Luke wanted to login on his PC without having to type in a password. He solved this by using a RC522 RFID reader and an Arduino Leonardo.
There are various products on the market that would solve this problem from fingerprint readers to proximity dongles but i decided to see what i could knock up with parts i mainly already had.
Looking in my micro stuff i had a RC522 RFID tag reader 3.3v :
Also an 3.3v arduino Leonardo clone aswell based on a sparkfun pro micro which also can act as a USB device such as a keyboard. This is useful as if a 5v arduino was used a level shifter would be required due to the RC522 not being 5v torrent.
RFID Computer login – [Link]