Secret Knock Unlocks Door

Here’s a fantastic project using an arduino, a motor, and a piezo sensor which allows you to both record and detect knocking patterns to unlock a door.  The video below does a fantastic job of demonstrating how it works: It’s completely mobile and can be suction cupped to any dead bolt. Press a button to record a new sequence.  Upon detecting the correct sequence of knocks, the motor turns the lock open.

For more details on the project including detailed photos and code, check out the project build.

[Source] Hack-n-Mod