[Shawn] recently overhauled his access control by fitting the doors with some RFID readers. Though the building already had electronic switches in place, unlocking the doors required mashing an aging keypad or pestering someone in an adjacent office to press a button to unlock them for you. [Shawn] tapped into that system by running some wires up into the attic and connecting them to one of two control boxes, each with an ATMega328 inside. Everything functions as you would expect: presenting the right RFID card to the wall-mounted reader sends a signal to the microcontroller, which clicks an accompanying relay that drives the locks.
You may recall [Shawn's] RFID phone tag hack from last month; the addition of the readers is the second act of the project. If you’re looking to recreate this build, you shouldn’t have any trouble sourcing the same Parallax readers or building out your own Arduino on a stick, either. Check out a quick walkthrough video after the jump.