Matrix - MQ-3 Gas Sensor

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1 Introduction

MQ-3 Alcohol sensor
  • The Matrix-MQ_3_Gas_Sensor module uses the MQ-3 gas sensor which is sensitive to alcoholic vapors and thus can be used to detect the density of an alcoholic vapor.
  • The output voltage of the module is non-linear but close to linear to the concentration of alcoholic vapors.
  • In order to increase its accuracy before use it to detect a gas warm it up for one minute as long as it is not overheated.

2 Features

  • Standard 3 PIN header
  • PCB dimension(mm): 24 x 32

MQ-3 Gas Sensor.PCB

  • Pin Description:
Pin Description
V Supply Voltage 5V
G Ground

3 Basic Device Operation

The Matrix-MQ_3_Gas_Sensor module employs a responsive MQ-3 gas sensor. Its gas sensitive material is SnO2. When the alcohol concentration in the air increases the sensor conductivity will increase accordingly and the module will convert the change of conductivity to analog signals. The sensitivity can be adjusted by the potentiometer.

4 Applications

The Matrix-MQ_3_Gas_Sensor module outputs analog signals which can be converted to digital signals through an ADC converter e.g. the Matrix-Analog_to_Digital_Converter module.
For more details about the Matrix-Analog_to_Digital_Converter module refer to wiki: Matrix_-_Analog_to_Digital_Converter.

4.1 Connect to NanoPi M1

Refer to the following connection diagram to connect the module to the NanoPi M1:

Connection Details:

GND NanoPi M1 Pin9
5V NanoPi M1 Pin2
S Matrix-Analog_to_Digital_Converter A0

4.2 Connect to NanoPi 2

Refer to the following connection diagram to connect the module to the NanoPi 2:

Connection Details:

GND NanoPi 2 Pin9
5V NanoPi 2 Pin2
S Matrix-Analog_to_Digital_Converter A0

4.3 Connect to NanoPi M2 / NanoPi 2 Fire

Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire:

Connection Details:

GND NanoPi M2 Pin9
5V NanoPi M2 Pin2
S Matrix-Analog_to_Digital_Converter A0

4.4 Connect to NanoPC-T2

Refer to the following connection diagram to connect the module to the NanoPC-T2:

Connection Details:

5V NanoPC-T2 USB Host 5V
S Matrix-Analog_to_Digital_Converter A0

5 Compile & Run Test Program

Boot your ARM board with Debian and copy the matrix code:

$ apt-get update && apt-get install git
$ git clone

If your cloning is done successfully a "matrix" directory will be generated.

Compile and install Matrix:

$ cd matrix
$ make && make install

Run test program:

$ matrix-adc

Note: this module is not plug and play therefore before running the module please make sure it is connected to an ARM board.
Here is what you should observe:

The channel0 value is 2460

When the concentration of alcoholic vapors reaches a threshold value an event will be triggered. As the concentration increases the value will increase.

6 Code Sample

This Matrix code sample can work with all the ARM boards mentioned in this module's wiki. The name of this code sample is "matrix-analog_to_digital_converter". Here is its source code:

int main(int argc, char ** argv)
    int i = 0;
    int value = 0;
    int channel = 0;
    if (boardInit() < 0) {
        printf("Fail to init board\n");
        return -1;
    if (argc == 2)
        channel = atoi(argv[1]);
    system("modprobe "DRIVER_MODULE);
    signal(SIGINT, intHandler);
    for (i=0; i<ADC_READ_TIMES; i++) {
        if (pcf8591Read(channel, &value) != -1) {
            printf("The channel%d value is %d\n", channel, value);
        } else {
            printf("Fail to get channel%d value\n", channel);
    system("rmmod "DRIVER_MODULE);
    return 0;

For more details about this APIs called in this code sample refer to Matrix API reference manual

7 Resources

8 Update Log

8.1 June-21-2016

  • Created English wiki