Sound Sensor Switch Using LM358N

Introduction:

Sound sensor switch circuits can be used as a module for any system that might be assigned to trigger by detecting some kind of sound pressure level or simply applications such as a voice-activated alarm security circuit. Sound sensor switches can be used in home automation projects where a light bulb turns on responding to the sound of a knock at the door. A simple sound sensor switch can easily be made using LM358N IC.

LM358N is a dual high-gain op-amp IC, which contains two independent op-amps in one package. The circuit uses both op-amps to sense the sound. A relay is then used for switching depending on the signal received from the IC.

Hardware Required

Pin configuration of LM358N

Circuit Diagram

Working

This simple sound switch circuit can be operated through a 9V to 12V battery. However, it can also be operated on lower voltages like 5V to 6V. LM358N IC is the key component of this project. It has two high-gain op-amps. The first op-amp, LM358A is used as an amplifier for amplifying the sound received from the microphone. The amplified sound signal at pin 1 is then passed through the 1µF decoupling capacitor and fed to the 1N4148 diodes which convert the signal into DC. The second op-amp LM358B is used as a DC amplifier which amplifies the DC signal coming from the diodes. The amplified DC signal is received at the output pin 7 of the LM358B. This amplified output then goes to the 2N3904 transistor which is used at the output to drive the relay and the LED.

Applications and Uses:

Sound sensor switches can be used in home automation projects where a light bulb turns on responding to the sound of a knock at the door. It can also be used in toys where lights turn on or off at the sound of clapping.