/*  
    Arduino with PIR motion sensor
    For complete project details, visit: http://RandomNerdTutorials.com/pirsensor
    Modified by Rui Santos based on PIR sensor by Limor Fried
*/
 
int led = 14;                // the pin that the LED is attached to
int sensor = 12;             // the pin that the sensor is attached to
int state = LOW;             // by default, no motion detected
int prevState = LOW;         // previous state of the sensor
int val = 0;                 // variable to store the sensor status (value)

void setup() {
  pinMode(led, OUTPUT);      // initialize LED as an output
  pinMode(sensor, INPUT);    // initialize sensor as an input
  Serial.begin(9600);        // initialize serial
}

void loop(){
  val = digitalRead(sensor);   // read sensor value
  
  if (val == HIGH && prevState == LOW) {  // check if the sensor went from LOW to HIGH
    digitalWrite(led, HIGH);   // turn LED ON
    Serial.println("Motion detected!"); 
    state = HIGH;              // update variable state to HIGH
  } 
  
  if (val == LOW && prevState == HIGH) {  // check if the sensor went from HIGH to LOW
    digitalWrite(led, LOW);    // turn LED OFF
    Serial.println("No motion detected!"); 
    state = LOW;               // update variable state to LOW
  }
  
  prevState = val;             // update previous state of the sensor
}