#include <Wire.h>                  
#include <LiquidCrystal_I2C.h>      
LiquidCrystal_I2C lcd(0x27, 16, 2);
const int redPin = 13;
const int greenPin = 12;
const int bluePin = 14;
const int mq135Pin = 34;

void setup() {
  
  lcd.begin(16, 2);  
  lcd.backlight();    

 
  pinMode(redPin, OUTPUT);
  pinMode(greenPin, OUTPUT);
  pinMode(bluePin, OUTPUT);


  lcd.setCursor(0, 0);
  lcd.print("Air Quality:");
  delay(1000);
}

void loop() {

  int airQuality = analogRead(mq135Pin);        
  airQuality = map(airQuality, 0, 4095, 0, 500);  

 
  lcd.setCursor(0, 1);            
  lcd.print("AQI: ");
  lcd.print(airQuality);
  lcd.print(" ppm  ");            

  
  if (airQuality < 100) {
    // Good air quality - Green LED
    digitalWrite(redPin, LOW);
    digitalWrite(greenPin, HIGH);
    digitalWrite(bluePin, LOW);
  } else if (airQuality < 200) {
    // Moderate air quality - Yellow (Red + Green)
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, HIGH);
    digitalWrite(bluePin, LOW);
  } else {
    // Poor air quality - Red LED
    digitalWrite(redPin, HIGH);
    digitalWrite(greenPin, LOW);
    digitalWrite(bluePin, LOW);
  }

  delay(1000);  
}