Arduino-Based RFID Door Lock

An Arduino Uno RFID access-control prototype that unlocks an electronic latch when a registered card is scanned. The firmware reads card UIDs through an MFRC522 RFID module, displays access status on a 16x2 I2C LCD, triggers a relay to control the lock, and uses buzzer tones for quick feedback.

Table of Contents

• Preview
• Tech Stack
• Repository Overview
• Features
• Hardware and Software
• Installation Guide
• Hardware Design Notes
• License

Preview

Preview	Description
	Schematic-style wiring diagram showing the Arduino Uno, RFID-RC522 reader, relay module, buzzer, LCD display, 12 V battery, and electronic latch.
	Component-level layout that maps the MFRC522 RFID sensor, 16x2 LCD, relay module, buzzer, and latch connections to the Arduino Uno R3.

Tech Stack

Category	Technology	Use in This Project
Firmware Language	C++ / Arduino	Implements card scanning, UID validation, relay control, LCD messaging, buzzer feedback, and serial logging.
Microcontroller	Arduino Uno R3	Main controller for the RFID reader, display, buzzer, and relay module.
Build Tool	PlatformIO	Manages the Arduino build environment, board configuration, library dependencies, firmware upload, and serial monitor workflow.
RFID	MFRC522 / RFID-RC522	Reads RFID card UIDs over SPI for access-control decisions.
Display	LiquidCrystal_I2C	Drives the 16x2 I2C LCD at address 0x27 for lock and access status messages.
Communication	SPI	Connects the Arduino Uno to the MFRC522 RFID reader.
Communication	I2C	Connects the Arduino Uno to the LCD through the A4 and A5 pins.
Actuation	5 V Relay Module	Switches the electronic latch circuit when access is granted.
Power	12 V Battery	Powers the electronic latch separately from the Arduino control circuit.
Feedback	Buzzer	Plays different tones for granted and denied access attempts.
Access Data	Hard-coded RFID UID	Stores the authorized card UID directly in firmware as authorizedUID.
Development Tools	Visual Studio Code, PlatformIO IDE, Arduino IDE	Provides the local development, build, upload, and prototype programming workflow.
Circuit Design Tools	Tinkercad, Cirkit, Circuit Diagram	Used during the case-study design process for virtual prototyping, wiring references, and diagram preparation.

Repository Overview

.
|-- README.md
|-- LICENSE
`-- arduino-based-rfid-door-lock/
    |-- platformio.ini
    |-- src/
    |   `-- main.cpp
    |-- preview/
    |   |-- Circuit Diagram 1.png
    |   `-- Circuit Diagram 2.png
    |-- include/
    |-- lib/
    `-- test/

The PlatformIO project lives inside the nested arduino-based-rfid-door-lock/ directory. The firmware entry point is src/main.cpp, while platformio.ini defines the Arduino Uno target and external library dependencies.

Features

• RFID card detection and UID comparison using the MFRC522 module.
• Single-card authorization through a firmware-defined UID.
• LCD status messages for startup, scanning, locked, unlocked, granted, and denied states.
• Relay-controlled electronic latch output.
• Buzzer feedback with separate tones for granted and denied access.
• Automatic relock after a 10-second unlock interval.
• Serial monitor output at 9600 baud for debugging card and lock state events.

Hardware and Software

Category	Item	Project Role
Controller	Arduino Uno R3	ATmega328P-based board that runs the access-control firmware and coordinates every connected module.
RFID Reader	MFRC522 / RFID-RC522	13.56 MHz contactless RFID reader used to read card or tag UIDs. The project uses SPI wiring for this module.
Display	16x2 LCD with I2C Adapter	Shows user-facing status messages while using only the Arduino Uno's I2C pins.
Lock Control	5 V Relay Module	Allows the Arduino's low-voltage output to switch the higher-current latch circuit.
Door Hardware	Electronic Door Latch	Physical locking mechanism controlled through the relay.
Latch Power	12 V Rechargeable Battery	Dedicated latch supply used to avoid overloading the Arduino's 5 V output.
Feedback	Passive Buzzer	Audio indicator for successful and failed card scans.
Prototyping	Jumper Wires, Breadboard, Perfboard, Soldering Tools	Used to build the initial circuit, then stabilize the final prototype after loose connections caused unreliable behavior.
Development Software	Arduino IDE and PlatformIO	Arduino IDE was used during the original prototype workflow; this repository is organized as a PlatformIO project for repeatable builds.
Design Software	Tinkercad, Cirkit, Circuit Diagram	Used as design, simulation, and circuit-reference tools during development.

Installation Guide

Prerequisites

• Arduino Uno R3 or compatible ATmega328P board.
• MFRC522 / RFID-RC522 reader module and compatible RFID card or tag.
• 16x2 I2C LCD, configured at address 0x27.
• 5 V relay module.
• Electronic latch with a suitable external power supply.
• Buzzer, jumper wires, USB cable, and breadboard or soldered prototype.
• Visual Studio Code with the PlatformIO IDE extension, or the PlatformIO CLI.

Setup

1. Clone the repository:

   git clone https://github.com/shoichiideologies/arduino-based-rfid-door-lock.git
   cd arduino-based-rfid-door-lock/arduino-based-rfid-door-lock

2. Install PlatformIO if you are using the CLI:

   python -m pip install platformio

3. Open the nested PlatformIO project in VS Code, or stay in the nested directory when using the CLI.

4. Check the configured board and dependencies in platformio.ini:

   [env:uno]
   platform = atmelavr
   board = uno
   framework = arduino

5. Update the authorized RFID card UID in src/main.cpp:

   byte authorizedUID[] = {0xE2, 0x7E, 0x1B, 0x2F};

   To get a new card UID, run the MFRC522 library's DumpInfo example or temporarily print the scanned UID bytes over serial during development.

6. Wire the circuit using the diagrams in the preview/ directory and the pin map below.

7. Build the firmware:

   pio run

8. Upload the firmware to the Arduino Uno:

   pio run --target upload

9. Open the serial monitor:

   pio device monitor --baud 9600

Hardware Design Notes

Pin Map

Component	Arduino Uno Pin	Notes
MFRC522 SDA / SS	D10	SPI slave select pin configured as SS_PIN.
MFRC522 RST	D9	Reset pin configured as RST_PIN.
MFRC522 MOSI	D11	SPI data from Arduino to RFID reader.
MFRC522 MISO	D12	SPI data from RFID reader to Arduino.
MFRC522 SCK	D13	SPI clock.
MFRC522 VCC	3.3V	Use 3.3 V power for the RFID module. Check module-level logic compatibility before connecting to a 5 V Arduino.
16x2 I2C LCD SDA	A4	I2C data line on Arduino Uno.
16x2 I2C LCD SCL	A5	I2C clock line on Arduino Uno.
Relay IN	D8	Relay signal pin configured as RELAY_PIN.
Buzzer	D7	Buzzer output pin configured as BUZZER_PIN.

License

This project is licensed under the MIT License.