Infrared proximity sensor

Infrared proximity sensor

All infrared proximity sensors work on the same principle. The basic idea is to send infrared light through an infrared LED, which is then reflected by any object in front of the sensor. Next, you simply pick up the reflected infrared light. To detect the reflected infrared light, we'll use a rather original technique: we'll use another infrared LED to detect infrared light emitted from another LED of the same type! This is due to an electrical characteristic of a light-emitting diode (LED): when an LED is illuminated, it generates a voltage difference across its leads. It's like a photovoltaic cell, but with a much smaller output current.