Alarm Pintu Arduino Uno

// ============================================================
// ALARM PINTU MAGNETIK — ARDUINO UNO
// Sensor pintu : D2
// Buzzer       : D3
// LED hijau    : D4
// ============================================================

const int PIN_SENSOR_PINTU = 2;  // sensor pintu (kabel biru)
const int PIN_BUZZER = 3;  // sinyal buzzer (kabel hijau, baris 11)
const int PIN_LED_HIJAU    = 4;  // LED hijau (kabel merah, baris 20c)

// Modul buzzer yang dipakai bertipe LOW trigger.
// Artinya buzzer berbunyi saat pin D3 diberi LOW (0V).
// Kalau modulmu justru HIGH trigger, ubah true menjadi false.
const bool BUZZER_ACTIVE_LOW = true;
const int BUZZER_ON  = BUZZER_ACTIVE_LOW ? LOW : HIGH;
const int BUZZER_OFF = BUZZER_ACTIVE_LOW ? HIGH : LOW;

void setup() {
  Serial.begin(9600);

  // Sensor memakai resistor internal Arduino,
  // jadi tidak perlu resistor tambahan.
  pinMode(PIN_SENSOR_PINTU, INPUT_PULLUP);

  pinMode(PIN_BUZZER, OUTPUT);
  pinMode(PIN_LED_HIJAU, OUTPUT);

  // Saat baru menyala, alarm harus mati.
  digitalWrite(PIN_BUZZER, BUZZER_OFF);
  digitalWrite(PIN_LED_HIJAU, LOW);

  Serial.println("Alarm pintu siap.");
}

void loop() {
  // Baca sensor: pintu tertutup = LOW, pintu terbuka = HIGH.
  int pintu = digitalRead(PIN_SENSOR_PINTU);

  if (pintu == HIGH) {
    // Pintu terbuka: kedipkan LED dan bunyikan buzzer.
    Serial.println("Pintu terbuka! Alarm aktif.");

    digitalWrite(PIN_LED_HIJAU, HIGH);
    digitalWrite(PIN_BUZZER, BUZZER_ON);
    delay(150);

    digitalWrite(PIN_LED_HIJAU, LOW);
    digitalWrite(PIN_BUZZER, BUZZER_OFF);
    delay(150);
  }
  else {
    // Pintu tertutup: semuanya mati.
    Serial.println("Pintu tertutup. Aman.");

    digitalWrite(PIN_LED_HIJAU, LOW);
    digitalWrite(PIN_BUZZER, BUZZER_OFF);
    delay(100);
  }
}