PIR stands for passive infrared sensor it is basically used to detect the motion of an object, person, or any other thing. It is mainly used in the place where there is a need of detection of motion like in smart dustbin , sensor just tell the controller that there is an object and that lets the dustbin door to open.

Basically a PIR sensor looks like below which is interfaced with a opensource board like arduino ,raspberry pi and many more

It is a passive component which consists of a pyroelectric sensor which detects the heat changes around it and gives a high value as a out put .

This is how a PIR sensor look like


Actually under the white plastic dome shaped material there is a pyro-electric sensor . This white cap is called as frensal glass that converges all the rays towards the centre where the pyro electric sensor is present.

Let us discuss each part briefly one by one with their use and need below

Pyroelectric sensor

The pyroelectric sensor is a sensor which gives us a high value when it detects any infrared radiation in its area. As we know that every body emits infrared rays even we human beings also emit some infrared waves though they are not that strong.

These rays are enough for a pyro electric sensor to give a output.

A pyroelectric sensor looks like below


Now then it is mounted by a frensel glass.

Frensal glass

The main aim of this frensal glass is to converge all the infrarred radiations to the pyro electric sensor present at the middle. The dome is designed in such a way that all the rays converge at a point that gives the user accurate output .

Now lets discuss the other important parts of it



The Vcc pin provides power supply to the sensor it ranges from 3 to 5 volts as the sensor works at an operating voltage of 3v there is a step down transformer to convert 5v supply to 3v .


It consists of  a general ground pin to complete the circuit which is connected to ground pin in the arduino board.

Data pin

Data pin gives the out put which acts as input to the arduino board it gives only two values high or low high indicates there is a change or motion detected amd low indicates there is no motion change.

There are two potentiometes present near the end


Delay time adjust

Delay time adjust potentiometer allow us change the cycle time so that we can detect the motion for regular intervals.



Sensitivity adjust

It is used to adjust the range . We can set our range for longer to shorter distances using this potentiometer.


Retriggering jumper

This helps us to switch between two modes one mode provides as continuous information about the motion while the other provides us the information for regular intervals.


  • Wide Working Voltage Range: DC 4.5V- 20V
  • Current Drain: <60uA
  • Detection Angle: <140°
  • Detection Distance: 3 to 7m (can be adjusted)
  • Blockade time: 2.5s (Default)
  •  Work temperature: -20-+80°C

Hope this article helps you in understanding the motion sensor .

For any queries the comment section below is always open for you.


Leave a Reply