Arduino - Capacitive Soil Moisture Sensor

Arduino Jul 30, 2020

This tutorial will go over how to use a Capacitive Soil Moisture Sensor 🌱

Supplies

(1) Arduino Mega2560
(1) Capacitive Soil Moisture Sensor

For reference I have included the pinout diagram for the Arduino Mega2560

Setup

Connecting the Capacitive Soil Moisture Sensor to the Mega2560 is as easy connecting:

GND -> GND
VCC -> 3.3v
AOUT -> A0

Capacitive Soil Moisture Sensor Setup Diagram

Calibration

Capacitive Soil Moisture Sensors require calibration before use by doing the following;

Get the value when the sensor is exposed to the air
Get the value when the sensor is in water

void setup() {
  Serial.begin(9600); // open serial port, set the baud rate to 9600 bps
}

void loop() {
  Serial.println(analogRead(A0));
  delay(250);
}

Code

Once you get the numbers from the calibration above, put those numbers as the defaults for AirValue and WaterValue.

const int AirValue = ?;   // This is the value of your sensor when you place it in the open air
const int WaterValue = ?;  // This is the value when you place your sensor in a glass of water

int value = 0;
int percent = 0;

void setup() {
  Serial.begin(9600); // open serial port, set the baud rate to 9600 bps
}

void loop() {
  value = analogRead(A0);

  percent = map(value, AirValue, WaterValue, 0, 100);
  
  if (percent > 100) {
    Serial.print(value);
    Serial.print(" | ");
    Serial.println("100 %");
  } else if (percent < 0) {
    Serial.print(value);
    Serial.print(" | ");
    Serial.println("0 %");
  } else if (percent > 0 && percent < 100) {
    Serial.print(value);
    Serial.print(" | ");
    Serial.print(percent);
    Serial.println("%");
  }
  delay(250);
}