PIR Motion Sensor Interfacing with Arduino UNO

The Pyro-electric Infra-Red (PIR) sensor is an extremely useful device for detecting the presence of a moving body. This is due to its ability to sense the infrared radiation that every living body emits. A PIR sensor is an electronic sensor that measures infrared light radiating from objects in its field of view. Normally this type of sensor would be used as a motion or proximity sensor.

More about PIR Sensor Here!

Wiring diagram:

Arduino Uno Code:

int led = 13;     // the pin that the LED is attached to
int sensor = 2;   // the pin that the sensor is attached to
int state = LOW;  // by default, no motion detected
int val = 0;      // variable to store the sensor status 
void setup() {
  pinMode(led, OUTPUT);  // initialize 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(200);              // delay 200 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
     }
}

Sample Output: