MQ Gas Sensors – Initialization (Qwiic)

In this example, we will go over how to initialize the Qwiic version of the MQ sensor.

Connections for this example

First, we have to include the library, specify the number of readings the sensor will take during the calibration procedure, and create an instance of the MQ sensor object:

// Include the library
#include <MQ-Sensor-SOLDERED.h>

// How many R0 readings to take to get an average measurement
#define numOfCalibrations 10 

// Create an instance of the sensor object
MQ8 mq8;

Next, in the setup() function, we are initializing the serial communication as well as the sensor.

// Initialize the serial port communication at 115200 baud. It's used to print measured data.
Serial.begin(115200);

// Initialize I2C connection with the sensor; if it fails, inform the user
if(!mq8.begin(0x30))
{
    Serial.println("Failed to initialize I2C communication, check wiring");
    while(1)
    {}
}

mq8.begin(int _addr)

Initializes the MQ sensor, setting up communication over I2C and configuring its regression method.

Returns value: Boolean value; returns true if the sensor was successfully initialized, false otherwise.

Function parameters:

Type	Name	Description
int	_addr	Specifies the I2C address of the sensor

Next, we have to calibrate the sensor. Calibration is done in a clean air environment after the sensor has been heated. You can find preheat times for the sensor in their datasheets, which are linked here. All the calibration does is take measurements of the resistance, which will be used later for resistance measurements in an environment with the specific gas calculated.

// In the setup() function...

/*****************************  MQ Calibration ********************************************/
// Explanation:
// In this routine, the sensor will measure its resistance after it has been pre-heated for 48h
// and is now in a clean air environment, and it will set up the R0 value.
// This routine does not need to be executed on every restart; you can load your R0 into flash memory and read it on startup

Serial.print("Calibrating please wait.");
bool calibrationResult = mq8.calibrateSensor(numOfCalibrations);
if(!calibrationResult) // Check if the sensor was properly calibrated
{
  Serial.println("There was an error reading the sensor, check connection and try again");
  while(1)
  {}
}
Serial.print("Calibration done!");

/*****************************  MQ Calibration ********************************************/

mq8.calibrateSensor(int numOfCalibrations)

Calibrates the sensor by taking multiple readings and averaging them.

Returns value: Boolean value; true if calibration is successful, false if the calculated R0 is invalid.

Function parameters:

Type	Name	Description
int	numOfCalibrations	Number of calibration readings to take

Full example

See the full example below:

// Include the library
#include <MQ-Sensor-SOLDERED.h>

// How many R0 readings to take to get an average measurement
#define numOfCalibrations 10 

// Create an instance of the sensor object
MQ8 mq8;

void setup()
{
    // Initialize the serial port communication at 115200 baud. It's used to print measured data.
    Serial.begin(115200);

    // Initialize I2C connection with the sensor; if it fails, inform the user
    if(!mq8.begin(0x30))
    {
      Serial.println("Failed to initialize I2C communication, check wiring");
      while(1)
      {}
    }

    /*****************************  MQ Calibration ********************************************/
    // Explanation:
    // In this routine, the sensor will measure its resistance after it has been pre-heated for 48h
    // and is now in a clean air environment, and it will set up the R0 value.
    // This routine does not need to be executed on every restart; you can load your R0 into flash memory and read it on startup
    
    Serial.print("Calibrating please wait.");
    bool calibrationResult = mq8.calibrateSensor(numOfCalibrations);
    if(!calibrationResult) // Check if the sensor was properly calibrated
    {
      Serial.println("There was an error reading the sensor, check connection and try again");
      while(1)
      {}
    }
    Serial.print("Calibration done!");

    /*****************************  MQ Calibration ********************************************/
}

void loop()
{
  
}