Grove Resistive Plant Moisture Sensor

The Grove - Moisture Sensor can be used to detect the moisture of soil. It can be used to decide if the plants in a garden need watering. It can be used in gardens to automate watering plants. It can be used very easily by just inserting the sensor into the soil and reading the output using ADC.

This uses a Grove Analog port.

NOTE: This sensor is not hardened against contamination or exposure of the control circuitry to water and may be prone to electrolytic corrosion across the probes. It is designed for experimenting and prototyping only. It isn’t well suited to being used outdoors.

Features

• Grove compatible interface
• Easy to use

Interpreting the Output

Software for Arduino

The Arduino has a 10 bit ADC (Analog to digital converter). See specifications above.

// Test code for Grove - Moisture Sensor 
int sensorPin = A0; // select the input pin for the moisture sensor
int sensorValue = 0; // variable to store the value coming from the sensor7=

void setup() {
    
    Serial.begin(9600);
}
void loop() {
    // read the value from the sensor:
    sensorValue = analogRead(sensorPin);
    Serial.print("sensor = " );
    Serial.println(sensorValue);
    delay(1000);
}

Software for the Raspberry Pi

(using the 4 Channel 16 bit ADC for the Raspberry Pi)

This Python code snippet is taken from SmartPlantPi. This uses a 16 bit ADC.

            if (config.ADS1115_Present):
                Moisture_Raw   = ads1115.readADCSingleEnded(config.moistureADPin, gain, sps)/7 # AIN0 wired to AirQuality Sensor
                state.Moisture_Humidity   = Moisture_Raw/7
                if (DEBUG):
                        print "Pre Limit Moisture_Humidity=", state.Moisture_Humidity
                if (state.Moisture_Humidity >100):
                    state.Moisture_Humidity = 100;
                if (state.Moisture_Humidity <0):
                    state.Moisture_Humidity = 0;

Specification

• Operating voltage: 3.3~5V
• Operating current: 35mA
• ŸSensor Output Value in dry soil: 0~ 300 (10 bit ADC - 0 - 1024)
• ŸSensor Output Value in humid soil: 300~700 (10 bit ADC - 0 - 1024)
• Sensor Output Value in water: 700 ~ 950 (10 bit ADC - 0 - 1024)
• ŸPCB size: 2.0cm X 6.0cm