5 RFID RC522 Projects That Add Contactless Access Control

Build secure entry systems: smart door lock, library scanner, pet feeder, attendance logger, and gym locker

Project 1: Smart Door Lock

Goal: Unlock door with authorized RFID card

Hardware

RC522, Arduino Nano, SG90 servo, Red/Green LEDs

Code

void loop() {
  if (rfid.PICC_ReadCardSerial()) {
    String uid = getUID();
    if (isAuthorized(uid)) {
      servo.write(UNLOCK_ANGLE);
      digitalWrite(GREEN, HIGH);
      delay(5000);
      servo.write(LOCK_ANGLE);
      digitalWrite(GREEN, LOW);
    } else {
      digitalWrite(RED, HIGH);
      delay(1000);
      digitalWrite(RED, LOW);
    }
  }
}

---

Project 2: Library Book Scanner

Goal: Scan books and check them in/out

Hardware

RC522, Arduino Mega, 16×2 LCD, Computer via USB

Code

void loop() {
  if (rfid.PICC_ReadCardSerial()) {
    String bookID = getUID();
    lcd.clear();
    lcd.print("Scanning...");
    Serial.println("BOOK:" + bookID);
    delay(1000);
  }
}

---

Project 3: Pet Feeder Access

Goal: Only dispense food for pet with authorized chip

Hardware

RC522, Arduino Nano, SG90 servo, LCD

Code

void loop() {
  if (detectTag()) {
    if (isCat(tag)) {
      dispenseFood();
      lcd.print("Enjoy meal!");
    } else {
      lcd.print("Not for you!");
    }
  }
}

---

Project 4: Class Attendance Logger

Goal: Log student attendance with timestamp

Hardware

RC522, Arduino Mega, SD card module, RTC

Code

void loop() {
  if (rfid.PICC_ReadCardSerial()) {
    String id = getUID();
    DateTime now = rtc.now();
    logAttendance(id, now);
    lcd.print("Logged!");
  }
}

---

Project 5: Gym Locker Lock

Goal: Open locker with membership card

Hardware

RC522, Arduino Nano, Servo, Red/Green LEDs

Code

void loop() {
  if (detectCard()) {
    if (isMember(getUID())) {
      digitalWrite(GREEN, HIGH);
      servo.write(UNLOCK);
      delay(3000);
      servo.write(LOCK);
      digitalWrite(GREEN, LOW);
    }
  }
}

---

How It Works

// WF1 Run #047 - Basic RFID Read
#include <SPI.h>
#include <MFRC522.h>

#define SS_PIN  10
#define RST_PIN  9

MFRC522 rfid(SS_PIN, RST_PIN);

void setup() {
  Serial.begin(115200);
  SPI.begin();
  rfid.PCD_Init();
}

void loop() {
  if (!rfid.PICC_IsNewCardPresent()) return;
  if (!rfid.PICC_ReadCardSerial()) return;
  Serial.print("UID:");
  for (byte i = 0; i < rfid.uid.size; i++) {
    Serial.print(rfid.uid.uidByte[i], HEX);
  }
  rfid.PICC_HaltA();
}

---

Troubleshooting

Problem	Cause	Fix
RFID reads intermittently	Antenna interference	Keep RC522 away from metal surfaces and other inductive loads
UID changes each read	PICC not properly halted	Always call rfid.PICC_HaltA() after reading
Authorization check fails	UID string comparison error	Normalize UID to uppercase without colons

Start Here

Affiliate disclosure: As an Amazon Associate, I earn from qualifying purchases.

RC522 RFID Module —
RFID Cards 13.56MHz —
Arduino Nano —
SG90 Servo Motor —

Next Step: From Scene to Sensor, Without Writing Code

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Tags: Arduino RFID RC522 Access Control Security