💧 Weather-Based Irrigation Decisions

📊 Decision Matrix Using Weather Data

• 🌧️ Rain detected in last 6 hours
  → ✓ Skip irrigation (rain provides natural watering)
  💧 Water saved: 100% of scheduled amount
• 🌡️ Temperature > 35°C + No rain
  → ⚠️ Increase watering by 50% (high evaporation)
  💧 Without adjustment: 30-40% water lost to evaporation
• 💨 Humidity < 30% + No rain
  → ⚠️ Plants stressed - water immediately + increase duration by 25%
  💧 Low humidity causes rapid transpiration (plants lose water faster)
• 🌤️ Forecast rain + soil moisture > 50%
  → ✓ Skip irrigation (rain expected soon)
  💧 Prevents over-watering and runoff
• ⚠️ Soil moisture < 30% + No rain forecast
  → ⚠️ WATER IMMEDIATELY - critical stress level
  💧 Yield loss if delayed: 15-25% reduction

🔌 Hardware Setup for Weather Monitoring

• 🔹 Rain Sensor (LM393) — $6 · Detects rain/water
• 🔹 DHT22 Sensor — $10 · Temperature + humidity
• 🔹 Soil Moisture Sensor — $8 · Core soil data
• 🔹 Optional: Anemometer — $25 · Wind speed (high wind = more evaporation)

🔌 Wiring Diagram (Add Rain Sensor)

ESP32 → Rain Sensor (LM393)
GPIO35 → DO (Digital output - rain detected)
3.3V   → VCC
GND    → GND

ESP32 → DHT22 (Temperature + Humidity)
GPIO15 → DATA pin
3.3V   → VCC
GND    → GND

ESP32 → Soil Moisture Sensor
GPIO34 → AO (analog out)
3.3V   → VCC
GND    → GND
    

📖 Complete Weather-Based Irrigation Code

#include <DHT.h>
#include <WiFi.h>

#define RELAY_PIN 26
#define SOIL_PIN 34
#define RAIN_PIN 35
#define DHT_PIN 15

DHT dht(DHT_PIN, DHT22);
const unsigned long CHECK_INTERVAL = 1800000; // 30 minutes

// Weather thresholds
const int RAIN_DETECTED = LOW;     // Rain sensor output LOW when wet
const float HOT_TEMP = 35.0;       // >35°C = increase watering
const float LOW_HUMIDITY = 30.0;   // <30% = plant stress

// Soil thresholds
const int DRY_THRESHOLD = 30;
const int OPTIMAL_THRESHOLD = 60;

unsigned long lastCheck = 0;
bool rainDetected = false;
float temperature = 0;
float humidity = 0;

void setup() {
    Serial.begin(115200);
    pinMode(RELAY_PIN, OUTPUT);
    pinMode(RAIN_PIN, INPUT_PULLUP);
    digitalWrite(RELAY_PIN, HIGH);  // Pump OFF
    dht.begin();
    Serial.println("🌤️ Weather-Based Irrigation Started");
}

int getSoilMoisture() {
    int raw = analogRead(SOIL_PIN);
    return map(raw, 4095, 1500, 0, 100);
}

float getTemperature() {
    return dht.readTemperature();
}

float getHumidity() {
    return dht.readHumidity();
}

int calculateWateringDuration(int baseMinutes) {
    int duration = baseMinutes;
    
    if (rainDetected) {
        Serial.println("🌧️ Rain detected - skipping irrigation");
        return 0;
    }
    
    if (temperature > HOT_TEMP) {
        int extra = baseMinutes * 0.5;  // +50% for high heat
        duration += extra;
        Serial.printf("🌡️ Hot (%0.1f°C) - adding %d min\n", temperature, extra);
    }
    
    if (humidity < LOW_HUMIDITY) {
        int extra = baseMinutes * 0.25; // +25% for dry air
        duration += extra;
        Serial.printf("💨 Low humidity (%0.1f%%) - adding %d min\n", humidity, extra);
    }
    
    return min(duration, 30); // Max 30 minutes (fail-safe)
}

void loop() {
    unsigned long now = millis();
    
    if (now - lastCheck >= CHECK_INTERVAL) {
        lastCheck = now;
        
        // Read all sensors
        rainDetected = (digitalRead(RAIN_PIN) == RAIN_DETECTED);
        temperature = getTemperature();
        humidity = getHumidity();
        int moisture = getSoilMoisture();
        
        Serial.println("=================================");
        Serial.printf("🌧️ Rain: %s\n", rainDetected ? "YES" : "NO");
        Serial.printf("🌡️ Temp: %0.1f°C\n", temperature);
        Serial.printf("💧 Humidity: %0.1f%%\n", humidity);
        Serial.printf("🌱 Soil: %d%%\n", moisture);
        
        // Decision logic
        if (rainDetected) {
            Serial.println("✅ Skipping irrigation (rain provides water)");
        }
        else if (moisture < DRY_THRESHOLD) {
            int duration = calculateWateringDuration(10); // Base 10 min
            if (duration > 0) {
                Serial.printf("💧 Watering for %d minutes\n", duration);
                digitalWrite(RELAY_PIN, LOW);  // Pump ON
                delay(duration * 60000);
                digitalWrite(RELAY_PIN, HIGH); // Pump OFF
            }
        }
        else if (moisture > OPTIMAL_THRESHOLD) {
            Serial.println("✅ Soil moisture optimal - no watering");
        }
        else {
            Serial.println("🌿 Soil moisture acceptable - no action");
        }
    }
}