🕒 Portable RFID Clocking Machine & Logger

A high-reliability, low-power portable logging solution designed for time-attendance tracking and race waypoint monitoring. This system integrates 125KHz RFID telemetry with ATmega328P deterministic memory management.

Tamper-Proof Design: Developed for care agencies to verify worker attendance, this device utilizes a physical handshake between the logger and site-fixed tags to prevent remote log falsification.

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Firmware, Custom Fonts & Schematics

Final Hardware Build

How It Works: Data Integrity & Validation

To ensure logs cannot be falsified or corrupted, the system employs a dual-stream recording method and hardware-level stabilization:

• Authenticity Verification: Each log entry includes the RFID UID, high-precision timestamp, ambient temperature, and battery voltage for audit trailing.
• DS3231 RTC Integration: By utilizing a temperature-compensated crystal oscillator (TCXO), the system eliminates clock drift caused by outdoor environmental variance.
• SD Bus Management: Implements a synchronous write-ahead protocol to ensure .CSV stability on FAT32 partitions during low-battery events.

Technical Specifications

Engineering Challenges & Solutions

• Clock Drift: Swapping the DS1307 for the DS3231 reduced timing errors from minutes-per-week to seconds-per-year.
• Stable Rails: The DC-DC boost converter ensures a rock-solid 5V rail for the SD card and RFID reader even as the AAA battery voltage drops to 0.9V per cell.
• Data Format: Standard RFC 4180 CSV output allows for instant integration into existing administrative spreadsheets without parsing software.