Arduino - Automatic Irrigation System

The automatic irrigation system is a part of the smart garden. In this tutorial, We are going to learn how to make an automatic irrigation system for the garden using Arduino, a soil moisture sensor, relay, and pump. In detail:

When soil moisture is dry, Arduino automatically controls a relay to turn a pump on to water plants.
When soil moisture is wet, Arduino automatically controls a relay to turn a pump off.

Hardware Required

1	×	Official Arduino Uno
1	×	Alternatively, DIYables ATMEGA328P Development Board
1	×	USB 2.0 cable type A/B (for USB-A PC)
1	×	USB 2.0 cable type C/B (for USB-C PC)
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	×	Recommended: Screw Terminal Block Shield for Arduino Uno
1	×	Recommended: Breadboard Shield for Arduino Uno
1	×	Recommended: Enclosure for Arduino Uno
1	×	Recommended: Prototyping Base Plate & Breadboard Kit for Arduino UNO

Or you can buy the following sensor kits:

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

Disclosure: Some links in this section are Amazon affiliate links. If you make a purchase through these links, we may earn a commission at no extra cost to you.
Additionally, some links direct to products from our own brand, DIYables .

Buy Note: Many capacitive soil moisture sensors on the market are low-quality, regardless of the version. We highly recommend buying the sensor with TLC555I Chip from the DIYables brand using the link above. We tested it, and it worked well.

About soil moisture sensor and Pump

If you do not know about pump and soil moisture sensor (pinout, how it works, how to program ...), learn about them in the following tutorials:

Arduino - Soil Moisture Sensor tutorial
Arduino - Controls Pump tutorial

Wiring Diagram

This image is created using Fritzing. Click to enlarge image

Arduino Code

/* * Created by ArduinoGetStarted.com * * This example code is in the public domain * * Tutorial page: https://arduinogetstarted.com/tutorials/arduino-automatic-irrigation-system */ #define RELAY_PIN 2 // Arduino pin that connects to relay #define MOISTURE_PIN A0 // Arduino pin that connects to AOUT pin of moisture sensor #define THRESHOLD 530 // 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(500); }

Quick Steps

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

COM6

Send

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

Newline

Code Explanation

Read the line-by-line explanation in the comment lines of the source code!

Video Tutorial

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