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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”. Xmas projects & soldering SMDs It’s good to see another round of Xmas Ornaments from Tim Blythman (November 2020; siliconchip.com.au/ Article/14636). Tim has successfully introduced me to working with SMT devices with the tiny Xmas Tree last year (November 2019; siliconchip. com.au/Article/12086). I have found that soldering SMT devices is less difficult than some people imply. In particular, I found the reverse (or self-closing) tweezers much easier to use than a clothes peg which turned out to be much too big to conveniently handle tiny components. I use solder paste in a syringe which has a very fine nozzle, which allows a suitably small amount of paste to be applied to pads. The fine point soldering iron is adequate for the soldering, and I’ve only made one or two mistakes which were easily corrected. Thanks again, Tim, for some engaging projects that the grandkids have, and will, I hope, enjoy. Eric McAndrew, Capel. WA. Response: thanks for your feedback. Note that when melting solder paste with the tip of a soldering iron, the solder paste can splatter, causing solder balls to make their way to unwanted locations. Reflowing the solder paste with hot air is safer, as long as it is done carefully. Article on capacitors desired I second your reader’s request in the November issue regarding a guide to capacitor usage. While there are plenty of web pages covering aspects of this topic, I would really value such an article as I know I can trust what you publish and that it would be up to date. At the end of your response, to show how complicated this topic is, you list all the various issues that would need to be addressed. Surely that in4 Silicon Chip dicates how worthwhile such a guide would be. Kim Windsor, Melbourne, Vic. Response: we agree that it would make for a good article and plan to start working on it soon. Oscillator rotary encoder reversed I would like to thank Silicon Chip and Andrew Woodfield for the Pocket Audio Oscillator kit (September 2020; siliconchip.com.au/Article/14563), it works well, is easy to use and I love the readout. The supplied kit needed a few minor construction hacks and interpretations but nothing insurmountable. I built the kit following the layout of Fig.3 on page 46. But I noticed that the frequency decreases as the knob is turned clockwise. I assume that either the rotary encoder is sending the opposite command to the ones that were used in the prototypes, or that the 1.8kW and 3.9kW resistors in Fig.3 are swapped. I swapped those two resistors and the unit is operating correctly. I understand the reasons that the maximum frequency is 10kHz, but I would find it far more useful if it could get to 18kHz or maybe 25kHz, even with excessive distortion and a flaky readout. I can’t hear these frequencies; I am just trying to catch the distortion caused by them. I really appreciate the magazine as it has a nice mix of topics. You folks are making many people happy, stimulating a swag of future professionals, exposing theoretical types to a lot of real-world experiences etc. In other words, doing a bloody magnificent public service! One of my many pleasures/aims/desires in life is to gently work at making the world a better place. Thank you for your efforts in that direction. Well done! Before Silicon Chip, I read Australia’s electronics magazine Electronics Australia, and I was reading electronics magazines even before that – struth! Len Braithwaite, North Sydney, NSW. Response: we built our prototype with the resistors in the positions shown, and it worked correctly, so we have to assume that different batches of encoders can have the encoder pins swapped. That’s frustrating, especially since it’s almost impossible to tell until you’ve mounted the encoder, but luckily swapping those two resistors is all that’s required to fix it. Vintage Radio index at Radiomuseum We have put up an index on www. radiomuseum.org to help enthusiasts locate models mentioned in Silicon Chip Vintage Radio columns in our ‘museum’. You can find a link to the latest version of the index (as a PDF) at the bottom of this page: siliconchip. com.au/link/ab5o Gary Cowans, Australian Administrator for Rmorg, Woodvale, WA. Lack of DAB+ reception in tunnels Unless my memory is mistaken or technology has changed over the years, the lack of digital radio reception in Sydney tunnels is due to the way the system is set up. If the setup was purely a high-gain antenna feeding a highpower amp connected to leaky coax, then every AM and FM service that can be received outside the tunnel should be received inside the tunnel. However, this is not the case. You will find that only the mainstream Sydney broadcasts can be received in the tunnels. For example, I have no trouble receiving 2GO/MMM Central Coast 107.7FM or The EDGE 96.1FM in Sydney in general, but