See GitHub for details of the code, theory of operation and schematics. Here's a quick demo:

Some decisions for the final build:

  • I replaced the 3 LEDs with the Boldport Cordwood for the final build (because it's purdy).
  • stuck with an Arduino Uno as the base board (as it has the 3.3V and 5V supply already taken care of)
  • still left out the level shifters for the MFRC522 data lines. So far, so good (fingers crossed)
  • an 8x8 matrix is used to display the card identity and flash various effects
  • a dinky piezo buzzer is used to play the dinky sound effects