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Advertising Index Altronics.................................27-30 Control Devices............................. 9 Dave Thompson........................ 111 Digi-Key Electronics...................... 3 element14..................................... 7 Emona Instruments.................. IBC Hare & Forbes............................. 13 Jaycar.........................IFC,11,39-40, ..................................... 50-51,59-61 Keith Rippon Kit Assembly....... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology.................. 5 Mouser Electronics..................OBC Ocean Controls........................... 10 SC Pico BackPack.................... 105 SC SMD Test Tweezers............ 110 SC USB Cable Tester.................. 79 Silicon Chip Binders................ 111 Silicon Chip Shop............ 106-107 Silicon Chip Subscriptions........ 93 The Loudspeaker Kit.com.......... 91 Tronixlabs.................................. 111 Errata and Next Issue Wagner Electronics..................... 12 112 Where to get inductors for Battery Zapper I want to build the Lead-Acid Battery Zapper & Desulphator Mk.3 (July 2009; siliconchip.au/Article/1500), but both kits have been discontinued, and the specified 220μH and 1mH aircored inductors are no longer available from Jaycar. Do you know where I can get them? ● You have a few options. Air-cored inductors are often used for crossovers, and ‘crossover inductors’ are available from other sources. The Jaycar inductors used 20AWG wire (0.8mm diameter). We found an Australian website called Speakerbug with 220μH and 1mH air-cored inductors at reasonable prices, wound with either 18AWG or 21AWG wire. 18AWG would be preferable, but either should work; see: siliconchip. au/link/abex Another option would be to wind your own. There are online calculators that tell you how many turns of what diameter wire on what sized former are needed to make a specific inductance value. If you have an LC meter, you can also keep winding until you reach the desired inductance value. You might even find that reels of enamelled copper wire have close to the correct inductance by just using the whole reel or unwinding a part of it. We used that approach in the Easyto-build Bookshelf Speaker System (January-March 2020; siliconchip.au/ Series/341), which used reels of ECW as 390μH and 900μH inductors. 900μH is probably close enough to 1mH for the Battery Zapper, and for the 220μH inductor, you could use the same reels of ECW that measured 390μH for the Bookshelf Speakers but MOS Air Quality Sensors, June 2022: in the Useful Links box, the secondlast link should be https://fs.keyestudio.com/KS0457 Railway Semaphore Signal, April 2022: be aware that some vendors are selling DF9GMS-360 360° servos under the same model code as the DF9GMS 180° servos specified for this project. The 360° servo motors will not work. You need to use a 180° servo. High Power DC Motor Speed Control, January & February 2017: the IPP023N10N5AKSA1 Mosfets specified are currently unobtainable. Constructors can substitute the FDP2D3N10C, which is available at the time of writing. Next Issue: the August 2022 issue is due on sale in newsagents by Thursday, July 28th. Expect postal delivery of subscription copies in Australia between July 27th and August 12th. Silicon Chip Australia's electronics magazine unwind some turns (probably about 1/3 of them) to get a value closer to 220μH. MC34063 regulator chips failing I have just built the Pocket TENS Unit (January 2006; siliconchip.au/ Article/2532), and I have had problems with the repeated failure of the MC34063 chip. When setting the inverter output voltage, the IC fails. I can get the output close to 60V before that happens. I got the MC34063s from eBay. As for the toroidal transformer, I could not find the original Neosid core, so I used another of unknown origin but with the same physical dimensions. Do you have any ideas? (M. A., Wurtulla, Qld) ● The MC34063 is generally very reliable, but it is a ubiquitous chip, and we suspect there are plenty of clones on the market, some of which might be dodgy. We suggest trying an MC34063 from Jaycar (Cat ZK8837) or Altronics (Cat Z2750). For the ferrite core, use Jaycar Cat LO1234. Those combinations seem to be reliable. High voltage track clearances I designed a new PCB for the Multi Spark CDI System (September 1997; siliconchip.au/Article/4837) with a full ground plane and am having some problems. Would a ground plane cause any problems? I set the track clearance at 0.305mm. Do you think that’s enough? (J. M., New Haven, USA) ● For tracks with up to 300V between them, more clearance would be preferable. Arc-over would be likely at 0.305mm, especially without a solder mask layer. The IPC-2221 standards require 1.25mm or more (see www.smps.us/pcbtracespacing.html). Clearance may not be your only problem, though, and maybe photos of the PCB could help us see where problems might lie. Note that we published a CDI design much more recently (December 2014 & January 2015; siliconchip. au/Series/279), and we can supply both the PCB and hard-to-get parts for that project. These are available from our website at: siliconchip.au/Shop/? article=8120 SC siliconchip.com.au