not in our tunnels. Way back in my Telstra days, about 20 years ago, I attended to a data service fault at one of the tunnel control siliconchip.com.au centres. In one of the rooms, there were racks of AM and FM receivers and corresponding transmitters. All radio reception in our tunnels has to have the ability to be interrupted for tunnel announcements and emergency information. The only way to do this is to bring each radio service back to audio with a receiver, feed that audio into the info switch and then back into individual transmitters for that corresponding station. When 2UW was multicasting on both AM and FM before it officially stopped its AM transmission, it took about four weeks to get the FM reception in our tunnels. Hence the lack of digital reception in our tunnels. I retuned my digital radio, and currently there are nearly 70 services spread across the three digital frequencies of 9A, 9B and 9C. I can see several problems with retransmitting these services in tunnels. Firstly, every tunnel will require at least another 70 individual receivers to bring each station back to audio to feed via the info switch. This is complicated by the fact that the bitrates for stations can vary from 32kbps (eg, The EDGE) up to 128kbps or more (2CH, 2GB). These individual audio streams would then have to be fed back into the appropriate transmitter in the correct slot set up to the right bitrate. This could add to the 10-or-so seconds delay already heard in DAB+ broadcasts, compared to the same content on AM or FM. Then there is what I think is the biggest problem, the constant reshuffling and changing of digital stations. In the early years, 2DAY only had one service, now it has six. What problem will this cause the arrangement of digital in the tunnels? I can’t imagine a simple solution. Simon Kareh Penshurst, NSW. Calculating series & parallel resistor values On page 108 of the October 2020 issue, there is a link to a suggested website for calculating series and parallel resistors. That site works OK, but you might find this one more useful: siliconchip.com.au/link/ab5r It has conversions and calculators for 24 types of data, including series and parallel resistors and capacitors. I won’t list the other items, but I’m sure 6 Silicon Chip they will be useful to many people. It also includes a section to request an additional calculator if needed. Bob Denton, Hastings, Vic. Experimenting with PV hot water I have seen a few articles in Silicon Chip over the years about using solar panels to generate power for an electric hot water system. This interested me, but it never seemed feasible. However, second-hand solar panels are now cheaply available on Facebook and Gumtree. Also, technology has improved to reduce the cost of necessary devices further. So, I have made up a system that is working well. It only uses two 250W panels, as it is just a project to see if it stacks up. It is still a work in progress, as I am presently manually switching the inverter on in the morning, and off in the afternoon. I am using an ESP32 to monitor the solar power, and this is currently powered from a mains plugpack. In the near future, I will be adding a DC-DC converter to power the ESP32, and automating the stop/start for the inverter depending on the available light. I am using a 60V, 2kW “power frequency inverter board” sourced from AliExpress for $50. This board produces a sinewave from the DC supply voltage, giving around 36V AC from 60V DC. This is then fed to a large, heavy transformer to step up the voltage for driving the 3.6kW element in my hot water system. The efficiency of the inverter/transformer arrangement is 80%. I connected a Variac into this system to find the optimal voltage to drive the hot water element. Rotating it allowed me to find the maximum power point (MPP). Above the MPP, the power from the panels decreases exponentially. Unfortunately, the MPP is not static, and changes with clouds, time of day etc. To avoid going past the MPP, I selected a transformer with an output voltage slightly less than the peak with the panels in direct sunlight. This compensates somewhat for the many cloudy days in Cairns, but means I am not extracting maximum power from the panels during excellent sunny periods. So it’s a bit of a compromise, but it works reasonably well. The ESP32 sends solar data to a Raspberry Pi, which uploads data to Australia’s electronics magazine PVOutput at pvoutput.org/intraday. jsp?id=30164&sid=79430 Now that the concept has been shown to be feasible, I plan to set up a bigger installation with eight solar panels driving our primary hot water system (which has a 2.4kW element). When it rains for a month in Cairns, the backup option is to have a threepin plug on the hot water system, so I can manually change it over to mains power. I estimate the total cost outlay for the bigger system will be recouped within 1-2 years if I build