Arduino RFID project for beginners

Do you know what skipasses, credit cards and clothes have in common? You may think about plastic but connecting plastic to the Arduino wouldn’t make anything functionally amazing. What we will do today is reading and authorizing RFID tags using the Arduino Uno board.

RFID stands for Radio Frequency Identification. It is commonly confused with NFC which means Near Field Communication.

What can you use this technology for? How about replacing your door key with an RFID tag? Or a safe where you can hide important stuff and safely close it with RFID tags?

The possibilities are endless. We will make a simple project that let us read a tag and check if it is the right one then switch ON the green LED otherwise switch ON the red LED.

Parts needed

  • 1 x Arduino Uno board
  • 1 x RFID reader with tags
  • 1 x Breadboard
  • 2 x LEDs (preferably one red and one green)
  • 2 x 200Ω resistors
  • Jumper wires

Most of those RFID readers are sold without gold pins soldered to it, so you probably will have to do that.

When you have all of your parts, and gold pins soldered, we can connect the whole together using the schematic below.

One pin of the RFID reader is not connected as you can see on the schematic, it is just not needed in this project.

LEDs are connected to pins 7 and 8 but you can use any other pin if you wish, just don’t forget to specify the right pins in your code if you happen to use different pins.

To connect LEDs to the Arduino with resistors, I suggest using a breadboard. And the last thing we need is to upload the program below to the Arduino board.

I wanted to make it as simple as possible. Unfortunately, the RFID library is not as simple to use as it should be. That will make some parts of the code hard to understand for beginners.

If you want to authorize your tag, you have to upload this code, read a tag, check out what is its value is in the serial monitor and paste it in your code.

For this project, we will need an additional library. To download it open the library manager and type RFID, then install the first library on the list.

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

MFRC522 mfrc522(10, 9);

void setup()
pinMode(8, OUTPUT);
pinMode(7, OUTPUT);
void loop()
//here we have to wait for the card, when it is near to the sensor
if ( ! mfrc522.PICC_IsNewCardPresent()){
//we can read it's value
if ( ! mfrc522.PICC_ReadCardSerial()) {

String content= "";
for (byte i = 0; i < mfrc522.uid.size; i++) {
Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(mfrc522.uid.uidByte[i], HEX);
content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
content.concat(String(mfrc522.uid.uidByte[i], HEX));
content = content.substring(1);
if(content == "A6 4A 76 AC"){
digitalWrite(8, HIGH);
digitalWrite(8, LOW);
digitalWrite(7, HIGH);
digitalWrite(7, LOW);

As you can see in the video below, the tag is recognized and signalized by the green LED. The card is not recognized so the red LED blinks.

This simple code can be extended to open the door or to build a more complicated system. Over to you!


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