// Mine Safety Gas Detection System
// ESP32 + MQ2 Gas Sensor + Buzzer + LED
// For detecting hazardous gases in mines

#define MQ2_ANALOG_PIN 34  // Analog pin for MQ2 gas sensor (AO)
#define BUZZER_PIN 2       // Digital pin for buzzer
#define LED_PIN 23         // Digital pin for warning LED
#define GAS_THRESHOLD 2000  // Gas threshold value (mid-range for safety)

void setup() {
  Serial.begin(115200);
  
  // Initialize pins
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  pinMode(MQ2_ANALOG_PIN, INPUT);
  
  // Initial state - safe
  digitalWrite(BUZZER_PIN, LOW);
  digitalWrite(LED_PIN, LOW);
  
  Serial.println("Mine Safety Gas Detection System Initialized");
  Serial.println("Monitoring gas levels...");
  delay(2000); // Sensor warm-up time
}

void loop() {
  // Read gas sensor value
  int gasValue = analogRead(MQ2_ANALOG_PIN);
  
  // Display readings on serial monitor
  Serial.print("Gas Level: ");
  Serial.print(gasValue);
  Serial.print(" (Range: 843-4041)");
  
  // Check if gas level exceeds threshold
  if (gasValue > GAS_THRESHOLD) {
    // Danger - activate alarm
    digitalWrite(LED_PIN, HIGH);
    tone(BUZZER_PIN, 1000); // 1kHz alarm tone
    Serial.println(" - DANGER: Gas detected!");
  } else {
    // Safe - deactivate alarm
    digitalWrite(LED_PIN, LOW);
    noTone(BUZZER_PIN);
    Serial.println(" - Safe");
  }
  
  delay(500); // Check every 500ms
}