const int relayPin = 2;
const int buzzerPin = 7;
const int photoPin = A0;

void setup () {

  Serial.begin(9600);

  pinMode(relayPin, OUTPUT);
  pinMode(buzzerPin, OUTPUT);
  pinMode(photoPin, INPUT);
}

void loop() {

  int photoStatus = analogRead(photoPin);  

  if (photoStatus <= 500) {

    tone(buzzerPin, 2217);
    digitalWrite(relayPin, HIGH);
    delay(150);

    noTone(buzzerPin);
    digitalWrite(relayPin, LOW);
    delay(150);

    Serial.println("- ALARMA ACTIVADA -"); 
  }
  else {

    tone(buzzerPin, 100);
    digitalWrite(relayPin, LOW);
    delay(150);
    noTone(buzzerPin);
    digitalWrite(relayPin, HIGH);
    delay(1000);

    Serial.println("ALARMA DESACTIVADA");
  }
}