Gas Sensors with Arduino + Interfacing Circuit

Question

I am intended to use Gas Sensors (MQ series) on protoboard so I connect it to Arduino and perform analogue read. I would like to request if possible to get the interfacing circuit (resistors, amplification.. etc.) or if there are schematics available.

Also, when I read the data digitized into 10bits ADC value, how can I convert it into units (ppm)?

Thank you so much in advance.

Answer 1

I would suggest checking out one of the gas sensors that comes with a breakout board. I've found the pins don't quite match the spacing of a protoboard and make it a little difficult to set up. Seeed Studio sells some of the sensors with a breakout board and has some nice examples of how to convert the values to PPM.

http://www.seeedstudio.com/wiki/Grove_-_Gas_Sensor(MQ5)

• Badreddine Zebbiche: Thanks @kbuck3 Those SeedStudio sensors are ready to be connected but I believe they need special board as shield for the Arduino. or can we connect them directly if you used them before? Thank you.
• kbuck3: The "special board" they have in the screenshots is just a shield that makes it easy to use the connector cable. You should be able to just use some female-to-male wires and connect the sensor to your protoboard or Arduino.

Answer 2

You can connect the directly to the Arduino +5, Gnd and Signal.

I don't know of any calibration data for the sensors that I have. I suppose you could take the maximum concentration the sensor can measure and divide this by 1024, but I don't know if the value returned is linear or logarithmic.
The data sheet does have some info on, but this page may be more helpful http://forum.arduino.cc/index.php?topic=230945.0

Oh and don't forget the warm up time on the sensors!