In Indoor Air Quality (IAQ) measurement unit, the MG811 could be used to evaluate the amount of C02 in the air. The aim of this project is to provide a library for simple usage of these modules.

Checkout the docs directory to found intterresting documents about this sensor and the way it operate.

While it is useful to checkout the documents on the sensor, it is important to accentuated that the sensor require 140mA ± 20mA for is heater. So, when using this sensor with multiple others on the Arduino board, make sure to have enought current or it.

This library is quite straightforward.

    MG811 mySensor = MG811(A0) // Analog pin A0

For the sensor's calibration follow the steps describe below:

Power on the sensor

• First step

  • Put the sensor outdoor or indoor with good ventilation
  • Wait at least two (02) hours - for warming up
  • Read it's measurement - You get 400ppm reference voltage

• Second step

  • Put the sensor in a bag filled with exhaled air
  • Wait a couple of minutes
  • Read it's measurement - You get 40000ppm reference voltage

The reference value measured by this function should be used with the begin method in order to use tthe sensor. The methods calibrate help you out with the calibration process.

    mySensor.calibrate()

Note: The sensor must be first calibrated to get some reference value.

After calibration, you can keep going with the following:

    float v400 = 4.535;     // should be set after calibration
    float v40000 = 3.206;   // should be set after calibration
    
    mySensor.begin(v400, v40000); // set the reference value in the library

The sensor could be used then by read raw voltage value or CO2 concentration in ppm

    mySensor.raw();     // read raw value
    mySensor.read();    // read CO2 concentration in ppm