How Science Can Help You Open a Locked Door! A passive infrared (PIR) motion sensor is an electronic device that detects motion by sensing changes in infrared radiation, primarily emitted by warm objects like humans and animals. Unlike active sensors, PIR sensors do not emit any signals; instead, they passively detect infrared radiation through two or more pyroelectric elements that generate a voltage when they detect changes in radiation levels. Typically, these sensors have a detection range o