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This stereo FM wireless microphone also makes a great quality audio link. We tested it to beyond 50 meters and it was rock solid. It’s certainly not the first wireless microphone we’ve ever published but this one is a little different. It’s stereo, providing surprisingly good quality sound. Second, it has a really good range. We tested it at well over 50m and it was still performing very well – noise-free, in fact – but at the time we couldn’t get our receiver any further away. So it’s likely to have even better range than that.... [read more]

Sure, listening to VHF FM has great advantages over MW/LW AM from the old days — now we have bright stereo free from interference, fading and noise! However, your FM radio will no longer predict the arrival of a thunderstorm as did the AM radio many years ago-reliably and hours before the trouble was upon you! The crux is that AM detection will faithfully reproduce the effects of lightning and other massive static discharges approaching in a very simple way: they’re audible as slight crackling noises in the loudspeaker, almost irrespective of the tuning of the radio! Assuming no AM radio is available anymore, a dedicated VLF receiver tuned to about 300 kHz can faithfully detect the crackle of approaching lightning.... [read more]

This frequency doubler using a single 4069 hex inverter IC, a frequency doubler can be constructed to give an output pulse train whose frequency is twice that of a squarewave input signal.... [read more]

Power supplies that are intended to be used with TTL logic circuitry must guard against over-voltage, which can destroy TTL chips very rapidly. The duration of over-voltage that can destroy TTL chips is much too brief to trigger any conventional fuse, so that only other semiconductor circuits can play any useful part in protecting a circuit against the type of failure of a stabilizer that leads to excessive voltage. As it happens, this is the most common type of stabilizer failure, so that the protection is necessary for any TTL circuit of any significance. Many modern digital circuits make extensive use of MOS devices, which are less susceptible to damage from over-voltage, but it is unusual to find a large digital circuit, which does not contain at least one or more TTL devices.... [read more]

This little circuit can be used to dim lights up to about 350 watts. It uses a simple, standard TRIAC circuit that, in my expirience, generates very little heat. Please note that this circuit cannot be used with fluorescent lights.... [read more]

IR Receiver Toggle Switch... [read more]