Knock Box
This is cherry wood box I built for my nephew. The box locks from the inside using a servo and a groove in the wooden top. When turned on with a large switch ( my nephew wanted that specific "fighter jet" switch ) it will listen for a "shave and a haircut - two bits" knock. If the knock matches the servo turns and unlocks the box. The lock can be locked again by pressing a button OR by power cycling.
Features: