Automated Soil Moisture Sensing & Plant Watering System with Arduino

Under-watering causes wilting; over-watering leads to root rot. This automated drip irrigation system samples capacitive soil moisture levels every hour, activates a miniature submersible 5V water pump when soil falls below dry thresholds, and shuts off automatically once the target saturation is achieved.

1. Parts List

• 1× Arduino Nano / UNO
• 1× Capacitive Soil Moisture Sensor v1.2 (corrosion-resistant)
• 1× 5V Submersible Water Pump with Silicon Tubing
• 1× 5V Relay Module or TIP120 Darlington Transistor
• 1× 1N4007 Flyback Diode (absorbs pump kickback)
• 1× Water reservoir container

2. Arduino Code

cpp
const int SENSOR_PIN = A0;
const int PUMP_PIN = 7;

// Calibrate these values with dry air vs wet soil
const int DRY_THRESHOLD = 650;
const int WET_THRESHOLD = 380;

void setup() {
  Serial.begin(9600);
  pinMode(PUMP_PIN, OUTPUT);
  digitalWrite(PUMP_PIN, HIGH); // Relay off
}

void loop() {
  int moisture = analogRead(SENSOR_PIN);
  Serial.print("Soil Moisture Value: ");
  Serial.println(moisture);

  if (moisture > DRY_THRESHOLD) {
    Serial.println("Soil is Dry! Pumping water...");
    digitalWrite(PUMP_PIN, LOW); // Relay ON
    delay(3000);                 // Pump for 3 seconds
    digitalWrite(PUMP_PIN, HIGH);// Relay OFF
    delay(10000);                // Wait for water to seep through
  } else {
    Serial.println("Soil moisture is optimal.");
    delay(5000);
  }
}