the old grease and replaced and cleaned switches and pots. 6 Silicon Chip Australia’s electronics magazine With the help of a CRO, I was able to establish that the electronics were at least working. I treated the rubber wheels and pinch roller gingerly with Rubber Renue, as some people had said that it was great. When the belts arrived, I installed them and put on a tape that I had recorded all those years ago. It sounded clean enough, but not right. Most of the recording was instrumental, and it wasn’t until a vocal track was reached that I realised that the tape was running just a little fast. I had no logical explanation as to why that was happening. It was set for 50Hz and the motor, pinch roller and drive were free, so why was it running fast? I checked everything and even changed the 4µF motor capacitor, to no avail. After becoming very frustrated at not being able to come up with a solution, I mentioned the problem to my wife. “Are you sure that the new belts are correct?”, she said. “Of course they are”, said I, as I thought that a difference in belt size would be obvious. “You should measure them as you never know” was her response. I did, and to my surprise, the new pinch roller belt was marginally thicker. I put the old one back as it was only a little stretched, and lo and behold; it sounded perfect. The new thicker belt sat just a tiny bit proud of the bottom of the capstan drive. It was unnoticeable by eye, but enough to cause an increase in speed by slightly changing the ratio of the pulleys. Paul Walsh, Montmorency, Vic. Satnav receiver prefix variations I recently wrote to you regarding the GPS-synched Frequency Reference (October-November 2018; siliconchip. com.au/Series/326). I could not easily get a fix with the recommended GPS receiver (VK2828U7G5LF); however, the same receiver worked seamlessly at the same indoor location with my High Visibility 6-Digit LED GPS Clock (December 2015 & January 2016; siliconchip.com. au/Series/294). You recommended that I try with an external antenna, so I swapped that receiver for a new unit that incorporates one. The pinout was slightly different, but I was able to get a fix very quickly with that new unit. siliconchip.com.au ai159607652011_Silicon Chip--mouser-widest-selection-205x275.pdf 1 30/7/2020 10:35 AM C M Y CM MY CY CMY K siliconchip.com.au Australia’s electronics magazine October 2020  7 While the VCO frequency would display once the 1PPS signal was present, I was never able to get the GPS date, time, latitude and longitude with the new receiver. That puzzled me. I made sure this receiver was TTL-compliant when I ordered it, and I doublechecked on the scope. I decided to investigate the NMEA messages available at the output (TX pin) from both receivers to find out if there was any difference. I decoded both serial streams with my scope and was able to read the full messages as per NMEA standards. I could clearly see the different GPS data embedded in the serial messages. So the problem was not with the signal. I noticed the VK receiver used “GP” prefix for the RMC data type whereas my new receiver used “GN” for the same RMC sentences. There was no difference with the other data types. So I thought the Micromite was not parsing the messages from my receiver because of that. I looked at the Basic code and found out one reference to the message type line 1227, which is the IF loop that calls the parsing function in case it receives the GPRMC identifier: IF LEFT$(GPSSENTENCE$,6)=“$GPRMC” THEN GPSFEED=GPSPARSE() ‘process I replaced GPRMC with GNRMC. I also took the opportunity to upgrade the firmware of the Micromite LCD BackPack V2 using a PICkit 3 (actually very handy!) because I could not use the pic32prog utility. Then I reloaded the modified BASIC code into the PIC32 with MMEdit and bingo! The GPS time, date, longitude and latitude are now showing on the Micromite screen! My Programmable Frequency Reference now sits on my desk, and the antenna goes all the way to the window; it works flawlessly. Olivier Aubertin, Singapore. Response: We have also noticed newer receivers using different NMEA prefixes. It has to do with these receivers supporting multiple satellite systems. GPS-only receivers use the GP prefix whereas multi-system receivers (GPS, GLONASS, Beidou etc) use GN. Future software designed to work with GPS receivers will take this into account. Note that with some GPS receivers, you can change the prefix back to GP to make them compatible with existing equipment that expects it. Mains power monitor seconded Graham Goeby raises some interesting ideas for projects in the June 2020 issue (Mailbag, p11). I add my vote for his first suggestion, the mains power interruption monitor, as I have already had my retailer query my version of events after a string of power outages recently. Two of his other suggestions can probably be more easily satisfied by purchasing an Amazon Alexa Echo Dot which is often on sale for $49. Out of the box, it will happily answer a voice request for the time or (local outdoor) temperature or humidity. Indoor temperature requires other modules and apps or extra IoT devices that you could build yourself. I’m keen to read some articles covering IoT and integration of commercial sensors and controls with talking devices like Alexa. Julian Robinson, Narrabundah, ACT. Checking GPOs for correct wiring I read with interest the item in the August 2020 edition Mailbag section about problems with incorrect Active/ Neutral wiring in power points. Years ago, I lived in mining town accommodation which was thrown together and often had the wiring connected in an almost random fashion. I eventually purchased a device which was like a plug without wires. It had red/green lamps on the face of it that indicated whether the connec- tions were correct or not. I lost it over the frequent moves and have often wished that I could replace it. How about a project to build a device that will identify whether the wiring is correct without dismantling the power point to inspect it? Cliff King, Oxley, Qld. Comment: Bunnings sells a similar device at a modest price. We haven’t tested it, but we assume that it works as advertised. See siliconchip.com. au/link/ab4t Suggestion for motorbike alarm On pages 4 & 6 of the June 2020 issue (in Mailbag), Mr Westerhoff requested a bike alarm design. I built one that is very effective, based on an Electronics Australia project from January 1999, “The Screecher Car Alarm MkII”. To this, I added a small vibration sensor. The PCB code is 99al1. Altronics still sell the kit, Cat K4362, for $27.75. It just needs the sensor, and the one I used is available from RS Components here: siliconchip.com.au/link/ab4u It is super sensitive, and if triggered, it powers a Jaycar Cat LA5255 “Tweetie Pie” siren. I call it my protect anything alarm; when travelling, we used to put it under the tarp, on our trailer in case of tampering during the night or in my golf bag when I leave it outside the clubhouse. I built the unit into a UB3 jiffy box, which it just fits into. I mounted the small piezo on the side of the case. I run it off a 9V battery; I don’t know how long it would last as I don’t use the alarm that much. As for switching it on and off, I fitted a 3.5mm phono socket on one end of the box. The switch in the socket is connected to the battery, and removing the plug activates the alarm. One alteration I would like to make to the circuit is to make the alarm times adjustable. Paul Cahill, Balgal Beach, Qld. SC The example motorbike alarm described above, with the PCB shown inside a UB3 jiffy box. 8 Silicon Chip Australia’s electronics magazine siliconchip.com.au Wide range of fully equipped products up to R&S Essentials Promotion FULL BENCH. HIGH VALUE. 50 % off Order now through 31 March 2021 Up to 50 % off our signature instrument bundles. Pre-configured for you. Distributors www.rapid-tech.com.au/ https://au.element14.com/b/rohde-schwarz siliconchip.com.au Australia’s electronics magazine October 2020  9 SATNAV . . . That’s right – satellite navigation signals, including those from the Global Positioning System (GPS), can be picked up in space and used to determine the receiver’s position. It’s a bit tricky since signals from these satellites were only intended to be used within the Earth’s atmosphere. But with some intelligent engineering and calculations, it can be done. There is even the possibility that our Moon might get its own navigation satellites! W ith the likely forthcoming return to the Moon (possibly as early as 2024), and ongoing space exploration, it is vital to have reliable and accurate means to navigate in space. Of particular interest for lunar exploration are ice deposits in craters near the south pole of the Moon, which could be used for drinking water and also turned into hydrogen and oxygen for rocket fuel and breathing. We have GPS and other satellite navigation systems here on Earth, as described in detail in the November 2019 issue (siliconchip.com.au/Article/12083). Those systems were designed for determining location in the terrestrial, atmospheric and the near-Earth space environment. But could those same signals be used in space or on the Moon? GPS and other GNSS satellites orbit at an altitude of around 20,000km so, in principle, any vehicle below that altitude should be able to ‘see’ the satellites and make a position fix. Since the antennas look down, one might think it’s not possible to get a signal above the orbit of a GPS satellite, but that is not the case. 10 Silicon Chip According to NASA, GPS signals can be received and used in space in the same manner as on Earth, up to an altitude of 3000km. NASA calls the space between the surface of the Earth and an altitude of 3000km the “Terrestrial Service Volume” (see Fig.1). In this volume, GPS works normally according to the GPS Standard Positioning Service (SPS) Performance Standard (www.gps.gov/ technical/ps/). The volume at altitudes between 3000km and 36,000km (geosynchronous satellite orbit) is defined by NASA as the “Space Service Volume”. In this volume, which is subdivided into two parts, performance is not guaranteed to be as good as in the Terrestial Service Volume. As 36,000km is well above the 20,000km altitude of the GPS satellite constellation, you might think that the signals could not be received because the GPS antennas are pointing down toward Earth and not up. But there is another way the GPS signal can be received. Instead of receiving a signal from a satellite above you, you could receive a signal from a satellite on the opposite side of the Earth (see Fig.2). Its antenna is pointing Australia’s electronics magazine siliconchip.com.au . IN SPACE! by Dr David Maddison Fig.1: the “service volumes” for GPS, with the Terrestrial Service Volume being everything below 3000km altitude. The GPS satellite and geosynchronous orbit altitudes are also shown for comparison. down toward Earth, but some of the signal would reach your receiver. A high Earth orbit (HEO) satellite and its trajectory, which varies in altitude, is shown in Fig.2. Its path extends from the Terrestrial Service Volume, below 3000km, to beyond the geosynchronous orbit altitude of 35,887km (rounded to 36,000km) which is beyond even the Space Service Volume. The signal from one GPS satellite is shown, along with the first side lobes (off-axis antenna radiation pattern) for the L1 GPS frequency of 1575.42MHz. Fig.3 shows this radiation pattern in more detail. The receiving satellite can obtain a GPS signal from the satellite shown from either the main lobes or the first side lobes, or the signal may be entirely blocked by the Earth. Around 97% of radio energy is located in the main lobe and just 3% in the side lobes, so a sensitive receiver is needed. Only one GPS satellite is shown for simplicity; in reality, other satellites will be visible and not blocked by the Earth. As with terrestrial GPS, four satellites are required for an accurate position fix. siliconchip.com.au Fig.2: this shows how GPS signals are received in space, even when the receiving spacecraft is above the orbit of the GPS satellites. The dark green circle is the Earth, while the lighter green shaded area is the umbra or shadow of the Earth, where the satellite signals are blocked. The receiving satellite is in an elliptical orbit encompassing all possible volumes of space accessible with GPS. Australia’s electronics magazine October 2020  11 Fig.3: a simplified generic diagram showing the radiation pattern from GPS or similar antennas. The main lobe of a GPS satellite is generally not available in space as it is blocked by the Earth, but the first side lobe may be available. The other side lobes and back lobe would be too weak to be usable. Source: NASA. Earlier versions of GPS satellites did not consider performance in the Space Service Volume and performance was variable due to different side lobe radiation patterns and power levels. This was addressed by NASA and the US Department of Defense by writing specifications for performance levels for the Space Service Volume during 2003-2005. These specifications were implemented on Block III, SV 11+ (Space Vehicle 11) and subsequent GPS satellites. It doesn’t matter where the receiver is located; if the signals from four GPS satellites can be received, then you can identify your position in space. This should even work on the surface of the Moon. However, additional calculations would be needed to establish the relationship between the Fig.4: GPSPAC was the first attempt to pick up GPS signals in space. It was launched aboard LANDSAT 4 in 1982. Source: USGS. location of the Moon and the Earth to establish one’s position on the surface of the Moon. Positional accuracy on the Moon will be less than on Earth due to the much greater distances involved, resulting in more significant timing and thus distance errors. The distance from the centre of the Earth to the centre of the Moon averages 385,000km. But it varies by over 50,000km, and it can change as rapidly as 75m/s (270km/h). These are important factors to keep in mind when using GPS on the Moon, and they need to be incorporated in the relevant calculations. Based on an Earth radius of 6371km, a Moon radius of 1737km and a GPS satellite altitude of 20,183km, the closest a GPS receiver on the Moon could be to a GPS satellite Figs.5&6: command and telemetry boards carried by TEAMSAT. This gives you an idea of the relatively basic electronics used in the late 90s. Interestingly, both boards seem to be centred around FPGAs (field-programmable gate arrays). 12 Silicon Chip Australia’s electronics magazine siliconchip.com.au is 356,709km. That’s more than 17 times further than the same receiver on Earth. However, to receive a GPS signal on the Moon, that signal would have to come from a satellite on the far side of the Earth, over 409,817km away. That’s 20 times further away than the nearest a GPS receiver could be to a satellite on Earth. Hence, timing and distance errors will be around 20 times greater than on Earth (as rough figures), assuming the accuracy of the receiver clock is the same in both locations. Note that GPS is already routinely used in the near-Earth environment with vehicles such as low Earth orbit satellites and the International Space Station and its Crew Return Vehicle, as they are all well below the altitude of the GPS satellites. The limits of GPS Currently, the formal altitude limit of GPS is that of the outer limits of the Space Service Volume of 36,000km; but the real practical limits are not yet known. Limits are imposed by the available signal strength, signal availability as determined by geometric limitations imposed by satellite antenna main and sidelobe patterns, and the occultation (blocking) of GPS satellite signals by the Earth. Uses for high orbital altitude GPS The ability for satellites and other space vehicles to use GPS at high orbital altitude confers many advantages due to better knowledge of space vehicle location. These include: • better satellites station-keeping • improved space vehicle rendezvous and docking • geosynchronous satellite servicing possibilities • better Earth science measurements including atmospheric, ionospheric, geodesy and geodynamics • better navigation by uncrewed launch vehicles • formation flying of constellations of satellites such as MMS (magnetospheric multiscale mission; see below) • improved weather satellites • improved space weather observations • improved astrophysical observations due to better navigation by orbiting telescopes • better navigation en-route to the Moon and on the Moon • closer spacing of satellites in geostationary orbit due to better location fixes • use of GNSS for time synchronisation of science experiments and space vehicle clock. High orbital altitude GPS experiments It had long been speculated that GPS could be used above the maximum orbital altitude of the constellation. Many GPS receivers were launched into space from 1982, and especially from 1991 onwards, mainly in the Terrestrial Service Volume (below 3000km). For a complete list up to 2003 see http://gauss.gge.unb. ca/grads/sunil/missions.htm Note that GPS became available to civilians in 1983. Significant early experiments with high altitude GPS use were as follows: • The first time GPS was installed on a satellite was LANDSAT 4 in 1982 (Fig.4). It carried a package known as GPSPAC. Three more GPSPAC units were also launched on LANDSAT 5 in 1984 and US Department of Defense vesiliconchip.com.au Fig.7: TEAMSAT, launched in 1997, carried YES (Young Engineers’ Satellite). Its primary purpose was to study GPS reception at altitudes above the GPS constellation (20,183km). Source: ESA. hicles in 1983 and 1984. The GPS constellation was not fully operational at that time, and four satellites were in view for just a few hours per day. The GPSPACs provided essential data that was used in the development of the rest of the Global Positioning System. • Falcon Gold was an experiment of the US Air Force Academy in 1997 to use a GPS receiver above the altitude of GPS satellites. The GPS signal was received up to an altitude of 33,000km. The experiment confirmed the possibility of using GPS in locations above the orbit of the GPS satellite constellation, plus the ability to use GPS sidelobe signals for navigation, previously a matter of debate. • YES (Young Engineers’ Satellite) was launched in 1997 as a sub-satellite of TEAMSAT (Figs.5-7), which itself was part of MaqSAT H. An orbit of 531 × 26,746 km was achieved, with its primary purpose to study GPS reception at altitudes above the GPS constellation. • Also in 1997, a GPS receiver was flown in the high Earth orbit satellite Equator-S (Fig.8), above the altitude of the GPS satellites. No navigation solution was possible because the required four satellites could not be simultaneously seen; however, useful signals were received at an altitude up to 61,000km. Australia’s electronics magazine October 2020  13  Fig.8: Equator-S was also launched in 1997 and carried a GPS receiver. It was not able to get a location fix, but it was determined that useful signals could be picked up at altitudes of up to 61,000km. Fig.9: the AMSAT (OSCAR-40) amateur satellite was launched in 2000. In 2001, its onboard GPS receiver picked up valid signals to the satellite’s maximum altitude of 60,000km, and mapped the main and sidelobe signals. • In 2000, Kronman et al. were able to perform orbit determination of a geosynchronous satellite which received GPS signals from the far side of the Earth and then retransmitted them to a ground-based receiver where all data processing was performed, to determine the satellite’s orbit (see Fig.10). The use of a satellite just to relay signals is known as “bent pipe architecture”. No suitable receiver was available off the shelf, so one had to be made. According to Kronman, the following features were required but not commercially available at the time in one unit: The ability to navigate off the Earth (for acquisition), a second-order tracking loop to accommodate anomalous Doppler, the ability to accept commands to track specific PRNs (Pseudorandom Noise code), the availability of individual PRN pseudorange data referenced to a precise local time source, Selective Availability correction without P(Y)-code capability (military encryption). • In 2000, the AMSAT Phase 3-D (OSCAR-40) amateur satellite (Fig.9) was launched with NASA-sponsored GPS experiments onboard, using existing receiver technology. The actual GPS experiment was done in 2001. It received signals up to the satellite’s maximum altitude of 60,000km, and mapped main and sidelobe signals. As with the previous experiments, actual GPS locations were computed on the ground rather than the satellite, and not in real time. Based on the results, it was determined that navigation considerably above 60,000km could be performed with a suitable receiver and antenna. • Also in 2000, two STRV-1 (Space Technology Research Vehicle) missions were launched, the STRV-1c and STRV1d spacecraft (Fig.11). They had a 615 x 39,269km orbit. They were equipped with GPS receivers which mapped GPS signals to geosynchronous orbit, approximately 36,000km up. • GIOVE-A (Galileo In-Orbit Validation Element-A) was a European Space Agency (ESA) satellite launched in 2005 and retired in 2012 (Fig.12). Its purpose was to test aspects of Europe’s GNSS navigation system, Galileo. According to the ESA, its primary objective was to “secure vital frequency filings, generate the first Galileo navigation signals in space, characterise a prototype rubidium atomic clock, and model the radiation environment of Medium Earth Orbit (MEO) for future Galileo spacecraft”. The satellite was equipped with a GPS receiver. In 2006, the receiver was activated for 90 minutes, and it was confirmed that it could receive GPS data and it downloaded a full almanac. After its retirement, it was moved to a “graveyard” orbit 100km above the Galileo constellation altitude of 23,222km. That is beyond the 20,183km altitude of the GPS constellation. In the retirement phase, in 2013, new software was up- 600 nmi (1.5 SCD at GEO) GPS 26 ,5 60 km Nominal Visibility Region 12.2° GEO 42,200km Fig.10: the relative geometry of a GPS satellite, geosynchronous satellite (GEO) and Earth for the Kronman et al. experiment in 2000. It is the sidelobes of the GPS satellite transmissions that are being received. The GEO satellite receives signals in the shaded zone from 1.5 to 3.5 degrees above the limb of the Earth. EARTH 14 Silicon Chip Australia’s electronics magazine siliconchip.com.au Fig.11: STRV-1c and STRV-1d (Space Technology Research Vehicle), launched in the year 2000. They were equipped with GPS receivers which mapped GPS signals to geosynchronous orbit, approximately 36,000km up. loaded to the GPS receiver on the satellite, and more extensive tests were made. Particular emphasis was made on measuring properties of the GPS satellite sidelobe signals. Current civilian missions using high-altitude GPS In 2015, NASA launched the MMS (Magnetospheric Multiscale) mission (Phase 1) which is a four-satellite constellation which flies in a tetrahedral formation 7.2km apart, to study aspects of the Earth’s magnetic field (Fig.13). Each was equipped with a highly sensitive high-altituderated GPS receiver called Navigator for real-time position x Fig.12: GIOVE-A (Galileo In-Orbit Validation Element-A) was launched in 2005, to test aspects of Europe’s GNSS navigation system, Galileo. measurements (see Fig.14). In 2016 and 2019, the highest altitude GPS fixes to date were obtained at 70,006km and 187,167km respectively. The Navigator GPS receiver is designed for fast and weak GPS signal acquisition, and it is the highest operational GPS receiver to date, at a distance of around halfway to the Moon. It is designed to work in a variety of space regimes such as low Earth orbit (LEO), geosynchronous orbit (GEO), high Earth orbit (HEO), up to and beyond 12 Earth radii (76,452km+), at launch and re-entry. Pseudorange is the distance measured between the GPS Other means of navigating the Moon There is no significant magnetic field on the Moon, so a compass cannot be used. Also, the lack of atmosphere makes it hard for astronauts to judge distances. The Apollo 14 crew missed a crater they had intended to visit by only 30m because of these difficulties. When Neil Armstrong landed the LEM on the Moon in 1969, he used his eyes and maps to find the appropriate place to land (the famous Apollo Guidance Computer was not intended to locate the exact landing place). In space it is always good to have a backup plan, so apart from NASA developing lunar GPS, they are also developing “terrain relative navigation” (see below). This is similar to what Neil Armstrong did, but instead of using eyes to compare lunar terrain to a map, a computer compares the lunar terrain (imaged with a camera) to maps in the computer’s memory. Apart from terrain relative navigation, returning astronauts will also use GPS, navigation Doppler lidar and hazard detection lidar. Other methods that will be used to navigate on the Moon include: • radiometric methods utilising the existing Deep Space Network to measure range and speed (updated to allow for lunar tracking). • lunar orbiting spacecraft such as the LRS (see separate panel). and lunar surface stations such as the LCT (same panel). • inertial navigation. • optical techniques such as viewing stars relative to lunar surface features. Images from a test of NASA’s terrain relative navigation in the Mojave Desert. The live image is on the left, and a reconstructed image is on the right. It identifies and matches known features in the images to determine the current position. siliconchip.com.au Australia’s electronics magazine October 2020  15 The Lunar Relay Satellite (LRS) and Lunar Communications Terminal (LCT) Apart from navigation on the Moon via GPS, for effective communications (especially if people are living on the Moon’s surface), it will be desirable or even necessary to have lunar relay satellites along with a Lunar Communications Terminal (LCT). NASA has proposed a system of two satellites to relay communications between the surface of the Moon and the Earth, as well as crewed lunar vehicles, all part of the Artemis program. These vehicles include Orion, to launch from Earth and orbit the Moon, and the Altair lunar lander, to take the crew from Orion to the surface of the Moon. The orbit will be a “12 hour frozen elliptical lunar orbit”. This is a special type of highly elliptical stable orbit. It is required because above about 1200km altitude, Moon orbits are usually unstable and short-lived (tens of days) due to the ‘tug-of-war’ with the Earth’s gravity. Below 1200km, the inherent ‘lumpiness’ of the Moon and thus variations in gravity cause orbits to be unstable and shortlived as well. The proposed LRS satellites will have a service life of 7-10 years, a data bandwidth of 100Mbps from lunar habitats and the LCT, and 50Mbps from elsewhere on the lunar surface. The LCT will be a communications node for rovers, crew, habitats, science experiments etc. It will provide some navigational support, 802.16 wireless LAN and line of sight communications to 6km and have a 1m Ka-band antenna. Navigation support will be in the form of one- and two-way ranging to determine the range of a vehicle to the LCT, Doppler satellite and the receiving satellite, and differs somewhat from the true range due to several physical effects. Its measurement precision depends on the signal strength received (see Fig.15), but simulations show that the pseudorange with strong signals is better than ±1.5m. The pseudorange with weak signals is better than ±13m, and for measurements when a strong carrier phase signal is present, precision is better than ±1mm. The receiver has been tested at velocities up to 10km/s. An artist’s rendering of NASA’s proposed Lunar Relay Satellite (LRS) along with the Moon based Lunar Communications Terminal (LCT). tracking for measurement of the range from space vehicles to the LCT and beacon signals. There are no official Internet top-level domains (TLDs) currently assigned to the Moon but, .ln, .le (lunar embassy) and .lunar have been unofficially proposed. However, they are not currently supported by the root servers. It has also tracked as many as 12 GPS satellites simultaneously, many more than expected. GOES-16 or Geostationary Operational Environmental Satellite was launched in 2016; it is a weather satellite in geostationary orbit. It is the first civilian geostationary satellite to use GPS for orbit determination. This will be used, along with other equipment, to maintain an orbital position within a 100m radius. Extending GPS to the Moon High-altitude GPS research has the ultimate objective of extending GPS for use on the Moon, and NASA plans to use existing GPS infrastructure to do this. The GPS receiver that Fig.13: an artist’s concept of the MMS satellite constellation examining so-called “magnetic reconnection” phenomena in the Earth’s magnetic field (represented by blue lines). The exact satellite locations must be known to create accurate magnetic field maps, hence the use of GPS. Source: NASA. 16 Silicon Chip Fig.14: the Navigator GPS receiver, as used on MMS mission satellites for high-altitude GPS fixes. Australia’s electronics magazine siliconchip.com.au Perigee Apogee Perigee Hz Strong (main lobe) signals Apogee: most signals in side lobes Weak (side lobe) signals Fig.15: measurements of signal strengths vs position in orbit for MMS mission satellites. Strong main lobe signals are shown above the dotted line, while weaker side lobe signals (the majority) are below. This shows the importance of sidelobe signals for satellites orbiting above the GPS constellation. Apogee is the point of an orbit farthest from Earth and perigee is closest to Earth. Source: NASA. will be used for this is based on the Navigator described above, and the NavCube which we will soon discuss. For use beyond its current orbit of almost halfway to the Moon, the Navigator GPS will be enhanced with a higher-gain antenna (up to 14dB of gain), antenna steering to keep the antenna pointed towards Earth and the GPS constellation, a more accurate clock and various other updated electronics. While NASA is intending to leverage existing GPS infrastructure for Lunar use, it is not a perfect solution and will also not work on the dark (far) side. It will be augmented by other methods. The idea of building a mini GPS-like system around the Moon called LunaNet is also still under consideration for the much longer term (see Fig.16). Apart from Fig.16: an artist’s concept of LunaNet, providing navigation, communications and other services on the Moon. siliconchip.com.au navigation, it would provide many other services, such as communications. NavCube NavCube (Fig.17) is a combination of two NASA technologies. One is SpaceCube, which is a reconfigurable and fast flight computing platform, and the other is the Navigator GPS receiver used in the MMS mentioned above. For high-altitude and near- or on-Moon real-time GPS fixes, a powerful computer is needed for data processing. The NavCube combines both the GPS receiver and the com- Fig.17: NASA’s NavCube. It uses a Navigator GPS receiver and has substantial computing abilities for processing GPS signals in lunar orbits and on the surface of the Moon. It measures 25 x 20 x 15cm and weighs around 5kg. Australia’s electronics magazine October 2020  17 puter. NavCube can also provide precise timing signals for another experiment using X-rays for communications (XCOM). A NavCube was recently placed on the International Space Station for testing. Estimates of the accuracy of GPS on the Moon with NavCube vary. The worst accuracy is considered to be around 1km, which is useful enough but not ideal. With a highly accurate atomic clock onboard, or accurate time signals beamed from the proposed Lunar Gateway (see Figs.18 & 19), it could be improved to around 100m. The Lunar Gateway is a mini space station proposed to orbit the Moon in 2024 as a communications hub, labo- 18 Silicon Chip ratory, habitation module and a holding station for lunar equipment. Cheung, Lee et al. have estimated an accuracy figure of 200-300m based on modelling. Meanwhile, Winternitz, Bamford et al. came up with several estimates depending on whether the Lunar Gateway is crewed or uncrewed, as the presence of crew causes perturbations which affect accuracy. For GPS in conjunction with an onboard rubidium atomic frequency and an uncrewed vessel, the lateral position accuracy is 31m, and the range accuracy is 9m; for a crewed vessel, the figures are 77m lateral and 21m in range. With ground tracking from the Earth using the Deep Space Net- Australia’s electronics magazine siliconchip.com.au work (no GPS), uncrewed accuracy is 468m lateral and 33m in range; crewed is 8144m lateral and 451m in range. The first demonstration of lunar GPS could be in November 2021, with the launch of an uncrewed Orion capsule on the Artemis 1 mission (to be launched with the Space Launch System). Orion will record GPS signals throughout the mission to determine the usefulness, and measure signal characteristics of GPS around the Moon. Problems with using GPS in space The speed of space vehicles requires fast signal acquisition. There is also the problem of much lower signal strength due to having to rely on side lobe signals, and also the long ranges from the GPS satellites. Additional problems include large dynamic ranges between “weak” and “strong” satellites with wide signal gain variability; high Doppler and Doppler rates of change of GPS signals; fewer GPS satellite signals visible; mission antenna placement causing visibility problems; multipath reflections and radiation on very dynamic platforms. Table 1 expands on these problems and their solutions. How much accuracy does Lunar GPS require? Terrestrial GPS can achieve accuracies of around one Fig.18: the Lunar Gateway “lunar space station” concept, showing an Orion spacecraft docking. The Orion will carry GPS and test it in the lunar environment as early as November 2021. The Lunar Gateway, when placed into lunar orbit in 2024, will also carry GPS with signals augmented by a very accurate onboard atomic clock. siliconchip.com.au Australia’s electronics magazine October 2020  19 Fig.19: an artist’s rendering of the Lunar Gateway. It could help provide navigation services on the Moon by transmitting a highly accurate timing signal to improve the accuracy of lunar-based GPS. Fig.20: an artist’s concept of a mining operation on the Moon. Accurate navigation will be necessary for such activities. Note the mirrors used to illuminate the area. metre or better. Lunar GPS will be somewhat less accurate; however, there are no roads to locate on the Moon, and any target location such as a crater, mining site or base will be visually apparent. So accuracies of even a few hundred metres will be adequate. For autonomous vehicles or other applications requiring greater navigational accuracy, this could be achieved by augmentation with beacons and machine vision, plus artificial intelligence (AI) to avoid obstacles or locate targets in outer space.. Regime Altitude Problems Terrestrial Service Under 3000km High Doppler rates, Volume fast signal rise and set, accurate ephemeris upload required, signal strength and availability comparable to Earth use Lower Space 3000-8000km Service Volume More GPS signals available than for terrestrial service volume; very high Doppler rates Upper Space 8000-36,000km Earth shadow Service Volume significantly reduces main lobe signal; significant periods with fewer than four satellites available; weak signal strength Beyond Space 36,000-360,000km Very weak signals Service Volume (Moon) and very poor signal geometry Mitigation Development of In widespread use purpose-built space receivers; fast acquisition eliminates the need for ephemeris upload (data for estimated position of GPS receiver relative to satellites) Improved antennas; receivers must be able to process higher Doppler rates Silicon Chip In use by the USA and others Higher gain antennas, In use by the USA more sensitive receivers, and others use of GPS side lobe transmissions, algorithms such as in GEONS software to navigate with fewer than four satellites Higher gain antennas and receivers; accept degraded performance; use other signals of opportunity if possible, eg, beacons, perhaps from LCT or LRS (see panel) Table 1 – Problems and solutions for spaceborne GPS. Based on J.J.K. Parker, NASA. 20 Status Australia’s electronics magazine In use to 187,000km by MMS (USA); will be extended to lunar orbit on Artemis 1 mission in 2021 SC siliconchip.com.au Mini LCD BackPack Besides a colour touchscreen, another very handy feature to have in a microcontroller module is wireless communications. WiFi is probably the most versatile method, as most homes and offices have WiFi networks. Once the micro has Internet access, the list of things you can do with it explodes! This low-cost project uses an ESP8266-based module which is both powerful and inexpensive. By Tim Blythman W hile this BackPack has a so it’s perfect for connecting to 12V vices to access the Internet also puts a plethora of potential uses, lights or a small motor to raise and vast array of useful information within easy reach. some of the most promising lower a blind, for example. But unless you run some extensive are in the area of home automation. This is a rapidly growing field, and wiring through wall cavities or pre- The D1 Mini The D1 Mini is one of the smallest it’s getting much easier to implement. installed conduits, they have little Systems that can be built onto exist- chance of working beyond their im- fully-contained Arduino-compatible microcontroller boards. And being ing WiFi networks are common, and mediate vicinity. Unless you’re installing it in a build- based on the 32-bit ESP8266 microlittle wiring is required. Our D1 Minibased LCD BackPack makes adding a ing under construction, depending on controller, it has a 2.4GHz WiFi radio custom WiFi-enabled touchscreen in- how it was built, running that wiring built-in. can be a trying exercise. The ESP8266 has very quickly beterface quite easy. With WiFi-enabled devices being come a favourite of both hobbyists and For a bit of background, last October, we reviewed Altronics’ range of In- readily available and getting cheaper, manufacturers. It appears in many commercial venta Maker Plates (siliconchip.com. it makes sense to have a panel with a WiFi products, including those used au/Article/12023). These are standard- WiFi interface instead. You could have the user interface in in home automation, such as smart size wallplates that incorporate an Arduino-compatible microcontroller a convenient location and another hid- WiFi globes and smart mains switches. Of the handful of commercial wirealong with user controls and a display. den, WiFi-enabled box near the device They’re great for adding custom fea- to be controlled. The only wiring you less home automation products we’ve need to run then is for power, which tried recently, almost all of them were tures to a home automation system. Being compatible with existing Ar- is usually available in many locations ESP8266-based. This is one of the reasons for the duino boards means that they are easy throughout the premises. The ability for the WiFi-enabled de- continued popularity of the Arduino to program, while the display (either platform, as we note in our a text-based or colour LCD) Arduino Retrospective in and user controls (tactile Features & specifications March (siliconchip.com.au/ switches or touch panel) Display: ...............3.5in 480x320 colour LCD Article/12575). mean that they are intuitive Processor: ...........ESP8266, 160MHz 32-bit The D1 Mini is based on to use. But what these units Flash memory: ....4MB the ESP-12 module, which lack is connectivity. contains an ESP8266 microIt’s intended that they be RAM: ...................80kB controller and a 4MB flash directly wired to some exInterface: .............Touch panel IC. It also incorporates a ternal hardware. The LCD Other features: ....WiFi, remote (OTA) reprogramming, CH340 USB-serial converter, Shield Maker Plate has two prototyping space, 12V power supply a 3.3V regulator and a handbuilt-in (low-voltage) relays, 22 Silicon Chip Australia’s electronics magazine siliconchip.com.au ful of passives. Twelve I/O pins are broken out for external use. We used the D1 Mini in our Clayton’s GPS Time Source (siliconchip. com.au/Article/11039). This connects to the Internet via WiFi to simulate a GPS time source by retrieving accurate time from an NTP (Network Time Protocol) server. This is an example of a simple and useful data source that can be accessed via WiFi. The ESP8266 includes a 32-bit micro running at 80MHz and has 80kB of user-accessible RAM, so it is much more capable than many AVR-based Arduino boards. All the ESP8266 boards we have seen have at least 512kB of flash memory; many have much more. They are perfect for adding both WiFi and a graphical user interface to a small project. In particular, the ample flash memory allows colourful graphics to be embedded and displayed. To help you turn the D1 Mini LCD BackPack into something useful, we’ve created a demonstration program for it which shows off its WiFi, graphical and touch features. The program fetches time and weather data from the Internet; the time comes from an NTP server, while the weather data comes from https:// openweathermap.org/ This data is displayed as a combisiliconchip.com.au nation of text and images. The touch interface supplies a small number of user functions, such as setting the weather location and WiFi network settings. Circuit details The Micromite and its various BackPack incarnations have been extremely popular, not just in their own right, but as a basis for numerous projects. We also published an adaptor in the May 2019 issue to allow Arduino R3-compatible boards to drive 3.5in or 2.8in touchscreen LCDs (siliconchip.com. au/Article/11629) (see above). So we thought it would make sense to use the same principle in designing a board to allow these types of touchscreen to be driven by a D1 Mini. Our demonstration software is designed for the 3.5in display, but the hardware also supports the slightly cheaper 2.8in displays. Given the small difference in price, unless your application can’t fit the 3.5in screen, that is the best option. Fig.1 shows the circuit of our new D1 Mini BackPack. As you might imagine, there isn’t a lot to it. It routes the necessary SPI control signals from the D1 Mini (MOD1) to headers for either type of LCD panel, connected to CON1 and CON1a (mounting pads for CON1a are provided in two different Australia’s electronics magazine locations, to support the two different screen sizes). The hardware SPI signals on the D1 Mini are at pins D5 (SCK), D6 (MISO) and D7 (MOSI). Due to the way that the pins are mapped, these actually correspond to general-purpose I/O (GPIO) pins numbered 14, 12 and 13 respectively. We’ve used the numbers with the ‘D’ prefixes as this is how the D1 Mini is labelled. See Table1 for more information about the curious and slightly confusing numbering used on this board. The CS pin for the LCD is wired to pin D8, and D/C (data/command) is wired to pin D4. Due to the low number of pins available, the RST pin for the LCD is wired to RST pin on the D1 Mini; this works well and saves a pin. The separate CS pin for the touch controller is connected to pin D3. Although the panel includes an SD card socket, we’ve also opted to add a micro SD card socket to our board. There are two reasons for this: the PCB traces to the SD socket on the LCD panel are quite circuitous, which makes the card more susceptible to interference. Also, when the SD card is fitted, it protrudes quite a bit. The micro SD card is smaller, and being attached to the board, is less likely to interfere with the display and October 2020  23 Fig.1: the circuit diagram of the D1 Mini BackPack primarily involves connecting the pins of the D1 Mini module to a 2.8in or 3.5in SPI colour touchscreen via headers CON1 & CON1a. The remainder of the circuit is a basic power supply, a backlight control section, some jumper options, a convenient micro SD card socket and a header which gives you access to the few remaining free pins of the micro. mounting hardware. The CS pins of both the SD and micro SD card sockets are connected to the D1 Mini’s D2 I/O pin. Since the card sockets are nothing more than direct connections, these pins can be shared, as long as there isn’t a card in both sockets at the same time. Indeed, if you don’t need the micro SD card feature, I/O pin (D2) can be reused. We’ve also added a DC jack and a 7805 5V linear regulator. Thus, if 12V is needed for operating lights, motors or relays, a single 12V supply (such as a DC plugpack) can be provided. 