This sketch reads the state of a PIR sensor

pir_sensor.ino

/*
* PIR sensor tester
*/

int ledPin = 13; 	  // choose the pin for the LED
int inputPin = 2; 	// 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
			
      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
		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;
	}
}