IR Sensor Circuit Using LM358 - Simple

Here, I am going to explain the working of simple IR Sensor circuit. We know that the white surface reflects all the radiations which falls on it whereas black color absorbs them. When the supply is given to IR Sensor, the LED starts emitting light radiations. If the surface is of white color then it reflects all the radiations. As these radiations start falling on the photo diode, which is connected in reverse bias, the resistance ofthe photo diode

starts decreasing rapidly and the voltage drop across the diode also decreases. The voltage at Pin 3 starts increasing and as it reaches just beyond the voltage of Pin 2, the comparator gives a high output. In case of the black surface, the LED emits light but it is not reflected by the surface, so the photo diode detects nothing and its resistance remains infinite. hence the comparator gives low output.

Circuit Diagram For PCB(for Connecting Components On PCB)

Circuit Diagram, When an obstcle is came between IR Tx and IR Rx

In previous posts, I give two below circuits, their links are as

1. http://param-world.blogspot.in/2012/11/ir-receiver-circuit-using-555-with-tsop.html
2. http://param-world.blogspot.in/2012/11/ir-transmitter-circuit-using-555.html

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