Light to Frequency converter circuit using IC 555

Light to Frequency converter

Converter circuits are generally used to convert a signal from one parameter to another. And it also possess a significant advantage in the Circuit designing. We are about to see the working of a similar light to frequency converter circuit which converts the incident light to equivalent frequency in the output signal.


The circuit is built around a Astable Multivibrator using IC 555 and we all know that a multivibrator emits square wave as output. The Resistor and Capacitor connected to the pins 3,6 and 2 of the IC forms the backbone as the output frequency depends of the values of these three components.

In the above Circuit the similar principle was used to make the IC 555 gives a equivalent frequency in the output when light in incident on the LDR. We all know that LDR gives low resistance in dark whereas high resistance in the presence of light. And this resistance in turn alters the output frequency when light in incident in it.

The above circuit will give maximum frequency signal as output when the light intensity incident on the LDR is maximum. And minimum frequency when the light incident on the LDR is very less. Therefore this circuit is capable of converting the input light to equivalent frequency output.

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Frank Donald

Frank Donald

Junior Network Engineer at Tata Communications
Frank Donald is an Electronics and Communication Engineer who loves building stuff in his free time. Video games, blogging and programming are the things he loves most

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