#include <Wire.h>
#include <LiquidCrystal_I2C.h>
LiquidCrystal_I2C lcd(0x27, 16, 2);
const int MQ2_PIN = A0; // Potentiometer = MQ2 sensor
const int FAN_PIN = 8; // LED = Fan indicator
const int THRESHOLD = 500; // Above this = poor air
void setup() {
lcd.init();
lcd.backlight();
pinMode(FAN_PIN, OUTPUT);
lcd.setCursor(0, 0);
lcd.print("Air Quality Sys");
delay(2000);
lcd.clear();
}
void loop() {
int airValue = analogRead(MQ2_PIN);
lcd.setCursor(0, 0);
if (airValue > THRESHOLD) {
digitalWrite(FAN_PIN, HIGH); // Fan ON
lcd.print("Air: POOR ");
lcd.setCursor(0, 1);
lcd.print("Fan: ON ");
} else {
digitalWrite(FAN_PIN, LOW); // Fan OFF
lcd.print("Air: GOOD ");
lcd.setCursor(0, 1);
lcd.print("Fan: OFF ");
}
delay(500);
}