Sensors
RC522 RFID reader and tag
Read a nearby 13.56 MHz tag for identification experiments.
What it does
The reader energizes a compatible passive tag and exchanges data over radio. The tag UID is an identifier, not proof of a person’s identity.
Connections and compatibility
Common boards use 3.3 V power and SPI logic. In SPI mode the board’s pin labeled SDA is chip select, not I²C SDA. Level-shift Uno outputs.
Choosing one
Buy a reader with a compatible test card and documented pinout. A 125 kHz key fob will not work simply because it is called RFID.
Common mistakes
UIDs can be copied and are not all four bytes long. Use this for inventory or a toy access demo, not the sole credential for a real lock.
Use it in a tutorial
- Using an RFID module — Read an RC522 tag identifier with correct voltage translation, and understand why a UID is not a secure key.