PIR Motion Sensor

[Lorenzo M. Oliver]

Passive infrared (PIR) sensors detect motion by comparing the amount of infrared radiation that reaches a pair of detectors. When the two detectors “see” different values, the sensor indicates it as movement of an object, such as a person or an animal. PIR sensors are often used in driveway security systems, which turn on a light (but only at night) when someone approaches the house...

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