#define GAS_SENSOR A0
#define LED_PIN 7
#define BUZZER_PIN 8
#define RELAY_PIN 6

int threshold = 400;

void setup()
{
  pinMode(LED_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(RELAY_PIN, OUTPUT);

  Serial.begin(9600);

  digitalWrite(RELAY_PIN, HIGH);
}

void loop()
{
  int gasValue = analogRead(GAS_SENSOR);

  Serial.print("Gas Value: ");
  Serial.println(gasValue);

  if(gasValue > threshold)
  {
    digitalWrite(LED_PIN, HIGH);

    tone(BUZZER_PIN, 1000);

    digitalWrite(RELAY_PIN, LOW);

    Serial.println("GAS LEAK DETECTED!");
  }
  else
  {
    digitalWrite(LED_PIN, LOW);

    noTone(BUZZER_PIN);
    digitalWrite(RELAY_PIN, HIGH);
  }

  delay(1000);
}