Matrix - MQ-2 Gas Sensor

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1 Introduction

MQ-2 Gas Sensor

• The Matrix-MQ-2_Gas_Sensor uses the MQ-2 gas sensor which is sensitive to LPG, i-butane, propane, methane ,alcohol, Hydrogen, smoke and etc and is used to detect multiple gas leakage. This makes it suitable in various applications of gas leak detection.
• The output voltage of the module is positively proportional to the gas concentration.

2 Features

• Standard 3 Pin Interface
• PCB Dimension(mm): 24 x 32

• Pin Description:

Pin	Description
S	GPIO
V	Supply Voltage 5V
G	Ground

3 Basic Device Operation

• The MQ-2_Gas_Sensor module mainly consists of a MQ-2 gas sensor which is stable and responsive. The sensor uses SnO2 as its gas sensitive material. When its surrounding environment has combustible gases its conductivity change is positively proportional to the gas concentration and this change will be converted to analog output signals. Its sensitivity can be adjusted via the potentiometer.

4 Applications

The Matrix-MQ_2_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:

Matrix-MQ_2_Gas_Sensor
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:

Matrix-MQ_2_Gas_Sensor
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:

Matrix-MQ-2_Gas_Sensor
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:
Matrix-MQ-2_Gas_Sensor_NanoPC-T2

Connection Details:

Matrix-MQ-2_Gas_Sensor
GND	NanoPC-T2 USB Host GND
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 https://github.com/friendlyarm/matrix.git

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

当有液化气、丙烷、氢气、天然气等泄露时会检测到事件，气体的浓度越大，读取到的值越大。 When there is leakage of gases e.g. LPG, i-butane, propane, methane ,alcohol, Hydrogen, smoke and etc an event will be triggered and detected.The more the density of gas is the more the value will be.

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

8 Update Log

8.1 Feb-24-2016

• Added Sections 1, 2, 3 and 4

8.2 June-21-2016

• Re-organized and simplified wiki