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

#define MQ2_PIN A0
#define BUZZER 8

LiquidCrystal_I2C lcd(0x27, 16, 2);

int gasValue = 0;
int threshold = 300; // batas gas (bisa diubah)

void setup() {
  pinMode(BUZZER, OUTPUT);
  Serial.begin(9600);

  lcd.init();
  lcd.backlight();

  lcd.setCursor(0, 0);
  lcd.print("Gas Detector");
  delay(2000);
  lcd.clear();
}

void loop() {
  gasValue = analogRead(MQ2_PIN);

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

  lcd.setCursor(0, 0);
  lcd.print("Gas: ");
  lcd.print(gasValue);
  lcd.print("   ");

  if (gasValue > threshold) {
    lcd.setCursor(0, 1);
    lcd.print("BAHAYA GAS!");
    digitalWrite(BUZZER, HIGH);
  } else {
    lcd.setCursor(0, 1);
    lcd.print("AMAN        ");
    digitalWrite(BUZZER, LOW);
  }

  delay(500);
}