it using secondhand panels. Sid Lonsdale, Cairns, Qld. Micromite Plus capacitor problem I came across a problem with the Micromite Plus recently. When I upgraded to MMBasic 5.05.03, one of my MM+ boards would not run the DAB+ digital radio software. It crashed many times every second, rebooting with a “bus error”. My other Micromite crashed differently; it would throw “font #16” or “font #8” errors, despite neither of them being used by the BASIC program. Versions 5.05.01 and 5.05.02 both worked fine on the same hardware and with the same BASIC code. I had seen this sort of thing on a previous (old) PIC32 design I had built years ago, and it turned out to be the 10µF capacitor on the PIC32’s Vcap pin. Increasing the Vcap capacitance fixed the problem both then, and again now. I piggy-backed a 47µF tantalum capacitor onto the 10µF X5R on the micromite board, and the problems went away. I guess that 5.05.03 is ‘exercising’ the internal 1.8V rail a little harder than previous MMBasic versions exercised it. It may be that either that the 10µF value specified in the data sheet is marginal, or the capacitors supplied in the Silicon Chip Micromite kits are marginal or not as low in ESR as they are claimed to be. Either way, the fix is easy. Stefan Keller-Tuberg, Fadden, ACT. Response: we purchase brand-name 10µF X5R capacitors (eg, Samsung or Taiyo Yuden) from reputable distributors. Their ESR ratings are much lower than the maximum of 1W specified by Microchip; they should be in the range of 0.01-0.1W. So we suspect 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 December 2020  7 DEAD OR DYING BATTERIES IN YOUR EBIKE? Advancements in automotive electronics SEGWAY? MOBILity BUGGY? GOLF CART? ESCOOTER? Premier Batteries can recell and/or custom manufacture Lithium Ion batteries for Segways, Ebikes, Electric Golf Carts, Scooters and Mobility Buggies – often with increased capacity and range etc. Quality cells are used and batteries are Fully Guaranteed PREMIER BATTERIES High quality batteries for all professional applications SUPPLIERS OF QUALITY BATTERIES FOR OVER 30 YEARS email: info.premierbatteries.com.au Web: www.premierbatteries.com.au 8 Silicon Chip that your first suggestion, of the 10µF specification being marginal, is the correct one. Of course, nominally 10µF capacitors can have values of around 8-9µF, or even lower at elevated voltages and temperatures. Still, we thought that the person writing the specification for the PIC32 would have taken that into account. Regardless, it looks like we will have to switch to supplying 15µF or 22µF ceramic capacitors in future kits to solve this. I thoroughly enjoyed the article on OBD2 (September 2020; siliconchip. com.au/Article/14576). When I first came to Australia, fuel injection, engine management and electronic ignition systems were still in their infancy. It seemed at that time that Bosch had a monopoly on the various electronic modules used. I have no idea how many Bosch 024 ignition modules I fitted or how many complete distributors I fitted to various vehicles (especially the early Ford Falcon with centrepoint injection). I used to exchange one of those distributors pretty much every day. We overhauled the old unit in-house with new bushes and sensors, except where the shaft itself had worn. I became a dab hand at reinserting those distributors back into the engine and slotting them into the oil pump feed, which was a hex-headed drive deep in the bowels of the motor. That vehicle had a rudimentary diagnostic system which would flash a light plugged into a socket under the bonnet. You could then trace out the fault with a wiring diagram. We also saw a lot of imported vehicles with various methods of diagnostics, usually by shorting a particular pin to GND and watching the CEL (check engine lamp) on the dashboard. Subaru had a few harness connectors below the steering shaft and above the driver’s knees, and connecting two would start the CEL flashing. Then came the Holden VL Commodore with the Nissan engine. Oh, what a car, very fast and powerful but with a few problems. For example, the optical pickup in the distributor (crank angle sensor) had a plate with holes punched through it to send the crank position and RPM to the ECU. Those sensors gave a lot of trouble, Australia’s electronics magazine as did the mass airflow meter also fitted to this Commodore. That optical disc could also be inserted into the distributor the wrong way around, resulting in a misfire on the number four cylinder. I also saw several of these vehicles with the optical slots filed wider, which I was told elicited a bit more power from the engine. The onboard diagnostic system was activated by turning a very small variable resistor through a small aperture on the side of the ECU, with the ignition on but the engine not running. Considering the ECU is behind the left-hand kick panel, this meant lying down on the floor in