Features
- Analog capacitive soil moisture sensing
- Uses capacitive sensing instead of resistive sensing
- Corrosion resistant material for long service life
- Provides real time soil moisture data
- Onboard voltage regulator
- Operating voltage range from 3.3 V to 5.5 V
Principle of Work
A capacitor consists of two conductive plates separated by a dielectric material. A capacitive soil moisture sensor works by detecting changes in capacitance caused by variations in the dielectric properties of the soil. Water content significantly affects the dielectric constant of the soil.
The sensor does not directly measure water since pure water is a poor electrical conductor. Instead it measures the ions dissolved in the moisture. A 555 timer based circuit converts the capacitance into a proportional voltage which is then read using an analog to digital converter and converted into a soil moisture percentage.
Pinout of the Module
| Pin | Description |
|---|---|
| GND | Ground connection 0 V |
| VCC | Power supply 3.3 V or 5 V |
| AOUT | Analog output proportional to soil moisture level |
Applications
- Gardening monitoring systems
- Automatic watering systems
Circuit
Connect the GND pin to Arduino ground and the VCC pin to Arduino 5 V or 3.3 V. Connect the AOUT pin to analog pin A0 on the Arduino board.
Library
No external library is required to use this sensor.
Example Code
const int AirValue = 600;
const int WaterValue = 350;
int soilMoistureValue = 0;
int soilMoisturePercent = 0;
void setup() {
Serial.begin(9600);
}
void loop() {
soilMoistureValue = analogRead(A0);
Serial.println(soilMoistureValue);
soilMoisturePercent = map(soilMoistureValue, AirValue, WaterValue, 0, 100);
if (soilMoisturePercent >= 100) {
Serial.println("100 percent");
} else if (soilMoisturePercent <= 0) {
Serial.println("0 percent");
} else {
Serial.print(soilMoisturePercent);
Serial.println(" percent");
}
delay(250);
}
Calibration Procedure
Measure the weight of an empty container and fill it with dry soil up to 200 ml. Record the dry soil weight. Add 10 ml of water mix thoroughly and refill to 200 ml. Record the new weight. Repeat the process until the soil becomes saturated. Spread the soil thinly to dry and record the final dry mass. These measurements are used to calibrate the sensor accurately.
Technical Details
- Operating voltage 3.3 V to 5.5 V DC
- Operating current 5 mA
- Analog output
- Three pin interface
- Dimensions 98 x 23 x 4 mm
- Weight 15 grams
Comparison
Capacitive soil moisture sensors provide better accuracy and longer lifespan compared to resistive sensors by avoiding probe corrosion. They measure dielectric changes in the soil rather than electrical resistance which can be affected by fertilizer and soil composition. Compared to combined soil moisture modules capacitive sensors provide only analog output but offer improved reliability and durability.
Features
- Analog capacitive soil moisture sensing
- Uses capacitive sensing instead of resistive sensing
- Corrosion resistant material for long service life
- Provides real time soil moisture data
- Onboard voltage regulator
- Operating voltage range from 3.3 V to 5.5 V
Principle of Work
A capacitor consists of two conductive plates separated by a dielectric material. A capacitive soil moisture sensor works by detecting changes in capacitance caused by variations in the dielectric properties of the soil. Water content significantly affects the dielectric constant of the soil.
The sensor does not directly measure water since pure water is a poor electrical conductor. Instead it measures the ions dissolved in the moisture. A 555 timer based circuit converts the capacitance into a proportional voltage which is then read using an analog to digital converter and converted into a soil moisture percentage.
Pinout of the Module
| Pin | Description |
|---|---|
| GND | Ground connection 0 V |
| VCC | Power supply 3.3 V or 5 V |
| AOUT | Analog output proportional to soil moisture level |
Applications
- Gardening monitoring systems
- Automatic watering systems
Circuit
Connect the GND pin to Arduino ground and the VCC pin to Arduino 5 V or 3.3 V. Connect the AOUT pin to analog pin A0 on the Arduino board.
Library
No external library is required to use this sensor.
Example Code
const int AirValue = 600;
const int WaterValue = 350;
int soilMoistureValue = 0;
int soilMoisturePercent = 0;
void setup() {
Serial.begin(9600);
}
void loop() {
soilMoistureValue = analogRead(A0);
Serial.println(soilMoistureValue);
soilMoisturePercent = map(soilMoistureValue, AirValue, WaterValue, 0, 100);
if (soilMoisturePercent >= 100) {
Serial.println("100 percent");
} else if (soilMoisturePercent <= 0) {
Serial.println("0 percent");
} else {
Serial.print(soilMoisturePercent);
Serial.println(" percent");
}
delay(250);
}
Calibration Procedure
Measure the weight of an empty container and fill it with dry soil up to 200 ml. Record the dry soil weight. Add 10 ml of water mix thoroughly and refill to 200 ml. Record the new weight. Repeat the process until the soil becomes saturated. Spread the soil thinly to dry and record the final dry mass. These measurements are used to calibrate the sensor accurately.
Technical Details
- Operating voltage 3.3 V to 5.5 V DC
- Operating current 5 mA
- Analog output
- Three pin interface
- Dimensions 98 x 23 x 4 mm
- Weight 15 grams
Comparison
Capacitive soil moisture sensors provide better accuracy and longer lifespan compared to resistive sensors by avoiding probe corrosion. They measure dielectric changes in the soil rather than electrical resistance which can be affected by fertilizer and soil composition. Compared to combined soil moisture modules capacitive sensors provide only analog output but offer improved reliability and durability.