Why This Project Matters
RFID systems are everywhere — offices, hotels, gyms, parking lots. Understanding how they work from scratch, at the hardware level, gives you a serious edge whether you're learning electronics or building a real access control system.
This project teaches SPI communication, EEPROM storage, relay control, and basic security concepts all in one build.
Parts List
| Component | Notes |
|---|---|
| Arduino Uno/Nano | Nano preferred for compact builds |
| RC522 RFID Reader | SPI interface, 3.3V logic |
| RFID cards/fobs | Usually included with RC522 kit |
| 16x2 LCD (I2C) | 4-pin I2C version, much easier to wire |
| 5V Solenoid Lock | 12V version also works with external supply |
| 5V Relay Module | To drive the solenoid |
| Red + Green LED | Visual status indication |
| Buzzer | Active buzzer, not passive |
Wiring
RC522 → Arduino (SPI)
| RC522 | Arduino Uno |
|---|---|
| SDA | Pin 10 (SS) |
| SCK | Pin 13 |
| MOSI | Pin 11 |
| MISO | Pin 12 |
| RST | Pin 9 |
| 3.3V | 3.3V |
| GND | GND |
LCD (I2C) → Arduino
- SDA → A4, SCL → A5, VCC → 5V, GND → GND
Relay → Arduino
- IN → Pin 4, VCC → 5V, GND → GND
Complete Code
C++
Getting Your Card's UID
Upload the code, open Serial Monitor at 9600, and scan your card. The UID will print. Copy it into the authorizedUIDs array.
