This Gas sensor will allow the user to measure gases such as carbon monoxide and methane as well as flammable gases and act as a breathalyzer.

Step 1: Acquire Parts

Gas Sensor Breakout Board * 4

MQ-7 carbon monoxide, MQ-4 methane, MQ-3 alcohol, MQ-6 LPG (liquefied petroleum gas)

Jump Wires

RGB LED Common Anode * 1

10k Ohm Resistors * 4, 100 Ohm Resistors * 2, 220 Ohm Resistors * 1

Bread Board for Testing

Arduino Uno

USB a to B Cable

LCD Screen

Power Supply for Arduino Uno

Step 2: Breakout Board Prep

Solder wires to each of the breakout boards and attach a sensor to each board.

Step 3: Wiring

https://goo.gl/DvbR9V

The link above redirects you to a website that supplies a schematic. Use the part of the schematic responsible for connecting the sensor to the Arduino and replicate for each additional sensor added. You can have a maximum of four sensors with an Arduino Uno, however you can have more if you used a larger Arduino, i.e. an Arduino Mega.

Step 4: Code

We found some example code for the LCD display; we modified it to show the sensor names and values in real time.The code can be downloaded in from the attached file.

Step 5: Testing and Burn In

Burn in and test each sensor individually. For the burn in, leave the sensor wired up and the Arduino on over night, it may get warm so make sure it has space to cool.