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:

Arduino Nano ESP32 will be used to control the relay in order to switch on the pump when the soil moisture is dry.
When the soil moisture is wet, Arduino Nano ESP32 will be used to control the relay to turn the pump off.

Hardware Preparation

1	×	Arduino Nano ESP32
1	×	USB Cable Type-C
1	×	Capacitive Soil Moisture Sensor
1	×	Relay
1	×	12V Pump
1	×	Vinyl Tube
1	×	12V Power Adapter
1	×	DC Power Jack
1	×	Jumper Wires
1	×	Breadboard
1	×	(Recommended) Screw Terminal Expansion Board for Arduino Nano
1	×	(Recommended) Breakout Expansion Board 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.
Additionally, some of these links are for products from our own brand, DIYables.

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:

Arduino Nano ESP32 - Soil Moisture Sensor tutorial
Arduino Nano ESP32 - Controls Pump tutorial

Wiring Diagram

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Arduino Nano ESP32 Code

/* * This Arduino Nano ESP32 code was developed by newbiely.com * * This Arduino Nano ESP32 code is made available for public use without any restriction * * For comprehensive instructions and wiring diagrams, please visit: * https://newbiely.com/tutorials/arduino-nano-esp32/arduino-nano-esp32-automatic-irrigation-system */ #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 1500 // CHANGE YOUR THRESHOLD HERE void setup() { Serial.begin(9600); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); 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.

COM6

Send

The soil is DRY => turn pump ON (1927) The soil is DRY => turn pump ON (1824) The soil is DRY => turn pump ON (1749) The soil is DRY => turn pump ON (1648) The soil is DRY => turn pump ON (1565) The soil is WET => turn pump OFF (1466) The soil is WET => turn pump OFF (1417) The soil is WET => turn pump OFF (1366) The soil is WET => turn pump OFF (1373) The soil is WET => turn pump OFF (1271)

Autoscroll Show timestamp

Clear output

9600 baud

Newline

Code Explanation

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

※ NOTE THAT:

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.

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