IR proximity Sensor module

         IR sensor pair mainly consist of an Infrared(IR) LED and a Photodiode. An IR LED is a special purpose LED, it is can emit infrared rays ranging from 700 nm to 1 mm wavelength. These types of rays are invisible to our eyes. In contrast, a photodiode or IR Receiver LED detects infrared rays.

          When we connect the IR sensor module to a 5v power supply. At the same time, Infrared LED (IR-TX) starts emitting infrared rays. The module contains a comparator circuit formed with LM393 IC. Set the threshold voltage at the Non-Inverting input (3) of the IC by rotating the potentiometer knob for the sensor sensitivity.

If infrared rays reach to object’s surface and some of the radiation is reflected back to the IR receiver (IR-RX). The Photodiode or IR receiver (IR-RX) detects infrared light. When reflected infrared light Falls on the Photodiode, the resistance of the photodiode falls down from a huge value, and the voltage across the photodiode drops. So, a High amount of voltage from the photodiode is reached to the Inverting input (2) of the IC. Then the comparator IC compares this voltage with the threshold voltage. If the Inverting input voltage is greater than the Non-Inverting input voltage so the IC output is Low (0). So, the sensor output is Low (0).

When the Photodiode or IR receiver (IR-RX) does not detect the infrared light, then the resistance of the photodiode will very high. So, a Low amount of voltage from the photodiode is given to the Inverting input (2) of the IC. Then the comparator IC compares this voltage with the threshold voltage. In this condition, the Inverting input voltage is less than the Non-Inverting input voltage so the IC output is High (1). So, the sensor output is High (1).