Knock-pattern door lock

Wed, Nov 4 2009
A work colleague just pointed out this cool project to me. It uses a piezo element to detect knocks on a door, and then processes the pattern to figure out if it matches a pre-set acceptable "secret knock". If the pattern is acceptable it uses a motor to turn the lock handle and unlock the door. The original project site is here but the traffic level seems to have knocked it offline, so in the meantime you can read more about it at Gizmodo and Make. Very nice work.