gistfile1.txt

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

LiquidCrystal_I2C lcd(0x27, 16, 2); // Replace 0x27 with your I2C address

const int mq135Pin = A0;  // MQ-135 sensor pin
const int buzzerPin = 8;  // Buzzer connected to pin 8

void setup() {
    Serial.begin(9600);      // Start serial communication
    pinMode(buzzerPin, OUTPUT); // Set buzzer pin as output

    lcd.init();      // Initialize LCD
    lcd.backlight(); // Turn on backlight
    
    lcd.setCursor(0, 0); // Move to first row, first column
    lcd.print("CO2 Level"); // Print message
}

void loop() {
    int sensorValue = analogRead(mq135Pin); // Read sensor value
    Serial.print("MQ-135: ");
    Serial.println(sensorValue * 2.5);
    lcd.setCursor(0, 0); // Move to first row, first column
    lcd.print("CO2 Level"); // Print message
    lcd.setCursor(0, 1); // Move to second row
    lcd.print(sensorValue * 2.5);
    if (sensorValue * 2.5 >= 800) { 
        tone(buzzerPin, 1000);  // Play 1 kHz tone
        delay(500);             // Wait 500ms
        noTone(buzzerPin);      // Stop buzzer
    }
    //lcd.clear();
    delay(100); // Wait for next reading
}