PIR SENSOR (PASSIVE INFRARED SENSOR)
A passive infrared sensor (PIR sensor) is an electronic sensor that measures the infrared (IR) light radiating from objects in its field of observation. They’re most frequently utilized in PIR-based motion detector systems. PIR sensors are commonly called simply "PIR", or sometimes "PID", for "passive infrared detector". The term passive refers to the very fact that PIR devices don't radiate energy for detection purposes. They work entirely by detecting infrared (radiant heat) emitted by or reflected from the objects. The PIR sensor itself is housed during a sealed metal can to enhance noise/temperature/humidity immunity. There’s a window made from IR-transitive material that protects the detector . Behind the window there are two balanced sensors. In its internal structure, there's actually a JFET inside (a sort of transistor) which is extremely low-noise and buffers the extremely high impedance of the sensors into s
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