24 Silicon Chip The regulator will work with input voltages down to around 7V. When running off a 12V supply, the regulator dissipates around 2W and gets quite warm. You might like to substitute our Switchmode 78xx Replacement from the August 2020 issue (siliconchip. com.au/Article/14533) if you need to draw more current from the 5V rail, or just to reduce the heat output. There are four bypass capacitors on the PCB; two for the 5V regulator and two for the micro SD card socket. We’ve provided PCB pads that suit both 3216 (1206 imperial) SMD or Australia’s electronics magazine 0.2in-pitch through-hole parts. Four sets of jumpers are provided. These can be left off if a feature is not needed, for example, if the I/O pins are needed for another application. JP1 can be used to connect the MISO pin for the LCD (which is not usually needed) to the SPI bus. We have found that some 3.5in displays do not behave correctly; hence, we have not connected these two lines directly. For our demo application, and indeed most applications, it can be simply left open. JP2 can be used to connect the LCD backlight to the 5V rail or I/O pin D0. siliconchip.com.au Construction options There are a few options for you to consider during assembly. MOD1 can be permanently mounted to the PCB siliconchip.com.au 1k 19 18 1 Antenna TX A0 RX D0 D5 LCDMISO D6 D7 MOD1 D1 Mini D1 SPI: D5 D6 D7 LCD CS: D8 D4 D8 LCD D/C: D4 3V3 TOUCH CS: D3 124106201 0260142 RST SD CS: D2 D2 17 16 15 14 13 12 11 10 9 7 6 5 10 F 100nF 10 F D3 G 5V 8 10 F 8 76 5 43 2 1 CON2 3 2 1 12V REG1 7805 No Track Area! USB 4 24106201 RevB JP1 RST CON3 Q1 1 CON1A 1k D1 Mini LCD BackPack D1 CD Q2 D0 5V 3.3V GND TX RX D0 D1 A0 FREE: D0=GPIO16 D1=GPIO5 TX=GPIO 1 47k 1 10k 5V LED TIRQ SDCD 1 JP2 JP3 JP4 CON1 CON4 TIRQ MI MO TS CK MI LD CK MO DC We imagine that most applications will be powered from fixed wiring, so the necessity to turn off the backlight using D0, to save power, is reduced. The centre pin of JP2 goes to a pair of Mosfets and two pull-up/pulldown resistors which provide the high-current drive needed for the backlight LEDs. On the 3.5in display, this can be up to 250mA. An identical arrangement is used on the Micromite BackPacks. For our sample application, JP2 is set to the 5V position. JP3 and JP4 are the remaining connections and go to the touch interrupt pin (TIRQ) and SD card detect switch (SDCD). These can be set to connect either signal to pin D0 or D1. The connection to D0 is brought through a series 1kΩ resistor, as this pin is actively driven high at powerup. This prevents excessive current flowing if the pin D0 is used for the SD card detect function, as the pin is simply shorted to ground by a switch inside the card socket. To help the card-detect function, a 47kΩ pull-up resistor is also provided, as pin D0 does not have an internal pull-up. These two resistors can be changed if you require a different role for this I/O pin. To fill out the substantial space that is left on the PCB that’s sized to suit the touchscreens, we’ve provided a large prototyping area that isn’t shown on the circuit diagram. This consists of 17 rows of eight pads which are arranged to fit a 0.3in DIL packaged device, although it can be used for other types of components. An adjacent row of headers breaks out the spare signals from D1, D0, TX, RX (UART) and the single analog input A0, along with strips of pads to connect to ground (GND), 5V and 3.3V. The PCB itself follows the theme used for both the Micromite BackPack V3 and the 3.5-inch Touchscreen Arduino Adaptor. The PCB can be slightly shortened if using a 2.8in LCD panel. Two sets of mounting holes allow either size of panel to be securely mounted with 3mm machine screws and tapped spacers. Fig.2: use this PCB overlay diagram and the matching photo below as a guide during assembly. There aren’t all that many components, so as long as you take care with the SMDs, you should have it up and running in no time. Pretty much all the components are obscured by the touchscreen once it is fitted. For that reason, you might want to mount external I/O header CON4 on the reverse side. by soldering it directly, or you may like to make it removable by using suitable header sockets. In the latter case, you will probably need to increase the space between the PCB and LCD panel, to give the extra height required when using these headers. We created some spacers for the LCD by soldering a row of male headers to female headers. Of course, you may also be restricted by the space available for mounting if you are planning to fit the unit in a wall cavity or similar. In that case, soldering MOD1 in place is a good idea. We’ll describe the assembly with MOD1 fixed in place, although it will be the last step. If you don’t need a micro SD card socket then CON2 and its two associated capacitors can be left off. But note that they will be much trickier to install later, so it’s best to fit them anyway if there’s any chance you’ll be needing the socket. If you are planning only to use the 2.8in display, then you can cut or snap Australia’s electronics magazine off the right-hand portion of the PCB before starting assembly. But there’s no harm in leaving the PCB whole if you have space. To avoid inhaling fibreglass dust, trim the PCB outdoors and wear a face mask. Carefully score the four PCB traces to prevent them from tearing. With flat-nosed pliers, flex the PCB at the three places it’s joined; it should snap at the naturally weak points. You should also file or sand any rough edges left after snapping; again, be careful to avoid inhaling the dust. Fitting the components The D1 Mini BackPack is built on a double-sided PCB coded 24106201, measuring 99 x 54.5mm. Refer to the photos and PCB overlay diagram (Fig.2) during assembly. There are a few surface-mounted parts to install; we recommend using a fine-tipped, temperature-adjustable soldering iron, solder flux, tweezers, solder braid (wick) and a magnifier of some sort. Fit the micro SD card socket first, as October 2020  25 The completed PCB (left) and married with the Micromite BackPack display (right). The prebuilt WiFi module is the blue PCB at lower left of the main board. it has the closest pins. It has a pair of locating pins, so it is straightforward to get it into position. Apply flux to its pads and place the part, checking that the pins line up. Turn up the iron a little and solder one of the larger mechanical pads to fix it in place. Solder the electrical pins by adding a small amount of solder to the iron, then touch the tip of the iron to each pin. The flux should induce the solder to run off and form a clean fillet. If you make a solder bridge, leave it for now and ensure that the remaining pins are connected. Now go back and remove any bridges using the solder braid (wick). Apply more flux to the bridged pads, then push the braid against the excess solder with the iron. Once it melts, slowly draw the braid away from the pads. With the electrical pins complete, the remaining mechanical pads can be finished. Leaving these until last will make it easier to completely remove the part if this is necessary. Apply more flux if necessary, and don’t forget to turn the iron down to a setting for regular components afterwards. The two SOT-23 package transistors are the smallest parts but have more space around their leads, so fit them next. Check the markings to ensure that Q1 and Q2 are not mixed up. Q1 should be marked with a code that starts with an “X” while Q2 may be marked 72, 702 or possibly something else depending on the manufacturer (these codes are tiny, so you will need a magnifier to read them). A good process for surface mounted components is to apply flux to the PCB pads and load the tip of the iron with a small amount of excess solder. Hold the part in place with tweezers and apply the iron to one lead only. If it is not flat and square, adjust it until it is. Then solder the other leads. Now that the part is secure, the solder fillets can be tidied up. This can be as simple as applying some extra flux to the solder, then touching it with the iron. There are four resistors to be fitted; install these next, ensuring the correct values are used, as per the silkscreen and Fig.2. If you are using through-hole capacitors, then solder and trim as per standard through-hole procedure. Follow the above process for surfacemounted parts. Place the 100nF capacitor first; it will possibly be smaller than the other capacitors and is closest to the micro SD card socket. Repeat with the re- Another view of the way the PCB mates with the Micromite BackPack – it simply plugs into the 14-pin header socket (CON1) at extreme left and the four-pin socket (CON1A) at right. Power is supplied via the DC socket (CON3); alongside is the microSD card socket (CON2) with the USB socket under the WiFi module. 26 Silicon Chip Australia’s electronics magazine maining capacitors, ensuring they are flat and square. Bend the leads on REG1 down 90° about 6mm from the body and place them in the PCB pads. Fit the machine screw and affix the washer and nut; if this is done before soldering, then you can be sure that the regulator is situated correctly. Now solder the leads of REG1 and trim the excess. Jumpers and headers It is easier to fit JP1-JP4 before CON1 and CON1A. Slot JP1 in place and solder one pin. If it is not square, then you can hold the header by the other pin and adjust it while remelting the solder. When you are satisfied that it is flat and flush, solder the other pin. To keep JP2-JP4 aligned, push them all into the female headers that will be used for CON1 and CON1A. As for JP1, solder one pin of the group, then adjust to be level and square before soldering the remaining pins. Then unplug the female headers. If you are planning to use the SD card socket on the LCD, then you will need to fit CON1A, at a location depending on whether you plan to use the 2.8in or 3.5in display. Or you can fit both. Even if you don’t plan to use this SD card socket, the extra headers help to secure the boards mechanically and align them. So it’s a good idea to fit them. Many LCD panels do not have the four-pin header fitted, so this will need to soldered too. The best way we’ve found to fit all the LCD headers is to plug the four-pin (male and female) headers together, then attach the 14way female header to the LCD panel. Rest the LCD panel face-down and place the four-way headers in their pads, with the male pins facing down (matching the orientation of the 14-way header). Then rest the PCB on top and siliconchip.com.au line up the pins with their holes. Solder the pins to the BackPack PCB, then flip the assembly over and solder the male pins into the LCD panel. This process ensures that all the pin headers and sockets are as square as possible, making it easier to change out the LCD panel if necessary; say, if you are swapping from the 3.5in to the 2.8in variant. By the way, you might notice that we’re mounting the touchscreen rotated by 180° in comparison to our previous Micromite BackPack projects. As the LCD and touch drivers are capable of rotating the display in increments of 90°, this does not cause any problems later. Next, solder the DC jack. This may need some extra heat on the iron, and the large pads will need a fair amount of solder. Like the other parts, you can solder one lead, check that the part is orientated correctly, then solder the remaining pins. The final component is MOD1, the Di Mini. Many of these (such as Jaycar’s XC3802) come with an assortment of loose headers. We are assuming that the D1 Mini is fitted with male header pins underneath (in a fashion that would allow it to be used in a breadboard), so if you have different headers fitted, you may need to change them. If you wish to remove the D1 Mini in the future, this will mean that the PCB should be fitted with header sockets. As noted earlier, you may need to find a way to space the LCD panel to account for the space these headers take up. We’ll assume you’re soldering the D1 Mini directly to the PCB, as we have done. Sandwich the male header pins between the MOD1 and the PCB and tack a few pins from the top, then flip over and tack a few pins on the bottom. Check that everything is square and correct. You may also like to check that a USB cable can be plugged in. Even if you don’t plan to power the unit from USB, it’s a good idea to leave it accessible for programming. Once you are happy with this, solder the remaining pins and trim them. For the demonstration software we have written, only one jumper is needed, for JP2, on the 5V side. See the photos and overlay to check the position to fit it. The final step to a functional unit is to fit the LCD panel. Plug the 3.5in LCD into CON1 and CON1A. Installation in, siliconchip.com.au Parts list – Mini WiFi LCD BackPack 1 double-sided PCB coded 24106201, 99 x 54.5mm 1 UB3 Jiffy Box 1 laser-cut lid to suit UB3 Jiffy box for 3.5in screen (optional) [SILICON CHIP Cat SC5083] 1 D1 Mini development board (MOD1) [Jaycar XC3802 or similar] 1 14-way female header socket (CON1) 1 4-way female header socket (CON1A) 2 8-way female header sockets (to make MOD1 pluggable; optional) 1 3.5in SPI LCD touchscreen with ILI9488 controller [eg, SILICON CHIP Cat SC5062] 1 4-way male header (usually comes with the touchscreen) 1 2-way male header (JP1) 3 3-way male headers (JP2,JP3,JP4) 4 jumper shunts (JP1-JP4) 1 SMD micro SD card socket (CON2) 1 PCB-mount DC jack socket, ID to suit plugpack (usually 2.1 or 2.5mm) (CON3) 1 M3 x 10mm panhead machine screw, hex nut and washer (for REG1) 8 M3 x 6mm panhead machine screws 4 12mm-long M3 tapped spacers (or longer if mounting MOD1 on sockets) Semiconductors 1 7805 5V 1A linear voltage regulator, TO-220 (REG1) A complete kit of parts (as 1 IRLML2244TRPBF P-channel Mosfet, SOT-23 (Q1) specified here) is available from the SILICON CHIP ONLINE 1 2N7002 N-channel MOSFET, SOT-23 (Q2) SHOP – Cat SC5503 <at> $70.00 Capacitors 3 10µF 16V X7R SMD ceramic, 3216 (1206) size or through-hole equivalent 1 100nF 50V X7R SMD ceramic, 3216 (1206) size or through-hole equivalent Resistors (all SMD 3216/1206 size, 1%) 1 47kW (Code 473/4702 ) 1 10kW (Code 103/1002) say, a wall cavity, will require further steps, but these will be specific to your circumstances. We’ll look at mounting options once the unit is operational. To secure the LCD panel, attach the tapped spacers to the front of the PCB with machine screws from behind, then slot the LCD panel into the headers and secure it with the four remaining machine screws from the front. Software To make use of our software, you’ll need the Arduino IDE and the ESP8266 Board file; we’ll assume you’re familiar with the IDE (Integrated Development Environment). It can be downloaded from siliconchip.com.au/link/aatq We’re using version 1.8.5; you should use this or a later version. Installing the ESP8266 add-on for the Arduino IDE requires adding the URL http://arduino.esp8266.com/stable/ package_esp8266com_index.json to the Additional Board Manager list (found under File > Preferences). With the URL added, the ESP8266 add-on can be installed by opening the Boards Manager (Tools > Board > Board Manager), searching for ESP8266 and clicking “Install”. This Australia’s electronics magazine 2 1kW (Code 102/1001) can take a while as it is a complete toolchain and board support files. You may also need USB-serial drivers for the CH340 used on the D1 Mini. We used drivers from siliconchip. com.au/link/ab2g for our WeatherDuino in 2015 (siliconchip.com.au/ Article/8457). The D1 Mini corresponds to the “LOLIN (WEMOS) D1 R2 & Mini” in the Arduino Tools > Board Menu. Ensure that you have selected this and also selected the correct serial port. Unzip our sketch to your Arduino sketch folder and open it with the IDE. There are no external libraries needed; the WiFi libraries used are included with the ESP8266 board download. There are some LCD-specific library files that we have included in the sketch folder. As with any project which uses WiFi, there needs to be a means to select a WiFi network and enter the network password. Many ESP8266 projects simply hard-code this into the sketch itself, but that’s a bit crude. Our sketch is a bit smarter. If it detects that no WiFi network has been set, it scans for nearby networks and presents a list for the user to choose October 2020  27 Details of this are provided at https:// openweathermap.org/price In any case, the free account and API key are sufficient for us to get a modest amount of data updated at a useful rate. This needs to be set in the sketch before upload. Look for the line defining the OWM_API_KEY in the main sketch file and change it to the key you’ve been given. It should be surrounded by quote marks. Now we can upload the sketch to the D1 Mini, by pressing the Upload button on the IDE. The compilation and upload process may take a minute or two, after which the LCD should clear. The sketch Fig.3: if all goes well with registration, you will get an email from openweathermap. org with your API key (we’ve redacted ours so you can’t steal it!). Copy this into the Arduino sketch at the OWM_API_KEY define between the quote marks. Keep your API key secret, as anyone that has it can use your allowance. from. The user can then enter the password; the settings are saved to nonvolatile storage. The result is a much friendlier end-product. Thus, no WiFi settings in the sketch need to be changed before uploading; these can all be set later. your OpenWeatherMap account. The free API key allows a limited number of accesses per day, with paid accounts allowing more frequent access to more detailed data. A lot of the sketch is dedicated to providing control of the LCD and providing a useful user interface, including a GUI routine which displays and monitors things such as the buttons and on-screen keyboard. The sketch uses two sources of Internet data to update its display. The first of these is NTP (Network Time Protocol) data for the current time. Since NTP only provides the time as UTC (similar to GMT), a timezone offset is needed to calculate and display the actual local time. Fortunately, the OpenWeatherMap data includes timezone information. It is also used to show things such as the current and forecast temperatures and graphics representing these. Sunrise and sunset times are shown too. The time is pulled from the NTP OpenWeatherMap One feature of our demo program is to retrieve weather information and display it on the LCD screen. This data comes from the openweathermap.org website. Although it is free to use this data, an account is required. This is used to limit free access, and also to provide access to more data for paid accounts. An email address is needed to set up an account; open siliconchip.com. au/link/ab2h in a web browser and enter your details. An email will be sent with a confirmation link; after clicking this, you’ll receive a second email. This second email contains an API key, which is a hexadecimal code our sketch needs to access OpenWeatherMap data (see Fig.3). There is an option to generate further API keys from 28 Silicon Chip Screen1: the main page of our demo application shows a swathe of information from OpenWeatherMap. We tried to use a PNG decoding library to display the icons, but it still had a fairly high dynamic memory requirement and did not work. So instead, the icons are stored in the flash memory. Australia’s electronics magazine siliconchip.com.au server hourly, with the D1 Mini’s internal timer being used to keep track of time in between. The weather data is updated every 10 minutes. Operation After the sketch is uploaded, you can open the serial monitor to get debugging information. On the LCD, a message “Scanning...” will appear, after which a list of WiFi network names (SSIDs) will appear. Tapping on one will result in a prompt to enter the password using an onscreen keyboard. This will be followed by a prompt to enter a location. This is the location used by the sketch to query OpenWeatherMap. We found a simple “Sydney” was sufficient to get accurate data for our location in Australia, but if, say, you lived in Sydney, Nova Scotia, you might need to be more specific. Entering “Melbourne” displayed data more consistent with Melbourne, Florida than Melbourne, Victoria. “Melbourne,AU” appeared to provide the correct data. If you aren’t sure, open the Serial Monitor and watch the displayed info; a lot of data is output for debugging. The data retrieved from OpenWeatherMap will appear as a single, long line. Information such as the latitude, longitude or country can be used to check that you have the correct location. User information (such as WiFi network and location) is saved in nonvolatile storage. The ESP8266 doesn’t D1 Pin Comments pin name number D0 16 Initially high D1 5 Default Arduino I2C SCL D2 4 Default Arduino I2C SDA D3 0 Has pull-up resistor to set the run mode at reset. D4 2 Has pull-up resistor to set the run mode at reset. D5 14 Hardware SPI SCK D6 12 Hardware SPI MISO D7 13 Hardware SPI MOSI D8 15 Has pull-down resistor to set the run mode at reset. TX 1 Can be used as GPIO RX 3 Can be used as GPIO. A0 - Analog input with a nominal full-scale value of 3.2V Table 1: D1 Mini pin numbering have dedicated EEPROM, but the Arduino IDE provides EEPROM emulation by using a small amount of flash storage. Thus these settings are retained during power-down and are loaded at power-up. Once set up, the screen usually displays complete information within around ten seconds of power being applied. Mounting If you simply wish to use the unit in a freestanding enclosure, then mounting is much the same as for the Micromite LCD BackPack V3, and you can use the lid designed for that project to mount it into a UB3 Jiffy box. You may like to provide a DC input jack on flying leads to be mounted on the case, if the existing cable entry doesn’t suit your application. Like the Altronics Inventa Plates, we expect some people will install these into a wall cavity. This could be as simple as using the acrylic piece noted above as a bezel. Another simple way to do this is to make a square cutout in a blank wall plate, as well as four round 3mm holes for the screws. The D1 Mini BackPack can then mount similarly to other BackPacks, using a screw in each corner to secure it. You could use the blank PCB as a template for the holes; this may be easier than a populated PCB or the LCD with its protruding headers. If you are mounting it to a wall which has mains wiring behind, consider adding a spacer block to keep it separate. This will also reduce the size of the hole which needs to be made in the wall. Beyond the demo Screen2: the WiFi setup page provides a similar interface to many ‘smart’ devices. Nearby networks are scanned and listed; the user simply has to enter the appropriate password. siliconchip.com.au Australia’s electronics magazine Our software provides a useful function, but it really shows only a tiny fraction of what can be done with this hardware. Many other useful features can be added relatively easily. With the popularity of the Arduino IDE and ESP8266, there are numerous examples of what can be done online. This includes tapping into online resources to display data, plus protocols to interact with other devices within your LAN, or even via a VPN. Table 1 shows the D1 Mini’s pin configuration, which should be very helpful if you plan to modify the code. Unlike AVR based boards, many of the pins on the D1 Mini have individual characteristics, meaning they are not entirely interchangeable. October 2020  29 Screen3: the benefits of a large touchscreen come to the fore on the password page. Here we can use the ample space to implement a full QWERTY keyboard that allows all ASCII characters to be entered. Most keys are at familiar locations; some have been moved for compactness. A similar screen is used to enter the weather location. We have therefore carefully chosen the pins used for the D1 Mini LCD BackPack. Over-the-air programming One of the libraries within the Arduino ESP8266 board profile provides a very useful feature, especially if you plan to mount the unit in a wall permanently. ‘Over The Air’ (OTA) programming means that sketches can be uploaded to the unit via WiFi. The sketch needs to have the OTA library included, so the first sketch upload must be done through the serial port, but as long as subsequent code uploads include the OTA library, OTA can continue to be used. Some limitations exist; for example, the ESP8266 must have enough space to hold the currently running sketch alongside the new sketch. This effectively cuts the available sketch flash space in half. The mechanism means that the ESP8266 must be connected to the same WiFi network as the user; if it has lost its WiFi credentials, then OTA will not work. Being programmable over WiFi also means that someone else with WiFi access could reprogram the unit, although a basic password feature is provided. Still, it’s a handy feature to have, especially if you need to test the unit in situ, or if it’s difficult to connect a USB cable. 30 Silicon Chip There are example sketches (under the ArduinoOTA heading) and more information can be found at siliconchip.com.au/link/ab2i Summary While the demonstration program shown here is quite useful in its own right, it’s intended to be a starting point for other projects. For example, many public transport operators make their data available. So it would be possible to display when the next bus is scheduled to leave your nearest stop, or even when it is coming down to the minute if realtime data is available. While many of these services re- quire user registration, there is a freely available service for Melbourne tram information. It is documented at siliconchip.com.au/link/ab2j This project also provides the perfect means of controlling other devices. An increasing number of home automation devices are becoming available, and many of them are suitable for integration in such a system. Even in the case that this can’t be done directly, there are alternative open-source firmwares which make this possible. In particular, many of the ESP8266based smart globes and switches can be modified by loading the open-source Tasmota firmware (https://tasmota. github.io/docs/). This software and many others use the MQTT protocol; there are numerous MQTT libraries for the ESP8266, so interfacing to this protocol is not hard. Because it uses a publish/subscribe model, multiple devices can act on the same information. There are also mobile phone applications which can be set up to provide an MQTT dashboard, for example, allowing MQTT data to be displayed or MQTT messages to be sent at the push of a button. The big opportunity here is to automate actions based on the information that the D1 Mini can access. For example, turning on lights at sunset or turning off the heater if the outside temperature increases. While the D1 Mini BackPack would only be a very small part of such a project, it is clearly a useful device in its SC own right. Fitting into a UB3 Jiffy box: because it uses the same LCD panel as the 3.5in Micromite BackPack, it can be mounted in a UB3 Jiffy Box using the same laser-cut acrylic lid (our Cat SC5083). This is the perfect way to mount and protect the unit if it needs to be installed in a wall cavity. Australia’s electronics magazine siliconchip.com.au Cable Assembly & Box Build Assembly Metal Work Label and Wire Marker CNC Engraving and Machining Functional Test and Logistic Service Electrical box assembly <at>Ampec we specialise in manufacturing of custom design cable assemblies as well as turnkey electronic and electric product assemblies. Fully automatic cut, strip and crimp machines High mix low volume and quick turnaround +61 2 8741 5000 e sales<at>ampec.com.au w www.ampec.com.au Improved ADS-B reception on a computer Three new products give you much-improved reception of ADS-B signals from aircraft on your computer, allowing you to track most nearby flights. After reviewing them, we’ll also give you some tips regarding the best ADS-B reception software. by JIM ROWE B ack in the August 2013 issue of SILICON CHIP, we published a couple of articles on receiving ADS-B signals broadcast from aircraft. The first article (“ADS-B & flightradar24.com”) provided an introduction to ADS-B – where it came from, what it is and how it works; see siliconchip.com.au/Article/4204 The second article (“Track Aircraft On Your Own ADS-B Receiving Station”; siliconchip.com.au/ Article/4209) explained how you could make your own low-cost setup for receiving ADS-B signals using a computer and a low-cost USB DVBT dongle. Since then, improved USB dongles have appeared, offering significantly better performance for SDR (software defined radio) reception (like ADS-B) compared with first-generation DVBT dongles. 32 Silicon Chip Also, some of the ADS-B receiving software available in 2013 is no longer available – specifically, freeware programs like ADSB# and ADSBScope. But new software has appeared to take their place. Some of the earlier non-freeware software has also been improved and is still not overly expensive. Since so much has changed recently, we tried out three new products aimed at providing improved ADSB reception for your computer, and (Above): the FlightAware 1090MHz bandbass filter, which significantly improves ADS-B reception by attenuating unwanted signals outside the ADS-B band. (Opposite): the ProStick Plus, a USB dongle specifically intended for optimum ADS-B reception. Australia’s electronics magazine siliconchip.com.au we’ll describe what we found. But before that, let’s quickly go back over the concept of ADS-B, in case you haven’t read the August 2013 articles. ADS-B stands for “Automatic Dependent Surveillance – Broadcast”, an aircraft information and identification system. Most modern aircraft are fitted with a high-integrity GPS receiver, which continuously monitors their exact position (latitude and longitude). They also have a suite of equipment which monitors their barometric and geometric altitudes, the rate of climb or descent, the tracking angle (heading) and their ground speed. They are also fitted with a Mode-S transponder which takes all of this information (together with the aircraft’s unique ICAO 24-bit Aircraft Address and Flight Identification) and broadcasts it automatically as a 120-bit ADS-B digital ‘squitter’ at 1090MHz, twice per second. These ADS-B squitters can be received by ground stations and other aircraft; many large aircraft are able to receive the ADS-B signals as well, so their pilots can be fully aware of other aircraft in their vicinity. As we explained in the 2013 articles, it’s quite easy to receive these ADS-B signals via a low-cost SDR using your computer and a USB dongle capable of reception at 1090MHz, a suitable omnidirectional UHF antenna and appropriate software. I measured the insertion loss of the FlightAware 1090MHz bandpass filter at a commendable 1.92dB (its specs say 2.5dB!). Other measurements revealed a bandwidth of 1015-1140MHz and an attenuation of around -35dB at 960MHz and 1210MHz. New gear The FlightAware ADS-B 1090MHz bandpass filter is designed to improve ADS-B reception quality by attenuat- After we published the article in the May 2020 issue reviewing the siliconchip.com.au new RTL-SDR Blog V3 USB-linked dongle (which we found an excellent performer; see siliconchip.com. au/Article/14429), we were contacted by the local agents South Eastern Communications. They told us about three products are specifically designed for high-performance ADS-B reception, all from a company in Houston, Texas called FlightAware: • a low insertion loss 1090MHz bandpass line filter; • an omnidirectional antenna specifically designed for 1090MHz ADSB reception; • and a new dedicated ADS-B dongle called the ProStick Plus. All three are made in Taiwan. We evalulated the 1090MHz bandpass line filter first. The ADS-B line filter Australia’s electronics magazine ing signals outside a 15MHz frequency band centred on 1090MHz. This makes it very suitable for use with an RTL-SDR dongle, as most of these are wideband devices and lack any front-end tuning. So they can have difficulty rejecting strong interfering signals close to 1090MHz. The FlightAware filter is a passive unit and very compact, measuring only 56mm in length (or 78mm overall, including the input and output connectors), with a diameter of 19.5mm. It is fitted with an SMA plug at one end (to connect to the antenna) and an SMA socket at the other end, to connect to the input of your dongle. The rated bandwidth is 9801150MHz, with an impedance of 50Ω and an insertion loss of less than 2.5dB. Its cost is quite modest, at $40.00 plus postage. I measured the filter response using my Signal Hound USB-SA44B spectrum analyser and USB-TG44A tracking generator, together with the Spike software. The result is shown above, which indicates that the filter’s performance is impressive. It has a measured insertion loss of only 1.92dB at 1090MHz, a bandwidth of 1015-1140MHz and an attenuation of around -35dB at 960MHz and 1210MHz. So it should significantly improve the ability of a ‘standard’ SDR to receive ADS-B signals, by reducing interference from signals outside this band. October 2020  33 Even at the height of the COVID-19 lockdown, there was significant aircraft movement around Sydney, as shown here on my computer screen grab. The near-solid red “blob” marks the many aircraft on the ground at Sydney airport. Zooming in will separate these into individual aircraft IDs. To confirm that this would improve the ability of any ‘standard’ SDR to receive ADS-B signals, I connected the filter between my RTL-SDR Blog V3 dongle and an external discone antenna, and fired up the RTL1090 ADS-B decoding software and the Planeplotter graphical plotting software on Windows 10. And despite the modest aircraft activity during the COVID-19 pandemic, the setup was able to detect, decode and plot ADS-B squitters from every aircraft in the air within a radius of at least 150km – plus quite a few parked on the ground at Sydney Airport, just a few kilometres away. I also tried the same setup without the FlightAware filter, and the results were not nearly as good. So this filter can definitely make a worthwhile improvement in your ADS-B reception, if you are using a standard wideband RTL-SDR like the Blog V3. The FlightAware 1090MHz antenna Next, I tested the FlightAware 1090MHz antenna. This is a compact little unit, housed in a cylindrical plastic tube 550mm long and 20mm in diameter, with a weatherproof cap at the top. It has a cylindrical metal base 100mm long and 25mm in diameter at the bottom, ending in a female N-type connector for attaching the feeder cable. It’s solidly made and comes complete with a cylindrical mounting bracket, two U-bolts and a full set of washers and nuts to mount the antenna atop a 25mm vertical mast. The antenna is claimed to be fully omnidirectional and to have a gain of +5dBi average. When mounted at a suitably high point without obstructions, it is claimed to be able to receive ADS-B data from aircraft up to 400km away. The antenna’s internal construction seems to be a sleeved dipole with a loaded whip above it. This combination gives higher gain relative to other omnidirectional antennas, plus a flattened response which makes it especially suited for receiving ADSB signals from aircraft at a distance. It is currently available from South Eastern Communications for $99.00 plus postage. I mounted it on the top of the mast for a UHF TV antenna, as shown in the photo, at almost the same height above ground as my discone antenna, and with a very similar ‘view’ in most directions. I hooked it up to the combination of the FlightAware 1090MHz inline filter plus RTL-SDR Blog V3 dongle, as before plugged into a laptop running the RTL1090 ADS-B decoding software feeding Planeplotter. The results were quite impressive, as you can see from the screen grab above. The FlightAware antenna delivered at least as many clean ADS-B signals as the discone, if not more. Note that although the screen grab only covers the greater Sydney area, I also expanded the coverage to include an area extending up to Newcastle and down to Wollongong. I could then see aircraft somewhat further away. So although I didn’t carry out any fancy technical tests on the antenna, my impression is that it performs at Current ADS-B software Things have changed in the last seven years when it comes to freeware and low cost software for receiving ADS-B signals using a USB dongle and your PC. For example, ADSB# (ADSBSharp) is no longer available, while ADSBScope still is, but without the ability to cope with locations “down under”. Luckily RTL1090 is still available, although from a different website from the one we gave in the August 2013 articles (see the list of useful links). And it’s still freeware. PlaneSpotter is also still available, although its name has been changed to PlanePlotter. The latest version (V6.4.6.2) is not freeware, though. You can download it for a 21-day free trial, but after that you need to pay for a licence, which costs AU$49.23 including GST. Since it also makes use of Google maps, you have to make a separate payment of AU$20 for every 1000 maps downloaded. After trying out a few of the software packages currently avail34 Silicon Chip able, I settled on using the combination of RTL1090 for the decoding and PlanePlotter for the display. They work well together, and it’s fairly easy to get RTL1090 communicating with either an RTLSDR Blog V3 dongle or the FlightAware Prostick Plus. Both of the applications will run happily with Windows 7, 8 or 10. The easiest way to install RTL1090 is by downloading the rtl1090imu.zip file, unzipping it and then running it as Administrator. Note that you can’t install it in the usual “C:\Program Files\” subdirectory though, as it writes to files in its installation directory. So you have to install it somewhere that you have write access. RTL1090-IMU is an installer and maintenance utility, which automatically downloads all of the components needed to get RTL1090 working. That includes Zadig, the driver installing program needed for Windows applications like RTL1090 to communicate with USB devices like RTL-SDR dongles. It even includes a step-by-step tutorial to help you use Zadig to install the correct driver. Australia’s electronics magazine siliconchip.com.au Useful ADS-B links • https://en.wikipedia.org/wiki/ADS-B • https://flightaware.com/ • www.flightradar24.com • www.rtl-sdr.com/ • www.rtl-sdr.com/adsb-aircraft-radar-with-rtl-sdr/ • www.rtl-sdr.com/review-flightaware-ads-b-antenna-and-filter • https://rtl1090.com/ • https://rtl1090.com/installation-manual-2/ • www.coaa.co.uk/planeplotter.htm • http://planeplotter.pbworks.com/w/page/17117302/FrontPage (Inset above): the ADS-B (1090MHz) receiving antenna and its mounting hardware . . . shown here mounted above a UHF TV antenna. Keep them more than a wavelength apart (~250mm <at> 1090MHz) and they shouldn’t affect each other. least as well as the more expensive discone, and probably better. The FlightAware ProStick Plus dongle The ProStick Plus USB dongle is an RTL-SDR dongle specifically designed for optimum ADS-B reception. At 70 x 32 x 13mm, it is almost exactly the same size as a modern RTL-SDR dongle like the Blog V3 we reviewed in May 2020. It has a female SMA input connector at one end and the usual type-A USB plug at the other. The Prostick Plus comes in a moulded plastic case rather than the extruded metal case of the Blog V3. siliconchip.com.au So superficially, it has less shielding, although there may be shielding foil inside the case (it wasn’t clear how to open the case without damaging it). Inside that case there’s more than the usual combination of a Rafael Micro R820T2 programmable tuner chip driving a Realtek RTL2832U COFDM digital demodulator chip. You also get a built-in 1090MHz bandpass filter at the input, plus an RF amplifier delivering a rated gain of +19dB with a noise figure of 0.4dB. The inbuilt 1090MHz bandpass filter has a passband covering 10751105MHz (ie, 1090±15MHz), with a rated insertion loss of 2.3dB and Australia’s electronics magazine around 30dB of attenuation outside this range. So together, the filter and amplifier combination provides an effective gain of around 16.5dB inside the passband centred on 1090MHz, plus a high degree of rejection outside that band. That should make the Prostick Plus very well suited for ADS-B reception, especially in noisy urban areas. And it’s just $45.00 plus postage, from South Eastern Communications – not much more than the RTL-SDR Blog V3 (for which they charge $35.00 plus postage). I tried out the Prostick Plus with both my existing discone antenna and the new FlightAware 1090MHz omni antenna, using as before the RTL1090 decoding program linked to the Planeplotter program. With the Prostick Plus, there’s no need to use the external bandpass filter, since it has its own built-in filter. The results were very impressive with both antennas. An example is shown in the screen on page 32. As well as showing the ‘pile’ of aircraft parked on the ground at Sydney airport, you can clearly see two aircraft flying away from Sydney out over the water, plus about eight others flying in various directions over the greater Sydney area – and one on the ground at Bankstown airfield, around 20km away! So to summarise, the FlightAware Prostick Plus dongle seems to be topof-the-line for ADS-B reception using your PC. Whether you use it with FlightAware’s own 1090MHz omnidirectional antenna or a discone antenna, itis hard to see how you could get better performance. But if you already have an RTL-SDR dongle like the Blog V3, you should be able to get almost the same results simply by getting one of the FlightAware 1090MHz bandpass filters to remove most of the EMI picked up by your antenna. These products can probably all be found on the internet, at marketplaces like eBay and Amazon. But if you’d prefer to get them from a reliable Aussie source, we can recommend South Eastern Communications. You’ll find them on the web at www.secomms.com.au, but you can also contact them by email at sales<at> secomms.com.au, or by phone to 1300 382 385 or 0434 720 006. Or if you wish, by “snail mail” to PO Box 251, McCrae, Victoria 3938. SC October 2020  35 You won’t believe what you can do with this one! Flexible Digital Lighting Controller Create a truly spectacular lighting display – large or small – with this very flexible, very expandable Digital Lighting Controller. It’s sensational for Christmas lights but it could be used for other things like amateur theatre lighting control or even controlling lamps around your home. Incidentally, we aren’t pretending that the incredible display on this page either came from this controller or, indeed, was put together by us. (It’s actually from England). The point is, if you wanted to produce something like this . . . you could! By Tim Blythman 36 Silicon Chip Australia’s electronics magazine siliconchip.com.au I t’s been exactly ten years since we published a Digital Lighting Controller – the last one was in October 2010 (siliconchip.com.au/Series/14). It used one control unit that could control up to four slave units with eight lights each, so it could manage up to 32 mains-powered lights. It was a popular project, with Altronics producing kits. Some of these were used to create amazing Christmas displays. You can see one of these at https://youtu.be/mBgLltJ5br8 Unfortunately, those kits have now been discontinued, and the question arose: should we design a new Digital Lighting Controller, and could we make it easier to build with more capabilities? The answers are yes, yes and yes! Ten years later A lot has happened in the last ten years. In particular, the Arduino ‘ecosystem’ has flourished, making it much easier for the average person to program a microcontroller. Stunning LED light displays are now possible using chainable LED strips such as those using the WS2812 type ‘smart’ LEDs. But there are still times when you might want to control mains-powered lights, or indeed, a mixture of mainspowered lights and DC-powered LEDs or LED strips. Controlling mains-powered lights with an Arduino (or any microcontroller) can be hard. One simple way is to use our Opto-isolated Mains Relay project from October 2018 (siliconchip. com.au/Article/11267). That makes it possible to switch mains devices off and on easily and safely. But it can only control one device at Features & specifications • • • • • • • Modern solid-state lighting controller with trailing-edge dimming Four channels per slave unit 16 slave addresses available for up to 64 channels total Up to 250W of lights per channel (limited by fuse & PCB tracks) 256 brightness steps (0-100%) per light Serial control interface works with just about any microcontroller Informative front panel a time, and only switches it on or off. For a great lighting display, you need to be able to control lots of lights and vary their brightness, not just switch them on or off. Hence, our new Digital Lighting Controller which can do all of this. New and improved The new Digital Lighting Controller uses a very similar overall philosophy to the previous design. A single ‘master’ unit can interface to and control many ‘slave’ units, each of which drives multiple mains outlets. The old design used an eight-wire shift register interface to trigger a Triac every mains half-cycle via an optocoupler. That meant that the master unit had to drive the bus continuously for the outlets to be activated on time. The nature of the shift-register interface also means that there were only 20 Triac trigger points in each half-cycle and thus 20 distinct