[Alex] sent us this slick little keyless entry system. He wanted a discreet way to trigger the door to unlock. Knocking was too loud, and would give away his secret access code. He decided that touch sensors would be the best. Initially he planned on using the doorknob itself, which would have been awesome, but it was just too much surface area for his touch sensor. Ultimately, he settled for a wire he could touch. An Arduino detects whether or not the correct code has been put in and initializes a high torque servo which turns the doorknob from the inside. In the video, after the break, you can see that it works fairly well.
One thing that is pretty cool about this is that it could be removed and reinstalled somewhere else in a matter of minutes. That’s good, since he’s in a dorm and would probably be in some trouble for damaging the door. It would be nice to see this put into an enclosure that hooked over the top of the door so it could be truly portable.