#define MQ135_PIN 34   // Analog pin for MQ-135
#define BUZZER_PIN  26 // Buzzer pin
#define GREEN_LED   19 // Green LED (Safe)
#define RED_LED     21 // Red LED (Danger)

int threshold = 200;   // Adjust based on environment calibration

void setup() {
    Serial.begin(115200);
    pinMode(BUZZER_PIN, OUTPUT);
    pinMode(GREEN_LED, OUTPUT);
    pinMode(RED_LED, OUTPUT);
}

void loop() {
    int gasValue = analogRead(MQ135_PIN); // Read gas sensor value
    Serial.print("Gas Level: ");
    Serial.println(gasValue);

    if (gasValue > threshold) {  
        digitalWrite(RED_LED, HIGH);   // Turn on danger LED
        digitalWrite(GREEN_LED, LOW);  // Turn off safe LED
        digitalWrite(BUZZER_PIN, HIGH); // Activate buzzer
        Serial.println("Warning! Harmful gas detected!");
    } else {
        digitalWrite(RED_LED, LOW);
        digitalWrite(GREEN_LED, HIGH);
        digitalWrite(BUZZER_PIN, LOW);
        Serial.println("Air quality is safe.");
    }

    delay(1000); // Wait 1 second before next reading
}