dimming levels. Our new design does not have this limitation and can produce 256 different levels, giving seamless ‘fades’ in and out. Using Triacs also meant that only leading-edge dimming was possible, as the Triacs latch on until the end of the half-cycle at the next mains zerocrossing (see Fig.1 overleaf). That limits its usage pretty much just to incan- descent or halogen lamps. In February 2019, we introduced the Versatile Trailing Edge Dimmer (siliconchip.com.au/Series/332). It uses a pair of back-to-back Mosfets to switch the connected lamps on and off at the correct times. Rather than applying power midcycle and shutting it off at the end of the cycle like a traditional dimmer, a trailing-edge dimmer applies power from the zero-crossing and shuts it off at some later point in the mains cycle (Fig.2). This makes little difference to incandescent lamps, as the brightness of the light depends on what fraction of the cycle it is being powered and not much else. But for more modern lamps, mainly LEDs (which often have a capacitor at their input), the difference is critical. Because the leading edge design switches on at mid-cycle, there can be a huge inrush current as the capacitor(s) charge up. Since the trailing edge design only switches on at the zero-crossing, when the voltage is at a minimum, the inrush current is no different to what it would be if there was no dimming occurring. And this is how most dimmable LEDs are designed to operate. For more details on leading vs trailing edge dimming, see page 25 of our This is the Slave Unit – the bit that takes the signal from the master controller and drives the lights. We’ll describe the master controller next month. siliconchip.com.au Australia’s electronics magazine October 2020  37 A EARLY TRIGGERING: HIGHER OUTPUT B LATER TRIGGERING: LOWER OUTPUT A LATER TRIGGERING: HIGHER OUTPUT SC Ó SC B EARLIER TRIGGERING: LOWER OUTPUT Ó Fig.1: a leading-edge dimmer varies the switch-on point during the mains cycle, but always switches off at the zero crossings. So the earlier it switches on, the more power is applied to the load and the brighter the light. But this does not work well with LEDs or with other lamps that have electronic drivers. Fig.2: a trailing-edge dimmer achieves a similar result, but it instead switches the lamp on at the zero crossings and then switches it off at some point later in the mains cycle. The later the switch-off, the brighter the lamp. This scheme is compatible with lights that have electronic drivers, including most dimmable LEDs. February 2019 issue. As you might have seen in the Versatile Trailing Edge Dimmer article, the circuitry for controlling the Mosfets is more involved than that needed for Triacs (and that is why leadingedge dimmers were the standard until recently). In the Trailing Edge Dimmer, a small transformer is used to provide an isolated, ‘floating’ supply to drive the Mosfets, which is switched by an optoisolator under the supervision of a microcontroller. To simplify things for our Digital Lighting Controller, we are using a clever little chip that bundles all of the features of isolation and power transfer into a tiny SOIC-8 package. It is the Si8751AB isolated Mosfet driver IC, previously used in our Smart Battery Charge Controller from December 2019 (siliconchip.com.au/Article/12159). (bipolar) RS-485 signalling. To keep our circuit simple, we’re using singleended serial at a lower rate of 38,400 baud. This still allows us to transmit enough data to update the brightness of 64 lights once per mains cycle. The lower rate means that the circuit will be less sensitive to outside noise and interference, despite lacking the bipolar signalling. Using a single-ended serial signal means that just about anything which can produce a serial waveform can control our lighting ‘slaves’. Rather than a microcontroller, you could use a USB-serial converter to connect the To make the Digital Lighting Controller more flexible, we’ve adopted a simple two-wire serial interface between the master and slave units. This is inspired heavily by the DMX-512 protocol, which is used in professional studio and stage lighting applications. As the name suggests, DMX-512 can address up to 512 individual devices. This is many more than we need, even for a big display. The DMX-512 protocol runs at 250,000 baud using Silicon Chip Fig.3: the measured current drawn by a lamp as a function of the requested brightness level set (0-255). The straight line shows an ideal linear response. In practice, the varying filament resistance is responsible for some slight deviation from the ideal. There are also minor deviations at the extremes due to the turn-on time of the Mosfets. Slave circuit The full circuit diagram for each four-channel lighting slave unit is shown opposite. This is separated into three sections (red-shaded, greenshaded and the rest) which correspond to separate, isolated areas on the PCB. Mains voltages are restricted to the redshaded part, while the isolated input stage is shaded in green. The remaining section operates at 5V DC, but is not necessarily ‘safe’. The main reason for this is that Digital Lighting Controller current vs brightness value 160 140 Measured current Ideal linear response 120 Lamp current (mA) Communications for light control 38 Digital Lighting Controller to a computer. We’ll show you how to connect the slaves up to various controllers in our follow-up article next month, as well as how to build a Micromite-based controller to provide similar functions to the previous design. This article will concentrate on describing the slave side of the design. As touched on above, it’s also easy to use an Arduino board to drive the Digital Lighting Controller slave unit, and this means you can also mix our mains lighting control slaves with other lighting elements such as addressable RGB strips. One thing to note is that you will need to add a simple transistor buffer to most serial sources if you intend to drive multiple slaves, especially if you plan to approach the maximum number of 16. That’s because a microcontroller pin can’t supply enough current to drive many slaves, especially with longish wires between them. Luckily, a transistor buffer is elementary to add. 100 80 60 40 20 0 0 32 64 96 128 160 192 224 256 Brightness value (0-256) Australia’s electronics magazine siliconchip.com.au                 SC  Fig.4: the slave circuit is quite simple thanks to the SI8751AB isolated Mosfet drivers. Adding a microcontroller allows a much simpler communications protocol compared to our earlier designs, eliminating the need for the master to send signals continually. DIGITAL LIGHTING CONTROLLER siliconchip.com.au Australia’s electronics magazine October 2020  39 the devices that we’ve used to separate the mains from the 5V sections are only available in a SOIC package. While rated for 630V of isolation, the SOIC package dimensions mean that necessary safety clearance requirements cannot be met; there is only 4.7mm between pins on opposite sides. Even with a slot down the middle of the device, this is not quite good enough. 4.7mm is sufficient separation in most cases, but it may not be adequate in conditions of high humidity or low air pressure (eg, at high altitudes). So we cannot rely on IC2-IC5 to provide safety isolation. Thus, there are two degrees of isolation between the mains voltages and the input control signals. The 5V section is completely closed off from the outside during operation. Opto-isolator OPTO1 comes in a DIL package which easily meets the safety clearance requirements. Slots are cut in the PCB down the middle of each isolation device, to improve creepage separation. Serial reception CON1/CON1a, CON9 and CON10 are used to receive the serial signal or pass it along to another slave unit. CON9 and CON10 are RJ45 sockets, allowing cheap CAT5 cables to be used. The two sockets allow the signal to be daisy-chained between slave units. CON1 and CON1a are provided for testing purposes, or if you wish to provide some other means of routing the control signal. We’ll discuss some options for this later. The incoming signal passes through a current-limiting 220Ω resistor into the LED of the 6N137 high-speed optoisolator, OPTO1. A 1N4148 diode (D1) is wired in reverse across OPTO1’s LED to protect it in case reverse voltage is applied. When the LED inside OPTO1 is driven, OPTO1’s pin 6 is pulled to ground (pin 5). At other times, it is pulled up to 5V by a 1kΩ resistor connected to pin 8. This signal goes to pin 5 on microcontroller IC1, which is configured to work as a UART receiver. IC1’s pins 3, 11, 12 and 13 are connected to each of the switches in four-way DIP switch S1, with the other terminals connected to ground. During operation, the microcontroller applies a weak pull-up to each of these pins, allowing it to detect the switch state. The four switches allow sixteen address combinations to be set, so that sixteen unique slave units can control up to 64 lamps. The switches are switched off during ICSP programming, as having pins 12 and 13 pulled to ground will interfere with the programming process. IC1 is a PIC16F1705 microcontroller which receives signals from the serial bus and controls the Mosfets to provide the required brightness for each controlled light. The PIC16F1705 is a close ‘cousin’ of the PIC16F1455 that we’ve used in a fair number of projects to date (eg, the Microbridge and Micromite LCD BackPack V2/V3). The main difference is that the PIC16F1705 lacks a USB controller, as we do not need it for this circuit. The 16F1705 is thus also slightly cheaper than the 16F1455. IC1’s pin 4 MCLR input is pulled up to 5V by a 10kΩ resistor. This pin, along with pins 12 and 13 connect to CON2, the ICSP (in-circuit serial programming) header. CON2 must never be used while the slave unit is connected to mains power; it is only for initial programming, Fig.5: the overlay diagram for the front panel board. The underside is externally visible and has cut-outs for the RJ45 connectors plus labels, including for the LEDs. Note that all the components are fitted to the underside in an unusual manner. The SMD LEDs are soldered in place upside-down, so that they shine through (and are diffused by) the fibreglass, while the header is surface-mounted so that the fibreglass forms an insulation barrier between the internal circuitry and the outside world. 40 Silicon Chip Australia’s electronics magazine siliconchip.com.au and is not needed if you build the unit using a pre-programmed chip. Mains-powered light control Pins 6, 7, 8 and 9 of IC1 drive the input pins (pin 3) of IC2-IC5. These are SI8751 isolated Mosfet gate drivers which contain RF circuitry capable of transmitting enough power across their internal silicon isolation gap to drive a Mosfet gate directly. IC2-IC5 also have a TT pin (pin 2) which sets the internal drive strength and thus the Mosfet gate turn-on time. In this case, it is connected to ground for the fastest turn-on. On the output side, IC2-IC5 generate a positive voltage on their pin 8 relative to pin 5. These are connected to the gate and source of the output transistors, respectively. The Mosfets are connected back-to-back, with gates and sources commoned. Their drains form the external connections between the Active and load. Using this arrangement means that the intrinsic diodes are connected back-to-back to prevent conduction when the Mosfets are off. In practice, the gate turn-on is actually quite slow, taking hundreds of microseconds. This is due to the fairly weak drive of the SI8751 ICs, combined with the doubled Mosfet gatesource capacitance. Fortunately, as we turn on the Mosfets at the zero crossings, when the instantaneous mains voltage is very low and minimal current is flowing, Mosfet dissipation during switching is low. The turn-off is much quicker, which is crucial as it can occur at any point in the mains cycle. The Mosfet drains are also connected via high-voltage 10pF capacitors to the Miller clamp pins (pins 6 and 7) on IC2-IC5. The SI8751 devices have circuitry to clamp the source to the gate (thus forcing the Mosfet off) if conditions are detected which might inadvertently turn the Mosfet on. This would mainly be due to parasitic internal capacitance between each Mosfet drain and gate. The pairs of back-to-back Mosfets connect between the incoming Active and the respective output Active connection on CON4-CON7. The Neutral and Earth connections on CON4CON7 connect straight back to the input, CON3. So when a Mosfet pair is off, no current flows to its load, but when the Mosfet pair is on, current can flow so the attached lamp can light. Zero-crossing detection To detect the phase and zero crossings of the mains sinewave, two 4.7MΩ seriesconnected high-voltage safety resistors connect the incoming Neutral to the 5V circuit’s ground, with an identical arrangement connecting Active to IC1’s pin 10. This high-impedance circuit is sufficient to safely sense the polarity and thus (when the polarity changes The “business end” of the front panel showing how the SMD LEDs are soldered in position. All the bottomemitting SMD LEDs we found were designed to shine through a hole, which would breach the fibreglass isolation barrier. Hence, our use of standard SMD LEDs soldered upside-down. siliconchip.com.au Australia’s electronics magazine at the zero crossing), the phase of the mains waveform. Status indication Several front-panel LEDs, mounted on a separate front panel PCB, indicate the state of the slave. Each LED has a 1kΩ current-limiting resistor on the main board. LED1 lights up when OPTO1’s output is low. Since the idle state of the serial data is high, LED1 is off until serial activity occurs. The remaining LEDs are lit when their associated signal level is high. LED2-LED5 are driven by the same signals that are fed to the Mosfet drivers, and thus show the output states. Due to persistence of vision, even a very low lamp output level shows clearly on the LEDs. LED6 is connected to IC1’s pin 2 (which is not used for anything else) and is used to flash error codes. LED7 is driven by the 5V rail, and so indicates when 5V power is available. The front panel PCB connects to the main PCB by a short 10-way ribbon cable. The LEDs are fitted upsidedown to shine through the PCB and illuminate the letters made from the PCB solder mask. As well as providing clear lettering, the use of a PCB as front panel also means that a better level of isolation is provided than if, say, the LEDs were mounted through holes in the front panel. Power supply Mains power is applied via barrier terminals CON3. The Active current passes through 5A fuse F1, which protects against any faults on the PCB and further downstream, including connected lamps. As well as going to the lamps (via Mosfets in the case of Active), the Active and Neutral lines also both feed into MOD1, an integrated 230V AC to 5V DC converter. It’s capable of delivering 2W (ie, 400mA) which is easily sufficient for this circuit. MOD1 has an isolation voltage rating of over 3kV AC and has more than 25mm between its input and output pins. Its 5V output powers all the ICs on the board (IC1-IC5) and OPTO1. Each of these has a local 100nF supply bypass capacitor. Serial protocol For the correct signal polarity, the incoming DATA- line (which connects October 2020  41               Fig.6: assembly of the main PCB is relatively straightforward. It uses a mix of SMD and through-hole parts; it’s generally easiest to fit the SMDs first, then the low-profile through-hole parts, then the taller parts like the connectors. Be careful with the orientations of the ICs, polarised headers, DIP switches and the diode; all other parts either only go in one way around, or it doesn’t matter. Clean off any flux residue around the isolators, slots or safety resistors to ensure sufficient creepage distances. Note that this diagram and the photo opposite are reproduced slightly smaller than life size to fit on the page (about 85%). to pin 2 of the RJ45 sockets CON9 and CON10) is the serial data source, while the DATA+ line should connect to the signal source’s supply rail (eg, 3.3V or 5V). This way, current will flow through OPTO1’s LED when a logic low is transmitted, meaning that OPTO1’s output will be in-phase with the incoming signal. You could run the slave unit from an RS-232 level signal, which usually has a swing of something like ±12V. In this case, DATA+ connects to the TX signal, with DATA- goes to the RS232 bus’ ground. As RS-232 signals are inverted compared to TTL signals, the resulting inversion due to OPTO1 means that the signal going to IC1 has the correct phase. In any case, D1 prevents damage if the signal is misconnected. Much of our serial protocol has been borrowed from DMX-512, which should make it possible to use existing software libraries to generate the necessary data, even though the electrical signal levels are different. How42 Silicon Chip ever, you will need to adjust the baud rate to 38,400. A DMX-512 ‘frame’ contains enough data to set the state of all addressed devices; the slave unit state (brightness levels) doesn’t change until it receives a frame telling it to update this state. The DMX-512 protocol documentation refers to ‘mark’ and ‘space’ states. Like most serial protocols, the mark state is the same as the idle (no data being sent) state, which is a logical ‘1’. A space is the same as a logical ‘0’. For the most part, it is similar to other serial formats. A single ‘0’ (space) starts each byte, followed by the eight data bits and a single ‘1’ (mark). To synchronise the transmitter and receiver, a ‘break’ condition is sent down the serial line. This is a space state of at least 20 bit times. This is recognised by the receiver as normal data must not spend more than nine bit times in the space state. In our case, IC1’s serial peripheral can detect a break of 13 bit times or longer, so we simply use this condiAustralia’s electronics magazine tion. It manifests as a data framing error with a data byte of 0x00 (all spaces). The first byte after the ‘break’ is called a start code, which identifies the type of data which is in the frame being sent. A start code of 0x00 is used to indicate that the following data should be used to set the channel levels; in our case, the dimmer duty cycle and thus the lamp brightness. After this, the bytes are sent in order of the devices they are addressed to. The second byte after the break is for device 0, the next for device 1, and so forth. At 38400 baud, it takes around 17ms to transmit data for 64 channels, so updates can occur 60 times per second, if necessary. Software operation When power is applied, IC1 checks its address by querying the states of the switches in S1. Thus, the address cannot be changed during operation (you shouldn’t have the enclosure open anyway!) As each slave unit can control siliconchip.com.au While none of the SMD parts on this board are hard to solder, you do need to use the right technique to avoid frustration or bad joints. We strongly suggest spreading flux paste on the large pads for Mosfets Q1-Q8 before placing the part. This way, when you apply solder to the tabs, it will readily flow under the devices and form a good connection with the PCB. You need a hot iron to solder those tabs due to the thermal mass of those parts. The installation of ICs IC2-IC5 is straightforward, but make sure that if you bridge any pins, you clean up those bridges with solder wick and some extra flux. four outlets, the address switches are marked +4, +8, +16 and +32. Setting all switches off will mean that this slave unit responds to addresses 0, 1, 2 and 3. To set the next addresses, 4, 5, 6 and 7, set switch +4 to on. With all the switches set, the total base address is +60, so that the slave responds to addresses 60, 61, 62 and 63. When the UART receives a break signal, an internal counter is reset. The first byte is checked to ensure that channel data is being sent (start code 0x00) and the counter continues to increment for each byte received. Any other start codes are ignored. If the incoming data is addressed to one of the outputs controlled by the slave unit, an internal variable is updated with the new intensity setting. There is no synchronising latch, as the output can only be turned on at the start of each cycle, but the software continually checks if it needs to be turned off. Due to the relatively slow turn-on time of the Mosfet gate drive ICs, we siliconchip.com.au need to set the outputs high slightly in advance, and this is possible because the threshold of the zero crossing is not quite at zero. This means that the zero detection pin changes state slightly before the zero crossing in one direction and slightly after in the other. So we use the early pin state change to trigger the start of the Mosfet cycle, with an internal counter keeping track of when the Mosfets should be switched off. We also use the internal counter to time when the Mosfet turn-on should occur at the other zero-crossing. The software logic also avoids triggering for a period early in each cycle, which makes it more resistant to noise on the mains line. With this in mind, IC1 turns on each output around the zero crossing (if the brightness setting is not zero). It then turns it off at the appropriate time during each mains half-cycle, unless a 100% duty cycle is requested, in which case the output remains on continuously. Australia’s electronics magazine An array loaded with scaling factors is used to give a more linear relationship between the input value and output brightness. This is necessary because of the way the voltage varies across each half-cycle. For example, to achieve one quarter lamp intensity, the output is set for the first third of the cycle, as the area under an ideal (sinusoidal) mains waveform is the same for the central (peak) third as for the other two-thirds combined (because the integral of a sinewave between 0° and 60° has the same value as the integral of a sine wave between 60° and 90°). Of course, the actual response will depend a lot on the nature of the connected lamp; incandescents and LEDs will all differ, but this result will be closer to linear than without this compensation (see Fig.3). Finally, pin 2 is brought high if a fault occurs, for example, if no zero crossing is detected for a longer period than expected. The way the outputs are controlled means that they October 2020  43 will default to off if no zero crossing is detected. An interesting feature of the software is that it does not need to use interrupt routines to respond to events, because there usually is nothing happening. Thus the main body of the program consists of nothing more than checking the interrupt status flags and reacting as needed. The software is designed to work with 50Hz mains, but will work with 60Hz. As the mains cycles are shorter, any brightness values above 238 will result in full intensity. Also, the linearity compensation will not be as wellmatched as with a 50Hz supply, but otherwise, it will be fully functional. The power supply module we are using is capable of working down to 100V. Thus, the slave unit is fully capable of working with practically all common mains voltage and frequency standards. Construction Start construction with the front panel PCB, which is coded 16110203 and measures 251mm x 75mm. It hosts a few surface-mounted parts, but they are not difficult to solder and space is plentiful. Refer to its PCB overlay diagram, Fig.5, to see which parts go where. The usual surface mount gear is helpful. This includes tweezers, magnifiers, flux paste and solder braid. In a pinch, a fine-tipped soldering iron may be sufficient. Fume extraction is a very good idea too, especially when using flux as it will generate some smoke. The seven LEDs are mounted unusually, with their lenses towards the PCB. This allows the light to be diffused by the PCB material and be masked by the front copper layer. While reversemount SMD LEDs exist, they are usually designed to slot into a hole in the PCB, and having such a hole would defeat the purpose of using the panel for isolation. You could use through-hole LEDs, but we found that they did not shine as well as the surface-mounted types. It isn’t difficult to solder the LEDs in place upside-down; you just need to be generous with the solder. Work with each colour in turn to avoid mixing them up. Apply a blob of solder to one pad for each LED. Then hold the LEDs in place with tweezers, observing the orientation of the cathode as marked on the PCB (usually indicated by a green dot or ‘T’). Carefully manipulate the LED as you 44 Silicon Chip apply heat, aiming to get the LED in the correct location. Once this is done, solder the other lead, using plenty of solder. If necessary, apply flux to the first lead and reapply the iron to dress the joint. When moving from one lead to the other, wait for a few seconds to ensure that the solder has hardened. The LED may slip off if both leads are heated at the same time. While CON11 is a regular throughhole header, it is surface-mounted to maintain isolation. You might like to fit a header socket onto the pins to align them while soldering. This will keep the pins located correctly in case the plastic holder melts slightly. Check the orientation of the locking tab against the silkscreen and rest the locking header in place. The usual philosophy for surface mount parts applies, just with much larger clearances. Tack one pin in place, check that the other pins are centred and flat on their pads, then apply solder to the remaining pins. If necessary, go back and refresh the first pin. You might wish to apply solder to the other end of the pins to add extra strength. The downside of this mounting method is that the mechanical strength of the header is not as good as if it were mounted normally. So take care when plugging and unplugging the cable later. Once you have confirmed that everything is working, you might like to secure the header with neutral-cure silicone sealant. Don’t use acetic cure sealant as it may cause corrosion. Main PCB assembly Continue assembly now with the main PCB, which is coded 16110202 and measures 216 x 133mm. Fig.6 is its overlay diagram, which you should refer to as you read the following instructions. Fit the SMD parts (IC2-IC5) by applying flux paste to the pads and tacking the SOIC ICs by one pin. Observe the orientation dot and bevel, which should be on the side closest to IC1. Adjust the ICs if necessary and then solder the remaining pins. If a bridge occurs between pins, solder the remaining pins and carefully use the solder braid to draw the excess solder from the pins, using extra flux if needed. The eight output Mosfets (Q1-Q8) are also SMDs, but are not small, which makes them easier to manage. Fit these next. Australia’s electronics magazine Rest each Mosfet within its footprint. Ensure the large drain pad is visible under the edge of the Mosfet to allow better access with your soldering iron. As with other surface-mounted parts, apply flux paste (especially important on the large pad) and tack one of the smaller (source or gate) leads in place. Using tweezers, adjust the positioning if necessary, ensuring it is flat against the PCB. With this done, solder the other small lead to its pad. There should be enough room to gently push down on the lead with the iron while introducing the solder into the side, where the lead touches the pad. For the larger drain lead, add some solder to the iron tip and press it gently against where the large tab meets its pad. Feed the solder in nearby, using the heat of the component tab to melt the solder. Once the tab is hot enough, the solder will melt and spread freely. You may need to increase your iron temperature to achieve this. Feed in enough solder to form a fillet that goes the full width of the part, then remove the solder and then the iron. Leave the board stationary for a few seconds until the solder solidifies. Once IC2-IC5 and Q1-Q8 are fitted, clean any excess flux from the PCB using a recommended cleaner, especially as some of these parts sit astride an isolation slot. Once clean, allow the PCB to dry thoroughly. Through-hole parts For all the remaining parts on this board, it’s essential to ensure that they have reliable solder joints without excess solder and to trim the leads properly, to avoid affecting the safety isolation. Start by fitting the four 4.7MΩ safety resistors next; these are slightly larger than the others. Ensure that the joints are solid and clean without excess solder. Then mount the remaining resistors, followed by the capacitors. None of these are polarised; refer to Fig.6 to see which types go where. Install the single diode (D1), being sure to orientate its cathode band as shown. Then fit the fuse into the fuse clips to align them and ensure that they are orientated correctly, before soldering them in place. Remove the fuse for now. Fit OPTO1 next. Gently bend its leads inwards and slot it into the PCB, with pin 1 on the ‘safe’ side of the isolation barrier. Solder one pin on siliconchip.com.au each side, checking that the part is flat against the PCB before soldering the remainder. You might like to fit a socket for IC1, but this is probably not necessary if it is programmed already. It should be fitted with its pin 1 adjacent to the 100nF capacitor. Now mount pin header CON2 but only if you still need to program IC1. Then fit CON8, but being a locking type header, you also need to orientate it correctly. You can also fit a two-way header to either CON1 or CON1a now (they are connected in parallel). These are not needed for regular operation, but can be useful for testing. CON9 and CON10 are the RJ45 sockets that pass through the front panel. Thus they must both be fitted, regardless of whether you plan to use them, or else there will be a hole in the panel (and that would be unsafe). Working with one socket at a time, slot it into the PCB and tack in place with one pin. Double-check that it is straight, as it may not fit the front panel otherwise. It’s a good idea to test-fit the front panel before soldering the remaining pins. S1 can be fitted either way, but it makes sense to fit it so that the switches are on when towards the addresses near the board edge. Use a multimeter to check this if necessary before soldering in place. If you need to program IC1, ensure that all the switches are off initially. MOD1 should only fit one way, but double-check the markings first. The side marked AC must be closest to the mains input connector. Then solder and trim its leads. The final parts on the PCB are the five barrier terminals for connecting the mains cables. Solder them in place, keeping them flat against the PCB. Front panel cable The front panel connection cable is a 10-way ribbon cable with polarised line sockets at either end, wired straight through (ie, pin 1 to pin 1 etc). Both ends will look the same, and it doesn’t matter which way it is fitted. Refer to Fig.7 for details. Separate the wires at each end of the ribbon cable, strip off a little insulating, then crimp and/or solder them into the pins. When pushing the pins into the plastic blocks, ensure that they click into place (use a tiny screwdriver to push them in further if necessary), siliconchip.com.au Parts list (for one slave unit) 1 double-sided main PCB coded 16110202, 216mm x 133mm 1 double-sided front panel PCB coded 16110203, 251mm x 75mm 1 ABS instrument case (260mm x 190mm x 80mm) [Altronics H0482, Jaycar HB5910] 3 M3 x 6mm panhead machine screws 2 M3 x 20mm machine screws 2 12mm Nylon untapped spacers 1 sheet Presspahn or similar insulation, cut to 215 x 100mm [eg Jaycar HG9985] 1 2-pin header (CON1; optional) 1 5-pin header (CON2; optional, for ICSP) 5 3-way barrier terminals, 8.25mm pitch (CON3-CON7) [Altronics P2102] 1 10-pin 2.54mm locking header (CON8) [Jaycar HM3420, Altronics P5500] 2 PCB-mount RJ45 sockets (CON9,CON10) [Altronics P1448] 1 10-pin 2.54mm right-angle locking header (CON11) [Jaycar HM3430, Altronics P5520] 2 10-pin 2.54mm locking line sockets [Jaycar HM3410, Altronics P5480 + 10 x P5470A] 1 10cm length of 10-way ribbon cable or similar 1 covered M205 fuseholder (for F1) [Altronics S5985] 1 5A M205 fast-blow fuse (F1) 1 Meanwell IRM-02-5 230V AC to 5V DC 2W switchmode converter # (MOD1) [Digi-key 1866-3009-ND] 1 4-way DIP switch (S1) 1 14-pin DIL IC socket (optional; for IC1) Semiconductors 1 PIC16F1705-I/SP microcontroller programmed with 1611020A.HEX (IC1) 4 Si8751AB isolated Mosfet drivers, SOIC-8 (IC2-IC5) # 1 6N137 high-speed opto-isolator, DIP-8 (OPTO1) # 8 SiHB15N60E 600V SMD Mosfets*, TO-263 (Q1-Q8) # 1 green SMD LED, 3216/1206-size (LED1) # 5 yellow SMD LEDs, 3216/1206-size (LED2-LED6) # 1 red SMD LED, 3216/1206-size (LED7) # 1 1N4148 small signal diode (D1) Capacitors 6 100nF 63V MKT 8 10pF 3kV SL0 ceramic # Resistors (all 1/2W 1% metal film axial, except where noted) 1 10kW (brown black orange brown or brown black black red brown) 8 1kW (brown black red brown or brown black black brown brown) 1 220W (red red brown brown or red red black black brown) 4 4.7MW 3.5kV safety-rated resistors # (eg, VR37000004704JA100) Mains connectors (see text for alternatives) 4 mains flush-mount panel sockets [Jaycar PS4094, Altronics P8243] 1 mains lead with fitted 3-pin plug [Jaycar PS4110], or extension lead with socket end cut off 1 cable gland to suit mains lead 1m 10A-rated 3-core mains cable (could be cut from an extension lead) 10 small cable ties # These components are available as part of a pack of hard-to-get parts from the SILICON CHIP ONLINE SHOP (cat SC5636). The programmed micro and PCBs are sold separately and also check that the pins are in the right order at each end. Once it’s finished, plug it in at both ends to connect the two boards. Programming the PIC If you need to program the PIC, now Australia’s electronics magazine is a good time. We recommend using a PICkit 3 or PICkit 4 with the MPLAB X IPE software. MPLAB X can be downloaded from www.microchip.com/ mplab/mplab-x-ide The latest version only supports computers with 64-bit processors, October 2020  45 Fig.7: the front panel cable is made from a pair of 10-way polarised crimp headers. Each end is wired the same, so the cable is reversible. The pins will also line up directly between the front panel and the main PCB when both are correctly mounted in the enclosure. but you can download older versions from https://www.microchip. com/development-tools/pic-anddspic-downloads-archive Connect the programmer to CON2 and open the IPE. Select PIC16F1705 from the “Device” dropdown menu. You will also need to enable “Power target from tool” on the Power tab. Click “Apply”, then “Connect”, and ensure that communication is working. If not, you should check that the PCB is assembled correctly. Next to HEX file, click “Browse” and find “1611020A.HEX” (available for download from our website), then click “Program”. If you watch the front panel LEDs, you should see the PWR LED light up as the PICkit applies power to the circuit. Final assembly The two PCBs can now be fitted into the case. The main PCB sits towards the front of the case, to allow room at the rear for the mains sockets. It attaches to five moulded plastic posts using M3 machine screws, with the longer screws and spacers used for the two holes closest to the mains terminals. Once that’s in, you can slot the front panel PCB in place. To keep the slave unit as compact as possible, we are using flush-mount style mains sockets. These require a specific cut-out to be held securely; we recommend tracing our template (available as a PDF download from our website) and drilling them as accurately (a drill press will make this much easier) before finishing with a file or hobby knife. It’s essential to cut these accurately, if too much material is removed, there may not be sufficient left to retain the socket properly. Also, drill the hole as shown for the incoming mains lead. 46 Silicon Chip Fig.8: a simple test lead can be made from a cable with an RJ45 plug at one end (eg, an Ethernet cable cut in half) with header plugs or male jumper wires attached to two of the bare wires. The cables we used had the colours shown, although others could be wired differently. Pin 1 goes to the Uno 5V, with the adjacent wire to pin D1 (TX). This lets you use a Micromite or Arduino board to test the Slave unit. This is sized to suit the cable gland. Pre-wire each socket before fitting into the panel, as access will be more difficult once they are on the panel. Cut four 15cm pieces of three-core mains cable and strip the outer insulation from about 5cm at each end. Cut 2cm off the end of the Active and Neutral wires at one end. As the Earth lead is longer, it will be disconnected from the barrier terminals last if the cable is yanked out. Then strip 6mm from both ends of each inner core. Screw the un-shortened ends into the panel sockets; brown for Active (A or L), blue for Neutral (N) and green/ yellow for Earth (E). Separate the panel sockets and attach them to the rear panel via the mounting holes. Then secure the free ends of the mains leads into the terminals of CON4-CON7. Insulation To ensure that you can’t accidentally come in contact with any of the exposed metal at mains potential, cut a 215x100mm sheet of Presspahn or similar and drill or cut two 3.5mm holes in it, centred 6.5mm from the short ends of the sheet (ie, 202mm apart). If you aren’t sure what it should look like, refer to our photos. Place this over the high-voltage section and attach it using the two longer PCB mounting screws with spacers. Mains input Since the rear panel space is already quite cramped, the incoming mains lead is captive and secured by a cable gland. To reduce the possibility of tampering and the chance of the lead being pulled through, the nut of the cable gland is installed inside the case. While working, plug the mains plug lead into one of the sockets. This will eliminate the possibility of it being Australia’s electronics magazine inadvertently powered up while you are working on it. Thread the body of the cable gland in place as shown in the photos, then thread the free end in from the outside. As with the other leads, cut the Active and Neutral leads around 2cm shorter, then trim 6mm from the bare ends. Screw these into the Mains In barrier terminal (CON3), observing the correct colour coding, then slot the rear panel in place. Before closing the case, use the cable ties to secure the groups of mains leads together as shown and tighten up the cable gland firmly. You can add a drop of cyano-acrylate (eg superglue) to the threads to secure it, although as it’s on the inside, as long as you do it up tight, it should be fine. The final step before closing the case is to fit the fuse. It should be a 5A fastblow type. Fit the top of the case and fasten with the included screws. Alternative mains connections We’ll describe two alternative connector arrangements, but like all mains wiring, they should be approached with caution. These have the advantage of requiring less work on the rear panel. Both require running three-core mains lead through the rear panel. If the lamps you are using do not need to be disconnected from the slave unit, they can be permanently wired into the barrier terminals. You should use the same procedure as described above for the incoming mains lead, securing the cords with cable glands fitted inside the enclosure and also secure the leads with cable ties. Another option is to use pre-wired mains sockets cut from extension cables. These can be found for just a few siliconchip.com.au dollars each. They must also be secured to the rear panel using a cable gland and with cable ties fitted. Testing If you have lamps that you wish to plug in for testing, do that before connecting the slave unit to the mains. It’s a good idea to have good access to a switched socket, so you can quickly shut off the power in the event of a problem. Make sure the enclosure lid is secure, then plug in the mains lead and switch on the power. You should see the PWR LED light up, possibly followed by the AUX LED. Your attached test lamps should not light, nor should any of the CH0-CH3 LEDs or the COM LED. If all is well, you can continue testing with a control signal. Test controls The COM LED is active whenever the OPTO1 input is being driven, so this part of the circuit can be tested by merely applying 3V-5V between the DATA+ (positive) and DATA- (negative) connections. When mains power is disconnected, the AUX light should light up briefly as the 50Hz waveform disappears but IC1 continues to receive power from the capacitors in MOD1 for a few seconds. As we noted near the start, the slave unit uses a straightforward serial protocol. If you have an Arduino board (we used the Uno, but boards such as the Mega should work too), then we’ll show a simple test rig you can make to inject control signals into the slave unit. You could use this as the basis of your controller, depending on what you have in mind. Upload our test sketch file (available for download from our website) to the Uno, and wire up a CAT5 lead as shown in Fig.8. The Uno simply produces patterns to cycle through each lamp in turn (using addresses 0-3), ramping each up and down in brightness. Even with no mains lamps connected, you should see the CH0-CH3 LEDs on the front panel cycling on and off in turn. If all these things are working, then the slave unit is fully functional. You might like to experiment with your own Master controller, or wait until next month when we will describe our design. SC siliconchip.com.au (Above): the wired slave unit from the rear, which also shows the four flush-mounted mains outlets. To complete the unit, we drilled a sheet of Presspahn insulation (as shown at right) which fits over the exposed mains circuitry on the PCB, (as shown below). m 50m You may need to trim some of the mounting posts m 202m inside the bottom of the enclosure so that they don’t foul the component 225 x 100mm leads on the Presspahn or similar underside. Australia’s electronics magazine October 2020  47 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. Automatic solar panel checker I built this unit for our local recycling shop so they can test solar panels. A lot of solar photovoltaic panels go to waste in Australia. This is a perverse outcome of the way we encourage the uptake of solar power through the issuing of renewable energy certificates. If you have an existing installation you wish to expand, the only commercial solution available to you is to remove your existing system and replace it with a larger one. This is feeding our recycling industry with thousands and thousands of perfectly serviceable solar panels. While there is no technical 48 Silicon Chip reason why these panels can’t be reused in grid-connected applications, there are various regulatory hurdles. So a fantastic resource is available for those who have non-grid-connected applications. The ability to test a solar panel in the field quickly and easily helps greatly. People are led to believe that these panels are being scrapped because they are faulty. In my experience, this is not the case. Apart from physical damage or moisture damage, both of which you can evaluate from an inspection, I have never seen a faulty panel. Australia’s electronics magazine I have seen short-circuited bypass diodes which make a panel appear faulty, but these can be removed (and replaced if desired, but the panel will work without them). I haven’t tested hundreds of panels; I’m sure faulty panels exist, but the majority of panels being scrapped are perfectly serviceable. A portable panel tester enables someone buying a used panel to test it first. Panel performance can be evaluated by a short-circuit current test and an open-circuit voltage test. This essentially quantifies the endpoints of the panel’s IV performance curve. By siliconchip.com.au 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 comparing these to the factory-specified values on the panel’s label, you can determine the state of the panel. Note though that the open-circuit voltage is temperature-dependent, and the short-circuit current is dependent on the level of illumination. In short, the factory-specified performance may be hard to replicate at the dump. The illumination problem can be solved by having a reference cell; I used a salvaged panel from a discarded solar garden light, which measures the ambient illumination and normalises the measured short-circuit current back to reference conditions. This device is cheap and easily assembled by a hobbyist. The circuit is powered from the panel. The zener diode based Darlington series preregulator limits the supply to the input of REG1 to about 20V. The 470µF capacitor at the cathode of D1 acts as an energy store to keep the microcontroller and display going while we short out the panel to test the short circuit current. The panel sensing conditioning electronics consist of a resistive voltage divider to measure the open-circuit voltage while logic-level switching Mosfet Q3 momentary short-circuits the panel. The short-circuit current is measured using an integrated Hall-Effect current sensor module, but a resistive shunt would work too (eg, two 0.1W resistors in parallel). We short the panel for about 10ms every second or two, so a shunt needn’t be