MQ2 gas/smoke sensor

Hello, new Arduino user here. Having fun so far but I have a question about a sensor called the "MQ2". It is a gas sensor but it is also advertised as a Smoke sensor. Would this mean I could use it as a smoke detector to detect cigarette smoke?

I run a small 12 room motel in Michigan where state law prohibits smoking in hotel/motel rooms. I have battery operates smoke detectors in the rooms, however, sometimes guests remove the batteries just long enough to smoke and air out the room.

I would like to possibly build an added line of defence. An arduino-based smoke detector that reports back to me wirelessly when smoke is detected. It would be hard wired to power, but would NOT replace the current ones in the rooms, but would be an added and more intelligent component.

Has anyone had experience with these sensor (MQ2) and do they detect cigarette smoke reliably?

Would it not be easier to create a battery removed detector? It would involve just 2 wires from every detector to the central reception.

  • Most simple form you need 2 arduino’s each monitoring 6 batteries.
    make a voltage dividers +9V–[ R1 ] —±–[ R2 ]— GND (R1 = ~20K, R2 = ~10K)
    A measurement with an analogRead() at the + would give you approx 3 volt. (readings around 600)
    You can copy that 6 times for the six analog inputs of an arduino board
    As you have 12 rooms you need 2 Arduino’s,

The minimal code looks like: (not tested as I don’t smoke :wink:

// int room[] = { 1,2,3,4,5,6 };
int room[] = { 7,8,9,10,11,12 };

void setup()
  Serial.begin("Smoke monitor");

void loop()
  for (Int i = 0; i< 6; i++)
     int x = analogRead(i);
     if (x < 500 || x > 700) 
        Serial.print("Battery low in room ");
        Serial.println( room[i] );
        // doBUZZ();

The advantage of this approach is that you will not only detect removed batteries by smoking guests,
but you will also detect low batteries which increases the safety of your (non smoking) guests …

my 2 cents …

I don’t know if taping the vents also disables smoke detectors, but monitoring batteries wouldn’t fix that.

Also, adding circuitry to the smoke detector might be frowned upon by an inspector.

As you have 12 rooms you need 2 Arduino's,

Or may be one arduino mega or to multiplex the analog pins of one arduino ino/duemilanove board...

Just only ideas to have on mind. Cheers,

The wikipedia article on smoke detectors only mentions ionisation and optical detectors - if the MQ2 is very sensitive to carbon monoxide it might be useful - perhaps you need to experiment to see if it works at all.