Fullscreen HTML5Med Res (??MB)HTML4

If you decide to go ahead with the ETI 309, the BC177 and BC178 transistors could be replaced with BC327 types. The 2N3642 could be replaced with a BC337, and the C20D SCR could be replaced with the C122E (Jaycar ZX7012), although new-old-stock items are still available (siliconchip. com.au/link/ab7x). The bridge rectifier can be the MB354 30A 400V type. For D3 and D4, use 1N4004s. The enclosure needed is similar to the Jaycar HB5046 but is only 55mm tall instead of 100mm. The transformer might need to be specially wound. Is my Barking Dog Blaster working? Some years ago, you helped me build the Ultrasonic Cleaner, and it still works perfectly. In January of this year, I bought the September 2012 issue of your magazine for the Barking Dog Blaster project (siliconchip.com. au/Series/28). I built it, but I have a problem. It works, but it seems like it is too weak. You said it would consume about 1.4A with four piezo tweeters, but I measured a maximum of 250mA. I also have a question about the voltage on the drain terminal of the Mosfet. During operation, I measured only about 2V. On the secondary side of the transformer, I measured around 0.5V, but according to the article, it should be around 40V peak. Do you have any idea what the problem is? How can I increase the power? (Simon, Slovenia) • The current drain at 350mA per tweeter adds up to 1.4A; however, be aware that this is peak current and not the current that would be measured us- ing a multimeter. A meter would average out the peak current, so a measurement of 250mA is correct. The exact multimeter reading is dependent on the particular multimeter model and its frequency response. Similarly, a drain voltage of 40V peak will not measure as 40V using a multimeter; it would average it out to a much smaller value. The frequency response of the multimeter would be severely limited at ultrasonic frequencies. An oscilloscope is needed to measure the voltage accurately. We do show how to test the output by using the audible frequency test. This is described under the Testing cross-heading section. Note that the volume level is reduced for this test, as it would otherwise be very loud. So your unit is probably working correctly; the voltages and current you are measuring are likely due to the way the meter measures them, taking into account the difference between peak and averaged values as measured with a multimeter. Where to get a Barking Dog Blaster kit? Do you know where I can buy the Barking Dog Blaster kit? I know Altronics do not have it any more. (J. H., Queenstown, New Zealand) • You are right that the Altronics Cat K4500 kit has been discontinued. That was the only kit for this project. As usual, you can still get the programmed PIC microcontroller and the printed circuit board (PCB) from our online shop; see siliconchip.com.au/ Shop/?article=529 The remaining parts are available from Altronics or Jaycar. SC Advertising Index Altronics...............................75-82 Ampec Technologies................. 11 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 element14................................... 7 Emona Instruments................. IBC GME Australia............................. 6 Hare & Forbes........................... 23 Jaycar............................ IFC,53-60 Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEDsales................................. 111 Microchip Technology.................. 5 Mouser Electronics...................... 9 Ocean Controls........................... 8 PMD Way................................ 111 Silicon Chip Binders................. 19 Silicon Chip RTV&H DVD........ 33 Silicon Chip Shop.................... 37 Silicon Chip Wallchart.............. 63 Switchmode Power Supplies..... 85 The Loudspeaker Kit.com......... 10 Tronixlabs................................ 111 Vintage Radio Repairs............ 111 Wagner Electronics................... 99 Weller Soldering Iron............. OBC Notes & Errata ESR Meter with LCD readout, Circuit Notebook, May 2016: there are some errors in this circuit diagram. Two capacitors were left out: one 470μF electrolytic and one 100nF ceramic or MKT type. They should connect between pins 3 & 5 of IC3, with the electrolytic capacitor’s negative terminal to pin 5 (the -5V rail) and positive terminal to pin 3 (GND). Also, the two 10MW resistors’ connections to pins 2 & 3 of IC4a are swapped. The resistor from the output should go to pin 2 (the inverting input), while the resistor from the wiper of VR2 goes to pin 3 (the non-inverting input). Barking Dog Blaster, September 2012: The initial timer duration differs to that set by the trimpot due to a software bug. Subsequent timer runs after the first are correct. The revised firmware, supplied by reader AJB, is named 2510812B and is available for download from our website. The June 2021 issue is due on sale in newsagents by Thursday, May 27th. Expect postal delivery of subscription copies in Australia between May 25th and June 11th. 112 Silicon Chip Australia’s electronics magazine siliconchip.com.au