rated for very high power. The Arduino Nano monitors the panel voltage and current, the reference voltage from the small solar panel and controls Mosfet Q3 while displaying the results on a 16x2 Alphanumeric LCD. You could also use an Arduino Uno; that way, a standard LCD pushbutton shield can be used, and the solar panel tester is reduced to a piggyback shield between the Arduino and the display shield. The Arduino sketch for this design is available for download from siliconchip.com.au the Silicon Chip website. It provides logarithmic correction for the opencircuit voltage and a linear correction for the short-circuit current according to the level of illumination. This works quite well; in the late afternoon of an overcast day (9% illumination), it estimated a 250W panel to be rated at 196W; not a perfect result, but good enough to let you know that the panel is probably OK. Note that when using this test, a visual inspection of the panel is still important. A common failure is delamination of the plastic backing ma- terial which lets moisture in. If the panel has bypass diodes, the shortcircuit test may suggest a good panel if the unbypassed section of the panel is still functioning. Bypass diodes can also fail shortcircuit, which will make a good panel look faulty. Shorted diodes cause the panel’s open circuit voltage to read low even though the panel itself is undamaged. So in summary, to be 100% sure, disconnect the bypass diodes before testing. Dennis Stanley, Crawley, WA. ($120) Touch-switch using a 4011B IC The touch-operated switch described here is very easy and cheap to build. The switch uses minimal current when not activated, so it is ideal for battery-operated projects. The RS flip-flop made by the two NAND gates is set when a finger bridges the “ON” touch plate contacts and is reset when the finger bridges the “OFF” touch plate contacts. That’s because input pins 1 and 6 of IC1 have very weak pull-ups via 10MW resistors, and the resistance of human skin is much lower (generally under 100kW), so can pull those inputs down briefly. The changing level of output pin Australia's Australia’s electronics magazine 3 of IC1 drives transistor Q1 to energise or de-energise the coil of relay RLY1, switching the attached load on or off. It is shown powered from a separate battery, but it could be the same one. A normally reverse-biased diode across the relay coil protects Q1 from the back-EMF induced when the relay coil is de-energised. You can make touch plates by cutting a piece of copper laminate or sheet in half. There should be a little gap between the two halves of each touch plate. Raj. K. Gorkhali, Hetauda, Nepal. ($65) October ctober 2020  49 2020  49 Induction headphones for hearing aid users Being retired and with a five-acre property, I spend considerable time on a tractor and ride-on mower, which results in a fair level of noise exposure. But, being bilaterally profoundly deaf, I am immune to the noise and only aware of it when wearing my cochlear implant sound processors. For safety, I need to hear some level of noise for situational awareness. Furthermore, my very expensive sound processors need to be protected from accidental removal by tree branches and shrubs. Headbands tend to be too flimsy for the task, and most hats don’t come down to ear level. Recently, I came across my old hearing protection muffs which provide full ear coverage. While not perfect, they cover the hearing aids and sound processors. Having already installed a hearing loop in the TV room (as described in Circuit Notebook, August 2020; siliconchip.com.au/Article/14538), I thought, why not try to make a pair of induction headphones? The result is I can now ride around the property and listen to my favourite AM news programs and FM stereo music coming from a small pocket radio. My noise protectors had a conveniently-shaped plastic profile behind the soft earmuffs, almost like a bobbin. This shape made a good coil former on which to wind 24 turns of 0.25mm diameter enamelled copper wire, as shown in the photo. I terminated the windings inside the plastic earcup through a 1mm hole drilled for the purpose. I then drilled more holes in the lefthand ear cup; one for the incoming two-core shielded cable, plus one for a small screw to anchor an internal solder lug. The cable’s shield braid is soldered to the lug for strain relief. A third hole at the top of the left cup allows a lightduty figure-8 cable to connect the right sound channel to the right ear cup, also through a right-side hole drilled for the purpose. I then attached the cable to the headband using hot-melt glue. The wiring is hidden behind the foam acoustic pads inside the ear cups. To limit the current load on the radio’s stereo audio output amplifiers, I wired 47W series resistors in the left and right channels. The small resis50 Silicon Chip tors can be either wired into the stereo plug at the radio end of the cable, or inside the left-side ear cup, insulated with heatshrink tubing. The second option affords more working space. It is worthwhile using a good-quality stereo plug to achieve reliable connections to the radio and the exiting cable. When internally connecting to the fine enamelled copper wire, strain relief can be achieved by soldering very light stranded hookup wire to the ends of the solid copper and insulating it with heatshrink tubing. The joints can be further protected with hot-melt glue or another suitable adhesive. When using these, I find that external machinery noise is still audible but greatly reduced by the hearing aid or sound processor attenuation combined with attenuation from the earmuffs. The performance and listening comfort is really pleasing from something that costs very little to build, especially if you already have a radio and earmuffs lying around. Anthony Leo, Cecil Park, NSW ($80). Between the earmuff cover and the housing there was a large enough gap to wind copper wire for the hearing loop. Three holes were drilled in the earmuffs, two at the bottom for the incoming audio plus solder lug, and one at the top to provide audio to the right-side ear. Australia’s electronics magazine siliconchip.com.au SILICON CHIP .com.au/shop ONLINESHOP PCBs, CASE PIECES AND PANELS 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 COLOUR MAXIMITE 2 PCB (BLUE) JAN20 JAN20 FEB20 FEB20 MAR20 MAR20 MAR20 APR20 APR20 APR20 APR20 MAY20 MAY20 JUN20 JUN20 JUN20 JUN20 JUL20 01112191 06110191 27111191 01106192-6 01102201 21109181 21109182 01106193/5/6 01104201 01104202 CSE200103 06102201 05105201 04104201 04104202 01005201 01005202 07107201 Subscribers get a 10% discount on all orders for parts $10.00 $2.50 $5.00 $20.00 $7.50 $5.00 $5.00 $12.50 $7.50 $7.50 $7.50 $10.00 $5.00 $7.50 $7.50 $2.50 $5.00 $10.00 ↳ 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 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 JUL20 JUL20 JUL20 JUL20 JUL20 AUG20 AUG20 AUG20 SEP20 SEP20 SEP20 SEP20 SEP20 SC5500 19104201 SC5448 15005201 15005202 01106201 18105201 04106201 04105201 04105202 08110201 01110201 01110202 $10.00 $5.00 $7.50 $5.00 $5.00 $12.50 $2.50 $5.00 $7.50 $5.00 $5.00 $2.50 $1.50 OCT20 OCT20 OCT20 24106121 16110202 16110203 $5.00 $20.00 $20.00 NEW PCBs D1 MINI LCD WIFI BACKPACK FLEXIBLE DIGITAL LIGHTING CONTROLLER SLAVE ↳ FRONT PANEL (BLACK) PRE-PROGRAMMED MICROS As a service to readers, Silicon Chip Online Shop stocks microcontrollers and microprocessors used in new projects (from 2012 on) and some selected older projects – pre-programmed and ready to fly! Some micros from copyrighted and/or contributed projects may not be available. $10 MICROS ATtiny85V-10PU ATtiny816 PIC10F202-E/OT PIC12F617-I/P PIC12F675-I/SN PIC16F1455-I/P PIC16F1455-I/SL PIC16F1459-I/P PIC16F1705-I/P PIC16F88-I/P PIC16LF88-I/P $15 MICROS Shirt Pocket Audio Oscillator (Sep20) ATtiny816 Development/Breakout Board (Jan19) Ultrabrite LED Driver (with free TC6502P095VCT IC, Sep19) Door Alarm (Aug18), Steam Whistle (Sept18), White Noise (Sept18) Trailing Edge Dimmer (Feb19), Steering Wheel to IR Adaptor (Jun19) Car Radio Dimmer Adaptor (Aug19) Tiny LED Xmas Tree (Nov19) Microbridge and BackPack V2 / V3 (May17 / Aug19) USB Flexitimer (June18), Digital Interface Module (Nov18) GPS Speedo/Clock/Volume Control (Jun19) Ol’ Timer II (Jul20) 5-Way LCD Panel Meter (Nov19), IR Remote Control Assistant (Jul20) Ultrasonic Cleaner (Sep20) Flexible Digital Lighting Controller Slave (Oct20) UHF Repeater (May19), Six Input Audio Selector (Sept19) Universal Battery Charge Controller (Dec19) GPS-synchronised Analog Clock Driver (Feb17) ATmega328P RF Signal Generator (Jun19) PIC16F1459-I/SO Four-Channel DC Fan & Pump Controller (Dec18) PIC32MM0256GPM028-I/SS Super Digital Sound Effects (Aug18) PIC32MX170F256D-501P/T 44-pin Micromite Mk2 (Aug14), 4DoF Simulation Seat (Sept19) PIC32MX170F256B-50I/SP Micromite LCD BackPack V1-V3 (Feb16 / May17 / Aug19) GPS-Synched Frequency Reference (Nov18), Air Quality Monitor (Feb20) RCL Box (Jun20) PIC32MX270F256B-50I/SP ASCII Video Terminal (Jul14), USB M&K Adaptor (Feb19) $20 MICROS PIC32MX470F512H-I/PT Stereo Echo/Reverb (Feb 14), Digital Effects Unit (Oct14) PIC32MX470F512H-120/PT Micromite Explore 64 (Aug 16), Micromite Plus (Nov16) PIC32MX470F512L-120/PT Micromite Explore 100 (Sept16) $30 MICROS PIC32MX695F512L-80I/PF PIC32MZ2048EFH064-I/PT Colour MaxiMite (Sept12) DSP Crossover/Equaliser (May19), Low-Distortion DDS (Feb20) DIY Reflow Oven Controller (Apr20) KITS & SPECIALISED COMPONENTS FLEXIBLE DIGITAL LIGHTING CONTROLLER (CAT SC5636) 4 x Si8751AB ICs, 8 x S1HB15N60E-GE3 Mosfets, switchmode converter module, 6N137 opto, high-voltage resistors and capacitors plus SMD LEDs. (OCT 20) $100.00 D1 MINI LCD WIFI BACKPACK (OCT 20) SHIRT POCKET AUDIO OSCILLATOR (SEP 20) ULTRASONIC CLEANER (SEP 20) SWITCHMODE 78XX KIT (CAT SC5553) (AUG 20) COLOUR MAXIMITE 2 (JUL 20) Complete kit including 3.5-inch touchscreen, PCB and ESP8266-based module Kit: including 3D-printed case, and everything else except the battery and wiring - 64x32 pixel white OLED (0.49-inch/12.5mm diagonal) - Pulse-type rotary encoder with integral pushbutton 40kHz 50W ultrasonic transducer (Cat SC5629) ETD29 transformer components + three Mosfets (Q1-2,Q6) (Cat SC5632) Includes PCB and all onboard parts (choice of 3.3V, 5V, 8V, 9V, 12V & 15V versions) Short form kit: includes everything except the case, CPU module, power supply, optional parts and cables (SC5478) Short Form kit (with CPU module): includes the programmed Waveshare CPU modue and everything included in the short form kit above (SC5508) DCC BASE STATION HARD-TO-GET PARTS (CAT SC5260) Two BTN8962TA motor driver ICs & one 6N137 opto-isolator $70.00 $40.00 $10.00 $3.00 $54.90 $35.00 $12.50 $80.00 $140.00 (JAN 20) $30.00 SUPER-9 FM RADIO (NOV 19) MICROMITE EXPLORE-28 (CAT SC5121) (SEP 19) CA3089E IC, DIP-16 (Cat SC5164) MC1310P IC, DIP-14 (Cat SC4683) 110mm telescopic antenna (Cat SC5163) Neosid M99-073-96 K3 assembly pack (two required) (Cat SC5205) Complete kit – includes PCB plus programmed micros and all onboard parts Programmed micros – PIC32MX170F256B-50I/SO + PIC16F1455-I/SL VARIOUS MODULES & PARTS - 16x2 I2C LCD (Digital RF Power Meter, Aug20) - DS3231 real-time clock SMD IC (Ol’ Timer II, Jul20) - WS2812 8x8 RGB LED matrix module (Ol’ Timer II, Jul20) - MAX038 function generator IC (H-Field Transanalyser, May20) - MC1496P double-balanced mixer (H-Field Transanalyser, May20) - AD8495 thermocouple interface (DIY Reflow Oven Controller, Apr20) - Si8751AB 2.5kV isolated Mosfet driver IC (Charge Controller, Dec19) - I/O expander modules (Nov19): PCA9685 – $6.00 ¦ PCF8574 – $3.00 ¦ MCP23017 – $3.00 - SMD 1206 LEDs, packets of 10 unless stated otherwise (Tiny LED Xmas Tree, Nov19): yellow – $0.70 ¦ amber – $0.70 ¦ blue – $0.70 ¦ cyan – $1.00 ¦ pink (1 only) – $0.20 - ISD1820-based voice recorder / playback module (Junk Mail, Aug19) - 23LCV1024-I/P SRAM & MCP73831T (UHF Repeater, May19) - MCP1700 3.3V LDO regulator (suitable for USB M&K Adapator, Feb19) - LM4865MX amplifier & LF50CV regulator (Tinnitus/Insomnia Killer, Nov18) - 2.8-inch touchscreen LCD module with SD card socket (Tide Clock, Jul18) $3.00 $5.00 $7.50 $6.00ec $30.00 $20.00 $7.50 $3.00 $15.00 $25.00 $2.50 $10.00 $5.00 $4.00 $11.50 $1.50 $10.00 $22.50 $10 flat rate for postage within Australia. Overseas? Place an order via our website for a quote. All items subect to availability. Prices valid for month of magazine issue only. All prices in Australian dollars and included GST where applicable. PAYPAL (24/7) INTERNET (24/7) MAIL (24/7) PHONE – (9-5:00, Mon-Fri) eMAIL (24/7) To Use your PayPal account siliconchip.com.au/Shop Your order to PO Box 139 Call (02) 9939 3295 with silicon<at>siliconchip.com.au Place siliconchip.com.au Australia’s electronics magazine October silicon<at>siliconchip.com.au Collaroy NSW 2097 with order 2020  51 & credit card details Your You can also order and pay by cheque/money order (Orders by mail only). Make cheques payable to Silicon Chip Publications. Order: 10/20 An NTP clock that works anywhere I was very impressed with Tim Blythman’s “Clayton’s GPS Time Source” in the April 2018 issue (siliconchip. com.au/Article/11039). Then, in August 2018, Les Kerr described a GPS clock in Circuit Notebook using a PIC (siliconchip.com.au/Article/11200). This gave me the idea to design an NTP clock around an ESP8266 module. This clock can show the time in a virtually unlimited number of time zones. I have created a table with 38 timezones, but there is room for more. The time is automatically corrected for Daylight Saving in either hemisphere, under the control of the entries in the table. The data in the table is tightly compacted to save space but quite easily understood. The circuit is pleasingly simple. The LCD module I used has an I2C interface, so it only needs to be wired up with SCL to D1 and SCL to D2, plus 5V power and ground. The pushbutton is used as a way to step through the timezones, going west around the globe until the International Date Line 52 Silicon Chip is reached. So the next zone after Hawaii is Suva. You can also choose a time zone via the USB interface. The clock displays the time in the zone it was last set for each time it powers up. If you want just to have two time zones, such as NSW and the UK, comment out all zones except the two that you want and the End one, then change the table index to 3. This is very useful for the times when the UK has started daylight savings and NSW has not finished. I have found that there are many versions of the LiquidCrystal_I2C.h library and not all of them are compatible. I used the one from https://github. com/lucasmaziero/LiquidCrystal_I2C It works with 16 x 2 and 20 x 4 displays, and also with the ESP-01 microcontroller module. The clock will run on an ESP-01, but the hassle of setting it up far outweighs the cost and size advantages. John Nestor, Woorim, Qld. ($70) Australia’s electronics magazine siliconchip.com.au What's New Hardcore electronics by On Sale 24 September to 23 October, 2020 THREE FILAMENT 3D PRINTER DOBOT MOOZ-3Z TRIPLE FILAMENT COLOUR MIXING TECHNOLOGY JAYCAR EXCLUSIVE: FIRST IN AU & NZ RETAIL MARKET! 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Comes in red or blue. • Prints with Flashforge PLA filament (sold seperately) • Controlled via SD card • Prints up to: 100(L) x 100(W) x 80(H)mm TL4210 Allows you to combine colours and materials creating high-quality prints. Oversized bed screws for leveling the print bed. Dual cooling fans. SD memory card slot. • Prints up to: 300(L) × 300(W) × 400(H)mm TL4410 The best fabrication tool for entry level users. 3D print, engrave and laser cut with a single machine. Easy swap & interchangeable modules. Includes easy to use software. • 3.5" Touchscreen • Heated Build Plate • Prints up to: 125(L) x 125(W) x 125(H)mm TL4400 See website for details. ONLY ARDUINO® COMPATIBLE RGB LED STRIP LIGHT DON'T FORGET THE FILAMENT!! AVAILABLE IN-STORE OR ONLINE FROM $19.95 1080P HDMI CAT5E/CAT6 OVER IP EXTENDER Send high definition AV signals to a screen in another room up to 150m away using a Cat5e/6 cable through a common router or Ethernet switch. Includes transmitter, receiver and power supplies. • 100m (Cat5e), 150m (Cat6) transmission distance • HDMI pass-through • Multicast receiver support • Infrared remote control extender AC1752 Additional Receiver To Suit AC1753 $99.95 USB STREAMING MICROPHONE JUST 179 $ HELPFUL HINT Sending HDMI signals through an IP network has advantages over just sending the signal through a Cat5/6 ethernet balun. You can utilize your existing network and save the hassle of installing extra wires. You can also route the signal to a larger number of receivers and over a greater distance. Best results are obtained through a high performance Gigabit network. Shop the catalogue online! Uni-directional USB microphone suitable for podcasting and audio recordings. Solid construction with an adjustable desk tripod for optimum positioning. Mac® and Windows compatible. • 24-Bit resolution • 192kHz Sample rate • -34dB Sensitivity • 20Hz - 20kHz Frequency response • 5VDC USB powered AM4136 ONLY Exclusions apply - see website for full T&Cs. * 7995 $ Free delivery on online orders over $99* ONLY 1299 $ 1349 $ FIND OUT MORE AT: jaycar.com.au/3dprinting DUAL FILAMENT 3D PRINTER 3D PRINTER/CNC/LASER ETCHER $ We have an extensive range of 3D printers including reputable big brands to suit your budget and modelling aspirations! Come and talk to our knowledgeable staff to find the best solution for your needs. • DUAL COLOUR PRINTING • 4.3" COLOUR TOUCH SCREEN • SILICON PRINTING PLATFORM ADVENTURER 3 3D PRINTER ALSO AVAILABLE IN RED GREAT RANGE OF 3D PRINTERS IN-STORE OR ONLINE A 2m long flexible LED strip light with 120 (60 LEDs/m) addressable WS2812B RGB LEDs to create amazing lighting displays using your favourite microcontroller. IP65 water resistant rating. 5V. • Flexible and waterproof • 2m long XC4390 2995 $ NON-CONTACT THERMOMETER ONLY Measure from -50°C up to 600°C. Includes a 12 point laser to indicate the measured area. • 12:1 Distance to Spot Ratio • Adjustable emissivity • Large colour LCD display • Powered from 2 x AAA batteries (included) QM7424 ALSO AVAILABLE: Non-Contact Infrared Thermometer QM7422 $149 ONLY 9995 $ www.jaycar.com.au 1800 022 888 think. possible. Your destination for... projects & DIY PROJECT: Ultrasonic Voice Alert Build a simple alert that speaks or chimes when people come within range. The project uses an Arduino® Record and Playback Module to playback a pre-recorded message e.g “Try me”, “Buy me”, "Keep distance", "Wash your hands" or anything you want, and an Ultrasonic Sensor that detects distances up to 4.5m. An easy to build project useful in retail shops, home, office etc. SKILL LEVEL: Beginner WHAT YOU NEED: 1 x Uno r3 Development Board 1 x Record and Playback Module 1 x Dual Ultrasonic Sensor Module 1 x 150mm Plug to Socket Jumper Leads - 40 Pieces 1 x 9V Battery Snap DC Cable 2.1mm Plug 0.3m 1 x 76mm All Purpose Replacement Speaker 1 x 9V Battery Alkaline XC4410 XC4605 XC4442 WC6028 PH9251 AS3006 SB2423 $29.95 $9.95 $7.95 $5.95 $5.45 $4.95 $4.50 CLUB OFFER BUNDLE DEAL 4995 $ SAVE 25% SEE PARTS & STEP-BY-STEP INSTRUCTIONS AT: www.jaycar.com.au/ultrasonic-voice-alert See other projects at www.jaycar.com.au/arduino KIT VALUED AT: $68.70 ADD SOUND TO YOUR PROJECT ONLY 1495 $ JUMPER LEAD MIXED PACK - 100 PIECES A mixed pack of jumper leads for your Arduino®, breadboarding and prototyping projects. WC6027 Build Your Own Radio ASSEMBLY REQUIRED Quality 13 x 0.12mm tinned hook-up wire on plastic spools. 8 rolls of different colour included. • 25m on each roll WH3009 100G ENAMELLED COPPER WIRE For winding chokes, crossover coils etc. Supplied on its own plastic reel. • 0.5mm-1.25mm sizes available WW4016-WW4024 1595 $ CRYSTAL RADIO KIT 21 Enjoy AM broadcasting without using a battery or other power sources. • Kit supplied with silk-screened PCB, crystal in the form of a small signal schottky diode, pre-wound coil, earphone and all components • 81(L) x 53(W)mm KV3540 54 click & collect EA. ONLY BREADBOARD 95 3995 $ LIGHT DUTY HOOK-UP WIRE PACK ONLY $ ONLY WITH 830 TIE POINTS Ideal for electronic prototyping and Arduino® projects. Labelled rows and columns. Adhesive back for mounting. PB8815 ONLY 14 $ 95 Buy online & collect in store All purpose replacement speakers for your next project. 8-Ohms. 27mm 0.25W AS3002 $3.75 40mm 0.25W AS3004 $4.50 57mm 0.25W AS3000 $4.50 76mm 1.00W AS3006 $4.95 50 x 90mm 5W AS3025 $6.95 SMD IC BK1198 RADIO RECEIVER All-in-one radio receiver chip that will do AM, FM and shortwave from 2.7-22MHz. • Comes in 16 pin SOIC package ZK8829 ONLY 795 $ 60 - 160PF MINIATURE TUNING CAPACITOR AS3002 28 PIN SOIC/SOP TO DIP BREADBOARD ADAPTOR Allows SMD IC’s and other smaller pitch components to be used with standard 0.1” prototyping equipment. PI6530 ONLY 295 $ Used in most transistor radios. Supplied with 35mm dia. plastic knob and screw. RV5728 AERIAL FERRITE ROD WITH COIL ONLY ONLY 6 $ 75 FROM 375 $ Small ferrite rod complete with pre-wound standard broadcast band coil. LF1020 595 $ ON SALE 24.09.2020 - 23.10.2020 think. possible. Your destination for... Arduino® compatible boards, shields & modules ARDUINO® COMPATIBLE This icon indicates that the product will work in your Arduino® based project. 100% Arduino® Compatible Boards NANO BOARD Small in size, but packs virtually all the features of the full duinotech boards into a tiny DIP-style board that drops directly into your breadboard. • ATMega328P microcontroller ONLY • 46(L) x 18(W) x 18(H)mm XC4414 2995 $ UNO R3 DEVELOPMENT BOARD Stackable design makes adding expansion shields at ease. Powered from 7-12VDC or from your computers USB port. • ATMega328P Microcontroller • 53(L) x 75(W) x 13(H)mm ONLY XC4410 ALSO AVAILABLE: Uno Board with Wi-Fi XC4411 $39.95 29 $ 95 RASPBERRY PI COMPATIBLE This icon indicates that the product will work in your Raspberry Pi project. AUDIO AMPLIFIER MODULE WITH SPEAKER ACTIVE BUZZER MODULE An easy way to add audio effects or music to your next project. Features 23mm diameter speaker, 2W amplifier, and a trimpot for volume control. XC3744 The easy way to add sound to your project. Hook up a digital pin and ground, and use the tone() function to get your Arduino® beeping. XC4424 ONLY ONLY 9 $ 95 RECORD AND PLAYBACK MODULE Includes a small built-in amplifier capable of directly driving an 8 ohm speaker. Ideal if you need to playback a specific sound. Records up to 10 seconds. XC4605 ONLY 9 $ 495 $ 95 2 X 3W AMPLIFIER MODULE Provides a complete 2 x 3W stereo audio amplifier, ideal for driving small speakers and earphones. XC4448 ONLY 495 $ MEGA 2560 R3 BOARD Our most powerful Arduino® compatible board. Boasting more IO pins, more memory, more PWM outputs, more analogue inputs and more serial ports. • 256KB program memory • ATMega2560 Microcontroller • 53(L) x 108(W) x 15(H)mm XC4420 ONLY ALSO AVAILABLE: Mega Board with Wi-Fi XC4421 $59.95 4995 $ Dot Matrix Display Modules 8 X 8 LED DOT MATRIX MODULE Featuring 64 x red LED matrix, this module is easily controlled with the LED Control library. Display your own custom characters, or use multiple modules together to make a scrolling display. • Chipset: MAX7219 • 62(W) x 32(H) x 14(D)mm XC4499 ONLY 7 $ 95 16 X 16 LED DOT MATRIX MODULE A compact LED Matrix display featuring 256 individually addressable LEDs. Stack multiple boards side by side for a larger display. • 74HC138 decoder IC’s • Includes jumper cables and header strips • 113(L) x 64(W) x 12(H)mm XC4607 ONLY 24 $ 95 In the Trade? AUDIO MODULE Play MP3, WAV, or WMA files from an onboard microSD card slot (SD card sold separately) with your next electronics project. 5W power. Features on-board controls (play, stop, etc.) XC3748 MICROPHONE SOUND SENSOR MODULE ONLY ONLY 1495 $ LCD Display Modules 84 X 48 LCD DISPLAY MODULE These compact LCD displays are identical to those found in some old Nokia phones. An easy way to add a small black and white graphics display to your project. • Chipset: PCD8544 • 44(L) x 44(W) x 13(D)mm XC4616 ONLY 1995 $ 128 X 64 LCD DISPLAY MODULE OLED Display Modules 1.3" 128 X 64 OLED MONOCHROME DISPLAY MODULE For projects that don't require full colour, this display is perfect. Wide viewing angle to eliminate eye strain. • IIC/SPI • 39(L) x 36(W) x 6(D)mm XC3728 2495 $ ONLY ONLY 29 ONLY 2995 $ ONLY 1.5" 128 X 128 OLED COLOUR DISPLAY MODULE 95 795 $ A larger display than XC4616 above, with cool white on blue graphics. Similar to the character LCD’s with inbuilt character ROM, but the flexibility to show graphics. • 8 bit, 4bit and serial interfaces available • 95(L) x 70(W)mm XC4617 $ Great for any project that needs to detect sounds. Includes both analogue (for waveform) and digital output with adjustable threshold for simple sound detection. XC4438 Provides an attractive colour display in a small format for your next project. • SSD1351 Chipset • 34(L) x 34(W) x 2(D)mm XC3726 6995 $ 240 X 320 LCD TOUCH SCREEN FOR ARDUINO® Large, colourful touch display shield which piggybacks straight onto your UNO or MEGA. Fast parallel interface. microSD card slot. • Resistive touch interface • 77(L) x 52(W) x 19(H)mm XC4630 55 think. possible. Your destination for... audio & video FROM 695 $ WA7010 Quality Audio Leads 2 X 18WRMS STEREO AMPLIFIER Simple, fairly bullet-proof transistor amp and its surprisingly loud! Ideal as a small office or workshop PA amp in churches, community halls etc. • Signal to Noise Ratio: 106dB • 240V Mains power • 170(L) x 157(H) x 77(W)mm AA0472 STEREO TO STEREO 3.5mm Stereo Plug to 3.5mm Stereo Socket 3.0m WA7010 $8.95 3.5mm Stereo Plug to 3.5mm Stereo Plug 2.0m Slim WA7500 $9.95 ONLY 4495 3.5mm Stereo Plug to 2 X RCA Plugs: 1.5m WA7014 $6.95 3.0m WA7015 $9.50 WA7014 Visit in-store or online for full range. 2 X 120WRMS STEREO AMPLIFIER WITH REMOTE CONTROL Audio Converters Provides crisp audio power. Ideal for powering a second set of speakers elsewhere in your home or office. • 6.5mm headphone output ONLY • Two line-level inputs • RCA stereo line output • 240V Mains power • 250(W) x 275(D) x 90(H)mm AA0520 249 $ ONLY 3995 $ SUITABLE FOR USE IN A VEHICLE OR ON A BOAT - commonly called the gain. Audio amplifiers have traditionally been placed into one of 3 classes - A, B, and AB. Class A amplifiers have very low distortion, but are not very power-efficient; Class B is much more efficient but has higher distortion; Class AB is the most common type and lies somewhere in between. Modern day classes include D and H, but they involve radically different circuitry. Class C amplifiers are the most efficient but produce very high distortion, and are normally only used in radio transmitters. 2 X RCA Plugs to 2 X RCA Plugs: 1.5m WA7062 $6.95 10m WA7068 $15.95 4-WAY DIGITAL AUDIO SWITCHER $ STEREO AMPLIFIERS: Amplifiers increase the amplitude of an audio signal by a given factor RCA TO RCA WA7062 Stream music via Bluetooth®. Ideal for powering speakers in an entertainment area, etc. • Signal to Noise Ratio: 102dB • RCA line input • Extruded aluminium enclosure • 12V power • 150(L) x 86(W) x 51(H)mm ONLY AA0522 119 $ STEREO TO RCA 2 X 15WRMS COMPACT STEREO AMPLIFIER WITH BLUETOOTH® TECHNOLOGY 2 X 25WRMS COMPACT STEREO AMPLIFIER Compact, ideal for a small office or workshop PA system. • Signal to Noise Ratio: 72dB • Microphone input ONLY • Volume, bass & treble controls • 240V Mains power • 216(L) x 150(D) x 65(H)mm AA0486 139 $ Manually switch up to 4 digital audio devices to analogue via TOSLINK RCA or 3.5mm socket. Supports a wide range of audio formats such as PCM, LPCM, DTS, DOLBY-AC3 and THX. • Inputs: 2 x Coaxial, 2 x SPDIF/TOSLINK • Outputs: 1 x SPDIF/TOSLINK, 1 x RCA, 1 x 3.5mm Stereo AC1723 FROM ONLY 59 $ DIGITAL AUDIO CONVERTER & REPEATER 95 Bi-directional converter for changing digital audio signals. Simultaneous output to TOSLINK and Coax ports. USB powered. • Inputs: 1 x Coaxial RCA, 1 x TOSLINK • Outputs: 1 x Coaxial RCA, 1 x TOSLINK AC1592 DIGITAL TO ANALOGUE AUDIO DECODER ONLY 109 $ Convert digital audio sources that use Dolby Digital AC3 Pro logic, DTS, PCM or other formats into 2.0 channel analogue audio output. • Inputs: 1 x TOSLINK/SPDIF, 1 x Coaxial • Outputs: 2 x RCA, 1 x 3.5mm AUX AC1658 56 click & collect 2495 $ 25MM TITANIUM DOME TWEETER Excellent for replacement or for new speaker design construction. • Clean bass output • Strong steel frame basket • High power magnet and voice coils 4” 27WRMS CW2190 $24.95 5” 50WRMS CW2192 $29.95 8" 90WRMS CW2196 $39.95 10" 225WRMS CW2198 $69.95 12" 225WRMS CW2199 $89.95 14/0.14mm Figure 8. Grey with black trace. AWG: 24 x 2. • For 15W speakers WB1703 ONLY 14 $ 95 Buy online & collect in store 1995 12 95 Does not require a crossover and is perfect for general PA applications. 100WRMS. 8-Ohms. CT1930 HEAVY DUTY SPEAKER CABLE - 30M ROLL 24/0.20mm Figure 8. Clear with black trace. AWG: 18 x 2. • For 50W speakers WB1709 ONLY 3595 $ EA ONLY BANANA PLUGS $ PIEZO HORN TWEETER QUALITY JUST 225 $ Produces very crisp and clear high frequencies. 50WRMS. 8-Ohms. CT2007 WOOFER/MIDRANGE SPEAKER DRIVERS LIGHT DUTY SPEAKER CABLE - 30M ROLL ONLY $ Piggy back style. Another banana plug can be inserted into the back of the plug. Red PP0390 Black PP0391 EXTRA HEAVY DUTY SPEAKER CABLE - 30M ROLL 79/0.20mm Figure 8. Clear with black trace. AWG: 13 x 2. • For 100-200W speakers WB1713 ONLY 8995 $ We also sell it by the metre too! See in-store or online. ON SALE 24.09.2020 - 23.10.2020 think. possible. Your destination for... audio & video Switchers Splitters Switch HDMI signals from multiple sources to a single output. Especially useful when you're feeding multiple sources (Blu-ray, media centre etc.) into one display. 4K Split a single HDMI input to multiple HDMI outputs. Ideal for sending to a TV and HiFi for sound or sending to multiple displays. Quality Video Leads BACK 4K HDMI MATRIX SWITCHER/SPLITTER ONLY 249 $ FRONT Simultaneously routes up to four HDMI sources to two HDMI displays with up to 4K resolution on all ports. Includes IR remote control and mains power adaptor. • Support for 3D signals, High Dynamic Range (HDR), audio up to 7.1 surround, and smart EDID management • Inputs: 4 x HDMI • Outputs: 1 x HDMI, 1 x TOSLINK Optical AC5012 ONLY 129 $ 4-WAY 4K HDMI SWITCHER Built-in 3.5mm audio extractor for playing audio through an amplifier or active speakers. Includes infrared remote control. • High-Dynamic-Range (HDR) video support • Inputs: 4 x HDMI • Outputs: 1 x HDMI, 1 x 3.5mm Stereo Audio AC5010 ONLY 89 $ 95 2-WAY 4K HDMI SPLITTER Smooth picture quality. Supports audio up to 7.1 surround sound and HDCP 2.2 for the latest hardware compatibility. • High Dynamic Range (HDR) video support • Input: 1 x HDMI • Outputs: 2 x HDMI AC5000 FROM 595 $ F-Plug to F-Plug 1.5m WV7386 $6.95 RCA Plug to RCA Plug 3.0m WV7306 $8.50 WV7386 COAX PLUG TO F-PLUG: 1.5m WV7384 $5.95 5.0m WV7385 $11.95 F-PLUG TO F-PLUG RG6 QUAD: WV7384 1.5m WV7390 $8.95 5.0m WV7394 $16.95 Visit in-store or online for full range. WV7390 AV Wall Plates 4K HDMI CAT5E/6 EXTENDER ONLY 249 $ Send UHD 4K signals from a set top box, media player, or other video source to another room up to 50m away over an ethernet Cat6 cable. • High-Dynamic-Range (HDR) video support • Integrated remote control extender • Up to 50m (Cat6), 40m (Cat5e) AC5020 149 $ 4-WAY 4K HDMI SWITCHER WITH VOICE ASSIST Support Alexa smart voice command. Includes infrared remote control and mains power adaptor. • High-Dynamic-Range (HDR) video support • Inputs: 4 x HDMI • Outputs: 1 x HDMI, 1 x TOSLINK Optical AC5014 COMPOSITE AV TO HDMI CONVERTER VGA TO HDMI CONVERTER & UPSCALER WITH STEREO AUDIO Ideal for older laptops and other devices with a VGA output, to display on a HDMI device. Plug and play. • Input: VGA • Output: HDMI AC1718 RG59 75 OHM COAX CABLE Standard RG59 coax cable on a 30m roll. White WB2001 Black WB2005 ONLY 22 $ 95 EA More ways to pay: 179 $ 4-WAY 4K HDMI SPLITTER WITH DOWSCALLING Built-in downscaling function allows 4K video to suit 1080p screens. • Analogue and digital audio extractor • Input: 1 x HDMI • Outputs: 4 x HDMI, 1 x TOSLINK Optical, 3.5mm Stereo Audio AC5004 HDMI TO COMPOSITE AV CONVERTER ONLY 89 $ 95 ONLY 89 $ 95 Supports PAL and NTSC standards. USB powered. • Input: HDMI • Output: Composite video and audio AC1773 Take advantage of high performance USB Type-C connectors to convert to an existing VGA signal. • 1080p 60Hz Resolution • Input: USB Type C • Output: D15 HD (VGA) XC4931 18AWG steel centre conductor, copper plated, gas injected. Per Metre WB2009 $1.95 Per 30m Roll WB2014 $49.95 1 $ 95 /M ONLY 7495 $ 995 $ Single gang brush plate for cable entry through walls etc. Suitable for pre terminated cables going to LCD or plasma screens, and particularly suited to HDMI cables as they can't be split, spliced or field-terminated. PS0291 1195 ONLY 34 95 • 6mm diameter • High durability Gas Injected WB2004 85¢/m Domestic WB2002 $1.15/m 85 ONLY $ $ ¢ Allows you to easily run a preterminated cable through a wall. Brushed entry and concave extrusion will help protect against dust and keep the cables secured when cleaning or moving furniture. PS0296 ONLY RG59 75 OHM HIGH GRADE TV COAX CABLE FROM BRUSHED REAR CABLE ENTRY WALL PLATE BRUSH CABLE ENTRY WALL PLATE USB 3.1 TYPE-C TO VGA CONVERTER QUAD SHIELD RG6 75 OHM COAX CABLE FROM ONLY New Devices ► Old Monitors Old Devices ► New Monitors Playback video & audio on HDMI equipped displays. • Input: Composite video and audio • Output: HDMI AC1722 ONLY WB2004 WB2002 HDMI 2.0 WALL PLATE WITH FLYLEAD Standard size HDMI connection wall plate for connecting HDMI cables within wall cavities. • Flexible flylead for easy connection of in-wall cable PS0281 ONLY 1595 $ /M 57 think. possible. Your destination for the best rewards & perks. love jaycar? you're going to love our rewards! SHOP In store & online EARN POINTS For dollars spent GET REWARDS eCoupons for future shops in store 1 point = $1 + PERKS offers, event invitations, 200 points = $10 eCoupon account profile and more... Receiver CLUB OFFER SAVE 20 CLUB OFFER 24 $ 95 CLUB OFFER % USB MIDI INTERFACE Connects your older MIDI equipped musical instrument that has 5-pin DIN to your computer via USB. XC4934 RRP $29.95 199 $ IN-CEILING 2 WAY SPEAKERS SAVE 15% Sender Excellent audio quality compared to traditional PA speakers. Combination of coaxial woofer with dome tweeter. Sold as a pair. 5.25” 30WRMS CS2451 RRP $69.95 CLUB $55.95 SAVE $14 6.5" 40WRMS CS2453 RRP $84.95 CLUB $67.95 SAVE $17 8" 50WRMS CS2455 RRP $99.95 CLUB $79.95 SAVE $20 SAVE $30 PORTABLE 5.8GHZ WIRELESS 1080P HDMI AV SENDER Connect your HDMI device without using wires! Transmit crystal clear 1080p signals up to 15m wirelessly. Includes two USB power cables and two HDMI extensions cables. AR1901 RRP $229 CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE GOOT - DESOLDERING TOOL METAL CASE - 184 X 70 X 160MM ALUMINIUM FOIL TAPE - 50MM ENCAPSULATED MINI AC/DC POWER SUPPLIES CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE IPX8 WATERPROOF ABS CASE PROBE K-TYPE THERMOCOUPLE 32-PCE DRIVER BIT SET CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE CLUB OFFER SAVE FEMALE 3 PIN CANNON/XLR TO 6.5MM PLUG ADAPTOR 8000μF 80VDC ELECTROLYTIC RG CAPACITOR CONDUCTIVE CARBON GREASE 50G 6-WAY AUTOMOTIVE FUSE BOX 20% Strong suction. 330mm long. TH1856 RRP $31.95 CLUB $24.95 10% 210 x 120 x 90mm. Lanyard included. HB6425 RRP $34.95 CLUB $29.95 20% High quality. Metal construction. PA3682 RRP $12.95 CLUB $9.95 25% Black finish steel cover. Ventilated. HB5446 RRP $23.95 CLUB $17.95 30% Temp ranges from -50°C to +250°C. QM1282 RRP $14.95 CLUB $9.95 20% Heavy duty. 85°C rated. RU6710 RRP $14.95 CLUB $11.95 25% 50mm width x 50m roll length. NM2860 RRP $17.95 CLUB $12.95 Tamperproof Torx, Tri-wing, In - Hex (allen) etc. TD2035 RRP $19.95 CLUB $14.95 15% Protection from moisture & corrosion. NA1034 RRP $11.95 CLUB $9.95 15% OFF MICROPHONES* *Includes wired and wireless microphones. See T&Cs for details. 58 click & collect Buy online & collect in store 240VAC Mains input. Screw terminal connections. 5VDC<at>6A & 12VDC<at>2.5A output available. MP3301 OR MP3302 RRP $42.95 CLUB $34.95 CLUB OFFER SAVE 25% EXCLUSIVE CLUB OFFER 15% 20% DVI-A PLUG TO VGA SOCKET For connecting DVI-A or DVI-I video cards with VGA monitors. PA0897 RRP $12.95 CLUB $9.95 30% 32VDC max. 15Acircuit max. 45A block max. SZ2002 RRP $14.95 CLUB $9.95 YOUR CLUB, YOUR PERKS KEEP UP TO DATE WITH THE LATEST OFFERS & WHAT'S ON! Visit www.jaycar.com.au/makerhub ON SALE 24.09.2020 - 23.10.2020 think. possible. Your destination for... workbench essentials 1. SPRAY-ON CONTACT ADHESIVE SPRAY CAN • Bonds to almost any surface • Great for laying innerbond and speaker carpet in/on speaker cabinets etc ONLY • 400g NA1504 1695 $ 2. RECHARGEABLE LITHIUM-ION SCREWDRIVER • Includes 55-pce S2 tool steel bits to open just about anything • USB rechargeable ONLY • Reversible rotation • LED light TD2510 89 $ 95 3. 48W HOBBYIST SOLDERING STATION • Adjustable temperature (150450°C) • Ceramic element and lightweight pencil • Mains powered TS1564 ONLY 119 $ 4. SPEAKER POLARITY TESTER WITH TONE GENERATOR • Sinewave tone generator, speaker polarity and RCA cable tester • Output range: 0V-8V • RCA or alligator clips • Requires 1 x 9V battery AA0414 WAS $34.95 5 NOW 2995 $ SAVE $5 5. 4-IN-1 MULTIFUNCTION ENVIRONMENT METER WITH DMM 3 • Sound level meter, light meter, humidity meter and temperature meter in one unit • 600V, 4000 count • AC/DC voltages up to 250V NOW • AC/DC current up to 10A • Resistance, non-contact voltage measurement SAVE $20 QM1594 WAS $139 1 119 $ 6 2 6. 10 DIOPTRE LED MAGNIFIER WITH SCALE • All metal construction • Satin chrome finish • Ground glass optics QM3539 WAS $29.95 NOW 2495 $ SAVE $5 4 Sound Level Meters Uses a built-in microphone to display sound levels in decibels (dB), with a choice of three frequency weighting standards: • Z-Weighting: The actual sound power level at all frequencies • A-Weighting: Reduces response at high and low frequencies to indicate perceived loudness • C-Weighting: Boosts low frequencies for measuring loud sound sources (over 100dB) PROFESSIONAL WITH CALIBRATOR Ideal for vehicle, traffic, aircraft noise, race or evidence-based noise testing. • Dislay: 4 Digit • Range: 30 - 130dB • A & C weighted • USB connectivity • Fast (125ms) & Slow (1s) NOW responses QM1598 WAS $299 279 $ COMPACT MICRO Great for car audio installers, clubs and PA. • Display: 3.5 Digit • Range: 30 - 130dB • A & C weighted • Data hold & min/max function, backlit QM1589 NOW WAS $129 Ideal for environmental, safety and sound system testing. • Display: 3 Digit • Range: 40 - 130dB • A-weighted • Pocket size, min/max hold, backlit QM1591 119 $ SAVE $20 SAVE $10 Keep Cables Neat & Tidy F-Connector Tools SELF-CLOSING BRAIDED WIRE WRAP F-TYPE / BNC INSERTION & EXTRACTION TOOL Protect cabling from abrasion. Flexible and lightweight. Wear and tear. 2m long. 6mm Dia. WH5630 $8.95 9mm Dia. WH5632 $9.95 13mm Dia. WH5634 $13.95 19mm Dia. WH5636 $16.95 FROM 8 $ 95 CARPET CABLE COVER Conceal unsightly cords and eliminate trip hazards. For use on any nylon based carpet. Comes in dispenser box. Black (Per Metre) HP2000 $12.95 Yellow (Per Metre) HP2002 $12.95 Black (5m Roll) HP2004 $49.95 FROM 1295 $ LOOM TUBES Keep your cables neat and tidy. • Assorted sizes from 125 to 180mm • Pack of 16 HP1232 Keep wiring in place and suits many types of applications. The tube has a slit so that cables can enter/leave at any point along its length. • 3 Diameters available: 7, 10 or 19mm • Comes in 2m or 10m lengths HP1221 - HP1227 ONLY FROM MIXED HOOK AND LOOP CABLE TIES PK16 13 $ 95 More ways to pay: 3 $ 45 HEX RATCHET CRIMPING TOOL • Insert or unscrew F-type or BNC connector • Comfortable grip • Carbon steel • 255mm long TD2000 Crimp F, N, BNC, TNC, UHF, ST, SC & SMA connectors onto RG6 or RG58 coax cable. TH1833 ONLY 14 $ /M COMPRESSION CRIMPING TOOL FOR F-TYPE PLUGS Accurately positions the plug, and a spring-loaded clamp holds the cable in position. • 143mm long. TH1803 ONLY 29 $ 95 ONLY 4995 $ JUST 3995 95 $ RATCHET CRIMPING TOOL FOR F-TYPE CONNECTORS Strong, heavy duty tool for crimping F-type CAT-V connectors onto RG6 or RG59 coax. TH1831 JUST 3995 $ 59 Learn To Solder FLASHING LED Soldering is a fundamental skill you need to learn in order to enjoy your hobby as an electronic enthusiast. Why not learn, have fun at the same time by making one or two of these wearable badges or the electronic dice kit? 2 WEARABLE BADGES & ELECTRONIC DICE SOLDER TRAINING KITS 1 ONLY 1995 These kits are a great way for your kids and grand kids to start soldering and pick up some electronics on the way. They will also learn about how various components work including LEDs, transistors, integrated circuits and more. Each kit requires a CR2032 battery (SB2522 $3.25 sold separately). $ 6 40W 240V SOLDERING IRON Ideal for the hobbyist and handy person. Stainless steel barrel and orange cool grip impact resistant handle. • Fully electrically safety approved TS1475 1. Skull Badge 2. Owl Badge 3. Rocket Badge 4. Pirate Badge 5. Robot Badge 6. Electronic Dice JUST 9 $ 200G DURATECH SOLDER 95 1695 ONLY 9 ONLY 16 95 $ SOLDER SUCKER & BLOWER BULB ONLY 95 Take your soldering skills to the next level then put it to good use by placing this traffic light onto the kids car or train set. Based on the 4071 IC, you will see first hand how logic gates operate. XC3758 $ $ with Alternating Flashing LEDs with Touch Sensitive LEDs with Flashing LEDs with Flashing LED Eyes with Touch Sensitive LEDs & Buzzer with Flashing LEDs 19 $ 9V Battery (SB2423 $4.50) sold separately 3D TRAFFIC LIGHTS LEARN TO SOLDER KIT 60% Tin / 40% Lead. Resin cored. 0.71mm size. NS3005 ALSO AVAILABLE: ONLY 15g Tube NS3008 $2.25 ONLY 4 5 SOUND EFFECTS 17 95 $ DELUXE SOLDERING IRON STAND Affordable, compact and effective. 110mm long. TH1850 General purpose stand. Large, tip cleaning sponge & pressed metal base. TS1507 95 SOLDER FLUX PASTE Provide superior fluxing and reduce solder waste. Nonflammable, non-corrosive. 