Monitor Soil Moisture with Your Arduino

Find out exactly how wet your plant’s soil is with this Soil Moisture Sensor for Arduino. This resistive-type soil moisture sensor module comes with an LM393 comparator board and a 2-pin soil probe, and it is ideal for Arduino, ESP32 and ESP8266 based plant care and agriculture projects. Push the probe into the soil, connect a few wires, and your board can “read” how much water the soil holds.

Key Features

• Analog and digital output – read exact moisture levels from the analog pin, or get a simple wet/dry signal from the digital pin.
• On-board potentiometer – turn the small preset knob to adjust the sensitivity (the wet/dry threshold) of the digital output.
• 2-pin soil probe with connecting wire – the probe plugs into the driver module through the included wire; just push it into the soil.
• Wide compatibility – works with Arduino, ESP32, ESP8266 and other microcontroller boards.
• Made for real projects – home gardening, automatic irrigation systems, smart agriculture and plant health monitoring.

How to Connect (Wiring)

Use jumper wires to connect the module to your Arduino Uno as follows:

Probe: plug the 2-pin probe connector into the module’s probe header.

Arduino Example Code

1. Read soil moisture (analog)

Upload this sketch, open the Serial Monitor at 9600 baud, and watch the values change as the soil gets wetter or drier:

void setup() {
  Serial.begin(9600);
}

void loop() {
  int moisture = analogRead(A0);   // read the AO pin
  Serial.print("Soil moisture: ");
  Serial.println(moisture);        // lower value = wetter soil
  delay(1000);
}

2. Digital threshold example (D2)

This sketch uses the digital output. Turn the on-board potentiometer to set the wet/dry switching point:

const int dryPin = 2;   // DO pin connected to Arduino D2

void setup() {
  pinMode(dryPin, INPUT);
  Serial.begin(9600);
}

void loop() {
  if (digitalRead(dryPin) == HIGH) {
    Serial.println("Soil is DRY - time to water the plant!");
  } else {
    Serial.println("Soil is WET - no watering needed.");
  }
  delay(1000);
}

Frequently Asked Questions

1. What is the difference between the analog and digital outputs?
The analog output (AO) gives a value between 0 and 1023 that shows exactly how wet the soil is. The digital output (DO) simply switches HIGH or LOW when the moisture crosses the threshold you set with the potentiometer.

2. How do I adjust the sensitivity?
Turn the small on-board potentiometer with a screwdriver. This sets the wet/dry threshold for the digital output.

3. What voltage does the sensor need?
The module runs on 3.3V to 5V, so you can power it directly from your Arduino’s 5V pin (or 3.3V on an ESP32/ESP8266).

4. Can I leave the probe in wet soil? Is the module waterproof?
The 2-pin probe is designed to sit in damp soil, but the LM393 electronics board is not waterproof – keep the module itself dry and above the soil.

5. Which boards does it work with?
Any board with analog and digital inputs: Arduino Uno/Nano/Mega, ESP32, ESP8266 (NodeMCU) and other similar microcontrollers.

6. What can I build with it?
Plant watering reminders, automatic irrigation systems, smart gardening projects, greenhouse monitoring and school science projects.

Order your Soil Moisture Sensor for Arduino from QKZee Technologies today – the best price in Pakistan, with fast delivery to students and hobbyists across the country.