PIR Sensor

pir.ino

// http://henrysbench.capnfatz.com/henrys-bench/arduino-sensors-and-input/arduino-hc-sr501-motion-sensor-tutorial/
int ledPin = 13;                
int pirPin = 2;
int default_remaining = 30;
int remaining = 0;

int val = 0;

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(pirPin, INPUT);
 
  Serial.begin(9600);
  Serial.println("Initializing... It takes around 60 seconds");
  delay(60000);
  Serial.println("Initialized");
}
 
void loop(){
  val = digitalRead(pirPin);

  Serial.print("DEBUG: ");
  Serial.print(remaining);
  Serial.print(" - ");
  Serial.print(val);
  Serial.println();

  if (val == HIGH) {
    Serial.println("Motion Started!");
    digitalWrite(ledPin, HIGH);
    remaining = default_remaining;  
  } else {
    if(remaining <= 0) {
      Serial.println("Motion ended!");
      digitalWrite(ledPin, LOW);
    } else {
      remaining = remaining - 1;
    }
  }

  delay(1000);
}