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Lesson 43: Plant Monitor

This project intelligently automates plant watering by triggering a water pump whenever the soil’s moisture level dips below a predetermined threshold. It also features an LCD display that showcases the temperature, humidity, and soil moisture levels, offering users valuable insights into the plant’s environmental conditions.

Required Components

In this project, we need the following components.

It’s definitely convenient to buy a whole kit, here’s the link:

Name	ITEMS IN THIS KIT	LINK
Universal Maker Sensor Kit	94	Universal Maker Sensor Kit

You can also buy them separately from the links below.

Component Introduction	Purchase Link
ESP32 & Development Board (ESP32 Board)	BUY
Breadboard	BUY
Power Supply Module	-
I2C LCD 1602	BUY
Centrifugal Pump	-
L9110 Motor Driver Module	-
Capacitive Soil Moisture Module	BUY
Temperature and Humidity Sensor Module (DHT11)	-

Wiring

Note

The kit may contain different versions of the DHT11 module. Please confirm the wiring method according to the module you have.

Code

Note

To install the library, use the Arduino Library Manager and search for “LiquidCrystal I2C” and “DHT sensor library” and install it.

Code Analysis

The code is structured to seamlessly manage plant watering by monitoring environmental parameters:

1. Library Inclusions and Constants/Variables:

   Incorporate Wire.h, LiquidCrystal_I2C.h, and DHT.h libraries for functionality. Specify pin assignments and settings for the DHT11 sensor, soil moisture sensor, and water pump.

   #include <Wire.h>
   #include <LiquidCrystal_I2C.h>
   #include <DHT.h>
   
   #define DHTPIN 14              // Digital pin for DHT11 sensor
   #define DHTTYPE DHT11         // DHT11 sensor type
   #define SOIL_MOISTURE_PIN 35  // Analog pin for soil moisture sensor
   #define WATER_PUMP_PIN 25      // Digital pin for water pump
   
   
   // Initialize sensor and LCD objects
   DHT dht(DHTPIN, DHTTYPE);
   LiquidCrystal_I2C lcd(0x27, 16, 2);
   

2. setup():

   Configure pin modes for the moisture sensor and pump. Initially deactivate the pump. Initialize and backlight the LCD. Activate the DHT sensor.

   void setup() {
       // Set pin modes
       pinMode(SOIL_MOISTURE_PIN, INPUT);
       pinMode(WATER_PUMP_PIN, OUTPUT);
   
       // Initialize water pump as off
       digitalWrite(WATER_PUMP_PIN, LOW);
   
       // Initialize LCD and backlight
       lcd.init();
       lcd.backlight();
   
       // Start DHT sensor
       dht.begin();
   }
   

3. loop():

   Measure humidity and temperature via the DHT sensor. Gauge soil moisture through the soil moisture sensor. Display the temperature and humidity on the LCD, then show soil moisture levels. Assess soil moisture to decide on water pump activation; if soil moisture is under 500 (adjustable threshold), run the pump for 1 second.

   void loop() {
       // Read humidity and temperature from DHT11
       float humidity = dht.readHumidity();
       float temperature = dht.readTemperature();
   
       // Read soil moisture level
       int soilMoisture = analogRead(SOIL_MOISTURE_PIN);
   
       // Display temperature and humidity on LCD
       lcd.clear();
       lcd.setCursor(0, 0);
       lcd.print("Temp: " + String(temperature) + "C");
       lcd.setCursor(0, 1);
       lcd.print("Humidity: " + String(humidity) + "%");
   
       delay(2000);
   
       // Display soil moisture on LCD
       lcd.clear();
       lcd.setCursor(0, 0);
       lcd.print("Soil Moisture: ");
       lcd.setCursor(0, 1);
       lcd.print(String(soilMoisture));
   
       // Activate water pump if soil is dry
       if (soilMoisture > 650) {
           digitalWrite(WATER_PUMP_PIN, HIGH);  // Turn on water pump
           delay(1000);                         // Pump water for 1 second
           digitalWrite(WATER_PUMP_PIN, LOW);   // Turn off water pump
       }
   
       delay(2000);  // Wait before next loop iteration
   }