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 microcontroller or used to drive an external load. This particular device has a large detection angle of 180°.

180˚ detection angle for wide area motion detection
Typically detects people up to 10m away
User-selectable "night-time mode" for detection after dark only
Adjustable sensitivity
Output: logic high = movement detected
Movement detected LED
Optimised for IR wavelength range: 5500 to 14000nm
Power supply: +3.0 to +6.0Vdc @ 3mA
Idle current: 150uA
Dimensions: 36 x 36 x 20.2mm
Operating temperature range: 0 to +50°C

Parallax offer an extensive range of sensor, communication and interface modules for the experimenter working on robotic systems. Most are supplied with extensive documentation making them ideal for use in education. Further information and tutorials are available from the Parallax website: http://learn.parallax.com/