PIR Sensor

What is a PIR (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 have used in 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 acts as a switch.

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

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

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

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pir sensor

PIR Sensor Pinout

pir pinout


Operating voltage5V to 20V
Power Consumption65 mA
TTL output3.3V, 0V
Delay timeAdjustable (.3 to 5min)
Sensing rangeabout 120° and 7 meters

Hardware Connections

  • Vcc to 5V of Arduino.
  • GND to GND of Arduino.
  • OUT to Digital pin 8(D8) of Arduino.

How PIR Sensor Works

pir working

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

PIR Element

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 / Applications

  • 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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