MG811

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.

How does the sensor work

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

Electricial requirement

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.

Characteristics	Value
Model	MG811
Sensor type	Solid Electrolyte
Target gas	CO2
Detection range	350ppm - 10000ppm
Heater resistance	35Ω ± 3Ω
Heater current	140 ± 20mA
Heater voltage	6.0V ± 0.1V AC or DC
Heater consumption	850mW ± 120mW
Standard working condition	20 ~ 50°C, under 95%RH
Zero point EMF	200mV - 600mV
DEMF output signal	≧ 25mV/1000ppm CO2

Usage

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 values measured should be used with the begin method in order to use the sensor. The method calibrate helps 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 values in the library

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

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