A PIR (short for passive infrared) sensor is an electronic sensor that measures infrared (IR) light radiating from objects present in its field of view. Mostly, these sensors are used in PIR-based motion detectors.
If you look at the following diagram picture, a PIR sensor has two slots in it, and each slot is prepared with the help of special materials that are IR sensitive. The Fresnel lens helps the two slots in the sensor to widen the detecting area of the sensor as well as its distance, that is, the sensitivity of the sensor. Both slots detect the same amount of IR when there is no movement in front of the sensor or the detection area; we call this the idle state of the sensor, during which the slots detect the ambient amount of IR radiated from the room or outdoors. The sensor calibrates itself and waits for the movement of a warm body.
When half of the PIR sensor intercepts any warm body, such as a human or animal, it causes a positive differential change...