Infrared IR Sensor Module for Arduino

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An IR sensor is an electronic device that emits and detects IR radiations in order to sense the changes that occur in their surroundings. The change may be in temperature, moisture, color, sound, heat, etc. Infrared radiations have a wavelength between 0.75 to 1000µm, which falls between visible and microwave regions of the electromagnetic spectrum.

The IR sensor module basically consists of three components:

IR LED (Transmitter)
Photodiode (Receiver)
Op-Amp (LM358)

IR LED (Transmitter)

An IR LED is a light-emitting diode that emits light in the range of Infrared frequency. IR light is invisible to us as its wavelength is much higher than the visible light range. The basic function of this emitter LED is to convert electricity into light. The light-emitting angle of an IR LED is approximately 20-60 degree and the range is around a few centimeters to several feet. The color of the IR LED is white or transparent, so it can give out the maximum amount of light.

Photodiode (Receiver)

The photodiode acts as an IR receiver, it converts the light which falls on it into electricity. A photodiode is a p-n junction diode that is operated in reverse bias direction. Which means it will start conducting the current in reverse direction when light falls on it. When there is no light falling on the photodiode, it has infinite resistance and acts as an open switch but as the light starts falling on the photodiode, the resistance becomes low and it starts acting like a closed switch.

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Op-Amp (LM358)

The Op-Amp used in most of the IR sensor is LM358, which acts as a voltage comparator. It will compare the threshold voltage set at pin 2 to the photodiode’s series resistor voltage at pin 3. When the photodiode’s series resistor voltage drop is greater than threshold voltage the output of the Opamp will be High and this will turn on the LED, connected at the output which indicates the detection of an object.