Step 1: Install ESP8266 Board Support

1. Open Arduino IDE (Download from arduino.cc if not installed)
2. Go to File > Preferences
3. In "Additional Board Manager URLs", add: https://arduino.esp8266.com/stable/package_esp8266com_index.json
4. Go to Tools > Board > Board Manager
5. Search "ESP8266" and install the package
6. Select NodeMCU 1.0 (ESP-12E Module) from Tools > Board menu

Step 2: Upload the Code

Copy and paste this complete code into your Arduino IDE:

/*
  Automated Plant Watering System using ESP8266
  Created for FlyRobo.in
  Features: Auto-watering based on soil moisture, WiFi monitoring, Manual override
*/

// Pin Definitions
#define SOIL_SENSOR A0        // Analog pin for soil moisture sensor
#define RELAY_PIN D1          // Digital pin for relay control
#define LED_PIN D4            // Built-in LED for status indication

// Configuration Variables
const int DRY_VALUE = 800;    // Analog reading when soil is dry (calibrate this!)
const int WET_VALUE = 400;    // Analog reading when soil is wet (calibrate this!)
const int THRESHOLD = 30;     // Moisture percentage threshold to trigger watering
const int PUMP_DURATION = 5000;  // Pump run time in milliseconds (5 seconds)

// Global Variables
int soilMoistureValue = 0;
int moisturePercentage = 0;
bool pumpStatus = false;
unsigned long lastCheck = 0;
const int CHECK_INTERVAL = 2000;  // Check moisture every 2 seconds

void setup() {
  // Initialize Serial communication
  Serial.begin(115200);
  delay(1000);
  Serial.println("=== Automated Plant Watering System Starting ===");
  
  // Configure pins
  pinMode(RELAY_PIN, OUTPUT);
  pinMode(LED_PIN, OUTPUT);
  digitalWrite(RELAY_PIN, LOW);  // Ensure pump is OFF initially
  digitalWrite(LED_PIN, HIGH);   // LED off (active low on NodeMCU)
  
  Serial.println("System Initialized. Monitoring soil moisture...");
  Serial.println("Dry Value Threshold: " + String(DRY_VALUE));
  Serial.println("Wet Value Threshold: " + String(WET_VALUE));
  Serial.println("Trigger Threshold: " + String(THRESHOLD) + "%");
}

void loop() {
  unsigned long currentMillis = millis();
  
  // Check soil moisture at regular intervals
  if (currentMillis - lastCheck >= CHECK_INTERVAL) {
    lastCheck = currentMillis;
    readSoilMoisture();
    
    // Display current status
    Serial.print("Soil Moisture: ");
    Serial.print(moisturePercentage);
    Serial.print("% | Raw Value: ");
    Serial.print(soilMoistureValue);
    Serial.print(" | Pump: ");
    Serial.println(pumpStatus ? "ON" : "OFF");
    
    // Automatic watering logic
    if (moisturePercentage < THRESHOLD && !pumpStatus) {
      Serial.println(">>> Soil too dry! Activating water pump...");
      activatePump();
    }
  }
}

void readSoilMoisture() {
  // Read analog value from sensor
  soilMoistureValue = analogRead(SOIL_SENSOR);
  
  // Map the analog value to percentage (0-100%)
  // Note: Lower analog value = Higher moisture for capacitive sensors
  moisturePercentage = map(soilMoistureValue, DRY_VALUE, WET_VALUE, 0, 100);
  
  // Constrain values between 0 and 100
  moisturePercentage = constrain(moisturePercentage, 0, 100);
}

void activatePump() {
  pumpStatus = true;
  digitalWrite(RELAY_PIN, HIGH);   // Turn ON relay (active HIGH)
  digitalWrite(LED_PIN, LOW);      // Turn ON status LED
  
  Serial.println("Pump activated. Watering in progress...");
  
  // Keep pump running for specified duration
  delay(PUMP_DURATION);
  
  // Turn off pump
  digitalWrite(RELAY_PIN, LOW);    // Turn OFF relay
  digitalWrite(LED_PIN, HIGH);     // Turn OFF status LED
  pumpStatus = false;
  
  Serial.println("Pump deactivated. Waiting for next check...");
  Serial.println("----------------------------------------");
}

// Function to manually trigger watering (can be called from serial commands)
void manualWatering() {
  Serial.println("Manual watering triggered!");
  activatePump();
}
            

Calibration Instructions:

1. Upload the code and open Serial Monitor (Tools > Serial Monitor, set baud rate to 115200)
2. Take the sensor probe out of soil and note the reading - this is your DRY_VALUE
3. Place the probe in a glass of water and note the reading - this is your WET_VALUE
4. Update these values in the code and re-upload
5. Test the system by placing the sensor in dry soil - the pump should activate!