ESP32 IoT Light Monitoring System

Project developed as part of my university degree.

A complete IoT system based on ESP32, MQTT (TLS), a Python backend client, and InfluxDB.

The project consists of two main parts:

• Light Probe – ESP32 integrated with a VEML7700 light sensor
• Server – MQTT broker, Python client, InfluxDB, and Grafana

The ESP32 reads light intensity from a VEML7700 sensor and publishes data securely via MQTT within a local Wi-Fi network.
A Python client subscribes to the MQTT topic and stores the data in InfluxDB.

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📊 Measurement Results

The figure above presents real-time light intensity measurements collected by the ESP32 probe, stored in InfluxDB, and visualized using Grafana.

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🎯 System Requirements and Design Goals

The system was developed to achieve the following engineering objectives:

• Continuous acquisition of high-precision light intensity measurements
• Robust and reliable wireless communication over MQTT
• Fault tolerance against temporary Internet connection loss
• Firmware optimized for embedded, resource-constrained hardware environments
• Runtime control of probe operation via a command interface (CMD module)
• Efficient memory utilization and power management
• Visual indication of probe operating status (power and server connectivity LEDs)
• Secure data transmission using TLS encryption and authenticated access
• Centralized aggregation of measurement data in a time-series database (InfluxDB)
• Real-time graphical visualization of sensor data (Grafana)

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🏗 System Architecture

→ ESP32-DevKitV1 (VEML7700)
→ MQTT Mosquitto Broker (TLS, port 8883)
→ Python MQTT Client, paho-mqtt
→ InfluxDB → Grafana (data visualization)

📁 Project Structure

ESP32-Projekt/
│
├── esp_32_firmware/
│
├── main/
│   ├── app_main.c              # Application entry point
│   ├── CMakeLists.txt
│   ├── idf_component.yml       # Component metadata and dependencies
    └── Kconfig.projbuild       # Custom menuconfig options
│
├── components/
│   ├── wifi/                   # Wi-Fi connection management
│   ├── mqtt_conn/              # Secure MQTT communication (TLS)
│   │   └── certs/
│   │       └── ca.crt          # CA certificate for broker verification
│   ├── veml7700/               # Light sensor driver (I2C)
│   ├── led/                    # Status LED control
│   ├── app_sntp/               # Time synchronization (NTP)
    └── cmd/                    # Command interface
│
├── CMakeLists.txt              # Project-level CMake configuration
└── dependencies.lock           # Managed component dependencies

🔌 ESP32 Firmware

Built on FreeRTOS to support concurrent measurement processing and MQTT communication The system is divided into three main tasks:

• task_measure – responsible for acquiring light intensity measurements from the VEML7700 sensor and timestamping the data.
• task_send_MQTT – creates JSON messages, buffers measurement data, and prepares it for transmission.
• Wi-Fi/MQTT task – manages network connectivity and handles secure MQTT communication with the server.

Data is transferred between tasks using FreeRTOS queues, ensuring safe inter-task communication and concurrent execution.

🔌 ESP32 Firmware – Features

• Configurable via idf.py menuconfig:

  • Wi-Fi settings
  • MQTT settings (host, port, topic, credentials)
  • I2C parameters (SDA/SCL pins, frequency)

• Continuous lux measurement using the VEML7700 sensor (I2C)

• Secure MQTT communication over TLS (broker CA certificate embedded in firmware)

• JSON payload publishing with synchronized timestamp (SNTP-based time synchronization)

• QoS support for reliable message delivery

• Status LED indication (power and server connection state)

• Fault-tolerant behavior during temporary network interruptions

• Runtime probe control and diagnostics via command interface (CMD module)ol and diagnostics via command interface (CMD module)

• System logs

Example MQTT Payload

{
  "lux": 123.45,
  "time": 2026-02-25 14:37:52
}

🌐 MQTT Broker – Features

• Central message hub for IoT devices and backend services
• TLS-enabled listener (secure encrypted transport)
• Optional access control (username/password authentication)
• Topic-based message routing (publish/subscribe)
• Supports multiple clients (ESP32 probe + backend consumer)
• Logs and diagnostics for connection and authentication events

🐍 Python MQTT Client – Features

• Secure connection to MQTT broker using TLS (CA certificate)
• Topic subscription and real-time message processing
• JSON payload validation and parsing
• Writes measurement data to InfluxDB (time-series database)
• Clear console output for monitoring and debugging
• Configuration separated from code (config/config.py from template)
• Designed as a bridge: MQTT → InfluxDB

Each component contains its own detailed README with configuration instructions.

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🔧 Setup Overview

To run the complete system, follow the steps below.

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1️⃣ ESP32 Firmware

Configure and flash the ESP32 firmware.

See detailed instructions in:
esp_32_firmware/README.md

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2️⃣ MQTT Broker & InfluxDB

Ensure that the following services are running:

• MQTT broker (TLS, port 8883)
• InfluxDB 2.x
• Existing bucket and valid write token

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3️⃣ Python Backend Client

Navigate to: mqtt_client_py/. See configuration instructions in: mqtt_client_py/README.md.

Install dependencies

pip install paho-mqtt 
pip install influxdb-client