Creating an RFID Security Door Lock Access Control System

Ditch standard brass keys for digital tags! This RFID access terminal validates tags and operates a micro servo latch accordingly.

Introduction & Concept

This project uses the RC522 card reader, which emits radio frequency fields at 13.56 MHz. When an RFID tag or key fob passes close to the reader, it energizes and transmits its unique identification number (UID). The Arduino matches the UID against stored authorization codes. If valid, a servo turns 90 degrees to unlock the latch.

Key Parts

Component Name	Store Link
RFID RC522 Reader Set	Buy RC522 RFID Set
SG90 Micro Servo	Buy SG90 Servo

SPI Wiring Table

RC522 Pin	Arduino Uno Pin
SDA (SS)	Pin 10
SCK	Pin 13
MOSI	Pin 11
MISO	Pin 12
RST	Pin 9
3.3V	3.3V Pin (Do not use 5V!)

Source Code

#include <SPI.h>
#include <MFRC522.h>
#include <Servo.h>

MFRC522 mfrc522(10, 9); // SS, RST
Servo lockServo;

void setup() {
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();
  lockServo.attach(6);
  lockServo.write(0); // Latch locked position
}

void loop() {
  if ( ! mfrc522.PICC_IsNewCardPresent()) return;
  if ( ! mfrc522.PICC_ReadCardSerial()) return;
  
  // Read card UID
  String uid = "";
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    uid += String(mfrc522.uid.uidByte[i], HEX);
  }
  
  if (uid == "e324a1b") { // Master Key UID
    lockServo.write(90); // Unlock
    delay(5000);
    lockServo.write(0); // Relock
  }
}