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Also, gate driver IC3 could have been damaged when the IGBT failed by applying a high voltage to the drive pin via the gate. The series-connected thermistor could also have become faulty, so check or replace that. Suitable white LED for tachometer I have several machine tools, some with variable speed drives (up to 12,000rpm) for which a reasonably accurate tachometer would be very useful. I have a couple of cheap Hall effect tachos but find them rather limited. After looking through many designs, I selected your August 2008 design as a suitable basis for a built-in tachometer (siliconchip.com.au/ Series/52). I have all the parts required for construction except the PCB. I produced very mediocre results with toner transfer and failed completely with the paint ablation method using a 7W laser. I am now waiting for the delivery of photo-sensitive film, with which I hope to get satisfactory boards. I have been experimenting with cupric chloride etchant and have been very pleased with the results. I made the initial cupric chloride by direct solution of copper metal into hydrochloric acid with air bubbling (as widely referenced on the web) before realising that I could have started with readily available copper sulphate/hydrochloric acid and saved some work. I think a strobe could be useful, so I added it to the project. However, I find that the types specified (eg, Cree XR-C white) appear to be no longer available. Jaycar does list them but as a discontinued line. An internet search found many high-intensity LEDs, but I struggled to find any that seemed equivalent or suitable. Can you offer any suggestions? (D. F., Bentleigh, Vic) • We suggest that you use the 1W LED available from LEDsales (www. ledsales.com.au), which is listed as a replacement for the star or Cree LED specified: siliconchip.com.au/link/ ab9a SMS Controller is out of date I bought a kit to build the SMS controller project, described in two parts in your magazine in 2004 (October & November; siliconchip.com.au/ Series/100), but I never got it working. I want to have another crack at it and was wondering if it is still possible to purchase a copy of the articles. (D. W., Currumbin Valley, Qld) • You can purchase back issues through our website. Those two particular issues are available at the following links: siliconchip.com.au/ Shop/2/423 & siliconchip.com.au/ Shop/2/425 For those back-issues that are unavailable (eg, due to being sold out), you also have the option to purchase the digital version or an article scan. Having said that, we don’t think you would be able to get the SMS Controller working now since all GSM networks in Australia have been shut down. You would need to build something like our 4G Remote Monitoring Station instead (February 2020; siliconchip. com.au/Article/12335). SC Advertising Index AEE ElectroneX........................ 25 Altronics...............................87-90 Ampec Technologies................... 9 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 element14................................... 7 Emona Instruments................. IBC Hare & Forbes....................... OBC Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.................. 5 Mouser Electronics.................... 11 Ocean Controls......................... 94 PMD Way................................ 111 Silicon Chip Shop...........104-105 Switchmode Power Supplies....... 8 The Loudspeaker Kit.com......... 95 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 10 Notes & Errata Advanced GPS Computer, June 2021: in the parts list on p29, the catalog code given for the laser-cut lid was SC5083, but that is the original ‘inset’ lid to suit the 3.5in touchscreen. As mentioned in the article, a different lid is needed to give enough clearance inside the box. The correct catalog code is SC5856. Mini Arcade Pong, June 2021: if you can’t get the 7450 or 74LS50, you can use the 74LS51, which is more readily available. To use the 74LS51, pins 11 and 12 need to be tied high (they must be left open if using the 7450). You can do this by bridging them together and then running a short wire link to pin 14. Refined Full-Wave Motor Speed Controller, April 2021: we have created an alternative version of the PIC firmware, 1010221B. HEX. This works identically to the original (A) version, except that it won’t start the motor if the speed pot is not at zero when power is applied. You need to rotate the speed pot to zero and then back up to start the motor. This safety feature could be useful in some situations. USB Flexitimer, June 2018: in the circuit diagram (Fig.1) on page 26, LED2 and LED3 are swapped. LED2 (ON) connects to pin 5 of IC1 via a 3.3kW resistor, while LED3 (OFF) connects to pin 2 via another 3.3kW resistor. The August 2021 issue is due on sale in newsagents by Monday, July 26th. Expect postal delivery of subscription copies in Australia between July 23rd and August 10th. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au