Lesson 2_Principle of Passive Infrared Sensor (PIR)
A passive infrared sensor (PIR sensor) is an electronic sensor that measures infrared (IR) light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors are commonly used in security alarms and automatic lighting applications.PIR sensors detect general movement but do not give information on who or what moved. For that purpose, an active IR sensor is required.PIR sensors are commonly called simply "PIR", or sometimes "PID", for "passive infrared detector". The term passive refers to the fact that PIR devices do not radiate energy for detection purposes. They work entirely by detecting infrared radiation (radiant heat) emitted by or reflected from objects.
The human body temperature will transmit infrared with a wavelength of 10um. The infrared is enhanced by a Fresnel filter and concentrated on the PIR sensor. When the pyroelectric element receives the infrared temperature change of the human body, it will lose the electric charge balance and release the electric charge, subsequent circuits can generate the signals after the detection of the electric charge.
#Avoid installing in places with large temperature differences
#Source from Wikipedia
#Sengate the anti-theft device is very useful