PIR SENSOR (PASSIVE INFRARED SENSOR)

A passive infrared sensor (PIR sensor) is an electronic sensor that measures the infrared (IR) light radiating from objects in its field of observation. They’re most frequently utilized in PIR-based motion detector systems.

PIR sensors are commonly called simply "PIR", or sometimes "PID", for "passive infrared detector". The term passive refers to the very fact that PIR devices don't radiate energy for detection purposes. They work entirely by detecting infrared (radiant heat) emitted by or reflected from the objects.

The PIR sensor itself is housed during a sealed metal can to enhance noise/temperature/humidity immunity. There’s a window made from IR-transitive material that protects the detector. Behind the window there are two balanced sensors.
In its internal structure, there's actually a JFET inside (a sort of transistor) which is extremely low-noise and buffers the extremely high impedance of the sensors into something that a low-cost chip (like the BIS0001) can sense.

The lens in this sensor is simply a bit of plastic, but meaning that the detection area is simply two rectangles. Usually we'd wish to have a detection area that's much larger. To try that, we use an easy lens like those found during a camera: they condenses an outsized area (such as a landscape) into a little one (on film or a CCD sensor). For reasons which will be apparent soon, we might wish to make the PIR lenses small and thin and mouldable from cheap plastic, albeit it's going to add distortion. For this reason the sensors are literally Fresnel lenses.

However, we have two sensors, and more importantly we don’t want two really big sensing-area rectangles, but rather a scattering of multiple small areas. So what we do is break up the lens into multiple section, each section of which may be a Fresnel lens.
The different faceting and sub-lenses create a variety of detection areas, interleaved with one another. That's why the lens centres within the facets above are 'inconsistent' - every other one points to a special half the PIR detector

The PIR sensor circuit is employed in numerous electronics projects which are to discover a person's being entering or leaving the actual area or room. These passive infrared sensors are flat control, consists of a good range of lens, and PIR sensors are often easily interfaced with electronics circuits.

Pin Configuration of PIR Sensor
PIR sensor consists of three pins

 Ground

 Signal

Power

 Generally, the PIR sensor power is up to 5V, but, the massive size PIR modules operate a relay rather than direct output. It’s very simple and straightforward to interface the sensor with a microcontroller. The output of the PIR is (usually digital output) either low or high.

Practical Applications of PIR Sensor
PIR sensors have numerous applications in several fields like automatic switching operation of outside lights, lift lobby, common staircases, automatic switching operation of garden lights supported the presence of a person's being, for covered parking lot , automatic door OS in shopping malls, and so on. allow us to discuss a few few innovative electronics projects designed employing a PIR sensor circuit.

Interfacing PIR with Arduino
The program and code to interface PIR sensor and Arduino is as given below! If you discover any difficulty in grasping the code, try reading our other interfacing articles to realize more insights!

 

 

 

Diagram

The Program
int sensor=7; //The output of PIR sensor connected to pin 7
int sensor_value; //variable to carry read sensor value
void setup()
{
pinMode(sensor,INPUT); // configuring pin 7 as Input
Serial.begin(9600); // to point out output value of sensor in serial monitor
}

void loop()
{
sensor_value=digitalRead(sensor); // Reading sensor value from pin 7
Serial.println(sensor_value); // Printing output to serial monitor
}