#include <LiquidCrystal.h>
#include <DHT.h>

#define MQ135_PIN A0         // MQ-135 Gas Sensor pin
#define DHTPIN 2             // DHT sensor pin
#define PIR_PIN 3            // PIR sensor pin
#define BUZZER_PIN 4         // Buzzer pin
#define DHTTYPE DHT11        // DHT sensor type

LiquidCrystal lcd(7, 8, 9, 10, 11, 12);
DHT dht(DHTPIN, DHTTYPE);

int gasThreshold = 300;      // Gas detection threshold
float tempThreshold = 50.0;  // Temperature threshold for fire

void setup() {
  Serial.begin(9600);
  dht.begin();
  lcd.begin(16, 2);
  lcd.print("Fire & Gas Alarm");
  delay(2000);
  lcd.clear();

  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(PIR_PIN, INPUT);
}

void loop() {
  // Read sensor values
  int gasLevel = analogRead(MQ135_PIN);
  float temperature = dht.readTemperature();
  int motionDetected = digitalRead(PIR_PIN);

  // Display sensor readings
  lcd.clear();
  lcd.setCursor(0, 0);
  lcd.print("Gas: " + String(gasLevel));
  lcd.setCursor(0, 1);
  lcd.print("Temp: " + String(temperature) + "C");
  delay(1000);

  // Check for gas and fire
  if (gasLevel > gasThreshold || temperature > tempThreshold || motionDetected == HIGH) {
    digitalWrite(BUZZER_PIN, HIGH); // Turn on buzzer
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("ALERT!");
    lcd.setCursor(0, 1);
    lcd.print("FIRE/GAS DETECTED");
    delay(2000);
  } else {
    digitalWrite(BUZZER_PIN, LOW); // Turn off buzzer
  }
}