Sound detector to detect alarm clock output for switching light ON when alarm rings

Thread Starter


Joined Sep 21, 2014
Guys I want to make a circuit which turns ON a light and and simultaneously turns off a fan on detecting the sound from an alarm clock. Please help me. Is it possible to get a high signal always when the alarm sound is pulsating type one. I was planning to do this with a microphone. Later i found that there is a sound detector module available online. Is it possible that the sound detector module output will be high even the sound is a pulsating one
Pls suggest some ideas and circuits


Joined Aug 1, 2013
The online sound detectors from China are a microphone, preamp, and comparator, and probably will drop out between alarm beeps. But you probably can add a capacitor to the circuit to get it to have a longer detection window. The exact circuit will vary depending on the module, but they all are very simple with 1 or 2 layer pc boards. If you trace out the circuit, I'm sure we can suggest a modification. After that, you'll need a power supply for the controller and the power relay for the light and fan. If it always is the case that the fan is off when the light is on, a SPDT relay can switch AC power between the two loads.



Joined Jul 19, 2011
simplest might be a relay with fan on the NC side and light on NO side, relay activated with sound trigger driving an SCR, Supplying DC to the SCR/relay will cause it to latch on when triggered. False triggering could happen with noise in the room, turn the sensitivity down enough and it should work OK provided the alarm is the loudest thing it would normally hear.