Overview of PIR Sensors and its Working Principle

Learning about the different sensors used in some of the commonly used devices and daily objects we use today is interesting. In this blog, we are going to give you an overview of PIR Sensors and their working principle. Smart homes, light controls, alarm systems, etc. are some of the common facilities that are using these sensors. Another great use of PIR motion sensors is in human detection robots. These kinds of robots are now widely used in rescue operations worldwide. Before starting with the overview of these passive infrared sensors, let’s make a basic awareness of IR sensors.  

PIR Sensor Guruface Blog Post Intro

Table of content

We recently published a detailed blog on IR Sensors. It will give you detailed information on all its important characteristics. Let’s still give you a brief intro.

IR SENSOR: A sensor that measures and detects infrared radiation in its environment is known as an infrared (IR) sensor. It is a tool that can recognize when something is in front of it.

Types of IR Sensors

There are two types of infrared sensors

1) Active IR Sensor

2) Passive IR sensor

Passive infrared sensor: PIR sensors do not emit infrared light as an LED does; they simply detect it. They can both detect motion and gauge an object’s heat. This kind of sensor is referred to as a passive IR sensor because it simply detects infrared radiation.

A PIR Sensor Consists Of

  • Piezoelectric sensor
  • A filter for IR
  • A Fresnel lens that covers or concentrates all light at a single point (where the pyroelectric sensor is placed)
  • A casing shields the sensor from external factors such as humidity and rain.

Working of Passive Infrared Sensor

Pyroelectricity is the basis for how these sensors functions. Pyroelectric components used in these sensors absorb thermal energy and produce an equivalent amount of electrical power.

  • The capacity of some materials to produce a momentary voltage when they are heated or cooled is known as pyroelectricity.
  • The crystalline substance used to make pyroelectric sensors produces a surface electric charge when heated by infrared radiation.
PIR sensor working principle - Guruface blog

Each of the two slots in the sensor is made of a unique substance that is IR-sensitive. Both slots pick up the same amount of IR while the sensor is not in use. A warm body, such as a person or animal, will cause a difference in the amount of IR in the slots.

Passive infrared sensor detecting area - Guruface blog

PIR Sensor Interface with Arduino

Automatic room light with PIR SENSOR

Automatic Room Lights System using Arduino uses a motion sensor to sense motion and turn on the lights automatically. In this way, we can conserve energy and also have automation which makes our life simple.

PIR Sensor blog - Guruface

Program for automatic room light:

int ledPin = 13; int pirsensor = 9; int val = 0;
void setup()
pinMode(ledPin, OUTPUT); pinMode(pirsensor, INPUT);
void loop()
val = digitalRead(pirsensor); digitalWrite(ledPin, val);
if (val ==1)
digitalWrite(ledPin, HIGH);


PIR sensors are most commonly used in motion-based detection, such as in-home security systems, smart light systems, etc.

Advantages of Infrared Sensor

• Low power requirement

• High noise immunity

• Not affected by environmental factors like rust, corrosion, etc.

• Compact in size and are reliable

• Can be applied to a large area for a real-time sensing

Disadvantages of Infrared Sensor

• High-force infrared waves can damage the eyes.

• It can only operate one device at a time in the screen and control application.

• Be obstructed by everyday items.

• A small range.

• Can be affected by Environmental conditions such as rain, fog, dust, and pollution.

• Transmission Data rate is slow compared to wired devices


With this information, we hope you got a clear picture of how modern devices are doing many astonishing things easily. Motion sensor technology is even used in the Qatar World Cup’s official match ball – Al Rihla as well for accurate VAR decisions and offside calls. No doubt that the PIR sensors will surely keep improving in the coming years and they will be used for many more great applications.

Do you think these exciting technology topics are worth studying for your little ones?

Check out the Robotics and Coding courses for kids offered by Guruface Academy to make kids learn about these technologies as early as possible. This extra knowledge will boost their career choices and overall tech knowledge. You can also signup for our weekly live webinar on Robotics for Kids topic to get an understanding of how these online sessions are conducted. Register now to book your seats before they are full.

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Marini is the Senior Robotics Trainer at Guruface Academy. She holds a Master's Degree (MS) in Electronics and is an experienced Instructor with a demonstrated history of Training students across the Globe in Various Robotics platforms. Marini is also a Professional Stem Educator with sound knowledge of Electronics, Coding, Robotics, Artificial Intelligence, etc.