Bruce McArdle shares with us how he designed and built his own automatic secret bookcase doors.
This project describes how I used an Arduino, motor controller and linear actuators to allow automatic opening and closing of a pair of doors (secret doors; secret bookcase doors!). The bookcases were hand made to support fully loaded shelves and have a unique hinge and slide mechanism so the bookcases look like they are resting against the outside wall. To open, they slide apart slightly, and pivot inward into the ‘secret lair’ and then slide outward so as to not block too much space inside. This part of the project is described in my first Instructable.
After a couple of years of reliable service, I realized 2 things: 1. I’m lazy and leave the door open most of the time. 2. An open secret door defeats the whole purpose.
So I began this project's phase 2 – add motors to close and open the doors automatically.
The design required these features:
Reliable, a fully automatic "open and close" mechanism for both door hinges/sliders.
Outside open switch should be hidden.
Inside manual switches to open/close doors.
Automatically close doors if no motion is detected in the room for 2 hours.
Low electric power use when in standby.
Emergency ingress/egress in case of power/Arduino failure.
Pinch free if a person or object is between the closing doors
A key component was the Progressive Automations PA-14 linear actuators. These have sufficient force and speed in a compact size. Four 8” linear actuators were used to move both doors. One moves the bookcase door along with the slides and one pivot around the hinges. The 2nd door was a mirror image of the first and required 2 more linear actuators.
One Arduino Uno was responsible for all inputs, outputs and motor control. A RobotPower Multimoto high power quad motor shield provided the power control to the 4 linear actuator motors. I look forward to using Progressive Automations linear actuators in other projects I have in mind.