#define MQ2pin A0
int LED=13;
float sensorValue; //variable to store sensor value
void setup()
{
  Serial.begin(9600); // sets the serial port to 9600
  pinMode(MQ2pin, INPUT);
  pinMode(13,OUTPUT);
  Serial.println("MQ2 warming up!");
  delay(20000); // allow the MQ2 to warm up
}
void loop()
{
 sensorValue = analogRead(MQ2pin); // read analog input pin 0
 Serial.print("Sensor Value: ");
 Serial.println(sensorValue);
  if(sensorValue > 350)
  {
  Serial.println(" | Smoke detected!");
  digitalWrite(LED,HIGH);
  }
  else
  {
  Serial.println(" NO Smoke detected!");
  digitalWrite(LED,LOW);
  }
 delay(2000); // wait 2s for next reading
}