#define DO_PIN 14  // D14 or GPIO14 connected to DO pin of the MQ2 sensor

void setup() {
  Serial.begin(9600);
  pinMode(DO_PIN, INPUT);

  Serial.println("Warming up the MQ2 sensor");
  delay(20000);  // wait for the MQ2 to warm up
}

void loop() {
  int gasState = digitalRead(DO_PIN);

  if (gasState == HIGH)
    Serial.println("The gas is NOT present");
  else
    Serial.println("The gas is present");
}
								
							
							

	
								
/**/

const int mq2Pin = 36;
float sensorValue = 0; 

void setup() {
  Serial.begin(9600); 
  pinMode(mq2Pin, INPUT);
}

void loop() {

  sensorValue = analogRead(mq2Pin);
  
  Serial.println("Sensor Value: "+String(sensorValue));

  if(sensorValue>300 )
  {
    Serial.println("found gas");
  }
  else
  {
    Serial.println("no gas");
  }
  
  delay(1000); 
}