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