Sound Scanner Circuit

This sound scanner circuit will scan the sound vibration present near the vicinity and convert them into audible sound or beeps to alert you. Many of us live alone in home and always fear that somebody is walking in the corridor especially in nights. So, to solve this, just install this circuit in your sit outs, car porch and many other places in your house. So when ever any person walk around microphone it will pick up the sound and will give you beep sound to alert you. The main advantage of this circuit is it can detect vibration up to a distance of 3 meters.

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Fig. 1: Prototype of Sound Scanner Circuit on Breadboard

The sound scanner circuit comprises of Operational amplifier 741 which is used as a sensitive voltage comparator. IC1 is used to sense the sound signal present near the condenser microphone. And resistor R1 is used to increase the sensitivity of microphone. When vibration is picked up by the microphone it converts them into electrical signals and feed it to inverting terminal that is pin 2 of IC1 through capacitor C1 and resistor R2. Here capacitor C1 is act as a coupling capacitor. And adjust VR1 to get maximum gain. Now this signals from output pin 6 are feed to non-inverting pin 3 of IC2 through capacitor C2 .

Here IC2 is configured in comparator mode. It will compare the inputs at pin 2 and 3 that is at inverting and non-inverting pin and whenever non inverting input is more than inverting terminal, it will make the pin 6 of IC2 high and trigger the alarm in the form of beep. Sensitivity of pin 2 of IC2 can be adjusted with the help of VR2.

Now whenever pin 6 output goes high it will trigger the Darlington pair transistor T1 and T2. Which are used to amplify the weak signals and speaker connected through emitter will give you a sound. If you are hearing a continuous beep without producing any sound in front of microphone then adjust the sensitivity of VR2 near to ground. Assemble the circuit properly and place sensor outside the home or the place to be monitor and speaker inside the room.