ESP8266 Environmental Data Logger

Low-power, modular environmental data logging system with optional Wi-Fi web interface

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Overview

This project is a dual-mode ESP8266-based environmental data logger designed for long-term, unattended monitoring of environmental parameters such as temperature, barometric pressure, and soil humidity.

The system can operate either in:

• Low-power battery mode, using deep sleep for extended autonomous operation
• Continuous powered mode, providing Wi-Fi access and a built-in HTML web interface

This project demonstrates embedded firmware development, hardware integration, and production-aware documentation, and is suitable for prototyping, field testing, and small-scale deployments.

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Key Features

• ESP8266 controller (LoLin NodeMCU)
• Dual operating modes:
  • 🔋 Battery-powered low-power mode (deep sleep)
  • 🔌 5V-powered Wi-Fi mode with web interface
• Environmental sensing:
  • Temperature
  • Barometric pressure (BMP280)
  • Soil humidity (analog sensor)
• Data logging:
  • Local storage on MicroSD card (SPI)
• Timekeeping:
  • RTC module (I²C) for timestamped logs
• Modular design:
  • Sensors and peripherals easily replaceable
• Web-accessible data when externally powered

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Operating Modes

🔋 Battery Mode (Low Power)

• ESP8266 wakes periodically
• Reads all sensors
• Logs data to SD card
• Returns to deep sleep
• Approximate battery life: ~10 days (configuration-dependent)

This mode is intended for unattended data collection where power consumption is critical.

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🔌 Powered Mode (Wi-Fi Enabled)

• Continuous operation from external 5V supply
• ESP8266 runs as a Wi-Fi access point
• Embedded HTML page served directly by the ESP8266
• Enables data visualization and access without removing the SD card

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Hardware Overview

Main Components

• LoLin NodeMCU (ESP8266)
• BMP280 temperature & pressure sensor (I²C)
• DS1307 RTC module (I²C, 3.3 V logic compatible)
• MicroSD card adapter (SPI)
• Soil moisture sensor (analog)

Communication Interfaces

• I²C → BMP280, RTC
• SPI → MicroSD card
• ADC → Soil moisture sensor

Power

• 3.3 V regulated rail
• Battery or external 5 V supply
• Deep sleep wake-up via GPIO16 → RST

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Example Data Output

Logged data is stored on the SD card in a simple, readable format:

2026-02-09 12:00, 24.8°C, 1012 hPa, 42% 2026-02-09 12:15, 24.7°C, 1012 hPa, 43%

This format allows easy import into spreadsheets or data analysis tools.

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Firmware

The firmware is written in Arduino C++ and built using PlatformIO.

Firmware Features

• Deep sleep power management
• Modular sensor drivers
• SD card file logging
• Optional Wi-Fi web server
• Non-blocking design principles

Build & Upload

cd firmware pio run pio run -t upload pio device monitor Platform Details

Framework: Arduino

Board: LoLin NodeMCU (ESP8266)

Toolchain: PlatformIO

Firmware-specific details are documented in firmware/README.md.

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Applications

This design can be adapted for:

• Environmental monitoring

• Agricultural soil sensing

• Remote sensor nodes

• Battery-powered data loggers

• IoT proof-of-concept systems

What I Can Build for You:

Based on this project, I can help with:

• Custom ESP8266 / ESP32 firmware

• Low-power IoT system design

• Sensor integration and data logging

• KiCad schematic and PCB design

• Prototype-to-production transition (JLCPCB-ready files)

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Author

Nick Christodoulou

• Electronics & Firmware Engineer
• Email: nichrist71@gmail.com

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License

This project is released under the MIT License. Contact me for commercial use, customization, or consulting work.