This is a super simple project that involved 3D printing, a bit of wiring and soldering, and arduino coding! It can be improved upon by miles and it is just a small idea that I wanted to execute out of fun and curiosity. Here are all the parts I used:

servo

https://www.amazon.com/SunFounder-Digital-Helicopt...

arduino uno

https://www.amazon.com/ELEGOO-Board-ATmega328P-ATM...

limit switch

https://www.amazon.com/MXRS-Hinge-Momentary-Button...

Step 1: 3D Print!

Print all your parts using the STL file provided below! The print fits any standard regular hobby servo motor size, and one that is non_continuous but only goes from 0 to 180 degrees. Any material for printing works! The holes are bored to fit M4 screws with corresponding M4 nuts.

secret_compartment.stl
Download View in 3D

Step 2: Mount Servo and Switch!

The 3D print fits a standard limit switch, and the specific one I used is linked above. The screws I used are M4 screws that are paired with their nuts to mount the servo in place! Do not mount the arduino uno before coding it, as the 3D print is designed in a way where the cable cannot be plugged in after mount. So make sure to code it first.

Step 3: Code Arduino Uno!

The code is super super simple! Just works so that a button is pressed to trigger a servo motor. Code will be provided in the description box.

secret_comp.ino
Download

Step 4: Wire and Soldering!

The wiring is according to the schematic given in the picture! It is extremely easy, as there is only a pushbutton paired to the arduino and a servo.

Step 5: Add a 9V Battery!

I chose to use a 9V battery out of the ease and convenience to use, but in the future a goal would be to add a power supply that does not require a battery! so that the compartment can be active at all times.

Step 6: Find Bookshelf and Mount With Adhesive!

My bookshelf happens to be overhead and the books make a gap between them and the wall, so I found this to be a perfect place to add the components! I used heavy duty double-sided adhesive tape by Scotch!

Step 7: Finished!

Please let me know if you have any other questions. This project is fun and very simple to do, and can be improved by miles! First off, I think I could put all my components in a box to house the naked electronics, and in the future I would want a power cable to give the secret compartment power, instead of a battery.