The figure below shows a project of sound activated LEDs using CA3140 IC. The circuit will blink or flashes three LEDs according to the sound received by the electret microphone. The circuit has a good sensitivity to sound.
The heart of the circuit is a CA3140 opamp IC that is
used in comparator mode and when the input voltage will increase as compare to the reference voltage the output will go high. The two transistors at the output of the IC are used to further amplify the output to drive the LEDs. The sensitivity of the circuit can be adjusted with the 10k variable resistor.

The number of LEDs can also be increased and 8 to 10 more LEDs can be added in the same manner as we have added in the circuit with a 470 ohms current limiting resistor. For further increasing the number of LEDs you can use a BD140 transistor in the place of 2N3906. BD140 has higher output current as compare to 2N3906 due to which it can drive more LEDs.


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Sound Activated LEDs Using CA3140 IC