front of the passenger seat to turn that resistor. There are also two LEDs inside that aperture, one red and one green. The red showed tens when flashing, and the green showed the ones. Two red flashes and two green flashed meant the code was 22. Those same LEDs would show the sweep of the voltage coming from the oxygen sensor when the engine was running and the sensor up to temperature. That ECU also had inbuilt testing; on the initial DTC readout, several codes would be sent. It would send a code for the throttle position sensor, cleared by opening and closing the throttle. Then we would see a gear position sensor fault, cleared by moving the gear selector from park through each position and then back to park. Next would be a start inhibit fault, cleared by just quickly flicking the ignition switch into the start position. Usually, the last inbuilt test code was for the air conditioning and again, cycling the A/C switch on then off would clear that code. Next came the actual trouble code(s). The company I worked for at that time spent a large sum of money on a diagnostic package which connected to various engine points: the ignition coil negative, an inductive sensor on the cylinder number one plug lead, a second on the ignition coil to distributor lead, a pair of leads to the battery terminals and one to the battery connection on the alternator. With the DFI system (direct fire ignition or wasted spark ignition) in the next-generation Commodore, our diagnostic package was updated with new software and a new sensor lead package to help find problems on a car with no distributor and with multipoint injection. siliconchip.com.au I fixed a great many ECUs in my time; most had burnt out transistors and components that had been destroyed because someone had tried to jump-start the car with the jumper cables the wrong way around. I also saw many transmission sensors and solenoids fail, especially when people used standard transmission fluid (DEX III) instead of the automatic transmission correct fluid (TQ95). Standard fluid has an additive which strips the layer of varnish from the coils in the solenoids, causing all kinds of problems; TQ95 does not have that additive. When I left that employer to start work in a whole new town, I discovered problems with the ECU used in the Mitsubishi Magna. The electros used in that ECU would leak or burst, and that area of the PCB would heat up, eventually burning a hole all the way through the PCB! It was an easy diagnosis; you could smell the burnt ECU as soon as you opened the car door. I would repair the PCBs where I could, but a great many had large holes and severe damage. These required a new ECU to be fitted. I made sure that the suspect electros were replaced with high-quality components before doing so. After that, ECUs started becoming more complicated. They handled not only engine management and transmission control, but also air conditioning and climate control. Then security was added, keyless entry, cruise control, anti-skid braking and SRS (supplementary restraint systems), ie, airbags and seat belt tensioners. Then we had a body control module; the list goes on and on until we reach today’s vehicles, with multiple computers controlling an entire library of systems including drive-by-wire and intelligent braking, intelligent cruise control, lane centring, blind spot warnings and self-parking. I imagine that in the years to come, manufacturers will master all the issues with self-driving cars, flying cars and myriad other science-fiction inventions. Dave Sargent, Maryborough, Qld. Preparing for disaster Silicon Chip is a fine magazine. I know what it’s like to edit a technical journal, having managed two so far. I have also been a technical writer in siliconchip.com.au charge of producing responses to requests for tender where risk management was a major factor. I have fitted Solar PV panels on my roof to learn about using El Sol for electric power. Your approach on backup power (January 2020; siliconchip.com. au/Article/12215) left me wondering if there were a better way to achieve your end. So, I went back to some of my writings on risk management, in particular, based on AS/NZS 4360. Here is a generalised risk management approach that can be applied to all manner of potential problems we face. 1. List every possible event that could lead to damage or loss. 2. Assess the consequence of each such event. 3. Estimate the probability of occurrence of each precipitating event. 4. Multiply the consequence by the probability for each precipitating event. List these in decreasing order. 5. Assess the cost of dealing with each event, whether attenuating or eliminating each precipitating event, or providing a work-around for the inevitable. 6. Put these mitigation costs against the products list from step 4. 7. Discuss the results of your analysis with others likely to be affected. 