--- title: "ESP32 AsyncMQTT_ESP32 MQTT DHT22" url: "https://maker.wiznet.io/matthew/projects/esp32-asyncmqtt-esp32-mqtt-dht22/" markdown_url: "https://maker.wiznet.io/matthew/projects/esp32-asyncmqtt-esp32-mqtt-dht22/md" type: "UCC: User Created Content" author: "alex9ufo" author_url: "https://alex9ufoexploer.blogspot.com/2025/01/" editor: "WIZnet" editor_url: "https://maker.wiznet.io/" original_author: "alex9ufo" original_url: "https://alex9ufoexploer.blogspot.com/2025/01/" published: "2025-05-29" language: "en" likes: 0 views: 1902 comments: 0 source: "WIZnet Makers (https://maker.wiznet.io/)" --- # ESP32 AsyncMQTT_ESP32 MQTT DHT22 > A real-time IoT system using ESP32, DHT22, MQTT, and Node-RED to monitor temperature and humidity, visualize data, store it in SQLite, and send LINE alerts. Original author: alex9ufo (source: https://alex9ufoexploer.blogspot.com/2025/01/) ## Article ## **Hardware ComponentsESP32 Dev Board** – Serves as the main microcontroller, responsible for handling sensor readings and MQTT communication. **DHT22 Sensor** – A digital sensor used to measure temperature and humidity. **W5500 Ethernet Module(optional)** – Enables wired Ethernet connectivity for environments requiring stable network performance. **LAN8720 / ENC28J60 Modules(optional)** – Other supported Ethernet options for versatile network integration. **USB Cable** – Used to power and program the ESP32 board. **Breadboard & Jumper Wires(for physical builds)** – Used for prototyping sensor and module connections. --- ## **Software, Applications & Online ServicesWokwi Simulator** – Web-based ESP32 simulation platform used to test and demonstrate the system without physical hardware. **Arduino IDE** – Development environment used to write, compile, and upload code to the ESP32. **AsyncMQTT_ESP32 Library** – Provides MQTT communication over both Wi-Fi and Ethernet for ESP32. **ArduinoJson Library** – Handles JSON serialization of sensor data. **Node-RED** – A flow-based visual programming tool used to create dashboards, automate database interactions, and visualize live data. **Mosquitto Public MQTT Broker** – `test.mosquitto.org` is used for MQTT message publishing and subscribing. **SQLite** – Lightweight local database used to store environmental sensor records. **LINE Notify API** – Sends real-time notifications directly to the LINE messaging app. ## **Building a Real-Time Temperature & Humidity Monitoring System Using ESP32, DHT22, MQTT, and Node-RED** This project showcases a practical implementation of an **IoT-based temperature and humidity monitoring system**, developed using the **ESP32 microcontroller, DHT22 sensor, MQTT protocol, and Node-RED dashboard**. Designed in the **Wokwi simulator environment**, it serves as a great demonstration of how embedded systems can interact with cloud-based services and user interfaces in real time. --- ## **Capturing and Transmitting Environmental Data with ESP32 and DHT22** The core of the system is the ESP32, which periodically reads temperature and humidity values from a connected DHT22 sensor. The sensor data is formatted into a JSON object and published every 2.5 seconds to the MQTT topic `**alex9ufo/esp32/dht/temphumi**`. Communication is handled using the **AsyncMQTT_ESP32** library, and the system is designed to auto-reconnect using **FreeRTOS software timers** in case of network disconnections. Each payload includes a serialized JSON string with both temperature and humidity values. If an error occurs during data reading (e.g., a sensor failure), the system outputs a corresponding error message to the serial monitor for debugging purposes. --- ## **Data Visualization and Storage Using Node-RED** On the Node-RED side, the project implements a comprehensive dashboard and data management system: An **MQTT input node** subscribes to the topic `alex9ufo/esp32/dht/temphumi` to receive real-time sensor data. The received values are displayed on two **dashboard gauges**, representing temperature and humidity respectively. Incoming data is parsed and stored in a **SQLite database table named **`**DHT22STATUS**`, which holds temperature, humidity, date, and time entries. Users can interact with the database through the Node-RED UI, with features such as: Creating and deleting the database table. Viewing all or specific entries. Editing or deleting individual entries. Displaying the latest 50 entries in a table view. All database operations are dynamically triggered using **Function nodes**, which construct and execute SQL queries based on user input. --- ## **LINE Notify Integration for Remote Monitoring** An additional feature includes **LINE Notify integration**, enabling remote alerts via LINE messages. When triggered, the system formats a message such as **“---ESP32 Data Received--- Temperature XX℃ , Humidity XX%”** and sends it to the configured LINE channel using the Notify API. This enables instant awareness of environmental changes without needing to access the dashboard directly. --- ## **System Architecture Overview** | Component | Description | | --- | --- | | **Sensor** | DHT22 (Temperature & Humidity) | | **Microcontroller** | ESP32 (Simulated using Wokwi) | | **Communication Protocol** | MQTT (Broker: `test.mosquitto.org`) | | **Libraries Used** | AsyncMQTT_ESP32, ArduinoJson, Adafruit DHT Library | | **Database** | SQLite (Table: DHT22STATUS) | | **Dashboard Tool** | Node-RED (Real-time visualization with gauges and tables) | | **Notification Service** | LINE Notify (For remote environmental alerts) | --- ## **Conclusion and Future Enhancements** This project effectively demonstrates how to combine **ESP32-based sensor monitoring with cloud communication protocols and real-time dashboards**. It is an ideal project for beginners and intermediate makers to understand the fundamentals of IoT system design, from sensor integration to cloud data handling. Potential future improvements could include: Support for Ethernet (LAN8720 or W5500) communication instead of Wi-Fi. Cloud data synchronization with platforms like Firebase or Google Sheets. Advanced analytics or machine learning for trend prediction. Triggered alerts for abnormal readings (e.g., extreme temperatures). **Overall, this system is a powerful, scalable, and educational IoT project that can serve as a solid foundation for more advanced environmental monitoring solutions.** --- Source: https://maker.wiznet.io/matthew/projects/esp32-asyncmqtt-esp32-mqtt-dht22/