Hidden Bookshelf Door Shows Incredible Motion

Who didn’t dream of a hidden door or secret passage in the house when they were kids? Some of us still do! [SPECTREcat] had already built a secret door in a fully functioning bookcase with a unique opening mechanism. The intriguing mechanism allows the doors to start by sliding slightly away form one another before hinging into the hidden space. Their operation was, however, was manual. The next step was to automate the secret door opening mechanism with electronics.

The project brain is an off-the-shelf Arduino Uno paired with a MultiMoto Arduino shield to drive 4 Progressive Automations PA-14 linear actuators. These linear actuators have 50lb force, allowing the doors to fully open or close within 10 seconds and maintain a speed that wouldn’t throw the books off the bookcases.

Not wanting to drill a hole through the bookshelf for a switch or other opening mechanisms, [SPECTREcat] added a reed switch that is activated on the other side by a DVD cover with a magnet inside. In addition to that, there is a PIR sensor on the inside room to automatically close the doors if no motion is detected for 2 hours. Dont worry, there’s also a manual switch inside just in case.

Using one of the items on the shelf to trigger the secret passage is a classic move. He could also have used a secret knock code, like the Secret Attic Library Door we covered in the past. Check out the video below to see the hinge and slide movement in action.

42 thoughts on “Hidden Bookshelf Door Shows Incredible Motion

    1. Yep. Highly illegal, and not just because of the doors, but also because there don’t appear to be any windows in the room itself.

      That’s a death trap, ladies and gents.

    1. The noise is coming from the actuators being so tightly coupled to the wood. Cork/rubber gaskets between the actuator and its mounting surfaces will quiet that down radically.

    1. I also thought it’s way too expensive, so here are some links to making your own linear actuators:
      https://hackaday.com/2016/03/31/3d-printed-case-turns-servo-into-quality-linear-actuator/ (We need more 3D printed articles like this; need to scale it up…)
      https://hackaday.com/2014/04/12/diy-linear-actuators-for-a-flight-sim/
      https://hackaday.com/2011/10/09/linear-motor-can-be-built-from-trash/
      https://hackaday.com/2010/01/19/servo-hacked-linear-actuator/

      Window lifter mechanisms apparently work great as well, and they are relatively quiet.

      1. I’ve been looking at those over in the UK for automating my windows.
        Here they are insanely expensive. Over in the US it seems you can get them at discount DIY stores.
        There isn’t a Chinese option either which makes it cheap.

        1. As mentioned above: use window ‘regulators’. You’ll have to pop off some door panels, and should probably bring along a gel cell 12v battery+leads to test the motor, but they work great.

    1. First of all, there’s no need for the doubled up motors because a mechanical linkage can pull the shelves apart as the door is being swung open in one action. You don’t need to first separate the shelves and then open the door – it can open as the door swings.

        1. There is actually pound force (lbf) and pound mass (lbm). They have the same numerical value (on Earth, if you’re looking at weight). Pound force (lbf) is the natural unit for force in the imperial system, and pound mass is NOT the natural unit of mass (that would be the slug – 1/32.17 pound mass).

          This right here is the problem with the imperial system. All other problems are liveable, but when you have to infer from the use whether it’s mass or force, just because someone got lazy and wrote lb instead of lbf or lbm, there is a problem.

  1. The ‘ol hinged first book at a convenient height. With regular use the floor and one worn and smudged book wouldn’t fool Sherlock Holmes or Agent 77. Make it a reference book?

    1. Great idea, and +1 for Get Smart reference.

      On another show…
      Columbo would ‘accidentally’ bumble into it, triggering the mechanism. Or he would talk about all the interesting books and make the suspect sweat. ;)

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