Difficulty Level = 6 [What's this?]
After tearing down an old CD player, I was inspired by the CD laser scanning assembly to build a door lock for my subterranean lab. The assembly has two motors: one for turning the CD (I’m not using this one) and one for slowly moving the laser across the CD’s surface. This second motor provides a nice linear motion that I wanted to use to build an electronically-controlled dead bolt lock for my lab.
Here’s the assembled lock. The circuit board in the middle is an H-bridge circuit I built to allow the motor to move in both directions. There are two position sensing switches so the Arduino senses when the motor has reached its limit in either direction. A 9V power supply powers the Arduino board, and a separate 5V supply drives the motor through the H-bridge. The dead bolt is literally a bolt — connected to the assembly with a piece of scrap circuit board — that travels through the door jamb and into the door.
The black CAT5 cable connected to pins 2-8 goes through a small hole in the wall (under a desk) to the keypad on the outside of the lab (I wasn’t sure I wanted to permanently mount the keypad in the wall). The user types in the correct code and presses the # key to open or close the lock. The green LED indicates the door is unlocked. Red indicates locked.
Let’s see the lock in action. (While recording, I gave instructions to my son to lock and unlock using the keypad off camera.)