Parallax 555-28027 PIR Sensor, Passive, 1.41" x 1.0" x 0.8" Size

The PIR (Passive Infra-Red) sensor is a pyroelectric device that detects motion by measuring changes in the Infrared (heat) levels emitted by surrounding objects. When motion is detected the PIR sensor outputs a high signal on its output pin. This logic signal can be read by a controller or used to drive an external load. Dual output modes and a sensible design that performs within stated data sheet specifications are a few reasons over 100,000 units are in use around the world.