int led = 13;               
int sensor = 2;
int state = LOW;
int val = 0;
void setup() {
  pinMode(led, OUTPUT);
  pinMode(sensor, INPUT);
  Serial.begin(9600);
}
void loop(){
  val = digitalRead(sensor);
  if (val == HIGH) {
    digitalWrite(led, HIGH);
    if (state == LOW) {
      Serial.println("Motion detected!"); 
      state = HIGH;
    }
  } 
  else {
      digitalWrite(led, LOW);
      if (state == HIGH){
        Serial.println("Motion stopped!");
        state = LOW;
    }
  }
}