HC-SR501 PIR Sensor

This example shows how to use an HC-SR501 PIR sensor (movement sensor). You will connect it up to pin 8 of your Arduino board and the input will be used to trigger the onboard LED.

Hardware Required

Circuit

Connect power and ground as illustrated. Then connect the sensor pin to digital pin 8 on your Arduino.

Code

// Uses a PIR sensor to detect movement and turn on a LED

int ledPin = 13; // choose the pin for the LED
int inputPin = 8; // choose the input pin (for PIR sensor)
int pirState = LOW; // we start, assuming no motion detected
int val = 0; // variable for reading the pin status

void setup() {
  pinMode(ledPin, OUTPUT); // declare LED as output
  pinMode(inputPin, INPUT); // declare sensor as input
  Serial.begin(9600);
}

void loop(){
  val = digitalRead(inputPin); // read input value
  if (val == HIGH) { // check if the input is HIGH
    digitalWrite(ledPin, HIGH); // turn LED ON
    delay(150);

    if (pirState == LOW) {
      // we have just turned on
      Serial.println("Motion detected!");
      // We only want to print on the output change, not state
      pirState = HIGH;
    }
  } else {
    digitalWrite(ledPin, LOW); // turn LED OFF
    delay(300);
    if (pirState == HIGH){
      // we have just turned off
      Serial.println("Motion ended!");
      // We only want to print on the output change, not state
      pirState = LOW;
    }
  }
}