Code and schematics for an original and probably inefficient Arduino door lock. The key is a user configurable knock pattern entered either on a button or on the door itself, via a microphone, instead of a physical key, or a keypad that almost always has a rather difficult and destructive installation process.
The user can easily write their own unlock function, depending on how they plan on having the Arduino unlock the door. The included unlock function works with a normal DC motor, if the timings are adjusted to its speed.