Bob Parker's Electronic Stuff
No bleating sheep here: Twittey & Farcebook-free zone :-)
Here they are in chronological order... The dates correspond to the edition of Electronics Australia magazine each project appeared in. Click on the photo for more information. I hope you find them interesting!
SCA Subcarrier Demodulator for FM Radio (Sep '93)
'SCA' stands for 'Subsidiary Communications Authorization', and is a technique which allows FM broadcast stations to add up to two 'invisible' medium-quality audio channels to their normal stereo transmission. It's widely used in the USA and Australia for distributing background music and broadcasting for ethnic / disabled / special interest listeners. Normally the only way to listen to these additional channels is with a special purpose receiver, but this little board will allow most standard FM radios and tuners to produce an SCA audio output.
Voice Message Recorder / Player (Feb '95)
This microcontroller-driven gadget allows you to record up to eight short voice messages in a chip which will retain them for up to 100 years(!) even with no power applied. Then each message can be individually played back under the control of its very flexible trigger input. Its main uses are for replacing beepers and sirens etc, where more information about the cause of an audio alarm needs to be known. It can optionally generate a pre-message chime, and includes a relay for activating a transmitter or PA system etc.
LED Voltage Indicator (Sep '95)
This teensy little board is only 1 inch (25mm) square, and is handy as a combined power on and low battery voltage indicator. The two colour LED changes from green to red when the battery voltage drops below the adjustable trigger voltage. It's usable between about 6V and 30VDC, and uses a precision LM336Z-2.5 voltage reference. The LED can be reversed so it changes from green to red if the preset voltage is exceeded, if required.
ESR & Low Ohms Meter (Jan '96)
I originally designed this instrument for my own use, to help identify partly-open-circuit electrolytic capacitors in-circuit, which cause so many faults in switching power supplies, camcorders, TVs, monitors, etc. If you already have one, take a look at the ESR meter hints page, and if you're having problems with a meter you just built, check out the ESR meter problems page.
Line Output / Flyback transformer tester (Aug '98)
This is a 'ringer'-type tester I originally designed for in-circuit testing of Line Output (Flyback) transformers in TVs and computer monitors. After a couple of technician-years of evaluation in actual servicing situations, it's also proved to be helpful in locating shorted diodes, capacitors and deflection yokes in horizontal deflection stages. LOPT/FBT condition is shown on an 8 LED 'bargraph' display.
Selective Calling Decoders
This isn't an Electronics Australia/Dick Smith project, but if you're interested in decoding and logging the selective calling (Selcall) and Automatic Number Indication (ANI) signals used in mobile radio communications networks, take a look at the Anzac Comms selcall decoder page. I did the (Zilog) microcontroller software and the PCB layouts for them!
Australia's Silicon Chip magazine
is written by electronics enthusiasts for electronics enthusiasts. Take a look at all the ex- Electronics Australia magazine faces on the WHO'S WHO AT SILICON CHIP page! :-)
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