Soil Moisture Sensor Arduino Code

8 in 1 Soil moisture sensor Rs485 for arduino

In this guide, we will explore how to interface a 8 in1 Soil Moisture & Temperature Sensor with Arduino using the RS485 protocol. This setup will allow us to monitor the moisture content and temperature of the soil, which are crucial parameters for agriculture and gardening.

Soil moisture sensors measure the volumetric water content in soil. By understanding the moisture levels, farmers and gardeners can make informed decisions about irrigation, ensuring optimal plant growth. The temperature of the soil also plays a significant role in plant health, affecting root growth and nutrient uptake.

For this project, we will utilize the Niubol 8 in1 Soil Moisture & Temperature Sensor, which is specifically designed for in-ground measurements. 

Therefore we are using Industrial Grade Soil Sensor for this project. To interface the sensor with the Arduino, we will use the RS485 communication protocol. The data from the Soil Moisture & Temperature Sensor will be presented on an OLED screen connected to the Arduino.

Here are the 4 wires for the sensor:

Brown Wire:  VCC (5V-24V)

Black Wire: GND

Yellow Wire: RS485-A

Blue Wire: RS485-B

Requirements:

Hardware

DFRduino UNO R3 (or similar) x 1

RS485 Shield for Arduino x1

RS485 Soil Sensor(Temperature & Moisture & EC & Salinity & Ph & NPK) x 1

Software:

Arduino IDE

Here is a connection mapping between MAX485 & Soil Humidity Temperature Sensor.

VCC -> 5V (Soil Sensor)

GND  -> GND (Soil Sensor)

A (MAX485) -> Soil Sensor A Pin (Yellow Color)

B (MAX485) -> Soil Sensor B Pin (Blue Color)

Soil Humidity Temperature Sensor Connection with Arduino. You may use a breadboard for assembly and a jumper wires for connecting the sensor and RS485 Module with Arduino.

Source Code/Program for Reading 8 in1 Soil Moisture & Temperature 

Source Code Program for Reading Soil Moisture sensor.txt

#include <SoftwareSerial.h>

// Define the pins for RS485 communication

#define RO 2

#define DI 3

#define RE 8

#define DE 7

#define RESPONSE_FRAME_SIZE 21

char sensorDataTextBuffer[200];

struct SoilSensorData

{

  bool isSensorTimeout {false};

  bool isValid {false};

  float temperature {-1.0};

  float humidity {-1.0};

  unsigned int conductivity {-1};

  float ph {-1.0};

  unsigned int nitrogen {-1};

  unsigned int phosphorus {-1};

  unsigned int potassium {-1};

  unsigned int salinity {-1};

};

class SoilSensor

{

  public:

    SoilSensor()

    {

      modbus = new SoftwareSerial(RO, DI);

    }

    void initialise()

    {

      Serial.begin(9600); // Initialize serial communication for debugging

      modbus->begin(9600);    // Initialize software serial communication at 9600 baud rate

      pinMode(RE, OUTPUT); // Set RE pin as output

      pinMode(DE, OUTPUT); // Set DE pi

    }

    void sendDataRequest()

    {

      digitalWrite(DE, HIGH);

      digitalWrite(RE, HIGH);

      delay(10);

      // Send the request frame to the soil sensor

       modbus->write(soilSensorRequest, sizeof(soilSensorRequest));

    }

    SoilSensorData read()

    {

      SoilSensorData soilSensorData;

       // End the transmission mode and set to receive mode for RS485

      digitalWrite(DE, LOW);

      digitalWrite(RE, LOW);

      delay(10);     

      //Wait for the response from the sensor or timeout after 1 second

      unsigned long startTime = millis();

      while (modbus->available() < RESPONSE_FRAME_SIZE && millis() - startTime < 1000)

      {

        delay(1);

      }

      if (modbus->available() >= RESPONSE_FRAME_SIZE) // If valid response received

      {

       // Read the response from the sensor

        byte index = 0;

        while (modbus->available() && index < RESPONSE_FRAME_SIZE)

        {

          soilSensorResponse[index] = modbus->read();

          index++;

        }

                soilSensorData = computeData();

      }

      else

      {

        soilSensorData.isSensorTimeout = true; 

      }

       return soilSensorData;

    } 

    ~SoilSensor()

    {

      if (modbus != nullptr) delete modbus;

      delete[] soilSensorResponse;

    }

    private:

    const byte soilSensorRequest[8] = {0x01, 0x03, 0x00, 0x00, 0x00, 0x08, 0x44, 0x0C};

    SoftwareSerial* modbus = nullptr;

    byte soilSensorResponse[RESPONSE_FRAME_SIZE];   

    int convertBytesToDecimal(unsigned int offset)

    {

      return soilSensorResponse[offset] * 256 + soilSensorResponse[offset + 1];

