Matrix - Soil Moisture Sensor

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Introduction

Soil Moisture Sensor Module
  • The Matrix-Soil_Moisture_Sensor is a simple and straightforward-to-use soil moisture detection module.
  • Before plug the module to a target soil make sure the target soil doesn’t contain rocks. Then point the pads perpendicular to the soil, push it in and make the module close contact to the soil and the module will output analog signals which are proportional to the soil’s moisture condition.
  • To improve the test result it is suggested to take the average of multiple test results.
  • The test result can be influenced by various factors: soil density, soil composition and etc.

Hardware Specification

  • Standard 3 PIN Interface
  • PCB Dimension(mm): 20 x 60

Soil_Moisture_Sensor.PCB

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

Basic Device Operation

  • The resistance of the two pads(probes) is proportional to the moisture of surrounding environment. When the measured soil becomes increasingly drier the output voltage becomes lower and vice versa. The output analog signals of the module can be converted to digital signals (values of soil moisture) via AD conversion.
  • It measures surrounding soil's apparent dielectric constant(ε) and calculates its moisture value(θv).
  • This module uses adc inputs/outputs and converts analog signals to digital signals (moisture value) with PCF8591.

Applications

Connect to NanoPi M1

Refer to the following connection diagram to connect the module to the NanoPi M1:
Matrix-Soil_Moisture_Sensor_nanopi_m1

Connection Details:

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

Connect to NanoPi 2

Refer to the following connection diagram to connect the module to the NanoPi 2:
Matrix-Soil_Moisture_Sensor_nanopi_2

Connection Details:

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

Connect to NanoPi M2/NanoPi 2 Fire

Refer to the following connection diagram to connect the module to the NanoPi M2/ NanoPi 2 Fire:
Matrix-Soil_Moisture_Sensor_nanopi_m2

Connection Details:

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

Connect to NanoPi M3

Refer to the following connection diagram to connect the module to the NanoPi M3:
Matrix-Soil_Moisture_Sensor_nanopi_m3

Connection Details:

Matrix-Soil_Moisture_Sensor
GND NanoPi M3 Pin9
5V NanoPi M3 Pin2
S Matrix-Analog_to_Digital_Converter A0

Connect to NanoPC-T2

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

Connection Details:

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

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

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

Resources

Update Log

August-10-2016

  • Created English wiki