Automated Greenhouse Climate Control

System Overview

Greenhouse automation maintains optimal growing conditions 24/7. By monitoring environmental parameters and automating climate control equipment, you can increase yields by 20-40% while reducing water and energy consumption.

System Architecture

[Sensors] → [ESP32 Controller] → [WiFi/LoRa] → [Home Assistant]
     ↓              ↓                    ↓              ↓
DHT22/BME280   Relay Module        MQTT Broker    Dashboard
Soil Sensors   Motor Drivers                      Mobile App
CO2 Sensor     Water Valves                       Alerts

Hardware Components

Controller

• ESP32 DevKit: Main controller with WiFi/Bluetooth
• Alternative: Raspberry Pi for more complex logic
• Power: 5V 2A USB power supply

Sensors

• BME280: Temperature, humidity, pressure (I2C)
• SCD30/SGP30: CO2 sensor (optional, for enrichment)
• Capacitive Soil Moisture: Corrosion-resistant probes
• BH1750: Light intensity sensor
• Water Level: Ultrasonic sensor for tank monitoring

Actuators

• 4-Channel Relay Module: Control high-power devices
• Window Actuators: 12V linear actuators for roof vents
• Extraction Fans: Temperature-controlled ventilation
• Solenoid Valves: 12V/24V for irrigation zones
• Circulation Fans: Internal air movement
• Grow Lights: LED with dimming capability

Sensor Network

Deploy sensors strategically throughout the greenhouse:

Sensor Placement

• Air Temperature/Humidity: At plant canopy height, shaded from direct sun
• Soil Moisture: In root zone, multiple locations
• Light: Unobstructed view of sky/grow lights
• CO2: Near air intake, away from plant respiration

Wiring Diagram

ESP32
│
├── BME280 (I2C)
│   ├── VCC → 3.3V
│   ├── GND → GND
│   ├── SDA → GPIO21
│   └── SCL → GPIO22
│
├── Soil Moisture x4 (Analog)
│   ├── VCC → 3.3V
│   ├── GND → GND
│   └── SIG → GPIO34,35,32,33
│
├── Relay Module
│   ├── VCC → 5V
│   ├── GND → GND
│   └── IN1-4 → GPIO25,26,27,14
│
└── Optional: LoRa Module
    ├── VCC → 3.3V
    ├── GND → GND
    ├── NSS → GPIO5
    ├── MOSI → GPIO23
    ├── MISO → GPIO19
    └── SCK → GPIO18

Control System

Complete ESP32 firmware for greenhouse automation:

#include <WiFi.h>
#include <PubSubClient.h>
#include <Adafruit_BME280.h>
#include <ArduinoJson.h>

// WiFi & MQTT
const char* ssid = "GREENHOUSE_WIFI";
const char* password = "your_password";
const char* mqtt_server = "192.168.1.100";

// Sensor pins
#define SOIL_MOISTURE_1 34
#define SOIL_MOISTURE_2 35
#define SOIL_MOISTURE_3 32
#define SOIL_MOISTURE_4 33

// Relay pins
#define RELAY_FAN 25
#define RELAY_PUMP 26
#define RELAY_LIGHTS 27
#define RELAY_HEATER 14

// Setpoints
float TEMP_HIGH = 28.0;
float TEMP_LOW = 18.0;
float HUMIDITY_HIGH = 70.0;
float SOIL_MOISTURE_LOW = 30.0; // Percentage

Adafruit_BME280 bme;
WiFiClient espClient;
PubSubClient client(espClient);

void setup() {
  Serial.begin(115200);
  
  // Initialize BME280
  if (!bme.begin(0x76)) {
    Serial.println("BME280 not found!");
  }
  
  // Initialize relay pins
  pinMode(RELAY_FAN, OUTPUT);
  pinMode(RELAY_PUMP, OUTPUT);
  pinMode(RELAY_LIGHTS, OUTPUT);
  pinMode(RELAY_HEATER, OUTPUT);
  
  // All relays OFF (HIGH for active-low modules)
  digitalWrite(RELAY_FAN, HIGH);
  digitalWrite(RELAY_PUMP, HIGH);
  digitalWrite(RELAY_LIGHTS, HIGH);
  digitalWrite(RELAY_HEATER, HIGH);
  
  // WiFi & MQTT setup
  setupWiFi();
  client.setServer(mqtt_server, 1883);
  client.setCallback(callback);
}

void setupWiFi() {
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("WiFi connected");
}

void reconnect() {
  while (!client.connected()) {
    if (client.connect("GreenhouseController")) {
      client.subscribe("greenhouse/setpoints");
    } else {
      delay(5000);
    }
  }
}

void callback(char* topic, byte* payload, unsigned int length) {
  // Handle setpoint updates
  StaticJsonDocument<256> doc;
  deserializeJson(doc, payload, length);
  
  if (doc.containsKey("temp_high")) {
    TEMP_HIGH = doc["temp_high"];
  }
  if (doc.containsKey("temp_low")) {
    TEMP_LOW = doc["temp_low"];
  }
}

void controlClimate(float temp, float humidity, float soilMoisture) {
  // Temperature control
  if (temp > TEMP_HIGH) {
    digitalWrite(RELAY_FAN, LOW); // Turn ON extraction fan
  } else if (temp < TEMP_LOW) {
    digitalWrite(RELAY_HEATER, LOW); // Turn ON heater
  } else {
    digitalWrite(RELAY_FAN, HIGH);
    digitalWrite(RELAY_HEATER, HIGH);
  }
  