    }

    SoilSensorData computeData() const

    {

      SoilSensorData soilSensorData;

      if (soilSensorResponse[0] != 1 || soilSensorResponse[1] != 3 || soilSensorResponse[2] != 16)

      {

        soilSensorData.isValid = false;

        return soilSensorData;

      }

      soilSensorData.isValid = true;

      soilSensorData.temperature = convertBytesToDecimal(3) / 10.0; //degrees celcius

      soilSensorData.humidity = convertBytesToDecimal(5) / 10.0; // percent

      soilSensorData.conductivity = convertBytesToDecimal(7); // microSiemens per centimetre

      soilSensorData.ph = convertBytesToDecimal(9) / 100.0;

      soilSensorData.nitrogen = convertBytesToDecimal(11); // miligram per Kilogram

      soilSensorData.phosphorus = convertBytesToDecimal(13); // miligram per Kilogram

      soilSensorData.potassium = convertBytesToDecimal(15); // miligram per Kilogram

      soilSensorData.salinity = convertBytesToDecimal(17); // miligram per Kilogram

      return soilSensorData;

    }

 };

SoilSensor soilSensor;

void writeSensorDataToString(SoilSensorData & sensorData)

{

  if (sensorData.isSensorTimeout)

  {

      sprintf(sensorDataTextBuffer, "Incomplete data or sensor time out");  

  }

  else

  {

    if (sensorData.isValid)  

    {

      char* tempStr = malloc(6 * sizeof(char));

      char* humidityStr = malloc(6 * sizeof(char));

      char* phStr = malloc(6 * sizeof(char));

      dtostrf(sensorData.temperature, 4, 1, tempStr);

      dtostrf(sensorData.humidity, 4, 1, humidityStr);

      dtostrf(sensorData.ph, 4, 2, phStr);

      auto conductivity = sensorData.conductivity;

      auto n = sensorData.nitrogen;

      auto p = sensorData.phosphorus;

      auto k = sensorData.potassium;

      auto salinity = sensorData.salinity;

      sprintf(sensorDataTextBuffer, "Temperature: %s; Humidity: %s; Conductivity: %u; PH: %s; N: %u; P: %u; K: %u; Salinity: %u", tempStr, humidityStr, conductivity, phStr, n, p, k, salinity);  

      if (tempStr != NULL) free(tempStr);

      if (humidityStr != NULL) free(humidityStr);

      if (phStr != NULL) free(phStr);

    }

    else

    {

      sprintf(sensorDataTextBuffer, "Data read from sensor is invalid");  

    }

  }

}

void setup() 

{

 soilSensor.initialise();

}

void loop() 

{

  soilSensor.sendDataRequest();

  SoilSensorData sensorData = soilSensor.read();

  writeSensorDataToString(sensorData);

  Serial.println(sensorDataTextBuffer);

  delay(2000); // Wait for a second before the next loop iteration

}

Thanks to Phil Ogun for the code!

The 8-in-1 Soil Sensor is a sensor that integrates multiple parameters such as temperature, humidity, conductivity, NPK, salinity, and PH. With such a sensor, users can easily access multiple key data of the soil, helping them to better understand the condition of the soil and make adjustments and decisions accordingly.

By measuring the dielectric constant of soil, it can directly and stably reflect the real moisture content of various soils. It is suitable for soil moisture monitoring, scientific experiments, water-saving irrigation, greenhouses, flowers and vegetables, grass pastures, soil quick test, plant cultivation, sewage treatment, fine agriculture and other occasions. The sensor's input power supply, sensing probe, signal output three parts are completely isolated, safe and reliable, beautiful appearance, easy to install, the probe is made of stainless steel, corrosion resistance, stable performance.

Soil Sensor Data Sheet：

1.NBL-S-THR Soil Temperature Moisture Sensor datasheet

NBL-S-THR-Soil-temperature-and-moisture-sensors-Instruction-Manual-V4.0.pdf

2. NBL-S-TMC Soil Temperature Moisture EC Sensor datasheet

NBL-S-TMC-Soil-temperature-and-moisture-conductivity-sensor.pdf

3. NBL-S-TM Soil Temperature Moisture Sensor datasheet

NBL-S-TM-Soil-temperature-and-moisture-sensor-Instruction-Manual-4.0.pdf

4. NBL-S-TMCS Soil Temperature, Moisture, Conductivity and Salinity Integrated Sensor

NBL-S-TMCS-Soil-Temperature-Humidity-Conductivity-and-Salinity-Sensor.pdf

5. NBL-S-TMCS-7 Soil Temperature, Moisture, NPK, Conductivity and pH Integrated Sensor

7-in-1-Soil-Composite-Sensor-Manual.pdf

4. NBL-S-TMCS-8 Soil Temperature, Moisture, NPK, pH, Conductivity and Salinity Integrated Sensor

8-in-1-Soil-Composite-Sensor-Manual.pdf