Arduino RFID Access Control System with MFRC522 - Wokwi Simulator Tutorial

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Step-by-Step Instructions for Wokwi Simulator

Step 1: Set Up Your Wokwi Project

  1. Go to https://wokwi.com
  2. Click "New Project"
  3. Select "Arduino Uno"

Step 2: Add Components

Click the "+" button to add these components:

  • 1x Arduino Uno (already added)
  • 1x MFRC522 RFID Module
  • 1x Green LED
  • 1x Red LED
  • 2x 220Ω Resistors (for LEDs)
  • Breadboard (optional, for cleaner layout)

Step 3: Wire the MFRC522 Module to Arduino

Connect the MFRC522 pins as follows:

Diagram.json:

{
  "version": 1,
  "author": "Anonymous maker",
  "editor": "wokwi",
  "parts": [
    { "type": "wokwi-breadboard-mini", "id": "bb1", "top": 142.6, "left": 7.2, "attrs": {} },
    { "type": "wokwi-arduino-uno", "id": "uno", "top": -18.6, "left": 181.8, "attrs": {} },
    { "type": "wokwi-led", "id": "led1", "top": 73.2, "left": -34.6, "attrs": { "color": "red" } },
    {
      "type": "wokwi-led",
      "id": "led2",
      "top": -3.6,
      "left": -34.6,
      "attrs": { "color": "green" }
    },
    { "type": "wokwi-servo", "id": "servo1", "top": 170.8, "left": 268.8, "attrs": {} },
    { "type": "board-mfrc522", "id": "rfid1", "top": 150.95, "left": -73.36, "attrs": {} },
    {
      "type": "wokwi-resistor",
      "id": "r1",
      "top": 23.15,
      "left": 28.8,
      "attrs": { "value": "270" }
    },
    {
      "type": "wokwi-resistor",
      "id": "r2",
      "top": 80.75,
      "left": 19.2,
      "attrs": { "value": "270" }
    }
  ],
  "connections": [
    [ "led2:C", "uno:GND.1", "green", [ "v0" ] ],
    [ "led1:C", "uno:GND.1", "green", [ "v0" ] ],
    [ "servo1:GND", "uno:GND.1", "black", [ "h0" ] ],
    [ "servo1:V+", "uno:5V", "green", [ "h0" ] ],
    [ "servo1:PWM", "uno:6", "green", [ "h0" ] ],
    [ "rfid1:3.3V", "uno:3.3V", "green", [ "h0" ] ],
    [ "rfid1:GND", "uno:GND.1", "black", [ "h0" ] ],
    [ "rfid1:SDA", "uno:10", "green", [ "h0" ] ],
    [ "rfid1:SCK", "uno:13", "green", [ "h0" ] ],
    [ "rfid1:MOSI", "uno:11", "green", [ "h0" ] ],
    [ "rfid1:MISO", "uno:12", "green", [ "h0" ] ],
    [ "rfid1:RST", "uno:9", "green", [ "h0" ] ],
    [ "r2:1", "led1:A", "green", [ "v0" ] ],
    [ "r1:1", "led2:A", "green", [ "v0" ] ],
    [ "r2:2", "uno:5", "green", [ "v0" ] ],
    [ "r1:2", "uno:4", "green", [ "v0" ] ]
  ],
  "dependencies": {}
}
MFRC522 PinArduino Pin
SDA (SS)Pin 10
SCKPin 13
MOSIPin 11
MISOPin 12
IRQNot connected
GNDGND
RSTPin 9
3.3V3.3V

Step 4: Wire the LEDs

Green LED (Access Granted):

  • Anode (long leg) → 220Ω resistor → Arduino Pin 2
  • Cathode (short leg) → GND

Red LED (Access Denied):

  • Anode (long leg) → 220Ω resistor → Arduino Pin 3
  • Cathode (short leg) → GND
Code:
#include <SPI.h>
#include <MFRC522.h>
#include <Servo.h>

#define SS_PIN 10
#define RST_PIN 9

#define GREEN_LED 4
#define RED_LED 5
#define SERVO_PIN 6

MFRC522 mfrc522(SS_PIN, RST_PIN);
Servo gateServo;

// CHANGE THIS TO YOUR CARD UID
byte authorizedUID[] = {0x11, 0x22, 0x33, 0x44};

void setup() {
  Serial.begin(9600);
  SPI.begin();
  mfrc522.PCD_Init();

  pinMode(GREEN_LED, OUTPUT);
  pinMode(RED_LED, OUTPUT);

  gateServo.attach(SERVO_PIN);
  gateServo.write(0); // Gate closed

  Serial.println("RFID Gate System Ready");
}

void loop() {
  if (!mfrc522.PICC_IsNewCardPresent()) return;
  if (!mfrc522.PICC_ReadCardSerial()) return;

  Serial.print("UID: ");
  for (byte i = 0; i < mfrc522.uid.size; i++) {
    Serial.print(mfrc522.uid.uidByte[i], HEX);
    Serial.print(" ");
  }
  Serial.println();

  if (isAuthorized()) {
    accessGranted();
  } else {
    accessDenied();
  }

  mfrc522.PICC_HaltA();
}

bool isAuthorized() {
  if (mfrc522.uid.size != 4) return false;

  for (byte i = 0; i < 4; i++) {
    if (mfrc522.uid.uidByte[i] != authorizedUID[i]) {
      return false;
    }
  }
  return true;
}

void accessGranted() {
  Serial.println("Access Granted");
  digitalWrite(GREEN_LED, HIGH);
  digitalWrite(RED_LED, LOW);

  gateServo.write(90); // Open gate
  delay(3000);

  gateServo.write(0); // Close gate
  delay(500);

  digitalWrite(GREEN_LED, LOW);
}

void accessDenied() {
  Serial.println("Access Denied");
  digitalWrite(RED_LED, HIGH);
  delay(2000);
  digitalWrite(RED_LED, LOW);
}


Step 6: Configure Libraries

  1. Click on "Library Manager" (book icon)
  2. Add MFRC522 library by GithubCommunity

Step 7: Run the Simulation

  1. Click the Green "Start Simulation" button
  2. Open the Serial Monitor to see output
  3. Click on the RFID reader to simulate scanning a card
  4. In Wokwi, you can edit the card UID in the RFID component properties

Step 8: Test Different Cards

  1. Click on the MFRC522 module in the simulation
  2. You'll see RFID card properties on the right
  3. Change the UID values to test authorized/unauthorized access
  4. Authorized card: Set UID to 11 22 33 44
  5. Unauthorized card: Use any other UID like 01 02 03 04

Expected Behavior:

  • When authorized card is scanned: Green LED turns on, Serial Monitor shows "Access Granted"
  • When unauthorized card is scanned: Red LED turns on, Serial Monitor shows "Access Denied"
  • LEDs turn off after 2 seconds

Troubleshooting Tips:

  • If RFID module isn't detected, check the SPI connections (pins 10, 11, 12, 13)
  • Make sure the MFRC522 is powered from 3.3V (NOT 5V)
  • Verify RST pin is connected to pin 9
  • Check that the MFRC522 library is properly installed




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