int mq3_analogPin = A0; // connected to the output pin of MQ3 void setup(){ Serial.begin(9600); // open serial at 9600 bps } void loop() { // give ample warmup time for readings to stabilize int mq3_value = analogRead(mq3_analogPin); Serial.println(mq3_value); delay(500); //Just here to slow down the output. }