Fullscreen HTML5Med Res (??MB)HTML4

on many projects, so we can’t start on anything new, but we might consider updating these older projects at some point. We published a Universal Safety Timer for Appliances (August 1990; siliconchip.au/Article/6923), although admittedly, that design could do with an update. For example, it uses a Triac as the switching device, so it would not handle capacitive loads very well. It also draws a little standby power. We have also published numerous soldering iron timer designs in Circuit Notebook, including one in July 2020 (siliconchip.au/Article/14510) along with March 2016, January 2007 and October 1992. Regarding the Soft Starter for Power Tools with a switched slave output, we published two master/slave mains power projects which could have soft starting incorporated. They are the PowerUp Master/Slave Power Switch (July 2003; siliconchip.au/ Advertising Index Altronics.................................27-30 Dave Thompson........................ 111 Digi-Key Electronics...................... 3 Emona Instruments.................. IBC Jaycar.......................IFC, 10-11, 39, ...............................53, 60-61, 74-75 Keith Rippon Kit Assembly....... 111 LD Electronics........................... 111 LEDsales................................... 111 Microchip Technology.................. 5 Mouser Electronics..................OBC Article/3905) and the Circuit Notebook entry titled “Anto-sensing master/ slave power control“ (October 2010; siliconchip.au/Article/321). Given the age of these designs, it is probably worthwhile for us to revisit these ideas when we get a chance. Wanted: comprehensive portable audio test set I have recently been helping my son install subwoofers in his friends’ cars, along with a couple of head units. They pick up an amplifier, speakers and subwoofer pretty cheaply second-hand from online marketplaces. We’ve found that sometimes it doesn’t work, so you need some way of testing each segment, which has proven cumbersome. Has there been a project or two that would make a set of test tools to work through the pieces? Should we make one? For instance, the following things need to be checked: Head-unit: are the speaker outputs working? Are the line-level outputs working? Is the line-level output LF only, or full-frequency? What voltage level/volume is being produced? Amplifier: what is the power supply voltage? Does it fluctuate under load? Does the ignition key switch the power, or is it a direct battery feed? What is the output level and what is the signal frequency range? It would be helpful to be able to feed in a line-level signal and provide a frequency sweep. Control wire: did we find the right one? When does it switch? Speakers: an impedance tester would be helpful, along with a way to determine the phasing of dual-coil drivers (they are relatively rare). Ocean Controls............................. 9 SC USB Cable Tester................ 107 Silicon Chip PDFs on USB....... 109 Silicon Chip Shop.................88-89 Silicon Chip Subscriptions........ 47 Silicon Chip Test Tweezers..... 106 Silicon Chip 500W Amplifier..... 12 Silvertone...................................... 6 The Loudspeaker Kit.com............ 7 Tronixlabs.................................. 111 Wagner Electronics..................... 13 112 Silicon Chip Errata and Next Issue SC GPS Analog Clock................... 8 Cables: check for resistance and continuity. Some of these tests do fit under the basic multimeter regime. Some might be as simple as an audio cable from a smartphone with the correct impedance/level. (L. C., Donvale, Vic) ● There is no easy way to make up a universal test set for what you want. However, you can use separate items such as a multimeter, oscillator and load resistances. A multimeter can be sufficient for most of the tests required, especially if it is suitable for measuring AC voltages up to 1kHz or more. A signal generator would be helpful to provide a source for the amplifiers under test. We’ve published a few useful portable oscillators: • Shirt-pocket, Crystal-locked Audio DDS Oscillator (September 2020; siliconchip.au/Article/14563) • Roadies’ Test Oscillator (June 2020; siliconchip.au/Article/14466) • Digital Audio Signal Generator (March-May 2010; siliconchip.au/ Series/1) Both the Shirt-pocket Oscillator and Digital Audio Signal Generator would be helpful for testing subwoofers as they have adjustable frequencies. Alternatively, a low-cost commercial audio oscillator could be used. A load for the amplifier can be made using a heatsink and power resistors. element14 and RS Components both sell high-power resistors. You can connect them in series or parallel to achieve the required resistance and power rating(s). element14 also sells 100W-rated 4Ω & 8Ω chassis-­ mount resistors (Cat Nos 2925455 and 2925462). SC WiFi DC Electronic Load, September & October 2022: (1) REG1 is shown reversed on the main Load PCB silkscreening and in Fig.10. Fit it the other way around, as shown in the photo on page 91 of the October 2022 issue. (2) a design error on the main Load PCB means that the SDA line (pin 5 on the CONTROL header, CON1) is likely to be shorted to GND due to a GND via placed too close to that track. The via is just above and to the left of IC5 (labelled “DAC” on the PCB). Run a sharp knife between the GND fill and the SDA track to clear the short, or drill out the top side of that via with a small (eg, 2mm) drill bit. (3) the sole 240W resistor on the main Load board should be 470W, to match the source impedance of pin 1 of IC3 (1kW || 1kW). If built with the 240W resistor, the resulting error will be minimal and likely cancelled out during calibration. (4) IC3 & IC4 were incorrectly listed as the INA180B4 type (gain = 200) in the parts list. They must be the B1 type (gain = 20) for correct operation. Next Issue: the January 2022 issue is due on sale in newsagents by Thursday, December 29th. Expect postal delivery of subscription copies in Australia between December 28th and January 13th. Australia's electronics magazine siliconchip.com.au