A passive infrared sensor is an electronic sensor that measures infrared light radiating from objects in its field of view. They are most often used in PIR-based motion detectors. PIR sensors allow you to sense motion, almost always used to detect whether a human has moved in or out of the sensors range-sensing motion with passive infrared sensors (PIR).
PIR sensors detect a human being moving around within approximately loam from the sensor. PIR motion detectors commonly used in burglar alarms and automatically activated lighting systems. In this video, we will see the automatic room lights using arduino and PIR sensor, where the lights in the room will automatically turn on and off by detecting the presence of human such automatic room light can be implement in your garages, stair case, bathroom, office room etc.
Where we do not continuous-light but only when we are present. Also with the help od this system, you need not worry about electricity as the light get automatically off when there is no person. Automatic room light circuit, there are two important component in this circuit, first is PIR sensor and second is relay.