Photo Interrupter Module

Upright part of this sensor is an infrared emitter and on the other side, it’s a shielded infrared detector. By emitting a beam of infrared light from one end to other end, the sensor can detect an object when it passes through the beam. It is used for many applications including optical limit switches, pellet dispensing, general object detection, etc. 
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Specification 
Supply Voltage: 3.3V to 5V 
Interface: Digital