Interface PIR With 8051

Passive Infrared Sensor which uses the IR to detect the motion.

  • PIR are basically made of a pyroelectric sensor.
  • It detects an object has moved in or out of the sensor range.
  • The round metal with a rectangular crystal in the centre , which can detect level of infrared radiation.
  • The sensor in a motion detector is actually split in two halves.
  • When sensor is idle, both slots detect the same amount of IR.
  • When motion detected it first intercepts one half of the PIR sensor.
  • When the warm body leaves the sensing area, the reverse happens, whereby the sensor generates a negative differential change.
  • The PIR detects motion, the output pin will go “high” to 3.3V.


  • Motion Detection System.

Hardware Required

  • Pir Sensor.
  • 8051 MicroController.


  • Vcc: +5v.
  • OutPut:Digital Pulse.
  • Gnd: Gnd.