An IR sensor is basically a device consisting of a pair of an IR LED and a photodiode, collectively referred to as photocouplers or optocouplers. The IR LED emits IR radiation whose reception and / or reception intensity from the photodiode determines the output of the sensor.
An infrared sensor is an electronic device that emits to capture some aspects of the environment. An IR sensor can measure the heat of an object and detect the movement. These types of sensors only measure infrared radiation rather than being referred to as a passive IR sensor. Normally, all objects in the infrared range emit a form of thermal radiation. This type of radiation is invisible to our eyes and can be detected by an infrared sensor.
The emitter is simply an IR (Light Emitting Diode) LED and the detector is simply an IR photodiode that is sensitive to IR light of the same wavelength as that emitted by the IR LED. When IR light falls on the photodiode, the resistors and these output voltages change in proportion to the intensity of the received IR light.
An infrared sensor circuit is one of the basic and popular sensor modules in an electronic device. This sensor is analogous to human visual perception of obstacles, and it is one of the most common real-time applications.
Working Principal of IR photodiode.
The IR photodiode is used to detect the light rays reflected by an IR LED. When the photodiode is exposed to light, the electrical resistance across the diode decreases, increasing the reverse current. If the photodiode is not exposed to light, the resistance across it will be high.