by JOJO @ circuitstoday.com:
Its quiet fun to work with RFID based projects! In the previous article, we saw how to interface RFID with Arduino. Interfacing is the first step to create any useful project. So why don’t we create an RFID based Access Control System or an RFID based Door Lock using Arduino? The system I have designed here is a simple version of the project. This project can be enhanced with a lot of features (which I will be doing in the next version of this project – Advanced RFID based Door Lock). So lets begin!
Simple RFID based Door Lock using Arduino – [Link]