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The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency. For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage. The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the (0.1 ohm) equalizing resistors (1volt at 10 amps), so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage.... [read more]

Imagine that is morning , you barely anticipate the bus for work and you can't find your keys. If you suffer from this situation frequently, this circuit is ideal for you. A fizzle is the only thing you have to do. The overall circuit is small enough to attach it to your keys.... [read more]

This circuit generates an astonishingly real imitation of the chirping of the cricket. A suitable audio wave form is generated by IC2 and related components, driving the loudspeaker through Q1. To allow a more real-life behavior, the chirp is interrupted in a pseudo-casual way by two timers built around IC1C and IC1D, whose outputs are mixed into IC1B and further time-delayed by IC1A, driving the reset pin of IC2.... [read more]

The circuit described here is that of a metal detector. The opera- tion of the circuit is based on superheterodyning principle which is commonly used in superhet receivers. The circuit utilises two RF oscillators.... [read more]

This is a selection of small self-contained alarm circuits. They have a very low standby current; and are suitable for battery operation. Some are triggered by normally-open and normally-closed switches. Some react to changes in light or temperature. The result is a variety of output times and patterns.... [read more]

Don't like your little brother's TV channel selection? Hate the volume your wife sets the stereo at? Want to just annoy someone? This circuit does all that and more by jamming most IR remote signals. The circuit releases a flood of pulsing IR light that confuses the reciever by corrupting the data stream.... [read more]