#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// LCD I2C 16x2 alamat 0x27
LiquidCrystal_I2C lcd(0x27, 16, 2);

#define MQ2pin A0

int buzzer = 13;
int sensorValue;

void setup() {
  pinMode(buzzer, OUTPUT);

  Serial.begin(9600);

  // Untuk library LiquidCrystal_I2C yang digunakan
  lcd.begin(16, 2);
  lcd.backlight();

  lcd.setCursor(0, 0);
  lcd.print(" GAS SENSOR ");

  lcd.setCursor(0, 1);
  lcd.print(" WARMING UP!");

  delay(20000); // pemanasan MQ-2
}

void loop() {

  sensorValue = analogRead(MQ2pin);

  lcd.clear();

  lcd.setCursor(0, 0);
  lcd.print("VALUE: ");
  lcd.print(sensorValue);

  if (sensorValue > 300) {

    lcd.setCursor(0, 1);
    lcd.print("SMOKE DETECTED");

    tone(buzzer, 500, 2000);

  } else {

    lcd.setCursor(0, 1);
    lcd.print("NO SMOKE");

    noTone(buzzer);
  }

  Serial.print("MQ-2 Value: ");
  Serial.println(sensorValue);

  delay(2000);
}