  // Humidity control
  if (humidity > HUMIDITY_HIGH) {
    digitalWrite(RELAY_FAN, LOW); // Ventilate to reduce humidity
  }
  
  // Irrigation control
  if (soilMoisture < SOIL_MOISTURE_LOW) {
    digitalWrite(RELAY_PUMP, LOW); // Turn ON water pump
    delay(5000); // Water for 5 seconds
    digitalWrite(RELAY_PUMP, HIGH);
  }
}

void loop() {
  if (!client.connected()) reconnect();
  client.loop();
  
  // Read sensors
  float temp = bme.readTemperature();
  float humidity = bme.readHumidity();
  float pressure = bme.readPressure() / 100.0;
  int soil1 = analogRead(SOIL_MOISTURE_1);
  int soil2 = analogRead(SOIL_MOISTURE_2);
  
  // Convert soil moisture to percentage (calibrate for your sensor)
  float soilPercent = map(soil1, 4095, 1500, 0, 100);
  soilPercent = constrain(soilPercent, 0, 100);
  
  // Control climate
  controlClimate(temp, humidity, soilPercent);
  
  // Publish to MQTT
  StaticJsonDocument<512> doc;
  doc["temperature"] = temp;
  doc["humidity"] = humidity;
  doc["pressure"] = pressure;
  doc["soil_moisture"] = soilPercent;
  doc["fan_state"] = (digitalRead(RELAY_FAN) == LOW);
  doc["pump_state"] = (digitalRead(RELAY_PUMP) == LOW);
  doc["timestamp"] = millis();
  
  char jsonBuffer[512];
  serializeJson(doc, jsonBuffer);
  client.publish("greenhouse/climate", jsonBuffer);
  
  delay(10000); // Read every 10 seconds
}

Automation Logic

Temperature Control Strategy

Condition	Action	Priority
Temp > 32°C	Open roof vents + extraction fan	High
Temp > 28°C	Open roof vents only	Medium
Temp < 15°C	Close vents + activate heater	High
15°C < Temp < 18°C	Close vents, no heating	Low

Irrigation Schedule

Morning (6:00 AM):
  - Check soil moisture
  - If < 40%, irrigate for 10 minutes
  
Midday (12:00 PM):
  - Check soil moisture
  - If < 30%, irrigate for 5 minutes
  
Evening (6:00 PM):
  - Check soil moisture
  - If < 35%, irrigate for 8 minutes
  
Night:
  - No irrigation (prevent fungal growth)

Mobile App Integration

Use Home Assistant for dashboard and mobile control:

Home Assistant Configuration

# configuration.yaml
mqtt:
  sensor:
    - name: "Greenhouse Temperature"
      state_topic: "greenhouse/climate"
      value_template: "{{ value_json.temperature }}"
      unit_of_measurement: "°C"
    
    - name: "Greenhouse Humidity"
      state_topic: "greenhouse/climate"
      value_template: "{{ value_json.humidity }}"
      unit_of_measurement: "%"
    
    - name: "Greenhouse Soil Moisture"
      state_topic: "greenhouse/climate"
      value_template: "{{ value_json.soil_moisture }}"
      unit_of_measurement: "%"
  
  switch:
    - name: "Greenhouse Fan"
      state_topic: "greenhouse/climate"
      command_topic: "greenhouse/fan/command"
      value_template: "{{ value_json.fan_state }}"
    
    - name: "Greenhouse Pump"
      state_topic: "greenhouse/climate"
      command_topic: "greenhouse/pump/command"
      value_template: "{{ value_json.pump_state }}"

# Automations
automation:
  - alias: "High Temperature Alert"
    trigger:
      platform: numeric_state
      entity_id: sensor.greenhouse_temperature
      above: 30
    action:
      service: notify.mobile_app
      data:
        message: "Greenhouse temperature is high!"

Optimization Tips

Energy Efficiency

• Use thermal mass (water barrels) to stabilize temperature
• Install reflective mulch to reduce heating needs
• Time irrigation for early morning (reduce evaporation)
• Use LED grow lights with spectrum tuning
• Harvest rainwater for irrigation

Crop-Specific Settings

Crop	Temp Range	Humidity	Light Hours
Tomatoes	21-27°C	60-70%	14-16h
Lettuce	16-22°C	50-60%	10-12h
Peppers	24-29°C	60-70%	14-16h
Cucumbers	22-28°C	70-80%	12-14h