PIR Sensor

The passive infrared sensor (PIR sensor) can detect whether a human being or homeothermic animal passes by.

Working principle

The PIR sensor uses a human pyroelectric infrared sensor as a core component. The normal temperature of a human body is 37 °C, corresponding to the infrared light of 10 μm in wavelength. The PIR sensor detects the movement of a human body or heat source nearby by detecting the change of the infrared light of 10 μm in wavelength.


To sensitively detect the change of the 10 μm infrared light, the PIR sensor uses a Fresnel filter to concentrate the infrared light so that the sensor can receive as much infrared light as possible in the environment.

Real-life example

  • A shopping mall uses a PIR sensor on its automatic door to determine whether to open or close the door.


  • Dimensions: 24 × 20 (mm)
  • Detection range: 3–5 (m)
  • Detection angle range at the x-axis: 80 degrees
  • Detection angle range at the y-axis: 55 degrees
  • Operating duration after being triggered: 3s
  • Operating current: 15 mA
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