Sound-Activated Lamp (Relay/Switch)


Posted on Feb 5, 2014

This simple circuit shown int the schematic diagram actives the switch using sound. We can use this circuit for various applications, such as automatic (sound-controlled) disco light or car`s LED light show. The Q1 amplify the audio from mic. The R1 is used to adjust the peak of signal to greater than about 0. 7 volts, act as sensitivity adjuster.


Sound-Activated Lamp (Relay/Switch)
Click here to download the full size of the above Circuit.

A certain level, the signal coming from microphone, after amplification by Q1, will trigger the SCR and light lamp I1. If we change the lamp with a relay, then we can get a sound-activated relay/switch, which can be used to control more powerful / high wattage high voltage lamps. If we use a relay, place a 1N4007 diode in parallel with the relay coil to prevent the back-emf from relay coil destroying the SCR. Here is the schematic diagram of the circuit:




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