56g tub. NS3070 ONLY 1995 $ 6 DIFFERENT KITS AVAILABLE: THIRD HAND PCB HOLDER TOOL WITH 2 CLIPS Ideal aid for any application where a third hand is needed i.e PCB assembly, soldering work etc. • Heavy cast iron base • Movable arms TH1982 3 KM1090 KM1092 KM1094 KM1096 KM1098 KM1099 EA 4 X 4 X 4 BLUE LED CUBE KIT Learn to solder in 3 dimensions by building a dazzling array of 64 ultra-bright blue LEDs. Using the supplied template, you will arrange this 4 x 4 x 4 matrix into a work of art. Fifteen different psychedelic patterns are included, with instructions on how to create your own. • 65(W) x 88(H) x 65(D)mm KM1097 JUST 24 $ 95 STAY BRITE SILVER SOLDER KIT 5 times stronger than regular solder and 100% lead free. • 96% tin, 4% silver. • 14g solder with 14g flux NS3045 Arduino® Uno Board (XC4410 $29.95) sold separately. ONLY 1995 $ JUST 2495 $ SOLDER STAND WITH SOLDER DISPENSER • It will hold our 1kg solder rolls • 16mm diameter shaft • Wall mountable TS1504 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 2: Club Offer: Ultrasonic Voice Alert project includes 1 x each of XC4410, XC4605, XC4442, WC6028, PH9251, AS3006 & SB2423 for $49.95. Page 6: Club Offer: 15% OFF Microphones applies to Jaycar 525A & 525B: Microphones – Wired and Wireless product category excluding AM4136 & AM4015. GERARD DR MASTRACOLAS RD OFFICEWORKS FORTY WINKS ADAIRS PARK BEACH HOMEBASE 1800 022 888 www.jaycar.com.au REPCO BBQ GALORE Y FIC C PA HW CI PA C IFI N HW Y NEW LOCATION Coffs Harbour For your nearest store & opening hours: Shop 5, Park Beach HomeBase, 252 Pacific Highway Coffs Harbour, NSW 2450 (02) 6651 5238 Over 100 stores & 130 resellers nationwide HEAD OFFICE 320 Victoria Road, Rydalmere NSW 2116 Ph: (02) 8832 3100 Fax: (02) 8832 3169 ONLINE ORDERS www.jaycar.com.au techstore<at>jaycar.com.au Arrival dates of new products in this flyer were confirmed at the time of print but delays sometimes occur. Please ring your local store to check stock details. Occasionally there are discontinued items advertised on a special / lower price in this promotional flyer that has limited to nil stock in certain stores, including Jaycar Authorised Resellers. These stores may not have stock of these items and can not order or transfer stock. Savings off Original RRP. Prices and special offers are valid from catalogue sale 24.09.2020 - 23.10.2020. SERVICEMAN'S LOG Decisions, decisions, decisions... Dave Thompson Ford or Holden? CD or vinyl? Mica or polystyrene? Hybrid or electric? Digital or analog? PC or Mac? Petrol or diesel? Topics like these generate a lot of debate in workshops, pubs and internet forums. While there are no correct answers, this doesn’t usually stop us from holding strong opinions. Which brings me to my love of analog multimeters... I’d like to think I’m not the only one who ponders these important philosophical questions. Servicemen of my generation have had the good fortune to have plied their trade in an era of almost unparalleled technological growth. Believe it or not, there are still people around – they are admittedly getting on now – who cut their servicing teeth on valve-based hardware. They then had to ‘upskill’ to stay current as transistors and integrated circuits became more commonplace, while tubes disappeared into history (and expensive guitar amplifiers!). Many industries lag behind the “bleeding edge” due to the systems involved, meaning there can be considerable overlap in old and new technologies. I started work at our national airline as a know-nothing slip of siliconchip.com.au a lad in early 1980. Even then, there was still some valve-based aircraft hardware being serviced in the various avionics workshops. Don’t get me wrong; it wasn’t a lot, but because at that point there were some relatively old aircraft still being maintained by the airline, I did get to work on a few tube-based components of that era. Remember, this is “only” 40 years ago, and there were many other areas aside from the aircraft industry where vacuum tube technology was still in wide use (broadcasting and music amps to name a few). While it might seem old-fashioned by today’s standards, I was experiencing the Australia’s electronics magazine tail-end of an era of huge technological growth brought about by World War 2. To the people involved at the time, it was just as awe-inspiring as anything we see happening today. The evolution of digital displays Digital displays are one example. Of course, they were around even in my earliest days of dabbling in hobby electronics. In my early days, I saw the exotic (for the time) Nixie tubes, which could spell out numbers and letters, and it seemed like the devil’s magic. Nowadays, Nixie tubes are considered retro-chic and while relatively expensive, such is their popularity that they are still being manufactured. October 2020  61 I still clearly recall seeing my first LED display, a red bubble-style arrangement on a clunky HP calculator my dad bought in the mid-70s. Aside from the mind-boggling capabilities of the device itself (four functions!) with that LED display, the whole machine seemed nothing short of miraculous. I’d seen calculating machines before, and had even built a crude model as part of a team of school pupils for an early science-fair project. However, that device used switches, potentiometers and analog meters to calculate and display basic mathematical functions. While it worked, it was underwhelming, and didn’t win any prizes. It did demonstrate the basic principles that all modern computers run on though (royalty cheques accepted!). The biggest issue was reading those inherently inaccurate analog meters and trying to analyse the results of our calculations. It would have been so much easier if we’d had a digital readout. That is why I was so impressed with that HP calculator; tap in your figures, press a button and there it was; even the dimmest among us could read directly from the display. Shortly after that, I saw my first digital watch. These so-called “moon watches” were unbelievably modern and a much sought-after accessory. At the press of a tiny button, the time (and day and date in some versions) was displayed on a miniature red LED array for around five seconds before going dark. This was a trade-off between functionality and battery life; the tiny ‘watch’ batteries of the day would soon run out, so the time was only displayed briefly at a press of the button. These watches were so über-cool that everyone who saw one immediately desired one, though not many could afford them in the early days. Nobody really wanted to wear those old-timey analog Rolex, Citizen and Seiko watches anymore; all that mattered was having a timepiece with a sleek stainless-steel body and a mysterious LED display! As time went on (LOL!), prices fell, especially with the advent of back-lit liquid crystal displays, whose powersaving properties and increased functionality made moon watches old-hat almost overnight. But those early LED watches are now a sought-after item, with the hipster crowd especially prepared to pay big money for original models. The sad fact is that many of those old-style LED displays are now so weak as to be unreadable because (like me) time has robbed them of their glamour. Analog vs digital: this time it’s personal From an electronics measurement point of view, digital displays were regarded as revolutionary. Way back when, I only used analog meters because that was all that was widely available. Those of a certain age will recall those large, heavy Bakelite Avo-style multimeters (and their clones) that cornered the market in the 60s, 70s and 80s, before the likes of Fluke and others popularised the digital multimeter, driving analog meters increasingly out of fashion. On the face of it, having a digital meter made sense. For one, you could read the exact value on the display, so there was no misinterpretation of the results, or pesky parallax errors. And you could see it in the dark, which alone was bordering on voodoo to many servicemen. Many digital meters also featured a ‘hold’ function, meaning you could measure in cramped quarters and extricate yourself before checking the results on the meter. This was something just not possible with the analog meters of the time. This is what they call progress. However, there were problems. Digital displays require actual reading. Pilots, for example, don’t need to know their exact exhaust gas temperature; they just need to know the needle is in the right place and a quick glance tells them all they need to know. Reading EGT on a digital readout takes time and breaks concentration. It takes me longer to note my car’s speed on a digital speedo than an analog dial, requiring me to take my eyes off the road for longer. Editor’s note: I find the exact opposite to be true, despite using analog speedometers exclusively for almost 20 years before getting a car with a digital readout. These days, I often find myself using my analog multimeters, but it also depends on the task in-hand. I’m lucky to have options, because I’ve built up a collection of both analog and digital types over the years. And given that I can buy a digital multimeter for just a few bucks that (on paper at least) matches the specs of any multi-hundred dollar analog model of just a decade ago, there is no excuse not to own more than one. Items Covered This Month • • • • • Decisions and hard choices Yamaha amplifier and Simmons subwoofer repair Battery replacement for tablet Vox valve guitar amp repair Mitsubishi aircon repair *Dave Thompson runs PC Anytime in Christchurch, NZ. Website: www.pcanytime.co.nz Email: dave<at>pcanytime.co.nz 62 Silicon Chip Australia’s electronics magazine siliconchip.com.au For one project, it was cheaper for me to buy two digital multimeters from the local electronics store than to buy dedicated volt and ammeters. And if I am only reading the battery voltage under the bonnet of the car, or using the continuity beep function to ring out a cable loom, I don’t need anything as fancy or as inconvenient as those bulky, olde-worlde movingcoil models anyway. However, like many service people, I still love my analog multimeters! Disaster strikes I only bring this up because the other day I was moving an amplifier chassis around my workshop and as I picked it up from my (admittedly overcrowded) workbench, I accidentally snagged one of the leads of my oldest and dearest multimeter. Not realising I was caught up, I dragged the meter off the bench and it fell and hit the barely-carpeted concrete floor of my shop with a sickening crunch. Yikes! This particular meter has a nice leather case, and while you’d think that this might help save it, alas, no. While not appearing physically damaged, the meter’s needle now sat fixed at a weird angle at around 30% of the scale, and wouldn’t move when the meter was lightly shaken from side to side. This is a classic sign the meter’s armature had either been shocked free of the pivots it usually sits in, or was just broken. It wasn’t looking good. Many people would just shrug their shoulders, throw the meter in the bin and get another one out of the drawer, but you know me; if this wasn’t repairable I might consider chucking it, but until I ran out of options, binning it wasn’t going to be one of them. The first thing I did was undress it. The leather case might look authentically vintage, but it didn’t do much to prevent the meter from getting clobbered. Then again, perhaps things might have been worse if it didn’t have any protection at all. Ah, yet another philosophical question to ponder! I quickly removed the few screws that held the back on. No pointless anti-tamper fasteners here, just good, old-fashioned self-tapping screws. There were two batteries inside, one PP3 and one AA. This slightly surprised me; while I am obviously siliconchip.com.au aware these things have batteries, this meter is at least 30 years old and I can’t recall ever replacing them! I’d take the opportunity to do that now, but first I’d need to get the meter working again. The PCB was held in with another couple of screws, and with those out, only the front panel knobs prevented it from being lifted straight out. The knobs popped off without too much effort. The four main connectors, what I call banana sockets (but are also known as 4mm connectors) were hardwired to the PCB and came out with it as an assembly. I de-soldered the few flying leads connecting the batteries and meter, but I was careful to leave the rotary switch components sitting in the top cover, as there are lots of small bits and bobs that make up the switch and these are easily lost. I’d made this mistake before years ago, creating a lot of extra work for myself, so I was prepared for it this time. I took a digital photograph of the positions of all those bits before removing them and putting them aside in a parts tray. I was now left with the plastic top ‘half’ of the body and the meter assembly. The clear plastic meter facia simply pried off with some gentle persuasion applied to the slots provided. From this point, I had to be ultracareful, as the meter movement was now totally exposed and I didn’t want to damage it further. The white meter face was also vulnerable to contamination with dirt, fingerprints and wayward tools, and any mistakes at this point would really decrease my chances of a good outcome. Analog meter 101 This movement is what is known as a moving-coil meter, and they are used in many indicator and measurement roles. Their operational theory is simple; a soft iron armature, with a needle attached and a coil of wire wrapped around it, is suspended within the magnetic fields of a permanent magnet. When a current is applied to the coil through two tiny counter-wound hairsprings (which also assist with meter damping), a rotational force is created proportional to that current. The amount the needle deflects is then apparent against a scaled meter face. Australia’s electronics magazine October 2020  63 The trick is making the armature as friction-free as possible, increasing sensitivity, and in really goodquality meters this means mounting the pointed ends of the armature into jewels embedded in the meter frame. Mechanical wristwatches also commonly use this technique. Cheaper devices use either bronze or steel bushings to do the same thing, and usually work just as well; the only downside being they may not last as long without adjustment. In this case, one end of the armature’s mounts is adjustable via a setscrew, which also fine-tunes the ‘endfloat’ of the assembly, and correct adjustment means an almost friction-free movement. End-float is usually set at the factory, then sealed with a dab of paint. This adjustment lasts (hopefully) a lifetime. Most meters also have a zeroadjustment screw accessible from the outside that engages and alters the armature spring tension, allowing a null balance point to be set. I thought the armature might have simply been jolted out of its mounts by the fall, which would explain the cock-eyed angle the needle was sitting at, and the lack of free movement. Visual inspection under magnification confirmed this was the case. The only way to replace the armature into its mounts was to back off the top adjustment screw until I had enough room to reposition the pointed ends back into the bearings. I could then re-set the end-float for maximum free movement without any play. I backed off the set-screw by breaking the paint seal and gently coaxed the armature back into place with tweezers, a job made trickier by the springs, as they tried to pull the armature in different directions. I managed to position it, tightened the screw and carefully adjusted it. However, the needle still read half-way up the scale, and the zero-adjuster had minimal effect. With the armature in place, the movement should have been free to find its natural balance against the spring tension, and would be adjustable with the mechanical zeroset screw. However, the needle was still ‘sticky’ and moved erratically, so something else was going on. Another inspection showed the outer coil of the bottom hair-spring was wrapped around one of the tiny, sol64 Silicon Chip dered coil connections. It wasn’t going to move freely if that spring was impaired, so with two pairs of tweezers, I gingerly extracted the spring from the obstruction. This is trickier than you might think, as these coil springs are extremely thin and fragile, and any kink or other anomaly would alter its tension and would prevent the meter from ever being accurate. Luckily, I managed to unhook it, and the needle immediately fell back into place. With a sigh of relief, I reassembled everything and checked calibration against some known values. I used a 50W reference resistor and a regulated 5V output from a power supply, and after some adjustment, both results were close enough. Disaster averted, and my favourite analog meter lives for another day! Yamaha AX-300 amplifier and Simmons S-10W subwoofer repair R. W., of Lismore, NSW took a punt on buying some cheap old audio gear in the hope that he could fix any problems that might crop up due to its age. As it turns out, his confidence was not misplaced… Motivated by letters in Silicon Chip on repairing older hifi amplifiers, I Australia’s electronics magazine kept an eye on an internet auction site with a view to obtaining a decent amplifier and a small subwoofer. Eventually, I bought a 1980s Yamaha 30W per channel amplifier and a 100W subwoofer with an odd 10-inch driver for a bargain-basement price. The vendor of the amplifier stated that one should not expect it to perform as it did when new, but I was not perturbed as it cost less than $50 and could use the case if it was a write-off. After performing some safety checks, I powered up the amplifier and sampled its performance. What a disappointment! It had quite a lot of hum in both channels, the volume pot was noisy, and the sound could best be described as “thin” – lacking in fidelity and dynamic range. On removing the cover, the innards were relatively clean but 6000µF power supply filter capacitors had noticeable bulging. I was unable to obtain a schematic for the amp but decided to take a punt and replace the caps and see how things went from there. As it happens, Altronics sell similarly sized electrolytics rated at 10,000µF, so I decided to mail-order some. The cost was well below their minimum for mail order, so I decided to change every electrolytic capacitor in the amp. siliconchip.com.au On powering up with the new caps, the hum had completely disappeared, and the performance was probably as good as new. Some contact cleaner for the pot and a new coat of satin black paint on the cover, and it was like new. I remember being impressed with the Yamaha amps in the 80s and this one was no different now. A few days later, the subwoofer arrived. It had clearly been stored somewhere damp, as there was mould residue on the driver, the case and the grille. This was easily cleaned off, and the enclosure was then immaculate. Powering the speaker with nothing connected and I was greeted with – yes, you guessed it – hum! Removing the integral amplifier again showed bulging filter electros in the power supply with a value of 10,000µF that were the same physical size as the ones from Altronics. Two more of these fixed the hum issue, so I set the system up with my TV. On switch-on, after the speaker protection relay engaged on the subwoofer, I was yet again greeted by hum! This had to be an Earth loop as both the sub and the Yamaha amp were quiet when separated. The AX-300 has a shielded power transformer but is supplied with a two-pin mains plug and had an Earth binding post for use with a turntable. The sub has a 3-wire IEC power input socket. I made a 3-pin mains plug with just a green wire connected to the Earth pin, and I connected the other end to the binding post on the amplifier. The hum disappeared, so it was definitely an Earthing problem! So I replaced the amplifier’s power cord with a 3-wire mains lead, properly secured and Earthed. For less than the cost of a soundbar, I had obtained a sound system that would blow any of them out of the water, and saved some old but still useful pieces of equipment from the scrap heap. I’ve been using a Samsung Galaxy S 10.5 tablet for a few years now. Lately, I noticed that its screen was bulging in the middle and it had come loose from the frame. I immediately realised that the battery must be failing. I’ve seen this happen to other devices, so I knew it was time to replace the battery. Before I started working on my tablet, I found a good video on replacing the battery in this particular tablet on YouTube. Watching that, I picked up some useful tips. The first thing to do was to remove the back of the tablet to access the battery. This proved to be somewhat tricky, as the back had not been removed previously, but with some effort and a couple of phone repair tools, I was able to remove the back and gain access to the battery. With the back removed, I could see just how badly the battery was bulging. I was also able to press the screen back into place. I was hoping that the screen had survived being bent; I later determined that it had not suffered any damage from being bent away from the frame. Removing the battery is fairly easy; it just entails disconnecting two ribbon cables and the battery connector, then undoing the four screws that hold the battery in place. I was going to or- der a new battery via eBay; but first I thought I would try the battery from another identical tablet I had, to see if it was still usable. The other tablet’s battery charging circuitry had failed, and I couldn’t fix it, so it was a suitable donor. Because this battery had been flat for months, I was concerned that it might not charge, but decided to install it anyway and give it a go. After moving it from one tablet to the other, I reconnected the ribbon cables, plugged in the charger and left it for several hours. I occasionally checked it to see whether it was charging. The charge indicator sat on 0% for quite some time, leading me to think that it wasn’t going to charge. Eventually, it went up to 2%, which was a good sign. It took a long time to charge the battery fully, but it did reach 100%. The next thing would be to see if it retained its charge, after being flat for months. I checked it the next morning, and it was still 100% charged, so it looked like the battery was still viable. I was a bit concerned when I noticed that there was a “no go” symbol next to the battery charge indicator on the screen. But I thought this might be because the back was off, so I refitted it. Now that the back was on, the “no go” symbol was no longer present, so The bulging case of the Samsung tablet is shown above, with the battery shown below. Samsung tablet battery replacement B. P., of Dundathu, Qld has become quite adept at keeping old electronics going. This time, he noticed a quite worrying symptom in his tablet and luckily, had a ‘donor’ device which provided the parts he needed to fix it... siliconchip.com.au Australia’s electronics magazine October 2020  65 that confirmed that the assumption was correct. Often when a lithium-ion battery is flat for some time, it will no longer accept a charge. Whether this battery’s bad start to life will come back to haunt it in the future remains to be seen, but for the moment at least, it seems that it’s still good. I tried fitting the damaged battery into the other tablet with the faulty charging circuitry, but it wouldn’t switch on, and I noticed some parts of it getting very hot, so that tablet is only useful for spare parts now. Regardless, this was another repair that ended up not costing me anything, thanks to having access to the defunct tablet for spares. These batteries are around $25-30 on eBay, so they aren’t that expensive, but it was nice to be able to complete the repair at no cost. I hope to get a lot more use from this tablet before it becomes obsolete. Vox valve guitar amplifier repair S. W., of Fulham Gardens, SA had to guess at the values of some burnt components to repair a guitar amplifier. While it turns out that the values he chose weren’t the same as the originals, they must have been close enough as the repaired amplifier worked well enough... Some time ago, I was asked by a family member to repair a Vox AC4TVH 4W valve guitar amplifier that was inadvertently operated without the speaker connected. Apparently, the user was unaware that this amplifier does not have a built-in speaker, and should only be used with an external speaker plugged in. After removing the amplifier module from the case, I observed that heat stress on several resistors had caused their values to become unreadable. High-voltage supply fuse FS2 was also blown. I checked the audio output transformer and found it to be OK. I then powered up the amp and found that the mains transformer secondary voltage was acceptable, and the filaments of the two valves were alight. Hence the two major components appeared to be undamaged. Great! Further testing revealed that three of the heat-stressed resistors were opencircuit. I was unable to find a circuit on the web to identify their values. Therefore, I saw no alternative except to trace out the circuit of the module using some valve circuit theory from decades past. This resulted in the circuit diagram shown here where R5, R17 and R24 (highlighted in red) were the open-circuit resistors. Using basic circuit theory, I selected a value of 180W for R5 to allow the EL84 to self-bias at about 8V with an anode current of around 50mA, and 820W for R17 and R24, to keep the anode and screen voltages for the EL84 below 300V when operating. Once the resistors were replaced, I soon discovered that the major problem was an internal short between the screen and grid of the EL84. With a new tube in place, the amplifier fired up as expected. The only problem was that the power output was only about 3.8W across a resistive 15W load before amplitude limiting set in. I contemplated lowering the value of R17 and R24 to increase the available power to 4W. However, the owner was not concerned about the lower power level and was just happy to get the working amplifier back. As I was working on it, I noticed signs that the amplifier had some problems in the past. For example, blown fuse FS2 was labelled 200mA, while the value written on the circuit board was 125mA. This may indicate that sometime in the past FS2 was replaced with the higher-rated fuse. Possibly, this was The full circuit diagram for the Vox AC4TVH valve-based guitar amplifier, which was found online. 66 Silicon Chip Australia’s electronics magazine siliconchip.com.au done as a quick fix for an intermittent short in the EL84. One can only speculate! Some time later, while I was searching the web for information on singleended valve amplifiers, I came across a full circuit diagram of the AC4TVH. In this circuit, R17 and R24 are shown as 220W while R5 is 180W. So I got R5 right, but went a bit high on R17 and R24, hence the slightly reduced output power. Mitsubishi aircon repair D. S., of Maryborough, Qld took a look at an aircon that had been deemed unrepairable by a professional. And guess what, he managed to fix it with just a bit of effort and a less than a dollar’s worth of parts. Sadly, this is far from an uncommon story... Air conditioners, in both vehicles and homes, usually come up for repairs and service during summer. So, I wasn’t surprised when I got a phone call from a friend in January asking if I could take a look at his home aircon. I was told that a service agent had already looked at the system but had told the owner that the mainboard had been destroyed by gecko urine, and that replacement mainboards were not available, so the whole system would have to be replaced. I thought there must be a cheaper way to fix it, so I switched off the power and took off the covers. Many covers... I have to admit, the chances of a gecko getting into the enclosure which held the circuit boards seemed slim with all the covers in place. Upon initial visual inspection, I found no physical damage, so I grabbed my drivers again. After rechecking to ensure the power was off, I disconnected the mainboard, marking all the various connectors and taking photos on my phone to ensure that I could reassemble it later. 15 minutes later, I had the mainboard out. A much closer inspection showed nothing of interest, no damage, no swollen electros, no burnt-out transistors, nothing! I searched the rear of the board, checking for dry or broken solder joints. The board did have a few heat marks and discolouration on it from thermal stress, but removing and checking the affected components, I found no problems. It’s a Mitsubishi split system aircon, and these units are very well made. siliconchip.com.au The boards are fully marked with all components types, values and test voltages silkscreened to the board, so it was a pleasure to find everything as it should be. So I refitted the board, plugged everything back in and turned it on. The head unit lit up like it should for about five seconds, then shut down again. The condenser section was doing the same. The main condenser fan started up and ran for about two minutes before shutting down, but the compressor did nothing. I searched the internet hoping to find that this unit had on-board diagnostics and it did. However, we could not locate the remote to press the appropriate buttons to get any fault codes. After further checking, I noticed that the mainboard switched mains to the various mains components, but the control circuitry ran from 24V DC, 12V DC and 9V DC rails. The mainboard did not have any form of power step-down circuitry, so where were the logic supplies coming from? I removed the mainboard again and discovered another board hidden beneath it, inside its own plastic enclosure. Another 15 minutes of fiddling finally got it out. Close inspection revealed several leaking electros and quite a bit of corrosion across this smaller board. Replacing the leaky electros and cleaning up the mess was easy. All the caps were common value, high-temperature through-hole components. I also found the remains of a very small signal diode that had virtually rotted away. I had to guess its type as the corrosion had also destroyed that part of the silkscreen. I used a 1N4007 type rated at 1000V, 1A. This power board supplied the various DC rails to the mainboard via a small relay, so I reasoned that this was a good choice. I also found a tiny ceramic capacitor fitted across two wires of a five-wire connector. I backtraced this small harness back to the mainboard where it connected to the processor chip. The power board had several ICs controlling the various switchmode sections, along with the usual opto-isolators, SMD transistors and various other surface mount components. This harness carried control data to and from the mainboard to the power board, although I could not locate any other information on its function online. I cleaned up the corrosion, re-drilled the through-holes and concentrated on the remains of this small capacitor. It’s difficult to clean off corrosion without removing the markings, but after some very gentle wiping, I found the value 104 marked. Thus it was a 100nF capacitor, which I had in my parts box. After replacing that capacitor, I began to reassemble the various boards. That’s when I found that the corrosion on the small harness had eaten through one of the conductors. I have heard many times that “it just fell off in my hand”. Well, this time it really did! I cut off the damaged section of cable, reattached the connector and refitted the board into its hiding place. The mainboard went back without a hitch, and I plugged all the wiring back into their clips. On went the power; no bangs or puffs of smoke occurred so I flicked the manual off/on switch on the head unit and it sprang to life. After 30 minutes, I refitted the external covers and gave my friends the good news. There was some bad news; he would need a new remote control, but at $65, that was going to be a lot cheaper than a whole new system! Another air conditioner saved from landfill; it was almost chucked out because a service technician could not be bothered to diagnose it fully. I have no idea which fault or faults were actually stopping it from working, but I have always been a firm believer in fixing that which can be fixed! SC Servicing Stories Wanted Do you have any good servicing stories that you would like to share in The Serviceman column in SILICON CHIP? If so, why not send those stories in to us? In doesn’t matter what the story is about as long as it’s in some way related to the electronics or electrical industries, to computers or even to car electronics. 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 October 2020  67 See SOUND in COLOUR! The CAE SoundCam Because of a neurological disorder called ‘synesthesia’, some people can actually ‘see’ sound or ‘hear’ light (albeit involuntarily). However, most of us would need a device such as this CAE SoundCam, which uses a video camera and a phased microphone array to provide spectral and visual analysis of sounds in real-world scenarios. Its capabilities are fascinating. O ne of the difficulties of reviewing a product like this is that there is nothing that we can compare it to! It’s not like a new scope or spectrum analyser, where we’ve seen dozens of similar devices, and the latest one might offer better performance or some new features. This device can do things that we’ve never seen done before. It’s a genuine first! Like Galileo’s telescope, Marconi’s radio, Edison’s first sound recordings or light bulb, Alexander Graham Bell’s telephone or John Logie Baird’s TV, this instrument is a pioneer. “Everything that can be invented, has been invented” was loudly announced by Charles H. Duell in 1899. He was the Commissioner of US patent office! That just goes to show how right Yogi Berra was when he commented 68 Silicon Chip that “It’s tough to make predictions, especially about the future.” The SoundCam is a product which has been in the making for over 15 years, and has now materialised as CAE’s flagship product. It is a (somewhat) affordable and portable instrument which we think is incredibly innovative, and it’s likely to have numerous applications, many of which haven’t even been thought of yet. You could use it to locate a drone in the dark, find sound leaks in soundproof rooms, spot birds in distant trees at night, identify which part of an engine is starting to fail; the possibilities are many. According to Sales Chief Maik Kuk- “Hands-on” review by Allan Linton-Smith linski, some of the main applications that they see for the SoundCam are in the automotive industry. Not only can it potentially find mechanical problems, but it can also assist with vehicle noise reduction. It can instantly pinpoint annoying squeaks, rattles, engine and wind noise. It has even been used for Formula 1 wind tunnel tests. Not only can it pinpoint sound sources, but it can also quantify the frequency and amplitude and record sessions for downloading. You can watch a short (four-minute) video on the SoundCam at https://youtu.be/-VmPZeYx2II You can also read more technical info and download data from their website at siliconchip.com.au/link/ ab45 Fig.1 shows the SoundCam being Australia’s electronics magazine siliconchip.com.au Fig.1: the first thing we thought of when testing the SoundCam was whether it could be useful to us for loudspeaker development. While we use electronic instruments for analysis as much as possible, we still have to rely on our ears quite often to detect problems such as drivers rubbing on the cabinet, and to assess things like off-axis response. The SoundCam can provide a more objective measurement of these things, and much more. used to examine the high-frequency output from our Senator two-Way Loudspeaker System (September-October 2015; siliconchip.com.au/Series/291) at a 45° angle. The spectrum analysis shows that the tweeter is reproducing sound up to the specified 20kHz maximum frequency at this angle. It also indicates the amplitude distribution is very evenly spread away from the horn. Fig.2 is a closeup of the SoundCam screen during this test, so you can see the results in more detail. Fig.3 shows a grand piano while it is being played. The highest intensity sound (yellow/orange/red) seems to be emanating from the holes opposite the soundboard, not directly from the strings. The SoundCam filters are set to respond from 1.4kHz to 18.4kHz, with the sound mainly being detected up to about 5kHz. The bars represent each chord being played; the lower yellow bars are the bass notes. Fig.4 shows the action side of the instrument, which has 64 MEMS microphones placed in concentric circles, each covered by a Gore-Tex screen for protection from rain, wind and dust. There are four bright LEDs near the centre to assisting with photography and videos. We’ll take a detailed look at MEMS microphones in a forthcoming issue. siliconchip.com.au First impressions The camera arrived in a large foamlined suitcase and is surprisingly sturdy, incorporating the best of German engineering. You could call it “bulletproof”, but it is also beautifully and stylishly designed and is ergonomically correct, which enhances its natural ‘feel’. As soon as you lift it out of its case, it looks and feels really strong. CAE has spent much time with this aspect of its design, which is great for field technicians and others who need to hold its 3.5kg bulk in the air. When used in the field, it might even take some knocks or (shock horror) be dropped. I was convinced that it would survive an explosion, but still handled it with kid gloves because it isn’t mine! We borrowed the review unit from Pulse Acoustic Consultancy who use the SoundCam for various projects, including pinpointing noise problems in squeaky rooftops, air conditioner duct noise and for soundproofing studios. For those who want a fixed setup, an exceptionally sturdy Rollei tripod and carry strap are cleverly included in the case. This has a quick-release attachment, and the whole setup can be assembled in a couple of minutes. We tried tested the unit in as many different applications as possible, but it rained continuously for the whole time it was on loan. We have no doubts that the unit is waterproof as claimed, but were not game to get it soaking wet, especially when the instrument was booked to do some serious work at a local TV studio the next day. So we mainly tested it on loudspeakers Fig.2: while showing the location and intensity of sounds on the image captured by the camera, by default the SoundCam also gives you a ‘waterfall’ type spectrum-over-time display as well as an instantaneous spectrum display to its right. Australia’s electronics magazine October 2020  69 Fig.3 (left): here is a SoundCam view of the strings of a grand piano. Interesting (but perhaps not surprisingly), this shows that much of the sound comes off the sounding board rather than the strings themselves. Fig.4: the array of MEMS microphones that make up the SoundCam, along with the four bright white LEDs surrounding the video camera at the centre of the unit. It is sturdily built. and musical instruments. While they did not make a big deal out of this sort of application, this instrument has excellent potential for speaker and sound equipment manufacturers. It can be used to examine and analyse sound patterns, dispersion factors, directional radiation, buzz and rub and also identify problems such as leaky cabinets and cabinet vibration, rattles and squeaks. Operating principles The SoundCam contains 64 MEMS microphones, each covered by a GoreTex type of material for protection against moisture and dust. The sockets for LAN, recharging and USB are also nicely covered by a rubberised material which can be flipped to one side for use. The four ultra-bright white LEDs come in handy for illuminating objects, for a clear image of the device under test. The instrument identifies the origin of sound sources and pinpoints them by analysing the time of sound arrival at the various microphones on the receiver. The device is totally passive, and unlike a radar which emits signals, the SoundCam is undetectable. That might make it very useful for military and surveillance applications (as well as bird-watching)! The manufacturer advises that there is significantly less resolution at lower frequencies; this particular model has some difficulty pinpointing sounds below about 800Hz. 70 Silicon Chip CAE has larger models to cope with longer sound wavelength (ie, lower frequencies), but this model is their flagship instrument, designed for general field applications. User interface On the operator side of the instrument, there is a large 7-inch 800x480 pixel colour touchscreen. At startup, the screen is split into three sections: a viewing area, a small second screen which shows a vertical spectrum analysis, also with the controls for user-settable filters for upper and lower frequencies. At the lower left, a third screen records frequency over time for the time recording settings selected, or continuous logging. There is also a bargraph calibrated in dB which indicates areas of sound intensity, and this can be adjusted for sensitivity. Adjustments can be made for the distance from sound-generating objects, but this is not a critical setting, and just about any distance setting will typically suffice. You can also switch to a full-screen view, without the spec- Fig.5: the SoundCam can quickly pinpoint sound leaks in places like recording studios. Australia’s electronics magazine siliconchip.com.au Fig.6 the SoundCam mounted on its tripod. Here the four LEDs can be seen brightly glowing. Fig.7 (below): the SoundCam is supplied, with accessories, in a sturdy carry case. trum or filter settings. Still images or videos can be recorded onto an SD card for subsequent analysis and interpretation. Specifications Physical Properties Dimensions Weight Waterproof Anti Theft System Battery Life 340 x 340 x 95mm 3kg IP54 Kensington Lock Min 2.5h Display Size Resolution Touch 155 x 86mm 800 x 400px 10-finger capacitve Embedded Controller Processor Internal Storage Operating System ARM A53 4x1.2GHz with 1GB RAM 32GB Linux for ARM Interfaces USB Ethernet Audio For data export LAN (for running softwae on laptop/PC) 3.5mm for headphones Sensors Microphones Frequency range Sound pressure Sample rate Resolution 64 digital MEMS 10Hz - 24kHz Max 120dB 48kHz 24-bit Optical Camera Type Resolution Lighting Aperture angle Shutter Digital 320x240 (50fps) or 640x480 (16fps) 4 LEDs ±38° Global shutter Power Battery Supply Input Management Li-ion rechargeable (48Wh) Power Adaptor 19V Smart work and charge simultaneously SoundCam applications Finding an annoying noise in a vehicle is always a problem. Often, mechanics have to use a trial and error approach, and some difficult noise problems may never be solved. But with the SoundCam, unwanted sounds can be isolated in a matter of minutes with either an internal “shoot” or an external video of the passing vehicle. Even the weirdest engine noises or external wind-related noises can be isolated and fixed quickly, making it great for body shops as well for mechanics. And note that many parts of an engine or transmission which are worn, damaged or otherwise failing will often make noise, so by pinpointing the source of that noise, it may be possible to determine what needs to be fixed or replaced. Fig.5 shows the SoundCam picking up a sound ‘leak’ entering a soundproofed studio, so that it can be blocked. Annoying noises can also be a real problem in buildings. This includes sound transmissions or leaks between adjacent apartments, offices and factories where soundproofing is insufficient or faulty. Other noise problems can be caused by worn bearings in machinery, badly designed or installed ducting etc. The SoundCam can quickly pinpoint these noise locations. Annoying noises such as rattles, squeaks and buzzes can also emanate from devices such as hair dryers, blowers, washing machines, vacuum cleaners etc. If these problems can be identified during manufacturing, they can be fixed before reaching customers’ hands, improving the user experience and reducing costs associated with returns. This instrument clearly has many other applications not mentioned in the CAE literature. It can spot drones and other “stealth” aircraft (which may be invisible to radar), as well as to detect ground vehicle movement and even people walking in concealed locations such as forests or jungles. It could be used in mining, to detect underground movesiliconchip.com.au ment, locate avalanches and falls, locate vehicles and to assist with the detection of lost or trapped personnel. As you can see from the images earlier, we have also investigated its use in loudspeaker development. Driver buzzing and rubbing are common problems during loudspeaker production, so devices like the SoundCam can simplify quality checks. Loudspeaker cabinets can also be checked for rattles, leaks and unwanted vibration. Conclusion The SoundCam is a highly developed and (relative to its capabilities) affordable instrument which has many applications, and is also easy to use. It is extremely rugged and can easily and quickly set up by just about anyone with minimal instruction. There is no doubt that such an innovative device will find success in many, many different applications. Also, I really want one! This instrument was kindly loaned for review by the Australian distributor, Pulse Acoustic Consultancy, Level 4, 73 Walker Street, North Sydney NSW 2060. For enquiries, contact Mathew Harrison on 0425 467 764 or visit www.pulseacoustics.com.au SC Australia’s electronics magazine October 2020  71 USB Part III: Construction by Phil Prosser Over the last two issues, we’ve introduced our new USB Sound Card, which we’ve dubbed the SuperCodec, and described its performance and operation in some detail. You would agree it offers extremely high recording and playback performance – so much so that our Audio Precision system can barely even measure its distortion! Now it’s time to put it all together, and get it up and running. I t’s best to build the SuperCodec in stages, checking after each stage is complete that everything you have just assembled is working properly. Before starting, check that the PCB slides neatly into the case. This board is specifically made to fit a Hammond 1455N2201 case, which is sold by both Altronics and Mouser, as stated in the parts list published previously. The part codes given are for the case with black end panels, as we have used, but note that Mouser stocks it in several other colours too. Now let’s move on to mounting the components on the PCB. Mounting the pre-regulators Loading this section is pretty straight forward, as it is all through-hole. The PCB has a section marked to indicate this part of the circuit. Referring to the PCB overlay diagram, Fig.17 and the photograph alongside (which you should do throughout the construction process), this section is at lower right. Start by fitting the six resistors in this section, in the positions shown in Fig.17. Follow with the three diodes, D1 (1N4004) and D2-D3 (1N5822). Note that they are not all aligned in the same direction. They have been oriented to minimise path length and radiation loops, so double-check that your diode cathode stripe is aligned as shown in the overlay diagram and on the PCB, before soldering each. The next job is to install the seven MKT capacitors, which are not polarised, followed by the DC input barrel connector and the fuse clips, marked F1. Then you can fit the eight electrolytic capacitors; these are polarised, so their longer (positive) leads need to go into the pads nearest the + marks on the PCB and in Fig.17. Oh no! I put an IC in the wrong way around! Everybody makes mistakes! So what to do if you got a part the wrong way around or in the wrong spot? For through-hole parts, there are two ways to proceed. For electrolytic capacitors, you are best off using a solder sucker to get as much of the solder from the holes as you can, then judiciously heating one pin and “pushing” the capacitor to lever up the component on the hole you have hot. Be careful and make sure that the leads are straight and will not tear the through-hole plating out as they go. 72 Silicon Chip For op amps, resistors and diodes, the easiest and safest way by far is to cut the component from its leads, then remove the leads individually from the board and clean up the holes. It sounds wasteful, but this could save you tearing a track from your PCB, a lot of frustration and many naughty words. Surface mount parts are