8. Make plans for agreed mitigations. If that seems very complicated, consider the following: 1. You might want to focus on just a few nasties such as loss of electricity, loss of gas pressure, water management problems (loss of potable water, sewerage or flood), transport disruption, damage to roads, land management issues (eg, erosion, landslide, tremors or earthquakes). 2. Calculate the consequences in monetary terms. Look to insurance firm valuations if unsure. 3. Energy providers can tell you the likelihood and duration of outages based on historical records. The Bureau of Meteorology can provide estimates of temperatures, rain, wind and wave movements. State governments can probably tell you the likelihood and duration of water management failures; they can also tell you the likelihood of unplanned events, such as road, rail and bridge disruptions. Local councils can advise on land management issues, such as anticipated subsidence, road resurfacing. Australia’s electronics magazine December 2020  9 even though we were sitting by the phone. We’ve since pur4. Wilfredo Pareto observed that 80% of the costs of dochased an office mobile phone, so we can redirect calls ing things were accounted for by around 20% of the inwhen necessary. puts. This has become known as the 80/20 rule. Your list We spent hours with NBN tech support to no avail. So of consequence-probability products will probably show we decided to try rebooting the Telstra-supplied NBN routthis effect; ie, the first few items in your list will account er, which was working fine for internet access at the time. for the majority of your potential woes. That fixed it. 5. For each of the items high on your list, identify several solutions to deal with each event. These might preComments on backup power and DCC vent the untoward event or provide a work-around because Thank you for both the January 2020 and the February the event is inevitable but unpredictable (eg, running the 2020 editions of Silicon Chip. As usual, they were worth fridge on a UPS in case of a possible power outage). Or you reading. might decide to take out insurance against it, or consider The January 2020 Editorial Viewpoint and the accompaputting up with the nuisance (eg, wear warmer clothes if nying article on emergency backup power raised the quesyour heater fails mid-winter). tion: is it economical to maintain emergency backup pow6. By listing the costs of your ‘solutions’ against the er? To decide, there are two basic questions. How much consequence-probability products, and running a cumupower is required, and for how long? lative total on the solutions, you get an idea of the size of For a refrigerator, the cheapest and most reliable method your problem(s). for short term backup is to maintain “freezer bricks” in their 7. Present the results of your analysis to your family. RAYMING TECHNOLOGY frozen state and for the long term, maintain a working petSome solutions may require the co-operation of neighbours engined generator. Batteries are simply not economical or local authorities. PCB Manufacturing and PCB rol Assembly Services for the occasional short term power failure. 8. How will you pay for your solutions? For instance, Fuyong Bao'an Shenzhen China For our ‘must-have’ electronic devices, a generator is some insurance firms offer incentives to prevent problems, 0086-0755-27348087 overkill except for extended power outages, and batteries such as by offering reduced premiums on home and conSales<at>raypcb.com become more viable. Regardless, our governments and the tents insurance if you install a burglar alarm, or a UPS for power suppliers will do their best to maintain power and your freezer. www.raypcb.com to restore it when it is lost. Brian Clarke, BE, MBA, PhD, CPEng, Fellow Eng I have been trying to develop a DCC interface, which Aust, IPEC Eng (Aust), Loftus, NSW. has taken most of my energy of late. The DCC standard is such a mad dog’s breakfast, and I had written quite a large NBN reliability not as good as POTS comment/complaint about it, but decided not to send it to I have been on NBN for 2½ years and still have problems you. It was more appropriate for a model railway magazine. from time to time. When first connected, I lost my landline I was hoping to get some tips for my system from the DCC number and had to have this number redirected to my mostation article in the January 2020 edition (siliconchip.com. bile until it was fixed. Even now, I lose my landline conau/Article/12220), but I was disappointed. However, the nection and have to switch off my modem for five minutes. project did introduce me to the BTN8962TA half-bridges When the Telephone Directory came out early last year, and they are impressive. If I didn’t have a large quantity after 25 years I was no longer listed because I had changed of N and P channel FETs, I would use them. to the NBN and had to apply to be relisted. If I had the I’ve found that I could not