Here’s an awesome lock hack that uses Arduino to create a door lock that can detect your “secret knocks” to open the door. I like everything except that people might be able to hide nearby and hear your “secret knock”. Regardless of practicality, this is a really awesome hack, perhaps the best door lock hack I’ve seen in awhile.
Seeeeecret knocks? And if we could detect a secret knock, shouldn’t it unlock a door? If you can’t tell by looking this was cobbled together from spare stuff around the lab, it’s not much more than a piezo speaker, a tiny gear reduction motor, and an Arduino. And PVC pipe.
See video of the secret knock detecting door lock in action here: