Super Simple! Monitor Plant Health with Arduino UNO and Soil Moisture Sensor

Want to keep track of the soil moisture in your flower pot at any time? Today, I will teach you how to build a low-cost smart monitoring system using Arduino UNO + Soil Moisture Sensor, allowing you to view data in real-time on your phone!

1. Project Highlights

✅ Low Cost: Materials cost less than 20 yuan✅ Easy to Use: No complex circuit knowledge required✅ Highly Practical: Suitable for home gardening and agricultural IoT✅ Strong Expandability: Can be linked to an automatic irrigation system

2. Materials List

3. Hardware Connection Diagram

1. Analog Sensor Version

Soil Moisture Sensor → Arduino UNO:
  VCC → 5V
  GND → GND
  AO → A0 (Analog Signal Input)

2. Digital Sensor Version (e.g., SHT30)

SHT30 → Arduino UNO:
  VCC → 3.3V
  GND → GND
  SDA → A4
  SCL → A5

4. Code Implementation (Analog Sensor Example)

const int sensorPin = A0;    // Sensor connected to A0 pin
const int ledPin = 9;        // Alarm LED

void setup() {
  Serial.begin(9600);
pinMode(sensorPin, INPUT);
pinMode(ledPin, OUTPUT);
}

void loop() {
int moistureValue = analogRead(sensorPin); // Read analog value
float moisturePercentage = map(moistureValue, 0, 1023, 0, 100); // Convert to percentage

  Serial.print("Soil Moisture: ");
  Serial.print(moisturePercentage);
  Serial.println("%");

// Threshold judgment (example: trigger alarm below 30%)
if (moisturePercentage < 30) {
    digitalWrite(ledPin, HIGH);
} else {
    digitalWrite(ledPin, LOW);
}

delay(1000);
}

5. Data Calibration Guide

Different soil types require separate calibration, the steps are as follows:

1. Prepare Standard Moisture Samples:

• Dry Soil: Bake in the oven at 100℃ for 2 hours
• Moist Soil: Soak in water and let sit for 24 hours

// Calibration array (example, actual values need to be measured)
const int dryValue = 600;    // Analog value for dry soil
const int wetValue = 300;    // Analog value for moist soil

float getCalibratedMoisture(int rawValue) {
return map(rawValue, dryValue, wetValue, 0, 100);
}

6. Advanced Function Extensions

1. LCD Real-time Display

#include <LiquidCrystal.h>

LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  lcd.begin(16, 2);
// ...other initialization code
}

void loop() {
  lcd.setCursor(0, 0);
  lcd.print("Soil Moisture:");
lcd.setCursor(0, 1);
lcd.print(moisturePercentage + "%");
}

2. WiFi Data Upload

Use the ESP8266 module to connect to the router:

#include <ESP8266WiFi.h>

void sendToServer(float moisture) {
  WiFiClient client;
if (client.connect("api.yourserver.com", 80)) {
    String url = "/log?moisture=" + String(moisture);
    client.print(String("GET ") + url + " HTTP/1.1\r\n" +
               "Host: api.yourserver.com\r\n" +
               "Connection: close\r\n\r\n");
}
}

7. Precautions

1. Sensor Insertion Depth It is recommended to insert 5-10cm into the soil (to avoid surface moisture interference)
2. Power Supply Stability Digital sensors should use a 3.3V regulated power supply
3. Interference Prevention Measures

• Add 100nF Capacitor Filtering to the analog signal line
• Avoid running parallel to strong power lines

8. Application Scenarios

• Home Plant Care Automatically reminds when to water
• Agricultural IoT Achieves smart irrigation with water pumps
• Environmental Monitoring Used for scientific experiment data collection

Give it a try! If you successfully create it, feel free to share your creative modifications!