Clap Switch Using 555 Timer

This circuit actually works (built and tested). (This might not work on the simulation). The momentary switch in series with the 100mV (DC values were used so that simulation timebase could be extended) acts as the electret microphone (observe polarity). It basically consists of an audio transducer which toggles the upper relay connected to the 555 module responsible for toggling the states. The output from the 555 then drives the lower relay to switch external devices (lamps and etc. depending on the relay rating). Relays rated at 6V (no values for inductance and resistance). Transistors could be any general purpose BJTs (BC547-NPN,BC557-PNP). At 9V the 555 IC partially heats up, while at 8V it seems fine (555 is rated up to 15V so i don't know why, maybe because.. Nevermind) Extend the microphone with a sufficiently long (6in) wire to prevent it from picking up the click when the relays switches (or else the circuit would oscillate). Diodes protects the circuit from the relay coil's back EMF (I don't know if it's really that crucial for this kind of circuit, built it first without the diodes and worked fine but then they say i need it so yeah, there it is.) If toggling problems occur, play with the values of the 330 ohms resistor and 10uF capacitor connected on the 555 output. Constructive criticisms are encouraged.

published 8 years ago