Arduino Nano ESP32 - Automatic Irrigation System

This tutorial instructs you how to use Arduino Nano ESP32, soil moisture sensor, relay, and pump to build an automatic irrigation system for the garden with. Specifically:

Hardware Preparation

1×Arduino Nano ESP32
1×USB Cable Type-C
1×Capacitive Soil Moisture Sensor
1×12V Pump
1×Vinyl Tube
1×12V Power Adapter
1×DC Power Jack
1×Jumper Wires
1×(Recommended) Screw Terminal Adapter for Arduino Nano

Or you can buy the following sensor kits:

1×DIYables Sensor Kit (30 sensors/displays)
1×DIYables Sensor Kit (18 sensors/displays)
Disclosure: Some of the links provided in this section are Amazon affiliate links. We may receive a commission for any purchases made through these links at no additional cost to you. We appreciate your support.

Buy Note: Many soil moisture sensors available in the market are unreliable, regardless of their version. We strongly recommend buying the sensor from the DIYables brand using the link provided above. We tested it, and it worked reliably.

Overview of soil moisture sensor and Pump

If you are not familiar with pump and soil moisture sensor (including pinout, functioning, programming, etc.), the following tutorials will be helpful:

Wiring Diagram

The wiring diagram between Arduino Nano ESP32 and soil moisture sensor Pump

This image is created using Fritzing. Click to enlarge image

Arduino Nano ESP32 Code

/* * This Arduino Nano ESP32 code was developed by * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * */ #define RELAY_PIN D2 // The Arduino Nano ESP32 pin connected to the relay #define MOISTURE_PIN A2 // The Arduino Nano ESP32 pin connected to the moisture sensor #define THRESHOLD 2800 // CHANGE YOUR THRESHOLD HERE void setup() { Serial.begin(9600); pinMode(RELAY_PIN, OUTPUT); } void loop() { int value = analogRead(MOISTURE_PIN); // read the analog value from sensor if (value > THRESHOLD) { Serial.print("The soil is DRY => turn pump ON"); digitalWrite(RELAY_PIN, HIGH); } else { Serial.print("The soil is WET => turn pump OFF"); digitalWrite(RELAY_PIN, LOW); } Serial.print(" ("); Serial.print(value); Serial.println(")"); delay(200); }

Detailed Instructions

  • If you are new to Arduino Nano ESP32, refer to the tutorial on how to set up the environment for Arduino Nano ESP32 in the Arduino IDE.
  • Wire the components as shown in the diagram.
  • Connect the Arduino Nano ESP32 board to your computer using a USB cable.
  • Open Arduino IDE on your computer.
  • Choose the correct Arduino Nano ESP32 board, such as (e.g. NodeMCU 1.0 (ESP-12E Module)), and its respective COM port.
  • Perform calibration to identify the wet-dry THRESHOLD, as outlined in Arduino Nano ESP32 - Calibrates Soil Moisture Sensor.
  • Insert the calibrated THRESHOLD value into the code.
  • Launch Serial Monitor on Arduino IDE.
  • Upload the code to Arduino Nano ESP32.
  • View the result on Serial Monitor.
The soil is DRY => turn pump ON The soil is DRY => turn pump ON The soil is DRY => turn pump ON The soil is DRY => turn pump ON The soil is WET => turn pump OFF The soil is WET => turn pump OFF The soil is WET => turn pump OFF The soil is WET => turn pump OFF
Autoscroll Show timestamp
Clear output
9600 baud  

Code Explanation

Check out the line-by-line explanation contained in the comments of the source code!


This tutorial uses the analogRead() function to read values from an ADC (Analog-to-Digital Converter) connected to a sensor or component. The Arduino Nano ESP32's ADC is suitable for projects that do not require high accuracy. However, for projects needing precise measurements, keep the following in mind:

  • The Arduino Nano ESP32's ADC is not perfectly accurate and might require calibration for correct results. Each Arduino Nano ESP32 board can vary slightly, so calibration is necessary for each individual board.
  • Calibration can be challenging, especially for beginners, and might not always yield the exact results you want.

For projects requiring high precision, consider using an external ADC (e.g ADS1115) with the Arduino Nano ESP32 or using another Arduino, such as the Arduino Uno R4 WiFi, which has a more reliable ADC. If you still want to calibrate the Arduino Nano ESP32's ADC, refer to the ESP32 ADC Calibration Driver.

Video Tutorial


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