Sound Activated LEDs Using CA3140 IC

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In this tutorial, we are going to make a project of sound-activated LEDs using a CA3140 IC. This circuit will blink/flash three LEDs according to the sound received from the microphone. You must have seen these kinds of projects using transistors and other ICs as well but the reason for using this particular IC is that it combines the advantages of high-voltage bipolar transistors and PMOS transistors.

CA3140 is a BiMOS op-amp that combines the features of Bipolar and MOS technologies its input stage is MOSFET and the output stage is Bipolar. This circuit has a high sensitivity to sound because it uses an electret microphone

Hardware Components

The following components are required to make Sound Activated LED Circuit

S.no	Component	Value	Qty
1.	IC	CA3140	1
2.	Variable resistor	10K	1
3.	Transistor	2N3904, 2N3906	1, 1
4.	LEDs	–	3
5.	Resistor	39K, 10K, 1K, 470Ω	1, 2, 2, 3
6.	DC Supply	9-12V	1

CA3140 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of CA3140

2N3904 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3904

2N3906 Pinout

For a detailed description of pinout, dimension features, and specifications download the datasheet of 2N3906

Sound Activated LED Circuit

Working Explanation

The operating voltage of this circuit is 9-12V, CA3140 IC is used in comparator mode which means that when the input voltage increases as compared to the reference voltage the output will go high. An Electret Microphone is used to sense the sound and receive input signal for the IC, this microphone is very sensitive and its sensitivity can be adjusted through the 10K variable resistor.

The output from the IC is further amplified through two transistors. Now the amplified output from the transistor will drive the LEDs. The number of LEDs can be increased, you can add 8-10 more LEDs and connect them in the same manner with a 470 ohms resistor.

If you are increasing the LEDs then you should replace the 2N3906 transistor with the BD140 transistor since it has higher output and will be able to drive more LEDs