#include <Wire.h>;
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2); // Default address of most PCF8574 modules, change according to the module
int seconds = 0;  
int Sensor_gas = A0; // declare sensor to analog 0
int redLED = 4;  // declare red LED to pin 4
int greenLED = 3;  // declare green LED to pin 3
int buzzer = 5;  // declare buzzer to pin 5
int sensorThreshold = 400; // gas sensor treshold on 400, adjustable

void setup() {
  // put your setup code here, to run once:
    pinMode(Sensor_gas, INPUT);
    pinMode(redLED, OUTPUT);
    pinMode(greenLED, OUTPUT);
    pinMode(buzzer, OUTPUT);
    lcd.backlight(); // to turn on the LCD backlight
    lcd.display(); // to turn on the LCD display
    lcd.begin(16,2);
    lcd.clear(); // to clear the LCD display
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  int analogSensor = analogRead(Sensor_gas);
  if (analogSensor > sensorThreshold) // if the sensor detects above the treshold
{
    digitalWrite(redLED, HIGH);
    digitalWrite(greenLED, LOW);
    lcd.setCursor(0, 0);
    lcd.print("Kondisi Ruangan:");
    lcd.setCursor(0, 1);
    lcd.print("GAS BOCOR!      ");
     tone(buzzer, 750, 1000); // buzzer on for 750 hz for 1 second
   }
else // 
   {
    lcd.setCursor(0, 0);
    lcd.print("Kondisi Ruangan:");
    lcd.setCursor(0, 1);
    lcd.print("Gas aman       ");
     digitalWrite(redLED, LOW);
     digitalWrite(greenLED, HIGH);
     noTone(buzzer); // buzzer sound off
   }
   delay(1000);  // delay for 1 second to next sensor reading
}