Hello friends! Today we will interface an RC522 RFID reader with Arduino and read the identifier of a compatible card. We will begin with the radio and wiring requirements, install the MFRC522 library and then build a complete sketch that prints the whole UID and compares it with a demonstration record. The original tutorial used this idea as the starting point for an attendance project. That is a useful learning exercise, but reading a card identifier is only one part of such a system. We must also handle repeated scans, unknown cards, reliable records and the difference between identification and secure authentication. Our example uses an Uno R3 and an MFRC522-based RC522 module communicating over SPI. The original module and connection images remain below. Because the Uno uses 5 V logic ...