Sound Operated LED

The LED start glowing as intensity of sound varies. This project can be used to measure the intensity of sound present in the room as sound intensity increase number of LED glows also increases. The image below details with the pin diagram of 324 IC. For more details on it, check the link here.

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Fig. 1: Pin Diagram Of 324 IC

This sound operated LED circuit is based on LM324 which is 14 pin IC consisting of 4 independent operational amplifiers. The output voltage of LM324 is many times higher than the voltage difference between the input terminals of an op amp.

LM324 IC is used as a comparator and when input voltage rises above the reference voltage, output is attained. When no noise or audio signals are present in the room, output voltage on pin 1 is zero as voltage on pin 2 is lower than that at pin 3. Since, the IC works as comparator, less voltage on pin 2 in comparison to pin 3 will not make the LED glow. Let’s find out the working of this interesting project.

Working

As one provides some input noise, voltage on pin 2 rises as compared to pin 3 and high voltage is attained on pin1 of IC. This makes the LED to start glow. The pins between which the LED is placed are also provided with an additional 1K resistor. A 22K resistor is used to keep the signal input at low level. Mic positive should be connected to supply and negative should be connected to 22k resistor. Intensity of sound signals for which LED must glow on can be varied with the help of variable resistor.

Note –If one wants to increase the number of LED then you can use more than one LM324.