int MQ2_digitalout=13; //Set Digital Input D0 for Mq2.
void setup()
{
  Serial.begin(9600);
  pinMode(MQ2_digitalout,INPUT);
}
void loop()
{
  int value=digitalRead(MQ2_digitalout);
  Serial.println("Sensor value is :");//Prints the value of MQ2 sensor to Serial Monitor.
  Serial.println(value);
  if(value)
  {
    Serial.println("| Smoke detected!");
  }
  else
  {
    Serial.println(" NO Smoke");
  }
}