Air Sheet Cooler

const byte TRIGGER_PIN = 2; // PIN ECHO TRIGGER
const byte ECHO_PIN = 3;    // PIN ECHO

int FAN_PIN = 4; //pin for the fan (transistor as a relay)

const unsigned long MEASURE_TIMEOUT = 25000UL; // 25ms = ~8m à 340m/s


const float SOUND_SPEED = 340.0 / 1000;

void setup() {
// initializing the arduino
  pinMode(TRIGGER_PIN, OUTPUT); // the trigger pin is an output pin
  digitalWrite(TRIGGER_PIN, LOW); // pin is low to have no bugs
  pinMode(ECHO_PIN, INPUT); // the echo pin is an input to receive the ultra soud
  pinMode(FAN_PIN, OUTPUT); //the pin for the fan to activate 
}

void loop() {
//this will repeat indenfinitely
  digitalWrite(TRIGGER_PIN, HIGH); //Activate the pin during 10 milliseconds
  delayMicroseconds(10);
  digitalWrite(TRIGGER_PIN, LOW);


  long measure = pulseIn(ECHO_PIN, HIGH, MEASURE_TIMEOUT); //measur the time the sound comme back


  float distance_mm = measure / 2.0 * SOUND_SPEED; //wi divide it by 2 * the speed of sound ( line 7) to give us the distance in millimetre


  if ( distance_mm <= 50) //if the distance is inferior or equal to 5 cm the fan will activate during 10 minutes
  {
    digitalWrite(FAN_PIN, HIGH);
    delay ( 60000); //10 minutes 
    digitalWrite(FAN_PIN, LOW); //and then turn off
  }


  delay(50); //every half a second it repeat if the fan isn't turned on
}