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Published March 18, 2026 © MIT

ACEBOTT Smart Home: Automatic Watering System

Keep your plants happy and healthy even when you're away – an intelligent automatic watering system for your ACEBOTT smart home.

BeginnerFull instructions provided1 hour80

Things used in this project

Hardware components

https://acebott.com/product/acebott-qe024-esp32-5-in-1-smart-home-education-kit-level-2/

Story

📖 Introduction

Not only do plants enhance the environment aesthetically, but they also aid in photosynthesis, absorbing carbon dioxide and releasing oxygen, effectively purifying indoor air and reducing the concentration of harmful substances (such as formaldehyde, benzene, etc.), thereby improving indoor air quality. But what happens to your green friends when you're away for an extended period?

This project solves that problem! We'll build an automatic watering system that:

Continuously monitors soil moisture using a soil moisture sensor
Displays the moisture level on a 1602 LCD screen
Automatically activates a water pump when the soil gets too dry
Stops watering when sufficient moisture is detected

All logic runs on the ACEBOTT ESP32 using simple threshold-based decision making. This project introduces sensor reading, relay control (for high-power devices), and I2C LCD display – essential skills for any smart home enthusiast!

🛠 Things Used

Hardware

ACEBOTT ESP32 Smart Home Edu Kit – Level 2 (QE024)
ESP32 Controller Board
Soil Moisture Sensor
5V Relay Module
Water Pump
1602 I2C LCD Display
Acrylic structural parts
Jumper wires (included)
Small container for water
Plant (not included)

Software

ACECode (Scratch‑based) OR Arduino IDE

🌱 Understanding the Components

1. Soil Moisture Sensor

A moisture sensor measures the moisture level in soil by detecting the resistance between two metal electrodes. The moisture in the soil affects this resistance – wetter soil = lower resistance = higher analog reading (or vice versa depending on your sensor). The sensor outputs an analog signal that we can read with the ESP32's ADC pins.

Soil Moisture Sensor

Pinout:

S: Connect to analog I/O pin (GPIO25 in our code)
V: Connect to 5V
G : Connect to GND

2. Water Pump

The water pump is a mechanical device that operates by driving an impeller with an electric motor.

Water Pump

This rotation generates centrifugal force, drawing liquid into the pump body and delivering it through pipes to the desired location.

Water Pump

Important: The ESP32's I/O pins cannot provide enough current to drive the pump directly. That's why we need a relay module!

Pinout:

Red wire: Connect to 5V
Black wire: Connect to GND (through the relay)

3. 5V Relay Module

A relay is an electrical switch that allows a low-power signal (from the ESP32) to control a high-power device (like the water pump). It works like this:

Relay Module

In our circuit:

5V Relay Module

Pinout:

S (Signal): Connect to GPIO33 (digital output)
V: Connect to 5V
G: Connect to GND
COM: Connect to GND (yes, this is correct – check your kit's manual!)
NO: Connect to pump negative (black wire)
NC: Leave unconnected

4. 1602 I2C LCD Display

The 16x2 character LCD with I2C backpack simplifies wiring dramatically – only 4 wires (VCC, GND, SDA, SCL) instead of 8+! We'll use it to display the current soil moisture reading and pump status.

16x2 character LCD

Pinout:

VCC: Connect to 5V
GND: Connect to GND
SDA: Connect to GPIO21 (I2C data)
SCL: Connect to GPIO22 (I2C clock)

🏠 Assembly

Follow the kit's official Assemble documentation – Level 2 for detailed visuals. Here's a summary:

Step 1: Prepare the Base

Assemble the base where all components will be mounted.

Step 2: Install the LCD Display

Mount the 1602 LCD in a visible spot on your smart home structure.

Step 3: Install the Relay Module

Fix the relay module onto the base near the pump.

Step 4: Install the Water Pump

Place the pump securely. Ensure the inlet tube reaches your water container and the outlet tube reaches the plant.

Step 5: Install the Soil Moisture Sensor

Mount the sensor so its prongs can be inserted into the plant's soil.

Step 6: Wire Everything

Follow the wiring diagram below.

Hardware Wiring Diagram

Step 7: Final Arrangement

Place a small water container next to the pump and position your plant nearby.

💻 Code

🔹 Logic Overview

Read analog value from soil moisture sensor
Display the value on the LCD (e.g., "H: 850")
If moisture value is below threshold (dry soil):

Activate relay (HIGH) → pump runs for 500ms

Display "Water: Turn on"

If moisture value is above threshold (wet enough):

Deactivate relay (LOW) → pump stops

Display "Water: Turn off"

Repeat every second

Program Flow Chart

🔹 Arduino Sketch

🧪 How to Calibrate Your Moisture Sensor

The magic number 1000 in the code is just a starting point. You need to find the right threshold for your soil and plant:

Insert the sensor into dry soil – note the value (e.g., 800).
Water the plant thoroughly – wait a few minutes, then note the value (e.g., 2500).
Choose a threshold somewhere in between. For example, if dry=800 and wet=2500, set threshold to 1500.

Condition Typical Value Range

Very dry 0 – 1000

Moist 1000 – 2500

Wet 2500 – 4095

⚠️ Note: These values depend on your specific sensor and soil type. Always calibrate for your setup!

Update the threshold in the code:

if (moisture_value < 1500) {   // Use YOUR calibrated value

📹 Project Demo

Watch the automatic watering system in action 🍒😊

🏡 Conclusion

With a soil moisture sensor, a relay, a water pump, and an LCD display, I added an intelligent plant care system to my ACEBOTT smart home. Now my plants stay hydrated even when I'm on vacation!

This project teaches:

✅ Analog sensor reading and calibration

✅ Controlling high-power devices with relays

✅ I2C LCD display usage

✅ Threshold-based automation logic

✅ Real-world problem solving

The code

#include <Wire.h>
#include <hd44780.h>
#include <hd44780ioClass/hd44780_I2Cexp.h>
#define moistureSensor 25 
#define relay 33 //declare the number of the Relay Module
const int i2cAddress = 0x27; // I2C address
const int numRows = 2; //Number of rows in LCD1602
const int numCols = 16;//Number of columns in LCD1602
hd44780_I2Cexp lcd(i2cAddress,numRows,numCols);
void setup(){
Wire.begin();//Start I2C communication
lcd.begin(numCols,numRows); // Initialize LCD display
lcd.backlight();//Turn on backlight
delay(500);
lcd.clear();//Clear LCD display characters
pinMode(relay,OUTPUT);//Set relay pin as output
pinMode(moistureSensor,INPUT);//Set moisture sensor as input
Serial.begin(115200);
}
void loop(){ //Read moisture sensor value
int moisture_value = analogRead(moistureSensor);
Serial.println(moisture_value);
lcd.setCursor(0, 0);
lcd.print("H:");
lcd.print(moisture_value);//Display soil moisture value on LCD
lcd.setCursor(0, 1);
lcd.print("Water:");
if(moisture_value<1000){
    lcd.print("Turn on");//Turn on water pump：
    digitalWrite(relay,HIGH);
    delay(500);
    digitalWrite(relay,LOW);
  }
  else{
    lcd.print("Turn off");//Turn off water pump：
    digitalWrite(relay,LOW);
  }
  delay(1000);
  lcd.clear();
}