ESP32 - Automatic Irrigation System

This tutorial instructs you how to make an automatic irrigation system for the garden using ESP32, a soil moisture sensor, relay, and pump. In detail:

When soil moisture is dry, ESP32 automatically turns a pump on to water plants.
When soil moisture is wet, ESP32 automatically turns a pump off.

Hardware Used In This Tutorial

1	×	ESP-WROOM-32 Dev Module
1	×	USB Cable Type-A to Type-C (for USB-A PC)
1	×	USB Cable Type-C to Type-C (for USB-C PC)
1	×	Capacitive Soil Moisture Sensor
1	×	Relay
1	×	12V Pump
1	×	Vinyl Tube
1	×	12V Power Adapter
1	×	Optionally, DC Power Jack
1	×	Breadboard
1	×	Jumper Wires
1	×	Recommended: Screw Terminal Expansion Board for ESP32
1	×	Recommended: Breakout Expansion Board for ESP32
1	×	Recommended: Power Splitter for ESP32

Or you can buy the following kits:

1	×	DIYables ESP32 Starter Kit (ESP32 included)
1	×	DIYables Sensor Kit (30 sensors/displays)
1	×	DIYables Sensor Kit (18 sensors/displays)

Disclosure: Some of the links in this section are Amazon affiliate links, meaning we may earn a commission at no additional cost to you if you make a purchase through them. Additionally, some links direct you to products from our own brand, DIYables .

Buy Note: Numerous capacitive soil moisture sensors available in the market are of poor quality, regardless of the version. We strongly advise purchasing the sensor with TLC555I Chip from the DIYables brand via the link above; we conducted tests, and it performed reliably.

Introduction to Soil Moisture Sensor and Pump

We have specific tutorials about soil moisture sensor and pump. Each tutorial contains detailed information and step-by-step instructions about hardware pinout, working principle, wiring connection to ESP32, ESP32 code... Learn more about them at the following links:

ESP32 - Soil Moisture Sensor tutorial
ESP32 - Controls Pump tutorial

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

If you're unfamiliar with how to supply power to the ESP32 and other components, you can find guidance in the following tutorial: The best way to Power ESP32 and sensors/displays.

ESP32 Code

/* * This ESP32 code is created by esp32io.com * * This ESP32 code is released in the public domain * * For more detail (instruction and wiring diagram), visit https://esp32io.com/tutorials/esp32-automatic-irrigation-system */ #define RELAY_PIN 17 // ESP32 pin GPIO17 that connects to relay #define MOISTURE_PIN 36 // ESP32 pin GPIO36 (ADC0) that connects to AOUT pin of moisture sensor #define THRESHOLD 1500 // CHANGE YOUR THRESHOLD HERE void setup() { Serial.begin(9600); pinMode(RELAY_PIN, OUTPUT); // set the ADC attenuation to 11 dB (up to ~3.3V input) analogSetAttenuation(ADC_11db); } 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); }

Quick Instructions

Do calibration to determine the wet-dry THRESHOLD, see ESP32 - Calibrates Soil Moisture Sensor
Update the calibrated THRESHOLD value in the code
Open Serial Monitor on Arduino IDE
Upload the code to ESP32 board
See the result on Serial Monitor. It looks like the below:

COM6

Send

The soil is DRY => turn pump ON (1921) The soil is DRY => turn pump ON (1821) The soil is DRY => turn pump ON (1741) The soil is DRY => turn pump ON (1645) The soil is DRY => turn pump ON (1564) The soil is WET => turn pump OFF (1465) The soil is WET => turn pump OFF (1411) The soil is WET => turn pump OFF (1365) The soil is WET => turn pump OFF (1375) The soil is WET => turn pump OFF (1279)

Autoscroll Show timestamp

Clear output

9600 baud

Newline

Code Explanation

Read the line-by-line explanation in the comment lines 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 soil moisture sensor. The ESP32 ADC is good for projects that do NOT need high accuracy. However, for projects that need precise measurements, please note:

The ESP32 ADC is not perfectly accurate and might need calibration for correct results. Each ESP32 board can be a bit different, so you need to calibrate the ADC for each individual board.
Calibration can be difficult, especially for beginners, and might not always give the exact results you want.

For projects that need high precision, consider using an external ADC (e.g ADS1115) with the ESP32 or using an Arduino, which has a more reliable ADC. If you still want to calibrate the ESP32 ADC, refer to ESP32 ADC Calibration Driver

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