Door Lock (Complete)

The original motivation:

Both Noelle and I are pretty active people and we dislike bringing our room keys with us when we’re out running. Additionally, on really busy days, I sometimes forget my keys and I have to call the RA to unlock the door. 😦 I thought it would be extremely useful if we had a way to unlock our locked door. This project was inspired by our good MechE friend Mike, who had a card reader secured to the outside of his door. When he swiped his Duke card, a servo would unlock his door. Given that I already had the chance to tinker with the Arduino LCD shield, I thought I could modify his door-lock idea and replace the card reader with an LCD shield that asks for a four-number code.

The process:

The coding was done over the summer. The code consists of several functions: a button reader, a servo state, and a number enterer. The button reader reads the button voltages, which determines which button was pressed. The servo state dictates the position of the servo arms. When the user enters the correct four numbers, the servo rotates to the left.

Installing the Arduino and servo onto the door was relatively simple. I used 3M scotch heavy duty mounting tape to attach both the servo and Arduino to the door. I used the same mounting tape to attach part of a spoon to the servo. The spoon is connected to a string which is attached to the door lock. When the servo rotates to the left, the spoon pulls on the lock, which rotates the lock to the left.

Arduino LCD shield is attached to an Arduino Uno, which is attached to the door with 3M heavy duty tape
Arduino Uno is attached to a servo. Used a part of a broken spoon in order to attach the string to the lock
My life in a picture: tools, command hooks, pretzels, and running shoes

Here’s the Door Lock in ACTION:

From the outside:

From the inside:

Things to improve upon (future directions):

  • Buy a second servo and attach it to the right side of the lock in order to lock the door

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