Circuit for Secret Door Lock

[Dan Stuewe]

For a long time I’ve wanted to make a secret room under our stairs. There is a perfect spot for a “built-in” bookcase that I’d like to be able to swing open into the space under the stairs. I’ve never been able to decide on a locking/unlocking mechanism that would be appropriate for a secret door until the other night when I saw a show on HGTV on just this subject (secret rooms). Besides the fancy fingerprint sensors and remote controls there were some devices that used magnetic reed switches to unlock the doors. So, I came up with this simple schematic and wanted to know if this could be done with off the shelf items and by a non-electrical type of guy.

The way I see it working is a decoration with a magnet embedded in it would be set in the proper location to turn on the 9V circuit which would turn on the 120V circuit via the relay or contactor (which ever would be appropriate in this situation). This circuit would power the solenoid which would unlock the door (not sure of the latching mechanism, but I’m thinking just a simple gate latch).

Would it be this simple? Or are there safety concerns? Or does it need more sophisticated control? Or is there something I can buy that already does all this with all the safety concerns accounted for?

Thanks for any advice you can offer.

[Joe Pelonio]

I do some work for the custom car shops, and they door door/trunk opening and closing mechanisms all the time using 12 volt linear actuators. You can use a 12 volt DC transformer as is used for things like a doorbell, and it would be safer. These only go up to 12" lift but I'm sure you can find bigger ones by googling.


http://www.truckcustomizers.com/category/-DM-AM.html

[Jim Cook]

Your theory will work. There are open curcit and closed curcit switches. If you use battery power, use the one you show as to not drain your battery, ie it is only supplying power when you move the magnet close to the switch. Go to Radio Shack or such and get some stuff to experiment with. Just lay them out and connect wires.
Also the door lock that Joe talkes about is a pretty goo idea too.
I saw the same show, it was interesting

Good Luck
Jim

[Ken Garlock]

Hi Dan.

You might give some thought to using a garage door transmitter/receiver. The receiver would depend on your house electricity being on. That might pose a problem for you.

In any event, you will want to have a way to open the door in an emergency, at least I would.... If you have a basement, you could drop a rope/cable down through the floor as a release. cover the end with a 1x2 to make it look like just another piece of floor bracing.

If you are going to use a bookcase as a 'front' for the room, consider placing a bogus book on a top shelf that would operate the lock.

Anyway, it sounds like a neat project.

Think like a crook, and then mitigate what one would do.

[Von Bickley]

Could you use a switch that is rated for 120 VAC and eliminate the relay and battery? I would hate to depend on a 9 volt battery.:D

[Rob Bodenschatz]

Whatever you do, don't let the cat use the toilet.

[Travis Hirst]

Whatever you do, don't let the cat use the toilet.


HUH!!!????

[Dan Stuewe]

Thanks for the replys.

Going with a 12V device for opening the door sounds like a good option. I had the 120VAC in there since I found several solenoids on grainger's web site that are 120V.

I looked at the linear actuators may be I could find one that opened and closed the door. Now that would be cool (if expensive).

I went with the 9V - 120V since I think magnetic switches rated for 120V wouldn't be available. But, maybe if the whole system was 12VDC, than I wouldn't have a problem with just one circuit.

I was thinking of the gate latching hardware to make "manual over-ride" easy.



HUH!!!????

I believe that is a reference to the movie "Meet the Parents"

Thanks again, and keep the ideas flying!

[Wes Bischel]

Dan,
On the 12V theme, there are a lot of kits for cars that use solenoids to pull the latches - 40lb pull on some. Then a little device called a "popper" pushes the door open. Maybe not exactly what you were looking for, but may spawn other ideas.

FWIW,
Wes

Some info if so inclined:
http://www.slickcar.com/info_shaved_door_handle_kits.asp

[Rob Russell]

Dan,

I'd come up with a mechanism that doesn't depend on electricity.

You could use some rare earth magnets to create a latching mechanism that required the use of a "key" with a magnet to open the latch. That way if the power is off, you can still open your secret compartment.

Rare earth magnets have a lot of pull, so you could really do some fun stuff.

Rob

[David Epperson]

I think Rob is onto something. Particularly since it sounds like you want to use a magnet to operate another magnet. Why not get one magnet that's enough to operate the latch. That way it would work with or without external power.

[Matt Meiser]

Whatever you do, don't let the cat use the toilet.

The same movie immediately came to mind when reading this thread! :D

For the lock, I would use 12V for everything. I found this solenoid (http://www.surpluscenter.com/item.asp?UID=2007030817024515&item=11-2298&catname=electric) at Surplus Center that might work. Radio Shack sells a 1-1/2 amp 12V ac adapter that I used on my dust collection. I would use a relay between the solenoid and the reed switch though to keep the switch from burning up.

[Ken Fitzgerald]

Dan.....I'd look at someway to do it mechanically ...especially if you are putting the book case in. Work the latch into the book case design. Then....loss of electricity.......it still works.....no batteries to worry about running down......mechanically it works. No solenoid to fail......We have such a room. We could never use it for security though....the LOML stores all of our luggage in there. There is no room for anything else.

You could mount the bookcase on hidden rollers....have a secret latch hidden within the bookcase design. Have one corner of the bookcase hinged to the wall.....trip the latch......one end of the bookcase swings out.....pretty simple yet effective.