PIR in PIR Sensor stands for a passive infrared sensor it is used to detect the motion of an object, person, or any other thing. PIR SENSOR is mainly used in the place where there is a need for detection of motion like in smart dustbin, the sensor just tells the controller that there is an object and that lets the dustbin door open.
A PIR sensor looks like below which is interfaced with an opensource board like Arduino, raspberry pi and many more
It is a passive component that consists of a pyroelectric sensor that detects the heat changes around it and gives a high value as an output.
This is how a PIR sensor look like
Actually, under the white plastic dome-shaped material there is a pyroelectric sensor. This white cap is called frensal glass that converges all the rays towards the center where the pyroelectric 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 everybody emits infrared rays even we human beings also emit some infrared waves though they are not that strong.
These rays are enough for a pyroelectric sensor to give an output.
A pyroelectric sensor looks like below
Now then it is mounted by a fresnel glass.
Frensal glass
The main aim of this frensal glass is to converge all the infrared radiations to the pyroelectric sensor present in 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 let’s discuss the other important parts of it
Vcc
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.
Ground
It consists of a general ground pin to complete the circuit which is connected to the ground pin in the Arduino board.
Data pin in PIR Sensor
Data pin gives the output 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 and low indicates there is no motion change.
There are two potentiometers present near the end
Potentiometer.1
Delay time adjust
Delay time adjust potentiometer allow us to change the cycle time so that we can detect the motion for regular intervals.
Potentiometer.2
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 continuous information about the motion while the other provides us the information for regular intervals.
