Plant Monitor (ESP32)

Real-time soil moisture, temperature, humidity, and light level monitoring using an ESP32 with OLED display, Wi-Fi connectivity, and live web interface.

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✨ Current Features

• Sensors
  • DHT11 for temperature and humidity\
  • Capacitive soil moisture sensor (ADC)\
  • Photoresistor for ambient light (ADC)\
• Continuous ADC Sampling
  • Uses ESP-IDF continuous ADC driver for higher accuracy\
  • Averaged readings for stable light & soil values\
• Smart Light Tracking
  • Stores 24-hour rolling light data (48 samples)\
  • Computes daily average light exposure\
• Display
  • Live readings + status indicators on SSD1306 OLED\
• Wi-Fi + Web Server
  • Connects to Wi-Fi (station mode)\
  • Hosts HTTP server for remote monitoring\
  • mDNS enabled for easy local access\
• Status Analysis System
  • Each parameter labeled (Good / Bad)\
  • Drives alert logic + UI\
• LED Indicators
  • Status LED (heartbeat blink)\
  • Alert LED when any condition is not "Good"

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🧭 Removed / Changed Features

• Removed manual calibration routine (handled via normalization)
• Sampling now handled via FreeRTOS task instead of fixed loop timing
• Sensor averaging improved (especially light)

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📸 Demo

Pending hardware completion (OLED link below): https://www.amazon.com/HiLetgo-Serial-128X64-Display-Color/dp/B06XRBTBTB

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🧱 System Overview

flowchart LR
  DHT[DHT11 Sensor] --> MCU[ESP32]
  PHOTO[Photoresistor] --> MCU
  SOIL[Soil Sensor] --> MCU
  MCU --> OLED[OLED Display]
  MCU --> LEDS[Status & Alert LEDs]
  MCU --> WIFI[Wi-Fi + HTTP Server]

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🔩 Hardware

Component Interface Notes

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ESP32 Main MCU Wi-Fi enabled DHT11 GPIO26 Temp & humidity Soil Sensor GPIO39 (ADC1 CH3) Inverted moisture % Light Sensor GPIO36 (ADC1 CH0) % brightness OLED (SSD1306) I²C Live display LED (Status) GPIO2 Blinks every cycle LED (Alert) GPIO4 Turns on when issue detected

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⚙️ Firmware Architecture

• FreeRTOS Task (sensor_task)
  • Reads sensors
  • Processes ADC buffer
  • Updates rolling averages
  • Runs analysis
  • Updates OLED + LEDs
  • Sends data to web server
• Modules
  • analysis.c → Determines status strings\
  • plant_data.c → Stores global plant state\
  • wifi_sta.c → Wi-Fi connection\
  • http_server.c → Web dashboard backend\
  • display_oled.c → OLED rendering

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🌐 Web Interface

• Runs automatically when Wi-Fi connects\
• Accessible via:
  • IP address\
  • mDNS hostname (e.g., plant.local)\
• Displays:
  • Live sensor values\
  • Status indicators

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📤 Example Data (Internal Representation)

{
  "temp_c": 24.3,
  "humidity": 48.1,
  "light_avg": 67.5,
  "soil": 42.0,
  "status": {
    "temp": "Good",
    "humidity": "Good",
    "light": "Low",
    "soil": "Dry"
  }
}

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🧰 Repo Layout

plant-monitor/
├─ components/
├─ main/
│  └─ main.c
├─ CMakeLists.txt
└─ README.md

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🧪 Testing

• OLED confirms real-time updates\
• LED behavior validates alert logic\
• Serial logs show sensor + error states\
• Web UI verifies remote access

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🗺️ Roadmap

• Data logging (SPIFFS / SD)
• MQTT integration
• OTA updates
• Mobile-friendly dashboard
• Auto-watering system

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📚 References

• ESP-IDF ADC Continuous Mode docs\
• DHT11 datasheet\
• SSD1306 datasheet