Smart Door Lock using RFID with Access Logging

RFID access control is everywhere — office doors, hostels, labs — yet most students only ever see the finished reader on a wall, never the sensing, decision and actuation chain behind it. This project opens that box. A 13.56 MHz RC522 reader scans tags presented at the door; the ESP32 checks the UID against an enrolled list, and on a match it pulses a solenoid strike plate to unlock the door while recording the event (UID, granted/denied, date-time) to an SD card using a DS3231 real-time clock. Denied tags trigger a buzzer and a red LED; a tamper switch on the enclosure sounds a continuous alarm if the reader housing is forced open. The build teaches the full access-control loop: RF UID acquisition, whitelist management, timestamped logging, and safe driving of an inductive load with a relay and flyback diode.

1. A tag is presented to the RC522 reader; the module returns the tag's UID to the ESP32 over SPI.
2. The firmware compares the UID with the whitelist held in flash memory and reads the current date-time from the DS3231 RTC.
3. On a match, the ESP32 energizes the relay for the configured unlock interval, pulsing the 12 V solenoid strike to release the door, and logs a GRANTED event to the SD card.
4. On an unknown tag, access stays denied: the red LED flashes, the buzzer beeps, and a DENIED event is logged.
5. Recent log entries can be scrolled on the LCD; the full log file is readable by removing the SD card.
6. Holding the master tag for 3 seconds enters enroll mode, where new tags are added; a long hold deletes a tag. A tamper switch on the housing drives the continuous alarm until the reset key sequence is entered.

Tech stack:

• ESP32 development board (Wi-Fi capable, used here as the controller)
• RC522 13.56 MHz RFID reader module + keyfob/card tags
• 12 V solenoid door strike / latch
• Single-channel 5 V relay module with flyback diode
• DS3231 real-time clock module
• MicroSD card module (SPI logging)
• 16x2 character LCD
• Arduino IDE (C/C++ firmware)

• [Contactless RFID authentication] RC522 13.56 MHz reader reads tag UIDs from a distance of approximately 3–5 cm; the UID is matched against an enrolled whitelist stored in the ESP32's flash.
• [Solenoid strike actuation] On an authorized tag, a relay pulses the solenoid door strike for a configurable interval (design target 5 s), then re-locks automatically.
• [Time-stamped access log] Every granted and denied attempt is written to a microSD card with UID, result and DS3231 date-time; recent events scroll on the LCD.
• [Enroll/delete from the panel] Master-tag mode enrolls new tags or wipes the whitelist without re-flashing, demonstrating real key-management behavior.
• [Tamper alarm] A micro-switch on the enclosure triggers a continuous buzzer alarm if the reader housing is opened, with a reset key sequence on the panel.
• [LCD status display] A 16x2 LCD shows LOCKED / UNLOCKED, last UID and log count, so the examiner can follow the demo live.
• [Inductive-load-safe driving] The solenoid is switched through a relay with a flyback diode and a separate 12 V supply, documenting how embedded boards safely drive inductive actuators.

• Working RFID door lock prototype (ESP32, RC522 reader, solenoid strike, relay, RTC, SD module, LCD, tamper switch)
• Complete firmware source code (UID scan, whitelist, logging, enroll mode, tamper alarm)
• Circuit and wiring documentation with relay/flyback safety notes
• Component list with ratings
• Tag enrollment and demo procedure guide
• Project report PDF (access-control background, RFID theory, methodology, test procedure)
• PPT presentation for final review
• Viva Q&A preparation document (RFID fundamentals, UID security limits, RTC logging)
• Setup and demonstration guide

• UID-only RFID is identification, not strong authentication: UIDs can be cloned, so this is a demonstration of access-control concepts, not a security-certified lock.
• Read distance is limited to approximately 3–5 cm by the RC522 antenna; tags must be held close to the reader.
• The solenoid strike suits a demonstration door frame; it is not a replacement for a building's installed locking hardware.
• Log timestamps depend on the DS3231 battery-backed clock — the RTC battery must be fitted, or time resets on power loss.
• The SD log is plain CSV with no encryption; physical access to the card means access to the log.