There are some very low cost MQ-2 sensors  ($3-$5) that can be used to measure common combustible gases such as hydrogen, butane, methane, propane and liquid petroleum gas (LPG).

My goal for this project was to make a handheld monitor that we could use to measure potential leaks in our propane BBQ or natural gas leaks in and around our furnace.

Setup

For our setup we used:

• a MQ-2 sensor
• 4 digit LED display ($3)
• Arduino Nano
• Small bread board
• USB battery charger
• jumpers and duct tape

Some duct tape can be used to secure the bread board to the USB battery unit. We used a low cost 4 digit display and we mounted it direct to the bread board.

Code

We were only interested in a “GAS” or “NO GAS” reading, so because of this our code was super simple.

#include <Arduino.h>
#include <TM1637Display.h>

// Module connection pins (Digital Pins)
#define CLK 2
#define DIO 3
TM1637Display display(CLK, DIO);

int smokeA0 = A0;
// Your threshold value
int sensorThres = 400;

void setup() {
  pinMode(smokeA0, INPUT);
  Serial.begin(9600);
  display.setBrightness(0x0f);
}

void loop() {
  int analogSensor = analogRead(smokeA0);

  Serial.print("Pin A0: ");
  Serial.println(analogSensor);
  display.showNumberDec(analogSensor, false);
  delay(1000);
}

If you want to get accurate gas measurements then you’ll need to do some calibration. We were only interested in a seeing something above a “clear air” reading.  For our setup a “clear air” reading was about 100-115. To test our project we used a butane lighter and we open it very quickly (<1 second).