Open Access is a security system that was born out of a project out of Fullerton, Calif.’s 23B Shop hackerspace. It keeps the doors of a building locked until a recognized RFID fob is applied to the reader.
Open Access consists of a circuit board with an on-board Atmega328P microcontroller IC (the same that runs an Arduino Uno) which controls four relays which trigger the various locks in the facility. There are also RFID reader ports and a realtime clock chip with a coin cell keeping the time. The Atmega can store up to 200 users, or you can attach a Raspberry Pi to the front of the board; this adds additional capabilities including the ability to control your security system with Python scripts and vastly increases its storage abilities.
Open Access is open source and you can find the source files on the project’s Google Code repository. Conversely, if you just want want a system up and running, you can buy everything you need at the AccxProducts store.