MQ3 Gas Detector for Ethanol

The MQ3 is one of a series of gas detectors and is sensitive to alcohol (ethanol). The same sketch used for the MQ2 can be used and for a discussion on theses gas sensors see my post here.

When placed over a half full glass of wine it gave a reading around 200 and when placed over a small amount of whiskey a reading of around 450 was obtained. This reading over whiskey triggered the digital output.

/* GAS Sensor MQ-3
This sensor detects flammable gasses
the board has four pins
connect AO to Arduino pin A0
connect DO to Arduino pin 2
connect Gnd to Arduino Gnd
connect Vcc to Arduino 5 volts
int sensorPin = A0; // select the input pin for the potentiometer
int DOPin = 2; // select the pin for the LED
int sensorValue = 0; // variable to store the value coming from the sensor

int ledPin =13;
void setup() {

// declare the ledPin as an OUTPUT:
pinMode(DOPin, INPUT);
pinMode(ledPin, OUTPUT);

void loop() {
// read the value from the sensor:
sensorValue = analogRead(sensorPin);
Serial.print("Analog Output = ");
// turn the ledPin on if triggered
if (digitalRead(DOPin) ==HIGH){
digitalWrite(ledPin, LOW);
Serial.println("Digital Output = OFF");
else {
digitalWrite(ledPin, HIGH);
Serial.println("Digital Output = ON");


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