A brief presentation of my project:

• My project is a Door Lock Access Control System designed to simulate the entry mechanism of a residential building based on RFID card authentication
• The main purpose of this system is to allow or deny access based on a registered RFID card. When a valid card is scanned, the servo motor pulls an iron latch to simulate unlocking the door, a green LED turns on to indicate successful access, and the LCD displays a confirmation message. If the card is invalid, a red LED lights up and access is denied.
• The idea came from my own apartment building, where the entry system is often broken. I thought it would be useful to build a working prototype—not just to solve my own problem, but maybe even to help neighbors in the future if this ever gets implemented.

Block Diagram:

Hardware Modules:

- Arduino UNO Acts as the central controller, reading input data from the RFID reader and controlling output devices like the servo motor, LCD, and LEDs.

- RFID Module (RC522) Scans RFID cards using SPI communication. The Arduino compares the scanned UID with a predefined list of authorized UIDs.

- Servo Motor Simulates a door latch. It rotates to unlock the door when a valid card is detected and locks it again afterward.

- LCD with I2C Module Displays access status messages such as “Access Granted” or “Access Denied”.

- LEDs (Green and Red) Provide quick visual feedback:

- Iron Latch Connected to the servo, simulates the actual door locking mechanism.

Softare Flow

1. The user scans an RFID card using the RC522 module.

2. The UID is sent to the Arduino via SPI.

3. The Arduino checks if the UID matches one from the authorized list: If authorized: The servo motor rotates to unlock the latch. Green LED turns on. LCD displays: Access Granted. If unauthorized: Servo remains in locked position. Red LED turns on. LCD displays: Access Denied.

4. After a short delay, the system resets the servo to the locked position and turns off the LED.

This firmware was developed in PlatformIO (VS Code) with the *Arduino* framework, but it can be uploaded from the regular Arduino IDE as well.

➤ 1. Tool-chain & Build Settings

  • Framework : Arduino AVR  
  • MCU : ATmega328P @ 16 MHz  
  • Compiler : avr-gcc 11.x (packaged with PlatformIO)  
  • Upload : avrdude, 115 200 baud  
  • Debug : Serial (9600 baud) – progress messages when scanning cards  

➤ 2. External Libraries

• LiquidCrystal_I2C – drives the 16×2 LCD over I²C at address 0x27
• MFRC522 – high-level driver for the RC522 RFID reader (SPI)
• SPI – Arduino core SPI interface
• No `Servo.h`: the hobby-servo PWM is generated manually with Timer-1 for tighter control.

➤ 3. Core Ideas & Algorithms

➤ 4. Principal Functions

servoInit() – sets up Timer-1 for 50 Hz PWM

setServoPosition() – writes a new duty (0–180 °) to OCR1A

loop() – handles UI text, card scan, decision, LED + servo actions

rfid.PICC_HaltA() – gracefully halts the tag after each transaction

All logic resides in a single file (`src/main.cpp` in PlatformIO).

No dynamic memory or interrupts are used; timing is managed with short, fixed `delay()` calls for simplicity.

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