Schematics: Simple IR barrier
By Ibrahim Kamal
12/09/2007

Brief Circuit explanation:

This Infra-Red barrier have many application like:
- Detecting the presence of objects between a transmitter and a receiver
- Counting the number of object passing on a rolling belt

Note: this circuit's behavior is affected by exposition to direct sunlight or strong indoor light directly falling on the receiver.

The sender and receiver part are separated, but they may share the same power supply

The distance between the sender and the receiver can be from 5 cm. to 2 meters approximately

The LEDs D1 and D3 are normal transparent Infra Red LEDs.

This circuit is a direct application of this tutorial.

The Potentiometer R is used to adjust the sensitivity of the receiver, to adapt to different ambient light conditions. When correctly adjusted, the LED D2 should glow as long as the barrier is intact. When an object comes between the sender and the receiver, breaking the barrier, the LED D2 will stop glowing. the output of the OpAmp can be directly connected to a microcontroller or to relay via a switching transistor.

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