much easier to remove with a hot air gun. Set it to about 300°C, heat the part until all the leads come loose and use tweezers to lift it free of the PCB before the solder solidifies – job done. If you don’t have one, you can alternatively Australia’s electronics magazine heat each side of the part until it comes loose. If it’s an IC, this is easiest to do if you join all the pins on each side with one big blob of solder. It’s easy enough to clean up afterwards. If you won’t pay what your local electronics shop is asking for a hot air station, look on eBay; there are ‘decent’ hot air guns available at giveaway prices. Search for “hot air SMD rework”; some are well under $100. These are brilliant for heatshrink work too. Note that it’s best to keep these switched off when not in use! siliconchip.com.au Make sure that the 2200µF 10V capacitor goes to the right, as shown by the smaller circle, with the larger 2200µF 25V type to its left. Also ensure that the two 470µF capacitors fitted in this section are rated at 25V; the 470µF 6.3V capacitor goes elsewhere. You can then solder LED2 in place. For now, mount it vertically, with the base of its lens 10mm above the top surface of the PCB. Make sure its longer anode lead goes into the pad marked “A”. It’s then time to solder switchmode regulators REG1 & REG2 in place. They have five pins; if yours are all in a row, crank them out with needle-nose pliers to fit the pad pattern on the PCB. They don’t need heatsinks. Now solder the inductors to the board. L1 and L3 are both bulky toroidal types while L2 and L4 are smaller bobbin types. Put a dab of RTV or neutral cure silicone sealant under each inductor to help hold it into place, and prevent vibration, as shown in the photo overleaf. Finally, add the 0Ω link; we used a length of 0.7mm tinned copper wire bent to form an Earth connection point, but you can also use a zero-ohm resistor as shown on the PCB overlay diagram. Testing the pre-regulators Connect a voltmeter from ground (eg, either end of the 0Ω link) to the near end of FB12’s pad. This is a convenient point to measure the -12V rail, as marked on the PCB. Connect your 12V DC plugpack to CON1. The specified plugpack is a switch mode unit capable of delivering at least 1.5A continuously. Switch on the power and look for the -12V rail coming up. Check that it is between -11 and -13V. Ours measured -11.5V. Then move the red probe to the near end of FB8 (another empty pad) and check that the +6.5V rail measures 6.0-7.5V. Ours was close to 7V. Finally, move the probe to the near end of FB11 and check that the +12V rail is OK. It will possibly be close to 11V due to the forward voltage drop of diode D1. You can then disconnect the plugpack and proceed with Soldering tips • Use a very fine tip on your soldering iron, the finest solder you have, with gel or liquid flux and a magnifying lens. • Stay calm. Remember that if you only solder down one pin of each device at the start, you can easily melt this and move things around to get it all aligned. • Then by soldering a second pin, you can lock the part in place. Go easy on the solder and remember you can reflow one pin if you need to nudge the part a bit. • Use less solder than you think you need. You will be surprised! the construction. If any of the readings are off, look for short circuits or bad solder joints. Also make sure that your plugpack has the current capacity to kick that negative regulator into operation. Mounting the linear regulators This section is in the middle of the board and includes regulators REG3, REG4, REG6-REG8 and the surrounding components. Start by loading all the ferrite beads in this section, FB8 through FB13. These can be any small ferrite that fits; they are there to offer a high impedance at high frequencies to keep the noise on the rails down. If your beads came loose (as they often do), feed component lead off-cuts from the previous section through each one before soldering, or sections of tinned copper wire cut to length. When soldering them, try to ensure they are held tightly to the board to prevent rattling. Dabs of RTV or neutral cure silicone under each one should help in that regard. Next, fit REG7, the sole SMD regulator, while there is plenty of room around it. Follow with the ten resistors in this section, each being near one of the regulators. Then fit 1N4004 diodes D22-D29. As before, watch their orientations. Then install the six MKT capacitors, followed by the 12 polarised electrolytics. As usual, make sure their longer The completed project, albeit upside down! The main SuperCodec PCB “hangs” off the rear panel with no connection at all to the front panel – even the power LED shines through a hole in the panel. The daughter board (at left of main pic and inset above) is the MCHStreamer USB to I2S interface which plugs into the two 12-pin sockets on the underside of the main PCB. siliconchip.com.au Australia’s electronics magazine October 2020  73 leads go into the pads marked +. Keep in mind that they are not all orientated the same way. Again, with the two 470µF capacitors, they must be 25V-rated types, not 6.3V. Finally, fit TO-220 package regulators REG3, REG4, REG6 and REG8. Three of these (REG3, REG4 & REG6) are mounted on small heatsinks. In each case, place a lockwasher over a 6-10mm M3 machine screw shaft, followed by a flat washer. Insert an insulating bush into the hole on the regulator tab, then feed the machine screw through this. Slide a TO-220 insulating washer over the screw shaft, then feed the screw into the tapped hole on the heatsink. Do the screw up loosely, then drop the regulator leads into the PCB pads, while also lining up the heatsink posts with their mounting holes. Make sure the heatsink is pushed down fully and solder its posts to their pads. You will need a hot iron to do this, and it also helps to add a little flux paste to the area around the bottom of the posts. Then hold the regulator vertical and do up the machine screw tightly before soldering and trimming the regulator leads. Note that if you are using the recommended NE5532 op amps, in theory, you could leave off the heatsinks for REG3 & REG4. But they would run hotter. We recommend that you fit all three, just to be safe. Testing the linear regulators Reconnect the plugpack and measure the voltage at either end of FB9, on the left side of the PCB. You should get a reading in the range of 3.2-3.4V. Ours measured a touch over 3.4V – this is OK since the rail is currently unloaded. Measure either end of FB7 for +5V; this should read between 4.75 and 5.25V. Then measure the voltage on the tab of REG6, which is the +2.5V rail. This should give a reading between 2.3V and 2.7V. Next, check the voltages on the right-hand pads for the two 10Ω resistors in the upper-right corner of the board. The pad nearest the top edge of the board should be -9V (-8V to -10.5V) while the one immediately below should be +9V (+8V to +10.5V). If there are any problems, check the plugpack output voltage – is it working OK, or has it overloaded and shut down? If it shut down, look for a short circuit on the board. If you have not used the specified Coming up: a balanced attenuator add-on Phil Prosser has designed an add-on board for this project which adds balanced inputs and a switched attenuator with settings of 0dB, 10dB, 20dB and 40dB. This add-on board greatly improves the flexibility of the SuperCodec when used as a measurement instrument, and only slightly degrades its performance. If you’d like to build this add-on board, go ahead and start building the SuperCodec but don’t fit the headers for the MCHStreamer just yet, and don’t drill the case end panels either, as both the MCHStreamer and the main PCB are mounted slightly differently to make room for the addon board. The article describing this add-on board will be published within the next few months. 74 Silicon Chip Fig.17: the PCB overlay for the SuperCodec shows all components in place. However, as discussed in the text, it’s best to assemble the board section-by-section, allowing you to test each on completion and if necessary, fix any errors as you go. This overlay does not show the MCH daughter board, which plugs into the two header sockets (bottom left) on the underside of the main board. Australia’s electronics magazine siliconchip.com.au plugpack, is that negative regulator overloading it on startup? Try a beefier supply. Also check that all the diodes and capacitors are the right way around and all solder joints are good. Once the power supplies are all up and running, you are well on the way. We can now mount the remaining SMDs without fear of damaging them. Galvanic isolator and ASRCs This section is in the lower left-hand corner of the board, referring to Fig.17. Start by loading all the surface-mount capacitors in this section, then all the SMD resistors. The capacitors will be unmarked; while the resistors will be marked with codes indicating their values, you will need a magnifier to read them. In all cases, it’s easiest to rely on what’s written on the packaging, and fit one set of values at a time. Adding a little flux paste (or liquid flux) on each SMD pad before placing the component will make soldering easier. With the capacitors and resistors in place, proceed to solder IC6, IC7 and IC12. Note that pin 1 faces towards the bottom of the board in each case. Check and doublecheck the pin 1 marking on top of the IC package before soldering them, as they are difficult to remove. Again, flux paste will make soldering these parts much easier. Given the proximity of the pins on these ICs, it’s best not to worry about bridging pins when soldering them. Instead, check carefully after soldering using a magnifier, and use a dab of flux paste and some solder wick to clean up any bridges which have formed. If you are lucky, you will have a microscope; if not, you can use a smartphone camera to zoom in close to the soldered pins and take a photo. This is a good way to check for hidden bridges between pins. Next, mount the 4N28 and associated through-hole resistors, plus transistor Q1 and reset chip IC13. Finally, install the headers for the MiniDSP MCHStreamer which go on the back of the board. These should be ESQT-106-03-F-D-360 elevated headers providing 10mm clearance, to ensure the MCHStreamer fits. Testing this section And here’s the matching PCB photo which should also help you assemble the board. There’s a mix of through-hole and SMD components to be soldered in – you shouldn’t have a great deal of drama with the resistors and capacitors but some of the SMD ICs have quite fine pin spacing so you’ll need to take your time with these. Any solder bridges between pins must, of course, be removed! siliconchip.com.au Follow the instructions in the text box below to install the driver and get the MCHStreamer running. Once you’ve connected it to your computer, check that it has been detected by clicking on the volume control and checking that it comes up with Speakers (MCHStreamer Multi Channels), as shown in that panel. Operating systems other than Windows will use a different method. Once you’ve verified that it has been detected, unplug it from the computer and then fit it into the two matching sockets on the underside of the PCB. It should seat firmly onto the connectors. Power the sound card back up and connect the USB socket to your computer. You then need to make sure that the MCHStreamer is selected as the current sound output. To do this in Windows 10, left-click on the sound icon, and you will get a pop-up window as shown in the panel. If the MCHStreamer is already selected, then you’re all set. Otherwise, left-click on the caret (“^”) to get a list of available sound devices. You can then switch to the MCHStreamer. Now play some music or another audio file. It does not Australia’s electronics magazine October 2020  75 You can solder fine-pitched SMDs with a standard iron . . . matter what you choose, as we just want data to come out of the MCHStreamer. Check that the collector of Q1 (the pin towards the bottom of the PCB) goes high. Check for fixed-frequency square waves on the test points labelled on the PCB: MCLK (25MHz), BCLK_DAC (12.5MHz) and LRCLK_DAC (195.3125kHz). If you have trouble, check the power supplies. Anything odd here needs to be tracked down. The individual power supplies will assist you in isolating power-related problems to a small group of components. Also check for solder bridges, bad solder joints (especially on SMD IC pins) and check those capacitors. If you are lucky enough to own one, a PCB microscope can help identify problems in soldering – or alternatively, confirm you’ve done a great job! If you don’t own one, you could try using the camera in your smartphone to take close-up shots which you could then enlarge via your photoediting software to help you spot any “oopses”. Don’t have photo-editing software? Try downloading GIMP (it’s free!). The seven op amps are next. They are all orientated with pin 1 towards the upper right-hand corner of the board. You can either solder sockets and then plug the ICs in, or solder the ICs directly to the board (which will give better reliability, but make it harder to swap them later). Follow with all the MKT and ceramic capacitors, then the electrolytics. As usual, be careful to insert the longer leads Loading the DAC and ADC sections These sections are in the top half of the board and include all the remaining components. Start by fitting all the remaining surface mount capacitors. Make sure that the two 2.7nF (2700pF) caps go where indicated as these are critical to good performance. There is also one SMD resistor remaining (220Ω) so install that now. Then solder the ADC and DAC chips, IC1 and IC2. Orientate both with pin 1 towards the top of the board, with the power supplies are at the bottom. Use lots of flux paste, thin solder wire and tack down one corner to allow you to align the IC before soldering the remaining pins. Check there are no missed SMDs now, as after we load the through-hole parts, it is harder to get the soldering iron in there. Now mount REG5, the LP2950-3.3V in a TO-92 package. Follow with the seven ferrite beads left, FB1-FB7, then all the rest of the through-hole resistors and diodes. The diodes left are all BAT85s, but they don’t all face in the same direction, so check the PCB overlay, Fig.17, to make sure they’re all installed with the correct orientation. 76 Silicon Chip Australia’s electronics magazine siliconchip.com.au A view of the board with the power supply sections completely assemble and nothing else. This way, we can check that all the supply rails are correct without risking any damage to the expensive chips they will be powering. of the latter into the pad nearest the + symbol, which varies in orientation for each capacitor. The 470µF capacitor below IC9 is the 6.3V-rated type, to allow it to be closer to the chip, while the four 22µF capacitors are non-polarised types. (You could use 47µF or 100µF NP capacitors, as we did in our prototype, although we didn’t find this to give any benefits.) Now fit LED1, again with its lens 10mm above the PCB and with its anode to the pad marked “A”. Then fit polarised headers CON4 and CON5, and the PCB assembly is complete. Testing this section Check that there are no missing parts on the board. If there are, look them up and fit them. Also check your sol- Fig.18 (opposite): drilling/cutting diagram for the rear and front panels (most holes are on the rear panel with only one LED hole requrired on the front). Above are the rear panels (yes, we made two prototypes!) with masking tape holding down the panels and also providing a handy means of marking out the holes required. siliconchip.com.au Test points are provided to help you verify correct operation. dering to make sure it’s all good, especially on the SMD ICs. It’s best to clean flux residue off so you can get a good look at the solder joints. Now apply power, without the sound card plugged into a PC. It is not even necessary that the MCHStreamer is plugged in, but this does not matter as it is isolated from the rest of the board! Connect the ground of your DVM to a convenient ground point. We soldered a PCB pin to a few of the larger GND vias; there is a convenient one just above the 3.3V regulator. But you can also just hold the black probe in one of those holes. Apply power and board and re-check the 3.3V rail, the +5VA rail, the +2.5V rail and the ±9V rails, as before. This is to make sure that you haven’t introduced any short circuits across any of the rails. Assuming these are OK, and there is no part emitting smoke or getting hot, we can proceed. If something is wrong, follow the usual checks for solder bridges, especially on the ADC and DAC where the pins are close to one another. Also check the component orientations. Now it is time to get into some of the fun tests. Switch the power off, plug the MCHStreamer into the sound card and the PC, then plug its outputs into some sort of amplifier. Power it back up and play some sound (eg, music). Then you can check that you get appropriate sounds from the amp! Alternatively, you may choose to put a scope on the output(s) and look for the audio. Assuming that works, connect a stereo RCA-RCA cable from the outputs to the inputs, play some audio and then simultaneously make a recording. Check that the recorded sound file matches the playback audio. If any of these tests fail, check the data paths from the MCHStreamer to the DAC and ADC chips. This is ideally done using a scope with its timebase set to 50ns/division. Check the MCLK, LRCLK, SDATA, BCLK and RESET lines. If the RESET line is not high, the MCHStreamer is probably not connected properly. Is its light on? Why not? Check the clock and data lines on the USB card side of the galvanic isolators – they should be there is they are on the PC side. If not, why not? Metalwork If you are using the recommended case, the Hammond 1455N2201, there is refreshingly little metalwork to do. Cut and drill the front and rear panels as shown in Fig.18. Australia’s electronics magazine October 2020  77 After crimping and/or soldering the crimp pins to the end of the wires, push them into the plastic housings and they will click into place. The front panel has a single hole for the ADC Clip LED. The rear panel has cutouts for the USB input, power input, power LED and four RCA connectors. Rectangular holes are always a nuisance to cut. As these are small, we recommend marking the outlines on the panel, then drilling a series of small holes around the inside perimeter with a 1.5-2.5mm drill bit. Keep the holes close together and err on the side of drilling well inside the marked square, rather than touching the outline. Once you have broken free the tab of aluminium from the middle of the hole, use a square or triangular file to neaten the hoes to the required square. Touch up the edges with black paint or at a pinch, a marker, to make this neat. To finish the front panel, stick a small rubber stopper on the front panel in a location that will ensure that the SuperCodec is held tightly against the rear panel. This will minimise strain on the MCHStreamer connectors when power is being plugged in and out. If you have foam tape, a thick layer of this along the edge of the PCB would also work fine. The SuperCodec slides into slots in the case and is held tight by the rubber stopper at the front, and the MiniDSP MCHStreamer, which is attached to the rear panel. Final assembly You need to make up some cables using the two polarised header plugs and matching pins, two 30cm lengths of figure-8 screened cable, the four RCA panel-mount connectors and some heatshrink tubing. The result is two cables, each with two RCA connectors at one end and a four-pin header plug at the other. At the header ends, start by separating the two channels of coax, then striping 25mm of the outer sheath of each, exposing the shield braid. Tease the inner conductor from the braid, and strip the end by 5mm. Twist the braid wires together into a neat bundle. Next, cut two 20mm lengths of heatshrink, one around 3mm diameter and one 5mm. Slide the 5mm piece over both the shield braid and central conductor. Do not shrink this yet. Slide the 3mm heatshrink over the braid; there ought to be 4-5mm of wire protruding. Shrink this down. Slide the 5mm heatshrink sleeve to cover about 3mm of the junction where the braid and inner core separate, then shrink it down. Present the bare wires to a crimp pin. You need to trim off excess braid wire, so that the strain relief crimp (at the back of the pin) will go over the braid, with about 3mm of wire in the main crimp as shown. Crimp the middle section using sharp-nosed pliers. Make sure the crimping doesn’t cause the pin to splay out so wide 78 Silicon Chip A 10nF capacitor between the input grounds and rear panel Earth lug minimises hum pickup. that it will no longer fit into the plastic block. Then add a tiny amount of solder to the crimp, being careful not to allow it to wick down to the connector spring. Then crimp the strain relief onto the heatshrink around the braid. Next, strip back 3mm from each of the inner conductors and crimp and solder to another pin as above. Now push the pins into the header plug. The shield braids go into the middle two pins, with the left and right signals on the outside. You will feel and/or hear a click when they seat properly. Then take the two pairs of RCA socket and mount them to the rear panel using the supplied plastic insulating washers, to isolate them entirely from the back panel. As before, separate the twin coax cables into left and right wires, and strip back 25mm of the outside insulation. Cut two more pieces of 5mm and 3mm heatshrink and twist the braids, insulate them and then shrink the braid and overall sleeving, as with the header end. You can then solder the input and output wires to the RCA connectors, as shown in the photo above. The two things to check for are that the input pair and output pair are wired to the same cables and that the left (white/black) and right (red) sockets are wired to the appropriate pins on those headers – see Fig.17. Check the orientation of your polarised headers to determine which pin will go the left signals on the board, and which goes to the right. You can make these checks most easily by plugging the cables into the sockets on the board and then using a DMM set to continuity mode. Probe from the centre of each RCA connector to the pins on the headers (through the slots in the plastic housing), to verify that each one goes where it should. Mounting the USBStreamer The USBStreamer needs to be isolated from the case of the SuperCodec. This optimises the effectiveness of the galvanic isolation and improves hum rejection. This is achieved by using TO-220 bushes on the M3 machine screws that attach the USBStreamer through the rear panel, and placing fibre washers on the inside of the rear panel, between it and the USB Streamer brackets. See the photo overleaf, where you can see the insulating washers under the screw heads on the rear panel. This is required to prevent ground noise from the USBStreamer card being conducted through the case and injecting itself into the very sensitive ADC stages. While you’re doing this, something to note is that the mounting lugs on our MCHStreamer board were not lined up properly. We reckon this was due to sloppiness on the Australia’s electronics magazine siliconchip.com.au The pre-assembled USB Streamer PCB plugs into the two 12-pin header sockets on the underside of the PCB. part of whoever (or whichever robot) soldered the threaded standoffs to the board. This can result in the MCHStreamer sockets looking crooked on the rear panel. If, after mounting your board to the panel, it is noticeably crooked, all you have to do is pack one of its mounting screws on the inside of the panel with an extra fibre washer or two. That should straighten it right up. It’s also very important that you stick a 7.5-8mm tall rub- A piece of insulating material such as Presspahn, located as shown here, will ensure the MCHStreamer is always isolated from the case. ber foot on the bottom of the MCHStreamer board as shown in our photos. As this board is only attached to the main board via headers, and it’s only mechanically mounted at one end (to the rear panel), it’s possible for its pins to lose contact due to shock or vibration. The rubber foot rests on the bottom of the case and holds the far end of the MCHStreamer up so that the headers can’t come out of their sockets. Getting the USB interface up and running First, you’ll need to install the driver on Windows or macOS. Log onto the MiniDSP website with the password you used to buy the MCHStreamer, and navigate to the download section. Download the driver for the MHCStreamer. Follow the instructions to install this from the MiniDSP Website, which in summary are: 1. Plug the MHCStreamer module in via its USB cable. It does not need to be plugged into the sound card PCB; it can just be on your workbench (but make sure it’s on a non-conductive surface). It is powered from the computer via the USB cable 2. Our Windows 10 PC popped up a window saying it was “setting up the MCH Streamer”, then a second window saying “the MCHStreamer was ready to go” 3. Extract the contents of the ZIP file you downloaded from their website 4. Navigate to the “Drv_DFU\WinDrv” subdirectory and doubleclick on the installer, which in our case was named “miniDSP_ UAC2_v4.67.0_2019-08-15_setup.exe” 5. When asked if you want to allow the App to make changes, click “Yes” 6. Follow the prompts in the installer, selecting defaults including file locations. The SuperCodec should now be up and running. To set the sampling rate, right-click the speaker icon in the taskbar, usually in the bottom-right corner of the screen. Select “Open Sound Settings” and check that the system has “Speakers (USBStreamer Multi Channels)” selected as the output device (see below). This should automatically be selected. If not, select it. Then click on “Device Properties” in blue, just below the device selection pulldown box. In the new window that appears, look for “Additional Device Properties”, again in blue. Click this. In the pop-up window, go across to “Advanced”. Here you can select your sampling rate, and also click a “Test” button. We recommend selecting “24 bit, 192,000 Hz (Studio Quality)”. Then click “Apply” down the bottom left. While the download package includes the firmware, the MCHStreamer is shipped with the firmware already installed. This does not need to be changed. If you have fiddled with this, you will need to install the I2S_TOSLINK firmware. To do this, follow the instructions in the manual. Several other configurations will work for us, as all we need are I2S channels 1 and 2 in and out on the header. Once the drivers are installed and the MCHStreamer is plugged into your PC via USB, it is set as the default output device automatically. If for some reason it isn’t, you can select it from the list of available audio output devices by clicking the caret on the right. siliconchip.com.au Australia’s electronics magazine October 2020  79 board. You should also have a 10mm M3 machine screw, three locking washers, a solder lug and an M3 nut, again specified in the parts list. Cut a 6mm length of 3mm diameter heatshrink, then mount the M3 machine screw through the hole in the rear panel with a locking washer either side. Place the solder lug on top, then the third locking washer and finally the M3 nut. Do it up tight. Put the 6mm heatshrink over the capacitor leg, and solder this to the solder lug. Then solder the other lead of the capacitor to one of the shield braid wires of the output connectors. Tip: if you envisage using this as a measurement system, put a solder lug on the outside of the case as well. This can use the same screw. As we found in our tests, access to the unit’s ground can be useful in some cases to minimise overall system noise. Adding this while building it will be a lot easier than adding it later. Slide everything into the case once it is all working, then mount the panels and you are set! If you envisage this device being moved around a lot or vibrated, then you might want to add a piece of Presspahn or Elephantide as shown above. This is optional. A section of Kapton tape on the USB socket ensures it can’t short to any components on the main PCB. When you slide the PCB into the case, the foot should press against the bottom and provide a little extra resistance to sliding the board in, but not so much that it becomes impossible. This is how you know that it’s providing enough force to hold the boards together. Grounding If you want to get the 50Hz hum down below -120dB, as we achieved in our prototype, Earthing is very important. To be honest, in testing this, we found that even the slightest change in the configuration can cause changes of 10dB or more. That just shows how difficult it is to achieve such performance. In most tests of amplifiers etc, you will need the galvanic isolation that the system provides to measure really low noise floors. Where super-low noise is critical, you might find with some system configurations that the Earth of the PC does need to be tied to the device under test to eliminate induced 50Hz signals being picked up. This will require experimentation with your overall setup. You should establish the noise floor with no signal to the unit under test before running any tests. You should have a 10nF MKT capacitor left over, which was specified in the parts list (in part one) but not used on the Using it If you want to use the SuperCodec for playback, you can use just about any audio software. But if you want to take advantage of its full capabilities, you will need high-resolution content such as 96kHz or 192kHz, 24-bit FLAC files along with a player that can properly decode such files. For recording, we suggest that you try the free software package called Audacity (www.audacityteam.org). It is available for Windows, macOS and Linux and can take advantage of the Card’s full capabilities. For audio analysis use, such as measuring distortion (THD+N or THD), signal-to-noise ratios (SNRs), frequency responses and so on, various packages are available. We use audioTester (www.audiotester.de). This is ‘shareware’ so you can download and install it for free, but you can only use it for a limited time without paying for it. It only costs €39 or about AU$65 for the full version. We recommend this software because it is easy to use and has many comprehensive features that are ideal for testing audio equipment. That includes a low-distortion sinewave generator, spectral analysis with automatic display and calculation of the signal level and total harmonic distortion (THD) and much more. SC Here’s what the back panel of your SuperCodec should look like when finished. Note the comments in the text re the grounding/ insulaton of the sockets to avoid ground loops. 80 Silicon Chip Australia’s electronics magazine siliconchip.com.au Build It Yourself Electronics Centres® The Big Build SALE! Our best selling 3D printer! K 8602 819 $ deals in power, Exciting electronic tools. audio & workbench October 31st. Sale pricing ends Carry 240V Power Anywhere! Creality® Ender 5 Pro | Desktop 3D printer. Produce one off prototypes, replacement parts and hobby pieces with printing up to 22Wx22Dx30Hcm! The Ender 5 Pro offers workhorse 3D printing for your workshop with excellent print speed and accuracy using PLA, ABS and more. 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Sleek aluminium design turns a Pi 4 into a desktop computer with fan cooling and features a sub board which brings all the Pi connectors to one side of the case for easy connection. Order online <at> altronics.com.au | Sale pricing ends October 31st 2020. Expand your home sound system. C 5285 C 0876 299 $ 229/pr 139 /pr $ /pr $ SAVE $100 NEW! SAVE $80 C 0881 8” Magnetic ‘edge to edge’ grilles. C 0871 6.5” Includes easy to mount ball joint bracket Opus One® 2x30W Bluetooth® Wireless Ceiling Speakers 179/pr $ SAVE $80 Built to stream the best content from your favourite music streaming service, app or podcast player. Bluetooth 5.0 technology offers superb audio performance and range. In-built high performance 2x30W RMS amplifier. The ideal way to add permanent wireless sound to any room in the house. A modern, low profile finish is provided by frameless magnetic fit grilles. Includes power supply. Sold in pairs. Premium sound in a tiny package. Redback® 2.75” Mini Satellite Speakers. Deliver full and rich sound you’d hardly believe these speakers are only 10cm tall! They’re the perfect home and small commercial sound solution - especially when paired with our C 5210 subwoofer and A 4860 bluetooth amplifier. 8Ω 10W rated. Stunning hi-fi clarity by Opus One® The perfect partner for our A 1116 Bluetooth amplifier (see below). Can be installed yourself, fliplock brackets secure each speaker for flush mount screwless finish. Sold in pairs. Opus One® 140W Soundbar Wireless Subwoofer SAVE $46 NEW! 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 you TV (cable included). 139 $ 389 $ A 1116 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. A great addition to any alfresco area these wall speakers offer high performance music reproduction for an affordable price! 3.5” 30W RMS drivers. 8Ω input. 239 $ C 5064 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. A 2548 Instantly add wireless audio to any 3.5mm input - like your car, headphones or home amp. USB rechargeable. AE1101 SAVE 12% 20 $ SAVE $66 129/pr Demo in store! $ SAVE $40 Opus One Bluetooth Bookshelf System ® A 2384 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. C 0900 White C 0901 Black Get creative with streaming & podcasts... 4 Channel USB Mixer With Equaliser & FX Bluetooth® 3.5mm Jack NEW! A 1116 SUMMER ENTERTAINER PACK! Buy a $240. Bluetooth amplifier & C 0900/1 speakers for SAVE $28 Quality outdoor sound for entertaining. C 5059 Soundbar: 97 x 8 x 7.5cm, Subwoofer: 30 x 25 x 30cm 109 Extend your sound system with ease! Connect up to two additional pairs of speakers to your stereo amp without risk of damage. Each speaker “zone” has on/off & volume control. 50W RMS per channel (4/8Ω speakers). 49.95 $ 29.95 $ SAVE $40 D 0984 $ D 0982 3.5mm Lapel Mic Ideal for audio recording on smartphones, laptops, vlogging cameras. 3.5mm TRRS or TRS connection. 2m lead. Condenser type. USB Podcast Microphone A premium finish USB microphone with all metal case, stand and protective grille. Adds high clarity sound to your desktop for live streams & podcast recording. . Pro condenser mic for clear, crisp sound Electret Lapel Mic Need to record high quality audio for YouTube or live demos? This 6m electret mic offers excellent audio clarity and 3.5mm TRRS or 6.35mm TS connections. Buying for business? Save with a VIP-Trade Card 130 $ D 0980 149 $ Sale pricing ends October 31st 2020. Upgrade & save on tools. Desolder parts in seconds! High Output Blow Torch Super hot 1350°C flame with high output nozzle. Handheld or self standing design for tasks such as heatshrinking, model making, silver soldering! Easy to refill. 66 $ 199 This excellent multi purpose 80W soldering iron is ideal for service technicians, schools, engineers, R&D, production work etc. Japanese long life ceramic element. 200°-480°C. 0.8mm tip. 2 year warranty. Designed to desolder through hole componentry, removing molten solder quickly and easily from solder pads and components. In-handle reservoir is easily removed and cleaned. Includes three desoldering tip, nozzle cleaner and filter pads. 160°-480°C. NEW! 95 68.95 $ $ T 1539 T 2690A SAVE 23% 160 $ T 1289 35 $ SAVE $30 30W Lithium ‘Go Anywhere’ Soldering Iron T 2161 Ideal for DIY DC power wiring 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 - also recharges from a battery bank. Includes replaceable 18650 battery. Provides 300W of hot air for quick and easy desolder and re-work of surface mount boards. Melts solder in seconds allowing you to remove devices easily. 200-500°C adjustable. Includes desk stand - plus narrow, medium and wide nozzles for different tasks. 62pc Precision Servicing Driver Kit A quality servicing kit for high tech devices - including special bits for iPhone disassembly. Includes a huge variety of 4mm driver bits, opening tools, spudger, tweezers & extension. All in a neat self opening case. Ratchet Lug Crimper Quick and easy crimping for Anderson SB50 connectors and other uninsulated lugs between 20AWG & 8AWG. 60 $ T 2188 SAVE 18% 19 $ T 2175A 1000V Precision Drivers Smaller sizes than most 1000V rated driver sets. Ideal for servicing AC equipment. 3 flat blade (2.0, 2.5 & 3mm) and 3 phillips (#000, #00, #0). T 1499 NEW! 11.50 $ Screen Removal Suction Cup Pliers Iroda® Butane 4 Pack SAVE 25% Ideal for technicians working on mains powered equipment. Includes cutters, pliers, wire strippers, 5 screwdrivers plus a neon test driver and 2 rolls of insulation tape - all in a handy carry case. SAVE $30 Upgrade your old clunker iron! Micron® Vacuum Desoldering Station Not just for desoldering works great as a regular hot air gun! 1000V Rated Insulated Tool Kit T 2418A T 2065 T 2496 SMD Hot Air Re-Work Desoldering Gun $ SAVE $56 SAVE 18% NEW! 169 $ Don’t forget the gas. See below! For removing outer glass from phones tablets & laptops. Cups rotate for larger screens. Stock up the workbench with this value pack of quality double scrubbed butane. Doesn’t clog your tools like many brands. SAVE 30% 55 $ SAVE 13% Lockable Tool Field Case With tool pocket & perforated foam inner to keep equipment secure. Ext. size: 445x330x128mm. 4 for $ 30 T 2451 T 5021 SAVE 19% SAVE 13% 60 SAVE 19% 10 $ 25 $ T 2749 Stay sharp longer! $ Must have for any tool T 1490A kit SAVE 24% T 2735 Spring loaded & super comfy! Tungsten Carbide Side Cutters Stainless Steel Scissor Snips Precision Long Nose Pliers Tough HRC 72° tungsten carbide construction for 5 times the life of standard side cutters. 130mm. Multi-purpose snippers made from SK4 carbon steel. Spring loaded with comfort grip. 160mm. Premium quality precision fine point pliers with jaw serrations. Ideal for general electronics use. 140mm. Shop online 24/7 at altronics.com.au 20 $ T 1527 A toolbox essential! Strip Wires Faster! Easy squeeze spring loaded quick action wire strippers for 0.5 to 2.0mm2 conductor wire. Sale pricing ends October 31st 2020. Get more power for your dollar... SAVE $20 79 49 N 1130F 209 HALF PRICE 20 14.95 $ $ M 8632 USB-C Type Car Charger M 8864 Handy 4 Way USB Charger 18W power delivery charger with QuickCharge 3.0 for faster device charging. Four USB mains charger with 4.5A total output. SAVE 16% 80 $ SAVE 24% P 7824 XT60 DC Plugs Male & female included. 60A rated. SAVE 28% 4 $ ea 14 $ Charges any USB-C laptop M 8606 EC5 Style DC Power Plugs 60A rated 5mm battery plugs. NEW! Top up your batteries with solar power. These compact solar panels are designed for keeping your vehicle batteries topped up when parked. Easy croc clip or car accessory plug connection. Can even be permanently installed outdoors. 10W: 377L x 212W x 17D mm. 15W: 40L x 343W x 17Dmm. M 8994 P 7823 SAVE 26% 5 $ ea Deans Style Plugs Offset 2 pin DC power plugs. 60A rated. Need an extra laptop charger? This 90W USB-C power delivery (PD) charger offers fast recharging for MacBooks, Nintendo Switch and other type “C” devices. Plus a standard 2.4A USB charger output. P 7828 SAVE 33% 3 $ ea Got two phones with wireless charging? This handy pad will charge both devices at once. Suits iPhone and most Android. For fast charging you’ll also need a QC3.0 USB wall charger, such as M 8863 $20. Includes USB cable. 68 $ High Current Twin Flex Figure 8 Cable Rated up to 80A this handy 8AWG cable is ideal for solar installs, battery charging and other auto/ marine uses. .95 SAVE 24% 38 $ D 2327 Build wireless charging into your desk D 2322 An ultra-slim desk mount 10W wireless fast charger. Requires 60mmØ hole. Includes power adaptor & USB cable. 10 per metre $ W 4162 SAVE 24% 30A 10 Metre Handy Hook Up Reels Popular 30A high current red and black cable. Tinned for reduced corrosion. W 2426 Red W 2427 Black 35.95 $ NEW! Joondalup Store NOW OPEN 2/182 WINTON RD JOONDALUP, WA. OPEN 7 DAYS. Western Australia Build It Yourself Electronics Centres Sale Ends October 31st 2020 Phone: 1300 797 007 Fax: 1300 789 777 Mail Orders: mailorder<at>altronics.com.au » Joondalup: 2/182 Winton Rd » Perth: 174 Roe St » Balcatta: 7/58 Erindale Rd » Cannington: 5/1326 Albany Hwy » Midland: 1/212 Gt Eastern Hwy » Myaree: 5A/116 N Lake Rd 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. Victoria 08 9428 2166 08 9428 2188 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 Find a local reseller at: altronics.com.au/resellers © Altronics 2020. E&OE. Prices stated herein are only valid until date shown or until stocks run out. Prices include GST and exclude freight and insurance. See latest catalogue for freight rates. 08 8164 3466 B 0091 Plus dual USB charger for keeping your devices powered up on the road. GREAT FOR: • Motorbikes • Caravans • Boats • Jet Skis & more! This MPPT regulator employs special circuitry to gain up to 20% additional charge from your existing solar panels. Suits 12 or 24V systems. Easy to set up and connect yourself. Also available in 20A, N 2024 $159. SAVE 32% Charges 4 x AAA/AA cells via USB. Great for use at home or in the car. Use rechargeables & save batteries from landfill! 3x Car Accessory Adaptor N 0706A 15W Say goodbye to messy charging cables! USB NiMH & NiCad Charger A 0290 69 $ Get the most from your panels with an MPPT regulator $ Going bush? Have power wherever you go on your next 4WD/camping adventure. Includes 130W panel, solar regulator, battery connection cables and canvas carry case. 3 stage solar charger. Adjustable stand for best sun placement. 664x631x75mm (folded). SAVE 24% SAVE $10 N 2023 10A 130W Remote Power Folding Solar Panel 15 SAVE $10 $ SAVE $30 $ N 0704A 10W $ Includes regulator, 5m battery cable & carry bag. Vintage Radio 1940 1940 AWA AWA “Fisk” “Fisk” Radiola Radiola model model 501 501 By Associate Professor Graham Parslow The Radiola model 501 is the console version of a series of similar circuit designs by AWA. It’s featured in a simple timber cabinet with a 12-inch Rola speaker. It measures about 86.5cm tall and weighs around 16.3kg. Console radios were used as display centrepieces through the 1920s and 1930s. Some elaborate examples of the carpenter’s craft in making large cabinets now look hideously overornamented. We have progressed to an age where we accept the minimalist styling made popular by Scandinavian designers in the 1950s and beyond. Paradoxically, this now elevates the simple design of the model 501, compared to how it would have been considered in 1940, sitting beside other elaborate and more expensive consoles in a shop. The simple dial and escutcheon and the lack of wave-changing also contribute to the economy of this model. However, the sound is equally as magnificent and sumptuous as the expensive models, because that quality is largely determined by a 12-inch (300mm) speaker mounted on a reasonable baffle. In the late 1930s, AWA took the same chassis and components and packaged them as several different models: the model 301 (a radiogram), models 84 & 194 (mantels; the 194 is incorrectly listed as a console radio in some service manuals), and models 193 & 501 (consoles). This is a clever use of resources; just as car manufacturers don’t design a bespoke engine or transmission for every model, why should a radio maker design unique circuitry for each set, just because its cabinet is a different shape? Radio evolution in the 30s The set has a width of 58cm and depth of 30cm, with the front-facing veneer likely stained white oak, and the sides Queensland walnut. siliconchip.com.au Australia’s electronics magazine The 1930s was a decade of remarkable evolution in radio design and presentation. At the beginning of the decade, floor-standing console models looked like cabinets with ornate elaborations featuring sculpted wooden feet, which would have suited a lounge chair. Most radios in the early 1930s were based on tuned radio frequency (TRF) circuits that used multiple tuned October 2020  85 stages to achieve selectivity between stations. The valves in those sets had four or more pins at the base and a range of matching sockets. That would soon change as the eight-pin octal base became a standard that would prevail for twenty years, before 7-pin and 9-pin miniature valves took over. Many heritage valves were simply repackaged with an octal socket, like the 5Y3 valve in the radio featured here. The 5Y3 was designated type 80 when produced with a four-pin socket. The patent problems preventing Australian manufacturers producing superhet radios were resolved in 1934. The all-octal-valve model 501 encapsulates the change from the dominance of TRF radios to mature superhet technology in only six years. Circuit details A paper label glued inside the lefthand panel (reproduced overleaf) shows the complement of valves and the location of components on top of the chassis. The same label was attached to all models sharing this chassis. The circuit is a fairly basic superhet design with a mixer/oscillator stage based around a 6A8G pentagrid converter valve, one 455kHz IF gain stage using a 6U7G variable-mu pentode, a detector/audio preamplifier stage based on a 6B6G dual diode-triode and a Class-A audio output stage using the 6F6G power pentode. The set has delayed AGC, and an HT voltage of 265V once warmed up. The circuit diagram for the model 501 was drawn to suit four differ- The chassis is mounted in the typical location for console radios, with the 12inch Rola loudspeaker below it (marked type AS7 in the service manual). 