Soil Moisture Sensor

Components Needed

• 1x ESP32
• 1x USB Programming Cable
• 1x Double Width Breadboard
• 1x Soil Moisture Sensor Module + Probe
• 2x Female-to-Female Jumper Wires
• 4x Male-to-Female Jumper Wires

Connections

1. Using the breadboard, connect the Soil Moisture Sensor Module to the ESP32 as follows:
2. VCC → ESP32 3V3
3. GND → ESP32 GND
4. DO (Digital Output) → ESP32 D35
5. AO (Analog Output) → ESP32 D34
6. Using the two female-female jumper wires, connect the Soil Moisture Sensor Module to the Soil Moisture Sensor Probe. Here, the polarity does not matter.

Code

Upload the following code onto the ESP32:

const int analogPin = 34;   // Soil moisture sensor AO pin
const int digitalPin = 35;  // Soil moisture sensor DO pin
const int ledPin = 2;       // ESP32 onboard LED pin

void setup() {
  pinMode(analogPin, INPUT);   // Configure analog pin as input
  pinMode(digitalPin, INPUT);  // Configure digital pin as input
  pinMode(ledPin, OUTPUT);     // Configure onboard LED pin as output
  Serial.begin(115200);
}

void loop() {
  int moistureValue = analogRead(analogPin);  // Read analog moisture level
  int dryStatus = digitalRead(digitalPin);    // Read digital signal

  Serial.print("Moisture Level (Analog): ");
  Serial.println(moistureValue);

  if (dryStatus == LOW) {
    // Soil is dry
    digitalWrite(ledPin, HIGH);  // Turn on LED
    Serial.println("Soil is Dry!");
  } else {
    // Soil is wet
    digitalWrite(ledPin, LOW);  // Turn off LED
    Serial.println("Soil is Wet.");
  }

  delay(1000);  // Delay for stability
}

Explanation

The Soil Moisture Sensor Module measures the moisture level in the soil. It provides both an analog output (AO) that gives a range of values indicating the moisture level and a digital output (DO) that toggles between HIGH and LOW based on a preset threshold. The onboard potentiometer adjusts this threshold. This code reads the analog value from the AO pin to get a moisture level. If the moisture value falls below the threshold (e.g., 2500), the onboard LED lights up to indicate dry soil. The values are displayed in the Serial Monitor.

Results

After uploading the code, open the Serial Monitor in the Arduino IDE to observe real-time moisture readings. The Serial Monitor will display the analog moisture value. If the soil moisture is below the threshold, the

• nboard LED on the ESP32 will turn on to indicate that the soil is dry.

Try for Yourself

1. Modify the code to trigger a watering system or send an alert when the soil is too dry.