Fullscreen HTML5Med Res (??MB)HTML4

That signal could then be applied to the motor drive circuit. The motor drive circuit would need to convert the speedometer sensor signal to a voltage drive for the motor driving the mechanical speedometer. The required circuitry would depend on the components used. A simple voltage-controlled PWM driver might not be effective, as it will only provide open-loop control. Some form of motor speed feedback is required to ensure the motor rotates at the correct speed despite the varying battery voltage and temperature. You might be able to convert the speed sensor signal to a voltage using a simple RC filter that is then used to control a PWM motor controller such as our DC Motor Speed Controller Mk.2 (June 2011; siliconchip.com.au/ Article/1035). Alternatively, a vehicle instrument specialist can supply many of the parts you need. See www.attspeedautoinstruments. com 2-layer PCBs supplied for older designs I am currently building the Electrolytic Capacitor Reformer (August & September 2010; siliconchip.com. au/Series/10). I have received the PCB from you and am very impressed with the quality. The instructions say to solder in 11 wire links. However, the supplied board is double-sided with plated through-holes, and I assume it has printed wire links on the component side. Can I skip fitting the wire links? (K. C., Strathfield, NSW) • When we supply boards that were single-sided designs these days, we tend to place the links in the top layer as it costs very little to do so. That includes the board you have. You can check one or two of the links using a continuity meter, pressing the probes into the vias/throughholes at either end of where the link is supposed to be. That will verify the presence of those top-layer tracks. Rarely would we get boards made based on old designs without adding links to the top layer. Higher supply voltage for SC480 amp Can I use a 60V centre-tapped transformer to power SC480 Audio Amplifier modules (January & February 2003; siliconchip.com.au/Series/109) instead of a 56V centre-tapped transformer? (J. A., via email) • No SOA curves were published for the SC480, so it’s hard to evaluate the effect of changing the supply voltages. Given that you’re only talking about a couple of extra volts per rail, if you plan to drive 8W or 6W speakers, it should be OK. Still, we suggest changing the BC557s to BC556s for a bit of extra safety margin. It would help to know the VA rating of the transformer, and it would also be helpful to measure the actual voltage, as it can vary quite a bit from the nominal voltage. The DC supply rails are given as ±40V, so if you build the supply and get unloaded readings of around ±42V or ±43V, that would not be particularly worrisome. ±45V or higher might cause problems, though. SC Advertising Index Altronics...............................87-90 Ampec Technologies................... 9 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona Instruments................. IBC Hare & Forbes....................... OBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.................. 5 Ocean Controls........................... 8 PMD Way................................ 111 Premier Batteries...................... 37 SC Vintage Radio Collection..... 63 Silicon Chip Shop.................... 97 Switchmode Power Supplies....... 7 The Loudspeaker Kit.com......... 93 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 10 Notes & Errata Programmable Hybrid Lab Supply with WiFi, May 2021: in the parts list on page 36, the item at the top of the right-hand column should have read VXO7805-500 (5V) rather than VXO7803-500 (3V). The circuit should still work even with the 3V part fitted. Also, the MCP4725 DAC specified comes in several versions; MCP4725A0T-E/CH is the required part. Arduino-based Power Supply, February 2021: the 51kW resistor’s five-band colour code is incorrect. It should read “green brown black red brown”. DIY Reflow Oven Controller, April & May 2020: in the May 2020 issue on page 90, Fig.11 shows the 20-wire ribbon cable between the control board and LCD screen connected incorrectly. It is shown correctly in the photo at the top of p89, with the red stripe going to pin 1 on both boards. Deluxe Touchscreen eFuse, July 2017: The HEX file we have been providing has not had the AUTORUN flag set, meaning eFuses built with a preprogrammed chip or using the HEX file from the Silicon Chip website will not work without being run manually from MMBasic. We’ve updated the HEX and MMBasic files to fix this and also to fix a bug that may cause the Micromite to crash and reset if the screen timeout was set to certain values. The July 2021 issue is due on sale in newsagents by Monday, June 28th. Expect postal delivery of subscription copies in Australia between June 25th and July 9th. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au