Sound Operated LED

Summary
The LED start glowing as intensity of sound varies. This can be used to measure the intensity of sound present in the room as sound intensity increase number of LED glows also increases.
Description
Circuit is based on LM324 which is 14 pin IC consisting of 4 independent operational amplifier in a single package. The output voltage of LM324 is many times higher than the voltage difference between the input terminals of an op amp.
Working of circuit is very simple we are using LM324 IC as a comparator when input voltage rises above the reference voltage then only we will get the output. When no noise or audio signals is present in the room output voltage on pin 1 is zero because voltage on pin 2 is lower than pin 3 as it work as comparator it will compare the voltage as voltage is less on pin 2 in compare to pin 3 LED will not glow.
As we provide some input noise voltage on pin 2 rises as compare to pin 3 and we will get high on pin1 of IC as a result Led start glowing. Here we are using 1K resistor with between pins a we want that different LED’s should glow on different audio signals and 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 you want to increase the number of LED then you can use more than one LM324.
Components used

IC
IC1(LM324)	1
Resistor
R1(22K)	1
R2-R5(1K)	4
R6-R9(220E)	4
R10-R11(15K)	2
VR1(10K)	1
Miscellaneous
MIC	1
LED1-LED4	4