Published August 19, 2025

Portable Arduino-Based Soil Moisture Detection System

Build a compact and reliable soil moisture detector using an Arduino and a moisture sensor—perfect for gardening, small-scale agriculture.

BeginnerShowcase (no instructions)4 hours83

Portable Arduino-Based Soil Moisture Detection System

Things used in this project

Hardware components

Arduino UNO

SparkFun Soil Moisture Sensor (with Screw Terminals)

LED (generic)

Resistor 220 ohm

Breadboard Mates Pi Adaptor

Jumper wires (generic)

Software apps and online services

Microsoft VS Code

Story

Instead of staring at your plants and guessing, why not let a sensor do the talking? With just a soil moisture sensor and a tiny Arduino board, we can measure the water content of the soil and give instant feedback using colored light.

Red light → Soil is too dry, time to water!

Red light → Soil is too dry, time to water!

Green light → Soil moisture is just right.

Green light → Soil moisture is just right.

Blue light → Soil is overly wet, hold off watering.

Blue light → Soil is overly wet, hold off watering.

It’s like giving your plants their own traffic light system 🚦.

🔧 How It Works

The soil moisture sensor reads how much water is present in the soil.

The soil moisture sensor reads how much water is present in the soil.

The Arduino converts this raw sensor value into a percentage (0–100%).

The Arduino converts this raw sensor value into a percentage (0–100%).

Depending on the reading, the RGB LED changes color to visually indicate the soil’s condition.

Depending on the reading, the RGB LED changes color to visually indicate the soil’s condition.

The readings are also printed to the Serial Monitor for debugging and calibration.

The readings are also printed to the Serial Monitor for debugging and calibration.

🧪 Testing the System

I tested it with three simple experiments:

Dry soil (no water) → The sensor reading was high, and the LED glowed red.

Dry soil (no water) → The sensor reading was high, and the LED glowed red.

Moist soil (moderately watered) → The LED turned green, signaling healthy conditions.

Moist soil (moderately watered) → The LED turned green, signaling healthy conditions.

Wet soil (after heavy watering) → The LED switched to blue, showing the soil was too wet.

Wet soil (after heavy watering) → The LED switched to blue, showing the soil was too wet.

🚀 Next Steps

This basic project can be expanded in many exciting directions:

Hook it up to a relay + water pump for automatic irrigation.

Hook it up to a relay + water pump for automatic irrigation.

Send data to the cloud using Wi-Fi/Bluetooth modules.

Send data to the cloud using Wi-Fi/Bluetooth modules.

Add an OLED display to show real-time moisture percentage.

Add an OLED display to show real-time moisture percentage.

What started as a fun weekend build turned into a useful gardening companion. Now, instead of guessing when to water, I just look at the LED.

Code

Soil Moisture code

// Pin definitions
#define MOISTURE_PIN A1     // Analog pin for soil moisture sensor
#define LED_R 6             // Red channel of RGB LED
#define LED_G 5             // Green channel of RGB LED
#define LED_B 3             // Blue channel of RGB LED

void setup() {
  // Configure RGB pins as outputs
  pinMode(LED_R, OUTPUT);
  pinMode(LED_G, OUTPUT);
  pinMode(LED_B, OUTPUT);

  // Start serial communication
  Serial.begin(9600);
}

void loop() {
  // Read raw analog value from soil sensor
  int rawValue = analogRead(MOISTURE_PIN);
  Serial.print("Raw Moisture Value: ");
  Serial.println(rawValue);

  // Convert raw sensor data to percentage (0 = dry, 100 = wet)
  int percentMoisture = map(rawValue, 1023, 0, 0, 100);

  // Control RGB LED colors based on soil condition
  if (percentMoisture < 35) {
    setRGB(255, 0, 0);   // Red → Soil is dry
  } 
  else if (percentMoisture >= 35 && percentMoisture <= 70) {
    setRGB(0, 255, 0);   // Green → Soil is healthy
  } 
  else {
    setRGB(0, 0, 255);   // Blue → Soil is too wet
  }

  delay(1000); // Delay for stability
}

// Function to update RGB LED using PWM values
void setRGB(int redVal, int greenVal, int blueVal) {
  analogWrite(LED_R, redVal);
  analogWrite(LED_G, greenVal);
  analogWrite(LED_B, blueVal);
}