86 Silicon Chip Australia’s electronics magazine ent models. The circuit also serves the model 301, but that was drawn separately to include the gram-radio switching circuitry. The main drawing is for models 84 and 194, with alternative wiring to represent console models 193 and 501. Starting at the aerial, it can be seen that the smaller cabinets incorporated a loop antenna that served as the tuning inductance for station selection. The loop antennas worked well in strong signal areas. The 501 has a conventional aerial coil with the secondary acting as the tuning inductor. The tuning capacitor connection to the grid of the 6A8 and the first IF transformer connection to the grid of the 6U7 are both top cap connections. This minimises stray capacitance that can cause unstable operation. All of the top caps are at low voltage (usually 3V or less), so accidental contact is not dangerous, but ill-advised as a general principle, because top-cap anodes on output valves can be lethal! The local oscillator is L5/L6 with the tuned section L6 providing a frequency that is 455kHz offset from the station frequency. L5 functions to provide positive feedback to sustain oscillation, a method developed by Edwin Armstrong, the acknowledged inventor of the superhet principle. After IF amplification by the 6U7 valve, D2 of the 6B6 detector provides a negative AGC voltage. This is directed to the control grids of the 6A8 and 6U7 via R5. The negative potential across R13 ensures that the AGC is delayed until stronger stations are tuned. D1 in the 6B6 feeds the detected audio signal to 500kW potentiometer R6, which then goes to the 6B6 triode section via 100nF capacitor C16. A more advanced circuit might have featured negative feedback from the output and bass-enhancing circuitry acting at this audio preamplification stage. The 6F6 output pentode is a solid performer, easily putting out 3W at the voltages used in this radio. The 6F6 is unlike most other common output valves in requiring a high grid bias voltage, specified as -17V for this radio. Economy of components is achieved by tapping the 6F6 grid bias off the HT line using a 300W resistance (R12 plus R13), inserted between the power transformer centre tap and earth. This eliminates an electrolytic capacsiliconchip.com.au This circuit diagram was scanned from the Australian Official Radio Service Manual Vol.4 (indexed under the Fisk name at the time). There are two notes just below the circuit which state: “L3,L4,C1 replaces loop L1,L2 on console models” and “external speaker connections included for console models”. Both of these obviously apply to the 501. itor that would otherwise be needed across a bias resistor in series with the 6F6 cathode. The tone control is the ultimate in economy, featuring a three-position switch that offers either no top cut, top cut via C21 (35nF), or less top cut with R11 (5kW) in series. In practice, this gives reasonable choice. The electrodynamic speaker has a 2kW field coil that generates the magnetic field and also acts as a filter choke for the HT line. The speaker is mounted in the lower section of the siliconchip.com.au cabinet, and is connected via a plugin four-conductor cable that delivers audio from the 6F6 anode (plate), two HT lines, plus an earth strap for safety and hum minimisation. Construction details Both the IF amplifier and audio preamplifier valves are in Earthed canister shields, serving to minimise hum and maintain stable performance. As mentioned earlier, the first three octal valves also have topcap control grids that allow for short Australia’s electronics magazine lengths of wire to their signal source when that source is mounted above the chassis. C22 is a large aluminium can capacitor mounted adjacent to the tuning capacitors, and is the only component not placed next to its area of function. Although it has no markings, the component list specifies it as 8µF 500VW. Electrolytic capacitors were large bulky components at this time, and C22 needed to cope with the high start-up voltage generated by the 5Y3 rectifier. October 2020  87 The AWA 501 chassis underside with a matching layout diagram shown below. These are from the service manual and can be found at www.kevinchant.com The inclusion of valve base pin labels is a welcome addition when checking sets. The centre of the chassis is reserved for a pressed dome with parallel ventilation slots, below which the power transformer is mounted. The downside of this arrangement is impaired heat dissipation and a cluttered underside relative to top-mounting the transformer. But the advantage of having the power transformer under the metal chassis is shielding of any 50Hz radiation that might create hum if the transformer was top-mounted. Restoration I bought this radio from a secondhand barn at Watsons Creek near the Yarra Valley, in Victoria. I remember the young salesman urging me on with “go ahead and buy it, you know you want to”. Somehow this also mollified my wife, so it came home with us. That was twelve years ago, when my primary interest was to restore the cabinet to glory. I did that by completely stripping the cabinet to bare timber and spraying it with satin polyurethane. To my eye, the character of the veneers gives great presence to this radio. The radio had its mains cord cut off, and no speaker was fitted, so I elected to leave it as it was. This may seem 88 Silicon Chip like sacrilege to some, but I installed a digital stereo AM-FM CD player with its speakers all mounted in the lower space of the cabinet. A 6V transformer to power the dial lamps made it look like the radio was functional when the transplanted hifi system was switched on. The radio then stood patiently in a corner of our back entertainment area, niggling away at me to do a proper restoration. COVID-19 restrictions brought the niggle to a climax. The first step was to remove all the valves. This revealed that the top cap of the 6A8 mixer was missing and an ingenious handyman had used tape to wedge the top cap connector around the glass nipple at the top. This could Australia’s electronics magazine only have provided capacitive coupling to the grid, because the grid wire was eroded back inside the glass envelope beyond the possibility of making a new connection (a conclusion reached after breaking the envelope). Luckily, I had a replacement 6A8 in stock. At first glance under the chassis, it looked like the restoration would be straightforward due to most of the original components still being in place. Only one capacitor, coupling audio from the 6B6 to the 6F6, had obviously been replaced. Several paper capacitors looked like the pitch sealant at the ends had dried and failed. I replaced all of these, except the audio coupling capacitor that had previously been upgraded. siliconchip.com.au The AWA 501 chassis with a layout diagram shown below. The capacitor at the tone control switch measured as a dead short, and the others exhibited various grades of leakage. It is a miracle that this radio could have struggled on with so many marginal components and faults that became evident later. R2, specified as 20kW 1W, was two 40kW resistors in parallel with the identity colours burnt off by sustained heat. Even so, the value was still correct. Nevertheless, I replaced them with two 10kW 2W resistors in series. I fitted a permanent magnet 12-inch Rola model M as the new speaker. This required fitting two 1kW 7W resistors in series in place of the 2kW electrodynamic speaker coil. This pair of resistors can be seen mounted on top of siliconchip.com.au the chassis, next to the dome of the power transformer. As a result of this substitution, I needed to fit a new speaker transformer, but there was no convenient mounting position available either above or below the chassis. I decided to mount it at the side of the chassis as this meant that the chassis metalwork would act as a shield against any hum radiating from the mains transformer. I removed 8µF electrolytic capacitor C22 and replaced it with a modern 47µF 450VW electrolytic capacitor. That high voltage rating is essential because the power transformer produces 2 x 370V AC for rectification by the 5Y3 valve, resulting in a measured switch-on DC voltage of 450V DC, re- Australia’s electronics magazine ducing to 375V when other valves begin conducting. The 2kW field coil replacement resistor drops the main HT line to 265V. The last operation before switchon was to add an Earthed three-core power line. I do this last because the cord gets in the way needlessly if done earlier. Initial switch-on was a singular disappointment – nothing happened! The faults included an open-circuit R8 feeding HT to the 6B6, and a dead 6B6 valve due to an open filament. Leakage through C18 reduced the 6F6 bias to 0V, a situation where the valve is forced into potentially destructive high conduction and is ineffective as an amplifier. C18 was the “new” capacitor that I had not bothered replacing. There was also a fault in the volume control resistance track; it had lost contact with the lug connecting it to the audio feed from the second IF transformer (L10). Once I had fixed all those problems, it came to life. I then aligned the IF transformers, resulting in significantly better performance. Finally, my tribulations were repaid by having a grand icon of its era working superbly well. SC October 2020  89 This large and powerful Ultrasonic Cleaner is ideal for bulky items such as mechanical parts and delicate fabrics. Last month we described its features and explained how it works. Now let’s move on to building it and getting it going! Part 2 – by John Clarke Ultrasonic High Power Cleaner A s mentioned in the last article, the microcontroller PCB construction The Ultrasonic Cleaner is built using two PCBs. The in the Ultrasonic Cleaner uses three Mosfets and a step-up transformer to produce around 100V AC to main PCB is coded 04105201 and measures 103.5 x 79mm while the smaller front-panel PCB is coded 04105202 and drive an ultrasonic transducer at just under 40W. This transducer is attached to the side of a vessel con- measures 65 x 47mm. The assembled PCBs are housed in a diecast box measurtaining cleaning liquid and objects to be cleaned. You seing 115 x 90 x 55mm. The overlay diagrams for both boards lect a power level and a time, and it does the rest. The electronic components are mounted on two PCBs are shown in Figs.6 & 7. Start by fitting the resistors on both PCBs where shown. which are housed in a diecast aluminium box. The lid of The resistor colour codes were in the parts list last month, the box has all the controls and the indicator LEDs. The only external wiring is for 12V DC power to the but it’s always best to check the values with a DMM set unit (it draws around 4A at full power) and one twin lead to measure resistance to make sure they’re going in the which emerges from the box via a cable gland and goes to right places. The 0.1 SMD resistors the transducer that’s glued to mount on the top of the PCB, the liquid vessel. Warning! soldering one end first and Building the Ultrasonic Warning! check alignment before solderCleaner isn’t too difficult. The transducer is driven at 100V AC which is more than The transducer is driven at 100V AC which is more than ing the other end. The main steps are winding enough enoughtotogive giveyou youaashock. shock.Touching Touchingboth bothofofthe thetranstransContinuing with just the the transformer, soldering ducer ducerterminals terminalsduring duringoperation operationwill willgive giveyou youan anelectric electric main PCB, fit diodes D1 the components to the PCBs, shock, shock,and andititwill willbe beworse worseififyour yourhands handsare arewet. wet.You Youmust must and D2 and make sure that drilling the case, mounting the enclose the transducer in the PVC housing described in enclose the transducer in the PVC housing described in their cathode stripes face parts in the case and wiring it this thisarticle articleand andonly onlyrun runititwhen whenso soenclosed enclosedand andattached attached toward the top edge of the up. We shall now describe all totoaabath bathfilled filledtotothe thecorrect correctlevel levelwith withcleaning cleaningfluid. fluid. PCB as shown. ZD1 can also the necessary steps in detail. 90 Silicon Chip Australia’s electronics magazine siliconchip.com.au  SILICON CHIP                     Fig.6: fit the components to the main Cleaner PCB as shown here. Watch the orientation of the diodes, ICs, electrolytic capacitors and box header CON4. Mosfets Q1 and Q2 are mounted on the underside, with their leads coming up through six pads next to transformer T1. Two holes in the PCB give access to their tabs, so that they can be mounted to the bottom of the case for heatsinking. This final version PCB is slightly different to the photo of the early prototype at right. be mounted, orientated as shown. We recommend that IC1 and IC2 are mounted in sockets. Make sure that the notched faces toward the lower edge of the PCB. The three PC stakes can also be fitted now; they are marked as GND, TP1 and TP2 (you can leave these off and probe the PCB pads later, if desired). Now mount REG1 flat onto the PCB with its leads bent down 90° to fit into the holes in the PCB. Secure it to the PCB using an M3 x 6mm screw and nut, then solder and trim its leads. Also mount the 3AG fuse clips now, making sure that they have the correct orientation, with the end stops toward the outside of the fuse. It is a good idea to insert the fuse before soldering the clips in place to ensure the fuse is aligned in the clips and that the clips are orientated correctly. Ideally, the fuse clips should also be soldered on the top of the PCB on one side of each clip, to minimise the connection resistance. The DC socket (CON1) and the 2-way pluggable terminal block socket (CON2) can then be installed. Take care with CON2’s orientation; insert the plug into the socket before soldering the socket. This will ensure the orientation is correct, as the screws need to face towards the fuse so that the assembly will fit on the PCB. Also fit the 2-way screw terminal (CON3), with the wire entry toward the edge of the PCB. Mount the 14-way IDC box header (CON4) now. Make sure the notch is orientated as shown and it is pushed all the way down before soldering its pins. Fit the capacitors next, noting that the electrolytic capacitors must be orientated with the longer positive leads through the holes marked “+”. Then solder the three small transistors (Q3-Q5), which are all BC547s. Mosfet Q6 (the SUP53P06-20) is mounted vertically with the mounting hole 22mm above the top of the PCB. Mosfets Q1 and Q2 mount on the underside of the PCB. Bend the three leads for each Mosfet upward by 90°, 5mm from the bottom edge of the Mosfet body. Then insert the leads into the PCB from the underside but do not solder them yet. Now place the PCB into the enclosure, sitting on the internal mounting corners. Mark where the Mosfets sit, including their mounting hole locations, then remove the PCB and place the silicone insulating washers at these locations. Fig.8 shows how these Mosfets will be mounted, although we aren’t attaching them to the case just yet. Reinsert the PCB and adjust the Mosfets so that they sit flat on the bottom of the case, on the silicone washers. Now SILICON CHIP siliconchip.com.au Australia’s electronics magazine Fig.7: IDC header CON5 mounts on the back of this front panel board, while the LEDs, switches and potentiometer VR1 protrude through holes in the front panel. Make sure that VR1’s body is grounded via the pads provided and also check that the LEDs are all orientated as shown. October 2020  91 Fig.9: follow these transformer winding instructions carefully, to make sure that your finished transformer has the correct phasing and turns ratio. Fig.8: this is how the Mosfets are mounted to the board and the case (for heatsinking). Ensure that the tabs are fully isolated from the case before powering the Cleaner up. Initially, the Mosfets can be attached to the outside of the box for testing, then later moved to the inside (the mounting method is the same either way). enamelled copper wire. Using bifilar winding, wind 2 x 7 turns in a single layer. One winding starts from pin 7 and ends at pin 12; the other winding starts from pin 19 and ends and pin 7. When both windings are terminated, cover them with a layer of plastic insulating tape. wind the secondary,  Then using 0.63mm diameter enamelled copper wire: 57 turns in two layers, starting from pin 4 and ending at pin 3. Place one layer of plastic insulating tape over each layer. solder the leads on the top of the PCB. Then remove the PCB and solder the leads on the bottom of the PCB as well. Similarly, for Q6, solder the leads on both sides of the PCB. Winding the transformer wind the primaries  First using 1.0mm diameter 4, 7, 8 & 12 of the transformer and the PCB pads for those pins. This is so that it will be easier to change the secondary windings, should the ultrasonic transducer require fewer or extra turns. More on this later. Now insert both IC1 and IC2 into their sockets, taking care to orientate them as shown on the overlay diagram. Fig.9 shows the transformer winding details. The primary windings are made from 1mm diameter enamelled copper wire (ECW) while the secondary winding uses 0.63mm di- Front panel control board assembly ameter enamelled copper wire. There only a few parts left on this PCB, but be careful to Start with the primary windings. First, cut two 400mm mount them on the correct side. Most parts go on the top lengths of the 1mm ECW and remove the enamel from one side, but the 14-way IDC transition header (CON5) goes end of each wire using fine emery paper or a hobby knife. on the underside. Fit CON5 first, taking care to orientate it Tin the wire ends and wrap one wire around pin 7 on the with the pin 1 triangle as shown in Fig.7. Solder from the underside of the transformer bobbin, and the other onto pin top side of the PCB. 8. Solder both close to the bobbin. Now close-wind seven turns of both wires (sideby-side) until the windings reach the opposite end of the former. The winding direction does not matter as long as both wires are wound together. Cover the windings in a layer of insulation tape. Pass the wires back along the spine of the former. Using a multimeter on the ohms setting, find the wire that’s terminated to pin 7 and terminate its other end to pin 12 in the same way as before. The other wire end terminates at pin 7. Cover the windings in a layer of insulation tape. PIHC NOCILIS The secondary winding uses the 0.63mm ECW. Terminate one end to pin 3 and wind on 29 turns (the direction does not matter). Then wrap a layer of insulation tape over this winding and continue winding back over the first layer, in the same direction as before (clockwise or anticlockwise) to complete 57 turns. Terminate this to pin 4. Once wound, slide the cores into the former Fig.10: this is how the and secure with the clips. These clips push on ribbon cable connects to the core ends and clip into lugs on the side of to the front panel board. the bobbin. If CON4 has been fitted It is best not to install the transformer directly correctly to the main board, onto the PCB just yet. It can be temporarily wired then it should plug straight in. Note that the ‘IDC transition header’ up using some short lengths of 0.7mm diameter used for CON5 on the front panel board is captive, ie, there is no tinned copper wire or similar, between pins 3, socket. Its pins are soldered directly to the PCB. 92 Silicon Chip Australia’s electronics magazine siliconchip.com.au The finished controller shown “opened out”, albeit with the ribbon cable disconnected from CON4. Now the IDC cable needs to be attached to this header. Fig.10 shows how the IDC cable is arranged in CON5. The wire can be secured by adding a small piece of soft timber (eg, pine) over the soldered pins on the PCB and another piece of timber on the other side of the PCB, and compressing the lot with a G-clamp or bench vice. The other end of the IDC cable goes to the socket, again taking care to orientate the socket correctly with the locating tab as shown. Compress as before, with protective timber and a G-clamp or bench vice (or use a specialised tool like Altronics Cat T1540). The resistors can also now be installed, if you haven’t already. Also insert the five PC stakes from the top side of the PCB for the potentiometer mounting and connections, and fit the 100nF capacitor. The remaining assembly work for this board is done after the enclosure lid has been prepared. Cut the potentiometer shaft so that it is 12mm long from the threaded boss, or to suit the knob used. The front panel label (Fig.11) shows the position of the LEDs, power, start and stop switches and the potentiometer on the lid. This label can also be downloaded from our website as a PDF file. Print it and attach it to the lid, ensuring that the paper template is centred correctly. Mark out and cut the holes. The hole for the power switch can be made by drilling a series of small holes around the perimeter, knocking out the piece and filing to shape until the switch fits and is held in position firmly. Break off the locating spigot on the potentiometer and mount the potentiometer onto the lid. Place the washer besiliconchip.com.au tween the pot and lid, with the nut on the outside of the lid. Also attach the switches, with one nut on either side of the lid. Switch orientation doesn’t matter. Insert the LEDs into their pads from the top side of the PCB, taking care to orientate them all with the longer lead (anode) going into the pads marked “A”. Do not solder the LEDs in yet. Place the PCB onto the switch terminals and solder them in place. Scrape off the coating on the pot body where the two mounting PC stakes are to solder to the pot body (don’t inhale the dust). This allows the solder to wet the pot body for a good solder joint. Solder the PC stakes to the pot terminals after bending the pot terminals over to meet the PC stakes. The LEDs can now be pushed up into the holes on the lid and soldered in place, then trimmed. The PCB is held in position by the switches and potentiometer. There is no need for extra support. If you absolutely must, you could attach 15mm-long standoffs to the corner holes. Front panel label The front panel label can be made using overhead projector film, printing the label as a mirror image so that the ink will be between the enclosure and film when affixed. Use projector film that is suitable for your printer (either inkjet or laser) and affix using clear neutral-cure silicone sealant. Roof and gutter silicone is suitable. Squeegee out the lumps and air bubbles before the silicone cures. Once cured, cut out the holes through the film with a Australia’s electronics magazine October 2020  93 Fig.11: the lid/front panel artwork for the Ultrasonic Cleaner, which also serves as the lid drilling/cutting template. You can download this as a PDF file from the SILICON CHIP website, print it and optionally laminate it (or print onto adhesive label paper – see the text for more details). nuts as shown in Fig.8. Check that the metal tabs are isolated from the case using a multimeter on a high ohms setting. A reading in the megohm region means that isolation is good. Lower readings indicate a shorted connection to the case. Wire switch S1 to the board using 5Arated hookup wire, with heatshrink tubing over the soldered terminations. Once the other ends of the wires are secure in the screw terminals for CON2, plug it into the CON2 socket. Preparing the ultrasonic transducer hobby or craft knife. For other options and more detail on making labels, see siliconchip.com.au/Help/FrontPanels Two holes are required in the side of the box for the DC power connector and the ultrasonic transducer lead, plus one for mounting Q6. The locations and sizes are shown in Fig.12. Holes are also required in the base of the enclosure for mounting Mosfets Q1 and Q2. You should have marked the positions earlier; drill these to 3mm. Lightly countersink these holes inside the enclosure, plus the one for Q6 on the side, to prevent the insulating washer from being damaged by a rough hole edge. Also lightly countersink the holes for Q1 and Q2 on the outside of the enclosure. This is so these Mosfets can be mounted temporarily on the outside of the enclosure for testing purposes. This way, you will have better access to the PCB for testing and fixing any problems without having to remove it from the box. Fit the four M3 x 9mm standoffs to the underside of the PCB using 6mm screws, then attach Mosfets Q1 and Q2 using silicone washers, insulating bushes and M3 screws and There are many suitable 50W/60W 40kHz ultrasonic transducers available online. One such part is the Beijing Ultrasonic BJC-4050T- 45HS PZT-4, Altronics plan to stock a suitable transducer, Cat Z1690. If you can’t get it from Altronics, try the following links: siliconchip.com.au/link/ab3g or siliconchip.com.au/link/ ab3h The wiring can be soldered to the transducer terminals; 0.75mm2 figure-8 wire or sheathed dual cable is suitable. The terminals on the transducer are exposed and need to be protected within a housing to prevent accidental contact as they are a shock hazard. The 100V AC can cause a nasty shock, but only if both contacts are touched. Touching one contact or the front face of the transducer will not cause a shock since the transformer output is floating from the main circuit. Don’t rely on this to protect you, though! A suitable housing can be made using 50mm PVC DWV (Drain, Waste and Vent) fittings. We used an end cap and a screw thread adaptor (with the screw thread section cut off) Fig.12: only three holes need to be drilled in the side of the case, two 12mm and one 3mm in diameter. The 3mm hole is for mounting the tab of Mosfet Q6, while the others are for the DC socket and transducer cable gland. 94 Silicon Chip Australia’s electronics magazine siliconchip.com.au be re-calibrated later. The procedure to do that is described in the Calibration section below. Once calibrated, the power level will be shown, and the power LED will light once the transducer is being powered at the set level. If no transducer is connected, the power LED will go out momentarily and one or two level LED(s) will light. Then the level LED or LEDs will extinguish, and the power LED will relight. No calibration will occur. To properly test the board, you Here’s the transducer (left) and mounted inside our need to have the transducer at least “plumber’s special” DWV PVC “case”. This photo temporarily attached to a suitable was taken before we secured the transducer to the vessel, filled with a liquid such as “case” with neutral-cure silicone sealant. water. That’s because you need to check that the transformer is supplying the right voltage to achieve to extend the length of the end cap to an overall outside full power. Your transducer could differ from the one we length of 50mm. You could use the end cap and a short have used, either by being a different type or just coming from a different batch. length of 50mm pipe instead of the adaptor. Wire entry is via a cable gland that is secured in the side of the end cap. Place the cable gland hole in the side of the Diagnostics We have included a diagnostic display for the power end cap, allowing sufficient room for the nut inside. The adaptor or pipe will require an area removed with a file so level so that you can check whether your transducer is that it clears the gland nut when inserted into the end cap. delivering full power. With the unit powered up and the The terminals on the transducer will need to be bent transducer connected and attached to a bath, set the power level to 100%. The display will indicate if the transducer over at their ends to fit into the housing. The transducer should be mounted within the enclosure can or cannot deliver full power. If it can, the 100% LED using neutral-cure silicone sealant (such as roof and gutter will stay lit. If the transducer cannot deliver that power level, the sealant). Use just sufficient silicone to secure the transducer to the inside of the housing, around the outside of the power will begin to reduce automatically until it shows lower bell-shaped section. Fully potting it in silicone will what can actually be produced by the transducer. If this happens to you, you may be able to achieve full dampen the ultrasonic movements a little. The face of the transducer should be kept clear of the power by removing water from the bath. However, this sealant. This is so that the transducer can be secured to the may leave you with insufficient water for practical cleaning. If you decide to lower the water level, make sure to outside of the bath with an epoxy resin. Connect the ultrasonic driver cable to the PCB at CON3. re-run the calibration procedure (see below) before testing Make sure there are no strands of copper wire emerging for full power again. The alternative to reducing the water level is to add more from the terminals which could short out. The other ends turns on the secondary of transformer T1. This will increase of this cable connect to the ultrasonic transducer. Testing Before testing, insert the 3AG fuse into the clips if you haven’t already done so. If you’re powering the unit from a battery, or your power supply doesn’t already have a DC barrel plug to match the socket on the Cleaner, attach the plug to the end of the power supply wires. When ready, apply power to the circuit and check the main 5V supply between pins 20 and 1 of IC1 and between pins 4 and 8 for IC2. You should get a reading of 4.75-5.25V across these pins. When first powered up and after the Start switch is pressed, the Ultrasonic Cleaner will run the calibration for the transducer. While you can do that now, as long as the transducer is attached, the calibration will be incorrect. This is because the impedance of the transducer differs between when unloaded and loaded. When loaded (by attaching to the bath with fluid), the impedance is higher, so if you run it now, it will need to siliconchip.com.au Here’s the transducer glued to the cleaning bath (in this case a stainless steel cooking tray). We used J-B Weld, a two-part epoxy which we find works better than any other. Australia’s electronics magazine October 2020  95 Another view of the PCBs sitting inside the diecast box – one mounted on the lid. Here you can clearly see one of the two MOSFETS with its mounting screw accessible through the hole in the PCB. Don’t forget the insulating washer and bush underneath! the transducer drive voltage to allow the extra power to be delivered. How many turns need to be added can be determined on a trial-and-error basis. Once full power is possible, the transducer may not be able to be driven at the very low power levels. This can be determined by setting the level to the lowest setting. If this low power is not possible, the level display will increase by itself to a higher level, indicating the lowest power level available. Note that the over-current indication (the left, middle and right level LEDs flashing simultaneously) may show instead. If so, that suggests you have too many turns on the transformer secondary (see the troubleshooting section below) The lowest power level available will depend on the steepness of the transducer’s power/frequency curve. This is a measure of how sharply the power drops away when off-resonance. Steep sides on the power/frequency curve for the transducer will mean that it can be driven at the lowest power. In contrast, other transducers with shallower curves might only be able to be operated one level above the minimum (ie, 20% rather than 10%). Finalising construction Once you are happy with the available power range, detach the PCB from the case. Transformer T1 can now be permanently installed on the PCB, rather than via short lengths of connecting wire. Before fitting the PCB in the box, disconnect the ultrasonic driver cable (making sure that the power is off!), then feed its cable through the cable gland, the hole in the enclosure and the gland securing nut, then re-connect it to CON3. Make sure there are no strands of copper wire emerging from the terminals which could short out. The three Mosfets are attached to the inside of the enclosure using the silicone washers and insulating bushes, M3 screws and nuts. Refer to Fig.8 (the same as before, but this time on the inside). Once again, check that the metal tabs are isolated from the case using a multimeter set for reading ohms, using the same procedure as before. The PCB is secured to the enclosure using the two supplied screws. Insert the supplied Neoprene seal in the lid channel and cut it to length before attaching the lid using the screws provided. Finally, stick the four rubber feet to the base. 96 Silicon Chip Calibration As mentioned earlier, calibration happens automatically the first time you press the Start switch. To re-calibrate the unit, hold down the Stop switch, press the Start switch and then release both. This should be done while the transducer is loaded, ie, attached it to the fluid-filled bath. Running the transducer unloaded will cause a large current flow to the transducer due to its lower impedance. While the circuit prevents excessive current by switching off, it is still a good practice to avoid driving the transducer except when under load. During calibration, the resonance of the transducer will be found and stored in non-volatile flash memory. This means that the unit doesn’t have to find the resonance frequency each time the Cleaner is used. At the beginning of the calibration procedure, all five level LEDs will light, and then they will switch off. See the troubleshooting section if you are experiencing problems with the calibration. Using the timer When cleaning parts, set the timer for the maximum duration you want. The time can be changed while the Cleaner is running, and it will use the new time, providing that it is longer than what has already transpired. Setting to a time setting to less than what has already Australia’s electronics magazine siliconchip.com.au transpired will cause it to stop immediately, as will pressing the Stop button. Troubleshooting If you are having difficulty achieving calibration, you can run a more comprehensive diagnostics routine that will provide more information. This is initiated by switching the power off, waiting 10 seconds, then pressing and holding the Start and Stop switches together while switching on the power. The diagnostics routine will start, as indicated by all five level LEDs lighting up. In this mode, the frequency to the ultrasonic transducer can be manually adjusted using the timer potentiometer (VR1). The frequency is 40kHz when the timer pot is set midway and can be varied from 37.6kHz to 42.4kHz by rotating VR1. Further frequency changes can be made by setting the pot either fully anticlockwise or fully clockwise and pressing the Start switch. When holding the pot fully anticlockwise and pressing the Start switch, the frequency will drop by about 540Hz so that overall adjustment range is 540Hz lower, ie, 37.06-41.86kHz rather than 37.6-42.4kHz. You can reduce this further in 540Hz steps to a minimum of 34.88kHz with the pot fully anticlockwise, by pressing the Start switch repeatedly with VR1 at its fully anticlockwise position Similarly, the frequency range can be increased in 540Hz steps by holding the pot fully clockwise and pressing the Start switch. The maximum frequency can be increased up to 45.45kHz by doing this repeatedly. You can monitor the drive frequency by connecting a frequency counter or meter at TP2. You can monitor the cur- rent draw with a voltmeter at TP1. You don’t really need to know the frequency, so if you don’t have the means to measure this, it is not critical. The most critical measurement is the current readings at TP1. Adjust VR1 to find the resonance point, where the current is at a maximum. For the transducer to be able to deliver full power, the current measurement at TP1 needs to be 4.2V just below or above resonance. 4.2V equates to 300mV across the 0.1Ω resistors, so a 3A current. With a 12V supply, this represents a 36W power delivery. If there is a current overload and the voltage at TP1 goes above 4.8V, the transducer drive will be cut off. This is to limit power applied to the transducer to a safe level. Overload is indicated by the outside and centre LEDs on the level display lighting. The drive is restored momentarily every two seconds to check the current. Adjust the potentiometer to restore continuous drive. You can also press the Stop switch to switch off the transducer. To resume, you need to switch off the power and reenter the diagnostics routine as described above. As mentioned previously, if when at the resonance there is an insufficient voltage at TP1, then you will need more secondary turns on the transformer (or take water out). The correct number of turns or amount of water is when the TP1 voltage is close to 4.5V at resonance. This allows some leeway in frequency control to achieve 4.2V is at TP1, for 36W into the transducer when slightly off-resonance. If the TP1 voltage when approaching resonance is too high (ie, above 4.5V), reduce the number of secondary turns or use more water in the bath. SC Subscribe to SILICON CHIP and you’ll not only $AVE $AV AVE MONEY AV but we GUARANTEE you’ll get your copy! When you subscribe to SILICON CHIP (printed edition) in Australia we GUARANTEE you’ll never miss an issue! Subscription copies are despatched well before the on-sale date (the magazine is due on sale around the end of the previous month). It is unusual for copies to go astray in the post – but when we’re mailing out many thousands of copies, it does happen occasionally. 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To subscribe, simply go to our website – www.siliconchip.com.au – click on the “subscriptions” tab and follow the prompts. We accept payment by Paypal, Visa, Mastercard, EFT/Direct Deposit or Cheque/Money Order (sorry, no Amex or Diners). We’re waiting to welcome you to the SILICON CHIP family! siliconchip.com.au Australia’s electronics magazine October 2020  97 PRODUCT SHOWCASE Authorised distributor Mouser Electronics ships the newest genuine parts An update from Mark Burr-Lonnon: Senior VP of Sales and Global Service & EMEA and APAC Business, Mouser Electronics. While some engineers may be tempted to buy the least expensive parts on the market, those parts may be from questionable sources or, worse, counterfeit. This can lead to design problems, manufacturing delays, and customer dissatisfaction — something that is hard to recover from. Mouser Electronics customers can expect 100% certified, genuine products that are fully traceable to each of our 800+ manufacturers from our stock of over one million different components. Mouser is the industry’s first authorised distributor to be accredited with AS6496, the aerospace industry’s high standard for anti-counterfeit measures. This standard sets requirements for the avoidance, detection, mitigation and disposition of counterfeit products in the supply chain. The threat of counterfeit components entering the supply chain has been a growing concern in recent years as demand increases and fake parts are harder to detect. That’s why it’s more important than ever to buy from an authorised distributor like Mouser. Mouser is also registered to AS9100D/ISO 9001:2015 and ANSI/ ESD S20.20-2014, the industry’s gold standards for quality, control, and electrostatic discharge (ESD) protection. Mouser’s AS9100D/ISO 9001:2015 Quality Management System adds additional aviation, space and defence industry requirements, including procedures and processes for the prevention of counterfeit parts. In the quickly evolving world of electronic components, where technical development is in a constant state of advancement, Mouser customers can order with confidence. It’s also reassuring to know that Mouser goes to great lengths to identify products that are “not recommended for new designs” (NRND). Buying from Mouser, design engineers and buyers can be confident they’re always designing with the most advanced electronics available, and can even subscribe to receive these product notifications online. Mouser clearly identifies end-of-life, obsolete and NRND products to avoid the use of older components in new designs, providing a speed-to-market advantage for customers and avoiding early obsolescence. Mouser also gives suggestions for component alternatives, along with the risk level for those potential replacements. Mouser delivers easy and rapid access to essential technical data and application resources — such as product datasheets, application design notes, white papers, videos, and other solution-based content — to aid in the design process. Mouser has just completed a massive expansion of our global headquarters and distribution centre in Texas, USA, which now stands at 1 million square feet (93,000m²), with state-ofthe-art automation technologies. Currently, Mouser has 27 locations worldwide, including new facilities in Brazil, the Philippines, Vietnam and Poland, all of which offer customers local language, currency and sametime-zone support. Mouser now also offers a new Price and Availability Assistant, which allows customers to easily check prices and availability on millions of electronic components. Customers can simply drag and drop, type in or load (copy and paste) a parts list with desired quantities for rapid pricing and availability results. Customers can add up to 200 part numbers, with up to three different quantities per part number. The tool returns exact part matches for each line and offers replacement options for any non-orderable part numbers. Of course, customers can still browse products and narrow down product information via the Mouser website. Featuring a streamlined user interface, smart filtering and prominent search results, www.mouser.com enables engineers to spend less time searching and more time finding the right parts. Mouser Electronics 1000 North Main Street Mansfield, TX 76063 USA Tel: (800) 346 6873 www.mouser.com 98 Silicon Chip Australia’s electronics magazine siliconchip.com.au Tektronix’s TBS1000C oscilloscope – compact and affordable performance The new TBS1000C series of oscilloscopes from Tektronix, which can be purchased from Vicom, are designed for quick hands-on learning and ease of operation. New features include: a 7-inch WVGA display; dedicated front panel controls; bandwidths from 50MHz to 200MHz; compact design; improved user & programming interface; built-in education features; and triggering & acquisition modes for troubleshooting a variety of mixed signal designs. This is all backed by a 5-year warranty, to provide longterm performance and reliability. Vicom is an authorised partner of Tektronix. Vicom Australia 1064 Centre Road, Oakleigh South, VIC 3167 Tel: 1300 360 251 Website: www.vicom.com.au Clean your parts with a HAFCO sandblaster Whether you’re cleaning rust or dirt off your car parts or maybe etching your name into your favourite beer glass, the HAFCO SB-200 Sandblasting Cabinet is a must-have item for every home workshop or garage. Featuring fully sealed side door access with a secure single-lock latch, an internal cabinet size of 835 x 510mm and an internal height of 360-550mm front to back, this sandblasting cabinet has ample room for your larger jobs. This model also includes a LED internal work light, protective glove, blast gun, hopper and stand, replacement protective screens and an assortment of ceramic tips. The included hopper effectively recycles your abrasive blast beads so that you can continue to use them until they break down into fine dust. To remove the used blast material, simply open the spring-loaded hatch on the bottom of the hopper. This model also has provisions to connect a dust collector system so you can always have a clear vision of your job while blasting. For more information, visit your local Hare & Forbes Machineryhouse showroom or www.machineryhouse. com.au/S289 Hare & Forbes Machineryhouse 1/2 Windsor Road Northmead, NSW 2152 Web: www.machineryhouse.com.au New integrated bandpass filters for WiFi 6E devices WiFi 6E (IEEE 802.11ax) is expected to operate up to 7.125GHz. This gives a significant speed increase over WiFi 5 (802.11ac) and also reduces latency by about 75%. Bandpass filters are critical components for RF (radio-frequency) wireless devices, to keep the signal within the assigned frequencies. WiFi RF chipsets must have proper filtering for legal compliance in a small footprint. Johanson Technology are releasing passive surface-mounted bandpass filters for the new WiFi 6E standard. They are cost-effective, available in small footprints, as shown below, and have low insertion