Seeed 101020617 Grove - Adjustable PIR Motion Sensor

Seeed 101020617 Grove - Adjustable PIR Motion Sensor is an easy-to-use Passive Infrared motion sensor which can detect infrared object motion up to 3 meters. The PIR Sensor has 2 slots, and the slots are made of sensitive material. When the sensor is inactive, then the two slots will sense the same amount of IR. The ambient amount radiates from the outdoors, walls or room, etc.When a human body or any animal passes by, it intercepts the first slot of the PIR sensor. This causes a positive differential change between the two bisects. But when the body leaves the sensing area, the sensor generates a negative differential change between the two bisects.