It seems like every Hackerspace should have some type of kludged together access system on their entry door. [Vasilis] wrote in to share the system called Jarvis that controls access to P-Space, a Hackerspace in Patras, Greece. It’s an RFID-based system that offers a few nice features.
They already have a server running the webpage, so basing their entry system off of a computer was an easy option. You can get in one of two ways; by presenting your valid RFID tag to a reader at the front door, or by ringing the bell and having a member inside press the Big Button of Doom (BBoD) which is a wireless controller.
The BBoD has an Xbee module inside which lets it send an unlock command back to the computer. The remote is powered by two AA batteries, and since it’s never on unless the button is pressed the team estimates these batteries should last around one year.
There’s even a feedback system. The computer posts the last few events to the webpage. So you can go online and see when the BBoD was used, or who’s tag has recently unlocked the entrance to tell if your friends are there.