create a DCC station using chance to go back to the old reliable system, I would do a PIC microcontroller alone. I was forced to implement it in a flash. I think the NBN should be renamed to No a double-buffered counter using a few discrete logic ICs Bloody Network. to create the DCC waveform and use the PIC to control Richard Cannan, it. The reason was jitter in the polarity reversals of the Warilla, NSW. DCC waveform. The small PICs that I wanted to use have Comment: we had a day-long dropout of the phone sera double-buffered PWM duty register but not a doublevice at our office a few months after switching to the NBN. buffered period register. It was frustrating because customers could not reach us 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 10 Silicon Chip Australia’s electronics magazine siliconchip.com.au Considering that the DCC standard allows for a large period variation of the “0” pulse but only a few microseconds for the “1” pulse, it was impossible to ensure that the necessary precision would be met using an interrupt service routine without a double-buffered period register. I then wondered about the Arduino that was used in your project. What did the programmers of DCC++ do? I checked the specifications of the ATmega328P, and found that the Timer1 module has a double-buffered period register. But there was no mention in the October 2018 project of the quality of the DCC waveform. I can only assume it was acceptable. The project did raise one big concern with me which I believe is also partly to blame for the susceptibility of IoT devices to hacking. That problem was the subject of the February 2020 Editorial Viewpoint. Unless a person is very familiar with a language and particularly with tricks and short-cuts, it is very easy to miss flaws in the routines. When using a library, how many programmers check the validity of its routines before using them? I doubt that there are very many, and I am sure that inexperienced programmers will use anything that is stated to do a task without question. George Ramsay, Holland Park, Qld. Comments: I believe I covered the reasons for choosing a battery backup system quite thoroughly in the article. Granted, I had a somewhat unusual reason for preferring batteries. If you have the space to operate a generator, don’t need automatic fail-over and are willing to do the maintenance to keep the fuel fresh, it is indeed the cheapest option for a given amount of power over a long period. But keep in mind that you can get much cheaper batteries than the one I bought. For example, Rockby is currently selling a 12V 110Ah AGM deep cycle battery for $291.50 (Cat 38698, pickup only). Add a 2kW modified sinewave inverter from Jaycar (Cat MI5024, $299) and a charger you probably already have, and you can keep a typical fridge/ freezer running for around 24 hours for less than $600. Granted, Jaycar’s Cat MG4508 2kW inverter generator will keep the same fridge/freezer and other appliances running for a lot longer for just $100 more. But I think both solutions deserve consideration. Regarding DCC, if you have precise waveform generation requirements, it pays to check the microcontroller data sheets carefully to choose the best one. Micros designed for motor control generally have much more sophisticated and precise PWM generators, and keep in mind that serial interfaces are often a good way to generate an accurately timed pulse train. Another factor to consider is that some of the better micros (eg, PIC32s) allow you to set interrupt priority levels. So you could have a timer interrupt generating a pulse train set to maximum priority. Communications interrupt handler like those for USB or serial can then be set up with a lower priority so that they won’t interrupt the critical timer ISRs. You are right that blindly using libraries can cause problems. We had many problems with some popular software I2C libraries, and when we had a look at what they were doing, it was pretty clear that the authors either hadn’t read the I2C standard or didn’t understand it! For good security, you either can’t rely on third-party communications libraries, or you need to audit them. 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The 3 wire cable has a silicone sheath and is 1 metre long. Temperature range is -50 to 200 ºC. Class B.. SKU: CMS-005 Price: $66.00 ea + GST 4 Channel Opto-Isolator 4 independent channels with switch-selectable NPN or PNP input and NPN or PNP output. Can be used as a NPN - PNP converter or as an isolator to eliminate noise and ground loops. DIN-rail mount. SKU: KTD-258 Price: $99.95 ea + GST PR200 programmable relay 24VDC A universal and easy-to-use controller designed in a plastic enclosure for DIN rail mounting as an alternative to PLC. Comes with 8DI + 8DO + 4AI + 4AO LED and 2x RS485 Modbus ports. SKU: AKC-001 Price: $399.95 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 December 2020  11