pir sensor

PIR Sensor

Passive Infrared sensor

A passive infrared sensor (PIR) is an electronic sensor which is used to detect motion. The sensor measures infrared (IR) light radiating from objects in its field of view. Mainly they are used in a PIR based motion detectors.

When a person in the field of the sensor moves, it detects a sudden change in infrared energy and the sensor is triggered (activated). It act like a switch.

They don't  detect or measure Heat, but they detect infrared radiation emitted from from objects.

These sensors commonly used in security, lighting, and alarm systems.

The range of PIR sensors is approximately 6 meters, depending on conditions.

pir sensor


Operating voltage 5V to 20V
Power Consumption 65 mA
TTL output 3.3V, 0V
Delay time Adjustable (.3 to 5min)
Sensing range about 120° and 7 meters

PIR Sensor Pinout

PIR Sensor pinout

Hardware Connections

-->    Vcc to 5V of Arduino

-->    Gnd to Gnd of Arduino

-->    out to Digital pin 8(D8) of Arduino

PIR Working

PIR working

  • When PIR detects motion of any object the output voltage is high because of it sense infrared radiation whereas it is low when there is no motion.

PIR Element


  • PIRs are made of pyroelectric sensors which can use to detect levels of infrared radiation.
  • In the above image, PIR has a round metal can in which there is a rectangular crystal in the center.

Uses of PIR Sensor

  • Automatic Doors which open and close on Motion Detection.
  • All Outdoor Lights.
  • Lift Lobby.
  • Motion Cameras.
  • Lights on/off by Motion Detection.
  • Basement Parking Areas.
  • Escalator Lights(Staircase).

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