The sensor used is the GH-312 and from the datasheet it is capable of sensing gases like smoke, liquefied gas, butane and propane, Methane, alcohol, hydrogen, etc.
I've used a 9V
battery for this project because the sensor requires a 9V input. The output when the sensor is triggered is always 5V which is perfect for a direct connection to any microcontroller. Although I've used a 9V battery, any 12V power supply ( a small wall transformer for example ) will work perfectly since the sensor can handle from 9V up to 20V and the microcontroller's voltage is regulated by a 7805 regulator.
The first tests were made with the
circuit mounted on a breadboard. After initialization the circuit will enter a normal state where it detects no gas. The display shows "Sensing...No Gas !".
To test the sensor I used my portable gas soldering iron with the gas coming out pointed to the sensor. The sensor is able to detect the gas and the microcontroller will trigger a flashing led warning and sound. The sound is produced by a small piezo and the display show the message "Found Gas".