loss. For example, the 6530BP44A1190 has a passband of 5.925-7.125GHz. It’s made with a proprietary ceramic mate- rial in an LTCC (low temperature cofired ceramic) manufacturing process, designed to provide a high Q factor. The filters are packaged in a monolithic device called an Integrated Passive Component (IPC). These combine multiple discrete passives into a single surface-mounted device that reduces the board space required. Because the LTCC manufacturing process is precise and repeatable, Johanson Technology can guarantee the IPC will pass its RF performance requirements. Johanson Technology 4001 Calle Tecate Camarillo, CA 93012 USA Tel: (805) 389 1166 Web: www.johansontechnology.com siliconchip.com.au Australia’s electronics magazine October 2020  99 THE MATROX ALT-256 the world's first graphics card! Today’s graphics cards have awesome computing power, with teraflops of processing speed, enabling amazingly realistic 3D graphics from cuttingedge custom silicon. Not this one, though. It’s made from bog-standard through-hole chips and provides a less-than-awe-inspiring 256x240 pixel display. But it’s a clever design; in fact, groundbreaking in its day. E arly home computers in the 1970s generally had text-only screens. The shape of each character (letter, number or symbol) was stored in dedicated ROM ICs. By the late 1970s, there was a hunger for graphics screens in home computers. So Matrox, a Canadian company, came up with the ALT-256. This was the product which launched their company, which later became a one billion dollar enterprise. They’re still in business today, making video cards and other graphics products! See www.matrox.com for more details. The ALT-256 generated a 256 x 240 visible pixel display on a standard composite video monitor. The card itself had a single video plane and contained 38 TTL (transistor-transistor logic) ICs and 16 RAM (random access memory) ICs. The RAM ICs are TMS4027 types, although the documentation cites them as the “4096”. Each of these ICs has a storage ca100 Silicon Chip pacity of 4096 bits, and each IC has a one-bit (on/off) output. So there were no shades of grey; the pixel is either on or off. However, with three cards combined, one output of each can be assigned to the R, G & B channels of a colour video system. And in that case, eight shades of grey are possible on a monochrome monitor, or eight different colours (black, red, green, blue, yellow, cyan, mauve and white) on a colour monitor. Later, Matrox produced the ALT512 which was more advanced than the ALT-256, with twice the memory. This accommodated two video planes, so four shades of grey could be attained from a single card by displaying two pixels (one from each plane) with different intensity weighting simultaneously. We’ll get to that a bit later. When Matrox released the ALT-256 By Dr Hugo Holden Australia’s electronics magazine graphics card, around 1977, it was a revolutionary step forward for S-100 computer owners interested in graphics. There was a review of the ALT256 in Byte Magazine in 1978. This was one remark after mentioning that three boards could enable animation and a colour display: For the Star Trek freak, now there is available a real (if imaginary) universe to save, rather than a slow printer banging out descriptions. For the artist, a canvas; the researcher, a window; and the kids, an electronic sketch pad. Perhaps the word “freak” should have been “fan” to be more diplomatic. However, those remarks are quite profound when one considers what computer graphics cards in modern computers have evolved into. Byte Magazine cited the price of the ALT256 board at $395, which is about $1700 today. Then imagine having to buy three of them! Matrox also produced a companion 2480 card, to generate text, which can siliconchip.com.au Screen 1: a sample image I drew and loaded into the ALT256’s RAM. It may seem crude, but this was sci-fi type stuff back in the late 70s. My monitor has an amber phosphor, hence the colour; it is, in fact, monochrome. be linked with the ALT-256 for a simultaneous text and graphics display. The TV sync generators on these boards can operate as a master or slave, and the video signals either from the graphics card or the text card can be mixed to obtain one video output signal. Circuit diagram I searched the internet for a decent scanned copy of the ALT-256 manual, which included a circuit diagram and the PCB component layout. I kept finding the same scan repeated over the net in many places. It was kind of somebody to scan it in the past; however, when they did, they accidentally left page 84 blank. Wouldn’t you know it, that just happened to be the central section of the circuit diagram! So I hunted around for months, unable to find the full ALT-256 schematic. I was about to reverse engineer the PCB. I tried to contact Matrox, but unless you have a modern product of theirs, it is very difficult. I then found out there was an ALT256 card in a computer museum in Canada, and they had the manual, and the curator copied out the page for me. That was quite a treasure hunt, but it was very useful to have, and it helped me to repair my board. The block diagram from that manual is reproduced in Fig.1, and the full circuit diagram that was so hard to find is shown in Fig.2 It still amazes me what they were are to achieve at the time, just with the 74-series TTL ICs and a small amount of memory. siliconchip.com.au Screen 2: the same image as Screen 1 but shown in ‘reverse video’. The card doesn’t have the capability to do this, so I had to write the image into its memory with the pixel values inverted (ie, one for zero and zero for one). Sample ALT-256 screens Matrox published a software package called MTXGRAPH, as a .PRN listing in the ALT-256 manual. Presumably, this was also on disk at the time, but it would be very rare now. I plan to assemble and test this software in the future. For now, though, I had to write my own program to test the card. Screen 1 shows the image I drew, displayed by the ALT-256. It started as a 180kB, 256 x 240 pixel monochrome .BMP file which I processed to convert into a format that the SOL20 computer could load and then display on the ALT-256. I drew this image in “Microsoft Picture It” by tracing over some drawings of the DeLorean. The wheel hubs were the most difficult part. I found it best Fig.1: the ALT-256 block diagram shows how the RAM array, comprising ICs A32-47, feed into shift registers A27-28 and then the video generator to create a continuous composite video signal. At the same time, the S100 bus interface (A51-55) can write pixels via A1 & A9 or clear the screen via A1 & A19. Australia’s electronics magazine October 2020  101 Fig.2: the complete ALT-256 circuit diagram was hard to track down, but I’m so glad I managed to get a copy. It makes working on the card a lot easier! It may seem complicated, but when you consider that it is a complete video system with a computer interface, it’s actually quite elegant. 102 Silicon Chip Australia’s electronics magazine siliconchip.com.au to draw in the native resolution, rather than start with a higher-resolution file and try to scale it down. I also created an image file for the reversed (negative) image shown in Screen 2. This is easy to do in hardware by inverting the video signal (and not the sync), but the ALT-256 does not have this facility. So it required a separate image file. This ALT-256 card has likely not produced any graphics since the 1970s, so it was a gratifying experience to see this image come up after all the work required to process the image file to suit the card. Repairing my ALT-256 Actually, before I could display those images, I had to repair the card – a process which I shall now describe. I acquired the ALT-256 card from eBay. My experience with this card is very little different than any other vintage S-100 card from that era. There are usually one or two faulty 74LS series TTL ICs, and in cases where there are IC sockets, these sockets and the IC pins require significant cleaning to re-establish a good connection. In the case of the ALT-256 though, Matrox decided not to use any sockets for any of the ICs. This makes for a more reliable card, especially after more than 40 years. However, there were two faulty ICs on the card I acquired (a 74LS367 and a 74LS04) in the TV sync generator circuitry. So I had to desolder them and replace them with suitable, period-correct ICs. I did the fault-finding with the aid of the schematic and a 2465B Tektronix Oscilloscope. Also, somebody had worked on this PCB in the past; three jumpers were cut, one IC pin was cut and a 7812 regulator IC had failed. One TMS4027 RAM IC, A42, also required replacing. One cannot acquire a card of this age and expect it to be working off the bat. Locating faulty RAM ICs As you can see from Fig.3, the 16 RAM ICs are located in the upper-left corner of the card and are labelled A32 through A47. You can figure out which may be faulty based on looking at columns of pixels on the display. One good thing about fault-finding graphics cards with video RAM is that the screen image serves as the diagnostic window. Each of the TMS4027 RAM ICs looks after an area of screen pixels in 16 vertical rows. If each row were 256 pixels high, then this would correspond to the 4096 single-bit storage locations within that IC. While all of these locations can be “written to” with software commands, there are only 240 active scanning lines on the monitor (the remainder are in the blanked out vertical retrace time), so only pixels on the Y-axis labelled 0 to 239 are visible. On the other hand, on the x or horizontal axis, all 256 pixels are seen (labelled 0 to 255). In this video card, coordinates x=0 and y=0, specified in the card’s registers, are at the top left-hand corner of the video monitor. With a RAM IC failure, the output pin (pin 14 on the TMS4027) could be stuck low or high. In the case it is stuck high, 16 rows of vertical pixels will be turned on. These will only be seen easily if the background or all surrounding pixels are off. You can switch all pixels off in BASIC. Assuming the address jumpers on the PCB are set so that A7, A6, A5, A4, A3 & A2 are tied low, the Erase port address is 03: OUT 3,0 ; sets all pixels off Conversely, if a RAM IC output is stuck low, to see it, all the pixels need to be set on: OUT 3,1 ; sets all pixels on The Matrox ALT-512 was produced a shortly after the ALT-256 and has a display resolution of 512 x 256 pixels (or 256 x 256 with two layers). Further details on this board will be detailed in part two of this article next month. Photo source: siliconchip.com.au/link/ab3y (https://deramp.com/) siliconchip.com.au Australia’s electronics magazine October 2020  103 Fig.3: this diagram shows where each component is located on the card PCB. Most significantly, it shows the positions of all 57 ICs. No doubt, mounting them all with the same orientation helped with the designer’s sanity. 104 Silicon Chip Australia’s electronics magazine siliconchip.com.au Program to help find defective pixels (shown in Screen 3) 10 B=0 20 FOR X = 0 TO 255 30 OUT 1,(X+B) 40 OUT 2,X 50 OUT 0,1 60 IF (X+B) = 255 GOTO 100 70 NEXT X 80 B=16 90 GOTO 20 100 END I run MBASIC in the operating system CP/M (Control Program for Microcomputers) on my SOL-20 computer. To figure out which row of pixels is defective (and therefore which IC), I found it helped to plot two diagonal lines spaced 16 pixels apart (the finished program is shown above), either a black or a lit line. Select a 0 or a 1 for the pixel to be displayed (line 50) depending on whether all the pixels are previously off or on with the OUT 3 instruction above. This program, when RUN, plots two ; ; ; ; ; ; initialize offset number of pixels x coordinate y coordinate “1” plots an on pixel, “0” plots an off pixel limit max x pixel coordinate to 255. ; set offset for second line ; plot second line diagonal lines which can be used as a RAM diagnostic to determine which physical RAM IC is defective. Firstly, if pixels are stuck on, use “OUT 3,0” initially to set all pixels off, and then change code line 50 to be “OUT 0,1” and run the program. (Conversely, if pixels are stuck off, type “OUT 3,1” to set all pixels on and code line 50 to be “OUT 0,0”). Which IC looks after which column is shown in Fig.4. The boxes in grey represent the lines plotted by the BASIC program, called “locator lines”. The columns looked after by each RAM IC are shown at the top. As can be seen, for this example (where IC A42 has failed) the defect is in the 6th column. Therefore, by examining the video display, to see where the locator lines and the defective pixel coincide, the failed column can be found and the IC corresponding to it physically located. The purpose of the lines being diagonal is to make it easy to visually count the pixels, which is very difficult if they are on the same row. Physical ICs and pixel assignments for the ALT-256 Fig.4: this diagram shows which RAM ICs control which display columns, and how you can draw diagonal lines on the screen to figure out which IC is faulty if the display is not right. A faulty RAM IC will usually cause either black or white vertical stripes, but some faults could result in just one or a few pixels in those columns being stuck on or off. siliconchip.com.au Australia’s electronics magazine October 2020  105 ► Screen 3: RAM IC A42 had failed on the ALT-256 card I bought, and here is the display I got when drawing the diagonal lines. By counting pixels, I quickly pinpointed the faulty part. ► Screen 4: this is what the output of the program looks like if you set all the pixels on on the screen on first. This would normally be used to find a fault where columns of pixels were stuck off. However, in my case they were stuck on and you can see here that this mode can still be used to determine which RAM IC is faulty. Screen 3 shows the result of running this program with my eBay card. In this example, IC A42 has failed, its output pin 14 being stuck high. Screen 4 shows what the screen looks like when running the program to detect a RAM output that’s stuck low. The locator lines are plotted in black, with all other pixels switched on. It is straightforward to count along the pixels on the x-axis to see that it is column 6, 22, 38 etc that are defective and we can then tell from Fig.4 that A42 is responsible. If there were single or more defec106 Silicon Chip tive pixels, related to one or more of the 4096 locations inside a single TMS4027 IC, these would show up somewhere in one of the columns provided by that IC. Conclusion So you can now see how computer graphics got its start. As shown earlier, not long after the ALT-256 was released, Matrox came along with the more capable ALT-512, and I also got my hands on one of these. I shall describe it in the follow-up article next month. Australia’s electronics magazine One thing to note about the ALT256 is that, once you put the data into graphics memory, there is no way to read it back out. So if you want a copy of what is on the screen, you have to write that data elsewhere in general memory too. With the ALT-512, you can interrogate the graphics memory. This is helpful say in a program like a light pen, where you alter the pixel values in graphics memory, then you want to save the image you have drawn later. More details on this will be published next month. SC siliconchip.com.au ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Send your email to silicon<at>siliconchip.com.au Colour Maximite 2 external oscillator I am interested in building the Colour Maximite 2. In the text, you mention there is a problem with the 8MHz oscillator and that you can fit an external oscillator module on the main board. Do you have to make any changes except for removing the crystal on the Waveshare board and fitting the two parts to the main board? Looking at the Waveshare pinout, I can’t see an external clock input pin. (D. W., Hornsby, NSW) • Geoff Graham responds: the Silicon Chip PCBs include provision for an external 8MHz oscillator. If you want to fit this, all you need do is follow the steps outlined in the article. However, you will be very unlikely to need an external oscillator. Since the PCB was designed, we have made many firmware improvements which have mostly eliminated the need for this feature. If we were designing the PCB now, we would not bother with the option for an external oscillator. Editor’s note: one person who built a CMM2 from one of our kits reported display problems which appeared to be due to clock instability. We are therefore stocking the parts needed to add this option (siliconchip.com.au/ Shop/7/5654). Oven Controller shows wrong temperature I built your DIY Reflow Oven Controller (April & May 2020; siliconchip. com.au/Series/343). I discovered that not all 20-pin displays have the same pinout, but a custom adaptor cable fixed that. The buttons and rotary switch work and the settings are being stored on power off. All functions work except for the measured temperature display. It starts at about 16000 after the splash screen then ramps up to 16383, sometimes 16385, over about two seconds and stays there. The °C symbol is not there, perhaps written over. I siliconchip.com.au confirmed that the output of the thermocouple amplifier is about 1.3V and goes up and down with temperature change. I measured it all the way to the pin on the PIC. Can you please help. (B. G., Pennant Hills, NSW) • We think that you have not set the temperature coefficient for the thermocouple. This needs to be done in the setup menu. Refer to the setup section of the article and follow the instructions for setting this parameter. We recommend that you enter 0 for OFFSET and 0.161 for TEMPCO. If this has been set, then the next most likely problem is that the thermocouple adapter is miswired or faulty. But your voltage measurement sounds about right, as you would expect 1.25V + 5mV/°C. So we think that part of the circuit is probably working correctly. You can verify by popping the thermocouple in a cup of hot water; the voltage should increase by 300mV or so. Also, check the power connections to the thermocouple adaptor, and that the thermocouple is connected the right way around. Using ceramic resonators Have you published a primer on ceramic resonators? If so, when? Some have two leads, while others have three leads. What is the significance of the centre lead? (M.P., via email) • We haven’t published an article on ceramic resonators. They work similarly to crystals. Ceramic resonators are generally not as accurate as crystals but are usually cheaper and more compact. The central lead in a 3-pin resonator would generally be connected to ground, and that provides the ground connection for the onboard load capacitors. You don’t need external load capacitors with a 3-pin ceramic resonator, unlike a two-pin crystal or resonator. It might help you to examine page six of the Murata Ceralock data sheet which you can download from siliconchip.com.au/link/ab4s Australia’s electronics magazine That shows the equivalent circuit of one of their 3-pin ceramic resonators, incorporating the two load capacitors, along with an example driver circuit which is essentially identical to the canonical crystal oscillator circuit. RF Power Meter display not working I compiled the Wideband Arduinobased RF Power Meter software sketch OK (May-June 2020; siliconchip.com. au/Article/14542). But after building the unit up, the display just shows one line of white blocks. I’ve cycled the pot on the rear through its range, and no info appears. If I plug the IDE in via the USB/programming cable, and use the serial monitor, up comes the “Silicon Chip Digital RF Power Meter” splash, and then RF Pwr + -68.6dbm etc. So the sketch is working, but the display appears not to be. Do you think I have a faulty display or a sketch problem? (G. M. N., Torquay, Qld) IC variants • Some I2C I/O expander respond to different I2C addresses. The sketch defaults to 0x3F (hexadecimal), which is set at line 36 in the current version of the sketch. Try changing this to 0x27 (as shown in that line for the PCF8574T variant). If that doesn’t work, try using an I2C scanner sketch. It should be able to figure out the I2C address for your display. Mains voltage switch for 45V Bench Supply I am building the 45V 8A High Power Linear Bench Supply (OctoberNovember 2019; siliconchip.com.au/ Series/339). Could I include a mains voltage selection switch that switches the primary side of the transformer windings between series and parallel connections? What is the maximum current drawn from mains? I believe the article called for a 6A fuse in the IEC block. Considering this adds risk with October 2020  107 more mains-side wiring and the potential to plug it in switched wrong, I’m probably going to leave it out, especially because I doubt it’s going to be used outside of Australia. But I’m curious about your input. (S. B., Banyo, Qld) • You could add a switch to select between 115V AC and 230V AC operation but the fuse rating would have to be doubled for use with 115V AC. The 6A fuse is specified by the transformer manufacturer. While the unit doesn’t draw anywhere near 6A, a lower-rated fuse would likely blow at power-up due to the transformer inrush current. If you do this, make sure that the windings are connected in parallel for 115V AC operation and not antiparallel. It would also be a good idea to add suitably rated MOVs or similar across the primaries to protect the rest of the circuit in case 230V AC is applied while the switch is in the 115V AC position. For example, if you connect 200V 1200A MOVs across both primaries and accidentally apply 230V AC to the paralleled windings, the fuse should blow pretty quickly; hopefully, before any other damage occurs. Calculating series & parallel resistors Have you ever published a BASIC program to calculate series/parallel resistors? What about one for the great circle (finding distance between two points on Earth)? (R. M., Melville, WA) • We published a BASIC program for calculating parallel and series resistor combinations (November 1989; siliconchip.com.au/Article/7355). But depending on what you want this for, it may be easier for you to use the program on the following web page: www. qsl.net/in3otd/parallr.html We published BASIC code for calculating great circle bearings and distances on pages 78 & 79 of the February 1990 issue – see siliconchip.com. au/Article/7293 Other remote triggering preamp input switching I built several of your Ultra Low Noise Remote Controlled Stereo Preamps (March-April 2019; siliconchip.com. au/Series/333) from Altronics kits (K5171/5172). They are working fine, but a strange anomaly has occurred. 108 Silicon Chip Occasionally the standby button on our Panasonic PVR remote control affects the preamp. It switches it to input one. No other buttons seem to have any effect, and it doesn’t happen every time. I have conducted experiments with a spare IR detector and oscilloscope. The Universal Control I have for the preamp produces Philips’ RC5 coding (as expected); I can clearly see the two start bits. The Panasonic remote is definitely not producing RC5 signals. My ‘scope isn’t sophisticated enough to trigger correctly on it, but it looks nothing like RC5. It might be the NEC protocol, but I’m not convinced. Has anyone else noticed a similar problem, or do you have any ideas about how to prevent it? (J. H., via email) • It seems to be responding to an alternative code where the IR signal is on, an off edging is near to the required RC5 code of the channel one input for the preamplifier. It could be prevented by using one of the alternative codes from what is being used (TV, SAT1 or SAT2) so that the coding differs sufficiently from the standby button for the Pansonic remote. The details for changing the preamplifier remote codes are on page 44 of the April 2019 issue. If that does not solve it, the software could be revised to be more stringent on IR decoding. However, we have used the same software for many projects without problems so far. It may be just that the frequency of operation for the two remotes is just close enough to sometimes cause a response from a different code. Remote controls use a ceramic resonator (rather than a crystal) for the oscillator, and so have a considerable frequency tolerance. Motor speed control feedback instability I am having a problem with your Full Wave 230V Universal Motor Speed Controller from March 2018 (siliconchip.com.au/Article/10998). When using it to control an incandescent lamp, or a motor with an incandescent lamp in parallel, it exhibits speed instability at particular speed/ feedback-gain settings. Do you know why this is happening? (T. S., Perth, WA) Australia’s electronics magazine • The speed control feedback is not meant for use when controlling incandescent lamps. Firstly, there is no benefit. Secondly, the non-linear lamp current with a voltage applied to the incandescent lamp will cause feedback control problems. That is because the lamp resistance and hence current varies non-linearly with the brightness setting. The lamp resistance increases nonlinearly with lamp brightness and temperature. When speed control is adjusted from off (with the feedback control), the feedback system has problems finding a suitable settling point, leading to variation in lamp brightness and hunting. So the feedback gain should be set to minimum (off) when used with a lamp. When used on motors, the feedback gain control is adjusted so that the motor speed varies little with changes in load. Setting the feedback gain too high will cause the motor to run in an unstable manner. This is because it monitors the current, and when the motor is loaded, it slows and the current will rise. The control feedback causes an increase in the speed setting to increase the motor speed. That, in turn, increases the motor current. It can rapidly become an unstable positive feedback system. So the feedback gain control must be adjusted so that the gain is not so high as to cause overcompensation and instability. The feedback gain was provided with a wide range of adjustment; usually, a position of around 25-30% clockwise from the fully anticlockwise position would be sufficient for motor speed control. Note that using both incandescent lamps and a motor as a load will reduce any speed control effectiveness because the lamp current variation with voltage will tend to dominate the feedback. This will lead to instability as the feedback gain will need to be increased to have any speed control under load. Touchscreen Altimeter gives incorrect readings I have run into some problems after building the Touchscreen Altimeter and Weather Station (December 2017; siliconchip.com.au/Article/10898). It worked for a while, but it displayed siliconchip.com.au inaccurate temperature and altitude readings. Attempting to correct those, the screen froze in the Weather Station Mode. When turning the unit on since, it always starts up with the same screen. (H. M., Bowral NSW) • We suspect a connection problem with your sensors. With regards to the display not responding, we have found that you have to press the button for around a second for it to respond. At one stage, we received a batch of displays which had a rotated touch sensor. If you have one of those, you may find that the button responds to touches elsewhere on the screen. Please tell us if the screen responds to touches elsewhere (or anywhere on the screen) or not at all. If you have the rotated touch panel display, you can fix it by running the touch sensor calibration procedure. Also please send images of your construction and wiring, as that might help us rule out other problems. Problem with DC Motor Speed Controller I have built your High Power DC Motor Speed Controller from the January and February 2017 issues (siliconchip. com.au/Series/309). All the components seem to work, but there is no speed control. The controller goes from zero to full power instantly. There is 12V at the output of REG1 and 5V at the output of REG2. I chose R1 and R2 for 24V. The on/off switch has no effect, on or off the motor keeps on going as soon as power is applied. The on/off LED follows the state of the on/off switch. The low-battery adjustment works but the corresponding LED doesn’t seem to work. When the emergency stop is engaged, the LED comes on, but doesn’t stop the motor. If the on/off switch is turned off then on it will make the LED go off, but doesn’t affect what the motor is doing. The speed LED blinks when the motor is going. Can you help? (B. E., Taroona, Tas) • We wonder if you have the linking correct. Check that links 1, 2 & 3 are installed for high-side switching or links 4, 5 & 6 for low-side switching. There should be no jumper shunt in JP2 for high-side switching, but it should be fitted for low-side switching. Check the orientation of the low siliconchip.com.au battery LED (LED3). Also check its anode connection to the 1kW resistor and from this to pin 11 of IC1. Verify that LED3’s cathode is connected to circuit ground. If this is all correct, please send photos of the top and bottom of each PCB. We might be able to spot the cause. Digi-Key Cat PB328-ND (TE Connectivity K10P-11D55-24) is rated at 15A and looks like it’s probably a drop-in replacement. That would be suitable for amplifiers delivering at least 300W into 4W or 600W into 8W. Can the Loudspeaker Protector (October 2011; siliconchip.com.au/ Article/1178; Altronics kit K5167) be adapted for use in amplifiers with higher power ratings than the 135W amplifier it was designed for? (J. S., Thirroul, NSW) • We give resistor values in the circuit diagram on page 35 for supply rails of up to 70V. That implies it can be used in amplifiers that can deliver up to about 400W. However, we are not sure that the 10A-rated relay will be capable of reliably interrupting the fault current of an amplifier that can deliver more than 200W into 4W or 400W into 8W (ie, more than 7A RMS or 10A peak). We would upgrade the relay for amplifiers larger than that. plied to loudspeakers? (P. B., Pennant Hills, NSW) • Most loudspeaker power displays that you find on audio amplifiers and the like are essentially just voltmeters with a scale calibrated to show the power that would be delivered by that signal voltage into a particular load impedance (typically 8W or 4W). We published a circuit in the Circuit Notebook section of our October 2009 issue (pages 58-59; siliconchip.com. au/Article/1594) which will calculate and display audio power for various common load impedances (8W, 4W and 2W) on a digital voltmeter. We also published a basic design which showed audio power on an LED bar graph based on a voltage reading in the April 1993 issue Displaying audio power for loudspeakers Using speaker protector level Are you aware of any projects that with high-power amp show the amount of power being sup- What's an Erlang? My electronics interests include the accuracy and precision of measuring things; if you can measure it, then it is real. My wife describes this as Obsessive Measurement Disorder. It is not really a mental disorder, but I am working on it! I recently bought a beautiful 200mm diameter Erlang meter. It was made by Paton Electrical in Sydney, and the rim is labelled as 100mA FSD. My research suggests that Erlangs are a measure of the call saturation on multiple line trunk phone lines. Can someone help me find how this was measured by the meter and a rough guess of its date? Does the NBN have a “MegaErlang” meter, to measure the use saturation, of their networks? (D. D., Berowra Hts, NSW) • Sorry, we haven’t heard of an Erlang meter. There is some information online, though. See https:// en.wikipedia.org/wiki/Erlang_ (unit) The Erlang was defined in 1946 Australia’s electronics magazine so that’s the earliest year your meter could be made. We guess, based on the lettering and condition of your instrument, it was made in the 50s or early 60s. Here is a history of Paton: siliconchip.com.au/link/ab4r They ceased local manufacturing around 1970, lending credence to our guess that your instrument was made no later than the 60s (and probably in the late 50s). October 2020  109 (siliconchip.com.au/Article/5400). Note that as loudspeaker impedance varies with frequency, all of these circuits will only give you a rough idea of the power level. None of them measure the actual power going to the speakers, although it is possible to do, if a bit complex. Transformer for battery charging I built your Deep Cycle Battery Charger (November & December 2004; siliconchip.com.au/Series/102) using a TLC549 instead of the discontinued TLC548 specified. It seems to be working well. I have a transformer with adequate power for battery charging, but the output voltage is less than 18V. I measured 16.65V on the output without load. Do you think this transformer might be suitable for the charger? (V. V., via email) • Given the 16.65V reading with no load, the transformer output voltage will likely drop too low to properly charge a deep-cycle battery when under load. If the transformer is a toroidal type, you could add more secondary windings for more voltage. Otherwise, you will need to test the transformer under load to check if the output voltage is adequate to charge the battery. Guitar preamp buzzes loudly I have built the 2-Channel Guitar Preamplifier (November 2000-January 2001; siliconchip.com.au/Series/134) from an Altronics K5340 kit. When switched on, it has a low buzz with all pots set on zero and the master volume at 50%. When I raise the “level” pot to 1%, the buzzing gets louder, and the distortion is at maximum. I have checked my construction but can’t find any problems. What might be wrong? (J. D., Rotorua, NZ) • You could have an open circuit between pins 6 and 7 of IC1a, leading to this op amp operating in open-loop mode (maximum gain). Check the resistance (and resistor value) between these pins, as it should be 4.7kW. Also check the solder joints and make sure that the IC has been properly inserted into its socket if using a socket (make sure it doesn’t have any pins bent under its body). 110 Silicon Chip Capacitor polarity for LM3876 amp I have been thinking about building the 50W Audio Amplifier (March 1994; siliconchip.com.au/Article/5292), and the subsequent Notes and Errata for this project mentions that the 22µF capacitor connected to pin 8 of the LM3876 and the 220µF capacitor on the -ve supply rail are both shown the wrong way round. Looking at the data sheet for the LM3876, and Rod Elliot’s “Single Chip 50 Watt / 8 Ohm Power Amplifier” at https://sound-au.com/project19.htm, it seems that the 22µF capacitor from pin 9 is also depicted incorrectly, ie, all three capacitors should have their +ve terminals connected to ground. Please let me know if this assumption is correct. (I. M., Point Cook, Vic) • Pin 9 is the inverting input to the amplifier. It would typically be held at close to 0V. The specification quotes a maximum of +15mV with respect to ground (pin 7). So we believe that the capacitor connected in series with the feedback resistor at pin 9 is shown correctly, with its positive side to pin 9. That being said, electrolytic capacitors will tolerate a small negative bias (under say 1V) continuously. This is taken advantage of when using them as coupling capacitors between two points that are nominally at the same (or very similar) DC levels, where the exact bias is not always known. So that capacitor should be fine either way around. Regardless, you could check the actual DC voltage across polarised capacitors after building the circuit to make sure they are correct. No easy solution for flickering LED lights Here in southeast Qld, we have the unfortunate problem of LED mains lights flicker when using a dimmer. This is caused by the ripple injection to turn on/off off-peak devices. Even though I have installed a “ripple filter”, they still flicker. I have noticed that when no dimmer is in the circuit, the lights no longer flicker. My thoughts to eliminate this flicker would be to rectify the 230V AC to ~350V DC after the dimmer and before the LEDs, seeing as the LEDs would do this internally anyway, and add filtering to clean up the DC. Australia’s electronics magazine I’ve tried using my adjustable power supply but can only get up to 60V, so I added a 30V supply in series to make 90V DC, the lights happily worked off 90V, just not as bright as they should be. What are your thoughts? (D. D., Petrie, Qld) • Theoretically, virtually all mainspowered devices with capacitor-input switchmode supplies can run off rectified mains. But we are reluctant to suggest this because of various safety problems with such an approach, and because we don’t know the details of your particular devices. Also, we don’t think it will solve your problem. While we agree that it’s much easier to filter out the control tones after rectification, it is likely to be the dimmer itself that is responding to the mains control tones, so putting the filter after it probably won’t have the desired effect. The dimmer will not work running off 350V DC. When we’ve investigated this in the past, we’ve concluded that the solution is a notch filter tuned to the ripple injection frequency. Unfortunately, multiple control tone frequencies are used in different places, so it’s hard to come up with a ‘one-size-fits-all’ approach. If you can figure out what your local control tone frequency/frequencies are then it probably wouldn’t be too hard to build a notch filter that can handle mains voltages at several amps, and tune it to null that frequency quite effectively. Upgrading op amps in old graphic equaliser My Electronics Australia Playmaster Graphic Equaliser has developed a couple of dead bands. After my experience quite a few years ago with the companion Graphic Analyser unit, I suspect the RC4136 op amps. When I first built the Analyser, I had multiple dead op amps supplied with the kit (16 out of 40). The µA/RC4136 is now difficult to source, and there must be newer, better performing op amps available. Can you recommend any readily available pin-for-pin substitutes? (R. A., Hunter’s Hill, NSW). • Op amps can usually be upgraded, but unfortunately, the RC4136 used an unusual pinout for a quad op amp that doesn’t seem to have been shared with any other devices. Here is an imsiliconchip.com.au MARKET CENTRE Cash in your surplus gear. Advertise it here in SILICON CHIP KIT ASSEMBLY & REPAIR FOR SALE VINTAGE RADIO REPAIRS: electrical mechanical fitter with 36 years ex­ perience and extensive knowledge of valve and transistor radios. Professional and reliable repairs. All workmanship guaranteed. $17 inspection fee plus charges for parts and labour as required. Labour fees $38 p/h. Pensioner discounts available on application. Contact Alan, VK2FALW on 0425 122 415 or email bigalradioshack<at>gmail. com GREAT VALUE PARTS and more are found in the Tronixlabs ebay store via tronixlabs.com.au – for enquiries or support please email support<at> tronixlabs.com DAVE THOMPSON (the Serviceman from S ILICON C HIP) is available to help you with kit assembly, project troubleshooting, general electronics and custom design work. No job too small. Based in Christchurch, NZ but service available Australia/NZ wide. Email dave<at>davethompson.co.nz KEITH RIPPON KIT ASSEMBLY & REPAIR: * Australia & New Zealand; * Small production runs. Phone Keith: 0409 662 794 keith.rippon<at>gmail.com Silicon Chip Binders REAL VALUE AT $19.50 * PLUS P & LEDs, BRAND NAME and generic LEDs. Heatsinks, fans, LED drivers, power supplies, LED ribbon, kits, components, hardware, EL wire. www.ledsales.com.au ASSORTED BOOKS FOR $5 EACH Selling assorted books on electronics and other related subjects – condition varies. All books can be viewed at: siliconchip.com.au/link/aawx Email for a postage quote: Silicon Chip silicon<at>siliconchip.com.au PCB PRODUCTION PCB MANUFACTURE: single to multi­ layer. Bare board tested. One-offs to any quantity. 48 hour service. Artwork design. Excellent prices. Check out our specials: www.ldelectronics.com.au P Keep your copies safe, secure and always available with these handy binders These binders will protect your copies of SILICON CHIP. They feature heavy-board covers, hold 12 issues & will look great on your bookshelf. Silicon Chip Publications Order online from www. siliconchip.com.au/Shop/4 ADVERTISING IN MARKET CENTRE Classified Ad Rates: $32.00 for up to 20 words (punctuation not charged) plus $1.20 for each additional word. Display ads in Market Centre (minimum 2cm deep, maximum 10cm deep): $82.50 per column centimetre per insertion. All prices include GST. Closing date: 5 weeks prior to month of sale. To book, email the text to silicon<at>siliconchip.com.au and include your name, ad­ dress & credit card details, or phone Glyn (02) 9939 3295 or 0431 792 293. age showing the difference between the RC4136 and virtually every other quad op amp like the TL074 or LM324: siliconchip.com.au/link/ab4p There’s a discussion of the problem at siliconchip.com.au/link/ab4q As you can see, the pinout is entirely different so it would be a lot of work to rewire the sockets. The RC4136 is still available, so we think your only real option is to get new ones. See https://au.mouser.com/Search/ Refine?Keyword=rc4136 SC siliconchip.com.au Notes & Errata Four USB power supplies for laptop charger, Circuit Notebook, August 2020: instead of 220µF choke, it should read 220µH choke. Velco 1937 radio chassis restoration, August 2020: in the circuit diagram on page 85, the 100nF capacitor below valve V4 should be shown connected to the other end of the 1MW resistor, ie, to the AGC line. Infrared Remote Control Assistant, July 2020: on page 77, the second paragraph of the text refers to a “47µF series capacitor”. It should instead read “47W series resistor”. Australia’s electronics magazine October 2020  111 Coming up in Silicon Chip Balanced Inputs & Attenuator for the USB SuperCodec Rather than resting on his laurels, Phil Prosser has produced an add-on board for his SuperCodec USB Sound Card which adds two balanced inputs and selectable attenuation settings of 0dB, 10dB, 20dB or 40dB. It fits in the same case as the SuperCodec and provides professional balanced audio recording. Making PCBs with a laser engraver Advertising Index Altronics...............................81-84 Ampec Technologies................. 31 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Andrew Woodfield describes how you can use a low-cost laser engraver to transfer a PCB pattern onto a blank fibreglass/copper laminate. This avoids the need to purchase pre-sensitised PCBs or sensitising film, and once you have the procedure down, it allows for easy and relatively painless etching. Emona Instruments................. IBC Jaycar............................ IFC,53-60 MicroElectroMechanical Systems (MEMS) Keith Rippon Kit Assembly...... 111 We’ve used MEMS devices before but haven’t described how they work in detail. Dr David Maddison’s article explains what they are, how they are made and shows the many different types of MEMS available. The article includes electron microscope images showing the amazing precision of these tiny devices. LD Electronics......................... 111 Leach PCB Assembly............ OBC LEDsales................................. 111 Ten LED Christmas Ornaments We will have multiple Christmas projects in our November issue, including two different, impressive LED Stars that you can fit atop your Christmas tree (or just put on display). Plus, we will describe eight mini LED Ornaments which are cheap, easy to build, and look great. The latest 8-pin PIC features Microchip continues to improve their 8-bit portfolio, having introduced several parts over the last few years which are cheaper than their predecessors, but also faster with more memory and better peripherals. Tim Blythman takes a look at what's available and which parts give you the best bang-for-your-buck. Microchip Technology................ 21 Mouser........................................ 7 Ocean Controls........................... 5 RayMing PCB & Assembly.......... 4 Rohde & Schwarz........................ 9 Silicon Chip Binders............... 111 Vintage Radio Battery Power Supply Silicon Chip Shop.................... 51 A relatively compact circuit which generates A- and B-battery voltages suitable for most battery-powered vintage radios from four Li-ion cells (eg, 18650s).This means you can easily bring your battery-powered vintage radio into the modern age! Silicon Chip Subscriptions....... 97 Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. Tronixlabs................................ 111 The November 2020 issue is due on sale in newsagents by Thursday, October 29th. Expect postal delivery of subscription copies in Australia between October 27th and November 11th. The Loudspeaker Kit.com........... 6 Vintage Radio Repairs............ 111 Wagner Electronics................... 63 WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Competition & Consumer Act 2010 or as subsequently amended and to any governmental regulations which are applicable. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au “Rigol Offer Australia’s Best Value Test Instruments” Oscilloscopes NEW 200MHz $649! New Product! 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