Arduino with PIR Motion Sensor

In this project you’re going to create a simple circuit with an Arduino and PIR motion sensor that can detect movement. An LED will light up when movement is detected.

Introducing the PIR Motion Sensor

The PIR motion sensor is ideal to detect movement. PIR stand for “Passive Infrared”. Basically, the PIR motion sensor measures infrared light from objects in its field of view.

So, it can detect motion based on changes in infrared light in the environment. It is ideal to detect if a human has moved in or out of the sensor range.

The sensor in the figure above has two built-in potentiometers to adjust the delay time (the potentiometer at the left) and the sensitivity (the potentiometer at the right).

Pinout

Wiring the PIR motion sensor to an Arduino is pretty straightforward – the sensor has only 3 pins.

• GND – connect to ground
• OUT – connect to an Arduino digital pin
• 5V – connect to 5V

Parts required

Here’s the required parts for this project

• 1x PIR Motion Sensor (HC-SR501)
• Arduino UNO – read Best Arduino Starter Kits
• 1x LED
• Jumper Cables

Schematics

Assemble all the parts by following the schematics below.

Code

Upload the following code.

/*  
    Arduino with PIR motion sensor
   
*/
 
int led = 13;                // the pin that the LED is atteched to
int sensor = 2;              // the pin that the sensor is atteched to
int state = LOW;             // by default, no motion detected
int val = 0;                 // variable to store the sensor status (value)

void setup() {
  pinMode(led, OUTPUT);      // initalize LED as an output
  pinMode(sensor, INPUT);    // initialize sensor as an input
  Serial.begin(9600);        // initialize serial
}

void loop(){
  val = digitalRead(sensor);   // read sensor value
  if (val == HIGH) {           // check if the sensor is HIGH
    digitalWrite(led, HIGH);   // turn LED ON
    delay(100);                // delay 100 milliseconds 
    
    if (state == LOW) {
      Serial.println("Motion detected!"); 
      state = HIGH;       // update variable state to HIGH
    }
  } 
  else {
      digitalWrite(led, LOW); // turn LED OFF
      delay(200);             // delay 200 milliseconds 
      
      if (state == HIGH){
        Serial.println("Motion stopped!");
        state = LOW;       // update variable state to LOW
    }
  }
}

Wrapping Up

This post shows a simple example on how to use the PIR motion sensor with the Arduino. Now, you can use the PIR motion sensor in more advanced projects. For example, you can build a Night Security Light project.

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Thanks for reading